JP2018128350A - Position detecting device, stage device, and shape measuring device - Google Patents

Abstract

A correction table having a small memory capacity and capable of performing high-accuracy position correction capable of coping with a change in a local position detection signal caused by a change in scale shape such as a joint or a flaw is created with a low processing load. An X laser scale and an X laser scale head that scans the scale and generates two-phase scale signals having different phases are provided. The correction value calculation unit 118 calculates a correction parameter for correcting the two-phase scale signal used for detecting the position information. The stage position calculation unit 114 detects position information corresponding to the relative movement amount of the scale / head from the two-phase scale signal corrected by the correction parameter. The correction table 116 stores a record in which the correction parameter is associated with the applicable section of the correction parameter. The correction table record is updated when the corrected change in the two-phase scale signal exceeds a predetermined range. [Selection] Figure 1

Description

  The present invention relates to a position detection device including a scale and a detector that scans the scale and generates two-phase scale signals having different phases, a stage device and a shape measurement device using the position detection device, and a position detection device. Relates to the control method.

  In precision processing machines, precision measuring machines, and the like, a stage device called a so-called XY stage is used. This type of stage device realizes relative movement between the tool and sensor and the object by moving the stage. In the stage position control device that controls this relative movement, a linear encoder called a laser scale or the like is used as a highly accurate position detection device. The laser scale is a two-phase sinusoidal signal having scale position information when an optical head (laser scale head) having a laser light source and a light receiving element moves on a scale on which a diffraction grating is periodically engraved. Is output. This two-phase scale signal is converted into digital data by an A / D converter and taken into a stage position control device, so that highly accurate position detection can be performed. In the signal processing inside the stage position control device, for example, a change in the phase angle of both signals is obtained using an arc tangent function with respect to the acquired two-phase scale signal, and the moving distance of the stage position is detected.

  In the laser scale, an ideal two-phase scale signal capable of detecting a position with a desired accuracy is a signal having the same amplitude, no offset, and a phase difference of 90 degrees from each other. A perfect Lissajous waveform is formed. However, in an actual apparatus, the two-phase signal may have a deviation in amplitude, offset, and phase difference due to various manufacturing problems and assembly errors. For this reason, the actual two-phase scale signal may be an elliptical Lissajous waveform having an inclination deviated from the origin in, for example, orthogonal coordinates. If such a deviation occurs, it also affects the change in the phase angle, which may cause a large error in the detected stage position.

  As a countermeasure, conventionally, each part of the encoder has been manually adjusted, but this manual adjustment has a limit. For this reason, configurations for correcting an offset error, an amplitude error, and a phase error of a scale signal have been proposed in Patent Document 1 and Patent Document 2 below.

  In the technique of Patent Document 1, a correction value is always calculated from a Lissajous waveform obtained by performing an interpolation process. Then, the correction value is updated by continuously accumulating the change in the correction value, and the deviation is dynamically eliminated. In the technique of Patent Document 2, a correction table that stores data for correcting deviations in amplitude ratio, phase difference, and offset is used. In Patent Literature 2, a configuration is used in which an offset is replaced with an approximate expression and stored in a table.

JP 2014-25871 A JP 2002-168654 A

  As the scale of the stage device, for example, the stroke of the stage increases, the scale of the encoder needs to be increased. However, in manufacturing a long scale, for example, it may be necessary to divide the diffraction grating into a plurality of processes.

  For example, such a process division may cause a part where the joints and optical characteristics are discontinuous in the diffraction grating. In such a part, the sinusoidal signal obtained from the optical head is localized. Misalignment increases. This situation is the same when there are scratches on the scale.

  When the correction value is sequentially updated with respect to the deviation as described in Patent Document 1 with respect to such a local change in the detection signal, a time lag occurs in the correction processing for the local change. There is a possibility that. In addition, in the technique of the above-mentioned Patent Document 2, a method of holding the correction table itself finely so as to cope with irregular changes in local detection signals can be considered, but the memory capacity may become too large.

  In the prior arts such as Patent Document 1 and Patent Document 2, it is considered that a change in scale shape caused by a joint or a flaw and a detection error caused by the change can be reduced to some extent. However, the conventional techniques as described above may not be able to obtain sufficient measurement accuracy to be applied to position measurement in ultra-precision machining.

  Accordingly, an object of the present invention is to provide a correction table with a small memory capacity that can perform high-accuracy position correction that can cope with local changes in position detection signals caused by scale changes such as joints and scratches. The purpose is to enable creation according to the processing load.

  In order to solve the above-described problems, in the position detection device of the present invention, a scale, a detector that moves relative to the scale, scans the scale, and generates two-phase scale signals having different phases, and a position A correction value calculation unit for calculating a correction parameter for correcting the two-phase scale signal used for information detection, and a relative movement amount of the scale and the detector from the two-phase scale signal corrected by the correction parameter. In accordance with the relative movement of the scale and the detector, the position calculation unit for detecting the position information, the correction parameter, the correction table for storing a record in which the correction parameter is applied, and the application section of the correction parameter. According to the change of the two-phase scale signal corrected by the correction parameter corresponding to the application section of the correction table, A control device for updating the record in Tadashiyo table and employs a configuration having a.

  According to the above configuration, the correction table record can store the correction parameter and the application interval of the correction parameter. Therefore, the correction table can be updated so as to have a record that associates a specific correction parameter and its application section according to a change in the two-phase scale signal. As a result, a correction table with a small memory capacity that can perform high-accuracy position correction that can cope with changes in the local position detection signal caused by scale shape changes such as joints and scratches is created with a low processing load. be able to.

