JP2608945B2 - 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 that irradiates an optical image formed on a light valve with illumination light and projects the optical image on a screen by a projection lens.

2. Description of the Related Art In order to display a large screen image, a relatively small light valve forms an optical image corresponding to a video signal as a change in optical characteristics, irradiates the optical image with illumination light, and screens the image with a projection lens. A method of enlarging and projecting above is well known in the art. In this type of projection display device, the resolution of the projected image is almost determined by the resolution of the light valve,
If the light source is strengthened, the light output is increased. Therefore, if a high-resolution light valve is used, a high-resolution, large-light-output projection display device can be realized even if its display area is small. Recently, a method 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 emitted from the lamp 1 is converted into nearly parallel light by the condenser lens 2 and the concave mirror 3, and transmitted through the heat ray absorbing filter 4. Thereafter, the light enters the color separation unit 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 exiting the color separation means 5 travels straight through the plane mirrors 11 and 12, the green light travels straight through, and the blue light travels 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 a 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 very fine so that its effects do 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 there is only one projection lens.

Problems to be Solved by the Invention In the configuration shown in FIG. 5, the optical path length from the condenser lens 2 to each of the liquid crystal panels 14, 15, 16 is 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 lengthens, so that the blue and green lights have high light use efficiency, but the red light has a low light use efficiency due to the long light path length. . In consideration of the white balance of the projected image, for example, it is necessary to insert an attenuation filter in the optical path of blue and green light to obtain an optimal illuminance ratio of red, green, and blue. Since the light utilization efficiency of the entire apparatus is determined by the light of the color that is also the most insufficient for the illuminance ratio of red, green and blue, the light utilization efficiency of the entire apparatus is low in the configuration shown in FIG. Is small. Further, if the light output of the light source is increased, the light output of the device can be increased. However, there is a problem that the entire device is correspondingly increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a compact projection display device having a high light output by improving the light use efficiency of an optical system.

Means for Solving the Problems In order to solve the above problems, a projection display apparatus of the present invention decomposes a light source that emits light including three primary color components, and decomposes output light from the light source into three primary color lights. Separating means for arranging first and second flat type dichroic mirrors substantially in parallel, three field lenses to which each of the three primary colors separated by the color separating means is incident, and the three field lenses Three light valves, each of which emits each color light emitted from the lens to form an optical image according to a video signal, and a multilayer film surface for combining output light from each of the light valves into one are crossed in an X shape. The first flat plate die, comprising: a light combining means, a projection lens for receiving an output light from the light combining means and projecting an optical image of the light valve on a screen, a return mirror, and a light transmitting means. The first color light selectively separated by the croic mirror is bent in the optical path by the return mirror to reach the corresponding field lens, and is selectively reflected by the second flat dichroic mirror. The second color light travels straight as it is to reach the corresponding field lens, and the third color light transmitted through the second flat dichroic mirror is made to reach the corresponding field lens by the light transmitting means. Each of the two field lenses makes its outgoing light reach the projection lens, and the second color light makes the light synthesizing means go straight, and the light transmitting means has an input convergent lens arranged at an input end, and an output. An output part converging lens disposed at an end, and the input part converging lens and the output part converging lens. A central convergent lens disposed in the optical path, an input-side flat mirror that bends an optical path between the input convergent lens and the central convergent lens, and a lens between the central convergent lens and the output convergent lens. An output-side flat mirror that bends the optical path of the input unit, wherein the focal length of the input unit convergent lens and the focal length of the output unit convergent lens are approximately twice the focal length of the central convergent lens, The converging lens and the output section converging lens are arranged such that their focal points are both substantially at the center of the center section converging lens, and the input section converging lens is arranged to emit light in the light source near the center section converging lens. Forming a real image of the body, the central convergent lens forming a real image of the object near the input convergent lens near the output convergent lens, from the light source to the three light valves; The pathlength is obtained so as to equivalently equal.

