JP2016080546A - Shape measuring device and shape measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shape measuring device for easily and speedily measuring a surface shape of a measurement object, while achieving space saving even in the measurement object having a curbed surface.SOLUTION: A shape measuring device 10 is conveyed in one-dimensional direction, and includes: an imaging part 101 having an area sensor for imaging an image of a measurement object having a texture pattern on the surface, and a tilt lens provided with a tilt shaft in such a manner as to be in parallel to an imaging surface of the area sensor and orthogonal to a conveying direction; and an arithmetic processing part 103 for handling imaged data imaged by the imaging part as a set of one-dimensional signal for each width direction position of the measurement object, specifying a focusing position in the conveying direction of the imaged data, and converting the focusing position into a shape of the measurement object on the basis of the linear line determined according to a Scheimpflug condition from the focusing distance of the tilt lens, a tilt angle, and an imaging magnification of the imaging part, and imaging resolving power.SELECTED DRAWING: Figure 1A

Description

  The present invention relates to a shape measuring device and a shape measuring method.

  Conventionally, the surface of a measurement object is imaged and the surface shape of the measurement object is measured based on an image signal obtained by the imaging.

  For example, in Patent Document 1 below, line light using laser light or the like and an imaging camera are used to image the reflected light from the surface of the measurement object of the line light, so that the measurement target is obtained by a so-called light cutting method. A technique for measuring the surface shape of an object is disclosed.

  Patent Document 2 below discloses a technique for measuring the surface shape of a measurement object using a so-called stereo method by imaging the surface of the measurement object using a plurality of imaging cameras.

  On the other hand, Non-Patent Document 1 below uses a high-speed variable focus lens to capture an image of a measurement object while changing the focal position, and memorizes the depth of focus at each position on the screen. Techniques for measuring the three-dimensional shape of an object have been proposed.

Japanese Patent Laid-Open No. 2004-3930 JP 2013-69100 A

Hiromasa Oku, Masaaki Kadouchi, Masatoshi Ishikawa, “Millisecond high-speed liquid variable focus lens and its potential for robot vision application”, 26th Annual Conference of the Robotics Society of Japan, RSJ2008AC3I1-03, September 2008.

  However, for the measurement object being transported on the production line or the like, the light cutting method disclosed in Patent Document 1 or the stereo method as described in Patent Document 2 in which a plurality of cameras are installed in the transport direction are used. When applied, the size of the measuring device in the transport direction increases, and installation may be difficult when equipment is added to an existing production line.

  In addition, when applying the stereo method as in Patent Document 2 in which a plurality of cameras are installed in the width direction of the measurement object (direction orthogonal to the conveyance direction) and measuring the measurement object having a curved surface, Since the stereo method can measure only the overlapping part of the camera field of view, the number of cameras increases.

  Furthermore, when the variable focus lens as in Non-Patent Document 1 is used, it is necessary to image the same part while changing the focal position, so the imaging process must be slow and applied to the production line. It is difficult to do.

  Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to measure more simply and at high speed while saving space even for a measurement object having a curved surface. The object is to provide a shape measuring apparatus and a shape measuring method capable of measuring the surface shape of an object.

  In order to solve the above-described problem, according to an aspect of the present invention, an area sensor that captures an image of a measurement object that is conveyed in a one-dimensional direction and has a ground pattern on a surface, and a tilt axis that is the area sensor. A tilt lens provided so as to be parallel to the imaging surface and perpendicular to the conveyance direction, and the imaging data captured by the imaging unit for each position in the width direction of the measurement object A straight line determined by Shineproof conditions from the focal length and tilt angle of the tilt lens and the imaging magnification of the imaging unit; A shape measuring device is provided that includes an arithmetic processing unit that converts the in-focus position into the shape of the measurement object based on the imaging resolution.

  In the shape measuring apparatus, it is preferable that the focusable range determined by the Scheimpflug condition and the length of the area sensor in the conveyance direction is set so as to include the depth range of the measurement object.

  The arithmetic processing unit has a passband lower limit of 0.1 to 0.3 and an upper limit of 0.5 to 0. 0 with respect to the frequency normalized with the Nyquist frequency when the pixel interval is the sampling interval. Preferably, a bandpass filter that is 7 or less is used, and a position where the intensity of the one-dimensional signal that has passed through the bandpass filter is maximum is specified as the in-focus position.

  The arithmetic processing unit is configured to convert an absolute value waveform defined by an absolute value of the one-dimensional signal that has passed through the bandpass filter into a left-right symmetrical convex shape and a value that gradually approaches 0 as the distance from the convex peak increases. It is preferable that the peak position of the function is approximated to a position where the intensity of the one-dimensional signal is maximized.

  The arithmetic processing unit preferably uses a triangular wave function or a Gaussian function as the function.

  The arithmetic processing unit may subtract the mode value of the absolute value waveform data from the absolute value waveform data prior to the approximation by the function.

  The arithmetic processing unit may subtract the median value of the absolute value waveform data from the absolute value waveform data prior to the approximation by the function.

  In order to solve the above-described problem, according to another aspect of the present invention, an area sensor that captures an image of a measurement object that is conveyed in a one-dimensional direction and has a ground pattern on the surface, and a tilt axis A step of imaging the measurement object by an imaging unit having a tilt lens provided so as to be parallel to the imaging surface of the area sensor and orthogonal to the conveyance direction, and the captured imaging data, Handling as a set of one-dimensional signals for each position in the width direction of the measurement object, specifying a focus position in the transport direction of the imaging data, focal length and tilt angle of the tilt lens, and imaging of the imaging unit Converting the identified in-focus position into the shape of the measurement object based on the straight line determined by the Scheinproof condition from the magnification and the imaging resolution. Shape measuring method are provided.

  As described above, according to the present invention, a measurement object having a curved surface is obtained by imaging a measurement object using a tilt lens set to a predetermined tilt angle and performing a predetermined calculation process. However, it is possible to measure the surface shape of the measurement object more easily and at high speed while saving space.

It is explanatory drawing shown about the structural example of the shape measuring apparatus which concerns on the 1st Embodiment of this invention. It is explanatory drawing shown about the structural example of the shape measuring apparatus which concerns on the same embodiment. It is explanatory drawing shown typically about the imaging part of the shape measuring apparatus which concerns on the same embodiment. It is explanatory drawing for demonstrating the imaging part of the shape measuring apparatus which concerns on the same embodiment. It is explanatory drawing for demonstrating the imaging part of the shape measuring apparatus which concerns on the same embodiment. It is a block diagram for demonstrating an example of a structure of the arithmetic processing part of the shape measuring apparatus which concerns on the same embodiment. It is a block diagram for demonstrating an example of a structure of the data processing part which the arithmetic processing part which concerns on the same embodiment has. It is explanatory drawing for demonstrating the process implemented by the data processing part which concerns on the same embodiment. It is explanatory drawing for demonstrating the process implemented by the data processing part which concerns on the same embodiment. It is explanatory drawing for demonstrating the process implemented by the data processing part which concerns on the same embodiment. It is the flowchart which showed an example of the flow of the shape measuring method implemented with the shape measuring apparatus which concerns on the same embodiment. It is the flowchart which showed an example of the flow of the shape calculation process in the shape measuring method which concerns on the embodiment. It is the block diagram which showed an example of the hardware constitutions of the arithmetic processing part which concerns on the same embodiment. FIG. 10 is an explanatory diagram for explaining an experimental example 1; FIG. 10 is an explanatory diagram for explaining an experimental example 1; FIG. 10 is an explanatory diagram for explaining an experimental example 1; FIG. 10 is an explanatory diagram for explaining an experimental example 1; FIG. 10 is an explanatory diagram for explaining an experimental example 1;

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

(Embodiment)
<Overall configuration of shape measuring device>
First, an overall configuration of a shape measuring apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1A and 1B. 1A and 1B are explanatory views schematically showing the overall configuration of the shape measuring apparatus according to the present embodiment.

  The shape measuring apparatus 10 according to the present embodiment images the surface of the measurement object being conveyed in a predetermined one-dimensional direction by a conveyance line or the like, and performs a predetermined calculation process on the captured image data. This is a device for calculating the surface shape of the measurement object. The measurement object that can be measured by the shape measuring apparatus 10 according to the present embodiment is not particularly limited. For example, it is generally used from various industrial products such as various steel plates, steel pipes, and wire rods conveyed on an iron making line. It is possible to target various products, up to various products used in the industry.

  In the following description, the case where the shape measuring apparatus 10 captures an image of visible light emitted from the measurement object or visible light reflected by the measurement object will be described as an example.

  For example, as illustrated in FIG. 1A, the shape measuring apparatus 10 mainly includes an imaging unit 101 and an arithmetic processing unit 103.

  The imaging unit 101 captures an image of the surface of the measurement object being transported in a predetermined direction by, for example, a transport line, and corresponds to entity data corresponding to the captured image (corresponding to each coordinate position of the captured image that is a two-dimensional image). This is data representing a luminance value, and is hereinafter also referred to as imaging data). The detailed configuration of the imaging unit 101 according to the present embodiment will be described in detail later. Imaging data generated by the imaging unit 101 is output to the arithmetic processing unit 103.

  The arithmetic processing unit 103 performs arithmetic processing as will be described in detail below on the imaging data generated by the imaging unit 101 to calculate the surface shape of the measurement object. The arithmetic processing unit 103 can also control various imaging processes performed by the imaging unit 101 as necessary. The detailed configuration of the arithmetic processing unit 103 will be described in detail below.

  As shown in FIG. 1A, the shape measuring apparatus 10 including the imaging unit 101 and the arithmetic processing unit 103 may be integrally mounted in a certain housing to form one shape measuring apparatus. As shown in FIG. 5, the imaging unit 101 and the arithmetic processing unit 103 may be distributed and installed in different devices and apparatuses.

  For example, in the example illustrated in FIG. 1B, an example in which the imaging unit 101 is mounted on an imaging device having a lens, an imaging element, and the like, and the arithmetic processing unit 103 is mounted on an arithmetic processing device such as a personal computer or a process computer is illustrated. ing. Thus, the shape measuring apparatus 10 according to the present embodiment may be realized as a measurement system including a plurality of devices.

  In the shape measuring apparatus 10 according to the present embodiment, each function of the arithmetic processing unit 103 may be realized by being distributed to a plurality of devices. That is, a mode in which a part of the functions of the arithmetic processing unit 103 is implemented in an imaging device having the imaging unit 101 and another function of the arithmetic processing unit 103 is implemented in the arithmetic processing device may be employed.

  The overall configuration of the shape measuring apparatus 10 according to the present embodiment has been described above with reference to FIGS. 1A and 1B.

<About the configuration of the imaging unit>
Next, the imaging unit 101 included in the shape measuring apparatus 10 according to the present embodiment will be described in detail with reference to FIGS. FIG. 2 is an explanatory diagram schematically showing the imaging unit of the shape measuring apparatus according to the present embodiment. 3 and 4 are explanatory diagrams for explaining the imaging unit of the shape measuring apparatus according to the present embodiment.

  As illustrated in FIG. 2, the imaging unit 101 according to the present embodiment includes an imaging device (hereinafter also referred to as “area camera”) 111 having an area sensor 113, and a tilt lens 115 attached to the area camera 111. Is mainly provided. In addition, the imaging unit 101 may further include an illumination light source 117 that irradiates predetermined illumination light onto an imaging surface that is at least a part of the surface of the measurement object, if necessary.

  For example, as shown in FIG. 2, the area camera 111 is provided so that the light receiving surface of the area sensor 113 is parallel to the imaging surface of the measurement object. Image data captured by the area camera 111 is output from the area sensor 113 to the arithmetic processing unit 103 and used for arithmetic processing described later.

  The tilt lens 115 is a lens capable of performing an operation (tilt operation) to tilt the lens main surface with respect to the imaging surface. The lens characteristics such as the focal length and the open aperture value of the tilt lens 115 are not particularly limited, and depend on the imaging conditions such as the distance between the tilt lens 115 and the measurement object, the brightness around the measurement object, and the like. Can be set as appropriate. In the present embodiment, a single biconvex lens is shown as a representative example of the tilt lens 115, but the tilt lens 115 according to the present embodiment may be composed of a plurality of lens groups. Each lens may be a spherical lens or an aspherical lens.

