JP2000193428A - Method and device for measuring object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for measuring an object wherein the object to be measured such as cream solder can be three-dimensionally measured with sure in a low-cost configuration. SOLUTION: A laser beam from a laser light source 1 is projected to an object 11 to be measured through a line generator lens 5 as a line beam. A projector unit 7 is moved at a constant speed by a linear actuator 8, and when it comes to a light shielding position, the laser light source is turned on to shield the light, measuring the height of the object. For 2-dimension measurement of the object, a line beam is projected with the laser light source turned on so that the object is irradiated with the line beam for acquiring an image. With this configuration, a 2-dimension form can be imaged with a single line beam scanning, resulting in a shorter image analysis time.

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 50 μm in order to obtain a three-dimensional shape of cream solder printed on a 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.

Also, when analyzing the planar shape of the cream solder, that is, the unevenness of the two-dimensional shape in detail, it is necessary to move the measuring unit minutely so that a large number of images are taken so as to have a fine light cutting pitch. Therefore, there is a problem that measurement time is required.

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

[0009]

SUMMARY OF THE INVENTION The present invention relates to a method and an apparatus for measuring an object to be measured by three-dimensionally measuring the object based on a light section method using line light. It is characterized in that the two-dimensional shape of the object to be measured is measured by scanning the line light, and the height position of the object to be measured is measured by scanning the line light while intermittently turning on the light source of the line light.

In such a configuration, the two-dimensional shape of the object to be measured is measured by scanning the line light while the light source of the line light is turned on. Also, a two-dimensional shape can be imaged by one scanning of the line light, and the image analysis can be completed in a short time.

[0011]

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 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 15 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 the diffuse reflection light from the DUT is imaged by the CCD camera 6.

The linear actuator 8 has a function of linearly moving its axis back and forth, and the light projection unit 7 including the focusing lens 3, the light projection mirror 4 and the line generator lens 5 is mounted on the axis. And the light projecting unit 7 moves toward the parallel light beam formed by the collimating lens 2 as shown by the 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 line actuator 8 moves and moves to the light cutting positions P1 to P3, the respective laser diodes are turned on, and the cream solder 30 projecting from the pad surface 30b is turned on.
The state in which a is light-cut by the line light and is imaged is shown.

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.

On the other hand, when analyzing the planar shape of the cream solder, that is, the unevenness of the two-dimensional shape in detail, it is necessary to make the light cutting pitch narrower than when the height is measured.
However, if the pitch is narrowed in such a manner, the light-section lines overlap, so that it is necessary to capture a number of images by rough-pitch light-section without overlapping the light-section lines while shifting the light-cutting start position. This takes an imaging time, so in the present invention, the laser light source is not intermittently turned on as in the height measurement, but a two-dimensional image is obtained by scanning the line light while the laser light source is turned on. ing.

FIG. 5 shows a two-dimensional image obtained when the laser light source is continuously turned on and the line light is scanned in this manner. The very high brightness portion is the pad surface, and the halftone portion in between is the cream solder surface. FIG. 6 is an image of the same one as in FIG. 5 taken by coaxial epi-illumination using LEDs. However, the image has a lot of noise, and it is difficult to distinguish the resist portion, the pad portion, and the solder portion. Even the wrinkles on the resist surface are shown, and it is very difficult to process the data after imaging.

The two-dimensional image shown in FIG. 5 is subjected to a binarization process, or the two-dimensional shape of the two-dimensional image is analyzed by a method such as external tracing with the analog data as it is. This method is illustrated in FIG. First, in step S1, a gray-scale image is captured, a predetermined area is cut out (step S2), the image is binarized, and the ΔΩ shown in FIG.
Send to work area (memory space). In step S4, the stylus is moved along the χ axis, and when the stylus has reached the circumference, the circumference is taken out and the island is taken out. Generally, a plurality of islands occur as shown by 40 and 41. If the largest island 40 is detected, it is determined that the island is a cream solder two-dimensional shape (step S5). Subsequently, in step S6, the distance from the pad shape 42 is observed, and the protruding abnormal portion 43 and the pull-in abnormal portion 44 are detected.
Thereafter, the process returns to step S2, where the same process is performed if there is a next cutout destination, and the process ends if there is no next cutout destination.

As described above, according to the present invention, a two-dimensional shape can be imaged and image data can be processed by one line light scanning. A short question was taken. Scanning an image by oblique projection of line light and capturing an image is the same as projecting and imaging light collimated in an oblique direction over the entire field of view, so that a very uniform image can be obtained.

In the above-described embodiment, a laser light source including a laser diode is used as the light source.
It can also be realized by using a light source such as D. However, LEDs have a lower light intensity than laser diodes and tend to attenuate. Therefore, it is necessary to use a plurality of LEDs to make the light uniform by an integrating optical system. Therefore, laser diodes are far superior in this application. ing.

In the above-described example, the two-dimensional shape of the cream solder is recognized. However, the two-dimensional shape of the substrate mark serving as a reference for the substrate position can be recognized by this method.

[0023]

As described above, according to the present invention, when three-dimensionally measuring an object to be measured based on the light section method using line light, the line light is scanned while the light source of the line light is turned on. Since the two-dimensional shape of the measured object is measured, it is possible to image the two-dimensional shape by one line light scanning, rather than capturing the two-dimensional shape only by the light cutting method,
Image analysis can be completed in a short time.

In addition, since a light source for light cutting can be used for imaging without providing a separate light source for imaging a two-dimensional image, an inexpensive configuration is obtained.

Further, since the line light is projected obliquely and the line light is scanned to capture an image, the same effect as that obtained by projecting collimated light from the oblique direction over the entire field of view and capturing an image is obtained. As a result, a very uniform image can be obtained, image processing can be facilitated, and measurement accuracy can be improved. In particular, when projecting and illuminating the object to be measured with a large area, interference fringes are generated and a uniform image cannot be obtained.However, in the present invention, the projecting illumination is performed by narrowing down the line light. A uniform image is obtained without occurrence of interference fringes.

[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 a photograph of a fine pattern formed on a cream solder substrate obtained when a line light is scanned by continuously lighting a laser diode.

FIG. 6 is a photograph of a fine pattern formed on a cream solder substrate obtained by coaxial epi-illumination using LEDs.

FIG. 7A is a flowchart illustrating a flow of analyzing a two-dimensional image of cream solder, and FIG. 7B is an explanatory diagram illustrating an image subjected to two-dimensional analysis.

[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

Claims (7)

[Claims] 1. A method for measuring an object to be measured in which an object to be measured is three-dimensionally measured based on a light section method using line light, wherein the line light is scanned while the light source of the line light is turned on. A method for measuring an object to be measured, comprising: measuring a dimensional shape, scanning a line light while intermittently turning on a light source of the line light, and measuring a height position of the object to be measured. 2. The method according to claim 1, wherein the projection angle of the line light during the scanning of the line light is constant. 3. The light source according to claim 1, wherein the line light used for measuring the two-dimensional shape of the object to be measured and the line light used for measuring the height position are obtained from the same light source. 3. The method for measuring an object to be measured according to 2. 4. An apparatus for measuring an object to be measured three-dimensionally based on a light section method using line light, wherein: a means for illuminating the object to be measured with the line light; Means for measuring the two-dimensional shape of the device under test by scanning the line light while maintaining the position, and means for scanning the line light while measuring the light source of the line light intermittently to measure the height position of the device under test. An apparatus for measuring an object to be measured, comprising: 5. An apparatus for measuring an object to be measured according to claim 4, wherein the projection angle of the line light during the scanning of the line light is constant. 6. The line light used for measuring a two-dimensional shape of an object to be measured and the line light used for measuring a height position are obtained from the same light source. 6. The measuring device for an object to be measured according to 5. 7. The apparatus according to claim 4, wherein said line light is generated from a laser light source comprising a laser diode.
7. The device for measuring an object to be measured according to any one of items 1 to 6.