WO2020008713A1

WO2020008713A1 - Measurement device

Info

Publication number: WO2020008713A1
Application number: PCT/JP2019/017337
Authority: WO
Inventors: 山田　智明
Original assignee: Dmg森精機株式会社
Priority date: 2018-07-04
Filing date: 2019-04-24
Publication date: 2020-01-09
Also published as: JP2020008348A; JP7083282B2

Abstract

Provided is a measurement device provided with an image acquisition unit, an illumination unit, and a control unit, the image acquisition unit acquiring an image in a case in which the illumination unit and an imaging object are in a first positional relationship, and an image in a case in which the illumination unit and the imaging object are in a second positional relationship symmetrical to the first positional relationship, and the control unit measuring the surface position of the imaging object on the basis of the images in the first positional relationship and the second positional relationship. Highly precise measurement of the imaging object using an image sensor can thereby be realized even when error occurs in the light distribution characteristics due to the illumination.

Description

measuring device

The present invention relates to an apparatus for measuring an object to be photographed, and particularly to a measuring apparatus for measuring an object to be photographed on a machine tool.

測定 In a measuring device for measuring an object to be photographed on a machine tool, an image sensor can be attached to a moving part (for example, a main shaft) of the machine tool to measure the object to be photographed. When an image sensor is used, there is a possibility that image unevenness, in particular, unevenness in luminance may occur. To cope with this, there has been proposed an image processing apparatus that corrects luminance unevenness by performing shading correction (for example, see Patent Document 1).

JP 2012-94951 A

画像 The image processing apparatus described in Patent Literature 1 aims to easily calculate correction information for shading correction. This makes it possible to correct uneven brightness. However, the image sensor attached to the moving part of the machine tool needs to be small, lightweight, and practically inexpensive in consideration of storage in an automatic tool changer. To cope with this, it is preferable to use an image sensor in which ring illumination such as an LED is arranged around the imaging lens.

画像 With an image sensor equipped with such a ring illumination, it is necessary to consider not only uneven brightness but also differences in light distribution characteristics. In particular, image unevenness in an imaging target having a three-dimensional structure occurs due to a variation in the angle of view of illumination viewed from each point on the surface of the imaging target. For example, as shown in FIG. 6, when an image sensor in which a ring illumination is arranged around an image acquisition unit (imaging lens) is used to measure the edge portions e and f of the convex portion, arrows E and E of the profile are used. As in the portion indicated by F, a large error may occur in the profile due to a difference in light distribution characteristics.

The present invention has been made in view of the above-described problem, and provides a measuring apparatus capable of realizing highly accurate measurement of an imaging target using an image sensor even when an error in light distribution characteristics occurs due to illumination. The purpose is to provide.

In order to solve the above-mentioned problem, a measuring device according to one embodiment of the present invention includes:
An image acquisition unit;
Lighting part,
A control unit;
With
The image acquisition unit captures an image when the illumination unit and the imaging target are in a first positional relationship, and the illumination unit and the imaging target are in a second positional relationship symmetrical to the first positional relationship. If the imaging and get,
The control unit measures a surface position of the imaging target based on the imaging of the first positional relationship and the second positional relationship.

According to the above-described embodiment, it is possible to provide a measuring apparatus capable of realizing highly accurate measurement of a photographing target using an image sensor even when an error in light distribution characteristics occurs due to illumination.

It is a perspective view showing typically composition of a measuring device concerning one embodiment of the present invention. It is a perspective view which shows typically an example of the image sensor provided with the illumination part and the image acquisition part. It is a figure which shows typically an example which acquires the imaging | photography when a lighting part and an imaging target have a 1st positional relationship. It is a figure which shows typically an example which changes the positional relationship between a lighting part and a photography target object from a 1st positional relationship to a 2nd positional relationship. It is a figure showing typically an example which acquires an image pick-up in case a lighting part and a photography subject have the 2nd positional relation. 3 is a flowchart illustrating an example of a process of measuring by offsetting an error in light distribution characteristics using the measurement device illustrated in FIG. 1. 2 is a flowchart illustrating a process for canceling an error in light distribution characteristics and performing a measurement using the measurement device illustrated in FIG. 1 and other examples. It is a figure which shows typically the influence by the error of a light distribution characteristic.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The embodiment described below is for embodying the technical idea of the present invention, and the present invention is not limited to the following unless otherwise specified.

