JPH0629864B2 - Surface defect inspection method - Google Patents
Surface defect inspection methodInfo
- Publication number
- JPH0629864B2 JPH0629864B2 JP63225274A JP22527488A JPH0629864B2 JP H0629864 B2 JPH0629864 B2 JP H0629864B2 JP 63225274 A JP63225274 A JP 63225274A JP 22527488 A JP22527488 A JP 22527488A JP H0629864 B2 JPH0629864 B2 JP H0629864B2
- Authority
- JP
- Japan
- Prior art keywords
- defect
- grade
- ratio
- inspection method
- area
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Landscapes
- Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
Description
この発明は圧延鋼板等の被検材の表面欠陥を効率良く、
且つ、高精度で検査することができるようにした被欠陥
検査方法に関する。This invention efficiently removes surface defects of the test material such as rolled steel plate,
Further, the present invention relates to a defect inspecting method capable of inspecting with high accuracy.
従来の表面欠陥検査方法、例えばレーザータイプの表面
疵検査方法にあつては、被検材表面に照射したレーザー
光の反射光から、第５図に示されるように、重欠陥、中
欠陥、軽欠陥の閾値との関係から、欠陥のグレード判定
を行う簡易方式がある。 又、特公昭５４−３６８７６号に開示されるように、疵
信号を量子化し、疵の長さ、幅、面積等の情報により疵
種を判定し、疵種毎の閾値との関係からグレード判定を
行う方法等がある。In the conventional surface defect inspection method, for example, the laser type surface defect inspection method, as shown in FIG. 5, from the reflected light of the laser beam irradiated on the surface of the material to be inspected, heavy defect, medium defect, light defect There is a simple method for judging the grade of a defect based on the relationship with the threshold value of the defect. In addition, as disclosed in Japanese Patent Publication No. Sho 54-36876, the flaw signal is quantized, and the flaw type is determined based on the information such as the length, width, and area of the flaw, and the grade is determined from the relationship with the threshold value for each flaw type. There is a method to do.
前記従来の簡易方式は、欠陥部の輝度レベルと正常部の
輝度レベルの比、即ちＳ／Ｎに基づく判定であるため
に、人間の目視による判定と齟齬が多いという問題点が
あつた。 又、前記特公昭５４−３６８７６号の場合は、量子化さ
れた疵信号から疵の特徴を抽出し、その情報から種々の
判断基準に基づいて疵種を推定しているが、この疵種と
実際の疵種とが合致しない場合がある。この場合でも、
推定された疵種の閾値に基づいてのグレード判定をする
ことになるので、誤判定が生じることが多いという問題
点がある。Since the conventional simple method is based on the ratio of the luminance level of the defective portion and the luminance level of the normal portion, that is, S / N, there is a problem that there are many discrepancies in the determination by human eyes. In the case of Japanese Patent Publication No. 54-36876, the feature of the flaw is extracted from the quantized flaw signal and the flaw type is estimated from the information based on various judgment criteria. It may not match the actual defect type. Even in this case,
Since the grade determination is performed based on the estimated threshold value of the defect type, there is a problem that an erroneous determination often occurs.
この発明は上記従来の問題点に鑑みてなされたものであ
つて、高精度に表面欠陥のグレード判定を行うことがで
きるようにした表面欠陥検査方法を提供することを目的
とする。The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a surface defect inspection method capable of highly accurately determining a grade of a surface defect.
この発明は、被検材に照明光を照射し、被照射部をカメ
ラにより撮像し、静止画として捕え、該静止画に基づき
欠陥判定する表面欠陥検査方法において、前記静止画に
より捕えられた表面欠陥の面積と、欠陥部の輝度レベル
と正常部の輝度レベルの比であるＳＮ比と、を検出し、
該検出された面積及びＳＮ比から欠陥グレードを判定す
る表面欠陥検査方法により上記目的を達成するものであ
る。In the surface defect inspection method of the present invention, in a surface defect inspection method of irradiating a material to be inspected with illumination light, capturing an image of a portion to be irradiated with a camera, and capturing the image as a still image, and determining a defect based on the still image The defect area and the SN ratio, which is the ratio of the luminance level of the defective portion to the luminance level of the normal portion, are detected,
The above object is achieved by a surface defect inspection method for determining a defect grade from the detected area and SN ratio.
