JPH07218910A - Liquid crystal projector - Google Patents

Abstract

PURPOSE:To provide a high-contrast image without generating the shadow of a lamp on a screen by providing a first lamp reflector and a spare reflector out of an optical axis and providing a second reflector on the optical axis. CONSTITUTION:The liquid crystal projector is composed of a lamp 1, first lamp reflector 2 combining rotationally symmetric paraboloids equipped with different focal distances, spare reflector 9 out of the optical axis, and second reflector 8 arranged on the optical axis. In light flux 6 from the lamp 1, the light flux reflected by the paraboloid reflector nearer to the optical axis is turned to light flux 61 almost parallel to the optical axis and lights up the image display plane of a liquid crystal panel. In this case, the light flux near the optical axis is shielded by a glass tube sealing the electrode of the lamp 1, and the light flux is reduced in comparison with the other part. On the other hand, the light flux away from the optical axis is reflected by the reflector and turned to the light flux directed toward the spare reflector 9. Then, the light flux reflected by the spare reflector 9 is reflected in the direction of the second reflector 9 and turned to the light flux to be converged on the optical axis.

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 projecting an image on a liquid crystal panel onto a screen using a projection lens to obtain a magnified image. The present invention relates to a liquid crystal projector suitable for reproducing a high-contrast image by illuminating a liquid crystal panel in a light scattering mode and increasing the aperture ratio (F value) of a projection optical system.

[0002]

2. Description of the Related Art Conventional liquid crystal projectors using a TN (twisted nematic) liquid crystal panel, a light scattering mode liquid crystal panel, etc. are known.
There is one disclosed in Japanese Patent No. 4921.

An example of the structure of a liquid crystal projector using a TN liquid crystal panel is shown in FIG. This liquid crystal projector comprises a lamp 1, a lamp reflector 2, a liquid crystal panel 3, a projection lens 4 and a screen 5. The light beam 6 emitted from the lamp 1 is reflected by the lamp reflector 2 of a parabolic mirror which is rotationally symmetric with respect to the optical axis to become a parallel light beam 61, which illuminates the TN type liquid crystal panel 3. The image reproduced on the liquid crystal panel 3 is projected by the projection lens 4 and the enlarged image is displayed on the screen 5.

FIG. 11 shows an example of the structure of a liquid crystal projector using a liquid crystal panel in the light scattering mode. This liquid crystal projector has a lamp 1, a lamp reflector 2, a light scattering mode liquid crystal panel 3 as in the TN type liquid crystal projector.
1, a projection lens 4, and a screen 5. The light flux 6 emitted from the lamp 1 is reflected by the lamp reflector 2 which is a parabolic mirror, and becomes a parallel light flux 61 which becomes light for illuminating the liquid crystal panel 31 of the light scattering mode type. The image reproduced on the liquid crystal panel 31 is projected by the projection lens 4 and the enlarged image is displayed on the screen 5. The light-scattering mode liquid crystal panel transmits the incident lamp light as it is or scatters it in a wide range according to the supplied voltage. In order to reproduce a high-contrast image on a screen with a light scattering mode liquid crystal projector, the liquid crystal panel is illuminated with lamp light having a high degree of parallelism and the light scattered from the liquid crystal panel 31 is stopped by a diaphragm 45 arranged in the projection optical system. And transmitted light to prevent scattered light from being projected on the screen 5.

The liquid crystal projector uses a lamp 1 and a lamp reflector 2 of a paraboloid of revolution to obtain a light beam 61 parallel to the optical axis. Further, by using the condenser lens 41, the lamp light flux 6 is generated by the aperture stop 42 arranged at the position where the lamp light flux becomes the thinnest, that is, near the focal plane of the lens 41.
By blocking the non-parallel light component of 1, the parallelism of the lamp light is improved. The parallelism of the lamp light is determined by the aperture stop 4
Aperture ratio determined by the aperture diameter D1 of 2 and the focal length f1 of the convex lens (parallelizing lens) 43 (hereinafter, F value of the illumination optical system (F
1 = f1 / D1)). Then, the lamp luminous flux 61 is converted into a parallel luminous flux 68 by the convex lens 43 and illuminates the liquid crystal panel 31.

