JP2008170281A - Shape measuring apparatus and shape measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring device and measuring method capable of performing accurate three-dimensional shape measurement by preventing influence of time variation of a specimen or influence of rapid state change of a specimen surface. <P>SOLUTION: This shape measuring device comprises a projection section for projecting a projection pattern to the specimen having optical wavelength and phase depending on the position, an image acquiring section for acquiring the image of the specimen to which the projection pattern is projected as imaging divided based on at least two wavelength characteristics corresponding to the color tone, a correction phase acquiring section for acquiring the correction phase where an error due to duplication of the wavelength characteristics is corrected from the imaging corresponding to a plurality of positions of the specimen, a shape measuring section for measuring the shape of the specimen from the correction phase acquired by the correction phase acquiring section. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an apparatus for measuring a three-dimensional shape by pattern projection.

  Various techniques for measuring the surface shape of an object such as an industrial product have been proposed, and one of them is an optical three-dimensional shape measuring apparatus. There are various types of optical three-dimensional shape measurement devices and configurations, but a predetermined projection pattern (a striped pattern or a lattice pattern) is projected onto the test object, and the test object is imaged. From the above, there is a method for calculating the height of each image position by calculating the phase of the stripes at each image position (each pixel) and measuring the three-dimensional surface shape of the test object (see Patent Document 1).

  In such an apparatus, for example, a projection pattern composed of a fringe pattern is projected onto the surface of the test object, and a fringe pattern projected onto the test object from an angle different from the projection direction is imaged. The phase distribution of the fringe pattern is calculated from the captured image of the surface, and the three-dimensional shape of the surface of the test object is obtained using the principle of triangulation or the like.

  An example of the configuration is shown in FIG. 4, and the light from the light source 51 is projected onto the surface of the test object 54 through the projection pattern mask 52 having a striped pattern and the projection lens 53. The stripe pattern of the projection pattern mask 52 projected on the surface of the test object 54 is deformed according to the three-dimensional shape of the surface of the test object 54, and the pattern of the surface of the test object 54 thus deformed is projected. The image is picked up by an image pickup device 56 (for example, a CCD sensor) through an image pickup lens 55 from an angle different from the direction, and sent to the arithmetic processing device 57, where the picked-up image data is processed. The arithmetic processing unit 57 calculates the phase distribution of the fringe pattern from the captured image data of the surface of the test object imaged in this way, and calculates the three-dimensional shape of the test object surface using the triangulation principle or the like. Processing is performed.

JP 2000-9444 A

  By the way, in the three-dimensional measurement using the phase shift method as described above, the phase of each pixel is obtained from the picked-up image picked up multiple times by changing the phase of the projection pattern, and the resolution in the horizontal direction is high. If the test object moves within the time for acquiring the captured image (because of vibration or the like), there is a problem that the accuracy decreases. In addition, in the three-dimensional measurement using the one-step method using Fourier transform, there is no problem with temporal change (movement) of the test object, but it is impossible to detect a sudden state change of the test object surface. There's a problem.

  The present invention has been made in view of such problems, and it is not possible to be affected by the temporal change of the specimen or the sudden state change of the specimen surface. It is an object of the present invention to provide a measuring apparatus and a measuring method capable of performing original shape measurement.

  In order to solve the above-described problems and achieve the object, a shape measuring apparatus according to the present invention projects a projection pattern having a different optical wavelength and phase depending on the position onto a test object, and the projection pattern is projected An imaging acquisition unit that acquires an image of the test object as an imaging divided based on at least two wavelength characteristics corresponding to color tone, and an overlap between the wavelength characteristics from the imaging corresponding to a plurality of positions of the test object A correction phase acquisition unit that acquires a correction phase in which the error due to the correction is corrected, and a shape measurement unit that measures the shape of the test object from the correction phase acquired by the correction phase acquisition unit.

  The shape measuring device is preferably configured to include a projection pattern generation unit that generates a projection pattern having an arbitrary wavelength and an arbitrary phase depending on a position.

