JP2013011631A - Angle measuring method and angle measuring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a rotation angle with high accuracy and in a short time.SOLUTION: The angle measuring system includes: an encoder body 2a to be a non-rotor regulated in rotation; and a rotation shaft 3 to be a rotor rotatably journaled to the encoder body 2a. The angle measuring system further includes: a rotary encoder 2 as relative angle detection means for detecting a relative rotation angle of the rotation shaft 3 in relation to the encoder body 2a; and non-contact angle detection means 20 as absolute angle detection means for detecting an absolute rotation angle of the encoder body 2a. Accordingly, the rotation angle detected by the rotary encoder 2 can be corrected on the basis of the rotation angle detected by the non-contact angle detection means 20, and the rotation angle can be measured with high accuracy and in a short time.

Description

  The present invention relates to an angle measurement method and an angle measurement system that can be suitably used in a technical field that requires precise measurement of the rotation angle of a rotating body.

  Conventionally, in order to accurately measure the angle indexing accuracy of a rotating body in a machine tool or the like, an angle measuring method using a polygon mirror and an autocollimator (hereinafter referred to as “polyhedral mirror method”), a hearth coupling and a laser interferometer are used. An angle measurement method (hereinafter referred to as “Heas coupling method”) has been performed.

  In the polygon mirror method, the difference between the rotation angle of the object on which the polygon mirror is mounted and the angle of the polygon mirror is measured with a highly accurate autocollimator.

  In the hearth coupling method, the workpiece to which the hearth coupling is attached is rotated at a predetermined target angular displacement, and the hearth coupling is reversely rotated by the amount corresponding to the target angular displacement after disconnecting the hearth coupling. The sum of the reverse angular displacement and the angular displacement from the reference position measured by the laser interferometer is compared with the target angular displacement of the object to be measured (see Patent Document 1).

Japanese Translation of National Publication No. 06-502727

  However, the conventional angle measurement technique has the drawbacks that it takes time to measure and it is difficult to improve measurement accuracy.

  In the polygon mirror method, the phase angle between the angle of the polygon mirror and the angle of the object to be measured is changed in various ways, and the measurement is repeated. Need to continue for hours. Further, since the resolution is coarse and it is difficult to keep the apparatus stable for a long time, there is a limit to the improvement of measurement accuracy.

  In the Hearth coupling method, after the object to be measured is rotated at the target angular displacement, a swing operation is required to reversely rotate the Hearth coupling by the amount of the target angular displacement and return the laser interferometer reflector to its original position. Therefore, the entire measurement time becomes long. In addition, the accuracy of angle measurement depends on the resolution of the hearth coupling teeth, and transmission errors occur in the teeth of the hearth coupling when the forward rotation and the reverse rotation are repeated, so that there is a limit to improving the measurement accuracy.

  In addition, a rotary encoder is known as a device for detecting the rotation angle, but in order to keep the measurement accuracy within an allowable range, it is necessary to attach the rotary encoder with high accuracy to the rotation axis of the object to be measured. However, since it is not easy to mount the rotary encoder with high accuracy, there is a problem that the use of the rotary encoder is hindered.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an angle measuring method and an angle measuring apparatus capable of measuring a rotation angle with high accuracy and in a short time.

  In order to achieve the above object, the present invention provides a main body, a rotary shaft rotatable with respect to the main body, a cord attached to the rotary shaft, and a code fixed to the main body to read the code of the cord. An angle measurement method using a rotary encoder having a reading unit, wherein a rotary shaft of the rotary encoder is attached to a rotary shaft of a workpiece to be rotated, and the rotary shaft of the workpiece and the rotation of the rotary encoder are rotated. In order to allow eccentricity with respect to the shaft, the displacement of the main body of the rotary encoder within a plane orthogonal to the rotary shaft of the rotary encoder is regulated within a certain play range, and the code read by the reading unit of the rotary encoder Non-contact angle detection means for measuring the rotation angle of the rotary shaft of the rotary encoder based on the above and detecting the angle in a non-contact manner And detecting a rotation angle measured using the rotary encoder by the non-contact angle detection means. An angle measurement method is provided, wherein correction is performed based on a changed angle of the main body of the rotary encoder. With this configuration, the measured value of the rotary encoder is corrected by the measured value of the non-contact angle detecting means, so that the rotation angle can be accurately and quickly compared with conventional angle measuring techniques using the polygon mirror method or the hearth coupling method. Can be measured. In addition, since the allowable range of the eccentric amount of the rotary shaft of the rotary encoder with respect to the rotary shaft of the object to be measured can be made larger than the specification of the rotary encoder, it is very easy to attach the rotary encoder to the object to be measured. That is, according to the present invention, the rotation angle can be measured with high accuracy and in a short time by using the rotary encoder, which greatly contributes to an increase in production capacity of machine tools and the like.

