CN1667693A - multi-view display - Google Patents

Abstract

The invention provides a multiple view display (e.g. a dual view display) for displaying unrelated images in different viewing regions. The display is equipped with a liquid crystal display device (20-28) having pixels (101 102) with asymmetric viewing angle characteristics. The display is equipped with a driving device (29) to drive pixels to display a first image in a first viewing direction and to display a second image in a second different viewing direction. The pixel (101) to display the first image appears dark in the second direction, while the pixel (102) to display the second image appears dark in the first direction.

Description

multi-view display

The present invention relates to multi-view displays. Such a display can be used to display two or more views containing images that are substantially different from each other. Such displays enable different viewers to view images that may not be related to each other.

Accompanying drawing 1 has described the concept of the multi-view display, and in this example, the multi-view display is composed of dual-view displays. Viewers 1 and 2 located in viewing areas 1 and 2 watch the dual view display 10 . Display 10 has discrete viewing areas in which substantially different images can be displayed. For example, while Viewer 1 can watch a movie, Viewer 2 can view a map. Such an example could be applied, for example, to a display used in a motor vehicle so that the driver can view navigation information while the passenger watches a movie.

FIG. 2 depicts another example of using a dual view display 10 . In this example, the display is placed in the plane of the desk or counter 11 so that viewers 1 and 2 on opposite sides of the desk or counter can view different images. Similarly, Figure 3 depicts a horizontally oriented multi-view display, in this example the multi-view display displays four unrelated images to viewers 1-4 on four sides of the display.

The viewing angle characteristics of the twisted nematic (TN) liquid crystal (LC) mode are well known, and the viewing angle characteristics of this liquid crystal display (LCD) are described in John Wiley and Sons Inc., 1999, P, Yeh and C. Disclosed in Chapter 9 of Gu's "Optics of Liquid Crystal Displays". These characteristics are generally relatively uniform in the angular direction of the horizontal viewfinder, but asymmetrical in the angular direction of the vertical viewfinder. Techniques for optimizing viewing angles for LCDs are known, allowing the same image to be viewed from a wide range of angles.

A multi-view video display is disclosed in JP06-236152. In this example, a bi-convex lens is used to create different viewing areas.

In JP2-146087, JP60-211418, JP60-211420, JP60-211428 and Okada et al., "Possibility of Stereoscopic Displays by Using a Viewing Angle Dependence of Twisted Nematic Liquid Crystal Cells” discloses the directional viewing characteristics of TN and guest-host (GH) LCDs. These documents disclose two images being spatially multiplexed on an LCD with pixels displaying one image having a different alignment than pixels displaying the other image. These documents generally relate to autostereoscopic or stereoscopic displays for displaying associated images providing a 3D picture.

JP08-101367 discloses a dual layer autostereoscopic display. One layer displays spatially multiplexed images, and another layer on the back acts as a direction control layer, which directs the images into different viewing areas for autostereoscopic viewing.

In the configurations disclosed in these documents, the pixels displaying one image are the same configuration as the pixels displaying the other image. However, the pixels that display one image are actually a rotation of the pixels of the other displayed image, or are actually a mirror image of the other displayed image.

In the configuration disclosed by Chen et al. in Japanese Journal of Applied Physics, Vol.36(1997), pp. L1685-L1688 "Simple Multimode Stereoscopic Liquid Crystal Display", a passive spatially patterned liquid crystal layer is overlaid on the display spatially complex Use the left and right view on the image screen. The passive layer includes a double-twisted nematic liquid crystal region and a Freedericksz mode liquid crystal region that rotates one view of polarized light but not the other. These images can be viewed autostereoscopically without the use of viewing tools, or stereoscopically using polarized lenses.

JP60-211428 discloses a stereoscopic display comprising a pair of stacked guest-host (GH) liquid crystal display devices. Each device shows its own view, and the devices are aligned to be oriented perpendicular to each other. In this way the left and right views are polarized perpendicular to each other, and polarized glasses are used to view the stereoscopic display.

US6 424 323 discloses an arrangement using a lenticular screen to provide two or more 2D or 3D images.

In the arrangement disclosed in EP1 250 013, a display screen displays spatially multiplexed left and right images, with multiple other devices in front of the display screen controlling the sharpness of the image through the left and right eyes of the observer.

JP09-043540 discloses a stereoscopic display using electronic exchange of two liquid crystal barrier layers to switch the effective position of the parallax barrier layer. This leads to an autostereoscopic 3D display configuration.

WO9527973 discloses the use of a twisted nematic liquid crystal mode to optimally display one image from one panel to two viewers by controlling the direction of maximum contrast ratio midway between two viewing positions.

WO9945527 discloses the use of a twisted nematic liquid crystal mode. By changing the voltage range used, the extension of the viewing angle range provides switching between a public mode of viewing and a dedicated mode of viewing, in which the contrast ratio is sufficient to produce a recognizable image, and in the public mode all viewers can watch a image, in dedicated mode only viewers at normal incidence can view the image.

US5059957 discloses a solution to prevent the TV image from inside the car from affecting the driver by using the LC layer by moving the area of maximum contrast ratio to the observation position of the passenger.

US5526065 and US20030007227 disclose schemes for using an LC layer to prevent the TV image from inside the car from affecting the driver by moving the LC layer so that it appears black to the driver.

US5936596 discloses the use of pixels with different viewing angle characteristics to display different images in different viewing angle ranges from one display. It also discloses a scheme for changing the viewing angle characteristics of a pixel by applying a voltage.

US6593904 discloses the use of varying voltages with light twisting of liquid crystals. Changing the voltage range used can change the viewing angle, so that one image can be observed in one viewing angle range of the display, and the second image can be observed in another viewing angle range of the display.

US6724450 discloses the use of dual field pixels using separate electrical controls so that one field can display one image and the other field can display a second image. Having different subtitles or liquid crystal twists between each field allows different images to be displayed in different ranges of viewing angles.

WO2004/036286 discloses the use of at least two differently assigned observation angle pixels which are interleaved to produce a multiple view display. It is possible to have more than one display layer.

When applying liquid crystal display (LCD) pixels (picture elements), the concept of "different configuration" is specified to indicate that these pixels are different from any one or any combination of the following: at the interface of one or two liquid crystal substrates forward tilt angle; bulk liquid crystal director direction; liquid crystal thickness; director twist; doping of liquid crystal material with optical additives, dyes or polymeric materials; polarizer transmission axis direction; azimuth and/or zenith Anchoring strength; retardation layer amplitude and/or optical axis orientation; compensation layer effects; liquid crystal material; and drive scheme, but excluding cases where one pixel is a rotation or mirror image of the other.

In the application of liquid crystal display pixels, the concept of "different LC modes" is specified to indicate that these pixels are different from any one or any combination of the following: forward tilt angle at the interface of one or two liquid crystal substrates; bulk ) liquid crystal director direction; liquid crystal thickness; director twist; azimuth and/or zenith anchor strength; polarizer transmission axis direction, where the polarizer is placed in the liquid crystal cell; retardation or compensation effects, where the retarder or The compensator is provided in the liquid crystal cell; the liquid crystal material; and the doping of the liquid crystal material with optical additives, dyes or polymeric materials, but excluding the case where one pixel is a rotation or mirror image of the other.

According to one aspect of the present invention, there is provided a multi-view display comprising: at least one liquid crystal display device comprising a plurality of pixels having an asymmetric viewing angle characteristic; and driving means for driving the pixels in a first viewing direction displaying a first image on the top, and displaying a second image in a second viewing direction different from the first viewing direction, characterized in that: the driving device cooperates with at least one display device so that the pixels displaying the first image are displayed in the second A dark color appears in the first direction, and the pixels displaying the second image appear dark in the first direction.

Pixels displaying the first and second images may be rendered maximally dark in the second and first directions, respectively. The light intensity supplied in the second and first directions may be lower than X% of the maximum light intensity by pixels displaying the first and second images capable of supplying light in the first direction respectively. and in the second direction, X is a real number lower than 20. X can be equal to 10. Alternatively, X may be equal to 3.5. As another alternative, X could be equal to one.

The first and second images may be unrelated to each other.

The first and second images may be in a plane that is normal to the display surface of the at least one device and contains the direction of maximum viewing angle asymmetry. The first and second directions may be relative to a normal to the display surface. The first and second directions are substantially symmetric about the normal, or alternatively the first and second directions may be asymmetric about the normal.

The pixels displaying the first image may be configured to provide a first contrast ratio greater than 1 in a first direction, and to provide a contrast ratio substantially equal to 1 in a second direction, and the pixels displaying the second image may be configured to provide a contrast ratio in A second contrast ratio greater than 1 in the second direction and providing a contrast ratio substantially equal to 1 in the first direction.

The angle between the first and second directions may be substantially greater than or equal to 10 degrees.

At least one device may include sets of pixels having pixels each of the same color and a different color than the other sets of pixels. At least one device may include a liquid crystal layer having different thicknesses for different colored pixels. At least one device may include a patterned retarder with regions of different retardations that are optically aligned with pixels of different colors. Areas of different retardation contain different colored dyes acting as color filters.

At least one device may be a transmission mode device.

The at least one display device may have a uniform alignment and an asymmetric liquid crystal mode with an asymmetric viewing angle characteristic, and the driving device may be configured to drive the at least one device using a first driving scheme for displaying a first image, and for displaying a second image. A second driving scheme is used to drive the at least one device, and the first driving scheme is different from the second driving scheme.

The first and second driving schemes may respectively include first and second voltage ranges different from each other.

The liquid crystal mode may be one of twin-twisted nematic, mixed alignment nematic, and twin-twisted vertical alignment nematic.

The first and second views may be spatially multiplexed on at least one device. At least one display device may comprise a liquid crystal layer and a uniform retarder disposed between uniform input and output polarizers. In the plane of the retarder, the retarder may have an optical axis oriented at substantially 45 degrees to the transmission axis of an adjacent polarizer, and an optical axis oriented at substantially 67 degrees to the normal to the plane of the retarder. The retarder may have a retardation of substantially 494nm. At least one device may include a patterned polarizer having first and second regions for first and second views, respectively, having a first region transmission axis different from the second region transmission axis. The transmission axis of the first region may be substantially orthogonal to the transmission axis of the second region.

At least one device may include a patterned retarder. Patterned retarders can be transformed to substantially zero delay for single view mode operation.

At least one device may include a parallax barrier.

The first and second views may be time multiplexed on at least one device. At least one device may include a switchable delay. The retardation of the retarder can be switched between odd and even half wavelengths of visible light.

The at least one device may comprise a first pixel having a first configuration of a first asymmetric viewing angle characteristic, and a second pixel having a second configuration of a second asymmetric viewing characteristic different from the first configuration , the second asymmetric viewing characteristic is oriented differently from the first asymmetric viewing characteristic, and the driving means may be configured to drive the first pixel displaying the first image, and drive the second pixel displaying the second image.

The first and second images may be viewable in a third viewing direction between the first and second directions.

The first pixels and the second pixels may be spatially dispersed.

The first and second asymmetric viewing properties may be oriented in substantially opposite directions.

The first and second pixels may respectively have first and second liquid crystal modes different from each other. At least one of the first and second patterns may be double twisted nematic, hybrid aligned nematic and double twisted vertical aligned nematic, Freedericksz, vertical aligned nematic and pi-cell ) in a pattern. The first and second pixels may have different liquid crystal director twists in the absence of an applied field. Different twists can have different magnitudes. Different twists have different twist directions. A different twist can be 0 degrees.

The first and second pixels may have different liquid crystal director pretilt angles at at least one liquid crystal substrate interface. Different pretilt angles can have different magnitudes. Different pretilt angles can have different directions.

The first and second pixels may have different orientations of the large liquid crystal directors. The first and second pixels may have different surface anchoring strengths at at least one liquid crystal substrate interface.

The first and second pixels may have different liquid crystal materials.

At least one of the first and second pixels may have a liquid crystal material comprising at least one chiral dopant, polymeric network and dye.

The first and second pixels may have liquid crystal layers of different thicknesses.

The first pixel may have a first polarizer with its transmission axis oriented at a first angle relative to the liquid crystal optical axis of the first pixel, and the second pixel may have a second polarizer with its transmission axis oriented at a first angle relative to the liquid crystal optical axis of the first pixel. The second angle related to the liquid crystal optical axis of the two pixels, the first angle is different from the second angle.

The first and second pixels may have first and second retarders of different delays.

The first and second pixels may have first and second compensation layers that provide different compensation effects.

The driving means may be configured to drive the first and second pixels with different voltage ranges.

At least one device may include a parallax barrier.

The display consists of a liquid crystal device configured to be viewed at all times, and employs the first mentioned device for the manipulation of time and space.

The at least one device may comprise a first liquid crystal device having a first asymmetric liquid crystal mode with a first asymmetric viewing angle characteristic, and a second liquid crystal device having a second asymmetric liquid crystal mode having a second asymmetric viewing angle characteristic, Where the second asymmetric viewing characteristic is oriented differently than the first asymmetric viewing characteristic, the drive means may be configured to drive the first device with a first drive scheme for displaying the first image, and for driving the first device with a second drive scheme for displaying the second image. A driving scheme is used to drive the second device.

The first and second drive schemes may include first and second voltage ranges, respectively. The first and second voltage ranges may be substantially the same.

The second device is visible through the first device. The second device may be disposed between the first device and the backlight.

The first means and the second means may be substantially parallel to each other.

Each first device and second device may have a uniform calibration.

Each of the first device and the second device may be a transmission mode device.

The first and second liquid crystal modes may be of the same type.

The first and second asymmetric viewing properties may be oriented in substantially opposite directions.

The first device and the second device may have alignments oriented in substantially opposite directions.

At least the first and second liquid crystal modes are one of twisted nematic, mixed aligned nematic and twisted homeotropic aligned nematic.

Each of the first means and the second means may comprise a different colored set of pixels.

One of the first and second means may include red, green and blue pixel sets, and the other of the first and second means may include cyan, magenta and yellow pixel sets. Each of the first means and the second means may include color filter stripes extending substantially parallel to a plane containing the first and second directions.

