JP4874657B2 - Three-dimensional shape measuring method and apparatus - Google Patents

Description

  The present invention relates to a method and apparatus for measuring a three-dimensional shape, and more particularly, a method for measuring a three-dimensional shape using a spatial coding method for generating an absolute code value for a space by a binary projection pattern. And to the device.

  Generally, there are a passive measurement method and an active measurement method as a technique for measuring the three-dimensional shape of a measurement object using light in a non-contact manner.

  Here, the passive measurement method is a method of measuring using ambient light without having a light projecting unit on the measurement device side, as represented by a stereo method.

  On the other hand, the active measurement method is a method of irradiating light from a light projecting means on the measurement device side toward a measurement object and measuring the reflected light.

  Among these active measurement methods, the slit light projection method and the spatial encoding method are known as methods using the principle of triangulation.

Here, the spatial encoding method is a method of projecting a plurality of binary projection patterns, which are striped light patterns composed of a light transmission region and a light non-transmission region, onto a measurement object, thereby forming the stripe shape. When one point on the measurement object projected with the light pattern is observed, the light beam projected onto the one point being observed blinks to form a code. This is a technique of measuring the three-dimensional shape of a measurement object using a code.

  In this spatial coding method, the value indicated by the code (spatial code value) and the direction of the light beam have a one-to-one relationship, and the direction of the line of sight of the observation position from the position of the light spot on the measurement object is determined. Since the direction of the light ray is known from the spatial code value of the light spot, the distance to all the light spots on the measurement object can be obtained by the principle of triangulation, and this allows the three-dimensional measurement object to be measured. The shape can be measured in a non-contact manner.

  By the way, it is known that the measurement resolution of a three-dimensional shape in the above-described spatial coding method depends on the width of the stripe pattern.

  Therefore, in the spatial encoding method, the measurement resolution improves as the width of the stripe-shaped pattern is reduced. However, as the width of the stripe-shaped pattern is reduced, the intensity of light on the light projecting side is increased. It is difficult to identify the stripe pattern on the light receiving side due to irregular reflection at the imaging space and the measurement object, and there is a limit to narrowing the width of the stripe pattern.

  In other words, the spatial coding method has a limit on the segmentation of the code due to the influence of the resolution of the projector and the photographing machine and the shape and surface state of the measurement object, and the measurement resolution of the three-dimensional shape cannot be made so fine. The problem was pointed out.

Therefore, as a technique for solving the problems of the spatial coding method described above, for example, a technique combining the spatial coding method and the multi-slit image encoder method is disclosed in Japanese Patent Application Laid-Open No. 2005-3409. Proposed in the Gazette.

  In the method disclosed in Japanese Patent Laid-Open No. 2005-3409, a projector connected to a computer is used to first project a multi-slit pattern onto a measurement object and photograph the image, and then use the same projector. Thus, a plurality of stripe patterns coded so that the absolute position of the space can be identified by a combination of the brightness and darkness of the stripes are sequentially projected.

  At that time, the projection pattern is photographed with a camera from a direction different from the projection direction, and an image corresponding to each projection pattern is obtained.

  Here, according to the projection patterns of the multi-slit pattern and the stripe pattern, the respective projection images will be referred to as the multi-slit projection image and the stripe projection image, respectively. A change in brightness over time is checked, and a relative projection angle image is generated with the relative projection position (projection angle) of the slit at the timing when the pixel exhibits the maximum luminance as the value of the pixel.

  Based on the triangulation principle, the precise partial shape of the region corresponding to the minimum width of the stripe pattern is calculated from the value of each pixel of the relative projection angle image and the geometric relationship between the pattern projection means and the imaging means. Ask.

  On the other hand, with respect to the stripe projection image, the temporal change in the brightness of each pixel is checked for each pixel, and coding is performed using a stripe pattern. For example, the sequence of the light and dark changes is encoded to create an absolute projection angle image having the pixel value.

  In this way, each pixel is associated with the minimum width stripe indicated by the code, that is, the zone of the projection angle.

  Then, based on the triangulation principle from the geometric relationship between the value of each pixel (projection angle) of the absolute projection angle image, pattern projection means, imaging means, and target reference plane (coordinate system for shape calculation). This is obtained by calculating the shape of the stripe projected on the surface of the measurement object.

  Therefore, according to the technique disclosed in Japanese Patent Application Laid-Open No. 2005-3409, a rough overall shape with the minimum stripe width can be obtained.

However, in the technique disclosed in the above Japanese Patent Application Laid-Open No. 2005-3409, that is, a technique that combines the spatial coding method and the multi-slit image encoder method, the imaging space can be multi-coded by the spatial coding method that can recognize the absolute shape. The same n-division as the slit (n-coding), and high-resolution 3D shape recognition is made possible by synthesizing high-resolution data using the multi-slit image encoder method for each division. In addition to this system, there is a problem that a complicated configuration such as a slit generation function, a peak detection and holding function, a projection angle storage function, or an angle / time conversion function for configuring a multi-slit image encoder is required. It was.

Furthermore, in order to process such a complicated configuration, there is a problem that a burden on a control system such as a central processing unit (CPU) increases and a long time is required for processing.
Japanese Patent Laid-Open No. 2005-3409

  The present invention has been made in view of the various problems of the conventional techniques as described above, and an object thereof is to improve the measurement resolution of shape measurement of a three-dimensional shape with a simple configuration. It is an object of the present invention to provide a method and apparatus for measuring a three-dimensional shape that can be used.

  In order to achieve the above object, the present invention provides a binarized projection pattern that is not affected by the resolution, that is, a binarized projection pattern that does not reach the limit of the width of the stripe pattern. The spatial code is subdivided by shifting, and oversampling technology is used.

