JP4882203B2 - Optical display device and projection display device - Google Patents

Description

  The present invention relates to an apparatus for displaying an image by modulating light from a light source via a plurality of light modulation elements, and in particular, an optical display apparatus suitable for realizing a luminance dynamic range and an increase in the number of gradations, and The present invention relates to a projection display device.

In recent years, LCD (Liquid Crystal Display), EL, plasma display, CRT (Cathode Ray Tube), projectors, and other optical display devices have seen remarkable improvements in image quality, and the resolution and color gamut have achieved performance that is almost comparable to human visual characteristics. It is being done. However, regarding the luminance dynamic range, the reproduction range is limited to about 1 to 10 ² [nit], and the number of gradations is generally 8 bits. On the other hand, human visual perception has a luminance dynamic range perceived at a time of about 10 ⁻² to 10 ⁴ [nit], and the luminance discrimination capability is about 0.2 [nit], which is the number of gradations. Is converted to 12 bits. Looking at the display image of the current optical display device through such visual characteristics, the narrowness of the luminance dynamic range is conspicuous, and in addition, the reality and power of the display image are insufficient due to the lack of gradation in the shadow part and highlight part. Will feel unsatisfactory.

  Further, in computer graphics (hereinafter abbreviated as CG) used in movies, games, etc., display data (hereinafter referred to as HDR (High Dynamic Range) display data) that represents a luminance dynamic range and gradation number close to human vision. The movement of pursuing the reality of depiction is being mainstream. However, since the performance of the optical display device that displays it is insufficient, there is a problem that the expressive power inherent in the CG content cannot be fully exhibited.

Further, the next OS (Operating System) is scheduled to adopt a 16-bit color space, and the luminance dynamic range and the number of gradations are dramatically increased as compared with the current 8-bit color space. Therefore, it is desired to realize an optical display device that can make use of the 16-bit color space.
Among optical display devices, projection display devices such as liquid crystal projectors and DLP (Digital Light Processing, trademark of TI) projectors are capable of displaying large screens and are effective in reproducing the reality and power of displayed images. Device. In this field, the following proposals have been made to solve the above problems.

  As a projection display device with a high dynamic range, for example, there is a technique disclosed in Patent Document 1, which includes a light source, a first light modulation element that modulates luminance in the entire wavelength region of light, and a wavelength region of light. Among these, each wavelength region of the RGB three primary colors is provided with a second light modulation element that modulates the luminance of the wavelength region, and the light from the light source is modulated by the first light modulation element to form a desired luminance distribution, and its optical image Is imaged on the display surface of the second light modulation element, color modulated, and secondarily modulated light is projected. Each pixel of the first light modulation element and the second light modulation element is individually controlled based on the first control value and the second control value determined from the HDR display data. As the light modulation element, a transmittance modulation element having a pixel structure or a segment structure whose transmittance can be controlled independently and capable of controlling a two-dimensional transmittance distribution is used. A typical example is a liquid crystal light valve. Further, a reflectance modulation element may be used instead of the transmittance modulation element, and a representative example thereof is a DMD (Digital Micromirror Device) element.

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. With a single light modulation element, the luminance dynamic range is 60 / 0.2 = 300. Since the conventional projection display apparatus corresponds to optically arranging light modulation elements having a luminance dynamic range of 300 in series, a luminance dynamic range of 300 × 300 = 90000 can be realized. The same idea holds for the number of gradations, and an 8-bit gradation light modulation element is optically arranged in series, whereby a gradation number exceeding 8 bits can be obtained.
Japanese Patent Laid-Open No. 2001-1000068

However, in the invention described in Patent Document 1, the optical length of the illumination light path of each separated light after being separated into three primary color lights is different from the separated light of the other two colors for one separated light. A luminance difference between the separated lights due to this optical path length difference occurs. This luminance difference causes color blur, color blur, and the like in the optical image after combined separated light.
Therefore, the present invention has been made paying attention to such an unsolved problem of the conventional technology, and the first light modulating element for modulating white light and the first light modulating for each color light separated by wavelength. Provided are an optical display device and a projection display device in which two light modulation elements are arranged in series and light modulation is performed in two stages to improve the display image quality and to reduce the size of the entire device. It is aimed.

[Invention 1] In order to achieve the above object, an optical display device of Invention 1 includes a first light modulation element that controls light propagation characteristics of light from a light source, and
Light separating means for separating the light from the first light modulation element into light of a plurality of different specific wavelength regions and emitting separated light;
A plurality of second light modulation elements for controlling light propagation characteristics of separated light from the light separating means;
A light combining unit that combines light from each of the second light modulation elements to emit combined light, and displays an image by modulating light from the light source based on display image data,
The light separating means has an incident surface on which light from the first light modulation element is incident, and a plurality of exit surfaces from which the separated light is emitted.
The light synthesizing means has a plurality of incident surfaces corresponding to the respective emission surfaces of the light separating means, and an emission surface for emitting the combined light,
For each exit surface of the light separating means, the separated light emitted from the exit surface is transmitted to the corresponding incident surface of the light combining means, and the optical path length of the separated light is the same as the optical path length of the other separated light Alternatively, the light transmission means is provided so as to be substantially the same, and the second light modulation element is arranged on each optical path of the exit surface of the light separation means and the entrance surface of the light combining means corresponding to the exit surface. It is a feature.

  With such a configuration, each light beam emitted from each light exit surface of the light separating unit is combined with the light by the light transmission unit so that each optical path length is the same as or substantially the same as the other optical path lengths. Since the light can enter each incident surface of the means, the length of each optical path between the first light modulation element and the second light modulation element can be easily made substantially the same. Therefore, the intensity distribution of light reaching the second light modulation element from the first light modulation element can be made uniform between the optical paths, and the display image formed on the first light modulation element is accurately and efficiently applied to the second light modulation element. Can communicate well.

  Further, since the light from the light source is modulated via the first light modulation element and the second light modulation element, an effect that a high luminance dynamic range and the number of gradations can be realized is obtained.

[Invention 2] The optical display device of Invention 2 is the optical display device of Invention 1, wherein at least one relay lens is provided between each exit surface of the light separating means and each second light modulation element. It is characterized by that.
With such a configuration, the characteristics of the relay lens and the position on the optical path can be adjusted for each optical path of the separated light, and the separated light can be adjusted by making these characteristics and positions appropriate. The transmission accuracy can be improved.
Here, the characteristics of the relay lens include the shape, material, curvature, refractive index, and the like of the lens.

[Invention 3] The optical display device of Invention 3 is characterized in that in the optical display device of Invention 1 or Invention 2, a first condenser lens is provided on the incident side of the light separating means.
With such a configuration, it is possible to improve the incident efficiency of the light emitted from the first light modulation element to each relay lens by the first condenser lens.
That is, the first condenser lens is a lens having a function of collecting incident light.

[Invention 4] The optical display device of Invention 4 is the optical display device of any one of Inventions 1 to 3, wherein a second condenser lens is provided on the incident side of each of the second light modulation elements. It is a feature.
With such a configuration, the incident angle distribution of the light from the relay lens to the light combining unit can be adjusted by the second condenser lens, so that it is possible to improve the efficiency and accuracy of light combining in the light combining unit.
That is, the second condenser lens is a lens having a function of adjusting the angular distribution of the emitted light of the incident light.