  In the imaging unit 101 according to the present embodiment, the tilt lens 115 is attached to the area camera 111 so that the light receiving tilt axis is parallel to the imaging surface and perpendicular to the transport direction.

  The optical relationship among the imaging surface of the measurement object, the area sensor 113 of the area camera 111, and the tilt lens 115 will be described in detail below with reference to FIGS.

  The illumination light source 117 is a light source that emits illumination light applied to the imaging surface, and is provided as necessary when the imaging environment is in a dark state when imaging the measurement object. The illumination light from the illumination light source 117 is not particularly limited, and light belonging to the visible light band may be used.

  Further, the installation position when the illumination light source 117 is installed is not particularly limited, and may be determined as appropriate according to the imaging environment of the measurement object.

[Optical relationship of the imaging unit]
Next, an optical relationship that is established between the area sensor 113 and the tilt lens 115 in the imaging unit 101 and the imaging surface of the measurement target will be described in detail with reference to FIGS. 3 and 4.

  As described above, in the imaging unit 101 according to the present embodiment, the light receiving surface of the area sensor 113 and the imaging surface of the measurement object are in a positional relationship parallel to each other, and the light receiving surface of the area sensor 113 is tilted. The main surface of the lens 115 is not parallel to each other, but has a positional relationship such that it intersects. One of the optical principles in such an optical positional relationship is the Scheimpflug principle. This principle is that “when the photosensitive surface of the film and the lens main surface intersect with one straight line, the object surface that is in focus also intersects with the same straight line”.

  When this Scheimpflug principle is applied to the imaging unit 101 according to the present embodiment, “the light receiving surface of the area sensor 113 (corresponding to the surface S1 in FIG. 3) and the main surface of the tilt lens 115 (the surface in FIG. 3). The object plane (hereinafter also referred to as the in-focus plane, which corresponds to S3 in FIG. 3), which is in a focused state when intersecting with one straight line (corresponding to the straight line P in FIG. 3) with It crosses on the same straight line. " As shown in FIG. 3, the condition based on the principle of such Scheimpflug (hereinafter also referred to as Scheinproof condition) is “the light receiving surface S1, the lens main surface S2, and the focusing surface S3 are on the same straight line P. Cross each other. " Further, for image formation, the image formation conditions include “the intersection of the optical axis of the lens (main optical axis Z1) and the light receiving surface S1, and the optical axis of the lens (main optical axis Z1) and the focusing surface S3. It is necessary that the image formation relationship (1 / a) + (1 / b) = (1 / f) is established at each of the intersections. In this imaging condition, f represents the focal length of the tilt lens, a represents the separation distance between the intersection of the main optical axis Z1 of the lens and the light receiving surface S1, and the main point of the lens, and b represents The distance between the intersection of the main optical axis Z1 of the lens and the focusing surface S3 and the main point of the lens is shown.

  Here, in addition to the above Scheimpflug condition and imaging condition, the focal length and tilt angle of the tilt lens 115 (angle representing the degree of tilt operation), the separation distance from the tilt lens 115 to the measurement object, and the area sensor The size along the conveyance direction of 113 (the size of the area sensor 113) is further considered. Due to these conditions, as shown in FIG. 3, the in-focus state (front focusable range) in front of the imaging surface (tilt lens 115 side) and the in-focus state in the rear of the imaging surface. The range (the range in which rear focusing is possible) is determined.

  As a result, by measuring the measurement object using the tilt lens 115, the measurement object included in the focusable range defined by the front focusable range and the rear focusable range is the focus plane S3. An in-focus state occurs at any of the above locations (any location on the straight line representing the focusing surface S3 in FIG. 3). For this reason, even when a measurement object having a curved surface is used as a measurement object, a region in focus exists in the obtained imaging data. Therefore, the shape measuring apparatus 10 according to the present embodiment specifies a region in focus on the imaging data, and the position of the region in focus corresponds to any position on the focusing surface S3. The position on the focusing surface S3 is converted to the height direction position of the measurement object, that is, the surface shape. In other words, in the shape measuring apparatus 10 according to the present embodiment, a line (focusing line) obtained by cutting the measuring object at the focusing surface S3 is measured, and the surface shape of the measuring object is based on the focusing line. It can be said that it is specified.

Incidentally, when the depth of focus range of the above, which is represented as D _B, the shape measuring apparatus 10 according to the present embodiment, the depth range D _A corresponding to the normal direction of the imaging surface of the focusing range Depth limits to be included in D _B, it is preferable to use the imaging unit 101.

The extent to which the depth range D _A should be reduced with respect to the depth D _B of the focusable range is determined based on the design value of the measurement target, past operating conditions, etc. The depth range D _A ) can be determined by analyzing in advance how large the depth range D _A ) is.

Further, after determining the condition between the depth D _B depth range D _A and the focusing range as described above, it may be determined the tilt angle of the tilt lens 115 so as to satisfy the condition .

  For example, as shown in FIG. 4, the magnitude of the inclination angle φ of the focusing surface S3 with respect to the horizontal plane is determined from the geometrical positional relationship among the light receiving surface S1, the lens main surface S2, and the focusing surface S3. Can be determined.

  In other words, when attention is paid to ΔPAC in FIG. 4, d · tan θ = a is established, and when ΔPBC is noted, d · tan θ ′ = b is established. Therefore, tan θ / tan θ ′ = (a / b) can be obtained by combining both equations. On the other hand, as is apparent from FIG. 4, φ = θ + θ ′. Here, the separation distances a and b are preset to values determined from the imaging formula according to the imaging magnification M = a / b required for the image to be captured and the focal length f of the tilt lens. Therefore, by determining the tilt angle θ, the tilt angle φ of the focusing surface S3 is uniquely determined based on the above two relational expressions.

Using such an inclination angle φ, the separation distances a and b, and the size l in the transport direction of the area sensor 113 (the size between the end points J and K of the area sensor 113), the depth of the focusable range. the method of obtaining the D _B, will be described with reference to FIG. FIG. 4 shows a case where the optical axis Z1 passes through the center (point A) in the transport direction of the area sensor 113, but the following description is not limited to such an example.

In FIG. 4, when the size l and the separation distance a of the area sensor 113 are determined, ΔJKC is uniquely determined. Therefore, the intersection M of the straight line KC and the focusing plane S3, the intersection N of straight lines JC and S3, can be obtained, is D _B obtained from the difference between the position in the height direction of the M and N.

In summary, since the depth D _B is uniquely determined from the tilt angle θ, the focal length f, the intersection M, and the size l of the area sensor 113, in order to make D _B larger than D _A , Obviously, the parameter needs to be determined in consideration of the imaging resolution of the object. l is will be determined by the specification of the area camera 111 uses, f, M, because determined by the distance and the imaging resolution of the measurement object, the degree of freedom to decide D _B independently of the other conditions, the tilt angle θ.

As apparent from FIG. 3, in the imaging unit 101 according to the present embodiment, a tilt angle (angle θ in FIG. 5) defined as an angle formed by the light receiving surface of the area sensor 113 and the main surface of the tilt lens 115 is set. by changing, it is possible to control the depth D _B of the focusing range.

  The imaging unit 101 according to the present embodiment has been described in detail above with reference to FIGS.

<About the configuration of the arithmetic processing unit>
Next, the arithmetic processing unit 103 included in the shape measuring apparatus 10 according to the present embodiment will be described in detail with reference to FIGS. FIG. 5 is a block diagram for explaining an example of the configuration of the arithmetic processing unit of the shape measuring apparatus according to the present embodiment. FIG. 6 is a block diagram for explaining an example of the configuration of the data processing unit included in the arithmetic processing unit according to the present embodiment. 7 to 8B are explanatory diagrams for explaining data processing performed by the data processing unit according to the present embodiment.

  As shown in FIG. 5, the arithmetic processing unit 103 according to the present embodiment includes an imaging control unit 151, a data acquisition unit 153, a data processing unit 155, a processing result output unit 157, a display control unit 159, And a storage unit 161.

  The imaging control unit 151 is realized by, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a communication device, and the like. The imaging control unit 151 can control the entire imaging process of the measurement object by the imaging unit 101 according to the present embodiment. For example, the imaging control unit 151 may periodically transmit a shift pulse signal (for example, 1 mm for the measurement object) from a driving mechanism such as a conveyance line that changes the relative position between the measurement object and the imaging unit 101. A trigger signal for starting imaging is sent to the imaging unit 101 on the basis of a PLG signal output every time it moves. Thereby, the imaging unit 101 can generate imaging data at each position in the conveyance direction of the measurement object as needed.

  When the imaging unit 101 includes the illumination light source 117, the imaging control unit 151 causes the illumination light source 117 to start irradiating illumination light when starting imaging of the measurement object. The control signal may be sent.

  The data acquisition unit 153 is realized by, for example, a CPU, a ROM, a RAM, a communication device, and the like. The data acquisition unit 153 acquires the imaging data generated by the imaging unit 101 and output from the imaging unit 101, and transmits the acquired imaging data to the data processing unit 155 described later. In addition, the data acquisition unit 153 may associate the acquired imaging data with time information related to the date and time when the data is acquired, and store it in the storage unit 161 described later as history information.

  The data processing unit 155 is realized by a CPU, a ROM, a RAM, and the like, for example. The data processing unit 155 calculates the surface shape of the measurement object by using the imaging data generated by the imaging unit 101 and performing arithmetic processing described below on the imaging data. When the data processing unit 155 finishes the calculation process of the surface shape, the data processing unit 155 transmits information on the obtained processing result to the processing result output unit 157.

  The surface shape calculation process in the data processing unit 155 will be described in detail below.

  The processing result output unit 157 is realized by a CPU, a ROM, a RAM, and the like, for example. The processing result output unit 157 outputs information on the surface shape of the measurement object output from the data processing unit 155 to the display control unit 159 described later. Thereby, the information regarding the surface shape of a measuring object will be output to a display part (not shown). Further, the processing result output unit 157 may output the obtained processing result to an external device such as various computers, or may create various forms related to the product using the obtained processing result. Good. Further, the processing result output unit 157 may store the obtained information regarding the surface shape as history information in the storage unit 161 or the like in association with time information regarding the date and time when the information is calculated.

  The display control unit 159 is realized by, for example, a CPU, a ROM, a RAM, an output device, and the like. The display control unit 159 transmits the information related to the surface shape of the measurement object transmitted from the processing result output unit 157, such as an output device such as a display provided in the shape measuring device 10 or an output device provided outside the shape measuring device 10. Display control when displaying on the screen. Thereby, the user of the shape measuring apparatus 10 can grasp various processing results such as the surface shape of the measurement object on the spot.

  The storage unit 161 is realized by, for example, a RAM or a storage device provided in the shape measuring apparatus 10 according to the present embodiment. In the storage unit 161, various parameters, processing progresses, and the like that need to be saved when the imaging unit 101 and the arithmetic processing unit 103 according to the present embodiment perform some processing, or various databases and programs Etc. are recorded as appropriate. In this storage unit 161, the imaging control unit 151, the data acquisition unit 153, the data processing unit 155, the processing result output unit 157, the display control unit 159, and the like can freely perform data read / write processing.

[Calculation processing in the data processor]
Next, the arithmetic processing (more specifically, the surface shape calculation processing) performed by the data processing unit 155 according to the present embodiment will be described in detail with reference to FIGS.

  The role of the data processing unit 155, which will be described in detail below, is to determine a focus line by specifying a focus position in an image generated by the imaging unit 101. For that purpose, the data processing unit 155 uses a ground pattern existing on the surface of the measurement object (for example, a steel plate). When focusing on the background pattern, the spatial frequency spectrum of the captured image spreads to a high frequency band, so focus on the size of the component in the frequency band and focus on the maximum size. What is necessary is just to specify a position.

  For example, as illustrated in FIG. 6, the data processing unit 155 according to the present embodiment includes a filter processing unit 171, a preprocessing unit 173, an approximation processing unit 175, and a shape calculation unit 177.

  The filter processing unit 171 is realized by a CPU, a ROM, a RAM, and the like, for example. The filter processing unit 171 converts the captured data as the two-dimensional captured image transmitted from the data acquisition unit 153 into a set of one-dimensional signals (that is, a one-dimensional signal (luminance data) along the conveyance direction of the measurement object). , A signal group associated with each position in the width direction). In addition, the filter processing unit 171 performs a filter calculation process as described below on each one-dimensional signal (L (x) in FIG. 13 shown below).

  In the imaging unit 101 according to the present embodiment, since digital imaging processing is performed, electrical noise is superimposed on the imaging data output from the area sensor 113. Therefore, it is preferable to use a low-pass filter in order to remove such electrical noise from the imaging data. Further, in the surface shape calculation process described below, in-focus determination of imaging data is performed. Since the in-focus determination needs to pay attention to local texture, it is preferable to use a high-pass filter. From the above two viewpoints, it is preferable that the filter processing unit 171 performs a filter calculation process using a bandpass filter on the imaging data transmitted from the data acquisition unit 153.

  Here, in order to examine what band pass filter should be applied to the imaging data, the present inventor measured a flat plate having a ground pattern on the surface as a measurement object. Then, the focus position specifying process as described in detail below is performed, the transport direction coordinates of the focus position are specified in units of pixels, and the degree of variation (that is, standard deviation) of the coordinates is calculated. did. More specifically, the focus position specifying process as described in detail below using bandpass filters having various pass bands was performed, and the degree of variation in the focus position obtained was examined.

The obtained results are shown in FIG.
In FIG. 7, the horizontal axis represents the frequency on the lower limit side (hereinafter also referred to as the low frequency side) of the transmission band of the bandpass filter, and the vertical axis represents the upper limit side (hereinafter referred to as the high frequency side) of the transmission band of the bandpass filter. The circle at each lattice point indicates the standard deviation (unit: pixel). Here, the transmission band frequency of the bandpass filter is represented by assuming that the spatial frequency corresponding to the pixel interval is 1/2, that is, the Nyquist frequency is 1. In FIG. 7, the diameter of the circular shape is shown to be proportional to the standard deviation, and for the case where the standard deviation is 100 or more, for example, at the position of (low frequency side 0, high frequency side 0.1). The illustration is made as a circle having a constant diameter as represented by a circle.

As is apparent from FIG. 7, the lower limit of the passband is 0.1 or more and 0.3 or less and the upper limit is 0.5 or more with respect to the frequency normalized by the Nyquist frequency when the pixel interval is the sampling interval. It was found that the standard deviation becomes extremely small when a band pass filter having a value of 0.7 or less is used. Therefore, the filter processing unit 171 according to the present embodiment has a passband of the imaging data that is a set of one-dimensional signals with respect to the frequency frequency normalized with the Nyquist frequency when the pixel interval is the sampling interval. It is preferable to perform a filter calculation process using a bandpass filter having a lower limit of 0.1 to 0.3 and an upper limit of 0.5 to 0.7. Thereafter, the filter processing unit 171 outputs the obtained data after filtering (L _bpf (x) in FIG. 13) to the preprocessing unit 173.

  The preprocessing unit 173 is realized by, for example, a CPU, a ROM, a RAM, and the like. The preprocessing unit 173 calculates the absolute value waveform of the one-dimensional signal based on the imaging data (the set of one-dimensional signals) after the filter calculation processing by the filter processing unit 171 is performed, Various pre-processing such as baseline processing is performed. By performing such preprocessing, the data processing unit 155 can accurately determine the in-focus position and calculate the surface shape more accurately. Hereinafter, these pre-processing will be described in detail.

The preprocessing unit 173 first performs a process of calculating an absolute value waveform on the imaging data (one-dimensional signal group) after the filter calculation process. The calculation process of the absolute value waveform (L _abs (x) in FIG. 13) is performed by taking an absolute value for each one-dimensional signal.

  Thereafter, the preprocessing unit 173 performs a process of subtracting the mode value (mode) or median value (median) of the data of the absolute value waveform from the obtained absolute value waveform. Since the data of the absolute value waveform is calculated by the operation of taking the absolute value, the value at the bottom of the waveform is not often zero. On the other hand, since the function used in the approximation processing in the approximation processing unit 175 described later has a function skirt value of zero, if the absolute value waveform skirt value is not zero, the function described later is approximated. It becomes a factor of error in processing. Therefore, the preprocessing unit 173 subtracts the mode value or median value of the absolute value waveform data from the absolute value waveform data, thereby further improving the accuracy of approximation processing described later.

The pre-processing unit 173 performs pre-processing as described above on the absolute value waveform data, and then uses the obtained absolute value waveform data (L _o (x) in FIG. 13) to approximate processing described later. Output to the unit 175.

  The approximation processing unit 175 is realized by a CPU, a ROM, a RAM, and the like, for example. For each of the data groups of the pre-processed absolute value waveforms output from the pre-processing unit 173, the approximation processing unit 175 has the absolute value waveform having a symmetrical symmetrical convex shape and a value of 0 as the distance from the convex peak is increased. Is approximated by a function that is asymptotic to. For the approximation, it is required to adjust the function parameters by an optimization method. At this time, the function parameters are set to the minimum necessary values (that is, the peak position, the peak width, and the peak size). It is desirable to obtain a stable optimal solution.

  Examples of such left-right symmetrical convex functions include a triangular wave function as shown in FIG. 8A and a Gaussian function as shown in FIG. 8B.

The triangular wave function shown in FIG. 8A is a triangular function defined by height A, half width W, and center p, and is represented by max (0, A × (1− | x−p | / w)). The The Gaussian function shown in FIG. 8B is a function represented by A × exp ((x−p) ² / σ ² ) using the height A, the center p, and the variance σ. By using such a function, the peak position of the absolute value waveform can be specified with high accuracy. Further, when a Gaussian function is used as the convex function, the absolute value waveform can be approximated by a smooth function, and the approximation process can be performed more simply (L in FIG. 13). _fit (x)).

  A technique for approximating the absolute value waveform data to the function as described above is not particularly limited, and various known techniques such as a multivariable quasi-Newton method can be used.

  The approximation processing unit 175 performs an approximation process on each of the preprocessed absolute value waveform data groups output from the preprocessing unit 173 using the convex function as described above, and then calculates the peak position. Identify. The approximation processing unit 175 handles the peak position obtained in this way as a focus position in the one-dimensional signal of interest. The approximation processing unit 175 can identify the in-focus position at each position in the width direction by performing such an approximation process on the one-dimensional signal at each position in the width direction.

  The approximation processing unit 175 outputs information regarding each in-focus position in the imaging data of interest to the shape calculation unit 177 described later.

  The shape calculation unit 177 is realized by a CPU, a ROM, a RAM, and the like, for example. The shape calculation unit 177 is based on the information regarding the in-focus position calculated by the approximation processing unit 175, the imaging resolution in the imaging unit 101, and the inclining angle φ of the focusing surface determined from the tilt angle θ of the tilt lens 115. The surface shape of the measurement object is calculated.

  More specifically, the shape calculation unit 177 has, for each position in the width direction, an in-focus position p (unit: pixel, origin: center of the area sensor 113 in the conveyance direction) along the conveyance direction, and imaging resolution d (unit: mm / pixel) and the tilt angle φ (unit: degree) of the focal plane, a value H (i) defined by the following equation 101 is calculated, and the optical axis Z1 at the width direction position i is calculated. The height of the intersection point of the focal plane S3 is treated as the height of the surface with the origin.

  H (i) = p × d × tan φ (Formula 101)

  Information regarding the size of the tilt angle φ of the focal plane is acquired in advance by the shape calculation unit 177 from the imaging control unit 151, or a user inputs a value to the calculation processing unit 103 in advance prior to the calculation processing. It is possible to obtain. Moreover, since the imaging resolution b is a value that can be grasped in advance based on the optical design value of the imaging unit 101 or the like, it may be stored in advance as a database in the storage unit 161 or the like.

  When the shape calculation unit 177 calculates the height distribution of the measurement object by the arithmetic processing as described above, the shape calculation unit 177 outputs the obtained calculation result to the processing result output unit 157 as the measurement result.

  The arithmetic processing unit 103 included in the shape measuring apparatus 10 according to the present embodiment has been described in detail above with reference to FIGS.

  Heretofore, an example of the function of the arithmetic processing unit according to the present embodiment has been shown. Each component described above may be configured using a general-purpose member or circuit, or may be configured by hardware specialized for the function of each component. In addition, the CPU or the like may perform all functions of each component. Therefore, it is possible to appropriately change the configuration to be used according to the technical level at the time of carrying out the present embodiment.

  It should be noted that a computer program for realizing each function of the arithmetic processing unit according to the present embodiment as described above can be produced and installed in a personal computer or the like. In addition, a computer-readable recording medium storing such a computer program can be provided. The recording medium is, for example, a magnetic disk, an optical disk, a magneto-optical disk, a flash memory, or the like. Further, the above computer program may be distributed via a network, for example, without using a recording medium.

<Flow of shape measurement method>
Subsequently, an example of the flow of the shape measuring method performed by the shape measuring apparatus 10 according to the present embodiment will be briefly described with reference to FIGS. 9 and 10. 9 and 10 are flowcharts showing an example of the flow of the shape measuring method according to the present embodiment.

[Overall flow]
First, the overall flow of the shape measuring method will be briefly described with reference to FIG.
The imaging unit 101 of the shape measuring apparatus 10 generates imaging data by scanning a measurement object conveyed in a predetermined direction in the conveyance direction under the control of the imaging control unit 151 of the arithmetic processing unit 103 ( In step S101), the obtained imaging data is output to the arithmetic processing unit 103.

  When the data acquisition unit 153 of the arithmetic processing unit 103 acquires the imaging data generated by the imaging unit 101, the data acquisition unit 153 outputs the acquired imaging data to the data processing unit 155.

  The data processing unit 155 of the arithmetic processing unit 103 performs shape calculation processing using the transmitted imaging data (step S103). Thereafter, the data processing unit 155 outputs the obtained measurement result of the measurement object to the processing result output unit 157.

  The processing result output unit 157 outputs information on the surface shape of the measurement target calculated by the data processing unit 155 to the user and various devices provided outside (step S105). Thereby, the user can grasp the measurement result regarding the surface shape of the measurement object.

[Surface shape calculation processing flow]
Next, the flow of the surface shape calculation process performed by the data processing unit 155 will be briefly described with reference to FIG.

  When the data processing unit 155 acquires the imaging data I (x, y) (x: transport direction, y: width direction) output from the data acquisition unit 153 (step S201), the data processing unit 155 sets the parameter i = 1. (Step S203), the one-dimensional signal L (x) to be processed is set to I (x, i) (Step S205).

Subsequently, the filter processing unit 171 of the data processing unit 155 performs the bandpass filter processing as described above on the one-dimensional signal L (x) to be processed, and the filtered signal L _bpf (x ) Is generated (step S207). Thereafter, the filter processing unit 171 outputs the obtained signal L _bpf (x) to the preprocessing unit 173.

First, the preprocessing unit 173 performs absolute value processing on the signal L _bpf (x) to generate a signal L _abs (x) after absolute value processing (step S209). Subsequently, the preprocessing unit 173 performs baseline processing using the median value or the mode value on the obtained signal L _abs (x), and the signal L _o (x) after the baseline processing is performed. Is generated (step S211). Thereafter, the preprocessing unit 173 outputs the obtained preprocessed signal L _o (x) to the approximation processing unit 175.

Subsequently, the approximation processing unit 175 performs function approximation processing on the signal L _o (x) using a convex function such as a Gaussian function or a triangular wave function (step S213), and specifies the peak position p. . Thereafter, the approximation processing unit 175 outputs information on the obtained peak position p to the shape calculation unit 177.

Subsequently, the shape calculation unit 177 uses the peak position p calculated by the approximation processing unit 175, the imaging resolution d, and the tilt angle φ of the focal plane to distribute the surface height in the width direction i. A function H _i (x) = p × d × tan φ is calculated (step S215).

Thereafter, the data processing unit 155 determines whether or not the parameter i is equal to the image height (step S217). If the parameter i is not equal to the image height, the parameter i is set to i + 1 (step S219), and the data processing unit 155 executes the processing after step S205 again. On the other hand, when the parameter i is equal to the image height, the obtained set of H _i (x) is set as the height distribution in the width direction in the imaging data of interest (step S221), and the processing result output unit 157 Output to.

  The example of the flow of the shape measuring method performed by the shape measuring apparatus 10 according to the present embodiment has been briefly described above with reference to FIGS. 9 and 10.

(About hardware configuration)
Next, an example of a hardware configuration of the arithmetic processing unit 103 according to the embodiment of the present invention will be described in detail with reference to FIG. FIG. 11 is a block diagram for explaining an example of the hardware configuration of the arithmetic processing unit 103 according to the embodiment of the present invention.

  The arithmetic processing unit 103 mainly includes a CPU 901, a ROM 903, and a RAM 905. The arithmetic processing unit 103 further includes a bus 907, an input device 909, an output device 911, a storage device 913, a drive 915, a connection port 917, and a communication device 919.

  The CPU 901 functions as an arithmetic processing device and a control device, and controls all or a part of the operation in the shape measuring device 10 according to various programs recorded in the ROM 903, the RAM 905, the storage device 913, or the removable recording medium 921. The ROM 903 stores programs used by the CPU 901, calculation parameters, and the like. The RAM 905 primarily stores programs used by the CPU 901, parameters that change as appropriate during execution of the programs, and the like. These are connected to each other by a bus 907 constituted by an internal bus such as a CPU bus.

  The bus 907 is connected to an external bus such as a PCI (Peripheral Component Interconnect / Interface) bus via a bridge.

  The input device 909 is an operation unit operated by the user, such as a mouse, a keyboard, a touch panel, a button, a switch, and a lever. The input device 909 may be, for example, remote control means (so-called remote control) using infrared rays or other radio waves, or may be an external connection device 923 such as a PDA corresponding to the operation of the shape measuring apparatus 10. May be. Furthermore, the input device 909 includes, for example, an input control circuit that generates an input signal based on information input by a user using the operation unit and outputs the input signal to the CPU 901. The user of the shape measuring apparatus 10 can input various data and instruct a processing operation to the shape measuring apparatus 10 by operating the input device 909.

  The output device 911 is configured by a device that can notify the user of the acquired information visually or audibly. Examples of such devices include CRT display devices, liquid crystal display devices, plasma display devices, EL display devices and display devices such as lamps, audio output devices such as speakers and headphones, printer devices, mobile phones, and facsimiles. The output device 911 outputs results obtained by various processes performed by the shape measuring device 10, for example. Specifically, the display device displays the results obtained by various processes performed by the shape measuring device 10 as text or images. On the other hand, the audio output device converts an audio signal composed of reproduced audio data, acoustic data, and the like into an analog signal and outputs the analog signal.

  The storage device 913 is a data storage device configured as an example of a storage unit of the arithmetic processing unit 103. The storage device 913 includes, for example, a magnetic storage device such as an HDD (Hard Disk Drive), a semiconductor storage device, an optical storage device, or a magneto-optical storage device. The storage device 913 stores programs executed by the CPU 901, various data, various data acquired from the outside, and the like.

  The drive 915 is a recording medium reader / writer, and is built in or externally attached to the shape measuring apparatus 10. The drive 915 reads information recorded on a removable recording medium 921 such as a mounted magnetic disk, optical disk, magneto-optical disk, or semiconductor memory, and outputs the information to the RAM 905. The drive 915 can also write a record on a removable recording medium 921 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory. The removable recording medium 921 is, for example, a CD medium, a DVD medium, a Blu-ray (registered trademark) medium, or the like. The removable recording medium 921 may be a CompactFlash (registered trademark) (CompactFlash: CF), a flash memory, an SD memory card (Secure Digital memory card), or the like. Further, the removable recording medium 921 may be, for example, an IC card (Integrated Circuit card) on which a non-contact IC chip is mounted, an electronic device, or the like.

  The connection port 917 is a port for directly connecting a device to the shape measuring apparatus 10. Examples of the connection port 917 include a USB (Universal Serial Bus) port, an IEEE 1394 port, a SCSI (Small Computer System Interface) port, and an RS-232C port. By connecting the external connection device 923 to the connection port 917, the shape measuring apparatus 10 acquires various data directly from the external connection device 923 or provides various data to the external connection device 923.

  The communication device 919 is a communication interface configured with, for example, a communication device for connecting to the communication network 925. The communication device 919 is, for example, a communication card for wired or wireless LAN (Local Area Network), Bluetooth (registered trademark), or WUSB (Wireless USB). The communication device 919 may be a router for optical communication, a router for ADSL (Asymmetric Digital Subscriber Line), or a modem for various communication. The communication device 919 can transmit and receive signals and the like according to a predetermined protocol such as TCP / IP, for example, with the Internet and other communication devices. The communication network 925 connected to the communication device 919 is configured by a wired or wireless network, and may be, for example, the Internet, a home LAN, infrared communication, radio wave communication, satellite communication, or the like. .

  Heretofore, an example of the hardware configuration capable of realizing the function of the arithmetic processing unit 103 according to the embodiment of the present invention has been shown. Each component described above may be configured using a general-purpose member, or may be configured by hardware specialized for the function of each component. Therefore, it is possible to change the hardware configuration to be used as appropriate according to the technical level at the time of carrying out this embodiment.

  Although the case where visible light is used has been described above, it is apparent that the present invention can be applied by combining an appropriate image sensor and lens material even in cases other than visible light. For example, when using far-infrared light, a microbolometer may be used as the imaging element, and germanium or zinc selenium may be used as the lens material.

  As is apparent from the above, the target background pattern contains a higher frequency component than the high-frequency side of the bandpass filter, and its size needs to be larger than the electrical noise on the high-frequency side.

  In addition, when the texture of the measurement object has periodicity such as embossing, there is no need for function approximation, and a narrow bandpass filter that transmits only the frequency component corresponding to the period is used. The position where the absolute value of the bandpass filter output is maximized may be set as the in-focus position p.

  Subsequently, the shape measuring apparatus and the shape measuring method according to the embodiment of the present invention will be specifically described with specific examples. Here, the experimental example shown below is merely an example of the shape measuring apparatus and the shape measuring method according to the embodiment of the present invention, and the shape measuring apparatus and the shape measuring method according to the embodiment of the present invention are shown below. It is not limited to experimental examples.

(Experimental example 1)
In Experimental Example 1 shown below, the shape measuring apparatus 10 according to the embodiment of the present invention was used to image a measurement object having a curved surface, and whether or not an accurate surface shape was measured was verified. .

  Note that a tilt lens having a focal length f = 85 mm and an F value = 2.8 was used as the imaging unit 101, the tilt angle was set to 8.5 °, and the imaging magnification was set to 1. Further, the imaging device (area sensor) of the area camera was 2352 pixels in the width direction × 1726 pixels in the integration direction, and the imaging resolution was 0.01 mm / pixel. The separation distance from the tilt lens to the measurement object was 190 mm.

  Further, a steel bar having a diameter of 24 mm was used as a measurement object having a curved surface.

  Furthermore, as a band pass filter used for the shape calculation process, a band pass filter having a pass band of 0.2 to 0.6 with respect to a frequency with a pixel interval of 2 is used. The median (median) was subtracted from the value waveform data. In addition, a Gaussian function was used as a convex function for approximating the absolute value waveform.

  FIG. 12 shows imaging data imaged by the imaging unit 101 as described above, and the horizontal direction in FIG. 12 is the conveying direction (longitudinal direction of the steel bar) x, and the vertical direction is the width direction y. . As can be seen from FIG. 12, the obtained imaging data includes a region in focus and a region out of focus and in a blurred state.

The intensity distribution L (x) of the one-dimensional signal is shown at the top of FIG. 13 with respect to the position in the width direction of the imaging data shown in FIG. As a result of performing the filtering process using the bandpass filter as described above on the one-dimensional signal L (x), a signal L _bpf (x) as shown in the second stage from the top in FIG. 13 is obtained. It was. Next, as a result of performing absolute value processing on the signal L _bpf (x), the absolute value waveform signal L _abs (x) shown in the third row from the top in FIG. 13 is obtained, As a result of performing the baseline processing on the signal, the signal L _o (x) shown in the second row from the bottom of FIG. 13 was obtained. As a result of fitting this signal L _o (x) with a Gaussian function, a Gaussian function as shown at the bottom of FIG. 13 was obtained. X = 1680 was output as the x coordinate of the peak position of the Gaussian function.

  As a result of performing such processing as needed in the width direction of the imaged data, a distribution of in-focus positions as shown in FIG. 14 was obtained. The surface height H calculated from the distribution of in-focus positions is shown by a solid line in FIG. 15A. In FIG. 15A, the result after the 7-point moving average is applied to the obtained measured value is shown. Moreover, in FIG. 15A, the theoretical value calculated on the assumption that the cross-sectional shape of the steel bar having a diameter of 24 mm is a perfect circle is also shown by a broken line.

  As is clear from FIG. 15A, it can be seen that the measured value of the surface height of the steel bar measured by the shape measuring apparatus 10 according to the embodiment of the present invention is very consistent with the theoretical value. FIG. 15B shows an error of the obtained measured value from the theoretical value, and the standard deviation of the obtained measured value was 0.12 mm.

  Here, it is known that the error of the height measurement in the stereo method as disclosed in Patent Document 2 is about 1-2% of the depth. On the other hand, since the separation distance in the depth direction in this experimental example is 190 mm as described above, the above error corresponds to 0.12 mm / 190 mm × 100 = 0.06%. Therefore, it has been clarified that the measurement result of the surface shape obtained by the shape measuring apparatus 10 according to the embodiment of the present invention has extremely superior accuracy than the surface shape measured by the stereo method.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Shape measuring apparatus 101 Imaging part 103 Arithmetic processing part 111 Area camera 113 Area sensor 115 Tilt lens 117 Illumination light source 151 Imaging control part 153 Data acquisition part 155 Data processing part 157 Processing result output part 159 Display control part 161 Storage part 171 Filter processing Unit 173 pre-processing unit 175 approximation processing unit 177 shape calculation unit

Claims (8)

An area sensor that is transported in a one-dimensional direction and captures an image of a measurement object having a background pattern on the surface, and a tilt axis that is parallel to the imaging surface of the area sensor and orthogonal to the transport direction An imaging unit having a provided tilt lens;
The imaging data captured by the imaging unit is handled as a set of one-dimensional signals for each position in the width direction of the measurement object, the in-focus position in the transport direction of the imaging data is specified, and the focal length of the tilt lens An arithmetic processing unit that converts the in-focus position into the shape of the measurement object based on a straight line determined by the Scheinproof condition from the tilt angle and the imaging magnification of the imaging unit, and the imaging resolution;
A shape measuring device.   The shape measuring apparatus according to claim 1, wherein a focusable range determined by the Shineproof condition and a length in the conveyance direction of the area sensor is set so as to include a depth range of the measurement object. The arithmetic processing unit includes:
A band pass whose lower limit of the passband is 0.1 or more and 0.3 or less and whose upper limit is 0.5 or more and 0.7 or less with respect to the frequency normalized with the Nyquist frequency when the pixel interval is set as the sampling interval Use filters,
The shape measuring apparatus according to claim 1, wherein a position where the intensity of the one-dimensional signal that has passed through the bandpass filter is maximum is specified as the in-focus position. The arithmetic processing unit includes:
The absolute value waveform defined by the absolute value of the one-dimensional signal that has passed through the bandpass filter is approximated by a function that is a convex shape that is symmetrical to the left and right and that gradually approaches 0 as the distance from the peak of the convex portion increases.
The shape measuring apparatus according to claim 3, wherein the peak position of the function is a position where the intensity of the one-dimensional signal is maximized.   The shape measurement apparatus according to claim 4, wherein the arithmetic processing unit uses a triangular wave function or a Gaussian function as the function.   The shape measuring device according to claim 4, wherein the arithmetic processing unit subtracts the mode value of the absolute value waveform data from the absolute value waveform data prior to approximation by the function.   6. The shape measuring apparatus according to claim 4, wherein the arithmetic processing unit subtracts a median value of the absolute value waveform data from the absolute value waveform data prior to approximation by the function. An area sensor that is transported in a one-dimensional direction and captures an image of a measurement object having a background pattern on the surface, and a tilt axis that is parallel to the imaging surface of the area sensor and orthogonal to the transport direction A step of imaging the measurement object by an imaging unit having a tilt lens provided;
Treating the captured image data as a set of one-dimensional signals for each position in the width direction of the measurement object, and specifying a focus position in the transport direction of the image data;
The identified in-focus position is converted into the shape of the measurement object based on a straight line determined by Shineproof conditions from the focal length and tilt angle of the tilt lens and the imaging magnification of the imaging unit, and the imaging resolution. Steps,
A shape measuring method.