JPH0961117A - Three-dimensional position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the distance to an object by picking up the image of a ring beam applied to the object with a camera and detecting one portion or the entire part of the image which is registered in advance from the picked-up images along one scanning line on an image memory in the horizontal direction. SOLUTION: The image of aring beam 12 is stored in a registration memory 7 in advance and an image outputted from a camera 3 is stored at an image memory 5. An image obtained by binarizing the image from the memory 5 and aregistered image from the memory 7 are inputted to a correlation operator 8. Since the ring beam image travels only in lateral direction on the memory 5, the operator 8 detects one or a plurality of regions which are highly correlated to one portion or the entire part of the trgostered image in the memory 7, namely those which extremely match, and output them to an image coordinate detection means 9. The means 9 detects the center image coordinates of a ring beam image inducing the region from one portion or the entire part of the registered image based in the input from the operator 8. The center coordinates of the ring beam image detected by the means 9 are inputted to a three-dimensional coordinate calculating means 10, thus calculating the distance to a target surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is a tertiary robot which is equipped in an industrial robot such as a painting robot or a welding robot and is used for measuring a distance to an object or detecting an end portion when performing a painting work or a welding work. The present invention relates to an original position detection device.

[0002]

2. Description of the Related Art When an industrial robot such as a painting robot or a welding robot is made to perform a desired work, it is necessary to previously give work data for instructing the robot what kind of work should be performed. There is a so-called teaching playback method as the simplest method of giving work data. In this teaching playback system, an operator manually operates an industrial robot in a state where a work object is installed, operation data at this time is stored, and subsequent work is performed using the stored data. It is a thing.

However, in the above teaching playback system, the object has to be installed in the same state as when the data is input during the actual work, and therefore, there are drawbacks such as a large number of steps and a low work efficiency. Moreover, there are problems such as the deflection of the industrial robot itself and weakness in disturbance.

Therefore, a device for measuring the position from the hand of the industrial robot or another position to the object and determining the relative positional relationship with the industrial robot for positioning is required. It should be noted that if the industrial robot itself can copy the surface of the object, it is not necessary to input data by the teaching playback method, and it is expected that the man-hours will be reduced and the work efficiency will be improved.

FIG. 4 is a diagram showing a conventional three-dimensional position detecting device, which is attached to the hand of an industrial robot or at another position to measure the distance and shape to an object. As shown in FIG. 4, in this three-dimensional position detecting device, the slit light 15 emitted from the slit laser light source 14 is irradiated toward the object 13. The slit laser light source 14 is one in which a cylindrical lens (not shown) is installed in front of the laser tube. When the slit laser light source 14 is driven by being supplied with power from the drive circuit 2, the slit laser light source
It is converted into 5 and output.

The slit light 15 applied to the object 13 is imaged by the camera 3. Camera 3 has slit light 1
The slit laser light source 1 is arranged in a direction perpendicular to the plane of FIG.
It is installed at a position separated from D4 by a constant distance D. An optical bandpass filter 4 is mounted on the front surface of the camera 3. The optical bandpass filter 4 has its maximum transmission wavelength matched with the oscillation wavelength of the slit laser light source 14, and has a sufficiently narrow transmission wavelength width. By doing so, only the slit light 15 is reflected in the image captured by the camera 3.

The image output from the camera 3 is stored in the image memory 5. The images stored in the image memory 5 are
The data are sequentially read out in the horizontal direction from the upper scanning line and input to the binarization circuit 6.

The binarization circuit 6 compares the density of the input image with a preset threshold value, outputs an H signal if the density is equal to or higher than the threshold value, and outputs an L signal if the density is lower than the threshold value. It is supposed to do. The output of the binarization circuit 6 is input to the image coordinate detecting means 9.

The image coordinate detecting means 9 is reset to "0" at the start of image transfer from the binarizing circuit 6 and counts the number of scanning lines, and "0" at the beginning of each scanning line. And a second counter which is reset to count the number of data. When the H signal data is input from the binarization circuit 6, the value of the first counter at that time is taken as the ordinate (j coordinate) on the image, and the value of the second counter is taken as the abscissa (i coordinate). Output as. The coordinate value (i, j) output from the coordinate detecting means 9 is input to the three-dimensional coordinate calculating means 10.

As described above, the camera 3 is installed at a position separated from the slit laser light source 14 by a distance D in the direction perpendicular to the plane of the slit light 15, so that the camera 3
The position of the slit light 15 shown on the image differs depending on the distances L1 and L2 from the object to the object 13.

FIG. 5A shows how the position of the slit light image changes when the slit laser light source 14 is located on the left side of the camera 3. The slit light image on the lower side of FIG. 5A shows the position at the distance L1.
The slit light image on the upper side shows the position at the distance L2. That is, the i coordinate of the slit light 15 on the image indicates the distance to the object 13, and the closer to the left in the figure, the closer to the camera 3. This is a known triangulation principle.

