JP6086002B2 - Shape analysis apparatus and shape analysis method - Google Patents

Description

  The present invention relates to a shape analysis device and a shape analysis method, and more particularly to a shape analysis device and a shape analysis method that can realize highly accurate analysis.

  2. Description of the Related Art A shape analysis apparatus that analyzes the shape of a target based on an image obtained by shooting a target with a grid pattern in which marks are arranged in a grid is known. In such a shape analysis apparatus, a sampling moire method may be used to analyze a target shape (for example, see Patent Documents 1 to 3 and Non-Patent Document 1).

JP 2009-264852 A JP 2011-174874 A JP 2012-107896 A

Li Shien, Hiroshi Tsuda, "Automatic Determination Method of Optimal Analysis Pitch for High-Precision Displacement Measurement in Sampling Moire Method", The 44th Symposium on Stress and Strain Measurement Symposium, January 2013

  An object of the present invention is to provide a shape analysis apparatus and a shape analysis method capable of performing shape analysis by a sampling moire method with high accuracy.

  In one aspect, the analysis device calculates a lattice pitch, which is a period in which the marks are arranged in the image, based on an image obtained by photographing an object to which a lattice pattern in which marks are arranged in a lattice shape is captured. Using a lattice pitch calculation unit, a plurality of decimation numbers, a moire fringe generation unit that generates a moire fringe corresponding to each decimation number from the image, and a phase distribution for each decimation number based on the moire fringes The phase distribution calculation unit to calculate, and the phase at the position in the phase distribution calculated using the thinning number corresponding to the lattice pitch at the position of the phase distribution at the position corresponding to each pixel of the image An optimized phase distribution generation unit that generates an optimized phase distribution with a value set, and an optimized phase of the phase connection in which phase connection is performed on the optimized phase distribution And a shape calculation section that calculates the shape of the object by using the fabric.

  In another aspect, the analysis method calculates a lattice pitch, which is a period in which the mark is arranged in the image, based on an image obtained by photographing an object having a lattice pattern in which the mark is arranged in a lattice shape. Generating a moire fringe corresponding to each thinning number from the image using a plurality of thinning numbers; calculating a phase distribution for each thinning number based on the moire fringes; and An optimized phase distribution in which the phase value of the position in the phase distribution calculated using the thinning number corresponding to the lattice pitch in the position is set in the position corresponding to each pixel of the image And calculating the shape of the object using the optimized phase distribution of the phase connection obtained by applying phase connection to the optimized phase distribution. Includes a step, a.

  The analysis system and the analysis method can realize highly accurate analysis in one aspect.

FIG. 1 is a configuration diagram illustrating a shape analysis system according to an embodiment. FIG. 2 is a block diagram illustrating functions of the shape analysis apparatus illustrated in FIG. FIG. 3 is a diagram illustrating an example of a digital image obtained by photographing a test tire using a camera. FIG. 4 is a diagram illustrating an example of the operation of the lattice pitch calculation unit. FIG. 5 is a diagram illustrating an example of operations of the moire fringe generation unit and the phase distribution calculation unit when pixels are thinned out in the horizontal direction. FIG. 6 is a diagram for explaining generation of moire fringes in the sampling moire method. FIG. 7 is a diagram illustrating an example of the operation of the optimized phase distribution generation unit when pixels are thinned out in the horizontal direction. FIG. 8 is a diagram illustrating an example of the operation of the shape calculation unit. FIG. 9 is a flowchart illustrating an example of a procedure of a shape analysis method performed by the shape analysis apparatus. FIG. 10 is a diagram showing an example of an image in which the analysis lattice plane attached to the test tire is shown. FIG. 11 is a diagram illustrating an example in which an irregular shape is calculated. FIG. 12 is a diagram illustrating an example of an analysis result obtained by the shape analysis method according to the embodiment. FIG. 13 is a block diagram illustrating functions of the shape analysis apparatus according to the modification. FIG. 14 is a diagram illustrating an example of the operation of the lattice pitch correction unit. FIG. 15 is a flowchart illustrating an example of a procedure of a shape analysis method performed by the shape analysis apparatus according to the modification. FIG. 16 is a diagram illustrating an example of operations of the moire fringe generation unit and the phase distribution calculation unit when pixels are thinned out in the vertical direction. FIG. 17 is a diagram illustrating an example of the operation of the optimized phase distribution generation unit when pixels are thinned out in the vertical direction. FIG. 18 is a configuration diagram showing a shape analysis system for analyzing the shape of a rim.

  Hereinafter, the present invention will be described in detail with reference to the drawings. In the following, an embodiment will be described taking as an example the case where the present invention is used for analysis of the shape of a tire.

  Note that the present invention is not limited to the embodiments. Further, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

[Shape analysis system]
FIG. 1 is a configuration diagram showing a shape analysis system according to an embodiment of the present invention. FIG. 2 is a block diagram showing functions of the shape analysis apparatus of the shape analysis system shown in FIG. In these drawings, FIG. 1 schematically shows the overall configuration of the shape analysis system, and FIG. 2 shows the main functions of the shape analysis apparatus.

  The shape analysis system 1 is applied to a system that performs tire behavior analysis (tire response evaluation) by measuring changes in tire shape and tire surface distortion when a predetermined condition is input. The shape analysis system 1 includes a tire testing machine 2, an imaging device 3, and a shape analysis device 4a (see FIG. 1).

  The tire testing machine 2 is an apparatus that imparts test conditions to the test tire, and includes, for example, a drum type tire testing machine, a belt type tire testing machine, and the like. In the configuration of FIG. 1, the tire testing machine 2 is a drum type tire testing machine, and includes a support device 21 and a driving device 22. The support device 21 is a device that rotatably supports the test tire 10 and includes a rim 211 on which the test tire 10 is mounted. The driving device 22 is a device that applies a driving force to the test tire 10, and includes a rotating drum 221, a motor 222 that drives the rotating drum 221, and a motor control device 223 that drives and controls the motor 222.

  In the tire testing machine 2, the support device 21 mounts and supports the test tire 10 on the rim 211, and presses the test tire 10 against the rotating drum 221 of the driving device 22 to apply a load to the test tire 10. In addition, the support device 21 displaces the rim 211 to adjust the positional relationship between the test tire 10 and the rotating drum 221, thereby giving the test tire 10 a slip angle or an angle angle. Further, the drive device 22 drives the motor 222 by the motor control device 223 to rotate the rotating drum 221, thereby giving the test tire 10 a rotational speed. As a result, the rolling state of the tire during vehicle travel is reproduced with the circumferential surface of the rotating drum 221 as the road surface. In addition, the test conditions can be changed by the support device 21 and the drive device 22 adjusting the load, rotation speed, slip angle, angle angle, and the like.

  The imaging device 3 includes a pair of cameras 31 and 31 and a pair of illumination lamps 32 and 32. The camera 31 is a means for imaging the test tire 10, and is constituted by, for example, a CCD (Charge Coupled Device) camera. The camera 31 is, for example, a high speed camera. Moreover, a pair of cameras 31 and 31 are arrange | positioned in the position which can image the test tire 10 from a mutually different direction. These cameras 31 and 31 simultaneously image the test tire 10 from the left-right direction to generate a tire image (digital image data of the test tire 10). The illumination lamp 32 is a lamp that illuminates the imaging range of the camera 31, and is composed of, for example, a halogen lamp. These illumination lamps 32 may be a constantly lit type or a flash lit type.

  The shape analysis device 4a is, for example, a PC (personal computer) in which a predetermined analysis program is installed, and performs shape analysis processing by processing the tire image from the imaging device 3 (see FIG. 2). The shape analysis device 4a analyzes the shape of the target based on a digital image (tire image) obtained by photographing the target with a grid pattern in which marks are arranged in a grid pattern. The shape analysis device 4 a includes a lattice pitch calculation unit 41, a moire fringe generation unit 42, a phase distribution calculation unit 43, an optimized phase distribution generation unit 44, and a shape calculation unit 45.

  The lattice pitch calculation unit 41 calculates a lattice pitch. The “lattice pitch” is a period in which marks are arranged in a digital image obtained by photographing an object provided with a lattice pattern in which marks are arranged in a lattice pattern. In this embodiment, the unit of the lattice pitch is a pixel.

  The moire fringe generation unit 42 generates a moire fringe corresponding to each thinning number from the digital image using a plurality of thinning numbers. The phase distribution calculation unit 43 calculates the phase distribution of the digital image for each thinning number based on the moire fringes generated by the moire fringe generation unit 42. The “phase distribution” is a distribution quantified as 1 lattice pitch = phase value 2π, and is a striped pattern with a discontinuous distribution that is a repetition of phase values 0 to 2π.

  The optimized phase distribution generation unit 44 generates a phase distribution for shape analysis based on the lattice pitch calculated by the lattice pitch calculation unit 41 and the phase distribution calculated by the phase distribution calculation unit 43. The shape calculation unit 45 calculates a target shape using the optimized phase distribution of the phase connection obtained by performing phase connection on the phase distribution generated by the optimization phase distribution generation unit 44. “Phase connection” is a numerical process that makes a discontinuous phase distribution that is a repetition of phase values 0 to 2π continuous, and 2π is added or subtracted at the boundary of the discontinuous portion as shown in the following equation (1). To do.

  Here, φ (x, y) and θ (x, y) represent the phase value after phase connection at the pixel position (x, y) and the phase value of the discontinuous phase distribution before phase connection, respectively. Is the fringe order (n =..., -1, 0, +1,...). Thereby, the position in the screen on the lattice pattern can be uniquely determined.

[Shape analysis method]
The shape analysis device 4a uses a sampling moire method as a method for analyzing the shape of the object. The sampling moire method is a mathematical method for generating a moire fringe from a digital image and calculating a three-dimensional shape of the object. The sampling moire method has an advantage that a highly accurate shape analysis can be performed.

  In the sampling moire method, the accuracy is highest when the thinning-out number used when generating moire fringes from a digital image is an integer closest to the lattice pitch. On the other hand, when the lattice pitch varies, the accuracy of shape analysis by the sampling moire method may decrease.

  In the example shown in FIG. 1, a plurality of analysis lattice planes SA (SA # 1 to SA # n) are circularly provided on the tire circumference of the test tire 10. The analysis lattice plane SA is a sheet having a lattice pattern in which marks having substantially the same shape are arranged in a lattice pattern with periodicity. For example, the analysis lattice plane SA includes a plurality of circular marks having a size of 5 [mm] arranged in a matrix at intervals of 5 [mm]. The shape, size, and interval of the marks are not limited to the example in FIG. The shape of the mark may be, for example, a square, a rectangle, a triangle, or a star.

  The shape analysis device 4a analyzes the shape of the test tire 10 by the sampling moire method using the lattice pattern of the analysis lattice surface SA, and the analysis lattice surface SA is pasted along the side surface of the test tire 10. Therefore, there are variations in the lattice pitch on the digital image. Specifically, the lattice pitch is large in a portion perpendicular to the imaging surface of the camera 31, and the lattice pitch is small in a portion having a large inclination with respect to the imaging surface.

  FIG. 3 is a diagram illustrating an example of a digital image 50 obtained by photographing the test tire 10 using the camera 31. In the digital image 50 shown in FIG. 3, when an enlarged image 51 of a portion 50a in which one analysis lattice plane SA is shown, a portion having a pixel pitch of 7 pixels, a portion having a pixel pitch of 8 pixels, and the like are shown. It is mixed. Thus, in the digital image which image | photographed the test tire 10, since the lattice pitch varies, if the sampling moire method is simply applied, the accuracy of the shape analysis may be lowered.

  The shape analysis device 4a is configured to reduce a decrease in shape analysis accuracy due to such a variation in lattice pitch. The operation of the shape analysis apparatus 4a will be specifically described with reference to FIGS. Below, the example which analyzes the shape of the test tire 10 based on the image 51 shown in FIG. 3 is demonstrated.

  FIG. 4 is a diagram illustrating an example of the operation of the lattice pitch calculation unit 41. The lattice pitch calculation unit 41 generates an image 52 in which a lattice pattern is smoothed in a direction orthogonal to a direction in which pixels are thinned out from an image 51 in which the analysis lattice plane SA is reflected. In the image 52, the marks constituting the lattice pattern are connected to the adjacent marks in a direction orthogonal to the direction in which the pixels are thinned out.

  The lattice pitch calculation unit 41 scans the image 52 thus generated in a direction parallel to the direction in which pixels are thinned out, and obtains luminance for each pixel. Then, the lattice pitch calculation unit 41 calculates the lattice pitch based on the magnitude of the luminance change.

  For example, the lattice pitch calculation unit 41 obtains a curve indicating the relationship between the pixel position and the luminance as shown in the graph 53 by scanning the pixel along the line L1. Then, the lattice pitch calculation unit 41 calculates a luminance derivative indicating the magnitude of the change in luminance between adjacent pixels, thereby obtaining a curve indicating the relationship between the pixel position and the luminance derivative as shown in the graph 54. obtain.

  In the graph shown in the graph 54, the position where the luminance derivative changes from a positive value to a negative value, or the position where the luminance derivative changes from a negative value to a positive value is a position where the lattice pitch changes, and the positions of those adjacent positions are changed. The interval corresponds to the lattice pitch of the section. For example, while scanning the pixel along the line L1, the luminance differentiation changes from a positive value to a negative value at the position of the pixel A, and the luminance differentiation changes from a negative value to a positive value at the position of the pixel B. When the luminance differentiation changes from a positive value to a negative value, the value of the lattice pitch corresponding to each pixel between the pixel A and the pixel C is the distance between the pixel A and the pixel C.

  The lattice pitch calculation unit 41 calculates a lattice pitch for each region included in the image 51 as shown in an image 55 by executing a plurality of lines of scanning in a direction parallel to the pixel thinning direction. The lattice pitch calculation unit 41 may calculate the lattice pitch for at least a portion of the image 51 where the analysis lattice plane SA is shown.

  Scanning in a direction parallel to the pixel thinning direction is preferably performed in units of pixels. For example, when the image 51 has 500 pixels in the direction perpendicular to the direction of thinning out pixels, it is preferable to perform scanning 500 times. When scanning is not performed in units of pixels, the lattice pitch calculation unit 41 linearly sets the lattice pitch corresponding to the pixels belonging to the unscanned line and the lattice pitch corresponding to the pixels belonging to the scanned line in the direction perpendicular to the scanning direction. You may calculate by interpolating.

  Thus, the lattice pitch calculation unit 41 calculates the lattice pitch corresponding to each pixel included in the image to be analyzed by analyzing the image. For this reason, compared with the case where an operator sets a lattice pitch based on visual observation, the lattice pitch can be set with higher accuracy, and the load on the operator is further reduced.

  The lattice pitch calculation unit 41 may perform a smoothing process on the curve shown in the graph 54 before calculating the lattice pitch from the curve shown in the graph 54. Thereby, the grating pitch can be set with higher accuracy.

  FIG. 5 is a diagram illustrating an example of operations of the moire fringe generation unit 42 and the phase distribution calculation unit 43. The moire fringe generation unit 42 generates a moire fringe corresponding to each thinning number from the image 51 in which the analysis lattice plane SA is reflected using a plurality of thinning numbers. The same number of moire fringes as the thinning number is generated for each thinning number.

  For example, the moire fringe generating unit 42 generates five moire fringes including the moire fringe 56 using a thinning number of 5. For example, the moire fringe generation unit 42 generates eight moire fringes including the moire fringes 58 using a thinning number of 8. Moire fringes may be generated in the form of an image as shown in FIG. 5, or may be generated as data indicating the correspondence between pixel positions and luminance.

  The range of the thinning number used by the moire fringe generating unit 42 is preferably the range of the maximum value and the minimum value of the lattice pitch calculated by the lattice pitch calculating unit 41. For example, when the minimum value of the lattice pitch calculated by the lattice pitch calculation unit 41 using the image 51 is 3 pixels and the maximum value is 8 pixels, the moire fringe generation unit 42 is an integer between 3 and 8. Is preferably used as a decimation number to generate moire fringes. In this way, by matching the range of the thinning number with the calculated range of the lattice pitch, the amount of calculation of the moire fringe generation unit 42 is reduced, and the optimization phase distribution generated by the optimization phase distribution generation unit 44 is reduced. Accuracy can be increased.

  The phase distribution calculation unit 43 calculates a phase distribution for each thinning number based on the moire fringes generated by the moire fringe generation unit 42. For example, the phase distribution calculation unit 43 calculates the phase distribution 57 corresponding to the decimation number of 5 based on the 5 moire fringes including the moire fringe 56 generated by the moire fringe generation unit 42 using the decimation number of 5. To do. For example, the phase distribution calculation unit 43 calculates the phase distribution 59 corresponding to the thinning number of 8 based on the 8 moire fringes including the moire fringe 58 generated by the moire fringe generation unit 42 using the thinning number of 8. To do.

  Generation of moire fringes by the moire fringe generation unit 42 and calculation of phase distribution by the phase distribution calculation unit 43 are the same as normal processing by the sampling moire method, except that processing is performed for each of a plurality of decimation numbers. .

  Generation of moire fringes and calculation of phase distribution in the sampling moire method will be described in more detail with reference to FIG. FIG. 6 is a diagram for explaining generation of moire fringes in the sampling moire method. The example shown in FIG. 6 is an example in which moire fringes are generated using a thinning number of 4.

  In step S11, four images 91a to 91d are generated by thinning the image 90 every four pixels. The images 91a to 91d have different pixels for starting thinning. The number of images generated by thinning out the pixels matches the thinning number. For example, when the thinning-out number is 10, ten images are generated.

  As step S12, for each of the images 91a to 91d, a process of setting the luminance of the pixels for which the thinned pixels are not set by linear interpolation using the luminance of the pixels for which the thinned pixels are set. Applied. Thereby, moire fringes 92a to 92d are obtained.

  The phase value θ (x, y) at the position corresponding to the pixel position (x, y) in the phase distribution corresponding to the thinning-out number is calculated using the following equation (2).

  Here, N is a thinning-out number, n is the number of moire fringes, and I (x, y, n) is the luminance at the pixel position (x, y) of the nth moire fringes. . In the example shown in FIG. 6, the moire fringes 92a, 92b, 92c, and 92d correspond to the first, second, third, and fourth moire fringes, respectively.

  By calculating the phase value corresponding to each pixel position using Equation (2) with reference to the moire fringes 92a to 92d, the phase distribution when the image 90 is thinned by the thinning number of 4 can be calculated. it can.

  FIG. 7 is a diagram illustrating an example of the operation of the optimized phase distribution generation unit 44. The optimization phase distribution generation unit 44 is calculated using the thinning number corresponding to the lattice pitch at the position among the phase distributions calculated by the phase distribution calculation unit 43 at the position corresponding to each pixel of the digital image. An optimized phase distribution in which the phase value at the position in the phase distribution is set is generated.

  For example, the optimized phase distribution generation unit 44 refers to data indicating the correspondence between the pixel position and the grid pitch as shown in the image 55, and the grid at the position 55 a corresponding to the pixel position (x1, y1) of the digital image 51. Get the pitch. Then, the optimized phase distribution generation unit 44 specifies a thinning number corresponding to the acquired grating pitch. The thinning-out number corresponding to the acquired lattice pitch is a thinning-out number that is the same as or closest to the acquired lattice pitch among the thinning-out numbers used by the moire fringe generation unit 42 and the phase distribution calculation unit 43.

  When the lattice pitch at the position 55a is 5 pixels, the optimized phase distribution generation unit 44 specifies 5 as the thinning-out number corresponding to the lattice pitch. Then, the optimized phase distribution generation unit 44 acquires the phase value at the position 57 a corresponding to the pixel position (x1, y1) of the digital image 51 from the phase distribution 57 corresponding to the thinning number of 5. The optimized phase distribution generation unit 44 sets the phase value acquired in this way in the optimized phase distribution 60 as the phase value at the position 60a corresponding to the pixel position (x1, y1) of the digital image 51.

  Similarly, the optimized phase distribution generation unit 44 refers to data indicating the correspondence between the pixel position and the grid pitch as shown in the image 55, and at the position 55b corresponding to the pixel position (x2, y2) of the digital image 51. Get the grid pitch.

  When the lattice pitch at the position 55b is 8 pixels, the optimized phase distribution generation unit 44 specifies 8 as a thinning-out number corresponding to the lattice pitch. Then, the optimized phase distribution generation unit 44 acquires the phase value at the position 59b corresponding to the pixel position (x2, y2) of the digital image 51 from the phase distribution 59 corresponding to the thinning number of 8. The optimized phase distribution generation unit 44 sets the phase value acquired in this way in the optimized phase distribution 60 as the phase value at the position 60 b corresponding to the pixel position (x2, y2) of the digital image 51.

  The optimized phase distribution generation unit 44 generates the optimized phase distribution 60 by performing the above processing for each pixel of the digital image 51. The optimized phase distribution 60 is generated by combining phase distributions adapted to the grating pitch. For example, in the optimized phase distribution 60, a phase value calculated with a decimation number of 5 is set at a position where the grid pitch is 5 pixels, and a phase calculated with a decimation number of 8 is set at the position where the grid pitch is 8 pixels. Generated to set the value.

  By combining the phase distributions suitable for the lattice pitch in this way, it is possible to generate an optimized phase distribution 60 in which a phase value suitable for shape analysis is set at a position corresponding to any pixel position. That is, by combining the phase distributions suitable for the grating pitch, it is possible to reduce the deterioration of the shape analysis accuracy due to the variation of the grating pitch.

  As shown in FIG. 8, the shape calculating unit 45 is based on the optimized phase distribution 60p of the phase connection obtained by performing phase connection on the optimized phase distribution 60 generated by the optimized phase distribution generating unit 44. The shape of the test tire 10 is calculated. The shape calculation unit 45 calculates the shape of the test tire 10 by the same process as the normal process by the sampling moire method. However, since the shape analysis is performed using the optimized phase distribution 60, high analysis accuracy is realized.

  The procedure of the shape analysis method by the shape analysis device 4a will be described with reference to FIG. FIG. 9 is a flowchart illustrating an example of a procedure of a shape analysis method performed by the shape analysis apparatus 4a. In step S101, the lattice pitch calculation unit 41 calculates a lattice pitch based on the digital image. In step S <b> 102, the moire fringe generation unit 42 determines the range of thinning numbers based on the range of the lattice pitch calculated by the lattice pitch calculation unit 41.

  In step S103, the moire fringe generation unit 42 selects one unselected thinning number from the determined range. In step S104, the moire fringe generating unit 42 generates moire fringes using the selected thinning number. In step S105, based on the moire fringes generated by the moire fringe generator 42, the phase distribution calculator 43 calculates a phase distribution corresponding to the selected thinning number.

  In step S106, the shape analysis device 4a determines whether all the thinning numbers within the range determined in step S102 have already been selected. When all the thinning-out numbers have not been selected (No at Step S106), Step S103 and subsequent steps are re-executed. When all the thinning-out numbers are selected (step S106, Yes), the shape analysis apparatus 4a proceeds to step S107.

  In step S107, the optimization phase distribution generation unit 44 generates an optimization phase distribution based on the lattice pitch calculated by the lattice pitch calculation unit 41 and the phase distribution calculated by the phase distribution calculation unit 43. In step S108, the shape calculation unit 45 calculates a target shape based on the optimized phase distribution of the phase connection obtained by performing phase connection on the optimized phase distribution.

[effect]
As described above, the shape analysis device 4a calculates the grid pitch, which is the period in which the mark is arranged in the image, based on the image obtained by photographing the target with the grid pattern in which the mark is arranged in a grid. And a moire fringe generator 42 for generating moire fringes corresponding to each thinning number from an image using a plurality of thinning numbers, and a phase distribution for each thinning number based on the moire fringes. At the position corresponding to each pixel of the image and the phase distribution calculating unit 43 to calculate, the phase value of the position in the phase distribution calculated using the thinning out number corresponding to the lattice pitch at the position of the phase distribution is Using the optimized phase distribution generation unit 44 that generates the set optimized phase distribution, and the optimized phase distribution of the phase connection in which the phase connection is performed on the optimized phase distribution It comprises a shape calculating unit 45 for calculating the elephant shape, a.

  In such a configuration, the target shape is calculated based on the optimized phase distribution generated by combining the phase distributions suitable for the grating pitch. For this reason, highly accurate shape analysis becomes possible.

  The effect of the present embodiment will be described with reference to FIGS. FIG. 10 is a diagram illustrating an example of an image in which the analysis lattice plane SA attached to the test tire 10 is reflected. The image 61 shown in FIG. 10 includes a portion having a lattice pitch of 5 pixels, a portion having a lattice pitch of 6 pixels, a portion having a lattice pitch of 7 pixels, and the like.

  If the shape analysis of the line L2 portion is simply performed by the sampling moire method using such an image 61, an irregular shape may be calculated like the portion 62a in the analysis result 62 shown in FIG. . On the other hand, when the shape analysis method according to the present embodiment is used, the shape of the portion 63b corresponding to the portion 62a is calculated with high accuracy as in the analysis result 63 shown in FIG.

[Modifications and application examples]
Modifications and application examples of the above embodiment will be described.

  FIG. 13 is a block diagram illustrating functions of the shape analysis apparatus according to the modification. The shape analysis apparatus 4b shown in FIG. 13 is different from the shape analysis apparatus 4a in that it further includes a grating pitch correction unit 46 and in that an optimization phase distribution generation unit 47 is provided instead of the optimization phase distribution generation unit 44.

  The lattice pitch correction unit 46 corrects the lattice pitch calculated by the lattice pitch calculation unit 41 in order to further improve the accuracy of shape analysis. FIG. 14 is a diagram illustrating an example of the operation of the lattice pitch correction unit 46. The lattice pitch correction unit 46 performs phase connection on the phase distribution calculated by the phase distribution calculation unit 43, and corrects the lattice pitch corresponding to each pixel of the digital image based on the phase distribution after the phase connection. Specifically, in the phase distribution after phase connection, the phase value of the pixel in the phase distribution calculated using the thinning number corresponding to the lattice pitch, and the thinning number corresponding to the lattice pitch in the adjacent pixel The phase value of the pixel in the phase distribution calculated using is acquired, and the phase difference between the two is calculated. The lattice pitch correction unit 46 corrects the lattice pitch corresponding to each pixel of the digital image based on the ratio between the phase difference between them and the phase per lattice pitch (= 2π).

  For example, the grid pitch correction unit 46 refers to data indicating the correspondence between the pixel position and the grid pitch as shown in the image 55, and the pixel position (x3, y3) of the digital image 51 and the adjacent pixel position (x4, x4). The lattice pitch at the positions 55c and 55e corresponding to y4) is acquired. And the lattice pitch correction | amendment part 46 specifies the thinning number corresponding to the acquired lattice pitch, respectively.

  When the grid pitch at the position 55c is 5 pixels, the grid pitch correction unit 46 specifies 5 as the thinning-out number corresponding to the grid pitch. Then, the lattice pitch correction unit 46 acquires the phase value at the position 67c corresponding to the pixel position (x3, y3) of the digital image 51 from the phase distribution 67 after the phase connection corresponding to the thinning number of 5. Next, when the lattice pitch at the position 55e is 6 pixels, the lattice pitch correction unit 46 specifies 6 as the thinning-out number corresponding to the lattice pitch. Then, the lattice pitch correction unit 46 acquires the phase value at the position 68c corresponding to the pixel position (x4, y4) of the digital image 51 from the phase distribution 68 after the phase connection corresponding to the thinning number of 6. The lattice pitch correcting unit 46 corrects the lattice pitch corrected based on the ratio between the difference between the two phase values thus obtained and the phase per lattice pitch to the pixel position (x3, y3) of the digital image 51. This is set as the lattice pitch after correction at 55c.

  Similarly, the grid pitch correction unit 46 refers to the data indicating the correspondence between the pixel position and the grid pitch as shown in the image 55, and the pixel position (x5, y5) of the digital image 51 and the adjacent pixel position (x6). , Y6), the grid pitches at the positions 55d and 55f are obtained.

  When the grid pitch at the position 55d is 8 pixels, the grid pitch correction unit 46 specifies 8 as the thinning-out number corresponding to the grid pitch. Then, the lattice pitch correction unit 46 acquires the phase value at the position 69c corresponding to the pixel position (x5, y5) of the digital image 51 from the phase distribution 69 after the phase connection corresponding to the thinning number of 8. Next, when the lattice pitch at the position 55f is also 8 pixels, the lattice pitch correction unit 46 specifies 8 as a thinning number corresponding to the lattice pitch. Then, the lattice pitch correction unit 46 acquires a phase value at a position 69d corresponding to the pixel position (x6, y6) of the digital image 51 from the phase distribution 69 after the phase connection corresponding to the thinning number of 8. The lattice pitch correction unit 46 corrects the lattice pitch corrected based on the ratio of the difference between the two phase values thus obtained and the phase per lattice pitch to the pixel position (x5, y5) of the digital image 51. This is set as the lattice pitch after correction at 55d.

  By performing the above processing for each pixel of the digital image 51, the lattice pitch correction unit 46 can calculate the lattice pitch more finely. Specifically, the correction of the lattice pitch is performed using one or both of the following formulas (3) and (4). Formula (3) is a correction formula for the lattice pitch in the horizontal direction. Formula (4) is a correction formula for the lattice pitch in the vertical direction.

  Here, p (x, y) is a corrected lattice pitch at the pixel position (x, y). φ (x, y) is a phase value after phase connection at the pixel position (x, y), abs is an absolute value of a value in parentheses, and Int is an integer value obtained by truncating the decimal point in square brackets. On the right side of Expression (3), φ (x + 1, y) may be replaced with φ (x−1, y). Also on the right side of Expression (4), φ (x, y + 1) may be replaced with φ (x, y−1). By using the phase values that are continuous in this way, the calculations of equations (3) and (4) can be performed more easily than when using phase values of discontinuous phase distribution.

  The optimization phase distribution generation unit 47 generates an optimization phase distribution based on the lattice pitch corrected by the lattice pitch correction unit 46 instead of the lattice pitch calculated by the lattice pitch calculation unit 41. As a result, an optimized phase distribution that can be analyzed with higher accuracy is generated.

  The procedure of the shape analysis method by the shape analysis device 4b will be described with reference to FIG. FIG. 15 is a flowchart illustrating an example of a procedure of a shape analysis method performed by the shape analysis apparatus 4b. Steps S201 to S206 are the same as steps S101 to S106 shown in FIG.

  In step S207, the grating pitch correction unit 46 uses the phase distribution of the phase connection obtained by performing phase connection on the phase distribution calculated by the phase distribution calculation unit 43 using the grating pitch calculated by the grating pitch calculation unit 41. to correct. In step S <b> 208, the optimized phase distribution generation unit 47 generates an optimized phase distribution based on the lattice pitch corrected by the lattice pitch correction unit 46 and the phase distribution calculated by the phase distribution calculation unit 43. In step S209, the shape calculation unit 45 calculates the target shape based on the optimized phase distribution of the phase connection obtained by performing phase connection on the optimized phase distribution.

  In the above embodiment, an example in which pixels are thinned out in the horizontal direction has been described. However, the direction in which pixels are thinned out is not limited to this. For example, the shape analysis device 4a and the shape analysis device 4b may thin out pixels in the vertical direction as shown in FIGS. FIG. 16 is a diagram illustrating an example of operations of the moire fringe generation unit 42 and the phase distribution calculation unit 43 when pixels are thinned out in the vertical direction. FIG. 17 is a diagram illustrating an example of operations of the optimization phase distribution generation unit 44 and the optimization phase distribution generation unit 47 when pixels are thinned out in the vertical direction.

  As illustrated in FIG. 16, the moire fringe generation unit 42 generates moire fringes corresponding to each thinning number from an image 51 in which the analysis lattice plane SA is captured using a plurality of thinning numbers. For example, the moire fringe generation unit 42 generates seven moire fringes including the moire fringes 76 by thinning pixels in the vertical direction using a thinning number of 7. For example, the moire fringe generation unit 42 generates eight moire fringes including the moire fringes 78 by thinning pixels in the vertical direction using a thinning number of 8.

  As illustrated in FIG. 16, the phase distribution calculation unit 43 calculates a phase distribution for each thinning number based on the moire fringes generated by the moire fringe generation unit 42. For example, the phase distribution calculating unit 43 calculates the phase distribution 77 corresponding to the thinning number of 7 based on the seven moire fringes 76 including the moire fringe 76 generated by the moire fringe generating unit 42 using the thinning number of 7. To do. For example, the phase distribution calculating unit 43 calculates the phase distribution 79 corresponding to the thinning number of 8 based on the 8 moire fringes 78 including the moire fringes 78 generated by the moire fringe generating unit 42 using the thinning number of 8. To do.

  As shown in FIG. 17, the optimization phase distribution generation unit 44 and the optimization phase distribution generation unit 47 include the phase distribution calculated by the phase distribution calculation unit 43 at the position corresponding to each pixel of the digital image. An optimized phase distribution 80 in which the phase value of the position in the phase distribution calculated using the thinning-out number corresponding to the lattice pitch at the position is generated. The lattice pitch at the position corresponding to the pixel is obtained by referring to data indicating the correspondence between the pixel position and the lattice pitch as shown in the image 75. Data indicating the correspondence between the pixel position and the grid pitch as shown in the image 75 is calculated by the grid pitch calculation unit 41 scanning the image 51 in the vertical direction. Alternatively, for the data indicating the correspondence between the pixel position and the grid pitch as shown in the image 75, the grid pitch correction unit 46 corrects the grid pitch calculated by the grid pitch calculation unit 41 scanning the image 51 in the vertical direction. Obtained by.

  In the above embodiment, the example in which the shape of the test tire 10 is analyzed based on the image including the analysis lattice plane SA attached on the tire circumference of the test tire 10 has been described. It is not limited to.

  For example, the shape analysis device 4a and the shape analysis device 4b are based on an image including an analysis lattice plane SB attached to a rim 211 or an annular disc 212 attached to an end of the rim 211, as shown in FIG. Thus, the shape of the rim 211 may be analyzed. The analysis lattice plane SB is a sheet having a lattice pattern in which marks having substantially the same shape are arranged in a lattice pattern with periodicity. Thereby, for example, deformation of the rim 211 during traveling can be analyzed.

  The shape analysis device 4a and the shape analysis device 4b can also be applied to the analysis of the shapes of various objects other than tires. Examples of objects other than tires include, but are not limited to, products, parts, and buildings.

  1: shape analysis system, 2: tire testing machine, 21: support device, 211: rim, 212: annular disc, 22: drive device, 221: rotating drum, 222: motor, 223: motor control device, 3: imaging device , 31: camera, 32: illumination lamp, 4a: shape analysis device, 4b: shape analysis device, 42: moire fringe generation unit, 43: phase distribution calculation unit, 44: optimization phase distribution generation unit, 45: shape calculation Part 46: lattice pitch correction part 47: optimization phase distribution generation part

Claims (5)

A grid pitch calculation unit that calculates a grid pitch, which is a period in which the mark is arranged in the image, based on an image obtained by photographing an object having a grid pattern in which marks are arranged in a grid pattern;
A moiré fringe generating unit that generates a moiré fringe corresponding to each thinning number from the image using a plurality of thinning numbers;
A phase distribution calculating unit that calculates a phase distribution for each of the thinning numbers based on the moire fringes;
An optimized phase in which the phase value of the position in the phase distribution calculated using the thinning number corresponding to the lattice pitch in the position is set in the position corresponding to each pixel of the image An optimized phase distribution generator for generating a distribution;
A shape calculating unit that calculates the shape of the target using the optimized phase distribution of the phase connection, which is phase-connected to the optimized phase distribution;
A shape analysis apparatus comprising:   The shape analysis apparatus according to claim 1, wherein the lattice pitch calculation unit calculates the lattice pitch based on a magnitude of a change in luminance of a pixel included in the image.   Among the phase distributions of the phase connection in which the phase connection is applied to the phase distribution, the phase value of the pixel in the phase distribution calculated using the thinning number corresponding to the lattice pitch, and the lattice pitch in the adjacent pixel The phase value of the pixel in the phase distribution calculated using the corresponding thinning number is obtained, and the pixel corresponds to each pixel of the image based on the ratio of the phase difference between the two and the phase per grid pitch. The shape analysis apparatus according to claim 1, further comprising a lattice pitch correction unit that corrects the lattice pitch.   4. The shape analysis apparatus according to claim 1, wherein the moire fringe generation unit determines a range of the plurality of thinning-out numbers based on the range of the lattice pitch calculated by the lattice pitch calculation unit. 5. . Calculating a lattice pitch, which is a period in which the mark is arranged in the image, based on an image obtained by photographing an object to which a lattice pattern is arranged in which the marks are arranged in a lattice pattern;
Generating moiré fringes corresponding to each thinning number from the image using a plurality of thinning numbers;
Calculating a phase distribution for each decimation number based on the moire fringes;
An optimized phase in which the phase value of the position in the phase distribution calculated using the thinning number corresponding to the lattice pitch in the position is set in the position corresponding to each pixel of the image Generating a distribution;
Calculating the shape of the object using the optimized phase distribution of the phase connection obtained by performing phase connection on the optimized phase distribution;
A shape analysis method comprising: