JP5136108B2 - 3D shape measuring method and 3D shape measuring apparatus - Google Patents

Description

  The present invention relates to a three-dimensional shape measuring method and a three-dimensional shape measuring apparatus using an optical cutting method.

  Conventionally, as a non-contact type three-dimensional shape measurement technique, there is a technique called a light cutting method (see, for example, Patent Document 1). In such a technique, a measurement object (hereinafter referred to as “work”) is irradiated with slit-shaped light (hereinafter referred to as “slit light”) by laser light or the like. On the surface of the workpiece irradiated with the slit light, a light cutting line (bright line of reflected light) is formed according to the cross-sectional shape. The light cutting line formed on the surface of the workpiece is received and imaged by imaging means such as a camera. Based on the imaged light cutting line, the principle of triangulation is used to measure the three-dimensional coordinates of each point on the surface of the workpiece (on the light cutting line). Such measurement is performed while the slit light is scanned (scanned) with respect to the workpiece, whereby the three-dimensional shape of the workpiece is measured.

  The measurement of the three-dimensional shape by such a light cutting method is based on the assumption that the slit light (laser sheet) irradiated on the workpiece is an ideal plane (the cross section of the slit light is linear). Has been done. In other words, when measuring the three-dimensional shape by the conventional light cutting method, the measurement theory built on the assumption that the slit light applied to the workpiece is an ideal plane is used. Calculations for calculating shape data (three-dimensional shape data) are performed.

  However, the slit light irradiated on the workpiece is actually projected in a bent state due to problems of the optical system such as aberration in a cylindrical lens used for converting the laser light into a slit shape. That is, the slit light applied to the workpiece is not an ideal plane but a curved surface. For this reason, the light cutting line formed on the surface of the workpiece by the irradiation of the slit light does not ride on the two-dimensional cross section (planar cross section) when the slit light is assumed to be flat. As a result, an error of the obtained three-dimensional shape data with respect to the actual three-dimensional shape occurs due to the deviation of the optical cutting line from the plane cross section, and high-accuracy three-dimensional shape data cannot be obtained. Therefore, under the measurement of the three-dimensional shape by the conventional light cutting method, in which the slit light is assumed to be flat, a reference plate (planar reference) that guarantees that the workpiece is flat is measured. Even if it is a board | plate), the measurement result that the three-dimensional shape is not a plane but a curved surface will be obtained.

  Shape distortion such as bending of slit light caused by such problems of the optical system can be dealt with by increasing the cost of equipment and adjustment in the optical system. However, from the viewpoint of cost, it is considered impossible to eliminate the problem of the optical system that causes the shape distortion of the slit light. Therefore, as a technique for eliminating the decrease in measurement accuracy caused by the shape distortion of the slit light, there is one disclosed in Patent Document 2, for example.

  In the technique disclosed in Patent Document 2, in the non-contact type three-dimensional measurement by the light projection method in which the workpiece is irradiated with detection light such as slit light, the detection light such as the bending of the slit light described above is used. The existence of the shape distortion is recognized, and measures are taken for the shape distortion of the detected light. In other words, in the technique disclosed in Patent Document 2, the imaging surface of the imaging element on which the optical cutting line is imaged is divided into a plurality of regions. In calculating the three-dimensional coordinates of the workpiece, individual parameters are used for each area divided on the imaging surface.

  Specifically, as shown in FIG. 11, the imaging surface 113 of the imaging element (image sensor) is divided into a plurality (nine in the drawing) of regions 113a to 113i. For each of these areas, appropriate parameters obtained experimentally in advance are stored in the form of a numerical table for each type. Then, parameters corresponding to each area on the imaging surface 113 are used as parameters used when calculating the three-dimensional coordinates of the workpiece.

  For example, as shown in FIG. 11A, when a workpiece that is a plane is imaged, the slit light is bent, so that a curved slit image 120 is actually obtained as the imaged light cutting line. It is done. When no countermeasure is taken for the shape distortion of the slit light, the curved slit image 120 is processed as a linear slit image 120a indicated by a broken line, and calculation of three-dimensional coordinates is performed. Therefore, in this case, the difference between the slit images 120 and 120a becomes a measurement error, and high measurement accuracy cannot be obtained.

  On the other hand, in the technique of Patent Document 2, as shown in FIG. 11 (b), a curved slit image 120 (see the broken line) actually obtained by using parameters calibrated for each divided area. ) Is obtained. Based on the approximate slit image 120b, the calculation of the three-dimensional coordinates is performed. As the slit image 120b approximated to the curved slit image 120, for example, as shown in FIG. 11B, the curved slit image 120 is approximated to a straight line for each region, and the straight line for each region is continuous. An image is obtained. In this manner, the curved slit image 120 actually obtained is the slit image 120b that approximates the curved slit image 120, thereby correcting the shape distortion such as bending of the slit light.

  However, the technique of Patent Document 2 has the following problems. First, since appropriate parameters are individually obtained for each area segmented on the imaging surface, it is difficult to obtain parameters corresponding to each area. That is, when acquiring the parameters corresponding to each region, actual measurement is performed for each imaging means (camera), and the numerical value of the most appropriate parameter is experimentally obtained for each region. For this reason, it takes time and effort to acquire the parameters, making it difficult to acquire the parameters.

  Further, as described above, in the method in which the actually obtained slit image is approximated as a straight line for each divided area, for example, an error with respect to the actually obtained slit image may not be sufficiently eliminated. In this regard, it is considered that the error can be reduced by increasing the number of regions divided on the imaging surface. However, an increase in the number of area divisions increases the difficulty in obtaining parameters for each area as described above. In addition, it is considered that the variation by the operator is likely to affect the measurement of the three-dimensional shape based on the acquisition of the parameters for each region and the calculation of the three-dimensional coordinates using the parameters. As described above, in the technique of Patent Document 2, it is difficult to obtain parameters for each region, and therefore, the treatment for the shape distortion of the slit light is not systematic and lacks measurement stability and versatility. is there.

Further, as described above, the technique of Patent Document 2 recognizes the presence of the geometric distortion of the detection light and takes countermeasures. However, the geometric distortion of the detection light is on the side where the workpiece is irradiated with slit light. Without clarifying whether it is caused by distortion of the lens (projection lens such as a cylindrical lens) or distortion of the lens (light receiving lens for measurement) that receives the reflected light (light cutting line) from the workpiece It has become compatible.
JP-A-8-327336 JP 2005-321278 A

  The present invention has been made in view of the above-described problems, and a problem to be solved by the present invention is a bending that exists with respect to slit light irradiated on a measurement object in three-dimensional shape measurement by an optical cutting method. 3D shape measurement that can improve the stability and versatility of measurement by reducing the measurement error caused by the shape distortion of the slit light. It is to provide a method and a three-dimensional shape measuring apparatus.

  The problem to be solved by the present invention is as described above. Next, means for solving the problem will be described.

