JP4653416B2 - Image display device - Google Patents

Description

  The present invention relates to an image display device such as a liquid crystal projector using a spatial light modulation element, and more particularly to an image display device having both a pixel shifting unit and a pixel reduction unit.

In a projector apparatus that projects a display image on a panel of a spatial light modulation element (hereinafter referred to as a light valve) onto a screen using an enlargement optical system, the resolution of the projection image is increasing due to an increase in the number of pixels of the projection image. .
The most common method for increasing the definition of a projected image is to increase the number of pixels of the light valve. However, in order to increase the number of pixels of the light valve, it is necessary to reduce the size of one pixel. This affects the cost increase of the light valve.
In order to increase the number of pixels without reducing the pixel size, the area of the light valve may be increased. However, it is difficult to increase the area of the light valve and reduce the illumination optical system and the projection optical system. It is important to reduce the size and weight of the projection device, and the size of the light valve is reduced.

As another method, there has been proposed a display method in which the number of pixels of the enlarged projection image is apparently increased without increasing the number of pixels of the light valve.
This is a method of projecting and displaying the light valve pixel projection position with a slight shift. Hereinafter, this method is referred to as a pixel shift display method.
In order to perform the pixel-shifted display method, display information of one frame when pixel-shifted display is not performed is divided into two or more subframe display information, and the display position of the divided subframe display information is slightly shifted. Project.
As a method of shifting, there are a method of statically superimposing a plurality of different screens composed of a plurality of subframes, and a method of projecting and displaying these in a time division manner.
The amount of movement of the projection pixel should be smaller than the projection pixel size. It is preferable to shift about 1/2 of the projected pixel.

As a method of shifting the projection position of the pixel, in the case of static superimposed projection display, there is a method of projecting sub-frame images each divided by using a plurality of projection devices. In the case of dynamic time-division projection display, the sub-frame image is time-divisionally projected and displayed using active pixel shifting means.
In the case of time-division projection display, the projection position of the image is moved on the projection plane at a speed higher than the frequency at which the image is displayed. Assuming that the standard frame frequency is 60 Hz, the display frequency of each subframe is 120 Hz when divided into two subframes and displayed by alternately shifting the pixels. Similarly, when the display is divided into four subframes and the pixels are alternately shifted and displayed, the display frequency of each subframe is 240 Hz.

As a method for moving the display position of the image, for example, a laminated component of a light transmissive substrate, an ITO electrode layer, a liquid crystal layer, an ITO electrode layer, and a light transmissive substrate is placed in the optical path of the projection system, and ITO is placed on the liquid crystal layer. There is a method in which an electric field is applied by an electrode to electrically switch the alignment direction of the liquid crystal, and the optical path passing through the liquid crystal layer is parallel-shifted by a birefringence effect.
By switching the direction of the long axis of the vertical alignment type ferroelectric liquid crystal so that it is tilted to ± with respect to the optical axis in the plane including the optical axis, the emission position of the light beam passing through the liquid crystal layer is changed to the optical axis. Can be shifted to ± in the plane including the. Details of such pixel shifting elements are described in Japanese Patent Application Laid-Open No. 2002-214579, and are omitted here. Pixel shift display is also possible by other methods, and there are many disclosed examples.

By the way, when the pixels of the light valve are projected and displayed, the ideal display area size of the pixel image of the light valve that is projected and displayed is pixel size × projection magnification in a normal projector apparatus. At this time, the images of adjacent pixels are projected with almost no gap. Strictly speaking, since there is a gap between the pixels of the light valve body, the gap area is displayed in black, but the area displayed in black is much thinner than the pixels. If pixel-shifted display is performed in this state, the images of adjacent pixels that are displayed partially overlap.
As shown in FIG. 9, in a state where two pixels are displayed with a shift of ½ pitch of the pixel size, some of the two pixels overlap as shown in FIG. The overlapping area is hatched. In such a display state, the CTF value deteriorates, and an image with a blurred outline / edge is obtained depending on the image pattern. The blurring of the outline is particularly noticeable where the image has a large difference in shading. This blur is noticeable when displaying images with conspicuous edges such as characters and drawings.

As a method of improving the above-described image blur, there is a method of reducing the size of the pixel of the light valve projected onto the projection plane. This method is hereinafter referred to as a pixel reduction display method.
Here, the pixel reduction display method does not reduce the size of the entire projection screen, but reduces only the size of the display image on the projection surface of the light valve pixels without changing the size of the entire screen. Is a special display method. Since only the size of the projected image of the pixel is reduced and displayed, adjacent pixel images are projected with a gap.
As shown in FIG. 11, when the pixels of the spatial modulation element are reduced and the image is enlarged and projected, the size of the image of the enlarged and projected pixel is smaller than in the example shown in FIG. Assuming that the pixel reduction ratio is 0.5, the size of the pixel to be enlarged and projected is ½ of the conventional size. Therefore, the pixel shift equivalent to this pixel size, that is, the pixel size in FIG. As shown in FIG. 12, there is almost no overlap between the two pixel images.

