JP2000227313A - Transmitted wavefront measuring instrument using reflecting mirror - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily measure various transmitted wave fronts, such as planar wave fronts, spheric wave fronts, aspheric wave fronts, etc., with accuracy by constituting a reflecting mirror of a mirror which reflects light in the same direction as that of incident light. SOLUTION: As a reflecting mirror which reflects a wave front transmitted through a single lens body or an optical system, such a mirror as the micro corner-cube mirror, rectangular mirror, etc., which reflects light in the same direction as that of incident light is used. The micro corner-cube mirror is composed of a plurality of corner-cube mirrors and has an apex angle of, for example, 90 deg.. Therefore, the mirror can reflect light in the same direction as that of incident light though the phase is shifted from the incident angle. In addition, the phase shifting amount can be reduced by adjusting the diameters of the corner cubes. The rectangular mirror can reflect light in the same direction as that of the incident light though the phase is linearly shifted from the incident light, because rectangular V-grooves are arranged on the mirror.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for measuring a transmitted wavefront of an optical system composed of a single lens or a plurality of lenses.

[0002]

2. Description of the Related Art Conventionally, the transmitted wavefront (wavefront shape) of an optical system composed of a single lens or a plurality of lenses has been measured using a laser interferometer. FIGS. 3 and 4 are schematic views of a transmission wavefront measuring apparatus according to the prior art. First, the method shown in FIG. 4 will be described. When measuring the transmitted wavefront using the laser interferometer 1, an optical system for correcting the incident light to the test object 3 into a plane wave serving as a reference is arranged in the optical path of the laser light from the laser light source, and the optical path in this optical path is adjusted. The test object 3 is arranged on an extension of the system, and the number of interference fringes (usually Newton number) generated between the reflected light from the reference plane 4 of the reference lens and the transmitted light of the test lens reflected by the folding mirror 5 Is measured on the monitor 6, for example, to measure the transmitted wavefront of the test object 3.
However, when trying to measure a wavefront transmitted through a lens having an aspherical surface using the apparatus shown in FIG. 4, the aberration of the transmitted wavefront becomes large, and it is difficult to form and measure interference fringes. Further, even with a lens having a spherical surface, if the curvature is large, aberrations are likely to occur, and accurate measurement is difficult. Therefore, when measuring the transmitted wavefront of a spherical or aspherical lens having a large curvature, a null lens 2 as shown in FIG. 3 was used to correct the aberration of the test object, or the folded reflecting mirror was adapted to the transmitted wavefront. It had a reflective surface shape.

[0003]

However, whether a null lens or a reflecting mirror is used, a dedicated load is required for the measurement of one test object, so that the burden on manufacturing is large. Alignment also requires labor, which has been a problem. In addition, the incident light on the test object is formed as interference light by forming a single optical component (lens) having various shapes such as a flat surface, a spherical surface, or an aspherical surface and a transmitted wavefront of an optical system constituted by the components. It was very difficult to perform measurement using a single measuring device because of complicated optical adjustment. An object of the present invention is to solve this problem and to provide an apparatus for simply and accurately measuring various transmitted wavefronts such as a plane, a spherical surface, and an aspherical surface.

[0004]

According to the present invention, the following means are used to solve the above-mentioned problems. As a first means, for a transmitted wavefront measuring device having an interferometer, a reference surface, and a turning mirror for turning the wavefront transmitted through the test object, the turning mirror transmits light in the same direction as the incident light. It is made of a reflecting mirror. This eliminates the need to design and manufacture a null lens according to the test object, and to design and manufacture a folding mirror according to the shape of the wavefront transmitted through the test object.

[0005] As a second means, when implementing the first means, the folding mirror is made of a minute corner cube mirror. By this means, a highly accurate folding mirror required for the means 1 can be easily obtained, and a high-performance measuring device can be obtained at low cost. As a third means, when implementing the first means, the return reflecting mirror is constituted by a right-angle mirror. As a result, a folding mirror required for the means 1 can be obtained easily and inexpensively, and a high-performance measuring device can be obtained at low cost.

As a fourth means, the measuring apparatus of the first or second or third means has an interferometer or an optical system for correcting light from the test object into a plane wave. This facilitates alignment during measurement.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic technical idea of the present invention is as follows.
If a folding mirror having a characteristic of reflecting light in the incident direction is used, interference fringes can be sufficiently formed and observed within a practical range even if the test object has aberration. For this reason, in the present invention, a mirror that reflects light in the same direction as incident light, such as a minute corner cube mirror or a right angle mirror, is used as a lens alone or a folding mirror that reflects a wavefront transmitted through the optical system. The small corner cube mirror is composed of a plurality of corner cubes as shown in FIG. 2A, and has a vertical angle of 90 °. Therefore, the light can be reflected in the same direction although the phase is shifted from the incident light. Also, since the amount of this phase shift can be reduced by the diameter of the corner cube, the diameter of a single corner cube is preferably about 0.1 to 10 mm. On the other hand, the right-angle mirror has a right-angle V as shown in FIG.
The groove is arranged. Therefore, although it is linear, it can be reflected in the same direction although it is out of phase with the incident light.
Also, since the amount of this phase shift can reduce the V-groove, the width of a single V-groove is preferably about 0.1 to 10 mm. The folding mirror is manufactured by stacking cubes or by manufacturing a mold and molding it by resin molding, or by heating and softening a glass material to form it. By using the above-mentioned folding mirror,
In the transmitted wavefront measuring device, even if the aberration caused by the device and the transmitted wavefront of the test object have an aberration, they are all reflected by the return mirror, so that the interference light can be formed with good reproducibility. Therefore, the transmitted wavefront of the lens alone or the optical system can be measured without complicated optical adjustment,
It becomes possible to evaluate. Further, a null lens, which was conventionally required for exclusive use, is no longer necessary, thereby improving workability. The procedure of the transmitted wavefront measurement using the apparatus of the present invention will be described below. 1) Folding mirror adjustment: Adjusting the tilt and the distance so as to be smaller than one pixel of the image sensor. 2) Sample measurement: Scan a reference surface to capture an image and measure it. As described above, measurement with a measurement accuracy of about pv λ / 2 has become possible.

[0008]

According to the present invention, various transmitted wavefronts such as flat, spherical and aspherical surfaces can be easily and accurately measured.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of the apparatus of the present invention.

FIG. 2 shows an example of a folding mirror according to the present invention. (A) Micro cube mirror, (b) Right-angle V-groove mirror

FIG. 3 is a conceptual diagram 1 of a transmitted wavefront measuring apparatus according to a conventional technique.

FIG. 4 is a conceptual diagram 2 of a transmitted wavefront measuring apparatus according to a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Interferometer 2 ... Null lens 3 ... Test object 4 ... Reference plane 5 ... Reflecting mirror 6 ... Monitor 7 ... Reflecting of the present invention mirror

Claims (4)

[Claims] An apparatus for measuring a transmitted wavefront having an interferometer, a reference surface, and a turning mirror for turning a wavefront transmitted through a test object, wherein the turning mirror transmits light in the same direction as incident light. A measuring device comprising a reflecting mirror. 2. The measuring device according to claim 1, wherein said mirror is a minute corner cube mirror. 3. The measuring device according to claim 1, wherein the mirror is a right-angle mirror. 4. The measuring apparatus according to claim 1, further comprising an interferometer or an optical system for correcting light from the test object into a plane wave.