Operation According to the above configuration, a real image of the illuminant in the light source is formed near the central portion converging lens by the converging lens and the input portion converging lens of the light transmission means, and the central portion converging lens is used to form a real image near the input portion converging lens. Since the real image of the object is formed near the output portion convergent lens, all the light that enters the input portion convergent lens and reaches the central portion convergent lens is output through the output portion convergent lens. The input side plane mirror and the output side plane mirror only bend the optical path in the light transmitting means. The light emitted from the color separation means and the light emitted from the light transmission means are made to reach the projection lens by the field lens. In this way, the light that the input part convergent lens and the central part convergent lens are about to diverge is converted into convergent light, and the light is prevented from spreading in the light transmitting means.
By using a lens system, the optical path length of each color can be equivalently equal,
It is possible to prevent a decrease in light use efficiency in a portion having a long optical path length. Therefore, by using the light transmitting means combined with the converging lens, it is possible to realize a projection display device with improved light use efficiency.

Embodiment An embodiment of a projection display according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows the configuration of an optical system according to an embodiment of the present invention. Reference numeral 30 denotes a light source, 38 denotes color separation means, 39 denotes light transmission means, 40 denotes a folding mirror, and 41, 42, and 43 denote field lenses. Reference numerals 44, 45 and 46 denote a light valve 47 and a projection lens. In the color separation means 38, 49 is a blue-reflecting flat-plate dichroic mirror, 50 is a green-reflecting flat-plate dichroic mirror, and their normals 51 and 52 are the optical axes 37 and 4 respectively.
It is arranged at an angle of 5 degrees. In the light transmitting means 39, 53 is an input part converging lens, 54 is an input side flat mirror, 55 is a central part converging lens, 56 is an output side flat mirror, 57
Is an output convergent lens. The color separating means 38 and the light combining means 47 are the same as those used in the conventional example shown in FIG.

The light source 30 includes a lamp 31, a condenser lens 32, a concave mirror 33, and a heat ray absorbing filter 34.
It emits light containing three primary color components, green and blue. Lamp 31
Is converted into near parallel light by the condenser lens 32 and the concave mirror 33. Strictly speaking, the emitter of the lamp 31
Light rays emitted from the center 36 of 35 are emitted from the condenser lens 32 in parallel with the optical axis 37. Light emitted from the condenser lens 32 is subjected to removal of infrared rays by the heat ray absorbing filter 34. light source
The output light 30 enters the color separation means 38 and is separated into red, green, and blue light. The red light exiting the color separation means 38 is transmitted to the light transmission means 39.
Through, the green light goes straight, the blue light is a mirror
After the optical path is bent at 40 and passes through the corresponding field lenses 41, 42, and 43, the light enters the red, green, and blue light valves 44, 45, and 46. The light valves 44, 45, and 46 are transmissive liquid crystal panels, and optical images are formed as changes in transmittance according to video signals. Light valves 44, 45, 46
Is incident on the projection lens 48 by the field lenses 41, 42, and 43. At this time, the output lights are combined into one by the light combining means 47, and a color image is combined substantially at the position of the light valve 45. This color image is enlarged and projected by a projection lens 48 on a screen (not shown).

The field lenses 41, 42, 43 are plano-convex lenses with the planes 58, 59, 60 facing the light valves 44, 45, 46, and light rays parallel to the optical axis 37 enter the field lenses 41, 42, 43. Then, the output light beam reaches the vicinity of the center 62 of the pupil 61 of the projection lens 48. The shapes and directions of the field lenses 41, 42, and 43 are set in this manner because the spherical aberration is not increased and the planar polishing is relatively inexpensive.

The projection lens 48 is a projection lens having a small angle of view on the light valve 44, 45, 46 side. This is for the following reasons. In general, a light valve has the property that the optical characteristics vary depending on the angle of incidence of the incident light beam.When a normal wide-angle projection lens is used, the farther from the center of the light valve, the greater the angle of incidence of the main light beam to the light valve. Because
The image quality may differ between the center and the periphery of the screen.
To avoid this, the half angle of view on the light valve side is preferably set to 10 degrees or less.

