JP2020041976A - Three-dimensional shape measuring device - Google Patents

Abstract

To provide a three-dimensional shape measuring device with which it is possible to suitably specify the three-dimensional shape of surface of an inspection object even when it is an unknown shape.SOLUTION: A three-dimensional shape measuring device 10 measures a three-dimensional shape of an inspection object. The three-dimensional shape measuring device 10 comprises: an imaging unit 11 including a camera for imaging an inspection object the distance of which to an in-focus position is constant, the imaging distance from the camera to the inspection object being variable; an imaging control unit 12 for causing the inspection object to be imaged at a plurality of imaging distances by the imaging unit; an in-focus position calculation unit 13 for acquiring each image imaged by the imaging unit and calculating an in-focus position on the basis of an in-focus degree in each portion of each image; a shape specification unit 14 for calculating an in-focus distribution that is a set of in-focus positions on the basis of the in-focus position calculated by the in-focus position calculation unit and specifying the three-dimensional shape of the inspection object on the basis of the calculated in-focus distribution; and a shape extraction unit 15 for calculating a feature at each position on the three-dimensional shape of the inspection object specified by the shape specification unit and extracting a prescribed type of shape that constitutes the three-dimensional shape on the basis of the calculated feature.SELECTED DRAWING: Figure 1

Description

  The present invention relates to three-dimensional shape measurement for measuring a three-dimensional shape of a surface of an object.

  It is important for quality assurance to inspect for fine foreign substances on the surface of the product. Therefore, for example, a fine three-dimensional shape of the surface is measured based on the degree of focus of an image of a product. Japanese Patent Application Laid-Open No. H11-163873 takes a plurality of images of a bonded wire as a three-dimensional shape while changing the focus position, and generates a focus position distribution in a cross section in the shooting direction based on the degree of focus in each of the shot images. It discloses that the three-dimensional shape of the wire is extracted.

JP-A-2017-92187

  In the method disclosed in Patent Document 1, since the position, direction, and thickness of the wire are known, it is easy to specify the shape of the wire from the focus position distribution. However, it is difficult to specify the shape of the wire when the shape is unknown such as a foreign matter. It may be.

  The present invention has been made in view of the above-described problems, and has as its object to provide a three-dimensional shape measuring apparatus that can appropriately specify a three-dimensional shape of a surface of an inspection target even if the three-dimensional shape is unknown.

  In order to solve the above-described problem, one aspect of the present invention is a three-dimensional shape measurement apparatus that measures a three-dimensional shape of an inspection target, and a camera that captures an inspection target, in which a distance to a focus position is constant. Including a photographing unit having a variable photographing distance from the camera to the inspection object, a photographing control unit for causing the photographing unit to photograph the inspection object at a plurality of photographing distances, and acquiring each image photographed by the photographing unit. A focus position calculation unit that calculates a focus position based on the degree of focus in each part of each image; and a focus distribution that is a focus position set based on the focus positions calculated by the focus position calculation unit. Based on the calculated focus distribution, a shape specifying unit that specifies the three-dimensional shape of the inspection object, and a feature at each position of the three-dimensional shape of the inspection object specified by the shape specification unit are calculated and calculated. Predetermined seeds that construct a three-dimensional shape based on features And a shape extraction unit for extracting a shape, a three-dimensional shape measuring apparatus.

  According to the present invention, it is possible to provide a three-dimensional shape measurement apparatus that can appropriately specify even a three-dimensional shape of the surface of an inspection target even when the three-dimensional shape is unknown.

Functional block diagram of a three-dimensional shape measuring apparatus according to an embodiment of the present invention A schematic side view of a photographing unit according to an embodiment of the present invention. Flowchart showing processing according to an embodiment of the present invention FIG. 4 is a diagram illustrating a captured image and a focus degree according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a captured image and a focus degree according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a captured image and a focus degree according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a captured image and an in-focus position thereof according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a focus position and a focus distribution according to an embodiment of the present invention. The figure which shows the feature extraction of the three-dimensional shape which concerns on one Embodiment of this invention. FIG. 6 is a diagram illustrating an example of a focus distribution according to an embodiment of the present invention and an example in which the shape type of each part of a three-dimensional shape is color-coded.

(Embodiment)
The three-dimensional shape measuring apparatus according to the present invention calculates a focus distribution of the inspection target based on an image of the surface of the inspection target, specifies a three-dimensional shape of the inspection target surface based on the focus distribution, Further, features are extracted from the three-dimensional shape, and the type of the shape of each part of the three-dimensional shape is extracted.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

<Structure>
FIG. 1 shows a functional block diagram of a three-dimensional shape measuring apparatus 10 according to the present embodiment. The three-dimensional shape measuring apparatus 10 includes a photographing unit 11, a photographing control unit 12, a focus position calculating unit 13, a shape specifying unit 14, and a shape extracting unit 15. FIG. 2 schematically shows an example of a side view of the photographing unit 11. The imaging unit 11 includes a camera 111, a camera support unit 112 that supports the camera 111, and a mounting unit 113 that mounts the inspection object 900. The camera 111 has a fixed distance from the camera 111 to the in-focus position. The camera support 112 variably supports the height of the camera 111. Thus, the shooting distance, which is the distance between the camera 111 and the inspection object 900, can be made variable. Note that the inspection object 900 is, for example, a metal component, and may have a foreign substance such as a fine protruding portion (whisker) 901 protruding from the surface.

  The photographing control unit 12 can control the photographing unit 11 to cause the camera 111 to photograph the inspection object 900 at a plurality of photographing distances. The photographed image is stored in a storage unit (not shown) in association with a photographing distance at the time of photographing the image. The focus position calculation unit 13 acquires each image from the storage unit, calculates the degree of focus of each part of the image, and further calculates the focus position based on the degree of focus. The shape specifying unit 14 calculates a focus distribution, which is a set of focus positions, based on the focus positions, and specifies the three-dimensional shape of the inspection object 900 based on the focus distribution. The shape extraction unit 15 extracts a feature from the specified three-dimensional shape, and extracts a predetermined type of shape that forms the three-dimensional shape.

<Process>
An example of a process according to the present embodiment will be described. FIG. 3 is a flowchart illustrating processing performed by the three-dimensional shape measurement device 10 to specify a three-dimensional shape. This processing is started by mounting the inspection object 900 on the mounting section 113.

  (Step S101): The imaging control unit 12 controls the imaging unit 11 to cause the camera 111 to image the same area of the inspection object 900 in the same imaging direction at different imaging distances. The initial height of the camera 111 can be set based on a design shape or the like of CAD data of the inspection object 900 acquired in advance, for example. Further, the change range of the photographing distance can be set based on, for example, the length of the assumed minute protrusion 901.

  (Step S102): The imaging control unit 12 acquires the approximate shape of the surface of the inspection object 900. This may be obtained based on a design shape or the like of CAD data or the like of the inspection object 900, or a measurement result of the inspection object 900 by a 3D sensor or the like provided near the three-dimensional shape measurement device 10. May be acquired. Alternatively, as described later, the approximate shape of the surface of the inspection object 900 may be obtained by calculating a shooting distance corresponding to the surface of the inspection object 900 based on each image. Since the photographing distance to the surface of the inspection object 900 can be known from the approximate shape, in each processing described later, the image of the photographing distance focused inside the inspection object 900 is excluded from the processing object, and the processing amount can be reduced.

  (Step S103): The focus position calculation unit 13 acquires each image, and calculates the degree of focus of each part in the image photographed at the photographing distance at which the surface of the inspection object 900 and the area above it become the focus position. I do. The focus position calculation unit 13 sets a certain area of each image as a target area, and calculates a focus degree based on various calculation methods such as an absolute value of a luminance gradient, a variance of luminance, or an edge intensity in the target area. Can be calculated. The luminance gradient is calculated based on, for example, a difference between a luminance value of each pixel constituting an image in the target area and one or more luminance values of a plurality of adjacent pixels. Although there are various calculation methods, any of them can be used as appropriate.

  4, 5, and 6 show examples of actual images and the distribution of the degree of focus. In the first image shown in FIG. 4, the degree of focus of a portion along the dotted line L, which is the target area, on the surface of the inspection target 900 is high. Therefore, the change in the luminance value along the dotted line L is large and steep in a wide range in which the surface of the inspection object 900 is photographed. As described above, since there are many portions with a high degree of focus in the image, it can be detected that the surface of the inspection object 900 is in focus, and the shooting distance to the surface can be calculated.

  The second image shown in FIG. 5 is obtained by photographing the same range as the first image, but has a longer photographing distance than the first image, and is to be inspected along the dotted line L at the same position as the dotted line L of the first image. Although the degree of focusing on the surface of the object 900 is small, the fine projection 901 projecting from the surface in the direction of the camera 111 can be identified, and the degree of focusing on that part is large. Therefore, the change in the luminance value along the dotted line L is large and steep only in a specific range in which the minute projection 901 is photographed.

  The third image shown in FIG. 6 is obtained by shooting the same range as the first image and the second image, but has a longer shooting distance than the second image, and has the same position as the dotted line L of the first image and the second image. The degree of focus of the surface of the inspection object 900 and the fine projection 901 along the dotted line L is small. Therefore, the change in the luminance value along the dotted line L is small in the entire range. In the examples shown in FIGS. 4, 5, and 6, the average of the absolute values of the luminance gradients along the dotted line L becomes smaller in the order of the first image, the second image, and the third image.

  (Step S104): Based on the calculated degree of focus in each image, the focus position calculation unit 13 determines, for example, a position where the degree of focus is equal to or more than a predetermined value on the surface of the inspection object 900 and a portion thereabove. It is calculated as the in-focus position. FIG. 7 shows an example of each image (left column) photographed at different photographing distances and each image (right column) indicating a focus position calculated from each image. Each image in the left column is obtained by decreasing the photographing distance to the surface of the inspection object 900 in order from top to bottom. In the image in the right column, the in-focus position is shown brightly. It can be confirmed that there is a portion focused on the fine projection 901 above the surface of the inspection object 900. Further, the shape specifying unit 14 calculates a set of focus positions (a distribution range of the focus positions) as a focus distribution based on the focus positions in each image calculated by the focus position calculation unit 13. FIG. 8 shows an example of each image showing the focus position and an image showing the focus distribution calculated based on these images. The focus distribution is brighter as the height (z direction) of the focus position is higher, and a part of the contour is indicated by a dotted line for easy viewing.

  (Step S105): The shape specifying unit 14 specifies the three-dimensional shape of the inspection object 900 based on the focus distribution of the inspection object 900. FIG. 9A shows an example of a cross-sectional view of the vicinity of the minute protruding portion 901 in the three-dimensional shape of the specified inspection object 900. As shown in FIG. 9A, the three-dimensional shape is represented, for example, as a set of points representing a focus position.

  (Step S106): The shape extraction unit 15 calculates a feature from the specified three-dimensional shape. The shape extraction unit 15 calculates, for example, at least one of a distribution direction and a distribution density of each point representing the in-focus position and a normal line of the three-dimensional shape at each point as a feature of the three-dimensional shape, based on the calculation result. The shapes that make up each part of the three-dimensional shape are extracted. FIG. 9B shows an example of feature extraction. In the example illustrated in FIG. 9B, the shape extracting unit 15 calculates a normal line at each point of the three-dimensional shape based on the arrangement of each point representing the focus position. Further, the shape extracting unit 15 calculates the curvature of the three-dimensional shape at each point based on the normal line at each adjacent point. Then, the shape extracting unit 15 extracts shapes such as a plane, a curved surface, and a protrusion from each part of the three-dimensional shape based on the curvature. In the example illustrated in FIG. 9C, the shape extraction unit 15 extracts, as a plane portion, an area indicated by a circle where the arrangement of the points is substantially in the same plane and the curvature along each direction is small. As shown by the mark, each point is distributed in an elongated area inclined from the plane portion, and the area where the curvature along the in-plane direction of the paper at each point is small, but the curvature along the front-back direction of the paper is large, for example, a line It is extracted as a protruding shape. This is an example, and the type of shape and the method of extraction are not limited. In addition, the shape extraction unit 15 may calculate various dimensions, such as a surface area of a plane portion and a length of a linear portion, of a three-dimensional shape or a portion thereof based on the calculated features or the extracted shape. Good.

  FIG. 10A is a diagram illustrating a three-dimensional shape according to a focus distribution, with a partial outline supplemented by dotted lines, and FIG. 10B is a diagram illustrating a three-dimensional shape color-coded according to the shape extraction result. Is shown. As shown in FIG. 10, as a result of extracting the shape of each part based on the feature of the three-dimensional shape, the shape of the minute projection 901 can be appropriately distinguished from the surface of the inspection object 900 and can be identified. Note that the shape extraction unit 15 may use the characteristics of the approximate shape of the surface of the inspection object 900 acquired in step S102 to distinguish between the approximate shape portion and the minute protrusion 901 not included in the approximate shape. In particular, the fine protruding portion 901 can be extracted particularly suitably.

(effect)
According to the present invention, the focus distribution is calculated based on the photographed image, the three-dimensional shape of the inspection object is specified, and the feature of the three-dimensional shape is extracted to extract the shape of each part. Thus, even if the three-dimensional shape of the object such as a foreign substance on the surface of the inspection object is unknown, it can be clearly distinguished from the flat surface of the inspection object and can be specified appropriately.

  In addition, the present invention can be considered not only as a three-dimensional shape measurement device, but also as a three-dimensional shape measurement method, a program executed by a computer of the three-dimensional shape measurement device, and a computer-readable non-temporary recording medium storing the program. It is.

  INDUSTRIAL APPLICABILITY The present invention is useful for an apparatus for measuring a three-dimensional shape of an object surface.

DESCRIPTION OF SYMBOLS 10 Three-dimensional shape measuring apparatus 11 Imaging part 12 Imaging control part 13 Focus position calculation part 14 Shape specification part 15 Shape extraction part 111 Camera 112 Camera support part 113 Mounting part 900 Inspection object 901 Fine projection part

Claims (1)

A three-dimensional shape measurement device that measures a three-dimensional shape of an inspection object,
A distance to the in-focus position is constant, including a camera for photographing the inspection object, an imaging unit in which the imaging distance from the camera to the inspection object is variable,
A photographing control unit that causes the photographing unit to photograph the inspection object at a plurality of the photographing distances;
A focus position calculation unit that obtains each image captured by the imaging unit and calculates a focus position based on the degree of focus in each part of each image;
A shape specification that calculates a focus distribution that is a set of focus positions based on the focus position calculated by the focus position calculation unit, and specifies a three-dimensional shape of the inspection object based on the calculated focus distribution. Department and
A shape extraction unit that calculates a feature at each position of the three-dimensional shape of the inspection object identified by the shape identification unit, and extracts a predetermined type of shape configuring the three-dimensional shape based on the calculated feature. 3D shape measuring device.