JP5055191B2 - 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 of an object to be measured.

  Conventionally, a so-called phase shift method is known as a method for measuring the three-dimensional shape of an object to be measured by non-contact and automatic processing. The phase shift method uses a plurality of fringe pattern images captured under illumination conditions with sinusoidal fringe pattern lights whose phases are shifted from each other, that is, a plurality of luminance distribution data, and pixel points for one phase state determined for the entire image. Each phase is obtained, and the distribution data of the phase is used as basic data for determining the three-dimensional coordinates. The three-dimensional shape measurement result is obtained from the phase distribution data and the geometric conditions of imaging, and is obtained as a distance image in which the three-dimensional coordinates of the surface of the measurement object are assigned to each pixel.

  When performing three-dimensional shape measurement using the phase shift method, if there are parts with different reflectivities on the surface of the object being measured, such as characters or patterns, measurement errors occur at the boundaries between these characters or patterns and the background part. To do. This is because the luminance of the pixel of interest in the boundary portion is affected by the luminance of the surrounding pixels and is blurred and changes from the true luminance. This blur is due to, for example, a blur due to a focal blur at the time of imaging or a modulation transfer function characteristic of a lens. When the fringe pattern image is blurred, the phase distribution data as the basic data includes an error, and a measurement error occurs.

  The generation of the error will be described with reference to FIGS. 23 to 28 by simulation. FIG. 23 shows an image G obtained by imaging a measurement region including regions with different reflectivities under uniform illumination, and FIG. 24 shows a change in luminance value along the x0 direction in the image G of FIG. As shown in these figures, for a target area having contrast where the bright part (area w2) and the dark part (areas w1 and w3) have binary luminance values L1 and L2 under uniform illumination. Compare with blurring. 25 (a) to 25 (d) show that the phase change δφ is changed from 0 (initial phase state) to π / 2, π, and 3π / 2 under the illumination whose brightness changes in a sine wave shape in the x direction. The calculated value of the luminance change along the x0 direction is shown. This is unblurred data. 26A to 26D are data obtained by performing a Gaussian moving average process with a standard deviation σ on the luminance changes of FIGS. 25A to 25D and forcibly blurring the luminance changes by calculation. is there. FIG. 27 shows the phase distribution calculated from FIGS. 25A to 25D and the phase distribution calculated from FIGS. 26A to 26D in an overlapping manner. FIG. 28 shows an enlarged portion D where the phase difference ΔP occurs in FIG. As shown in FIGS. 27 and 28, the phase value with blurring indicated by the broken line at the position of the light / dark boundary xb is changed from the correct phase value without blurring indicated by the solid line, and the error of the phase difference ΔP is changed. Have.

  The generation of the measurement error of the three-dimensional coordinate due to the above-described phase value error will be described. FIG. 29 shows a pinhole model for identifying a three-dimensional measurement point in three-dimensional measurement by the phase shift method. The fringe pattern projection apparatus includes a pattern generation unit 22, and the imaging apparatus (camera) includes an imaging element 31. Point A is the optical center of the fringe pattern projector, point C is the optical center of the camera, and point O is the intersection of the optical axis of the fringe pattern projector and the optical axis of the camera. The phase value obtained from the image captured by the camera has a one-to-one correspondence with the coordinates on the pattern generation unit 22 inside the projection apparatus. Therefore, when the phase is obtained for a certain pixel in the image sensor 31, the position of the point P on the pattern generation unit 22 and the position of the point Q on the image sensor 31 corresponding to this are specified.

  Further, the position of the point M to be measured is obtained as the intersection M of the extension lines of the straight line AP and the straight line CQ. When the above-described phase value error occurs, the position of the point P on the pattern generation unit 22 is recognized as a point P1 slightly shifted according to the phase value error. At this time, the position of the measured point is the intersection M1 of the extension line of the straight line A-P1 and the straight line CQ. That is, due to the phase value error, the error corresponding to the length of the line segment M-M1 becomes the error of the three-dimensional measurement value.

  In the phase shift method having the above-described characteristics, if there is a part with different reflectance on the object to be measured, the brightness state of that part does not reflect the surface shape and a measurement error occurs. The object is painted white and measured. Therefore, the three-dimensional shape measurement by the phase shift method is performed on a white-painted prototype stage object, for example, in order to verify whether a product manufactured based on the three-dimensional CAD has a correct shape. It is rarely used for in-line measurement in the actual production process.

In addition, in the phase shift method, in addition to the difference between the viewing direction of the camera and the projection direction by the projection device, self-concealment (so-called occlusion), shadows, diffuse reflection, etc. In order to eliminate the influence, it has been proposed to increase the measurement accuracy by projecting the stripe pattern light from a plurality of different directions or rotating the object to be measured (see, for example, Patent Document 1).
JP-A-7-19825

  However, as described above, the conventional phase shift method is hardly used for in-line measurement in an actual production process. In addition, the measurement method based on the phase shift method as described in Patent Document 1 described above cannot solve the measurement error caused by the difference in the reflectance of the surface of the object to be measured.

  The present invention solves the above-mentioned problems, and with a simple configuration, a measurement object in which areas with different reflectances such as characters and patterns are mixed on the surface and a measurement object in which a shadow due to self-concealment occurs are also present. It is an object of the present invention to provide a three-dimensional shape measurement method and apparatus by a phase shift method that can improve measurement accuracy.

In order to achieve the above-mentioned object, the invention according to claim 1 is directed to projecting and imaging a fringe pattern whose brightness changes in a sinusoidal shape on an object to be measured three or more times with different phases, and using a plurality of obtained images. In a three-dimensional shape measurement method for obtaining a three-dimensional coordinate of an object to be measured at each pixel by a phase shift method, an imaging unit is installed above the measurement region of the object to be measured, and is projected onto a plane including the optical axis of the imaging unit A measurement step of setting two optical axes, projecting a fringe pattern onto a measurement region independently from each direction of the optical axis for projection, and capturing two types of three-dimensional coordinates by imaging with the imaging unit; step by looking contains a calculating step, the calculating the average value of the two three-dimensional coordinates obtained corresponding to a point on the image sensor of the imaging unit, the fringe pattern from one of the two projection optical axis To project When the shadow image is generated, the region which extends the portion of the shadow arbitrary distance, those using three-dimensional coordinates based on the captured image by projecting the stripe pattern from the other projection optical axis It is.

  According to a second aspect of the present invention, in the three-dimensional shape measurement method according to the first aspect, the two projection optical axes are set symmetrically with respect to the optical axis of the imaging unit.

A third aspect of the present invention, the three-dimensional shape measuring method according to claim 1 or claim 2, the projection lens for projecting a fringe pattern from the imaging unit of the imaging lens or the two projection optical axis, A telecentric lens is used for either.

