WO2006129797A1

WO2006129797A1 - Rear projection type display device

Info

Publication number: WO2006129797A1
Application number: PCT/JP2006/311101
Authority: WO
Inventors: Ichiro Matsuzaki
Original assignee: Kuraray Co., Ltd.
Priority date: 2005-06-03
Filing date: 2006-06-02
Publication date: 2006-12-07
Also published as: JPWO2006129797A1; TW200705088A

Abstract

It is possible to provide a rear projection type display device capable of suppressing moire. A rear projection type display device projects/displays a video light generated by a DMD to a lenticular lens sheet (111) formed by a plurality of lenticular lenses (211). The display device Fourier-transforms the luminance pattern in the pixels during a black image display and satisfies the relationship A/B < 0.045 wherein A is the amplitude intensity value at the cycle matched with the one cycle of the DMD pixel and B is the average luminance value in the imaging area range.

Description

Specification

Rear projection display

Technical field

[0001] The present invention relates to a rear projection display device that projects and displays an image from behind a screen.

Background art

Conventional screens generally used in rear projection televisions have used concentric Fresnel lenses and vertical stripe lenticular lenses. In such a rear projection screen, moiré failure occurs due to the periodic structure of the pixels and the screen projected on the screen. Therefore, the pitch ratio between the pixel pitch Gp and the lens pitch of the lenticular lens (hereinafter abbreviated as the wrench pitch Lp) is optimized and used. For example, Patent Document 1 discloses the preferred U and combination of the pitch ratio between the pixel pitch and the wrench pitch (pixel pitch Z lens pitch; this is abbreviated as GpZLp).

In recent years, a rear projection display device using a digital micromirror device (hereinafter sometimes referred to as DMD) has been proposed. In such a rear projection display device, light is applied to the light source power DMD, and the reflected light reflected by the mirror surface of the DMD is projected onto the rear projection screen through the lens. An example of a projection apparatus using a DMD that projects light onto the rear projection screen is disclosed in Patent Document 2.

[0004] In the projector apparatus using the DMD disclosed in Patent Document 2, the minute DMD is arranged in the same manner as the arrangement of pixels for one screen (frame) of the image data. When each DMD becomes valid / invalid as a pixel based on the video data, each DMD tilts in a predetermined direction and is turned on / off accordingly.

Reflected light reflected by the reflecting surface of the DMD that is turned on is emitted to the outside of the projector device via various lenses. Thereafter, an image is formed on an image display surface of an image display object (not shown) such as a screen, and thereby an image is projected on the image display surface. In such a DMD, a mirror that reflects light is supported by a support portion. The drive device changes the inclination of the reflecting surface by controlling the mirror supported by the support portion. The support portion is a force supported on the back surface of the reflection surface of the mirror. The reflection diffusion characteristics, particularly the reflection angle, of the reflection surface on the back side of the support portion, that is, the support portion changes.

[0006] Originally, when displaying a black screen (hereinafter sometimes referred to as a dark screen), light from the light source is not reflected in the video viewing direction on the mirror surface. However, the DMD mirror reflects part of the light in a direction that is not originally intended because the reflection characteristics of the reflecting surface at the support part have changed. This partially unintended reflected light is emitted in the video viewing direction, so it is recognized as a bright spot in the pixels on the screen surface.

[0007] In a rear projection display device using DMD, when a black screen is displayed, a pixel where a bright spot is generated interferes with a lenticular lens, and a moire failure may occur. Furthermore, since the bright spot of the pixel is very small, it tends to interfere with a lenticular lens with a high degree of modulation. In particular, when a black screen is displayed, this bright spot is noticeable visually, and therefore a moire disorder in the black screen display is easily visible.

Hereinafter, the moire on the black screen is referred to as dark moire. On the other hand, moire on a white screen (hereinafter sometimes referred to as a bright screen) is referred to as a bright moire.

[0008] Patent Document 1: Japanese Patent Laid-Open No. 8-032424

Patent Document 2: JP-A-7-020586

Disclosure of the invention

Problems to be solved by the invention

The present invention has been made in view of the above problems, and an object thereof is to provide a back projection display device capable of suppressing moire.

Means for solving the problem

[0010] A rear projection display device according to the present invention includes a light source, a digital micromirror device that modulates light emitted from the light source by a minute mirror for each pixel according to an image signal, and the digital micromirror device. In a rear projection type display device having a projection optical system that projects modulated image light and a screen having a periodic structure on which the projected image is formed, a black image signal is input to the digital micromirror device. When Includes 4 or more pixels arranged in the horizontal direction and 1 or more pixels arranged in the vertical direction at the center of the image projected on the diffusion plate with a gain of 7.5 installed in place of the screen at the screen mounting position When the luminance of the area is measured from the front side of the anti-projection side with a resolution of 25 or more per pixel, and the luminance is integrated in the direction perpendicular to the periodic structure of the screen, the luminance pattern is Fourier transformed, and one cycle of the DMD pixel A / B <0.045, where A is the amplitude intensity value in the period that coincides with the minute, and B is the average luminance value in the imaging area range. In such a configuration, it is possible to reduce the degree of modulation of the bright spot in the pixel when displaying a black screen, so that dark moire can be suppressed.

Furthermore, the projection optical system is provided with a stop for limiting the exit pupil. Preferably, the stop restricts the exit pupil only in the direction of driving the mirror of the digital micromirror device. This makes it possible to suppress moire without restricting the projection light more than necessary.

The invention's effect

[0012] According to the present invention, it is possible to provide a rear projection display device capable of suppressing dark moire.

Brief Description of Drawings

FIG. 1 is a schematic diagram showing a configuration example of a rear projection type apparatus according to the present invention.

FIG. 2 is a schematic diagram showing a configuration example of a pixel of a rear projection screen according to the present invention.

FIG. 3 is a schematic diagram showing a configuration example of a pixel of a rear projection screen according to the present invention.

FIG. 4 is a schematic diagram showing an example of the overall configuration of a projector according to the present invention.

FIG. 5 is a block diagram showing an example of an internal configuration of a projector according to the present invention.

FIG. 6 is a diagram for explaining a bright spot generation mechanism in a display device using DMD.

FIG. 7 is a diagram showing a luminance pattern in the embodiment.

FIG. 8 is a diagram showing the result of Fourier transform on the luminance pattern in the example. Explanation of symbols

[0014] 1 ... rear projection display device, 11 ... rear projection screen, 12 ... projector, 111— lenticular lens sheet, 211 ... lenticular lens, 212 ... shading pattern, 11 2 ... Fresnel lens sheet, 221 ... Fresnel lens

30 ... Drive device 31 ... Light source 32 ... Condenser lens 33 ... Reflection mirror 34 ... Color wheel 341 ... Color filter 342 ... Rotation control device 35 ... Shaping lens, 361 ... Reflection mirror, 371--DMD, 381 ··· Relay 'lens, 391 ··· Wobbling part, 40 ··· Projection lens, 41 ··· Iris

51 ... Power supply unit, 52 ... Light source drive unit, 53 ... Signal processing unit, 54 ... Control unit, 551 ... Frame 'memory, 561 ... Small movable mirror, 571 ... Dichroic mirror', 581 ... Mirror Best Mode for Carrying Out the Invention

Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

First, the configuration of a rear projection display device according to the present invention will be described with reference to FIG. FIG. 1 is a schematic plan view showing an example of the configuration of a rear projection display device according to the present invention. As shown in FIG. 1, the rear projection display device 1 includes a rear projection screen 11 and a projector 12. In the following, rear projection screen 11 may be abbreviated as screen 11.

The rear projection screen 11 includes a lenticular lens sheet 111 and a Fresnel lens sheet 112.

The lenticular lens sheet 111 has a lenticular lens 211 and a light shielding pattern 212. The lenticular lens 211 is provided on the light incident surface side of the lenticular lens sheet 111. The lenticular lens 211 is composed of a plurality of vertically long cylindrical lenses having a force-marrow shape, and they are arranged at equal intervals. The light shielding pattern 212 is a light absorption layer made of black ink or the like, and is provided in a part other than the light condensing part by the lenticular lens 211.

The Fresnel lens sheet 112 is close to the lenticular lens sheet 111. The Fresnel lens sheet 112 includes a Fresnel lens 221 and the Fresnel lens 212 is provided on the light emission surface. The Fresnel lenses 212 are lenses arranged concentrically at a fine pitch at equal intervals.

In FIG. 1, the direction perpendicular to the paper surface is the extending direction of the lenticular lens 211, and the direction parallel to the paper surface is the arrangement direction of the lenticular lens 211. Also later As described above, the extending direction and the arranging direction of the lenticular lenses 211 correspond to the vertical direction and the horizontal direction of the screen 11. In other words, the extending direction and the arranging direction are a vertical direction and a horizontal direction in a state where the screen 11 is installed. When the viewer visually recognizes the screen 11, the extending direction and the arranging direction are the vertical direction and the horizontal direction in such an installation state.

As shown in FIG. 1, in the rear projection display device 1, the light from the projector 12 is also projected on the rear surface of the screen 11. Specifically, the opposite side force of the Fresnel lens 221 is also incident, and the incident light passes through the Fresnel lens sheet 112 and is emitted to the Fresnel lens 221 side. The emitted parallel light or convergent light is greatly diffused in the horizontal direction by the lenticular lens sheet 111. As a result, it is possible to observe an image in a wide visual field range in the horizontal direction.

FIG. 2 shows an example of a pixel arrangement in the rear projection screen 11 according to the present invention.

As shown in FIG. 2, the pixels 23 of the screen 11 according to the present invention are arranged in a diamond shape. Specifically, the pixel 23 has a shape in which a rectangular pixel is inclined when observed from the viewing side. The plurality of pixels 23 are arranged in such an inclined state, and are arranged in a state in which the sides are arranged substantially parallel to each other. Therefore, the pixels 23 are arranged in the inclined direction in an inclined state. In other words, the pixel 23 is a tilted pixel arrayed in the horizontal and vertical directions as in the conventional pixel.

FIG. 3 shows the pixel width and pixel arrangement period of the screen 11 according to the present invention. FIG. 3 (a) is a schematic plan view illustrating a rhombus pixel according to the present invention, and FIG. 3 (b) is a schematic plan view illustrating a conventional square pixel.

As shown in FIG. 3 (a), the pixels 23 arranged in an inclined state are obtained by rotating the square pixels 24 by 45 °. Therefore, the pixel width of the pixels 23 arranged in an inclined state is about (2) dT ^ l.4dT when the pixel width dT of the square pixel 24 is set. The pixel arrangement period Δ of the pixels 23 arranged in an inclined state is half the width in the horizontal direction, while the pixel arrangement period T of the square pixels 24 is the length of one side of the square. For this reason, the pixel arrangement period Δ of the pixels 23 arranged in the inclined state is equal to the square pixel 24. For the pixel array period T, Δ = (2) ΤΖ2 ^ 0.7. Also, the pixel effective portions 230 and 240 shown in FIG. 3 are the opening portions of the pixels 23 and 24, respectively. As shown in Fig. 3, X and y are the horizontal and vertical position coordinates, and the origin is the pixel center.

[0021] Next, the configuration of the projector 12 of the rear projection display device 1 according to the present invention will be described with reference to FIG.

FIG. 4 shows an example of the overall configuration of the projector 12 according to the present invention. 4A is a schematic perspective view, and FIG. 4B is a schematic plan view showing the optical arrangement.

As shown in FIG. 4, when the driving device 30 of the projector 12 drives the light source 31, the light source 31 emits white light as projection light. This white light is incident on the color wheel 34 through the condenser lens 32 and the reflection mirror 33 after unnecessary ultraviolet rays are removed by a UV filter (not shown). When the incident white light passes through the color wheel 34, one of red light, green light, and blue light is separated as will be described later. The separated light is incident on the shaping lens 351 and is bent by the reflection mirror 361 through the shaping lens 351. Any of the bent red light, green light, and blue light is irradiated to the DMD 371 via the total reflection prism 364.

[0023] As described above, the minute movable mirror 561 of the DMD 371 is turned on by the video data, so that any one of the irradiated red light, green light, and blue light is reflected as effective reflected light. The The reflected image light is guided to the superimposing unit 391 through the relay lens 381. Thereafter, the image light is combined and projected as color image light on the screen 11 through the projection lens 40 and the aperture 41 while being waved up and down by the wobbling unit 391.

[0024] Next, the drive device 30 for the projector 12 according to the present invention will be described in detail with reference to FIG.

FIG. 5 is a block diagram showing an example of the internal configuration of the drive device 30. As shown in FIG.

The drive device 30 includes a power supply unit 51, a light source drive unit 52, a signal processing unit 53, and a control unit 54. The power supply unit 51 includes a power supply circuit, a DC power supply, and the like, and supplies power to various functional units to start the operation of the projector 12. The light source driving unit 52 drives the light source 31 to turn on and emits image light from the light source 31. The signal processing unit 53 includes, for example, an AD conversion circuit, a gamma correction circuit, an interface circuit, and the like. Various display signals displayed by the projector 12 are input to the signal processing unit 53 from an external device (not shown) such as a video device or a personal computer. The signal processing unit 53 performs signal processing such as AZD conversion on the input display signal, and converts it into a digital display signal that can be processed inside the driving device 30. This digital display signal is input from the signal processing unit 53 to the control unit 54.

[0026] The control unit 54 includes various control circuits, an MPU, a CPU, and the like, generates a wheel control signal (color control signal), and controls the operation of the color wheel 34 based on the wheel control signal. . As shown in FIG. 5, the color wheel 34 includes a color filter 341 and a rotation control device 342. The color filter 341 is also configured with three color filter forces of red, green, and blue. The rotation control device 342 fixes the color filter 341 so as to be rotatable, and controls rotation at a predetermined rotation angle ′. Specifically, a color wheel control signal is generated using the system clock and input to the rotation control device 342. The rotation control device 342 rotates the color filter 341 at a predetermined rotation speed 'rotation angle based on the input rotation control signal. The rotation control device 342 arranges a part of the red, green, or blue filter on the optical path by changing the rotation speed. Thereby, the color filter 341 also separates the white light from the light source 31 from red light, green light, and blue light.

The control unit 54 controls the operation of the DMD 371 based on the light valve control signal, turns on the micro movable mirror 561, and generates effective reflected light. The minute movable mirrors 561 are arranged corresponding to the frame 'memory 551. The frame 'memory 551 writes the video data to the minute movable mirror 561 sequentially for each frame according to the valve control signal. The minute movable mirror 561 in which the video data is written is turned on. Specifically, each micro movable mirror 561 is tilted by a predetermined angle, for example, + 12 ° with respect to the reference state when the frame memory 551 is turned on. When video data is written to the minute movable mirror 5 61, video light is generated as effective reflected light from the video data.

[0028] Conversely, each of the micro movable mirrors 561 is the opposite of the frame 'memory 551 when it is turned off. Tilt in the direction by a certain angle, eg –12 °. As a result, the reflected light reflected by the mirror surface of the minute movable mirror 561 is switched so that the effective reflected light necessary for forming the image and the invalid reactive reflected light have an optical path difference of 24 °. As described above, the on-off state of the micro movable mirror is controlled based on the light control signal from the control unit 54 via the frame 'memory 551', and the effective reflected light Z is invalid reflected in response to the on-Z state. Produce light.

At this time, the control unit 54 synchronizes the operation of the DMD 371 with the operation of the color wheel 34. Specifically, the control unit 54 inputs a light valve control signal synchronized with the wheel control signal to the DMD 371. As an example, the controller 54 synchronizes the DMD 371 with the operation of the color wheel 341 by generating this light valve control signal from the wheel control signal.

For example, when white color from the light source 31 becomes red light by the color filter 341, the control unit 54 transmits the white light to a part of the red filter of the color filter 341. In synchronization with this, the control unit 54 reflects the effective reflected light as red light on the small movable mirror 561 of the DMD 371.

In such a projector 125 with one DMD 371, the color wheel 34 divides red, green, and blue color video light in a time-division manner and displays a color image on the screen 11. In this one-chip system, red, green, and blue power image lights are projected alternately on the screen 11 in a time-sharing manner. Because there is a limit to recognizing red, green, and blue images that the human eye switches at high speed, each projected image light is superimposed on the afterimages of red, green, and blue as color images. Visible.

[0031] Generally, in the screen 11, the directional characteristics in the horizontal direction are widened and enlarged compared to the directional characteristics in the vertical direction. Therefore, as shown in FIG. 1, a lenticular lens 211 in which lenticular lenses 211 are periodically arranged in a vertical stripe shape is often used! In this case, the vertical stripe moire is generated by the interference between the vertical stripe structure of the lenticular lens 211 and the arrangement structure of the DMD 371.

When a DMD is used as a light bulb, the pixel boundary is narrow, so the pixel modulation is low and moire is not noticeable in a bright image. However, as described above, when displaying a dark image, the support part of the micromirror Due to the reflection of the As a result, a bright spot is generated at the center of the pixel corresponding to the support portion of the mirror, and moire may occur.

[0032] Such moire has a ratio between the pixel arrangement pitch Gp and the lenticular lens pitch Lp. Gp / Lp is 2.5! / ヽ ί or 2. 8 <Gp / Lp <3.5! / ヽ ί 3. It stands out in the range of 8 <Gp / Lp <4.2. Special [Gp / Lp <l. 4 Yes! / ヽ ί or 1. 6 <Gp / Lp <2. 5 Yes! / ヽ ί 2. 85 <Gp / Lp <3. 15 Yes! /, Ί 3. Easily noticeable in the range of 88 <Gp / Lp <4.15. Furthermore, it is most noticeable in the range of GpZLp <1.3 or 1.7 <Gp / Lp <2.3.

[0033] In the present invention, the modulation degree of the pixel array is lowered, and the harmonics included in the spatial frequency component of the pixel array have a frequency around the frequency of the vertical stripe structure of the lenticular lens 211. Since the intensity can be attenuated, the vertical stripe moire can be reduced. In conventional display devices, moire is particularly noticeable in the range of the pixel pitch and wrench pitch, but in the display device of the present invention, vertical stripe moire can be reduced even in these ranges.

[0034] This will be described more specifically with reference to FIG.

Fig. 6 shows an outline of the direction in which the light incident on the DMD panel is emitted. The light incident on the DMD enters the output optical system as effective reflected light by regular reflection in the on state, but is not incident on the output optical system in the off state and is absorbed by the trap as ineffective reflected light. However, since there is diffuse reflection light at the DMD micromirror support, a part of the light enters the output optical system regardless of the DMD being off. Therefore, when a black image signal is input to the DMD, the pixel center area corresponding to the mirror support portion becomes bright and bright on the screen.

Therefore, the larger the angle at which the DMD mirror is driven, the lower the luminance of the bright spot in the pixel. The upper limit of the drive angle is regulated by force such as manufacturing conditions and response speed, but in the above example, it is ± 12 °, and it is preferably ± 15 or more from the viewpoint of preventing moire.

Example

[0036] A translucent resin with a gain of 7.5 is provided on the screen surface of a rear transmissive display device having a DMD. A translucent diffuser plate having a light diffusing fine particle force was attached. At this time, the horizontal period Gp of the DMD pixels projected on the diffusion plate was 0.5 mm.

[0037] First shooting camera "FVAS_5MIC" was placed in front of the display device to display a black screen, and the brightness was measured in a dark room. In addition, the aperture 41 was not installed. There were about 10 DMD pixels in the horizontal direction and about 8 DMD pixels in the vertical direction. At this time, the resolution of the camera, that is, the number of CCD elements, was about 100 per 0.5 mm, which is the horizontal direction of DMD.

[0038] The luminance of the black screen display was measured under the above conditions, the luminance of two DMD pixels was integrated in the vertical direction, and the horizontal luminance pattern in the black screen was measured. As a result, a concavo-convex pattern with luminance for one cycle of the DMD pixel was measured. In Example 1, the ratio of the maximum value to the minimum value of the periodic luminance was 1.15. (See Figure 7)

[0039] Next, a lenticular lens sheet was attached to the display device, and a black screen display was observed. The pitch Lp of the lenticular lens is 0.518, 0. 311, 0. 295, 0. 2 65mm (with Gp / Lp = l. 04, 1.61, 1.69, 1.89) Moire was inconspicuous even in the case of the applied power.

[0040] As a method of reducing the modulation degree of the bright spot, the following methods are conceivable, and by combining them, the luminance pattern is Fourier-transformed, and the period of time coincides with one period of the DMD pixel. Assuming that the amplitude intensity value is A and the luminance average value in the imaging area range is B, the value of AZB in Example 1 was 0.020 (see FIG. 8).

1. Improve the flatness of the mirror at the support and reduce diffuse reflection.

2. Reduce the support area.

3. Spread the support to almost the entire area of the mirror.

4. Limit the exit pupil of the exit optical system.

5. Increase the angle between mirror ON and Z OFF.

Of course, the means capable of reducing the modulation degree of the bright spot is not limited to the above-described means. Further, if AZB is 0.045, the object of the present invention is achieved, but AZB is preferably 0.04 or less, more preferably 0.02 or less.

[0041] With the means 1 and 2 described above, the brightness of the bright spot is reduced by reducing the amount of diffusely reflected light itself. The degree of modulation is lowered. The third means increases the brightness when the entire unit pixel is off and decreases the modulation degree of the bright spot. The means 4 and 5 described above are for reducing the amount of diffusely reflected light passing through the outgoing optical system.

[0042] In the above means 4, as a method of limiting the exit pupil, it is effective to insert a stop in the optical system. In the embodiment shown in FIG. 4, the diaphragm 41 is not limited to the position of the force provided on the projection side of the projection lens 40. The diaphragm width is preferably 4 mm to 8 mm, more preferably 5 mm to 6 mm, from the viewpoint of the balance between brightness and moire prevention.

[0043] Table 1 shows the relationship between the AZB and the moire state when the exit pupil is limited by the stop.

The measurement of AZB was performed in the same manner as in the above example. Moire was observed with a pixel pitch Gp of 0.764 mm and a lens pitch Lp of the lenticular lens of 0.265 mm (hence Gp / Lp = 2.89).

[0044] [Table 1]

[0045] Limiting the direction of driving the mirror when the exit pupil changes the on-Z off state in the DMD with a diaphragm or the like is effective in terms of both preventing dark moire and maintaining image luminance. This is because the aperture of light can be reduced while lowering the degree of horizontal modulation that causes moiré.

[0046] In the above embodiment, the present invention can also be applied to the force and other configurations shown in the example using one DMD panel. For example, a configuration may be adopted in which three DMDs are used and white light is separated, and then three primary colors of video light are incident and then combined to generate a color image.

[0047] In the best mode for carrying out the present invention, the present invention is applied to a diamond-shaped pixel. However, the present invention is not limited to this, and can be applied to a rectangular pixel, particularly a square pixel. Specifically, since the present invention suppresses moire caused by the pixel arrangement structure and the lens arrangement structure, images of various shapes arranged periodically like a rhombus pixel. It can also be applied to the element.

Claims

The scope of the claims

[1] A light source, a light source power, a digital micromirror device that modulates emitted light by a minute mirror for each pixel in accordance with an image signal, and projection optics that projects image light modulated by the digital micromirror device When a black image signal is input to the digital micromirror device, a rear projection display device having a system and a screen having a periodic structure on which a projected image is imaged, The brightness of an area including four or more pixels arranged in the horizontal direction and one or more pixels arranged in the vertical direction at the center of the image projected on the diffusion plate with a gain of 7.5 provided in place of the screen is 1 When the front surface of the projection side is measured with a resolution of 25 or more per pixel, and the luminance is integrated in a direction perpendicular to the periodic structure of the screen, the luminance pattern is A / B O. 045, where A is the amplitude intensity value in a period that coincides with one period of the DMD pixel, and B is the average luminance value in the imaging area range. A rear projection display device characterized by

2. The rear projection display device according to claim 1, wherein the projection optical system is provided with a diaphragm for limiting an exit pupil.

3. The rear projection display device according to claim 2, wherein the diaphragm restricts the projection pupil only in a driving direction of the mirror of the digital micromirror device.