It is explanatory drawing which shows the outline of a function structure at the time of preparation of the correction table of the position detection apparatus which employ | adopted this invention. The shape measuring apparatus using the position control apparatus which employ | adopted this invention is shown, (a) is explanatory drawing which showed the shape measuring apparatus from the front direction, (b) is explanatory drawing which showed the same apparatus from the back direction. It is explanatory drawing which shows the outline of a function structure at the time of performing the position correction process of a stage using the position detection apparatus which employ | adopted this invention. It is the flowchart figure which showed the table for correction | amendment creation in the position detection apparatus which employ | adopted this invention. (A), (b), and (c) are table | surface figures which illustrate the content of the correction | amendment table created or updated by the procedure of FIG. It is explanatory drawing which shows the outline of a function structure in the form which mounted the correction table of the position detection apparatus which employ | adopted this invention. It is explanatory drawing which shows the outline of the function structure for automatically updating the correction table in the position detection apparatus which employ | adopted this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In addition, the structure shown below is an example to the last, For example, it can change suitably for those skilled in the art in the range which does not deviate from the meaning of this invention about a detailed structure. Moreover, the numerical value taken up by this embodiment is a reference numerical value, Comprising: This invention is not limited.

  In the embodiment described below, a position having a detector (X laser scale head 20) that moves relative to the scale (X laser scale 35) and scans the scale to generate two-phase scale signals having different phases. The detection apparatus is illustrated. This position detection device can be used, for example, in a stage device of a shape measuring device (FIGS. 2A and 2B) that measures the cross-sectional shape of an object using a contact probe (38).

  In this stage apparatus, for example, the scale (35) and the detector (20) are arranged to detect the relative position of the driven stage on which the relative movement is performed. Then, a driving amount for driving the stage is determined based on position information corresponding to the relative position of the stage detected by the position calculation unit (114).

  In particular, in the embodiment described below, a scale (X laser scale 35) and a detector (X laser scale head 20) for detecting the scanning position of the X stage that scans the probe (38) of the position detection device in the X-axis direction are provided. Illustrate.

  For example, in the following embodiment, a correction value calculation unit (118) for calculating correction parameters for correcting the A-phase and B-phase two-phase scale signals used for detecting position information is provided (FIG. 1).

  The position information of the X stage is detected by the stage position calculation unit (114) as the relative movement amount of the scale (35) and the detector (20) from the two-phase scale signal corrected by the correction parameter.

  Further, the correction parameter stores a record of the correction table (116) in association with the applicable section (correction application range) of the correction parameter.

  Then, according to the relative movement of the scale (35) and the detector (20), the correction table according to the change of the two-phase scale signal corrected by the correction parameter corresponding to the applicable section of the correction table (116). The record of (116) is updated.

  The correction value calculation unit (118) can be configured to calculate a correction parameter for correcting the correction value of the mutual amplitude ratio, phase difference, or offset of the A-phase and B-phase two-phase scale signals.

  More specifically, for example, when the difference between the correction parameter calculated by the correction value calculation unit (118) and the correction parameter in the immediately preceding section exceeds a predetermined range, the record of the correction table (116) is updated. To do. In this case, the end of the correction parameter application section (correction application range) of the record being used is determined, and a new record is created for a new correction parameter.

  Further, for example, when the difference between the position calculated by the position calculation unit (114) and the position corrected using the correction parameter obtained from the correction value calculation unit (118) exceeds a predetermined range, the correction table (116 ) Records can be updated.

  Further, for example, when a plurality of square sums of the corrected two-phase scale signals calculated by the correction value calculation unit (118) are sampled and the change in the values of the plurality of square sums exceeds a predetermined range, the correction Control to update the record of the table (116) can also be performed.

  Further, the correction parameter includes, for example, a waveform signal storage unit (117) that stores the waveform of the corrected two-phase scale signal, and can be calculated through analysis of the Lissajous waveform of the two-phase scale signal. For example, the correction value calculation unit (118) calculates the correction parameter based on the Lissajous waveform data acquired using the data of the two-phase scale signal stored in the waveform signal storage unit (117).

  The correction value calculation unit (118) calculates the correction parameter based on the mutual phase difference of the two-phase scale signal stored in the waveform signal storage unit (117) that stores the waveform of the corrected two-phase scale signal. It may be.

  The analysis of the Lissajous waveform of the two-phase scale signal can be performed, for example, by monitoring the difference between the Lissajous waveform and a perfect circle by the waveform determination unit (119). In that case, when the difference between the Lissajous waveform and the perfect circle becomes large, the error data storage unit stores the two-phase scale signal and the position data corrected from the corrected two-phase scale signal. Then, the correction table (116) is updated using the new correction parameter calculated by the correction value calculation unit from the two-phase scale signal and the position data corrected from the corrected two-phase scale signal.

<Embodiment 1>
FIGS. 2A and 2B show the overall configuration of a shape measuring apparatus employing the present invention. FIGS. 2A and 2B correspond to a state in which no employment is attached to the shape measuring apparatus. FIG. 2A is a perspective view showing the shape measuring apparatus from the front direction, and FIG. 2B is a perspective view showing the apparatus from the rear. Hereinafter, the main body configuration and operation of the shape measuring apparatus of the present invention will be described with reference to FIGS. 2 (a) and 2 (b).

  2A and 2B, the rotary stage 2 is fixed to the reference base 1, and the X work stage 3 and the Y work stage 8 are mounted on the rotary stage 2. 2A and 2B show the directions of the X, Y, and Z coordinate axes of the three-dimensional coordinate system used for measurement control of the shape measuring apparatus.

