JP5163163B2 - Three-dimensional shape measuring apparatus and three-dimensional shape measuring method - Google Patents

Description

  The present invention relates to a three-dimensional shape measuring apparatus and a three-dimensional shape measuring method for measuring a three-dimensional shape of a test object based on an output of an imaging means.

2. Description of the Related Art Conventionally, a measuring apparatus that projects a pattern light having a predetermined pattern and measures a three-dimensional shape is known (see, for example, Patent Document 1). In such an apparatus, the three-dimensional shape of the test object is measured based on the deformation state of the pattern light corresponding to the shape of the portion of the test object that projects the pattern light.
Sho 63-279110

  However, in the above-described apparatus, if there is a texture due to unevenness on the surface of the object to be examined, detection of the pattern light deformation becomes unstable. In such a case, there is a problem that erroneous detection or detection error occurs and it is not suitable for precise measurement.

  An object of the three-dimensional shape measuring apparatus and the three-dimensional shape measuring method of the present invention is to suppress the influence due to the texture of the surface of the object to be measured and perform highly accurate measurement.

The three-dimensional shape measuring apparatus of the present invention includes a light projecting unit that projects pattern light having a predetermined slit shape from a first direction onto a test object, and a two-dimensional photoelectric conversion element. Changing the relative position between the imaging means for imaging the image of the pattern light reflected from the object by the two-dimensional photoelectric conversion element from a direction different from the first direction, and the light projecting means and the test object; A changing means for scanning pattern light by the light projecting means on the test object, an estimation means for estimating texture due to irregularities on the surface of the test object, and an image generated by the imaging means and correcting means for correcting, based on the texture estimated by means, on the basis of the corrected image corrected by said correction means, wherein comprising calculating means for calculating the three-dimensional shape of the test object, wherein the object to be detected on the so Based on the combined composite image along said image at a plurality of different positions in the scanning direction, the estimating means you estimate texture due to unevenness of the surface of the test object.

Also, the image generated by the imaging means further includes an extraction means for extracting an image of the pattern light having a slit shape, the scanning image of the pattern light in a plurality of different positions extracted by the extraction means Based on the synthesized image synthesized along the direction, the estimating means may estimate the texture due to the unevenness of the surface of the object to be examined.
In addition, the imaging unit generates an image by imaging the surface of the object to be inspected by light different from the light projecting unit, and uses the image by the different light to generate the image by the pattern light of the light projecting unit. The estimation means may estimate the texture resulting from the irregularities on the surface of the specimen.
Further, the synthesized image is an image synthesized so that the images at the plurality of different positions are aligned in the longitudinal direction of the slit shape while being shifted in the scanning direction by a predetermined feed amount by the changing means. Also good.
Further, the texture may be a non-uniform luminance component in an image generated by the imaging unit due to unevenness on the surface of the object to be examined.

  It is also effective as a specific aspect of the present invention to express the configuration related to the above invention by converting it into a three-dimensional shape measuring method for measuring the three-dimensional shape of the object to be examined based on the output of the imaging means.

  According to the three-dimensional shape measuring apparatus and the three-dimensional shape measuring method of the present invention, it is possible to suppress the influence of the surface texture of the object to be inspected and perform highly accurate measurement.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration of a three-dimensional shape measuring apparatus 1 according to the present embodiment. As shown in FIG. 1, the three-dimensional shape measuring apparatus 1 includes a light projecting unit 2, a test object holder 3, a test object holder driving stage 4, and an imaging unit 5, and a control unit 6 that controls each unit. Is provided.

  The light projecting unit 2 includes a laser emitting unit 7 that emits a light beam, and a cylindrical lens 8 that shapes the light beam emitted from the laser emitting unit 7 into a slit shape.

  The test object holder 3 holds the test object T on its upper surface. Further, the test object holder driving stage 4 is a uniaxial stage, and drives the test object holder 3 in a direction (in the direction of arrow A) perpendicular to the longitudinal direction of the slit described above. The imaging unit 5 includes a lens (not shown) and a two-dimensional photoelectric conversion element 5a, and images a reflected image of the test object T on which the light beam is projected from a direction different from the direction in which the light beam is projected.