A fourth aspect of the present invention, in the three-dimensional shape measuring method according to any one of claims 1 to 3, to project a fringe pattern from the imaging unit of the imaging lens, and the two projection optical axis For this purpose, a telecentric lens is used for each projection lens.

A fifth aspect of the present invention is a three-dimensional shape measurement apparatus using the three-dimensional shape measurement method according to any one of the first to fourth aspects.

According to the first aspect of the present invention, an average value of two types of three-dimensional coordinates can be used as a measurement result, so that a three-dimensional coordinate measurement error caused by a phase value error or random noise can be reduced. Highly accurate measurement is possible. Further, the measurement error of the three-dimensional coordinates due to the error of the phase value generated around the shadow portion due to self-hiding can be eliminated, and the measurement accuracy can be improved.

  According to the second aspect of the present invention, the measurement error of the three-dimensional coordinates caused by the phase value error can be canceled out, so that regions having different reflectivities due to characters, patterns, etc. are mixed on the surface. Measurement accuracy can be improved even for an object to be measured in which an error occurs.

According to the third aspect of the invention, since the optical characteristics can be improved by using the light emitted from the projection device and the light incident on the imaging unit as parallel rays in the space on the measured object side, the measurement accuracy can be improved.

According to the invention of claim 4 , the same effect as that of claim 3 can be obtained.

According to the invention of claim 5, the phase shift method that can improve the measurement accuracy even for a measurement object in which a shadow due to self-concealment occurs or an area with different reflectivity due to characters or patterns is mixed on the surface is used. A three-dimensional shape measuring apparatus can be provided.

(First embodiment)
A three-dimensional shape measuring apparatus according to the first embodiment will be described with reference to FIGS. The configuration shown in FIG. 1 is common to the other embodiments, and is also referred to in the other embodiments. Further, in the present embodiment and the next second embodiment, the shape measurement of a three-dimensional surface without self-hiding is described, and the shape measurement of an object to be measured having a shadow due to self-hiding is described in the third and fourth. The embodiment will be described.

  1 and 2 show the configuration of a three-dimensional shape measuring apparatus. The three-dimensional shape measuring apparatus 1 is an apparatus that can accurately measure a three-dimensional shape in a non-contact manner using a phase shift method even for an object to be measured in which regions having different reflectances due to characters, patterns, etc. are mixed on the surface. Thus, the three-dimensional coordinates of the measured object can be obtained for each pixel in the image. The three-dimensional shape measuring apparatus 1 basically performs a three-dimensional shape measurement by a normal phase shift method a plurality of times, and determines the best measurement result from the measurement result, so that a high-precision three-dimensional shape is finally obtained. Enables shape measurement.

  For this reason, the three-dimensional shape measuring apparatus 1 projects two patterns (first and second) of fringe patterns that project the fringe patterns onto the measurement area 10 of the measurement object from different directions (in the opposite direction in this example). Control unit 2a, 2b (generically described as stripe pattern projection unit 2), imaging unit 3 installed above measurement region 10 and imaging measurement region 10, stripe pattern projection unit 2 and imaging unit 3 And a three-dimensional measurement processing unit 4 that performs calculation for obtaining a three-dimensional shape of the measurement region 10 based on data output from the fringe pattern projection unit 2 and the imaging unit 3. The measurement region 10 is a surface region of an object to be measured having an arbitrary three-dimensional uneven surface.

  The fringe pattern projection units 2a and 2b include illumination units 21a and 21b (collectively 21), stripe pattern generation units 22a and 22b (collectively 22), and projection optical units 23a and 23b (collectively 23). I have. The illumination unit 21 is configured using a light source and a condenser lens that converts light from the light source into parallel light. The fringe pattern generation unit 22 is a part that generates a fringe pattern that becomes a parallel stripe on a plane, in which the light transmittance changes in a sinusoidal shape along one direction, and uses a transmissive liquid crystal plate and a polarizing plate. Composed. The projection optical unit 23 includes a lens for projecting the fringe pattern created by the fringe pattern generation unit 22 onto the measurement target.

  The projection optical axes 20a and 20b (collectively 20) of the fringe pattern projection units 2a and 2b are set to be included in a plane including the optical axis 30 of the imaging unit 3. The fringe pattern projection units 2a and 2b do not need to actually prepare a plurality of devices, and the two-line operation may be realized by changing the arrangement of the one-line fringe pattern projection unit 2. This is because images are not captured simultaneously under illumination from a plurality of systems. However, in consideration of the time required for changing the imaging setup, it is preferable to use a plurality of systems without moving them.

  The transmission type liquid crystal plate and the polarizing plate constituting the above-described stripe pattern generation unit 22 are a combination of a reflection type liquid crystal plate and a polarizing plate, and a film on which the stripe pattern is baked and a film for shifting a predetermined phase are moved. An equivalent function may be realized by a combination with an actuator or a digital mirror device (DMD).

  The imaging unit 3 is an imaging optical unit that includes an imaging element 31 for photoelectrically converting light from the measurement region 10 to generate image data, and an optical lens for forming an image of the measurement region 10 on the imaging element 31. 32.

  The three-dimensional measurement processing unit 4 includes a fringe pattern data creation unit 41, a central control unit 42, a memory 43, a calculation unit 44, a display unit 45 that displays measurement results and captured images, and the like. And necessary input / output units (not shown). Moreover, the calculating part 44 is provided with the measurement result determination part 4a for determining a final measurement result. Such a three-dimensional measurement processing unit 4 is configured using a computer having a general configuration including a CPU, an external storage device, a display device, an input device, and the like, and a set of processes and functions on the computer. Can do.

  The display unit 45 can be configured by a liquid crystal display, a CRT, or the like used as a normal computer peripheral device. The input / output unit is configured by a simple switch group or by using a mouse, a keyboard, or the like in a normal computer peripheral device. The fringe pattern data creation unit 41 generates data that is the basis of the fringe pattern generated in the fringe pattern generation unit 22 of the fringe pattern projection units 2a and 2b.

  The central control unit 42 performs transmission control of data based on the fringe pattern to be sent to the fringe pattern projection units 2a and 2b, projection control of the fringe pattern projection units 2a and 2b, imaging control of the imaging unit 3, and the like. In addition to shifting the phase of the fringe pattern projected onto the image at a constant phase interval, the imaging by the imaging unit 3 of the measurement region 10 illuminated under each phase is controlled. In addition, the central control unit 42 controls the display unit 45, the input / output unit, and other units.

  The memory 43 is a place where data necessary for three-dimensional shape measurement is recorded. Data regarding the spatial arrangement of the imaging unit 3 and the stripe pattern projection units 2a and 2b, the resolution of the imaging unit 3, the pitch of the stripe pattern, the amount of phase shift, Data such as image data captured by the imaging unit 3 is recorded.

  The calculation unit 44 obtains the phase value at each pixel of the captured image in the phase shift method using the data recorded in the memory 43, and based on the obtained phase value, the three-dimensional measurement region 10 is obtained for each pixel point. Calculate the shape coordinates.

