JP6225719B2 - Straightness measuring device, straightness measuring method, and program - Google Patents

Description

  The present invention relates to a straightness measuring device that measures the straightness of a measurement object.

Conventionally, various means for measuring the straightness of a measurement object have been provided. For example,
Patent Document 1 discloses an invention in which straightness is measured with a simple and compact configuration by using a laser beam for a two-dimensional displacement detector and analyzing a generated speckle image.

  On the other hand, Patent Document 2 discloses an invention for simply and accurately measuring and evaluating wire bending of a wire. The wire is dropped and photographed from a direction perpendicular to the hanging direction of the wire. A center line is obtained, converted into a two-dimensional continuous meandering curve, divided into a plurality of sections 2 to 25 times the wire length, and the straightness of the section is evaluated for each section of the divided two-dimensional curve. It is said.

Patent No. 4970204 Japanese Patent No. 4050772

  On the other hand, when the measurement object has many linear patterns, the amount of measurement becomes enormous according to the number of the linear patterns. In such a case, it is important to increase the measurement speed while ensuring the measurement accuracy.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a straightness measurement device that performs straightness measurement at high speed and with high accuracy.

1st invention for achieving the objective mentioned above is a straightness measuring apparatus which measures the straightness of a measuring object pattern, Comprising: The reference pattern by which straightness was confirmed, the said reference pattern, and the said measuring object pattern An imager that simultaneously captures the imager, an imager transport unit that transports the imager along the reference pattern, and the reference pattern and the measurement target pattern based on image data acquired by capturing the image while transporting And a straightness calculation means for calculating the straightness of the pattern to be measured from the distance between the patterns.
It is.
According to the first invention, since the measurement is performed while the image pickup device is conveyed without stopping, the straightness of the measurement target pattern can be measured at high speed. In addition, since the straightness of the measurement target pattern is calculated from the relative value (distance between patterns) to the reference pattern in the same image, even if the image pickup device is meandering, the effect can be offset with high accuracy. Measurement of straightness.

It is desirable that correction means for correcting the inter-pattern distance according to the inclination of the measurement target pattern is further provided, and that the straightness calculation means calculates straightness of the measurement target pattern from the corrected inter-pattern distance. .
As a result, even when the measurement target pattern is inclined obliquely with respect to the axial direction of the reference pattern, the inclination is corrected and the straightness of the measurement target pattern is calculated. Measurement errors can be reduced, and more accurate straightness can be measured.

According to a second aspect of the present invention, the straightness of the measurement target pattern is determined using a straightness measurement apparatus including a reference pattern whose straightness is confirmed and an imager that images the reference pattern and the measurement target pattern at the same time. A straightness measurement method for measuring, wherein a conveyance imaging step of imaging the imager while conveying the imager along the reference pattern, and the reference pattern and the image based on image data acquired by imaging while conveying A straightness measurement method comprising: calculating a distance between patterns with a measurement target pattern, and calculating a straightness of the measurement target pattern from the distance between the patterns.
According to the second invention, since the measurement is performed while the imaging device is conveyed without stopping, the straightness of the measurement target pattern can be measured at high speed. In addition, since the straightness of the measurement target pattern is calculated from the relative value (distance between patterns) to the reference pattern in the same image, even if the image pickup device is meandering, the effect can be offset with high accuracy. Measurement of straightness.

A third invention is a program for causing a computer to function as a straightness measuring device for measuring the straightness of a measurement target pattern, wherein the straightness measuring device includes a reference pattern whose straightness is confirmed, An image pickup device that simultaneously picks up the reference pattern and the measurement target pattern, and a transfer image pickup means for picking up an image while carrying the image pickup device along the reference pattern. A program for functioning as a straightness calculation unit that calculates an inter-pattern distance between the reference pattern and the measurement target pattern based on the image data, and calculates a straightness of the measurement target pattern from the inter-pattern distance. is there.
According to the third invention, since the measurement is performed while the image pickup device is conveyed without being stopped, the straightness of the measurement target pattern can be measured at high speed. In addition, since the straightness of the measurement target pattern is calculated from the relative value (distance between patterns) to the reference pattern in the same image, even if the image pickup device is meandering, the effect can be offset with high accuracy. Measurement of straightness.

  According to the present invention, since the measurement is performed while transporting the image pickup device without stopping, the straightness of the measurement target pattern can be measured at high speed. In addition, since the straightness of the measurement target pattern is calculated from the relative value (distance between patterns) to the reference pattern in the same image, even if the image pickup device is meandering, the effect can be offset with high accuracy. Measurement of straightness.

