JP2012215566A - Flaw detecting apparatus, flaw detecting method and sheet-shaped object - Google Patents

Flaw detecting apparatus, flaw detecting method and sheet-shaped object Download PDF

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JP2012215566A
JP2012215566A JP2012062159A JP2012062159A JP2012215566A JP 2012215566 A JP2012215566 A JP 2012215566A JP 2012062159 A JP2012062159 A JP 2012062159A JP 2012062159 A JP2012062159 A JP 2012062159A JP 2012215566 A JP2012215566 A JP 2012215566A
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sheet
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defect detection
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Toshimasa Takahashi
俊匡 高橋
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Kaneka Corp
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Abstract

PROBLEM TO BE SOLVED: To provide a flaw detecting apparatus and a flaw detecting method enabling any convexo-concave flaw having arisen on the surface of a light-transmissive sheet-shaped object to be effectively detected irrespective of brightness distribution attributable to an optical system, and a sheet-shaped object whose flaw or flaws have been detected.SOLUTION: A detecting apparatus for convexo-concave flaws comprises irradiating means 2b that irradiates a light-transmissive sheet-shaped object 1 with parallel light rays on the running route of the sheet-shaped object; a screen 3 that is installed on the side opposite to the irradiating means with respect to the face of the sheet-shaped object and onto which the light rays from the irradiating means having been transmitted by the sheet-shaped object are projected; and an imaging means 4 that images the light rays projected on the screen from the dark field direction. The diffuse reflectance of the screen is lower in the part where the luminous energy level is highest than in the part where the luminous energy level is lowest when the light rays having been transmitted by the sheet-shaped object in a flawless state are projected.

Description

本発明は、光透過性を有するシート状物の製造ライン又は加工ラインに沿って設けられ、シート状物の凹凸欠陥を検出する欠陥検出装置、欠陥検出方法及びこれらにより凹凸欠陥が検出されたシート状物に関する。   The present invention provides a defect detection apparatus, a defect detection method, and a sheet in which a concavo-convex defect is detected by these, provided along a production line or a processing line of a sheet-like material having optical transparency, Concerning the object.

近年、高分子フィルムに対する品質要求が厳しくなりつつあり、高分子フィルムに生じる欠陥に対する要求規格も年々高まっている。そのため、高分子フィルムに代表されるシート状物の製造工程においては、シート状物の欠陥検査が一般的に行なわれている。従来、検査対象となっていた欠陥として、埃やフィルム片等の付着異物、混入異物の他、フィッシュアイなどの凹凸欠陥、穴、キズなど多岐に亘っていたが、シート状物の高品質化に伴い、正常部分との光学歪が微小な凹凸欠陥等も検査対象として要求されつつある。   In recent years, quality requirements for polymer films are becoming stricter, and requirements standards for defects occurring in polymer films are increasing year by year. Therefore, in the process of manufacturing a sheet-like material represented by a polymer film, a defect inspection of the sheet-like material is generally performed. Conventionally, defects that have been inspected include a wide variety of defects such as dust and film pieces, and other foreign materials, mixed foreign materials, and irregularities such as fish eyes, holes, and scratches. Along with this, an uneven defect having a small optical distortion with respect to a normal part is being demanded as an inspection object.

従来、光透過性を有するシート状物の欠陥検査における凹凸欠陥の検出手法としては、照射手段によりシート状物を照射し、透過あるいは反射した光をＣＣＤラインセンサなどの撮像手段で受光し、受光量の変化により欠陥を検出・判定する方法が一般的である。   Conventionally, as a method for detecting irregularities in a defect inspection of a light-transmitting sheet-like object, the sheet-like object is irradiated by an irradiating means, and the transmitted or reflected light is received by an imaging means such as a CCD line sensor. A general method is to detect and judge defects by changing the amount.

例えば、複数の撮像手段を用いて、相異なる方向かつシート状物面に対して傾斜した角度からシート状物面を撮像し、凹凸欠陥の検出や種類検出を行う方法が提案されている（例えば、特許文献１参照）。この方法によれば、得られた凹凸欠陥画像と欠陥の高さ情報を比較して、凹凸欠陥の検出や判定が可能である。しかし、複数の撮像手段の撮像対象位置を厳密に一致させる必要があるほか、フィルムの振動や微小な走行皺の影響で各撮像手段の撮像位置にずれが生じ、情報の比較が困難になるため、連続的に安定した検査を行うには更なる改良が求められていた。   For example, a method has been proposed in which a plurality of imaging units are used to image a sheet-like object surface from different directions and from an angle inclined with respect to the sheet-like object surface, and detect uneven defects and type detection (for example, , See Patent Document 1). According to this method, it is possible to detect and determine an uneven defect by comparing the obtained uneven defect image and defect height information. However, it is necessary to precisely match the imaging target positions of a plurality of imaging means, and the imaging position of each imaging means is displaced due to the influence of film vibrations and minute running rods, making it difficult to compare information. In order to perform continuous and stable inspection, further improvement has been demanded.

一方、シート状物を透過した点光源の光をスクリーン上に投影し、凹凸欠陥部分のレンズ効果で生じる陰影を撮像手段で検出する検査方法が提案されている（例えば、特許文献２参照）。この方法によれば、撮像位置が常時スクリーン上で一定であるため、安定した検査を行うことが可能である。しかし、スクリーン上には点光源の照射光が球面波であることに起因する山形の輝度分布が生じ、シェーディング補正などの輝度補正処理を行っても、元の輝度分布の暗部と明部の輝度差に起因する地合ノイズ信号が大きく残り、欠陥部分のＳ／Ｎ比を小さくするという問題があった。   On the other hand, an inspection method has been proposed in which light of a point light source that has passed through a sheet-like material is projected on a screen, and a shadow caused by the lens effect of a concave-convex defect portion is detected by an imaging means (see, for example, Patent Document 2). According to this method, since the imaging position is always constant on the screen, stable inspection can be performed. However, a mountain-shaped luminance distribution is generated on the screen due to the spherical light emitted from the point light source. Even if luminance correction processing such as shading correction is performed, the luminance of the dark and bright portions of the original luminance distribution There was a problem that a large amount of ground noise signal due to the difference remained and the S / N ratio of the defective portion was reduced.

形状変化の緩やかな凹凸欠陥は、欠陥部分のレンズ効果による受光量の変化が僅かであるため、検査においてはＳ／Ｎ比向上のためにノイズ信号量を抑制する必要がある。しかし上記先行技術では、正常なシート状物の地合信号の中にノイズ成分が大きく残るため、結果として凹凸欠陥の検出に至らないケースがあった。   Since the unevenness defect having a gradual change in shape has a slight change in the amount of received light due to the lens effect of the defective portion, it is necessary to suppress the amount of noise signal in order to improve the S / N ratio in inspection. However, in the above prior art, a large noise component remains in the formation signal of a normal sheet-like material, and as a result, there has been a case where the uneven defect is not detected.

従って、照射手段の輝度分布による検査への影響を抑制したシート状物表面の凹凸欠陥の検出手段の開発・改良が求められている。   Accordingly, there is a need for development / improvement of detecting means for detecting irregularities on the surface of a sheet-like object in which the influence of the luminance distribution of the irradiation means on the inspection is suppressed.

