JP2003227775A - Striae inspection apparatus for optical part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method that can easily inspect a striae without using a liquid with an index of refraction close to that of a member, in which the conventional striae inspection immerses the member to inspect with transmission light without the influence of the curvature of the surface of the member. <P>SOLUTION: Parallel optical flux from a Zygo interferometer is divided into with a half-mirror, and one of the flux is entered into an afocal system formed with a collimator and reference lens, and reflected with a total reflection mirror at the back of the system to be returned to a same optical path. The other flux is entered into an afocal system formed with a collimator and a lens to be inspected, and reflected with a total reflection mirror to be interfered with the flux of the reference lens. In these processes, the phase state of an interference fringe is observed with using double-fetching and the repair functions of the Zygo interferometer. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention An apparatus for inspecting striae by measuring wavefront aberration by an interferometer.

[0002]

2. Description of the Related Art As shown in FIG. 2, in order to remove the influence of refraction due to the curvature of a lens under test, the lens under test is immersed in a liquid (matching oil) having a refractive index close to that of the lens under test. This eliminates the influence of refraction due to the curved surface of the lens, and changes in the refractive index due to striae can be independently detected. However, the refractive index of the lens to be inspected is large, and it is difficult to prepare a liquid corresponding thereto. Also, there is not much liquid (matching oil) that exactly matches the refractive index of the lens under test, and some errors occur.

[0003]

A method for easily inspecting striae and quantifying them once without infiltrating an object to be inspected with a liquid.

[0004]

[Means for solving the problem] Prepare an afocal system made of a striation-free reference lens and a collimator lens,
An interferometer that finds the difference in wavefront aberration between the lens to be inspected and an afocal system made up of a collimator lens having the same shape as described above is used to detect the wavefront aberration caused by the striae of the lens to be inspected.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Halfman mirror, two afocal system lenses, two total reflection mirrors, a light source for emitting an afocal light beam of a Zygo interferometer, and a Twyman for detecting the phase of an interference fringe by an interference fringe phase detector. Type interferometer.

FIG. 1 shows a first embodiment of the present invention, which is a commercialized Fizeau interferometer, such as a Zygo interferometer 1, a half mirror 2, a collimator lens 3, an inspected lens 4, a reference lens 5, and a total reflection mirror. 6, monitor 7, and piezo element 12.

A parallel light beam is emitted from the Zygo interferometer 1,
It is divided into a transmitted light flux and a reflected light flux by the half mirror. One of the transmitted light flux and the reflected light flux enters the afocal system including the collimator lens 3 and the reference lens 5, is reflected by the total reflection mirror 6, and returns along the same optical path. The other light flux passes through an afocal system including a collimator lens 3 and a lens 4 to be inspected, and a total reflection mirror 6
Is reflected, and returns along the same optical path. These two light fluxes are superposed by the half mirror 2 and interfere with each other. Due to this interference, the difference between the wavefront aberrations of the two afocal systems is detected by the observation system of the Zygo interferometer. This difference in wavefront aberration is an aberration caused by the striae of the lens under test. It is also possible to measure the phase of the interference fringes by microvibrating either one of the two total reflection mirrors of this Twanman interferometer with a piezo element or the like.

[0008]

EFFECTS OF THE INVENTION By preparing a collimator lens, forming two afocal systems and causing them to interfere with each other, the presence / absence of striae can be immediately identified, and a liquid having a refractive index close to that of the conventional example is searched for. It is easier and more accurate than the method of immersing the test object in the liquid and taking it out of the liquid and drying it when finished.

[Brief description of drawings]

FIG. 1 is a diagram of the present embodiment.

FIG. 2 is a diagram of a conventional example.

[Explanation of symbols]

1 Zygo interferometer 2 half mirror 3 collimator lens 4 Test lens 5 Reference lens 6 Total reflection mirror 7 monitors 8 Imaging lens 9 Matching oil 10 screens 11 parallel light flux 12 Piezo element

Claims (5)

[Claims] 1. An afocal system is formed by a lens to be inspected and a collimator, and interference is performed so as to obtain a difference between this wavefront aberration and a wavefront aberration of the afocal system made by a collimator lens and a reference lens having no striae. A striae inspection device that constitutes a meter and detects the influence of the striae of the lens under test as wavefront aberration. 2. A Twyman type interferometer is formed by a half mirror which is coupled with a Fizeau type interferometer (Zygo interferometer) and divides a parallel light flux emitted from the Fizeau type interferometer into two parts, which comprises the reference lens and a collimator. The striae inspection apparatus according to claim 1, wherein a difference in wavefront aberration between the afocal system and the afocal system including the lens to be inspected and the collimator is detected. 3. A phase reading device of a Fizeau interferometer (Zygo interferometer) by slightly vibrating a total reflection mirror placed behind an afocal system consisting of a reference lens and a collimator using a piezo element. . MI.) To read the interference fringes quantitatively. 4. The striae inspecting apparatus according to claim 1, wherein an afocal system is formed by a collimator lens designed with an optimum curvature, thickness and refractive index for the lens to be inspected. 5. The striae inspection apparatus according to claim 1, further comprising a mechanism capable of finely adjusting the lens to be inspected in x, y and z directions.