JP2009250927A - Eccentricity measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an eccentricity measuring device capable of suppressing an influence of misalignment between an optical axis of the eccentricity measuring device and an optical axis of an imaging optical system, on the measurement of an eccentricity amount. <P>SOLUTION: The eccentricity measuring device 1 comprises the imaging optical system 5 having a prescribed focal distance, a first right angled mirror 8 which reflects a light from the imaging optical system 5 into an object to be measured S, a second right angled mirror 11 which reflects the light from the object to be measured S into the imaging optical system 5. The second right angled mirror 11 condenses the reflected light, and a position sensor 13 is prepared to observe the position of the light intensity center of the condensed light. The first and second right angled mirrors 8, 11, when edge lines 8c, 11c are projected to a reference plane which is parallel to both edge lines 8c, 11c, are arranged so as to intersect perpendicularly between the straight line in alignment with the edge line 8c projected on the reference plane and the straight line in alignment with the edge line 11c. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an eccentricity measuring apparatus.

2. Description of the Related Art Conventionally, as an eccentricity measuring apparatus, an apparatus including a high-precision rotating shaft (spindle) that can rotate at a high speed with a rotationally symmetric subject attached is known (for example, see Patent Document 1). In such an eccentricity measuring apparatus, the amount of eccentricity of the subject is measured by measuring the shake of the image of the light reflected by the subject's test surface. In the decentration measuring apparatus described in Patent Document 1 for measurement, in order to measure decentration using a parallel light beam, an imaging optical system is inserted into the optical path of the measuring apparatus, and light is transmitted through the imaging optical system. Is incident on the subject, and the reflected light from the subject is made incident on the eccentricity detection sensor via the imaging optical system.
JP-A-11-287742

  When the imaging optical system is inserted into the optical path of the eccentricity measuring device, if the optical axis of the imaging optical system and the optical axis of the eccentricity measuring device are misaligned, accurately measure the eccentricity. It is difficult.

  An object of the present invention is to provide an eccentricity measuring device capable of suppressing the influence of the deviation between the optical axis of the eccentricity measuring device and the optical axis of the imaging optical system on the measurement of the eccentricity. .

  According to an embodiment of the present invention, an apparatus for measuring the amount of eccentricity of a subject, an apparatus for measuring the amount of eccentricity of the subject, an imaging optical system having a predetermined focal length; A first reflecting member that reflects light from the imaging optical system toward the subject, a second reflecting member that reflects light from the subject toward the imaging optical system, and a connection to the optical axis of the apparatus. An inclination detecting means for detecting the inclination of reflected light from the second reflecting member that has passed through the image optical system, and the first reflecting member includes a pair of reflecting surfaces orthogonal to each other and the pair of reflecting surfaces. The second reflecting member has a pair of reflecting surfaces orthogonal to each other and a ridge line formed by the pair of reflecting surfaces, and the second reflecting member has a ridge line formed by the first reflecting member and the second reflecting member. With respect to a reference plane parallel to both of the ridge lines of the reflection member, the ridge line of the first reflection member and the second reflection member When the line is projected, the first and second reflections are such that the straight line along the ridge line of the first reflecting member projected onto the reference plane is orthogonal to the straight line along the ridge line of the second reflecting member. There is provided an eccentricity measuring device in which members are arranged.

  ADVANTAGE OF THE INVENTION According to this invention, the eccentricity measuring apparatus which can suppress the influence which the shift | offset | difference of the optical axis of an eccentricity measuring apparatus and the optical axis of an imaging optical system has on the measurement of eccentricity can be provided. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used for the same elements or elements having the same function, and redundant description is omitted.

  With reference to FIG. 1, the structure of the eccentricity measuring apparatus 1 which concerns on embodiment is demonstrated. FIG. 1 is a configuration diagram of an eccentricity measuring apparatus according to the present embodiment.

  An eccentricity measuring apparatus 1 shown in FIG. 1 includes a light source 2, a collimator lens 3, a polarizing beam splitter 4, an imaging optical system 5, a polarizing beam splitter (light reflecting / transmitting member) 6, and a quarter wavelength plate. 7, 9, 10, a first right-angle mirror (first reflection member) 8, a second right-angle mirror (second reflection member) 11, a condensing optical system 12, and a position sensor 13. ing. The eccentricity measuring apparatus 1 causes the light L output from the light source 2 to enter the subject S via the imaging optical system 5 and the first right-angle mirror 8, and is reflected by the subject surface Sm of the subject S. This is a device for measuring the amount of eccentricity of the subject S by making the incident light L incident on the position sensor 13 via the second right-angle mirror 11 and the imaging optical system 5.