  [Invention 5] The optical display device of Invention 4 is the optical display device of any one of Inventions 1 to 4, wherein at least one of the light separating means and the light synthesizing means is a plurality of prisms each having a substantially triangular prism shape. And a dichroic film that reflects or transmits light in a specific wavelength region is formed of a cross dichroic prism having an X-shaped cross section.

  With such a configuration, the respective light beams emitted from the respective light exit surfaces of the light separating means are respectively equal to or substantially the same as the other light path lengths on the respective light incident surfaces of the light combining means. Therefore, the length of each optical path between the first light modulation element and the second light modulation element can be easily made substantially the same. Therefore, the intensity distribution of light reaching the second light modulation element from the first light modulation element can be made uniform between the optical paths, and the display image formed on the first light modulation element is accurately and efficiently applied to the second light modulation element. Can communicate well.

[Invention 6] The optical display device of Invention 5 is the optical display device of any one of Inventions 1 to 4, wherein at least one of the light separating means and the light synthesizing means emits light in a specific wavelength region. It is characterized in that it is constituted by a cross dichroic mirror in which two flat plates on which a dichroic film to be reflected or transmitted is formed have an X-shaped cross section.
With such a configuration, at least one of the light separating unit and the light combining unit is configured by a cross dichroic mirror having a simple structure as compared to a cross dichroic prism. Therefore, the light separating unit and the light combining unit The effect that at least one can be comprised comparatively cheaply is acquired.

[Invention 7] The optical display device according to Invention 7 is the optical display device according to any one of Inventions 1 to 6, wherein the light separating means and the light synthesizing means are integrated with each other. It is characterized by that.
With such a configuration, the light separating means and the light synthesizing means can be constituted by a single cross dichroic prism or cross dichroic mirror, so that the light separating means and the light synthesizing means can be constructed relatively inexpensively. can get.

  [Invention 8] The optical display device of Invention 8 is characterized in that, in the optical display device of any one of Inventions 1 to 6, the light separating means and the light synthesizing means are provided separately.

With such a configuration, since the light separating unit and the light combining unit are provided separately, the effect of separately optimizing the characteristics of both can be obtained in the separation or combination of light.
Further, by providing the light separating unit and the light combining unit adjacent or close to each other, it is possible to obtain an effect that it is possible to suppress a reduction in luminance when transmitting separated light.

[Invention 9] Further, the optical display device of Invention 9 is the optical display device according to any one of Inventions 1 to 4, wherein the light separating means and the light synthesizing means are each a polyhedron having a plurality of substantially triangular prisms. The dichroic film is formed of a cross dichroic prism having an X-shaped cross section that reflects or transmits light in a specific wavelength region, and the light separating means and the light combining means are provided separately. ,
The intersecting line formed by the two dichroic films existing inside the light separating means and the intersecting line formed by the two dichroic films existing inside the light synthesizing means are on the same line or substantially on the same line. The light separating means and the light synthesizing means are arranged so as to be positioned.

  With such a configuration, the light separating means and the light synthesizing means are arranged so that the intersecting lines formed by the two dichroic films inside the light separating means and the light synthesizing means are located on the same line or substantially on the same line. Therefore, by arranging the light separating means and the light synthesizing means close to each other or adjacent to each other, one of them can be arranged on the other, thereby reducing the installation area of the light separating means and the light synthesizing means. The effect that the whole apparatus can be reduced in size is acquired.

[Invention 10] The optical display device of Invention 10 is the optical display device of any one of Inventions 1 to 4, wherein the light separating means and the light synthesizing means reflect or transmit light in a specific wavelength region. The two flat plates on which the dichroic film is formed are constituted by a cross dichroic mirror having an X-shaped cross section, and the light separating means and the light synthesizing means are provided separately,
The light separating means and the intersection are formed so that the intersecting line formed by the dichroic mirror of the light separating means and the intersecting line formed by the dichroic mirror of the light combining means are located on the same line or substantially the same straight line. It is characterized by arranging photosynthesis means.

  In such a configuration, the light separating means and the light combining means are arranged so that the intersecting lines formed by the dichroic mirrors constituting the light separating means and the light combining means are located on the same line or substantially on the same line. By making the separating means and the light synthesizing means close or adjacent to each other, one of them can be stacked on the other, thereby reducing the installation area of the light separating means and the light synthesizing means and reducing the size of the entire apparatus. The effect that it can be made is obtained.

[Invention 11] Further, in the optical display device of Invention 11, in the optical display device of any one of Inventions 2 to 10, the relay lens has a characteristic different for each optical path of the separated light. It is characterized by.
With such a configuration, it is possible to improve the transmission accuracy of each separated light by making the characteristics of the relay lens appropriate for each separated light.
Here, the characteristics of the relay lens include the shape, material, curvature, refractive index, and the like of the lens.

[Invention 12] Furthermore, the optical display device of Invention 12 is the optical display device of any one of Inventions 4 to 11, wherein the second condenser lens has different characteristics for each optical path of the separated light. It is characterized by providing.
In such a configuration, a second condenser lens having characteristics suitable for adjusting the incident angle of each light to the light synthesizing means according to the properties of each separated light is provided. As a result, it is possible to improve the transmission accuracy of each separated light.
Here, the characteristics of the second condenser lens include the shape, material, curvature, refractive index, and the like of the lens.

[Invention 13] Furthermore, the optical display device of Invention 13 is the optical display device of any one of Inventions 1 to 12, wherein the first light modulation element and the second light modulation element corresponding to each of the separated lights. The distance between the two is different for each optical path of the separated light.
With such a configuration, since the distance between the first light modulation element and the second light modulation element can be adjusted for each separated light, optical aberrations such as lateral chromatic aberration depending on the distance can be reduced. The effect that correction can be performed easily is obtained.

[Invention 14] Furthermore, in the optical display device of Invention 14, in the optical display device of any one of Inventions 1 to 13, one or more aspherical lenses are provided on an optical path after the first light modulation element. It is characterized by that.
With such a configuration, it is possible to correct the shift of the focal position of each transmitted light by the aspheric lens, thereby obtaining the effect of improving the light imaging accuracy.
Here, the aspherical lens is a lens in which at least one of the lens surfaces is a quadratic curve such as an ellipsoid, a hyperboloid, and a paraboloid.

  [Invention 15] Further, in the optical display device of Invention 15, in the optical display device of any one of Inventions 1 to 14, one or more achromat lenses are provided on an optical path after the first light modulation element. It is characterized by.

With such a configuration, it is possible to correct the shift of the focal position of each transmitted light by the achromat lens, thereby obtaining the effect of improving the light imaging accuracy.
Here, the achromat lens is a lens that corrects a focal position shift of two colors (usually red and blue) by bonding two lenses (convex lens and concave lens) having different refractive indexes and chromatic dispersions together. is there. In other words, since light has a property that its refractive index varies depending on the wavelength, for example, visible light that has passed through a single lens forms an image of blue light with a short wavelength in the foreground and red light at the back This is called “upper chromatic aberration”). That is, an achromatic lens is suitable for suppressing this blur. Of course, even if the lens provided on the optical path after the light separating means is a combined lens composed of three or more lenses, the same effect as that of an achromatic lens or an aspherical lens can be obtained.

