JPH09197147A - Gradient refractive index type optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a gradient index type optical element which has a large diameter and a free refractive index distribution pattern by concentrically combining a specific number of element transparent bodies which are different in refractive index from one another and made hollow like a cylinder. SOLUTION: Cylindrical element transparent bodies E2 , E3 , E4 , E5 , E6 , E7 , and E8 which have mutually different refractive indexes n2 , n3 , n4 , n5 , n6 , n7 , and n8 and nearly the same internal diameters as other external diameters and an element transparent body E1 which is a column having nearly the same external diameter as the internal diameter of the element transparent body E2 and has a refractive index n1 are prepared. Those are concentrically combined and then heated in this state by a proper heating means for, for example, high-frequency heating, and consequently mutual contact surfaces are molten and stuck to unite the respective element transparent bodies. The cylindrical lens which is thus obtained has a refractive index distribution which is parabolic from the center to the outer periphery and the respective element transparent bodies are made thick to obtain a state which is substantially the same with an ideal parabola.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractive index distribution type optical element which exhibits a lens-like function and a light transmission function by a refractive index distribution.

[0002]

2. Description of the Related Art A gradient index optical element is formed by diffusing a modified refractive index material for refractive index distribution in a radial direction in a matrix having a uniform refractive index with a predetermined gradient. For example, if the material is glass, a glass rod pre-doped with monovalent ions, which has a large electronic polarizability and easily moves in the glass at high temperature, is immersed in the molten salt for a long time, whereby the monovalent ions are dissolved in the molten salt. By exchanging it with the alkali ion, a parabolic ion diffusion distribution is given to form a required refractive index distribution (for example, Japanese Patent Publication No. 55-18882 and Japanese Patent Publication No. 60-127251). When the material is a synthetic resin, the required refractive index distribution can be formed by diffusing the modified refractive index material from the outside at a temperature higher than the glass transition temperature of the matrix material (for example, Japanese Patent Publication No.
No. 5-18882), or a monomer forming a polymer having a refractive index different from that of the matrix material is diffused and moved during the polymerization of the matrix material to form a required refractive index distribution (for example, Japanese Patent Laid-Open No. 4-
97303).

These conventional methods are excellent in that they can give a continuous refractive index distribution in the radial direction with high accuracy. However, due to the difficulty of controlling the diffusion of the modified refractive index material, there is a problem that the diameter and thickness that can be manufactured are limited to those with relatively small diameters, and highly precise control is required for the diffusion of the modified refractive index material. Therefore, there is a problem in terms of manufacturing cost, and there is also a problem that only a refractive index distribution with a fixed pattern can be obtained.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a gradient index optical element capable of solving the above-mentioned problems in the conventional gradient index optical element.

[0005]

In the present invention, a gradient index optical element is formed by integrating a plurality of element transparent bodies having different refractive indexes in a combination according to a desired gradient index pattern. I have to.

Further, in the present invention, for a gradient index optical element having a refractive index portion that continuously changes in the radial direction, a solid element transparent body is used as a core, and the refractive index is different from each other, for example. It is formed by concentrically combining a predetermined number of element transparent bodies formed in a hollow such as a cylinder and integrating them.

Further, according to the present invention, the gradient index optical element formed as described above is stretched as a base material to form, for example, an elongated rod-shaped optical transmission body, or a fiber-shaped optical transmission body, that is, an optical fiber. As a result, a gradient index optical element is formed.

According to such a gradient index optical element, the diameter can be freely selected within the range of the maximum value and the minimum value of the refractive index of the transparent element, and the diameter is larger than that of the conventional one. Can be easily obtained. Further, each element transparent body may have a uniform refractive index and does not require the diffusion control of the modified refractive index material which requires a high degree of control as in the conventional case, and therefore the manufacturing becomes easy. Furthermore, since the combination of element transparent bodies can be freely selected, it is possible to obtain an arbitrary refractive index distribution pattern.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described by taking an example of a cylindrical lens. First, as shown in FIG. 2, different refractive indices n ₂ , n ₃ , n ₄ , n ₅ , n ₆ , n ₇ , and n _{8 are used.}
The a, and a cylindrical element transparent body having approximately the same inner diameter as the other outer diameter _{E 2, E 3, E 4} , E 5, E 6, E 7, E
₈ and element transparent body E ₂ having an inner diameter nearly identical cylindrical an outer diameter providing an element transparent body E ₁ of refractive index n _1. Then, these are concentrically combined as shown in FIG. 1, and in this state, they are heated by an appropriate heating means such as high-frequency heating so that their contact surfaces are welded and each element transparent body is integrated.

The cylindrical lens thus obtained has a refractive index distribution which is a parabolic distribution from the center toward the outer periphery, as schematically shown in FIG. Then, such a refractive index distribution can be made substantially equivalent to the ideal curve C shown in the figure by reducing the thickness of each element transparent body. The vertical axis in the figure is the refractive index and the horizontal axis is the radius.

[0011]

As described above, according to the present invention, it is possible to easily obtain a gradient index optical element having a diameter larger than that of the conventional one, and to manufacture the gradient index optical element more easily. This makes it possible to manufacture a gradient index optical element having a free refractive index distribution pattern, and contributes to more effective utilization of the usefulness of the gradient index optical element.

[Brief description of drawings]

FIG. 1 is a perspective view of each element transparent body used in an embodiment of the present invention.

FIG. 2 is a perspective view showing a state in which the respective element transparent bodies according to the embodiment of the present invention are combined.

FIG. 3 is a graph showing a refractive index distribution in the gradient index optical element according to the embodiment of the present invention.

[Explanation of symbols]

E _{1 to} E ₈ element transparent body

Claims (3)

[Claims] 1. A gradient index optical element formed by integrating a plurality of element transparent bodies having different refractive indexes in a combination according to a desired refractive index distribution pattern. 2. In a gradient index optical element having a refractive index portion that continuously changes in a radial direction, a plurality of hollow element transparent bodies having different refractive indexes are used with a solid element transparent body as a core. , A gradient index optical element characterized by being integrally formed by concentric combinations. 3. A gradient index optical element having a refractive index portion that continuously changes in the radial direction, wherein a plurality of hollow element transparent bodies having different refractive indexes are used as cores of a solid element transparent body. A gradient index optical element, characterized in that the base material is formed by concentric combination to form a base material, and the base material is stretched.