特開２００５−３５１８２５号公報JP 2005-351825 A 特開２００５−２４１５８６号公報JP 2005-241586 A

本発明は、光透過性を有するシート状物表面に生じた凹凸欠陥を、光学系起因の輝度分布に関わらず効果的に検出できる欠陥検出装置、欠陥検出方法、及び欠陥検出されたシート状物を提供することを目的とする。   The present invention relates to a defect detection apparatus, a defect detection method, and a sheet-like object in which a defect is detected, which can effectively detect uneven defects generated on the surface of a sheet-like object having light transmittance regardless of the luminance distribution caused by the optical system. The purpose is to provide.

本発明者は、課題を解決するために鋭意検討した結果、光透過性を有するシート状物表面に生じた凹凸欠陥を検出するにあたり、投影式検査において、スクリーン表面の拡散反射率と、照射手段に対する撮像手段の撮像角度によって、撮像手段における受光量が異なることに着目し、シート状物に点光源の光を照射し、スクリーンに投影された光を撮像手段で受光し、得られた受光量情報から欠陥を判定する光学系において、スクリーン表面の拡散反射率に分布を付与して、具体的には、シート状物の欠陥のない状態を透過した光のうち、光量レベルの最も高い部分が投影される箇所の拡散反射率が、光量レベルの最も低い部分が投影される箇所の拡散反射率よりも低くして、撮像手段における受光量分布を均一に補正する方法を見出すことにより、本発明を完成させるに至った。   As a result of diligent investigations to solve the problems, the present inventor, in detecting a concavo-convex defect generated on the surface of a light-transmitting sheet-like object, in the projection inspection, the diffuse reflectance of the screen surface and the irradiation means Paying attention to the fact that the amount of light received by the imaging means varies depending on the imaging angle of the imaging means relative to In an optical system for determining defects from information, a distribution is given to the diffuse reflectance of the screen surface, and specifically, the portion having the highest light amount level among the light transmitted through the sheet-free state without defects. To find a method for uniformly correcting the received light amount distribution in the imaging means by making the diffuse reflectance of the projected portion lower than the diffuse reflectance of the portion where the lowest light amount level is projected More, it has led to the completion of the present invention.

すなわち、本発明の第一は、光透過性を有するシート状物の走行経路上において、シート状物に平行光を照射する照射手段と、シート状物面に対して照射手段と反対側に設置され、シート状物を透過した照射手段からの光を投影するスクリーンと、スクリーンに投影された光を暗視野方向から撮像する撮像手段を有する凹凸欠陥の検出装置であって、スクリーンは、シート状物の欠陥のない状態を透過した光のうち、光量レベルの最も高い部分が投影される箇所の拡散反射率が、光量レベルの最も低い部分が投影される箇所の拡散反射率よりも低いことを特徴とする、欠陥検出装置に関する。   That is, the first of the present invention is an irradiation unit that irradiates the sheet-like material with parallel light on the traveling path of the light-transmitting sheet-like material, and is installed on the opposite side of the irradiation means with respect to the sheet-like surface. An uneven defect detection device having a screen for projecting light from an irradiating means that has passed through a sheet-like object and an imaging means for imaging light projected on the screen from a dark field direction. The diffuse reflectance of the portion where the highest light intensity level is projected among the light that has passed through the defect-free state is lower than the diffuse reflectance of the location where the lowest light intensity level is projected. The present invention relates to a defect detection apparatus.

好ましい実施態様としては、スクリーン表面の拡散反射率が、スクリーン周辺部よりも中央部が低くなっていることを特徴とする欠陥検出装置に関する。   As a preferred embodiment, the present invention relates to a defect detection apparatus characterized in that the diffuse reflectance of the screen surface is lower in the central part than in the peripheral part of the screen.

好ましい実施態様としては、スクリーン表面の拡散反射率を面粗度により付与したことを特徴とする欠陥検出装置に関する。   As a preferred embodiment, the present invention relates to a defect detection apparatus characterized in that the diffuse reflectance of the screen surface is given by the surface roughness.

好ましい実施態様としては、スクリーン表面の面粗度のＲｚが、スクリーン周辺部よりも中央部が大きいことを特徴とする欠陥検出装置に関する。   As a preferred embodiment, the present invention relates to a defect detection apparatus characterized in that the surface roughness Rz of the screen surface is larger in the central portion than in the peripheral portion of the screen.

好ましい実施態様としては、撮像手段の視野領域全域における受光量分布の最小値が最大値の５０％以上となるよう、照射手段の照射軸と撮像手段の撮影軸とスクリーンの傾斜角度が調整されていることを特徴とする、欠陥検出装置に関する。   As a preferred embodiment, the irradiation axis of the irradiation unit, the imaging axis of the imaging unit, and the inclination angle of the screen are adjusted so that the minimum value of the received light amount distribution in the entire visual field region of the imaging unit is 50% or more of the maximum value. The present invention relates to a defect detection device.

好ましい実施態様としては、照射手段は点光源であることを特徴とする欠陥検出装置に関する。   As a preferred embodiment, the present invention relates to a defect detection apparatus characterized in that the irradiation means is a point light source.

好ましい実施態様としては、照射手段は、照射光の平行性を向上させるために１枚または複数枚のレンズを具備すること特徴とする欠陥検出装置に関する。   As a preferred embodiment, the irradiation means relates to a defect detection apparatus comprising one or a plurality of lenses in order to improve the parallelism of the irradiation light.

好ましい実施態様としては、照射手段で使用するランプは、アーク放電式であることを特徴とする欠陥検出装置に関する。   As a preferred embodiment, the present invention relates to a defect detection apparatus characterized in that the lamp used in the irradiation means is an arc discharge type.

好ましい実施態様としては、撮像手段は、ＣＣＤラインセンサカメラであることを特徴とする欠陥検出装置に関する。   As a preferred embodiment, the imaging means is a CCD line sensor camera, and relates to a defect detection apparatus.

本発明の第二は、記載の欠陥検出装置を用いて、シート状物の走行経路上において、シート状物表面に生じた凹凸欠陥を検出することを特徴とする、欠陥検出方法に関する。   A second aspect of the present invention relates to a defect detection method, characterized in that an uneven defect generated on the surface of a sheet-like object is detected on the travel route of the sheet-like object using the defect detection apparatus described.

本発明の第三は、記載の欠陥検出装置を用いて凹凸欠陥が検出されたシート状物に関する。   A third aspect of the present invention relates to a sheet-like object in which an uneven defect is detected using the described defect detection apparatus.

本発明においては、スクリーン表面の拡散反射率によって、スクリーンに照射された光の鏡面反射成分と拡散反射成分の割合が異なることを利用している。   In the present invention, it is utilized that the ratio of the specular reflection component and the diffuse reflection component of the light irradiated on the screen differs depending on the diffuse reflectance of the screen surface.