[Invention 16] Further, in the optical display device of Invention 16, in the optical display device of any one of Inventions 1 to 15, the first light modulation element displays higher than the display resolution of the second light modulation element. It is characterized by having a resolution.
With such a configuration, it is not necessary to set a high MTF (Modulation Transfer Function) in light transmission from the first light modulation element to the second light modulation element, so that the first light modulation element to the second light modulation element. In the meantime, it is possible to reduce the cost of necessary optical elements. In addition, since the plurality of first light modulation elements have a lower resolution than the second light modulation element, the first light modulation element can be made smaller than the second light modulation element. The effect that it is possible is also acquired. Furthermore, when the present invention is applied to a projection display device such as a projector, the second light modulation element has a lower display resolution than the first light modulation element, so that the size thereof can be made smaller than that of the first light modulation element. In accordance with this, it is possible to reduce the size of the exit side lens, the light synthesizing unit, the projection lens, and the like, so that an effect of reducing the cost can be obtained.
Here, the MTF is also called a contrast transfer function, and indicates the modulation of the image of a sinusoidal object with respect to an increase in spatial frequency.

  [Invention 17] Further, in the optical display device of Invention 17, in the optical display device of any one of Inventions 1 to 15, is the second light modulation element higher than the display resolution of the first light modulation element? Alternatively, it has the same display resolution.

  With such a configuration, in the creation of display image data corresponding to each light modulation element, display image data prepared in accordance with the display resolution of the second light modulation element having a display resolution higher than that of the first light modulation element Since it is only necessary to perform image processing only once in accordance with the display resolution of the first modulation element, an effect of facilitating generation of display image data can be obtained. That is, when the display resolution of the first light modulation element is higher than that of the second light modulation element, a plurality of image processes are required for the plurality of second light modulation elements.

[Invention 18] Furthermore, the optical display device of Invention 18 is the optical display device of any one of Inventions 1 to 17, wherein the size of the display surface (image display region) in the first light modulation element is set to the second value. It is characterized by being larger than the size of the display surface (image display area) in the light modulation element.
With such a configuration, for example, when a liquid crystal light valve is applied to the first light modulation element and the second light modulation element, the size relationship of the display surface composed of a plurality of pixels in the liquid crystal light valve is large. , “Display surface of first light modulation element> display surface of second light modulation element”, the second light modulation element can be made smaller than the first light modulation element. For example, since it is possible to reduce the size of the second light modulation elements that are required when controlling the propagation characteristics of the three primary colors of RGB, the cost can be reduced, and the size of the second light modulation element can be reduced. In addition, the downstream optical element such as the light combining means can be reduced in size, so that the cost can be further reduced. In addition, the configuration of the first light modulation element and the second light modulation element according to the above-described dimensional relationship of the display surface is obtained by setting the resolution of the first light modulation element and the second light modulation element as “resolution of second light modulation element <first This is suitable for the relationship of “resolution of one light modulation element”.

  Here, the display surface (image display region) differs depending on the element used as the light modulation element, and if it is a liquid crystal light valve, it becomes the display surface described above, and if it is a DMD element, it is a reflection composed of a plurality of micromirrors. It becomes a surface. Note that the overall size of the display surface varies depending on the size and number of pixels, and the size of the reflective surface varies depending on the size and number of micromirrors. Hereinafter, the same applies to the optical display device of the nineteenth aspect.

[Invention 19] Furthermore, the optical display device of Invention 19 is the optical display device of any one of Inventions 1 to 17, wherein the display surface dimensions of the second light modulation element are the same as those of the first light modulation element. It is characterized by being larger or the same as the dimensions of the surface.
With such a configuration, for example, when a liquid crystal light valve is applied to the first light modulation element and the second light modulation element, the size relationship of the display surface composed of a plurality of pixels in the liquid crystal light valve is large. “Display surface of second light modulation element> Display surface of first light modulation element”, the first light modulation element can be made smaller than the second light modulation element. Accordingly, the downstream optical element such as the light separating means can be miniaturized in accordance with the miniaturization of the first light modulation element, so that the effect of reducing the cost can be obtained. In addition, the dimensional relationship between the first light modulation element and the second light modulation element is suitable when “the resolution of the first light modulation element <the resolution of the second light modulation element”.

[Invention 20] On the other hand, in order to achieve the above object, a projection display apparatus according to Invention 20 projects the optical display apparatus according to any one of Inventions 1 to 19 and output light from the optical display apparatus. And a projecting means.
With such a configuration, it is possible to display an image by projecting a high-precision optical image formed by the optical display device according to any one of Inventions 1 to 19 onto a screen or the like. Is obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 16 are diagrams showing an embodiment of an optical display device and a projection display device according to the present invention.
First, the configuration of the projection display device 1 according to the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a main optical system configuration of a projection type display apparatus 1 according to the present invention, FIG. 2 is a diagram showing a configuration of a cross dichroic prism, and FIG. 3 transmits an optical image at an equal magnification. It is a figure which shows an example of a relay optical system.

  As shown in FIG. 1, the projection display device 1 includes a light source 10, a liquid crystal light valve 30 that modulates white light from the light source 10, and spectrally modulates the modulated light from the liquid crystal light valve 30 into light of three primary colors of RGB. The spectral cross dichroic prism 70, the liquid crystal light valves 60B, 60G, and 60R that modulate the RGB primary color light from the spectral cross dichroic prism 70 for each color, and the RGB 3 that is incident from the liquid crystal light valves 60B, 60G, and 60R. The configuration includes a photosynthesis cross dichroic prism 80 that synthesizes primary color light, and a projection lens 110 that projects synthesized light emitted from the photosynthesis cross dichroic prism 80.

The light source 10 is composed of a light source lamp such as an ultra-high pressure mercury lamp or a xenon lamp, and a reflector that collects light from the light source.
The liquid crystal light valve 30 has a configuration in which a plurality of pixels whose transmittance can be controlled independently are arranged in a matrix, and modulates the intensity of light from the light source 10 over the entire wavelength region based on display image data. The modulated light containing the optical image is emitted to the incident side lens 50.

  The spectroscopic cross dichroic prism 70 is disposed close to and below the photosynthesis cross dichroic prism 80 (both are vertically stacked in the Y-axis direction of the drawing). As shown in FIG. The blue light reflecting dichroic film 71 and the red light reflecting dichroic film 72 are arranged in an X shape inside. That is, a blue light reflecting dichroic film 71 for reflecting blue light on the liquid crystal light valve 60B side is formed on the joint surface of the prism, and a red light reflecting dichroic film 72 for reflecting red light on the liquid crystal light valve 60R side. It is formed on the joint surface of the prism. Thereby, the modulated white light from the liquid crystal light valve 30 is split into three color lights of RGB which are the three primary colors of light, and each color light is emitted from the surface corresponding to each color light among the six surfaces. In order to allow white light having a wide wavelength range to enter the spectral cross dichroic prism 70, it is desirable to use a prism made of an optical material having a small refractive index wavelength dependency (for example, zero dispersion or low dispersion glass). As a result, it is possible to reduce optical aberration that is likely to occur in each optical path where the light emitted from the liquid crystal light valve 30 passes through the spectral cross dichroic prism 70. Here, of the six surfaces described above, the surface on which the white light from the liquid crystal light valve 30 is incident is defined as the incident surface 70a, and after the spectrum, the surface that emits the blue light is the first emitting surface 70b, and the green light is emitted. A surface to be emitted is a second emission surface 70c and a surface from which red light is emitted is a third emission surface 70d.

