JP2007093412A - Three-dimensional shape measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a three-dimensional shape measuring device capable of determining with high accuracy the three-dimensional shape of a surface to be measured based on the principle of triangulation, even when the shape change of the surface to be measured is large. <P>SOLUTION: This device is equipped with a projection scanning system 2 for scanning by projecting a bright line onto the surface 7 to be measured, first and second imaging systems 3, 4 for imaging the bright line projected onto the surface 7 to be measured and deformed from mutually different directions, and a projection direction detection means 5 for detecting the projection direction of the bright line. Hereby, the device can properly execute in combination with shape analysis, based on the three-dimensional coordinate data by a stereo method acquired by the first three-dimensional coordinate acquisition part 61, and shape analysis, based on three-dimensional coordinate data by an optical cutting method acquired by means of the second three-dimensional coordinate acquisition means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a three-dimensional shape measuring apparatus that obtains a three-dimensional shape of a surface to be measured using the principle of triangulation, and more particularly to a three-dimensional shape measuring device that is suitable for application to a surface to be measured with a large change in shape.

  Conventionally, as a three-dimensional shape measuring apparatus using the principle of triangulation, one using a method called a stereo method in which a surface to be measured is picked up by two imaging systems from different directions and a shape is obtained from parallax information is known. ing. In the stereo method, it is necessary to search for corresponding points to obtain corresponding points between images captured by two imaging systems. If this can be performed with high accuracy, a highly accurate measurement result can be obtained. Japanese Patent Application Laid-Open No. 2004-228561 describes that a point-like or linear measurement pattern is projected on a surface to be measured in order to easily determine a corresponding point between two images.

  Also, there is a method using a light cutting method in which one of two imaging systems in the stereo method is replaced with a projection scanning system of a light spot (dotted measurement pattern) or a bright line (linear measurement pattern). It is known (see Patent Document 2 below). The light cutting method projects and scans a light spot or bright line on the surface to be measured and images it from a direction different from the projection direction, detects the projection direction of the light spot or bright line at the time of imaging, and Although it is necessary to obtain the distance (base line length) between the projection scanning system and the imaging system, the corresponding point search in the general stereo method is not necessary, so that the analysis becomes easy.

Japanese Patent Laid-Open No. 5-26640 Japanese Patent Laid-Open No. 10-122837

  However, in the conventional stereo method and light cutting method, when measuring a surface to be measured having a large shape change, a partial region of the surface to be measured cannot be observed depending on the orientation of the imaging system with respect to the surface to be measured. There is a problem that a highly accurate measurement result cannot be obtained.

  In the case of the stereo method, images taken simultaneously from two different directions are required over the entire area of the surface to be measured. If the orientations of the two imaging systems with respect to the surface to be measured are fixed, a part of the surface to be measured is obtained. An area may be imaged only by one imaging system. Although Patent Document 1 discloses changing the positional relationship between the surface to be measured and the two imaging systems, there is a possibility that a measurement error may occur due to a change in the positional relationship.

  Even in the case of the light cutting method, a region where a light spot or a bright line (part of it) cannot be observed may occur on the surface to be measured. For such a region, three-dimensional data of the surface to be measured is obtained. It becomes difficult. For example, there is a method of complementing the three-dimensional data of the missing area by utilizing the fact that the bright line is a straight line when a part of the bright line is observed, but the accuracy cannot be denied. .

  The present invention has been made in view of such circumstances, and can obtain the three-dimensional shape of the surface to be measured with high accuracy based on the principle of triangulation even when the shape of the surface to be measured is large. An object is to provide a possible three-dimensional shape measuring apparatus.

  In order to solve the above problems, the three-dimensional shape measuring apparatus of the present invention can perform a combination of shape analysis by a stereo method and shape analysis by a light cutting method as appropriate.

