JP2010256108A - Distance measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method which makes a corner part of an object to be measured correspond, with superior quality, to the image of the corner part in an image acquired by photographing the corner part in a stereo measurement method. <P>SOLUTION: The method relates to a distance measuring method for measuring the distance between a workpiece and an image capturing apparatus. The method includes: the reference part setting step in step S1 of setting a reference part by using information on the shape of the workpiece, and forming reference-part images acquired by looking the reference part from a plurality of directions; the imaging step in step S3 of photographing the workpiece from the plurality of directions with the image capturing apparatus, and forming a plurality of photographed images; the reference part detection step in step S4 of detecting the places of reference-part images wherein the reference part is photographed in the plurality of photographed images, by using the reference-part images; and the distance measuring step in step S5 of detecting the distance between the workpiece and the image capturing apparatus by using information on the places of the reference-part images. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a distance measuring method, and more particularly to a method for measuring the distance between an object to be measured and an imaging device using a plurality of images taken by the imaging device.

  A stereo measurement method is known in which an object to be measured is photographed from a plurality of locations using an imaging device, and a distance from the imaging device to the object to be measured is measured. The stereo measurement method is a method of measuring the distance from the imaging device to each measurement point of the object to be measured based on the principle of triangulation using images taken from a plurality of viewpoints.

  In the stereo measurement method, it is necessary to detect where a measurement point image obtained by photographing a measurement point is located in a plurality of images. A method for facilitating detection of the measurement point image is disclosed in Patent Document 1. According to this, images taken from two directions are divided by the frequency component of the video signal to form a multi-level image. Edges (hereinafter referred to as corners) are detected by subjecting the image to quadratic differentiation and ternary processing. And the place which the measurement point image respond | corresponded was detected by comparing the image image | photographed from two directions.

Japanese Patent No. 3539788

  When the object to be measured has a small number of corners, the number of corners in each photographed image decreases. And it becomes difficult to detect the location of the corner | angular part corresponding to the corner | angular part with a to-be-measured object in several image | photographed images. At that time, the possibility of erroneous measurement of the distance between the imaging device and the object to be measured increases. There has been a demand for a method of matching a corner portion of the object to be measured with an image of the corner portion in the photographed image with high quality.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

[Application Example 1]
The distance measurement method according to this application example is a distance measurement method for measuring the distance between the object to be measured and the imaging device, and sets a reference unit using shape information of the object to be measured, and includes a plurality of reference units. A reference part setting step for generating a reference part image viewed from the direction of the image, an imaging step for photographing the object to be measured by the imaging device from a plurality of directions and generating a plurality of photographed images, and the reference part image. A reference unit detecting step for detecting a location of a reference portion image obtained by photographing the reference portion in a plurality of the photographed images, and using the information on the location of the reference portion image, the measurement object and the imaging device. And a distance measuring step for detecting the distance.

  According to this distance measurement method, the reference part image is generated in the reference part setting step. A captured image is generated in the imaging step, and the location of the reference portion in the captured image is detected in the reference portion detection step. At this time, the location of the reference portion image is detected by searching for a location that matches or is similar to the reference portion image in the captured image.

  Thereafter, in the distance measurement step, the distance between the object to be measured and the imaging device is detected. Since the location of the reference portion in the captured image is detected, the direction in which the reference portion is located with respect to the optical axis direction of the imaging device can be detected. Shooting is performed from a plurality of directions. Then, a plurality of pieces of information on the position of the imaging device at the time of shooting and the direction in which the reference unit is located with respect to the optical axis direction of the imaging device is obtained. By using this information and the triangulation method, the distance between the imaging device and the reference unit can be calculated. Therefore, the distance between the imaging device and the object to be measured can be calculated.

  When detecting the location of the reference image in the captured image, a location that matches or is similar to the reference image in the captured image is searched. Therefore, it is possible to make it difficult to select the location of the reference portion as an incorrect location.

[Application Example 2]
In the distance measurement method according to the application example, in the reference portion setting step, a corner portion of the measurement object is extracted using shape information of the measurement object, and the reference portion sets a location including the corner portion. It is characterized by that.

  According to this distance measuring method, the corner is extracted from the shape information of the object to be measured. When photographing an object to be measured, the corner easily becomes a place where the luminance changes. And it becomes a place where it is easy to search from a picked-up image. Therefore, the reference portion can be easily searched by setting the location including the corner portion as the reference portion.

[Application Example 3]
In the distance measurement method according to the application example, when there are a plurality of locations that are candidates for the reference portion, a selection order for selecting the reference portion from the shape of the corner is set, and the candidate with a high selection order is selected as the candidate It selects as a reference part, It is characterized by the above-mentioned.

  According to this distance measurement method, the selection order for selecting the reference portion is set. Therefore, even when there are a plurality of locations that are candidates for the reference portion, it is possible to select a reference portion that is easy to detect.

[Application Example 4]
In the distance measurement method according to the application example described above, the reference portion image is formed by calculating an image when a three-dimensional model of the object to be measured is projected on a predetermined plane.

  According to this distance measurement method, the reference portion image is formed by calculation. When the reference object image is formed by photographing the object to be measured, the corner portion may not be clearly photographed depending on photographing conditions. Compared to this method, it is possible to form the reference portion image with higher accuracy by calculating and forming the reference portion image.

[Application Example 5]
In the distance measuring method according to the application example described above, an inner product amount obtained by calculating an inner product of a normal direction vector of a surface constituting the object to be measured and a unit vector indicating a predetermined direction is calculated, and the distribution of the inner product amount is changed. The corner is detected by searching for a place to perform.

  According to this distance measuring method, the inner product amount obtained by calculating the inner product of the normal direction vector of the surface constituting the object to be measured and the unit vector indicating the predetermined direction is calculated. And the corner | angular part is the place where distribution of the inner product amount changes. Therefore, a place where the directions of adjacent surfaces are different can be detected as a corner.

The schematic perspective view which shows the structure of a picking apparatus. The electric control block diagram of a picking apparatus. The flowchart which shows the process of picking a workpiece | work. The schematic diagram for demonstrating the method of picking a workpiece | work. The schematic diagram for demonstrating the method of picking a workpiece | work. The schematic diagram for demonstrating the method of picking a workpiece | work. The schematic diagram for demonstrating the method of picking a workpiece | work. The schematic diagram for demonstrating the method of picking a workpiece | work. The schematic diagram for demonstrating the method of picking a workpiece | work.

  Hereinafter, specific embodiments will be described with reference to the drawings. In addition, each member in each drawing is illustrated with a different scale for each member in order to make the size recognizable on each drawing.

(Embodiment)
A picking apparatus that detects and picks a workpiece location in the present embodiment, and an example of picking after measuring the workpiece location using a characteristic measurement method will be described with reference to FIGS. The picking device includes a measuring device that detects the location of the workpiece.

(Picking device)
First, the picking apparatus will be described with reference to FIGS. FIG. 1 is a schematic perspective view showing the configuration of the picking apparatus. As shown in FIG. 1, the picking apparatus 1 is mainly configured by a work table 2, a storage table 3, a measuring device 4, a robot 5, a control device 6, and the like.

  The work table 2 is disposed substantially at the center of the picking apparatus 1 and has a rectangular parallelepiped shape. In the present embodiment, the longitudinal direction of the work table 2 is the X direction, and the direction orthogonal to the X direction on the horizontal plane is the Y direction. The vertical direction is the Z direction. A rectangular loading plate 7 is arranged on the work table 2. A plurality of workpieces 8 as objects to be measured are placed on the loading plate 7. The work 8 is formed in a square plate shape on one side and is stacked facing multiple directions.

  A measuring device 4 is disposed on the Y direction side of the work table 2. The measuring device 4 includes a base 9 formed in a rectangular parallelepiped shape that is long in the Z direction. An XY table 10 is disposed on the upper side of the base 9, and a first support portion 11 is disposed on the XY table 10. The XY table 10 includes a linear motion mechanism that moves in the X direction and a linear motion mechanism that moves in the Y direction. The XY table 10 can move the first support portion 11 in the X direction and the Y direction. Further, the XY table 10 is provided with a detection unit that detects the movement amount. And the position of the 1st support part 11 with respect to the base 9 is detectable.

  The linear motion mechanism is, for example, a screw type linear motion mechanism provided with a screw shaft (drive shaft) extending in one direction and a ball nut screwed to the screw shaft, and the drive shaft receives a predetermined pulse signal. Are connected to a step motor (not shown) that rotates forward and backward in predetermined step units. When a drive signal corresponding to a predetermined number of steps is input to the step motor, the step motor rotates forward or reverse, and the table moves forward or backward by an amount corresponding to the number of steps. ing. The linear motion mechanism is not limited to this mechanism. In addition, a linear motor can be used for the linear motion mechanism.

  A first support part rotating part 12 is disposed on the first support part 11. The 1st support part rotation part 12 is provided with the rotation mechanism. This rotation mechanism is composed of, for example, a motor, a reduction gear, a rotor encoder, and the like. The rotation mechanism can rotate the first support portion 11 with respect to the XY table 10 around the Z direction.

  A plate-like second support portion 13 formed long in the X direction is disposed on the work support 2 side of the first support portion 11. A second support rotating unit 14 is disposed in the first support unit 11 at a location facing the second support unit 13. The 2nd support part rotation part 14 is provided with the rotation mechanism. As this rotation mechanism, a mechanism similar to the rotation mechanism in the first support portion rotation unit 12 can be used. And the 2nd support part rotation part 14 can rotate the 2nd support part 13 centering on the Y direction with respect to the 1st support part 11. FIG.

  A first imaging device 15 and a second imaging device 16 are arranged on the second support portion 13. The first imaging device 15 and the second imaging device 16 are installed so as to be able to photograph the direction of the work table 2 and can photograph the loading plate 7 and the workpiece 8. An illumination device 17 is disposed between the first imaging device 15 and the second imaging device 16. Further, illumination devices 17 are arranged on both sides of the first imaging device 15 and the second imaging device 16. The lighting device 17 is installed toward the stacking plate 7 and irradiates the stacking plate 7 and the work 8 with light.

  The measuring device 4 can photograph the workpiece 8 from a desired angle by driving the XY table 10, the first support unit rotating unit 12, and the second support unit rotating unit 14.

  A robot 5 is disposed on the right side of the work table 2 in the figure. In the present embodiment, a vertical articulated robot is used as the robot 5, but the present invention is not limited to this, and a horizontal articulated robot or an orthogonal robot can be used. The robot 5 has a plurality of arms arranged with joints therebetween. And the arm part 20 is arrange | positioned at the front-end | tip of a some arm. The arm portion 20 includes a linear motion mechanism, and a pair of finger portions 20a is disposed in the linear motion mechanism. By driving this linear motion mechanism, the robot 5 changes the interval between the finger portions 20a. And the arm part 20 can hold | grip the workpiece | work 8 between the finger parts 20a.

  A storage table 3 is arranged in the X direction of the robot 5. A work 8 is placed on the storage table 3 in an overlapping manner. The robot 5 picks the work 8 on the loading plate 7 and places the work 8 on the storage table 3 with the direction of the work 8 aligned. As a result, the workpieces 8 are arranged and arranged on the storage table 3. A control device 6 is disposed on the left side of the work table 2 in the drawing. The control device 6 is a device that controls the measuring device 4 and the robot 5.

  FIG. 2 is an electric control block diagram of the picking apparatus. In FIG. 2, the control device 6 includes a CPU (Central Processing Unit) 21 that performs various arithmetic processes as a processor, and a memory 22 as a storage unit that stores various types of information.

  The measurement device drive circuit 23, the first imaging device 15, and the second imaging device 16 are connected to the CPU 21 via the input / output interface 24 and the data bus 25. Further, the input device 26, the display device 27, and the robot drive circuit 28 are also connected to the CPU 21 via the input / output interface 24 and the data bus 25.

  The measurement device drive circuit 23 is connected to the XY table 10, the first support part rotating unit 12, and the second support unit rotating unit 14. The measuring device drive circuit 23 is a circuit that drives motors installed on the XY table 10, the first support unit rotating unit 12, and the second support unit rotating unit 14. The measurement device drive circuit 23 inputs the output of the position detection device provided in the XY table 10, the first support unit rotation unit 12, and the second support unit rotation unit 14. And the measuring device drive circuit 23 can move the 2nd support part 13 to a desired position, and can stop it. Since the first imaging device 15 and the second imaging device 16 are set in the second support unit 13, the measurement device drive circuit 23 tilts the first imaging device 15 and the second imaging device 16 in a desired direction. be able to. Accordingly, the first imaging device 15 and the second imaging device 16 can photograph the workpiece 8 from a desired direction.

  The first imaging device 15 and the second imaging device 16 include an area sensor inside. The area sensor incorporates a conversion circuit that converts a captured image into a digital signal. This conversion circuit transmits image information as a digital signal. When an instruction signal for capturing an image is received from the CPU 21, the image is captured and a digital signal of the image is transmitted to the memory 22. The memory 22 stores an image digital signal.

  The first imaging device 15 and the second imaging device 16 are provided with a focus mechanism. Then, the focus mechanism performs focus adjustment so that the focus of the image projected by the imaging lens matches the area sensors of the first imaging device 15 and the second imaging device 16. In accordance with an instruction from the CPU 21, the focus mechanism changes the place where the image is focused.

  The input device 26 is a device for inputting various data related to the shape of the workpiece 8, measurement conditions, operation instructions of the robot 5, and the like. For example, the input device 26 inputs shape data of the workpiece 8 from an external device. The display device 27 is a device that displays measurement conditions and work conditions, and an operator performs an input operation using the input device 26 based on information displayed on the display device 27.