In this way, by using the pixel reduction display method together and performing pixel-shifted display with a movement amount equivalent to a half pixel, the problem of overlapping of adjacent pixel images can be almost solved, thereby causing blurring of the image. Has been thought to be reduced.
A pixel shift display method has been proposed as means for increasing the resolution of a projector apparatus. This is a method of increasing the number of display pixels without increasing the number of pixels of a spatial modulation element such as a DMD (digital micromirror device: registered trademark: manufactured by Texas Instruments) or a light valve. In other words, time-division display is performed by shifting the position where the pixels on the spatial modulation element are enlarged and displayed by optical means or the like by about one pixel or less, and different image information is given to each pixel displayed by being shifted. Thus, the number of pixels that are apparently larger than the number of pixels of the spatial modulation element is displayed.
In addition to the time-division display method, a plurality of image projection devices are used to divide a piece of image information into a plurality of images, and the divided images are superimposed on the same projection plane, and the projection positions are shifted to each other. There is also a method of projecting so that the pixels are shifted.

As a method for optically displacing an image of a spatial light modulator (for example, a liquid crystal element) for each pixel and projecting an image having a resolution higher than that of the spatial light modulator, JP-A-4-113308 (Patent No. 293926) is disclosed. JP-A-5-289044, JP-A-9-152572, JP-A-6-324320, JP-A-2000-98968, and the like.
These can be achieved on the screen by changing the subfield to be displaced by 2 or 4 by optically displacing the pixel by optical axis shift at two positions perpendicular to the scanning line, or at four vertical and horizontal positions. It is said that it is possible to obtain double and quadruple resolutions, respectively.

JP-A-8-194207, JP-A-9-230329, JP-A-9-015548, and the like disclose that one direction is obtained by controlling the pixel arrangement, the displacement amount and the displacement direction of the optical axis shift. The RGB pixels, which are spatially divided by the filter, are overlapped with three positions displaced in the same direction to improve the resolution by a factor of three, or by shifting to realize an RGB delta arrangement. An apparatus is also disclosed in which only a specific pixel is shifted to increase the resolution only in a specific portion.
Japanese Laid-Open Patent Publication No. 4-113308 discloses a configuration of a spatial light modulator having pixels whose pixel size is smaller than 1/2 the pixel pitch, and uses this and a pixel shifting means to increase the resolution. A projection image forming apparatus is disclosed. In addition, the overlap between adjacent pixels is not pointed out here.

  In the above-described pixel shifting method, if the size of the displayed pixel image is the same as when not shifting the pixel, the pixel area overlaps when the pixel is shifted, so the size of the display pixel is reduced. It is preferable to do. In order to reduce the pixel image, a means for intermediately generating a reduced image of the pixel is provided between each pixel of the spatial light modulator and the enlarged projection optical system, and the reduced intermediate image is displayed by the enlarged projection optical system. You can do it.

  Japanese Patent Application Laid-Open No. 9-054554 discloses a method of condensing light with a condensing lens smaller than the opening of the transmissive liquid crystal panel when the resolution is increased by the pixel shifting means. As means for changing the pixel size, a configuration in which a microlens is combined with a transmissive liquid crystal panel is shown. An active element is provided to face a pixel (opening) of a transmissive liquid crystal light valve having an opening having a predetermined shape size. The active element reduces the overall aperture. In order to reduce the pixel size further than the opening, a microlens having a circular outer shape is provided here. In addition, a projection enlargement device using a liquid crystal light valve and a pixel shifting element increases the resolution twice in one direction, and a display image is constructed using a condensing optical system group corresponding to each pixel opening of the light valve. An example of reducing the size of each pixel is shown. Note that details of the light intensity distribution forming the pixels are not described here.

JP-A-4-113308 Japanese Patent Laid-Open No. 5-289044 JP-A-9-152572 JP-A-6-324320 JP 2000-98968 A JP-A-8-194207 Japanese Patent Laid-Open No. 9-230329 Japanese Patent Laid-Open No. 9-015548 JP-A-9-055454

However, as will be described later, the explanation that the overlap between the display pixels is eliminated by adding the pixel reduction means is actually insufficient. This is because the image quality is not the same regardless of the light intensity distribution profile of each display pixel at that time.
Similar to the one described in Japanese Patent Application Laid-Open No. 4-113308, when a projection lens having a high MTF is used, the resolution becomes high, but visibility problems such as “jaggy” become obvious.
If the MTF of the projection lens is made relatively low at this time, “jaggy” or the like becomes inconspicuous, but “sharpness” is greatly reduced. As a result, high-resolution video projectors and high-resolution data projectors are originally aimed. Image characteristics cannot be formed by pixel shifting means. That is, it is not sufficient to use only the pixel shifting means, and it is still insufficient to reduce the pixels.

When displaying by shifting pixels, a better image can be obtained by using the pixel reduction display method together. For example, when the display is sequentially shifted in the vertical and horizontal directions, the area of the projected pixel image is preferably about 1/4 of the normal area.
However, the actually projected pixel image does not have a rectangular light intensity distribution as shown in FIG. 13, but has a distribution characteristic in which the vicinity of the center of the pixel image is bright and the periphery is dark as shown in FIG. . FIG. 13 shows an ideal pixel image light intensity distribution L0. The rectangular light intensity distribution L0 does not protrude into the adjacent pixel area, and the intensity falls to zero at the boundary of the pixel area. In FIG. 13, the vertical axis indicates the light intensity, and the horizontal axis indicates the distance (the same applies to other drawings).
As shown in FIG. 14, the light intensity distribution L1 of the actual pixel image protrudes into the adjacent pixel area, and the intensity does not drop to zero at the boundary of the pixel area.

