JP2001222002A - Liquid crystal projector device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the contrast of a liquid crystal projector device. SOLUTION: A light-shielding plate 22 is disposed on the entrance side of a second relay lens 23 disposed in the optical path of blue light B as the illumination optical system in accordance with the viewing angle characteristics of a liquid crystal panel so as to cut a part of the beam entering at a specified beam angle the liquid crystal panel 27. Thereby, the contrast on the screen can be improved.

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, and more particularly to a liquid crystal projector suitable for improving the contrast of a projected image projected on a screen.

[0002]

2. Description of the Related Art There is known a liquid crystal projector which modulates light output from a light source by, for example, a transmissive liquid crystal panel to form image light, and enlarges and projects the image light on a screen or the like. For example, a liquid crystal projector device capable of forming a color image on a screen converts light emitted from a light source into red (R), green (G), and blue (B).
An illumination optical system that separates light beams of the respective colors into light beams and converges them on a predetermined optical path, a liquid crystal panel (light valve) that light-modulates the RGB light beams separated by the illumination optical system, and a liquid crystal panel that performs light modulation. And a light synthesizing unit for synthesizing the luminous flux of each of the RGB colors. The color image synthesized by the light synthesizing unit is enlarged and projected on a screen by a projection lens.

[0003]

A liquid crystal panel provided in a liquid crystal projector has a so-called viewing angle characteristic in which contrast changes depending on an incident angle of a light beam incident from an illumination optical system. Is known to be. Further, in the liquid crystal projector device, the incident light incident on the liquid crystal panel from the illumination optical system has all light incident angles within a range of, for example, about ± 10 ° (deg), and the light intensities are different. For this reason, the contrast of the projected image actually observed on the screen depends on the viewing angle characteristics of the liquid crystal panel and the light intensity distribution such as the light incident angle and the light intensity of the light incident on the liquid crystal panel from the illumination optical system. Are weighted by.

FIG. 7 shows an example of viewing angle characteristics of a liquid crystal panel. FIG. 7A is a diagram showing changes in contrast due to viewing angle characteristics of the liquid crystal panel by contour lines, and FIG. 7B is a diagram showing measurement conditions. Note that the viewing angle characteristics of the liquid crystal panel 100 shown in FIG. 7A are, as shown in FIG.
The viewing angle at the position P where the plane (panel surface) intersects with the Z axis orthogonal to the panel surface is measured from the observation position on the emission surface side (front surface side) of the liquid crystal panel. in this case,
The light source 101 is arranged on the incident surface side (rear side) of the liquid crystal panel on an extended line of a broken line connecting the observation position and the measurement position P as shown in FIG. From the Z axis by θ ° (θ = 0 ° to 10 °)
It is assumed that the measurement is made while tilting and rotating φa (φa = 0 ° to 360 °) from the starting Y axis (φ = 0 °) with the Z axis as the rotation axis. The contrast of the liquid crystal panel is, for example, a luminance level of 0 IRE and a luminance level of 100 IRE.
Is defined by the ratio of the luminance level to the luminance level.

FIG. 7A shows that the contrast in the region A near the center is maximum, and that the contrast decreases as the distance from the region A increases. That is, in the liquid crystal panel 100 shown in FIG. 7A, since the observation angle θ between the Z axis and the observation position is large, the contrast is reduced. That is, the light source 101 is
It can be seen that the contrast decreases as the ray incident angle θ of the ray incident from FIG. Also, it can be seen that the contrast changes depending on the observation direction φa of the liquid crystal panel 100 on the two-dimensional plane of XY, that is, the direction of incidence of light rays from the light source 101.

For example, when the observation direction φa is the Y-axis direction (φa = 0 °, 180 °) when the liquid crystal panel 100 is viewed from the front side, even if the observation angle (light ray incident angle) θ becomes large, the comparison is made. The change in the contrast is small, but the observation direction φa is in the X-axis direction (φa = 90 °, 270
°), the contrast is greatly reduced as the observation angle (light ray incident angle) θ is increased. That is, the contrast tends to deteriorate. FIG.
When the front surface of the liquid crystal panel 100 is observed from below, that is, when the observation direction φa is in the range of 180 ° to 360 °, the contrast greatly changes depending on the observation angle (light incident angle) θ. This indicates that the contrast is significantly deteriorated. The liquid crystal panel 1
The cause of the viewing angle characteristic at 00 is not described in detail, but is related to, for example, the orientation direction of the liquid crystal molecules forming the liquid crystal panel 100, ie, the rubbing direction.