The display may include a multi-color time-sequential backlight, and drive means arranged to drive the first and second device colors in time-sequence.

The drive means may be arranged to provide time-multiplexed images to the first and second means, and to synchronously control the direction-switchable backlight. Each of the first and second means may comprise a spatial phase modulator.

The display may include a switchable light diffuser switchable between a substantially non-diffusing state exhibiting a multi-view display mode and a diffuse state exhibiting a single-view display mode.

According to a second aspect of the present invention, there is provided a multi-view display comprising: a liquid crystal display device having a uniform alignment, and an asymmetric liquid crystal mode having an asymmetric viewing angle characteristic, characterized in that it comprises a driving device which Driving the device with a first drive scheme for displaying a first image in a first viewing direction and with a second drive scheme different from the first drive scheme for displaying in a second direction different from the first direction on the second image.

According to a third aspect of the present invention, there is provided a multi-view display comprising: a liquid crystal device including a first pixel having a first configuration with a first asymmetric viewing angle characteristic, and a second pixel having a second a second configuration of the asymmetric viewing characteristic, the second configuration being different from the first configuration, the second asymmetric viewing angle being different from the orientation of the first asymmetric viewing characteristic; a driving device for driving the first pixel at the first viewing The first image is displayed in a direction, and the second pixel is driven to display a second image in a second observation direction, and the first observation direction is different from the first observation direction.

According to a fourth aspect of the present invention, there is provided a multi-view display comprising: a liquid crystal device including a first pixel having a first configuration with a first asymmetric viewing angle characteristic, and a second pixel having a second A second configuration of asymmetric viewing characteristics, the second configuration being different from the first configuration; a driving device for driving the first pixel to display the first image in the first and second viewing directions, and driving the second pixel in the second The second image is displayed in the second viewing direction.

According to a fifth aspect of the present invention, there is provided a multi-view display, comprising: a first liquid crystal device having a first asymmetric liquid crystal mode with a first asymmetric viewing angle characteristic, a second liquid crystal device having a second asymmetrical liquid crystal mode A second asymmetric liquid crystal mode of symmetrical observation characteristics, the second asymmetric liquid crystal mode is oriented differently than the first asymmetric liquid crystal mode; a driving device, using the first driving scheme to drive the first device, for the first observation A first image is displayed in a direction, and a second driving scheme is used to drive the second device to display a second image in a second viewing direction, the first viewing direction being different from the second viewing direction.

This makes it possible to provide multi-view displays which allow different images to be viewed in different directions with a relatively high contrast ratio. This yields improvements in displayed image quality.

The invention will be described in more detail by way of example with reference to the accompanying drawings; wherein,

1 to 3 are diagrams describing the use of multi-view displays;

4 is a cross-sectional view of a display constituting an embodiment of the present invention;

FIG. 5 is an exploded orientation view depicting the components of the display of FIG. 4;

Figure 6 is a polar plot depicting display contrast ratios at different viewing angles;

Figure 7 is a plot of intensity relative to viewing angles for different gray levels of the display of Figure 4;

Figure 8 is a graph of intensity versus gray level at two different viewing angles;

Figure 9 is a graph of brightness versus voltage depicting two different voltage ranges;

Fig. 10 is a graph of brightness with respect to gray levels for different viewing angles and for different pixel colors;

Fig. 11 is a simplified diagram of correcting the gray level relative to the gray level of the image, which describes the results of the gray correction for different colors;

12 is a cross-sectional view of a display constituting another embodiment of the present invention;

13 is a cross-sectional view of a display constituting yet another embodiment of the present invention;

Figure 14 shows a cross-sectional view illustrating a method of constructing a pixelated retarder;

Figure 15 is a simplified diagram of the transmission of voltage with respect to two different viewing directions;

Figure 16 is a diagram illustrating the operation of the time multiplexed mode of the display;

Figure 17 is an operational diagram describing a combined spatial and temporal multiplexing mode of a display;

Figure 18 depicts a graph of luminance versus applied voltage describing an ideal display drive scheme;

Figure 19 is a cross-sectional view of a display constituting another embodiment of the present invention;

Figures 20 and 21 show transfer diagrams for voltages describing the operation of the display in Figure 19;

Fig. 22 schematically depicts a display part constituting yet another embodiment of the present invention and a transfer diagram of voltages for describing its operation;

FIG. 23 is a voltage diagram of transmissions for single view mode operation of the display of FIG. 23;

Figure 24 schematically depicts another display constituting an embodiment of the present invention and a transfer diagram with respect to voltages describing its operation;

FIG. 25 is a diagram depicting the transfer of voltages for single view mode operation of the display of FIG. 25;

Figure 26 is a sectional view of another embodiment of the present invention;

Figure 27 is a diagram depicting different sized displays and their viewing conditions;

Figure 28 is a cross-sectional view of a display constituting an embodiment of the present invention;

Figure 29 is an exploded view depicting the orientation of the components of the display of Figure 28;

Figures 30 and 31 depict brightness in transmission of voltage relative to device configuration;

Figure 32 depicts the variation of brightness ratio versus voltage;

Figure 33 is an exploded view depicting the orientation of the components of the display;

Figures 34 and 35 describe the brightness in the transmission of the voltage for the device configuration;

Figure 36 describes the variation of brightness ratio versus voltage;

Figure 37 shows the use of a dual view display;

Figure 38 describes the use of polymer walls to separate different LC materials;

Figure 39 describes the operation of a dual display with a central crosstalk area;

Figure 40 describes the operation of a dual display with use of the central crosstalk region;

Figures 41 and 42 illustrate a configuration using four devices.

Figure 43 is a cross-sectional view of a display constituting an embodiment of the present invention;

Figure 44 is an exploded view depicting the orientation of the components of the display example of Figure 43;

Figures 45 and 46 are simplified graphs of transmittance versus LCD voltage for the display of Figure 43;

Figure 47 is a simplified graph of transmittance versus voltage for a display of the type shown in Figure 43 omitting the intermediate polarizer;

Fig. 48 shows two diagrams similar to Fig. 9 describing the driving scheme for the LCD of the display in Fig. 43;

Figure 49 schematically depicts a display having a set of color filters constituting an embodiment of the present invention.

Figure 50 schematically depicts a display having two color filter sets constituting one embodiment of the present invention.

Figure 51 is a cross-sectional view of a display constituting another embodiment of the present invention;

Figure 52 depicts examples of pixel and color filter configurations;

Figure 53 schematically describes a timing display constituting an embodiment of the present invention;

Figure 54 is a cross-sectional view of a display constituting another embodiment of the present invention;

Figure 55 depicts an alternate mode operation of the display of Figure 54;

Figures 56 and 57 describe the timing mode operation of the display of Figure 54;

Figure 58 describes the operation of the higher resolution single view mode of the display in Figure 54;

Figure 59 depicts a modification of the schema described in Figure 58;

Figure 60 schematically describes the operation of the timing mode;

Figure 61 shows two simplified graphs of transmittance versus voltage for a display comprising two TVAN LCDs but without an intermediate polarizer;

Figure 62 shows two simplified graphs of transmittance versus voltage for a display comprising two TVAN LCDs with intermediate polarizers;

Figure 63 depicts a display with more sequential modes of operation;

Figure 64 depicts the use of a tilted or non-parallel LCD to adjust the angle between viewing directions;

Figure 65 is a cross-sectional view of a display incorporating a parallax blocking layer and constituting another embodiment of the present invention;

Figure 66 is a view similar to that of Figure 5 constituting the direction of the display components of an embodiment of the present invention;

Figure 67 is a graph of emission versus voltage describing the operation of the display in Figure 66;

Figures 68 and 69 are similar to Figures 30 and 31 but for different viewing angles.

Figure 4 depicts a dual-view thin-film transistor (TFT) active-matrix LCD used to direct potentially unrelated images in two views into observation areas 1 and 2 of viewers 1 and 2, respectively, depicted in Figures 1 and 2. The display includes a front linear polarizer 20 attached to or formed on the outer surface of a substrate 21 . Substrate 21 may be constructed of glass or any suitable transparent non-birefringent material of sufficient stability. The substrate 21 has on its inner surface a transparent electrode 22 made of, for example, indium tin oxide (ITO). The electrode 22 serves as the counter electrode of the active matrix and uniformly covers the entire active area of the display 10 . An alignment surface such as an alignment layer 23 , for example rubbed polyimide, is formed on the electrodes 22 and rubbed uniformly so as to have the same uniform alignment direction throughout the active area of the display 10 .

The second substrate 27 has a rear linear polarizer 28 , a TFT and an electrode layer 26 . The electrode layer 26 is patterned to define pixels (picture elements). Such TFT and electrode configurations are known arrangements and will be described later. An alignment surface such as an alignment layer 25 , for example rubbed polyimide, is formed on layer 26 . Alignment layer 25 also provides a uniform alignment direction across the active area of display 10 .

Substrates 21 and 27 are formed together with layers 22, 23, 25 and 26 and are produced with alignment layers 23 and 25 facing each other to define a liquid crystal cell with liquid crystal layer 24 therebetween. Liquid crystal layer 24 is a nematic liquid crystal comprising, for example, ZLI4792 available from Merck UK. Polarizers 20 and 28 may be formed or provided before or after formation of the liquid crystal cell. Layer 26 includes or is connected to drive means described at 29 for providing suitable signals for addressing individual pixels with defined gray scale voltages. The means 29 may be formed as all or part of an external component for providing the first and second drive schemes for the first and second images to be displayed. As an alternative, the device 29 can be integrated on the panel.

FIG. 5 schematically depicts an exploded view of polarizers 20 and 28 and layers 23 to 25 . FIG. 5 also depicts the vertical and horizontal directions relative to the normal directions of the display 10 described in FIG. 1 . The vertical upward reference direction is expressed as 0 degrees, and the horizontal rightward direction is expressed as 90 degrees. All directions describing the components in FIG. 5 refer to the upward vertical direction of 0 degrees.

The front polarizer 20 has a transmission axis 30 oriented at an angle of +90 degrees relative to the upward vertical. The alignment layer 23 has a uniform alignment direction 33 oriented at an angle of -45 degrees relative to the upward vertical direction. The alignment layer 25 has a uniform alignment direction 35 oriented at an angle of +45 degrees relative to the upward vertical direction. Polarizer 28 has a transmission axis 38 oriented at an angle of +180 degrees relative to the upward vertical. Thus, for what is generally described as the white mode operation of display 10, the transmission axes of polarizers 20 and 28 are both orthogonal to each other. Similarly, calibration directions 33 and 35 are orthogonal to each other. When no voltage is applied across the pixel, liquid crystal layer 24 is aligned with a 90 degree twist so that incident light polarized by rear polarizer 28 , which is transmitted through polarizer 20 , has a polarization direction rotated by layer 24 .

When a sufficiently large electric field is applied across a pixel, the liquid crystal molecules in the pixel are oriented substantially perpendicular to the surface of layer 24 with little or no effect on polarized light passing through the display. In this way, the light passing through the rear polarizer is substantially eliminated by the front polarizer 20, and the pixel appears to be maximally dark or black. For applied fields of intermediate values, the polarized light from polarizer 28 is rotated by varying amounts and analyzed by front polarizer 20 to provide a variety of gray levels constituting gray scales with black and white levels.

FIG. 6 depicts the variation of the contrast ratio at different viewing angles of the display 10 depicted in FIGS. 4 and 5 . Display 10 is effectively rotated 90 degrees compared to the typical orientation of TN LCDs so that the asymmetric viewing angle orientation is substantially horizontal. In this example, the display is set to be viewed at -30 degrees to +30 degrees on either end of the horizontal plane of the normal to the display.

The viewing angle characteristics of display 10 are depicted in FIG. 7, which has characteristics that are prominent at viewing angles of -30 degrees and +30 degrees. The display is of the type where discrete gray levels 0 to 255 are addressable. Figure 7 depicts the selected intensities of the gray levels at various viewing angles, and when viewed on-axis the display is expected to provide substantially evenly spaced gray levels. Flat conventional drive scheme.

Figure 8 depicts the transmission of the intensity of the gray level with respect to the -30 degree and +30 degree viewing directions. For example, when displaying a gray level of 96, those pixels displaying that level will appear essentially black from a +30 degree viewing area, but will appear at exactly half maximum brightness when viewed from a -30 degree viewing area the following. By suitable selection of the voltage levels for selecting the gray level according to the first and second driving schemes for the first and second images, the first image can be made substantially only visible in the first viewing area, making the second The second image is essentially only visible in the second viewing area. The drive schemes are chosen such that they establish a contrast ratio suitable for displaying a corresponding image in the direction of desired viewing, while displaying a very low or substantially zero contrast ratio in other viewing areas.

A suitable drive scheme is illustrated graphically in Figure 9, which depicts the luminance (in transfer mode) relative to the voltage applied to the pixel that selects the gray level to be displayed when viewed from -30 degrees to +30 degrees . When addressing these pixels displaying the first image, by using the voltage range described at 40, the first image is visible in the viewing direction of -30 degrees, but the first image is displayed in the viewing area of +30 degrees of pixels appear black. Conversely, for those pixels displaying the second image, by using the voltage range 41 of image 2, the second image is visible in the +30 degree viewing area, whereas in the -30 degree viewing direction these pixels appear white. In this way, the display 10 establishes two viewing areas for the viewer to view unrelated images or sequences of images in their respective viewing areas without requiring any parallax glasses or using multiple sensors with different calibrations for the pixels displaying the different images. field liquid crystal technology.

In order to be able to provide a color LCD, the effect of color on the LC mode must be considered when choosing a driving scheme for the first and second images. In a typical color display, color filters filter light from corresponding sets of pixels. These tints can be red, green, blue or cyan, crimson and yellow. Due to the dispersion of the liquid crystal layer 24, the optical characteristics of the liquid crystal mode used in the LCD vary with the wavelength of light. For example, Figure 10 depicts the variation in intensity versus the gray level of an individual color for red, green, and blue pixels at -30° and +30° viewing directions.