In the above distribution, an ideal pixel image display area is a square area having one side of “pixel size of spatial modulation element × enlarged projection magnification × 0.5”. The appearance and image quality of the image change depending on the light intensity distribution of the pixel image inside and outside the ideal display area.
For example, if all of the light intensity of the pixel image falls within the ideal display area of the pixel image, the center is very bright in the pixel image area but is too dark near the edge of the area. In such a case, image continuity between adjacent pixel areas is lost.

On the other hand, when the light amount ratio in the adjacent region of the ideal display area is too large, the resolution between adjacent pixels is deteriorated as described above. In such a case, for example, when a line-and-space image pattern in units of one pixel is displayed, the sharpness of the boundary between the line and the space deteriorates.
Therefore, as shown in FIG. 15, it is desirable to have a light intensity distribution L2 in which the light intensity is high in the display area of the pixel image, and the light intensity falls sharply in the adjacent region beyond the display area. As the light intensity in the adjacent pixel display area is lower, an image with higher CTF characteristics can be reproduced.
In order to obtain such a light intensity distribution L2, the light intensity distribution of the pixel reduced image obtained by the pixel reducing means is controlled, and the light intensity distribution of the pixel image projected by the enlargement projection optical system is controlled. It will be.

Here, when the size of the projection pixel image projected by the enlargement projection optical system is used as a reference and the magnification of the enlargement projection optical system is N times, the size of the reduced intermediate image generated by the pixel reduction system is the projection pixel image. 1 / N, the size of the projected pixel image should be the desired size, but in reality it will be larger than this, and the light quantity ratio of the area that protrudes from the ideal display area will increase. I found out that
The magnifying projection optical system having the magnifying magnification M enlarges the size of the entire display screen to M times. At this time, the enlarged display size of the pixels constituting the M-magnified screen becomes larger than M times. That's what it means.

  Accordingly, the main object of the present invention is to provide a projection pixel image having a desired size in a projection type image display apparatus having a pixel reduction means and a pixel shifting means.

To achieve the above object, according to the first aspect of the present invention, at least an illumination light source, a spatial light modulation element having a plurality of pixels, a pixel reduction means for generating a reduced image of the pixels, and a pixel shifting means, An enlarged projection optical system, and the reduced image of the pixel is enlarged and projected onto a projection surface by the enlarged projection optical system, and the position of the image of the pixel displayed on the image plane by the pixel shifting means is In the image display device displayed in a shifted manner, the pixel projected on the projection plane via the enlargement projection optical system, wherein a reduced image of the pixel of the spatial light modulation element generated by the pixel reduction means is used as a pixel reduced image Is an enlarged pixel image, the reduced pixel image is smaller in size than the enlarged pixel image divided by the enlarged projection magnification.

In the invention according to claim 2, in the image display device according to claim 1, in the normalized light intensity distribution obtained by normalizing the light intensity distribution of the pixel enlarged image and the pixel reduced image with each maximum light intensity, In particular, the normalized light intensity in the peripheral part of the distribution has a relationship of pixel reduced image <pixel enlarged image.
In particular, an object of the present invention is to provide an image display device having a high effect of correcting image blur due to overlapping of enlarged pixel images projected with pixel shift.

According to a third aspect of the present invention, in the image display device according to the second aspect, the pixel reduction means is a positive array arranged in a one-to-one correspondence with each of the plurality of pixels of the spatial modulation element. A microlens array having power is included.
Here, it aims at providing the concrete pixel reduction means in Claim 1 or 2.

According to a fourth aspect of the present invention, in the image display device according to the third aspect, the microlens array has an aspherical surface.
In particular, an object of the present invention is to provide an image display apparatus having a pixel reduction means that makes the characteristics of a pixel reduced image good.

According to a fifth aspect of the present invention, in the image display device according to the fourth aspect, a conic constant in an expression defining the aspheric surface is negative.
In particular, an object of the present invention is to provide an image display device in which the characteristics of the reduced pixel image are good.

According to a sixth aspect of the present invention, in the image display device according to the fifth aspect of the present invention, the collection of rays incident non-parallel to the optical axis rather than the condensing characteristic of the rays incident parallel to the optical axis of the microlens array. The optical characteristics are better.
In particular, an object of the present invention is to provide an image display device in which the characteristics of the reduced pixel image are good.

According to a seventh aspect of the present invention, in the image display device according to the fifth aspect, the object plane of the magnifying projection optical system is disposed at a position closer to the spatial modulation element than a position where the pixel reduced image is minimized. Features.
In particular, an object of the present invention is to provide an image display device capable of obtaining a light intensity distribution of a pixel enlarged image suitable for obtaining a good image.

In the invention of claim 8, wherein, in the image display apparatus according to claim 7, wherein a pixel reduced image plane is a position where it is the pixel reduced image by the pixel reduction unit, the pixel enlarged image plane as the projection plane optical It is characterized by satisfying a conjugate relationship.
Here, particularly, when an enlarged image of a reduced pixel image is projected onto a projection surface, an image display device is provided that accommodates the enlarged pixel image in a desired size and projects and displays the entire screen at a normal lateral magnification. It is aimed.

According to a ninth aspect of the present invention, in the image display device according to the eighth aspect, the chromatic aberration generated by the pixel reducing means and the spatial modulation element and the chromatic aberration generated by the other optical system have the same amount and opposite signs. It is characterized by that.
Here, it aims at suppressing chromatic aberration especially.

According to a tenth aspect of the present invention, in the image display device according to the eighth aspect, the chromatic aberration generated by the pixel reducing means or the spatial modulation element and the chromatic aberration generated by another optical system have the same amount and opposite signs. It is characterized by that.
Here, it aims at suppressing chromatic aberration especially.

