JP2005189205A - Three-dimensional shape measuring apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain entire perimeter range data of an object, even if it has in part a complicated shape, using means of a similar operation to objects of simple shape. <P>SOLUTION: On a rotating table 2, a measured object 3 is held at relatively fixed position to the rotating table 2. An irradiation device 4 for laser beam irradiates laser beam 5 directed toward the central axis of the rotating table 2, as shown by the dashed line. The emitted laser beam 5 is reflected by the measured object 3, because the measured object 3 is arranged such that it covers the central axis of the rotating table 2. A reflection spot photodetector 108 identifies reflection spots, and, for example, when reflection spots disappear, a corresponding angle position is added as an additional stopping angle by deciding that the surface shape of the concerned part is complicated. After the rotating table 2 is forced to stop at the stopping angle of default and an additional stopping angle, the three-dimensional coordinates of the measured object 3 are acquired from a three-dimensional coordinate acquiring system 1, to be combined. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a three-dimensional shape measurement technique for acquiring a three-dimensional shape of an object, and in particular, acquires the entire circumference shape of the object by rotating the object relative to a three-dimensional coordinate acquisition unit. The present invention relates to a dimensional shape measurement technique.

  There are two methods for acquiring a three-dimensional shape: an active method and an passive method. The active method uses (1) a laser method that emits laser light, measures the amount of light reflected from the object and the arrival time, extracts depth information, and (2) uses a special pattern light source such as slit light. There are a pattern projection method for estimating a target shape from image information such as geometric deformation of a target surface pattern, and (3) a method for obtaining three-dimensional information by forming contour lines with moire fringes by optical processing. On the other hand, the passive method uses knowledge about the object's appearance, light source, illumination, shadow information, etc., and uses the monocular stereoscopic method to estimate 3D information from a single image, and the depth information of each pixel by the triangulation principle. There is a stereo method for estimating. The distance information of the measurement target obtained by applying the above-described method is data representing the surface shape of the measurement target and is called range data. The range data is a set of distance data and sample points at a certain point on the measurement target.

By the way, in general, the range data only needs to be the range data to be measured in the field of view from a certain viewpoint where the measurement was performed in a single measurement. Therefore, when obtaining the three-dimensional shape of the entire object, it is necessary to perform processing for aligning and synthesizing range data from a plurality of measurement points for each measurement position. For alignment of a plurality of range data, for example, as disclosed in Patent Document 1, a measurement object is set on a rotary stage, and a plurality of range data is acquired by associating an imaging direction with a rotation angle of the rotary stage. A method is known in which rotation conversion is performed based on the rotation angle of the rotary stage, and a plurality of range data is synthesized.
JP 2002-328013 A

  However, in the conventional method, it is common to acquire a plurality of range data by setting the rotation angle in advance. For a complex object, specify a fine rotation angle even if the complicated part is a part. As a result, the number of times the range data is acquired increases, and there are problems such as the time required for the entire measurement and the time and effort required to synthesize a plurality of range data in a later process. Conversely, if a rough rotation angle is specified for such an object, range data of a complicated shape cannot be obtained accurately.

  The present invention has been made in view of such a problem, and even if an object has a complicated shape in part, it is possible to acquire all-round range data by an operation similar to that of an object having a simple shape. It is an object of the present invention to provide a dimension shape measuring method and apparatus.

  According to this invention, in order to achieve the above-mentioned object, the configuration as described in the claims is adopted. Here, prior to explaining the invention in detail, a supplementary explanation will be given of the claims.

  For convenience, the embodiment will be described with reference to the embodiment shown in FIG. 1, but the present invention is not limited to this.

  That is, according to one aspect of the present invention, in order to achieve the above-mentioned object, a three-dimensional shape measuring apparatus for measuring a three-dimensional shape of a measurement object 3 installed in a measurement space: Holding means 2 for holding the relative position with respect to the holding means main body so as not to change during measurement; three-dimensional coordinate acquisition means 1 for acquiring three-dimensional coordinates of a plurality of points on the measurement object by an image input element; A light beam irradiating means 4 for irradiating the measurement object with a light beam; a relative position between the holding means and the three-dimensional coordinate acquiring means is changed, and each of the relative positions is determined by the three-dimensional coordinate acquiring means; A plurality of measurement control means 106 that performs measurement; and the relative relationship between the holding means and the three-dimensional coordinate acquisition means according to the state of reflected light that the light emitted from the light irradiation means hits the measurement object. And it is provided with a relative position control means 104 for controlling the magnitude of the change in location.

