JP2000266523A - Method and apparatus for measuring object under test - Google Patents

Abstract

An object of the present invention is to provide a method and an apparatus for measuring an object to be measured, such as cream solder, which can surely perform three-dimensional measurement with an inexpensive configuration. SOLUTION: A light projecting unit 7 is sequentially moved to project line light onto a device under test 11, an image of which is taken by a CCD camera 6, and height data of the device under test is measured based on a light cutting method. You. A plurality of line lights are sequentially drawn at a first pitch from the light cutting start position, and an image thereof is captured. Subsequently, the light cutting start position is shifted by a distance corresponding to a second pitch shorter than the first pitch from the light cutting start position, and line light is sequentially drawn at the first pitch from the shifted light cutting start position. Imaging is performed. Such imaging is performed a plurality of times, and height data based on a plurality of light cutting lines drawn at the second pitch from the captured images is acquired. In such a configuration, a plurality of line lights are drawn in one imaging field of view and an image is taken, so that the measurement time can be significantly reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring an object to be measured, and more particularly, to a method for measuring an object to be measured three-dimensionally based on a light section method using line light. And its device.

[0002]

2. Description of the Related Art Cream solder is printed on a substrate on which electronic components are mounted in order to electrically connect the electronic components to wiring. In order to measure the shape of the printed cream solder, three-dimensional measurement using a light cutting method is performed. The light cutting method uses a thin slit-shaped light beam for the target object (cream solder)
Irradiation is performed so as to cut the surface, and the surface shape or surface unevenness of the object to be measured is measured from the shape of the cutting line generated on the surface. An example of the configuration is shown in FIG.

In FIG. 1, a line light 22 generated from a line light generator 21 as a light source is projected from a diagonally upper part onto an object 23 at a predetermined angle to form a surface formed on the surface of the object 23. Image formed along the shape is CC from above vertically
Photographed by the D camera 24. The image captured by the CCD camera is A / D converted by the CCD camera controller 25 and captured by the image capturing device 26. Then, the captured data is converted into three-dimensional coordinates of the DUT 23 by the next coordinate calculation device 27. In a cream solder height measuring device which is used by being incorporated in a cream solder printing machine, a portion (measurement unit) surrounded by a dotted line in FIG.
Incorporated in a Y-movement gantry.

In such a configuration, when a wiring board for printing is carried into the cream solder printing machine, the cream solder is printed on the pad surface of the wiring board after the positioning of the wiring board and the stencil is completed. After the printing on the pad surface of the wiring board is completed, the above-described measurement unit is moved from the initial expected retreat position to the target measurement position by the XY movement gantry. Then, the image of the line light 22 formed along the cream solder shape on the pad surface on the wiring board is
The image is captured by the CCD camera 24. The measuring unit is then moved again to the initial retract position, where it retracts.

From the above image data, the coordinates of the center of gravity of the pad surface of the wiring board in the height direction and the coordinates of the center of gravity of the cream solder portion in the height direction are calculated. Then, from the subtraction of the coordinates of the center of gravity of the pad surface of the wiring board in the height direction and the coordinates of the center of gravity of the cream solder portion in the height direction, the height of the cream solder portion after printing is determined based on the pad surface of the wiring board. The calculated height of the cream solder portion over each pad surface is calculated. In order to obtain a three-dimensional shape, a plurality of data at different light cutting positions are required. For example, length 2
It is assumed that light cutting is performed at a pitch of 0.05 mm in order to obtain a three-dimensional shape of the cream solder printed on the pad of mm. In this case, after the cream solder printing, it is necessary to image the line light image formed along the shape of the cream solder 40 times with a CCD camera while changing the light cutting position. That is, the measuring unit is minutely moved every time one light cutting is performed.

[0006]

In the conventional apparatus as described above, when the position of the light cutting is slightly changed, the CC
A heavy measurement unit equipped with a D camera must be moved, and the XY moving gantry is provided with two functions: a skip function to a target measurement position and a minute movement at a measurement target position. However, there is a problem that the servo system for driving the XY moving gantry becomes complicated. In addition, there is a problem in that the measurement unit must be slightly moved every time one light cut is performed, and line light is projected to capture an image.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to solve such a problem, and an object to be measured such as cream solder which can surely perform three-dimensional measurement with an inexpensive configuration. It is an object of the present invention to provide a measuring method and apparatus.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method and an apparatus for measuring an object to measure an object to be measured three-dimensionally based on an optical sectioning method by imaging an object to be measured along a light section line.
A light cutting line is sequentially drawn at a first pitch from the light cutting start position to image the object to be measured, and the light cutting start position is separated from the light cutting start position by a distance corresponding to a second pitch shorter than the first pitch. From the shifted optical cutting start position.
A light cutting line is sequentially drawn at a pitch to image the object to be measured, and the light cutting start position is sequentially shifted and imaged a plurality of times, and the image is drawn at a second pitch from the plurality of imaged images. It is characterized in that height data by a plurality of light cutting lines is obtained.

In such a configuration, since a plurality of light cutting lines are drawn in one field of view for imaging, the measurement time can be greatly reduced. In addition, a plurality of images are captured by shifting the light cutting start position by a desired light cutting pitch, and the height data from the plurality of image data is arranged in the order of the shifted pitch to thereby achieve a fine desired light cutting pitch height. Since data can be obtained, high measurement accuracy can be obtained.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 2 is a perspective view showing a configuration of a three-dimensional measuring apparatus according to one embodiment of the present invention, and FIG. 3 is a side view thereof. In each figure, a laser beam emitted from a laser diode 1 is converted into a parallel light beam by a collimator lens 2 and enters a line generator lens 5 via a focusing lens 3 and a light projecting mirror 4. The laser light is projected by the line generator lens 5 onto the object to be measured (cream solder or the substrate surface on which it is printed) 11 as line light 9, and the image of the line light is captured by the CCD camera 6.
Is imaged. The focusing lens 3, the light projecting mirror 4 and the line generator lens 5 are configured as a light projecting unit 7, and are reciprocated in a direction indicated by an arrow 10 by a linear actuator 8.

The bonding surface of the laser diode 1 is configured so as to be parallel to the surface of the substrate to be measured, and the light is condensed by the collimating lens 2 to become parallel light. The focusing lens 3 narrows the parallel light into a spot light, and the light from the focusing lens 3 is bent by the light projecting mirror 4 so as to form an angle of 45 degrees with the vertical axis. The focusing lens 3 is placed on the DUT 11,
Although it acts so as to connect a small spot diameter, it is elongated in one direction by the action of the line generator lens 5 placed in the optical path from the focusing lens 3 to the device under test 11 to become line light. Thus, the laser beam has a width of 14 to 20 μm (14 μm in the present embodiment),
The light is projected on the DUT 11 as a line light 9 having a length of 10 mm, and diffusely reflected light from the DUT is imaged by the CCD camera 6.

The linear actuator 8 has a function of linearly moving back and forth on its axis, and the light emitting unit 7 including the focusing lens 3, the light emitting mirror 4 and the line generator lens 5 is mounted on the axis. , The light projecting unit 7 directs parallel light rays formed by the collimating lens 2 as shown by an arrow 10,
Make a linear motion back and forth. Even if the linear motion is performed back and forth toward the parallel rays, the imaging action of the focusing lens 3 is not affected. Therefore, a line light having a constant width is always formed on the DUT 11. Then, the image of the line light is picked up by the CCD camera 6 mounted directly above. The field of view of the CCD camera 6 is 6 mm × 6 mm, non-interlaced, and the stroke of the linear actuator 8 is 10 mm.

In FIG. 3, the light projecting unit 7 is moved from the right end to the left at a constant speed of 4.8 mm / sec. CC
The laser diode 1 is turned on for 2 msec when it reaches a position where light can be projected to a predetermined position in the field of view of the D camera 6.
FIG. 4 shows a captured image by this. In FIG. 4, when the linear actuator 8 moves and moves to the light cutting positions P1 to P3, the respective laser diodes are turned on, and the cream solder 30a protruding from the pad surface 30b.
3 shows a state in which the light is cut by the line light and an image is taken.

As described above, a large number of line light images formed along the shape of the cream solder while the linear actuator 8 is slightly moved are imaged by the CCD camera while changing the position of the light cutting. For example, by using a coordinate calculator as shown in FIG.
b, the coordinates of the center of gravity in the height direction and the cream solder portion 30a
The coordinates of the center of gravity in the height direction are calculated, and the height of the cream solder portion after printing is calculated based on the subtraction of the coordinates of each center of gravity with reference to the pad surface of the wiring board. Then, the average height of the cream solder portion over each pad surface is calculated.

When analyzing the uneven shape of the cream solder in more detail, it is necessary to narrow the light cutting pitch. However, it takes a very long time to take an image for each light cutting line by the above-described method. Therefore, in the present invention, a method of sequentially arranging a plurality of light cutting lines in one image pickup is adopted. In such a case, if the light cutting lines are normally drawn at a narrow pitch, the cutting lines will overlap. For example, a solder having a height of 0.12 mm is irradiated with light at an angle of 45 degrees and a height of 0.05 m
If a light cutting line is drawn at a pitch of m and an image is taken, the light cutting lines overlap in the height direction by more than half on the imaged screen. Therefore, in the present invention, imaging is performed by sequentially arranging a plurality of light cutting lines of a uniform pitch such that light cutting lines do not overlap while shifting the light cutting start position by a distance corresponding to a narrow pitch, and such imaging is repeated a plurality of times. Height data is obtained by light cutting lines drawn at a narrow pitch.

FIG. 5 shows one embodiment. FIG.
(A) is the first imaging, at a pitch of t1, for example, 0.3
The line light is projected at a pitch of mm, and three light cutting lines are sequentially drawn in the field of view of the image to perform light cutting, and this is imaged. FIG. 5 (B) shows the second imaging, in which 0.
Although light is cut at a pitch of 3 mm, a position shifted by a distance of t2, for example, 0.05 mm, from the light cutting start position of the first imaging is the second light cutting start position. From the light cutting start position, 3 mm at a pitch of 0.3 mm as in the first imaging.
A light cutting line is drawn and imaging is performed. FIG. 5C shows the third imaging, in which the light cutting start position when performing light cutting at a pitch of 0.3 mm is a position shifted by 0.05 mm from the light cutting start position in the second imaging.

As described above, the image is taken six times while shifting the position by 0.05 mm, the image data is subjected to a binarization process, the center of gravity is calculated, height data is obtained, and the height data is set to 0.
By rearranging in the order of the pitch of 05 mm, light cutting data with a narrow pitch of 0.05 mm can be obtained. The rough light cutting pitch t1 (0.3 mm) is set to be an integral multiple of the target fine light cutting pitch t2 (0.05 mm). That is, 0.3 mm / 0.05 mm = 6, and in this embodiment, the light cutting pitch t1 in the visual field is six times the desired light cutting pitch t2.

Next, as a binarization method, an average value and a standard deviation of luminance are obtained for each row, and a threshold value of standard deviation + n × standard deviation is provided to perform binarization for each row. Here, n is a coefficient. However, binarization is performed for each light cutting line.
If binarization is performed in a state where a plurality of light cutting lines are drawn on one screen, the value of the coefficient n cannot be fixed. This is because the number of light cutting lines drawn on one screen is not always the same. Therefore, since the approximate height of the solder is known, a position half as high as the light cutting position is obtained. Then, image data is taken out along with the light cutting position information at a rough cutting pitch width (0.3 mm) centered on the half height position, and binarization processing and subsequent height calculation processing are performed. This is performed for each light cutting line. Since the height calculation processing is performed for each light cutting line, the coefficient n can be fixed. Therefore, it is possible to select an arbitrary light cutting pitch with a single coefficient n without determining the coefficient n for each light cutting pitch.

In the above embodiment, the line light is used as the light cutting line. However, the light cutting line can be formed by scanning the spot light to the length of the line light using a galvanometer mirror or the like. . In that case, the spot light is continuously turned on while the line light is being drawn, and is turned off while moving to the next light cutting position.

In the case of performing the light cutting, since the linear actuator is provided with a position information sensor for detecting the movement, the linear actuator is moved forward or backward to draw a light cutting line. Also, it is possible to capture a light section image.

[0022]

As described above, according to the present invention, a plurality of light-section lines are drawn in one field of view, and an image is taken.
The measurement time can be greatly reduced as compared with the case where one light section line is drawn and imaged. Also, in the present invention, a plurality of images are captured by shifting the light cutting start position by a desired light cutting pitch, and height data is arranged from the plurality of image data in the order of the shifted pitch, whereby a fine desired light cutting is performed. Since pitch height data can be obtained,
High measurement accuracy can be obtained. In addition, since the image data is cut out along with the light cutting position data for each cutting line from the plurality of drawn light cutting lines and height calculation processing such as binarization is performed, light cutting can be performed at an arbitrary pitch. become.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a conventional measuring device.

FIG. 2 is a perspective view showing a schematic configuration of a measuring device according to the present invention.

FIG. 3 is a side view of FIG. 2;

FIG. 4 is an explanatory view showing an image of cream solder captured by a light cutting method.

FIG. 5 is an explanatory diagram illustrating a state in which a plurality of light cutting lines are drawn and imaged.

[Explanation of symbols]

 Reference Signs List 1 laser diode 2 collimating lens 3 focusing lens 5 line generator lens 6 CCD camera 7 light emitting unit 9 line light 11 DUT

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaru Saito 1-Fuku term in Juke Corporation, 8-2 Kokuryo-cho, Chofu-shi, Tokyo 2F065 AA04 AA17 AA24 AA53 CC26 DD06 FF01 FF02 FF04 FF09 GG06 HH05 HH12 JJ03 JJ09 JJ26 LL10 MM14 QQ03 QQ04 QQ41 QQ42

Claims (6)

[Claims] 1. A method for measuring an object to be measured, wherein an image of the object on which an optical section line is drawn is imaged and the object is three-dimensionally measured based on an optical section method. A light cutting line is sequentially drawn to image the object to be measured, and the light cutting start position is shifted from the light cutting start position by a distance corresponding to a second pitch shorter than the first pitch, and the shifted light cutting start position is shifted. From a plurality of times, the light cutting line is sequentially drawn at a first pitch to take an image of an object to be measured, and the light cutting start position is sequentially shifted to take an image a plurality of times. A method for measuring an object to be measured, characterized by acquiring height data based on a plurality of drawn optical cutting lines. 2. The method according to claim 1, wherein the first pitch is an integral multiple of a second pitch. 3. An image data having a width equal to the first pitch is taken out together with the light cutting position data from the taken image and centered on a position obtained by adding approximately 1/2 of the height data to the light cutting position. 3. The method for measuring an object to be measured according to claim 1, wherein a binarization process is performed for each light cutting line. 4. An apparatus for measuring an object to be measured, wherein an image of an object to be measured on which a light cutting line is drawn is three-dimensionally measured based on a light cutting method. Means for sequentially drawing light cutting lines, and means for imaging the object to be measured on which the light cutting lines have been drawn, and image the object to be measured by sequentially drawing light cutting lines at a first pitch from the light cutting start position Then, the optical cutting start position is shifted by a distance corresponding to a second pitch shorter than the first pitch from the optical cutting start position, and optical cutting lines are sequentially drawn at the first pitch from the shifted optical cutting start position. The object to be measured is imaged, the light cutting start position is sequentially shifted, and the image is picked up a plurality of times, and the height data by a plurality of light cutting lines drawn at a second pitch from the plurality of imaged images An apparatus for measuring an object to be measured, wherein 5. The device for measuring a device under test according to claim 4, wherein the first pitch is an integral multiple of a second pitch. 6. An image data having a width equal to the first pitch is taken out together with the light cutting position data from the imaged image and centered on a position obtained by adding approximately 1/2 of the height data to the light cutting position. The device for measuring an object to be measured according to claim 4 or 5, wherein the binarization process is performed for each light cutting line.