  In the shape measuring apparatus, the projection pattern generation unit generates the projection pattern by synthesizing at least three wavelength characteristics, and the imaging acquisition unit acquires as an imaging divided based on at least the three wavelength characteristics. Preferably, it is configured.

  The shape measuring apparatus according to the present invention projects a projection pattern generation unit that generates a projection pattern of an arbitrary wavelength band and an arbitrary phase, and the projection pattern generated by the projection pattern generation unit onto a test object. A projection unit; an imaging unit that images the object on which the projection pattern is projected; and the projection pattern generation unit that generates three or more correction projection patterns having different wavelength bands, and the projection unit. To project the correction projection pattern onto the object to be detected and to capture three or more correction captured images by capturing with the imaging unit, and in each of the correction captured images, the light amount for each wavelength band A correction data detection unit that detects a ratio and acquires the light amount ratio as correction data for each of the correction captured images; and the projection pattern generation unit. , Generating three or more base projection patterns each having the same wavelength band as the correction projection pattern and having different phases, and further combining the base projection patterns to generate a composite projection pattern; In the composite projection pattern captured image obtained by projecting the composite projection pattern onto the test object by the projection unit and capturing an image by the imaging unit, the correction data is divided by the wavelength band for each wavelength band. A correction data acquisition unit that corrects three or more correction images with different phases, and a shape calculation unit that measures the shape of the test object from the correction image obtained by the correction image acquisition unit; Is provided.

In order to solve the above-described problems and achieve the object, a shape measuring method according to the present invention projects a projection pattern having a different optical wavelength and phase depending on the position onto a test object, and the projection pattern is projected. An imaging acquisition step of acquiring an image of the test object as an imaging divided based on at least two wavelength characteristics corresponding to color tone, and overlapping of the wavelength characteristics from the imaging corresponding to a plurality of positions of the test object The correction phase acquisition step of acquiring a correction phase in which the error due to the correction is corrected, and the shape of the test object are measured from the correction phase acquired by the correction phase acquisition step.

It is preferable that the shape measuring method further includes a projection pattern generation step of generating a projection pattern having an arbitrary wavelength and an arbitrary phase depending on the position.

In the shape measuring method, the projection pattern generation step generates at least three wavelength characteristics to generate the projection pattern, and the imaging acquisition step acquires as imaging divided based on at least the three wavelength characteristics. Preferably, it is configured.

  The shape measurement method according to the present invention projects a projection pattern generation unit that generates a projection pattern having an arbitrary wavelength band and an arbitrary phase, and the projection pattern generated by the projection pattern generation unit onto a test object. A method for measuring a three-dimensional shape of the test object using a shape measuring device including a projection unit and an imaging unit that images the test object on which the projection pattern is projected, the projection pattern generation Three or more correction projection patterns each having a different wavelength band are generated by the unit, and the correction projection pattern is projected onto the test object by the projection unit and imaged by the imaging unit, and three or more In each of the step of obtaining the correction captured image and the correction captured image obtained by imaging by the imaging unit, a light amount ratio for each wavelength band is detected, A step of acquiring a light amount ratio as correction data for each of the correction captured images, and the projection pattern generation unit, each of which has the same wavelength band as that of the correction projection pattern and has three different phases. Generating the above base projection pattern, further combining the base projection pattern to generate a composite projection pattern, projecting the composite projection pattern onto the test object by the projection unit; and In the step of capturing the composite projection pattern projected on the specimen to obtain a composite projection pattern captured image, and in the composite projection pattern captured image obtained by the imaging unit, the amount of light in each pixel is set for each wavelength band. Separately, correction is performed using the correction data, and three or more corrected images having different phases are obtained. And a step to determine the three-dimensional shape of the test object from the corrected image.

  According to the present invention configured as described above, three correction projection patterns having different wavelength bands are generated, each having the same wavelength band as that of the correction projection pattern and a phase. Generating three or more base projection patterns different from each other, further combining the base projection patterns to generate a combined projection pattern, and projecting the combined projection pattern from the combined projection pattern captured image, The amount of light is divided for each wavelength band and corrected using the correction data, three or more corrected images having different phases are obtained, and the three-dimensional shape of the test object is obtained from the corrected image. It is possible to provide a 3D shape measuring device with high measurement accuracy by reducing the effects of temporal changes in the specimen or the sudden changes in the surface of the specimen. .