  In this configuration, it is possible to determine the complexity of each position of the measurement object based on the behavior of the reflection spot, and to set the measurement position finely as necessary to obtain the necessary three-dimensional coordinate data.

  In this configuration, it is preferable that the holding means is a rotary stage. In this case, the plurality of measurement control means includes rotation control means for the rotary stage, and the relative position control means includes rotation angle control means for the rotation stage.

  Preferably, the image input element is a camera, and the light beam irradiation means is a laser beam irradiation device.

  Further, the light beam irradiation device may be provided on both sides of the three-dimensional coordinate acquisition means.

  The light beam irradiation device may be driven to blink.

  The light beam irradiation device may generate irradiation spots at a plurality of positions substantially simultaneously.

  The present invention can be realized not only as an apparatus or a system but also as a method. Of course, part of such an invention can be configured as software. Of course, software products used to cause a computer to execute such software are also included in the technical scope of the present invention.

  The above and other aspects of the invention are set forth in the appended claims and are described in detail below using examples.

  According to the present invention, in the three-dimensional shape measurement that measures the entire circumference of the measurement object, the measurement object is irradiated with light from a direction different from the measurement direction, and the reflected image is monitored from the measurement direction. It is possible to detect the location (direction) of the complexity of the surface shape of the object to be measured, and by performing measurement from that direction without fail, accurate three-dimensional measurement of the entire circumference without missing data is possible. .

  Embodiments of the present invention will be described below.

  An embodiment of a three-dimensional shape measuring apparatus according to the present invention will be described with reference to the drawings.

  FIG. 1 schematically shows a three-dimensional shape measuring apparatus according to an embodiment of the present invention. In this figure, the three-dimensional shape measuring apparatus includes a three-dimensional coordinate acquisition device 1, a rotary table (both a rotary stage and a rotary table). 2) includes a laser beam irradiation device 4 and a control device 100. On the rotary table 2, the measurement object 3 is held in an arrangement that is fixed relative to the rotary table 2. The laser beam irradiation device 4 irradiates the laser beam 5 toward the central axis of the turntable 2 as indicated by a broken line. Since the measurement object 3 is arranged so as to cover the central axis of the turntable 2, the laser beam 5 is reflected by the measurement object 3. The control device 100 is, for example, a personal computer, and is connected to the three-dimensional coordinate acquisition device 1, the rotary table 2, the laser light irradiation device 4, etc., and performs operation control of each part, coordinate calculation, and the like.

  The control device 100 includes, for example, a three-dimensional coordinate acquisition unit 101, a three-dimensional sitting image synthesis unit 102, a reflected spot determination unit 103, an additional stop angle determination unit 104, a default stop angle storage unit 105, a rotation drive control unit 106, and irradiation drive control. A functional block such as the unit 107 is included.

  The rotation drive control unit 106 rotates the rotary table 2 and arranges it at a desired angular position. As the rotary table 2 rotates, the viewpoint from the three-dimensional coordinate acquisition unit 101 to the measurement object 3 on the rotary table 2 is sequentially changed. Basically, the rotary table 2 is rotationally driven by a predetermined angular interval, for example, 60 degrees, and the viewpoint is changed. This angle interval is a default value and is stored in the default stop angle storage unit 104. The default stop angle may be changed by the user according to the measurement target.

  The three-dimensional coordinate acquisition unit 101 acquires three-dimensional coordinates (three-dimensional images) of a plurality of points on the measurement object 3 for each viewpoint. The three-dimensional coordinate acquisition apparatus 1 is not particularly limited in its method, but since it is necessary to perform imaging a plurality of times, a CCD camera as disclosed in Japanese Patent Application Laid-Open No. 2000-65542 is incorporated once. From the viewpoint of time required for measurement, it is desirable that the distance information can be obtained by imaging. An example of the three-dimensional coordinate acquisition apparatus 1 will be described later with reference to FIGS.

  The three-dimensional coordinate synthesis unit 102 synthesizes the three-dimensional coordinates acquired for each viewpoint by the three-dimensional coordinate acquisition unit 101 to obtain the entire circumference data of the measurement object.

