JPH068986B2 - Projection display device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection display device which illuminates an image formed on a light valve with illumination light and projects the image on a screen by a projection lens.

Conventional technology In order to obtain a large screen image, light from a light source is applied to a small light valve that forms an optical image according to a video signal,
A method of projecting and enlarging the optical image on a screen is known. In this type of projection display device, the resolution of the projected image is almost determined by the resolution of the light valve, and the light output increases when the luminous flux of the light source is increased. It is possible to realize a projection display device having a high resolution and a large light output even if the size is small. Further, recently, a method using a liquid crystal for a light valve has been drawing attention (for example, SID86 digest page 375).

A conventional projection display device using a liquid crystal panel as a light valve will be described.

FIG. 6 shows an example of the configuration of a conventional projection display device using a liquid crystal panel as a light valve.

The light emitted from the lamp 1 is converted into substantially parallel light by the concave mirror 2 and the condenser lens 3, and the heat ray absorbing glass 4
And then enters the color separation optical means 7. The color separation optical means 7 is composed of a red reflecting dichroic mirror 5 and a blue reflecting dichroic mirror 6. The red color light emitted from the color separation optical means 7 is passed through plane mirrors 8 and 9 to
The green color light goes straight, and the blue color light goes through the plane mirrors 10 and 11, respectively, and the active matrix type liquid crystal panel.
It is incident on 12, 13, and 14. The liquid crystal panels 12, 13 and 14 have thin film transistors (Thin Film Transistor) for each pixel.
or; hereinafter, abbreviated as TFT), a polarizing plate 16 on the entrance side and a polarizing plate 17 on the exit side, which are formed by orthogonal Nicols or parallel Nicols, are arranged on both sides of a liquid crystal cell 15 of twisted nematic (TN) mode. Composed. An adhesive is applied to one surface of each of the polarizing plates 16 and 17, and is attached to the glass substrate of the liquid crystal cell 15. Optical images are formed on the liquid crystal panels 12, 13, and 14 according to the video signals. The red, blue, and green color lights output from the liquid crystal panels 12, 13, and 14 are color combining dichroic prisms.
Synthesized from 18. The optical image formed on the liquid crystal panels 12, 13 and 14 is enlarged and projected on a screen (not shown) by a telecentric projection lens 19.

Problems to be Solved by the Invention In the configuration shown in FIG. 6, in order to obtain a projected image with high contrast, the angle formed by the alignment direction of liquid crystal molecules on the wall surface of the liquid crystal cell 15 and the absorption axis of the polarizing plate 16 on the incident side is determined. The polarizing plate must be arranged so that the angle formed by the absorption axis of the polarizing plate 17 on the output side and the absorption axis blocks the most light. However, it is difficult to accurately attach the polarizing plate to the liquid crystal cell at an angle that most blocks light, and thus it is difficult to obtain the best contrast.

Next, the liquid crystal cell 15 has a
It is necessary to optimize the birefringence anisotropy Δn of the liquid crystal and the gap thickness of the liquid crystal cell 15 according to the wavelength of the incident light. But,
Depending on the wavelength of the incident light on the three liquid crystal panels 12, 13 and 14,
The use of a liquid crystal cell in which the Δn of the liquid crystal and the gap thickness are optimized has the problems that the manufacturing process becomes complicated and the manufacturing cost becomes high because the best contrast cannot be obtained due to manufacturing variations. Was there.

Further, in order to project the optical image formed by the liquid crystal panels 12, 13, and 14 with high contrast without reducing the amount of peripheral light, it is necessary to use a telecentric projection lens 19. However, a completely telecentric projection lens has problems that the number of lenses increases, the length of the lens increases, and the projection lens becomes expensive, when the projection optical system is made compact with a wide angle.

In view of the above problems, the present invention provides a projection display device that obtains a high-contrast projected image.

Means for Solving the Problems In order to solve the above problems, a projection display device according to a first aspect of the present invention includes a light source, a field lens including a polarizing plate on which light emitted from the light source is incident, and the field lens. A light valve that emits light emitted from the optical valve and forms an optical image corresponding to a video signal, and a projection lens that receives the light emitted from the light valve and projects the optical image on a screen.
The field lens is rotated, and the contrast of the projected image can be adjusted by rotating the field lens.

