JP2010286305A - Eccentricity measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an eccentricity measuring device capable of measuring the amount of eccentricity of a measuring object surface with constant measurement sensitivity, irrespective of the curvature radius of the measuring object surface. <P>SOLUTION: The illumination part 10 of the eccentricity measuring device 1 includes: a first illumination optical system 11a for irradiating the measuring object surface 5 while condensing illumination light at the focal point of the measuring object surface 5; a second illumination optical system for irradiating the measuring object surface 5 while condensing the illumination light at the center of curvature of the measuring object surface 5; and a switching device 19 for switching an optical system to be used for irradiation with the illumination light, to either the first illumination optical system 11a or the second illumination optical system. Focal distance is adjustable in the first illumination optical system 11a, and focal distance is constant in the second illumination optical system. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an eccentricity measuring apparatus that measures the eccentricity of a lens system used in an optical apparatus or the like.

  In a conventional eccentricity measuring device, light from a light source is collected at the center of the paraxial curvature of the measurement target surface by a focus lens system, and light reflected by the measurement target surface (measurement light) is collected through the focus lens system. There is a configuration in which light is focused on a position sensitive detector (PSD) by an optical lens. In such an eccentricity measuring apparatus, the measurement target surface is rotated about the optical axis, the angular deviation of the measurement light is detected from the amount of measurement light shake detected by the optical position sensor, and the eccentricity amount of the measurement target surface is calculated. . In addition, in a conventional eccentricity measuring device, light from a light source is focused on a paraxial focal point of a measurement target surface by a focus lens system, and light that is reflected by the measurement target surface to become parallel light is converted into a focus lens system. There is also a configuration in which light is condensed on an optical position sensor by a condensing lens without being interposed (see, for example, Patent Document 1).

JP 2000-205998 A

  However, in such an eccentricity measuring apparatus, the eccentricity amount of the measurement target surface is measured with a constant measurement sensitivity regardless of the curvature radius of the measurement target surface (particularly when the curvature radius of the measurement target surface is small). It was difficult.

  The present invention has been made in view of such problems, and provides an eccentricity measuring device capable of measuring the amount of eccentricity of a measurement target surface with a constant measurement sensitivity regardless of the radius of curvature of the measurement target surface. With the goal.

  In order to achieve such an object, according to an aspect of the present invention, an illumination unit that irradiates illumination light onto a measurement target surface and reflected light from the measurement target surface irradiated with the illumination light are collected in a predetermined manner. Based on the condensing unit that condenses on the light surface, the detection unit that detects the spot light generated by condensing on the condensing surface, and the position of the spot light on the condensing surface detected by the detection unit A measurement unit that measures the amount of eccentricity of the measurement target surface, and the illumination unit irradiates the measurement target surface with the illumination light focused on the focus of the measurement target surface. An optical system, a second illumination optical system that irradiates the measurement target surface so that the illumination light is focused on the center of curvature of the measurement target surface, and an optical system that is used for irradiation of the illumination light are the first Cut into either one of the illumination optical system or the second illumination optical system A decentering measuring device, wherein the first illumination optical system is adjustable in focal length, and the second illumination optical system has a constant focal length. The

  According to the present invention, it is possible to measure the amount of eccentricity of the measurement target surface with a constant measurement sensitivity regardless of the curvature radius of the measurement target surface.

In the eccentricity measuring apparatus of 1st Embodiment, it is a figure which shows the state which inserted the 2nd lens and the 2nd polarizing beam splitter on the optical path of an illumination part. In the eccentricity measuring apparatus of 1st Embodiment, it is a figure which shows the state which extracted the 2nd lens and the 2nd polarizing beam splitter from the optical path of an illumination part. It is a figure which shows an example in which light reflects in a measuring object surface. It is a figure which shows an example in which light reflects in a measuring object surface. In the eccentricity measuring apparatus of 2nd Embodiment, it is a figure which shows the state which inserted the 2nd lens and the 2nd quarter wavelength plate on the optical path of an illumination part. In the eccentricity measuring apparatus of 2nd Embodiment, it is a figure which shows the state which inserted the 1st quarter wavelength plate on the optical path of an illumination part.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the eccentricity measuring apparatus 1 of the first embodiment includes an illumination unit 10 that irradiates illumination light onto a measurement target surface 5 of a lens that is a measurement target, and a measurement target surface that is irradiated with illumination light. 5 and the first and second condenser lenses 20a and 20b for condensing the reflected light on the predetermined condensing surfaces 26a and 26b, respectively, and spot light generated by condensing on the condensing surfaces 26a and 26b. First and second optical position sensors 25a and 25b that are detected, and an arithmetic processing unit that measures the amount of eccentricity of the measurement target surface 5 based on detection signals from the first or second optical position sensors 25a and 25b, respectively. 30.