  The light source 2 is a laser device, for example, and makes the light L incident on the collimator lens 3. The collimator lens 3 converts the light L output from the light source 2 into a parallel light beam and makes it incident on the polarization beam splitter 4. The polarization beam splitter 4 reflects the light L that has passed through the collimator lens 3 and causes the light L to enter the imaging optical system 5. The polarization beam splitter 4 also transmits the light L that has passed through the imaging optical system 5.

  The imaging optical system 5 is a focusing optical system having a finite focal length. The imaging optical system 5 is also a variable focal length optical system that can change the focal length. The imaging optical system 5 is disposed at a position away from the center of curvature of the test surface Sm of the subject S along the optical axis Ax of the eccentricity measuring apparatus 1 by the focal length. The light L that has passed through the imaging optical system 5 from the light source 2 side enters the polarization beam splitter 6. On the other hand, the light L transmitted through the imaging optical system 5 from the subject S side enters the polarization beam splitter 4.

  The polarization beam splitter 6 reflects the light L transmitted through the imaging optical system 5 and makes it incident on the quarter-wave plate 7. The polarization beam splitter 6 also transmits the light L reflected by the first right-angle mirror 8 and transmitted through the quarter-wave plate 7 to be incident on the quarter-wave plate 9 and the subject S. The polarization beam splitter 6 also reflects the light L reflected by the test surface Sm of the subject S and transmitted through the quarter-wave plate 9 to be incident on the quarter-wave plate 10 and the second right-angle mirror 11. . The polarization beam splitter 6 also transmits the light L reflected by the second right-angle mirror 11 and transmitted through the quarter-wave plate 10 to enter the imaging optical system 5.

  The quarter-wave plates 7, 9, 10 are circularly polarized when the incident light L is linearly polarized, and are linearly polarized when the incident light L is circularly polarized. And

  The first right-angle mirror 8 polarizes the light L incident from the imaging optical system 5 after passing through the imaging optical system 5 through the polarization beam splitter 6 and the quarter-wave plate 7. The light is reflected toward the subject S so as to enter the subject S via the beam splitter 6 and the quarter-wave plates 7 and 9. The first right-angle mirror 8 has a pair of reflecting surfaces 8a and 8b orthogonal to each other and a ridge line 8c formed by the pair of reflecting surfaces 8a and 8b. In the first right-angle mirror 8, the reflection surface 8a and the reflection surface 8b are adjacent to each other with the ridge line 8c interposed therebetween so that the reflection surface 8b forms 90 °.

  The first right-angle mirror 8 is arranged so that the ridge line 8 c is orthogonal to the optical axis Ax of the eccentricity measuring apparatus 1. The first right-angle mirror 8 is preferably arranged so that the angle formed by the reflecting surfaces 8a and 8b and the optical axis Ax is 45 °. Further, the first right-angle mirror 8 may be arranged so that the ridge line 8 c is parallel to one side of the rectangular parallelepiped polarization beam splitter 6.

  The first right-angle mirror 8 reflects the incident light L on the pair of reflecting surfaces 8a and 8b. Specifically, the light incident on the reflecting surface 8 a is reflected in the order of the reflecting surface 8 a and the reflecting surface 8 b and enters the quarter-wave plate 7. The light incident on the reflecting surface 8 b is reflected in the order of the reflecting surface 8 b and the reflecting surface 8 a and then enters the quarter-wave plate 7.

  The second right-angle mirror 11 reflects the light L incident on the polarization beam splitter 6 and the quarter wavelength plates 9 and 10 after being reflected by the subject S, into the polarization beam splitter 6 and the quarter wavelength plate 10. Is reflected toward the imaging optical system 5 so as to be incident on the imaging optical system 5 via the. The second right-angle mirror 11 has a pair of reflecting surfaces 11a and 11b orthogonal to each other and a ridge line 11c formed by the pair of reflecting surfaces 11a and 11b. In the second right-angle mirror 11, the reflection surface 11a and the reflection surface 11b are adjacent to each other with the ridge line 11c interposed therebetween so that the reflection surface 11b forms 90 °.

  The second right-angle mirror 11 is arranged so that the ridge line 11 c is orthogonal to the optical axis Ax of the eccentricity measuring device 1. The second right-angle mirror 11 is preferably arranged such that the angle formed by the reflecting surfaces 11a and 11b and the optical axis Ax is 45 °. The second right-angle mirror 11 may be arranged so that the ridge line 11 c is parallel to one side of the rectangular parallelepiped polarization beam splitter 6.

  Here, the arrangement of the first and second right-angle mirrors 8 and 11 will be described with reference to FIG. As shown in FIG. 2, the first and second right-angle mirrors 8 and 11 are arranged with respect to a reference plane S parallel to both the ridge line 8 c of the first right-angle mirror 8 and the ridge line 11 c of the second right-angle mirror 11. When these ridge lines 8c and 11c are projected, the straight line SL1 along the ridge line 8c projected onto the reference plane S and the straight line SL2 along the ridge line 11c are arranged to be orthogonal to each other. That is, the first and second right-angle mirrors 8 and 11 are arranged so that the ridge lines 8c and 11c are in a twisted position relationship and the direction vectors of the ridge lines 8c and 11c are orthogonal to each other. Has been.

  Returning to FIG. 1 again, the configuration of the eccentricity measuring apparatus 1 will be described. The second right-angle mirror 11 reflects the incident light L on the pair of reflecting surfaces 11a and 11b. Specifically, the light incident on the reflecting surface 11 a is reflected in the order of the reflecting surface 11 a and the reflecting surface 11 b and enters the quarter-wave plate 10. The light incident on the reflecting surface 11 b is reflected in the order of the reflecting surface 11 b and the reflecting surface 11 a and then enters the quarter-wave plate 10.

  The condensing optical system 12 condenses the reflected light L from the second right-angle mirror 11 that has passed through the imaging optical system 5 on the position sensor 13. The position sensor 13 observes the position of the center of the light amount of the light L collected by the condensing optical system 12. The position sensor 13 may be composed of, for example, a screen and a CCD camera. In this case, the CCD camera images spot light collected on the screen. Or the position sensor 13 may be an optical position sensor (Position Sensitive Detector; PSD), for example. Or the position sensor 13 is a screen, for example, Comprising: You may observe the position of the spot light condensed on the screen by surveying.

  The position sensor 13 further detects the inclination of the reflected light L at the second right-angle mirror 11 that has passed through the condensing optical system 12 with respect to the optical axis Ax, based on the position of the center of the amount of the reflected light L observed. Thus, the condensing optical system 12 and the position sensor 13 function as tilt detection means.

  The imaging optical system 5, the collimator lens 3, and the condensing optical system 12 are represented by one optical lens in FIG. 1, but may actually be configured by a plurality of optical lenses.

  Next, a method for measuring the eccentricity of the subject S using the eccentricity measuring apparatus 1 will be described. First, the light L emitted from the light source 2 passes through the collimator lens 3 to become a parallel light beam and is reflected by the polarization beam splitter 4. The imaging optical system 5 changes the focal length so as to focus on the center of curvature of the test surface Sm of the subject S. The light L reflected by the polarization beam splitter 4 passes through the imaging optical system 5 and is reflected by the polarization beam splitter 6. The light L reflected by the polarization beam splitter 6 passes through the quarter wavelength plate 7 and is reflected by the first right-angle mirror 8. The light reflected by the first right-angle mirror 8 passes through the quarter-wave plate 7 and the polarization beam splitter 6 again, and further passes through the quarter-wave plate 9 and then enters the test surface Sm of the subject S. To do. The light L reflected by the test surface Sm passes through the quarter-wave plate 9 again and is then reflected by the polarization beam splitter 6. The light L reflected by the polarizing beam splitter 6 passes through the quarter-wave plate 10, then is reflected by the second right-angle mirror 11, passes through the quarter-wave plate 10 again, and passes through the polarizing beam splitter 6. The light L further passes through the imaging optical system 5, passes through the polarization beam splitter 4, and is then condensed on the position sensor 13 via the condensing optical system 12. From the position of the spot on the position sensor 13, the inclination of the reflected light L at the second right-angle mirror 11 transmitted through the condensing optical system 12 with respect to the optical axis Ax is detected. Then, the amount of eccentricity of the test surface Sm of the subject S can be detected.

  Next, the principle of suppressing the influence of the deviation between the optical axis of the imaging optical system 5 and the optical axis Ax of the eccentricity measuring apparatus 1 on the measurement of the eccentricity will be described with reference to FIG. In the decentration measuring apparatus 1, when the imaging optical system 5 is arranged with its optical axis 5a shifted from the optical axis Ax of the decentering measuring apparatus 1, the light L passing through the imaging optical system 5 is connected to the apparatus. The optical axis 5a of the image optical system 5 proceeds as the optical axis of the apparatus. Therefore, the optical axis after the imaging optical system 5 is deviated from the optical axis Ax of the original apparatus.

  A specific example will be described with reference to FIG. FIG. 3 shows an example in which light is emitted from the point P 1 of the imaging optical system 5. The point P1 is located at a point shifted from the optical axis Ax of the eccentricity measuring apparatus 1 in the + Y direction and the + Z direction. Here, the direction from the imaging optical system 5 toward the polarization beam splitter 6 along the optical axis Ax of the eccentricity measuring apparatus 1 is defined as the + X direction, and from the polarization beam splitter 6 along the optical axis Ax of the eccentricity measuring apparatus 1. A direction toward the first right-angle mirror 11 is defined as a + Z direction, and a direction orthogonal to both the X direction and the Y direction and toward the back of the sheet of FIG. 3 is defined as a + Y direction. In the eccentricity measuring apparatus 1 according to the present embodiment, the ridge line 8c of the first right-angle mirror 8 is parallel to the Y-axis direction, and the ridge line 11c of the second right-angle mirror 11 is parallel to the Z-axis direction. Has been placed.

  The light emitted from the point P1 of the imaging optical system 5 is reflected by the polarization beam splitter 6 and enters the point P2 on the reflecting surface 8a of the first right-angle mirror 8. The point P2 is located at a point shifted from the optical axis Ax of the eccentricity measuring apparatus 1 in the + X direction and the + Y direction. The light reflected at the point P2 on the reflecting surface 8a of the first right-angle mirror 8 is incident on the point P3 on the reflecting surface 8b of the first right-angle mirror 8. The point P3 is located at a point shifted from the optical axis Ax of the eccentricity measuring apparatus 1 in the −X direction and the + Y direction. The first right-angle mirror 8 is arranged so that the ridge line 8 c is orthogonal to the optical axis Ax of the eccentricity measuring device 1. Therefore, the point P3 is symmetrical with the point P2 with respect to the plane including the optical axis Ax and the ridgeline 8c.

  The light reflected at the point P3 on the reflecting surface 8b of the first right-angle mirror 8 passes through the polarization beam splitter 6 and is collected at a point P4 that is shifted from the center of curvature O of the surface Sm to be detected. The point P4 is located at a point shifted from the center of curvature O of the test surface Sm in the −X direction and the + Y direction. Here, if the test surface Sm is not decentered, the image point of the light reflected by the test surface Sm is a point P5 that is symmetrical with respect to the point P4 with respect to the center of curvature O. Therefore, the light L reflected by the test surface Sm travels like the light emitted from the point P5. The point P5 is located at a point shifted from the curvature center O of the test surface Sm in the + X direction and the −Y direction.

  The light L reflected by the test surface Sm is reflected by the polarization beam splitter 6 and enters the point P6 on the reflection surface 11a of the second right-angle mirror 11. The point P6 is located at a point shifted from the optical axis Ax of the eccentricity measuring apparatus 1 in the −Y direction and the + Z direction. The light reflected at the point P6 on the reflecting surface 11a of the second right-angle mirror 11 is incident on the point P7 on the reflecting surface 8b of the second right-angle mirror 11. The point P7 is located at a point shifted from the optical axis Ax of the eccentricity measuring apparatus 1 in the + Y direction and the + Z direction. The second right-angle mirror 11 is arranged so that the ridge line 11 c is orthogonal to the optical axis Ax of the eccentricity measuring device 1. Therefore, the point P7 is symmetric with respect to the point P6 with respect to the plane including the optical axis Ax and the ridge line 11c.

