JPH07181470A - Image display device - Google Patents

Abstract

PURPOSE:To obviate degradation in image quality by shades of nonlinear element parts and electrodes and to less degrade in an image contrast by arranging two-dimensional phase gratings which have grating patterns in two directions intersecting with each other and having a specified grating height. CONSTITUTION:A liquid crystal cell 4 is irradiated with light of a light source 1 from its rear surface side R and the two-dimensional phase gratings 5 are arranged in the display optical path 2 of the liquid crystal cell 4. The front surface side F of the phase gratings 5 is provided with a lens group 3 and the image on the liquid crystal 4 is visually observed by a viewer 6. The phase gratings 5 have the grating patterns in the two directions (X, Y) intersecting with each other. The grating heights of the respective grating patterns are fixed exclusive of errors in production. Namely, the grating patterns exist only in the two directions intersecting with each other in the phase gratings 5 and, therefore, the intensity of the diffracted light of lower order is extremely higher than the intensity of the diffracted light of higher order. Then, the degradation of the contrast by leaking of the diffracted light of the higher order to the image region of the liquid crystal cell is lessened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device such as a rear projection type liquid crystal display device using a liquid crystal cell as a light valve.

[0002]

2. Description of the Related Art In a liquid crystal display device of this type, light from a light source is applied to a liquid crystal cell from its back surface, and an image of the liquid crystal cell is visually observed on the front surface side of the liquid crystal cell. Since the light passing through the liquid crystal cell is visually observed in this way, the shadows of the pixel electrodes and conducting wires of the liquid crystal cell may be projected and the image quality may deteriorate. In particular, as a liquid crystal cell driving method, by adopting an active matrix method in which a non-linear element such as a thin film transistor is incorporated in each pixel, the amount of display information is increased and a TV image can be displayed. Since the non-linear element portion and the pixel electrode portion for driving this active matrix type liquid crystal are opaque,
These fairly dark shadows are projected. In particular, when the image is magnified by the lens and visually observed on the screen or in the virtual image on the lens, the shadow is magnified and the image quality is significantly deteriorated.
It has been proposed to provide a phase grating on the front surface side of the liquid crystal cell, that is, on the viewer side in order to eliminate the deterioration of the image quality due to the shadow of the non-linear element portion or the electrode.

[0003]

Although the phase grating can prevent the image quality from being deteriorated due to the shadow of the pixel electrode portion or the like, it has a problem that the contrast of the image is deteriorated and the image looks blurred. The present invention has been made in view of the above points, and provides an image display device that eliminates the deterioration of image quality due to the shadow of the non-linear element portion, the electrode, and the like, and that reduces the reduction ratio of the image contrast. To aim.

[0004]

According to the present invention, the above object is to provide a grid pattern in two directions intersecting with each other in a display optical path of an image display in which a large number of dot-shaped pixels are arranged two-dimensionally. A two-dimensional phase grating having a grating height of a grating pattern in one direction is substantially constant in an arbitrary cross section, and a grating height of a grating pattern in another direction is substantially constant in an arbitrary cross section. This is achieved by the image display device being arranged.

As the two-dimensional phase grating in the image display device of the present invention, the intensity of the (± 1,0) order light and the (0, ± 1) order light with respect to the intensity of the 0th order light at the center wavelength of the image display. Is in the range of 60 to 180%, the intensity of the (± 1, ± 1) order light with respect to the intensity of the 0th order light is in the range of 20 to 330%, and the intensity of the 0th order light is (± 1, 0). Next light,
The sum of the intensity of the (0, ± 1) order light and the intensity of (± 1, ± 1) is 70 at the center wavelength with respect to the intensity of all diffracted light.
% Or more is preferable. The central wavelength in the present invention means the central value of the wavelength region of the display light incident on the image display (for example, the average value of red light and blue light in the case of a color image display), and the total diffracted light. Means 0th order light and all diffracted light of ± 1st order or higher.

[0006]

2 is a schematic perspective view of an example of a two-dimensional phase grating according to the present invention. As shown in FIG. 2, the two-dimensional phase grating according to the present invention has a grating pattern in two directions (X, Y) intersecting with each other. FIG. 3 shows a cross-sectional view of the two-dimensional phase grating taken along line I- (I) corresponding to the X direction or the Y direction. As shown in FIG. 3, the grating height (difference in height between the convex portion and the concave portion) h of each grating pattern in the two-dimensional phase grating is substantially constant except for manufacturing errors. Here, the height of the lattice pattern in the X direction and the height of the lattice pattern in the Y direction do not necessarily have to be the same. Incidentally, it seems that there is a grating pattern having a constant height in a direction that does not match the direction of the grating pattern in the two-dimensional phase grating, but the section taken along line II- (II) shown in FIG. As is clear from the figure, no grating pattern having a constant grating height is formed except in the X and Y directions of the two-dimensional phase grating. When parallel light is incident on the two-dimensional phase grating in the present invention, a diffraction pattern as shown in FIG. 5 is obtained. As described above, in the two-dimensional phase grating of the present invention, since the grating pattern exists only in two directions intersecting with each other, the intensity of the low-order diffracted light is significantly higher than that of the high-order diffracted light. That is, as shown in FIG.
1) next light, (-1,0) next light and (0,1) next light, and (1,1) next light, (1, -1) next light, (-1,-)
1) The intensities of the order light and the (−1,1) order light are remarkably higher than the intensities of higher order diffracted light (eg, (2,2) order light, (2, −2) order light, etc.). high.