  Although not shown in detail, the lens to be measured is a lens system composed of a plurality of lenses, and one of the optical surfaces in the lens system is the measurement target surface 5. Further, the lens to be measured is placed on a high-precision rotary table (not shown) so that the optical axis thereof overlaps the optical axis of the illumination unit 10, and can be rotated around the optical axis of the lens. ing. Therefore, the paraxial curvature center and the paraxial focal point of the measurement target surface 5 are located on the optical axis of the illumination unit 10.

  The illumination unit 10 includes, in order from the light source side, a first polarizing beam splitter (PBS) 12, a first lens 13, a second lens 14, a second polarizing beam splitter 15, and 1/4. And a wave plate 16. The second lens 14 and the second polarization beam splitter 15 are configured to be movable in a direction perpendicular to the optical axis of the illumination unit 10 by a switching device 19 using a revolver or the like. The second polarization beam splitter 15 can be inserted into and removed from the optical path of the illumination unit 10.

  Thereby, as shown in FIG. 1, in the state where the second lens 14 and the second polarization beam splitter 15 are inserted on the optical path of the illumination unit 10, the first lens 13 and the second lens 14 are the first illumination. The optical system 11a is configured. The first illumination optical system 11a is an optical system for irradiating the measurement target surface 5 with the illumination light focused on the paraxial focal point of the measurement target surface 5, and includes a first lens 13 and a second lens. 14 is adjusted to adjust the focal length of the first illumination optical system 11a, so that the position of the condensing point (condensing position) of the illumination light is changed to the illumination unit 10 (first illumination optical system 11a). It can be moved along the optical axis. The illumination light, which is linearly polarized light emitted from a light source (not shown), passes through the first polarizing beam splitter 12 and then passes through the first lens 13 and the second lens 14 (the paraxial axis of the measurement target surface 5). It is incident on the second polarizing beam splitter 15 while being condensed (to the focal point). The illumination light transmitted through the second polarization beam splitter 15 passes through the quarter wavelength plate 16 and reaches the measurement target surface 5. The light source (not shown) may be a laser light source, or a combination of LED illumination or the like and a pinhole.

  The reflected light from the measurement target surface 5 irradiated with the illumination light using the first illumination optical system 11a becomes parallel light because the illumination light is collected at the paraxial focal point of the measurement target surface 5, and is 1 / The light passes through the four-wave plate 16 and enters the second polarizing beam splitter 15. At this time, the second polarized beam splitter 15 is set so that S-polarized light is incident as reflected light from the measurement target surface 5. Therefore, the reflected light from the measurement target surface 5 is reflected by the second polarizing beam splitter 15, passes through the first condenser lens 20a, and is collected at the detection unit of the first optical position sensor 25a. It is condensed on the surface 26a. Note that linearly polarized light (illumination light) emitted from a light source (not shown) passes through the second polarizing beam splitter 15 as P-polarized light and is reflected as reflected light from the measurement target surface 5. Since the light passes through the quarter-wave plate 16 twice before returning to 15, the reflected light incident on the second polarization beam splitter 15 becomes S-polarized light.

  The first optical position sensor 25a is disposed on the rear focal plane of the first condenser lens 20a, and is generated by the first condenser lens 20a and condensed on the condenser surface 26a (spot light). Is detected. The first optical position sensor 25a can detect the position of the spot light (spot centroid) on the detection unit of the first optical position sensor 25a, that is, the light condensing surface 26a, and the detection signal is sent to the arithmetic processing unit 30. Output.