The schematic diagram which shows the structure of the straightness measuring apparatus which concerns on embodiment of this invention. Diagram showing an example of a reference pattern (a) An enlarged view showing an example of a reference pattern (b) An enlarged view showing another example of a reference pattern Diagram showing an example of a measurement object Enlarged view of measurement object The figure which shows the conveyance state of a camera and illumination Functional diagram showing an example of control mechanism Flow chart explaining basic operation of straightness measuring device The figure which shows an example of the imaged image data Flow chart explaining straightness calculation processing (a) The figure which shows the edge of a reference pattern and a measurement object pattern (b) The figure which shows the gravity center position of a reference pattern and a measurement object pattern (c) The figure which shows the distance between the gravity centers of a reference pattern and a measurement object pattern (a) Two-dimensional plot of distance data between centroids (b) Figure fitting a linear function to distance data between centroids (c) Two-dimensional plot of distance data between centroids after correction Diagram showing the result of straightness of the measurement target pattern

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

[Embodiments of the present invention]
FIG. 1 is a schematic diagram illustrating a configuration example of a straightness measuring apparatus 1 according to an embodiment of the present invention.
As shown in FIG. 1, the straightness measuring apparatus 1 includes a measuring mechanism 1a and a control mechanism 1b.

  The measuring mechanism 1 a of the straightness measuring apparatus 1 includes a measurement table 2, a reference pattern 3 installed on the measurement table 2, a measurement object 4 arranged on the measurement table 2, and a reference pattern 3 above the measurement table 2. And a camera 5 for imaging the measurement object 4 simultaneously, a camera conveyance stage 6 for conveying the camera 5, and illumination for irradiating the reference pattern 3 and the measurement object 4 below the measurement table 2 from the back side. 7 and an illumination transport stage 8 that transports the illumination 7.

The measurement table 2 is formed in a flat plate shape, and has a long rectangular recess (not shown) at the center, and a glass plate for forming a reference pattern 3 described later is fixed to the recess.
The measurement table 2 may have a mechanism for transporting the measurement object 4 in the axial direction orthogonal to the longitudinal direction of the reference pattern 3.

  The reference pattern 3 is a linear pattern serving as a reference for measuring straightness, and straightness is guaranteed.

  FIG. 2 is a diagram illustrating an example of the reference pattern 3. In this embodiment, the reference pattern 3 is formed by coating a chromium film on a glass plate having a length of 2000 mm and a thickness of 5 mm. The glass plate on which the reference pattern 3 is formed is fixed to a recess (not shown) of the measurement table 2.

FIG. 3A is an enlarged view of a part of the reference pattern 3 of FIG. As shown in FIG. 3A, the reference pattern 3 is formed by uniformly coating a chromium film with a certain width in the longitudinal direction. The width of the chromium film is arbitrary, but in this embodiment, it is 100 microns.
FIG. 3B is an enlarged view showing an example of a reference pattern different from that in FIG. 3A, and a chromium film is coated in stripes at predetermined intervals in the longitudinal direction.

  FIG. 4 is a diagram showing the measurement object 4. In the present embodiment, the measurement object 4 is a film in which a linear pattern whose straightness has not been confirmed is coated at equal intervals. FIG. 5 is an enlarged view of a part of the measuring object 4 in FIG.

The camera 5 includes an imaging lens (not shown), an electronic imaging unit such as a CCD (Charge Coupled Device) and a CMOS (Complementary Metal-Oxide Semiconductor) that converts a subject image that has passed through the imaging lens into a two-dimensional image signal. It is installed so as to be able to be transferred to the camera transfer stage 6 (see FIG. 1).
In the present embodiment, a telecentric lens is used as the imaging lens. The telecentric lens is designed so that the chief ray travels in parallel with the lens optical axis, so that distortion aberration hardly occurs and the position of the subject can be measured with high accuracy.
The subject image captured by the camera 5 is stored as image data in the storage unit 24 of the control mechanism 1b via the transmission / reception unit 22 described later.

  The camera transport stage 6 is installed above the reference pattern 3 (see FIG. 1). The camera transport stage 6 holds the camera 5 and transports the camera 5 along the longitudinal direction of the reference pattern 3 while maintaining a certain distance from the reference pattern 3. The said conveyance is performed according to the control command of the control part 20 mentioned later. Note that a stop limiter may be provided at both ends of the camera transport stage 6 so that the camera 5 is automatically stopped when the camera 5 is transported beyond the stop limiter.

  The illumination 7 is installed so as to be able to be transported to the illumination transport stage 8 and irradiates light from the back (lower side) of the reference pattern 3 and the measurement object 4 (see FIG. 1). The illumination 7 is preferably transmitted illumination. By using transmitted illumination, in the straightness calculation process of the image processing unit 24 described later, the edges (contours) of the linear pattern of the reference pattern 3 and the measurement object 4 are clearly imaged, and the edge extraction accuracy is improved. .

  The illumination transport stage 8 holds the illumination 7 (see FIG. 1) and transports the illumination 7 along the longitudinal direction of the reference pattern 3 while maintaining a certain distance from the reference pattern 3. The said conveyance is performed according to the control command of the control part 20 mentioned later. Note that stop limiters may be installed at both ends of the illumination transport stage 8 so that the illumination 7 is automatically stopped when the illumination 7 is transported beyond the stop limiter.

  FIG. 6 is a diagram showing how the camera 5 and the illumination 7 are conveyed, and the straightness measuring device 1 is viewed from the side. The camera 5 and the illumination 7 are disposed facing each other across the measurement table 2, and the camera 5 and the illumination 7 are transported in cooperation while maintaining the same horizontal position. Thereby, even if a camera moves, it can measure, always ensuring a fixed illumination condition.

  FIG. 7 is a diagram illustrating the function of the control mechanism 1 b of the straightness measuring apparatus 1. The control mechanism 1b includes a control unit 20, a setting unit 21, a transmission / reception unit 22, an input unit 23, a storage unit 24, an image processing unit 25, and a display unit 26. The control mechanism 1b is usually realized by a computer including a ROM, a RAM, and the like.

  The control unit 20 controls the straightness measuring device 1 as a whole. Specifically, the control unit 20 performs transfer control of the camera 5 of the camera transfer stage 6, transfer control of the illumination 7 of the illumination transfer stage 8, and imaging control of the camera 5. At this time, the control unit 20 performs control according to the control conditions (conveyance conditions, imaging conditions) set in the setting unit 21.

The setting unit 21 holds the control conditions of the control unit 20. Specifically, “transport conditions” such as the transport speed and transport distance of the camera 5 and the illumination 7 and “imaging conditions” such as the imaging interval of the camera 5 are held. What is necessary is just to determine suitably the conveyance speed of the camera 5 and the illumination 7 according to the measurement speed etc. which are requested | required. Further, the transport distance of the camera 5 and the illumination 7 may be appropriately determined according to the size of the measurement object 4 and the like.
The imaging interval of the camera 5 refers to a time interval for imaging such as “execute imaging every 5 seconds” and “execute imaging every 10 seconds”. The imaging interval is appropriately determined according to the conveyance speed of the camera 5 and the angle of view of the camera lens. The value is set so that at least a portion (dead angle) where the reference pattern 3 is not captured cannot be formed. Is desirable.
In the case of the present embodiment, both the conveyance speed of the camera 5 and the illumination 7 are set to 15 (mm / second), and the conveyance distance is set to 1500 mm which is the same as the dimension of the reference pattern. The imaging interval was 10 seconds.

  The transmission / reception unit 22 has a function as an interface that transmits and receives information according to a predetermined format. In the present embodiment, the transmission / reception unit 22 is connected to the camera 5, the camera transport stage 6, the illumination 7, and the illumination transport stage 8. .

  The input unit 23 includes a keyboard, a mouse, and the like, and accepts input of control conditions (conveyance conditions, imaging conditions, etc.), measurement start and measurement stop operations of the control unit 20.

The storage unit 24 includes a hard disk that stores information magnetically, and a memory that loads a control program for executing control of the control mechanism 1a from the hard disk and electrically stores it.
The storage unit 24 stores the subject image captured by the camera 5 as image data via the transmission / reception unit 22.

  The image processing unit 25 performs straightness calculation processing described later on the image data stored in the storage unit 24 to calculate the straightness of the measurement object 4.

  The display unit 26 is configured by a display or the like, and displays an image captured by the camera 5, a result of straightness calculation processing described later, and the like.

<Basic motion processing>
Next, the basic operation of the straightness measuring apparatus 1 will be described with reference to the flowchart of FIG.
As a measurement preparation, the camera 5 is moved to the measurement start position. Then, a measurer or the like places the measurement object 4 at a predetermined position on the measurement table 1. When the measurement object 4 is arranged, both the reference pattern 3 and the linear pattern for which the straightness of the measurement object 4 is to be measured are simultaneously captured in the imaging field of the camera 5. Hereinafter, a linear pattern for which the straightness of the measurement object 4 is to be measured is referred to as a “measurement object pattern”.

  In step 1, the control unit 20 starts the conveyance of the camera 5 and the illumination 7 according to the conveyance conditions set in the setting unit 21 by accepting the measurement start operation of the measurer, and simultaneously sets in the setting unit 21. The imaging of the camera 5 is started according to the imaging conditions that have been set. The subject image captured by the camera 5 is accumulated in the storage unit 24 as image data via the transmission / reception unit 22. FIG. 9 is an example of captured image data. In FIG. 9, the left is the reference pattern 3 and the right is the measurement target pattern.

  In step 2, when the control unit 20 transports the camera 5 and the illumination 7 by the transport distance set in the setting unit 21, the control unit 20 ends the transport of the camera 5 and the illumination 7 and simultaneously ends the imaging of the camera 5.

  In step 3, the image processing unit 25 (control unit 20) calculates the straightness of the measurement target pattern based on the image data stored in the storage unit 24 (straightness calculation processing). Details of the straightness calculation processing will be described later.

  In step 4, the control unit 20 displays the straightness result of the measurement target pattern calculated in step 3 on the display unit 26 and ends the measurement.

  When it is desired to measure the next linear pattern of the measurement object 4, the measurer or the like again arranges the measurement object 4, returns to step 1, and starts measurement.

  If the measurement table 2 has a mechanism for transporting the measurement object 4 in the axial direction perpendicular to the longitudinal direction of the reference pattern 3 as described above, after the step 4 ends, the control unit 20 The measurement object 4 is conveyed by a predetermined interval, and after the conveyance, the control unit 20 starts conveyance and imaging of the camera 5 and performs measurement of the next linear pattern of the measurement object 4. Good. That is, in addition to the present embodiment, a mechanism for transporting the measurement object 4 in the axial direction orthogonal to the longitudinal direction of the reference pattern 3, and the controller 20 transports the camera 5, imaging control, and transport control of the measurement object 4. And a means for switching between the two, it is possible to automate the measurement of all the linear patterns of the measuring object 4 without the work of the measurer. In this case, it is desirable to adopt the interval of the linear pattern of the measurement object 4 as the predetermined interval for conveying the measurement object 4.

Next, specific contents of the straightness calculation process will be described.
<Straightness calculation processing>
FIG. 10 is a flowchart illustrating a process for calculating the straightness of the measurement target pattern. Hereinafter, the straightness calculation process will be described using the image data of FIG. 9 stored in the storage unit 24 as an example.

  In step 11, the image processing unit 25 (control unit 20) calculates the centroid position of the reference pattern 3 and the measurement target pattern based on the image data (see FIG. 9) stored in the storage unit 24 (centroid position calculation). processing).

  In the center-of-gravity position calculation processing, first, edge extraction processing is performed on image data, and edges (contours) of both ends of the reference pattern 3 and the measurement target pattern are extracted at regular intervals in the longitudinal direction (see FIG. 11A). . Then, the center position of each pattern is calculated by calculating the center positions of the edge coordinates of both ends of the extracted reference pattern 3 and measurement pattern (see FIG. 11B).

In the following description, it is assumed that the center of gravity is calculated as N points in the longitudinal direction of the image data.
Here, the centroid position of the reference pattern 3 obtained by the centroid position calculation process in step 1 is defined as A ₁ , A ₂ ,..., A _N, and the centroid position of the measurement target pattern is defined as B ₁ , B ₂ , ..., defined as B _N.

In step 12, the image processing unit 25 (control unit 20) calculates the distance between the centroid positions of the reference pattern 3 and the measurement target pattern obtained by the process of step 11 (distance between centroids, see FIG. 11C). (Inter-centroid distance calculation processing). Specifically, the calculated distance between center of gravity _{D 1,} D 2 of the N-point, ..., and _{D N,} as follows.

  In step 13, the image processing unit 25 (control unit 20) corrects the distance between the centers of gravity calculated in step 12 (correction processing). In the correction process, first, the data of the distance between the centroids of the N points obtained by the distance calculation process between the centroids in step 12 is plotted on the two-dimensional graph (see FIG. 12A), and the first order fitting to the plotted data is performed. A function is calculated (see FIG. 12B). The linear function is obtained, for example, by performing regression analysis on the data of the distance between the centers of gravity of N points. Here, assuming that the slope of the obtained linear function is α and the center-of-gravity position interval is 1 (unit length), the corrected center-to-center distance can be calculated as follows.