FIG. 2 shows the configuration of the light transmitting means 39. In order from the color separation means 38 side, an input part converging lens 53, an input side plane mirror 54, a central part converging lens 55, and an output side plane mirror
56 and an output section converging lens 57. Both the input part convergent lens 53 and the output part convergent lens 57 are flat surfaces 6
3, 64 are the same plano-convex lenses directed toward the central convergent lens 55, and their focal lengths are twice the focal length of the central convergent lens 55. The central converging lens 55 has two sides 65, 66,
Are biconvex lenses having the same radius of curvature. The input part convergent lens 53 and the output part convergent lens 57 are arranged such that their focal points are both near the center 67 of the central part convergent lens 55. In order to bend the optical path at a right angle, an input side flat mirror 54 is provided between the input section converging lens 53 and the central section converging lens 55.
Are arranged, and the central portion converging lens 55 and the output portion converging lens 57
The output side flat mirror 56 is arranged between the first and second mirrors. The input part converging lens 53 and the output part converging lens 57 are plano-convex lenses, and the planes 63 and 64 are directed to the central part converging lens 55, because the spherical aberration is not increased and the planar polishing is relatively inexpensive. It is. The central converging lens 55 is
The reason why the biconvex lenses having the same radius of curvature of 5, 66 are used is that the aberration generated in the central converging lens 55 is not increased.

The operation of the red 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 48. For simplicity, only relevant optical components are shown. The light transmitting means 39 has the following properties.

First, based on the focal length of the central convergent lens 55 and the positional relationship between the convergent lenses 53, 55 and 57, the real image of the object 69 near the center 68 of the input convergent lens 53 is obtained by the central convergent lens 55.
70 is formed near the center 71 of the output section converging lens 57, and the object 69 and the real image 70 have the same size. For this reason, a light beam input from an arbitrary position of the input part convergent lens 53 to an arbitrary position of the central part convergent lens 55 always enters the output part convergent lens 57. Moreover, the luminous flux diameters of the light incident on the light valves 44, 45, 46 are substantially the same.

Second, both the focal point of the input part convergent lens 53 and the focal point of the output part convergent lens 57 are near the center 67 of the central part convergent lens 55, and the central part of the central part convergent lens 55 has no refractive power. The light beam incident on the periphery of the input part convergent lens 53 in parallel with the optical axis 37 passes through the center 67 of the central part convergent lens 55 as it is, and passes around the output part convergent lens 57. For this reason, when a light beam emitted from the center 36 of the light emitting body 35 of the lamp 31 is refracted by the condenser lens 32 and emitted parallel to the optical axis 37, the condenser lens 32 and the input section converging lens 53 A real image 73 of the light emitting body 35 of the lamp 31 is formed near the center 67 of the central convergent lens 55.

From the above, if the effective area of the central convergent lens 55 is larger than the real image 73, all light incident on the input convergent lens 53 exits from the output convergent lens 57, and the light transmitting means
It can be seen that there is no loss due to the spread of light inside 39. For this reason, the use efficiency of red light is higher than that of the conventional configuration shown in FIG. 5, and as a result, the light use efficiency of the entire apparatus is higher.

As can be seen from FIG. 3, the center of the luminous body 35 of the lamp 31
Since the light ray 72 exiting from the condenser lens 32 and exiting from the condenser lens 32 and the light ray 74 exiting from the output section exit lens 57 are parallel to the optical axis 37, these rays are focused on the focal points of the field lenses 41, 42 and 43. Will be reached. Since the focal points of the field lenses 41, 42, and 53 are located near the center 62 of the pupil 61 of the projection lens 48, the real image of the light emitter 35 of the lamp 31 is divided into red, green, and blue, and the pupil of the projection lens 48 It is formed near the center 62 of 61. Therefore, the light emitted from the light valves 44, 45, 46 efficiently reaches the screen. Note that, in the configuration shown in FIG.
Since the optical path length up to the optical path can be freely selected, a sufficient space for disposing the plane mirrors 54 and 56 for bending the optical path can be secured.