In order to produce a good color dual-view display, the dispersion effect of the liquid crystal mode on the gray scale curve can be overcome by finely mapping the gray level of each color component separately. Figure 11 depicts the result of this mapping process to allow the same gray level to be selected and displayed for each color. In this way, the intensity of the image is the same as a given gray level, regardless of the color of the image being displayed.

Color mapping can be selected according to the application of the display. For example, for some applications it may be desirable to have a higher intensity relative to green light in one or both images relative to red and/or blue. Images can be chosen to account for this requirement.

Figure 12 depicts an alternative dual view display for displaying color images. Figure 12 differs from the display of Figure 4 in that color filters 45 are provided on the inner surface of the substrate 21 and the liquid crystal layer thickness 46 is different for different colored pixels.

The optical properties of a pixel are determined by the retardation in the liquid crystal layer 24 of the pixel. The retardation is a result of the birefringence and thickness 46 of the liquid crystal layer 24 . Thus, by varying the thickness of layer 24 for different colored pixels, each pixel can have its optimum characteristics, or at least the desired displayed color or range of colors can be enhanced.

Alternatively, liquid crystal materials with different birefringence values, which are separated by polymer walls, can be used. The delay is matched to the wavelength of the corresponding colored pixel.

The display of Figure 12 has discrete graduated thicknesses for pixels of different colors. In this particular example, this can be achieved by forming a polymer pitch, such as 47 on the TFT substrate 26, 27 with an alignment layer 25 formed on top of the pitch. Such a pitch can be formed on the other substrate or on both substrates below the alignment layer. Pitches 47 may be formed by photolithographic processing of a suitable resist material. Alternatively, pitches 47 may be formed by screen printing a suitable polymeric material directly onto the or each substrate. In another alternative, the color filter 45 may have a graded thickness. In another example, the variation in thickness of the liquid crystal layer can be achieved without sharp edges by using wedge-shaped structures of suitable inclination or similar structures, so as to reduce any misalignment of the LC caused by the sharp edges of the pitch. standard impact.

Figure 13 depicts another technique for compensating for liquid crystal dispersion. In this display, a pixelated retarder 50 is provided. Each "pixel area" of the retarder provides an amount of retardation that essentially compensates for the dispersion effects of the liquid crystal of the associated pixel. To reduce parallax, a pixelated retarder 50 is arranged between the substrates 21 and 26,27. In FIG. 13 , the retarder 15 is shown disposed on the TFF substrates 26 , 27 , but the retarder may instead be disposed on the color filter substrate 21 .

Various techniques can be used to fabricate pixelated retarder 50 . An example of this technique is disclosed in van der Zander et al. in Sid 03 Digest, "Technologies towards Patterned Optical Foils", pp. 194-197. A specific example of a suitable technique is depicted in Figure 14 using a polymerisable liquid crystal such as reactive mesogen, an example of which is RMM34 available from Merck UK.

The substrate 53 is prepared using an alignment surface such as alignment layer 52 for alignment of the optical axis of the active mesogen. The active mesogen is coated on the alignment layer 52 using a suitable technique such as spin coating. Active mesogens are of the type whose birefringence changes with temperature when unpolymerized, and are polymerized upon exposure to light such as ultraviolet light in order to fix the direction of the optical axis.

In order to form retardation regions for the first color, layer 51 is exposed to ultraviolet radiation through light shielding film 52 with layer 51 maintained at a suitable temperature to control its birefringence. The first region is the region that requires the greatest retardation and is therefore birefringent.

After the first UV polymerization, layer 51 is heated to a second temperature in order to provide ideal birefringence for light retardation in the second region. This is depicted at 55 of FIG. 14 . After the second region of the next color is exposed to infrared radiation through the mask 56, the birefringence of the unpolymerized active mesogen is reduced to the expected value. The second regions are thus aggregated, their properties fixed.

The temperature is then increased again as described at 57 in order to reduce the birefringence of the remaining unpolymerized regions, which are polymerized by exposure to ultraviolet radiation through a third mask 58 . The retarder is then effectively ready for use and can be removed from the substrate 53 and alignment layer 52 contained in a display device of the type shown in FIG. 13 . Alternatively, the retarder can be constructed directly on the TFT substrate depicted at 59 in Figure 14 with an alignment layer formed on its upper surface, before using the upper surface and its associated layers to form the liquid crystal cell.

Suitable dyes can be added to the polymerisable liquid crystals to form color filters for displays. In this case, the retarder and color filter can be fabricated on a single layer in order to reduce the number of layers required in the display, which simplifies manufacturing and reduces the number of alignment pitches necessary.

For non-normal incident light, the viewing angle characteristics of polarizer 20 and/or polarizer 28 may be selected and optimized to improve performance, particularly image quality in the display viewing area.

The voltages used to address the gray levels for the different views can be selected or optimized using techniques like gamma correction, which is well known in the art and described for example at www.inforamp. net/~poynton/ available in Charles Poynton's "Frequently Asked Questions about Gamma". This is accomplished by first remapping the gray levels in the original image for each view to the gray levels that can be seen from the viewing area of that view. Remapping can be for a single linear range or can be for a range of two or more intensity levels. Adjustments can be made to enhance the appearance of the image based on the appearance of the image in the area from which it is viewed. This can be achieved by suitable gamma correction of the image data. This type of correction may not use grayscales outside of the view's existing grayscale range. Any suitable gamma value can be used depending on the desired effect. For example, a gamma correction value of 2.2 or lower such as 1.7 may be used. Applying gamma correction to images after they have been color corrected is not likely to produce good results. So gamma correction can be applied to the color correction curve or the original image before color correction.

Other image intensity adjustment techniques such as "histogram flattening" may be used.

The gray level ranges for the pixels of the first and second viewing areas may be suitably selected or optimized. For example, the gray level range may be chosen so as to provide good image quality in the observation area from the observation image, and to produce an optimal gray level state when observing pixels from this observation area or a mutual observation area, throughout This level in the gray scale range can be substantially black or white and have a minimum contrast ratio.

The drive means 29 need to be able to drive the pixels according to different drive schemes, such as voltage ranges as previously described, so that each pixel receives the appropriate voltage selected for displaying an image. In case the display is designed to allow operation in a single view mode, another drive scheme such as a greater voltage range may be used, the drive means 29 must be able to apply the appropriate voltage to each pixel.

Although the implementations described so far are based on a twisted nematic (TN) liquid crystal mode, any liquid crystal mode that produces a suitable asymmetric viewing angle can be used. For example, suitable smectic or ferroelectric liquid crystal modes may be used. Also, other twisted nematic modes may be used, such as hybrid aligned nematic (HAN) mode or twisted vertically aligned nematic (TVAN) mode, eg as disclosed in EP1103840. The TVAN mode has a substantially non-twisted vertical structure for substrates below the threshold voltage for switching. Above this threshold voltage, the mode transitions progressively to a more planar double-twisted structure, which is similar to that of the double-twisted nematic mode below its threshold voltage. An example of the transfer voltage characteristic of a TVAN mode liquid crystal device at -30° and +30° is depicted in FIG. 15, and this mode can be used for dual view display by proper gray level mapping as described above.

In the case of a multiple view display such as the dual view display described above, the images can be spatially multiplexed across the active area of the display device by assigning each image an appropriate set of pixels. For example, these images can be displayed as interlaced vertical bars or columns of pixels. In the case of video images, assuming that the pixels are divided substantially evenly across the image, the field or frame rate is not altered, but the spatial resolution of each image is equal to that of the display device divided by the number of images being displayed. spatial resolution. Alternatively, where the display device is capable of operating at refresh rates higher than standard video field or frame rates, the images may be time multiplexed. In this case, the images are displayed one after the other in a repeating cycle fast enough for the brain to merge the intermittently displayed images for each view. The refresh rate of the display device must be high enough to be able to avoid visible flicker.

Using time multiplexing allows each image to be displayed with the full spatial resolution of the display device. However, since each image is only displayed a portion of the time, the perceived brightness of each view is reduced to the specified illumination level.

The time-multiplexed or "time-sequential" operation of the display 10 shown in Figure 4 is depicted in Figure 16 . At 70 depicting the voltage range with Image 1 and Image 2 for View 1 and View 2, the transfer characteristic of FIG. 9 is again shown.

During the period indicated by "time 1", image 1 is displayed as illustrated at 71 . Therefore, the viewer in the first viewing area sees the image 1 , while the viewer in the second viewing area sees a black display device.

During a second time period indicated by "Time 2", Image 2 is displayed as illustrated at 72 . In this case, the viewer in the first viewing area sees the white display device, while the viewer in the second viewing area sees the image 2 .

The brain repeats this cycle fast enough for still or moving images to perform image composition. In this way, the viewer in the first viewing area merges the alternately displayed image 1 with the white appearance of the display device and perceives the image 1 with a reduced contrast ratio. In contrast, a viewer in the second viewing area merges the image 2 with the black appearance of the display device so as to perceive only the image 2 .

Figure 17 depicts another mode of operation in which time multiplexing and spatial multiplexing are combined. During each frame period, the image is divided into vertical stripes which are interleaved through the display device as previously described and as described in time periods 1 and 2 at 73 and 74 . However, in the time 1 period, the stripes of image 1 are displayed by the odd pixel columns, and the stripes of image 2 are displayed by the even pixel columns. On the contrary, during time 2, the stripes of image 2 are displayed by the odd-numbered pixel columns, and the stripes of image 1 are displayed by the even-numbered pixel columns. As previously stated, a viewer in the first viewing area sees the stripes and white of Image 1, but a viewer in the second area sees the stripes and black of Image 2. Thus, the mode described in Fig. 17 corresponds to dividing each image frame into two sequentially displayed regions.

An advantage of the previously described embodiment is that one viewer sees pixels displaying an image that appears white to another viewer. This has the effect of reducing the image contrast ratio. It is therefore contemplated for use in modes of operation where one viewer sees pixels displaying an image that appears black to another viewer. For example, Figure 18 depicts two examples of drive schemes that effectively provide implementations. This type of drive scheme can be obtained by using a retarder with a liquid crystal device and the example described in FIG. 19 .

The display 10 of FIG. 19 is operated in the time-multiplexed or time-sequential mode described in FIG. 16 , which includes a switchable retarder 80 between the front polarizer 20 and the substrate 21 . Switchable retarder 80 includes substrates 81 and 82 , electrodes 83 and 84 , alignment layers 85 and 86 , and liquid crystal layer 87 . Electrodes 83 and 84 are common electrodes and extend over the entire active area of the display to switch the entire liquid crystal layer 87 between the first and second states. Alignment layers 85 and 86 provide proper alignment of liquid crystal layer 87 in the absence of an applied electric field, which changes when a voltage greater than the switching threshold is applied across electrodes 83 and 84 . The switching is controlled by the drive means 29 supplying a suitable voltage to the electrodes 83 and 84 .

Switchable retarder 80 may use any suitable liquid crystal mode that is switchable between a first state in which it provides retardation to odd half wavelengths of visible light frequencies, and a second state in which it Provides retardation to even half-wavelengths of visible light frequencies. For example, switchable retarder 80 may comprise a switchable half-wave plate that is switchable between providing half-wavelength retardation and substantially zero retardation. Liquid crystal modes suitable for this application include vertical alignment nematic mode and Freedericksz mode, both of which are well known in the art. Figure 20 describes the principle of operation in adjacent pairs of time periods. During a first time period, a first image viewed at a viewing angle of -30 degrees is displayed using switchable retarder 80 switched to provide substantially zero delay. These pixels appear black in the +30 degree viewing direction.

During the second time period, retarder 80 is switched to provide a half-wavelength retardation, and image 2 viewed in the +30 degree viewing direction is displayed. The display device appears black in the viewing direction -30 degrees.

FIG. 21 depicts the performance of a specific example of the embodiment depicted in FIG. 19, in which switchable retarder 80 comprises a half-wave thickness vertically corrected nematic device with transmission axes at 45 degrees to polarizers 20 and 28. Optical axes, polarizers 20 and 28 are orthogonal to each other. The display device comprising elements 20 to 28 is of the double twisted homeotropic nematic type having the optical axis of liquid crystal layer 24 oriented at 45 degrees to the transmission axis of polarizers 20 and 28 . The liquid crystal layer 24 has a thickness of 5 microns, and the liquid crystal material of layers 24 and 87 has a negative dielectric anisotropy.

During the first time period of the time series, no voltage is applied between electrodes 83 and 84 of delayer 80 . In this way the liquid crystal directors of layer 87 are aligned substantially homeotropically. Devices 20 to 28 display images for viewing in the 30 degree direction, while the device appears substantially black in the -30 degree viewing direction. During a second time period, an external voltage of, for example, 23 volts is applied between electrodes 83 and 84 to render the liquid crystal director of layer 87 substantially planar. The display devices 20 to 28 display images for viewing in the -30-degree viewing direction, and present black in the +30-degree viewing direction.

The embodiment described in FIG. 19 is not limited to the liquid crystal mode as previously described. For example, it can be materialized by the following combinations: TN and Freedericksz; TN and VAN; TVAN and Freedericksz.

Figure 22 depicts another technique using spatially multiplexed display to allow pixels displaying an image intended for another viewing area to appear black or substantially black. The display is of the type described in Figure 4, but where the polarizer 28 is a patterned polarizer. Pixel set 1 for displaying the first image is arranged between crossed or orthogonal polarizer regions and pixel set 2 for displaying the second image is arranged between parallel polarizer regions. The device uses a 90 degree TVAN mode with a liquid crystal layer 24 having a thickness of 5 microns and negative dielectric anisotropy. The diagram in Figure 22 depicts the transfer of voltages relative to these two sets of pixels. The pixels displaying set 1 of the first image in the first viewing area appear black when viewed from the second viewing area. The pixels of set 2 displaying the second image in the second viewing area appear relatively black in the first viewing area, but this black appearance can be improved by suitable optimization and selection of the gray level voltage range.

In order to reduce parallax effects between the liquid crystal pixels and the patterned polarizer 28, the spacing between them will be constructed to be small enough. For example, the patterned polarizer 28 may be provided inside the substrate 27, or the substrate 27 may be made relatively thin.

