JP2000121631A - Paint inspecting method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely judge the quality of a paint from a received image by irradiating light to an object coated and dried with the paint to be inspected, and forming the received image based on the reflected light. SOLUTION: The light emitted from an irradiating means 1 is irradiated to the paint coated face of an object 4 coated with a paint. The light reflected on the coated face is received by a receiving means 2 and converted into an analog electric signal, and the analog electric signal is fed to an image processing means 3. The analog electric signal is A/D-converted by the image processing means 3, a received image is formed from the converted signal, a moving average process is applied to the received image to remove noises by an arithmetic means 6 in an image processing means, a double differential process is applied to emphasize defects, then a binalization process is applied. The number of picture elements having a high concentration value is obtained from the result of the binalization process, defects of the paint occurring on the coated face are extracted, and the quality of the paint is judged. A method for calculating the area and length of an image group having a high concentration value is also preferably used other than the method for calculating the number of picture elements having a high concentration value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method suitable for inspecting paint quality.

[0002]

2. Description of the Related Art Paints, such as those used for exterior painting of building materials, are applied to aluminum sashes through a process such as electrodeposition coating and baking. In some cases, dried and dried building materials have uneven gloss defects that differ in gloss from the surroundings.

One of the causes of this drawback is the quality of the paint. For example, polymer-based paints are usually manufactured through a process of mixing and aging raw materials, but slight differences in composition and slight changes in reactions in this process generate unnecessary substances. . When this unnecessary material is applied to building materials and dried,
It is believed that they precipitate out and cause the above-mentioned drawbacks. Building materials or the like that suffer from paint defects cannot be shipped because their appearance is impaired.

[0004] Usually, since a large amount of building material is painted at once, even if defects of the paint can be found after the paint, the loss is extremely large. Therefore, it is necessary to inspect the quality of the paint before painting. However, in general inspection methods based on viscosity, yield value, etc., paints with high viscosity such as paints used for exterior painting of building materials, paints that have defects and normal paints that do not occur Since no difference is observed even when the yield values are compared, the defective paint cannot be determined. Also,
Even if an unnecessary substance that causes a defect is generated in paint, it is impossible to measure only that substance.Therefore, the paint quality cannot be known without painting. It was very difficult.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and an apparatus for accurately inspecting the quality of a paint.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention irradiates an object, which has been coated with a paint to be inspected and dried, with light, creates a light-receiving image based on the reflected light, and receives the light. It is characterized by a paint inspection method for judging paint quality from an image.

At this time, light is applied to the coating surface at an angle in the range of 25 to 65 degrees, and
Receiving light at an angle in the range of 5 to 155 degrees, converting the received reflected light into an analog electric signal, subtracting a certain level from the analog electric signal to create a received image, and adding noise to the received image. It is preferable to perform the removal processing and the defect emphasis processing, then perform the binarization processing on the processed image, and determine the quality of the paint from the characteristics of the binarized image. When irradiating an object with light and receiving the light, the reflected light from the object is sequentially received while moving the object so that the main direction of the formation of the object and the light receiving direction are parallel to form a one-dimensional received image. A plurality of one-dimensional light-receiving images sequentially obtained are stored in a memory to form a two-dimensional light-receiving image, and then the average of the two-dimensional light-receiving image in a direction parallel to the main direction of the formation of the object is obtained. The image data value profile f (x) and the average image data value profile g (y) in the direction orthogonal to the main direction of the formation of the object
Is obtained, and the image data value f (x) at the pixel position (x _i , y _j ) is obtained.
_i ) and a two-dimensional average image is created from the average value of g (y _j ), and the image data value of the two-dimensional average image is
It is also preferable to divide or subtract by the image data value of the pixel at the same position in the two-dimensional light receiving image, and determine the quality of the paint from the image pattern after the operation. And applying the paint to be inspected to a punched plate mainly composed of aluminum,
It is also preferable to use a paint containing an acrylic resin or a melamine resin as a main component as the paint to be inspected.