  A hiring mounting surface 5 is provided on the Y work stage 8, and hiring mounting standards 6 and 7 for positioning the hiring are installed on the upper surface of the hiring mounting surface 5. Columns 36 and 37 (supports) are fixed on the reference base 1, and the X guide fixing portion 15 is fixed on the columns 36 and 37.

  The X guide including the X guide fixing portion 15 and the X guide movable portion 16 is constituted by, for example, a static pressure guide. The X guide movable part 16 is supported on the X guide fixing part 15 by a static pressure pad (not shown). The X guide movable part 16 is driven by a driving force generated between an X linear motor stator 17 fixed to the X guide fixed part 15 and an X linear motor movable element 19 fixed on the X guide movable part 16. The Thereby, the X guide movable part 16 can be moved in the X axis direction along the X guide fixing part 15, and the probe 38 is scanned in the X axis (probe scanning) direction.

  In the configuration of FIGS. 2A and 2B, a laser scale is used for coordinate measurement and drive control in the X and Z axis directions. An X laser scale head 20 (FIG. 2B) is attached to the X guide movable portion 16. In synchronism with the probe scanning, the X laser scale head 20 of the X guide movable unit 16 scans the X laser scale 35 mounted on the reference base 1 via the X scale base 29 and uses the X laser scale 35 as a reference. Measure the X coordinate.

  Further, a Z guide fixing part 24, Z linear motor stators 25 and 26, and Z laser scale heads 27 and 28 are fixed on the X guide movable part 16. The Z guide fixing part 24 supports the Z guide movable part 30 via a static pressure pad (not shown). The Z guide movable unit 30 supports a probe 38 for measuring a workpiece. Z linear motor movable elements 31 and 32 are attached to the Z guide movable part 30, and the Z linear motor is movable in the Z-axis direction by driving forces generated between the movable elements and the Z linear motor stators 25 and 26, respectively. The children 31 and 32 are moved. Z laser scales 33 and 34 are fixed to the Z guide movable unit 30, and the Z coordinates with respect to the Z laser scale heads 27 and 28 are measured.

  The above-described X guide fixing portion 15, X guide movable portion 16, Z guide fixing portion 24, Z guide movable portion 30 and the like constitute a probe scanning portion that causes the probe 38 to scan the workpiece along a scanning line in one direction. .

  The rotary stage 2 on the reference base 1 is provided for controlling the rotation posture of the X work stage 3 and the Y work stage 8 on the upper side. The rotary stage 2 can be configured using an air bearing, a coupling, a servo motor, or the like (details not shown), for example. The configuration of the rotary stage 2 is not limited to the above, and any configuration may be used for the rotary stage 2 as long as the rotation postures of the X work stage 3 and the Y work stage 8 can be controlled. . By providing the rotary stage 2, it is possible to automatically correct the rotational deviation in the Z center direction of the hire. However, when automatic correction described later is not performed, the rotary stage 2 is not necessarily provided.

  The X work stage 3 and the Y work stage 8 can be configured as general uniaxial stages using, for example, a cross roller guide, a ball screw, a coupling, and a stepping motor (not shown in detail). The structure of the drive mechanism and guide of these work stages does not particularly limit the present invention, and any mechanism may be used for these work stages. By providing the X work stage 3 and the Y work stage 8, it is possible to automatically correct, for example, a work in a translational direction or an installation error of employment. However, the X work stage 3 and the Y work stage 8 may be omitted if automatic correction of the position and orientation of the hiring is not performed. It is desirable that the X work stage 3 and the Y work stage 8 are adjusted so that their drive directions are orthogonal to each other on the rotary stage 2.

  In the above, static pressure guides (by compressed air) are exemplified as the X guide and the Z guide. However, these guides may be configured using other types of guides such as an LM guide and a cross roller guide. . In the above description, a shaft type linear motor is assumed as the X drive motor, and two similar linear motors are assumed as the Z drive motor. However, the configuration of these drive mechanisms is arbitrary as long as the movable part can be moved directly, such as a combination of a rotary motor and a ball screw, and the configuration of the drive mechanism does not particularly limit the present invention.

  The probe 38 can be configured as, for example, a laser displacement meter that measures the distance between a contact supported by a leaf spring (not shown) and the like. However, the probe 38 only needs to be capable of measuring the distance on the surface of the workpiece, and the probe 38 uses any configuration of a distance measuring mechanism such as a non-contact distance measuring mechanism that measures the distance by the focus of the laser beam. It doesn't matter.

  Although details of the motor for driving each movable member, each scale, the sensor wiring of the scale head, or the piping of the static pressure pad are not shown in the drawing, these are appropriately connected via a support means such as a cable bear (registered trademark). To be supported.

  On the right side of FIG. 2A, the configuration of the control device 600 of the shape measuring apparatus shown in FIGS. 2A and 2B is shown in block diagram form. As illustrated, the control device 600 includes a CPU 601, a ROM 602, a RAM 603, and various interfaces (604, 606), which are main parts of the control device. The functional configuration shown in FIGS. 1, 3, 6, and 7 to be described later can be realized by the hardware and software of the control device 600.

  The CPU 601 of the control device 600 is connected with a ROM 602, a RAM 603, and interfaces 604 and 606 using various input / output methods. The ROM 602 can store a control program describing a measurement control procedure (FIG. 4) described later, in addition to a basic program such as BIOS. The RAM 603 is a storage device that temporarily stores the calculation processing result of the CPU 601. The CPU 601 executes a later-described measurement control procedure based on a program recorded (stored) in the ROM 602 (or an HDD not shown).

