JPS63206638A - Inspection of surface flaw - Google Patents

Abstract

PURPOSE:To simultaneously detect various kinds of flaw parts different in a reflecting characteristic, by superposing a plurality of illumination conditions fitted to the respective characteristic of plural kinds of the flaw parts to be detected. CONSTITUTION:The surface W' to be inspected of an object W to be inspected contains flaw parts A, B different in a reflecting characteristic, and the angle thetaA of illumination fitted to the detection of the flaw part A and the angle thetaB of illumination fitted to the detection of the flaw part B are respectively set as the illumination conditions of light sources 1a, 1b. For example, when the flaw parts A, B respectively have the reflecting characteristics shown by the S/N ratio shown in a drawing, it is pref. not only to set the angle thetaA of illumination to the flaw part A to 70 deg. or more but also to set the angle thetaB of illumination to the flaw part B to 20 or less. Then, the flaw parts A, B are detected using illumination light set by superposing a plurality of the illumi nation conditions fitted to the reflective characteristics of various kinds of the flaw parts A, B to be detected different in a reflecting characteristic. At this time, the reflected lights from the flaw parts A, B are received by one television camera to make it possible to simply detect the flaws.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a non-contact optical surface defect inspection method.

[Conventional technology]

In general, reflected illumination means are used to detect surface defects on products made of materials that do not transmit light, and in particular, in non-contact optical surface defect inspection methods, illumination means that match the surface texture of the surface to be inspected are used. This is important for improving defect detection ability.

Conventionally, when inspecting a very smooth flat surface such as a magnetic disk, a spot light is applied to the surface to be inspected, and the specularly reflected light is received by the image sensor of a television camera. Inspection methods using specular reflection methods such as flying spot methods have been put into practical use.

However, with this method, it is necessary to eliminate or keep the change in the amount of reflected light in normal areas other than defective areas to be extremely small in order to improve the defect detection ability. It is difficult to apply this method to the inspection of objects to be inspected that have curved surfaces and may also include curved surfaces, as the spread and scattering of reflected light due to surface roughness impedes defect detection. A diffuse reflection method has been devised.

In this diffuse reflection method, the optical system is configured so that it does not receive specularly reflected light from normal parts of the surface to be inspected, and defects are detected by the presence or absence of specularly reflected light from defective parts or by the increase or decrease in diffusely reflected light. It is something. According to this method, the permissible range of the optical axis is expanded, making it easier to set conditions, the configuration of the light receiving system is simplified, and the amount of reflected light is greatly reduced due to surface roughness in areas other than the defective area. Effects such as reduction in size are also observed.

[Problem that the invention seeks to solve]

In surface defect inspection using the diffuse reflection method, it is important to set lighting conditions that match the reflection characteristics of the defect so that the best amount of reflected light can be obtained from the defect. Regarding defects, it is difficult to accurately detect defects, identify the type of defects, and judge whether the product is good or bad using only one illumination condition. For this reason, for example, as shown in FIG. 8, when trying to detect two types of defective parts (a) and (b) (not shown) that have different reflection characteristics, the illumination condition θ1 that matches the reflection characteristics of the defective part (a)
Using the light projecting part (11) set with the following conditions and the light projecting part (12) set with the illumination condition θ2 that matches the reflection characteristics of the defective part (b), the object to be inspected is illuminated by the light emitted from the light projecting part (11). Thing (W)
A television camera (1
The defective part (a) is detected by receiving the light with the image sensor (3), and the reflected light from the surface to be inspected (w') by the light emitted from the light projector (12) is detected by the television camera (14). The defective portion (b) can be detected by receiving light with an image sensor. However, with this configuration, the TV camera (
13) There is a problem in that the entire inspection device including (14), processing device (15), etc. becomes large-scale and complicated.

In view of the above problems, the present invention provides a method for efficiently and reliably detecting a plurality of types of defective parts having different reflection characteristics.

[Means for solving problems]

That is, the surface defect inspection method according to the present invention uses irradiation light that is set by superimposing a plurality of illumination conditions that match the respective reflection characteristics of a plurality of types of defect parts with different reflection characteristics to be detected, The present invention is characterized in that the plurality of types of defective parts are detected.

[For production]

The method of the present invention can be carried out by simultaneously illuminating the surface to be inspected with a plurality of irradiation lights whose illumination conditions are set to match the reflection characteristics of each of the plurality of types of defects to be detected. Defects can be easily detected by receiving reflected light from a plurality of types of defective parts with a single television camera or the like.

〔Example〕

Hereinafter, the method of the present invention will be explained in more detail based on the illustrated embodiments.

In the first embodiment shown in FIG. 1, (11) is an object to be inspected made of a black elastic polymer used as a sealing material;
(la) and (Ib) are light sources such as tungsten lamps that project light onto the object to be inspected (W), and (2) is a television camera that receives reflected light from the object to be inspected (W).

(3) is the image information (512X) from the TV camera (2).
512, that is, resolved into 282,144 pixels). The surface to be inspected (-°) of the object to be inspected (11) includes defective parts (A) and (B) (not shown) having different reflection characteristics, and the light source (1a) is suitable for detecting the defective part (A). illumination angle θA, and light source (l
In b), an illumination angle θB suitable for detecting the defective portion (B) is set as the illumination condition.

For example, the defective part (A) (B) is I! As is clear from the figure, if each has the reflection characteristics shown in the S/N ratio in the g2 figure, the defective part (A) □
It is preferable that the illumination angle θA for the defective portion (B) is 70° or more, and the illumination angle θB for the defective portion (B) is preferably 20° or less. Figure 3 shows the detected image of the defective part (A), and Figure 4 shows the detected image of the defective part (B).
is an image obtained when the illumination angle is 15°, [mouth] is an illumination angle of 70°, and [c] is an image when simultaneous illumination is performed from both angles. In other words, in this example, the detection effect is large at an illumination angle of 70° for detecting the defective part (A), and at an illumination angle of 15° for detecting the defective part (B), and simultaneous illumination from both angles can detect the defective part ( It is clear that both A) and (B) can be detected well.

Next, in the first embodiment, different illumination conditions (angles)
In contrast, the second embodiment shown in FIG. 5 uses a plurality of light sources to set the irradiation light (
L) is divided into irradiation lights (La) and (Lb) at different angles by a combination of a half mirror (4) and a mirror (5) for illumination.
The embodiment similarly has a configuration in which irradiation light from one light source (1) is obtained by using an optical fiber (6) having branch parts (8a) and (llb) to obtain irradiation light (La) and (Lb) at different angles. That is.

Note that in order for the method of the present invention to work, it is necessary that optical superposition of the defect images work. Therefore, as shown in Fig. 7, the defect image [A] detected under the condition of illumination angle OA and the defect image [mouth] detected under the condition of illumination angle θB are divided into brightness for each corresponding pixel. A composite image [C] is synthesized by image processing and addition, and both angles θ are
As a result of comparing the defect image [2] detected by the method of the present invention that performs simultaneous illumination from A and θB with this composite image [C], it was confirmed that optical superposition of the defect images was established.

In the illustrated embodiment, the television camera (2) is arranged in a direction perpendicular to the surface to be inspected (ill'), but this is not particularly limited.

〔Effect of the invention〕

As explained above, the surface defect inspection method of the present invention detects multiple types of defects having different reflection characteristics by superimposing multiple illumination conditions that match the reflection characteristics of multiple types of defects to be detected. can be detected simultaneously,
An inexpensive and high-performance inspection machine can be provided without complicating the device.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing the first embodiment of the present invention;
The figures are graphs showing the reflection characteristics of defective parts, Figures 3 and 4.
The figures show detected images of defective parts with different reflection characteristics, each figure [A] has an illumination angle of 15°, [mouth] has an illumination angle of 70°,
[C] shows the simultaneous illumination from inside angles, FIGS. 5 and 6 are schematic configuration diagrams showing other embodiments, and FIG.
Figure [A] is the detected image at illumination angle θA, [mouth] is the detected image at illumination angle θB, and [c] is [A] and [mouth].
[2] is a detected image obtained by simultaneous illumination from illumination angles θA and θB, and FIG. 8 is a schematic diagram showing the conventional method. (1) (la) (Ib) Light source (2) Television camera (
3) Processing device (4) Half mirror (5) Mirror
(6) Optical fiber (L) (La) (Lb) Irradiation light (W) Test object (
w゛) Surface to be inspected Ir-1'-v-Ichinomai NS Figure 5 Figure 6 Procedures Amendment (Format) May 28, 1985 Commissioner of the Patent Office Kuro 1) Akio Tono 1, Display of the case Patent Application No. 39072, filed in 1982 2, Name of the invention Surface defect inspection method 3, Person making the amendment Relationship to the case Patent Applicant's name (name) 4, Agent Address: 105, 1982 3 June 31st, 6, column ``4. Brief description of drawings'' of the specification subject to amendment and drawing ■ ``In the detected image'' in line 6 on page 11 of the specification was changed to ``orthographic drawing showing the detected image.'' So, I'll correct it to ``. ■ "Detected images" on page 11, line 13 of the specification will be corrected to "orthographic projection drawings showing each detected image." (2) Of the drawings originally attached to the application for drawing amendment, Figures 3, 4, and 7 will be reprinted as shown in the attached sheet (no changes to the contents). that's all

Claims (1)

[Claims] In a non-contact optical surface defect inspection method, a defective part is detected by irradiating light onto a surface to be inspected of an object to be inspected and electrically detecting the amount of light reflected from the surface to be inspected using an image sensor, Detecting the plurality of types of defective parts to be detected using irradiation light set by superimposing a plurality of illumination conditions that match the respective reflection characteristics of the plurality of types of defective parts having different reflection characteristics to be detected. Characteristic surface defect inspection method.