The projection optical system is composed of a convex lens (field lens) 44, a diaphragm 45 and a projection lens 4.
5 allows the transmitted light from the liquid crystal panel 31 to pass through,
Blocks most of the scattered light. Therefore, the contrast representing the ratio of the brightness of the bright portion and the dark portion of the image projected on the screen is determined by the aperture D2 of the diaphragm 45 of the projection optical system and the focal length f2 of the convex lens 44.
= F2 / D2).

An optical system for selecting light from the light scattering mode liquid crystal panel by the diaphragm and reproducing an image having a good contrast ratio on the screen is called a Schlieren optical system.

The liquid crystal projector using the above-mentioned light scattering mode liquid crystal panel has a feature that a bright image can be reproduced as compared with the TN liquid crystal projector in which the polarizing plate absorbs more than half of the lamp light.

[0009]

However, FIG. 9 and FIG.
In the conventional liquid crystal projector shown in FIG. 1, since the lamp 1 is arranged at the center of the lamp reflector 2, the light flux near the optical axis of the lamp light flux reflected by the lamp reflector 2 is reflected by the glass tube 11 of the lamp. There was a problem in that the shadow 62 was generated and a shadow 62 was generated in the central portion of the illumination light. That is, the shaded area 62 in FIGS.
Since the light flux of the lamp is smaller than that of other parts, it becomes dark and produces a so-called shadow.

FIG. 10 (a) shows the shadow on the screen of the liquid crystal projector shown in FIG. 9, and FIG. 10 (b) shows the illuminance distribution in the XX 'direction at the center of the screen. . 12 and 13 are diagrams showing a shadow on the screen of the liquid crystal projector shown in FIG. 11 and an illuminance distribution of XX ′ in the horizontal direction on the screen.

Since the TN liquid crystal projector shown in FIG. 9 uses an optical system having a small F value, the shadow at the center of the screen was not visible. However, in order to reproduce a high-contrast image in the light-scattering mode liquid crystal projector shown in FIG. 11, the liquid crystal panel is illuminated with lamp light having good parallelism and the scattered light from the liquid crystal panel is used as described above. Since most of the light is blocked by the diaphragm in the projection optical system, it is necessary to increase the F value of the projection optical system. To improve the parallelism of the lamp light, the aperture diameter D1 of the aperture stop 42 should be reduced.
That is, the F value (F1 = f1 / D1) of the illumination optical system 46 is increased. In addition, the diaphragm 4 of the projection optical system 47
To make the aperture diameter of 5 smaller is the F value (F2
= F2 / D2). When the F value of the illumination optical system and the projection optical system is increased, the lamp shadow becomes clearly visible on the screen as shown in FIG. 13A, and there is a problem that the central portion of the screen becomes dark. . Therefore, the F value of the optical system has to be used below a certain value, and there is a problem that the contrast of the liquid crystal projector in the light scattering mode is not sufficient.

On the other hand, with respect to the problem of the shadow of the lamp, in Japanese Patent Laid-Open No. 3-196134, a lamp, a lamp reflector of a spheroidal mirror, a spherical mirror having an aperture stop, a convex lens, and two conical surfaces substantially parallel to each other are used. There is proposed an illuminating device including a light refraction plate. FIG. 14 shows the main part of the publication, and the operation thereof will be described. With the two conical surfaces of the light refracting plate 7, the light flux is converted to the optical axis side without changing the traveling direction of the lamp light flux 61, and the area where the shadow near the optical axis is generated is reduced. However, when the plate thickness t of the central part of the light refraction plate necessary for reducing the shadow of the central part by such a light refraction plate is estimated, the plate thickness needs to be about 50 mm. Therefore, the light refraction plate becomes thick and has a large prismatic shape, which is expensive. Further, the distance l between the center of the lamp 1 and the apex 72 of the conical surface 71 of the light refracting plate 7 needs to be set to a value larger than the central thickness t, so the distance 1 also becomes a very large value, There is also a problem that the shadow removal is insufficient.