  In the eccentricity measuring apparatus 1, the point P7 is on the extension line of the optical axis 5a of the imaging optical system 5, as shown in FIG. Therefore, when the test surface Sm is not decentered, the light reflected by the second right-angle mirror 11 and then transmitted through the imaging optical system 5 is converted into a parallel light beam parallel to the optical axis Ax of the decentering measuring device 1. Become. On the other hand, when the test surface Sm is decentered, the light reflected by the second right-angle mirror 11 and then transmitted through the imaging optical system 5 is decentered as in the normal measurement. The light beam is not a parallel light beam parallel to the optical axis Ax, and the position of the light amount center of the spot on the position sensor 13 changes.

  As described above, in the eccentricity measuring apparatus 1, when the optical axis 5a of the imaging optical system 5 and the optical axis Ax of the eccentricity measuring apparatus 1 are deviated, the reflection on the test surface Sm of the subject S is performed. The light L is returned to the imaging optical system 5 with the optical axis 5a of the imaging optical system 5 as the optical axis. This is because the first and second right-angle mirrors 8 and 11 have a pair of reflecting surfaces 8a, 8b, 11a, and 11b that are orthogonal to each other, and the direction vectors of the ridge lines 8c and 11c are This is because they are arranged orthogonally.

  That is, since the pair of reflecting surfaces 8a, 8b, 11a, and 11b of the first and second right-angle mirrors 8 and 11 are orthogonal to each other, the incident light to the first and second right-angle mirrors 8 and 11 and The reflected light from these becomes parallel. Further, as understood from FIG. 3, when the optical axis 5 a of the imaging optical system 5 is deviated from the optical axis Ax of the eccentricity measuring device 1, the light L that has passed through the imaging optical system 5 is condensed. The point P4 and the image point P5 of the light reflected by the test surface Sm have a point-symmetric relationship with respect to the center of curvature O on the optical axis Ax. On the other hand, in the first right-angle mirror 8, the incident position P2 and the emission position P3 of the light are reflected so as to be plane-symmetric with respect to the plane including the ridge line 8c parallel to the Y axis. Then, the light incident position P6 and the light emitting position P7 are reflected so as to be plane-symmetric with respect to the plane including the ridge line 11c parallel to the Z axis. Therefore, in the eccentricity measuring apparatus 1, the point-symmetric image point movement with respect to the center of curvature O that occurs during reflection at the test surface Sm is performed on two orthogonal axes (for example, the Y axis and the Z axis in FIG. 3). It is substantially canceled by plane-symmetric reflection point movement with respect to the respective planes.

  As a result, when the test surface Sm is not decentered, the reflected light L on the test surface Sm of the subject S that has passed through the imaging optical system 5 can be a parallel light beam. Thereby, in the eccentricity measuring apparatus 1, even when the optical axis 5a of the imaging optical system 5 and the optical axis Ax of the eccentricity measuring apparatus 1 are shifted, the eccentricity amount of the subject is accurately measured. It becomes possible to do.

  Further, in the eccentricity measuring apparatus 1, even if the optical axis 5a of the imaging optical system 5 is deviated from the optical axis Ax of the eccentricity measuring apparatus 1 as described above, the influence of the deviation is suppressed and the eccentricity is measured. Is possible.

  In addition, since a turntable is not required for measuring eccentricity, measurement time can be shortened and costs can be reduced. Furthermore, the posture of the subject S is not limited by the installation of the turntable, and measurement can be performed in various arrangements.

  In the eccentricity measuring apparatus 1, the first and second right-angle mirrors 8 and 11 are arranged so that their ridgelines 8 c and 11 c are orthogonal to the optical axis Ax of the eccentricity measuring apparatus 1. Therefore, for example, it is possible to suppress an increase in the size of the polarization beam splitter 6 and the like. As a result, the eccentricity measuring apparatus 1 can be reduced in size.

  Further, the eccentricity measuring apparatus 1 includes a polarization beam splitter 6 that reflects or transmits incident light. Then, the first right-angle mirror 8 directs the light from the imaging optical system 5 incident through the polarization beam splitter 6 to the subject S so as to enter the subject S through the polarization beam splitter 6. Reflect. The second right-angle mirror 11 transmits the light from the subject S reflected by the subject S and entering through the polarizing beam splitter 6 to the imaging optical system 5 through the polarizing beam splitter 6. Reflected toward the imaging optical system 5 so as to be incident. Thus, since the eccentricity measuring apparatus 1 uses the polarization beam splitter 6, it is possible to reduce the size of the apparatus.

