JP2011174994A - Image display apparatus - Google Patents

Abstract

An image display apparatus according to the present invention can display an image composed of a plurality of arranged pixels on a display screen, and the pixels of the image are displayed on the display screen. The image display device includes a plurality of sub-pixels corresponding to colored lights having different wavelengths. Positions of a plurality of sub-pixels constituting each of the plurality of pixels when the number of pixels arranged in the pixel arrangement direction is less than 20 pixels within the range of 1 ° of the viewer's angle of view with respect to the display image displayed on the display screen Are displayed at substantially the same position, and when the number of pixels is 20 pixels or more, at least one of the plurality of sub-pixels constituting each of the plurality of pixels is displayed at a position different from the other sub-pixels. .
[Selection] Figure 6

Description

  The present invention relates to an image display device.

  Conventionally, a projector is known as one of image display apparatuses. The projector has features such as being easy to install and capable of displaying a large screen image. As a conventional projector, for example, there is one having a configuration disclosed in Patent Document 1.

  The projector of Patent Document 1 includes a light source, a color separation optical system, three liquid crystal light valves, a color synthesis optical system, and a projection lens. The light emitted from the light source is separated into red, green, and blue color light by the color separation optical system. Each of the three types of color light enters the corresponding liquid crystal light valve and is modulated. The three kinds of modulated color lights are combined by the color combining optical system so that the positions of the pixels coincide with each other on the screen. The synthesized light is projected onto the screen by the projection lens, so that a color image is displayed.

  By the way, the projector is expected to have a high resolution display image. When displaying an image formed by a light modulation element such as a liquid crystal light valve, the number of pixels of the display image is usually the same as the number of pixels of the light modulation element. When the light modulation element has a high resolution, the display image also has a high resolution, but the manufacturing cost increases remarkably.

  As a technique for obtaining a high-resolution display image without setting the light modulation element to have a high resolution, a technique disclosed in Patent Document 2 can be cited. In the image display device of Patent Document 2, one pixel (for example, a green image) of a red image, a green image, and a blue image is displayed at a position shifted from the pixels of the other color images. The brightness of the pixels of the green image is recognized independently of the brightness of the pixels of the red image and the blue image, and the apparent number of pixels increases, so that the resolution is enhanced.

Japanese Patent Laid-Open No. 61-150487 JP 2009-116216 A

  According to the technique of Patent Document 2, the resolution of a display image can be improved without causing an increase in device cost, but the display image may be falsely colored (colored) and image quality may be deteriorated. This is presumably because the displacement of the pixel position is recognized by the difference in the color of the pixel depending on conditions such as the size of the display image and the distance from the viewer to the screen.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an image display device capable of enhancing the sense of resolution while suppressing generation of false colors.

In the present invention, the following means are adopted in order to achieve the object.
The image display device of the present invention can display an image composed of a plurality of arranged pixels on a display screen, and the pixels of the image are composed of a plurality of sub-pixels corresponding to colored lights having different wavelengths. In the image display device, when the number of pixels arranged in the pixel arrangement direction is less than 20 pixels within a range of an angle of view of an observer with respect to a display image displayed on the display screen, the plurality of pixels The positions of the plurality of sub-pixels constituting each are displayed at substantially the same position, and when the number of pixels is 20 pixels or more, at least one of the plurality of sub-pixels constituting each of the plurality of pixels. One sub-pixel is displayed at a different position from the other sub-pixels.

  The inventor of the present application paid attention to the fact that the resolution capable of distinguishing colors is different from the resolution capable of distinguishing luminances, and conducted a sensory evaluation experiment to investigate human visual characteristics. Although details will be described later, if the number of pixels arranged in the pixel arrangement direction is 20 pixels or more in the range of the angle of view of 1 ° from the investigation result, it is possible to distinguish the luminance, although it is possible to distinguish the luminance. I got the knowledge. In the following description, the number of pixels arranged in the pixel arrangement direction in the range of 1 ° of the angle of view may be referred to as display resolution (unit: pixels / °).

  According to the image display device of the present invention, when the display resolution is 20 pixels / ° or more, a plurality of sub-pixels constituting one pixel are displayed at different positions, so that the resolution can be enhanced. Further, since the plurality of sub-pixels constituting one pixel are displayed at substantially the same position when the display resolution is less than 20 pixels / °, generation of false colors can be suppressed.

The image display apparatus according to the present invention can take the following aspects as typical aspects.
An illumination system that emits color light corresponding to each of the plurality of sub-pixels; a plurality of light modulation elements that include light modulation elements that modulate each of the plurality of color lights emitted from the illumination system; and the plurality of lights A color synthesis optical system that synthesizes the color light modulated by the modulation element, a projection optical system that projects the color light synthesized by the color synthesis optical system onto the display screen, and a view between the observer and the display screen About at least one color light of the plurality of color lights modulated by the plurality of light modulation elements based on a determination result of whether the number of pixels is 20 pixels or more based on a distance and the size of the display image And an optical path control unit that variably controls the optical path after being projected from the projection optical system.

  In this way, a plurality of color lights emitted from the illumination system are modulated by the plurality of light modulation elements for each color light and then synthesized by the color synthesis optical system, and the synthesized color light is projected by the projection optical system. A display image is displayed. The optical path control unit determines the display resolution based on the size of the viewing distance display image, and variably controls the optical path after being projected from the projection optical system based on the determination result. It is possible to switch between a mode for displaying pixels at the same position (hereinafter referred to as a normal mode) and a mode for displaying pixels at different positions (hereinafter referred to as a high resolution mode) with high accuracy.

The optical path control unit may include a size acquisition unit that acquires the size of the display image based on a projection distance of the projection optical system.
In this way, the size of the display image can be acquired with high accuracy, and the display resolution can be determined with high accuracy.