Further, a paint inspection apparatus having means for performing any one of the above methods, a paint inspection using any of the above methods, and management of the paint production process based on the inspection result. Is also a preferred embodiment.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A paint inspection apparatus according to the present invention is shown in FIG.
As shown in (1), irradiation means is applied to an object 4 such as a punched plate made of aluminum, to which a paint to be inspected is applied, so that an irradiation angle is 25 to 65 degrees with respect to the paint application surface of the object 4. 1 is arranged. Further, the light receiving means 2 has a light receiving angle in a plane substantially including the irradiation means and substantially perpendicular to the application surface, and furthermore, from 115 to 115 with respect to the application surface.
It is arranged to receive light at an angle in the range of 155 degrees. The light receiving unit 2 is connected to the image processing device 3 so as to receive the reflected light from the object 4, convert the reflected light into an analog electric signal, and transmit the signal to the image processing device 3. The image processing device 3 creates a received light image from the A / D converter of the analog electric signal taken in and the converted signal,
The arithmetic unit 6 performs a binarization process on the received light image by a moving average process or a difference process, and a determination unit that determines the quality of the paint based on the process.

In the above inspection apparatus, the light emitted from the irradiating means 1 irradiates the paint-coated surface of the paint-coated object 4. The light reflected on the application surface is received by the light receiving unit 2 and converted into an analog electric signal. The analog electric signal is taken into the image processing unit 3. The image processing means 3 performs A / D conversion of the analog electric signal, creates a light receiving image from the converted signal, and performs a moving average process or the like on the light receiving image by the calculating means 6 in the image processing means to reduce noise. Removal is performed, and two-time difference processing is performed to emphasize the defect, and further, binarization processing is performed. Then, from the result of the binarization processing, the number of pixels having a high density value is obtained, for example, to extract the defect of the paint on the application surface, and determine the quality of the paint. In addition, as a method of determining the quality of the paint from the result of the binarization processing, besides calculating the number of pixels having a high gray value, a method of calculating the area or length of a pixel group having a high gray value is also preferably used. Can be

Here, the state of light reflection on the paint-coated surface of the object 4 will be described. Gloss unevenness defects that occur along the dry trace of paint are, for example, when the paint is an electrodeposition paint containing acrylic resin or melamine resin as a main component, when the paint is electrodeposited and then dried, certain substances in the paint are dried. Is generated by concentration and precipitation. Since this defective portion has a slightly different reflectance from the surrounding normal portion, a slight difference occurs in the amount of reflected light. Therefore, 25
Irradiate from an angle of ~ 65 degrees, 115-1
It is preferable to make the difference in the amount of reflected light appear remarkably by receiving light at an angle of 55 degrees. Then, image processing is performed using the difference in the amount of reflected light to extract the defects of the paint,
Further, the quality of the paint is determined.

The object 4 to which the paint to be inspected is applied is
Other than a punched plate made of aluminum may be used. However, in order to obtain a highly accurate inspection result, a test piece such as a building material to which a paint is applied in an actual application is preferable.

FIG. 2 shows an apparatus according to another embodiment of the present invention in which another operation means 11 is added to the image processing means 3 in FIG.

According to the present invention, as described above, the quality of the paint is determined by emphasizing the minute gloss difference of the paint applied to the test piece. However, when emphasizing the minute gloss difference of the paint, formations called dice eyes that occur on the object to which the paint is applied are also emphasized,
When the dice are strongly observed, it is preferable to determine the quality of the paint by removing the dice from the received light image using the apparatus shown in FIG. The formation of the surface of the object called the dice is, for example, when the object is made of aluminum, the object is usually manufactured by extruding from a base. A formation (a die) parallel to is generated. Due to the dice, even when the paint is applied to the surface of the object, irregularities are formed along the dice, and the irregularities cause a difference in the amount of reflected light. Then, this difference is also emphasized by image processing for emphasizing the minute gloss difference due to the defective paint, and it is considered that even if the paint passes, it is determined to be defective, and the quality of the paint may not be accurately determined. . If the occurrence pattern of the dice is constant, the dice can be removed by storing the pattern of the dice in advance by a method such as pattern matching, but the position and amount of foreign matter adhering to the base are constant. Therefore, the degree of occurrence of the dice differs for each object. Therefore, dice cannot be removed by a technique such as pattern matching.

Therefore, in the present invention, the object 4 to which the paint is applied is transferred to the main direction, the light receiving direction, and the irradiation direction of the dice on the surface of the object by using the apparatus shown in FIG. Are irradiated so that the object 4 is irradiated with light by the irradiation means 1 and the reflected light from the application surface is sequentially received linearly by the light receiving means 2 while moving so as to be parallel. The received reflected light is converted into an analog electric signal, and the analog electric signal is taken into the image processing means 3. Then, the following processing is performed by the arithmetic means 11. First, the analog electric signal captured by the image processing means 3 is converted into an A / D signal.
After conversion, a one-dimensional received light image is created based on the digital electric signal. Then, a plurality of one-dimensional light receiving images are sequentially stored in a memory in the image processing means 3 to create a two-dimensional light receiving image. In the two-dimensional light-receiving image, the dice occurs substantially in parallel to one direction of the image, while the uneven gloss due to the defective paint is inclined with respect to the dice in the process of occurrence.

Next, the following processing is performed by the arithmetic means 6. First, the average image data value profile f (x) in the direction parallel to the main direction of the dice (for example, the vertical direction of the image) of the two-dimensional light receiving image and the direction orthogonal to the main direction of the dice (for example, the horizontal direction of the image) average image data value profile sought g (y), to create a two-dimensional average image from the average value of the pixel position (x _i, y _j) image data value f (x _i) of and g (y _j) of the. Then, the two-dimensional average image is divided or subtracted by the image data value of the pixel at the same position in the two-dimensional light-receiving image, and the calculated data is amplified at a fixed magnification and an offset is added. In the two-dimensional light receiving image, if the dice are generated in parallel to the vertical direction of the image, the information of the dice is reflected in the average image data value profile in the vertical direction. During the generation process, the image is inclined with respect to the dice, and the difference in gloss from the surroundings is smaller than that of the dice, so that it is hardly reflected in the average image data value profile in the vertical direction. Therefore, the image after the division or the subtraction has the dice removed and the gloss unevenness defect remains, and the quality of the paint can be determined with high accuracy. Therefore, when dice are strongly seen, it is preferable to use an apparatus as shown in FIG.

FIG. 3 shows an apparatus according to another embodiment of the present invention in which a signal enhancement circuit 5 is added to the apparatus shown in FIG.
Gloss unevenness due to paint defects has a very small difference in gloss from the surroundings.To improve inspection accuracy, extract signals in the effective range and further increase the contrast of the signals in that range to increase the contrast between the defects and the surroundings. It is preferable to increase the gloss difference between the two. Therefore, it is preferable that the signal enhancement circuit 5 first subtracts a constant value from the analog electric signal to extract a signal in an effective range, and then amplifies the signal by a constant magnification. By doing so, the difference in gloss from the surroundings is enlarged, and the accuracy of determining the defect of the paint can be improved.

As described above, according to the present invention, since the quality of the paint is determined from the pattern of the received light image, the quality of the paint can be easily and accurately inspected even by a skilled inspector. In addition, when the above inspection is applied in the paint manufacturing process, a defective portion in the manufacturing process can be immediately corrected and the manufacturing process can be managed, so that the paint manufacturing cost can be reduced and Since defective defects can also be removed, damage due to defective paint can be suppressed.

[0019]

EXAMPLES Example 1 Paints were inspected using the apparatus shown in FIG.

The irradiating means is disposed so as to irradiate the coating surface from an angle of 45 degrees, and the light receiving means is opposed to the irradiating means and receives light at an angle of 135 degrees with respect to the applying surface. Placed. The light source 1 has an effective light emission length of 300
mm, a high-frequency fluorescent lamp having a frequency of 30 KHz was used. As the light receiving section 2, an area sensor camera having 512 × 480 CCD elements arranged two-dimensionally was used, and the object 4 to be coated with a paint was a flat aluminum plate having a size of 50 × 150 mm and a thickness of 1 mm. As the paint to be inspected, 10 lots of paint for exterior appearance of a building material containing acrylic resin as a main component were used, each of which was applied to the object 4 by electrodeposition coating.

The received image was subjected to a moving average process at 10 pixels in the horizontal direction, and a difference process was performed twice at 10 pixels in the horizontal direction, and the subsequent image data was binarized.

FIG. 4 shows an example of a two-dimensional light receiving image and an image after processing. 4A and 4C show received light images, and FIGS.
(D) is the processed image. When the number of high-level pixels (white portions) in (b) and (d) was measured, (b) was about 5
000, (d) was about 50,000.

FIG. 5 shows the number of high-level pixels in the processed images of all lots. Lots with many high-level pixels generated a lot of gloss unevenness even when paint was actually applied to an aluminum sash. Example 2 A paint was inspected using the apparatus shown in FIG.

The object 4 was the same aluminum plate as that of the first embodiment, but had a sharp die. The irradiating means and the image processing means were set to be the same as those in the first embodiment. As the light receiving means 2, a line sensor camera having 512 CCD elements arranged in one line was used. Further, a uniaxial stage is used as a transporting means 7 for moving the object to which the paint is applied,
The plate was moved at a speed of 20 mm / sec so as to be parallel to the die.

960 lines of one-dimensional light-receiving images were generated to inspect the entire coating range of the paint. Then, a two-dimensional light receiving image is created from the one-dimensional light receiving image of 960 lines, and the average image data value profile f (x) in the vertical direction and the average image data value profile g (y) in the horizontal direction of the two-dimensional light receiving image are calculated. calculated to create an image data value f (x _i) and g 2-dimensional average image from the average value of (y _j) of the pixel position (x _i, y _j), pixels at the same position between the two-dimensional average image Was calculated by dividing the image data values, and the processed image data was processed in the same manner as in the first embodiment.

FIG. 6 shows the received light image (a) and the processed image (b). Although many dice appear in the received light image, the dice is removed from the processed image, and the paint can be determined with higher accuracy by this method. Example 3 The paint was inspected using the apparatus shown in FIG.

For the object 4, the same aluminum plate as in Example 1 was used.

The signal emphasizing circuit 5 subtracts a value corresponding to 30% of the maximum value that the electric signal can take from the analog electric signal received by the light receiving means and further converted,
Processing was performed in the same manner as in Example 2 except that the amplification was further performed 50 times.

FIG. 7 shows a received light image (a) obtained without using the signal enhancement circuit and a received light image (b) obtained using the signal enhancement circuit. The gloss unevenness defect that could not be captured in (a) can be captured in (b),
Gloss unevenness due to the defect of the paint could be easily detected from this image, and highly accurate determination could be made.

[0030]

According to the present invention, a paint is applied to a test piece, a received light image is created based on the reflected light from the applied surface, and the quality of the paint is determined. In addition, it is possible to easily and accurately inspect the quality of the paint, and to determine the defective paint before applying it to an actual plate material such as a building material, so that the loss due to the defective paint can be suppressed.

Further, irradiation is performed at an angle in the range of 25 to 65 degrees with respect to the coating surface, and 115 to 15
When light is received at an angle in the range of 5 degrees, streak-like gloss unevenness can be reliably detected, and inspection accuracy can be improved.

Further, when the received light image is subjected to moving average processing in one direction and differential processing twice, and further to binarization processing, noise removal and defect emphasis can be performed, and the number of high-level pixels can be reduced. The quality of the paint can be easily determined by calculating

Then, when the received reflected light is transmitted by an analog electric signal, and a certain level is subtracted from the analog electric signal and amplified to form a light-receiving image, a minute gloss difference is also detected. And a more precise paint quality inspection can be performed.