  The liquid crystal light valves 60B, 60G, and 60R have a configuration in which a plurality of pixels whose transmittance can be controlled independently are arranged in a matrix, and the liquid crystal light valve 60B is the first of the photosynthesis cross dichroic prism 80 described later. The liquid crystal light valve 60G is disposed facing and close to the first incident surface 80b, and the liquid crystal light valve 60G is disposed facing and close to the second incident surface 80c of the photosynthesis cross dichroic prism 80 described later. The photosynthesis cross dichroic prism 80 is disposed so as to face and be close to the third incident surface 80d. The liquid crystal light valve 60B modulates blue light based on display image data and emits modulated light including an optical image. Similarly, the liquid crystal light valve 60G modulates green light, and the liquid crystal light valve 60R emits red light. Modulate. The liquid crystal light valves 60B, 60G, and 60R are arranged so that the distances between the center of the photosynthesis cross dichroic prism 80 and the three liquid crystal light valves 60B, 60G, and 60R are substantially equal.

  The photosynthesis cross dichroic prism 80 is an optical element having the same structure as that of the spectroscopic cross dichroic prism 70. The emission surface of the synthesized light is an emission surface 80a, the surface on which blue light is incident is a first incidence surface 80b, and green. If the light incident surface is the second incident surface 80c and the red light incident surface is the third incident surface 80d, the blue light and the red light incident from the first incident surface 80b and the third incident surface 80d respectively correspond to each other. The dichroic film is reflected to the exit surface 80a side, while the green light incident from the second entrance surface 80c is transmitted as it is to the exit surface 80a, thereby synthesizing the three primary colors of RGB as the combined light of the color. It injects from the injection surface 80a. Also in this photosynthesis cross dichroic prism 80, it is desirable to use a prism made of an optical material (for example, zero-dispersion or low-dispersion glass) whose refractive index has a small wavelength dependency. As a result, it is possible to reduce optical aberrations that are likely to occur in each optical path where light emitted from the three liquid crystal light valves 60B, 60G, and 60R passes through the photosynthesis cross dichroic prism 80 and reaches the projection lens 110.

  Here, the spectroscopic cross dichroic prism 70 and the photosynthesis cross dichroic prism 80 are arranged such that the intersecting line by the two dichroic films existing in each of them is located substantially on the same line, and the spectroscopic cross dichroic prism 70 is incident. The surface 70a and the exit surface 80a of the photosynthesis cross dichroic prism 80 are arranged so as to be positioned on substantially the same plane, in other words, in a positional relationship such that they are stacked in the Y-axis direction. Due to this arrangement relationship, the incident surface 70a and the exit surface 80a, the first exit surface 70b and the first entrance surface 80b, the second exit surface 70c and the second entrance surface 80c, the third exit surface 70d and the third entrance surface 80d are: Each pair is positioned close to the Y-axis direction, and the optical paths of the three color lights from the spectroscopic cross dichroic prism 70 to the light combining cross dichroic prism 80 can be set to substantially the same length.

  An incident side lens 50 is provided downstream of the liquid crystal light valve 30 so as to face the incident surface 70 a of the spectroscopic cross dichroic prism 70, and light modulated by the liquid crystal light valve 30 passes through the incident side lens 50. The light is incident on the incident surface 70a of the spectroscopic cross dichroic prism 70. Here, the incident side lens 50 is for efficiently making the light from the liquid crystal light valve 30 incident on three relay lenses 370B, 370G, and 370R, which will be described later, and condensing the modulated light from the liquid crystal light valve 30. Then, the light is incident on three relay lenses 370B, 370G, and 370R through the cross dichroic prism for spectroscopy 70.

  In the spectroscopic cross dichroic prism 70, a reflection mirror 380B is opposite to the first emission surface 70b, a reflection mirror 380G is opposite to the second emission surface 70c, and a reflection mirror 380B is opposite to the third emission surface 70d. 1 is arranged in a predetermined manner with respect to the corresponding surfaces of the first to third emission surfaces 70b to 70d so as to bend each color light from the corresponding first to third emission surfaces 70b to 70d in the Y-axis direction of FIG. Arranged at an angle.

  In the photosynthesis cross dichroic prism 80, a reflection mirror 385B is opposite to the first incidence surface 80b, a reflection mirror 385G is opposite to the second incidence surface 80c, and a reflection mirror 385R is opposite to the third incidence surface 80d. The respective color lights from the corresponding reflecting mirrors 380B, 380G, and 380R are arranged in a predetermined manner with respect to the corresponding surfaces of the first to third incident surfaces 80b to 80d so as to bend in the center direction of the photosynthesis cross dichroic prism 80. Arranged at an angle.

  The relay lens 370B is on the blue light path between the reflection mirror 380B and the reflection mirror 385B, the relay lens 370G is on the green light path between the reflection mirror 380G and the reflection mirror 385G, and the reflection mirror 380R. A relay lens 370R is disposed on the optical path of red light between the reflecting mirror 385R. These relay lenses 370B, 370G, and 370R show the optical image (light intensity distribution) formed on the display surface of the liquid crystal light valve 30 and the intensity distribution on the display surfaces of the three liquid crystal light valves 60B, 60G, and 60R. It has a function of accurately transmitting it in a substantially preserved state with almost no light loss, and transmits light from the liquid crystal light valve 30 to the incident side lens 50, the spectral cross dichroic prism 70, and an emission side lens 375B described later. The liquid crystal light valves 60B, 60G, and 60R are led through 375G and 375R.

  An exit side lens 375B is disposed on the entrance side of the liquid crystal light valve 60B, an exit side lens 375G is disposed on the entrance side of the liquid crystal light valve 60G, and an exit side lens 375R is disposed on the entrance side of the liquid crystal light valve 60R. Each color light from the three relay lenses 370B, 370G, and 370R is incident on the corresponding liquid crystal light valves 60B, 60G, and 60R via the reflection mirrors 385B, 385G, and 385R. Here, the three exit-side lenses 375B, 375G, and 375R have angles of incident light with respect to the liquid crystal light valves 60B, 60G, and 60R whose display characteristics are dependent on the incident angle of light and the photosynthesis cross dichroic prism 80. It has a function of suppressing the spread of the distribution, and each color light from the corresponding three relay lenses 370B, 370G, 370R is made substantially parallel and incident on the corresponding three liquid crystal light valves 60B, 60G, 60R. When the optical elements arranged in the subsequent stage of the exit side lenses 375B, 375G, and 375R have the incident angle dependence of the display characteristics, the spread of the angular distribution of the light incident on these optical elements is suppressed. Thus, the exit side lenses 375B, 375G, and 375R are disposed for the purpose of improving display performance and light utilization efficiency. Therefore, the exit side lenses 375B, 375G, and 375R may be omitted depending on the optical elements after the exit side lenses 375B, 375G, and 375R.

