JP4124193B2 - Image display device, projector - Google Patents

Description

  The present invention relates to an image quality improvement technique of an image display device, and more particularly to an optical configuration suitable for realizing an expansion of a dynamic range of display luminance and an increase in gradation.

In recent years, electronic display devices such as LCD (Liquid Crystal Display), EL (Electro-luminescence) displays, plasma displays, CRTs (Cathode Ray Tubes), and projectors have been remarkably improved, and the resolution and color gamut have become human visual characteristics. Devices with nearly comparable performance are being realized. However, regarding the luminance dynamic range, the reproduction range is about 1 to 10 ² [nit], and the number of gradations is generally 8 bits. On the other hand, human vision has a range of luminance dynamic range that can be perceived at a time of about 10 ⁻² to 10 ⁴ [nit], and the luminance discrimination capability is 0.2 [nit]. It is said to be equivalent to 12 bits. When viewing the display image of the current display device through such visual characteristics, the narrowness of the luminance dynamic range is conspicuous, and in addition, the gradation of the shadow part and highlight part is insufficient. You will feel unsatisfactory with reality and power.

  In CG (Computer Graphics) used in movies, games, etc., display data (hereinafter referred to as HDR (High Dynamic Range) display data) has a luminance dynamic range and gradation characteristics close to human vision. The movement to pursue the reality of depiction is becoming mainstream. However, since the performance of the display device that displays it is insufficient, there is a problem that the expressive power inherent in the CG content cannot be fully exhibited.

  Furthermore, in the next OS (Operating System), adoption of a 16-bit color space is planned, and the dynamic range and the number of gradations are dramatically increased as compared with the current 8-bit color space. Therefore, it is expected that the demand for realizing a high dynamic range and high gradation electronic display device capable of utilizing the 16-bit color space will increase.

  Among display devices, a projection display device (projector) such as a liquid crystal projector or a DLP (Digital Light Processing (trademark)) projector can display a large screen, and is effective in reproducing the reality and power of a display image. A display device. In this field, in order to solve the above problems, the following proposals have been made (for example, see Patent Document 1).

  The basic configuration for expanding the luminance dynamic range is to form a desired illumination light amount distribution by modulating the light beam emitted from the light source with the first light modulation element, and the illumination light amount distribution is formed on the second light modulation element. And then illuminate it. As the light modulation element, for example, there is a transmission type modulation element having a structure in which a plurality of pixels are periodically arranged two-dimensionally and capable of controlling a two-dimensional transmittance distribution. A typical example is a liquid crystal light valve. A reflective modulation element may be used instead of the transmissive modulation element. A typical example is a DMD (Digital Micromirror Device) element. The first and second transmission type modulation elements (reflection type modulation elements) are individually driven and controlled by the first and second modulation signals generated from the video signal.

Consider a case where a light modulation element having a dark display transmittance of 0.2% and a bright display transmittance of 60% is used. In the configuration in which the light modulation element is used alone, the luminance dynamic range is 60 / 0.2 = 300. On the other hand, in the configuration in which the above-described first and second light modulation elements are combined, this corresponds to optically arranging light modulation elements having a luminance dynamic range of 300 in series, so theoretically 300 × 300 = 90000. The luminance dynamic range can be realized. Further, the same idea holds for the gradation characteristics, and the gradation characteristics exceeding 8 bits can be obtained by optically arranging the 8-bit gradation light modulation elements in series.
JP-A-6-167690

  However, in the image display device having the above configuration, the optical image formed by the first light modulation element is transmitted to the second light modulation element, which is caused by optical superposition of pixel patterns of each light modulation element. Image quality degradation may occur.

  For example, when the first and second light modulation elements have a light shielding pattern having a periodic structure (black stripe, black matrix, etc.), a slight misalignment of both causes moiré and degrades the image quality of the display image.

  The present invention has been made in view of the above-described circumstances, and is an image display device capable of suppressing image quality degradation caused by optical superposition of a plurality of light modulation elements while increasing the luminance dynamic range. And a projector.

A first device of the present invention is a device that displays an image by modulating light from a light source based on display image data, and includes a first light modulation element that modulates light from the light source, and the first light. An optical image formed by the first light modulation element is arranged between the second light modulation element that modulates light from the modulation element, the first light modulation element, and the second light modulation element. A relay optical system that transmits the light to the pixel surface of the two-light modulation element, and is arranged between the first light-modulation element and the second light-modulation element, and refracts at least part of the light from the first light-modulation element an optical low-pass filter which allowed Ru is a feature in that it has, a microlens array for collecting each pixel of the second optical modulation element with light from the optical low-pass filter including a light refracted by the optical low-pass filter To do.

  In this image display device, light from a light source is modulated by two-stage image forming processes through two optical modulation elements optically arranged in series. As a result, this image display apparatus can realize an expansion of the luminance dynamic range and an increase in the number of gradations.

  In addition, by arranging a relay optical system between the first light modulation element and the second light modulation element, optical aberration can be reduced. That is, in this image display device, light from the first light modulation element is transmitted to the second light modulation element with relatively high accuracy.

  The relay optical system may be configured using either one of a transmissive optical element (such as a lens) or a reflective optical element (such as a mirror), or may be configured using both. Since the relay optical system has both-side telecentricity, the image transmitted on the pixel surface of the second light modulation element can be surely made uniform in brightness, color, contrast, etc., and the image display quality is good. It will be something. Further, it is possible to make a relatively wide allowable error range regarding the arrangement position of the second light modulation element in the optical axis direction, thereby simplifying the design and configuration and reducing the manufacturing cost.

  In the above image display device, since the optical low-pass filter is disposed between the first light modulation element and the second light modulation element, the optical connection between the first light modulation element and the second light modulation element. Peculiar image quality degradation caused by superposition is suppressed. The optical low-pass filter has a function of blurring an image, and various types such as a prism type, a diffraction grating type, and a crystal type are applicable. Since the optical image formed by the first light modulation element is blurred by the optical low-pass filter, image quality deterioration phenomenon due to optical superposition of pixel patterns such as moire is less likely to occur.

  Further, in the above image display device, a decrease in luminance due to the arrangement of the optical low-pass filter is suppressed by the microlens array. That is, the light from the optical low-pass filter gathers at each pixel of the second light modulation element by the microlens array, and the brightness of the display image is improved.

  In the image display device, each pixel of the first light modulation element and the second light modulation element includes an opening and a light shielding part, and the optical low-pass filter includes the first light modulation element. It is preferable that a part of the light passing through the opening is bent and the light is overlapped on a dark part formed by the light shielding part of the first light modulation element.

  According to this configuration, the dark portion formed by the light shielding portion of the first light modulation element becomes inconspicuous on a predetermined surface such as the light incident surface of the second light modulation element, and the light overlapping patterns such as moire are optically overlapped. The pixel deterioration phenomenon accompanying the alignment is more reliably suppressed.

  The optical low-pass filter can be configured to include a prism group formed of an assembly of prism elements having at least a refractive surface.

  In this case, the prism element can include a flat portion and a prism portion having a polygonal pyramid shape.

  The microlens array may include a lens group that is disposed on the light incident side of the second light modulation element and has a one-to-one correspondence with each pixel of the second light modulation element.

  A second device according to the present invention is a projector, and includes the above-described image display device and a projection unit.

  Since the projector includes an image display device that is excellent in expanding the luminance dynamic range and improving the image quality of the display image, the reality and force of the display image can be effectively reproduced by a large screen display.

Embodiments of the present invention will be described below with reference to the drawings.
In the present embodiment, as the first light modulation element, a transmissive liquid crystal light valve is provided for each color light of R (red), G (green), and B (blue), and the transmissive liquid crystal is also provided in the second light modulation element. An example of a projection type liquid crystal display device (projector) using a light valve will be described.

[Overall configuration of projector]
FIG. 1 is an example of an embodiment of an image display device of the present invention and a projector of the present invention, and is a diagram showing a main optical configuration of a projector PJ1.
As shown in FIG. 1, the projector PJ 1 includes a light source 10, a uniform illumination system 20 that uniformizes the luminance distribution of light incident from the light source 10, and RGB three primary colors in a wavelength region of light incident from the uniform illumination system 20. Color modulator 25 (including three transmissive liquid crystal light valves 60B, 60G, and 60R as first light modulators), optical low-pass filter 80, and light incident from color modulator 25 A relay lens 90 that relays light, a transmissive liquid crystal light valve 100 as second light modulation means for modulating the luminance in the entire wavelength region of light incident from the relay lens 90, and light incident from the liquid crystal light valve 100 on a screen ( And a projection lens 110 for projecting to a not shown.

