JP2016156745A - Measurement method and measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measurement method advantageous to simplifying adjustment when calculating information relating to the shape of an object, or advantageous to reducing a measurement time.SOLUTION: This measurement method is designed to calculate information relating to the shape of an object on the basis of an image obtained by capturing the image of the object using an image-capturing element, the method including: an acquisition step S101 for acquiring the design information of the object; a setup step S102 for setting the focus position of an optical system that includes the image-capturing element to a measurement position in the focus direction of the object specified from the design information acquired in the acquisition step S101; an image-capturing step S104 for capturing the image of the object at the focus position set in the setup step S102; and a calculation step S107 for calculating information relating to the shape of the object on the basis of the image captured in the image-capturing step S104.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a measurement method and a measurement apparatus.

  There is a method of measuring the size (shape) of an object by illuminating an object placed on a mounting table and performing edge detection from an image obtained by imaging the object. In this method, when an object is imaged, a part of the image that is out of the depth of focus may be blurred and unclear, and such unclearness of the image is not desirable for obtaining a shape with high accuracy. Therefore, Patent Document 1 acquires a plurality of images, extracts an image area within the depth of focus range from each image, and connects the respective image areas, thereby acquiring an in-focus image for the entire object. A three-dimensional shape inspection machine is disclosed.

JP 2006-313086 A

  However, in the technique disclosed in Patent Document 1, in order to acquire a plurality of in-focus images, focus position adjustment is performed by autofocus in the Z-axis direction every time an image is acquired, or focus position adjustment is performed. It is necessary to create a teaching program to be performed.

  The present invention has been made in view of such a situation. For example, an object of the present invention is to provide a measurement method that is advantageous for simplification of adjustment when calculating information related to the shape of an object or shortening measurement time. And

  In order to solve the above problems, the present invention is a measurement method for calculating information related to the shape of an object based on an image obtained by imaging the object using an image sensor, and obtains design information of the object. An acquisition step, a setting step for setting the focus position of the optical system including the image sensor at the measurement position in the focus direction of the object identified from the design information acquired in the acquisition step, and the object at the focus position set in the setting step An imaging process for imaging the object, and a calculation process for calculating information related to the shape of the object based on the image captured in the imaging process.

  According to the present invention, for example, it is possible to provide a measurement method that is advantageous for simplifying adjustment when calculating information related to the shape of an object or shortening measurement time.

It is a figure which shows the structure of the measuring device which concerns on one Embodiment. It is a flowchart which shows the flow of the measurement process in one Embodiment. It is a figure which shows the relationship between the reference plane position of an object, and the height in design information. It is a figure which shows the relationship between the design information of an object, XY projection shape, and an image.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  First, in describing the measurement method according to an embodiment of the present invention, the configuration of a measurement apparatus to which this measurement method can be applied will be described. FIG. 1 is a schematic diagram illustrating a configuration of a measurement device 12 according to the present embodiment. The measuring device 12 calculates a piece of information about the shape of the object 4 by measuring the surface position of the object 4 in a non-contact manner using the object 4 such as a mold or a mold for manufacturing the part as an object to be measured. 4 is a non-contact three-dimensional measuring apparatus that specifies the shape of the four. In each of the following drawings, an X axis and a Y axis perpendicular to each other are taken in the surface 5a of the mounting table 5 on which the object 4 is placed, and a Z axis is taken in a direction perpendicular to the XY plane.

  The measuring device 12 includes a light source 1, a collimating lens 2 a, an objective lens 2 b, an imaging lens 2 c, a half mirror 3, an image sensor 7, a mounting table 5, and a control unit 10. Among these, the collimating lens 2a, the objective lens 2b, the imaging lens 2c, the half mirror 3, and the imaging device 7 are optical systems including a light projecting system and a light receiving system. The light source 1 is an incoherent light source, such as an LED or a lamp. The light beam emitted from the light source 1 is collimated by the collimator lens 2a, passes through the half mirror 3, passes through the objective lens 2b, and is irradiated onto the object 4 placed on the mounting table (member) 5. In the present embodiment, the surface 5a of the mounting table 5 is a reference surface in the Z-axis direction. The focus direction of the optical system is assumed to be a direction along the Z-axis direction. The measurement device 12 further includes a drive unit (position variable means) 8 that can move the mounting table 5 in the Z-axis direction in order to adjust the focus position to the position to be measured on the object 4 with high accuracy, and the mounting table. And a Z-axis position measuring unit 9 that measures the amount of movement of 5. The drive unit 8 is, for example, an actuator. The Z-axis position measurement unit 9 is an encoder, for example. The light reflected by the object 4 returns to the half mirror 3 through the objective lens 2b, is partially reflected, and further passes through the imaging lens 2c, and an image is acquired by the image sensor (image sensor) 7. The control unit 10 acquires and analyzes the operation control of each component in the measurement device 12 and the measurement result obtained with each operation. In particular, the control unit 10 performs edge detection based on the image acquired from the image sensor 7 and causes the object 4 to measure dimensions.

  Next, a measurement method according to this embodiment will be described. FIG. 2 is a flowchart showing the flow of the measurement process in the present embodiment. First, when starting the measurement process, the object 4 is placed on the reference surface 5 a of the placing table 5. Here, the distance between the reference surface 5a and the focus surface 6 is guaranteed in advance. Specifically, the Z-axis position of the mounting table 5 where the reference position Z0 (see FIG. 3) on the reference surface 5 is a condition conjugate with the image sensor 7 is set in advance. However, the reference surface 5a is not limited to the same surface (the same height) as the surface on which the object 4 is placed as shown in FIG. Therefore, it is not always necessary to have the same surface as the surface on which the object 4 is placed.

  Next, the control part 10 acquires the design information of the object 4 (acquisition process: step S101). Here, the design information of the object 4 is information including a dimension value, a surface shape, and an edge position used when the object 4 is manufactured or molded, for example, CAD data. This design information is preferably stored in advance in the storage unit 11 that is electrically connected to the control unit 10 via a line. In this case, the control unit 10 appropriately reads design information from the storage unit 11 in step S101.

  Next, the control unit 10 sets a focus position when measuring dimensions in the XY direction (hereinafter simply referred to as “XY measurement”) from the design information acquired in step S101 (setting process: step S102). Specifically, the control unit 10 calculates the focus position at the time of XY measurement based on the height information (measurement position in the focus direction) of the object 4 read from the design information and the reference plane 5a. FIG. 3 is a conceptual diagram showing height information based on design information of the object 4 and a reference surface 5a in the Z-axis direction. Since the XY measurement position may not be registered in the design information, it is desirable that the user can easily set it based on the design information. In particular, in the present embodiment, the measurement device 12 measures the first measurement position X1 and the second measurement position X2 as XY measurement positions. Here, after the object 4 is mounted on the mounting table 5, the focus positions for measuring the first measurement position X1 or the second measurement position X2 are at the height positions Z1 and Z2 from the reference surface 5a, respectively. Is set. When the edge (ridge line) of the measurement position is chamfered, the focus position is lowered from the height positions Z1 and Z2 by a specified offset amount (position moved toward the reference surface 5a). ) May be set. Thereby, the measurement error by chamfering is given can be reduced. In this case, the offset amount may be set by the user as a parameter during XY measurement, or the chamfering amount may be read from the design information and automatically set accordingly.

  Next, based on the focus position calculated in step S102, the control unit 10 adjusts the object 4 so that the focus position of the optical system matches the position of each surface of the object 4, that is, the height position of Z1 or Z2. Is appropriately moved in the Z-axis direction (step S103). For the movement of the mounting table 5, a driving unit 8 and a Z-axis position measuring unit 9 are used. Next, the control unit 10 causes the light source 1 to emit light, and causes the imaging element 7 to capture a reflection intensity image (two-dimensional image) of the light irradiated to the object 4 (imaging process: step S104).

  Next, the control unit 10 determines whether image acquisition has been completed at all focus positions (two height positions Z1 and Z2 in this embodiment) (step S105). If the control unit 10 determines that only the image having the height position Z1 as the focus position has been acquired (No), the process returns to step S103. Then, the control unit 10 moves the mounting table 5 so that the focus position becomes the height position Z2, captures an image at a position with respect to the height position Z2, and acquires an object image. On the other hand, if the control unit 10 determines in step S105 that image acquisition has been completed at all focus positions corresponding to the position of the surface of the object 4 (Yes), the process proceeds to the following step S106. .

  Next, the control unit 10 recognizes the position (or orientation) of the object 4 from the image acquired in step S104, and specifies the XY measurement position of the object 4 by matching the image with the position of the object based on the design information ( Positioning step: Step S106). FIG. 4 is a diagram illustrating the relationship between the design information of the object 4 and the image of the XY projection shape. First, the control unit 10 calculates an XY projection shape shown as (B) from the design information of the object 4 shown as (A). Next, the control unit 10 obtains a correlation between the two data while moving or rotating the XY projection shape between the XY projection shape and the image acquired in step S104. Next, the control unit 10 determines the position of the object 4 by using a method such as calculating the position (or posture) of the XY projection shape having the highest correlation. Then, the control unit 10 acquires the XY measurement position registered in advance in the design information of the object 4 or the XY measurement position designated by the user from the storage unit 11, and finally matches the XY measurement position to specify To do. As a result, the measurement device 12 can automatically acquire the XY measurement position as shown in (C), so that it is not necessary to manually set the reference plane in the XY directions, and the complexity during measurement is reduced. can do.

  Then, the control unit 10 detects the edge of the image from the XY measurement position specified in step S106 and the position of the object 4, and calculates the dimension of the object 4 in the XY direction (calculation step: step S107). Here, examples of the edge detection method include a method of detecting an edge based on a change in luminance information of an image.

  Thereby, in the measurement direction (measurement device 12) according to the present embodiment, first, since the distance between the focus position of the optical system and the reference surface 5a in the Z-axis direction is guaranteed in advance, the reference surface 5a is used as the user. There is no need to manually adjust. Further, since the focus position is set from the design information of the object 4 and the mounting table 5 is moved based on the focus position, it is not necessary for the user to give an autofocus instruction. Similarly, since it is not necessary for the user to create (prepare) a teaching program in which the focus position is specified in advance, information regarding the shape of the object 4 can be calculated easily and at high speed. Therefore, even if the object 4 has a step greater than the depth of focus of the imaging lens 2c, the user can simply place the object 4 on the mounting table 5 without performing troublesome adjustment work. High-precision measurement can be performed while suppressing the measurement time.

  As described above, according to the present embodiment, it is possible to provide a measurement method and a measurement apparatus that are advantageous in simplifying adjustment when calculating information related to the shape of an object or shortening measurement time.

  In the above description, the position variable means for changing the focus position is the mounting table 5 on which the object 4 is mounted, and the mounting table 5 is moved in the Z-axis direction. However, the present invention is not limited to this. For example, by moving an optical system that includes the image sensor 7 or an optical system that does not include the image sensor 7 and includes the objective lens 2b or the like as a position variable unit, the focus position is set. It may be changed. Furthermore, both the mounting table 5 and the above optical system may move as position changing means. Further, the embodiment in which the object 4 has two surfaces having different heights has been described, but the measurement method can also be applied to the case of measuring the object 4 composed of one plane. In the above embodiment, the size of the object is calculated as information on the shape of the object. However, only the position of the edge of the object can be calculated, or the contour of the surface of the object can be obtained.

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

7 Image sensor 10 Control unit 12 Measuring device

Claims (7)

A measurement method for calculating information related to the shape of an object based on an image obtained by imaging the object using an imaging element,
An acquisition step of acquiring design information of the object;
A setting step of setting a focus position of an optical system including the image sensor at a measurement position in the focus direction of the object specified from the design information acquired in the acquisition step;
An imaging step of imaging the object at the focus position set in the setting step;
A calculation step of calculating information on the shape of the object based on the image captured in the imaging step;
A measurement method comprising: In the obtaining step, as the design information of the object, the positions of two surfaces having different heights are obtained,
In the setting step, the focus position is sequentially set to the positions of the two surfaces,
In the imaging step, the object is imaged at each focus position;
The measurement method according to claim 1, wherein: A positioning step of matching the image captured in the imaging step with the position of the object based on the design information;
The calculation step calculates information on the shape of the object based on the image combined in the alignment step.
The measuring method according to claim 1 or 2, wherein   The measuring method according to claim 1, wherein the calculating step calculates the size of the object by detecting an edge of the object from the image. When chamfering is given to the edge at the measurement position of the object,
The setting step includes an offset amount determined by the chamfering amount in the set focus position.
The measurement method according to claim 1, wherein:   The measurement method according to claim 1, wherein the design information is CAD data of the object. A measurement device that calculates information related to the shape of the object based on an image obtained by imaging the object,
An optical system including an image sensor that images the object;
Position varying means for varying the focus position of the optical system;
The focus position of the optical system is set to the measurement position in the focus direction of the object specified from the design information of the object, and the position variable unit is configured to adjust the set focus position. A control unit that images the object and calculates information on the shape of the object based on the captured image;
A measuring apparatus comprising:

Images