JP2011252774A - Measuring apparatus for inspection target surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring apparatus for measuring an inspection target surface capable of measuring the inclination angle, shape, diameter size and the like of an inspection target surface composed of a rotationally symmetric ruled surface or a plurality of plane surfaces separated from each other in a short time.SOLUTION: An optical deflection element 30 composed of a conical lens 31 and a diffraction optical element 32 is arranged and irradiated with a measuring beam. A part of the measuring beam entering the optical deflection element 30 is reflected by a reference standard surface 31b as a reference beam, and the rest of the beam is radially deflected by the optical deflection element 30 to be perpendicularly incident on each part of an inspection surface 71. A part of the measuring beam retroreflected by each part of the inspection surface 71 returns to the reference standard surface 31b as an inspection light via the optical deflection element 30. A detour distance is adjusted in a detour section 13 so that the optical path length difference between the inspection beam and the reference beam is smaller than or equal to the coherence length of output light from a low coherent light source 11. On the basis of an interference fringe image taken by an imaging camera 23, the inclination angle, shape and diameter size of each part of the inspection surface 71 are measured and analyzed.

Description

  The present invention relates to a test surface measuring apparatus for measuring a test surface comprising a rotationally symmetric ruled surface such as a cylindrical surface or a conical surface or a plurality of planes spaced apart from each other, and in particular, the inclination angle and shape of the test surface. In addition, the present invention relates to a test surface measuring apparatus suitable for measuring the diameter of the test surface and the separation distance of each part of the test surface.

  Conventionally, as a technique for arranging a plurality of lenses side by side in the optical axis direction without decentering them in a lens barrel, conical fitting surfaces are respectively formed on adjacent lenses, and the respective fitting surfaces are connected to each other. There is known a method of installing a lens that enables alignment between lenses by fitting.

  In a lens having such a fitting surface, unless the forming accuracy of the fitting surface is good, each lens cannot be installed at the correct position, and it becomes difficult to obtain the desired optical performance. Therefore, there is a demand to improve the forming accuracy by measuring the forming error (inclination angle, surface shape, and diameter error) of the fitting surface and feeding back the obtained forming error to the manufacturing process.

  Conventionally, a three-dimensional shape measuring device using an optical stylus has been used to measure such a fitting surface, but there is a problem that it takes a lot of time for the measurement.

  On the other hand, Patent Document 1 below proposes a technique for measuring the shape of a conical test surface in a short time using an interferometer, and this technique is applied to the measurement of the above-described fitting surface. It is also possible.

Japanese Unexamined Patent Publication No. 7-318307

  However, although the measuring device described in Patent Document 1 can measure the inclination angle and shape error of the fitting surface in a short time, it can measure the size of the diameter of the fitting surface. Can not. Therefore, there is a demand for a measuring device that can measure the diameter of the fitting surface in a short time.

  Moreover, although the measuring apparatus described in Patent Document 1 is based on the premise that the test surface to be measured is a conical surface, it is convenient if other types of test surfaces can be used as the measurement target. is there. For example, when the test surface is a cylindrical surface, or when the test surface is composed of a plurality of planes arranged at positions separated from each other (for example, when the above-described fitting surface is provided on a cylindrical lens, the fitting Even if the mating surface may be composed of multiple planes), in addition to the inclination angle and shape of the test surface, the diameter of the test surface and the separation distance of each part of the test surface can be measured in a short time If it becomes, it will become very useful.

  The present invention has been made in view of such circumstances, and not only the inclination angle and shape of the test surface, but also the test surface composed of a rotationally symmetric ruled surface or a plurality of planes separated from each other. It is an object of the present invention to provide a test surface measuring apparatus capable of measuring in a short time also the size of the test surface diameter and the separation distance of each part of the test surface.

  In order to achieve the above object, a test surface measuring apparatus according to the present invention has the following features.

That is, the test surface measurement device according to the present invention is a test surface measurement device that measures a test surface consisting of a rotationally symmetric ruled surface or a plurality of planes separated from each other,
An interferometer for branching output light from the light source into measurement light and reference light at the reference standard plane, and emitting the measurement light along the measurement optical axis;
Disposed on the optical path of the measurement light between the interferometer and the test surface, deflects the measurement light emitted from the interferometer and vertically enters each part of the test surface; and A light deflecting element that deflects the test light retroreflected from each part of the test surface and emits the light toward the interferometer;
Imaging means for imaging an interference fringe image formed by optical interference between the test light from the light deflection element and the reference light;
An optical distance measuring means for measuring an optical distance on an optical path of the measurement light from the reference standard surface to the test surface;
Analyzing means for analyzing the interference fringe image picked up by the image pickup means.

In the present invention, the light source is a low coherence light source that outputs low coherence light including a plurality of wavelength components,
The optical distance measuring unit diverts the low coherent light output from the low coherent light source into two light beams, detours one light beam with respect to the other light beam, and then re-combines the light into one light beam. Adjusting the detour distance of the one light beam with respect to the other light beam in the path portion and the detour route portion, the optical path length difference between the test light and the reference light is less than the coherence distance of the low coherence light And an optical distance calculation unit that calculates the optical distance based on the interference fringe image captured by the imaging unit and the value of the detour distance. be able to.

On the other hand, the light source is a tunable laser light source,
The optical distance measuring unit includes a wavelength scanning unit that scans the wavelength of output light from the wavelength tunable laser light source, and interference fringes that are sequentially captured by the imaging unit while scanning the wavelength of the output light by the wavelength scanning unit. An optical distance calculation unit that calculates the optical distance based on the number of interference fringe changes in a predetermined pixel of the image may be included.

Further, when the test surface is a rotationally symmetric ruled surface,
The light deflecting element includes a diffractive optical element having a plurality of ring-shaped diffraction gratings formed concentrically, a refractive element having a conical light transmitting surface, and a conical shape. Any of those having a reflective element having a light reflecting surface, or any combination thereof can be used.

On the other hand, when the test surface is composed of a plurality of planes separated from each other,
The light deflection element may include a reflection element having a plurality of measurement light deflection reflection planes arranged in different directions.

  The test surface measurement apparatus according to the present invention has the above-described features, and thus has the following effects.

  That is, in the test surface measurement apparatus of the present invention, the measurement light is deflected by the optical deflection element disposed on the optical path of the measurement light between the interferometer and the test surface and is perpendicular to each part of the test surface. An interference fringe image is formed by the light interference between the test light that is incident on the test surface and retroreflected from each part of the test surface and returns to the interferometer via the light deflection element, and the reference light.

  By providing an analysis means for analyzing the interference fringe image, it is possible to measure and analyze the inclination angle and shape of each part of the test surface, and to measure the measurement light from the light deflection element to the test surface. By providing an optical distance measuring means for measuring the optical distance on the optical path, it is possible to measure the diameter of the test surface when the test surface is a rotationally symmetric test surface. In the case where the test surface is composed of a plurality of planes spaced apart from each other, it is possible to measure the separation distance of each part (a plurality of planes) of the test surface.

It is a schematic block diagram of the to-be-measured surface measuring apparatus which concerns on 1st Embodiment. It is a block diagram which shows the structure of the analysis control apparatus in 1st Embodiment. It is the schematic which shows another aspect of the optical deflection | deviation element in 1st Embodiment. It is a schematic block diagram of the to-be-measured surface measuring apparatus which concerns on 2nd Embodiment. It is a block diagram which shows the structure of the analysis control apparatus in 2nd Embodiment. It is a schematic block diagram of the test surface measuring apparatus which concerns on 3rd Embodiment. It is a perspective view of the optical deflection element in a 3rd embodiment. It is the schematic which shows another aspect of an optical deflection | deviation element and a to-be-tested surface. It is the schematic which shows the other aspect of an optical deflection | deviation element and a to-be-tested surface. It is the schematic which shows the other aspect of a light deflection | deviation element and a to-be-tested surface. It is a schematic block diagram of the to-be-measured surface measuring apparatus which concerns on 4th Embodiment. It is a block diagram which shows the structure of the analysis control apparatus of 4th Embodiment. It is the schematic for demonstrating the alignment adjustment method of the to-be-measured surface measuring apparatus which concerns on 1st Embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the above-mentioned drawings. In addition, each figure used for description of embodiment is rough explanatory drawing, and does not show a detailed shape and structure, The size of each member, the distance between members, etc. are changed suitably and shown. .