Returning to FIG. Three-dimensional coordinate calculation means 1
At 0, paying attention to the i coordinate of the input coordinate value (i, j), the distance to the object 13 is obtained by the principle of triangulation. The distance to the object 13 obtained by the three-dimensional coordinate calculation means 10 is displayed on the display 11. Further, the above distance information is directly input to the industrial robot and used for controlling the industrial robot.

[0013]

In the conventional device described above, since the slit light 15 is used, (a) in FIG.
As shown in FIG.
When and are substantially orthogonal to each other, the end portion of the target object 13 can be copied, but as shown in FIG. 5B, the member end portion of the target object 13 and the slit light 15 are substantially parallel to each other. At times, the member end portion of the object 13 becomes unknown. Therefore, it is necessary to separately scan the slit light 15 with a scanner or the like to detect it, and the size of the apparatus increases. Also, slit light 1
Since the shape of 5 is simple, when some noise is included in the image, the true slit light image and the noise cannot be distinguished from each other, and there is a risk of erroneous measurement. Furthermore, the slit light 15 may be imaged in all areas on the image,
There is a problem that a long processing time is required because the entire image is always processed.

An object of the present invention is to provide a three-dimensional position detecting device having the following effects. (a) It is possible to detect the member end of the object in the entire circumferential direction with respect to the laser optical axis, and there is no need to scan the laser light,
The device can be miniaturized, and the moving part such as the scanner is not required, so that the reliability is improved.

(B) It is possible to clearly distinguish between small noises and noises of different shapes, so that erroneous measurement is extremely reduced and measurement accuracy can be improved. (c) Only one scanning line in the image memory needs to be searched for the detection, and the processing time can be shortened.

[0016]

Means for Solving the Problems In order to solve the above problems and achieve the object, the following means are used in the present invention. The three-dimensional position detecting device of the present invention is a ring laser light source for irradiating a ring light having a conical spread, and a light beam in a direction perpendicular to a straight line connecting the projection center of this ring laser light source and the center of its own lens. A camera having an axis, an image memory for storing an image output from the camera, a registration memory for pre-registering the image of the ring light, and a horizontal direction along one scanning line in the image memory. Correlation calculator for detecting at least a part of the ring light image registered in the registration memory while moving to, and image coordinates for detecting coordinates on the image of the region detected by the correlation calculator It comprises a detecting means and a three-dimensional coordinate calculating means for calculating the distance from the coordinates detected by the image coordinate detecting means to the object, and the front of the ring light radiated toward the object. Captured by the camera,
It is configured to measure a distance to an object by laterally detecting a part or all of an image registered in advance from the captured image along one scanning line on the image memory. .

In the above three-dimensional position detecting device, ring light is emitted from the ring laser light source toward the object. On the other hand, the camera has an optical axis in a direction perpendicular to a straight line connecting the projection center of the ring laser light source and the center of its own lens, and a plane including the optical axis of the camera and the projection center of the ring laser light source. When the object is imaged so that the line of intersection with the object plane is orthogonal to the camera optical axis, the ring light image on the image is always the same size, and the image is taken according to the distance between the camera and the object. It only moves laterally up. Therefore, the ring light image is stored in advance in the registration memory, and the image output from the camera is stored in the image memory. The binarized image of the image from the image memory and the registered image from the registered memory are input to the correlation calculator.

As described above, since the ring light image moves only laterally on the image memory, the correlation calculator calculates a part or all of the registered image in the registered memory at a constant j coordinate on the image memory. One or a plurality of highly correlated regions, that is, well-matched regions are detected and output to the image coordinate detecting means.

The image coordinate detecting means detects the image coordinate of the center of the ring light image including the region from a part or the whole of the registered image based on the input from the correlation calculator. The center coordinates of the ring light image detected by the image coordinate detection means are
It is input to the three-dimensional coordinate calculation means, and the distance to the object surface is calculated.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is a view showing the arrangement of a three-dimensional position detecting apparatus according to the first embodiment of the present invention. As shown in FIG. 1, the ring light 1 emitted from the ring laser light source 1
2 is irradiated toward the object 13. The ring laser light source 1 has a conical lens (not shown) installed in front of the laser tube, and when driven by power supplied from the drive circuit 2, converts the laser beam light into ring light 15 and outputs it. To do.

The camera 3 has an optical axis in a direction perpendicular to a straight line connecting the projection center of the ring laser light source 1 and the center of its own lens, and the optical axis of the camera 3 and the projection center of the ring laser light source 1 The object is imaged so that the line of intersection between the plane including the and the plane of the object 13 is orthogonal to the camera optical axis.

An optical bandpass filter 4 is mounted on the front surface of the camera 3. The optical bandpass filter 4 is
The maximum transmission wavelength is matched with the oscillation wavelength of the ring laser light source 1, and the transmission wavelength width is sufficiently narrowed. By doing so, only the ring light 12 is captured in the image captured by the camera 3. The principle of position detection by the image pickup system will be described with reference to FIG.

FIG. 2A is a view showing the coordinate system of the image pickup system in this apparatus. The origin of the coordinate system is placed at the center of the lens of the camera 3, the optical axis direction of the camera 3 is the Z axis, the axis extending from the origin to the projection center of the laser is the X axis, and the axis perpendicular to the XZ plane including the X axis and the Z axis. The direction is the Y axis.

The ring light 12 has a conical divergence whose apex is the laser projection center, and the divergence angles are θ1 and θ2 when viewed from a straight line parallel to the Z axis. Further, the camera 3 has an imaging surface at a position separated from the center of the lens by a focal length f, and the position P of the ring light 12 irradiated on the object surface.
The incident angles of the images from 1 and P2 are ω1 and ω2, respectively.

When the size of the ring light image is first obtained in the above state, x in FIG. 2A indicates the size of the ring light. Next, the positions P1 and P2 of the ring light 12 on the object surface at a position separated from the camera 3 by the distance L are expressed by equation (1).

P1 = (L, D + tan θ1) P2 = (L, D + tan θ2) (1) Therefore, the incident angle of the image from the positions P1 and P2 to the imaging surface of the camera 3 is expressed by the following equation.

The ^{ω1 = tan -1 {(D +} Ltanθ1) / L} ω2 = tan -1 {(D + Ltanθ2) / L} ... (2) As a result, the size x of the ring light image on the imaging surface, (3)
It becomes an expression.

X = f (tanω 2 −tanω 1) = f [{(D + Ltan θ 2) / L}-{(D + Ltan θ 1) / L}] = f (tan θ 2 −tan θ 1) ... (3) As is clear from the equation (3), , Ring light image size x
Does not depend on the distance L.

That is, even if the distance L changes, the size of the ring light image is constant. Similar calculations can be performed for all planes around the X axis using the above equation. Further, since the laser projection center and the lens center of the camera 3 are arranged side by side on the X-axis, θ is set in the direction perpendicular to the paper surface of FIG.
1 = ω1, θ2 = ω2, which is also constant regardless of the distance L.

From the above, the image of the ring light 12 taken by the camera 3 is the distance L between the camera 3 and the object 13.
It can be seen that the size and shape are exactly the same regardless of. Next, the center position of the ring light image on the image is obtained. The center position x ₀ on the image pickup surface is expressed by equation (4).

X ₀ = f {(D + Ltan θ) / L} = (fD / L) + ftan θ (4) That is, the lateral movement is in inverse proportion to the distance L between the camera 3 and the object 13. In the vertical direction, the laser projection center and the camera 3
Since it is installed so that the center of the lens is aligned with the X axis, no movement occurs.

To summarize the above, as shown in FIG. 2B, a ring light image of the same size changes from left to right on the image as the distance L changes from small to large. You will move to the right. The straight line locus of the center position of the ring light image at this time is hereinafter referred to as an epipolar line.

Returning to FIG. The registration memory 7 stores in advance a ring light image of a perfect shape obtained as a result of irradiating the flat plate or the like with the ring light 12. The registered image is binarized in order to simplify the correlation calculation.

The image output from the camera 3 is stored in the image memory 5. The image output from the image memory 5 is input to the binarization circuit 6. The binarization circuit 6 compares the density of the input image with a preset threshold value, outputs an H signal if the density is higher than the threshold value, and outputs an L signal if the density is lower than the threshold value.

FIG. 3A is a diagram showing an example of a binarized image obtained when the object 13 having a step as shown in FIG. 1 is imaged. As is apparent from FIG. 3A, a part of the ring light 12 reflected by the upper plane of the object 13 is on the left side of the screen and the ring light 1 reflected by the lower plane is 1.
Parts of 2 are separated and imaged on the right side of the screen.

The output of the binarization circuit 6 and the output of the registration memory 7 are input to the correlation calculator 8. The correlation calculator 8 is composed of a logical product circuit and a counter, and operates so as to count the correlation value when both of the two input binary images are H signals.

As shown in FIG. 3B, the registration memory 7
A binarized image of a complete ring light image is registered in. As shown in (c) of FIG. 3, in the input image as shown in (a) of FIG. 3, the j1 (= j2) coordinate is the epipolar line. Since this epipolar line is determined when the camera 3 and the ring laser light source 1 are installed, it can be treated as known information when measuring the object 13.

The correlation calculator 8 finds the logical product of the registered image and the input image along the epipolar line while shifting the center position of the registered image by one pixel from the left end of the input image. When the center of the registered image reaches the (i1, j1) coordinate, the reflected light image at the upper part of the target object 13 in the input image and the left side portion of the registered image match. Then, when the logical product of the two is taken, the "H" region corresponding to the reflected light image at the upper part is obtained. Therefore, the counter in the correlation calculator 8 counts as many correlation values as about half of the ring light image.

Similarly, the center of the registered image is (i2, j2)
When the coordinates are reached, the reflected light image of the lower part of the object 13 in the input image and the right side portion of the registered image match. Then, when the logical product of the two is taken, the "H" region corresponding to the reflected light image at the lower part is obtained. Therefore, in the counter in the correlation calculator 8,
Only about half the number of the ring light images will be counted. Almost no correlation value is counted at other positions on the epipolar line.

The description will be returned to FIG. 1 again. The output of the correlation calculator 8 is input to the image coordinate detecting means 9. The image coordinate detecting means 9 is reset to “0” at the start of inputting a correlation value from the correlation calculator 8 and a comparison circuit that compares the input correlation value with a threshold value, and every time one correlation value is input. To 1
And a threshold value for determining that the input correlation value is close to the registered image to some extent, for example, a value equal to or larger than about half the number of pixels of the ring light image in the registered image. Then, the value of the counter at that time, that is, the i coordinate on the image is output. Since the j coordinate is the position of the epipolar line, this is a fixed value (j1)
Is output.

The coordinates output from the image coordinate detecting means 9 are input to the three-dimensional coordinate calculating means 10. In the three-dimensional coordinate calculation means 10, the input coordinates (i1, j1
) And the i coordinate of (i2, j2), the distance L to the object 13 is calculated using the equation (4). Here, the relationship between the i coordinate and x ₀ of the equation (4) is expressed by the equation (5). x ₀ = αi (5) Here, α is a constant coefficient and is obtained by (width of image sensor) / (number of horizontal pixels of image memory).

The distance L to the object 13 obtained by the three-dimensional coordinate calculation means 10 is displayed on the display 11. Information indicating the distance L is directly input to the industrial robot and used for controlling the industrial robot.

[0043]

According to the present invention, it is possible to provide a three-dimensional position detecting device having the following effects. (a) Since the beam shape is circular, it is possible to detect the member end portion of the object in the entire circumferential direction with respect to the laser optical axis, it is not necessary to scan the laser light, and the device can be downsized, and Reliability is improved because there is no need for moving parts such as a scanner.

(B) In the detection of ring light, the correlation value with the ring light of perfect shape is obtained and the comparison judgment with the threshold value is performed, so it is clear to distinguish between small noise and noise of different shapes. Therefore, erroneous measurement is extremely reduced, and measurement accuracy can be improved. (c) Since the ring light moves only on the epipolar line, only one scanning line on the image memory needs to be searched for the detection, and the processing time can be shortened.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a three-dimensional position detection device according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the principle of position detection by the image pickup system of the three-dimensional position detection device according to the first embodiment of the present invention.

FIG. 3 is an operation explanatory view of the three-dimensional position detecting device according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a three-dimensional position detecting device according to a conventional example.

FIG. 5 is an explanatory diagram of a detection operation of a member end portion by the three-dimensional position detecting device according to the conventional example.

[Explanation of symbols]

 1 ... Ring laser light source 2 ... Laser light source drive circuit 3 ... Camera 4 ... Optical bandpass filter 5 ... Image memory 6 ... Binarization circuit 7 ... Registration memory 8 ... Correlation calculator 9 ... Image coordinate detection means 10 ... Three-dimensional coordinates Calculation means 11 ... Display device 12 ... Ring laser light 13 ... Object 14 ... Slit laser light source 15 ... Slit light

Claims (1)

[Claims] 1. A ring laser light source for irradiating a ring light having a conical spread, and a camera having an optical axis in a direction perpendicular to a straight line connecting a projection center of the ring laser light source and its own lens center. An image memory for storing an image output from this camera, a registration memory for pre-registering the image of the ring light, and a horizontal memory that moves along one scanning line in the image memory. A correlation calculator that detects at least a part of the ring light image registered in the registration memory, an image coordinate detection unit that detects the coordinates on the image of the region detected by the correlation calculator, and the image coordinates And a three-dimensional coordinate calculation means for calculating the distance from the coordinates detected by the detection means to the object, the ring light emitted toward the object is imaged by the camera, Tertiary characterized by measuring the distance to the object by detecting a part or all of the image registered in advance from the imaged image along one scanning line on the image memory. Original position detection device.