JP2955686B2 - Surface defect inspection equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a surface defect inspection device for detecting the position of a surface defect existing on a painted surface of a smooth plate having a curved surface shape such as an automobile body. The present invention relates to an apparatus for irradiating a surface to be inspected with light and inspecting for the presence or absence of a surface defect based on information of the light reflected from the surface to be inspected.

2. Description of the Related Art In a production line of a vehicle such as an automobile, painting of a vehicle body is generally performed in a painting station provided in the production line.

In such a station, inspection of defects caused by the painting after the painting of the vehicle body has been conventionally performed by visual inspection by a human. In such an inspection, the inspector must find a minute defect from the surface of the coating film, which imposes a heavy burden on the inspector and requires a physically demanding operation.

In light of such circumstances in inspection of paint defects, light is irradiated to the surface to be inspected of an object, the reflected light is projected on a screen, and surface defects on the surface to be inspected are automatically determined from the sharpness of the projected image. There has been proposed a surface inspection apparatus capable of performing automatic detection (for example, see JP-A-62-233710).

If this surface inspection apparatus is applied to the detection of a paint defect on a vehicle body, the above-described paint defect can be automatically detected, and the inspector can be released from the conventional visual inspection work.

By the way, when the above-mentioned surface inspection technique by light irradiation is applied to an automatic inspection of a vehicle body coating, as shown in FIG. By irradiating linear (or spot) light, the coating surface 1 is formed in a light irradiation area sufficiently smaller than a camera field of view F of the video camera 3 described below, and reflected light from this light irradiation area is converted into a video. A device for receiving light by the camera 3 is conceivable.

In this apparatus, as shown in FIG. 9, the light received from the video camera 3 is such that the light reflected from the light irradiation area of the coating film surface 1 enters the camera field of view F, and the camera field of view F (see FIG. 8). The light-irradiated area of the coating film surface 1 is captured as a bright line image 6 in the dark light-receiving image 5 as a whole that covers When there is a paint defect 7 (see FIG. 8) in the light irradiation area, the specular reflection direction of the light changes at the paint defect 7, and if the defect 7 does not exist, the light is reflected normally. As a result, light that should have entered the camera field of view F does not enter the camera field of view F. As a result, a black defective portion 7 (see FIG. 9) appears in the bright line image 6.

Therefore, the defective portion 7 can be detected by identifying the black defective portion 7 by the image processing technique. In addition, according to this apparatus, since the coating film surface 1 is linearly and narrowly irradiated, the amount of irradiation is small, the regular reflection direction of the light incident on the light irradiation area at the defect portion 7 changes, and the video camera 3 The amount of incident light is clearly different between the defective portion 7 and the other portion, so that a minute defect can be detected.

However, according to the narrow light irradiation as in the above-described apparatus, the light irradiation area is too small with respect to the camera field of view F, while the defective portion 7 that can be captured by the video camera 3 is in the light irradiation area (that is, the received light image). 5 is only inside or near the line image 6), so that only the surface inspection using only a part of the camera field of view F can be performed at all times, and there is a problem that the inspection efficiency is lacking.

When the surface to be inspected is the body of a vehicle such as an automobile, the inspection is performed while moving the light source 2 and the video camera 3 of FIG. 8 along the surface of the vehicle with a robot device (not shown).

However, in this case, since the vehicle body has many curved surfaces, when the inspection location moves to these curved surface portions, the linear irradiation shape formed on the vehicle body surface by the light source 2 is distorted. Therefore, the line image 6 in the received light image 5 of the video camera 3 is also
As shown in FIG. 10, distortion occurs, and in extreme cases, it deviates from the camera field of view F.

For this reason, it is difficult to normally inspect the coating film surface 1 in the body of a vehicle such as an automobile, and control of the robot apparatus is complicated in order to always keep the line image 6 within the camera view F. There was a problem.

In order to solve the above-mentioned difficulties, as shown in FIG. 11, the coating surface 1 is broadly illuminated by the light source 2 'in a range equal to or larger than the camera field of view F, and this wide light irradiation area is set. Can be captured by the video camera 3.

However, when the coating film surface 1 is irradiated widely as described above, the irradiation light amount is greatly increased, so that halation of light at the defective portion 7 occurs, and the video camera 3 cannot clearly detect the minute defective portion 7. .

For example, the lights L ₁ and L ₂ from the light source 2 ′ are reflected by the coating film surface 1, and the reflected light enters the light receiving surface of the video camera 3. Since the amount of incident light is the same in any part, the received light image is brighter on one side.

On the other hand, if there is a defect 7 in the light irradiation area, the regular reflection direction of light incident on the light irradiation area changes at the defect 7, and the amount of incident light on the light receiving surface corresponding to the defect 7 decreases. It should be reduced and appear in the received light image as a black dot.

However, the light source 2 ', as described above, since the irradiation of broad Nurimakumen 1, a light source 2' light L ₃ from the other parts of, L ₄
Is reflected by the defective portions 7, 7 and enters the light receiving surface portion where the amount of light should decrease.

Therefore, the brightness in the received image does not significantly decrease, and therefore, when the defective portions 7, 7 are minute, a difference in brightness between the defective portions 7, 7 and the other portions is less likely to occur, It becomes difficult to identify the defective portions 7, 7 even by image processing.

As an apparatus for solving such a problem, as shown in FIGS. 1A and 1B, the luminous intensity m gradually changes from large to small in one predetermined direction along the light exit surface 13a (the magnitude of the luminous intensity). Light irradiation means 13 capable of emitting light
Using the light receiving means 14 receives the reflected light emitted from the light irradiation means 13 and reflected by the surface 11 to be inspected, and then converts the received image into a video signal, and differentiates the video signal. A technique for recognizing a surface defect when the level of the differential signal is equal to or higher than a predetermined value is considered.

According to such a technique, the inspection surface 11 has an emission surface 13a.
Since light is emitted by the light irradiating means 13 whose luminous intensity changes in one direction, when a defect 12 is present on the surface 11 to be inspected, a change in the intensity of the reflected light is disturbed by the defective portion. By detecting the video signal output from the video signal generating means from the differentiated value, the presence or absence of a surface defect can be easily and accurately determined.

(Problems to be Solved by the Invention) According to the above-described technology, when the surface defect 12 of the surface to be inspected 11 is a convex portion, as shown in FIG. 1 (a) and FIG. On one side 12a, the illuminance is higher than the vicinity, and on the other side 12b, the illuminance is lower than the vicinity. Therefore, the level of the video signal is not only in the outer shape of the protrusion but also in the protrusion. It changes greatly in the region. Surface defects
The same phenomenon occurs as shown in FIGS. 1 (b) and 2 (b) when 12 is a recess. Therefore, when these video signals are differentiated and their absolute values are taken, surface defects 12
In addition to the outer shape, there is a problem that a peak is also generated in an intermediate portion thereof, which causes an erroneous inspection and complicates the process of determining a surface defect.

The present invention has been made in view of such circumstances, and in an apparatus for determining the presence or absence of a surface defect based on the level of a differential video signal corresponding to a surface defect of a surface to be inspected, only the outer region of the defect is accurately determined. It is an object of the present invention to provide a surface defect inspection apparatus capable of improving the accuracy of defect detection and simplifying the defect determination process by identifying the defect.

(Means for Solving the Problems) According to the surface defect inspection apparatus of the present invention, the level of the differential video signal corresponding to the surface defect of the surface to be inspected is larger than a first threshold value of a predetermined level. Determining whether or not the value is within a predetermined range smaller than a second threshold value of a predetermined level which is set to be larger than the threshold value; and detecting a position of the surface defect based on a result of the determination. Things. That is, the apparatus comprises a light irradiating means for irradiating the surface to be inspected with light whose luminous intensity gradually changes from large to small in a predetermined direction along the light exit surface, and a reflection from the light irradiating region of the surface to be inspected. A video signal converting means for converting a light receiving image from the light irradiation area received on the light receiving surface into a video signal, and differentiating the video signal output from the video signal converting means; A signal differentiating means, a first threshold value at which a signal level of a differentiated video signal output from the signal differentiating means is larger than a change level of imaging luminous intensity in a region where no defect is present on the surface to be inspected; Signal level determining means for determining whether or not the image is included in a range between a second threshold value smaller than the change level of the imaging luminous intensity at the defective portion of the surface and larger than the first threshold value; Level discriminator Based on the determination result by those, characterized by comprising a defect position detecting means for detecting the position of a defect existing in the test surface. One of the two thresholds is for eliminating a portion where the level change of the video signal is extremely small, and the other is for excluding a portion where the level change of the video signal is extremely large. Only the level change at both ends of the surface defect is set to be included in the level range between these two threshold values.

When the above-mentioned determination is performed by taking the absolute value after differentiating the video signal, a portion having a small level change is excluded by the first threshold value, and an extreme level change is determined by the second threshold value. Will be excluded.

It is to be noted that the “gradual change” includes one that changes stepwise.

(Operation) According to the above configuration, when determining the magnitude of the level change of the video signal, two thresholds are set, and a portion having a small level change by one threshold is determined by the other threshold. Extremely large portions of the level change are excluded. If there is a surface defect, the level change between the outer portion and the central region of the surface defect becomes large, and the other portions have a small level change and are excluded by the one threshold. Also, the level change of the video signal occurring in the central region of the surface defect is considerably larger than the level change in the outer portion of the surface defect. Therefore, the level change portion in the central region of the surface defect is excluded by the second threshold value. As a result, the portion included in the range between the two thresholds is only the level change portion in the outer portion of the defect, and the outer portion of the surface defect is detected by detecting a peak existing between the thresholds in the differential video signal. Can be accurately identified.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

First, the principle of the present invention will be described with reference to FIGS. 1 (a) and 1 (b).

FIG. 1A shows a case where a surface to be inspected 11 has a convex defect portion 12, and FIG. 1B shows a case where the surface to be inspected 11 has a concave defect portion.
Shows the case with 12.

1 (a) and 1 (b), 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. Plane arrow
Changes Tsuyokara weak in one direction indicated by A _1. The light source 13 irradiates the light irradiation region S of the inspection target surface 11 with light emitted from the emission surface 13a.

As described above, the light emitted from the exit face 13a of the light source 13, as indicated by the arrow A _1, light curve is attached with respect to one direction of the exit surface 13a. For this reason, the above-mentioned arrow corresponding to the above-mentioned luminous intensity change
A light irradiation area S having a change in illuminance in a direction corresponding to A ₁
Occurs. Then, the light irradiation area S is captured in the camera field F of the video camera 14 as a video signal generating means having the camera field F included therein.

Therefore, as shown in FIGS. 2 (a) and 2 (b), in the light receiving image 15 of the video camera 14 which captures the reflected light of the light irradiation area S, the light emitting surface 13 of the light source 13
Arrow A _{1 in} which the intensity of light emitted from a changes from strong to weak
Brightness in the direction indicated by arrow A ₂ in response to the direction indicated by changes in Tsuyokara weak.

In such a state, if a defect 12 is formed on the surface 11 to be inspected, the regular reflection direction of the light from the light source 13 at the defect 12 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 .

Then, as shown in FIG.
In the case of a convex shape, the light from the position 16 where the luminous intensity is large on the emission surface 13a of the light source 13 is mainly the emission surface 13a.
The direction of specular reflection changes on the surface 12a of the defect portion 12 opposite to the above, and a part thereof enters the video camera 14. But,
On the surface 12b on the back side of the defect portion 12 with respect to the emission surface 13a,
Only the light from the position 17 where the luminous intensity of the emission surface 13a is relatively small enters, and the reflected light from the rear surface 12b of the defective portion 12 hardly enters the video camera 14.

Therefore, received-light image 15 of the video camera 14, as shown in FIG. 2 (a), intended defect portion 12 is convex, arrow A ₂ toward the dark from light Toko of received-light image 15 of the video camera 14 In the direction indicated by, the defective portion 12 becomes brighter than the other portions at first, and becomes darker than the other portions after passing the bright portion.

When the defect portion 12 is concave, light from the position 16 having a large luminous intensity on the emission surface 13a of the light source 13 mainly collides with the surface 12c on the side opposite to the emission surface 13a of the defect portion 12, and is specularly reflected. The direction changes, and a part of the direction changes into the video camera 14. However, the surface 1 opposite to the surface 12c of the defect 12
Only light from the position where the luminous intensity of the emission surface 13a is relatively small enters 2d, and almost no light enters the video camera 14 from the opposite surface 12d of the defect portion 12.

