JPH04279846A - Optical inspection instrument - Google Patents

Abstract

PURPOSE:To increase scanning speed of an optical inspection instrument by detecting intensity of reflected light of the first laser beam radiating means by means of the first laser beam detecting means, and adjusting a detected result of the second laser beam detecting means according to this detected result. CONSTITUTION:A laser beam A scans the surface of an object to be measured, and signal intensity of its reflected light is judged by means of an intensity judging unit 6. At this time, an output value of the laser beam suitable for detecting a point on the surface of the object is determined by means of a range selecting unit 7, and in the timing when next scanning of a laser beam B reaches to this point, an output of the laser beam B is set so as to be an output of the laser beam suitable for detecting the point on the surface of the predetermined object by means of a timing control unit 10. The reflected light of the laser beam B is quantized by means of a quantization unit 9, and by repeating this operation, the output of the laser beam B can be set always as an optimum value. While adjusting dynamic range, scanning speed can be increased.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical inspection device, and more particularly to an optical inspection device that scans the surface of an object with a laser beam and detects the reflected light while adjusting the dynamic range of the intensity.

[0002] In recent years, many optical inspection devices have been developed that scan the object surface with a laser beam and detect the intensity of the reflected light to determine, for example, the shape, shade, presence or absence of defects on the object surface. There is.

However, in order to determine the shape, density, and presence or absence of defects on the surface of an object based on the intensity of reflected light, it is necessary to be able to deal with a wide range of intensity distribution and to accurately detect minute intensity information.

Therefore, it is necessary to adjust the dynamic range of the intensity of the reflected light in accordance with the intensity of the reflected light.

[0005]

2. Description of the Related Art An example of a conventional optical inspection device of this type is shown in FIG.

This optical inspection device is roughly divided into a laser beam irradiation means 1 and a laser beam detection means 2. The laser beam irradiation means 1 is composed of a light source 3 and a scanning system 4. , an optical sensor 5, an intensity determination section 6, a range selection section 7, an amplification section 8, and a quantization section 9.

In the above configuration, first, the laser beam irradiated from the light source 3 is scanned by the single scanning system 4 onto the surface of the object to be measured, and the reflected light is detected by the optical sensor 5.

[0008] Then, the detection signal of the intensity of the reflected light detected by the optical sensor 5 is judged by the intensity judgment part 6, and based on this judgment result, the amplification level of the amplification part 8 is switched by the range selection part 7. The intensity of the reflected light amplified by the amplification unit 8 based on the amplification level is determined by the quantization unit 9.
quantized by

That is, by determining the intensity of the reflected light by the intensity determining section 6, the range selecting section 7 selects and switches the amplification level of the amplifying section 8, thereby adjusting the dynamic range.

0010

However, in such a conventional optical inspection device, the detection signal detected by the optical sensor 5 is judged by the intensity judgment section 6, and the range is selected based on the judgment result. Amplifying section 8 by section 7
Since the configuration was such that the amplification level was switched, there were problems as detailed below.

That is, the adjustment of the dynamic range of the conventional optical inspection device involves calculations from the time when the intensity of the reflected light is determined by the intensity determination section 6 to the time when the amplification level of the amplification section 8 is selected by the range selection section 7. Since it is a prerequisite that there is no sudden change in the detection signal from the optical sensor 5 within the time, for example, if the scanning speed of the laser beam is increased to increase the inspection speed, the detection signal will be subject to the above-mentioned intensity judgment. Another problem is that calculations for selecting the amplification level cannot be made in time, making it impossible to increase the scanning speed of the laser beam above a certain predetermined speed.

[Objective] Therefore, it is an object of the present invention to provide an optical inspection device that can increase the scanning speed while adjusting the dynamic range.

[0013]

[Means for Solving the Problems] In order to achieve the above object, an optical inspection apparatus according to the present invention includes a first laser beam irradiation means for irradiating a laser beam onto the surface of an object to be measured; a second laser beam irradiation means for irradiating a laser beam onto the surface of an object to be measured at predetermined time intervals on the same scanning plane; comprising first and second laser beam detection means for separately detecting intensity information,
The detection result of the second laser light detection means is adjusted based on the detection result of the first laser light detection means.

The detection result of the second laser beam detection means may be adjusted by adjusting the laser beam irradiation output of the first laser beam irradiation means or by adjusting the detection amplification degree of the laser beam of the second laser beam detection means. It may be possible to adjust the

[0015]

[Operation] In the present invention, before the intensity of the reflected light from the second laser beam irradiation means is detected by the second laser beam detection means, the intensity of the reflected light from the first laser beam irradiation means is determined in advance by the first laser beam detection means. is detected, and based on this detection result, the second
The detection result of the laser beam detection means is adjusted.

That is, since the detection signal is calculated in advance by the first laser beam detection means, even if the scanning speed is increased, the detection result of the second laser beam detection means is based on the detection result of the first laser beam detection means. The dynamic range is adjusted.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on the drawings. FIG. 1 is a diagram showing a first embodiment of an optical inspection apparatus according to the present invention, and FIG. 1 is a block diagram showing the main part configuration of this embodiment.

First, the configuration will be explained.

In FIG. 1, the same numbers as those given to the conventional example shown in FIG. 5 indicate the same parts. The optical inspection device of this embodiment is roughly divided into a first laser beam irradiating means 1a, a second laser beam irradiating means 1b, a first laser beam detecting means 2a, and a second laser beam detecting means 2b.

The first laser beam irradiation means 1a is composed of a light source 3a and a scanning system 4a, and the second laser beam irradiation means 1b is composed of a light source 3b and a scanning system 4b. The first laser beam detection means 2a is composed of an optical sensor 5a, an intensity determination section 6, a range selection section 7, and a timing control section 10, and the second laser beam detection means 2b is composed of an optical sensor 5b and a quantization section 9. has been done.

Next, the operation will be explained. First, as shown in FIG. 1, a detection signal A' from a laser beam A that precedes a scanning line emitted from a light source 3a is used to adjust the dynamic range of the apparatus.

That is, the laser beam A is scanned by the scanning system 4a on the surface of the object to be measured, the reflected light of the laser beam A is detected by the optical sensor 5a as the detection signal A', and the signal intensity of the detection signal A' is It is determined by the strength determining section 6.

The output value of the laser beam suitable for detecting the point on the object surface that has been irradiated with the laser beam A at this point is determined by the range selection section 7, and the output value of the laser beam that is suitable for detecting the point on the object surface that has been irradiated with the laser beam A at this point is determined by the range selection section 7, and the output value of the laser beam that is suitable for detecting the point on the object surface that has been irradiated with the laser beam A at this point is determined by the range selection section 7. The output of the laser beam B irradiated from the light source 3b by the timing control unit 10 at the timing when the scanning of the laser beam B reaches this point is the output value of the laser beam suitable for detecting the point on the object surface determined previously. is set to

Then, the reflected light of the laser beam B is transmitted to the optical sensor 5.
The detection signal B' detected at point b is quantized by the quantization unit 9, and this operation is repeated at each point on the scanning line, so that the output of the laser beam B is always set to the optimum value.

Therefore, detection data with a wide dynamic range and high accuracy can be obtained from the series of output values of the laser beam B and the series of quantized values of the detection signal B'.

2 and 3 are diagrams showing a second embodiment of the optical inspection device according to the present invention, FIG. 2 is a block diagram showing the main part configuration of this embodiment, and FIG. 3 is a diagram showing the specific structure of FIG. FIG. 2 is a block diagram showing a circuit configuration.

In FIG. 2, the same numbers as those given to the first embodiment and the conventional example shown in FIGS. 1 and 5 indicate the same parts.

The first laser beam detection means 2a of this embodiment is as follows:
It is composed of an optical sensor 5a, an intensity determination section 6, a range selection section 7, and a timing control section 10, and the second laser beam detection means 2
b is composed of an optical sensor 5b, an amplifying section 8, and a quantizing section 9, and as shown in FIG.
Consisting of a converter 11 and a lookup table 12,
The range selection section 7 includes a buffer 13 and a multiplexer 14.
, 15, and the quantization section 9 is composed of an A/D converter.

In this embodiment, unlike the first embodiment, the output of the laser beam B is not controlled by the range selection section 7, but the degree of amplification of the detection signal B' by the amplification section 8 is switched.

That is, the detection signal A' is digitized by the A/D converter 11, and the optimum range corresponding to this digitized value is determined from the look-up table 12.
The data is read from the buffer 13 and temporarily stored in the buffer 13. Then, the optimum range calculated by the timing control section 10 using the detection signal A' two scans before the current detection signal is read out from the buffer 13, and the multiplexers 14 and 15 are switched to this range.

On the other hand, the detection signal B' is sent to the multiplexer 14
and is amplified for each range by the amplifying section 8,
The A/D converter converts the data into digital quantized data.

Therefore, the detection signal B' is always amplified within the optimum range and quantized data is obtained.

As described above, in this embodiment, before the intensity of the reflected light from the second laser beam irradiation means is detected by the second laser beam detection means, the first laser beam detection means
The intensity of the reflected light from the laser beam irradiation means can be detected, and the detection result of the second laser beam detection means can be adjusted based on this detection result.

Therefore, even when the scanning speed is increased, the dynamic range of the detection result of the second laser light detection means can be adjusted based on the detection result of the first laser light detection means, and the inspection speed can be increased. .

The optical systems of Examples 1 and 2 above are as follows:
It is constructed using two sets of light sources and scanning systems each.
As shown in FIG. 4, the light source and scanning system are composed of a set of laser light source 16, beam expander 17, and beam splitter 1.
8a, 18b, a polygon scanner mirror 19, and a scan lens 20, and a photoelectron image intensifier, for example, may be used as the optical sensor.

In this case, in the above configuration, the laser light emitted from the laser light source 16 is transmitted to the beam splitter 18.
a, one passes through the optical path α to the polygon scanner mirror 19, and the other passes through the beam splitter 18b.
The light is reflected by the light beam, passes through the optical path β, and is irradiated onto the polygon scanner mirror 19. At this time, the beam splitter 18a
, 18b are adjusted so that the laser beams passing through the optical paths α and β are reflected at the same point on the polygon scanner mirror 19.

Here, the angle formed by the optical path α and the optical path β is θ
(rad) and the rotation speed of the polygon scanner mirror 19 is u (rad/sec), then the two scanning lights scan the same point on the scanning plane with a time difference of θ/2u (sec).

That is, the reflected light on the scanning surface is
Similar to and 2, it follows exactly the same optical path and is detected by the optical sensor.

Therefore, by applying this embodiment, the light source and scanning system of Embodiments 1 and 2 can be simplified;
It can contribute to miniaturization and cost reduction of devices. In addition, in the second embodiment, the detection signal A' is input to the A/D converter 11 as it is, but the invention is not limited to this, and by passing it through a log amplifier before inputting it to the A/D converter 11,
It can handle data with a wider dynamic range.

[0040]

According to the present invention, before the second laser beam detection means detects the intensity of the reflected light from the second laser beam irradiation means, the first laser beam detection means detects the reflected light from the first laser beam irradiation means in advance. The intensity of the laser beam can be detected, and the detection result of the second laser beam detection means can be adjusted based on this detection result.

Therefore, even when the scanning speed is increased, the dynamic range of the detection result of the second laser light detection means can be adjusted based on the detection result of the first laser light detection means, and the inspection speed can be increased. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main configuration of a first embodiment of the present invention.

FIG. 2 is a block diagram showing the main configuration of a second embodiment of the present invention.

FIG. 3 is a block diagram showing a specific circuit configuration of FIG. 2;

FIG. 4 is a diagram showing the configuration of an optical system according to Example 3 of the present invention.

FIG. 5 is a block diagram showing the main part configuration of a conventional example.

[Explanation of symbols]

1 Laser light irradiation means 1a First laser light irradiation means 1b Second laser light irradiation means 2 Laser light detection means 2a First laser light detection means 2b Second laser light detection means 3 Light sources 3a, 3b Light sources 4 Scanning systems 4a, 4b Scanning system 5 Optical sensor 5a, 5b Optical sensor 6 Intensity determination section 7 Range selection section 8 Amplification section 9 Quantization section 10 Timing control section 11 A/D converter 12 Lookup table 13 Buffers 14, 15 Multiplexer 16 Laser light source 17 Beam Ex Panda 18a, 18b Beam splitter 19 Polygon scanner mirror 20 Scan lens

Claims (3)

[Claims] 1. First laser beam irradiation means for irradiating a laser beam onto the surface of an object to be measured; a second laser beam irradiation means for irradiating;
first and second laser light detection means for separately detecting intensity information of reflected light of the laser light irradiated by the first and second laser light irradiation means,
An optical inspection device characterized in that the detection result of the second laser light detection means is adjusted based on the detection result of the laser light detection means. 2. The optical inspection apparatus according to claim 1, wherein the laser beam irradiation output of the first laser beam irradiation means is adjusted based on the detection result of the first laser beam detection means. 3. The optical inspection apparatus according to claim 1, wherein the detection amplification degree of the laser beam of said second laser beam detection means is adjusted based on the detection result of said first laser beam detection means.