JP2011237206A - Oblique incidence interferometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oblique incidence interferometer which can easily make optical axes of measurement light and reference light align with each other.SOLUTION: An oblique incidence interferometer 1 comprises: a light source 2; lenses 3 and 4 for turning light into parallel light; a light separation part 5 which separates the parallel light into measurement light and reference light and emits the measurement light obliquely relative to a measured surface S; a light combining part 6 which combines the reference light with the measurement light reflected at the measured surface to obtain interference light; a detection part for detecting the interference light; and a spot forming part 8 which is provided in an optical path from the light source 2 to the light separation part 5, which has a light passage hole 81 of a smaller size than the size of cross section of light, and which passes light only through the light passage hole 81.

Description

  The present invention relates to an oblique incidence interferometer that irradiates a measurement target with light from an oblique direction and causes measurement light reflected by the measurement target to interfere with reference light to measure the shape of the measurement target.

  Conventionally, a light wave interferometer is known as an apparatus for measuring the shape of a measurement object. This light wave interferometer divides the light from the light source into two or more, irradiates one of the light to the object to be reflected, reflects the other light by the reflecting mirror, combines these lights again, and combines them The shape of the measurement object is measured by analyzing the interference fringes generated by the above. As such a light wave interferometer, there are known a normal incidence interferometer that makes light incident on a measurement object vertically and an oblique incidence interferometer that makes light incident from an oblique direction. When measuring the flatness of a large surface or a non-mirror surface (rough surface), an oblique incidence interferometer is used (for example, see Patent Document 1).

The oblique incidence interferometer described in Patent Document 1 collimates light emitted from a light source, then divides the light into two polarized light by a light beam dividing unit, and uses one as measurement light and the other as reference light. Then, the measurement light is reflected by the first light beam bending part and emitted toward the measurement object, and the measurement light reflected by the measurement object is reflected by the second light beam bending part and enters the light beam combining part. The Further, the reference light separated by the light beam splitting unit enters the light beam combining unit. The light beam combining unit combines these measurement light and reference light again, and the combined light is incident on the detection unit.
As another example, after collimating the light emitted from the light source, it is incident obliquely on the triangular prism, transmitted through the prism bottom surface, and reflected by the measurement target and reflected by the prism bottom surface. A configuration in which the reference light is combined and the combined light is incident on the detection unit is shown.

JP 2010-32342 A

By the way, in the oblique incidence interferometer described in Patent Document 1, when the distance between the oblique incidence interferometer and the measurement object changes, the optical axis of the measurement light and the optical axis of the reference light are displaced.
Here, when the measurement light and the reference light are separated using the triangular prism, in theory, when the distance between the bottom surface of the triangular prism and the measurement target is 0, the optical axis of the measurement light and the optical axis of the reference light However, in reality, it is impossible to set the distance between the grazing incidence interferometer and the measurement target to zero, and the optical axes of the measurement light and the reference light can be matched. Have difficulty. For this reason, there is a problem that the wavefront of the measurement light and the wavefront of the reference light do not coincide with each other, and the measurement accuracy is lowered due to the influence of wavefront distortion.

  In contrast, in the configuration in which the measurement light is guided to the light beam combining unit using the first light beam bending unit and the second light beam bending unit, the measurement light is adjusted by adjusting the distance between the oblique incidence interferometer and the measurement target. And the optical axis of the reference light can be made coincident with each other. However, since the optical axis is shifted only by slightly changing the distance between the oblique incidence interferometer and the measurement object, there is a problem that it is difficult to carry out adjustment to match the optical axis without any index. Further, every time the measurement object is changed, the adjustment work as described above is necessary, and there is a problem that a complicated work is generated every measurement.

  In view of the above problems, an object of the present invention is to provide an oblique incidence interferometer capable of easily matching the optical axes of measurement light and reference light.

  The oblique incidence interferometer according to the present invention includes a light source that emits light, a light collimator that converts the light into parallel light, the parallel light is separated into measurement light and reference light, and the measurement light is measured A light separating unit that emits obliquely with respect to a surface, a light combining unit that combines the reference light and the measurement light reflected by the surface to be measured into interference light, and a detection unit that detects the interference light. A spot that is provided in the optical path of the light from the light source to the light separation unit and that has a light passage hole having a size smaller than the light cross-sectional size of the light, and allows the light to pass only through the light passage hole. And a forming portion.

Here, as the arrangement position of the spot forming unit, it may be provided at any position as long as it is in the optical path between the light source and the light separating unit. For example, when a spot forming unit is provided between the light collimating unit and the light separating unit, the light emitted from the light source is converted into parallel light by the light collimating unit, and then the light cross section of the parallel light at the spot forming unit. It is emitted as spot light having a size smaller than the size of the shape. Here, the cross-sectional size of parallel light and the size of the light passage hole refer to dimensions or areas. For example, when the parallel light is a beam having a circular cross section and the light passage hole is circular, it is sufficient that the aperture diameter of the light passage hole is smaller than the beam diameter of the parallel light. It is sufficient that only a part of the light is extracted as spot light.
In this oblique incidence interferometer, parallel light is separated into measurement light and reference light in the light separation section, and the measurement light is emitted toward the surface to be measured. Then, in the light combining unit, the measurement light reflected by the measurement surface and the reference light are combined to form interference light, and this interference light is incident on the detection unit. In the oblique incidence interferometer of the present invention, the spot forming unit adjusts the relative position of the oblique incidence interferometer with respect to the surface to be measured and adjusts the optical axes of the measurement light and the reference light. Then, spot light is formed, and position adjustment is performed based on the formed spot light.
In this position adjustment operation, since the parallel light incident on the light separation unit becomes spot light, the measurement light and reference light also become spot light (hereinafter referred to as measurement spot light and reference spot light). Since such a spot light has a small beam diameter, it is easy to confirm the deviation of the optical axes of the measurement light and the reference light. Therefore, for example, by adjusting the position of the grazing incidence interferometer so that these spot lights coincide with each other, the optical axes of the reference light and the measurement light can be easily matched to reduce the influence of wavefront distortion. Can do.

