JP2002168792A - Appearance inspection method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] The present invention inspects the appearance of an inspection object in which the background tone fluctuates, visually detects a portion exhibiting a different color, and does not rely on visual observation. Provides a high way. Particularly, the present invention provides a highly reliable inspection method suitable for surface inspection of dirt and foreign matter in a synthetic rubber veil manufacturing process line. SOLUTION: The inspection range of the inspection object is divided into small areas, brightness and / or hue are converted into numerical values using a spectrometer for each small area, an average value is calculated from the measured numerical values, and the average value is calculated. Relative evaluation is used to determine a small area in which the deviation amount of each small area from the area exceeds a set reference value as an abnormal small area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for inspecting the appearance of a test object whose background color tone fluctuates, detects a portion exhibiting a different color, and identifies foreign matter in a product inspection process without visual inspection. About the method.

[0002]

2. Description of the Related Art The appearance inspection of an inspection object whose background color tone does not change or changes only slightly is automated by a system in which a color CCD camera and an image processing device are combined. However, automation of the appearance inspection of an inspection object whose background color fluctuates is difficult in a system in which a conventional color CCD camera and an image processing device are combined, and it is difficult to determine a subtle color difference. This is extremely difficult due to erroneous operation due to shadows due to minute irregularities, and is effective only in the case of detecting a foreign substance exhibiting an extreme color difference. For this reason, they have actually relied on human visual inspection or have been used only as a supplement to it.

[0003]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for inspecting the appearance of a test object whose background color tone fluctuates, detecting a portion presenting a different color, and recognizing a foreign substance without visual inspection. The aim is to provide a high method. It is another object of the present invention to provide a method for easily inspecting an inspection object having irregularities on the surface. Another object of the present invention is to provide a highly reliable inspection method suitable for surface inspection of dirt and foreign matter in a synthetic rubber veil manufacturing process line.

[0004]

Means for Solving the Problems To solve the above problems, the present inventors have intensively studied a method of judging abnormalities, and have found that a highly reliable inspection suitable for inspecting the surface of an inspection object whose color tone fluctuates. A method has been found, which has led to the present invention. That is, the present invention has been achieved by the following method.

(1) An inspection range of an inspection object whose color tone fluctuates is set, the inspection range is divided into small areas, and brightness and / or hue are converted into numerical values by using a spectrometer for each small area. In the visual inspection method for determining the presence or absence of an abnormality in a small area from the measured value, an average value was calculated from the measured values of a plurality of small areas, and the deviation amount of the measured value of each small area from the average value was set. An appearance inspection method characterized by using a relative evaluation for determining a small area exceeding a reference value as an abnormal small area.

(2) The appearance inspection method as described in (1) above, wherein the inspection range is determined to be abnormal when a plurality of small areas determined to be abnormal are consecutive.

(3) The visual inspection described in (1) or (2) above, wherein a standard deviation of measured values used for calculating the average value is obtained, and a reference value is set to a value of 3 to 8 times the standard deviation. Method.

(4) In the appearance inspection method of (3) above, which involves relative evaluation of hues, the hues are converted into numerical values by using two variables, and the numerical values used for calculating the average are represented on the coordinates of the two variables. , Find a regression line, convert the coordinates so that the regression line is parallel to the main axis, and furthermore, set the average value to be the coordinate origin, and automatically set a rectangular area indicating each reference value of the two variables in the converted coordinates. An appearance inspection method characterized by performing a relative evaluation of hue using a conversion method.

(5) In addition to the relative evaluation, an absolute evaluation for comparing a measured value with a set reference value and determining a small area whose measured value exceeds the reference value as an abnormal small area is also used. An appearance inspection method according to any one of the above items 1 to 4, which is characterized by the following.

(6) In addition, the average value of the measured values when the color tone of the inspection object is stable is set in advance as a standard average value, and this standard average value and a plurality of small areas in the inspection range are set. The method according to any one of the above 1 to 5, wherein a method of calculating a difference between the measured value and the average value and using the method of determining that the inspection range is abnormal when the difference exceeds a preset reference value of the average value is used. Appearance inspection method according to any of the above.

(7) The inspection range of the inspection object whose color tone fluctuates is set, the inspection range is divided into small areas, and the brightness and / or hue are measured and digitized by using a spectrometer for each small area. In the visual inspection method that determines the presence or absence of abnormality in a small area from measured values, the measured value is compared with a preset reference value, and a small area whose measured value exceeds the reference value is determined as an abnormal small area. Calculates the average value from the measured values of a plurality of small areas, calculates the deviation of the measured value of each small area from the average value, and anomalies the small area where the deviation exceeds the set reference value. When using both of the relative evaluations to determine that the area is a small area, the range of the measurement value that is not determined to be abnormal by the absolute evaluation and the boundary value of the overlapping area and the non-overlapping area with the range of the measurement value that is not determined to be abnormal by the relative evaluation To Appearance inspection method characterized by the standard value, to determine an abnormal small areas from the measurement numerical this reference value.

(8) The visual inspection method as described in (7), wherein the inspection range is determined to be abnormal when a plurality of small areas determined to be abnormal are continuously present.

(9) The appearance inspection method according to any one of (1) to (8) above, wherein the spectrometer is an imaging spectrometer.

(10) The lightness and / or hue are L ^* ,
The visual inspection method according to any one of the above items 1 to 9, which is converted into numerical values a ^* and b ^* .

(11) A linear or planar light source is installed on at least both sides of the spectrometer, and the measuring light is emitted from the light source at an irradiation angle within 20 degrees from a vertical line to the inspection object. The visual inspection method according to any one of the above 1 to 10.

(12) The appearance inspection method as described in any one of (1) to (11) above, wherein a white or colorless reflector is provided close to the inspection object when inspecting the inspection range.

(13) The appearance inspection method according to any one of (1) to (12) above, wherein the inspection object is a synthetic rubber veil.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below.

In the present invention, the object to be inspected whose color tone fluctuates is essentially a solid substance having a uniform or uniform appearance, and its field is the chemical industry (synthetic resin, synthetic rubber, ceramics, metallurgy). Etc.), food and fermentation industry, household goods, machinery industry, agriculture, etc.
The variation in color tone includes subtle differences in raw materials, subtle variations due to slight changes in manufacturing conditions, etc., and changes due to brand switching for the same brand.

The most suitable test object is a synthetic rubber veil.

In the present invention, it is necessary to set the inspection range of the inspection object. Preferably, in one plane or curved surface representing the inspection object, a portion having relatively few irregularities is determined as the inspection range in advance, and the inspection range is set to be as large as １ ／ or more of one representative plane or curved surface. It is preferable to set. Further, it is more preferable to set an area equal to or more than 2/3 of one representative plane or curved surface as the inspection range. If necessary, one inspection range or a plurality of inspection ranges can be set on one representative plane or curved surface. Further, it is also possible to select one or two or more surfaces other than the representative one surface in one inspection object, and to set more surfaces as the inspection range. When the inspection object is large, it is also possible to divide one surface into a plurality of inspection ranges and inspect each of them using separate spectrometers. This way,
Multiple divided inspection areas can be inspected simultaneously,
Inspection can be accelerated.

In the case of a synthetic rubber veil, it is preferable to set as wide an area as possible on one surface of the rectangular parallelepiped as the inspection range. However, in practice, the outer edge and the four corners may be irregular or low in height. Therefore, it is preferable to remove the outer edge and the four corners from the inspection range as necessary. The width of the outer edge portion excluded from the inspection range is preferably from 10 to 100 mm, and more preferably from 15 to 80 mm. As the four corners excluded from the inspection range, the length of the side is preferably 10 to
It is a portion including a corner which forms a rectangle or a square of 150 mm, more preferably 30 to 80 mm. Further, if necessary, the back surface and the side surface can be added to the inspection object.

In the present invention, it is necessary to divide the inspection range into small areas and to convert the brightness and / or hue into numerical values using a spectrometer for each of the small areas. The present invention is performed by converting one or both of the brightness and the hue of the small area into a numerical value.In order to improve the determination accuracy, it is preferable to make the determination based on at least the hue. More preferably, the determination is made based on both.

The shape of each small area when divided into small areas may be any of a square, a rectangle, a parallelogram, a circle, an ellipse, and the like. Even if there is a gap between adjacent small areas, there is an overlap. Although it does not matter, we eliminate the area that can not be inspected,
In addition, in order to prevent the duplicate inspection, it is preferable that the adjacent small areas continuously cover the inspection target range without any gap or overlap. A preferable small area is a rectangle or a square connected in parallel to the scanning direction of the spectrometer so that the spectrometer can be inspected by scanning over the entire inspection range.

It is preferable that the size of each small area is set with a minimum size of a different color portion (hereinafter referred to as "foreign matter") that needs to be detected, and particularly smaller than the minimum target size. Preferably, the area is used. Generally, it is more preferable to set the area to １ ／ or less of the minimum target to be detected as a foreign substance. Further, when the small area is a rectangle or a square, it is preferable that the length of the side is shorter.
Specifically, when the small area is a rectangle or a square, it is preferable to divide the small area into small areas each having a side having a length of 1.5 times or less of the longest diameter of the minimum target, and more preferably 1 times or less. That is, it is divided into small areas each of which is made up of the sides of a circle. If the size of the small area is large, the result is that the reliability of detecting a small foreign substance is deteriorated.

In the present invention, the minimum target to be detected as a foreign substance has a size within a range that can be visually detected, and can be arbitrarily set as needed. For example,
As a small one, a circle with a diameter of 0.5 mm and a side of 0.5
It is possible to set a square of mm or the like. In the case of a synthetic rubber veil, a minimum target to be detected as a foreign substance can be set to, for example, a circle having a diameter of 0.5 to 10 mm, a square having a side of 0.5 to 10 mm, or the like.

In the present invention, the size of the small area is preferably divided into small areas having an area smaller than the minimum target to be detected as a foreign substance, and can be arbitrarily set as necessary. For example, as a small one, one side is .0.
A 1 mm square or the like can be set. In the case of a synthetic rubber veil, it is preferable to set a rectangle or square having a side of 0.1 to 8 mm, which is smaller than the minimum target to be detected as a foreign substance.

As the spectrometer, a device capable of converting the brightness and / or hue of each small area into a numerical value and automatically inputting the numerical value to a computer can be used. For example, there are a spectral colorimeter and an imaging spectrometer.

The method of digitizing brightness and hue is L ^* a.
^* b ^* Color system method (JIS Z / 8729), L ^*
U ^* v ^* color system method (JIS Z8729), X
Method using YZ color system (JIS Z8701), U ^*
Although there are various methods such as a method using a V ^* W ^* color system, a method using an L ^* a ^* b ^* color system is preferable because it is close to the sensitivity of human eyes. Further, as the spectrometer, L ^* ,
It is preferable to use an imaging spectrometer that numerically expresses a ^* and b ^* with high precision. In addition, L ^* , a ^* , b ^{* of} this specification
Is based on JIS Z 8729.

An imaging spectrometer is a device that splits input light into respective wavelength bands by a prism and a grating structure and records the light with a two-dimensional camera as a sensor. Alternatively, it can serve as an imaging type spectrometer capable of detecting a wavelength in a small area. The product name includes “Imspector”.

By moving the imaging spectrometer, which can detect the wavelength in a line shape, by moving the imaging spectrometer or moving the inspection object so as to cover the entire inspection range, the entire imaging range is scanned. For each small area, the intensity of light at each wavelength step in the wavelength band is measured and converted to an electrical signal, and the L ^* ,
a ^* and b ^* are converted and recorded. The wavelength band is used as needed from a visible light region, an ultraviolet region, an infrared region, and the like, but generally, a visible light region is used. The visible light range is between 380 nm and 780 nm, and may be as narrow as needed. In the wavelength band, the width is measured with a wavelength step width of 5 nm to 20 nm, preferably 5 nm to 10 nm.

In the present invention, the numerical values of the lightness and / or the hue of each small area are converted into numerical values, and the measured numerical values are compared with corresponding reference values previously set in common for each inspection object, and the measured numerical values are calculated. Absolute evaluation for determining a small area exceeding the reference value as abnormal can be used together.

In this specification, the reference value refers to an upper limit value and / or a lower limit value for determining the absolute evaluation or the relative evaluation described later. If it is the upper limit, it will be a large number exceeding it, and if the reference value is the lower limit,
It means that the numerical value becomes smaller than that.

The absolute evaluation is a method in which an upper limit and / or a lower limit of an allowable measurement value is absolutely designated as a limit value of the measurement value, and a small area having a measurement value exceeding the limit is regarded as abnormal. is there. This is the simplest and most effective evaluation method when there is little change in the brightness and hue of the background. The reference value for the absolute evaluation may be one that determines either the upper limit or the lower limit of the permissible measured value, but preferably defines both the upper limit and the lower limit. The reference value of the absolute evaluation is usually determined by a measured value of a standard product of the inspection object.

The reference values used for the above-mentioned absolute evaluation will be specifically described below. Among the synthetic rubber veil, those which are oil-extended with aroma oil, which is a dark oil, those which are added with a dark stabilizer, etc. Except for the so-called white veil of synthetic rubber, when the reference value used for absolute evaluation of lightness is represented by L ^* value, the range of L ^* is 0 to 10
For 0, the upper limit is 90-100 and the lower limit is 50-8.
Preferably, it is set to zero. Similarly, when the reference value used for the absolute evaluation of the hue is represented by two numerical values using a ^* and b ^* , a
The upper limit of ^* is set to +5 to +20, the lower limit is set to -2 to -15, and the upper limit of b ^* is set to +10 to +30 and the lower limit is set to -2 to
It is preferable to set to -15.

In the present invention, it is necessary to use relative evaluation in order to determine whether at least the measured values of lightness and / or hue satisfy a predetermined standard. Specifically, an average value is calculated from the measured values of a plurality of small areas, and a small area in which the deviation of the measured value of each small area from the average value exceeds the corresponding reference value of the relative evaluation is determined as an abnormal small area. It is necessary to use an evaluation method to judge.

The plurality of small areas used for calculating the average value in the relative evaluation may be part or all of the small area within one inspection range, part of the small area over the plurality of inspection ranges of the same inspection object, or All or a part or all of a small area of a plurality of inspection ranges extending over a plurality of inspection targets,
From the viewpoint of simplicity of the inspection procedure, it is preferable that the inspection area is part or all of a small area within one inspection range of the inspection object to be inspected for appearance. When a part of the small area is used as the basis for calculating the average value, it is preferable that 50% by number or more of the small area be used as the basis for calculating the average value, and 80% by number or more of the small area in order to enhance the determination accuracy. Is more preferably used as a basis for calculating the average value. Optimally, all the small areas are used as the basis for calculating the average value.

The above-described relative evaluation is an effective method for detecting an unacceptable lightness and / or hue when the background lightness and / or hue fluctuate within an allowable range. is there. The average value may be an arithmetic average value, a geometric average value, or any other average value used as a statistical method. In general, an arithmetic average is preferable including the case of inspection of a synthetic rubber veil.

In the present invention, the relative evaluation may be performed for all the measured values, but it is also possible to perform a relative evaluation for some measured values and an absolute evaluation for the other measured values. Specifically, when the inspection is performed from both the lightness and the hue, for example, the lightness can be absolutely evaluated and the hue can be relatively evaluated. In addition, when a certain type of measured numerical value is relatively evaluated, usually, both the upper limit and the lower limit are relatively evaluated. For example, one upper limit is relatively evaluated, and the lower limit is an absolute evaluation. You can use relative evaluation and absolute evaluation to evaluate the measured values of, or use both absolute evaluation and relative evaluation to evaluate all measured values. Is determined, it is preferable to determine an abnormality even if the other side does not determine an abnormality. Further, if necessary, it is possible to use both the absolute evaluation and the relative evaluation for some types of measured values, and to use only the absolute evaluation for other measured values.

For setting the reference value for the relative evaluation, a value that determines the upper limit and / or the lower limit of the deviation amount from the average value of the measured values of lightness and / or hue is used. As the value for determining the upper and / or lower limit of the deviation of the measured value of the lightness and / or hue from the average value, a common fixed value may be used for each inspection object. Among the measured values, the standard deviation of the measured values used for calculating the average value is determined, and the standard deviation of 3 to
It is preferable to use a value obtained as an eight-fold value.
As a result, the allowable range is set in a range of 3 to 8 times the standard deviation, and it is easy to prevent erroneous determination when the brightness and / or hue of the background greatly fluctuate. Note that a numerical value multiplied by the standard deviation in a range of 3 to 8 times is called a limit multiple. In particular, in the case of a so-called white veil of synthetic rubber veil, a preferable limit multiple is 3 to 8 times, and more preferably 4 to 6 times.

The comparison between the reference value of the relative evaluation and the measured value for determination in the relative evaluation is performed by calculating the amount of deviation of each measured value from the average value, and calculating the amount of deviation from the upper limit of the amount of deviation and / or Alternatively, an upper limit value and an upper limit value of an allowable measurement value, which are compared with a reference value (a reference value of a shift amount) which is a lower limit value, or obtained from a sum of the average value and the upper limit value and / or the lower limit value of the shift amount, It can be performed by comparing a reference value (reference value of measured value), which is a lower limit value, with each measured value. For example, the upper limit of the allowable deviation is set to +
If α, the lower limit is −β, and the average value is γ, the reference values of the measured values can be obtained as γ + α and γ−β. In any case, it is determined whether or not the deviation amount of each measured value from the average value exceeds a set reference value.

