JP5561109B2 - Apparatus and method for measuring three-dimensional dimensions - Google Patents

Description

  The present invention relates to an apparatus for measuring a three-dimensional dimension that measures a three-dimensional dimension of a measurement object in a non-contact manner with high accuracy and at high speed, and a method for measuring the three-dimensional dimension.

  In recent years, a method for restoring the three-dimensional shape of an object from an image taken from a free position by holding the camera in a hand, for example, has been studied. In this case, it is necessary to obtain the position and orientation of the camera at each photographing time. One of the techniques for this is camera calibration (also called camera calibration).

  There are several methods for camera calibration. In Patent Document 1 of that document, a plurality of markers (LEDs) are provided on the upper surface of a measurement head that measures a three-dimensional shape by a light cutting method, and a measurement head that is freely arranged with respect to an object is provided above. A method for obtaining the position and orientation of the measurement head in the coordinate system (also referred to as the world coordinate system) by photographing with a three-dimensional measurement camera is shown.

  In this method, the coordinates of each point of the object in the measurement head central coordinate system measured by the measurement head are converted using the information on the position and orientation of the measurement head obtained by the three-dimensional measurement camera, and the world coordinates The shape of the object in the system is being sought.

  Since the method of Patent Document 1 uses an LED that emits light as a marker for determining the position and orientation of the measurement head, the influence of illumination differences on marker identification can be significantly reduced.

  However, in this method, the same LED is used for a plurality of markers, and individual markers are not identified based on the characteristics of each marker, but are determined based on the arrangement pattern of the markers on the top surface of the head. .

  For this reason, if any of the markers on the upper surface of the head becomes a shadow of the target and cannot be captured by the three-dimensional measurement camera, it is automatically determined which of the plurality of markers the marker in the captured image corresponds to. Sometimes it becomes virtually impossible.

  In order to improve this, the method of Patent Document 2 has been developed. In Patent Document 2, light-emitting markers such as light-emitting diodes that can actively switch between bright and dark states are used as markers used as camera calibration standards, and the light-emitting markers are switched according to a unique switching pattern. .

  Then, a light-dark change pattern is obtained for each marker from an image frame group obtained by continuously photographing the light-emitting markers, and each marker is identified from the obtained pattern. With such a mechanism, it is said that individual markers can be identified even when ambient light changes or when some markers are hidden by an object.

  In the measurement procedure in the three-dimensional measurement system described in Patent Document 2, first, the reference position is moved from each viewpoint position while sequentially moving the three-dimensional measurement apparatus to N (natural number) viewpoint positions freely selected by the photographer. The work process is started by photographing the panel and the measurement object placed on the panel.

JP 2001-241927 A Japanese Patent No. 3779308

  As described above, the three-dimensional coordinates of each point in the image in the image capturing device central coordinate system are converted into a common world coordinate system from the images captured by the image capturing device from a plurality of viewpoint positions freely selected by the photographer. Although the device is known, in applications where parts manufactured at the factory are measured one after another, the set position of the measurement object is shifted and becomes unstable, so the entire reference panel is imaged with the imaging device There is a need.

  As a method for starting 3D measurement from an arbitrary position arbitrarily selected, a method of photographing the entire reference panel at once, or a method of photographing the entire reference panel in a divided manner is conceivable. In the method of photographing, a high-definition image is required to increase the measurement accuracy, and there is a problem that the photographing device is expensive. In addition, the method of taking an image by dividing the whole requires a large number of times of shooting, which causes a problem of a long measurement time.

  The present invention has been made paying attention to such problems existing in the prior art, and its purpose is to automatically determine the viewpoint position of the three-dimensional measurement camera in accordance with the position of the measurement object. An object of the present invention is to provide an apparatus and a method for measuring a three-dimensional dimension in a non-contact manner that can increase the measurement accuracy and reduce the measurement time.

  Descriptions of patent documents listed as prior art can be introduced or incorporated by reference as explanations of technical elements described in this specification.

In order to achieve the above object, the present invention employs the following technical means. That is, according to the first aspect of the present invention, there is provided an apparatus for measuring a three-dimensional dimension of a fixture included in a measurement object, wherein a plurality of markers are regularly arranged and photographed as a background of the measurement object. And a position measurement camera that captures the measurement object including the fixture and the reference plate at fixed positions, and an image of the measurement object and the reference plate captured by photographing the measurement object at multiple viewpoint positions . A three-dimensional measurement camera that acquires the image, an actuator that moves the three-dimensional measurement camera to a plurality of viewpoint positions, and a control device that controls the actuator and the three-dimensional measurement camera. The control device captures an image captured by the position measurement camera. 2D coordinate calculation means for calculating a 2D coordinate of a measurement object in a reference plate coordinate system which is a coordinate system based on the reference plate Based on the two-dimensional coordinates calculated by the two-dimensional coordinate calculation means, the search means for searching a plurality of viewpoint positions of the three-dimensional measurement camera by image recognition of the fixture, and the three-dimensional measurement camera at the viewpoint position searched by the search means It has a three-dimensional coordinate calculation means for obtaining the three-dimensional coordinates of the fixture in the three-dimensional measurement camera reference coordinate system, which is a coordinate system based on the position of the three-dimensional measurement camera, based on the formed image. .