  The operation at the time of measurement of the three-dimensional shape measuring apparatus 1 having the above-described configuration will be described with reference to the flowchart shown in FIG.

  First, a problem that occurs in an image generated by the imaging unit 5 when there is texture due to the unevenness of the surface of the test object T will be described. Some textures are caused by scratches or fine irregularities on the surface of the test object T. When such a texture exists on the surface of the test object T, the image generated by the imaging unit 5 becomes dark, the brightness of the image of the light beam in the image becomes uneven, or a bright spot is partially present. Occur. When such a problem occurs, detection of the light beam image becomes unstable. For example, when the peak position is detected as described later, if no texture exists, the peak position P can be detected as shown in FIG. 3A. However, when the texture exists, for example, as shown in FIG. 3B, the shape of the curve is deformed, the center of gravity shifts, and the peak position may not be detected or may be erroneously detected. The flowchart in FIG. 2 shows an example of processing for dealing with such a problem.

  In step S1, the control unit 6 starts scanning the light beam. The control unit 6 controls the light projecting unit 2 to start projecting the light beam onto the test object T, and controls the test object holder driving stage 4 so as to place the test object holder 3 in FIG. Drive in the direction of arrow A. As a result, scanning of the light beam with respect to the test object T is started. The control unit 6 controls the test object holder drive stage 4 to drive the test object holder 3 in 80 μm steps, for example.

  In step S <b> 2, the control unit 6 controls the imaging unit 5 to start imaging of the test object T. Note that imaging by the imaging unit 5 is repeatedly performed at predetermined time intervals. At this time, if the portion of the test object T where the light beam is projected is flat, the image of the light beam generated by imaging is a straight line. Further, if the portion of the test object T where the light beam is projected has irregularities, the image of the light beam is deformed according to the position in the depth direction. The control unit 6 once records an image generated by imaging in a memory (not shown) in the control unit 6. Note that the control unit 6 repeatedly performs imaging every 80 μm, which is the step feed amount described above. By such repeated imaging, a plurality of slit-shaped images are generated in time series as shown in FIG. 4A.

  In step S3, the control unit 6 corrects the ambient light component. When the surface of the test object T is a metal surface, the above-described texture is strongly influenced by the incident angle due to the instability of diffused light. Accordingly, the texture by the light beam to be measured is generally different from the texture by the ambient light. Therefore, the control unit 6 corrects the ambient light component of the image generated in step S2. As a result, it is possible to obtain an image of only the texture by the light beam to be measured.

  There are the following two methods for correcting the ambient light component. The first is a method in which the light projecting unit 2 is temporarily turned off, only the ambient light component is captured by the imaging unit 5 to generate an image, and correction is performed based on the generated image. In this image, only an output corresponding to the ambient light component appears. When this method is used, the control unit 6 temporarily turns off the light projecting unit 2 and controls the imaging unit 5 to perform imaging in step S3. The second is a method of analyzing an image captured by the imaging unit 5 during normal measurement and correcting based on the analysis result. When this method is used, the control unit 6 extracts only the slit-shaped part corresponding to the light beam based on the luminance of the image generated in step S2, and subtracts the other part as the ambient light component.

  In step S4, the control unit 6 determines whether or not the imaging in the entire predetermined range has been completed. If the control unit 6 determines that imaging in the entire range has been completed, the process proceeds to step S5. On the other hand, if it is determined that imaging in the entire range has not been completed, the control unit 6 returns to step S2 and continues imaging at a predetermined time interval. When it is determined in step S4 that imaging in the entire range has been completed, as shown in FIG. 4B, a plurality of slit-shaped images in which the ambient light components are corrected are generated.

  In step S5, the control unit 6 combines all the images generated by the imaging in step S2. The controller 6 generates a texture image by combining a plurality of slit-shaped images in which the ambient light component is corrected. However, the control unit 6 combines in consideration of the shift when combining. Assuming that 1 pixel = 40 μm in terms of the test object T, for example, as described above, the step feed amount is 80 μm, so that the two-pixel shifts are combined.

  In this way, by synthesizing a plurality of slit-shaped images to generate a texture image, even if the fine structure of the surface of the test object T is not uniform, it can be comprehensively captured. FIG. 4C shows an example of generating a composite image. However, in FIG. 4C, the texture image is indicated by diagonal lines for the sake of explanation, but in reality, a pattern or the like due to the unevenness of the surface of the test object T appears as the texture image.

  In step S6, the control unit 6 corrects the texture of the image generated by the imaging in step S2 based on the synthesized image synthesized in step S5. For example, the control unit 6 reads a plurality of images generated by imaging in step S2 from a memory (not shown) in the control unit 6, and corrects each image based on the texture image generated in step S5. For example, the control unit 6 corrects the luminance of a certain image generated by the imaging in step S2 by dividing the luminance value of the position corresponding to the image generated by the imaging in step S2 among the texture images. The luminance value of the texture image reflects the reflectance of the test object T. Therefore, the reflectance can be converted to 1 and corrected by dividing by the luminance value of the texture image. When such correction is performed, the brightness of the image can be restored, the luminance can be made uniform, and the bright spots that have been partially generated can be eliminated.

  In step S7, the control unit 6 obtains a peak, a center of gravity, and the like based on the image in which the texture is corrected in step S6.

  In step S8, the control unit 6 calculates the three-dimensional shape of the test object T based on the detection result of step S7.

  As described above, according to the first embodiment, the texture caused by the unevenness of the surface of the object to be examined is estimated, and the image generated by the imaging unit is corrected based on the estimated texture. Then, the three-dimensional shape of the test object is calculated based on the corrected image after correction. Therefore, the influence of the texture of the surface of the test object can be suppressed, and the measurement can be performed with higher accuracy and more faithful to the test object.

  Further, according to the first embodiment, the texture is estimated based on a composite image generated by combining a plurality of images. Therefore, it is possible to suppress the influence of the texture more reliably.

  In addition, according to the first embodiment, the projector further includes a changing unit that changes the relative position between the light projecting unit and the object to be examined, and the light projecting unit projects the pattern light having the slit shape. Then, the texture is estimated based on a composite image obtained by combining images at a plurality of different relative positions. Therefore, the texture can be estimated more accurately, and the texture can be corrected more accurately.

  In addition, according to the first embodiment, the image processing apparatus further includes extraction means for extracting a pattern light image having a slit shape, and the texture is obtained based on a composite image obtained by combining the pattern light images extracted at a plurality of different relative positions. presume. Therefore, more accurate measurement can be realized in consideration of the influence of the ambient light component.

Second Embodiment
The second embodiment of the present invention will be described below with reference to the drawings. In the second embodiment, only different parts from the first embodiment will be described.

  The three-dimensional shape measuring apparatus of the second embodiment has the same configuration as the three-dimensional shape measuring apparatus 1 of the first embodiment. Below, it demonstrates using the symbol similar to FIG. 1 of 1st Embodiment.

  FIG. 5 is a flowchart showing an operation during measurement of the three-dimensional shape measuring apparatus according to the second embodiment.

  In step S11, the control unit 6 acquires texture information. There are the following two methods for acquiring texture information. The first is a method of generating an image by imaging with the imaging unit 5 using a diffusion light source (not shown). The generated image is an image corresponding to the texture image described in the first embodiment, and texture correction to be described later can be performed using this image. In addition, when the light projection part 2 is the structure which consists of a diffused light source and a slit mask, the image equivalent to a texture image can be produced | generated by removing a slit mask and imaging. The second method is a method of acquiring an image corresponding to a texture image or information equivalent thereto from the outside of the three-dimensional shape measuring apparatus 1.

  In step S <b> 12, the control unit 6 starts scanning with a light beam as in step S <b> 1 of the first embodiment.