  In the oblique incidence interferometer according to the aspect of the invention, it is preferable that the spot forming unit includes a plurality of light passage holes.

In the oblique incidence interferometer, when the interference light is generated by combining the measurement light and the reference light in the light combining unit, there are a part that is combined so as to cancel each other and a part that is combined so as to strengthen each other. Here, when the light passage holes are formed at the positions of interference fringes that cancel each other's light, the light amount of the interference light becomes weak and it is difficult to determine whether or not the optical axes coincide with each other. .
On the other hand, in the present invention, the spot forming portion includes a plurality of light passage holes. For this reason, for example, even if it is not possible to determine whether or not the optical axis of the measurement light and the optical axis of the reference light match with the spot light formed by one light passage hole, The coincidence state of the optical axes can be determined from the spot light formed by the passage hole. Therefore, it is possible to more appropriately adjust the position of aligning the optical axis of the measurement light and the optical axis of the reference light.

  In the oblique incidence interferometer according to the aspect of the invention, it is preferable that the spot forming portion is a stop capable of adjusting an opening diameter of the light passage hole.

In the oblique incidence interferometer of the present invention, as described above, when the position adjustment is performed, the spot light is formed by the spot forming unit, but the diameter dimension is measured at the time of measuring the surface shape of the surface to be measured. Large parallel light is incident on the light separation unit without changing the beam diameter, and the measurement processing of the surface to be measured is performed.
Here, the spot forming unit may be detachable, and the spot forming unit may be attached at the time of position adjustment, and the spot forming unit may be removed at the time of shape measurement. The workload increases.
In addition, for example, a spot forming portion in which a light-passing hole such as a slit or a through hole is formed on a light-shielding plate member, for example, is rotated around a shaft portion provided outside the optical path, and is moved forward and backward in and out of the optical path. In such a configuration, a moving mechanism is required, and the size of the apparatus can be increased.
On the other hand, in the present invention, the spot forming portion is formed by a diaphragm such as an iris diaphragm. In such a configuration, a complicated moving mechanism or the like is unnecessary, the opening diameter of the light passage hole can be easily changed, and when the position adjustment is performed, the opening diameter of the light passage hole is reduced. When the light passage hole is formed and the measurement process is performed, the opening diameter of the light passage hole may be expanded to be equal to or larger than the beam diameter of the parallel light. Therefore, a configuration for moving the spot forming unit is not required, the configuration can be simplified, and the transition from the position adjustment operation to the shape measurement process can be easily performed.

  In the oblique incidence interferometer of the present invention, a light passing state where light passes and a light blocking state where light is blocked can be switched on one of the optical path of the measurement light and the optical path of the reference light. It is preferable that a simple light passage state switching unit is provided.

The light combining unit combines the measurement spot light and the reference spot light and emits them as interference light to the detection unit. For this reason, if the positions of the measurement spot light and the reference spot light are close to each other and overlap, it is difficult to grasp the outline and center point of each spot light. On the other hand, in the present invention, the light passage state in which the light passage state in which the light passes and the light shielding state in which the light is blocked can be switched on one of the measurement light and the reference light by the light shielding plate. A switching unit is provided. For example, the light passage state switching unit may be configured to move the light shielding plate in and out of the optical path. For example, the light passage state and the light shielding state may be switched by a diaphragm such as an iris diaphragm. In addition, when the S-polarized light and the P-polarized light are separated by the light separation unit and one of them is the measurement light and the other is the reference light, the light passing state switching unit serves as light in a predetermined linear polarization direction. It is good also as a structure etc. which provide this polarizing plate rotatably, using the polarizing plate which permeate | transmits only this.
In such a configuration, for example, when the light passage state switching unit is installed on the optical path of the reference light, the reference spot detected by the detection unit is alternately switched between the light passage state and the light shielding state of the light passage state switching unit. It is possible to blink the light. Therefore, the outline of the measurement spot light can be confirmed with the reference spot light turned off, and the outline of the combined light of the measurement spot light and the reference spot light can be confirmed with the reference spot light turned on. Can be confirmed. Therefore, by adjusting the position of the oblique incidence interferometer so that the contour of the measurement spot light and the contour of the combined light match, the optical axes of the measurement light and the reference light can be easily and accurately matched. Can do.

  Further, in the oblique incidence interferometer of the present invention, a light passage state in which light can be switched between a light passage state in which light passes and a light shielding state in which light is blocked on the optical path of the measurement light and the optical path of the reference light, respectively. It is preferable that a switching unit is provided.

