JP2017133892A - Rotation angle detector and rotation angle detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotation angle detector and a rotation angle detection method which realize angle detection over a wide angle range while enjoying the benefit of high measurement resolution due to a small spot diameter.SOLUTION: A reflection part 19 mounted on a measurement object 12 is irradiated with a collimated beam 15 generated by collimating divergent laser beams 14, and a measurement beam 21 reflected from the reflection part 19 is condensed by an objective lens 46, which is then measured by a photodetector 28 for measurement. The photodetector 28 for measurement is arranged so that the center of a light spot 31 obtained by condensing the measurement beam 21 is located at the boundary of a sensitive zone 29 and nonsensitive zone 30 of the photodetector 28 for measurement, and is mounted on a positioning stage 32. The position of the photodetector 28 for measurement is controlled by the positioning stage 32 so that when the measurement object 12 rotates, the center of a light spot 31 remains located at the boundary, and the rotation angle of the measurement object 12 is determined on the basis of information pertaining to the position control.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rotation angle detection device and a rotation angle detection method based on a laser autocollimation method.

  With the progress of ultra-precision machining and multi-axis machining, it is important to improve the relative positioning between workpiece and tool. At that time, not only high accuracy of the displacement detection sensor used for positioning, but also means for detecting the change in the posture angle of the workpiece or tool with high accuracy is indispensable. In particular, machine tools are often not easily mounted with displacement / posture angle detection sensors due to physical limitations due to their structure, and small sensors that can be easily measured on a processing machine are preferred.

  Conventionally, a laser interferometer or a linear encoder has been used to detect the position of a stage or moving slide on which a workpiece or tool is mounted (for example, Non-Patent Document 1). Laser interferometers can be measured over long strokes, but due to physical limitations from the structure, it may be difficult to place optical components around the laser beam of a laser interferometer on a machine tool. Many. On the other hand, linear encoders must have an encoder scale on the slide side and a small optical sensor head to enable highly accurate position detection and have good robustness even in harsh environments such as factories. Therefore, in recent years, linear encoders tend to be preferred as position detection sensors.

  On the other hand, when using a linear encoder as a slide position detection sensor, it is not easy to match the slide motion axis with the linear encoder measurement axis due to the physical constraints of the structure. There is a certain amount of physical offset. In the ideal case where the slide moves linearly along the axis of motion without attitude error, this physical offset is not a problem. On the other hand, in an actual machine tool, a slight attitude angle error always occurs when the slide moves linearly, and this attitude angle error and Abbe error, which is a positioning error due to the offset between the movement axis and the sensor measurement axis, occur. (For example, see Non-Patent Document 2). Posture error during slide movement can be reduced to some extent by improving the accuracy of the slide guide surface, but it is not possible to completely eliminate the effect, and we want to achieve nanometer and sub-nanometer scale ultra-precision positioning. In such a case, it is necessary to detect a minute posture angle error during a slide motion with a highly accurate angle sensor.

  Conventionally, for this attitude angle measurement, a laser interferometer having a plurality of measurement laser beams or an optical autocollimator is used (for example, see Non-Patent Document 3), but a slide attitude that requires high angle detection resolution. In angular error measurement, an optical autocollimator having a higher measurement resolution than a laser interferometer is frequently used. Currently, a commercially available autocollimator is capable of high-resolution measurement of up to about 0.0005 angle seconds.

  An ultra-sensitive angle sensor that uses a high-speed, high-sensitivity photodiode as the light-receiving element and reduces the laser spot diameter on the light-receiving element to a micrometer size to achieve resolution exceeding 0.0001 angular seconds. Is also under development (see, for example, Patent Document 1 and Non-Patent Document 4).

