JPH1055027A - Projection type display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device capable of performing time division display and displaying a picture with high resolution by simple constitution without lowering the transmissivity of light and contrast even when an optical modulation element having a small number of picture elements is used in the case of displaying the picture by dividing the picture of one frame into plural fields. SOLUTION: A microlens array 5 is arranged on an optical path leading to a projection lens 7 from the optical modulation element 3, and one convex lens is formed corresponding to four picture elements of the optical modulation element 3. An image forming optical system 4 is arranged to make the light from the element 3 incident on a corresponding microlens. An actuator 6 moves or vibrates the microlens array 5 in horizontal and vertical directions orthogonal to the optical axis of the light made incident on the microlens array 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection display device for obtaining a large-screen display by enlarging and projecting an image displayed on a light modulation element, and more particularly to a projection display in which an image of one frame is divided into a plurality of fields and displayed. The present invention relates to a type display device.

[0002]

2. Description of the Related Art FIG. 9 shows a schematic configuration of a conventional typical projection display device. In FIG. 9, 1 is a light source, 3 is a light modulation element, 7 is a projection lens, and 9 is a screen. A transmissive liquid crystal panel is used for the light modulation element 3 of the projection display device. As the light source 1, a metal halide lamp or a halogen lamp having a relatively uniform spectrum in a visible light region is used. An image is formed by performing light modulation according to an image signal on the light of the light source 1 condensed by a reflector or the like using a light modulation element 3 such as a liquid crystal panel. The formed image is enlarged and projected on the screen 9 by the projection lens 7 and displayed.

A projection display device can display a large area as compared with other display devices because an image is enlarged and projected by a projection lens, but has a problem of low resolution. The resolution of the projected image is determined by the number of pixels of the light modulation element and the size of the screen. In order to display a high-resolution image on a screen, it is necessary to increase the number of pixels of the light modulation element. However, when the number of pixels is increased, the manufacturing yield is reduced and the cost is increased. For example, SXGA (1280 × 102
The light modulation element having the number of pixels of 4) is a VGA (640 × 48
The cost is about 10 times that of the light modulation element having the number of pixels 0). In addition, the aperture ratio per pixel (the ratio of the effective area that transmits light to one pixel) decreases as the density of the pixels increases, so that it is difficult to obtain an image with a desired brightness. As described above, since the density of the pixels and the brightness of the image are in conflict with each other, a high-quality image cannot be obtained by simply increasing the density of the pixels of the light modulation element.

[0004] In order to solve this problem, there is a method of projecting using a plurality of light modulation elements. In the method using a plurality of light modulation elements, for example, a plurality of images are displayed vertically and horizontally using a plurality of display units like a multi-vision using a CRT (cathode ray tube) on a display device. However, in this method, since a plurality of display units are used, there is a problem that a screen cannot be made continuous at a connection portion of each display unit and a boundary is conspicuous. In addition, since it is difficult to manufacture a plurality of display units with exactly the same display characteristics, there is a problem that brightness of each display unit becomes uneven, and a joint between the display units becomes conspicuous. I have.

[0005] In order to solve this problem, a method of superimposing and displaying one image by using a plurality of display units is known. The projection display device described in Japanese Patent Application Laid-Open No. 3-166536 discloses an image distribution function unit that arbitrarily samples and divides display data of an original image, a plurality of display function units, and optically converts each display image. An image synthesizing function unit that synthesizes and displays an original image, and a projection function unit that projects a synthesized image are provided. FIG. 10 shows the basic configuration. FIG.
, 7 is a projection lens, 13 is a light supply unit composed of a plurality of light sources, 14 is a light modulation element group composed of a plurality of transmissive liquid crystal panels, and 15 is a composite image projected by the light modulation element group 14 and projected. This is an optical device for making the light enter the lens 7. For example, when superimposed display is performed using four transmissive liquid crystal panels 14, the aperture ratio of each pixel of each transmissive liquid crystal panel 14 is set to about 25%, and the projection is shifted by a half pixel pitch in the horizontal and vertical directions. By doing so, it is possible to obtain an image with four times the resolution. FIG.
FIG. 11B shows four images as shown in FIG.
11A is shifted by a half pixel pitch in the horizontal direction with respect to the image of FIG. 11A, and the image of FIG. 11C is shifted by a half pixel pitch in the vertical direction with respect to the image of FIG.
If the image of (d) is projected with a half pixel pitch shift in the horizontal and vertical directions with respect to the image of FIG.
An image having four times the resolution as shown in FIG. 11E is obtained. By performing the superimposed display in this way, the non-uniformity of the display characteristics of the plurality of display units can be made inconspicuous. However, there is a problem in that it is difficult to adjust an optical system for projecting the images with a half pixel pitch shifted from each other, and in that a plurality of display units are used, so that the configuration is complicated and the cost is high.