  In this configuration, when detecting the position of the measurement spot light, the light passage state switching unit provided on the optical path of the reference light is blocked, and the light passage state switching unit provided on the optical path of the measurement light is provided. Let light pass. Thereby, since the reference spot light is shielded by the detection unit, the position of the measurement spot light can be detected more easily. Similarly, when detecting the position of the reference spot light, the light shielding plate provided on the optical path of the measurement light is set in a light shielding state, and the light shielding plate provided on the optical axis of the reference light is set in a light passing state. . Thereby, since the measurement light is blocked, the position of the reference spot light can be detected more easily. Therefore, even when the positions of these spot lights are close to each other, each position can be detected with high accuracy, and position adjustment can be performed with high accuracy.

  Here, the grazing incidence interferometer of the present invention includes a storage unit capable of storing data, and the detection unit images the spot light of the measurement light and the reference light, and the captured spot light is imaged. The data is preferably stored in the storage unit.

  In this invention, a detection part images the interference light by which the measurement spot light and the reference spot light were combined, and memorize | stores it in a memory | storage part. Thereby, the position of the measurement spot light and the position of the reference spot light are stored in the storage unit. Therefore, for example, by outputting each spot light stored in the storage unit to a display or the like, the position thereof can be reliably grasped, and the optical axes of the measurement light and the reference light can be easily and accurately determined. Positioning adjustment can be performed.

  In the present invention, it is preferable that an arithmetic unit that obtains the center of gravity in the contour shape of the optical section of each spot light based on the imaging data of the spot light stored in the storage unit is preferably provided.

  In the present invention, when detecting the optical axis of the spot light, the calculation unit obtains the center of gravity of each light cross-sectional shape from the captured image data of the light cross-sectional shape of the spot light. The position of the center of gravity is the same position when the cross-sectional shape of the spot light does not change, and for example, in the case of a circle, it is the center point of the circle. In addition, the center of gravity position can be easily obtained by calculation if the contour shape of the light cross section can be grasped, and by making each spot light coincide based on such a center of gravity position, the measurement light can be measured more easily and accurately. And the position adjustment which matches the optical axis of reference light can be implemented.

The schematic diagram which shows schematic structure of the oblique incidence interferometer of 1st embodiment which concerns on this invention. The figure which shows the example of the measurement spot light and reference spot light which are detected by a detection part. The figure which shows the state in which each spot light corresponded in 1st embodiment. The schematic diagram which shows schematic structure of the grazing incidence interferometer of 2nd embodiment which concerns on this invention. The schematic diagram which shows schematic structure of the grazing incidence interferometer of 3rd embodiment which concerns on this invention. The schematic diagram which shows schematic structure of the grazing incidence interferometer of 4th embodiment which concerns on this invention.

[First embodiment]
Hereinafter, an oblique incidence interferometer according to a first embodiment of the present invention will be described with reference to the drawings.

[1. Configuration of oblique incidence interferometer]
FIG. 1 is a schematic diagram showing a schematic configuration of the oblique incidence interferometer according to the first embodiment of the present invention.
As shown in FIG. 1, the oblique incidence interferometer 1 of the first embodiment includes a light source 2, lenses 3 and 4 constituting a light collimating unit, a light separating unit 5, a light combining unit 6, and a detecting unit 7. And a spot forming unit 8, and a measurement control device 9 is connected to the detection unit 7. The oblique incidence interferometer 1 may be configured to include a measurement control device.

As the light source 2, for example, a laser light source that has a good coherence and can emit laser light whose separation ratio of P-polarized light and S-polarized light separated by the light separation unit 5 does not change with time is used. It is preferable.
The light source 2 is not limited to the laser light source as described above, and may be any configuration as long as it can emit light of a predetermined wavelength. For example, an incandescent bulb and a wavelength selection filter are included. In this case, only light of a predetermined wavelength is extracted from the white light emitted from the incandescent light bulb by the wavelength selection filter and emitted.

  The lenses 3 and 4 constitute an optical collimating unit in the present invention. These lenses 3 and 4 expand the beam diameter of the laser light emitted from the light source 2 and emit light having the expanded beam diameter as parallel light (coherent light).

  The light separation unit 5 separates the parallel light incident from the lenses 3 and 4 side into measurement light and reference light. Specifically, the light separation unit 5 is configured by, for example, a polarization beam splitter, and separates incident parallel light into S-polarized light and P-polarized light. Then, the P-polarized light passes through the polarization beam splitter and is emitted as measurement light toward the measurement surface S, and the S-polarized light is reflected by the polarization beam splitter and emitted as reference light toward the light combining unit 6. Is done.

  The light combining unit 6 combines the reference light, which is S-polarized light emitted from the light separating unit 5, and the measurement light reflected by the measurement surface S into interference light (combined light). It injects into the detection part 7. Specifically, the light combining unit 6 is configured by a polarization beam splitter or the like, and combines the light by reflecting the reference light and transmitting the measurement light.

  The detection unit 7 receives the interference light combined by the light combining unit 6 and passed through the lens 61, and outputs a signal based on the amount of received light to the measurement control device 9. Specifically, the detection unit 7 includes an imaging unit in which a plurality of imaging elements are arranged in an array, images the interference light, and outputs the imaging data to the measurement control device 9.

  The measurement control device 9 is configured by, for example, a personal computer and measures the shape of the measurement target surface S by analyzing the interference fringes of the input image data of the interference light. Furthermore, the measurement control device 9 includes a storage unit 91 that stores captured image data of spot light incident on the detection unit 7 at the time of position adjustment described later, and stores the captured image data in the storage unit 91, for example, a display or the like. Output to other output devices.