  The irradiation drive control unit 107 drives the laser beam irradiation device 4. The laser light irradiation device 4 may be driven to blink so that the reflection spot of the laser light can be easily identified. The reflected spot is determined by the reflected spot light receiving element 108 which is also used by, for example, a camera (described later) of the three-dimensional coordinate acquisition apparatus 1. The additional stop angle determination unit 104 determines an additional stop angle position according to the behavior of the reflection spot based on the discrimination output of the reflection spot light receiving element. That is, when the surface shape of the measurement target of the spot position is determined to be complicated due to the behavior of the reflected spot, the corresponding angular position is set as an additional stop angular position. In this embodiment, as described later, when the reflected spot deviates from the field of view, it is determined that the surface shape of the measurement target is complicated.

  The rotation drive control unit 106 stops the rotation table 2 at an additional stop angle position in addition to the default stop angle position described above, and acquires the three-dimensional coordinates of the measurement object 3.

  An example of the three-dimensional coordinate acquisition apparatus 1 is shown in FIG. In FIG. 3, a three-dimensional coordinate acquisition device 1 includes a projection device (projector) 11, a monitor imaging device (first camera, CCD camera) 12, a triangulation imaging device (second camera, CCD camera) 13, and a half mirror. 14. The projection device 11 projects a pattern onto a measurement target in order to acquire three-dimensional coordinates. The monitor imaging device 12 is arranged at substantially the same principal point and the same optical axis as the projection device 11 and monitors the pattern. The triangulation imaging device 13 is arranged on an optical axis different from that of the imaging device. This is the same configuration as that described in Japanese Patent Laid-Open No. 2000-65542. The projector 11 uses a projector or a laser slit projection system. The projection apparatus 11 forms a projection pattern with a luminance value corresponding to a predetermined code and performs projection. For the projection pattern, a slit pattern with shading as shown in FIG. 4 is used, and for example, the pattern is projected onto the object (measurement target) shown on the right side of FIG. The projection pattern is projected onto the measurement object via the half mirror 14, and the reflected light is reflected by the half mirror 14 and enters the monitor imaging device 12. The reflected light from the measurement object enters the triangulation image pickup device 13 through an optical path different from that of the monitor image pickup device 12.

  The pattern projection and its imaging will be described in detail with reference to FIG. The monitor imaging device (camera 1) 12 and the projection device (projector) 11 are arranged at substantially the same principal point and the same optical axis by using the half mirror 14 or the like as described above. The triangulation imaging device (second camera) 13 is disposed on another optical axis. A projection device (projector) 11 projects a stripe pattern as shown in FIG. Re-encoding is performed from an image (captured image of the first camera) observed by the monitor imaging device (first camera) 12 having substantially the same principal point and the same optical axis, and further, the monitoring imaging device (camera 1) A distance image is calculated from the image observed at 12 (captured image of the first camera) and the image observed by the triangulation imaging device (second camera) 13 (captured image of the second camera). Re-encoding is necessary for high-precision measurements, but is not essential.

  The reflection spot light receiving element of FIG. 1 may be either the monitor imaging device 12 or the triangulation imaging device 13 or may be provided separately.

  The positional relationship among the three-dimensional coordinate acquisition device 1, the rotary table 2, and the laser beam irradiation device 4 is shown in FIG. The laser beam irradiation device 4 is installed so as to irradiate the laser beam toward the rotation center of the turntable 2, and is arranged so as to have a specific angle with the three-dimensional coordinate acquisition device 1 with the rotation center as an axis. This angle can be theoretically set from 0 degrees to 90 degrees, but is preferably set to about 30 degrees to 60 degrees. In the following description, 45 degrees is taken as an example.

  6 and 7 briefly describe the principle of this embodiment. A measurement object 3a as shown in FIG. 6 having a smooth and simple shape is obtained by rotating the rotary table 2 while irradiating laser light from the laser light irradiation device 4, and using a camera in the three-dimensional coordinate acquisition device 1. When monitored, a laser reflection spot appears on the camera image and does not disappear throughout the entire circumference. On the other hand, a part of the measurement object 3b shown in FIG. 7 that is partially uneven and has a complicated shape is an angle region (rotation table) where the laser reflection spot disappears in the monitor image of the camera in the three-dimensional coordinate acquisition apparatus 1. The input data for control is θa to θb). When the laser reflection spot disappears in this way, it is determined that the shape unevenness is severe. Therefore, it is necessary to always perform measurement in the vicinity of angle data θA to θB obtained by adding 45 degrees to θa to θb as input data for rotating table control.