  The interface 604 is connected with an output device 605 for notifying a user (an operator who handles this apparatus), for example, in measurement control described later. As the output device 605, a display device (display) such as an LCD panel, an audio output device (speech synthesis circuit + amplifier + speaker, etc.), or an output device of any output format can be used.

  The interface 606 corresponds to an interface that controls the motors of the respective units, the respective scales, and the sensors of the scale head and inputs / outputs information to / from them. The interface 606 is shown as one block for convenience, but may actually be configured using interface blocks having different circuit configurations according to input / output specifications necessary for communication with the above-described units. The CPU 601 of the control device 600 can acquire measurement information of the Z laser scale heads 27 and 28 that measure the detection position of the probe 38 via the interface 606. Measurement information of the X laser scale head 20 that measures the position (X coordinate) on the scanning line along the X axis can also be acquired via the interface 606, and the same applies to other sensors.

  When a program for causing the CPU 601 to execute a measurement control procedure described later is recorded (stored) in the ROM 602 (or another recording medium such as an HDD), these recording media are computers storing the control procedure for carrying out the present invention. A readable recording medium is configured. Note that a shape measurement program corresponding to a measurement control procedure described later is stored in a fixed recording medium such as a ROM 602, and a removable computer-readable recording medium such as various flash memories and optical (magnetic) disks. May be stored. Such a storage form can be used when installing or updating the shape measurement program of this embodiment. In addition, when installing or updating the shape measurement program of this embodiment, in addition to using the removable recording medium as described above, a method of downloading the program via a network or the like as described later is used. Also good.

  A workpiece is set in the shape measuring apparatus shown in FIGS. 2 (a) and 2 (b), a desired workpiece region is scanned with the probe 38, and the distance to the workpiece surface is measured. During this probe scanning, the position of the probe 38 is measured as XZ coordinates at any time on the X laser scale and the Z laser scale.

  2A and 2B, an X laser scale and a Z laser scale are used as a position detection device for detecting the position (XZ coordinates) of the probe 38. FIG. The configuration for correcting the position detection signal related to these laser scales in this embodiment can be applied to both the X and Z laser scales. However, for ease of explanation, the configuration related to the X laser scale will be exemplified below, and correction processing related thereto will be described.

  FIG. 3 shows a functional configuration for performing position correction processing related to the stage 101 realized by the control device 600 of the shape measuring apparatus of FIGS. 2 (a) and 2 (b). In FIG. 3, a stage 101 corresponds to a portion of an X stage that detects the position of the probe of the shape measuring apparatus of FIGS. 2 (a) and 2 (b). However, it goes without saying that the same configuration can also be implemented for the Z stage of the shape measuring apparatus.

  The stage 101 in FIG. 3 corresponds to the mechanical configuration of the position control apparatus for the X stage, and the other functional blocks in the figure are realized by the hardware and software of the control apparatus 600.

  The stage 101 in FIG. 3 is divided into a fixed part and a movable part. The fixing portion corresponds to the X laser scale 35 installed on the upper surface of the reference base 1 in FIGS. The movable portion corresponds to the X guide movable portion 16 installed on the upper surface of the X guide fixing portion 15 in FIGS. 2A and 2B, and the X guide movable portion 16 includes an X linear motor movable element 19 and the X guide movable portion 16. An X laser scale head 20 is provided.

  At the time of shape measurement, the X guide movable portion 16 is moved relative to the X laser scale 35 by the X linear motor movable element 19. The scale of the X laser scale 35 and the X laser scale head 20 are configured so as to obtain scale signals of A phase and B phase that are 90 ° out of phase by this relative movement. The two-phase scale signals are sampled by the A / D converters 111 and 112 at a specific period. The sampled A and B phase scale signals can be expressed as in the following equation (Equation 1).

Here, a ₁ and b ₁ represent the amplitudes of the A and B phase scale signals, a ₂ and b ₂ represent offset deviations of both signals, and b ₃ represents a phase difference deviation, respectively.

  Each functional block of the control device 600 of FIG. 3 is configured as follows. The operation command generator 108 outputs a position command to the position controller 109. The hardware part of the position control unit 109 or the motor controller 110 described below can be configured by an interface 606 in FIG. 2A, for example.

  The position command output to the position control unit 109 is feedback-controlled by information on the current position of the stage position calculated by the stage position calculation unit 114 as indicated by the symbol of the adder.

  In the position control unit 109, the motor controller 110 converts it into a drive command and drives the stage 101. By driving the stage 101, the A and B phase scale signals are obtained, and the A and B phase scale signals digitized via the A / D converters 111 and 112 are input to the correction unit 113.

In the correction unit 113, for example, by digital data processing, the deviation of the amplitude ratio (a ₁ and b ₁ ), the offset (a ₂ and b ₂ ), and the phase difference (b ₃ ) between the scale signals of both phases A and B is a _1. = B ₁ , a ₂ = b ₂ = 0, and b ₃ = 0 are corrected to an ideal state. Further, a value set for correcting the above-mentioned deviation is set as a correction parameter (S described later).

  The stage position calculation unit 114 takes in the scale signal corrected by the correction unit 113, calculates the position information of the stage from the change in the electrical angle of the scale signals of both A and B phases, and uses the position control as a return value of the feedback control. Position information is sent to the unit 109. As long as the present invention is configured as shown in FIG. 3, any mechanism may be used.