That is, the three-dimensional shape measuring apparatus according to the present invention includes a projection scanning system that projects and scans a measurement pattern on a measurement surface;
First and second imaging systems for imaging the measurement pattern projected and scanned on the measurement surface from different directions;
A projection direction detecting means for detecting a projection direction of the measurement pattern;
The coordinates of the measurement pattern on the image captured by the first imaging system and the coordinates of the measurement pattern on the image captured by the second imaging system at the same timing as the first imaging system And a first base line length set between the first and second imaging systems to obtain a three-dimensional coordinate of the surface to be measured at a position where the measurement pattern is projected 3D coordinate acquisition means,
The coordinates of the measurement pattern on the image captured by the first imaging system, the second baseline length set between the first imaging system and the projection scanning system, and the projection direction And / or the coordinates of the measurement pattern on the image captured by the second imaging system, and the third baseline length set between the second imaging system and the projection scanning system, A second three-dimensional coordinate acquisition means for obtaining a three-dimensional coordinate of the measurement surface at a position where the measurement pattern is projected based on the projection direction;
In the process in which the measurement pattern scans the surface to be measured, the three-dimensional shape of the surface to be measured is appropriately combined by combining the three-dimensional coordinate data respectively obtained by the first and second three-dimensional coordinate acquisition means. 3D shape analysis means to be obtained.

  In the three-dimensional shape measurement apparatus of the present invention, the second three-dimensional coordinate acquisition unit is configured such that when only one of the first and second imaging systems can capture the measurement pattern, Based on the coordinates on the image of the measurement pattern imaged by the one imaging system, the baseline length corresponding to the one imaging system among the second and third baseline lengths, and the projection direction, It can be configured to obtain the three-dimensional coordinates of the surface to be measured at the position where the measurement pattern imaged by the one imaging system is projected.

  In addition, the projection scanning system can be configured to project and scan the measurement pattern onto the surface to be measured via the rotating reflection mirror. In this case, the first and second imaging systems are the reflection mirrors. It is preferable that they are arranged symmetrically with respect to the rotation center.

  According to the three-dimensional shape measuring apparatus of the present invention, having the above configuration, shape analysis based on the three-dimensional coordinate data obtained by the first three-dimensional coordinate acquisition means (shape analysis by stereo method), It is possible to implement a suitable combination of shape analysis based on the three-dimensional coordinate data obtained by the second three-dimensional coordinate acquisition means (shape analysis by the light cutting method).

  Thus, for example, when the measurement pattern can be simultaneously imaged by two imaging systems, the shape analysis by the stereo method is performed, and only one of the two imaging systems captures the measurement pattern. If the image can be captured, shape analysis can be performed by a light cutting method.

  Even when the shape change of the surface to be measured is large, each area of the surface to be measured is obtained by imaging the measurement patterns projected and scanned on the surface to be measured by the projection scanning system from different directions by the two imaging systems. In at least one of the imaging systems, the probability that the measurement pattern can be imaged increases. Therefore, according to the three-dimensional shape measuring apparatus of the present invention, the three-dimensional coordinate data of the surface to be measured having a large shape change can be obtained over substantially the entire area without changing the relative position between the surface to be measured and the imaging system. Therefore, the three-dimensional shape can be measured with high accuracy.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing the overall configuration of a three-dimensional shape measuring apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic diagram showing the measurement principle.

  The three-dimensional shape measuring apparatus shown in FIG. 1 measures and analyzes the three-dimensional shape of the surface 7 to be measured using the principle of triangulation. From the apparatus main body 1 supported on a tripod (not shown), a computer, and the like. And an analyzing device 6.

The apparatus body 1 has a projection scanning system 2 that projects and scans a bright line (linear measurement pattern) K (see FIG. 2) on the measurement surface 7 and a bright line K ₀ (projected and deformed on the measurement surface 7). 1 and 2), and a projection direction detecting means 5 for detecting the projection direction of the bright line K.

