JP2009204343A - Three-dimensional shape measurement method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a three-dimensional shape measurement method and device using a phase shift process, capable of improving the measurement accuracy, using a simple constitution, even in measured bodies having mixed areas with different reflectances due to characters, patterns, or the like, on their surfaces. <P>SOLUTION: The device 1 includes: two stripe pattern projection sections 2 for projecting a stripe pattern on a measurement area 10 of the measured body from directions different each other; an imaging section 3; and a three-dimensional measurement processing section 4 for compute, for obtaining the three-dimensional shape of the measurement area 10, based on the data output from the imaging section 3, in order to measure the three-dimensional shape by two or more times in the phase shift process and to select and decide the best measurement result from the measurement results; the measurement result determining section 4a of the three-dimensional measurement processing section 4 determines the angle for a target pixel, between the gradient direction of the luminance of the pixel and the changing direction of the stripe pattern for the two stripe pattern projection sections 2 and determines a measurement result of the pixel, by selecting three-dimensional coordinates from the data of the projection sections 2 and to give an angle which is closer to 90°, after a mutual comparison. <P>COPYRIGHT: (C)2009,JPO&INPIT

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 caused by a focus blur at the time of imaging or a blur based on a modulation transfer function characteristic of the 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. 16 to 21 by simulation. As shown in FIGS. 16 and 17, for a target region having a contrast in which a bright portion (region x2) and a dark portion (regions x1 and x3) have binary luminance values L1 and L2 under uniform illumination. Forcibly generate blur and compare. 18 (a) to 18 (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. 19A to 19D are data obtained by performing a Gaussian moving average process with a standard deviation σ on the luminance changes of FIGS. 18A to 18D and forcibly blurring the luminance changes by calculation. is there. FIG. 20 shows the phase distribution calculated from FIGS. 18A to 18D and the phase distribution calculated from FIGS. 19A to 19D in an overlapping manner. FIG. 21 is an enlarged view of a portion D where the phase difference ΔP occurs in FIG.

  As shown in FIG. 20, the phase value with blurring indicated by the broken line at the position of the light / dark boundary xb changes from the correct phase value without blurring indicated by the solid line, and has an error of phase difference ΔP. Yes. The magnitude of the phase difference ΔP is defined as an angle (γ) formed by a direction perpendicular to the boundary between light and dark, that is, a gradient direction of luminance (brightness) and a change direction of the fringe pattern (x direction in FIGS. 17 to 21). ). According to the simulation, the error is the largest when the angle γ is 0 °, and the error is minimized when the angle γ is 90 °, and the magnitude of the error decreases monotonously with the magnitude of the angle γ.

  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.

By the way, 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), shadow, irregular 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-described problem, and has a simple configuration and a three-dimensional phase shift method that can improve the measurement accuracy even for an object to be measured in which areas having different reflectances such as characters and patterns are mixed on the surface. An object is to provide a shape measuring method and apparatus.

  In order to achieve the above object, the invention of claim 1 projects a plurality of images from a fixed position by projecting a fringe pattern whose brightness changes in a sinusoidal shape onto a measured object three or more times with different phases. In a three-dimensional shape measurement method based on a phase shift method for obtaining a three-dimensional coordinate of an object to be measured for each pixel in the image using an image, an imaging unit is installed above the measurement region of the object to be measured, and light from the imaging unit A plurality of planes configured by an axis and one projection optical axis, and a direction of a straight line having a predetermined angle with respect to the plane and orthogonal to the optical axis of the imaging unit. The fringe pattern whose brightness changes along the pattern change direction is projected onto the measurement area from the direction of the projection optical axis constituting the plane, and is imaged by the imaging unit, and the three-dimensional coordinates of the measurement area are obtained by the phase shift method. Step to get A coordinate measurement step for acquiring a plurality of types of three-dimensional coordinate data by performing each of the planes independently, and a differential processing of an image obtained by imaging the measurement area under uniform illumination light. Gradient acquisition step of acquiring a plurality of types of gradient direction data by performing the step of obtaining the gradient direction of the brightness for each plane independently by illumination from the projection optical axis direction and imaging by the imaging unit. And the luminance gradient direction and the pattern change direction for each of the pixels corresponding to the pixels in the other set of images in the plurality of sets of three-dimensional coordinate data and gradient direction data for each plane. The angle formed by or the inclination component corresponding to the angle is obtained, and the three-dimensional coordinates for the pixel in each set are synthesized based on the angle or inclination component. A pixel data determining step of a measurement result of the three-dimensional coordinates in the pixel Te is intended to include.

  According to a second aspect of the present invention, in the three-dimensional shape measurement method according to the first aspect, when the pixel data determining step synthesizes the three-dimensional coordinates, the luminance gradient direction and the pattern change in the plurality of sets are combined. A three-dimensional coordinate is selected from a set that gives an angle closer to 90 ° by comparing the angle formed with the direction with each other to obtain a measurement result at the pixel.

  According to a third aspect of the present invention, in the three-dimensional shape measurement method according to the first aspect, in the pixel data determination step, pixels whose differential values obtained by the differential processing in the gradient acquisition step correspond to each other in the plurality of sets. If any of these is smaller than a predetermined threshold value, the three-dimensional coordinates for the pixel in each set are evenly combined with each other to obtain a measurement result of the three-dimensional coordinates for the pixel.

  A fourth 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 third aspects.

  According to the first aspect of the present invention, the angle formed by the gradient direction of the brightness and the pattern change direction or an inclination component corresponding to the angle is obtained, and the three-dimensional coordinates for the target pixel in each set are obtained based on the angle or the inclination component. As a result of combining and measuring the three-dimensional coordinates at the pixel, even if there is a region with different reflectivity due to characters, patterns, etc. on the object to be measured, the reflectance change portion (luminance change in the image) The measurement error generated in (Part) can be reduced, the measurement error due to random noise can be reduced, and highly accurate measurement can be performed. In the synthesis of three-dimensional coordinates (coordinate values), a measurement result under a plurality of pattern change directions is obtained by calculating the angle between the luminance gradient direction and the pattern change direction in each measurement or the magnitude of the inclination component corresponding to the angle. It may be performed by adding weights according to the above.

  According to the invention of claim 2, since the measurement result of the three-dimensional coordinates considered to be optimum is selected by comparing the angle formed between the luminance gradient direction and the pattern change direction, it is easy to perform by a simple operation that only requires selection. High-precision measurement with a simple configuration. This corresponds to a case where weighting in synthesis is “1” and “0”.

  According to the invention of claim 3, when the magnitude of the differential value obtained by the differentiation process, that is, the magnitude of the luminance gradient is smaller than a predetermined threshold value, the average value of the plurality of measurement results is calculated as the measurement result of the three-dimensional coordinates. Therefore, measurement errors due to random noise can be reduced, and highly accurate measurement can be performed. This is because, when the luminance change is small, the stripe pattern image is less likely to be blurred due to the luminance change, and the measurement error due to such blur is small. Therefore, the error can be reduced by paying attention to random noise.

  According to the fourth aspect of the present invention, it is possible to provide a three-dimensional shape measuring apparatus based on the phase shift method capable of improving the measurement accuracy even for an object to be measured in which areas having different reflectances such as characters and patterns are mixed on the surface.

  Hereinafter, a three-dimensional shape measuring apparatus and method according to embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 shows a schematic configuration of the three-dimensional shape measuring apparatus according to the first embodiment, FIG. 2 shows the arrangement of the projection unit and the imaging unit of the apparatus, and FIG. 3 shows the projection unit, imaging unit, FIG. 3 shows the positional relationship between the stripe patterns (FIG. 3 is a view seen from the direction of arrow 30a in FIG. 2).

  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 is installed above the measurement area 10 with the two fringe pattern projection units 2 that project the stripe pattern onto the measurement area 10 of the measurement object from different directions. The imaging unit 3 for imaging, the fringe pattern projection unit 2 and the imaging unit 3 are controlled, and calculation for obtaining the three-dimensional shape of the measurement region 10 is performed based on data output from the stripe pattern projection unit 2 and the imaging unit 3. And a three-dimensional measurement processing unit 4. 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 unit 2 includes an illumination unit 21, a fringe pattern generation unit 22, and a projection optical unit 23. 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.

  A plurality of fringe pattern projection units 2 are provided, and in this embodiment, an example using two systems A and B is shown. The fringe pattern projection unit 2 does 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 arrangement relationship between the two stripe pattern projection units 2 and the imaging unit 3 will be described later.

  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 unit 2.

  The central control unit 42 performs fringe pattern data to be transmitted to the fringe pattern projection unit 2, performs transmission control of data, projection control of the fringe pattern projection unit 2, imaging control of the imaging unit 3, and the like, and is projected onto the measurement region 10. The phase of the pattern is shifted at a constant phase interval, and imaging by the imaging unit 3 in 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 used to record data necessary for three-dimensional shape measurement. Data relating to the spatial arrangement of the imaging unit 3 and the stripe pattern projection unit 2, the resolution of the imaging unit 3, the pitch of the stripe pattern, the phase shift amount, the imaging unit Data such as image data captured by 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 unit 2 and the imaging unit 3)
In the present embodiment, two stripe pattern projection units 2 of A and B are used, and these are arranged in two planes (A plane and B plane in FIG. 2) orthogonal to each other. Accordingly, the projection optical axis 20 of each fringe pattern projection unit 2 is included in the A plane or the B plane. Further, the imaging unit 3 is arranged above the measurement region 10 with its optical axis 30 coinciding with the intersecting line of the A plane and the B plane orthogonal to each other.

  Here, the coordinate axes X, Y, Z of the space constituting the orthogonal coordinate system and the coordinate axes x, y in the image plane are defined. The Z axis is the optical axis 30 of the imaging unit 3, and the X axis and the Y axis are on the A plane and the B plane, respectively. The coordinate axes x and y can be defined to match or correspond to the coordinate axes X and Y.

(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 to the X and x axis directions and the Y and y axis directions. The pattern change direction 5 does not necessarily need to be included in the A and B surfaces including the projection optical axis 20, and can have any non-zero angle with respect to these surfaces. Further, in general, the A surface and the B surface are not necessarily perpendicular to each other.

(Description of operation)
Next, the operation of the three-dimensional shape measuring apparatus 1 will be described with reference to FIGS. As described above, the three-dimensional shape measuring apparatus 1 basically performs three-dimensional shape measurement by a normal phase shift method a plurality of times, and determines the best measurement result from the measurement result, thereby finally increasing the high-order shape measurement apparatus 1. This enables accurate three-dimensional shape measurement. Therefore, in this embodiment, first, normal three-dimensional shape measurement is performed using the above-described two-line stripe pattern projection unit 2 of A and B. Thereafter, the measurement result determination unit 4a of the calculation unit 44 determines the best measurement result for each pixel.

  An image G shown in FIG. 4 is an image of the measurement region 10 illuminated with light of uniform brightness. In the image G, a dark image portion is reflected in a bright background image. FIG. 5 shows an enlarged peripheral image of the pixel g at the boundary between the light and dark regions. The coordinate axes x and y determine the position of the pixel g in the image G. Further, the pattern change direction 5 of each stripe pattern SP is set in the x-axis direction and the y-axis direction.

  In FIG. 5, the gradient direction h of luminance is shown. The luminance gradient direction h is a vector direction having each differential intensity obtained by differentiating the luminance value of each pixel of the image G along the x-axis direction and the y-axis direction as a component for each pixel g. Calculated. Note that the gradient direction is not defined for an image portion with uniform luminance. In this case, there is no measurement error due to blur described as a problem in the prior art.

  As described with reference to FIG. 21, the three-dimensional shape measurement apparatus 1 of the present invention can reduce the measurement error due to the difference in reflectance on the surface of the object to be measured, in particular, the image blur that occurs at the position of the light / dark boundary xb. It is a solution. The magnitude of the measurement error due to the blur varies depending on the direction perpendicular to the light / dark boundary line, that is, the angle (gamma) between the gradient direction of brightness (brightness) and the change direction of the fringe pattern. It can be seen that the error is the largest when γ is 0 °, the error is minimum when 90 °, and the error decreases monotonously with the angle γ when 0 ° <γ <90 °. ing.

  In order to eliminate the measurement error due to the blur described above, the measurement result determination unit 4a selects the best measurement result and determines the final measurement result as shown below.

  The unit vectors ua and ub in the pattern change direction 5 in each stripe pattern SP and the unit vector u0 in the luminance gradient direction h are defined. In the present embodiment, the directions of the unit vectors ua and ub are made to coincide with the directions of the x-axis and the y-axis, respectively, but such coincidence is essential for measurement in the three-dimensional shape measuring apparatus 1. It is not a thing.

When the angle formed by the unit vector ua and the unit vector u0 is α, and the angle formed by the unit vector ub and the unit vector u0 is β, the absolute value of the inner product of the vectors has the following relationship.
| U0 · ua | = | cosα |,
| U0 · ub | = | cosβ |.

  For an angle θ (where 0 ° <θ <180 °), θ is closer to 90 ° as | cos θ | is closer to zero. Therefore, the measurement result determination unit 4a compares | cosα | and | cosβ | described above, finds the one closer to zero, and pays attention to the measurement result by the fringe pattern projection unit 2 that gives such a result. The result is a three-dimensional shape measurement result at pixel g. In the case of the pixel g in FIGS. 4 and 5, the measurement result by the stripe pattern SP in which the stripe pattern change direction 5 is oriented in the x-axis direction (unit vector ua direction) (measurement result by the A system stripe pattern projection unit 2). Is determined as the best measurement result. The measurement result determination unit 4a determines such measurement results for all the pixels g.

  According to the three-dimensional shape measuring apparatus 1 of the present embodiment, the luminance value at the pixel in the imaged image changes from the true value due to a mixture of regions having different reflectances such as characters and patterns on the surface. Measurement accuracy can also be improved for such an object to be measured.

(Second Embodiment)
6 shows a flowchart of the three-dimensional shape measurement method according to the second embodiment, FIG. 7 shows a flowchart of point cloud data acquisition in the method, and FIG. 8 shows a flowchart of image data acquisition in the method. 9 shows a flowchart of determining pixel data in this method. This embodiment shows a method for performing three-dimensional shape measurement using the three-dimensional shape measurement apparatus 1 in the first embodiment described above, and appropriately refer to FIGS.

  The overall flow of this measurement method is shown in FIG. 6, and the main subroutines are shown in FIGS. In this measurement method, two sets of point cloud data are acquired in the first half of the process (S1, S2), and in the second half, selection determination is performed to determine the best three-dimensional shape data for each pixel from the two sets of three-dimensional shape data. Is performed (loops LP1 to LP11, LP2 to LP22). The first half of the processing is performed using the two fringe pattern projection units 2 (projection units A and B) under the control of the central control unit 42. Further, the latter half of the determination process is performed by the measurement result determination unit 4a. Hereinafter, it demonstrates along the flow of a process.

(Point cloud data acquisition)
First, point cloud data acquisition (S1, S2) in the first half will be described with reference to a subroutine flowchart (FIG. 7). The basic part excluding individual data in this process is a process common to the projection units A and B. In the following, the subscript k in expressions and variables represents A or B for identifying the projection parts A and B. In this point cloud data acquisition process, three-dimensional shape data and luminance gradient 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). Point cloud data is a general term for data relating to these specific points, that is, data such as luminance, XYZ coordinate values, and the gradient direction of luminance at that point for a given 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 luminance gradient data which is characteristic processing of the present invention are performed (S13).

The image data acquisition process (S10) will be further described with reference to a subroutine flowchart (FIG. 8). 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 stripe pattern is recorded as luminance data I _ki (x, y), i = 0, 1, 2, 3 (LP5 to LP55), and the image by uniform illumination is recorded as luminance data I _k (x, y). (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 unit 2 under the control of the central control unit 42, and the fringe pattern projection unit 2 sends the fringe pattern data to the measurement region 10 of the object to be measured as a fringe pattern SP whose brightness changes in a sine wave shape. Projected (S21).

The fringe pattern L _ki (u, v) created by the fringe pattern generation unit 22 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 unit 2, 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 unit 2 (S24), images by the imaging unit 3 (S25), and the fringe pattern. Luminance data I _k (x, y) in uniform illumination without any data 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. 7, 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 unit 2, respectively, and satisfy the following expressions (4) and (5).

Based on the above-described processing, the 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 the combination of one fringe pattern projection unit 2 and the imaging unit 3. The defined three-dimensional point cloud data P _k (x, y; X, Y, Z) is obtained.

(Brightness gradient data calculation)
In the latter half of the processing in FIG. 7, calculation for obtaining luminance gradient data is performed for luminance data I _k (x, y) in uniform illumination (S13). The luminance gradient is obtained by calculating a differential value of luminance data in the x direction and y direction of the image. For this calculation, for example, a Sobel filter can be used. The differential value D _kx (x, y) in the x direction and the differential value D _ky (x, y) in the y direction corresponding to the luminance data I _k are obtained by the following equations (6) and (7), respectively.

The angle θ _k (x, y) representing the luminance gradient direction is obtained from the differential value by the following equation (8). This angle θ _k (x, y) is defined as an angle formed with the x-axis direction in the image.

In the three-dimensional shape measurement method of the present embodiment, it is used for determination whether the angle formed by the luminance gradient direction and the change direction of the fringe pattern SP is closer to 90 ° in either of the projection portions A and B. Therefore, the value of θ _k (x, y) may be in the range of 0 ° to 90 °. Therefore, the angle Θ _k (x, y) obtained by the following equation (9) using the absolute values of the x-direction differential value and the y-direction differential value can also be used. Hereinafter, for the sake of convenience, description will be made assuming that the angle Θ _k (x, y) is used. Further, when these angles θ _k (x, y) or angles Θ _k (x, y) cannot be defined and do not exist, a predetermined abnormal value such as “999” is given as an angle value. And

With the above processing, two sets of point cloud data acquisition by the projection units A and B in steps S1 and S2 in FIG. 6 is completed, and the three-dimensional shape data P _k (x, y; X, Y, Z), k = A, B, luminance gradient data Θ _k (x, y), D _kx (x, y), D _ky (x, y), k = A, B are acquired. Hereinafter, a process of determining pixel data by selecting the best three-dimensional shape data in each pixel in FIG. 6 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 (loops LP1 to LP11, LP2 to LP22), it is determined whether or not P _A (x, y), P _B (x, y) exists for a specific pixel specified by coordinates x, y. When only one of them exists, the value is selected and P (x, y) = P _A (x, y) or P (x, y) = P _B (x, y) is set. (S6 or S8). If neither 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) has no measurement result due to concealment (so-called occlusion where a shadow is formed) due to a three-dimensional solid shape generated depending on the projection direction from each fringe pattern projection unit 2. This is a case handling process. Thereby, when one of the two types of measurement results is affected by concealment, the other can be selected as a correct measurement result.

When both P _A (x, y) and P _B (x, y) exist (Yes in S3 and S4), the pixel data is determined based on the luminance gradient (S5).

The selection of pixel data based on the luminance gradient will be described with reference to a subroutine flowchart (FIG. 8). First, it is determined whether or not the angles Θ _A (x, y) and Θ _B (x, y), which are brightness gradient data, exist (# 1), and one of the angles is “999” as described above. If it does not exist (No in # 1), the default is P (x, y) = P _A (x, y) (# 4). Note that when none of these angles exists, it indicates that the luminance gradient is not defined, that is, there is no luminance gradient, and the luminance distribution is uniform in the peripheral pixels of the target pixel.

When both of the angles Θ _A (x, y) and Θ _B (x, y) exist (Yes in # 1), the angle in the pattern change direction (referred to as η _A and η _B ) and the angle Θ _A The angles α and β as absolute values of the difference from (x, y), Θ _B (x, y) are obtained (# 2). The angles α and β correspond to the angles α and β shown in FIG. 5 in the first embodiment. Also, the angles η _A and η _B correspond to the directions of the unit vectors ua and ub shown in FIG. 5, and in this embodiment, η _A = 0 and η _B = 90 ° with respect to the x-axis direction. It is.

Next, it is determined which of the angles α and β is closer to 90 °. If the angle α is closer to 90 ° than the angle β, that is, if β <α ≦ 90 ° (Yes in # 3), P (x, y) = P _A (x, y) is set (# 4). When the angle α is not closer to 90 ° than the angle β (No in # 3), P (x, y) = P _B (x, y) is set (# 5).

In the above description, it has been described that the best data is selected and determined using the angles Θ _A (x, y) and Θ _B (x, y). It can also be performed using D _kx (x, y) and the differential value D _ky (x, y) in the y direction. According to this method, it is not necessary to calculate an arc tangent for obtaining the angles Θ _A (x, y) and Θ _B (x, y). Therefore, there is an advantage that the processing can be performed with a smaller calculation processing amount.

In the case of the present embodiment, the angles η _A and η _B are η _A = 0 and η _B = 90 °. Therefore, the selection determination using the differential value can be performed by the following relationship. However, since the following equation is determined based on the data of the projection unit A, it is applied when the directions of the luminance gradients obtained by the projection units A and B are substantially equal to each other.
If D _Ay ≧ D _Ax , P (x, y) = P _A (x, y),
If D _Ay <D _Ax , then P (x, y) = P _B (x, y).

  The pixel data determination process as described above is performed for all pixels, so that the optimally selected final three-dimensional coordinate data, that is, the three-dimensional shape measurement result P (x, y), more explicitly P (x , Y; X, Y, Z).

  According to the three-dimensional shape measurement method of this embodiment, the measurement result of the three-dimensional coordinates considered to be optimal is selected by comparing the angle formed between the gradient direction of the brightness and the pattern change direction, so that characters, patterns, etc. are applied to the surface. Even an object to be measured in which regions having different reflectivities due to the above can be measured with high accuracy by a simple operation only by selecting. Further, by comparing and selecting the point cloud data from the projection units A and B from different directions, it is possible to avoid a loss of measurement results due to occlusion.

(Third embodiment)
FIG. 10 shows a positional relationship between a projection unit, an imaging unit, and a fringe pattern for explaining a three-dimensional shape measurement method and apparatus according to the third embodiment. In the present embodiment, the two striped pattern projection units 2 in the first or second embodiment are configured to be three. The arrangement planes A, B, and C of each fringe pattern projection unit 2 have angles between the planes of φ1 and φ2, and the pattern change direction 5 of the stripe pattern SP is also set according to the arrangement planes A, B, and C. . By setting each of the angles φ1 and φ2 to 60 °, for example, it is possible to more effectively avoid errors with respect to blur than in the case of 90 ° in the first embodiment, so that three-dimensional shape measurement can be performed with higher accuracy. .

  More generally, the three-dimensional shape measuring method and apparatus of the present invention can be provided with two or more fringe pattern projection units 2 (more basically, projection optical axes, the same applies hereinafter), and by increasing the number thereof. , It is possible to more effectively avoid errors due to blur. Further, random noise errors can be reduced by statistically processing a large number of measurement results. The number of the fringe pattern projection units 2 may be determined in consideration of the measurement time, necessary measurement accuracy, equipment cost, and the like.

  Here, a general three-dimensional shape measurement method when an arbitrary number of the fringe pattern projection units 2 are provided will be described. For convenience of explanation, the names and symbols of the respective parts shown in FIGS. 1 to 10 are referred to, but the present invention is not limited to these configurations. In this three-dimensional shape measurement method, as in the first and second embodiments, the fringe pattern SP whose brightness changes in a sine wave shape is projected onto the measurement area 10 of the object to be measured three or more times with different phases, and a fixed position is obtained. The plurality of images in which the pixel positions are associated with each other are captured by the imaging unit 3 disposed in the image, and 3 of the measured object is obtained for each pixel in the image using these images. A phase shift method for obtaining dimensional coordinates is used.

  This three-dimensional shape measurement method includes a coordinate measurement step, a gradient acquisition step, and a pixel data determination step, and each step will be described in detail below.

In the coordinate measurement step, the imaging unit 3 is installed above the measurement area 10 of the object to be measured, a plurality of planes configured by the optical axis 30 of the imaging unit 3 and one projection optical axis 20 are set, and the plane One stripe pattern SP having a predetermined angle with respect to the plane and having a brightness change along a pattern change direction 5 that is a straight line direction orthogonal to the optical axis 30 of the imaging unit 3 constitutes the plane. The step of projecting from the direction of the projection optical axis 20 onto the measurement area 10 and picking up an image by the imaging unit 3 and acquiring the three-dimensional coordinates (X, Y, Z) of the measurement area by the phase shift method is independent for each plane. To obtain a plurality of types of three-dimensional coordinate data P _k (x, y; X, Y, Z). Here, X, Y, and Z are spatial coordinates set in the measurement region 10, and x and y are coordinates set in the image. Here, the subscript k is a variable for identifying each projection optical axis 20 and the like, and is a subscript for identifying A, B, and the like in the first embodiment.

In the gradient acquisition step, the step of differentiating the image obtained by imaging the measurement region 10 under uniform illumination light to obtain the luminance gradient direction h for each pixel in the image is performed independently for each plane. A plurality of types of gradient direction data are acquired by performing illumination from the direction of the axis 20 and imaging by the imaging unit 3. The luminance gradient direction h is represented by an angle θ _k (x, y), a differential value D _kx (x, y) in the x direction, a differential value D _ky (x, y) in the y direction, and the like.

  The gradient acquisition step and the coordinate measurement step described above can be executed with the order reversed. Further, these steps may be collectively performed by steps for each plane (each projection optical axis 20) without performing them all at once.

In the pixel data determination step, the three-dimensional coordinate data P _k (x, y; X, Y, Z) and gradient direction data θ _k (x, y), D _kx (x, y) for each projection optical axis 20 are used. , D _ky (x, y), the angle γ formed by the luminance gradient direction h and the pattern change direction 5 or the angle γ for each pixel corresponding to the pixels in the other set of images. The three-dimensional coordinates X, Y, and Z for the pixel in each set are synthesized based on the angle γ or the inclination component, and the measurement result P (x, y of the three-dimensional coordinate at the pixel is obtained. X, Y, Z).

  Further, in the pixel data determination step described above, when the three-dimensional coordinates are synthesized, the angle γ formed by the luminance gradient direction obtained for each of the corresponding pixels and the pattern change direction is compared and is closer to 90 °. A three-dimensional coordinate can be selected from the set that gives the angle γ, and the measurement result P (x, y; X, Y, Z) at the pixel can be obtained. This corresponds to a case where the weighting at the time of synthesis is “1” for one selected data and “0” for all other data.

(Fourth embodiment)
FIG. 11 is a flowchart for explaining a three-dimensional shape measuring method according to the fourth embodiment, and FIG. 12 is a flowchart for determining pixel data in the method. The three-dimensional shape measurement method of this embodiment is based on “differential intensity (that is, a differential value of a luminance distribution)” in “process of determining pixel data based on luminance gradient (that is, angle)” in the second embodiment. The operation is different and the other points are the same as in the second embodiment.

Therefore, the flowchart shown in FIG. 11 is obtained by replacing step S5 in the flowchart (FIG. 6) of the second embodiment with the content of pixel data determination based on the luminance intensity (S50). In steps S1 and S2 in the flowchart of FIG. 11, it is not necessary to derive the angles θ _k (x, y) and Θ _k (x, y) representing the angle gradient. Further, the “differential intensity” here is a differential value of a luminance change in the image, and includes a differential intensity D _kx in the x direction and a differential intensity D _{ky in the} y direction (k is A or B). These are the above-described gradient direction data, and D _kx = D _kx (x, y) and D _ky = D _ky (x, y).

  Below, the subroutine (FIG. 12) which shows the specific process of step S50 is demonstrated, and other description is abbreviate | omitted. Here again, FIGS. 1 to 5 and FIG. 6 are referred to as appropriate.

In the first step of the pixel data determination subroutine, the differential intensities obtained under the two projection parts A and B are compared with each other in the x direction component and the threshold value T _x , and in the y direction component and the threshold value T _y . (# 10). For example, in the x direction, when the differential intensity D _Ax is larger than the value obtained by adding the threshold T _x to the differential intensity D _Bx (D _Ax > D _Bx + T _x ) (Yes in # 10), the three-dimensional by the projection unit B The shape data is selected and determined as final data for the pixel of interest having xy coordinates, and P (x, y) = P _B (x, y) is set (# 14).

The determination of the selection decision described above is for avoiding erroneous measurement due to occlusion. That is, in a place where a shadow is generated in the image due to concealment and the differential intensity becomes strong due to the boundary line of the shadow, it is a process of selecting a more reliable measurement result considered to be less affected by such a shadow. . In the above example, since the differential intensity D _Ax is larger than the value obtained by adding the threshold T _x to the differential intensity D _Bx (D _Ax > D _Bx + T _x ), the three-dimensional shape data P _A (x, y by the projection unit A) ) Is determined to have a shadow effect due to concealment, and P _B (x, y) is selected and determined.

Similarly, in the y direction, if the differential intensity D _Ay is larger than the value obtained by adding the threshold T _y to the differential intensity D _By (D _Ay > D _By + T _y ) (Yes in # 10), P (x, y) = P _B (x, y) (# 14). In other words, it can be said that the three-dimensional shape data having an abnormally large luminance differential intensity in either the x direction or the y direction is excluded because it may include the influence of shadows due to concealment.

In the opposite case, that is, when the differential intensity by the projection unit B is abnormally large (Yes in # 11), P (x, y) = P _A (x, y) for the same reason. (# 13).

When none of the differential intensities has a large abnormal value as judged by the thresholds T _x and T _y (No in # 10, No in # 11), the differential intensity of the differential intensity related to the projection unit A in the xy direction A size comparison is performed (# 12). This size comparison is performed in order to avoid the occurrence of a measurement error due to the influence of blurring at the boundary part of the region where the reflectance is different due to characters, patterns, etc., under the situation where there is no influence by concealment. In this case, since there is no concealment and the differential intensity of the luminance based on the image under uniform illumination, it is considered that the differential intensity based on either of the projection parts A and B has an equivalent value. It can be considered that the magnitude can be effectively compared even using the differential intensity of.

The measurement error due to the above-described blur is smaller as the angle between the gradient direction of the luminance of the image and the change direction of the fringe pattern is closer to 90 °. Therefore, when D _Ay ≧ D _Ax (Yes in # 12), P _{(x, y) = P a} (x, y) and may be (# 13).

  Supplementally, since the three-dimensional shape measurement method of the present embodiment is assumed to use the three-dimensional shape measurement apparatus having the configuration of the first embodiment, similarly to the second embodiment, the projection unit A The change direction of the fringe pattern due to is the X-axis direction (x-axis direction). Further, the change direction of the fringe pattern by the projection unit B is the Y-axis direction (y-axis direction).

Therefore, when D _Ay ≧ D _Ax , the luminance gradient direction is inclined in the y-axis direction rather than the x-axis direction. That is, since the x-axis and the y-axis are at right angles, the luminance gradient direction has a larger angle close to 90 ° with respect to the x-axis direction, and the stripe pattern change direction in the x-axis direction. The three-dimensional shape data P _A (x, y) is selected as data with less error. In the opposite case, that is, when D _Ay ≧ D _Ax is not satisfied (No in # 12), P (x, y) = P _B (x, y) is set (# 14).

(Fifth embodiment)
FIG. 13 shows a flowchart of pixel data determination in the three-dimensional shape measurement method according to the fifth embodiment. The three-dimensional shape measurement method of this embodiment performs “pixel data determination processing” based on “differential intensity (that is, differential value of luminance distribution)” as in the above-described fourth embodiment. Instead of selecting one of the data, the data obtained by synthesizing two pieces of measurement data under a predetermined weight is used as final “pixel data”, that is, three-dimensional shape measurement data. This is the same as in the fourth embodiment.

  The flowchart of the subroutine of this embodiment shown in FIG. 13 is an alternative to the flowchart of the fourth embodiment (FIG. 12). The processing in steps # 20 and # 21 is the same as the processing in steps # 10 and # 11 in FIG.

When none of the differential intensities has a large abnormal value as judged by the thresholds T _x and T _y (No in # 20, No in # 21), as shown in the following equation (10), the parameter t Is set (# 22).

For setting the parameter t, differential intensity data D _Ay (x, y) and D _Ax (x, y) by the projection unit A are used, but there is no concealment and under uniform illumination. Therefore, it is considered that the parameter t can be set equally with the differential intensity data based on either of the projection parts A and B.

When t in the above equation (12) is considered with the denominator being 1, t corresponds to the x component and (1-t) corresponds to the y component. If t = 1, the differential intensity is only the x component, the luminance gradient direction is the x-axis direction, and the three-dimensional shape measurement value P _B is the stripe pattern change direction in the y-axis direction orthogonal to this direction. (X, y) is selected and determined.

If t = 0, the differential intensity is only the y component, the luminance gradient direction is the y-axis direction, and the three-dimensional shape measurement value P _A is the fringe pattern change direction in the x-axis direction orthogonal to this direction. (X, y) is selected and determined.

When the parameter t is 0 <t <1, the contributions from P _A (x, y) and P _B (x, y) are respectively calculated by weighting (1−t) and t. , P (x, y) can be calculated.

From the above, using the parameter t, the three-dimensional shape measurement values P _A (x, y) and P _B (x, y) by the projection units A and B are synthesized as shown in the following equation (11). The final data P (x, y) for the pixel of interest having xy coordinates is determined (# 23).

  According to the three-dimensional shape measurement method of the present embodiment, the two stripe pattern change directions are perpendicular to each other, and the three-dimensional shape measurement data acquired by the projection units A and B is converted into the angle of the luminance gradient direction (differential intensity). Since the weighted average is performed according to the magnitude relationship between the two components), the influence of random noise can be reduced, and the measurement error (the influence of blur) due to the mixture of reflectance can be reduced. Accuracy can be improved.

(Sixth embodiment)
FIG. 14 is a flowchart for determining pixel data in the three-dimensional shape measurement method according to the sixth embodiment. The three-dimensional shape measurement method of the present embodiment is different from the fifth embodiment described above in that processing when the differential intensity of luminance at the target pixel is small is incorporated, and the other is the same as the fifth embodiment. It is the same. That is, in the flowchart shown in FIG. 14, steps # 30 and # 31 are added to the flowchart of FIG.

When none of the differential intensities has a large abnormal value as judged by the thresholds T _x and T _y (No in # 20, No in # 21), the differential intensity component D _Ay (x , Y) and D _Ax (x, y) are compared to determine whether each is smaller than the threshold T ₀ (# 30). When both are small, that is, when D _Ay (x, y) <T ₀ and D _Ax (x, y) <T ₀ (Yes in # 30), the above-described parameter t is t = 0.5. (# 31).

  Since the above-described processing is not concealed and is a differential intensity of luminance based on an image under uniform illumination, it is considered that the differential intensity based on either of the projection parts A and B has an equivalent value. Therefore, it is determined by the differential intensity component related to the projection part A.

  Further, the condition that all the components of the differential intensity of the luminance are small means that the magnitude of the differential intensity itself is small. The above processing has little change in luminance around the pixel of interest, and there is little occurrence of blurring of the fringe pattern image due to the change in luminance.Therefore, measurement errors due to such blur are small, so pay attention to random noise. This is a process for reducing the error.

  According to the three-dimensional shape measurement method of the present embodiment, the calculation of the parameter t is simplified, and t = 0.5 is set to a fixed value, thereby reducing the calculation process and averaging the measurement results. The influence of noise can be reduced, and measurement errors can be reduced and highly accurate measurement can be performed.

(Seventh embodiment)
FIG. 15 shows the positional relationship between a projection unit, an imaging unit, and a fringe pattern for explaining the three-dimensional shape measurement method and apparatus according to the seventh embodiment. In the present embodiment, the two fringe pattern projection units 2 in the first or second embodiment are arranged at positions facing each other, and the pattern change directions 5 of the fringe patterns SP projected on the measurement region 10 are orthogonal to each other. It is a configuration.

  According to the three-dimensional shape measurement method and apparatus of the present embodiment, since the two fringe pattern projection units 2 are arranged at positions facing each other, measurement data of occlusion generated by illumination from one side is stored. The deficiency can be complemented by measurement data from illumination from the other side.

  In addition, since the pattern change directions 5 of the stripe patterns SP projected by the two stripe pattern projection units 2 are configured to be orthogonal to each other, either the best measurement result is selected, or both measurement results are synthesized. In addition, the measurement accuracy can be improved by reducing the measurement error due to the occurrence of blurring in the portions of the measurement region 10 having different reflectivities.

  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 within a consistent range, and such embodiments that can be combined are naturally included in the present invention even if they are not specified. Further, in any of the fringe pattern projection units 2, the projection optical axis 20 and the optical axis 30 of the imaging unit 3 do not necessarily need to be included in the same plane, and the geometrical spatial arrangement of each other is clear. What is necessary is just to have a twist position relationship 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 typical perspective view which shows arrangement | positioning of the projection part and imaging part of an apparatus same as the above. 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 example of the image imaged in an apparatus same as the above. The figure of the gradient direction of the brightness | luminance used for three-dimensional coordinate data selection in an apparatus same as the above. The flowchart explaining the three-dimensional shape measuring method which concerns on 2nd Embodiment. 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. 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 3rd Embodiment. The flowchart explaining the three-dimensional shape measuring method which concerns on 4th Embodiment. The flowchart of the pixel data determination in a method same as the above. The flowchart of the pixel data determination in the three-dimensional shape measuring method which concerns on 5th Embodiment. The flowchart of the pixel data determination in the three-dimensional shape measuring method which concerns on 6th Embodiment. The top view which shows the positional relationship of the projection part, imaging part, and striped pattern for demonstrating the three-dimensional shape measuring method and apparatus which concern on 7th 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 of the image in FIG. 16 changes sinusoidally in the x direction. 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. 18 (a)-(d), respectively, and blurred the luminance change. The graph showing the change in the x direction of the initial phase calculated from FIGS. 18A to 18D is overlapped with the graph showing the change in the x direction of the initial phase calculated from FIGS. 19A to 19D. Graph. The graph which expanded the D section of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 3D shape measuring device 2 Imaging part 3 Projection part 4 Measurement processing part 5 Pattern change direction 10 Measurement area 20 Imaging part Optical axis 30 Projection optical axis g Pixel h Gradient direction G Image SP Stripe pattern X, Y, Z 3D Coordinate

Claims (4)

A fringe pattern whose brightness changes in a sine wave shape is projected onto the object to be measured three or more times with different phases, and a plurality of images are taken from a certain position. Using these images, the object to be measured is detected for each pixel in the image. In the three-dimensional shape measurement method by the phase shift method for obtaining three-dimensional coordinates,
An imaging unit is installed above the measurement area of the object to be measured, a plurality of planes configured by the optical axis of the imaging unit and one projection optical axis are set, and one of the planes is predetermined with respect to the plane. A fringe pattern whose brightness changes along a pattern change direction having a straight line direction orthogonal to the optical axis of the image pickup unit is projected onto the measurement region from the direction of the projection optical axis constituting the plane. And a coordinate measurement step of acquiring a plurality of types of three-dimensional coordinate data by independently performing the step of acquiring the three-dimensional coordinates of the measurement region by the phase shift method by imaging with the imaging unit,
The step of differentiating an image obtained by imaging the measurement area under uniform illumination light and obtaining a luminance gradient direction for each pixel in the image is independently performed for each plane from the direction of the optical axis for projection. A gradient acquisition step of acquiring a plurality of types of gradient direction data by performing illumination and imaging by the imaging unit;
For each pixel corresponding to a pixel in another set of images in a plurality of sets of three-dimensional coordinate data and gradient direction data for each plane, the luminance gradient direction and the pattern change direction are respectively formed. A pixel data determining step of obtaining an angle or an inclination component corresponding to the angle, and combining three-dimensional coordinates for the pixel in each set based on the angle or inclination component to obtain a measurement result of the three-dimensional coordinates in the pixel; The three-dimensional shape measuring method characterized by including.   In the pixel data determining step, when the three-dimensional coordinates are synthesized, the angle formed by the gradient direction of the brightness and the pattern change direction in the plurality of sets is compared with each other to give an angle closer to 90 °. The three-dimensional shape measurement method according to claim 1, wherein a dimensional coordinate is selected to obtain a measurement result at the pixel.   In the pixel data determination step, when the magnitude of the differential value obtained by the differential processing in the gradient acquisition step is smaller than a predetermined threshold value for any of the corresponding pixels in the plurality of sets, the pixel data determination step The three-dimensional shape measurement method according to claim 1, wherein the three-dimensional coordinates for the pixel are evenly combined with each other to obtain a measurement result of the three-dimensional coordinates at the pixel.   A three-dimensional shape measuring apparatus using the three-dimensional shape measuring method according to any one of claims 1 to 3.

Images