(Spatial arrangement of the fringe pattern projection units 2a and 2b and the imaging unit 3)
In the present embodiment, the imaging unit 3 is installed above the measurement area 10 of the measurement object, and the optical axis 30 of the imaging unit 3 and the projection optical axes 20a and 20b of the two stripe pattern projection units 2a and 2b. Are set in the same plane, and the two fringe pattern projection units 2a and 2b are arranged so as to sandwich the imaging unit 3 therebetween. The three optical axes 20a, 20b, and 30 are arranged so as to intersect with each other at one point O, but it is not always necessary to do so.

  Here, for the sake of convenience, coordinate axes X, Y, Z in the space constituting the right-handed orthogonal coordinate system and coordinate axes x, y in the image plane are defined. It is assumed that the Z axis is the optical axis 30 of the imaging unit 3 and the X axis is on a plane including three optical axes. The coordinate axes x and y can be defined to match or correspond to the coordinate axes X and Y. For convenience, the x-axis direction may be referred to as the horizontal direction.

(Arrangement of stripe pattern SP)
The fringe pattern SP used in the phase shift method of the present embodiment is a pattern in which the brightness changes in a sine wave shape along a certain direction (hereinafter, pattern change direction 5). In the present embodiment, the pattern change direction 5 is set in the X and x axis directions.

(Description of operation)
The three-dimensional shape measurement apparatus 1 according to the present embodiment improves measurement accuracy even for an object to be measured in which a phase value error occurs due to a mixture of regions having different reflectivities due to characters and patterns on the surface of the object to be measured. Explain what you can do. The main point is that the shape measurement is performed using the two stripe pattern projection units 2a and 2b arranged so as to sandwich the image pickup unit 3, and the two kinds of measurement results are averaged to obtain individual stripe pattern projection units 2a and 2b. This is because the measurement errors of the three-dimensional coordinates caused by the error of the phase value in the measurement by 2b can be canceled each other.

  FIG. 3 shows the relationship between the measurement light and each optical path of the illumination light from the fringe pattern projection units 2a and 2b and the incident light to the imaging unit 3. As a conventional problem in the phase shift method, referring to FIG. 23 to FIG. 28 and FIG. 29, the occurrence of an error in the phase value in the object to be measured in which regions having different reflectances are mixed, and the phase value The generation of measurement accuracy due to errors was explained. Here, the three-dimensional shape measuring apparatus 1 of the present embodiment includes two fringe pattern projection units 2a and 2b, thereby reducing the measurement error of the three-dimensional coordinates using the average value of the two types of three-dimensional coordinates as a measurement result. The principle that can be done is shown.

  FIG. 3 is obtained by adding a second projection device having an optical center as a point B in the three-dimensional measurement pinhole model by the phase shift method described in FIG. In this figure, two fringe pattern projection units 2a and 2b are provided with pattern generation units 22a and 22b, respectively, and the imaging unit 3 is provided with an imaging device 31. Points A and B are the optical centers of the stripe pattern projection units 2a and 2b, point C is the optical center of the imaging unit 3, and point O is the optical axes 20a and 20b of the stripe pattern projection units 2a and 2b and the optical axis 30 of the imaging unit 3. Is the intersection of The points A and B are arranged so as to face each other across the point C. The phase value obtained from the image captured by the imaging unit 3 has a one-to-one correspondence with the coordinates on the pattern generation units 22a and 22b. Therefore, when the phase is obtained for a certain pixel in the image sensor 31, the position of the point P on the pattern generation unit 22a and the position of the point Q on the image sensor 31 corresponding thereto are specified.

  Further, the position of the point M to be measured is obtained as the intersection M of the extended lines of the straight line AP and the straight line CQ. When the above-described phase value error occurs, the position of the point P on the pattern generation unit 22a is recognized as a point P1 slightly shifted according to the phase value error. At this time, the position of the measured point is the intersection M1 of the extension line of the straight line A-P1 and the straight line CQ. Due to the error in the phase value, the error corresponding to the length of the line segment M-M1 becomes the error in the three-dimensional measurement value. The optical center is a virtual point where incident light or outgoing light converges to one point in each optical device.

  In the fringe pattern projection unit 2b, if the point on the pattern generation unit 22b corresponding to the point M to be measured is R, the point R is an intersection of the straight line B-M and the plane of the pattern generation unit 22b. Here, the case where the same error as the phase obtained by the combination of the fringe pattern projection unit 2a and the imaging unit 3 occurs also in the phase obtained by the combination of the stripe pattern projection unit 2b and the imaging unit 3 will be considered. In this case, the position of the point R is erroneously recognized as the point R1 due to the phase value error. As a result, the position of the measurement point obtained by the fringe pattern projection unit 2b is an intersection M2 of the extended lines of the straight line B-R1 and the straight line CQ. In this case, considering the straight line CQ, the point M1 and the point M2 have a positional relationship with the point M interposed therebetween.

  The above means that the measurement error that occurs when the fringe pattern projection units 2a and 2b are used becomes an error having a different sign. Therefore, by obtaining an average value of the coordinate value of the measured point M1 and the coordinate value of the point M2, the error is canceled out, and a measurement result close to the coordinate value of the point M that is the original position can be obtained. This is the principle of reducing the measurement error of the three-dimensional coordinates in the three-dimensional shape measuring apparatus 1.

  Here, the concept of an error vector is introduced. The error generated on the pattern generation unit 22a of the fringe pattern projection unit 2a is represented by the direction and magnitude of the vector on the pattern generation unit 22a from the position without error on the pattern generation unit 22a to the position moved by the error. Can do. This vector is defined as an error vector Va (in the figure, the size is enlarged and displayed). Similarly, an error vector Vb on the pattern generation unit 22b is defined.

  When the above error vectors Va and Vb are used, the condition for the positional relationship between the point M1 and the point M2 between the points M on the straight line CQ is that the error vectors Va and Vb have the optical axis 30. When the components in the orthogonal direction are components va and vb, it is expressed that the directions of the components va and vb are the same. For example, in the case of FIG. 3, this means that an error occurs on the same side so that the point P1 moves to the right of the point P and the point R1 moves to the right of the point R.

  The condition of the apparatus for the phase value error generated during the measurement to satisfy the above-described condition is that the fringe pattern projection units 2a and 2b are arranged so as to face each other with the imaging unit 3 interposed therebetween, and two fringe pattern projections are performed. This is satisfied when the same stripe pattern SP is projected from the parts 2a and 2b. This condition is defined as [Projection unit arrangement condition 1].

  Here, the same stripe pattern SP projected from the stripe pattern projection units 2a and 2b means that at least the pattern change direction 5 of the stripe pattern SP is the same direction. For example, in the case of FIG. 1 and FIG. 2, the two pattern change directions 5 are both the X direction.

