JP2007132786A - Apparatus and method for measuring shape of cell on gravure plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method for measuring the shapes of cells on gravure plates and capable of automatically and accurately measuring the shapes of the cells, without being affected by irregular reflections, even if adjacent cells are connected to cause irregular reflections from the inner walls of the cells in the photographed images of the gravure plates. <P>SOLUTION: The apparatus for measuring the shapes of cells on gravure plates is provided with an imaging means for acquiring photographed images by imaging a plurality of cells formed in the surface of a gravure plate; a correction means for acquiring corrected images by filtering and reducing light noise of the photographed images due to the state of properties of their surfaces; an enhancement means for acquiring enhanced images by performing Robert's processing which enhances parts having large gradient changes on the corrected images; an addition means for acquiring added images, by adding the pixel values of, corresponding pixels between the corrected images and the enhanced images; and a cell shape measuring means for measuring the shapes of cells on the basis of added images. The method for measuring the shapes of cells on gravure plates is applied to the apparatus. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention belongs to the technical field of gravure printing and gravure coating. In particular, the present invention relates to an apparatus and method for measuring a cell shape formed on a gravure plate.

  The cells formed on the gravure plate have a role of storing ink to be transferred to a substrate such as paper or film. In order to obtain a desired transfer amount of the ink, it is important to manage the cell shape. As a cell shape management method, cell depth, cell width (maximum width), cell length (maximum length), cell area, cell volume, etc., which are cell shape parameters, are measured and managed based on the measured values. Is called. If the formation method and type of the cell are specified, the cell shape as a three-dimensional shape can be almost estimated from these parameters. The cell forming method is, for example, an engraving method, and the type is, for example, compressed, elon gate, coarse, fine, or custom dot. Taking into account the cell formation method and type, the parameters represent the cell shape itself.

Therefore, there is a proposal for a cell shape measuring method and apparatus for measuring such parameters. For example, there is an invention in which the volume (or opening area) of a cell engraved on a gravure plate is measured and compared with a target cell volume (or opening area) (Patent Documents 1, 2, and 3). In addition, there is an invention for measuring the volume (or opening area) of a cell having a channel connecting cells adjacent to each other in the printing direction (Patent Document 4). In addition, there is an invention that measures the volume (or open area) of a cell semi-automatically when a measurer instructs and inputs the edge of a cell when the boundary (bank) between adjacent cells is interrupted (patent) Reference 5)
JP-A-10-138440 JP-A-11-115143 JP-A-11-188831 JP 2000-65550 A JP 2000-267341 A

  The cell shape of the 100% mesh portion having the largest cell size in the gravure plate affects the maximum density in the printed matter. Therefore, when inspecting whether or not the state of the gravure plate is appropriate, it is necessary to inspect the portion having the maximum density particularly strictly. However, in a cell near 100% of the mesh, there is a case where a channel for intentionally connecting cells arranged in the printing direction exists to increase the amount of ink transfer (see FIG. 6). . When measuring the cell shape in a gravure plate in which such a channel exists, it is easily affected by irregular reflection from the inner wall of the cell.

  For example, there is a problem that an accurate outline of a cell cannot be automatically extracted due to the influence of irregular reflection (see FIG. 7). At that time, it is necessary for the measurer to manually input the exact contour of the cell to the gravure cell shape measuring apparatus. The suitability of the work depends on the skill of the worker, and there is a problem that the measurement takes time. In addition, when measuring the cell shape of a large number of cells in order to evaluate the variation of the cells, it takes a very long time, so that the gravure plate inspection work is one of the major production impediments. There's a problem.

  The present invention has been made to solve the above problems. The purpose of the gravure plate cell shape is to automatically measure the cell shape accurately without being affected by the diffuse reflection even if adjacent cells are connected in the gravure image and there is diffuse reflection from the inner wall of the cell. It is to provide a measuring apparatus and method. In addition, an unskilled ordinary worker can complete accurate measurement in a short time, and the gravure inspection work does not become an obstacle to production.

The gravure plate cell shape measuring apparatus according to claim 1 of the present invention includes an imaging unit that captures a plurality of cells formed on the surface of the gravure plate to obtain a captured image, and a property state of the surface with respect to the captured image. Correction means for obtaining a corrected image by performing filter processing to reduce optical noise due to, enhancement means for obtaining an enhanced image by performing Roberts processing for enhancing a portion having a large gradation change on the corrected image, and the corrected image The enhancement image includes addition means for adding pixel values of corresponding pixels to obtain an addition image, and cell shape measurement means for measuring a cell shape based on the addition image.
The gravure plate cell shape measuring method according to claim 2 of the present invention includes an imaging process of capturing a plurality of cells formed on the surface of the gravure plate to obtain a captured image, and a property of the surface with respect to the captured image. A correction process for obtaining a corrected image by performing filter processing to reduce optical noise depending on a state, an enhancement process for obtaining an enhanced image by performing a Roberts process for enhancing a portion having a large gradation change on the corrected image, and the corrected image And the emphasized image are provided with an addition process for adding pixel values of corresponding pixels to obtain an added image, and a cell shape measurement process for measuring a cell shape based on the added image.

According to the gravure plate cell shape measuring apparatus according to claim 1 of the present invention, a plurality of cells formed on the surface of the gravure plate are picked up by the image pickup means to obtain a picked up image, and the picked up image is obtained by the correction means. Filter processing is performed to reduce the optical noise due to the surface property state, and a corrected image is obtained. The emphasis means performs a Roberts process that emphasizes a portion with a large gradation change on the corrected image to obtain an enhanced image. The pixel values of the corresponding pixels in the corrected image and the emphasized image are added by the means to obtain an added image, and the cell shape is measured based on the added image by the cell shape measuring means. That is, optical noise due to scratches on the surface of the gravure plate can be removed by filtering, and the emphasis image obtained by Roberts processing is added to the original image (corrected image), so that the bank regardless of filtering. And the cell boundary can be clarified. Therefore, even if adjacent cells in a gravure image are connected and there is irregular reflection from the inner wall of the cell, the gravure cell shape measuring device can automatically measure the cell shape accurately without being affected by the irregular reflection. Is provided.
According to the gravure plate cell shape measuring method according to claim 2 of the present invention, a plurality of cells formed on the surface of the gravure plate are imaged in the imaging process to obtain a captured image, and the captured image is corrected in the correction process. Filter processing to reduce the light noise due to the property state of the surface is obtained and a corrected image is obtained, and in the enhancement process, Roberts processing is performed to emphasize the portion with a large gradation change with respect to the corrected image, and an enhanced image is obtained. In the addition process, pixel values of corresponding pixels are added to the corrected image and the enhanced image to obtain an added image, and in the cell shape measurement process, the cell shape is measured based on the added image. That is, optical noise due to scratches on the surface of the gravure plate can be removed by filtering, and the emphasis image obtained by Roberts processing is added to the original image (corrected image), so that the bank regardless of filtering. And the cell boundary can be clarified. Therefore, even if adjacent cells in a gravure image are connected and irregular reflection from the inner wall of the cell occurs, the gravure cell shape measurement method can automatically measure the cell shape accurately without being affected by the irregular reflection. Is provided.

  Next, embodiments of the present invention will be described with reference to the drawings. An example of the configuration of the cell shape measuring apparatus of the present invention is shown in FIGS. 1 and 2, 1 is a microscope, 2 is a camera, 3 is a light source, 31 is a light intensity adjusting unit, 32 is an optical fiber, 4 is a personal computer, 401 is an image input / output unit, 402 is a cell volume measuring unit, and 403 is An image processing program, 41 is a keyboard, 42 is a mouse, 43 is a display, 44 is an A / D converter, 5 is a moving device, 6 is an elevating stage, 7 is a plate cylinder turntable, and 8 is a gravure plate.

  The microscope 1 is an imaging optical system for enlarging the cell formed on the plate surface of the gravure plate 8 with the camera 2. The microscope 1 is fixedly supported on a moving table 51 in the moving device 5. The microscope 1 may be a support structure that can be removed from the movable table 51, and the microscope 1 may be used in a portable manner. The microscope 1 includes a focus adjustment unit 11 that moves the lens barrel portion in the optical axis direction for focusing. The distance from the plate surface of the gravure plate 8 to the lens barrel portion can be adjusted by movement in the optical axis direction.

  An objective lens and a relay lens are disposed in the lens barrel portion of the microscope 1. The total magnification when the objective lens and the relay lens are used can be obtained by a calculation formula: (total magnification) = (magnification of objective lens) × (magnification of relay lens). In general, convex lenses are used for both the objective lens and the relay lens, and the configuration can also be applied in the present invention. However, the preferred configuration of the imaging optical system in the present invention uses a convex lens for the objective lens and a concave lens for the relay lens. That is, the magnification of the objective lens is higher than the desired magnification, and the magnification of the relay lens is configured to be 1 or less. By applying the imaging optical system having this configuration, high resolution can be obtained. Generally, the numerical aperture (NA) increases as the magnification of the objective lens increases, and the higher the numerical aperture (NA), the higher the resolution can be obtained.

  The camera 2 includes an image sensor such as a charge coupled device (CCD) and a metal oxide semiconductor (MOS), a driving circuit thereof, and the like, and converts a light image formed on the image sensor into an electric signal and outputs the electric signal. Here, the relay lens can also be called an imaging lens or an eyepiece in the sense that an optical image is formed on an image sensor. The camera 2 is connected to the personal computer 4, and the operation of the camera 2 related to imaging is performed by the personal computer 4. Also, the captured image of the camera 2 is read by the personal computer 4.

  The light source 3 is a light source for illuminating the imaging region of the camera 2 on the plate surface of the gravure plate 8. As the light source, a halogen lamp, a metal halide lamp, an LED (light emitting diode), or the like is used. Light rays emitted from the light source 3 are collected at one end of the optical fiber 32 and guided to the microscope 1 through the optical fiber 32. In general, the imaging region is illuminated as coaxial epi-illumination. The light intensity of the normal light source 3 changes with time immediately after power is supplied and after a certain time has elapsed. Moreover, even if it uses and applies a fixed voltage, a luminous intensity changes with long-term use. Therefore, the light source 3 includes a light intensity adjusting unit 31 for adjusting the light intensity.

  The light intensity adjusting unit 31 adjusts the light intensity of the light source 3 so that a predetermined pixel in a captured image of the reference plate by the camera 2 has a predetermined pixel value. The light intensity is adjusted by adjusting the power supplied to the light source 3. The light intensity adjustment unit 31 is connected to the personal computer 4, and the light intensity adjustment unit 31 is operated by the personal computer 4 when the light intensity adjustment unit 31 adjusts the light intensity.

The personal computer 4 takes a captured image of the camera 2 and performs image processing to calculate a cell shape. Therefore, the personal computer 4 includes an image input / output unit 401, a cell volume measuring unit, an image processing program, and the like. The personal computer 4 includes a keyboard 41, a mouse 42, a display 43, an A / D converter (analog-to-digital converter).
) 44 is attached.

  An imaging signal (analog signal) output from the camera 2 is converted into a digital signal by an A / D converter (analog-to-digital converter) 44. The image input / output means 401 of the personal computer 4 inputs the digital signal and stores it in the image memory of the personal computer 4 as a captured image. The image input / output unit 401 stores the input captured image or the captured image stored in the image memory in a video memory (video memory) for display on the display 43.

The cell volume measuring means 402 of the personal computer 4 performs a process of calculating the cell volume from the cell area, cell width, etc. in the captured image. Regarding processing for calculating cell shape parameters (cell depth, cell width (maximum width), cell length (maximum length), cell area, cell volume, etc.) from the captured image, Patent Document 3 (Japanese Patent Laid-Open No. 11-188831) , Patent Document 4 (Japanese Patent Application Laid-Open No. 2000-65550), etc., and therefore detailed description thereof is omitted here.
The image processing program 403 of the personal computer 4 performs image processing on the captured image (details will be described later). For example, a correction image is obtained by performing corrections such as shading correction in the captured image and correction that makes it easy to distinguish the bank and the cell. Moreover, the process which detects the connection part of an adjacent cell is performed. In addition, a process for extracting a cell area and deriving a cell area is performed. In addition, a process for detecting whether the connection portion is an appropriate connection portion (channel) or an inappropriate connection portion (bank cut) is performed. Further, a process for extracting a parameter representing the cell shape for an appropriate cell is performed.

  The moving device 5 is a device that linearly moves the microscope 1. As shown in FIG. 1, the moving device 5 is arranged such that the direction of the linear movement coincides with the axial direction of the gravure plate. Therefore, the microscope 1 can be stopped at an arbitrary position in the axial direction of the gravure plate 8, and imaging of the surface of the gravure plate 8 at that position can be performed by the camera 2.

  The elevating stage 6 is a moving device 5, that is, a device that moves the microscope 1 in the vertical direction. As shown in FIG. 1, the upward direction is a direction away from the surface of the gravure plate 8, and the standby position of the microscope 1 in the cell shape measuring apparatus exists in that direction. Further, the downward direction is a direction approaching the surface of the gravure plate 8, and the measurement position of the microscope 1 in the cell shape measuring apparatus exists in that direction.

The plate cylinder rotating table 7 is a table on which the gravure plate 8 is mounted for measurement and the mounted gravure plate 8 is rotated. By rotating the gravure plate 8, an arbitrary position in the circumferential direction of the gravure plate 8 can be stopped just below the microscope 1. Then, the camera 2 can image the surface of the gravure plate 8 at that position. The moving device 5 and the plate cylinder turntable 7 described above can image an arbitrary position on the plate surface of the gravure plate 8.
Although the plate cylinder turntable 7 is used for measurement here, it may be a unit for placing a gravure plate to be engraved in a gravure engraving apparatus.

The configuration has been described above. Next, the operation of the cell shape measuring apparatus of the present invention will be described with reference to FIG.
First, in step S1 (microscope installation) in FIG. 3, the operator operates the lift stage 6 to move the microscope 1 in the cell shape measuring apparatus from the standby position to the measurement position. By moving to the measurement position, imaging by the camera 2 in the cell shape measuring apparatus is performed. The imaging signal output from the camera 2 is converted into a digital signal by the A / D converter 44. The digital signal is input by the image input means 401 of the personal computer 4 and stored as a captured image in the video memory. The captured image is displayed on the display 43. On the display 43, an operation screen for operating the cell shape measuring apparatus is displayed together with an imaging screen.

Imaging by the camera 2 is repeated at predetermined time intervals, and the displayed captured image is updated accordingly. The operator operates the moving device 5 and the plate cylinder turntable 7 while confirming with the captured image displayed on the display 43, so that the portion where the test engraving on the plate surface of the gravure plate 8 is directly below the microscope. 1 positioning is performed. At this time, a plurality of engraving cells are present on the same screen in the captured image. Therefore, the microscope 1 has an appropriate magnification (desired magnification).
The light intensity adjustment in the light intensity adjustment unit 31 of the light source 3 is completed in advance. A correction coefficient for performing shading correction is stored in advance in a correction coefficient memory.

Next, in step S2 (focusing), the operator adjusts the focus by adjusting the focus adjustment unit 11 of the microscope 1 while confirming with the captured image displayed on the display 43, and performs focusing on the captured image. .
Next, in step S <b> 3 (image input), the operator operates the keyboard 41, mouse 42, and the like, and inputs an instruction so that the personal computer 4 performs shape measurement on the operation screen of the display 43. Upon receiving this instruction input, the image input / output means 401 of the personal computer 4 stores the image captured by the camera 2 in the image memory of the personal computer 4.

