JP7379045B2 - Calculation method, article manufacturing method, program, information processing device, system - Google Patents

Description

The present invention relates to a calculation method, an article manufacturing method, a program, an information processing device, and a system.

Three-dimensional position measurement technology that photographs an object to be measured and measures the three-dimensional position of the object from the photographed image of the object is used for various purposes. In recent years, robots have begun to perform some of the tasks traditionally performed by humans in the production process of industrial products. For example, in a picking process where a robot grasps parts piled up in a container and transports them to a designated location, three-dimensional position measurement technology that can stably and accurately measure the position and orientation of parts is required.

One of the three-dimensional position measurement techniques is a pattern projection method that uses the principle of triangulation. In this method, a projector irradiates a target object with bright and dark pattern light created by a pattern generation means, and an imaging unit captures an image of the curved pattern light according to the shape of the target object from an angle different from the irradiation direction. This is a method of measuring the shape and position of an object.

Since the imaging unit and the optical system of the projector expand and contract depending on the temperature, their relative positions and postures change. This change may cause deviations in the measurement results of points on the object.

Particularly in projection systems, the temperature of the object and the temperature distribution with the surroundings are likely to change due to the heat generated by the light source.Furthermore, when a reflective display element is used as a pattern generation means, the optical system includes a reflective surface, which causes deformation due to temperature. They are often sensitive to such things.

Therefore, it is necessary to correct temperature changes, but in environments with large temperature changes, the deviation in measurement results may not change constantly, making it difficult to perform highly accurate temperature correction, and the generation of correction residuals is also a problem. Become.

Therefore, a method has been disclosed in which the position and orientation measured by the three-dimensional position measuring device are calibrated by performing calibration measurements on the three-dimensional position measuring device using a reference object with a known shape and pattern (patent Literature 1, Patent Literature 2).

Japanese Patent Application Publication No. 2008-170279 Japanese Patent Application Publication No. 2013-231900

In the inventions described in Patent Document 1 and Patent Document 2, the calibration target, which is a reference object used for calibration, requires position information of many known patterns and shapes, and is likely to be large-sized. Therefore, in order to calibrate three-dimensional position measuring devices used in the production process of industrial products, it is necessary to evacuate the measurement object and install a reference object for calibration after the measurement work is interrupted or completed. This may lead to a decrease in efficiency.

On the other hand, the three-dimensional position measuring device calculates the amount of change in the measurement result of a simple reference object, uses that amount of change as a correction value, and uniformly corrects the measurement error of the measurement target regardless of the location within the measurement range. There is a way.

However, in a three-dimensional position measuring device, the amount of deviation in measurement results due to temperature changes may vary depending on the location within the measurement range, and if uniform correction is performed, a correction residual error will occur depending on the location within the measurement range. As a result, in the picking process of the production process, there may be places where the robot cannot grasp the object even within the measurement range of the three-dimensional position measuring device, and the production process may be interrupted.

Therefore, the present invention aims to exemplify a three-dimensional position measuring device that can be calibrated more easily and reduces deterioration in measurement accuracy.

A calculation method as an aspect of the present invention for solving the above problems is a calculation method for calculating the position of a target object, and the calculation method uses the measurement result obtained by measuring a reference member using a three-dimensional measuring device to A first step of calculating a first position measurement value of the reference member in the depth direction of the measurement range of the measuring device, and using the measurement results obtained by measuring the reference member and the target object using the three-dimensional measuring device, a second position measurement value of the reference member in the depth direction, and a second step of calculating a first position of the object in the depth direction and an orthogonal direction perpendicular to the depth direction , Using the first position measurement value and the second position measurement value of the reference member with respect to the first position of the target object, errors of different sizes depending on the position in the depth direction are corrected, and the error of the reference member is corrected according to the position in the depth direction. The object after correction in the depth direction and the orthogonal direction is corrected by correcting the position in the orthogonal direction that does not change depending on the position in the depth direction using the first position measurement value and the second position measurement value. It is characterized by calculating the position of an object.

According to the present invention, a three-dimensional position measuring device can be calibrated more easily and deterioration in measurement accuracy can be reduced.

1 is a diagram showing a configuration example of a three-dimensional position measuring device. FIG. 2 is a diagram explaining the definition of coordinates. 3 is a flow diagram in Example 1. FIG. FIG. 3 is a diagram for explaining Z-direction correction according to the first embodiment. FIG. 3 is a diagram for explaining XY direction correction according to the first embodiment. FIG. 3 is a diagram for explaining XY direction correction according to the first embodiment. FIG. 3 is a flow diagram in Example 2. FIG. 7 is a diagram for explaining Z-direction correction in Example 2. FIG. 3 is a flowchart in Example 3. FIG. FIG. 7 is a diagram for explaining Z-direction correction according to the third embodiment. FIG. 4 is a flow diagram in Example 4. FIG. FIG. 7 is a diagram for explaining correction according to the second embodiment. FIG. 1 is a diagram showing a system.

A detailed description will be given below with reference to the drawings. In each figure, the same reference numerals are given to the same parts.

<Embodiment 1>
FIG. 1 is a configuration diagram of a three-dimensional position measuring device (three-dimensional measuring device) 100 in this embodiment. The three-dimensional position measuring device 100 includes a projector 1 , an imaging section 2 (three-dimensional measuring section), and an arithmetic processing section 3 . The projector 1 includes an LED light source for measurement, a pattern generation unit using a liquid crystal panel for generating pattern light, and a projection lens (projection optical system) that projects the generated pattern light.

