JPH01202611A - Three-dimensional measurement method and apparatus - Google Patents

Abstract

PURPOSE:To enable accurate correction of measuring errors attributed to a lobing characteristic of a probe, by detecting the lobing characteristic in terms of a measuring direction actually measuring a division area of a reference ball from a normal to correct a measured value. CONSTITUTION:A reference ball measuring mechanism 156 divides the surface of a reference ball 150 having a specified diameter and a sufficient sphericity into specified areas and brings a touch signal probe 122 into contact with the surface from a normal of the areas to obtain a measurement signal. Then, a corrected value computing mechanism 158 determines a vertical spherical shape of the reference ball 150 from the measured value obtained by the mechanism 156 to be projected to a reference spherical shape so that a deviation is determined between the virtual spherical shape and the reference spherical shape to be stored corresponding to the divided surface as correction value. Then, a measured value correction mechanism 160 brings the probe 122 into contact with the measuring surface of work 124 roughly from a normal to detect position coordinates and a direction of movement at a contact point and a division area of the reference ball 150 in which the direction of movement almost coincides with the direction of measurement is selected. Thus, a correction value corresponding to the division area is read out to correct position coordinates.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in three-dimensional measurement methods and apparatus, particularly methods and apparatus using touch signal probes.

[Prior Art] A three-dimensional measuring device is well known for measuring the three-dimensional shape of an object to be measured, and is used in various fields to inspect the processing state of an object to be measured.

Such a three-dimensional measuring device is generally configured as shown in FIG.

The three-dimensional measuring device shown in the figure consists of a table 12 provided on a bed 10, and pillars 1 erected on both sides of the table.
4.16, an X beam 18 supported by the support column 14.16 so as to be slidable in the Y-axis direction, a slider supported by the X-beam 18 so as to be slidable in the X-axis direction, and an A Z-axis spindle 20 is slidably supported in the axial direction.

A touch signal probe 22 is installed at the lower end of the Z-axis spindle 20 .

In step 1, the touch signal probe 22 is brought into contact with the workpiece 24 placed on the table 2 based on the manual information from the keyboard 23, and the position coordinates detected by the contact signal generated are detected by the microcomputer. 26 performs arithmetic processing and outputs the dimensions of the workpiece etc. to a printer or the like.

By the way, the measurement error of such a three-dimensional measuring device is caused by the accuracy of the measuring device itself and the probe detection accuracy.
Conventionally, the accuracy of the main body due to deflection of the spindle of the measuring device, etc. has been lower than the detection accuracy of the probe, and the factors on the probe side have been allowed from the accuracy balance of each factor.

However, due to the recent demand for high-precision measurement, highly rigid and highly accurate structures and effective correction methods are being established for factors on the measuring device main body side, and the accuracy of the measuring device main body is improving.

On the other hand, factors on the probe side include various improvements in roving characteristics, such as supporting the contact with a disk, increasing the number of support points for the contact, and using a piezoelectric element as a means of detecting the displacement of the contact. has been done.

This roving characteristic is a measurement error that occurs differently depending on the direction in which the probe contacts the workpiece. For example, when the contact at the tip of the probe is supported at three points, the contact moves in the direction of the support points and the workpiece is moved. There is a difference in the measuring force generated between the contact and the workpiece when the contactor touches the workpiece, and when the contactor moves in the middle direction between each support point and contacts the workpiece, causing deflection of the contactor or dead amount. Errors occur due to differences in the numbers.

[Problems to be Solved by the Invention] / 18 However, in the past, no sufficient solution to this roving characteristic (directivity) has been made yet.

In other words, such a conventional touch signal probe with improved structure requires a complicated and precise probe structure, which is expensive, and it is difficult to sufficiently improve the roving characteristics in the three-dimensional direction. Not quite yet.

The present invention was made in view of the problems of the prior art, and its purpose is to provide a three-dimensional measuring method and apparatus that are easy to handle and that can accurately correct the roving characteristics of a probe. It is about providing.

[Means for Solving the Problems] In order to achieve the above object, a three-dimensional measurement method according to the present invention includes a reference sphere measurement step, a correction value calculation step, and a measured value correction step.