  This will be described in detail with reference to FIG. The cross-sectional shape of the measurement object in FIG. 8 has a dent. If there is no dent, usually a sufficient circumference shape can be obtained by measurement from six directions. However, because of the dent, the shape of the portion indicated by the bold curve cannot be measured well. In the configuration as shown in FIG. 1, the laser reflected spot disappears in the monitor image of the camera in the three-dimensional coordinate acquisition apparatus 1 between θ1 and θ3 in the input data for rotation table control. Therefore, it is necessary to perform additional measurement from 45 degrees + θ1 to 45 degrees + θ3 with the input data for rotating table control. Here, additional measurement is performed at 45 degrees + θ2 which is an intermediate value from 45 degrees + θ1 to 45 degrees + θ3. For example, three additional measurements of 45 degrees + θ1 and 45 degrees + θ2 and 45 degrees + θ3 are performed. Needless to say, it may be within the range of 45 degrees + θ1 to 45 degrees + θ3.

  Next, the measurement procedure of the embodiment of the present invention will be described.

  FIG. 9 shows one measurement procedure, and FIG. 10 shows another measurement procedure.

  In the example of FIG. 9, the stop position determination process using laser irradiation is performed prior to the measurement of the three-dimensional coordinates of the measurement object 3. In the example of FIG. 10, the stop position determination process using laser irradiation is performed in parallel with the measurement of the three-dimensional coordinates of the measurement object 3.

The process of FIG. 9 is as follows.
[Step S10]: A default stop angle is set.
[Step S11]: The measurement object 3 is irradiated with laser light while rotating the rotary table 2 once to monitor the reflected spot.
[Step S12]: An additional stop angle is set based on the disappearance of the reflection spot or based on the disappearing angle range. Thereafter, in steps S13 to S16, the rotary table 2 is rotationally driven for the default stop angle and the additional stop angle, and three-dimensional coordinate acquisition is performed.
[Step S13]: The rotary table 2 is rotated to the next stop angle position.
[Step S14]: Measurement conditions are set at the stop angle position.
[Step S15]: At the stop angle position, three-dimensional coordinates of a plurality of points on the measurement object are acquired under measurement conditions.
[Step S16]: It is determined whether the processing is completed at all stop angle positions. If not completed, the process returns to step S13 to repeat the process. If completed, the process proceeds to step S17.
[Step S17]: Three-dimensional coordinate data at each stop angle are pasted together to obtain all-round data.

The process of FIG. 10 is as follows.
[Step S20]: A default stop angle is set.
[Step S21]: Measurement conditions are set.
[Step S22]: The first three-dimensional coordinates are measured at the initial stop angle position.
[Step S23]: The rotary table 2 is rotationally driven with the next stop angle as a target value.
[Step S24]: In parallel with the rotational drive in Step 2, the measurement object 3 is irradiated with laser light to monitor the reflected spot.
[Step S25]: It is determined whether or not the reflection spot has disappeared. If it is determined that it has disappeared, the process proceeds to step S26, and if not, the process proceeds to step S27.
[Step S26]: An angle position obtained by adding a predetermined angle to the angle when the reflection spot disappears is added as an additional stop angle.
[Step S27]: Stop at the target stop angle.
[Step S28]: Three-dimensional coordinates of a plurality of points on the measurement object are acquired at the stop angle position.
[Step S29]: It is determined whether or not the measurement is completed at all stop angles. If not completed, the process returns to step S23 to repeat the process. If completed, the process proceeds to step S30.
[Step S30]: Three-dimensional coordinate data at each stop angle are pasted together to obtain all-round data.

  This is the end of the description of this embodiment. The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention. For example, as shown in FIG. 11, two laser light irradiation devices 4 a and 4 b may be arranged so as to sandwich the three-dimensional coordinate acquisition device 1. In this case, two laser reflection spots usually appear in the camera image, but the two laser beams are directed toward the center of the rotating table, and the center of the rotating table is always placed so that the measurement object is covered. The laser reflection spot in the left half of the camera image can be distinguished from the laser light from the left, and the right half from the laser light from the right. Further, the determination may be made by changing the wavelengths of the two laser beams.

  In the above-described embodiment, only one laser beam is used in the vertical direction. However, a plurality of laser beams may be irradiated in the vertical direction. For this purpose, a plurality of laser beam irradiation devices may be provided. , The beam of one laser beam irradiation device may be branched. Further, the same effect can be realized even when laser light is vibrated at high speed and the reflected light is irradiated in a linear shape.