A projection display apparatus according to a second aspect of the present invention is a light source, color separation optical means for separating emitted light from the light source into red, blue, and green color lights, and polarized light to which each color light from the color separation optical means is incident. Three field lenses provided with plates, three light valves that are irradiated with the light emitted from the field lens to form an optical image according to a video signal, and the optical image that receives the light emitted from the light valve Is provided on the screen, and means for rotating the field lens are provided, and the contrast of the projected image can be adjusted by rotating the field lens.

The present invention has the structure described above, which is provided with the means for rotating the field lens provided with the polarizing plate, so that the arrangement of the polarizing plate can be adjusted so that the light valve obtains the best contrast, and the projection image with high contrast can be obtained. Can be obtained.

In a projection display device using three light valves, red,
Depending on the wavelengths of the blue and green lights, the arrangement of the polarizing plates can be adjusted so that the light valve has the best contrast. Therefore, it is possible to obtain a high-contrast projected image by using the three light valves having the same configuration, simplify the manufacturing process, and reduce the manufacturing cost.

The field lens can increase the amount of peripheral light while relaxing the telecentricity of the projection lens. As a result, the number of projection lenses is reduced, the lens length is shortened, the projection optical system can be made compact, and the projection lens becomes inexpensive.

Embodiment A projection display apparatus according to a first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a projection type display device in a first embodiment of the present invention, which uses a liquid crystal panel as a light valve. 31 is a lamp, 32 is a concave mirror, 33 is a condenser lens, 34 is a heat-absorbing glass, 35 is a field lens, 36 is a TN mode liquid crystal cell with a TFT for each picture element, 37 is a polarizing plate on the incident side, 38 Is a polarizing plate on the emitting side, and 39 is a liquid crystal panel including a liquid crystal cell 36 and polarizing plates 37 and 38.

Light emitted from a lamp 31, such as a metal halide lamp, a xenon lamp, or a halogen lamp, is converted into substantially parallel light by a concave mirror 32 and a condenser lens 33, and infrared rays are absorbed by a heat ray absorbing glass 34, and heat is not conducted to the front surface. I am trying. The light converted into the substantially parallel light enters the liquid crystal panel 39 after passing through the field lens 35. The liquid crystal panel 39 is a transmissive type and is an active matrix type having a TFT for each pixel, and an optical image is formed according to a video signal. The optical image formed on the liquid crystal panel 39 is enlarged and projected on a screen (not shown) by the projection lens. The polarizing plate 37 on the incident side is coated with an adhesive on one side, and is adhered to the flat side of the field lens 35 so that the liquid crystal cell
Separated from 36.

The field lens 35 is for making the light passing through the peripheral portion of the liquid crystal panel 39 incident on the projection lens 40, and is a plano-convex lens with its flat side facing the liquid crystal panel 39. As shown in FIG. 2, the outer peripheral portion of the field lens 35 has a circular or arcuate shape so that the field lens 35 can rotate while being in contact with the guide means 41. The field lens 35 is provided with a brim on its outer peripheral portion so that it can be easily fixed and rotated. The focus of the field lens 35 is set near the center of the pupil of the projection lens 40. The reason for making the direction and shape of the lens as described above is to bring the polarizing plate 37 on the incident side into close contact,
This is because the spherical aberration is not increased and the plane polishing is relatively inexpensive.

The field lens 35 can increase the amount of peripheral light while relaxing the telecentricity of the projection lens 40. As a result, the number of projection lenses 40 is reduced, the lens length is shortened, the projection optical system can be made compact, and the projection lenses are less expensive than telecentric projection lenses.

The polarizing plate 37 on the incident side is a field lens having a rotating means.
Since it is in close contact with 35, there is no optical loss at the boundary surface, and separation from the liquid crystal cell 36 and rotation of the polarization direction of incident light are possible. By rotating the polarizing plate 37, the angle between the alignment direction of the liquid crystal molecules on the wall surface of the liquid crystal cell and the absorption axis of the polarizing plate 37 can be adjusted to obtain the best contrast. Moreover, even if the Δn or the gap thickness of the liquid crystal cell 36 varies a little during manufacturing, it is possible to obtain a high-contrast projected image by adjusting the arrangement of the polarizing plate.

The incident side polarizing plate 37 absorbs about half the amount of the incident light and generates heat in order to convert the naturally polarized incident light into linearly polarized light. When the polarizing plate 37 is attached to the liquid crystal cell 36, the heat is conducted to the liquid crystal cell 36 and raises the temperature of the liquid crystal and the TFT formed on the liquid crystal cell 36. Due to the temperature rise, Δn of the liquid crystal is changed, the off resistance of the TFT is reduced and the off characteristic is deteriorated, and the contrast is lowered. Therefore, the polarizing plate 37 and the liquid crystal cell
36 is separated, heat radiation and heat conduction from the polarizing plate 37 are reduced, and the temperature rise of the liquid crystal cell 36 is suppressed.

