JPH0715375B2 - Shape detection method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a shape detection method for detecting a mounting state of an electronic component on an electronic circuit board.

(Prior Art) Conventionally, a prior application (Patent application: Japanese Patent Application Laid-Open No. Hei 10-27) has already been proposed by the present applicant as a method for projecting a light beam such as a laser beam to detect an uneven shape on a flat plate. 1-
5650), and had the configuration shown in FIG. In the figure, 20 is a laser light source.
The emitted laser light is refracted by the synchronous oscillating mirror 22 through the collimator 21, and is irradiated onto the object to be detected 24 through the lens 23. Through the lens 25 separately provided to detect the spot light irradiated on the object to be detected 24, the reflected light refracted by the synchronous vibration mirror 26 is configured to be detected by the optical position detector 27. . In this case, the synchronous oscillating mirrors 22 and 26 synchronously refract light at the same angle so that laser light scanning in the X direction is performed. Further, the detected object is moved in the Y direction, which is different from the scanning in the X direction. With such a configuration, the laser beam is scanned in the X direction, the beam spot height position in the X direction is detected by the light receiving element synchronized with the projection scanning, and the object to be detected is moved in the Y direction by X,
The height of the object on the secondary plane of Y was measured.

FIG. 6 shows a case where a light beam is projected onto a glossy or mirror-finished surface such as a soldered portion in a visual inspection of the mounting state of electronic components on an electronic circuit board with such a shape detection device. As shown, in addition to the primary reflected beam spot S ₁ , abnormal reflection such as the secondary reflected beam spot S ₂ and the tertiary reflected beam spot S _{3 of the} light beam occurs, and the light receiving element 28 for detecting the beam spot height position is detected. In some cases, a plurality of beam spots P _{S1 to} P _{S3 and the} like having different beam spot height positions were imaged on.

Further, not only the secondary reflection and the tertiary reflection but also the beam spot may enter into the blind spots of the electronic parts and the like which are provided adjacent to each other, so that the detection becomes impossible.

(Problems to be solved by the invention) In the above-mentioned conventional measurement, it is more and more accurate that there are abnormal reflections such as secondary reflections and tertiary reflections, and non-detection due to blind spot which is a basic problem of triangulation. There is a drawback that it is difficult to select and detect the primary reflected beam spot position.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a three-dimensional position, shape, and size of an object having a glossy surface or specularity that causes secondary reflection and tertiary reflection. An object of the present invention is to provide a shape detection method capable of accurately measuring and detecting the like without being affected by a blind spot.

(Means for Solving the Problem) In order to achieve the above object, the shape detection method of the present invention is a triangulation method in which a light beam is projected from above an object to be detected to generate a beam spot on the object to be detected. In the method of detecting the height position of the beam spot by detecting the shape, by disposing a plurality of light receiving elements for detecting the beam spot image from the angular position opposite to the projection axis of the light beam, Among the one or more spot image position outputs by the light receiving element, the light receiving element that outputs the lowest position is selected, and the highest position among the one or more spot image position outputs of the selected light receiving element is selected. The output is at the beam spot height position.

(Operation) In the shape detecting method of the present invention, the projected laser light undergoes secondary reflection and tertiary reflection due to the gloss and specularity of the soldered portion,
3 with the beam spot first order reflection beam spot S _1, 2-order reflected beam spot S _2, 3 order reflection beam spot S ₃
It is generated in the place. The generated S ₁ , S ₂ , and S ₃ can detect the height position of each beam spot with a line image sensor. However, when entering the adjacent the blind spot of the part may S _1, S _2, S ₃ is not detected, the other side of the light receiving provided at a position of the measurement of the S _1, S _2, S ₃ in this case The element enables detection. Since the beam spot position output of S ₁ to be obtained is selected from the beam spots detected by the plurality of light receiving elements, the accurate beam spot position can be detected.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 is a configuration diagram of a shape detection device, in which L is an L-side detection unit and R is an R-side detection unit. The L-side detection unit and the R-side detection unit are detection units provided at an angle opposed to the optical axis of the projected laser light, and both the light-receiving elements L1 and R1 and the lens.
It has a symmetrical configuration with L2 and R2. When the circuit board 1 on which the components A and B are mounted is mounted on the measuring table of the shape detecting device having such a configuration and laser light is vertically emitted from a light source unit (not shown) to detect the point S,
Spot of the laser light is focused spot images of P _'S1 on the light receiving element R1 of the R-side detecting section. However, the L-side detection unit enters the blind spot of the component A and is not detected. Further, the secondary reflected beam spot S _{2 at the} point S enters any of the detection units of L and R to obtain images of P _S2 and P ′ _S2 . Furthermore, S
The third reflection S ₃ emitted from the two points forms a spot image of P _S3 on the light receiving element L1 of the L-side detector, but the spot image of P _S3 enters the blind spot of the component B and is not detected by the R-side detector.

Here, the line image sensors shown in FIG. 2 are used as the light receiving elements L1 and R1, and the output of each of these line image sensors is detected by the line image sensor drive detection unit.
Beam spot position detector L4 and L3 and R3
The output of L4 and R4 is input to R4, and the primary reflected beam spot position detection unit 5 performs a composite operation to obtain the primary reflected beam spot position output. Timing signals from the detection timing control unit 6 are input to the line image sensor drive detection units L3 and R3, the beam spot position detection units L4 and R4, and the primary reflected beam spot position detection unit 5, respectively. The primary reflected beam spot position is selected by detecting the beam spot position.

Further, when obtaining the outputs of the R1 of the light receiving element L1 as shown in FIG. 3, since in the case of Figure 1 is in the blind spot of each P _S1 and P _'S3 component A and component B Although not shown in the figure, the height positions P _S1 and _P'S1 are the same,
Since the other P _S2 and P ′ _S2 and P _S3 and P ′ _S3 are at different positions, the detection peak showing the same height position among the outputs of the respective light receiving elements can be detected as the primary reflected beam spot position.

In fact, if there is a blind spot as shown in FIG. 1, the dotted lines below the slanted lines a and b in FIG. 3 cannot be detected, and the algorithm described below is used in the present invention. This algorithm is based on the method shown in FIG. That is, the L-side detector and the R-side detector each measure one or a plurality of beam spot positions according to the detection start command. Next, in the primary reflected beam spot detection unit, of the beam spot positions measured by the L-side detection unit and the R-side detection unit, the detection unit that has detected the lowest beam spot position is selected, and the highest detection unit of the detection units is selected. Beam spot position is 1
The next reflected beam spot position is output.

Since such an algorithm can be applied without contradiction even when there is no blind spot, it is not necessary to determine the presence or absence of a blind spot, and detection of an object in which a blind spot does not occur can also be applied.

As described above, at least the primary reflected beam spot is
If the detection can be performed by one of the detection units, the primary reflected beam spot position can be accurately selected and detected even if secondary and tertiary reflections are mixed.

In the embodiment, two detectors are arranged as a pair, but in the case of three, the positions are divided into three equal parts around the projection beam, and in the case of four, left, right, front. By arranging them at the subsequent four equal positions, the primary reflected beam spot position can be accurately selected and detected.

Further, as shown in FIG. 5, the present invention has a light receiving detector for projecting and scanning a laser beam in the X direction and synchronously following the projecting scanning to detect the beam spot height. In the direction, the object to be detected is moved on the Y-axis table to detect the height of the unevenness of the object on the XY plane, or the light emitting and receiving system detects the height of one point without scanning and the object to be inspected. Objects on the XY table
It can be used for a method of detecting the height of an object by scanning in the XY directions.

(Advantages of the Invention) Conventionally, the principle of triangulation of the position, shape, and size of a mounted circuit board on which electronic components are mounted and soldered, a component having a metal surface, or an object having gloss or specularity such as a product When performing non-contact measurement or inspection by using, it is affected by extraordinary reflection and blind spot.

However, as described above, the shape detection method of the present invention projects a light beam from above the detected object to generate a beam spot on the detected object, and the height position of the beam spot is determined by triangulation. In the method for detecting a shape by detecting a beam spot image, a plurality of light receiving elements for detecting a beam spot image are arranged from an angular position opposite to the projection axis of the light beam. Of the spot image position outputs, the light receiving element that outputs the lowest position is selected, and the highest position output of one or more spot image position outputs of the selected light receiving elements is set as the beam spot height position. Therefore, when either abnormal reflection or blind spot occurs, or when both are mixed, the paired reflected beam spot position is accurately selected and detected. Bets can be, as a result, accurate measurement of the three-dimensional shape, there is an effect that the inspection becomes possible.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention, and FIG.
2 is a block diagram of the shape detection processing unit, FIG. 3 is an output diagram of a light receiving element, and FIG.
FIG. 4 is a flow chart showing the algorithm of the present invention,
5 and 6 are conventional examples, FIG. 5 is a perspective view of the shape detecting device, and FIG. 6 is a plan view showing an abnormal reflection state. L1, R1 ... Light receiving element

Claims (1)

[Claims] 1. A method for detecting a shape by projecting a light beam from above an object to be detected to generate a beam spot on the object to be detected, and detecting a height position of the beam spot by a triangulation method. , A plurality of light receiving elements for detecting a beam spot image are arranged from an angular position opposite to the projection axis of the light beam, and the lowest of one or a plurality of spot image position outputs by each light receiving element Select the light receiving element that has output the position, and select 1 of the selected light receiving elements.
A shape detection method, wherein the highest position output of the one or more spot image position outputs is the beam spot height position.