  Further, the laser beam may be blinked to facilitate the recognition of the reflected spot. In this case, for example, the reflected spot may be recognized by differentiating the image.

  In the above example, the rotary table is used. However, a fixed table may be used instead of the rotary table, and one or more three-dimensional coordinate acquisition devices may be moved. In this case, the laser beam irradiation device is moved in the same manner.

  A light source other than laser light may be used.

It is a figure which shows the structure of the Example of this invention as a whole. It is a figure explaining the positional relationship of the three-dimensional coordinate acquisition apparatus of the above-mentioned Example, and a laser beam irradiation apparatus. It is a figure explaining the structural example of the three-dimensional coordinate acquisition apparatus of the said Example. It is a figure explaining the three-dimensional coordinate acquisition apparatus of FIG. It is a figure explaining the three-dimensional coordinate acquisition apparatus of FIG. It is a figure explaining operation | movement of the said Example. It is a figure explaining operation | movement of the said Example. It is a figure explaining operation | movement of the said Example. It is a flowchart explaining one of the measurement procedures of the above-mentioned Example. It is a flowchart explaining the other measurement procedure of the above-mentioned Example. It is a figure explaining the modification of the above-mentioned Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 3D coordinate acquisition apparatus 2 Rotation table 2 Rotation table 3 Measuring object 4 Laser beam irradiation apparatus 5 Laser beam 11 Projection apparatus 12 Imaging device for monitor 13 Imaging device for triangulation 14 Half mirror 100 Control apparatus 101 3D coordinate acquisition part 102 three-dimensional sitting image composition unit 103 reflection spot discrimination unit 104 default stop angle storage unit 104 additional stop angle determination unit 105 default stop angle storage unit 106 rotation drive control unit 107 irradiation drive control unit 108 reflection spot light receiving element

Claims (7)

A three-dimensional shape measuring apparatus for measuring a three-dimensional shape of a measurement object installed in a measurement space,
Holding means for holding the measurement object so that the relative position with respect to the holding means main body does not change during measurement;
Three-dimensional coordinate acquisition means for acquiring three-dimensional coordinates of a plurality of points on the measurement object by an image input element;
A light beam irradiation means for irradiating the measurement object with a light beam;
A plurality of measurement control means for changing the relative position between the holding means and the three-dimensional coordinate acquisition means and performing measurement by the three-dimensional coordinate acquisition means for each of the relative positions;
A relative position control means for controlling the magnitude of a change in the relative position between the holding means and the three-dimensional coordinate acquisition means according to the state of reflected light that has been irradiated from the light beam irradiating means on the measurement object;
A three-dimensional shape measuring apparatus comprising:   The three-dimensional shape measuring apparatus according to claim 1, wherein the holding unit is a rotary stage, the plurality of measurement control units include a rotation control unit of the rotary stage, and the relative position control unit is a rotation stage of the rotary stage. A three-dimensional shape measuring apparatus including a rotation angle control means.   3. The three-dimensional shape measuring apparatus according to claim 1, wherein the image input element is a camera and the light beam irradiation means is a laser beam irradiation apparatus.   4. The three-dimensional shape measuring apparatus according to claim 1, 2, or 3, wherein the light irradiation device is provided on both sides of the three-dimensional coordinate acquisition means.   5. The three-dimensional shape measuring apparatus according to claim 1, wherein the light beam irradiation device is driven to blink.   The three-dimensional shape measuring apparatus according to any one of claims 1 to 5, wherein the light beam irradiation device is a moving plane when changing a relative position between the holding unit and the three-dimensional coordinate obtaining unit. A three-dimensional shape measuring apparatus for forming a plurality of irradiation spots on the measurement object at intervals in a perpendicular direction. A three-dimensional shape measurement method for measuring a three-dimensional shape of a measurement object installed in a measurement space,
Holding the measurement object on the holding means so that the relative position with respect to the holding means does not change during measurement;
Measuring a three-dimensional shape of the measurement object for each of the relative positions by changing a relative position between the holding unit and the three-dimensional coordinate acquisition unit by a three-dimensional coordinate acquisition unit;
Irradiating the measurement object with a light beam from a different direction from the three-dimensional coordinate acquisition means;
Controlling the magnitude of the change in relative position between the holding means and the three-dimensional coordinate acquisition means according to the state of the reflected light that the light emitted from the light irradiation means hits the measurement object;
A three-dimensional shape measuring method characterized by comprising: