JPH0315972B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a surface defect inspection device, and more particularly to an improvement in a device for optically inspecting a surface to be inspected consisting of a rotation locus surface for defects.

BACKGROUND ART Inspecting surface defects on the desired inspection surface of an object to be inspected is one of the main inspection items in the inspection process of various processed parts.It is one of the main inspection items in the inspection process of various processed parts. It is also suitable for inspecting scratches, etc. during processing. In particular, it is required to reliably detect such surface defects for parts that require good surface finishing accuracy, such as the rubbing surfaces of seal valves in hydraulic pressure equipment. inspection equipment has been put into practical use.

For example, as a recent inspection device, JP-A-16593
As shown in , a device that uses laser light to inspect surface defects has been proposed. In this conventional device, for example, in order to inspect surface defects in a thin metal wire, a laser beam is applied to the thin metal wire that is the object to be inspected. It is utilized that the diffraction pattern generated during orthogonal scanning exhibits a specific pattern according to surface defects. In other words, when there is a defect on the surface of a thin wire, the central peak value decreases and the peripheral light increases due to laser beam diffraction, and this is achieved by arranging photoelectric conversion elements according to the shape of the diffraction pattern. The presence or absence of surface defects is inspected based on the characteristics of the diffraction pattern by detecting the movement of the point of the strongest light intensity which is detected electrically.

According to the conventional device described above, two rows of photoelectric conversion elements arranged corresponding to the diffraction pattern are placed close to the thin metal wire that is the object to be inspected, and are extremely sensitive to minute defects on the surface of the thin wire. Although it exhibits good sensitivity, it has the disadvantage that it is not possible to reliably inspect the entire surface to be inspected for various processed parts that have a relatively wide inspection surface.

For example, when inspecting the valve surface of intake and exhaust valves used in vehicle engines, there are various surface defects such as pinholes, scratches, missing parts, and black spots. However, in the conventional apparatus described above, the laser inspection light is often asymmetrically scattered or the diffracted light is not sufficient, and the inspection accuracy cannot be increased to a level that is satisfactory for practical use.

In addition, in the above-mentioned intake and exhaust valves, the surface to be inspected has a truncated conical shape, and defects such as the valve width direction indicated by the ridge length not being a predetermined value or parts processing errors can be detected using the above-mentioned diffraction pattern. There were problems that could not be addressed through testing.

As other conventional inspection devices, various optical surface inspection devices have been proposed that use inspection light with monochromatic sharp directional characteristics such as laser light, but all of these devices simply detect specular reflection from the surface to be inspected. However, it is not possible to expect satisfactory inspection results for objects to be inspected that require high surface accuracy, such as valve surfaces.

Purpose of the Invention The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to improve the surface defects of an inspected object having an inspected surface consisting of a rotation locus surface, such as a vehicle intake/exhaust valve. An object of the present invention is to provide an improved surface defect inspection device capable of inspecting accurately and quickly.

Composition of the Invention In order to achieve the above object, the present invention inspects surface defects using both specular reflection and diffused reflection from a non-inspection surface, and also examines the inspection width of the inspection light and the reflection width obtained by specular reflection. The feature is that defects or parts machining errors in the width direction of a surface to be inspected having a rotation locus surface can be simultaneously inspected by comparing with the rotation trajectory surface.

Embodiments Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

In FIG. 1, an intake/exhaust valve for a vehicle engine is used as an object to be inspected 10, and a surface defect on the inspection surface 10a, which is an airtight sealing surface, is inspected.As is well known, this inspection surface 10a is It has a truncated conical shape.

The object to be inspected 10 is placed and held on a rotary stage 12, and the rotation axis (x-axis) of the rotary stage 12 is provided to coincide with the rotation locus axis of the surface to be inspected 10a. In practice, the rotary stage 12 has a protrusion or a positioning claw for positioning the object 10 on at least a part of its surface, and by simply placing the object 10 on the stage 12, it is possible to It is configured so that a match is taken.

A gear 14 is fixed below the rotary stage 12, and a worm 18 fixed to the main shaft of a motor 16 meshes with the gear 14. Rotating stage 1
2, the object to be inspected 10 can be rotated at a predetermined speed.

On the other hand, the surface 10a to be inspected is irradiated with inspection light 100 for optical surface defect inspection of the surface 10a,
In the present invention, the inspection light 100 is a laser beam having monochromatic sharp directional characteristics, and this laser beam is scanned at a predetermined period perpendicular (y-axis) to the rotation axis (x-axis) and parallel to the rotation axis (x-axis). irradiated.

That is, in the embodiment, a laser beam is used as the monochromatic, sharply oriented thin beam, and this laser beam is output from a laser oscillator 20, which is then passed through an optical deflector 22 such as a galvanometer mirror and a light projecting lens 24.
The surface to be inspected 10a is irradiated with a narrow beam of light that is scanned perpendicularly and parallel to the rotation axis described above.

The optical deflector 22 performs a well-known periodic deflection action, and its deflection period _T1 is controlled by the oscillation period of the oscillator 26, and the sector beam from the optical deflector 22 is collimated by the projection lens 24. converted into light rays.

The inspection light scanning mechanism consisting of the optical deflector 22 and the oscillator 26 has a deflection period T ₁ that is sufficiently smaller than the rotation period T ₂ of the rotary stage 12. A light scanning locus indicated by reference numeral 200 is drawn on the surface of the surface 10a, so that the inspection light 100 is scanned over the entire surface of the surface to be inspected 10a without omission.

In the present invention, the scanning width of the inspection light 100 by the inspection light scanning mechanism is set to a size that sufficiently covers the inspected surface 10a, and this scanning width is arbitrarily adjusted depending on the shape or size of the inspected object 10. It is possible.

As is well known, the inspection light 10 on the surface to be inspected 10a
When the surface 10a to be inspected has no surface defects, the main energy of the 0 reflection travels in a direction symmetrical to the normal to the surface 10a, that is, in a regular reflection direction. Therefore, in the present invention, in order to electrically detect this specular reflection, specular reflection detection means 28 is provided in the specular reflection direction, and the specular reflection detection means is formed by, for example, a photoelectric conversion element. .

Further, in the present invention, a diffused reflection detection means is provided to detect diffused reflection such as diffraction or scattering that occurs when a defect exists on the surface to be inspected 10a. A pair of optical fiber bundles 30a with one end open near the surface to be inspected 10a on both sides of the reflection,
30b, and a photodetector 32 made of a photoelectric conversion element is provided at the other end of both optical fiber bundles 30. Therefore, if a defect exists on the surface to be inspected 10a, this diffused reflection detection means allows the photodetector 32 to reliably detect the diffused reflection caused by the defect, such as diffraction or scattering, as an electrical signal. .

Both of the reflection detection means each have a surface to be inspected 10a.
It is configured to have a detection width that can sufficiently capture specular reflection and diffuse reflection from the inspection light 100 in the entire scanning area of the inspection light 100.
Specular reflection and diffused reflection can be detected as electrical signals for each deflection scan of zero.

Therefore, the presence or absence of a surface defect is detected as an electrical signal by these regular reflections and diffuse reflections, and both signals are converted into digital signals by signal processing circuits 34 and 36 (in the embodiment, for example, an AD converter), respectively. A defect determination circuit 40 comprising these signal processing circuits 34, 36 and the OR circuit 38 detects the presence or absence of a defect on the surface to be inspected 10a based on the regular reflection and diffuse reflection signals. be done.

In the present invention, further, the surface to be inspected 10a
A width inspection circuit 42 is provided to determine defects in the width direction or component processing accuracy, and the width inspection circuit 42 in the embodiment is composed of a comparison circuit, and is configured to detect deflection scanning signals obtained from the oscillator 26 of the inspection light scanning mechanism described above. and the specular reflection signal obtained from the specular reflection detection means 28, and if the width of specular reflection is smaller than a predetermined value with respect to the deflection scanning width of the inspection light 100 determined by the inspection light scanning mechanism, the width is determined. Detect defects.

Both the detection signals of the defect discrimination circuit 40 and the width inspection circuit 42 are supplied to a display section 44, and
The test results will be displayed.

The embodiment of the present invention has the above configuration, and its operation will be explained below using the time chart shown in FIG.

First, the operation of determining the presence or absence of a defect on the surface to be inspected 10a by the defect determining circuit 40 is shown in FIGS. 2A to 2E. FIG. 2A shows an enlarged optical scanning trajectory 200 of the inspection light 100 with respect to the surface to be inspected 10a, and during the deflection period _T1 , the inspection light 100 sufficiently exceeds the width W of the surface to be inspected 10a. Deflection scanning is performed with a scanning width of When such a deflection scan is performed, the specular reflection detection means 28 and the photodetector 32 of the diffuse reflection detection means obtain detection signals as shown in FIG. Indicates that there are no defects. That is, in a state where there is no defect, most of the inspection light 100 is specularly reflected at the surface to be inspected 10a, and as a result, the specular reflection detection signal 102 shows that the light scanning locus 200 is aligned with the surface to be inspected 10a.
The signal 104 maintains a substantially constant high level while crossing 0a, while the diffusely reflected signal 104 maintains a substantially constant low level.

On the other hand, if there is some kind of defect on the surface to be inspected 10a, diffuse reflection occurs at the defective part,
Specular reflection 102' as shown in FIG. 2D and E.
and the diffused reflection 104' exhibit signal changes a and b corresponding to the defect, respectively.

Therefore, by electrically processing these signal changes a and b in the defect discrimination circuit 40, it is possible to reliably detect the presence or absence of a defect on the surface to be inspected 10a.

According to the present invention, not only regular reflection but also diffuse reflection on the surface to be inspected 10a is detected at the same time, so that all defects can be reliably detected regardless of differences in reflection characteristics depending on the type of defect. In other words, although Fig. 2 D and E show a state in which the defect appears in both specular reflection and diffuse reflection detection signals, some types of defects appear only in either specular reflection or diffuse reflection. There are some reflection characteristics that do not appear, and even in such cases,
According to the present invention, since the defect discrimination circuit 40 detects defects for both specular reflection and diffuse reflection, it is possible to perform extremely reliable defect discrimination without making such defect detection errors. It is possible.

In the present invention, surface defects on the surface to be inspected 10a are detected not only by reflection but also by monitoring the specular reflection width in the width direction of the surface to be inspected 10a, thereby detecting defects in the width direction mainly caused by underfilling, black spots, etc. Defects, dimensional errors, and any other errors in the width direction can be detected extremely well, and this state is shown in Figure 2 F~
It is shown in K.

That is, when the widthwise length of the surface to be inspected 10a is shortened due to a black spot or other dimensional error or defect, the detection signal from the specular reflection detection means 28 has a signal width as shown in FIG. 2F. is shortened (1
02″) This can be detected electrically.

In the present invention, a deflection scanning signal 106 (FIG. 2G) is outputted from the oscillator 26 of the inspection light scanning mechanism for comparison with the signal in the width direction, and its pulse width is shown in FIG. 2H. It is counted by clock pulses. On the other hand, the specular reflection detection signal 102'' of FIG. 2F is converted into a waveform as shown in FIG. H and J are compared with each other, and the output thereof is detected as shown in FIG. , thereby making it possible to reliably identify width defects.

Therefore, according to the present invention, it is possible to superimpose and distinguish not only the regular reflection of the surface to be inspected but also the diffused reflection, and the width of the surface to be inspected can be inspected at the same time, making it possible to perform extremely high-precision inspection. It becomes possible.

In the above embodiment, the detection signals of both reflection detection means are converted into digital signals by the signal processing circuits 34 and 36, and the signal processing circuit 3 is used as the defect discrimination circuit 40 as shown in FIG.
4 and 36, both signal outputs are taken out by an OR circuit 38, and in FIG.
Differentiation circuit 142 and window comparator 144
including a specular reflection detection signal 102 shown in FIG.
and the diffused reflection detection signal 104 can be electrically processed to detect defects.

Effects of the Invention As explained above, according to the present invention, a surface to be inspected consisting of a rotation trajectory surface is deflected and scanned over a predetermined width using a monochromatic sharp directional inspection light, and both specular reflection and diffuse reflection based on this inspection light are detected. The defects on the surface to be inspected are determined by detecting them, and the width of the surface to be inspected is simultaneously inspected by comparing the deflection scan of the predetermined width with the detection width of the specular reflection signal. Since the entire surface defect inspection is performed, it has the advantage of being able to perform surface inspection with extremely high inspection accuracy and stability compared to conventional devices.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing a preferred embodiment of the surface defect inspection device according to the present invention, FIG. 2 is a time chart explaining the operation of FIG. 1, and FIG. 3 is a defect discrimination circuit in FIG. 1. FIG. 3 is a block circuit diagram showing another embodiment of the invention. 10... object to be inspected, 10a... surface to be inspected, 12
...Rotating stage, 20...Laser oscillator, 22...
... Optical deflector, 26 ... Oscillator, 28 ... Regular reflection detection means, 30a, 30b ... Optical fiber bundle, 32
...Photodetector, 40...Defect discrimination circuit, 42...
Width inspection circuit, 100...Test light, 102...Specular reflection detection signal, 104...Diffuse reflection detection signal, 200
...Light scanning trajectory.

Claims (1)

[Claims] 1. A rotary stage on which a test object having a surface to be inspected consisting of a rotation trajectory surface is placed rotatably about the axis of the rotation trajectory surface, and a monochromatic and sharply oriented thin beam of light directed toward the surface to be inspected. an inspection light scanning mechanism that scans perpendicularly to the rotation axis of the rotary stage and in parallel with a predetermined width that exceeds at least the surface to be inspected; and specular reflection detection means that detects specular reflection of the inspection light from the surface to be inspected. a diffused reflection detection means for detecting diffused reflection of the inspection light by the surface to be inspected; and a defect determination circuit for electrically processing the detection signals of both the detection means to detect the presence or absence of a defect from the reflection characteristics of the surface to be inspected; A surface defect inspection apparatus comprising: a width inspection circuit that compares the detection signal of the specular reflection detection means with the scanning signal of the inspection light scanning mechanism to inspect the width of the surface to be inspected.