JP2007292650A - Optical interferometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical interferometer capable of enhancing measurement precision and capable of measuring a wide area. <P>SOLUTION: The optical interferometer 100 includes a lighting optical system 110, a noninterference beam generation part 120 for multiplexing an object light with a reference light under a noninterference condition to form a noninterference beam, an interference fringe generation means 130 for generating an interference fringe by interference of the noninterference beam, and a CCD camera 140 for imaging the interference fringe. Polarization axes are orthogonal each other in the object light and the reference light, and the object light and the reference light pass the same route under the condition multiplexed as the noninterference beam. A Wollaston prism 131 and a polarization plate 132 are arranged as the interference fringe generation means 130, in a position in a just front side of a position where the noninterference beam gets incident into the imaging means. In the Wollaston prism 131, an advancing direction of the object light of noninterference beam is made different from an advancing direction of the reference light of noninterference beam to make incident angles of the object light and the reference light different when getting incident into the CCD camera 140. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical interferometer. For example, the present invention relates to an optical interferometer that measures surface irregularities of a measurement object.

  An optical interferometer is known as a device for measuring unevenness of a test surface, and it is known that a Fizeau interferometer can be used when measuring unevenness of a wide surface (for example, Patent Document 1). It is known that when the reference plane is inclined and the wavefront is inclined with reference light and object light, the fringe density of the interference fringes is increased and the resolution can be improved.

FIG. 5 is a view showing the Fizeau optical interferometer 10 with the reference surface inclined.
An optical path of light in the Fizeau interferometer shown in FIG. 5 will be briefly described.
In FIG. 5, the light (L10) emitted from the light source 11 is converted into a parallel light beam by the collimating lens system 12, reflected (L11) by the half mirror 13 on the way, and irradiated onto the workpiece surface S. The light emitted from the light source 11 passes through the collimating lens system 12, then becomes linearly polarized light by the polarizing plate 18, and further passes through the half-wave plate 19 to become light having an arbitrary polarization axis (knitting wave surface). .
Here, a quarter-wave plate 14 also serving as a reference surface is disposed between the half mirror 13 and the workpiece W. The quarter wavelength plate 14 is disposed in a tilted state. Part of the light (L11) incident on the quarter-wave plate 14 from the light source 11 is reflected and the rest is transmitted. The light (L12) reflected by the quarter wavelength plate 14 returns to the half mirror 13 as reference light. The light (L13) transmitted through the quarter-wave plate 14 is irradiated onto the workpiece surface S, reflected by the workpiece surface S, and returned to the quarter-wave plate 14 as object light (L14). The light passes through the plate 14 and enters the half mirror 13.

  At this time, since the object light (L14) from the workpiece surface S passes through the quarter-wave plate twice, the vibration direction is rotated by 90 degrees and has a polarization direction orthogonal to the reference light (L12). Therefore, the reference light (L12) and the object light (L14) return to the half mirror 13 without interference. The light beam returning to the half mirror 13 passes through the half mirror 13 and then enters the interference fringe acquisition unit 15. At this time, the object light (L14) is perpendicularly incident on the interference fringe acquisition unit 15, while the quarter-wave plate 14 also serving as a reference surface is inclined, so that the reference light L12 is transmitted to the interference fringe acquisition unit 15. And incident at an inclination angle (see FIG. 6). In the interference fringe acquisition unit 15, when the reference light L12 and the object light L14 pass through the polarizing plate 16 having a polarization axis of 45 degrees, the reference light L12 and the object light L14 interfere with each other to generate an interference fringe. This interference fringe is imaged by the CCD camera 17. By analyzing the acquired interference fringes, irregularities on the workpiece surface S are detected.

  At this time, the incidence angle is made different between the reference beam (L12) and the object beam (L14), and the angle of the wavefronts is increased to increase the density of interference fringes. Therefore, the interference fringe analysis accuracy is improved.

