【発明の詳細な説明】［産業上の利用分野］本発明は表面欠点検出方法に関するものであり、特に精
密に研磨されたガラス表面の如き高平坦性を有する表面
の欠点検出方法に関するものである。[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for detecting surface defects, and particularly to a method for detecting defects on a highly flat surface such as a precisely polished glass surface. .
［従来の技術］レーザー光を被検体表面に照射してその表面に存在する
欠点を検出する方法としては従来、反射光の鏡面反射光
量の変化を検出する方法（一般に明視野法とよばれる）
、鏡面反射光が検出器に受光されないように受光器を配
置して欠点からの散乱光のみを検出器に受光する方法（
一般に暗視野法とよばれる）が知られている。また、被
検体がガラスの如き透明体にあっては透過光についても
上述の明視野法、あるいは暗視野法による検出が可能で
あるが、この場合は被検体内部に存在する欠点をも検出
してしまう問題がある。[Prior Art] A conventional method for detecting defects on the surface of an object by irradiating it with laser light is a method of detecting changes in the amount of specular reflection of reflected light (generally called bright field method).
, a method in which the detector is arranged so that the specularly reflected light is not received by the detector, and only the scattered light from the defect is received by the detector (
(generally called the dark field method) is known. In addition, if the object to be examined is a transparent material such as glass, it is possible to detect transmitted light using the above-mentioned bright field method or dark field method, but in this case, defects existing inside the object can also be detected. There is a problem with this.
［発明が解決しようとする課題］近時、被検体表面に存在する欠点の種類を識別する技術
が必要とされており、従来法による前述の明視野法およ
び暗視野法によって得られる検出信号を組み合わせて識
別することが試みられており、この方法では被検体表面
に付着した異物と被検体表面に固有のキズ等の欠点とを
識別することを可能とするが、それ以上の被検体表面固
有の欠点間の識別が困難であった。[Problems to be Solved by the Invention] Recently, there has been a need for a technology to identify the types of defects present on the surface of an object to be examined. Attempts have been made to identify them in combination, and this method makes it possible to distinguish between foreign substances attached to the surface of the specimen and defects such as scratches that are unique to the surface of the specimen. It was difficult to distinguish between the defects.
［課題を解決するための手段］本発明は上述の課題を解決すべくなされたものであり、
レーザー光を被検体表面に照射してその反射光により表
面の欠点を検出する方法であって、被検体表面からの鏡
面反射光の一部を欠点による散乱光成分と共に検出器に
受光することを特徴とする表面欠点検出方法を提供する
ものである。[Means for Solving the Problems] The present invention has been made to solve the above problems,
This is a method of irradiating a laser beam onto the surface of an object and detecting defects on the surface using the reflected light.It is a method in which a part of the specularly reflected light from the surface of the object is received by a detector along with a scattered light component due to the defect. The present invention provides a characteristic method for detecting surface defects.
第１図を用いて本発明による表面欠点検出方法の構成を
説明する。ただし本発明は第１図に限定されるものでは
ない。レーザー光源１を出射したレーザー光２はミラー
３、集光レンズ４によって被検体表面５に照射される。The configuration of the surface defect detection method according to the present invention will be explained using FIG. However, the present invention is not limited to FIG. 1. Laser light 2 emitted from a laser light source 1 is irradiated onto a surface 5 of a subject by a mirror 3 and a condensing lens 4.
被検体表面５からの鏡面反射光６の一部を排除し、残り
の鏡面反射光７を被検体表面５に存在する欠点８による
散乱光９と共に検出器ｌＯに受光させるように視野制限
素子１１が配置される。The field-of-view limiting element 11 excludes a part of the specularly reflected light 6 from the subject surface 5 and causes the remaining specularly reflected light 7 to be received by the detector 1O together with the scattered light 9 due to the defect 8 existing on the subject surface 5. is placed.