 Next, a description will be given using specific numerical examples.

The display dimensions of the light valves 44, 45, and 46 are 40 mm x 60 mm, the projection lens 48 has a focal length of 150 mm, the brightness is F2.5, the field lenses 41, 42, and 43 have a focal length of 170 mm, and the input section converging lens 53 and the output section converge. The lens 57 has a focal length of 130 mm, and the central convergent lens 55 has a focal length of 65 mm. In the configuration shown in FIG. 5, the illuminance immediately before the red light valve 14 is about 50% of the illuminance immediately after the color separation means 5, but in the configuration shown in FIG. The illuminance immediately before 44 was approximately 75% of the illuminance immediately after the color separation means 38, and although the presence or absence of a field lens was observed, the light use efficiency was clearly improved.

Next, another embodiment of the present invention will be described. The input convergent lens 53 and the output convergent lens 57 of the light transmitting means 39 shown in FIG. 2 need not be plano-convex lenses. FIG. 4 shows an example of this case. The input part converging lens 75 and the output part converging lens 76 are the same biconvex lens, and the surfaces 77 and 78 having small curvature are directed to the central part converging lens 55. . In general,
If the F-number of the spherical lens is small, the spherical aberration increases, and the spread of light cannot be ignored. In this case, the spherical aberration of the biconvex lens in which the radii of curvature of the surfaces 77 and 78 facing the central convergent lens 55 are about twice the radius of curvature of the other surface is smaller than that of the plano-convex lens. Considering the cost at the time of mass production, it is preferable that the input part convergent lens 75 and the output part convergent lens 76 be the same lens. In addition, at least one of the input portion convergent lens 53, the central portion convergent lens 55, and the output portion convergent lens 57 shown in FIG. Then, the loss due to the spread of the light in the light transmitting means 39 can be further reduced. This is the same in the case of the light transmitting means shown in FIG.

In the light transmitting means 39, at least one of the input-side flat mirror 54 and the output-side flat mirror 56 may be a red-reflective flat-plate dichroic mirror. In this case, by appropriately selecting the spectral reflection characteristics of the red-reflection plate type dichroic mirror, red color light with higher color purity can be obtained as compared with the case where a plane mirror is used. As a result, high color reproducibility can be realized in the color image synthesized by the light synthesis means 47.

In the configuration shown in FIG. 1, the field lenses 41, 42, 43
Is a plano-convex lens, but it is possible to optimize the illuminance ratio of the peripheral portion to the central portion on the screen by using a spherical lens of another shape or a lens having an aspheric surface on at least one surface. In this case, the surface with small curvature
Aiming at 44, 45, 46 is advantageous in terms of aberration.

In the configuration shown in FIG. 1, the field lenses 41, 42, 43,
It is also possible to use the same lens for all or at least two of the three types of lenses, the input portion convergent lens 53 and the output portion convergent lens 57. In this case, the types of lenses are reduced, and cost reduction in mass production can be achieved.

In the configuration shown in FIG. 2, the input portion converging lens 53 and the output portion converging lens 57 are the same plano-convex lens, and the relationship between the focal lengths and the positional relationship of the three converging lenses 53, 55, 57 is defined. , You do n’t have to worry about it, but with a few changes,
It is also possible to optimize the illumination ratio of red, green and blue.

FIG. 1 shows an example in which a liquid crystal panel is used as the light valves 44, 45, and 46. 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
In the figure, an example in which a prism type dichroic mirror is used as the light combining means 47 is shown. However, when high resolution is not required, a flat dichroic mirror crossed in an X shape like the color separating means 38. Can be used. In each case, the same effects as those of the above-described embodiment can be obtained.

