JP2843479B2 - Image display device - Google Patents

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 A liquid crystal display of this type irradiates a liquid crystal cell with light from a light source from the back thereof, and visually observes an image of the liquid crystal cell on the front side of the liquid crystal cell. By observing the light passing through the liquid crystal cell in this way, a shadow of a pixel electrode or a conductive wire of the liquid crystal cell may be projected, and the image quality may be degraded. In particular, as a driving method of a liquid crystal cell, an active matrix method in which a non-linear element such as a thin film transistor is incorporated in each pixel is adopted to increase the amount of display information and display a TV image. Because the non-linear element part and the pixel electrode part for driving this active matrix liquid crystal are opaque,
These rather dark shadows are projected. In particular, when the image is visually observed after being enlarged by a lens, the shadow is enlarged and the image quality is greatly reduced. It has been proposed to provide a phase grating on the front side of the liquid crystal cell, that is, on the viewer side, in order to eliminate the deterioration of image quality due to the shadow of the non-linear element portion and the electrode.

[0003]

Although such a phase grating can prevent a decrease in image quality due to a shadow of a pixel electrode portion or the like, there is a problem that the contrast of an image is reduced and the image appears blurred. The present invention has been made in view of the above points, and has been made to provide an image display device that eliminates a decrease in image quality due to a shadow of a non-linear element portion or an electrode and that reduces a rate of decrease in image contrast. Aim.

[0004]

According to the present invention, an object of the present invention is to provide an image display in which a large number of dot-like pixels are two-dimensionally arranged, and an image display which is arranged in a display optical path of the image display.
And a phase grating having a grating pattern in the direction, wherein at the center wavelength of the image display, the intensity of the zero-order light is (±
The intensity of (1,0) order light and (0, ± 1) order light is 60 to 1
It is in the range of 80%, and (± 1, ±
1) The intensity of the next light is in the range of 20 to 330% and 0
The sum of the intensity of the next order light and the intensity of the (± 1,0) order light, the (0, ± 1) order light, and the (± 1, ± 1) order light is the center wavelength with respect to the intensity of all the diffracted lights. Is at least 70%. Note that the center wavelength in the present invention refers to a center value between the shortest wavelength and the longest wavelength of display light emitted from an image display (for example, in the case of a color image display, an average value of red light and blue light). , Total diffracted light refers to zero-order light and all diffracted lights of ± 1 or more orders.

[0005]

When a parallel light is incident on a phase grating having a grating pattern in two directions, a diffraction pattern as shown in FIG. 2 is obtained. On the other hand, the liquid crystal cell 4 used in the present invention is a TV, VT
An image is displayed by receiving an R video signal or the like, and has an opaque nonlinear element section 11 and a wiring section 12, as shown in FIG. Therefore, the opening (shown by oblique lines in the figure) is only a part. When the 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), light incident on the phase grating through the opening is diffracted. As shown in FIG. 2,
The shadow caused by the opaque nonlinear element portion 11 and the wiring portion 12 is not conspicuous. Further, the phase grating according to the present invention has the following characteristics:
Since the sum of the intensity of the (± 1,0) -order light and the like with respect to the zero-order light intensity and the intensity of the 0-order light and the like with respect to the intensity of all the diffracted lights is within the above specific range, the (1,1) -order light, ( 1, -1)
The intensity of light in a region surrounded by the next-order light, the (−1, −1) -order light and the (−1, 1) -order light is high, and the ratio of the brightness of the central portion to the brightness of the peripheral portion in the same region is high. Since it is appropriate, a decrease in contrast and blurring of an image can be extremely suppressed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIG. FIG. 1 is a schematic configuration diagram of an example of an image display device according to 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 disposed on the front side of the liquid crystal cell 4, that is, on a display optical path 2 through which image display light passes, and a lens group 3 is provided on the front side F thereof. The image on the liquid crystal cell is visually observed through the group 3. As the backlight, a combination of a lamp such as a halogen lamp, a xenon lamp, a metal halide, or a fluorescent lamp and a diffusion plate, or a combination of the lamp, the light guide plate, and the diffusion plate is used. Further, the phase grating 5 may be arranged on the front side F of the lens group 3.