That is, in claim 1, the slit light is irradiated to the measurement object, the light cutting line formed on the surface of the measurement object is picked up by the imaging means, and measured from the image of the picked light cutting line. A three-dimensional shape measurement method for measuring a three-dimensional shape of an object to be measured based on the three-dimensional coordinates of each point on the light cutting line , wherein the imaging means includes a plane provided on a calibration plate of the imaging means. A calibration step for calibrating the imaging means that captures a reference plane that is known to be and corrects the amount of deviation of the surface attribute of the reference plane in the captured image from the actual surface attribute of the reference plane When, in a state where the use of a calibration plate and irradiated with a constant slit light with respect to the reference plane, is formed on the reference plane That imaging by the imaging means of the cross-section line of the slit light is a light section line, by performing for a plurality of different positions and orientations of the calibration plate, wherein for said reference plane at each position and orientation of the calibration plate Obtaining a cross-sectional line of the slit light, and based on the cross-sectional line of the slit light corresponding to the reference plane in each position and orientation, a common curved surface in which the cross-sectional lines of the plurality of slit light approximately match, The curved surface modeling step of modeling the slit surface shape of the slit light irradiated to the measurement object as the curved surface, and the slit surface shape of the slit light as the modeled curved surface when measuring the three-dimensional shape , and a shape measuring step of measuring the three-dimensional coordinates, the key in the calibration step And imaging of the reference plane of the calibration plate, and imaging the cross-section line of the slit light at the curved surface modeling step, in which the position and orientation of the calibration plate are alternately performed each time be varied.

  According to a second aspect of the present invention, in the three-dimensional shape measurement method according to the first aspect, the shape of the curved surface is a conical surface or a partial shape of a cylindrical surface.

In Claim 3 , The irradiation means which irradiates slit light with respect to a measurement object, The imaging means which images the light cutting line formed in the surface of a measurement object by the slit light irradiated by the said irradiation means, Calculating means for measuring the three-dimensional shape of the measuring object based on the three-dimensional coordinates, and measuring the three-dimensional coordinates of each point on the light cutting line from the image of the light cutting line imaged by the imaging means; A reference plate that is provided on a calibration plate of the imaging unit and is known to be a plane, and that is irradiated with a fixed slit light by the irradiation unit. the imaging section line of said slit light is a light section lines formed on a plane, with a plurality of different positions and orientations of the calibration plate by the image pickup means By performing the slit-section acquiring means for acquiring cross-sectional line of the slit light for the reference plane at each position and orientation of the calibration plate, the slit-sectional shape of the slit beam irradiated on the measurement object by the radiation means Based on the cross-sectional line of the slit light corresponding to the reference plane at each position and orientation acquired by the slit cross-section acquiring means, and a common curved surface to which the cross-sectional lines of the plurality of slit light approximately match Slit surface shape modeling means for modeling as, when measuring the three-dimensional shape, by photographing the reference plane of the calibration plate by the imaging means, the surface attribute of the reference plane in the captured image, The imaging hand for correcting a deviation amount with respect to a surface attribute in the actual reference plane The calibration plate is photographed, the reference plane of the calibration plate when the calibration is performed, and the slit light cross-sectional line when the cross-sectional line of the slit light is obtained by the slit cross-section obtaining means Imaging is alternately performed each time the position and orientation of the calibration plate is changed, and the calculation means determines the slit surface shape of the slit light as the slit surface shape model when measuring the three-dimensional shape. The three-dimensional coordinates are measured as the curved surface modeled by the converting means.

According to a fourth aspect of the present invention, in the three-dimensional shape measuring apparatus according to the fourth aspect, the shape of the curved surface is a partial shape of a conical surface or a cylindrical surface.

As effects of the present invention, the following effects can be obtained.
That is, according to the present invention, in the three-dimensional shape measurement by the light cutting method, it is possible to systematically deal with shape distortion such as bending existing in the slit light irradiated to the measurement object, and Measurement errors due to shape distortion can be reduced, and measurement stability and versatility can be improved.

  The present invention is conventionally ideal for slit-shaped light (hereinafter referred to as “slit light”) irradiated on a measurement object (hereinafter referred to as “work”) when measuring a three-dimensional shape by a light cutting method. The slit surface shape, which is assumed to be a plane but actually becomes a curved surface due to a problem with the optical system (which causes shape distortion), is modeled as a predetermined curved surface.

  FIG. 10 shows an example (measurement example) of the shape distortion of the slit light. FIG. 10 illustrates a cross-sectional line of slit light (hereinafter also referred to as “slit cross-sectional line”) irradiated to a plate surface of a reference plate (planar reference plate) that is guaranteed to be flat by measurement or the like. It is a measurement example. Since the measurement target surface according to this example is guaranteed to be a plane as described above, the slit cross-section line should ideally be a straight line. However, as can be seen from the measurement result shown in FIG. 10, the shape distortion occurs in the slit cross-sectional line obtained by the measurement of this example. Specifically, the slit cross-section line according to this measurement example has a curved shape that is warped in a concave shape with a visual field width of about 70 mm and a flatness of about 0.2 mm (about ± 0.1 mm). As described above, when the slit light is irradiated onto the plane, the shape distortion occurs in the slit cross-section line, as described above, the problem of the optical system, for example, the laser light forming the slit light is converted into the slit shape. This is due to aberrations in the cylindrical lens used for this purpose.

  Therefore, the present invention recognizes the existence of the shape distortion of the slit light as shown in FIG. 10 when measuring the three-dimensional shape by the light cutting method, and the slit surface shape as the curved surface shape is approximated to a predetermined curved surface. Modeling. Embodiments of the present invention will be described below.

  As shown in FIG. 1, the three-dimensional shape measuring apparatus 1 according to the present embodiment includes a laser projection unit 2 as an irradiating unit, a camera 3 as an imaging unit, and a calculation control unit 5 as a calculation unit. Device 4.

  The laser projector 2 irradiates the workpiece 10 with slit light 11. The laser projector 2 is configured as a laser output unit having a laser transmitter, a cylindrical lens (cylindrical lens), or the like, which is a light source of laser light such as an infrared semiconductor laser. That is, in the laser projector 2, the laser light emitted from the laser transmitter is converted into slit light (laser sheet) 11 by passing through the cylindrical lens. Then, the workpiece 10 is irradiated with slit light 11 projected from the laser projector 2. A light cutting line (bright line of reflected light) 12 is formed on the surface of the workpiece 10 irradiated with the slit light 11 from the laser projector 2 according to the cross-sectional shape.

  The camera 3 images the light cutting line 12 formed on the surface of the workpiece 10 by the slit light 11 irradiated by the laser projector 2. The camera 3 is a light receiving sensor that receives a light cutting line 12, that is, a laser beam (reflected light) reflected on the surface of the workpiece 10, and is configured by an image pickup device such as a CCD image sensor or a CMOS image sensor. The camera 3 receives and images the light cutting line 12 formed on the surface of the workpiece 10, thereby capturing an image of the light cutting line 12 (hereinafter also referred to as “slit image”) by the imaging device. Obtained as a two-dimensional image on the surface 13 (see FIG. 2). The camera 3 includes a light receiving lens 14 (see FIG. 2) that receives reflected light from the surface of the workpiece 10 when the light cutting line 12 is imaged on the imaging surface 13.

  The camera 3 is arranged in a state where the optical axis (light receiving axis) is shifted by a predetermined angle with respect to the irradiation direction (light projecting axis direction) of the slit light 11 from the laser light projecting unit 2. For example, the camera 3 is arranged in such a posture that the portion of the light cutting line 12 formed on the horizontal plane portion of the workpiece 10 is in the horizontal direction on the image. Image data about the optical cutting line 12 imaged by the camera 3 is sent to the control device 4.

