JPH01107103A - Surface flaw inspection apparatus - Google Patents

Abstract

PURPOSE:To rapidly and accurately inspect a different kind of uneven flaws on a surface to be inspected at once, by photoelectrically converting the reflected beam from the surface to be inspected by a regular reflected beam detection means and an irregular reflected beam detection means. CONSTITUTION:The laser beam L from an inspection beam supply means 20 is allowed to irradiate a surface 22 to be inspected as inspection beam and received by the regular reflected beam detection means 24 arranged to a regular reflected beam path and the irregular reflected beam detection means 26 having an aperture part 26a provided thereto arranged between said detection means 34 and the surface 22 to be inspected. These means 24, 26 are composed of photoelectric converters and supply the electric signals respectively corresponding to the receiving beams to an operational processing means 28. By the comparison of the respective regular and irregular reflected beams with reference values, desired qualitative discrimination is performed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a surface defect inspection device, particularly for non-contact inspection of defects on metal or plastic painted surfaces and other smooth surfaces of automobiles, home appliances, etc. using inspection light. The present invention relates to a possible improved surface defect inspection device.

[Conventional technology]

Defects on the smooth surfaces of industrial products reduce the appearance quality of these products, and depending on the type of product, may lead to deterioration of important functional properties such as rust prevention properties, insulation properties, or conductive properties. These surface defects must be closely inspected.

Conventionally, the most common defect inspection has been performed by an inspector visually observing the object to be inspected and inspecting for various surface defects. However, such general inspection methods require the inspectors to be highly skilled, and even experienced inspectors have problems such as oversights, misinterpretations, and inspector fatigue. Defect inspection is shifting to non-contact equipment inspection using light reflection.

The difficulty in conventional equipment inspection of such surface defects is that surface defects include an extremely wide range of defect types for each inspection target, and typical examples of these defects include scratches (width of 5 μm or less). , butsu (diameter 1111
0.01 or less), rough skin or waviness (wavelength of 1-10 mm), uneven gloss or roughness (wavelength of 0.1 mm or less), etc., and it is possible to obtain a device that can easily and easily inspect these various defects at once. It was extremely difficult.

FIG. 4 shows the principle of a surface defect inspection device that uses inspection light such as a laser beam, in which a laser beam L irradiated from a laser oscillator 10 is supplied to the surface to be inspected 12, and the specular reflection at this time is The light LO is received by the photoelectric sensor 14 to obtain an electrical signal.

According to the principle of the conventional defect inspection apparatus shown in FIG. Since the photoelectric conversion output changes, it is possible to determine whether the defect on the surface to be inspected 12 is acceptable or not based on this output change.

[Problems to be Solved by the Invention] However, with such a conventional device using a simple inspection light, it is not possible to simultaneously inspect the various defects described above having different sizes or flaw characteristics. There was a problem.

That is, in FIG. 4, considering the defect detection sensitivity, in order to improve this sensitivity, the beam diameter of the laser beam L must be made as small as possible.

An improved conventional device for reducing the beam diameter is shown in FIG. 5, in which a convex lens 16 with a short focal length is provided in the optical path of the laser beam L. As a result,
Even if the beam diameter of the laser beam L is large, the surface to be inspected 12
The beam is focused on the surface, making it possible to significantly reduce the inspection beam diameter, thereby making it possible to improve detection sensitivity.

However, in practice, the above-mentioned convex lens 16 needs to maintain a fixed position with high precision with respect to the surface to be inspected 12 due to its optical characteristics, and in practice, it is extremely difficult to easily obtain such a focusing device. Ta.

Furthermore, in the conventional apparatus shown in FIGS. 4 and 5, only specularly reflected light is detected, and the diffused reflection on the surface of the surface to be inspected 12 cannot be correctly received, so it is not possible to inspect all defects. The problem was that there was no.

FIG. 6 shows a conventional device in which a beam expander 18 is used for focusing instead of the convex lens 16, and the laser beam L
This makes it possible to reduce the beam diameter.

However, in this conventional apparatus, although the arrangement of the beam expander 18 is facilitated, diffraction increases as the beam diameter is reduced, and there is a limit to the reduction in the beam diameter.

As mentioned above, the actual size of the conventional laser beam diameter is 0.511 Il when using a helium neon laser or semiconductor laser with a wavelength of 0.7 to 0.8 μm.
The extent was the limit.

Therefore, with such a laser beam, it is possible to inspect particles smaller than 1 nm with good sensitivity, but
On the other hand, there was a problem in that it was not possible to inspect flaws with a width of around 5 μm.

Furthermore, as mentioned above, when the surface to be inspected is a painted surface, most of the irradiated beam L is the specularly reflected beam LO.
As a result, changes in the specular reflection beam due to other defects such as uneven gloss can only receive blood stains, and as a result, there is a problem in that it is unsuitable for inspecting uneven gloss.

As described above, with the conventional apparatus, it is extremely difficult to obtain an apparatus that can inspect various surface defects having different characteristics at the same time.

The purpose of the present invention is to be able to simultaneously inspect uneven defects of various sizes that exist on the surface to be inspected as described above, and in particular to easily inspect scratches, bumps, rough skin, uneven gloss, etc. that exist on painted surfaces. An object of the present invention is to provide an improved surface defect inspection device.

Means for Solving Problems] In order to solve the above-mentioned conventional problems, the present invention focuses on the fact that there are regular reflections and diffuse reflections in the reflection of inspection light, and uses different photoelectric detection means to detect both. It is characterized by detecting

That is, when a scratch is irradiated with inspection light such as a laser beam, a diffraction phenomenon occurs in a direction perpendicular to the longitudinal direction of the scratch, and if there is rough skin (the wavelength of the unevenness is small and the amplitude is large),
It is known that the deviation of specular reflection increases when the direction of the specular reflection beam changes and there is uneven gloss (change in roughness).In response to these optical characteristics, two types of photoelectric detection In this embodiment, a specular reflection light detection means and a diffused reflection light detection means are provided.

More specifically, the present invention includes an inspection light supply means for irradiating inspection light onto a surface to be inspected, and a specular means for receiving regular reflection light reflected by the surface to be inspected, converting it into an electrical signal, and outputting it. a reflected light detecting means; a diffusely reflected light detecting means for receiving the diffusely reflected light including the diffusely reflected light and non-zero-order diffracted light reflected from the surface to be inspected, converting it into an electrical signal and outputting it; and the electrical signals of both the detecting means. an arithmetic processing means for performing arithmetic processing to determine the pass/fail of defects on the surface to be inspected, and the specular reflection light detection means includes a photoelectric converter for specular reflection disposed in the optical path of the specular reflection light. The diffused reflection light detection means is a diffused reflection photoelectric converter that is disposed between the specular reflection photoelectric converter and the surface to be inspected, has an opening for the optical path of the specular reflection light, and has a relatively wide light-receiving surface. It is characterized by including a container.

Therefore, according to the present invention, the specular reflection light detection means photoelectrically detects the intensity and position of the specular reflection light, and the diffuse reflection detection means photoelectrically detects the intensity and position of the specular reflection light, and the diffuse reflection detection means detects the scattered reflection light from the inspection surface and the diffracted light other than the zero-order (specular reflection light). It is possible to photoelectrically detect the diffusely reflected light including the surface defects, detect multiple types of defects at the same time using these two types of detection signals, and determine whether the surface defects are acceptable or not.

FIG. 1 shows the principle of the surface defect inspection apparatus according to the present invention, in which inspection light shown as a laser beam irradiated from an inspection light supply means 20 such as a laser oscillator is irradiated onto a surface 22 to be inspected. , the reflected light is detected by a specular reflection light detection means 24 disposed in the optical path of the specular reflection light LO, and a specular reflection light detection means 24 disposed between the specular reflection light detection means 24 and the surface to be inspected 22, said 1'-,
The reflected light LO is received by the diffusely reflected light detection means 26, which has an opening 26a in its optical path.

Both the detection means 24 and 26 each include a photoelectric converter, and the diffused reflection photoelectric converter of the diffused reflection light detection means 26 is
A relatively wider light-receiving surface than the photoelectric converter of the specular reflection light detection means 24 is provided.

Then, the outputs of both the detection means 24 and 26 are processed by the calculation processing means 2.
8, and desired pass/fail determination is performed.

[Operation] In FIG. 1, the laser beam L emitted from the inspection light supply means 20 is specularly or diffusely reflected on the inspection surface 12.

If the surface 22 to be inspected has no surface defects and is kept in a good smooth state, most of the laser beam becomes a specularly reflected beam LO, and the remaining small amount becomes a diffusely reflected light L2. becomes.

As is clear from FIG. 1, the specularly reflected beam LO passes through the aperture 26a of the diffusely reflected light detecting means 26 and reaches the specularly reflected light detecting means 24, and an electrical signal corresponding thereto is supplied to the arithmetic processing means 28. be done. - On the other hand, a small amount of diffuse reflected light L
2 cannot pass through the opening 26a, so
The diffusely reflected light detection means 26 receives the light, and supplies a predetermined electrical signal to the arithmetic processing means 28.

The arithmetic processing means 28 compares and arithmetic-processes both human power signals and a preset reference value, and outputs a good signal if the specularly reflected light is larger than the reference value and the diffusely reflected light is smaller than the reference value. .

On the other hand, if there are large irregularities such as bumps on the surface 22 to be inspected, most of the laser beam is reflected in a direction far away from the direction of the specularly reflected beam LO, and the irregularly reflected beam L1
Therefore, both the detection means 24 and 26 are irradiated with only a small amount of the remaining specularly reflected beam LO and diffusely reflected light L2.

Therefore, the arithmetic processing means 28 processes both of these detection means 24.
The output signals from 26 are compared with the reference values mentioned above, and if the specularly reflected light is smaller than the reference value or if the diffusely reflected light is larger than the reference value, a negative signal is output.

Next, if there is an elongated irregularity defect such as a scratch on the surface 22 to be inspected,
The laser beam is diffracted in a direction perpendicular to the longitudinal direction of the unevenness.

In this case, among the diffracted lights, the zero-order diffracted light cannot be distinguished from the specularly reflected beam LO, so it is irradiated onto the specularly reflected light detection means 24, but the diffracted light L3 of orders higher than the zeroth order is irradiated to the diffusely reflected light detecting means 26. The light is received at

Therefore, the arithmetic processing means 28 outputs a failure signal when the specularly reflected light is smaller than the reference value or when the diffusely reflected light is larger than the reference value, and on the other hand, when the specularly reflected light is larger than the reference value and the diffusely reflected light is smaller than the reference value. Output a signal.

Further, when the surface to be inspected 22 has uneven gloss, most of the laser beam L becomes a specularly reflected beam LO with reduced brightness in a portion with poor gloss, and the diffusely reflected light L2 also increases slightly. Therefore, the arithmetic processing means 28 outputs a negative signal when the specularly reflected light is smaller than the reference value or when the diffusely reflected light is larger than the reference value, and when the specularly reflected light is larger than the reference value and the diffusely reflected light is smaller than the reference value. outputs a good signal.

Next, when the surface to be inspected 22 has rough skin, most of the laser beam L is a specularly reflected beam LO with a slightly different reflection angle.
− becomes. At this time, the light receiving position of the specularly reflected light detecting means 24 is shifted depending on the condition of the rough skin, and an electric signal corresponding to the amount of shift can be obtained depending on this position.

Therefore, the arithmetic processing means 28 outputs a rejection signal when the amount of deviation exceeds a predetermined reference value, and also outputs a rejection signal when the specularly reflected light is smaller than the reference value or the diffusely reflected light is larger than the reference value. Output a signal.

As described above, according to the present invention, attention is paid to the fact that the surface to be inspected 22 exhibits different reflection characteristics depending on the state of various different defects, and specularly reflected light and diffusely reflected light are detected differently. It is possible to determine whether the surface defect is good or bad by receiving light by the light receiving means and processing the electrical signals from each light receiving means.

[Example 1 Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows a preferred embodiment of the surface defect inspection apparatus of the present invention. The illustrated embodiment is a stationary inspection apparatus, and the optical system of the apparatus is installed and fixed within a frame 30.

Positioning feet 32.3 are provided on the lower surface of this frame 30.
4, the frame 30 can be correctly positioned and held at a predetermined position on the surface to be inspected 22.

Of course, in the present invention, the frame 30 can also be held in close proximity to the continuously moving surface to be inspected 22 and out of contact with the surface to be inspected 22.

An inspection light supply means 20 is provided within the frame 30, and the inspection light O1-1 means 20 in the embodiment includes a semiconductor laser 36 and a collimator lens 38, and a laser beam is used as the inspection light. The optical path of this laser beam inspection light is bent by a mirror 40 provided within the frame 30, and a predetermined inspection portion of the surface to be inspected 22 is irradiated with the inspection light.

The reflected light from the surface to be inspected 22 is guided to the light receiving side by a mirror 42 fixed to the frame 30, and the light receiving portion of the frame 30 is equipped with a specular reflection light detection means 24 and a diffuse reflection light detection means 26, which are the features of the present invention. It is located.

In the embodiment, the inspection light is irradiated onto the surface to be inspected 22 as a parallel beam with a diameter of 1a+i by the collimator lens 38, and each of the inspection means 24 and 26 also has a light receiving surface of a size corresponding to this reflected light.

In the embodiment, the specularly reflected light detection means 24 is composed of a CCD image sensor, and its fixed position is selected so that the center of its photosensitive portion coincides with the optical path of the specularly reflected light.

Therefore, the specularly reflected light detection means 24 receives the reflected light in the specularly reflected direction from the surface to be inspected 22, photoelectrically detects the intensity of the reflected light and the beam spot position of the CCD image sensor L, and detects the magnitude of the specularly reflected light and the beam spot position of the CCD image sensor L. The amount of vibration can be output as an electrical signal.

On the other hand, the diffusely reflected light detecting means 26 is composed of a photodiode in the embodiment, and as described above, this photodiode is disposed between the specularly reflected light detecting means 24 and the surface to be inspected 22, and is connected to the optical path of the specularly reflected light. An opening 26a is provided. Therefore, the detection means 24 is capable of receiving specularly reflected light or specularly reflected light having a predetermined amount of deviation allowed by the aperture 26a. Then, the diffused reflected light detection means 2
The photodiode 6 itself forms a larger light-receiving surface than the CCD image sensor of the specular reflection light detection means 24.

Therefore, this photodiode can reliably receive diffusely reflected light including diffusely reflected light and diffracted light around specularly reflected light, and photoelectrically detect the intensity of this diffusely reflected light. The analog electrical signals output from both the detection means 24 and 26 are processed by the arithmetic processing means 28.

In the embodiment, the arithmetic processing means 28 includes an amplifier 44a and a filter 46a for amplifying the output of the specularly reflected light detecting means 24, and an amplifier 44b and a filter 46b for amplifying the output of the diffusely reflected light detecting means 26. The outputs of both filters 46a and 46b are converted into digital signals by the AD converter 48, and this digital signal is output to the CPU 50. The CPU 50 holds reference values for each signal, and compares each input signal with these reference values to determine pass/fail for surface defects. Displayed as a pass/fail judgment result.

The present embodiment has the above configuration, and its operation will be explained below.

Examples of the inspected surface 22 include bumps with a diameter of about 1 ms, scratches with a width of about 5 μm, rough skin or undulations with a wavelength of about 1-10 mm, and uneven gloss (roughness) with a wavelength of 0.1 mm or less.
Consider the case where defects on a painted surface are inspected.

When inspecting the painted surface described above using the surface defect inspection device of the embodiment, the frame 30 of the device is placed on the surface to be inspected 22 with the positioning feet 32 and 34, and the inspection light is directed onto a predetermined surface to be inspected. irradiated.

In the present invention, the arithmetic processing means 28
It is also possible to conduct predetermined arithmetic processing and display at a location different from the inspection section by leading the signal from the frame 30 via a cable or the like.

Such a separate device is suitable for inspections in locations with poor working environments or in dangerous locations.

When the positioning of the frame is completed, the power of the apparatus is turned on, and as a result, a laser beam is emitted from the semiconductor laser 36 of the inspection light supply means 20, and a parallel beam with a beam diameter of 1 wa is emitted by following the above-mentioned optical path. Inspection surface 22
is irradiated onto a predetermined inspection area.

The mirror 40 performs beam bending of 115@,
As a result, the surface to be inspected 22 is irradiated with the laser beam inspection light having an incident angle of 65@.

On the inspected surface 22, specular reflection or diffuse reflection occurs depending on the various surface defects described above, and these reflected lights are bent by the mirror 42 at an angle of 115@ to each detection means 24.
．． 26.

The specularly reflected light irradiated onto the CCD image sensor forming the specularly reflected light detecting means 24 is sequentially converted into an analog electrical signal for each pixel of the image sensor, and is converted into an analog electrical signal by the arithmetic processing means 2.
8.

FIG. 3 schematically shows the light-receiving surface of the CCD image sensor of the specular reflection light detection means 24, and in the figure, each pixel of the light-receiving surface divided by XY coordinates is indicated by 60. .

In the arithmetic processing means 28, the analog electrical signal for each pixel 60 is amplified by an amplifier 44a, noise components are removed by a filter 46a, and the AD converter 48 supplies the signal to the CPU 50 as a digital signal. On the other hand, among the reflections having a distribution of reflected light according to the unevenness defects on the surface to be inspected 22, the diffused reflected light is reflected by the mirror 42 at 115
'After being bent, it is irradiated onto the photodiode of the diffusely reflected light detection means 26.

Therefore, this diffusely reflected light is converted into an analog electrical signal by a photodiode, and after being amplified and noise components removed in the same manner as the specularly reflected light, it is supplied to the CPU 50 as a digital signal. The CPU 50 compares the signals from both the detection means 24 and 26 with a reference value to make a predetermined pass/fail judgment. For specularly reflected light, the signal obtained from each pixel 60 of the CCD image sensor is compared in position and magnitude with a predetermined reference value. For example, diameter 1
For one or more dots, most of the reflected light deviates from the specular reflection optical path, and as a result, the intensity of the reflected light irradiated onto the CCD image sensor is significantly reduced, so if this size is smaller than the reference value, Outputs a rejection signal.

On the other hand, even if the intensity of the specularly reflected light is greater than the reference value, if the position, that is, the coordinates of the pixel that received the light, is, for example, at the mouth more than a predetermined distance from the origin A, the deflected portion of the specularly reflected light will be 22 indicates rough skin or undulation, and a negative signal is also output when this amount of deviation exceeds a predetermined value.

On the other hand, the signal from the diffusely reflected light detection means 26 is used to determine pass/fail by comparing the output intensity of the photodiode with the reference value.

That is, when the surface of the surface to be inspected 22 has uneven gloss, or when the surface to be inspected has scratches, diffusion due to surface roughness, or diffraction due to scratches, the diffusely reflected light increases, and the CPU 50 determines whether the diffusely reflected light has reached a predetermined value. Outputs a rejection signal when the limit is exceeded.

As described above, the CPU 50 compares the output of each detection means 24 and 26 with a predetermined reference value, determines whether the surface to be inspected is acceptable or not according to the result, and displays the result on the display 50. .

Therefore, according to the present invention, even when different types of large and small uneven defects coexist on the surface to be inspected 22, it is possible to accurately inspect such defects at once.

Although the above-described embodiments have been described for inspecting unevenness defects on painted surfaces, the present invention can of course be widely used for inspecting defects on the surfaces of various products or objects.

[Effects of the Invention] As explained below, according to the present invention, reflected light from a surface to be inspected is photoelectrically converted by two types of detection means, that is, a specular reflection light detection means and a diffused reflection light detection means, and the resulting , the size and deflection of the specularly reflected light, and the size of the diffusely reflected light are separately output as electrical signals.As a result, different types of uneven defects on the surface to be inspected can be quickly and accurately inspected at the same time. This provides an excellent effect in that defects can be inspected.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram explaining the principle of the surface defect inspection device according to the present invention, FIG. 2 is an explanatory diagram showing a preferred embodiment of the surface defect inspection device according to the present invention, and FIG. 3 is the same as in FIG. Specular reflection light detection means 24 in the embodiment
Explanatory diagram showing the light receiving surface of the CCD image sensor of 4th. 5. FIG. 6 is an explanatory diagram showing the principle of a conventional surface defect inspection device. 20... Inspection light supply means 22... Surface to be inspected 24... Specular reflection light detection means 26... Diffuse reflection light detection means 28... Arithmetic processing means 26a... Aperture Applicant Toyota Co., Ltd. Central Research Institute

Claims (1)

[Claims] (1) Inspection light supply means for irradiating inspection light onto the surface to be inspected; specular reflection light detection means for receiving the specularly reflected light reflected by the surface to be inspected, converting it into an electrical signal, and outputting it; and the surface to be inspected. a diffusely reflected light detecting means for receiving diffusely reflected light including diffusely reflected light and non-zero-order diffracted light reflected by the object, converting it into an electrical signal, and outputting it; arithmetic processing means for determining whether the defect is acceptable, the specular reflection light detection means includes a specular reflection photoelectric converter disposed on the optical path of the specular reflection light, and the diffused reflection light detection means A surface defect characterized by comprising a photoelectric converter for diffuse reflection that is disposed between the photoelectric converter for reflection and a surface to be inspected, has an opening for the optical path of specularly reflected light, and has a relatively wide light-receiving surface. Inspection equipment.