JP2014130059A - Contact type three-dimensional shape measuring apparatus and probe control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contact type three-dimensional shape measuring apparatus and a probe control method capable of minimizing adverse effects on measurement accuracy of a measuring instrument by reducing deviation amplitude without generating a pressing pressure deviation of probe control.SOLUTION: The contact type three-dimensional measuring apparatus includes: a probe control part for controlling pressing pressure of a contact type probe to an object to be measured; a guide for driving a stage for moving the contact type probe in a pressing direction according to control of the control part; a displacement meter for detecting a position of the stage; a frequency characteristic measuring instrument for previously obtaining mechanical resonance frequency characteristics; a filter device for suppressing control vibration due to a mechanical resonance frequency; means for obtaining inclination information of the object to be measured; means for obtaining a filter parameter corresponding to an inclination from the inclination information of the object to be measured and the mechanical resonance frequency characteristics; and means for setting the filter parameter in the filter device.

Description

  The present invention relates to a contact type three-dimensional shape measuring apparatus and a probe control method.

  2. Description of the Related Art Shape measuring apparatuses that measure a shape of an object to be measured by scanning a contact-type probe while making contact with the object to be measured and measuring a three-dimensional position of the probe are known. Such a shape measuring apparatus has a problem that a vibration measurement error occurs due to the influence of mechanical resonance of the shape measuring apparatus accompanying the movement of the probe. For this reason, conventionally, for example, a measurement error is reduced by applying a filter such as a high cut filter or a notch filter. As a conventional control system for a shape measuring apparatus, for example, there is a measuring instrument as described in Patent Document 1. The structure is shown in FIG. In FIG. 8, the host computer is for controlling the main body of the measuring instrument, and includes a drive control unit, a measurement value acquisition unit, and a filter device. The filter device applies a digital filter to the measurement value acquired by the measurement value acquisition unit to reduce the influence of measurement error based on the mechanical resonance frequency characteristic of the measuring machine body. The filter device includes a parameter acquisition unit, a filter design unit, and a filter processing unit.

The parameter acquisition unit acquires conditions that change the mechanical resonance frequency characteristics of the main body of the measuring instrument, such as the probe type, measuring position, measuring instrument attitude, and measuring conditions represented by the measuring force applied to the measurement object. To do. As described above, the mechanical resonance frequency characteristic of the main body of the measuring machine changes depending on the type of probe, measurement conditions, and the like.
The filter design unit designs a digital filter that follows the change in the mechanical resonance frequency characteristics of the measuring machine based on the type of probe, measurement conditions, and the like in the parameter acquisition unit. The filter processing unit applies the digital filter designed by the filter design unit to the measurement value acquired by the measurement value acquisition unit.

  With such a configuration, the mechanical resonance frequency characteristic of the measuring machine that changes according to the measurement conditions is estimated, and the measurement error is reduced by performing a filtering process that follows the estimated change in the mechanical resonance frequency characteristic of the measuring machine. Can do.

JP 2010-38779 A

  In the conventional example described in Patent Document 1, the mechanical resonance frequency characteristic of the measuring instrument that changes according to the measurement conditions such as the type of probe, the measurement position, the attitude of the measuring instrument, and the measuring force applied to the object to be measured. Can handle fluctuations.

  However, regarding the control vibration generated under the influence of the mechanical resonance frequency of the measuring machine, the control vibration in the XY direction is added to the control vibration in the probe pressing direction which is the Z direction depending on the inclination angle and direction of the probe and the object to be measured. This is difficult.

  The frequency characteristic and amplitude characteristic in the probe pressing direction due to the mechanical resonance frequency characteristic of the measuring machine, that is, the control vibration characteristic changes depending on the contact position and contact angle between the probe and the object to be measured. When a control vibration having such characteristics is applied in the probe pressing direction, a deviation occurs in the probe pressing pressure.

  There are the following problems related to the occurrence of the deviation of the probe pressing pressure. The probe control system quickly controls the movement of the probe according to the surface shape of the object to be measured while keeping the pressure against the object to be measured constant. However, when the surface of the object to be measured is continuously scanned, the probe pressing pressure changes, resulting in a deviation of the probe pressing pressure. As the probe pressing pressure changes, the surface shape of the object to be measured changes or deforms. Then, the posture changes such as the probe falling, and the probe is deformed. In a three-dimensional shape measuring device that uses the position of the probe as the shape of the surface of the object to be measured, the change in the surface shape of the object to be measured and deformation, the change in posture such as the tilt of the probe posture, and the deformation of the probe directly increase the measurement accuracy. It will decrease.

  The band rejection filter is effective for the control vibration, but the filter is designed with the frequency and amplitude fixed, and thus the effect is small for the control vibration whose characteristics change.

  It is an object of the present invention to achieve stable control without causing a deviation in the pressing pressure of the probe control and reducing the deviation amplitude even under conditions in which the mechanical resonance frequency characteristic of the measuring machine changes depending on the tilt angle. This is to minimize the influence on the measurement accuracy of the measuring machine.

  Furthermore, the tracking type filter processing corresponding to the control vibration whose frequency characteristics and amplitude characteristics change depending on the tilt angle of the object to be measured can suppress the occurrence of probe deviation and reduce the measurement error directly. An object of the present invention is to provide a contact-type three-dimensional shape measuring apparatus and a probe control method.