Kunzmann h., Pfeifer T., Flugge J., “Scales Vs Laser Interferometers, Performance and Comparison of Two Measuring Systems”, Annals of the CIRP, 1993, 42 (2), p.753-767 J.B. Bryan, “The Abbe Principle Revisited: An Updated Interpretation”, Prec. Eng., 1979, 1 (3), p.129-132 W. Gao, “Precision nanometrology-sensors and measuring systems for nanomanufacturing”, Springer, 2010 Murata Univ., Hiroki Shimizu, Satoshi Ito, Kowei, “Research on Ultra High Sensitivity Angle Sensor”, 2013 JSPE Spring Conference Annual Conference, 2013, p.919-920 Akinori N., Takuto O., Taro I., “Trajectory Tracking Control on a Spiral Slope Using Inclination Sensors”, Trans. Japan Soc. Mech. Eng., 2010, Vol. 76, No. 767 (C series), p .1735-1742

Japanese Patent No. 5322099

  However, in the ultra-high sensitivity angle sensor as described in Patent Document 1 and Non-Patent Document 4, when the laser spot diameter on the light receiving element is reduced to improve the measurement resolution, the measurable angle range is narrowed. I have a problem in principle. When a resolution exceeding 0.001 angular seconds is to be realized, the measurable angular range is about ± 10 angular seconds. There is also a problem that the nonlinearity of the angle sensor output is extremely increased. Furthermore, recently, an example in which the optical angle sensor is applied not only to measurement of a minute angle such as a posture angle error during a slide motion but also to measurement of a precise aspherical shape (for example, Non-Patent Document 5). (See)), and it is desired to achieve both ultra-high resolution and a wide measurement angle range.

  In view of the above, the present invention provides an optical rotation angle detection device that realizes angle detection over a wide angle range while enjoying the benefits of high measurement resolution due to a small spot diameter, and a rotation angle detection method using the same The purpose is to provide.

  In order to achieve the above object, the present inventors relatively increase the measurable angle range while maintaining the effect of improving the measurement resolution by reducing the light spot diameter on the light receiving element in the ultrasensitive angle sensor. For this purpose, the idea was to construct an angle sensor optical system that mounts a light receiving element on a precision positioning system and performs minute position control so that the light receiving element follows the movement of the light spot accompanying the change in angle of the measurement target. . In the ultra-high sensitivity angle sensor, the angle detection sensitivity is maximized when the light spot is on the boundary between the sensitive band and the non-sensitive band of the light receiving element. Therefore, feedback control is performed by the positioning system so that the light spot is always on the boundary between the sensitive and non-sensitive bands of the light receiving element, and measurement is performed based on the light receiving element position information obtained by the displacement sensor in the positioning system. By calculating the angle change of the target, it solves the problems of conventional angle sensors, such as narrowing of the measurement range accompanying the reduction of the light spot diameter and increase of nonlinearity of the sensor output, and realizes an ultrasensitive angle sensor with a wide measurement range. can do.

  That is, according to the present invention, in a minute rotation angle detection based on the laser autocollimation method, a light receiving element for measurement is mounted on a precision positioning system, and the center of the light spot condensed on the light receiving element by the objective lens is the sensitive band of the light receiving element. High accuracy over a wide angle range by calculating the minute rotation angle of the measurement target based on the amount of displacement of the light-receiving element read by the high-precision displacement sensor. It is characterized by realizing accurate angle detection.

  Specifically, a rotation angle detection device according to the present invention includes a single wavelength laser light source, a collimating lens that collimates a divergent laser light emitted from the single wavelength laser light source to generate a collimated light beam, and an object to be measured. A reflection unit that is mounted and on which the collimated light beam is incident; an objective lens that collects the measurement light beam reflected from the reflection unit; and a measurement light receiving element that measures the measurement light beam collected by the objective lens; The measuring light-receiving element, and a positioning stage for positioning the measuring light-receiving element, and an angle calculation unit, the measuring light-receiving element at the back focal length position of the objective lens, The center of the light spot obtained by condensing the measurement light beam is arranged so as to be located on the boundary between the sensitive band and the non-sensitive band of the light receiving element for measurement. The determination stage performs position control of the light receiving element for measurement so that the center of the light spot continues to be positioned on the boundary when the object to be measured rotates, and the angle calculation unit is configured to perform the position calculation by the positioning stage. The rotation angle of the object to be measured is obtained based on the position control information of the light receiving element for measurement.

  In the rotation angle detection device according to the present invention, the measurement light receiving element may have at least one sensitive band capable of independently outputting a current obtained by photoelectric conversion.

  The rotation angle detection device according to the present invention further includes a beam splitter that divides a reflected light beam from the reflecting portion into the measurement light beam and a reference light beam, and a reference light receiving element that measures the reference light beam, The entire reference light beam may be configured to be located inside the sensitive band of the reference light receiving element even if the object is rotated by a minute angle. In this case, the reference light receiving element may have at least one sensitive band that can independently output a current obtained by photoelectric conversion. The rotation angle of the object to be measured that is allowed because the entire reference light beam is located inside the sensitive band of the reference light receiving element is approximately within 1 degree.

  In the rotation angle detection device according to the present invention, based on the driving unit that drives and controls the positioning stage, the measurement photocurrent generated in the measurement light receiving element, and the reference photocurrent generated in the reference light receiving element. And a control unit that generates a positioning signal for the driving unit. In this case, the drive unit may use a piezoelectric element as an actuator. And a measurement current-voltage conversion circuit for converting the measurement photocurrent into a measurement voltage signal, and a reference current-voltage conversion circuit for converting the reference photocurrent into a reference voltage signal. The control unit may generate a positioning signal for the driving unit based on the measurement voltage signal and the reference voltage signal. Further, the angle calculation unit is configured to detect the position control information and the sensitivity band of the measurement light receiving element when the frequency component included in the angle change of the object to be measured is equal to or higher than the control band frequency of the drive unit. The rotation angle of the object to be measured may be obtained based on the shift amount of the center of the light spot with respect to the boundary with the sensitive band.

  The rotation angle detection apparatus according to the present invention further includes a displacement sensor that measures the position of the positioning stage, and the angle calculation unit uses the output signal of the displacement sensor as the position control information. The rotation angle may be calculated.

  In the rotation angle detection apparatus according to the present invention, the objective lens may be a microscope objective lens, an aspherical lens, or an achromatic lens. Thus, by using a lens with corrected aberration, the light spot diameter can be further reduced.

  In the rotation angle detection device according to the present invention, in order to prevent a reflected light beam from the reflection unit from returning to the single wavelength laser light source between the collimating lens and the reflection unit, a polarization beam splitter, and 1 An optical isolator made of a / 4 wavelength plate may be arranged. If it does in this way, it can prevent that the reflected light beam from a reflective mirror returns to a single wavelength laser light source, and can stabilize the laser beam output from a single wavelength laser light source.

  In the rotation angle detection device according to the present invention, the reflecting section may be a reflecting mirror or a diffraction grating having a uniaxial or biaxial pattern.

  In the rotation angle detection method according to the present invention, a collimated light beam generated by collimating a divergent laser beam emitted from a single wavelength laser light source by a collimator lens is incident on a reflection unit mounted on a measurement object, and is reflected from the reflection unit. A method of detecting a rotation angle of the object to be measured by collecting the reflected measurement light beam by an objective lens and measuring the light beam with a measurement light-receiving element. At the rear focal length position of the lens, the center of the light spot obtained by condensing the measurement light beam is disposed on the boundary between the sensitive band and the non-sensitive band of the measurement light receiving element. Mounted on a positioning stage for positioning the light receiving element for measurement, and when the object to be measured is rotated, the center of the light spot is positioned on the boundary By the positioning stage to continue performs position control of the measuring light receiving element, and determines a rotation angle of the object to be measured based on the information of the position control.

  According to the present invention, in a minute rotation angle detection based on a laser autocollimation method using a single wavelength laser light source as measurement light, the measurement light receiving element is mounted on the precision positioning system and is collected on the light receiving element by the objective lens. By performing feedback control so that the center of the illuminated light spot is on the boundary between the sensitive band and the non-sensitive band of the light receiving element, highly accurate angle detection can be realized over a wide angle range. In principle, the measurement angle range can be extended to the limits of the physical size of the objective lens and the movement range of a precision positioning system with a measuring light receiving element. In addition, by using the high-precision displacement sensor output for feedback control of the precision positioning system, an ultra-high sensitivity resolution exceeding 0.001 angular seconds is obtained without being affected by the nonlinearity of the angle sensor output at any angular position. be able to. Thus, according to the present invention, an optical rotation angle detection device that realizes angle detection over a wide angle range while enjoying the benefits of high measurement resolution due to a small spot diameter, and a rotation angle using the same A detection method can be provided.