The light source and the pattern generation unit can be electrically controlled by an arithmetic processing unit (information processing device) 3 such as a processor, and generate a pattern of light having only bright areas or stripes of bright and dark areas, which is the object to be measured. The object to be inspected (work) 4 and the reference mark 5 which is a reference member are irradiated. The pattern generation section may use a DMD or a mask having a light-shielding pattern instead of the liquid crystal panel.

The reference mark 5 is installed in a range that can be measured by the three-dimensional position measuring device 100. However, if it is possible to measure the reference mark 5, for example, it can be mounted on a robot, etc., and it can be fixed or moved to a predetermined position by a robot at a position that does not fall outside the guaranteed measurement range of the test object 4 or interfere with the test object 4. It may be placed by moving.

The imaging unit 2 has a lens (optical system) for receiving light from the measurement target on which a pattern is projected, and an imaging element such as a CCD, and the optical axis of the optical system is aligned with the projector 1 (projection lens). ) is placed at a different angle from the optical axis. The imaging unit 2 captures a pattern of light curved according to the shapes of the test object 4 and the reference mark 5 as a two-dimensional image. A plurality of images are obtained by capturing images of the object 4 and the reference mark 5 (arranged object) multiple times while changing the projected pattern light. Then, the arithmetic processing unit 3 calculates the positions (distance information) of the plurality of measurement points on the object from the plurality of captured images (measurement data) using the principle of triangulation. In this way, it is possible to obtain coordinates, which are the position (distance) measurement results of the object 4 and the reference mark 5 from the three-dimensional position measuring device, from the position measurement results by the three-dimensional position measuring device 100. .

Immediately after calibration without the test object 4, the test object 4 and the reference mark 5 can be measured with little error relative to their actual positions. In FIG. 2, 5a is the measurement result of the reference mark in this state, and the coordinates (X _b 0, Y _b 0, Z _b 0) at this time are called mark reference coordinates. 4a is the expected measurement result of the test object 4 when measured in this state (a state close to the true position), and the coordinates (X _w 0, Y _w 0, Z _w 0) at this time are These are called reference coordinates.

Here, the origin is the center A of the apex of the exterior from the three-dimensional position measuring device 100, and the Z-axis direction is the depth direction in the measurement range seen from the three-dimensional position measuring device 100. In addition, an axis on a plane that is orthogonal to the Z axis and includes the direction of the base line length of the projection optical system of the three-dimensional position measuring device 100 and the optical system of the imaging unit is defined as the X axis, and an axis that is orthogonal to the X and Z axes (orthogonal direction) is the Y-axis.

When a temperature change occurs in the three-dimensional position measuring device 100, the optical systems of the imaging unit 2 and the projector 1 expand or contract depending on the usage environment such as temperature, and thus their relative positions and orientations change. This change may cause a deviation in the measurement results of the test object. Therefore, for example, if the temperature of the three-dimensional position measuring device 100 changes after calibration, the measurement results of the object 4 and the reference mark 5 by the three-dimensional position measuring device 100 after the temperature change will not include errors that are measurement deviations. The result is In FIG. 2, the measurement result of the test object 4 in the state after the temperature change is indicated as 4b, and the measurement result of the reference mark 5 is indicated as 5b. The coordinates of 4b are the work coordinates (X _w n, Y _w n, Z _w n), and the coordinates of 5 b are the mark coordinates (X _b n, Y _b n, Z _b n).

Although FIG. 2 shows how one reference mark 5 is measured, the number of reference marks is not limited to this and may be two or more. However, instead of arranging a large number of reference marks to cover the entire measurement range of the three-dimensional position measuring device, it is possible to simplify the configuration by arranging a small number of reference marks in a part of the measurement range and performing calibration. Calibration can be done with .

The measurement error in the Z-axis direction caused by changes in the posture of the main components of the three-dimensional position measuring device 100 has a characteristic that changes approximately at the square of the ratio of the distance in the Z-axis direction from the three-dimensional position measuring device 100. I found out something. This is due to the shift (displacement) of the position of the lens of the projector 1 of the three-dimensional position measuring device 100, the pattern generation section, and the image sensor of the imaging section 2, and the convergence angle of the projector 1 and the imaging section 2, etc. This is because the change is a component corresponding to a change in the tilt of the optical axis. Therefore, the relationship between the position in the Z-axis direction and the error due to temperature changes etc. is expressed by the following equation 1.
(Z _b n - Z _b 0): (Z _w n - Z _w 0) = Z _b n^2: Z _w n^2... (Formula 1)

In other words, the error of Z _w n included in the position measurement result of the test object 4 can be determined by the following procedure. First, the mark reference coordinate Z _b 0 is obtained in advance in a state where the relative position of the coordinates of the test object and the reference object can be accurately measured. Next, when measuring the test object 4, the reference mark 5 is also measured, and from the obtained workpiece coordinates Z _w n and mark coordinates Z _b n, the error of Z _w n at the measurement point of the test object 4 can be calculated from equation 1. You can ask for it.

In the above, an example is shown in which correction is made based on the measurement results of the test object 4, but this is not necessarily necessary, and the amount of change is calculated from the mark coordinates 5b and the mark reference coordinates 5a by adjusting the device parameters (for example, the convergence angle). You can replace it with change. Thereby, the measurement result of the test object 4 may be obtained by correcting the coordinates of the entire measurement space.

Note that the error was determined using the distance in the Z-axis direction from the origin A of the three-dimensional position measuring device 100. However, since the distances in the Z-axis direction between the three-dimensional position measuring device 100, the test object 4, and the reference mark 5 are sufficiently large, unless there is a large difference, the distance from an arbitrary point near the three-dimensional position measuring device 100 can be used. You may also calculate the error.

Next, each example will be described.

FIG. 3 is a flowchart of the measurement method (calculation method) in Example 1. Each step is performed by the projector 1, the imaging section 2, and the arithmetic processing section 3 of the three-dimensional position measuring device 100, but the arithmetic processing may be performed using an external computer (information processing device). Further, such a calculation method can be realized, for example, by supplying a program capable of executing each step of the flowchart to a computer, which is an information processing device, via a network or a recording medium, and having the information processing device read and execute the program. be done. It can also be realized by the information processing device reading and executing a program stored in a storage medium such as a memory.

First, in step 1 (first step), the reference mark 5 is measured after the relative position of the test object 4 and the reference mark 5 has been correctly measured, for example after calibration, and the coordinate information of the reference for correction is obtained. The mark reference coordinates (first position measurement value) 5a are calculated as follows. Step 1 is performed when the actual position of the reference mark 5 deviates, or when the position deviates from the mark reference coordinates obtained when step 1 was performed in the past.

Step 2 and subsequent steps are steps for position correction (second step). In step 2, after step 1, the reference mark 5 is measured and mark coordinates (second position measurement values) 5b representing the position of the reference mark are calculated. Although the actual position of the reference mark 5 in step 2 is the same as in step 1, there is a possibility that the position measurement result of the reference mark 5 deviates from the actual position due to a measurement error. Step 2 can be performed after Step 1 at any time or at a predetermined period. However, if a measurement error occurs due to a change in the posture of the main components of the three-dimensional position measuring device 100 due to a change in the usage environment such as temperature, it is effective to perform Step 2 and subsequent steps. Therefore, step 2 may be performed when it is detected that the usage environment, such as temperature, has changed since step 1 was performed, and a predetermined condition such as a temperature difference is satisfied. Note that when the time interval between Step 1 and Step 2 is smaller, the mark coordinates do not change greatly from the mark reference coordinates, and the amount of change in the correction value calculated thereafter is small, so that the correction accuracy can be improved.

Next, in step 3 (second step), the object 4 to be inspected is measured to calculate workpiece coordinates (object position) 4b. The workpiece coordinates 4b may be the coordinates of a plurality of measurement points on the test object 4 or the coordinates of a representative position of the test object 4. The timing of step 3 may be the same as or different from step 2. The shorter the interval between the measurement of the reference mark 5 in step 2 and the measurement of the test object 4 in step 3, the smaller the difference in measurement conditions can be, and the lower the accuracy of the correction amount calculated later can be suppressed. .

Next, in step 4, the amount of change ΔZ _b n, which is the error in the Z-axis direction of the reference mark 5, is determined from the mark coordinates and the mark reference coordinates. When the position of the mark coordinates in the Z-axis direction is Z _b n and the position of the mark reference coordinates in the Z-axis direction is Z _b 0, the amount of change ΔZ _b n in the Z-axis direction is expressed by the following (Equation 2).
ΔZ _b n = Z _b n - Z _b 0... (Formula 2)

Next, in step 5, a correction value ΔZ _w n for the position of the object 4 in the Z-axis direction is calculated. Based on the relationship between the position in the Z-axis direction and the error in Equation 1 above, the correction value ΔZ _w n can be calculated using Equation 3. The relationship of Equation 3 is shown in FIG. Here, the position in the Z-axis direction of the workpiece coordinates of the test object 4 obtained in step 3 is defined as Z _w n.
ΔZ _w n=ΔZ _b n×(Z _w n/Z _b n)^2... (Formula 3)

The correction value ΔZ _w n is the amount of change ΔZ _b n in the Z-axis direction of the reference mark 5 obtained in step 4, and the position Z _w n of the workpiece coordinates of the test object 4 in the Z-axis direction obtained in step 3. can be calculated using the position Z _b n of the mark coordinates in the Z-axis direction obtained in step 2. The correction value ΔZ _w n has a different size depending on the position Z _w n of the workpiece coordinate of the test object 4 in the Z-axis direction, that is, the position of the measurement point of the test object 4 .

Next, in step 6, correction values ΔX _w n and ΔY _w n of the position of the object 4 in the X-axis direction and the Y-axis direction are calculated. _{Specifically , the X} -axis The correction values ΔX _w n and ΔY _w n in the Y-axis direction are calculated using equations 4 and 5. The relationship of Equation 4 is shown in FIG. Equation 5 also has the same relationship as Equation 4. The correction values ΔX _w n and ΔY _w n have different (change) sizes depending on the position Z _w n of the workpiece coordinate of the test object 4 in the Z-axis direction, that is, the position of the measurement point of the test object 4. .
ΔX _w n = ΔZ _w n × (X _w n / Z _w n) (Formula 4)
ΔY _w n = ΔZ _w n × (Y _w n / Z _w n) (Formula 5)

Next, in step 7, correction values in the X-axis direction and the Y-axis direction that do not change (depend) depending on the position of the test object 4 are determined from the mark coordinates and the mark reference coordinates. First, _the component that changes _depending on the position of the reference mark _{( ΔX b} n_ _calc, ΔY _b n_ _calc ) is calculated using Equations 6 and 7. The relationship of Equation 6 is shown in FIG.
ΔX _b n _calc = ΔZ _b n × (X _b 0/Z _b 0) (Formula 6)
ΔY _b n _calc = ΔZ _b n × (Y _b 0/Z _b 0) (Formula 7)

These are compared with the mark coordinates (X _b n, Y _b n) obtained from the actual measurement results, and the difference is calculated as correction values ΔX b n_r, ΔY _{b n_r} in the X-axis direction and Y-axis direction that do not change depending on the position. It is calculated using Equation 8 and Equation 9.
ΔX _b n_r=(X _b n−X _b 0)−ΔX _b n _calc ...(Formula 8)
ΔY _b n_r = (Y _b n - Y _b 0) - ΔY _b n _calc ... (Formula 9)

Finally, in step 8, the workpiece coordinates are corrected as shown in equations 10, 11, and 12 using the correction values obtained in steps 5, 6, and 7. Here, as a result of the correction, the corrected work coordinates are (X _w n_correct _, Y _w n_correct _, Z _{w n_correc} ).
X _w n_ _correct =X _w n - ΔX _w n - ΔX _b n_r... (Formula 10)
Y _w n_ _correct = Y _w n - ΔY _w n - ΔY _b n_r... (Formula 11)
Z _w n_ _correct = Z _w n - ΔZ _w n... (Formula 12)

In the above, the correction value (measurement error) ΔZ _w n for the position of the test object 4 in the Z-axis direction is expressed as the square of the ratio of the Z-axis coordinates Zbn and Zwn of the test object 4 and the reference mark 5. It was found using However, in consideration of errors that occur due to changes other than changes in the posture of the main parts and the accuracy improvement effect thereof, the distance may be determined using a multiplier that is greater than or equal to the 1.5th power and less than or equal to the 2.5th power of the distance ratio.

The reason is as follows. For example, if the measurement range of the three-dimensional position measuring device 100 in the Z-axis direction is 1500 to 2000 mm, and there is a measurement error of 20 mm at a position of 1500 mm, the measurement result will be 1520 mm to 2036 mm, including the error of the square of the Z position. Therefore, the maximum error is 36 mm.

Here, when measurement is performed with the reference mark 5 placed at 1500 mm, and the correction value when the Z position is 1500 mm is calculated using the square of the ratio of the Z position, the error will be 0. When the correction value is obtained using the 1.5th power of the Z position, the measurement result after correction is 1500 mm to 2005 mm, and the error is 5 mm at the maximum, making it possible to relatively reduce the error. Furthermore, when measurement is performed with the reference mark 5 placed at 1500 mm, and the correction value is determined by the ratio of the Z position (distance) to the 2.5 power, the error can be reduced to 5 mm. In other words, within the range of 1.5 to 2.5 power, the error can be reduced to about 30% or less.

As described above, the three-dimensional position measuring device 100 can accurately correct measurement errors for each position in the Z-axis direction using a simple reference object, and can reduce deterioration in measurement accuracy.

Note that, after completion of step 8, for example, when successively measuring another test object 4 one after another, the next measurement may start from step 3 without performing steps 1 and 2. This is because when the temperature change from the previous measurement is small, the change in mark coordinates is not large, and the changes in the correction values in steps 5, 6, and 7 are small.

Although the description has been made using one reference mark 5, two or more may be used. When two or more reference marks 5 are used, in steps 1 and 2, mark reference coordinates and mark coordinates are acquired for each reference mark 5. Then, in step 3, ΔZ _b n may be obtained by averaging the mark reference coordinates and mark coordinates for each reference mark 5.

Next, a three-dimensional position measuring device 100 according to a second embodiment will be described based on FIGS. 7 and 8. FIG. 7 is a flowchart of measurement in this embodiment. First, as in Example 1, steps 1 and 2 are performed to obtain mark reference coordinates and mark coordinates.

Next, in step 3, the correction value is the relative angular difference between the optical axes of the projector 1 and the imaging unit 2, which is one of the device parameters used to calculate the position measurement result of the three-dimensional position measurement device 100. The amount of change ΔR _Ex in the convergence angle R _Ex is determined. FIG. 8 is a diagram showing the amount of change in the convergence angle R _Ex . The amount of change in the convergence angle ΔR _Ex can be obtained from the position Z _b 0 of the mark reference coordinates in the Z-axis direction, the position Z _b n of the mark coordinates in the Z-axis direction, and the baseline length D of the projector 1 and the imaging unit 2. can. Here, the correction value of the convergence angle has been explained, but if it is a device parameter whose error changes with the square of the ratio of the distance in the Z-axis direction from the three-dimensional position measuring device 100, the pattern generation unit of the projector 1 or A shift (positional deviation) of the image sensor of the image capturing section 2 may be used as a correction item.

Next, in step 4, correction values ΔX _b n_r and ΔY _b n_r in the X-axis direction and Y-axis direction that do not change depending on the position of the test object 4 are determined. As in step 7 of the first embodiment, the correction value can be determined from the amount of change in the Z-axis direction of the mark coordinates and the mark reference coordinates, and the mark reference coordinates, as shown in Equations 6 to 9. Alternatively, the mark coordinates of the reference mark 5 are recalculated using the device parameters of the three-dimensional position measuring device 100 corrected with the correction values obtained in step 3, and the mark coordinates of the recalculated reference mark 5 and the mark reference are The correction values ΔX _b n_r and ΔY _b n_r may be calculated from the difference with the coordinates.

Next, in step 5, the device parameters of the three-dimensional position measuring device 100 are corrected using the correction values obtained in steps 3 and 4. However, in step 5, the result after calculation in step 6 may be corrected with the X, Y correction values without correcting with the X, Y correction values obtained in step 4.

Finally, in step 6, the object 4 to be inspected is measured, and the position of the object 4 to be inspected is calculated using the corrected device parameters and obtained as corrected workpiece coordinates.

As described above, the three-dimensional position measuring device 100 can be calibrated using a simple reference object, and a three-dimensional position measuring device that reduces deterioration in measurement accuracy is realized.

In addition, when measuring the test object 4 continuously, you may start from the process 4 after the completion of the process 6. This is because if the temperature change from the previous measurement is small, the change in mark coordinates will not change significantly, and the change in the correction value in step 4 will be small. For example, it is sufficient to check the temperature difference from the previous measurement, set conditions such as an arbitrary temperature difference, and start from step 4 if the conditions are satisfied.

Next, a three-dimensional position measuring device 100 according to a third embodiment will be described based on FIGS. 9 and 10. FIG. 9 is a flow diagram of the measurement method in this example. This embodiment differs from Embodiment 1 in that three reference marks 5, 6, and 7 are arranged at different positions in the Z-axis direction, as shown in FIG. Therefore, this differs from step 4 in the flowchart of FIG. 3 of the first embodiment in that the amount of change is determined for each reference mark. Furthermore, the method for calculating the correction amount in the Z-axis direction in step 5 is different.

First, in step 1, the reference marks 5, 6, and 7 are measured in a state in which the relative positions of the test object 4 and the reference mark 5 are correctly measured, and the reference coordinates of each mark are used as the coordinate information of the correction reference. get.

Normally, Step 1 is re-executed when the reference marks 5, 6, and 7 actually deviate from the positions where they were placed, or when the marks deviate from the mark reference coordinates of Step 1 that was previously executed.

Step 2 and subsequent steps are operations when measuring the actual test object 4. In step 2, the reference marks 5, 6, and 7 are measured in order to calculate the amount of correction. At this time, as in step 1, each mark coordinate is acquired for each reference mark.

Next, in step 3, similarly to step 3 of the first embodiment, the object 4 to be inspected is measured to obtain workpiece coordinates. In addition, when measuring the test object 4 continuously, you may start from the process 3 after the completion of the process 8. This is because when the temperature change from the previous measurement is small, the change in mark coordinates does not change significantly and the amount of change in the correction value is small. For example, it is sufficient to check the temperature difference from the previous measurement, set conditions such as an arbitrary temperature difference, and start from step 3 if the conditions are satisfied.

Next, in step 4, the reference coordinates of the reference marks 5, 6, and 7 and the amounts of change in the Z-axis direction of the reference coordinates ΔZ _b 5, ΔZ _b 6, and ΔZ _b 7 are determined.

Next, in step 5, a correction value ΔZ _w n of the measurement object 4 in the Z-axis direction is determined. The Z-axis direction errors ΔZ _b 5, ΔZ _b 5, and ΔZ _b 7 of the reference marks 5, 6, and 7 from the three-dimensional position measuring device 100 are the Z-axis errors of each of the reference marks 5, 6, and 7 from the three-dimensional position measuring device. When the coordinates in the axial direction are Z _b 5, Z _b 6, and Z _b 7, it can be expressed by Equation 13, Equation 14, and Equation 15.
A+B+C=ΔZ _b 5...(Formula 13)
A×(Z _b 6/Z _b 5)^2+B×(Z _b 6/Z _b 5)+C=ΔZ _b 6...(Formula 14)
A×(Z _b 7/Z _b 5)^2+B×(Z _b 7/Z _b 5)+C=ΔZ _b 7...(Formula 15)

Here, A, B, and C are error values at the reference mark 5, A is an error component that changes with the square of the distance ratio in the Z-axis direction, and B is an error that changes with the distance ratio in the Z-axis direction. The component C is an error component that uniformly changes regardless of the Z-axis direction.

From Equations 13, 14, and 15, the error values A, B, and C of the reference mark 5 are calculated, and from the workpiece coordinates of the object 4, the error component that changes with the square of the ratio of the distance of the object 4 and Error components Z _w n _{A and} Z _w n _B that change depending on the distance ratio are determined. (Equation 16, Equation 17)
ΔZ _w n _A = A × (Zwn/Z _b 5)^2... (Formula 16)
ΔZ _w n _B = B × (Zwn/Z _b 5) (Formula 17)

Regarding the error that changes uniformly in C, external factors such as a change in the overall position of the three-dimensional position measuring device 100 or a change in the position where the reference mark 5 is placed can be considered. Therefore, if the error is more affected than the error caused by error components A and B, the relative position of the coordinates of the test part and the coordinates of the reference object is measured correctly, for example, the position and orientation of the three-dimensional position measuring device 100. It is recommended to perform calibration and re-measure.

Next, in step 6, from the Z direction correction values ΔZ _w n _A and ΔZ _w n _B calculated in step 5 and the workpiece coordinates (X _w n, Y _w n, Z _w n), the An error component that changes depending on the position is determined, and correction values ΔX _w n and ΔY _w n are calculated. (Equation 18, Equation 19)
ΔX _w n = (ΔZ _w n _A + ΔZ _w n _B ) × (X _w n / Z _w n) (Formula 18)
ΔY _w n = (ΔZ _w n _A + ΔZ _w n _B ) × (Y _w n / Z _w n) (Formula 19)

Next, in step 7, XY correction values that do not change depending on the position of the object 4 are determined for each of the reference marks 5, 6, and 7. Here, using the error components A and B obtained in step 5, as in step 6, the XY error components that vary depending on the positions of the reference marks 5, 6, and 7 are determined. For each of the reference marks 5, 6, and 7, calculate the XY error component that does not change depending on the position from the XY error component that changes depending on the position, the mark coordinate, and the change in the mark reference coordinate, in the same way as in step 7 of Example 1. The average correction values ΔX _b n_r and ΔY _b n_r are determined.

Finally, in step 8, the workpiece coordinates are corrected using the correction values obtained in steps 5, 6, and 7, and from (Equations 20, 21, and 22), the corrected workpiece coordinates (X _w n_ _{correct ,} Y _w n_correct _, Z _{w n_correc} ).
X _w n_ _correct =X _w n - ΔX _w n - ΔX _b n_r... (Formula 20)
Y _w n_ _correct = Y _w n - ΔY _w n - ΔY _b n_r... (Formula 21)
Z _w n_ _correct =Z _w n-(ΔZ _w n _A +ΔZ _w n _B )...(Formula 22)

As described above, the three-dimensional position measuring device 100 is able to separate the correction components that change from position to position using a small number of reference marks, and obtain the correction amount of each component. A three-dimensional position measuring device that reduces deterioration in measurement accuracy even more than the first and second embodiments is realized.

Next, a three-dimensional position measuring device according to a fourth embodiment will be described based on FIG. 11. FIG. 11 is a flow diagram of the measurement method in this example. Steps 1 and 2 similar to those in Example 3 are performed to obtain each mark reference coordinate and each mark coordinate.

First, in step 1, the reference marks 5, 6, and 7 are measured in a state where the relative positions of the test object 4 and the reference mark 5 have been correctly measured (for example, after calibration), and the reference marks for correction are determined. Acquire each mark reference coordinate as coordinate information. Normally, Step 1 is re-executed when the reference marks 5, 6, and 7 actually deviate from the positions where they were placed, or when the reference marks deviate from the original coordinates of the previously executed Step 1.

Step 2 and subsequent steps are operations when measuring the actual test object 4. In step 2, the reference marks 5, 6, and 7 are measured in order to calculate the amount of correction. At this time, as in step 1, each mark coordinate is acquired for each reference mark.

Next, in step 3, correction values for the parameters of the device used for position measurement calculations of the three-dimensional position measuring device 100 are determined from each mark reference coordinate and each reference coordinate. As in Example 3, the error value of the reference mark 5 is an error component A that changes with the square of the distance ratio in the Z-axis direction, an error component B that changes with the distance ratio in the Z-axis direction, and an error component B that changes with the distance ratio in the Z-axis direction. Find the error component C that uniformly changes regardless of the Next, correction amounts are determined from A and B as parameters of the apparatus. Here, A is an error that changes with the ratio of the square of the distance ratio, and as in the second embodiment, the amount of change in the convergence angle of the projector 1 and the imaging section 2, and the amount of change in the convergence angle of the projector 1 and the imaging section 2. A correction value is obtained as a shift component of the image sensor. Next, a correction value for the baseline length of the projector 1 and the imaging section 2 is determined from the error component B that is proportional to the distance ratio. Regarding the error that changes uniformly in C, external factors such as a change in the overall position of the three-dimensional position measuring device 100 or a change in the position where the reference mark 5 is placed can be considered. Therefore, if the error is more affected than the error caused by error components A and B, the relative position between the coordinates of the test part and the coordinates of the reference object is measured correctly, for example, the position and orientation of the three-dimensional position measuring device 100. It is recommended to carry out calibration calibration and re-measure.

Next, in step 4, XY correction values ΔX _b n_r and ΔY _b n_r that do not change depending on the position of the test object 4 are determined. As in step 7 of the third embodiment, the correction value is determined from the amount of change in the Z-axis direction of each mark coordinate and each mark reference coordinate and the mark reference coordinate. Alternatively, the coordinates of the reference marks 5, 6, and 7 are recalculated using the device parameters of the three-dimensional position measuring device 100 corrected with the correction values obtained in step 3, and the recalculated coordinates of the reference mark 5 and the mark reference coordinates are The correction values ΔX _b n_r and ΔY _b n_r may be obtained by averaging the respective differences.