  The spot forming unit 8 is a member that includes a light blocking unit 80 and a light passage hole 81, and is disposed on the optical path from the light source 2 to the light separating unit 5. The light passage hole 81 of the spot forming unit 8 restricts the beam diameter of parallel light (the diameter dimension of the optical section perpendicular to the optical axis), and emits spot light having a small beam diameter to the light separating unit 5. . In this embodiment, the spot forming unit 8 adjusts the distance between the oblique incidence interferometer 1 and the surface S to be measured to align the optical axis positions of the measurement light and the reference light. Parallel light is used as spot light. As a result, the spot light is separated into measurement light and reference light by the light separation unit 5, and the separated lights are combined by the light combining unit 6 and incident on the detection unit 7. At this time, when the optical axes of the measurement light and the reference light do not match, as shown in FIG. 1, the spot light (reference spot light) of the reference light and the spot light (measurement spot light) of the measurement light are respectively The light enters the detector 7 at a different position. Here, at the time of position adjustment, the position deviation of the measurement light and the reference light can be adjusted by adjusting the position of the oblique incidence interferometer 1 so that the measurement spot light and the reference spot light coincide with each other. It becomes possible.

  Further, in the oblique incidence interferometer 1 of the present embodiment, a stop capable of changing the opening diameter of the light passage hole 81, for example, an iris stop, is used as the spot forming unit 8. In such a spot forming portion 8, at the time of position adjustment as described above, it is possible to adjust the position with high accuracy by narrowing the opening diameter of the light passage hole 81 so that the beam diameter of the spot light is reduced. When measuring the shape of the surface to be measured S, it is possible to emit a sufficient amount of measurement light to the surface to be measured S by expanding the diameter of the light passage hole 81 to the maximum.

Here, FIG. 2 is a diagram illustrating the imaging results and the light intensity distribution of the measurement spot light and the reference spot light incident on the detection unit 7.
When the opening shape of the light passage hole 81 is circular, as shown in FIG. 2, spot light whose optical cross-sectional shape orthogonal to the optical axis is circular is detected by the detection unit 7. In the position adjustment, the position of the oblique incidence interferometer 1 is adjusted so that the contours of the measurement spot light and the reference spot light match.
At this time, the smaller the beam diameters of the measurement spot light and the reference spot light, the easier it is to align the contour position, and it is possible to perform alignment with higher accuracy. However, the aperture diameter that can be detected by the detection unit 7 depends on, for example, the size of each image sensor, the arrangement pitch of the image sensors, the light receiving sensitivity of the image sensor, and the like. Therefore, the minimum value of the opening diameter of the light passage hole 81 is preferably formed to the minimum diameter capable of detecting the spot light depending on the performance of the detection unit 7 and the like.
On the other hand, at the time of measuring the shape of the surface S to be measured, it is preferable to measure the surface shape in a wider range of the surface S to be measured, so that the parallel light output from the light source 2 can be reduced without reducing the beam diameter. The measurement light and the reference light are preferably separated. Therefore, the maximum value of the opening diameter of the light passage hole 81 is preferably set to be equal to or larger than at least the beam diameter of the parallel light emitted from the light source 2.

  Note that the spot forming unit 8 is not limited to the configuration using the iris diaphragm as described above. For example, the plate member in which the light passage hole 81 is formed may be configured to be movable with respect to the inside and outside of the optical path. In this case, the spot forming unit 8 is inserted into the optical path during position adjustment, and the spot forming unit 8 is removed from the optical path during measurement. As a result, similar to the spot forming unit 8 using the iris diaphragm as described above, the position adjustment can be performed with high accuracy using the measurement spot light and the reference spot light at the time of position adjustment, and the shape of the surface S to be measured can be measured. Sometimes, the parallel light from the light source 2 can be directly incident on the light separation unit 5, and the measurement efficiency can be improved. Alternatively, the light passing hole 81 may be formed by a gap between the light shielding plates by moving a plurality of light shielding plates close to and away from the inside and outside of the optical path of the parallel light. Furthermore, the shape of the light passage hole 81 is not limited to a circle, and can be formed in an arbitrary shape such as a rectangular shape or a slit shape. In this case, the opening size of the light passage hole 81, that is, the opening area, the diameter dimension of the outer circumference circle, and the like are formed smaller than the area of the light section of the parallel light that is the light section size of the parallel light and the beam diameter. Just do it.

  Further, in the present embodiment, the measurement light separated by the light separation unit 5 is directly incident on the measurement surface S, and the measurement light reflected on the measurement surface S is directly incident on the light combining unit 6. However, for example, the light emitted from the light combining unit 6 is reflected by a reflection mirror or the like and is incident on the measurement surface S, and the measurement light reflected by the measurement surface S is reflected by a reflection mirror or the like. It is good also as a structure etc. which enter into the photosynthesis part 6. FIG.

[2. Position adjustment of oblique incidence interferometer]
Next, position adjustment in the oblique incidence interferometer 1 as described above will be described.
In the oblique incidence interferometer 1 of the present embodiment, the position adjustment is performed based on the detection positions of the measurement spot light and the reference spot light as described above.
For this purpose, the aperture diameter of the light passage hole 81 of the spot forming unit 8 is reduced, and the beam diameter is made smaller than the parallel light emitted from the light source 2. As a result, the spot light is incident on the light separation unit 5 and separated into measurement spot light and reference spot light. Further, the reference spot light and the measurement spot light reflected by the measurement surface S are combined by the light combining unit 6, and the combined light is incident on the detection unit 7.

Here, when the distance between the oblique incidence interferometer 1 and the surface S to be measured is not appropriate, the optical axis of the measurement spot light and the reference spot light are respectively incident on different positions of the detection unit 7, and the captured image data is measured and controlled. It is output to the device 9.
The measurement control device 9 stores the captured image data in the storage unit 91 and displays the captured image data on the display as shown in FIG.
Therefore, the user adjusts the position of the oblique incidence interferometer 1 so that the contour positions of these spot lights coincide with each other, so that the influence of the wavefront distortion between the measurement light and the reference light is reduced to the optimum position. The oblique incidence interferometer 1 can be easily installed. For example, in the example shown in FIGS. 1 and 2, the reference spot light a is detected at the center point of the detection unit 7, whereas the measurement spot light b is detected on the outer peripheral side of the detection unit 7. In this case, from the state shown in FIG. 1, the position of the oblique incidence interferometer 1 is slightly shifted upward in the drawing to increase the distance between the oblique incidence interferometer 1 and the surface S to be measured. As shown in FIG. 3, the reflection position of the measurement spot light b changes, and the reference spot light and the optical axis of the measurement spot light coincide with each other. In this state, the optical axes of the reference light and the measurement light are aligned, and the influence of wavefront distortion is reduced in the interference wave formed by the measurement light and the reference light. Therefore, it is possible to obtain a highly accurate measurement result by detecting such interference light by the detection unit 7.

  As the position adjusting operation, the distance between the oblique incidence interferometer 1 and the surface S to be measured may be adjusted manually, for example, or may be configured to be automatically adjustable. When the position adjustment is automatically performed, for example, a stage that holds the oblique incidence interferometer 1 and a moving mechanism that moves the stage forward and backward with respect to the measurement surface S are provided. To adjust the distance between the oblique incidence interferometer 1 and the surface S to be measured.

  Further, in the above, the example of performing the alignment of the oblique incidence interferometer 1 by aligning the contours of the respective spot lights as shown in the upper diagram of FIG. 2 is not limited to this. For example, As shown in the lower diagram of FIG. 2, profile information indicating the light intensity distribution of each spot light is acquired, and the distance between the oblique incidence interferometer 1 and the measured surface S is adjusted so that the profile information matches. Good.

[3. Effects of First Embodiment]
In the oblique incidence interferometer 1 of the first embodiment, spot formation having a light passage hole 81 having a diameter smaller than the beam diameter of the parallel light emitted from the light source 2 in the optical path from the light source 2 to the light separation unit 5. A part 8 is provided. In such a configuration, when the position of the oblique incidence interferometer 1 is adjusted, the spot light that has passed through the light passage hole 81 of the spot forming unit 8 is separated by the light separating unit 5 and emitted as measurement spot light and reference spot light. Is done. Here, when the optical axis of the measurement light is shifted from the optical axis of the reference light, the positions of the measurement spot light and the reference spot light incident on the detection unit 7 are also shifted. Therefore, the user can easily recognize the shift amounts of the optical axes of the measurement light and the reference light by grasping the detection positions of the measurement spot light and the reference spot light. That is, by changing the distance between the oblique incidence interferometer 1 and the surface S to be measured so that the measurement spot light and the reference spot light are combined, it is possible to easily reduce the influence of wavefront distortion of the measurement light and the reference light. State. Further, while maintaining this installation state, the light passing hole 81 of the spot forming unit 8 is expanded to allow the parallel light from the light source 2 to pass, and based on the interference light detected by the detecting unit 7, the surface to be measured By performing the shape measurement of S, it is possible to perform a highly accurate measurement that suppresses the influence of wavefront distortion during the synthesis of the measurement light and the reference light.

  The spot forming unit 8 is configured by an iris diaphragm that can adjust the opening diameter of the light passage hole 81. Therefore, when the position of the oblique incidence interferometer 1 is adjusted, the opening diameter of the light passage hole 81 can be reduced, and when the surface shape of the surface S to be measured is measured, the opening diameter of the light passage hole 81 can be expanded. That is, for example, in the case of a configuration in which the spot forming unit 8 is attached / detached at the time of position adjustment and at the time of surface shape measurement, complicated operations are involved at the time of operation switching. On the other hand, if it is the above structures, since the opening diameter dimension of the light passage hole 81 can be easily changed only by operating the iris diaphragm, the work load can be reduced.

  The oblique incidence interferometer 1 includes a measurement control device 9, and the measurement control device 9 includes a storage unit 91 that stores imaging data of each spot light imaged by the detection unit 7. For this reason, it becomes possible to output and display the imaged data recorded in the storage unit 91 on a display, for example, and the user adjusts the position of the oblique incidence interferometer 1 based on the output data. Can do.