In the liquid crystal projector having the liquid crystal panel 100 as described above, the viewing angle characteristic of the liquid crystal panel 100, particularly, the contrast of the projected image projected on the screen is greatly deteriorated due to the vertical viewing angle. was there.

Further, a liquid crystal panel 100 is provided for each of the RGB colors.
In the three-panel type liquid crystal projector device provided with, the contrast of the blue light B is deteriorated compared to the other two colors due to, for example, the wavelength dependence of the liquid crystal panel 100. In this case, when the white balance is adjusted in the liquid crystal projector device, the overall contrast is set based on, for example, the blue light B having the most deteriorated contrast. The deterioration has deteriorated the contrast of the projected image projected on the screen. For this reason, the liquid crystal projector device has been required to improve the contrast of the blue light B.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of such problems, and separates a light source and a light beam emitted from the light source into light beams of red, green, and blue colors. An illumination optical system that converges on a predetermined optical path; a liquid crystal panel that optically modulates the light flux condensed by the illumination optical system; In the liquid crystal projector device having the means and a projection lens for enlarging and projecting a color image, an attenuating plate for attenuating a part of a light beam incident on the liquid crystal panel is provided according to a viewing angle characteristic of the liquid crystal panel.

The attenuating plate is arranged on the optical path of the blue light of the illumination optical system, or on the incident side or the output side of the second relay lens provided on the optical path of the blue light of the illumination optical system, or on both sides. did. Further, the attenuating plate was a light shielding plate that shields a part of the light beam incident on the liquid crystal panel.

According to the present invention, an attenuating plate for attenuating a part of a light beam incident on the liquid crystal panel at an angle in accordance with the viewing angle characteristics of the liquid crystal panel is provided. It is possible to suppress the deterioration of contrast caused by the viewing angle.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a liquid crystal projector as an embodiment of the present invention will be described. Note that the liquid crystal projector device of the present embodiment is a three-panel liquid crystal projector device including a liquid crystal panel for each of RGB colors.

FIG. 1 is a diagram showing a configuration of an optical system of a liquid crystal projector according to the present embodiment. This figure 1
In the lamp 2, the light source 2a is disposed at the focal position of the reflector 2b, and light substantially parallel to the optical axis of the reflector 2b is emitted from the opening. In addition,
As the lamp 2, for example, a metal halide lamp or the like is used. The light emitted from the lamp 2 is emitted to an illumination optical system arranged at a subsequent stage. In the light beam emitted from the lamp 2, unnecessary light in the infrared and ultraviolet regions is first cut off (cut) by the IR-UV cut filter 3, and only the effective light beam is bent by, for example, 90 ° by the mirror 4. Then, it is led to a multi-lens array as the next optical means.

As a multi-lens array, a first multi-lens array 5 and a second multi-lens array 6 are arranged. A first multi-lens array 5 and a second
The liquid crystal panels 13, 18,
A plurality of lens cells having a similar external shape are arranged, which are almost equal to the aspect ratio of the 27 effective apertures. The lens cells of the first multi-lens array 5 and the lens cells of the second multi-lens array are arranged to face each other. Light rays collected by these first and second multi-lens arrays 5, 6 are P / S
The light is polarized by the integrator 7 into light having a predetermined polarization direction. That is, the unpolarized light (P-polarized wave +
The light of the S-polarized wave passes through the P / S integrator 7, is converted into a predetermined polarized wave (for example, a P-polarized wave) corresponding to the liquid crystal panels 13, 18, and 27 and enters the plano-convex lens 8. The plano-convex lens 8 condenses the incident light beam that has passed through each lens array, and efficiently collects the liquid crystal panel 13,
It is provided so as to be able to overlap and illuminate on 18 and 27.

The light beam emitted from the plano-convex lens 8 enters a dichroic mirror 9. The dichroic mirror 9 is configured to reflect the red light R included in the light from the plano-convex lens 8 and transmit the green light G and the blue light B. Thereby, the light flux of the red light R reflected by the dichroic mirror 9 is bent by 90 ° by the mirror 10 and guided to the liquid crystal panel 13 via the plano-convex lens 11 and the polarizing plate 12.

On the other hand, the light beams of the green light G and the blue light B transmitted through the dichroic mirror 9 are incident on the dichroic mirror 15. The dichroic mirror 15 is configured to reflect the light beam of the green light G and transmit the light beam of the blue light B. The light beam of the green light G reflected by the dichroic mirror 15 passes through the plano-convex lens 16 and the polarizing plate 17. To the liquid crystal panel 18. The light flux of the blue light B transmitted through the dichroic mirror 15 is guided to the liquid crystal panel 27 via the first relay lens 20, the mirror 21, the second relay lens 23, the mirror 24, the plano-convex lens 25, and the polarizing plate 26. It is configured as follows.