The display depicted in Figure 22 may be set to operate in a single view mode intended for viewing at normal incidence. In particular, the standard white and standard black TVAN modes of crossed and parallel polarizers have nearly opposite grayscale curves for normal incidence observations depicted in FIG. 23 . To operate a display viewed at normal incidence, the gray level voltage of a first set of pixels between the regions of the crossed polarizers is increased, while the gray level voltage of a second set of pixels is decreased, displayed by all pixels of the display same image. This mode of operation can be used for other liquid crystal modes.

In liquid crystal display modes such as TN and TVAN, another technology that can use a spatially multiplexed type of display consists between the polarizers 20 and 28 of a patterned retarder, such as a patterned half-wave plate. Figure 24 depicts an example of such a display using a 90 degree TVAN pattern with its optical axis oriented at 45 degrees to the crossed polarizers. The liquid crystal layer has a thickness of 5 microns and negative dielectric anisotropy. An active mesongen retarder is disposed between the device substrates and is patterned such that it provides a half-wavelength retardation to the second set of pixels and substantially zero retardation to the first set of pixels . This is diagrammatically depicted as half wave layer 90 .

With crossed polarizers, the pixels of the first set operate in the standard black mode, while the presence of the half-wave plate with the pixels of the second set causes them to operate in the standard white mode. The transfer diagram in Figure 24 depicts this effect so that in each viewing area, pixels displaying images viewed in a different viewing area appear black or substantially black.

In addition to increasing contrast ratios, patterned retarders can be used to modify or optimize viewing angles and gray scale characteristics. For example, the patterned retarder may have non-zero retardation regions aligned with the first set of pixels for this purpose. Also, more than one retardation layer may be provided in order to improve the color performance of the display. The second retardation layer may be uniform or patterned, and the or each patterned retarder may be disposed between display device substrates in order to reduce parallax effects.

Patterned retarders suitable for this application can be realized using various methods. For example, polymerizable liquid crystals, such as reactive mesogens, can be selectively attached by screen printing and then polymerized, for example by exposure to ultraviolet light. Examples of suitable techniques are disclosed in EP0887692 and GB2384318.

This display can be used in single image display mode for viewing at or around normal incidence. For the normal incidence observation depicted in Figure 25, the standard white and standard black TVAN modes have nearly opposite grayscale curves. For this observation, the drive scheme can be changed to increase the voltage to produce a grayscale output for a standard black pixel, and to decrease the voltage to produce a grayscale output for a standard white pixel. The same image is displayed by all pixels of the active area of the display device.

In an alternative technique to provide a display switchable to single view mode operation, the patterned delay period may be of a switchable type, for example using VAN mode or Freedericksz mode. When a single view is required, the retarder is switched to the operation of transforming all pixels to standard black or standard white.

In an additional technique that provides switchable to single view mode operation, when a single view is desired, the same image can be displayed for both views.

Another way to prevent pixels from displaying an image in one viewing area but appearing as white pixels in another viewing area is to use a parallax barrier 95 as described in FIG. 26 . Such a blocking layer 95 is arranged to limit the viewing angle of the display pixels so that only those pixels intended to display a visible image in the viewing area are visible in that area, the other pixels being blocked.

The parallax barrier can be made, for example, from latex. However, conventional latex using a parallax barrier reduces the brightness of the display. An alternative approach could be to use a partial transmission barrier to provide improved brightness and contrast. A parallax barrier can be made from a patterned retarder, such as the example disclosed in GB2390172. Where a switchable retarder is used, the blocking layer can be disconnected to provide single view mode operation observing at or near normal normal incidence.

The number of pixels for the images of the different views is not necessarily equal, although an equal number is advantageous, since the same spatial resolution is required for each image. Furthermore, the distribution of pixels allocated to display different views need not be uniform, or vary across the display device. For example, it may be desirable to provide high resolution regions for displaying a view with small font text. This way, the increased number of pixels in that area will be allocated to that view. In some embodiments, the multi-view effect is substantially dependent on the driving of the display device, which may otherwise be uniform. In this way, each pixel of the display device can be assigned to any one view, which can be changed at any time by selecting the appropriate applied voltage.

As shown in Figure 27, when an individual views a dual view display, both the size of the panel and the person's distance from the panel affect the angle that the end edge of the panel presents to the person's eyes. In the case of an 8 cm wide panel 100, the angular range over the gamma correction operation would be 23 to 35 degrees, but for a 30 cm wide panel 101 this increases to 16 to 41 degrees. As the angular range increases, software image correction techniques can be used to prevent changes observed at the end of the image.

Figure 28 depicts a dual-view thin film transistor (TFT) active matrix LCD for directing images 1 and 2 in two views, which may be unrelated, to viewing areas 1 of viewers 1 and 2, respectively, as described in Figures 1 and 2 and 2 in. The display includes a front linear polarizer 20 attached and formed on the outer surface of a substrate 21 . Substrate 21 may be constructed of glass or any suitable transparent non-birefringent material of sufficient stability. The substrate 21 has a transparent electrode 22 on its inner surface, which may consist of, for example, indium tin oxide (ITO). The electrode 22 serves as the counter electrode of the active matrix and uniformly covers the entire active area of the display 10 . An alignment surface such as alignment layer 23, one example of which is rubbed polyimide, is formed on electrode 22.

The second substrate 27 has a rear linear polarizer 28 and a TFT and electrode layer 26 . The electrodes of layer 26 are patterned so as to define pixels (picture elements). Such TFT and electrode configurations are well known and will be described later. An alignment surface such as alignment layer 25 is formed on layer 26, one example of alignment layer 25 being rubbed polyimide.

Substrates 21 and 27 are formed together with layers 22, 23, 25 and 26 and are produced with alignment layers 23 and 25 facing each other so as to define a liquid crystal cell with liquid crystal layer 24 therebetween. The liquid crystals of layer 24 are nematic liquid crystals. Polarizers 20 and 28 may be formed or provided before or after the liquid crystal cell is formed. Layer 26 includes or is connected to the drive means described at 29 for providing a suitable drive scheme to address individual pixels with voltages of specified gray scales. The means 29 may form in whole or in part an external component for providing a suitable drive scheme for displaying the first and second images. Alternatively, the device 29 may be integrated into the panel, eg using continuous grain silicon.

The LCD is pixelated to provide first and second sets of pixels 101 and 102 for displaying images 1 and 2 viewed in different directions. Pixels 101 and 102 are spatially multiplexed or alternated with each other so that each image is viewable from a viewing direction across the entire display surface of the display. For example, pixels 101 and 102 may be arranged in a checkerboard pattern, or as alternating vertical stripes of one or more columns of pixels.

Pixels 101 are a first configuration and pixels 102 are a second configuration different from the first configuration. Different configurations may be characterized by differences in any one or more of the following characteristics: pretilt angle on one or both surfaces of liquid crystal layer 24; orientation of bulk liquid crystal directors in layer 24; Thickness of layer 24; twist in no applied field; doping of liquid crystal layer 24; direction of transmission axis in either or both polarizers 20 and 28; liquid crystal-substrate interface at alignment layers 23 and 25 Azimuth and/or zenith fixation; retarder and/or compensation film (not shown in FIG. 28 ); liquid crystal layer 24 material; and a driving scheme such as the voltage range provided by driving means 29.

In embodiments where the pretilt angles are different for pixels 101 and 102 , either or both calibration layers 23 and 25 may be suitably patterned to provide different pretilt angles for pixels 101 and 102 . Pretilt can be a difference in magnitude or direction or both.

Where a number of liquid crystal director directions are different between pixels 101 and 102, alignment layers 23 and 25 may be patterned to provide different pretilt angles and/or alignment directions at the surface of the liquid crystal layer. The combination of the pretilt characteristic and the alignment direction determines the orientation of the liquid crystal director in the bulk liquid crystal layer 24 .

The thicknesses of the liquid crystal layer 24 at the pixels 101 and 102 may be different from each other. This is described more below.

Where the twist differs between pixels 101 and 102, it may be a difference in the angle of twist and/or in the absence of an applied field between electrodes 22 and 26, a difference in twist direction between pixels, for example clockwise or counterclockwise. Also, there may be zero distortion, such as in pixel 101 , and a non-zero distortion in pixel 102 in the absence of an applied field between electrodes 22 and 26 .

The liquid crystal layer 24 may include a chiral dopant. The difference in thickness and alignment orientation between pixels 101 and 102 together with this chiral dopant affects the mass director orientation in layer 24, for example forcing it to form distorted structure.

The LC layer 24 may include dopants such as dyes or polymer materials to enhance viewing characteristics of the LCD.

Polarizer 20 and/or polarizer 28 may be patterned such that the transmission axis of the polarizer region of pixel 101 may be different from the transmission axis of the polarizer region of pixel 102 relative to the optical axis of layer 24 of the pixel.

By providing a difference in the anchoring strength of the liquid crystal director at the interface between any one or both of the alignment layers 23 and 25 and the adjacent liquid crystal material of layer 24, the switching characteristics of the liquid crystal material with an applied voltage can be varied between Formation differs between pixels 101 and 102 .

Although not shown in FIG. 28 , a retarder and/or a compensation film may be provided to any one or both of the pixels 101 or 102 . For example, a patterned retarder and/or compensation film with different retardation and compensation effects between pixels 101 and 102 may be used.

As described more below, different liquid crystal materials may be used for pixels 101 and 102 . By using different materials, the birefringence, elastic constant and dielectric constant can be chosen appropriately, which can be different for pixels 101 and 102 .

Differences in liquid crystal director structure and anchoring can be combined with differences in dielectric and elastic constants to use different voltage ranges for pixels 101 and 102 . In this way, the drive means 29 provides suitable drive schemes, such as different voltage ranges, in order to optimize the image quality of the first and second images in their respective observation areas while minimizing the contrast ratio in other observation areas, And make the pixels appear relatively dark or black in other areas.

FIG. 29 schematically depicts an exploded view of polarizers 20 and 28 and layers 23 through 25 for a particular embodiment of the display 10 shown in FIG. LCD mode. FIG. 29 also depicts the vertical and horizontal directions of the normal directions of display 10 as described in FIG. 1 . The vertical upward reference direction is referred to as 0 degrees, and the horizontal rightward direction is referred to as 90 degrees. The various orientations of the components depicted in FIG. 29 refer to the upward vertical 0 degree direction.

The front polarizer 20 has a transmission axis 30 oriented at +180 degrees to the upward vertical (equivalent to the stated 0 degrees). The alignment layer 23 has a patterned alignment direction with an alignment direction 33a of pixels 101 oriented at 90 degrees from the upward vertical direction and an alignment direction 33b of pixels 102 oriented at +70 degrees from the upward vertical direction . Alignment layer 25 is patterned with alignment direction 35a oriented at +180 degrees from the upward vertical direction of pixel 101 and alignment direction 35b oriented at 0 degrees from the upward vertical direction of pixel 102. Polarizer 28 has a transmission axis 38 oriented at +90 degrees from upward vertical. As such, polarizers 20 and 28 are uniform and unpatterned.

In the particular example of the display depicted in FIGS. 28 and 29 , liquid crystal layer 24 has a thickness of 3.7 microns in region 34 a of pixel 101 and a thickness of 4.0 microns in region 34 b of pixel 102 . The liquid crystals are of the known type such as MJ97174 available from Merck UK.

Patterned alignment layers 23 and 25 can be formed by multiple rubbing techniques, such as disclosed in "3D display systems hardware research at Sharp Laboratories of Europe; an update" by Harrold et al., Sharp technical journal, issue number 74, August 1999 content.

Materials such as PI2555, available from Dupont UK, can be applied to the substrate, for example by spin coating. The layer is suitably cured, eg by heat treatment, and then rubbed uniformly in order to define a specific alignment direction and pretilt angle when finally reaching contact with the liquid crystal material. A photoresist such as S1865 available from Shipley UK is coated on the rubbed polyimide layer. A photoresist such as S1865 available from Shipley UK is exposed to ultraviolet radiation through a suitable mask such that areas corresponding to eg pixel 101 are exposed while other areas corresponding to pixel 102 are not exposed. A resist is developed such that areas of the calibration layer for one set of pixels are protected by the photoresist while areas of the other pixels are exposed. Another rubbing operation is then performed in a different direction from the first rubbing operation and with a different rubbing intensity in order to produce a different alignment direction and pretilt angle. The photoresist is then removed to provide two sets of areas for pixels 101 and 102 with different alignment directions and pre-tilt angles.

Alternatively, optical alignment techniques can be used instead of rubbing techniques. For example, a second patterning exposure may be used after the first uniform exposure to change the alignment direction and pretilt angle of the first exposure. Light alignment can be achieved using bond breaking, bond creation, or by using light redirecting materials such as azo dyes.

Alternatively, a combination of rubbing and optical alignment can be used to dictate the alignment direction and pre-tilt angle of the patterned alignment layer.

As another possibility, microstructured alignment surfaces of the type disclosed in GB2384318 may be provided.

Other techniques such as photolithography and polymer embossing may be used, for example simultaneously providing microstructured alignment surfaces and creating pitches in the thickness of the polymer layer between different sets of pixels 101 and 102 . This technique can be used to provide pixels with different liquid crystal layer thicknesses without requiring any additional processing steps beyond the formation of the alignment layer.

The displays of Figures 28 and 29 are of the standard black type because, in the absence of an applied field between electrodes 22 and 26, pixels 101 and 102 appear maximally dark or "black" in their respective viewing directions. In this case, the liquid crystal layer 24 is aligned substantially homeotropically. When a voltage is applied across the liquid crystal layer of any one of the pixels 101 and 102, light is transmitted in the viewing direction of the pixel. As the luminance in transfer with respect to the applied voltage, for observations in the horizontal plane from -30° to +60° from the normal to the display surface, the transfer functions of pixels 101 and 102 are depicted in Figures 30 and 31, respectively . Driving means 29 are provided for generating voltages in the gray scale range in the +60 degree direction, the pixels 101 appear substantially black in the -30 degree direction. Conversely, the driving means 29 provide voltages for selecting the gray level of the pixels 102 in the viewing direction of -30 degrees, which appear black in the viewing direction of +60 degrees.

FIG. 32 depicts the luminance ratio with respect to the applied voltage of the pixel 101, and particularly depicts the luminance ratio of an image observed from +60 degrees divided by the luminance in the black state at -30 degrees. This ratio is very high, such as more than 100 or even 25% of the transmission.

Figure 33 depicts another embodiment of the display shown in Figure 28 with pixels 101 operating in Freedericksz or non-twisted planar alignment nematic mode, and operating in twin-twisted nematic mode 102 pixels. Front polarizer 20 has a transmission axis oriented at +180 degrees from upward vertical. The alignment layer 23 is patterned with an area corresponding to a pixel 101 having an alignment direction 33a oriented at +45 degrees from the upward vertical direction and an area corresponding to a pixel 102 having an alignment direction 33a oriented at +45 degrees from the upward vertical direction and a pixel 102 having an Alignment direction 33b at +90 degrees. Alignment layer 25 is similarly patterned with an area corresponding to pixel 101 having alignment direction 35a oriented at +45 degrees from the upward vertical direction and an area corresponding to pixel 102 having alignment direction 35a oriented at +45 degrees from the upward vertical direction and pixel 102 having an into a calibration direction 35b of +180 degrees. Polarizer 28 is uniform with transmission axis 38 oriented at +90 degrees from vertical upward. The liquid crystal layer 24 is of uniform thickness, eg 2 microns, and may comprise known materials such as E7 available from Merck UK.

The displays depicted in Figures 28 and 33 operate in a standard white mode. In the absence of an applied voltage between electrodes 22 and 26 , liquid crystal layer 24 is aligned with the in-plane non-twisted alignment of pixel 101 and is 90 degrees in-plane with the twist of pixel 102 . In this way, the liquid crystal layer 24 rotates the direction of the transmitted polarized light by 90 degrees. When a voltage is applied between the electrodes 22 and 26 for any one of the pixels 101 and 102, the pixel transmits light and provides a gray scale according to the applied voltage. Figures 34 and 35 depict the transfer functions of pixels 101 and 102, respectively, as luminance in transfer with respect to applied voltage at observation angles of +60 degrees and -30 degrees. The drive means 29 provides voltages to the pixels 101 in the voltage range to display a grayscale image so that it is visible in the -30 degree direction, but the pixels appear substantially black in the +60 degree direction. Conversely, the drive means provide voltages to pixels 102 for displaying a grayscale image in the +60 degree direction, and these pixels appear substantially black in the -30 degree viewing direction. The luminance ratio (defined earlier) for Freedericksz pixels 101 and twisted nematic (TN) pixels 102 is depicted in FIG. 36 , which shows that the luminance ratio is very high, e.g. it is at least for these two types of pixels. 200% transfer above is 200.

FIG. 37 schematically depicts a display 10 in which the liquid crystal layer 24 has different thicknesses for pixels 101 and 102 . The different thicknesses may be obtained using any suitable technique, such as disclosed herein. FIG. 37 also depicts different viewing angle directions a ₁ and a ₂ in the horizontal plane with respect to the normal to the display of the image displayed using the set of pixels 101 and 102 . Typically, the viewing angles a ₁ and a ₂ are required to be sufficiently larger than the viewing angles of displays typically used for autostereoscopic displays. For example, for a typical autostereoscopic display, the angle between viewing directions may be on the order of 10 degrees. In order to display uncorrelated or non-stereoscopic images to two different viewers, the angular separation between the viewing directions is usually larger than this angle, and the angular separation may be asymmetric (a ₁ not equal to a ₂ ). For example, if the display 10 is implemented in the dashboard of a vehicle, where viewers may be of different heights and thus may be seated at different distances from the display, the viewing angles _a1 and _a2 may be of different magnitudes. It is also possible to optimize the operation of displays with variable viewing angles so that different audience positions can be accommodated.

Patterned collimated or multi-field configurations of the known type, such as those described above, are not capable of providing optimal or uniformly sufficient image quality with the required relatively wide or relatively large viewing angles. The techniques disclosed herein allow this effect to be achieved and allow pixels to appear relatively black when viewed from directions in which those pixels are not intended to be viewed.

The combination of liquid crystal material and alignment surface has a substantial impact on the final bulk liquid crystal director configuration. By providing different materials to different pixels, and using this method to form the calibration surface, differences in anchoring strength (zenith and/or azimuth) can be obtained, which can lead to differences in the structure of the liquid crystal director and The difference in switching performance from one type of pixel 101 to another type of pixel 102 . This approach can be used to provide two or more sets of pixels in a single liquid crystal device so that each set of pixels displays a grayscale image in its viewing direction and appears dark or black in the other viewing direction.

In order to provide pixels with different liquid crystal layer thicknesses, it is possible on either or both substrates, e.g. Lithographically formed pitch. Alignment surfaces are then formed on the pitch surfaces. Liquid crystal cells having different thicknesses for the liquid crystal layers of pixels 101 and 102 may be formed using two pitch substrates or one pitch substrate and one uniform counter substrate.

In displays using different liquid crystal materials for different pixels 101 and 102, it is necessary to provide arrangements that confine each liquid crystal material and separate it from the others. This can be achieved by forming polymer walls on either or both substrates, for example by photolithography on highly binary resist materials such as those available from MicroChem The SU8. Figure 38 depicts this type of configuration where the polymer wall 110 is in a serpentine trajectory from the fill hole 111 to the first liquid crystal material (LC1) and from the fill hole 112 to the second liquid crystal material (LC2) Usually extends vertically.

For example, one liquid crystal material LC1 can be chirally doped in order to define a specific twist direction while not doping the other material LC2. This allows preferential selection of warp detection when the calibration condition is otherwise warp degradation. Alternatively, different dopings can be used for different materials. One material may have positive dielectric anisotropy and the other material may have negative dielectric anisotropy. Liquid crystal materials with different birefringence and/or different elastic constants can be used.

Figure 39 depicts a dual view display 10 which, in addition to the viewing area where essentially only a single corresponding view is visible to viewers 1 and 2, also has a "crosstalk area" 115 in which both images 1 and 2 are visible, which is due to the overlap of the observation angle characteristics of the pixels 101 and 102 . In some applications, crosstalk region 115 is not required and display 10 is designed or optimized to minimize crosstalk. In some applications, the crosstalk area can be replaced by a black central area. However, in other applications, the crosstalk region 115 may constitute an application. For example, for an office display or for a customer application where a first person wishes to display information to a second person on a laptop or PC monitor, the first person (Viewer 1) can benefit from the crosstalk described in Figure 40 Display 10 is observed in the area. Viewer 1 may thus see images 1 and 2 effectively superimposed on each other, for such applications the display may be controlled or optimized to increase the superimposed image in area 115 , for example in a manner that depletes the image quality in viewing area 1 . Viewer 2 in viewing area 2 sees essentially only the images intended for him or her. For example, where audience 1 is presenting, image 1 may hold additional instructions for image 2, such as introductory prompts or menu options to provide audience 2 with display image data to select. The display 10 is controllable so that when the presentation is over, the display can be operated as a dual "split" view display or as a single view display of higher spatial resolution, eg optimized for normal incidence viewing.

In other applications, it may be desirable to use observation areas 1 and 2 where viewers 1 and 2 can only see images 1 and 2, respectively, and crosstalk area 115 where both images can be seen simultaneously. elephant. An example of this is a multi-player game where players in the crosstalk area 115 can see all of the image data, while players in either end area can only see part of the image data.

A display as previously described is of the type that displays two unrelated images, for example non-stereoscopic, eg different images are seen simultaneously by two viewers from different viewing areas. However, through optimization of the viewing angle characteristics, crosstalk regions can be sufficiently reduced, or eliminated sufficiently to allow for a display that can display more than two views. For example, as illustrated in Figure 41, by using four different types of pixel configurations in a liquid crystal device, it is possible to direct four uncorrelated (or correlated) images into four viewing areas for four viewers Different images displayed simultaneously on the same device can be seen.

Alternatively as depicted in FIG. 42 , four device configurations 120 can be displayed by two liquid crystal devices 121 and 122 with stacked devices so that one device 122 can be viewed through the other device 121 . For example, the devices could be operated in a spatio-temporal manner so that in one time frame one device provides images to two viewing areas and black to the other area, while in a second time frame the role of the liquid crystal device is reversed. This configuration provides images with twice the spatial resolution (assuming all images are displayed with the same spatial resolution) compared to the configuration shown in Figure 41 .

Suitable holograms can be used to eliminate or reduce crosstalk areas.

To avoid or reduce the variation as previously described with reference to FIG. 27, an alternative or additional software correction technique may be employed to optimize the patterning of the calibration layer via the position of the panel. This approach can be used, for example, to vary the twist angle of the panel passing each aggregate pixel 101 and 102, for example in the opposite direction from which the viewing direction has been chosen. By exploiting the effect of the angular variation of the light-collimated direction of exposure energy, variation in the angle at which an aggregate of pixels passes through the panel can be achieved. For example, such an angular change can be achieved by scanning an incident UV source across the light-collimating layer, and by varying the UV flux as the beam is scanned across the surface so as to induce a change in the angle across the surface. Other areas can be shaded in the process. The UV source can be polarized.

Alternatively, a variable amplitude mask can be used with a uniform UV exposure source. As another alternative, a phase mask can be used to rotate the angle with which the alignment is formed eg by passing differently oriented waveplates through the panel. This can be applied with bond cut-off or bond-generated light alignment.

Alternatively, different liquid crystal materials can be used across the panel in order to optimize the image quality.

The gray level range for pixel 101 and the gray level range for pixel 102 may be optimized. For example, it may be optimized to provide the best image quality in the viewing direction in which each pixel displays one image, and for other viewing directions to produce the best gray level conditions such as full black. Where different voltage ranges are required for dual or multi-view displays and/or operating such displays in single view normal incidence mode, the drive means 28 is required to provide the appropriate voltage range.

Dual view displays can be used as single view or 2D displays. When using such a display for the case of syntactic line incidence observation, the range of vertical and horizontal angles over which a single view with good quality can be seen can be reduced compared to conventional single view type displays. To improve normal-incidence observation for multi-view displays, depending on the configuration, different sets of pixels may be required to be driven differently in order to improve or optimize the range of visible individual images with acceptable quality.

By varying the gray scale used until it is corrected or optimal for the user to optimize the angle of the image, by adjusting the angle, an adaptation can be achieved to harmonize the required viewing angle characteristics within a limited range. For example, where such a display is used in the instrument panel of a vehicle, these adjustments can be done while the driver or passenger is adjusting the position and mirrors. Alternatively, suitable tracking devices can be used to set the spectator position in the vehicle so that compensation for different viewing angles can be performed automatically.

In applications where a single view needs to be seen in the viewing area of multiple views, but not at normal incidence to the display, all aggregated pixels can display the same image. This does not require any changes, such as changes to the voltage ranges used for the pixel sets. However, each viewer sees the same image with reduced spatial resolution compared to an embodiment where all pixels are used to display a single image.

To be able to provide a color LCD, the techniques described in Figures 10 and 14 and previously described can be used.

Although the embodiment with two aggregated pixels 101 and 102 is based on TVAN, TN and Freedericksz liquid crystal modes, all liquid crystal modes that result in suitable asymmetric viewing angles can be used. For example, suitable smectic or ferroelectric liquid crystal modes may be used. Also, other twisted nematic modes such as hybrid aligned nematic (HAN) mode or pi-mode mode may be used.

Viewing angle compensators are known and published, for example in P.Van de Witte et al. in Japan Journal of Applied Physics vol.39, pp. 101-108, 2000 "Viewing angle compensators for liquid crystal displays based on layers with a positive birefringence". This film is used to optimize liquid crystal mode characteristics such as viewing angle characteristics and black/white and gray level states. In known single view displays, such films are used to produce viewing angle characteristics that are as uniform as possible for both vertical and horizontal directions and to optimize the black level.

For the multi-view displays disclosed herein, different demands on the gray-scale viewing angle characteristics of the liquid crystal modes require different optimizations from known configurations, thus requiring different designs of the viewing angle compensating films, in which such films are used. This viewing angle wavelength film requirement is used to optimize each image when viewed in its viewing direction, and to make the appearance of pixels displaying images as black as possible when viewed in other directions.

More than one retarder can be used to improve the color characteristics of the image. For example, two retarders may be used, each retarder being patterned or uniform. Such retarders can be fabricated from liquid crystal polymers or polymerizable liquid crystals, such as reactive mesogen polymerizable liquid crystals, which can be used inside liquid crystal cells in order to reduce or eliminate parallax effects. Alternatively, a thin substrate can be used between the patterned retarder and the liquid crystal layer.

Alternatively, such a retarder can be located outside the liquid crystal cell. As another alternative, uniform retarders could be laminated or fixed on the outside of the unit.

The patterned retarder may be fabricated by any suitable technique as well as some prior examples of techniques disclosed in GB2384318 and EP0887692.

Figure 43 depicts a dual-view display 10 comprising two thin-film transistor (TFT) active-matrix twisted vertically aligned nematic (TVAN) LCDs for directing images, which may be uncorrelated, respectively to In the observation areas 1 and 2 of the audiences 1 and 2 described in 2. The first LCD includes a front linear polarizer 20 attached to or formed on an outer surface of a substrate 21 . Substrate 21 may be made of glass or any suitable transparent non-birefringent material of sufficient stability. The substrate 21 has on its inner surface a transparent electrode 22 which may for example consist of indium tin oxide (ITO). Electrode 22 serves as the counter electrode of the active matrix, which uniformly covers the entire active area of display 10 . A calibration surface such as a calibration layer 23, such as a rubbed polyimide, is formed on the electrodes 22, the calibration surface being rubbed uniformly to have the same uniform calibration throughout the active area of the display 10. direction.

The second substrate 27 has an intermediate linear polarizer 28 , a TFT and an electrode layer 26 . The electrode layer 26 is patterned so as to define pixels (picture elements). Such TFT and electrode configurations are known arrangements and will be described later. An alignment surface such as alignment layer 25 is formed on layer 26, one example of alignment layer 25 being rubbed polyimide. Alignment layer 25 also provides a uniform alignment direction across the active area of display 10 .

Substrates 21 and 27 are formed together with layers 22, 23, 25 and 26 and are produced with alignment layers 23 and 25 facing each other to define a liquid crystal cell with liquid crystal layer 24 therebetween. The liquid crystal layer 24 is a nematic liquid crystal comprising, for example, MJ97174 available from Merck UK. Polarizers 20 and 28 may be formed or provided before or after formation of the liquid crystal cell. Layers 22 and 26 include or are connected to drive means described at 29 for providing suitable signals to address individual pixels with defined gray scale voltages. Configuration 29 may be formed as all or part of an external element. Alternatively, configuration 29 may be integrated on the LCD, for example using continuous die silicon.

The second LCD comprises a substrate 21' of the same type as the corresponding components 21 to 28, an electrode 22', an alignment layer 23', a liquid crystal layer 24', an alignment layer 25', a TFT and electrode layer 26', a substrate 27 ', polarizer 28'. Layers 22' and 26' are connected to drive means 29. The display is provided with a backlight 30 which can be controlled by drive means 29 .

The drive means 29 provides the first and second drive schemes for the first and second images, which are both displayed on the first and second LCDs. These driving schemes will be described in detail later.

Although the first and second LCDs are described as substantially separate devices connected together, these LCDs may be constructed by a single unitary device. For example, substrates 27 and 21' could be replaced by a single common intermediate substrate. Also, in some embodiments, intermediate polarizer 28 may be omitted.

Figure 44 schematically depicts an exploded view of polarizers 20, 28 and 28' and layers 23 to 25 and 23' to 25'. FIG. 44 also depicts the vertical and horizontal directions of the normal directions of the display 10 as described in FIG. 1 . The vertical upward reference direction is referred to as 0 degrees, and the horizontal rightward direction is 90 degrees. The various orientations of the components shown in FIG. 44 refer to a vertically upward 0 degree orientation.

The front polarizer 20 has a transmission axis 31 oriented at +90 degrees to the upward vertical. The alignment layer 23 has a uniform alignment direction 32 oriented at +90 degrees with respect to the upward vertical direction. The alignment layer 25 has a uniform alignment direction 33 oriented at 0 degrees to the upward vertical. Polarizer 28 has a transmission axis 34 oriented at +180 degrees from the upward vertical. The alignment layer 23' has a uniform alignment direction 35 oriented at +270 degrees from the upward vertical. The alignment layer 25' has a uniform alignment direction 36 oriented at +180 degrees from the upward vertical. Polarizer 28' has a transmission axis 37 oriented at +90 degrees to the upward vertical.

The configuration depicted in Figures 43 and 44 includes two TVAN (Twisted Vertical Alignment Nematic) LCDs operating in standard black mode of operation. In the absence of an applied voltage across either liquid crystal layer 24 and 24', the liquid crystal is substantially homeotropically aligned such that no light is transmitted. If the two layers 24 and 24' have a sufficiently large voltage applied across them, light is transmitted. However, when the voltage across the liquid crystal layer 24' is reduced, the amount of light entering the other liquid crystal layer 24 is gradually attenuated, so that the range of gray levels that can be displayed is gradually reduced. A similar effect occurs when the voltage across the liquid crystal layer 24 is reduced.

This effect is depicted in Figures 45 and 46. Figure 45 depicts the transmission of light through the liquid crystal layer 24 relative to an applied voltage to the liquid crystal layer 24' switching in the direction of the voltage selection at an viewing angle of -30 degrees from the display normal. In contrast, Fig. 46 depicts the transmission through a liquid crystal layer 24' having a liquid crystal layer 24 switched in a voltage selection in the direction of the viewing angle of +30 degrees.

FIG. 47 depicts the effect of eliminating or omitting the intermediate polarizer 28 . If voltage is applied through a layer with other layers 24', such as through layer 24, which has no voltage applied, the display is equivalent to a standard white TVAN LCD. When a switching voltage above the threshold is applied on layer 24', the display gradually increases like a standard black TVAN LCD. Figure 47 depicts the transmission of the voltage of the switching layer 24' through the liquid crystal layer 24 with respect to the voltage selection at the viewing angle -30 degrees.

Techniques for overcoming or reducing the problem of switching one liquid crystal layer affecting light that can pass through other liquid crystal layers are described below.

Figures 6 to 9, as previously described, describe the characteristics of a single LCD similar to that described in Figures 43 and 44, but operating in a twin-twisted nematic (TN) mode.

FIG. 48 describes a driving scheme that may be used for two LCDs forming a display as shown in FIG. 43 . The driving scheme for the upper LCD comprising the LC layer 24 is shown at 42 and the driving scheme for the lower LCD comprising the LC layer 24' is shown at 43. The LCDs are the same type, they are essentially identical to each other, but the lower LCD is effectively rotated 180 degrees relative to the upper LCD. In this way, the alignment directions of alignment layers 23' and 25' are rotated by 180 degrees relative to (or opposite to) the alignment directions of alignment layers 23 and 25, respectively.

A voltage range of 40 can be used as a driving scheme for each LCD. Thus, by properly mapping the voltages in range 40 to suitable gray levels, as shown at 42, the upper LCD can be used to display an image, resulting in an image viewable in the -30 degree viewing direction. However, when viewed in the +30 degree direction, the pixels of the upper LCD appear sufficiently black to have a contrast ratio substantially equal to one.

The same drive scheme is shown at 43, but with a viewing direction corresponding to that of the lower LCD. Thus, in the viewing direction of +30 degrees, the lower LCD displays images that can be seen by the viewer. However, the lower LCD exhibits sufficient black in the -30 degree viewing direction, which has a contrast ratio substantially equal to 1. The display 10 thus establishes two viewing areas for the viewer to view unrelated images or sequences of images in their respective viewing areas without the need for any parallax glasses and without the use of different calibrations for the pixels displaying the different images. Multi-field liquid crystal technology. Such displays are therefore easier and cheaper to manufacture. Techniques for overcoming or reducing all problems of switching one liquid crystal layer affecting light that can pass through the other liquid crystal layer are described below.

As an alternative to the driving scheme described above, a voltage range 41 can be used for each LCD. In this case, the upper LCD displays a visible image at the +30 degree viewing direction, but a bright or "white" image at the -30 degree viewing direction. In contrast, the lower LCD displays a visible image at a viewing direction of -30 degrees, but a white image at a viewing direction of +30 degrees.

Due to the use of two "stacked" or "sequential" LCDs in the light path through display 10, consideration must be given to the use of color filters in order to provide a color display. If only one LCD is provided with color filters, the light from the other LCDs must be routed correctly through the color filters to avoid displaying incorrect color images. For example, Figure 49 schematically depicts liquid crystal layers 24 and 24' The LCD is pixelated with the same pixel pitch, such as shown at 45 . The display is of such a type that the first and second viewing angles are substantially the same and are defined by a minimum angle and a corresponding maximum angle, a and b, respectively. In order to ensure that light passes along the correct light path through the display, absorbing regions as described in part of black masks 48 and 49 are provided to block at least some of the incorrect light paths. Figure 50 depicts an embodiment where both LCDs have color filters. The filtering of each color is depicted by the same cross-hatching in the liquid crystal layers 24 and 24'. Light passing through the pixels 50 is coded with a corresponding color and is incident in the color filters of the upper LCD. Depending on the color of the incident color filter, light will be transmitted or absorbed. FIG. 50 depicts the relative positions of the color filters for two LCDs with pixels 51 and 52 having the same color filtering as pixel 50 .

As shown in FIG. 49 , FIG. 50 depicts the initial angular range for light from pixel 50 to pass through pixel 51 . This can be determined by the relationship between the color pixels in layers 24 and 24' and the spacing 44 between the LCD liquid crystal layers. The spacing 44 is important because light must be able to reach layer 24' in order to be encoded with data to form the image to be displayed. This therefore provides a limit on the pitch 44 between layers specifying the color pixel pitch. usually. For practical purposes, the spacing 44 needs to be relatively small, and may be less than allowable for conventional LCD components as described in FIG. 43 .

To reduce thickness, the two substrates 27 and 21' can be replaced by a common substrate, as depicted at 55 in Figure 51, which is an embodiment without an intermediate polarizer. Common substrate 55 is processed at both ends to provide alignment and electrode layers 25, 26, 22' and 23'. The color filters for these two LCDs are described at 56 and 57.

Alternatively or additionally, an intermediate substrate or substrate can be formed from very thin glass. A suitable glass is the known "microsheet" available from Schott, Germany.

There are various different pixel configurations that provide flexibility in the angles at which light of a particular color can pass through the two LCDs. For example, the configuration described in Fig. 50 can be used. For a pixel pitch of 200 microns and a liquid crystal layer pitch 44 of 700 microns, light in a spatial angle range from about 12 degrees to about 61 degrees passes through the same color filters in layers 24 and 24' . There is a second range of angles where light from a pixel 50 will pass through a pixel 52 of the same color, but this light is reflected by the glass at all interior:air interfaces. By taking into account the effect of the interface between media of different refractive indices, configurations can be produced in which light not in the intended first angular range is reflected completely internally in order to avoid undesired visual effects.

In the configuration depicted in Figure 50, each liquid crystal layer is provided with the same type of filtering, for example so that each layer has red, green and blue filters. However, LCDs can be provided with different color filters so that for example the filters for one LCD can include red, green and blue filters while the filters for another LCD can include cyan, magenta and yellow filters .

Figure 52 depicts another form of color filtering in which a single color filter comprises horizontal stripes that extend across the width of the display. For example, as shown in FIG. 52, the color filter includes a repeating set of red 60, green 61 and blue 62 filters. The individual color filters for the two LCDs are aligned with each other so that the red filter for the upper LCD is directly above the red filter for the lower LCD. This arrangement thus allows a wider range of viewing angles in the horizontal plane for the light transmission display, but by itself cannot avoid light propagation in suitable angles.

To avoid having to take into account the geometry of the color filters, the display can be embodied using a time-sequential color technique. In this case, no color filtering is required because the LCD displays different color portions of the image in adjacent time frames or time slots, and uses a backlight that switches multiple colors. For example, in order to obtain a frame rate high enough that the colored portion of the image is fused into a color image by human vision, colored light-emitting diodes are used to form a backlight with red, green and blue diodes that are aperiodic control.

Alternatively, a color wheel and a white light source can be used for this purpose. Such an arrangement is depicted in Figure 53, which comprises a display unit 20 to 28, 21' to 28' with a backlight in the form of a white light source 30a and a color wheel 30b. The wheel 30b comprises three color filters in the form of quadrants of equal size, the wheel being configured to rotate so that each color filter passes in turn between the light source 30a and the remainder of the display.

As another alternative, to avoid the problems of color separation that may be associated with spatiotemporal color displays, color scrolling bands may be used. Such configurations have been disclosed, for example, by Katoh et al. in LN-5, Eurodisplay 2002 "A Novel High-Definition Projection System using SingleCG-Silicon TFT-LCD and Optical Image Shift Device".

In this time sequential color embodiment, since only one color is displayed per time slot, the gamma correction used in each time slot can be different for each color in order to compensate for color dispersion in the LCD.

With an embodiment as previously described, the effect of the two LCDs on the variable attenuation of light passing through the display with two images must be considered. To reduce and avoid this difficulty, the two LCDs can be arranged as two spatial phase modulators between the polarizers described in FIG. 54 . In this configuration, the LCD includes spatial phase modulators SPM 170 and 171 disposed between polarizers 20 and 28' with modulators 170 and 171 pixelated to provide of pixels. The display can then be controlled to provide spatial phase modulation, whereby light intensity modulation across the display occurs in a first direction such as R1 and R2 and in a second direction such as L1 and L2. In particular, by suitable control of the modulators 170 and 171, the light propagation in the first and second direction can be modulated independently of each other. The two images are formed with the same spatial resolution as that of each modulator 170 and 171 .

Light propagation in direction L1 for the "left" image and through pixel b also passes through pixel c. The resulting intensity is the combination of the phase changes caused by pixels b and c. Similarly, light propagation in direction L2 has an intensity resulting from the combination of phase changes induced by pixels d and e. For the "right" image, light propagating in directions R1 and R2 is affected by a combination of phase changes in phases b and a, and phases d and c, respectively. Each pixel is capable of providing a range of phase changes spanning substantially 180 degrees.

The boundary condition for one direction must be chosen for the first or last pixel of each modulator 170 and 171 . This provides independent control of the intensity of individual image pixels by solving a sufficiently large set of simultaneous equations. For example, for the transmission paths L1, L2, R1 and R2 described in Figure 54, the resulting light intensity (I) can be expressed as the following simultaneous equation:

I(R1)=C(A(a)+A(b))

I(R2)=C(A(c)+A(d))

I(L1)=C(A(b)+A(c))

I(L2)=C(A(d)+A(e))

where A is the phase change produced by the corresponding pixel, and C is a constant. The value of the phase change can be found so that the intensities of the two images being displayed can be chosen independently of each other.

The above system of simultaneous equations includes four equations with five variables. However, when pixel a is the last pixel of modulator 170 and the phase of light passing in only one direction needs to be changed, unlike eg pixel c which controls the phase of light passing in two directions, pixel a can be set to The value (boundary) of the left image, for example, provides a symbolic black pixel for the left image. In this case, the phase change A(a) of pixel a can be set to nπ, where n is an integer. This provides a fifth equation and thus enables simultaneous equations to be solved for a fifth variable.

The phase change is preferably optimized for the angle of light passing through the liquid crystal layers, so as to account for the viewing angles associated with these layers. The phase change is preferably optimized for the wavelength passing through the liquid crystal layer. The phase change can be the same or different for each LCD used. Performance is best optimized for viewing positions at specific angles and will substantially correct for viewing angle ranges.

The spacing between viewing areas can be changed by changing the distance between the LCDs.

