JP2008082745A - Workpiece measuring method and its apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a workpiece measuring method which performs point measurement by a copying probe with high precision. <P>SOLUTION: The workpiece measuring apparatus 10 comprises: a measurement control means 24 for collecting a displacement amount from the copying probe 12 and a coordinate value from a coordinate value detection means 16 when the copying probe 12 is brought into contact with a workpiece measurement surface 20 from a predetermined approach direction; a normal calculation means 26 for calculating the normal direction of the workpiece measurement surface 20 on the basis of the displacement amount; a judgement means 28 for judging that the approach direction is inappropriate when the angle difference between the normal direction and the approach direction is larger than a threshold; and an instruction means 30 for correcting the setting of the approach direction so that the approach direction of the copying probe 12 toward the workpiece measurement surface 20 becomes the normal direction of the workpiece measurement surface 20 on the basis of the angle difference when judged that the approach direction is inappropriate and issuing instructions to reexecute the measurement, the normal calculation, and the judgement. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a workpiece measurement method and apparatus, and more particularly to improvement in accuracy of point measurement using a scanning probe.

Conventionally, in order to measure, for example, the shape and position of a workpiece, coordinate value information of points on the workpiece is detected using a scanning probe (see, for example, Patent Document 1).
By the way, recently, point measurement using a scanning probe has attracted attention. In the prior art, a plane including points on the workpiece measurement surface is assumed to be a plane. First, three or more points on the workpiece measurement surface are measured, and a plane including these measurement points is obtained. Then, the scanning probe is brought into contact with the workpiece measurement surface from the normal direction of the obtained plane to perform measurement. By obtaining the measurement values of the measurement points obtained in this way, the shape, position, etc. of the workpiece measurement surface are grasped.

JP-A-9-178463 (FIG. 12)

By the way, even with the conventional method, although further improvement has been demanded with respect to measurement accuracy, there has been no appropriate technique that can solve this problem. In the past, the cause was still unknown.
The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a workpiece measuring method and apparatus capable of improving the accuracy of point measurement using a scanning probe.

  As a result of intensive studies on the point measurement by the scanning probe by the present inventors, the bottleneck in improving the measurement accuracy is actually the fact that the scanning probe is approached from the normal direction of the workpiece measurement surface in the conventional method. It was found that it was difficult to make it approach from the normal direction accurately. Based on the elucidation of the cause, the inventors have corrected the approach direction to the workpiece measurement surface based on the displacement information at one point when the scanning probe is brought into contact with the workpiece measurement surface. The present inventors have found that the measurement accuracy can be improved by calculating the measurement value at the measurement point after sufficiently correcting the above, and have completed the present invention.

That is, in order to achieve the above object, a workpiece measuring method according to the present invention performs point measurement using a scanning probe using a workpiece measuring apparatus including a scanning probe, a moving unit, and a coordinate value detecting unit. The workpiece measurement method includes a measurement process, a normal calculation process, a determination process, an instruction process, and a measurement value calculation process.
Here, the scanning probe has a probe at the tip of a stylus that can be displaced relative to a reference point of the probe body, and the stylus is relative to the reference point when the probe contacts the workpiece measurement surface. Output displacement information.
The moving means performs relative movement between the workpiece and the scanning probe in order to perform point measurement using the scanning probe.
The coordinate value detection means outputs relative coordinate value information of the scanning probe with respect to the workpiece.

In the measurement step, when the scanning probe is brought into contact with a workpiece measurement surface from a preset approach direction, relative displacement amount information from the scanning probe and relative coordinate value information from the coordinate value detection unit To collect.
In the normal line calculation step, a normal direction of the workpiece measurement surface is calculated based on the relative displacement information obtained in the measurement step.
The determination step determines that the approach direction is inappropriate when the angle difference between the normal direction obtained in the normal calculation step and the approach direction is greater than a threshold value, and the angle difference is less than the threshold value. If it is too small, it is judged that the approach direction is appropriate.
In the instruction step, when the approach direction is determined to be inappropriate in the determination step, the approach direction of the scanning probe to the workpiece measurement surface is a normal direction of the workpiece measurement surface based on the angle difference. The approach direction setting is corrected, and re-execution of the measurement step, the normal calculation step, and the determination step is instructed based on the corrected approach direction setting. In addition, the instruction step instructs the calculation of the measurement value when the approach direction is determined to be appropriate in the determination step.
In the measurement value calculation step, a measurement value at a measurement point is obtained based on the relative displacement amount information and the relative coordinate value information for which the approach direction is determined to be appropriate in the determination step.