In the reference sphere measurement step, the surface of the reference sphere having a predetermined diameter and sufficient sphericity is divided into a plurality of predetermined regions, and a touch signal probe is brought into contact with each divided region from the normal direction to obtain a measurement signal. get.

The correction value calculation step calculates a virtual spherical shape of the reference sphere from the measured values obtained in the reference sphere measurement step, projects the virtual spherical shape onto the reference spherical shape, and calculates the virtual spherical shape and the reference spherical shape. The deviation is determined, and this deviation is stored as a correction value corresponding to the divided surface.

In the correction value calculation step, a touch signal probe is brought into contact with the workpiece measurement surface from a substantially normal direction, the position coordinates and movement direction at this contact point are detected, and from this movement direction, the reference sphere whose measurement direction substantially coincides with the touch signal probe is detected. A divided area is selected, a correction value corresponding to this divided area is read out, and the position coordinates are corrected.

In addition, in the correction value calculation step, it is preferable to also correct and store correction values for errors caused by the measuring instrument main body.

Further, the three-dimensional measuring device according to the present invention includes a touch signal probe, a probe driving mechanism, a coordinate reading mechanism,
It includes a reference sphere, a reference sphere measurement mechanism, a correction value calculation mechanism, and a measured value correction mechanism.

The reference sphere has a predetermined diameter and sufficient sphericity.

The reference sphere measuring mechanism divides the reference sphere into a plurality of predetermined regions, brings a probe into contact with a representative point of the divided regions, and reads the coordinates thereof.

The correction value calculating mechanism calculates a virtual shape of a reference sphere from the measurement value obtained by the reference sphere measuring mechanism, projects the virtual sphere shape onto the reference sphere shape, and calculates the deviation between the virtual sphere shape and the reference sphere shape. is determined, and this deviation is stored as a correction value corresponding to the divided surface.

The measurement value correction mechanism brings the touch signal probe into contact with the workpiece measurement surface from a substantially normal direction, detects the position coordinates and movement direction at this contact point, and detects the position coordinates and movement direction of the reference sphere from this movement direction, with which the measurement direction substantially coincides. A divided area is selected, a correction value corresponding to this divided area is read out, and the position coordinates are corrected.

In the present invention, it is preferable that the correction value calculation mechanism also corrects and stores errors caused by the measuring instrument itself.

[Operation] Since the three-dimensional measuring method and measuring device according to the present invention have the above-described means, the reference sphere on the table is divided into predetermined divided regions, and the probe moving mechanism is used to place the probe at the representative point of each divided region. It is moved and brought into contact in the normal direction, and the coordinates of the representative point of each divided area are read by the coordinate reading mechanism.

Then, the virtual shape of the reference sphere calculated from the coordinates of the representative point and the actual shape of the reference sphere are compared, and the deviation thereof is used as a correction value for the roving characteristic.

Therefore, it is possible to obtain correction values corresponding to the roving characteristics for each direction of movement of the probe in three-dimensional directions.

In addition, by taking into account the correction value for errors originating from the measuring device itself at the stage of calculating the correction value, it is possible to eliminate the interference of the main body correction with the correction of the roving characteristics, making it possible to perform more accurate measurements. can.

As described above, according to the present invention, it is possible to obtain the optimum correction amount depending on the position coordinates and movement direction for each measurement, and it is possible to appropriately correct the roving characteristics that differ depending on the individual probe etc. .

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 schematically shows the main configuration of a three-dimensional measuring device according to an embodiment of the present invention. Note that parts corresponding to those in the prior art described above are indicated by the reference numeral 100, and their explanation will be omitted.

The three-dimensional measuring device according to this embodiment is intended to remove the influence of roving characteristics by installing a reference sphere 150 on the table 112 and measuring the reference sphere 150 before measuring the workpiece 124. .

That is, the device shown in the figure has a probe drive mechanism 152.
, a coordinate reading mechanism 154 , and a reference sphere measuring mechanism 156
, a correction value calculation mechanism 158 , and a measurement value correction mechanism 160 .

The probe drive mechanism 152 includes drive motors 1 installed on the pillar, X beam, and slider of the measuring instrument.
62 to move the touch signal probe 122 to a predetermined position.

