JPH04293081A - Projective image display device - Google Patents

Abstract

PURPOSE:To offer the projective image display device which has faithful color reproducibility, high definition, and high picture quality while displaying a large picture at a short distance by shortening the focus of a projection lens and suppressing variation in spectral characteristic and surface accuracy due to the moisture absorption of dichroic mirrors as to a projective image display device which uses the dichroic mirrors. CONSTITUTION:This display device consists of liquid crystal panels 12, 25, and 29, the projection lens 21, the dichroic mirrors 17 and 18, a surface mirror 31, driving circuits for the liquid crystal panels, a power source 2, and a housing 6; and the dichroic mirrors 17 and 18 contact a cooling medium 32 and parallel plane plates 16, 26, and 30 are provided between the liquid crystal panels 12, 25, and 29 and cooling medium 32, and the projection lens 21 and cooling medium 32 to minimize the variation in the spectrum characteristic and surface accuracy of the mirrors due to a temperature rise and the moisture absorption and also shorten the back focus of the projection lens 21 in terms of air. Consequently, a large image of high picture quality can be offered at a short projective 1 distance.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the arrangement of a color composition dichroic mirror and the surrounding structure thereof in a projection type image display apparatus.

0002

2. Description of the Related Art In the optical system configuration of a conventional projection type image display device using a liquid crystal as a light valve, the color synthesis system can be roughly classified into two types. One is a method using a dichroic-coated prism, and the other is a method using a dichroic mirror and a surface mirror, each of which has a dichroic-coated parallel plane plate.
In the former case, there is no problem if the LCD panel is small, but
As we move toward higher brightness and higher image quality, the LCD panel becomes larger. As a result, the color synthesis prism also becomes large, and its marketability is lost in terms of cost and weight.
Therefore, currently, the latter type of dichroic mirror is used for liquid crystal panels whose display portions have a diagonal length close to 3 inches.

0003

[Problems to be Solved by the Invention] For the above reasons, the method using a dichroic mirror, which is currently the mainstream on the market, requires a longer distance from the liquid crystal panel to the projection lens than the prism method, so it is difficult to back focus the projection lens. need to be taken for a long time. This makes it difficult to shorten the focus of the projection lens, making it difficult to provide a large projected image with a short projection distance. In addition, the thickness of the dichroic coat deposit changes as it absorbs moisture, so its spectral characteristics change depending on the environment in which it is placed, making it difficult to obtain the required image quality even with white balance adjustment. be. At the same time, since the image on the liquid crystal panel is projected onto the color synthesis mirror, high surface accuracy is required.

However, it is difficult to ensure the surface accuracy due to the aforementioned changes due to moisture absorption and stress changes in the deposited film due to temperature. If this cannot be ensured, it will not be possible to perform reliable convergence adjustment, and it will be impossible to obtain high definition and high image quality.

Therefore, the present invention overcomes the above-mentioned problems and provides a projection type image display device that can obtain a large screen even at a short distance, and also can obtain high-definition, high-quality images with faithful color reproducibility. The purpose is to provide.

[0006]

[Means for Solving the Problems] An image display device of the present invention includes at least three image display elements, a projection lens provided to be able to project images of the image display elements, and a combination of the image display elements and the projection lens. Two dichroic mirrors arranged between, a front mirror also arranged between the image display element and the projection lens, a drive circuit for driving the image display element, and the power necessary for the drive circuit. A power supply circuit is provided, of which both sides of the dichroic mirror are in contact with a refrigerant, and parallel plane plates are provided between the image display device and the refrigerant, and between the projection lens and the refrigerant. do.

[0007]

[Operation] The spectral characteristics and surface accuracy of the dichroic mirror are affected by the temperature rise inside the casing due to the image display element being driven by its drive circuit by the means described above, or due to the temperature rise inside the casing due to heat emitted from the light source. This makes it possible to minimize changes in This makes it possible to provide beautiful images with good white balance and good convergence. In addition, by filling the space from the image display element to the projection lens, including the dichroic mirror, with a refrigerant that has a higher refractive index than air,
The back focus of the projection lens can be shortened by converting it into air. Therefore, it is possible to develop a projection lens with a shorter focal length than conventional ones.

[0008] This makes it possible to provide the market with large-screen images at a shorter projection distance than before. Compared to the conventional type that uses prisms, it can be provided at a much lower cost, and as image display devices become larger, the prism type is easier to obtain and work with. Not realistic.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the configuration of a two-type projection type image display device using a liquid crystal panel. Reference numeral 1 indicates a light source, which is driven by a light source drive circuit 3 operated by power supplied from a power supply circuit 2 to emit light. The light emitted from this is sent by the reflector 4 to the ultraviolet and infrared cut mirror 7 supported by the inner wall 5 of the first housing 6.
Of the light incident on the ultraviolet and infrared cut mirror 7, only the visible light component is incident on the blue-transmitting dichroic mirror 8. At this time, only the blue wavelength light is transmitted through the condenser lens 10 by the surface mirror 9, and then enters the polarizing plate 11 attached to the flat glass plate. This polarizing plate 1
1, only the necessary polarized light components enter the liquid crystal panel unit 12, which is an image display element.

The liquid crystal panel unit 12 has a built-in liquid crystal drive circuit (not shown). This liquid crystal drive circuit is connected to the signal processing circuit 13. and,
The signal processing circuit 13 is supplied with power from the power supply circuit 2 and has an input terminal 14 for receiving signals from the outside. The blue light transmitted through the liquid crystal panel unit 12 enters a parallel plane plate 16 fixed to the second housing 15 so that the optical axis is approximately centered as shown in the figure. After that, it passes through the red reflective dichroic mirror 17 and is reflected by the green transparent dichroic mirror 18, and then the parallel plane plate 1 is fixed to the second housing 15 in the same way as the parallel plane plate 16.
9 and enters a projection lens 21 supported by a lens barrel 20 . Here, the projected image on the liquid crystal panel unit 12 is enlarged and projected to a required size. Further, the focus is adjusted so that the projected image is formed at a required distance. In addition, the second casing 1 mentioned earlier
5 is hermetically sealed and the inside thereof is filled with a refrigerant 32. Next, the light reflected by the blue-transmitting dichroic mirror 8 is separated by the red-reflecting dichroic mirror 22 into light in the red wavelength range and light in the green wavelength range. Of these, the red light is reflected, passes through the condenser lens 23 in the same way as the blue light, and then enters the polarizing plate 24 attached to the flat glass plate. This polarizing plate 24 allows only the necessary polarized light components to enter the liquid crystal panel unit 25. The liquid crystal panel unit 25 has a built-in liquid crystal drive circuit not shown in the figure. This liquid crystal drive circuit is connected to the signal processing circuit 13. The red light transmitted through the liquid crystal panel unit 25 enters the parallel plane plate 26 fixed to the second housing 15 so that the optical axis is approximately centered as shown in the figure. Thereafter, it is reflected by the red reflecting dichroic mirror 17, reflected by the green transmitting dichroic mirror 18, transmitted through the parallel plane plate 19, and then passed through the lens barrel 2.
The light is incident on the projection lens 21 which is supported at zero. The green light that has passed through the red reflecting dichroic mirror 22 passes through the condenser lens 27 in the same way as the blue and red lights, and then enters the polarizing plate 28 attached to the flat glass plate. This polarizing plate 28 allows only the necessary polarized light components to enter the liquid crystal panel unit 29. The liquid crystal panel unit 29 has a built-in liquid crystal drive circuit not shown in the figure. This liquid crystal drive circuit is connected to the signal processing circuit 13. The red light transmitted through the liquid crystal panel unit 29 enters the parallel plane plate 30 fixed to the second casing 15 in the figure so that the optical axis is approximately centered as shown in the figure. Thereafter, it is reflected by the surface mirror 31, transmitted through the green-transmitting dichroic mirror 18, transmitted through the parallel plane plate 19, and then incident on the projection lens 21 supported by the lens barrel 20.

According to this embodiment, the temperature rise inside the housing due to the liquid crystal panel units 12, 25, 29, which are image display elements being driven by their drive circuits, or the light source section 1
This makes it possible to minimize changes in the spectral characteristics and surface accuracy of the dichroic mirror due to temperature rise inside the housing due to heat emitted from the mirror. This makes it possible to provide beautiful images with good white balance and good convergence.

Furthermore, by filling the space from the image display element to the projection lens 21 including the dichroic mirror with the coolant 32 having a higher refractive index than air, the projection lens 21
The back focus can be shortened by converting it into air.
Therefore, it is possible to develop a projection lens with a shorter focal length than conventional ones.

In this embodiment, the characteristics of the color synthesis dichroic mirror are red reflection and green transmission, but it goes without saying that the characteristics will change as the color separation optical system changes, and are not limited to this. . Furthermore, the parallel plates 16, 19, 26, and 30 do not necessarily have to have a right angle with the optical axis passing through their centers.

[0014]

As described above, according to the present invention, at least three image display elements, a projection lens provided to be able to project images of the image display elements, and a projection lens disposed between the image display elements and the projection lens are provided. two dichroic mirrors, a front mirror also placed between the image display element and the projection lens, a drive circuit that drives the image display element, and a power supply circuit that supplies the necessary power to the circuit. Both sides of the dichroic mirror are in contact with the coolant, and parallel plane plates are provided between the image display element and the coolant, and between the projection lens and the coolant, so that the characteristics of the dichroic mirror are improved. By maintaining this, you can obtain beautiful images.

Furthermore, since the focal length of the projection lens can be shortened, it is possible to provide on the market a projection type image display device that can obtain a large screen with a short projection distance.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of a projection type image display device according to the present invention.

[Explanation of symbols]

1 Light source 2 Power supply circuit 3 Light source drive circuit 4 Reflector 5 Inner wall of first housing 6 First housing 7 Ultraviolet and infrared cut mirror 8 Blue transmitting dichroic mirror 9, 31 Front mirror 10, 23, 27 Condenser lens 11, 24 ,
28 Polarizing plate 12, 25, 29 Liquid crystal panel unit 13 Signal processing circuit 14 External signal input terminal 15 Second housing 16, 19, 26, 30 Parallel plane plate 17, 22
Red reflecting dichroic mirror 18 Green transmitting dichroic mirror 20 Lens barrel 21 Projection lens 32 Refrigerant

Claims (1)

[Claims] 1. At least three image display elements, a projection lens provided to be able to project images of the image display elements, and two dichroic mirrors disposed between the image display elements and the projection lenses, The dichroic mirror also includes a front mirror disposed between the image display element and the projection lens, a drive circuit for driving the image display element, and a power supply circuit for supplying the necessary power to the drive circuit. 1. A projection type image display device, wherein both surfaces are in contact with a coolant, and parallel plane plates are provided between an image display element and a coolant, and between a projection lens and a coolant.