  The arithmetic control unit 5 provided in the control device 4 measures the three-dimensional coordinates of each point on the light cutting line 12 from the slit image captured by the camera 3, and the three-dimensional shape of the workpiece 10 based on the three-dimensional coordinates. Measure. That is, based on the image data of the slit image captured by the camera 3, the arithmetic control unit 5 determines the position of the laser projector 2, the position of the lens center O 1 of the light receiving lens 14 (see FIG. 2), and the workpiece 10. The three-dimensional coordinates of each point (irradiation point) on the light cutting line 12 on the surface of the workpiece 10 are measured by the principle of triangulation from the incident angle of the reflected light from the surface on the camera 3 and the like. That is, the three-dimensional coordinates of each point on the light cutting line 12 become measurement data (position data corresponding to the cross-sectional shape of the workpiece 10) by the arithmetic control unit 5. The contour line as the object of the workpiece 10 is measured by the measurement data for one light cutting line 12. Then, the position of the slit light 11 applied to the workpiece 10 is scanned (scanned) and updated at predetermined intervals, so that the arithmetic control unit 5 can detect the slit light 11 with respect to the workpiece 10 at each scanning position (irradiation position). Measurement data is continuously obtained, and the three-dimensional shape of the workpiece 10 is measured.

  When scanning the slit light 11 on the workpiece 10, the three-dimensional shape measuring apparatus 1 of the present embodiment has the following configuration. That is, as shown in FIG. 1, in the three-dimensional shape measuring apparatus 1 of the present embodiment, the laser projection unit 2 and the camera 3 are accommodated in the case 6 in a predetermined positional relationship with each other. . The case 6 is provided so as to be movable by a moving means (not shown) in the scanning direction of the slit light 11 irradiated from the laser projector 2 with respect to the workpiece 10.

  In this embodiment, as shown in FIG. 1, the workpiece 10 has a flat surface portion 10a and a rectangular parallelepiped convex portion 10b formed on the flat surface portion 10a. With respect to the workpiece 10, the slit light 11 from the laser projector 2 is substantially vertically downward so that the slit surface direction (the direction in which the light cutting line 12 is formed) is the short direction of the convex portion 10b. Irradiated and scanned in the longitudinal direction (left and right direction in FIG. 1) of the convex portion 10b. That is, in the present embodiment, the longitudinal direction of the convex portion 10b is the scanning direction of the slit light 11 with respect to the workpiece 10, and this direction is the moving direction of the case 6 (see arrow A1).

  Note that the configuration for scanning the slit light 11 with respect to the workpiece 10 is not limited to this embodiment. When scanning the slit light 11, for example, a configuration including a mirror that is rotatably provided and reflects the slit light 11 may be used. In such a configuration, the slit light 11 is scanned with respect to the workpiece 10 by deflecting the reflection direction of the slit light 11 by the mirror according to the angle of the mirror.

  The control device 4 includes the input unit 16 and the display unit 17 in addition to the calculation control unit 5 that measures the three-dimensional shape of the workpiece 10 as described above.

  The arithmetic control unit 5 controls a series of operations of the three-dimensional shape measuring apparatus 1. The calculation control unit 5 includes a storage unit that stores a program and the like, a development unit that expands the program and the like, a calculation unit that performs a predetermined calculation according to the program, a storage unit that stores a calculation result and the like by the calculation unit, and the like. The programs and the like stored in the storage unit include a later-described slit section acquisition program and a slit surface shape modeling program.

  Specifically, a configuration in which a CPU, a ROM, a RAM, an HDD, or the like is connected by a bus, or a configuration that includes a one-chip LSI or the like is used as the arithmetic control unit 5. As the arithmetic control unit 5, in addition to a dedicated product, a commercially available personal computer, a workstation, or the like in which the above program is stored is used.

  The input unit 16 is connected to the calculation control unit 5 and inputs various information / instructions related to the operation of the three-dimensional shape measuring apparatus 1 to the calculation control unit 5. As the input unit 16, a commercially available keyboard, mouse, pointing device, button, switch, or the like is used in addition to a dedicated product.

  The display unit 17 is connected to the calculation control unit 5 and displays the operation status of the three-dimensional shape measurement apparatus 1, the input content from the input unit 16 to the calculation control unit 5, the measurement result by the three-dimensional shape measurement apparatus 1, and the like. The display content by the display unit 17 includes a slit image 20 that is an image of the light cutting line 12. Specifically, as shown in FIG. 1, as described above, the slit image 20 for the workpiece 10 having the flat surface portion 10a and the convex portion 10b corresponds to the linear portion 20a corresponding to the flat surface portion 10a and the convex portion 10b. It has the convex-shaped part 20b to do. As the display unit 17, in addition to a dedicated product, a commercially available monitor, a liquid crystal display, or the like is used.

  A three-dimensional shape measurement method according to the present embodiment performed using the three-dimensional shape measurement apparatus 1 having the above-described configuration will be described. In the three-dimensional shape measurement method of this embodiment, the workpiece 10 is irradiated with the slit light 11, the optical cutting line 12 formed on the surface of the workpiece 10 is imaged, and an image (slit) about the captured optical cutting line 12. The three-dimensional shape of the workpiece 10 is measured based on the three-dimensional coordinates of each point on the light cutting line 12 measured from the image.

  Then, in such a three-dimensional shape measuring method using the light cutting method, the slit surface shape (sheet surface shape of the laser sheet) of the slit light 11 irradiated to the workpiece 10 is modeled into a predetermined curved surface. Then, the slit light 11 modeled on a predetermined curved surface is used, and the three-dimensional shape of the workpiece 10 is measured. Therefore, in the three-dimensional shape measurement method of the present embodiment, a curved surface on which the slit light 11 irradiated to the workpiece 10 is modeled into a curved surface (hereinafter referred to as “curved surface modeling” for the slit light 11). A modeling step and a shape measurement step in which the slit light 11 that is modeled as a curved surface is used to measure the three-dimensional shape of the workpiece 10, that is, three-dimensional data about the shape of the workpiece 10.

  The curved surface modeling process in the three-dimensional shape measurement method of this embodiment will be described. In the curved surface modeling in the curved surface modeling step, as shown in FIG. 3, a flat reference plate 30 that is a reference object having a reference plane 31 that is known to be a flat surface is used.

  Then, in the curved surface modeling process performed using the flat reference plate 30, the light cutting formed on the reference plane 31 in a state where the constant slit light 11 is irradiated on the reference plane 31 of the flat reference plate 30. Imaging of the cross-sectional line (slit cross-sectional line) 22 of the slit light 11 that is a line is performed for a plurality of different positions and orientations of the flat reference plate 30.

  That is, as shown in (a) to (e) in FIG. 3, measurement on the reference plane 31 of the plane reference plate 30 from various positions and postures of the plane reference plate 30 with respect to the laser projector 2 and the camera 3 ( Irradiation of the slit light 11 and imaging of the slit section line 22 are performed. The position of the plane reference plate 30 with respect to the laser projector 2 and the camera 3 corresponds to the relative distance of the plane reference plate 30 with respect to the laser projector 2 and the camera 3, and the plane reference with respect to the laser projector 2 and the camera 3. The posture of the plate 30 corresponds to the degree of inclination of the reference plane 31 of the plane reference plate 30 with respect to the slit light 11.