Effect of the Invention As described above, according to the present invention, the optical path length of each color is equivalently made equal by using a light transmitting means in which a converging lens is combined with a long part of the optical path, thereby reducing the light use efficiency in that part. Therefore, the light utilization efficiency of the entire apparatus can be improved, and a compact projection display apparatus having a large light output can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a configuration of a projection display device according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a light transmitting means used in the projection display device shown in FIG. 1, and FIG. FIG. 4 is a schematic diagram for explaining the operation of the light transmitting means shown in FIG.
FIG. 5 is a schematic configuration diagram showing a configuration of a light transmitting means according to another embodiment of the present invention, and 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, 40
…… Folding mirror, 41,42,43 …… Field lens,
44,45,46 …… Light valve, 47 …… Photosynthesis means, 48 ……
Projection lens, 53: input part converging lens, 54: input side flat mirror, 55: central part converging lens, 56 ... output side flat mirror, 57 ... output part converging lens.

Continuation of the front page (56) References JP-A-63-46490 (JP, A) JP-A-63-284592 (JP, A) JP-A-61-122637 (JP, A) JP-A-63-196192 (P JP-A-63-216025 (JP, A) JP-A-56-142509 (JP, A) JP-A-63-106785 (JP, A)

Claims (10)

(57) [Claims] 1. A light source that emits light containing three primary color components and first and second flat dichroic mirrors for decomposing output light from the light source into three primary color lights are arranged substantially in parallel. Color separation means, three field lenses into which each of the three primary color lights separated by the color separation means is incident, and each color light emitted from the three field lenses is irradiated to form an optical image according to a video signal And the output light from each of the light valves is
A light combining means having X-shaped cross-sections of the multilayer films to be combined, a projection lens for receiving an output light from the light combining means and projecting an optical image of the light valve on a screen; Means, and the first color light selectively separated by the first flat dichroic mirror has its optical path bent by the folding mirror to reach the corresponding field lens,
The second color light selectively reflected by the second flat dichroic mirror travels straight as it is and reaches the corresponding field lens, and the third color light transmitted through the second flat dichroic mirror is The light transmitting means is caused to reach the corresponding field lens, and each of the three field lenses causes the light emitted from the three field lenses to reach the projection lens, and the second color light travels straight through the light synthesizing means. The means includes an input convergent lens disposed at an input end, an output convergent lens disposed at an output end, and a central convergent lens disposed in an optical path between the input convergent lens and the output convergent lens. An input-side flat mirror that bends an optical path between the input part convergent lens and the central part convergent lens; and the central part convergent lens. And an output-side flat mirror that bends an optical path between the output part convergent lens and the output part convergent lens. The focal length of the input part convergent lens and the focal length of the output part convergent lens are the focal length of the central part convergent lens. The input part convergent lens and the output part convergent lens are arranged so that their focal points are both substantially at the center of the central part convergent lens, and the input part convergent lens is disposed at the central part convergent lens. A real image of the illuminant in the light source is formed near the lens, the central convergent lens forms a real image of the object near the input convergent lens near the output convergent lens, and the three light sources from the light source. A projection display device wherein an optical path length to a bulb is equivalently equalized. 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. 3. The projection display apparatus according to claim 1, wherein at least two of the field lens, the input section converging lens, and the output section converging lens are the same lens. 4. The projection display device according to claim 1, wherein both the input portion convergent lens and the output portion convergent lens are lenses whose surfaces having small curvatures face the central portion convergent lens. 5. The projection display device according to claim 1, wherein both the input part convergent lens and the output part convergent lens are plano-convex lenses whose planes face the central part convergent lens. 6. The projection display device according to claim 1, wherein the field lens has a surface having a small curvature facing the light valve. 7. The field lens according to claim 1, wherein the field lens is a plano-convex lens having a flat surface facing the light valve.
The projection type display device according to the above. 8. The projection display device according to claim 1, wherein the central convergent lens is a biconvex lens having the same radius of curvature on both surfaces. 9. The projection display device according to claim 1, wherein at least one of the input side flat mirror and the output side flat mirror is a flat type dichroic mirror. 10. The projection type according to claim 1, wherein at least one of the field lens, the input portion convergent lens, the central portion convergent lens, and the output portion convergent lens includes at least one aspheric surface. Display device.