  The robot drive circuit 28 is a circuit that drives the robot 5. The robot 5 is provided with a plurality of servo motors. The robot drive circuit 28 controls the rotation angle of each motor to be a predetermined angle. The robot drive circuit 28 controls the posture of the robot 5 to a desired posture.

  The memory 22 is a concept including a semiconductor memory such as a RAM and a ROM, and an external storage device such as a hard disk and a CD-ROM. Functionally, a storage area for storing the program software 29 in which the operation control procedure in the picking apparatus 1 is described is set. In addition, a storage area for storing robot-related data 30 such as dimensions of each part of the robot 5 and driving conditions of the motor is also set. In addition, a storage area for storing the workpiece shape data 31 when the shape of the workpiece 8 is designed is set.

  Furthermore, a storage area for storing imaging data 32 that is data of images taken by the first imaging device 15 and the second imaging device 16 is also set. Further, storage areas such as reference portion selection data 33 serving as a reference when selecting a reference portion from the image of the work 8 and reference portion image data 34 which is data obtained by calculating an image obtained by viewing the reference portion from multiple directions are stored. A storage area is set. In addition, a work area for the CPU 21, a storage area that functions as a temporary file, and other various storage areas are set.

  The CPU 21 performs control for measuring the height of the place where the workpiece 8 is located in accordance with the program software 29 stored in the memory 22. And the operation | movement which picks the workpiece | work 8 located in the top is controlled. As a specific function realization part, it has the work shape analysis part 37 which analyzes the corner | angular part which comprises the solid shape of the workpiece | work 8 using the design information of the workpiece | work 8. FIG. In addition, a reference unit setting unit 38 that sets a characteristic place as a reference unit from among a plurality of corners constituting the workpiece 8 is provided.

  Furthermore, it has an imaging control unit 39 that outputs an instruction signal in the direction in which the measuring device 4 takes an image to the measuring device drive circuit 23 and outputs an instruction signal for taking an image of the workpiece 8 to the first imaging device 15 and the second imaging device 16. . In addition, a reference unit detection unit 40 that detects a reference unit in two captured images is provided. Furthermore, it has the distance calculating part 41 which calculates the distance of the workpiece | work 8 and the 1st imaging device 15 and the 2nd imaging device 16 using the information of the location of the reference part in each image. In addition, a robot control unit 42 that outputs an instruction signal for picking the robot 5 is provided.

(Measuring method)
Next, a method of measuring the distances between the first imaging device 15 and the second imaging device 16 and the workpiece 8 using the above-described picking device 1 and picking the workpiece 8 will be described with reference to FIGS. FIG. 3 is a flowchart showing a process of picking a workpiece. 4 to 9 are schematic views for explaining a method of picking a workpiece.

  In FIG. 3, step S1 corresponds to a reference part setting step. The workpiece shape analysis unit extracts corner portions constituting the workpiece shape using the workpiece design information. Next, the reference part setting part sets the reference part from the pattern composed of the corners. The reference unit setting unit forms image data when the reference unit is observed from a plurality of viewpoints. Step S2 corresponds to a work placement process, and is a process of placing a work on the work table. Next, the process proceeds to step S3. Step S3 corresponds to an imaging step and is a step of photographing a workpiece using two imaging devices. Next, the process proceeds to step S4. Step S4 corresponds to a reference portion detection step, and is a step of detecting the location of the image corresponding to the reference portion in the photographed image. Next, the process proceeds to step S5. Step S5 corresponds to a distance measurement step, and is a step of calculating the distance between the imaging device and the workpiece. Next, the process proceeds to step S6.

  Step S <b> 6 corresponds to a workpiece moving process, in which the robot picks the workpiece and moves from the work table to the storage table. Next, the process proceeds to step S7. Step S7 corresponds to an end determination step, and is a step of determining whether all scheduled workpieces have been moved. When there is a workpiece that has not yet moved and the movement is continued, the process proceeds to step S3. When all the scheduled works have been moved, the work of picking the work is finished when the movement is finished. The work process for picking a workpiece is completed by the above process.

