JP3448074B2 - Correlation detection type 3D position measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a correlation detection type three-dimensional position meter.
For measuring equipment, especially for teaching work procedures for industrial robots, etc.
This is useful when applied to measurement of work coordinates. [0002] 2. Description of the Related Art Industrial robots such as painting robots and welding robots
In order for the robot to work automatically, the work procedure must be
Must be taught in three-dimensional coordinates. According to such teaching
The robot moves according to the taught coordinates and
Perform business. During the execution of this work, it operates as taught.
Measure whether it is working and take corrective action if there is an error
By doing so, more accurate work can be performed. [0003] In order to carry out such work, the prior art
As a first example, in the teaching process, an operator directly
Work with the robot and the same operation
Teaching playback method to perform
Can be. As a second example of the prior art, FIG.
, A laser light source 68 and first and second scanners
66, 67, first and second television cameras 61, 62,
Cut off the image signals output from the two TV cameras 61 and 62
Switching unit 63, image coordinate detector 64, and coordinate calculator
Using a measuring device having a scanner 65 and a scanner driving device 69
Techniques can be mentioned. In the second example, the robot 5 is instructed.
The laser light source 68 irradiates the work target 8 on the target object 7
The first scanner 66 and the second scanner 66
The canner 67 is driven by the scanner drive circuit 69. This
In the state described above, the image of the object 7 including the work target 8 is
An image is taken with the Levi camera 61 and the second television camera 62.
You. [0006] The switch 63 is firstly connected to the first television camera 6.
1 is input to the image coordinate detector 64. Picture
In the image coordinate detector 64, the image is detected based on a preset threshold value.
Of the laser light image with the highest brightness on the image.
Detect the position on the image. The image output from the first television camera 61 is
When the processing is completed, the switch 63 switches to the second television camera 6.
2 is input to the image coordinate detector 64. Picture
In the image coordinate detector 64, the second TV camera 62
The position of the laser light image on the output image is detected. A first television camera 61 and a second television
Since there is an appropriate interval between the cameras 62,
Position of laser light image detected on images of cameras 61 and 62
Has parallax. Therefore, the detected laser light image
The position on the image and the distance between the two TV cameras 61 and 62
From the third order of the point where the laser beam hits by the well-known technology
Original coordinates can be calculated. The coordinate calculator 65 includes an image coordinate detector 64
Of the first and second television cameras 61 and 62 detected by
The source of the triangulation from the position of the laser light image on each image
The three-dimensional position of the work target 8 on which the laser beam is
The target is calculated, and the calculation result is sent to the control device 6 of the robot 5.
Send out. [0010] SUMMARY OF THE INVENTION As described above,
In the teaching playback method, the worker
If you cannot easily approach the installation position of the
Not applicable to robots. On the other hand, the laser shown in the second example of the prior art
The method using light and stereo vision has its own large device.
When measuring the entire work area with
Since it is necessary to provide a mechanism and rotate the entire device,
Increase in size. In addition, measurement by two TV cameras
For this reason, the
The position detection error on the image of the light image is three-dimensional
Affects coordinate calculation errors and limits the accuracy. Change
In addition, since laser light is used, the surface of the target
Or a black body that absorbs laser light
In the case of, there is a problem that measurement is impossible. In view of the above prior art, the present invention provides a robot
Non-contact teaching with a small, lightweight device
To provide a correlation detection type three-dimensional position measurement device
And [0013] [MEANS FOR SOLVING THE PROBLEMS]
Lighting configuration is for teaching operation of industrial robots, position detection, etc.
In the three-dimensional position measuring device applied to
Placed and rotated this rotation mechanism3 or less
It is configured to shoot the same object at each position above
didOne photographing means and the rotation angle of the rotation mechanism are detected.
Angle detector, and an image captured by the imaging means.