According to an eleventh aspect of the present invention, in the image display device according to any one of the eighth to tenth aspects, the illumination light is separated into three wavelength bands of RGB, and the spatial light modulation element is separated into three wavelengths of RGB. There are three correction optical elements for correcting chromatic aberration of magnification in the optical path corresponding to each wavelength band of RGB when generating three RGB images, combining them, and enlarging and projecting them. It is characterized by.
Here, in particular, the illumination light is separated into three wavelength bands of RGB, a spatial light modulation element and a pixel reduction means are separately provided for each wavelength band, and an RGB image is generated. An object of the present invention is to provide an image display device capable of correcting lateral chromatic aberration in the case of combining images and projecting the combined image by shifting pixels.

According to the first aspect of the present invention, at least an illumination light source, a spatial light modulation element having a plurality of pixels, a pixel reduction means for generating a reduced image of the pixels, a pixel shifting means, and an enlarged projection optical system , The reduced image of the pixel is enlarged and projected on the projection plane by the enlargement projection optical system, and the image of the pixel image displayed on the image plane is shifted and displayed by the pixel shifting means. In the display device, a reduced image of the pixel of the spatial light modulation element generated by the pixel reduction unit is used as a reduced pixel image, and the image of the pixel projected on the projection surface via the enlargement projection optical system is an enlarged pixel image. Since the reduced pixel image is smaller than the size obtained by dividing the enlarged pixel image by the enlarged projection magnification, the image of the pixel on the projection surface can be projected to an appropriate size. Expansion Overlap each other decreases, the effect of correcting the image blurring becomes higher. That is, if the pixel reduced image is made smaller, the enlarged projected pixels can be prevented from overlapping between adjacent ones.

  According to a second aspect of the present invention, in the image display device according to the first aspect, a normalized light intensity distribution obtained by normalizing the light intensity distributions of the enlarged pixel image and the reduced pixel image with each maximum light intensity. In particular, since the normalized light intensity at the periphery of the distribution is in the relationship of pixel reduced image <pixel enlarged image, the edge blur of the image is improved due to the overlap between adjacent pixels when the pixels are shifted and projected. The

According to a third aspect of the present invention, in the image display device according to the second aspect, the pixel reduction means is arranged in a one-to-one correspondence with each of the plurality of pixels of the spatial modulation element. Since a microlens array having a positive power is included, a screen having a gap between adjacent enlarged pixel images can be generated.
If the size of the gap is made substantially the same as the size of the enlarged pixel image and the pixel shift distance is displayed equal to the size of the gap, there is very little overlap between adjacent enlarged pixel images, and the number of display pixels can be increased apparently. it can. By satisfying the conditions of claim 1 or 2, the overlap between adjacent enlarged pixel images is reduced, and the edge blur of the image is improved.

  According to the invention of claim 4, in the image display device of claim 3, since the microlens array has an aspherical surface, the light intensity distribution of the reduced pixel image can be favorably controlled. In particular, the spread of the peripheral portion of the light intensity distribution can be suppressed. As a result, the light intensity distribution of the pixel magnified image is also prevented from spreading to the adjacent pixel magnified image area, the overlap between the adjacent magnified pixel images is reduced, the CTF characteristics are improved, and the edge blur of the image is improved. Is done.

  According to a fifth aspect of the present invention, in the image display device according to the fourth aspect, the conic constant in the expression defining the aspheric surface is negative, so that the spread of the light intensity distribution of the reduced pixel image is suppressed. The function to perform is obtained further. The overlap between enlarged pixel images is reduced, the CTF characteristics are further improved, and the edge blur of the image is improved.

  According to a sixth aspect of the present invention, in the image display device according to the fifth aspect, the light ray incident non-parallel to the optical axis rather than the light condensing characteristic of the light ray incident parallel to the optical axis of the microlens array. Because the light condensing characteristic is better,

  According to a seventh aspect of the present invention, in the image display device according to the fifth aspect, the object plane of the enlargement projection optical system is disposed at a position closer to the spatial modulation element than a position where the pixel reduced image is minimized. Therefore, the spread of the light intensity distribution of the reduced pixel image is further suppressed, and the spread of the enlarged pixel image projected on the projection surface is also suppressed. The orientation distribution of lamp illumination light often has no light intensity peak at 0 °. By using a microlens having a condensing characteristic in consideration of this, the above function can be obtained, the overlap between adjacent enlarged pixel images is reduced, the CTF characteristic is improved, and the edge blur of the image is improved. The

  According to the eighth aspect of the present invention, in the image display device according to the seventh aspect, the reduced pixel image plane and the enlarged pixel image plane satisfy an optically conjugate relationship. The size of the magnified pixel magnified image can be reduced to a desired size, and the entire screen can be projected and displayed at a normal lateral magnification.

  According to the ninth aspect of the present invention, in the image display device according to the eighth aspect, the chromatic aberration generated by the pixel reducing means and the spatial modulation element and the chromatic aberration generated by the other optical system have the same amount and opposite signs. Therefore, the chromatic aberration of the projected image can be suppressed.

  According to a tenth aspect of the present invention, in the image display device according to the eighth aspect, the chromatic aberration generated by the pixel reducing means or the spatial modulation element and the chromatic aberration generated by the other optical system have the same amount and opposite signs. Therefore, the chromatic aberration of the projected image can be suppressed.

