JP2008032609A - Three-dimensional shape measuring apparatus and three-dimensional shape measuring method - Google Patents

Abstract

An object of the present invention is to provide a three-dimensional shape measuring apparatus and method thereof that are not affected by the reflectance of an object to be measured, and that each fringe of the fringe pattern light can be easily separated and the calculation error is small.
A three-dimensional shape measuring apparatus according to the present invention projects a fringe pattern light in which high bright stripes 301 and low bright stripes 302 having lower luminance than the high bright stripes 301 are alternately positioned onto a measurement object 2. A three-dimensional shape measuring apparatus 1 having a camera 4 that receives reflection of the fringe pattern light hitting the object to be measured 2 and outputs image data, and a computer 5 that generates three-dimensional coordinate data from the image data. The projection unit 3 includes a light source 31 that outputs a laser beam 30, an enlarging unit 32 that expands the laser beam 30 to a predetermined size, and a fringe pattern forming that molds the laser beam 30 spread by the enlarging unit 32 into a fringe pattern light. And means 33.
[Selection] Figure 1

Description

  The present invention relates to an apparatus and a method for measuring a three-dimensional shape of an object to be measured from image data obtained by projecting a binary stripe pattern light onto the object to be measured and photographing the projected object to be measured.

  One technique for quantifying and grasping the three-dimensional shape of a human body or an object (object to be measured) is a three-dimensional measurement method. Three-dimensional measurement methods include a contact type and a non-contact type. The contact method is a method of measuring a three-dimensional shape by directly contacting an object for measurement (probe) with an object to be measured. Non-contact type includes active measurement and passive measurement.

  A typical technique for active measurement is a pattern projection method. Using a special pattern light source such as a slit, the shape of the object to be measured is estimated from image information such as geometric deformation of the surface pattern of the object to be measured. As a representative technique of passive measurement, there is a method of collating feature points of an object to be measured by stereo vision using two cameras and acquiring three-dimensional shape information based on the principle of triangulation.

  The pattern projection method is a method of projecting pattern light onto a measured object and photographing the measured object on which the pattern light is projected from a position different from the position where the pattern light is projected. The photographed pattern light image is deformed depending on the shape of the object to be measured, and the three-dimensional shape of the object to be measured is measured by associating this image with the projected pattern light. Specifically, there are a light cutting method and a spatial coding method as a measuring method. The light cutting method is a method in which a single slit light is projected onto an object to be measured, and the slit light is scanned with the object to be measured and photographed with a camera, and three-dimensional shape information is acquired based on the principle of triangulation. . This method takes time because it is necessary to sequentially shoot with a camera at each time and repeat this until the slit light has been scanned. The spatial coding method prepares multiple binary stripe patterns with different spatial resolutions and projects them sequentially onto the object to be measured. This is a method for acquiring information on the three-dimensional shape of an object. Furthermore, a method of preparing a single multi-valued stripe pattern light instead of preparing a plurality of binary stripe patterns and performing projection and photographing a number of times is considered. For example, the invention of Patent Document 1 projects stripe pattern light having five kinds of gradations (luminances) onto an object to be measured. In the spatial coding method, it is difficult to specify the space of the object to be measured unless the respective stripes captured by projecting pattern light onto the object to be measured can be clearly separated. For this reason, the invention of Patent Document 1 projects the fringe pattern light that emphasizes the edge of the border between the fringes. Patent Document 2 proposes a method of arranging stripes so that the gradation difference between adjacent stripes is not reduced when the gradation of the stripe pattern light is increased.

  However, when the luminance is changed to multiple values, it is easily affected by the reflectance of the measured object. If the surface of the object to be measured is dark or has a metallic surface, the stripes may not be clearly captured by the camera. The invention of Patent Document 1 is effective for a dark object to be measured, but the edge portion of the stripe pattern is too bright on the metal surface, and the stripe pattern may not be separated. In the invention of Patent Document 2, separation is easy because there is an intensity difference between the fringe patterns, but depending on the surface state of the object to be measured, the fringe pattern may not be recognized correctly, and erroneous separation may occur.

Optical interferometry is known as another technique for active measurement. Patent Document 3 proposes a method for generating concentric fringe pattern light by interfering with laser light, and acquiring information on a three-dimensional shape from an image projected and photographed on an object to be measured. From the center of the circle to the outer periphery, concentric circles formed on the projection plane all have the same pitch, and the pitch is proportional to the distance. Therefore, the center of the circle of the concentric circle can be calculated from the curvature of the concentric circle, and the three-dimensional shape of the object to be measured is measured by calculating the distance on the optical axis from the pitch to the light source of the laser beam.
JP 2004-226186 A JP 2005-43333 A JP-A-2005-331413

  In the invention of Patent Document 3 described above, since a laser and a filter are used, a good fringe pattern can be captured even when the surface of the object to be measured is in the above state. However, since the captured fringe pattern is concentric, the three-dimensional coordinates must be calculated from the change in curvature, which is a method of increasing the calculation error.

  The present invention has been made in view of the above problems, and is a three-dimensional shape measuring apparatus and method thereof that are not affected by the reflectance of an object to be measured, each fringe of the fringe pattern light is easily separated, and the calculation error is small. The purpose is to provide.

  The three-dimensional shape measuring apparatus of the present invention projects a fringe pattern light in which high bright stripes and low bright stripes having lower luminance than the high bright stripes are alternately positioned on the object to be measured, and the object to be measured. In the three-dimensional shape measuring apparatus having a camera that receives the reflection of the fringe pattern light and outputs image data, and a computer that generates three-dimensional coordinate data from the image data, the projection means outputs laser light. And a fringe pattern forming means for shaping the laser light spread by the enlarging means into the fringe pattern light.

  The three-dimensional shape measuring apparatus of the present invention projects binary stripe pattern light made of laser light onto an object to be measured, receives the reflection with a camera, and acquires image data. Then, the computer generates three-dimensional coordinate data from the acquired image data. The laser beam is magnified by the magnifying means to a size that can irradiate the entire object to be measured because the light diffuses in a straight line. Then, the enlarged laser beam is shaped by a fringe pattern shaping unit to be a binary fringe pattern light, and projected onto the object to be measured.

  In the three-dimensional shape measuring apparatus of the present invention, the fringe pattern projected onto the object to be measured is not affected by the color, pattern, reflectance, etc. of the surface of the object to be measured by using laser light, and has high brightness. A distinction is made between high brightness stripes and low brightness low brightness stripes. Therefore, image data that can be easily analyzed by a computer can be acquired, and highly accurate three-dimensional coordinate data can be generated. In addition, since laser light is not easily affected by indoor lighting or outdoor natural light, there is no need to darken indoors as in the case of projectors. Can also be measured.

  The camera used in the three-dimensional shape measuring apparatus of the present invention preferably has a filter that blocks visible light and transmits laser light. By receiving only the laser beam reflected on the object to be measured with a camera, image data with a clear stripe pattern of the laser beam can be obtained.

  The fringe pattern forming means used in the three-dimensional shape measuring apparatus of the present invention is preferably a diffractive optical element. Since the diffractive optical element can condense the light by controlling the light by the diffraction phenomenon, the fringe pattern light can be easily created by condensing the laser light into the stripe pattern. One of the diffractive optical elements is a Fresnel lens or a binary lens. By using a Fresnel lens or a binary lens, it is possible to easily generate a fringe pattern light obtained by alternately condensing laser light. Since the fringe is whether the laser beam is condensed or not condensed, the boundary can be clearly divided, and image data of the measured object that can be easily analyzed can be obtained.

  The fringe pattern forming means used in the three-dimensional shape measuring apparatus of the present invention preferably forms laser light into a linear stripe pattern light. Because laser light diffuses in a straight line, for example, by using a straight slit in parallel, create a stripe pattern with a clear separation between the part where the laser light passes and the part where the laser light is blocked be able to. Since a mask having slits can be easily produced, it is possible to provide a three-dimensional measuring apparatus capable of projecting a suitable fringe pattern light without labor and cost.

  The three-dimensional shape measuring method of the present invention includes a light output step for outputting laser light, an enlargement step for expanding the laser light to a predetermined size, a high brightness fringe for the enlarged laser light, and a brightness higher than the high brightness fringe. A fringe pattern forming step for forming a fringe pattern in which low-low fringe fringes are alternately positioned, a projecting step for projecting laser light shaped into the fringe pattern onto the object to be measured by the projecting means, and the object to be measured The camera receives the reflection of the laser beam formed into the stripe pattern hit, and receives the image data signal received, the storage step for receiving the image data signal and storing it in the storage means, And a three-dimensional coordinate data generation step for generating three-dimensional coordinate data from the image data.

  The three-dimensional shape measuring method of the present invention projects binary stripe pattern light made of laser light onto an object to be measured, receives the reflection with a camera, and acquires image data. Then, three-dimensional coordinate data is generated from the acquired image data. The laser beam is expanded in an expansion process to a size that can irradiate the entire object to be measured because the light diffuses in a straight line. Then, the enlarged laser beam is formed into a binary stripe pattern light in a stripe pattern forming step and projected onto the object to be measured.

  In the three-dimensional shape measuring method of the present invention, the fringe pattern projected onto the object to be measured is not affected by the color, pattern, reflectance, etc. of the surface of the object to be measured by using laser light, and has high brightness. A distinction is made between high brightness stripes and low brightness low brightness stripes. Therefore, image data that can be easily analyzed by a computer can be acquired, and highly accurate three-dimensional coordinate data can be generated. In addition, since laser light is not easily affected by indoor lighting or outdoor natural light, there is no need to darken indoors as in the case of projectors. Can also be measured.

  The camera used in the three-dimensional shape measurement method of the present invention preferably has a filter that blocks visible light and transmits laser light. By receiving only the laser beam reflected on the object to be measured with a camera, image data with a clear stripe pattern of the laser beam can be obtained.

  The fringe pattern forming step used in the three-dimensional shape measuring method of the present invention preferably forms a fringe pattern with a diffractive optical element. Since the diffractive optical element can condense the light by controlling the light by the diffraction phenomenon, the fringe pattern light can be easily created by condensing the laser light into the stripe pattern. One of the diffractive optical elements is a Fresnel lens or a binary lens. By using a Fresnel lens or a binary lens, it is possible to easily generate a fringe pattern light obtained by alternately condensing laser light. Since the fringe is whether the laser beam is condensed or not condensed, the boundary can be clearly divided, and image data of the measured object that can be easily analyzed can be obtained.

  The fringe pattern forming step used in the three-dimensional shape measuring method of the present invention is preferably one that forms laser light into a linear stripe pattern light. Because laser light diffuses in a straight line, for example, by using a straight slit in parallel, create a stripe pattern with a clear separation between the part where the laser light passes and the part where the laser light is blocked be able to. Since a mask having slits can be easily produced, it is possible to provide a three-dimensional measurement method capable of projecting a suitable fringe pattern light without labor and cost.

  According to the three-dimensional shape measuring apparatus and the three-dimensional shape measuring method of the present invention, the fringe pattern projected on the object to be measured is changed to the surface color, pattern, reflectance, etc. of the object to be measured by using laser light. It is not affected and is clearly distinguished by a high brightness stripe and a low brightness stripe having a lower luminance than the high brightness stripe. Therefore, image data that can be easily analyzed by a computer can be acquired, and highly accurate three-dimensional coordinate data can be generated. In addition, since laser light is not easily affected by indoor lighting or outdoor natural light, there is no need to darken indoors as in the case of projectors. Can also be measured. The camera has a filter that blocks visible light and transmits laser light, so that image data with a clear stripe pattern of the laser light can be acquired.

  By using a diffractive optical element, the fringe pattern can be diffracted into a portion where the laser light is condensed and a portion where the laser light is not condensed, thereby creating a fringe pattern. One of the diffractive optical elements is a Fresnel lens or a binary lens. By using a Fresnel lens or a binary lens, a laser beam and a Fresnel lens that can easily generate fringe pattern light obtained by alternately condensing laser light. Or, according to the binary lens, the part where the laser beam is focused and the part that is not focused are clearly separated, so the image data of the object to be measured on which the pattern light with clear stripes is projected is acquired. can do.

  Alternatively, since the laser light is diffused in a straight line, a striped pattern can be formed using a mask having slits. Since the laser light passes through only the slit portion and does not diffuse, a stripe pattern with a clear separation between the portion where the laser light is projected and the portion where the laser light is blocked can be created. Since a mask having slits can be easily produced, it is possible to provide a three-dimensional measuring apparatus and method capable of projecting a suitable fringe pattern light without labor and cost.

  Hereinafter, the present invention will be specifically described with reference to examples.

(Example)
The configuration of the three-dimensional shape measuring apparatus of this embodiment is shown in FIG.

  The three-dimensional shape measuring apparatus 1 according to this embodiment projects a fringe pattern light in which high-luminous fringes 301 with high luminance and low-luminous fringes 302 with lower luminance than the high-luminous fringes 301 are alternately positioned onto the measurement object 2. And a camera 4 that receives reflection of the fringe pattern light hitting the object to be measured 2 and outputs image data, and a computer 5 that generates three-dimensional coordinate data from the image data.

  As shown in FIG. 2, the projection unit 3 includes a light source 31 that outputs a laser beam 30, an expansion unit 32 that expands the laser beam 30 to a predetermined size, and a laser beam 30 that is expanded by the expansion unit 32. It comprises a fringe pattern forming means 33 for forming light, and is controlled by the computer 5. As the laser light 30, monochromatic light of infrared light or ultraviolet light that diffuses in a straight line from one point of the light source 31 is used. The magnifying means 32 uses a collimating lens for enlarging and shaping the straight laser beam 30 oscillated from the light source 31 into a square. As shown in FIG. 3, the fringe pattern forming means 33 uses a Fresnel lens capable of controlling the laser light 30 so as to be a stripe pattern. In the Fresnel lens, a semicircular portion 331 and a circular portion 332 are alternately arranged on the surface of the lens. The projection means 3 has a fringe pattern forming means 33 for N patterns of alternating combinations of the semicircular part 331 and the circular part 332, and by switching these, as shown in FIG. The fringe pattern light can be projected.

  The camera 4 is arranged in a place where an image of an object can be taken from a position different from the projection unit 3, and a filter 42 that blocks visible light and transmits laser light 30 between the camera body 41 and the measured object 2. Have. The camera body 41 receives the reflection of the measured object 2 that has passed through the filter 42 using a digital camera, and outputs the image data to the computer 5.

  The computer 5 includes a storage device 51 that stores the image data output from the camera 4, and three-dimensional coordinate data generation means 52 that generates three-dimensional coordinate data of the measured object 2 from the stored image data.

  The three-dimensional shape measuring apparatus 1 according to the present embodiment projects the stripe pattern light, which is a light stripe pattern in which the high bright stripes 301 and the low bright stripes 302 are alternately arranged, by the projection unit 3 onto the object to be measured 2. The reflection is received by the camera 5, and the received image data is calculated by the computer 5 to generate three-dimensional coordinate data. FIG. 4 is a flowchart showing a three-dimensional shape measuring method used in the three-dimensional shape measuring apparatus 1 of this embodiment. The three-dimensional shape measuring method is executed every predetermined time during a predetermined period after the three-dimensional shape measuring apparatus 1 is activated.

  After the start of the processing of the three-dimensional shape measurement method, the projection unit 3 sets the fringe pattern forming unit 33 that can create the fringe pattern light (n = 1) for each of the high brightness stripes 301 and the low brightness stripes 302, and the light source 31. The laser beam 30 is oscillated from (light output step S1). The laser beam 30 passes through the magnifying means 32 (magnifying process S2) and the fringe pattern forming means 33 (stripe pattern forming process S3), and the fringe pattern light is projected onto the object to be measured 2 (projection process S4). The camera 5 receives the fringe pattern light of the laser beam 30 reflected on the object 2 to be measured, and outputs the received image data to the computer 5 (image receiving step S5). The computer 5 stores image data (not shown). (Memory step S6). The computer 5 instructs the projection means 3 to set the fringe pattern forming means 33 capable of creating the next fringe pattern light (n = 2), and returns to the light output step S1. S1 to S5 are repeated until all image data can be acquired for the N striped pattern forming means 33 (S7).

  Next, in the three-dimensional coordinate data generation step, the computer 5 generates a coded image from the n pattern image data stored in the storage means by a spatial coding method (S8), and from the coded image by a light cutting method. Three-dimensional coordinate data is calculated (S9).

  According to the three-dimensional shape measuring apparatus 1 and the three-dimensional shape measuring method of the present embodiment, the stripe pattern projected onto the object to be measured 2 uses the laser beam 30 so that the surface color and pattern of the object to be measured 2 can be obtained. The high bright stripes 301 having high brightness and the low bright stripes 302 having low brightness are clearly distinguished from each other without being influenced by the reflectance and the like. As a result, image data that can be easily analyzed by a computer can be acquired, and highly accurate three-dimensional coordinate data can be generated. In addition, since the laser beam 30 is not easily affected by indoor lighting or outdoor natural light, it is not necessary to darken the interior as in the case of using a projector. The original shape can also be measured. By using a Fresnel lens, the fringe pattern is easily diffracted into a portion where the laser light is condensed and a portion where the laser light is not condensed, and the stripe pattern can be easily created.

  As mentioned above, although the suitable Example of this invention was described, this invention is not limited to the said Example. For example, the fringe pattern forming means 33 can be a diffractive optical element such as a binary lens or a mask with slits in addition to the Fresnel lens. Further, the magnifying means 32 may be a simple magnifying lens capable of magnifying the laser beam 30 to a size that can cover the object 2 to be measured, instead of a collimating lens that magnifies a circle into a quadrangle.

It is a block diagram of the three-dimensional shape measuring apparatus 1 of a present Example. It is a block diagram of the projection means 3 used with the three-dimensional shape measuring apparatus 1 of a present Example. It is a shape schematic diagram of the stripe pattern formation means 33 used with the three-dimensional shape measuring apparatus 1 of a present Example. It is an example of the fringe pattern used with the three-dimensional shape measuring apparatus 1 of a present Example. It is a flowchart of the three-dimensional shape measuring method used with the three-dimensional shape measuring apparatus 1 of a present Example.

Explanation of symbols

1: Three-dimensional shape measuring device 2: Object to be measured 3: Projection means 4: Camera 5: Computer 30: Laser light 31: Light source 32: Enlarging means 33: Stripe pattern forming means 41: Camera body 42: Filter 301: High brightness stripes 302: Low brightness stripe 331: Semi-circular portion 332: Circular portion

Claims (6)

Projection means for projecting stripe pattern light on which the high brightness stripes and low brightness stripes having lower brightness than the high brightness stripes are alternately positioned on the object to be measured, and receiving the reflection of the stripe pattern light hitting the object to be measured In a three-dimensional shape measuring apparatus having a camera that outputs image data and a computer that generates three-dimensional coordinate data from the image data,
The projection means includes a light source that outputs laser light, an enlargement means that expands the laser light to a predetermined size, and a fringe pattern forming means that shapes the laser light spread by the enlargement means into the stripe pattern light. And a three-dimensional shape measuring apparatus.   The three-dimensional shape measuring apparatus according to claim 1, wherein the camera includes a filter that blocks visible light and transmits the laser light.   The three-dimensional shape measuring apparatus according to claim 1, wherein the fringe pattern forming unit is a diffractive optical element.   The three-dimensional shape measuring apparatus according to claim 3, wherein the diffractive optical element is a Fresnel lens or a binary lens.   The three-dimensional shape measuring apparatus according to any one of claims 1 to 4, wherein the fringe pattern forming means is a mask having a slit for shaping the laser light into a linear stripe pattern light. A light output process for outputting laser light;
An expansion step of expanding the laser beam to a predetermined size;
A stripe pattern forming step for forming the enlarged laser beam into a stripe pattern in which high brightness stripes and low brightness stripes having lower brightness than the high brightness stripes are alternately positioned;
A projecting step of projecting the laser beam formed into the stripe pattern onto the object to be measured by the projecting means;
An image receiving step in which a camera receives the reflection of the laser beam formed in the stripe pattern that hits the object to be measured, and outputs a signal of the received image data;
A storage step of receiving a signal of the image data and storing it in a storage means;
A three-dimensional coordinate data generation step for generating three-dimensional coordinate data from the image data.

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