JPS63255646A - Method for detecting flaw of object to be inspected - Google Patents

Abstract

PURPOSE:To detect a flaw without omission regardless of the size thereof, by irradiating the surface of an object to be inspected with beam having wavelengths, whose difference in the reflectivities to the surface and lower layer parts of the object to be inspected is 0.8 or more, from a beam irradiation system. CONSTITUTION:The laser beam emitted from the beam emitting part 11 of a beam irradiation system 10 is allowed to irradiate the surface of an object 30 to be inspected by a polygon mirror 12 to optically scan said surface in the lateral direction thereof. This irradiation beam is reflected from the surface of the object 30 to be inspected to be incident to a beam receiving detection system 20 while the detection system 20 receiving said reflected beam detects whether a flaw 33 is present on the surface of the object 30 to be inspected on the basis of the quantity of said reflected beam. At this time, the beam having wavelengths whose difference in the reflectivities to the surface layer part 31 an lower layer part 32 of the object to be inspected is 0.8 or more is used. Therefore, when the flaw 33 is present in the surface layer part 31 of the object 30 to be inspected and the lower layer part 32 is exposed from said flaw 33, the quantity of regular reflected beam incident to the detection system 20 from said flaw part is reduced and the flaw 33 can be detected without omission by he detection system 20.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of the Invention The present invention relates to a method for optically detecting defects in an object having a layered structure.

``Conventional technology J'' Flying spot J1 , Flying Image V, and Nato have been adopted.

In the flying spot method, spot light is applied to the surface of an object to be inspected, and the specularly reflected light is used to inspect whether or not there is a defect on the surface of the object to be inspected.

For example, when there is a defect on the surface of the object to be inspected, the specularly reflected light is scattered due to the defect] 7. Since the amount of light entering the light receiving detection system decreases, it becomes clear that there is a defect on the surface of the object to be inspected. do.

The flying image method inspects the surface of the object to be inspected for defects by scanning the surface of the object to be inspected with white light in the field of view of a camera or the like.

1. Problems to be Solved by the Invention In the flying spot method, a light source that emits monochromatic light, generally a He-Ne laser light source, is used.
With such laser light, it is disadvantageous to detect color changes.

For example, if a defect on the object to be inspected does not cause large scattering, the defect cannot be detected.

In order to deal with this, the invention disclosed in Japanese Patent Application Laid-Open No. 55-129733 emits a plurality of laser beams from a light irradiation system toward an object to be inspected, and separates the reflected light from the object by a light receiving system. However, when using such means, the apparatus configuration becomes complicated.

In the case of the flying image method, white light is used as a light source, so by monitoring the intensity of reflected light over the entire visible light range, it is possible to distinguish color differences to some extent, but the accuracy depends on the field of view of the camera. , the camera field of view must be narrowed to identify small defects, which increases cost.
Space issues arise.

In view of the above-mentioned problems, the present invention provides a method for detecting defects of an object to be inspected whose surface layer portion and lower layer portion are made of different materials by optical means, regardless of the size of the defect.
The purpose of this invention is to provide a method by which such defects can be detected without omission using economical equipment.

Means for Solving Problem 1 In order to achieve the intended purpose, the present invention irradiates light through a light irradiation system onto the surface of an object to be inspected, the surface layer and the lower layer of which are made of different materials. , a method of detecting defects in the object by detecting reflected light from the surface of the object with a light receiving detection system, the wavelength at which the difference in reflectance between the surface layer portion and the lower layer portion is 0.8 or more. The light irradiation system is characterized in that the surface of the object to be inspected is irradiated with light, and the reflected light from the surface of the object to be inspected is made to enter the light reception and detection system.

1 Effect 1 The method of the present invention irradiates the surface of an object to be inspected with light and detects the reflected light from the surface of the object to be inspected to detect whether or not there is a defect in the object to be inspected. The object to be inspected is irradiated with light having a wavelength in which the difference in reflectance between the surface layer portion and the lower layer portion is 0.8 or more.

During the above inspection, if there are no scratches on the surface of the object to be inspected that is receiving the irradiation light, the reflected light from the surface enters the light reception detection system at a nearly constant level, and the light reception level by the light reception detection system increases. Since no fluctuation occurs, it is found that there are no defects on the surface of the object to be inspected due to this light receiving state.

During the above inspection, if there is a scratch on the surface of the object to be inspected and the lower layer is exposed than the scratch, the light reflected from the surface layer and the light reflected from the scratch (lower layer exposed surface) Since the reflectance of the received light is different, a peculiar fluctuation occurs in the level of light received by the light receiving and detecting system.

Therefore, when a change occurs in the level of light received by the light detection system, it becomes clear that there is a defect on the surface of the object to be inspected.

In the case of the method of the present invention, the presence or absence of defects in the object to be inspected is determined by the optical means described above, and the irradiation light at that time has a predetermined reflectance characteristic for the surface and lower layers of the object to be inspected. Therefore, when there is no defect on the inspected object, there will be a large difference in the amount of specularly reflected light when there is a defect. Therefore, even if the surface defect of the inspected object is a minute scratch, it will not be overlooked. It can be detected without

In the case of the method of the present invention, only one type of light source is required to obtain the above-mentioned irradiation light, and the light irradiation system, light reception detection system, etc. can be simplified, so that the complexity of the equipment can be avoided and the cost efficiency can be achieved. Can be done.

"Examples" Examples of the method of the present invention will be described below with reference to the drawings.

FIG. 1 shows a flying spot method as an embodiment of the method of the present invention.

The light irradiation system 10 in FIG.
The laser light source emits argon laser light.

The light reception and detection system 20 in FIG. 1 converts changes in the amount of reflected light into changes in electromotive force using a detection element, amplifies the electrical signal with a preamplifier, and sends the amplified signal to a control system etc. as an output signal of the sensor. It has become.

The inspected object 30 in FIG. 1 includes a surface layer 31 and a lower layer 32, and the surface layer 31 is made of a white silver plating film.
The lower layer portion 32 is made of a reddish copper plate.

In FIG. 1, when inspecting the surface of an object to be inspected 30 traveling in the direction of the arrow, the laser beam emitted from the light emitting part 11 of the light irradiation system 10 is irradiated onto the surface of the object to be inspected by the rotating polyhedral mirror 12. and optically scan in the width direction.

The irradiation light is reflected by the surface of the object to be inspected 30 and enters the light reception detection system 20, and the light reception detection system 20 receives the reflected light.
detects whether there is a defect on the surface of the object to be inspected 30 based on the amount of reflected light.

In general, the reflectance of the silver surface (surface layer 31) shows a constant value over the entire visible light range, as shown by the dotted line in Figure 2, but the reflectance of the copper surface (lower layer 32) shows a constant value as shown by the solid line in Figure 2. As shown, it is largely wavelength dependent within the visible light range.

In the method of the present invention, as described above, since light of a wavelength with which the difference in reflectance between the surface layer (silver) 31 and the lower layer (copper) 32 is 0.8 or more is used, the surface layer of the object to be inspected 30 is (Silver) 3
1 has a defect 33, and from the defect 33 the lower layer (copper) 3
2 is exposed, the amount of specularly reflected light that is reflected at the defective portion and enters the light receiving and detecting system 20 decreases as shown in FIG. 3.

The decrease in the amount of specularly reflected light in Figure 3 is a detection signal,
It can be taken out at about three times the size of the conventional one.

Therefore, when there is a defect on the surface of the object to be inspected 30, the defect can be detected by the light receiving detection system 20.

In addition, even if the difference in reflectance mentioned above is 0.8 or less, "
A signal difference between "no defect" and "defect present" can be obtained, but considering the noise of the entire defect detection means, the reflectance difference is 0.8
Below, a sufficient detection signal cannot be obtained, and therefore it is essential to set the reflectance difference to 0.8 or more.

In the embodiments described above, the surface layer portion 31. The wavelength range for selecting light having a reflectance difference of 0.8 or more with respect to the lower layer portion 32 is visible light from 40 On+s to 580 nm.

As a laser light source for obtaining a predetermined irradiation light, in addition to argon laser light (input -515n), helium-neon laser light (input -544n), helium-cadmium laser light (input = 442nm), etc. can be used. .

FIG. 4 shows a flying image method as another embodiment of the method of the present invention.

In FIG. 4, the light irradiation system 1O includes a laser light source (white light source), and the light reception detection system 20 includes a CCD camera connected to a control system and the like.

Furthermore, in FIG. 4, in order to bring the light from the light source closer to monochromatic light, a bandpass filter 40 that transmits only light within a wavelength range of 400 nm to 580 nm is placed on the light irradiation system 10 side or the light reception detection system 20. has been done.

The inspected object 30 in FIG. 4 includes a surface layer portion 31 and a lower layer portion 32 similar to those described above.

In FIG. 4, when inspecting the surface of the object to be inspected 30 traveling in the direction of the arrow, the surface of the object to be inspected is irradiated with light from the light irradiation system IO, and the reflected light reflected from the surface of the object to be inspected is The light receiving detection system 20 detects whether or not there is a defect on the surface of the object 30 to be inspected.

Also in this embodiment, if there is a defect on the surface of the object to be inspected 30, the defect is detected based on the difference in the amount of specularly reflected light, as in the previous embodiment.

In each of the above-mentioned embodiments, an inspection example was described in which the inspected object 30 was a silver-plated copper plate, but plated products including bar-shaped, plate-shaped, coated products, ground processed products, etc.
Surface defects of various objects to be inspected, such as laminate products, whose surface layer portion and lower layer portion are made of different materials can also be detected in the manner described in each embodiment.

Effects of the Invention J As explained above, when using the method of the present invention, the light irradiation system emits light of a wavelength such that the difference in reflectance between the surface layer and the lower layer of the object to be inspected is 0.8 or more. The surface of the inspected object is irradiated with light, and the reflected light from the surface of the inspected object is incident on the light receiving and detection system to detect defects on the inspected object, so not only large defects but also minute defects can be detected. The equipment can be economical because the detection can be performed without any need for detection, and because the predetermined detection can be performed using one type of light source.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of water saving in an embodiment of the detection method of the present invention;
Figure 2 shows the relationship between the reflectance of silver and copper and wavelength. 3A is a diagram showing the detection results of the method of the present invention, and FIG. 4 is an explanatory diagram of another embodiment of the detection method of the present invention in which water is saved. 10...Light irradiation system 20...Light reception detection system 30.1...Inspected object 3I...Upper part of the inspected object, 32... ,...The lower part of the object to be examined. 33: Defect of inspected object ・Agent Patent attorney Yoshinobu Saito Figure 1 Figure 2 Wavelength (gate)

Claims (4)

[Claims] (1) Irradiating light through a light irradiation system to the surface of an object to be inspected whose surface layer portion and lower layer portion are made of different materials, and detecting the reflected light from the surface of the object by a light receiving detection system,
In the method for detecting defects in the object to be inspected, the surface of the object to be inspected is irradiated with light having a wavelength in which the difference in reflectance between the surface layer portion and the lower layer portion is 0.8 or more, and A method for detecting defects in an object to be inspected, characterized in that light reflected from the surface of the object to be inspected is incident on the light receiving and detecting system. (2) A method for detecting defects in an object to be inspected according to claim 1, wherein the surface of the object to be inspected is irradiated with light, the surface layer of which is white and the lower layer of which is red. (3) A defect detection method for an object to be inspected according to claim 1 or 2, wherein the irradiation light comprises visible light having a wavelength of 400 nm to 580 nm. (4) A method for detecting defects in an object to be inspected according to claim 1, 2, or 3, wherein the irradiation light is any one of argon laser light, helium-neon laser light, and helium-cadmium laser light. .