JP3062293B2 - Surface defect inspection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface defect inspection apparatus which irradiates a surface to be inspected functioning as a mirror surface with light, and inspects the reflected light for the presence or absence of a surface defect such as a coating defect.

[0002]

2. Description of the Related Art Generally, in a production line of a vehicle such as an automobile, painting of a vehicle body is performed at a painting station provided in the production line. After the body is painted in such a painting station, inspection for paint defects caused by the painting is performed.
Here, this inspection for paint defects has been conventionally performed by visual inspection of humans. In this visual inspection,
You have to find a small defect on the coating surface.
This imposes a heavy burden on the examiner and requires physically demanding work.

As a technique for inspecting a coating defect without relying on a visual inspection of an operator, for example, Japanese Patent Application Laid-Open No. Sho 62-2
No. 33710 discloses an inspection technique for irradiating a surface to be inspected of an object with light, projecting the reflected light on a screen, and automatically detecting a surface defect on the surface to be inspected from the sharpness of the projected image. Is disclosed. Therefore, if the technology disclosed in the above-mentioned conventional publication is applied, it is possible to automatically detect a coating defect generated on a painted surface of a vehicle body, and to relieve the inspector from the conventional visual inspection work. .

When the surface inspection technique by light irradiation disclosed in the above-mentioned conventional publication is applied to an automatic inspection of paint of a vehicle body, as shown in FIG. the coated surface Y to the line manner from the light source a ₁ (or a Supotsuto manner) by irradiating light, on Nurimakumen Y, than the camera field of view F of the CCD camera B to be described below sufficiently small light irradiation Create an area and use the reflected light from this
An inspection device for receiving light by the D camera B is conceivable.

[0005] In this inspection apparatus, the received light image formed by the CCD camera B is as shown in FIG. Becomes a bright line D. Here, when there is a paint defect X that can be simulated in the light irradiation area, for example, a shape having a spherical surface,
Regular reflection occurs on the spherical surface of the paint defect X. In particular, in the coating defect X, the surrounding landscape, mainly it is a fact to be displayed a relatively wide range including a light source A ₁ in a state condensed. The image was projected to the coating defect X is bright but is intended to include a light source A ₁ Projected small and large dark portion of the periphery of this. Accordance connexion, focusing the incident light amount of coating defect X with respect to the camera light receiving surface, in the portion corresponding to the dark peripheral portion of the light source A _1, the light amount decreases, as a result, in the bright line D The surface defect X is projected in black.

As described above, according to the image processing technique,
By identifying the black spot, the paint defect X can be detected. Further, according to this inspection apparatus, since the coating film surface Y is irradiated linearly and narrowly, even if the irradiation light amount is small,
The direction of regular reflection of the light incident on the light irradiation area at the coating defect portion X changes, and the amount of light entering the camera B can be clearly different between the coating defect portion X and the other portion, and even a minute defect can be detected. You can do it.

However, since the narrow light irradiation is performed as described above, the light irradiation area is too small with respect to the camera field of view F, while the defective portion X that can be captured by the camera B is located in the light irradiation area (ie, the light receiving area). (In the line image in the image) or near it. For this reason, only the surface inspection using only a part of the camera field of view F can always be performed, and there is a problem that the inspection efficiency is lacking.

Further, when the object to be inspected is a vehicle body painted surface will be inspected while moving Te graduation to the body of the painted surface by the light source A ₁ and robot device CCD camera B. However, the vehicle body is composed of many curved surfaces having different curvatures. Therefore, when the inspection point on these curved surfaces move, the linear specific illumination profile distortion that can turn by connexion body surface light source A _1, the is also a line image D in the light receiving image C of connexion camera B 9 Will be distorted as shown in FIG. As a result, in extreme cases, the line image D deviates from the camera field of view F. Therefore, normal inspection cannot be performed.

For this reason, it is difficult to normally inspect the coating film surface of a vehicle body such as an automobile, and in order to keep the line image D within the field of view F of the camera, complicated control is performed by the robot apparatus. There is a problem that must be applied.

[0010] In order to solve the above difficulties, FIG.
A light source A ₂ having a wide light irradiation area as shown in FIG.
It is conceivable that the light is radiated by the camera B, and the light is broadly radiated in the area equal to or larger than the field of view F of the camera.

[0011]

However, when the coating film surface Y is illuminated in such a wide manner, the amount of irradiation is greatly increased, and halation of light at the coating defect portion X is caused. You will not be able to catch it clearly. Specifically, the image to be displayed in the painting defect X, most light sources A ₂ only becomes, and it is also displayed brightly the coating defect X. Accordance connexion, focusing the incident light amount of coating defect X with respect to the camera light receiving surface, a light amount of irradiated portion by the light source A _2, becomes the amount of projected portions in the painting defect X is substantially the same, the As a result, a bright surface defect X is displayed in the bright line D, and the CCD camera B cannot clearly catch the minute paint defect X.

The present invention has been made in view of the above circumstances, and an object of the present invention is to accurately and efficiently detect the position of a surface defect existing on a surface to be inspected and its unevenness. An object of the present invention is to provide a surface defect inspection device that can perform the inspection.

[0013]

Means for Solving the Problems The above-mentioned problems are solved,
In order to achieve the object, a surface defect inspection apparatus according to the present invention is disposed so as to face a surface to be inspected that functions as a mirror surface, and the luminous intensity decreases from large to small along a predetermined direction toward the surface to be inspected. A light irradiating means for irradiating light having a light intensity distribution set so as to gradually change, and an image of the light irradiating means reflected on the surface to be inspected, and corresponding to the light intensity distribution of the light irradiating means An image pickup means for creating a bright and dark light-receiving image to be formed, and a part of the light part and the dark part whose brightness is significantly different from the surroundings is identified based on the light-receiving image formed by the image pickup means. Image processing means for detecting the spot as a surface defect on the surface to be inspected.

Further, in the surface defect inspection apparatus according to the present invention, the imaging means is set so as to photograph an image of the light irradiating means reflected on the surface to be inspected over the entire area of the light receiving image. It is characterized by having a limited field of view.

Further, in the surface defect inspection apparatus according to the present invention, the imaging means includes a video signal generation means for converting the received light image into a video signal, and the image processing means outputs the video signal from the video signal generation means. Processing the processed video signal, and from the timing when the processed value exceeds a preset value and its change state, it is necessary to identify the position of the defective portion present on the surface to be inspected and the state of the unevenness. Features. Further, the surface defect inspection apparatus according to the present invention is characterized in that the apparatus further comprises a light diffusing means for diffusing the light irradiated from the light irradiating means. Further, in the surface defect inspection apparatus according to the present invention, the luminous intensity distribution of the light irradiating means is changed by controlling a voltage applied to the light irradiating means.

[0016]

According to the above arrangement, the light irradiating means irradiates light having a luminous intensity distribution set such that the luminous intensity gradually changes from large to small along a predetermined direction. If there is a surface defect, the direction of regular reflection of light at that portion changes, and the object light from the surface defect differs from the brightness around the surface defect. Thus, if there is a surface defect on the surface to be inspected that reflects and reflects the image of the light irradiation means,
Due to this surface defect, the direction of regular reflection of light changes, and the state of reflected light changes. The state of the change of the reflected light differs depending on the state of the unevenness of the surface defect. Therefore, the state of the change of the reflected light from the surface defect is detected by performing image processing on the received light image by the image processing means, and from the timing and the change state of the change, the position of the surface defect and the state of the unevenness of the surface defect Is detected.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the structure of an embodiment of a surface defect inspection apparatus according to the present invention, the principle of operation of the present invention will be described with reference to FIGS. Here, FIG. 1 shows a case where the inspection target surface 11 has a convex defect portion 12,
FIG. 2 shows a case where a surface to be inspected 11 has a concave defect portion 12.

In FIG. 1 and FIG. 2, a light source 13 as a light irradiating means has a light intensity (represented by the length of a line m) of light emitted from a light emitting surface 13a as indicated by an arrow A on the emitting surface.
It is set to change from strong to weak in one direction indicated by ₁ .

[0019] Here, as described above, the light emitted from the exit face 13a of the light source 13, as indicated by the arrow A _1, the light intensity with respect to one direction of the exit surface 13a is changed uniformly as, in particular, so as to decrease along connexion gradually intensity in the direction indicated by the arrow a _1, it is set. The image of the light source 13 is reflected by the surface 11 to be inspected, and is captured by the video camera 14. In other words, the video camera 14 is adjacent to the light source 13 so as to have a camera field of view F set so that the light from the light source 13 reflected on the surface 11 to be inspected can be directly projected. It is disposed so as to face the inspection surface 11.

With such a configuration, FIG. 3 and FIG.
As shown respectively, the reflected light from the light irradiation area S
In the received light image 15 of the video camera 14
Is the light emitted from the light exit surface 13a of the light source 13.
Direction A in which the degree changes from strong to weak ₁ Arrow A corresponding to
_Two The brightness changes from strong to weak along the direction indicated by.
In FIGS. 3 and 4, the density of the vertical lines is low.
Brightness is high, and the density of vertical lines is high
The lower the brightness, the lower the brightness.

In this state, if a defect 12 is formed on the surface 11 to be inspected, the light source 13
The direction of the specular reflection of light from the object changes. The specular reflection direction of the change of the light receiving image 15 of the video camera 14, in a state in which the illuminance is changed in the direction indicated by arrow A _2, the brightness of the changing state of the defect portion 12 is different from the rest of It will be.

When the above-mentioned defective portion 12 is convex as shown in FIG.
Surface substantially functions as a so-called convex mirror. As a result, according to the reflection theory of the convex mirror, light from the high luminous intensity portion 16 of the emission surface 13a of the light source 13 mainly hits the surface 12a of the defect portion 12 facing the emission surface 13a in accordance with the reflection theory of the convex mirror. The direction of specular reflection changes, and the reflected light from the defective portion 12 enters the video camera 14 as object light of the defective portion 12. In addition, as described above, the defect 12
The focus position of the video camera 14 is adjusted so that the video camera 14 is focused on the surface 11 to be inspected in order to clearly display the image in the received light image 15.

Here, the defective portion 12 related to the exit surface 13a
Only the light from the portion 17 of the emission surface 13a where the luminous intensity is relatively small is incident on the surface 12b on the rear side. As a result, the reflected light from the rear surface 12b of the defective portion 12 hardly enters the video camera 14.

Accordingly, as shown in FIG. 3, when the defective portion 12 has a convex shape, the light reception image 15 of the video camera 14 has an arrow A from the bright part to the dark part of the light reception image 15 of the video camera 14. Defect part 1 in the direction indicated by ₂
2 first becomes lighter than the other parts, and after this light part, it becomes darker than the other parts.

When the defect 12 is concave, the surface of the defect 12 substantially functions as a so-called concave mirror. As a result, according to the reflection theory of the concave mirror, the light from the high-intensity portion 16 of the emission surface 13a of the light source 13 is mainly transmitted to the surface of the concave defect portion 12 farther from the emission surface 13a of the defect portion 12. 12c, the direction of specular reflection changes, and a part thereof
Incident on. However, only light from the portion 17 of the emission surface 13a where the luminous intensity is relatively small enters the surface 12d of the defect portion 12 on the opposite side to the surface 12c (that is, the surface closer to the emission surface 13). 14 has a surface 12d of the defect 12
Light hardly enters from

Accordingly, as shown in FIG. 4, when the defective portion 12 has a concave shape, the light receiving image 15 of the video camera 14 has a directional arrow A from the bright portion to the dark portion of the light receiving image 15 of the video camera 14. Defect 1 along ₂
2 first becomes darker than the other parts, and after passing through this dark part, it changes to become lighter than the other parts.

The video camera 14 outputs a video signal that changes according to the change in the brightness of the received light image 15. Thereafter, a value obtained by processing and calculating a video signal output from the video camera 14, for example, a scanning line corresponding to a video signal in which a differential signal of the video signal exceeds a preset threshold, and a differential signal on this scanning line By detecting the timing exceeding the above-mentioned threshold value and the change in the sign of the above-mentioned differential signal near this timing, the position of the surface defect portion 12 in the light receiving image 15 and the unevenness state of the surface defect portion are detected. You can do it.

Next, the configuration of an embodiment of the surface defect inspection apparatus according to the present invention using the above-described operation principle will be described in detail with reference to FIGS. As shown in FIG. 5, the coating inspection station 20 for the vehicle body is mounted on a pedestal B, and inspects the coating surface 27 of the vehicle body 26 carried therein to detect a coating defect. An inspection robot device 21 as an inspection device is provided.

The robot device 21 includes a distal arm 22 which can be moved to an arbitrary position and can take an arbitrary posture. This tip arm 2
At the front end of the light source 2, a light irradiation mechanism 23 corresponding to the light source 13 (see FIGS. 1 and 2) and a CCD camera 24 corresponding to the video camera 14 (see FIGS. 1 and 2) are supported. 25 is attached. Light irradiation mechanism 23 attached to robot device 21 and CC
The D camera 24 traces the coating surface 27 (corresponding to the surface 11 to be inspected in FIGS. 1 and 2) of the vehicle body 26 carried into the coating inspection station 20, and irradiates the light with the light irradiating mechanism 23. The reflected light is reflected by the coating film surface 27 on the surface of the vehicle body 26 and enters the CCD camera 24. In other words, C
In the received light image 15 of the CD camera 24, the positions of the light irradiation mechanism 23 and the CCD camera 24 are set so that the light irradiation mechanism 23 is mainly projected through the coating surface 27 functioning as a mirror surface. I have.

The light irradiation mechanism 23 and the CCD
In a coating defect inspection apparatus (inspection robot apparatus) 21 provided with a camera 24, a robot controller 32 is driven and controlled by a command given by a host computer 31, and the robot controller 32
The robot device 21 is specifically driven.

The robot unit 21 operates the light irradiating mechanism 23 and the CCD camera 24 so that the light irradiating mechanism 23 and the CCD camera 24 trace the surface of the vehicle body 26 when an actuator (not shown) provided therein is operated. While moving, the video signal obtained by the CCD camera 24 is output to the image processing processor 33.

In the image processing processor 33, as described above, the video signal is amplified and then differentiated, and the differentiated signal is used to detect the scanning line of the video signal exceeding a preset threshold and the timing on this scanning line. Is transmitted to the host computer 31 for analysis.
By this analysis, the coordinates of the position of the paint defect 12 and whether the paint defect 12 is convex or concave is detected.

Based on the detection result obtained by such information processing, the paint defect 12 existing on the painted surface of the vehicle body 26 is determined.
Repair is performed according to the irregularities of the surface. In this repair work, when the defective portion 12 is convex, the protruding portion is cut off small, and when the defective portion 12 is concave, the coating film covers a relatively wide area including the defective portion 12. Is carried out so that is scraped off.

This repair can be performed manually, but is usually performed by the above-described robot device 21 or a repair robot device (not shown) provided separately from the robot device.
Done automatically.

As shown in FIG. 6, the light irradiation mechanism 23 includes a box 41 having one side open to the coating surface 27 and a plurality of fluorescent lamps disposed inside the box 41. 42 (not particularly limited to the fluorescent lamp 42). On one open side of the box 41, an optical filter 43 is installed.
A diffusion screen 44 is attached so as to cover the entire surface of the optical filter 43.

The optical filter 43 is provided for uniformly changing the luminous intensity distribution of the light emitted from the fluorescent lamp 42 in one direction of the light exit surface 13a formed by the diffusion screen 44. . Specifically, this optical filter 43
The light transmittance at points having the same x-coordinate value of the xy coordinates set on the light exit surface 13a as shown in FIG. 6, for example, is equal, and the light transmission at points having different y-coordinate values is obtained. The degree is set differently according to the y coordinate value.
Thereby, the coating film surface 27 on the surface of the vehicle body 26 shown in FIG.
Is formed a light irradiation area S (see FIGS. 1 and 2) in which the illuminance changes in one direction.

On the other hand, the diffusion screen 44 diffuses the light transmitted through the optical filter 43 and arranges the fluorescent lamps 42 at an interval, thereby forming the fluorescent lamps 4 adjacent to each other.
In the portion of the coating film surface 27 corresponding to the area between the two, a region with low illuminance is not provided.

The light intensity change (gradient) applied to the light irradiating mechanism 23 is controlled by providing a light irradiating mechanism controller 34 as shown by a dotted line in FIG. The voltage can also be created by changing the voltage by the light irradiation mechanism controller 34. In this case, the optical filter 43 can be omitted.

In the paint defect inspection apparatus configured as described above, the paint defect inspection operation is started as the painted vehicle body 26 is carried into the paint inspection station 20. That is, the robot device 21 is connected to the robot controller 32.
The light temporary irradiation mechanism 23 and the CCD camera 24 are maintained in an integral relationship, and the light irradiation mechanism 23 and the CCD camera 24 are placed on the surface of the vehicle body 26 at an appropriate distance. It is moved so as to trace along the surface shape of 26.

At this time, as described with reference to FIGS.
Thus, the light emission surface 13a in which the luminous intensity distribution in the light irradiating mechanism 23 reflected uniformly by the light irradiation mechanism 23 uniformly changes in one direction is projected. That is, in the CCD camera 24, the light receiving image 15 whose brightness uniformly changes in one direction corresponding to the luminous intensity distribution of the light irradiation mechanism 23 is created.

Therefore, the coating defect portion 12 is formed on the coating film surface 27.
Occurs, the direction of the regular reflection of the light from the light source 13 changes at that portion, and as described in the principle description with reference to FIGS. , The received light image 15 of the CCD camera 24 is
As shown in the figure, along the direction A ₂ B from the bright part to the dark part of the received light image 15 of the CCD camera 24,
The portion corresponding to the paint defect 12 first becomes brighter than the other portions, and after passing through the bright portion, changes to become darker than the other portions.

Further, if the coating defect 12 is of concave, as shown in FIG. 4, along connexion the direction of arrow A ₂ toward the dark from where bright light image 15 of the CCD camera 24, paint The part corresponding to the defective part 12 is
At first, it becomes darker than other parts, and after passing through this dark part, it changes to become lighter than other parts. And
The CCD camera 24 outputs a video signal that changes according to the change in the brightness of the received light image 15 to an image processor 33.
Output to

When this video signal is input to the image processing processor 33, the image processing processor 33 sets the differential signal of the video signal output from the CCD camera 24 based on the presence of the paint defect 12 to a predetermined threshold value. A video signal scanning line exceeding the timing, a timing at which the differential signal on the scanning line exceeds the threshold value, and a change in the sign of the differential signal near the timing are detected. By this detection, the position of the paint defect 12 in the received light image 15 and the uneven shape of the paint defect 12 are detected. The detected data and the position of the tip arm 22 of the robot device 21 are stored in a memory. At the time of repairing the defective paint portion 12, the stored contents of the memory are taken out, and the repair of the defective paint portion 12 is performed as described above.

As described in detail above, in this embodiment, even if the surface 11 to be inspected is irradiated over a wide area, the paint defect 12 has a clear difference in brightness from its surroundings. It can be taken as a perfect image.

Further, as described above, the change in the video signal output from the CCD camera 24 due to the presence of the paint defect portion 12 is caused by the difference between the video signal scanning line and the video signal scanning line whose differential signal exceeds a preset threshold value. By detecting the timing at which the differentiated signal exceeds the above-described threshold value on this scanning line and the change in the sign of the differentiated signal near this timing, the position of the paint defect portion 12 in the light-receiving image 15 and the paint defect portion are detected. The unevenness of the coating 12 can be detected, and even if the coating defective portion 12 is minute, it can be reliably recognized as the coating defective portion 12.

It is needless to say that the present invention is not limited to the configuration of the above-described embodiment, but can be variously modified without departing from the gist of the present invention. For example, in the embodiment described above, the detection of the paint defect 12 is performed by the image processing processor 33. However, the present invention is not limited to such a configuration, and the video from the CCD camera 24 is not limited to such a configuration. By monitoring the signal on the monitor television, the inspector can detect the paint defect 12 and store the information such as the shape and position of the paint defect 12 in the recording device.

[0047]

As described above in detail, the surface defect inspection apparatus according to the present invention is disposed so as to face a surface to be inspected functioning as a mirror surface, and is directed along a predetermined direction toward the surface to be inspected. A light irradiating unit for irradiating light having a luminous intensity distribution set so that the luminous intensity gradually changes from large to small; and taking an image of the light irradiating unit reflected on the surface to be inspected, and Imaging means for creating a bright and dark light-receiving image corresponding to the luminous intensity distribution of the means, and, based on the light-receiving image formed by the imaging means, identify portions of the bright portion and the dark portion in which the brightness is significantly different from the surroundings. Therefore, the image processing device is characterized by including image processing means for detecting the identified portion as a surface defect on the surface to be inspected.

Further, in the surface defect inspection apparatus according to the present invention, the camera is set so as to photograph the image of the light irradiating means reflected on the surface to be inspected over the entire area of the light receiving image. It has a featured visual field.

Further, in the surface defect inspection apparatus according to the present invention, the image pickup means includes a video signal generation means for converting the received light image into a video signal, and the image processing means outputs the video signal from the video signal generation means. The video signal is processed, and the position of the defective portion on the surface to be inspected and the state of the unevenness are identified from the timing at which the processed value exceeds a preset value and its change state. Features. Therefore, according to the present invention, a surface defect inspection apparatus capable of accurately and efficiently detecting a surface defect existing on a surface to be inspected is provided.

[Brief description of the drawings]

FIG. 1 and

FIG. 2 is a diagram for explaining the operation principle of the surface defect inspection device according to the present invention.

FIG. 3 and

FIG. 4 is a diagram illustrating a state in which an image is formed by a camera when a surface to be inspected has a convex defect and a concave defect.

FIG. 5 is a perspective view showing a case in which the configuration of one embodiment of the surface defect inspection apparatus according to the present invention is applied to a coating defect inspection apparatus for an automobile body.

FIG. 6 is an exploded perspective view showing the configuration of the light irradiation mechanism shown in FIG. 5;

FIG. 7 is a diagram schematically showing a configuration of a conventional surface defect inspection apparatus.

8 is a diagram showing a state of forming an image obtained by a camera of the surface defect inspection device of FIG. 7;

FIG. 9 is a diagram showing a state of forming an image obtained by a camera when the surface to be inspected is a curved surface.

10 is a diagram schematically showing a configuration of a conventional surface defect inspection device different from the conventional device shown in FIG. 7;

[Explanation of symbols]

11 inspection surface, 12 defect part, 13 light source, 1
4 video camera, 15 received light image, 16 position with high luminous intensity, 17 position with low luminous intensity, 21 robot unit, 23 light irradiation mechanism, 24 CCD camera,
25 support bracket, 26 vehicle body, 27 coating surface, 3
1 host computer, 32 robot controller, 33 image processing processor, 41 box, 42 fluorescent lamp, 43 light filter, 44 diffusion screen.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akinori Utsunomiya 3-1 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Co., Ltd. (56) References JP-A-64-3547 (JP, A) Real-life Sho-61 -199661 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/88 G01B 11/30 H04N 7/18

Claims (5)

(57) [Claims] 1. A luminous intensity distribution disposed opposite a surface to be inspected functioning as a mirror surface and set so that the luminous intensity gradually changes from large to small along a predetermined direction toward the surface to be inspected. Light irradiating means for irradiating light having an image capturing means for taking an image of the light irradiating means reflected on the surface to be inspected and creating a bright and dark light-receiving image corresponding to a luminous intensity distribution of the light irradiating means; Based on the light-receiving image formed by the imaging means, a bright portion and a dark portion of the light-receiving image each identify a portion where the brightness is significantly different from the surroundings, so that the identified portion is located on the surface of the surface to be inspected. A surface defect inspection apparatus comprising: an image processing unit that detects a defect. 2. The imaging device according to claim 1, wherein the imaging unit has a field of view set so as to capture an image of the light irradiation unit reflected on the surface to be inspected over the entire area of a light receiving image. The surface defect inspection device according to claim 1. 3. The image pickup means includes a video signal generation means for converting the received light image into a video signal, and the image processing means processes a video signal output from the video signal generation means, and performs the processing. 2. The surface according to claim 1, wherein the position of the defective portion existing on the surface to be inspected and the state of the unevenness thereof are identified from the timing at which the value exceeds a preset value and the change state thereof. Defect inspection equipment. 4. The surface defect inspection apparatus according to claim 1, further comprising a light diffusing unit for diffusing light emitted from the light irradiating unit. Light distribution according to claim 5, wherein said light irradiating means, a surface defect inspection apparatus according to claim 1, wherein the changing by controlling the voltage applied to the light emitting means.