In the following embodiments and examples, description of matters common to the above will be omitted, and only different points will be described. In particular, the same operation and effect of the same configuration will not be sequentially described in each embodiment and example. The size, positional relationship, and the like of the members shown in each drawing may be exaggerated for clarity of description.
In FIGS. 1 and 3A to 3C, directions orthogonal to each other in the horizontal direction of the machine tool are defined as an X-axis direction and a Y-axis direction, a direction perpendicular to the machine tool is defined as a Z-axis direction, and a rotation direction around the Z-axis is defined as C. Shown as axial direction.

(Measurement device according to one embodiment)
First, an outline of a measuring device according to the present invention will be described with reference to FIGS. FIG. 1 is a perspective view schematically showing a configuration of a measuring device according to one embodiment of the present invention. FIG. 2 is a perspective view schematically illustrating an example of an image sensor provided with an illumination unit and an image acquisition unit.

The measurement device 2 according to the present embodiment includes an image sensor 10 and a control unit 20 that performs control for measurement. The image sensor 10 is electrically connected to the control unit 20. Further, the image sensor 10 is attached to a tool spindle 30 which is a moving part of the machine tool.
The drive unit of the moving unit (tool main shaft) 30 of the machine tool is electrically connected to the NC device 40, and the driving unit (tool main shaft) 30 is controlled by the NC device 40 so that the moving unit (tool main shaft) 30 has an X axis, a Y axis, and a Z axis. Direction and can rotate about a main axis. The control unit 20 of the measurement device 2 and the NC device 40 are electrically connected.

FIG. 1 shows a case where the photographing target W is attached to the table 50 of the machine tool. The moving unit (tool main shaft) 30 to which the image sensor 10 is attached has a main axis oriented in the Z-axis direction (vertical direction), and the image sensor 10 can image the photographing target W from vertically above.

The image sensor 10 attached to the moving part (tool spindle) 30 of the machine tool needs to be small, lightweight, practical and low cost in consideration of storage in an automatic tool changer. To cope with this, the image sensor 10 according to the present embodiment has an image acquisition unit 12 and an illumination unit 14 arranged around the image acquisition unit 12, as shown in FIG.
More specifically, an illumination unit 14 that is a ring illumination using six LEDs is arranged around the imaging lens of the image acquisition unit 12. Further, the image sensor 10 includes a shank 16, and the shank 16 is inserted and fixed in a tool holder of a tool spindle 30, which is a moving member of a machine tool.

With such a configuration, the image sensor 10 acquires the imaging target W by the image acquisition unit 12 while illuminating the imaging target W fixed on the table 50 from above with the illumination unit 14. be able to. The image sensor 10 attached to the moving unit (tool spindle) 30 can be moved in the X-axis direction and the Y-axis direction under the control of the NC device 40, and can be rotated in the C-axis direction around the Z-axis.

(Measurement method using imaging in which the illumination unit and the imaging target are in the first and second positional relationships)
The image sensor 10 including the ring illumination (illumination unit) 14 according to the present embodiment is small, lightweight, and excellent in cost. However, as shown in FIG. 6, when an edge sensor e, f of a convex portion is measured using an image sensor in which a ring illumination is arranged around an image acquisition unit (imaging lens), arrows E, As in the portion indicated by F, a large error may occur in the profile due to a difference in light distribution characteristics. Therefore, it may be difficult to measure an imaging target with high accuracy due to a difference in light distribution characteristics.
In order to cope with this, even when an error in the light distribution characteristics occurs due to the illumination unit 14, by canceling the error, highly accurate measurement of the imaging target can be realized. This will be described in detail below.

<Imaging in First Positional Relationship>
First, with reference to FIG. 3A, description will be given of imaging in a case where the illumination unit 114 and the imaging target object W are in the first positional relationship. FIG. 3A is a diagram schematically illustrating an example of acquiring an image when the illumination unit 14 and the imaging target object W are in the first positional relationship.

矩形 The rectangular frame in FIG. 3A indicates the field of view (FOV) of the image acquisition unit 12. 6 shows an arrangement of six LEDs L1 to L3 and R1 to R3 constituting a lighting unit 14 around an image acquisition unit 12. The illumination unit 14 (L1 to L3, R1 to R3) and the imaging target W are in the first positional relationship, and the upper surface shape of the imaging target W is shown at the upper left of the field of view (FOV) of the image acquisition unit 12. I have. The upper surface shape of the photographing target W shows a rectangle having four edges a to d. The rotation center when rotating the image sensor 10 is indicated by P.

<Change from the first positional relationship to the second positional relationship>
Next, a description will be given of a case where the first positional relationship between the illumination unit 14 and the imaging target object W shown in FIG. 3A is changed to the second positional relationship with reference to FIG. 3B. FIG. 3B is a diagram schematically illustrating an example in which the positional relationship between the illumination unit 14 and the imaging target object W is changed from the first positional relationship to the second positional relationship.

{Circle around (3)} on the right side of FIG. 3B shows solid-state imaging when the illumination unit 14 and the imaging target W are in the first positional relationship. As indicated by the white arrow, the moving unit (tool spindle) 30 to which the image sensor 10 is attached moves from the position Ps1 corresponding to the first positional relationship to the second positional relationship under the control of the NC device 40. Move to position Ps2. Furthermore, it is rotated 180 degrees in the C-axis direction around the Z-axis. Thereby, the illumination unit 14 and the imaging target W are changed to the second positional relationship. The position of the relative second positional relationship in the field of view (FOV) of the image acquiring unit 12 having the first positional relationship in FIG. 3A is indicated by a dotted line.

<Imaging in the second positional relationship>
Next, with reference to FIG. 3C, imaging in a case where the illumination unit 14 and the imaging target object W are in the second positional relationship will be described. FIG. 3C is a diagram schematically illustrating an example of acquiring an image when the illumination unit 14 and the imaging target object W are in the second positional relationship. If the image sensor 10 is rotated 180 degrees without moving in the X-axis and Y-axis directions from the first positional relationship shown in FIG. 3A, the photographing target W is shown at the position shown by the dotted line in FIG. 3C. It is.

Therefore, as shown by the outline arrow in FIG. 3B, by moving the image sensor 10 in the X-axis and Y-axis directions, the measurement position in the field of view (FOV) of the image acquisition unit 12 is changed to a symmetrical edge. It can be in the same position above. Specifically, the edge a at the first position matches the second one edge c, the edge b at the first position matches the second one edge d, and the edge c at the first position Coincides with the second edge a, and the edge d at the first position coincides with the second edge b. Therefore, even if an error occurs in the light distribution characteristics due to the illumination unit 14, the error can be offset.

If the center coordinates of the imaging target W coincide with the rotation center P of the image sensor 10, it is not necessary to move the image sensor 10 in the X-axis and Y-axis directions. The movement indicated by the white arrow in FIG. 3B corrects an offset amount of the photographing target object W with respect to the rotation center P of the image sensor 10. Therefore, it is necessary to obtain the center coordinates of the photographing target W in plan view and move the symmetrical edges so as to be at the same position in the field of view in consideration of the offset of the center coordinates from the rotation center P.

As described above, the image acquisition unit 12 of the image sensor 10 captures the image when the illumination unit 14 and the imaging target W are in the first positional relationship, and sets the illumination unit 14 and the imaging target W in the first positional relationship. The control unit 20 measures the surface position of the imaging target based on the images of the first positional relationship and the second positional relationship.

Since the surface position of the photographing target object W is measured based on the first positional relationship and the imaging of the second positional relationship symmetrical to the first positional relationship, an error in the light distribution characteristics may occur due to the illumination unit 14. However, this error can be canceled out, and highly accurate measurement of the photographing object W can be realized.

In the above example, the case where the illumination unit 14 and the imaging target object W are rotated by 180 degrees is shown as the “symmetric positional relationship”, but this is merely an example, and even if the relative position is slightly shifted, Seen from the intermediate point before and after the shift, it is also included in the “symmetric positional relationship”.

As a specific example for canceling the error in the light distribution characteristics, the control unit 20 of the measurement device 2 performs imaging when the illumination unit 14 and the imaging target W are in the first positional relationship, and performs imaging in the second position. It is conceivable to superimpose the imaging in the case of the relationship. As a result, errors in the light distribution characteristics can be effectively canceled, and highly accurate measurement of the imaging target can be efficiently realized.

In addition, measurement data is acquired from the imaging when the illumination unit 14 and the imaging target W are in the first positional relationship, and the measurement data is obtained from the imaging when the illumination unit 14 and the imaging target W are in the second positional relationship. It is also conceivable to acquire and obtain the respective measurement data obtained. By canceling out the measurement data obtained by the imaging in the first positional relationship and the imaging in the second positional relationship, it is possible to reliably measure the object to be photographed with high accuracy.

The first and second positional relationships are not limited to the case where the image sensor 10 to which the image acquisition unit 12 and the illumination unit 14 are fixed is moved and rotated as described above. For example, the image acquisition unit may not move with respect to the imaging target, but may move only the illumination unit, may move the imaging target side, or may combine them.

In order to move from the first positional relationship to the second positional relationship, the table 50 on which the photographing object W is placed is rotated, not only when the moving unit (tool spindle) 30 of the machine tool is rotated and translated. The translation may be performed, or both may be combined. The control unit 20 may exist as a control device unique to the measurement device, or may use a control device of a machine tool.
Further, the measuring device 2 may have a unique moving mechanism, and may move from the first positional relationship to the second positional relationship without using the moving mechanism of the machine tool.

(Step of measuring by offsetting the error of light distribution characteristics)
Next, a description will be given of a process of using the measuring device 2 according to the above-described embodiment to perform measurement while canceling out an error in the light distribution characteristics of the illumination unit 14.
<One example of process>
With reference to FIG. 4, one example of a process of measuring by offsetting an error in the light distribution characteristics of the illumination unit 14 will be described. FIG. 4 is a flowchart showing one example of a process of measuring by offsetting an error in light distribution characteristics using the measurement device shown in FIG.

In FIG. 4, first, a signal of a preparation command is transmitted from the control unit 20 of the measuring device 2 to the image sensor 10, and after the image sensor 10 completes the preparation, the preparation completion signal is transmitted from the image sensor 10 to the control unit 20. Send Next, an instruction signal for moving the moving unit (tool spindle) 30 to which the image sensor 10 is attached to the position Ps1 corresponding to the first positional relationship is transmitted from the control unit 20 to the NC device 40. The NC device 40 moves the moving unit (tool spindle) 30 to the position Ps1. After the movement is completed, a signal indicating the completion of the movement is transmitted from the NC device 40 to the control unit 20. Thereby, the illumination unit 14 and the photographing target W are arranged in the first positional relationship.

(4) In this state, a signal of a shooting command is transmitted from the control unit 20 to the image sensor 10. The image sensor 10 performs photographing, and after photographing, transmits a signal indicating that photographing has been completed from the image sensor 10 to the control unit 20. Through the above steps, the imaging in the case where the illumination unit 14 and the imaging target W are in the first positional relationship is completed.

Next, an instruction signal for moving the moving unit (tool spindle) 30 to which the image sensor 10 is attached to the position Ps2 corresponding to the second positional relationship is transmitted from the control unit 20 to the NC device 40. The NC device 40 moves the moving unit (tool spindle) 30 to the position Ps2. After the movement is completed, a signal indicating the completion of the movement is transmitted from the NC device 40 to the control unit 20.
Subsequently, the control unit 20 transmits to the NC device 40 an instruction signal for rotating the main shaft of the moving unit (tool main shaft) 30 to which the image sensor 10 is attached by 180 degrees. The NC device 40 rotates the main shaft of the moving unit (tool main shaft) 30 by 180 degrees. After the rotation of the spindle is completed, a signal indicating the completion of spindle rotation is transmitted from the NC device 40 to the control unit 20. Thereby, the illumination unit 14 and the photographing target W are arranged in the second positional relationship.

In this state, a signal of a shooting command is transmitted from the control unit 20 to the image sensor 10. The image sensor 10 performs photographing, and after photographing, transmits a signal indicating the end of photographing from the image sensor 10 to the control unit 20. Through the above steps, the imaging in the case where the illumination unit 14 and the imaging target W are in the second positional relationship is completed. Thereby, in the field of view (FOV) of the image acquisition unit 12, imaging of the first positional relationship and the second positional relationship in which the symmetrical edge is at the same position in the visual field is obtained.
Note that the control for moving in the X-axis and Y-axis directions and the control for rotating can also be performed in the same single step.

By superimposing the imaging of the first positional relationship and the imaging of the second positional relationship, an error in the light distribution characteristics of the illumination unit 14 can be effectively canceled, and the measurement of the imaging target W with high accuracy can be performed.
Further, by canceling the measurement data obtained by the imaging having the first positional relationship and the measurement data obtained by the imaging having the second positional relationship, it is possible to measure the imaging target W with high accuracy. .

For example, the measurement position Ps1a of the edge a of the imaging target W is calculated based on the imaging having the first positional relationship, and the measurement position Ps1c of the edge c of the imaging target W is calculated. Similarly, the measurement position Ps2a of the edge a of the photographing target W is calculated based on the imaging having the second positional relationship, and the measurement position Ps2c of the edge c of the photographing target W is calculated.
The measurement data can be offset by “Ps1a-Ps2a” and “Ps1c-Ps2c”.
At this time, it is possible to simultaneously estimate and correct the deviation between the rotation center of the main shaft of the moving unit (tool main shaft) 30 and the rotation center of the image sensor 10. For example, it can be obtained as １／ of a difference between a measured value obtained by imaging in the first positional relationship and a measured value obtained by imaging in the second positional relationship.

(4) The displacement between the moving unit (tool spindle) 30 and the image sensor 10 calculated in this way is transmitted from the control unit 20 to the NC device 40 as a coordinate correction value of the photographing target W, and the setting is performed. Accordingly, even when an error in the light distribution characteristics occurs due to the illumination unit 14, the error can be canceled out, and highly accurate measurement of the imaging target W can be realized.

<Other examples of process>
Next, with reference to FIG. 5, another example of the step of measuring by offsetting an error in the light distribution characteristics of the illumination unit 14 will be described. FIG. 5 is a flowchart showing another example of the step of performing measurement by offsetting an error in light distribution characteristics using the measurement apparatus shown in FIG.

In one example of the process illustrated in FIG. 4, the image acquisition unit 12 of the image sensor 10 acquires an image having a positional relationship obtained by rotating the positional relationship between the illumination unit 14 and the imaging target W by 180 degrees. In another example shown in FIG. 5, the image acquisition unit 12 of the image sensor 10 is rotated 90, 180, and 270 degrees with respect to the predetermined positional relationship between the illumination unit 14 and the photographing target W as 0 degree. The difference is that an image is acquired. At each rotation angle, the moving unit (tool spindle) 30 to which the image sensor 10 is attached is moved in the X-axis direction and the Y-axis direction so that the symmetrical edge is located at the same position in the field of view.

As described above, the image acquisition unit 12 sets the predetermined positional relationship between the illumination unit 14 and the imaging target W to 0 degree, rotates the image by 90 degrees, 180 degrees, and 270 degrees, and captures images having symmetrical positional relationships. By acquiring, the error of the light distribution characteristic can be offset, and highly accurate measurement of the two-dimensional imaging target can be realized.
Other points are the same as those of the above-described one example of the process, and thus further description is omitted.

(Measurement with reduced influence of external light)
Furthermore, when both the illumination unit 14 and the white light source are turned on, and when only one of them is turned on, the illumination unit 14 emits outgoing light of various wavelengths and outputs a difference in luminance or a ratio of luminance. Can detect a large wavelength. For example, in a case where the illumination unit 14 is a ring illumination including a red LED, a green LED, and a blue LED, by changing the output of the LED of each wavelength, a wavelength difference or a ratio of the luminance in the emitted light is large. Can be detected. Note that, as the white light source, it is conceivable to use the in-machine illumination of the machine tool or the indoor lighting in which the machine tool is installed.

Here, the image acquisition unit 12 acquires an image of the imaging target W in a state where the illumination unit 14 and the white light source are turned on, and further, turns on only the illumination unit 14 or turns on only the white light source. An image of the imaging target W in the state is acquired. Then, of the emitted light that can be emitted from the illumination unit 14, in the two acquired images, light having a wavelength with a large difference in luminance or a large luminance ratio in a region where the object to be photographed W is measured is determined. The image acquisition unit 12 measures the surface position of the imaging target W using the emission light having the determined wavelength.

As described above, in a state where the illumination unit and the white light source are turned on, and in a state where only the illumination unit and the white light source are turned on, a wavelength having a large difference in luminance or a large luminance ratio in the measurement region of the imaging target W is used. By performing the measurement, measurement in which the influence of external light is reduced can be realized.

Although the embodiments and modes of the present invention have been described, the disclosed contents may be changed in the details of the configuration, and combinations of elements and changes in the order in the embodiments and the modes of the present invention are the claimed invention. Can be realized without departing from the scope and spirit of the present invention.

2 Measurement device 10 Image sensor 12 Image acquisition unit 14 Illumination unit 16 Shank 20 Control unit 30 Moving unit (tool spindle)
40 NC device 50 Table W Object to be photographed

Claims

An image acquisition unit;
Lighting part,
A control unit;
With
The image acquisition unit captures an image when the illumination unit and the imaging target are in a first positional relationship, and the illumination unit and the imaging target are in a second positional relationship symmetrical to the first positional relationship. If the imaging and get,
The measurement device, wherein the control unit measures a surface position of the imaging target based on the imaging of the first positional relationship and the second positional relationship.
2. The image acquisition unit according to claim 1, wherein a predetermined positional relationship between the illumination unit and the object to be photographed is set to 0 degree, and an image having a positional relationship rotated by 90 degrees, 180 degrees, and 270 degrees is acquired. The measuring device according to item 1.
The control unit measures the surface position of the imaging target object by superimposing the imaging in the first positional relationship and the imaging in the second positional relationship. The measuring device according to claim 1 or 2, wherein
The control unit cancels the measurement data obtained by the imaging in the first positional relationship and the measurement data obtained by the imaging in the second positional relationship to perform the imaging. The measuring device according to claim 1, wherein a surface position of the object is measured.
The image acquisition unit acquires an image of the imaging target in a state where the illumination unit and the white light source are turned on, and acquires an imaging of the imaging target in a state where only the illumination unit or the white light source is turned on,
The image acquisition unit, among the emitted light that can be emitted from the illumination unit, in the two imaging, using light of a wavelength having a large luminance difference or a large luminance ratio in a region where the measurement of the imaging target is performed, The measuring device according to claim 1, wherein a surface position of the imaging target is measured.