  Hereinafter, preferred embodiments of the present invention will be described. FIG. 1 shows a schematic configuration of a three-dimensional shape measuring apparatus according to the present invention. First, the shape measuring apparatus will be described with reference to FIG.

  The shape measuring device projects a light source 1, a projection pattern mask 2 for giving a stripe pattern to the light from the light source 1, and light from the light source 1 that has passed through the projection pattern mask 2 onto the surface of the test object 20. A pattern projection unit including the projection lens (group) 3 and an imaging unit including the imaging device 5 that captures the reflected light from the test object 20 via the imaging lens (group) 4 are configured. .

  In the pattern projection unit, the projection pattern mask 2 is composed of, for example, a liquid crystal element, and a projection pattern generation device 6 generates a projection pattern having an arbitrary wavelength band and an arbitrary phase (in this embodiment, a sinusoidal fringe pattern is generated). Can be generated. Thereby, the light from the light source 1 passes through the projection pattern mask 2, is condensed by the projection lens 3, and a desired projection pattern formed by the projection pattern mask 2 is projected onto the surface of the test object 20. it can. In the figure, the projection pattern mask 2 is a binary pattern (monochrome pattern) so that it can be easily understood visually. However, as described above, the projection pattern mask 2 is actually a stripe pattern in which the phase due to shading changes to a sine wave.

  The imaging unit includes an imaging device 5 (for example, a CCD camera) that captures an image of the test object 20 through the imaging lens 4 with reflected light from the test object 20. The image data of the test object 20 imaged by the imaging device 5 is sent to the arithmetic processing device 7, where the image arithmetic processing described below is performed, and the surface shape of the test object 20 is measured. Note that the pattern projection unit and the imaging unit are integrally fixed by a single frame, and the test object 20 is placed and supported on a support table (not shown).

  The arithmetic processing device 7 detects the light amount ratio of different wavelength bands in the captured image obtained by the imaging device 5, and obtains the light amount ratio as correction data, and the correction data detection unit 8 obtained by the imaging unit. In the captured image, the light amount in each of the different wavelength bands is corrected for each pixel using the correction data, and the correction image acquisition unit 9 acquires a correction image having a different phase, and the correction image acquisition unit 9 obtains the correction image. And a shape calculation unit 10 for measuring the shape of the test object from the corrected image.

  A method of measuring the surface shape of the test object 20 using the surface shape measuring apparatus configured as described above will be described below with reference to the flowchart of FIG.

  In the present embodiment, the projection pattern generation device 6 synthesizes three projection patterns having different wavelength bands (sine wave-like red, green, and blue stripe patterns) or three projection patterns having phases different from each other. A composite projection pattern is generated and used.

  In this measurement, first, the projection pattern generation device 6 generates the projection pattern mask 2 into a red stripe pattern (sinusoidal red stripe pattern) (step S1). The test object 20 is irradiated with light from the light source 1 through the projection pattern mask 2 and the projection lens 3 to project a red stripe pattern on the surface of the test object 20. The light thus projected and reflected from the test object 20 is collected through the imaging lens 4, and the red stripe pattern projected on the test object surface is imaged by the imaging device 5 (step S2).

  The captured image obtained by the imaging device 5 is sent to the arithmetic processing device 7. In the correction data detection unit 8 in the arithmetic processing unit 7, the light intensity ratio of each wavelength band of the captured image obtained by projecting the red stripe pattern onto the test object 20 (the captured image obtained by projecting the red stripe pattern). Red, blue, and green light amounts) are detected (step S3). Here, the light amount ratio of each wavelength band obtained by projecting the red stripe pattern is Rrr (X, Y) (the red light amount ratio), Grr (X, Y) (the green light amount ratio), Brr. (X, Y) (the blue light amount ratio).

As described above, in the captured image obtained by projecting the red stripe pattern onto the test object 20,
The wavelength band of the captured image is not necessarily 1: 1 with respect to each wavelength band of the light source 1. That is, in the captured image, not only the red light amount is detected but also there is some sensitivity to the green light amount or the blue light amount (there is a leak as a signal). Therefore, as will be described below, the accuracy of the shape measurement of the test object 20 is improved by simultaneously correcting the reflection characteristic of the test object surface as well as the sensitivity difference of the imaging unit (including the leak amount as described above). It is something to try.

  Next, the projection pattern generation device 6 generates the projection pattern mask 2 into a green stripe pattern (sinusoidal green stripe pattern), and the green stripe pattern projected onto the surface of the test object by the imaging device 5 in the same manner as described above. Is imaged (step S4).

  In the correction data detection unit 8 in the arithmetic processing unit 7, the light intensity ratio of each wavelength band of the captured image obtained by projecting the green striped pattern onto the test object 20 (the captured image obtained by projecting the green striped pattern). Red, blue and green light amounts) are detected (step S5). Here, the light intensity ratio of each wavelength band obtained by projecting the green stripe pattern is Rrg (X, Y) (the red light intensity ratio), Grg (X, Y) (the green light intensity ratio), Brg, respectively. (X, Y) (the blue light amount ratio).

  Further, the projection pattern generation device 6 generates the projection pattern mask 2 into a blue stripe pattern (sinusoidal blue stripe pattern), and the blue stripe pattern projected onto the surface of the test object by the imaging device 5 in the same manner as described above. An image is taken (step S6).

  In the correction data detection 8 in the arithmetic processing unit 7, the light quantity ratio of each wavelength band of the captured image obtained by projecting the blue stripe pattern onto the test object 20 (the captured image obtained by projecting the blue stripe pattern). Red, blue and green light quantities) are detected (step S7). Here, the light amount ratio of each wavelength band obtained by projecting the blue stripe pattern is Rrb (X, Y) (the light amount ratio of red), Grb (X, Y) (the light amount ratio of green), Brb, respectively. (X, Y) (the blue light amount ratio).

  Therefore, the amount of light of the captured image obtained by projecting the projection pattern (red, green, blue stripe pattern) of each wavelength band is the same as the amount of light of the captured image originally projected by projecting the projection pattern of each wavelength band. On the other hand, when expressed using the light quantity ratio of each wavelength band obtained by projecting the projection pattern of each wavelength band, the following expression (1) is obtained.

  Here, Rr, Gr, and Br are the amounts of light of the captured image obtained by projecting the projection patterns in the respective wavelength bands, and R, G, and B are originally imaged by projecting the projection patterns in the respective wavelength bands. This is the amount of light of the captured image.

  Obtained by projecting the projection pattern of each wavelength band to the amount of light of the captured image originally projected by projecting the projection pattern (red, green, blue stripe pattern) of each wavelength band obtained as described above. The ratio of the amount of light of the captured image, that is, the reciprocal of the light amount ratio of each wavelength band obtained by projecting the projection pattern of each wavelength band is obtained by projecting the projection pattern of each wavelength band. The correction data for correcting the amount of light can be obtained, and can be obtained by modifying equation (1) (see equation (2) below) (step S8).

  In the above, the coefficient term on the right side of Equation 2 is correction data for correcting the light amount of the captured image obtained by projecting the projection pattern (red, green, blue stripe pattern) of each wavelength band.

  Next, the shape measurement of the test object 20 is performed using the correction data for correcting the light amount of the captured image obtained by projecting the projection patterns (red, green, and blue stripe patterns) of the respective wavelength bands obtained above. The procedure to be performed will be described.

  As shown in FIG. 3, the projection pattern generation device 6 causes the projection pattern mask 2 to have different phases in each wavelength band (red, green, and blue) (for example, 2 / 3π phases are shifted from each other, and the fringe pitches are equal). A three-color composite stripe pattern is generated by synthesizing three stripe patterns (step S9).