In the present embodiment, for example, in the optical path of the blue B light flux transmitted through the dichroic mirror 15 and the liquid crystal panel 27, for example, at a position near the second relay lens 23, B
The feature is that a light shielding plate 22 for blocking a part of the light beam is provided. The light shielding plate 22 will be described later.

The luminous flux of each color light modulated in each of the liquid crystal panels 13, 18 and 27 is incident on a dichroic prism 29 via polarizing plates 14, 19 and 28. The dichroic prism 29 has, for example, an outer shape formed by joining a plurality of glass prisms, and an interference filter 29a having predetermined optical characteristics is provided on the joining surface of each glass prism.
29b are formed. In the example shown in this figure, the interference filter 29a reflects, for example, blue light B and transmits green light G and red light R, and the interference filter 29b reflects red light R and transmits green light G and blue light. B is transmitted. Accordingly, the red light R is reflected toward the projection lens 30 by the interference filter 29b, and the blue light B is reflected toward the projection lens 30 by the interference filter 29a. The green light G is transmitted through the interference filters 29a and 29b.
, And reaches the projection lens 30. As a result, in the dichroic prism 29, the respective color lights of RGB are combined on one optical axis, and the combined image is projected from the projection lens 30 onto a screen (not shown).

In the liquid crystal projector of the present embodiment, as described above, for example, the contrast of blue light B is deteriorated compared to the other two colors due to the wavelength dependence of the liquid crystal. The brightness of the black level of the light B is not reduced to the brightness of the black levels of the other two colors. For this reason, for example, when the white balance is adjusted, the contrast of the other two colors must be adjusted to the blue light B whose contrast has deteriorated, and as a result, the contrast of the projected image projected on the screen Had deteriorated.

For example, when the brightness of the black level of the blue light B does not decrease compared with the brightness of the black levels of the other two colors due to the deterioration of the contrast of the blue light B, the black of the color image projected on the screen is bluish. Color. Therefore,
In order to solve this, in the conventional liquid crystal projector device, the other two colors of red light R and green light G at the black level are used.
By adjusting the white balance by increasing the number of colors, black was not colored. That is, the contrast of the other two colors is adjusted to the contrast of the blue light B. As a result, in the conventional liquid crystal projector, the contrast of the projected image projected on the screen is equal to the deteriorated contrast of the blue light B.

Therefore, in the liquid crystal projector device of the present embodiment, the second relay lens disposed in the optical path of blue light B as shown in FIG. 1 according to the viewing angle characteristics of the liquid crystal panel 27, for example. A light-shielding plate 22 is provided on the incident side of the light-shielding member 23, and a part of the light beam of the blue light B is shielded by the light-shielding plate 22 to improve the contrast.

For example, when the viewing angle characteristics of the blue liquid crystal panel 27 have the same viewing angle characteristics as the liquid crystal panel 100 shown in FIG. 7A, when the liquid crystal panel 27 is observed from below. That is, the observation direction φa is 180 ° to 360 °
When viewed from a direction set in the range of °, the contrast is greatly deteriorated. In this case, the contrast of the liquid crystal panel 27 is improved by blocking the light beam incident on the liquid crystal panel 27 from above.

The viewing angle characteristic of the liquid crystal panel is mainly determined by the rubbing direction of the liquid crystal panel. For example, when the rubbing direction of the liquid crystal panel is set to 0 ° with respect to the XY plane. Is obtained by shifting the viewing angle characteristic shown in FIG.

Hereinafter, an arrangement position of the light shielding plate 22 provided in the liquid crystal projector device according to the present embodiment will be described with reference to FIGS. FIG. 2 is a diagram schematically showing the relationship between the optical path of blue light B of the liquid crystal projector device according to the present embodiment and the position of the light shielding plate. The same parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. As shown in FIG. 2, the luminous flux of blue light B passing through each lens cell of the first and second multi-lens arrays 5, 6 is
The light reaches the liquid crystal panel 27 via the plano-convex lens 8, the first relay lens 20, the second relay lens 23, and the plano-convex lens 26. In this case, the luminous flux of the blue light B passing through each lens cell is condensed by the plano-convex lenses 8 and 26 and superimposed on the liquid crystal panel 27.
The light flux passing through the lens cells arranged below the multi-lens array 6 enters the liquid crystal panel 27 at a certain angle from above with respect to the liquid crystal panel 27. Therefore, the liquid crystal panel 27 is, for example, as shown in FIG.
When having the viewing angle characteristics as shown in FIG. 7A, the light shielding plate 22 is arranged so as to shield the light flux incident on the liquid crystal panel 27 from above.