The projection scanning system 2 includes a light source unit 21 composed of a semiconductor laser device or the like, a projection lens 22, and a scanning mirror 23 composed of a rotatable reflection mirror. The light source unit 21 is configured to output light with high straightness. The projection lens 22 converts the output light from the light source unit 21 into a luminous flux for generating bright lines, and the center of rotation of the scanning mirror 23. is configured to emit toward the (a rotation axis C of the scanning mirror 23 (see FIG. 2), located at the intersection between the optical axis L ₁ of the imaging scanning system 2. hereinafter referred to as "base point P _1") ing. The scanning mirror 23 is supported on the apparatus housing via a rotating device (not shown), and reflects the luminous flux K from the projection lens 22 while being rotated by the rotating device. Scanning is performed within a predetermined angle range.

The first imaging system 3, the projection surface to be measured 7, the scanned bright lines K _0, the projection direction of the bright lines K ₀ is intended for imaging from different directions, as shown in FIG. 1, the imaging lens 31 and an imaging camera 32. The imaging camera 32 includes an imaging surface 33 formed by an imaging surface such as a CCD or a CMOS. The imaging lens 31 projects an image of the bright line K ₀ projected and scanned on the measurement surface 7 on the imaging surface 33. To form an image. The imaging camera 32 converts image information imaged on the imaging surface 33 into an image signal and outputs the image signal to the analysis device 6.

The second image pickup system 4 picks up the bright line K ₀ projected and scanned on the measurement surface 7 from the projection direction of the bright line K ₀ and the direction different from the first image pickup system 3. As shown in FIG. 2, the imaging lens 41 and the imaging camera 42 are provided. The imaging camera 42 includes an imaging surface 43 formed of an imaging surface such as a CCD or CMOS, and the imaging lens 41 projects an image of the bright line K ₀ projected and scanned on the measurement surface 7 on the imaging surface 43. To form an image. Further, the imaging camera 42 converts image information imaged on the imaging surface 43 into an image signal and outputs it to the analysis device 6.

In the present embodiment, the first and second imaging systems 3 and 4 are disposed symmetrically with respect to the base point P ₁ (the rotation center of the scanning mirror 23). That is, in FIG. 1, the center of the entrance pupil of the imaging lens 31 in the first imaging system 3 (hereinafter referred to as “base point P ₂ ”) and the center of the entrance pupil of the imaging lens 41 in the second imaging system 4 (hereinafter referred to as “base point P ₂ ”). The term “base point P ₃ ” is arranged symmetrically with respect to the base point P ₁ . Further, the directions of the optical axes L ₂ and L ₃ of the first and second imaging systems 3 and 4 are arranged so as to be symmetrical with each other. As a result, the measurement error caused by the aberrations of the first and second imaging systems 3 and 4 can be made symmetrical, so that there is an advantage that error correction becomes easy.

In addition, the length between the first and second imaging systems 3 and 4 and between the imaging system 3 and the projection scanning system 2 is calculated in the calculation performed in the shape analysis of the surface 7 to be measured. Baseline lengths are set as important parameters. In the present embodiment, the first base line length d ₁ is set between the base points P ₂ and P ₃ described above, and the second base line length d ₂ is set between the base points P ₁ and P ₂ and the base points P ₁ and P _3. third base-line length d ₃ in between, are set, respectively. Note that due to the symmetry described above, in the present embodiment, d ₂ = d ₃ and d ₁ = d ₂ + d ₃ .

  The projection direction detection means 5 has a rotary encoder or the like, detects the projection direction of the bright line K based on the rotation angle of the scanning mirror 23, and outputs the detection signal to the analysis device 6. Yes.

  On the other hand, the analysis device 6 includes a first three-dimensional coordinate acquisition unit 61, a second three-dimensional coordinate acquisition unit 62, and a three-dimensional unit that are configured by a processing program stored in a memory, a CPU, an arithmetic circuit, and the like. A shape analysis unit 63 is provided.

