JP2006308452A - Method and apparatus for measuring three-dimensional shape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for measuring a three-dimensional shape, which employ a simple structure and can precisely measure the shape of an object collectively. <P>SOLUTION: The apparatus for measuring the three-dimensional shape comprises; a projection device 3 which projects a stripe pattern 2 in the form of concentric circles onto the object 1; a photographing device 4 which photographs the stripe pattern 2; and an arithmetic processing device 5 which measures the three-dimensional shape of the object 1 based on information of a distance from the object 1 being acquired from photographing information of the stripe pattern 2. The stripe pattern 2 in the form of the concentric circles can be formed by using a projector or an optical interference projection device having a semiconductor laser, for example. The arithmetic processing device 5 can acquire the distance information based on a pixel number representing the minimum or maximum value of image density of the photographed stripe pattern 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a three-dimensional shape measurement method and apparatus for measuring a three-dimensional shape of an object.

  Various methods have been proposed for measuring the shape of an object. Typical methods include a stereo image method, a light section method, and an optical interference method suitable for high-precision measurement. In the stereo image method, for example, two right and left object images with different viewpoints are taken in, parallax is calculated by extracting corresponding points of both images, and the distance to the object is obtained by the principle of triangulation. is there.

  In addition, the light cutting method is, for example, that the light source and the imaging surface are arranged geometrically known, and the angle of the light emitted from the light source with respect to the line (base line) composed of the emission part and the imaging surface and the imaging surface Based on the principle of triangulation, the distance to the object is obtained from the angle between the base line and the line connecting the reflected image and the image on the object.

Further, in the optical interferometry, for example, as described in Patent Document 1, light emitted from a laser light source is divided into two parts using a beam splitter or the like, one of which is irradiated onto an object, and the other is used as reference light. In this method, the mirror is irradiated to return to the original optical path, and the reflected light from the object and the reference light are overlapped to interfere with each other. This method is characterized in that the position and displacement can be measured with a resolution less than the wavelength.
JP 2000-171209 A

  However, the stereo image method has a simple device configuration, but cannot measure an object with a monotonous texture, or there is no characteristic image information in the two left and right images, and there is ambiguity in determining the corresponding points. There is a problem that measurement accuracy is lowered. In addition, the optical cutting method is excellent in measurement accuracy, but it takes time to measure, the apparatus configuration is complicated and expensive, or the entire object must be irradiated and scanned, and the measurement time There is a problem that it takes a long time. Furthermore, the optical interferometry enables high-accuracy measurement in a lump, but the optical system is complicated and the apparatus is large and expensive. That is, there are problems that optical parts such as a beam splitter and a reflecting mirror are necessary, the number of parts is large, and the cost is high. In addition, assembly of these parts requires high positional accuracy, and is troublesome and costly.

  Accordingly, an object of the present invention is to provide a three-dimensional shape measurement method and apparatus capable of solving these problems and performing high-precision shape measurement of objects all at once with a simple apparatus configuration.

  The object is to project a concentric striped pattern onto an object using a projector, photograph the striped pattern, and measure the three-dimensional shape of the object based on distance information from the striped pattern photographing information to the object. This is achieved by a three-dimensional shape measurement method that performs the following. The object is to project a concentric striped pattern on the object, photograph the striped pattern, and measure the three-dimensional shape of the object based on distance information to the object acquired from the striped pattern photographing information. The three-dimensional shape measurement method is achieved by the three-dimensional shape measurement method, wherein the distance information is acquired based on a pixel number representing a minimum value or a maximum value of the captured image density of the striped pattern. Here, the concentric striped pattern can be formed using an optical interference projection device using a projector or a semiconductor laser.