  According to the eleventh aspect of the present invention, in the image display device according to any one of the eighth to tenth aspects, the illumination light is separated into three wavelength bands of RGB, and the spatial light modulation element is made of RGB. A correction optical element that corrects chromatic aberration of magnification in the optical path corresponding to each wavelength band of RGB when three images corresponding to the three wavelength bands are provided, and RGB images are generated, combined, and enlarged and projected. Therefore, the correction means for the remaining chromatic aberration can be independently and independently corrected in each system separated into the three wavelength bands of RGB, and the lateral chromatic aberration of the projected image shifted by the pixel can be obtained with high accuracy. Correct and display images without color misregistration.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
First, an outline of the configuration of the image display apparatus according to the present embodiment will be described.
The illumination light generated from the lamp light source is unpolarized white light. The spatial distribution of illuminance is made uniform using a fly-eye lens array or the like. This is converted into linearly polarized light by the polarizing plate. Next, the illumination light is reflected by the polarization separation element. A typical example of the polarization separation element is a polarization beam splitter.
The reflected illumination light is passed through the skew correction plate. Next, it is separated into three colors of RGB by a color separation prism. From this point onward, since the optical paths are separated into RGB three colors, one of the optical paths will be described. The color-separated illumination light is passed through the pixel reduction means. Next, the pixel surface of the reflective light valve is irradiated. The illumination light is reflected. This reflected light is again passed through the pixel reduction means.
In this process, the illumination light conveniently passes through the pixel reduction means twice. Here, since the pixel reduction means wants to generate a pixel reduced image for each of the pixels of the light valve, it is set to correspond to each of the plurality of pixels on a one-to-one basis. When passing through the pixel reducing means for the first time, the illumination light is slightly condensed. Thereby, the illumination light illuminates a part including the center, not the entire pixel of the light valve.

Further, the illumination light is also condensed when the illumination light reflected from the light valve passes through the pixel reduction means for the second time. In this way, the light beam that illuminates one pixel is brought into a narrowed state. Since the aperture is narrowed, the cross section of the light beam can be smaller than the pixel. This state is referred to as a pixel reduced image.
Such a reduced pixel image is made for all pixels. After the light beam is focused once, it shifts to the divergent state again. The illumination light that has shifted to the diverging state is passed through the skew correction plate described above. Here, the illumination lights of the three colors returned from the three optical paths are synthesized by the color synthesis prism. Next, the synthesized illumination light is passed through the wave plate. This wave plate is provided so as to satisfy the arrangement condition of the deflecting plate and the crossed Nicols.
The illumination light that has passed through the wave plate is passed through the pixel shifting means. As the pixel shifting means, a pixel shifting means having an optical path shift function using liquid crystal has been proposed so far, and this can be used. The illumination light that has passed through the pixel shifting means is passed through the magnification projection optical system. The illumination light passes through the magnifying projection optical system and reaches the projection surface.

Next, a specific example of the configuration of the image display apparatus according to this embodiment will be described with reference to FIG.
The illumination light emitted from the lamp light source 31 passes through the UV cut filter 32 and the IR cut filter, and the spatial distribution of illuminance is made uniform by the two microlens array plates 34.
Thereafter, the illumination light is optically separated by the color separation filter 35 and deflected by the mirror 36. Reference numerals 37 and 38 denote lenses for correcting two optical path lengths separated from each other, and reference numeral 39 denotes a color separation filter. The illumination light is converted into linearly polarized light by the half-wave plate 40 and enters the polarization beam splitter 41.
Reference numeral 42 denotes an element in which a reflective light valve element and an image reduction element are integrated, and reference numeral 43 denotes a magnification chromatic aberration correction lens.
The illumination light separated into RGB by the color separation filters 35 and 39 is color-synthesized by the cross prism 44. Illumination light exiting the cross prism 44 passes through a retarder polarizer 45, a pixel shifting element 46 having a pixel shifting function in the X direction, a pixel shifting element 47 having a pixel shifting function in the Y direction, and an enlarged projection optical system 48. Through to a projection surface (not shown).

In the above configuration and illumination light path conditions, as a configuration example of the reflective light valve element, a configuration in which a pixel surface, a liquid crystal layer, and a cover glass layer are stacked on a silicon backplane is known. The liquid crystal layer and the microlens array substrate are bonded via an adhesive layer. The microlens array functions as a pixel reduction unit as described below.
As shown in FIG. 1, the reflective light valve element 15 includes a plurality of pixel areas (hereinafter also simply referred to as “pixels”) 14. As shown in FIG. 2, the microlens 12 is disposed in the pixel area 14 via the adhesive layer 13. In FIG. 2, reference numeral 11 denotes a light transmissive substrate for the array of microlenses 12.
A plurality of microlenses 12 are arranged on the above-described microlens array substrate, and they are arranged in one-to-one correspondence with the plurality of pixels 14 included in the reflective light valve element 15. These optical axes and the center of the pixel 14 are configured to coincide with each other. Here, the opening shape of the microlens 12 is a square.

