JP6155924B2 - Dimension measuring apparatus and dimension measuring method - Google Patents

Description

The present invention relates to a dimension measuring apparatus and a dimension measuring method using the iris unit which provides a stop of the optical system.

  2. Description of the Related Art Conventionally, a telecentric optical system is known in which a stop with a small aperture is disposed at a focal position of a lens and a principal ray parallel to the lens principal axis can be selectively imaged. In such a telecentric lens optical system, since the principal ray is parallel to the lens principal axis, the size of the image does not change even if the position of the object moves. Using this property, a telecentric optical system is used for measuring the size of a deep object.

  Usually, dimension measurement using a telecentric optical system measures a dimension in a direction orthogonal to the lens main axis. When performing this dimension measurement, it is assumed that the measurement object is correctly arranged so that the depth direction is parallel to the lens main axis. For example, when the object to be measured is arranged at an inclination, the shape captured as an image is different, and accurate dimension measurement is impossible. In this case, it is necessary to perform a correction operation such as correcting the inclination of the object to be measured or physically matching the lens angle with the inclination of the object to be measured. In particular, in the measurement process of industrial products, since the correction operation is performed, problems such as a complicated apparatus and a long measurement cycle time become significant.

  Therefore, in the dimension measurement system described in Patent Document 1, a small aperture stop arranged at the focal position of the first lens in the telecentric optical system is configured to be movable on a plane orthogonal to the lens main axis. . In this dimension measurement system, an image in which the angle of the image is corrected can be acquired by selecting the inclination of the light beam incident on the stop with respect to the lens principal axis. Accordingly, it is possible to accurately measure the tilted object to be measured without moving the lens, the object to be measured, and the imaging unit.

JP 2009-92596 A

  However, in the dimension measurement system described in Patent Document 1, an operation for moving the position of the diaphragm is necessary for each imaging, and the operation takes time, so that the measurement cycle time becomes long.

The present invention has been created in view of the above points, and an object of the present invention is to tilt an object to be measured using an iris unit that can move the position of a diaphragm at high speed on a plane orthogonal to the optical axis. even is to provide a dimension measuring apparatus and a dimension measuring method the exact dimensions can be measured at high speed.

The dimension measuring apparatus according to the present invention uses an iris unit that provides a movable stop of an optical system . The iris unit includes a fixed diaphragm portion having an opening in the optical axis direction of the optical system, and a slit group that includes a plurality of slits that rotate about the rotation axis and that have different positions in the circumferential direction and distances from the rotation axis. , And an iris board whose width in the radial direction of the slit extends from the exit side to the entrance side of the optical system, and drive means for rotating the iris board. In the circumferential direction of the iris board, the length of each slit is longer than the length in the radial direction, and the length of each slit is longer than the length of the opening, and each slit is at least one in the optical axis direction when the iris board rotates. It arrange | positions so that a part may overlap with opening.

According to the above configuration, the plurality of slits included in the slit group overlap with the opening of the fixed diaphragm portion in order by the drive unit rotating the iris board. A portion where each slit of the iris board and the opening of the fixed diaphragm portion overlap functions as a diaphragm of the optical system. Therefore, the iris unit used in the dimension measuring apparatus according to the present invention can move the position of the diaphragm at a high speed on a plane orthogonal to the optical axis.

The dimension measuring apparatus according to the present invention includes an irradiating means for irradiating a measurement object having a shape whose length and width can be considered, a telecentric optical system for forming an image of the measurement object, and a movable telecentric optical system. a luer iris unit to provide a diaphragm such, a plurality of images, each of which is formed by the light passing through the aperture of the fixed throttle portion and the slit iris plate was provided through the trigger hole in the iris plate timing An imaging unit that captures images based on information, and an image processing unit that acquires a captured image based on a plurality of images captured by the imaging unit, and measures the minimum width of the image in the captured image as the width of the object to be measured And comprising.