  A three-dimensional shape measuring apparatus according to the present invention includes a projection device that projects a concentric striped pattern on an object using a projector, an imaging device that captures the striped pattern, and an object acquired from shooting information of the striped pattern. And an arithmetic processing unit for measuring the three-dimensional shape of the object based on the distance information. The three-dimensional shape measuring apparatus according to the present invention includes a projection device that projects a concentric striped pattern on an object, an imaging device that captures the striped pattern, and a distance to the object acquired from the striped pattern imaging information. An arithmetic processing unit that measures the three-dimensional shape of the object based on the information, and the arithmetic processing unit determines the distance information based on a pixel number that represents a minimum value or a maximum value of the captured image density of the striped pattern. To get. Here, the concentric striped pattern can be formed using an optical interference projection device using a projector or a semiconductor laser.

  ADVANTAGE OF THE INVENTION According to this invention, the three-dimensional shape measurement method and apparatus which can perform the highly accurate shape measurement of an object collectively with a simple apparatus structure can be obtained.

  FIG. 1 is a diagram showing an embodiment of a three-dimensional shape measuring apparatus according to the present invention. In this embodiment, as shown in the figure, a projection device 3 that projects a concentric striped pattern 2 onto an object 1, an imaging device 4 that captures the striped pattern 2, and an object acquired from the shooting information of the striped pattern 2 And an arithmetic processing unit (PC) 5 that measures the three-dimensional shape of the object 1 based on the distance information up to 1. In this embodiment, the arithmetic processing device 5 is a personal computer (PC) connected to the outside of the imaging device 4, but may be built in the imaging device 4.

  In FIG. 1, the projection device 3 and the imaging device 4 are separated from each other in the vertical direction on the paper surface, and the lens principal points of the projection device 3 and the imaging device 4 are arranged at different positions. A concentric striped pattern 2 is projected from the projection device 3 onto the object 1 at a predetermined angle of view 6. This is imaged at a predetermined angle of view 7 by the imaging device 4. This concentric striped pattern 2 may be formed using a projector, or may be formed using an optical interference projection device using a semiconductor laser (LD). The optical interference projection apparatus used in the present invention is configured as follows, for example.

FIG. 2 is a diagram illustrating an example of an optical interference projection apparatus used in the present invention. The optical interference projection apparatus of this example is a combination of a semiconductor laser light source and a lens that forms a concentric stripe pattern (concentric interference pattern). Using this optical interference projection device, concentric circles having equal intervals are formed. As shown in FIG. 2, the optical interference projection device 21 is composed of a semiconductor laser light source 22 having a wavelength of 850 nm and a ring-shaped lens 23 that forms a concentric interference pattern. The lens outer diameter was 6 mm. The cross section of the lens entrance surface by a plane passing through the optical axis was an aspherical surface of x = 0.3 * (y−1.5) ^1.55 (unit: mm). Here, x is the optical axis and the light traveling direction is positive, and y is a radial axis perpendicular to the optical axis. The light exit surface of the lens 23 is a concave spherical surface having a radius of curvature R = −62 mm. The refractive index of the lens material was 1.51, and the lens thickness on the optical axis was 3 mm.

  Light emitted from the semiconductor laser light source 22 was incident on the lens 23 as parallel light by the collimator lens 24. In this case, the light that has passed above the optical axis is irradiated to the object via the ray trajectory 25. Similarly, the light that has passed below the optical axis is irradiated to the object via the ray trajectory 26. The light reaching the same point (interference point) 27 on the object interferes because it is a laser beam emitted from the same light source. In this way, the laser light emitted from one light source is projected onto the object so that it is virtually emitted from two light sources on the optical axis plane.

  When the distance from the lens exit surface to the projection plane is 3 m, the pitch of all the concentric interference patterns formed on the projection plane is 0.85 to 0.86 mm from the center of the circle to the outer periphery. It was found from the simulation results. This is shown in FIGS. 3 (a) and 3 (b). That is, it was found that if the optical axis of the light source is perpendicular to the plane, the pitch of the concentric interference pattern is almost the same everywhere in the plane. This pitch is proportional to the distance. Therefore, the distance on the optical axis from the concentric circle pitch to the optical interference projector can be obtained.

  The relationship between the pitch and distance of this concentric circle interference pattern is stored in a table in the storage device (not shown) of the arithmetic processing unit 5 in FIG. If the position of the pixel number representing the minimum value or maximum value of the pitch or concentric circle interference pattern (sine curve) is known, the distance from the imaging device to the object is uniquely determined.

  Next, the three-dimensional shape measuring method in the present invention will be described. For convenience of explanation, it is assumed that the optical axes of the projection apparatus and the imaging apparatus can be regarded as substantially coaxial, and that the measurement object is a plane and faces the optical axis of the imaging apparatus. Graphs representing the density gradient of the captured image in the a direction of the object 1 in FIG. 1 are shown in FIGS. The vertical axis of each graph is the density of the captured image (the value is large when the color is dark), and the optical axis direction is the origin. The horizontal axis is the pixel number. The origin is the center of a concentric circle. The graph draws a sine curve. In the arithmetic processing unit 5 of FIG. 1, the number of a plurality of minimum values and maximum values from the origin is counted. The pixel number representing the minimum value or the maximum value whose number is known can uniquely represent the distance. Therefore, the three-dimensional shape measurement of the object can be performed by combining the distance information of each pixel.

  The example of FIG. 4 represents the time when the distance from the imaging device to the object is 50 cm. That is, when the first minimum value is the 10th pixel, the distance between the object and the imaging apparatus is uniquely determined to be 50 cm by referring to the above-described table of PC5. The example of FIG. 5 shows a case where the distance from the imaging device to the object is 100 cm. When the object is separated, the angle of view of the projection apparatus is larger than that of the imaging apparatus, so the period of the sine curve is increased, and the pixel number representing the first minimum value is 18th from the 10th pixel of 50 cm. Change to the pixel eye. That is, when the first minimum value is the 18th pixel, the distance between the object and the imaging device is uniquely determined to be 100 cm by referring to the above-described table of PC5. In this way, the three-dimensional shape measurement of the object is performed by combining the distance information of the pixel number representing the minimum value or the maximum value whose number is known.

  In the case of FIG. 1, the object 1 is a plane and faces the optical axis of the imaging device 4. Therefore, the density gradient of the captured image of the concentric interference pattern is the same as that in the a direction even in directions other than the a direction of the object 1. A simple sine curve. However, when the object 1 is not directly facing the imaging device 4, the period of the sine curve in the captured image is not constant. This will be described next.

  FIG. 6 is a diagram for explaining a three-dimensional shape measurement method when an object is not directly facing the imaging apparatus. As shown in the figure, when the object 61 is not directly facing the imaging apparatus 4, the period of the sine curve of the captured image in the a direction of the object 61 is constant, but in other b directions and c directions, etc. The period of the sine curve in the captured image is not constant. However, the distance is calculated in the same manner as in the case of FIG. 1 from the relationship with the pixel number representing the minimum value or the maximum value that is known from the origin. Also in this example, the relationship between the period (pitch) and distance of the sine curve is stored in a table in the storage device (not shown) of the PC 5 in FIG. 1, so that the minimum pitch or concentric interference pattern (sine curve) is minimized. If the position of the pixel number representing the value or the maximum value is known, the distance from the imaging device to the object is uniquely determined. It is possible to measure the three-dimensional shape of the object by combining the distance information of the pixel number representing the minimum value or the maximum value that is known.

  FIG. 7 is a diagram showing another embodiment of the three-dimensional shape measuring apparatus according to the present invention. This embodiment is different from the embodiment of FIG. 1 in that the optical axes of the projection device 3 and the imaging device 4 are made to coincide with each other by a half mirror 71 as shown in the figure, but the other is the same as the embodiment of FIG. . Also in the present embodiment, the lens principal points of the projection device 3 and the imaging device 4 are arranged at different positions. A concentric striped pattern 2 is projected from the projection device 3 onto the object 1 through the half mirror 71 at a predetermined angle of view 6. This is imaged by the imaging device 4 via the half mirror 71. The concentric stripe pattern 2 may be formed using a projector, or may be formed using an optical interference projection device using a semiconductor laser (LD). An advantage of using the projector is that the user can easily change the striped pattern with a predetermined pitch according to the shape of the measurement object.