すなわち、投影光学系を用いた欠陥検査において、照射手段からスクリーン表面に照射された光の輝度分布に対して、輝度の高い領域の拡散反射率を予め低く調整し、輝度の低い領域の拡散反射率を予め高く調整し、照射手段の照射軸と撮像手段の撮像軸がスクリーン上で正反射方向にならない暗視野方向の角度から、撮像手段でスクリーン表面の輝度を撮像することで、輝度分布のバラつきに関わらず均一な受光量が得られるため、ノイズ信号を抑制して光量変化の少ない形状の緩やかな凹凸欠陥でも効果的に検出でき、光透過性を有するシート状物の凹凸欠陥を、長期に亘り安定して検出することが可能となる。   That is, in the defect inspection using the projection optical system, the diffuse reflectance of the high luminance region is adjusted to be low in advance with respect to the luminance distribution of the light irradiated from the irradiation means to the screen surface, and the diffuse reflection of the low luminance region is performed. By adjusting the brightness of the screen surface with the imaging unit from the angle of the dark field direction where the irradiation axis of the irradiation unit and the imaging axis of the imaging unit are not in the regular reflection direction on the screen, the luminance distribution is adjusted. A uniform amount of received light can be obtained regardless of variations, so that it is possible to effectively detect even a concavo-convex defect with a shape with little change in light intensity by suppressing a noise signal. It is possible to detect stably over the range.

従来の実施形態に係る欠陥検査装置の一例を示す図である。It is a figure which shows an example of the defect inspection apparatus which concerns on the conventional embodiment. 従来の実施形態に係る欠陥検査装置の一例を示す図である。It is a figure which shows an example of the defect inspection apparatus which concerns on the conventional embodiment. 本発明の実施形態に係る欠陥検出方法とその装置の一例を示す図である。It is a figure which shows an example of the defect detection method and its apparatus which concern on embodiment of this invention. 本発明の実施形態に係る欠陥検出方法とその装置の一例を示す図である。It is a figure which shows an example of the defect detection method and its apparatus which concern on embodiment of this invention.

本発明は、光透過性を有するシート状物の走行経路上において、シート状物に平行光を照射する照射手段と、シート状物面に対して照射手段と反対側に設置され、シート状物を透過した照射手段からの光を投影するスクリーンと、スクリーンに投影された光を暗視野方向から撮像する撮像手段を有し、スクリーンは、シート状物の欠陥のない状態を透過した光のうち、光量レベルの最も高い部分が投影される箇所の拡散反射率が、光量レベルの最も低い部分が投影される箇所の拡散反射率よりも低いことを特徴とする凹凸欠陥の欠陥検出装置、欠陥検出方法及び欠陥検出装置により欠陥が検出されたシート状物に関する。   The present invention relates to an irradiation means for irradiating the sheet-like material with parallel light on the traveling path of the light-transmitting sheet-like material, and a sheet-like material installed on the side opposite to the irradiation means with respect to the sheet-like material surface. A screen for projecting light from the irradiation means that has passed through and an imaging means for imaging the light projected on the screen from the dark field direction. The defect detection apparatus for defect, characterized by the fact that the diffuse reflectance of the portion where the portion with the highest light level is projected is lower than the diffuse reflectance of the portion where the portion with the lowest light level is projected The present invention relates to a sheet-like object in which a defect is detected by a method and a defect detection apparatus.

本発明における「シート状物」とは、光透過性を有し、面方向に対し厚み方向のスケールが非常に小さい、いわゆるシート状物であって、特に厚みや幅などは限定されるものではない。シート状物として、例えば、フィルム、シート、薄膜などが挙げられる。   The “sheet-like material” in the present invention is a so-called sheet-like material having light transmittance and a very small scale in the thickness direction with respect to the surface direction, and the thickness and width are not particularly limited. Absent. Examples of the sheet-like material include a film, a sheet, and a thin film.

また、本発明において、シート状物の「走行経路」とは、例えば、製造、加工等の生産工程内で連続的に搬送されている経路を指す。   In the present invention, the “traveling route” of the sheet-like material refers to a route that is continuously conveyed in a production process such as manufacturing and processing.

本発明における「暗視野方向」とは、照射手段の照射軸と撮像手段の撮影軸がスクリーン上で正反射の関係で交わらない方向をいう。   The “dark field direction” in the present invention refers to a direction in which the irradiation axis of the irradiation unit and the imaging axis of the imaging unit do not intersect on the screen due to regular reflection.

さらに、本発明において「凹凸欠陥」とは、シート状物厚みに対する突起厚み及び凹み深さの割合が＋２５％〜−２５％であり、欠陥がスジのように連続的ではない場合は大きさ５０μｍ〜２ｃｍである無色欠陥を指す。ここで、無色欠陥とは、シート状物と同色である欠陥のことを指す。例えば、一般的なフィッシュアイの他、異物の噛み込みによる打痕や、走行皺などによるスジ、キャストフィルムやキャストロール等の成形ガイド体の表面形状ムラに起因する模様などが例示され、シート状物表面に生じたものであれば特に限定されるものではない。   Furthermore, in the present invention, the “concave defect” means that the ratio of the protrusion thickness and the dent depth to the sheet-like material thickness is + 25% to −25%, and the size is 50 μm when the defect is not continuous like a streak. Refers to colorless defects that are ~ 2 cm. Here, the colorless defect refers to a defect having the same color as the sheet-like material. For example, in addition to general fish eyes, examples include dents caused by biting of foreign matter, streaks caused by running rods, patterns resulting from uneven surface shape of molding guide bodies such as cast films and cast rolls, etc. There is no particular limitation as long as it occurs on the surface of the object.

そのほか、本発明において「レンズ効果」とは、光透過性を有するシート状物の凹凸形状部分が凹レンズ、及び凸レンズと同様の効果を発揮し、入射光に対して射出光の進行方向が変化する現象のことを言う。   In addition, in the present invention, the “lens effect” means that the uneven shape portion of the light-transmitting sheet-like material exhibits the same effect as the concave lens and the convex lens, and the traveling direction of the emitted light changes with respect to the incident light. Say the phenomenon.

また、本発明において「鏡面反射成分」とはスクリーン表面で正反射する反射光を言い、「拡散反射成分」とは正反射する反射光以外の反射光を言う。「拡散反射率」とは、スクリーン表面で反射した反射光全体に対する、拡散反射した反射光の割合を言う。   In the present invention, “specular reflection component” refers to reflected light that is specularly reflected on the screen surface, and “diffuse reflection component” refers to reflected light other than the specularly reflected light. “Diffusion reflectance” refers to the ratio of diffusely reflected light to the total reflected light reflected on the screen surface.

以下、本発明に係る凹凸欠陥検出装置及び欠陥検出方法に関して、図１、２、３、４に基づいて説明する。なお、以下の実施形態は本発明を具体化した一例であって、本発明の技術的範囲を限定する性格のものではない。   Hereinafter, the concavo-convex defect detection apparatus and the defect detection method according to the present invention will be described with reference to FIGS. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not.

図１は、従来の欠陥検出装置の概略構成を示す模式図である。   FIG. 1 is a schematic diagram showing a schematic configuration of a conventional defect detection apparatus.