  Specifically, for example, as shown in FIGS. 3A to 3C, the linear direction including the irradiation direction (downward in FIG. 3) of the slit light 11 with respect to the laser projector 2 and the camera 3 (see FIG. 3). 3), the relative distance between the flat reference plate 30 and the laser projector 2 and the camera 3 is changed. Here, since the slit light 11 has a shape that spreads in a substantially fan shape toward the irradiation direction side (lower side in FIG. 3), the more the flat reference plate 30 is located on the irradiation direction side of the slit light 11, the more the slit light 11 The length of the slit cross-section line 22 formed on the reference plane 31 is increased. That is, in FIG. 3, since the flat reference plate 30 is located on the irradiation direction side of the slit light 11 in the same drawings (a) to (c), the length of the slit cross-section line 22 in each drawing is as shown in FIG. The slit section line 22a shown in a), the slit section line 22b shown in the figure (b), and the slit section line 22c shown in the figure (c) become longer in this order. Further, as shown in FIGS. 3D and 3E, when the plane reference plate 30 is rotated, the degree of inclination of the reference plane 31 of the plane reference plate 30 with respect to the slit light 11 is changed.

  In addition, the slit light 11 emitted from the laser projection unit 2 is constant when the slit light 11 is applied to each position and orientation of the plane reference plate 30 and the slit cross-section line 22 is imaged. That is, by changing the position and orientation of the plane reference plate 30 with respect to the common slit light 11 irradiated with constant irradiation conditions such as intensity and irradiation direction, the slit cross-section lines corresponding to the respective positions and orientations 22 images are taken. Further, when imaging the slit cross section line 22 for each position and orientation of the plane reference plate 30, the laser projector 2 and the camera 3 are accommodated in the case 6 in a predetermined positional relationship as described above. The imaging position of the camera 3 with respect to the optical unit 2 (slit light 11) is also constant.

  By irradiating the slit light 11 with respect to each position and orientation of the plane reference plate 30 and imaging the slit section line 22, slit section lines 22 (22 a to 22 e) for the reference plane 31 in each position and orientation of the plane reference plate 30 are acquired. The That is, the slit cross-section line 22 for each position and orientation of the plane reference plate 30 is sampled as measurement data. Each slit cross-sectional line 22 acquired here is a curved line because the reference plane 31 is a known plane, and the slit light 11 irradiated to the reference plane 31 is distorted due to problems with the optical system. It becomes.

  In acquiring the slit cross-section line 22 corresponding to each position and orientation of the plane reference plate 30 as described above, in the three-dimensional shape measuring apparatus 1 of the present embodiment, as shown in FIG. An acquisition unit 51 is provided.

  That is, the slit cross-section acquisition unit 51 is an embodiment of the slit cross-section acquisition means, and is formed on the reference plane 31 in a state in which the slit light 11 is irradiated on the reference plane 31 by the laser projector 2. The slit cross section line 22 is imaged at a plurality of different positions and orientations of the plane reference plate 30 by the camera 3, so that the slit cross section lines 22 (22 a to 22 a on the reference plane 31 in each position and orientation of the plane reference plate 30 are obtained. 22e). Substantially, the calculation control unit 5 performs a predetermined calculation or the like according to the slit section acquisition program stored in the storage unit, thereby functioning as the slit section acquisition unit 51.

  Subsequently, based on the slit cross-section line 22 corresponding to the reference plane 31 at each position and orientation of the plane reference plate 30, a common curved surface to which the plurality of slit cross-section lines 22 approximately match is derived.

  That is, as shown in FIG. 4, a curved surface 40 in which these are best-fit is derived from the slit cross-sectional lines 22 a to 22 e for each position and orientation of the flat reference plate 30 (see FIGS. 3A to 3E). That is, each slit cross-sectional line 22a-22e respond | corresponds to the slit cross-sectional shape in the different position of the slit light 11 irradiated from the laser projection part 2. FIG. The curved surface 40 is a common (single) curved surface in which each of the plurality of slit cross-sectional lines 22a to 22e is approximately matched (becomes along). Therefore, the shape of the curved surface 40 is a shape that approximates the shape of the slit surface of the slit light 11. As shown in FIG. 4, in this embodiment, the shape of the curved surface 40 guided from the plurality of slit cross-sectional lines 22 is a partial shape of a cylindrical surface.

  The curved surface 40 thus derived from the plurality of slit cross-sectional lines 22 is used as a curved surface model for the slit light 11. That is, the slit surface shape of the slit light 11 irradiated on the workpiece 10 is modeled (formulated) as a curved surface 40.

  In the curved surface modeling of the slit light 11 as described above, in the three-dimensional shape measurement apparatus 1 according to the present embodiment, as shown in FIG.

  That is, the slit surface shape modeling unit 52 is an embodiment of the slit surface shape modeling unit, and the slit surface shape of the slit light 11 irradiated to the workpiece 10 by the laser projecting unit 2 is converted into a slit section acquisition unit. Based on the slit cross-section line 22 corresponding to the reference plane 31 at each position and orientation of the plane reference plate 30 acquired by 51, the plurality of slit cross-section lines 22 are modeled as a common curved surface 40 that approximately matches. Substantially, the calculation control unit 5 functions as the slit surface shape modeling unit 52 by performing a predetermined calculation or the like according to the slit surface shape modeling program stored in the storage unit.

  As described above, the curved surface modeling step in the three-dimensional shape measurement method of the present embodiment is performed.

  In the present embodiment, as shown in FIGS. 3A to 3E and FIG. 4, when the curved surface of the slit light 11 is modeled, the number of slit section lines 22 acquired is five (slit section lines 22a). (E.g., there are five different positions and orientations of the plane reference plate 30 from which the slit cross-section line 22 is acquired), but the number of slit cross-section lines 22 used in the curved surface modeling of the slit light 11 is as follows. There is no particular limitation. For example, when the shape of the curved surface 40 on which the slit light 11 is modeled is a partial shape of a cylindrical surface as in the present embodiment, the slit cross-section line 22 used when modeling the curved surface of the slit light 11 is used. It is known from experiments and the like that the number of is preferably about 10 to 20 in consideration of accuracy and productivity for curved surface modeling.

  Further, the curved surface used for modeling the curved surface of the slit light 11 may be a conical surface as well as a cylindrical surface like the curved surface 40 in the present embodiment. When modeling the curved surface of the slit light 11, for example, when it is difficult to fit the slit light 11 to a cylindrical surface or a conical surface, the curved surface to which the slit light 11 is fitted is a NURBS curved surface, a B-spline curved surface, or a Bezier. (Bezier) A parametric curved surface such as a curved surface or a Gregory curved surface may be used.

  However, when modeling the curved surface of the slit light 11, it is considered that the shape of the curved surface used as the curved surface model is advantageously a partial shape of a conical surface or a cylindrical surface. That is, a parametric curved surface such as the above NURBS curved surface is geometrically more complicated than a curved surface that can be expressed by an elementary function such as a conical surface or a cylindrical surface. For this reason, depending on the calculation processing capability of the calculation control unit 5, calculation processing in the curved surface modeling of the slit light 11 and the subsequent measurement of the three-dimensional shape of the workpiece 10 may be somewhat heavy. In this respect, since basic forms such as a conical surface and a cylindrical surface can be expressed mathematically and concisely, it is considered that the burden on processing in the arithmetic control unit 5 is relatively small and good workability can be obtained. On the other hand, from the viewpoint of versatility when modeling the curved surface of the slit light 11, a parametric curved surface such as a NURBS curved surface having a higher degree of freedom of shape than a conical surface or a cylindrical surface is preferable to a conical surface or a cylindrical surface. It can be said.

