JP2001013581A - LCD projector - Google Patents

Abstract

(57) [PROBLEMS] To appropriately limit the effective angle of a projection lens in both the vertical and horizontal directions with a simple structure. A light beam emitted from a pixel of a liquid crystal panel is projected on a screen via a field lens and a projection lens. On the optical path of the projection lens 17, there is provided an aperture stop 18 for controlling the size of the opening 19 for transmitting the light beam in the vertical or horizontal direction and for stopping the light beams of a plurality of colors emitted from the liquid crystal panel 14. Is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projector for displaying an image by projecting image light onto a projection target.

[0002]

2. Description of the Related Art Conventionally, as a single-panel type liquid crystal projector, one of red (R), green (G) and blue (B) color filters is superposed on each pixel of a liquid crystal panel. In general, a liquid crystal projector that performs full-color screen display by expressing the color of one pixel with three pixels has a widespread use. Many,
Further, a large cooling structure had to be provided to dissipate the heat generated from the color filters.

In response to this, in recent years, MCS (Mi
A liquid crystal projector of a (crolens Color Splitter) type has been put to practical use.

FIG. 4 is a plan view showing a main part of the internal structure of such a conventional MCS type liquid crystal projector.

In FIG. 4, a light source (not shown), B, R, and G reflection dichroic mirrors 81B, 81R, and 81G, an incident-side polarizing plate (not shown), a microlens plate 82, a liquid crystal Panel 83
, An output side polarizing plate (not shown), and a projection lens 84 are provided.

B, R and G reflection dichroic mirror 8
1B, 81R, and 81G are arranged at different angles with respect to the substantially parallel light from the light source, and separate the substantially parallel light from the light source into B, R, and G light fluxes, and pass through the incident-side polarizing plate. The polarized light is incident on the microlens plate 82 from the diagonally left, center, and diagonally right sides. Micro lens plate 82
R, G, and B light beams incident on a plurality of lens surfaces are individually condensed and made incident on R, G, and B pixels of a plurality of pixel sets of the liquid crystal panel 83, respectively. The liquid crystal panel 83 modulates and emits the light beam incident on the pixel. The light beam emitted from the pixels of the liquid crystal panel 83 is projected on the screen by the projection lens 84 via the emission-side polarizing plate.

FIG. 5 is an enlarged view showing the micro lens plate 82 and the liquid crystal panel 83 of FIG.

In FIG. 5, the B, R and G reflection dichroic mirrors 81B, 81R, 81G of FIG.
The R and G luminous fluxes enter the lens surface 86 of the microlens plate 82 from different directions via the incident side polarizing plate, are condensed, and enter the pixels of the liquid crystal panel 83 corresponding to B, R, and G. . The light incident on the B, R, and G pixels of the liquid crystal panel 83 is modulated based on the video signal supplied to the liquid crystal panel 83, emitted through a not-shown emission-side polarizing plate, and transmitted through a projection lens 84. Projected to the screen. In this case, the adjacent dichroic mirror 8
5 (in FIG. 5, B and R from the B and R color reflecting dichroic mirrors 81B and 81R).
Is the effective illumination angle θ0.

According to such a conventional liquid crystal projector, there is no light loss due to the color filter of the liquid crystal panel, but it is necessary to reduce the effective illumination angle θ0. this is,
This is because if the effective illumination angle is large, light of each color enters the opening adjacent to the corresponding opening, causing a phenomenon of color mixing, which deteriorates color purity and contrast.

In order to reduce the effective illumination angle θ0, the optical path length must be increased or an aperture stop or the like must be provided to limit the effective angle of the projection lens, and a highly efficient optical system is required.

Generally, an appropriate effective illumination angle θ0 is determined by the shape of the opening of the liquid crystal panel and the shape of the lens of the microlens plate. Here, the pixels of the liquid crystal panel used in the single-panel liquid crystal projector have three pixels of RGB which are horizontal with respect to vertical.
Since the image is divided into colors, the opening shape is a vertically long rectangle. Therefore, when the effective angle of the projection lens is restricted by the aperture, the effective angle is set in accordance with the horizontal effective lighting angle θ0 where color mixing is likely to occur.

On the other hand, the contrast of a liquid crystal panel greatly changes depending on the viewing angle.

FIG. 6 is a graph showing the viewing angle characteristics of such a liquid crystal panel. The vertical axis indicates the contrast, and the horizontal axis indicates the viewing angle of the liquid crystal panel.

In FIG. 6, the contrast of the liquid crystal panel is maximum when the viewing angle of the liquid crystal panel is around +2 degrees.
When the angle is away from +2 degrees, it greatly decreases.