<First Embodiment>
As shown in FIG. 1, the test surface measurement apparatus according to the first embodiment includes an interferometer 10, a light deflection element 30, and an analysis control unit 40, and a test surface 71 (optical axis C) of the test lens 70. ₇₀ is configured to measure an inclination angle, a shape, and a diameter of each part of a conical surface which is a rotationally symmetric ruled surface. The test lens 70 is a fitting lens used in combination with another lens (not shown), and the test surface 71 is formed as a fitting surface with another lens.

The interferometer 10 is a combination of a low coherence light source 11 that outputs low coherence light including a plurality of wavelength components (for example, an SLD or LED, a white light source, and a bandpass filter that limits the wavelength band of the output light). A collimator lens 12, and the low coherence light output from the low coherence light source 11 via the collimator lens 12 is branched into two light beams, and one light beam is divided into the other light beam. , The detour unit 13 for re-combining with one beam after detouring, the beam diameter conversion lens 19, and the beam output from the detour unit 13 via the beam diameter conversion lens 19 a beam splitter 20 for reflecting the figure downwards in the light beam splitting surface 20a, the light beam from the beam splitter 20 and converts the measurement light into parallel light and emitted along the measurement optical axis C ₁₀ coli And a meter lens 21. Further, it includes an imaging lens 22 and an imaging camera 23 (which constitutes imaging means in the present embodiment and has an imaging element 24 made of CCD, CMOS, or the like).

  The detour unit 13 splits the low coherent light incident from the collimator lens 12 into a first light beam directed rightward in the drawing and a second light beam directed upward in the drawing on the light beam splitting surface 14a. The movable mirror 15 disposed on the optical path of the first light beam from the beam splitter 14, the fixed mirror 16 disposed on the optical path of the second light beam from the beam splitter 14, and the movable mirror 15 are illustrated in FIG. A movable mirror position adjusting unit 17 (having a PZT element 18) that moves in the middle and right and left directions, and a first light beam with respect to the second light beam by a predetermined distance (from the light beam splitting surface 14a of the beam splitter 14 to the movable mirror). 15 and twice the difference of the optical distances to the fixed mirror 16) and then re-combined into one beam at the beam splitting surface 14 a of the beam splitter 14. Towards diameter changing lens 19 is configured to output.

The light deflection element 30 deflects the measurement light emitted from the interferometer 10 so as to vertically enter each part of the test surface 71, and the test light retroreflected from each part of the test surface 71. The light is deflected and emitted toward the interferometer 10, and is composed of a conical lens 31 and a diffractive optical element 32 as refractive elements. Conical lens 31 has its rotationally symmetrical cone with respect to the optical axis C ₃₁ light transmitting surface 31a, and a vertical reference surface 31b with respect to the optical axis C _31, the measurement light from the interferometer 10 The reference reference surface 31 b is divided into two parts, one of which is reflected as reference light toward the interferometer 10, and the other is refracted and emitted toward the diffractive optical element 32. On the other hand, the diffractive optical element 32 is a transmission type in which a plurality of annular diffraction gratings are formed concentrically around the optical axis C ₃₂ , and deflects by diffracting the measurement light from the conical lens 31. Thus, it is configured to enter perpendicularly to each part of the test surface 71.

As the measuring light perpendicularly incident on each part of the test surface 71, usually in the + 1st-order diffracted light or -1 order diffraction light (herein from the diffractive optical element 32, closer to the optical axis C ₃₂ The diffracted light emitted is positive diffracted light, and the diffracted light emitted so as to be away from the optical axis is used as negative diffracted light), but higher order diffraction such as ± 2nd order diffracted light and ± 3rd order diffracted light is used. It is also possible to use light as measurement light.

  As shown in FIG. 1, the analysis control unit 40 includes an analysis control device 41 including a computer, a monitor device 42 that displays an interference fringe image and the like, and an input device 43 for performing various inputs to the analysis control device 41. As shown in FIG. 2, the analysis control device 41 includes a storage unit such as a CPU and a hard disk mounted in a computer, and a detour distance adjustment configured by a program stored in the storage unit. A control unit 44, an analysis image generation unit 45, an optical distance calculation unit 46, and an image analysis unit 47 are provided.

  The detour distance adjustment control unit 44 controls the drive of the movable mirror position adjusting unit 17 (see FIG. 1), thereby adjusting the detour distance of the first light beam with respect to the second light beam, The optical path length difference from the reference light is configured to be equal to or less than the coherence distance of the low coherence light output from the low coherence light source 11.

  The analysis image generation unit 45 is an interference fringe image (hereinafter referred to as “analysis interference fringe image”) for performing various analyzes on the test surface 71 based on the image signal of the interference fringe image captured by the imaging camera 23. For example).

  The optical distance difference calculation unit 46 is referred based on the analysis interference fringe image generated by the analysis image generation unit 45 and the detour distance value (the value after adjustment by the detour distance adjustment control unit 44). The optical distance on the optical path of the measurement light from the reference surface 31b to the test surface 71 is calculated.

  The image analysis unit 47 constitutes an analysis unit in the present embodiment, and the inclination angle, shape, and diameter of the test surface 71 are based on the generated analysis interference fringe image and the calculated optical distance. It is configured to measure and analyze the size of.

  In the present embodiment, the detour distance adjustment control unit 44 and the movable mirror position adjustment unit 17 constitute an optical path length difference adjustment unit. The detour distance adjustment control unit 44 and the movable mirror position adjustment unit 17 The detour unit 13 and the optical distance difference calculation unit 46 described above constitute an optical distance measuring unit.

  Hereinafter, the operation of the test surface measuring apparatus according to the first embodiment will be described. Note that the optical characteristics of the light deflection element 30 such as the refractive index and the refraction angle of the conical lens 31 and the diffraction angle of the diffractive optical element 32 with respect to the wavelength of the measurement light are known.

Prior to the measurement, alignment adjustment of the test lens 70 is performed. This alignment adjustment is (the details will be described later) after the alignment of the optical deflection element 30 (the conical lens 31 and diffractive optical element 32) relative to the measurement optical axis C _10, an alignment mechanism for holding the sample lens 70 (shown with substantially) coincides with the optical axis C ₇₀ is the measurement optical axis C ₁₀ of the lens 70, and so that the measuring light emitted radially from the diffractive optical element 32 is incident perpendicular to the test surface 71 This is done by adjusting the position and orientation of the lens 70 to be examined.

  After the alignment of the test lens 70 is adjusted, the test surface 71 is measured. Hereinafter, the operation during the measurement will be described.

(Function during measurement)
<1> Low coherent light is emitted from the low coherent light source 11 shown in FIG. The low coherent light is converted into parallel light by the collimator lens 12 and then enters the detour unit 13.

  <2> The low coherent light incident on the detour unit 13 is branched into a first light beam directed toward the movable mirror 15 and a second light beam directed toward the fixed mirror 16 on the light beam branching surface 14 a of the beam splitter 14. Each of them is retroreflected by the movable mirror 15 and the fixed mirror 16 and recombined at the light beam splitting surface 14a. In the present embodiment, the respective optical path lengths from branching to re-multiplexing are set so that the first light flux is longer than the second light flux.

  <3> The light beam recombined and emitted from the beam splitter 14 enters the beam splitter 20 through the beam diameter conversion lens 19, is reflected by the light beam splitting surface 20 a, and enters the collimator lens 20. The light beam incident on the collimator lens 21 is converted into parallel light and emitted toward the light deflection element 30.