JP-A-11-337321

However, if the quarter-wave plate 14 as the reference surface is tilted to increase the density of interference fringes, the object light (L14) and the reference light (L12) do not pass through a common path. Since the reference surface is inclined, the paths of the object light (L14) and the reference light (L12) are different over a long path from the reference surface to the interference fringe acquisition unit 15. Thus, if the path is different between the object light (L14) and the reference light (L12), an optical path difference is generated between the reference light (L12) and the object light (L14).
Then, there arises a problem that measurement accuracy is reduced.

In addition, the reference surface is inclined in order to make an angle between the wavefront of the object light (L14) and the wavefront of the reference light (L12). However, if the reference surface is inclined so as to sufficiently increase the density of interference fringes. The traveling direction is greatly shifted between the object beam (L14) and the reference beam (L12). Since the distance between the reference surface and the interference fringe acquisition unit 15 is long, if the path between the object light (L14) and the reference light (L12) is greatly shifted, the interference fringe acquisition unit 15 refers to the object light (L14). The area where light (L12) overlaps becomes small. Then, since the area where an interference fringe is generated becomes small, there arises a problem that the measurement area becomes small.
In particular, in the Fizeau type, for example, since the size of the measurement area can be one of the advantages, it is a great disadvantage that the measurement area is reduced.

  An object of the present invention is to provide an optical interferometer with improved measurement accuracy and a wide measurement area.

  In the optical interferometer of the present invention, the interference fringe obtained by causing the object light reflected on the test surface and the reference light reflected on the reference surface to interfere with each other is picked up by the image pickup means, and the interference fringe is based on the interference fringe. In the optical interferometer for measuring the test surface, the object light and the reference light are polarized light whose polarization axes are orthogonal to each other, and the object light and the reference light are combined as a non-interfering light beam. The object light and the reference light are transmitted by changing the traveling directions of the object light and the reference light of the non-interfering light flux at a position immediately before the incoherent light flux enters the imaging unit through the same path. An incident angle difference generating unit that makes a difference in an incident angle incident on the imaging unit, and a polarizer that causes the object light and the reference light that have been given an angle difference by the incident angle difference generating unit to interfere with each other. It is characterized by being arranged.

  In such a configuration, first, the light from the light source is separated into two light beams, one light beam is irradiated toward the test surface, and the other light beam is irradiated onto the reference surface. Then, the light irradiated on the test surface is reflected as object light having phase information (spatial information) of the test surface. The light irradiated on the reference surface is reflected as reference light. Then, the object light and the reference light are combined and travel to the imaging unit through the same path. At this time, the object light and the reference light are respectively polarized light, and the polarization directions of each other are orthogonal. Therefore, the light obtained by combining the object light and the reference light is a non-interfering light beam. The non-interfering light beam enters the incident angle difference generating unit before the non-interfering light beam directed to the imaging unit enters the imaging unit. Then, the traveling directions of the object light and the reference light of the non-interfering light flux are separated into different directions by the incident angle difference generating means, and the object light and the reference light are incident on the imaging means at different angles. Further, the object light and the reference light separated in different traveling directions interfere with each other before entering the imaging unit, and interference fringes are generated. Then, the interference fringes enter the imaging unit, and the interference fringes are imaged by the imaging unit. Based on the imaged interference fringes, the shape of the surface to be inspected is analyzed.

  According to such a configuration, the object beam and the reference light are separated in front of the imaging unit, and the incident angle when entering the imaging unit is differentiated, so that the density of interference fringes can be increased. Therefore, the interference fringe analysis accuracy can be improved. Further, the object light and the reference light travel on the same optical path in a state of being combined as a non-interfering light beam, and the traveling directions of the object light and the reference light are separated by the incident angle difference generation means before the imaging means. Therefore, there is almost no optical path difference between the object light and the reference light. As a result, a stable and highly accurate optical interferometer can be obtained.

Further, since the object light and the reference light are separated in front of the image pickup means, the object light and the reference light are not greatly deviated before entering the image pickup means. The overlapping area with the reference light can be made sufficiently large.
Conventionally, since the reference surface is inclined, the optical path until the reference light is incident on the imaging means becomes long, and the reference light is greatly deviated from the object light. For this reason, the overlapping area of the object beam and the reference beam has been reduced when entering the imaging means.

  In this regard, in the present invention, since the distance from the separation of the object light and the reference light to the incidence on the imaging means is short, the object light and the reference light are not greatly separated before entering the imaging means. . Therefore, the area where the interference fringes are generated can be increased by increasing the overlapping area of the object light and the reference light. As a result, a single measurement area can be widened. Further, since the distance from the separation to the imaging means is short, the overlapping area can be sufficiently increased even if the reference light and the object light are angled so that the density of the interference fringes is sufficiently high. As a result, it is possible to achieve an epoch-making effect that the interference fringe density can be sufficiently increased and the interference area can be increased.

  In the present invention, it is preferable that the incident disparity generating means is constituted by a Wollaston prism.

In such a configuration, when light enters the Wollaston prism, light having polarization axes orthogonal to each other is emitted with a predetermined opening angle. That is, when a non-interfering light beam obtained by combining reference light and object light having polarization axes orthogonal to each other enters the Wollaston prism, the reference light and object light are emitted with a predetermined opening angle. Then, the incident angles of the reference light and the object light with respect to the imaging unit are different, and a high-density interference fringe is obtained. By configuring the incident angle difference generating means with the Wollaston prism in this way, the incident angle difference generating means is configured with a single member, so that the number of parts can be reduced.
In the case of a Wollaston prism, the opening angle between the object beam and the reference beam is set to a predetermined angle, so there is no need to adjust the angle again, and the opening angle does not change. Can be obtained.

  In the present invention, the incident angle difference generating means includes an optical path separating means for separating an optical path between the object light and the reference light of the non-interfering light beam, the object light separated by the optical path separating means, and the reference. It is preferable to include an incident angle adjusting unit that causes light to enter the imaging unit at a different angle.

  In such a configuration, for example, a polarization beam splitter can be used as the optical path separation means. Then, the light from the polarization beam splitter can be reflected by a mirror or the like, and the incident angle to the imaging means can be adjusted.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be illustrated and described with reference to reference numerals attached to respective elements in the drawings.
(First embodiment)
A first embodiment according to the optical interferometer of the present invention will be described.
FIG. 1 is a diagram showing the configuration of this optical interferometer.
The optical interferometer 100 combines the illumination optical system 110 that emits light (L10), the object light (L14), and the reference light (L12) in a non-interference state to produce a non-interference light beam (L15). The light beam generation unit 120, the interference fringe generation unit 130 that generates interference fringes by causing the non-interference light beam (L 15) to interfere, the CCD camera 140 (imaging unit) that images the interference fringes, and the light from the illumination optical system 110 ( A half mirror 150 that reflects L10) toward the non-interfering light beam generation unit 120 and transmits the non-interference light beam (L15) from the non-interference light beam generation unit 120 toward the interference fringe generation unit 130.

The illumination optical system 110 includes a light source 111, a collimating lens system 112, a polarizing plate 113, and a half-wave plate 114.
The half-wave plate 114 is rotatably provided. The light (L10) from the illumination optical system 110 is incident on the half mirror 150, and a part of the light incident on the half mirror 150 is reflected at right angles (L11), so that the incoherent light flux generation unit 120 and the workpiece W are reflected. Head for.

The non-interference light flux generation unit 120 is configured by a wire grid 120.
The wire grid 120 includes a light transmissive plate member 121 and a plurality of wires 122 arranged in parallel with each other on one surface of the light transmissive plate member 121. The line width of the wires 122 is, for example, about 60 nm, and the distance between the wires is, for example, about 140 nm. Of the light incident on the wire grid 120 (L11), the component parallel to the wire 122 is reflected by the wire grid 120 (L12), and the component perpendicular to the wire 122 is transmitted through the wire grid 120 (L13).
Here, when light is reflected (L12) by the wire grid 120, the reflection surface of the wire grid 120 becomes the reference surface (reference surface) 123.
The wire grid 120 is disposed substantially parallel to the workpiece surface S.

  The interference fringe generating unit 130 includes a Wollaston prism 131 as an incident angle difference generating unit and a polarizing plate 132 having a polarization axis disposed at an angle of 45 degrees. A Wollaston prism 131 is disposed immediately before the CCD camera 140, and a polarizing plate 132 is disposed between the CCD camera 140 and the Wollaston prism 131. When light enters the Wollaston prism 131, light (L12, L14) having polarization axes orthogonal to each other is emitted with a predetermined opening angle. When the two light beams (L12, L14) emitted from the Wollaston prism 131 and having mutually orthogonal polarization axes enter the polarizing plate 132, the two light beams (L12, L14) interfere with each other to generate interference fringes. The The interference fringes thus generated enter the CCD camera 140 and are imaged by the CCD camera 140.

An optical path until light (laser light) from the light source 111 reaches the CCD camera 140 in the first embodiment having such a configuration will be described.
The light (L10) emitted from the light source 111 is converted into a parallel light beam by the collimating lens system 112, and is further converted into polarized light having a predetermined polarization direction by the polarizing plate 113. Then, the light is incident on the half mirror 150 with the polarization direction rotated by a predetermined angle by the half-wave plate 114. Part of the light incident on the half mirror 150 is reflected toward the wire grid 120 (L11).

The light (L 11) reflected by the half mirror 150 enters the wire grid 120. Then, in the light (L11) incident on the wire grid 120, a component orthogonal to the wire 122 of the wire grid 120 is transmitted through the wire grid 120 (L13).
Here, the polarized light passing through the wire grid 120 is S-wave.
After the S wave (L13) transmitted through the wire grid 120 is irradiated onto the workpiece surface S, it is reflected by the workpiece surface S and returns to the wire grid 120 as object light (L14), passes through the wire grid 120, and is a half mirror. Head to 150.

In addition, among the light (L11) incident on the wire grid 120 from the half mirror 150, a component parallel to the wire 122 of the wire grid 120 is reflected (L12) by the wire grid 120.
Here, the polarized light in the direction reflected by the wire grid 120 is P wave. The P wave reflected by the wire grid 120 travels to the half mirror 150 as reference light (L12).

  Since the wire grid 120 is disposed substantially parallel to the workpiece surface S, the traveling direction of the object light (L14) that is the reflected light from the workpiece surface S and the reference light (L12) that is the reflected light from the wire grid 120 Are the same. The object light (S wave, L14) that is reflected light from the workpiece W and the reference light (P wave, L12) that is reflected light from the wire grid 120 interfere with each other because their polarization directions are orthogonal to each other. Without being combined, and travels toward the half mirror 150 as a non-interfering light beam (L15).

  The non-interfering light beam (L15) passes through the half mirror 150 and enters the Wollaston prism 131. When light enters the Wollaston prism 131, light beams having mutually orthogonal polarization axes are emitted with a predetermined opening angle, and the reference light (L12) and object light (L14) having mutually orthogonal polarization axes are multiplexed. When the incoherent light beam (L15) is incident on the Wollaston prism 131, the reference light (L12) and the object light (L14) are emitted with a predetermined opening angle. Then, the reference light (L12) and the object light (L14) interfere with each other by the polarizing plate 132, and interference fringes are generated. The interference fringes are imaged by the CCD camera 140. The captured interference fringes are sent to a predetermined analysis means (not shown) to perform fringe analysis. Based on the result of the fringe analysis, the shape of the workpiece surface S such as irregularities is obtained.

According to such 1st Embodiment, there can exist the following effects.
(1) Since the object light (L14) and the reference light (L12) are separated by the Wollaston prism 131 before the CCD camera 140 and are incident on the CCD camera 140, the interference fringe density is different. Can be high. Therefore, the interference fringe analysis accuracy can be improved.