  By the way, from the dichroic film of the blue light after the spectrum in the spectral cross dichroic prism 70, the first exit surface 70b, the reflection mirror 380B, the relay lens 370B, the reflection mirror 385B, the exit side lens 375B, and the first entrance surface 80b. The optical path length until reaching the dichroic film of the photosynthesis cross dichroic prism 80 is L1, and similarly, the optical path lengths from the green light and red light spectral cross dichroic prism 70 to the photosynthesis cross dichroic prism 80 are L2 and L3, respectively. And In the present embodiment, the reflection mirrors 380B, 380G, 380R, 385B, 385G, and 385R are respectively arranged so that L1 to L3 are L1 = L2 = L3 (equal distance). That is, when the optical path length from each dichroic film to each exit surface and each entrance surface is equal, the reflection mirrors 380B, 380G, and 380R are respectively connected to the first exit surface 70b, the second exit surface 70c, and the third exit surface 70d. The reflection mirrors 385B, 385G, and 385R are disposed at equal distances from the first incident surface 80b, the second incident surface 80c, and the third incident surface 80d, respectively. With such an arrangement, the distances between the liquid crystal light valve 30 and the three liquid crystal light valves 60B, 60G, and 60R can be easily set to be approximately equal. Thus, the optical images (light intensity distribution) formed on the display surface of the liquid crystal light valve 30 by the relay lenses 370B, 370G, and 370R can be converted into the three liquid crystal light valves 60B, It is possible to transmit accurately and with high efficiency on the display surfaces of 60G and 60R. In addition, the three optical images formed on the three liquid crystal light valves 60B, 60G, and 60R can be accurately combined into one optical image.

  Here, in the liquid crystal light valves 30, 60B, 60G, 60R, a common electrode is formed over the entire surface of the glass substrate on which pixel electrodes and switching elements such as thin film transistor elements and thin film diodes for driving the pixel electrodes are formed in a matrix. This is an active matrix type liquid crystal display element in which a TN liquid crystal is sandwiched between the glass substrate and a polarizing plate is disposed on both sides of the outer surface. The transmittance can be changed in accordance with the control value (applied voltage), and the intensity of light passing through the liquid crystal light valve can be modulated. For example, white / bright (transmission) state when no voltage is applied, and black / dark (non-transmission) state when voltage is applied, and gradation between them is controlled in an analog manner according to a given control value (applied voltage). Is done.

  The liquid crystal light valve 30 and the liquid crystal light valves 60B, 60G, and 60R are all the same in that the intensity of the transmitted light is modulated and an optical image corresponding to the degree of the modulation is included. While the light in the wavelength range (white light) is modulated, the latter liquid crystal light valves 60B, 60G, and 60R are light (R, R) in the specific wavelength region that is spectrally separated by the spectroscopic cross dichroic prism 70 that is a light separating means. Both are different in that the color light (G, B, etc.) is modulated. Therefore, hereinafter, the light intensity modulation performed by the liquid crystal light valves 60B, 60G, and 60R may be referred to as color modulation, and the light intensity modulation performed by the liquid crystal light valve 30 may be referred to as luminance modulation for convenience. From the same viewpoint, the liquid crystal light valves 60B, 60G, and 60R may be referred to as color modulation light valves, and the liquid crystal light valve 30 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 this embodiment, the color modulation light valve has a higher resolution than the luminance modulation light valve, and therefore the color modulation light valve has a display resolution (when the observer views the display image of the projection display device 1). Is the resolution perceived by the observer). 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.

  Next, the overall light transmission flow of the projection display device 1 will be described. First, white light from the light source 10 is modulated by the liquid crystal light valve 30 (brightness modulation light valve), and the white light containing an optical image based on the display image data is passed through the incident side lens 50 to the spectral cross dichroic prism 70. Is incident on the incident surface 70a. In the spectroscopic cross dichroic prism 70, the white light incident on the incident surface 70a is split into three primary color lights of red (R), green (G), and blue (B), and the split blue light, green Light and red light are emitted from the second to fourth emission surfaces 70b to 70d, respectively. The blue light, the green light, and the red light emitted from the second to fourth emission surfaces 70b to 70d are respectively corresponding reflection mirrors 380B, 380G, and 380R, relay lenses 370B, 370G, and 370R, reflection mirrors 385B, 385G, and 385R. The light is incident on the liquid crystal light valves 60B, 60G, and 60R through the exit side lenses 375B, 375G, and 375R.

Blue light, green light, and red light incident on the liquid crystal light valves 60B, 60G, and 60R are color-modulated based on external data corresponding to the respective wavelength regions, and emitted as modulated light including a final optical image. The Each color light from the liquid crystal light valves 60B, 60G, and 60R is incident on the corresponding first to third incident surfaces 80b to 80d of the light combining dichroic prism 80 and is combined into one light, and is projected on a screen (not shown) by the projection lens 110. Projected on. Thereby, a desired color image is displayed on the screen.
In the projection type display device 1, the liquid crystal light valve 60B, which is the second light modulation element, is displayed on the final display image by using the modulated light formed with the optical image (image) by the liquid crystal light valve 30, which is the first light modulation element. , 60G, 60R, and a two-stage image forming process realizes display image excellent in gradation expression (high luminance dynamic range). Therefore, it is necessary to transmit the optical image (image) formed by the liquid crystal light valve 30 to the liquid crystal light valves 60B, 60G, 60R accurately and with high efficiency. For this purpose, an achromatic lens or an aspherical lens is added to the light transmission system including the incident side lens 50, the relay lenses 370B, 370G, and 370R and the emission side lenses 375B, 375G, and 375R, It is effective to apply an achromatic lens or an aspherical lens as the side lens 50, the relay lenses 370B, 370G, and 370R and the exit side lenses 375B, 375G, and 375R. Furthermore, the material of the relay lenses 370B, 370G, and 370R and the exit side lenses 375B, 375G, and 375R, the optical characteristics such as the refractive index and the lens curvature, and the like may be optimized for each optical path. Furthermore, the number of incident side lenses, relay lenses, and emission side lenses is not limited to one for each optical path, and a plurality of lenses may be provided, or the number may be changed for each optical path. By adopting such a configuration, it is possible to suppress the occurrence of optical aberrations due to focal position shifts in the optical image (image) transmission process, and to realize accurate and highly efficient optical image (light intensity distribution) transmission. Can do.

  When the resolution and dimensions of the liquid crystal light valve 30 and the liquid crystal light valves 60B, 60G, and 60R are the same, the incident side lens 50, the relay lenses 370B, 370G, and 370R and the emission side lenses 375B, 375G, and 375R are used. It is possible to make the configured relay optical system an equal-magnification relay optical system. In the case of a relay optical system of the same magnification, as shown in FIG. 3 (here, in order to facilitate understanding only for the optical path including the liquid crystal light valve 60G, two reflecting mirrors 380G and 385G are provided. For example, the optical image 55W formed on the liquid crystal light valve 30 is inverted and the same size inverted image 55G without changing the size while being inverted. The image is accurately formed (transmitted) on the top. FIG. 3 shows the case of green light as an example, but other blue light and red light are similarly formed on the corresponding liquid crystal light valves 60B and 60R as the same magnification inverted image.

