JPS62203003A - Apparatus for measuring shape of convex nonspherical surface - Google Patents

Abstract

PURPOSE:To attain to enhance the measuring accuracy of the shape of a convex nonspherical surface to be measured, by using only one half mirror without using other mirror system at all and further using a reflecting type zone plate. CONSTITUTION:The laser beam emitted from a laser beam source 2 is converted to a plane wave by a collimator mirror 3 and divided into reflected beam and transmitted beam by a half mirror 3. The reflected beam passes through a convex lens 4 to reach the observing surface 9 of an interference fringe by an image forming lens 8 through the half mirror 3. The beam passing through the half mirror 3 to reach the convex lens 5 is diffracted by a reflecting type zone plate 7 and again passes through the convex lens 5 to be reflected by the half mirror 3 while the reflected beam reaches the observing surface of the interference fringe through the image forming lens 8. Herein, the convex lenses 4, 5 have the perfectly same shape and the distances thereof from the half mirror 3 are equal to each other and the reflecting type zone plate 7 is formed so that the diffracted beam of said zone plate 7 becomes equal to the reflected beam of a convex nonspherical surface 6 and, by this constitution, the interference fringe corresponding to the shift part from the original shape of the convex nonspherical surface 6 can be observed on the interference fringe observing surface 9.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a convex aspherical surface shape measuring device that measures the shape of a convex aspherical surface using a reflective sound plate.

2. Prior Art Below, a conventional technology for measuring the shape of a convex aspherical surface will be explained based on FIG.

First, as shown in FIG. 2, a laser plane wave incident from arrow A is divided into two equal parts by a half mirror 21 into transmitted light and reflected light. After passing through the half mirror 22, the transmitted light passes through the convex lens 23, is reflected by the convex aspherical surface 24 to be measured, passes through the convex lens 23 again, is reflected by the half mirror 22, and proceeds in the direction of the convex lens 25. .

On the other hand, the light reflected by the half mirror 21 is reflected by the mirror 26,
It is reflected by 27, diffracted by hologram 28, and becomes a half mirror.
22 and reaches the convex lens 25. Here, the position of the hologram 28 is assumed to be a position conjugate with the image position of the convex aspherical surface 24 to be measured with respect to the convex lens 23 . At this time, the convex lens 25
The light that reaches the point passes through the convex lens 25 and enters the pinhole 29.
The diffracted light of the hologram 28 and the convex aspherical surface 24 to be measured
The light interferes with the light forming the image on the convex lens 23.

By measuring the interference fringes, the shape of the convex aspherical surface to be measured can be determined.

In addition, as an introduction to such technology, see page 198.
2-1992) etc.

Problems to be Solved by the Invention However, in the configuration shown in FIG.
There are many components of the interferometer, including two mirrors and two mirrors, which makes it extremely difficult to eliminate errors in the shape and alignment of the mirrors and half mirrors. Furthermore, since a transmission hologram is used, the light utilization efficiency is low, leading to a decrease in the contrast of the interference fringe shape and causing recognition errors in the measured shape.

SUMMARY OF THE INVENTION The present invention addresses the above-mentioned shortcomings of the prior art, reduces error factors in the mirror system, increases light utilization efficiency, and enables highly accurate recognition of the measured shape of a convex aspherical surface to be measured.

Means for Solving the Problems The present invention provides a half mirror that divides a plane wave emitted from a laser light source into transmitted light and reflected light, and is provided at a position equally divided by the half mirror, and the transmitted light of the half mirror is and the reflected light are incident on the first . The light emitted from the second convex lens and the first convex lens is reflected by the convex aspherical surface to be measured, the light emitted from the second convex lens is reflected by a reflective zone plate, and the light emitted from the convex aspherical surface to be measured is reflected. A means for superimposing the light after the light passes through the first convex lens and the light after the reflected light from the reflective zone plate passes through the second lens, and interference caused by the superposition of the light. The above object is achieved by providing an observation means for observing the stripes.

Effects As in the above configuration, the present invention uses only one half mirror and a reflective zone plate to greatly reduce alignment errors and shape errors in the mirror system, and also improves the utilization of light. The efficiency is increased, the contrast of the interference fringes is improved, the causes of errors in reading the interference fringes are reduced, and convex aspheric surfaces can be measured with high precision.

Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a conceptual diagram of the main parts of a convex aspherical surface shape measuring device according to an embodiment of the present invention.

In FIG. 1, 1 is a collimator lens that converts the laser light from the laser light source 2 into a plane wave; 3 is a half mirror 14 that divides the plane wave of the laser beam incident through the collimator lens 1 into transmitted light and reflected light; 5 is a convex lens of the same shape through which the transmitted light and reflected light enter, 6 is a convex aspherical surface to be measured, 7 is a reflective zone plate, and 8 is a convex lens 4
, 5 is imaged through a half mirror 3, and 9 is an observation surface for observing the shape of the convex aspherical surface 6 to be measured by interference fringes generated by the imaging lens 8.

The operation of the above configuration will be explained below.

First, the laser light emitted from the laser light source 2 becomes a plane wave by the collimator lens 1, and is split into two parts by the half mirror 3: reflected light and transmitted light. The reflected light from the half mirror 3 passes through a convex lens 4, is reflected by a convex aspherical surface 6 to be measured, passes through the convex lens 4 again, and reaches an observation surface 9 for interference fringes via an imaging lens 8 via the half mirror 3.

On the other hand, the light that passes through the half mirror 3 and reaches the convex lens 5 is diffracted by the reflective zone plate 7, passes through the convex lens 5 again, is reflected by the half mirror 3, and then passes through the imaging lens 8. This leads to the observation plane of interference fringes. Here, the convex lenses 4 and 5 have exactly the same shape, the distances of the convex lenses 4 and 5 from the half mirror 3 are equal to each other, and the diffracted light by the reflective zone plate 7 is By creating the reflective zone plate 7 so that the reflected light is equal to the reflected light of .

As described above, the present invention uses only one half mirror without using any other mirror system, greatly reduces alignment errors and shape errors in the mirror system, and improves reflection. By using a type zone plate, the efficiency of light utilization is increased, the contrast of interference fringes is improved, and the causes of errors in reading interference fringes are reduced. The effect is great.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of the main parts of a convex aspherical surface shape measuring device according to an embodiment of the present invention, and FIG. 2 is a conceptual diagram of the main parts of a conventional convex aspherical surface shape measuring device. 1. Collimator lens, 2. Laser light source, 3.
... Half mirror 14, 5... Convex lens, 6... Convex aspherical surface to be measured, 7... Reflective zone plate, 8...
・Imaging lens, 9... Observation surface. Name of agent: Patent attorney Toshio Nakao (1 person)
Figure "f T v-h town's wy entrance

Claims (1)

[Claims] a half mirror that divides the plane wave emitted from the laser light source into transmitted light and reflected light; and a mirror of the same shape that is provided at a position equally divided by the half mirror and receives the transmitted light and reflected light from the half mirror. 1. A second convex lens, the light emitted from the first convex lens is reflected by the convex aspherical surface to be measured, the light emitted from the second convex lens is reflected by a reflective zone plate, and the light emitted from the convex aspherical surface to be measured is reflected by the convex aspherical surface to be measured. means for superimposing the light after the reflected light of the reflective zone plate passes through the first convex lens and the light after the reflected light of the reflective zone plate passes through the second lens, and by superimposing the lights. A convex aspherical surface shape measuring device comprising observation means for observing generated interference fringes.