  The object 20 is irradiated with light from the light source 1 through the projection pattern mask 2 and the projection lens 3 to project a three-color composite stripe pattern on the surface of the object 20. The light thus projected and reflected from the test object 20 is collected through the imaging lens 4, and the three-color composite fringe pattern projected on the test object surface is imaged by the imaging device 5 (step S10).

  The captured image obtained by the imaging device 5 is sent to the arithmetic processing device 7, and each wavelength band for each pixel of the three-color composite fringe pattern captured image obtained by projecting the three-color composite fringe pattern onto the test object 20. Are detected (red, green, and blue light amounts of the three-color composite stripe pattern captured image obtained by projecting the three-color composite stripe pattern) (step S11).

  Then, in the corrected image acquisition unit 9 in the arithmetic processing unit 7, the correction data detection unit 8 for each pixel of the three-color synthetic fringe pattern captured image obtained by projecting the three-color synthetic fringe pattern onto the test object 20. Using the correction data obtained by the above, each light quantity in each wavelength band (red, green, blue) is corrected, and each phase is different (for example, a sine wave shape with a 2 / 3π phase shift and a fringe pitch equal to each other). Three images are acquired as corrected images (step S12).

  Further, the shape of the test object 20 is measured by using the principle of triangulation based on the phase value of the corrected image obtained by correction using the correction data obtained by the correction data detection unit 8 (step) S13).

  As described above, it is possible to project a three-color composite projection pattern having three different wavelength bands at the same time and having different phases, and simultaneously obtaining three captured images having different phases. Correction data is detected from the light quantity ratio, the captured image is corrected using the correction data, three images having different phases are obtained as correction images, and based on the principle of triangulation based on the phase value of the correction image Thus, the three-dimensional shape of the test object 20 is obtained.

  Accordingly, the test object 20 can be accurately measured without being affected by the temporal change of the test object 20 (the test object 20 moves due to vibration or the like) or the rapid change in state of the test object surface. Three-dimensional shape measurement can be performed.

  In the present embodiment, as described above, in the captured image, not only the amount of light corresponding to the wavelength band of the projection pattern is detected, but there is some sensitivity to the amount of light in a different wavelength band (see as a signal). And there is a leak). Therefore, the accuracy of shape measurement of the test object 20 is to be improved by simultaneously correcting the reflection characteristics of the test object surface as well as the sensitivity difference of the imaging unit (including the leak amount as described above). However, it is also possible to adopt a configuration in which only the amount of light corresponding to the wavelength band of the projection pattern is detected. However, there is a problem that a high-precision optical filter or the like is required and the apparatus is expensive, and the method in this embodiment is effective.

In this embodiment, in order to determine (unwrap) the order of the fringes of the projection pattern in the captured image of the projection pattern projected on the surface of the test object, the projection patterns (red and green) of three different wavelength bands are used. , Blue stripe pattern), and three captured images with different phases were used. However, unwrapping is not limited to using three captured images, and it is possible to use at least two captured images having different phases.

1 is a schematic configuration explanatory diagram showing a configuration of a three-dimensional shape measuring apparatus according to an embodiment of the present invention. It is a flowchart which shows the shape measuring method which concerns on the said invention. It is schematic structure explanatory drawing which shows the structure of the 3 color synthetic | combination fringe pattern which concerns on embodiment of this invention. It is schematic structure explanatory drawing which shows the structure of the conventional shape measuring apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Projection pattern mask 3 Projection lens 4 Imaging lens 5 Imaging device 6 Projection pattern production | generation apparatus (projection pattern production | generation part)
7 Arithmetic processing device 8 Correction data detection unit 9 Correction image acquisition unit (corrected phase acquisition unit)
10 Shape calculation part (Shape measurement part)
20 Test object

Claims (8)