The focal length of the microlens 12 is preferably longer than twice the distance from the principal point of the microlens 12 to the surface of the pixel 14. In this way, when the illumination light is guided from the microlens 12 side, the illumination light is transmitted through the microlens 12 to be focused and irradiates the pixels 14. The illumination light that has been applied to the pixel 14 is reflected by the pixel 14, passes through the microlens 12, and is further condensed.
More specifically, as shown in FIG. 3, the illumination light enters from the right side of the drawing, is reflected by the surface of the pixel 14 of the reflective light valve element 15 through the microlens 12 and the adhesive layer 13, and is then applied to the adhesive layer. 13, the microlens 12, and the light-transmitting substrate 11 proceed in this order. An enlarged projection optical system 48 is located on the right side of the figure. When AA ′ is a reduced image plane position, a projection plane (not shown) is arranged at a position optically conjugate with the position of AA ′.

Since the illumination light generated from the lamp light source 31 is a light beam composed of a light beam component in a predetermined angle range, the light beam at the condensing position is not completely condensed at one point, and has a finite size.
Therefore, the position AA ′ where the luminous flux is condensed is defined as a pixel reduced image plane, and an intermediate image on this plane is defined as a pixel reduced image.
It can be understood from the above description that the reduced pixel image is smaller than the pixel 14 of the reflective light valve element 15. This state is defined as pixel reduction.
As described above, the light beam condensed on the pixel reduced image plane AA ′ becomes divergent light again and is guided to the enlarged projection optical system 48. When the reduced pixel image plane AA ′ is arranged so as to be the object plane of the enlargement projection optical system 48, the reduced pixel image on the object plane can be enlarged and projected onto the image plane in the enlargement projection optical system 48.

At this time, as shown in FIG. 4, when the relative light intensities in the normalized spatial light intensity distributions of the reduced pixel image and the enlarged pixel image, particularly in the peripheral part, are L3 and L4, respectively, L3 <L4. It is preferable to do.
The light intensity distributions L3 and L4 are standardized so that the width of the light intensity distribution L3 is narrower than that of the light intensity distribution L4. Further, the light intensity distribution L3 has a smaller normalized light intensity value in the peripheral portion than the light intensity distribution L4.
Here, the “peripheral portion” is a region outside the ideal pixel image display area described above. The definition of the “peripheral part” will be described in detail. Here, it means an area beyond the ideal display area of the pixel image, that is, a part extending to the adjacent pixel image display area.
The ideal display area of the enlarged pixel image here is that the vertical length of the display screen is A, the horizontal length is B, the vertical display pixel count is C, and the horizontal display pixel count is D. Is a rectangular area in which the vertical direction is A / C and the horizontal direction is B / D. The ideal display area of the reduced pixel image here is A / M for the entire length of the entire screen of the intermediate image plane composed of the reduced pixel image, and B / M (M is the horizontal length). (Enlarged projection magnification) is a rectangular area in which the vertical direction is A / M / C and the horizontal direction is B / M / D. Strictly speaking, in the case of a reduced pixel image, it is not actually displayed, but here it is expressed as a display area for convenience of explanation.

If L3 ≧ L4, the light intensity distribution of the pixel magnified image on the projection surface is widened and the screen is blurred.
For example, the pixel 14 of the reflective light valve element 15 is square, its side length is 10 microns, the enlargement magnification of the enlargement projection optical system 48 is 60 times, and normal enlargement projection without pixel reduction and pixel shift display is performed. In this case, the image formed on the reflection type light valve element 15 is enlarged and projected by 60 times.
That is, the size of the entire screen is enlarged 60 times. At this time, the side length of the display area of the ideal pixel magnified image on the projection surface is 600 microns, but the pixel magnified image on the projection screen is 600 microns or more.

Next, in the case of performing 60 times enlargement projection using both pixel reduction and pixel shift display, the ideal side length of the pixel display area on the projection plane is half that of the previous area, that is, 300 microns. At this time, if the side length of the reduced pixel image is 300 microns / 60 = 5 microns, the size of the pixel image that is actually enlarged and projected is 300 microns or more. However, in this embodiment, the side length in the reduced pixel image is smaller than 5 microns, and in this way, the sides of the enlarged pixel image on the enlarged projection surface generated via the enlarged projection optical system 48 The problem of extending the length to 300 microns or more can be avoided.
FIG. 5 shows the relationship between the size of the enlarged projection image / magnified projection magnification pixel reduced image and the size of the enlarged projection image / magnification projection magnification smaller pixel reduction image.

The numerical values used in the above description are merely an example, but in short, the size of the reduced pixel image is smaller than the value obtained by grading the size of the enlarged pixel image by the enlargement factor. This is very important in an image display apparatus using means.
Here, the definition of “small” will be described. With the vertical axis representing the light intensity and the horizontal axis representing the distance from the center of the pixel image, the light intensity distribution curves of the reduced pixel image and the enlarged pixel image can be expressed. This light intensity distribution is normalized with the maximum light intensity on the vertical axis and with the ideal display area of the pixel image on the horizontal axis. The normalized light intensity distribution is defined as a normalized light intensity distribution. Next, the normalized light intensity distribution of the reduced pixel image is compared with the normalized light intensity distribution of the enlarged pixel image. At this time, the normalized light intensity distribution curve (L3 in FIG. 4) of the reduced pixel image overlaps the normalized light intensity distribution curve (L4 in FIG. 4) of the enlarged pixel image at any position on the horizontal axis of the graph. It is defined as “small” when it is inside or inside it.

