WO2009090771A1

WO2009090771A1 - Laser interferometer and measuring instrument using the same

Info

Publication number: WO2009090771A1
Application number: PCT/JP2008/064150
Authority: WO
Inventors: Toshihiro Nakayabu; Youichi Tamura; Hideo Yachi; Akihiro Shimizu
Original assignee: Prefecture Ishikawa; Sigma Koki Co., Ltd
Priority date: 2008-01-18
Filing date: 2008-08-06
Publication date: 2009-07-23
Also published as: CN101918788A; JP2009168709A

Abstract

A laser interferometer (1) includes a reflecting mirror (2) having two plane mirrors (4, 5), and a laser interferometry section (3) having a polarizing beam splitter (8) to accept two linear polarized light intersecting orthogonal to each other for dispersion and a biprism (6) to refract each of dispersed optical components to be incident and reflective vertically to/from the plane mirrors (4, 5) to output each optical component after reciprocating each optical component twice between the biprism (6) and the reflecting mirror (2). The laser interferometry section (3) is provided with a deflecting section (15) having a pair of wedge prisms (15a, 15b) that are arranged between the polarizing beam splitter (8) and the biprism (6) such that one optical component is passing when each optical component is reciprocating at the beginning, while the other optical component is passing when each optical component is reciprocating next, and that allow flexible adjustment of a deflecting direction of the passing-through optical component. Such an arrangement ensures simplified deflection adjustment work for each optical component, improved parallelism of each optical component of the outgoing laser beam, and enhanced accuracy in measurement of the positional deviation in the roll direction.

Description

Laser interferometer and measuring apparatus using the same

The present invention relates to a laser interferometer for measuring a positional deviation caused when a moving member such as a table of a machine tool moves in an axial direction with respect to a support member, and more specifically, outputs each light component. The present invention relates to a laser interferometer that can be adjusted in parallel and a measurement apparatus using the same.

For example, in machine tools such as lathes, milling machines, and grinding machines that require high-precision work, a bed that is fixed to a floor in a factory or the like and a table that moves on the bed are provided. At the time of work, a work piece or the like is set on the table, and the work is performed while moving the table in a predetermined axial direction. In moving the table, there is a possibility that six positional deviations (errors) in the axial direction, the horizontal direction, the vertical direction, the pitch direction, the yaw direction, and the roll direction (that is, in the direction of 6 degrees of freedom) may occur. These positional deviations need to be measured for purposes such as delivery and maintenance.

Conventionally, in order to measure the above six position deviations, various types of measurement using a laser length measuring machine have been proposed, and the position deviations in the axial direction, horizontal direction, vertical direction, pitch direction, and yaw direction are measured. Some have been put to practical use. However, the measurement in the roll direction is specified to be measured with a precision level or a dial gauge (for example, JIS B 6336-1, ISO 10791-1). However, when the table of the machine tool is moved, the center of gravity of the machine tool itself moves, so that the entire machine tool is inclined. Therefore, when the roll direction is measured with the above-described level or the like, the measurement including the inclination of the machine tool is performed, and the accurate roll direction cannot be measured. Further, in the table moving in the vertical direction, since the roll direction is horizontal, it is impossible to measure the roll direction with the above-described level. In view of this, there has been proposed a technique for measuring a positional deviation with respect to the roll direction using a laser interferometer (see Japanese Patent Laid-Open Nos. 62-223604 and 2004-138433).

This type of laser interferometer inputs a reflecting mirror as a reflecting means having two plane mirrors inclined at a predetermined angle so as to be substantially V-shaped, and a laser beam having two polarization components orthogonal to each other. A laser interference unit serving as a laser beam path generating unit that outputs each light component after being reciprocated twice by a reflecting mirror. The laser interference unit is disposed in a direction perpendicular to the polarization beam splitter with respect to the axial direction, a polarization beam splitter having a polarization plane as a spectroscopic unit, a biprism as a refraction unit disposed between the polarization beam splitter and the reflecting mirror And a turning mirror. The polarization beam splitter has an input / output unit that allows laser light to be input and also allows laser light that has been reciprocated twice to and from a reflecting mirror to be output.

In this laser interferometer, when laser light having two polarization components orthogonal to each other is emitted from the laser head and input to the input / output section of the polarization beam splitter, it is separated into each light component at the polarization plane of the polarization beam splitter. Is done.

One light component separated by the polarizing beam splitter passes through the turning mirror and the biprism sequentially, is reflected by the reflecting mirror, passes through the biprism and the turning mirror sequentially, and returns to the polarizing beam splitter. Thereafter, one light component is emitted from the polarizing beam splitter, passes through the biprism, is reflected by the reflecting mirror, passes through the biprism, and returns to the polarizing beam splitter. One light component separated in this way by the polarization beam splitter reciprocates twice between the biprism and the reflecting mirror.

Next, the other light component separated by the polarizing beam splitter passes through the biprism, is reflected by the reflecting mirror, passes through the biprism, and returns to the polarizing beam splitter. Thereafter, the other light component sequentially passes through the turning mirror and the biprism, is reflected by the reflecting mirror, passes through the biprism and the turning mirror in sequence, and returns to the polarizing beam splitter. In this way, the other light component reciprocates twice between the biprism and the reflecting mirror along an optical path different from the one light component.

Then, each optical component of the laser light that has reciprocated between the biprism and the reflecting mirror is output from the laser interference unit. The laser light (interference signal) of each light component output from this laser interference unit is received by a photoelectric converter, and by measuring the relative change of the two optical path lengths based on the phase difference of the wavelength of each light component. The positional deviation in the roll direction can be calculated.

By the way, if the laser light that goes to the biprism via the turning mirror and the laser light that goes to the biprism without going through the turning mirror are parallel, the laser light refracted by the biprism and emitted is reflected in the reflecting mirror. The light beams are vertically reflected and follow the same optical path as the forward path in the return path of the laser beam, so that each light component of the laser beam output from the laser interference unit is parallel.

However, in the above-described laser interferometer, if the manufacturing accuracy of an optical component such as a polarization beam splitter is low, the parallelism of the two light components output from the laser interference unit may decrease.

Specifically, a polarizing beam splitter as an optical component is generally known in the form of a cube in which a polarizing surface is provided between the inclined surfaces of two 45 ° right-angle prisms and bonded with an adhesive. Production accuracy may be reduced due to shrinkage of the agent when it is dried. If the manufacturing accuracy of the optical component is reduced, the optical path may be shifted in the reciprocal process of each light component, and the parallelism of the two light components output from the laser interference unit may be reduced.

If the parallelism of the two light components output from the laser interference unit decreases in this way, the interference signal due to the two light components becomes weak, and a good interference signal cannot be detected. There is a problem that the measurement accuracy of the position deviation is lowered.

To solve this problem, the angle of the turning mirror can be adjusted to make the two light components output from the laser interference section parallel, but the adjustment work is very difficult and easier to adjust. A laser interferometer that can be used has been desired.

Therefore, the present invention makes it easy to adjust the deflection of each light component, improves the parallelism of each light component of the laser light output from the laser light path generation means, and improves the measurement accuracy of the positional deviation in the roll direction. It is an object of the present invention to provide a laser interferometer that can be used, and a measuring apparatus using the same.

The present invention (see, for example, FIG. 3, FIG. 7, FIG. 14) includes a reflecting means (2) having two plane mirrors (4, 5) inclined at a predetermined angle;
A spectroscopic unit (8, 208) that inputs and splits laser light having two polarization components whose polarization planes are orthogonal to each other, and is disposed between the spectroscopic unit (8, 208) and the reflecting means (2). The refracting section (6) refracts each light component dispersed by the spectroscopic section (8, 208) at the predetermined angle so as to enter and reflect perpendicularly to the plane mirror (4, 5) of the reflecting means (2). And laser light path generation means (3, 103, 203) for outputting each light component after reciprocating twice between the refraction part (6) and the reflection means (2),
When the reflecting means (2) and the laser beam path generating means (3, 103, 203) are relatively moved in the axial direction (for example, the Z-axis direction), the reflecting means (2) and the laser beam path generating means ( 3, 103, 203) In a laser interferometer (1, 101, 201) in which the distance of the optical path through which each light component passes is relatively changed by the relative positional relationship with
The laser beam path generation means (3, 103, 203)
The light splitting unit (8, 208) and the refraction so that one light component passes when the light components first reciprocate and the other light component passes when the light components reciprocate next time. A laser interferometer comprising a deflection unit (15) disposed between the unit (6) and having a pair of wedge prisms (15a, 15b) that can adjust a deflection direction of a light component passing therethrough. (1, 101, 201).

This makes it possible to easily adjust the deflection direction of each light component passing through the deflecting unit simply by operating a pair of wedge prisms. Each light component that is incident on the refracting unit by adjusting the deflecting unit is made parallel so that each light component is incident and reflected perpendicularly to the plane mirror of the reflecting unit. The parallelism of the components can be improved. When measuring the positional deviation in the roll direction, a good interference signal can be obtained, and the measurement accuracy of the positional deviation in the roll direction is improved.

Further, according to the present invention (see, for example, FIGS. 3, 7, and 14), the laser beam path generation means (3, 103, 203) is configured such that the axial direction (for example, the Z-axis direction) of the spectroscopic unit (8, 208). ) And a reflecting portion (9, 209) that is arranged in a direction perpendicular to the optical axis (for example, the Y-axis direction) and reflects the laser light incident through the spectroscopic portion (8, 208) toward the refracting portion (6). Prepared,
The deflection unit (15) is disposed between the reflection unit (9, 209) and the refraction unit (6).

Thereby, since the deflecting unit is disposed between the reflecting unit and the refracting unit, it is not necessary to adjust the reflecting unit when adjusting the polarization direction of each light component, and the adjustment work is easy.

Further, according to the present invention (see, for example, FIG. 14), the laser beam path generation unit (203) is perpendicular to the axial direction (eg, Z-axis direction) of the spectroscopic unit (208) (eg, Y-axis direction). A reflection unit (209) that is disposed and reflects the laser beam incident through the spectroscopic unit (208) toward the refraction unit (6);
The deflection unit (15) is disposed between the spectroscopic unit (208) and the reflection unit (209).

Thereby, since the deflecting unit is disposed between the spectroscopic unit and the reflecting unit, it is not necessary to adjust the reflecting unit when adjusting the polarization direction of each light component, and the adjustment work is easy.

Furthermore, the present invention (see, for example, FIG. 4, FIG. 5, FIG. 8, FIG. 9) includes a housing (3a) for storing the laser light path generation means (3, 103),
The deflection unit (15) includes ring-shaped operating elements (16a, 16b) formed on the outer periphery of the wedge prism (15a, 15b),
The wedge prisms (15a, 15b) are arranged in the casing (3a) so that the operating elements (16a, 16b) are exposed from the casing (3a).

Thereby, since the operation element is exposed from the casing, the deflecting unit can be operated without disassembling the casing, and adjustment work is easy.

Furthermore, according to the present invention (see, for example, FIGS. 7 and 9), the spectroscopic unit (8) can freely input laser light and can output laser light reciprocated twice to the reflecting means (2). An input / output unit (8a)
The laser beam path generation means (103) includes a re-input unit (17) for returning the laser beam output from the input / output unit (8a) to the input / output unit (8a). .

As a result, the laser beam output by the re-input unit reciprocating twice between the refracting unit and the reflecting means is reciprocated twice between the refracting unit and the reflecting means, so that the sensitivity is improved. The measurement accuracy of the positional deviation in the roll direction is improved.

Further, the present invention (see FIGS. 1 and 2), the laser interferometer (1),
Based on the phase difference of the wavelength of the laser light of each light component output from the laser light path generation means (3), the relative change in the distance of the light path of each light component is measured. Laser length measuring means (12) to obtain,
Either one of the reflecting means (2) and the laser beam path generating means (3) is fixed to a support member (21) supported by a reference floor (30);
The other of the reflecting means (2) and the laser beam path generating means (3) is fixed to a moving member (22) supported so as to be movable in the axial direction (for example, the Z-axis direction) with respect to the supporting member (21). And
When the moving member (22) is moved in the axial direction (for example, the Z-axis direction) with respect to the support member (21), a positional deviation of the moving member (22) with respect to the support member (21) is measured. It exists in the measuring apparatus (50) characterized by doing.

Thereby, the relative positional relationship between the moving member and the supporting member can be measured without including the inclination of the supporting member due to the movement of the moving member, and the positional deviation in the roll direction can be measured well.

In addition, although the code | symbol in the said parenthesis is for contrast with drawing, this is for convenience for making an understanding of an invention easy, and has an influence on the structure of a claim. is not.

The perspective view which shows the measuring apparatus and machine tool at the time of fixing a laser interference part to a table. The perspective view which shows the measuring apparatus and machine tool at the time of fixing a reflective mirror to a table. The perspective schematic diagram which shows the laser interferometer which concerns on 1st Embodiment. The perspective view of a laser interference part. Sectional drawing of the laser interference part which follows the AA line in FIG. It is explanatory drawing which shows the optical path of the laser beam which passes a deflection | deviation part, (a) is explanatory drawing which shows the optical path at the time of adjusting the deflection direction of a laser beam with a deflection | deviation part in a laser interference part, (b) is deflection | deviation. Explanatory drawing which shows the deflection | deviation range of the laser beam which passes a part. The perspective schematic diagram which shows the laser interferometer which concerns on 2nd Embodiment. The perspective view which shows a laser interference part. FIG. 9 is a cross-sectional view of the laser interference section along the line BB in FIG. 8. The top view of the laser interference part seen from the arrow C direction in FIG. The figure which shows the roll detection sensitivity measured with the measuring apparatus of 1st Embodiment. The figure which shows the roll detection sensitivity measured with the measuring apparatus of 2nd Embodiment. The figure which shows the result of having detected the position deviation of the roll direction of an optical experiment stand. The perspective schematic diagram which shows the laser interferometer which concerns on 3rd Embodiment.

<First Embodiment>
Hereinafter, a first embodiment according to the present invention will be described with reference to the drawings. 1 is a perspective view showing a measuring device and a machine tool when the laser interference unit is fixed to the table, FIG. 2 is a perspective view showing the measuring device and the machine tool when the reflecting mirror is fixed to the table, and FIG. It is a perspective schematic diagram which shows the laser interferometer which concerns on this embodiment. 4 is a perspective view of the laser interference portion, and FIG. 5 is a cross-sectional view of the laser interference portion along the line AA in FIG. FIG. 6 is an explanatory diagram showing the optical path of the laser beam passing through the deflecting unit, and FIG. 6A is an explanatory diagram showing the optical path when the deflection direction of the laser beam is adjusted by the deflecting unit in the laser interference unit. FIG. 6B is an explanatory diagram showing the deflection range of the laser light that passes through the deflecting unit.

As shown in FIG. 1, a measuring device 50 that can measure the positional deviation of the machine tool 20 includes a laser interferometer 1 and a laser head (laser length measuring means) 12. The machine tool 20 includes, for example, a bed (support member) 21 that is placed and supported on a floor 30 of a factory, and the bed 21 supports a guide member 21a. A table (moving member) 22 is supported on the guide member 21a so as to be movable in the Z-axis direction (axial direction). The table 22 moves in the Z-axis direction by driving a motor (not shown), for example.

Further, a tool post 23 is provided on the bed 21 of the machine tool 20, and an arm 24 provided on the tool post 23 has a chuck 25. When working with the machine tool 20, a tool such as a tool is attached to the chuck 25, a work piece is set and fixed on the table 22, and the work piece and the tool are brought into contact with each other by moving the table 22. Do the work. Note that the machine tool 20 shown in FIG. 1 is a schematic diagram that is simply shown for convenience of explanation, and has been described as an example that moves in the Z-axis direction. The operation is performed.

The laser head 12 is arranged on the floor 30 with, for example, a tripod 12b, and the laser head 12 has laser light having two polarization components orthogonal to each other, specifically, P waves (for example, linearly polarized light) (Longitudinal wave) and a laser oscillator capable of irradiating a laser beam having an S wave (for example, a transverse wave) that is a linearly polarized light having a plane of polarization orthogonal to the P wave and a different frequency, and the P wave of the input laser beam And a photoelectric converter capable of measuring the amount of change in the optical path length, which will be described in detail later, based on the wavelengths of the S wave and the S wave. In addition, the laser head 12 is provided with an input / output head 12a that coaxially performs the irradiation of the laser light of the laser oscillator and the input of the laser light to the photoelectric converter. The head 12a is directed to the input / output unit 8a of the laser interference unit 3 of the laser interferometer 1 to be described later, and is arranged so as to input / output laser light in the Z-axis direction.

The bed and table of the machine tool 20 have various names depending on their shapes and roles. For example, there are names such as a spindle head, a tool post, a column, and a stage. The bed 21 is a support member supported by the floor 30, and the table 22 is a moving member that moves relative to the bed 21. Further, the laser head 12 is integrally provided with the laser oscillator and the photoelectric converter, but may be provided separately.

A laser interferometer 1 which is a main part of the present invention includes a reflecting mirror (reflecting means) 2 and a laser interfering section (laser optical path generating means) 3, and the reflecting mirror 2 is shown in FIG. As described above, the two

plane mirrors

4 and 5 are inclined at a predetermined angle substantially symmetrical with respect to the laser interference unit 3 so as to be substantially V-shaped. As shown in FIG. 1, the reflecting mirror 2 has a substantially rectangular parallelepiped reflecting mirror case 2a, and the plane mirrors 4 and 5 are stored in the main body case 2a. In addition, a slit-like hole 2b through which laser light passes is formed on the surface of the main body case 2a that faces the laser interference portion 3.

As shown in FIGS. 3 to 5, the laser interference unit 3 includes a biprism (refractive unit) 6 having two

wedge prisms

6a and 6b, quarter wavelength plates (second wavelength plates) 7a and 7b, polarization It has a beam splitter (spectral part) 8, a planar reflector (reflecting part) 9, a quarter wavelength plate (first wavelength plate) 10, a cube corner prism (optical path axis changing part) 11, and a deflecting part 15. It is comprised and is stored in the interference part case (casing) 3a of a substantially rectangular parallelepiped shape. 4 and 5, the biprism 6 and the cube corner prism 11 are attached to the interference part case 3a and exposed, but each optical component may be arranged inside the interference part case 3a. In the first embodiment, in any case, it is expressed as being stored in the interference unit case 3a. The interference case 3a is formed with holes 3b through which the laser beam for the laser head 12 passes and

holes

3c and 3d through which the laser beam for the reflecting mirror 2 passes.

As shown in FIGS. 3 to 5, the polarization beam splitter 8 includes a polarization plane 8b inclined at an angle of about 45 ° with respect to the Z-axis direction, and an input / output plane (input / output section) 8a for inputting and outputting laser light. The input / output surface 8a is located on the opposite side of the Z-axis direction of the polarizing beam splitter 8 with respect to the reflecting mirror 2, that is, the input / output head 12a of the laser head 12 is in the Z-axis direction. Are positioned so as to face each other.

The planar reflector 9 is disposed in a direction perpendicular to the Z-axis direction of the polarizing beam splitter 8 (Y-axis direction), and has an angle of approximately 45 ° with respect to the Z-axis direction of the polarizing beam splitter 8. It is integrally formed on an inclined surface that is inclined in the direction.

The biprism 6 and quarter-

wave plates

7a and 7b are disposed on the Z-axis direction between the polarizing beam splitter 8 and the planar reflector 9 and the reflector 2, respectively. Further, the cube corner prism 11 is disposed on the opposite side of the polarizing beam splitter 8 with respect to the planar reflector 9, and a quarter wavelength is provided between the cube corner prism 11 and the polarizing beam splitter 8. A plate 10 is arranged.

As shown in FIG. 3, the positions of the biprism 6 and the

quarter wavelength plates

7a and 7b in the Z-axis direction are as follows: the reflecting mirror 2, the biprism 6, the

quarter wavelength plates

7a and 7b, and the polarization beam splitter. 8 and the planar reflector 9 are preferable, but the reflector 2, the quarter-

wave plates

7a and 7b, the biprism 6, the polarization beam splitter 8, and the planar reflector 9 may be disposed in this order. Moreover, although the

quarter wave plates

7a and 7b are separate bodies, they may be integrated.

The quarter-wave plate is a crystal piece sliced accurately with respect to the crystal axis. The quarter-

wave plates

7a and 7b are tilted at 45 ° on the crystal axis in the XY plane. The quarter-wave plate 10 is used with the crystal axis inclined at 45 ° in the XZ axis plane.

In the first embodiment, the deflecting unit 15 is formed on the outer periphery of a pair (two) of

wedge prisms

15a and 15b that can adjust the deflection direction of the passing laser beam and the

wedge prisms

15a and 15b. Ring-shaped

holders

16a and 16b for holding the

prisms

15a and 15b, and more specifically between the polarizing beam splitter 8 and the biprism 6, more specifically between the planar reflector 9 and the biprism 6. Are disposed between the quarter-wave plate 7 a and the flat reflector 9.

Each of the

wedge prisms

15a and 15b has a disk shape in which both end surfaces are formed as planes, and one plane is a predetermined angle θ _{w with} respect to the other plane (XY plane) (see FIG. 6A). It is a wedge-shaped prism formed on an inclined surface that is inclined.

Then, as shown in FIG. 5, the

wedge prisms

15a and 15b are arranged close to each other so that the planes of the

wedge prisms

15a and 15b face each other, and the

holders

16a and 16b of the

wedge prisms

15a and 15b are aligned with the central axes of the

wedge prisms

15a and 15b. It is supported in the interference part case 3a so as to be rotatable about the center.

The

holders

16a and 16b are supported in the interference part case 3a so that the outer circumferences of the

holders

16a and 16b are exposed to the outside of the interference part case 3a. When the operator operates the

wedge prisms

15a and 15b, The exposed

holders

16a and 16b may be operated, and it is not necessary to disassemble the interference case 3a. Therefore, the adjustment operation of the

wedge prisms

15a and 15b is simple.

Then, as shown in FIG. 6A, the

wedge prisms

15a and 15b are rotated about the central axes of the

wedge prisms

15a and 15b in the direction of arrow A (clockwise) or in the direction of arrow B (counterclockwise). The deflection direction of the passing laser beam can be adjusted.

Specifically, since the pair of

wedge prisms

15a and 15b are arranged so as to face each other in close proximity, as shown in FIG. 6B, each

wedge prism

15a and 15b is moved in the direction of arrow A or the arrow. by rotating in the direction B, the laser beam emitted from the wedge prism 15b enters the wedge prism 15a is

wedge prism

15a, 15b of the inclined surface of the inclined angle θ predetermined substantially conical region R corresponding to _w Is deflected in any direction that passes through. Therefore, the deflection direction of the laser beam can be adjusted by rotating the

wedge prisms

15a and 15b in the direction of arrow A or arrow B.

The laser interferometer 1 of the first embodiment inputs laser light having S wave and P wave from the input / output surface 8a of the polarization beam splitter 8, and each light component dispersed by the polarization beam splitter 8 is A laser beam having two light components from the laser head 12 is configured to reciprocate twice between the biprism 6 and the reflecting mirror 2 of the laser interference unit 3 and output from the input / output surface 8a of the polarization beam splitter 8. Is input to the laser interferometer 3 of the laser interferometer 1 and the positional deviation in the roll direction is measured based on the interference signals generated by the two light components that are the outputs of the laser interferometer 3. Prior to this measurement operation, the laser head 12 emits laser light having two light components, and the reflecting mirror 2 and the laser interference unit 3 are deflected so that the respective light components output from the laser interference unit 3 are parallel to each other. It is necessary to adjust the part 15.

Hereinafter, a case where the laser interferometer 1 is irradiated with laser light will be described in detail.

Laser light having P and S waves is output in parallel to the Z-axis direction from the laser oscillator of the laser head 12 and is input / output surface 8a of the polarization beam splitter 8 via optical paths a1 and b1 shown in FIG. Is input. The laser beam input to the input / output surface 8a of the polarization beam splitter 8 is split into a first light component (P wave) and a second light component (S wave) by the polarization surface 8b, and the P wave is transmitted to the first optical path ( 3 passes through a2 to a11), and the S wave passes through the second optical path (b2 to b11 in FIG. 3). More specifically, the P wave passes through the polarization plane 8b of the polarization beam splitter 8 as it is and is output to the optical path a2 in the straight traveling direction, that is, the Z-axis direction, and the S wave is perpendicular to the polarization plane 8b, that is, Y The light is reflected in the axial direction, passes through the polarization beam splitter 8, and reaches the planar reflecting mirror 9. Here, in FIG. 3, the first optical path through which the first light component passes is indicated by a broken line, and the second optical path through which the second light component passes is indicated by a solid line.

First, a description will be given of a case where each light component dispersed by the polarization beam splitter 8 is first reciprocated when reciprocating twice between the laser interference unit 3 and the reflecting mirror 2.

As a first light component passing through the first optical path (broken line in FIG. 3), the P-wave laser light output to the optical path a2 passes through the quarter-wave plate 7b and becomes circularly polarized laser light. The biprism 6 is refracted at an angle φ with respect to the Z-axis direction by the wedge prism 6b and output to the optical path a3. The circularly polarized laser light, which is the first light component in the optical path a3, is input perpendicularly to the plane mirror 4 at the point 4b of the plane mirror 4 of the reflection mirror 2, and is reflected by the optical path a3. In other words, the angle of the plane mirror 4 of the reflecting mirror 2 is adjusted by the operator so that the first light component is vertically incident and reflected. The reflected circularly polarized laser beam in the optical path a3 is again refracted in the Z-axis direction by the wedge prism 6b, passes through the quarter-wave plate 7b, becomes S-wave laser light, and is output to the optical path a2. , Returned to the polarization beam splitter 8.

That is, the first light component that has traveled straight in the Z-axis direction through the polarization plane 8b sequentially passes through the optical path a2, the quarter-wave plate 7b, the biprism 6, and the optical path a3, and is reflected by the plane mirror 4 of the reflecting mirror 2. Thus, the optical path a3, the biprism 6, the quarter wavelength plate 7b, and the optical path a2 which are the same optical path as the forward path sequentially pass through the return path and return to the polarization plane 8b, and the biprism 6 of the laser interference unit 3 and The first light component reciprocates with the reflecting mirror 2.

On the other hand, as the second light component passing through the second optical path (solid line in FIG. 3), the S-wave laser light, which is the light component dispersed by the polarization beam splitter 8, is transmitted by the bi-prism 6 by the planar reflecting mirror 9. The light is reflected in the arranged direction and output to the optical path b2.

The S-wave laser light in the optical path b2 passes through the

wedge prisms

15a and 15b of the deflection unit 15 and is output to the optical path b3. The deflection unit 15 deflects the S-wave laser light as the second light component. The direction is adjusted.

More specifically, as shown in FIG. 6A, when the manufacturing accuracy of the polarization beam splitter 8 that is an optical component is low, the S-wave laser light that is the second light component reflected by the polarization plane 8b is The optical path deviated from the Y-axis direction is traced. The second light component reflected by the planar reflecting mirror 9 is parallel to the first light component that is shifted from the Z-axis direction and passes through the optical path b2 as in the optical path b3 ′ in the absence of the deflecting unit 15. In other words, the parallelism is extremely low. On the other hand, in the first embodiment, as shown in FIG. 6B, the operator rotates the

wedge prisms

15a and 15b of the deflecting unit 15 in the arrow A direction or the arrow B direction. Thus, the laser light passing through the deflecting unit 15 can be deflected within a predetermined substantially conical region R, and the second light component output to the optical path b3 is converted into the optical path a2 as shown in FIG. Since the deflection direction can be adjusted to be parallel to the first light component output to the first light component, the parallelism of the second light component passing through the optical path b3 with respect to the first light component passing through the optical path a2 is improved. Can be made.

In this way, the S-wave laser light, which is the second light component adjusted in parallel with the first light component passing through the optical path a2 by the deflecting unit 15 and passed through the optical path b3 in the Z-axis direction, passes through the quarter-wave plate 7a. The laser beam passes through to become circularly polarized laser light, and is refracted at an angle φ with respect to the Z-axis direction by the wedge prism 6b of the biprism 6, and is output to the optical path b4. The circularly polarized laser beam, which is the second light component of the optical path b4, is reflected at the point 4a of the plane mirror 4 of the reflecting mirror 2.

Here, since the second light component passing through the optical path b3 is adjusted by the deflecting unit 15 to be parallel to the first light component passing through the optical path a2, the second light component passing through the optical path b4 is Similar to the first light component vertically incident / reflected at the point 4 b of the plane mirror 4, the light is vertically reflected at the point 4 a of the plane mirror 4.

The circularly polarized laser beam, which is the second light component of the reflected optical path b4, is refracted in the Z-axis direction again by the wedge prism 6b and passes through the quarter-wave plate 7a to become a P-wave laser beam. , And output to the optical path b3. The P-wave laser light in the optical path b3 is adjusted in the deflection direction by the deflecting unit 15 and output to the optical path b2, and is reflected by the planar reflecting mirror 9 toward the polarization plane 8b.

That is, the second light component reflected by the polarization plane 8b sequentially passes through the planar reflector 9, the optical path b2, the deflecting unit 15, the optical path b3, the quarter wavelength plate 7a, the biprism 6, and the optical path b4. The optical path b4, the biprism 6, the quarter-wave plate 7a, the optical path b3, the deflecting unit 15, the optical path b2, and the planar reflecting mirror 9 that are reflected by the plane mirror 4 of the reflecting mirror 2 are the same path as the forward path. The laser beam passes through the polarization surface 8b in sequence, and the second light component reciprocates between the biprism 6 and the reflecting mirror 2 of the laser interference unit 3.

Next, a description will be given of a case where each light component dispersed by the polarization beam splitter 8 is reciprocated between the laser interference unit 3 and the reflecting mirror 2 for the second time.

As the second light component that passes through the second optical path (solid line in FIG. 3), the laser light that has passed through the optical path b2 and returned to the polarization plane 8b is a P wave, and thus travels straight through the polarization plane 8b. And pass through as it is and output to the optical path b5. The P-wave laser light in the optical path b5 passes through the quarter-wave plate 10 and becomes circularly polarized laser light and is output to the optical path b6. The circularly polarized laser light in the optical path b6 is transmitted by the cube corner prism 11. The optical path b7 is output after being folded back onto the optical path b7 which is parallel to the axial direction of the optical path b6 and is on a different axis in the X-axis direction. The circularly polarized laser light in the optical path b7 passes through the quarter wavelength plate 10 again to become S-wave laser light and is output to the optical path b8.

Since the laser beam in the optical path b8 is an S wave, the laser beam is reflected by the polarization plane 8b of the polarization beam splitter 8 to the optical path b9 in the perpendicular direction, that is, the Z-axis direction. Here, as shown in FIG. 6, the second light component output to the optical path b9 is reflected on the polarization plane 8b at the same angle as the angle at which the second light component that has passed through the optical path b1 is reflected on the polarization plane 8b. Therefore, the first light component is output in parallel with the optical path a2 that has passed during the first round trip.

The S-wave laser light in the optical path b9 passes through the quarter-wave plate 7b to become circularly polarized laser light, and is refracted at an angle φ with respect to the Z-axis direction by the wedge prism 6a of the biprism 6, and the optical path is output to b10. The circularly polarized laser light, which is the second light component of the optical path b10, is input perpendicularly to the plane mirror 5 at the point 5b of the plane mirror 5 of the reflecting mirror 2 and reflected by the optical path b10. In other words, the angle of the plane mirror 5 of the reflecting mirror 2 is adjusted by the operator so that the second light component is vertically incident and reflected. The reflected circularly polarized laser beam in the optical path b10 is refracted in the Z-axis direction again by the wedge prism 6a, passes through the quarter-wave plate 7b, becomes P-wave laser light, and is output to the optical path b9. The Since the laser beam in the optical path b9 is a P wave, it passes through the polarization plane 8b of the polarization beam splitter 8 in the straight traveling direction as it is, and the first optical component in the optical path a1 and the second optical component in the optical path b1 To the parallel optical path b11.

That is, the second light component reflected by the polarization plane 8b sequentially passes through the optical path b9, the quarter-wave plate 7b, the biprism 6, and the optical path b10, and is reflected by the plane mirror 5 of the reflecting mirror 2 so as to travel forward. The optical path b10, the biprism 6, the quarter-wave plate 7b, and the optical path b9, which are the same optical path, sequentially pass through the return path and return to the polarization plane 8b, and the biprism 6 and the reflecting mirror 2 of the laser interference unit 3 are returned. The second light component reciprocates between the two.

Then, the second light component reciprocated twice with respect to the plane mirrors 4 and 5 of the reflecting mirror 2 is output to the optical path b11 from the input / output surface 8a, and then input to the photoelectric converter of the laser head 12.

On the other hand, as the first light component passing through the first optical path (broken line in FIG. 3), the laser light returning to the optical path a2 is an S wave, so that the cube corner is formed by the polarization plane 8b of the polarization beam splitter 8. The light is reflected in the direction in which the prism 11 is disposed and output to the optical path a4.

Specifically, the first light component that has returned through the optical path a2 is reflected at the same angle as the reflection angle of the second light component that has passed through the optical path b1 and is reflected by the polarization plane 8b, and the second light component at this time Is output to the optical path a4 in a direction parallel to and opposite to the optical path a4.

The S-wave laser light in the optical path a4 passes through the quarter-wave plate 10 and becomes circularly polarized laser light and is output to the optical path a5. The circularly polarized laser light in the optical path a5 is transmitted by the cube corner prism 11. The optical path a6 is output after being folded back onto an optical path a6 that is parallel to the axial direction of the optical path a5 and is on a different axis in the X-axis direction. The circularly polarized laser light in the optical path a6 passes through the quarter wavelength plate 10 again to become P-wave laser light and is output to the optical path a7.

Since the laser beam in the optical path a7 is a P wave, the laser beam travels straight through the polarization plane 8b of the polarization beam splitter 8 and is output to the planar reflecting mirror 9. The planar reflecting mirror 9 causes the biprism 6 to The light is reflected in the arranged direction and output to the optical path a8.

Here, a second light component reflected by the polarization plane 8b during the first reciprocation and traveling toward the planar reflecting mirror 9, and a first light component returning to the planar reflecting mirror 9 through the optical path b8 by folding the cube corner prism 11 Are parallel. Accordingly, the first light component of the optical path a8 is parallel to the second light component of the optical path b2.

The P-wave laser light that is the first light component that has passed through the optical path a8 is deflected by the deflecting unit 15 in the same direction as the deflection direction of the second light component that has passed through the optical path b3, and passes through the optical path b9. It is adjusted parallel to the component and output to the optical path a9.

That is, the second light component passes through the deflecting unit 15 during the first reciprocation, and the first light component passes through the deflecting unit 15 during the next reciprocation, so that the deflection direction of both light components is adjusted by the deflecting unit 15. It becomes.

The P-wave laser light, which is the first light component in the optical path a9, passes through the quarter-wave plate 7a to become circularly polarized laser light, and is angled with respect to the Z-axis direction by the wedge prism 6a of the biprism 6. The light is refracted by φ and output to the optical path a10. The circularly polarized laser beam, which is the first light component in the optical path a10, is reflected at the point 5a of the plane mirror 5 of the reflecting mirror 2.

Here, since the P-wave laser light, which is the first light component that passes through the optical path a9, is adjusted to be parallel to the second light component that passes through the optical path b9, the first light component that has passed through the optical path a10 is Similarly to the second light component vertically incident / reflected at the point 5 b of the plane mirror 5, the light is vertically reflected at the point 5 a of the plane mirror 5.

The circularly polarized laser beam, which is the first light component of the reflected optical path a10, is refracted in the Z-axis direction again by the wedge prism 6a and passes through the quarter-wave plate 7a to become an S-wave laser beam. , And output to the optical path a9. The S-wave laser light in the optical path a9 is adjusted in the deflection direction by the deflecting unit 15 and output to the optical path a8, and is reflected by the planar reflecting mirror 9 toward the polarization plane 8b. Since the laser beam that has returned to the polarization plane 8b of the polarization beam splitter 8 along the same optical path as the forward path is an S wave, the polarization plane 8b of the polarization beam splitter 8 causes the second light component in the optical path b1 to be converted to the polarization plane 8b. Is reflected in the Z-axis direction at the same angle as the reflection angle when reflected at, and is parallel to the first light component of the optical path a1 and the second light component of the optical path b1, and is output from the input / output surface 8a to the optical path a11. .

That is, the first light component that has passed through the polarization plane 8b sequentially passes through the planar reflecting mirror 9, the optical path a8, the deflecting unit 15, the optical path a9, the quarter wavelength plate 7a, the biprism 6, and the optical path a10, Reflected by the plane mirror 5 of the reflecting mirror 2, the optical path a 10, the biprism 6, the quarter-wave plate 7 a, the optical path a 9, the deflecting unit 15, the optical path a 8, and the planar reflecting mirror 9 are sequentially returned as the return path. It passes through and returns to the polarization plane 8b, and the first light component reciprocates between the biprism 6 and the reflecting mirror 2 of the laser interference unit 3.

The first light component reciprocated twice with respect to the plane mirrors 4 and 5 of the reflecting mirror 2 is output from the input / output surface 8a to the optical path a11 and then input to the photoelectric converter of the laser head 12.

As described above, since the first light component of the optical path a11 and the second light component of the optical path b11 that have reciprocated twice with respect to the plane mirrors 4 and 5 of the reflecting mirror 2 are parallel to the input laser light, They are output in parallel with each other.

The optical paths a1 and b1, optical paths a4 and b5, optical paths a5 and b6, optical paths a6 and b7, optical paths a7 and b8, and optical paths a11 and b11 shown in FIG. 3 are shown as parallel axes for convenience of explanation. However, these optical paths are optical paths on the same axis.

In the first embodiment, the laser light having the first light component and the second light component irradiated from the laser head 12 is input from the input / output surface 8a, is split by the polarization surface 8b, and is reflected by the biprism 6. Since the second light component passes through the deflecting unit 15 during the first reciprocation with the mirror 2, and the first light component passes through the deflecting unit 15 during the next reciprocation, the pair of

wedge prisms

15a and 15b of the deflecting unit 15 is used. Can be rotated to adjust the deflection direction of each light component. By the adjustment operation, each light component emitted to the biprism 6 can be made parallel, and each light component can be made perpendicular to the reflecting mirror 2. Can be incident and reflected. Since the light is vertically incident and reflected by the reflecting mirror 2, each light component can follow the same light path in the forward path and the return path, and each light component output from the input / output surface can be made parallel to each other. Therefore, the parallelism of each light component output from the laser interference unit 3 can be improved.

In addition, in order to adjust the deflection direction of each light component, it is not necessary to adjust the angle of the planar reflecting mirror 9 formed integrally with the polarizing beam splitter 8, and the pair of

wedge prisms

15 a and 15 b of the deflecting unit 15. The adjustment work is very simple because it is only necessary to rotate the.

Further, since both light components pass through the pair of

wedge prisms

15a and 15b, it is not necessary to prepare a pair of wedge prisms for each light component, so the number of parts is reduced and the structure is simple. It becomes.

Next, for example, it is assumed that the reflecting mirror 2 moves relative to the laser interference unit 3 in the roll direction, which is the γ direction around the Z axis. Then, the

points

4a and 5b and the

points

4b and 5a at which the laser beams passing through the first optical path and the second optical path are reflected are the

points

4a and 5b on the valley side (that is, the inner side). ) Or the mountain side (that is, the outside), the point 4 b and the point 5 a move to the mountain side (that is, the outside) or the valley side (that is, the inside) with respect to the inclination of the plane mirrors 4 and 5. That is, the optical path lengths of the optical path a3 and the optical path a10 are shortened or extended with respect to the optical path lengths of the optical path b4 and b10, and a relative change occurs in the optical path lengths of the first optical path and the second optical path.

When a relative change occurs in the optical path length between the first optical path and the second optical path, the S-wave laser light that is the first optical component of the optical path a11 output from the input / output surface 8a and the second light in the optical path b11 A Doppler frequency shift with the component P-wave laser light occurs, and an interference signal is obtained. A change in the optical path length (hereinafter referred to as “detection light length”) can be detected by the photoelectric converter of the laser head 12 to which the interference signal is input. In addition, since detection of the Doppler frequency shift by this photoelectric converter is a well-known technique, the description is abbreviate | omitted.

Further, when the distance between the point 4a and the point 4b (the point 5a and the point 5b) is 2v, the angle θ _{γ in the} roll direction and the change amount Δ of the optical path length are expressed by an equation:
θ _γ = tan−1 (Δ / (8v · sinφ))...
It becomes. The relationship between the angle θ in the roll direction and the change amount Δ of the optical path length does not depend on the distance 2u between the point 4a and the point 5a (the point 4b and the point 5b), that is, the distance between the reflecting mirror 2 and the laser interference unit 3. Has no effect.

Since the distance 2v between the point 4a and the point 4b (the point 5a and the point 5b) is constant and the angle φ is also constant, the relationship of the above formula 1 is that the detected light length (mm) and the generated rolling (square second) Obtained as a relationship. By accumulating the generated rolling, it is possible to calculate the positional deviation in the roll direction between the reflecting mirror 2 and the laser interference unit 3, that is, calculating the positional deviation in the roll direction based on the detected light length. Is possible.

Therefore, in the first embodiment, since each light component output from the laser interference unit 3 can be made parallel, a good interference signal can be obtained and detected when measuring the positional deviation in the roll direction. Since the error of the change Δ in the optical path length is also reduced, the measurement accuracy of the positional deviation in the roll direction is improved.

As in the prior art, there were displacements in the horizontal direction (X direction), vertical direction (Y direction), axial direction (Z direction), pitch direction (α direction), and yaw direction (β direction). In this case, the optical path lengths of the optical path b4 and the optical path b10 and the optical path lengths of the optical path a3 and the optical path a10 are not expanded, contracted, or changed, and no relative change occurs between the two optical path lengths.

When measuring the machine tool 20 using the laser interferometer 1, a measuring device 50 including the laser interferometer 1 is installed in the machine tool 20 as shown in FIG. First, the reflecting mirror 2 of the laser interferometer 1 is fixed on the bed 21 of the machine tool 20, and the laser interference unit 3 is fixed on the table 22. At the time of fixing, the reflecting mirror 2 and the laser interference unit 3 are accurately aligned in the Z-axis direction, and the angle of the plane mirrors 4 and 5 and the angle of the laser interference unit 3 are accurate with respect to the Z-axis direction. It is preferable to fix the optical path so that the optical path length between the first optical path (especially the optical path a3 and the optical path a10) and the second optical path (especially the optical path b4 and the optical path b10) is different even if there is a slight deviation. Since there is no, there is no particular problem. Further, the laser head 12 is installed on the floor 30 so that the input / output head 12a is aligned with the input / output surface 8a of the laser interference unit 3 in the Z-axis direction.

Thereafter, laser light is emitted from the laser oscillator of the laser head 12, and measurement of the relative change in the optical path length between the first optical path and the second optical path is started by the photoelectric converter. Then, the table 22 of the machine tool 20 is moved in the Z-axis direction with respect to the bed 21, and the position deviation in the roll direction (γ direction) accompanying the movement of the table 22 is measured by the measuring device 50. At this time, the input / output surface 8a of the laser interference unit 3 moves in the Z-axis direction, and the input / output head 12a of the laser head 12 is also directed in the Z-axis direction. Even if it moves in the direction, the input / output of the laser beam to the input / output surface 8a does not shift. Further, if the laser interference unit 3 only moves in the Z-axis direction, the optical path lengths of the first optical path and the second optical path only expand and contract, and no relative optical path length difference occurs.

Further, when measuring the machine tool 20 using the laser interferometer 1, the reflecting mirror 2 of the laser interferometer 1 is fixed on the table 22 of the machine tool 20 as shown in FIG. It may be fixed on the bed 21. Similarly, the laser head 12 is installed on the floor 30 so that the input / output head 12a is aligned with the input / output surface 8a of the laser interference unit 3 in the Z-axis direction.

Thereafter, laser light is emitted from the laser oscillator of the laser head 12 and measurement of the relative change in the optical path length between the first optical path and the second optical path is started by the photoelectric converter, and the table 22 of the machine tool 20 is placed on the bed 21. On the other hand, it is moved in the Z-axis direction, and the position deviation in the roll direction (γ direction) accompanying the movement of the table 22 is measured by the measuring device 50. At this time, if the input / output of the laser light from the laser head 12 to the input / output surface 8a is not shifted and the reflecting mirror 2 only moves in the Z-axis direction, the optical path between the first optical path and the second optical path. The lengths only expand and contract together, and there is no relative optical path length difference.
As described above, according to the measurement apparatus 50 of the first embodiment, prior to the measurement, it is possible to easily perform the operation of adjusting each light component output from the laser interference unit 3 of the laser interferometer 1 in parallel. In addition, when measuring the positional deviation in the roll direction, a good interference signal can be obtained, and the measurement accuracy of the positional deviation in the roll direction can be improved.

<Second Embodiment>
Next, a second embodiment according to the present invention will be described with reference to the drawings. FIG. 7 is a schematic perspective view showing a laser interferometer according to the second embodiment. FIG. 8 is a perspective view showing the laser interference unit. FIG. 9 is a cross-sectional view of the laser interference portion taken along line BB in FIG. FIG. 10 is a plan view of the laser interference unit viewed from the direction of arrow C in FIG. In the second embodiment, the same reference numerals are given to the same parts as those in the first embodiment except for some changed parts, and the description thereof is omitted.

A laser interferometer 101 according to the second embodiment includes a reflecting mirror 2 and a laser interference unit 103. The laser interference unit 103 is further added to the configuration of the laser interference unit 3 according to the first embodiment. A cube corner prism (re-input unit) 17 is provided.

The cube corner prism 17 is disposed in the vicinity of the input / output surface 8a of the polarization beam splitter 8, and is fixed to the interference part case 3a by a fixing bracket 18. Further, as shown in FIG. 10, the cube corner prism 17 is arranged avoiding the point D1 where the laser beam is input and the point D4 for outputting the laser beam on the input / output surface 8a. The cube corner prism 17 is disposed so as to face a point D2 where the laser beam is output by two reciprocations between the biprism 6 and the reflecting mirror 2 and a point D3 where the laser beam is re-input.

In the second embodiment, as shown in FIG. 10, the cube corner prism 17 is fixed to the outside of the interference portion case 3a and exposed to the outside. However, the cube corner prism 17 is exposed to the interference portion case 3a. In either case, it is expressed as being stored in the interference part case 3a.

Hereinafter, the case where the laser beam is irradiated to the laser interferometer 101 will be described.

Laser light having a P wave and an S wave is output in parallel to the Z-axis direction from the laser oscillator of the laser head, and is input to the input / output surface 8a of the polarization beam splitter 8 via the optical paths c1 and d1 shown in FIG. Is done. At this time, the laser beam is input to the point D1 on the input / output surface 8a shown in FIG. The laser beam input to the input / output surface 8a of the polarization beam splitter 8 is split into a first light component (P wave) and a second light component (S wave) by the polarization surface 8b, and the first light component is the first light component. The light passes through the optical path (c2 to c22 in FIG. 7), and the second light component passes through the second optical path (d2 to d22 in FIG. 7). More specifically, the P wave passes through the polarization plane 8b of the polarization beam splitter 8 as it is and is output to the optical path c2 in the straight direction, that is, the Z-axis direction, and the S wave is perpendicular to the polarization plane 8b, that is, Y The light is reflected in the axial direction, passes through the polarization beam splitter 8, and reaches the planar reflecting mirror 9. Here, in FIG. 7, the first optical path through which the first light component passes is indicated by a broken line, and the second optical path through which the second light component passes is indicated by a solid line.

First, the first light component passing through the first optical path (broken line in FIG. 7) sequentially passes through the optical path c2, the quarter wavelength plate 7b, the wedge prism 6b of the biprism 6, and the optical path c3. The light enters and reflects perpendicularly to the plane mirror 4, and sequentially passes through the optical path c <b> 3, the wedge prism 6 b, the quarter wavelength plate 7 b, and the optical path c <b> 2 and returns to the polarization beam splitter 8.

Next, the laser light that has returned to the optical path c2 is an S wave, and is reflected by the polarization surface 8b of the polarization beam splitter 8 in the direction in which the cube corner prism 11 is disposed, and the optical paths c4 and 1/4. The wave plate 10 and the optical path c5 are sequentially passed, and the cube corner prism 11 returns to the optical path c6 which is parallel to the axial direction of the optical path c5 and is on an axis having a different diagonal position in the XZ plane. . Next, the first light component sequentially passes through the optical path c6, the quarter wavelength plate 10, and the optical path c7.

The laser beam in the optical path c7 is a P wave, and travels straight through the polarization plane 8b of the polarization beam splitter 8 and passes through the planar reflecting mirror 9 and the optical path c8 sequentially. The optical path c9, the quarter-wave plate 7a, the wedge prism 6a of the biprism 6 and the optical path c10 are sequentially passed, and enters and reflects perpendicularly to the plane mirror 5 of the reflecting mirror 2, and the optical path c10, the

wedge prism

6a, 1 / The light passes through the four-wavelength plate 7 a, the optical path c 9, the deflecting unit 15, the optical path c 8, and the planar reflection mirror 9 and returns to the polarization plane 8 b of the polarization beam splitter 8.

The laser beam that has returned to the polarization plane 8b of the polarization beam splitter 8 is an S wave, is reflected in the Z-axis direction by the polarization plane 8b of the polarization beam splitter 8, and is output from the input / output plane 8a to the optical path c11. . At this time, the laser beam output to the optical path c11 is output from the point D2 that is positioned diagonally to the point D1 on the XY plane of the input / output surface 8a shown in FIG.

In the second embodiment, the first light component output to the optical path c11 passes through the optical path c12 on the axis parallel to the axis of the optical path c11 and different in the Y-axis direction by the cube corner prism 17, and again. The light is input to the input / output surface 8 a of the polarization beam splitter 8. At this time, the laser beam output to the optical path c12 is input to a point D3 that is shifted by a predetermined distance in the Y-axis direction from the point D2 on the input / output surface 8a shown in FIG.

Since the first light component that has passed through the optical path c12 is an S wave, it is reflected by the polarization plane 8b, sequentially passes through the planar reflector 9 and the optical path c13, and the deflection direction is adjusted by the deflecting unit 15, and the optical path c14, the quarter-wave plate 7a, the wedge prism 6a of the biprism 6, and the optical path c15 are sequentially entered and reflected perpendicularly to the plane mirror 5 of the reflecting mirror 2, and the optical path c15, the wedge prism 6a, and the quarter-wave plate 7a. Then, the light passes through the optical path c14, the deflecting unit 15, the optical path c13, and the planar reflecting mirror 9 and returns to the polarization plane 8b of the polarization beam splitter 8.

The laser light that has returned to the polarization plane 8b of the polarization beam splitter 8 is a P-wave, passes straight through the polarization plane 8b of the polarization beam splitter 8, and passes through the optical path c16, the quarter wavelength plate 10, and the optical path. The light passes through c17 sequentially, and is output by the cube corner prism 11 by folding back to an optical path c18 which is parallel to the axial direction of the optical path c17 and is on an axis having a different diagonal position in the XZ plane. The laser beam in the optical path c18 sequentially passes through the quarter-wave plate 10 and the optical path c19, and returns to the polarization plane 8b of the polarization beam splitter 8 as S-wave laser light. The returned laser light is reflected by the polarization plane 8b and sequentially passes through the optical path c20, the quarter wavelength plate 7b, the wedge prism 6b of the biprism 6, and the optical path c21, and enters the plane mirror 4 of the reflecting mirror 2 perpendicularly. The light passes through the optical path c 21, the wedge prism 6 b, the quarter wavelength plate 7 b, and the optical path c 20, and returns to the polarization plane 8 b of the polarization beam splitter 8. The returned laser light of the first light component is a P wave, passes straight through the polarization plane 8b of the polarization beam splitter 8, and is output from the input / output plane 8a to the optical path c22. At this time, the laser beam output to the optical path c22 is output from the point D4 that is at the diagonal position of the point D3 on the XY plane of the input / output surface 8a shown in FIG. .

That is, the laser beam of the first light component is reciprocated between the biprism 6 and the reflecting mirror 2 and output to the cube corner prism 17, and then returned to the input / output surface 8a by the cube corner prism 17. Furthermore, since the bi-prism 6 and the reflecting mirror 2 are reciprocated twice and output from the input / output surface 8a, the bi-prism 6 and the reflecting mirror 2 are twice as large as the first embodiment. It is output from the input / output surface 8a after four reciprocations.

The first light component reciprocating four times with respect to the plane mirrors 4 and 5 of the reflecting mirror 2 is output from the input / output surface 8a to the optical path c22 and then input to the photoelectric converter of the laser head.

On the other hand, as the second light component passing through the second optical path (solid line in FIG. 7), the S-wave laser light, which is the light component dispersed by the polarization beam splitter 8, sequentially passes through the planar reflector 9 and the optical path d2. And the deflection direction is adjusted by the deflecting unit 15, sequentially passes through the optical path d3, the quarter-wave plate 7a, the wedge prism 6b, and the optical path d4, and is vertically incident and reflected by the plane mirror 4 of the reflecting mirror 2, and the optical path d4, The light passes through the wedge prism 6 b, the quarter-wave plate 7 a, the optical path d 3, the deflecting unit 15, the optical path d 2, and the planar reflection mirror 9, and returns to the polarization plane 8 b of the polarization beam splitter 8.

Since the returned laser light of the second light component is a P wave, it travels straight through the polarization plane 8b and passes through the optical path d5, the quarter wavelength plate 10, and the optical path d6 in order, and the cube corner. By the prism 11, the light is returned to the optical path d 7 which is parallel to the axial direction of the optical path d 6 and is on an axis having a different diagonal position in the XZ plane. The laser beam in the optical path d7 sequentially passes through the quarter-wave plate 10 and the optical path d8, and returns to the polarization plane 8b of the polarization beam splitter 8 as S-wave laser light. The returned laser light is reflected by the polarization plane 8b, sequentially passes through the optical path d9, the quarter-wave plate 7b, the wedge prism 6a, and the optical path d10, and enters and reflects perpendicularly by the plane mirror 5 of the reflecting mirror 2, and the optical path. It passes through d10, the wedge prism 6a, the quarter wavelength plate 7b, and the optical path d9 in order, and returns to the polarization plane 8b of the polarization beam splitter 8.

The returned laser light of the second light component is a P wave, passes through the polarization plane 8b of the polarization beam splitter 8 in the straight traveling direction, and is output from the input / output plane 8a to the optical path d11. At this time, the laser beam output to the optical path d11 is output from a point D2 opposite to the cube corner prism 17 at the diagonal position of the point D1 on the XY plane of the input / output surface 8a shown in FIG. .

In the second embodiment, the second light component output to the optical path d11 passes through the optical path d12 on the axis parallel to the axis of the optical path d11 and different in the Y-axis direction by the cube corner prism 17, and again. The light is input to the input / output surface 8 a of the polarization beam splitter 8. At this time, the laser beam output to the optical path d12 is input to a point D3 that is shifted by a predetermined distance in the Y-axis direction from the point D2 on the input / output surface 8a shown in FIG.

Since the second light component that has passed through the optical path d12 is a P wave, it passes through the polarization plane 8b as it is, and sequentially passes through the optical path d13, the quarter wavelength plate 7b, the wedge prism 6a, and the optical path d14, and the reflecting mirror. 2 is reflected vertically by the plane mirror 5, passes through the optical path d 14, the wedge prism 6 a, the quarter-wave plate 7 b, and the optical path d 13 in order, and returns to the polarization plane 8 b of the polarization beam splitter 8.

The laser beam returning to the polarization plane 8b of the polarization beam splitter 8 is an S wave, is reflected by the polarization plane 8b of the polarization beam splitter 8, and sequentially passes through the optical path d15, the quarter wavelength plate 10, and the optical path d16. Then, the cube corner prism 11 returns the light to the optical path d17 which is parallel to the axial direction of the optical path d16 and is on an axis having a different diagonal position in the XZ plane. The laser beam in the optical path d17 sequentially passes through the quarter-wave plate 10 and the optical path d18, and returns to the polarization plane 8b of the polarization beam splitter 8 as a P-wave laser beam. The returned laser light travels straight through the polarization plane 8b of the polarization beam splitter 8, passes through as it is, sequentially passes through the planar reflector 9 and the optical path d19, the deflection direction is adjusted by the deflecting unit 15, and the optical path d20, The ¼ wavelength plate 7a, the wedge prism 6b, and the optical path d21 are sequentially passed, and vertically incident and reflected by the plane mirror 5 of the reflecting mirror 2, and the optical path d21, the wedge prism 6b, the ¼ wavelength plate 7a, the optical path d20, and the deflecting unit. 15, sequentially passes through the optical path d 19 and the planar reflector 9, and returns to the polarization plane 8 b of the polarization beam splitter 8.

The laser light that has returned to the polarization plane 8b of the polarization beam splitter 8 is an S wave, is reflected in the Z-axis direction by the polarization plane 8b of the polarization beam splitter 8, and is output from the input / output plane 8a to the optical path d22. . At this time, the laser beam output to the optical path d22 is output from the point D4 that is at the diagonal position of the point D3 on the XY plane of the input / output surface 8a shown in FIG. .

That is, the laser light of the second light component is reciprocated between the biprism 6 and the reflecting mirror 2 and output to the cube corner prism 17, and then returned to the input / output surface 8a by the cube corner prism 17. Furthermore, since the bi-prism 6 and the reflecting mirror 2 are reciprocated twice and output from the input / output surface 8a, the bi-prism 6 and the reflecting mirror 2 are twice as large as the first embodiment. It is output from the input / output surface 8a after four reciprocations.

Then, the second light component reciprocated four times with respect to the plane mirrors 4 and 5 of the reflecting mirror 2 is output from the input / output surface 8a to the optical path d22 and then input to the photoelectric converter of the laser head.

As described above, in the second embodiment, the laser light outputted by the cube corner prism 17 by reciprocating twice between the biprism 6 and the reflecting mirror 2 is returned to the biprism 6 and the reflecting mirror 2 again. Since the optical path length of each light component is twice that of the first embodiment, and the positional deviation in the roll direction occurs, the amount of change in the optical path length is double. Become. Accordingly, the detection sensitivity is doubled in the photoelectric converter of the laser head 12 that detects the change in the optical path length, and the measurement accuracy of the positional deviation in the roll direction is improved.

In the second embodiment, the laser light having the first light component and the second light component irradiated from the laser head 12 is input from the input / output surface 8a and dispersed by the polarization surface 8b, and the biprism 6 Since the second light component is adjusted in the polarization direction in the deflecting unit 15 during the first round-trip between the mirror 2 and the reflecting mirror 2, and the first light component is adjusted in the polarization direction in the deflecting unit 15 during the next round-trip. Each light component output to the prism 17 can be made parallel. Furthermore, each light component of the parallel laser light input again from the input / output surface 8 a by the cube corner prism 17 is also split by the polarization surface 8 b and is first reciprocated between the biprism 6 and the reflecting mirror 2. Since the polarization direction of one light component is adjusted in the deflecting unit 15 and the polarization direction of the second light component is adjusted in the deflecting unit 15 at the next reciprocation, the amount of adjustment of the deflecting unit 15 is adjusted when laser light is input again. Even if it does not change, each output light component can be made parallel. Therefore, when measuring the positional deviation in the roll direction, a good interference signal can be obtained, and the measurement accuracy of the positional deviation in the roll direction can be improved.

Next, the roll detection sensitivity of the measurement apparatus including the laser interferometer 1 according to the first embodiment is compared with the roll detection sensitivity of the measurement apparatus including the laser interferometer 101 according to the second embodiment. The experimental results will be described. FIG. 11 is a diagram showing roll detection sensitivity measured by the measurement apparatus of the first embodiment, and FIG. 12 is a diagram showing roll detection sensitivity measured by the measurement apparatus of the second embodiment. is there. Incidentally, the reflection mirror 2 in the laser interferometer 1 of the first embodiment is incident and reflected four times in total including the first light component and the second light component, and the laser interference of the second embodiment. The total reflection of the first light component and the second light component on the reflecting mirror 2 in the total 101 is 8 times.

11 and 12, the horizontal axis is an angle (roll) obtained by rotating the reflecting mirror 2 in the roll direction, and the vertical axis is detected using the

laser interferometers

1 and 101 with respect to the roll of the reflecting mirror 2. Is the detected light length. 11 and 12, L is the distance between the reflecting mirror 2 and the biprism 6. In the drawing, the plotting position of the data is shifted upward as the value of L increases to make it easy to see. . For example, when L = 300 (mm), the detection light length is shifted upward by 0.01 (mm) and plotted, but the actual detection light length is 0.01 (mm) from the plot position. ) Is a low value.

Here, the roll detection sensitivity of the measuring apparatus including the

laser interferometers

1 and 101 is the slope of the regression line of the measurement data, and the greater the slope of the regression line of the measurement data, the higher the detection sensitivity. The roll detection sensitivity of the measurement apparatus according to the first embodiment shown in FIG. 11 is 0.81 × 10 ⁻⁵ regardless of the value of L, and is equal to the distance between the reflecting mirror 2 and the biprism 6. It was confirmed that it did not depend.

In addition, the roll detection sensitivity of the measurement apparatus of the second embodiment shown in FIG. 12 is 1.63 × 10 ⁻⁵ regardless of the value of L, which also causes It was confirmed that it did not depend on the distance to the prism 6. It was confirmed that the roll detection sensitivity of the measurement apparatus of the second embodiment is twice the roll detection sensitivity of the measurement apparatus of the first embodiment.

Next, a case where the positional deviation in the roll direction of the optical test bench is actually detected using the measurement apparatus including the laser interferometer 101 according to the second embodiment will be described. FIG. 13 is a diagram illustrating a result of detecting a positional deviation in the roll direction of the optical experimental bench. In this experiment, a table was placed on the optical test bench, and the position deviation in the roll direction was detected by moving the table.

Here, what is obtained from the laser interferometer 101 is the detection light length. By using the roll detection sensitivity (1.63 × 10 ⁻⁵ ) shown in FIG. 12 as calibration data, the positional deviation in the roll direction is calculated. Yes. More specifically, the roll shown in FIG. 13, that is, the positional deviation in the roll direction, is obtained by dividing the detection light length obtained from the laser interferometer 101 by the roll detection sensitivity, which is calibration data.

As shown in FIG. 13, the measurement of the positional deviation in the roll direction was performed five times. However, since the roll detection sensitivity was doubled, there was almost no variation in the measurement results. Therefore, it was confirmed that the measurement accuracy of the positional deviation in the roll direction was improved.

<Third Embodiment>
Next, a third embodiment according to the present invention will be described with reference to the drawings. FIG. 14 is a schematic perspective view showing a laser interferometer according to the third embodiment. In the third embodiment, the same reference numerals are given to the same parts as those in the first or second embodiment except for some changed parts, and the description thereof is omitted.

In the third embodiment, as shown in FIG. 14, the laser interference unit 203 of the laser interferometer 201 separates the polarization beam splitter (spectral unit) 208 and the planar reflector (reflecting unit) 209. And a planar reflecting mirror 209 is arranged in a direction perpendicular to the Z-axis direction of the polarizing beam splitter 208 (Y-axis direction).

Also in the third embodiment, the deflecting unit 15 is disposed between the planar reflecting mirror 209 and the quarter-wave plate 7a. Thus, according to the third embodiment, it is not necessary to adjust the angle of the planar reflecting mirror 209 when adjusting each light component output from the laser interference unit 203 in parallel, and each of the deflecting units 15 can be adjusted. Since only the

wedge prisms

15a and 15b need to be adjusted, the adjustment work is simple.

In the third embodiment, the case where the deflecting unit 15 is disposed between the planar reflector 209 and the quarter-wave plate 7a has been described. However, the present invention is not limited to this. As indicated by a broken line, the deflecting unit 15 may be disposed between the polarizing beam splitter 208 and the planar reflecting mirror 209. This also makes it unnecessary to adjust the angle of the planar reflecting mirror 209 when adjusting the output light components in parallel, and it is only necessary to adjust the

wedge prisms

15a and 15b of the deflecting unit 15. Easy to work.

In the first to third embodiments, the deflecting unit 15 is disposed between the

planar reflectors

9 and 209 and the quarter-wave plate 7a. Instead, for example, a broken line in FIG. As shown, the deflecting unit 15 may be disposed between the quarter-wave plate 7 a and the biprism 6. Further, instead of providing the deflecting unit 15 in the optical path passing through the

polarizing beam splitters

8 and 208, the reflecting

mirrors

9 and 209, the quarter wavelength plate 7a, and the biprism 6, the

polarizing beam splitters

8, 208 and quarter wavelength plates are provided. 7b, an optical path passing through the biprism 6, that is, the deflecting unit 15 is disposed between the

polarization beam splitters

8 and 208 and the quarter wavelength plate 7b, or between the quarter wavelength plate 7b and the biprism 6. You may make it do.

In the first to third embodiments, the case where the

laser interference units

3, 103, and 203 have the

planar reflecting mirrors

9 and 209 as the reflection units has been described. However, the present invention is not limited to this. The interference part may have an amic prism (not shown) as a reflection part.

In the first to third embodiments, the

laser interferometer

1, 101, 201 is used to measure the positional deviation in the roll direction (γ direction). , 201 can be used in a shape rotated 90 degrees, that is, in a horizontal direction.

In the first embodiment, the measurement device 50 for measuring the machine tool 20 has been described. However, the measurement device 50 is not limited to the machine tool, and is not limited to the machine tool, but in the axial direction with respect to the support member and the support member. As long as it is a moving member that can be installed (fixed) to the reflecting mirror 2 and the

laser interference units

3, 103, 203, the positional deviation of them can be measured. Is possible.

In the first to third embodiments, the input / output surfaces of the

laser interference units

3, 103, and 203 are positioned on the opposite side in the axial direction of the

polarization beam splitters

8 and 208 with respect to the reflecting mirror 2. Although described above, the present invention is not limited to this, and the input / output surface of the polarization beam splitter is formed in a direction perpendicular to the axial direction so that the laser interference unit inputs and outputs laser light in the direction perpendicular to the axial direction. It may be configured.

In the second embodiment, the laser interference unit 103 includes one cube corner prism 17 as a re-input unit, and the laser beam is reciprocated four times between the biprism 6 and the reflecting mirror 2. However, the present invention is not limited to this, and the laser interference unit includes a plurality of cube corner prisms (N: N is an integer of 2 or more) as a re-input unit. It may be a case where it is configured to reciprocate 2 × (N + 1).

The laser interferometer and measuring apparatus according to the present invention are used for measuring a positional deviation that occurs when a moving member such as a table of a machine tool moves in an axial direction with respect to a supporting member, and in particular, a positional deviation in a roll direction. Suitable for measurement.

Claims

Reflecting means having two plane mirrors inclined at a predetermined angle;
A spectroscopic unit that inputs and splits laser light having two polarization components whose polarization planes are orthogonal to each other, and each light component that is disposed between the spectroscopic unit and the reflection unit and is spectrally separated by the spectroscopic unit, A laser having a refracting portion that refracts at the predetermined angle so as to enter and reflect perpendicularly to the plane mirror of the reflecting means, and outputs each light component after reciprocating twice between the refracting portion and the reflecting means. An optical path generating means,
Laser in which the distance of the optical path through which each light component passes is relatively changed by the relative positional relationship between the reflecting means and the laser light path generating means when the reflecting means and the laser light path generating means are relatively moved in the axial direction. In the interferometer,
The laser beam path generation means includes
One light component passes when each light component first reciprocates, and the other light component passes when each light component reciprocates next time. A laser interferometer, comprising: a deflecting unit that includes a pair of wedge prisms that are arranged and allow the deflection direction of a light component passing therethrough to be adjustable.
The laser beam path generation means includes
A reflection unit that is arranged in a direction perpendicular to the axial direction of the spectroscopic unit and reflects the laser light incident through the spectroscopic unit toward the refractive unit;
The laser interferometer according to claim 1, wherein the deflection unit is disposed between the reflection unit and the refraction unit.
The laser beam path generation means includes
A reflection unit that is arranged in a direction perpendicular to the axial direction of the spectroscopic unit and reflects the laser light incident through the spectroscopic unit toward the refractive unit;
The laser interferometer according to claim 1, wherein the deflecting unit is disposed between the spectroscopic unit and the reflecting unit.
A housing for storing the laser beam path generation means;
The deflection unit has a ring-shaped operation element formed on the outer periphery of the wedge prism,
4. The laser interferometer according to claim 1, wherein the wedge prism is disposed in the casing so that the operation element is exposed from the casing. 5.
The spectroscopic section has an input / output section that allows laser light to be input and output laser light that has been reciprocated twice to the reflecting means,
5. The laser light path generation unit according to claim 1, further comprising a re-input unit configured to input the laser beam output from the input / output unit to the input / output unit. Laser interferometer.
The laser interferometer according to any one of claims 1 to 5,
Laser measurement capable of measuring the relative change in the optical path distance of each light component based on the phase difference of the wavelength of the laser light of each light component output from the laser light path generation means. A long means,
Either one of the reflecting means and the laser beam path generating means is fixed to a support member supported with respect to a reference floor;
The other of the reflecting means and the laser beam path generating means is fixed to a moving member that is supported so as to be movable in the axial direction with respect to the supporting member,
A measuring apparatus for measuring a positional deviation of the moving member with respect to the supporting member when the moving member is moved in the axial direction with respect to the supporting member.