JPH0376846B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Object of the Invention [Field of Industrial Application] This invention relates to a hologram interferometer for measuring the surface shape of an ellipsoidal mirror. An ellipsoidal mirror is an aspherical mirror that can condense a diverging spherical wave from one point to another point without aberration, and is one of the important optical elements.For example, it is used in a xenon flash lamp collection for laser oscillation. It is used as an optical device and an X-ray reflecting mirror (toroidal mirror).

[Prior Art] A method for inspecting the shape of this ellipsoidal mirror and measuring it quantitatively and with high precision has not yet been established.

Conventionally used techniques for inspecting and measuring the shape of ellipsoidal mirrors include the Foucault test, the Ronchi test, the spherical reference laser interferometry, the immersion method, the dual wavelength method, and the computer-generated hologram interferometer.

[Problems to be Solved by the Invention] However, the Foucault test and the Ronchi test are qualitative inspection means, and cannot quantitatively measure the shape of an ellipsoidal mirror.

Further, the spherical reference laser interferometry requires analysis of interference fringes, and the inspection process is complicated. Also,
In the liquid immersion method, the object to be measured must be immersed in a liquid, and the refractive index of the liquid must be accurately measured. Furthermore, in the two-wavelength method, it is difficult to align two wavefronts. Furthermore, the computer-generated hologram interferometer has a problem in that it takes time and effort to create a computer-generated hologram.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to be able to measure the surface shape of an ellipsoidal mirror with high precision and quantitatively, and to do so easily, reliably, and inexpensively. The aim is to provide measurement technology that can

(B) Structure of the Invention [Means for Solving the Problem] Corresponding to this object, a hologram interferometer for measuring the surface shape of an ellipsoidal mirror of the present invention includes a laser light source and a light beam from the laser light source that at least a beam splitter that splits the beam into two beams; a reference beam optical system that generates a parallel reference beam from one of the two beams; and a hologram that records an object beam that is a diverging spherical wave beam using the reference beam. , an illumination light optical system that generates illumination light, which is a diverging spherical wave light that illuminates the object elliptical mirror surface, from the other of the two light beams, and after the illumination light is reflected by the object elliptical mirror surface, the hologram The hologram is illuminated with the reference light, and interference fringes between the reproduced object light reproduced by illuminating the hologram and the illumination light illuminating the hologram are observed.

Hereinafter, details of the present invention will be explained with reference to the drawings showing one embodiment.

In this embodiment, parallel light is used as the reference light, divergent spherical wave light is used as the object light, and divergent spherical wave light is used as the illumination light.

In FIG. 1, 1 is a hologram interferometer. The hologram interferometer 1 is equipped with a hologram HP. First, we will explain the production of the hologram HP.

In FIG. 2, 2 is an optical system for producing the hologram HP. The optical system 2 includes, for example, a laser light source 3 that generates an argon ion laser, a reference light optical system 4, an object light optical system 5, and beam splitters (or semi-transparent mirrors) BS1 and BS2.

The reference light optical system 4 includes a reflecting mirror M1, a microscope objective lens Mo1, a pinhole P1, and a collimator lens L1. The object light optical system 5 is a reflecting mirror M
2. Microscope objective lens Mo2 and pinhole P2
It is equipped with

When creating a hologram HP, the laser light from the laser light source 3 is divided into two parts using the beam splitter BS2.
The light beam is divided into two beams, one beam is input into the reference beam optical system 4, the optical path is changed by the reflector M1, the beam is made into a diverging spherical wave by the microscope objective lens Mo1 and the pinhole P1, and then the parallel beam is referenced by the collimator lens L1. Generate light. The other beam enters the object beam optical system 5, is reflected by a reflecting mirror M2, and then is generated by a microscope objective lens Mo2 and a pinhole P2 to generate a diverging spherical wave object beam. This object light is exposed and recorded on a photographic plate at the position of the hologram HP using the reference light, and photographically processed to complete the hologram HP, which is then set at the original position.

The interferometer 1 shown in FIG. 1 is connected to the optical system 2 shown in FIG.
The object light optical system 5 is removed from the above, an illumination light optical system 6 is added, and the set position of the ellipsoidal mirror surface EM to be tested is set.

The illumination light optical system 6 consists of a microscope objective lens Mo3, a pinhole P3, and a reflector M3, and after converting the other light beam split by the beam splitter BS1 into diverging spherical wave light by the microscope objective lens Mo3 and pinhole P3, This diverging spherical wave light illuminates the ellipsoidal mirror surface EM to be tested. The reflected light from the ellipsoidal mirror surface EM to be tested illuminates the hologram HP.

The set position of the ellipsoidal mirror EM surface to be tested is such that one focal point coincides with the pinhole P3.[Operation] In the hologram interferometer 1 as shown in FIG. 1, the surface shape of the ellipsoidal mirror EM to be tested is To measure, the beam from the laser light source 3 is split by the beam splitter BS1, and one beam is guided to the reference beam optical system 4 to generate a parallel reference beam, which is incident on the hologram HP. The recorded object light of divergent spherical wave light is reproduced. The other light flux is guided to the illumination light optical system 6 to generate a divergent spherical wave illumination light, which is reflected by the test ellipsoidal mirror surface EM to generate a divergent spherical wave, and then the hologram HP.
incident on .

The illumination light is affected by the unevenness which is the shape error of the mirror surface of the ellipsoidal mirror surface EM to be tested, and after being reflected, it deviates from the standard object light, so the reproduced object light and illumination light are shown in Figure 3. Interference fringes as shown are produced.

The relationship between the interference fringe pitch D in this interference fringe, the amount of deviation d, and the shape error △h of the surface to be measured is △h=(d/D)・(λ/2), where λ is the wavelength. As shown in FIG. 3, the shape error Δh is obtained from the interference fringe pitch D and the amount of deviation d, and the surface shape of the ellipsoidal mirror surface EM to be tested can be measured.

(C) Effects of the Invention As described above, the hologram interferometer of the present invention does not require a standard ellipsoidal mirror surface, and can be manufactured easily and at low cost. Moreover, the measurement operation does not become complicated, and highly accurate quantitative surface shape measurement becomes possible.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a hologram interferometer for measuring the surface shape of an ellipsoidal mirror according to the present invention, Fig. 2 is a block diagram showing an optical system for producing a hologram, and Fig. 3 is a line diagram showing an example of interference fringes. It is a diagram. 1... Hologram interferometer, 2... Hologram production optical system, 3... Laser light source, 4... Reference light optical system, 5... Object light optical system, 6... Illumination light optical system, HP... Hologram , BS1, BS2...beam splitter, M1, M2, M3...reflector,
Mo1, Mo2, Mo3...Microscope objective lens, P
1, P2, P3...Pinhole, L1...Collimator lens, EM...Test ellipsoidal mirror surface.

Claims (1)

[Claims] 1 a laser light source, a beam splitter that splits the light beam from the laser light source into at least two light beams, a reference light optical system that generates a parallel reference light from one of the two light beams, and a diverging spherical wave light. and an illumination light optical system that generates illumination light, which is a diverging spherical wave light that illuminates an elliptical mirror surface of the object, from the other of the two light beams, The configuration is such that the light illuminates the hologram after being reflected by the object elliptical mirror surface, and interference fringes between the reproduced object light that is reproduced by illuminating the hologram with the reference light and the illumination light that illuminates the hologram. A hologram interferometer for measuring the surface shape of an ellipsoidal mirror, characterized in that it is configured to observe.