被検体表面５上のレーザー光照射位置は被検体表面５あ
るいはレーザー光源１がら検出器１゜までの光学系を相
対的に移動させることにより行われる。集光レンズ４は
被検体表面５におけるレーザー光２の大きさを所定の大
きさにするためのもので、検出すべき欠点の大きさによ
り選択される。レーザー光２の被検体表面５への入射角
は特に限定はないが、被検体が研磨されたガラスの如き
透明体の場合は裏面がらの反射光および散乱光との干渉
をさけるために垂直入射をさけて行うことが望ましく、
光学系の製作、調整の容易さから入射角は３０’〜６０
”の範囲で設計すればよい、特に被検体がガラス（屈折
率ｎ”１１．５）でその厚さが薄い場合（１ｍｍ程度以
下）の場合には入射角を４９°付近に設定すると裏面か
らの反射光による干渉を排除することが最も容易となる
。受光器１ｏは通常の光電子増倍管（フォトマル）また
はシリコンフォトダイオードを用いることができる０本
発明の重要な構成要素である視野制限素子１１はその位
置が微調整し得るような機構の上に配置されることが望
ましい。The laser beam irradiation position on the object surface 5 is determined by relatively moving the optical system from the object surface 5 or the laser light source 1 to the detector 1°. The condensing lens 4 is used to adjust the size of the laser beam 2 on the surface 5 of the object to a predetermined size, and is selected depending on the size of the defect to be detected. The angle of incidence of the laser beam 2 on the surface 5 of the object to be examined is not particularly limited, but if the object to be examined is a transparent material such as polished glass, vertical incidence is required to avoid interference with reflected light and scattered light from the back surface. It is desirable to avoid
The angle of incidence is between 30' and 60' due to the ease of manufacturing and adjusting the optical system.
In particular, if the object to be examined is glass (refractive index n'' 11.5) and its thickness is thin (approximately 1 mm or less), setting the incident angle to around 49° will allow the object to be designed from the back side. It is easiest to eliminate interference caused by reflected light. The photodetector 1o can be an ordinary photomultiplier tube (Photomultiplier) or a silicon photodiode. It is desirable that the
本発明の方法によれば、被検体表面の欠点、例えば凸状
、テーブル状の形状を有する欠点をキズと識別して検出
することができる。According to the method of the present invention, a defect on the surface of a subject, for example, a defect having a convex or table-like shape, can be identified as a flaw and detected.
［実施例］本発明による実施例を第１図に示す。第１図においてレ
ーザー光源１に出力３ｍＷのｔ（ｅ−Ｎｅレーザー ミ
ラー３に表面鏡、集光レンズ４に焦点距離４０ｍｍの平
凸レンズ、被検体５に精密研磨された厚さ１．２７ｍｍ
のガラス板（平均粗さ約３０人）、視野制限素子１１に
先端径４１ＩＩ１１のアルミ棒、集光レンズ１２に焦点
距離２６ｍｍ、直径３０ｍｍの非球面レンズ、検出器１
０に受光面２ａ＋ｍＸ２ｍｍの大きさを有するシリコン
フォトダイオードを用い、レーザー光２の被検体表面５
への入射角は４５°とした。このとき、被検体表面５に
おけるレーザー光径は約５０μ口である。[Example] An example according to the present invention is shown in FIG. In Fig. 1, the laser light source 1 is a t (e-Ne laser) with an output of 3 mW, the mirror 3 is a surface mirror, the condenser lens 4 is a plano-convex lens with a focal length of 40 mm, and the object 5 is a precisely polished 1.27 mm thick
glass plate (average roughness of about 30 mm), an aluminum rod with a tip diameter of 41II11 as the field-limiting element 11, an aspherical lens with a focal length of 26 mm and a diameter of 30 mm as the condenser lens 12, and a detector 1.
A silicon photodiode having a size of light receiving surface 2a + m x 2 mm is used as the object surface 5 of the laser beam 2.
The angle of incidence was 45°. At this time, the diameter of the laser beam on the surface 5 of the subject is approximately 50 μm.
被検体表面５に直径約５０μｍにわたって高さ約０．１
５μ■の凸状欠点があるときの本実施例による検出器出
力波形を第２図に示す。A height of about 0.1 over a diameter of about 50 μm on the object surface 5
FIG. 2 shows the output waveform of the detector according to this embodiment when there is a convex defect of 5 μι.
第１図における視野制御￥２素子１１は紙面と垂直方向
に設置された。視野制限素子によって視野がさまたげら
れない側をレーザー光が欠点の一部を横切って走査した
ときは検出器に得られる光電流の波形は第２図（ａ）に
示すようになり、反対に、視野制限素子によって視野が
さまたげられる側をレーザー光が欠点の一部を横切って
走査したときは検出器に得られる光電流の波形は第２図
（ｃ）に示すようになった。レーザー光が欠点の直上を
走査したときは検出器に得られる光電流の波形は第２図
（ｂ）に示すように特徴的なＳ字状波形となった。The visual field control element 11 in FIG. 1 was installed in a direction perpendicular to the plane of the paper. When the laser beam scans across a part of the defect on the side where the field of view is not obstructed by the field-of-view limiting element, the waveform of the photocurrent obtained by the detector is as shown in Fig. 2(a); When the laser beam scanned across a part of the defect on the side where the field of view is obstructed by the field-of-view limiting element, the waveform of the photocurrent obtained by the detector was as shown in FIG. 2(c). When the laser beam scanned directly above the defect, the waveform of the photocurrent obtained by the detector became a characteristic S-shaped waveform as shown in FIG. 2(b).
キズを走査したときに得られる充電流波形は常に第２図
（ａ）のように増加の形となる。The charging current waveform obtained when scanning a flaw always has an increasing shape as shown in FIG. 2(a).
上記のように本発明の方法によれば、被検体表面のキズ
と凸状欠点を区別して識別することができる。As described above, according to the method of the present invention, scratches and convex defects on the surface of a subject can be distinguished and identified.
視野制限素子１１の位置は被検体表面５からの鏡面反射
光量の２０〜８０％が検出器ＩＯに受光されるように調
整される。受光量が２０％未満の場合は従来法における
暗視野法に近くなり、また８０％を超える場合には従来
法における明視野法に近くなるため共に検出感度が低下
して本発明の提供する機能が得られ難くなる。The position of the visual field limiting element 11 is adjusted so that 20 to 80% of the amount of specularly reflected light from the subject surface 5 is received by the detector IO. When the amount of received light is less than 20%, it becomes close to the conventional dark field method, and when it exceeds 80%, it becomes close to the conventional bright field method, so the detection sensitivity decreases and the function provided by the present invention is becomes difficult to obtain.
［発明の効果］本発明は検出器により得られる出力波形を高速演算処理
することなしに、比較的容易に被検体表面のキズ（損傷
により生じた表面形状）と凸状欠点を区別して識別し得
るので検出装置のコストが低減され、産業上その実施効
果が大きい。[Effects of the Invention] The present invention can relatively easily distinguish and identify scratches (surface shape caused by damage) and convex defects on the surface of the object without performing high-speed calculation processing on the output waveform obtained by the detector. As a result, the cost of the detection device is reduced, and the implementation effect is large from an industrial perspective.
また、本発明は鏡面反射成分の一部を視野制限素子によ
って排除するため被検体の平坦度すなわち測定位置にお
ける被検体の法線方向の変化により検出器出力レベルが
変動するが、これを利用して被検体の平坦度を評価する
ことも同時に可能である。In addition, in the present invention, since a part of the specular reflection component is eliminated by the field-of-view limiting element, the detector output level fluctuates depending on the flatness of the object, that is, the normal direction of the object at the measurement position. It is also possible to evaluate the flatness of the object at the same time.
被検体に反りや表面にうねり等がある場合でも、検出す
べき欠点は一般にそれらに比較して充分に小さいので、
検出器信号を高域フィルターな通過させること番こより
、本発明の目的とする欠点の検出に支障を生じることは
ない。Even if the object to be inspected has warps or undulations on its surface, the defects to be detected are generally sufficiently small compared to them.
Passing the detector signal through a high-pass filter does not impede the detection of defects, which is the object of the invention.
第１図は本発明の詳細な説明図、第２図は実施例による
凸状欠点の検出信号波形図であり、同図（ａ）および（
ｃ）は照射レーザー光が欠点を部分的に走査照射したと
きの信号波形図、（ｂ）は中心上を走査照射したときの
信号波形図である。第３図は同欠点の従来法の暗視野法
により得られる検出信号波形図、第４図は同欠点の従来
法の明視野法により得られる検出信号波形図である。１・・・レーザー光源、２・・・照射レーザー光、３・・・ミラー４・・・集光レンズ、５・・・被検体表面、６・・・鏡面反射法、７・・・視野制限された鏡面反射光、８・・・被検体表面上の欠点、９・・・散乱光、１０・・・検出器、１１・・・視野制限素子、郷圀FIG. 1 is a detailed explanatory diagram of the present invention, and FIG. 2 is a detection signal waveform diagram of a convex defect according to an embodiment.
(c) is a signal waveform diagram when the irradiation laser beam scans and irradiates a defect partially, and (b) is a signal waveform diagram when the irradiation laser beam scans and irradiates the center. FIG. 3 is a detection signal waveform diagram obtained by the conventional dark field method for the same defect, and FIG. 4 is a detection signal waveform diagram obtained by the conventional bright field method for the same defect. DESCRIPTION OF SYMBOLS 1...Laser light source, 2...Irradiation laser light, 3...Mirror 4...Condensing lens, 5...Object surface, 6...Specular reflection method, 7...Visual field restriction specularly reflected light, 8... Defect on the surface of the object, 9... Scattered light, 10... Detector, 11... Field of view limiting element, Gokuni
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25213989AJPH03115844A (en) | 1989-09-29 | 1989-09-29 | Surface defect detection method |
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25213989AJPH03115844A (en) | 1989-09-29 | 1989-09-29 | Surface defect detection method |
| Publication Number | Publication Date |
|---|---|
| JPH03115844Atrue JPH03115844A (en) | 1991-05-16 |
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP25213989APendingJPH03115844A (en) | 1989-09-29 | 1989-09-29 | Surface defect detection method |
| Country | Link |
|---|---|
| JP (1) | JPH03115844A (en) |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1997028429A1 (en)* | 1996-01-31 | 1997-08-07 | General Scanning Inc. | Method and system for suppressing unwanted reflections in an optical system |
| JP2009295299A (en)* | 2008-06-02 | 2009-12-17 | Tamura Seisakusho Co Ltd | Illumination body |
| JP2010199145A (en)* | 2009-02-23 | 2010-09-09 | Ushio Inc | Light source equipment |
| JP2017111121A (en)* | 2015-11-13 | 2017-06-22 | コグネックス・コーポレイション | System and method for detecting defects on specular surfaces in a vision system |
| US11493454B2 (en) | 2015-11-13 | 2022-11-08 | Cognex Corporation | System and method for detecting defects on a specular surface with a vision system |
| WO2024111187A1 (en)* | 2022-11-24 | 2024-05-30 | 日東電工株式会社 | Inspection method for film |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1997028429A1 (en)* | 1996-01-31 | 1997-08-07 | General Scanning Inc. | Method and system for suppressing unwanted reflections in an optical system |
| JP2009295299A (en)* | 2008-06-02 | 2009-12-17 | Tamura Seisakusho Co Ltd | Illumination body |
| JP2010199145A (en)* | 2009-02-23 | 2010-09-09 | Ushio Inc | Light source equipment |
| JP2017111121A (en)* | 2015-11-13 | 2017-06-22 | コグネックス・コーポレイション | System and method for detecting defects on specular surfaces in a vision system |
| US11493454B2 (en) | 2015-11-13 | 2022-11-08 | Cognex Corporation | System and method for detecting defects on a specular surface with a vision system |
| WO2024111187A1 (en)* | 2022-11-24 | 2024-05-30 | 日東電工株式会社 | Inspection method for film |
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