JP2015075444A - Method for inspecting luminous printed matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for inspecting a luminous printed matter capable of imaging a streak one by one distinctively even in a case where an inspection object is a printed pattern composed of streaks made of photo-luminescent ink having bulges.SOLUTION: A method for inspecting a luminous printed matter images a printing pattern composed of luminous streaks having a plurality of bulges provided on a substrate using an inspection device having at least coaxial epi-illumination and a line camera, obtains an image, and performs quality determination of the printed matter by comparing the obtained image with a normal image that is pre-stored and composed of a plurality of streaks. The method includes at least an irradiation direction setting process, an irradiation process, a reflected image photographing process, and a determination process.

Description

  The present invention relates to an inspection method for detecting a quality defect of a glitter printed matter printed using glitter ink such as pearl ink or metal ink.

  In recent years, there has been a demand for printing technology that has a new design and a high anti-counterfeiting effect for valuable printed matter that requires security. For example, an optical security element such as a hologram whose image changes depending on an observation angle, There are those using glitter ink such as pearl ink and gold ink having an optical function.

  As an example, the present applicant observed obliquely by forming a plurality of printed image lines made of glittering ink having a bulge and making the image line angle different between the latent image portion and the background portion around it. Only in such a case, a latent image printed material having an effect that a latent image portion appears is filed (for example, refer to Patent Document 1).

Conventionally, printing defects generated in the manufacturing process of printed matter formed with glitter ink have been visually observed by an operator during manufacturing. However, there is a problem that the operator overlooks the visual inspection. Therefore, in recent years, a method of automatically inspecting using an image processing apparatus has been introduced. In the inspection method using the image processing apparatus, for example, non-defective product image data is stored in advance as reference image data, and after the surface of the printed matter on which the pattern is formed is imaged, the captured image data is compared with the reference image data. The pass / fail judgment is made.

  As an inspection method for printed matter formed with glitter ink using an image processing apparatus, for example, in Patent Document 2, an area type coaxial incident illumination is applied to a printed pattern formed with glitter ink on a substrate. A method of performing pass / fail judgment by taking an image with an area camera after irradiating light and comparing the captured image data with reference image data that is non-defective grayscale image data is disclosed.

Japanese Patent No. 3718712 JP-A-9-136403

  According to the inspection method of Patent Document 2, it is possible to inspect a printed pattern made of glitter ink using an image processing apparatus. However, since the entire printed pattern made of glitter ink is imaged using an area camera, coaxial incident illumination is applied to the entire printed pattern at the time of imaging.

  Therefore, although an inspection image can be captured for a printed pattern formed by flat solid printing, as in Patent Document 1, a printed pattern made up of a plurality of pearl print lines having a swell is applied to irradiation light. On the other hand, since the lines are reflected in multiple directions, it is impossible to distinguish and capture the lines one by one.

  Accordingly, an object of the present invention is to provide a glittering property that can distinguish and image one line at a time even in a printed pattern composed of glittering ink having a bulge that is an object to be inspected. It is to provide an inspection method for printed matter.

  In order to achieve the above-mentioned object, the invention according to claim 1 is a glittering image line having a plurality of swells provided on a base material using an inspection apparatus having at least a coaxial epi-illumination and a line camera. An image of a printed pattern is captured to obtain an image, and the quality of the printed material is judged by comparing the acquired image with a regular image that is stored in advance and is composed of a plurality of image lines. In accordance with the inspection items of the glittering image line, the imaging is performed so that the arrangement direction of the glittering image line and the linear irradiation light from the coaxial incident illumination are orthogonal, parallel, or sequentially orthogonal to each other. An irradiation direction setting process for setting conditions, an irradiation process for irradiating visible light from coaxial incident illumination on a printed pattern, and reflected light from the printed pattern is detected, and a line camera captures a reflected image consisting of multiple lines. Anti An image capturing step, and a reflection image, a method of inspecting a brilliant printed matter, characterized in that at least and a determination step of performing quality determination by comparing the reference image data set in advance.

  Further, in the method for inspecting the glitter printed matter according to claim 2, the printed pattern has at least two regions in which the arrangement direction of the glittering image lines having swells is different, and the change in the observation angle is caused by the arrangement direction being different. The print pattern changes according to the above, and for all the areas constituting the print pattern, in the irradiation direction setting step, the imaging condition is set for each area in accordance with the inspection item of the glitter image. The area obtained by the imaging conditions set for each area in the determination step, with the arrangement direction of the glittering image lines to be configured and the irradiation light from the coaxial epi-illumination set to be orthogonal, parallel or sequentially orthogonal and parallel By determining whether or not each area is visible at a predetermined observation angle based on each reflection image, whether or not the printed pattern of each area has changed due to a change in the observation angle. Good or bad And performing constant.

  Further, in the method for inspecting the glitter printed matter according to claim 3, in the irradiation direction setting step, the arrangement direction of the glitter image lines constituting the printed pattern is determined based on the shade of the reflected image obtained from the scanner or the coaxial incident illumination. It has the arrangement direction confirmation process to confirm.

  In the method for inspecting a glittering printed matter according to the present invention, the imaging conditions are set so that the line-shaped irradiation light from the coaxial incident illumination is orthogonal or parallel to the arrangement direction of the image lines constituting the printed pattern. As a result, it is possible to separately pick up images of printed image lines made of glittering ink having swell.

The top view which shows an example of printed matter (H) which is a test subject. The top view which shows the inferior goods which have a defective part (K) in printed matter (H '). The schematic diagram which shows an inspection apparatus (M). The flowchart which shows an inspection method. The schematic diagram which shows an irradiation direction setting process. The schematic diagram which shows the imaging principle of the glittering image line which has a swell. The schematic diagram which shows a 1st reflected image (P1). The schematic diagram which shows a reference | standard latent image (P2). The schematic diagram which shows a template matching. The figure which shows a reference | standard latent image image (P2) and its density | concentration cross section. FIG. 3 is a schematic diagram showing a broken line (K1). The schematic diagram which shows a reference | standard latent image line-cut image (P3). The schematic diagram which shows an image line connection (K2). The schematic diagram which shows the inspection method of an image line connection. The schematic diagram which shows a reference | standard image line connection image (P5). The schematic diagram which shows the printing pattern (2) which consists of one image line direction. The schematic diagram which shows three or more printed patterns (2). The schematic diagram which shows three area | regions which comprise a printing pattern (2).

  Fig.1 (a) is a top view which shows an example of printed matter (H) which is a test subject of this invention. A printed pattern (2) formed by arranging a plurality of glittering image lines having swells is provided on a printable base material (1) such as paper or card. The printed pattern (2) is composed of a star-shaped latent image portion (3) and a background portion (4) surrounding it.

  FIG. 1B is an enlarged view showing the latent image portion (3), and FIG. 1C is an enlarged view showing the background portion (4). As shown in FIGS. 1B and 1C, the plurality of image lines (3a) constituting the latent image portion (3) are arranged in the first direction (X1), and the background portion (4 ) Are arranged in a second direction (X2) different from the first direction (X1).

  For example, in FIG. 1, the first direction (X1) and the second direction (X2) are different from each other by 90 degrees.

  When the printed image (H) is observed from the front because the arrangement direction of the glittering image lines having bulges forming the latent image portion (3) and the background portion (4) is different, the latent image portion (3) and the background portion Since (4) is hardly affected by light reflection, it is visually recognized as a solid print area.

  Also, when observed from an oblique direction, one of the latent image portion (3) and the background portion (4) reflects light and is visually recognized brightly, and the other is visually recognized dark without reflecting light. Due to the difference, the star-shaped latent image portion (3) becomes visible.

  A glittering image line having a bulge is formed using glittering ink or ink mixed with glittering material. The glitter ink is not particularly limited as long as it is a material capable of observing regular reflected light of incident light, such as pearl ink, metallic ink such as gold and silver ink, and transparent ink. Also, it may be colored or colorless.

  The details of the configuration of the printed pattern (2) are described in Japanese Patent No. 3718712 “Printed matter capable of determining authenticity and its manufacturing method” and Japanese Patent Publication No. WO2003 / 013871 “Authentication determination”. Since it is described in “Possible printed matter and its manufacturing method”, it is omitted.

  FIG. 2 is a plan view showing a defective product having a defective portion (K) on the printed material (H ′).

  In the present invention, the defective portion (K) means that in the printed pattern (2), the image line is missing, the width of the image line or the ink film thickness is changed, the image lines are connected, and the ink adheres to the non-image area. The image line configuration constituting the latent image portion (3) and the background portion (4) is a region different from the non-defective product specification.

  When the printed matter (H ′) having the defective portion (K) is viewed from an oblique direction, the latent image portion (3) and / or (4) cannot be visually recognized, or a part of the printed product (H ′) is visually recognized with a part missing. Under the conditions, the latent image portion (3) and / or the background portion (4) cannot be clearly seen.

  Therefore, in the present invention, as shown in FIG. 1, in the printed pattern (2) having at least two or more regions in which the arrangement direction of the glittering image lines having swells is different, the image lines are distinguished one by one. Provided is an inspection method for a printed matter (H) that can be imaged.

  Next, an inspection apparatus (M) that performs the inspection method of the present invention will be described with reference to a schematic diagram showing the configuration of FIG. The inspection device (M) includes at least a line camera (5), a coaxial incident illumination (6), a transport unit (7), a control unit (8), an image processing unit (9), and a determination unit (10).

  The inspection device (M) places the printed matter (H) on the transport unit (7), and then drives the transport unit (7) with a motor (not shown) or the like, thereby lowering the coaxial epi-illumination (6). Pass the printed matter (H) through. Next, after the reflected light from the printed material (H) is imaged by the line camera (5), the printed image (H) is inspected based on the captured image by the image processing unit (9), and finally the determination unit ( In step 10), the quality of the printed matter (H) is determined.

  Next, the configuration of the inspection apparatus (M) will be described in detail.

  The line camera (5) is a means for capturing an input image to be inspected for performing a pass / fail inspection of the printed matter (H), such as a light receiving element (not shown), a lens, a sensor that outputs a trigger signal at the time of imaging, an encoder, and the like. It consists of image input means.

  The line camera (5) faces the transport unit (7) via the transport path of the printed matter (H), and is in a position parallel to the light receiving element of the line camera (5) and coaxial incident illumination (6) described later. Deploy. In that case, it arrange | positions so that the light-receiving surface of a line camera (5) and the surface of printed matter (H) may become parallel. As the line camera (5), a known line camera such as a line camera (“S3-24-02K40” manufactured by TELEDYNE DALSA) is used. Further, the number of line cameras (5) is not limited to one, and a plurality of line cameras (5) may be arranged according to the size of the printed matter (H) to be inspected and the resolution of the line camera (5).

  The coaxial epi-illumination (6) irradiates the printed matter (H) with line-shaped light when capturing an input image to be inspected in order to perform a pass / fail inspection of the printed matter (H), and is specularly reflected coaxially with the irradiated light. It is a means for obtaining light and comprises a light source (R), a rod lens (6L), a half mirror (J), and the like.

  The coaxial epi-illumination (6) includes an area camera and a line camera. Either environment may be used as long as it is an environment in which line-shaped light with high parallelism can be irradiated and imaged, but the irradiation area can be reduced for a line camera having a smaller imaging area. In addition, the parallelism in this invention is how much light (L1) radiated | emitted from the light source (R) of coaxial epi-illumination (6) spread | diffused via the rod lens (6L), as shown in FIG. Is the degree of spread. When the degree of spread is small, the degree of parallelism is high, and when the degree of spread is large, the degree of parallelism is low.

  For example, in FIG. 3, the emitted light (L1) and the light (L2) via the rod lens (6L) are parallel. Therefore, since there is no difference between the two angles, it can be said that the degree of parallelism is high without the degree of spread. Therefore, it is preferable because it is possible to irradiate light with high parallelism for each fine print image line (3a) constituting the latent image portion (3).

  The coaxial epi-illumination (6) is disposed between the line camera (5) and the printed material (H). At this time, the optical axis of the irradiation light and the reflected light of the coaxial epi-illumination (6) and the optical axis received by the line camera (5) are arranged on the same axis. For the coaxial epi-illumination (6), a known coaxial epi-illumination such as a coaxial epi-illumination (“LNSPV-400SW” manufactured by CCS) is used.

  The transport unit (7) is means for placing and transporting the printed material (H) in order to capture an input image to be inspected with the line camera (5) in order to perform a pass / fail inspection of the printed material (H). (H) is placed on a stage, and driving means such as a motor that drives the stage at a constant speed parallel to the light receiving surface of the line camera (5).

  A conveyance part (7) is arrange | positioned in the position facing a line camera (5) through the conveyance path | route of printed matter (H).

  By driving the conveyance unit (7) arranged in the same direction as the conveyance direction (v1) by a motor (not shown), the printed matter (H) is maintained in the flatness in the inspection apparatus (M). Can be conveyed one by one.

  The transport unit (7) includes a mechanism for fixing the printed matter (H) using a material that does not bend or distort in order to stabilize the imaging conditions.

  When the printed material (H) is conveyed, flapping may occur and an accurate input image may not be acquired from the line camera (5). Therefore, at the time of conveyance, it is preferable to fix the printed matter (H) to the conveyance unit (7). For example, a plurality of suction holes may be provided in the transport unit (7), and the printed product (H) may be transported while sucking the printed product (H) placed on the transport unit (7). Furthermore, you may attach the instrument which hold | suppresses the upper surface of printed matter (H) on a conveyance part (7).

  In FIG. 3, the transport unit (7) is illustrated as a table. However, the configuration is not limited to the table as long as the input image can be acquired by capturing the printed matter (H) one by one with the line camera (5). For example, the printed matter (H) may be conveyed by a conveyor belt or a gripper to capture an input image, or the line camera (5) may be moved while the printed matter (H) is fixed.

  The control unit (8) transfers the input image to be inspected for performing the pass / fail inspection of the printed matter (H) captured by the line camera (5) to the image processing unit (9) and the inspection device (M ) Is a means for controlling each part, a camera control means for controlling the line camera (5), a communication means for transmitting / receiving a signal such as a trigger signal that is a timing for imaging, and a captured image to the image processing section (9). It consists of transfer means for transferring. For the control unit (8), a known control device such as a line camera power supply ("PL315A" manufactured by TELEDYNE DALSA) is used.

  The image processing unit (9) performs quantification in order to compare the input image transferred from the control unit (8) with threshold data serving as a reference when performing non-defective product determination registered in advance as a reference. A means for transferring, and a transfer means for transferring the calculation result from the calculation means to the determination unit (10), and a storage means.

  The calculation means performs calculation using the input of each image used in the printed matter (H) inspection method and the input images and / or images and data stored in the storage means. The storage means stores data necessary for the inspection such as each image and each reference value used in the printed matter (H) inspection method.

  Based on the calculation result in the image processing unit (9), the determination unit (10) compares with the determination data that is registered in advance as a reference and serves as a reference when performing pass / fail determination, and the input image is set in advance. This is means for determining whether or not the value is within the threshold value.

  As the means for determining pass / fail, known image processing means such as various filter processes, feature point extraction, pattern matching and the like are used.

  The determination result in the determination unit (10) is transferred to the control unit (8) and then output by a monitor (not shown) or a printer (not shown) connected to the control unit (8). In addition, a configuration may be adopted in which a paper discharge unit (not shown) is provided in the inspection apparatus (M) and the printed matter (H) is automatically selected.

  Next, a printed matter (H) inspection method using the above-described inspection apparatus (M) will be described according to the flowchart shown in FIG.

  First, in step (hereinafter referred to as “S”) 1, an irradiation direction setting step is performed, and the glittering property corresponding to the inspection items of the glittering image lines constituting the region to be inspected of the printed pattern (2) in advance is provided. The imaging conditions are set so that the arrangement direction of the image lines and the line-shaped irradiation light from the coaxial incident illumination (6) are orthogonal to each other.

  For example, if the region to be inspected is the latent image portion (3) and the inspection item of the glitter image line is whether or not the latent image portion (3) appears clearly, the latent image portion (3) is configured. If the background direction (4) is set so that the illumination direction is orthogonal to the arrangement direction of the image line to be inspected and the region to be inspected is the background part (4), it is coaxial with the arrangement direction of the image line constituting the background part (4) It sets so that the linear illumination light from epi-illumination (6) may become orthogonal. Hereinafter, as an example, an inspection method for the latent image portion (3) will be described.

  FIG. 5 is a schematic diagram showing S1. When it is considered that the image line constituting the printed matter (H) is composed only of the image line (3a) constituting the latent image portion (3), the arrangement direction (v1a) of the image line (3a) is coaxial. When the incident light is in the direction perpendicular to the longitudinal direction (v2) of the rod lens (6L) in the epi-illumination (6), the effect of the three-dimensional image line shape of the brilliant image line having a bulge is suppressed, and the entire surface of the image line It becomes possible to image the regular reflection light. Hereinafter, in the coaxial epi-illumination (6), the longitudinal direction (v2) of the rod lens (6L) is referred to as “width direction”.

  FIG. 6 is a schematic diagram illustrating the imaging principle of a glittering image line having a bulge. FIGS. 6 (a1) and 6 (a2) show a case where the image line (3a) and the width direction (v2) of the coaxial epi-illumination (6) are perpendicular to each other, and FIGS. b2) shows a case where the width direction of the image line (3a) and the coaxial epi-illumination (6) is parallel.

  6 (a1) and 6 (b1) are views of the printed matter (H) as viewed from the front, respectively, and FIGS. 6 (a2) and 6 (b2) respectively show the printed matter (H) in the horizontal direction (E1). ). As described above, the arrangement direction (v3) of the light receiving elements of the line camera (5) and the coaxial incident illumination (6) are arranged in parallel.

  As shown in FIG. 6 (a1) and FIG. 6 (a2), when the width direction of the image line (3a) and the coaxial epi-illumination (6) is orthogonal, the line shape from the coaxial epi-illumination (6) Irradiation light is reflected on the entire surface of the image line (3a) having a bulge. As a result, a large amount of reflected light enters the light receiving element of the line camera (5), so that each of the plurality of image lines (3a) can be captured as an image that is clearly distinguished and captured. Become.

  On the other hand, as shown in FIGS. 6 (b1) and 6 (b2), when the width direction of the image line (3a) and the coaxial epi-illumination (6) is parallel, the line from the coaxial epi-illumination (6). -Shaped irradiation light is reflected only at the apex of the image line (3a) having a bulge. As a result, since the light receiving element of the line camera (5) receives only a small amount of reflected light, it is impossible to clearly distinguish and image each of the plurality of image lines (3a). Captured as an image.

  Therefore, in the printed pattern (2), the imaging conditions are set so that the arrangement direction of the image lines (3a) constituting the latent image portion (3) and the irradiation light from the coaxial incident illumination (6) are orthogonal to each other. Thus, it is possible to distinguish and individually capture the image lines (3a) constituting the latent image portion (3).

  The orthogonality in the present invention does not need to be strictly orthogonal, and the effect of the present invention can be obtained as long as it is about plus or minus 10 degrees. However, the arrangement direction of the image line (3a) constituting the latent image portion (3) and the imaging condition where the irradiation light from the coaxial epi-illumination (6) is 90 degrees and the latent image portion (3) In the case of an imaging condition in which the arrangement direction of the image line (3a) and the incident light from the coaxial epi-illumination (6) are 80 degrees, the imaging condition of 90 degrees is more latent in the captured image. It is preferable because the image lines constituting the image portion (3) are bright and each image can be clearly captured. Therefore, the adjustment is appropriately performed within the range of about plus or minus 10 degrees as described above so that the effect of the present invention can be obtained.

  In the irradiation direction setting step (S1), when the arrangement direction of the glitter image lines is known in advance, the imaging condition is adjusted while adjusting the linear irradiation light so as to be orthogonal to the arrangement direction. Can be set. On the other hand, if the arrangement direction of the glittering image line is not known, the arrangement direction of the glittering image line is confirmed as an arrangement direction confirmation step (S1-1) before setting the imaging conditions.

  In the arrangement direction confirmation step (S1-1), the printed pattern (2) is read by a scanner, and a reflection image for arrangement direction confirmation such as BMP format and TIFF format, which is the read result, is obtained. As described above, when the irradiation light from the coaxial incident illumination (6) is set to be orthogonal to the arrangement direction of the image line (3a), the image line (3a) is imaged brightly (high density), On the other hand, when set to be parallel, the image line (3a) is imaged dark (the density is low).

  In the acquired reflected image, the portion with the lowest density can be said to have an orthogonal relationship between the irradiation light from the coaxial epi-illumination (6) and the arrangement direction of the glittering image line when the reflected image is acquired in S1-1. It can be said that the place where the density is highest is a relationship in which the irradiation light from the coaxial epi-illumination (6) and the arrangement direction of the glittering image lines are parallel.

  Therefore, based on the density of the acquired reflected image, by confirming the arrangement direction of the incident light from the coaxial epi-illumination (6) at the time of imaging and the glittering image line, the angle at that time is used as a reference. It is possible to appropriately set the epi-illumination (6) and the glitter image line so that the arrangement directions thereof are orthogonal to each other.

  As another method, the irradiation light from the coaxial epi-illumination (6) is sequentially provided with an appropriate interval (for example, every 5 degrees) within the range of 0 to 90 degrees with respect to the printed pattern (2). Then, the image is captured by a line camera, and a reflection image for confirming the arrangement direction in the BMP format, TIFF format, etc. is acquired for each angle.

  Among the plurality of acquired reflected images, the image having the lowest density has a relationship in which the arrangement direction of the glittering image lines is orthogonal to the irradiation light from the coaxial incident illumination (6) when the reflected image is acquired in S1-1. It can be said that the image with the highest density is in a parallel relationship. Accordingly, it is possible to appropriately set the coaxial epi-illumination (6) and the glitter image line so that the arrangement directions thereof are orthogonal to each other based on a plurality of reflection images acquired sequentially.

  Next, in the irradiation step (S2), the region to be inspected in the printed pattern (2) is irradiated with visible light from the coaxial incident illumination (6).

  The latent image portion (3) is configured with visible light as irradiation light from the coaxial incident illumination (6) for the latent image portion (3) which is an inspection target area of the printed pattern (2) after S1. By irradiating so as to be orthogonal to the glitter image line, the image line (3a) constituting the latent image portion (3) can be clearly imaged. In S1, when the region to be inspected is the latent image portion (4), in S2, the background portion (4) is irradiated with visible light from the coaxial incident illumination (6).

  Next, in the reflected image imaging step (S3), the printed pattern (2) applied to the printed matter (H) by detecting the reflected light of the light irradiated from the coaxial incident illumination (6) by the line camera (5). Is input to the image processing unit (9) via the control unit (8), and a reflection image that is a captured image of the print pattern (2) is acquired.

  FIG. 7 is a schematic diagram illustrating a first reflected image (P1) that is a reflected image of the printed pattern (2). The first reflection image (P1) is composed of a plurality of pixels. The first reflected image (P1) has a latent image portion (3) and a background portion (4), and the image lines constituting the latent image portion (3) are one by one. The book is clearly imaged. On the other hand, the image lines constituting the background portion (4) cannot be clearly imaged one by one, and the entire image is captured as a dark solid image. The format of the first reflected image (P1) is not particularly limited, such as BMP or TIFF.

  Next, as a determination step (S4), the first reflected image (P1) is compared with reference latent image data that serves as a reference as to whether or not the latent image portion (3) that is a preset latent image appears. Then, pass / fail judgment is performed based on the comparison result. Hereinafter, in the present invention, when data that is a reference for determining pass / fail that is set in advance corresponding to the inspection item of the glittering image line is generically referred to as “reference data”.

  The quality determination method is based on the captured first reflected image (P1) and an image line that allows the latent image portion (3) to appear clearly when the printed matter (H) shown in FIG. A method of determining a reference latent image (P2), which is image data of reference latent image data, which is image data serving as a shape reference, by pattern matching; a density value of the captured first reflected image (P1); There are two determination methods, which are determination methods by comparing the density values of the reference latent image (P2).

  First, a determination method based on pattern matching will be described. When determining by pattern matching, there is no particular limitation on the algorithm or the like, but, for example, general template matching can be used.

  FIG. 9 is a schematic diagram showing template matching. In template matching, first, the reference latent image (P2) shown in FIG. 9A and the first reflection image (P1) to be inspected are set to the same image width and image height by the image processing unit (9). Convert to Hereinafter, template matching is performed by the image processing unit (9).

  Next, at least three arbitrary points at common positions in the first reflection image (P1) and the reference latent image (P2) are set as reference points for each image.

  Since each image has the same size, by setting at least three corners among the four corners in each image as reference points (Q1, Q2, Q3), the reference point can be set at a common position in each image. Is possible.

  Note that a general image format such as the TIFF format, JPEG format, or BMP format has a characteristic that pixels are always arranged in parallel along two axial directions perpendicular to each other in the vertical and horizontal directions. Therefore, when each image has the characteristic that all pixels are always arranged in parallel along two orthogonal vertical and horizontal axis directions, the vertical and horizontal directions of each image are self-explanatory, and there is no need to consider rotation. Therefore, only one reference point is required for each image.

  Next, matching is performed by superimposing the first reflection image (P1) and the reference latent image (P2) so that the reference points match. Matching is image processing for calculating how much a density difference exists between overlapping pixels after overlapping two images composed of a plurality of pixels. Since the two images are more similar when the density difference is smaller, the similarity is higher. On the other hand, when the density difference is large, the two images are not similar, and the similarity is low.

  For example, as shown in FIG. 9A, when there is no defect (K) in the first reflection image (P1), there is no density difference (G) in the comparison result (A1). As shown in FIG. 3, when the first reflection image (P1 ′) has a defect (K), a density difference (G) occurs in the comparison result (A1 ′). As described above, the larger the density difference is, the more similar the two images are. Therefore, the size (number of pixels) of the defect portion (K) at which the density difference (G) is equal to or greater than a predetermined value is set as a threshold, When the density difference (G) is reached, the printed matter (H) is detected as a defective product in which the latent image portion (3) does not appear clearly.

  The size of the defective portion (K) is appropriately set in accordance with the image line width, the ink used, the image line height, and the like constituting the latent image portion (3) described above.

  In FIG. 9, the entire image is pattern-matched. However, after each image is divided into a plurality of n × m predetermined pixels, pattern matching can be performed for each divided pixel.

  Next, another determination method in the latent image determination step, which is a determination method by comparing the density value of the reference latent image (P2) and the acquired density value of the first reflected image (P1), will be described. .

  FIG. 10A1 is a diagram showing a reference latent image (P2), and FIG. 10A2 is a diagram showing a density cross section of X1-X2 in the reference latent image (P2). The density cross section indicates the density value of the pixel located in the X1-X2 direction indicated by a dotted line in FIG. The density value is an integer value from 0 (black) to 255 (white).

  FIG. 10B1 is a diagram showing a first reflection image (P1) to be inspected, and FIG. 10B2 shows an X3-X4 density cross section in the first reflection image (P1). FIG. Note that X1-X2 in the reference latent image (P2) and X3-X4 in the first reflected image (P1) are cross-sections at the same position in the image.

  In the comparison method based on the density value, for example, the density cross section of the reference latent image (P2) shown in FIG. 10 (a2) is compared with the density cross section of the first reflected image (P1) shown in FIG. 10 (b2). The comparison method is performed by comparing the density values of pixels at the same position. When there is no defective portion (K) in the first reflected image (P1), there is no difference in density value between pixels, or a density difference within a range acceptable as a regular paper set in advance.

  On the other hand, as shown in FIG. 10 (c1), when the first reflection image (P1 ′) has a defective portion (K), the density cross section of the reference latent image (P2) and FIG. 10 (c2). When the density cross-sections of the first reflected image (P1 ′) are compared, if the density difference is outside the range acceptable as a non-defective product set in advance, the printed product (H) is clearly displayed in the latent image portion (3). Detected as a defective product that does not appear in

  In this manner, the image processing unit (9) determines whether the image is good or bad according to the determination result obtained by pattern matching or density value comparison. As described above, from S1 to S4, it is possible to mechanically inspect whether or not the latent image portion (3) of the printed matter (H) including the glittering image line appears, not visually.

  In addition, the printing pattern (2) which is a test object of the present invention is formed on the substrate (1) by printing. For this reason, as shown in FIG. 11, image line breakage (K1) may occur due to ink transfer failure, plate clogging, or the like. When the image line break (K1) occurs, the latent image portion (3) is visually recognized in a partially missing state, which is not preferable in terms of print quality.

  Therefore, in addition to the inspection of whether or not the latent image portion (3) is visible, an inspection step of inspecting whether or not the print image line constituting the latent image portion (3) has an image line break (K1). Further, it may be provided.

  When inspecting the image line breakage (K1) of the latent image portion (3), the image line breakage of the first reflected image (P1) and the latent image portion (3) set in advance in the determination step (S4) described above. The reference latent image line break data, which is the reference data for whether or not there is, is compared, and pass / fail judgment is performed based on the comparison result.

  In the inspection of image line breakage (K1), there are a method of determining by pattern matching and a method of determining by comparing with density values, as in the determination step (S4) of determining image change.

  FIG. 12 is a diagram illustrating a reference latent image line cut image (P3) that is image data of the reference latent image line cut data. The reference latent image line-cut image (P3) is image data that serves as a reference of the image line constituting the latent image portion (3) when the printed matter (H) is tilted and observed. Composed.

  If the reference latent image line-cut image (P3) is an image in which the image lines in the region to be inspected are clear one by one and can be inspected, the latent image portion (3) described above. The same image as the reference latent image (P2) that determines whether or not can be visually recognized may be used, or a different image may be used. Note that the method for determining by pattern matching and the method for determining by comparing with the density value are the same as the method for comparing the first reflection image (P1) described above, and thus the description thereof is omitted.

  As described above, in the determination step (S4), by using the reference latent image line break image (P3), it is possible to determine the line break in the region to be inspected. Further, in the determination step (S4), the first reflected image (P1) is compared with the two images of the reference latent image (P2) and the reference latent image line-cut image (P3), respectively. In addition to whether or not the image part (3) is visible, it is possible to determine whether the image line of the visible latent image part (3) is broken.

  Since the printed pattern (2) to be inspected according to the present invention is formed on the substrate (1) by printing, an ink as shown in FIG. Due to poor transfer of ink, poor curing of ink, increase / decrease in ink amount, and so on, adjacent image lines may be connected to form an image line connection (K2).

  The printed pattern (2) of the present invention is different in the arrangement direction of the image lines constituting the latent image portion (3) and the background portion (4), and when the substrate (1) is tilted to one or the other, By reflecting only either the latent image portion (3) or the background portion (4), the latent image portion (3) becomes visible due to the difference in reflectance. Therefore, when the image line connection (K2) occurs in the latent image portion (3), the portion is always reflected regardless of whether it is tilted to one side or the other. The visibility of (3) decreases.

  Therefore, in addition to the inspection as to whether or not the latent image portion (3) is visible, an inspection process for inspecting whether or not there is an image line connection (K2) may be further provided.

  When the image line connection (K2) of the latent image portion (3) is used as an inspection item, in the irradiation direction setting step (S1) described above, the arrangement direction of the glitter image lines constituting the latent image portion (3) in advance, The imaging conditions are set so that the irradiation light from the coaxial incident illumination (6) is parallel.

  FIG. 14 is a schematic diagram illustrating an image capturing method for image line connection (K2). When it is considered that the image line constituting the printed matter (H) is composed only of the image line (3a) constituting the latent image portion (3), the arrangement direction (v1a) of the image line (3a) is coaxial. When the direction is parallel to the width direction (v2) of the epi-illumination (6), the reflected light on the entire surface of the image is imaged while suppressing the influence of the three-dimensional image shape of the brilliant image line having a rise. It becomes possible.

  When the image line shape of the latent image portion (3) is inspected as described above, it is coaxial with the image line (3a) in order to clearly photograph each image line constituting the latent image portion (3). The irradiation direction was set so that the width direction of the illumination (6) would be orthogonal. The line connection (K2) is visually recognized by the naked eye as in solid printing, and is always reflected and brightly viewed regardless of the direction of inclination. Therefore, when the latent image portion (3) is imaged under the same imaging conditions as when the image line shape of the latent image portion (3) is inspected, the image line connection (K2) is also reflected and brightly imaged. Therefore, it is impossible to pick up an image separately from the image line constituting the other latent image portion (3).

  As described above, in the case where the width direction of the image line (3a) and the coaxial incident illumination (6) is parallel, the latent image portion (3) is captured as a dark solid image as a whole. On the other hand, since the image line connection (K2) is formed by connecting the image lines, the image is captured as a bright image reflected at any observation angle without depending on the observation angle as in solid printing.

  Therefore, when the image line connection (K2) is generated by setting the image pickup condition in which the image line (3a) and the coaxial incident illumination (6) are parallel to each other, the latent image portion (3) is darkly imaged. In this case, since only the image line connection (K2) is imaged brightly in the dark captured image, it is possible to image only the image line connection (K2) generated in the latent image portion (3).

  After setting the imaging conditions in which the width direction of the image line (3a) and the coaxial epi-illumination (6) are parallel, the printed pattern (2) is irradiated with visible light from the coaxial epi-illumination (6) in the same manner as S2 described above. Thus, only the image line connection (K2) in the latent image portion (3) can be clearly imaged. When the image line connection (K2) is not generated, the entire latent image portion (3) is captured as a dark image having a uniform density.

  Note that the term “parallel” in the present invention does not need to be strictly parallel as in the case of the above-described orthogonality, and the effect of the present invention can be obtained as long as it is about plus or minus 10 degrees. However, the arrangement direction of the image line (3a) constituting the latent image portion (3) and the imaging condition where the irradiation light from the coaxial incident illumination (6) is 180 degrees, and the latent image portion (3) In the case of the imaging condition in which the arrangement direction of the image line (3a) and the incident light from the coaxial epi-illumination (6) are 170 degrees, the imaging condition where the angle is 180 degrees is greater in the captured image. Only the line connection (K2) can be brightly and clearly imaged, which is preferable. Therefore, the adjustment is appropriately performed within the range of about plus or minus 10 degrees as described above so that the effect of the present invention can be obtained.

  In S4, when the image line connection (K2) of the latent image portion (3) is inspected, the image after the image capture is set to the first reflected image (P1) and the previously set latent image in the determination step (S4). Comparison is made with reference latent image line break data, which is data serving as a reference for whether or not there is a line break in the image portion (3), and a pass / fail judgment is made based on the comparison result.

  Similarly to the determination step (S4) for determining whether or not the image has been changed, the method for determining by pattern matching and the method for determining by comparison with the density value are also used in the inspection of the line connection (K2). is there.

  FIG. 15 is a diagram illustrating a reference line connection image (P5) that is image data of the reference line connection data. The reference image line connection image (P5) includes a plurality of pixels.

  As long as the reference latent image line connection image (P5) is an image in which the image lines in the region to be inspected are clear one by one and the image line can be inspected, the latent image portion (3) described above. The same image as the reference latent image (P2) that determines whether or not can be visually recognized may be used, or a different image may be used.

  As described above, in the irradiation direction setting step (S1), the latent image portion (3) is darkly imaged and the image line (3a) and the coaxial incident illumination (6) are set to the imaging conditions in which the width directions are parallel. Whether or not the latent image portion (3) and the background portion (4) are clearly changed can be determined.

  In the irradiation direction setting, when inspecting the image line break, the irradiation light from the coaxial incident illumination is set to be orthogonal, and when inspecting the image line connection, the imaging conditions are set to be parallel. However, when inspecting both the broken line and the line connection, first set to orthogonal (or parallel), inspect the broken line (or line connection), and then parallel (or orthogonal) Set to, and inspect the line connection (drawn line). In this way, by sequentially setting the arrangement direction of the image lines and the irradiation light in parallel with the orthogonal direction, it is possible to inspect both the image line break and the image line connection.

  In addition, although the inspection method for the broken line of the glittering image line constituting the latent image part (3) has been described, the image line (4) in which the background part (4) is darkly imaged in the irradiation direction setting step (S1). By setting the imaging conditions such that the width direction of 4a) and the coaxial epi-illumination (6) are parallel, it is possible to inspect the line drawing of the glittering image line constituting the background portion (4). In addition to the latent image portion (3), printing that allows the latent image portion (3) to be more clearly visible by inspecting the lines of the bright lines constituting the background portion (4). It is possible to inspect whether or not the pattern is (2).

  Further, the printed pattern (2) described above was composed of two regions of the latent image portion (3) and the background portion (4), but using the inspection method of the present invention, as shown in FIG. The inspection can be performed even in one region, that is, a configuration in which the arrangement direction of the glitter image lines constituting the printed pattern (2) is one direction.

  Furthermore, as shown in FIG. 17, a print pattern (2) composed of three or more regions, each region having a glitter image line in which a plurality of print image lines are arranged in different arrangement directions, It is possible to inspect.

  For example, the printed pattern (2) in FIG. 17A is composed of eight areas 2-1 to 2-8, and each area is formed by arranging a plurality of glitter image lines in different arrangement directions. . When the print pattern (2) of FIG. 17A is tilted and observed, the arrangement direction of the glittering image line is different for each region, and therefore a difference occurs in the amount of reflected light of the image line forming each region. Therefore, the printed pattern (2) is visually recognized as a pattern in which the color or brightness is gradually changed from the region (2-1) toward the region (2-8) in the clockwise direction.

  The details of the configuration of the printed pattern (2) shown in FIG. 17A are described in Japanese Patent No. 4395586 “Counterfeit Prevention Printed Material” previously filed by the present applicant, and will not be described.

  When inspecting the printed pattern (2) in FIG. 17A, the irradiation direction setting step (S1) corresponding to the inspection item of the glittering image line for all the areas constituting the printed pattern (2). The imaging conditions for each region are set so that the arrangement direction of the glittering image lines constituting the region and the irradiation light from the coaxial epi-illumination are orthogonal or parallel.

  Specifically, when the inspection item of the glittering image line is an inspection of image line connection (K2), in the irradiation direction setting step (S1), an area to be inspected first is appropriately set in the eight areas. After that, the imaging conditions are set so that the arrangement direction of the glitter image lines in the region to be inspected and the line-shaped irradiation light from the coaxial incident illumination are parallel to each other. Hereinafter, S2 to S4 are performed in the same manner as described above. Thereafter, S1 to S4 are sequentially performed for the remaining seven regions.

  In that case, as shown in FIG.17 (b), it is preferable that the conveyance part (7) in the test | inspection apparatus (M) to be used further provides the stage (7a) which has a rotation function in the arrow direction. By providing the stage (7a), a desired area can be easily imaged by rotating the stage (7a) in accordance with the arrangement direction of the image lines in the area to be inspected in the printed pattern (2). Is possible.

  In the determination step (S4), eight regions (2-1, 2-2,...) Shown in FIG. 17A are obtained based on the reflection image for each region acquired according to the imaging conditions set for each region. .., 2-7 and 2-8) determine whether or not each can be visually recognized at a predetermined observation angle.

  FIG. 18 is a schematic diagram showing three regions (2-1, 2-7, and 2-8) extracted from the eight regions constituting the printed pattern (2) shown in FIG. As shown in FIG. 18A, the glittering image line is in the X3 direction in the region (2-1), in the X4 direction in the region (2-7), and in the region (2-8). Are arranged in the X5 direction.

  When each area (2-1, 2-7, 2-8) shown in FIG. 18A has no printing defect, the print pattern (2) is changed to each area (2-1, 2-7). , 2-8), when viewed from an observation angle that is the same direction as the arrangement direction of the glittering image lines, only the area is visually recognized brightly, and the other areas are visually recognized darkly. Only one area is visible with the naked eye. Therefore, the printed pattern (2) is visually recognized by changing the brightness due to the change in the observation angle.

  Therefore, by determining whether each area is visible at a predetermined observation angle based on the reflection image for each area constituting the printed pattern (2), the printed pattern (2) It is possible to determine whether the color or brightness changes due to the change in the observation angle and to determine whether the color is good or not.

  In the determination by replacement, as a result of determining each area based on the reflection image for each area in the print pattern (2) composed of a plurality of areas, all areas are areas without print defects, and each area is When it is determined that each of the print patterns (2) is visible at a predetermined observation angle corresponding to the arrangement direction of the image lines constituting the area, the print pattern (2) is determined to have changed in color or brightness due to a change in the observation angle. It is to be.

  Conventionally, the pass / fail judgment of the printed pattern (2) in which the glitter lines in different arrangement directions are arranged is performed by checking whether the operator can visually recognize each area while changing the observation angle with respect to the printed pattern (2). It was judged visually. Therefore, the problem that the operator overlooked has occurred. However, even when the printed pattern (2) is composed of a plurality of areas, the printed pattern is created based on the reflected image for each area. It is possible to determine whether (2) has changed.

DESCRIPTION OF SYMBOLS 1 Base material 2 Print pattern 3 Latent image part 3a Image line 4 Background part 4a Image line 5 Line camera 6 Coaxial epi-illumination 6L Rod lens 7 Conveyance part 8 Control part 9 Image processing part 10 Judgment part A1, A1 'Comparison result G density Difference P1, P1 ′ First reflection image P2 Reference latent image P3 Reference latent image line cut image P4 Second reflection image P5 Reference line connection image P6 Reference background line cut image H Printed material J Half mirror M Inspection device K defective part K1 line cut K2 line connection R light source v1 transport direction v1a arrangement direction v2 longitudinal direction v3 arrangement direction

Claims (3)

Using an inspection apparatus provided with at least a coaxial epi-illumination and a line camera, an image is obtained by capturing a printed pattern composed of glitter lines having a plurality of swells provided on the substrate, and the obtained image A method for inspecting a glossy printed material, wherein the quality of the printed material is determined by comparing with a regular image that is stored in advance and is composed of a plurality of lines,
Corresponding to the inspection items of the glittering image line, the imaging condition is set so that the arrangement direction of the glittering image line and the linear irradiation light from the coaxial incident illumination are orthogonal, parallel, or sequentially orthogonal. An irradiation direction setting step to be set;
An irradiation step of irradiating the printed pattern with visible light from the coaxial incident illumination;
A reflected image capturing step of detecting reflected light from the printed pattern and acquiring a reflected image composed of a plurality of image lines in the line camera;
A method for inspecting a glittering printed material, comprising at least a determination step of determining pass / fail by comparing the reflected image with preset reference image data. The printed pattern has a configuration in which the arrangement direction of the glittering image lines having swells is different and has at least two regions, and the arrangement direction is different, so that the printing pattern changes due to a change in observation angle,
For all the areas constituting the printed pattern, in the irradiation direction setting step, the imaging condition is set for each area, and the brightness constituting the area is corresponding to the inspection item of the glitter image. The direction of the orientation lines and the irradiation light from the coaxial epi-illumination is set to be orthogonal, parallel or sequentially orthogonal and parallel,
In the determination step, it is determined whether or not each region can be visually recognized at a predetermined observation angle based on the reflected image for each region acquired according to the imaging condition set for each region. The method for inspecting glittering printed matter according to claim 1, wherein whether or not the printed pattern composed of each of the regions is changed by a change in observation angle is determined.   The irradiation direction setting step includes an arrangement direction confirmation step of confirming the arrangement direction of the glitter lines constituting the printed pattern based on the density of a reflected image obtained from a scanner or the coaxial incident illumination. The method for inspecting a glittering printed matter according to claim 1 or 2, characterized in that

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