JPS61105404A - Pattern detecting device - Google Patents

Abstract

PURPOSE:To correct reflected light to a proper position even if it is displaced owing to the displacement of a body to be measured by irradiating the pattern of the object body with light from a light source through a deflecting means and controlling the deflecting means with the output of a line image detecting means. CONSTITUTION:The laser light emitted by a laser light source 2 is incident slantingly on the body 1 to be measured through the deflecting means 5 and a cylindrical lens 6 and its reflected light is supplied to the 1st and the 2nd line image detecting means 4 and 8. If the object body 1 is displaced in the direction of the optical axis of reflected light to a position 1', the reflected light from the light source 2 does reach a detecting means 4. Then, the beam of the reflected light is detected by a detecting means 8. Displacement from a light intensity distribution at a reference position A is detected by a peak position detecting circuit 9 and a displacement-voltage converting means 10 and fed back to the deflecting means 5 to adjust the laser light as shown by a broken line, so the reflected irradiation light is incident on the detecting means 4 all the time to obtain a pattern image of the object body 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a pattern detection device, and in particular, the present invention relates to a pattern detection device, in particular, which irradiates an object to be measured having a pattern, such as a printed circuit board, with light irradiated obliquely from a light source to detect the object to be measured. detects the amount of change when the position of The present invention relates to a pattern detection device capable of detecting reflected light.

[Conventional technology]

In recent years, patterns on printed circuit boards have become increasingly finer.

It is becoming more dense. In particular, it is necessary to detect pattern defects in advance because it is impossible to repair the intermediate layer of laminated prints and TT after assembly and lamination.
Generally, these pattern inspections are often performed visually, and these visual inspections are becoming impossible due to the amount of work required. In response to these requirements, a pattern detection device that automatically detects the pattern of a printed circuit board is designed to detect the pattern of the printed circuit board as shown in Fig. 6 in order to reduce the influence of positional fluctuations of the pattern of the printed circuit board, which is the object to be measured. An optical system was used in which a laser light source 2 was arranged perpendicular to the pattern surface and one reflected light was detected by a line image detection means 4 via a half mirror 3. According to such an optical system, even if the object 1 to be measured is displaced ΔZ to the 1' position, the reflected light does not fail to reach the image detecting means, and the influence of the change in the 0 position of the object to be measured is small.

However, on the other hand, the contrast of the pattern is low.

A problem arises in that the S/N ratio deteriorates.

[Problem that the invention seeks to solve]

The present invention aims to solve such problems.

This method uses a light irradiation method that irradiates the object to be measured with light from a light source obliquely to increase the contrast and prevent deterioration of the S/N ratio. When the position of the object to be measured changes, a problem arises in that the incidence on the line image detection means (for example, CCD) is completely shifted. Factors that cause the position of the DUT to vary include changes in the position of the mounting table on which the DUT is placed, and if the DUT is a printed circuit board, its thickness and whether the copper foil pattern is on one or both sides of the board. This is due to the difference in

[Means to solve the problem]

The present invention provides a pattern detection device that solves the above-mentioned problems, and FIG. 1 shows the basic configuration of the present invention. In FIG. 1, 1 represents an object to be measured such as a printed circuit board, and 1' represents an object to be measured whose position has changed by ΔZ due to various factors as described above.

Reference numeral 2 denotes a light source such as a laser, and the laser beam 2a from the light source is transmitted to the object to be measured 1 via a polarizing means 5 and a cylindrical lens 6.
is irradiated. The irradiated laser beam is reflected at an angle θ on the pattern surface of the object to be measured, passes through the lens 7 and the half 13, and enters the first line image detection means 4 made of COD or the like, which generates a pattern image of the object to be measured 1. Detect. Furthermore, the reflected light from the half mirror 3 between the first line image detection means 4 arranged in the reflected light and the lens 7 is the same <C
The light is irradiated onto a second line image detection means 8 made of OD or the like. The second line image detection means 8 is arranged perpendicular to the arrangement direction of the first line image detection means 4.

The signal obtained by the second line image detection means 8 is
Light intensity distribution curve 1 in the width direction of the reflected beam as shown in the figure.
1 is shown. The output from the second line image detection means 8 is applied to a peak position detection circuit 9. Then, the displacement of the peak position of the light intensity distribution from the reference position when the measured object 1 is displaced to the 1' position is detected by the displacement-voltage conversion circuit 10, and the deflection means 5 is controlled by the detected output. This is what I did.

[For production]

Laser light emitted from the laser light source 2 obliquely enters the object to be measured 1 through the deflection means 5 and the cylindrical lens 6, and the reflected light is transmitted to the first and second line image detection means 4.
given to 8. If the gold wave measurement object l is displaced by Δ2 in the direction of the reflected optical axis and reaches the 1' position, the irradiation beam from the laser light source 2 will be incident on the measurement object 1' at position B, and the reflected light will be reflected as shown by the dashed line. The reflected light does not reach the first line image detecting means 4 as it passes through the lens 7 along a certain trajectory. Therefore, the second line image detection means 8 detects the reflected light beam. This represents the light intensity distribution in the width direction of the reflected light as shown in FIG. and feedbank the laser beam to the deflection means 5 at point A, that is, Δ, as shown by the broken line.
If the adjustment is made so that h=o, the illuminated reflected light is always incident on the first line image detection means 4, and a pattern image of the object to be measured 1 can be obtained.

〔Example〕

One embodiment of the invention will now be described in detail with reference to FIG.

Note that the same parts as in FIG. 1 are given the same reference numerals, and redundant explanation will be omitted. The deflection means 5 rotates the laser light from the laser light source 2 that is irradiated onto the deflection mirror 5a by a drive motor 5b to correct the optical axis shift of the reflected light due to the displacement of the object to be measured 1' as shown by the broken line. to irradiate position A. Although a mechanical configuration is shown as the deflection means, for example, an optical deflection means such as an ultrasonic light deflection element may also be used. Fourth
In the figure, when the reflected light of the laser beam irradiated onto the object to be measured l or 1' is incident on the first and second line image detecting means 4, 8 by the half mirror 3, the line image detecting means 4.
8 is shown in a perspective view when they are arranged perpendicularly to each other in the longitudinal direction. When the second line image detection means 8 has obtained the light intensity distribution in the width direction of the reflected light shown in FIG.
) are applied to the negative input terminal of the first differential amplifier AMP+. -Multiple terminal T
A voltage from a reference voltage source is applied to I, and the reference voltage adjusted by the reference voltage setting resistor R8 is applied to A of the first differential amplifier.
The reference voltage applied to the positive input terminal of MP+ is set to threshold 1.
A waveform 14 shown in FIG. 5(b) with a value of 3 is output to the output terminal of the first differential amplifier AMP+. On the other hand, the output from the second line image detection means 8 applied to the input terminal T2 is formed into a differentiated waveform 15 as shown in FIG. It is applied to the positive input terminal of the dynamic amplifier AMP2. Since the negative input terminal is connected to the ground position,
The waveform shown in FIG. 5(d) is output from the differential amplifier AMP2. In this way, the outputs of the first and second differential amplifiers AMP+ and AMP2 are applied to the AND gate circuit AND, and the waveform 17 shown in FIG. 5 (el) is taken out at the output terminal T3. Reason for passing it through the AND gate circuit This is to ensure that the zero cross point waveform shown in FIG. 5 is obtained.

The output from the AND gate circuit AND is applied to the displacement-voltage conversion circuit IO. The displacement-voltage conversion circuit 10 may be a displacement-current conversion circuit or a displacement-frequency conversion circuit depending on the usage of the deflecting means. What is necessary is to convert the deviation Δh from point A) into an electrical output such as a voltage. For this.

For example, the computer IQa compares it with a reference position in the memory 10b and applies a corresponding voltage to the drive motor 5b.
By feeding back the drive motor, the laser beam is adjusted so as to be incident on point A of the object to be measured 1' which has been displaced as shown by the broken line. Of course, a hardware configuration is also possible.

〔Effect of the invention〕

Since the present invention is constructed and operated as described above, it is possible not only to increase the contrast of the pattern of the object to be measured, but also to prevent the reflected light incident on the first line image detection means from being shifted due to the displacement of the object to be measured. It is possible to always detect the correct pattern image because the correct position can be corrected even if the line pattern detection means It has the feature of being able to obtain a light distribution intensity output of .

[Brief explanation of drawings]

FIG. 1 is a basic system diagram of the pattern detection device of the present invention.
2 is a waveform explanatory diagram of the second line image detection means in FIG. 1, FIG. 3 is an optical system and circuit diagram showing an embodiment of the pattern detection device of the present invention, and FIG. Fig. 3 is a perspective view showing the relationship between the line image detection means and the reflected light entering and reflecting on the half mirror, Fig. 5 is a waveform explanatory diagram of the peak position detection circuit of Fig. 3, and Fig. 6 is a conventional FIG. 3 is a schematic diagram showing the arrangement of the optical system. 1.1'...Object to be measured, 12...Laser light source, 3...Half mirror, 4...First
Line image detection means, 5... Deflection means, 5a... Deflection mirror. 5b... Drive motor, 6... Cylindrical lens, 7... Lens, 8...
2nd line image detection means, 9... Peak position detection circuit, 10... Displacement-voltage conversion circuit. Figure 1 Figure 2 Figure 4 Figure 5

Claims (1)

[Claims] The light from the light source is irradiated onto the pattern of the object to be measured via the deflection means, the reflected light from the object is detected by the first line image detection means, and the object to be measured and the first line image are detected. A second line image detecting means arranged orthogonally to the first line image detecting means detects the reflected light intensity distribution of the object to be measured through a half mirror arranged between the means. A pattern detection device characterized in that the output of the line image detection means is converted into an electrical output to control the deflection means.