  In step S <b> 13, the control unit 6 controls the imaging unit 5 to start imaging of the test object T, similarly to step S <b> 2 of the first embodiment.

  In step S14, the control unit 6 corrects the ambient light component as in step S3 of the first embodiment.

  In step S15, the control unit 6 corrects the texture of the image based on the texture information acquired in step S11, as in step S6 of the first embodiment. In the present embodiment, since the texture information has already been acquired in step S11 as described above, the image in which the ambient light component is corrected in step S14 without waiting for completion of imaging in the entire range as in the first embodiment. The texture can be corrected in order.

  In step S <b> 16, the control unit 6 determines whether or not imaging in the entire predetermined range has been completed as in step S <b> 4 of the first embodiment. If the control unit 6 determines that imaging in the entire range has been completed, the process proceeds to step S17. On the other hand, if it determines with the imaging in the whole range not being completed, the control part 6 will return to step S12, and will continue the process of step S12 to step S15.

  In step S17, as in step S7 of the first embodiment, the control unit 6 obtains a peak, a center of gravity, and the like based on the image in which the texture is corrected in step S15.

  In step S18, the control unit 6 calculates the three-dimensional shape of the test object T based on the one detection result in step S7, as in step S8 of the first embodiment.

  As described above, according to the second embodiment, the texture is estimated based on the texture image previously captured by the imaging unit. Therefore, texture correction can be started without waiting for completion of imaging in the entire range, and in addition to the effects of the first embodiment, a reduction in processing time can be expected.

  In each of the above-described embodiments, the example in which the object holder 3 is driven to change the relative position with the object to be examined has been described. However, the object holder 3 is fixed and the light projecting unit 2 is connected to the slit. The relative position may be changed by driving in a direction perpendicular to the longitudinal direction. Furthermore, in an application in which the measurement range is given priority over the measurement accuracy, a configuration in which the projection angle of the light beam is scanned with a polygon mirror or the like may be employed. In this case, when the light beam passes through a certain pixel, the projection angle to the object to be measured may change. For this reason, in the case of a test object in which diffused light is unstable, measurement accuracy may be reduced. In any case, when the object holder 3 is fixed and the projection position is scanned, the slit light moves on the two-dimensional photoelectric conversion element 5a, so that the image described in step S5 of the first embodiment. There is no need to consider the shift when synthesizing.

  Further, in each of the above-described embodiments, the light beam projected from the light projecting unit 2 has an example of a single slit shape. However, as long as discrimination is possible, a plurality of slit shapes may be used. good.

  In each of the above-described embodiments, the case where the space centroid method is used has been described as an example, but the time centroid method may be used.

  In each of the above-described embodiments, a so-called light-cutting three-dimensional shape measuring apparatus has been described as an example. However, the present invention can be similarly applied to three-dimensional shape measuring apparatuses using other methods. it can. For example, when applied to a phase shift type three-dimensional shape measuring apparatus, a texture image can be generated by combining images generated at a plurality of different phases.

It is a figure which shows the structure of the three-dimensional shape measuring apparatus 1 of 1st Embodiment. It is a flowchart which shows the operation | movement at the time of the measurement of the three-dimensional shape measuring apparatus 1 of 1st Embodiment. It is a figure explaining a texture. It is a figure explaining the flow of a measurement. It is a flowchart which shows the operation | movement at the time of the measurement of the three-dimensional shape measuring apparatus of 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Three-dimensional shape measuring apparatus, 2 ... Projection part, 3 ... Test object holder, 4 ... Test object holder drive stage, 5 ... Imaging part, 5a ... Two-dimensional photoelectric conversion element, 6 ... Control part, 7 ... Laser emission part, 8 ... Cylindrical lens

Claims (10)