  The contact-type three-dimensional shape measuring apparatus of the present invention is a contact-type three-dimensional shape measuring apparatus for measuring the three-dimensional shape of the object to be measured by scanning the surface of the object to be measured with a contact probe, A probe control unit for controlling the pressing pressure of the contact probe against an object, a guide for driving a stage for moving the contact probe in the pressing direction according to the control of the control unit, and detecting the position of the stage A displacement characteristic meter, a frequency characteristic measuring device for obtaining mechanical resonance frequency characteristics in advance, a filter device for suppressing control vibration caused by the mechanical resonance frequency, means for obtaining inclination information of the object to be measured, and inclination information of the object to be measured. Means for obtaining a filter parameter corresponding to an inclination from the mechanical resonance frequency characteristic, and means for setting the filter parameter in the filter device. And wherein the door.

  Further, the probe control method of the present invention is a probe that controls the contact probe in a three-dimensional shape measuring apparatus that measures the three-dimensional shape of the measurement object by scanning the surface of the measurement object with a contact probe. A control method for controlling a pressing pressure of the contact probe against an object to be measured; driving a stage for moving the contact probe in a pressing direction according to a control amount in the control step; Detecting the amount of movement of the stage, suppressing control vibration due to the mechanical resonance frequency by a filter device based on the mechanical resonance frequency characteristic obtained in advance, obtaining tilt information of the object to be measured, A filter parameter corresponding to the inclination is obtained from the inclination information and the mechanical resonance frequency characteristic, and the obtained filter parameter is obtained as the filter parameter. It provided to set the motor unit, thereby characterized by inhibiting the control vibration of the mechanical resonance frequency.

  As described above, according to the probe control method of the present invention, the probe control unit can grasp the contact angle and the contact direction between the probe and the object to be measured based on the angle information and the XY position command information of the scan control system in advance. .

  As a result, it is possible to set a band rejection filter that band-rejects probe control vibration that occurs under the influence of the mechanical resonance frequency. Further, probe control can be performed by setting a band rejection filter that follows changes in the control vibration frequency and amplitude accompanying changes in the contact angle and contact direction between the probe and the object to be measured. As a result, the control vibration associated with changes in the contact angle and contact direction between the probe and the object to be measured is always suppressed, so that the probe control is more robust than before and the shape measurement data error of the measuring machine is reduced. There is an effect.

It is a control block diagram of the probe control method which concerns on the Example of this invention. It is an overhead view which shows the structure of a contact-type three-dimensional shape measuring apparatus and a contact-type probe. It is a schematic sectional side view which shows the structure of a contact-type three-dimensional shape measuring apparatus and a contact-type probe. It is an overhead view which shows the structure of a contact type three-dimensional shape measuring apparatus and a contact type probe position measuring method. It is a graph which shows the side sectional view and mechanical resonance frequency of the structure which can acquire the mechanical resonance frequency characteristic of a contact-type three-dimensional shape measuring apparatus. It is a conceptual diagram which shows the mode of a contact probe and a to-be-measured object, a probe contact angle, and a contact direction change. It is a graph which shows the side sectional view and probe control frequency characteristic of the structure which can acquire the probe control frequency characteristic of a contact type three-dimensional shape measuring apparatus. It is a control system block diagram of the conventional shape measuring apparatus.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a control block of a probe control method to which the present invention can be applied. In FIG. 1, the probe control block 11 includes a filter setting unit 12 and a probe control unit 13.

  The probe control method can be applied to a contact-type three-dimensional shape measuring apparatus 200 described later. The filter setting unit 12 includes an X-direction command 122 and a Y-direction command 123 of the scan direction position command commanded by the XY scan axis control device 121 and the tilt angle of the measured object held by the tilt information of the measured object of the measurement management device 124. Is provided with an inclination calculation unit 125 applicable to input. The tilt information of the object to be measured includes a tilt angle and a tilt direction.

  The filter setting unit 12 further includes a filter table 126 that holds parameters of a band rejection filter capable of band-rejecting mechanical resonance frequencies having different amplitude components and frequency components depending on the XYZ directions in the X direction, the Y direction, and the Z direction.

With respect to the filter table 126, it is also possible to provide a single pattern of the filter table 126 with parameters of a plurality of band rejection filters (also referred to as a band stop filter and a band elimination filter) in order to simultaneously band reject a plurality of mechanical resonance frequencies. is there. The filter table 126 tilts the parameters of the band rejection filter capable of band rejection with respect to the XYZ directions while optimizing the mechanical resonance frequency that changes depending on the contact angle and the contact direction between the contact probe 228 and the measured object 26 described later. Patterned and held in angle and tilt direction.
Hereinafter, in the embodiments of the present invention, the term “filter parameter” will be described as a term indicating a set value of a filtering function in a filter device, such as a stop band in a band stop filter.
Note that the term “parameter” in the above-mentioned prior art 1 means the mechanism of the measuring machine body such as the type of probe, the measuring position, the attitude of the measuring machine, and the measurement conditions represented by the measuring force applied to the object to be measured. It is completely different in that it indicates a condition for changing the resonance frequency characteristic.

  In obtaining the parameters of the band rejection filter and patterning the parameters, it is necessary to measure and analyze the characteristics of the mechanical resonance frequency of the contact type three-dimensional shape measuring apparatus 200 in advance to obtain the filter parameters.

  The probe control unit 13 includes a scale (SCL) 131 applicable for measuring the current probe pressing pressure, a conversion unit 132 for converting the value of the scale 131 into a digital value, and the current probe pressing pressure converted into a digital value. A feedback loop for feeding back 133 is provided.

  The probe control unit 13 further includes a subtracter 136 that obtains a probe pressing pressure deviation 135 from the current probe pressing pressure and the target probe pressing pressure 134. The probe control unit 13 includes a probe operation amount control calculation unit 138 that can be applied to calculate the probe pressing pressure operation amount 137 from the probe pressing pressure deviation 135. The probe control unit 13 further includes a filter unit 139 that performs a band rejection filter process for attenuating a specific mechanical resonance frequency from the probe pressing pressure operation amount 140 to a low level.

  The filter unit 139 sets the filter parameter of the optimum band rejection filter based on the contact tilt angle and the tilt direction between the probe and the measured object 26 obtained from the XY direction command pulse and measured object information by the tilt calculating unit 138 as a filter table. 126 is selected.

  The band rejection filter parameter selected by the filter unit 139 is set in the filter unit 139 before the probe control is started, and the filter processing is performed in the control loop of the probe control unit 13.

  In the contact-type three-dimensional shape measuring apparatus 200 to which the probe control method of the present invention can be applied, the X-direction command value during the XY scan operation, the contact tilt angle and the contact tilt direction between the probe and the measurement object 26 from the Y-direction command value. Is calculated. For example, even when the mechanical resonance frequency changes according to the contact inclination angle and the contact inclination direction, the change follows.

  The probe control unit 13 includes a conversion unit 141 that performs an analog conversion process on the probe pressing pressure manipulated variable 140 that has been filtered by the filter unit 139, and an amplifier 143 that can be used to generate the stage manipulated variable 142. . A constant probe pressing amount can be controlled by transmitting a stage operation amount 142 obtained by operating a stage for moving the contact probe 228 in the pressing direction to the Z-axis to which the contact probe 228 is attached. The actuator (M) 144 is provided.

  The timing for calculating the contact inclination angle and the contact inclination direction between the probe 228 and the DUT 26 from the X direction command value and the Y direction command value may be performed in real time, for example.

  The timing for setting the band rejection filter from the filter table 126 of the filter setting unit 12 to the filter unit 139 of the probe control unit 13 may be performed in real time, for example.

  2 and 3 show the structures of a contact type three-dimensional shape measuring apparatus and a contact type probe that can apply the present invention and confirm the effects of the probe control method of the present invention. FIG. 2 is a perspective view showing a configuration of a three-dimensional shape measuring apparatus according to an embodiment of the present invention, and FIG. 3 is a schematic sectional side view of FIG.

  2 and 3, a bed 216 serving as a base for the entire apparatus is disposed on the vibration isolation tables 215a, 215b, and 215c constituting the base of the three-dimensional shape measuring apparatus 200, and these vibration isolation tables 215a, 215a, It is supported at three locations by 215b and 215c. With this structure, minute control vibrations on the floor surface are attenuated and are not transmitted to the bed 216.

  The bed 216 has a support surface 244 for supporting the base surface plate 21, and supports the base surface plate 21 at three support points on the support surface 244. The first support point is provided with a substantially conical recess 245 on both the bottom surface of the base surface plate 21 and the support surface 244, and sandwiches the sphere 247a. The second support point is located on a straight line passing through the first support point and parallel to the Y axis, and the direction of the ridge line is aligned with the direction of the Y axis on both the bottom surface of the base surface plate 21 and the support surface 244. A substantially triangular prism-shaped recess 246 is provided to sandwich the sphere 247b. The third support point is located at a predetermined distance from the first and second support points in the XX axis direction, and the sphere 247c is sandwiched between both the bottom surface of the base surface plate 21 and the support surface 244. .

  With this configuration, the XYZ direction is constrained at the first support point, the XZ direction is constrained at the second support point, and the Z direction is constrained at the third support point. Here, consider a case where the bed 216 is deformed and the distance between the three support points is changed. In response to a change in the distance between the first support point and the second support point, the sphere 247b arranged at the second support point moves along the depression 246 having a triangular prism shape. In this case, unnecessary force caused by the deformation of the bed 216 is not transmitted.

  Further, even if the distance between the second support point and the third support point of the bed 216 and the distance between the first support point and the third support point are changed, the third support of the base surface plate 21 is changed. Since the point can move freely in the XY plane with respect to the bed 216, unnecessary force caused by the deformation of the bed 216 is not transmitted to the base surface plate 21. Therefore, even if the bed 216 is deformed, the base surface plate 21 can be prevented from being deformed.

  An object to be measured 26 is fixed on the base surface plate 21, and three columns 25a, 25b, and 25c are fixed, and a reference mirror holding frame 232 is supported at three positions on the column. In the first support part 229 on the first support column 25a, the reference mirror holding frame 232 is firmly fixed. The second support portion 231 on the second support column 25b is on a straight line passing through the first support portion 229 and parallel to the Y axis, and the cross section is long in the XX axis direction and thin in the Y axis direction (thin plate shape). ). Further, the third support portion 230 is located at a position separated from the first support portion 229 by a predetermined distance in the X-axis direction, and is formed in a columnar shape having a small diameter.

  With this configuration, the first support portion 229 restrains the reference mirror holding frame 232 in the XYZ directions with respect to the base surface plate 21, and the second support portion 231 constitutes the second support portion 231. Since the thin plate-like column is easily bent and deformed in the Y direction, the XZ direction is constrained. Further, in the third support portion 230, the thin columnar column constituting the third support portion 230 is easily bent and deformed in the X direction and the Y direction, so that only the Z direction is constrained.

  Here, a case is considered where the base surface plate 21 is deformed by the influence of the weight of the object to be measured 26 and the distance between the three support points is changed. Since the second support point is movable in the Y direction with respect to the change in the distance between the first support point and the second support point, the reference mirror holding frame 232 has a deformation of the base surface plate 21. Unnecessary force caused by is not transmitted. In addition, even if the distance between the second support point and the third support point and the distance between the first support point and the third support point are changed, the third support point is relative to the base surface plate 21. Therefore, unnecessary force caused by the deformation of the base surface plate 21 is not transmitted to the reference mirror holding frame 232. Therefore, even if the base surface plate 21 is deformed, it is possible to suppress the deformation of the reference mirror holding frame 232.

  Three X reference mirrors 27, a Y reference mirror 28, and a Z reference mirror 29 are attached to the reference mirror holding frame 232.

  Next, the configuration of a probe for measuring the surface shape of the measurement object 26 in contact with the measurement object 26 will be described.

  2 and 3, an X-axis slide guide 217 is fixed on a bed 216, and an X-slide 23 is supported on the X-axis slide guide 217 so as to be slidable in the X-axis direction. The X slide 23 is driven to slide by an X slide drive motor 218 and a ball screw 219. A Y-axis slide guide 220 is fixed to the X slide 23 along the Y-axis direction, and a Y-slide 22 is supported by the Y-axis slide guide so as to be slidable in the Y-axis direction.

  The Y slide 22 is driven to slide by a Y slide drive motor 221 and a ball screw 222. Further, a Z-axis slide guide 223 is fixed to the Y slide 22 along the Z-axis direction, and the Z-slide 24 is supported by the Z-axis slide guide 223 so as to be slidable in the Z-axis direction. The Z slide 24 is slidably driven by a Z slide drive motor 224 and a ball screw 225. The Z slide drive motor 224 is provided with an encoder 245 for detecting the rotation angle of the motor. Further, a housing 226 that supports a contact probe 228 is fixed to the Z slide 24. With the above configuration, the contact probe 228 can be moved three-dimensionally in the XYZ directions with respect to the bed 216.

  The contact probe 228 contacts the surface of the object to be measured 26 and measures the height of the surface of the object to be measured in the Z-axis direction. The contact probe 228 is supported by the housing 226 so as to be movable only in the Z-axis direction via parallel leaf springs 227a to 227d. A master ball 240, which is a sphere compensated for high shape accuracy, is attached to the lower end of the contact probe 228, and a mirror 241 is provided on the upper part. A displacement meter 214, which is an optical interferometer, is provided at a position directly above the contact probe 228 on the Z slide 24, and a distance Z1 between the Z reference mirror 28 and the mirror 229 above the probe 228 (FIG. 4). ).

  The housing 226 is provided with a displacement sensor (not shown) that detects the position of the mirror 229 and detects the relative displacement of the contact probe 228 with respect to the housing 226. The output signal of the displacement sensor is input to a contact pressure control circuit (not shown), and the contact pressure control circuit detects the deformation amount of the parallel leaf springs 227a to 227d based on the relative displacement amount of the probe 228 detected by the displacement sensor. Then, a signal for controlling the position of the Z slide 24 is output so that the pressing pressure of the probe 228 against the object to be measured 26 becomes constant. This control signal is input to a motor amplifier (not shown), and the Z slide drive motor 224 is driven through this motor amplifier.

  The output signal of the encoder 245 is input to a position control circuit (not shown) that controls the position of the Z slide 24 in the Z-axis direction. The position control circuit (not shown) rotates the rotation angle of the Z slide drive motor 224 detected by the encoder 245. Based on the above, a signal for controlling the position of the Z slide 24 is output. This control signal is input to a motor amplifier (not shown), and the Z slide drive motor 224 is driven through this amplifier.

  The state of controlling the contact pressure of the contact probe 228 and the state of controlling the position of the Z slide 24 are switched by a switch (not shown). The operation of the switch (not shown) is further controlled by a general controller (not shown) that controls the entire apparatus.

  Displacement meters 210 and 211 (see FIG. 4) that are optical interferometers for measuring the distance in the X direction of the Z slide 24 are provided at the tip of the Z slide 24. The distances X1 and X2 between the points and the X reference mirror 27 are measured. Displacement meters 212 and 213 (see FIG. 4), which are similar optical interferometers, are also provided in the Y direction, and measure the distance between two points above and below the Z slide 24 and the YY reference mirror 28. .

  Here, as shown in FIG. 4, the measurement axis of X1 and the measurement axis of Y1 intersect at a point C1 on the measurement axis of Z1, and the measurement axis of X2 and the measurement axis of Y2 intersect at a point C2 on the measurement axis of Z1. Set each measurement axis in the same way. The distance between C1 and C2 is L1, the distance between C2 and the mirror 241 fixed to the upper end of the probe 228 is L2, and the distance from there to the center C3 of the master ball 240 at the probe tip is L3.

Under this condition, the center position coordinate (Xp, Yp, Zp) of the master ball 240 at the tip of the probe 228 is obtained by the following equation.
Xp = X1 + (X2-X1) × (L1 + L2 + L3) ÷ L1 + δX (1)
Yp = −Y1− (Y2−Y1) × (L1 + L2 + L3) ÷ L1 + δY (2)
Zp = −Z1 + δZ (3)
However, δX, δY, and δZ are constants.

Here, the meaning of the above formula will be described. In the three-dimensional movement mechanism using the X slide, Y slide, and Z slide as described above, when the probe 228 is moved, a movement error occurs in the Z slide due to the movement error of each slide. In general, the movement error is the following six errors defined by the movement of the axis.
(A) Position error
There are three types of errors in the XYZ directions, and are described as ΔX, ΔY, ΔZ.
(B) Posture error
Attitude errors are rotation-related errors of three types around the XYZ axes, and are described as ΔθX, ΔθY, and ΔθZ.

  Since the above six types of movement error components are generated for each of the XYZ slides, the position and posture of the probe arranged at the tip thereof are affected by the accumulation of the movement errors and change with the movement of the XYZ axes. To do.

It will be shown below that the center position of the master ball at the tip of the probe can be measured without being affected by this movement error by calculating the position of the probe using the above equations (1) to (3).
(About position error)
Since the position errors ΔX and ΔY in the XYZ directions are reflected on the lengths X1 and X2 measured by a displacement meter such as an optical interferometer as they are, they do not constitute a probe position measurement error. Further, since the length Z1 measured by the displacement meter is the distance between the probe and the Z reference mirror, ΔZ does not affect the measured value in the Z direction.
(Attitude error)
For example, when a posture error ΔθY about the Y axis occurs, the center position (point C3) of the master ball 230 is shifted in the X direction by ΔθY × (L1 + L2 + L3) when viewed from the position of the point C1. Therefore, the correct position Xp in the X direction of the center of the master ball (point C3) is that the X direction position of the point C1 is X1,
Xp = X1 + ΔθY × (L1 + L2 + L3) + δX (4)
It is expressed as Here, δX is an error caused by an attachment position error of the object to be measured 26, and is a constant rather than a change.

On the other hand, when viewed from the position of the point C1, the point C2 is also shifted in the X direction by ΔθY × L1 due to the attitude error ΔθY. Here, since the position in the X direction of the point C2 is measured as X2 by a displacement meter, the amount of deviation ΔθY × L1 in the X direction of the point C2 is
ΔθY × L1 = (X2−X1). When ΔθY is obtained from this equation,
ΔθY = (X2−X1) ÷ L1. If this is substituted into the above equation (4), Xp becomes
Xp = X1 + (X2-X1) × (L1 + L2 + L3) ÷ L1 + δX
Thus, the above equation (1) is obtained.
If the attitude error ΔθX around the X axis is considered in the same way, the correct position in the Y direction of the center of the master ball can be obtained as shown in Equation (2).
Further, the posture error ΔθZ around the Z axis does not cause a measurement error because the tip of the probe is a sphere.

  In equations (1), (2), and (3), δX, δY, and δZ are constant errors caused by attachment position errors of the object to be measured 26 and are unknown, There is no problem because the relative position is sufficient for the purpose of measuring the shape. In other words, it is not necessary to know exactly where the object to be measured is fixed with respect to the three reference mirrors as the measurement reference.

  As described above, by using the above equations (1) to (3), the three-dimensional position of the probe can be measured without being affected by the movement error of the moving axis.

Next, a procedure for measuring the shape of the DUT 26 in the above configuration will be described.
First, the device under test 26 is attached to the base surface plate 21. At this time, the base surface plate 21 is deformed by the weight of the object 26 to be measured. However, as described above, the deformation of the reference mirror holding frame 232 is suppressed by the action of the three support points 229, 230, and 231. Therefore, the three reference mirrors 27, which are the reference of the position of the three-dimensional shape measuring apparatus are suppressed. The relative positions of 28 and 29 do not change. Further, the deformation of the base mirror holding frame 232 is suppressed by the same action against the deformation of the base surface plate 21 due to the change of the environmental temperature.

  Next, a position control circuit (not shown) is selected by a switch (not shown), and the position of the probe 228 in the Z-axis direction is controlled to a predetermined position away from the measured object 26 (step S1). Next, the X slide 23 and the Y slide 22 are driven to move the probe 228 above the first measurement point of the measurement object 26 (step S2). At this time, as the X and Y slides move, the position at which the weight of the slide 22 acts on the bed 216 changes, so that the bed 216 is deformed. However, as described above, the base surface plate 21 is not deformed by the action of the three support points 245, 246, and 247. The same applies to the case where the Z slide is moved. Even if the bed 216 is deformed as the Z slide is moved, the base surface plate 21 is not deformed. Furthermore, the base surface plate 21 is not deformed by the same action even when the bed 216 is deformed due to a change in environmental temperature.

  Next, the Z slide 24 is driven and lowered until the tip of the probe 228 comes into contact with the surface of the object to be measured 26 (step S3). At this time, the output of the displacement sensor 231 is monitored, and the Z slide 24 is lowered until the displacement amount of the parallel leaf springs 227a to 227d, in other words, the contact pressure of the probe 228 to the object to be measured 26 reaches a predetermined value (step). S4). When the displacement amount of the parallel leaf springs 227a to 227d reaches a predetermined value, the contact pressure control circuit 239 is selected by switching a switch (not shown) so that the output of the displacement sensor 231 becomes constant, in other words, the contact of the probe 228. The position of the Z slide 24 is controlled so that the pressure becomes constant (step S5).

  Next, the position of the master ball 230 at the tip of the probe is calculated from the outputs of the displacement meters 210, 211, 212, 213, and 214, which are optical interferometers, using equations (1) to (3) (step S6). Then, the calculated coordinate position is stored in a memory in the general control apparatus (not shown) (step S7).