The optical path control unit may include a display image data correction unit that corrects image data displayed by the at least one color light based on a change amount of the optical path of the color light.
The amount of shift of the sub-pixel is determined by the amount of change in the optical path, and the image data is corrected based on the amount of change in the optical path. Therefore, the gradation value of the sub-pixel displayed at the shifted position is corrected to a value that matches the position. Can do.

When the number of pixels is 20 pixels or more, a sub-pixel corresponding to color light having the highest human visibility among the plurality of sub-pixels constituting each of the plurality of pixels is shifted from other sub-pixels. It should be displayed at the selected position.
In this way, the luminance of the sub-pixel corresponding to the color light with high visibility can be easily seen, and the resolution of the display image can be effectively increased.

When the number of pixels is 20 pixels or more, at least one of the plurality of sub-pixels configuring each of the plurality of pixels may be disposed between sub-pixels configuring another pixel.
In this way, gaps between pixels can be reduced, and the resolution of the display image can be effectively increased.

The optical path control unit may detect the viewing distance and the size of the display image, and obtain the number of pixels based on the detection result.
In this way, since the display resolution is obtained using the detected viewing distance and the size of the display image, the normal mode and the high resolution mode are automatically switched according to changes in the viewing distance and the size of the display image. It becomes possible.

The optical path control unit may obtain the number of pixels based on data indicating the viewing distance input from a user and data indicating the size of a display image.
In this way, since the display resolution is obtained based on the input value of the data indicating the viewing distance and the input value of the data indicating the size of the display image, it is necessary to provide a sensor for detecting the viewing distance and the size of the display image. Thus, the configuration of the image display device can be simplified.

(A) is a conceptual diagram of the image display method by pixel shift, (b) is a figure which shows an example of the pixel arrangement | sequence on a display screen. It is a schematic diagram which shows schematic structure of the projector of 1st Embodiment. It is a block diagram which shows the structure of an optical path control part. It is a figure which shows the other structural example which produces a pixel shift | offset | difference. It is a figure which shows the positional relationship of a projector, a display screen, and an observer's viewpoint. It is a figure which shows the processing flow of a projector when displaying an image. It is a graph which shows the experimental result of the subjective evaluation index value of the feeling of resolution with respect to viewing distance. It is a figure which shows the structure of the optical path control part in 2nd Embodiment. It is a table | surface which shows the example of the viewing distance linked | related with the use environment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings used for explanation, in order to show characteristic parts in an easy-to-understand manner, dimensions and scales of structures in the drawings may be different from actual structures. In addition, in the embodiment, the same components are illustrated with the same reference numerals, and detailed description thereof may be omitted.

[First Embodiment]
FIG. 1A is a conceptual diagram of an image display method using pixel shifting, and FIG. 1B is a diagram illustrating an example of a pixel arrangement on a display screen. As shown in FIG. 1A, the projector 1 projects the color lights L1 to L3 on a display screen S such as a screen. The colored lights L1 to L3 have different wavelengths and are modulated independently of each other. For example, the color light L1 is red color light, the color light L2 is green color light, and the color light L3 is blue color light.

  The projector 1 can display an image in a mode for displaying an image by shifting pixels (hereinafter referred to as a high resolution mode) or a mode for displaying an image without shifting pixels (hereinafter referred to as a normal mode). It has become. Focusing on the optical path for each color light emitted from the projector 1, in this embodiment, when displaying an image in the high resolution mode, the optical path of the color light L1 substantially matches the optical path of the color light L3, and the optical path of the color light L2 Is deviated from the optical paths of the color lights L1 and L3. When displaying an image in the normal mode, the optical paths of the color lights L1 to L3 after being emitted from the projector 1 substantially coincide with each other.

  On the display screen S, the first color image B1 is displayed with the color light L1, the second color image B2 is displayed with the color light L2, and the third color image B3 is displayed with the color light L3. The first to third color images B1 to B3 are combined to display a color display image B. In the high resolution mode, the second color image B2 is displayed at a position different from the first and third color images B1 and B3 because the optical path of the color light L2 is deviated from the optical paths of the color lights L1 and L3. . In the normal mode, the first to third color images are displayed at substantially the same position.

  As shown in FIG. 1B, the display image B includes a plurality of pixels P. Each of the plurality of pixels P includes a sub pixel P1 corresponding to red color light, a sub pixel P2 corresponding to green color light, and a sub pixel P3 corresponding to blue color light. The sub-pixel P1 is displayed with the color light L1, the sub-pixel P2 is displayed with the color light L2, and the sub-pixel P3 is displayed with the color light L3.

  When attention is paid to the display positions on the display screen S of the sub-pixels P1 to P3 belonging to the same pixel P, the sub-pixels P1 to P3 are displayed at substantially the same positions in the normal mode, and the sub-pixel P2 is displayed in the high-resolution mode. It is displayed at a position different from the sub-pixels P1 and P3. The sub-pixels P1 to P3 are all arranged two-dimensionally (X direction and Y direction). Since one pixel P is composed of a set of sub-pixels P1 to P3, the plurality of pixels P are arranged two-dimensionally (X direction and Y direction). For example, the X direction is the horizontal scanning direction, and the Y direction is the vertical scanning direction.

  The sub-pixel P2 belonging to one pixel P in the high-resolution mode overlaps a part of the sub-pixels P1 and P3 belonging to this pixel P and also belongs to another pixel P adjacent to this pixel P. , Overlaps part of P3. The pitch of the sub pixels P2 in each of the arrangement directions of the pixels P (X direction or Y direction) is substantially the same as the pitch of the sub pixels P1 and P3. In the arrangement direction (X direction or Y direction) of the pixels P, the amount of displacement of the position of the sub pixel P2 with respect to the sub pixels P1 and P3 is approximately half the pitch of the sub pixels in this direction.