  By the way, as shown in FIG. 2, in a state where the second lens 14 and the second polarization beam splitter 15 are removed from the optical path of the illumination unit 10, the first lens 13 constitutes the second illumination optical system 11b. . The second illumination optical system 11b is an optical system for irradiating the measurement target surface 5 with the illumination light focused on the paraxial curvature center of the measurement target surface 5, and is only for the first lens 13. Since the focal length is constant, for example, by moving the first lens 13 along the optical axis, the position of the condensing point (condensing position) of the illumination light is changed to the illumination unit 10 (second illumination optical system 11b). ) Along the optical axis. The illumination light, which is linearly polarized light emitted from a light source (not shown), passes through the first polarizing beam splitter 12 and then passes through the first lens 13 (toward the paraxial curvature center of the measurement target surface 5). ) Condensed light passes through the quarter-wave plate 16 and reaches the measurement target surface 5.

  The reflected light from the measurement target surface 5 irradiated with the illumination light using the second illumination optical system 11b becomes regular reflection light because the illumination light is condensed at the paraxial curvature center of the measurement target surface 5. The light passes through the ¼ wavelength plate 16 and the first lens 13 so as to return to the same optical path as that of the illumination light, and enters the first polarizing beam splitter 12. At this time, the first polarized beam splitter 12 is set such that S-polarized light is incident as reflected light from the measurement target surface 5. Therefore, the reflected light from the measurement target surface 5 is reflected by the first polarization beam splitter 12, passes through the second condenser lens 20b, and is collected at the detection unit of the second optical position sensor 25b. It is condensed on the surface 26b. Note that linearly polarized light (illumination light) emitted from a light source (not shown) passes through the first polarizing beam splitter 12 as P-polarized light and is reflected as reflected light from the measurement target surface 5. Since the light passes through the quarter-wave plate 16 twice before returning to 12, the reflected light incident on the first polarization beam splitter 12 becomes S-polarized light.

  The second light position sensor 25b is disposed on the rear focal plane of the second condenser lens 20b, and is generated by the second condenser lens 20b and condensed on the condenser surface 26b (spot image). Is detected. The second optical position sensor 25 b can detect the position of the spot light (spot centroid) on the detection unit of the second optical position sensor 25 b, that is, the condensing surface 26 b, and sends the detection signal to the arithmetic processing unit 30. Output.

  The arithmetic processing unit 30 determines the amount of eccentricity of the measurement target surface 5 based on the position of the spot light on the condensing surface (26a or 26b) detected by the first optical position sensor 25a or the second optical position sensor 25b. Measure. When actually measuring the eccentricity of the measurement target surface 5, a lens (not shown) placed on a turntable (not shown) is rotated. Then, when the measurement target surface 5 is irradiated with illumination light using the first illumination optical system 11a, the Lissajous (trajectory) of the spot light (spot centroid) on the condensing surface 26a is detected by the first optical position sensor 25a. Then, based on the radius of the Lissajous detected by the first optical position sensor 25a, that is, the shake amount of the spot light according to the rotation of the lens, the arithmetic processing unit 30 determines the tilt eccentricity amount (measurement target) of the measurement target surface 5 The amount of eccentricity due to the inclination of the surface 5 is determined. On the other hand, when the measurement target surface 5 is irradiated with illumination light using the second illumination optical system 11b, the second light position sensor 25b detects a Lissajous (trajectory) of spot light (spot centroid) on the light condensing surface 26b. Based on the radius of the Lissajous detected by the second optical position sensor 25b, that is, the shake amount of the spot light according to the rotation of the lens, the arithmetic processing unit 30 shifts the amount of shift eccentricity (measurement target) of the measurement target surface 5 The amount of eccentricity due to the displacement of the surface 5 in the direction perpendicular to the optical axis) is obtained.

  A method of measuring the amount of eccentricity of the measurement target surface 5 using the eccentricity measuring apparatus 1 configured as described above will be described. By the way, the influence of the eccentricity of the measurement target surface 5 on the optical system of the eccentricity measuring device 1 varies depending on the radius of curvature of the measurement target surface 5. When the radius of curvature of the measurement target surface 5 is large, the shift of the measurement target surface 5 (displacement in the direction perpendicular to the optical axis) has a small effect on the optical system. For example, when the measurement target surface 5 is a flat surface, the shift of the measurement target surface 5 hardly affects the optical system. Therefore, when the radius of curvature of the measurement target surface 5 close to a plane is large, it is effective to manage the eccentricity of the measurement target surface 5 by measuring the tilt of the measurement target surface 5 (the inclination of the measurement target surface 5). . On the other hand, when the radius of curvature of the measurement target surface 5 is small, the tilt of the measurement target surface 5 has a small effect on the optical system. For example, when the radius of curvature of the measurement target surface 5 is close to 0, the tilt of the measurement target surface 5 hardly affects the optical system. Therefore, when the radius of curvature of the measurement target surface 5 is small, it is effective to manage the eccentricity of the measurement target surface 5 by measuring the shift of the measurement target surface 5.

  Therefore, when the radius of curvature of the measurement target surface 5 is a predetermined value (for example, 50 mm) or more, the tilt eccentric amount of the measurement target surface 5 (the eccentric amount due to the inclination of the measurement target surface 5) is measured. In this case, as shown in FIG. 1, the second lens 14 and the second polarization beam splitter 15 are inserted into the optical path of the illumination unit 10 by the operation of the switching device 19, and the first illumination optical system 11a is used. The illumination light is irradiated onto the measurement target surface 5 so as to be focused on the paraxial focal point of the measurement target surface 5. At this time, by adjusting the focal length of the first illumination optical system 11a by changing the distance between the first lens 13 and the second lens 14, the position (condensing position) of the condensing point of the illumination light is adjusted. Match to the paraxial focus of the surface 5 to be measured.

  Then, the illumination light emitted from a light source (not shown) passes through the first polarizing beam splitter 12 and then passes through the first lens 13 and the second lens 14 (toward the paraxial focus of the measurement target surface 5). ) The light is incident on the second polarization beam splitter 15 while being condensed. The illumination light transmitted through the second polarization beam splitter 15 passes through the quarter wavelength plate 16 and reaches the measurement target surface 5. Reflected light from the measurement target surface 5 is transmitted through the quarter-wave plate 16 and reflected by the second polarizing beam splitter 15, and is transmitted through the first condenser lens 20a to be transmitted from the first optical position sensor 25a. It is condensed on the condensing surface 26a. Then, the first optical position sensor 25a detects the position of the spot light generated by being condensed on the condensing surface 26a and outputs the detection signal to the arithmetic processing unit 30. The arithmetic processing unit 30 Based on the position of the spot light detected by the optical position sensor 25a, that is, the amount of shake of the spot light according to the rotation of the lens, the angular shake (tilt) of the light reflected by the measurement target surface 5 is calculated and measured. The amount of tilt eccentricity of the target surface 5 is obtained.

  As shown in FIG. 3, when the tilt eccentricity of the measurement target surface 5 is θ and the tilt angle of the optical axis of the light reflected from the measurement target surface 5 is α, α = 2θ. From this equation, it can be seen that the amount of tilt eccentricity of the measurement target surface 5 does not depend on the radius of curvature of the measurement target surface 5. That is, if illumination light is irradiated using the first illumination optical system 11a, the tilt eccentric amount of the measurement target surface 5 can be detected with a constant sensitivity regardless of the curvature radius of the measurement target surface 5. Note that the tilt angle α of the optical axis of the light reflected by the measurement target surface 5 is almost proportional to the amount of spot light shake.

  On the other hand, when the radius of curvature of the measurement target surface 5 is less than a predetermined value (for example, 50 mm), the shift eccentric amount of the measurement target surface 5 (the eccentric amount due to the displacement of the measurement target surface 5 in the direction perpendicular to the optical axis). Measure. In this case, as shown in FIG. 2, the second lens 14 and the second polarization beam splitter 15 are removed from the optical path of the illumination unit 10 by the operation of the switching device 19, and the second illumination optical system 11b is used. Illumination light is irradiated onto the measurement target surface 5 so as to be focused on the paraxial curvature center of the measurement target surface 5. At this time, since the focal length of the second illumination optical system 11b is constant, for example, by moving the first lens 13 along the optical axis, the position (condensing position) of the condensing point of the illumination light is set. Align with the paraxial curvature center of the surface 5 to be measured.

  Then, illumination light emitted from a light source (not shown) passes through the first polarizing beam splitter 12 and then passes through the first lens 13 (toward the paraxial curvature center of the measurement target surface 5) and is condensed. However, it passes through the quarter-wave plate 16 and reaches the measurement target surface 5. The reflected light from the surface to be measured 5 is transmitted through the quarter-wave plate 16 and the first lens 13, reflected by the first polarizing beam splitter 12, and transmitted through the second condenser lens 20b. It is condensed on the condensing surface 26b of the optical position sensor 25b. Then, the second optical position sensor 25b detects the position of the spot light generated by being condensed on the condensing surface 26b, and outputs the detection signal to the arithmetic processing unit 30, and the arithmetic processing unit 30 Based on the position of the spot light detected by the light position sensor 25b, that is, the amount of shake of the spot light according to the rotation of the lens, the angular shake (tilt) of the light reflected from the measurement target surface 5 is calculated and measured. The shift eccentricity of the target surface 5 is obtained.

By the way, as shown in FIG. 4, the amount of shift eccentricity of the measurement target surface 5 is s, the focal length of the first lens 13 (second illumination optical system 11 b) is f, and the light reflected by the measurement target surface 5. If the tilt angle of the optical axis is β, β≈2 tan ¹ (s / f) ≈2 s / f. From this equation, it can be seen that the amount of shift eccentricity of the measurement target surface 5 does not depend on the radius of curvature of the measurement target surface 5. That is, if illumination light is irradiated using the second illumination optical system 11b in a state where the focal length is constant, the shift eccentricity amount of the measurement target surface 5 can be maintained at a constant sensitivity regardless of the curvature radius of the measurement target surface 5. Can be detected. Note that the tilt angle β of the optical axis of the light reflected by the measurement target surface 5 is substantially proportional to the amount of spot light shake.

  As described above, in the conventional eccentricity measuring device, the light from the light source is collected on the paraxial curvature center of the measurement target surface by the focus lens system, and the light reflected by the measurement target surface is transmitted through the focus lens system. There exists a structure which condenses to an optical position sensor with a condensing lens. In such an eccentricity measuring apparatus, since the light reflected by the measurement target surface passes through the focus lens system again, the relationship between the inclination of the light reaching the optical position sensor and the eccentricity of the measurement target surface is described in the focus lens system. Affected by. Therefore, even if the sensitivity of the optical position sensor is constant, the measurement sensitivity of the eccentricity amount of the measurement target surface varies depending on the radius of curvature of the measurement target surface.

  In addition, in a conventional eccentricity measuring device, light from a light source is focused on a paraxial focal point of a measurement target surface by a focus lens system, and light that is reflected by the measurement target surface to become parallel light is converted into a focus lens system. There is also a configuration in which light is condensed on an optical position sensor by a condensing lens without being interposed. In such an eccentricity measuring device, the light reflected by the measurement target surface and converted into parallel light is directly collected by the condensing lens on the optical position sensor, so that the measurement target surface regardless of the radius of curvature of the measurement target surface. Can be measured with a constant measurement sensitivity. However, if the radius of curvature of the surface to be measured becomes very small, the beam diameter of the light reflected from the surface to be measured becomes small, and the spot diameter of the light collected by the optical position sensor increases due to diffraction. In addition, the dynamic range becomes smaller, and spot light protrudes from the optical position sensor, making measurement impossible.

  On the other hand, according to the eccentricity measuring apparatus 1 of the first embodiment, the illumination unit can adjust the focal length, and the first illumination optical system 11a that focuses the illumination light on the focus of the measurement target surface 5; And a second illumination optical system 11b for condensing illumination light at the center of curvature of the measurement target surface 5 with a constant focal length, so that the illumination optical system is switched according to the radius of curvature of the measurement target surface 5 If the tilt eccentricity amount or the shift eccentricity amount is measured, the eccentricity amount of the measurement target surface 5 can be measured with a constant measurement sensitivity regardless of the radius of curvature of the measurement target surface 5. .

  At this time, when the radius of curvature of the measurement target surface 5 is a predetermined value (for example, 50 mm) or more, the first illumination optical system 11a is switched, and when the curvature radius of the measurement target surface 5 is less than the predetermined value, the second illumination is performed. By switching to the optical system 11b, it is possible to reliably measure the eccentric amount of the measurement target surface 5 with a constant measurement sensitivity for the tilt eccentric amount and the shift eccentric amount.

  Next, a second embodiment of the eccentricity measuring device will be described with reference to FIGS. Since the eccentricity measuring device 51 of the second embodiment is different from the eccentricity measuring device 1 of the first embodiment only in the configuration of the illumination unit 10 and the other configurations are the same, the same member is used. The same numbers are assigned and detailed description is omitted. As shown in FIG. 5, the illumination unit 60 in the second embodiment includes, in order from the light source side, a first polarization beam splitter 62, a first lens 63, a second lens 64, and a first quarter wavelength. A plate 65, a second polarizing beam splitter 66, and a second quarter-wave plate 67 are included. Further, the second lens 64, the first quarter-wave plate 65, and the second quarter-wave plate 67 are each provided in the illumination unit 60 by a switching device (not shown) similar to the first embodiment. The second lens 64 and the second quarter-wave plate 67 or the first quarter-wave plate 65 can be placed on the illumination unit 60. It can be inserted in the optical path.

  Thereby, as shown in FIG. 5, the second lens 64 and the second quarter-wave plate 67 are inserted on the optical path of the illumination unit 60, and the first quarter-wave plate 65 is removed from the optical path. In this state, the first lens 63 and the second lens 64 constitute the first illumination optical system 61a. The first illumination optical system 61a is an optical system for irradiating the measurement target surface 5 with the illumination light focused on the paraxial focal point of the measurement target surface 5, and is the same as in the case of the first embodiment. It is the composition. The illumination light, which is linearly polarized light emitted from a light source (not shown), passes through the first polarization beam splitter 62, and then passes through the first lens 63 and the second lens 64 (the paraxial axis of the measurement target surface 5). The light is incident on the second polarization beam splitter 66 while being condensed (to the focal point). The illumination light transmitted through the second polarization beam splitter 66 passes through the second quarter-wave plate 67 and reaches the measurement target surface 5.

  The reflected light from the measurement target surface 5 irradiated with the illumination light using the first illumination optical system 61a becomes parallel light because the illumination light is collected at the paraxial focal point of the measurement target surface 5, and the second light. , And is incident on the second polarization beam splitter 66. At this time, similarly to the case of the first embodiment, the second polarized beam splitter 66 is set such that S-polarized light is incident as reflected light from the measurement target surface 5. Therefore, the reflected light from the measurement target surface 5 is reflected by the second polarization beam splitter 66, passes through the first condenser lens 20a, and is collected at the detection unit of the first optical position sensor 25a. It is condensed on the surface 26a.

  On the other hand, as shown in FIG. 6, the first quarter-wave plate 65 is inserted on the optical path of the illumination unit 60, and the second lens 64 and the second quarter-wave plate 67 are removed from the optical path. In this state, the first lens 63 constitutes the second illumination optical system 61b. The second illumination optical system 61b is an optical system for irradiating the measurement target surface 5 with the illumination light focused on the paraxial curvature center of the measurement target surface 5, as in the case of the first embodiment. It is the same composition. The illumination light, which is linearly polarized light emitted from a light source (not shown), passes through the first polarization beam splitter 62 and then passes through the first lens 63 (toward the paraxial curvature center of the measurement target surface 5). ) Condensed light passes through the first quarter-wave plate 65 and the second polarizing beam splitter 66 and reaches the measurement target surface 5.

  The reflected light from the measurement target surface 5 irradiated with the illumination light using the second illumination optical system 61b becomes regular reflection light because the illumination light is condensed at the paraxial curvature center of the measurement target surface 5, The light passes through the second polarization beam splitter 66, the first quarter-wave plate 65, and the first lens 63 so as to return to the same optical path as that of the illumination light, and enters the first polarization beam splitter 62. At this time, as in the case of the first embodiment, the first polarized beam splitter 62 is set so that S-polarized light is incident as reflected light from the measurement target surface 5. Therefore, the reflected light from the measurement target surface 5 is reflected by the first polarization beam splitter 62, passes through the second condenser lens 20b, and is collected at the detection unit of the second optical position sensor 25b. It is condensed on the surface 26b.

  In order to measure the amount of eccentricity of the measurement target surface 5 using the eccentricity measuring device 51 configured as described above, the radius of curvature of the measurement target surface 5 is a predetermined value as in the case of the first embodiment. In the case of (for example, 50 mm) or more, as shown in FIG. 5, the second lens 64 and the second quarter-wave plate 67 are inserted into the optical path of the illumination unit 60 by the operation of a switching device (not shown). Using the first illumination optical system 61 a, the illumination light is irradiated onto the measurement target surface 5 so as to be condensed on the paraxial focal point of the measurement target surface 5. At this time, by changing the distance between the first lens 63 and the second lens 64 to adjust the focal length of the first illumination optical system 61a, the position (condensing position) of the condensing point of the illumination light is adjusted. Match to the paraxial focus of the surface 5 to be measured.

  Then, the illumination light emitted from the light source (not shown) passes through the first polarization beam splitter 62 and then passes through the first lens 63 and the second lens 64 (toward the paraxial focus of the measurement target surface 5). ) The light is incident on the second polarizing beam splitter 66 while being condensed. The illumination light transmitted through the second polarization beam splitter 66 passes through the second quarter-wave plate 67 and reaches the measurement target surface 5. The reflected light from the measurement target surface 5 is transmitted through the second quarter-wave plate 67, is reflected by the second polarizing beam splitter 66, is transmitted through the first condenser lens 20a, and is transmitted to the first light position. It is condensed on the condensing surface 26a of the sensor 25a. Then, the first optical position sensor 25a detects the position of the spot light generated by being condensed on the condensing surface 26a and outputs the detection signal to the arithmetic processing unit 30. The arithmetic processing unit 30 Based on the position of the spot light detected by the optical position sensor 25a, that is, the amount of shake of the spot light according to the rotation of the lens, the angular shake (tilt) of the light reflected by the measurement target surface 5 is calculated and measured. The amount of tilt eccentricity of the target surface 5 is obtained.

  On the other hand, when the curvature radius of the measurement target surface 5 is less than a predetermined value (for example, 50 mm), as shown in FIG. 6, the first quarter-wave plate 65 is moved to the illumination unit by the operation of a switching device (not shown). 60, and the second illumination optical system 61b is used to irradiate the measurement target surface 5 with the illumination light so as to be condensed at the paraxial center of curvature of the measurement target surface 5. At this time, since the focal length of the second illumination optical system 61b is constant, for example, by moving the first lens 63 along the optical axis, the position of the condensing point of the illumination light (condensing position) is changed. Align with the paraxial curvature center of the surface 5 to be measured.

  Then, the illumination light emitted from the light source (not shown) is transmitted through the first polarization beam splitter 62 and then transmitted through the first lens 63 (toward the paraxial curvature center of the measurement target surface 5). Meanwhile, the light passes through the first quarter-wave plate 65 and the second polarization beam splitter 66 and reaches the measurement target surface 5. The reflected light from the measurement target surface 5 passes through the second polarizing beam splitter 66, the first quarter-wave plate 65, and the first lens 63 and is reflected by the first polarizing beam splitter 62, and the second Is condensed on the condensing surface 26b of the second optical position sensor 25b. Then, the second optical position sensor 25b detects the position of the spot light generated by being condensed on the condensing surface 26b, and outputs the detection signal to the arithmetic processing unit 30, and the arithmetic processing unit 30 Based on the position of the spot light detected by the light position sensor 25b, that is, the amount of shake of the spot light according to the rotation of the lens, the angular shake (tilt) of the light reflected from the measurement target surface 5 is calculated and measured. The shift eccentricity of the target surface 5 is obtained.

  As a result, according to the eccentricity measuring apparatus 51 of 2nd Embodiment, the effect similar to the case of 1st Embodiment can be acquired.

  In each of the above-described embodiments, the method of measuring the shift eccentricity of the measurement target surface 5 with the second lens 14 (64) removed from the optical path of the illumination unit 10 (60) has been described. It is not limited to. For example, the distance between the first and second lenses and the measurement target surface is adjusted in a state where the distance between the first lens and the second lens is constant and the combined focal length of the first and second lenses is constant. The shift eccentricity of the measurement target surface may be measured regardless of the radius of curvature of the measurement target surface by condensing the illumination light at the paraxial curvature center of the measurement target surface. At this time, if the second lens is arranged in the vicinity of the focal point of the first lens, the condensing effect by the second lens can be eliminated, and the first lens is substantially the same as in each of the embodiments described above. It is possible to configure an optical system (second illumination optical system) consisting only of the above.

  In each of the above-described embodiments, when the radius of curvature of the measurement target surface 5 is equal to or greater than a predetermined value (for example, 50 mm), the first illumination optical system 11a (61a) is switched, and the curvature radius of the measurement target surface 5 is predetermined. When the value is less than the value, the second illumination optical system 11b (61b) is switched, but the present invention is not limited to this. For example, if measurement can be performed with a constant measurement sensitivity, the first illumination optical system 11a (61a) and the second illumination optical system 11b (within a predetermined range in which the radius of curvature of the measurement target surface 5 is about 50 mm are used. 61b) may be switched to measure both the tilt eccentricity amount and the shift eccentricity amount.

1 Eccentricity measuring apparatus (first embodiment)
5 Measurement target surface 10 Illumination unit 11a First illumination optical system 11b Second illumination optical system 19 Switching device (switching unit)
20a 1st condensing lens (condensing part) 20b 2nd condensing lens (condensing part)
25a First optical position sensor (detection unit) 25b Second optical position sensor (detection unit)
26a Condensing surface 26b Condensing surface 30 Arithmetic processing part (measurement part)
51 Eccentricity Measuring Device (Second Embodiment)
60 Illumination Unit 61a First Illumination Optical System 61b Second Illumination Optical System

Claims (4)

An illumination unit for illuminating the measurement target surface with illumination light;
A condensing unit that condenses the reflected light from the measurement target surface irradiated with the illumination light on a predetermined condensing surface;
A detection unit for detecting spot light generated by being condensed on the light collecting surface;
A measurement unit that measures the amount of eccentricity of the measurement target surface based on the position of the spot light on the light collection surface detected by the detection unit;
The illumination unit collects the illumination light at a center of curvature of the measurement target surface, and a first illumination optical system that irradiates the measurement target surface with the illumination light focused on the focus of the measurement target surface. A second illumination optical system that irradiates the surface to be measured so as to emit light, and an optical system that is used for irradiation of the illumination light is either the first illumination optical system or the second illumination optical system. A switching unit for switching,
The first illumination optical system can adjust a focal length, and the second illumination optical system has a constant focal length.   The switching unit switches to the first illumination optical system when the radius of curvature of the measurement target surface is greater than or equal to a predetermined value, and the second illumination optical system when the radius of curvature of the measurement target surface is less than a predetermined value. The eccentricity measuring apparatus according to claim 1, wherein   The first illumination optical system includes a first lens and a second lens, and adjusts a focal length of the first illumination optical system by changing an interval between the first lens and the second lens. The eccentricity measuring apparatus according to claim 1 or 2.   The second illumination optical system has the first lens, and the position of the condensing point of the illumination light can be moved along the optical axis by moving the first lens along the optical axis. The eccentricity measuring apparatus according to claim 3, wherein

Images