FIG. 6 shows a schematic plan view of an example of a liquid crystal cell used in the present invention. The liquid crystal cell receives an image signal of a TV or a VTR and displays an image thereof, has an opaque nonlinear element portion 11 and a wiring portion 12 as shown in FIG. 2, and has an opening (in the figure, (Shown in perspective) is only a portion. When the above-mentioned two-dimensional phase grating is arranged between the liquid crystal cell and the lens or on the viewer side of the lens (that is, on the side opposite to the liquid crystal cell), the light that has passed through the opening and is incident on the two-dimensional phase grating. Spreads as shown in FIG. 5 due to the diffraction effect, so that the opaque nonlinear element portion 11 and the wiring portion 12 are opaque.
The shadow due to is inconspicuous. Further, in the two-dimensional phase grating of the present invention, the intensity of the low-order diffracted light is significantly higher than the intensity of the high-order diffracted light, so that the high-order diffracted light leaks to the image area of each adjacent liquid crystal cell. The degree of contrast reduction and image blurring is small.

The central wavelength of the image display (for example, 550n
m), the two-dimensional phase in which the total of the intensities of the (± 1,0) -order light with respect to the zero-order light intensity of the two-dimensional phase grating and the intensity of the zero-order light with respect to the intensity of all diffracted light is within the above specific range When the grating is used, the intensity of the light surrounded by the (1,1) -order light, the (1, -1) -order light, the (-1, -1,)-order light and the (-1,1,)-order light is high. , And because the ratio of the brightness of the central part to the brightness of the peripheral part is appropriate in the same area,
It is possible to suppress the deterioration of image quality and the deterioration of contrast due to the shadow of the non-linear element portion and the like to an extremely low level.

[0009]

Embodiments of the present invention will be described in detail below with reference to FIG. FIG. 1 is a schematic configuration diagram of an example of an image display device of the present invention, in which light from a backlight (light source) 1 is emitted from a back side R of an active matrix type liquid crystal cell 4. A phase grating 5 is arranged on the front surface side of the liquid crystal cell 4, that is, on the display optical path 2 through which the image display light passes, and a lens group 3 is provided on the front surface side F thereof. The image on the liquid crystal cell is visible through group 3. As the backlight, a combination of a lamp such as a halogen lamp, a xenon lamp, a metal halide, a fluorescent lamp and a diffusion plate, or a combination of the above lamp, a light guide plate and a diffusion plate is used. Further, the phase grating 5 may be arranged on the front side F of the lens group 3.

Here, as a result of a two-dimensional phase grating produced by variously changing the height and shape of the grating, the result of a comparative examination of the resolution of the image quality deterioration due to the shadow of the non-linear element part and the electrode and the influence of the image contrast. Is shown in Table 1.
From Table 1, 550 nm (center wavelength of the liquid crystal display device)
, The intensities of the (± 1,0) -order light and the (0, ± 1) -order light are 60 to 180% of the intensity of the 0th-order light, respectively.
And the intensity of the (± 1, ± 1) next light is 20 to 33.
Within the range of 0%, the total of the intensities of the 0th-order light and the (± 1,0) -order light, the (0, ± 1) -order light, and the (± 1, ± 1) -order light is the total diffraction. When the intensity is 70% or more with respect to the light intensity, the deterioration of the image quality due to the shadow of the non-linear element portion or the electrode is further solved, and the reduction ratio of the image contrast is extremely low.

[Table 1]

It should be noted that the direction of the grating pattern of the phase grating of the two-dimensional phase grating may be horizontal or vertical to the pixels of the liquid crystal cell, and may be horizontal or vertical to the pixels. It may be diagonal. Further, the angle formed by the grid patterns in the two directions is not limited to 90 °. The two-dimensional phase grating is, for example, the first exposure on a photosensitive resin film coated on a substrate such as glass by a mask exposure method using a photomask having a one-way grating pattern, an interference exposure method, or the like. After performing the above step, the substrate is rotated, then the second exposure is performed, and then the photosensitive resin is developed to produce it. If necessary, a stamper (mold) may be produced from the two-dimensional phase grating produced by the above method, and a replica may be produced by an injection molding method, a compression molding method, a photopolymer (2P) method or the like.

