JPH07117387B2 - Shape detection method - Google Patents

Description

The present invention relates to shape detection for detecting uneven shapes on a flat plate, which is suitable for non-contact visual inspection of the mounting state of electronic components on an electronic circuit board. Regarding the method.

(Prior Art) Conventionally, as a method for projecting a light beam such as a laser beam to detect an uneven shape on a flat plate, a prior application (Patent Document 1) already proposed by the applicant of the present application and entitled “Shape Detection Device” (Japanese Patent Application No. 1-5650) and had a configuration as shown in FIG. In the figure, reference numeral 20 denotes a laser light source which refracts laser light emitted from the laser light source 20 through a collimator 21 by a synchronous oscillating mirror 22 and irradiates an object to be detected 24 through a lens 23. The spot light reflected by the synchronous oscillating mirror 26 is refracted through a lens 25 separately provided to detect the spot light radiated on the object to be detected 24 and is detected by the light position detection unit 27. It had been.
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 system synchronized with the light projection scanning, and the object to be detected is moved in the Y direction by moving the X, The height of the object on the quadratic plane of Y was measured.

When performing a visual inspection of the mounting state of electronic components on an electronic circuit board with such a shape detection device, when a light beam is projected onto a glossy or mirror-finished surface such as a soldered portion, the result shown in FIG. As shown, abnormal reflection such as secondary reflection S ₂ and tertiary reflection S ₃ of the light beam may occur, and a plurality of beam spots may be imaged on the light receiving element 28 that detects the beam spot height position. It was

In another conventional example, a position sensitive detector (PSD) was used for the light receiving element, but in this PSD, secondary reflection, third order reflection, etc. are performed to detect the illuminance barycentric position on the entire light receiving surface. Was greatly influenced by.

(Problems to be Solved by the Invention) With respect to a plurality of beam spots in the above-described conventional shape detection, it is necessary to correctly select and detect a beam spot (first-order reflected beam spot S ₁ ) to be detected. However, in the conventional example, the primary reflected beam spot S ₁ was detected by detecting the maximum light amount position of the light receiving element output, but the beam of secondary reflection or tertiary reflection is detected from the primary reflected beam spot S _1. The spots S ₁ and S ₃ are brighter as can be seen from the light receiving outputs P _{S1 to} P _S3, and there is a drawback that erroneous detection occurs when the light receiving element output becomes large.

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 and shape of an object having a glossy surface or specularity that causes secondary reflection and tertiary reflection. We are going to submit a shape detection method that enables measurement and detection of dimensions with a simple configuration.

(Means for Solving the Problems) In order to achieve the above object, the shape detecting method of the present invention is configured such that the scanning direction of the laser light and the moving method of the detected object are relatively X,
While moving in the Y direction, a light beam is emitted from above to the object to be detected to generate a beam spot, and the height and position of the beam spot at each X, Y position is detected by triangulation to determine the shape. In the detection method, when the light receiving element detects two or more beam spot image positions, the previous timing signal of the beam spot position output obtained by being controlled by the detection timing control unit upon receiving the timing signal of the light projection scanning unit Difference from beam spot position output due to
It is characterized in that d is obtained, and the beam spot image position where this Δd is the minimum is selected as the beam spot height position.

(Operation) In the shape detecting method of the present invention, when the light receiving element detects two or more beam spot image positions, the beam spot position output obtained by being controlled by the detection timing control unit upon receiving the timing signal of the projection scanning unit Using the one-dimensional image sensor (line image sensor) to determine the difference Δd from the beam spot position output by the previous timing signal of, and select the beam spot image position where this Δd is the minimum, A detection timing control unit that changes the detection processing method from the light position detection unit configured by the control unit, the line image sensor drive detection unit, the beam spot position detection unit, and the beam spot position storage unit, and also receives the timing signal of the light emission scanning unit. Is the operation of the line image sensor drive detector, beam spot position detector, and beam spot position memory Since the timing is controlled, the closest spot spot image position can be selected.

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

FIG. 1 is a configuration for carrying out the shape detecting method of the present invention, and 1 is a line image sensor as a one-dimensional image sensor. This line image sensor 1 is used in place of the optical position detecting section of the conventional shape detecting device (see FIG. 4), and the other basic structure is the same. The signal of the line image sensor 1 is input to the line image sensor drive detection unit 2, while the signal as a peak value is input to the beam spot position detection unit 3 on the output side. On the other hand, the timing signal of the projection scanning unit (timing signal of the synchronous vibration mirror 22 in FIG. 4) is sent to the separately provided detection timing control unit 4, and the output side of this signal is the line image sensor drive detection. It is input to the unit 2 and the beam spot position detection unit 3, respectively. Also, one of the output signals of the detection timing control unit 4 is input to the beam spot position storage unit 5, and its output side is input to the beam spot position detection unit 3. The output of the beam spot position detection unit 3 is input to the beam spot position storage unit 5.

The operation of such a configuration will be described with reference to FIG.
The detection timing signal a output from the detection timing control unit 4 is transmitted at the same timing as t _i , t _{i + 1} , ... And the line image sensor drive detection unit 2 according to the detection timing signal a The output signal b outputs the peak value of the spot light received by the line image sensor 1. This output transmits the beam spot position output c as a falling signal in the beam spot position detector 3. Now, at time t _i , the line image sensor detection output b has one peak waveform, so this is designated as the beam spot position D ₀ . It is assumed that three peak waveforms occur at time t _{i + 1} , and the peak positions are D ₁ , D ₂ , and D ₃ , respectively. At this time, the difference from the previous beam spot position output D ₀ (time t _i ) is calculated, and Δd ₁ = | D ₁ −D ₀ | Δd ₂ = | D ₂ −D ₀ | Δd ₃ = | D ₃ −D ₀ | is found and the smallest Δd is selected. In FIG. 2, since Δd ₁ is the minimum, D ₁ is the beam spot position output at time t _{i + 1} .

Hereinafter, the same operation is repeated t _{i + 2} , t _{i + 3} , ... To detect the beam spot position output. These detection operations are performed in the steps shown in FIG.
Beam spot position measurement is performed by detection start,
If there is a single beam spot, it is detected as the primary reflected beam spot position output, and if there are multiple beam spots, the beam spot position close to the previous beam spot position is selected and detected as the primary reflected beam spot position output. . Then, for the previous beam spot position to be compared, the same result can be obtained by using a value near the detection point or an average value.

Further, according to the shape detecting method of the present invention, the light receiving element is fixed and the change of the light beam spot position in the height direction is detected by scanning with the two synchronous oscillating mirrors. Even in an optical system not including, it is possible to detect by relatively moving the object to be detected, and the shape detection method of the present invention can be applied.

(Effects of the Invention) As described in detail above, the shape detection method of the present invention makes the scanning direction of the laser beam and the moving direction of the detected object relatively.
While moving in the X and Y directions, a light beam is emitted from above to the object to be detected to generate a beam spot, and the height and position of the beam spot at each X and Y position is detected by triangulation. In the method of detecting the shape, the number of light receiving elements is 2
When more than one beam spot image position is detected, the difference between the beam spot position output obtained by controlling the detection timing control unit receiving the timing signal of the light emission scanning unit and the beam spot position output by the previous timing signal Δ The characteristic is that the beam spot image position where Δd is minimized is selected and the beam spot height position is set as the beam spot height position, so that a shape or glossy surface that causes secondary reflection or tertiary reflection, etc. There is an advantage that it is possible to easily measure and detect the three-dimensional position, shape, and dimension of a specular object with a simple configuration.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is a block diagram of an optical position detector, FIG. 2 is a timing chart showing the operation of FIG. 1, and FIG. 4 and 5 are conventional examples, and FIG. 4 is a perspective view of the shape detecting device,
FIG. 5 is a plan view showing an abnormal reflection state. 1 ... Line image sensor light receiving part

Claims (1)

[Claims] 1. A beam spot is generated by irradiating a light beam onto the object to be detected from above while moving the scanning direction of the laser light and the moving direction of the object to be detected in relative X and Y directions. In the method of detecting the height and position of the beam spot at each X and Y position by the triangulation method to detect the shape, when the light receiving element detects two or more beam spot image positions, the projection scanning unit The difference Δd between the beam spot position output obtained by controlling the detection timing control unit and the beam spot position output by the previous timing signal is calculated, and the beam spot image position that minimizes this Δd is selected. Then, the shape detection method is characterized in that the beam spot height position is set.