JPH11305131A - Catadioptric optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system having a light aperture ratio, wide field of view, high resolution and flat image surface by satisfying specified conditions concerning a catadioptric optical system constituted by combining a hyperbolic reflector and a refraction type optical aberration correction system directly facing the side of an object. SOLUTION: Concerning the catadioptric optical system constituted by combining the hyperbolic reflector and the refraction type optical aberration correction system directly facing the object side, this system is composed of element satisfying the inequalities. Thus, light is made incident in the order of the hyperbolic reflector, refraction type optical aberration correction system, concave meniscus lens, biconvex lens, biconcave lens, biconvex lens, filter and CCD camera protection glass. Thus, the image surface can be made flat, any high-order aspherical surface is not used, a full length can be made into about 1/2 in comparison with a Schmidt optical system and problems in the Schmidt optical system can be solved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catadioptric optical system comprising a hyperboloid reflecting mirror and a refraction-type aberration correcting optical system. The present invention relates to an optical system for use in the above-mentioned application.

[0002]

2. Description of the Related Art Conventionally, a Schmidt optical system has been widely used to simultaneously obtain a bright aperture ratio, a wide field of view, and a high resolution. This is a problem when an image is received by an electronic imaging device such as the one described above. Introducing a higher-order specific sphere into the compensator is essential. There are drawbacks such as the total length becomes nearly twice the focal length.

In order to avoid the above problems, a hyperboloid reflecting mirror and a reducing lens system disposed behind the hyperboloid reflecting mirror are provided, and the image of the hyperboloid reflecting mirror is reduced and corrected to obtain an image. A system has been proposed in JP-A-60-6915.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problem in the Schmidt optical system by employing a catadioptric optical system consisting of a hyperboloid reflecting mirror and a refractive aberration correcting optical system.

[0005] Flatten the image plane

Avoid using higher order aspheric surfaces

[0007] The total length is 1/2 that of the Schmidt optical system.
degree

Further, a catadioptric optical system having a high resolution which can obtain a flat image surface with a bright aperture ratio and a wide field of view, which cannot be obtained with the conventional catadioptric optical system, has been developed. The purpose is to provide.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the present invention is directed to a hyperboloid reflecting mirror and a refraction-type aberration correcting optical system which are directly opposed to the object side. In a catadioptric optical system consisting of a combination of

[0010]

(Equation 2)

A catadioptric optical system comprising elements satisfying the following condition:

According to a second aspect of the present invention, in the first aspect of the present invention, a reflecting flat mirror inclined by 45 ° is disposed between the hyperboloid reflecting mirror directly facing the object side and the refractive aberration correcting optical system. Is a catadioptric optical system.

In general, a parabolic reflecting mirror with zero spherical aberration is used as the main reflecting mirror of the reflecting optical system. However, the parabolic reflector has the disadvantage that coma aberration occurs for a light beam incident at an angle to the optical axis.

In the present invention, the use of a hyperboloid reflector as the main reflector reduces the occurrence of coma, and corrects the spherical aberration generated by the hyperboloid reflector with a refraction-type aberration correcting optical system. The refraction-type aberration correcting optical system is configured to simultaneously correct not only spherical aberration but also astigmatism, field curvature, and chromatic aberration.

The conditions (1) and (2) are factors involved in the image formation of the optical system of the present invention. It becomes difficult to correct aberration. If the power of the hyperboloid reflecting mirror is increased beyond the upper limit, the power of the refractive aberration correcting optical system is also increased, and it becomes difficult to correct coma and spherical aberration.

If the conical coefficient of the hyperboloid is smaller than the lower limit of the condition (2), coma, curved surface aberration and chromatic aberration of magnification occur, making it difficult to correct. It is difficult to correct astigmatism and axial chromatic aberration.

Condition (3) is a condition relating to the positional relationship between the hyperboloid reflecting mirror and the refraction-type aberration correcting optical system. When the value exceeds the lower limit, it becomes difficult to correct coma aberration. Correction becomes difficult, and the aperture of the refraction-type aberration correcting optical system increases, so that the light amount loss due to shielding increases.

Condition (4) is the magnification of the hyperboloid reflecting mirror and the refractive aberration correcting optical system. When the magnification B is smaller than 1, the optical system becomes a reduction optical system. When the magnification B is larger than 1, the magnification becomes larger. It becomes an optical system. When the value exceeds the lower limit, it becomes difficult to correct coma aberration. When the value exceeds the upper limit, the aberration generated by the hyperboloid reflector is enlarged (because of the enlarged optical system).
Each power of the refractive aberration correction optical system becomes stronger,
It becomes difficult to correct spherical aberration and coma.

[0019]

FIG. 1 shows an optical path diagram of a first embodiment of the present invention. In the order of incidence of light, 1 is a hyperboloid reflecting mirror,
2 is a refractive aberration correction optical system, 3 and 4 are concave meniscus lenses, 5 is a biconvex lens, 6 is a biconcave lens, 7 is a biconvex lens, 8 is a filter, 9 is a protection glass for a CCD camera,
Reference numeral 10 denotes a combined focal position.

Table 1 below shows data based on the first embodiment.

[0021]

[Table 1]

FIGS. 2 and 3 show various aberrations of the first embodiment. As a whole, distortion, astigmatism, spherical aberration, and coma are well corrected, and a bright value of F / 3 is obtained. A wide field of view with an aperture ratio of 2.77 ° was obtained, the distortion was 0.1% or less, and a flat image plane was obtained at the combined focal position 10 of all the optical systems.

FIG. 4 is an optical path diagram of the second embodiment of the present invention in the case of the Newton type. The difference from the first embodiment is that a plane reflecting mirror R is provided and a refractive aberration correcting optical system 2 '. Is that the first lens is a biconvex lens 3 '.

Table 2 below shows data based on the second embodiment.

[0025]

[Table 2]

FIGS. 5 and 6 show the aberrations of the second embodiment. In the case of the configuration of the second embodiment shown in FIG. 4, as can be seen from FIG. 1
Similarly to the above, a flat image plane was obtained at a combined focal position 10 of all optical systems with a bright aperture ratio of F / 3, a wide field of view of 2.77 °, and a distortion of 0.1% or less.

[0027]

As described above, according to the present invention, a bright aperture ratio, a wide field of view, a high resolution, and a flat image surface,
An optical system suitable for receiving an image with an electronic imaging device such as a CCD is obtained.

[Brief description of the drawings]

FIG. 1 is an optical path diagram according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating spherical aberration, astigmatism, and distortion according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating coma aberration according to the first embodiment of the present invention.

FIG. 4 is an optical path diagram according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating spherical aberration, astigmatism, and distortion according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating coma aberration according to the second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hyperboloid reflecting mirror 2 Refractive aberration correcting optical system 3, 4 Concave meniscus lens 5, 7 Biconvex lens 6 Biconcave lens 8 Filter 7 Protective glass 10 Synthetic focal position

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hitoshi Yoshizawa 4-14-15 Shida, Setagaya-ku, Tokyo (72) Inventor Geisei 4-12-1, Shimorenjaku, Mitaka-shi, Tokyo

Claims (2)

[Claims] 1. A catadioptric optical system comprising a combination of a hyperboloid reflecting mirror directly facing an object and a refractive aberration correcting optical system. A catadioptric optical system having a bright aperture ratio, a wide field of view, and a high resolution, characterized by elements satisfying the condition of: 2. A catadioptric optical system having a high aperture ratio and a wide field of view according to claim 1, wherein a reflecting plane mirror inclined at 45 ° is arranged between the hyperboloid reflecting mirror and the refractive aberration correcting optical system. .