The first three-dimensional coordinate acquisition unit 61 constitutes a first three-dimensional coordinate acquisition unit, and the coordinates of the bright line K _L (see FIG. 2) on the image captured by the first imaging system 3 , The correspondence with the coordinates of the bright line K _R (see FIG. 2) on the image captured by the second imaging system 4 at the same timing as the first imaging system 3, and the first and second imaging systems 3, On the basis of the first base line length d ₁ set between 4, the three-dimensional coordinates of the surface to be measured 7 at the position where the bright line K ₀ is projected are obtained.

Second three-dimensional coordinate acquisition unit 62, constitutes a second three-dimensional coordinate acquiring means, the coordinates of the bright lines K _L on the captured image by the first imaging system 3, the first imaging Bright lines on the image captured by the second imaging system 4 based on the second baseline length d ₂ set between the system 3 and the projection scanning system 2 and the projection direction of the bright line K ₀ the coordinates of K _R, and the third base-line length d ₃ that is set between the second imaging system 4 and the projection scanning system 2, based on the projection direction of the bright lines K _0, position emission line K ₀ is projected The three-dimensional coordinates of the surface 7 to be measured are determined.

The three-dimensional shape analysis unit 63 constitutes a three-dimensional shape analysis unit, and in the process in which the bright line K ₀ scans the surface to be measured 7, the first and second three-dimensional coordinate acquisition units 61 and 62 respectively. The obtained three-dimensional coordinate data is appropriately combined to obtain the three-dimensional shape of the measured surface 7.

  Next, the operation of the three-dimensional shape measuring apparatus according to this embodiment and the measurement analysis procedure will be described.

  (1) The projection scanning system 2 projects and scans the bright line K with respect to the measurement surface 7 installed substantially in front of the three-dimensional shape measuring apparatus. As shown in FIG. 2, the bright line K is a linear pattern extending in the vertical direction, and the scanning direction is the horizontal direction.

(2) The bright line K ₀ projected on the measurement surface 7 and deformed according to the shape of the measurement surface 7 is generated by the first and second imaging systems 3 and 4 at predetermined timings during the scanning period. Images are taken simultaneously from different directions. Both pieces of captured image information are sequentially sent to the first and second three-dimensional coordinate acquisition units 61 and 62. In the first and second imaging systems 3 and 4, the imaging magnification and the like are adjusted in advance so that the bright line K ₀ is formed across a plurality of pixels on the imaging surfaces 33 and 43. ing.

  (3) The projection direction detection means 5 detects the projection direction of the bright line K in synchronization with the imaging timings of the first and second imaging systems 3 and 4, and the information is sent to the second three-dimensional coordinate acquisition unit 62. Sent.

(4) based on the image information transmitted from the first imaging system 3, the first three-dimensional coordinate acquisition unit 61, each point on the bright line K _L on the captured image by the first imaging system 3 Coordinates (exemplified as (x _i , y _i ) in FIG. 2). In particular this coordinate, as it is necessary to obtain a line width center of the bright lines K _L on the image, but as a specific method of line width center, and the method according to the binarization processing, the intensity distribution follows a Gaussian distribution, a line A method for obtaining a position where the intensity reaches a peak within the width can be used.

(5) based on the image information transmitted from the second imaging system 4, the first three-dimensional coordinate acquisition unit 61, each point on the bright line K _R on the captured image by the second imaging system 4 (In FIG. 2, (x ′ _p , y ′ _q ) as an example) is obtained. The method for specifying the coordinates is the same as described above.

(6) captured in the first three-dimensional coordinate acquiring unit 61 performs corresponding point search which points on the bright line K _L asks whether located anywhere on the bright line K _R, thereby, the first imaging system 3 the coordinates of the bright line K _L on image, the correspondence between the coordinates of the bright line K _R in the first imaging system 3 and at the same time the second on the captured image of the imaging system 4 obtains. As a method for searching for corresponding points, on a line (referred to as an “epipolar line”) obtained by projecting a line of sight on one image onto the other image, a corresponding point is found using a method such as pattern matching. A searching method can be used.

(7) In the first three-dimensional coordinate acquisition unit 61, and the bright lines K _L, the coordinate information of K _R which are associated with each other, based on the above first base length d _1, a position where the bright line K ₀ is projected The three-dimensional coordinates (illustrated as (X, Y, Z) in FIG. 2) of the surface 7 to be measured are obtained using the principle of triangulation. As a method for obtaining the three-dimensional coordinates (hereinafter referred to as “three-dimensional coordinates by the first method”), a general calculation method used in the stereo method can be used.

(8) In the second three-dimensional coordinate acquiring unit 62, based on the image information transmitted from the first imaging system 3, each point on the bright line K _L on the captured image by the first imaging system 3 with determination of the coordinates, on the basis of the image information sent from the second imaging system 4 obtains the coordinates of each point on the bright line K _R on the captured image by the second imaging system 4.

(9) In the second three-dimensional coordinate acquisition unit 62, and the coordinates of the bright lines K _L obtained, and the second baseline length d _2, based on the projection direction of the bright lines K _0, bright lines K ₀ is projected together determine the three-dimensional coordinates of the surface to be measured 7 (hereinafter referred to as "three-dimensional coordinates by the second method") in the position, also the coordinates of the bright line K _R determined, and the third base length d _3, bright line K Based on the projection direction of ₀ , the three-dimensional coordinates of the surface to be measured 7 at the position where the bright line K ₀ is projected (hereinafter referred to as “three-dimensional coordinates by the third method”) are obtained using the principle of triangulation. In addition, as a method for obtaining the three-dimensional coordinates by the second method and the third method, a general calculation method used in the light cutting method can be used.

The procedure of (10) (4) to (9), at each predetermined timing during the scanning period of the emission line K _0, for each image information captured by the first and second imaging systems 3 and 4 Do. Thereby, a total of three sets of three-dimensional coordinates related to the measured surface 7 from the three-dimensional coordinates by the first method to the three-dimensional coordinates by the third method can be obtained over the entire area of the measured surface 7. Become.

(11) In the three-dimensional shape analysis unit 63, three sets of three-dimensional coordinate data related to the measurement surface 7 respectively obtained by the first and second three-dimensional coordinate acquisition units 61 and 62 are appropriately combined to be measured. The three-dimensional shape of the surface 7 is obtained. This combination of data is performed as follows, for example. That is, three-dimensional coordinates of the first approach can be determined only if both the first and second imaging systems 3 and 4 obtained by imaging the emission line K _0. On the other hand, the three-dimensional coordinates according to the second method can be obtained only when only the first imaging system 3 can image the bright line K _0, and the three-dimensional coordinates according to the third method are determined according to the second imaging system 3. only it can be obtained even only if obtained by imaging the emission line K _0. Therefore, basically, the three-dimensional shape of the surface to be measured 7 is obtained based on the three-dimensional coordinates by the first method, and the region of the surface to be measured 7 for which the three-dimensional coordinates by the first method cannot be obtained is the second. 3-dimensional coordinates according to methods (only the first imaging system 3 may obtained by imaging a bright line K _0), or 3-dimensional coordinates according to the third method (only the second imaging system 3 is obtained by imaging the emission line K ₀ 3) is used in a complementary manner.

In the above-described procedure, the second three-dimensional coordinate acquisition unit 62 always obtains both the three-dimensional coordinates by the second method and the three-dimensional coordinates by the third method. When both of the imaging systems 3 and 4 can image the bright line K ₀ , the area of the measured surface 7 onto which the bright line K ₀ is projected is expressed in the three-dimensional coordinates by the second method and the third method. calculation is not performed, only one of the imaging system of the first and second imaging systems 3 and 4 only if obtained by imaging the emission line K _0, of the measurement surface 7 of the bright line K ₀ is projected For the region, the three-dimensional coordinates based on the image information of the image pickup system that can be picked up (if only the first image pickup system 3 can pick up the image, the three-dimensional coordinates by the second method, only the second image pickup system 3 May be obtained, the three-dimensional coordinates by the third method may be obtained.