The pixel pitch can be adjusted to configure a properly formed observation window.

There may be "black masked" opaque areas between the pixels of an LCD. Increasing the width of the black mask can be used to increase the size of the observation window so that the angular range at which incorrect image data is displayed can be substantially blocked.

Applications made of pixels in different combinations can be used to vary the angle between the viewing directions for the two views being displayed, such as that described in FIG. 55 . To increase the angular spacing in the viewing direction, each pixel of each modulator does not cooperate with the nearest pixel of the other modulator, but with the next closest pixel. In this way, the intensity of a pixel of the image on the right can be determined by the effect of pixels c and f, which are the inverse of pixels c and d described in Figure 54. In practice, switching between the different angles of split view can be accomplished electronically by changing the angular range for which modulators 170 and 171 are optimized.

Figure 56 depicts how a wider angular range is achieved using time multiplexing and directional backlighting. A directional backlight (not shown) provides illumination only at specific different angular ranges at different times.

For example, during time frame 1 depicted in the upper portion of Figure 56, the backlight is set to illuminate the view only in the direction of the right image 1 and left image 2 directions. During this frame, modulators 170 and 171 operate according to the operation described in FIG. 55 . During the next time frame 2, the backlight is set to illuminate the view only in the direction of image 2 on the right and image 1 on the left. During this frame, modulators 170 and 171 operate as described in FIG. 54 .

This configuration provides four views displayed in different viewing directions. This can be used to provide a multi-view display or can be used to form a dual autostereoscopic 3D display. As another alternative, this configuration can be used to increase the observation range of a dual view display in which the right images 1 and 2 are identical and the left images 1 and 2 are identical.

Alternatively, the views may be displayed in a different order as described in FIG. 57 .

This configuration can be applied in another high resolution single view mode as described in FIG. 58 . Light for each image pixel passes through the pixel in each modulator 170 and 171 . Except for the border pixels of modulators 170 and 171, each pixel modulates the light of two image pixels. Simultaneous equations as described above can be set up and solved so that all image pixels can be controlled independently of each other. A viewer viewing the display from a range of angles of normal incidence sees an image with twice the spatial resolution of each modulator 170 and 171 .

A corrected view of the image will be produced within a specific angular range, for example around the normal incidence view of the display. To increase the angular range, a diffuser or defuser 175 may be provided at the front of the display as depicted in FIG. 59 . The diffuser 175 can be switched to a non-diffuse mode to return to multi-view mode operation.

Figure 60 depicts the operation of an alternative time series transformation mode that does not require solving simultaneous equations. In each time frame, one LCD displays an image, and the other LCD is transformed into a uniform configuration, such as a uniform retarder or a homeotropic layer. Each LCD displays its image in alternate time frames. Thus, as shown in FIG. 60, in odd time frames, one LCD displays an image that is visible in the first viewing direction but appears black in the second viewing direction. In even time frames, one LCD displays an image that is visible in the second viewing direction but appears black in the first viewing direction. By choosing a sufficiently high frame rate, the images can be merged for viewers in each viewing direction.

LCDs may or may not have polarizers in between. The LCD can operate in a liquid crystal mode, such as standard black or standard white TN or standard white or standard black TVAN (twin twisted vertically aligned nematic). For example, Figure 61 depicts the grayscale transmitted as applied voltage relative to different viewing angles of a TVAN LCD, which has no polarizer and which has a 90 degree twist. Figure 62 depicts the effect of a polarizer between 90 degree twisted TVANs.

Consideration will be given to avoid situations where there is a polarizer between the LCDs and one LCD is switched so that it cannot transmit sufficient light for the image produced by the other visible LCD.

In another single view mode of operation, for sufficient normal incidence observation, one LCD can remain switched so as to act as a uniform layer and the image can be displayed by the other LCD. The homogeneous layer can have a substantially planar alignment, in which case the LCD acts as a homogeneous retarder, it can be substantially homeotropic, or it can be switched to a state in between. Figures 61 and 62 illustrate the substantially homeotropic behavior of an LCD displaying no image for the curve label 0 degrees.

When using the display in single view time-sequential mode, the plane on which the image is produced is different from the two LCDs forming the display. This results in parallax between images when the viewer changes position. This problem can be overcome or reduced by using a switchable diffuser as previously described or using a switchable lens as described in FIG. 63 . The display shown in FIG. 63 includes a backlight in the form of a light source 180 and a collimator 181 . Between the collimator 181 and the LCDs 170 and 171, a switchable lens configuration 182 is provided, which switches between the passive mode of the first time frame and the active mode of the second time frame, as shown on the left and right of Fig. 63 respectively section described. In passive mode, the lens configuration 182 is index matched to the adjacent medium so as to have no substantial effect on the collimated light from the collimator 181 . In active mode, index matching is disabled so that the lens acts as a converging lens.

In the first time frame, LCD170 displays the image observed at normal incidence, and LCD171 acts as a uniform retarder. In the second time frame, lens 182 is activated and centers the pixels of LCD 171 to the same plane as the pixels of LCD 170 were centered in the previous time frame. LCD170 now acts as a uniform retarder. These images are thus formed on the same plane for both types of time frames in order to avoid parallax problems.

Figure 64 depicts LCDs 170 and 171 arranged substantially parallel to each other at 183 as in the previously described embodiment. For a single LCD, the LCD has a relatively large optimum viewing angle from normal to the device, such as 30 degrees, which provides a relatively large angular separation between viewing angles. However, where it is desired to use this type of LCD to provide slight differences between optimum viewing angles, the LCDs can be arranged in mutually non-parallel orientations, as depicted at 184 in FIG. 65 . In this example, LCDs 170 and 171 are rotated 5 degrees in opposite directions in the horizontal plane to the respective normal. In this way, the angle between the best viewing directions is reduced from 60 degrees to 50 degrees.

Figure 65 depicts a dual view display that can be used to form two pairs of stereoscopic images in a first and a second viewing direction so that the display functions as a dual autostereoscopic display. The main or only difference between this display and the previously described embodiments is that a parallax blocking layer 185 is provided between the LCDs. Parallax barrier layer 185 acts as a rear parallax barrier layer for LCDs comprising components 21, 24 and 27, and as a front parallax barrier layer for LCDs comprising components 21', 24' and 27'. An appropriate value can be selected from the interval to the parallax barrier layer 185 and the distance to the parallax barrier layer in each pixel plane of the liquid crystal layers 24 and 24'. Different pixel pitches may be required for LCDs. The operation of front and rear parallax barrier autostereoscopic displays is already well known and will not be described further here.

All of the techniques described above with reference to Figures 10 to 15 can be applied to either or both 20-28 and 20'-28' displays.

The voltage range chosen for each LCD to operate the dual view display depends on the characteristics of the liquid crystal mode used. For example, each LCD can be driven with a different voltage range. Alternatively, the two LCDs can be driven with substantially the same voltage range. The drive means 29 provides a suitable voltage range for dual view operation and, where appropriate, a suitable voltage range for single view or dual autostereoscopic view modes.

Although the dual LCD embodiments described above are based on TN and TVAN modes, any liquid crystal mode that produces suitable asymmetric viewing angles can be used. For example, suitable smectic or ferroelectric liquid crystal modes may be used. Also, other twin-twisted nematic modes, such as Hybrid Aligned Nematic (HAN) modes, may be used.

With the appropriate liquid crystal mode, each LCD of the display can have a different viewing angle. This can be adjusted for each specific application of the display. This provides enhanced flexibility in obtaining and adjusting viewing angle characteristics. For example, each view can be optimized for different angles, which may be advantageous in some applications such as automotive applications. With the appropriate LCD mode, the optimized viewing angle can be adjusted to the best effect for a specific audience by adjusting the gray scale range used.

An advantage of not using a parallax glass or a pattern forming layer is that no alignment steps are required for the LCD. Alignment of parallax glasses or patterning layers for LCDs is generally time consuming and expensive. A uniform LC panel using an LCD mode such as a uniform TN or TVAN can be constructed such that pixel 1 presents an image for view 1 and black for view 2, while pixel 2 presents an image for view 2 by means of an additional uniform wave plate, Whereas for view 1 it renders black.

Figure 66 schematically depicts an exploded view of the polarizers and layers forming such an LCD. Also, the vertical and horizontal directions relative to the normal direction of the display are described. The vertical upward reference direction is called 0 degrees, and the horizontal rightward direction is called 90 degrees. Each direction described for the components shown in FIG. 66 refers to the upward vertical 0 degree direction.

The front polarizer 20 has a transmission axis 30 oriented at an angle of +90 degrees to the upward vertical. The alignment layer 23 has a uniform alignment direction 33 oriented at an angle of 0 degrees with respect to the upward vertical direction. The alignment layer 25 has a uniform alignment direction 35 oriented at +90 degrees with respect to the upward vertical. Polarizer 28 has a transmission axis 38 oriented at +180 degrees with respect to the upward vertical. Liquid crystal layer 24 is a nematic liquid crystal, such as E7 available from Merck.

An additional homogeneous wave plate 200 is arranged between the polarizer 20 and the liquid crystal layer 24 . The homogeneous wave plate 200 is oriented with its optical axis 210 at an angle of 315 degrees to the upward vertical direction, it has a birefringence of 494 nm, and the optical axis is inclined at an angle of 64 degrees from the normal to the display plane to the plane of the retarder outside. This results in the operation of the display shown in Figure 67 (brightness with respect to applied voltage) in the viewing direction along the upward vertical direction inclined at +30 degree and -30 degree angles from the plane normal of the display.

Figure 67 shows that from the intersection of the two curves (at about 1.5V) to about 4 volts, there is an approximately uniform black state for the curve at +30 degrees, and there is an increasing brightness range for -30 degrees. This means that images can be rendered down to -30 degrees, while an approximately constant black state is provided down to +30 degrees. In the crossover point from about 1.5V down to about 0.75V, there is an approximately uniform black state to -30 degrees, while there is an increasing brightness range to +30 degrees. This means that images can be rendered down to +30 degrees, while an approximately constant black state is provided down to -30 degrees. This provides different high-contrast images simultaneously in each viewing direction.

The black state obtained in each case is not optimal black. The black state can also be optimized by varying the properties of the wave plate. Alternatively, two wave plates may be used in combination. For example the optical axes of the waveplates may be mutually orthogonal. By carefully choosing the orientation of the optical axis, one waveplate can be used to optimize one viewing direction, and another waveplate can be used to optimize another viewing direction. Alternatively, two wave plates can be used to simultaneously compensate for the two viewing directions. Alternatively, more than two wave plates can be used to compensate for different viewing directions. In addition to optimizing the black state, the transmitted chromaticity can be compensated. Furthermore, the range of observation angles of the compensated system can be optimized by using additional wave plates.

Uniform wave plates can be fixed layers, such as fixed retarder films, or they can be switchable layers, such as liquid crystal layers. If they are transformable layers, then an added advantage is that when applied to operation in 2D mode, they can be transformed from providing a high-contrast dual-view image to providing a compensation layer to produce a more uniform viewing angle profile. This transformation can be through the thickness of the element, or can be in the plane.

Alternatively, two switchable viewing angle compensators can be used to create a dual view display that combines to provide the LCD image. A transformable view angle compensator can be used in a time-series fashion. In time frame 1, the observation angle compensator 1 compensates the pixels so that they provide black for view 1 and images for view 2. The observation angle compensator is switched to a configuration that has no effect on the optical system. In time frame 2, the observation angle compensator 2 compensates the pixels so that they provide black for view 2 and images for view 1 . The observation angle compensator is switched to a configuration that has no effect on the optical system. Alternatively, the viewing angle compensators 1 and 2 can be switched between two configurations in which their combined effect provides a high contrast image for each view. View angle compensators 1 and 2 can be transformed into a third configuration in which they are used to generate enhanced 2D modes.

Figures 30 and 31 depict the performance of TVAN-based displays for viewing angles from -30 degrees to +60 degrees. Figures 68 and 69 depict the performance of the same display for viewing angles from -30 degrees to +30 degrees. In this way, the display can be used over a substantial angular range of operation.

In the embodiment of FIGS. 4 and 5 , the first pixel presents an image for view 1 and black for view 2 and the second pixel presents an image for view 2 and black for view 1 . The second pixel 2 can be switched from appearing white to appearing black in view 1 by using an additional switchable retarder such as the example depicted in FIG. 19 .

If a large number of regions of pixels are assigned as first pixels and another large number of regions are assigned as second pixels, then the switchable retarder can be converted to provide a half-wave plate to the second pixel 2, but no half-wave plate to the first pixel . This converts the white from the second pixel to black, improving the contrast ratio. Due to the use of a large number of areas, there is no need to provide an exchangeable retarder within the LCD panel when the parallax effect is to be neglected. This area can be selected by the user, in which case the area of the switchable retarder needs to be switched for selection. Pixels can be assigned to any view in any configuration at any time. Alternatively, they may be predetermined, in which case fixed delays may be used.

Claims (80)

1. A multi-view display comprising: at least one liquid crystal display device (20-28, 21 '-28') comprising a plurality of pixels (101, 102) having an asymmetric viewing angle characteristic; and driving means (29) for driving the pixels to display a first image in a first viewing direction (1) and to display a second image in a second viewing direction (2) different from the first viewing direction (1), characterized in that: the drive means (29) cooperate with at least one display means (20-28, 21 '-28') such that pixels displaying the first image appear dark in the second direction and pixels displaying the second image appear dark in the first direction.

2. The display of claim 1, wherein: the pixels (101, 102) displaying the first and second images exhibit a maximum dark color in the second and first directions (2, 1), respectively.

3. The display of claim 2, wherein: by means of the pixels (101, 102) displaying the first and second images, the light intensity supplied in the second and first directions (2, 1) is lower than X% of the maximum light intensity that the pixels (101, 102) displaying the first and second images can supply in the first and second directions (1, 2), respectively, wherein X is a real number lower than 20.