In the first embodiment, the liquid crystal panel 36 has a red,
The blue and green color filters may be formed to form a full-color display projection display device.

A projection type display apparatus according to a second embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows the configuration of the projection display apparatus according to the second embodiment of the present invention. The projection display apparatus for color display is constructed by using three light valves and three projection lenses. There is. A liquid crystal panel is used for the light valve.

Reference numeral 51 is a lamp, 52 is a concave mirror, 53 is a condenser lens, and 54 is a heat ray absorbing glass. The above is the same as the configuration of FIG. 55 is a blue reflection dichroic mirror, 56 is a green reflection dichroic mirror, 57 is a red reflection dichroic mirror, 58 is a color separation optical means, 59B, 59G and 59R are field lenses, and 60B, 60G and 60R are each pixel. TFT
61B, 61G, 61R are incident side polarization plates, 62B, 62G, 62R are emission side polarization plates, and 63
B, 63G, and 63R are liquid crystal panels composed of a liquid crystal cell and a polarizing plate, and 64B, 64G, and 64R are projection lenses.

Light emitted from a lamp 51 such as a metal halide lamp, a xenon lamp, or a halogen lamp is converted into substantially parallel light by a concave mirror 52 and a condenser lens 53, and infrared rays are absorbed by a heat ray absorbing glass 54, so that heat is not conducted to the front surface. I am trying. The light converted into substantially parallel light enters the color separation optical means 58. In the color separation optical means 58, the incident light is
First, it is incident on the blue-reflecting dichroic mirror 55, the blue component is reflected, and the red and green components are transmitted. Next, the transmitted light is incident on the green reflection dichroic mirror 56, reflects only the green component, and transmits the red component. Finally, the red component is reflected by the red reflecting dichroic mirror 57, and unnecessary color components are transmitted. The decomposed blue, green, and red lights are three field lenses 59 arranged on the same plane.
After entering B, 59G, and 59R, they enter three transmissive liquid crystal panels 63B, 63G, and 63R arranged on the same plane. The liquid crystal panels 63B, 63G, 63R are of the active matrix type, and an optical image is formed as a change in transmittance according to a video signal. The optical image formed by the liquid crystal panels 63B, 63G, 63R is magnified and projected on a screen (not shown) by three projection lenses 64B, 64G, 64R whose optical axes are arranged in parallel with each other, and blue, green, The red projected image is composited on the screen. In order to combine the images formed by the three liquid crystal panels 63B, 63G, 63R on the screen, the two liquid crystal panels 63B, 63R other than the central portion of the three liquid crystal panels 63B, 63G, 63R are connected to the projection lens 64B, 64G,
By shifting the position on the plane with respect to the optical axis of 64R, blue,
The green and red projected images are superimposed on the screen.

The field lenses 59B, 59G and 59R are the liquid crystal panel 63.
The light emitted from the peripheral portions of B, 63G, and 63R is projected by the projection lens 64.
This is a plano-convex lens for making the light incident on B, 64G, and 64R, and the flat side facing the liquid crystal panels 63B, 63G, and 63R.
Polarizing plate on the plane side of the field lenses 59B, 59G, 59R
61B, 61G and 61R are closely attached. As shown in FIG. 4, the outer peripheral portions of the field lenses 59B, 59G, 59R are circular or arc-shaped, and the field lenses 59B, 59G, 59
The R can rotate while being in contact with the guide means 41. In addition, three field lenses 59B, 59G, 59R
Cut away parts of the lens so that they do not come into contact as they rotate.

The three liquid crystal cells 60B, 60G and 60R have the same Δn and the same gap thickness. Since the incident-side polarization plates 61B, 61G, and 61R can rotate, liquid crystal molecule orientation directions of the liquid crystal cells 60B, 60G, and 60R wall surfaces and the absorption axis of the incident-side polarization plate are determined according to blue, green, and red light. The angle formed by and can be adjusted, and a high-contrast projected image can be obtained. 3 LCD panels 63
B, 63G, 63R optical image formed by three projection lenses
Since it is projected on the screen with 64B, 64G, and 64R and is combined with the color image on the screen, full-color image display with high resolution can be performed.

With the above structure, a projected image having a contrast of 100: 1 or more could be realized by using three liquid crystal panels having the same structure.

Hereinafter, a projection type display apparatus according to a third embodiment of the present invention will be described with reference to the drawings.

FIG. 5 shows the configuration of a projection type display device in the third embodiment of the present invention. The difference from the second embodiment is that blue, green from the three liquid crystal panels 63B, 63G and 63R,
Color synthesis dichroic prism 65 that synthesizes red light
Is provided, and one projection lens 66 constitutes a projection display device for color display. 67, 68, 69, and 70 are plane mirrors that bend the optical path. Since the projection is performed by one projection lens 66, it is easy to change the size of the projected image. As in the second embodiment, since the liquid crystal molecule orientations of the liquid crystal cells 60B, 60G, 60R and the arrangement of the incident side polarizing plates 61B, 61G, 61R can be adjusted according to each color light,
A high-contrast projected image can be obtained.

In the above embodiment, an example in which a liquid crystal panel is used as a light valve is shown. However, if a polarizing plate is used to form an optical image according to a video signal as a change of birefringence such as electro-optical effect, optical rotation. It can be used as a light valve.

As described above, according to the present invention, since the means for rotating the field lens provided with the polarizing plate is provided, the arrangement of the polarizing plate can be adjusted so that the light valve obtains the best contrast. A projected image with contrast can be obtained. Since the three light valves can be configured in the same way to obtain a high-contrast color display projection image,
Cost reduction can be achieved.

Since the field lens can increase the amount of peripheral light while alleviating the telecentricity of the projection lens, the projection optical system can be made compact and the projection lens can be made inexpensive.

[Brief description of drawings]

FIG. 1 is a block diagram of the projection type display device in the first embodiment of the present invention, FIG. 2 is a schematic view of the field lens shown in FIG. 1, and FIG. 3 is a view of the second embodiment of the present invention. FIG. 4 is a schematic diagram of the projection type display device, FIG. 4 is a schematic diagram of the field lens shown in FIG. 3, FIG. 5 is a configuration diagram of the projection type display device in the third embodiment of the present invention, and FIG. FIG. 3 is a configuration diagram of the projection display device of FIG. 31,51 …… Light source, 32,52 …… Concave mirror, 33,53 …… Condenser lens, 34,54 …… Heat absorption glass, 39,59B, 59
G, 59R ... Field lens, 36, 60B, 60G, 60R
...... Liquid crystal cell, 37,61B, 61G, 61R …… Injection side polarization plate, 38,62B, 62G, 62R …… Emission side polarization plate, 39,63
B, 63G, 63R ... Liquid crystal panel, 40, 64B, 64G, 64
R, 66 ... Projection lens, 65 ... Color synthesis dichroic prism, 67, 68, 69, 70 ... Plane mirror.

Claims (10)

[Claims] 1. A light source, a field lens including a polarizing plate on which light emitted from the light source is incident, and a light valve on which light emitted from the field lens is irradiated to form an optical image according to a video signal. A projection lens for receiving the light emitted from the light valve and projecting the optical image on a screen; and a means for rotating the field lens. By rotating the field lens, the contrast of the projected image is adjusted. Projection display device. 2. The projection display device according to claim 1, wherein the field lens is a plano-convex lens, and a polarizing plate is closely attached to the plane thereof. 3. The projection display device according to claim 2, wherein the plane of the field lens is directed to the light valve side. 4. The projection display device according to claim 1, wherein the outer periphery of the field lens is a circle or an arc, and the field lens rotates while the circle or the arc is in contact with the guide means. 5. A light source and light emitted from the light source are red, blue,
Color separation optical means for separating into green color light, three field lenses provided with a polarizing plate on which each color light from the color separation optical means is incident, and light emitted from the field lens are irradiated to respond to a video signal. And a projection lens that receives the light emitted from the light valve and projects the optical image on a screen, and a unit that rotates the field lens. A projection display device in which the contrast of a projected image is adjusted by rotating. 6. The projection display device according to claim 5, wherein the field lens is a plano-convex lens, and a polarizing plate is closely attached to the plane thereof. 7. The projection display device according to claim 6, wherein the plane of the field lens is directed to the light valve side. 8. The projection display device according to claim 5, wherein the field lens has an outer peripheral portion of a circle or an arc, and the field lens rotates while the circle or the arc is in contact with the guide means. 9. The projection display device according to claim 5, wherein a part of the field lens is cut off. 10. The projection display device according to claim 5, wherein the three light valves have the same structure.