It is a schematic block diagram which shows the rotation angle detection apparatus of 1st embodiment concerning this invention. It is explanatory drawing which shows the positional relationship of the reference condensing spot and the measurement condensing spot on the reference light receiving element of the rotation angle detection apparatus shown in FIG. (A) Explanatory drawing which shows the positional relationship of the measurement condensing spot on a light receiving element and the light receiving element for measurement in the measurement by the angle sensor based on the conventional laser autocollimation method which fixed the light receiving element for measurement, (b) FIG. 2 is an explanatory diagram showing a positional relationship between a measurement light-converging spot on a light-receiving element and a measurement light-receiving element in angle measurement of the rotation angle detection device shown in FIG. 1. It is a graph which shows the result compared with the conventional angle sensor which calculated | required (a) angle sensor output and (b) angle detection sensitivity which are anticipated in the rotation angle detection apparatus shown in FIG. 1 by simulation, respectively. In the rotation angle detection apparatus shown in FIG. 1, it is explanatory drawing which shows the outline of the method of detecting the minute rotation angle of a measuring object using the displacement information of the light receiving element for a measurement, and the error signal of feedback control. It is a schematic block diagram which shows the rotation angle detection apparatus of 2nd embodiment concerning this invention. It is a schematic block diagram which shows the rotation angle detection apparatus of 3rd embodiment concerning this invention.

A rotation angle detection device according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram of a device configuration used in the first embodiment according to the present invention. Here, the linear slide 12 including the moving table 10, the guide rail 11, and the like will be described as an object to be measured. This optical system includes a laser light source 13, a collimating lens 16 that collimates the diverging light 14 emitted from the laser light source 13 to generate a collimated light beam 15, a polarization beam splitter 17 that changes the traveling direction of the collimated light beam 15, A quarter-wave plate 18 that changes the polarization state of the collimated light beam 15 bent by the polarizing beam splitter 17, a reflecting mirror 19 that is mounted on the moving table 10 of the linear slide 12 that is the object to be measured, and the reflecting mirror 19. A beam splitter 22 that splits the collimated light beam 15 whose polarization state has been changed again by the quarter-wave plate 18 into a reference light beam 20 and a measurement light beam 21, a reference light receiving element 23 that detects the reference light beam 20, and a reference light On the sensitive band 25 of the reference light receiving element 23, so that a part of the reference light beam 20 does not enter the non-sensitive band 24 of the light receiving element 23. A condensing lens 27 for condensing the illumination condensing spot 26, a measurement light receiving element 28 for detecting the measurement light beam 21, an objective lens 46 for condensing the measurement light beam 21 on the measurement light receiving element 28, and a measurement light reception A precision positioning stage 32 on which the light receiving element for measurement 28 is placed and precisely positioned so that the center of the light collecting spot 31 for measurement comes to the boundary between the sensitive band 29 of the element 28 and the non-sensitive band 30 of the light receiving element 28 for measurement; A precision displacement sensor 33 for detecting the position of the precision positioning stage 32; a reference current-voltage conversion circuit 36 for converting a reference photocurrent signal 34 from the reference light receiving element 23 into a reference voltage signal 35; and a measurement light receiving element. A measurement current-voltage conversion circuit 39 for converting the measurement photocurrent signal 37 from the measurement signal 28 into a measurement voltage signal 38, and a precise position based on the reference voltage signal 35 and the measurement voltage signal 38. A control signal generator 42 for generating a positioning control signal 41 to be input to the stage 32, a stage driver 43 for driving the precision positioning stage 32 based on the positioning control signal 41, and an output signal 40 of the precision displacement sensor 33. And an angle calculating unit 51 for calculating a posture angle change (θ _Z ) 45 about the Z axis of the moving table 10. In the present invention, an optical system, an electronic circuit, a displacement sensor, a precision positioning system and a controller thereof used for processing the measurement light beam 21 are collectively referred to as an autocollimation unit 44.

The relationship between the output signals from the reference light receiving element 23 and the measurement light receiving element 28 and the attitude angle change (θ _Z ) 45 around the Z axis of the moving table 10 will be described with reference to FIG. FIG. 2 is a schematic diagram showing the positional relationship between the reference condensing spot 26 and the measurement condensing spot 31 on the reference light receiving element 23 and the measurement light receiving element 28. Assuming an ideal optical system with no loss of light quantity in each optical element, the total light quantity contained in the reference light beam 20 and the total light quantity contained in the measurement light beam 21 are the same. Therefore, the reference voltage signal 35 and the measurement voltage signal 38 are set so that the measurement photocurrent signal 37 from the measurement light receiving element 28 is 50% of the reference photocurrent signal 34 from the reference light receiving element 23. On the other hand, when the positioning control signal 41 is generated by the control signal generator 42 and the fine position control is performed by the precision positioning stage 32, the measurement light receiving element 28 has the center 47 of the measurement focused spot 31 at the measurement light receiving element 28. Therefore, the control is always performed so that the sensitive band 29 and the non-sensitive band 30 come to the boundary.

Difference between detection of posture angle change θ _Z 45 around Z-axis of moving table 10 in the optical system used in the first embodiment and measurement by an angle sensor based on a conventional laser autocollimation method in which the position of a light receiving element for measurement is fixed Will be described with reference to FIG. FIG. 3A shows the measurement light-converging spot 31 and the measurement light-receiving element 28 on the measurement light-receiving element 28 in the angle measurement based on the conventional laser autocollimation method in which the position of the measurement light-receiving element 28 is fixed. FIG. 3B shows the positional relationship between the measurement light-converging spot 31 on the measurement light-receiving element 28 and the measurement light-receiving element 28 in the angle measurement according to the present invention. Is. When Z-axis attitude angle change 45 to moving table 10 is generated, the measuring light beam 21 incident on the autocollimation unit 44 will have an angle of incidence 2 [Theta] _Z to the objective lens 46. The displacement (δ) 49 of the measurement focused spot 31 on the measurement light receiving element 28 at this time is expressed by the following equation using the focal length (f) 50 of the objective lens 46.

  In the conventional angle sensor, the relationship between the displacement 49 of the measurement condensing spot 31 and the measurement photocurrent signal 37 from the measurement light receiving element 28 is calibrated in advance using a high-precision autocollimator or the like as a comparison reference. The change in the measurement photocurrent signal 37 is converted into an angle. The smaller the diameter of the measurement condensing spot 31, the higher the change in the measurement photocurrent signal 37 with respect to the displacement 49 of the measurement condensing spot 31, that is, the sensitivity of angle measurement, and measurement with high resolution becomes possible. On the other hand, in this method, if the displacement 49 of the measurement focused spot 31 exceeds the radius of the measured focused spot 31, the angle cannot be measured.

On the other hand, in the rotation angle detection device disclosed in the present invention, as shown in FIG. 3B, when the attitude angle change 45 around the Z axis occurs in the moving table 10, the reference photocurrent signal 34, the measurement light Based on the current signal 37, the position of the measurement light receiving element 28 is finely controlled using the precision positioning stage 32, and the center 47 of the measurement light collecting spot 31 is set to the sensitive band 29 and the non-sensitive band 30 of the measurement light receiving element 28. Positioning is controlled so that it is at the boundary of At this time, since the movement amount of the precision positioning stage 32 detected by the precision displacement sensor 33 corresponds to δ in the equation (1), by using the output of the precision displacement sensor 33, the attitude angle around the Z axis of the moving table 10 is obtained. A change (θ _Z ) 45 can be obtained. In this method, in principle, the measurement angle range can be expanded to the limit of the physical size of the objective lens 46 and the movement range of the precision positioning stage 32 on which the measurement light receiving element 28 is mounted.

The angle detection sensitivity of the conventional angle sensor and the angle detection sensitivity expected in the rotation angle detection device disclosed in the present invention were obtained by simulation and compared. FIG. 4 shows the angle sensor output for the attitude angle change 45 around the Z axis of the moving table 10 and the output change amount (angle sensor sensitivity) for each rotation angle. In the simulation, the diameter of the collimated light beam 15 is 10 mm, the focal length of the objective lens 46 is 100 mm, and the wavelength of the laser beam emitted from the laser light source 13 is 685 nm. Each output S _OUT was calculated using the following equation.

In the equation (2), I _Meas and I _Ref are the reference photocurrent signal 34 and the measurement photocurrent signal 37, respectively. When the collimated light beam 15 is condensed by the objective lens 46, the measurement light-converging spot 31 has a Gaussian distribution-like light intensity distribution on the measurement light-receiving element 28. Therefore, as shown in FIG. The angle sensor has an output curve having strong nonlinearity in a range exceeding ± 5 angular seconds. On the other hand, in the rotation angle detection device disclosed in the present invention, the position of the measurement light receiving element 28 is always controlled, so the output is constant. FIG. 4B shows the result of obtaining the sensor output change amount (sensitivity) per second displacement angle based on this result. In the conventional angle sensor, high sensitivity can be obtained only in a very narrow angle range of about ± 2 angle seconds. On the other hand, in the rotation angle detection device disclosed in the present invention, since the measurement focused spot 31 is always at the boundary between the sensitive band 29 and the non-sensitive band 30 of the measurement light receiving element 28, the sensitivity is constant and High standards can be maintained.

In the first embodiment according to the present invention, feedback control of the precision positioning stage 32 may be incomplete. FIG. 5 shows an outline of a technique for detecting the minute rotation angle of the measurement object using the displacement information of the measurement light receiving element 28 and the error signal of the feedback control. In the rotation angle detection device disclosed in the present invention, the deviation (e) 48 of the center 47 of the measurement focused spot 31 with respect to the boundary between the sensitive band 29 and the non-sensitive band 30 of the measurement light receiving element 28 and the measurement photocurrent signal 37, if a high-precision autocollimator or the like is calibrated in advance in the same manner as the conventional angle sensor, an error occurs in the feedback control of the precision positioning stage 32, and the measurement focused spot Even when the center 47 of 31 is shifted from the boundary between the sensitive band 29 and the non-sensitive band 30 of the light receiving element 28 for measurement, the shift amount 48 can be obtained from the positioning control signal 41 generated by the control signal generating unit 42. This is used together with the displacement (Δs) of the precision positioning stage 32 obtained by the precision displacement sensor 33, and is calculated using the following equation to obtain a moving table. Z-axis attitude angle change of 0 (theta _Z) 45 can be obtained.

  This technique is effective when the time frequency component included in the attitude angle change 45 around the Z-axis of the moving table 10 exceeds the feedback control band of the precision positioning stage 32, and is used for feedback control of the precision positioning stage 32. It is possible to relax the required conditions for high-speed tracking.

A rotation angle detection device according to a second embodiment of the present invention will be described with reference to FIG. FIG. 6 is a schematic diagram of an apparatus configuration used in the second embodiment according to the present invention. The main configuration is the same as the optical system used in the first embodiment shown in FIG. 1, but in the second embodiment, the measurement light beam 21 is divided into a pitch angle measurement light beam 52 and a yaw angle measurement light beam 53. A beam splitter 54 is used, and an autocollimation unit 55 is added. Thereby, in addition to the posture angle change (θ _Z ) 45 around the Z axis of the moving table 10, the posture angle change (θ _Y ) 56 around the Y axis can be detected.

A rotation angle detection device according to a third embodiment of the present invention will be described with reference to FIG. FIG. 7 is a schematic view of a device configuration used in the third embodiment according to the present invention. The main configuration is the same as the optical system used in the first embodiment and the second embodiment shown in FIG. 1, but in the third embodiment, a diffraction grating 57 is used instead of the reflecting mirror 19. It mounts on the moving table 10 of the linear slide 12 which is a measurement object. The diffraction grating 57 has a fine pattern 58 with a constant pitch on the surface. When laser light is incident on the diffraction pattern 57, primary diffraction light 59 having a diffraction angle in a direction perpendicular to the grating pattern is generated. The 0th-order diffracted light is the measurement light beam 21. In the third embodiment, an autocollimation unit 61 is added for detecting a change in attitude angle (θ _X ) 60 about the X axis of the moving table 10 using the first-order diffracted light 59. As a result, it is possible to collectively detect the posture angle change of the moving table 10 about the X, Y, and Z3 axes. The diffraction grating 57 used here only needs to have a fine pattern 58 with a constant pitch, and the pattern shape may be either a uniaxial pattern or a biaxial pattern.

  In the first embodiment, the second embodiment, and the third embodiment, the measurement photocurrent signal from the measurement light receiving element 28 is taken into consideration in consideration of the light amount fluctuation of the laser light emitted from the laser light source 13. 37 and the reference photocurrent signal 34 from the reference light receiving element 23 are input to the control signal generation unit 42. If the fluctuation in the amount of laser light is so small that it can be ignored, it is possible to simplify the apparatus configuration by omitting the reference signal optical components and circuit components and providing a reference signal in place of the reference photocurrent signal 34.

  In the first embodiment, the second embodiment, and the third embodiment, the polarization beam splitter 17 and the quarter wavelength plate 18 are used, and the optical path before the collimated light beam 15 is reflected by the reflecting mirror 19. However, the configuration may be changed so that the optical path is bent by 90 ° after reflection by the reflecting mirror 19. Furthermore, in order to make the apparatus configuration more compact, it is possible to apply a device in which the precision displacement sensor 33 and the precision positioning stage 32 are integrated.

  In the first embodiment, the second embodiment, and the third embodiment, the measurement light-receiving element 28 and the reference light-receiving element 23 can at least output a current obtained by photoelectric conversion at least. It may have one or more sensitive bands. The stage driver 43 may use a piezoelectric element as an actuator. In addition, the measurement photocurrent generated in the measurement light receiving element 28 and the reference photocurrent generated in the reference light receiving element 23 without using the measurement current-voltage conversion circuit 39 and the reference current-voltage conversion circuit 36 The control signal generator 42 may generate the positioning control signal 41 based on the above. The objective lens 46 may be a microscope objective lens, an aspherical lens, an achromatic lens, or the like. By using a lens in which such aberration is corrected, the light spot diameter can be further reduced.

  According to the present invention, a light receiving element for measurement that has been conventionally fixed in the apparatus is mounted on a precision positioning system to be movable, and the center of the light spot condensed on the light receiving element for measurement is not in contact with the sensitive band of the light receiving element. By always feeding back so as to be on the boundary with the sensitive band, it is possible to realize angle detection with high resolution and high accuracy over a wide angle range. Furthermore, by utilizing the high-precision displacement sensor output and the feedback control error of the light receiving element for measurement, the angle change including high frequency components exceeding the control band of the precision positioning device equipped with the light receiving element for measurement Measurement is possible. These features satisfy the demand for ultra-precision and high-speed sensitivity measurement in the precision machinery industry, and its industrial applicability is high.

DESCRIPTION OF SYMBOLS 10 Moving table 11 Guide rail 12 Linear slide 13 Laser light source 14 Diverging light 15 Collimated light beam 16 Collimating lens 17 Polarizing beam splitter 18 1/4 wavelength plate 19 Reflector 20 Reference light beam 21 Measuring light beam 22 Beam splitter 23 Reference light receiving element 24 Reference Non-sensitive band of light receiving element for reference 25 Sensitive band of light receiving element for reference 26 Condensing spot for reference 27 Condensing lens 28 Light receiving element for measurement 29 Sensitive band of light receiving element for measurement 30 Non-sensitive band of light receiving element for measurement 31 For measurement Focusing spot 32 Precision positioning stage 33 Precision displacement sensor 34 Reference photocurrent signal 35 Reference voltage signal 36 Reference current-voltage conversion circuit 37 Measurement photocurrent signal 38 Measurement voltage signal 39 Measurement current-voltage conversion circuit 40 Precision displacement Sensor output signal 41 Positioning control signal No. 42 Control signal generator 43 Stage driver 44 Auto collimation unit 45 Change in posture angle around Z axis (θ _Z )
46 Objective lens 47 Center of focused spot for measurement 48 Deviation of center of focused spot for measurement (e)
49 Displacement of focused spot for measurement (δ)
50 Focal length of objective lens (f)
51 Angle Calculation Unit 52 Pitch Angle Measurement Light Beam 53 Yaw Angle Measurement Light Beam 54 Beam Splitter 55 Auto Collimation Unit 56 Change in Posture Angle around Y-axis (θ _Y )
57 Diffraction grating 58 Fine pitch pattern with constant pitch 59 First-order diffracted light 60 Change in attitude angle around X axis (θ _X )
61 Autocollimation unit

Claims (13)

A single wavelength laser light source;
A collimating lens for generating a collimated light beam by collimating the divergent laser light emitted from the single wavelength laser light source;
A reflection unit mounted on the object to be measured and on which the collimated light beam is incident;
An objective lens for condensing the measurement light beam reflected from the reflection unit;
A light receiving element for measurement that measures the measurement light beam collected by the objective lens;
A positioning stage mounted with the light receiving element for measurement and positioning the light receiving element for measurement;
An angle calculation unit,
The measurement light-receiving element has a center of a light spot obtained by condensing the measurement light beam at a rear focal length position of the objective lens on a boundary between a sensitive band and a non-sensitive band of the measurement light-receiving element. Arranged to be located,
The positioning stage performs position control of the light receiving element for measurement so that the center of the light spot continues to be positioned on the boundary when the object to be measured rotates,
The rotation angle detecting device, wherein the angle calculation unit is configured to obtain a rotation angle of the object to be measured based on information on position control of the light receiving element for measurement by the positioning stage.   The rotation angle detection device according to claim 1, wherein the measurement light receiving element has at least one sensitive band capable of independently outputting a current obtained by photoelectric conversion. A beam splitter that divides the reflected light beam from the reflecting portion into the measurement light beam and the reference light beam;
A reference light receiving element for measuring the reference light flux;
3. The rotation angle according to claim 1, wherein the entire reference light beam is located inside a sensitive band of the reference light receiving element even if the object to be measured is rotated by a small angle. Detection device.   The rotation angle detection device according to claim 4, wherein the reference light receiving element has at least one sensitive band capable of independently outputting a current obtained by photoelectric conversion. A drive unit that drives and controls the positioning stage;
And a control unit that generates a positioning signal for the driving unit based on the measurement photocurrent generated in the measurement light-receiving element and the reference photocurrent generated in the reference light-receiving element. The rotation angle detection device according to claim 3 or 4.   The rotation angle detection device according to claim 5, wherein the driving unit uses a piezoelectric element as an actuator. A measurement current-voltage conversion circuit for converting the measurement photocurrent into a measurement voltage signal;
A reference current-voltage conversion circuit for converting the reference photocurrent into a reference voltage signal;
The rotation angle detection device according to claim 5 or 6, wherein the control unit generates a positioning signal for the driving unit based on the measurement voltage signal and the reference voltage signal.   When the frequency component included in the change in the angle of the object to be measured is equal to or higher than the control band frequency of the drive unit, the angle calculation unit includes the position control information, the sensitive band and the non-sensitive band of the light receiving element for measurement. The rotation angle detection device according to claim 5, wherein a rotation angle of the object to be measured is obtained based on a deviation amount of the center of the light spot with respect to a boundary between the measurement object and the object. A displacement sensor for measuring the position of the positioning stage;
The said angle calculation part calculates the rotation angle of the said to-be-measured object using the output signal of the said displacement sensor as the information of the said position control, The any one of Claims 1-8 characterized by the above-mentioned. Rotation angle detection device.   The rotation angle detection device according to claim 1, wherein the objective lens is a microscope objective lens, an aspherical lens, or an achromatic lens.   Between the collimating lens and the reflecting portion, a polarizing beam splitter and an optical isolator comprising a quarter wavelength plate are arranged to prevent the reflected light beam from the reflecting portion from returning to the single wavelength laser light source. The rotation angle detection device according to claim 1, wherein the rotation angle detection device is a rotation angle detection device.   The rotation angle detection device according to claim 1, wherein the reflection unit is a reflection mirror or a diffraction grating having a uniaxial or biaxial pattern. A collimated light beam generated by collimating a divergent laser beam emitted from a single wavelength laser light source with a collimating lens is incident on a reflecting portion mounted on the object to be measured, and the measuring light beam reflected from the reflecting portion is reflected by an objective lens. A rotation angle detection method for obtaining a rotation angle of the object to be measured by condensing and measuring with a light receiving element for measurement,
The measurement light-receiving element has a center of a light spot obtained by condensing the measurement light beam at a rear focal length position of the objective lens on a boundary between a sensitive band and a non-sensitive band of the measurement light-receiving element. And is mounted on a positioning stage for positioning the light receiving element for measurement,
When the object to be measured rotates, the position of the light receiving element for measurement is controlled by the positioning stage so that the center of the light spot continues to be positioned on the boundary, and the object to be measured is based on the information on the position control. A rotation angle detection method characterized in that a rotation angle is obtained.

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