FIG. 4 shows the relationship between the angle formed by the two projection optical axes 20a and 20b and the relative error. Conditions for reducing the error (relative error Re) remaining after performing the averaging process for obtaining the average value of the measured values after satisfying the above-mentioned [projection part arrangement condition 1] [projection part arrangement condition 2] Will be explained. As shown in FIG. 4, the angle θ _A formed by the optical axis 20a of the fringe pattern projection unit 2a and the optical axis 30 of the imaging unit 3 is fixed at 20 °, and the optical axis 20b of the fringe pattern projection unit 2b and the imaging unit 3 are fixed. When the angle θ _B formed with the optical axis 30 is changed, the relative error Re is minimum when θ _B = 20 °, that is, θ _A = θ _B. This condition is the [projection part arrangement condition 2] to be obtained.

As described above, the angles are equal (θ _A = θ _B ) when the two projection optical axes 20 a and 20 b are set to be symmetrical with respect to the optical axis 30 of the imaging unit 3, for example. It holds. In the case of line symmetry, the three optical axes 20a, 20b, and 30 intersect with each other at one point O. However, this is not necessarily required in order to satisfy θ _A = θ _B. Further, it will be described that [projection part arrangement condition 1] and [projection part arrangement condition 2] are not necessarily strictly satisfied, but the measurement accuracy can be improved by approaching such a condition.

  According to the three-dimensional shape measuring apparatus 1 of the present embodiment, the measurement errors of the three-dimensional coordinates caused by the phase value error can be canceled out by satisfying the above-mentioned [projection unit arrangement conditions 1, 2]. Therefore, it is possible to improve the measurement accuracy even for an object to be measured in which a phase value error occurs due to a mixture of regions having different reflectivities due to characters and patterns on the surface of the three-dimensional object to be measured.

(Second Embodiment)
A three-dimensional shape measuring apparatus according to the second embodiment will be described with reference to FIG. The three-dimensional shape measuring apparatus 1 of the present embodiment uses a telecentric lens 11 as the imaging lens of the imaging unit 3 in the first embodiment, and is a projection for projecting the fringe pattern SP from the two fringe pattern projection units 2a and 2b. Telecentric lenses 12a and 12b are used for the lenses, respectively.

  Even if the [projection part arrangement conditions 1 and 2] in the first embodiment is satisfied, the error does not become zero. This is because the rays in the space on the measured object side from the elements on the image pickup device 31 of the image pickup unit 3 and the pattern generation units 22a and 22b of the stripe pattern projection units 2a and 2b are not parallel to each other.

  Therefore, the above-mentioned problems are solved by using telecentric lenses 11, 12a, and 12b as the lenses on the objective side of the pattern generation units 22a and 22b and the objective side of the image sensor 31. FIG. 5 shows that the object side telecentric lens 11 is also applied to the image pickup unit 3 by using the object side telecentric lenses 12a and 12b having the same projection field of view in the two fringe pattern projection units 2a and 2b satisfying [projection unit arrangement condition 2]. The positional relationship between the points M, M1, and M2 when used is shown.

  The positions on the telecentric lens 12a of the chief rays passing through the points P and P1 on one pattern generation unit 22a are Pt and Pt1. Similarly, points R, R1, Rt, Rt1 on the other pattern generation unit 22b and the telecentric lens 12b are defined. At this time, the straight line Pt-M and the straight line Pt1-M1 are parallel. The straight line Rt-M and the straight line Rt1-M2 are parallel. Therefore, a proportional relationship of (M−M1) :( M−M2) = (Pt−Pt1) :( Rt−Rt1) holds for the distance between the points. Further, since the lenses having the same projection field are used in the two fringe pattern projection units 2a and 2b, a proportionality of (Pt−Pt1) :( Rt−Rt1) = (P−P1) :( R−R1) is established. A relationship is established.

  The distance between two points (P-P1) and the distance (R-R1) are the magnitudes of phase value errors when the respective fringe pattern projection units 2a and 2b are used. , (M−M1) = (M−M2). Therefore, by averaging the measurement result obtained using one stripe pattern projection unit 2a or 2b and the measurement result obtained using the other stripe pattern projection unit 2b or 2a, the measurement error is reduced. Can be offset. This does not depend on where the points P, Q, and R are on the pattern generation units 22a and 22b or on the image sensor 31, that is, on the pattern generation units 22a and 22b or on the image sensor 31. It holds on the entire surface.

  As described above, the averaging process can make the error zero in any case only when the object side telecentric is used for the imaging unit 3 and the two fringe pattern projection units 2a and 2b. is there. However, even if only one of the imaging unit 3 and the two fringe pattern projection units 2a and 2b is made object-side telecentric, the error cannot be reduced to zero, but the error is more than that of the non-telecentric system. Can be improved. Accordingly, such a configuration can also be effectively employed when there are restrictions in terms of apparatus cost and apparatus dimensions.

  According to the three-dimensional shape measuring apparatus 1 of the present embodiment, the optical characteristics can be improved by using the light emitted from the fringe pattern projection units 2a and 2b and the light incident on the imaging unit 3 as parallel rays in the space on the object to be measured. Therefore, measurement accuracy can be improved.

(Third embodiment)
A three-dimensional shape measurement method according to the third embodiment will be described with reference to FIGS. The present embodiment shows a method for performing three-dimensional shape measurement using the three-dimensional shape measurement apparatus 1 in the first and second embodiments described above. In the present embodiment, description will be given of improving measurement accuracy when a shadow occurs in a measurement region of an object to be measured due to self-hiding.

  FIG. 6 shows an outline of this measurement method. In this measurement method, two sets of point cloud data are acquired independently in the first measurement step (# 1, # 2), and based on the differential intensity from the two sets of three-dimensional shape data in the second calculation step. Data selection or averaging processing is performed for each pixel to determine the best three-dimensional shape data (# 3).

  As shown in FIGS. 7A, 7B, and 7C, the first half of the process is a process of performing imaging, phase restoration, and three-dimensional shape restoration, and includes two stripes under the control of the central control unit 42. This is performed using the pattern projection units 2a and 2b. This process is the same as the measurement using a general phase shift method. Further, as shown in FIG. 7D, the latter half of the process is a process of selecting from two three-dimensional coordinate data or combining them by averaging, and is performed by the measurement result determining unit 4a.

  FIG. 8 shows an overall flowchart of this measurement method. Two sets of point cloud data are acquired (S1, S2), and then data processing is performed for each pixel from the two sets of three-dimensional shape data (loops LP1-LP11, LP2-LP22).

(Point cloud data acquisition)
FIG. 9 shows a subroutine for performing the point cloud data acquisition process (S1, S2) in the flowchart described above. This process is common to the fringe pattern projection units 2a and 2b. In the following, the subscript k in expressions and variables represents A or B for identifying the fringe pattern projection units 2a and 2b. In this point cloud data acquisition process, three-dimensional shape data and differential intensity data are acquired as point cloud data.

  Here, the term “point cloud data” will be described. In the three-dimensional shape measurement using the phase shift method, various images are captured and referenced by the imaging unit 3 fixed at a fixed position with respect to the measurement region 10. These images have the same number of pixels and the same pixel arrangement under the same x and y coordinate systems (see FIG. 1). Each pixel corresponds to a specific point on the surface of the measurement region 10 in a three-dimensional space defined by the XYZ coordinate system (see FIG. 1). The point cloud data is a general term for data relating to these specific points, that is, data such as luminance, XYZ coordinate values, and differential intensity of luminance at that point for a predetermined image. Usually, for each type of data, the same number of data as the number of pixels is collected (that is, a point group).

  As described above, the point cloud data is data acquired for each pixel in the image, and the point cloud data acquisition processing includes the image data acquisition processing (S10) for capturing an image and the calculation unit 44 for each pixel. This is performed by image processing for acquiring point cloud data (loops LP3 to LP33, LP4 to LP44). In this image processing, processing relating to the phase shift method (S11, S12) and acquisition of differential intensity data are performed (S13).

FIG. 10 shows a subroutine for performing the image data acquisition process (S10). In this subroutine processing, four image data under illumination with four stripe pattern lights for the four-phase phase shift method and one image data under uniform illumination are acquired. . The image by the striped pattern illumination is recorded as luminance data I _ki (x, y), i = 0, 1, 2, 3 (LP5 to LP55), and the image by the uniform illumination is represented as luminance data I _k (x, y). It is recorded (S24-S26). Here, x and y are coordinates indicating the position of the pixel on the image, and x = 0, 1,..., M, y = 0, 1,. In addition, although the example which uses the phase shift method of 4 phases is shown here, in order to acquire three-dimensional shape data, not only this but the phase shift method of 3 phases or 5 phases or more can also be used.

(Acquire image data with fringe pattern light)
In the phase change loop (LP5 to LP55), the central control unit 42 changes the value of the variable i to i = 0, 1, 2, 3 for each loop to generate projected fringe pattern data (S20), fringe pattern. Projection (S21), imaging (S22), and luminance data recording (S23) are performed. That is, the central control unit 42 changes the phase of the sine wave by π / 2 and fetches the image data into the memory 43 four times as luminance data.

  More specifically, the fringe pattern data creation unit 41 of the three-dimensional measurement processing unit 4 generates projection fringe pattern data (S20). The generated fringe pattern data is transferred to the fringe pattern projection units 2a and 2b under the control of the central control unit 42, and the fringe pattern projection units 2a and 2b of the object to be measured as the fringe pattern SP whose brightness changes sinusoidally. It is projected onto the measurement area 10 (S21).

The fringe pattern L _ki (u, v) created by the fringe pattern generation units 22a and 22b is expressed by the following equation (1). In the fringe pattern, the brightness changes in a sine wave shape. Here, (u, v) are coordinates on the transmission type liquid crystal plate constituting the fringe pattern generation unit 22 of the fringe pattern projection units 2a and 2b, b (u, v) is a bias value, and a (u, v) ) Is the amplitude, φ (u) is the initial phase (phase when i = 0), and iπ / 2 is the phase shift amount from the initial phase (i = 0, 1, 2, 3).

The imaging unit 3 images the measurement area 10 of the measurement object on which the fringe pattern is projected (S22), and the luminance data I _ki (x, y) including the luminance data of each captured pixel is a three-dimensional measurement process. It is recorded in the memory 43 of the unit 4 (S23).

(Image data acquisition by uniform illumination)
Next, the central control unit 42 projects illumination light with uniform brightness on the measurement area 10 of the measurement object by the fringe pattern projection units 2a and 2b (S24), and images by the imaging unit 3 (S25). Luminance data I _k (x, y) in uniform illumination without a stripe pattern is recorded in the memory (S26).

An image without a fringe pattern can be obtained by imaging the state of uniform illumination where the fringe pattern is not projected as described above, but the image of the fringe pattern obtained for the phase shift method measurement is synthesized. It can also be acquired. That is, the following two methods can be used as a specific method for obtaining the luminance data _Ik .
(1) An image having a constant brightness without a pattern is projected from the projection unit and picked up.
(2) I _k = I _k0 + I _k1 + I _k2 + I _k3

(Phase calculation)
Next, returning to FIG. 9, the phase calculation (S11) will be described, and then the three-dimensional data calculation (S12) will be described. First, from the luminance value I _ki (x, y) (i = 0, 1, 2, 3) of each pixel obtained by the above-described fringe pattern projection and imaging, the phase φ ( x, y) is calculated (S11). The calculation is performed in the calculation unit 44.

  This phase φ (x, y) is distribution data of a phase (phase value) for each pixel point determined by coordinates (x, y) in one phase state determined for the entire image. A so-called distance image in which the three-dimensional coordinates of the surface of the object to be measured are assigned to each pixel is obtained from the phase distribution data represented by this equation and the geometric conditions of imaging. More specifically, the fringe pattern SP projected on the measurement region 10 is modulated (distorted) by the three-dimensional shape of the measurement region 10. Since the phase φ (u) at the time of projection and the phase φ (x, y) obtained from the captured image are originally the same, the coordinates on the image sensor 31 of the imaging unit 3 and the coordinates on the liquid crystal plate Can be obtained. Therefore, the three-dimensional coordinates X, Y, Z of the measurement area 10 on the surface of the object to be measured are obtained by the following equation (3) by the principle of triangulation (S12).

Here, (X, Y, Z) is the coordinate of the point on the surface of the measurement region 10 in the three-dimensional space, and u (φ) is the coordinate of the pixel on the liquid crystal plate (the coordinate in the direction in which the phase changes). P ^c and p ^p are parameters obtained by calibration of the imaging unit 3 and the fringe pattern projection units 2a and 2b, respectively, and satisfy the following expressions (4) and (5).

Based on the above processing, spatial coordinate data (X, Y, Z) at the pixel position (x, y) on the image is obtained as a three-dimensional shape measurement result by a combination of one stripe pattern projection unit 2a or 2b and the imaging unit 3. ) Is defined, three-dimensional point group data P _k (x, y; X, Y, Z) is obtained. The three-dimensional point cloud data represented in this way is a discrete function having a three-dimensional coordinate vector (X, Y, Z) as a value since one point on the image corresponds to one point of the three-dimensional point. .

By the way, about the point of the to-be-measured area | region (shadow part) where the fringe pattern SP is not projected by concealment, and the pixel of the to-be-measured area | region point which does not fully reflect light toward the imaging part 3, 3 correctly. Dimensional coordinates cannot be obtained. Therefore, the point where the amplitude A (x, y) of the sine wave defined by the following equation (6) is a certain value or less is treated as such an unmeasurable point. A three-dimensional coordinate corresponding to the pixel of such a point is not defined. A point where the three-dimensional coordinates are not defined is expressed as P _k (x, y) = NULL using the symbol NULL.