When relative evaluation of hue is performed, the hue is converted into a numerical value by measurement with two variables, and a regression line in a distribution chart in which measured values used for calculating an average value are represented on the coordinates of the two variables is obtained. The coordinate axis is rotated so as to be parallel to the main axis, and the coordinate axis is further translated by using the average value of the measured values as the coordinate origin to convert the coordinates. It is preferable to use a coordinate conversion method for automatically setting the rectangular area shown. The deviation from the origin of each measured value converted on the transformed coordinates is
Whether or not the corresponding small area is abnormal can be determined based on whether or not the area exceeds the rectangular area indicating the reference value. Further, when setting a reference value of the deviation amount of the two variables from the standard deviation and the limit multiple, the standard deviation of the two variables on the transformed coordinates is obtained and set as a value obtained by multiplying the standard deviation by the limit multiple. can do.

More specifically, the hue is a ^* ,
b ^* is converted into a numerical value for measurement, and a ^* and b ^* are each represented by x
A ^* , which is measured and quantified at the coordinates of the axis and the y-axis,
From b ^* , a rectangular area surrounding a normal value centered on the average value is obtained by statistical calculation, and the area outside the rectangular area is determined to be abnormal.

As a method of the statistical calculation, a regression line y = mx + b for the a ^* value of the b ^* value is obtained from the measured numerical values a ^* and b ^* , and the regression line m is obtained from the slope m of this line. Angle θ = t around the origin so that the straight line is parallel to the x-axis
An ^-1 (-m) coordinate rotation is performed to set the main axis as the X axis and the Y axis, and each point after the coordinate rotation is X = a ^* cos θ-b ^* sin
θ, Y = a ^* sin θ + b ^* cos θ, and further calculate the respective average values of (X, Y) after the rotation of the coordinate axes. Each point is calculated as Xs = X−Xav from the average value (Xav, Yav).
By calculating Ys = Y−Yav, parallel movement is performed with the average value as the coordinate origin, and this data set (Xs, Y
s), standard deviations σ _X and σ _Y are obtained, and then two lines parallel to the Y axis passing through points of ± nσ _X , which are values obtained by multiplying these standard deviations by a limit multiple n, and ± nσ _Y A method of obtaining a rectangular area surrounded by two lines parallel to the X axis passing through each point can be used. In this method, when the measured values of the small area serving as the basis for calculating the average value are represented by points determined by these two variables in the coordinates where a ^* and b ^* are the x axis and the y axis, respectively, Except in the case of a substantially circular shape or an elliptical shape in which the major axis is parallel to the x-axis or the y-axis, the distribution of points is more accurately tolerable when the major axis is inclined with respect to the axis. Can be set. This method can be applied to various inspection objects in addition to the synthetic rubber veil.

As another relative evaluation, there is a method using a color difference from an average value (absolute value of difference between lightness and hue).

In the present invention, in both the absolute evaluation and the relative evaluation described above, if there is at least one abnormal area, the inspection range may be determined to be abnormal. When there are multiple small areas in a row,
Preferably, the inspection range is determined to be abnormal.
By doing so, the probability of an error in determining a normal inspection object as abnormal is reduced as compared with the case where an inspection range in which only one small area is determined to be abnormal is determined to be abnormal, and the reliability is improved. The performance is improved. The inspection object is determined to be abnormal when an abnormal inspection range exists.
Also, when multiple inspection ranges are set for the inspection object,
When it is determined that there is an abnormality in at least one of the inspection ranges, the inspection target is preferably determined to be abnormal.

In the present invention, preferably, the average value of the measured values when the color tone of the object to be inspected is stable is set in advance as a standard average value. A difference between the measured value of the plurality of small areas in the inspection range and the average value, and when the difference exceeds a preset reference value of the average value, a method of determining that the inspection range is abnormal is also used. It is also effective. Also,
When this is performed for lightness and hue, it is preferable to use the absolute value of the difference as the difference. It can also be used for brightness or hue. When using for hue, it is preferable to use the absolute value of the difference similarly. Specifically, L
^* , A ^* , b ^*, etc., each of which is set in advance with a standard average value,
Calculate the difference between this standard average value and the average value of each of the measured values L ^* , a ^* , b ^*, etc., and check if the absolute value of the difference exceeds a preset reference value. The range can be determined to be abnormal. This makes it easy to detect a foreign substance having a large specific color that occupies a large area of the inspection range as an abnormality in the inspection range. The standard average value is preferably set for each product brand.

The absolute value of the difference between lightness and hue, that is, the color difference is represented by ΔE = [(L−1) ² + (A−a) ² + (B−b) ² ] ^1/2 . Here, ΔE: absolute value of difference, L, A, B:
Average values of L ^* , a ^* , b ^* when stable, l, a,
b: L which is a measured value for all small areas of the inspection range
Average values of ^* , a ^* , and b ^* . The limit value for ΔE is generally in the range of 5-20. Further, the absolute value of the difference from the average value of the hue is represented by ΔE = [(A−a) ² + (B−b) ² ] ^1/2 .

In the case of a so-called white veil of synthetic rubber veil, it is preferable to evaluate the difference between the standard average value and the average value of the measured values at least for the hue. In that case, the reference value of the hue ΔE is 5 to 20,
More preferably, it is set to 7 to 15.

FIG. 1 shows a flow when the inspection is performed by both the absolute evaluation and the relative evaluation described above.

In the present invention, when both the absolute evaluation and the relative evaluation are used, as shown in FIG. 1, a method of sequentially performing an absolute evaluation test and a relative evaluation test may be used. , As shown in FIG.
The absolute evaluation and the relative evaluation can be performed at once. Specifically, a boundary value of a range that is not determined to be abnormal in the absolute evaluation and a boundary value of an overlapping region and a non-overlapping region in a range that is not determined to be abnormal in the relative evaluation are used as a reference value, and an abnormal value is obtained from the measured value and the reference value. A small area can be determined. In other words, the reference value of the absolute evaluation,
Of the reference values for the relative evaluation (reference values of the measured values), a narrower range can be used as the reference value for determination. According to the evaluation based on the overlapping boundary value of the allowable range of the absolute evaluation and the relative evaluation, the inspection procedure can be omitted and the process can be promptly performed. Also, in this case, as described above, if there is a small area determined to be abnormal even in one place, the inspection range may be determined to be abnormal. When a plurality of inspection ranges exist, it is preferable to determine that the inspection range is abnormal. When a plurality of inspection ranges are set for the inspection object, it is preferable that the inspection object is determined to be abnormal when at least any one of the inspection ranges is determined to be abnormal.

In the present invention, when the surface of the object to be inspected has irregularities, a linear or planar light source installed on at least both sides of the spectrometer measures the irradiation angle within 20 degrees from the vertical line to the object to be inspected. It is preferable to irradiate the inspection light with. By doing so, it is possible to suppress the generation of shadows due to unevenness in the inspection range, and to reduce the probability of an error in determining a normal inspection target as abnormal, as compared with other methods, and to improve reliability. improves.

In the present invention, the light source preferably has a continuous spectrum in the visible light range, and is preferably a halogen lamp, a xenon lamp, an incandescent lamp, or the like.
Particularly, a halogen lamp is preferable.

In the present invention, when inspecting the inspection range, it is preferable to provide a white or colorless reflector near the inspection object. Thereby, the brightness up to the peripheral portion becomes uniform. When the inspection object is translucent, it is preferable that the reflection plate is further extended to a flat surface or a curved lower surface of the inspection range. By these methods, a wider inspection range can be realized.

In the present invention, when the inspection object is a synthetic rubber veil, when inspecting the inspection area excluding the outer edge and four corners of one surface of the synthetic rubber veil, at least two of the outer surface perpendicular to the inspection surface of the synthetic rubber veil are inspected. It is preferable to provide a white or colorless reflector close to the surface. The reflector preferably has a height of 5 to 50 cm from the inspection surface, and when the inspection object is translucent, it is preferable that the reflection plate protrudes 5 to 15 cm below the inspection surface. The width is slightly larger than the length of the inspection surface and is provided at a fixed position, but it may be provided as a plate having a width of about 5 to 30 cm so as to move together with the camera. By doing so, the brightness around the outer edge of the inspection range becomes uniform, and the probability of errors in determining that a normal inspection object is abnormal is reduced as compared with a case where this is not performed, and reliability is further improved. I do. In particular, in the inspection of a synthetic rubber veil, it is preferable to use a white Teflon (registered trademark) plate to which rubber is unlikely to adhere as a reflection plate.

In the present invention, it is preferable that the depth of focus of the spectrometer used is deeper than the unevenness of the inspection range of the inspection object. This makes it possible to find a target minute abnormality.

By practicing the present invention, in the product inspection process, the appearance of the inspection object whose background color fluctuates is inspected without visual observation, a portion exhibiting a different color is detected, and foreign matter is identified. A reliable method can be implemented. Furthermore, it is possible to easily inspect an inspection object having irregularities on the surface. Therefore, in the chemical industry (including synthetic resin, synthetic rubber, ceramics, metallurgy, etc.), food and fermentation industry, household goods, machinery industry, agriculture, etc. It provides an extremely useful invention.

The most suitable inspection object is a synthetic rubber veil, and the present invention can provide a highly reliable automatic inspection method suitable for surface inspection of dirt and foreign matter in a synthetic rubber veil manufacturing process line. The synthetic rubber can be applied to all of polybutadiene, styrene-butadiene copolymer rubber, polyisoprene rubber, EP rubber, and other veiled rubbers. Further, in synthetic rubber, both so-called white matter and black matter can be applied. In particular, as an object, it is suitable for inspection of white matter where appearance is important.

[0059]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on embodiments.

Example 1 Polybutadiene for resin modification, which is a synthetic rubber white veil, was used as a test object whose color tone fluctuates. The crumb-shaped polybutadiene is weighed and compression molded in a baler to form a 35 kg rectangular bale. The veil is almost white in appearance, but occasionally has a slightly yellow, orange, or green hue, and the background color fluctuates.

The size of the rectangular bale is 355 mm on average on the short side (length), 710 mm on average on the long side (width), and 190 mm on average, depending on the bias of the crumbs in the baler, compression conditions, and the like. fluctuate. Especially the height is 170m
It is oblique or uneven between m and 200 mm.

The inspection range is one surface of the upper surface, the outer edge of the short side is 50 mm in width, the outer edge of the long side is 20 mm in width, and the four corners are 3 mm.
The inspection range was set by excluding the inspection range in a rectangular area of 5 mm × 65 mm, and dividing the center part into two elongated ranges with the center line in the longitudinal direction as a boundary. The minimum target to be detected as a foreign substance was set to a square having a side of 2 mm.

A gantry is installed so as to straddle the conveyor on which the bale is conveyed, and two spectrometers are set in parallel with the short side so that the optical axis is vertical, and the two spectrometers are sandwiched. As described above, a linear halogen lamp was attached to each side at an angle of 10 degrees from the vertical line. The bale flowing on the conveyor was stopped at a fixed position, and the base on which the spectrometer and the illumination were mounted was driven by a servomotor to scan the entire inspection range.

The spectrometer is an “Imspector” line type imaging spectrometer V7 (Sectral I).
Scanning inspection was performed at a scanning speed of 60 mm / sec using a monochrome CCD area camera (30 shutters / sec.). The size of the small area is 0.4 mm in the short side direction and 2 mm in the long side direction. The depth of focus of the objective lens of the spectrometer is ± 25.
mm.

The spectral data was converted from 400 to 700.
over 5 nm in 5 nm increments, and according to the inspection program, L ^* ,
a ^* and b ^* were calculated and stored as data.

According to the analysis program, the upper limit of the absolute evaluation is L ^* : 99, a ^* : +15, b ^* : +25, and the lower limit of the absolute evaluation is L ^* : 70, a ^* : -5, b ^* : −
5 and the standard value (upper limit and lower limit) of the relative evaluation was set to five times the standard deviation of each distribution of L ^* , a ^* , and b ^* . Further, when stable, a ^* was set to +4.5 and b ^* was set to +12.5, and the reference value of the absolute value of the hue difference was set to 10.

The small area was determined by performing an absolute evaluation and a relative evaluation, respectively, and an area in which either one was out of the reference value was determined to be an abnormal small area. In the relative evaluation, a coordinate conversion method was adopted. If two or more abnormal small areas are consecutively present, the inspection range is determined to be abnormal. If at least one of the two inspection ranges of one veil is abnormal, the inspection target is determined. Was determined to be abnormal.

The judgment result was transmitted to the conveyor control sequencer. If the judgment was good, the conveyor was started and discharged to the next step. If the judgment was abnormal, an alarm was issued and the operator was called.

8,640 bale samples were continuously inspected, and 35 abnormal products were detected. The results agreed well with the visual inspection, confirming that the inspection was performed correctly.

Embodiment 2 The determination of the small area is based on the boundary value between the overlapping area and the non-overlapping area in the range of the measured values not determined to be abnormal in the absolute evaluation and the range of the measured values not determined to be abnormal in the relative evaluation as a reference value. Those whose measured values deviated from this reference value were determined to be abnormal small areas. Except for this point, the inspection was performed in the same manner as in Example 1.

3430 veiles were continuously inspected, and 11 abnormal products were detected. The results agreed well with the visual inspection, confirming that the inspection was performed correctly.

[0072]

According to the present invention, a highly reliable automatic appearance inspection can be performed in the appearance inspection of an inspection object whose color tone fluctuates.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an example of a visual inspection method according to the present invention.

FIG. 2 is a flowchart showing another example of the appearance inspection method of the present invention.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masahiro Kanazawa 1-3-1 Yoko, Kawasaki-ku, Kawasaki-shi, Kanagawa F-term in Asahi Kasei Kogyo Co., Ltd. 2F065 AA49 AA61 CC02 DD09 FF01 FF04 GG02 JJ03 JJ05 JJ26 LL30 LL67 MM02 MM22 NN12 PP15 QQ23 QQ25 QQ42 RR02 RR08 SS04 UU02 UU05 2G051 AA90 AB01 BA20 CA03 CA04 CC15 DA01 DA06 EA14 EA16 EA17 EA20 EB01 EB02 EC02 EC03 5B057 AA01 DA03 DB06 DC30

Claims (13)

[Claims] 1. An inspection range of an inspection object whose color tone fluctuates is set, the inspection range is divided into small areas, and lightness and / or hue are converted into numerical values using a spectrometer for each small area, and the measurement is performed. In the visual inspection method for determining the presence or absence of an abnormality in a small area from a numerical value, an average value is calculated from the measured numerical values of a plurality of small areas, and a deviation amount of the measured numerical value of each small area from the average value is set according to a set standard. An appearance inspection method using relative evaluation for determining a small area exceeding a value as an abnormal small area. 2. The visual inspection method according to claim 1, wherein the inspection range is determined to be abnormal when a plurality of small areas determined to be abnormal are consecutive. 3. The visual inspection according to claim 1, wherein a standard deviation of measured values used for calculating the average value is obtained, and a reference value is set to a value that is 3 to 8 times the standard deviation. Method. 4. The appearance inspection method according to claim 3, wherein the hue is measured relative to two variables and the numerical values used for calculating the average are represented on the coordinates of the two variables. , Find a regression line, convert the coordinates so that the regression line is parallel to the main axis, and furthermore, set the average value to be the coordinate origin, and automatically set a rectangular area indicating each reference value of the two variables in the converted coordinates. An appearance inspection method characterized by performing a relative evaluation of hue using a conversion method. 5. In addition to the relative evaluation, an absolute evaluation for comparing a measured value with a set reference value and determining a small area whose measured value exceeds the reference value as an abnormal small area is used in combination. The visual inspection method according to claim 1. 6. In addition, an average value of measured values when the color tone of the inspection object is stable is set in advance as a standard average value, and the standard average value and measurement of a plurality of small areas in the inspection range are measured. Calculate the difference between the numerical value and the average, and calculate the difference
The visual inspection method according to any one of claims 1 to 5, wherein a method of determining that the inspection range is abnormal when the average value exceeds a preset reference value is used. 7. An inspection range of an inspection object whose color tone fluctuates is set, the inspection range is divided into small areas, and lightness and / or hue are converted into numerical values using a spectrometer for each small area. In the visual inspection method that determines the presence or absence of abnormality in a small area from numerical values, the measured value is compared with a preset reference value, and the small area where the measured value exceeds the reference value is determined as an abnormal small area. An average value is calculated from the measured values of a plurality of small areas, a deviation amount of the measured value of each small area from the average value is calculated, and a small area in which the deviation amount exceeds a set reference value is regarded as abnormal. When using both of the relative evaluations that determine the small area, the range of the measurement values that are not determined to be abnormal in the absolute evaluation and the boundary value of the overlapping area and the non-overlapping area in the range of the measurement values that are not determined to be abnormal in the relative evaluation are used as the basis. value And determining an abnormal small area from the measured value and the reference value. 8. The appearance inspection method according to claim 7, wherein the inspection range is determined to be abnormal when a plurality of small areas determined to be abnormal are consecutive. 9. The appearance inspection method according to claim 1, wherein the spectrometer is an imaging spectrometer. 10. The lightness and / or hue are represented by L ^* , a ^* ,
The appearance inspection method according to any one of claims 1 to 9, wherein the numerical value is expressed as b ^* . 11. A linear or planar light source is provided on at least both sides of a spectrometer, and the measuring light is emitted from the light source at an irradiation angle of 20 degrees or less from a vertical line with respect to an inspection object. The appearance inspection method according to claim 1. 12. The appearance inspection method according to claim 1, wherein a white or colorless reflector is provided close to the inspection object when inspecting the inspection range. 13. The appearance inspection method according to claim 1, wherein the inspection object is a synthetic rubber veil.