The coordinate reading mechanism 154 also includes an encoder 164 provided on the support, X beam, and slider of the measuring instrument.
The amount of movement of the probe is read for each of the X, Y, and Z axes, and the (X, Y, Z) coordinates of the probe 122 are output.

The reference sphere measuring mechanism 156 includes a temporary center coordinate calculation section 166, a divided area calculation section 16, and a direction signal calculation section 170.

Then, the temporary center coordinate calculating section calculates a reference sphere 1 having a predetermined radius R.
The tentative center coordinates of the reference sphere 150 are calculated from the coordinate values obtained by touching the probe 122 at three points on the reference sphere 150.

The divided area calculation unit 168 divides the reference sphere 150 specified from the temporary center coordinates and radius R of the reference sphere 150 into a predetermined number of divided areas.

The direction signal calculation unit 170 determines a representative point of each of the divided regions, and calculates a direction signal so as to bring the blow 1122 into contact with the representative point from the direction normal to the representative point.

Then, the direction signal is manually applied to the probe driving mechanism 152 to bring the probe 122 into contact with each representative point of the reference sphere 150, and the coordinate reading mechanism 154 reads the coordinates of each representative point.

The correction value calculation mechanism 15B includes a center coordinate calculation section 172, a representative point position calculation section 174. It consists of a correction value calculation section 176 and a correction value storage section 178.

The center coordinate calculation unit 172 statistically calculates the center coordinates of the reference sphere 150 from the coordinates of each representative point of the reference sphere 150.

The representative point position calculation unit 174 calculates the separation distance r of each representative point from the center.

The correction value calculation section 176 compares the radius R of the reference sphere 150 and the separation distance r of each representative point from the center, and stores the difference in the correction value storage section 178 as a correction value for the divided area.

On the other hand, the measured value correction mechanism 160
．． Correction value reading unit 182. It consists of a measured value correction section 184.

Then, the moving direction determining unit 180 determines the moving direction of the probe 122 when the probe 122 actually measures the workpiece 124 .

The correction value reading unit 182 selects a divided area in a direction that substantially coincides with the probe moving direction, and reads out a correction value corresponding to the divided area from the correction value storage unit 178.

Then, the measured value correction unit 184 corrects the measured coordinates of the workpiece using the read correction value and outputs the corrected value.

In this embodiment, each mechanism is controlled by the control unit 186, initial data is input via the keyboard 18B, and corrected measurement coordinates are input to the control unit 186.
6 to an output device 190 such as a display or printer.

The three-dimensional measuring device according to this embodiment is roughly configured as described above, and its operation will be explained below.

First, the measurer inputs the radius R of the reference sphere 150 from the keyboard, and then moves the probe 122 to form the reference sphere 150.
0 at three points. Note that since the radius R is fixed, the reference sphere 150 can be specified by three-point measurement.

Then, the tentative center coordinate calculation unit 166 calculates the coordinates (x o') of the tentative center 09 of the specified reference sphere 150.

yo', zo') and set the reference point (0, 0, 0)
shall be.

Next, as shown in FIG.
8, the reference sphere 150 is divided into a predetermined number.

That is, the reference sphere 150 is moved at a predetermined pitch θl in the longitude and latitude directions, respectively, using the xZ plane and the XY plane in the coordinate system of the three-dimensional measuring machine body as references.

When dividing by φ1, the coordinates of each division boundary point projected onto the spherical surface are obtained as a spherical coordinate vector (θC9φj)R.

Now, considering each divided region of the spherical surface, its fine surface is divided into four adjacent vectors (θ1.φJ) Rt (θi+1.φj)R, (
θi, φJ”l) Re (θi+1.φj+1)
R, and in this embodiment, the direction signal calculation unit 1
70, the representative point vector (θ10°φjO) is calculated from the four vectors using the center point of each microscopic surface as the representative point.
Find R.

(θi0. φjO) R Then, as shown in FIG. 4, the direction signal calculation unit 170 uses this representative point vector to calculate the direction signal ( 1,
m, n).