  In one embodiment of the present invention, a jig for locking the main body portion of the rotary encoder while allowing the displacement of the main body portion of the rotary encoder within the certain play range is used.

  In one embodiment of the present invention, a weight is attached to the main body of the rotary encoder, and the main body of the rotary encoder is biased in the direction of gravity.

  The present invention also provides a rotary having a main body, a rotary shaft that is rotatable with respect to the main body, a cord attached to the rotary shaft, and a reading unit that is fixed to the main body and reads the code of the code. An angle measurement method using an encoder, wherein the rotary encoder main body is attached to a rotary shaft of a device to be rotated, and eccentricity between the rotary shaft of the device to be measured and the rotary shaft of the rotary encoder is allowed. As described above, the displacement of the rotary shaft of the rotary encoder in a plane orthogonal to the rotary shaft of the rotary encoder is regulated within a certain play range, and the rotary encoder is based on the code read by the reading unit of the rotary encoder. And measuring the rotation angle of the main body portion of the main body and non-contact angle detecting means for detecting the angle in a non-contact manner. The angle at which the rotary shaft of the rotary encoder has changed since the rotation angle measurement start time of the main body of the coder is detected, and the rotation angle measured using the rotary encoder is detected by the non-contact angle detecting means. Provided is an angle measuring method characterized by correcting based on a changed angle of a rotary shaft of a rotary encoder. With this configuration, the measured value of the rotary encoder is corrected by the measured value of the non-contact angle detecting means, so that the rotation angle can be accurately and quickly compared with conventional angle measuring techniques using the polygon mirror method or the hearth coupling method. Can be measured. In addition, since the allowable range of the eccentric amount of the rotary shaft of the rotary encoder with respect to the rotary shaft of the object to be measured can be made larger than the specification of the rotary encoder, it is very easy to attach the rotary encoder to the object to be measured. That is, according to the present invention, the rotation angle can be measured with high accuracy and in a short time by using the rotary encoder, which greatly contributes to an increase in production capacity of machine tools and the like.

  In one embodiment of the present invention, a jig that locks the rotary shaft of the rotary encoder while allowing the displacement of the rotary shaft of the rotary encoder within the certain play range is used.

  In one embodiment of the present invention, a weight is attached to the rotary shaft of the rotary encoder, and the rotary shaft of the rotary encoder is biased in the direction of gravity.

  In addition, the present invention includes a main body, a rotating shaft that is rotatable with respect to the main body, a cord attached to the rotating shaft, and a reading unit that is fixed to the main body and reads the code of the code. A rotary encoder to which the rotary shaft is attached to a rotationally driven object to be measured, and an orthogonal to the rotational axis of the rotary encoder so as to allow eccentricity between the rotational axis of the object to be measured and the rotational axis of the rotary encoder. A regulating member that regulates the displacement of the main body of the rotary encoder within a certain play range within the surface to be rotated, and a changed angle of the main body of the rotary encoder from the start of measurement of the rotational angle of the rotary shaft of the rotary encoder. The non-contact angle detecting means for detecting non-contact and the rotation angle corresponding to the code read by the reading unit of the rotary encoder is the non-contact angle. And correcting means for correcting, based on the changed angle of the main body of the rotary encoder is detected by detecting means, to provide an angle measurement system, comprising the.

  In one embodiment of the present invention, the restricting member includes a jig for locking the main body portion of the rotary encoder while allowing the displacement of the main body portion of the rotary encoder within the certain play range. To do.

