JPH05272915A - Method and screen for positioning sample under test when cylindrical surface is measured - Google Patents

Abstract

PURPOSE:To make it possible to perform simple position alignment by adjusting the shifting amount of a sample under test with respect to a positioning screen and the rotating amount of the positioning screen at the centers of a horizontal axis, a vertical axis and orthogonally intersecting axes, respectively. CONSTITUTION:Reflected reffraction light 3, which has passed through a slot-shaped light transmitting part 63, is reflected from a cylindrical (omitted hereinafter) surface 51a. A sample under test 51 is moved in the direction of a (z) axis so that an adjusting projected image 73 of the luminous flux reflected from the surface 51a is projected in thin line. Thus, the amount of displacement is adjusted. The surface 51a is turned so as to make the projected image 73 vertical, and the amount of the rotating displacement at the center of the (z) axis is adjusted. Then, a positioning screen 61 is moved in the lateral direction, and the diffraction light 35 is incident on a passing light transmitting part 65. For the luminous flux, which can not be transmitted through the light transmitting part 65, a reference projected image is formed on the screen 61. For the reflected light of the passed luminous flux, the projected image 73 is formed. At this time, the surface 51a is turned at the center of the (x) axis. The projected image 73 is aligned with the same position of the passing luminous flux in the direction of the (x) axis. The amount of the rotating displacement of the center of the (x) axis is adjusted. The surface 51a is turned at the center of the (y) axis, and the projected image 73 is moved so as to be overlapped with the projected image 71. Then, the amount of the rotating displacement at the center of the (y) axis is adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is directed to a cylindrical light from an interferometric system which is converged at a focal point and then diverged to irradiate the cylindrical surface of a sample to be tested, and the irradiated light is reflected by the cylindrical surface to cause a reverse optical path. The present invention relates to a method of aligning a test sample when the shape of the cylindrical surface of the test sample is measured by an interferometry method, and a positioning screen used at that time.

[0002]

2. Description of the Related Art Interferometry is known as a method for precisely measuring the surface shape of optical elements such as lenses and mirrors having spherical or aspherical surfaces. To measure the surface shape by the interferometry method, an interference prototype having an ideal surface shape is used, and the reflected light from the prototype interferes with the reflected light from the sample to be inspected, and the generated interference fringes are observed to observe the interference pattern. This is a very convenient method because it measures the amount of displacement of the inspection surface, and the manufacturing error of the surface to be inspected can be detected with high accuracy without contact.

Further, since it is difficult to manufacture an aspherical prototype such as a cylindrical surface, a hologram optical element (HOE) which reproduces the same wavefront as the ideal shape of the surface to be tested by using computer hologram has been recently used. An interferometry method is adopted which is created and used in place of the conventional prototype.

The applicant takes the conventional hologram interferometry one step further, and provides a hologram interferometer capable of forming a flat reflecting surface without requiring an aspherical surface or a spherical surface as a surface for generating reference light. Filed (Japanese Patent Application No. 3-18
7646, Japanese Patent Application No. 3-187647).

In the interferometer, the plane for generating the reference wave can be positioned and fixed in the measurement of the same plane,
It is necessary to replace the test sample for each test. Therefore, every time the test sample is replaced, the alignment is accurately performed, and the object wave from the test sample and the reference wave are superimposed on the projection surface such as a projector or the CCD of the TV camera to obtain a desired interference fringe. It is important to generate it.

When the measurement of the spherical surface is considered for the alignment of the sample to be inspected, the sample to be inspected is fixed on the sample table, and the X-axis, Y-axis and Z-axis are adjusted so as to obtain a desired interference pattern while observing the interference pattern. The test sample was adjusted by moving it in the axial direction. However, when considering the measurement of the cylindrical surface, there are an axial displacement and a rotational displacement about the axis in a total of three directions, that is, the central axial direction of the cylindrical surface and two directions orthogonal to this. It was difficult to easily adjust the.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a method and a screen for alignment that enable easy alignment when measuring the surface accuracy of a cylindrical surface by an interferometry method.

[0008]

A method of aligning a sample to be tested at the time of measuring a cylindrical surface of the present invention is such that a cylindrical light from an interferometric system is converged at a focus and then diverged to irradiate the cylindrical surface to be tested. , When the reflected light from the cylindrical surface is guided to the interferometric system through the reverse optical path and the shape of the cylindrical surface to be measured is measured by the interferometry method, the central axis of the cylindrical surface to be measured is the y-axis, and the y-axis is the y-axis in the spreading direction of the cylindrical surface When the axis orthogonal to the x axis is the x axis and the axis orthogonal to the x axis and the y axis is the z axis, interference measurement is performed using a positioning screen made of a light diffusing plate having a slotted through hole extending in the y axis direction. Arrange the alignment screen so that the cylindrical light from the system passes through the slotted hole at or near its focal point, and reflect it from the cylindrical surface to be tested. There adjusting the projected image projected formed on a screen for alignment is moved adjust the position of the test cylindrical surface so as to focus linearly in the z-axis direction,
Moreover, the cylindrical surface to be measured is rotationally adjusted about the z-axis so that the linear projection image for adjustment is horizontal to the long hole-shaped through hole, and the light having the through hole for partially passing is also used. Using a positioning screen consisting of a diffuser, a part of the cylindrical light in the central axis direction of the cylindrical surface to be tested is selectively passed through at or near its focal position of the cylindrical light from the interferometric system. The alignment screen is arranged so that the remaining cylindrical light forms a linear reference projection image on the alignment screen while passing through the hole, and the cylindrical surface to be tested is rotated about the x-axis. As a result, the reflected light from the test cylindrical surface moves the adjustment projection image formed on the alignment screen in the length direction of the reference projection image, and the y-axis By rotating the cylindrical surface to be inspected as the center, the adjustment projection image is moved in the direction orthogonal to the length direction of the reference projection image, and the reference projection is made up to the passage position of the cylindrical light in the through hole for partial passage. Characterized by moving the image.

Further, the screen for aligning the sample to be tested at the time of measuring the cylindrical surface of the present invention has a slotted through hole,
A light having a part-passing through hole, which is shorter than the elongated hole-like hole provided continuously or independently to the elongated hole-like hole, is formed on the longitudinal side portion of the elongated hole-like hole. It is characterized by comprising a diffusion plate.

[0010]

EXAMPLES As described above, the present applicant previously applied for an interferometer using a reflective or transmissive hologram optical element.

An interferometer using this reflection-type hologram optical element collimates a light source for outputting a laser beam, a beam diverging means for diverging a laser beam output from the light source, and a laser beam output from the beam diverging means. The parallel light converting means for converting the light into parallel light, the reflection type hologram optical element for reflecting the parallel light emitted from the parallel light converting means in one direction and reflecting and diffracting to the sample side, and the reflection type hologram optical element are reflected. It is equipped with a flat reference reflector that reflects parallel light, and the reflected light reflected from the reference reflector and the reflected light reflected from the test sample can be reflected by the reflective hologram optical element and interfere with each other. It is characterized in that it is configured as follows.

On the other hand, an interferometer using a transmissive hologram optical element is a semi-transparent mirror plane on which the parallel light output from the parallel light converting means is vertically incident instead of the reflective hologram optical element and the reference reflection plate. And transmission type hologram optics having a hologram surface for separating parallel light incident from the plane of the semi-transparent mirror into refracted light and transmitted diffracted light with which the test sample is irradiated, and emitting these two lights in different directions. An element is provided, and it is configured so that the transmitted diffracted light reflected from the test sample, re-diffracted by the hologram surface and passed through the hologram optical element, and the reflected light reflected from the semi-transparent mirror plane can interfere with each other. It is characterized by

The case where the present invention is applied to the above-mentioned reflection type hologram interferometer will be described below as an example.

FIG. 1 is an explanatory diagram showing a configuration example of the above-mentioned transmission hologram interferometer. He-Ne laser light source 11
The laser beam emitted from the pinhole 1 is narrowed down by the condenser lens 13, the noise component is removed, and the pinhole 1
Diverging from 5. This divergent light is emitted from the beam splitter 17
After passing through, the light enters the collimator lens 19 (parallel light conversion means), is transmitted and becomes a parallel light flux, and enters the reflection hologram optical element 31.

The reflection type hologram optical element 31 has a reflection type diffraction grating (striped pattern) formed in the direction perpendicular to the paper surface, and the pitch width (P) of the diffraction grating is changed to change the wavelength (λ) of the laser beam. ) And P · (sin α-sin
By controlling the size of the first-order diffraction angle θ from the relationship of θ) = λ (α is the incident angle of a parallel light beam), the same as a cylindrical reflecting surface having a central axis (y-axis in FIG. 2) in the direction perpendicular to the paper surface. Act on. Therefore, when the parallel light flux (plane wave) enters from the collimator lens 19, two reflected light fluxes of the normal reflected light 37 and the reflected diffracted light 35 are generated.
The reflection type hologram optical element 31 is formed by applying a photolithography method using electron beam drawing based on computer calculation and forming a reflection diffraction grating film of chromium, aluminum or the like by a conventional method. Therefore, the cylindrical light having the same wavefront as the ideal cylindrical surface 51a of the test sample 51 can be reproduced.

The test sample 51 is aligned so that the reflected diffracted light 35 enters the cylindrical surface 51a of the sample 51 to be reflected, passes through the reverse optical path, and enters the reflective hologram optical element 31 again. Are arranged. 6
Reference numeral 1 is a screen for this alignment, which will be described in detail later. The reflected diffracted light 35 (cylindrical light, that is, an aspherical wave) from the reflective hologram optical element 31 converges once, then diverges and is reflected by the cylindrical surface 51a of the sample 51 to be an object wave light, and again the reflective hologram. A plane wave is generated by being diffracted by the optical element 31.

On the other hand, the normal reflected light 37 from the reflection type hologram optical element 31 is reflected by the reference reflection plate 33 and enters the reflection type hologram optical element 31 again, and this reference wave light and the above object wave light are holograms. The optical elements 31 overlap with each other and interfere with each other, and form an interference fringe on the light receiving surface (CCD) of the TV camera 23 by the imaging lens 21 through the collimator lens 19 and the beam splitter 17. When the cylindrical surface 51a of the test sample 51 has a surface shape as designed (no displacement from the ideal surface), no stripes are observed at all or linear stripes at equal intervals are observed. The configurations 11 to 23 in FIG. 1 indicate the Fizeau interferometer body. Further, since it is possible to efficiently obtain the interference fringes when the light quantities of the reference wave light and the object wave light are about the same, it is possible to prepare the standard reflection plate 33 having the reflectance according to the reflectance of the sample 51 to be tested. desirable.

According to the interferometer and the measuring method as described above, it is possible to use a planar reflector as a surface for generating a reference wave, and an aspherical or spherical reference reflector is not required. It is extremely easy, and the positioning of the reference reflector is simple, and the measurement is extremely easy.

However, as described above, conventionally, the alignment of the sample 51 to be tested has been troublesome. In the present invention, at the time of this alignment, the alignment screen 6
1 is used. FIG. 2 shows a reflection hologram optical element 31,
6 is an explanatory diagram showing a positional relationship between a test sample 51 and a positioning screen 61. FIG. 3 to 6 are explanatory views showing an embodiment at the time of position alignment.

The alignment screen 61 is made of a light diffusing plate such as frosted glass, and when visible laser light from the He-Ne laser 11 or the like is irradiated and projected onto the surface of the screen 61 other than the through hole forming portion. , Its position and shape are clearly visible. The positioning screen 61 has a through hole 63 having a long hole-like hole 63 and a partially passing through hole 65 formed continuously from a substantially central portion thereof so as to project in a right angle direction. Has been drilled.