(Differential intensity data calculation)
In the process shown in FIG. 9, calculation is performed to obtain differential intensity data (differential intensity image) for luminance data I _k (x, y) in uniform illumination (S13). The differential intensity image is obtained by calculating a differential value of luminance data in the x direction (horizontal direction) of the image and taking the absolute value (that is, intensity). For this calculation, for example, a Sobel filter can be used. A differential value D _k (x, y) in the x direction corresponding to the luminance data I _k is obtained by the following equation (7).

  The differential intensity of the luminance data is obtained in the x direction of the image as in the above equation for the following reason. That is, the x direction is the direction of the illumination light illuminated by the fringe pattern projection units 2a and 2b (the directions are different from each other), and a shadow due to the self-concealment of the object to be measured occurs in front of or behind the x direction. The shadow boundary has a direction component orthogonal to the x direction as a dominant component. In order to detect such a shadow area, the differential intensity in the x direction is effectively used.

With the above processing, two sets of point cloud data acquisition by the fringe pattern projection units 2a and 2b in steps S1 and S2 of FIG. 8 is completed, and the three-dimensional shape data P _k (x, y; X, Y, Z). , K = A, B, differential intensity data D _k (x, y), k = A, B are acquired. Hereinafter, pixel data determination and averaging processing by selecting the best three-dimensional shape data for each pixel in FIG. 8 will be described (loops LP1 to LP11, LP2 to LP22). Note that P _k (x, y; X, Y, Z) is expressed as P _k (x, y), and the final selected three-dimensional shape data is P (x, y; X, Y, Z). Or P (x, y).

(Determination of pixel data)
In the loop processing in FIG. 8 (loops LP1 to LP11, LP2 to LP22), whether or not P _A (x, y) and P _B (x, y) exist for a specific pixel specified by coordinates x and y. If only one of them is present, the value is selected and P (x, y) = P _A (x, y) or P (x, y) = P _B (x, y ) (S6, S8). If none exists (No in S3 and S7), P (x, y) is not present, and a predetermined abnormal value such as “999” is given to P (x, y) ( S9).

  The above-described processing (S6, S8, S9) is a measurement result due to concealment (so-called occlusion that can cause a shadow) due to a three-dimensional solid shape generated depending on the projection direction from each of the fringe pattern projection units 2a, 2b. This is a response process when there is no more. Thereby, when one of the two types of measurement results is affected by concealment, the other can be selected as a correct measurement result and the concealed portion can be complemented.

When both P _A (x, y) and P _B (x, y) exist (Yes in S3 and S4), the pixel data selection decision based on the differential intensity is performed (S5). In this process, the pixel data to be processed is differentiated depending on whether it is the data of the boundary part of the shadow generated in the image by concealment or the data away from the shadow, and is optimized respectively. It is considered that the luminance value has changed from the normal value (blurred) due to the influence of the shadow at the shadow boundary. Differential intensity is used to detect shadow boundaries.

FIG. 11 shows a subroutine for performing the pixel data determination process (S5) based on the above-described differential intensity. Here, the differential intensity data _{D k (x, y),} k = A, B easily and differential intensity _D A, expressed as _{D B.} For the pixel at the coordinates x, y currently being processed, the differential intensity difference D _A −D _B is compared with a predetermined threshold T, and if the difference is greater than the threshold (D _A −D _B > T, Yes at # 10). , P (x, y) = P _B (x, y) (# 11). Conversely, if the differential intensity difference D _A −D _B is smaller than the threshold T, that is, if − (D _A −D _B )> T (Yes in # 12), then P (x, y) = P _A (x, y) is set (# 13).

If the difference D _A −D _B is not larger than the threshold T and smaller than −T, that is, if the absolute value of the difference is equal to or smaller than the threshold and | D _A −D _B | ≦ T (# 10 , # 12, No), and the average value is calculated to be P (x, y) = (P _A (x, y) + P _B (x, y)) / 2 (# 14).

The principle of the above selection and averaging process will be further described with reference to FIGS. Figure 12 (a) shows an image I _A captured under uniform illumination from a direction LA by fringe pattern projection unit 2a, a shadow due to concealment occurs along the y-direction in the region 15. FIG. 12 (b), the same measurement area and the by fringe pattern projection unit 2b shows an image I _B captured under uniform illumination from the direction LB, is not generated shadow in the region 15.

FIGS. 13A and 13B are differential intensity images D _A and D _B obtained from the above-described images I _A and I _B , respectively, according to the above equation (7). In the image D _A, it observed traces traces the boundary portion of the shadow region 15 and region 16, in the image D _B, is not observed trace.

FIG. 14 (a), the three-dimensional shape measurement data of the measurement region there is a step corresponding to the image I _A above, variable value measurements of Z-coordinate at a y-coordinate values (Y coordinate value) for the X coordinate As shown. In this measurement result, the measurement value in the region x1 (the true coordinate value of the broken line is not obtained) due to the concealment by the step, and the deviation from the true value occurs in the region x2 which is the boundary portion due to the influence of the shadow. ing.

Figure 14 (b) shows the measured values of the Z coordinate corresponding to the image I _B described above as well. In this measurement result, since no shadow is generated, a result along the true value is obtained. The regions x1 and x2 correspond to the above-described regions 15 and 16.

FIGS. 14A2 and 14B2 are diagrams corresponding to the above-described images I _A and I _B , respectively. Here, in the image I _A, region a1 and the shadow portion due to concealment as regions x1, and in the boundary portion of the shadow region a2, the other partial regions a3 as region x2. In the image _{I B,} the portion corresponding to the region a1, a2, a3, and regions b1, b2, b3.

The process of step S8 in FIG. 8 described above is a process that employs the measurement value in the area b1, and the process of step # 11 in FIG. 11 is a process that employs the measurement value in the area b2, and step # in FIG. The process 14 is a process that employs an average value of the measurement values in the area a3 and the area b3. With regard to these processes, P _A (x, y) and P _B (x, y) are complementary to each other, and when one side has a shadow and the other cannot have a shadow, or both cannot shadow. By complementing each other, the measurement accuracy of P (x, y) can be improved.

FIG. 15 (a) shows the change in the x direction of the luminance value I _Ax and the differential intensity D _Ax (which is an absolute value) for a certain y value in FIG. 14 (a2), and FIG. 14 shows changes in the x-direction of the luminance value I _Bx and the differential intensity D _Bx in FIG. From these figures, it can be seen that the region x2 can be detected by the difference in differential intensity (D _A -D _B ). In other words, it is possible to determine that a portion having a large differential intensity difference between I _A and I _B is a location where a shadow boundary is formed on either side, and a three-dimensional point with no shadow can be selected. .

This is because in the case of textures (characters and patterns) on the object surface, the differential intensity is almost the same regardless of the projection from either, whereas in the case of shadows created by either projection due to concealment Uses the fact that a large differential intensity value appears only on one side. Therefore, for example, in step # 10 in FIG. 11, since D _A −D _B > T is established and the region a2 is detected, the measured value P _B (x, y) in the region b2 is set as P (x, y). ) Is adopted.

  According to the three-dimensional shape measurement method of this embodiment, the measurement data is selected based on the differential intensity obtained by differentiating the luminance along the illumination direction from the three-dimensional shape measurement data acquired by the two stripe pattern projection units 2a and 2b. In addition, since the average value of the measurement data is calculated and used as the measurement result, the optimum measurement result is obtained for the shadow portion due to concealment, the shadow boundary portion, and the portion that is not the shadow or shadow boundary. It is possible to improve the accuracy of three-dimensional shape measurement. Moreover, according to the averaging process, the influence of random noise can be reduced, and the accuracy of three-dimensional shape measurement can be improved.

  Further, since the three-dimensional shape measuring method of the present embodiment uses only the device characteristics due to the two fringe pattern projection units 2a and 2b being arranged to face each other (FIGS. 1 and 2), each fringe pattern This is a process that does not depend on the direction of the pattern change direction 5 of the fringe pattern SP projected by the projection units 2a and 2b.

(Fourth embodiment)
A three-dimensional shape measurement method according to the fourth embodiment will be described with reference to FIGS. In the present embodiment, the method of obtaining (specific method) the concealment portion (region a1) and the shadow boundary portion (region a2) in the third embodiment described above is not a differential image, but a differential image, 2 This is performed by the value processing and the expansion processing. Accordingly, the point cloud data acquisition part is the same as in the third embodiment.

Figure 16 (a) shows an image I _A captured under uniform illumination from the left in the drawing by fringe pattern projection unit 2a, and the shadow S _A is generated by concealment to the right, FIG. 16 ( b) is the same measurement area and the by fringe pattern projection unit 2b shows an image I _B captured under uniform illumination from the right, the shadow S _B are generated on the left side.

FIG. 17A shows a difference image (I _A −I _B ) between the two images, and FIG. 17B similarly shows a difference image (I _B −I _A ). In this difference processing, for example, when the luminance value of the dark part of the image is set to zero and the luminance value of the bright part is set to a positive value corresponding to the brightness, the portion corresponding to the shadow (dark part) in one image is Extracted from the bright part of the image. A negative value of the difference between the luminance values is a dark part in the image.

FIGS. 18A and 18B show binary images G _A and G _{B in which the} difference images (I _A −I _B ) and (I _B −I _A ) are converted into light and dark (black and white) binary values with a predetermined threshold. It is. This process, shadow _{S A} portion of the image _{I A} is extracted as an area _{e A} the binary image _{G B,} shadow _{S B} portion in the image _{I B} is extracted as a region _{e B} to the binary image _{G A} .

19 (a) and 19 (b) show an expansion 2 in which the bright portions, that is, the regions e _A and e _B are expanded in the binarized images G _A and G _B to form expansion regions E _A and E _B , respectively. These are the digitized images G _AE and G _BE . This expansion process is a process in which the surrounding pixels are white by a predetermined pixel number α, for example, α = 5, for each pixel in the bright part (white part). By this processing, the peripheral part of the extracted shadow area is expanded (expanded) by the number of pixels α, and the shadow boundary part is taken into the extended areas E _A and E _B.

FIG. 20 shows a flowchart of processing until point cloud data is acquired and the above-described extended areas E _A and E _B are generated. Steps S31 and S32 are the same as steps S1 and S2 in FIG. In step S33, a so-called difference image I _D (x, y) = I _D = I _A −I _B is calculated, which is composed of the difference in luminance value of each pixel. Each pixel in the difference image generally has a positive / negative difference value, and a pixel having a large absolute value corresponds to a shadow portion due to concealment.

In order to clarify the shadow portion due to the above-described concealment, binarization is performed with positive and negative threshold values (D _TH > 0 and −D _TH ), and binarized images G _A and G _B are calculated (S34). . When I _D (x, y) ≧ D _TH , the pixel value is 1 (bright), and when I _D (x, y) <D _TH , the pixel value is 0 (dark). The thus obtained image G _{A (x,} y) is an image having a portion of the shadow under I _B as a light unit (see description of FIGS. 16 to 19). Similarly, when I _D (x, y) ≦ −D _TH , the pixel value is 1 (bright), and when I _D (x, y)> − D _TH , the pixel value is 0 (dark). The image G _B (x, y) obtained in this way is an image having a shadow portion in I _A as a bright portion.

Next, in order to include the boundary portion of the shadow in the shadow portion described above, the pixels having the value 1 in the images G _A (x, y) and G _B (x, y) are expanded by α (constant) pixels, respectively. The obtained images are _designated as G _AE (x, y), G _BE (x, y) (S35).

Pixel regions having a value of 1 in the two images in which the bright parts are expanded are extracted as regions E _A and E _B each including a shadow boundary portion (S36).

(Determination of pixel data)
FIG. 21 shows a processing routine corresponding to the xy loop portion in the flowchart of FIG. 8 of the third embodiment. In the xy loop processing (loops LP1 to LP11, LP2 to LP22), the presence of P _A (x, y) and P _B (x, y) is present for a specific pixel (target pixel) designated by coordinates x and y. If it is judged and none of them exists (No in S3 and S7), P (x, y) is not present, and a predetermined abnormal value such as “999” is set to P (x, y). (S42).

Further, if at least one is present (Yes in S41), the pixel of interest is determined whether the area _{E B,} if the _{E B} (Yes in S43), P (x, y ) = P _A (x, y) is set (S44). Further, if not the _{E B} (No in S43), it is judged further whether the area _{E A,} if the _{E A} (Yes in _{S45), P (x, y} ) = P B (x, y) (S46).

When the pixel of interest is not in any of the areas E _A and E _B (No in S45), an average value is calculated, and P (x, y) = (P _A (x, y) + P _B (x, y )) / 2 (S47).

  According to the three-dimensional shape measurement method of the present embodiment, an appropriate measurement result can be obtained for the shadow portion due to concealment and the boundary portion of the shadow without depending on the discrete differential intensity based on the difference in luminance value between adjacent pixels. Can be reliably executed, measurement errors can be reduced, and highly accurate measurement can be performed. In addition, the measurement method of the present embodiment is a process that does not depend on the direction of the pattern change direction 5 of the fringe pattern SP projected by each of the fringe pattern projection units 2a and 2b, as in the third embodiment. It is.

(Fifth embodiment)
FIG. 22 shows a three-dimensional shape measurement apparatus and measurement method according to the fifth embodiment. This embodiment is the same as the first or second embodiment in parallel to each other, in which the pattern change direction 5 of the stripe pattern SP projected by the stripe pattern projection units 2a and 2b is shifted from the X-axis direction (x-axis direction). The direction is different, and the other points are the same.