[Second Embodiment]
Next, a grazing incidence interferometer according to a second embodiment of the present invention will be described with reference to the drawings.
FIG. 4 is a schematic diagram showing a schematic configuration of the oblique incidence interferometer of the second embodiment. In the following description of the embodiments, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

In the oblique incidence interferometer 1 of the first embodiment described above, a configuration in which one light passage hole 81 is provided in the spot forming unit 8 is shown. On the other hand, in the oblique incidence interferometer 1A of the second embodiment, an example in which a plurality of light passage holes 81 are formed in the spot forming portion 8A is shown.
Specifically, the spot forming portion 8 </ b> A of the second embodiment includes a light shielding portion 80 and two light passage holes 81. For example, the spot forming portion 8A is pivotally supported at the end of the light shielding portion 80, and rotates the spot forming portion 8A in the optical path when adjusting the position, while spot measuring when measuring the shape of the surface S to be measured. It becomes possible to rotate the forming portion 8A out of the optical path.

In such a spot forming unit 8A, when adjusting the position of the oblique incidence interferometer 1A, two spot lights are formed as shown in FIG.
These spot lights are separated into a measurement spot light and a reference spot light, respectively, in the light separating section 5, and among these, the measurement spot light is emitted to the measured surface S side, and the reference spot light is directed to the light combining section 6. And injected. Then, the reference spot light and the measurement spot light reflected by the measurement surface S are combined in the light combining unit 6 and incident on the detection unit 7.
At the time of position adjustment, as in the first embodiment, the oblique incident interferometer 1A and the surface to be measured are arranged so that the contour of the measurement spot light detected by the detection unit 7 and the contour of the reference spot light coincide with each other. Adjust the distance to S.

At this time, as shown in FIG. 4, when the contours of the measurement spot light and the reference spot light coincide with each other, these spot lights interfere with each other. Therefore, depending on the reflection position of the measurement spot light, the light of each other is weakened. There is a case. In this case, the light intensity of the spot light detected by the detection unit 7 decreases, and it becomes difficult to match the contours of the measurement spot light and the reference spot light.
On the other hand, in the second embodiment, two light passage holes 81 are provided. For this reason, the spot light emitted from each light passage hole 81 is separated into the reference spot light and the measurement spot light by the light separation unit 5, and the reference spot light and the measurement spot light are synthesized by the light synthesis unit. At this time, even when the reference spot light and the measurement spot light corresponding to the spot light emitted from the one light passage hole 81 are weakened to each other in the light combining unit 6, the reference spot light and the measurement spot light corresponding to the other spot light. Can be used to adjust the position of the grazing incidence interferometer 1.
In the present embodiment, the configuration in which the two light passage holes 81 are provided in the spot forming portion 8A is illustrated, but a configuration in which, for example, three or more light passage holes 81 are formed may be employed.

[Effects of Second Embodiment]
As described above, in the oblique incidence interferometer 1A of the second embodiment, a plurality of light passage holes 81 are formed in the spot forming portion 8A. Therefore, based on the spot light formed by these light passage holes 81, for example, even when one set of measurement spot light and reference spot light are weakened to each other by synthesis, another set of measurement spot light and reference The distance between the oblique incidence interferometer 1 and the measured surface S can be adjusted based on the spot light. For this reason, position adjustment can be easily performed without performing work such as shifting the position of the light passage hole 81.

[Third embodiment]
Next, an oblique incidence interferometer according to a third embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a schematic diagram showing a schematic configuration of the grazing incidence interferometer according to the third embodiment of the present invention.

In the first embodiment, the oblique incident interferometer 1 and the contour information of the reference spot light a and the measurement spot light b as shown in FIG. 2 and profile information indicating the light intensity distribution of each spot light are combined. The position was adjusted by adjusting the distance of the surface S to be measured. By the way, when two spot lights overlap, these spot lights are combined, so that it is difficult to clearly distinguish the respective contour positions. Even when the profile information is combined, it is difficult to determine whether or not the peak points with the highest light intensity overlap.
On the other hand, the third embodiment has a configuration that allows the spot light of the measurement light and the reference light spot light to be superimposed more easily.

  Specifically, in the oblique incidence interferometer 1B of the third embodiment, as shown in FIG. 5, the light passage state switching unit of the present invention is placed on the optical path of the reference light between the light separating unit 5 and the light combining unit 6. A light shielding plate 11 is provided. The light shielding plate 11 is connected to a moving mechanism (not shown), and is configured so that the light shielding plate 11 can move in and out of the optical path of the reference light by the moving mechanism. The moving mechanism may have any configuration such as a configuration for rotating the light shielding plate 11 or a configuration for sliding the light shielding plate.

[Operational effects of the third embodiment]
In the oblique incidence interferometer 1B of the third embodiment, the reference spot light detected by the detection unit 7 is blinked by alternately moving the light shielding plate 11 in and out of the optical path of the reference light at the time of position adjustment. As a result, even when the detection position of the measurement spot light and the reference spot light are close and partially overlapped, the outline of the measurement spot light and the light intensity distribution can be confirmed when the reference spot light is turned off. It is possible to check the misalignment between the measurement spot light and the reference spot light when the reference spot light is turned on. Therefore, the positions of the measurement spot light and the reference spot light can be aligned with higher accuracy, and the influence of wavefront distortion can be more reliably reduced when a combined wave of the reference light and measurement light is generated.

  In the third embodiment, the light shielding plate 11 that can move in and out of the optical path of the reference light is provided and the reference spot light blinks when adjusting the position. For example, the light can be moved in and out of the optical path of the measuring light. It is good also as a structure provided with a light-shielding plate. In this case, when adjusting the position of the oblique incidence interferometer 1B, the measurement light can be blinked.