(2) Since the wire grid 120 is disposed substantially parallel to the workpiece surface S, the reference beam (L12) that is reflected light from the wire grid 120 and the object beam (L14) that is reflected from the workpiece surface S. Travels on the same optical path in a state of being combined as a non-interfering light beam (L15). The traveling directions of the object light (L14) and the reference light (L12) are separated by the Wollaston prism 131 in front of the CCD camera 140.
Since the object light (L14) and the reference light (L12) pass through the same optical path in this way, there is almost no optical path difference between the object light (L14) and the reference light (L12). An accurate optical interferometer 100 can be obtained.

(3) Since the Wollaston prism 131 is disposed in front of the CCD camera 140 and the distance from the separation of the object light (L14) and the reference light (L12) to the incidence on the CCD camera 140 is short, the CCD The object light (L14) and the reference light (L12) are not greatly separated before entering the camera 140. Therefore, the overlapping area of the object light (L14) and the reference light (L12) can be increased to increase the area where interference fringes are generated, and the measurement area for one time can be increased.

(4) Since the distance to the CCD camera 140 after the separation of the object light (L14) and the reference light (L12) by the Wollaston prism 131 is short, the Wollaston prism 131 is sufficiently high that the interference fringe density is sufficiently high. Thus, even when the reference light (L12) and the object light (L14) are angled, the overlapping area of the object light (L14) and the reference light (L12) can be sufficiently increased. As a result, it is possible to achieve an epoch-making effect that the interference fringe density can be sufficiently increased and the interference area can be increased.

(5) Since the incident angle difference generating means is constituted by a single Wollaston prism 131, the number of parts can be reduced. In the case of the Wollaston prism 131, the opening angle between the object beam (L14) and the reference beam (L12) is determined to be a predetermined angle, so that there is no need to adjust the angle again, and the opening angle may change. Therefore, stable measurement results can be obtained.

(Modification 1)
Next, Modification 1 of the present invention will be described with reference to FIG.
In the first embodiment, the Fizeau type optical interferometer 100 using the wire grid 120 has been described as an example. However, as shown in FIG. Even applicable.
In FIG. 2, since it is a Michelson interferometer 200, the non-interference light beam generation means 210 is constituted by a polarization beam splitter (PBS) 211 and a reference mirror 212. The point that the Wollaston prism 131 and the polarizing plate 132 are arranged in front of the CCD camera 140 is the same as in the first embodiment. In such a configuration, the light from the light source 111 is separated into a P wave and an S wave by the PBS 211, and one becomes object light and the other becomes reference light. Then, the object light and the reference light are combined as a non-interfering light beam. The non-interfering light beam passes through the Wollaston prism 131 in front of the CCD camera 140 and is separated into reference light and object light having a predetermined opening angle, and interferes with the polarizing plate 132. The interference fringes are imaged by the CCD camera 140.

  Also in the first modification, the path between the reference light and the object light is the same as that in the first embodiment, and the same effect as that in the first embodiment can be obtained.

(Modification 2)
Next, a second modification of the present invention will be described with reference to FIG.
The basic configuration of Modification 2 is the same as that of the first embodiment, but has a feature in the configuration of the incident angle difference generation unit 300.
In the first embodiment, the case where the incident angle difference generating means is configured by the Wollaston prism 131 has been described. However, the incident angle difference generating means 300 is configured by a plurality of members as shown in FIG. May be.
In FIG. 3, the incident angle difference generating unit 300 includes a polarizing beam splitter (optical path separating unit) 310 and a triangular prism (incident angle adjusting unit) 320. When a non-interfering light beam in which the reference light and the object light are combined enters the polarization beam splitter 310, one of the reference light and the object light passes through the polarization beam splitter 310 and enters the polarizing plate 132. Further, the other of the reference light and the object light is reflected by the polarization beam splitter 310 in a right angle direction. The light reflected by the polarizing beam splitter 310 is further reflected by the reflecting surface of the triangular prism 320 and enters the polarizing plate 132.
Here, the angle of the reflection surface of the triangular prism 320 is adjusted so that the reflected light is incident on the polarizing plate 132 and a predetermined incident angle difference is generated between the reference light and the object light. Then, after the reference light and the object light interfere with each other by the polarizing plate 132, the interference fringes are imaged by the CCD camera 140.

  Also in the second modification, the path between the reference light and the object light is substantially the same as that in the first embodiment, and the same effects (1) to (4) as in the first embodiment can be achieved. .

(Modification 3)
Next, Modification 3 of the present invention will be described with reference to FIG.
The basic configuration of the third modification is the same as that of the first embodiment, but has a feature in the configuration of the incident angle difference generation unit 300.
In the first embodiment, the case where the incident angle difference generating means is configured by the Wollaston prism 131 has been described. However, the incident angle difference generating means 300 is configured by a plurality of members as shown in FIG. May be.
In FIG. 4, the incident angle difference generating unit 400 includes a polarizing beam splitter (optical path separating unit) 410 and two sets of reflecting units (incident angle adjusting units) 420 and 430.
As the reflecting means, the first reflecting means 420 that reflects the reflected light from the polarizing beam splitter 410 and returns it to the polarizing beam splitter 410, and the transmitted light from the polarizing beam splitter 410 is reflected and returned to the polarizing beam splitter 410. Second reflecting means 430 is provided.
The first reflecting means 420 and the second reflecting means 430 include reflecting mirrors 421 and 431 and quarter-wave plates 422 and 432, respectively. The reflecting mirror 421 of the first reflecting means 420 is tilted, while the reflecting mirror 431 of the second reflecting means 430 has a reflecting surface perpendicular to the optical axis.

In such a configuration, when a non-interfering light beam obtained by combining the reference light and the object light is incident on the polarization beam splitter 410, one of the reference light and the object light is reflected at a right angle by the polarization beam splitter 410 and the first light is reflected. The light is incident on the first reflecting means 420, and the other is transmitted through the polarizing beam splitter 410 and incident on the second reflecting means 430.
Here, it is assumed that the reference light is a P wave and is reflected by the polarization beam splitter 410, and the object light is an S wave and passes through the polarization beam splitter 410.
The reference light (P wave) reflected by the polarization beam splitter is reflected by the first reflection mirror 421 and returns to the polarization beam splitter 410. At this time, the light passes through the quarter-wave plate 422 of the first reflecting means 420 twice, so that the polarization axis is rotated 90 degrees to become an S wave. Then, the light passes through the polarization beam splitter 410 and travels toward the CCD camera 140.
Further, since the reflecting mirror 421 of the first reflecting means 420 is tilted, the reflected light from the reflecting mirror 421 is reflected at a slight angle, and the incident angle to the CCD camera 140 is slightly shifted from 90 degrees.

The object light (S wave) transmitted through the polarizing beam splitter 410 is reflected by the reflecting mirror 431 of the second reflecting means 430 and returns to the polarizing beam splitter 410.
At this time, the light passes through the quarter-wave plate 432 of the second reflecting means 430 twice, so that the polarization axis is rotated 90 degrees to become a P wave.
Then, the light is reflected by the polarization beam splitter 410 and travels toward the CCD camera 140.

The light traveling from the polarization beam splitter 410 to the CCD camera 140 is S-wave reference light and P-wave object light, and passes through the polarizing plate 132 whose polarization axis is disposed at an angle of 45 degrees. Is generated. At this time, since there is an incident angle difference between the reference light and the object light, the density of interference fringes increases.
This interference fringe is imaged by the CCD camera 140.

  Even in the third modification, the path between the reference light and the object light is substantially the same as in the first embodiment, and the same effects (1) to (4) as in the first embodiment can be achieved. .

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.
In the Fizeau-type optical interference of the first embodiment, a configuration using a wire grid has been described as an example, but a ¼ wavelength plate may be used instead of the wire grid.
As the incident angle difference generating means, the configurations of FIGS. 3 and 4 are shown in addition to the Wollaston prism, but various other configurations can be adopted.

In order to obtain a high resolution, it is preferable that the width of the interference fringes is about four of the light receiving elements of the CCD camera.
For example, when laser light having a wavelength of 633 nm is used and the size of the light receiving element of the CCD camera is 6 μm, the opening angle between the reference light and the object light by the Wollaston prism is set to about 1.6 degrees. Then, the width of the interference fringes is about 22.6 μm, which is about four of the light receiving elements of the CCD camera. Then, good resolution can be obtained.
Further, in order to image the interference fringes satisfactorily with the CCD camera, the interference fringes are preferably oblique with respect to the light receiving element of the CCD camera. That is, it is preferable that the fringes of the interference fringes are oblique with respect to the direction in which the light receiving elements are arranged. For example, the CCD camera may be rotated with respect to the Wollaston prism so that the alignment direction of the light receiving elements of the CCD camera is 45 degrees with respect to the optical axis of the Wollaston prism.

  The present invention can be used for an optical interferometer.

The figure which shows the structure of the optical interferometer of 1st Embodiment. The figure which shows the structure of the modification 1. FIG. The figure which shows the structure of the modification 2. The figure which shows the structure of the modification 3. The figure which shows the Fizeau type optical interferometer which inclined the reference surface in description of a prior art. In description of prior art, the figure which expanded the interference fringe acquisition part and represented a mode that the interference fringe was produced | generated by the polarizing plate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Optical interferometer, 11 ... Light source, 12 ... Collimating lens system, 13 ... Half mirror, 14 ... Wave plate, 15 ... Interference fringe acquisition part, 16 ... Polarizing plate, 17 ... CCD camera, 100 ... Optical interferometer, 110 DESCRIPTION OF SYMBOLS ... Illumination optical system, 111 ... Light source, 112 ... Collimating lens system, 113 ... Polarizing plate, 114 ... Half-wave plate, 120 ... Wire grid (non-interference light beam production | generation part), 121 ... Light transmissive board | plate material, 122 ... Wire, 130 ... Interference fringe generation means, 131 ... Wollaston prism, 132 ... Polarizing plate, 140 ... CCD camera, 150 ... Half mirror, 200 ... Michelson interferometer, 210 ... Non-interference light flux generation means, 212 ... Reference mirror, 300 ... Incident angle difference generating means 310... Polarizing beam splitter 320 320 Triangular prism 400. Incident angle difference generating means 410. Splitter, 420 ... first reflecting means, 421 ... reflecting mirror, 422 ... quarter wave plate, 430 ... second reflecting means, 431 ... reflecting mirror, 432 ... quarter wave plate, S ... work surface, W ... workpiece .

Claims (3)

Optical interference in which an interference fringe obtained by causing the object light reflected by the test surface and the reference light reflected by the reference surface to interfere with each other is imaged by an imaging means, and the test surface is measured based on the interference fringe In total
The object light and the reference light are polarized light whose polarization axes are orthogonal to each other,
The object light and the reference light pass through the same path in a combined state as a non-interfering light beam,
At the position immediately before the non-interfering light beam enters the imaging means,
Incident angle difference generating means for making the object light and the reference light enter the imaging means different in the traveling direction of the object light and the reference light of the incoherent light flux, and
An optical interferometer, comprising: a polarizer that causes interference between the object light and the reference light that have been given an angle difference by the incident angle difference generation unit. The optical interferometer according to claim 1.
The incident disparity generating means is configured by a Wollaston prism. The optical interferometer according to claim 1.
The incident angle difference generating means is an optical path separating means for separating an optical path between the object light and the reference light of the non-interfering light beam,
An optical interferometer, comprising: an incident angle adjusting unit that causes the object light and the reference light separated by the optical path separating unit to enter the imaging unit at different angles.

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