JP2003035870A - Cata-dioptric imaging optical system for rear projection type monitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To propose a compact optical system having a bright f-number, and consisting of only one sheet of an aspherical mirror, and also inheriting technique for mitigating the angle of an incident light beam on a screen by compositing a dioptric lens system and a catoptric system in order to provide an optical system for a thinned large-screen rear projection type monitor. SOLUTION: In this cata-dioptric imaging optical system for a rear projection type monitor, one aspherical reflection mirror in addition to the dioptric lens system and further a spherical reflection mirror are installed just before the screen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The optical system according to the present invention is used as a projection image forming optical system of a rear projection type monitor having a built-in reflection type image element projector or a liquid crystal projector.

[0002]

2. Description of the Related Art As prior art to the present invention, Japanese Patent Application No. 2000-104095 filed by the present inventor, and various documents cited therein, namely Reishi G.I. Cook's reference (previous application reference-1), JP-A-10-111458 (previous application reference-2), and Infocom Japan 2000
I will list four points of the materials distributed by Sanyo Electric Co., Ltd. at the exhibition (Reference 3 in the previous application). Regarding the references in the previous application, the previous historical application and Japanese Patent Application No. 2000-104095 have already described the outline of the historical or technical correlation, and therefore duplication will be avoided. I will describe the development of. The previous application provides an optical system that solves the technical problems up to that point to a considerable extent, and constitutes the optical system only with a reflective system. In order to further develop this invention, the present invention uses a hybrid system of a refraction system and a reflection system to make the F-number brighter and make the device more compact, and use one aspherical reflecting mirror.
We propose an optical system reduced to a single sheet.

[0003]

The three remaining problems to be further developed from the previous invention are to make the F-number brighter, to make the device more compact, and to make aspherical surfaces (freedom). Curved surface) to reduce the number of mirrors.

[0004]

In order to solve the above three problems, the optical system is changed from a pure mirror system to a hybrid system of a lens and a mirror. As a result, a brighter F number was realized, the number of aspherical mirrors was reduced to one, and the device was successfully made compact.

There is no dispute among experts regarding the possibility of introducing a refracting lens system into a pure mirror system to make the F number brighter, at least for its possibility. However, as always in optical design, it is not the only solution,
As one possibility of various solutions. In the case of the present application, the above three problems are solved by this device, that is, by introducing a refraction lens.

[0006]

First of all, in the pure mirror system, of course, it is necessary to create positive power as an image-forming system only by the mirror system, and moreover, all aberrations of the optical system must be within the practical range.
By inserting a refracting lens system there, most of the positive power can be loaded into the lens system, which increases the degree of freedom in optical design in all aspects and leaves room for improvement in specifications of the optical system. In the case of an optical system, generally, the correlation between the optical element (parameter space) and the aberration to be corrected (aberration space) is not one-to-one, but various elements are intricately entangled with each other. However, roughly speaking boldly, in the optical system of the present application, most of the positive power creation and aberration correction are performed by the refraction lens system, and the distortion correction is performed by the aspherical mirror, which works to bring the principal ray to the screen close to vertical. The starting point is the idea of performing (screen side telecentricization) with a spherical reflection mirror. Based on these considerations, a brighter F number, a more compact device, and an optical design with only one aspherical mirror became possible.

[0007]

Example-1 R, D, and n data of Example-1 are shown below. However, in the above, Coordinate Break
The surface R is ∞ where there is eccentricity (angle change or parallel movement of the optical axis), the rotationally symmetric aspherical surface is where EvAs is used, and the bilaterally symmetrical free-form surface is used where ExPoly is used. The above 25 surface (ExPoly) is a symmetrical free-form surface, and its equation is as follows: The first term of the above equation is the first term of the usual aspherical expression, Ai after the second term is the coefficient of the i-th term, and Ei (x, y)
Is a simple power series of x and y. The sixth and eighth surfaces of the above lens data are rotationally symmetric aspherical surfaces, the equations of which are as follows: The size of the screen is 50 inches (16: 9), the maximum thickness of the optical system is 28.8 cm, and the F number is 3.0. The thickness of the portion projecting from the screen is the optical path effective diameter, which is 163 mm. Further, the reason why the final reflection surface is a spherical surface is to make the chief ray of the light beam incident on the screen as vertical as possible, as described in detail in the previous application (Reference Document-1). I am following it.

[0008]

EFFECT OF THE INVENTION In an extremely thin optical system for a large-screen monitor, the f-number is improved in the bright direction by the combined system of the refracting lens system and the reflecting system, the thickness of the lower part of the screen is reduced, and the number of aspherical reflecting mirrors is 1 A catadioptric imaging optical system has been realized in which the angle of the chief ray incident on the screen is relaxed.

[Brief description of drawings]

FIG. 1 is a sectional view of an optical system according to an example of the present application. Ray is Config
drawing all from 1 to 6;
See. Since the entrance pupil is installed far to the right, the rays are drawn to the outside of the right frame.

FIG. 2 is a sectional view of an optical system of a refracting lens unit according to the embodiment of the present application.

FIG. 3 is a perspective view of an optical system for explaining an optical system sampling position of an example of the present application.

FIG. 4 is a wave optical MTF diagram of an example of the present application. The spatial frequency max value on the screen is 0.7 [line-pa
res / mm]

FIG. 5 is a distortion simulation diagram of the embodiment of the present application.

[Explanation of symbols]

1 image panel (reflection type or transmission type) 2 cross dichroic prism or prism for introducing illumination light 3 refraction lens part 4 aspherical reflection mirror 5 spherical surface mirror 6 screen 31 refraction lens system first lens 32 same second lens 33 same 3 lens 34 4th lens 35 5th lens 36 6th lens 37 7th lens 38 8th lens 39 9th lens

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Claims (5)

[Claims] 1. A catadioptric imaging system for a rear-projection type monitor, wherein in addition to a refracting lens system, one aspherical reflecting mirror and a spherical reflecting mirror as a reflecting mirror in front of the screen are installed. 2. A cross dichroic prism is placed in the order from the image element panel side to the screen side, if necessary, in proximity to the image element panel, or an illumination prism for guiding illumination light is placed, and then Place the refracting lens system, place the first reflecting surface of the aspherical surface at a slight distance, place the second reflecting surface with the concave surface of the spherical surface as the reflecting surface at a slight distance, and then reach the screen surface. The constructed catadioptric imaging optics. 3. The catadioptric imaging optical system according to claim 2, wherein the first reflecting surface is a bilaterally symmetrical free-form surface, and the others are the construction of claim 2. 4. A catadioptric imaging optical system having the structure of claim 2 which is a lens system employing a rotationally symmetric aspherical surface in the refractive lens system of claim 2. 5. The refracting lens system according to claim 4, wherein the refracting lens system is arranged in order from the image element panel side to the screen side.
The first lens has a rotationally symmetric aspherical surface on one side, and the second lens has a rotationally symmetric aspherical surface on one side.
The lens is a negative lens, the fourth lens is a biconvex lens, the fifth lens is a negative lens, and the sixth lens is a biconvex lens.
The lens is cemented, the seventh lens is a meniscus lens with the convex surface facing the panel side, the eighth lens is a concave lens, the ninth lens is a convex lens, and the eighth and ninth lenses are cemented lenses with a nine-lens configuration, and the others are The catadioptric imaging optical system according to claim 2.