JP5786999B2 - Three-dimensional shape measuring device, calibration method for three-dimensional shape measuring device - Google Patents

Description

  The present invention relates to a calibration technique for a three-dimensional shape measuring apparatus.

The slit light emitted in a fan shape from the slit light source is irradiated onto the measurement object, and the bright line (light cutting line) of the slit light reflected on the surface of the measurement object is imaged with the camera, and the three-dimensional of the measurement object In a three-dimensional shape measuring apparatus using a light cutting method for measuring a shape, calibration (calibration) is required for associating a position of a measurement object in a camera image with a position in a real space. In the calibration of a conventional three-dimensional shape measuring apparatus using the light cutting method, there are many cases where camera distortion correction and height correction are calibrated separately, and it takes a long time to calibrate.

In order to solve this problem, a calibration method and apparatus have been proposed that can simultaneously perform camera distortion correction and height correction to reduce the time required for calibration (see, for example, Patent Document 1). ). In the calibration method and apparatus disclosed in Patent Document 1, a stair-like block is arranged for each column and a calibration operation is performed using a calibration block in which every other stair-like block is arranged one step lower than the previous row. It is.

JP 2007-33039 A

However, since the calibration method and apparatus disclosed in Patent Document 1 use calibration blocks having regularly arranged staircase shapes, feature points in the bright lines of slit light irradiated on the calibration blocks There is a problem that the accuracy of the calculation is limited to the resolution of the camera. Further, since the calibration block has a regular shape periodically, it is difficult to specify the block position by imaging reflected light from the surface of each block. Therefore, in this calibration method and apparatus, it is necessary to accurately arrange the calibration blocks on the stage so as not to be displaced, and there is a problem in terms of usability because the calibration work is heavy.

Therefore, the present invention has been made in view of the above problems, and can perform calibration of a three-dimensional shape measuring apparatus that measures a three-dimensional shape by a light cutting method without depending on the camera resolution. An object of the present invention is to provide an easy-to-use three-dimensional shape measuring apparatus for calibration work.

In order to solve the above problems, the present invention provides means [1]-[3] below.
[1] In a three-dimensional shape measuring apparatus that performs three-dimensional shape measurement by irradiating slit light from an irradiating means, and imaging a light cutting line generated on the irradiated surface by an imaging means
It has a plurality of plane parts with different height dimensions from the bottom part to be placed, and each of these plane parts has a straight outline that is non-parallel to the light cutting line generated by the irradiation of the slit light. , A calibration block in which a pattern having a different reflectance is formed with the outline as a boundary,
Storage means for storing reference data of a height dimension from the bottom of the calibration block to each of the planar portions and position coordinates of the pattern;
Mounting means for mounting the calibration block;
A moving means for moving any one of the combination of the irradiation means and the imaging means and the placement means;
Detection means for detecting a feature point from the imaged light section line and obtaining a feature point coordinate in the captured image;
Generating means for calculating coordinates related to the pattern from the feature point coordinates, and generating calibration data based on the calculated coordinates and the reference data;
Control means for calibrating the irradiation means and the imaging means in a three-dimensional direction using the generated calibration data;
A three-dimensional shape measuring apparatus comprising:
[2] The calibration block is:
A plurality of geometric patterns each having a linear outline that is non-parallel to the light cutting line generated by the irradiation of the slit light is two-dimensionally arranged on each of the plurality of plane portions, and the plurality of geometric shapes The three-dimensional shape measuring apparatus according to the above [1], wherein a pattern having different reflectivity is formed inside and outside the target pattern.
[3] A plurality of geometric patterns of the calibration block are formed so that a unique pattern or an adjacent geometric pattern is not the same for each column substantially parallel to the scanning direction of the light cutting line. The three-dimensional shape measuring apparatus according to [2] above, wherein

According to the present invention, the calibration of the three-dimensional shape measuring apparatus that measures the three-dimensional shape by the light cutting method can be performed with high accuracy without depending on the camera resolution of the imaging unit and the moving resolution of the mounting unit. it can. Further, according to the present invention, it is possible to perform a calibration operation with a light work load without requiring strict accuracy in the arrangement of the calibration blocks.