  In the present embodiment, the two imaging systems of the first and second imaging systems 3 and 4 are provided, but three or more imaging systems may be provided. Furthermore, in this embodiment, one linear measurement pattern (bright line K) is projected onto the surface to be measured 7 and scanned, but a plurality of linear measurement patterns are measured on the surface to be measured. 7 is projected and scanned, a point-like projection pattern is projected and scanned on the surface to be measured 7, and a projection pattern composed of other figures is projected and scanned on the surface to be measured 7. It is also possible to do.

1 is an overall configuration diagram of a three-dimensional shape measuring apparatus according to an embodiment of the present invention. Schematic showing the measurement principle of the three-dimensional shape measuring device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Apparatus main body 2 Projection scanning system 3 1st imaging system 4 2nd imaging system 5 Projection direction detection means 6 Analysis apparatus 7 Surface to be measured 21 Light source part 22 Projection lens 23 Scanning mirror 31, 41 Imaging lens 32, 42 Imaging camera 33, 43 Imaging surface 61 First three-dimensional coordinate acquisition unit 62 Second three-dimensional coordinate acquisition unit 63 Three-dimensional shape analysis unit L _{1 to} L ₃ optical axes P _{1 to} P ₃ base points d ₁ first baseline length d ₂ Second baseline length d ₃ Third baseline length K Bright line K ₀ (Projected and deformed) Bright line K _L (on the image taken by the first imaging system) Bright line K _R (taken by the second imaging system) Bright line (on the measured image)

Claims (4)

A projection scanning system for projecting and scanning a measurement pattern on a measurement surface;
First and second imaging systems for imaging the measurement pattern projected and scanned on the measurement surface from different directions;
A projection direction detecting means for detecting a projection direction of the measurement pattern;
The coordinates of the measurement pattern on the image captured by the first imaging system and the coordinates of the measurement pattern on the image captured by the second imaging system at the same timing as the first imaging system And a first base line length set between the first and second imaging systems to obtain a three-dimensional coordinate of the surface to be measured at a position where the measurement pattern is projected 3D coordinate acquisition means,
The coordinates of the measurement pattern on the image captured by the first imaging system, the second baseline length set between the first imaging system and the projection scanning system, and the projection direction And / or the coordinates of the measurement pattern on the image captured by the second imaging system, and the third baseline length set between the second imaging system and the projection scanning system, A second three-dimensional coordinate acquisition means for obtaining a three-dimensional coordinate of the measurement surface at a position where the measurement pattern is projected based on the projection direction;
In the process in which the measurement pattern scans the surface to be measured, the three-dimensional shape of the surface to be measured is appropriately combined by combining the three-dimensional coordinate data respectively obtained by the first and second three-dimensional coordinate acquisition means. 3D shape analysis means to be obtained;
A three-dimensional shape measuring apparatus comprising:   The second three-dimensional coordinate acquisition unit captures an image with the one imaging system when only one of the first and second imaging systems can capture the measurement pattern. Based on the coordinates of the measured pattern on the image, the baseline length corresponding to the one of the second and third baseline lengths, and the projection direction, the one imaging system A three-dimensional shape measuring apparatus configured to obtain a three-dimensional coordinate of the surface to be measured at a position where the imaged measurement pattern is projected.   3. The three-dimensional shape according to claim 1, wherein the projection scanning system is configured to project and scan the measurement pattern onto the surface to be measured via a rotating reflecting mirror. measuring device. The three-dimensional shape measuring apparatus according to claim 3, wherein the first and second imaging systems are arranged symmetrically with respect to the rotation center of the reflection mirror.

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