Light projecting means for projecting pattern light having a predetermined slit shape from the first direction to the object to be examined;
An imaging means comprising a two-dimensional photoelectric conversion element, and imaging the pattern light image reflected from the object to be examined by the two-dimensional photoelectric conversion element from a direction different from the first direction;
Changing the relative position between the light projecting means and the test object, and changing means for scanning the test object with the pattern light by the light projecting means;
Estimating means for estimating texture caused by irregularities on the surface of the object to be examined;
Correction means for correcting the image generated by the imaging means based on the texture estimated by the estimation means;
A calculation unit that calculates a three-dimensional shape of the test object based on the corrected image corrected by the correction unit ;
Based on a combined image obtained by combining the images at a plurality of different positions on the test object along the scanning direction, the estimation unit estimates texture caused by unevenness on the surface of the test object.
3-dimensional shape measuring device comprising a call. The three-dimensional shape measuring apparatus according to claim 1,
An extraction means for extracting an image of the pattern light having a slit shape from the image generated by the imaging means ;
Based on a composite image obtained by combining the pattern light images extracted at the plurality of different positions extracted by the extraction unit along the scanning direction, the estimation unit performs a texture caused by unevenness on the surface of the test object. A three-dimensional shape measuring apparatus characterized by estimating. In the three-dimensional shape measuring apparatus according to claim 1 or 2 ,
The imaging unit generates an image by imaging the surface of the object to be inspected by light different from the light projecting unit ,
Said different using an image due to light, a texture due to the unevenness of the surface of the test object by the pattern light of the light projecting means, said estimating means the three-dimensional shape measuring apparatus and estimating. In the three-dimensional shape measuring apparatus according to any one of claims 1 to 3,
The composite image, wherein the Ru composite image der to align in the longitudinal direction of the slit-shaped while shifting the scanning direction at a predetermined feed amount each image by the changing means in said plurality of different positions A three-dimensional shape measuring apparatus. In the three-dimensional shape measuring apparatus according to any one of claims 1 to 4,
The three-dimensional shape measuring apparatus according to claim 1, wherein the texture is a non-uniform luminance component in an image generated by the imaging unit due to unevenness of a surface of the object to be examined. A light projecting procedure for projecting pattern light having a predetermined slit shape from the first direction to the object to be examined;
An imaging procedure for capturing an image of the pattern light reflected from the test object from a direction different from the first direction by a two-dimensional photoelectric conversion element;
A change procedure for changing the relative position between the light projecting means for projecting the pattern light and the test object, and scanning the pattern light by the light projecting means on the test object,
An estimation procedure for estimating texture due to irregularities on the surface of the test object;
A correction procedure for correcting the image generated by the imaging procedure based on the texture estimated by the estimation procedure;
A calculation procedure for calculating the three-dimensional shape of the test object based on the corrected image corrected by the correction procedure,
Based on a composite image obtained by combining the images at a plurality of different positions on the test object along the scanning direction, the estimation procedure estimates texture caused by unevenness on the surface of the test object. A three-dimensional shape measuring method characterized by the above. The three-dimensional shape measuring method according to claim 6,
An extraction procedure for extracting an image of the pattern light having a slit shape from the image generated by the imaging procedure ;
Based on the synthesized image obtained by synthesizing the pattern light images at the different positions extracted by the extraction procedure along the scanning direction, the estimation procedure performs the texture caused by the unevenness of the surface of the object to be examined. A three-dimensional shape measuring method characterized by estimating. In the three-dimensional shape measuring method according to claim 6 or 7,
In the imaging procedure, an image is generated by imaging the surface of the object to be inspected with light different from the light projecting means ,
Said different using an image due to light, three-dimensional shape measuring method of the texture caused by the unevenness of the surface of the test object by the pattern light of the light projecting means, the estimation procedure is characterized in that estimation. In the three-dimensional shape measuring method according to any one of claims 6 to 8,
The synthesized image is an image synthesized such that the images at the plurality of different positions are aligned in the longitudinal direction of the slit shape while being shifted in the scanning direction by a predetermined feed amount according to the changing procedure.
A three-dimensional shape measuring method characterized by the above. The three-dimensional shape measuring method according to any one of claims 6 to 9,
The three-dimensional shape measuring method, wherein the texture is a non-uniform luminance component in an image generated by the imaging procedure due to unevenness of a surface of the test object.

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