JP4378128B2 - 3D shape measurement method - Google Patents

Description

  The present invention relates to a three-dimensional shape measuring method for optically measuring the outer shape of an object to be measured in three dimensions.

Conventionally, using stripes as typified by moire topography, projecting a striped pattern onto the object to be measured, superimposing the stripe pattern deformed according to the shape of the object to be measured, and the reference stripe pattern, and the difference frequency As a method of measuring the three-dimensional shape of the object to be measured by analyzing moire fringes indicating contour lines generated as described above, for example, methods disclosed in Patent Document 1 and Patent Document 2 are known. In such a method, a striped pattern formed on the object to be measured is imaged and analyzed by a CCD camera.
JP-A-53-68267 JP 61-260107 A

  However, in such a conventional method, when the object to be measured is small, sufficient measurement accuracy can be obtained even if the entire object to be measured is imaged and analyzed with a CCD camera. If the whole object to be measured is imaged, sufficient resolution may not be obtained.

  In such a case, image a part of the object to be measured to measure the three-dimensional shape, and then change the location and image another part of the object to be measured to measure the three-dimensional shape. The whole three-dimensional shape is measured by repeating this, but there is a problem that the work of combining the measured values separately measured into the measured values of one reference coordinate system is complicated.

  An object of the present invention is to provide a three-dimensional shape measuring method capable of easily measuring three-dimensionally even a large object to be measured.

In order to achieve this problem, the present invention has taken the following measures in order to solve the problem. That is,
A plurality of markers each having a different three-dimensional shape are attached to the measurement location of the object to be measured, and at the same time , a partial region of the object to be measured including two of the markers is optically three-dimensionally measured together with the marker by the shape measuring means. After obtaining the value, the shape measuring means is moved, and a measured value is obtained by optically measuring three-dimensionally a partial region of another measurement location including one of the two markers and another one of the markers. The three-dimensional shape measuring method is characterized in that, based on the three-dimensional shape of the marker, each measured value is converted into the same coordinate system, and the outer shape of the object to be measured is measured. The marker preferably has an asymmetric three-dimensional shape.

Or, the plurality of markers may be each different heights so.

  As described above, according to the three-dimensional shape measuring method of the present invention, there is an effect that even a large object to be measured can be easily three-dimensionally measured with sufficient accuracy.

The best mode for carrying out the present invention will be described below in detail with reference to the drawings.
As shown in FIG. 1, reference numeral 1 denotes an object to be measured, which has, for example, a large three-dimensional shape such as a car body of a passenger car. A shape measuring device 2 that optically measures the three-dimensional shape of the object to be measured 1 is provided. The shape measuring device 2 includes a CCD camera 4, a fringe projector 6, and a control device 8. The CCD camera 4 and the fringe projector 6 are connected to the control device 8.

  In the shape measuring instrument 2, the fringe projector 6 projects a plurality of gratings on the surface of the device under test 1, and the CCD camera 4 images the lattice deformed according to the external shape of the device under test 1. And based on this deformation | transformation grating | lattice and a reference | standard grating | lattice, the control apparatus 8 measures the three-dimensional shape of the to-be-measured object 1, and obtains the measured value of a three-dimensional shape.

  In the shape measuring instrument 2, if the area S imaged by the CCD camera 4 is wide, the resolution decreases and the measurement accuracy becomes rough. If the area S to be imaged is narrow, sufficient resolution is obtained and the measurement accuracy becomes precise. Therefore, if an attempt is made to obtain the required measurement accuracy, the area of the region S imaged by the CCD camera 4 is limited, and the partial region of the DUT 1 is measured. The shape measuring instrument 2 outputs a measurement value based on a three-dimensional partial coordinate system. The partial coordinate system is a coordinate system that the shape measuring instrument 2 has, and when the shape measuring instrument 2 is moved to measure another location, the partial coordinate systems of those measured values are different. Measurement values cannot be joined together to form one measurement value.

  Therefore, the first marker M1 is pasted when measuring the three-dimensional shape. As shown in FIG. 3A, the first marker M1 is formed in a three-dimensional shape and is attached to the DUT 1. The affixing may be affixed to the DUT 1 with a magnet provided on the first marker M1, or may be affixed with an adhesive or a double-sided adhesive tape.

  The shape of the first marker M1 is formed in a three-dimensional solid shape, and in this embodiment, a rectangular parallelepiped or a part of a cube is cut out obliquely from the upper surface 12 to form two inclined surfaces 14 and 16. ing. The intersection of the upper surface 12 and the two inclined surfaces 14 and 16 is used as a reference point 18, and the upper surface 12 is formed to be a square or a rectangle whose sides are orthogonal.

  Accordingly, the first marker M1 is formed in a three-dimensional solid shape and is formed in an asymmetric shape. That is, the first marker M1 is formed so that the difference in measurement direction can be determined from the shape of the first marker M1 when the first marker M1 is measured by changing the direction with the shape measuring instrument 2. That is, when the shape is a symmetric shape such as a cone, the shape is the same from any direction, and the direction cannot be determined from the shape.

In the present embodiment, a plurality of markers having different shapes are prepared. There is prepared a second marker M2 having a height h2 shown in FIG. 3 (b) in which the height h1 below the inclined surfaces 14, 16 of the first marker M1 shown in FIG. 3 (a) is different. The three-dimensional shapes of the first and second markers M1 and M2 are measured in advance and stored in the control device 8. The difference between the first and second markers M1 and M2 is not limited to this height difference, and the difference in size of the upper surface 12 may be determined .

Next, the measurement process performed by the control device 8 will be described with reference to the flowchart of FIG.
First, prior to the measurement of the three-dimensional shape, the first and second markers M1 and M2 are attached to the measurement location. As shown in FIG. 2, the first and second markers M <b> 1 and M <b> 2 are affixed in the areas of the partial areas S <b> 1, S <b> 2 and S <b> 3 captured by the CCD camera 4. For example, the imaging region by the shape measuring instrument 2 is a rectangle, the first marker M1 is attached to the corner end of the first partial region S1, and the second partial region S2 is attached to the first partial region S1. The first marker M1 is set as a region including the corner end.

  In the second partial region S2, another second marker M2 having a different height is attached to the corner end of the second partial region S2. The third partial region S3 is set as a region including the second marker M2 attached to the second partial region S2 at the corner end. In the present embodiment, the measurement of the first to third partial areas S1 to S3 has been described. However, when measuring more partial areas, similarly, the measurement should be performed so as to include a common marker. That's fine.

  And after sticking the 1st and 2nd marker M1, M2, each 1st-3rd partial area | region S1-S3 of the to-be-measured object 1 is imaged with the shape measuring device 2. FIG. The imaged data is stored in the control device 8. When the first to third partial areas S1 to S3 are imaged by the shape measuring device 2, the measurer moves the image to measure the shape measuring device 2, or the shape measuring device 2 is attached to the tip of the robot arm. The robot may be moved by a robot. The movement does not need to be a parallel movement, and it is not necessary to measure the movement amount.

  In the three-dimensional shape measurement process, first, a measurement value Ps1 (s1xn, s1yn, s1zn) of the first partial region S1 is calculated from the captured data (step 100). The subscript n indicates that there are n measurement points. The same applies to the second and third partial regions S2 and S3.

  Next, the first marker M1 is recognized from the measured value Ps1 (s1xn, s1yn, s1zn) of the first partial region S1 (110). For the recognition of the first marker M1, the three-dimensional shape of the first marker M1 is stored in advance, and the first marker M1 is recognized based on the stored three-dimensional shape.

  Subsequently, the position and orientation of the recognized first marker M1 are calculated (120). The position is a three-dimensional coordinate value (x11, y11, z11) of the reference point 18 of the first marker M1. The posture indicates a three-dimensional direction in the partial coordinate system of the first marker M1, for example, a value (a11, which indicates an angle formed by the orthogonal coordinates in the partial coordinate system and the side and perpendicular of the upper surface 12 of the first marker M1. b11, c11).

  Next, individual recognition of whether the marker is the first marker M1 or the second marker M2 is executed (130). In the present embodiment, individual recognition is determined based on the difference between the heights h1 and h2. In the case of the same shape, it may be individually recognized by characters or barcodes displayed on the upper surface 12. Alternatively, the shape of the upper surface 12 of each first marker M1 may be different, and individual recognition may be performed based on the shape of the upper surface 12.

  With respect to the imaged data for each of the second and third partial areas S2 and S3 stored in the control device 8, the above-described steps 100 to 130 are repeated, and the second and third partial areas S2 and S2 of the DUT 1 are measured. The measured values Ps2 and Ps3 of S3 are calculated (step 100). Next, the first and second markers M1 and M2 are recognized (step 110), and the positions and orientations of the first and second markers M1 and M2 are calculated (step 120). Then, individual recognition of the first and second markers M1 and M2 is executed (step 130).

1st partial area S1 1st marker M1 x11, y11, z11, a11, b11, c11
Second partial region S2 First marker M1 x21, y21, z21, a21, b21, c21
Second partial region S2 Second marker M2 x22, y22, z22, a22, b22, c22
Third partial region S3 Second marker M2 x32, y32, z32, a32, b32, c32
Further, if there is a partial area (step 140), the process is repeatedly executed repeatedly to recognize the marker for each partial area, calculate the position / posture, and individually recognize the marker.

N-th partial region Sn m-th marker Mm xnm, ynm, znm, anm, bnm, cnm
Subsequently, a process of converting the measurement values Ps1 to Psn of the first to nth partial regions S1 to Sn into a common three-dimensional coordinate system is executed (step 200). In the three-dimensional position conversion process, as shown in FIG. 5, first, based on the position / posture of the reference point 18 of the first marker M1, a coordinate conversion coefficient R1 is calculated by the following equation (step 210). Here, [R1] is a matrix.

(X11, y11, z11, a11, b11, c11) = [R1] × (x21, y21, z21, a21, b21, c21)
That is, the position (x11, y11, z11) and posture (a11, b11, c11) of the reference point 18 of the first marker M1 calculated from the measured value Ps1 of the first partial region S1, and the measured values of the second partial region S2. From the position (x21, y21, z21) and posture (a21, b21, c21) of the reference point 18 of the same first marker M1 calculated from Ps2, the partial coordinate system of the measured value Ps2 of the second partial region S2 is A coordinate conversion coefficient R1 for conversion into the partial coordinate system of one partial area S1 is calculated.

  Translation is performed with the reference point 18 of the first marker M1 in the second partial region S2 being superimposed on the reference point 18 of the first marker M1 in the second partial region S2 with respect to the reference point 18 of the first marker M1. The coordinate conversion coefficient R1 is a transformation component that is rotated and overlapped so that the orientation of the first marker M1 in the first partial region S1 and the orientation of the marker in the second partial region S2 are the same. Contains.

Subsequently, the measured value Ps2 of the second partial region S2 is converted into the partial coordinate system of the first partial region S1 using the coordinate conversion coefficient R1 (step 220).
Ps2 ′ = [R1] × Ps2
Next, the second marker M2 in the second partial area S2 is converted into the partial coordinate system of the first partial area S1 (step 230).

(X22 ′, y22 ′, z22 ′, a22 ′, b22 ′, c22 ′) = [R1] × (x22, y22, z22, a22, b22, c22)
That is, in order to convert the measurement value Ps3 of the third partial region S3 into the partial coordinate system of the first partial region S1, first, the position / posture of the second marker M2 of the second partial region S2 is determined by the coordinate conversion coefficient R1. Conversion into the partial coordinate system of the first partial region S1 is performed.

  Subsequently, using the position / posture of the second marker M2 converted into the partial coordinate system of the first partial region S1 and the position / posture of the second marker M2 of the third partial region S3, the third partial region S3 is used. A coordinate conversion coefficient R2 for converting the measured value Ps3 into the partial coordinate system of the first partial region S1 is calculated (step 240). Here, [R2] is a matrix.

(X22 ′, y22 ′, z22 ′, a22 ′, b22 ′, c22 ′) = [R2] × (x32, y32, z32, a32, b32, c32)
Next, the measurement value Ps3 of the third partial region S3 is converted into the partial coordinate system of the first partial region S1 (step 250).

Ps3 ′ = [R2] × Ps3
Further, when there is a measurement value of the partial area (step 260), the same processing as the above-described steps 230 to 250 is executed (step 270), and converted into the partial coordinate system of the first partial area S1, This control process is once terminated. Thereby, each measured value Ps1-Psn is converted into the coordinate system of 1st partial area | region S1, and the whole to-be-measured object 1 can be easily measured with sufficient precision with sufficient resolution.

  The present invention is not limited to such embodiments as described above, and can be implemented in various modes without departing from the gist of the present invention.

It is a schematic block diagram of the shape side fixed device used for implementation of the three-dimensional shape measuring method as one Embodiment of this invention. It is explanatory drawing of the attachment location of the some marker of this embodiment. It is a perspective view of the marker of this embodiment. It is a flowchart of the three-dimensional shape measurement process performed in the control apparatus of this embodiment. It is a flowchart of the three-dimensional position conversion process performed in the control apparatus of this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Object to be measured 2 ... Shape measuring instrument 4 ... CCD camera 6 ... Fringe projector 8 ... Control device 12 ... Upper surface 14, 16 ... Inclined surface 18 ... Reference point M1 ... 1st marker M2 ... 2nd marker S1 ... 1st part Region S2 ... Second partial region S3 ... Third partial region

Claims (3)

A plurality of markers each having a different three-dimensional shape are attached to the measurement location of the object to be measured, and at the same time , a partial region of the object to be measured including two of the markers is optically three-dimensionally measured together with the marker by the shape measuring means. After obtaining the value, the shape measuring means is moved, and a measured value is obtained by optically measuring three-dimensionally a partial region of another measurement location including one of the two markers and another one of the markers. And measuring the outer shape of the object to be measured by converting the measured values into the same coordinate system based on the three-dimensional shape of the marker. The three-dimensional shape measuring method according to claim 1, wherein the marker has an asymmetric three-dimensional shape. The three-dimensional shape measuring method according to claim 1 , wherein the plurality of markers have different heights.

Images