  That is, the present invention shifts the binarized projection pattern by an arbitrary amount of movement and uses an oversampling technique using a spatial coding method for generating an absolute code value for the space by the binarized projection pattern. By using it, a high measurement resolution can be obtained.

  According to the present invention, since the algorithm of the spatial coding method can be used as it is, the hardware and software configurations can be used as they are, and the three-dimensional configuration can be achieved with a simple configuration. The measurement resolution of shape measurement can be improved.

Among these aspects of the invention, the invention according to claim 1 projects the binarized projection pattern onto the measurement object, and based on the image of the measurement object onto which the binarized projection pattern is projected, the measurement object In the three-dimensional shape measurement method for measuring the three-dimensional shape of an object, a predetermined binary projection pattern that is configured with a stripe shape having a minimum width that allows each width of the stripe-shaped pattern to be discriminated by an image , Shifting to a half-phase inversion range where the positions of the light transmission region and the light non-transmission region of the predetermined binarized projection pattern are switched, and the minimum resolution related to the measurement resolution of the three-dimensional shape measurement on the measurement object; become such while shifting by a predetermined movement amount sequentially projected on the measuring object, the surface of the measuring object projected the predetermined binary projection pattern for each of the shift Get all the images captured for each of the acquired images, to create a binary image from each of the luminance information of the positive pattern and a negative pattern of the acquired images, the sample pixels in the shift direction In order to satisfy the chemical theorem, the shift width in the X direction is multiplied by an integer by an integer so that it is at least twice the sampling pitch of the image input. The coordinates at which the positive pattern luminance distribution curve and the negative pattern luminance distribution curve intersect are obtained as sub-pixels as real values, the coordinates are set as pixel coordinates, and the pixel to the left of the coordinates including the coordinates is set to 1 or 0. create a binary image by more inverted value of the right pixel, and all the first type of the binary image to shift the image of the image Gets Te, including the predetermined binary projection pattern, a plurality of binary projection pattern having a width of different patterns respectively projected respectively to the measured object, a plurality of different said each binarized projection pattern Every time each is projected , all the images obtained by photographing the surface of the measurement object onto which each of the plurality of different binary projection patterns is projected are multiplied by an integer multiple using the above arbitrary integer in the X direction. All the images are combined, acquired as a second type of image having an absolute code value with respect to the shooting space with a shift pitch as resolution, and the first type of image and the second type of image are acquired. The code value is obtained from the third type of image synthesized by adding together the image. At this time, the number of pixels in the shift direction is used for the code value. Is corrected to a value obtained by dividing the image coordinate value by the arbitrary integer for each arbitrary number of pixels in the shift direction, and the three-dimensional shape of the measurement object is acquired.

The invention of claim 2 is the invention according to claim 1 of the present invention, the direction of shifting the predetermined binary projection pattern with respect to the measurement object, the It is intended to be in the width direction.

According to a third aspect of the present invention, the binarized projection pattern is projected onto the measurement object, and the measurement is performed based on the image of the measurement object onto which the binary projection pattern is projected. In a three-dimensional shape measuring apparatus for measuring a three-dimensional shape of an object, a predetermined binarized projection pattern is formed such that each width of the stripe-shaped pattern has a minimum width that can be discriminated by an image. , Shifting to a half-phase inversion range where the positions of the light transmission region and the light non-transmission region of the predetermined binarized projection pattern are switched, and the minimum resolution regarding the measurement resolution of the three-dimensional shape measurement on the measurement object while shifting by a predetermined moving amount such that the sequentially projected on the measuring object, the surface of the predetermined said measurement object binarized projection pattern is projected for each of the shift Binarization projection image acquiring means for acquiring all the images shadow, for each of the acquired images, to create a binary image from each of the luminance information of the positive pattern and a negative pattern of the obtained image In order to satisfy the sampling theorem, the pixels in the shift direction are multiplied by an arbitrary integer so that the shift width in the X direction is not less than twice the sampling pitch of the image input, and the light transmission region and the light non-transmission region The coordinates at which the positive pattern luminance distribution curve and the negative pattern luminance distribution curve near the pattern boundary intersect with the negative pattern luminance distribution curve are obtained as sub-pixels as real values, the above coordinates are set as pixel coordinates, and the pixel to the left of the above coordinates including the above coordinates 1 is set to 1 or 0, and a binary image is created by setting the pixel on the right side of the coordinates as an inverted value. A first image acquiring means for acquiring an image as a first type of image, including the predetermined binary projection pattern, a plurality of binary projection pattern having a width of different patterns respectively in the measurement object Each time each of the plurality of different binarized projection patterns is projected and each of the different binarized projection patterns is projected , all the images obtained by photographing the surface of the measurement object onto which the different binarized projection patterns are projected. In the X direction, all the images are combined by using the above-mentioned arbitrary integers to obtain an integer multiple, and the images are acquired as a second type image that is an image having a shift pitch as resolution and an absolute code value with respect to the imaging space. a second image acquisition unit, collected the code value from the third type of images synthesized by combining the sum first type of image and the said second type of image At that time, for the code value, the number of pixels in the shift direction is corrected to a value obtained by dividing the image coordinate value by the arbitrary integer for each arbitrary number of pixels in the shift direction, And a three-dimensional shape acquisition means for acquiring the three-dimensional shape of the measurement object.

Further, the invention according to claim 4 of the present invention is the invention according to claim 3 of the present invention, wherein the direction of shifting the predetermined binarized projection pattern with respect to the measurement object is the above. It is intended to be in the width direction.

  Since the present invention is configured as described above, there is an excellent effect that the measurement resolution of the shape measurement of the three-dimensional shape can be improved with a simple configuration.

  Hereinafter, an example of an embodiment of a method and an apparatus for measuring a three-dimensional shape according to the present invention will be described in detail with reference to the accompanying drawings.

(1) Overall Configuration FIG. 1 is a schematic configuration explanatory diagram showing an example of an embodiment of a three-dimensional shape measuring apparatus according to the present invention.

  That is, a three-dimensional shape measuring apparatus (hereinafter simply referred to as “measuring apparatus” as appropriate) 10 according to an example of an embodiment of the present invention includes a central processing unit (CPU) 12b connected via a bus 12a, A read only memory (ROM) 12c storing a program executed by the CPU 12b, a buffer memory for temporarily storing data signals, and a random access memory (RAM) as a working area in which various registers necessary for executing a program by the CPU 12b are set. ) 12d, which is configured to control the overall operation by a computer 12 having various input devices 12e such as a keyboard and a mouse and a display device 12f that outputs and displays the processing results of the CPU 12b. To the measuring object 14 under the control of the computer 12 A projector 16 for projecting a binary projection pattern number, is configured to include an imaging device 18 for photographing a measuring object 14 by the projector 16 is projected binarization projection pattern.

  That is, in the measuring apparatus 10, the projector 16 is connected to the computer 12 and is arranged so that various binary projection patterns generated by the computer 12 can be projected onto the surface of the measurement object 14. Has been. The photographing machine 18 is arranged so that the surface of the measuring object 14 can be photographed from a direction different from the projection direction of the projector 16, and the image photographed by the photographing machine 18 is digitized. Are taken into the computer 12.

(2) Binary Projection Pattern Here, FIGS. 2A, 2B, 2C, and 2D show examples of various binary projection patterns generated by the computer 12. FIG.

  Each of these binarized projection patterns includes a slit-like light transmission region 100a having a constant width W and extending in a predetermined direction orthogonal to the width W direction, and a light non-transmission region 100b corresponding to a slit frame. It is formed so as to be continuous alternately. The width W between the light transmission region 100a and the light non-transmission region 100b can be set to an arbitrary size.

  Further, in the binarized projection patterns shown in FIGS. 2A, 2B, 2C, and 2D, the binarized projection pattern having the narrowest width W is as shown in FIG. As shown in FIG. 2D, a binarized projection pattern having the narrowest width W among a plurality of different binarized projection patterns is generally referred to as an “LSB pattern”.

  In addition, since such a binarized projection pattern is a conventionally well-known technique, the detailed description is abbreviate | omitted.

(3) Control System of Measuring Device 10 Next, FIG. 3 is a block diagram illustrating a control system of the measuring device 10 realized by the computer 12.

  The control system determines a plurality of binarized projection patterns to be used for the process of projecting by the projector 16, projects the determined binarized projection patterns onto the surface of the measurement object 14, and Binary projection for controlling to project any one of the determined binary projection patterns onto the surface of the measuring object 14 while shifting (moving) a predetermined movement amount in the width W direction. The pattern projection means 20, the image input means 22 that digitizes the image taken by the photographing machine 18 and sends it to the image processing means 24 (described later), and the image sent from the image input means 22 to process the measurement object 14 image processing means 24 for extracting three-dimensional information.

  Here, the binarized projection pattern projecting means 20 includes a binarized projection pattern generation unit 20a that generates a binarized projection pattern as shown in FIG. 2 and 2 generated by the binarized projection pattern generation unit 20a. A binarized projection pattern projection control unit 20b that controls the projector 16 so as to project the binarized projection pattern onto the measurement object 14 is configured.

  That is, in the binarized projection pattern projecting means 20, the binarized projection pattern generation unit 20a generates a plurality of binarized projection patterns including a light transmission region 100a and a light non-transmission region 100b having a predetermined width W. To do.

  When the oversampling spatial code image generation process (described later) is not performed, the binarized projection pattern projection control unit 20b controls the projector 16 to generate the binarized projection pattern generation unit 20a. A plurality of different types of binarized projection patterns are respectively projected onto the surface of the measurement object 14. At this time, the binarized projection pattern projection control unit 20b does not shift the binarized projection pattern projected onto the surface of the measurement object 14 in the width W direction.

  On the other hand, when performing an oversampling phase shift image generation process (described later), the binarized projection pattern projection control unit 20b controls the projector 16, and a plurality of binarization projection pattern generation units 20a generate. Any one of the binarized projection patterns is projected onto the surface of the measurement object 14. At this time, the binarized projection pattern projection control unit 20b projects the binarized projection pattern projected onto the surface of the measurement object 14 while sequentially shifting the binarized projection pattern by a predetermined amount of movement in the width W direction.

  This amount of movement is arbitrary and may be smaller or larger than the width W, but this amount of movement becomes the minimum resolution regarding the measurement resolution of the shape measurement of the three-dimensional shape in the measurement object 14.

  Next, the image input unit 22 captures the binarized projection pattern projected on the surface of the measurement object 14 with the photographing machine 18, digitizes the image obtained by the photographing, and inputs the digitized image to the image processing unit 24. Is.

  Furthermore, the image processing means 24 processes the image sent from the image input means 22 and extracts the three-dimensional information of the measurement object 14, and the types generated by the binarized projection pattern generation unit 20a are different. A plurality of binarized projection patterns are respectively projected onto the surface of the measurement object 14, and the surface of the measurement object 14 onto which the binarized projection pattern is projected by the photographing machine 18 is a plurality of binary projections of different types. An image captured for each pattern is sent from the image input means 22, and the sent image is oversampled to obtain an oversampled binary image (details of processing for generating an oversampled binary image by oversampling will be described later). .) And an image obtained by synthesizing the generated oversampling binary image (hereinafter referred to as “oversampling space code image”). The oversampling space code image generation unit 24a that performs oversampling space code image processing and the binarized projection pattern generation unit 20a generates any one of the binarized projection patterns. An image obtained by projecting onto the surface of the measurement object 14 while sequentially shifting by a predetermined amount of movement in the W direction, and imaging the surface of the measurement object 14 onto which the binarized projection pattern is projected by the photographing machine 18 for each shift. An image (hereinafter referred to as an “oversampling phase-shifted image”) sent from the image input means 22, oversampled the sent image to generate an oversampling binary image and synthesize the generated oversampling binary image. Phase shift for performing oversampling phase shift image generation processing. Oversampling spatial code image (spatial code value) obtained by the image generation means 24b, oversampling spatial code image generation means 24a, and oversampling phase shift image (shift code value) obtained by the oversampling phase shift image generation means 24b ) And an oversampling phase shift space code image generation unit 24c that generates an oversampling phase shift space code image, and an oversampling phase shift space code image obtained by the oversampling phase shift space code image generation unit 24c. And a three-dimensional shape information acquisition means 24d for obtaining three-dimensional shape information of the measurement object 14 by processing the above.

  The three-dimensional shape information of the measurement object 14 acquired by the three-dimensional shape information acquisition unit 24d is output to the display device 12f and the like for use.

  Since the oversampling phase shift space code image, which is an image obtained by the oversampling phase shift space code image generation unit 24c, is a space code image, the three-dimensional shape information acquisition unit 24d remains the algorithm of the space coding method. Thus, the three-dimensional shape information of the measurement object 14 can be acquired. In other words, the three-dimensional shape information acquisition unit 24d can be constructed by a conventionally known technique, and three-dimensional shape information can be obtained using a conventionally known technique.

(4) Operation In the above configuration, the operation of the measurement apparatus 10 will be described with reference to the flowchart shown in FIG.

  That is, in order to obtain the three-dimensional shape information of the measurement object 14 in the measurement apparatus 10, first, in order to code the space, a plurality of binarized projection patterns having different predetermined widths W are generated (steps). S402).

Here, if the number of slits for dividing the space is n, log ₂ n different binary projection patterns must be prepared.

  Next, an arbitrary one of the binarized projection patterns generated in step S402 is selected, and an oversampling phase shift image generation process for generating an oversampling phase shift image is performed (step S404). In other words, the selected binarized projection pattern is projected onto the surface of the measuring object 14 by the projector 16 while being sequentially shifted by a predetermined movement amount in the width W direction, and the binarized projection pattern is projected by the photographing machine 18. An image obtained by photographing the surface of the measured object 14 for each shift is sent from the image input means 22, and the oversampling 2 generated by oversampling the sent image to generate an oversampling binary image. An oversampling phase shift image obtained by synthesizing the value images is generated.

  That is, in the oversampling phase shift image generation process, any one of the binarized projection patterns necessary for the oversampling spatial code image generation process described later is selected and used. The binarized projection pattern used in the image generation process will be appropriately referred to as a “shift pattern”.

  As a shift pattern, any binarized projection pattern may be used in principle, and any binarized projection pattern can obtain the same effect. However, the width W is the largest in consideration of the number of shifts. It is preferable to use a narrow binarized projection pattern, that is, an LSB pattern.

  That is, as a shift pattern, in principle, the same effect can be obtained by using any binarized projection pattern. However, in the oversampling phase shift image generation process, a binarized projection pattern for each shift. In order to capture an image of the measurement object 14 projected with the above, it is preferable to shift the LSB pattern using the LSB pattern that minimizes the number of captured images, in other words, minimizes the number of shifts.

  Further, the amount of movement for each shift when shifting the shift pattern (hereinafter referred to as “shift pitch” as appropriate) may be the pitch of the measurement resolution desired by the user of the measurement apparatus 10, and this shift pitch is the minimum resolution. It becomes. If the minimum dot pitch of the projector 16 is adopted, the measurement resolution can be maximized without being affected by the resolution of the projector 16.

  The shift pattern is shifted a plurality of times within one cycle of the pattern. That is, the shift width of the shift pattern is shifted to, for example, a range in which the phase of the LSB pattern is inverted by half phase in which the positions of the light transmission region 100a and the light non-transmission region 100b are switched.

  Here, when generating an oversampling phase shift image by synthesizing an oversampling binary image generated from an image obtained by photographing the surface of the measurement object 14 for each shift, each oversampling binary image for each shift is generated. Are added without weight (or may have the same weight) to generate an oversampling phase-shifted image that is an oversampling spatial code image having a minimum resolution of the shift pitch.

  In the oversampling phase shift image, code values are repeated at the width W interval, which is the stripe width interval of the binarized projection pattern, and a plurality of identical code values exist in the generated phase shift image. For this reason, in the oversampling phase shift image generation process, an absolute code value is not generated for the imaging space.

  Further, as will be described later, when a “gray code” is adopted for the binarized projection pattern, it is desirable to perform a bit calculation before adding.

  When the process of step S404 is completed, the process proceeds to step S406, and an oversampling spatial code image for generating an oversampling spatial code image is generated using a plurality of binary projection patterns having different predetermined widths W generated in step S402. A sampling space code image generation process is performed. That is, the projector 16 projects a plurality of different types of binarized projection patterns onto the surface of the measurement object 14, and the surface of the measurement object 14 onto which the binarized projection pattern is projected by the photographing machine 18, Images taken for each of a plurality of different types of binarized projection patterns are sent from the image input means 22, oversampling the sent images to generate an oversampling binary image, and the generated oversampling An oversampling space code image obtained by synthesizing the binary image is generated.

  That is, in the oversampling spatial code image generation process, for example, if an LSB pattern is selected as a shift pattern, a binarized projection pattern including the LSB pattern before the shift is projected onto the surface of the measurement object 14, A so-called spatial code image known in the art is generated.

  The resolution of this oversampling space code image is the stripe width of the LSB pattern, but is an absolute code for the shooting space.

  Next, an oversampling phase shift space code image generation process for generating an oversampling phase shift space code image by synthesizing the oversampling phase shift image generated in step S404 and the oversampling space code image generated in step S406 is performed. This is performed (step S408). This oversampling phase shift space code image is a combination of an oversampling phase shift image that is an image with a code value relative to the shooting space and an oversampling space code image that is an image with an absolute code value with respect to the shooting space. Therefore, the oversampling phase shift space code image generated thereby is an image having a shift pitch as a measurement resolution and an absolute code value with respect to the imaging space. That is, an absolute code image (code value) subdivided (high resolution) up to the shift pitch is generated.

  When the process of step S408 is completed, the process proceeds to the process of step S410, and the three-dimensional shape information acquisition process of acquiring the three-dimensional shape information of the measurement object 14 based on the oversampling phase shift space code image generated in step S408. I do. That is, since the oversampling phase shift spatial code image is a spatial code image, the oversampling phase shift spatial code image is treated as a spatial code image, and the three-dimensional shape information of the measurement object 14 is obtained using a conventionally known technique. To do.

  Then, the three-dimensional shape information of the measurement object 14 acquired by the three-dimensional shape information acquisition process in step S410 is output to the display device 12f and the like for use in various ways.

(5) Principle of Shift Pattern Shift Next, an image of a binarized projection pattern projected on the surface of the measurement object 14 for each shift while shifting the shift pattern (hereinafter referred to as “binarized projection pattern image”). The principle of the method of photographing will be described in more detail below. In the explanation of “(5) Shift pattern shift principle”, in order to facilitate understanding of the principle, an image obtained by photographing the surface of the measurement object 14 is oversampled for each shift of the shift pattern. The phase shift image, which is an image generated by simply synthesizing the image, and the image obtained by photographing the surface of the measurement object 14 for each of a plurality of binarized projection patterns are generated by simply synthesizing the image without oversampling. A spatial code image (a conventional spatial code image) as an image will be described as an example.

  First, in FIGS. 5A, 5B, and 5C, the light non-transmission region (the region indicated by hatching in FIG. 5) is obtained by shifting the shift pattern from the left side to the right side with a shift pitch width divided into 16 parts. The shift state of each shift pattern and the code value corresponding to each shift pitch when the light transmission region (the non-hatched region in FIG. 5) and the light non-transmission region are shifted to the reverse position are shown. Yes. In FIGS. 5A, 5B, and 5C, black 1 to n indicate how many times the light non-transmission region includes the shift pattern by shifting the shift pattern.

  Here, FIG. 5A shows a case where the shift pitch is divided into a space with the resolution as the resolution, and an image obtained by photographing the shift pattern and binary of the same pixel in each image photographed for each shift. The space is divided by simply adding the normalized values.

  For example, as shown in FIG. 5B, if the shift pattern is divided into two in advance, the number of shifts is halved, and the number of shots and the shooting time are both halved.

  Similarly, as shown in FIG. 5C, if the shift pattern is divided into four, the number of shifts is reduced to ¼, and if further divided, the number of shots is reduced and the shooting time is shortened. Can do.

  For this reason, as the shift pattern, it is more efficient to select the LSB pattern having the smallest stripe width among the binarized projection patterns, that is, the number of divisions.

  In addition, as shown in FIGS. 5B and 5C, the phase shift image includes code values that are repeated at intervals of the width W of the stripes of the binarized projection pattern. There will be multiple identical code values. For this reason, an absolute code value is not generated for the shooting space.

  However, the same code value obtained by shifting the shift pattern has a feature that it does not occur a plurality of times in the binarized values of the light transmission region and the light non-transmission region of the shift pattern.

  For example, in FIG. 5C, when the pattern divided into four by the binarized projection pattern “light non-transmission area | light transmission area | light non-transmission area | light transmission area” is used as the shift pattern, “black 1 "Has occurred in four places.

  However, only one place occurs in the “light transmission region” in the shift pattern. Similarly, there is only one code value “black 1” in the “light non-transmission region” in the shift pattern.

  Here, when a binary code pattern including a shift pattern before shifting is projected and photographed to generate a spatial code image, the resolution of the spatial code image is the stripe width of the LSB pattern, Absolute code value.

  That is, as shown in FIG. 6, the shooting space is uniquely coded such that “right light transmissive area” of the shift pattern is “space code 0” and “left light non-transmissive area” is “space code 3”. it can.

  Therefore, as shown in FIG. 7, a composition by adding together a phase shift image having a code value relative to the imaging space and a space code image having an absolute code value is not required. Thus, it is possible to generate a phase shift space code image that is an image having a shift pitch as a resolution and an absolute code value with respect to the imaging space.

  As a result, for example, the number of shots can be reduced without performing 16 shifts or shooting to divide the space into 16, so that the shooting time can be shortened.

  In the above description, the case where a binary code is used has been described. However, the principle is the same for a commonly used gray code.

  Here, FIG. 8 shows the result of processing a phase shift space code image using a known spreadsheet software using a binarized projection pattern expressed in Gray code.

  In FIG. 8, the light transmission area is represented by “1”, the light non-transmission area is represented by “0”, and the space code value is actually up to 255, but only up to 35 is displayed.

  Further, since the resolution of the projector is shifted assuming that it is four times the stripe width of the LSB pattern in the binarized projection pattern, the shift is four times if it is a binary code, but it is 7 because it is a gray code. It has been shifted times.