  Next, the X slide 23 and the Y slide 22 are driven, and the position of the probe 228 is sequentially measured while scanning the probe 228 while being in contact with the surface of the object 26 to be measured. Store it (step S8). Then, it is determined whether or not the entire measurement area has been scanned (step S9). If scanning has not been completed, the process returns to step S6, and if scanning has been completed, the process proceeds to step S10. In step S10, a switch (not shown) is switched to place the probe 228 in the position control state, and the probe 228 is further retracted from the object to be measured 26 to complete the measurement (step S11).

  As described above, according to the above-described embodiment, the base surface plate 21 is supported at three points with respect to the bed 216, and at one point, the base surface plate 21 is firmly fixed, and the other 1 The point is movably supported only in the Y-axis direction, and the remaining one point is movably supported in the XY direction, so that the deformation of the bed 216 is not transmitted to the base surface plate 21, and high-precision measurement is possible.

  Also, the reference mirror holding frame 232 is supported at three points with respect to the base surface plate 21, and at one point, the reference mirror holding frame 232 is firmly fixed, and at the other point, it is movable only in the Y-axis direction. The remaining one point is movably supported in the XY directions, so that the deformation of the base surface plate 21 is not transmitted to the reference mirror holding frame 232, and high-precision measurement is possible.

  Since the reference mirrors 27, 28, and 29 are held on the reference mirror holding frame 232 at three pressing points and at three or more pulling points, deformation due to the weight of the reference mirror can be reduced, and high precision Measurement is possible.

  In addition, by forming the base, the reference mirror holding frame, and the reference mirror using a material with a small coefficient of thermal expansion, even when the environmental temperature changes, the amount of deformation of these members can be kept small, and high precision Measurement is possible.

  In addition, since the position of the Z slide is measured with five displacement meters, it is possible to measure the position with high accuracy without being affected by the movement error of the X, Y, and Z axes by using these measured values. Become.

  Since the mirror surface of the Z-axis reference mirror 29 is arranged downward, it is possible to prevent the performance of the reference mirror from being deteriorated due to accumulation of dust or the like in the air.

  In addition, since the lightest Z slide 24 provided at the end of the XYZ moving mechanism causes the probe 228 to follow the height direction of the measurement object 26, the probe follows the height direction of the measurement object 26. High performance, high speed and high accuracy measurement.

  In the above embodiment, the third support point 230 is described as being formed in a thin cylindrical shape. However, if the cross-sectional area is small, the same applies to a pillar having a regular polygonal cross section such as a square. In addition, the second support point 231 has been described as being formed in a thin plate shape, but is not limited thereto, and may be a cross-sectional shape that is easily deformable in the Y direction, or may be an elliptical cross-sectional column.

  In the above embodiment, five lengths measured using a displacement meter such as five optical interferometers are used as the basis for position measurement. The accuracy of the length measured by the interferometer depends on the light source used. It depends on the wavelength. Therefore, if a system of six interferometers is added by adding a commercially available interferometer for wavelength correction, shape measurement that is not affected by changes in wavelength due to changes in temperature and pressure during shape measurement becomes possible.

  In addition, the circuit that guides the output of the displacement sensor 231 to the Z-axis drive motor 224 via the feedback circuit 239 and a switch (not shown) is necessary to keep the pressing force of the probe 228 constant. High responsiveness is required. Therefore, in order to improve the response performance of the Z axis, for example, the slide guide 223 is used as an air bearing to reduce friction, or the driving system using a rotating motor and a ball screw is replaced with a linear motor, thereby eliminating non-linear elements such as backlash. It is good also as a structure.

  In this embodiment, three axes of the XYZ axes are used to move the probe, and the surface of the object to be measured is scanned two-dimensionally. However, the X axis is omitted, and only the Y axis and the Z axis are scanned. A configuration may be used in which only one section of the surface of the object to be measured is scanned.

  Moreover, although the application example to the measuring machine of this invention was mentioned, it does not need to be limited to a measuring machine and can be applied to an apparatus having a configuration similar to the measuring machine, such as a processing machine.

  FIG. 5 is a side cross-sectional view of a structure capable of acquiring mechanical resonance frequency characteristics of a contact-type three-dimensional shape measuring apparatus, and a band rejection filter capable of band rejection by measuring the mechanical resonance frequency and analyzing the mechanical resonance frequency in advance. This is a device configuration that can acquire the parameters. FIG. 6 is a graph showing the mechanical resonance frequency, and shows a characteristic example of the mechanical resonance frequency characteristic that can be acquired by the contact-type three-dimensional shape measurement device, the peripheral device for mechanical resonance frequency analysis, and the contact-type three-dimensional shape measurement device. .

  In FIG. 5, the contact-type three-dimensional shape measuring apparatus connects an XYZ direction acceleration sensor 250, which is an external measuring device capable of measuring a mechanical resonance frequency that is not used at least during a three-dimensional shape measurement operation, and a frequency characteristic measuring device 251.

  In order to measure the mechanical resonance frequency characteristics, the Z-direction movable stage is position-controlled at a certain position where it does not come into contact with the object to be measured. -Add to the drive amplifier output signal. By adding an analog signal to the amplifier output signal, the actuator 224 is rotated into a sweep sine wave shape, and the rotational force is converted into a linear motion direction, thereby moving the Z-direction movable stage 24 in a sweep sine wave shape in the probe pressing direction. To do.