  According to the present invention, the entire reference plate is photographed by the position measurement camera, the viewpoint position at which the three-dimensional position of the fixture can be easily measured is searched, the three-dimensional measurement camera is moved to this viewpoint position, and the optimum position is obtained. Therefore, the measurement accuracy can be increased. In addition, two-dimensional coordinates in the reference plate coordinate system are obtained based on the images taken by the position measurement camera, the viewpoint position is searched based on the two-dimensional coordinates, and the three-dimensional measurement camera is driven to the viewpoint position by the actuator. Therefore, the measurement time can be shortened as compared with the case of shooting from an arbitrary viewpoint position.

  In the invention according to claim 2, the exploration means attaches a standard measurement object in order to determine the viewpoint position of the three-dimensional measurement camera based on the two-dimensional coordinates in the reference plate coordinate system of the measurement object. The viewpoint position is determined by executing image recognition in a plurality of predetermined search areas on the basis of the position of the tool.

  According to this invention, since it has the exploration means for performing image recognition in a plurality of exploration areas, even if the measurement object is placed on the reference plate in a shifted manner, the image recognition in the exploration area determined in advance, The viewpoint position of the three-dimensional measurement camera related to the position of the fixture can be calculated within a relatively short time.

  In the invention according to claim 3, the fixture is a pin or a bracket of the measurement object, and the three-dimensional coordinate calculation means is based on an image photographed by the three-dimensional measurement camera, between the pins or between the brackets. It is characterized by measuring dimensional dimensions.

  According to the present invention, since the three-dimensional dimensions between pins or between brackets are measured based on images taken by the three-dimensional measurement camera, defective products whose dimensions are not normal can be eliminated.

  In the invention according to claim 4, the actuator comprises a multi-axis orthogonal robot, the actuator is controlled by a robot controller that controls the multi-axis orthogonal robot, and the exploration means is a reference plate coordinate system of the measurement object in the robot controller. A plurality of viewpoint positions of the three-dimensional measurement camera are determined on the basis of the two-dimensional coordinates.

  According to the present invention, the actuator is composed of a multi-axis orthogonal robot, and the viewpoint position is determined in the controller of the robot. Therefore, the three-dimensional measurement camera can be moved to the viewpoint position at high speed.

  In the invention described in claim 5, the three-dimensional measurement camera is a stereo camera that captures an image necessary for three-dimensional measurement by the passive stereo method, and is driven by an actuator to photograph a fixture at a plurality of viewpoint positions. An image in which the fixture and the reference plate are reflected is transmitted to the control device.

  According to this invention, the stereo camera that performs three-dimensional measurement by the passive stereo method can be easily moved to the viewpoint position by the actuator, and the three-dimensional measurement of the fixture can be easily performed.

  In the invention according to claim 6, the control device performs a parameter calculation for calculating a coordinate conversion parameter from a coordinate system based on the three-dimensional measurement camera to a world coordinate system based on the reference plate, and has a plurality of viewpoints. From the image captured by the 3D measurement camera from the position, a 3D coordinate system based on the 3D measurement camera for each of the plurality of viewpoint positions is obtained using a coordinate conversion parameter for each viewpoint position obtained by parameter calculation. It is characterized in that it is integrated with the world coordinate system and the dimensions of the measurement object are measured based on the three-dimensional coordinates in the world coordinate system.

  According to this invention, coordinate conversion parameters from a plurality of three-dimensional coordinate systems based on each viewpoint position of a three-dimensional measurement camera moved by an actuator to a world coordinate system based on a reference plate are calculated, Since the position and dimensions of the measurement object can be calculated based on the three-dimensional coordinates in the world coordinate system, the coordinates of the actuator are the same as those specified in the coordinate system in the general-purpose actuator that drives the three-dimensional measurement camera. It is possible to measure the dimension of the measurement object with higher accuracy without being affected by the positional accuracy in the system.

  The invention according to claim 7 is a method for measuring a three-dimensional dimension using an apparatus for measuring a three-dimensional dimension for measuring a three-dimensional dimension of a fixture included in a measurement object, and measuring the three-dimensional dimension. The apparatus has a reference plate having a plurality of markers regularly arranged on the background of the object to be measured, a position measurement camera for photographing at least the fixture and the reference plate, and an image necessary for three-dimensional measurement of the fixture. A three-dimensional measurement camera that moves to a position and shoots an image in which a measurement object and a reference plate are reflected; an actuator that moves the three-dimensional measurement camera to a viewpoint position that is shot and calculated by the position measurement camera; Then, using a control device for controlling the actuator and the three-dimensional measurement camera, the reference plate is photographed by the position measurement camera disposed opposite to the reference plate. A position measurement camera photographing step for photographing an image including the measurement object placed on the reference plate and the measurement object based on the positional relationship between the marker in the image photographed in the position measurement camera photographing step and the measurement object. A two-dimensional coordinate calculation step for calculating two-dimensional coordinates in the reference plate coordinate system of the object, a search region specifying step for specifying the positions of a plurality of search regions input in advance on the two-dimensional coordinates, and a fixture in the search region A viewpoint position calculating step for calculating a plurality of viewpoint positions that are photographing positions of the three-dimensional measurement camera, driving the three-dimensional measurement camera to the viewpoint position by an actuator, from the viewpoint position, the reference plate, A three-dimensional measurement camera photographing step for photographing a measurement object with a reference plate as a background, and each of a plurality of viewpoint positions. A three-dimensional coordinate calculation step for calculating a plurality of three-dimensional coordinate systems based on the positions of the three-dimensional measurement camera of the measurement object and the marker from the image photographed in the three-dimensional measurement camera photographing step. A parameter calculation step for calculating a coordinate conversion parameter from a plurality of reference three-dimensional coordinate systems to a world coordinate system based on a reference plate, and a three-dimensional measurement using the coordinate conversion parameters calculated in the parameter calculation step A coordinate system integration step for integrating a plurality of three-dimensional coordinate systems based on the camera into the world coordinate system, and a dimension calculation step for calculating the dimensions of the measurement object based on the world coordinate system integrated in the coordinate system integration step. It is characterized by including.

  According to the present invention, a plurality of search areas are calculated on two-dimensional coordinates, and a plurality of viewpoint positions are calculated from within the limited search area, so that high-speed search calculation is possible. In addition, a coordinate conversion parameter from the coordinate system based on the 3D measurement camera to the world coordinate system based on the reference plate is calculated, and the object to be measured is calculated based on the 3D coordinates in the highly accurate world coordinate system. Since the position and dimensions can be calculated, high accuracy can be achieved without being affected by the position accuracy in the coordinate system of the actuator as in the case of calculating the dimension in the coordinate system in the actuator that drives the 3D measurement camera. Measurement becomes possible.

  In the invention according to claim 8, the measurement object has a front surface and a back surface, has a depth dimension smaller than the vertical dimension and the horizontal dimension of the front surface and the back surface, and the fixture is within the range of the depth dimension. This is a flat assembly part that is mounted on the reference plate and the reference plate with a position measurement camera that is placed facing the reference plate with either the front or back surface superimposed on the flat surface of the reference plate. It includes a position measurement camera photographing step for photographing an image including both of the placed measurement objects.

  According to this invention, the measurement object is a flat assembly part, and a plurality of viewpoint positions related to the fixture are determined simply by specifying a two-dimensional position on the reference plate. Since the three-dimensional measurement camera has only to be driven to the viewpoint position with an actuator similar to the XY plotter, the actuator structure can be simplified and can be driven at high speed. Thereby, the three-dimensional dimension measuring method which can measure a three-dimensional dimension at high speed is obtained.

  In the invention according to claim 9, the exploration area specifying step includes a step in which an exploration area including the position of the fixture to be measured is input by teaching, and the viewpoint position calculating step includes the shape of the fixture in the exploration area. And a plurality of viewpoint positions that are photographing positions of the three-dimensional measurement camera are calculated based on the two-dimensional coordinate position related to the position of the fixture.

  According to the present invention, since the viewpoint position is searched by recognizing the inside of the search area input by teaching, even if the position of the measurement object placed on the reference plate is displaced slightly deviated, that is, tilted. Even if it moves in parallel, the position of the fixture is identified by recognizing the image within the limited exploration area, and multiple viewpoint positions, which are the shooting positions of the three-dimensional measurement camera, are automatically determined from the position of the identified fixture. Can be calculated automatically.

It is a typical perspective view which shows the apparatus which measures the three-dimensional dimension as one Embodiment of this invention. It is a flowchart which shows the process sequence of the three-dimensional dimension measurement in the apparatus which measures the three-dimensional dimension of FIG. It is a perspective view of the capacitor used as the measuring object in the above-mentioned embodiment. It is a model enlarged view of the pin of the measuring object in the said embodiment. It is a model enlarged view of the bracket of the measuring object in the said embodiment. It is a block diagram which shows the structure of the actual pin in the said embodiment. It is a block diagram which shows the structure of the actual bracket in the said embodiment.

(One embodiment)
Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 is a schematic perspective view showing an apparatus for measuring a three-dimensional dimension as one embodiment of the present invention. FIG. 2 is a flowchart showing a processing procedure of three-dimensional dimension measurement in the apparatus for measuring three-dimensional dimensions of FIG.

  First, an outline of one embodiment will be described. In this embodiment, a configuration similar to that of Patent Document 2 is used, but the configuration of changing the blinking pattern of the light emitting marker 8 of the reference plate 6 in FIG. 1 is not employed. However, the present invention does not limit this adoption, and the blinking pattern may be changed.

  In this embodiment, the viewpoint position of the three-dimensional measurement camera 3 is determined in accordance with the position of the measurement object 1. For this purpose, basically, a position measurement camera 2 different from the three-dimensional measurement camera 3 is used (the same camera can also be used as will be described later), and measurement on the reference plate 6 serving as a pedestal in advance is performed. The position of the target object 1 is imaged, and a plurality of viewpoint positions that are locations to be imaged by the three-dimensional measurement camera 3 are determined.

  In the determination of the viewpoint position, the image recognition time is shortened by setting an exploration area of a predetermined size, and the measurement accuracy is increased compared to the conventional case where the arbitrary position is the viewpoint position. And the measurement time is shortened.

  Incidentally, in the case where an arbitrary position is set as the viewpoint position, the measurement object 1 is installed at some position on the reference plate 6 so that the entire reference plate 6 is photographed once with a high-precision camera, or It is necessary to shoot many times with a segmented field of view.

  In the camera calibration method, the camera calibration refers to the calibration of the installation position and direction of the camera, and specifically, the positional relationship of the measurement object 1 installed on the reference plate 6 with respect to the three-dimensional measurement camera 3. Is specified by the use of the marker 8 drawn in a polka dot shape in FIG.

  Capacitor (a measurement object 1 in this embodiment, which is a measurement object 1 in this embodiment. In this embodiment, the capacitor is a measurement object) 3 has a rectangular front surface 10 and a rear surface 11 through which an air flow for heat exchange flows, as shown in FIG. 3, and a depth dimension (FIG. 3) smaller than the vertical dimension and the horizontal dimension of the square. It is a relatively flat shape with a vertical direction).

  This measuring object 1 is fixed by inserting a pin 12 into a mounting portion on the vehicle side (not shown), overlapping a hole 14 of its own bracket 13 on a bracket serving as a mounting portion of another vehicle, and tightening with a bolt (not shown). .

  Therefore, it is important for the subsequent assembly to the vehicle to accurately manufacture the positions of the pin 12 and the bracket 13 that form the fixture of the measurement object 1. For example, if the distance between the fixtures (hereinafter referred to as fixtures 12 and 13) including the pins 12 and the brackets 13 is shifted from the vehicle side, it will be difficult to assemble the vehicle.

  Therefore, when the measuring object 1 is inspected using the apparatus for measuring a three-dimensional dimension of this embodiment and a defective product is found with respect to the mutual distance between the fixtures 12 and 13, the defective portion is repaired. Thus, it is important to manufacture the measurement object 1.

  In this embodiment, in the three-dimensional dimension measurement of the attachments 12 and 13 for attaching the measurement object 1 to the vehicle, the viewpoint that is the photographing position of the three-dimensional measurement camera 3 in accordance with the positions of the plurality of attachments 12 and 13. By determining the position, the three-dimensional measurement camera 3 achieves high accuracy of three-dimensional measurement by limiting the photographing field of view and high speed by limiting the photographing position.

  Hereinafter, an embodiment of an apparatus and method for measuring a three-dimensional dimension will be specifically described with reference to FIGS. 1 and 2. In FIG. 1, reference numeral 1 denotes a measurement object that is an object having a three-dimensional shape. The measuring object 1 is provided with fixtures 12 and 13 for a vehicle to be measured.

  Reference numeral 2 denotes a position measurement camera installed to measure the entire position of the measurement object 1. The position measurement camera 2 is composed of a single-lens CCD camera, takes an image of the entire reference plate 6 once, and transmits a one-frame image in which the measurement object 1 and the reference plate 6 are reflected to a calculation device 7 to be described later. The positional relationship of the position measuring camera 2 with respect to the reference plate 6 does not need to be grasped in advance by the calculation device 7.

  The positions of the holes 14 of the two brackets 13 (FIG. 3) of the measurement object 1 photographed by the position measuring camera 2 and the positions of the tips of the two pins 12 are calculated by the driver of the apparatus for measuring the three-dimensional dimensions. It is taught to the device 7. The procedure for this will be described below.

  First, a master work (in this case, a standard capacitor to be a standard measurement object not shown) whose dimensions are accurate is placed at a predetermined position on the reference plate 6 in FIG. In this state, the position measurement camera 2 captures the master work, and inputs the teaching corner positions of the master work and the positions of the search areas (frames) where the brackets 13 (FIG. 3) and the pins 12 exist. This teaching input is performed by an operator using a keyboard (not shown), and is performed for each product number whose shape and dimensions are changed even for the same measurement object.

  Specifically, the driver calculates the search areas SA1, SA2, SA3, and SA4, which are schematically shown in FIG. 3 and includes pixel collection areas based on the positions of the pins 12 and the brackets 13 to be measured, or will be described later. Teaching input to the robot controller 5

  The search areas SA1 to SA4 are frames that serve as a range in which the three-dimensional measurement camera 3 searches for a viewpoint position to be photographed by performing image recognition described later. Even if the position of the measuring object 1 placed on the reference plate 6 in FIG. 1 is slightly shifted, that is, tilted or translated, the four corners of the capacitor serving as the measuring object 1 are recognized. The quadrant search areas SA1 to SA4 are automatically specified based on the specified four corners.

  Next, if the image captured by the position measurement camera 2 (FIG. 1) in the specified search areas SA1 to SA4 is image-recognized and the shapes of the fixtures 12 and 13 are searched, the pins 12 of the measurement object 1 and The viewpoint position of the three-dimensional measurement camera 3 with reference to the position of the bracket 13 can be specified.

  Note that the measurement object 1 on the screen imaged by the position measurement camera 2 in FIG. 1 and the actuator 4 and thus the position of the three-dimensional measurement camera 3 need to be calibrated in advance. As a result, the three-dimensional measurement camera 3 can be moved by the actuator 4 to a desired viewpoint position photographed by the position measurement camera 2.

  This calibration work can be performed by a known method. As a result, the calculation device 7 can grasp the correspondence between the position measured by the position measurement camera 2, the position photographed by the three-dimensional measurement camera 3, and the position where the actuator 4 moves.

  Reference numeral 3 denotes a three-dimensional measurement camera that forms a camera that captures an image necessary for three-dimensional measurement by the passive stereo method. The fixture 12 such as the pin 12 and the bracket 13 of FIG. 13 is moved while being moved by the actuator 4, and an image in which the measurement object 1 and the reference plate 6 are reflected is transmitted to the calculation device 7.

  The passive stereo method is a technique for measuring the three-dimensional shape of the measurement object 1 using the principle of triangulation, and the measurement object 1 is photographed by the three-dimensional measurement camera 3 from a plurality of viewpoint positions. This is a method of measuring a three-dimensional position with reference to the position of the three-dimensional measurement camera 3. In the passive stereo method, a three-dimensional measurement camera including two cameras provided at a viewpoint position is also called a stereo camera.

  Reference numeral 4 denotes an actuator for moving the three-dimensional measurement camera 3 to a designated viewpoint position, and is composed of a multi-axis orthogonal robot. Reference numeral 5 denotes a robot controller serving as an actuator control device.

  The robot controller 5 calculates the viewpoint position of the three-dimensional measurement camera 3 based on the two-dimensional coordinates in the reference plate coordinate system of the measurement object 1 transmitted from the calculation device 7 and controls the drive axis of the actuator 4. . Here, the reference plate coordinate system is a coordinate system based on an arbitrary position of the reference plate 6.

  The viewpoint position of the three-dimensional measurement camera 3 is information including a plurality of positions photographed by the three-dimensional measurement camera 3 and a photographing direction. As described above, if the identified search areas SA1 to SA4 are image-recognized and searched, the viewpoint positions of the pin 12 and the bracket 13 of the measurement object 1 can be specified.

  After the viewpoint position is specified, the viewpoint position of the three-dimensional measurement camera is calculated in the coordinate system in the controller 5 based on the two-dimensional coordinates in the reference plate coordinate system of the measurement object 1 transmitted from the calculation device 7. .

  In this embodiment, the viewpoint position is specified only by plane information from the position measurement camera 2. Therefore, the actuator 4 only needs to have a function as an XY plotter that can move the three-dimensional measurement camera 3 to an arbitrary position on the X-axis and Y-axis in a plane. This is because when the measurement object 1 has a flat shape and is placed on the reference plate 6, the position to be searched for in the Z-axis direction, which is the vertical direction in FIG.

  Reference numeral 6 denotes a reference plate on which the measurement object 1 is placed and taken by the position measurement camera 2 and the three-dimensional measurement camera 3 together with the measurement object 1. A plurality of markers 8 (FIG. 1) provided in rows and columns are provided at different positions on the reference plate 6.

  The reference plate 6 is a light-impermeable plate portion (as shown in FIG. 1 that is simplified) as shown in the polka dot pattern of FIG. And a light-emitting diode (not shown) serving as a light source installed on the back surface of the light-impermeable plate portion.

  Although the number of the light emitting diodes is smaller than the number of holes constituting the marker 8, they are arranged so that the illuminance of each hole is as uniform as possible. The marker 8 functions as a light-emitting marker when the holes in the plate portion emit light.

  A large number of black aluminum bars (not shown) are arranged on the upper surface of the light-impermeable plate portion of the reference plate 6, and the measuring object 1 is placed on the bars. The glass plate portion 6 is not damaged.

  A part of the marker 8 composed of a large number of holes provided in the plate portion is hidden by placing the back surface of the measurement object 1 on the crosspiece, but the marker 8 has regular positions. The position of the luminescent marker can be specified from the images seen from the position measurement camera 2 and the three-dimensional measurement camera 3.

  The calculation device 7 performs a two-dimensional calculation for obtaining a two-dimensional coordinate in the reference plate coordinate system of the measurement object 1 in the image based on the image taken by the position measurement camera 2. Further, the calculation device 7 performs three-dimensional calculation for obtaining three-dimensional coordinates in the three-dimensional measurement camera reference coordinate system for each viewpoint position based on the image taken by the three-dimensional measurement camera 3. Here, the three-dimensional measurement camera reference coordinate system is a coordinate system based on the position of the three-dimensional measurement camera. Further, the calculation device 7 performs parameter calculation for calculating a coordinate conversion parameter from the three-dimensional measurement camera reference coordinate system to a predetermined world coordinate system.

  Next, the calculation device 7 calculates the three-dimensional coordinates for each viewpoint position in the three-dimensional measurement camera reference coordinate system from the images photographed by the three-dimensional measurement camera 3 from the respective viewpoint positions. Using the coordinate transformation parameters for, transform to a common world coordinate system and integrate the coordinate system. Such integrated calculation is well known and is also disclosed in Patent Document 2.

  Next, a description will be given with reference to FIG. 2 which is a flowchart showing a processing procedure of three-dimensional dimension measurement. The capacitor constituting the measurement object 1 has a front surface 10 and a back surface 11 as shown in FIG. 3, and has a depth dimension (vertical direction in FIG. 3) smaller than the vertical and horizontal dimensions of the front surface 10 and the back surface 11. And it is an assembly | attachment part to the flat vehicle in which the fixtures 12 and 13 were provided in the range of the depth dimension.

  In FIG. 2, when the control is started, in step S1, the entire reference plate 6 is photographed by the position measurement camera 2 of FIG. 1 arranged above the reference plate 6, and the reference plate 6 and the measurement placed thereon are measured. An image including both of the object 1 is taken. Prior to this photographing, the back side of the measurement object 1 is placed on the plane of the reference plate 6 and the front side of the measurement object 1 is placed on the position measurement camera 2 side.

  In step S2, two-dimensional coordinates in the reference plate coordinate system of the measurement target 1 are calculated based on the positional relationship between the plurality of markers 8 on the reference plate 6 and the measurement target 1 in the image photographed in step S1. Therefore, step S2 constitutes a two-dimensional coordinate calculation means. And the position of four search area | regions SA1-SA4 (FIG. 3) by which teaching input is carried out previously on a two-dimensional coordinate is pinpointed.