In the present invention, it is preferable that the determination step estimates an angular difference between the normal direction and the approach direction based on relative displacement amount information from the scanning probe obtained in the measurement step. .
Further, in the present invention, the measurement value calculating step obtains a coordinate value of the probe center position as a measurement value of the measurement point, and the approach direction is further set to the coordinate value of the probe center position. It is preferable to perform an offset process according to the size of the measuring element in the approach direction when it is determined to be appropriate, and obtain the coordinate value of the contact position between the workpiece measurement surface and the scanning probe.

In order to achieve the above object, a workpiece measuring apparatus according to the present invention includes a scanning probe, a moving unit, and a coordinate value detecting unit. In the workpiece measuring apparatus that performs point measurement using the scanning probe, measurement control is performed. Means, normal calculation means, determination means, instruction means, and measurement value calculation means.
Here, the scanning probe has a probe at the tip of a stylus that can be displaced relative to a reference point of the probe body, and the relative displacement of the stylus with respect to the reference point when the probe is brought into contact with a workpiece. Output information.
The moving means performs relative movement between the workpiece and the scanning probe in order to perform point measurement using the scanning probe.
The coordinate value detection means outputs relative coordinate value information of the scanning probe with respect to the workpiece.

The measurement control means controls the operation of the workpiece measuring device, and when the scanning probe is brought into contact with the workpiece measurement surface from a preset approach direction, information on relative displacement from the scanning probe, and Relative coordinate value information from the coordinate value detection means is collected.
The normal calculation means calculates a normal direction of the workpiece measurement surface based on the relative displacement information obtained by the measurement.
The determination means determines that the approach direction of the scanning probe to the workpiece measurement surface is inappropriate when the angle difference between the normal direction obtained by the normal calculation means and the approach direction is larger than a threshold value. When the angle difference is smaller than the threshold value, it is determined that the approach direction is appropriate.
The indicating means is configured so that, when the determination means determines that the approach direction is inappropriate, the approach direction of the scanning probe to the workpiece measurement surface is a normal direction of the workpiece measurement surface based on the angle difference. The approach direction setting is corrected, and based on the corrected approach direction setting, control by the measurement control unit, calculation by the normal calculation unit, and re-execution of determination by the determination unit are instructed. The instructing unit instructs the measurement value to be calculated when the determining unit determines that the approach direction is appropriate.
The measurement value calculation means calculates the measurement value at the measurement point based on the relative displacement information from the scanning probe and the relative coordinate value information from the coordinate value detection means when the determination means determines that the approach direction is appropriate. Ask.

  Point measurement here refers to touch measurement using a scanning probe, that is, collecting coordinate value information of one point on the workpiece measurement surface when the stylus tip contactor is brought into contact with the workpiece measurement surface. Say. As an example of the timing of collecting the coordinate value information, for example, a point in time when a displacement amount from an encoder built in the scanning probe exceeds a threshold value, or a point in time when the scanning probe stops.

According to the workpiece measurement method (apparatus) according to the present invention, since the measurement, the determination, and the instruction are performed, the approach direction error of the scanning probe to the workpiece measurement surface can be reliably reduced. Therefore, it is possible to improve the accuracy of point measurement using the scanning probe.
Further, in the present invention, by performing the offset process in the appropriate approach direction obtained by the determination, the contact position between the workpiece measurement surface and the scanning probe can be accurately obtained, so that the measurement accuracy can be improved. Can be further planned.

Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of a workpiece measuring apparatus for performing a workpiece measuring method according to an embodiment of the present invention.
A workpiece measuring apparatus 10 shown in FIG. 1 includes, for example, a three-dimensional measuring machine, and includes a scanning probe 12, a moving unit 14, and a coordinate value detecting unit 16, and a workpiece measuring surface placed on a table 18. The X, Y, and Z coordinate values on 20 are point-measured by the scanning probe 12.
Therefore, in the present embodiment, the measurement control means 24 for causing the measurement apparatus main body 22 to perform the measurement process of the present invention, the normal calculation means 26 for performing the normal calculation process of the present invention, and the present invention. The determination means 28 for performing the determination process, the instruction means 30 for performing the instruction process of the present invention, and the measurement value calculation means 32 for performing the measurement value calculation process of the present invention are provided.

Here, the scanning probe 12 includes a probe main body 40, a stylus 42, and an encoder 44. The probe main body 40 is movable in the X, Y, and Z directions by the moving means 14. The stylus 42 has a contact ball (measuring element) 46 at its tip, and is held so as to be relatively displaceable in the X, Y, and Z directions with reference to a reference point 48 of the probe body 40. The encoder 44 outputs the displacement amount (Δx, Δy, Δz) of the stylus 42 with reference to the reference point 48 when the contact ball 46 and the workpiece measurement surface 20 come into contact with each other.
The moving means 14 makes the scanning probe 12 movable in the X, Y, and Z directions with respect to the workpiece measurement surface 20 on the table 18 in order to perform point measurement by the scanning probe 14.
The coordinate value detection means 16 outputs the coordinate values (x ₁ , y ₁ , z ₁ ) of the reference point 48 of the scanning probe 12 with respect to the workpiece measurement surface 20.

The measurement control unit 24 causes the measurement apparatus main body 22 to perform point measurement using the scanning probe 12. That is, the measurement control unit 24 controls the operation of the measurement apparatus main body 10 to cause the scanning probe 12 to approach the workpiece measurement surface 20 from the approach direction determined based on the setting value of the setting value storage unit 50. Then, when the contact ball 46 of the scanning probe 12 comes into contact with the workpiece measurement surface 20, the displacement amount (Δx, Δy, Δz) from the encoder 44 built in the scanning probe 12 and the coordinates built in the measuring apparatus main body 22. The coordinate values (x ₁ , y ₁ , z ₁ ) from the value detection means 16 are collected.
The normal calculation means 26 calculates the normal direction of the workpiece measurement surface 20 based on the displacement amounts (Δx, Δy, Δz) obtained by the measurement.
The determination unit 28 determines that the approach direction is inappropriate when the angle difference between the normal direction obtained by the normal calculation unit 26 and the approach direction based on the setting value of the setting value storage unit 50 is larger than the threshold value. To do. The determination unit 28 determines that the approach direction is appropriate when the angle difference is smaller than the threshold value. In the present embodiment, the determination unit 28 is based on the square sum square root SQRT (Δx × Δx + Δy × Δy + Δz × Δz) of each component included in the displacement amounts (Δx, Δy, Δz) from the scanning probe 12. The angle difference between the direction and the approach direction is estimated. In this embodiment, the square sum of squares is called an E value, and the E value is compared with a threshold value.

When the determination unit 28 determines that the approach direction is inappropriate, the instruction unit 30 moves to the workpiece measurement surface 20 of the scanning probe 12 based on the displacement amounts (Δx, Δy, Δz) when the normal direction is obtained. The setting value of the setting value storage means 50 is corrected so that the approach direction of the workpiece is the normal direction of the workpiece measurement surface 20, and the measurement by the measurement control means 24 is performed in the approach direction determined based on the corrected setting value. The process, the normal calculation process by the normal calculation means 26, and the re-execution of the determination process by the determination means 28 are instructed. The instruction unit 30 instructs the execution of the measurement value calculation step when the determination unit 28 determines that the approach direction is appropriate.
The measurement value calculation means 32 is based on the displacement (Δx, Δy, Δz) and the coordinate values (x ₁ , y ₁ , z ₁ ) when the determination means 28 determines that the approach direction is appropriate. The coordinate value (x ₂ , y ₂ , z ₂ ) of the center position of the contact sphere 46 with respect to 20 is obtained. Furthermore, the measurement value calculation means 32 is configured so that the contact sphere 46 moves in the approach direction when the approach direction is determined to be appropriate with respect to the coordinate values (x ₂ , y ₂ , z ₂ ) of the center position of the contact sphere 46. Offset processing for the radius is performed, and coordinate values (x ₃ , y ₃ , z ₃ ) of the contact position between the workpiece measurement surface 20 and the scanning probe 12 are obtained. From the obtained coordinate values (x ₃ , y ₃ , z ₃ ), the required hole diameter, hole position, step size, and other dimensions are obtained by data processing by the computer 52.