  <4> The light beam incident on the light deflection element 30 is split into a retroreflected light beam and a transmitted light beam on the reference standard surface 31 b of the conical lens 31. In the present embodiment, among the light beams that are retroreflected by the reference standard surface 31b, a light beam component that follows the path of the first light beam (hereinafter referred to as “first light beam component”) is used as the reference light, and the reference standard surface 31b. The light beam that passes through is used as measurement light.

  <5> The measurement light transmitted through the reference standard surface 31 b is refracted by the conical lens 31 and incident on the diffractive optical element 32, and then diffracted by the diffractive optical element 32. In the present embodiment, of the measurement light diffracted by the diffractive optical element 32, the −1st order diffracted light is used as measurement light that is perpendicularly incident on each part of the test surface 71.

  <6> The measurement light incident perpendicularly on each part of the test surface 71 is retroreflected from the test surface 71 and returns to the conical lens 31 via the diffractive optical element 32. In the present embodiment, of the measurement light that returns to the conical lens 31 and passes through the reference reference surface 31b again, a light beam component that traces the path of the second light beam (hereinafter referred to as “second light beam component”) is the test light. Is done.

  <7> The test light is combined with the reference light on the reference standard surface 31b to obtain interference light. This test light enters the imaging lens 22 via the collimator lens 21 and the beam splitter 20, and is imaged on the imaging element 24 of the imaging camera 23 by the imaging lens 22. At this time, the optical path length difference between the reference light and the test light (in the order of the numbers shown in FIG. 1, the optical path length from 11 → 12 → 14a → 15 → 14a → 19 → 20a → 21 → 31b, 11 → 12 → 14a → 16 → 14a → 19 → 20a → 21 → 31b → 31a → 32 → 71 → 32 → 31a → 31b) is less than the coherence distance of the low coherence light. If not, no optical interference occurs between the reference light and the test light, and no interference fringe image is formed.

  <8> Adjust the detour distance of the first light beam with respect to the second light beam in the detour unit 13 so that the optical path length difference between the reference light and the test light is equal to or less than the coherence distance of the low coherent light. . The detour distance is adjusted by adjusting the position of the movable mirror 15 by the detour distance adjustment control unit 44 controlling the drive of the movable mirror position adjusting unit 17.

  <9> When the optical path length difference between the reference light and the test light is adjusted to be equal to or less than the coherence distance of the low coherence light, an interference fringe image is formed on the image sensor 24 by the interference light. More specifically, the detour distance is finely adjusted so that the fringe contrast (modulation is possible) of the interference fringe image is maximized. The interference fringe image is picked up by the image pickup camera 23, and the image signal is output to the analysis image generation unit 45.

  <10> Based on the image signal input to the analysis image generation unit 45, the analysis image generation unit 45 generates an analysis interference fringe image (a ring-shaped image), and the image data (analysis image data). Are output to the optical distance calculation unit 46 and the image analysis unit 47, respectively.

  <11> In the optical distance calculation unit 46, from the reference reference surface 31b to the test surface 71 based on the analysis interference fringe image and the value of the detour distance (the value after adjustment by the detour distance adjustment control unit 44). The optical distance of the measurement light on the optical path is calculated. Specifically, the optical distance from the reference reference surface 31b to the test surface 71 on the optical path of the measurement light is half of the value of the detour distance of the first light beam with respect to the second light beam in the detour unit 13. Therefore, it can be calculated from the data of the detour distance value.

  <12> The image analysis unit 47 analyzes the analysis interference fringe image, and obtains the inclination angle and shape of the test surface 71 based on the analysis result. Further, based on the analysis result of the interference fringe image for analysis and the optical distance between the reference reference surface 31b and the test surface 71 obtained by the optical distance calculation unit 46, the diameter of the test surface 71 (strictly, Is the size of the region corresponding to the analysis interference fringe image on the test surface 71). A cat's eye point is set on the optical path of the measurement light from the reference standard surface 31b to the test surface 71, the optical distance from the reference standard surface 31b to the cat's eye point on the optical path of the measurement light, and the reference standard surface 31b. And the optical distance from the cat's eye point to the test surface 71, and by taking the difference between these two optical distances, the cat's eye point to the test surface 71 on the optical path of the measurement light is obtained. The optical distance may be calculated, and the diameter of the test surface 71 may be obtained based on the calculation result.

Since the low interference light is used as the measurement light, the analysis interference fringe image is in a very narrow region centered on the position where the phases of the light of each wavelength of the measurement light are aligned on the test surface 71. In some cases, information about the entire area of the test surface 71 cannot be obtained in one measurement. Therefore, the detour distance of the first light beam with respect to the second light beam in the detour unit 13 is changed by a minute distance so that the region corresponding to the analysis interference fringe image is scanned over the entire surface 71 to be measured. Then, it becomes possible to obtain information regarding the entire area of the test surface 71. Incidentally, if it is not possible to irradiate the measurement light at once to the whole area of the test surface 71 is moved in the direction of the measurement optical axis C ₁₀ of the sample lens 70 by a small distance, for each movement thereof above By repeating the procedure, it is possible to obtain information regarding the entire area of the test surface 71.

  The conical lens 31 can be used in the same manner even if it is installed such that its apex faces the collimator lens 21 side.

In the first embodiment, a combination of the conical lens 31 and the diffractive optical element 32 is used as the light deflecting element 30. Depending on the inclination angle of the test surface 71, the conical lens 31 or the diffractive optical element is used. It is also possible to use 32 alone as a light deflection element. When the diffractive optical element 32 is used alone as a light deflection element, it is possible to cope with a case where the inclination angle of the test surface 71 is large by using high-order diffracted light as measurement light. For example, when the center wavelength λ of the low coherent light is set to λ = 800 nm and the second-order diffracted light is used as measurement light, the diffraction angle θ ₁ of the second-order diffracted light in the diffractive optical element 32 is set to 75 degrees. The grating pitch d of the optical element 32 may be set to d = 828 nm because of the relationship of 2dsin θ ₁ = 2λ.

Further, instead of the optical deflection element 30, an optical deflection element 30A as shown in FIG. 3 may be used. This light deflection element 30A uses a reference standard plate 33 with a diffraction grating instead of the conical lens 31. The reference reference plate 33 with a diffraction grating is formed by forming a plurality of annular transmission diffraction gratings 33a on the reference reference surface 33b (the lower surface in the figure) with the optical axis _C33 as the center. Functionally, in the same manner as the conical lens 31 described above, a part of the incident measurement light is retroreflected at the reference standard surface 33b to become reference light, and the other measurement light is deflected by the transmission diffraction grating 33a. (For example, + 1st-order diffracted light is used) and is emitted toward the diffractive optical element 32.

Second Embodiment
As shown in FIG. 4, the test surface measurement apparatus according to the second embodiment includes an interferometer 10A, a light deflection element 30B, and an analysis control unit 40A, and an inner peripheral surface (a rotationally symmetric ruled surface) of the cylindrical body 80. It is configured to measure the inclination angle, shape and diameter of each part of the test surface 81).

The interferometer 10A includes a tunable laser light source 11A, a beam diameter conversion lens 19A, a beam splitter 20A, a collimator lens 21A, an imaging lens 22A, and an imaging camera 23A configured to change the wavelength of output light. The measurement light composed of parallel light is emitted toward the light deflection element 30A along the measurement optical axis _C10A . Further, the test light incident from the test surface 81 side via the light deflection element 30A is combined with the reference light to form interference light, and an interference fringe image formed by the interference light is captured by the imaging camera 23A. It is comprised so that it may image.

The light deflection element 30B is formed by integrally forming a transmissive reference standard plate 34 and a conical mirror 35 as a reflection element. The reference plate 34 has a vertical reference surface 34a to the optical axis C _30B of the optical deflection element 30B, a part of the measurement light from the interferometer 10A as the reference light at the reference surface 34a While retroreflecting, it is configured to emit other measurement light toward the conical mirror 35. On the other hand, the conical mirror 35 has a conical light reflecting surface 36 disposed at a predetermined angle (in this embodiment, an inner angle of 45 degrees (an outer angle of 135 degrees)) with respect to the reference reference surface 34a. The measurement light from the reference standard plate 34 is radially deflected with respect to the optical axis C _30B and irradiated to each part of the test surface 81. In addition, the test light retroreflected from each part of the test surface 81 is deflected (reflected at a right angle) on the light reflection surface 36 and is emitted toward the reference standard plate 34.

  As shown in FIG. 4, the analysis control unit 40A includes an analysis control device 41A composed of a computer or the like, a monitor device 42A that displays an interference fringe image or the like, and an input device 43A for performing various inputs to the analysis control device 41A. As shown in FIG. 5, the analysis control device 41A includes a storage unit such as a CPU and a hard disk mounted in a computer, and a wavelength scanning unit configured by a program stored in the storage unit. 48, an image generation unit 49, an optical distance calculation unit 46A, and an image analysis unit 47A.

  The wavelength scanning unit 48 is configured to scan the wavelength of the laser light output from the wavelength tunable laser light source 11A within a predetermined range (for example, about ± 5 nm).

  The image generation unit 49 performs light deflection based on the image signals sequentially obtained by the imaging camera 23A during the period in which the wavelength scanning unit 48 scans the wavelength of the laser light from the wavelength tunable laser light source 11A. Interference fringe images (hereinafter referred to as “distance interference fringe images”) for calculating the optical distance of the measurement light on the optical path from the element 30 </ b> B to the test surface 81 are sequentially generated, and various types of test surface are obtained. An interference fringe image (hereinafter referred to as “analysis interference fringe image”) for analysis is generated.

  The optical distance difference calculation unit 46A measures from the light deflection element 30B to the test surface 81 based on the number of interference fringe changes in predetermined pixels of the interference fringe image for distance measurement sequentially generated by the image generation unit 49. The optical distance on the light path is calculated.

  The image analysis unit 47A constitutes analysis means in the present embodiment, and the inclination angle, shape, and diameter of the test surface 81 are based on the generated analysis interference fringe image and the calculated optical distance. It is configured to measure and analyze the size of.

  In the present embodiment, the wavelength scanning unit 48 and the optical distance difference calculation unit 46A constitute an optical distance measuring unit.

Hereinafter, the operation of the test surface measuring apparatus according to the second embodiment will be described. Incidentally, in advance, alignment of the optical deflection element 30B with respect to the measurement optical axis C _10A is assumed to be completed. The relative position between the reference standard surface 34a of the reference standard plate 34 and the conical mirror 35 and the shape (including size) of the light reflecting surface 36 of the conical mirror are assumed to be known.

Prior to the measurement, alignment adjustment of the cylindrical body 80 is performed. This alignment, as the optical axis _{C 80} of the cylinder 80 coincides with the optical axis _{C 30B} of the measurement optical axis _{C 10A} and the light deflection element 30B, interferometers 10A and relative to the optical deflection element 30B and the cylindrical body 80 This is done by adjusting the position.

  After the alignment adjustment of the cylindrical body 80, the test surface 81 is measured. Hereinafter, the operation during the measurement will be described.

(Function during measurement)
<1> Laser light is emitted from the wavelength tunable laser light source 11A shown in FIG. This laser light is incident on the collimator lens 21A via the beam diameter conversion lens 19A and the beam splitter 20A (reflected downward in the drawing by the light beam splitting surface 20Aa), and is converted into parallel light by the collimator lens 21A. The light is emitted toward the deflection element 30B.

<2> The parallel light incident on the light deflection element 30B is branched into two on the reference standard surface 34Aa of the reference standard surface plate 34, one of which is retroreflected toward the collimator lens 21A as the reference light, and the other is the measurement optical axis. incident on the light reflecting surface 36 of the conical mirror 35 as parallel measurement light C _10A.

  <3> The measurement light incident on the light reflecting surface 36 of the conical mirror 35 is deflected radially on the light reflecting surface 36 and irradiated on each part of the test surface 81.

  <4> The measurement light applied to each part of the test surface 81 is retroreflected from each part of the test surface 81 and enters the reference standard face plate 34 as the test light via the light reflecting surface 36 of the conical mirror 35. To do.

  <5> The test light incident on the reference standard plate 34 is combined with the reference light on the reference standard surface 34Aa to form interference light, and is imaged through the collimator lens 21A, the beam splitter 20A, and the imaging lens 22A. The light enters the camera 23A and forms an interference fringe image on the image sensor 24A. The formed interference fringe image is captured by the imaging camera 23A.

  <6> Image data of the interference fringe image captured by the imaging camera 23A is output as a video signal from the imaging camera 23A, and an analysis interference fringe image is generated by the image generation unit 49.

  <7> The generated interference fringe image for analysis is analyzed by the image analysis unit 47A, and the inclination angle and shape of each part of the test surface 81 are obtained based on the analysis result.

  <8> On the other hand, in order to calculate the optical distance from the light deflection element 30B to the test surface 81, the wavelength of the laser light output from the wavelength tunable laser light source 11A by the wavelength scanning unit 48 is within a predetermined range. Scanned.

  <9> Interference fringe images are sequentially captured by the imaging camera 23A at a predetermined timing during a period in which the wavelength of the laser beam is scanned. Each of these image signals is output as a video signal, and each interference fringe image for distance measurement is generated by the image generation unit 49.

  <10> In the optical distance difference calculating unit 46A, the number of interference fringe changes in a predetermined pixel of each ranging interference fringe image is obtained. Based on this number of times, measurement from the light deflection element 30B to the test surface 81 is performed. The optical distance on the optical path of light is calculated. The calculation of the optical distance is specifically performed in the following procedure.

That is, when the wave number is scanned from k ₁ to k ₂ by scanning the wavelength of the laser light output from the wavelength tunable laser 11A and an interference fringe image is captured every Δk, the interference fringe intensity change I (x, y, k ) Is represented by the following formula (1).

Here, L (x, y) is the optical path length difference between the test light and the reference light, I ₀ (x, y) is the intensity distribution, and γ is the interference fringe modulation. When the interference fringe change in the predetermined pixel at this time is n times, it is expressed by the following equation (2).

  Here, since k = 2π / λ, the following expression (3) is obtained.

  That is, it is possible to calculate the optical path length difference between the test light and the reference light by obtaining the frequency n (number of interference fringe changes in a predetermined pixel) when scanning the wavelength. Details of such a method are described in Japanese Patent No. 4100653.

  In the case of this embodiment, the calculated optical path length difference between the test light and the reference light is measured light from the reference standard surface 34Aa of the light deflection element 30B to the test surface 81 via the light reflecting surface 36. The optical distance on the optical path of the measurement light between the reference standard surface 34Aa and the test surface 81 can be calculated.

  <11> Based on the calculated optical distance and the analysis result of the interference fringe image for analysis, the image analysis unit 47A determines the diameter of the test surface 81.

Incidentally, in the case of measuring the entire area of the test surface 81, the relative position of the cylindrical body 80 with respect to the interferometer 10A and the light deflection element 30B, is successively moved in the direction of the measurement optical axis C _10, for respective movement, The above procedure may be repeated.

<Third Embodiment>
As shown in FIG. 6, the test surface measurement apparatus according to the third embodiment includes an interferometer 10B (measurement optical axis C _10B ), a transmission-type reference standard plate 50 (optical axis C ₅₀ ), and an optical deflection element 30C ( Relative inclination angles of the test surfaces 91A and 91B (corresponding to a plurality of planes spaced apart from each other) of the two plate-shaped subjects 90A and 90B which are provided with the optical axis _C30C ) and are spaced apart from each other. It is configured to measure (parallelism), shape and separation distance.