  In the present embodiment, a calibration plate for calibration of the camera 3 is used as a reference object used for curved surface modeling of the slit light 11. That is, in the present embodiment in which the flat reference plate 30 is used as the reference object, a calibration plate for camera calibration of the camera 3 is used as the flat reference plate 30. As described above, in the present embodiment, the reference plane 31 on which the slit light 11 is irradiated when the slit section line 22 is acquired in the curved surface modeling process is the imaging surface of the calibration plate for calibration of the camera 3. Is done.

  Usually, calibration is performed on a camera used when a two-dimensional image is restored to a three-dimensional shape, such as measurement of a three-dimensional shape by a light cutting method. Some camera calibration methods use a calibration plate. Since this technique is a known technique, a detailed description thereof will be omitted, but is roughly performed as follows.

  In other words, the camera calibration is based on a projection matrix that defines the projection between a point in the world coordinate system where the camera is located and a point in the two-dimensional image. It is a process to seek. Camera variables include internal parameters (internal variables) such as focal length, pixel size (aspect ratio), image center and lens distortion, and external parameters (external variables) that indicate the position and orientation (orientation) of the camera. There is. When such camera parameters are determined, a calibration plate is used.

  The calibration plate is an object having a known three-dimensional shape and surface attribute. The calibration plate is photographed a plurality of times at different distances and postures with respect to the camera, for example. Thereby, the positional relationship between the three-dimensional position on the calibration plate and the two-dimensional position on the camera image of the calibration plate is measured. Then, the projection matrix as described above is obtained from the positional relationship, and various parameters of the camera are calculated from the projection matrix. As the surface attribute of the calibration plate, a marker, a lattice pattern or the like whose size and shape are all known is used.

  In the present embodiment, when measuring the three-dimensional shape of the workpiece 10, calibration is performed on the camera 3 that is a means for imaging the light section line 12. A flat reference plate 30 is used as a calibration plate used for calibration of the camera 3. The plane reference plate 30 as a calibration plate is a rectangular plate-like member, and the plate surface on one side thereof is a known reference plane 31 that is a plane. A reference plane 31 included in the plane reference plate 30 is a surface to be imaged when the camera 3 is calibrated. Then, on the reference plane 31 used for the calibration of the camera 3, dots (white circles) 32 arranged in a grid pattern at predetermined intervals are drawn over almost the entire surface as the surface attribute of the calibration plate ( (See FIG. 3).

  As an example of the calibration of the camera 3 performed using the plane reference plate 30 on which such dots 32 are drawn, the reference plane 31 is photographed so as to be parallel to the imaging surface 13 of the camera 3. In this photographed image, the dot 32 on the reference plane 31 is displaced from the position that should be originally captured due to lens distortion (distortion aberration such as barrel distortion or pincushion distortion) of the lens (light receiving lens 14) of the camera 3. The shift amount due to lens distortion in the camera 3 is calculated by image processing, and lens distortion which is an internal parameter of the camera 3 is obtained. The image in the camera 3 is corrected so that the displacement of the dots 32 based on such lens distortion corresponds to the arrangement of the dots 32 on the actual flat reference plate 30. This correction amount is stored in advance in a storage unit or the like in the arithmetic control unit 5.

  As described above, in this embodiment, the plane reference plate 30 used for modeling the curved surface of the slit light 11 is also used as the calibration plate of the camera 3. This eliminates the need to separately prepare a member that functions as the flat reference plate 30 when modeling the curved surface of the slit light 11, and performs curved surface modeling of the slit light 11 in association with the calibration performed on the camera 3. Therefore, workability can be improved. In the following description, the plane reference plate 30 is referred to as “calibration plate 60”.

  Following the curved surface modeling step, a shape measuring step is performed in which the three-dimensional shape of the workpiece 10 is measured. That is, the three-dimensional shape of the workpiece 10 is measured using the slit light 11 that has been curved-surface modeled in the curved-surface modeling step.

  Specifically, in the shape measurement step, when the three-dimensional shape of the workpiece 10 is measured, the slit surface shape of the slit light 11 irradiated on the workpiece 10 is the modeled curved surface 40, and the surface of the workpiece 10 is measured. The three-dimensional coordinates are measured for each point on the light cutting line 12 formed in the step. In the following description, the slit light 11 that has been curved as a curved surface 40 is referred to as a “slit curved surface model 41”.

  When measuring the three-dimensional shape of the workpiece 10, as described above, the laser projection is performed by irradiating the workpiece 10 with the slit light 11 by the laser projection unit 2 and based on the image data of the slit image captured by the camera 3. From the position of the part 2 and the like, the three-dimensional coordinates for each point on the light cutting line 12 on the surface of the workpiece 10 are measured by the principle of triangulation. Each point on the optical cutting line 12 where the three-dimensional coordinates are measured is a point on the slit surface of the slit light 11. Therefore, in the shape measurement process of the present embodiment, as shown in FIG. 2, light from each point on the slit image 20 on the imaging surface 13 in the camera 3 (an image of the captured optical cutting line 12). The slit curved surface model 41 is used when measuring the three-dimensional coordinates for each point on the cutting line 12.

  Therefore, in the present embodiment, when measuring the three-dimensional shape of the workpiece 10, the arithmetic control unit 5 uses the slit surface shape of the slit light 11 as the curved surface 40 modeled by the slit surface shape modeling unit 52. The three-dimensional coordinates of each point on the optical cutting line 12 formed on the surface of 10 are measured.

  As described above, the three-dimensional shape measurement method of this embodiment including the curved surface modeling step and the shape measurement step will be described with reference to the flowchart shown in FIG.

  In the three-dimensional shape measurement method of the present embodiment, first, calibration of the camera 3 (of the light receiving lens 14) is performed (S110). That is, the camera 3 captures the reference plane 31 that is the imaging surface of the calibration plate 60, and various parameters of the camera 3 are obtained based on the dots 32 and the like in the captured image. Various parameters obtained by calibration of the camera 3 are stored in advance in a storage unit or the like in the arithmetic control unit 5.

  Next, curved surface modeling of the slit light 11 is performed (S120 to S140). In modeling the curved surface of the slit light 11, first, the slit light 11 is irradiated onto the calibration plate 60 (S 120). That is, as described above, the slit light 11 is irradiated from the laser projector 2 to the calibration plate 60 used for the calibration of the camera 3.

  Next, acquisition of the plurality of slit cross-sectional lines 22 using the calibration plate 60 is performed (S130). That is, as shown in FIGS. 3A to 3E, the position and orientation of the calibration plate 60 that receives the irradiation of the slit light 11 with respect to the laser projector 2 and the camera 3 are changed, and the slit for each position and orientation is changed. A section line 22 is acquired.