  FIG. 12C is a diagram in which data of the distance between the centers of gravity after correction is plotted.

  In step 14, the image processing unit 25 (control unit 20) normalizes the data of the distance between the centers of gravity after correction of the N points obtained in step 13 to an average of 0, and finally determines the straightness of the measurement target pattern. Calculate as follows.

The straightness distribution of the measurement target pattern is obtained by the above processing (see FIG. 13). The straightness of the measurement target pattern may be a standard deviation of the obtained distribution. For example, | max {σ _i } −min {σ _j } |, max {σ _i }, min {σ _i } (1 ≦ An index characterizing the distribution such as i, j ≦ N) may be straightness. The final straightness may be output as a pixel value or may be output as an actual size value.

  According to the present embodiment, imaging is performed while the camera 5 is transported, and the straightness of the measurement target pattern is calculated. Therefore, the straightness of the measurement target pattern can be measured at high speed.

  In addition, since the distance between the center of gravity of the reference pattern 3 and the measurement target pattern is calculated as a relative value based on the position of the center of gravity of the reference pattern 3, the measurement can be performed even when the camera transport stage 6 meanders. The influence on the calculation accuracy of the straightness of the target pattern can be minimized.

  Furthermore, even if the measurement target pattern has an inclination with respect to the axial direction of the reference pattern 3 due to the arrangement of the measurement object 4, the influence of the inclination can be offset by the correction processing in step 13, so Measurement errors due to the influence of the arrangement can be reduced, and more accurate straightness can be measured.

  In this embodiment, a two-dimensional film in which a linear pattern is coated at equal intervals is used as the measurement object 4. However, if the linear pattern can be imaged by the camera 5, a three-dimensional measurement object is used. Even straightness can be measured.

  The preferred embodiments of the straightness measuring apparatus 1 and the like according to the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and these naturally belong to the technical scope of the present invention. Understood.

1 ··· Straightness measuring device 1a ··· Measurement mechanism 1b ··· Control mechanism 2 ··· Measurement table 3 ··· Reference pattern 4 ···・ ・ ・ ・ Measurement object 5 ・ ・ ・ ・ ・ ・ Camera 6 ・ ・ ・ ・ ・ ・ Camera transfer stage 7 ・ ・ ・ ・ ・ ・ Lighting 8 ・ ・ ・ ・ ・ ・ Lighting transfer stage 20 Control unit 21 ... Setting unit 22 Transmission / reception unit 23 Input unit 24 Storage unit 25 Image processing unit 26 ... Display section

Claims (4)

A straightness measuring device that measures the straightness of a measurement target pattern,
A reference pattern whose straightness has been confirmed, and
An imager that simultaneously images the reference pattern and the measurement target pattern;
Image pickup device transporting means for transporting the image pickup device along the reference pattern;
Straightness calculation means for calculating an inter-pattern distance between the reference pattern and the measurement target pattern based on image data acquired by imaging while being conveyed, and calculating a straightness of the measurement target pattern from the inter-pattern distance. When,
A straightness measuring apparatus comprising: Correction means for correcting the distance between the patterns according to the inclination of the measurement target pattern, further comprising:
The straightness measurement apparatus according to claim 1, wherein the straightness calculation means calculates straightness of the measurement target pattern from the corrected inter-pattern distance. Straightness measurement method for measuring the straightness of the measurement target pattern using a straightness measurement device including a reference pattern whose straightness has been confirmed and an imager that simultaneously images the reference pattern and the measurement target pattern Because
A transport imaging step of capturing an image while transporting the imager along the reference pattern;
A straightness calculation step of calculating an inter-pattern distance between the reference pattern and the measurement target pattern based on image data acquired by imaging while being conveyed, and calculating a straightness of the measurement target pattern from the inter-pattern distance. When,
A straightness measurement method comprising: A program for causing a computer to function as a straightness measuring device that measures the straightness of a measurement target pattern,
The straightness measuring device includes a reference pattern whose straightness is confirmed, and an imager that images the reference pattern and the measurement target pattern simultaneously,
The computer,
Transport imaging means for capturing images while transporting the imager along the reference pattern;
Straightness calculation means for calculating an inter-pattern distance between the reference pattern and the measurement target pattern based on image data acquired by imaging while being conveyed, and calculating a straightness of the measurement target pattern from the inter-pattern distance. ,
Program to function as.

Images