Now, the cylindrical surface 5 of the test sample 51
The central axis of 1a is the y axis, the axis orthogonal to the y axis in the spreading direction of the cylindrical surface 51a is the x axis, and the axis orthogonal to the x axis and the y axis is the z axis. At this time, the alignment screen 61 is arranged so that the elongated hole-shaped through-hole portion 63 extends in the y-axis direction so that it is transparent at the focal position of the cylindrical light 35 (reflected diffracted light 35) from the reflective hologram optical element 31. The cylindrical light 35 is arranged so as to pass through the holes 63 or 65. The cylindrical light 35 is converged or diverged in the x-axis direction, and neither converged nor diverged in the y-axis direction.

For alignment, the sample to be tested is fixed on a sample mounting table (not shown), the position is visually adjusted in the y-axis direction and the x-axis direction, and then the shift amount in each axis direction is set as follows. And adjust the amount of rotation. It should be noted that in the y-axis direction and the x-axis direction, the light beam may be incident on the cylindrical surface 51a substantially vertically.

(1-0) At the time of adjustment, first, the screen 61 is visually inspected to make a rough adjustment so that an image appears on the monitor screen 25.

(1-1) Shift in z-axis direction: As shown in FIG. 2, the cylindrical light 35 from the reflection hologram optical element 31 is passed through the elongated hole-shaped hole portion 63 of the alignment screen 61 ( The passing light flux is not shown in FIG. 3). The light flux that has passed through the elongated hole-shaped hole portion 63 and is reflected by the cylindrical surface 51a of the test sample 51 has a back surface (cylindrical surface) of the screen 61 when the cylindrical surface 51a is displaced from the normal position in the z-axis direction. 51
3A cannot be converged on (a side) (cannot be focused), and FIG.
The projected image 73 for adjustment that is expanded as shown in FIG.

Here, as shown in FIG. 3B, the sample 5 to be inspected is so arranged that the adjustment projection image 73 is projected as a thin line.
By moving 1 in the z-axis direction, the adjustment of the displacement amount in the z-axis direction is completed.

(1-2) Rotation about the z-axis: The adjustment projection image 73 obtained by the above-mentioned operation is shown in FIG. Is inclined with respect to the cylindrical light 35), the cylindrical surface 51a is rotated around the z axis (Rz direction in FIG. 2), and the adjustment projection image 73 is vertically changed as shown in FIG. 4B. The adjustment of the displacement amount of the z-axis in the rotation direction is completed by setting.

(1-3) Rotation around the x-axis: FIG. 5 (A)
As shown in FIG. 5, the alignment screen 61 is moved in the lateral direction at the focal position of the cylindrical light 35 so that the cylindrical light 35 enters the partially passing through hole portion 65. At this time, in the cylindrical light 35, the entire light flux cannot pass through the partially passing through hole portion 65 in the y-axis direction, and a part thereof is projected on the screen 61 to form a reference projected image 71. To do. On the other hand, the light flux that has passed through the partially passing through-hole portion 65 (the passing light flux is not shown) is reflected by the cylindrical surface 51 a and forms the adjustment projection image 73 on the screen 61. The cylindrical surface 51a is rotated (Rx) about the x-axis to move the adjustment projection image 73 in the length direction of the elongated hole-shaped hole portion 63 as shown in FIG. By adjusting the position of the light flux that has passed through the through hole portion 65 in the y-axis direction, the adjustment of the displacement amount in the rotation direction of the x-axis ends.

(1-4) Rotation about the y-axis: The cylindrical surface 51a is rotated (Ry) about the y-axis, the above operation is completed, and the projected image for adjustment 73 at the position shown in FIG. 6 (A).
Is moved so as to be superposed on the light flux that has passed through the partially transmitting through-hole portion 65, whereby the adjustment of the displacement amount of the rotation about the y-axis is completed. As shown in the drawing, the width of the partially passing through hole portion 65 is gradually changed to allow the cylindrical light 35 to pass through the wide portion, and the adjustment projection image 73 is moved from the narrow portion to the wide portion during adjustment. As a result, until just before the reference projection image 71 and the adjustment projection image 73 overlap,
The adjustment projection image 73 is formed on the surface of the screen 61 and can be viewed, which is convenient.

When the alignment using the screen as described above is completed, the reflected light from the sample comes to hit the light receiving surface of the TV camera 23. Therefore, from here, the position of the sample can be adjusted while observing the image on the monitor screen 25.

(2-1) Rotation around the z-axis: When the reflected light from the sample has aberration, it does not become a point on the monitor image and is blurred as shown in FIG. 3 (C). By adjusting the rotation around the z-axis, it changes linearly as shown in FIG.

(2-2) Shift in z-axis direction: If the position of the sample in the z-direction is not aligned, the light spreads laterally. By combining these, the monitor screens shown in FIGS.
It becomes like (C).

(2-3) By adjusting the rotation around the x-axis, the monitor screens shown in FIGS.
It becomes like (C).

(2-4) By adjusting the rotation around the y-axis, the monitor screens shown in FIGS.
It becomes like (C).

With the above, the position adjustment of the sample is almost completed. Fine adjustment is performed so that the interference fringe can be observed on the TV monitor screen and a desired pattern is obtained.

The positioning method and the positioning screen of the present invention can be variously modified and applied, and one example thereof is as follows.

For example, as the alignment screen 61, the one of the embodiment shown in FIGS. 7 to 10 is used. Figure 7
Is a part of the through-hole 65 for passage is formed to have a uniform width. In FIG. 8, the through-hole portion 65 for passing a part of the through-hole portion 6
3 is formed from the end portion in the length direction. Also,
In FIG. 9, a long hole-shaped through hole portion 63 and a partially passing through hole portion 65 are formed independently on one screen 61. Further, FIGS. 10A and 10B show two alignment screens, a screen 61 having an elongated hole-shaped hole portion 63 formed therein and a screen 61 having a partially-passing hole portion 63 formed therein. It shows the case of using in combination.

Further, the adjustment order of each axis is not limited to the above embodiment, and for example, the x-axis rotation direction and the y-axis rotation direction may be adjusted simultaneously.

Further, the present invention is not limited to the interferometer using the reflection type hologram optical element, but can be applied to other hologram interferometers, interferometers using an interferometer having an ideal cylindrical surface, and the like.

FIG. 11 is a schematic diagram showing an example of the above-mentioned transmission hologram interferometer. A transmission hologram optical element 41 is used instead of the reflection hologram optical element 31 and the reference reflection plate 33 in FIG. Other than the above, the principle of measuring the interference fringes and the principle of aligning the test sample 51 are the same as those shown in FIGS. A semi-transparent mirror film 41a is formed on the incident surface of the transmissive hologram optical element 41, and partially reflected light from this is used as reference wave light. Also,
The first-order transmitted diffracted light 45 from the hologram surface 41b formed on the other surface of the transmissive hologram optical element 41 is made incident on and reflected by the sample 51 to be inspected to generate an object light wave, and an interference fringe is obtained. The hologram surface 41b reproduces a wavefront corresponding to an ideal cylindrical surface of the test sample 51 as the refracted diffracted light 45, and the positioning of the cylindrical surface 51a is performed by the positioning screen 61.

[0040]

According to the alignment method and the alignment screen of the present invention, when the displacement amount of the cylindrical surface of the test sample from the ideal surface is measured by the interferometry method,
The position of the test sample can be adjusted by an extremely simple operation. Moreover, since the necessary members only need to be a screen having a simple structure including a light diffusing plate, the interferometer does not become large and the cost does not increase.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of an interferometer used in the present invention.

FIG. 2 is a perspective explanatory view showing the relationship between the hologram optical element, the alignment screen, and the test sample during alignment according to the present invention.

FIG. 3 is an explanatory diagram showing a positioning method of the present invention.

FIG. 4 is an explanatory diagram showing a positioning method of the present invention.

FIG. 5 is an explanatory diagram showing a positioning method of the present invention.

FIG. 6 is an explanatory diagram showing a positioning method of the present invention.

FIG. 7 is a plan view showing an embodiment of the alignment screen of the present invention.

FIG. 8 is a plan view showing an embodiment of a positioning screen of the present invention.

FIG. 9 is a plan view showing an embodiment of the alignment screen of the present invention.

FIG. 10 is a plan view showing an embodiment of the alignment screen of the present invention.

FIG. 11 is an explanatory diagram showing a schematic configuration of an interferometer used in the present invention.

[Explanation of symbols]

 11 He-Ne Laser Light Source 13 Condenser Lens 15 Pinhole 17 Beam Splitter 19 Collimator Lens 21 Projection Lens 23 TV Camera 25 Monitor Screen 31 Reflective Hologram Optical Element 33 Reference Reflector 35 Reflected Diffracted Light (Cylindrical Light) 37 Reflected Light 41 Transmitted Holographic optical element 41a Semi-transparent mirror surface 41b Hologram surface 45 Refracted diffracted light 45 Refracted light 51 Test sample 51a Cylindrical surface 61 Positioning screen 63 Slotted through hole portion 65 Partial through hole portion 71 Reference projected image 73 Projected Image for Measurement 75 Image from Reference Reflector 33 77 Image from Cylindrical Surface 51a

Claims (3)

[Claims] 1. Cylindrical light from an interferometric measurement system is converged at a focal point, then diverged to irradiate a cylindrical surface to be inspected, and reflected light from the cylindrical surface is guided to the interferometric measurement system by a reverse optical path to detect the cylindrical surface to be inspected. When the shape of is measured by an interferometric method, the central axis of the cylindrical surface to be tested is the y axis, the axis orthogonal to the y axis in the spreading direction of the cylindrical surface is the x axis, and the axis orthogonal to the x axis and the y axis is the z axis. Then, using a positioning screen made of a light diffusion plate having a slotted hole extending in the y-axis direction, the cylindrical light from the interferometric system passes through the slotted hole at or near its focal position. The alignment screen is arranged in such a manner that the reflected light from the cylindrical surface under test is projected and formed on the alignment screen, and the adjustment projection image is focused linearly. So that the position of the cylindrical surface to be inspected is adjusted in the z-axis direction, and the projected image for adjustment in a straight line is horizontal with respect to the elongated through-hole, the cylindrical surface to be inspected around the z-axis. The surface is rotationally adjusted, and a positioning screen composed of a light diffusing plate having a through hole for partially passing is used to measure the cylindrical surface of the test surface at or near the focal position of the cylindrical light from the interferometric measurement system. For alignment so that some cylindrical light in the direction of the central axis selectively passes through the through holes for partial passage, and the remaining cylindrical light forms a linear reference projection image on the alignment screen. By arranging the screen and rotating the cylindrical surface to be inspected around the x-axis, the reflected light from the cylindrical surface to be inspected is formed on the alignment screen. It moved an integer for projected image in the longitudinal direction of the reference projection images and, y
By rotating the cylindrical surface to be inspected around the axis, the adjustment projection image is moved in the direction orthogonal to the length direction of the reference projection image, and the reference is made to the passage position of the cylindrical light in the through hole for partial passage. A method for aligning a sample to be tested at the time of measuring a cylindrical surface, characterized by moving a projection image for use. 2. A slotted hole and a slotted hole which is continuous or independent from the slotted hole and which is provided at the side of the slotted hole in the longitudinal direction. A positioning screen for measuring a cylindrical surface, characterized by comprising a light diffusing plate having a through hole for partially passing therethrough. 3. The alignment screen for measuring a cylindrical surface according to claim 2, wherein the partially passing through hole is provided substantially at the center of the elongated hole in the length direction.