1=-RcosφjOcosθ10 m=-Rcosφjosinθ10 n=-RsinφjO This direction signal is sequentially input to the probe drive mechanism 152, and the probe drive mechanism 152 automatically determines the representative point of each divided area of the reference sphere 150 according to the direction signal. Measure.

Then, when the coordinates of each representative point of the reference sphere 150 are read by the coordinate reading mechanism 154, the representative point coordinate signal is input to the center coordinate calculating section 172.

The center coordinate calculation unit 172 calculates the coordinates (Xo, yO9zO) of the center O of the reference sphere 150 by statistical calculation.

Then, the coordinates (xi, yi, zi
) is corrected to the value from the coordinates of the center O, and the separation distance r from the center coordinates of each measured value is determined.

At this stage, a virtual shape of the reference sphere including errors due to roving characteristics is obtained.

Then, by comparing the virtual shape and the actual shape of the reference sphere, the error due to the roving characteristic can be obtained.

Therefore, the reference sphere radius R is subtracted from the separation distance r from the center coordinates of each representative point, and the value is set as the correction value N1j=r−R corresponding to each divided area, and the correction value as shown in FIG. 5 is calculated. It is stored on the memory table of the storage unit 178.

After the correction amount of the roving characteristic for each moving direction of the probe 122 is determined as described above, the actual workpiece 12
4 measurements are taken.

That is, the probe 122 moves under predetermined control from the control unit 186, and when it comes into contact with the workpiece 124, the coordinate reading mechanism 154 reads the contact position coordinates.

Note that the movement of the probe is programmed in advance so that it contacts the workpiece 124 at a desired contact point from a substantially normal direction of the workpiece surface.

The coordinate signals output from the coordinate reading mechanism 154 are input to the moving direction determining section 180 and the measured value correcting section 184 of the measured value correcting mechanism 160.

The moving direction determining unit 180 detects the moving direction (bi, m', n') of the probe 122, and converts this moving direction into polar coordinate direction components (θ9, φ') as shown in FIG. .

φ') is compared with the direction component (θ1.φj) of the divided area of the table stored in the correction value storage section 178, a divided area that closely matches is selected, and its correction amount is read out.

The correction value is manually input to the measurement value correction section 184, and the measurement value is corrected and then output.

Then, the control unit 186 displays the corrected measurement value on the output device 190.

As described above, according to the three-dimensional measuring apparatus according to the present embodiment, it is possible to accurately correct the roving characteristics that differ depending on the contact direction of the probe 122 with the workpiece 124.

Note that in this example, the error in the measuring machine body was determined to depend on inspection by other means, but in the present invention, it is also suitable to correct the body error in addition to correcting the roving characteristics. be.

That is, although errors occur in the measuring instrument body due to, for example, deflection of the spindle, these errors are corrected by so-called spatial multi-point correction.

In this spatial multi-point correction, for example, a movable reflector is installed at a position where a probe is attached, and a laser oscillator is placed on another fixed point to face the movable reflector.

Then, the beam from the laser oscillator is separated by a beam splitter, the laser beam is irradiated to both the fixed reflector provided at the reference position and the movable reflector, and the relative positions of the fixed reflector and the movable reflector are determined by interference of the reflected light. Detect the person in charge.

Furthermore, by reading the difference between the distance output from the laser interferometer and the displacement output from the three-dimensional measuring device, it is possible to measure the error in the measuring device itself.

Therefore, in the present invention, as shown in FIG.
By inputting the error of the measuring device main body into the correction value calculation section 176 and storing it in the correction value storage section 17B,
It becomes possible to perform correction with extremely high precision.

In other words, according to this embodiment, a pure roving characteristic correction value can be obtained with the main body side error removed from the reference ball measurement value, and interference of the main body side correction value can be avoided in actual workpiece measurement, resulting in higher accuracy. Accuracy measurements can then be obtained.

[Effects of the Invention] Since the present invention is configured as described above, the following effects are achieved.

According to the three-dimensional measurement method according to claim 1, the divided regions of the reference sphere are actually measured from the normal direction thereof, the roving characteristics are detected in each measurement direction, and the measured values are corrected. Measurement errors based on the roving characteristics of the probe can be accurately corrected.