Here, the results of comparing and examining the effect of the image contrast on the elimination of the image quality deterioration due to the shadow of the non-linear element portion and the electrodes and the effect of the image contrast on the phase grating produced by variously changing the height and the shape of the grating are shown. It is shown in FIG. From Table 1, at 550 nm (the center wavelength of the liquid crystal display device), the intensity of the (± 1,0) order light and the intensity of the (0, ± 1) order light are 60 to 180% with respect to the intensity of the 0 order light, respectively. And the intensity of the (± 1, ± 1) order light is 20 to 330%.
, And the intensity of the zero-order light and the (± 1,0) -order light,
When the sum of the intensity of the (0, ± 1) -order light and the intensity of the (± 1, ± 1) -order light is 70% or more with respect to the intensity of all the diffracted lights, the image quality due to the shadow of the non-linear element portion or the electrode. The reduction can be eliminated, and the reduction ratio of the image contrast can be reduced.

[Table 1]

FIG. 4 shows an example of a phase grating having a grating pattern in two directions according to the present invention. The phase grating shown in FIG. 4 is formed by arranging projections 10 on a flat plate 9 vertically and horizontally in a dot shape.

FIG. 5 is a schematic perspective view showing another example of the phase grating according to the present invention. The phase grating shown in FIG. 5 has a grating pattern in two directions (X, Y) orthogonal to each other. FIG. 6 shows a cross-sectional view taken along the line I- (I) of the phase grating which coincides with the X direction or the Y direction. As shown in FIG. 6, the height h (difference between the height of the convex portion and the height of the concave portion) h of each grating pattern in the phase grating is substantially constant except for errors due to manufacturing or the like. Here, the height of the grid pattern in the X direction and the height of the grid pattern in the Y direction are not necessarily the same. In addition, it seems as if there is a lattice pattern having a certain height in a direction that does not coincide with the direction of the lattice pattern in the phase grating. However, from the sectional view taken along line II- (II) shown in FIG. As is apparent, no grating pattern having a constant grating height is formed except for the X and Y directions of the phase grating.

The direction of the lattice pattern of the phase grating may be horizontal or vertical with respect to the pixels of the liquid crystal cell, or may be oblique with respect to the horizontal and vertical directions of the pixels. Good. Further, the angle formed by the lattice patterns in two directions is not limited to 90 °.

As the pixel display device of the present invention, in addition to a liquid crystal display device, a plasma display panel (PD)
P), electroluminescence (EL), LED and the like. In addition, applications of the liquid crystal display device include a viewfinder, a liquid crystal projector, and the like.

[0012]

According to the image display device of the present invention, it is possible to reduce the image quality deterioration 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 and obtain an image having a high contrast. it can.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a diffraction pattern obtained from a phase grating having a grating pattern in two directions.

FIG. 3 is a schematic plan view of a liquid crystal cell used in the present invention.

FIG. 4 is a schematic perspective view of an example of a phase grating according to the present invention.

FIG. 5 is a schematic perspective view of another example of the phase grating in the present invention.

FIG. 6 is a sectional view taken along line I- (I) of the phase grating shown in FIG.

FIG. 7 is a sectional view taken along line II- (II) of the phase grating shown in FIG.

[Explanation of symbols]

 Reference Signs List 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 back side

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-311887 (JP, A) JP-A-5-227456 (JP, A) JP-A-6-43448 (JP, A) JP-A-7- 181470 (JP, A) JP-A-5-249449 (JP, A) JP-A-5-273540 (JP, A) JP-A-5-307174 (JP, A) JP-A-6-59257 (JP, A) JP-A-6-130356 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02F 1/1335

Claims (1)

(57) [Claims] An image display in which a large number of dot-shaped pixels are two-dimensionally arranged; and a phase grating having a grid pattern in two directions, which is arranged in a display optical path of the image display.
At the center wavelength of the image display, the intensity of the (± 1,0) order light and the intensity of the (0, ± 1) order light with respect to the intensity of the 0 order light is in the range of 60 to 180%, The intensity of the (± 1, ± 1) -order light is in the range of 20 to 330%, and the intensity of the zero-order light and the (± 1,0) -order light, (0, ±
1) The sum of the intensity of the next light and the (± 1, ± 1) order light is
An image display device, wherein the intensity is 70% or more at the center wavelength with respect to the intensity of all diffracted light.