JPS6295430A - Large-size plane primary standard hologram interferometer - Google Patents

Abstract

PURPOSE:To eliminate worry about the fluctuation of a liquid level and dust and to prevent a body to be measured from being wet with liquid at every time of measurement by recording a reference plane formed of a liquid surface in an excellent state by holography, and performing reproduction and using a reproduced image as the reference plane every time a measurement is taken. CONSTITUTION:Luminous flux reflected by a surface 25 to be measured is modulated by being affected by the surface to be measured. This reflected luminous flux travels the optical path of incidence on the liquid surface 21 backward and reaches a beam splitter 2 through a parabolic mirror 12, a pinhole 11, and a converging lens 8, thereby illuminating a hologram H through the beam splitter 2. One pieces of luminous flux recorded in the hologram H is reproduced by said illumination, but the reproduced illumination light is modulated by being affected by the object surface 25, so reproduced body light 22a is also modulated pairing with one piece of luminous flux 22 and the reproduced body light 22a and one piece of luminous flux 22 interfere with each other to form interference fringes on a screen 16 through an observation lens 15. For the purpose, the interference fringes are observed to measure the surface shape of the object surface 25.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Purpose of the invention [Field of industrial application] This invention relates to hologram interference techniques for measuring the surface shape of a large-diameter plane mirror.

U Prior Art 1 When manufacturing large-diameter plane mirrors such as polygon mirrors, astronomical telescopes, mirrors for Rayleigh fusion, etc., a technique for measuring such plane mirrors with high precision is required.

Conventionally, plane mirrors have been made by polishing glass and coating the surface with metal such as aluminum, and usually have a diameter of 20 cm or less and an accuracy of about 0.5 μm. However, with the recent development of the Gui ψ Mondo 1 & board, its size has increased to 500 mPi in diameter! It has become relatively easy to produce metal mirrors with a high diameter, and their viscosity is not as good as that of glass mirrors, but it is approaching that, but it is now possible to measure the shape of these large-diameter mirror surfaces with high precision inside the cylinder. The technology to do so has not been developed.

For example, it is extremely difficult to measure a large-diameter plane with a diameter of 500 m with high precision. The reason for this is that it is difficult to create a plane that can serve as a reference for n-diameter 500 matings. In order to create this reference plane, a high-precision collimator lens with a diameter of 500 mm must be manufactured by polishing it with glass, but even if it were manufactured, its performance would have to be measured, and in the end, the measurement method was determined. I have to think about it. A-
The optics group at the Stralia Metrology Institute puts the sample to be measured into a container, fills it with liquid, sets the liquid level to li, and measures the surface. FIG. 3 shows the dead tree optical system of such an apparatus. l-1e -N O laser light source 51
A collimator lens 52 converts the laser light from the container into a parallel beam of light to illuminate the container 53 from above. The light reflected from the liquid surface 54 and the light reflected from the surface to be measured 55 interfere with each other, producing interference fringes. These lights return to the original optical path, are taken out by a half mirror 56, and interference fringes are projected onto a screen 58 by a projection lens 57. The resulting interference fringes become contour lines for each 1/2 wavelength. .

In this measurement, considering that the liquid surface used is curved by 131% due to the earth's gravity, this curve h is given by h = (x2)/(2r) from Figure 4. For a surface with a diameter of 500 sn, x=
0.25m Earth's radius r=6.367xlO3Km then h=
0.01μ roar. Therefore, if you use the liquid level, the diameter will be 500.
It is possible to create a reference plane with an error of 0.01 μm for #.

[Problems to be solved by the invention] However, in this way, the surface m11 with the liquid level as the reference plane
In the fixed method, there is a problem of surface tension in the formation of the liquid level, and for example, surface tension cannot be ignored near a wall. It is also affected by the liquid used.
For example, silicone oil (Dow Corning 70
4) Stickiness becomes a problem. Furthermore, it is also affected by the thickness of the liquid layer; for example, if the thickness of the liquid layer is increased, the liquid surface will vibrate, making it impossible to convert the ideal In order to do this, the depth of the liquid layer must be 1~
It is necessary to dig to a depth of 2mm. In addition, dust is also a serious problem, and this dust affects the load as it passes through the air.Furthermore, air vibration is also a problem, so special attention must be paid to air conditioning.