  In one embodiment of the present invention, the restricting member includes a weight attached to the main body of the rotary encoder and biasing the main body of the rotary encoder in the direction of gravity.

  In addition, the present invention includes a main body, a rotating shaft that is rotatable with respect to the main body, a cord attached to the rotating shaft, and a reading unit that is fixed to the main body and reads the code of the code. A rotary encoder to which the rotary shaft is attached to a rotationally driven object to be measured, and an orthogonal to the rotational axis of the rotary encoder so as to allow eccentricity between the rotational axis of the object to be measured and the rotational axis of the rotary encoder. A restricting member that restricts the displacement of the rotary shaft of the rotary encoder within a certain play range, and a changed angle of the rotary shaft of the rotary encoder from the start of measurement of the rotational angle of the main body of the rotary encoder. The non-contact angle detecting means for detecting non-contact and the rotation angle corresponding to the code read by the reading unit of the rotary encoder is the non-contact angle. And correcting means for correcting, based on the changed angle of the rotating shaft of the rotary encoder detected in the detecting means, to provide an angle measurement system, comprising the.

  In one embodiment of the present invention, the restricting member includes a jig for locking the rotary shaft of the rotary encoder while allowing displacement of the rotary shaft of the rotary encoder within the certain play range. To do.

  In one embodiment of the present invention, the restriction member includes a weight attached to a rotary shaft of the rotary encoder and biasing the rotary shaft of the rotary encoder in a gravitational direction.

  In one embodiment of the present invention, the non-contact angle detecting means includes first and second reflecting elements installed on a surface orthogonal to the rotation axis of a portion of the rotary encoder that is restricted by the restricting member. Splitting the laser light source, and the light beam emitted from the laser light source into a first light beam directed to the first reflective element and a second light beam directed to the second reflective element, and the first reflective element An interference optical system that causes interference between the first reflected light beam reflected by the second reflected light beam and the second reflected light beam reflected by the second reflecting element, and the first reflected light beam interfered by the interference optical system and the first reflected light beam. Phase difference detection means for detecting a phase difference between the two reflected light fluxes, a phase difference between the first reflected light flux and the second reflected light flux detected by the phase difference detection means, and the first reflection. Based on the position difference between the element and the second reflective element. There are, and having an an inclined angle calculating means for calculating an inclination angle of a straight line connecting between the corresponding point of the first reflecting element and the second reflective element.

  In one embodiment of the present invention, the correction means includes the rotation angle corresponding to the code read by the reading unit of the rotary encoder, and the inclination angle calculated by the inclination angle calculation means of the non-contact angle detection means. It is characterized by taking the sum of

  In one embodiment of the present invention, static measurement for detecting a rotation angle at a timing when rotation of the rotation axis of the object to be measured stops, and detection of a rotation angle at a timing during rotation of the rotation axis of the object to be measured. It is characterized in that at least one of the dynamic measurements is performed.

  According to the present invention, it is possible to measure the rotation angle with high accuracy and in a short time as compared with the prior art. In addition, it is very easy to attach the rotary encoder to the object to be measured.

Overall configuration diagram of an example of an angle measurement system in the first embodiment Side view showing a state where the rotary shaft of the rotary encoder is attached to the object to be rotated. Front view showing a state where the rotary shaft of the rotary encoder is attached to the object to be rotated. Side view showing a state in which the interference unit of the non-contact angle detecting means is arranged facing the corner cube prism. Front view showing a state in which the interference unit of the non-contact angle detecting means is arranged facing the corner cube prism. Front view showing an example when the displacement of the encoder body is regulated by a weight Side view showing the case where the device under test is placed along the horizontal direction Explanatory drawing used for explanation of angle detected by non-contact detection means The whole block diagram of an example of the angle measurement system in 2nd Embodiment Side view showing how the encoder body is attached to the object to be rotated

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an overall configuration diagram of an example of an angle measurement system according to the first embodiment.

  The angle measuring system 100 shown in FIG. 1 measures the rotational angle of the rotating shaft 1a of the device under test 1 that is rotationally driven by using the rotary encoder 2. The rotary encoder 2 includes an encoder body 2a and a rotating shaft 3 that is rotatable with respect to the encoder body 2a.