Therefore, the present invention improves the problems of the prior art and improves the shadow near the optical axis of the illumination light of the liquid crystal panel.
In particular, the present invention realizes high contrast of a liquid crystal projector using a light scattering mode liquid crystal panel.

[0014]

In order to achieve the above object, in the present invention, a lamp, a first lamp reflector comprising a rotationally symmetric parabolic mirror, and an auxiliary reflector for changing the traveling direction of the lamp light are used as optical axes. In addition, a second reflector having a rotationally symmetric aspherical surface or a quadric surface is provided on the optical axis at the tip of one sealing portion of the lamp.

The first lamp reflector 2 is a combination of paraboloids 20 and 21 which are rotationally symmetric and have different focal lengths in the vicinity of the optical axis and the portion apart from the optical axis. The parabolic mirror 20 near the optical axis is the lamp 1 arranged at the focal position of the parabolic mirror.
The light emitted from is converted into a light flux 61 parallel to the optical axis.
On the other hand, the light reflected by the parabolic mirror 21 in the portion away from the optical axis becomes a light flux which is focused by the auxiliary reflector 9 in the vicinity of the focal point of the second reflector provided on the optical axis. The luminous flux is the second
After passing through the focal point of the reflector, it is reflected by the second reflector 8 and becomes a parallel light beam 66 in the vicinity of the optical axis.

[0016]

According to the above construction, since the light reflected by the peripheral portion of the lamp reflector is made into a light beam parallel to the optical axis by the second reflector provided at one end of the lamp, the vicinity of the optical axis for illuminating the liquid crystal panel is obtained. The shadow of the lamp light can be improved, and the uniformity of the illumination light can be improved. Therefore, in a liquid crystal projector using a light scattering mode liquid crystal panel, the F value of the optical system can be increased, that is, the parallelism of the illumination light can be improved and the aperture of the diaphragm of the projection optical system can be reduced, so that a high contrast image can be obtained. Can be played.

[0017]

FIG. 1 is a block diagram of a liquid crystal projector using one light scattering mode liquid crystal panel according to a first embodiment of the present invention. The liquid crystal projector shown in FIG.
An illumination optical system 46 including the lamp reflector 2 and the aperture stop 42, a liquid crystal panel 31, a projection optical system 47 including the stop 45 and the projection lens 4, and a screen 5. A light beam 6 emitted from a highly efficient lamp 1 such as a metal halide lamp or a xenon lamp is reflected by a lamp reflector 2 and a parallel light beam 68 is emitted by an illumination optical system 46.
The light is converted into the light and the light scattering mode liquid crystal panel 31 is illuminated.
In the liquid crystal panel 31 in the light scattering mode, the liquid crystal is transparent (incident light of the liquid crystal panel is transmitted as it is) or opaque (incident light is scattered in a wide range) depending on the voltage applied to the liquid crystal. The light transmitted through the transparent portion of the liquid crystal panel 31 passes through the opening of the diaphragm 45 and is projected on the screen 5 by the projection lens 4 to form a bright image. On the other hand, the light incident on the cloudy portion of the liquid crystal panel 31 is scattered over a wide range, and most of the scattered light is blocked by the diaphragm 45, so that only a part of the light that has passed through the aperture of the diaphragm 45 is projected onto the projection lens. 4, the screen 5 is darkened. As described above, the light-scattering mode liquid crystal projector reproduces the bright and dark parts of the image on the screen by selecting the transmitted light and scattered light from the liquid crystal panel by the diaphragm in the projection optical system. For the panel 31, for example, PDLC (Polymer Dispersed Liquid Crystal) is used.