In this way, even with a lifting platform that uses the liquid level as a reference plane, it is difficult to always form such a liquid level in an ideal state when necessary; There is a need for the development of a technology that can reproduce the liquid level under normal conditions and measure flat surfaces with high precision.

This invention has been made in view of the above circumstances, and aims to provide an interferometer that can reproduce the ideal liquid level during measurement and measure the C plane with high precision. It's Otsu's.

(B) Structure of the Invention [Means for Solving the Problem] In response to this purpose, the large-scale planar prototype hologram interferometer of the present invention divides the light beams from the laser light source and the Rade light source into one light beam and the other light beam. A beam splitter that splits the light beam into two light beams, and a hologram that records the other light beam using the reflected light generated by reflecting the one light beam on a liquid surface located at the sample position as a reference light, The hologram is illuminated with the reflected light generated by reflecting the -1 beam of light at the sample position, and interference fringes between the reproduced object beam and the other beam of light are observed. It is characterized by its composition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the shoreline of the present invention will be described below with reference to sized drawings.

In FIG. 1, 1 is a hologram interference link.

The hologram interferometer 1 is equipped with a hologram IXH.

First, the creation of hologram I will be explained.

In FIG. 2, 10 is a hologram creation optical system for creating a hologram H. In FIG.

The hologram creation optical system 10 includes a beam splitter 2, and on the incident side of the beam splitter 2, for example, He-
It is equipped with a 1F light source 3 for generating Ne silane F, a mirror 4 for changing the optical path, a microscope objective lens 6, and a collimator lens 7.

In addition, a converging lens 8 is provided on the reflection side of the beam splitter 2.
Equipped with a pinhole 11, a parabolic mirror 12, and a trial r++
T? Liquid level 2 of the liquid 18 placed in the container 17 on the foot rest 13
1 is located.

On the other hand, the transmission side of the beam splitter 2 is provided with an optical path changing mirror 5, an optical path changing mirror 9, and a photographic plate Ha.

When creating a hologram 1, the SEE 1F light from the Rede light source 3 is made into a diverging light by the microscope objective lens 6 and parallel light by the collimator lens 7, and then the optical path is changed by the optical path changing mirror 4 to form a beam. Cut into splitter 2.

The parallel light beam incident on the beam splitter 2 is split into one parallel light beam 22 and the other parallel light beam 23, and one parallel light beam 22 passes through the beam splitter 2 and passes through the optical path changing mirror 5 and the optical path changing mirror. Shun changed the optical path and entered the photographic plate 1-18. One of the parallel light beams 22 incident on the photographic plate Ha is an object beam recorded on the hologram 1-1 (photographic plate Ha) by a reference destination to be described later.

The other parallel light beam 23 is reflected by the beam splitter 2 and made into a diverging light by the converging lens 8 and pinhole 11, and then changed its optical path by the parabolic mirror 12 and converted into a parallel light beam to reach the liquid surface 2.
1 and is reflected by the liquid surface 21. A portion of the light beam that is roughly divided into the liquid surface 21 enters the liquid 18 and is reflected by the bottom surface 24 of the container 17;
Since the bottom surface 24 is tilted relative to the bottom surface 24, the light reflected from the bottom surface 24 is emitted outside the system.

The light beam reflected on the liquid surface 21 passes through the optical path in the opposite direction when it entered the liquid surface 21 and reaches the parabolic mirror 12 and the pinball 11.
, and a converging lens 8 to reach the beam splitter 2, and is transmitted through the beam splitter 2 to illuminate the photographic plate 1-1a. The light that is reflected on the liquid surface 21 and reaches the photographic plate Ha functions as a reference beam when one of the light beams 22 is recorded on the photographic plate 1a (hologram 11) as an object beam. In this way, the photographic plate 1-1a recorded with the other beam 23 as the reference beam and the one beam 22 as the object beam is photographically processed to complete the hologram 1-1.The hologram interference i1 shown in FIG. An observation lens 15 and a screen 1 are included in the hologram creation optical system shown in Figure 2.
6 is added, the liquid surface 21 at the sample setting position 13 is removed, and the surface to be measured 25 is placed at that position. The hologram () is set at the position where the photographic plate 1-1a was.

[Operation] In the hologram interferometer 1 not shown in FIG. 1, the surface shape of the surface to be measured 25 is measured as follows.

First, the laser light source 3 is made to emit light, and the laser beam from the laser beam Ki3 is made into a diverging beam by the microscope objective lens 6, and is made into a flat 11 beam by the collimator lens 7, and then the optical path is changed by the optical path changing mirror 4. The beam enters the beam splitter 2. The parallel light beam incident on the beam splitter 2 is split into one parallel light beam 22 and the other parallel light beam 23, and one parallel light beam 22 passes through the beam splitter 2 and passes through the optical path changing mirror 5 and the optical path changing mirror 9. After changing the optical path at , the beam enters the hologram H. The other parallel light beam 23 is reflected by the beam splitter 2 and made into a diverging light by the converging lens 8 and bottle ball 11, and then changed to a parallel light beam by the parabolic mirror 12, and is then incident on the surface to be measured 25. , reflected by the surface to be measured 25.

The light beam reflected from the surface to be measured 25 (modulated due to the influence of the surface to be measured). This reflected light beam passes through the parabolic mirror 12 and the pinhole in the opposite direction of the optical path when it was incident on the liquid surface 21. 11 and a converging lens 8 to reach the beam splitter 2, and is transmitted through the beam splitter 2 to illuminate the hologram H.

This illumination reproduces one of the light beams recorded in the hologram H, but since the reproduced illumination light is modulated by the influence of the surface to be measured 25, the reproduced object light is thereby reproduced. 22a is also modulated with respect to one of the light beams 22, and the reproduced object light 22a and one of the light beams 22 interfere, and interference fringes are generated on the screen 16 through the observation lens 15.

Therefore, by observing these interference fringes, the measured surface 2
5 surface shapes can be measured.

(C) Effects of the Invention As described above, according to the hologram interferometer of the present invention, the reference plane created at the liquid level in good condition is recorded on the hologram, and when measuring, the reference plane is reproduced from the hologram. Therefore, there is no need to worry about vibrations or dust on the liquid surface each time a measurement is made, and it is possible to prevent the object to be measured from getting wet with the liquid.

In addition, interferometers generally use many optical systems such as mirrors and lenses, and their accuracy and aberrations pose problems, but the interferometer of the present invention can also be used to create holograms. The same aberrations also occur when reproducing 1 gram, so the vibrations caused by these aberrations cancel each other out and are removed.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing hologram interference t1 of the present invention,
Figure 2 is a configuration diagram showing the optical system for creating holograms, Figure 3
The figure is a block diagram showing the conventional 1,7581 cm, and FIG. 4 is a dimensional line diagram showing the curvature of the liquid level. 1...Interferometer 2...Beam splitter 3.
...Ray light source 4...Mirror for changing optical path 5
... Mirror for changing optical path 6 ... Microscope objective lens 7 ... Collimeter lens 8 ... Converging lens 9 ... Mirror for changing optical path 10 ... Hologram creation optical system 11 ... Pinhole 12... Parabolic mirror 13... Sample setting position 14... Sample 15... Observation lens 16... Screent]... Hologram 1-18... Photographic plate
17... Container 18... Liquid 21... Liquid level
22...One parallel light beam 23...Parallel light beam used 24...Bottom surface 25...Measurement surface

Claims (1)

[Claims] a laser light source and a beam splitter that divides the light flux from the laser light source into two light fluxes, one light flux and the other light flux;
and a hologram in which the other light beam is recorded using the reflected light generated by reflecting the one light beam on a liquid surface located at the sample position as a reference light, and the one light beam is reflected on the sample position located at the sample position. A large flat prototype hologram interferometer, characterized in that it is configured to illuminate the hologram with reflected light generated by reflection and observe interference fringes between the reproduced object beam and the other light beam.