Here, a correction method for the A and B phase scale signals performed by the correction unit 113 will be described. When the A and B phase scale signals are represented by Lissajous waveforms, there is an inclination due to the deviations a ₁ , b ₁ , a ₂ , b ₂ , and b ₃ , resulting in an ellipse that deviates from the origin. When this ellipse is expressed by a general formula, it can be expressed by the following formula (Equation 2).

  When the above equation (Equation 2) is arranged with respect to the A and B phases, the following equation (Equation 3) is obtained.

  Next, when the above equation (Equation 3) is arranged and the unknown part is replaced with variables k, l, m, n, and o, the following equation (Equation 4) is obtained.

  Then, when the values of k to o are determined so that the sum of the squares of the above equation (Equation 4) is minimized by the least square method, the relationship of the following equation (Equation 5) is obtained.

Partial differentiation is performed with variables k, l, m, n, and o so as to satisfy this equation (Equation 5), and when this equation (Equation 5) is solved, a ₁ , b ₁ , a ₂ , b ₂ , b ₃ can be expressed in the form of each of the following equation (6 number 10).

As described above, a ₁ , b ₁ , a ₂ , b ₂ , and b ₃ that are deviations of the A and B phase scale signals can be calculated from the general equation of the ellipse. The data of the A and B phase scale signals are collected by the sampling data number α that can be elliptically approximated by the least square method, and the deviations a ₁ , b ₁ , a ₂ , b ₂ , and b ₃ can be respectively calculated. Then, it is possible to correct such that the ideal state of _{a 1 = b 1, a 2} = b 2 = 0, b 3 = 0 by the digital data processing.

  Next, a method for creating a correction table will be described. FIG. 1 shows an outline of the functional configuration of the stage position control apparatus when a correction table is created, and processes from 115 to 120 are added to the configuration of FIG. FIG. 4 is a flowchart of a control procedure for creating a correction table.

  As the preparatory measurement preparatory operation, the sampling data number α of the A and B phase scale signals is set, and when the correction table creation program 115 of FIG. 1 is started, the correction table 116 is initialized in step S101 of FIG. I do.

  Here, a configuration example of the correction table 116 is shown in FIGS. As shown in the figure, the correction unit 113 records information on correction parameters (right field) necessary for correcting the A and B phase scale signals and the application range (center field) to which the correction parameters are applied. It is a storage area. Further, although not essential, the correction table 116 in the same figure stores a table number (left field) corresponding to the record number.

  For example, the correction table 116 is assigned to a storage area such as the RAM 603 in FIG. In this case, the correction table 116 stores the correction table in a storage area such as the RAM 603 as matrix data.

In the correction table 116, it is assumed that a matrix of the correction table number (No = 1) is stored in one row (one record) as shown in FIG. At this time, the correction table (No = 1), the variable range of a real number X ₁ corresponding to the distance range of the X-axis direction from the program starting point 0 in the field of the correction application range is stored. A variable real number H ₁ (H ₁ = 0 at initialization) is stored in the field of the correction parameter (S). Each time correction processing described later proceeds, the correction table 116 has correction table numbers (No = 1, 2,..., N + 1,...) As shown in FIG. Correction table records are added.

  In step S102 in FIG. 4, as indicated by the broken line in FIG. 1, a determination execution ON command from the determination unit 119 is output from the operation command generation unit 108. In step S103, the stage is first moved from the operation command generation unit 108 to the position control unit 109 to either the left or right end, and then the stage 101 is driven so as to scan the entire X laser scale 35 at a constant speed. In step S104, the bottom row (latest) record of the matrix of the correction table 116 is read into the correction unit 113, and the correction parameter (S) is set. When only the correction table of the correction table number (No = 1) is stored in the correction table 116 as shown in FIG. 5A, the data of this correction table (No = 1) is used.

  In step S105, the A and B phase scale signals taken from the X laser scale head 20 via the converters 111 and 112 are corrected. This correction is performed, for example, by correcting the deviation of the A and B phase scale signals using the correction parameter (S) stored in the lowermost row of the correction table. Further, in step S106, the corrected A and B phase scale signals are sampled by the number of sampling data α set by the waveform signal storage unit 117 before activation. In step S107, it is determined whether or not the number of sampling data has reached a specified value α. When the number of sampling data reaches the specified value α in step S107, the correction value calculation unit 118 performs the above-described elliptic fitting on the sampled data to calculate the general formula of the Lissajous waveform.

And the correction parameter S mentioned above is calculated | required from this general formula. After determining the correction parameter S at step S108 the correction value calculating unit 118, the sampled data by using the correction parameter S, in digital data _{processing, a 1 = b 1, a} 2 = b 2 = 0, b 3 = 0 It corrects so that it may become the ideal state. Then, actual stage position information U is calculated from the corrected sampling data, and the stage position information U and the correction parameter S are sent to the determination unit 119.

  In step S109, the determination unit 119 compares the correction parameter S obtained by the correction value calculation unit 118 for each item of offset, phase difference, and amplitude, and determines whether or not they are within a preset specified value. In step S110, if the correction parameter S is within the specified value, the stage position information T at the time when the number of sampling data reaches α is obtained from the stage position calculation unit 114 and transmitted to the correction table update unit 120 (step S110). S110a). If the correction parameter S exceeds the specified value, the correction parameter S and the stage position information U are transmitted to the correction table update unit 120 (step S110b).

  In step S111, the correction table update unit 120 determines whether the correction table 116 is an initial matrix (one-row matrix). When only the stage position information T is transmitted in the initial matrix processing, the stage position information T is substituted into the correction application range (X1) of the first row of the correction table 116. When the correction parameter S and the stage position information U are sent via step S110, the correction parameter S is added to the correction parameter (H1) recorded in the record in the first row, and the correction application range. The stage position information U is substituted for X1.

On the other hand, a case where the correction table transmitted to the correction table update unit 120 is not the initial matrix as shown in FIG. 5A will be described using an n-row matrix as shown in FIG. In FIG. 5B, when the lowest layer (latest) matrix is the nth row, the correction parameter can be expressed as H _n and the correction application range can be expressed as X _n−1 to X _n . Here, H _n , X _n−1 , and X _n are variable real numbers. When only the stage position information T is sent, the stage position information T is substituted into _Xn to expand the correction application range.

When the correction parameter S and the stage position information U are sent, a new n + 1 row table (record) is first inserted below the lowest layer n row of the correction table 116. Then substitutes the sum of the correction parameter S calculated as a correction parameter H _n recorded in the n-th row in the correction parameter H _{n + 1.} Finally, the stage position information U is substituted into the correction application range _{Xn + 1} , thereby creating a correction table as shown in FIG.

  In step S112, the sampling data of the Lissajous waveform in the waveform signal storage unit 117 is initialized. In step S113, it is determined whether or not the entire scanning of the measurement range of the X stage has been completed. Here, for example, it is determined whether or not the stage 101 has scanned the entire range of the X laser scale 35. When step S113 is denied, it returns to the above-mentioned step S104 and repeats the above-mentioned process. If step S113 is positive, if the stage 101 scans the entire range of the X laser scale 35, the correction table creation process in FIG.

  In the present embodiment, the number of data of the A and B phase scale signals greatly affects the accuracy of the correction table. For this reason, for example, when the accuracy is increased, the number of data in the section can be increased by reducing the relative movement speed of the stage.

As described above, according to this embodiment, even when the X scale structure has irregular and local changes such as scratches and seams, it is possible to create a correction table that can handle this, and the corrected position. Detection data can be acquired. In particular, it is determined whether or not the acquired correction parameter S is within a specified value, and each time the correction parameter S exceeds the specified value, a record (matrix) in the correction table 116 having a different correction application range (X _{n to} X _{n + 1} ) is updated. One line is added to. As a result, the correction table 116 in which the application range of the correction value is variable according to the actual X scale state is created. That is, according to the present embodiment, a correction table that can perform high-accuracy position correction that can cope with changes in local position detection signals caused by scale shape changes such as joints and scratches is automatically created. Can do.

  Next, the control of the stage position control apparatus after the correction table 116 is created as described above will be described. FIG. 6 shows a state in which the correction table 116 created by the above-described creation processing shown in FIGS. 1 and 4 is mounted on the schematic configuration of the stage position control device of FIG. In the configuration of FIG. 6, when the stage 101 moves, the correction parameter S can be acquired by referring to the correction table 116 based on the stage position information from the position control unit 109, and this correction parameter is transmitted to the correction unit 113. The The correction unit 113 corrects the A and B phase scale signals using the correction parameters sent. Thus, more accurate stage position control can be performed by performing correction corresponding to local changes while moving the stage.

  In particular, according to the present embodiment, it is possible to correct the detection position corresponding to the local change of the scale without time lag, compared to the conventional sequential update correction method. Further, according to the present embodiment, the application range in which the correction parameter can be applied according to the range of the correction parameter value can be defined in the correction table with a variable length. According to the present embodiment, for example, addition of correction table data does not occur unless the correction parameter changes greatly. For this reason, the correction table can be created or updated at a higher speed with a lower processing load than the conventional method using the correction table carved with a fixed range length, and the storage capacity such as the RAM 603 necessary for the correction table can be increased. It can be effectively reduced.

<Embodiment 2>
The local change detection of the A and B phase scale signals in the first embodiment is performed by determining whether or not the value of the correction parameter (S) is within a specified value (step S109 in FIG. 4). However, the present invention is not limited to this, and local change detection of the A and B phase scale signals can also be performed by a method of comparing stage positions. In the present embodiment, a technique for detecting a local change using this stage position will be described.

  In the local change detection using the stage position of the present embodiment, the role of the determination unit 119 in FIG. 1 is changed. For example, in step S109 of FIG. 4, the determination unit 119 compares the stage position information T from the stage position calculation unit 114 with the stage position information U from the correction value calculation unit 118. Then, a local change is detected by determining whether the difference is within a preset specified value. In this determination (S109), if the difference between the stage position information T and U is within the specified value, the stage position information T is sent to the correction table update unit 120 in step S110a of FIG. On the other hand, if the difference between the stage position information T and U exceeds the specified value, the correction parameter S and the stage position information U are sent to the correction table update unit 120 in step S110b of FIG.

  According to the present embodiment, as described above, it is possible to detect a local change in the scale using the stage position information U and create a correction table corresponding to the local change in the scale. You can expect almost the same effect.

<Embodiment 3>
Furthermore, the local change detection of the A and B phase scale signals can also be performed by a method of comparing the radius change of the Lissajous waveform due to the A and B phase scale signals. In the present embodiment, a local change detection method using the radius change of the Lissajous waveform will be described.

  The radius change of the Lissajous waveform of the present embodiment refers to the Lissajous waveform drawn by the A and B phase scale signals on the two-dimensional coordinate plane in which the horizontal axis is A and the vertical axis is B, and the origin (A = 0, B = 0).

In the local change detection using the radius change of the Lissajous waveform of the present embodiment, the roles of the correction value calculation unit 118 and the determination unit 119 in FIG. 1 are changed. In addition to the role in the first embodiment, the correction value calculation unit 118 performs processing for calculating the square sum R of the A and B _two- phase scale signals corrected by the correction unit 113 by the sampling number α. The sum of squares R of the A and B _two- phase scale signals can be expressed, for example, by the following equation (Equation 11).

  The correction value calculation unit 118 calculates the difference W between the maximum value and the minimum value from the square sum R of the above equation (Equation 11) from the α samples, and sends the difference W to the determination unit 119. On the other hand, for example, in step S109 of FIG. 4, the determination unit 119 can detect a local change by determining whether the difference W is within a preset specified value. In this determination (S109), if the difference W is within a preset specified value, the stage position information T from the stage position calculation unit 140 is sent to the correction table update unit 120 in step S110a of FIG. . On the other hand, when the difference W is equal to or larger than a predetermined value set in advance, the correction parameter S and the stage position information U are sent to the correction table update unit 120 in step S110b of FIG.

  According to the present embodiment, as described above, it is possible to detect a local change of the scale using the radius change of the Lissajous waveform and create a correction table corresponding to the local change of the scale. The effect similar to 1 and 2 can be expected.

  In the above, the square sum R is calculated from α samples as in the above (Expression 11) in order to obtain the radius change of the Lissajous waveform. However, a value corresponding to the radius of the Lissajous waveform may be obtained by another appropriate calculation, and a change in the radius of the Lissajous waveform may be detected through a change in the value.

<Embodiment 4>
Also, those skilled in the art can make various changes and additions to the method for calculating the correction values of the A and B phase scale signals. In the present embodiment, a method of calculating a general equation using the A and B phase scale signals as sinusoidal signals and obtaining a correction parameter will be described. Here, a sine wave signal represented by the following equation (Equation 12) is considered.

If the unknown part of this equation (Equation 12) is arranged as P = x ₁ cos (x ₂ ) and Q = x ₁ sin (x ₂ ), it can be expressed as the following equation (Equation 13).

  Then, for example, P and Q can be identified so that the sum of the squares of the above equation (Equation 13) is minimized by the least square method by performing the calculation of the following equation (Equation 14).

Moreover, subjected to partial differential P to satisfy the above equation (Equation 14), Q, with respect to x _3, and rearranging the matrix using real N, so that the following expression (Expression 15).

Then, using the above equation (Equation 15), for example, the A and B phase scale signals are sampled by the sampling data number β sufficient to perform the least squares method, and P, Q, by calculating the x _3, it is possible to derive a formula for the scale signals of both phases.

  When the Lissajous waveform is used, the ideal value is considered to be a perfect circle, but when the scale signal is used, the ideal value can also be obtained by using one of the signals of both phases as a reference. As an example, when the A phase scale signal is used as a reference, the ideal value of the B phase scale signal is a signal in which only the phase difference is shifted by 90 degrees from the A phase scale signal. Therefore, the B-phase scale signal is compared with the ideal value, and it is determined whether the amplitude, phase difference, and offset are within a preset specified value.

  The local change of the scale can also be detected by the above-described method, and a correction table corresponding to the local change of the scale can be created, so that almost the same effect as the above-described Embodiments 1, 2, and 3 can be expected.

<Embodiment 5>
The correction table 116 used in each of the above embodiments can be updated if the X (or Z) stage is moving. For example, in the case of the shape measuring apparatus as shown in FIGS. 2A and 2B, the correction table 116 is not necessarily created or updated during the system initialization period, before the shipment or at the initial installation stage. It does not have to be done only in For example, the correction table 116 may be created or updated while the X (or Z) stage is moving in the (actual) measuring operation of the shape measuring apparatus.

  FIG. 7 shows the configuration of a stage position control apparatus in which automatic correction table updating is implemented in the same format as in FIGS. In the configuration of FIG. 7, when the X stage moves, the automatic determination unit 121 captures the two-phase scale signal corrected by the correction unit 113.

  Then, during the movement of the X stage, for example, the amplitude, the phase difference, and the offset are calculated by the method according to the method of the first embodiment, and it is determined whether the value is within the preset specified value (step S109 in FIG. 4). After the determination, if the specified value is exceeded, the position data and the corrected scale signal are recorded in the error data storage unit 122. Further, the determination method of the automatic determination unit 121 may be determined by comparing the radii from the A-phase and B-phase Lissajous waveforms as shown in the third embodiment. The correction value calculation unit 118 refers to the data in the error data storage unit 122 and derives correction parameters by the method described in the first embodiment, for example. However, at this time, the number of scale signal data within the same correction application range of the error data storage unit 122 needs to reach a predetermined number or more for obtaining correction parameters. The correction table automatic update unit 123 can update the correction table 116 using the derived correction parameter.

  As described above, for example, in the shape measuring apparatus as shown in FIGS. 2A and 2B, for example, when the X (or Z) stage is moving in the (actual) measuring operation of the shape measuring apparatus, The table 116 can be updated.

  Note that the local change detection process of the scale shown in the above-described embodiments does not necessarily have to be used only for creating or updating the correction table 116. For example, in the shape measuring apparatus as shown in FIGS. 2A and 2B, the detection of the local change of the scale shown in each of the above-described embodiments is performed, thereby automatically detecting an abnormality occurring in the apparatus, particularly the laser scale. Can be detected. The detection of the local change of the laser scale can be performed during any period of the initialization period, the calibration operation before shipment or in the initial stage of installation, and the (actual) measurement operation of the shape measuring apparatus. In this case, for example, even when a local change suddenly occurs in the laser scale for some reason, this can be detected, and an appropriate warning or error notification can be made accordingly.

  DESCRIPTION OF SYMBOLS 1 ... Standard base, 3 ... X work stage, 5 ... Hiring attachment surface, 15 ... X guide fixed part, 16 ... X guide movable part, 20 ... X laser scale head, 35 ... X laser scale, 38 ... Probe, 101 ... Stage 108... Operation command generator 109 109 Position controller 110 Motor controller 111 A / D converter (A phase) 112 A / D converter B phase 113 Correction unit 114 ... Stage position calculation unit, 115 ... Correction table creation program, 116 ... Correction table, 117 ... Waveform signal storage unit, 118 ... Correction value calculation unit, 119 ... Determination unit, 120 ... Correction table update unit, 121 ... Automatic determination , 122 ... Error data storage unit, 123 ... Correction table automatic update unit, 600 ... Control device, 601 ... CPU, 602 ... ROM, 603 ... RAM 604, 606 ... interface.

Claims (13)

Scale and
A detector that moves relative to the scale and scans the scale to generate two-phase scale signals of different phases;
A correction value calculation unit for calculating a correction parameter for correcting the two-phase scale signal used for detecting position information;
A position calculation unit for detecting position information corresponding to a relative movement amount of the scale and the detector from the two-phase scale signal corrected by the correction parameter;
A correction table for storing a record associating the correction parameter and the application interval of the correction parameter;
The record of the correction table is updated according to the change of the two-phase scale signal corrected by the correction parameter corresponding to the applicable section of the correction table according to the relative movement of the scale and the detector. A control device,
A position detection device comprising:   The position detection apparatus according to claim 1, wherein the correction value calculation unit calculates a correction parameter for correcting a correction value of a mutual amplitude ratio, phase difference, or offset of the two-phase scale signal.   3. The position detection device according to claim 1, wherein the control device corrects the correction when a difference between the correction parameter calculated by the correction value calculation unit and the correction parameter in the immediately preceding section exceeds a predetermined range. A position detection device that stores a new record in which a correction parameter and an application section of the correction parameter are associated with each other in the table.   3. The position detection device according to claim 1, wherein the control device has a predetermined range in which a difference between a position calculated by the position calculation unit and a position corrected using a correction parameter obtained from the correction value calculation unit is within a predetermined range. A position detection device that stores a new record in which the correction parameter is associated with an application section of the correction parameter in the correction table.   3. The position detection device according to claim 1, wherein the control device samples a plurality of square sums of the two-phase scale signals corrected by the correction parameter calculated by the correction value calculation unit, and A position detection device that stores a new record in which a correction parameter and an application section of the correction parameter are associated with each other in the correction table when a change in the value of the sum of squares exceeds a predetermined range.   The position detection device according to any one of claims 1 to 5, further comprising a waveform signal storage unit that stores a waveform of the two-phase scale signal corrected by the correction parameter, wherein the correction value calculation unit includes the correction value calculation unit, A position detection device that calculates a correction parameter based on Lissajous waveform data acquired using data of the two-phase scale signal stored in a waveform signal storage unit.   The position detection device according to any one of claims 1 to 5, further comprising a waveform signal storage unit that stores a waveform of the two-phase scale signal corrected by the correction parameter, wherein the correction value calculation unit includes the correction value calculation unit, A position detection device that calculates a correction parameter based on a mutual phase difference between the two-phase scale signals stored in a waveform signal storage unit. In the position detection device according to any one of claims 1 to 5, a waveform signal storage unit that stores a waveform of the two-phase scale signal corrected by the correction parameter;
A waveform determination unit that determines a difference between a Lissajous waveform acquired using data of the two-phase scale signal stored in the waveform signal storage unit and a perfect circle;
An error data storage unit for storing the corrected data of the two-phase scale signal,
The controller is
When the waveform determining unit determines that the difference between the Lissajous waveform and the perfect circle is large, the error data storage unit stores the two-phase scale signal and the corrected position data from the two-phase scale signal. Let
A position detection device that updates the correction table by using the new correction parameter calculated by the correction value calculation unit from the two-phase scale signal and position data corrected from the corrected two-phase scale signal. The position detection device according to any one of claims 1 to 8, comprising:
The scale and the detector are arranged to detect the relative position of a relatively driven stage to be moved;
A stage apparatus that determines a drive amount for driving the stage based on position information detected by the position calculation unit and corresponding to a relative position of the stage.   A shape measuring apparatus that measures the shape of the object by scanning a contact type probe with respect to the object by the stage device according to claim 9. A scale, a detector that moves relative to the scale, and scans the scale to generate two-phase scale signals having different phases; and a relative movement amount of the scale and the detector based on the two-phase scale signal In the control method of the position detection device for detecting the position information corresponding to
The position detection device includes:
A correction value calculation unit for calculating a correction parameter for correcting the two-phase scale signal used for detecting position information;
A position calculation unit for detecting position information corresponding to a relative movement amount of the scale and the detector from the two-phase scale signal corrected by the correction parameter;
A correction table for storing a record associating the correction parameter and the application interval of the correction parameter;
With
In response to the relative movement of the scale and the detector, the control device changes the two-phase scale signal corrected by the correction parameter corresponding to the application section of the correction table. A control method of a position detection device that executes correction processing for updating the record.   A control program for causing the control device to execute the correction process according to claim 11.   A computer-readable recording medium storing the control program according to claim 12.

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