Next, the configuration of the display control apparatus 200 will be described in detail with reference to FIGS.
FIG. 4 is a block diagram illustrating a hardware configuration of the display control apparatus 200.
As shown in FIG. 4, the display control device 200 reads out from the CPU 170 that controls the operation 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, as external devices, a light valve driving device 180 that drives a luminance modulation light valve (liquid crystal light valve 30) and a color modulation light valve (liquid crystal light valves 60B, 60G, 60R), data, tables, and the like. A storage device 182 stored as a file 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 pixel values indicating radiance levels for each of the three primary colors of RGB are stored as floating point values for one pixel. For example, the value (1.2, 5.4, 2.3) is stored as the pixel value 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 of generating the HDR display data, for example, publicly known document 1 “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. 5 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. 5, 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. 5, “0” is registered as the control value and “0.003” is registered as the transmittance in the first 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%. Note that FIG. 5 shows an example in which the number of gradations of the luminance 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 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 valve are registered for each color modulation light valve.
FIG. 6 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. 6, 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. 6, “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%. FIG. 6 shows an example in which the number of gradations of the color 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 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. 7 according to the program. .
FIG. 7 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, as shown in FIG. 7, first, the process proceeds to step S100.

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 luminance level of the HDR display data is tone-mapped to the luminance dynamic range of the projection display device 1 based on the analysis result of step S102.
FIG. 8 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 projection display device 1 is Dmin and the maximum value is Dmax. In the example of FIG. 8, 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.

For details of tone mapping, see, 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)”. It is posted.
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 the light modulation rate Tp is calculated for each pixel of the resized image by the above equation (1) based on the luminance level Rp of the pixel of the resized image and the luminance Rs of the light source 10.
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 30, 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 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 control value of the pixel. Determine as. In the reading of the control value, the transmittance that most closely approximates 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 pixel of the color modulation light valve, a weighted average value of the transmittance T1 determined for the pixel of the luminance modulation light valve overlapping with the pixel on the optical path is calculated, and the calculated average value, Based on the light modulation rate Tp and gain G calculated in step S108, the transmittance T2 of the pixel is calculated by the above equation (2). Weighting is performed based on the area ratio of overlapping pixels.

  Next, the process proceeds to step S120, and for each pixel of the color modulation light valve, a control value corresponding to the transmittance T2 calculated for that pixel is read from the control value registration table, and the read control value is used as the control value for that pixel. decide. 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 valves (liquid crystal light valves 60B, 60G, 60R) and the luminance modulation light valve (liquid crystal light valve 30) 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 pixels and a gradation number of 4 bits. ) Will be described by taking as an example the case of having a resolution of 15 horizontal pixels × 10 vertical pixels and a gradation number of 4 bits.
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 the luminance level of the HDR display data is determined based on the analysis result. Tone-mapped to 1 luminance 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 pixel of the resized image. For example, the light modulation rate Tp of the pixel p in the resized image is such that the luminance level Rp (R, G, B) of the pixel p is (1.2, 5.4, 2.3) and the luminance Rs (R, R, If (G, B) is (10000, 10000, 10000), then (1.2, 5.4, 2.3) / (10000, 10000, 10000) = (0.00012, 0.00054, 0.00023).

FIG. 9 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. When the pixels in the upper left four sections of the color modulation light valve are 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. Thus, an initial value T20 is given.

FIG. 10 is a diagram illustrating a case where the transmittance T1 ′ of the luminance modulation light valve is calculated for each pixel 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. When Tp1 = 0.00012, Tp2 = 0.05, Tp3 = 0.02, Tp4 = 0.01, and T20 = 0.1, T11 = 0.0012, T12 = 0.5, T13 = 0.2, and T14 = 0.1 according to the following equations (3) to (6). Become.

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

FIG. 11 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. When pixels in the upper left four sections of the luminance modulation light valve are p11 (upper left), p12 (upper right), p13 (lower left), and p14 (lower right), the pixel p11 has a color as shown in FIG. Since the 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 value as shown in FIG. Therefore, “8” is read from the control value registration table 400 as the control value of the pixel p11.

FIG. 12 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. 12A, 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. 12C 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 stored in the pixel. It 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 value 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 30) and the color modulation light valve (liquid crystal light valves 60B, 60G, 60R) are driven to project a display image on the screen.
According to the projection type display device 1 having the above configuration, the following effects can be obtained. In other words, the spectroscopic cross dichroic prism 70 and the photosynthesis cross dichroic prism 80 are arranged so that the incident surface 70a of the spectroscopic cross dichroic prism 70 and the exit surface 80a of the photosynthesis cross dichroic prism 80 are located on substantially the same plane. Are arranged close to each other in a positional relationship such that they are stacked in the Y-axis direction, and the optical path length L1 of each color light from the dichroic film of the above-described spectral cross dichroic prism 70 to the dichroic film of the photosynthesis cross dichroic prism 80 ( The reflection mirrors 380B, 380G, 380R, 385B, 385G, and 385R are arranged so that the blue light), L2 (green light), and L3 (red light) satisfy L1 = L2 = L3 (equal distance). As a result, the optical path length for each color light between the liquid crystal light valve 30 that is the luminance modulation light valve and the three liquid crystal light valves 60B, 60G, and 60R that are the color modulation light valves can be easily made substantially the same. The display image formed on the liquid crystal light valve 30 is displayed on the three liquid crystal light valves 60B while suppressing the occurrence of luminance differences between the blue light, the green light and the red light reaching the three liquid crystal light valves 60B, 60G and 60R. , 60G, 60R can be transmitted more accurately and efficiently.

  In addition, since the relay lenses 370B, 370G, and 370R and the exit side lenses 375B, 375G, and 375R are arranged for each optical path of each color light separated by the spectral cross dichroic prism 70, the positions of these lenses, By changing the lens material, lens configuration (for example, the number of lenses and the curved surface shape), etc., it is possible to obtain optimum optical characteristics for transmission of light (image) having a different wavelength range for each optical path.

  Further, two types of light modulation elements are arranged in the order of the luminance modulation liquid crystal light valve 30 and the color modulation liquid crystal light valves 60B, 60G, and 60R from the light source 10 toward the projection lens 110, and photosynthesis is performed. Since the optical element having a large wavelength dependency such as a liquid crystal light valve is not disposed on the exit side of the cross dichroic prism 80 for use, it is possible to accurately determine the color of the display image.

In addition, since the light from the light source 10 is modulated via two types of light modulation elements (color modulation light valve and luminance modulation light valve) arranged in series, a high luminance dynamic range and gradation number can be realized. it can.
[Modification 1]
In the above embodiment, the liquid crystal light valves 60B, 60G, and 60R are arranged so that the distance between the center of the photosynthesis cross dichroic prism 80 and the liquid crystal light valves 60B, 60G, and 60R is equal. It is not limited. Since the materials forming each lens, the photosynthesis cross dichroic prism, and the like have various wavelength dependencies (for example, refractive index), an accurate and highly efficient image between the first light modulation element and the second light modulation element ( In order to realize (light) transmission, it is necessary to reduce the influence of wavelength dependence and optical aberrations that are likely to occur in the transmission process. Further, in order to accurately combine the display images formed on the three second light modulation elements into one image, it is necessary to eliminate the influence of the wavelength dependency of the light combining cross dichroic prism 80.
As a measure for realizing the former, for example, the first light modulation element and the second light modulation element so as to correct various wavelength dependencies of the optical element interposed between the first light modulation element and the second light modulation element. It is effective to slightly change the distance between each color light path.

As a measure for realizing the latter, the center of the photosynthesis cross dichroic prism 80 and the liquid crystal light valves 60B, 60G, and 60R are corrected so as to correct various wavelength dependencies of the photosynthesis cross dichroic prism 80 and the projection lens 110. It is effective to slightly change the distance to each color light path. For example, the wavelength dependence of the refractive index of the material constituting the photosynthesis cross dichroic prism 80 is such that the refractive index is large on the short wavelength side and the refractive index is small on the long wavelength side (most glasses have this tendency). As shown in FIG. 13, the distance between the center of the photosynthesis cross dichroic prism 80 and the liquid crystal light valves 60B, 60G, and 60R is made longer as it corresponds to light having a shorter wavelength. It is possible to reduce optical aberration caused by the difference in focal length due to the wavelength dependence of the refractive index. In FIG. 13, when the distance between the center of the photosynthesis cross dichroic prism 80 and the liquid crystal light valves 60B, 60G, 60R is LB, LG, LR, the liquid crystal light valve is in a relationship of LB>LG> LR. 60B, 60G, and 60R are arranged. In addition, the optical path length in each optical path is corrected by changing the thicknesses of the prisms facing the liquid crystal light valves 60B, 60G, and 60R in the photosynthesis cross dichroic prism 80 in accordance with the wavelengths of the three primary colors, and optical aberrations. A configuration for reducing the above is also effective.
[Modification 2]
In the above embodiment, the cross dichroic prism is used to constitute the light separating means and the light combining means. However, the cross dichroic mirror 85 as shown in FIG. 14 is not limited to this, and the cross dichroic prism 70 for spectroscopy or the light combining means is used. Instead of the cross dichroic prism 80, it may be used. The cross dichroic mirror 85 is an optical element in which a plate-like transparent medium 86 such as glass or plastic on which a blue light reflecting dichroic film 71 and a red light reflecting dichroic film 72 are formed is arranged in an X shape. Has the same function as a cross dichroic prism. As a result, the light synthesizing means and the light separating means can be reduced in weight and can be constructed at a lower cost than when a cross dichroic prism is used. The cross dichroic mirror 85 may be a so-called liquid immersion structure cross dichroic mirror arranged in a cube filled with a transparent liquid. In this case, optical performance equivalent to that of the cross dichroic prism can be realized at a lower cost than that of the cross dichroic prism.
[Modification 3]
In the above embodiment, the two types of light modulation means (the liquid crystal light valve 30 and the liquid crystal light valves 60B, 60G, and 60R) are all provided with liquid crystal light valves having the same size and shape (the display surface has the same size and shape). Although used, it is not limited to this. For example, as shown in FIG. 15 (here, only the optical path including the liquid crystal light valve 60G is shown), the size of the color modulation light valve 60G ′ of the projection display device 1 is made smaller than the size of the luminance modulation light valve 30 ′. A configuration is also possible. In this case, if the resolution of the luminance modulation light valve and the color modulation light valve is the same, the size of the display surface of the luminance modulation light valve and the size of the display surface of the color modulation light valve will not match. It is necessary to change (reduce) the size of the image according to the size of the destination color modulation light valve.

By doing so, it is possible to reduce the size of the exit side lens 375G, the photosynthesis cross dichroic prism 80, and the projection lens 110 within the dotted line in FIG. 15 in accordance with the downsizing of the color modulation light valve. Therefore, the effect that cost reduction and weight reduction can be obtained.
[Modification 4]
In the above embodiment, the case where the resolution of the liquid crystal light valves 60B, 60G, and 60R (color modulation light valve) is higher than that of the liquid crystal light valve 30 (luminance modulation light valve) has been described as an example. The resolution of the means (color modulation light valve and 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 color modulation light valve has a display resolution higher than that of the luminance modulation light valve, the MTF (Modulation Transfer Function) in light transmission from the luminance modulation light valve to the color modulation light valve is set high. Therefore, there is no need to increase the transmission performance of the intervening relay lens or the like, and the optical system can be configured relatively inexpensively.

On the other hand, if the color modulation light valve has a display resolution lower than that of the luminance modulation light valve, it is usually easier to manufacture a low resolution light valve than a high resolution light valve. It is not necessary to use many resolution light valves, which is effective for reducing the cost of the display device.
[Modification 5]
In the above embodiment, the spectroscopic unit and the photosynthesis unit are divided into the spectroscopic cross dichroic prism 70 and the photosynthesis cross dichroic prism 80. However, the present invention is not limited to this. As in the projection display device 2 shown in FIG. 16, the spectral cross dichroic prism 70 and the photosynthesis cross dichroic prism 80 in the projection display device 1 are integrated to form a cross dichroic prism 390 for spectroscopy and photosynthesis. good.

  That is, since the spectral cross dichroic prism 70 and the photosynthesis cross dichroic prism 80 are both formed of a cross dichroic prism, the number of parts and cost can be reduced by making them into a common prism. Further, in the case where a cross dichroic mirror is used instead of the cross dichroic prism, it can be similarly integrated.

Here, the projection lens 110 shown in FIG. 1 corresponds to the projection means of the fourteenth aspect.
The liquid crystal light valve 30 shown in FIGS. 1, 3, 15 and 16 corresponds to any one of the first light modulation elements of the inventions 1, 13 and 16 to 19, and the liquid crystal light valves 60B, 60G and 60R are This corresponds to the second light modulation element of any one of Inventions 1, 2, 4, 13 and 16-19.

Moreover, the incident side lens 50 shown in FIGS. 1, 3, 15 and 16 corresponds to the first condenser lens of the invention 3, and the relay lenses 370B, 370G and 370R correspond to the relay lens of the invention 2 or 11. .
Moreover, the exit side lenses 375B, 375G, and 375R shown in FIGS. 1, 3, 13, 15, and 16 correspond to the second condenser lens of the invention 4 or 12.

Moreover, the reflecting mirrors 380B, 380G, 380R, 385B, 385G, and 385R shown in FIGS. 1 and 16 correspond to the light transmission means of the first aspect.
A spectral cross dichroic prism 70 shown in FIGS. 1, 3 and 15 corresponds to any one of the light separating means of the inventions 1, 3, 5 to 10, 14 and 15, and FIGS. The illustrated photosynthesis cross dichroic prism 80 corresponds to any one of the photosynthesis means of the inventions 1 and 5 to 10.

A spectral and photosynthesis cross dichroic prism 390 shown in FIG. 16 corresponds to the light separation means and the light synthesis means of the seventh invention.
Further, the aspherical lens applied to the light transmission system including the relay lenses 370B, 370G, and 370R and the emission side lenses 375B, 375G, and 375R described in the text corresponds to the aspherical lens of the fourteenth aspect. The achromatic lens applied to the light transmission system including the relay lenses 370B, 370G, and 370R and the emission side lenses 375B, 375G, and 375R corresponds to the achromatic lens of the fifteenth aspect.

  In the above embodiment, the liquid crystal light valves 30, 60B, 60G, 60R are configured using active matrix type liquid crystal display elements. However, the present invention is not limited to this, and the liquid crystal light valves 30, 60B, 60G, 60R are used. A passive matrix type 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-described embodiment, the projection display device 1 is configured by providing the transmissive light modulation element. However, the present invention is not limited to this, and the luminance modulation light valve or the color modulation light valve is a DMD (Digital Micromirror Device) or the like. The reflection type light modulation element can also be used.
Further, in the above embodiment, 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. 7 has been described, but the present invention is not limited to this, and these procedures are shown. 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.

It is a figure which shows the main optical structures of the projection type display apparatus 1 which concerns on this invention. FIG. 3 is a diagram illustrating a configuration of a spectroscopic dichroic prism 70. It is a figure which shows an example of the relay optical system which transmits an optical image by equal magnification. 3 is a block diagram illustrating a hardware configuration of a display control device 200. FIG. 6 is a diagram illustrating a data structure of a control value registration table 400. FIG. It is a figure which shows the data structure of the control value registration table 420R. It is a flowchart which shows a display control process. It is a figure for demonstrating a tone mapping process. It is a figure which shows the case where the transmittance | permeability T2 of a color modulation light valve is provisionally determined. It is a figure which shows the case where the transmittance | permeability T1 'of a luminance modulation light valve is calculated per pixel of a color modulation light valve. It is a figure which shows the case where the transmittance | permeability T1 of each pixel of a brightness | luminance modulation light valve is determined. It is a figure which shows the case where the transmittance | permeability T2 of each pixel of a color modulation light valve is determined. It is a figure which shows one structural example which changed each distance of the center of the cross dichroic prism 80 for a synthesis | combination, and liquid crystal light valve 60B, 60G, 60R. FIG. 4 is a diagram showing a configuration of a cross dichroic mirror 85. It is a figure which shows a part of main optical structure of the projection type display apparatus 1 at the time of making the dimension of a color modulation light valve smaller than the dimension of a luminance modulation light valve. It is a figure which shows the main optical structures of the projection type display apparatus 2 which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Projection type display apparatus, 10 ... Light source, 30 ... Liquid crystal light valve, 50 ... Incident side lens, 60B, 60G, 60R ... Liquid crystal light valve, 370B, 370G, 370R ... Relay lens, 375G, 375G, 375R ... Emission side Lens, 380B, 380G, 380R, 385B, 385G, 385R ... Reflection mirror, 70 ... Cross dichroic prism for spectroscopy, 80 ... Cross dichroic prism for photosynthesis, 71 ... Blue light reflection dichroic film, 72 ... Red light reflection dichroic film, 85 ... cross dichroic mirror, 110 ... projection lens, 170 ... CPU, 172 ... ROM, 174 ... RAM, 178 ... I / F, 179 ... bus, 180 ... light valve driving device, 182 ... storage device, 199 ... network, 400, 400R-400G, 420R 420G ... control value registration table, 440, 460 ... input value registration table

Claims (13)

A first light modulation element for controlling light propagation characteristics of light from the light source;
Light separating means for separating the light from the first light modulation element into light of a plurality of different specific wavelength regions and emitting separated light;
A plurality of second light modulation elements for controlling light propagation characteristics of separated light from the light separating means;
A light combining unit that combines light from each of the second light modulation elements to emit combined light, and displays an image by modulating light from the light source based on display image data,
The light separating means has an incident surface on which light from the first light modulation element is incident, and a plurality of exit surfaces from which the separated light is emitted.
The light synthesizing means has a plurality of incident surfaces corresponding to the respective emission surfaces of the light separating means, and an emission surface for emitting the combined light,
For each exit surface of the light separating means, the separated light emitted from the exit surface is transmitted to the corresponding incident surface of the light combining means, and the optical path length of the separated light is the same as the optical path length of the other separated light Alternatively, the light transmission means is provided so as to be substantially the same, and the second light modulation element is disposed on each light path of the emission surface of the light separation means and the incidence surface of the light combining means corresponding to the emission surface ,
The first condenser lens is disposed facing the incident surface of the light separating means, the first light modulation element is disposed facing the first condenser lens in the previous stage of the first condenser lens, At least one relay lens is disposed between each exit surface of the light separating means and the second light modulation element;
An optical display device , wherein light modulated by the first light modulation element is incident on the relay lens through the light separating means by the first condenser lens . The optical display device according to claim 1 , wherein a second condenser lens is provided on an incident side of each of the second light modulation elements. At least one of the light separating means and the light synthesizing means has a polyhedral shape including a plurality of substantially triangular prisms, and a dichroic film that reflects or transmits light in a specific wavelength region inside has an X-shaped cross section. 3. The optical display device according to claim 1, wherein the optical display device is configured by a cross dichroic prism formed on the substrate. At least one of the light separating means and the light synthesizing means is configured by a cross dichroic mirror in which two flat plates on which a dichroic film that reflects or transmits light in a specific wavelength region is formed are formed in an X-shaped cross section. the optical display device according to any one of claims 1 to 2, characterized in that there. The optical display device according to any one of claims 1 to 4 , wherein the light separating unit and the light combining unit are configured to be integrated with each other. The optical display device according to any one of claims 1 to 4, characterized in that provided by separating the light separating means and the light combining means. The light separating means and the light synthesizing means have a polyhedral shape including a plurality of substantially triangular prisms, and a dichroic film that reflects or transmits light in a specific wavelength region is formed in an X-shaped cross section. It comprises a cross dichroic prism, and the light separating means and the light synthesizing means are provided separately,
The intersecting line formed by the two dichroic films existing inside the light separating means and the intersecting line formed by the two dichroic films existing inside the light synthesizing means are on the same line or substantially on the same line. as positioned, the optical display device according to any one of claims 1 to 2, characterized in that placing said light combining means and said light separating means. The light separating means and the light synthesizing means are constituted by a cross dichroic mirror in which two flat plates on which a dichroic film that reflects or transmits light in a specific wavelength region is formed have an X-shaped cross section, and the light separation And the photosynthesis means are provided separately,
The light separating means and the intersection are formed so that the intersecting line formed by the dichroic mirror of the light separating means and the intersecting line formed by the dichroic mirror of the light combining means are located on the same line or substantially the same straight line. the optical display device according to any one of claims 1 to 2, characterized in that arranging the light combining means. The optical display device according to claim 1 , wherein the relay lens has a different characteristic for each optical path of the separated light. The optical display device according to claim 2 , wherein the second condenser lens has a different characteristic for each optical path of the separated light. The distance between the first optical modulation element and the second optical modulation element corresponding to each separation light of claims 1 to 10, characterized in that varied in the optical path for each of the separate light The optical display device according to any one of the above. A projection display device comprising: the optical display device according to any one of claims 1 to 11 ; and a projection unit that projects output light from the optical display device. A first light modulation element for controlling light propagation characteristics of light from the light source;
Light separating means for separating the light from the first light modulation element into light of a plurality of different specific wavelength regions and emitting separated light;
A plurality of second light modulation elements for controlling light propagation characteristics of separated light from the light separating means;
A light combining unit that combines light from each of the second light modulation elements to emit combined light, and displays an image by modulating light from the light source based on display image data,
For each separated light of the light separating means, the separated light is transmitted to the second light modulation element, and the optical path length of the separated light is the same as or substantially the same as the optical path length of the other separated light. Providing a transmission means, disposing the second light modulation element on each optical path on the incident side of the separated light of the light combining means ,
The first condenser lens is disposed facing the incident surface of the light separating means, the first light modulation element is disposed facing the first condenser lens in the previous stage of the first condenser lens, Arranging at least one relay lens on the optical path between the light separating means and the second light modulation element;
An optical display device , wherein light modulated by the first light modulation element is incident on the relay lens through the light separating means by the first condenser lens .

Images