  The imaging optical system 5 is a variable focal length optical system that can change the focal length. Therefore, even if the subject S is replaced and the position of the center of curvature of the subject surface Sm changes, the focal length of the imaging optical system 5 can be changed to change the position of the condensing point. As a result, the eccentricity measuring apparatus 1 can accurately measure the eccentricity amounts of subjects having various shapes.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, A various deformation | transformation is possible. For example, a right-angle prism may be used as the first or second reflecting member instead of the right-angle mirrors 8 and 11. Further, the imaging optical system 5 may be an optical system that cannot change the focal length and has a fixed focal length. The first and second right-angle mirrors 8 and 11 may not be arranged so that their ridgelines 8c and 11c are orthogonal to the optical axis Ax of the eccentricity measuring apparatus 1. The first and second right-angle mirrors 8 and 11 may not be arranged so that the ridgelines 8c and 11c are parallel to one side of the rectangular parallelepiped polarizing beam splitter 6, respectively.

It is a lineblock diagram of an eccentricity measuring device concerning an embodiment. It is a figure for demonstrating arrangement | positioning of the 1st and 2nd right-angle mirror. It is a figure for demonstrating the principle of the measuring method by the eccentricity measuring apparatus which concerns on embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Eccentricity measuring apparatus, 2 ... Light source, 3 ... Collimator lens, 4 ... Polarizing beam splitter, 5 ... Imaging optical system, 7, 9, 10 ... 1/4 wavelength plate, 8 ... 1st right angle mirror, 11 2nd right angle mirror, 12 ... Condensing optical system, 13 ... Position sensor.

Claims (8)

An apparatus for measuring the amount of eccentricity of a subject,
An imaging optical system having a predetermined focal length;
A first reflecting member that reflects light from the imaging optical system toward the subject;
A second reflecting member that reflects light from the subject toward the imaging optical system;
Inclination detecting means for detecting the inclination of the reflected light at the second reflecting member that has passed through the imaging optical system with respect to the optical axis of the apparatus,
The first reflecting member has a pair of reflecting surfaces orthogonal to each other and a ridge formed by the pair of reflecting surfaces,
The second reflecting member has a pair of reflecting surfaces orthogonal to each other and a ridge formed by the pair of reflecting surfaces,
The ridge line of the first reflective member and the ridge line of the second reflective member with respect to a reference plane parallel to both the ridge line of the first reflective member and the ridge line of the second reflective member. When projected, the first and first lines are arranged such that a straight line along the ridge line of the first reflecting member projected onto the reference plane and a straight line along the ridge line of the second reflecting member are orthogonal to each other. An eccentricity measuring apparatus, wherein two reflecting members are arranged.   Both the ridgeline formed by the pair of reflection surfaces of the first reflection member and the ridgeline formed by the pair of reflection surfaces of the second reflection member are orthogonal to the optical axis of the device. The eccentric measuring apparatus according to claim 1, wherein the first and second reflecting members are arranged.   3. The eccentricity measuring apparatus according to claim 1, wherein a pair of reflecting surfaces of the first and second reflecting members or both of the first and second reflecting members are mirrors. 4.   4. The eccentricity measuring apparatus according to claim 1, wherein both or one of the first and second reflecting members is a right-angle prism. A light reflection / transmission member that reflects or transmits incident light;
The first reflecting member reflects light from the imaging optical system toward the subject via the light reflecting / transmitting member,
The second reflection member reflects light from the subject toward the imaging optical system via the light reflection / transmission member. The eccentricity measuring apparatus as described.   The decentering measurement apparatus according to claim 1, wherein the imaging optical system can change the focal length.   7. The imaging optical system according to claim 1, wherein the imaging optical system has a finite focal length, and is disposed at a position away from the center of curvature of the subject along the optical axis by the focal length. The eccentricity measuring apparatus as described in any one of Claims. The tilt detecting means condenses the reflected light from the second reflecting member that has passed through the imaging optical system, and observes the position of the center of the amount of the collected light, whereby the optical axis of the apparatus The eccentricity measuring apparatus according to claim 1, wherein an inclination of reflected light from the second reflecting member that has passed through the imaging optical system is detected.

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