JP2621175B2 - Mirror image optics array - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a mirror image optical system array, and more particularly, to a mirror image in which a plurality of mirror image equal-magnification image forming systems for forming an image of an incident light beam as an equal-magnification image are arranged in a line. It relates to an optical system array.

(Prior Art) As a conventional optical system array using a plurality of lens systems arranged in parallel, an erecting equal-magnification imaging array is well known. In this method, each lens (or lens system) constituting an optical system array forms an erect equal-magnification image. An image of an incident light beam from an object is divided into a plurality of images and each image is formed on a fixed surface. Are combined to obtain one object image. For this purpose, a plurality of radial refractive index distribution type rod lenses called SELFOC are bundled in parallel, and in particular, the size of the reading system for input images such as copying machines and facsimile machines has been reduced. Used in imaging systems.

As the lens array configured by arranging the rod lenses as described above in parallel, a mirror image equal-magnification imaging array can be considered in addition to the erect equal-magnification imaging.

Conventionally, a method using an odd number of reflecting surfaces has been used to emit an incident light beam image in a mirror image relationship. Third
FIG. 1 is an explanatory view showing one embodiment of a conventional technique for obtaining a mirror image using an optical member called a Dove prism utilizing the method. However, when the prism shown in FIG. 3 is used, the high-speed light incident on the prism is bent through a reflection surface or a refraction surface, and further passes through an odd number of reflection surfaces, so that the optical axis is aligned between the entrance surface and the exit surface of the system. In order to form a coaxial system, it is necessary to change the state of the optical axis of the emitted light beam from the bent state to the same position and direction as the original state before the light beam incidence.

Therefore, the optical path length becomes longer as shown in FIG.
In addition, the optical axis of the object light beam entering the prism is bent once and the prism expands and expands in the radial direction of the incident optical axis, making it difficult to reduce the size of the entire system and tend to cause various aberrations. Was.

Further, in a system using this reflecting surface, only a mirror image inversion of an incident light beam image can be performed, and in order to use it as an imaging system, an imaging system is provided at least one of before and after the system using reflection. It is necessary to further install a lens system to
It was more difficult to downsize the entire system.

As one method for obtaining a mirror image without using a reflecting surface as described above, there is a method using a cylindrical lens. This is to obtain a mirror image by inverting the image in one of two directions, one direction of the image plane and one direction perpendicular thereto, and FIG. 4 schematically shows a system using the cylindrical lens. FIG. However, since it is necessary to use a plurality of cylindrical lenses in the above method,
It was difficult to reduce the size of the system. Further, in order to configure a system that obtains a mirror image using this cylindrical lens as an imaging system, it is necessary to arrange at least two systems using cylindrical lenses so as to be orthogonal to each other. It has a drawback that it is difficult to obtain good optical performance.

(Problems to be Solved by the Invention) An object of the present invention is to provide a mirror image optical system array having a simple configuration using a plurality of small image forming systems capable of easily obtaining a mirror image at the same magnification.

(Means for Solving the Problems) Among two directions perpendicular to the optical axis and orthogonal to each other, a light beam passing in one direction is an erect system that forms an erect equal-magnification image, and The passing light beam is an inverted system that forms an inverted image at the same magnification. When the object planes are coincident with each other, two directions perpendicular to the optical axis and orthogonal to each other so that the image planes of both systems coincide with each other. In this example, a plurality of mirror image equal-magnification imaging systems composed of single lenses having anamorphic refractive index distributions having different refractive powers are arranged in a line in the direction of the erecting equal-magnification imaging. It was done.

(Embodiment) FIG. 1 is a schematic view of an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an object plane, 2 denotes a mirror image equal-magnification imaging system (hereinafter, referred to as a "lens system"), and 20 denotes a mirror image optical system array. Are arranged in a line in the direction 3 is the image plane, L ₁ is the distance from the object plane 1 to the entrance plane of the lens system 2, L ₂ is the distance from the exit plane of the lens system 2 to the image plane 3, and Z ₀ is the length of the lens system 2 It is.

The light beam from the object plane 1 is divided into a plurality of parts by each lens system 2 constituting the mirror image optical system array 20, and each of them is incident. Then, when the light is transmitted through the lens system 2 and emitted from the lens system 2 to form an image on the image plane 3, the divided images are combined again and formed as a mirror image inverted image of the same magnification as a whole. I try to image it.

FIGS. 2A and 2B show the xy plane and the xz plane when the optical axis of the lens system for forming an image such as a mirror image used in the embodiment of FIG. FIG. 3 is a schematic view of an embodiment showing a light flux in the embodiment. The lens system shown in FIG.
It has an anamorphic refractive index distribution having non-zero mutually different refractive powers in two directions (y-axis direction, z-axis direction) perpendicular to the axis. FIGS. 3A and 3B respectively show a horizontal section (xy section) and a vertical section (xz section) of the light flux of the lens system.
Cross section).

In FIG. 1, reference numeral 1 denotes an object surface, 2 denotes a lens system, 2A denotes an entrance surface of the lens system 2, 2B denotes an exit surface of the lens system 2, 3 denotes an image forming surface, and 4 denotes an optical axis. The luminous flux incident on the entrance surface 2A from the object surface 1 is formed on the image plane 3 in the xy cross section by a lens system 2 having an anamorphic refractive index distribution in two cross sections including the optical axis and orthogonal to each other. On the xz cross section (vertical plane cross section), the light converges on the imaging plane 3 so that it becomes an inverted equal magnification. The lens length Z ₀ and the refractive index distribution are determined so that the light beam incident on the lens system 2 is refracted as described above. Even at various angles of the azimuth on the way from the xy plane to the xz plane, the light flux from the object plane 1 is imaged on the imaging plane 3 if the light flux is divided into the y component and the z component. As a whole, the light beam from the object plane 1 is imaged as a mirror image on the image plane 3. The mirror image mirror optical system array 20 of the embodiment shown in FIG. 1 has a configuration in which a plurality of lenses 2 shown in FIG. 2 are arranged in a line in the direction of erect equal magnification.

Here, the refractive index distribution of the lens system 2 will be described. n ₀
Is the refractive index on the optical axis, and g _y and g _z are the secondary refractive index distribution constants A, B, and C in the y and z directions, and the refractive index distribution n ( y, z) is represented by the following equation.

^{n 2 (y, z) =} n 0 2 {1-g y 2 y 2 -g z 2 z 2 + Ag y y 4 + Bg y 2 g z 2 y 2 z 2 + Cg z 4 g z 4 + (6 -order later Section)｝
... (1) or the following equation equivalent to the fourth-order refractive index distribution constant.

When the entrance surface 2A and the exit surface 2B of the lens system 2 are flat, the lens length is Z ₀ , and the refractive index distribution constant hρ is , The object plane 1 and the imaging plane 3 in the xy plane and the xz plane
The lens length Z ₀ and the distribution constant day ρ can be determined from the conditional expression that the two values coincide with each other. When forming an image at the same magnification, the conditional expression is represented by the following expression.

Here, the refractive index distribution constant ratio ρ and the converted lens length u are selected so as to satisfy Expression (4).

Table 1 shows a numerical example in which the refractive index distribution constant ratio ρ, the converted lens length u, and the product ρu of both are obtained from the equation (4).

Also, the distance from the object surface 1 to the entrance surface 2A of the lens system 2 is
L ₁ , the distance from the exit surface 2B of the lens system 2 to the image plane 3
When L _2, said L ₁ and L ₂ is expressed by the following equation.

As described above, the lens system 2 having an anamorphic refractive index distribution can be realized as a small-sized mirror image equal-magnification imaging system capable of obtaining an equal-magnification mirror image with only a single lens. Therefore, as described above, by arranging a plurality of the mirror image equal-magnification imaging systems in parallel and in a direction in which the erecting equal-magnification imaging is performed, the first image is obtained.
The mirror image optical system array 20 shown in the figure can be realized.

Incidentally, in the refractive index distribution of the single lens used in the embodiment shown in FIGS. 1 and 2, in the expressions (1) and (2),
Up to the second-order refractive index distribution constant was considered. However, since various aberrations increase as the lens diameter of the lens used increases, it is necessary to correct the various aberrations. Generally, in order to reduce the various aberrations,
It suffices to control the higher-order terms of the refractive index distribution in the expressions (1) and (2). However, in the case of an anamorphic refractive index distribution, it is not sufficient to control the higher-order distribution of the refractive index distribution in two directions perpendicular to each other and perpendicular to the optical axis. It is necessary to reduce various aberrations at the azimuth on the way. In this case, for example, (1),
By controlling the fourth-order distribution constant B or the like in the equation (2), the amount of aberration can be reduced by azimuth in the middle.

In each of the above embodiments, only the case where both ends of the refractive index distribution type lens system 2 are flat so as to facilitate analysis of the analytical formula is considered. However, the shape of the end face of the lens 2 is not necessarily flat, and at least one surface may be an aspheric surface such as a spherical surface, a cylindrical surface, or a toric surface. In such a case, a part of the bending of the light beam caused by the refractive index distribution is replaced by the refraction caused by the curved surface such as the spherical surface or the cylindrical surface. Has the effect of correcting In addition, even if the axial refractive index distribution is superimposed on the anamorphic refractive index distribution in the optical axis direction (x-axis direction) of the lens system 2, it is effective in correcting various aberrations and the like as described above.

Further, the lens system used to form a mirror image at the same magnification used in the above embodiment was a single lens having an anamorphic refractive index distribution.
Alternatively, a lens system using a rotationally asymmetric surface such as cylindrical or toric, or a lens system including a reflecting surface between the first refracting surface and the final refracting surface of the incident light beam may be used.

(Effects of the Invention) According to the present invention, a lens system having an anamorphic refractive index distribution having different refractive powers in directions orthogonal to each other and performing a mirror image equal-magnification image is erectly equalized. The object images can be divided and transmitted by arranging them in a line in the same direction, and can be synthesized as a mirror image at the image forming plane, and the distance between the object images, that is, the so-called conjugate length is short. Thus, a mirror image optical system array having a simple configuration capable of forming a mirror image at the same magnification can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic view of an embodiment of the present invention, FIG. 2 is a schematic view of an embodiment of a lens system according to the present invention, which forms a mirror image at the same magnification, and FIG. 3 shows a conventional Dove prism. FIG. 4 is an explanatory view showing a method of obtaining a mirror image using a conventional cylindrical lens. In the figure, 1 is the object plane, 2 mirror like Baiyui imaging system, 20 mirror optical system array, 3 imaging surface, 4 the optical axis, Z ₀ is the lens length, L ₁ from the object plane 1 of the lens 2 Distance to entrance surface, L ₂ is lens 2
Is the distance from the exit plane to the image plane 3.

Claims (1)

(57) [Claims] 1. A light beam passing through one of two directions perpendicular to the optical axis and orthogonal to each other is an erecting system that forms an erect equal-magnification image, and a light beam passing through the other direction is inverted. It is an inverted system that forms images at the same magnification, and when the object planes are matched in both systems,
A mirror image composed of a single lens having an anamorphic refractive index distribution having different refractive powers in two directions perpendicular to the optical axis and orthogonal to each other so that the image planes of both systems coincide with each other. A mirror image optical system array comprising a plurality of equal-magnification imaging systems arranged in a line in a direction in which the erect equal-magnification image is formed.