  Next, a method for measuring the distance between the imaging device and the workpiece and picking the workpiece will be described in detail with reference to FIGS. 4 to 9 in association with the steps shown in FIG. 4 to 6 are diagrams corresponding to the reference unit setting step in step S1. As shown in FIG. 4A, the workpiece shape analysis unit 37 forms a workpiece stereoscopic image 45 in the virtual space. The workpiece three-dimensional image 45 is an image in which the same shape as the workpiece 8 is formed in the virtual space using the workpiece shape data 31. The work stereoscopic image 45 includes a plurality of corner portions 46 and a surface 47. This corner 46 is a line where adjacent surfaces 47 are joined. When the space between adjacent surfaces 47 is a curved surface, a corner 46 is defined as a place where the change in the normal direction of the curved surface is large. First, the workpiece shape analyzing unit 37 extracts the corner 46 from the information on the surface 47 in the workpiece stereoscopic image 45.

  FIG. 4B is a schematic cross-sectional view seen from the line A-A ′ in FIG. In this cross section, a surface facing three directions is arranged on the Z direction side. The surface 47 from A to the A ′ side is defined as a first surface 47a, a second surface 47b, a third surface 47c, and a fourth surface 47d. The first surface 47a and the fourth surface 47d are the same surface. A unit vector indicating the normal direction of the surface in the first surface 47a is defined as a first surface vector 48a as a normal direction vector. Similarly, the second surface vector 48b, the third surface vector 48c, and the fourth surface are unit vectors indicating the normal directions of the surfaces of the second surface 47b, the third surface 47c, and the fourth surface 47d, respectively. It is assumed that the vector 48d.

  Next, the workpiece shape analysis unit 37 sets a first reference vector 49 and a second reference vector 50 as unit vectors. The first reference vector 49 and the second reference vector 50 are unit vectors set in the direction in which the first imaging device 15 and the second imaging device 16 are arranged. The first imaging device 15 and the second imaging device 16 can change the angle with respect to the workpiece 8. The first reference vector 49 and the second reference vector 50 are preferably directed in the direction of the range in which the first imaging device 15 and the second imaging device 16 move. Next, the workpiece shape analysis unit 37 calculates the inner product of the first reference vector 49 and each vector of the first surface vector 48a to the fourth surface vector 48d.

  FIG. 4C is a schematic diagram for explaining the calculation of the inner product. The inner product amount 51 of the first reference vector 49 and the second surface vector 48b will be described with reference to FIG. An angle formed by the first reference vector 49 and the second surface vector 48b is defined as an intersection angle 52. The workpiece shape analysis unit 37 calculates the inner product amount 51 by calculating the cosine function of the intersection angle 52. The workpiece shape analysis unit 37 calculates the inner product amount 51 at each location on the surface 47.

  FIG. 4D shows the transition of the inner product amount 51 of each surface with respect to the first reference vector 49. The vertical axis represents the inner product amount 51, and the upper side is larger than the lower side. The horizontal axis indicates the location of the surface 47. The first inner product distribution line 53 indicates the distribution of the inner product amount 51 at each location on the surface 47. As indicated by the first inner product distribution line 53, the inner product amount 51 is the same in the first surface 47a and the fourth surface 47d. The inner surface amount 51 is the same on the second surface 47b and the third surface 47c. The first inner product distribution line 53 changes between the first surface 47a and the second surface 47b. Therefore, it can be detected that the orientation of the surface 47 changes between the first surface 47a and the second surface 47b. Then, it is detected that this place is the corner 46. Similarly, it is detected that the place between the third surface 47c and the fourth surface 47d is the corner portion 46.

  FIG. 4E shows the transition of the inner product amount 51 of each surface with respect to the second reference vector 50. The vertical axis represents the inner product amount 51, and the upper side is larger than the lower side. The horizontal axis indicates the location of the surface 47. The second inner product distribution line 54 indicates the distribution of the inner product amount 51 at each location on the surface 47. As indicated by the second inner product distribution line 54, the second inner product distribution line 54 changes between the second surface 47b and the third surface 47c. Therefore, it can be detected that the orientation of the surface 47 is changed between the second surface 47b and the third surface 47c. Then, it is detected that this place is the corner 46. From the above, it is detected that the adjacent portion of each surface of the first surface 47a to the fourth surface 47d is the corner portion 46. As described above, the workpiece shape analyzing unit 37 detects the corner 46 using the first inner product distribution line 53 and the second inner product distribution line 54.

  FIG. 5A is a schematic plan view of the workpiece stereoscopic image 45 viewed from the Z direction. And the detected corner | angular part 46 is specified. Next, the reference part setting part 38 extracts the reference candidate part 55. The reference candidate part 55 is a place where a plurality of corners 46 intersect or a place where the corners 46 are circular. When the workpiece stereoscopic image 45 is viewed from the Z direction, nine reference candidate portions 55 are extracted.