As the image display device of the present invention, in addition to a liquid crystal display device, a plasma display panel (PDP), electroluminescence (EL), LE
D etc. are mentioned. Further, examples of applications of the liquid crystal display device include a viewfinder and a liquid crystal projector.

[0013]

According to the image display device of the present invention, it is possible to obtain a high-contrast image in which the deterioration of the image quality due to the shadow of the non-linear element portion and the pixel electrode portion for driving the liquid crystal of the liquid crystal cell is reduced. it can.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example of an image display device of the present invention.

FIG. 2 is a schematic perspective view of an example of a two-dimensional phase grating according to the present invention.

FIG. 3 is a cross-sectional view of the two-dimensional phase grating taken along line I- (I).

FIG. 4 is a sectional view taken along line II- (II) of the two-dimensional phase grating.

FIG. 5 is a diagram showing a diffraction pattern obtained from a two-dimensional phase grating.

FIG. 6 is a schematic plan view of an example of a liquid crystal cell used in the image display device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 light source 2 display optical path 3 lens group 4 liquid crystal cell 5 phase grating 6 observer's eye 11 nonlinear element section 12 wiring section F front side R rear side

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[Procedure amendment]

[Submission date] April 16, 1993

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

As the two-dimensional phase grating in the image display device of the present invention, the intensity of the (± 1,0) order light and the (0, ± 1) order light with respect to the intensity of the 0th order light at the center wavelength of the image display. Is in the range of 60 to 180%, the intensity of the (± 1, ± 1) order light with respect to the intensity of the 0th order light is in the range of 20 to 330%, and the intensity of the 0th order light is (± 1, 0). Next light,
The sum of the intensity of the (0, ± 1) order light and the intensity of (± 1, ± 1) is 70 at the center wavelength with respect to the intensity of all diffracted light.
% Or more is preferable. The center wavelength in the present invention means the center value of the shortest wavelength and the longest wavelength of the display light emitted from the image display (for example, the average value of red light and blue light in the case of a color image display). , Total diffracted light refers to 0th order light and all diffracted light of ± 1st order or higher.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

2 is a schematic perspective view of an example of a two-dimensional phase grating according to the present invention. As shown in FIG. 2, the two-dimensional phase grating according to the present invention has a grating pattern in two directions (X, Y) intersecting with each other. FIG. 3 shows a cross-sectional view of the two-dimensional phase grating taken along line I- (I) corresponding to the X direction or the Y direction. As shown in FIG. 3, the grating height (difference in height between the convex portion and the concave portion) h of each grating pattern in the two-dimensional phase grating is substantially constant except for manufacturing errors. Here, the height of the lattice pattern in the X direction and the height of the lattice pattern in the Y direction do not necessarily have to be the same. Incidentally, it seems that there is a grating pattern having a constant height in a direction that does not match the direction of the grating pattern in the two-dimensional phase grating, but the section taken along line II- (II) shown in FIG. As is clear from the figure, no grating pattern having a constant grating height is formed except in the X and Y directions of the two-dimensional phase grating. When parallel light is incident on the two-dimensional phase grating in the present invention, a diffraction pattern as shown in FIG. 5 is obtained. As described above, the two-dimensional phase grating in the present invention has the grating pattern only in two directions intersecting with each other.
(1,1) order light, (1, -1) order light, (-1,
The intensities of the −1) th order light and the (−1,1) th order light are high, and as a result, the intensities of the low order diffracted light ((1,0) th order light, (0, −)
1) next light, (-1,0) next light and (0,1) next light, and (1,1) next light, (1, -1) next light, (-1,-)
1) the intensity of the order light and the (−1,1) order light) is higher than the intensity of higher order diffracted light (for example, the (2, 2) order light, the (2, −2) order light, etc.) Remarkably high. The cross-sectional shape of the two-dimensional phase grating may be a rectangular wave shape, a triangular wave shape, etc. in addition to the substantially sine wave shape shown in FIG.

Claims (2)

[Claims] 1. A grid pattern in two directions intersecting with each other in a display optical path of an image display in which a large number of dot-shaped pixels are arranged in a two-dimensional manner, and a grid height of the grid pattern in one direction is arbitrary. A two-dimensional phase grating having a substantially constant cross section and a grating height of a grating pattern in one other direction that is substantially constant in an arbitrary cross section is arranged. 2. The intensity of the (± 1,0) order light and the (0, ± 1) order light with respect to the intensity of the 0th order light is in the range of 60 to 180% at the center wavelength of the image display, The intensity of the (± 1, ± 1) order light with respect to the intensity of the light is in the range of 20 to 330%, and the intensity of the 0 order light and the (± 1, 0) order light,
A two-dimensional phase grating whose total sum of the intensities of the (0, ± 1) -order light and the (± 1, ± 1) -order light is 70% or more at the central wavelength with respect to the intensity of all diffracted light is arranged. The image display device according to claim 1, wherein the image display device is provided.