  The interferometer 10B can have the same configuration as the interferometer 10 of the first embodiment and the interferometer 10A of the second embodiment. Moreover, although not shown in figure, the analysis control part similar to the analysis control part 40 of 1st Embodiment or the analysis control part 40A of 2nd Embodiment is provided.

The reference plate 50 has a vertical reference surface 50a to the optical axis C _50, a part of the measurement light from the interferometer 10B with retro-reflected as reference light in the reference surface 50a The other measurement light is configured to be emitted toward the light deflection element 30B.

  As shown in FIG. 7, the light deflection element 30C is composed of a triangular prismatic reflection element (reflection mirror) having two measurement light deflection reflection planes 37A and 37B arranged perpendicular to each other. The measurement light from the interferometer 10B is reflected and deflected by the measurement light deflection reflecting planes 37A and 37B and irradiated onto the test surfaces 91A and 91B. Further, the test light retroreflected from the test surfaces 91A and 91B is reflected and deflected by the measurement light deflection reflecting planes 37A and 37B, and is emitted toward the interferometer 10B. In addition, since the effect | action of this embodiment is the same as that of the above-mentioned 1st Embodiment or 2nd Embodiment, description is abbreviate | omitted.

<Optical deflection element and deformation mode of test surface>
In the test surface measurement apparatus shown in FIG. 6, the inner peripheral surface (rotation) of the illustrated cylindrical body 100 is obtained by using the optical deflection element 30D (optical axis C _30D ) shown in FIG. 8 instead of the optical deflection element 30B. It is possible to measure the inclination angle, shape, and diameter of the test surface 101 which is a conical surface that is a symmetric ruled surface.

  The light deflection element 30D is a reflection element having a conical light reflection surface 36A, and is configured to deflect measurement light incident on the light reflection surface 36A and irradiate each part of the test surface 101. Has been. In addition, the test light retroreflected from each part of the test surface 101 is deflected by the light reflecting surface 36A and emitted toward an interferometer (not shown).

The optical deflection element 30D is suitable for measuring a concave surface such as the test surface 101 shown in FIG. 8, but this is replaced with the optical deflection element 30E (optical axis C _30E ) shown in FIG. Accordingly, the inclination angle and shape of each part of the convex surface such as the test surface 111 which is the outer peripheral side surface (formed in the shape of a conical surface which is a rotationally symmetric ruled surface) of the truncated cone-shaped subject 110 shown in FIG. In addition, the size of the diameter can be measured.

  Similar to the light deflection element 30D, the light deflection element 30E is a reflection element having a conical light reflection surface 36B. The light deflection element 30E deflects the measurement light incident on the light reflection surface 36B, so It is comprised so that each part of 111 may be irradiated. In addition, the test light retroreflected from each part of the test surface 111 is deflected by the light reflecting surface 36B and emitted toward an interferometer (not shown).

Further, by using the optical deflection element 30F (optical axis _C30F ) shown in FIG. 10, the outer peripheral surface of the illustrated cone 120 (formed in the shape of a conical surface, which is a rotationally symmetric ruled surface). It is possible to measure the inclination angle, shape, and diameter of the inspection surface 121.

This light deflection element 30F is composed of a reflection type diffractive optical element in which a plurality of ring-shaped reflection type diffraction gratings 38 are formed concentrically around the optical axis C _30F , and diffracts and deflects incident measurement light. Further, each part of the test surface 121 is configured to irradiate. Further, the test light retroreflected from each part of the test surface 121 is diffracted and deflected, and is emitted toward an interferometer (not shown).

<Fourth embodiment>
The test surface measuring apparatus according to the fourth embodiment shown in FIG. 11 has two plate-like specimens (in this embodiment, two molds 290A and 290B for molding and the same as the third embodiment described above. ) To measure the relative inclination angle (parallelism), shape, and separation distance of each of the test surfaces 291A, 291B. The interferometer 200, the light deflection element 30C, and the analysis controller 240 It has. Further, reference standard plates 221A and 221B are arranged on the optical path between the light deflecting element 30C and the two molds 290A and 290B, and these reference standard plates 221A and 221B are used as reference plate inclination adjustment stages 270A and 270B. Are held by linear stages 280A and 280B.

The interferometer 200 includes a low coherence light source 201 that outputs low coherence light including a plurality of wavelength components (SLD is used in this embodiment), and a collimator lens 202 that collimates the light beam from the low coherence light source 201. From the detour unit 203, the parallel light from the collimator lens 202 is split into two light beams, and one light beam is detoured with respect to the other light beam and then re-combined into one light beam. A condensing lens 208 that condenses the emitted light beam, a polarization-maintaining single-mode fiber 209 that transmits the light beam collected by the condensing lens 208, and a light beam emitted from the polarization-maintaining single-mode fiber 209 Is reflected on the light beam splitting surface 210a toward the left in the figure, and the light beam from the beam splitter 210 is measured by parallel light. It converted to, a collimator lens 211 for emitting along the measurement optical axis _{C 200,} and includes an imaging lens 212 and an imaging camera 213.

  The imaging camera 213 constitutes the imaging means in the present embodiment, and includes a beam splitter 214 that branches the interference light incident from the imaging lens 212 side into two on the light beam splitting surface 214a, and Two image pickup devices 215A and 215B (consisting of a CCD, a CMOS, or the like) disposed on each light emitting end face side of the beam splitter 214 are provided.

  The detour unit 203 splits the parallel light incident from the collimator lens 202 into a first light beam traveling downward in the figure and a second light beam traveling left in the figure on the light beam splitting surface 204a, A movable mirror 205 disposed on the optical path of the first light beam from the beam splitter 204, a fixed mirror 206 disposed on the optical path of the second light beam from the beam splitter 204, and the movable mirror 205 are shown in FIG. A movable mirror position adjusting unit 207 that moves the first light beam to the second light beam by a predetermined distance (difference in optical distances from the light beam splitting surface 204a of the beam splitter 204 to the movable mirror 205 and the fixed mirror 206). 2), the beam is re-combined into one beam at the beam splitting surface 204a of the beam splitter 204, and the above-mentioned collection is performed. Towards the lens 208 is configured to output.

  The light deflection element 30C has the same configuration as that described in the third embodiment, and branches the measurement light from the interferometer 200 in two directions on the reflection planes 37A and 37B for measurement light deflection. One is irradiated to the test surface 291A of the mold 290A via the reference standard plate 221A, and the other is irradiated to the test surface 291B of the mold 290B via the reference standard plate 221B. .

The reference plate inclination adjustment stage 270A is configured to adjust the drawing _{X 1} about the axis and _{Z 1} axis tilt of the reference plate 221A is, the reference plate inclination adjustment stage 270B is the reference plate 221B It is configured to adjust the drawing X ₁ about the axis and Z ₁ axis posture.

The linear stage 280A is the reference plate 221A via the reference plate inclination adjustment stage 270A is moved in the drawing _{Y 1} axially, in the drawing _{Y 1} axial position of the reference surface 221A (hereinafter "reference plate position A)) is finely adjusted. Similarly, the linear stage 280B is the reference plate 221B via the reference plate inclination adjustment stage 270B is moved in the drawing _{Y 1} axially, in the drawing _{Y 1} axial position of the reference surface 221B (hereinafter " (Referred to as “reference plate position B”).

  The analysis control unit 240 includes an analysis control device 241 including a computer, a monitor device 242 for displaying an interference fringe image, and the like, and an input device 243 for performing various inputs to the analysis control device 241. As shown in FIG. 12, the analysis control device 241 includes a detour distance adjustment control unit 244 configured by a storage unit such as a CPU and a hard disk installed in a computer, a program stored in the storage unit, and the like. A generation unit 245, an optical distance calculation unit 246, and an image analysis unit 247 are provided.