As described above, the contrast performance of the liquid crystal panel has an angle dependency in the liquid crystal panel, and a design in consideration of the angle dependency is necessary in order for the liquid crystal projector to exhibit the inherent contrast performance of the liquid crystal. There is also a method of maximizing the contrast of the projected image by making the projection lens shiftable in response to this. However, in this case, the structure in this case is complicated, the cost is greatly increased, and the weight is increased. And the problem of upsizing.

[0016]

SUMMARY OF THE INVENTION The above-mentioned conventional MCS
In liquid crystal projectors, the aperture stop has a circular shape.Therefore, there is no difference between the vertical and horizontal directions in the effective angle of the projection lens due to this aperture. The color purity and contrast of the projected image were reduced. Furthermore, the contrast performance of the liquid crystal panel is angle-dependent, and if the projection lens can be shifted in order for the liquid crystal projector to exhibit the inherent contrast performance of the liquid crystal, the structure becomes complicated and the cost increases greatly. At the same time, problems such as an increase in weight and an increase in size occur.

An object of the present invention is to provide a liquid crystal projector capable of appropriately limiting the effective angle of the projection lens in both the vertical and horizontal directions with a simple structure.

[0018]

SUMMARY OF THE INVENTION A liquid crystal projector according to the present invention includes a spectral means for dispersing illumination light from a light source into light beams of a plurality of different colors, and irradiating the light beams of a plurality of colors at mutually different angles. A plurality of pixels respectively corresponding to the plurality of colors are combined to form a pixel set, the plurality of pixel sets are provided, and a light beam incident on each pixel of the plurality of pixel sets is subjected to light modulation for each pixel and emitted. And a plurality of lens surfaces respectively corresponding to a plurality of pixel sets of the liquid crystal panel, and are incident on each of the lens surfaces. A microlens plate for individually condensing light beams of a plurality of colors to a plurality of pixels of a corresponding pixel set,
A projection lens for projecting light beams of a plurality of colors emitted by the pixel liquid crystal panel, and provided on an optical path of the projection lens;
An aperture stop for limiting the size of the opening through which the light beam passes in the vertical direction or the horizontal direction, and for stopping the light beams of a plurality of colors emitted by the liquid crystal panel.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a main part of a liquid crystal projector according to a first embodiment of the present invention.

In FIG. 1, a light source (not shown), a blue (B), red (R) and green (G) reflecting dichroic mirrors 11B, 11R and 11 are provided in a housing of the liquid crystal projector.
G, the incident side polarizing plate 12, the micro lens plate 13,
A liquid crystal panel 14, an output-side polarizing plate 15, a field lens 16, and a projection lens 17 are provided.

B, R and G reflection dichroic mirror 1
1B, 11R, and 11G are spectral units that separate the illumination light from the light source into light beams of a plurality of different colors, and irradiate the liquid crystal panel 14 with the light beams of the plurality of colors from different directions. In this case, the B, R, and G reflection dichroic mirrors 11B, 11R, and 11G are arranged at different angles with respect to the substantially parallel light from the light source, and convert the substantially parallel light from the light source into B, R, and G light fluxes. And enters the microlens plate 13 via the incident-side polarizing plate 12 at different angles.

The microlens plate 13 includes the incident side polarizing plate 1.
B, R, and G from FIG. 2 are arranged on an optical path where they intersect, and have a plurality of lens surfaces corresponding to a plurality of pixel sets of the liquid crystal panel 14, respectively. The G light flux is individually focused on a plurality of pixels of the corresponding pixel set.

The liquid crystal panel 14 constitutes a pixel set for performing one color display by combining three pixels respectively corresponding to B, R and G, and has a plurality of pixel sets. The light beam incident on each pixel of the set is subjected to light modulation (control of polarization direction) for each pixel and emitted.

The luminous flux emitted from the pixels of the liquid crystal panel 14 is attenuated according to the polarization direction via the emission-side polarizing plate 15 and is projected on the screen via the field lens 16 and the projection lens 17. An aperture stop 18 is provided on the optical path of the projection lens 17. Aperture stop 1
Numeral 8 is formed so that the vertical direction and the horizontal direction of the opening 19 through which the light beam passes are different in length, and serves to stop the light beams of a plurality of colors emitted from the liquid crystal panel 14.

In the case of this embodiment, the horizontal and vertical effective illumination angles can be restricted by making the shape of the aperture stop 18 of the projection lens 17 different from that of a normal circle.

FIG. 2 is a front view showing a first example of the aperture stop shown in FIG.

In FIG. 2, in the case of the present embodiment, the aperture stop 18 cuts the upper and lower portions of the circle 21 of the opening 19 to increase the restriction on the effective angle of the projection lens in the vertical direction. If the horizontal projection lens effective angle is not sufficiently limited, the horizontal illumination effective angle and the projection lens effective angle can be limited by cutting the left and right sides of the circle 21 of the opening 19. .

FIG. 3 is a front view showing a second example of the aperture stop.

In FIG. 3, when the angle dependence of the contrast characteristic of the liquid crystal panel 14 is vertical, the center P1 of the opening 19 of the aperture stop 18 is shifted up and down from the optical axis center P2 of the projection lens. .

As described above, when the angle dependence of the contrast characteristic of the liquid crystal panel 14 is vertical, the aperture stop 18 of the projection lens is moved up and down when the angle dependence is horizontal. The contrast of the image projected from the liquid crystal panel can be improved by shifting from the axial center and restricting the direction of the light beam passing through the aperture stop to have an optimal value.

As described above, according to the embodiment of the present invention, the effective angle of the projection lens can be appropriately limited in both the vertical direction and the horizontal direction with a simple structure, so that the manufacturing cost is significantly increased. Without contrast, the image quality can be improved by improving the contrast and color purity of the projected and displayed image. Furthermore, by shifting the aperture stop of the projection lens according to the angle dependence of the contrast characteristic of the liquid crystal panel, it is possible to maximize the contrast performance of the liquid crystal panel.

In the embodiments of the invention shown in FIGS. 1 to 3, red, green and blue, which are three primary colors, are used as the light beams of a plurality of colors, but other light beams such as magenta, cyan and yellow are used. Luminous flux of three primary colors, red, green,
In addition to the three primary colors of blue, a yellow light beam may be used to improve the reproducibility of yellow. In addition, the embodiment of the invention shown in FIG.
Are provided at positions away from the liquid crystal panel 14, but the incident-side polarizing plate 12 and the outgoing-side polarizing plate 15 may be in close contact with the liquid crystal panel 14.

[0034]

As described above, according to the present invention, it is possible to appropriately limit the effective angle of the projection lens in both the vertical and horizontal directions with a simple structure, so that the manufacturing cost is not increased much. In addition, the contrast and color purity of an image to be projected and displayed can be improved to improve the image quality. Furthermore,
By shifting the aperture stop of the projection lens in accordance with the angle dependence of the contrast characteristic of the liquid crystal panel, it is possible to maximize the contrast performance of the liquid crystal panel.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing an embodiment of a liquid crystal projector according to the present invention.

FIG. 2 is a front view showing a first example of the aperture stop shown in FIG. 1;

FIG. 3 is a front view showing a second example of the aperture stop shown in FIG. 1;

FIG. 4 is a plan view showing a main part of an internal structure of a conventional MSC type liquid crystal projector.

FIG. 5 is an enlarged view showing the microlens plate and the liquid crystal panel of FIG. 4;

FIG. 6 is a graph showing viewing angle characteristics of such a liquid crystal panel.

[Explanation of symbols]

11B, 11R, 11GB, R, and G reflection dichroic mirrors 12 Incident side polarizing plate 13 Micro lens plate 14 Liquid crystal panel 15 Outgoing side polarizing plate 16 Field lens 17 Projection lens 18 Aperture stop 19 Opening

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 9/31 H04N 9/31 CF term (Reference) 2H088 EA13 HA13 HA18 HA21 HA24 HA25 HA28 MA02 MA07 2H091 FA05Z FA08Z FA14Z FA26X FA26Z FA29Z FA41Z LA12 LA17 LA19 MA07 5C058 AB06 BA08 BA31 EA11 EA12 EA26 EA51 5C060 DA04 GB05 HC00 HC01 HC20 JA17 JB06 5G435 AA02 AA04 BB12 BB17 CC12 DD02 DD04 DD11 FF05 GG01 GG02GG04

Claims (2)

[Claims] 1. A spectral means for dispersing illumination light from a light source into luminous fluxes of a plurality of different colors, respectively, and irradiating the luminous fluxes of a plurality of colors at mutually different angles; A liquid crystal panel that forms a pixel set by combining pixels, has a plurality of the pixel sets, and modulates and emits a light beam incident on each pixel of the plurality of pixel sets for each pixel; A plurality of lens surfaces respectively corresponding to a plurality of pixel sets of the liquid crystal panel, and a plurality of color light beams incident on each of the lens surfaces corresponding to the plurality of color sets. A microlens plate for individually condensing the plurality of pixels, a projection lens for projecting light beams of a plurality of colors emitted by the pixel liquid crystal panel, and a light beam provided on an optical path of the projection lens. LCD projector the size of the opening for the bulk to allow limited vertical or horizontal direction, the liquid crystal panel is characterized by comprising a aperture stop performing stop of a plurality of colors of light flux emitted. 2. The liquid crystal projector according to claim 1, wherein the center of the opening of the aperture stop is shifted from the center of the optical axis of the projection lens.