Next, in step 5, the device parameters of the three-dimensional position measuring device 100 are corrected using the correction values in steps 3 and 4. If the XY correction values obtained in step 4 are not used as parameters of the apparatus, in step 6 the calculation results are corrected using the correction values in step 4.

Finally, in step 6, the test object 4 is measured, and in step 5, calculations are performed using the corrected device parameters, and the corrected workpiece coordinates (X _w n_ _correct, Y _w n_ _correct, Z _{w n_correc} ).

As described above, the three-dimensional position measuring device 100 can separate the correction components that change from position to position using a small number of reference marks, and can determine the correction amount of each component. A three-dimensional position measuring device that reduces deterioration in measurement accuracy even more than the first and second embodiments is realized.

Note that this embodiment has a configuration in which a pattern is projected by a projector section and an image is captured by one imaging section (first optical system). However, a configuration may also be used in which a plurality of imaging units (first optical system) are installed in different directions with respect to a projector (second optical system) that illuminates the object. In this case, each combination of the projector and each imaging section may perform correction, and the measurement results may be combined. Further, in this embodiment, a three-dimensional position measuring device using a pattern projection method is used. However, a three-dimensional method using a stereo method using the principle of triangulation is based on images taken by two imaging units (first optical system, second optical system) whose relative positions and orientations are known. It may also be a position measuring device. Further, in this embodiment, the correction is performed using the (X, Y, Z) coordinate system, but correction may be performed using the origin A and rotation.

<Embodiment 2>
Next, a second embodiment will be described. In the second embodiment, the actual position of the reference mark 5 for determining the mark reference coordinates (first position measurement value), the actual position of the reference mark 5 for determining the mark coordinates (second position measurement value), are different. In the first embodiment, the actual position of the reference mark 5 for determining the mark reference coordinates was the same as the actual position of the reference mark 5 for determining the mark coordinates. Therefore, in the second embodiment, unlike the first embodiment, , it is necessary to perform correction including the difference in their positions.

FIG. 12 is a diagram illustrating measurement and correction in this embodiment. In this embodiment, in step 1, the reference mark 5 (reference member) is mounted on a robot, moved and placed at a predetermined position by the robot, and the reference mark 5 is measured. At this time, the measured mark reference coordinates 5a are assumed to be (X _b 0, Y _b 0, Z _b 0). Thereafter, in step 2, the robot moves and positions the reference mark 5 so that the actual position of the reference mark 5 is different from the actual position of the reference mark 5 in step 1. Then, the reference mark 5 is measured and the mark coordinates (X _b n, Y _b n, Z _b n) are determined. In steps 1 and 2, if the position of the robot is controlled with high precision, there will be almost no placement error, and the difference in the actual position of the reference mark 5 in steps 1 and 2 (ΔX _r n, ΔY _r n, ΔZ _r n) can be obtained from the control information of the robot.

Therefore, the mark reference coordinates were measured at the same position as the measurement position of the mark coordinates 5b based on the result of offsetting the difference between the above actual measurement positions when measuring the mark reference coordinates 5a and mark coordinates 5b with respect to the mark reference coordinates 5a. It is possible to obtain coordinate information equivalent to the object. For example, the measurement error (change amount) ΔZ _b n in the Z direction included in the measurement result of the mark coordinates is expressed by the following (Equation 23).
ΔZ _b n = Z _b n - Z _b 0 - ΔZ _r n... (Formula 23)

Measurement errors in the X direction and Y direction can also be determined using similar formulas.

Therefore, by using changes in the arrangement of the reference mark 5 such as the robot's position coordinates (mark position control information), even if the mark reference coordinates and the mark coordinate positions are different, the difference can be taken into account and the difference can be compared with the first embodiment. Similar corrections can be made. Therefore, since the mark reference coordinates and the mark coordinate positions are different, restrictions on the installation range of the test object 4 can be more relaxed than in the first embodiment.

As described above, since the three-dimensional position measuring device 100 can correct the position of the reference mark 5 without fixing it, it realizes a three-dimensional position measuring device that is less constrained in the installation range of the test object than in the first embodiment. be able to.

(system)
The three-dimensional position measuring device 100 can calculate the distance, shape, and posture of the test object 4 using the corrected position (distance information) of the test object 4. The three-dimensional position measuring device 100 is used as a system combined with a robot 200, for example. Figure 13 shows the system. The position and orientation of the object 4 calculated by the three-dimensional position measuring device 100 are output to the robot control unit 201, and the robot control unit 201 uses a gripping unit such as a hand of the robot 200 based on the position and orientation. The robot 200 is controlled to grip and move the object. Then, after moving one of the plurality of test objects 4 stacked in bulk with the hand of the robot 200, the plurality of test objects 4 stacked in bulk is measured using the three-dimensional position measuring device 100. Repeat.

(Article manufacturing method)
Next, a manufacturing method for manufacturing articles such as mechanical parts using the aforementioned three-dimensional position measuring device will be described. First, with a plurality of objects such as mechanical parts stacked in bulk, the objects are measured using the aforementioned three-dimensional position measuring device, and the positions and orientations of the objects are measured. Based on the position and orientation, the robot control unit 201 controls the robot 200 so that a gripping section such as a hand of the robot 200 grips and moves the object. The moved object is connected to, fastened to, or inserted into other parts. Further, processing may be performed in other processing steps. Then, an article including the object subjected to such treatment is manufactured.

Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist.

Claims (20)

A calculation method for calculating the position of a target object, the method comprising:
A first step of calculating a first position measurement value of the reference member in a depth direction of a measurement range of the three-dimensional measuring device using a measurement result obtained by measuring the reference member using a three-dimensional measuring device;
Using the measurement results obtained by measuring the reference member and the object using the three-dimensional measuring device, a second position measurement value of the reference member in the depth direction , the depth direction, and a value perpendicular to the depth direction are determined. a second step of calculating a first position of the object in an orthogonal direction ,
With respect to the first position of the object,
Using the first position measurement value and the second position measurement value of the reference member, correcting errors of different sizes depending on the position in the depth direction,
By using the first position measurement value and the second position measurement value of the reference member, correcting with a correction value of the position in the orthogonal direction that does not change depending on the position in the depth direction,
A calculation method, comprising calculating the corrected position of the object in the depth direction and the orthogonal direction . Claim characterized in that the position of the object is calculated by correcting an error proportional to a multiplier from the 1.5th power to the 2.5th power of the distance to the object in the depth direction. The calculation method described in 1. A first correction value in the depth direction with respect to the first position and a second correction value in the orthogonal direction with respect to the first position are calculated using the first position measurement value and the second position measurement value of the reference member. The process of
a correction step of correcting the first position using the first correction value and the second correction value ,
3. The calculation method according to claim 1 , wherein each of the first correction value and the second correction value includes a correction value of a different size depending on the position in the depth direction. The calculation method according to claim 3, characterized in that the first correction value is calculated using a first position measurement value and a second position measurement value of the reference member and a first position of the object. . 4. The first correction value includes a correction value proportional to a multiplier from the 1.5th power to the 2.5th power of the distance to the object in the depth direction. Calculation method described in. The first correction value includes a correction value proportional to the square of the distance to the object in the depth direction, and a correction value proportional to the distance to the object in the depth direction. 4. The calculation method according to claim 3, comprising: calculating a correction value for the parameter of the three-dimensional measuring device using the first position measurement value and the second position measurement value of the reference member;
correcting the parameter using a correction value for the parameter, and calculating the position of the object in the depth direction and the orthogonal direction using the corrected parameter and the measurement result of measuring the object; , has
Claim 1, wherein the parameter is a parameter that causes the position of the object to change in the depth direction by a different magnitude depending on the position of the object in the depth direction when the value thereof changes. Or the calculation method described in 2. When the value of the parameter changes, the position of the object changes in the depth direction with a magnitude proportional to a multiplier from the 1.5th power to the 2.5th power of the distance to the object in the depth direction. The calculation method according to claim 7, characterized in that the calculation method includes a parameter that changes. The three-dimensional measuring device is a measuring device that measures using a first optical system that receives light from the target object and a second optical system that receives light from the target object or illuminates the target object. And,
8. The calculation method according to claim 7, wherein the parameter is a convergence angle or baseline length of the first optical system and the second optical system. The three-dimensional measuring device is a measuring device that measures using an image sensor that receives light from the target object,
8. The calculation method according to claim 7, wherein the parameter is a position of the image sensor. The three-dimensional measuring device is a measuring device that measures using a projection optical system that projects light onto the target object,
The projection optical system includes a generation unit that generates pattern light to be projected,
8. The calculation method according to claim 7, wherein the parameter is a position of the generation unit. The parameters include a parameter whose value, when changed, causes the position of the object to change in the depth direction with a magnitude proportional to the square of the distance to the object in the depth direction; 8. The calculation method according to claim 7, further comprising: a parameter by which the position of the object changes in the depth direction with a magnitude proportional to the distance to the object. 9. The calculation method according to claim 2, wherein the multiplier is a square. 14. The calculation method according to claim 1, wherein the reference member includes three or less marks. The calculation method according to claim 14 , wherein the reference member includes three marks. Calculating the position of the object using the calculation method according to any one of claims 1 to 15 ;
A method for manufacturing an article, characterized in that the article is manufactured by performing processing on the target object based on the calculated position. A program for causing a computer to execute the calculation method according to any one of claims 1 to 15 . An information processing device that calculates the position of a target object,
Calculating a first position measurement value of the reference member in the depth direction of the measurement range of the three-dimensional measuring device using a measurement result obtained by measuring the reference member using a three-dimensional measuring device;
Using the measurement results obtained by measuring the reference member and the object using the three-dimensional measuring device, a second position measurement value of the reference member in the depth direction , the depth direction, and a value perpendicular to the depth direction are determined. a processing unit that calculates a first position of the object in an orthogonal direction ,
The processing unit includes:
With respect to the first position of the object,
Using the first position measurement value and the second position measurement value of the reference member, correcting errors of different sizes depending on the position in the depth direction,
By using the first position measurement value and the second position measurement value of the reference member, correcting with a correction value of the position in the orthogonal direction that does not change depending on the position in the depth direction,
An information processing device that calculates a corrected position of the object in the depth direction and the orthogonal direction . a three-dimensional measurement unit that measures the object;
19. A system comprising: the information processing device according to claim 18 , which calculates the position of the target object by performing arithmetic processing on measurement data by the three-dimensional measurement unit. 20. The system of claim 19 , further comprising a robot for moving the object.

Images