  Next, in step S4 (image preprocessing), the image processing program 403 of the personal computer 4 performs shading correction on the captured image stored in the image memory, and stores the captured image that has been subjected to the shading correction in the image memory. . In addition, a scratch on the printing plate is blurred by applying a median filter to a captured image that has been subjected to shading correction. By this processing, a corrected image obtained by performing shading correction processing and plate surface blurring processing can be obtained. Due to the property state including scratches on the surface of the gravure plate, improper specularly reflected optical noise is included in the captured image. This tendency becomes remarkable when the numerical aperture of the objective lens is increased and the resolution is increased. The median filter is more suitable than the low-pass filter because it can reduce noise without blurring the edge (border-bank boundary).

  Further, the image processing program 403 of the personal computer 4 obtains an enhanced image by performing a Roberts process for selectively enhancing a portion having a large gradation change on the corrected image. When the captured image is a high-quality image that does not require preprocessing such as shading correction processing, Roberts processing that emphasizes a portion with a large gradation change with respect to the captured image instead of the corrected image is performed. The emphasis image can be obtained.

  The Roberts process is a process of extracting an edge using a partial differential in an oblique direction in a 2 pixel × 2 pixel region in an original image (captured image or corrected image). Specifically, for example, g (x, y) = | f (x, y) −f (x + 1, y + 1) | + | f (x + 1, y) −f (x, y + 1) | This is a process for performing the operation. Here, f (x, y) is an input image (original image: captured image or corrected image) having integer pixel coordinates (x, y). G (x, y) is an output image (enhanced image) having integer pixel coordinates (x, y). As a result, a large value is obtained in the vicinity where the image density rapidly changes, and a small value is obtained at a position where the density is substantially constant.

  Furthermore, the image processing program 403 of the personal computer 4 adds the pixel values of the corresponding pixels in the original image (captured image or corrected image) and the enhanced image to obtain an added image. The processing for reducing optical noise such as scratches on the printing plate has the effect of blurring the boundary between the bank of the printing plate and the cell. In the added image, the boundary between the bank of the printing plate and the cell is clarified while reducing optical noise. An example of an image in the process is shown in FIG. 4A is an original image, FIG. 4B is a Roberts processed image, that is, an emphasized image, and FIG. 4C is a synthesized image, that is, an added image.

  Next, in step S5 (image binarization), the image processing program 403 binarizes the corrected image to obtain a binarized image. When a discriminant analysis method in multivariate analysis is applied as a method for determining a binarization threshold, a suitable binarized image can be obtained. Depending on the nature of the gravure plate, part of the reflected light becomes a noise component and there are isolated points, isolated holes, etc., but in this binarized image, the pixel values (the bank portion and the cell portion are different) 0 or 1).

  Next, in step S6 (cell outline extraction), the image processing program 403 performs a morphology process on the binarized image to remove isolated points and isolated holes. The morphology processing is configured by processing including basic operations such as dilation, erosion, opening, closing, and the like, and the expansion / contraction processing is an example. Noise components such as isolated points and isolated holes in the binarized image are corrected by this morphology processing, and the bank portion and the cell portion in the gravure can be properly separated. That is, a contour image is obtained as an image capable of measuring the cell shape with sufficient accuracy. FIG. 4D is a contour image.

  Next, in step S7 (determination 1), the image processing program 403 performs processing for determining the presence or absence of a channel. The presence or absence of a channel is determined by the following process. First, a process for detecting the cell width in the contour image is sequentially performed while proceeding in the engraving direction (printing direction) to detect a portion where the cell width is minimum. Next, it is detected whether the cell is open or closed in that portion, that is, whether or not there is a channel (a groove extending the cell). If the minimum cell width is not zero, there is a channel. The presence or absence of a channel is determined by these two processes. When it is determined that there is a channel, the process proceeds to step S8, and when it is determined that there is no channel, the process proceeds to step S12. FIG. 6 shows a cell having a channel, and FIG. 5A is an enlarged view thereof.

Next, in step S8 (channel division processing), the image processing program 403 performs processing for dividing the channel with the channel portion, that is, the portion having the smallest cell width as a boundary. By this division, in the processing target image (captured image, binarized image, contour image, etc.), the cell has a closed region surrounded by the contour, that is, an independent region. Since there are a plurality of cells in the captured image, a plurality of cells having independent regions are generated in the processing target image by this division. Each cell is assigned a code for identifying the cell, and the cell to be processed can be distinguished from other cells. FIG. 5B shows numbers for identifying each of a plurality of cells that have become independent areas due to channel division processing, and FIG. 5C is a diagram showing the independent areas of those cells.
Next, in step S9 (deletion of cells related to the four sides of the image), the image processing program 403 deletes cells related to the four sides forming the outer periphery of the processing target image among the plurality of cells. Further, the image processing program 403 selects one of the cells that has not been deleted and sets it as a measurement target cell.

  Next, in step S10 (cell shape measurement), the image processing program 403 measures the cell shape. For example, the cell depth, cell width (maximum width), cell length (maximum length), cell area, cell volume, and the like, which are parameters of the cell shape, are measured based on the above-described binarized image that leaves only the independent region. The cell depth and cell volume are three-dimensional shapes, so it is not possible in principle to measure from only a two-dimensional image. The shape can be calculated. The cells for which the cell shape measurement has been completed are deleted from the processing target. After deletion, the cell is not measured.

  Step S10 is repeated when cell shape measurement is performed for an unmeasured cell among measurement target cells in the processing target image. Further, when the measurement of the cell shape is continued to measure the cell shape formed in the other part of the gravure plate, the process returns to step S1 and the above-described steps are repeated. When the measurement of the cell shape is finished, the process exits from the image processing program 403.

It is a figure (overall view) which shows an example of the structure in the cell shape measuring apparatus of this invention. It is a figure (block diagram) which shows an example of a structure in the cell shape measuring apparatus of this invention. It is a flowchart which shows the process of the operation | movement in the cell shape measuring apparatus of this invention. It is a figure which shows an example of the image in the process of the image processing in the cell shape measuring apparatus of this invention. It is a figure which shows an example (A) of a cell with a channel, and (B) and (C) of a plurality of cells having independent areas. It is a figure which shows an example of the channel for connecting between the cells arranged in a printing direction. It is a figure which shows an example of the image which cannot extract the exact outline of a cell automatically under the influence of irregular reflection.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Microscope 2 Camera 3 Light source 31 Controller 32 Optical fiber 4 Personal computer 401 Image input / output means 402 Cell volume measuring means 403 Image processing program 41 Keyboard 42 Mouse 43 Display 44 A / D converter 5 Moving device 6 Elevating stage 7 Plate cylinder rotation Stand 8 Gravure version

Claims (2)

Imaging means for imaging a plurality of cells formed on the surface of the gravure plate to obtain a captured image;
Correction means for obtaining a corrected image by performing filter processing to reduce optical noise due to the surface property state on the captured image;
Enhancement means for obtaining an enhanced image by performing a Roberts process of enhancing a portion having a large gradation change on the corrected image;
Adding means for adding pixel values of corresponding pixels in the corrected image and the enhanced image to obtain an added image;
Cell shape measuring means for measuring a cell shape based on the added image;
A gravure plate cell shape measuring apparatus comprising: An imaging process of capturing a plurality of cells formed on the surface of the gravure plate to obtain a captured image;
A correction process for obtaining a corrected image by performing filter processing to reduce optical noise due to the property state of the surface on the captured image;
An emphasis process for obtaining an emphasized image by performing a Roberts process for emphasizing a portion having a large gradation change with respect to the corrected image;
An addition process of adding pixel values of corresponding pixels in the corrected image and the enhanced image to obtain an added image;
A cell shape measurement process for measuring a cell shape based on the added image;
A gravure plate cell shape measuring method comprising:

Images