  Moreover, although the light shielding plate 11 that blocks light is provided, for example, a polarizing plate that allows only light in a predetermined linear polarization direction to pass therethrough may be provided. In this case, by rotating the polarizing plate, it is possible to alternately switch between a state in which the reference light that is S-polarized light can be transmitted and a state in which the reference light is blocked, and the reference spot light can be blinked.

[Fourth embodiment]
Next, an oblique incidence interferometer according to a fourth embodiment of the present invention will be described with reference to the drawings.
FIG. 6 is a schematic diagram showing a schematic configuration of a grazing incidence interferometer according to a fourth embodiment of the present invention.

  In the third embodiment, when the position of the oblique incidence interferometer 1B is adjusted, the reference spot light is blinked so that the outline of the measurement spot light can be easily grasped and the outline of the measurement spot light and the reference spot light can be easily matched. The structure to perform was illustrated. On the other hand, in the fourth embodiment, the positions of the reference spot light and the measurement spot light are individually detected.

Specifically, in the oblique incidence interferometer 1C of the fourth embodiment, a light shielding plate 11A is provided on the optical path of the reference light between the light separating unit 5 and the light combining unit 6, as shown in FIG. . Similarly, the oblique incidence interferometer 1C is provided with a light shielding plate 11B that can move in and out of the optical path of the measurement light. The light shielding plates 11A and 11B are connected to a moving mechanism (not shown), and the light shielding plates 11A and 11B are configured to be movable in and out of the optical path by these moving mechanisms. The control of these moving mechanisms may be performed manually by the user, for example, or may be controlled by the measurement control device 9.
As in the third embodiment, the moving mechanism may have any configuration such as a configuration for rotating the light shielding plates 11A and 11B and a configuration for sliding the light shielding plate. Moreover, it is good also as a structure which can provide rotatably the polarizing plate which permeate | transmits only the light of predetermined linearly polarized light instead of the light-shielding plate which interrupts | blocks light.

  The measurement control device 9 connected to the detection unit 7 of the oblique incidence interferometer 1C of the fourth embodiment includes a storage unit 91 that stores the measurement spot light and the reference spot light imaged by the detection unit 7 as image data. And an arithmetic unit 92 that analyzes the image data of the measurement spot light and the reference spot light recorded in the storage unit 91 and calculates the position of the center of gravity from the contour shape.

In the oblique incidence interferometer 1C of the fourth embodiment, the position adjustment of the measurement spot light and the reference spot light is performed by the following method at the time of position adjustment.
That is, in the position adjustment operation of the oblique incidence interferometer 1B, first, the light shielding plate 11A is moved into the optical path to block the reference spot light, and the light shielding plate 11B is moved out of the optical path to pass the measurement spot light. . Thereby, the detection unit 7 detects only the measurement spot light, and the imaging data of the measurement spot light is stored in the storage unit 91 of the measurement control device 9.
Next, the light shielding plate 11A is moved out of the optical path and the light shielding plate 11B is moved into the optical path, for example, by a user operation or control of the measurement control device 9. Thereby, the detection unit 7 detects only the reference spot light, and the imaging data of the reference spot light is stored in the storage unit 91 of the measurement control device 9.

Thereafter, the calculation unit 92 of the measurement control device 9 reads the imaging data of the measurement spot light and the imaging data of the reference spot light stored in the storage unit 91, and the barycentric coordinate position of the outline shape of the measurement spot light, the reference spot The center-of-gravity coordinate position of the light contour shape is calculated. In addition, when the light passage hole 81 of the spot forming unit 8 is circular, each spot light is circular, and thus the circle center coordinates are calculated. Further, the measurement control device 9 outputs these calculated barycentric coordinate positions to an output device such as a display. Then, the user adjusts the distance between the oblique incidence interferometer 1C and the surface S to be measured so that these barycentric coordinate positions coincide with each other.
Here, the user manually moves the grazing incidence interferometer 1C. However, as described above, for example, the stage where the grazing incidence interferometer 1C is provided so as to be able to advance and retreat with respect to the measurement surface S. The stage may be configured to be movable under the control of the measurement control device 9 or the like. In this case, the measurement control device 9 calculates the movement amount of the stage for matching the barycentric coordinate positions of the spot light based on the reference spot light and the barycentric position table of the measurement spot light, and the calculated movement amount The stage may be moved based on the above.

[Effects of the fourth embodiment]
In the oblique incidence interferometer 1C of the fourth embodiment, the light shielding plates 11A and 11B that are movable in and out of the optical path are provided on the optical path of the reference light and the optical path of the measurement light, respectively.
For this reason, when adjusting the position of the oblique incidence interferometer 1C, only the detection position of the measurement spot light can be grasped by moving the light shielding plate 11A into the optical path and moving the light shielding plate 11B out of the optical path. By moving the light shielding plate 11B into the optical path and moving the light shielding plate 11A out of the optical path, only the detection position of the reference spot light can be grasped. Therefore, even when the detection positions of the measurement spot light and the reference spot light are close to each other, the spot lights are not detected in an overlapping manner, so that the incident position of each spot light can be reliably detected.

  Further, by storing the imaging data of these spot lights in the storage unit 91, the detection position of each spot light can be calculated based on the imaging data, and the oblique incidence interferometer 1C is calculated based on these calculated values. By performing the position adjustment, the optical axes of the reference light and the measurement light can be reliably matched.