  At that time, the conditioner 255 amplifies the XYZ direction acceleration signal output 254 from the XYZ direction acceleration sensor attached at a position where the XYZ direction acceleration sensor can be attached as close as possible to the probe tip of the probe support.

  In this state, an XYZ direction acceleration signal generated in a state where the Z direction movable stage 24 is moving in a sweep sine wave shape in the probe pressing direction is acquired. At that time, the XYZ direction acceleration signal and the sweep sine waveform analog signal of the XYZ direction acceleration sensor are input to the frequency characteristic measuring device 251, and the XYZ direction acceleration signal and the sweep sine waveform analog signal are FFT-analyzed by the frequency characteristic measuring device 251.

  Thereby, the XYZ direction mechanical resonance frequency of a contact-type three-dimensional shape measuring apparatus can be acquired. FIG. 5A is a Bode diagram showing the mechanical resonance frequency acquired in the X direction of the contact type three-dimensional shape measuring apparatus. FIG. 5B is a Bode diagram showing the mechanical resonance frequency acquired in the Y direction of the contact type 3D shape measuring apparatus. FIG. 5C is the Z direction of the contact type 3D shape measuring apparatus. The mechanical resonance frequency acquired in the above is displayed in a Bode diagram. Further, as the adjustment setting procedure of the filter table, a plurality of patterns can be set in the filter table up to 5 to 6 band rejection filters. That is, a band rejection filter capable of optimal band rejection can be mounted on the filter table by combining a mechanical resonance frequency having a large amplitude in accordance with the inclination angle and the inclination direction from FIGS. 5 (a), 5 (b), and 5 (c). .

  In the above description, the spring is, for example, a leaf spring, and the guide is, for example, a linear guide. The Z-direction actuator is, for example, a servo motor, and the displacement meter is, for example, a non-contact type laser displacement meter. Further, the frequency characteristic measuring instrument is, for example, an FFT analyzer, and the vibrator (not shown) is provided, for example, in the FFT analyzer.

  FIG. 6 is a conceptual diagram showing a contact-type probe and a model of an object to be measured, and how the probe contact angle and contact direction change. FIG. 7 is a side cross-sectional view of a structure that enables acquisition of probe control frequency characteristics of a contact-type three-dimensional shape measuring apparatus and a graph showing probe control frequency characteristics. In FIG. 6, for example, when measuring the three-dimensional shape of the object 26 having a concave sphere shape with the contact probe 228, the contact angle and the contact direction state between the object to be measured and the contact probe 228 are the same as those of the object 26 to be measured. It changes depending on the XYZ position. Even in such a state, in order to optimally block the mechanical resonance frequency band, filter parameters are prepared in advance according to 32 patterns of inclination angles and inclination directions from a1 to h4.

  The filter parameter is a value obtained by integrating the tangent of the X direction contact angle between the DUT 26 and the contact type probe 228, that is, a value converted into the probe pressing direction into the probe pressing direction. It is set so as to prevent the control vibration due to the resonance frequency characteristic from being applied.

  Similarly, the filter parameter is a value obtained by integrating the tangent of the Y-direction contact angle between the DUT 26 and the contact probe 228, that is, the value converted into the probe pressing direction into the probe pressing direction as shown in FIG. The control vibration due to the directional mechanical resonance frequency characteristic is prevented from being applied. Similarly, the filter parameter is a value obtained by dividing the sine of the Z-direction contact angle between the DUT 26 and the contact probe 228, that is, a value converted into the probe pressing direction into the probe pressing direction as shown in FIG. The control vibration due to the directional mechanical resonance frequency characteristic is prevented from being applied.

  In FIG. 6, for example, when a cross section of 606 is extracted from the object to be measured 26, the contact angle and the contact direction obtained at the position 602 change like positions 603, 604, and 605 depending on the concave XY horizontal position. At the position 602, the filter parameter pattern a1 exhibits the most effective band rejection. At the position 603, the filter parameter pattern a2 exhibits the most effective band rejection.

  As described above, the probe that is generated under the influence of the mechanical resonance frequency during the measurement of the object to be measured 26 by installing the filter parameter in the filter unit based on the two parameters of the contact angle and the contact direction by the tilt angle calculation unit. It is possible to suppress vibrations in the pressing direction control.

  In the above description, the concave spherical object is described as an example, but the present invention can be applied regardless of the shape of the object such as a convex spherical shape or an aspherical shape.

  The DUT 26 is a rigid object such as a glass lens or a mold.

  The filter table is divided into 32 patterns, for example, but the number may be set as long as the processing capability of a control device (not shown) that processes the probe control unit allows.

  Further, the filter table is divided into patterns in the diameter direction of the object to be measured 26, for example. However, any pattern may be divided, and any pattern may be divided according to the object to be measured 26. It doesn't matter.

  Next, a configuration capable of acquiring the frequency characteristics of the contact probe 228 of the contact three-dimensional shape measuring apparatus 200 will be described with reference to FIG.

  In FIG. 7 (a), a sweep sine waveform analog signal 252 of a vibrator (not shown) of the frequency characteristic measuring instrument 251 is added with the contact type probe 228 brought into contact with the surface of the object to be measured 26 and the probe control is applied. By 253, it is added to the Z direction actuator-drive amplifier output signal. By adding an analog signal to the amplifier output signal, the actuator 224 is rotated into a sweep sine wave shape, and the rotational force is converted into a linear motion direction, thereby moving the Z-direction movable stage 24 in a sweep sine wave shape in the probe pressing direction. To do. At that time, the probe displacement signal 256 output from the displacement meter 214 that detects the probe displacement is taken into the frequency characteristic measuring device 251 via the signal converter 257. The probe displacement signal and the sweep sine waveform analog signal of the displacement meter are input to the frequency characteristic measuring device 251, and the probe displacement signal and the sweep sine waveform analog signal are subjected to FFT analysis by the frequency characteristic measuring device 251. Thereby, the frequency characteristic of the contact probe control of the contact three-dimensional shape measuring apparatus 200 can be acquired.

  For example, in FIG. 7B, for example, the probe control frequency characteristics obtained when the contact type probe 228 is brought into contact with the flat point I which is the peak of the concave surface from the inclined points A to H of the concave surface of FIG. (C) It can be obtained by a Bode diagram as in (d).

  FIG. 7C is a Bode diagram obtained by setting the band rejection filter in the filter unit without considering the mechanical resonance frequency and without creating the filter table.

  FIG. 7D is a Bode diagram obtained by creating a filter table in consideration of the mechanical resonance frequency and setting the band rejection filter in the filter unit.

  When the mechanical resonance frequency is not taken into consideration, a band rejection filter is designed with a fixed pattern based on data obtained by frequency analysis using the displacement meter 214 as a feedback signal, and the filter is caused to function by the probe control unit. However, in that case, there are many control vibration modes affected by the mechanical resonance frequency, and the control vibration mode remains in the oscillation state. That is, the contact probe control cannot be brought into a stable state simply by setting the band rejection filter in a fixed pattern based on the frequency characteristics of the contact probe 228 of the contact three-dimensional shape measuring apparatus 200.

  On the other hand, when the mechanical resonance frequency is considered, as described above, the band rejection filter is designed from the mechanical resonance frequency by the filter table and set in the filter unit, and the filter is operated by the probe control unit. In that case, compared with the conventional method which does not consider the mechanical resonance frequency, the control vibration mode by the mechanical resonance frequency is eliminated, and the contact probe control can be made stable.

  When the stable state of the frequency characteristic cannot be confirmed, the contact type probe control can be made stable as shown in FIG. 7D by adjusting the combination of the filter parameters in the filter table.

  By patterning the acquired filter parameters in association with the contact angle and the contact direction between the contact probe and the object to be measured and recording them in the filter table 126, it is possible to create a filter table that can always stabilize the frequency characteristics.

  For example, 5 to 6 band rejection filters are set as the upper limit, but the number may be set as long as the processing capability of a control device (not shown) that processes the probe control unit allows.

DESCRIPTION OF SYMBOLS 11 Probe control block 12 Filter setting part 13 Probe control part 26 Measured object 121 XY scan axis control device 122 X direction command 123 Y direction command 124 Measured object information 125 Inclination calculation part 126 Filter table 131 Probe scale 132 Scale conversion part 133 Current probe pressing pressure 134 Target probe pressing pressure 135 Probe pressing pressure deviation 136 Subtractor 137 Probe pressing pressure operation amount 138 Control calculation unit 139 Filter unit 140 Probe pressing pressure operation amount 141 Analog conversion unit 142 Stage operation amount 143 Amplifier 144 Actuator
200 Contact-type three-dimensional shape measuring device 228 Contact-type probe

Claims (8)

A contact-type three-dimensional shape measuring apparatus for measuring a three-dimensional shape of the measurement object by scanning the surface of the measurement object with a contact probe,
A probe control unit for controlling the pressing pressure of the contact-type probe against an object to be measured;
A stage that movably supports the contact probe according to the control of the control unit;
A displacement meter for detecting the position of the probe;
A filter device that suppresses control vibration caused by the mechanical resonance frequency;
Means for obtaining tilt information of the object to be measured;
Means for obtaining a filter parameter corresponding to the inclination from the inclination information of the object to be measured and the mechanical resonance frequency characteristic;
And a means for setting the filter parameter in the filter device. The contact type three-dimensional shape measuring apparatus according to claim 1, wherein the tilt information includes a tilt angle and a tilt direction. The contact-type three-dimensional shape measuring apparatus according to claim 1, further comprising a frequency characteristic measuring device for obtaining a characteristic of a mechanical resonance frequency in advance. The contact type three-dimensional shape measuring apparatus according to claim 1, wherein the displacement meter is a non-contact type laser displacement meter.   The contact-type three-dimensional shape measuring apparatus according to claim 3, wherein the frequency characteristic measuring instrument is an FFT analyzer.   The contact type three-dimensional shape measuring apparatus according to claim 5, wherein the FFT analyzer includes a vibrator. The contact type probe controls the contact type probe in a three-dimensional shape measuring apparatus that detects the position of the contact type probe and measures the three-dimensional shape of the object to be measured by scanning the surface of the object to be measured with the contact type probe. A three-dimensional shape measurement method,
Control the pressing pressure of the contact probe against the object to be measured;
Driving a stage for moving the contact probe;
Obtaining a filter parameter corresponding to the inclination of the measurement object from the acquired inclination information of the measurement object and the mechanical resonance frequency characteristic of the three-dimensional shape measuring apparatus,
A contact-type three-dimensional shape measuring method for setting the obtained filter parameter in the filter device and thereby suppressing control vibration of the mechanical resonance frequency. The contact type three-dimensional shape measuring method according to claim 7, wherein the tilt information includes a tilt angle and a tilt direction.

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