JPH0723986B2 - Projection display device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a projection type display device which obtains a display image by synthesizing images formed by a plurality of matrix type liquid crystal panels.

[Conventional technology]

In recent years, there has been an increasing demand for display devices larger than CRTs, and various types of large display devices have been developed and marketed. One of them is a display device for enlarging and projecting an image composed of pixels arranged in a matrix. FIG. 2 shows the configuration of a projection display device using an LCD (liquid crystal display device) as an image forming means. The LCD 1 has pixels in a matrix, and the transmittance of each pixel is controlled by an external signal to form an original image. This original image is formed on the screen 3 by the projection optical system 2 and displayed.

As the LCD 1, an XY matrix type, an active matrix type or the like is used. As another image forming means, another matrix type light modulator or a light emitting type matrix display device (LED, etc.)
Can also be used.

[Problems to be Solved by the Invention]

By the way, in such a projection type display device, the resolution is limited by the original image, and in order to increase the resolution, it is necessary to increase the size of the original image and increase the number of pixels, or to reduce the pixels to increase the density. is necessary. The method of enlarging the former original image is
The manufacturing cost of the display device is high. Further, even if a plurality of display devices are arranged side by side, it is difficult to eliminate the discontinuity in the connection portion of the obtained projection images. on the other hand. There is a lower limit to the latter densification depending on the mounting with the external circuit of the display device and the manufacturing process. At present, the lower limit is several tens of μm.

As described above, the size and the pixel pitch are determined by the cost, availability of manufacturing, and the number of drivable lines, and there has been a limit to increase the resolution of the original image.

It is an object of the present invention to obtain a projection display having a high number of pixels and a high density without increasing the number of pixels and the density of the original image forming panel. Furthermore, it is to realize color display with high resolution.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the projection display device of the present invention is, firstly, a plurality of matrix type liquid crystal panels which form an image by modulating light from a light source with pixels formed in a matrix. A projection optical system for forming a display image by combining images formed by a plurality of matrix type liquid crystal panels, wherein the plurality of matrix type liquid crystal panels are arranged in a horizontal direction and a vertical direction, and a pixel arrangement pitch is a liquid crystal. The panels are equal to each other, and in the pixel arrangement in the horizontal direction of the display image, the pixels of the different liquid crystal panels of the plurality of matrix type liquid crystal panels are adjacently arranged in order, and are adjacent in the horizontal direction in each liquid crystal panel. The two pixels that partially overlap with one pixel of another liquid crystal panel in the horizontal pixel arrangement of the display image, In the pixel array in the vertical direction of the image, the pixels of the different liquid crystal panels of the plurality of matrix type liquid crystal panels are positioned adjacent to each other in order, and the two pixels vertically adjacent in each liquid crystal panel are the display pixels. The pixel arrangement in the vertical direction of the image is characterized by partially overlapping with one pixel of another liquid crystal panel.

Secondly, the plurality of matrix type liquid crystal panels are two matrix type liquid crystal panels, and in the pixel arrangement in the horizontal direction and the vertical direction of the display image, the pixels of the adjacent different display panels are displaced by a half pixel. It is characterized by being done.

[Summary of Invention]

The present invention obtains a composite image by displacing a plurality of original images composed of pixels arranged in a matrix and having the same pitch by a fraction of a pixel according to a specific arrangement rule. Here, the pixels forming the original image may have different sizes, but need to have the same pitch. In the display image synthesized from a plurality of original images, specifically, the pixel displacement is substantially one pixel or less, and the images of the plurality of matrix type liquid crystal panels forming the plurality of original images are geometrically They have the same pitch. It is assumed that the display information is sampled according to a specific rule and decomposed into a plurality of original images.

Next, a plurality of original images are projected so as to have a displacement according to the regularity, and a complete image is reproduced. Further, by combining the original images corresponding to color display, a color display device having high resolution is obtained.

〔Example〕

(Example 1) Example 1 is a projection type television device using a TFT (thin film transistor) matrix liquid crystal panel (hereinafter referred to as TFT LCD) as a display device for forming an original image. The liquid crystal display mode can utilize the electric field effect (hereinafter, FETN) of the twisted nematic liquid crystal, the scattering effect (DSM), the guest-host effect (GH), and the like. In this example, FETN mode was used. The reason why the matrix driving by TFT is selected is to improve the optical light valve performance. Therefore, there is no problem even if another matrix-type driving method is used. The configuration of this embodiment is shown in FIG.

In order to increase the utilization efficiency of the light source, the light source is
A series of condenser lenses 4 and condenser mirrors 5 are provided to obtain two illumination light fluxes from one light source 6. The direction of this illumination light is changed by the mirror 7, and TFTL
It is incident on CD8. The light modulated by the TFT LCD is imaged on the screen by the projection lens 9. Reference numeral 10 is a correction lens for correcting trapezoidal distortion due to projection.

In the case of the NTSC system, the TV signal is 525 in the vertical direction.
It has about 700 luminance signals in the horizontal direction. Therefore, in order to display the luminance signal completely, about 500
It is necessary to use a TFT LCD with × 700 pixels. However, it is difficult to manufacture such a large-scale matrix array in terms of cost, yield, and manufacturing equipment, and it is desirable that the number of pixels is as small as possible. Used in Figure 2
The TFT LCD has 240 × 240 pixels and a diagonal size of 2 inches. Therefore, if this TFT LCD is simply projected, the brightness information
It only displays 1/4. In this embodiment, a plurality of TFTLCDs (two here) are used as shown in FIG. 3, and the pixels of the TFTLCD are imaged so as to be displaced by a fraction, so that the number of pixels and the pixel density on the display image are determined. Is improving.

The pixel displacement is shown in FIG. The shaded areas are the pixels of panel A, and the dotted areas are the pixels of panel B. In the present invention, a plurality of original images composed of pixels arranged in a matrix and having the same pitch are displaced by a fraction of a pixel according to a specific arrangement rule and projected to obtain a composite image. Here, the pixels forming the original image may have different sizes, but need to have the same pitch. It is assumed that the display information is sampled according to a specific rule and decomposed into a plurality of original images. In this figure, the pixel arrangement is such that the pixels of both panels are displaced by half a pixel. The reason for this displacement is to efficiently disperse the luminance information in the horizontal direction and the luminance information in the vertical direction on the screen.

Although not included in the embodiment of the present invention, a combination of reducing the effective aperture ratio of the pixel as shown in FIG.
Furthermore, the resolution can be increased. In FIG. 1 (b), the shaded area is the effective pixel of panel A, the dotted area is the effective pixel of panel B, and the portion surrounded by the broken line and the one-dot chain line is according to the matrix pitch. A pixel portion is shown. In order to reduce the effective aperture ratio, the transparent electrode was made smaller, and the gate and source electrodes of the TFT were made of opaque wiring material to widen the electrode. In addition, 90 ° TN (twisted nematic) mode is adopted, which does not allow light to pass when no voltage is applied.

Next, driving of the TFT LCD will be briefly described. 2 TFs
The TLCD is alternately selected and AC-driven by the circuit shown in FIG. 4 according to the interlace system. The video signal input produces inverted and non-inverted outputs, and this and the black display level Vs of the panel are selected by the switch circuits (SW1 to 6) to produce a signal whose polarity is inverted every two fields (2F). This is supplied to the X driver.

FIG. 5 is the timing chart. CLf is a shift register clock corresponding to one field (1F), and Df is transmission data. In FIG. 4, 11 is a shift register for selecting SW1 to SW4, 12 is an inverting buffer, and 13 is a non-inverting buffer. CLx is a clock synchronized with the horizontal synchronizing signal, and Dx is data of the X driver. Similarly, CLy, Dy
Is the clock and data of the Y driver. In this way, panel A has odd fields (1stF, 3rdF, 5t in Fig. 5).
hF) and panel B is selected for even fields (2ndF, 4thf in FIG. 5).

As described above, in the case of Example 1, it was possible to obtain about twice the resolution as compared with one TFT LCD. Moreover, the utilization efficiency of the light from the light source could be improved.

(Example 2) Example 2 is a full-color display device using three display panels corresponding to three primary colors R (red), G (green), and B (blue). As shown in Fig. 8, R (red) panel 17, G (green)
The panel 18 and the B (blue) panel 19 combine light fluxes by a light flux branching / combining mirror (for example, a semi-transmissive mirror or a dichroic mirror) and form an image on the screen 3 by the projection lens 9. Reference numeral 21 is a relay lens, and 4 is a condenser lens. Here, the pixels of the R panel, the G panel, and the B panel are adjusted so as to be regularly displaced on the screen, and as shown in FIG. It overlaps with the pixels of other panels. Although FIG. 8 uses a TFT LCD as a display panel, any display panel that forms an accurate matrix can be replaced. With a projection television that projects a CRT (cathode ray tube) corresponding to the three primary colors of RGB onto the screen, it is difficult to obtain a distortion-free image with perfect convergence. However, according to the present invention in which image formation is performed by matrix pixels, pixel position adjustment between different panels can be performed. As a result, the color shift between each color can be reduced,
Since the luminance information included in R and B can be effectively displayed, the resolution can be substantially increased.

FIG. 9 shows a drive circuit used in this embodiment. R, G, B
The color-separated video signal is AC-inverted for each field and input to the X driver. CLx, Dx, CLy, Dy
Are clocks and shift data of the X driver and clocks and shift data of the Y driver. The same circuit as the R circuit is provided for G and B.

In this embodiment, a transmissive TFT LCD is used as a matrix type display device, but it can also be implemented as a reflective light valve structure in which light is incident from the same direction as the light source light and modulated. The display type liquid crystal mode can of course be used for other than 90 ° TN. Further, it is of course possible to display a color other than the full color.

Reference Example This example is a projection type display device that uses a plurality of (two in the following description) matrix liquid crystal panels and forms an image with one projection optical system. The liquid crystal panel is the same as that of the first embodiment.
TFTLCD was used. FIG. 6 shows the configuration of the reference example. The liquid crystal layer is a black guest-host liquid crystal that is homogeneously aligned, and the optical shutter opens when an electric field is applied. Reference numeral 14 is a polarizing plate for improving the optical shutter characteristic. 6 is a light source, 4 is a condenser lens,
9 is a projection lens. The panel A15 and the panel B16 are arranged in close contact or almost close contact with each other and have the same liquid crystal orientation. Images of both panels are formed on the screen 3. For this reason, thin glass (in this case, 0.1 mm thick polished glass) is used as the transparent substrate of the panel on one side. The pixels of both panels are displaced by a half pixel as shown in FIG. However, in this reference example, since the panels are overlapped with each other, it is difficult to interpolate the non-pixel region of the panel A with the pixels of the panel B on the display image as in the first and second examples. I won't.

Similar to the first embodiment, the television signal alternately displays the panel A and the panel B for every two fields according to the interlace system. As described above, the liquid crystal is of a type in which the optical shutter is opened when a voltage is applied, so that the voltage needs to be applied to open the optical shutter in an unselected field. Therefore, in driving, as in the first embodiment, the odd fields are assigned to panel A and the even fields are assigned to panel B. The level of the X driver input is selected by the switch circuit so that the white level is obtained in the unselected field. The X driver input thus created is shown in FIG. The entire panel driving method can be performed in the same manner as in FIG.

In this way, compared to the case of using one TFT LCD, about 2
Double resolution can be obtained. Although a GH mode liquid crystal is used here, any transmission type electro-optical effect that does not use rotation of the polarization plane can be applied.

〔The invention's effect〕

As described above, the projection display device of the present invention, the array pitch of the pixels formed in the horizontal direction and the vertical direction of the plurality of matrix type liquid crystal panels that modulate the light from the light source are equal to each other between the panels, In the pixel arrangement in the horizontal and vertical directions of the display pixels, the pixels of different liquid crystal panels of a plurality of matrix type liquid crystal panels are arranged adjacent to each other in order, and the horizontal and vertical directions are arranged in each liquid crystal panel. Two pixels that are adjacent to each other in the direction
In the horizontal and vertical pixel array of the display image,
Even if a liquid crystal panel with a small number of pixels and a low density is used, the number of pixels and the density of the combined display image are far larger than those of each liquid crystal panel because one pixel of another liquid crystal panel partially overlaps each other. Can be improved. The resolution of a projection display device depends largely on the number of pixels and the density of the panel. However, with the configuration of the present invention, it is possible to realize a pixel having high resolution even in a projection display device using a liquid crystal panel having a low number of pixels and a low density.

In addition, a pixel on the display image partially overlaps a plurality of pixels of another liquid crystal panel adjacent in the horizontal direction and the vertical direction on the display image, so that the non-pixel region existing between the pixels of the liquid crystal panel is The display image is covered by the pixels of other panels, and the non-display area of the display image becomes inconspicuous in the horizontal and vertical directions, and the luminance information is dispersed in the horizontal and vertical directions to display a smooth image. it can.

Furthermore, if the pixel density of the liquid crystal panel is increased, the yield will be significantly reduced and the manufacturing cost will be increased. However, since the liquid crystal panel does not have to have a high pixel density, the manufacturing cost can be suppressed.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of pixel displacement. FIG. 1A shows an example of pixel displacement according to the present invention when pixels overlap, and FIG. 1B shows a case where pixels do not overlap. FIG. 2 is a block diagram of a general projection type display device using an LCD. FIG. 3 is a diagram showing a configuration example of the synthetic projection method of the present invention. FIG. 4 is a diagram showing an example of a drive circuit when two TFT LCDs are used. FIG. 5 is a diagram showing signal waveforms at various parts of the circuit of FIG. FIG. 6 is a diagram showing the configuration of a reference example when two TFT LCDs are used. FIG. 7 is a diagram showing an X driver input waveform in the case of FIG. FIG. 8 is a block diagram of a full-color projection type display device of the present invention. FIG. 9 is a diagram showing an example of the drive circuit of FIG. 1 ... Matrix LCD 2 ... Projection optical system 3 ... Screen 4 ... TFT LCD 9 ... Projection lens 15,16,17,18,19 ... TFT LCD

Claims (2)

[Claims] 1. A plurality of matrix type liquid crystal panels for forming an image by modulating light from a light source by pixels formed in a matrix, and a display image obtained by combining the images formed by the plurality of matrix type liquid crystal panels. A plurality of matrix type liquid crystal panels, the arrangement pitch of pixels formed in the horizontal direction and the vertical direction is equal to each other in the liquid crystal panels, and in the pixel arrangement in the horizontal direction of the display image. Are arranged such that pixels of different liquid crystal panels of the plurality of matrix type liquid crystal panels are sequentially adjacent to each other, and two pixels adjacent to each other in the horizontal direction in each liquid crystal panel are arranged in the horizontal pixel arrangement of the display image. , Partially overlaps with one pixel of another liquid crystal panel, and in the vertical pixel arrangement of the display image, the plurality of pixels are arranged. Pixels of different liquid crystal panels of the trix type liquid crystal panel are positioned adjacent to each other in order, and two pixels adjacent to each other in the vertical direction in each liquid crystal panel are different from each other in the vertical pixel arrangement of the display image. The projection display device is characterized in that each pixel is partially different from the other pixel. 2. The plurality of matrix type liquid crystal panels are composed of two matrix type liquid crystal panels, and in the pixel arrangement in the horizontal direction and the vertical direction of the display image, the pixels of adjacent display panels different from each other are shifted by a half pixel. The projection type display device according to claim 1, wherein the projection type display device is arranged.