図１中、１はシート状物であり、矢印Ｘの方向に走行している。また、２ａはライン状の照射手段であり、蛍光灯のほか、ＬＥＤやハロゲンランプ、メタルハライドランプなどの光源を導光体やシリンドリカルレンズを用いてライン状にしたものが挙げられる。４は照射手段２ａから照射されシート状物１を透過した光を受光する撮像手段である。５は欠陥判定手段であり、撮像手段４で受光した光量の変化から欠陥の有無を判定する。図２は、図１の明視野撮影方式に対し、暗視野撮影方式とした模式図であり、検出対象とする凹凸欠陥に応じて、図１、図２いずれの方式をとることも可能である。   In FIG. 1, reference numeral 1 denotes a sheet-like object that runs in the direction of arrow X. Reference numeral 2a denotes a linear irradiation means, which includes a fluorescent light source, a light source such as an LED, a halogen lamp, and a metal halide lamp, which is formed into a linear shape using a light guide or a cylindrical lens. Reference numeral 4 denotes an image pickup unit that receives light irradiated from the irradiation unit 2a and transmitted through the sheet-like object 1. Reference numeral 5 denotes defect determination means, which determines the presence or absence of a defect from the change in the amount of light received by the imaging means 4. FIG. 2 is a schematic diagram in which the dark-field imaging method is used in contrast to the bright-field imaging method of FIG. 1, and either the method of FIG. 1 or FIG. 2 can be adopted depending on the uneven defect to be detected. .

図１、２では、シート状物１上に凹凸欠陥が存在する場合、凹凸欠陥のレンズ効果で散乱または集光した透過光による輝度信号の変化を、予め設定した閾値と比較照合することにより、欠陥として検出することが可能である。しかし、ライン状の照射手段２ａから照射される光はいずれかの方向に光線成分が重なる拡散光である。そのため、厚み変化が微細な凹凸欠陥の屈折効果で生じる受光量の変化は、他方向からの拡散光と干渉して殆ど検知することができない。よって、この方法は厚み変化が急激な凹凸欠陥のみに適応範囲が限られる。   In FIGS. 1 and 2, when there is an uneven defect on the sheet-like object 1, by comparing and comparing the change in the luminance signal due to the transmitted light scattered or collected by the lens effect of the uneven defect with a preset threshold value, It can be detected as a defect. However, the light irradiated from the line-shaped irradiation means 2a is diffused light in which light components overlap in any direction. For this reason, the change in the amount of received light caused by the refraction effect of the concave and convex defect having a fine thickness change hardly interferes with the diffused light from the other direction and can be hardly detected. Therefore, this method has a limited range of applicability only to uneven defects whose thickness changes abruptly.

厚み変化が微細な凹凸欠陥を検出する手段として、メタルハライドやキセノン光源のような、発光源に素子を持たない点光源を用いた投影式検査も一般的に行われている。   As a means for detecting an uneven defect having a minute thickness change, a projection type inspection using a point light source having no element as a light source, such as a metal halide or a xenon light source, is generally performed.

点光源を用いる投影式検査では、照射光は各光線成分同士が重ならない、いわゆる平行光に近い光であるため、欠陥部分での透過光の散乱、集光による光の分布の変化がスクリーン上に顕著に投影されることとなる。しかし、点光源から照射される光は球面波の性質を有する。そのため、平面であるスクリーン上に投影された照射光は中心が最も明るく、周辺が暗い光量分布を持つ。従って、撮像手段４を用いた自動検査を行う場合、撮像手段４側で受光量を均一とみなす補正が必要である。この受光量の補正によって、スクリーン上の光量が低い領域は信号のノイズ成分が拡大されるため、厚み変化の微小な凹凸欠陥での受光量変化はノイズ範囲に埋もれることが多く、欠陥として検出することは困難であった。   In projection inspection using a point light source, the irradiated light is light that is close to the so-called parallel light in which the light components do not overlap each other. Will be projected significantly. However, the light emitted from the point light source has a spherical wave property. Therefore, the irradiation light projected on a flat screen has a light quantity distribution with the brightest center and the dark periphery. Therefore, when performing an automatic inspection using the imaging unit 4, it is necessary to perform correction on the imaging unit 4 side so that the amount of received light is uniform. This correction of the amount of received light expands the noise component of the signal in the low light area on the screen. Therefore, the change in the amount of received light due to a minute uneven defect of thickness change is often buried in the noise range and is detected as a defect. It was difficult.

これに対して、図３は、本発明に係る欠陥検出方法とその装置の概略構成を示す模式図である。   On the other hand, FIG. 3 is a schematic diagram showing a schematic configuration of the defect detection method and apparatus according to the present invention.

本発明は、照射手段固有の光量分布、すなわち点光源でいう中心が最も明るく端部に進むにつれ暗くなる分布が、撮像手段での受光時には一定になるように、スクリーン表面に拡散反射率の分布が付与されている、具体的には、シート状物の欠陥のない状態を透過した光のうち、光量レベルの最も高い部分が投影される箇所の拡散反射率が、光量レベルの最も低い部分が投影される箇所の拡散反射率よりも低くなっている。ここで、一定とは、撮像手段の視野領域全域における受光量分布の最小値が最大値の５０％以上である状態のことをいう。検査の精度向上の観点から、撮像手段の視野領域全域における受光量分布の最小値が最大値の７０％以上であることが好ましい。   The present invention provides a diffuse reflectance distribution on the screen surface so that the light intensity distribution unique to the irradiation means, that is, the distribution where the center of the point light source is brightest and darker as it goes to the end is constant during light reception by the imaging means. Specifically, among the light that has passed through the sheet-like object without any defects, the diffuse reflectance of the portion where the portion with the highest light amount level is projected is the portion with the lowest light amount level. It is lower than the diffuse reflectance of the projected portion. Here, “constant” means a state in which the minimum value of the received light amount distribution in the entire visual field region of the imaging means is 50% or more of the maximum value. From the viewpoint of improving the accuracy of the inspection, it is preferable that the minimum value of the received light amount distribution in the entire visual field region of the imaging unit is 70% or more of the maximum value.

また本発明は、スクリーン表面の拡散反射率が、スクリーン周辺部よりも中央部が低くなっていることが好ましい。   In the present invention, it is preferable that the diffuse reflectance of the screen surface is lower in the central portion than in the peripheral portion of the screen.

図３中、１はシート状物であり、矢印Ｘの方向に走行している。２ｂは平行光を照射する照射手段である。３は照射手段２ｂから照射されシート状物１を透過した光を投影するスクリーンである。スクリーン３は、シート状物１の欠陥のない状態を透過した光のうち、光量レベルの最も高い部分が投影される箇所の拡散反射率が、光量レベルの最も低い部分が投影される箇所の拡散反射率よりも低い。また、スクリーン３中央部の拡散反射率を低く、スクリーン周辺の拡散反射率を高く調整していることが好ましい。４は撮像手段であり、照射手段２ｂに対して暗視野となるよう配置され、スクリーン３に投射された光量から欠陥情報を取得する。５は欠陥検出手段であり、撮像手段４で取得した受光量情報から、凹凸欠陥の有無を判定する。   In FIG. 3, reference numeral 1 denotes a sheet-like object that travels in the direction of the arrow X. Reference numeral 2b denotes irradiation means for irradiating parallel light. Reference numeral 3 denotes a screen that projects the light irradiated from the irradiation means 2b and transmitted through the sheet 1. The screen 3 diffuses the portion where the diffuse reflectance of the portion where the highest light amount level is projected out of the light transmitted through the defect-free state of the sheet-like object 1 and the portion where the lowest light amount level is projected. Lower than reflectivity. Further, it is preferable that the diffuse reflectance at the center of the screen 3 is low and the diffuse reflectance around the screen is adjusted high. Reference numeral 4 denotes an imaging unit, which is arranged so as to be in a dark field with respect to the irradiation unit 2b, and acquires defect information from the amount of light projected on the screen 3. Reference numeral 5 denotes defect detection means, which determines the presence / absence of a concavo-convex defect from received light amount information acquired by the imaging means 4.