According to the three-dimensional measurement method according to claim 2, since the measurement error caused by the main body side that is measured separately is also corrected, the roving characteristics can be corrected while the interference of the main body side error is removed. It becomes possible to do this.

According to the three-dimensional measuring device according to claim 3, a reference sphere;
Equipped with a reference sphere measurement mechanism that measures each divided area of the reference sphere and a correction value calculation mechanism that calculates a roving characteristic correction value based on the measurement results, high accuracy is achieved while eliminating errors caused by the probe's roving characteristics. can be measured.

According to the three-dimensional measuring device according to claim 4, the measurement value calculation mechanism also calculates and stores the error of the main body.
The roving characteristics can be corrected while eliminating the interference of main body errors, making it possible to perform more accurate measurements.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of the main parts of the three-dimensional measuring device according to the present invention, FIG. 2 is an explanatory diagram of a reference sphere used in the device shown in FIG. 1, and FIG. FIG. 4 is an explanatory diagram showing the calculation state of the direction signal when the probe moves. FIG. 5 is an explanatory diagram of the storage table of the correction value storage unit. , - is an external perspective view of a three-dimensional measuring device for boat fishing. 12.112 ... Table 22.122 ... Touch signal probe 24.
124... Work 150... Reference sphere 152... Probe drive mechanism 154
... Coordinate reading mechanism 156 ...
- Reference sphere measurement mechanism 15B... Correction value calculation mechanism 160... Measured value correction mechanism Fig. 2, Fig. 5, Fig. 6

Claims (4)

[Claims] (1) In a three-dimensional measuring device that brings a touch signal probe into contact with a workpiece and obtains the three-dimensional coordinates of the contact position between the workpiece and the probe using the touch signal emitted from the probe, a standard having a predetermined diameter and sufficient sphericity. a reference sphere measuring step of dividing the surface of the sphere into a plurality of predetermined regions and contacting each divided region with a touch signal probe from the normal direction to obtain a measurement signal; and a measurement value obtained in the reference sphere measuring step. Find a virtual shape of a reference sphere from , project the virtual sphere shape onto the reference sphere shape,
a correction value calculation step of determining a deviation between the virtual spherical shape and the reference spherical shape and further storing this deviation as a correction value corresponding to the dividing surface; and contacting a touch signal probe from a substantially normal direction to the workpiece measurement surface. Detect the position coordinates and movement direction at the contact point, select a divided area of the reference sphere whose measurement direction substantially coincides from this movement direction, read the correction value corresponding to this divided area, and calculate the position coordinates. A three-dimensional measurement method comprising: a measured value correction step for correcting; and a three-dimensional measurement method. (2) A three-dimensional measuring method according to claim (1), characterized in that in the correction value calculation step, correction values for errors caused by the measuring machine body are also corrected and stored. (3) A touch signal probe that is supported movably in three dimensions and that emits a touch signal upon contact with a workpiece on a table; a probe moving mechanism that moves the touch signal probe in a predetermined direction; and a touch signal that is emitted from the probe. A coordinate reading mechanism for reading the positional coordinates of the contact point between the probe and the workpiece based on the above, and a three-dimensional measuring device equipped with the following: a reference sphere having a predetermined diameter and sufficient sphericity; A reference sphere measuring mechanism that divides the divided areas into a plurality of areas and reads the coordinates of the divided areas by contacting a probe with a representative point thereof; A virtual shape of the reference sphere is determined from the measurement values obtained by the reference sphere measuring mechanism; Projecting the shape onto the reference spherical shape,
a correction value calculation mechanism that calculates a deviation between the virtual spherical shape and the reference spherical shape and further stores this deviation as a correction value corresponding to the divided surface; and a touch signal probe that contacts the workpiece measurement surface from a substantially normal direction. Detect the position coordinates and movement direction at this contact point, select a divided area of the reference sphere whose measurement direction substantially coincides with this movement direction, read the correction value corresponding to this divided area, and calculate the position coordinates. A three-dimensional measuring device comprising: a measured value correction mechanism for correcting; (4) In the device according to claim (3), the correction value calculation mechanism has a main body side correction value calculation section that calculates errors caused by the measuring machine main body, and also corrects and stores the main body side errors. A three-dimensional measuring device characterized by: