JPH0816828B2 - Projection display device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection display device that irradiates an optical image formed on a light valve with illumination light and projects it onto a screen by a projection lens.

2. Description of the Related Art In order to display a large-screen image, an optical image is formed on a relatively small light valve according to the image signal as a change in optical characteristics, and this optical image is illuminated by illumination light and projected by a projection lens. Conventionally, a method of enlarging and projecting on the top is well known. 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 light source is strengthened. Therefore, if a high-resolution light valve is used, the projection display has high resolution and high light output even if the display area is small. The device can be realized. Recently, a method of using a liquid crystal panel as a light valve has attracted attention (for example, SID87
Digest page 75). FIG. 5 shows an example of a conventional configuration of such a projection display device.

The lamp 1 emits light containing red, green, and blue color components, and the light projected from the lamp 1 is converted into almost parallel light by the condenser lens 2 and the concave mirror 3 and transmitted through the heat ray absorption filter 4. After that, the light enters the color separation means 5. The color separation means 5 has a flat-type blue reflecting dichroic mirror 6 and a flat-type green reflecting dichroic mirror 7 arranged in parallel, and their normals 8 and 9 are 45 degrees with respect to the input optical axis 10. It is arranged to become. The red light emitted from the color separation means 5 goes straight through the plane mirrors 11 and 12, the green light goes straight through, and the blue light goes through the plane mirror 13 to the corresponding liquid crystal panels 14, 15, 16 respectively. Incident on. Optical images are formed on the liquid crystal panels 14, 15, 16 as changes in transmittance according to the respective video signals. The output light from the liquid crystal panels 14, 15, 16 is used for photosynthesis.
A color image is formed at the position of the substantially green liquid crystal panel 15 by being combined into one by 17. This color image is enlarged and projected on a screen (not shown) by the telecentric projection lens 18. The light synthesizing means 17 is a prism type dichroic mirror in which four right-angle prisms 19, 20, 21, and 22 are joined, a red reflecting dichroic multilayer film on joining surfaces 23, 24, and a blue reflecting dichroic multilayer film on joining surfaces 25, 26. Has been deposited. The intersection 27 of the multilayer film is made very thin so that its influence does not appear on the screen.

The projection type display device shown in FIG. 5 has a feature that the screen size or the distance from the projection lens 18 to the screen can be easily changed because the projection type display device has one projection lens.

Problems to be Solved by the Invention In the configuration shown in FIG. 5, the optical path lengths from the condenser lens 2 to the liquid crystal panels 14, 15, 16 are short for blue and green light and long for red light. In general, the light emitted from the condenser lens 2 spreads as the optical path becomes longer, so that the light utilization efficiency of blue and green light is high, but the light utilization efficiency of red light is low due to the long optical path length. Considering the white balance of the projected image, for example, insert an attenuation filter in the optical path of blue and green light,
It is necessary to make the illuminance ratio of green and blue. Since the light utilization efficiency of the entire device is determined by the light of the color that is most insufficient for the optimal illuminance ratio of red, green, and blue, the light utilization efficiency of the entire device is low and the light output is low in the configuration shown in FIG. There is a problem of being small. Further, if the light output of the light source is increased, the light output of the device can be increased, but there is a problem that the device as a whole is increased accordingly.

The present invention has been made in view of the above points, and an object of the present invention is to improve the light utilization efficiency of an optical system and to provide a projection type display device that is compact and has a large light output.

Means for Solving the Problems In order to solve the above problems, a projection display apparatus of the present invention is a light source that emits light including color components of three primary colors, and decomposes output light of the light source into light of three primary colors. Therefore, two flat plate type dichroic mirrors are arranged substantially parallel to each other with an inclination of about 45 degrees with respect to the incident optical axis, and an optical image corresponding to a video signal is formed and each output from the color separating means is formed. Three light valves that are respectively irradiated with light, a photosynthesis unit that intersects a multilayer film surface that synthesizes the output light from each of the light valves into one in an X shape, and an output light from the photosynthesis unit A projection lens for projecting an optical image of the light valve onto a screen, a light transmission means for guiding light emitted straight through the color separation means to a corresponding light valve, and a first flat plate type dichroic of the color separation means. By the mirror A flat mirror for guiding the light emitted after being bent to a corresponding light valve, and the light emitted after being bent by the second flat plate type dichroic mirror of the color separation means goes straight through the light combining means, The light transmitting means includes an input convergence lens arranged at the input end, an output convergence lens arranged at the output end, and a center arranged in the optical path between the input convergence lens and the output convergence lens. -Side converging lens, an input-side plane mirror that bends the optical path between the input-side converging lens and the central-portion converging lens, and an output-side plane that bends the optical path between the central-portion converging lens and the output-portion converging lens And a mirror so that a real image of the light emitter in the light source is formed in the optical path of the light transmitting means.

Operation According to the above configuration, a real image of the light emitting body in the light source is formed near the central converging lens by the condensing lens and the input converging lens of the light transmitting means, and the object near the input converging lens is formed by the central converging lens. Since the real image is formed in the vicinity of the output-portion converging lens, all the light that enters the input-portion converging lens and reaches the central-portion converging lens passes through the output-portion converging lens and is output. The input side plane mirror and the output side plane mirror only bend the optical path in the light transmitting means. In this way, the light that is about to diverge by the input-portion converging lens and the central-portion converging lens is converted into convergent light, and the light utilization efficiency is prevented from lowering due to the spread of the light inside the light transmission means, thus improving the light utilization efficiency. It is possible to realize the administration type display device.

Example Hereinafter, a projection display device of an example of the present invention,
This will be described with reference to the drawings.

FIG. 1 shows the configuration of an optical system in the first embodiment of the present invention, in which 30 is a light source, 38 is color separation means, 39 is light transmission means, 40 is a plane mirror, 41, 42, 43 are Light valve, 44
Is a photosynthetic means, and 45 is an administration lens. In the color separation means of 38, 46 is a plate-type dichroic mirror with blue reflection,
Reference numeral 47 is a plate-type dichroic mirror with edge reflection, which is arranged so that their normals, 48 and 49, form an angle of 45 degrees with the optical axis 37. In the light transmitting means 39, 50 is an input-side converging lens, 51 is an input-side plane mirror, 52 is a central-side converging lens, 53 is an output-side plane mirror, and 54 is an output-side converging lens. The configuration shown in FIG. 1 is the same as the configuration of the conventional example shown in FIG. 5 except for the light transmitting means 39.

The light source 30 includes a lamp 31, a condenser lens 32, a concave mirror 33,
It is composed of a heat ray absorption filter 34, the lamp 31 is red,
It emits light containing the color components of the three primary colors of green and blue. Lamp 31
The light emitted from the light is converted by the condenser lens 32 and the concave mirror 33 into light that is nearly parallel. Strictly speaking, the luminous body of the lamp 31
A light ray emitted from the center 36 of the light source 35 is emitted from the condenser lens 32 in parallel with the optical axis 37. The infrared rays of the light emitted from the condenser lens 32 are removed by the heat ray absorption filter 34. light source
The output light of 30 enters the color separation means 38 and is separated into red, green and blue lights. The red light emitted from the color separation means 38 is the light transmission means 39.
Through, the green light goes straight, and the blue light enters the corresponding light valves 41, 42, 43 via the plane mirror 40. The light valves 41, 42, 43 are transmissive liquid crystal panels, and an optical image is formed as a change in transmittance according to a video signal. The output light from the light valves 41, 42, 43 is combined into one by the light combining means 44, and is substantially a ride valve.
The color image is combined at the position of 42. This color image is enlarged and projected by a dosing lens 45 on a screen (not shown).

The dosing lens 45 is a telecentric lens, and all the principal rays on the light valve side of the dosing lens 45 are made parallel to the optical axis 37. This is for the following reason. In general, a light valve has a property that optical characteristics differ depending on the incident angle of an incident light ray, and when a normal projection lens is used, the incident angle of the principal ray on the light valve increases as the distance from the center of the light valve increases. The image quality may differ between the center and the periphery on the screen. To avoid this, a telecentric dosing lens should be used and all chief rays incident on the dosing lens should be parallel.

FIG. 2 shows the configuration of the light transmitting means 39. The input part converging lens 50, the input side plane mirror 51, the central part converging lens 52, and the output side plane mirror are arranged in this order from the color separation means 38 side.
53 and an output unit converging lens 54. The input section converging lens 50 and the output section converging lens 54 are the same, and their focal lengths are twice the focal length of the central converging lens 52. Input lens 50 and output lens
54 are arranged so that their focal points are both located at the center of the central-portion converging lens 52. In order to bend the optical path at a right angle, the input side plane mirror 51 is arranged between the input section converging lens 50 and the central section converging lens 52.
An output-side plane mirror 53 is arranged between 52 and the output unit converging lens 54. The input converging lens 50 and the output converging lens 54 are plano-convex lenses, and the planes 55 and 56 are directed toward the central converging lens 52 because spherical aberration is not increased and planar polishing is relatively inexpensive. Is. Further, the reason why the central converging lens 52 is a biconvex lens in which the radii of curvature of the both surfaces 57, 58 are the same is because the aberration generated in the central converging lens 52 is not increased.

The operation of the light transmitting means 39 shown in FIG. 2 will be described below. FIG. 3 shows an optical system from the lamp 31 to the projection lens 45, and shows only relevant optical components for simplifying the description. The light transmitting means 39 has the following properties.

First, the focal length of the converging lens 52 and the converging lenses 50, 52,
From the relationship of the positions of 54, a real image 61 of the object 60 located near the center 59 of the input focusing lens 50 is formed by the central focusing lens 52 near the center 62 of the output focusing lens 54.
61 is the same size. Therefore, the input section converging lens
A light beam that enters from any position of 50 to any position of the central converging lens 52 always enters the output converging lens 54. Moreover, the luminous flux diameters of the light incident on the light valves 41, 42, and 43 are substantially the same.

Secondly, both the focal point of the input-portion converging lens 50 and the focal point of the output-portion converging lens 54 are near the center 63 of the central-portion converging lens 52, and there is no refractive power near the central portion of the central-portion converging lens 52. A light ray 64 incident on the periphery of the input-portion converging lens 50 in parallel with the optical axis 37 passes through the center 63 of the central-portion converging lens 52 as it is, passes through the periphery of the output-portion converging lens 54, and passes through the optical axis 37.
Emit in parallel with. Therefore, when the light rays emitted from the center 36 of the light emitting body 35 of the lamp 31 are refracted by the collective lens 32 and emitted parallel to the optical axis 37, the condenser lens 32 and the input section converging lens 50.
As a result, the real image 65 of the light-emitting body 35 of the lamp 31 is formed at the center 63 of the central converging lens 52.

As can be seen from FIG. 3, the center of the luminous body 35 of the lamp 31.
Since the light ray emitted from 36 and emitted from the condenser lens 32 and the light ray emitted from the output portion converging lens 54 are parallel to the optical axis 37, the chief rays on the input light side of the projection lens 45 are red, green, and blue. Any of the light is parallel to the optical axis 37. Since the administration lens 45 is a telecentric lens, the light emitted from the light valves 41, 42, 43 efficiently reaches the screen. In the configuration shown in FIG. 2, the optical path length from the input convergence lens 50 to the output convergence lens 54 can be freely selected.
A sufficient space for arranging the plane mirrors 51 and 53 for bending the optical path can be secured.

 Next, description will be made using a specific numerical example.

Display size of light valve is 40mm x 60mm, projection lens 45
Has a focal length of 150 mm, a brightness of F2.5, an input focusing lens 50 and an output focusing lens 54 have a focal length of 130 mm, and a central focusing lens 52 has a focal length of 65 mm. In the case of the configuration shown in FIG. 5, the illuminance immediately before the red light valve 14 was about 50% of the illuminance immediately after the color separation means 5, but in the configuration shown in FIG. The illuminance immediately before 41 was about 75% of the illuminance immediately after the color separation means 38, and it was clearly recognized that the light utilization efficiency was improved.

 Next, a second embodiment of the present invention will be described.

The input-portion converging lens 50 and the output-portion converging lens 54 of the light transmitting means 39 shown in FIG. 2 may not be plano-convex lenses. FIG. 4 shows an example of this case.
66 and the output section converging lens 67 are the same biconvex lens,
Both surfaces 68 and 69 having a small curvature are directed to the central converging lens 52. In general, a spherical lens has a large spherical aberration when the F number is small, and the spread of light cannot be ignored. In this case, the spherical aberration is smaller when using a biconvex lens in which the radii of curvature of the surfaces 68 and 69 facing the central converging lens 52 are approximately twice the radius of curvature of the other surface than the plano-convex lens. Considering the cost during mass production, it is preferable that the input-portion converging lens 66 and the output-portion converging lens 67 are the same lens. Also,
At least one of the input-portion converging lens 50, the central-portion converging lens 52, and the output-portion converging lens 54 shown in FIG. If suppressed, the loss due to the spread of light in the light transmitting means 39 can be further reduced. This also applies to the case of the light transmitting means shown in FIG.