この構成によれば、撮像手段４ではスクリーン３上で反射する照射手段２ｂからの光を暗視野方向から撮像する。そのため、スクリーン３中央部は反射光の鏡面反射成分が大きいために撮像手段４での受光量は小さくなり、一方スクリーン３端部の反射光は拡散反射成分が大きいために撮像手段４での受光量の低下は抑制されるため、撮像手段４が認識する受光量は、スクリーン３上の輝度分布と比較して均一な分布となる。これにより、撮像手段４における受光量均一化処理における補正割合が僅かとなるか、または、受光量均一化処理における補正が不要となり、地合ノイズ信号の少ない検査が行えるため、厚み変化の微小な凹凸欠陥でも漏れなく検出することが可能となる。   According to this configuration, the imaging unit 4 images the light from the irradiation unit 2b reflected on the screen 3 from the dark field direction. For this reason, since the specular reflection component of the reflected light is large at the center of the screen 3, the amount of light received by the image pickup means 4 is small. On the other hand, the reflected light at the end of the screen 3 has a large diffuse reflection component and is received by the image pickup means 4. Since the decrease in the amount is suppressed, the amount of received light recognized by the imaging unit 4 is a uniform distribution as compared with the luminance distribution on the screen 3. As a result, the correction ratio in the received light amount equalizing process in the imaging unit 4 becomes small, or correction in the received light amount uniformizing process becomes unnecessary, and inspection with less ground noise signal can be performed. Even uneven defects can be detected without leakage.

本発明は、スクリーン３表面の拡散反射率を面粗度により付与することが好ましい。   In the present invention, it is preferable that the diffuse reflectance of the surface of the screen 3 is given by the surface roughness.

また本発明は、スクリーン３表面の面粗度のＲｚが、スクリーン３周辺部よりも中央部が大きいことが好ましい。Ｒｚとは、ＪＩＳ規格「ＪＩＳＢ０６０１（１９９４）」に規定された十点平均粗さのことを言い、粗さ曲線からその平均線の方向に基準長さだけを抜取り、この抜取り部分の平均線から縦倍率の方向に測定した、最も高い山頂から５番目までの山頂の標高の絶対値の平均値と、最も低い谷底から５番目までの谷底の標高の絶対値の平均値との和を求め、この値をマイクロメートル（μｍ）で表したものをいう。   In the present invention, the surface roughness Rz of the surface of the screen 3 is preferably larger in the central portion than in the peripheral portion of the screen 3. Rz refers to the ten-point average roughness defined in the JIS standard “JISB0601 (1994)”. Only the reference length is extracted from the roughness curve in the direction of the average line, and the average line of this extracted part is extracted. Measured in the direction of the vertical magnification, find the sum of the average of the absolute values of the altitude of the highest peak from the highest peak to the fifth and the average of the absolute values of the elevation of the lowest peak from the lowest valley to the fifth, This value is expressed in micrometers (μm).

スクリーン３表面へ拡散反射率を付与する方法としては、研磨、表面の微細発泡、拡散剤塗付等、スクリーンの面粗度を調整できるものであれば特に制限は無いが、任意の粒径の砥粒を用いたブラストによる表面研磨が、所望の分布を付与できる点で好ましい。また、面粗度分布の態様としては、スクリーン３上の領域をマスキング等によって等分割または不等分割して段階的に付与するものや、スクリーン３上で面粗度の値が曲線状に変化するように付与するものなどでも十分に受光量の均一化の効果が得られるため、用途や要求レベル、元の輝度波形の分布状況に応じて、付与方法および分布パターンは適宜選択可能である。   The method for imparting diffuse reflectance to the surface of the screen 3 is not particularly limited as long as it can adjust the surface roughness of the screen, such as polishing, fine foaming of the surface, and application of a diffusing agent. Surface polishing by blasting using abrasive grains is preferable in that a desired distribution can be imparted. Further, the surface roughness distribution may be given in stages by dividing the area on the screen 3 equally or unequally by masking or the like, or the surface roughness value may change in a curved line on the screen 3. Since the effect of uniformizing the amount of received light can be sufficiently obtained even with such application, the application method and distribution pattern can be appropriately selected according to the application, required level, and distribution state of the original luminance waveform.

スクリーン３のサイズは、シート状物１の幅寸法、照射手段２ｂの照射角度、及び照射手段２ｂからの距離に合わせて適宜決定することが出来る。すなわち、スクリーン３は、シート状物１の幅方向に対して、照射手段２ｂから照射されてシート状物１を透過した光全てを投影可能であるよう配慮した寸法とし、撓みや歪の無いフラット性を備えたものが好ましい。また、スクリーン３の素材は光を吸収し難い明色系であることが好ましく、白色であることがより好ましい。   The size of the screen 3 can be appropriately determined according to the width dimension of the sheet-like object 1, the irradiation angle of the irradiation unit 2b, and the distance from the irradiation unit 2b. In other words, the screen 3 is dimensioned so that all the light irradiated from the irradiation means 2b and transmitted through the sheet-like material 1 can be projected with respect to the width direction of the sheet-like material 1, and is flat without any deflection or distortion. What provided the property is preferable. The material of the screen 3 is preferably a light color system that hardly absorbs light, and more preferably white.

照射手段２ｂは、高い平行性を有し、且つ撮像手段４で認識可能な光量の光をシート状物に均一に照射できるものであれば、光源に特に制限は無い。平行性の高い光を実現する手段としては、光源タイプとして点光源を採用することが、光の干渉を抑えた平行性の高い光を作り出すことが可能である点で好ましく、更に、点光源の光を１枚または複数枚のレンズに通すことが平行性を高める点でより好ましい。また、点光源に用いるランプにおいては、ＬＥＤやハロゲンランプなど光源にチップやフィラメントを有するランプよりも、クセノンランプや水銀ランプのように、アーク放電で発光するランプの方が、より点に近い光源とすることが出来る点で好ましい。本発明において用いることの出来る光源としては、例えば株式会社ウシオ電機製の超高圧水銀ランプ光源装置ＯＰＭ２−５０２Ｈなどが使用可能である。   The irradiation unit 2b is not particularly limited as long as it has high parallelism and can uniformly irradiate the sheet-like object with a light amount that can be recognized by the imaging unit 4. As a means for realizing highly parallel light, it is preferable to use a point light source as a light source type because it is possible to produce highly parallel light with reduced light interference. More preferably, the light is passed through one or more lenses from the viewpoint of improving parallelism. Also, in lamps used for point light sources, lamps that emit light by arc discharge, such as xenon lamps and mercury lamps, are closer to points than lamps such as LEDs and halogen lamps that have chips or filaments in the light source. It is preferable in that it can be. As a light source that can be used in the present invention, for example, an ultra-high pressure mercury lamp light source device OPM2-502H manufactured by USHIO INC. Can be used.

本発明は、撮像手段４の視野領域全域における受光量分布の最小値が最大値の５０％以上となるよう、照射手段２ｂの照射軸と撮像手段４の撮影軸とスクリーン３の傾斜角度が調整されていることが好ましい。照射手段２ｂの照射軸と撮像手段４の撮影軸はスクリーン３上で交わるが、軸同士がスクリーン３上で正反射方向となる場合、スクリーン３上で反射する光の鏡面反射成分が撮像手段４で受光されることとなる。そのため、スクリーン３の傾斜角度は、鏡面反射成分の光が撮像手段４に入射しない角度に調整する必要があり、好ましくは軸同士が正反射方向となるスクリーン傾斜角度から±５度以上６０度以下の角度に設定し、更には±５度以上２０度以下に設定するのがより好ましい。   In the present invention, the inclination angle of the irradiation axis of the irradiation unit 2b, the imaging axis of the imaging unit 4 and the inclination angle of the screen 3 is adjusted so that the minimum value of the received light amount distribution in the entire visual field region of the imaging unit 4 is 50% or more of the maximum value. It is preferable that The irradiation axis of the irradiation means 2b and the imaging axis of the imaging means 4 intersect on the screen 3, but when the axes are in the regular reflection direction on the screen 3, the specular reflection component of the light reflected on the screen 3 is the imaging means 4. Will be received. Therefore, it is necessary to adjust the inclination angle of the screen 3 to an angle at which the light of the specular reflection component does not enter the image pickup means 4, and preferably ± 5 degrees or more and 60 degrees or less from the screen inclination angle in which the axes are in the regular reflection direction. More preferably, the angle is set to ± 5 degrees or more and 20 degrees or less.

シート状物１とスクリーン３との距離Ｌ１や、シート状物１と照射手段２ｂの距離Ｌ２は、検出すべき凹凸欠陥の寸法に応じて適宜決定することが出来る。シート状物１とスクリーン３の距離Ｌ１が大きい程、凹凸の傾斜角度が小さい欠陥、すなわち突起や凹みなどの厚み変化が僅かである凹凸欠陥や、シート状物面方向のサイズが大きい凹凸欠陥を、鮮明にスクリーン３に投影することが可能となる。また、シート状物１と照射手段２ｂの距離Ｌ２が大きいほど、点光源からの照射光が平行光に近づき、欠陥部分のレンズ効果を顕著に発現させることが可能となるが、一方で照射距離の拡大に伴ってスクリーン３上の輝度が減衰するため、目的の欠陥に応じて距離を適宜設定する必要がある。更に、図４に示すように、照射手段２ｂから照射される光の光軸に対してシート状物１を傾けることにより、凹凸欠陥部のレンズ効果が強調されるため、照射手段２ｂからスクリーン３までの距離を小さく設定することも可能である。   The distance L1 between the sheet-like object 1 and the screen 3 and the distance L2 between the sheet-like object 1 and the irradiation means 2b can be appropriately determined according to the size of the concavo-convex defect to be detected. As the distance L1 between the sheet-like material 1 and the screen 3 is larger, defects having a smaller unevenness angle, that is, unevenness defects having a slight thickness change such as protrusions and depressions, and unevenness defects having a large size in the sheet-like object surface direction. It is possible to project the image on the screen 3 clearly. In addition, as the distance L2 between the sheet-like object 1 and the irradiation means 2b increases, the irradiation light from the point light source approaches the parallel light, and the lens effect of the defective portion can be remarkably exhibited. Since the brightness on the screen 3 is attenuated as the distance increases, it is necessary to set the distance appropriately according to the target defect. Furthermore, as shown in FIG. 4, since the lens effect of the concave / convex defect portion is emphasized by inclining the sheet-like object 1 with respect to the optical axis of the light irradiated from the irradiation means 2b, the irradiation means 2b to the screen 3 It is also possible to set the distance up to small.

撮像手段４は、ＣＣＤラインセンサカメラやＣＣＤエリアセンサカメラが適宜適用可能であるが、シート状物１の幅方向の分解能を細かく設定できる点において、ＣＣＤラインセンサカメラが好ましい。撮像手段４にＣＣＤラインセンサカメラを適用する場合、別途エンコーダを設置し、出力パルスからシート状物１の走行速度を積算し、検出した欠陥の位置情報を算出することも可能である。本発明において用いることの出来るＣＣＤラインセンサカメラには、例えば株式会社エクセル製のＴＩ５１５０ＴＳＳなどが使用可能である。   A CCD line sensor camera or a CCD area sensor camera can be applied as the imaging means 4 as appropriate, but a CCD line sensor camera is preferable in that the resolution in the width direction of the sheet-like object 1 can be set finely. When a CCD line sensor camera is applied to the image pickup means 4, it is also possible to install a separate encoder, integrate the traveling speed of the sheet-like object 1 from the output pulse, and calculate the position information of the detected defect. As a CCD line sensor camera that can be used in the present invention, for example, TI5150TSS manufactured by Excel Corporation can be used.

欠陥検出手段５は、撮像手段４から送られた受光量情報を表す信号に基づき、撮影位置での凹凸欠陥の有無や位置情報を抽出する回路と、予め設定入力した閾値情報を照合比較し、凹凸欠陥として判定する回路を備えるものであればよく、この目的を達成できる限り特に制限されるものではない。本発明における欠陥検出の流れとしては、例えば、撮像手段４の受光量に対して、凸欠陥を検出するための明側の閾値と凹欠陥を検出するための暗側の閾値を設定し、明側の閾値以上、或いは暗側の閾値以下の受光量の信号が入力された場合に欠陥と認識して位置情報を保存するとともに、二次元画像を作成する。ここで、撮像手段４の受光量分布に対して、カメラまたは信号処理装置内でシェーディング補正を施すことが、視野領域内の受光量分布をさらに均一する点で好ましい。また、シート状物１に凹凸欠陥以外の異物が生じるおそれのある場合には、本欠陥検出装置に対してシート状物１の走行方向の上流側に、別途異物除去手段や実体のある異物を検出する手段を設置することが、本発明において凹凸欠陥のみを検出できる点で好ましい。   The defect detection means 5 compares and compares the preset threshold information inputted in advance with a circuit that extracts the presence / absence and position information of the irregularities at the photographing position based on the signal representing the received light amount information sent from the imaging means 4. Any circuit may be used as long as it has a circuit for determining an irregularity defect, and the circuit is not particularly limited as long as this object can be achieved. As a flow of defect detection in the present invention, for example, a bright side threshold value for detecting a convex defect and a dark side threshold value for detecting a concave defect are set with respect to the amount of light received by the imaging unit 4, and When a light receiving amount signal that is equal to or greater than the threshold value on the side or equal to or less than the threshold value on the dark side is input, it is recognized as a defect and position information is stored, and a two-dimensional image is created. Here, it is preferable that the received light amount distribution of the imaging unit 4 is subjected to shading correction in the camera or the signal processing device from the viewpoint of further uniforming the received light amount distribution in the visual field region. In addition, when there is a possibility that foreign matters other than the irregularity defect may be generated on the sheet-like material 1, a separate foreign matter removing means or substantial foreign matter is provided on the upstream side in the traveling direction of the sheet-like material 1 with respect to this defect detection device. In the present invention, it is preferable to install a detecting means in that only the irregular defect can be detected.