  According to the three-dimensional shape measurement method and apparatus of the present embodiment, as in the first or second embodiment, the two stripe pattern projection units 2a and 2b are arranged at positions facing each other, and each stripe pattern Since the direction of the pattern change direction 5 of the fringe pattern SP projected by the projection units 2a and 2b is the same, the measurement error of the three-dimensional coordinates caused by the phase value error is the same as in the first and second embodiments. Can be offset each other, and the measurement accuracy can be improved even for an object to be measured in which areas having different reflectivities due to characters, patterns, and the like are mixed on the surface and a phase value error occurs.

  Further, according to the three-dimensional shape measurement method and apparatus of the present embodiment, since the two fringe pattern projection units 2a and 2b are arranged at positions facing each other, similarly to the third and fourth embodiments, Without depending on the direction of the pattern change direction 5 of the fringe pattern SP projected by each fringe pattern projection unit 2a, 2b, measurement data loss or shadow boundary due to occlusion caused by illumination from one side Data damage in the part can be supplemented by measurement data from illumination from the other side.

  The present invention is not limited to the configuration shown in the above embodiments, and various modifications can be made. For example, the configurations of the above-described embodiments can be combined with each other. Further, the stripe pattern SP used in the phase shift method does not necessarily have to be a pattern in which the brightness changes in a sine wave shape, and may be a stripe pattern in which the brightness changes periodically.

1 is a schematic configuration diagram of a three-dimensional shape measuring apparatus according to a first embodiment of the present invention. The top view which shows the positional relationship of the projection part of an apparatus same as the above, an imaging part, and a fringe pattern. The top view explaining the relationship between each optical path of the illumination light from the projection part in the same apparatus, and the incident light to an imaging part, and a measurement error. The graph which shows the relationship between the angle which two optical axes for projection in the same apparatus form, and a relative error. The top view which shows each optical path of the illumination light from the projection part in the three-dimensional shape measuring device which concerns on 2nd Embodiment, and the incident light to an imaging part. The flowchart which shows the outline | summary of the three-dimensional shape measuring method which concerns on 3rd Embodiment. (A)-(d) is a schematic conceptual diagram which shows the main point of a method same as the above in steps. The flowchart explaining a method same as the above. The flowchart of point cloud data acquisition in a method same as the above. The flowchart of the image data acquisition in a method same as the above. The flowchart of the pixel data determination in a method same as the above. (A) and (b) are images taken by illuminating the same measurement region from different directions. (A) and (b) are x direction differential images about the image of Drawing 12 (a) and (b). (A) is a graph showing the three-dimensional shape data of the measurement region including the concealed region as a Z-coordinate value with respect to the X coordinate, (b) is a graph showing the three-dimensional shape data measured under the condition of no concealment, (A1) is an image of the measurement region in (a), and (b1) is an image of the measurement region in (b). 14A is a graph of luminance values and differential values in the x-axis direction in the image of FIG. 14A2, and FIG. 14B is a graph of luminance values and differential values in the x-axis direction of the image in FIG. 14B2. (A) and (b) are images taken by illuminating the same measurement region from different directions for explaining the three-dimensional shape measurement method according to the fourth embodiment. (A) is a difference image obtained by subtracting the image of FIG. 16 (b) from the image of FIG. 16 (a), and (b) is a difference image obtained by subtracting the image of FIG. 16 (a) from the image of FIG. 16 (b). (A) and (b) are images obtained by binarizing the images of FIGS. 17 (a) and 17 (b), respectively. (A) and (b) are images obtained by expanding the white pixel region in the images of FIGS. 18 (a) and 18 (b), respectively. The flowchart of the point cloud data acquisition in the method same as the above, and pre-processing. The flowchart of the pixel data determination in a method same as the above. The top view which shows the positional relationship of the projection part, imaging part, and fringe pattern for demonstrating the three-dimensional shape measuring method and apparatus which concern on 5th Embodiment. The image under the uniform illumination of the measurement area | region containing the area | region where the reflectance differs in the past and this invention. The graph which shows the luminance value change along the x0 direction in the image of FIG. (A) to (d) in the case of changing the phase change amount from the initial phase 0 to π / 2, π, and 3π / 2 under the illumination in which the brightness changes sinusoidally in the x direction in the images of FIGS. The graph which shows the calculated value of the luminance value change along x0 direction. (A)-(d) is a graph of the state which carried out the moving average process to the luminance value of FIG.25 (a)-(d), respectively, and blurred the luminance change. The graph showing the change in the x direction of the initial phase calculated from FIGS. 25A to 25D and the graph showing the change in the x direction of the initial phase calculated from FIGS. Graph. The graph which expanded the D section of FIG. The top view explaining the relationship between each optical path of the illumination light from the projection part in the phase shift method, and the incident light to an imaging part, and a measurement error.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 3D shape measuring device 2, 2a, 2b Stripe pattern projection part 3 Imaging part 4 Measurement processing part 10 Measurement area 11, 12a, 12b Telecentric lens 20, 20a, 20b Projection optical axis 30 Imaging part Optical axis SP Stripe pattern X , Y, Z 3D coordinates

Claims (5)

A fringe pattern whose brightness changes in a sine wave shape is projected onto an object to be measured three or more times with different phases, and the three-dimensional coordinates of the object to be measured at each pixel are obtained by a phase shift method using the obtained images. In the 3D shape measurement method to be obtained,
An imaging unit is installed above the measurement area of the object to be measured, two projection optical axes are set in a plane including the optical axis of the imaging unit, and the measurement area is independently set from each direction of the projection optical axis. A measurement step of projecting a fringe pattern and capturing an image by the imaging unit to obtain two types of three-dimensional coordinates;
Seen including a calculation step, the calculating the average value of the two three-dimensional coordinates obtained corresponding to a point on the image sensor of the imaging unit by the measuring step,
When a shadow is generated in an image picked up by projecting a stripe pattern from one of the two projection optical axes, a stripe is formed from the other projection optical axis in a region in which the shadow is expanded by an arbitrary distance. A three-dimensional shape measuring method, wherein three- dimensional coordinates based on an image captured by projecting a pattern are used .   The three-dimensional shape measurement method according to claim 1, wherein the two projection optical axes are set symmetrically with respect to the optical axis of the imaging unit. 3D according to claim 1 or claim 2, characterized by using a telecentric lens to one of a projection lens for projecting a fringe pattern from the imaging unit of the imaging lens or the two projection optical axis, Shape measurement method. Imaging lens of the imaging unit, and any one of claims 1 to 3, characterized by using a telecentric lens in each of the projection lens for projecting a fringe pattern from said two projection optical axis The three-dimensional shape measurement method described. A three-dimensional shape measurement apparatus using the three-dimensional shape measurement method according to any one of claims 1 to 4 .