Specify from the image memory to be stored and the
Reference image memory that stores only the image of the
Among the captured images, the most compatible with the contents of the reference image memory
A correlation calculation circuit for extracting a region of high correlation, and the correlation calculation
Address for transferring the data of the image memory to the circuit
An address generator that outputsEach rotation angle of the above rotation mechanism
Degree,Three or more images taken at each of these rotation angle positions
Areas of the image that are highly correlated with the contents of the reference image memory
From the coordinates of the area, the area imaged in the reference image memory
Calculate the position coordinates of the representative points in,And this
Based on the position coordinates ofCalculate the three-dimensional coordinates of the object
And a coordinate calculating means. [0014] In the present invention having the above construction, the imaging means is provided for the work eye.
An object including a target is imaged. The image memory is the output of the imaging means.
Remember the image you press. First, store in image memory
From the captured image, the area near the work target was instructed by the operator.
Save the area in the reference image memory. The second and subsequent times
The stored image is stored in the image memory and is stored in the address generator.
The data in the area indicated by the arrow is sequentially read. address
The generator has a small area of the same size as the reference image memory.
From the image memory sequentially while shifting the position
To generate the address of the image memory. The image data read by the address generator
Correlation calculation circuit for the area on the memory and the image in the reference image memory
Calculates the correlation value. Furthermore, the correlation calculation circuit
Is read by changing the position slightly by the address generator
Detects the area with the highest correlation among the areas on the image memory
I do. One image is stored in the reference image memory.
Once the position that has the highest correlation with the volume is determined, the rotation mechanism
Rotate and change the direction of the line of sight of the TV camera. At this time
The rotation angle of the rotation mechanism is detected by an angle detector. In the same manner, from the viewpoint of the television camera,
The rotation mechanism rotates until the work target
The rotation angle at the time and the
The position with the highest correlation with the image stored in the quasi-image memory
Is detected. In the coordinate calculation means, the detection is performed as described above.
Rotation angle and the position in the image memory of the highly correlated area.
The three-dimensional coordinates of the work target on the object
Power. [0019] DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.
I will tell. FIG. 1 shows an embodiment of the present invention.
It is a block diagram shown with a robot. As shown in the figure
In addition, the robot 5 performs operations such as welding and painting on the object 7.
Do business. At this time, in order to teach the work procedure,
It is necessary to measure the position of the work target 8 on 7. The position measuring device according to the present embodiment
TV camera 1 for imaging an area including
Rotation mechanism 2 for changing the line of sight of Levi camera 1, rotation
An angle detector 3 for detecting a rotation angle of the mechanism 2 and a processing unit
Three-dimensional coordinates of the work target 8 measured by the
To the control device 6 of the robot 5. In the control device 6
Is the robot from the three-dimensional coordinates of the work target 8
The work procedure and work position of 5 are determined. FIG. 2 shows the processing apparatus 4 of the above embodiment in detail.
It is a block diagram shown in detail. As shown in FIG.
An image captured by the camera 1 is output from the A / D converter 11.
Are converted to digital values and stored in the image memory 12.
It is. The reference image memory 13 stores the image memory at the beginning of the measurement.
12, the image of the area including the work target 8 is displayed by the operator.
Read and save as directed. The address generator 14
From the image memory 12, the same as the reference image memory 13
Read a large area while shifting the position slightly
Thus, the address of the image memory 12 is generated and read. This
, The same image as in the reference image memory 13 is read in one area.
Each time the pulse is output, one pulse is output to the correlation calculation circuit 15 and all the pulses are output.
After reading the image, the coordinate calculation means 16 and the driving circuit 1
7 outputs one pulse. This function enables correlation calculation
The circuit 15 can detect the end of one area, and
And the drive circuit 17 can detect the end of one image. Image stored in reference image memory 13
When the address generator 14 reads an image of one area,
It is repeatedly read out in synchronization. In the correlation calculation circuit 15, the signals are input in synchronization with each other.