  In the display image B displayed by the projector 1 in the high resolution mode, the luminance of the sub-pixel P2 is identified separately from the luminance of the sub-pixels P1 and P3, and the number of pixels when the three sub-pixels are set as one pixel. The apparent number of pixels increases and the image is observed as a high resolution image.

  Of the red, green, and blue color lights, the color light having the highest human visibility (light absorption rate of human cone cells) is green color light. Since the position of the sub-pixel P2 corresponding to the green color light is shifted from the positions of the other sub-pixels P1 and P3, the resolution can be effectively enhanced. In addition, since the sub-pixel P2 is shifted so as to overlap the adjacent pixel P, it is difficult to observe the gap between the pixels P. In particular, the shift amount of the position of the sub-pixel P2 is approximately half the pitch of the sub-pixel. Therefore, it is possible to effectively enhance the resolution.

  The projector 1 is in the normal mode when the number of pixels arranged in the arrangement direction of the pixels P is less than 20, that is, the display resolution is less than 20 (pixels / °) within the range of the angle of view of 1 ° with respect to the display image B of the observer. The image is displayed with. Further, when the display resolution is 20 pixels / ° or more, an image is displayed in a high resolution mode. As will be described in detail later, the generation of false colors can be suppressed by displaying an image in the normal mode when the display resolution is less than 20 (pixels / °).

  Next, a configuration example of the projector 1 will be described. FIG. 2 is a schematic diagram illustrating a schematic configuration of the projector 1 according to the first embodiment, and FIG. 3 is a diagram illustrating a schematic configuration of the optical path control unit 7.

  As shown in FIGS. 2 and 3, the projector 1 includes an illumination system 2, a color separation optical system 3, a plurality of light modulation elements 4, a color synthesis optical system 5, a projection optical system 6, and an optical path control unit 7. . As the plurality of light modulation elements 4, a first light modulation element 4a, a second light modulation element 4b, and a third light modulation element 4c are provided.

  The projector 1 generally operates as follows. The light L emitted from the illumination system 2 is separated into a plurality of color lights L1 to L3 by the color separation optical system 3. The plurality of color lights L1 to L3 separated by the color separation optical system 3 are incident on different light modulation elements 4 for each color light, and are modulated by the light modulation elements 4 for each color light. When the display resolution is 20 or more, the optical path controller 7 causes the second light modulation element 4b to supply the corrected image data, and the second color image B2 is the first and third color images B1, B3. The optical path of the color light L2 emitted from the second light modulation element 4b is shifted so that it is displayed at a different position. The optical path controller 7 emits the color light L2 emitted from the second light modulation element 4b so that the first to third color images B1 to B3 are displayed at substantially the same position when the display resolution is less than 20. Control the optical path. The plurality of color lights L <b> 1 to L <b> 3 modulated by the light modulation element 4 are incident on the color synthesizing optical system 5 and their traveling directions are aligned. The color lights L <b> 1 to L <b> 3 emitted from the color synthesis optical system 5 are projected onto the display screen S by the projection optical system 6.

Next, components of the projector 1 will be described in detail.
The illumination system 2 includes a light source 21, a first lens array 22, a second lens array 23, a polarization conversion element 24, and a superimposing lens 25. The components constituting the illumination system 2 are arranged along the optical axis 20 of the light source 21.

  The light source 21 has a light source lamp 211 and a parabolic reflector 212. The light L emitted from the light source lamp 211 is reflected in one direction by the parabolic reflector 212 and becomes a substantially parallel light bundle. The light source lamp 211 is configured by, for example, a metal halide lamp, a xenon lamp, a high-pressure mercury lamp, a halogen lamp, or the like. Further, instead of the parabolic reflector 212, the reflector may be configured by an elliptical reflector, a spherical reflector, or the like. Depending on the shape of the reflector, a collimating lens that collimates the light emitted from the reflector may be used.

  The first lens array 22 has a plurality of lens elements 221 arranged on a surface substantially orthogonal to the optical axis 20 of the light source 21. Similar to the lens element 221, the second lens array 23 has a plurality of lens elements 231. The lens elements 221 and 231 are arranged in a matrix, for example, and the planar shape on a plane orthogonal to the optical axis 20 is similar to the illuminated area of the light modulation element 4 (here, substantially rectangular). Yes. The illuminated area is an area including the entire area where a plurality of modulation elements are arranged in the light modulation element 4.

  The polarization conversion element 24 has a plurality of polarization conversion units 241. Although the detailed structure of the polarization conversion unit 241 is not shown, the polarization conversion unit 241 includes a polarization beam splitter film (hereinafter referred to as a PBS film), a ½ phase plate, and a reflection mirror.

  The lens element 221 has a one-to-one correspondence with the lens element 231. The lens element 231 has a one-to-one correspondence with the polarization conversion unit 241. The lens elements 221 and 231 and the polarization conversion unit 241 that correspond to each other are arranged along an axis substantially parallel to the optical axis 20.

  The light L emitted from the light source 21 is spatially divided and incident on the plurality of lens elements 221 of the first lens array 22, and is collected for each divided light bundle incident on the lens element 221. The split beam bundle collected by the lens element 221 forms an image on the lens element 231 corresponding to the lens element 221. That is, a secondary light source image is formed on each of the plurality of lens elements 231 of the second lens array 23. Light from the secondary light source image formed on the lens element 231 enters the polarization conversion unit 241 corresponding to the lens element 231.

  The light incident on the polarization conversion unit 241 is separated into P-polarized light and S-polarized light with respect to the PBS film. One separated polarized light passes through the half phase plate after being reflected by the reflection mirror, and the polarization state of the other polarized light is aligned. The light (divided beam bundle) emitted from each of the plurality of polarization conversion units 241 enters the superimposing lens 25 and is refracted, and is superimposed on the illuminated region of the light modulation element 4. Each of the plurality of divided beam bundles illuminates substantially the entire illuminated area, whereby the illuminance distribution of the plurality of divided beam bundles is averaged, and the illuminance in the illuminated area is made uniform.

  The color separation optical system 3 includes dichroic mirrors 31 and 32, mirrors 33 to 35, field lenses 36a to 36c, and relay lenses 37 and 38. The dichroic mirrors 31 and 32 are formed by, for example, laminating a dielectric multilayer film on the glass surface. The dichroic mirrors 31 and 32 have a characteristic of selectively reflecting color light in a predetermined wavelength band and transmitting color light in other wavelength bands. Here, the dichroic mirror 31 reflects the green color light L2 and the blue color light L3, and transmits the red color light L1. The dichroic mirror 32 reflects the green color light L2 and transmits the blue color light L3.

The light L emitted from the illumination system 2 enters the dichroic mirror 31. The red color light L1 of the light L enters the mirror 33 through the dichroic mirror 31, is reflected by the mirror 33, and enters the field lens 36a. The red color light L1 is collimated by the field lens 36a and then enters the first light modulation element 4a.
Of the light L, the green color light L2 and the blue color light L3 are reflected by the dichroic mirror 31 and enter the dichroic mirror 32. The green color light L2 is reflected by the dichroic mirror 32 and enters the field lens 36b. The green color light L2 is collimated by the field lens 36b and then enters the second light modulation element 4b.
The blue color light L3 that has passed through the dichroic mirror 32 passes through the relay lens 37, is reflected by the mirror 34, passes through the relay lens 38, is reflected by the mirror 35, and enters the field lens 36c. The blue color light L3 is collimated by the field lens 36c and then enters the third light modulation element 4c.

  The light modulation element 4 is constituted by a spatial light modulation element in which a plurality of modulation elements are arranged. The plurality of modulation elements are capable of switching incident light independently of each other. Examples of the spatial light modulator include a transmissive liquid crystal light valve, a reflective liquid crystal light valve, and a digital mirror device (hereinafter referred to as DMD) in which MEMS mirrors as modulation elements are arranged. The light modulation element 4 of the present embodiment is configured by a transmissive liquid crystal light valve in which a plurality of modulation elements are two-dimensionally arranged.

  The light modulation element 4 modulates incident light for each modulation element based on the supplied image data to form an image. The first light modulation element 4a forms a red image, the second light modulation element 4b forms a green image, and the third light modulation element 4c forms a blue image.

  The color synthesis optical system 5 is constituted by a dichroic prism or the like. The dichroic prism has a structure in which four triangular prisms are bonded to each other. The surface to be bonded in the triangular prism becomes the inner surface of the dichroic prism. On the inner surface of the dichroic prism, a mirror surface that reflects the red color light L1 and transmits the green color light L2 and a mirror surface that reflects the blue color light L3 and transmits the green color light L2 are formed orthogonal to each other. .

  The green color light L2 incident on the dichroic prism is emitted as it is through the mirror surface. The red color light L1 and the blue color light L3 incident on the dichroic prism are selectively reflected or transmitted by the mirror surface and are emitted in substantially the same direction as the emission direction of the green color light L2. In this way, the light bundles of the three kinds of color light are superimposed and synthesized. The combined light is projected onto the display screen S by the projection optical system 6.

  In the present embodiment, the relative position of the second light modulation element with respect to the dichroic prism can be controlled by the optical path control unit 7 shown in FIG. When the position of the second light modulation element is changed, the optical path of the color light L2 after being projected from the projection optical system 6 changes. Thereby, it is possible to switch between a state in which the optical paths of the color lights L1 to L3 after being projected from the projection optical system 6 are substantially the same and a state in which the optical path of the color light L2 is shifted from the optical paths of the color lights L1 and L3.

  The optical path control unit 7 includes a display image data generation unit 71, a display image data correction unit 72, a calculation unit 73, a visual distance sensor 74, a display image size acquisition unit 75, and a movement unit 76. The optical path controller 7 calculates the display resolution based on the viewing distance and the size of the display image, displays the image in the normal mode when the display resolution is less than 20, and increases the display resolution when the display resolution is 20 or more. Display an image in resolution mode.

  The display image data generation unit 71 includes an interface, a color separation circuit, and the like, and receives input image data from a signal source (not shown) such as a PC. The input image data includes data indicating gradation values for each pixel and data indicating display timing. The display image data generation unit 71 separates tone value data for each color light and data indicating display timing from the input image data, and outputs these data to the display image data correction unit.

  The display image data correction unit 72 performs various image processing such as gamma processing on the data output from the display image data generation unit 71, thereby matching the data with the number of pixels of the light modulation element 4 and for normal mode use. The image data for each color light is generated. The generated image data is supplied to the first to third light modulation elements 4a to 4c. The display image data correction unit 72 receives a command to display an image in the high resolution mode from the calculation unit 73, generates corrected image data for the high resolution mode, and outputs the color light L2 that is a pixel shift target. The corrected image data is supplied to the second light modulation element 4b to be modulated. The corrected image data is data obtained by performing rendering processing on the image data for the normal mode so that the corrected image data becomes data indicating the gradation to be displayed on the sub pixel with the position of the sub pixel shifted from the normal mode. It is.

  The viewing distance sensor 74 detects the viewing distance between the observer and the display screen S, and outputs the detection result to the calculation unit 73. The configuration of the viewing distance sensor 74 is not particularly limited. As the visual distance sensor 74, for example, the following first to third visual distance sensors can be used.

  The first visual distance sensor includes a light emitting unit, a light receiving unit, and a calculation unit. The light emitting unit emits light such as infrared light when operated directly by an observer, and is provided, for example, on a remote control for operating the projector 1. The light receiving unit is provided in the projector main body, for example, receives light emitted from the light emitting unit, detects the intensity of the light and the direction in which the light is emitted, and outputs the detection result to the calculation unit. Based on the detection result, the calculation unit of the visual distance sensor 74 calculates the distance between the projector main body and the observer, and takes the distance (projection distance) between the projector main body and the display screen S into consideration. And the display screen S is calculated (viewing distance).

  The second visual distance sensor is configured by an imaging unit such as a CCD camera and a calculation unit, for example. The imaging unit is provided at a position away from the projector main body, and for example, images the display screen S and the observer from a bird's-eye view. The calculation unit performs processing such as pattern authentication on the image captured by the image capturing unit, detects the position of the display screen S and the position of the observer, and calculates the viewing distance in consideration of the installation position of the image capturing unit. . The first and second viewing distance sensors optically detect the position of the observer, but may be detected by ultrasonic waves, radio waves, or the like.

The third viewing distance sensor includes a first position detection unit provided alongside the display screen S, a second position detection unit provided alongside a remote controller operated by an observer, and a calculation unit. The first and second position detection units are configured by GPS or the like, for example. The calculation unit detects the viewing distance based on the position information of the display screen S output from the first position detection unit and the position information of the observer output from the second position detection unit.
The calculation units of the first to third visual distance sensors may be shared with the calculation unit 73.

  The display image size acquisition unit 75 includes a projection distance sensor that detects a projection distance, for example, and acquires the size of the display image B. The projection distance sensor captures the display image B with, for example, a CCD camera, determines the focus of the display image B, and detects the projection distance based on the focal length of the projection optical system 6 when the focus is in focus. As the projection distance sensor, for example, infrared light is emitted toward the display screen S, the infrared light reflected by the display screen S is received, the intensity is detected, and the projection distance is calculated based on the detected intensity. An active type may be used. When the projection optical system includes an autofocus mechanism, the projection distance can be detected using a part or all of the autofocus mechanism.

  When the second visual distance sensor is employed, the visual distance sensor can be used as a projection distance sensor. Further, when the visual distance sensor of the third example is employed, a projection is obtained by providing a third position detection unit in the projector body and comparing the detection results of the first and third position detection units. The distance may be obtained.

  In addition, since the optical characteristic of the projection optical system 6 is known, the distance between the imaging surface of the light projected by the projection optical system 6 and the projection optical system 6 is known. Usually, since the projector is used in a focused state, the distance between the imaging surface and the projection optical system 6 can also be used as the projection distance.

  The moving unit 76 receives the command from the calculation unit 73, and performs the second light modulation within a plane substantially orthogonal to the optical path (the traveling direction of the principal ray) of the colored light L2 emitted from the second light modulation element 4b. The element 4b is moved. The moving part 76 is comprised by an actuator etc., for example.

  Based on the detection result of the visual distance sensor 74 and the detection result of the projection distance sensor, the calculation unit 73 calculates the number of pixels arranged in the pixel arrangement direction in the range of the angle of view, that is, the display resolution. The calculation unit 73 determines whether the display resolution is 20 pixels / ° or more.

  When the display resolution is 20 pixels / ° or more, the calculation unit 73 causes the display image data correction unit 72 to generate correction image data for the color light L2 and moves so as to cause a pixel shift in the display image B. The unit 76 is controlled to move the second light modulation element 4b.

  When the display resolution is less than 20 pixels / °, the calculation unit 73 causes the display image data correction unit 72 to output image data for the normal mode and does not cause a pixel shift in the display image B. In response, the moving unit 76 is controlled to adjust the position of the second light modulation element 4b.

FIG. 4 is a diagram illustrating another configuration example that causes a pixel shift.
The optical path control system shown in FIG. 4 includes an optical element 77. The optical element 77 is disposed in the optical path between the second light modulation element 4 b and the color synthesis optical system 5. The optical element 77 is constituted by, for example, a transparent flat plate whose front and back surfaces are substantially parallel. The moving unit 76 displaces the optical element 77 to change the angle formed by the optical path between the second light modulation element 4 b and the color synthesis optical system 5 with the normal direction of the optical element 77. When this angle is changed, the optical path of the color light L2 after being emitted from the optical element 77 is shifted in parallel from the optical path of the color light L2 before being incident on the optical element 77, and the color light L2 at the stage of being emitted from the color synthesis optical system 5 Is shifted from the optical paths of the color lights L1 and L3.

  The configuration that causes the pixel shift is not limited to the first and second configuration examples. For example, when a DMD is used as the light modulation element, the pixel shift is caused by differentiating the amplitude of the MEMS mirror when reflecting the color light that is the pixel shift target and when reflecting the color light that is not the pixel shift target. Can be generated.

  The positional relationship between the sub-pixels P1 to P3 in the pixel shift is not particularly limited. For example, the positions of the three subpixels may not be the same, or the positions of the two subpixels may be the same, and the position of the remaining one subpixel with respect to these two subpixels may be It may be shifted. Further, the direction in which the sub-pixels are shifted may be shifted to one of the two arrangement directions of the pixels, or may be shifted to one and the other.

  In the high resolution mode, it is only necessary that the positions of the sub-pixels by the first to third color lights are shifted from each other during at least a part of the display period of one frame. For example, the display period of one frame may include a period in which the positions of the sub-pixels constituting one pixel are shifted from each other and a period in which the positions of the sub-pixels constituting one pixel are aligned.

  Next, a mechanism for determining the display resolution will be described. FIG. 5 is a plan view showing the positional relationship between the projector 1, the display screen S, and the viewpoint V of the observer, and FIG. 6 is a diagram schematically showing the processing flow of the projector when displaying an image.

In FIG. 5, a symbol d ₀ indicates the size of the display image B in one pixel arrangement direction (for example, the X direction), a symbol d ₁ indicates a viewing distance, a symbol d ₂ indicates a projection distance, and a symbol θ indicates an image. Each corner is shown. The size d ₀ [m] is determined by the projection distance d ₂ [m] of the projection optical system 6 and the like. The angle of view θ [°] is expressed by the following formula (1).
θ = 360 / π × arctan (d ₀ / 2d ₁ ) (1)
If the number of pixels arranged in the X direction is N (N is a positive integer), the number of pixels included in the angle of view of 1 ° in the X direction, that is, the display resolution is N / θ [pixel / °]. Based on such a relational expression, the calculation unit 73 calculates the display resolution using the size d ₀ and the viewing distance d ₁ of the display image. The display resolution can also be obtained from the pixel pitch, and the reciprocal of the angle of view corresponding to the pixel pitch is the display resolution. The computing unit 73 may read a numerical value from a numerical table of display resolutions according to the projection distance and the viewing distance.

  As shown in FIG. 6, in order to display an image, the viewing distance is measured by the viewing distance sensor 74 (step S11). Further, the display image size acquisition unit 75 acquires the size of the display image B (step S12). Then, using the measurement result of the visual distance sensor 74 and the measurement result of the display image size acquisition unit 75, the calculation unit 73 obtains the display resolution (step S13) and determines whether the display resolution is 20 or more. (Step S14). When the display resolution is 20 or more (step S14: Y), the second light modulation element 4b is moved by the moving unit 76 (step S15), and the corrected image for the high resolution mode is displayed by the display image data correcting unit 72. Data is generated (step S16). When the display resolution is less than 20 (step S14: N), the display image data correction unit 72 generates display image data for the normal mode (step S17). Based on the corrected image data for the high resolution mode or the display image data for the normal mode, an image is formed on the second light modulation element 4b (step S18). Further, by forming an image on the first and third light modulation elements, an image by pixel shift or an image not by pixel shift is displayed according to the display resolution.

  In the high resolution mode, an image having a display resolution of 20 or more is displayed, so that the observer cannot distinguish colors in units of sub-pixels of the display image B, and the generation of false colors due to pixel shift is not recognized. When the pixel pitch is different in the two arrangement directions of the pixels, an effect of suppressing the occurrence of false colors can be obtained by satisfying the above condition in the direction where the pixel pitch is small. By satisfying the above conditions in the direction in which the pixel pitch is large, the effect of suppressing the occurrence of false colors is enhanced.

  In the normal mode, an image having a display resolution of less than 20 is displayed. Therefore, if an image is displayed by shifting pixels, a false color is easily recognized. However, when the display resolution is less than 20, an image is displayed without pixel shifting, so that false colors do not occur.

  Note that it is not necessary to calculate the display resolution every time an image is displayed, and the display resolution may be calculated according to a command from a user of a projector such as an observer or another user. Further, it is only necessary to have an operation mode that automatically switches between the normal mode and the high-resolution mode so as to suppress false colors, and it may be possible to designate on / off of this operation mode.

Hereinafter, the results of investigation on the relationship between display resolution (N / θ) and image quality will be described.
As a survey method, a subjective evaluation method is adopted in which the subject is allowed to appreciate the display image and the image quality of the display image is comprehensively evaluated. The international standard ITU-R BT. The DSCQS method (double stimulus continuous quality scale method) defined in 500 was used. In the international standard of subjective evaluation method, select 15 or more non-experts as subjects, select a person who has the ability to judge correctly with normal visual acuity and normal color vision, stable evaluation with few errors It is stipulated that the person who can do it is selected, and these conditions are satisfied.

The outline of the experimental method is as follows.
On the display screen, the image of the example to which the present invention is applied and the image of the comparative example are displayed side by side as one evaluation image. The image of the embodiment is an image in which the green sub-pixel is shifted by approximately half the pitch of the sub-pixel in two directions of the pixel arrangement direction. The image of the comparative example is an image that is not subjected to pixel shifting. In the embodiment, an image in which the position of the green sub-pixel and the gradation value are matched is displayed by the data obtained by performing the rendering process on the same original image data as the image of the comparative example. A plurality of evaluation images are observed for each subject, and the image quality of the example and the image quality of the comparative example are evaluated as evaluation values ranging from 1.0 (very bad) to 5.0 (very good) for each evaluation image. I let you.

  The arrangement of images was randomly changed between the example and the comparative example, and the evaluation images before and after the change were evaluated. In addition to the evaluation image, a dummy evaluation image in which two identical images (for example, an image without pixel shifting) are arranged is evaluated, and the result is used to determine the evaluation stability and evaluation error of the subject. Provided. Before observing the next evaluation image, an opportunity to observe the gray image was provided so that the impression of the previous evaluation image does not affect the impression of the next evaluation image.

  The image quality was evaluated as an overall sense of resolution including factors such as resolution, sharpness, fine line reproducibility, shaggy, and moire. If a false color is observed, it is considered that the evaluation of the image quality is lowered due to a color blur or the like, and the presence or absence of the occurrence of the false color is considered to be reflected in the evaluation result. The same experiment was conducted with different viewing distances for each subject. That is, the number of pixels included in an angle of view of 1 ° was changed by changing the viewing distance while fixing the size of the display image.

The experimental conditions were set as follows.
Preliminary experiments were conducted to confirm the occurrence of false colors, and the range in which the viewing distance was changed was selected while avoiding the viewing distance where the false color was clearly recognized. The viewing distance was set in three stages of 1 m, 2 m, and 3 m. The projection distance was 3.54 m, and the display image size was 75 inches diagonal. The number of pixels of the entire display image was 1920 × 1080 (full HD format). Of the displayed images, approximately half is the image of the example, and the remaining half is the image of the comparative example. Three types of images were used as evaluation images: landscape images, portrait images, and still life images.

The experimental results were analyzed as follows.
First, the obtained evaluation value was normalized to 0 to 100 (%), and the difference between the evaluation values normalized between the image of the example and the image of the comparative example was obtained. The evaluation value for each subject was compared with the average of the evaluation values for the entire subject to determine the reliability of the subject. About the test subject who performed the evaluation remarkably different from the average of the whole test subject, the evaluation value was removed as an abnormal value. And the average value and standard deviation of the evaluation value were calculated about the data except the abnormal value. This average value was used as a psychological evaluation value, and a 95% confidence interval of the evaluation value was calculated from the standard deviation. Significant differences were determined from psychological evaluation values and confidence intervals.

  FIG. 7 is a graph showing the subjective evaluation index value of the resolution with respect to the viewing distance, and is based on the results of the above-described experiment and analysis. The horizontal axis of the graph of FIG. 7 is the viewing distance [m], and the display resolution [pixel / °] corresponding to the viewing distance is also shown in FIG. The vertical axis represents the subjective evaluation index value [%] of the example with respect to the comparative example. The subjective evaluation index value is a relative value indicating a decrease in image quality as a positive value, and the subjective evaluation index value is negative and the absolute value increases, the image quality of the example is felt higher than the image quality of the comparative example. It shows that.

  As shown in FIG. 7, the image quality of the example is evaluated to be superior to the image quality of the comparative example for any of the evaluation images 1 to 3 in the display resolution range of 20 to 60. It can be seen that the resolution is enhanced by shifting the pixels within the resolution range.

  As the display resolution increases, the absolute value of the subjective evaluation index value monotonously decreases and gradually approaches zero. This is presumably because the pixel size becomes smaller as the display resolution becomes higher, and the luminance of subpixels whose positions are shifted cannot be distinguished in units of subpixels. That is, it is considered that the resolution is not changed between the example and the comparative example by decreasing the apparent increase in the number of pixels due to pixel shifting. From this, it can be seen that the display resolution should be set to 20 in order to effectively enhance the resolution and to maximize the size of the display image.

  By the way, when a false color occurs, it is considered that the false color becomes noise and the image quality is lowered. If a false color is generated in a range where the display resolution is 20 or more and 60 or less, it is considered that the subjective evaluation index value protrudes downward near the display resolution where the false color does not occur and shows a minimum value. In the graph of FIG. 7, the absolute value of the subjective evaluation index value monotonously decreases as the display resolution increases, and is the maximum value when the display resolution is 20. Therefore, a false color occurs when the display resolution is 20 It is thought that it is not. In addition, the higher the display resolution, the lower the possibility that false colors will be generated. Therefore, if the display resolution is 20 or higher, the occurrence of false colors is considered to be suppressed, and the validity of the preliminary experiment results has been confirmed. It was.

  In the projector 1 having the above configuration, the luminance of the sub-pixel P2 of the display image B is identified separately from the luminance of the sub-pixels P1 and P3 in the high-resolution mode, and the resolution of the display image B is enhanced. . Since the position of the sub-pixel P2 corresponding to the green color light having the highest human visibility among the red, green, and blue color lights is shifted from the positions of the other sub-pixels P1 and P3, the resolution is effectively improved. Is increased. The sub-pixel P2 is shifted so as to overlap with the adjacent pixel P. In particular, since the shift amount of the position of the sub-pixel P2 is substantially half of the sub-pixel pitch, the sense of resolution is effectively enhanced.

  In addition, an image is displayed by shifting pixels when the display resolution is 20 or higher (high resolution mode), and an image is displayed without shifting pixels when the display resolution is less than 20 (normal mode). Therefore, the sense of resolution can be effectively enhanced under conditions where false colors are unlikely to occur.

  As described above, since the resolution can be obtained while suppressing the generation of false color without increasing the number of modulation elements of the light modulation element 4, it is possible to reduce the cost of the light modulation element 4 and reduce the cost. However, the projector 1 can obtain a high-quality display image. In addition, the mechanism for changing the optical path can be simplified as compared with the case of performing display by shifting the pixels in a time division manner by aligning the optical paths of the three types of color light.

[Second Embodiment]
Next, a projector according to a second embodiment will be described. The second embodiment is different from the first embodiment in that the optical path control unit determines the display resolution based on the data indicating the viewing distance input from the user and the data indicating the size of the display image, and high resolution. This is a point for switching between the mode and the normal mode.

FIG. 8 is a configuration diagram of the optical path control unit 8 in the second embodiment, and FIG. 9 is a table showing examples of viewing distances associated with the use environment.
As shown in FIG. 8, the optical path control unit 8 includes an input unit 81 and a storage unit 82 instead of the visual distance sensor 74 and the display image size acquisition unit 75 of the first embodiment. The input unit 81 receives data indicating the viewing distance and data indicating the size of the display image from a projector user such as an observer or a user other than the observer. The data indicating the viewing distance and the data indicating the size of the display image are numerical values indicating the actual viewing distance and the size (or projection distance) of the display image, for example. In the present embodiment, the optical path control unit 8 is configured so that the user selects and inputs the display mode and the data indicating the viewing distance and the data indicating the projection distance are substantially input. Has been.

  In general, a projector is designed with the intended use and usage environment, and a recommended display image size and viewing distance are described in a catalog or the like. As shown in Table 1 of FIG. 9, the reference value of the space where the projector is used is generally determined depending on the use environment, and the reference value of the viewing distance is approximately determined by the reference value of the space. It is known that the size of a display image that is easy to see is generally determined by the viewing distance, and the reference value of the display image size or the reference value of the projection distance according to the viewing distance is approximately determined.

  The storage unit 82 is configured by, for example, a non-volatile memory, and the storage unit 82 stores a reference value for the viewing distance and a reference value for the size of the display image in association with the display mode. The data indicating the display mode stored in the storage unit 82 is displayed as an image on a display panel (not shown), for example, and the user selects the display mode according to the application and usage environment of the projector, and selects the selected display mode. Input to the input unit 81. The calculation unit 73 receives the input result of the user, and reads the reference value of the viewing distance and the reference value of the size of the display image associated with the target display mode from the storage unit 82. Then, the calculation unit 73 calculates the display resolution in the same manner as in the first embodiment, assuming that the viewing distance reference value and the display image size reference value are the actual viewing distance or the display image size. Then, the computing unit 73 controls switching between the high resolution mode and the normal mode based on the calculated display resolution.

  In the projector of the second embodiment, for the same reason as in the first embodiment, it is possible to display an image that provides a sense of resolution while suppressing the occurrence of false colors at a low cost. Further, it is possible to omit a sensor for measuring the viewing distance and a sensor for measuring the size of the display image, and a projector having a simple configuration can be obtained.

  The technical scope of the present invention is not limited to the above embodiment. Various modifications are possible without departing from the gist of the present invention. For example, although the above embodiment has been described using an example in which there is one observer, the present invention can also be applied when there are a plurality of observers. For example, the viewing distance of each of a plurality of observers is detected, and switching between the high-resolution mode and the normal mode is performed based on the observer who has the shortest viewing distance, that is, the smallest number of pixels per 1 ° field of view. You may make it control. In addition, by performing known weighting evaluations based on the distribution of viewing distances of multiple observers, the high-resolution mode and normal mode are optimized so that the effect of suppressing false colors is optimized by multiple observers. You may make it control switching of. Further, depending on the use of the projector 1 or the like, the viewpoints of a plurality of observers may be represented by any one of the viewpoints to control switching between the high resolution mode and the normal mode.

1 ... projector, 2 ... illumination system, 3 ... color separation optical system,
4 ... light modulation element, 4a ... first light modulation element, 4b ... second light modulation element,
4c ... third light modulation element, 5 ... color synthesis optical system, 6 ... projection optical system,
7, 8 ... optical path control unit, 20 ... optical axis, 21 ... light source,
22 ... 1st lens array, 23 ... 2nd lens array,
24... Polarization conversion element, 25.
31, 32 ... Dichroic mirror, 33-, 35 ... Mirror,
36a-36c ... Field lens, 37, 38 ... Relay lens,
71 ... Display image data generation unit, 72 ... Display image data correction unit,
73 ... Calculation unit, 74 ... Visual distance sensor, 75 ... Display image size acquisition unit,
76 ... moving part, 77 ... optical element, 81 ... input part, 82 ... storage part,
211 ... light source lamp, 212 ... parabolic reflector, 221 ... lens element,
231 ... Lens element, 241 ... Polarization conversion unit, B ... Display image,
B1 ... first color image, B2 ... second color image, B3 ... third color image,
L ... light, L1-L3 ... color light, P ... pixel, P1-P3 ... sub-pixel,
S ··· display screen, V ··· point of _view, the size of the _d 0 ··· display _{image, d} 1 ··· viewing distance,
d ₂ ... Projection distance

Claims (8)

An image display device capable of displaying an image composed of a plurality of arranged pixels on a display screen, wherein the pixels of the image are composed of a plurality of sub-pixels corresponding to colored lights having different wavelengths,
The plurality of pixels constituting each of the plurality of pixels when the number of pixels arranged in the arrangement direction of the pixels within a range of an angle of view of an observer with respect to a display image displayed on the display screen is less than 20 pixels. When the positions of the sub-pixels are displayed at substantially the same position and the number of pixels is 20 pixels or more, at least one sub-pixel of the plurality of sub-pixels constituting each of the plurality of pixels is set as another sub-pixel. An image display device characterized by displaying at a position different from a pixel. An illumination system that emits colored light corresponding to each of the plurality of sub-pixels;
A plurality of light modulation elements including a light modulation element that modulates each of the plurality of color lights emitted from the illumination system;
A color synthesis optical system for synthesizing the color lights modulated by the plurality of light modulation elements;
A projection optical system that projects the color light synthesized by the color synthesis optical system onto the display screen;
Based on the viewing distance between the observer and the display screen and the determination result of whether or not the number of pixels is 20 pixels or more based on the size of the display image, modulation is performed by the plurality of light modulation elements. An optical path control unit that variably controls an optical path after being projected from the projection optical system for at least one color light of the plurality of colored lights,
The image display apparatus according to claim 1, further comprising:   The image display apparatus according to claim 2, wherein the optical path control unit includes a size acquisition unit that acquires a size of the display image based on a projection distance of the projection optical system.   4. The image according to claim 2, wherein the optical path control unit includes a display image data correction unit that corrects data of an image displayed by the at least one color light based on a change amount of an optical path of the color light. Display device.   When the number of pixels is 20 pixels or more, a sub-pixel corresponding to color light having the highest human visibility among the plurality of sub-pixels constituting each of the plurality of pixels is shifted from other sub-pixels. The image display device according to claim 1, wherein the image display device is displayed at a different position.   The at least one of the plurality of sub-pixels constituting each of the plurality of pixels is arranged between sub-pixels constituting another pixel when the number of pixels is 20 pixels or more. The image display apparatus as described in any one of Claims 1-5.   The said optical path control part detects the said visual distance and the size of the said display image, and calculates | requires the said pixel number based on this detection result, The Claim 1 characterized by the above-mentioned. Image display device.   The said optical path control part calculates | requires the said pixel number based on the data which show the said visual distance inputted from the user, and the data which show the size of the said display image, Any one of Claim 2-6 The image display device according to claim 1.

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