  The detour distance adjustment control unit 244 controls the drive of the movable mirror position adjusting unit 207 (see FIG. 11) to adjust the detour distance of the first light beam with respect to the second light beam, thereby The optical path length difference from the reference light is configured to be equal to or less than the coherence distance of the low coherent light output from the low coherent light source 201.

  The analysis image generation unit 245 generates an analysis interference fringe image for performing various analyzes on the test surfaces 291A and 291B based on the image signal of the interference fringe image captured by the imaging camera 213. It is configured.

  The optical distance difference calculation unit 246 is referred based on the analysis interference fringe image generated by the analysis image generation unit 245 and the detour distance value (the value after adjustment by the detour distance adjustment control unit 244). An optical distance on the optical path of the measurement light from the reference surfaces 221A and 221B to the test surfaces 291A and 291B is calculated.

  The image analysis unit 247 constitutes analysis means in the present embodiment, and the inclination angles and shapes of the test surfaces 291A and 291B are based on the generated analysis interference fringe image and the calculated optical distance. In addition, the distance between the test surfaces 291A and 291B is measured and analyzed.

  In the present embodiment, the detour distance adjustment control unit 244 and the movable mirror position adjustment unit 207 described above constitute an optical path length difference adjustment unit. The detour distance adjustment control unit 244 and the movable mirror position adjustment unit 207, The detour unit 203 and the optical distance difference calculation unit 246 described above constitute an optical distance measuring unit.

Hereinafter, the operation at the time of measurement of the test surface measuring apparatus according to the fourth embodiment will be described. Incidentally, in advance, alignment and test surface 291A of the optical deflection element 30C to the measurement optical axis _{C 200,} the alignment of 291B against interferometer 200 is assumed to have been completed. In addition, it is assumed that the alignment adjustment of the reference standard plates 221A and 221B is completed using the standard plate inclination adjustment stages 270A and 270B.

(Function during measurement)
<1> Low coherence light is emitted from the low coherence light source 201 shown in FIG. The low coherent light is converted into parallel light by the collimator lens 202 and then enters the detour unit 203.

  <2> The low coherent light incident on the detour unit 203 is branched into a first light beam directed toward the movable mirror 205 and a second light beam directed toward the fixed mirror 206 on the light beam branching surface 204a of the beam splitter 204. Each of the movable mirror 205 and the fixed mirror 206 is retroreflected and re-combined at the light beam splitting surface 204a. In the present embodiment, the respective optical path lengths from branching to re-multiplexing are set so that the first light flux is longer than the second light flux.

  <3> The light beam recombined and emitted from the beam splitter 204 enters the beam splitter 210 via the beam diameter conversion lens 208 and the polarization plane preserving single mode fiber 209 and is reflected by the light beam splitting surface 210a. The light enters the collimator lens 211. The light beam incident on the collimator lens 211 is converted into parallel light and emitted toward the light deflection element 30C.

  <4> The light beam incident on the light deflection element 30C is branched and deflected in two directions on the measurement light deflection reflection planes 37A and 37B, one of which is irradiated from the measurement light deflection reflection plane 37A onto the reference standard plate 220A. The other is irradiated from the reflection plane 37B for measuring light deflection to the reference standard plate 220A.

  <5> The light beam applied to the reference standard plate 220A is branched into a light beam retroreflected and a transmitted light beam on the reference standard surface 221A. In the present embodiment, among the light beams retroreflected by the reference standard surface 221A, a light beam component that has followed the path of the first light beam is used as reference light (hereinafter referred to as “first reference light”), and the reference standard surface 221A. Is the measurement light (hereinafter referred to as “first measurement light”) that is irradiated onto the test surface 291A.

  <6> Similarly, the light beam applied to the reference standard plate 220B is branched into a light beam retroreflected and a transmitted light beam on the reference standard surface 221B. In the present embodiment, among the light beams retroreflected by the reference standard surface 221B, a light beam component that has followed the path of the first light beam is used as reference light (hereinafter referred to as “second reference light”), and the reference standard surface 221B. Is the measurement light (hereinafter referred to as “second measurement light”) that is irradiated onto the surface to be measured 291B.

  <7> The first measurement light incident on the test surface 291A is retroreflected from the test surface 291A, returns to the reference standard plate 220A, and passes through the reference standard surface 221A again. In the present embodiment, of the first measurement light that again passes through the reference reference surface 221A, the light beam component that has followed the path of the second light beam carries test light (hereinafter referred to as “first light” that carries the wavefront information of the test surface 291A. Referred to as “one test light”).

  <8> Similarly, the second measurement light incident on the test surface 291B is retroreflected from the test surface 291B, returns to the reference standard plate 220B, and passes through the reference standard surface 221B again. In the present embodiment, of the second measurement light transmitted again through the reference reference surface 221B, the light beam component that has followed the path of the second light beam carries test light (hereinafter referred to as “first light”) that carries the wavefront information of the test surface 291B. 2).

  <9> The first test light is combined with the first reference light on the reference reference surface 221A (the combined light is hereinafter referred to as “first interference light”). Similarly, the first test light is combined with the second reference light on the reference standard plane 221B (the combined light is hereinafter referred to as “second interference light”).

  <10> The first interference light is reflected toward the interferometer 200 by the measurement light deflection reflection plane 37 </ b> A of the light deflection element 30 </ b> C, and the imaging camera 213 is passed through the collimator lens 211, the beam splitter 210, and the imaging lens 212. Then, a part of the light passes through the beam splitter 214 and enters the image sensor 215A. At this time, the optical path length difference between the first reference light and the first test light (in the order of the numbers shown in FIG. 11, 201 → 202 → 204a → 205 → 204a → 208 → 209 → 210a → 211 → 37A → 221A → The difference between the optical path length from 291A → 221A and the optical path length from 201 → 202 → 204a → 206 → 204a → 208 → 209 → 210a → 211 → 37A → 221A is less than the coherence distance of the low coherence light. If not, no optical interference occurs between the first reference light and the first test light, and no interference fringe image is formed by the first interference light. Although reflected downward by the light beam splitting surface 214a of the beam splitter 214, the magnification of the imaging lens 212 and the arrangement of the image sensor 215B are arranged so that the first interference light does not enter the image sensor 215B. Location has been set.

  <11> Similarly, the second interference light is reflected toward the interferometer 200 by the measurement light deflection reflection plane 37 </ b> B of the light deflection element 30 </ b> C, and passes through the collimator lens 211, the beam splitter 210, and the imaging lens 212. After entering the imaging camera 213, a part thereof is reflected downward by the light beam splitting surface 214a of the beam splitter 214 and enters the imaging device 215B. At this time, the optical path length difference between the second reference light and the second test light (in order of the numbers shown in FIG. 11, 201 → 202 → 204a → 205 → 204a → 208 → 209 → 210a → 211 → 37B → 221B → The difference between the optical path length from 291B → 221B and the optical path length from 201 → 202 → 204a → 206 → 204a → 208 → 209 → 210a → 211 → 37B → 221B is equal to or less than the coherence distance of the low coherence light. If not, optical interference between the second reference light and the second test light does not occur, and an interference fringe image is not formed by the second interference light. Although it passes through the beam splitter 214 and is emitted to the right in the figure, the magnification of the imaging lens 212 and the position where the image sensor 215A is disposed are set so that the second interference light does not enter the image sensor 215A. The That.

  <12> The optical path length difference between the first reference light and the first test light and the optical path length difference between the second reference light and the second test light are less than the coherence distance of the low coherence light. The detour distance of the first light beam with respect to the second light beam in the detour circuit unit 203 is adjusted. The detour distance is adjusted by the detour distance adjustment control unit 244 controlling the drive of the movable mirror position adjusting unit 207 to adjust the position of the movable mirror 205.

  <13> The optical path length difference between the first reference light and the first test light and the optical path length difference between the second reference light and the second test light are adjusted to be less than or equal to the coherence distance of the low coherent light. Then, an interference fringe image (hereinafter referred to as “first interference fringe image”) is formed on the image sensor 215A by the first interference light. More specifically, the linear adjustment 280A is used to finely adjust the distance between the test surface 291A and the reference reference surface 221A so that the fringe contrast (modulation is acceptable) of the first interference fringe image is maximized. Is made. This first interference fringe image is captured by the image sensor 215A.

  <14> The optical path length difference between the first reference light and the first test light and the optical path length difference between the second reference light and the second test light are adjusted to be less than or equal to the coherence distance of the low coherence light. Then, an interference fringe image (hereinafter referred to as “second interference fringe image”) is formed on the image sensor 215B by the second interference light. In more detail, the linear stage 280B is used to finely adjust the distance between the test surface 291B and the reference reference surface 221B so that the fringe contrast (modulation is acceptable) of the second interference fringe image is maximized. Is made. The second interference fringe image is picked up by the image sensor 215B (the timing of image pickup is the same as that of the first interference fringe image).

  <15> The image data of the first interference fringe image and the second interference fringe image simultaneously captured by the two image sensors 215A and 215B are output as separate video signals from the image sensors 215A and 215B, and the analysis image Two analysis images (the first interference fringe image for analysis generated from the image data of the first interference fringe image by the generation unit 245 and the “analysis of the image generated from the image data of the second interference fringe image” are generated. The second interference fringe image ”is generated, and the image data (analysis image data) is output to the optical distance calculation unit 246 and the image analysis unit 247, respectively.

  <11> In the optical distance calculation unit 246, based on the first interference fringe image for analysis and the value of the detour distance (the value after adjustment by the detour distance adjustment control unit 244), the reference surface 221A to the test surface The optical distance on the optical path of the first measurement light up to 291A is calculated. Specifically, the optical distance from the reference standard surface 221A to the test surface 291A on the optical path of the first measurement light is ½ of the value of the detour distance of the first light beam with respect to the second light beam in the detour unit 203. Since it corresponds to 1, it can be calculated from data of the value of this detour distance.

  <12> Similarly, in the optical distance calculation unit 246, based on the second interference fringe image for analysis and the value of the detour distance (value after adjustment by the detour distance adjustment control unit 244), from the reference reference plane 221B An optical distance on the optical path of the second measurement light to the test surface 291B is calculated. Specifically, the optical distance from the reference standard surface 221B to the test surface 291B on the optical path of the second measurement light is ½ of the value of the detour distance of the first light beam with respect to the second light beam in the detour unit 203. Since it corresponds to 1, it can be calculated from data of the value of this detour distance.

  <13> In the image analysis unit 247, the first interference fringe image for analysis is analyzed, and the inclination angle of the test surface 291A with respect to the reference reference surface 221A and the shape of the test surface 291A are obtained based on the analysis result. Similarly, based on the second interference fringe image for analysis, the inclination angle of the test surface 291B with respect to the reference standard surface 221B and the shape of the test surface 291B are obtained. Based on the obtained inclination angles, the relative inclination angles (parallelism) of the test surfaces 291A and 291B are obtained. Further, the optical distance between the reference standard surface 221A and the test surface 291A, the optical distance between the reference standard surface 221B and the test surface 291B, and the reference standard surface 221A obtained by the optical distance calculation unit 246 are calculated. Based on the optical distance (calculated from the adjustment values of the linear stages 280A and 280B) to the reference reference surface 221A, the optical distance between the test surfaces 291A and 291B is obtained. In addition, it is also possible to perform a level difference measurement when a level difference is formed on the test surfaces 291A and 291B by the same method.

  As described above, according to the test surface measurement apparatus of the present embodiment, the reference standard plates 220A and 220B are arranged on the respective optical paths between the measurement light deflection reflection planes 37A and 37B and the test surfaces 291A and 291B. As a result, the optical path length between the reference reference surfaces 221A and 221B and the test surfaces 291A and 291B can be shortened, so that it is difficult to be affected by air disturbance between the test surfaces 291A and 291B. It becomes possible.

  In addition, by configuring the first interference fringe image and the second interference fringe image to be separately captured using the two imaging elements 215A and 215B, the two interference fringe images are captured by one imaging element. Since the first interference fringe image and the second interference fringe image can be enlarged and captured as compared with the case where the imaging is configured, more accurate measurement can be performed.

  Next, an alignment adjustment method for the test surface measuring apparatus according to the present invention will be described by taking the first embodiment as an example. In this alignment adjustment, as shown in FIG. 13, a parallel plane plate 55 and an axis adjusting jig 60 are used.

The plane-parallel plate 55 is provided with a vertical reflection plane 56 with respect to its optical axis C _55, at the time of alignment, so as to be disposed on an optical path between the arrangement position of the collimator lens 21 and the conical lens 31 It is configured. Also, it is held by the two-axis inclination adjustment mechanism (not shown), and is configured so as to adjust the inclination with respect to the measurement optical axis C _10.

The axis adjusting jig 60 has a flat portion 61 perpendicular to the optical axis C ₆₀ and the alignment of the conical lens 31, the diffractive optical element 32, and the axis adjusting jig 60 is correctly adjusted. The first taper surface 62 (consisting of a conical surface with the optical axis _C60 as the central axis) formed at an inclination angle capable of retroreflecting the 0th-order diffracted light from the diffractive optical element 32 is also correctly adjusted. And a second tapered surface 63 (consisting of a conical surface with the optical axis _C60 as the central axis) formed at an inclination angle capable of retroreflecting the −1st order diffracted light from the diffractive optical element 32, At the time of alignment adjustment, the diffractive optical element 32 is arranged on the optical path of the measurement light on the lower side in the figure. Also, is held by the two-axis tilt adjustment mechanism and the in-plane adjusting mechanism (not shown), configured to allow positional adjustment in a plane perpendicular to the adjustment and the measurement optical axis C ₁₀ of the inclination with respect to the measurement optical axis C ₁₀ Has been.

Incidentally, the conical lens 31 and diffractive optical element 32 also, each different are held by the two-axis tilt adjustment mechanism and the in-plane adjusting mechanism, perpendicular to the adjustment and the measurement optical axis C ₁₀ of the inclination with respect to the measurement optical axis C ₁₀ The position can be adjusted in the plane.

(Alignment adjustment)
<1> conical lens 31, with respect to the diffractive optical element 32 and the axis adjustment jig 60 is plane-parallel plate 55 in the optical path in a state that is not disposed on the optical path, the reflection plane 56 is the measurement optical axis C ₁₀ Adjust the tilt so that it is vertical. This adjustment of inclination is formed by arranging a corner cube (not shown) on the reflection plane 56, irradiating the reflection plane 56 with measurement light, and reflecting light from the reflection plane 56 and return light from the corner cube. It is performed so that the interference fringe image is in a state closest to the null fringe. In order to form an interference fringe image, the detour distance is adjusted in the detour unit 13 (see FIG. 1) as in the measurement. This point is the same in the following alignment procedure, but the description is omitted.

<2> After removal of the corner cube, a diffractive optical element 32 is disposed on the optical path, so that the optical axis C ₃₂ of the diffraction optical element 32 is parallel to the measurement optical axis C _10, the diffraction optical element 32 Adjust the tilt. This tilt adjustment is performed by irradiating the diffractive optical element 32 with measurement light via the parallel flat plate 55, and the interference fringe image formed by the reflected light from the diffractive optical element 32 and the reflected light from the reflective plane 56 is null. It is performed so as to be in the state closest to the stripe.

