JP2006242906A - Surface defect inspection method and device therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface defect inspection method allowing grading for deciding whether delivery is allowed, in response to required quality in a customer side, and to provide a device therefor. <P>SOLUTION: In this surface defect inspection method for inspecting the surface of an inspected object for detecting the feature amount for determining a defect, based on the inspection signal therein, and for determining at least either the kind or the degree of the defect, based on the feature amount, the inspected object is divided a unit length by a unit length to determine a representative defect in each area formed therein, based on the kind and the degree of the defect, the ratio of the representative defect mixed into the inspected object is computed, and the quality of the inspected object is determined, based on a computed result and a preset allowance range to make quality decision of the inspected object. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface defect inspection method and apparatus for inspecting a surface defect of a strip-shaped object to be continuously conveyed, and particularly relates to a rating of an object to be inspected such as a metal band or a film such as a steel plate or an aluminum plate. .

  Conventionally, inspection of defects on the surface of a thin plate using a surface defect inspection apparatus with respect to a strip-shaped inspection object such as a steel plate or an aluminum plate has been performed.

  FIG. 2 is a diagram showing a schematic configuration of a conventional surface defect inspection apparatus. As shown in FIG. 2, an image input unit 11 (11 a, 11 b) is installed facing the surface of the inspection object 10. The image input unit 11 performs image input means such as a CCD camera or photomultiplier (photomultiplier tube), and a lens, mirror, or optical correction for guiding light from the surface of the object to be inspected to the image input means. It is made up of filters. The image input unit 11 is connected to an image processing unit 12. The image processing unit 12 receives an amplifier that amplifies an electrical signal from the image input unit, a filter that cuts electrical noise, and an analog output from the image input unit. From input means such as an A / D converter that converts to a digital signal, various correction processes such as shading correction to remove the influence of formation on the input signal, preprocessing parts such as spatial filters, and the obtained image It consists of a processing unit that extracts defect candidates based on n-valued classification into two or more values and a predetermined threshold value.

  The image processing unit 12 is connected to a feature amount calculation unit 13, and the feature amount calculation unit 13 extends in the longitudinal direction from the length, width and area of the defect candidate obtained by the image processing unit 12, and the inspection object reference line. A feature amount such as a distance and a distance in the width direction from the reference object end is calculated. The feature amount calculation unit 13 is connected to the defect type determination unit 14 and the defect degree determination unit 15, respectively. The defect type determination unit 14 determines the defect type from the feature amount of the defect candidate obtained by the feature amount calculation unit 13 according to a predetermined algorithm. The defect type determination unit 14 is connected to a defect degree determination unit 15. The defect degree determination unit 15 determines a defect degree from the defect feature amount obtained by the feature amount calculation unit 13 and the defect type determined by the defect type determination unit 14.

  A result output unit 18 is connected to the defect type determination unit 14 and the defect degree determination unit 15, and the result output unit 18 outputs the defect type and defect level to an annunciator such as a monitor such as a CRT, a printer, a lamp, and a buzzer. To do.

  Usually, it is very difficult to make all products defect-free. Therefore, the harmful defect portion for the customer is removed based on the defect information displayed on the CRT or the like in the line, or the harmful defect portion for the customer is removed by re-inspecting in the next process based on the defect information. After shipping. In addition, a document in which the defect information printed out together with the coil including the harmful defect portion is described may be submitted to the customer, and the customer may have the harmful defect removed.

  When removing a harmful defect part in the said line or the following process, it will often be an over action from a quality assurance side. Further, there may be a case where the harmful defect portion is not removed due to a determination error such as a missed or difficult-to-determine defect. Moreover, by removing the harmful defect portion, the unit weight of the coil is reduced, and there are problems such as a reduction in work efficiency on the customer side.

For this reason, for example, it is proposed to mark a defective portion of a steel plate detected by a defect detection device using a marking device so that the customer can easily identify the defective portion when re-inspecting the defective portion. (For example, Patent Document 1).
JP 2001-188046 A

  Although it depends on the quality required by the customer, there may be no problem even if it is a minor defect, and conversely, all these minor defects may be cut off or marked. It is an over action and a cost increase factor.

  The present invention takes into account the above-mentioned problems, and provides a surface defect inspection method and apparatus capable of performing a rating for judging whether or not the product can be shipped according to the quality required by the customer. It is to provide.

The surface defect inspection method according to the present invention inspects the surface of an object to be inspected, detects a feature quantity for defect determination from the inspection signal, and determines at least one of the type and degree of the defect from the feature quantity In the defect inspection method, based on the type and degree of the defect, the representative defect of each region formed by dividing the inspection object into unit lengths is determined, and the representative defect is mixed into the inspection object The test object is rated by performing pass / fail determination of the test object from the calculation result and a preset allowable range.
The surface defect inspection apparatus according to the present invention inspects the surface of the object to be inspected, detects at least a feature quantity for defect determination from the inspection signal, and determines at least one of the type and degree of the defect from the feature quantity. In the surface defect inspection apparatus to be determined, based on the type and degree of the defect, a representative defect of each region formed by dividing the inspection object for each unit length is determined, and the representative defect is in the inspection object. The apparatus includes a determination unit that calculates a mixing ratio and performs a pass / fail determination of the object to be inspected based on the calculation result and a preset allowable range.

  As described above, according to the present invention, since the inspected object is rated, overaction such as cutting and removing all defective portions or marking is prevented, and the required quality on the customer side is achieved. Corresponding coils can be manufactured and shipped, and the manufacturing cost can be reduced.

Embodiment 1. FIG.
FIG. 1 is a diagram showing a schematic configuration of a surface defect inspection apparatus according to Embodiment 1 of the present invention. As shown in FIG. 1, image input units 11 a and 11 b are installed to face the front side and the back side of a relatively thin object 10 such as a steel plate or aluminum. The image input units 11a and 11b include image input means such as a CCD camera and a photomultiplier (photomultiplier tube), and lenses, mirrors, and optical corrections for guiding light from the surface of the object to be inspected to the image input means. It consists of filters to do. Image processing units 12a and 12b are connected to the image input units 11a and 11b, respectively. The image processing units 12a and 12b are amplifiers that amplify the electrical signals from the image input units 11a and 11b, filters that cut electrical noise, A / D converters that convert analog output from the image input unit into digital signals, and the like. Input means, various correction processes such as shading correction to remove the influence of the formation on the input signal, pre-processing parts such as spatial filters, and n-valued classification into two or more classes from the obtained image Or a processing unit that extracts defect (疵) candidates based on a predetermined threshold.

  Feature amount calculation units 13a and 13b are connected to the image processing units 12a and 12b, respectively. The feature amount calculation units 13a and 13b are the length, width and area of the defect candidates obtained by the image processing units 12a and 12b, the distance in the longitudinal direction from the inspection object reference line, and the distance in the width direction from the inspection object reference end. The feature amount such as is calculated. A storage unit 16 is connected to the feature amount calculation units 13a and 13b. The storage unit 16 stores feature amounts such as the length, width, and area of defect candidates, the distance in the longitudinal direction from the inspection target reference line, and the distance in the width direction from the inspection target reference end. The defect type determination unit 14 determines the defect type from the feature amount of the defect according to a predetermined algorithm. In addition, the defect type determination unit 14 is connected to the defect degree determination unit 15, and the defect degree determination unit 15 includes the defect (defect) feature amount and the defect type determined by the defect type determination unit 14. Determine the degree of defects. In addition, a determination unit 17 is connected to the defect type determination unit 14 and the defect degree determination unit 15. A result output unit 18 is connected to the determination unit 17 and the result output unit 18 outputs the determined result to a monitor such as a CRT, an annunciator such as a printer, a lamp, and a buzzer.

  Next, the operation of the surface defect inspection apparatus of FIG. 1 will be described. The image input units 11a and 11b, the image processing units 12a and 12b, the feature amount calculation unit 13, the defect type determination unit 14, and the defect degree determination unit 15 are described. Since it is the same as that of the conventional apparatus in FIG. Data on the defect type and the defect level obtained by the defect type determination unit 14 and the defect level determination unit 15 are stored in the storage unit 16. Based on the data stored in the storage unit 16, the determination unit 17, as will be described below, (1) defect mixture rate, (2) front, back, double-sided defect mix rate, (3) defect mix rate by defect level (4) Defect mixing rate by defect occurrence factor and (5) Combined defect mixing rate are obtained, and (6) Coil rating is performed.

(1) Defect mixing rate When the unit length is n and the coil length is L, the defect mixing rate is calculated as follows.
<1> Divide coil defect information by unit length. In addition, when one defect straddles two areas divided by unit length, it is handled as one of the following, for example.
(A) Both areas are defective.
(B) Only one of them (for example, a region where a longer defect exists) has a defect. Even in the case of (b), if there is a very long defect extending over three or more regions, it may be exceptional that all the regions have defects. In any case, the processing is not particularly limited in the case of a long defect (flaw).
<2> A representative defect is determined for each unit length. The representative defect is assumed to be the worst defect. If there are a plurality of defects of the same level, the highest priority is given in the order of predetermined defect priority. For example, when “defect type: baldness, degree: C”, “defect type: scratches, degree: C”, and “defect type: push rod, degree: C” are detected, Defect type priority: (High) Hege → Scratch → Push (Low) and the representative defect is determined as “Defect type: Hege, degree: C”. In this case, the remaining two defects did not exist in the defect mixing ratio. For the above degree, see Table 1 described later.
<3> Here, for example, if there are m portions determined to be representative defects,
Defect mixing rate = (m × n / L) × 100 (%)
It is defined as

(2) Front, back, and double-sided defect mixing ratio The surface defect mixing ratio and the back surface defect mixing ratio are the defect mixing ratios due to representative defects on the front and back surfaces, respectively. Also, the representative defects on the front and back sides at the same unit length division position are compared, and the representative defects on both sides are determined in the same manner as in the above <1> and <2>, and the defect mixture rate is calculated by this. The double-sided defect mixing rate. This means that the front and back surfaces are not counted separately, but are counted as a single object. For example, on the front side, “Defect type: Hege, degree: C” and “Defect type: Scratch, degree : “B”, and “Defect type: squeezed, degree: C” on the back side, the “Defect type: Hege, degree: C” on the front side is the representative defect on the front and back sides. If the representative defects on the front and back are of the same defect type and grade, the same result is obtained even if the defect on either side is used as the representative defect. For example, the defect on the front side is set to be given priority (adopted). Keep it.

(3) Defect mixing rate by defect level When the defect level is divided into a plurality of ranks, the defect mixing rate is calculated for each defect level. In addition, the defect mixture rate is calculated by accumulating all the defects worse than a certain defect. For example, as shown in the following Table 1, when the degree is set to 5 ranks of the major classifications A to E (as bad as E), the defect mixture rates x1 to x5 of the respective degrees are set. Calculate (defect mixing rate by defect level). The maximum accumulation of x1 to x5 is 100%. It is. For example, when C to E are set as management items, x3 to x5 are accumulated (accumulated defect mixture rate).

(4) Defect contamination rate by defect occurrence factor Classify in advance into the cause of defect occurrence, for example, original plate defect that occurs before the upper process, self-line defect that occurred in own line, etc. Calculate the defect contamination rate. For example, the defect types detected by the surface defect meter are classified into four types, and the defect mixture rate, for example, as shown in Table 2 below, is arranged for each defect type. Here, the defect type and the cause of the defect have a relationship such as, for example, hege, sliver → steel making, scale → hot rolling, dross, non-plating → plating, scratch, push rod → threading trouble. .

(5) Combined defect mixing rate The defect mixing rate described above is calculated individually or combined. For example, in the case shown in Table 2, in each of the steelmaking-induced defects, hot-rolling-derived defects, plating-induced defects, and sheet-feeding trouble defects, the cumulative value of the defect mixing rate of degree C to E is calculated, The accumulation of the defect contamination rate combined with the hot-rolled defect is calculated. The combination of defect types is appropriately set according to necessary information.

(6) Coil rating For each customer requirement specification, an acceptable range of each defect mixing rate is determined in advance, and the rating is determined by comparing with each defect mixing rate described above.
For example, <1> customer (or application) α degree C or higher (bad items including CE) 1% or less allowable range of defect contamination → rating class A product <2> customer (or application) β degree C or higher The allowable range of defect contamination is 2% or less
→ Grade B product <3> Degree of customer (or application) γ C or higher Defect mixing rate tolerance 5% or less
→ If there is a condition of rating C grade, if the mixing rate is 1.5%, the rating is B grade and cannot be sold to customer α, but customers β and γ Can be sold. When the mixing rate is 3%, the rating is a C-class product and can only be sold to the customer γ. When the mixing rate is 7%, the rating is not a class C product, so the rating is scrap.

The schematic block diagram of the surface defect inspection apparatus of embodiment of this invention. The schematic block diagram of the conventional surface defect inspection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Inspected object 11 ... Image input part 12 ... Image processing part 13 ... Feature-value calculating part 14 ... Defect type determination part 15 ... Defect degree determination part 16 ... Memory | storage part 17 ... Determination part 18 ... Result output part

Claims (2)

In the surface defect inspection method for inspecting the surface of an object to be inspected, detecting a feature amount for defect determination from the inspection signal, and determining at least one of the type and degree of the defect from the feature amount,
Based on the type and degree of the defect, determine the representative defect of each region formed by dividing the inspection object for each unit length, calculate the ratio of the representative defect mixed in the inspection object, A method for inspecting a surface defect, wherein the inspection object is rated by performing a pass / fail determination on the inspection object from a calculation result and a preset allowable range. In the surface defect inspection apparatus that inspects the surface of the object to be inspected, detects at least a feature amount for defect determination from the inspection signal, and determines at least one of the type and degree of the defect from the feature amount,
Based on the type and degree of the defect, determine the representative defect of each region formed by dividing the inspection object for each unit length, calculate the ratio of the representative defect mixed in the inspection object, A surface defect inspection apparatus comprising: a determination unit that ranks an object to be inspected by performing pass / fail determination of the object to be inspected based on a calculation result and a preset allowable range.

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