According to the above configuration, even when the object to be measured is arranged to be inclined with respect to the telecentric optical system, it is correctly arranged in the telecentric optical system by measuring the minimum width of the image in the acquired captured image. Measurements similar to those obtained can be obtained. Therefore, according to the dimension measuring apparatus according to the present invention, even in the object to be measured which is inclined, it is possible to measure the exact dimensions at high speed. The dimension measuring method according to the present invention can achieve the same effect.

It is typical structure explanatory drawing which shows the dimension measuring apparatus which concerns on this embodiment. It is the top view which looked at the iris board concerning this embodiment from the image side. It is the perspective view which looked at the iris board concerning this embodiment from the object side. It is the fragmentary sectional view which cut | disconnected the iris board shown in FIG. 3 by the IV-IV line. It is a flowchart explaining the dimension measuring method which concerns on this embodiment. It is a schematic diagram which shows the to-be-measured object set perpendicular | vertical with respect to the backlight, and the captured image obtained. It is a schematic diagram which shows the to-be-measured object set diagonally with respect to the backlight, and the captured image obtained. It is sectional drawing which shows typically the heat exchanger as a to-be-measured object. It is a top view which shows the image side of the iris board which concerns on the modification of this embodiment.

Hereinafter, a dimension measuring apparatus 1 according to an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the dimension measuring apparatus 1 of this embodiment includes a backlight 2, a telecentric optical system 3, a copper mirror 4, an iris unit 5, a CCD camera 6, a photo interrupter 7, and an image processing unit 8.

  The backlight 2 is a surface light source installed on a measurement table, for example. An object to be measured 10 is disposed on the backlight 2. In the present embodiment, the object to be measured 10 is imaged as a shadow picture in order to easily perform dimension measurement. In the present embodiment, for convenience of explanation, it is assumed that the DUT 10 is a substantially rectangular parallelepiped and is arranged vertically on the backlight 2.

The telecentric optical system 3 is composed of a plurality of lenses that realize bilateral telecentricity, and is accommodated in a lens barrel 4 formed in a substantially conical shape. In the present embodiment, the telecentric optical system 3 schematically includes a first lens 31 having a relatively large aperture facing the backlight 2 and a second lens 32 having a smaller aperture than the first lens. The optical axes of the first lens 31 and the second lens 32 coincide with each other, and the coincident optical axis is a lens main axis Z.
Hereinafter, for convenience of explanation, the direction of the lens main axis Z is referred to as the z direction. The z direction corresponds to the vertical direction in FIG. Further, a direction orthogonal to the z direction and corresponding to the left-right direction in FIG. 1 is referred to as an x direction, and a direction orthogonal to the paper surface in FIG. 1 is referred to as a y direction.

  Further, the image side focal point of the first lens 31 and the object side focal point of the second lens 32 coincide. A position where the image side focal point of the first lens 31 coincides with the object side focal point of the second lens 32 in the z direction is defined as a focal position 9.

  As will be described in detail later, the iris unit 5 includes a fixed aperture portion 51, an iris board 52, and a servo motor 53 as a driving means, and passes through the focal position 9 in the telecentric optical system 3. Adjust the light. The fixed diaphragm 51 is disposed at the focal position 9, and the iris board 52 is provided on the object side of the fixed diaphragm 51. The iris board 52 has a disk shape and can be rotated around the center at a constant speed by a servo motor 53. The rotation axis 521 of the iris board 52 is parallel to the lens main axis Z.

  The CCD camera 6 as an imaging means is a line sensor camera provided with a CCD image sensor. The CCD image sensor is disposed along the x direction at the imaging position, and the center thereof coincides with the lens main axis Z. Thereby, the CCD camera 6 recognizes the difference in brightness in the x direction. Further, the CCD camera 6 images the device under test 10 and outputs the image information to the image processing unit 8.

  The light emitted from the backlight 2 is condensed when passing through the first lens 31, passes through the fixed aperture 51 and the iris board 52 of the iris unit 5, passes through the second lens 31, becomes parallel light, and is CCD Projected onto the camera 6.

  The photo interrupter 7 includes a light emitting unit 71 and a light receiving unit 72 that are arranged to face each other so as to sandwich a part of the outer peripheral side of the iris board 52. The photo interrupter 7 outputs the timing at which the light receiving unit 72 detects the light from the light emitting unit 71 to the image processing unit 8 as timing information.

The image processing unit 8 can use a known desktop personal computer. The image processing unit 8 is electrically connected to the photo interrupter 7 and the CCD camera 6, and controls the imaging timing of the CCD camera 6 based on the timing information acquired from the photo interrupter 7. Further, the image processing unit 8 acquires a captured image based on the imaging information output from the CCD camera 6 and measures the dimension of the DUT 10 from the acquired captured image. Further, the image processing unit 8 can display the captured image on a display, and the user can also check the displayed image.
Note that the illustration of the image processing unit 8 in FIG. 1 only shows the electrical connection between the photo interrupter 7 and the CCD camera 6, and shows the physical positional relationship with other components in the dimension measuring apparatus 1. It is not shown.

Next, the fixed diaphragm 51 and the iris board 52 of the iris unit 5 will be described with reference to FIG.
As shown in FIG. 2, the fixed aperture portion 51 has a rectangular opening 511 that opens in the z direction. The long side of the opening 511 extends in the x direction, and the short side extends in the y direction. The center of the opening 511 coincides with the lens main axis Z.

  The iris disk 52 is a disk that is rotatable around a rotation shaft 521 that extends in the z direction, and is arranged so that the image-side surface faces the fixed aperture section 51. The position of the rotation shaft 521 in the y direction coincides with the center of the opening 511 of the fixed diaphragm 51.

  A slit group 522 composed of a plurality of slits 523 is formed on the iris board 52. In the iris board 52 of the present embodiment, four slit groups 522 composed of 13 slits 523 are formed.

  When the image side of the iris board 52 is viewed from the direction of the rotation axis 521, the shape of each slit 523 is a substantially rectangular shape having a short side in the radial direction of the iris board 52 and a long side that draws an arc in the circumferential direction. is there. Specifically, in the radial direction of the iris board 52, the width Ws of each slit 523 is shorter than the length Dpx of the long side of the opening 511 of the fixed diaphragm 51. In the circumferential direction of the iris board 51, the length Ls of each slit 523 is longer than the length Dpy of the short side of the opening 511 of the fixed aperture portion 51.

  In the present embodiment, the four slit groups 522 are arranged in the circumferential direction, and each slit group 522 is formed in the range of the central angle of the iris board 52 of 90 °. The 13 slits 523 in each slit group 522 are formed continuously in the circumferential direction of the iris board 52.

  Further, the 13 slits 523 in each slit group 522 are formed such that the distance from the rotation shaft 521 is different in a stepwise manner. For example, in each slit group 522, the distance R01 between the slit 523 at the counterclockwise end as viewed from the central axis 521 and the rotating shaft 521 is the shortest, and the distance from the rotating shaft 521 is the clockwise slit 523. Becomes longer, and the distance R13 between the slit 523 at the end on the clockwise side and the rotating shaft 521 is the longest. Here, the distance R01 which is the shortest distance between the slit 523 and the rotation shaft 521 is longer than the shortest distance Rmin between the opening 511 of the fixed aperture portion 51 and the rotation shaft 521. The distance R13, which is the longest distance between the slit 523 and the rotation shaft 521, is shorter than the longest distance Rmax between the opening 511 of the fixed aperture portion 51 and the rotation shaft 521.

  With the above configuration, all the slits 523 formed in the iris board 52 can partially overlap the opening 511 in the z direction one by one as the iris board 52 rotates. The aperture in the z direction formed by overlapping the slit 523 and the aperture 511 is the diaphragm 55 of the telecentric optical system 3.

  Further, the position in the x direction of the diaphragm 55 formed by each slit 523 and the opening 511 changes as the iris board 52 rotates. Here, assuming that one position is “1 level”, in the present embodiment, the position of the diaphragm 55 in the x direction changes at 13 levels. For this reason, the inclination with respect to the z direction of the light beam incident on the stop 55 changes at 13 levels. In this embodiment, when the center (seventh) slit 523 of the thirteen slits 523 in each slit group 522 overlaps the opening 511, the diaphragm 55 coincides with the lens main axis Z.

Next, the shape of each slit 523 will be described in detail with reference to FIGS.
As shown in FIG. 3, the width of each slit 523 in the radial direction of the iris board 52 extends from the image side that is the exit side of the telecentric optical system 3 toward the object side that is the entrance side. Specifically, as shown in FIG. 4, the angle α1 with respect to the z direction of the wall portion 525 that forms the width of each slit 523 is larger than the angle α2 at which the light ray incident on the diaphragm 55 is inclined to the maximum with respect to the z direction. It is set to be large.

  Note that the angle of the light beam incident on the diaphragm 55 with respect to the z direction is determined by which slit 523 of the slit group 522 forms the diaphragm 55 together with the opening 511. When the slit 523 that overlaps the opening 511 at the position most displaced from the lens main axis Z forms the stop 55, the light incident on the stop 55 is tilted to the maximum with respect to the z direction.

  A trigger hole 524 through which light from the photo interrupter 7 passes is formed at the outer peripheral end of the iris board 52. The trigger hole 524 is formed corresponding to each slit 523 and provides imaging timing. Each trigger hole 524 is formed on the opposite side of the corresponding slit 523 across the rotation axis of the iris board 52.

(Dimension measuring method by the dimension measuring apparatus 1)
Next, the dimension measuring method of the DUT 10 by the dimension measuring apparatus 1 shown in FIG. 1 will be described with reference to the flowchart shown in FIG. In the description of the flowchart, the symbol “S” indicates a step.

  First, a substantially rectangular parallelepiped object to be measured 10 is set vertically on the backlight 2. Here, as shown in FIG. 6B, it is assumed that the DUT 10 is set so that the central axis in the height direction coincides with the lens main axis Z. In the present embodiment, the dimension in the x direction of the DUT 10 is referred to as “width”. The dimension measuring apparatus 1 measures the “width” of the DUT 10.

  After the measurement object 10 is set, the backlight 2 starts irradiation (S1), and the servo motor 6 rotates the iris board 52 at a constant speed (S2). The order of S1 and S2 may be reversed. After S <b> 1 and S <b> 2, the photo interrupter 7 detects light incident on the light receiving unit 72 from the light emitting unit 71 through the trigger hole 513, and outputs timing information to the video processing unit 8. The video processing unit 8 outputs trigger information to the CCD camera 6 based on the input timing information.

  The CCD camera 6 images the device under test 10 based on the input trigger information (S3). Here, it is assumed that one cycle is a period during which all thirteen slits 523 belonging to one slit group 522 pass through the opening 511 of the fixed aperture 51 by the rotation of the iris board 52. In S3, the CCD camera 6 performs imaging 13 times during one cycle. One imaging is performed while one slit 523 and the opening 511 overlap. In addition, when the slit 523 located in the center of the slit group 522 and the opening 511 overlap, an image by the parallel light beam 21 corresponding to the width of the DUT 10 is captured.

  The image processing unit 8 acquires a captured image 81 as shown in FIG. 6A based on the imaging information for one cycle (13 times) output from the CCD camera 6 (S4). In FIG. 6A, a portion surrounded by a dotted line in the captured image 81 is a unit image corresponding to one imaging. Since the unit images obtained by the respective imaging have different angles of view, the obtained captured image 81 has a different width in the length direction of the image 82.

  The minimum width W of the image 82 of the captured image 81 corresponds to a value closest to the true width of the DUT 10. Therefore, the image processing unit 8 measures the minimum width W as the width dimension of the DUT 10 (S5).

  On the other hand, as shown in FIG. 7B, it is assumed that the center axis of the DUT 10 is set to be inclined with respect to the lens main axis Z. In this case, the parallel rays 22 inclined along both inclined end surfaces of the DUT 10 pass through any slit 523 other than the center of the slit group 522 and the opening 511 and form an image on the CCD camera 6. Therefore, in S4, the image processing unit 8 acquires a captured image 83 as shown in FIG. In S <b> 5, the image processing unit 8 measures the minimum width W as the width dimension of the DUT 10 in the acquired image 84 of the captured image 83 in the same manner as described above.

  The dimension measuring apparatus 1 can continuously perform a plurality of measurements by repeating the steps S2 to S5. In the present embodiment, four measurements can be performed using the four slit groups 522 while the iris board 52 rotates once.

(effect)
As described above, according to the dimension measuring apparatus 1 of the present embodiment, even when the DUT 10 is tilted with respect to the telecentric optical system 3, accurate measurement is performed without performing a correction operation or the like. be able to. In addition, since it is possible to continuously perform multi-level imaging by rotating the iris board 52, it is possible to perform measurement in a shorter time than the conventional technique of Patent Document 1.

  Moreover, in the iris board 52 of this embodiment, since each slit 523 has a fixed length in the circumferential direction as described above, each slit 523 can overlap the opening 511 for a fixed time. Therefore, even when imaging is performed at high speed, it is possible to tolerate a deviation in imaging timing to some extent.

  Moreover, the iris board 52 of this embodiment has a larger shape than a general throttle part, and requires a certain thickness in order to ensure rigidity. When the plate thickness increases, a part of the light incident at an angle may interfere with the inner wall of the slit, and the field of view may be disturbed. However, in the present embodiment, as described above, since the width of the slit 523 widens from the image side toward the object side, the light incident on the stop 55 is inclined with respect to the lens main axis Z. Is not obstructed by the wall portion of the slit 523. Therefore, it is possible to prevent the field of view of the captured image 81 from being narrowed.

(Modification of dimension measurement method)
In the dimension measuring method described above, the DUT 10 is set at a fixed position on the backlight 2, but the present invention is not limited to this. That is, the dimension measuring apparatus 1 may perform dimension measurement while the DUT 10 moves under the telecentric optical system 3 in the y direction.

For example, as shown in FIG. 8, the case where the width | variety T of the flat tube 110 of the fin tube type heat exchanger 100 is measured is demonstrated to an example.
First, the height direction of the flat tube 110 is aligned with the z direction, and the center of the width T is aligned with the lens main axis Z in the x direction. Further, during the subsequent measurement process, the movement of the flat tube 110 is started so that the flat tube 110 moves under the telecentric optical system 3 in the y direction at a constant speed. Next, the backlight 2 starts irradiation, and the iris board 52 starts to rotate.

  Next, the CCD camera 6 images 13 different points in the y direction of the flat tube 110 while changing the angle during one cycle. Next, the image processing unit 8 acquires the captured image 81 based on the imaging information for 13 times, and measures the narrowest width W of the captured images 81 as the width dimension, as described above. In the obtained captured image 81, the unit image corresponding to each captured image is obtained by capturing a different portion of the flat tube 110 in the y direction.

  In this modification, while the flat tube 110 moves under the telecentric optical system 3 at a constant speed in the y direction, the width T of the flat tube 110 is measured at a constant interval in the y direction by repeating imaging and measurement. can do. Here, the fixed interval corresponds to the distance that the flat tube 110 moves during one cycle.

  In this modification, the width T can be accurately measured even when the flat tube 110 is tilted. Therefore, the image processing unit 8 can inspect whether the flat tube 110 conforms to the standard by determining whether or not the measured value is included in the predetermined range.

  In addition, since this modification does not require positioning in the y direction, a plurality of dimension measurements can be performed at higher speed. For example, when the servo motor 53 rotates the iris board 52 at 3000 rpm, the iris board 52 rotates once in 20 ms. Therefore, imaging for one cycle of the DUT 10 is performed in 5 ms.

(Other configurations)
The number of slit groups 522 and slits 523 formed in the iris board 52 is not limited to that shown in the present embodiment. It can be set as appropriate based on the standard of the object to be measured 10, the moving speed and the measurement interval, the rotation speed of the servo motor 7, the shutter speed of the CCD camera 6, the overall tact time, and the like. For example, when imaging one cycle during one rotation, an iris board 54 as shown in FIG. 9 can be used. In the iris board 54, one slit group 542 including 13 slits 543 is formed.

  The number of slits 523 included in one slit group 522 may correspond to the number of levels of measurement and may be at least two. If the number of slits 523 in one slit group 522 increases, more accurate measurement can be performed.

  As mentioned above, this invention is not limited to such embodiment, In the range which does not deviate from the meaning of invention, it can implement with a various form.

DESCRIPTION OF SYMBOLS 1 ... Dimension measuring apparatus 2 ... Backlight (irradiation means)
DESCRIPTION OF SYMBOLS 3 ... Telecentric optical system 5 ... Iris unit 51 ... Fixed aperture part 52 ... Iris board 521 ... Rotating shaft 522 ... Slit group 523 ... Slit 53 ... Servo motor ( Driving means)
55 ... Aperture 6 ... CCD camera 8 ... Image processing unit

Claims (4)

An irradiating means (2) for irradiating light to the object to be measured (10) having a shape whose length and width can be considered;
A telecentric optical system (3) for forming an image of the object to be measured;
A fixed diaphragm portion (51 ) having an opening (511) in the optical axis direction of the optical system , and a rotation shaft (521) as a center, and a plurality of positions in the circumferential direction and distances from the rotation shaft are different from each other. slit group including a slit (523) (522) is an iris plate formed (52) and a drive means (53) for rotating the pre-Symbol iris plate,
The radial width of the slit of the iris board widens from the exit side to the entrance side of the optical system,
The circumferential length (Ls) of the slit of the iris board is longer than the radial width (Ws) of the slit , and the length of the slit is longer than the length of the opening (Dpy),
The slit is an iris unit (5) arranged so that at least a part thereof overlaps the opening in the optical axis direction when the iris board rotates.
A plurality of images formed by light passing through the slit of the iris board and the opening of the fixed aperture portion are respectively picked up based on timing information provided via a trigger hole (524) provided in the iris board. Imaging means (6) to perform,
Image processing means (8) for obtaining a picked-up image based on a plurality of images picked up by the image pick-up means, and measuring a minimum width of the image in the picked-up image as the width of the object to be measured;
A dimension measuring device comprising: The dimension measuring apparatus according to claim 1, further comprising a measured object moving means for moving the measured object at a constant speed. Telecentric optics,
A plurality of fixed diaphragm portions (51) having an opening (511) in the optical axis direction of the telecentric optical system , rotating about the rotation axis (521), and having different positions in the circumferential direction and distances from the rotation axis An iris board (52) in which a slit group (522) including a slit (523) is formed, and drive means (53) for rotating the iris board,
The radial width of the slit of the iris board widens from the exit side to the entrance side of the optical system,
The circumferential length (Ls) of the slit of the iris board is longer than the radial width (Ws) of the slit, and the length of the slit is longer than the length of the opening (Dpy),
The slit has a shape whose length and width can be conceived using an iris unit (5) arranged so that at least a part thereof overlaps the opening in the optical axis direction when the iris board rotates. A dimension measuring method for measuring the width dimension of an object,
An irradiation step (S1) of irradiating the object to be measured so that an image of the object to be measured is formed by the telecentric optical system;
A rotating step (S2) of rotating the iris board;
A plurality of images formed by light passing through the slit of the iris board and the opening of the fixed aperture portion during rotation of the iris board are provided through trigger holes (524) provided in the iris board, respectively. An imaging step (S3) for imaging based on the performed timing information ;
An image acquisition step (S4) for acquiring a captured image based on a plurality of images captured in the imaging step;
A measurement step (S5) for measuring the minimum width of the image in the captured image as the width of the object to be measured;
A dimension measuring method comprising: The dimension measuring method according to claim 3, further comprising a measured object moving step of moving the measured object at a constant speed.

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