A projection unit that projects a projection pattern having different optical wavelengths and phases depending on the position onto a test object;
An imaging acquisition unit that acquires an image of the test object onto which the projection pattern is projected as an imaging divided based on at least two wavelength characteristics corresponding to a color tone;
A correction phase acquisition unit that acquires a correction phase that corrects an error due to duplication of the wavelength characteristics from the imaging corresponding to a plurality of positions of the test object;
A shape measuring apparatus comprising: a shape measuring unit that measures the shape of the test object from the corrected phase obtained by the corrected phase acquiring unit. In the shape measuring apparatus according to claim 1,
A shape measuring apparatus comprising: a projection pattern generation unit that generates a projection pattern having an arbitrary wavelength and an arbitrary phase according to a position. In the shape measuring apparatus according to claim 2,
The projection pattern generation unit generates the projection pattern by combining at least three wavelength characteristics;
The shape measurement apparatus characterized in that the imaging acquisition unit acquires as imaging divided based on at least the three wavelength characteristics. A projection pattern generation unit that generates a projection pattern of an arbitrary wavelength band and an arbitrary phase;
A projection unit that projects the projection pattern generated by the projection pattern generation unit onto a test object;
An imaging unit that images the object on which the projection pattern is projected;
The projection pattern generation unit generates three or more correction projection patterns having different wavelength bands, the projection unit projects the correction projection pattern onto the object, and the imaging unit captures the image. Three or more correction captured images are acquired, a light amount ratio for each wavelength band is detected in each of the correction captured images, and the light amount ratio is acquired as correction data for each of the correction captured images. A correction data detection unit;
The projection pattern generation unit generates three or more base projection patterns each having the same wavelength band as the correction projection pattern and having different phases, and further combines and synthesizes the base projection patterns. In the composite projection pattern captured image obtained by generating a projection pattern, projecting the composite projection pattern onto the test object by the projection unit, and capturing an image by the imaging unit, the amount of light in each pixel is determined for each wavelength band. A correction data acquisition unit that separately corrects using the correction data and acquires three or more corrected images each having a different phase;
A shape calculation unit for measuring the shape of the test object from the correction image obtained by the correction image acquisition unit;
A shape measuring apparatus comprising: A projection step of projecting a projection pattern having an optical wavelength and a phase different depending on the position onto the test object;
An imaging acquisition step of acquiring an image of the test object on which the projection pattern is projected as an imaging divided based on at least two wavelength characteristics corresponding to color tone;
A correction phase acquisition step of acquiring a correction phase in which an error due to duplication of the wavelength characteristics is corrected from the imaging corresponding to a plurality of positions of the test object;
A shape measuring method comprising: a shape measuring step of measuring the shape of the test object from the corrected phase obtained by the corrected phase acquisition step. In the shape measuring method according to claim 5,
A shape measurement method further comprising a projection pattern generation step of generating a projection pattern having an arbitrary wavelength and an arbitrary phase according to a position. In the shape measuring method according to claim 6,
The projection pattern generation step generates the projection pattern by combining at least three wavelength characteristics;
The shape measurement method according to claim 1, wherein the imaging acquisition step acquires as imaging divided based on at least the three wavelength characteristics. A projection pattern generation unit that generates a projection pattern of an arbitrary wavelength band and an arbitrary phase, a projection unit that projects the projection pattern generated by the projection pattern generation unit onto a test object, and the projection pattern is projected A method for measuring a three-dimensional shape of the test object using a shape measuring device including an imaging unit that images the test object,
The projection pattern generation unit generates three or more correction projection patterns having different wavelength bands, the projection unit projects the correction projection pattern onto the object, and the imaging unit captures the image. Acquiring three or more correction captured images;
Detecting a light amount ratio for each wavelength band in each of the correction captured images obtained by imaging by the imaging unit, and acquiring the light amount ratio as correction data for each of the correction captured images;
The projection pattern generation unit generates three or more base projection patterns each having the same wavelength band as the correction projection pattern and having different phases, and further combines and synthesizes the base projection patterns. Generating a projection pattern and projecting the composite projection pattern onto the object by the projection unit;
Capturing the composite projection pattern projected on the object by the imaging unit to obtain a composite projection pattern captured image;
In the composite projection pattern captured image obtained by the image capturing unit, the light amount in each pixel is corrected for each wavelength band and corrected using the correction data, and three or more corrected images having different phases are obtained. When,
A shape measuring method comprising: obtaining a three-dimensional shape of the test object from the corrected image.

Images