  The light source 10 includes a lamp 11 such as an ultrahigh pressure mercury lamp or a xenon lamp, and a reflector 12 that reflects and collects light emitted from the lamp 11.

  The uniform illumination system 20 includes two lens arrays 21 and 22 made of fly-eye lenses, a polarization conversion element 23, and a condenser lens 24. Then, the luminance distribution of the light from the light source 10 is made uniform by the two lens arrays 21 and 22, and the uniformed light is polarized by the polarization conversion element 23 in the polarization direction in which the color modulation unit can be incident, and the polarized light is condensed. The light is condensed by the lens 24 and emitted to the color modulation unit 25. The polarization conversion element 23 is composed of, for example, a PBS array and a half-wave plate, and converts random polarization into specific linear polarization.

  The color modulation unit 25 includes two dichroic mirrors 30 and 35 as light separating means, three mirrors (reflection mirrors 36, 45, and 46), and five field lenses (lens 41, relay lens 42, and collimating lens 50B). , 50G, 50R), three liquid crystal light valves 60B, 60G, 60R, and a cross dichroic prism 70.

  The dichroic mirrors 30 and 35 separate (split) the light (white light) from the light source 10 into RGB (primary) light of red (R), green (G), and blue (B). The dichroic mirror 30 is formed by forming a dichroic film having a property of reflecting B light and G light and transmitting R light on a glass plate or the like, and is included in the white light from the light source 10. Reflects light and G light and transmits R light. The dichroic mirror 35 is formed by reflecting a G light on a glass plate or the like and forming a dichroic film having a property of transmitting the B light. Of the G light and the B light reflected by the dichroic mirror 30, the dichroic mirror 35 reflects the G light. It transmits to the collimating lens 50G, transmits blue light, and transmits it to the lens 41.

  The relay lens 42 transmits light in the vicinity of the lens 41 (light intensity distribution) to the vicinity of the collimating lens 50B, and the lens 41 has a function of causing light to enter the relay lens 42 efficiently. The B light incident on the lens 41 is transmitted to the liquid crystal light valve 60B which is spatially separated with the intensity distribution almost preserved and almost no light loss.

  The collimating lenses 50B, 50G, and 50R substantially parallelize each color light incident on the corresponding liquid crystal light valves 60B, 60G, and 60R, and efficiently transmit the light transmitted through the liquid crystal light valves 60B, 60G, and 60R to the relay lens 90. It has the function to make it enter. The light of the three primary colors of RGB dispersed by the dichroic mirrors 30 and 35 passes through the above-described mirrors (reflection mirrors 36, 45, and 46) and lenses (lens 41, relay lens 42, collimating lenses 50B, 50G, and 50R). Are incident on the liquid crystal light valves 60B, 60G, and 60R.

  The liquid crystal light valves 60B, 60G, and 60R include a pixel substrate and a glass substrate on which switching elements such as thin film transistors and thin film diodes for driving the pixel electrode are formed in a matrix, and a glass substrate on which a common electrode is formed over the entire surface. This is an active matrix type liquid crystal display element in which a TN liquid crystal is sandwiched between and a polarizing plate is disposed on the outer surface.

  The liquid crystal light valves 60B, 60G, and 60R are normally white mode in which a white / bright (transmission) state is applied when no voltage is applied and a black / dark (non-transmission) state is applied when a voltage is applied, or vice versa. It is driven in the mode, and the gradation between light and dark is analog controlled according to a given control value. The liquid crystal light valve 60B optically modulates the incident B light based on the display image data, and emits modulated light including an optical image. The liquid crystal light valve 60G optically modulates the incident G light based on display image data, and emits modulated light including an optical image. The liquid crystal light valve 60R optically modulates the incident R light based on display image data, and emits modulated light containing an optical image.

  The cross dichroic prism 70 has a structure in which four right-angle prisms are bonded to each other, and a dielectric multilayer film that reflects B light (B light reflecting dichroic film 71) and a dielectric multilayer film that reflects R light are contained therein. (R light reflecting dichroic film 72) is formed in an X-shaped cross section. Then, the G light from the liquid crystal light valve 60G is transmitted, and the R light from the liquid crystal light valve 60R and the B light from the liquid crystal light valve 60B are bent to combine these three colors of light to form a color image. .

  The optical low-pass filter 80 is disposed between the liquid crystal light valves 60B, 60G, 60R as the first light modulation elements and the liquid crystal light valve 100 as the second modulation means, and the liquid crystal light valves 60B, 60G, 60R. It has a function to blur the formed optical image. As the optical low-pass filter 80, various types such as a prism type, a diffraction grating type, and a crystal type can be applied. In this example, a prism type is used. The low-pass filter 80 causes the optical images formed by the liquid crystal light valves 60B, 60G, and 60R to become blurred, resulting in optical superposition of the pixel patterns of the liquid crystal light valves 60B, 60G, and 60R and the liquid crystal light valve 100. Image quality degradation is avoided. The configuration and function of the low-pass filter 80 will be described in detail later.

  The relay lens 90 transmits an optical image (light intensity distribution) from the liquid crystal light valves 60B, 60G, and 60R synthesized by the cross dichroic prism 70 onto the display surface of the liquid crystal light valve 100.

  The liquid crystal light valve 100 has the same configuration as the liquid crystal light valves 60B, 60G, and 60R described above, and modulates the luminance of all wavelength regions of incident light based on display image data and includes a final optical image. The modulated light is emitted to the projection lens 110.

  The projection lens 110 displays a color image by projecting an optical image formed on the display surface of the liquid crystal light valve 100 onto a screen (not shown).

  Next, the overall light transmission flow of the projector PJ1 will be described. The white light from the light source 10 is split into three primary colors of red (R), green (G), and blue (B) by the dichroic mirrors 30 and 35, and the lenses and mirrors including the collimating lenses 50B, 50G, and 50R. Through the liquid crystal light valves 60B, 60G, and 60R. Each color light incident on the liquid crystal light valves 60B, 60G, and 60R is color-modulated based on external data corresponding to each wavelength region, and emitted as modulated light including an optical image. The modulated lights from the liquid crystal light valves 60B, 60G, and 60R are incident on the cross dichroic prism 70, where they are combined into a single light, and are passed through the optical low-pass filter 80 and the relay lens 90 to the liquid crystal light valve 100. Incident. The combined light incident on the liquid crystal light valve 100 is brightness-modulated based on external data corresponding to the entire wavelength range, and is emitted to the projection lens 110 as modulated light including a final optical image. Then, the projection lens 110 projects the final combined light from the liquid crystal light valve 100 on a screen (not shown) to display a desired image.

  In projector PJ1, liquid crystal light valve 60B, 60G, 60R as a first light modulation element is used for modulated light that forms an optical image (image), and a final display image is a liquid crystal light valve as a second light modulation element. 100 is adopted, and light from the light source 10 is modulated by two-stage image forming processes through two light modulation elements arranged in series. As a result, the projector PJ1 can realize expansion of the luminance dynamic range and increase of the number of gradations.

  Here, the liquid crystal light valves 60B, 60G, 60R and the liquid crystal light valve 100 are all the same in that the intensity of transmitted light is modulated and an optical image corresponding to the degree of modulation is included. 100 modulates light in the entire wavelength range (white light), whereas the former liquid crystal light valves 60B, 60G, and 60R emit light in a specific wavelength range (that is, spectrally separated by dichroic mirrors 30 and 35 as light separating means). The two are different in that they modulate R, G, B, etc.). Accordingly, the light intensity modulation performed by the liquid crystal light valves 60B, 60G, and 60R is referred to as color modulation, and the light intensity modulation performed by the liquid crystal light valve 100 is referred to as brightness modulation for convenience.

  From the same viewpoint, in the following description, the liquid crystal light valves 60B, 60G, and 60R may be referred to as color modulation light valves and the liquid crystal light valve 100 may be referred to as luminance modulation light valves. The contents of the control data input to the color modulation light valve and the luminance modulation light valve will be described in detail later. In the present embodiment, the color modulation light valve has a higher resolution than the luminance modulation light valve. Therefore, when the color modulation light valve displays the display resolution (the observer views the display image of the projector PJ1) It is assumed that the resolution to be perceived) is determined. Of course, the display resolution relationship is not limited to this, and a configuration in which the luminance modulation light valve determines the display resolution is also possible.