And the calculating part 92 of the measurement control apparatus 9 calculates the gravity center coordinate position in the outline shape of each spot light. Such a barycentric coordinate position can be obtained by a simple arithmetic expression. For example, in this embodiment, the contour shape of the spot light is circular. In this case, for example, the beam diameter of the spot light and the center coordinates can be easily calculated by calculating the maximum value of the difference value between the coordinates forming the contour shape.
Further, in the above, the case where the spot light is circular is illustrated, but for example, when the spot light is formed in a triangular shape and the measurement light is reflected a plurality of times and is incident on the detection unit, it is incident on the detection unit 7. The direction of the image of the measurement spot light may differ from the direction of the image of the reference spot light. Even in such a case, the position of the center of gravity does not change. Therefore, as described above, the calculation unit 92 calculates the center of gravity coordinate position of the contour shape of each spot light, and matches the center of gravity coordinate position. By performing the position adjustment, the optical axes of the measurement light and the reference light can be easily aligned.

[Other Embodiments]
It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.

  For example, an example in which the grazing incidence interferometers 1, 1A, 1B, and 1C and the measurement control device 9 are configured separately is shown. For example, the grazing incidence interferometers 1, 1A, 1B, and 1C are configured as the measurement control device 9. It is good also as a structure containing.

  For example, a configuration for analyzing interference fringes of interference light (for example, see Japanese Patent Application Laid-Open No. 2010-32342) may be applied as the detection unit 7 using, for example, a phase shift method. It is possible to provide an oblique incidence interferometer capable of performing the following.

  In the fourth embodiment, the calculation unit 92 obtains the centroid position coordinate table of the contour shape of each spot light, and shows an example in which the position adjustment is performed so that these centroid position coordinate tables match. Not exclusively. For example, the contour shape of the imaging data of the reference spot light stored in the storage unit is displayed on the display with the display color changed, for example, and the contour shape of the measurement spot light is changed to the contour of the reference spot light displayed on the display. The oblique incidence interferometer 1C may be moved to match.

  The light separation unit 5 exemplifies the configuration in which the parallel light is separated into S-polarized light and P-polarized light, the S-polarized light is used as reference light, and the P-polarized light is used as measurement light. The S-polarized light reflected by the unit 5 may be the measurement light and the P-polarized light may be the reference light.

  Further, although the light separating unit 5 separates the S-polarized light and the P-polarized light, the present invention is not limited to this, and an optical member having substantially the same reflectance and transmittance of light is used, and the transmitted light is measured and reflected. It is good also as composition which uses light as reference light.

  Although an example in which the position of the spot forming unit 8 is provided between the light separating unit 5 and the lenses 3 and 4 has been shown, for example, a configuration provided between the light source 2 and the lenses 3 and 4 may be used. And the lens 4 may be provided.

  In addition, the specific structure and procedure for carrying out the present invention can be appropriately changed to other structures and the like within a range in which the object of the present invention can be achieved.

  DESCRIPTION OF SYMBOLS 1,1A, 1B, 1C ... Oblique incidence interferometer, 2 ... Light source, 3, 4 ... Lens which comprises a parallelizing part, 5 ... Light separation part, 6 ... Photosynthesis part, 7 ... Detection part, 8, 8A ... Spot Forming unit, 11 ... light shielding plate as light passage state switching unit, 81 ... light passage hole, 91 ... storage unit, 92 ... calculation unit, S ... surface to be measured.

Claims (7)

A light source that emits light;
A light collimating unit for converting the light into parallel light;
A light separation unit that separates the parallel light into measurement light and reference light and emits the measurement light obliquely with respect to the surface to be measured;
A light combining unit that combines the reference light and the measurement light reflected by the surface to be measured to form interference light;
A detection unit for detecting the interference light;
Spot formation that is provided in the optical path of the light from the light source to the light separation unit and has a light passage hole having a size smaller than the light cross-sectional size of the light, and allows the light to pass only through the light passage hole. And
An oblique incidence interferometer comprising: The grazing incidence interferometer according to claim 1,
The grazing incidence interferometer, wherein the spot forming section includes a plurality of light passage holes. The oblique incidence interferometer according to claim 1 or 2,
The oblique incidence interferometer, wherein the spot forming unit is a stop capable of adjusting a diameter of the light passage hole. The oblique incidence interferometer according to any one of claims 1 to 3,
On either one of the optical path of the measurement light and the optical path of the reference light, a light passage state switching unit capable of switching between a light passage state where light passes and a light shielding state where light is blocked is provided. An oblique incidence interferometer. The oblique incidence interferometer according to any one of claims 1 to 3,
A light passage state switching unit capable of switching between a light passage state through which light passes and a light blocking state through which light is blocked is provided on the optical path of the measurement light and the optical path of the reference light, respectively. Oblique incidence interferometer. The oblique incidence interferometer according to claim 5,
It has a storage unit that can store data,
The detection unit images spot light of the measurement light and the reference light,
The oblique incidence interferometer, wherein the captured image data of the spot light is stored in the storage unit. The grazing incidence interferometer according to claim 6,
An oblique incidence interferometer, comprising: a calculation unit that obtains the center of gravity of the contour shape of the light section of each spot light based on the imaging data of the spot light stored in the storage unit.

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