  FIG. 5B is a list showing the selection order of the reference parts. As shown in FIG. 5B, in the reference part selection list 56, a selection order is set for the item field that is a condition for selecting one reference part from the reference candidate part 55. The reference part selection list 56 is stored in the memory 22 as reference part selection data 33. The contents and selection order of this item are not particularly limited. When there are a plurality of workpiece stereoscopic images 45, it is preferable to set so that only one characteristic pattern is selected.

  For the reference candidate portion 55 in the work stereoscopic image 45, the reference portion setting portion 38 determines whether or not there are candidates that are targets sequentially from the first item in the selection order of the reference portion selection list 56. Since there is a place corresponding to a single two-line intersection in the fourth selection order item, the reference unit setting unit 38 sets a place corresponding to this item as a reference unit. As a result, one reference portion 57 is set as shown in FIG. The information of the reference unit 57 is stored in the memory 22 as reference unit selection data 33.

  Next, as illustrated in FIG. 6, the reference unit setting unit 38 forms a reference unit image 58 when the reference unit 57 is viewed from a plurality of directions. When the first imaging device 15 and the second imaging device 16 photograph the workpiece 8, an image viewed from the direction in which the first imaging device 15 and the second imaging device 16 and the workpiece 8 may face each other is referred to. The setting unit 38 generates the reference image 58 as a reference image. Accordingly, the reference portion image 58 is formed by calculating an image obtained when the workpiece stereoscopic image 45 is projected onto a predetermined plane. A large number of reference portion images 58 are formed. Then, the reference unit setting unit 38 stores the reference unit image 58 in the memory 22 as the reference unit image data 34.

  FIG. 7A is a diagram corresponding to the workpiece placement process in step S2 and the imaging process in step S3. As shown in FIG. 7A, the loading plate 7 is installed on the work table 2 in step S2. A plurality of workpieces 8 are placed on the stacking plate 7. In the Z direction of the workpiece 8, the first imaging device 15, the second imaging device 16, and the illumination device 17 are arranged at a location facing the workpiece 8.

  Next, in the imaging process of step S <b> 3, the imaging control unit 39 causes the illumination device 17 to irradiate the work 8 with light. Then, the imaging control unit 39 causes the first imaging device 15 and the second imaging device 16 to image the workpiece 8. The captured image is stored in the memory 22 as the imaging data 32. FIG. 7B and FIG. 7C are diagrams corresponding to the imaging process in step S3. FIG. 7B shows a first image 61 as a photographed image photographed by the first imaging device 15, and FIG. 7C shows a second image 62 as a photographed image photographed by the second imaging device 16. Yes.

  The imaging control unit 39 applies a contour extraction filter to the first image 61 and the second image 62. Then, the line of the corner 63 in the first image 61 and the second image 62 is extracted. In the first image 61 and the second image 62, the corner 63 is a place where the brightness distribution changes greatly, and can be extracted by applying a contour extraction filter. As the contour extraction filter, for example, a Sobel filter, a Robinson filter, a Prewitt filter, a Roberts filter, a Kirsch filter, or the like can be applied. When the corner 63 has an arc shape, for example, the line of the corner 63 can be extracted by applying the Hough transform to the image.

  FIGS. 8A and 8B are diagrams corresponding to the reference portion detection step in step S4 and the distance measurement step in step S5. As shown in FIGS. 8A and 8B, in step S <b> 4, the reference part detection unit 40 searches for the reference part image 64 from the first image 61 and the second image 62. The reference unit detection unit 40 inputs one of the reference unit images 58 from the reference unit image data 34 in the memory 22. Then, the reference portion detection unit 40 searches for an image that matches the reference portion image 58 using a pattern matching method. Subsequently, the reference portion image 58 from the memory 22 is input, and the search for an image that matches the input reference portion image 58 is repeated. As a result, the reference image 64 is extracted from the first image 61 and the second image 62.

  Next, in step S5, the position in the X direction of each reference image 64 in the first image 61 and the second image 62 is measured. First, in the first image 61, the distance 65 from the left end of the first image 61 to each reference part image 64 is detected. In the first image 61, pixels are arranged in the X direction. Then, the position of each reference image 64 in the first image 61 in the X direction is detected by counting the number of pixels from the left end to each reference image 64. Similarly, in the second image 62, the distance 65 from the left end of the second image 62 to each reference part image 64 is detected.

  FIG. 8C and FIG. 9A are diagrams corresponding to the distance measuring step in step S5. As shown in FIG. 8C, in step S5, an angle 15c formed by the optical axis 15b and the direction 15a of the reference portion 8a on the work 8 with respect to the first imaging device 15 is calculated. At this time, the angle of the component in the X direction among the angles formed by the direction 15a and the optical axis 15b is defined as an angle 15c. An objective lens 15d and an area sensor 15e are arranged inside the first imaging device 15. The light reflected by the reference portion 8a of the work 8 passes through the objective lens 15d and forms an image on the area sensor 15e. A location in the X direction of the imaged reference portion image 64 is detected as a distance 65. A lens sensor distance 15f, which is a distance between the objective lens 15d and the area sensor 15e, is set in advance and has a predetermined value. In the area sensor 15e, the optical axis distance 15g, which is the distance between the end opposite to the X direction and the optical axis 15b, is also set in advance and has a predetermined value.

  The distance calculation unit 41 subtracts the distance 65 from the optical axis distance 15g to calculate the optical axis reference portion distance 15h, which is the distance in the X direction between the optical axis 15b and the reference portion image 64. Next, the distance calculation unit 41 calculates the angle 15c by using the optical axis reference unit distance 15h, the lens sensor distance 15f, and the trigonometric function. The distance calculation unit 41 performs the same calculation also in the second imaging device 16. Then, the distance calculation unit 41 calculates an angle 16c formed by the optical axis 16b and the direction 16a of the reference unit 8a on the work 8 with respect to the second imaging device 16.

  As shown in FIG. 9A, the first imaging device 15 and the second imaging device 16 are arranged side by side in the X direction. The optical axis distance 66, which is the distance between the optical axis 15b of the first imaging device 15 and the optical axis 16b of the second imaging device 16, is set in advance and has a predetermined value. A distance between the first imaging device 15 and the second imaging device 16 and the reference unit 8a on the workpiece 8 is referred to as a reference unit imaging device distance 67. The distance calculating unit 41 calculates the distance 67 between the reference unit imaging devices by using each value of the optical axis distance 66, the angle 15c, the angle 16c, and the trigonometric function.

  The distance calculating unit 41 sequentially calculates the distance 67 between the reference unit imaging devices with respect to the reference unit 8 a in the plurality of workpieces 8. Then, the distance calculation unit 41 selects a workpiece 8 that is located closest to the first imaging device 15 and the second imaging device 16 among the plurality of workpieces 8.

  FIG. 9B is a diagram corresponding to the workpiece moving process in step S6. As shown in FIG. 9B, in step S6, the robot control unit 42 drives the robot 5 to cause the arm unit 20 to grip the workpiece 8. At this time, the robot control unit 42 holds the workpiece 8 close to the first imaging device 15 and the second imaging device 16. Then, the robot control unit 42 moves the robot 5 to place the work 8 on the storage table 3.

  Subsequently, when it is determined in the end determination step of step S7 that the movement of the workpiece 8 is to be ended, the work is ended. The work process for picking a workpiece is completed by the above process.

As described above, this embodiment has the following effects.
(1) According to the present embodiment, the reference portion image 58 is generated in the reference portion setting step of step S1. A captured image is generated in the imaging process of step S3, and the location of the reference part image 64 in the first image 61 and the second image 62 is detected in the reference part detection process of step S4. At this time, the location of the reference image 64 is detected by searching the first image 61 and the second image 62 for a location that matches or is similar to the reference image 58. Accordingly, it is possible to make it difficult to select the location of the reference portion image 64 as an incorrect location.

  (2) According to the present embodiment, the corner 46 is extracted from the shape information of the workpiece stereoscopic image 45. The corner 46 tends to be a place where the luminance changes when the workpiece 8 is photographed. And it becomes a place where it is easy to search from the first image 61 and the second image 62. Therefore, the reference part image 64 can be easily searched by setting the reference part image 64 to include the corner part 63.

  (3) According to this embodiment, as shown in the reference part selection list 56, the selection order for selecting the reference part 57 is set. Therefore, even when there are a plurality of candidate locations for the reference unit 57, the reference unit setting unit 38 can select the reference unit 57 that is easy to detect.

  (4) According to the present embodiment, the reference part image 58 is formed by calculation by the reference part setting unit 38. When the workpiece 8 is photographed to form the reference portion image, the corner portion may not be clearly photographed depending on the photographing conditions. Compared to this method, the reference portion image 58 can be formed with higher accuracy when the reference portion image 58 is formed by calculation.

  (5) According to the present embodiment, the inner product obtained by calculating the inner product of the first surface vector 48 a to the fourth surface vector 48 d of the surface 47 constituting the workpiece stereoscopic image 45 and the first reference vector 49 and the second reference vector 50. The quantity 51 is calculated. And the corner | angular part 46 is the place where the 1st inner product distribution line 53 and the 2nd inner product distribution line 54 change. Therefore, a place where the direction of the adjacent surface 47 is different can be detected as the corner 46.

  (6) According to the present embodiment, the reference unit detection unit 40 searches the first image 61 and the second image 62 for a location that matches the reference unit image 58. Then, the reference part detection unit 40 detects the reference part image 64. As a method of detecting the reference image 64, there is a method of forming a multi-level image by dividing the frequency component of the video signal. In this method, a corner portion is detected by performing a second-order differentiation process on the image and performing a ternary process. Further, the reference portion is detected from the position of the corner portion in the two images. When the visual fields of the first imaging device 15 and the second imaging device 16 are wide, the reference portion can be detected more easily than this method.

  (7) According to the present embodiment, the reference unit detection unit 40 searches the first image 61 and the second image 62 for a location that matches the reference unit image 58. Accordingly, the reference portion 8a can be detected even in the case of the workpiece stereoscopic image 45 having a small number of corners 46.

In addition, this embodiment is not limited to embodiment mentioned above, A various change and improvement can also be added. A modification will be described below.
(Modification 1)
In the above embodiment, the place where the corner 46 intersects is set as the reference part 57, but the reference part 57 may be a characteristic place. For example, as shown in the reference part selection list 56, a circle, an ellipse, a polygon, or the like can be set. The corner 46 may be a concave corner or a convex corner. Moreover, the corner | angular part when a hole is formed may be sufficient.

(Modification 2)
In the embodiment described above, the optical axis 15b of the first image pickup device 15 and the optical axis 16b of the second image pickup device 16 are installed in parallel.

(Modification 3)
In the embodiment, two imaging devices, the first imaging device 15 and the second imaging device 16, are used. The number of imaging devices is not limited to two, and three or more may be used. And when the reference part 8a cannot image | photograph from one imaging device, you may make it image | photograph from another imaging device. It can handle workpieces of various shapes.

(Modification 4)
In the embodiment, two imaging devices, the first imaging device 15 and the second imaging device 16, are used. The workpiece 8 was photographed from two directions. One imaging device may be used. And you may image | photograph the workpiece | work 8 from several directions by moving an imaging device. When an imaging device with high resolution is used, it is not easy to manufacture the imaging device. At this time, the measuring device 4 can be easily manufactured by reducing the number of imaging devices.

(Modification 5)
In the embodiment, the reference portion 57 is selected from the corner portion 46. A mark may be arranged on the work 8 and the mark may be used as the reference unit 57. The reference portion 57 can be set even when the workpiece 8 has no characteristic corner portion 46.

  DESCRIPTION OF SYMBOLS 8 ... Work as a to-be-measured object, 8a, 57 ... Reference part, 15 ... 1st imaging device, 16 ... 2nd imaging device, 45 ... Work solid image as a three-dimensional model, 46 ... Corner | angular part, 48a ... Normal direction First surface vector as vector, 48b ... Second surface vector as normal direction vector, 48c ... Third surface vector as normal direction vector, 48d ... Fourth surface vector as normal direction vector, 49 ... Unit First reference vector as vector, 50... Second reference vector as unit vector, 51... Inner product amount, 58... Reference portion image, 61... First image as captured image, 62. 64: Reference portion image, 67: Distance between reference portion imaging devices.

Claims (5)

A distance measuring method for measuring a distance between an object to be measured and an imaging device,
A reference unit setting step for setting a reference unit using shape information of the object to be measured, and generating a reference unit image when the reference unit is viewed from a plurality of directions;
An imaging step of capturing the measured object from a plurality of directions with the imaging device and generating a plurality of captured images;
A reference part detection step of detecting a location of a reference part image obtained by photographing the reference part in the plurality of photographed images using the reference part image;
A distance measuring step of detecting a distance between the object to be measured and the imaging device using information on a location of the reference portion image. The distance measuring method according to claim 1,
In the reference part setting step, a corner part of the object to be measured is extracted using shape information of the object to be measured, and the reference part sets a location including the corner part. The distance measuring method according to claim 2,
When there are a plurality of locations that are candidates for the reference portion, a selection order for selecting the reference portion from the shape of the corner is set, and the candidate having a higher selection order is selected as the reference portion. Distance measurement method. The distance measuring method according to claim 3,
The distance measurement method according to claim 1, wherein the reference portion image is formed by calculating an image when a three-dimensional model of the object to be measured is projected on a predetermined plane. The distance measuring method according to claim 4,
The inner product amount is calculated by calculating the inner product of the normal direction vector of the surface constituting the object to be measured and the unit vector indicating a predetermined direction, and the corner portion is searched by searching for a place where the distribution of the inner product amount changes. A distance measuring method characterized by detecting.

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