JP2002350622A - Diffraction optical element and method for turning the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a diffraction optical element having the grating height with high accuracy. SOLUTION: The preform of the element is formed so that the machining allowance of the grating effective part of the diffraction optical element by final turning is made uniform in the whole area and then the preform is subjected to the finish machining.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffraction optical element having a lens function, that is, a so-called diffractive lens, and more particularly to a method of processing a diffraction grating by turning means.

[0002]

2. Description of the Related Art A conventional turning method for a diffractive optical element having an optical axis is, as shown in FIG. The cutting tool 2 is cut into the cut removal part 3 of the workpiece, and the cutting tool 2 is moved to a desired shape by a moving mechanism (not shown) as shown in FIG. The cutting removal part was removed. Here, the shape of the cut end face of the cut removal portion is not the conventional lattice shape, but is substantially the same as the reference portion shape of the lattice such as a flat surface or a spherical surface.

[0003]

When the diffraction grating shape is formed, the height dimension of the grating is about 1 to 10 μm, but the height accuracy of each grating is lower than the design value due to optical characteristics such as diffraction efficiency. On the other hand, an accuracy of about ± 30 nm is required.

However, in the conventional grid cutting example shown in FIG. 2, when cutting a grid slope, the thickness of the portion to be cut and removed at a place such as t1 or t2 is different, so that the cutting tool 2 and the workpiece are cut. 1, the cutting position acting on the cutting tool 2 and the relative position between the cutting tool 2 and the workpiece 1 are shifted from the desired shape.
Accuracy specification was not satisfied. In most cases, the cutting resistance is increased in a portion having a large number of cuts to be removed in a large amount, so that a predetermined cut cannot be made and the lattice height is reduced.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the problems of the conventional processing method, and has a desired diffraction effect by making the amount of cutting removed on the grating slope uniform and making the cutting resistance the same. It is intended to form an optical element shape.

[0006]

FIG. 1 shows the features and structure of the present invention.

[0007] As in the conventional example shown in FIG.
The cutting tool 2 is attached to a rotating mechanism 5 (not shown) that rotates about the rotation axis of FIG. Here, the workpiece 1 is formed in advance so that the cuts at the respective portions of the effective grid slope are the same (t1 = t2). The thickness of the t3 part is not particularly limited,
The same as or smaller than 1 is better.

Here, the cutting tool 2 to be machined in advance may be a tool for performing final finishing cutting, but another tool is better. By doing so, the cutting resistance when machining the lattice slope becomes uniform, so that the relative position between the workpiece 1 and the cutting tool 2 is stable, and it is possible to form a desired lattice shape by turning. Become.

[0009]

According to the present invention, as described above, since a diffractive optical element having a high-precision grating height can be formed, an optical system having good diffraction efficiency and optical characteristics can be formed, and the measurement and measurement of lenses can be performed. It has a great effect on downsizing.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a diffraction optical element cutting example according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a conventional example of cutting a diffractive optical element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Workpiece which forms a diffraction grating 2 Cutting tool which forms a diffraction grating by turning off 3 Parts removed by cutting and removing

Claims (2)

[Claims] 1. A method for turning an optical element forming a fine diffraction grating around an optical axis by turning the optical element around the optical axis by means such as a diamond cutting tool, wherein a turning allowance of a grating effective slope portion of the optical element is reduced. A diffractive optical element characterized in that it is made uniform with respect to a final finished shape, and a method of turning the same. 2. The diffractive optic according to claim 1, wherein the same allowance as the allowance of the grating effective slope portion of the diffractive optical element is provided in the grating ineffective vertical portion, and the final finished shape is turned. Element and its turning method.