In the present embodiment, a positioning control means 54, a separation control means 56, and a posture polarization means 58 are provided.
Here, the positioning control means 54 is used to cause the measuring apparatus body 22 to perform a positioning process described later.
Further, the detachment control means 56 is for causing the measurement apparatus main body 22 to perform a detachment process described later.
The posture changing means 58 is for changing the posture of the scanning probe 12 so that the approach direction of the scanning probe 12 to the workpiece measurement surface 20 is the normal direction of the workpiece measurement surface 20. Based on the set value stored in the means 50, the attitude of the scanning probe 12 is determined. In the present embodiment, the setting value stored in the setting value storage means 50 is corrected by an instruction from the instruction means 30 when the determination means 28 determines that the approach direction is inappropriate. The posture changing unit 58 sets the approach direction of the scanning probe 12 based on the set value of the set value storage unit 50.

The workpiece measuring apparatus 10 according to the present embodiment is configured as described above, and the operation thereof will be described below.
In this embodiment, the approach direction of the scanning probe to the workpiece measurement surface and the normal direction of the workpiece measurement surface are based on the stylus displacement obtained from one point when the scanning probe is brought into contact with the workpiece measurement surface. The angle difference can be estimated. The approach direction to the workpiece measurement surface is corrected by repeating the above steps so that this angle difference is less than or equal to a threshold value determined based on the desired measurement accuracy, so that the probe direction is sufficiently corrected. By calculating the measurement value at the measurement point, a highly accurate measurement value can be obtained.
In the present embodiment, even if the approach direction initially determined is not very accurate, the approach value of the scanning probe is automatically corrected and the measurement value is calculated. Point measurement from the normal direction of the workpiece measurement surface can be performed very easily and reliably.

That is, in this embodiment, as shown in FIG. 2, a positioning step (S10), a measurement step (S12), a separation step (S14), a normal calculation step (S16), and a determination step (S18). And an instruction step (S20) and a measurement value calculation step (S22).
That is, in the positioning step (S10), the scanning probe is moved by the moving means so that the reference point of the scanning probe coincides with a preset approach start position, and the approach angle of the scanning probe by the moving means or posture changing means. Is set.
In the measurement step (S12), the contact ball of the scanning probe is brought into contact with the workpiece measurement surface to perform point measurement. That is, in the measurement step (S12), when the scanning probe approaches the workpiece measurement surface from the approach start position from a preset approach direction, and the scanning probe contacts the workpiece measurement surface, the displacement amount from the scanning probe (Δx, Δy, Δz) and coordinate values (x ₃ , y ₃ , z ₃ ) from the coordinate value detecting means are collected. When the contact ball comes into contact with the workpiece, the encoder outputs a stylus displacement amount (Δx, Δy, Δz) with respect to the probe body.
In the separation step (S14), after the measurement step (S12) is completed, the scanning probe is returned so that the contact ball is separated from the workpiece measurement surface and the reference point of the scanning probe coincides with the approach start position.

In the normal calculation step (S16), the normal direction of the workpiece measurement surface is calculated based on the displacement amounts (Δx, Δy, Δz) obtained in the measurement step (S12).
In the determination step (S18), based on the angular difference between the normal direction obtained in the normal calculation step (S16) and the approach direction in the measurement step (S12), that is, based on the displacements (Δx, Δy, Δz). When the E value is larger than the threshold value, it is determined that the approach direction in the measurement step (S12) is inappropriate. In the determination step (S18), when the E value based on the displacement (Δx, Δy, Δz) is smaller than the threshold value, it is determined that the approach direction in the measurement step (S12) is appropriate. As a result, during the point measurement by the scanning probe, based on the displacement amount (Δx, Δy, Δz) from the encoder built in the scanning probe, the normal direction of the workpiece measurement surface or the slip between the workpiece measurement surface and the contact ball The presence or absence can be grasped.

  In the instruction step (S20), when the approach direction is determined to be inappropriate in the determination step (S18), the workpiece measurement of the scanning probe is performed based on the displacement amounts (Δx, Δy, Δz) used for calculating the normal direction. The setting value of the setting value storage means is corrected so that the approach direction to the surface is the normal direction of the workpiece measurement surface, and the approach direction setting is corrected based on the corrected setting value. Is instructed to re-execute the positioning step (S10), the measuring step (S12), the leaving step (S14), the normal calculation step (S16), and the determining step (S18). As a result, the workpiece measuring apparatus 10 according to the present embodiment repeats each process for the workpiece measurement surface until the determination unit (S18) determines that the approach direction is appropriate. In the instruction step (S20), if the approach direction is determined to be appropriate in the determination step (S18), execution of the subsequent measurement value calculation step (S22) is instructed.

In the measurement value calculation step (S22), the contact ball is based on the displacement amounts (Δx, Δy, Δz) and the coordinate values (x ₁ , y ₁ , z ₁ ) for which the approach direction is determined to be appropriate in the determination step (S18). The coordinate values (x ₂ , y ₂ , z ₂ ) of the center position of are obtained. In the measurement value calculation step (S22), the coordinate value (x ₂ , y ₂ , z ₂ ) of the center position of the contact sphere is further offset by the contact sphere radius in an appropriate approach direction, The coordinate values (x ₃ , y ₃ , z ₃ ) of the contact position with the scanning probe can be obtained.

As described above, according to this embodiment, the point measurement function of the scanning probe is used to measure the point by bringing the contact ball into contact with the workpiece measurement surface, and then the displacement amount from the scanning probe is compared with the threshold value. When the value exceeds the threshold value, the setting of the approach direction of the scanning probe is corrected based on the amount of displacement, and point measurement on the workpiece measurement surface is performed again.
As a result, in the present embodiment, the approach direction of the scanning probe is automatically corrected even if the approach direction initially determined is not very accurate. Therefore, compared with the conventional method, it is extremely simple and reliable. Point measurement from the normal direction of the workpiece measurement surface can be performed.

By the way, although point measurement with a scanning probe can be considered in the past, the following problems have been clarified.
(1) Approach direction In other words, in the conventional method, since the position or inclination of the workpiece measurement surface is unknown, it is necessary to measure three points with an approximate register, so the scanning probe is accurately in the normal direction of the workpiece measurement surface. Is difficult to approach.
(2) Normal line direction In the conventional method, the normal line direction may be different between a virtual workpiece measurement surface determined by three-point measurement and a workpiece measurement surface to be actually subjected to point measurement.
(3) Offset processing In the conventional method, since the approach direction and the normal direction of the actual workpiece measurement surface may be different, the coordinate position of the contact sphere center position is used to determine the contact position between the workpiece measurement surface and the scanning probe. When the offset processing for the radius of the contact sphere is performed, an error also occurs in the offset processing direction, so that an accurate contact position cannot be obtained.
(4) Slip In the conventional method, slipping of the contact ball may occur during point measurement, which causes a deviation between the position where the point measurement is desired (for example, the XY position) and the actual measurement position. The height at the desired position (for example, the Z position) cannot be obtained accurately.

