JP2010078485A - Method for inspecting printed matter - Google Patents

Method for inspecting printed matter Download PDF

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JP2010078485A
JP2010078485A JP2008247814A JP2008247814A JP2010078485A JP 2010078485 A JP2010078485 A JP 2010078485A JP 2008247814 A JP2008247814 A JP 2008247814A JP 2008247814 A JP2008247814 A JP 2008247814A JP 2010078485 A JP2010078485 A JP 2010078485A
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printed matter
inspection area
image
printed
inspection
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Shinichi Tozawa
伸一 戸沢
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Toppan Inc
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Toppan Printing Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for inspecting a printed matter, capable of accurately inspecting the printed matter, with less false-defect detections. <P>SOLUTION: The method for inspecting the printed matter, which inspects the printed matter having at least one printed surface on its substrate, includes: an irradiation step of having the printed matter irradiated with white light; a photographic step of photographing the printed matter, in synchronization with the conveyance of the printed matter or at a prescribed time interval; a non-inspection area setting step of setting a non-inspection area which is not an object to be inspected in image data of the printed matter obtained in the photographing step; and an image-processing defect determining step of determining a defect present in the printed matter by using the image data. The method is such that the non-inspection area is set to a portion having a luminance difference in the image data, and the size of the non-inspection area is adjusted according to the magnitude of the brightness difference, in the non-inspection area setting step. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

本発明は印刷物の欠陥検査方法に関する。   The present invention relates to a printed matter defect inspection method.

印刷機として例えば、グラビア印刷機がある。以下、グラビア印刷機でカラーの印刷物を印刷する場合を例に挙げて説明することとする。   An example of a printing machine is a gravure printing machine. Hereinafter, the case of printing a color print with a gravure printing machine will be described as an example.

一般に、グラビア印刷機では、原反に印刷して得られる帯状の印刷物を搬送し、検査装置が有するラインセンサカメラ等の撮像手段でその印刷物の絵柄を撮像し、その際に得られる画像データに基づいて、外観検査を実施している。このような印刷物の検査装置では、カラーの印刷物を高精度に検査を実施するため、主にカラーカメラが用いられている。   In general, in a gravure printing machine, a belt-like printed material obtained by printing on an original fabric is conveyed, an image of the printed material is imaged by an imaging means such as a line sensor camera included in an inspection apparatus, and image data obtained at that time is obtained. Based on this, visual inspection is conducted. In such a printed matter inspection apparatus, a color camera is mainly used in order to inspect a color printed matter with high accuracy.

一般的なカラーカメラは、赤(以下R)、緑(以下G)、青(以下B)の三種類の受光素子等により撮像された画像を、合成してカラー画像を形成している。カラーのラインセンサカメラには、R、G、B波長に感度を持つ受光素子が平行して配列されている3ライン方式と、カメラ内部にプリズム等の分光手段を配置させることで、受光した光をR、G、B波長に分解し、分解した波長別に受光素子が配列されている3CCD方式(又は3板式)という、二種類の方式が用いられている。   A general color camera forms a color image by combining images captured by three types of light receiving elements such as red (hereinafter R), green (hereinafter G), and blue (hereinafter B). The color line sensor camera has a three-line system in which light receiving elements having sensitivity to R, G, and B wavelengths are arranged in parallel, and a light beam received by arranging a spectroscopic means such as a prism inside the camera. Are divided into R, G, and B wavelengths, and two types of methods are used, namely a 3CCD system (or a 3-plate system) in which light receiving elements are arranged according to the decomposed wavelengths.

また、グラビア印刷機では、原反として紙だけではなく、透明プラスチックフィルム、アルミ蒸着などの特殊品を含め、複数種類の原反を同一の印刷機で印刷することが行われている。そのため、従来の印刷物の検査装置用の照明装置では、検査する印刷物の原反が切り換わる毎に、照明装置が有している乱反射、正反射、透過等の光源の中から、必要な光源を選択し、適切な光量調整を実施し、各種印刷物の検査に対応していた。   Moreover, in a gravure printing machine, not only paper but also a plurality of types of original fabrics including a special product such as a transparent plastic film and aluminum vapor deposition are printed by the same printer. For this reason, in the conventional illumination device for a printed matter inspection device, a necessary light source is selected from light sources such as irregular reflection, regular reflection, and transmission that the illumination device has every time the original of the printed matter to be inspected is switched. It was selected, and appropriate light intensity adjustment was performed to support inspection of various printed materials.

CCDカメラ等で印刷物を撮像し、画像処理を用いてその印刷物を検査する方法として、例えば特許文献1が提案されている
欠陥を検出する一般的な手法はパターンマッチング法である。この手法は、一周期の印刷物中に欠陥のない画像を基準画像、検査したい画像を検査画像とし、これらの両画像を比較処理することにより欠陥を分別するものである。比較処理というのは具体的には、カメラで取得した画像の同位置にある画素同士の差分をとり、差分値がスレッシュホールドを超えた場合欠陥と判定する。
As a method for picking up an image of a printed matter with a CCD camera or the like and inspecting the printed matter using image processing, for example, a general technique for detecting defects proposed in Patent Document 1 is a pattern matching method. In this method, an image having no defect in a printed material in one cycle is set as a reference image, and an image to be inspected is set as an inspection image, and these two images are compared to classify defects. Specifically, the comparison process is performed by taking a difference between pixels at the same position in the image acquired by the camera, and determining a defect when the difference value exceeds the threshold.

しかし、この手法では印刷工程のバラツキにより、カメラに映る両画像の位置が相対的に変動してしまい、単なる比較処理では欠陥が無い部分で輝度値の差分値がスレッシュホールドを超え、欠陥と判定されることがある。これが擬似欠陥というもので、検査としては過検出となる。   However, in this method, due to variations in the printing process, the positions of the two images reflected on the camera are relatively fluctuated, and the difference value of the brightness value exceeds the threshold in a portion where there is no defect in a simple comparison process, and it is determined as a defect. May be. This is a pseudo defect, which is overdetection as an inspection.

印刷中に欠陥が発生すると、真の欠陥か擬似欠陥かを目視で判断する必要があるが、擬似が多いとこの作業負荷が増大する。従って、作業者は検査条件を甘く設定して運用することになる。検査条件を甘くすると結果的に検出力が低下することになる。
特許第3808937号公報
When a defect occurs during printing, it is necessary to visually determine whether it is a true defect or a pseudo defect. However, if there are many false, this work load increases. Therefore, the operator sets the inspection conditions sweetly and operates. If the inspection conditions are made sweeter, the detection power is reduced as a result.
Japanese Patent No. 3808937

本発明は、上記問題点に鑑み考案されたもので、擬似欠陥の発生を抑止する検査方法を
提供することを目的としている。
The present invention has been devised in view of the above problems, and an object thereof is to provide an inspection method for suppressing the occurrence of pseudo defects.

本発明の請求項1に係る発明は、基材の少なくとも一方の面に印刷が施された印刷物を検査する方法であって、前記印刷物に白色光を照射する照明段階と、前記印刷物の搬送と同期を取るかまたは所定時間間隔で、前記印刷物を撮像する撮像段階と、前記撮像段階にて得られた印刷物の画像データ中で検査対象としない非検査エリアを設定する、非検査エリア設定段階と、前記画像データを用いて、前記印刷物に存在する欠陥を判定する画像処理欠陥判定段階と、を有し、前記非検査エリア設定段階では、非検査エリアは画像データ中の輝度差のある箇所に設定され、かつ、非検査エリアのサイズを輝度差の大きさによって調節することを特徴とする印刷物の検査方法としたものである。   The invention according to claim 1 of the present invention is a method for inspecting a printed material on which at least one surface of a substrate is printed, an illumination step of irradiating the printed material with white light, conveyance of the printed material, An imaging stage for capturing images of the printed matter in synchronization or at a predetermined time interval, and a non-inspection area setting stage for setting a non-inspection area not to be inspected in the image data of the printed matter obtained in the imaging stage, An image processing defect determination step for determining defects present in the printed matter using the image data, and in the non-inspection area setting step, the non-inspection area is located at a portion having a luminance difference in the image data. The printed matter inspection method is characterized in that the size of the non-inspection area that is set is adjusted according to the brightness difference.

本発明によれば、印刷物において擬似欠陥が発生しやすい領域に設定する非検査エリアの大きさを、輝度差により調節することが可能となる。   According to the present invention, it is possible to adjust the size of a non-inspection area to be set in an area where a pseudo defect is likely to occur in a printed material by a luminance difference.

以下、図面を参照してこの発明に係る印刷物の検査方法を説明する。図1は印刷物の検査装置を示す構成概略図である。   Hereinafter, a printed matter inspection method according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a printed matter inspection apparatus.

図1においては、印刷機が印刷物10を所定速度で搬送しているものとする。印刷物の検査装置は、印刷機の搬送速度と同期を取り、且つ印刷物10の表面を撮影する撮像手段30と、印刷物10の表面に白色光を照射する反射照明手段20と、印刷物10の裏面に白色光を照射する透過照明手段21と、撮像手段30により印刷物10の表面を撮影して得られた画像データを用いて、印刷物10に存在する欠陥部を抽出して、自動判定する制御・画像処理手段40とから構成されている。   In FIG. 1, it is assumed that the printing machine is transporting the printed material 10 at a predetermined speed. The printed matter inspection apparatus is synchronized with the conveyance speed of the printing press and captures the imaging unit 30 for photographing the surface of the printed matter 10, the reflective illumination means 20 for irradiating the surface of the printed matter 10 with white light, and the back surface of the printed matter 10. Control / image for automatic determination by extracting defective portions present in the printed matter 10 using image data obtained by photographing the surface of the printed matter 10 by the transmission illumination means 21 for irradiating white light and the imaging means 30 And processing means 40.

印刷物10は所定速度で被撮像領域を移動している。この際、印刷機に取り付けた印刷物10の移動量を高精度に計測するユニットから単位距離毎の信号を得て、その信号を場合によっては、分周分配して制御・画像処理手段40にこの信号を送ることによって、印刷機の速度変動の影響を受けないように走査撮像を行なう。撮像手段30の分解能の範囲内で印刷機の搬送速度を一定と見なすことができる場合は、トリガー信号による撮像開始、及び一定時間間隔の撮像のみで画像を得る方法も考えられるが、前述のように常に印刷機の搬送速度と同期を取った撮像の方が確実である。   The printed material 10 moves in the imaged area at a predetermined speed. At this time, a signal for each unit distance is obtained from a unit that measures the amount of movement of the printed matter 10 attached to the printing machine with high accuracy, and the signal may be divided and distributed to the control / image processing means 40 in some cases. By sending a signal, scanning imaging is performed so as not to be affected by the speed fluctuation of the printing press. When the conveyance speed of the printing press can be regarded as constant within the range of the resolution of the image pickup means 30, a method of obtaining an image only by starting image pickup by a trigger signal and image pickup at a constant time interval is also conceivable. However, it is always more reliable to take images that are synchronized with the conveyance speed of the printing press.

また、印刷機の速度変動以外にも印刷物10の原反がプラスチックフィルムなどの伸縮が発生しやすい原反を使用する可能性がある。印刷物10の原反に伸縮が発生した場合、印刷機の速度と同期を取った撮像を実施しても、画像に影響を与えてしまう可能性がある。よって、印刷機の搬送速度以外にも、印刷物10の伸縮の影響を考慮した計測が必要となる。一般的には、印刷物10にその一部を接触させた計測方法を採用することで、伸縮などの影響を軽減させていることが多い。   In addition to the speed fluctuation of the printing press, there is a possibility that the original fabric of the printed material 10 is an original fabric that tends to expand and contract, such as a plastic film. When the original fabric of the printed matter 10 is expanded or contracted, there is a possibility that the image will be affected even if imaging is performed in synchronization with the speed of the printing press. Therefore, in addition to the conveyance speed of the printing press, measurement in consideration of the expansion and contraction of the printed material 10 is necessary. Generally, the influence of expansion and contraction is often reduced by adopting a measurement method in which a part of the printed product 10 is brought into contact.

図2は、印刷物の検査装置の反射照明手段20と透過照明手段21を示す模式図である。   FIG. 2 is a schematic diagram showing the reflection illumination means 20 and the transmission illumination means 21 of the printed matter inspection apparatus.

撮像手段30には撮像用のレンズ32が取り付けられており、その垂直方向に撮像対象である印刷物10が配置されている。グラビア印刷機では、印刷物10はロール状にて製造されるため、搬送速度は一定速度である場合が多い。その場合には撮像対象が、常に撮像手段30の下を通過することになるので、撮像手段30は主にラインセンサを選択することが多いが、印刷機の種類、特に搬送の形態によってはエリアカメラを選択しても構わ
ない。また、撮像手段30の配置は、印刷物10に対して垂直に配置しているが、ラインセンサカメラの場合、適切な画像が得られる照明系を実現でき、且つラインセンサの横並び方向において各画素間で同じ距離にある印刷物10を撮像可能であれば、図2のθを傾いて(90°以外に)配置しても構わない。
An imaging lens 32 is attached to the imaging means 30, and the printed material 10 to be imaged is arranged in the vertical direction. In the gravure printing machine, since the printed material 10 is manufactured in a roll shape, the conveyance speed is often a constant speed. In this case, since the imaging target always passes under the imaging means 30, the imaging means 30 mainly selects a line sensor in many cases, but the area depends on the type of printing press, particularly the form of conveyance. You may select a camera. Further, although the image pickup means 30 is arranged perpendicular to the printed material 10, in the case of a line sensor camera, an illumination system that can obtain an appropriate image can be realized, and each pixel is arranged in the horizontal direction of the line sensor. As long as it is possible to pick up images of the printed matter 10 at the same distance, the θ in FIG. 2 may be inclined (other than 90 °).

反射照明手段20は、印刷物10と撮像手段30の間に配置され、印刷物10の表面に白色光を照射する第1の照明手段22と、白色光以外を照射する第2の照明手段23を備えている。反射照明手段20の種類には、適切な処理を行なえる画像が得られる光量を確保できるのであれば何を使用しても構わないが、撮像手段30にラインセンサを採用する場合、ライン状に照射可能な照明系が適している。具体的には、蛍光灯や伝送ライト、LED照明等を選択使用する。   The reflective illumination unit 20 includes a first illumination unit 22 that is disposed between the printed material 10 and the imaging unit 30 and that irradiates the surface of the printed material 10 with white light, and a second illumination unit 23 that irradiates light other than white light. ing. Any type of the reflective illumination means 20 may be used as long as the amount of light capable of obtaining an image that can be appropriately processed can be ensured. However, when a line sensor is used for the imaging means 30, a linear shape is used. An illumination system capable of irradiation is suitable. Specifically, a fluorescent lamp, a transmission light, an LED illumination or the like is selectively used.

また反射照明手段20は、乱反射、正反射、又はその両方、又は両方を配置させつつ印刷物10の原反によってそのうちいずれかを選択する、という配置が考えられるが、印刷機の種類(印刷方式)や原反によってどの配置を選択しても構わない。また、撮像手段30に最適な光量を受光させるため、白色光を照射する第1の照明手段22と、白色光以外を照射する第2の照明手段23をそれぞれ二個以上配置しても構わない。また、反射照明手段20に蛍光灯を採用した場合には、反射照明手段20周辺に反射部材を配置させ、光量を増加させても構わない。   Further, the reflection illumination means 20 may be arranged to select one of them depending on the original fabric of the printed matter 10 while arranging irregular reflection, regular reflection, or both, or both, but the type of printing machine (printing method) Any arrangement may be selected depending on the material. Further, in order for the imaging unit 30 to receive an optimal amount of light, two or more first illumination units 22 that emit white light and two or more second illumination units 23 that emit light other than white light may be arranged. . In addition, when a fluorescent lamp is employed for the reflective illumination unit 20, a reflective member may be disposed around the reflective illumination unit 20 to increase the amount of light.

反射照明手段20には撮像用のスリット31が設けられている。具体的には撮像手段30に受光する光量に影響が無ければ、空間であっても、透明アクリルのような透明部材であっても構わない。   The reflective illumination means 20 is provided with an imaging slit 31. Specifically, as long as the amount of light received by the imaging unit 30 is not affected, it may be a space or a transparent member such as transparent acrylic.

透過照明手段21は、撮像手段30と透過照明手段21の間に、印刷物10が配置されるような位置関係にて配置され、印刷物10の裏面に白色光を照射する第3の照明手段24を備えている。透過照明手段21の種類には、適切な処理を行なえる画像が得られる光量を確保できるのであれば何を使用しても構わないが、撮像手段30にラインセンサを採用する場合、ライン状に照射可能な照明系が適している。具体的には、蛍光灯や伝送ライト、LED照明等を選択使用する。また透過照明手段20は、最大の光量が確保できる方法として、撮像手段30に対して直線的に配置させる方法が考えられるが、欠陥の検出に支障が出ない光量が確保できるのであれば、直線的な配置である必要はない。   The transmitted illumination means 21 is arranged between the imaging means 30 and the transmitted illumination means 21 in such a positional relationship that the printed product 10 is arranged, and a third illumination unit 24 that irradiates the back surface of the printed product 10 with white light. I have. Any kind of transmitted illumination means 21 may be used as long as the amount of light capable of obtaining an image that can be appropriately processed can be secured. However, when a line sensor is used for the image pickup means 30, a linear shape is used. An illumination system capable of irradiation is suitable. Specifically, a fluorescent lamp, a transmission light, an LED illumination or the like is selectively used. In addition, as a method for ensuring the maximum light amount, the transmitted illumination unit 20 can be arranged linearly with respect to the imaging unit 30. It is not necessary to have a typical arrangement.

また、印刷機の種類(印刷方式)や原反によって、特に透過性が低い原反を使用する場合などは、透過照明手段21を採用しなくても構わない。但し、どの原反が搬送されるか未確定な印刷機に取り付ける場合などには、透過照明手段21をONとOFFを切り替え可能な形態であることが適している。また、撮像手段30に最適な光量を受光させるため、白色光を照射する第3の照明手段24をそれぞれ二個以上配置しても構わない。また、透過照明手段20に蛍光灯を採用した場合には、透過照明手段20周辺に反射部材を配置させ、光量を増加させても構わない。   In addition, the transmission illumination means 21 may not be used when using a raw material with particularly low transparency depending on the type of printing press (printing method) and the raw material. However, it is suitable that the transmission illumination means 21 can be switched between ON and OFF, for example, when it is attached to a printing machine in which the original fabric is to be conveyed. Further, two or more third illumination means 24 for irradiating white light may be disposed in order to cause the imaging means 30 to receive an optimal amount of light. In addition, when a fluorescent lamp is used for the transmission illumination unit 20, a reflection member may be disposed around the transmission illumination unit 20 to increase the amount of light.

カラーの印刷物10をモノクロカメラで撮像する場合、異なる色の組み合わせでも出力される階調値に差がない場合がある。一方カラーカメラの場合、R、G、Bそれぞれに感度を持つ三種類の素子によって光を受光するので、カラーの印刷物10を撮像しても、出力される結果画像にR、G、B別の印刷物10の情報を反映できるため、モノクロカメラよりもカラーの印刷物10の撮像には適している。   When the color printed matter 10 is imaged with a monochrome camera, there is a case where there is no difference in output gradation values even when different colors are combined. On the other hand, in the case of a color camera, light is received by three types of elements having sensitivity to R, G, and B, respectively. Since the information of the printed matter 10 can be reflected, it is more suitable for imaging the colored printed matter 10 than a monochrome camera.

撮像手段30であるカメラによる画像取り込みについて説明する。印刷機と同期をとって画像がカメラに取り込まれる。従って、印刷速度が変われば流れ方向では、取り込み時間に応じて画像分解能も変化する。次に取り込み視野内で照明による明るさに差が出るの
で、シェーディング補正を行う。その後、ノイズ除去フィルター等の前処理をかけた画像を取得する。
Image capture by a camera that is the imaging means 30 will be described. Images are captured by the camera in synchronization with the printing press. Therefore, if the printing speed changes, the image resolution also changes in the flow direction according to the capture time. Next, since there is a difference in brightness due to illumination within the capturing field, shading correction is performed. Thereafter, an image subjected to preprocessing such as a noise removal filter is acquired.

印刷工程では、印刷物10には所定のテンションをかけ、常に同じ位置に印刷絵柄が入るように制御している。しかし若干量ではあるが、巾方向には蛇行が発生するし、流れ方向では前述のテンションのために伸縮が発生する。従って、カメラに取り込まれた画像において、巾方向と流れ方向で少しずつ印刷絵柄の位置が変化する。   In the printing process, a predetermined tension is applied to the printed matter 10 and control is performed so that the printed pattern always enters the same position. However, although it is a slight amount, meandering occurs in the width direction, and expansion and contraction occur due to the aforementioned tension in the flow direction. Therefore, in the image captured by the camera, the position of the printed pattern changes little by little in the width direction and the flow direction.

上記位置ずれによりパターマッチングによる検査手法では、過検出が発生してしまう。現在この位置ずれの影響を最小にする方法として、基準画像を検査画像の直前の画像に設定して、順次更新していく方法が考案されている。さらに厳密な位置補正が必要とされる場合には、画像の中で特徴となる部分を抽出して、画像中の印刷絵柄の位置を巾方向および流れ方向で微調整してもよい。   In the inspection method using pattern matching due to the above-described positional deviation, overdetection occurs. Currently, as a method for minimizing the influence of this positional deviation, a method of setting a reference image as an image immediately before an inspection image and sequentially updating the image has been devised. When more precise position correction is required, a characteristic part in the image may be extracted, and the position of the printed pattern in the image may be finely adjusted in the width direction and the flow direction.

これらの手段により、印刷絵柄の位置のバラツキには対応できるが、過検出の要因は他にもある。すなわち、印刷物の印刷品質の、印刷周期ごとのにバラツキである。これは、印刷絵柄のエッジ部など濃淡の差がはっきり出る箇所に発生することが多いものである。   Although these means can cope with variations in the position of the printed pattern, there are other causes of overdetection. That is, the print quality of the printed material varies for each printing cycle. This often occurs in places where there is a clear difference in shading, such as the edge of a printed pattern.

図3(A)〜(C)は印刷絵柄のエッジ部の例を模式的に示したもので、いずれも左側に色の薄い部分51が、右側に色の濃い部分52が、中央付近にそれらの境界部分(エッジ部分)50がある場合を示している。基準画像の絵柄と検査画像の絵柄のエッジ部が、ともに図3(A)のように滑らかであれば、パターンマッチング処理を行った際に擬似欠陥が発生することはない。   FIGS. 3A to 3C schematically show examples of edge portions of a printed pattern, and in each case, a lightly colored portion 51 on the left side and a darkly colored portion 52 on the right side are those near the center. This shows a case where there is a boundary portion (edge portion) 50. If both the edges of the pattern of the reference image and the pattern of the inspection image are smooth as shown in FIG. 3A, no pseudo defect occurs when the pattern matching process is performed.

しかし印刷絵柄のエッジ部分を完全に滑らかにすることは困難であり、一般的には図3(B)、(C)のように凹凸のあるエッジ部となる。このエッジ部の凹凸の状態が基準画像の絵柄と検査画像の絵柄で全く同じであれば、パターンマッチング処理を行った際に擬似欠陥が発生することはない。しかしながら同じ絵柄の印刷物の間でもエッジ部の凹凸の状態は、例えば図3(B)および(C)に模式的に示したように、異なっているのが一般的であり、これが印刷物の印刷品質のバラツキである。   However, it is difficult to completely smooth the edge portion of the printed pattern, and generally, the edge portion is uneven as shown in FIGS. If the unevenness of the edge portion is exactly the same in the pattern of the reference image and the pattern of the inspection image, no pseudo defect occurs when the pattern matching process is performed. However, the unevenness of the edge portion is generally different between printed materials having the same pattern as shown schematically in FIGS. 3B and 3C, for example. This is the print quality of the printed material. This is a variation.

図3(B)および(C)を、それぞれ基準画像および検査画像として、パターンマッチング処理を行なうと、このエッジ部分で擬似欠陥が大量に発生することになる。   When pattern matching processing is performed using FIGS. 3B and 3C as a reference image and an inspection image, respectively, a large number of pseudo defects are generated at the edge portion.

上記課題を解決する方法の一つとして、濃淡の差が大きい絵柄のエッジ部分近傍の一定領域を非検査エリアとするというものがある。非検査エリアは、通常は手作業により領域設定される。この非検査エリアに設定された領域では、検査処理が全く行われないため実際にその部分に発生した欠陥も見逃すことになる。従って非検査エリアはできるだけ小さいサイズに抑えることが好ましい。   One of the methods for solving the above problem is to set a non-inspection area as a certain area in the vicinity of the edge portion of a pattern having a large difference in shading. The non-inspection area is usually set manually. In the area set as the non-inspection area, the inspection process is not performed at all, so that a defect actually generated in that portion is also overlooked. Therefore, it is preferable to keep the non-inspection area as small as possible.

しかし手作業による領域設定では、エッジ部両側の所定幅の領域を非検査エリアとする、というような一律的な設定を行うのが精一杯であり、絵柄の特徴を考慮して非検査エリアのサイズを設定するという手間や時間のかかる作業は困難である。本発明は、この非検査エリアの位置およびサイズを、検査対象の絵柄の特徴を考慮しつつ、設定可能とするものである。   However, in manual area setting, it is best to make a uniform setting such that the area of the predetermined width on both sides of the edge is set as the non-inspection area. The time-consuming and time-consuming work of setting the size is difficult. In the present invention, the position and size of the non-inspection area can be set in consideration of the characteristics of the pattern to be inspected.

比較のため、従来の処理フローを図4に示す。従来の処理フローでは、印刷物を撮像し(S2)、得られた検査画像に対して、シェーディング補正、前処理、位置補正を行った(S3,S4)後にエッジ部を抽出し、そのエッジ部近傍の所定個数の画素を非検査エリアとする(S5)。この非検査エリアとなる画素の個数はパラメータとして設定できるも
のとする。その後、パターンマッチング処理を行って、基準画像と検査画像の差分画像を作成する(S6)。さらにその差分画像を所定のしきい値で2値化して欠陥のある箇所を検出し、良否判定する(S7)。
For comparison, a conventional processing flow is shown in FIG. In the conventional processing flow, the printed matter is imaged (S2), and the obtained inspection image is subjected to shading correction, preprocessing, and position correction (S3, S4), and then an edge portion is extracted and the vicinity of the edge portion is extracted. The predetermined number of pixels is set as a non-inspection area (S5). It is assumed that the number of pixels serving as the non-inspection area can be set as a parameter. Thereafter, pattern matching processing is performed to create a difference image between the reference image and the inspection image (S6). Further, the difference image is binarized with a predetermined threshold value to detect a defective portion, and the quality is determined (S7).

このような従来の非検査エリアの設定方法では、前述のように印刷品質のバラツキの多少によらず非検査エリアのサイズを設定することになってしまう。そのためバラツキの小さい印刷物についても大きな非検査エリアを設定してしまい、その結果、非検査エリアのサイズが適正であれば検出できた欠陥を検出できないことになってしまう。   In such a conventional non-inspection area setting method, as described above, the size of the non-inspection area is set regardless of variations in print quality. Therefore, a large non-inspection area is set even for a printed matter with small variations, and as a result, a defect that can be detected cannot be detected if the size of the non-inspection area is appropriate.

本発明の方法の処理フローを図5に示す。本発明の方法においても、印刷物を撮像し(S12)、得られた検査画像に対して、シェーディング補正、前処理、位置補正を行う(S13,S14)ところまでは従来と同様である。   The processing flow of the method of the present invention is shown in FIG. Also in the method of the present invention, the same processing as before is performed until the printed matter is imaged (S12), and the obtained inspection image is subjected to shading correction, preprocessing, and position correction (S13, S14).

その後、検査画像のx方向(印刷物の流れ方向に対して直角方向)について、隣り合った各画素の輝度値の差分をとっていき(S15)、その差分値が所定のしきい値を超えた場合に、その前後の画素を非検査エリアと設定する(S16)。検査画像のy方向(印刷物の流れ方向)についても同様の処理を行う。なお、x方向とy方向のどちらの処理を先に行うかという順序には特に決まりはない。また検査対象の絵柄によっては、この処理をx方向とy方向の両方について行わなくてもよい場合もある(例えば印刷絵柄が縦縞の場合は、この処理はx方向についてのみ行えば非検査エリアの設定が可能である)。   Thereafter, in the x direction of the inspection image (perpendicular to the flow direction of the printed material), a difference in luminance value between adjacent pixels is taken (S15), and the difference value exceeds a predetermined threshold value. In this case, the pixels before and after that are set as non-inspection areas (S16). The same process is performed for the y direction (flow direction of the printed material) of the inspection image. Note that there is no particular order in which order of processing in the x direction or y direction is performed first. Further, depending on the pattern to be inspected, this process may not be performed in both the x direction and the y direction (for example, when the printed pattern is a vertical stripe, if this process is performed only in the x direction, the process is not performed in the non-inspection area. Can be set).

この後の処理フローは従来のものと同じで、パターンマッチング処理を行って基準画像と検査画像の差分画像を作成し(S17)、その差分画像を所定のしきい値で2値化して欠陥のある箇所を検出し良否判定する(S18)、というものである。   The subsequent processing flow is the same as the conventional one, and pattern matching processing is performed to create a difference image between the reference image and the inspection image (S17), and the difference image is binarized with a predetermined threshold value to detect defects. A certain point is detected and the quality is judged (S18).

上記の本発明の非検査エリア設定方法では、検査画像中のエッジ部の凹凸形状に合わせて、非検査エリアの位置やサイズを設定することが可能となる。従って、エッジ部に凹凸があったとしてもエッジ部のごく近傍だけが非検査エリアとして設定され、それ以外の箇所は検査対象エリアであり、欠陥を見逃す可能性を低減することが可能となる。   In the non-inspection area setting method of the present invention, the position and size of the non-inspection area can be set in accordance with the uneven shape of the edge portion in the inspection image. Therefore, even if there are irregularities in the edge portion, only the very vicinity of the edge portion is set as a non-inspection area, and other portions are inspection target areas, and the possibility of missing a defect can be reduced.

更に上記の本発明の非検査エリア設定方法では、検査画像上で輝度値の差分が小さい箇所、すなわち印刷物上でもともと濃淡の差が小さい箇所は、非検査エリアとはならず検査対象エリアとしたり、非検査エリアのサイズを小さくしたりすることができる。   Furthermore, in the above-described non-inspection area setting method of the present invention, a portion where the difference in luminance value is small on the inspection image, that is, a portion where the difference in shading is originally small on the printed material does not become a non-inspection area but becomes an inspection target area. The size of the non-inspection area can be reduced.

図6(A)、(B)に、このことを説明する模式図を示す。図6(A)、(B)はともに、検査画像中の絵柄のエッジ部分を含む領域の、横一列に並んだ画素8個(図6(A)ではG1〜G8で図6(B)H1〜H8)を模式的に示したものである。いずれも左側に輝度の高い(明るい)部分が、右側に輝度の低い(暗い)部分があるものとする。明るい部分の輝度は(A)と(B)で同じであるが、暗い部分の輝度は(A)のほうがより低く、明るい部分と暗い部分の輝度の差は(A)のほうが大きくなっているものとする。より具体的には、輝度差が、(A)では、(G1、G2、G3)とG4とG5と(G6、G7、G8)の4段階で各段階での輝度値の差分値は閾値を超えている場合である。(B)では(H1,H2,H3,H4)と(H5,H6,H7,H8)の2段階でありその段階での輝度値の差分値は閾値を超えている場合である。   6A and 6B are schematic views for explaining this. 6A and 6B both show eight pixels arranged in a horizontal row in the region including the edge portion of the pattern in the inspection image (G1 to G8 in FIG. 6A and H1 in FIG. 6B). -H8) are schematically shown. In any case, it is assumed that a portion with high brightness (bright) is on the left side and a portion with low brightness (dark) is on the right side. The brightness of the bright part is the same in (A) and (B), but the brightness of the dark part is lower in (A), and the difference in brightness between the bright part and the dark part is larger in (A). Shall. More specifically, in (A), when the luminance difference is (A), the difference value of the luminance value at each stage is a threshold value in four stages (G1, G2, G3), G4, G5, and (G6, G7, G8). This is the case. In (B), there are two stages (H1, H2, H3, H4) and (H5, H6, H7, H8), and the difference value of the luminance value at that stage exceeds the threshold value.

この図6の例においては、ごく単純に輝度差がある箇所を非検査エリアと設定するものとすれば、(A)では4画素分が、(B)では2画素分が非検査エリアに設定されることになる。このようにして、印刷絵柄の濃度に応じて、検査対象エリアのサイズを調節することが出来る。   In the example of FIG. 6, if a portion having a brightness difference is simply set as a non-inspection area, 4 pixels in (A) and 2 pixels in (B) are set as non-inspection areas. Will be. In this way, the size of the inspection target area can be adjusted according to the density of the printed pattern.

印刷絵柄中のエッジ部やバーコード印刷部分のように濃度差が大きい部分では、印刷品質のバラツキにより濃度勾配にもバラツキが発生し、差分画像における差分値がより大きくなる。一方、濃度勾配が少ないエッジ部の場合は、印刷品質のバラツキが濃度勾配のバラツキに与える影響が少なく差分画像における差分値も小さい。   In a portion where the density difference is large, such as an edge portion or a barcode printing portion in the printed pattern, the density gradient also varies due to variations in print quality, and the difference value in the difference image becomes larger. On the other hand, in the case of an edge portion having a small density gradient, the print quality variation has little influence on the density gradient variation, and the difference value in the difference image is also small.

従って、前者の場合には非検査エリアを大きく設定し、後者の場合に非検査エリアを小さく設定することにより、擬似欠陥が出にくく、検出力を上げられることになるので、カラーで構成された印刷物を高精度に検査することができるようになる。   Therefore, by setting the non-inspection area large in the former case and setting the non-inspection area small in the latter case, pseudo defects are less likely to occur and the detection power can be increased. The printed matter can be inspected with high accuracy.

本発明に係る検査装置の要部構成を示す概略構成図。The schematic block diagram which shows the principal part structure of the inspection apparatus which concerns on this invention. 本発明の撮像及び照明手段を示す断面説明図。Cross-sectional explanatory drawing which shows the imaging and illumination means of this invention. 印刷絵柄のエッジ部の例を模式的に示した図。The figure which showed the example of the edge part of a printing pattern typically. 従来の検査装置の全体概略動作を示すフローチャート。The flowchart which shows the whole schematic operation | movement of the conventional inspection apparatus. 本発明の検査装置の全体概略動作を示すフローチャート。The flowchart which shows the whole schematic operation | movement of the test | inspection apparatus of this invention. 輝度の差の大きさにより非検査エリアのサイズを変えることを説明する模式図Schematic diagram explaining changing the size of the non-inspection area depending on the difference in brightness

符号の説明Explanation of symbols

10・・印刷物
20・・反射照明手段
21・・透過照明手段
22・・第1の照明手段
23・・第2の照明手段
24・・第3の照明手段
30・・撮像手段
31・・撮像用のスリット
32・・撮像用のレンズ
40・・制御・画像処理手段
50・・エッジ部
51・・色の薄い部分
52・・色の濃い部分
10 .. Printed material 20 .. Reflective illumination means 21 .. Transmitted illumination means 22... First illumination means 23 .. 2nd illumination means 24 .. 3rd illumination means 30. The slit 32 of the imaging lens 40, the control, the image processing means 50, the edge portion 51, the light-colored portion 52, the dark portion

Claims (1)

基材の少なくとも一方の面に印刷が施された印刷物を検査する方法であって、前記印刷物に白色光を照射する照明段階と、前記印刷物の搬送と同期を取るかまたは所定時間間隔で、前記印刷物を撮像する撮像段階と、前記撮像段階にて得られた印刷物の画像データ中で検査対象としない非検査エリアを設定する、非検査エリア設定段階と、前記画像データを用いて、前記印刷物に存在する欠陥を判定する画像処理欠陥判定段階と、を有し、前記非検査エリア設定段階では、非検査エリアは画像データ中の輝度差のある箇所に設定され、かつ、非検査エリアのサイズを輝度差の大きさによって調節することを特徴とする印刷物の検査方法。   A method for inspecting a printed material on which at least one surface of a substrate is printed, the illumination step of irradiating the printed material with white light, and synchronizing with conveyance of the printed material or at predetermined time intervals, An imaging stage for imaging a printed matter, a non-inspection area setting stage for setting a non-inspection area not to be inspected in the image data of the printed matter obtained in the imaging stage, and the printed matter using the image data An image processing defect determination step for determining an existing defect, and in the non-inspection area setting step, the non-inspection area is set at a location having a luminance difference in the image data, and the size of the non-inspection area is set. A method for inspecting printed matter, wherein the printed matter is adjusted according to the magnitude of the luminance difference.
JP2008247814A 2008-09-26 2008-09-26 Method for inspecting printed matter Pending JP2010078485A (en)

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JP2015524059A (en) * 2012-05-28 2015-08-20 エムエスセ エ エスジェセセMsc & Sgcc Optical method for inspecting transparent or translucent containers with visible patterns
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