One area in the image memory 12 and the reference image memory 13
Calculate the correlation value of the image. For example, two correlation values
The sum of the absolute values of the differences for each pixel of the image is used. to this
If the two images are the same, the sum is 0,
If there is a difference between the images, the sum increases. That is, the correlation
The smaller the value, the greater the degree of correlation. The correlation calculation circuit 15 further transfers the data sequentially.
The largest correlation among the areas of the image memory 12
Detect the position of the area. All data in the image memory 12 is transferred.
In the coordinate calculation means 16, the correlation in the image is minimized.
The position of the large area is received from the correlation calculation circuit 15. Ma
At the same time, the drive circuit 17 is driven at a preset rotation pitch.
The rotation mechanism 2 is driven to capture the next image. At this time,
At the same time, the content of the reference image memory 13 is determined based on the correlation calculation result.
May be updated. The rotation angle of the rotation mechanism 2 depends on the rotation of the rotation mechanism 2.
Detected by the angle detector 3 connected to the shaft and inputting the angle
The data is input to the coordinate calculation means 16 via the circuit 18. Thereafter, in the same manner, the rotation mechanism 2
While changing the line-of-sight direction of the bi-camera 1, images are taken,
Detect the location of highly correlated areas for each image
You. In the coordinate calculating means 16, the work target 8 is
When it no longer exists, there is a specific magnitude of the correlation
If all are less than the threshold, the images detected so far
The position of the region showing the highest correlation of
Based on the rotation angle of the rotation mechanism 2 at the time of imaging,
Calculate the three-dimensional position. Next, the address generator 14 will be described in detail.
You. FIG. 3 shows a more detailed block of the address generator 14.
FIGS. 4A and 4B show an example of an image including the work target 8.
4 shows an image to be captured. Furthermore, FIG.
Change of image when image of work target 8 is taken while rotating
It is a figure showing a process. As shown in FIG. 4, the image memory 12
The top is the top address and the width is I_wIt has become. Address
Is increased by 1 in the horizontal direction, and when the first line is completed, two lines
Assigned to follow. The image menu shown in FIG.
The work target 8 is included in the reference image memory 13 from the memory 12.
When transferring the area, the three-dimensional coordinates of the work target 8
The point to be measured is designated as a representative point. Representative point address
A_tIs indicated, from there, の of the width W of the area
And the address A that is half the height H before_sStart point ad
And less. The starting point address A is stored in the reference image memory 13.
_sIs transferred to a region having a width W and a height H. The rotation mechanism 2 controls the line of sight of the television camera 1.
The direction changes counterclockwise as shown by the dotted line in FIG.
, The work target 8 moves from left to right on the image
Is imaged as follows. That is, the rotation angle is θ₀Image 5 at the time of
In FIG. 6, since the work target 8 is at the left end of the field of view 58,
Although it exists at the left end on 56, the rotation angle is θ₁Image 5 of
At 7, the work target 8 reaches the right end of the field of view 58,
An image is taken at the end. Therefore, first, the reference image memory 13
Start point address A of area specified for transfer _sThan
Cut out the area for correlation calculation only in the right direction
No. Also, the representative point address A_tIs the height of the image memory 12
If it is on the center line of the direction, rotate the TV camera 1
Only move on the center line,
Do not move to FIG. 3 shows a representative point address A_tIs image memory
In the address generation circuit when it is on the center line of 12
is there. Hereinafter, the circuit operation will be described. Representative point
An image is cut out to the reference image memory 13 in the register 21.
Representative point address A_tIs set in advance. Also the width
Register 22, height register 25, and image memory width
Each of the registers 26 has a width W of the reference image memory 13,
Height H and width I of image memory 12_wIs set in advance. In the first shift circuit 23, the width register 22
Is shifted right by one bit. That is, 1 / (width W)
Calculate 2. In the first subtractor 24, a representative point register
A value of 21_tFrom the value W / 2 of the first shift circuit 23
Calculate. At the same time, the second shift circuit 27
The value H of the data 25 to the right by one bit, and
Is calculated. In the first multiplier 28, the image memory width register
Star 26 width I_wOf the value H / 2 of the second shift circuit 27
Perform multiplication. In the second subtractor 29, the first subtractor 24
Is subtracted from the value of the first multiplier 28. Ie start
Point address A_sIs output. The first counter 30 stores the data in the image memory 12.
Each time one data is read, it is counted by one. That is, reading
Indicates the next address of the output data. First counter 3
0 is output from the first comparator 31 to the content W of the width register 22.
Are compared, and if they match, a pulse is output from the first comparator 31.
One is output. Pulse output from the first comparator 31
Resets the first counter 30 and at the same time
It is input to the counter 33. That is, the reference image memory 13
This means that the data for the width of is transferred. The output of the second counter 33 is a second comparator
36, and is compared with the value H of the height register 25.
If they match, one pulse is output from the second comparator 36
Is done. At the same time, the output of the second counter 33 is the second
Of the image memory width register 26
Data I_wIs multiplied by That is, of the read data
Indicates the address one line below. The second counter 33 has a second
It is reset by the pulse output from the comparator 36. That is,
This means that the data transfer of one area has been completed. The output of the second comparator 36 is the correlation calculation circuit 1
5 to notify the end of transfer of one area. The third cow
The counter 37 counts the pulses output from the second comparator 36.
To count. That is, the number of the area currently being transferred is output.
You. The output of the third counter is input to a third adder 38.
At the same time, it is input to the third comparator 40. Third
In the comparator 40, the inverter preset in the number register 39 is set.
The number of transmission areas is compared with the value of the third counter 37,
If the transfer of all areas is completed, one pulse
Output to the calculating means 16 and the driving circuit 17. In the third adder 38, the second subtractor 29
Is added to the output of the third counter 37. That is,
Start address A_sStarting at, and moving right by one pixel
Thus, the transfer start address of each transfer area is output. No.
The first adder 32 outputs the first adder 38 with the first
The output of the counter 30 is added. That is, the transfer start address
The right address is output one pixel at a time. Furthermore, the second
Of the first adder 32 and the second power of
The output of the arithmetic unit 34 is added. That is, the transfer start address
And outputs the address below one line at a time. As a result, the output of the second adder 35 is
First, representative point address A_tStarting from the area set by
Thus, an area of the same size as the reference image memory 13 is
Move the data in each area from top left to right while moving
Read one by one downward. Representative point address A_tBut
When it does not exist on the center line of the image memory 12, the second
The output of the subtracter 29 is used as the start address of the image memory 12.
Then, the value of the count register 34 is set to (the size of the image memory 12).
-I_w× (H-1)), the correlation value is
Can be calculated. Further, the rotation axis of the rotation mechanism 2 and the television camera
When the vertical axes of 1 are not parallel,
An area of the same size as the reference image memory 13 is set for each pixel.
Equivalent to axis misalignment than reading while moving to the right
Reading at an angle is more efficient. For this, the third
6 can be used instead of the counter 37 of FIG.
No. In other words, an increase in the lateral direction of the angle corresponding to the axis deviation in advance
Is written to the horizontal increment register 50, and the vertical increment is
Write to the vertical increment register 51. In the third multiplier 52,
The value of the vertical increment register 51 and the value of the image memory width register 26
The value is multiplied and input to the fifth adder 53. Fifth
Of the horizontal increment register 50 and the third power
The value of the calculator 52 is added. That is, the right address of one pixel
Address moved by the amount corresponding to the axis deviation instead of
Is output. The output of the fifth adder 53 is the sixth adder 5
4 is input. The other input of the sixth adder 54 is the fourth input.
The own output is input via the latch 55 of FIG. Fourth
The latch 55 receives one pulse from the second comparator 36.
The input data is latched each time it is executed. As a result, the sixth
Adder 54 and the fourth latch 55 make the second comparator
Every time a pulse from 36 enters, it is the amount equivalent to the axis deviation
The moved address is cumulatively added. Therefore, the image memo
Area of the same size as the reference image memory 13 from the
The area can be read out at an angle corresponding to the axis shift. Next, the correlation calculation circuit 15 will be described in detail.
You. FIG. 7 is a detailed block diagram of the correlation calculation circuit 15.
You. As shown in FIG.
Data read from the reference image memory 13
Is input to a third subtractor 41, and the difference is calculated.
You. The output of the third subtractor 41 is input to the absolute value circuit 42.
Then, the absolute value is obtained. The absolute value circuit 42
This is a memory that functions as a table. The output of the absolute value circuit 42 is supplied to a fourth adder 43
And the cumulative addition is performed for each pixel via the first latch 44.
You. The end of data of one area is notified from the address generator 14.
As it becomes known, the output of the first latch 44 becomes the second latch.
Latched by the latch 45. The minimum value register 46 is a television camera.
Preset to the maximum value when importing images from Camera 1
You. In the fourth comparator 47, the value of the minimum value register 46 is
The value of the second latch 45 is compared and the value of the second latch 45 is
If the output is smaller, one pulse is output. Fourth
The minimum value register 46 is determined by the pulse output from the comparator 47.
Latches the output of the second latch 45. That is, the minimum value
Update data. In the fourth counter 48, an address generator
1 every time the end of data of one area is notified from 14
Count each time. In other words, the number of the correlation calculation currently being executed is
It indicates whether it belongs to the eye area. Movement amount of each area is known
Therefore, the movement amount of the area is obtained by this. No.
The fourth latch 47 outputs the third latch 49
The output of the fourth counter 48 is latched, and the coordinate operation means 1 is latched.
Notify 6. In the coordinate calculation means 16, an address generator
When notified that transfer of all areas has been completed from 14,
The output of the third latch 49 is read. By repeating the above operation, coordinate calculation is performed.
Means 16 includes a rotation angle of the rotation mechanism 2 when an image is captured.
And the reference image memory 13 in each image.
The position of the region with the highest correlation, that is, the representative point in each image
Is determined. The operation of the three-dimensional coordinates in the coordinate calculating means 16
The calculation method will be described with reference to FIG. FIG.
2 shows an optical system. The world that is the basis for three-dimensional coordinates
The field coordinate system is OXYZ, and the rotation axis of the rotation mechanism 2 is Y axis.
Take parallel. On the rotation axis, in the lens of the TV camera 1
Heart O_VA point at the same height as the rotation center O_R(X_R, Y_R,
Z_R). Rotation center O_RHalf a rotation perpendicular to the rotation axis from
The center O of the lens at a position separated by the diameter I_VExists
become. The television camera 1 has a rotation angle θ of the rotation mechanism 2.
At 0 °, the center O of this lens_VCentering on the X axis,
Rotate by ω, φ, κ about Y axis and Z axis respectively
Think of it as an image. At this time, the direction of the line of sight of the television camera 1 is reversed.
The direction is the z axis, the horizontal direction of the image sensor 72 is the x axis, and the vertical direction is
Visual coordinate system O with y as the y-axis_Vxyz is defined. Imaging element
The child 72 is located at the center O of the lens._VAway from screen distance C
Perpendicular to the line of sight, and the line of sight is at the center of the image sensor 72
The image is taken to pass through. In addition, the rotation mechanism 2
Due to the movement, the visual coordinate system 71 is shifted by θ around the rotation axis.
It shall rotate. In the above optical system, the center O of the lens_VRank
(X₀, Y₀, Z₀) Is given by [Equation 1]. [0050] (Equation 1) The point P of the object is represented by (x_p,
y_p, Z_p) In the world coordinate system (X, Y, Z)
If expressed, Equation 2 holds. [0052] (Equation 2) Here, the matrix A is as follows. [0053] (Equation 3)The points P, p, O_vIs on a straight line
[Equation 4] is obtained from the above conditions. [0055] (Equation 4) Since the matrix A is a rotational coordinate transformation, the above equation is
It can be rewritten as [0057] (Equation 5) [Equation 5] represents the points P and O_vEquation of a straight line passing through
, The image at the rotation angle θ of the rotation mechanism 2
If you input the position (x, y) of the representative point above,
The least-squares method calculates the three-dimensional coordinates (X, Y, Z) of the object
Can be calculated. [0059] The present invention has been described specifically with the embodiments.
Thus, according to the present invention, it is not necessary to directly have a robot.
Robots that can work at heights, because they can perform non-contact teaching
Not only can it be applied to
Simple configuration consisting only of image pickup means, a rotation mechanism and an angle detector
The sensor head is compact, lightweight, andWide
IMeasurement range(In principle, a 360 ° range around the axis of rotation
Surround)The rotation device that rotates the entire device is not
It is important and can be made smaller. Also,3 or more eachCapture images at a rotation angle
Then, the position of the representative point on each image, that is,3 or more
Corresponding to the number of shooting positions3D position from the position of the work target
Error in detecting the work target in one image to calculate the target
Is canceled out, and higher precision can be achieved. Further, in order to detect a work target, an image is first taken.
The reference image is cut out from the
Uses a method to detect the area with the highest correlation with the image.
Laser light depending on the state of the surface of the object
There is no case where measurement is impossible due to non-reflection
Measurement that does not require specific indication on the object
Noh. As described above, according to the present invention, small and light
Quantity, high precision equipment can be configured, the surface of the object
Non-contact three-dimensional position measurement device that is not affected by
Can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram showing an embodiment of the present invention together with a robot to which the embodiment is applied. FIG. 2 is a block diagram showing the embodiment. FIG. 3 is a block diagram showing details of an address generator in the embodiment. FIG. 4 is an explanatory diagram showing a relationship between a position of a work target and an address in the image memory of the embodiment. FIG. 5 is an explanatory diagram showing a state of movement of an image due to rotation of a television camera in the embodiment. FIG. 6 is a block diagram illustrating details of an address generator for reading a correlation calculation area when the rotation axis is not parallel to the vertical axis of the television camera. FIG. 7 is a block diagram showing details of a correlation calculation circuit in the embodiment. FIG. 8 is an explanatory diagram for explaining a method of calculating three-dimensional coordinates in the embodiment. FIG. 9 is a configuration diagram showing a three-dimensional position measurement device according to the related art. [Description of Signs] 1 TV camera 2 Rotating mechanism 3 Angle detector 4 Processing device 5 Robot 6 Control device 7 Object 8 Work target 12 Image memory 13 Reference image memory 14 Address generator 15 Correlation calculation circuit 16 Coordinate calculation means 17 Drive circuit

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Claims (1)

(57) [Claims 1] In a three-dimensional position measuring device applied to operation teaching, position detection, etc. of an industrial robot or the like, the three-dimensional position measuring device is mounted on a rotating mechanism, and rotates the rotating mechanism. The same object is photographed at each of three or more positions.
One photographing means configured as described above, an angle detector for detecting a rotation angle of the rotating mechanism, an image memory for storing an image captured by the image capturing means, and an area designated from the captured images A reference image memory for storing only the image of the reference image; a correlation calculation circuit for extracting an area having the highest correlation with the contents of the reference image memory from the images captured thereafter; and transferring data of the image memory to the correlation calculation circuit. Address generator for outputting an address for the rotation, the rotation angles of the rotation mechanism, and the rotation angle positions.
The above reference image memo for each of three or more captured images
From the contents of the file and the coordinates of the highly correlated area,
The coordinates of the representative point in the area being imaged
And a coordinate calculating means for calculating the three-dimensional coordinates of the object based on each of the position coordinates .