以上に述べたように、光透過性を有するシート状物１の走行経路上において、シート状物１に平行光を照射する照射手段２ｂと、シート状物１面に対して照射手段２ｂと反対側に設置され、シート状物１を透過した照射手段２ｂからの光を投影するスクリーン３と、スクリーン３に投影された光を撮像する撮像手段４を有する凹凸欠陥の検出装置であって、スクリーン３は、スクリーン３表面に拡散反射率の分布が付与されている、具体的には、シート状物の欠陥のない状態を透過した光のうち、光量レベルの最も高い部分が投影される箇所の拡散反射率が、光量レベルの最も低い部分が投影される箇所の拡散反射率よりも低くなっていることを特徴とする、欠陥検出装置を用いることによって、シート状物１に発生する凹凸欠陥を検出し、発生した凹凸欠陥の原因特定や早期の対処を実施することが可能になり、凹凸欠陥の無いシート状物１を得ることが可能になる。   As described above, the irradiation means 2b for irradiating the sheet-like object 1 with parallel light on the travel path of the light-transmitting sheet-like object 1 is opposite to the irradiation means 2b for the surface of the sheet-like object 1. An uneven defect detection apparatus having a screen 3 for projecting light from an irradiating means 2b that has been transmitted through a sheet-like object 1 and an imaging means 4 for imaging light projected on the screen 3, 3 shows the distribution of the diffuse reflectance on the surface of the screen 3, specifically, the portion where the portion with the highest light amount level is projected among the light that has passed through the sheet-like object without any defects. By using the defect detection device, the uneven defect generated in the sheet-like object 1 is characterized in that the diffuse reflectance is lower than the diffuse reflectance of the portion where the lowest light amount level is projected. Detect It is possible to carry out the attribution and early action without the irregular defect, it is possible to obtain a sheet-like material 1 no irregular defect.

以下、本発明を実施例に基づきさらに詳細に説明するが、本発明はこれらの実施例に限定されるものではない。   EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

（実施例１）
光源は５００Ｗ超高圧水銀ランプ（株式会社ウシオ電機社製、ＯＰＭ２−５０２Ｈ）を用い、撮像手段は素子数５１５０ｂｉｔ、視野幅２００ｍｍのＣＣＤラインセンサカメラ（株式会社エクセル製、ＴＩ５１５０ＴＳＳ）を用いた。ラインセンサカメラからスクリーンまでの距離を１４００ｍｍとし、また、照射軸上で照射手段とスクリーンの間で、スクリーンからの距離が２００ｍｍとなる位置に、直径約５ｍｍ、深さ約２μｍの凹み欠陥を有するプラスチックフィルム（シート状物）を設置した。スクリーンは長さ３００ｍｍ、幅５０ｍｍの白色アクリル板を用い、面粗度がスクリーンの長手方向に領域を三等分した中央の領域でＲｚ＝１２７、両端領域でＲｚ＝２．５となるよう研磨処理を施した。ＣＣＤラインセンサカメラの撮影軸と照射手段の照射軸がスクリーン上で７５度の角度を為して交わるものとし、スクリーン上での反射光に対して暗視野撮像とするために、スクリーンを最小限動かしてＣＣＤラインセンサカメラの撮影軸とスクリーン面方向の為す角度が６０．０度となるようスクリーンの傾斜角度を調整した。この時、検査領域、すなわち撮像手段の視野領域内で検査対象となる領域における受光量の最小値は最大値の７１．４％となり、最大値の５０％を上回った。装置構成で得られた光量分布に対してシェーディング補正を行い、スクリーン上に投影された欠陥陰影の検出を行ったところ、欠陥陰影のみを欠陥として判定した。また、スクリーンに投影されたプラスチックフィルムの地合輝度に対する、欠陥陰影部分のＳ／Ｎ比を「Ｓ／Ｎ比＝２０×ｌｏｇ10（陰影部分の輝度立下り量）/（地合ノイズ変動量）」で算出した結果、Ｓ／Ｎ比＝２．２となり、検査で明確に欠陥を捉えることのできるＳ／Ｎ比２．０の値を上回った。 Example 1
The light source used was a 500 W ultra-high pressure mercury lamp (manufactured by Ushio Electric Co., Ltd., OPM2-502H), and the imaging means used was a CCD line sensor camera (TI5150TSS, manufactured by Excel Co., Ltd.) having 5150 bits of elements and a field of view width of 200 mm. The distance from the line sensor camera to the screen is 1400 mm, and there is a dent defect with a diameter of about 5 mm and a depth of about 2 μm at a position where the distance from the screen is 200 mm between the irradiation means and the screen on the irradiation axis. A plastic film (sheet-like material) was installed. The screen uses a white acrylic plate with a length of 300 mm and a width of 50 mm, and is polished so that the surface roughness is Rz = 127 in the central area obtained by dividing the area into three equal parts in the longitudinal direction of the screen and Rz = 2.5 in both end areas. Treated. The imaging axis of the CCD line sensor camera and the irradiation axis of the irradiation means shall intersect at an angle of 75 degrees on the screen, and the screen must be minimized in order to obtain dark field imaging with respect to the reflected light on the screen. The tilt angle of the screen was adjusted so that the angle formed between the photographing axis of the CCD line sensor camera and the screen surface direction was 60.0 degrees. At this time, the minimum value of the amount of received light in the inspection region, that is, the region to be inspected in the field of view of the image pickup means was 71.4% of the maximum value, which exceeded 50% of the maximum value. When the shading correction was performed on the light amount distribution obtained by the apparatus configuration and the defect shadow projected on the screen was detected, only the defect shadow was determined as a defect. Further, the S / N ratio of the defect shadow portion with respect to the ground brightness of the plastic film projected on the screen is expressed as “S / N ratio = 20 × log 10 (luminance falling amount of shadow portion) / (ground noise fluctuation amount). As a result, the S / N ratio was 2.2, which exceeded the value of S / N ratio 2.0 at which defects can be clearly detected by inspection.

（実施例２）
面粗度がスクリーンの長手方向に領域を五等分した中央の領域でＲｚ＝１２７、中央領域と両端領域の間に位置する領域でＲｚ＝２１、両端部でＲｚ＝２．５となるよう研磨処理を施したアクリル板をスクリーンとして用い、その他の構成は実施例１と同じとしたところ、欠陥陰影のみを検出した。また、欠陥陰影部分のＳ／Ｎ比＝２．７となり、Ｓ／Ｎ比２．０を大きく上回った。 (Example 2)
The surface roughness is Rz = 127 in the central region obtained by dividing the region into five in the longitudinal direction of the screen, Rz = 21 in the region located between the central region and both end regions, and Rz = 2.5 at both ends. When a polished acrylic plate was used as a screen and the other configurations were the same as in Example 1, only the defect shadow was detected. Further, the S / N ratio of the defect shadow portion was 2.7, which was much higher than the S / N ratio 2.0.