  Then, the slit curved surface model 41 using the plurality of slit cross-section lines 22 is constructed (S140). That is, as shown in FIG. 4, from the plurality of slit cross-sectional lines 22 a to 22 e acquired for each position and orientation of the calibration plate 60, a partial shape of the cylindrical surface is formed as a common curved surface to which these are approximately matched. A curved surface 40 is introduced. Then, the slit curved surface model 41 is constructed by modeling the slit surface shape of the slit light 11 irradiated on the workpiece 10 as a curved surface 40 (see FIG. 2).

  As described above, the above steps S120 to S140 in which the curved surface modeling of the slit light 11 is performed correspond to the curved surface modeling step in the three-dimensional shape measurement method of the present embodiment. However, the curved surface modeling of the slit light 11 may be performed in association with the calibration of the camera 3. When the curved surface modeling of the slit light 11 is performed in connection with the calibration of the camera 3, the method according to the present embodiment is as follows.

  That is, when the camera 3 is calibrated in step S110, the calibration plate 60 may be photographed a plurality of times at different positions and orientations with respect to the camera 3, and photographed images for each position and orientation may be used. In such a case, for each position and orientation of the calibration plate 60 photographed during the calibration of the camera 3, the slit cross-section line 22 used for the curved surface modeling of the slit light 11 is acquired.

  That is, for each position and orientation of the calibration plate 60 that is changed and different with respect to the laser projector 2 and the camera 3, the shooting for calibration of the camera 3 and the laser projector for the calibration plate 60 are performed. The slit section line 22 is acquired in a state where the irradiation of the slit light 11 from 2 is performed. Therefore, in this case, whenever the position and orientation of the calibration plate 60 are changed, the calibration plate 60 is imaged by the camera 3 without being irradiated with the slit light 11 (photographing for calibration of the camera 3). ) And imaging in the state where the slit light 11 is irradiated (acquisition of the slit cross-section line 22) are performed alternately (regardless of the order). Note that the photographing of the calibration plate 60 for calibration of the camera 3 may be performed in a state where the slit light 11 is irradiated.

  Thus, in this embodiment, since the plane reference plate 30 used for the curved surface modeling of the slit light 11 is also used as the calibration plate 60 for the calibration of the camera 3, the curved surface modeling of the slit light 11 is performed. Can be performed in connection with the calibration of the camera 3. As a result, the position and orientation of the calibration plate 60 to be changed can be shared by the calibration of the camera 3 and the curved surface modeling of the slit light 11, so that work efficiency can be improved.

  That is, the curved surface modeling of the slit light 11 using the calibration plate 60 (acquisition of the slit cross section line 22) is performed during the calibration process of the camera 3 (in connection with the calibration of the camera 3). Alternatively, it may be performed after the calibration process of the camera 3.

  Thus, the calibration including the curved surface modeling of the slit light 11 in measuring the three-dimensional shape of the workpiece 10 by the light cutting method of the present embodiment is completed.

  Subsequently, the slit curved surface model 41 constructed by the curved surface modeling of the slit light 11 is used to measure the three-dimensional shape of the workpiece 10. When measuring the three-dimensional shape of the workpiece 10, first, the workpiece 10 is irradiated with the slit light 11 (S210). That is, the slit light 11 is irradiated to the workpiece 10 by the laser projector 2 (see FIG. 1).

  Next, imaging of the light section line 12 and extraction of the center line of the slit image 20 (hereinafter referred to as “slit image center line”) are performed (S220). That is, the optical cutting line 12 formed on the surface of the workpiece 10 irradiated with the slit light 11 is imaged by the camera 3. As a result, a slit image 20 that is an image of the light cutting line 12 is obtained on the imaging surface 13 of the camera 3. Then, extraction of the slit image center line for the slit image 20 is performed.

  Specifically, for example, as illustrated in FIG. 6A, the slit image 20 that is a captured image of the optical cutting line 12 formed by the irradiation of the slit light 11 is a linear image. 13 has a finite width (line thickness). That is, the width of the slit image 20 is longer than the length of one pixel (pixel) on the imaging surface 13 and covers a plurality of pixels. Therefore, the slit image center line 20c is extracted based on the luminance distribution in the width direction of the slit image 20 on the imaging surface 13 (distribution of the output level of the imaging element).

  For the slit image 20, the distribution of the luminance L along the width direction of the slit image 20 at a certain position is, for example, a graph G1 shown in FIG. From such a luminance distribution in the width direction (w direction) of the slit image 20, the center position (center point) in the width direction is obtained. As the center position of the slit image 20 in the width direction, for example, the position in the width direction where the area surrounded by the w axis indicating the width direction and the graph G1 is equal in FIG. A position that is a weighted average of a portion that is equal to or greater than a predetermined threshold, an average position that is obtained when the distribution of luminance L is approximated to a normal distribution, and the like are used. A set along the length direction (line direction) of the slit image 20 of the center position (center point) in the width direction of the slit image 20 thus obtained is extracted as the slit image center line 20c.

  Subsequently, a point on the slit curved surface model 41 corresponding to each point on the slit image center line 20c is calculated (S230). That is, for each point on the slit image center line 20c, a straight line connecting each point and the lens center O1 of the light receiving lens 14 is calculated, and an intersection of this straight line with the slit curved surface model 41 is obtained.

  Specifically, as shown in FIG. 2, for example, a point P1 on the slit image center line 20c will be described. The position of the point P1 (x1, y1) represented by two-dimensional coordinates on the imaging surface 13, the position of the lens center O1 of the light receiving lens 14, the position of the imaging surface 13 with respect to the lens center O1, and the like are calibrated for the camera 3. It is measured from the parameters of the camera 3 obtained by the above. Further, the position of the slit curved surface model 41 in the world coordinate system is measured from the relationship with the actual slit light 11 when the curved surface modeling of the slit light 11 is performed. From these measured values, a straight line L1 passing through the point P1 on the slit image center line 20c and the lens center O1 of the light receiving lens 14 is calculated, and a point P2 that is the intersection of the straight line L1 with the slit curved surface model 41 is obtained. It is done. The point P2 on the slit curved surface model 41 becomes a measurement point in the three-dimensional space in the world coordinate system corresponding to the point P1 on the slit image center line 20c of the imaging surface 13 which is a two-dimensional image.

  That is, the slit image 20 on the imaging surface 13 is an image of the light cutting line 12 of the slit light 11 on the workpiece 10, and the slit curved surface model 41 is a curved surface model of the slit light 11. Therefore, points corresponding to individual points on the slit image center line 20 c exist on the slit curved surface model 41. A point on the slit curved surface model 41 corresponding to each point on the slit image center line 20c is a measurement point in the three-dimensional space.

  Next, the three-dimensional coordinates of the points on the slit curved surface model 41 are measured (S240). That is, the three-dimensional coordinates of the measurement point on the slit curved surface model 41 corresponding to each point on the slit image center line 20 c are the position of the laser projector 2, the position of the lens center O 1 of the light receiving lens 14, and the workpiece 10. It is measured by the principle of triangulation from the incident angle of the reflected light from the surface of the camera 3 with respect to the camera 3. That is, in the above example, from the position (x1, y1) of the point P1, which is a point on the slit image center line 20c, the three-dimensional coordinates (X, Y) about the corresponding point P2 on the slit curved surface model 41. , Z) is measured. Here, as shown in FIG. 2, a point (a point on the slit image center line 20c) recognized by the two-dimensional coordinates on the imaging surface 13 of the camera 3 is a slit curved surface model 41 having a partial shape of a cylindrical surface. Calculated as existing height data.