  FIG. 2 is a side view showing a state in which the rotary shaft 3 of the rotary encoder 2 is attached to the rotary shaft 1a of the DUT 1, and FIG. 3 is a front view thereof.

  As shown in FIG. 2, a disk-shaped encoder 14 (code portion) is attached to the rotary shaft 3 inside the encoder body 2a. The encoder 14 has a scale (code) formed on the entire circumference around the rotation shaft 3. The encoder 14 may be an incremental type or an absolute type. An encoder reading head 13 (reading unit) that reads the scale of the encoder 14 is fixed to the encoder body 2a. The encoder reading head 13 outputs a pulse signal (rotation angle signal) in accordance with the scale reading of the encoder 14. That is, the rotary encoder 2 generates a pulse signal corresponding to the amount of change in the relative rotation angle between the encoder body 2 a and the rotary shaft 3. The encoder body 2a may be a coupling built-in type.

  A rotary shaft 3 of the rotary encoder 2 is attached to the encoder body 2a via a bearing 15 made of a ball bearing. In this embodiment, the rotary shaft 3 of the rotary encoder 2 is detachably attached to the rotary shaft 1a of the DUT 1. After attachment, the rotating shaft 3 is in a state of being freely rotatable with respect to the encoder body 2a via the bearing 15. For this reason, even if the rotating shaft 1a of the DUT 1 rotates, the cable 16 connected to the rotary encoder body 2a does not get tangled. The rotating shaft 3 of this example has an attachment portion 3 a for attaching to the rotating shaft 1 a of the DUT 1. You may attach to the rotating shaft 1a of the to-be-measured object 1 via a special attachment.

  As will be described later, the encoder body 2a of the present embodiment has a surface orthogonal to the rotary shaft 3 (hereinafter referred to as "orthogonal") to allow eccentricity between the rotary shaft 1a of the DUT 1 and the rotary shaft 3 of the rotary encoder 2. It is arranged in such a manner that movement (displacement) within a certain play range is permitted. Further, the allowable range of the eccentric amount of the rotary shaft 3 of the rotary encoder 2 with respect to the rotary shaft 1a of the DUT 1 depends on the allowable mounting amount of the non-contact angle detecting means 20 described later. Therefore, since the allowable range of the eccentricity becomes wider than the original specification of the rotary encoder 2, the rotary encoder 2 can be attached to the DUT 1 very easily. Even if there is an axial runout of the DUT 1, no measurement error occurs, but the surface runout becomes a measurement error, and is therefore kept within a specified value calculated in accordance with the target measurement accuracy.

  The non-contact angle detection means 20 includes the interference unit 4 (the right-angle prism 5 and the polarization beam splitter 6), the corner cube prism 7 (7a, 7b), the laser light source 10, the phase difference detection head 11, and the data processing device 12. It is configured. The non-contact angle detection means 20 detects the changed inclination angle of the encoder body 2a from the start of the rotation angle measurement of the rotary shaft 3 using the rotary encoder 2 in a non-contact manner. Note that the rotation angle measurement can be performed at a timing during the rotation of the rotation shaft 1a of the device under test 1 even in the static measurement that detects the rotation angle when the rotation of the rotation shaft 1a of the device under test 1 stops. It may be a dynamic measurement that detects an angle. In static measurement, for example, the rotation start time is the rotation angle measurement start time. In the dynamic measurement, an arbitrary timing during rotation can be set as the rotation angle measurement start time.

  FIG. 4 is a side view showing a state in which the interference unit 4 is arranged, and FIG. 5 is a front view thereof.

  As shown in FIG. 5, a pair of corner cube prisms 7a and 7b (reflective elements) are installed on the orthogonal surface of the encoder body 2a (the surface orthogonal to the rotation shaft 3). The interference unit 4 (interference optical system) is disposed at a position facing the pair of corner cube prisms 7a and 7b.

  As shown in FIG. 1, the interference unit 4 includes a right-angle prism 5 and a polarization beam splitter 6. The interference unit 4 divides the laser light beam emitted from the laser light source 10 into a first laser light beam directed to the first corner cube prism 7a and a second laser light beam directed to the second corner cube prism 7b. To do. The first laser beam transmitted through the polarizing beam splitter 6 is directly incident on the first corner cube prism 7a. The first laser beam (first reflected beam) reflected by the first corner cube prism 7 a returns directly to the polarization beam splitter 6. The second laser beam reflected by the polarizing beam splitter 6 at a right angle is further reflected by the right angle prism 5 at a right angle and enters the second corner cube prism 7b. The second laser light beam (second reflected light beam) reflected by the second corner cube prism 7 b is reflected at a right angle by the right-angle prism 5 and returns to the polarization beam splitter 6. That is, the interference unit 4 causes the first and second laser beams parallel to each other to enter the first and second corner cube prisms 7a and 7b, respectively, and the first and second corner cube prisms 7a and 7b. The first and second reflected light fluxes reflected and recursed are caused to interfere with each other. Therefore, the interference unit 4 generates interference fringes of the first and second reflected light beams having different optical path lengths.

  In the polarization beam splitter 6, a part (first laser beam) of the laser beam emitted from the laser light source 10 passes through the polarization beam splitter 6 and enters the incident surface of the first corner cube prism 7a perpendicularly. Are arranged as follows. Further, the right-angle prism 5 is arranged so that the second laser beam passing through the right-angle prism 5 is parallel to the first laser beam.

  The phase difference detection head 11 (phase difference detection means) receives the interference light composed of the first reflected light beam and the second reflected light beam having different optical path lengths, and the first and second corner cube prisms 7a and 7b. The phase difference between the reflected light beams (first and second reflected light beams) is detected. In this example, the optical path length difference (phase difference) between the optical path of the first laser beam (solid line in FIG. 1) and the optical path of the second laser beam (dotted line in FIG. 1) is detected by counting the interference fringes. To do.

  When the interference unit 4 and the corner cube prisms 7a and 7b are opposed to each other, the corner cube prisms 7a and 7b are measured by the phase difference detection head 11 even if the corner cube prisms 7a and 7b move approximately 1 mm in all directions orthogonal to the laser beam. It is possible to keep the amplitude reduction of the interference signal within an allowable range. The allowable range of the positional deviation amount depends on the beam diameter of the laser light source 10 and the performance of the phase difference detection head 11 and the like. Since the allowable range of the misalignment amount of the corner cube prisms 7a and 7b is the allowable range of the eccentric amount between the rotary shafts 1a and 3, the rotary encoder 2 can be easily attached.

  As the laser light source 10, for example, a He—Ne laser is used. Even if wavelength stabilization is not performed, measurement accuracy is not greatly affected. When the laser light source 10 and the interference unit 4 are coupled by an optical fiber, the attachment becomes very easy. The phase difference detection head 11 may be a fringe count method using a Michelson interferometer or a heterodyne method. In the case of the heterodyne system, the laser light source 10 needs to have two orthogonal polarization frequencies, and for example, a Zeeman laser or an AOM (acousto-optic element) is used.

  The data processing device 12 is configured by a computer device such as a personal computer.

  The rotating shaft 1a of the DUT 1 is rotationally driven using a driving means (not shown) (not shown). The pulse signal (rotation angle signal) output from the rotary encoder 2 is sent to the rotation angle detector 9 via the cable 16. The rotation angle detector 9 converts the pulse signal into a rotation angle (hereinafter referred to as “θ1”), and sends the θ1 to the data processing device 12. The phase difference signal output from the phase difference detection head 11 and indicating the phase difference (optical path length difference) between the first laser beam and the second laser beam is sent to the data processing device 12 via the cable 21. It is done. The data processing device 12 constitutes a part of the non-contact angle detection means 20 (inclination angle calculation means), and the phase difference signal output from the phase difference detection head 11 and the apex of the first corner cube prism 7a. 8 and the vertex of the second corner cube prism 7b using a trigonometric function, as shown in FIG. 8, the vertex 70a of the first corner cube prism 7a and the second corner cube The inclination angle (hereinafter referred to as “θ2”) of the straight line 70 connecting the apex 70b of the prism 7b is calculated. The resolution of θ2 by the non-contact angle detection means 20 is higher than that of θ1 by the rotary encoder 2 and the rotation angle detector 9 (the resolution pitch is small).