4. A display as claimed in claim 3, characterized in that: x is equal to 10.

5. A display as claimed in claim 3, characterized in that: x is equal to 3.5.

6. A display as claimed in claim 3, characterized in that: x is equal to 1.

7. A display as claimed in any one of the preceding claims, characterised in that the first and second images are uncorrelated with each other.

8. A display according to any of the preceding claims, characterised in that the first and second images are in a plane which is orthogonal to the display surface of the at least one device (20-28, 21 '-28') and which contains a direction of maximum viewing angle asymmetry.

9. A display as claimed in claim 8, characterized in that the first and second directions (1, 2) are opposite sides of a normal to the display surface.

10. A display as claimed in claim 9, characterized in that the first and second directions (1, 2) are substantially symmetrical with respect to a normal.

11. A display as claimed in claim 9, characterized in that the first and second directions (1, 2) are asymmetrical with respect to the normal.

12. A display as claimed in any one of the preceding claims, characterised in that the pixels displaying the first image are arranged to provide a first contrast ratio larger than 1 in the first direction (1) and to provide a contrast ratio substantially equal to 1 in the second direction, and the pixels displaying the second image are arranged to provide a second contrast ratio larger than 1 in the second direction (2) and to provide a contrast ratio substantially equal to 1 in the first direction.

13. A display as claimed in any one of the preceding claims, characterised in that the angle between the first and second directions (1, 2) is substantially greater than or equal to 10 degrees.

14. A display as claimed in any one of the preceding claims, characterised in that at least one of the means (20-28, 21 '-28') comprises sets of pixels having pixels, each set of pixels being of the same colour and having a different colour to the pixels of the other sets.

15. The display of claim 14, wherein: at least one of the devices (20-28, 21 '-28') includes a liquid crystal layer having different thicknesses (46) for different colored pixels.

16. A display as claimed in claim 14 or 15, characterised in that at least one of the means (20-28, 21 '-28') comprises a patterned retarder (50) having areas of different retardation, the different retardations being photo-aligned with the pixels of different colours.

17. A display as claimed in claim 16, characterized in that the areas of different retardation contain dyes of different colors as color filters.

18. A display as claimed in any one of the preceding claims, characterised in that at least one of the devices (20-28, 21 '-28') is a transmissive mode device.

19. A display as claimed in any one of the preceding claims, characterized in that the at least one display device (20-28, 21 '-28') has a uniform alignment and an asymmetric liquid crystal mode with an asymmetric viewing angle characteristic, in that the drive means (29) are arranged to drive the at least one device (20-28, 21 '-28') with a first drive scheme (40) for displaying a first image and to drive the at least one device (20-28, 21 '-28') with a second drive scheme (41) for displaying a second image, the first drive scheme (40) being different from the second drive scheme (41).

20. A display as claimed in claim 19, characterized in that the first and second drive schemes comprise first and second voltage ranges (40, 41), respectively, which are different from each other.

21. A display as claimed in claim 19 or 20, characterized in that the liquid crystal mode is one of a twisted nematic, a hybrid aligned nematic and a twisted homeotropic aligned nematic mode.

22. A display as claimed in claim 19 or 21, characterized in that the first and second views are spatially multiplexed on at least one means (20-28, 21 '-28').

23. A display as claimed in claim 22, characterized in that at least one of the display means comprises a liquid crystal layer (24) and at least one uniform retarder (200) arranged between the polarizers (20, 28) of uniform input and output.

24. A display as claimed in claim 23, characterised in that in the plane of at least one retarder (200), at least one retarder (200) has its optical axis oriented at substantially 45 degrees to the transmission axis (30) of an adjacent one of the polarisers (20) and at substantially 67 degrees to the normal to the retarder plane.

25. The display of claim 24, wherein the retarder has a retardation of substantially 494 nm.

26. A display as claimed in claim 22, characterized in that at least one of the means (20-28, 21 '-28') comprises a patterned polarizer (28) having first and second regions for the first and second views, respectively, and having a first region transmission axis different from the second region transmission axis.

27. The display of claim 26, wherein the transmission axis of the first region is substantially orthogonal to the transmission axis of the second region.

28. A display as claimed in claim 22, characterized in that at least one of the means (20-28, 21 '-28') comprises a patterned retarder.

29. The display of claim 28 wherein the patterned retarder is switchable to substantially zero retardation for single view mode operation.

30. A display as claimed in any one of claims 22 to 29, characterised in that at least one of the means (20-28, 21 '-28') comprises a parallax barrier (95).

31. A display as claimed in any one of claims 19 to 30, characterised in that the first and second views are time multiplexed on at least one device (20-28, 21 '-28').

32. A display as claimed in claim 29, characterized in that at least one of the means (20-28, 21 '-28') comprises a switchable retarder (80).

33. A display as claimed in claim 32, characterized in that the retardation of the retarder (80) is switchable between odd and even half wavelengths of visible light.

34. A display as claimed in any one of claims 1 to 18, characterized in that at least one means (20-28, 21 '-28') comprises a first pixel (101) having a first configuration with a first asymmetric viewing angle characteristic and a second pixel (102) having a second configuration with a second asymmetric viewing characteristic, which second configuration is different from the first configuration, the second asymmetric viewing characteristic being oriented differently from the first asymmetric viewing characteristic, characterized in that the drive means (29) are arranged to drive the first pixel (101) displaying the first image and to drive the second pixel (102) displaying the second image.

35. A multi-view display according to claim 34, characterized in that the first and second images are visible in a third viewing direction (115) between the first and second directions (1, 2).

36. A display device as claimed in claim 34 or 35, characterized in that the first pixels (101) and the second pixels (102) are spatially dispersed.

37. A display as claimed in any one of claims 34 to 36, characterised in that the first and second asymmetric viewing characteristics are oriented in substantially opposite directions.

38. A display device as claimed in any one of claims 34 to 37, characterized in that the first and second pixels (101, 102) have a first and a second liquid crystal mode, respectively, which are different from each other.

39. The display of claim 38 wherein at least one of the first and second modes is one of twisted nematic, hybrid aligned nematic and twisted homeotropic aligned nematic, Freedericksz, homeotropic aligned nematic and circumference-factor-cell (pi-cell).

40. A display as claimed in claim 38 or 39, characterised in that the first and second pixels (101, 102) have different liquid crystal director distortions in the absence of an applied field.

41. A display as claimed in claim 40, characterized in that the different distortions have different amplitudes.

42. A display as claimed in claim 40 or 41, characterized in that the different twists have different twist directions.

43. A display as claimed in any one of claims 40 to 42, characterised in that one of the different twists is 0 degrees.

44. A display as claimed in any one of claims 38 to 43, characterised in that the first and second pixels (101, 102) have different liquid crystal director pretilt angles at least one liquid crystal substrate interface.

45. A display as claimed in claim 44, characterised in that the different pretilt angles have different amplitudes.

46. A display as claimed in claim 44 or 45, characterised in that the different pretilt angles have different directions.

47. A display as claimed in any one of claims 38 to 46, characterised in that the first and second pixels (101, 102) have different bulk liquid crystal director orientations.

48. A display device as claimed in any one of claims 38 to 47, characterised in that the first and second pixels (101, 102) have different surface anchoring strengths at least one liquid crystal substrate interface.

49. A display as claimed in any one of claims 38 to 48, characterised in that the first and second pixels (101, 102) have different liquid crystal materials.

50. A display device as claimed in any one of claims 38 to 49, characterized in that at least one of the first and second pixels (101, 102) is provided with a liquid crystal material comprising at least one chiral dopant, a polymer network and a dye.

51. A display as claimed in any one of claims 38 to 50, characterised in that the first and second pixels (101, 102) have liquid crystal layers of different thickness.

52. A display as claimed in any one of claims 34 to 51, characterised in that the first pixel (101) has a first polariser having its transmission axis oriented at a first angle in relation to the optic axis of the liquid crystal of the first pixel (101), and the second pixel (102) has a second polariser having its transmission axis oriented at a second angle in relation to the optic axis of the liquid crystal of the second pixel (102), the first angle being different from the second angle.

53. A display as claimed in any one of claims 34 to 52, characterised in that the first and second pixels (101, 102) have first and second retarders of different retardation.

54. A display as claimed in any one of claims 34 to 53, characterised in that the first and second pixels (101, 102) have first and second compensation layers providing different compensation effects.

55. A display as claimed in any one of claims 34 to 54, characterised in that the drive means (29) are arranged to drive the first and second pixels (101, 102) with different voltage ranges.

56. A display as claimed in any one of claims 34 to 55, characterised in that at least one of the means (20-28, 21 '-28') comprises a parallax barrier (95).

57. A display according to any one of claims 34 to 56, characterised by further comprising a liquid crystal device (121) arranged to be viewable throughout and adapted to perform spatiotemporal operations using the first-mentioned means (122).

58. A display as claimed in any one of claims 1 to 18, characterized in that at least one of the devices comprises a first liquid crystal device (20-28) having a first asymmetric liquid crystal mode with a first asymmetric viewing angle characteristic and a second liquid crystal device (21 '-28') having a second asymmetric liquid crystal mode with a second asymmetric viewing angle characteristic, wherein the second asymmetric viewing characteristic is oriented differently from the first asymmetric viewing characteristic, the drive means (29) being arranged to drive the first device (20-28) with a first drive scheme (40) for displaying the first image and to drive the second device (21 '-28') with a second drive scheme (41) for displaying the second image.

59. A display as claimed in claim 58, characterised in that the first and second drive schemes comprise first and second voltage ranges (40, 41), respectively.

60. The display of claim 59 wherein the first and second voltage ranges are substantially the same.

61. A display as claimed in any one of claims 58 to 60, characterised in that the second means (21 '-28') are visible through the first means (20-28).

62. A display as claimed in claim 61, characterized in that the second means (21 '-28') are arranged between the first means (20-28) and the backlight (30).

63. A display according to any one of claims 58 to 62, characterised in that the first means and the second means (20-28, 21 '-28') are substantially parallel to each other.

64. A display as claimed in any one of claims 58 to 63, characterised in that each of the first means and the second means (20-28, 21 '-28') has a uniform alignment.

65. A display as claimed in any one of claims 58 to 64, characterised in that each of the first means and the second means (20-28, 21 '-28') is a transmissive mode device.

66. A display as claimed in any one of claims 58 to 65, characterised in that the first and second liquid crystal modes are of the same type.

67. A display according to any one of claims 58 to 66, characterised in that the first and second asymmetric viewing characteristics are oriented in substantially opposite directions.

68. A display as claimed in any one of claims 58 to 67, characterised in that the first means and the second means (20-28, 21 '-28') have alignments which are oriented in substantially opposite directions.

69. A display as claimed in any one of claims 58 to 68, characterised in that at least the first and second liquid crystal modes are one of twisted nematic, hybrid aligned nematic and twisted homeotropic aligned nematic.

70. A display as claimed in any one of claims 58 to 69 when dependent on claim 14, characterised in that each of the first and second means (20-28, 21 '-28') comprises a set of pixels of different colours.

71. A display as claimed in claim 70, characterised in that one of the first means and the second means (20-28, 21 '-28') comprises sets of red, green and blue pixels and the other of the first means and the second means (20-28, 21 '-28') comprises sets of cyan, magenta and yellow pixels.

72. A display as claimed in claim 70 or 71, characterised in that each of the first means and the second means (20-28, 21 '-28') comprises colour filter stripes (60-62) extending substantially parallel to a plane containing the first and second directions.

73. A display as claimed in any one of claims 58 to 69, characterised by comprising a multi-colour time-sequential backlight (30a, 30b) and drive means (29), the drive means (29) being arranged to drive the colours of the first and second means (20-28, 21 '-28') in time sequence.

74. A display as claimed in any one of claims 58 to 73, characterised in that the drive means (29) are arranged to supply time-multiplexed images to the first and second means (20-28, 21 '-28') and to control the direction-switchable backlight synchronously.

75. A display as claimed in any one of claims 58 to 74, characterised in that each of the first and second means (20-28, 21 '-28') comprises a spatial phase modulator.

76. A display as claimed in any one of the preceding claims, comprising a switchable light diffuser which is switchable between a substantially non-diffusing state, which displays the multi-view display mode, and a diffusing state, which displays the single-view display mode.

77. A multi-view display comprising liquid crystal display means (20-28) having a uniform alignment and an asymmetric liquid crystal mode having an asymmetric viewing angle characteristic, characterized by driving means (29) for driving the means (20-28) with a first drive scheme (40) for displaying a first image in a first viewing direction (1) and with a second drive scheme (41) different from the first drive scheme (40) for displaying a second image in a second direction (2) different from the first direction (1).

78. A multi-view display, comprising: a liquid crystal device (20-28) comprising a first pixel (101) having a first configuration with a first asymmetric viewing angle characteristic, and a second pixel (102) having a second configuration with a second asymmetric viewing characteristic, the second configuration being different from the first configuration, the second asymmetric viewing angle being different from the orientation of the first asymmetric viewing characteristic; a driving means (29) for driving the first pixels (101) to display a first image in a first viewing direction (1) and the second pixels (102) to display a second image in a second viewing direction (2), the first viewing direction being different from the first viewing direction.

79. A multi-view display, comprising: a liquid crystal device (20-28) comprising a first pixel (101) having a first configuration with a first asymmetric viewing angle characteristic, and a second pixel (102) having a second configuration with a second asymmetric viewing characteristic, the second configuration being different from the first configuration; a driving means (29) for driving the first pixels (101) to display the first image in the first and second viewing directions (115) and the second pixels (102) to display the second image in the second viewing direction (2).

80. A multi-view display, comprising: a first liquid crystal device (20-28) having a first asymmetric liquid crystal mode with a first asymmetric viewing angle characteristic, comprising: a second liquid crystal device (21 '-28') having a second asymmetric liquid crystal mode of a second asymmetric viewing characteristic, the second asymmetric liquid crystal mode being oriented differently from the first asymmetric liquid crystal mode; a driving means (29) for driving the first means (20-28) with a first driving scheme for displaying a first image in a first viewing direction (1) and for driving the second means (21 '-28') with a second driving scheme for displaying a second image in a second viewing direction (2), the first viewing direction being different from the second viewing direction.

Images