It is a perspective view of a 3D shape measuring device and a block for calibration which showed typically signs that a 3D shape measuring device which is an embodiment of the present invention is calibrating. It is a schematic functional block diagram of a three-dimensional shape measuring apparatus. It is a perspective view of the block for calibration. It is an example of the pattern patterned by each step upper plane of the block for calibration. It is the flowchart which showed the procedure of the operation | movement which a three-dimensional shape measuring device produces | generates the data for calibration using the block for calibration. It is the figure which represented typically a mode that the pattern formed in the upper surface passed a bright line when the calibration block was conveyed. It is another example of the pattern patterned on each upper stage plane of the block for calibration. It is another example of the pattern patterned by each upper stage plane of the block for calibration.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a three-dimensional shape measuring apparatus and a calibration block schematically showing how the three-dimensional shape measuring apparatus according to the embodiment of the present invention performs calibration. The three-dimensional shape measuring apparatus in the figure is an apparatus that measures the external shape of a measurement target object by a light cutting method, and includes a slit light source unit 10, an imaging unit 20, and a mounting table 30. On the mounting table 30, a calibration block 40 for calibrating the slit light source unit 10 and the imaging unit 20 of the three-dimensional shape measuring apparatus is mounted.

FIG. 2 shows a schematic functional block diagram of the three-dimensional shape measuring apparatus. In addition, the same code | symbol is attached | subjected about the structure same as the structure shown in FIG. In FIG. 2, the three-dimensional shape measuring apparatus includes a slit light source unit 10, an imaging unit 20, a mounting table 30, a control unit 50, a storage unit 60,
A feature point detection unit 70, a calibration data generation unit 80, and a mounting table drive unit 90 are provided.

In order to collect three-dimensional calibration data, the control unit 50 gives an instruction to start or stop the operation to the slit light source unit 10, the imaging unit 20, and the mounting table driving unit 90, or is supplied from the outside. The correction data is stored in the storage unit 60. Further, after collecting the calibration data, the control unit 50 calibrates the slit light source unit 10 and the imaging unit 20.

The slit light source unit 10 is a light source that emits coherent light as slit light SL that spreads in a fan shape through the slit. Laser light is preferably used as the coherent light. The slit light source unit 10 is installed with a predetermined angle at which the central optical axis of the slit light SL is not parallel to the vertical axis.

The mounting table 30 on which the calibration block 40 is mounted is moved in the direction of arrow A in FIG. 1 by driving the mounting table driving unit 90, whereby the calibration block 40 is conveyed in the direction of arrow A. When the slit light SL emitted from the slit light source unit 10 is irradiated on the stepped plane provided on the upper surface side of the calibration block 40 being conveyed, reflected light RL from the irradiated portion is generated.

The imaging unit 20 is positioned at a position where the optical axis of the optical system is inclined at a predetermined angle that is not parallel to the central optical axis of the slit light SL, specifically at a position where the reflected light RL is incident on the optical system and can be imaged. Installed. At this time, the reflection part of the calibration block 40 is visualized as a bright line LL which is a light cutting line. The imaging unit 20 captures the bright line LL and supplies the captured image data to the feature point detection unit 70.

The feature point detection unit 70 receives captured image data, detects a feature point that is a luminance change point on the captured bright line LL, and obtains feature point coordinates in the captured image. Then, the feature point detection unit 70
Stores the feature point information in which the feature point coordinates are associated with the predetermined attribute data of the calibration block 40 corresponding to the feature point in the storage unit 60. This feature point information will be described in detail in the operation description section described later.

The calibration data generation unit 80 reads the feature point information stored in the storage unit 60 and the correction data when correction data is stored, and is perpendicular to the horizontal mounting surface of the mounting table 30. Direction and horizontal (three-dimensional) calibration data are generated and stored in the storage unit 60.

FIG. 3 is a perspective view of the calibration block 40. As shown in the figure, the calibration block 40 is a solid formed integrally with four steps. Note that the number of steps is not necessarily four, but may be a plurality of steps. The block may be hollow or concave. The calibration block 40 has a bottom 4
5 is mounted in accordance with the mounting surface of the mounting table 30, and the bottom 45 has a surface or at least four support portions in order to ensure the stability of the installation. A stepped flat surface 41-44 that is substantially parallel to the mounting contact surface of the bottom 45 and has different vertical dimensions is provided on the step-shaped portion opposite to the bottom 45.

Since the calibration block 40 is irradiated with coherent light such as laser light, the temperature of the irradiated portion tends to increase. Therefore, the calibration block 40 is preferably made of a material having a small coefficient of thermal expansion. For example, carbon black is preferably used as the material. Carbon black is also excellent in that the mass is not large. In addition to carbon black, glass or stainless steel can be used.

A predetermined pattern P is formed (patterned) on each of the upper planes 41 to 44 of the calibration block 40. In FIG. 4, the example of the pattern patterned by each step-up plane 41-44 is shown. In the figure, the pattern P1 is a pattern AP,
It consists of a pattern RP in which a plurality of geometric squares are two-dimensionally arranged. In the figure, for the sake of convenience, a black pattern RP is shown as having a colored pattern RP, but these pattern colors are not limited to the colors represented in the figure. What is important here is that the pattern AP and the pattern RP are patterned so as to have different reflectances. In the present embodiment, it is assumed that the pattern RP is patterned so that the reflectance is higher than that of the pattern AP. In the pattern RP, squares that are 4 × 18 geometric patterns are aligned such that the sides of the squares are not parallel to the direction of the arrow A.

As a patterning method for the pattern P1, it is preferable to use a fine patterning technique such as a thin film deposition method, an etching method, or a photoresist method.

The calibration block 40 is measured for its external dimensions and various coordinate positions of the pattern P1 by a measuring device other than the three-dimensional shape measuring device according to the present embodiment, and these measured values are stored in the storage unit 60 as reference data. Stored in advance. For example, for each geometric pattern of the pattern RP, the reference data includes the reference vertex coordinate value of the geometric pattern and the height dimension from the bottom 45 to the stepped plane on which the geometric pattern is patterned. Is associated with the identification number.

Next, an operation in which the three-dimensional shape measuring apparatus generates calibration data using the calibration block 40 will be described with reference to the flowchart of FIG. After placing the calibration block 4 on the mounting table 30 so that the conveying direction is the direction of the arrow A shown in FIG. 3, when an instruction to start the operation is given to the control unit 50, FIG. The process of the flowchart shown is started.

First, the control unit 50 instructs the slit light source unit 10 to start irradiation, and the slit light source unit 10 that has received this instruction starts irradiation of the slit light SL (S501). Next, the control unit 50 instructs the imaging unit 20 to start imaging, and the imaging unit 20 that has received this instruction starts imaging (S502).
. Next, the control unit 50 instructs the mounting table driving unit 90 to start driving, and the mounting table driving unit 90 that has received this instruction starts to move the mounting table 30 (S503).

When imaging the bright line LL, the imaging unit 20 supplies the captured image data to the feature point detection unit 70 (S504). When the feature point detection unit 70 detects a feature point from the bright line LL of the captured image data, the feature point detection unit 70 obtains the feature point coordinate in the captured image, and the feature point coordinate and the calibration block 40 corresponding to the feature point. Feature point information associated with attribute data is stored in the storage unit 6
It is stored in 0 (S505 YES → S506).

Here, the operation of feature point detection and feature point information storage by the feature point detection unit 70 will be specifically described. In FIG. 6, when the calibration block 40 is conveyed in the direction of the arrow A, the pattern P1 (in the figure, the portion of the pattern AP and the pattern RP is enlarged) passes through the bright line LL. The figure which represented a mode to do typically is shown. In the figure, in order to make the drawing easy to understand, the pattern P1 is fixed and the bright line LL is changed from the bright line LL1 to the bright line L.
The relative positional relationship when moved like L6 is shown.

In the figure, the imaging unit 20 sequentially captures the bright lines LL1, LL2, LL3... LL6. The interval between the bright lines can be adjusted according to the imaging time interval of the imaging unit 20 and the moving speed of the mounting table 30. In the present embodiment, it is assumed that the imaging time intervals of the imaging unit 20 are equal, the mounting table 30 moves at a constant speed, and therefore the intervals between the bright lines are the same distance.

In the figure, when the imaging unit 20 images the bright line LL1, the feature point detection unit 70 displays the bright line LL.
The location where the luminance changes on 1 is detected as feature points C1 and C2. That is, feature points C1, C
2 corresponds to the reflectance changing point on the pattern P1 where the bright line LL1 is reflected. When the feature point detection unit 70 detects the feature points C1 and C2, the feature point detection unit 70 obtains feature point coordinates corresponding to the feature points C1 and C2 in the captured image. Then, the feature point information in which the feature point coordinates are associated with the attribute data of the calibration block 40 corresponding to the feature points C1 and C2 is stored in the storage unit 60.

The attribute data is the height dimension from the bottom 45 of the calibration block 40 to the stepped plane on which the geometric pattern corresponding to the target feature point is patterned, and the identification number of the geometric pattern. . For example, the geometric pattern of the pattern RP corresponding to the feature points C1 and C2 in FIG. 6 is the geometric pattern in the pattern P1 patterned on the stepped plane 43 in FIG. In the case of the 95th geometric pattern counted from the first geometric pattern, the attribute data is the height dimension from the bottom 45 to the stepped plane 43 and the identification number “95”. In this case, the feature point detection unit 70 reads the reference data from the storage unit 60, and the bright line LL has four lines from the first line of the pattern RP of the upper plane 44 of the calibration block 40 to the pattern RP of the upper plane 41. The attribute data can be obtained by counting the number of geometric patterns while scanning up to the eye (last line).

Returning to the description of FIG. 6, the feature points C <b> 3 to C <b> 8 shown in FIG. 6 are detected in the same manner as the detection of the feature points C <b> 1 and C <b> 2 and the storage of the feature point information in the storage unit 60. The feature point information is stored in the storage unit 60.

Returning to the description of FIG. 5, after the feature point detection unit 70 stores the feature point information in the storage unit 60 in the process of step S506, or when no feature point is detected in the process of step S505 (NO in step S505), control is performed. The unit 50 includes 4 blocks of the calibration block 40.
Steps S504 to S506 are repeatedly executed until the four patterns P1 patterned on the two upper planes 41 to 44 are scanned by the bright lines LL (S507).
NO → S504).

When the scanning of the four patterns P1 is completed (YES in S507), the calibration data generation unit 8
0 reads the feature point information stored in the storage unit 60 and the correction data, if correction data is stored, generates calibration data, stores it in the storage unit 60, and ends the processing. (S508).

Here, the calibration data generation processing by the calibration data generation unit 80 will be specifically described with reference to FIG. It is assumed that the feature point information related to the feature points C1 to C8 detected by scanning the bright lines LL1 to LL6 is stored in the storage unit 60. The calibration data generation unit 80 reads out the feature point information from the storage unit 60, and first calculates the vertex coordinates of the vertex T1 of the pattern RP from the feature point coordinates corresponding to the feature points C1-C4. Then, the vertex coordinates of the vertex T4 of the pattern RP are calculated from the feature point coordinates corresponding to the feature points C5-C8. Furthermore, feature point C
The vertex coordinates of the vertices T2 and T3 of the pattern RP are calculated from the feature point coordinates corresponding to 1-C8.

By making the geometric pattern a geometrically simple shape (in this embodiment, a square) and having a contour that is not parallel to the bright line LL, each geometric shape of the pattern RP is as described above. The vertex coordinates of the pattern vertices can be easily obtained. Moreover, since the vertex is calculated from the geometric arrangement of the detected feature points, the vertex coordinates can be obtained with high accuracy without depending on the resolution of the imaging unit 20, the imaging time interval, and the moving resolution of the mounting table 30. Can be sought.

The calibration data generation unit 80 generates calibration data by associating each vertex coordinate of the vertices T1 to T4, the height dimension of the geometric pattern, and the reference vertex coordinate corresponding to the identification number, and a storage unit 60. Note that the calibration data generation unit 80 also stores the correction data in the storage unit 60.
In the case of reading out from, the calibration data generation unit 80 uses the correction data and the vertex T1-
Calibration data is generated by correcting each vertex coordinate of T4 or the height dimension of the geometric pattern.

The above description is based on the vertex T1- for one geometric pattern of the patterns RP.
This is an example of calculating T4. Such calculation is applied to all other geometric patterns of pattern RP,
Alternatively, it is performed according to a predetermined rule such as every other column or every other row.

After the calibration data is generated, the control unit 50 uses the calibration data stored in the storage unit 60 in the vertical and horizontal directions of the optical systems of the slit light source unit 10 and the imaging unit 20 by a known method. Perform calibration.

According to the embodiment of the present invention, the three-dimensional calibration of the three-dimensional shape measuring apparatus by the light cutting method is performed with high accuracy without depending on the camera resolution, the imaging time interval, and the moving resolution of the mounting table 30. Can do.

In the present embodiment, the example in which the pattern P1 shown in FIG. 4 is used as the pattern P that is patterned on the upper flat surfaces 41-44 of the calibration block 40 has been described.
Next, an example using the pattern shown in FIG. 7 will be described as a modification of the present embodiment. In the figure, the geometric pattern included in the pattern P2 is formed to be a unique pattern in units of columns (a set of four geometric patterns).

Since the geometric pattern is formed so as to have a unique pattern in units of columns, the position of the geometric pattern can be specified more easily, so that the calibration block 40 can be arbitrarily set on the mounting table 30. Even when placed at the position, calibration data can be easily generated, and the workability and usability of calibration are improved.

It is also preferable to use the pattern shown in FIG. In the figure, the pattern P3 is
A line pattern parallel to the bright line LL is formed. Since the combination of the number of line patterns and the arrangement position differs at regular intervals (three rows in the example in the figure), the uniqueness of the pattern in the geometric pattern unit for three rows is ensured. In this way, the geometric pattern can be obtained from the feature point coordinates of the detected feature points by changing the shape and size of the geometric pattern or the shading (reflectance) according to the columns and forming a so-called modulated pattern. This makes it easy to specify the position, and the same effect as in the above modification can be obtained.

As described above, an accurate position can be obtained regardless of the position of the imaging unit 20 by making the pattern P into a pattern having an outline that can be robustly obtained from the affine mapping or the lens distortion of the imaging unit 20. Can do. Specifically, for example, when the geometric pattern is a circle, the outline may appear as an ellipse or the center point may be shifted depending on the position of the imaging unit 20.

The embodiment of the present invention has been described in detail above. Note that the technical idea of the present invention can also be applied to a three-dimensional shape measuring apparatus that generates and uses a plurality of bright lines, which are light cutting lines, or irradiates spot light instead of slit light. Furthermore, the technical idea of the present invention can be applied to the stereo method, not the light cutting method.

In the present embodiment, the example in which the calibration block 40 placed on the mounting table 30 is conveyed has been described. However, the mounting table may be fixed and the imaging unit and the light source may be moved.

Further, the calibration block is not limited to one having a staircase shape portion. That is, since the calibration block only needs to have a three-dimensional shape including a plane, it can also have a triangular pyramid shape, a triangular prism shape, or the like.

Furthermore, the specific configuration is not limited to this embodiment, and includes a design and the like within a range not departing from the gist of the present invention.

10 slit light source, 20 imaging unit, 30 mounting table, 40 calibration block, 50 control unit, 60 storage unit, 70 feature point detection unit, 80 calibration data generation unit,
90 Mounting table driving unit, SL slit light, RL reflected light, LL emission line.

Claims (4)

A three-dimensional shape measuring apparatus that irradiates an irradiation surface with a bright line of light from an irradiation unit, images the bright line of light with an imaging unit, and performs three-dimensional shape measurement,
A calibration block having a flat portion having a different height from the bottom, having a contour, and having a pattern having a different reflectance of the light on the contour with the contour as a boundary;
Storage means for storing reference data of the height from the bottom of the calibration block to the flat surface and the position coordinates of the pattern;
A mounting means for mounting the calibration block;
A moving means for moving any one of the combination of the irradiation means and the imaging means and the placement means;
A feature point is detected based on the bright line of the light emitted from the irradiating unit to the calibration block, which is imaged by the imaging unit, and a feature point coordinate in the image captured based on the feature point is calculated. Detecting means for
Generating means for generating calibration data based on the coordinates related to the pattern calculated from the feature point coordinates and the reference data;
Control means for calibrating the irradiation means and the imaging means in a three-dimensional direction using the generated calibration data;
A three-dimensional shape measuring apparatus comprising: The three-dimensional shape measuring apparatus according to claim 1,
The pattern is a geometric pattern;
A three-dimensional shape measuring apparatus characterized by that. A three-dimensional shape measuring device,
A calibration block having flat portions having different heights with respect to the bottom portion placed on the placing means, having a contour, and having different patterns of light reflectivity on the flat portion with the contour as a boundary Irradiating means for irradiating the emission line of light to
Imaging means for imaging the bright line of the light irradiated to the calibration block;
Detecting means for detecting a feature point from the bright line of the light imaged by the imaging means, and calculating a feature point coordinate in an image captured based on the feature point;
The calibration is generated based on the coordinates related to the pattern calculated from the feature point coordinates, and the reference data of the height of each plane part with respect to the bottom of the calibration block and the position coordinates of the pattern. Using data, control means for performing calibration in the three-dimensional direction of the irradiation means and the imaging means;
A three-dimensional shape measuring apparatus comprising: A calibration method for a three-dimensional shape measuring apparatus,
A calibration block having flat portions having different heights with respect to the bottom portion placed on the placing means, having a contour, and having different patterns of light reflectivity on the flat portion with the contour as a boundary Irradiating the emission line of the light to
Imaging the emission line of the light irradiated on the plane portion;
Detecting feature points from the captured bright line of the light and calculating feature point coordinates in the captured image;
The calibration is generated based on the coordinates related to the pattern calculated from the feature point coordinates, and the reference data of the height of each plane part with respect to the bottom of the calibration block and the position coordinates of the pattern. Using data, performing a three-dimensional calibration of the irradiation means and the imaging means;
A calibration method for a three-dimensional shape measuring apparatus, comprising:

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