However, in the case where light beams incident on the liquid crystal panel 27 from above are shielded, all light beams that have passed through each lens cell arranged in the second multi-lens array 6 need to be shielded. is there. That is, when a light beam incident on the liquid crystal panel 27 from above is indicated by, for example, three light beams (chain lines) as shown in FIG. 4, it is necessary to shield all three light beams. is there. For example, if the light shielding plate 22 is arranged so as to shield only one of the three light beams, the liquid crystal panel 27
Are not uniformly illuminated, and luminance unevenness occurs in the panel surface.

Therefore, in the present embodiment, FIGS.
As shown in (2), for example, the light shielding plate 22 is arranged near the second relay lens 23 and above the incident surface.
As shown in FIG. 3, the light-shielding range d (light-shielding range from the upper end of the second relay lens 23) and the light-shielding position of the light-shielding plate 22 in this case differ depending on the viewing angle characteristics of the liquid crystal panel 27. It is assumed.

In the present embodiment, a part of the light beam of the blue light B is completely shielded by the light shielding plate 22. However, in the present invention, a part of the light beam of the blue light B is not necessarily completely removed. There is no need to block light, and an attenuating plate that can at least attenuate the blue light B may be provided.

Next, the present applicant has verified by experiment the relationship between the light shielding range d by the light shielding plate 22 and the contrast on the screen, and the relationship between the light shielding range d by the light shielding plate 22 and the light amount. One example of the experimental results is shown in FIGS. In the experiment, as in the above description, a liquid crystal panel having a liquid crystal panel 27 having a viewing angle characteristic as shown in FIG. Using a projector device, a luminance of 0IRE and 1
The luminance ratio of 00IRE is measured by the Pritchard luminance meter 1980.

From the experimental results shown in FIG. 5, if the light-shielding range d of the light-shielding plate 22 is set to a certain range or more (for example, 7 mm or more), the screen will be compared with the contrast when there is no light-shielding plate 22. It has been found that the contrast of the projected image displayed above can be improved. FIG.
According to the experimental results shown in (1), the light amount decreases when the light-shielding range d of the light-shielding plate 22 is increased. It was confirmed that there was not much change even when compared with the light amount at the time of performing (light amount at the time when the light shielding range d of the light shielding plate 22 is set to 0).

Incidentally, in the experimental results shown in FIG.
The reason that no improvement in contrast is seen when the light-shielding range d by the light-shielding plate 22 is, for example, 7 mm or less is that incident light incident from this range has a large ray angle and is extremely contrasted when viewed from the viewing angle characteristics of the liquid crystal panel 27. However, it is considered that the luminous flux from this range originally has low light intensity and is not in a range that has a significant effect on the overall contrast. This is easily presumed from the fact that when the light shielding range d is set to, for example, 15 mm or less in the experiment shown in FIG.

Therefore, for example, when a liquid crystal panel 27 having a viewing angle characteristic as shown in FIG. 7A is provided, if the light shielding range d by the light shielding plate 22 is set to about 7 mm to 15 mm, the It is possible to improve the contrast by about 15% as compared with the related art while suppressing the decrease in the amount of light in the panel 27. Then, for example, if the white balance of the liquid crystal projector is adjusted using the blue light emitted from the liquid crystal panel 27 for blue,
It is possible to improve the contrast of the projected image projected on the screen.

In the present embodiment, the position of the light shielding plate 22 is set to the incident side of the second relay lens 23, but this is merely an example, and the position of the light shielding plate 22 according to the present invention is In the vicinity of the second relay lens 23, for example, it can be arranged on the emission side of the second relay lens 23 or on both sides thereof.

In this embodiment, the light shielding plate 22 is provided for the optical path of the blue light B.
Also, the light path of the green light G can be provided as long as it does not affect other colors. In this case, the light blocking plate 22 is arranged near the first multi-lens array 5 or the second multi-lens array 6, or the plano-convex lens 8. For example, red light R and green light G
Liquid crystal panels 13 and 1 to improve the contrast of
In order to block the light beam incident on the upper surface of the light source from the upper side,
The light shielding plate 22 may be arranged above the second multi-lens array 6. However, in this case, since the blue light B blocks the light flux incident on the liquid crystal panel 27 from below, the light shielding plate 22 blocks, for example, the red light R and the green light G, and It is necessary to use a light shielding plate that transmits B light.

In the liquid crystal projector of this embodiment, the light-shielding plate 22 is provided for the optical path of the blue light B so as to improve the contrast before adjusting the white balance. That is, a part of the optical path of the specific light (for example, blue light B) having a low contrast ratio is formed by
After adjusting the white balance by improving the contrast of the blue light B by shading, the white balance is adjusted.
According to the present invention, the contrast can be improved at the same time when the white balance is adjusted. For example, when it is necessary to limit the light amount of the blue light B when adjusting the white balance, the light amount is not reduced uniformly according to the viewing angle characteristics of the liquid crystal panel 27, instead of decreasing the total light amount of the blue light B uniformly. If light is shielded by the plate 22, it is possible to simultaneously adjust white balance and improve contrast.

Further, in the present embodiment, the viewing angle characteristics of the liquid crystal panel include, for example, a case where the contrast is significantly deteriorated when the liquid crystal panel 100 is viewed from below as shown in FIG. For example, the light shielding plate 22 is disposed above the second relay lens 23. However, this is merely an example, and the position of the light shielding plate according to the present invention depends on the viewing angle characteristics of the liquid crystal panel. It can be arranged at a required position. For example, if the liquid crystal panel has a viewing angle characteristic that deteriorates the contrast when viewed from the left or right side depending on the rubbing direction, the liquid crystal panel is incident at an angle from the right side or left side of the liquid crystal panel. A light-shielding plate may be disposed so as to block incident light.

[0036]

As described above, the liquid crystal projector of the present invention has an attenuating plate for attenuating a part of a light beam incident on the liquid crystal panel at an angle in accordance with the viewing angle characteristics of the liquid crystal panel. It is provided to suppress the deterioration of contrast caused by the viewing angle characteristics of the liquid crystal panel.
Thereby, it is possible to improve the contrast of the projected image projected on the screen.

In particular, according to the viewing angle characteristics of the liquid crystal panel,
For example, if an attenuation plate is provided in the optical path of blue light having a lower contrast ratio than red light or green light, it is possible to improve the contrast of the entire color image projected on the screen.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of an optical system of a liquid crystal projector according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an optical path of blue light and an arrangement position of a light shielding plate of the liquid crystal projector device according to the present embodiment.

FIG. 3 is a diagram showing the relationship between the optical path of blue light and the position of a light shielding plate in the liquid crystal projector device according to the present embodiment.

FIG. 4 is a diagram for explaining an arrangement position of a light shielding plate of the liquid crystal projector device according to the present embodiment.

FIG. 5 is a diagram showing a relationship between a light-blocking range by a light-blocking plate and a contrast on a screen.

FIG. 6 is a diagram showing a relationship between a light shielding range by a light shielding plate and a light amount.

FIG. 7 is a diagram for explaining viewing angle characteristics of a liquid crystal panel.

[Explanation of symbols]

1 liquid crystal projector device, 2a light emitting unit, 2b reflector, 2 lamps, 3 IR-UV cut filter,
4 10 21 24 mirror, 56 multi-lens array, 7 P / S integrator, 8 11 16
25 plano-convex lens, 9 15 dichroic mirror,
12 14 17 19 26 28 polarizing plate, 131
8 27 liquid crystal panel, 20 23 relay lens, 2
2 light shielding plate, 29a 29b interference filter, 29 dichroic prism, 30 projection lens

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H088 EA14 EA15 HA13 HA14 HA18 HA21 HA23 HA24 HA28 MA02 MA07 2H091 FA05Z FA14Z FA21X FA26X FA26Z FA34Z FA41Z LA15 LA17 MA07

Claims (4)

[Claims] 1. A light source, an illumination optical system that separates light beams emitted from the light source into light beams of respective colors of red, green, and blue and converges them on a predetermined optical path; A liquid crystal projector comprising: a liquid crystal panel that modulates a light beam; a light synthesizing unit that forms a color image by synthesizing light beams of RGB colors light modulated by the liquid crystal panel; and a projection lens that enlarges and projects the color image. In the apparatus, an attenuating plate for attenuating a part of a light beam incident on the liquid crystal panel is provided according to a viewing angle characteristic of the liquid crystal panel. 2. The liquid crystal projector device according to claim 1, wherein the attenuating plate is disposed in an optical path of blue light of the illumination optical system. 3. The illumination device according to claim 2, wherein the attenuating plate is disposed on an incident side or an outgoing side or on both sides of a second relay lens provided in an optical path of blue light of the illumination optical system. 3. The liquid crystal projector device according to 1. 4. The liquid crystal projector according to claim 1, wherein the attenuating plate is a light blocking plate that blocks a part of a light beam incident on the liquid crystal panel.