  And the measurement of the three-dimensional coordinate about such a measurement point is performed about all the point groups obtained about the workpiece | work 10 (S250). That is, each scan of the slit light 11 is updated at predetermined intervals over the entire scanning range of the slit light 11 with respect to the workpiece 10 for the measurement points corresponding to the respective points on the slit image center line 20c. It is performed at the position (irradiation position). Accordingly, all the point groups obtained for the workpiece 10 here are all points on the slit image center line 20c obtained at all scanning positions in the scanning range of the slit light 11 with respect to the workpiece 10. The measurement values of the three-dimensional coordinates for the measurement points corresponding to each point in such a point group are stored in the arithmetic control unit 5 as needed.

  The three-dimensional shape of the workpiece 10 is measured from the three-dimensional coordinate measurement data for all point groups obtained for the workpiece 10 in this way. That is, since the point on the slit image center line 20c is calculated as height data in the slit curved surface model 41 as described above, the point on the slit image center line 20c corresponding to the scanning position (irradiation position) where the slit light 11 exists. A contour line 45 corresponding to the cross-sectional shape of the workpiece 10 at the scanning position is measured by measurement data (a set of measurement points) on the slit cross-section model 41 for the point group (see FIG. 2). The contour line 45 about the workpiece 10 is continuously acquired in the scanning direction of the slit light 11, whereby the three-dimensional shape of the workpiece 10 is measured from the set of the contour lines 45.

  Then, integration of all measurement points for the workpiece 10 and file storage as a three-dimensional point group are performed (S260). That is, the measurement points for all the point groups obtained for the workpiece 10 on which the three-dimensional coordinates are measured are integrated as the contour line 45 and a set thereof, and the three-dimensional point group of the workpiece 10, that is, the three-dimensional shape of the workpiece 10 is integrated. Is stored in the arithmetic control unit 5.

  Thus, said step S210-S260 by which the measurement of the three-dimensional shape of the workpiece | work 10 respond | corresponds to the shape measurement process in the three-dimensional shape measurement method of this embodiment. The three-dimensional shape of the workpiece 10 measured by the shape measuring step is displayed on the display unit 17 in the control device 4.

  The three-dimensional shape of the workpiece 10 measured as described above is used, and analysis and quality inspection are performed by comparison with a drawing or the like (S270). That is, as described above, the three-dimensional shape of the workpiece 10 displayed on the display unit 17 is compared with a master workpiece or the like selected from a design drawing such as a CAD drawing or a prototype. Thereby, quality inspections such as analysis of the three-dimensional shape of the workpiece 10 to be measured and quality determination are performed.

  According to the three-dimensional shape measurement apparatus 1 and the three-dimensional shape measurement method of the present embodiment described above, in the three-dimensional shape measurement by the light cutting method, the shape distortion such as the bending existing in the slit light 11 irradiated on the workpiece 10. Can be made systematic, measurement errors due to the shape distortion of the slit light 11 can be reduced, and measurement stability and versatility can be improved.

  That is, as described in the present embodiment, in the three-dimensional shape measurement by the light cutting method, the slit light 11 having a curved shape due to a problem of the optical system is explicitly modeled into a predetermined curved surface. The measurement performance can be improved as compared with the conventional case where the slit light 11 is modeled as a plane.

  In addition, since the slit light 11 is modeled (formulated) as a slit curved surface model, by adjusting the parameters of the mathematical formula representing the slit curved surface model, the measurement conditions such as the parameters of the camera 3 can be changed. Parametrics can be easily accommodated, and the amount of data necessary for measurement can be reduced. As a result, when measuring a three-dimensional shape corresponding to the shape distortion of the slit light 11, a method is used in which individual parameters are used for each segmented area on the imaging surface on which the optical cutting line is imaged, as in the prior art. In comparison, measurement is systematic and easy to manage, and high stability and versatility can be obtained.

  Application examples and effects of the three-dimensional shape measurement apparatus 1 and the three-dimensional shape measurement method of the present embodiment will be described with reference to FIGS. 1, 7, 8, and 9. FIG. This application example is for the case where the three-dimensional shape measurement of the present embodiment is used for in-line inspection of the three-dimensional shape of a machined part.

  First, an example of inspection by in-line straight scanning will be described. That is, as shown in FIG. 1, a case will be described in which the slit light 11 is linearly moved when the slit light 11 is scanned with respect to a three-dimensional shape measurement target (workpiece 10) to be inspected for in-line inspection. In addition, it is assumed that the workpiece 10 according to this example is a machined part without warping. In this case, as described above, the longitudinal direction of the convex portion 10 b in the workpiece 10 is the scanning direction, and this direction is the linear movement direction of the slit light 11. Moreover, since the workpiece | work 10 is a machined part without a curvature as mentioned above, all the surfaces which form the workpiece | work 10 become a plane.

  In such inspection of the workpiece 10 by linear scanning, when the curved surface modeling of the slit light 11 is not performed when measuring the three-dimensional shape of the workpiece 10, that is, the slit surface shape of the slit light 11 is corrected to be a predetermined curved surface. When the measurement is performed on the assumption that the slit surface shape is a flat surface without being performed, the measurement error generated for the three-dimensional shape of the workpiece 10 to be measured becomes large. Specifically, for example, as shown in FIG. 7A, when the measurement error about the three-dimensional shape of the workpiece 10 increases, a three-dimensional shape image 70a represented on the display unit 17 as a measurement result has a third order. A measurement result in which a warp (a concave warp in the drawing) occurs in the original shape is obtained. In other words, in this case, the influence of the warp as the shape distortion of the slit light 11 to be reflected in the measurement result is increased, and sufficient measurement accuracy cannot be obtained.

  On the other hand, in the inspection by the straight scanning of the workpiece 10, when the curved surface modeling of the slit light 11 is performed when measuring the three-dimensional shape of the workpiece 10, that is, the slit surface shape of the slit light 11 is corrected to be a predetermined curved surface. In this case, the measurement error that occurs for the three-dimensional shape of the workpiece 10 to be measured is reduced. Specifically, as shown in FIG. 7B, the measurement error about the three-dimensional shape of the workpiece 10 is reduced, so that in the three-dimensional shape image 70b represented on the display unit 17 as the measurement result, the third order is obtained. A measurement result in which the warpage in the original shape is corrected is obtained. That is, in this case, the influence of the warp as the shape distortion of the slit light 11 to be reflected in the measurement result is reduced, and sufficient measurement accuracy can be obtained.

  Next, an example of inspection by in-line rotational scanning will be described. As shown in FIG. 8, the workpiece 80 according to this example is a machined part having a cylindrical shape. When the slit light 11 is scanned with respect to the three-dimensional shape measurement target (work 80) to be inspected in the in-line inspection, the work 80 is cylindrical with the slit light 11 being irradiated on the cylindrical surface of the work 80. The cylinder axis direction (refer to the axial center line C1) is rotated as the rotation axis direction. Therefore, in this example, the direction opposite to the rotation direction of the workpiece 80 is the scanning direction with respect to the cylindrical surface of the workpiece 80.

  In the inspection by the rotational scan for the workpiece 80, as in the case of the straight scanning for the workpiece 10, the curved surface modeling of the slit light 11 is not performed when measuring the three-dimensional shape of the workpiece 80. FIG. 9 shows an example of measurement results for each of cases where curved surface modeling is performed.

  As shown in FIG. 9A, when the curved surface modeling of the slit light 11 is not performed, the measurement error about the three-dimensional shape of the workpiece 80 is increased, and the measurement result is displayed on the display unit 17. In the three-dimensional shape image 90a, for example, a measurement result in which the cylindrical shape is warped in a pincushion shape is obtained. On the other hand, as shown in FIG. 9B, when the curved surface modeling of the slit light 11 is performed, the measurement error about the three-dimensional shape of the workpiece 80 is reduced, and the measurement result is displayed on the display unit 17. In the three-dimensional shape image 90b, a measurement result is obtained in which the three-dimensional shape is correctly measured as a cylindrical surface shape.

  As described above, in the in-line inspection of the three-dimensional shape of the machined part, the slit light that is reflected in the measurement result when measuring the three-dimensional shape by applying the three-dimensional shape measurement of the present embodiment. 11 is reduced, and sufficient measurement accuracy can be obtained.

  The above-described three-dimensional shape measurement according to the present invention enables accurate shape digitization as compared with the conventional method when a curved surface such as a body panel is measured and inspected in the automobile industry, for example. And the possibility that the measurement result can be applied in the quality inspection of the press molding of the body becomes more strict.

  In addition, by using the three-dimensional shape measurement according to the present invention, when a three-dimensional shape is measured when inspecting a shaft-like or pipe-like part as an automobile part, the three-dimensional shape (for example, a diameter) is more accurately measured. Can be captured. Further, by using a systematic method of modeling the curved surface of the slit light, management adjustment in the in-line inspection of parts as described above becomes easy. In particular, in in-line inspection, it is difficult to implement time-consuming recalibration as a treatment for the shape distortion of the slit light applied to the workpiece. Therefore, as in the three-dimensional shape measurement according to the present invention, a curved surface model of the slit light is used. A method capable of performing parametric and efficient calibration becomes effective.

The figure which shows the structure of the three-dimensional shape measuring apparatus which concerns on one Embodiment of this invention. The figure which shows the correspondence of the imaging surface of a camera, and a slit curved surface model. Explanatory drawing about acquisition of the slit cross-section line at the time of curved surface modeling of slit light. The figure which shows an example of the curved surface guide | induced by the some slit cross section line. The flowchart about the three-dimensional shape measuring method which concerns on one Embodiment of this invention. Explanatory drawing about the centerline of a slit image. The figure which shows the example of a measurement result in the test | inspection by the in-line straight scan. The figure which shows the example of the test | inspection by the in-line rotational scan. The figure which shows the example of a measurement result in the test | inspection by the inline rotation scan. The figure which shows an example (measurement example) of the shape distortion of slit light. Explanatory drawing about an example of the three-dimensional shape measurement by the conventional light cutting method.

1 Three-dimensional shape measuring device 2 Laser projector (irradiation means)
3 Camera (imaging means)
5 Calculation control unit (calculation means)
10 Workpiece (object to be measured)
DESCRIPTION OF SYMBOLS 11 Slit light 12 Optical cutting line 20 Slit image 22 Slit cross section line 30 Plane reference board (reference object)
31 Reference plane 40 Curved surface 41 Slit curved surface model 51 Slit cross section acquisition unit 52 Slit surface shape modeling unit 60 Calibration plate

Claims (4)

Each point on the optical cutting line is measured by irradiating the measuring object with slit light, picking up an optical cutting line formed on the surface of the measuring target with an imaging means, and measuring the image of the picked optical cutting line. A three-dimensional shape measurement method for measuring a three-dimensional shape of a measurement object based on the three-dimensional coordinates of
The imaging unit is used to photograph a reference plane that is provided on the calibration plate of the imaging unit and is known to be a plane, and the surface attribute of the reference plane in the captured image is shifted from the actual surface attribute of the reference plane. A calibration step for calibrating the imaging means to correct the amount;
Using the calibration plate ,
In a state in which a certain slit light is irradiated on the reference plane, imaging by the imaging means of the cross-sectional line of the slit light, which is a light cutting line formed on the reference plane, is performed by a plurality of different calibration plates. By doing about position and orientation,
Obtaining a sectional line of the slit light for the reference plane at each position and orientation of the calibration plate ;
Based on the cross-sectional line of the slit light corresponding to the reference plane in each position and orientation, a common curved surface that approximately matches the cross-sectional line of the plurality of slit light,
A curved surface modeling step of modeling the slit surface shape of the slit light applied to the measurement object as the curved surface ;
When measuring the three-dimensional shape, comprising the shape measurement step of measuring the three-dimensional coordinates as the curved surface modeled slit surface shape of the slit light ,
The imaging of the reference plane of the calibration plate in the calibration process and the imaging of the sectional line of the slit light in the curved surface modeling process are alternately performed whenever the position and orientation of the calibration plate is changed. Done,
A three-dimensional shape measuring method characterized by that.   The three-dimensional shape measurement method according to claim 1, wherein the shape of the curved surface is a partial shape of a conical surface or a cylindrical surface. Irradiating means for irradiating the measurement object with slit light;
Imaging means for imaging a light cutting line formed on the surface of the measurement object by the slit light irradiated by the irradiation means;
An arithmetic unit that measures the three-dimensional coordinates of each point on the optical cutting line from an image of the optical cutting line imaged by the imaging unit, and measures the three-dimensional shape of the measurement object based on the three-dimensional coordinates; A three-dimensional shape measuring apparatus comprising:
The slit which is a light cutting line formed on the reference plane in a state where a fixed slit light is irradiated by the irradiation unit on a reference plane which is provided on a calibration plate of the imaging unit and is known to be a plane. The cross-sectional line of the slit light with respect to the reference plane at each position and orientation of the calibration plate is obtained by imaging the cross-sectional line of light at a plurality of different positions and orientations of the calibration plate by the imaging means. Slit cross-section acquisition means;
The slit surface shape of the slit light irradiated to the measurement object by the irradiation means is based on the sectional lines of the slit light corresponding to the reference plane acquired at the respective positions and orientations acquired by the slit cross-section acquisition means. Slit surface shape modeling means for modeling as a common curved surface to which the cross-sectional lines of the plurality of slit lights approximately match,
When measuring the three-dimensional shape, the reference plane of the calibration plate is imaged by the imaging means, and the deviation amount of the surface attribute of the reference plane in the captured image with respect to the actual surface attribute of the reference plane is corrected. Calibration of the imaging means is performed,
Imaging of a reference plane of the calibration plate when the calibration is performed, and imaging of a cross-sectional line of the slit light when the cross-sectional line of the slit light is acquired by the slit cross-sectional acquisition unit are the calibration. Every time the position and orientation of the plate is changed,
The arithmetic means measures the three-dimensional coordinates when measuring the three-dimensional shape, using the slit surface shape of the slit light as the curved surface modeled by the slit surface shape modeling means. 3D shape measuring device. The three-dimensional shape measuring apparatus according to claim 3, wherein the shape of the curved surface is a partial shape of a conical surface or a cylindrical surface.

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