FIG. 2 is a diagram illustrating a configuration example of the relay lens 90.
The relay lens 90 forms optical images of the liquid crystal light valves 60B, 60G, and 60R for color modulation on the pixel surface of the liquid crystal light valve 100. As shown in FIG. This is an equal-magnification imaging lens composed of a front lens group 90a and a rear lens group 90b arranged substantially symmetrically. In addition, it is desirable to have both-side telecentric characteristics in consideration of the viewing angle characteristics of the liquid crystal. The front lens group 90a and the rear lens group 90b include a plurality of convex lenses and concave lenses. However, the lens shape, size, arrangement interval and number, telecentricity, magnification and other lens characteristics can be appropriately changed according to required characteristics, and are not limited to the example in FIG. Since the relay lens 90 is composed of a large number of lenses, aberration correction is good, and the luminance distribution formed by the liquid crystal light valves 60B, 60G, 60R for color modulation can be accurately transmitted to the liquid crystal light valve 100. it can.

  FIGS. 3 and 4 are explanatory diagrams of telecentricity. FIGS. 3A and 4A show relay lenses having bilateral telecentricity, and FIGS. 3B and 4B are general diagrams. A typical relay lens is shown.

  As shown in FIG. 3A, a telecentric lens is a lens in which the chief ray indicated by a thick solid line is parallel to the optical axis, and is on the object side (front light valve side) and image side (rear light valve side). A telecentric lens on either side is called a double-sided telecentric lens. In a relay lens having bilateral telecentricity, the chief ray emitted from the front light valve (in this example, the liquid crystal light valve) is emitted almost vertically from any part of the front light valve, and the rear light valve (in this example, the liquid crystal light valve). Incidently perpendicular to the bulb. Therefore, when the emission angle distribution of the light beam emitted from the position (A) far from the optical axis of the front light valve is compared with the emission angle distribution of the light beam emitted from the position (B) close to the optical axis, they are almost equal. .

  On the other hand, as shown in FIG. 3B, in a general relay lens, the chief ray indicated by a thick solid line has an emission angle different depending on the emission position of the front light valve, and the incident angle to the rear light valve also depends on the incident position. Different. Therefore, when the emission angle distribution of the light beam emitted from the position (A) far from the optical axis of the front light valve is compared with the emission angle distribution of the light beam emitted from the position (B) close to the optical axis, they are quite different. .

  Generally, a liquid crystal light valve has a viewing angle dependency. That is, contrast characteristics, brightness characteristics, spectral characteristics, and the like vary depending on the angle of light emitted from the liquid crystal light valve. Therefore, in the general relay lens shown in FIG. 3B, the emission angle component of the emitted light beam is different for each region of the front light valve (liquid crystal light valve), and as a result, the screen of the rear light valve (liquid crystal light valve). In particular, a distribution (non-uniformity) occurs in the brightness, color, and contrast of the display image, which may cause a reduction in the image display quality of the projector.

  On the other hand, in the relay lens having both-side telecentricity shown in FIG. 3A, since the emitted light flux in any region of the front light valve (liquid crystal light valve) has substantially the same emission angle distribution, the rear light valve (liquid crystal The brightness, color and contrast of the display image in the light valve screen are substantially uniform, and the image display quality of the projector is good.

  Further, as shown in FIG. 4A, in the relay lens having both-side telecentricity, even if an error occurs in the arrangement position of the rear light valve in the optical axis direction (PS1 → PS2 shown in FIG. 4A). Since the chief ray is parallel to the optical axis, the size of the image of the front light valve is slightly changed although a slight blur occurs (AL1≈AL2 shown in FIG. 4A). That is, even if there is a slight arrangement error of the rear light valve, the image display quality as a projector does not deteriorate so much, and the manufacturing margin is large.

  On the other hand, as shown in FIG. 4B, in a general relay lens, when the rear light valve has an arrangement error equivalent to the above (PS1 → PS2 shown in FIG. 4B), the chief ray is Since it is non-parallel to the optical axis, the image of the preceding light valve changes in size simultaneously with the blur (AL1 <AL2 shown in FIG. 4B), and as a result, the image display quality may be greatly reduced. is there.

[Configuration and function of low-pass filter]
Next, the configuration and function of the optical low-pass filter 80 will be described with reference to FIGS.
FIG. 5 shows a pixel surface of the liquid crystal light valve 60B (color modulation light valve).
The pixel surface of the liquid crystal light valve 60B has a plurality of unit pixels 65 that are two-dimensionally and periodically arranged in a matrix form. Each pixel 65 is formed in a substantially rectangular shape, and includes an opening 65a through which light passes, and a light shielding part 65b disposed around the opening 65a. The light shielding portion 65b is formed by a pixel wiring, a TFT element, or the like, in addition to a light shielding pattern film (a black stripe film, a black matrix film, etc.) in which strips having a predetermined width are periodically arranged. In the liquid crystal light valve 60B, the light passing through the opening 65a of each pixel is modulated (transmittance modulation), thereby controlling the two-dimensional transmittance distribution in the pixel plane.

  The pixel surfaces of the liquid crystal light valves 60G and 60R (color modulation light valve) and the liquid crystal light valve 100 (luminance modulation light valve) are the same as described above.

FIG. 6 is an explanatory diagram conceptually showing the cause of moiré.
When a pixel surface of a color modulation light valve composed of repeating unit pixels is imaged by a relay lens, the optical image has a lattice-shaped dark portion and a substantially rectangular light portion as shown in FIG. It has a periodic structure that is repeated alternately. When the optical image of the color modulation light valve is transmitted onto the pixel surface of the luminance modulation light valve, as shown in FIG. 6B, the positional deviation or the attitude deviation (tilt deviation, etc.) between the two light valves. ), Moiré occurs and the quality of the displayed image is significantly reduced.

  FIG. 7 is an explanatory diagram of a schematic configuration and functions of the optical low-pass filter 80, (a) is a plan view of the optical low-pass filter 80, and (b) is a cross-sectional view taken along line AA shown in (a). FIG. 6C is a functional explanatory diagram of the optical low-pass filter 80.

  As shown in FIG. 7A, the optical low-pass filter 80 includes a prism group formed of an assembly of prism elements 85 having a refractive surface. The periodic array direction of the prism elements 85 is inclined at a predetermined angle (45 degrees in FIG. 7A) with respect to the periodic array direction of the pixels 65 of the liquid crystal light valve shown in FIG.

  As shown in FIG. 7B, one prism element 85 includes a flat portion 85a and a polygonal pyramid-shaped prism portion 85b. As shown in FIG. 7C, the light beam incident on the flat portion 85a of the prism element 85 among the light beams emitted from the color modulation light valves 60B, 60G, 60R is emitted from the low-pass filter 80 at the same angle as the incident angle. . On the other hand, the light beam incident on the prism portion 85 b of the prism element 85 is emitted from the low-pass filter 80 with its angle changed by refraction.

  8 and 9 are diagrams for more specifically explaining the function of the low-pass filter of FIG. FIG. 8A shows an optical system as a comparative example having no low-pass filter, and FIG. 9A shows an image of a unit pixel formed by the optical system of FIG. FIG. 8B shows an optical system having a low-pass filter, and FIG. 9B shows an image of a unit pixel imaged by the optical system of FIG. 8B.

  As shown in FIG. 8A, in an optical system without a low-pass filter, a light beam emitted from one point of the color modulation light valve is imaged at one point of the luminance modulation light valve by the relay lens. On the other hand, as shown in FIG. 8B, in an optical system having a low-pass filter, a light beam emitted from one point of the color modulation light valve forms an image at a plurality of points at different positions. That is, a part of the light beam that has passed through the pixel opening of the color modulation light valve is bent by a low-pass filter, and optical images (bright parts) of the pixel opening are formed at a plurality of positions at different positions (multi-image function). ).

  As shown in FIG. 9A, in an optical system without a low-pass filter, an optical image of a unit pixel of a color modulation light valve is formed by a rectangular annular dark portion formed by a pixel light shielding portion and a pixel opening portion. It has a bright part. In contrast, as shown in FIG. 9B, in the optical system having the low-pass filter 80, the optical image of the unit pixel of the color modulation light valve is obtained by the double image function of the low-pass filter 80 (prism element 85). The dark part formed by the light-shielding part of the unit pixel becomes inconspicuous.

  That is, as shown in FIG. 9B, in the low-pass filter, part of the light that has passed through the pixel opening of the color modulation light valve is emitted at a different angle due to refraction. Then, the light overlaps with a dark part formed by the light shielding part of the color modulation light valve.