（実施例３）
スクリーンの長手方向に領域を七等分し、一方の端から他方の端までの各領域における面粗度が、順にＲｚ＝２．５、１０．５、６３．５、１２７（スクリーン中央領域）、６３．５、１０．５、２．５となるよう研磨処理を施したアクリル板をスクリーンとして用い、その他の構成は実施例１と同じとしたところ、欠陥陰影のみを検出した。また、欠陥陰影部分のＳ／Ｎ比＝３．２となり、Ｓ／Ｎ比２．０を大きく上回った。 (Example 3)
The area is divided into seven equal parts in the longitudinal direction of the screen, and the surface roughness in each area from one end to the other end is Rz = 2.5, 10.5, 63.5, 127 (screen center area). , 63.5, 10.5, 2.5 Acrylic plates that had been subjected to a polishing treatment were used as the screen, and other configurations were the same as in Example 1, but only the defect shadows were detected. Further, the S / N ratio of the defect shadow portion was 3.2, which was much higher than the S / N ratio 2.0.

（比較例１）
表面全域の面粗度がおよそＲｚ＝１２７となるよう研磨処理を施したアクリル板をスクリーンとして用い、その他の構成は実施例１と同じとしたところ、欠陥陰影を検出したが、同時にプラスチックフィルムの地合ノイズ成分も欠陥として誤検出した。また、欠陥陰影部分のＳ／Ｎ比＝１．７となり、Ｓ／Ｎ比２．０を下回った。 (Comparative Example 1)
An acrylic plate that had been polished so that the surface roughness of the entire surface surface was approximately Rz = 127 was used as the screen, and the other configurations were the same as in Example 1. As a result, defect shading was detected. The ground noise component was also mistakenly detected as a defect. Further, the S / N ratio of the shadow portion of the defect was 1.7, which was lower than the S / N ratio of 2.0.

１ シート状物
２ａ ライン光の照射手段
２ｂ 平行光の照射手段
３ スクリーン
４ 撮像手段
５ 欠陥検出手段 DESCRIPTION OF SYMBOLS 1 Sheet-like object 2a Line light irradiation means 2b Parallel light irradiation means 3 Screen 4 Imaging means 5 Defect detection means

Claims (12)

光透過性を有するシート状物の走行経路上において、前記シート状物に平行光を照射する照射手段と、
前記シート状物面に対して前記照射手段と反対側に設置され、前記シート状物を透過した前記照射手段からの光を投影するスクリーンと、
前記スクリーンに投影された光を暗視野方向から撮像する撮像手段とを有する凹凸欠陥の検出装置であって、
前記スクリーンは、前記シート状物の欠陥のない状態を透過した光のうち、光量レベルの最も高い部分が投影される箇所の拡散反射率が、前記光量レベルの最も低い部分が投影される箇所の拡散反射率よりも低いことを特徴とする欠陥検出装置。 Irradiation means for irradiating the sheet-like material with parallel light on the travel path of the sheet-like material having light permeability;
A screen that is installed on the opposite side of the irradiation unit with respect to the sheet-like object surface and projects light from the irradiation unit that has passed through the sheet-like object;
An apparatus for detecting a concavo-convex defect having imaging means for imaging light projected on the screen from a dark field direction,
The screen has a diffuse reflectance of a portion where a portion with the highest light amount level is projected out of light transmitted through a defect-free state of the sheet-like material, and a portion where the portion with the lowest light amount level is projected. A defect detection apparatus characterized by being lower than diffuse reflectance. 前記照射手段固有の光量分布が、前記撮像手段での受光時には一定になるように、前記スクリーン表面に拡散反射率の分布が付与されていることを特徴とする請求項１に記載の欠陥検出装置。   The defect detection apparatus according to claim 1, wherein the screen surface is provided with a diffuse reflectance distribution so that a light amount distribution unique to the irradiation unit is constant when light is received by the imaging unit. . 前記スクリーン表面の拡散反射率が、スクリーン周辺部よりも中央部が低くなっていることを特徴とする請求項１または２に記載の欠陥検出装置。   The defect detection apparatus according to claim 1, wherein the diffuse reflectance of the screen surface is lower in the center than in the periphery of the screen. 前記スクリーン表面の拡散反射率を面粗度により付与したことを特徴とする請求項１〜３のいずれか一項に記載の欠陥検出装置。   The defect detection apparatus according to claim 1, wherein the diffuse reflectance of the screen surface is given by surface roughness. 前記スクリーン表面の面粗度のＲｚが、スクリーン周辺部よりも中央部が大きいことを特徴とする請求項４に記載の欠陥検出装置。   The defect detection apparatus according to claim 4, wherein a surface roughness Rz of the screen surface is larger in a central portion than in a screen peripheral portion. 前記撮像手段の視野領域全域における受光量分布の最小値が最大値の５０％以上となるよう、前記照射手段の照射軸と前記撮像手段の撮影軸とスクリーンの傾斜角度が調整されていることを特徴とする請求項１〜５のいずれか一項に記載の欠陥検出装置。   The tilt angle of the irradiation axis of the irradiation unit, the shooting axis of the imaging unit, and the screen is adjusted so that the minimum value of the received light amount distribution in the entire visual field region of the imaging unit is 50% or more of the maximum value. The defect detection apparatus according to any one of claims 1 to 5, wherein the defect detection apparatus is characterized. 前記照射手段は点光源であることを特徴とする、請求項１〜６のいずれか一項に記載の欠陥検出装置。   The defect detection apparatus according to claim 1, wherein the irradiation unit is a point light source. 前記照射手段は、照射光の平行性を向上させるために１枚または複数枚のレンズを具備すること特徴とする、請求項１〜７のいずれか一項に記載の欠陥検出装置。   The defect detection apparatus according to claim 1, wherein the irradiation unit includes one or a plurality of lenses in order to improve parallelism of irradiation light. 前記照射手段で使用するランプは、アーク放電式であることを特徴とする、請求項１〜８のいずれか一項に記載の欠陥検出装置。   The defect detection apparatus according to claim 1, wherein a lamp used in the irradiation unit is an arc discharge type. 前記撮像手段は、ＣＣＤラインセンサカメラであることを特徴とする、請求項１〜９のいずれか一項に記載の欠陥検出装置。   The defect detection apparatus according to claim 1, wherein the imaging unit is a CCD line sensor camera. 請求項１〜１０のいずれか一項に記載の欠陥検出装置を用いて、前記シート状物の走行経路上において、前記シート状物表面に生じた凹凸欠陥を検出することを特徴とする、欠陥検出方法。   Using the defect detection device according to any one of claims 1 to 10, a defect that is detected on the surface of the sheet-like material on the surface of the sheet-like material is detected. Detection method. 請求項１〜１０のいずれか一項に記載の欠陥検出装置を用いて凹凸欠陥が検出されたシート状物。   The sheet-like object by which the uneven | corrugated defect was detected using the defect detection apparatus as described in any one of Claims 1-10.
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