As another means for increasing the resolution, there is a method of performing time-division display using one light modulation element. Time-division display is a method of displaying one field (one screen) by displaying a plurality of fields in time series. For example, JP-A-4-
The projection display device described in JP-A-113308 shifts a projected image by using an element for turning the polarization direction of transmitted light in the optical path from the light modulation element to the screen and a transparent element having a birefringence effect. Means and means for discrete projection on the screen. FIG. 12 shows a basic configuration of the projection display device. In FIG. 12, reference numeral 1 denotes a light source, 3 denotes a light modulation element composed of a liquid crystal panel for display, 16 denotes a liquid crystal panel for controlling the polarization direction, 17 denotes a quartz plate, 7 denotes a projection lens, and 9 denotes a screen. A quartz plate 17 is used as a transparent element having a birefringence effect. In this method, one frame of image data is divided and stored in a frame memory, and time-division display is performed by displaying an image in synchronization with a means for shifting a projected image. Further, a high-resolution display is performed by shifting the image in time series so as to interpolate the discretized image by using means for making the image of the light modulation element discrete.

As means for making the image discrete, there are a means for lowering the effective aperture ratio by blocking a part of a pixel, and a means for condensing light by using a microlens corresponding to one pixel. Means for shielding a part of the pixel, for example, by devising the arrangement of the wiring of the switching element provided in each pixel to reduce the light transmission area, to make the light transmission area of the pixel discrete I have. On the other hand, the means for condensing light using a microlens corresponding to one pixel condenses the light emitted from the pixel, thereby substantially discretizing the image without reducing the amount of light.

The means for shifting the projected image utilizes the birefringence effect. Using a crystal with optical anisotropy,
An image is shifted on a screen by a difference in refraction angle between ordinary light and extraordinary light. Here, a TN (twisted nematic) liquid crystal is used to rotate linearly polarized light by 90 degrees to switch between ordinary light and extraordinary light for a transparent element having a birefringence effect. Ordinary light perpendicularly incident on a transparent element having a birefringence effect goes straight, while extraordinary light is refracted by a predetermined angle on the incident surface and refracted by the same angle on the exit surface on the opposite side.
Due to this effect, the extraordinary light is shifted by a distance corresponding to the thickness of the transparent element with respect to the ordinary light. Therefore, if the thickness of the transparent element is set so as to shift by a distance corresponding to the pixel pitch (1/2 of the pixel pitch), a shift amount for interpolating a discretely formed image can be obtained.

[0009]

In the above-described time-division display, a polarization direction turning element and a transparent element having a birefringence effect as means for projecting at least discretely and means for shifting an image are required. By using one set of the polarization direction rotating element and the transparent element having the birefringence effect, the display can be divided into two fields in the horizontal or vertical direction, but the display can be divided into more fields in the horizontal or vertical direction. When the display is performed in two fields in both the horizontal and vertical directions, or when the display is divided into more fields in both the horizontal and vertical directions, the polarization direction rotating element and the birefringence are used. There is a problem that a plurality of sets of transparent elements having an effect are required, and the configuration of the plurality of elements is complicated.

Further, the method of shading a part of the pixel as a means for making the image discrete is easy to produce by simply making a slight change to the conventional liquid crystal panel, so that the structure becomes complicated. However, since a part of the pixel is shielded from light and the light transmission area is reduced, the image becomes darker than a conventional liquid crystal panel.

Although the birefringence effect is used as a means for shifting an image, the light emitted from the light modulator must be linearly polarized in order to use the birefringence effect.
To convert natural light into linearly polarized light, a polarizing plate is necessary, but the light is absorbed by the polarizing plate at about 60%, and only about 40% is transmitted. Furthermore, since a liquid crystal element is used as the means for rotating the polarization direction, light transmittance in the liquid crystal element becomes a problem. The liquid crystal element of the polarization direction rotating means is constituted by sandwiching liquid crystal between two glass substrates on which transparent electrodes are formed. The light transmittance of the transparent electrode is 90 per sheet.
%, The transmittance is about 80% for two sheets. Further, in consideration of the transmittance of the liquid crystal itself, the glass substrate, the quartz plate, and the like, the transmittance of light by the polarization direction rotating means is further reduced to about 65%. Further, in the case where high resolution is to be achieved in both the horizontal and vertical directions, two sets of a polarization direction turning means and a quartz plate are required,
Further, the light transmittance is reduced to about 40%. Accordingly, the transmittance of the light passing through the polarizing plate for converting natural light into linearly polarized light and the light passing through the polarization direction rotating means is about 15 to 20%, and the resolution can be increased, but the light use efficiency is extremely reduced. I get only dark images.

Although TN liquid crystal is used as the light turning means, its responsiveness becomes a problem. The TN liquid crystal switches the orientation of molecules by turning on and off the voltage, and its response (switching time) is several milliseconds. When one frame (1/60 to 1/30 seconds) is divided into a plurality of fields when performing time-division display, the number of
Since it takes ten and several milliseconds, when the TN liquid crystal is used, the switching time of the polarization direction occupies several tens of% in one field. As a result, there arises a problem that the contrast of the image is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art.
It is an object of the present invention to provide a projection display device that can perform time-division display with a simple configuration without reducing light transmittance and contrast even when a light modulation element having a small number of pixels is used and display an image with high resolution.