In the configuration shown in FIG. 2, the input section converging lens 50 and the output section converging lens 54 are the same plano-convex lens, and the relationship between the focal lengths and the positional relationship of the three kinds of converging lenses 50, 52, 54 is defined. However, it is not necessary to be particular about this, and by making some changes, it is possible to achieve the optimum ratio of the illuminance ratio of the peripheral part to the central part on the screen, the illuminance ratio of red, green, and blue.

FIG. 1 shows an example in which a liquid crystal panel is used as the light valves 41, 42, and 43. However, if an optical image such as an electro-optic crystal can be formed as an optical characteristic change according to a video signal, it is used as a light valve. be able to. Also, the first
Although an example using a prism type dichroic mirror as the light combining means is shown in the figure, a flat type dichroic mirror crossed in an X shape can be used when high resolution is not required. In any case, the same operation and effect as those of the above-described embodiment can be obtained.

EFFECTS OF THE INVENTION As described above, according to the present invention, since the light transmitting means in which a converging lens is combined with a long optical path is used to prevent a decrease in the light utilization efficiency in that portion, the light utilization of the entire device is utilized. It is possible to improve the efficiency, thereby providing a compact projection-type display device having a large light output, which is extremely effective.

[Brief description of drawings]

1 is a schematic configuration diagram showing a configuration of a projection type display device in a first embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of a light transmission means used in the projection type display device shown in FIG. FIG. 3 is a schematic diagram for explaining the operation of the light transmitting means shown in FIG. 1, and FIG. 4 is a schematic configuration diagram showing a configuration of a projection type display device in a second embodiment of the present invention. FIG. 5 is a schematic configuration diagram showing a configuration of a conventional projection display device. 30 ... Light source, 38 ... Color separation means, 39 ... Light transmission means, 4
1,42,43 …… Light valve, 4 …… Photosynthesis means, 45 ……
Projection lens, 50 …… Input part converging lens, 51 …… Input side plane mirror, 52 …… Central part converging lens, 53 …… Output side plane mirror, 54 …… Output part converging lens.

Claims (7)

[Claims] 1. A light source that emits light containing color components of three primary colors, and first and second flat plate dichroic mirrors for splitting the output light of the light source into light of the three primary colors are arranged substantially in parallel. Color separation means, three light valves on which an optical image is formed according to a video signal and each of the output lights from the color separation means is irradiated, and a multilayer for combining the output lights from the light valves into one The light combining means has film surfaces intersecting in an X shape, a projection lens for receiving the output light from the light combining means and projecting an optical image of the light valve on a screen, a plane mirror, and a light transmission optical system. The light of the first color reflected by the first flat plate type dichroic mirror of the color separation means is guided to the corresponding light valve via the flat mirror, and the second flat plate type dichroic of the color separation means. A second color of light reflected by the color passes through the light combining means and the light valves corresponding to straight ahead allowed incident on the projection lens,
The light of the third color that goes straight out of the color separation means is guided to the corresponding light valve via the light transmission means, and the light transmission means has an input section converging lens arranged at an input end and an output. Between the output part converging lens arranged at the end, the central part converging lens arranged in the optical path of the input part converging lens and the output part converging lens, and between the input part converging lens and the central part converging lens. An input-side plane mirror that bends the optical path of the optical path, and an output-side plane mirror that bends the optical path between the central-portion focusing lens and the output-portion focusing lens, and the focal length of the input-portion focusing lens and the output-portion focusing lens. Is about twice the focal length of the central-portion converging lens, and the focal points of the input-portion converging lens and the output-portion converging lens are close to the center of the central-portion converging lens. Place manner, a projection display device characterized by real image of the light emitting element in the center the adjacent light source of the central portion converging lens is to be formed. 2. The projection display device according to claim 1, wherein the light emitted from the light source and the light emitted from the light transmitting means are close to parallel light, and the projection lens is a telecentric lens. 3. The projection type display device according to claim 1, wherein the central convergent lens is a biconvex lens having the same radius of curvature on both surfaces. 4. The projection type display device according to claim 1, wherein the input part converging lens and the output part converging lens are the same lens. 5. The projection display device according to claim 1, wherein both the input part convergent lens and the output part convergent lens are arranged such that surfaces having small curvatures face the central part convergent lens. 6. The projection display device according to claim 1, wherein both the input-portion converging lens and the output-portion converging lens are the same plano-convex lens with the planes facing the central-portion converging lens. 7. The projection display apparatus according to claim 1, wherein at least one lens of the input-portion converging lens, the central-portion converging lens, and the output-portion converging lens includes at least one aspherical surface.