On the other hand, in this embodiment, the said problem can be solved reliably.
(1) Approach direction In other words, in this embodiment, even if the approach direction initially determined is not very accurate, the approach direction of the scanning probe is automatically corrected by repeating the above steps. It becomes easy to approach the probe more accurately in the normal direction of the workpiece measurement surface.
(2) Normal line direction In this embodiment, since the normal line direction of the workpiece measurement surface is estimated, the stylus displacement amount for one point when the contact ball contacts the workpiece measurement surface is used. Compared with a method, that is, a method for obtaining a normal direction from a virtual workpiece measurement surface determined by three-point measurement, it is possible to accurately grasp the normal direction of the workpiece measurement surface to be actually measured.
(3) Offset processing In this embodiment, even if the approach direction initially determined is not very accurate as described above, the approach direction of the scanning probe is automatically corrected by repeating the above steps. Thus, the approach direction and the normal direction of the actual workpiece measurement surface can be matched more accurately. For this reason, since the direction of the offset process can also be determined accurately, the contact position between the workpiece measurement surface and the scanning probe can be determined more accurately.
(4) Slip In this embodiment, the approach direction of the scanning probe is automatically corrected to the normal direction by repeating the above steps even if the approach direction initially determined is not very accurate as described above. Therefore, the contact ball can be brought into contact with the workpiece measurement surface from a more accurate normal direction. Thereby, since the sliding of the contact ball can be surely reduced at the time of point measurement, the height (for example, Z position) at the position where the point measurement is desired can be accurately obtained.
Furthermore, in the conventional method, since the workpiece measurement surface is treated as a flat surface, it is difficult to accurately measure a workpiece measurement surface that is not actually a flat surface, whereas this embodiment is in contact with the workpiece measurement surface. Since the stylus displacement amount for one point when the sphere is in contact is used, even if the actual workpiece measurement surface is other than a flat surface, it can be measured accurately.

Hereinafter, a case where the height in the Z direction of a workpiece measurement surface substantially parallel to the XY plane is measured using this embodiment will be described with reference to FIG.
In the figure, since it is assumed that the workpiece measurement surface is substantially parallel to the XY plane, the normal direction 66 of the workpiece measurement surface 20 is determined in the Z direction.
First, in the positioning step (S10) as shown in FIG. 9A, the scanning probe 12 is positioned so that the reference point 48 matches the initial value (set value) 60 of the approach start position. Then, when the scanning probe 12 is approached from the Z direction with respect to the workpiece measurement surface 20 as shown in FIG. 5B, the scanning probe 12 contacts the workpiece measurement surface 20 as shown in FIG. The ball 46 comes into contact. At that time, the contact ball 46 slides as shown in FIG. 5C due to the step of the workpiece measurement surface 20, and stops at the contact position 62. This is the amount of displacement (Δx, Δy) from the scanning probe 12. Can be grasped by collecting In the figure, an E value based on the displacement amount (Δx, Δy) of the contact sphere 46, that is, SQRT (Δx × Δx + Δy × Δy) is calculated, whereby the approach direction 64 and the Z direction (normal direction 66) are calculated. The angle difference can be grasped.

Here, when the E value is equal to or greater than the threshold value of 0.01 mm, separation and positioning as shown in FIG. That is, in the same figure, after the scanning probe 12 is returned from the workpiece measurement surface 20 in FIG. 1C to the approach start position 60 in FIG. 1A, the approach start position 60 is moved by the displacement (Δx, Only Δy) is corrected. This is set as a set value 60 '. Accordingly, in the same figure, the posture of the scanning probe 12 can be corrected by using the moving means so that the approach direction 64 of the scanning probe 12 to the workpiece measurement surface 20 is the Z direction of the workpiece measurement surface 20. . For example, when the approach distance between the contact sphere 35 and the workpiece measurement surface 20 is 5 mm, if the threshold is 0.01 mm, the angle difference θ = tan ⁻¹ (0.01 / 5) = 0. 11 °. After the approach direction is corrected, the point measurement is re-executed as shown in FIG. In FIG. 9E, the approach direction 64 exactly matches the Z direction without causing the sliding of the contact sphere 46 as shown in FIG. In such a state, since the E value is less than the threshold value of 0.01 mm, the point measurement is terminated and the measurement value is calculated.
According to the present embodiment, even in the point measurement on the workpiece measurement surface as shown in the figure, the approach direction and the normal direction are based on the stylus displacement amount for one point when the scanning probe is brought into contact with the workpiece measurement surface. Since the angle difference from the Z direction is estimated and each step is repeated so that the angle difference is equal to or less than the threshold value, the point measurement from the normal direction can be reliably performed.