The spatial light modulation element (reflective light valve element 15) has a plurality of pixel regions 14 that are usually arranged in a matrix. As described above, the microlens 12 is arranged so that the center of the pixel area and the optical axis of the microlens 12 coincide with each pixel area. There are a plurality of pixels 14, and the microlenses 12 are arranged so as to correspond to each of them. That is, the microlenses 12 are also configured in a matrix.
In order for the microlens 12 to function as a means for generating a reduced image of a pixel, it is desirable that the power of the microlens 12 is positive (second embodiment). Further, if the focal length of the microlens 12 is f, the distance L from the principal point position of the microlens 12 to the pixel 14 is preferably shorter than f / 2.
In this way, the light beam focused by the microlens 12 illuminates a part of the pixel 14 including the center of the pixel 14, and the light beam reflected from the pixel 14 returns to the microlens 12, After passing through, the beam is most focused.

When the refracting surface of the microlens array is spherical, it is difficult to appropriately control the light intensity distribution of the reduced pixel image to be generated, but by making it aspheric (third embodiment), the pixel The light intensity distribution of the reduced image can be controlled, and in particular, the spread of the peripheral portion of the light intensity distribution of the pixel reduced image can be suppressed, so even when this reduced image is projected by the projection optical system, the projection surface The effect of suppressing the spread of the peripheral portion of the pixel image projected onto the image, reducing the overlap between adjacent pixels, improving the CTF characteristics, and improving the edge blur of the image is synergistic with the effect of the above embodiment. To do.
As shown in FIG. 7, the light intensity distribution obtained by normalization of the projection pixel profile has a smaller peripheral spread when the shape of the microlens 12 is an aspherical surface (L6) than when the shape of the microlens 12 is a spherical surface (L5). .

  When the microlens 12 is made aspherical, if the conic constant is set to a negative value, an effect of suppressing the peripheral spread of the reduced pixel image can be obtained (fourth embodiment), and this reduced pixel image is projected by the enlargement projection optical system. Even in the light intensity distribution of the enlarged pixel image directly obtained with the image quality, the spread of the peripheral portion is suppressed, and when the pixels are shifted and displayed, the overlapping of adjacent enlarged pixel images is reduced. As a result, the effect of improving the CTF characteristics and improving the edge blur of the image synergizes with the effect of the above embodiment. However, when calculated, there is no effect when the conic constant is positive. Experiments have shown that a numerical value of about −5 to −10 is desirable.

When the light beam incident on the microlens 12 is a lamp light source, as described above, the light emission characteristics of the lamp light source 31 do not necessarily have a light intensity peak when the radiation angle is zero, and the angle is around 2 to 3 degrees. There may be a peak in light intensity.
For the illumination light beam having such a characteristic, a light beam having a non-zero field angle, preferably the lamp light source 31 is used rather than using the microlens 12 having a performance that maximizes the condensing characteristic for a light beam having a zero field angle. The microlens 12 having a good light collection efficiency of a component corresponding to an angle at which the light intensity peak exists is more desirable (fifth embodiment).
As shown in FIG. 8, the light intensity distribution obtained by normalizing the projection pixel profile is obtained when the shape of the microlens 12 is aspherical and the optimization weight of the condensing characteristic with respect to the lens optical axis and the parallel incident component is maximized ( When the optimization weight of the condensing characteristic of the non-parallel incident component is maximized (L8), the peripheral spread is smaller than that of L7).
FIG. 8 shows an example in which the optimization weight at the incident angle of 3 degrees is maximized.
In this case, the effect of suppressing the spread of the peripheral portion of the light intensity distribution of the reduced pixel image is enhanced, and the pixel image projected on the projection surface even when the reduced image is projected by the enlarged projection optical system 48. Since the spread of the peripheral portion of the image is suppressed, when the pixels are shifted and displayed, the overlap between adjacent pixel enlarged images is reduced, the CTF characteristics are improved, and the edge blur of the image is improved.

When the obtained pixel reduced image is enlarged by the enlargement projection optical system 48 to generate an image of the pixel on the projection surface, when the image surface of the enlargement optical system is used as the projection surface, the object plane of the enlargement projection optical system 48 is The characteristics of the enlarged pixel image on the projection plane change depending on the positional relationship between the position and the image plane of the reduced pixel image.
When the object plane is disposed at a position substantially equal to the image plane of the reduced pixel image generated by the microlens array, or at a position closer to the spatial modulation element than the image plane (sixth embodiment), projection is performed. The light intensity distribution of the pixel image obtained by magnifying and projecting the image of the pixel on the surface is less spread around the periphery, so that when the pixels are shifted and displayed, the overlapping of adjacent pixel magnified images is reduced and the CTF characteristics are improved. The effect of improving the edge blur of the image is increased.

When the pixel reduction image plane and the pixel enlargement image plane are not in an optical conjugate relationship, the enlargement projection optical system 48 can display the characteristics of the pixel enlargement image even if the light intensity distribution characteristic of the pixel reduction image is optimized. Cannot be played on the surface.
For this reason, the reduced pixel image surface and the enlarged pixel image surface satisfy an optically conjugate relationship (seventh embodiment).

It is practically difficult to correct the chromatic aberration in the pixel reduction unit and the spatial modulation element or (pixel reduction unit or spatial modulation element) by the pixel reduction unit and the spatial modulation element or (pixel reduction unit or spatial modulation element). It is.
Thus, by generating these chromatic aberrations and chromatic aberrations (the same amount and the opposite sign) that cancel, the occurrence of chromatic aberrations in the entire system can be suppressed (eighth embodiment).

Next, a ninth embodiment will be described.
As in the example of the system described at the beginning, white illumination light is separated into RGB three wavelength bands by color separation elements, and each RGB light beam is modulated by three spatial modulation elements to generate an image. When the generated three RGB images are combined and projected by the color combining element, the amount of chromatic aberration of magnification generated in each RGB wavelength band is different. It was difficult to correct lateral chromatic aberration at the same time.
However, in the present embodiment, as shown in FIG. 6, the magnification chromatic aberration correction lens 43 as a correction optical element for correcting each of the three colors is provided in each of the RGB optical paths, thereby adjusting each color. Therefore, the effect of correcting the chromatic aberration of magnification of the combined image is higher than the case where the combined correction is performed after the combining.
In each of the above embodiments, an example using a reflective light valve element has been described, but the same function can be obtained even with a configuration using a transmissive light valve element.

It is an outline top view of a reflective light valve element in a 1st embodiment. It is a schematic sectional drawing of the reflection type light valve element in 1st Embodiment. It is a figure which shows the reflection characteristic of the illumination light in the reflection type light valve element in 1st Embodiment. It is a figure which shows the relationship between the light intensity distribution of the expansion projection pixel in 1st Embodiment, and the light intensity distribution of a pixel reduction image. It is a figure which shows the relationship of the magnitude | size of the pixel reduction image of the enlarged projection image / magnification projection magnification in 1st Embodiment, and the pixel reduction image smaller than an enlarged projection image / magnification projection magnification. 1 is a schematic diagram of an image display device according to a first embodiment. It is a figure which shows the relationship of the light intensity distribution in the case where a micro lens is a spherical surface and the case of an aspherical surface. It is a figure which shows the relationship of the light intensity distribution in the case where a micro lens is aspherical and injects in parallel and the lens optical axis. It is a figure which shows the relationship between the enlarged and projected pixel image, and the enlarged and projected pixel image shifted by 1/2 pitch pixel. It is a figure which shows the synthesized image of the enlarged and projected pixel image. It is a figure which shows the relationship between the pixel reduction image projected and enlarged, and the pixel reduction image enlarged and projected by shifting 1/2 pitch pixel. It is a figure which shows the synthesized image of the pixel reduction image by which the expansion projection was carried out. It is a figure which shows the light intensity distribution of an ideal pixel image. It is a figure which shows the light intensity distribution of an actual pixel image. It is a figure which shows light intensity distribution with low light intensity of an adjacent pixel display area.

Explanation of symbols

14 pixels 15 reflective light valve elements as spatial light modulation elements 31 lamp light sources as illumination light sources 42 elements as pixel reducing means 43 lenses for correcting chromatic aberration of magnification as correction optical elements 46 and 47 pixel shifting elements as pixel shifting means 48 Magnification Projection Optical System

Claims (11)

At least an illumination light source, a spatial light modulation element having a plurality of pixels, a pixel reduction unit that generates a reduced image of the pixel, a pixel shifting unit, and an enlarged projection optical system, and the reduced image of the pixel is In the image display device that is enlarged and projected onto the projection surface by the enlargement projection optical system, and is displayed by shifting the position of the image of the pixel displayed on the image plane by the pixel shifting means.
When the reduced image of the pixel of the spatial light modulation element generated by the pixel reducing means is a pixel reduced image, and the image of the pixel projected on the projection surface via the enlarged projection optical system is a pixel enlarged image, 2. The image display device according to claim 1, wherein the reduced pixel image is smaller than a size obtained by dividing the enlarged pixel image by an enlarged projection magnification. The image display device according to claim 1,
In the normalized light intensity distribution obtained by normalizing the light intensity distributions of the pixel enlarged image and the pixel reduced image with the respective maximum light intensities, the normalized light intensity particularly in the periphery of the distribution is the pixel reduced image <pixel enlarged An image display device characterized by being in an image relationship. The image display device according to claim 2,
The pixel reduction means includes a microlens array having positive power arranged in a one-to-one correspondence with each of a plurality of pixels of the spatial modulation element. . The image display device according to claim 3.
The image display apparatus, wherein the microlens array has an aspherical surface. The image display device according to claim 4.
An image display device, wherein a conic constant in an expression defining the aspheric surface is negative. The image display device according to claim 5,
An image display device characterized in that the condensing characteristic of light incident non-parallel to the optical axis is better than the condensing characteristic of light incident parallel to the optical axis of the microlens array. The image display device according to claim 5,
An image display apparatus, wherein an object plane of the enlargement projection optical system is arranged at a position closer to the spatial modulation element than a position where the pixel reduced image is minimized. The image display device according to claim 7,
The image display apparatus characterized by a pixel reduced image plane is a position where it is the pixel reduced image, and the pixel enlarged images surface as the projection plane meets optically conjugate relationship: by the pixel reduction unit. The image display device according to claim 8.
An image display device characterized in that the chromatic aberration generated by the pixel reduction means and the spatial modulation element and the chromatic aberration generated by another optical system have the same amount and opposite signs. The image display device according to claim 8.
An image display device characterized in that the chromatic aberration generated by the pixel reduction means or the spatial modulation element and the chromatic aberration generated by another optical system have the same amount and opposite signs. The image display device according to any one of claims 8 to 10,
When separating the illumination light into three wavelength bands of RGB, providing three spatial light modulation elements corresponding to the three wavelength bands of RGB, generating RGB images, synthesizing them, and enlarging and projecting, What is claimed is: 1. An image display apparatus comprising: a correction optical element that corrects chromatic aberration of magnification in an optical path corresponding to each wavelength band of RGB.

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