Next, the illumination optical system 4 which is the main part of the present invention.
FIG. 2 shows an enlarged view of the lamp portion of No. 6. It comprises a lamp 1, a first lamp reflector 2 in which rotationally symmetrical paraboloids 20 and 21 having different focal lengths are combined, an auxiliary reflector 9 outside the optical axis, and a second reflector 8 arranged on the optical axis. Of the light flux 6 emitted from the lamp 1, the light flux reflected by the parabolic reflector 20 in the portion close to the optical axis becomes a light flux 61 substantially parallel to the optical axis and illuminates the image display surface of the liquid crystal panel 31 (not shown). To do. Light flux near the optical axis (Fig. 1,
The shaded portion in FIG. 2) is blocked by the spherical glass tube 11 that seals the electrodes of the lamp 1, so that the luminous flux is smaller than in other portions. On the other hand, the light beam 6 distant from the optical axis is reflected by the reflector 21 and travels toward the auxiliary reflector 9 with the light beam 6.
It becomes 3. The luminous flux reflected from the auxiliary reflector 9 is the second
The light beams 64 and 65 are reflected in the direction of the reflector 8 and converge on the optical axis.

The second reflector 8 is formed by attaching a quadric curved mirror such as a rotationally symmetric parabolic mirror or an aspherical mirror to the tip of the lamp 1. The aperture of the second reflector 8 has a glass tube 11 of the lamp (about 11 m for the lamp used in this embodiment) so as not to block the lamp luminous flux 61 illuminating the liquid crystal panel 31.
m) is approximately equal to the diameter. The auxiliary reflector 9 converges the lamp luminous fluxes 64 and 65 to the focal position of the second reflector 8 on the optical axis. The light beams 64 and 65 are reflected after passing through the focal point of the second reflector 8, and a new parallel light beam 66 can be obtained in the vicinity of the optical axis. Therefore, the shade 62 of the lamp shown in FIG. 1 and FIG. 2 is improved to a small shade 67 and the cross-sectional area of the shade is improved to 30% or less. As a result, even if the F value of the projection optical system and the illumination optical system is set to 7 or more, which can obtain a practically good contrast image, a high-quality and high-contrast image is generated without causing a shadow on the screen. I made it playable.

On the other hand, in FIG. 2, a portion of the shadow 67 remains near the optical axis of the second reflector 8 due to the incident angle of the light beam 65 reflected by the auxiliary reflector 9, but as shown in FIG. Using an auxiliary reflector 90 that is long in the axial direction,
By reducing the incident angle of the light 65 (angle of the light ray 65 with respect to the optical axis), the shadow 67 near the optical axis can be further reduced.

FIG. 4A shows a shadow 52 on the screen 5 of the liquid crystal projector to which this embodiment is applied. In addition, in FIG. 4B, XX ′ in the center of the screen is displayed.
The illuminance distribution in the direction is shown. Even when the F value of the optical system is increased, the decrease in illuminance at the center of the screen due to the shadow of the lamp is reduced, the uniformity of the illuminance distribution is improved, and a high quality image can be produced.

The second reflector 8 is not limited to a rotationally symmetric parabolic mirror, and for example, a spherical mirror (radius of curvature r) is used, and the light flux reflected from the auxiliary reflector 9 is centered on the spherical mirror on the optical axis. Even if the light beam passes through a point at a distance of r / 2 from, a light beam substantially parallel to the optical axis can be obtained, and the same effect can be obtained.

FIG. 5 shows the auxiliary reflector 91 and the lamp portion used in the second embodiment of the present invention. Auxiliary reflector 9
Reference numeral 1 denotes a rotationally symmetric reflector having a plurality of reflecting surfaces arranged in a stepwise manner. By focusing the light flux reflected from the reflector 21 at the focal point of the second reflector 9 without aberration, a light flux 66 parallel to the optical axis is formed. To get Since the other operations are the same as those in the first embodiment, the description will be omitted.

FIG. 6 shows an illumination optical system used in the third embodiment of the present invention. The same components as those in the first embodiment (FIGS. 1 and 2) are designated by the same reference numerals. The difference from the first embodiment is that a reflecting surface 48 is provided on the side of the aperture stop 42 on which the lamp light 61 is incident, and the other points are the same as those of the first embodiment shown in FIG. The luminous flux 69 shown by the dotted line in FIG. 6 is reflected by the reflecting surface 48 of the lamp luminous flux 61, and the lamp 1
It returns to the side and is reused as lamp light for illuminating the liquid crystal panel 31. Therefore, the efficiency of the optical system can be improved and a bright image can be reproduced.

FIG. 7 is a structural diagram of a lamp portion used in the liquid crystal projector of the fourth embodiment of the present invention. The same parts as those in FIG. 2 are designated by the same reference numerals. Second in FIG.
The reflector 81 is equipped with a rotationally symmetric parabolic mirror, a spherical mirror, or an aspherical mirror having a convex surface on the liquid crystal panel 31 (not shown) side on the optical axis. The operation of the second reflector 81 is similar to that of the first embodiment shown in FIG. 2, and the light flux reflected from the portion 21 of the first reflector away from the optical axis is reflected by the auxiliary reflector 9 and the second reflector 81. , A beam 66 that is substantially parallel to the vicinity of the optical axis is obtained, and the shadow 62 in the central portion is improved to a small shadow 67.

FIG. 8 shows a second reflector 8 used in this embodiment.
FIG. 3 is a diagram for explaining a structure for holding and fixing one end of the lamp 1. In the lamp 1, the electrodes 12 and 13 are sealed inside the glass tube 11, and the base electrode 15 and the lead wire 14 are sealed.
A high voltage is applied to discharge between the electrodes 12 and 13.
The second reflector 8 is a connecting portion 8 with the sealing portion 15 of the lamp 1.
Have two. Further, the connecting portion 82 is the sealing portion 1 of the lamp.
A portion 83 for inserting 5 and a slit 84 for passing the lead wire 14 of the electrode are provided. The one sealing portion 15 of the lamp is put into the insertion portion 83 of the second reflector 8, and the second sealing member 15 is placed at a predetermined position.
The reflector 8 is arranged and fixed by a ceramic adhesive for use.

Although the above embodiments have been described with respect to a liquid crystal projector using one liquid crystal panel, the same can be applied to a liquid crystal projector using a plurality of liquid crystal panels. Further, although the liquid crystal projector using the light scattering mode liquid crystal panel has been described, the present invention is not limited to this, and it is apparent that the present invention can be applied to a liquid crystal projector using a TN liquid crystal panel and the like. That is, in the case of the TN liquid crystal panel, unlike the light scattering mode liquid crystal panel, the contrast characteristic does not depend on the F value of the projection optical system, so that it is not necessary to increase the F value of the projection optical system. However, in order to reproduce a high-contrast image on the TN liquid crystal panel, it is necessary to illuminate the liquid crystal panel with parallel light having a small spread, and the F value of the illumination optical system is increased to improve the parallelism of the light flux. It is obvious that the present invention can be applied in some cases.

[0028]

According to the present invention, particularly in a liquid crystal projector using a light-scattering mode liquid crystal panel, a shadow of a lamp is produced on a screen even if the F value of the illumination optical system and the projection optical system is increased. In addition, the uniformity of the illuminance distribution on the screen can be improved, and a bright, high-contrast image can be obtained, so that a high-quality image that is practically easy to see can be reproduced.

[Brief description of drawings]

FIG. 1 is a structural diagram of a liquid crystal projector showing a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a lamp unit according to the first embodiment and its operation.

FIG. 3 is a diagram illustrating another lamp unit used in the first embodiment and its operation.

FIG. 4 is a diagram illustrating a lamp shadow projected on a screen and a diagram showing an illuminance distribution in the horizontal direction at the center of the screen.

FIG. 5 is a diagram illustrating a lamp unit and its operation according to a second embodiment.

FIG. 6 is a diagram illustrating a lamp unit and its operation according to a third embodiment.

FIG. 7 is a diagram illustrating a lamp unit and its operation according to a fourth embodiment.

FIG. 8 is a diagram illustrating a connecting portion of a second reflector used in the present invention.

FIG. 9 is a diagram illustrating an operation of a conventional liquid crystal projector.

FIG. 10 is a diagram illustrating a shadow on a screen of a conventional liquid crystal projector.

FIG. 11 is a diagram illustrating an operation of a conventional liquid crystal projector.

FIG. 12 is a diagram illustrating a shadow on a screen of a conventional liquid crystal projector.

FIG. 13 is a diagram illustrating a shadow on a screen of a conventional liquid crystal projector.

FIG. 14 is a diagram illustrating an illumination optical system of a conventional liquid crystal projector.

[Explanation of symbols]

 1 ... Lamp, 2 ... First lamp reflector, 3, 31 ... Liquid crystal panel, 4 ... Projection lens, 5 ... Screen, 6 ... Lamp luminous flux, 8, 81 ... Second reflector, 9, 90, 91 ... Auxiliary reflector, 11 ... Lamp glass tube, 20, 21 ... Parabolic mirror, 42, 45 ... Diaphragm, 41, 43, 44 ... Lens, 48 ... Reflective surface provided on aperture diaphragm, 61, 66, 68 ... Illumination light of liquid crystal panel , 62, 67 ... Shadow of lamp light, 52 ... Shadow of lamp projected on the screen.

Claims (8)

[Claims] 1. A liquid crystal projector comprising a lamp, a first lamp reflector, a liquid crystal panel and a projection lens, which projects an image of the liquid crystal panel onto a screen, and at least a part of the lamp light is present between the lamp and the liquid crystal panel. And a second reflector for reflecting the light beam reflected by the auxiliary reflector to the liquid crystal panel side is provided on the optical axis. 2. A lamp, a first lamp reflector, an aperture stop for blocking a part of the lamp light, a liquid crystal panel and a projection lens, and the lamp light passing through the opening of the aperture stop illuminates the liquid crystal panel. In a liquid crystal projector for projecting an image of a liquid crystal panel on a screen, an auxiliary reflector for reflecting a part of the lamp light is provided outside the optical axis between at least the lamp and the aperture stop, and the auxiliary reflector is reflected by the auxiliary reflector. A liquid crystal projector comprising a second reflector on the optical axis for reflecting a light beam to the aperture stop side. 3. The liquid crystal projector according to claim 1 or 2, wherein the first lamp reflector is a parabolic mirror rotationally symmetrical with respect to the optical axis, and the lamp reflector has a focal length near the optical axis and Auxiliary reflectors are rotationally symmetric curved mirrors or compound reflecting mirrors consisting of many small reflecting surfaces, and second reflectors are rotationally symmetric aspherical mirrors or quadratic curved mirrors, since the focal lengths of the portions away from the optical axis are different. A liquid crystal projector characterized by the above. 4. The liquid crystal projector according to claim 3, wherein the opening of the second reflector faces the liquid crystal panel side. 5. A liquid crystal projector according to claim 3, wherein the opening of the second reflector faces the first lamp reflector side. 6. A liquid crystal project according to claim 1, 2, 3, 4 or 5, further comprising a liquid crystal panel of a light scattering mode which transmits or scatters the lamp light according to an input signal. Projector device. 7. A liquid crystal projector according to claim 2, 3, 4, 5 or 6, wherein a reflection surface is provided on a surface of said aperture stop on the lamp side, and a light flux from said lamp other than a light flux passing through the opening. Is a liquid crystal projector device characterized by being returned to the lamp side. 8. The liquid crystal projector according to claim 1, 2, 3, 4, 5, 6 or 7, further comprising a structure for inserting and holding a second reflector at one end of the lamp. Liquid crystal projector device.