  Specifically, as shown in FIG. 9B, the bright portion formed by the pixel opening of the color modulation light valve is located at the upper left by the upper left prism portion (refractive surface) of the prism element 85 of the low-pass filter 80. The light flux shifts and overlaps the dark part formed by the pixel light-shielding part of the color modulation light valve (image shift, (b-1) shown in FIG. 9B). Similarly, the bright portion is shifted to the lower left (b-2) by the lower left prism portion (refractive surface) of the prism element 85, and the bright portion is moved to the lower right by the lower right prism portion (refractive surface) of the prism element 85. The bright part shifts to the upper right (b-4) due to the deviation (b-3) and the upper right prism part (refractive surface) of the prism element 85. And by irradiating light to the whole dark part by said double image function, as for the optical image of the unit pixel of a color modulation light valve, a dark part becomes inconspicuous (b-5).

  As described above, in this example, when the optical image of the color modulation light valve is transmitted onto the pixel surface of the luminance modulation light valve, the dark portion, which is the optical image of the pixel light shielding portion, becomes inconspicuous due to the double image function of the low-pass filter 80. . That is, an optical image of the color modulation light valve with high brightness uniformity is formed on the luminance modulation light valve. For this reason, the pixel deterioration phenomenon accompanying the optical superposition of the light shielding patterns such as moire is reliably suppressed.

FIG. 10 shows a cross-sectional view of the luminance modulation light valve 100 (the liquid crystal light valve 100 shown in FIG. 1).
The luminance modulation light valve 100 includes two transparent substrates 101 and 102 arranged opposite to each other, a light shielding pattern film 103 having a periodic structure (black stripe film, black matrix film, etc.), a liquid crystal layer 104, a TFT / wiring 105, and a pixel electrode. 106, a microlens array 107, and the like.

  The microlens array 107 is disposed on the light incident side of the luminance modulation light valve 100 and includes a lens group corresponding to each pixel 108 of the light valve 100 on a one-to-one basis. Each lens 109 of the microlens array 107 is formed so as to collect the light from the low-pass filter 80 at the opening of each pixel 108 of the luminance modulation light valve 100. That is, in the luminance modulation light valve 100, one condenser lens 109 is disposed on the light incident side of each pixel 108.

  As described above, the light transmitted through the pixel openings of the color modulation light valves (liquid crystal light valves 60B, 60G, and 60R shown in FIG. 1) corresponds to the pixel openings by the low-pass filter 80 as shown in FIG. Reach a wider range than the range. As a result, the amount of light reaching the light-shielding pattern film 103 of the luminance modulation light valve 100 increases, causing a problem that the luminance of the display image decreases. In this example, since the microlens array 107 is arranged on the light incident side of the luminance modulation light valve 100, the light from the low-pass filter 80 gathers at the opening of each pixel 108 of the second light modulation element, and the display image The brightness is improved.

  That is, the incident light flux on the luminance modulation light valve 100 is collected by each lens 109 of the microlens array 107 and most of the light passes through the opening of the pixel 108 of the luminance modulation light valve 100. Therefore, it is avoided that a part of the light refracted by the low-pass filter 80 is blocked by the light shielding pattern film 103 of the luminance modulation light valve 100. As described above, in this example, although the optical low-pass filter 80 is used, a decrease in luminance is suppressed.

  The arrangement position of the optical low-pass filter 80 shown in FIG. 1 is not limited between the cross dichroic prism 70 and the relay lens 90, but between the relay lens 90 and the luminance modulation light valve (liquid crystal light valve 100). You may arrange in. Further, it may be arranged in the relay lens 90. Further, it may be arranged between the color modulation light valve (liquid crystal light valves 60B, 60G, 60R) and the cross dichroic prism 70. In this case, a low-pass filter is required for each of the R, G, and B color modulation light valves. However, since a low-pass filter optimized for each wavelength characteristic can be used, there is an advantage that moire can be reduced more effectively. is there.

  Further, the present invention is not limited to the optical system in which the color modulation light valve is disposed in the front stage and the luminance modulation light valve is disposed in the rear stage as viewed from the light source 10 side. The present invention can also be applied to an optical system in which a light valve is disposed in the subsequent stage. In this case, a low-pass filter and a relay lens are arranged between the luminance modulation light valve and the color modulation light valve. Further, a microlens array is disposed on the light incident surface of the color modulation light valve.

  In this example, the microlens array 107 is disposed adjacent to each pixel of the luminance modulation light valve 100 (second light modulation element, rear light valve), while the liquid crystal light valves 60B, 60G, 60R (first A microlens array is not disposed at a position adjacent to each pixel of one light modulation element or the preceding light valve. This is because when the first light modulation element (light valve arranged in the previous stage) includes a microlens, the emission angle of the light beam emitted from the first light modulation element is greatly expanded, and this light beam is then second light modulated. In order to transmit efficiently to the element (light valve arranged in the subsequent stage), the F-number of the transmission optical system (relay lens 90) must be reduced, resulting in an increase in the cost of the device and an increase in size and weight. Because. Therefore, it is desirable that the first light modulation element does not include a microlens.

  Further, the form of the low-pass filter is not limited to that shown in FIGS. 7A to 7C, and other forms may be used. The low-pass filter is not limited to a prism type, and a diffractive low-pass filter can also be used.

[Other forms of low-pass filter]
11 to 22 show other examples of low-pass filters.

11-16 show examples of various variations of the shape of the prism element.
For example, FIG. 11 shows a prism group 161 in which trapezoidal prism elements each having a refractive surface 161a and a flat portion 161b are provided at a predetermined interval.
FIG. 12 shows a prism group 162 that has a refracting surface 162a and a flat portion 162b and in which trapezoidal prism elements are provided without gaps.
FIG. 13 shows a prism group 163 having a refracting surface 163a and a flat portion 163b, and triangular prism elements provided at predetermined intervals.

FIG. 14 shows a blazed prism group 164 composed only of the refractive surface 164a.
FIG. 15 shows the prism group 165 in a state in which the height of the flat portion and the prism pitch are random, and there is almost no periodicity for generating diffraction by the prism edge.
FIG. 16 shows a prism group 166 in which the flat portions have a common height, but the prism pitch is random, and the periodicity, which is a diffraction generation condition, can be suppressed and the influence of diffraction can be reduced.
As described above, various variations can be made using the direction of the refracting surface, the inclination angle, and the area as parameters.

  FIG. 17 shows a schematic configuration in which a part of another form of the prism group is enlarged. The prism group 210 includes a first prism element 211 having a quadrangular pyramid shape and a second prism element 212 having a quadrangular pyramid shape. The first prism element 211 is formed so that one side thereof forms approximately 45 ° with respect to the center line CL. The second prism element 212 is formed so that one side thereof is substantially parallel to the center line CL. Further, a flat portion 215 is provided around the first prism element 211 and the second prism element 212.

As shown in FIG. 18, an aperture image (direct transmission image) 220P is formed by the light transmitted through the flat portion 215. Then, an opening portion image 213P is formed in the 45 ° direction with respect to the center line image CLP by the refractive surface 213 of the first prism element 211. The refraction surface 214 of the second prism element 212 forms an opening image 214P in a direction parallel to the center line image CLP. Then, the direction of the refracting surface and the inclination angle are set so that these projected images fill the dark part of the light shielding pattern without any gaps.
Thereby, unevenness in intensity of the projected image can be reduced.

  Further, the shape of the prism group that causes the same refraction action as that of the prism group 210 can be variously modified. For example, a prism group 230 having a refracting surface 231 and a flat portion 232 as shown in FIG. 19 can be used. In this way, it is possible to form the prism refracting surface and the flat surface in an arbitrary shape with a desired area ratio.

FIG. 20 shows another embodiment of the low-pass filter, and shows a perspective configuration of a main part of the prism group 240.
The prism group 240 includes two sets of prism elements 241a and 241b. The prism element 241a has a substantially trapezoidal cross-sectional shape in the y-axis direction that is the first direction. The prism element 241a has a longitudinal direction in the x-axis direction, which is a second direction substantially orthogonal to the y-axis direction, which is the first direction.

  Of the trapezoidal shape having a cross-sectional shape in the y-axis direction of the prism element 241a, the two inclined surfaces Y1 and Y2 function as refractive surfaces. Of the cross-sectional shape of the prism element 241a in the y-axis direction, the upper surface Y0 functions as a flat portion. For this reason, the light incident on the slope Y1 or the slope Y2 is refracted in a direction corresponding to the angle of the slope. A refracted transmission image is formed by the refracted light. Further, the light incident on the upper surface Y0 is transmitted as it is. A direct transmission image is formed by the light transmitted as it is.