この発明においては、静止画として捕えられた欠陥画像
から、表面欠陥の面積とＳＮ比を検出して、これら検出
された面積及びＳＮ比の両方から欠陥グレードを判定す
るようにしているので、高精度に表面欠陥を判定するこ
とができる。In the present invention, the area of surface defects and the SN ratio are detected from the defect image captured as a still image, and the defect grade is determined from both the detected area and the SN ratio. Surface defects can be accurately determined.
この発明は、本発明者が、多種類の欠陥サンプルを用
い、多くの実験を重ねた結果によるものであり、静止画
として捕えた欠陥画像における表面欠陥の面積と、欠陥
部の輝度レベルと正常部の輝度レベルの比、即ちＳＮ比
と、の２つの要素に基づいて欠陥サンプルを分類する
と、人間の目視判定による欠陥グレードの判定結果と一
致することが判明した。 具体的には、次の第１表に示される各種欠陥を、第１図
に示されるように、鋼帯１の表面をストロボ２によつて
照射し、被照射部を高精細度カメラ３で撮像し、画像視
野（４７．５m2）内の欠陥面積と、該欠陥のＳ／Ｎ（Ｓ
は欠陥部の輝度レベル、Ｎは正常部の輝度レベル）と、
の関係は第２図に示されるようになつた。 前記第１表の各種欠陥を、人間の目視判定によりＡ、
Ｂ、Ｃの３つのグレードに分類すると、第２図に示され
る３つの領域に分けられる。 即ち、第２図において右上側ほど欠陥グレードが悪化す
ることが判明した。 ここでグレードＡは、表面品質の最も厳しい用途の鋼帯
においては不可となる欠陥であり、グレードＣは表面品
質要求があまり厳しくない鋼帯でも不可となる領域であ
り、グレードＢは前２者の中間である。 上記第２図に示されるように、本発明者の実験により、
欠陥グレードの判定は単純に欠陥のＳＮ比のみでは行う
ことができず、欠陥の面積をも考慮して初めて正確に判
定できることが判明した。 従来は、欠陥のＳＮ比のみで判定していたので、例えば
ＳＮ比が小さく、欠陥の面積が大きい場合は目視ではＣ
グレードの欠陥であるにも拘らず、Ｂグレードとして判
定されたり、反対に、欠陥のＳＮ比は高いが、面積が小
さい場合は、目視検査よりも厳しい判定となり易く不正
確であつた。 次に、本発明方法により実際に鋼帯の表面欠陥を検査す
る過程について説明する。 第１図に示されるようになストロボ２及び高精細度カメ
ラ３により得られた画像Ｙ（第３図参照）における欠陥
Ｄ１、Ｄ２を走査する場合は、任意に決められた輝度レ
ベル（ＬＯＷ ＬＥＶＥＬ）以上をその連続性を見なが
ら走査し、当該欠陥の面積を算出すると同時に、該欠陥
における最も高い輝度レベル（ＳＩＧＮＡＬ ＬＥＶＥ
Ｌ）を検出する。 シグナルレベルが求められたら、ノイズレベル（ＮＯＩ
ＳＥ ＬＥＶＥＬ）とから、Ｓ／Ｎを求める。この求め
られた欠陥面積とＳ／Ｎから、予め作成された第４図に
示される判定基準に当てはめて、ここから、欠陥グレー
ド判定する。 即ち、第３図における欠陥Ｄ１はその欠陥面積及びＳＮ
比からＣグレード、欠陥Ｄ２はＢグレードと各々判定さ
れる。 なお上記実施例は鋼帯における表面欠陥を検査する場合
のものであるが、本発明はこれに限定されるものでな
く、ステンレス等の鋼帯以外の被検材にも当然適用され
得るものである。 その場合は、被検材の種類に応じて、予め第２図に示さ
れるようなグレード判定をするための基準を設けてお
く。The present invention is based on the results of many experiments conducted by the present inventor using many kinds of defect samples. The area of surface defects in a defect image captured as a still image, the brightness level of the defect portion and normal It was found that when the defect samples were classified on the basis of the two factors, that is, the ratio of the brightness level of the part, that is, the SN ratio, the result of the judgment of the defect grade by human visual judgment coincided. Specifically, as shown in FIG. 1, the surface of the steel strip 1 is irradiated by the strobe 2 with various defects shown in the following Table 1, and the irradiated portion is irradiated with the high-definition camera 3. The defect area in the image field of view (47.5 m 2 ) and the S / N (S
Is the brightness level of the defective part, N is the brightness level of the normal part),
The relationship was as shown in FIG. The various defects shown in Table 1 were evaluated by the human visual judgment as A,
When classified into three grades of B and C, they are divided into three regions shown in FIG. That is, it was found that the defect grade deteriorates toward the upper right side in FIG. Here, Grade A is a defect that cannot be applied to steel strips for which the surface quality is the strictest, Grade C is an area where steel strips with less stringent surface quality requirements cannot be used, and Grade B is the former two. Is in the middle of. As shown in FIG. 2 above, according to the experiment of the present inventors,
It has been found that the defect grade cannot be determined simply by the S / N ratio of the defect, and can be accurately determined only by taking the area of the defect into consideration. Conventionally, since the judgment was made only by the SN ratio of the defect, for example, when the SN ratio is small and the area of the defect is large, C is visually observed.
Despite being a grade defect, it was judged as B grade, or conversely, when the SN ratio of the defect was high, but when the area was small, the judgment was stricter than the visual inspection and it was inaccurate. Next, the process of actually inspecting the surface defects of the steel strip by the method of the present invention will be described. When scanning the defects D 1 and D 2 in the image Y (see FIG. 3) obtained by the strobe 2 and the high-definition camera 3 as shown in FIG. 1 , an arbitrarily determined brightness level ( LOW LEVEL) and above while scanning the continuity to calculate the area of the defect, and at the same time, calculate the highest brightness level (SIGNAL LEVE) of the defect.
L) is detected. When the signal level is required, the noise level (NOI
SE LEVEL) and S / N is calculated. From the obtained defect area and S / N, the judgment grade shown in FIG. 4 is applied, and the defect grade is judged from this. That is, the defect D 1 in FIG.
From the ratio, the C grade and the defect D 2 are determined to be the B grade, respectively. Although the above-mentioned embodiment is for inspecting surface defects in the steel strip, the present invention is not limited to this, and can naturally be applied to test materials other than steel strip such as stainless steel. is there. In that case, a standard for grade determination as shown in FIG. 2 is set in advance according to the type of material to be inspected.
本発明は上記のように構成したので、検検材の表面欠陥
のグレード判定を、人間の目視による判定と略一致する
程度に正確に行うことができるという優れた効果を有す
る。Since the present invention is configured as described above, it has an excellent effect that the grade determination of the surface defect of the inspection material can be accurately performed to the extent that the grade determination is substantially the same as the human visual determination.
第１図は本発明表面欠陥検査方法に利用する静止画像を
得るための装置を示す側面図、第２図は欠陥種類と該欠
陥の面積及びＳＮ比の関係を示す線図、第３図は本発明
方法により欠陥を検査する過程を示す線図、第４図は欠
陥面積、ＳＮ比と判定グレードとの関係を示す線図、第
５図は従来の欠陥判定方法を示す線図である。 １…鋼帯、 ２…ストロボ、 ３…高精細度カメラ。FIG. 1 is a side view showing an apparatus for obtaining a still image used in the surface defect inspection method of the present invention, FIG. 2 is a diagram showing the relationship between the defect type and the area and SN ratio of the defect, and FIG. FIG. 4 is a diagram showing a process of inspecting defects by the method of the present invention, FIG. 4 is a diagram showing a relationship between a defect area, an SN ratio and a judgment grade, and FIG. 5 is a diagram showing a conventional defect judgment method. 1 ... Steel strip, 2 ... Strobe, 3 ... High-definition camera.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 江本 秀樹 千葉県千葉市川崎町１番地 川崎製鉄株式 会社千葉製鉄所内 (72)発明者 吉田 守 神奈川県鎌倉市上町屋325番地 三菱電機 株式会社鎌倉製作所内 (72)発明者 銭場 敬 神奈川県鎌倉市上町屋325番地 三菱電機 株式会社鎌倉製作所内 (56)参考文献 特開 昭61−245045（ＪＰ，Ａ) 特開 昭55−40978（ＪＰ，Ａ) ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideki Emoto, No. 1 Kawasaki-cho, Chiba City, Chiba Prefecture Inside the Chiba Works, Kawasaki Steel Co., Ltd. (72) Mamoru Yoshida, 325 Kamimachiya, Kamakura City, Kanagawa Mitsubishi Electric Corporation Kamakura Works (72) Inventor Takashi Zenba, 325 Kamimachiya, Kamakura City, Kanagawa Mitsubishi Electric Corporation Kamakura Factory (56) Reference JP 61-245045 (JP, A) JP 55-40978 (JP, A) )
Claims (1)
ラにより撮像し、静止画として捕え、該静止画に基づき
欠陥判定する表面欠陥検査方法において、前記静止画に
より捕えられた表面欠陥の面積と、欠陥部の輝度レベル
と正常部の輝度レベルの比であるＳＮ比と、を検出し、
該検出された面積及びＳＮ比から欠陥グレードを判定す
ることを特徴とする表面欠陥検査方法。1. A surface defect inspection method in which a material to be inspected is irradiated with illumination light, a portion to be irradiated is imaged by a camera, captured as a still image, and a defect is determined based on the still image. The area of the surface defect and the SN ratio, which is the ratio of the luminance level of the defective portion and the luminance level of the normal portion, are detected,
A surface defect inspection method characterized by determining a defect grade from the detected area and SN ratio.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63225274A JPH0629864B2 (en) | 1988-09-08 | 1988-09-08 | Surface defect inspection method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63225274A JPH0629864B2 (en) | 1988-09-08 | 1988-09-08 | Surface defect inspection method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0273142A JPH0273142A (en) | 1990-03-13 |
| JPH0629864B2 true JPH0629864B2 (en) | 1994-04-20 |
Family
ID=16826757
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63225274A Expired - Fee Related JPH0629864B2 (en) | 1988-09-08 | 1988-09-08 | Surface defect inspection method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0629864B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPWO2003006969A1 (en) * | 2001-07-10 | 2004-11-04 | 株式会社東京精密 | Method and apparatus for inspecting scratches on work |
| JP6409606B2 (en) * | 2015-02-10 | 2018-10-24 | 東レ株式会社 | Scratch defect inspection device and scratch defect inspection method |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5540978A (en) * | 1978-09-18 | 1980-03-22 | Kobe Steel Ltd | Signal processing method in surface deficiency detection of hot steel material |
| JPS61245045A (en) * | 1985-04-23 | 1986-10-31 | Nisshin Steel Co Ltd | Automatic surface defect inspecting method for metallic band |
-
1988
- 1988-09-08 JP JP63225274A patent/JPH0629864B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0273142A (en) | 1990-03-13 |
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| Date | Code | Title | Description |
|---|---|---|---|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
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| LAPS | Cancellation because of no payment of annual fees |