Therefore, received-light image 15 of the video camera 14, as shown in FIG. 2 (b), intended defect portion 12 is concave, with an arrow A ₂ toward the dark from where bright light image 15 of the video camera 14 In the direction shown, the defect 12 first becomes darker than the other parts, and after this dark part it becomes 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, the video signal is input to the video signal determination unit 18 output from the video camera 14. The signal level on one scanning line near the defective portion 12 of the video signal input to the judging portion 18 is, as shown in FIG. 3 (a), when the defective portion 12 is convex, If the defect 12 is concave,
The shape is as shown in FIG.

The video signal is subjected to a differentiation process in the determination unit 18, and then an absolute value is obtained.

Accordingly, a video signal having a signal level as shown in FIGS. 3A and 3B is converted into a signal having three peaks as shown in FIG. Of these three peaks, peaks A and C represent the outer portion of the defective portion 12, while peak B represents a portion where the signal level greatly changes in the region of the defective portion 12. .

The peak A and the peak C provide useful information when determining the presence / absence and position of a surface defect, but the peak B not only provides little such effective information, but also the surface defect. This may cause erroneous position determination or complicate signal processing for the determination.

Therefore, in the present invention, as shown in FIG. 4, a first threshold value and a second threshold value are set for the differential video signal, and the determination is made only when the level is between these two threshold values. The detection signal is output from the section 18 so that only the signal corresponding to the outer shape of the defective section 12 is output. That is, a portion other than the defective portion 12 is excluded as a small level change by the first threshold value, and a portion where the level change in the area of the defective portion 12 is large is determined as an excessive level change by the second threshold value. Be eliminated.

Since the present apparatus detects the presence or absence and the position of a surface defect based on the detection signal output from the determination unit 18 in this way, it is possible to improve the determination accuracy and simplify the signal processing. .

Next, the configuration of an embodiment using the above principle will be described with reference to FIGS. 5, 6, and 7. FIG.

The vehicle body painting inspection station 20 is equipped with a robot device 21 mounted on a pedestal B as shown in FIG.

The robot device 21 includes a light irradiation means 23 corresponding to the light source 13 (see FIGS. 1 (a) and 1 (b)) and a video camera 14 (see FIG. 1 (a)). )
And a CCD camera 24 corresponding to FIG. 1 (b)). The light irradiation means 23 and the CCD camera 24 of the robot device 21 correspond to the coating surface 27 of the vehicle body 26 (the surface 11 to be inspected in FIGS. 1 (a) and 1 (b)) carried into the coating inspection station 20. The light radiated by the light irradiating means 23 is reflected by the coating film surface 27 on the surface of the vehicle body 26 and enters the CCD camera 24.

In the coating defect inspection by the light irradiation unit 23 and the CCD camera 24, the robot controller 32 is driven by a command given by the host computer 31. And by that the robot controller
32 signals are sent to the robot device 21.

The robot device 21 operates a built-in actuator (not shown), whereby the robot device 21 causes the light irradiating means 23 and the CCD camera 24 to trace the surface of the vehicle body 26. While moving 24, the video signal obtained by the CCD camera 24 is output to the image processor 33.

In the image processor 33, as described above,
After the video signal is amplified and differentiated to take an absolute value, the differentiated signal detects a scan line of the video signal and a timing on this scan line in a range between two preset threshold values, The data is transmitted to the host computer 31 and analyzed. Thus, the coordinates of the position of the defect 12 and whether the defect 12 is convex or concave is detected.

The comparison between the differential video signal and the two threshold values is performed for all the scanning lines of the image received by the CCD camera 24. FIG. 6 is a flowchart showing the sequence of the operation. That is, first, image information of one screen is taken into the screen processing processor 33 (S1),
Among them, one scan line of data is extracted by horizontal scanning (S2), and the extracted scan data is subjected to differential processing (S3) and absolute value processing (S4). The threshold value (S5) and the second threshold value (S6) are compared. When the differential data has a peak having a value between the first threshold value and the second threshold value, the defect outer shape processing is performed on this portion (S
7) A surface defect detection signal is output. When the defect outline processing is completed, and when the differentiated data becomes a value other than the value between the two thresholds, the above operation is repeated for the next differentiated data. (S8). When the above-mentioned scanning is completed for all the differential data of the scanning line, the same operation is repeated for the subsequent scanning line (S
9). Thus, for all the image information of one screen,
When the above operation is completed, the same operation is performed for the image information of the next screen received by the CCD camera 24.

Based on the detection result obtained by such an operation, the vehicle body
Repair is performed in accordance with the irregularities of the defective portion 12 of the coating existing on the 26 painted surface, and as described below, when the defective portion 12 is convex, the protruding portion is cut off small and the defective portion is removed. When 12 is concave, the coating film is cut off in a relatively wide area including the defective portion 12.

The repair can be performed manually, but is automatically performed by the robot device 21 or a repair robot device (not shown) provided separately from the robot device 21.

The light irradiating means 23 includes a box as shown in FIG.
A plurality of fluorescent lamps 42 (not particularly limited to the fluorescent lamp 42) are provided inside 41. An optical filter 43 is provided in front of the fluorescent lamps 42, and a diffusion screen 44 is attached so as to cover the entire surface of the optical filter 43.

The light filter 43 is 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, and For example, the light transmittances at points having the same x coordinate value of the xy coordinates set on the surface 13a as shown in FIG. 7 are equal, and the light transmittances at the points having different y coordinate values are different. It has become. Thereby, a light irradiation area S (see FIGS. 1 (a) and 1 (b)) having a change in illuminance in one direction is formed on the coating film surface 27 on the surface of the vehicle body 26 shown in FIG. .

On the other hand, the diffusion screen 44 diffuses the light transmitted from the optical filter 43 and arranges the fluorescent lamps 42 at intervals so as to prevent a low illuminance area from being formed on the coating film surface 27. is there.

The change (gradient) of the luminous intensity applied to the light irradiation means 23 is
As shown by the dotted line in FIG.
Can be created by changing the applied voltage of each fluorescent lamp 42 by the light irradiation means controller 34 in accordance with a command from the post computer 31. In this case, the optical filter 43 can be omitted.

In the above paint defect inspection equipment, the paint inspection station
As the painted vehicle body 26 is carried into the vehicle 20, a paint defect inspection operation is started. That is, the robot apparatus 21 is controlled by the robot controller 32 to keep the light irradiation means 23 and the CCD camera 24 in an integral relationship, and the light irradiation means 23 and the CCD camera 24 It is traced along the surface shape of the vehicle body 26 at a great distance.

At this time, as described with reference to FIGS. 1 (a) and 1 (b), the light
Is applied to the coating surface 27 of the vehicle body 26 and the light intensity distribution of which changes uniformly in one direction.

Therefore, the illuminance distribution changes uniformly in one direction on the coating film surface 27, as shown in FIGS. 1 (a) and 1 (b).
Is formed as shown in FIG. In the CCD camera 24 on which the reflected light from the light irradiation area S is incident, a light reception image 15 whose brightness uniformly changes in one direction corresponding to the luminous intensity distribution of the light irradiation means 23 is created. become.

Therefore, if a defect 12 is formed on the surface 11 to be inspected,
In that part, the regular reflection direction of the light from the light source 13 changes, and the first
FIG. 1 (a) and FIG. 1 (b), FIG. 2 (a) and FIG.
As described in the explanation of the principle of FIG. 2B, for example, when the defective portion 12 is convex, the received image 15 of the video camera 14 is, as shown in FIG. 14
In the direction indicated by the arrow A ₂ toward the dark from bright area of the light receiving image 15 becomes brighter than other portions Introduction defective portion 12 becomes darker than the other portions After this bright part.

If the defective portion 12 is concave, the second
As shown in FIG. (B), in the direction indicated by the arrow A ₂ toward the dark from where bright light image 15 of the video camera 14, darker than other portions Introduction defective portion 12, after this dark part And become brighter than 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.

When this video signal is input to the image processing processor 33, the image processing
A scanning line of a video signal in which a differential signal of a video signal output from the camera 24 has a peak between two predetermined threshold values, a timing at which the differential signal has the peak on the scanning line, and a timing near the timing. A change in the sign of the differential signal is detected. As a result, the position of the defective portion 12 in the received light image 15 and the uneven shape of the defective portion 12 are detected. This detection data and the position of the tip arm 22 of the robot device 21 are stored in the memory. When the defective portion 12 is repaired, the stored contents of the memory are taken out, and the defective portion 12 is repaired as described above.

As described above, even when the surface 11 to be inspected is irradiated in a planar manner, halation of light is eliminated, and the defective portion 12 can be captured as a clear image having a difference in brightness from the surroundings.

Further, as described above, the scanning line of the video signal having a peak at which the differential signal of the video signal has a value between two predetermined threshold values, the timing of the peak of the differential signal on the scanning line, and By detecting a change in the sign of the differential signal near the timing, the received light image
The position of the defective portion 12 and the uneven shape of the defective portion 12 within 15 can be detected, and even if the defective portion 12 is minute, it can be reliably detected as the defective portion 12.

In the above-described embodiment, the absolute value is obtained after differentiating the video signal. However, if two thresholds are set for each of the positive and negative values, it is not always necessary to obtain the absolute value. .

In the coating inspection by the image processing described above,
It is necessary to group detected defects at high speed according to their size. Conventionally, there has been known a method of obtaining the area by counting the number of pixels in which a defective portion exists, but such a method has a limitation in processing speed and cannot speed up grouping processing.

Therefore, in the above-described embodiment, the CCD camera 24
Is reduced by an averaging process, and a defect detection process is performed on the reduced image. That is, a defect detected in such a reduced image remains in a predetermined size even after the averaging process, and thus has a size that can withstand the averaging process. Therefore, a plurality of averaging widths are provided, and defect detection processing is performed in each of the reduced images of each averaging width, so that surface defects can be grouped in real time.

(Effect of the Invention) According to the surface defect inspection apparatus of the present invention, a signal obtained by differentiating a video signal is compared with two predetermined thresholds, and this signal has a peak between the two thresholds. Sometimes it is determined that there is a surface defect. As described above, the two threshold values are used to exclude a portion where the level change of the video signal is small and a portion where the level change is extremely large.
Not only the portion other than the surface defect but also the portion having a large level change in the surface defect can be excluded from the defect information, thereby eliminating the possibility of erroneous defect detection and facilitating the defect position detection processing.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are explanatory diagrams of the principle of the surface defect inspection apparatus according to the present invention, and FIGS. 2 (a) and 2 (b) are convex and concave, respectively. FIG. 3 (a) and FIG. 3 (b) are illustrations of a camera image when there is a concave defect, and FIG. 3 (b) shows the signal level of a video signal when there is a convex and concave defect on the surface to be inspected, respectively. FIG. 4 is a graph showing signal waveforms after differential processing and absolute value processing are performed on the video signals shown in FIGS. 3 (a) and 3 (b). FIG. 5 is a surface according to the present invention. FIG. 6 is an explanatory view of an embodiment in which the defect inspection apparatus is applied to a paint defect inspection apparatus for a vehicle body, FIG. 6 is a flowchart showing image data processing operations in the embodiment apparatus shown in FIG. 5, and FIG. FIG. 8 is an explanatory view of a conventional surface defect inspection apparatus. 9 is an explanatory view of an image obtained by the camera of the surface defect inspection apparatus of FIG. 8, FIG. 10 is an explanatory view of an image obtained by the camera when the surface to be inspected is a curved surface, and FIG. FIG. 9 is an explanatory diagram of a conventional surface defect inspection device different from the device of FIG. 8. 11 ... inspected surface, 12 ... defective part 13 ... light source, 14 ... video camera 15 ... received light image, 16 ... position with high luminous intensity 17 ... position with low luminous intensity, 18 ... determination unit 21 ... ... Robot device, 23 ... Light irradiation means 24 ... CCD camera, 25 ... Support bracket 26 ... Car body, 27 ... Coating surface 31 ... 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 (56) References JP-A-60-80744 (JP, A) JP-A-63-31360 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 21/88 G01B 11/30 G06T 1/00 H04N 7/18

Claims (1)

(57) [Claims] 1. A light irradiating means for irradiating a light whose intensity gradually changes from large to small along a light exit surface onto a surface to be inspected, and receiving light reflected from a light irradiation area of the surface to be inspected. A video signal converting means having a light receiving surface and converting a light receiving image from the light irradiation area received on the light receiving surface into a video signal; and a signal differentiating means for differentiating the video signal output from the video signal converting means. A first threshold value at which the signal level of the differentiated video signal output from the signal differentiating means is larger than a change level of the imaging luminous intensity in a defect-free area of the inspection surface; A signal level discriminating means for discriminating whether or not it is included in a range between a second threshold value smaller than the change level of the imaging luminous intensity and a larger value than the first threshold value. In the judgment result A defect position detecting means for detecting a position of a defective portion present on the surface to be inspected on the basis of the surface defect inspection device.