  Further, the data processing device 12 determines θ1 (which is a relative rotation angle between the encoder body 2a and the rotary shaft 3) based on θ2 (which is an inclination angle of a portion of the rotary encoder 2 in which movement is restricted). Correct. That is, θ1 measured using the rotary encoder 2 is corrected based on the inclination angle θ2 of the straight line connecting the corresponding points of the corner cube prisms 7a and 7b. The data processing apparatus 12 of this example corrects θ1 by taking the sum of θ1 and θ2 (θ1 + θ2).

  Next, a specific example of the regulating member will be described.

  In the example shown in FIGS. 1 and 5, the movement of the encoder main body 2 a is restricted by the anti-rotation jig 8. The anti-rotation jig 8 locks the rod 2b extended to the encoder body 2a by the locking claws 8a and 8b. The width of the gap between the two locking claws 8a and 8b corresponds to the allowable range of the eccentricity. As a result, the movement of the encoder main body 2a is restricted at least within the measurable range of the non-contact angle detecting means 20.

  Further, in the static measurement at the measurement point, it is required that variations in the measurement values of the rotary encoder 2 and the non-contact angle detection unit 20 are sufficiently reduced to be sufficiently smaller than the target measurement accuracy. The measurement of the angle indexing accuracy is often performed by static measurement. In this case, the measurement object 1 is repeatedly measured by rotating and stopping the measurement object 1 at a certain angle. In the measurement value capture, each measurement value is assumed to be sufficiently stable with respect to the target measurement accuracy. The rotation speed of the DUT 1 depends on the performance of the rotary encoder 2 and the non-contact angle detection means 20, and can be generally measured at a high speed. The measurement resolution is the same, and is generally superior to a method using a polygon mirror and an autocollimator (polyhedral mirror method), a method using a hearth coupling and a laser interferometer (hearth coupling method), and the like.

  In addition, when the performance of the bearing 15 is excellent and the encoder body 2a does not rotate in accordance with the rotation of the DUT 1, the anti-rotation jig 8 may be omitted. That is, depending on the performance of the bearing 15, the bearing 15 itself can function as a regulating member that regulates the movement of the encoder body 2a.

  FIG. 6 is a front view showing a case where the movement of the encoder body 2 a is restricted by the weight 17. As shown in FIG. 16, the weight 17 is attached to the encoder body 2a and lowered in the direction of gravity. The encoder body 2a is urged by the weight 17 in the direction of gravity, and the movement is restricted within a certain play range.

  FIG. 7 is a side view showing a case where the DUT 1 is arranged along the horizontal direction.

  Further, if the rotation prevention jig 8 has a weak magnetic force, the position of the encoder body 2a is easily determined, and measurement is easy. In particular, this is effective in the horizontal arrangement shown in FIG.

  In addition, although the case where the rotation prevention jig | tool 8 was used was shown in FIG.1, FIG.7 etc. and the case where the weight 17 was used in FIG. 6, these both may be used as a control member. Other regulating members (for example, a magnetic body that regulates movement by magnetic force) may be used.

  As described above, in the angle measurement method according to the first embodiment, the rotary shaft 3 of the rotary encoder 2 is attached to the rotary shaft 1a of the workpiece 1 to be rotationally driven, and the rotary shaft 1a and the rotary encoder of the workpiece 1 are measured. The movement (displacement) of the rotary encoder body 2a in the orthogonal plane orthogonal to the rotary shaft 3 of the rotary encoder 2 is restricted within a certain play range so as to allow eccentricity with the rotary shaft 3 of the encoder 2. The rotation angle θ1 of the rotary shaft 3 of the rotary encoder 2 is detected (measured) based on the code read by the encoder 13, and the encoder from the time when the rotation angle of the rotary shaft 2 of the rotary encoder 2 is measured by the non-contact angle detection means 20 The changed inclination angle θ2 of the main body 2a is detected, and θ1 is corrected based on θ2.