  Accordingly, in step S2, the two-dimensional coordinates in the reference plate coordinate system of the measurement object 1 are calculated based on the positional relationship between the marker 8 on the reference plate 6 and the measurement object 1 in the image photographed in the position measurement camera photographing step. A two-dimensional coordinate calculation step for calculating and a search region specifying step for specifying the positions of the plurality of search regions SA1 to SA4 on the two-dimensional coordinates are executed.

  In step S3, the viewpoint position that is the photographing position of the three-dimensional measurement camera 3 is calculated based on the two-dimensional coordinate positions related to the four search areas SA1 to SA4 of the measurement object 1 calculated in step S2. This step S3 is a search means for executing image recognition in a plurality of search areas SA1 to SA4 determined in advance with reference to the positions of the fixtures 12 and 13 in order to determine the viewpoint position of the three-dimensional measurement camera 3. Configure.

  In step S4 and step S5, the reference plate 6 and the reference plate 6 are moved from each viewpoint position while the three-dimensional measurement camera 3 is sequentially moved by the actuator 4 to the viewpoint positions of N (natural number, 4 in this case) calculated in step S3. Then, an image including both of the measurement objects 1 placed thereon is taken, and the taken image data is accumulated.

  In step S6, the three-dimensional coordinates of each of the markers 8 on the measurement object 1 and the reference plate 6 are obtained from the images of the three-dimensional measurement camera 3 photographed in step S5 for each of the N viewpoint positions. Calculate according to

  This step S6 constitutes a three-dimensional coordinate calculation means. The three-dimensional coordinates of each marker 8 are the three-dimensional positions of the white dots of the polka dots in FIG. 1 and represent the center positions of the holes that transmit light of the glass plate portion.

  Since the algorithm of the passive stereo method that uses two cameras to specify the three-dimensional position based on the principle of triangulation is well known, a description thereof will be omitted. The three-dimensional coordinates of each marker 8 and the like obtained by this calculation are coordinates in a three-dimensional coordinate system with the three-dimensional measurement camera 3 as a reference position.

  In step S7, for each of the N viewpoint positions, based on the three-dimensional coordinates of each marker 8 calculated in step S6, the world coordinates based on the reference plate 6 from the coordinate system based on the three-dimensional measurement camera 3 are used. Calculate the conversion parameters for the system.

  The reason for calculating the conversion parameter from the coordinate system based on the three-dimensional measurement camera 3 to the world coordinate system based on the reference plate 6 is that the resolution of the actuator 4 is relatively low.

  Although the dimensions of the fixtures 12 and 13 may be specified by the coordinate system in the actuator 4 that specifies the positional relationship in which the three-dimensional measurement camera 3 has moved, the position accuracy in the actuator 4, that is, the coordinate system of the robot is high. Since it is relatively low, conversion to the world coordinate system based on the reference plate 6 is performed.

  Since the four positions are photographed by the three-dimensional measurement camera 3 this time, the coordinate system based on the three-dimensional measurement camera 3 is composed of four coordinate systems. These four coordinate systems are integrated into a single world coordinate system based on the reference plate 6.

  Specifically, when conversion parameters for each of the four viewpoint positions are obtained in step S7, in step S8, the three-dimensional shape in the three-dimensional measurement camera reference coordinate system of the measurement object 1 viewed from each viewpoint position is obtained. , Using the corresponding conversion parameters, coordinate conversion to a common world coordinate system.

  Next, in step S9, it is confirmed whether shooting and calculation at N viewpoint positions are completed. If completed, the process proceeds to step S10. If not completed, the process returns to step S4, and the next Move to the viewpoint position.

  In step S10, the distance (dimension) between the fixtures 12 and 13 of the measurement object 1 is calculated based on the three-dimensional coordinates in the world coordinate system of the measurement object 1 obtained in step S8. Specifically, the dimension between the mounting holes 14 of the bracket 13 of the measurement object 1 and the dimension between the central axes of the pins 12 are specified based on the three-dimensional coordinates in the world coordinate system.

  FIG. 4 is a schematic enlarged view of the pin 12 of the measuring object 1, and FIG. 5 is a schematic enlarged view of the bracket 13 of the measuring object 1. The positions of the pin 12 and the bracket 13 of the measurement object 1 are grasped three-dimensionally, and the center position P12 of the circular side surface of the pin 12 through which the central axis J12 of the pin 12 in FIG. 4 passes and the surface of the bracket 13 in FIG. A three-dimensional position with the center position P13 of the hole on the plane is specified in the world coordinate system.

  FIG. 6 is a diagram showing a configuration of an actual pin in the exploration area SA2, and FIG. 6A is a plan view of the pin 12 viewed from the position measurement camera 2 of FIG. b) is a side view of the pin 12.

  Thus, even when the pin 12 is shifted to one side from the middle of the front surface 10 and the back surface 11 of the measurement object 1, the pin passing through the central axis J12 of the pin 12 accurately by the three-dimensional measurement camera 3. The center position P12 of 12 circular side surfaces can be measured. The arrow Y6 indicates the direction of the viewpoint position of the three-dimensional measurement camera 3, and the three-dimensional measurement camera 3 takes an image from an oblique direction so that the center position P12 of the circular side surface of the pin 12 is taken.

  FIG. 7 is a drawing showing the configuration of the actual bracket 13 in the exploration area SA4. FIG. 7 (a) is a plan view of the bracket 13, and FIG. 7 (b) is a side view of the bracket 13. . As described above, even when the bracket 13 is shifted from the middle of the front surface 10 and the rear surface 11 of the measurement object 1 or is located at the bending portion C13, the three-dimensional measurement camera 3 can accurately In addition, the three-dimensional position of the center position P13 of the hole on the plane of the surface of the bracket 13 can be specified in the world coordinate system.

  Thereby, in the assembly of the measurement object 1 to the vehicle, the center position P12 of the pin 12 and the center position P13 of the hole of the bracket 13 can be regulated, so that the dimensions of the fixtures 12 and 13 do not match when assembling the vehicle. Evil can be eliminated.

  Moreover, when the dimensions of the fixtures 12 and 13 are different from the regular ones, defective assembly occurs when the measurement object 1 is assembled to the vehicle, so that defective products can be eliminated in advance. As a result, the dimensions between fixtures of mass-produced products that have been measured using a jig in the past can be specified in a three-dimensional manner in a non-contact manner, and high-speed inspection and high accuracy can be achieved simultaneously.

(Other embodiments)
The present invention is not limited to the above-described embodiments, and can be modified or expanded as follows. For example, in the above-described embodiment, the apparatus for measuring a three-dimensional dimension is configured based on the passive stereo method, but instead of the passive stereo method, the space is divided into wedge-shaped regions by a laser pattern, A three-dimensional measurement apparatus can be configured using a spatial encoding method in which a region is regarded as a slit light plane and a distance is measured, or a light cutting method described in Patent Document 1.

  In the above embodiment, a rectangular flat plate is used as the reference plate, but the shape of the flat plate may not be a square. Moreover, it may be a three-dimensional shape with unevenness instead of a flat plate. Moreover, it is not restricted to what is used as a table | surface which installs a measurement target object, For example, it is good also as a background object of a measurement target object standing up on the side of a measurement target object.

  Further, the actuator is not limited to the multi-axis orthogonal robot, and for example, a vertical articulated robot may be used. When this vertical articulated robot is used, an arbitrary movement is possible, but there is a tendency that the movement becomes slower by that amount. Also, a dedicated actuator other than the robot may be used.

  In the above embodiment, a camera different from the position measurement camera and the three-dimensional measurement camera is used. However, a three-dimensional measurement camera may be used as the position measurement camera. When this camera is also used, only one of the three-dimensional measurement cameras composed of two cameras is used as the position measurement camera, and the camera adjusts the rotation angle of the two cameras of the three-dimensional measurement camera. It is necessary to adjust the direction of the camera by rotating the axis with a vertical articulated robot or the like.

  Moreover, although the measurement object 1 is a condenser (condenser), this may be a vehicle heat exchanger such as an evaporator (evaporator) or a radiator of a vehicle air conditioner, or a bracket or a pin. It may be other products with attachments.

  In order to speed up the operation using a simple structure that specifies only the X-axis and Y-axis positions of the three-dimensional measurement camera as an actuator, the position measurement camera and the three-dimensional measurement camera are separated. The measurement object placed on the flat reference plate preferably has a relatively flat shape that allows the visual field position to be specified on the photographing screen of the position measurement camera in terms of cost and speedup.

  In the present invention, the computing device and the robot controller are collectively referred to as a control device. However, the computing device and the robot controller may be integrated into a single device. Also, the marker need not be a luminescent marker. It may be a simple black circle pattern or white circle pattern or other set of easily distinguishable shapes.

  Further, the three-dimensional measurement camera reference coordinate system may be a coordinate system based on a part that moves together with the three-dimensional measurement camera, without directly using the three-dimensional measurement camera itself as a reference. Further, the search for the viewpoint position is performed in the robot controller, but may be performed in the calculation device.

DESCRIPTION OF SYMBOLS 1 Measurement object 2 Position measurement camera 3 Three-dimensional measurement camera 4 Actuator which consists of a multi-axis orthogonal robot 5 Robot controller 5, 7 Control apparatus 6 Reference plate 7 Calculation apparatus 8 Marker 10 Surface of measurement object 11 Back surface of measurement object 12 Pins 12 and 13 Mounting tool 13 Bracket SA1 to SA4 Exploration area for searching the viewpoint position

Claims (9)

An apparatus for measuring a three-dimensional dimension of a fixture included in a measurement object,
A reference plate in which a plurality of markers are regularly arranged and photographed as a background of the measurement object;
A position measurement camera for photographing the measurement object including the fixture and the reference plate at a fixed position ;
By capturing the measurement object in view point position of the multiple, the three-dimensional measurement camera for acquiring images yelling-through their measurement object and the reference plate,
An actuator for moving the three-dimensional measurement camera to a plurality of viewpoint positions;
A controller for controlling the actuator and the three-dimensional measurement camera;
The control device includes:
Two-dimensional coordinate calculation means for calculating two-dimensional coordinates of the measurement object in a reference plate coordinate system, which is a coordinate system based on the reference plate, based on an image captured by the position measurement camera;
Based on the two-dimensional coordinates calculated by the two-dimensional coordinate calculation means, a search means for searching the plurality of viewpoint positions of the three-dimensional measurement camera by image recognition of the fixture, and the viewpoint position searched by the search means 3D to obtain the three-dimensional coordinates of the fixture in the three-dimensional measurement camera reference coordinate system, which is a coordinate system based on the position of the three-dimensional measurement camera, based on the image formed by the three-dimensional measurement camera An apparatus for measuring a three-dimensional dimension, characterized by comprising coordinate calculation means. The exploration means determines the viewpoint position of the three-dimensional measurement camera based on the two-dimensional coordinates of the measurement object in the reference plate coordinate system. The apparatus for measuring a three-dimensional dimension according to claim 1, wherein the viewpoint position is determined by executing image recognition in a plurality of predetermined search areas on the basis of the position.
It is characterized by.   The fixture is a pin or a bracket of the measurement object, and the three-dimensional coordinate calculation means calculates a three-dimensional dimension between the pins or between the brackets based on an image taken by the three-dimensional measurement camera. The apparatus for measuring a three-dimensional dimension according to claim 1 or 2, wherein the apparatus measures the three-dimensional dimension. The actuator comprises a multi-axis orthogonal robot,
The actuator is controlled by a robot controller that controls the multi-axis orthogonal robot,
The search means determines a plurality of the viewpoint positions of the three-dimensional measurement camera based on two-dimensional coordinates of the measurement object in the reference plate coordinate system in the robot controller. The apparatus which measures the three-dimensional dimension as described in any one of 1 thru | or 3.   The three-dimensional measurement camera is a stereo camera that captures an image necessary for three-dimensional measurement by a passive stereo method, and is driven by the actuator to photograph the fixture at a plurality of the viewpoint positions. The apparatus for measuring a three-dimensional dimension according to any one of claims 1 to 4, wherein an image in which the reference plate is reflected is transmitted to the control device. The control device performs a parameter calculation for calculating a coordinate conversion parameter from a coordinate system based on the three-dimensional measurement camera to a world coordinate system based on the reference plate,
A three-dimensional coordinate system based on the three-dimensional measurement camera for each of the plurality of viewpoint positions is determined from the images taken by the three-dimensional measurement camera from the plurality of viewpoint positions, for each of the viewpoint positions determined by the parameter calculation. Using coordinate transformation parameters, integrate into the common world coordinate system,
The apparatus for measuring a three-dimensional dimension according to any one of claims 1 to 5, wherein the dimension of the measurement object is measured based on a three-dimensional coordinate in the world coordinate system. A method for measuring a three-dimensional dimension using an apparatus for measuring a three-dimensional dimension for measuring a three-dimensional dimension of a fixture included in a measurement object,
The apparatus for measuring the three-dimensional dimension includes a reference plate having a plurality of markers regularly arranged in the background of the measurement object, a position measurement camera for photographing at least the fixture and the reference plate, and the attachment An image required for three-dimensional measurement of the tool is moved to the viewpoint position and photographed, and a three-dimensional measurement camera for photographing an image in which the measurement object and the reference plate are reflected, and the position measurement camera. Using an actuator that moves the 3D measurement camera to the calculated viewpoint position, and a control device that controls the actuator and the 3D measurement camera,
A position measurement camera photographing step of photographing the reference plate by the position measurement camera disposed opposite to the reference plate and photographing an image including the reference plate and the measurement object placed on the reference plate. ,
A two-dimensional coordinate calculation step for calculating a two-dimensional coordinate in the reference plate coordinate system of the measurement object based on the positional relationship between the marker and the measurement object in the image photographed in the position measurement camera photographing step;
A search area specifying step for specifying the positions of a plurality of search areas input in advance on the two-dimensional coordinates;
A viewpoint position calculating step of performing image recognition of the fixture in the exploration area and calculating a plurality of viewpoint positions which are photographing positions of the three-dimensional measurement camera;
A three-dimensional measurement camera photographing step of driving the three-dimensional measurement camera to the viewpoint position by the actuator and photographing the reference plate and the measurement object with the reference plate as a background from the viewpoint position;
For each of the plurality of viewpoint positions, a plurality of three-dimensional coordinate systems based on the positions of the measurement object and the marker of the three-dimensional measurement camera are calculated from the images photographed in the three-dimensional measurement camera photographing step. 3D coordinate calculation step,
A parameter calculation step for calculating a coordinate conversion parameter from a plurality of three-dimensional coordinate systems based on the three-dimensional measurement camera to a world coordinate system based on the reference plate;
A coordinate system integration step of integrating a plurality of three-dimensional coordinate systems based on the three-dimensional measurement camera into the world coordinate system using the coordinate conversion parameters calculated in the parameter calculation step; and the coordinate system A method for measuring a three-dimensional dimension, comprising a dimension calculation step for calculating a dimension of the measurement object based on the world coordinate system integrated in an integration step. The measurement object has a front surface and a back surface, has a depth dimension smaller than the vertical and horizontal dimensions of the front surface and the back surface, and is a flat assembly in which the fixture is provided within the range of the depth dimension. Parts,
The measurement object placed on the reference plate and the reference plate by the position measurement camera arranged facing the reference plate with either the front surface or the back surface superimposed on the plane of the reference plate The method for measuring a three-dimensional dimension according to claim 7, further comprising the step of photographing the position measurement camera for photographing an image including both objects. The exploration area specifying step includes the step of teaching input the exploration area including the position of the fixture to be measured,
In the viewpoint position calculating step, a plurality of the viewpoints that are photographing positions of the three-dimensional measurement camera based on a two-dimensional coordinate position related to the position of the fixture by recognizing the shape of the fixture in the exploration area. The method for measuring a three-dimensional dimension according to claim 7 or 8, wherein a position is calculated.

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