[0014]

The object of the present invention is to provide a projection display device in which an image displayed by a light modulation element having a plurality of pixels is enlarged and projected on a screen by a projection means.
Light emitted from an adjacent (i × j) pixel among a plurality of pixels of the light modulation element is located on an optical path from the light modulation element to the screen so that an image on the screen is separated into a plurality of pixels. It is located between a micro-lens array in which a plurality of convex lenses included in each aperture are arranged adjacent to each other, and a light-modulating element and a micro-lens array. An image forming optical system, and a projection area changing means for changing an image projection area on the screen to project an image displayed on the light modulation element so as to interpolate an image separated on the screen by the microlens array. And a time-division display in which one frame is composed of a plurality of fields is performed.

Further, the above object is to provide a color separating means for separating light from a light source into light of a plurality of colors, a plurality of light modulating elements having a plurality of pixels for respectively modulating the lights of the separated colors, In a projection type display device having a color synthesizing means for synthesizing a plurality of modulated lights of colors and a projection means for enlarging and projecting a color image displayed by a plurality of light modulation elements on a screen, , And adjacent (i × x) of the plurality of pixels of the light modulation element so that the image on the screen is separated into a plurality of pixels.
j) A microlens array in which a plurality of convex lenses each including light emitted from a pixel within its respective aperture are arranged adjacent to each other, and a light emitting device which is located between a color synthesizing means and a microlens array and emits light from a plurality of light modulation elements. An image forming optical system that collects light and forms an image on the microlens array, and an image projection area on the screen is changed and displayed on the light modulation element so as to interpolate the image separated on the screen by the light collecting means. And a projection area changing means for projecting an image to be projected, and performing time-division display in which one frame is composed of a plurality of fields.

The image forming optical system of the projection type display device is characterized in that it is an afocal optical system having a plurality of lenses and emitting incident parallel light as parallel light.
Further, the projection area changing means of the projection type display device sets the micro lens array in a plane orthogonal to the optical axis of the light incident on the micro lens array in synchronization with a field signal supplied to the light modulation element. It is characterized in that it is moved by a movement change amount. The predetermined movement change amount is characterized by an amount obtained by multiplying an integral multiple of the pixel pitch of the light modulation element by a magnification of the imaging optical system.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A projection type display according to a first embodiment of the present invention will be described with reference to FIGS. The projection display device according to the present embodiment separates an image into a plurality of pixels on a screen in order to increase the definition of a projected display image without increasing the number of pixels of a light modulation element such as a liquid crystal light valve for display. A microlens array in which microlenses of a plurality of convex lenses including light emitted from a plurality of pixels adjacent to the light modulation element within respective apertures are arranged so as to interpolate an image separated on a screen by the microlens array. Basically, time-division display is performed by discretely reducing the light emitted from the light modulation element and interpolating the discrete gap by means of a projection area changing means for projecting a display image by the light modulation element. And Further, it is characterized in that an image forming optical system for forming an image displayed by the light modulation element on the microlens array is provided. In the projection type display device according to the present embodiment, a light source, a condensing optical component, a light modulation element such as a liquid crystal light valve for display composed of a large number of pixels arranged two-dimensionally, and a conventional light source such as a projection lens. In addition to the components used in the projection display device, an imaging optical system and an optical modulation element for imaging an image displayed on the optical modulation element on a microlens array on an optical path from the optical modulation element to the projection means. Has a micro-lens array that collects the light emitted from each pixel and reduces it discretely for each pixel, and enters the micro-lens array by synchronizing the discretely reduced gap with the field signal supplied to the light modulation element. The gap image is interpolated by moving the image on a plane perpendicular to the optical axis to increase the number of pixels and increase the definition of the display image. Further, in the projection display device according to the present embodiment, since there is no optical system with light absorption on the optical path from the light modulation element to the screen, a bright image can be obtained even if the number of pixels is increased and the definition is increased.

In this embodiment, a description will be given of a case where each of a plurality of pixels adjacent to the light modulation element is four pixels, and a plurality of light-collecting optical elements including the light emitted from the four pixels within the aperture are convex lenses. I do. FIG. 1 is a basic configuration diagram of a projection display device according to the present embodiment, FIG. 2 is a perspective view of a microlens array used in the present embodiment,
3 and 4 are explanatory views showing the positional relationship between the light modulation element and the convex lens according to the present embodiment, FIG. 3 is a plan view showing the positional relationship between the light modulation element and the convex lens, and FIG. 4 is a light modulation element. Fig. 3 of the plane parallel to the optical axis from the projection lens to the object plane
It is sectional drawing in AA '. FIG. 5 shows the positional relationship of the incident light beam on the projection lens object plane when one screen is divided into four images. FIG. 6 is a diagram showing a positional relationship between the light modulation element and the microlens array when there is no imaging optical system, and FIG. 7 is a diagram showing a positional relationship between the respective elements when the imaging optical system is inserted.

In FIG. 1, 1 is a light source, 2 is a collimating conversion lens for converting light from the light source into parallel light, 3
Is an optical modulation element composed of a number of pixels arranged two-dimensionally, 4 is an imaging optical system for imaging an image displayed by the optical modulation element on a microlens array, 5 is a microlens array, 6 Is an actuator composed of a piezoelectric element, 7
Denotes a projection lens, 8 denotes an object plane of the projection lens 7, and 9 denotes a screen. The micro lens array 5 includes the light modulation element 3
Are arranged on the optical path from to the projection lens 7, and one convex lens is formed corresponding to four pixels of the light modulation element 3. The imaging optical system 4 is arranged to make the light from the light modulation element 3 incident on the corresponding microlens. The actuator 6 includes an actuator 6a1 for vibrating the microlens array 5 in a vertical direction (vertical direction on the paper),
6a2 and actuators 6b1 and 6b2 (not shown) that vibrate in the horizontal direction (the direction normal to the paper surface). By driving the actuator 6 in synchronization with a field signal supplied to the light modulation element 3, a horizontal / horizontal direction orthogonal to the optical axis of light incident on the microlens array 5 is obtained.
The micro lens array 5 can be moved or vibrated in the vertical direction.

The light modulation element 3 used in the present embodiment has p
This is an active matrix type liquid crystal light valve using an poly-Si TFT (thin film transistor using polycrystalline silicon for a channel layer). A liquid crystal polymer composite (Liquid Crystal Polymer C) which does not require a polarizing plate is used as a liquid crystal material of a liquid crystal light valve.
omposite). The number of pixels of the light modulation element 3 is m × n, and the pixel pitch p is 50 μm, which is a general value both horizontally and vertically.

The microlens array 5 shown in FIG. 2 is formed by using, for example, an ion exchange method. In this method, certain kinds of ions are diffused into a transparent glass substrate to form layers having different refractive indices and are used as a lens effect. The microlens array 5 is designed to collect as much as possible light beams emitted from four pixels.
It is composed of a number of convex lenses formed at a pitch of 00 μm. Since the size of the microlens array 5 can be formed in substantially the same size as the light modulation element 3, the weight can be reduced to about several grams.

The actuator 6 uses a laminated piezoelectric element made of a high distortion piezoelectric ceramic material. The actuator 6 is adhered to the side surface of the microlens array 5, and a voltage is applied in synchronization with a field signal supplied to the light modulation element 3. The microlens array 5 can be moved and changed in the direction.

The operation of shifting an image by the microlens array 5 and the actuator 6 and displaying a high-definition image in the present embodiment will be described with reference to FIGS. In the present embodiment, one screen (frame) is divided into four images (fields) and displayed. Note that the actual planar shape of each microlens is 4 as shown in FIG.
Each pixel has a rectangular shape including the entirety of the pixels within its aperture, but in the plan views of FIGS. 3 and 5, each microlens is indicated by a solid or broken circle in order to clarify the position of each microlens.

Now, in the first field of the first frame, the relative positions of the pixels of the light modulation element 3 and the microlenses are as shown in FIG. For example, the central axis of the micro lens 5a is a pixel of the light modulation element 3,
, And outgoing light from the pixels,... Are collected by one microlens 5a.
As shown in FIG. 4, the outgoing lights 101 and 102 from the pixels of the light modulation element 3 enter the microlens array as an inverted image by the imaging optical system 4, and are emitted by the microlens array 5. The light becomes 101 ′ and 102 ′ and enters the projection lens 7. At this time, the object surface 8 of the projection lens 7 is located at a position where the light from the light modulation element 3 is condensed to approximately 1/4. The display image on the object plane 8 of the projection lens 7 is thinned out in the horizontal and vertical directions as shown in FIG. 5A, that is, discretely reduced.

Next, in the second field, the actuator 6a vibrates in the vertical direction in synchronization with the field signal.
By 1 and 6a2, the microlens array 5 is moved in a vertical direction in a plane orthogonal to the optical axis of the light incident on the microlens array 5. The center axis of the microlens 5a moves to the position of the intersection of the pixels of the light modulation element 3, that is, the position of FIG. Here, the movement amount of the microlens array 5 from the position of FIG. 3A to the position of FIG. 3B is 50 μm, which is the same as the pixel pitch p of the light modulation element 3. At this time, as shown in FIG. 4, the light beams 101 and 102 emitted from the pixels of the light modulation element 3 enter the microlens array 5 as an inverted image by the imaging optical system 4 and are collected by the microlens array 5. Outgoing light 10
1 ”and 102” are incident on the projection lens 7. In the object plane 8 of the projection lens 7, the light is condensed at the position shown in FIG. 5B, and the vertical gaps discretely reduced in the first field by the microlens array 5 are interpolated in the second field. It was done.

Next, in the third field, the actuator 6b vibrates in the horizontal direction in synchronization with the field signal.
The microlens array 5 is moved in the horizontal direction within a plane orthogonal to the optical axis of the light incident on the microlens array 5 by the steps 1 and 6b2. The central axis of the microlens 5a is the position of the intersection of the pixels of the light modulation element 3, that is, FIG.
Move to position (c). Here, the amount of movement of the microlens array 5 from the position in FIG. 3B to the position in FIG. 3C is 50 μm, which is the same as the pixel pitch p of the light modulation element 3. As a result, the light emitted from the light modulation element 3 is condensed at the position shown in FIG. 5C on the object plane 8 of the projection lens, and discretely reduced by the microlens array 5 in the second field. This means that the horizontal gap is interpolated in the third field.

Next, in the fourth field, the actuator 6a vibrates in the vertical direction in synchronization with the field signal.
The microlens array 5 is moved in the direction perpendicular to the optical axis of the light incident on the microlens array 5 in the direction 1 and 6a2. The central axis of the microlens 5a is the position of the intersection of the pixels of the light modulation element 3, that is, FIG.
Move to position (d). Here, the movement amount of the microlens array 5 from the position of FIG. 3C to the position of FIG. 3D is 50 μm, which is the same as the pixel pitch p of the light modulation element 3. As a result, the light emitted from the light modulation element 3 is focused on the object plane 8 of the projection lens 7 at the position shown in FIG.
The vertical gaps discretely reduced by the third field by the microlens array 5, ie, the horizontal gaps discretely reduced by the first field, are interpolated by the fourth field. .

By the first, second, third and fourth fields described above, the image information of all one frame is shown in FIG.
The object plane 8 of the projection lens 7, that is, the screen 9 as shown in FIG.
, And high-definition display can be realized using the light modulation element 3 with low definition.

Next, in the first field of the second frame, the actuators 6b1 and 6b2 which vibrate in the horizontal direction in synchronization with the field signal horizontally move in a plane orthogonal to the optical axis of the light incident on the microlens array 5. The micro lens array 5 is moved in the direction. Micro lens 5a
Moves to the position of the intersection of the pixels of the light modulation element 3, that is, the position of FIG. Here, FIG.
The amount of movement of the microlens array 5 from the position (d) to the position in FIG. 3A is 50 μm, which is the same as the pixel pitch p of the light modulation element 3. As a result, the light emitted from the light modulation element 3 is focused on the object plane 8 of the projection lens 7 at the position shown in FIG. 5A, and returns to the same position as the first field of the first frame. Thereafter, by interpolating the discretely reduced horizontal / vertical gaps as in the first frame, (m
× n) 4 × (m × n) using light modulation element 3 having pixels
A high-definition display having pixels is realized.

Here, the operation of the imaging optical system 4 will be described in detail with reference to FIGS. First, as shown in FIG.
The light emitted from the light source 1 is collimated by the collimating conversion means 2 and is incident on the light modulation element 3, where the light is modulated according to the image signal. The outgoing light for every four pixels modulated by the light modulation element 3 enters each micro lens of the micro lens array 5 by the imaging optical system 4. Assuming that the imaging optical system 4 is not inserted at this time, FIG.
As shown in (2), a part of the light emitted from the predetermined four pixels of the light modulation element 3 that is not parallel light enters the adjacent microlens without entering the microlens to be incident. Become. As a result, the object plane 8 of the projection lens 7
In FIG. 6B, as shown in FIG. 6B, a part of each pixel is condensed at a position distant from a position where light is originally condensed by a microlens, and is displayed on a screen at a distance from an original display position. Will be done. FIG. 6B shows a state in which some of the pixels to be condensed by the microlens in the center of the microlens array 5 in the figure are condensed by neighboring microlenses. . In such a state, an image different from the image that should be originally displayed on the screen is displayed, so that the contrast of the displayed image is reduced. Even when the light emitted from the light modulation element 3 is not an ideal parallel light, the light modulation can be performed by disposing the imaging optical system 4 on the optical path from the light modulation element 3 to the microlens as in the present embodiment. All of the light emitted from the four pixels of the element 3 can be made incident on one predetermined microlens. The imaging optical system 4 according to the present embodiment
This is an optical system that forms a one-to-one inverted image. FIG. 7A shows a state of imaging using the imaging optical system 4 according to the present embodiment. f is the focal length of the lens. Since the parallel light emitted from the light modulation element 3 needs to enter the microlens array 5 in parallel, the imaging optical system 4 uses an afocal optical system configured by combining at least two lenses. I have. Light emitted from the four pixels of the light modulation element 3 enters one microlens by the imaging optical system 4. The light from the light modulation element 3 which is not an ideal parallel light has a different angle of incidence on the microlens, so that the position where the light is condensed by the microlens is shifted. As a result, FIG.
As shown in FIG. 6B, in the object plane 8 of the projection lens, the pixels condensed by the central microlens take a slightly widened shape. Since a part of another pixel is not displayed, the contrast of the image is not reduced.

In the present embodiment, the imaging optical system 4 is an optical system that forms a one-to-one inverted image. An optical system that forms a k-fold image may be used. If the imaging optical system 4 forms a k-fold image, the size of the microlens becomes k-fold, and the amount of movement is k times the pixel pitch p of the light modulation element 3.
Double. If the imaging optical system 4 forms a 1 / k-fold image, the size of the microlens will be 1 / k times and the amount of movement will be 1 / k times the pixel pitch p of the light modulation element 3. .

In this embodiment, four adjacent pixels are displayed in a time-division manner. However, four field images are displayed within a short period of about one frame period (1/30 msec) of a normal television image. For example, human eyes can see a single high-definition image due to the afterimage effect.

In the conventional projection type display device, it was possible to display on the screen 9 only at a resolution determined by the number of pixels of the light modulation element 3, but according to the present embodiment, the horizontal / vertical resolution is reduced by the light modulation element. It is possible to display at twice the resolution determined by the number of pixels of 3. Since the microlens array 5 is used as a means for making the image discrete, the light use efficiency is not reduced unlike the means for blocking the light emitted from the light modulation element 3. Further, since the interpolation of the gap is performed by mechanical vibration by the actuator 6, an optical system with light absorption, such as a polarizing plate or a liquid crystal panel for rotating the polarization direction for shifting an image, is used for the light modulation element 3. Since it does not exist on the optical path from to the projection lens 7, a bright and high-definition image can be displayed without lowering the light use efficiency. Also, the light modulation element 3
Is emitted to the microlens array 5 using the imaging optical system 4, so that a part of the image of each pixel does not overlap with the image of another pixel on the screen, and the magnification does not lower the contrast of the image. Display can be performed.

In this embodiment, the light modulating element 3
The configuration is such that one frame is formed by four fields using a microlens array 5 composed of a plurality of microlenses corresponding to pixels (2 × 2 pixels), but 9 pixels (3 × 3 pixels) and 16 pixels (4 × 4 pixels), 6 pixels (2 × 3 pixels), 12 pixels (3 × 4 pixels), etc.
j) 1 (i × j) fields using a microlens array 5 composed of a plurality of microlenses corresponding to pixels.
It may be configured to form a frame. At this time, the amount of movement Lh, L in the horizontal / vertical direction with respect to one field signal of the microlens array 5 by the actuator 6
v is the number of pixels corresponding to the horizontal direction of the microlens corresponding to a plurality of pixels is i, the number of pixels corresponding to the vertical direction is j, the pixel pitch in the horizontal direction is ph, and the pixel pitch in the vertical direction is pv. , Ph ≦ Lh ≦ (i−1) × ph pv ≦ Lv ≦ (j−1) × pv, which is an integral multiple of the pixel pitch ph, pv. This is a case where the imaging optical system 4 forms a 1: 1 image.

In this embodiment, the actuator 6 uses a laminated piezoelectric element made of a high-strain piezoelectric ceramic material, but the microlens array is synchronized with the frequency of the field signal supplied to the light modulation element 3. Any means capable of moving and changing the microlens array 5 by an integral multiple of the pixel pitch p of the light modulation element 3 within a plane orthogonal to the optical axis of the light incident on the light modulation element 3 may be used. The frequency of the field signal supplied to the light modulation element 3 is several tens Hz to several hundreds H
Because of z, an electromagnetic actuator, a linear actuator, a stepping motor, or the like can be used as the actuator 6.

The same effect can be obtained by moving and changing the projection lens 7 instead of oscillating the microlens array 5. In this case, the pixel position on the screen 9 in each image when one screen (frame) is divided into a plurality of images (fields) is different from the case where the light condensing unit is moved and changed. The same effect can be obtained by moving and changing any lens of the projection lens 7, but it is desirable to move and change the lightest lens, and generally it is preferable to move and change the rear lens.

In the present embodiment, the microlens array 5 corresponding to a plurality of pixels is moved and changed. However, a plurality of condensing optical elements each including light emitted from a plurality of pixels adjacent to the light modulation element in each aperture are provided. It is sufficient if there is a light condensing means arranged adjacently and a means for changing the projection area so as to interpolate the projection image discrete by the light condensing means. Optical Technology Contact, Vol. 32, No. 11, p.
8, 1994), and a voltage may be selectively applied in synchronization with a field signal to change the lens formation position.

Next, a projection type display according to a second embodiment of the present invention will be described with reference to FIG. The projection display device according to the present embodiment is characterized by performing color display using three light modulation elements. FIG. 8 is a basic configuration diagram of the projection display device according to the present embodiment.

In FIG. 8, 1 is a light source, 2 is a collimating conversion lens for converting light from the light source into parallel light, 3
a to 3c are light modulation elements, 4 is an imaging optical system, 5 is a microlens array, 6 is an actuator composed of a piezoelectric element,
Reference numeral 7 denotes a projection lens, 8 denotes an object surface of the projection lens, 9 denotes a screen, 10 denotes a color separation unit including a dichroic prism, 11 denotes a mirror, and 12 denotes a color combining unit that includes a dichroic prism. Here, three light modulation elements 3a to 3c are used for color display, but the optical distances from these light modulation elements to the microlens array 5 are equal, and the three light modulation elements 3a to 3c are used. Are arranged such that their corresponding pixels overlap on the screen. The configuration of the projection display device in the present embodiment is as follows.
Except for the color separation / synthesis unit, the configuration is the same as that of the projection display device of the first embodiment.

In FIG. 8, the light emitted from the light source 1 is collimated by a collimating conversion means 2 and separated into three colors of RGB by a color separation means 10. The light separated into three colors is such that green (Green) light enters the light modulation element 3a, red (Red) light enters the light modulation element 3b, and blue (Blue) light enters the light modulation element 3c. And light modulation corresponding to each image signal is performed. Light modulation element 3
Green light emitted from a passes through the color synthesizing means 12 and proceeds straight as it is. The red light is emitted from the light modulation element 3b and is reflected by the reflection surface of the color synthesizing unit 12 that reflects the red light. Blue emitted from the light modulation element 3c
Is reflected by the reflecting surface of the color synthesizing unit 12 that reflects the Blue light. These three colors of light are combined by the color combining means 12 to form one image. Light modulation elements 3b, 3
c indicates that the corresponding pixel has a mirror image relationship with the light modulation element 3a. Each light modulation element 3a synthesized by the color synthesis means 12
3c are formed on the corresponding microlenses by the imaging optical system 4. Light incident on the microlens is collected, and a discrete image is obtained. The positional relationship between the pixels of each of the light modulation elements 3a to 3c synthesized by the color synthesizing unit 12 and the microlens array 5 and the operation of the microlens array 5 are the same as in the first embodiment, and will be described in detail here. Is omitted, but the horizontal /
Vibration is made in the vertical direction by the same distance as the pixel pitch. Since the color synthesizing unit 12 is located between the light modulation elements 3a to 3c and the imaging optical system 4, the focal length of the imaging optical system 4 needs to be longer than that of the first embodiment. is there.

In the case of a color display, the light modulation element 3a
3c and the microlens array 5
2, the distance from each of the light modulating elements 3a to 3c to the microlens array 5 becomes long, which causes a problem when the light emitted from the light modulating elements 3a to 3c deviates from the parallel light. . Therefore, if the imaging optical system 4 of the present embodiment is not provided, since the length of the color synthesizing unit 12 is several cm, the deviation angle of the light emitted from the light modulation element 3 from the optical axis direction is 10 ° or less. Even if the micro lens array 5
When the light is incident on the micro-lens, the amount of deviation from the optical axis is several hundred μm, and a part of the light emitted from the light modulation element 3 is incident on the adjacent microlens.

In the conventional projection type color display device, the image can be displayed on the screen 9 only at a resolution determined by the number of pixels of each of the light modulation elements 3a to 3c. Can be displayed at twice the resolution determined by the number of pixels of the light modulation elements 3a to 3c. Since the microlens array 5 is used as a means for making the image discrete, the light use efficiency is not reduced unlike the means for blocking the light emitted from the light modulation element 3. Further, since the interpolation of the gap is performed by mechanical vibration by the actuator 6, an optical system with light absorption such as a polarizing plate or a liquid crystal panel for rotating a polarization direction for shifting an image is provided by the color synthesizing unit 12. Since it does not exist on the optical path from to the projection lens 7, a bright and high-definition image can be displayed without lowering the light use efficiency. Further, since the imaging optical system 4 is used, even if the distance between each of the light modulation elements 3a to 3c and the microlens array 5 becomes long, the light emitted from the light modulation elements 3a to 3c can be a predetermined micro light. Since the light can enter the respective lenses, it is possible to perform enlarged color display without lowering the contrast of the image.

[0043]

As described above, according to the present invention, it is possible to increase the definition of a projected display image without increasing the number of pixels of the light modulation element. Also, in the present invention, the light use efficiency is not reduced unlike the means for blocking the light emitted from the light modulation element, and the gap is interpolated by mechanical vibration by the actuator. There is no need to dispose an optical system with light absorption, such as a polarizing plate or a liquid crystal panel that rotates the polarization direction for shifting the image, on the optical path from the light modulation element to the projection means, which reduces the light use efficiency. It is possible to display a bright and high-definition image without causing the image to be displayed.

Even if a color synthesizing means for performing color display is arranged between the light modulating element and the microlens array, an image forming optical system is arranged between the color synthesizing means and the microlens array. As a result, even if there is non-parallel light emitted from the light modulation element, it does not enter any part other than the predetermined microlens. Therefore, since different images do not overlap each other on the screen, a bright image without lowering the contrast of the image can be obtained.

An actuator such as a piezoelectric element as a vibration means has a vibration amplitude of several μm to several tens μm,
Since it operates at a low vibration frequency of Hz to several hundred Hz,
The switching time of the movement of the light collecting means can be set to 1 millisecond or less. Since the responsiveness is sufficient, the contrast of the image does not decrease.

Further, the optical component used in the present invention has a simple structure such as a microlens array formed on a glass substrate and an actuator such as a piezoelectric element, and has the same size (about several cm) as the light modulation element. Therefore, the projection type display device of the present invention can be made almost the same size as the conventional display device. Furthermore, even when the number of screen divisions is increased to perform higher-definition image display, the number of parts is increased according to the number of screen divisions as in a conventional display device using a crystal plate and a TN liquid crystal panel. Nothing,
The size of the device can be approximately the same as a conventional device. Further, the optical components newly used in the present invention can be manufactured with high precision and at low cost, so that the cost of the apparatus hardly changes from the conventional one.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of a projection display device according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a microlens array of the projection display device according to the first embodiment of the present invention.

FIG. 3 is a plan view showing a positional relationship between a light modulation element and a convex lens of the projection display device according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view of a plane parallel to an optical axis from a light modulation element to a projection lens object plane of the projection display device according to the first embodiment of the present invention, taken along the line AA ′ of FIG. 3;

FIG. 5 is a plan view showing a positional relationship of an incident light beam on a projection lens object plane when one screen of the projection display device according to the first embodiment of the present invention is divided into four images.

FIG. 6 is a diagram showing a position where light emitted from a light modulation element is focused on a microlens when there is no imaging optical system.

FIG. 7 is a diagram illustrating a position where light emitted from a light modulation element is focused on a microlens when the imaging optical system according to the first embodiment of the present invention is used.

FIG. 8 is a basic configuration diagram of a projection display device according to a second embodiment of the present invention.

FIG. 9 is an explanatory diagram showing a configuration of a conventional projection display device.

FIG. 10 is an explanatory diagram showing a configuration of a conventional projection display device.

FIG. 11 is an explanatory diagram showing a configuration of an image projected by a conventional projection display device.

FIG. 12 is an explanatory diagram showing a configuration of a conventional projection display device.

[Explanation of symbols]

 Reference Signs List 1 light source 2 collimating conversion lens 3 light modulation element 4 imaging optical system 5 micro lens array 6 actuator 7 projection lens 8 object surface of projection lens 9 screen 10 color separation means (dichroic prism) 11 mirror 12 color synthesis means (dichroic prism) 13) Light supply unit 14 Light modulation element 15 Optical device 16 Liquid crystal panel for controlling polarization direction 17 Quartz plate

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Keishi Fujimaga

Claims (5)

[Claims] 1. A projection display device for enlarging and projecting an image displayed by a light modulation element having a plurality of pixels on a screen by a projection means, wherein the projection display apparatus is located on an optical path from the light modulation element to the screen. A plurality of convex lenses including, in their respective apertures, outgoing light from adjacent (i × j) pixels among the plurality of pixels of the light modulation element so that an image on the screen is separated into a plurality of pixels. A microlens array, an imaging optical system located between the light modulation element and the microlens array, and configured to collect light emitted from the light modulation element and form an image on the microlens array; An image displayed on the light modulation element by changing an image projection area on the screen so as to interpolate an image separated on the screen by the microlens array. And a projection area changing means for projecting a projection display device which is characterized in that the time division display of one frame is composed of a plurality of fields. 2. A color separation means for separating light from a light source into light of a plurality of colors, a plurality of light modulation elements having a plurality of pixels for modulating the lights of the plurality of colors, respectively, A color combining unit that combines the plurality of colors of light, and a projection unit that enlarges and projects a color image displayed by the plurality of light modulation elements on a screen. Light emitted from adjacent (i × j) pixels among a plurality of pixels of the light modulation element is located on an optical path to the screen, so that an image on the screen is separated into a plurality of pixels. A microlens array in which a plurality of convex lenses included in the aperture of the microlens are arranged adjacent to each other; and the microphone is located between the color synthesizing unit and the microlens array to collect light emitted from the plurality of light modulation elements. An image forming optical system for forming an image on the lens array, and an image projection area on the screen is changed and displayed on the light modulation element so as to interpolate an image separated on the screen by the light condensing unit. A projection area changing means for projecting an image to be projected, and performing time-division display in which one frame is composed of a plurality of fields. 3. The projection type display device according to claim 1, wherein the imaging optical system is an afocal optical system having a plurality of lenses and emitting incident parallel light as parallel light. A projection type display device characterized by the above-mentioned. 4. The projection-type display device according to claim 1, wherein the projection area changing unit supplies the light modulation element to a plane orthogonal to an optical axis of light incident on the microlens array. A projection-type display device, wherein the microlens array is moved by a predetermined movement change amount in synchronization with a field signal to be applied. 5. The projection display device according to claim 4, wherein the predetermined movement change amount is an amount obtained by multiplying an integral multiple of a pixel pitch of the light modulation element by a magnification of the imaging optical system. Characteristic projection display device.