<3> the axis adjustment jig 60 is disposed on the optical path, such that the optical axis C ₆₀ of the shaft adjustment jig 60 is parallel to the measurement optical axis C _10, of the shaft adjustment jig 60 Adjust the tilt. This tilt adjustment is performed by irradiating the axis adjustment jig 60 with measurement light (zero-order diffracted light from the diffractive optical element 32) via the parallel flat plate 55 and the diffractive optical element 32, and the plane of the axis adjustment jig 60. The interference fringe image formed by the reflected light from the part 61 and the reflected light from the reflection plane 56 is performed so as to be in a state closest to the null stripe.

<4> The conical lens 31 is arranged on the optical path, so that the optical axis C ₃₁ of the conical lens 31 is parallel to the measurement optical axis C _10, adjusts the inclination of the conical lens 31. The tilt adjustment is performed by irradiating the conical lens 31 with measurement light through the parallel plane plate 55 and forming interference fringes formed by the reflected light from the reference reference surface 31 b of the conical lens 31 and the reflected light from the reflective plane 56. This is done so that the image is closest to the null stripes.

<5> The parallel planar plate 55 is moved out of the optical path, and the measurement light of the axis adjusting jig 60 is adjusted so that the optical axis C _{60 of the} axis adjusting jig 60 coincides with the optical axis C ₃₁ of the conical lens 31. adjusting the position of a plane perpendicular to the axis C _10. This position adjustment is performed by irradiating the axis adjustment jig 60 with measurement light (0th-order diffracted light from the diffractive optical element 32) via the conical lens 31 and the diffractive optical element 32. The interference fringe image formed by the reflected light from the tapered surface 62 and the reflected light from the reference standard surface 31b of the conical lens 31 is performed so as to be in a state closest to the null stripe.

<6> such that the optical axis C ₃₂ of the diffractive optical element 32 is coincident with the optical axis C ₃₁ of the conical lens 31 adjusts the position of a plane perpendicular to the measurement optical axis C ₁₀ of the diffraction optical element 32 . This position adjustment is performed by irradiating the axis adjustment jig 60 with measurement light (−1st order diffracted light from the diffractive optical element 32) via the conical lens 31 and the diffractive optical element 32, and adjusting the position of the axis adjustment jig 60. The interference fringe image formed by the reflected light from the two tapered surfaces 63 and the reflected light from the reference standard surface 31b of the conical lens 31 is performed so as to be in a state closest to the null fringes.

  As mentioned above, although embodiment of this invention was described, an aspect of this invention is not limited to the above-mentioned embodiment, The thing of a various aspect can be made into embodiment.

  For example, in the reference standard plate with diffraction grating 30A of the light deflection element 30A shown in FIG. 3, the transmission diffraction grating 33a and the reference standard surface 33b can be separated. Similarly, in the optical deflection element 30B shown in FIG. 4, the reference standard plate 34 and the conical mirror 35 can be separated from each other.

  Further, by using an optical deflecting element of a type in which a conical lens and a diffractive optical element are combined like the optical deflecting element 30 shown in FIG. 1, convex surfaces such as test surfaces 111 and 121 shown in FIG. 9 and FIG. It is also possible to configure to measure the surface.

10, 10A, 10B, 200 Interferometer 11, 201 Low coherence light source 11A Wavelength tunable laser light source 12, 21, 21, A, 202, 211 Collimator lens 13, 203 Detour unit 14, 20, 20A, 204, 210, 214 Beam Splitter 14a, 20a, 20Aa, 204a, 210a, 214a Beam splitting surface 15, 205 Movable mirror 16, 206 Fixed mirror 17, 207 Movable mirror position adjuster 18 PZT element 19, 19A, 208 Beam diameter conversion lens 22, 22A, 212 Imaging lens 23, 23A, 213 Imaging camera 24, 24A, 215A, 215B Imaging element 30, 30A, 30B, 30C, 30D, 30E, 30F Light deflection element 31 Conical lens 31a Light transmission surface 31b Reference reference surface 32 (Transmission Type of diffractive optical element 3 3 Reference standard plate with diffraction grating 33a Transmission type diffraction grating 33b, 34a, 221A, 221B Reference standard surface 34, 50, 220A, 220B Reference standard plate 35 Conical mirror 36, 36A, 36B Light reflection surface 37A, 37B For measurement light deflection Reflection plane 38 Reflective diffraction grating 40, 40A, 240 Analysis control unit 41, 41A, 241 Analysis control device 42, 42A, 242 Monitor device 43, 43A, 243 Input device 44, 244 Detour distance adjustment control unit 45, 245 For analysis Image generation unit 46, 46A, 246 Optical distance calculation unit 47, 47A, 247 Image analysis unit 48 Wavelength scanning unit 49 Image generation unit 55 Parallel plane plate 56 Reflection plane 60 Axis adjustment jig 61 Plane unit 62 First taper surface 63 Second tapered surface 70 Test lenses 71, 81, 91A, 91B, 101, 111, 21,291A, 291B test surface 80 cylindrical body 90A, 90B shaped object 100 tubular member 110 frustoconical subject 120 frustoconical subject _{C 10, C 10A, C 10B} , C 200 measurement optical axis 209 polarized maintaining single-mode fiber 270A, 270B reference plate adjusting stage 280A, 280B linear stage 290A, 290B mold _{C 30B ~C 30F, C 31,} C 32, C 33, C 40, C 50, C 55, C 60, C ₇₀ optical axis

Claims (7)

A test surface measuring device for measuring a test surface comprising a rotationally symmetric ruled surface or a plurality of planes spaced apart from each other,
An interferometer for branching output light from the light source into measurement light and reference light at the reference standard plane, and emitting the measurement light along the measurement optical axis;
Disposed on the optical path of the measurement light between the interferometer and the test surface, deflects the measurement light emitted from the interferometer and vertically enters each part of the test surface; and A light deflecting element that deflects the test light retroreflected from each part of the test surface and emits the light toward the interferometer;
Imaging means for imaging an interference fringe image formed by optical interference between the test light from the light deflection element and the reference light;
An optical distance measuring means for measuring an optical distance on an optical path of the measurement light from the reference standard surface to the test surface;
Analytical means for analyzing the interference fringe image picked up by the image pick-up means. The light source is a low coherence light source that outputs low coherence light including a plurality of wavelength components,
The optical distance measuring unit diverts the low coherent light output from the low coherent light source into two light beams, detours one light beam with respect to the other light beam, and then re-combines the light into one light beam. Adjusting the detour distance of the one light beam with respect to the other light beam in the path portion and the detour route portion, the optical path length difference between the test light and the reference light is less than the coherence distance of the low coherence light And an optical distance calculation unit that calculates the optical distance based on the interference fringe image captured by the imaging unit and the value of the detour distance. The test surface measuring apparatus according to claim 1. The light source is a tunable laser light source;
The optical distance measuring unit includes a wavelength scanning unit that scans the wavelength of output light from the wavelength tunable laser light source, and interference fringes that are sequentially captured by the imaging unit while scanning the wavelength of the output light by the wavelength scanning unit. The test surface measurement apparatus according to claim 1, further comprising an optical distance calculation unit that calculates the optical distance based on the number of interference fringe changes in a predetermined pixel of the image. The test surface is a rotationally symmetric ruled surface,
The said light deflection | deviation element has a diffractive optical element in which several ring-shaped diffraction gratings are formed concentrically, The to-be-covered object of any one of Claims 1-3 characterized by the above-mentioned. Surface measuring device. The test surface is a rotationally symmetric ruled surface,
The test surface measurement apparatus according to claim 1, wherein the light deflection element includes a refraction element having a conical light transmission surface. The test surface is a rotationally symmetric ruled surface,
The test surface measurement apparatus according to claim 1, wherein the light deflection element includes a reflection element having a conical light reflection surface. The test surface is composed of a plurality of planes separated from each other,
The said light deflection | deviation element has a reflective element which has the several reflective plane for measurement light deflection | deviation arrange | positioned in a mutually different direction, The any one of Claims 1-3 characterized by the above-mentioned. Test surface measuring device.

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