JP3410796B2 - Surface alignment method and apparatus for interferometer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a test surface alignment method and apparatus for adjusting the position of a test surface in an interferometer.

[0002]

2. Description of the Related Art Generally, an interferometer divides a light beam from a light source into two, reflects the divided light beam on a reference surface and a surface to be inspected which are arranged in a predetermined positional relationship, and reflects them. It is configured to form interference fringes on the screen by the interference action of the two light beams, and by observing the interference fringes, it is possible to evaluate the uneven shape of the test surface.

In order to accurately evaluate the surface to be inspected by this interferometer, it is essential that the reference surface and the surface to be inspected are accurately arranged in the above-mentioned predetermined positional relationship. For this reason,
Conventionally, an interferometer is provided with a surface-to-be-inspected alignment device that adjusts the position of the surface to be inspected so as to obtain the predetermined positional relationship.

For example, as shown in FIG. 7, an inspected surface alignment apparatus in a Fizeau interferometer has an interferometer main body 11 as shown in FIG.
0a includes an alignment optical system 160 and an object support adjusting mechanism 120 for mechanically adjusting the position of the surface 102a to be inspected. The alignment optical system 160 arranges the half mirror 162 in the optical path between the light source 112 and the reference surface 118a, and causes the imaging lens 164 to image the bright spot of the light source 112 on the alignment screen 166. There is. And
The reference plane 118 on the alignment screen 166
The bright spot formed by the reflected light from a and the test surface 102a
The subject support adjusting mechanism 120 is operated so that the bright spot formed by the reflected light from the subject overlaps with the bright spot.
The position of a (inclination angle, etc.) is adjusted.

[0005]

However, since the alignment optical system 160 is provided in the interferometer main body 110a in the above-mentioned conventional surface-to-be-inspected alignment apparatus, the interferometer becomes large and the cost is high. Was becoming.

The alignment optical system 1 as described above is used.
Instead of providing 60, it is also possible to perform the alignment of the surface to be inspected using a television camera. That is, FIG.
As shown in FIG.
26a functions as a screen for forming the interference fringes, but if the focal length of the lens system of this television camera is changed so that the bright spot of the light source 112 is imaged on its image plane 126a, the television monitor 128 is shown. CRT128
The position adjustment of the subject surface 102a is performed by operating the subject support adjusting mechanism 120 so that the two bright spots imaged by the respective reflected lights from the reference surface 118a and the subject surface 102a overlap on a. It is possible to

However, in this case,
It is necessary to adjust the focal length of the lens system of the TV camera 126 for alignment of the surface to be inspected, and a new structure is required for that purpose, which causes a problem that the interferometer becomes large and costly. .

The present invention has been made in view of the above circumstances, and it is possible to perform the alignment of the surface to be inspected without inviting the interferometer to be large-sized and costly. It is an object of the present invention to provide a surface alignment method and device.

[0009]

The present invention achieves the above object by providing a shield piece in the optical path of a light beam and using the image of the shield piece to perform surface alignment on a test surface. This is what was planned.

That is, the interferometer test surface alignment method according to the present invention, as described in claim 1, divides the light beam into two, and arranges the two divided light beams in a predetermined positional relationship. In an interferometer configured to reflect on a reference surface and a surface to be inspected and to form an interference fringe on a screen by an interference action of the two reflected light beams, the object to be measured is set to obtain the predetermined positional relationship. A method of aligning a surface to be inspected, comprising:
A shield piece for shielding a part of the light beam is inserted into the optical path of the light beam before being split, and in this state, the shield piece formed on the screen by each of the two divided light beams is inserted. It is characterized in that the position of the surface to be inspected is adjusted so that the two images are superposed on one another.

The interferometer surface to be inspected according to the present invention divides the light beam into two and arranges the divided two light beams in a predetermined positional relationship. In an interferometer configured to reflect on a reference surface and a surface to be inspected and to form an interference fringe on a screen by an interference action of the two reflected light beams, the object to be measured is set to obtain the predetermined positional relationship. A surface alignment device for adjusting a position of a surface to be inspected, comprising: a shielding piece provided in an optical path of the light beam so as to block a part of the light beam before being divided into two; A test surface position adjusting mechanism for adjusting the position of the test surface so that the two images of the shielding piece formed on the screen by each of the light beams overlap. It is a feature That.

The "shielding piece" is not particularly limited in its shape and size as long as it can form an image on the screen whose position on the test surface can be adjusted. A sewing needle, a member supporting a cross ultrafine metal wire, a transparent plate on which a cross is marked, or the like can be used.

The position of the "shielding piece" is not particularly limited as long as it is "in the optical path of the light beam before being divided into two", and in short, the position of the test surface can be adjusted. Any position may be used as long as it can form a different image on the screen.

Further, the "shielding piece" may be held by hand and inserted, or may be attached to an interferometer. In this case, the shielding piece may be left in the optical path of the light beam before being divided into two even after the alignment of the surface to be inspected is completed.
In view of the fact that when the shielding piece remains, it may be difficult to observe the interference fringes on the screen due to the image, and therefore, as described in claim 3, the shielding piece is disposed at a position within the optical path and the optical path. It may be movably provided so as to be able to take an external position.

[0015]

As described above, in the invention described in claim 1, in the optical path of the light beam before being divided into two, a shielding piece for blocking a part of the light beam is inserted, and In this state, the position of the surface to be inspected is adjusted so that the two images of the shielding piece formed on the interference fringe formation screen by each of the two divided light beams are adjusted so that the position of the surface to be inspected is adjusted. As described above, it is possible to perform the alignment of the surface to be inspected by a simple operation of inserting the shielding piece without needing to provide an alignment optical system or the like. Therefore, the interferometer can be significantly reduced in size and cost.

In the invention according to claim 2, 2
Two images of a shielding piece provided in the optical path of the light beam before being divided and a shielding piece formed on the screen by each of the two divided light beams are Since the test surface position adjusting mechanism for adjusting the position of the test surface to be overlapped with each other is provided, the test surface alignment can be performed with an extremely simple configuration. For this reason, the interferometer can be significantly reduced in size as compared with the case where the alignment optical system is provided in the interferometer or the focal length adjusting mechanism of the lens system of the TV camera is provided as in the conventional device for inspecting a surface. And cost can be reduced.

As described above, according to the present invention, the surface to be inspected can be aligned without increasing the size and cost of the interferometer.

In addition to the above structure, as described in claim 3, the shielding piece is movably provided so as to be able to take a position inside the optical path of the light beam before being divided into two and a position outside the optical path. With this configuration, it is possible to prevent the shielding piece from interfering with the observation of interference fringes.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for aligning a surface to be tested of an interferometer according to the present invention will be described below.

FIG. 1 is a block diagram showing a Fizeau interferometer 10 in which the test surface is aligned according to this embodiment.

Before describing the method for aligning a surface to be tested according to this embodiment, an outline of the Fizeau interferometer 10 will be first described.

This Fizeau interferometer 10 includes a laser 12
A diverging lens 14, a collimator lens 16, a reference plate 18, a subject support adjusting mechanism 20, and a half mirror 2.
2, an imaging lens 24, a television camera 26, and a television monitor 28, and the interferometer body 1 except for the reference plate 18, the subject support adjusting mechanism 20, and the television monitor 28.
0a, the reference plate 18 and the subject support adjusting mechanism 20 are attached to the interferometer main body 10a, and the television monitor 28 is connected to the television camera 26.

The light beam emitted from the laser 12 and diverged by the diverging lens 14 is collimated by the collimator lens 16 and then incident on the reference plate 18. The reference plate 18 is a flat plate member having a semi-transparent mirror plane 18a (reference plane) with extremely high flatness on the side opposite to the collimator lens, and parallel light from the collimator lens 16 is incident on the semi-transparent mirror plane 18a from a vertical direction. Is pre-positioned so that

On the anticollimator lens side of the reference plate 18, the subject 2 is supported by the subject support adjusting mechanism 20 at a predetermined distance from the reference plate 18. This subject 2
The surface of the collimator lens side is the test surface 2a (test surface), and the test object support adjusting mechanism 20 is arranged so that the test surface 2a is parallel to the semi-transparent mirror plane 18a of the reference plate 18.
The inclination angle of the test plane 2a is adjusted by the operation.

The half mirror 22 is a diverging lens 14
Is provided in the optical path between the collimator lens 16 and the collimator lens 16, and a part of the return light from the collimator lens 16 reflected by the semi-transparent mirror plane 18a and the plane 2a to be inspected is transmitted via the imaging lens 24 to the television camera. An image is formed on an image forming surface 26a composed of 26 CCDs. And
This image formation signal is input to the television monitor 28 and its CR
The image is displayed on T28a.

If the flat surface 2a to be inspected has irregularities or the like, a phase shift occurs between the reflected light from the semi-transparent mirror plane 18a and the reflected light from the flat surface 2a to be inspected, and the interference action of both reflected lights accompanying this occurs. As a result, interference fringes are formed on the image forming surface 26a of the television camera 26. Therefore, by observing the interference fringes on the CRT 28a of the television monitor 28, the inspection plane 2
It is possible to evaluate the uneven shape of a.

In order to accurately evaluate the surface to be inspected in this Fizeau interferometer, the plane 2a to be inspected is replaced by the semi-transparent mirror plane 18.
It is important to perform the above evaluation in the state of being placed exactly parallel to a.

Therefore, in this embodiment, prior to the evaluation of the surface to be inspected, the surface to be inspected is aligned by the following method so that the parallelism between the semi-transparent mirror plane 18a and the plane to be inspected 2a is sufficiently secured. Has become.

That is, as shown in FIG. 1, first, a needle-shaped shield piece 30 for shielding a part of the light beam is inserted into the optical path of the light beam between the collimator lens 16 and the reference plate 18. As a result, on the image forming surface 26 a of the television camera 26, the shield piece 30 is reflected by the reflected light from the semitransparent mirror plane 18 a of the reference plate 18 and the reflected light from the test plane 2 a of the subject 2.
CRT 28a of the TV monitor 28
These images will appear above.

Here, the semi-transparent mirror plane 18a of the reference plate 18
Has a very high flatness and is exactly perpendicular to the parallel light from the collimator lens 16, so that the shielding piece 30 formed by the reflected light from the semi-transparent mirror plane 18a.
The image of the CRT 28 on the TV monitor 28 is as shown in the figure.
The image P ₁ appears at a predetermined position on a.

On the other hand, the image P ₂ of the shield piece 30 formed by the reflected light from the test surface 2a of the test object 20 is as described above unless the test surface 2a is tilted with respect to the semi-transparent mirror plane 18a. overlaps the image P ₁ and the one, if該被detection plane 2a is long inclined with respect to the semitransparent mirror plane 18a, does not overlap the the one the image P _1, as shown, of the television monitor 28 C
The image P ₁ and the image P ₂ appear on the RT 28a at positions displaced from each other. Therefore, in this way, the TV monitor 28
When the two images P ₁ and P ₂ appear on the CRT 28a of FIG. 2, the subject support adjusting mechanism 20 is adjusted until the image P _{2 and the} image P ₁ overlap with each other as shown in FIG. Two
The surface to be inspected is aligned by changing the inclination angle of a.

After the alignment of the surface to be inspected is completed, the shield piece 30 is removed from the optical path to prepare for interference fringe evaluation on the CRT 28a of the television monitor 28.

As described above in detail, in the present embodiment, the shielding piece 30 for blocking a part of the light beam is inserted in the optical path of the light beam between the collimator lens 16 and the reference plate 18, and this state is set. Then, the subject is supported so that the two images P ₁ and P _{2 of the} shielding piece 30 appearing on the CRT 28a of the television monitor 28 are overlapped by the reflected light from the semi-transparent mirror plane 18a and the reflected light from the test plane 2a. Since the position of the flat surface 2a to be inspected is adjusted by operating the adjusting mechanism 20, the inspection surface can be aligned by a simple operation of inserting the shielding piece 30.

Therefore, according to the present embodiment, it is possible to carry out the alignment of the surface to be inspected without causing the Fizeau interferometer 10 to become large and expensive.

In this embodiment, the insertion portion of the shield piece 30 is set between the collimator lens 16 and the reference plate 18, but the shield piece 30 is inserted in the optical path closer to the laser 12 than the collimator lens 16. You may make it set a location. However, since the flat surface 2a to be inspected is normally formed by the lens 16 and the lens 24 so as to form an image on the image forming surface 26a, the shield piece 30 is shielded when it is closer to the subject 2 or the reference plate 18. A clear image of the piece 30 is obtained.

It is needless to say that the shielding piece 30 may be held by hand and inserted into the optical path during alignment of the surface to be inspected. However, the shielding piece 30 may be inserted into the Fizeau interferometer 1.
It may be configured as a part of 0. For example, as shown in FIG. 3, the needle-shaped shield piece 30 is attached to the interferometer body 10a.
A structure in which the shield piece 30 is rotated between the position inside the optical path and the position outside the optical path by operating the dial 30a provided at the base end of the shield piece 30. Can be With such a mounting structure, the shield piece 30 is inserted into the optical path for alignment of the surface to be inspected, while the shield piece 30 is removed from the optical path during the subsequent measurement to interfere with the interference fringe evaluation. Can be prevented.

Instead of the needle-shaped shield piece 30 as described above,
As shown in FIG. 4, a shield piece 30 'or the like in which a cross-shaped ultrafine metal wire is supported by a ring-shaped member may be used.

In the above embodiment, the alignment of the surface to be detected in the Fizeau interferometer 10 has been described.
In other interferometers, the surface to be inspected can be similarly aligned.

For example, as shown in FIG. 5, in the Michelson interferometer 40, by inserting the shielding piece 30 in the optical path closer to the laser 12 than the half mirror 42,
In addition, as shown in FIG. 6, a Mach-Zehnder interferometer 50
In the above, by inserting the shield piece 30 in the optical path closer to the laser 12 than the half mirror 52 closer to the laser 12, the shield piece formed by the reflected light from the semi-transparent mirror plane 18a is inserted, as in the above embodiment. 30 is an image P ₁ and an image P _{2 of the} shield piece 30 formed by the reflected light from the test plane 2a.
By using and to adjust the position of the plane to be inspected 2a so that the two images P ₁ and P _{2 of the} shield piece 30 appearing on the CRT 28a of the television monitor 28 overlap with each other, alignment of the surface to be inspected is performed. You can

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment in which a method for aligning an inspected surface of an interferometer according to the present invention is applied to a Fizeau interferometer.

FIG. 2 is a diagram showing an image of a shielding piece appearing on a CRT of a television monitor in the above embodiment.

3 and 4 are perspective views showing a specific example of the mounting structure of the shielding piece used in the above embodiment.

FIG. 5 is a diagram showing an embodiment in which the method for aligning a surface to be tested of an interferometer according to the present invention is applied to a Michelson interferometer.

FIG. 6 is a diagram showing an embodiment in which the method of aligning a surface to be tested of an interferometer according to the present invention is applied to a Mach-Zehnder interferometer.

FIG. 7 is a diagram showing an example in which a conventional method of aligning a surface to be tested of an interferometer is applied to a Fizeau interferometer.

[Explanation of symbols]

2 subject 2a test plane (test surface) 10 Fizeau interferometer 10a interferometer body 12 laser 14 diverging lens 16 collimator lens 18 reference plate 18a semi-transparent mirror plane (reference surface) 20 subject support adjusting mechanism 22 half mirror 24 an imaging lens 26 television camera 28 TV monitor 28a CRT 30, 30 'shielding piece 40 Michelson interferometer 50 image P ₂ test plane of the shield piece formed by the reflected light from the Mach-Zehnder interferometer P ₁ semitransparent mirror plane Image of shield piece formed by reflected light from

Claims (3)

(57) [Claims] 1. A light beam is divided into two, and the two divided light beams are respectively reflected by a reference surface and a surface to be inspected arranged in a predetermined positional relationship, and the reflected light beams interfere with each other. In an interferometer configured to form interference fringes on a screen, a test surface alignment method for adjusting the position of the test surface so as to obtain the predetermined positional relationship, which is before the division into two. A shielding piece that blocks a part of the light beam is inserted in the optical path of the light beam, and in this state, two images of the shielding piece formed on the screen by each of the two divided light beams are A method for aligning a surface to be tested of an interferometer, which comprises adjusting the position of the surface to be tested so that the two surfaces overlap each other. 2. A light beam is divided into two, and the two divided light beams are respectively reflected by a reference surface and a surface to be inspected arranged in a predetermined positional relationship, and the reflected light beams interfere with each other. In an interferometer configured to form interference fringes on a screen, a test surface alignment device for adjusting the position of the test surface so as to obtain the predetermined positional relationship, which is before the division into two. A shield piece provided in the optical path of the light beam so as to shield a part of the light beam, and two images of the shield piece formed on the screen by each of the two divided light beams are unified. An inspected surface alignment apparatus for an interferometer, comprising: an inspected surface position adjusting mechanism for adjusting the position of the inspected surface so as to be overlapped. 3. The inspected surface of the interferometer according to claim 2, wherein the shielding piece is provided so as to be movable so as to be able to take a position inside the optical path and a position outside the optical path. Alignment device.