In the above configuration, the example in which the height measurement in the Z direction is performed on the assumption that the workpiece measurement surface substantially coincides with the XY plane has been described, but the present invention is not limited to this, and the approach direction Is preferably applied in any direction, for example, the direction shown in FIG.
In the workpiece measurement surface as shown in the figure, the first approach direction can be obtained from, for example, CAD data, etc., so that it can be substantially normal to the workpiece measurement surface. After the first point measurement is completed, the normal direction of the workpiece measurement surface or the presence or absence of slippage of the contact ball is grasped based on the displacements (Δx, Δy, Δz) from the scanning probe obtained at the point measurement. can do. By correcting the approach direction from the obtained angle difference between the normal direction and the approach direction, and performing point measurement again, the point measurement from the normal direction can be accurately performed. If there is an angle difference in the second point measurement, correction and point measurement are repeated.

That is, as shown in FIG. 6A, the scanning probe 12 is approached from the first approach direction 64 with respect to the workpiece measurement surface 20. As shown in FIG. 5B, even if a slip occurs between the contact ball 46 and the workpiece measurement surface 20 when the scanning probe 12 comes into contact with the workpiece measurement surface 20, the amount of displacement from the scanning probe 12 Based on (Δx, Δy, Δz), the normal direction 66 can be obtained. The normal direction 66 is obtained from, for example, an XZ in-plane angle θ _xz = tan ⁻¹ (Δz / Δx) and an XY in-plane angle θ _xy = tan ⁻¹ (Δy / Δx). When the angle difference between the obtained normal direction 66 and the approach direction 64 in FIG. 5B is larger than the threshold value, the approach to the workpiece measurement surface 20 is based on the displacement amount (Δx, Δy, Δz). The posture of the scanning probe 12 is corrected by the posture changing means so that the direction 64 becomes a normal direction 66 as shown in FIG. After the posture changing means corrects the posture of the scanning probe 12, it instructs the re-execution of point measurement as shown in FIG. In FIG. 4D, since the approach direction 64 coincides with the normal direction 66, the point measurement can be performed without causing the contact sphere 46 to slip in FIG.
According to the present embodiment, even in the measurement of the workpiece measurement surface as shown in the figure, the approach direction and the normal line are based on the stylus displacement obtained from one point when the scanning probe is brought into contact with the workpiece measurement surface. Since the angle difference with the direction is estimated and each step is repeated so that the angle difference is equal to or less than the threshold value, the point measurement from the normal direction can be reliably performed.
Note that it is also preferable to provide a limit value when correcting the approach direction, so that unnecessary correction and measurement can be prevented.

As described above, in the present embodiment, since the point measurement by the scanning probe can be more reliably approached from the normal direction of the workpiece measurement surface, high accuracy can be achieved.
In this embodiment, the contact position between the workpiece measurement surface and the contact sphere is highly accurate by performing offset processing for the contact sphere radius in the appropriate approach direction with respect to the coordinate value of the center position of the contact sphere. Can also be calculated.
Furthermore, in the present embodiment, even if the workpiece measurement surface is a curved surface such as a sphere, the scanning probe can be approached accurately toward the center of the sphere, so that the measurement can be performed accurately. .

It is explanatory drawing of schematic structure of the workpiece | work measuring apparatus concerning one Embodiment of this invention. It is a flowchart which shows the process sequence of the workpiece | work measuring method concerning one Embodiment of this invention. It is explanatory drawing of an effect | action of the workpiece | work measuring method concerning one Embodiment of this invention. It is explanatory drawing at the time of applying the workpiece | work measuring method concerning one Embodiment of this invention to the workpiece | work measurement surface different from what was shown in the said FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Work measuring apparatus 12 Copy probe 14 Moving means 16 Relative coordinate value detection means 24 Measurement control means 26 Normal calculation means 28 Determination means 30 Instruction means 32 Measurement value calculation means 58 Posture change means

Claims (4)

A probe that has a probe at the tip of a stylus that can be displaced relative to the reference point of the probe body, and outputs information on the relative displacement of the stylus relative to the reference point when the probe contacts the workpiece measurement surface. In order to perform point measurement with the probe and the scanning probe, a moving unit that performs relative movement between the workpiece and the scanning probe, and a coordinate value detection unit that outputs relative coordinate value information of the scanning probe with respect to the workpiece are provided. In a workpiece measurement method for measuring points using the scanning probe using a workpiece measurement device,
A measurement step of collecting relative displacement amount information from the scanning probe and relative coordinate value information from the coordinate value detection means when the scanning probe is brought into contact with a workpiece measurement surface from a preset approach direction. When,
A normal calculation step of calculating a normal direction of the workpiece measurement surface based on the relative displacement information obtained in the measurement step;
When the angle difference between the normal direction obtained in the normal calculation step and the approach direction is larger than a threshold, the approach direction is determined to be inappropriate, and when the angle difference is smaller than the threshold A determination step of determining that the approach direction is appropriate;
If the approach direction is determined to be inappropriate in the determination step, the approach direction is set based on the angle difference so that the approach direction of the scanning probe to the workpiece measurement surface is the normal direction of the workpiece measurement surface. And instructing re-execution of the measurement step, the normal calculation step, and the determination step based on the setting of the corrected approach direction, and when the approach direction is determined to be appropriate in the determination step An instruction process for instructing the calculation of the measured value;
Based on the relative displacement amount information and relative coordinate value information when the approach direction is determined to be appropriate in the determination step, a measurement value calculation step for obtaining a measurement value of the measurement point;
A workpiece measuring method characterized by comprising: The work measuring method according to claim 1,
The determination step estimates the angular difference between the normal direction and the approach direction based on relative displacement amount information from the scanning probe obtained in the measurement step. In the work measuring method according to claim 1 or 2,
The measurement value calculation step obtains a coordinate value of the probe center position as a measurement value of the measurement point, and further approaches the coordinate value of the probe center position when the approach direction is determined to be appropriate. A workpiece measurement method, wherein an offset process is performed in the direction according to the size of the probe to obtain a coordinate value of a contact position between the workpiece measurement surface and the scanning probe. A scanning probe that has a probe at the tip of a stylus that can be displaced relative to a reference point of the probe body, and outputs information on the relative displacement of the stylus with respect to the reference point when the probe contacts the workpiece measurement surface; A moving means for performing a relative movement between the workpiece and the scanning probe and a coordinate value detecting means for outputting relative coordinate value information of the scanning probe with respect to the workpiece in order to perform point measurement by the scanning probe. In a workpiece measuring device that performs point measurement with a probe,
When controlling the operation of the workpiece measuring apparatus and bringing the scanning probe into contact with the workpiece measurement surface from a preset approach direction, the relative displacement amount information from the scanning probe and the coordinate value detection means Measurement control means for collecting relative coordinate value information;
Based on the relative displacement information obtained by the measurement, normal calculation means for calculating the normal direction of the workpiece measurement surface;
If the angle difference between the normal direction obtained by the normal calculation means and the approach direction based on the set value is larger than a threshold value, the approach direction is determined to be inappropriate, and the angle difference is smaller than the threshold value. A determination means for determining that the approach direction is appropriate if small,
When the determination unit determines that the approach direction is inappropriate, the approach direction setting is corrected so that the approach direction of the scanning probe to the workpiece measurement surface is a normal direction based on the angle difference, Based on the setting of the corrected approach direction, the control by the measurement control unit, the normal calculation by the normal calculation unit, and the re-execution of the determination by the determination unit are instructed, and the determination unit determines that the approach direction is appropriate. If so, instruction means for instructing the calculation of the measured value;
Based on the relative displacement amount information and the relative coordinate value information when the approach direction is determined to be appropriate by the determination means, a measurement value calculation means for obtaining a measurement value of the measurement point;
A workpiece measuring apparatus comprising:

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