JP2017015545A - Measuring device and article manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring device that is advantageous in terms of a measuring time.SOLUTION: A measuring device comprises: a projection part 1 that projects a light pattern on an object; an imaging part 2 that photographs the object to which the light pattern is projected and outputs image data; and a processing part 3 that obtains a measured value of the distance to the object on the basis of the image data. The processing part specifies the spatial frequency of the light pattern on the basis of first information for predicting reliability of the measured value and second information indicating the relationship between the first information and the reliability.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a measuring device and an article manufacturing method.

  A measuring device using a triangulation principle is known that has a measuring head that projects a light pattern onto a measurement object and images the object, and measures the shape of the object from image data obtained by the imaging. (Patent Document 1). The processing unit of the measurement device obtains information on the distance to the object or the shape of the object based on the image data. A spatial encoding method can be used for such measurement. Here, the space encoding method projects a light pattern in which bright portions (bright stripes) and dark portions (dark stripes) are alternately arranged, and binary encodes the space. In the spatial coding method, it is necessary to specify a boundary between a bright part and a dark part in image data.

  However, the contrast between the bright part and the dark part in the image data varies due to factors such as the distance between the measuring device and the object or the reflectance of the object. When the contrast is not appropriate, it is difficult to obtain the boundary between the bright part and the dark part. In view of this, the measurement apparatus disclosed in Patent Document 1 specifies and uses an optical pattern in which the reliability (for example, contrast) of image data is equal to or greater than a threshold among a plurality of optical patterns having different spatial frequencies.

JP 2012-103239 A

  However, since the measurement apparatus of Patent Document 1 obtains the reliability of image data for each light pattern and identifies the light pattern whose reliability is equal to or greater than a threshold value, it is disadvantageous in terms of measurement time or measurement throughput. It becomes. In addition, depending on the object, an optical pattern having a spatial frequency greater than or equal to a predetermined value may not be necessary from the viewpoint of necessary measurement accuracy.

  An object of the present invention is to provide a measurement device that is advantageous in terms of measurement time.

One aspect of the present invention is a projection unit that projects a light pattern onto an object;
An imaging unit that images the object projected with the light pattern and outputs image data;
A processing unit for obtaining a measurement value of the distance of the object based on the image data;
A measuring device having
The processor is
Identifying the spatial frequency of the light pattern based on the first information for predicting the reliability of the measurement value and the second information indicating the relationship between the reliability,
It is the measuring device characterized by this.

  According to the present invention, for example, it is possible to provide a measurement device that is advantageous in terms of measurement time.

The figure which illustrates the configuration of the measuring device Diagram illustrating light pattern according to gray code The figure which illustrates the positional relationship between a measurement part and a subject The figure which illustrates the relationship between the distance of a measurement part and a target object, and contrast The figure which illustrates a light pattern and light intensity distribution corresponding to it A diagram illustrating the distance between the object mounted on the pallet and the measurement unit FIG. 4 is a diagram illustrating an example of a flow of processing by a measurement device (first embodiment) A figure showing another example of a flow of processing by a measuring device (second embodiment) FIG. 10 is a diagram illustrating another example of the flow of processing by the measuring device (fifth embodiment). FIG. 10 is a diagram illustrating another example of the flow of processing by the measuring device (fifth embodiment). FIG. 10 is a diagram illustrating a flow of processing in preliminary measurement (fifth embodiment).

  Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that, throughout the drawings for explaining the embodiments, in principle (unless otherwise noted), the same members and the like are denoted by the same reference numerals, and repeated description thereof is omitted.

Embodiment 1
First, FIG. 1 is a diagram illustrating the configuration of a measurement device. The measurement apparatus of the present embodiment includes a head 10 (measurement unit) and a processing unit 3. The head 10 includes the following two optical units. One is a projection unit 1 that projects a light pattern (light intensity distribution) 16 onto the object 11, and the other is an image that captures the object 11 on which the light pattern 16 is projected and outputs image data. Part 2. In FIG. 1, the y axis is an axis parallel to the line of the line-shaped light pattern 16, the z axis is an axis parallel to the optical axis of the projection unit, and the x axis is the y axis and the z axis. It is an orthogonal axis. The xz plane is a plane including the object side principal point of the projection optical system 4, the image side principal point and the object point of the imaging optical system 7. The projection unit 1 includes a light source 17, an illuminance distribution uniformizing unit 18 (integrator), a light pattern forming unit 6, and a projection optical system 4. As the light source 17, a light emitting element such as an LED can be used. The integrator 18 may be a rod integrator or a fly-eye lens. The light pattern forming unit 6 is composed of a liquid crystal element, DMD (digital mirror device), or the like, and can form a light pattern to be projected. The projection unit 1 projects a light pattern forming unit 6 emitted from a light source and illuminated with light made uniform by an integrator onto a distance measurement space (measurement space) by the projection optical system 4. In the present embodiment, a linear light pattern 16 extending in the y direction is projected onto the object 11. The light pattern 16 may be an array of point-like patterns or circular patterns on a straight line. The imaging unit 2 includes an imaging element 8 and an imaging optical system 7 that guides light from the object to the imaging element. The image sensor 8 can be a photoelectric conversion element including a CMOS or CCD device. The imaging unit 2 receives light from the object by the imaging element 8 via the imaging optical system 7 and acquires an image (data) of the object.

  Next, a spatial encoding method used in the measurement apparatus of this embodiment will be described. The light pattern 16 used in the spatial coding method is a light irradiation pattern. As a spatial encoding method, the Gray code method is known. In the Gray code method, a plurality of light patterns having different spatial frequencies (periods) are sequentially projected onto an object. FIG. 2 is a diagram illustrating a light pattern according to the gray code. The light patterns (a) to (c) in FIG. 2 are projected in order, and each image is taken. Then, binarization is performed. Specifically, each pixel is set to 1 if its value is equal to or greater than a threshold value. If it is less than the threshold, it is set to 0. The binary values in each light pattern are arranged in order to obtain a gray code. The gray code is converted into the spatial code 1 (0 to 7) in FIG. 2, and the pixel of the light pattern forming unit 6 and the pixel of the image sensor 8 are associated with each other. On the other hand, when the light patterns of (a) and (b) in FIG. 2 are projected in order, the spatial code 2 (0 to 3) in FIG. 2 is obtained, and the light patterns of (a) to (c) are projected Half the resolution. As described above, the resolution at which the measurement value can be obtained varies in the direction orthogonal to the line of the light pattern depending on the highest spatial frequency of the projected light pattern.

  The projection unit 1 projects a plurality of types of light patterns 16 used in the spatial encoding method, the imaging unit 2 images each pattern, and the processing unit 3 processes image data obtained by the imaging. Since the relative position / posture relationship between the projection unit 1 and the imaging unit 2 is known, the distance (position) of each point on the surface of the object 11 is obtained based on the principle of triangulation. Thus, the shape of the object 11 is obtained.

When the light pattern is blurred because the distance between the measurement unit and the object is not within the allowable range, the accuracy of obtaining the boundary between the bright part and the dark part may be disadvantageous. FIG. 3 is a diagram illustrating the positional relationship between the measurement unit and the object. The distances in the Z direction between the object 102 / object 103 and the head 101 are D102 / D103, respectively. Further, positions (areas) that are distances D1 and D2 in the Z direction from the head 101 are indicated by broken lines D1a and D2a, respectively. There is a distance with respect to the head 101 where the accuracy of obtaining the boundary between the bright part and the dark part is within an allowable range. Here, when the light pattern of FIG. 5A is projected, the distance is between D1 and D2. That is, the object 102 is between the distances D1a and D2a. The contrast C related to the blur amount of the light pattern is expressed by Expression (1). Here, FIG. 4 is a diagram illustrating the relationship between the distance between the measurement unit and the object and the contrast.
C = (Imax−Imin) / (Imax + Imin) (1)

  FIG. 5 is a diagram illustrating a light pattern and a corresponding light intensity distribution. Image data when the light pattern of (a) in the figure is projected onto the object 102 (position D102) is shown in (c) of the figure. a102 indicates a pixel value distribution along the x direction, and Imax and Imin indicate a maximum value and a minimum value, respectively. Image data when the light pattern of (a) in the figure is projected onto the object 103 (position D103) is shown as a103 in (c) of the figure. In FIG. 4A, the horizontal axis represents the distance from the head 101 to the object, and the vertical axis represents the contrast. ca is a curve indicating the relationship between the distance and the contrast. Contrast values at distances D102 and D103 shown in FIG. 3 are c102a and c103a in FIG. 4A, respectively. Here, a contrast threshold value necessary to obtain a boundary between the bright part and the dark part is indicated by S1.

  Since the object 102 satisfies c102a ≧ S1, it can be measured with the light pattern shown in FIG. On the other hand, the object 103 cannot be measured with the light pattern because c103a <S1. Thus, the contrast (value) can be used as an index representing the reliability of the measurement value.

  Accordingly, image data when the light pattern of FIG. 5B having a lower spatial frequency than the light pattern of FIG. 5A is projected onto the objects 102 and 103 are shown in b102 and b103 of FIG. Cb shown in FIG. 4B is a curve showing the relationship between the distance from the head 101 and the contrast. Contrast values at distances D102 and D103 shown in FIG. 3 are c102b and c103b in FIG. 4B, respectively. Since the objects 102 and 103 satisfy c102b ≧ S1 and c103b ≧ S1, both can be measured with the light pattern of FIG. 5B.

  From the design value of the optical system of the measuring device, the relationship between the distance and the contrast as illustrated in FIG. 4 is known. For this reason, for each spatial frequency of the light pattern, the distance that satisfies the acceptable condition (typically equal to or greater than the threshold value) can be obtained in advance and stored in the processing unit 3. Alternatively, a table that specifies the light pattern (the spatial frequency) to be used (contrast is equal to or higher than the threshold) can be generated for each of a plurality of regions obtained by dividing the range of the distance where the object exists. . Therefore, information on the distance (range) from the head can be information (first information) for predicting the reliability (for example, contrast) of the measurement value in each light pattern. The information in the table can be information (second information) indicating the relationship between the first information and the reliability. An example of measurement using the table will be described with reference to FIGS. FIG. 6 is a diagram illustrating the distance between the object mounted on the pallet and the measurement unit. The distance from the head 101 to the top surface of the pallet p1 is D104, the distance to the region w1 of the stacked object is D105, and the distance to the bottom surface of the pallet p1 is D106. D3 shown in FIG. 4B and D1 and D2 shown in FIG. 4A satisfy the relationship D3 <D104 <D105 <D1 <D106 <D2.

  Here, FIG. 7 is a diagram illustrating an example of a flow of processing by the measurement device. In FIG. 7, in step s101, the processing unit 3 presents a user interface, for example, and inputs information (first information) related to the range of the distance where the object exists through a user operation on the user interface. . The range may be, for example, a range D105 to D106 where the object exists, or a range D104 to D106 of the pallet p1. Here, it is assumed that information in the range D105 to D106 is input.

  In step s102, the light pattern used for measurement is specified. The processing unit 3 specifies the highest spatial frequency of the light pattern with reference to the table (second information) described above. For the ranges D105 to D106, the highest spatial frequency of the light pattern is that of FIG. In step s103, the corresponding light pattern is projected and imaged. In step s104, a distance measurement value is obtained for each point (each part) on the surface of the object based on the image data obtained in step s103, thereby obtaining the shape (position / posture) of the object. In step s105, it is determined based on the information obtained in step s104 whether there is an object that can be gripped by a robot (not shown). If there is no object that can be gripped, the process ends in step s107. If there is a grippable object, in step s106, the object is gripped and a predetermined process (for example, conveyance) is performed. Thereafter, the processing is repeated from step s103.

  As described above, according to the present embodiment, by specifying the light pattern (the highest spatial frequency) used for measurement based on the input distance range, a measurement device advantageous in terms of measurement time can be obtained. Can be provided.

[Embodiment 2]
In the present embodiment, in addition to the configuration of the first embodiment, the spatial frequency of the light pattern is changed based on the measurement result of the object. FIG. 8 is a diagram illustrating another example of the flow of processing by the measurement device. Of the steps in FIG. 8, only the step s102 ′ is different from the step in FIG. The process of the first step s102 ′ is the same as that of step s102 of FIG. In step s106, the object is gripped and a predetermined process is performed, and then the process returns to step s102 ′. In step s102 ′ after the second time, based on the measurement result in step s104, the distance range of the target object after the object processed in step s106 disappears (conveyed) is obtained. And based on the said range, with reference to said table (refer Embodiment 1), the highest spatial frequency of a light pattern is specified. Although the object has been stacked up to w1 in FIG. 6 at the beginning of measurement, a case will be described in which the object is stacked up to w2 after the processing from steps s102 ′ to s106 is repeated. Here, as the amount of the object decreases, the range in which the object exists is up to w2, and the distance range is from D1 to D106. Therefore, since D1 <D106 <D2 and the contrast from the D1 to D2 is equal to or higher than the threshold value in the light pattern of FIG. 5A, the highest spatial frequency of the light pattern used for measurement is shown in FIG. Change to the one shown in.

  As described above, according to the present embodiment, based on the input distance range and the measurement result of the object (another example of the first information), the light pattern (the highest spatial frequency) used for measurement is determined. By specifying, a measuring device that is advantageous in terms of measuring time can be provided.

[Embodiment 3]
In the present embodiment, the spatial frequency of the light pattern is specified based on information on the reflectance of the object (another example of the first information). The reflectance is determined by the color and material of the object and the surface state. Here, differences from the first embodiment will be described with reference to FIG. In the present embodiment, in step s101, instead of inputting the distance range, information related to the reflectance of the object is input via a user interface, for example. In step s102, the light pattern (its highest spatial frequency) is specified based on the information on the reflectance. For this purpose, for example, the relationship between the information on the reflectance and the highest spatial frequency at which the reliability is equal to or higher than the threshold value is made into a table (second information), and the table is stored in the processing unit 3.

  As described above, according to the present embodiment, the measurement apparatus that is advantageous in terms of measurement time by specifying the light pattern (the highest spatial frequency) used for measurement based on the input information about the reflectance. Can be provided.

[Embodiment 4]
In the present embodiment, the information on the distance range and the information on the reflectance of the object are set as the first information, and the spatial frequency of the light pattern is specified based on the first information. Here, differences from the first to third embodiments will be described with reference to FIGS. 7 and 8. In the present embodiment, in step s101, information on the distance range and information on the reflectance of the object are input via, for example, a user interface. In step s102, the light pattern (the highest spatial frequency) used for measurement is specified based on the input information. For this purpose, for example, a table (second information) is used as a table (second information) for the relationship between the distance range information, the information about the reflectance of the object, and the highest spatial frequency at which the reliability is equal to or greater than the threshold, and the table is stored in the processing unit 3 Let me.

  As described above, according to the present embodiment, by specifying the light pattern (the highest spatial frequency) used for measurement based on the input distance range information and the information on the reflectance of the object. It is possible to provide a measurement device that is advantageous in terms of measurement time.

[Embodiment 5]
In this embodiment, instead of inputting information via the user interface, preliminary detection is performed to specify the light pattern to be used (its highest spatial frequency). FIG. 9 is a diagram illustrating another example of the flow of processing by the measurement device. In FIG. 9, preliminary detection is performed in step s201. The preliminary detection will be described with reference to FIG. Here, FIG. 11 is a diagram illustrating a flow of processing in the preliminary detection. In the figure, in step s301, a light pattern having the highest spatial frequency is projected onto an object and imaged. In the present embodiment, the light pattern shown in FIG. 5A is projected. In step s302, the contrast C of the image obtained by the imaging in step s301 is acquired. In step s303, it is determined whether the contrast C obtained in step s302 is greater than or equal to a threshold value. If the contrast value is greater than or equal to the threshold value, the process ends in step s905. Thereafter, the process can proceed to step s202 in FIG.

  On the other hand, if it is determined in step s303 that the contrast value is less than the threshold value, the process proceeds to step s304, and the light pattern having a spatial frequency lower than the spatial frequency of the light pattern in which the contrast value is determined to be less than the threshold value in s303. Is projected and imaged. Here, for example, when it is determined that the contrast value for the light pattern in FIG. 5A is less than the threshold value, the light pattern in FIG. 5B is projected. Then, the processes in steps s302 to s304 are repeated until the obtained contrast value is equal to or greater than the threshold value.

  FIG. 10 is a diagram showing another example of the flow of processing by the measuring device. Of the steps in FIG. 10, only the step s202 ′ is different from the step in FIG. The process of the first step s202 ′ is the same as that of step s202 of FIG. In step s106, the object is gripped and a predetermined process is performed, and then the process returns to step s202 ′. In step s202 ′ after the second time, based on the measurement result in step s104, the distance range (first information) of the object after the object processed in step s106 disappears (conveyed) is obtained. And based on the said range, with reference to said table (refer Embodiment 1), the highest spatial frequency of a light pattern is specified.

  As described above, according to the present embodiment, by specifying the light pattern (the highest spatial frequency) used for measurement based on (results of) preliminary detection, a measurement apparatus advantageous in terms of measurement time can be obtained. Can be provided.

[Modification]
The reliability (index) is not limited to contrast, and may include at least one of contrast, gradient, and range (difference between local maximum and local minimum, etc.) of image data. Further, it may be another index related to the S / N ratio of image data. The table (second information) indicating the relationship between the information for predicting the reliability of the measured value and the light pattern to be used (its highest spatial frequency) may be a relational expression (formula). The second information may be configured by both a table and an expression. Information input via the user interface may correspond to the spatial frequency of the light pattern. Further, the measuring device may include a detection unit that detects at least one of a distance range where the object exists and a reflectance of the object, and preliminary detection (step s201) may be performed by the detection unit. .

  Preliminary detection can also be performed using the method in the measurement apparatus of Patent Document 1 that obtains the reliability of image data for each light pattern and identifies the light pattern having a reliability equal to or higher than a threshold. For example, when a plurality of objects mounted on a pallet are sequentially measured and carried out as shown in FIG. 6, first, the method of Patent Document 1 is carried out until all the objects mounted on the pallet are carried out. A plurality of objects are sequentially measured and carried out while specifying the light pattern by. And based on the reliability and measurement results obtained by the series of measurements, information (second information) indicating the relationship between the information about the range of the distance where the object exists (first information) and the reliability is obtained. Generate. Thereafter, the measurement of the same object can be performed based on the second information. In this case, the first information is not always necessary. However, the initial value of the distance to the object can be acquired and used as the first information via the user interface or the detection unit as described above. In addition, information on the distance to the target obtained (estimated) based on the measurement result can be acquired and used as the first information.

  In addition, the processing unit 3 that identifies the light pattern (spatial frequency) may be any place as long as it can communicate with the head 10 by a communication device, and the installation location is not limited. Further, the information processing apparatus different from the processing unit 3 may store the table or the relational expression. Furthermore, the predetermined process performed by grasping the object is not limited to the conveyance, and may include, for example, at least one of processing, cutting, assembly (assembly), inspection, and selection.

[Embodiment related to article manufacturing method]
The measurement (inspection) apparatus according to the embodiment described above can be used in an article manufacturing method. The article manufacturing method may include a step of measuring (inspecting) an object using the measurement (inspection) apparatus, and a step of processing the object that has been measured (inspected) in the step. The process can include, for example, at least one of processing, cutting, conveyance, assembly (assembly), inspection, and selection. The article manufacturing method of the present embodiment is advantageous in at least one of the performance, quality, productivity, and production cost of the article as compared with the conventional method.

  As mentioned above, although preferred embodiment of this invention was described, it cannot be overemphasized that this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

DESCRIPTION OF SYMBOLS 1 Projection part 2 Imaging part 3 Processing part

Claims (14)

A projection unit for projecting a light pattern onto an object;
An imaging unit that images the object projected with the light pattern and outputs image data;
A processing unit for obtaining a measurement value of the distance of the object based on the image data;
A measuring device having
The processor is
Identifying the spatial frequency of the light pattern based on the first information for predicting the reliability of the measurement value and the second information indicating the relationship between the reliability,
A measuring device characterized by that.   The measurement apparatus according to claim 1, wherein the processing unit further specifies the spatial frequency based on the first information.   The measuring apparatus according to claim 1, wherein the processing unit specifies the spatial frequency so that the reliability satisfies an allowable condition.   The said process part produces | generates the said 2nd information by obtaining the said reliability based on the said image data obtained regarding the said 1st information, The any one of Claim 1 thru | or 3 characterized by the above-mentioned. The measuring device described in 1.   The processing unit obtains, as the first information, at least one of a distance range where the object exists and a reflectance of the object. The measuring apparatus of any one of Claims. A user interface for inputting the first information;
The processing unit obtains the first information via the user interface;
The measuring apparatus according to claim 1, wherein the measuring apparatus is one of the following. A detection unit for detecting at least one of the above,
The processing unit acquires the first information through the detection unit.
The measuring apparatus according to claim 5.   The measurement apparatus according to claim 1, wherein the processing unit further specifies the spatial frequency based on the measurement value.   The measurement apparatus according to claim 1, wherein the reliability includes at least one of a contrast, a gradient, and a range of the image data.   10. The device according to claim 1, wherein the second information includes at least one of a table or an expression indicating the relationship with respect to each spatial frequency of the light pattern. Measuring device.   The said processing part specifies the said spatial frequency regarding each of several area | region obtained by dividing | segmenting the range of the distance in which the said object exists, The any one of Claim 1 thru | or 10 characterized by the above-mentioned. The measuring device described in 1. The projection unit projects the light pattern onto the object from a first direction,
The imaging unit images the object on which the light pattern is projected from a second direction.
The measuring device according to claim 1, wherein the measuring device is any one of claims 1 to 11. A step of measuring an object using the measuring device according to any one of claims 1 to 12,
A step of processing the object subjected to the measurement in the step;
An article manufacturing method comprising: Project a light pattern onto the object,
Image data obtained by imaging the object projected with the light pattern,
A measurement method for obtaining a measurement value of the distance of the object based on the image data,
Identifying the spatial frequency of the light pattern based on the first information for predicting the reliability of the measurement value and the second information indicating the relationship between the reliability,
A measuring method characterized by this.

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