  G32 to G1 indicate binarized projection patterns expressed in gray code, and S1 to S7 indicate patterns obtained by phase shifting G1 (LSB).

  In the list of addition, a value obtained by simply adding the phase shift is shown. Here, the phase shift image that has been added must change from “0 to 3”, but the size and direction of change are not constant, “0 to 7” and “7 to 0”. .

  Although it can be combined with the spatial code image as it is, the calculation at the time of extracting the three-dimensional information becomes complicated. Therefore, by performing the Bit calculation shown in FIG. The direction of change is indicated by a value that matches the spatial code image generated from the binary code.

  The conversion data list shows values obtained by converting the G32 to G1 gray code patterns into binary code patterns. The binary spatial code indicates a spatial code image generated from the binary code.

  As shown in FIG. 10, the phase shift spatial code image obtained by synthesizing the phase shift image converted from the gray code to the binary code by the bit operation and the spatial code image generated from the binary code has a staircase graph as shown in FIG. In contrast to the spatial code image generated from the binary code, the phase shift spatial code image shows that the slope of the graph is linear and the resolution is improved.

(6) Generation of Oversampling Binary Image Here, when the shift width of the shift pattern is less than one pixel of the captured image, for example, a problem as shown in FIG. 11B may occur.

  That is, FIGS. 11A and 11B show images obtained by enlarging a part of an example of a phase shift image in which a relative spatial code that changes in four stages of 0 to 3 is represented by a gray scale value. However, when the shift width of the shift pattern is larger than one pixel width of the photographed image, a phase-shifted image is obtained in which the values of the four levels change in order as shown in FIG. It is done.

  However, when the shift width of the shift pattern is less than one pixel width of the photographed image, as shown in FIG. 11B, the sampling pitch for capturing the shift width is insufficient (that is, the sampling theorem is The code values that should have four levels are rounded, resulting in a phase-shifted image in which the values of the four levels change in sequence are not visible.

  In such a place as shown in FIG. 11B, in the section of the boundary between the light transmission region and the light non-transmission region of the shift pattern at each shift (hereinafter referred to as “(6) Generation of Oversampling Binary Image”). Is appropriately referred to as “pattern boundary”) (hereinafter referred to as “pattern boundary coordinates” in the section “(6) Generation of Oversampled Binary Image”). Since the spatial code cannot be obtained with high accuracy, there is a possibility that the three-dimensional coordinates cannot be calculated properly.

  Here, in order to sample the shift width of one step of the shift pattern with certainty, the shift width needs to be more than twice the sampling pitch of the image input according to the sampling theorem.

  For this reason, for example, when four stages of codes are integrated into one pixel, the sampling frequency may be multiplied by eight (by the sampling theorem, “4 × 2 = 8”).

However, if the number of captured pixels is actually increased by a factor of 8, for example, based on the VGA (Video Graphic Array) size,
640 × 8 = 5120
As a result, a 5120 pixel (pixel) camera is required as the camera 18.

  For this reason, in the present invention, an oversampling binary image is generated using an oversampling technique, and the sampling frequency is artificially multiplied.

  The generation of this oversampling binary image will be described by taking as an example a case where the sampling frequency is artificially increased by 8 times with reference to FIG. 12. First, the shift pattern is set to a shift width less than one pixel width of the photographed image. An image (hereinafter referred to as “(6) oversampling”), which is projected on the surface of the measurement object 14 while being sequentially shifted, and the surface of the measurement object 14 onto which the binarized projection pattern is projected by the photographing device 18 is photographed for each shift. In the section “Regarding the Generation of Binary Image”, it is referred to as “shift image” as appropriate.) For each shift image, a positive pattern (an image showing luminance information in a photographed state) and a negative pattern (positive image) for each shift image. When generating a binary image from the respective luminance information with the image in which the pattern is inverted, the shift direction (hereinafter referred to as the luminance information) In the section "(6) for generating the oversampled binary image" is appropriately referred. Number of pixels) to 8 times the original pixel and the "x direction". By doing so, the pattern boundary in the shift pattern can be specified with higher accuracy.

  Next, in the section where the positive pattern luminance distribution curve and the negative pattern luminance distribution curve intersect in the vicinity of the pattern boundary (hereinafter referred to as “(6) Generation of Oversampled Binary Image”) The coordinate value of xc × 8 (in FIG. 12, the crossing coordinate of the original pixel is indicated by “xc”) is obtained as a real value in units of subpixels (how to obtain this, (For example, see pages 113 to 114 of "Three-dimensional image measurement" by Seiji Iguchi and Kosuke Sato (published by Shoshodo in 1990)).

  Next, a value obtained by rounding down the fractional part of the real value obtained above is set as a coordinate value in a pixel unit of the intersection coordinate xc × 8, and a coordinate (hereinafter, referred to as “x”) on the left side in the x direction from the pixel of the intersection coordinate xc × 8. In the section “(6) Generation of Oversampled Binary Image”, the pixel of “luminance change left coordinate” is appropriately referred to as xl × 8 (in FIG. 12, the luminance change left coordinate of the original pixel). In the section “(6) Generation of Oversampling Binary Image” in the section of the right side in the x direction with respect to the pixel of the intersection coordinate xc × 8 (denoted by “xl”). When the pixel of “coordinate” is appropriately referred to as xr × 8 (in FIG. 12, the luminance change left side coordinate “xr” of the original pixel), the luminance change left side coordinate xl × 8 to the intersection coordinate xc Up to × 8 is "1" (or "0 ), And the intersection coordinate xc × 8 to the luminance change right coordinate xr × 8 is “0” (or “1”), that is, the binary image as the inverted value of the luminance change left coordinate xl × 8 to the intersection coordinate xc × 8 Is generated. In this specification, the binary image generated in this way is referred to as an oversampling binary image.

  Then, in the process of step S404 described above, oversampling binary images are generated for all the shifted images by the above-described method, and the generated oversampling binary images are synthesized, so that the number of pixels in the x direction is 8 times. An oversampling phase-shift image that is a phase-shift image that is still enlarged in size is generated.

  Here, FIG. 13 shows an oversampling phase shift image generated for the same region as the region shown in FIG. As is clear from comparison between FIG. 11B and FIG. 13, the phase shift width that could not be sampled in FIG. 11B is obtained with high accuracy.

  Further, in the process of step S406 described above, an oversampling binary image is generated for all images obtained by projecting a plurality of binarized projection patterns using the above-described method, and the generated oversampling binary image is generated. Are combined to generate an oversampling spatial code image that is a spatial code image with a size in which the pixels are enlarged eight times in the x direction.

  In step S408, the oversampling phase-shifted image generated in step S404 and the oversampling spatial code image generated in step S406 are synthesized, and the size of the pixel is expanded eight times in the x direction. An oversampling phase shift space code image that is a phase shift space code image as it is is generated.

  In step S410, three-dimensional shape information is acquired based on the oversampling phase shift space code image generated in step S408. Specifically, a three-dimensional coordinate is calculated using each pixel coordinate and code value of the oversampling phase shift space code image.

  At this time, since the number of pixels in the x direction, which is the shift direction of the shift pattern, is 8 times, it is necessary to calculate the three-dimensional coordinate value after reducing the image coordinate value to 1/8.

  Here, if the above calculation is performed for all the pixels, the number of data becomes enormous and wasteful, and therefore, the image coordinate value is set to 1 every 8 pixels in the x direction so that the number of data points is the same as when no oversampling is performed. The three-dimensional coordinate value may be calculated after setting to / 8.

  Note that if the calculation is simply performed every 8 pixels, the sub-pixel coordinate value of the pattern boundary obtained at the time of oversampling binary image generation cannot be sufficiently utilized. Sampling errors can be reduced by calculating the three-dimensional coordinate value using the coordinate value of the place where the pattern boundary is estimated as the subpixel.

(7) Operational effect of the measuring apparatus 10 As described above, by using the oversampling binary image, the pattern boundary can be accurately obtained even when photographing at a low resolution without requiring an extremely high resolution photographing machine. And the resolution of the spatial code method can be improved.

  That is, the above-described measurement apparatus 10 does not require a special configuration other than the function of shifting the shift pattern and the function of synthesizing the oversampling phase shift image and the oversampling spatial code image, and the conventional spatial coding method. Using the configuration used in the above, it is possible to generate a high-resolution spatial code image only by synthesizing the captured image, thereby improving the resolution of the three-dimensional shape measurement of the measurement object 14.

  In the measurement apparatus 10 described above, the measurement resolution depends on the shift pitch and is independent of the stripe width W of the binarized projection pattern. Depending on the resolution of the camera 18, the width of the LSB pattern stripes can be identified.

(8) Modification of Measurement Device 10 Note that the above-described embodiment may be appropriately modified as described in the following (a) to (d).

  (A) In the above-described embodiment, the case where the number of pixels is multiplied by 8 in the x direction has been described. However, the present invention is not limited to this, and any magnification can be used as long as the sampling theorem is satisfied. But you can.

  (B) In the above-described embodiment, the oversampling spatial code image generation process is performed after the oversampling phase shift image generation process. However, the present invention is not limited to this. The order of the above processes may be reversed, and after performing the oversampling space code image generation process, the oversampling phase shift image generation process may be performed.

  (C) In the above-described embodiment, the binarized projection pattern is generated. However, the present invention is not limited to this, and a plurality of binarizations having different widths W are stored in the storage means. The projection pattern may be stored in advance, and the binarized projection pattern stored in the storage unit may be read as appropriate.

  (D) You may make it combine the above-mentioned embodiment and the modification shown to said (a)-(c) suitably.

  The present invention can be used for shape acquisition in industrial design, human body shape acquisition, or building shape acquisition.

FIG. 1 is a schematic configuration explanatory diagram showing an example of an embodiment of a three-dimensional shape measuring apparatus according to the present invention. 2A, 2B, 2C, and 2D are explanatory diagrams showing examples of various binarized projection patterns. FIG. 3 is a block diagram illustrating the control system of the three-dimensional shape measuring apparatus according to the present invention. FIG. 4 is a flowchart showing the operation of the three-dimensional shape measuring apparatus according to the present invention. 5 (a), 5 (b), and 5 (c) are explanatory views showing the operation principle of the three-dimensional shape measuring apparatus according to the present invention. FIG. 6 is an explanatory diagram showing the operating principle of the three-dimensional shape measuring apparatus according to the present invention. FIG. 7 is an explanatory diagram showing the operating principle of the three-dimensional shape measuring apparatus according to the present invention. FIG. 8 is a table showing the result of processing a phase-shift space code image using a known spreadsheet software using a binary projection pattern expressed in Gray code. FIG. 9 shows the calculation contents of the Bit calculation. FIG. 10 is a graph showing a phase shift spatial code image obtained by synthesizing a phase shift image converted from a Gray code to a binary code by a Bit operation and a spatial code image generated from the binary code. FIGS. 11A and 11B are images obtained by enlarging a part of an example of a phase shift image in which relative spatial codes that change in four stages of 0 to 3 are represented by gray scale values. FIG. 12 is an explanatory diagram of a main gun for generating an oversampled binary image. FIG. 13 is an oversampling phase shift image generated for the same region as the region shown in FIG.

Explanation of symbols

10 Three-dimensional shape measuring device 12 Computer 12a Bus 12b Central processing unit (CPU)
12c Read only memory (ROM)
12d random access memory (RAM)
12e Input device 12f Display device 14 Measurement object 16 Projector 18 Camera 20 Binary projection pattern projection unit 20a Binary projection pattern generation unit 20b Binary projection pattern projection control unit 22 Image input unit 24 Image processing unit 24a Oversampling space code image generation means 24b Oversampling phase shift image generation means 24c Oversampling phase shift space code image generation means 24d 3D shape information acquisition means

Claims (4)

A three-dimensional shape measuring method for projecting a binary projection pattern onto a measurement object and measuring a three-dimensional shape of the measurement object based on an image of the measurement object onto which the binary projection pattern is projected In
A predetermined binarized projection pattern in which each width of the stripe-shaped pattern has a minimum width that can be discriminated by an image, a light transmission region and a light non-transmission of the predetermined binarized projection pattern Shift to a range where the phase is reversed by 1/2 to reverse the position of the region, and shift to the measurement object while shifting by a predetermined moving amount that becomes the minimum resolution regarding the measurement resolution of the three-dimensional shape measurement in the measurement object. Sequentially projecting and acquiring all images obtained by photographing the surface of the measurement object onto which the predetermined binarized projection pattern is projected for each shift ;
For each of the acquired images, when creating a binary image from the luminance information of each of the positive pattern and the negative pattern of the acquired image, the pixels in the shift direction satisfy the sampling theorem. The positive pattern luminance distribution curve and negative pattern luminance near the pattern boundary, which is the boundary between the light transmitting area and the light non-transmitting area, are multiplied by an integer so that the shift width is at least twice the sampling pitch of the image input. The coordinates at which the distribution curve intersects are obtained as sub-pixels as real values, the coordinates are set as pixel coordinates, the pixels on the left side of the coordinates including the coordinates are set to 1 or 0, and the pixels on the right side of the coordinates are set as inverted values. In this way, a binary image is created, and the binary image is acquired as the first type of image for all the shifted images .
A plurality of binarized projection patterns each having a different pattern width including the predetermined binarized projection pattern are respectively projected onto the measurement object, and each of the plurality of different binarized projection patterns is projected. For every image obtained by photographing the surface of the measurement object onto which each of the plurality of different binarized projection patterns is projected , every image is multiplied by an integer using the arbitrary integer in the X direction. Combining and obtaining as a second type of image , which is an image having an absolute code value with respect to the shooting space, with a shift pitch as resolution ,
The code value is obtained from the third type image synthesized by adding the first type image and the second type image, and at this time, the code value is shifted in the shift direction. The number of pixels is corrected to a value obtained by dividing the image coordinate value by the arbitrary integer for each arbitrary integer number of pixels in the shift direction, and the three-dimensional shape of the measurement object is acquired. Three-dimensional shape measurement method. The method for measuring a three-dimensional shape according to claim 1 ,
The method of measuring a three-dimensional shape, wherein a direction in which the predetermined binarized projection pattern is shifted with respect to the measurement object is the width direction. A three-dimensional shape measuring apparatus that projects a binarized projection pattern onto a measurement object and measures the three-dimensional shape of the measurement object based on the image of the measurement object onto which the binary projection pattern is projected. In
A predetermined binarized projection pattern in which each width of the stripe-shaped pattern has a minimum width that can be discriminated by an image, a light transmission region and a light non-transmission of the predetermined binarized projection pattern Shift to a range where the phase is reversed by 1/2 to reverse the position of the region, and shift to the measurement object while shifting by a predetermined moving amount that becomes the minimum resolution regarding the measurement resolution of the three-dimensional shape measurement in the measurement object. Binarized projection image acquisition means for sequentially projecting and acquiring all images obtained by photographing the surface of the measurement object onto which the predetermined binarized projection pattern is projected for each shift;
For each of the acquired images, when creating a binary image from the luminance information of each of the positive pattern and the negative pattern of the acquired image, the pixels in the shift direction satisfy the sampling theorem. The positive pattern luminance distribution curve and negative pattern luminance near the pattern boundary, which is the boundary between the light transmitting area and the light non-transmitting area, are multiplied by an integer so that the shift width is at least twice the sampling pitch of the image input. The coordinates at which the distribution curve intersects are obtained as sub-pixels as real values, the coordinates are set as pixel coordinates, the pixels on the left side of the coordinates including the coordinates are set to 1 or 0, and the pixels on the right side of the coordinates are set as inverted values. First image acquisition means for generating a binary image and acquiring the binary image as a first type of image for all shift images;
A plurality of binarized projection patterns each having a different pattern width including the predetermined binarized projection pattern are respectively projected onto the measurement object, and each of the plurality of different binarized projection patterns is projected. For every image obtained by photographing the surface of the measurement object onto which each of the plurality of different binarized projection patterns is projected, every image is multiplied by an integer using the arbitrary integer in the X direction. Second image acquisition means for combining and acquiring as a second type of image that is an image having an absolute code value with respect to the imaging space with a shift pitch as resolution;
The code value is obtained from the third type image synthesized by adding the first type image and the second type image, and at this time, the code value is shifted in the shift direction. The three-dimensional shape acquisition means for correcting the number of pixels in the shift direction to a value obtained by dividing the image coordinate value by the arbitrary integer for each arbitrary integer number of pixels in the shift direction, and acquiring the three-dimensional shape of the measurement object And a three-dimensional shape measuring apparatus . In the three-dimensional shape measuring apparatus according to claim 3 ,
The direction in which the predetermined binarized projection pattern is shifted with respect to the measurement object is the width direction.