  The prism element 241b has the same configuration as the prism element 241a. Of the cross-sectional shape of the prism element 241b in the x-axis direction, the two inclined surfaces X1 and X2 function as refractive surfaces. Of the cross-sectional shape of the prism element 241b in the x-axis direction, the upper surface X0 functions as a flat portion. The two sets of prism elements 241a and 241b are provided so that their longitudinal directions are substantially orthogonal to each other.

In the prism group 240 of this example, the plane side of the prism element 241a and the plane side of the prism element 241b face each other and are fixed. However, the present invention is not limited to this, and any of the following configurations (1) to (3) may be used.
(1) A configuration in which the surface on which the slopes Y1, Y2, etc. of the prism element 241a are formed and the surface on which the slopes X1, X2, etc. of the prism element 241b are formed face each other and are fixed.
(2) A configuration in which the surface on which the slopes Y1, Y2, etc. of the prism element 241a are formed and the plane side of the prism element 241b face each other and are fixed.
(3) A configuration in which the flat surface side of the prism element 241a and the surface on which the inclined surfaces X1, X2, etc. of the prism element 241b are formed face each other and are fixed.
Although FIG. 20 illustrates the configuration in which the prism surfaces are in contact, a configuration in which both surfaces are in contact with air may be employed.

FIG. 21 shows the splitting of incident light by the prism group 240.
In FIG. 21, the incident light XY travels from the left side toward the side. In addition, in a part of FIG. 21, for convenience of explanation, the light beam is specified by using the signs of the slopes Y0, Y1, and Y2. Incident light XY is split into three light beams, a light beam Y1 and Y2 refracted on the slope and a light beam Y0 that is transmitted through the upper surface as it is, by a prism element 241a indicated by a dotted line. The three branched light beams Y0, Y1, and Y2 are further branched into three light beams by the prism element 241b. As a result, the incident light XY is branched into nine light beams Y1X1, Y1X0, Y1X2, Y0X1, Y0X0, Y0X2, Y2X1, Y2X0, and Y2X2.

Next, the positions of the nine branched light beams on the projection plane will be described with reference to FIG.
A region of a direct transmission image by the light ray Y0X0 is shown surrounded by a thick frame. Projected images of the pixel portion by the refracted light can be formed in directions orthogonal to the longitudinal directions of the prism elements 241a and 241b. The prism group 240 is configured such that the longitudinal directions of the two sets of prism elements 241a and 241b are substantially orthogonal to each other. As a result, a region of a refracted transmission image by the eight light beams Y1X1, Y1X0, Y1X2, Y0X1, Y0X2, Y2X1, Y2X0, and Y2X2 is formed around the region of the direct transmission image by the light beam Y0X0. In FIG. 22, each region is shown with a light beam symbol. Further, the direct transmission image by the light beam Y0X0 is formed periodically adjacent to the positions of the plurality of pixel openings in the first light modulation element (the liquid crystal light valves 60B, 60G, and 60R shown in FIG. 1). The The prism group 240 forms a refracted transmission image in a region between the direct transmission images of the light beam Y0X0 by the prism elements 241a and 241b. Thereby, the periodicity of the projection light can be reduced.

The prism group 240 has a total light intensity of PW0 via the upper surface Y0 of the prism element 241a that is a flat surface and the upper surface X0 of the prism element 241b, and light that passes through the inclined surfaces Y1, Y2, X1, and X2 that are refractive surfaces. When the total strength is PW1,
PW0 ≧ PW1
Is satisfied. Note that PW0 and PW1 are the light intensities in the second light modulation element (liquid crystal light valve 100).

  The sum of the light intensities of the directly transmitted image by the light beam Y0X0 corresponds to the areas of the upper surfaces Y0 and X0 which are flat portions. Further, the sum of the light intensities of the refracted transmission images by the light rays Y1X1, Y1X0, Y1X2, Y0X1, Y0X2, Y2X1, Y2X0, and Y2X2 corresponds to the areas of the inclined surfaces Y1, Y2, X1, and X2 that are refracting surfaces. Here, if the total light intensity PW1 of the refracted transmission image by the light rays Y1X1, Y1X0, Y1X2, Y0X1, Y0X2, Y2X1, Y2X0, Y2X2 becomes larger than the total light intensity PW0 of the direct transmission image, the observer May recognize double images such as ghosts, for example.

In this example, PW0 ≧ PW1 is satisfied. Thereby, generation | occurrence | production of a moire can be reduced.
Moreover, it is preferable that PW0> PW1 is satisfied. More preferably, it is desirable to satisfy PW0> 0.9 × PW1. As a result, the original pixel information can be maintained while uniforming the light intensity distribution by the pixel arrangement, so that moire can be reduced and a higher definition projection image can be obtained.

Here, an example of the manufacturing method of the prism group which comprises a low-pass filter is demonstrated.
The prism group is integrally formed on the exit surface of the transparent plate. The transparent plate is a transparent parallel plate glass. A prism group is formed on one surface of the parallel plate glass by photolithography. Specifically, the photoresist layer is patterned on a parallel plate glass so as to have a desired prism shape, for example, a quadrangular pyramid shape, using a gray scale method to form a mask. Then, a prism group is formed by an RIE (reactive ion etching) method using a fluorine-based gas such as CHF3. The prism group can also be formed by a wet etching method using hydrofluoric acid.

Another example of the method for manufacturing the prism group will be described.
Optical epoxy resin is applied to one side of the parallel plate glass. Next, a mold having a pattern in which irregularities are reversed from a desired prism shape is prepared. Then, the mold is transferred by pressing the mold against the epoxy resin. Finally, the optical epoxy resin is irradiated with ultraviolet rays and cured to form a prism group.

  In addition, other methods can be adopted when performing mold transfer. The parallel plate glass is heated and softened to the extent necessary for mold transfer. Then, the above-described mold is pressed onto one surface of the softened parallel plate glass to perform mold transfer. This also makes it possible to form a prism group on the parallel plate glass.

  The prism group is not limited to being formed on a transparent plate. For example, a prism group having a desired prism shape is separately manufactured as a pattern sheet by a hot press method. Then, the pattern sheet is cut into a required size. Next, the cut pattern sheet is attached to the exit surface side of the parallel plate glass using an optically transparent adhesive. This also makes it possible to form a prism group on the parallel plate glass.

  Preferably, it is desirable to prevent dust and the like from adhering to the surface of the prism group. For this purpose, a coating layer made of a transparent resin having a low refractive index is formed on the exit side surface of the prism group. For example, the prism group is formed of an optical epoxy high refractive index resin having a refractive index n = 1.56. The coating layer is formed of, for example, an optical epoxy low refractive index resin having a refractive index n = 1.38. Moreover, the refractive index of the member which comprises a prism group, and the refractive index of a coating layer can also be made to correspond substantially. Thereby, it is possible to reduce the positional deviation of the refracted light on the predetermined surface due to variations in manufacturing errors of the refracting surface.

  Here, the angle at which the light is refracted by the refractive surface varies depending on the wavelength of the light. For this reason, it is desirable to consider the wavelength of light to be refracted when manufacturing the prism group. For example, an ultra-high pressure mercury lamp that is a light source unit has an emission spectrum distribution. Then, light having a peak wavelength of the emission line spectrum of about 440 nm is used as B light, and light of about 550 nm is used as G light. In addition, light in the vicinity of approximately 650 nm, which is the central wavelength of the light intensity integral value, is used as R light. When light of these wavelengths is refracted by the refracting surface, the inclination angle θ of the refracting surface is controlled so that a predetermined projection image is formed on the predetermined surface (luminance modulation light valve). Thereby, it is possible to obtain a high-quality image with a predetermined surface (luminance modulation light valve) and little color shift.

[Specific example of liquid crystal light valve modulation]
Next, specific examples of the modulation of the color modulation light valve and the luminance modulation light valve based on the display image data will be described in detail.
In the projector PJ1 (see FIG. 1), the color modulation light valve (the liquid crystal light valves 60B, 60G, and 60R shown in FIG. 1) is displayed with the color modulation signal generated from the video signal, and the brightness modulation light valve (FIG. The liquid crystal light valve 100) shown in FIG. 4 is driven, so that the luminance dynamic range is expanded and the number of gradations is increased. The modulation control of the liquid crystal light valve is performed by a display control device (display control device 200) described below.