  With this configuration, the rotation angle can be measured accurately in a short time. That is, first, by performing angle measurement using the rotary encoder 2, the manual operation of the operator, which is necessary in the conventional polygon mirror system, can be omitted, and reverse rotation such as the Hearth coupling system is involved. Since the swing motion can be omitted, not only high-precision measurement is possible, but also the overall measurement time can be shortened. Secondly, since the measurement value of the rotary encoder 2 is corrected by the measurement value of the non-contact angle detection means 20, the measurement accuracy can be further improved. Thirdly, the allowable range of the eccentric amount of the rotary shaft 3 of the rotary encoder 2 relative to the rotary shaft 1a of the device under test 1 can be made larger than the specification of the rotary encoder 2 itself. The installation of the encoder 2 is very easy and takes a short time. For example, when the non-contact angle detection means 20 is not used together, an attachment accuracy of about 100 μm is required. However, when the laser interference length measurement type non-contact angle detection means 20 is used together, an attachment of about 1 mm is required. The accuracy can be increased, and accordingly, the allowable range of eccentricity is widened.

Second Embodiment
FIG. 9 is an overall configuration diagram of an example of an angle measurement system according to the second embodiment. In FIG. 9, the same components as those in the first embodiment shown in FIGS. Below, description is abbreviate | omitted about the content demonstrated in 1st Embodiment, and a different point from 1st Embodiment is mainly demonstrated.

  In the first embodiment, the rotary shaft 3 of the rotary encoder 2 is attached to the rotary shaft 1a of the DUT 1 as shown in FIG. 2, whereas in the second embodiment, the DUT 1 is shown as shown in FIG. The encoder body 2a is attached to the rotary shaft 1a.

  In FIG. 10, the attachment attachment 18 is an interposed member for attaching the encoder body 2 a to the rotating shaft 1 a of the device under test 1, and the rotating shaft 3 of the rotary encoder 2 rotates the rotating shaft 1 a of the device under test 1. The rotary shaft 3 of the rotary encoder 2 is protected so as not to be affected so much.

  The anti-rotation jig 8 in the present embodiment allows the rotary encoder 2 to move (displace) within the fixed play range while allowing the movement (displacement) of the rotary shaft 2 in a plane orthogonal to the rotary shaft 3 of the rotary encoder 2. The rotating shaft 3 of 2 is locked.

  The corner cube prism 7 (7a, 7b) in the present embodiment is attached to the rotary shaft 3 of the rotary encoder 2. As in the first embodiment, the corner cube prism 7 is arranged to face the interference unit 4. Using the interference unit 4 and the phase difference detection head 11, the rotation of the rotary shaft 3 of the rotary encoder 2 is detected in a non-contact manner.

  In the present embodiment, unlike the first embodiment, the load of the encoder body 2a is not applied to the rotary shaft 3, and the load of the relatively lightweight corner cube prism 7 is sufficient, so the rotary shaft 3 and the bearing 15 can be small. Weight can be reduced. Therefore, this method is suitable depending on the loadable weight of the rotating shaft 1a of the DUT 1. On the other hand, care must be taken so that the cable connected to the encoder body 2a does not wind around the rotary encoder 2 as the encoder body 2a rotates.

  In the second embodiment, the encoder main body 2a is attached to the rotating shaft 1a of the object 1 to be rotated, and the eccentricity between the rotating shaft 1a of the object 1 to be measured and the rotating shaft 3 of the rotary encoder 2 is allowed. The movement of the rotary shaft 2 (displacement) in the orthogonal plane orthogonal to the rotary shaft 3 of the rotary encoder 2 is restricted within a certain play range, and the encoder body is based on the code read by the encoder read head 13. The rotation angle of 2a is detected (measured), and the non-contact angle detection means 20 detects the changed inclination angle of the rotary shaft 3 of the rotary encoder 2 from the start of the rotation angle measurement of the encoder body 2a. The rotation angle θ1 detected (measured) using the rotation of the rotary encoder 2 detected by the non-contact angle detection means 20 Corrected based on the inclination angle θ2 was changed three.

  In the first and second embodiments described above, the case where an optical rotary encoder is used as the rotary encoder has been described as an example. However, it goes without saying that another rotary encoder such as a magnetic encoder may be used. .

  Further, in the first and second embodiments described above, the case where a so-called laser interference length measuring device is used as the non-contact angle detecting means has been described as an example. However, non-contact capable of highly accurate angle measurement without contact. Any other angle detection means can be used. For example, an autocollimator or a level may be used.

  The measurement of the rotation angle may be a dynamic measurement. In the angle measuring method and the angle measuring system according to the present invention, static measurement for detecting the rotation angle at the timing when the rotation of the rotating shaft 1a of the device under test 1 stops, and during the rotation of the rotating shaft 1a of the device under test 1 At least one of the dynamic measurements for detecting the rotation angle at the timing is performed. In the dynamic measurement, the real-time property of the output of the non-contact angle detection means 20 used with the rotary encoder 2 is necessary.

  Further, in order to briefly explain the present invention, the case where the rotation angle θ1 is corrected using only the inclination angle θ2 has been described as an example, but it goes without saying that the correction may be made based on other measured values. . That is, in the present invention, the rotational angle θ1 is corrected based on at least the inclination angle θ2. For example, the eccentric amount between the rotating shaft 1a of the DUT 1 and the rotating shaft 3 of the rotary encoder 2 is detected, and the rotating angle θ1 is corrected based on the detected eccentric amount and the tilt angle θ2.

  Further, the object to be measured is not limited to the shape shown in the figure. For example, a disk shape may be sufficient. Further, the rotation axis of the object to be measured to which the rotary encoder 2 is attached need not have a specially formed shaft shape. For example, the rotation center of the object to be measured is the rotation axis of the object to be measured. What is necessary is just to attach a rotary encoder to.

  The present invention is not limited to the examples described in the present specification and the examples illustrated in the drawings, and various design changes and improvements may be made without departing from the scope of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Measured object, 1a ... Rotating shaft of measured object, 2 ... Rotary encoder, 2a ... Encoder main body, 3 ... Rotating shaft of rotary encoder, 4 ... Interference unit, 5 ... Right angle prism, 6 ... Polarizing beam splitter, 7 (7a, 7b) ... Corner cube prism (reflective element), 8 ... Anti-rotation jig, 9 ... Rotation angle detector, 10 ... Laser light source, 11 ... Phase difference detection head, 12 ... Data processing device, 13 ... Encoder reading Head (reading unit), 14 ... encoder (code unit), 15 ... bearing, 17 ... weight, 18 ... mounting attachment, 20 ... non-contact angle detection means

Claims (11)

Relative angle detection means for detecting a relative rotation angle of the rotating body with respect to the non-rotating body, including a non-rotating body whose rotation is restricted and a rotating body rotatably supported by the non-rotating body When,
Absolute angle detection means for detecting an absolute rotation angle of the non-rotating body;
An angle measurement system comprising:   The angle measurement system according to claim 1, wherein the absolute angle detection unit detects an absolute rotation angle of the non-rotating body simultaneously with detection of a relative rotation angle by the relative angle detection unit.   The angle measurement system according to claim 1, further comprising a correction unit that corrects the rotation angle detected by the relative angle detection unit based on the rotation angle detected by the absolute angle detection unit.   The angle measurement system according to claim 1, wherein the relative angle detection unit is a rotary encoder.   The said absolute angle detection means is a non-contact angle detection means which detects the absolute rotation angle of the said non-rotating body in non-contact with respect to the said non-rotating body. The angle measurement system according to item 1.   6. The angle measuring system according to claim 5, wherein the non-contact angle detecting means uses a laser interferometer.   The angle measuring system according to claim 1, further comprising a regulating member that regulates an absolute rotation angle of the non-rotating body within a certain range.   The angle measuring system according to claim 7, wherein the restricting member includes a weight member that biases a reference position of the non-rotating body vertically downward. A relative angle detection step of detecting a relative rotation angle of the rotating body rotatably supported by the non-rotating body with respect to the non-rotating body whose rotation is restricted;
An absolute angle detection step of detecting an absolute rotation angle of the non-rotating body;
An angle measuring method comprising:   The angle measurement method according to claim 9, wherein the absolute angle detection step detects an absolute rotation angle of the non-rotating body simultaneously with detection of a relative rotation angle in the relative angle detection step.   11. The angle measuring method according to claim 9, further comprising a correction step of correcting the rotation angle detected in the relative angle detection step based on the rotation angle detected in the absolute angle detection step.

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