When irradiating an object with light and receiving light,
While moving the object so that the main direction of the formation of the object and the light receiving direction are parallel, the reflected light from the object is linearly received to create a one-dimensional light-receiving image, and a plurality of one-dimensional images obtained sequentially are obtained. The received light image is stored in a memory to create a two-dimensional received light image, and then the average image data value profile f (x) in the vertical direction and the average image data value profile g (y) in the horizontal direction of the two-dimensional received image are calculated. The pixel position (x
_A two-dimensional average image is created from the average values of the image data values f (x _i ) and g (y _j ) of _i , y _j ), and the image data values of the two-dimensional average image are the same as those of the two-dimensional light-receiving image. When dividing or subtracting by the image data value of the pixel at the position and judging the quality of the paint from the pattern of the image after the operation, the inspection can be performed without being affected by the formation appearing on the surface of the object to which the paint is applied. In addition, the paint quality can be inspected with higher accuracy.

Further, when the above method is applied to a paint manufacturing process, a defective portion of the manufacturing process can be immediately corrected, and the paint manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of a paint inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram of a paint inspection apparatus according to another embodiment of the present invention.

FIG. 3 is a block diagram of a paint inspection apparatus according to still another embodiment of the present invention.

FIG. 4 shows a received light image obtained in Example 1 and an image after processing.

FIG. 5 is a graph showing the number of high-level pixels of a processed image in 10 lots of paint.

FIG. 6 shows a received light image obtained in Example 2 and an image after processing.

FIG. 7 shows a light receiving image obtained in Example 3 and an image after processing.

[Explanation of symbols]

 1: irradiating means 2: light receiving means 3: image processing means 4: object 5: signal emphasizing circuit 6: calculating means 7: transport means 11: calculating means

Continued on the front page F term (reference) 2G051 AA90 AB12 AB20 AC11 BA05 BA08 BB01 CA03 CA06 CB01 DA06 EA08 EA11 EA12 EA16 EB01 EC02 EC03 ED03 ED08 2G059 AA05 BB20 DD12 EE02 FF01 HH02 HH03 MM04 MM01 MM04

Claims (9)

[Claims] An object obtained by applying a paint to be inspected and irradiating a dried object with light, creating a light reception image based on the reflected light, and judging the quality of the paint from the light reception image. Inspection methods. 2. The method according to claim 1, further comprising irradiating the coating surface with light at an angle in the range of 25 to 65 degrees.
The paint inspection method according to claim 1, wherein the light is received at an angle in a range of degrees. 3. The paint inspection apparatus according to claim 1, wherein the received reflected light is converted into an analog electric signal, and a received light image is created by subtracting a certain level from the analog electric signal. 4. A light receiving image is subjected to a noise removal process and a defect emphasizing process, and then a binarized process is performed on the processed image, and the quality of the paint is determined based on the characteristics of the binarized image. The paint inspection method according to any one of claims 1 to 3, wherein the determination is made. 5. When irradiating an object with light and receiving the light, the reflected light from the object is sequentially received while moving the object so that the main direction of formation of the object and the light receiving direction are parallel to one-dimensionally. A light-receiving image is created, the sequentially obtained one-dimensional light-receiving images are stored in a memory to create a two-dimensional light-receiving image, and then the two-dimensional light-receiving image is parallel to the main direction of the formation of the object. Direction average image data value profile f (x);
The average image data value profile g (y) in the direction orthogonal to the main direction of the formation of the object is obtained, and the pixel position (x _i , y _j )
A two-dimensional average image is created from the average value of the image data values f (x _i ) and g (y _j ), and the image data value of the two-dimensional average image is converted to the image of the pixel at the same position in the two-dimensional light receiving image. The paint inspection method according to any one of claims 1 to 4, wherein the quality of the paint is determined from a pattern of an image after the operation by dividing or subtracting the data value. 6. The method for inspecting a paint according to claim 1, wherein the paint to be inspected is applied to a punched plate mainly composed of aluminum. 7. A paint containing acrylic resin or melamine resin as a main component is used as the paint to be inspected.
7. The method for inspecting a paint according to any one of claims 1 to 6. 8. An apparatus for inspecting a paint, comprising means for performing the method according to claim 1. 9. A method for producing a paint, wherein the paint is inspected by using the method according to claim 1, and a process for producing the paint is controlled based on the inspection result.