FIG. 23 is a block diagram illustrating a hardware configuration of the display control apparatus 200.
As shown in FIG. 23, the display control device 200 reads out from the CPU 170 that controls the calculation and the entire system based on the control program, the ROM 172 that stores the control program of the CPU 170 in a predetermined area, the ROM 172, and the like. It is composed of a RAM 174 for storing data and calculation results required in the calculation process of the CPU 170, and an I / F 178 that mediates input / output of data to / from an external device, and these are used for transferring data. The signal lines are connected to each other via a bus 179 so as to be able to exchange data.

  The I / F 178 includes a light valve driving device that drives a luminance modulation light valve (the liquid crystal light valve 100 shown in FIG. 1) and a color modulation light valve (the liquid crystal light valves 60B, 60G, and 60R shown in FIG. 1) as external devices. 180, a storage device 182 that stores data, tables, and the like as files, and a signal line for connecting to an external network 199 are connected.

  The storage device 182 stores HDR display data for driving the luminance modulation light valve and the color modulation light valve.

  The HDR display data is image data capable of realizing a high luminance dynamic range that cannot be realized by a conventional image format such as sRGB, and stores pixel values indicating pixel luminance levels for all pixels of the image. In the present embodiment, the HDR display data uses a format in which a pixel value indicating a luminance level for each of the three RGB primary colors is stored as a floating point value for one pixel. For example, values (1.2, 5.4, 2.3) are stored as pixel values of one pixel.

Here, the luminance level of the pixel p in the HDR display data is Rp, the transmittance of the pixel corresponding to the pixel p of the second light modulation element is T1, and the transmittance of the pixel corresponding to the pixel p of the first light modulation element is T2. Then, the following expressions (1) and (2) are established.

Rp = Tp × Rs (1)
Tp = T1 × T2 × G (2)

However, in the above formulas (1) and (2), Rs is the luminance of the light source, G is the gain, and both are constants. Tp is a light modulation rate.

  For details of the method for generating the HDR display data, for example, publicly known document 3 “PEDebevec, J. Malik,“ Recovering High Dynamic Range Radiance Maps from Photographs ”, Proceedings of ACM SIGGRAPH97, pp.367-378 (1997). It is published in.

  Further, the storage device 182 stores a control value registration table 400 in which control values for the luminance modulation light valve are registered.

  FIG. 24 is a diagram illustrating a data structure of the control value registration table 400.

  In the control value registration table 400, as shown in FIG. 24, one record is registered for each control value of the luminance modulation light valve. Each record includes a field in which the control value of the luminance modulation light valve is registered and a field in which the transmittance of the luminance modulation light valve is registered.

  In the example of FIG. 24, “0” is registered as the control value and “0.003” is registered as the transmittance in the first row record. This indicates that when the control value “0” is output to the luminance modulation light valve, the transmittance of the luminance modulation light valve is 0.3%. FIG. 24 shows an example in which the number of gradations of the luminance modulation light valve is 4 bits (0 to 15 values). However, in actuality, there is a record corresponding to the number of gradations of the luminance modulation light valve. be registered. For example, when the number of gradations is 8 bits, 256 records are registered.

  Further, the storage device 182 stores a control value registration table in which the control values of the color modulation light valves are registered for each color modulation light valve.

  FIG. 25 is a diagram showing a data structure of a control value registration table 420R in which control values for the liquid crystal light valve 60R are registered.

  In the control value registration table 420R, as shown in FIG. 25, one record is registered for each control value of the liquid crystal light valve 60R. Each record includes a field in which the control value of the liquid crystal light valve 60R is registered and a field in which the transmittance of the liquid crystal light valve 60R is registered.

  In the example of FIG. 25, “0” is registered as the control value and “0.004” is registered as the transmittance in the first row record. This indicates that when the control value “0” is output to the liquid crystal light valve 60R, the transmittance of the liquid crystal light valve 60R becomes 0.4%. Note that FIG. 25 shows an example in which the number of gradations of the color modulation light valve is 4 bits (0 to 15 values), but in reality, there is a record corresponding to the number of gradations of the color modulation light valve. be registered. For example, when the number of gradations is 8 bits, 256 records are registered.

  The data structure of the control value registration table corresponding to the liquid crystal light valves 60B and 60G is not particularly shown, but has the same data structure as the control value registration table 420R. However, it differs from the control value registration table 420R in that different transmittances are registered for the same control value.

  Next, the configuration of the CPU 170 and the processing executed by the CPU 170 will be described.

  The CPU 170 includes a microprocessing unit (MPU) or the like, starts a predetermined program stored in a predetermined area of the ROM 172, and executes display control processing shown in the flowchart of FIG. 26 according to the program. .

  FIG. 26 is a flowchart showing the display control process.

  The display control process is a process of determining the control values of the luminance modulation light valve and the color modulation light valve based on the HDR display data, and driving the luminance modulation light valve and the color modulation light valve based on the determined control value. When executed by the CPU 170, the process first proceeds to step S100 as shown in FIG.

  In step S100, the HDR display data is read from the storage device 182.

  In step S102, the read HDR display data is analyzed, and a histogram of pixel values, a maximum value, a minimum value, an average value, and the like of the luminance level are calculated. This analysis result is for use in automatic image correction such as brightening a dark scene, darkening a scene that is too bright, or coordinating intermediate contrast, or for tone mapping.

  Next, the process proceeds to step S104, and the brightness level of the HDR display data is tone-mapped to the brightness dynamic range of the projector PJ1 based on the analysis result of step S102.

  FIG. 27 is a diagram for explaining tone mapping processing.

  As a result of analyzing the HDR display data, it is assumed that the minimum value of the luminance level included in the HDR display data is Smin and the maximum value is Smax. Further, it is assumed that the minimum value of the luminance dynamic range of the projector PJ1 is Dmin and the maximum value is Dmax. In the example of FIG. 27, since Smin is smaller than Dmin and Smax is larger than Dmax, HDR display data cannot be appropriately displayed as it is. Therefore, normalization is performed so that the histogram of Smin to Smax falls within the range of Dmin to Dmax.

  Details of tone mapping are disclosed in, for example, publicly known document 2 “F. Drago, K. Myszkowski, T. Annen, N. Chiba,“ Adaptive Logarithmic Mapping For Displaying High Contrast Scenes ”, Eurographics 2003, (2003)”. Are listed.

  Next, the process proceeds to step S106, and the HDR image is resized (enlarged or reduced) in accordance with the resolution of the color modulation light valve. At this time, the HDR image is resized while maintaining the aspect ratio of the HDR image. Examples of the resizing method include an average value method, an intermediate value method, and a nearest neighbor method (nearest neighbor method).

  Next, the process proceeds to step S108, and based on the luminance level Rp of the pixel of the resized image and the luminance Rs of the light source 10, the light modulation rate Tp is calculated for each pixel of the resized image by the above equation (1).

  Next, the process proceeds to step S110, where an initial value (for example, 0.2) is given as the transmittance T2 of each pixel of the color modulation light valve, and the transmittance T2 of each pixel of the color modulation light valve is provisionally determined.

  Next, the process proceeds to step S112, and based on the calculated light modulation rate Tp, the provisionally determined transmittance T2 and the gain G, the transmission of the luminance modulation light valve in units of pixels of the color modulation light valve according to the above equation (2). The rate T1 ′ is calculated. Here, since the color modulation light valve is composed of the three liquid crystal light valves 60B, 60G, and 60R, the transmittance T1 'is calculated for each of the three primary colors of RGB for the same pixel. On the other hand, since the luminance modulation light valve is composed of one liquid crystal light valve 100, the average value thereof is calculated as T1 'of the pixel.

  Next, the process proceeds to step S114, and for each pixel of the luminance modulation light valve, the weighted average value of the transmittance T1 ′ calculated for the pixel of the color modulation light valve that overlaps the pixel on the optical path is set as the transmittance T1 of the pixel. calculate. Weighting is performed based on the area ratio of overlapping pixels.

  Next, the process proceeds to step S116, and for each image of the luminance modulation light valve, the control value corresponding to the transmittance T1 calculated for the image is read from the control value registration table 400, and the read control value is read from the image. Is determined as the control value. In the subsequent series of control values, the transmittance closest to the calculated transmittance T1 is searched from the control value registration table 400, and the control value corresponding to the transmittance found by the search is read. This search is performed using, for example, a binary search method, thereby realizing a high-speed search.

  Next, the process proceeds to step S118, and for each color modulation light valve image, the weighted average value of the transmittance T1 determined for the pixels of the luminance modulation light valve overlapping the image line and the optical path is calculated, and the calculated average Based on the value, the light modulation rate Tp and the gain G calculated in step S108, the transmittance T2 of the image is calculated by the above equation (2). Weighting is performed based on the area ratio of overlapping picture lines.

  Next, the process proceeds to step S120, and for each color modulation light valve image, a control value corresponding to the transmittance T2 calculated for the image is read from the control value registration table, and the read control value is read from the image. Determined as a control value. In the reading of the control value, the transmittance that most closely approximates the calculated transmittance T2 is searched from the control value registration table, and the control value corresponding to the transmittance found by the search is read. This search is performed using, for example, a binary search method, thereby realizing a high-speed search.

  Next, the process proceeds to step S122, the control values determined in steps S116 and S120 are output to the light valve driving device 180, the color modulation light valve and the luminance modulation light valve are driven to project a display image, and a series of operations are performed. End the process and return to the original process.

  Next, a process of generating image data to be written in the color modulation light valve (liquid crystal light valves 60B, 60G, 60R) and the luminance modulation light valve (liquid crystal light valve 100) will be described with reference to FIGS.

  In the following, all of the color modulation light valves (liquid crystal light valves 60B, 60G, 60R) have a resolution of 18 horizontal pixels × 12 vertical images and a gradation number of 4 bits. The valve 100) will be described by taking as an example a case where it has a resolution of horizontal 15 pixels × vertical 10 images and a gradation number of 4 bits. Further, both the color modulation light valve and the luminance modulation light valve are viewed from the light source 10 side.

  In the display control device 200, the HDR display data is read through steps S100 to S104, the read HDR display data is analyzed, and based on the analysis result, the brightness level of the HDR display data is the brightness of the projector PJ1. Tone mapped to dynamic range. Next, through step S106, the HDR image is resized in accordance with the resolution of the color modulation light valve.

  Next, through step S108, the light modulation rate Tp is calculated for each image of the resized image. For example, the light modulation rate Tp of the image p in the resized image is such that the luminance level Rp (R, G, B) of the image p is (1.2, 5.4, 2.3) and the luminance Rs (R, G, B) of the light source 10. Is (10000, 10000, 10000), (1.2, 5.4, 2.3) / (10000, 10000, 10000) = (0.00012, 0.00054, 0.00023).

  FIG. 28 is a diagram showing a case where the transmittance T2 of the color modulation light valve is provisionally determined.

  Next, through step S110, the transmittance T2 of each pixel of the color modulation light valve is provisionally determined. In the case of p21 (upper left), p22 (upper right), p23 (lower left), and p24 (lower right), the transmittance T2 of the pixels p21 to p24 is shown in FIG. As shown, an initial value T20 is given.

  FIG. 29 is a diagram illustrating a case where the transmittance T1 'of the luminance modulation light valve is calculated in units of pixels of the color modulation light valve.

  Next, through step S112, the transmittance T1 'of the luminance modulation light valve is calculated for each pixel of the color modulation light valve. When attention is paid to the pixels p21 to p24, the transmittances T11 to T14 of the luminance modulation light valves corresponding thereto correspond to the light modulation rates of the pixels p21 to p24 as Tp1 to Tp4 and the gain G to “1” as shown in FIG. It can be calculated by the following formulas (3) to (6).

Calculate using actual numerical values. In the case of Tp1 = 0.00012, Tp2 = 0.05, Tp3 = 0.02, Tp4 = 0.01, T20 = 0.1, T11 = 0.0012, T12 = 0.5, T13 = 0.2, T14 = 0.1 according to the following equations (3) to (6). It becomes.

T11 = Tp1 / T20 (3)
T12 = Tp2 / T20 (4)
T13 = Tp3 / T20 (5)
T14 = Tp4 / T20 (6)

  FIG. 30 is a diagram illustrating a case where the transmittance T1 of each pixel of the luminance modulation light valve is determined.

  Next, through step S114, the transmittance T1 of each pixel of the luminance modulation light valve is determined. Since the luminance modulation light valve and the color modulation panel are in an inverted image relationship with each other by the relay lens 90, the pixels in the upper left four sections of the color modulation panel are imaged on the lower right portion of the luminance modulation light valve. When the pixels in the lower right four sections of the luminance modulation light valve are p11 (lower right), p12 (lower left), p13 (upper right), and p14 (upper left), the pixel p11 is as shown in FIG. Since the color modulation light valve and the luminance modulation light valve have different resolutions, they overlap with the pixels p21 to p24 on the optical path. Since the resolution of the color modulation light valve is 18 × 12 and the resolution of the luminance modulation light valve is 15 × 10, the pixel p11 has a 6 × 6 rectangular area based on the least common multiple of the number of pixels of the color modulation light valve. Can be classified. Then, the overlapping area ratio of the pixel p11 and the pixels p21 to p24 is 25: 5: 5: 1 as shown in FIG. Therefore, the transmittance T15 of the pixel p11 can be calculated by the following equation (7) as shown in FIG.

  Calculate using actual numerical values. When T11 = 0.0012, T12 = 0.5, T13 = 0.2, and T14 = 0.002, T15 = 0.008 according to the following equation (7).

T15 = (T11 × 25 + T12 × 5 + T13 × 5 + T14 × 1) / 36 (7)
Similarly to the pixel p11, the transmittances T16 to T18 of the pixels p12 to p14 can be obtained by calculating a weighted average value based on the area ratio.

  Next, through step S116, for each pixel of the luminance modulation light valve, a control value corresponding to the transmittance T1 calculated for the pixel is read from the control value registration table 400, and the read control value is the pixel. Is determined as a control value. For example, since T15 = 0.008, referring to the control value registration table 400, 0.09 is the closest approximation as shown in FIG. Therefore, “8” is read from the control value registration table 400 as the control value of the pixel p11.

  FIG. 31 is a diagram illustrating a case where the transmittance T2 of each pixel of the color modulation light valve is determined.

  Next, through step S118, the transmittance T2 of each pixel of the color modulation light valve is determined. As shown in FIG. 31A, the pixel p24 overlaps the pixels p11 to p14 on the optical path because the color modulation light valve and the luminance modulation light valve have different resolutions. Since the resolution of the color modulation light valve is 18 × 12 and the resolution of the luminance modulation light valve is 15 × 10, the pixel p24 has a rectangular area of 5 × 5 based on the least common multiple of the number of pixels of the luminance modulation light valve. Can be classified. Then, the overlapping area ratio of the pixel p24 and the pixels p11 to p14 is 1: 4: 4: 16 as shown in FIG. Therefore, when attention is paid to the pixel p24, the transmittance T19 of the luminance modulation light valve corresponding to the pixel p24 can be calculated by the following equation (8). Then, the transmittance T24 of the pixel p24 can be calculated by the following equation (9) as shown in FIG. 31 (c) when the gain G is “1”.

Calculate using actual numerical values. When T15 = 0.09, T16 = 0.33, T17 = 0.15, T18 = 0.06, and Tp4 = 0.01, T19 = 0.1188 and T24 = 0.0842 are obtained from the following equations (8) and (9).

T19 = (T15 × 1 + T16 × 4 + T17 × 4 + T18 × 16) / 25 (8)
T24 = Tp4 / T19 (9)

Similarly to the pixel p24, the transmittances T21 to T23 of the pixels p21 to p23 can be obtained by calculating a weighted average value based on the area ratio.

  Next, through step S120, for each pixel of the color modulation light valve, a control value corresponding to the transmittance T2 calculated for the pixel is read from the control value registration table, and the read control value is the pixel. Is determined as a control value. For example, when T24 = 0.0842 for the pixel p24 of the liquid crystal light valve 60R, referring to the control value registration table 420R, 0.07 is the closest approximation as shown in FIG. Therefore, “7” is read from the control value registration table 420R as the control value of the pixel p24.

  Then, through step S122, the determined control value is output to the light valve driving device 180. As a result, the luminance modulation light valve (liquid crystal light valve 100) and the color modulation light valve (liquid crystal light valves 60B, 60G, 60R) are driven to project a display image on the screen.

  With the above-described modulation control of the liquid crystal light valve, it is possible to increase the luminance dynamic range and increase the number of gradations through a two-stage image formation process.

[Modification of Embodiment]
In the first embodiment, the resolution of the liquid crystal light valves 60B, 60G, and 60R (color modulation light valves) that are the first light modulation elements is the same as that of the liquid crystal light valve 100 (luminance modulation) that is the second light modulation element. However, the resolution of the two light modulation elements (the color modulation light valve and the luminance modulation light valve) may be the same or different. However, if the two resolutions are different, it is necessary to convert the resolution of the display image data as described in the first embodiment.

  For example, if the luminance modulation light valve has a display resolution higher than that of the color modulation light valve, the MTF (Modulation Transfer Function) in light transmission from the color modulation light valve to the luminance modulation light valve is set high. Therefore, it is not necessary to increase the transmission performance of the intervening relay optical system so much that the relay optical system can be configured at a relatively low cost.

  On the other hand, if the color modulation light valve has a display resolution higher than that of the luminance modulation light valve, the display image data is usually prepared according to the display resolution of the color modulation light valve. This conversion process only needs to be performed once in accordance with the display resolution of the luminance modulation light valve, so that the display image data conversion process is facilitated.

[Other variations]
In each of the above embodiments, the luminance modulation light valve and the color modulation light valve are used to modulate the luminance of light in two stages. However, the present invention is not limited to this, and two sets of luminance modulation light valves are used for light. It is also possible to configure so that the luminance of the signal is modulated in two stages.

  In the above embodiment, the liquid crystal light valves 60B, 60G, 60R, 100 are configured using active matrix liquid crystal display elements. However, the present invention is not limited thereto, and the liquid crystal light valves 60B, 60G, 60R, 100 are used. A passive matrix liquid crystal display element and a segment type liquid crystal display element can also be used. The active matrix type liquid crystal display has an advantage that precise gradation display can be performed, and the passive matrix type liquid crystal display element and the segment type liquid crystal display element have an advantage that they can be manufactured at low cost.

  In the above embodiment, a relay lens mainly composed of a transmission type optical element is used as a relay optical system for forming an optical image of the front-stage liquid crystal light valve on the rear-stage liquid crystal light valve. However, the present invention is not limited to this, and a reflective relay optical system mainly composed of a reflective optical element (mirror) may be used.

  In each of the above-described embodiments, the projector PJ1 is configured by providing a transmissive light modulation element. However, the projector PJ1 is not limited thereto, and the luminance modulation light valve or the color modulation light valve may be a reflective liquid crystal light valve, DMD (Digital It can also be composed of a reflective light modulation element such as a Micromirror Device).

  Further, in each of the above-described embodiments, the case where the control program stored in advance in the ROM 172 is executed when executing the processing shown in the flowchart of FIG. 23 has been described, but the present invention is not limited to this and shows the procedure. The program may be read from the storage medium storing the program into the RAM 174 and executed.

  Here, the storage medium is a semiconductor storage medium such as RAM or ROM, a magnetic storage type storage medium such as FD or HD, an optical reading type storage medium such as CD, CDV, LD, or DVD, or a magnetic storage type such as MO. / Optical reading type storage media, including any storage media that can be read by a computer regardless of electronic, magnetic, optical, or other reading methods.

  In each of the above embodiments, a single light source that emits white light is used as the light source 10 and the white light is split into RGB three primary colors. However, the present invention is not limited to this. Three light sources corresponding to the three primary colors, a light source that emits red light, a light source that emits blue light, and a light source that emits green light, and a means for spectrally separating white light may be removed. .

  As described above, the preferred embodiments according to the present invention have been described with reference to the accompanying drawings, but the present invention is not limited to the examples. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

The figure which shows the main optical structures of the image display apparatus (projector) which concerns on this invention. The figure which shows the structure of a relay lens. Illustration of telecentricity. Illustration of telecentricity. The figure which shows the pixel surface of a liquid crystal light valve (color modulation light valve). Explanatory drawing which showed notionally the cause of moiré. Explanatory drawing of schematic structure and function of an optical low-pass filter. FIG. 8 is a more specific explanatory diagram of the function of the low-pass filter in FIG. 7. Explanatory drawing of the optical image of a unit pixel. Sectional drawing of a liquid crystal light valve (luminance modulation light valve). The figure which shows the other form example of a low-pass filter. The figure which shows the other form example of a low-pass filter. The figure which shows the other form example of a low-pass filter. The figure which shows the other form example of a low-pass filter. The figure which shows the other form example of a low-pass filter. The figure which shows the other form example of a low-pass filter. The figure which shows the other form example of a low-pass filter. The figure which shows the other form example of a low-pass filter. The figure which shows the other form example of a low-pass filter. The figure which shows the other form example of a low-pass filter. Explanatory drawing which shows the branch state of the incident light by the prism group (low-pass filter) shown in FIG. In FIG. 21, explanatory drawing which shows the positional relationship in the projection surface of the branched light beam. The block diagram which shows the hardware constitutions of a display control apparatus. The figure which shows the data structure of a control value registration table. The figure which shows the data structure of a control value registration table. The flowchart figure which shows a display control process. The figure for demonstrating a tone mapping process. The figure which shows the case where the transmittance | permeability of a color modulation light valve is tentatively determined. The figure which shows the case where the transmittance | permeability of a luminance modulation light valve is calculated per pixel of a color modulation light valve. The figure which shows the case where the transmittance | permeability of each pixel of a brightness | luminance modulation light valve is determined. The figure which shows the case where the transmittance | permeability of each pixel of a color modulation light valve is determined.

Explanation of symbols

PJ1 ... projector (image display device), 10 ... light source, 11 ... light source lamp, 12 ... reflector, 20 ... uniform illumination system, 25 ... color modulator, 30, 35 ... dichroic mirror, 42 ... relay lens (relay optical system) , 60B, 60G, 60R ... liquid crystal light valve (color modulation light valve, first light modulation element), 65, 108 ... pixel, 65a ... opening, 65b ... light shielding part, 70 ... cross dichroic prism, 71 ... B light reflection Dichroic film, 72 ... R light reflecting dichroic film, 80 ... low pass filter, 85 ... prism element, 85a ... flat part, 85b ... prism part, 100 ... liquid crystal light valve (luminance modulation light valve, second light modulation element), 107 ... microlens array, 109 ... lens, 110 ... projection lens.

Claims (14)

An apparatus for displaying an image by modulating light from a light source based on display image data,
A first light modulation element for modulating light from the light source;
A second light modulation element that modulates light from the first light modulation element;
A relay optical system that is disposed between the first light modulation element and the second light modulation element and transmits an optical image formed by the first light modulation element to a pixel surface of the second light modulation element;
Disposed between the first optical modulation element and the second optical modulation element, an optical low-pass filter to be refracted at least a portion of the light from the first light modulation element,
An image display device comprising: a microlens array that collects light from the optical low-pass filter including light refracted by the optical low-pass filter at each pixel of the second light modulation element. Each pixel of the first light modulation element and the second light modulation element includes an opening and a light shielding part,
The optical low-pass filter bends a part of the light passing through the opening of the first light modulation element, and superimposes the light on a dark part formed by the light shielding part of the first light modulation element. The image display device according to claim 1, wherein   The image display device according to claim 2, wherein the optical low-pass filter includes a prism group including an assembly of prism elements having at least a refractive surface.   The image display device according to claim 3, wherein the prism element includes a flat portion and a prism portion having a polygonal pyramid shape.   The micro lens array includes a lens group that is disposed on a light incident side of the second light modulation element and has a one-to-one correspondence with each pixel of the second light modulation element. 5. The image display device according to any one of 4. 6. The image display device according to claim 1, wherein the optical low-pass filter is disposed adjacent to the microlens array with at least a part of the relay optical system interposed therebetween. . 6. The image display device according to claim 1, wherein the optical low-pass filter is disposed adjacent to the microlens array. A light separation system in which the light from the light source is separated into light of a plurality of different specific wavelength regions, and a plurality of separated light from the light is incident on the first light modulation element;
A light combining system for combining the plurality of separated lights from the first light modulation element;
The image display device according to claim 1, further comprising: The image display device according to claim 8, wherein the optical low-pass filter is disposed between the photosynthesis system and the relay optical system. The image display device according to claim 8, wherein the optical low-pass filter is disposed between the relay optical system and the second light modulation element. The image display device according to claim 8, wherein the optical low-pass filter is disposed in the relay optical system. The optical low-pass filter is disposed between the first light modulation element and the light combining system,
The first light modulation element has a plurality of elements corresponding to the plurality of specific wavelength regions,
The image display device according to claim 11, wherein the optical low-pass filter includes a plurality of filters corresponding to the plurality of elements. The image display device according to claim 1, wherein the relay optical system has double-sided telecentricity. A projector,
An image display device according to any one of claims 1 to 13 ,
And a projector.

Images