JP2005134362A

JP2005134362A - Inspection method and inspection device for surface irregularity

Info

Publication number: JP2005134362A
Application number: JP2004050038A
Authority: JP
Inventors: Masahito Sugiura; 雅人杉浦; Manabu Kuninaga; 学國永; Takamichi Kobayashi; 尊道小林; Yusuke Konno; 雄介今野
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2003-05-07
Filing date: 2004-02-25
Publication date: 2005-05-26

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for inspecting automatically the presence of micro irregularity on a surface at a low cost, as to an inspected object having the surface of nonspecular face such as rolled band steel. <P>SOLUTION: In this surface irregularity inspection method and device for inspecting the presence of the micro irregularity 15 on the surface 2 of the inspected object 1, an infrared ray emitting source 3 having a linear shape is arranged in the vicinity of the inspected object 1, an image 10 of the infrared ray emitting source reflected on the surface 2 of the inspected object is picked up by an infrared imaging device 5, and the presence of the micro irregularity 15 on the surface 2 of the inspected object is inspected based on a shape of the picked-up image 10 of the infrared ray emitting source. The infrared ray emitting source 3 having the linear shape is a plurality of linearly extended heating wires. A nonlinear shape of inspected object surface portion is determined as a micro irregularity generation part, in the picked-up image 10 of the infrared ray emitting source. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は、例えば非鏡面の表面を有する鋼板等の被検査体表面の微少凹凸有無を検査する検査方法及び検査装置に関するものである。 The present invention relates to an inspection method and an inspection apparatus for inspecting the presence or absence of minute irregularities on the surface of an object to be inspected, such as a steel plate having a non-mirror surface.

薄鋼板の製造プロセス、例えば冷延帯鋼の製造プロセスにおいて、製造ラインのロールに異物が付着していると、この異物に起因して帯鋼にロール疵が形成され、また、圧延ロールが微少振動を起こすと、鋼板表面に微細な横縞（チャタマーク）が形成される。これら帯鋼表面に形成される表面形状不良を、ここでは総称して微少凹凸と呼ぶ。ロール疵の原因となる異物がロールに付着したり、あるいはロール振動に起因するチャタマークが一旦発生すると、ロールを交換したりプロセスを改善したりするまで帯鋼表面に欠陥が連続して発生するので、早期に発見して対策を講じることが重要である。 In the manufacturing process of thin steel sheets, for example, in the manufacturing process of cold-rolled strip steel, if foreign matter adheres to the rolls in the production line, roll defects are formed in the strip steel due to the foreign matter, and the rolling roll is very small. When vibration occurs, fine horizontal stripes (chatter marks) are formed on the surface of the steel sheet. These surface shape defects formed on the surface of the steel strip are collectively referred to herein as minute irregularities. Once foreign matter that causes roll wrinkles adheres to the roll or chatter marks due to roll vibration occur, defects are continuously generated on the surface of the steel strip until the roll is replaced or the process is improved. Therefore, it is important to detect early and take measures.

このような疵を見つけるため、帯鋼の通板ラインにおいては、通板中に帯鋼の長手方向不連続に配置した検査部位において帯鋼の走行を一度停止あるいは低速通板とし、検査員が砥石がけを行った後に目視検査をしている。砥石がけを行うと、凹部に比べて凸部がより一層研磨されて鏡面に近づくのに対し、凹部が元の粗面のまま残るので、微少凹凸発生部が明瞭になり、目視で確認可能となる。 In order to find such wrinkles, in the strip passing line, in the inspection part arranged in the longitudinal discontinuity of the strip in the passing plate, the strip steel travel is once stopped or the low speed passing plate is inspected. Visual inspection is performed after grinding. When grinding with a grindstone, the convex part is further polished compared to the concave part and approaches the mirror surface, whereas the concave part remains as the original rough surface, so the minute unevenness generation part becomes clear and can be confirmed visually Become.

砥石がけのために帯鋼の走行を停止あるいは低速通板としている最中においても、検査箇所前後に設けたループカー等の機能に基づいて帯鋼通板ラインの他の部分では帯鋼の走行を継続する。ループカーの能力は有限であるため、砥石がけのために帯鋼を停止する時間は限られ、かつ前回の砥石がけ検査部位から今回の砥石がけ検査部位まで鋼帯を長い距離にわたって無検査で走行させる必要がある。今回の砥石がけ検査でロール疵が発見されると、前回砥石がけ箇所までロール疵発生の可能性があるので、大きな歩留りロスを生じることとなる。 Even when the running of the steel strip is stopped or a low speed plate is used for grinding stones, the steel strip runs in other parts of the steel strip line based on the function of the loop car provided before and after the inspection point. continue. Because the capacity of the loop car is limited, the time to stop the steel strip for grinding is limited, and the steel strip is run without inspection over a long distance from the previous grinding wheel inspection site to the current grinding wheel inspection site. There is a need. If roll wrinkles are found in the grinding wheel inspection this time, roll wrinkles may occur up to the previous grinding wheel location, resulting in a large yield loss.

被検査面に平行光を照射し、被検査面から反射した反射光をスクリーンに投影し、被検査面の凹凸部からの反射光がスクリーンにおいて像のパターンとして現れるいわゆる魔鏡現象を適用した検査方法が知られている。従来、魔鏡現象を適用して凹凸評価ができるのは、照射光をミラー反射することのできる鏡面表面のみであった。これに対し、帯鋼通板ラインにおいて、帯鋼の表面は非鏡面の粗面であるため、鏡面表面を対象とした凹凸検査方法は採用することができない。特許文献１においては、上記魔鏡現象を適用した検査方法において、入射光の角度を規定することによって、あるいは入射光として赤外域の波長を選定することにより、被検査面が粗面であっても鏡面反射を可能にし、粗面の微少凹凸性疵が検出できるとしている。具体的には、光源としてパルス発振のＣＯ₂レーザを用い、スクリーンに照射される像を撮像する２次元カメラとしてサーモカメラを用いる例が記載されている。 Inspection that applies so-called magic mirror phenomenon in which parallel light is irradiated on the surface to be inspected, reflected light reflected from the surface to be inspected is projected onto the screen, and the reflected light from the uneven portions of the surface to be inspected appears as an image pattern on the screen The method is known. Conventionally, unevenness can be evaluated by applying the magic mirror phenomenon only to the mirror surface that can mirror the irradiation light. On the other hand, in the strip passing plate line, since the surface of the strip is a non-mirror surface rough surface, the unevenness inspection method for the mirror surface cannot be adopted. In Patent Document 1, in the inspection method to which the magic mirror phenomenon is applied, the surface to be inspected is rough by specifying the angle of incident light or by selecting an infrared wavelength as incident light. Also enables specular reflection to detect minute irregularities on rough surfaces. Specifically, an example is described in which a pulsed CO ₂ laser is used as a light source and a thermo camera is used as a two-dimensional camera that captures an image irradiated on a screen.

特開２０００−２９８１０２号公報JP 2000-298102 A

特許文献１に記載の方法のうち、入射光の角度を規定する方法については、角度を８７°とし、入射光と鋼板とのなす角度を極めて鋭角にすることによって検査を成立させている。これでは、鋼板が振動したり形状が平坦でない場合、正反射方向がわずかに変化するだけで、反射光がスクリーンから外れてしまうことが懸念される。 Among the methods described in Patent Document 1, for the method of defining the angle of incident light, the angle is set to 87 °, and the angle formed between the incident light and the steel plate is made extremely acute. In this case, when the steel plate vibrates or the shape is not flat, there is a concern that the reflected light is off the screen only by a slight change in the regular reflection direction.

特許文献１に記載の方法のうち、入射光として赤外域の波長を選定する方法については、光源としてＣＯ₂レーザを用いている。魔鏡現象を適用する場合には、入射光として平行光あるいは点光源からの集束光を用いる必要があり、赤外域の波長でこのような光を得るためにはＣＯ₂レーザを用いことが必要である。一方、ＣＯ₂レーザは高価な装置であり、検査設備全体が大がかりと成らざるを得ない。また、魔鏡現象を適用する場合には、被検査面で反射した反射光をスクリーンに結像する必要があり、被検査面と同じ大きさあるいはそれよりも大きいスクリーンを準備し、このスクリーンに結像した像を間接的に撮像装置で撮像した上で画像処理を行うことが必要である。スクリーン全面の赤外光学特性が均一であることが求められるので、汚れ付着防止等の対策や管理が欠かせない。反射光をレンズで集光した上で、サイズの小さい２次元の撮像素子自体をスクリーンとして撮像素子上に直接結像させることも可能であるが、集光レンズとして被検査面と同等以上の大きさを有する赤外域レンズを準備する必要があり、光学的に製作できる赤外レンズサイズの制約から、検査視野は小さくなる。 Among the methods described in Patent Document 1, a method of selecting an infrared wavelength as incident light uses a CO ₂ laser as a light source. When applying the magic mirror phenomenon, it is necessary to use parallel light or focused light from a point light source as incident light, and to obtain such light at wavelengths in the infrared region, it is necessary to use a CO ₂ laser. It is. On the other hand, the CO ₂ laser is an expensive device, and the entire inspection facility is inevitably large. In addition, when applying the magic mirror phenomenon, it is necessary to form an image of the reflected light reflected from the surface to be inspected on the screen. A screen having the same size or larger than the surface to be inspected is prepared, and this screen is used. It is necessary to perform image processing after indirectly imaging the formed image with an imaging device. Since the infrared optical characteristics of the entire screen surface are required to be uniform, it is indispensable to take measures and control such as prevention of dirt adhesion. It is possible to focus the reflected light with a lens and directly form a small two-dimensional image sensor itself on the image sensor as a screen. It is necessary to prepare an infrared lens having a thickness, and the inspection field of view becomes small due to the restriction of the size of an infrared lens that can be optically manufactured.

以上のような理由により、非鏡面の表面を有する鋼板の微小凹凸検査について特許文献１に記載のような魔鏡現象を適用する検査方法には、技術的な課題が残る。 For the reasons as described above, there remains a technical problem in the inspection method that applies the magic mirror phenomenon as described in Patent Document 1 for the inspection of minute unevenness of a steel sheet having a non-mirror surface.

本発明は、圧延帯鋼のように非鏡面の表面を有する被検査体について、表面の微小凹凸の有無を自動的に検査する方法及び装置を安価に提供することを目的とする。 An object of the present invention is to provide a method and an apparatus for automatically inspecting a test object having a non-specular surface, such as rolled steel strip, for the presence or absence of minute irregularities on the surface at a low cost.

即ち、本発明の要旨とするところは以下の通りである。
（１）被検査体表面２の微少凹凸１５の有無を検査する方法であって、線状の形状を有する赤外線発光源３を被検査体１付近に配置し、被検査体表面２に映る赤外線発光源の像１０を赤外線撮像装置５で撮像し、該撮像した赤外線発光源の像１０の形状に基づいて被検査体表面の微少凹凸１５の有無を検査することを特徴とする表面凹凸の検査方法。
（２）線状の形状を有する赤外線発光源３は、直線状に伸張した複数の電熱線であることを特徴とする上記（１）に記載の表面形状の検査方法。
（３）線状の形状を有する赤外線発光源３の発光表面は、赤外線撮像装置５の検出波長における放射率が０．５以上であることを特徴とする上記（１）又は（２）に記載の表面凹凸の検査方法。
（４）前記撮像した赤外線発光源の像の形状が非直線となった被検査体表面部分を微少凹凸発生部と判定することを特徴とする上記（１）乃至（３）のいずれかに記載の表面凹凸の検査方法。
（５）前記撮像した赤外線発光源の像の映像信号について直線状の赤外線発光源の伸張方向に微分フィルタリングを施し、その後２値化処理を行い、像が消滅した部分は健全部と判定し、像が消滅しなかった部分を微少凹凸発生部と判定することを特徴とする上記（４）に記載の表面凹凸の検査方法。
（６）被検査体表面に映る赤外線発光源の像１０と被検査体表面の微小凹凸１５部位の双方で赤外線撮像画像のピントが合致するよう、赤外線撮像装置５のレンズ有効口径と被写体側焦点位置を調整することを特徴とする上記（１）乃至（５）のいずれかに記載の表面凹凸の検査方法。
（７）赤外線撮像装置３が、検出波長８〜１２μｍ帯のマイクロボロメータ素子の非冷却型赤外カメラであることを特徴とする上記（１）乃至（６）のいずれかに記載の表面凹凸の検査方法。
（８）被検査体１は、非鏡面の表面を有する鋼板であることを特徴とする上記（１）乃至（７）のいずれかに記載の表面凹凸の検査方法。 That is, the gist of the present invention is as follows.
(1) A method of inspecting the presence or absence of minute irregularities 15 on the surface 2 to be inspected. An infrared light source 3 having a linear shape is arranged in the vicinity of the body 1 to be inspected, and infrared light reflected on the surface 2 to be inspected. Inspection of surface irregularities characterized in that an image 10 of a light source is picked up by an infrared imaging device 5 and the presence or absence of minute irregularities 15 on the surface of the inspected object is inspected based on the shape of the image 10 of the picked up infrared light source. Method.
(2) The method for inspecting a surface shape according to (1) above, wherein the infrared light emitting source 3 having a linear shape is a plurality of heating wires extending linearly.
(3) The light emitting surface of the infrared light emitting source 3 having a linear shape has an emissivity at a detection wavelength of the infrared imaging device 5 of 0.5 or more, described in (1) or (2) above Inspection method for surface irregularities.
(4) In any one of (1) to (3), the surface portion of the object to be inspected where the shape of the image of the imaged infrared light emitting source is non-linear is determined as a minute unevenness generating portion. Inspection method for surface irregularities.
(5) The image signal of the imaged image of the infrared light source is subjected to differential filtering in the extending direction of the linear infrared light source, then binarized, and the part where the image disappeared is determined to be a healthy part. The method for inspecting surface unevenness according to (4) above, wherein a portion where the image has not disappeared is determined as a fine unevenness generating portion.
(6) The effective aperture of the lens of the infrared imaging device 5 and the focus on the subject side so that both the image 10 of the infrared emission source reflected on the surface of the object to be inspected and the fine irregularities 15 on the surface of the object to be inspected are in focus. The method for inspecting surface irregularities according to any one of (1) to (5) above, wherein the position is adjusted.
(7) The surface unevenness according to any one of (1) to (6), wherein the infrared imaging device 3 is a microbolometer element non-cooling infrared camera having a detection wavelength of 8 to 12 μm. Inspection method.
(8) The surface unevenness inspection method according to any one of (1) to (7), wherein the object to be inspected 1 is a steel plate having a non-mirror surface.

（９）被検査体表面２の微少凹凸１５の有無を検査する装置であって、被検査体付近に配置し線状の形状を有する赤外線発光源３と、被検査体表面に映る赤外線発光源の像１０を撮像することのできる位置に配置した赤外線撮像装置５と、赤外線撮像装置５で撮像した赤外線発光源の像１０の形状に基づいて被検査体表面２の微少凹凸１５の有無を判定する判定装置６とを有することを特徴とする表面凹凸の検査装置。
（１０）線状の形状を有する赤外線発光源３は、直線状に伸張した複数の電熱線であることを特徴とする上記（９）に記載の表面形状の検査装置。
（１１）線状の形状を有する赤外線発光源３の発光表面は、赤外線撮像装置５の検出波長における放射率が０．５以上であることを特徴とする上記（９）又は（１０）に記載の表面凹凸の検査装置。
（１２）判定装置６は、撮像した赤外線発光源の像１０の形状が非直線となった被検査体表面部分を微少凹凸発生部と判定することを特徴とする上記（９）乃至（１１）のいずれかに記載の表面凹凸の検査装置。
（１３）赤外線撮像装置５のレンズ有効口径は、赤外線撮像装置５の被写体側焦点位置を調整することにより、被検査体表面に映る赤外線発光源の像１０と被検査体表面の微小凹凸１５部位の双方で赤外線撮像画像のピントが合致するよう調整可能な口径であることを特徴とする上記（９）乃至（１２）のいずれかに記載の表面凹凸の検査装置。
（１４）赤外線撮像装置３が、検出波長８〜１２μｍ帯のマイクロボロメータ素子の非冷却型赤外カメラであることを特徴とする上記（９）乃至（１３）のいずれかに記載の表面凹凸の検査装置。
（１５）被検査体１は非鏡面の表面を有する帯鋼であり、帯鋼の通板ラインに配置されることを特徴とする上記（９）乃至（１４）のいずれかに記載の表面凹凸の検査装置。 (9) An apparatus for inspecting the inspected object surface 2 for the presence or absence of minute irregularities 15, an infrared light emitting source 3 disposed near the inspected object and having a linear shape, and an infrared light emitting source reflected on the inspected object surface The presence or absence of minute irregularities 15 on the surface 2 of the object to be inspected is determined based on the shape of the infrared imaging device 5 disposed at a position where the image 10 of the image can be captured and the image 10 of the infrared light emission source imaged by the infrared imaging device 5. And a surface irregularity inspection device characterized by comprising:
(10) The surface shape inspection apparatus according to (9) above, wherein the infrared light emission source 3 having a linear shape is a plurality of heating wires extending linearly.
(11) The light emitting surface of the infrared light emitting source 3 having a linear shape has an emissivity at a detection wavelength of the infrared imaging device 5 of 0.5 or more, described in (9) or (10) above Inspection device for surface irregularities.
(12) The determination device 6 determines the surface portion of the inspected object in which the shape of the captured image 10 of the infrared light emitting source is non-linear as the minute unevenness generating portion (9) to (11), The surface unevenness inspection apparatus according to any one of the above.
(13) The effective aperture of the lens of the infrared imaging device 5 is adjusted by adjusting the subject-side focal position of the infrared imaging device 5 so that the image 10 of the infrared light source reflected on the surface of the object to be inspected and the 15 minute irregularities on the surface of the object to be inspected. The surface irregularity inspection apparatus according to any one of (9) to (12) above, wherein the aperture is adjustable so that the focus of the infrared image is matched with both.
(14) The surface unevenness according to any one of (9) to (13), wherein the infrared imaging device 3 is an uncooled infrared camera of a microbolometer element having a detection wavelength band of 8 to 12 μm. Inspection device.
(15) The surface unevenness according to any one of the above (9) to (14), wherein the object to be inspected 1 is a steel strip having a non-specular surface, and is arranged on a plate passing line of the steel strip. Inspection equipment.

本発明により、被検査体表面が粗さを有する場合であっても、被検査体表面の微小凹凸の有無を光学的に検査することができ、かつ検査装置を安価に構築することができる。 According to the present invention, even if the surface of the object to be inspected has roughness, it is possible to optically inspect for the presence or absence of minute irregularities on the surface of the object to be inspected, and to construct an inspection apparatus at low cost.

溶融亜鉛メッキ鋼板、熱間圧延後にスケール除去を行った鋼板等の表面は、人の見た目には粗面である。このような鋼板の表面において可視光域の波長を有する光を反射させると、反射光は粗面において散乱してしまい、鏡面反射とすることができない。光の波長が被検査面の粗さよりも短いためである。一方、光の波長をλ（μｍ）、被検査面の粗さをＲ（μｍ）、被検査面に対する光の入射角度をθとすると、Ｒｃｏｓθ／λの値を小さくするほど鏡面性が増すことが知られている。 Surfaces of hot dip galvanized steel sheets, steel sheets from which scales have been removed after hot rolling, and the like are rough to the human eye. When light having a wavelength in the visible light region is reflected on the surface of such a steel sheet, the reflected light is scattered on the rough surface, and cannot be mirror-reflected. This is because the wavelength of light is shorter than the roughness of the surface to be inspected. On the other hand, when the wavelength of light is λ (μm), the roughness of the surface to be inspected is R (μm), and the incident angle of light with respect to the surface to be inspected is θ, the specularity increases as the value of R cos θ / λ decreases. It has been known.

本発明においては、光源として赤外線発光源を用いる。赤外線を発光源として用いれば、被検査体表面の粗さ（１〜２μｍ）において鏡面反射条件を実現することができ、被検査面で反射する光を鏡面反射とすることが可能となるからである。使用する赤外線の波長としては、３μｍ程度以上とすればよい。赤外線発光源として高温の発熱体を用いる場合には、当該発熱体の温度を１００℃以上とすれば、目標とする波長領域の赤外線を発生させることができる。 In the present invention, an infrared light source is used as the light source. If infrared rays are used as the light source, the specular reflection condition can be realized in the roughness (1 to 2 μm) of the surface of the object to be inspected, and the light reflected by the surface to be inspected can be specularly reflected. is there. The wavelength of infrared rays to be used may be about 3 μm or more. When a high-temperature heating element is used as an infrared light source, infrared rays in a target wavelength region can be generated by setting the temperature of the heating element to 100 ° C. or higher.

本発明においては、図１〜３に示すように、線状の形状を有する赤外線発光源３を被検査体１付近に配置する。線状の形状を有するとは、棒状あるいは好ましくは直線状であり、細い直線状であると最も好ましい。赤外線発光源３から被検査体表面に照射される赤外線は拡散光とする。拡散光であるとは、光源から発する光が一定の方向のみに集束せず、拡散あるいは散乱している意味である。光源から３６０°全周に拡散して発光する必要はないが、少なくとも被検査面表面２に向けて発光し、当該発光光は拡散光である。 In this invention, as shown in FIGS. 1-3, the infrared rays light emission source 3 which has a linear shape is arrange | positioned to the to-be-inspected object 1 vicinity. Having a linear shape is a rod shape or preferably a linear shape, and most preferably a thin linear shape. The infrared light irradiated from the infrared light source 3 onto the surface of the object to be inspected is diffused light. The diffuse light means that light emitted from the light source is not focused only in a certain direction but is diffused or scattered. Although it is not necessary to diffuse 360 ° from the light source and emit light, it emits light at least toward the surface 2 to be inspected, and the emitted light is diffuse light.

図１の場合を例にとって説明する。被検査体表面２には、図１（ｂ）に示すように微小凹凸１５が存在する。図１（ａ）に示すように、赤外線発光源３は直線状の形状を有し、被検査体表面２に平行に配置されている。赤外線発光源３から被検査体表面２に照射された赤外線は、被検査体表面２において鏡面反射する。当該反射光の通過位置に赤外線撮像装置５を配置して被検査面表面２を観察すると、被検査面表面には図１（ｃ）に示すように赤外線発光源の像１０が映って観察される。それは、被検査体表面２の位置に鏡を配置したときに、可視光で見ることのできる赤外線発光源の像が鏡に映って観察できるのと同様である。図１（ａ）には、赤外線発光源３から赤外線撮像装置５に至る光路１２の一部が記載されている。被検査体表面２で反射して赤外線撮像装置５に至る光路１２は、あたかも虚像１１からの直線光路で赤外線撮像装置５に入射するように形成される。 The case of FIG. 1 will be described as an example. On the surface 2 to be inspected, there are minute irregularities 15 as shown in FIG. As shown in FIG. 1A, the infrared light emission source 3 has a linear shape and is arranged in parallel to the surface 2 to be inspected. The infrared light irradiated from the infrared light source 3 to the surface 2 to be inspected is specularly reflected on the surface 2 to be inspected. When the infrared imaging device 5 is arranged at the reflected light passing position and the surface 2 to be inspected is observed, an image 10 of the infrared light source is reflected on the surface to be inspected as shown in FIG. The This is similar to the case where an image of an infrared light source that can be seen with visible light is reflected on the mirror and observed when a mirror is placed at the position of the surface 2 to be inspected. FIG. 1A shows a part of an optical path 12 from the infrared light emitting source 3 to the infrared imaging device 5. The optical path 12 reflected from the surface 2 to be inspected and reaching the infrared imaging device 5 is formed so as to be incident on the infrared imaging device 5 through a linear optical path from the virtual image 11.

本発明においては、線状の形状を有する赤外線発光源３から照射される赤外線が拡散光でよく、発光源からの光を平行光あるいは集束光に集光する必要はない。 In the present invention, the infrared light emitted from the infrared light emitting source 3 having a linear shape may be diffused light, and it is not necessary to condense light from the light emitting source into parallel light or focused light.

被検査体表面２が平面である場合、直線状の形状を有する発光源の像１０は、被検査体表面２に同じく直線状の形状として映り、そのままの姿で撮像装置５によって撮像される。これに対し、図１に示すように被検査体表面２の当該発光源の像が映る位置に微小凹凸１５が存在する場合には、この微小凹凸１５によって光の反射方向が乱されるため、微小凹凸の位置において像の形状も乱れ、図１（ｃ）に示すように直線形状からずれた形状で観察されることとなる。具体的には、細線状の発光源の像１０が微小凹凸１５の位置において広がったり（図３（ａ））、当該位置において一方の側に曲がって見えたり（図３（ｂ））、あるいは当該位置において像が消滅したり（図３（ｃ））する。従って、被検査体表面に映る赤外線発光源の像１０を赤外線撮像装置５によって撮像し、その形状を観察することにより、被検査体表面の微小凹凸１５の有無を検査できることとなる。 When the surface 2 to be inspected is a flat surface, the image 10 of the light source having a linear shape appears on the surface 2 to be inspected as a straight shape and is captured by the imaging device 5 as it is. On the other hand, as shown in FIG. 1, when the minute unevenness 15 is present at the position where the image of the light source on the surface 2 to be inspected is reflected, the reflection direction of light is disturbed by the minute unevenness 15. The shape of the image is also disturbed at the position of the minute unevenness, and the image is observed in a shape deviated from the linear shape as shown in FIG. Specifically, the image 10 of the thin light-emitting source spreads at the position of the minute unevenness 15 (FIG. 3A), bends to one side at the position (FIG. 3B), or At that position, the image disappears (FIG. 3C). Therefore, the presence or absence of the micro unevenness 15 on the surface of the inspection object can be inspected by capturing the image 10 of the infrared light source reflected on the surface of the inspection object with the infrared imaging device 5 and observing the shape thereof.

微小凹凸１５の位置における赤外線発光源の像１０の歪みは、微小凹凸部の傾斜が大きくなるほど大きくなる。また、微小凹凸部の傾斜が同じであれば、被検査体表面２と赤外線撮像装置５との距離が遠くなるほど大きくなる。従って、赤外線撮像装置５の位置を被検査体表面２から遠ざけることにより、よりわずかな微小凹凸を観察することが可能になる。例えば、微小凹凸部の表面傾斜が１ｍｍ当たり５μｍであり、被検査体表面から撮像装置までの距離を６００ｍｍとした場合、被検査体表面に映る赤外線発光源の像は微小凹凸部において約６ｍｍ歪むこととなる。 The distortion of the image 10 of the infrared light source at the position of the minute irregularities 15 increases as the inclination of the minute irregularities increases. Further, if the slopes of the minute uneven portions are the same, the distance between the surface 2 to be inspected and the infrared imaging device 5 increases as the distance increases. Therefore, by moving the position of the infrared imaging device 5 away from the surface 2 to be inspected, it becomes possible to observe a slight minute unevenness. For example, when the surface inclination of the minute uneven portion is 5 μm per 1 mm and the distance from the surface of the object to be inspected to the imaging device is 600 mm, the image of the infrared light source reflected on the surface of the object to be inspected is distorted by about 6 mm in the minute uneven portion. It will be.

被検査体表面２付近における線状の形状を有する赤外線発光源３の配置位置としては、図１（ａ）（ｃ）に示すように赤外線発光源３を被検査体表面２に対して平行に配置することとしても、あるいは図２（ａ）（ｂ）に示すように赤外線発光源３を被検査体表面２の垂直面上に配置することとしてもよい。 As an arrangement position of the infrared light emitting source 3 having a linear shape in the vicinity of the surface 2 to be inspected, the infrared light source 3 is parallel to the surface 2 to be inspected as shown in FIGS. Alternatively, the infrared light emission source 3 may be disposed on a vertical surface of the surface 2 to be inspected as shown in FIGS.

魔鏡現象を利用する従来の微小凹凸検出方法においては、光源として平行光または集束光を用い、被検査体表面で反射する光を一度スクリーンに結像させ、その結像した像を間接的に撮像装置で撮像して観察することが必要であった。本発明においては、スクリーンに像を結像させることなく、被検査体表面に映る像を直接撮像装置によって撮像することが可能であり、そのため装置構成がシンプルになり小型化できる。さらに、スクリーンを常に光学的に清浄に保つ維持管理が不要になることも工業的には大きなメリットである。 In the conventional method for detecting micro unevenness using the magic mirror phenomenon, parallel light or focused light is used as a light source, and the light reflected from the surface of the object to be inspected is once imaged on the screen, and the formed image is indirectly It was necessary to image and observe with an imaging device. In the present invention, an image reflected on the surface of the object to be inspected can be directly picked up by the image pickup device without forming an image on the screen. Therefore, the device configuration is simplified and the size can be reduced. Furthermore, the fact that maintenance that always keeps the screen optically clean is no longer an important industrial advantage.

被検査体表面２の微小凹凸のうち、検出できるのは線状の赤外線発光源の像１０が映っている線状の領域に存在する凹凸のみである。本発明においては、図２（ｃ）に示すように線状の形状を有する赤外線発光源３を多数並列に並べることにより、図２（ｄ）に示すように被検査体表面２の広い領域において赤外線発光源の像１０が映ることとなり、当該広い領域のいずれかに存在する微小凹凸１５を検出することが可能になる。隣り合う赤外線発光源３の間隔を、被検査体表面における微小凹凸１５の大きさと同等あるいはそれ以下の広さとすれば、検査対称面に存在する微小凹凸１５をもれなく検出することが可能となる。検査対象の微小凹凸１５が鋼板表面の押し疵である場合には、隣り合う赤外線発光源３の間隔を数ｍｍ程度とすることにより、適切な検査を行うことが可能である。多数の赤外線発光源３を並列に並べるに際し、個々の赤外線発光源３の配置方向としては、図２（ｃ）に示すように被検査体表面２の垂直面上に配置することとしても良く、あるいは被検査体表面２に平行に配置することとしても良い。 Of the minute irregularities on the surface 2 to be inspected, only the irregularities present in the linear region in which the image 10 of the linear infrared light source is reflected can be detected. In the present invention, as shown in FIG. 2 (c), by arranging a large number of infrared light emitting sources 3 having a linear shape in parallel, in a wide area on the surface 2 to be inspected as shown in FIG. 2 (d). The image 10 of the infrared light source is reflected, and it becomes possible to detect the minute unevenness 15 existing in any one of the wide areas. If the distance between the adjacent infrared light emitting sources 3 is set to be equal to or smaller than the size of the minute unevenness 15 on the surface of the object to be inspected, it is possible to detect all the minute unevenness 15 existing on the inspection symmetry plane. When the minute unevenness 15 to be inspected is a pressing bar on the surface of the steel sheet, it is possible to perform an appropriate inspection by setting the interval between adjacent infrared light emitting sources 3 to about several millimeters. When arranging a large number of infrared light emitting sources 3 in parallel, the arrangement direction of the individual infrared light emitting sources 3 may be arranged on a vertical surface of the surface 2 to be inspected as shown in FIG. Or it is good also as arrange | positioning in parallel to the to-be-inspected object surface 2. FIG.

本発明の線状の形状を有する赤外線発光源として直線状に伸張した複数の電熱線を用いると好ましい。電熱線、例えばニクロム線を直線状に伸張し、この電熱線に図１（ａ）に示すように配線２１によって電源２０を接続し、電流を流すことにより発熱させ、線状の形状を有する赤外線発光源３として機能させることができる。この電熱線を多数並列に並べ、各電熱線に電流を流すことによって発熱させれば、被検査体表面の２次元の広い範囲を同時に観察して微小凹凸の有無を検査することが可能になる。電熱線径は１ｍｍ以下の細線とすることができ、微小凹凸における像の歪み量は前述の通り１ｍｍより大きな歪みとすることができるので、直線状に伸張した電熱線を赤外線発光源として使用することにより、被検査体表面の微小凹凸を精度良く検出することが可能となる。 It is preferable to use a plurality of linear heating wires as the infrared light emitting source having the linear shape of the present invention. An infrared ray having a linear shape is formed by extending a heating wire, for example, a nichrome wire in a straight line, connecting a power source 20 to the heating wire by a wiring 21 as shown in FIG. It can function as the light emission source 3. By arranging a large number of these heating wires in parallel and generating heat by passing a current through each heating wire, it becomes possible to inspect the presence or absence of minute irregularities by simultaneously observing a two-dimensional wide range on the surface of the object to be inspected. . The diameter of the heating wire can be a fine wire of 1 mm or less, and the amount of distortion of the image on the minute unevenness can be larger than 1 mm as described above. Therefore, the heating wire linearly extended is used as the infrared light source. This makes it possible to detect minute irregularities on the surface of the inspection object with high accuracy.

赤外線発光源３として電熱線のような発熱体を用いる場合、赤外線の放射輝度は発光源表面の放射率の影響を受け、放射率が高いほど赤外線の放射輝度が高くなる。ニクロム線のような金属線を赤外線発光源３とする場合、赤外線の波長おける金属線表面の放射率は通常０．２程度の低い値である。これに対し、金属線の表面に酸化皮膜を形成したり、あるいは耐熱黒色塗料を塗布したり、化学処理を行うことにより、赤外線の波長における表面の放射率を高めることができる。赤外線発光源３の発光表面の放射率を０．５以上とすれば、発光源の温度が低い温度であっても微小凹凸を検査するに十分な赤外線を放射することが可能になるので、赤外線発光源の耐熱構造が簡易になり、また消費電力が小さくなり好ましい。赤外線発光源３の発光表面の放射率を０．７以上とするとより好ましい。放射率を０．９以上とするとさらに好ましい。即ち、電熱線の表面を酸化処理等で黒化処理することにより、赤外線をより効率的に発生させることができる。ここで黒化処理とは、赤外線の領域で放射率を増大させる処理を意味し、必ずしも可視光領域で黒い色にする必要はないのはいうまでもない。 When a heating element such as a heating wire is used as the infrared light source 3, the infrared radiance is affected by the emissivity of the surface of the light source, and the higher the emissivity, the higher the infrared radiance. When a metal wire such as a nichrome wire is used as the infrared light emission source 3, the emissivity of the surface of the metal wire at an infrared wavelength is usually a low value of about 0.2. On the other hand, the emissivity of the surface in the wavelength of infrared rays can be increased by forming an oxide film on the surface of the metal wire, applying a heat-resistant black paint, or performing a chemical treatment. If the emissivity of the light emitting surface of the infrared light emitting source 3 is 0.5 or more, it is possible to emit infrared rays sufficient for inspecting minute irregularities even when the temperature of the light emitting source is low. The heat-resistant structure of the light source is simplified, and power consumption is reduced, which is preferable. More preferably, the emissivity of the light emitting surface of the infrared light emitting source 3 is 0.7 or more. More preferably, the emissivity is 0.9 or more. That is, infrared rays can be generated more efficiently by blackening the surface of the heating wire by oxidation treatment or the like. Here, the blackening process means a process for increasing the emissivity in the infrared region, and it is needless to say that the black color is not necessarily required in the visible light region.

赤外線発光源３の赤外線放射強度に及ぼす発光表面放射率の影響度合は、赤外線撮像装置５の検出波長によっても変化する。赤外線撮像装置には、検出波長３〜５μｍ帯と８〜１２μｍ帯のものがある。図８は、温度と放射率で放射輝度がどのように変化するのかを、波長１０μｍと４μｍとにおいてプランクの放射理論式で計算した結果である。検出波長が３〜５μｍの場合、図８（ｂ）に示すように、この波長帯域では放射輝度が発光源温度の上昇とともに急峻に立ち上がる。そのため、温度２００℃、放射率０．６以上の場合と同じ放射輝度を放射率０．２で得るには、発光源温度を数十℃程度上昇させれば足りる。一方、検出波長が８〜１２μｍの場合、図８（ａ）に示すように、この波長帯域では発光源温度を上昇させたときの放射輝度の上昇はゆるやかである。従って、温度２００℃、放射率０．６以上の場合と同じ放射輝度を放射率０．２で得るには、発光源温度を５００℃程度まで上げなければならない。即ち、赤外線発光源３の発光表面放射率を０．５以上とすることによる効果は、検出波長が８μｍ以上の赤外線撮像装置５を用いるときに特に顕著となる。 The degree of influence of the light emitting surface emissivity on the infrared radiation intensity of the infrared light source 3 also varies depending on the detection wavelength of the infrared imaging device 5. Infrared imaging devices include those with detection wavelengths of 3 to 5 μm and 8 to 12 μm. FIG. 8 shows the result of calculating how the radiance changes with temperature and emissivity using Planck's theory of radiation theory at wavelengths of 10 μm and 4 μm. When the detection wavelength is 3 to 5 μm, as shown in FIG. 8B, the radiance rises sharply with the increase of the light source temperature in this wavelength band. Therefore, in order to obtain the same radiance as in the case of a temperature of 200 ° C. and an emissivity of 0.6 or more with an emissivity of 0.2, it is sufficient to raise the light source temperature by about several tens of degrees Celsius. On the other hand, when the detection wavelength is 8 to 12 μm, as shown in FIG. 8A, in this wavelength band, the increase in radiance when the light source temperature is increased is gradual. Therefore, in order to obtain the same radiance as in the case of a temperature of 200 ° C. and an emissivity of 0.6 or more with an emissivity of 0.2, the light source temperature must be increased to about 500 ° C. That is, the effect obtained by setting the light emitting surface emissivity of the infrared light emitting source 3 to 0.5 or more is particularly remarkable when the infrared imaging device 5 having a detection wavelength of 8 μm or more is used.

本発明の線状の形状を有する赤外線発光源３としては、図４に示すように、表面に線状のスリット２６を形成した遮光板２５と、その背後に配置した面状の赤外線発光源２７との組み合わせとしても良い。面状の赤外線発光源２７としては、面全体から赤外線を発光する平面発熱体を用いることができる。面状の赤外線発光源２７から発せられる赤外線は集束光ではないので、スリット２６を通過した赤外線も集束光ではなく、拡散する。その点で、スリットを用いるとはいってもいわゆるスリット光とは異なる。遮光板２５を水冷あるいは空冷構造とすれば、たとえ面状の赤外線発光源２７から熱を受けても、遮光板２５それ自体が昇温して赤外線を発することを防止することができる。 As shown in FIG. 4, the infrared light emitting source 3 having a linear shape according to the present invention includes a light shielding plate 25 having a linear slit 26 formed on the surface thereof, and a planar infrared light emitting source 27 disposed behind the light shielding plate 25. It is good also as a combination. As the planar infrared light source 27, a flat heating element that emits infrared light from the entire surface can be used. Since the infrared light emitted from the planar infrared light source 27 is not focused light, the infrared light that has passed through the slit 26 is not focused light but diffuses. In that respect, the use of slits is different from so-called slit light. If the light-shielding plate 25 has a water-cooling or air-cooling structure, even if heat is received from the planar infrared light emitting source 27, the light-shielding plate 25 itself can be prevented from being heated to emit infrared rays.

撮像した赤外線発光源の像の形状から微少凹凸の発生部を判定する手段としては、赤外線発光源の像の形状が非直線となった被検査体表面部分を微少凹凸発生部と判定すると良い。微小凹凸１５発生部において反射した光に基づく像は、図５（ａ）に示す通り、広がったり、あるいは一方の側に曲がったり、さらには消滅する場合もある。従って、像の形状が非直線となった部分を微小凹凸発生部と判断することが可能となる。 As a means for determining the generation portion of the minute unevenness from the shape of the image of the captured infrared light emission source, it is preferable to determine the surface portion of the inspection object where the shape of the image of the infrared light emission source is non-linear as the fine unevenness generation portion. As shown in FIG. 5A, the image based on the light reflected by the minute unevenness 15 generating part may spread, bend to one side, or disappear. Therefore, it is possible to determine a portion where the shape of the image is non-linear as a minute unevenness generating portion.

微小凹凸１５発生部を判定するための画像処理方法としては、撮像した赤外線発光源の像１０の映像信号について直線状の赤外線発光源の伸張方向に微分フィルタリングを施し、その後２値化処理を行い、像が消滅した部分は健全部と判定し、像が消滅しなかった部分を微少凹凸発生部と判定することができる。ここで、直線状の赤外線発光源の伸張方向とは、線状の形状を有する赤外線発光源の長手方向である。図５（ａ）に示す赤外線発光源の像１０について、当該方向に微分フィルタリングを施すと、健全部である直線部については当該方向の輝度変化がないので、微分係数がゼロになるので像が消滅する。一方、微小凹凸発生部で線が歪んだ部位ついては微分係数がたつので、図５（ｂ）に示すように像が残る。その後さらに２値化処理を行えば、微小凹凸発生部のみの像を残すことができる。従って、像が消滅した部分は健全部と判定し、像が消滅しなかった部分を微少凹凸発生部と判定することができる。 As an image processing method for determining the minute unevenness 15 generation portion, differential filtering is performed on the image signal of the captured image 10 of the infrared emission source in the extending direction of the linear infrared emission source, and then binarization processing is performed. The portion where the image disappeared can be determined as a healthy portion, and the portion where the image did not disappear can be determined as a minute unevenness generating portion. Here, the extending direction of the linear infrared light source is the longitudinal direction of the infrared light source having a linear shape. If differential filtering is performed in the direction of the image 10 of the infrared light emitting source shown in FIG. 5A, there is no luminance change in the direction for the straight line portion, which is a healthy portion, so the differential coefficient becomes zero, so the image becomes Disappear. On the other hand, the portion where the line is distorted at the minute unevenness generating portion has a differential coefficient, so that an image remains as shown in FIG. If further binarization processing is performed thereafter, an image of only the minute unevenness generation portion can be left. Therefore, the portion where the image disappeared can be determined as a healthy portion, and the portion where the image did not disappear can be determined as a minute unevenness generating portion.

本発明の赤外線撮像装置５としては、２次元の赤外カメラを用いることができる。 As the infrared imaging device 5 of the present invention, a two-dimensional infrared camera can be used.

赤外カメラを用いた赤外線撮像に際しては、ピント合わせのために被写体側の焦点位置調整を行う。ここで被写体側の焦点位置とは、その被写体側の焦点位置から発した光が、赤外線撮像装置５の撮像素子部分でちょうど結像するような位置をいう。赤外線撮像装置５のレンズ位置と撮像素子位置との距離を調整することにより、被写体側の焦点位置を調整することができる。 When performing infrared imaging using an infrared camera, the focus position on the subject side is adjusted for focusing. Here, the focus position on the subject side refers to a position where light emitted from the focus position on the subject side is just imaged on the imaging element portion of the infrared imaging device 5. The focal position on the subject side can be adjusted by adjusting the distance between the lens position of the infrared imaging device 5 and the imaging element position.

本発明の赤外カメラを用いた赤外線撮像に際しては、被検査体表面に映る赤外線発光源の像１０にピントが合うように被写体側の焦点位置を調整することは当然である。さらに、被検査体表面の微小凹凸有無を明確に検査するためには、被検査体表面の微小凹凸１５部位においてもピントが合うように被写体側の焦点位置を調整することとすると好ましい。被検査体表面に映る赤外線発光源の像１０と被検査体表面の微小凹凸１５部位の双方で赤外線撮像画像のピントが合致するように被写体側の焦点位置を調整することにより、微小凹凸を明瞭に識別することが可能になる。被検査体表面に映る赤外線発光源の像１０と被検査体表面の微小凹凸１５部位の両方にピントが合っていないと、両者が一対一に対応しなくなり、微小凹凸を明瞭に検出することができないからである。例えば、被検査体表面に映る赤外線発光源の像１０にのみピントが合っている場合には、被検査体表面の微小凹凸の位置では像がぼやけたのと同じ状態であるので、被検査体表面に映る赤外線発光源の像の変形が明瞭には起こらないのである。 When performing infrared imaging using the infrared camera of the present invention, it is natural to adjust the focal position on the subject side so that the image 10 of the infrared emission source reflected on the surface of the object to be inspected is in focus. Furthermore, in order to clearly inspect the presence or absence of minute irregularities on the surface of the object to be inspected, it is preferable to adjust the focal position on the subject side so that the fine irregularities 15 on the surface of the object to be examined are also in focus. By adjusting the focal position on the subject side so that the focus of the infrared image is matched with both the image 10 of the infrared light emitting source reflected on the surface of the object to be inspected and the 15 parts of the micro unevenness on the surface of the object to be inspected, the minute unevenness is clearly defined. Can be identified. If both the image 10 of the infrared light emitting source reflected on the surface of the object to be inspected and the minute unevenness 15 portion on the surface of the object to be inspected are not in focus, they do not correspond one-to-one, and the minute unevenness can be detected clearly. It is not possible. For example, when only the image 10 of the infrared light emitting source reflected on the surface of the inspection object is in focus, the image is blurred at the position of the minute unevenness on the surface of the inspection object, so the inspection object The deformation of the image of the infrared light source reflected on the surface does not occur clearly.

被検査体表面に映る赤外線発光源の像１０と被検査体表面の微小凹凸１５部位の双方で赤外線撮像画像のピントが合致するとは、言葉を換えれば、被検査体表面に映る赤外線発光源の像１０と被検査体表面の微小凹凸１５部位の双方が赤外線撮像装置５の焦点深度（被写界深度ともいう。）の範囲内に入るということである。 In other words, the focus of the infrared imaging image matches the image of the infrared light emitting source 10 reflected on the surface of the object to be inspected and the minute irregularities 15 on the surface of the object to be inspected. That is, both the image 10 and the minute unevenness 15 portion on the surface of the object to be inspected fall within the range of the depth of focus (also referred to as the depth of field) of the infrared imaging device 5.

本発明においてピントが合致するとは、被検査体表面の微小凹凸有無を検出することができる程度にピントが合致していることを意味する。被検査体表面の微小凹凸１５部位において、検出対象としての最小の微小凹凸１５の大きさｄ₀に応じて定まる一定の程度の距離ｄだけ離れた２点（Ｐ₁、Ｐ₂）を想定し、その２点と赤外線撮像装置とがなす角度をθとしたとき、角度θだけ離れた２点を分離して識別できる程度にピントが合っていればよい。ｄ₀が小さくなるほどｄが小さくなる関係を有している。赤外線発光源の像１０のピント合致、微小凹凸１５部位でのピント合致の双方とも、θの値としては同じ値を用いる。 In the present invention, “in-focus” means that the in-focus is in such a degree that the presence or absence of minute irregularities on the surface of the object to be inspected can be detected. Assuming two points (P ₁ , P ₂ ) separated by a certain distance d determined in accordance with the size d ₀ of the smallest minute unevenness 15 as the detection target in the 15 minute unevenness portions on the surface of the object to be inspected. If the angle between the two points and the infrared imaging device is θ, it is sufficient that the two points separated by the angle θ are in focus so that they can be separated and identified. There is a relationship in which d decreases as d ₀ decreases. The same value is used as the value of θ for both the focus match of the image 10 of the infrared light emitting source and the focus match at the 15 minute irregularities.

撮像装置レンズＬによって奥行きのある３次元物体を撮影する場合において、ある距離の物体にピントを合わせてもその前後にある物体についてはピント外れとなり像が劣化する。この劣化の程度が少なくて許容される物体距離の範囲を焦点深度と呼んでいる。そのおよその値は次のように幾何光学的に求めることができる。 When a three-dimensional object having a depth is photographed by the imaging device lens L, even if an object at a certain distance is focused, the objects before and after the object are out of focus and the image deteriorates. The range of the allowable object distance with a small degree of deterioration is called the depth of focus. The approximate value can be obtained geometrically as follows.

図７（ａ）に示すように、焦点距離ｆ、開口Ｄの撮像装置レンズＬが、ｓの距離にある物点Ｏに対してピント合わせされ、レンズから距離ｓ'にあるスクリーンに像点Ｏ'を結像しているとする。物点Ｏの前後の物点がピント外れのためつくる錯乱円の許容量を決めその直径をδで表すことにし、図７（ａ）の如く、レンズＬよりｓ₁の距離にある後方物点Ｏ₁、およびｓ₂の距離にある前方物点Ｏ₂がスクリーン面においてちょうど許容量δの錯乱円を作ったとする。このとき像点Ｏ'、Ｏ₁'、Ｏ₂'の像距離は簡単な幾何的関係より、
ｓ₁'=(Ｄ・ｓ')/(Ｄ＋δ)
ｓ₂'=(Ｄ・ｓ')/(Ｄ−δ)
となる。 As shown in FIG. 7A, an imaging device lens L having a focal length f and an aperture D is focused on an object point O at a distance s, and the image point O is projected onto a screen at a distance s ′ from the lens. Assume that 'is imaged. The diameter around the point of the object point O is determined the capacity of circle of confusion to make for out of focus to be expressed in [delta], FIGS. 7 (a) as the rear object point with the lens L to the distance s ₁ O _1, and the forward object point O ₂ at a distance of s ₂ is exactly made a circle of confusion tolerance δ at the screen surface. At this time, the image distances of the image points O ′, O ₁ ′, and O ₂ ′ are simple geometrical
s ₁ '= (D · s') / (D + δ)
s ₂ '= (D · s') / (D−δ)
It becomes.

ｓ'、ｓ₁'、ｓ₂'をレンズの近軸公式によりそれぞれの物体距離に変換し、このレンズのＦ値（＝ｆ／Ｄ）を代入すると、
ｓ₁＝(ｓ・ｆ²)/(ｆ²＋δＦ(ｓ＋ｆ))≒(ｓ・ｆ²)/(ｆ²＋δＦｓ)
ｓ₂＝(ｓ・ｆ²)/(ｆ²−δＦ(ｓ＋ｆ))≒(ｓ・ｆ²)/(ｆ²−δＦｓ)
を得る。上式の近似は、物体距離ｓが焦点距離ｆに比て大きい場合に適用される。このときＯ₁からＯまでの距離ｓ_b、ＯからＯ₂までの距離ｓ_fを求めると、
ｓ_b＝ｓ−ｓ₁＝(δＦｓ²)/(ｆ²＋δＦｓ) （１）
ｓ_f＝ｓ₂−ｓ＝(δＦｓ²)/(ｆ²−δＦｓ) （２）
で与えられ、ｓ_bを後方物体深度、ｓ_fを前方物体深度と呼んでいる。 When s ′, s ₁ ′, s ₂ ′ are converted into respective object distances by the paraxial formula of the lens, and the F value (= f / D) of this lens is substituted,
s ₁ = (s · f ² ) / (f ² + δF (s + f)) ≈ (s · f ² ) / (f ² + δFs)
s ₂ = (s · f ² ) / (f ² −δF (s + f)) ≈ (s · f ² ) / (f ² −δFs)
Get. The approximation of the above equation is applied when the object distance s is larger than the focal distance f. At this time, when the distance s _b from O ₁ to O and the distance s _f from O to O ₂ are obtained,
s _b = s−s ₁ = (δFs ² ) / (f ² + δFs) (1)
s _f = s ₂ −s = (δFs ² ) / (f ² −δFs) (2)
S _b is called the rear object depth and s _f is called the front object depth.

図７（ｂ）に基づいて前述のｄ、θとδとの関係について検討する。微小凹凸１５部位とレンズＬとの距離をｓとすると、ｄ≒ｓ・ｓｉｎθとなる。また、角度θだけ離れた２点を分離して識別できる程度にピントが合っているとは、角度θだけ離れた２点がスクリーンにおいて距離δ離れた位置に結像することを意味する。レンズとスクリーンとの距離をｓ'としているので、δ≒ｓ'・ｓｉｎθとなる。結局、
δ＝ｄ・ｓ'／ｓ≒ｄｆ／ｓ（３）
と記述することができる。 Based on FIG. 7B, the relationship between d, θ and δ described above will be examined. Assuming that the distance between the minute unevenness 15 portion and the lens L is s, d≈s · sin θ. Further, focusing so that two points separated by the angle θ can be separated and identified means that the two points separated by the angle θ form an image at a position separated by a distance δ on the screen. Since the distance between the lens and the screen is s ′, δ≈s ′ · sin θ. After all,
δ = d · s ′ / s≈df / s (3)
Can be described.

本発明においては、図７（ｃ）に示すように被検査体表面の微小凹凸１５部位から赤外線発光源３までの距離をｌとすると、
ｌ≦ｓ_b＋ｓ_f （４）
となるように設計することができれば、微小凹凸１５部位と赤外線発光源の像１０の双方が焦点深度内に入るように被写体側焦点位置を調整することが可能になる。このとき、赤外線撮像装置５から距離ｓにある被写体側焦点位置は微小凹凸１５部位と赤外線発光源の像１０の中間に位置することとなる。 In the present invention, as shown in FIG. 7 (c), when the distance from the 15 minute unevenness 15 part on the surface of the object to be inspected to the infrared light emitting source 3 is l,
l ≦ s _b + s _f (4)
If it can be designed to be, it becomes possible to adjust the subject-side focal position so that both of the minute irregularities 15 and the image 10 of the infrared light emission source fall within the depth of focus. At this time, the subject-side focal position at a distance s from the infrared imaging device 5 is located between the minute unevenness 15 portion and the image 10 of the infrared light source.

（１）（２）式より、レンズのＦ値（＝ｆ／Ｄ）が大きいほどｓ_b＋ｓ_fの値（焦点深度）も大きくなることがわかる。従って、検出すべき微小凹凸の最小の大きさｄ₀が定まったのならば、これからまずｄを定め、（３）式に基づいてδを定め、（１）（２）式に基づいて（４）式を満足するようにレンズのＦ値を選定する。さらに、微小凹凸１５部位と赤外線発光源の像１０の双方が焦点深度内に入るように焦点位置を調整することにより、被検査体表面に映る赤外線発光源の像１０と被検査体表面の微小凹凸１５部位の双方で赤外線撮像画像のピントを合致させることができる。 From (1) and (2), it can be seen that the larger the F value (= f / D) of the lens, the larger the value of s _b + s _f (depth of focus). Therefore, if the minimum size d ₀ of the minute unevenness to be detected is determined, d is first determined, δ is determined based on the equation (3), and (4) based on the equations (1) and (2) (4 The F value of the lens is selected so as to satisfy the formula. Furthermore, by adjusting the focal position so that both the micro unevenness 15 part and the image 10 of the infrared light source are within the depth of focus, the image 10 of the infrared light source reflected on the surface of the object to be inspected and the minute of the surface of the object to be inspected. The focus of the infrared image can be matched with both of the 15 uneven portions.

赤外線撮像装置５のレンズのＦ値を上記のように定めるに際しては、レンズ選択時においてレンズの口径が上記Ｆ値を満足する口径を有するものを選択することとしても良い。あるいは、レンズの口径としては上記Ｆ値よりも小さなＦ値を有する口径の大きなレンズを選択し、レンズ内に配設された絞りを調整することにより、レンズの有効口径が上記Ｆ値を満足するように調整することとしても良い。 When determining the F value of the lens of the infrared imaging device 5 as described above, it is possible to select a lens having a diameter that satisfies the F value when the lens is selected. Alternatively, as the lens diameter, a lens with a large aperture having an F value smaller than the F value is selected, and the effective aperture of the lens satisfies the F value by adjusting the diaphragm disposed in the lens. It is good also as adjusting so.

焦点深度を拡げるためにレンズの有効口径を小さくすると、必然的に集光量が減少することとなる。少ない集光量で赤外線撮像装置５に良好な像を結像させるためには、撮像素子として感度の高い素子を用いる必要が生じるときがある。必要な感度の撮像素子を選択することにより、小さな有効口径のレンズを用いた場合において良好な像を得ることができる。 If the effective aperture of the lens is reduced in order to increase the depth of focus, the amount of condensed light will inevitably decrease. In order to form a good image on the infrared imaging device 5 with a small amount of light collection, it may be necessary to use a highly sensitive element as the imaging element. By selecting an image sensor having a required sensitivity, a good image can be obtained when a lens having a small effective aperture is used.

検出対象としての最小の微小凹凸の大きさｄ₀と２点間の距離ｄとの関係については、経験的にはｄ≒１／２・ｄ₀程度である。 The relationship between the minimum fine unevenness size d ₀ as the detection target and the distance d between the two points is empirically about d ≒ 1/2 · d ₀ .

赤外カメラには、検出波長３〜５μｍ帯と８〜１２μｍ帯のものがある。これら以外の波長帯域では、大気中の炭酸ガスや水蒸気の吸収があり、一般に赤外線観察に適していない。本発明においては検出波長８〜１２μｍ帯のマイクロボロメータ素子の非冷却型赤外カメラが最も適している。当該赤外カメラは、ＩｎＳｂ素子やＰｔＳｉ素子を用いた冷却型の赤外カメラに比較して安価であり、耐用性も優れている。従って、検査装置を安価に提供することが可能になる。また、マイクロボロメータ素子カメラは画素数として３２０×２４０を実現することができ、十分に高解像度の画像を撮像することができる。 Infrared cameras include those with detection wavelengths of 3 to 5 μm and 8 to 12 μm. In wavelength bands other than these, there is absorption of carbon dioxide and water vapor in the atmosphere, and it is generally not suitable for infrared observation. In the present invention, an uncooled infrared camera with a microbolometer element having a detection wavelength band of 8 to 12 μm is most suitable. The infrared camera is cheaper and more durable than a cooling infrared camera using an InSb element or a PtSi element. Therefore, it is possible to provide an inspection apparatus at a low cost. In addition, the microbolometer element camera can realize 320 × 240 as the number of pixels, and can capture a sufficiently high-resolution image.

前述のとおり、検出波長８〜１２μｍの赤外線カメラを用いる場合であって、赤外線発光源として発熱体を用いる場合、赤外線発光源の発光表面放射率を０．５以上とすると特に好ましい。発光表面放射率を０．５以上とすることにより、赤外線発光源の温度を低い温度としても当該波長領域における十分な赤外線放射輝度を得ることができるからである。 As described above, when an infrared camera having a detection wavelength of 8 to 12 μm is used and a heating element is used as the infrared light source, it is particularly preferable that the emission surface emissivity of the infrared light source is 0.5 or more. This is because by setting the light emitting surface emissivity to 0.5 or more, sufficient infrared radiance in the wavelength region can be obtained even when the temperature of the infrared light source is low.

帯鋼の通板ラインにおいて帯鋼表面の微小凹凸有無を検査するに際しては、帯鋼の通板速度を低下させずに検査が可能であれば好ましい。一方、上記マイクロボロメータ素子の赤外カメラには高速シャッターが配備されていないので、通板速度が速すぎると撮像した画像にぶれが生じ、正確な検査ができなくなる。これに対し、微小凹凸検査時に鋼板が検査部を通過する速度を３０ｍ／分程度とすれば、マイクロボロメータ素子の赤外カメラを用いても十分に精度の良い検査を行うことができる。この程度の速度で検査を行うことができれば、帯鋼の同一長さ領域について検査を行うに当たり、従来の砥石がけ検査に比較して１／３程度の時間で検査を完了することができ、そのため検査インターバルを従来の１／３程度に狭めることが可能になる。検査インターバルが短いほど、押し疵が発見されたときに格落ちさせるべき帯鋼の長さを短くすることができるので、歩留向上にはたす役割が大きい。 When inspecting for the presence or absence of minute irregularities on the surface of the steel strip in the strip passing line, it is preferable if the inspection can be performed without reducing the strip passing speed of the strip. On the other hand, since the high-speed shutter is not provided in the infrared camera of the microbolometer element, if the plate passing speed is too high, the captured image is blurred and accurate inspection cannot be performed. On the other hand, if the speed at which the steel sheet passes through the inspection part at the time of the micro unevenness inspection is about 30 m / min, sufficiently accurate inspection can be performed using an infrared camera of a microbolometer element. If the inspection can be performed at such a speed, the inspection can be completed in about ３ time compared to the conventional grinding wheel scoring inspection for the same length region of the steel strip. The inspection interval can be reduced to about 1/3 of the conventional one. The shorter the inspection interval, the shorter the length of the strip steel that should be degraded when a pusher is found, and thus the greater the role of yield improvement.

帯鋼の通板ラインにおいて帯鋼表面を被検査体表面２として微小凹凸有無を検査するにあたり、帯鋼の全幅について微小凹凸有無を検査することが必要である。帯鋼の幅は最大２０００ｍｍを超えることもあるが、赤外線発光源の有効幅としてこの帯鋼の全幅をカバーするものを用いることができ、その場合には赤外線撮像装置を１台のみ用いてその１台で同時に全幅を観察することができる。あるいは、図６に示すように、赤外線撮像装置（３ａ〜３ｃ）を帯鋼の幅方向に複数台配置し、幅方向の領域を各撮像装置で分担して撮像することとしても良い。１台の撮像装置が担当する帯鋼の幅を狭くすれば、撮像の解像度を上げることができ、微小凹凸の検出分解能を高めることができる。 In inspecting the presence or absence of minute irregularities using the surface of the steel strip as the surface to be inspected 2 in the banding plate line, it is necessary to inspect the presence or absence of minute irregularities for the entire width of the band steel. Although the width of the steel strip may exceed 2000 mm at the maximum, the effective width of the infrared light source can be one that covers the entire width of the steel strip, and in that case, only one infrared imaging device is used. The entire width can be observed with one unit at the same time. Alternatively, as shown in FIG. 6, a plurality of infrared imaging devices (3a to 3c) may be arranged in the width direction of the steel strip, and a region in the width direction may be shared by each imaging device and imaged. If the width of the steel strip in charge of one imaging device is reduced, the resolution of imaging can be increased, and the detection resolution of minute irregularities can be increased.

撮像装置を帯鋼の幅方向に往復移動させつつ撮像を行うこととすれば、少ない撮像装置台数において、解像度の高い撮像を行うことが可能になる。この場合には、赤外線発光源の有効幅として１台の撮像装置の撮像範囲をカバーする幅のものを準備し、撮像装置の移動とともに赤外線発光源を移動させることとしても良い。 If imaging is performed while reciprocating the imaging device in the width direction of the steel strip, imaging with high resolution can be performed with a small number of imaging devices. In this case, an effective width of the infrared light emission source may be prepared with a width that covers the imaging range of one imaging device, and the infrared light emission source may be moved along with the movement of the imaging device.

線状の赤外線発光源の向きとしては、帯鋼に映る赤外線発光源像の線状形状の方向を帯鋼の長手方向に垂直な面上としても、あるいは帯鋼の幅方向としてもいずれでも良い。 As the direction of the linear infrared light source, the direction of the linear shape of the infrared light source image reflected on the steel strip may be either on the plane perpendicular to the longitudinal direction of the steel strip or the width direction of the steel strip. .

赤外線撮像装置の撮像データに基づいて微小凹凸の有無及びその発生位置を判定する判定装置６としては、パーソナルコンピュータなどの演算処理装置を用いることができる。判定結果に基づいて、微小凹凸の発生位置を被検査体表面の位置と対応させる。帯鋼の通板ラインにおける検査であれば、帯鋼の長手方向及び幅方向の位置と対応させる。こられのデータ処理は、検査装置が有する演算処理装置で行うこととしてもよく、あるいは検査装置が有する演算処理装置から帯鋼の通板装置が有する演算処理装置にデータを転送し、通板装置の演算処理装置において帯鋼の位置と微小凹凸の位置を対応させることとしても良い。 An arithmetic processing device such as a personal computer can be used as the determination device 6 that determines the presence / absence of minute unevenness and the generation position thereof based on the imaging data of the infrared imaging device. Based on the determination result, the occurrence position of the minute unevenness is made to correspond to the position of the surface of the object to be inspected. If it is the inspection in the strip passing plate line, it corresponds to the position in the longitudinal direction and the width direction of the strip. These data processing may be performed by an arithmetic processing device included in the inspection device, or data is transferred from the arithmetic processing device included in the inspection device to the arithmetic processing device included in the strip passing plate device. In the above processing unit, the position of the steel strip may correspond to the position of the minute irregularities.

微小凹凸が帯鋼の長手方向に周期的に繰り返し発生し、帯鋼幅方向に発生位置が同一であれば、ロールに起因する押し疵と判定することができる。通板装置の各ロールのロール円周と押し疵の発生間隔とを比較し、押し疵の発生間隔と等しい円周を有するロールに押し疵の原因が存在すると判定することができる。通板装置の演算処理装置においては、これらの判定結果を上位のコンピュータに転送し、あるいはプリンタ、ディスプレイ、音声発生装置などの出力装置に出力することができる。 If minute irregularities are periodically and repeatedly generated in the longitudinal direction of the steel strip, and the generation position is the same in the width direction of the steel strip, it can be determined that the pressed bar originates from the roll. The roll circumference of each roll of the threading device is compared with the generation interval of the push rod, and it can be determined that the cause of the push rod exists in the roll having the circumference equal to the generation interval of the push rod. In the arithmetic processing unit of the sheet passing device, these determination results can be transferred to a host computer or output to an output device such as a printer, a display, or a sound generator.

帯鋼の通板ラインにおける押し疵検査のために、本発明を適用した。帯鋼の幅は１６００ｍｍ、通常位置における通板速度は１５０ｍ／分である。帯鋼表面の粗さはＲａ＝０．７μｍ、Ｒｚ＝７μｍ程度である。帯鋼表面が被検査体表面２となる。 The present invention was applied for the inspection of the pushing bar in the strip passing line. The width of the steel strip is 1600 mm, and the plate passing speed at the normal position is 150 m / min. The surface roughness of the steel strip is about Ra = 0.7 μm and Rz = 7 μm. The surface of the strip steel becomes the surface 2 to be inspected.

本発明の赤外線発光源３として、直径０．５ｍｍのニクロム線を数ｍｍ間隔で並列にかつ直線状に伸張したものを用いた。ニクロム線の表面を黒化処理して赤外線の発生効率を高めた。具体的には、ニクロム線を大気中で高温に加熱して表面を酸化させ、赤外線領域における放射率を０．６程度とした。各ニクロム線に同一の電流を流し、ニクロム線の表面温度を２００℃程度とした。この程度の温度であれば、周囲からの外乱放射が影響せず、粗さを有する帯鋼表面で鏡面反射することのできる赤外線を発光することができる。赤外線発光源３を図６に示すように配置した。 As the infrared light emitting source 3 of the present invention, a nichrome wire having a diameter of 0.5 mm was used which was extended in parallel and linearly at intervals of several mm. The surface of the nichrome wire was blackened to increase the infrared generation efficiency. Specifically, the nichrome wire was heated to a high temperature in the atmosphere to oxidize the surface, and the emissivity in the infrared region was set to about 0.6. The same current was passed through each nichrome wire, and the surface temperature of the nichrome wire was about 200 ° C. At such a temperature, disturbance radiation from the surroundings does not affect, and infrared light that can be specularly reflected by the surface of the steel strip having roughness can be emitted. The infrared light emission source 3 was arranged as shown in FIG.

赤外線撮像装置５として検出波長８〜１２μｍ帯のマイクロボロメータ素子の非冷却型赤外カメラを用い、図６に示すように赤外カメラを帯鋼の走行方向２２と直角に４台配置し、各カメラで幅方向の検査部位を分担することとした。赤外カメラの配置位置及び撮像方向としては、上記赤外線発光源から発せられる光が帯鋼表面で反射し、帯鋼表面に映る赤外線発光源の像を撮像できる位置及び方向に配置した。帯鋼表面の像が映る位置から撮像装置までの距離は概略６００ｍｍとした。 Using an uncooled infrared camera with a microbolometer element having a detection wavelength of 8 to 12 μm as the infrared imaging device 5, four infrared cameras are arranged at right angles to the traveling direction 22 of the steel strip as shown in FIG. It was decided to share the inspection site in the width direction with the camera. As an arrangement position and an imaging direction of the infrared camera, the light emitted from the infrared light source is reflected on the surface of the steel strip, and the infrared camera is arranged at a position and a direction where an image of the infrared light source reflected on the surface of the steel strip can be taken. The distance from the position where the image of the steel strip surface was imaged to the imaging device was approximately 600 mm.

赤外カメラの絞りを調整することによってレンズのＦ値を調整し、被検査体表面に映る赤外線発光源の像１０と被検査体表面の微小凹凸１５部位の双方で赤外線撮像画像のピントが合致するように焦点深度を調整した。赤外線発光源３と鋼帯表面との間隔は５００ｍｍであり、レンズのＦ値が４となるようにレンズ絞りを調整した結果、大きさ３ｍｍの微小凹凸の有無を正確に判定することが可能になった。 The F value of the lens is adjusted by adjusting the aperture of the infrared camera so that the infrared image is in focus at both the image 10 of the infrared light source reflected on the surface of the object to be inspected and the 15 minute irregularities on the surface of the object to be inspected. The depth of focus was adjusted. The distance between the infrared light emitting source 3 and the steel strip surface is 500 mm, and the lens diaphragm is adjusted so that the F value of the lens is 4. As a result, it is possible to accurately determine the presence or absence of micro unevenness having a size of 3 mm. became.

赤外線撮像装置５によって赤外線発光源の像１０を撮像し、データを判定装置６である検査装置の演算処理装置に転送し、演算処理装置において撮像した赤外線発光源の像１０の映像信号について縦方向微分フィルタリングを施し、その後２値化処理を行い、像が消滅した部分は健全部と判定し、像が消滅しなかった部分を微少凹凸発生部と判定することとした。 The infrared imaging device 5 captures an image 10 of the infrared light emission source, transfers the data to the arithmetic processing unit of the inspection device which is the determination device 6, and the image signal of the image 10 of the infrared light emission source captured by the arithmetic processing device is longitudinal. Differential filtering was performed, and then binarization processing was performed. A portion where the image disappeared was determined as a healthy portion, and a portion where the image did not disappear was determined as a minute unevenness generation portion.

検査実施にあたっては、検査部を通過する帯鋼の通板速度を２０ｍ／分とした。検査部以外を通板する帯鋼の速度は定常速度のままであり、速度差はループカーによって調整した。その結果、帯鋼表面に押し疵が発生している部位については、確実に微小凹凸発生部として判定がくだされ、判定結果は通板装置の演算処理装置に転送され、帯鋼の長手方向及び幅方向の部位と押し疵発生部を対応させることができた。 In carrying out the inspection, the passing speed of the steel strip passing through the inspection section was set to 20 m / min. The speed of the steel strip passing through other than the inspection part remained at a steady speed, and the speed difference was adjusted by a loop car. As a result, the part where the pressing bar is generated on the surface of the steel strip is surely determined as the minute unevenness generating part, and the determination result is transferred to the processing unit of the plate passing device, and the longitudinal direction and width of the steel strip It was possible to make the directional part correspond to the pushing stick generating part.

検査装置の演算処理装置にはプリンタ、表示モニタ、ボイスガイダンス装置が接続され、オペレータの要求に応じて検査結果を出力することができる。 A printer, a display monitor, and a voice guidance device are connected to the arithmetic processing unit of the inspection apparatus, and an inspection result can be output according to an operator's request.

本発明の検査方法を示す図であり、（ａ）は全体斜視図、（ｂ）被検査体断面、（ｃ）は被検査体表面に映る像を示す図である。It is a figure which shows the inspection method of this invention, (a) is a whole perspective view, (b) A to-be-tested object cross section, (c) is a figure which shows the image reflected on the to-be-inspected object surface. 本発明の検査方法を示す図であり、（ａ）（ｃ）は全体斜視図、（ｂ）（ｄ）はそれぞれ被検査体表面に映る像を示す図である。It is a figure which shows the test | inspection method of this invention, (a) (c) is a whole perspective view, (b) (d) is a figure which shows the image reflected on the to-be-inspected object surface, respectively. 微小凹凸を有する被検査体表面に映る像を示す図である。It is a figure which shows the image reflected on the to-be-inspected object surface which has micro unevenness | corrugation. 本発明の赤外線発光源の１実施形態を示す図である。It is a figure which shows one Embodiment of the infrared rays light emission source of this invention. 微小凹凸を有する被検査体表面に映る像の画像処理状況を示す図であり、（ａ）は画像処理前、（ｂ）は画像処理後の状況を示す。It is a figure which shows the image processing condition of the image reflected on the to-be-inspected object surface which has micro unevenness | corrugation, (a) shows the state before image processing, (b) shows the state after image processing. 本発明の検査方法を示す全体斜視図である。It is a whole perspective view which shows the inspection method of this invention. 焦点深度を幾何光学的に説明する概念図である。It is a conceptual diagram explaining the depth of focus geometrically. 赤外線発光源の温度、放射率と赤外線の放射輝度との関係を示す図であり、（ａ）は波長１０μｍ、（ｂ）は波長４μｍの場合を示す図である。It is a figure which shows the relationship between the temperature and emissivity of an infrared light emission source, and the radiance of infrared rays, (a) is a figure which shows the case where wavelength is 10 micrometers and (b) is wavelength 4 micrometers.

Explanation of symbols

１被検査体
２被検査体表面
３赤外線発光源
５赤外線撮像装置
６判定装置
１０赤外線発光源の像
１１虚像
１２光路
１３データ処理後の像
１５微小凹凸
２０電源
２１配線
２２走行方向
２５遮光板
２６スリット
２７面状の赤外線発光源
Ｌレンズ
δ 錯乱円の直径
ｄ２点間の距離 DESCRIPTION OF SYMBOLS 1 Test object 2 Test object surface 3 Infrared light emission source 5 Infrared imaging device 6 Judgment device 10 Image of infrared light emission source 11 Virtual image 12 Optical path 13 Image 15 after data processing Micro unevenness 20 Power supply 21 Wiring 22 Traveling direction 25 Light shielding plate 26 Slit 27 Planar infrared light source L Lens δ Diameter of circle of confusion d Distance between two points

Claims

A method for inspecting the surface of an object to be inspected for microscopic irregularities, in which an infrared light source having a linear shape is arranged near the object to be inspected, and an image of the infrared light source reflected on the surface of the object to be inspected is an infrared imaging device And inspecting the surface of the object to be inspected for minute irregularities based on the image shape of the imaged infrared light source.

The surface shape inspection method according to claim 1, wherein the infrared light source having the linear shape is a plurality of heating wires extending linearly.

3. The method for inspecting surface irregularities according to claim 1, wherein the light emitting surface of the infrared light source having the linear shape has an emissivity of 0.5 or more at a detection wavelength of the infrared imaging device. .

4. The method for inspecting a surface unevenness according to claim 1, wherein the surface portion of the object to be inspected in which the shape of the image of the imaged infrared light emitting source is non-linear is determined as a minute unevenness generating portion. .

The image signal of the imaged infrared light source is subjected to differential filtering in the direction of expansion of the linear infrared light source, then binarized, and the part where the image disappears is determined to be a healthy part, and the image disappears. 5. The method for inspecting surface unevenness according to claim 4, wherein the portion that has not been determined is determined to be a minute unevenness generating part.

Adjusting the effective aperture of the lens of the infrared imaging device and the focal position on the subject side so that the infrared imaging image is in focus at both the image of the infrared light emitting source reflected on the surface of the object to be inspected and the minute irregularities on the surface of the object to be inspected. The method for inspecting surface irregularities according to claim 1, wherein:

6. The surface irregularity inspection method according to claim 1, wherein the infrared imaging device is an uncooled infrared camera of a microbolometer element having a detection wavelength band of 8 to 12 [mu] m.

The inspection method for surface irregularities according to any one of claims 1 to 7, wherein the object to be inspected is a steel plate having a non-mirror surface.

An apparatus for inspecting the surface of an object to be inspected for microscopic irregularities, an infrared light source disposed in the vicinity of the object to be inspected and having a linear shape, and an image of the infrared light source reflected on the surface of the object to be inspected An infrared imaging device arranged at a position where the object can be measured, and a determination device for determining the presence or absence of minute irregularities on the surface of the object to be inspected based on the shape of the image of the infrared light source imaged by the infrared imaging device. Inspection device for surface irregularities.

The surface shape inspection apparatus according to claim 9, wherein the infrared light source having the linear shape is a plurality of heating wires extending linearly.

The surface unevenness inspection device according to claim 9 or 10, wherein the light emitting surface of the infrared light source having the linear shape has an emissivity of 0.5 or more at a detection wavelength of the infrared imaging device. .

The said determination apparatus determines the to-be-inspected surface part from which the shape of the image of the imaged infrared light emission source became non-linear as a fine unevenness | corrugation generation | occurrence | production part. Inspection device for surface irregularities.

The effective aperture of the lens of the infrared imaging device is obtained by adjusting the subject-side focal position of the infrared imaging device, so that an infrared imaging image is obtained at both the image of the infrared light source reflected on the surface of the object to be inspected and the minute uneven portion on the surface of the object to be inspected. The surface irregularity inspection device according to claim 9, wherein the diameter of the surface irregularity is adjustable so as to match the focus.

The surface irregularity inspection device according to claim 9, wherein the infrared imaging device is a non-cooling type infrared camera having a microbolometer element having a detection wavelength band of 8 to 12 μm.

The surface unevenness inspection apparatus according to claim 9, wherein the object to be inspected is a steel strip having a non-specular surface and is disposed on a plate passing line of the steel strip.