  In the present embodiment, the three-dimensional shape measurement of the object can be performed by the same method as the embodiment of FIG. That is, also in this embodiment, since the relationship between the period (pitch) and distance of the concentric striped sine curve is stored in a table in a storage device (not shown) of the PC 5, the pitch or concentric interference pattern is stored. If the position of the pixel number representing the minimum value or maximum value of (sine curve) is known, the distance from the imaging device to the object is uniquely determined. It is possible to measure the three-dimensional shape of the object by combining the distance information of the pixel number representing the minimum value or the maximum value that is known. According to the present embodiment, a high-precision measurement type device can be obtained.

  As described above, according to the present invention, highly accurate three-dimensional shape measurement of objects can be performed collectively with a simple apparatus configuration. The measurement method according to the present invention is particularly suitable, for example, for measuring the degree of paper curl and the like.

  The present invention relates to a three-dimensional shape measurement method and apparatus for measuring a three-dimensional shape of an object, and has industrial applicability.

It is a figure which shows one Example of the three-dimensional shape measuring apparatus which concerns on this invention. It is a figure which shows an example of the optical interference projector used by this invention. (A), (b) is a figure which shows the simulation result of the concentric-circle interference pattern formed with an optical interference projector. It is a graph which shows an example of the density gradient of the captured image in the a direction of the object 1 of FIG. It is a graph which shows the other example of the density gradient of the captured image in the a direction of the object 1 of FIG. It is a figure for demonstrating the three-dimensional shape measurement method when an object is not facing with respect to an imaging device. It is a figure which shows the other Example of the three-dimensional shape measuring apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Object 2 Concentric striped pattern 3 Projection apparatus 4 Imaging apparatus 5 Arithmetic processing apparatus (PC)
6 Projection device angle of view 7 Imaging device angle of view 21 Optical interference projection device 22 Semiconductor laser 23 Ring-shaped lens 24 Ring-shaped lens 25, 26 Ray locus 27 Interference point (interference pattern)
71 half mirror

Claims (8)

  Projecting a concentric striped pattern onto an object using a projector, photographing the striped pattern, and measuring a three-dimensional shape of the object based on distance information to the object acquired from the striped pattern photographing information A characteristic three-dimensional shape measuring method.   A three-dimensional shape measurement method for projecting a concentric striped pattern onto an object, photographing the striped pattern, and measuring the three-dimensional shape of the object based on distance information to the object acquired from photographing information of the striped pattern The distance information is acquired on the basis of a pixel number representing a minimum value or a maximum value of the captured image density of the striped pattern.   The three-dimensional shape measuring method according to claim 2, wherein the concentric striped pattern is formed using a projector.   3. The three-dimensional shape measuring method according to claim 2, wherein the concentric striped pattern is formed using an optical interference projection device using a semiconductor laser.   A projection device that projects a concentric striped pattern onto an object using a projector, an imaging device that captures the striped pattern, and a three-dimensional image of the object based on distance information to the object acquired from shooting information of the striped pattern A three-dimensional shape measuring apparatus comprising: an arithmetic processing unit that performs shape measurement.   A projection device that projects a concentric striped pattern on an object, an imaging device that photographs the striped pattern, and a three-dimensional shape measurement of the object based on distance information to the object acquired from the striped pattern photographing information A three-dimensional shape measuring apparatus, comprising: an arithmetic processing device, wherein the arithmetic processing device acquires the distance information based on a pixel number representing a minimum value or a maximum value of the captured image density of the striped pattern.   The three-dimensional shape measuring apparatus according to claim 6, wherein the concentric striped pattern is formed using a projector.   The three-dimensional shape measuring apparatus according to claim 6, wherein the concentric striped pattern is formed using an optical interference projection apparatus using a semiconductor laser.

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