Method and system for processing raster image files

Abstract

A method for processing a raster image file is provided, comprising the steps of receiving a raster image file including image data for a plurality of pixels; analyzing the image data of the raster image file; determining control data, and optionally at least one new raster image file, based on the analyzed image data, wherein the control data is data for controlling settings of an imaging device to modify physical properties of generated imaging features corresponding to one or more of the plurality of pixels; and outputting the raster image file and / or the new raster image file, together with the control data, to an imaging device for imaging a relief master.

Description

[Technical field]

[0001] The field of the invention relates to methods and systems for processing raster image files, processing modules implementing such methods, and relief structures obtained by such methods. More particularly, the invention relates to methods and systems for processing raster image files for use in creating a relief master, more particularly a flexographic or letterpress printing plate master. [Background technology]

[0002] Flexography or letterpress printing is a technique commonly used for mass printing. A flexography or letterpress printing plate is a relief plate with image elements protruding above non-image elements to produce an image on a recording medium such as paper, cardboard, film, foil, laminate, etc. Cylindrical shaped printing plates or sleeves may also be used.

[0003] There are various methods for making flexographic printing plate precursors. According to conventional methods, flexographic printing plate precursors are made from a multilayer substrate that includes a backing layer and one or more photohardening layers. Such photohardening layers are imaged to obtain a relief plate by exposure to electromagnetic radiation through a mask layer that contains image information, or by direct and selective exposure to light, for example by scanning the plate to transfer image information.

[0004] In flexography or letterpress printing, ink is transferred from the plate to the printing medium. More precisely, ink is transferred in the relief areas of the plate and not in the non-relief areas. During printing, the ink in the relief areas is transferred to the printing medium. Grayscale images are usually created using halftoning, for example using a screening pattern. Grayscale means that in the printing of a plate of a certain color, the amount of that color is reproduced. For example, a printing plate may contain different halftone dot areas, which are printed with different densities. To increase the amount of ink transferred and to increase the so-called ink density on the substrate, an additional very fine structure is applied to the surface of the printing area, i.e. in the relief area. This surface screening is usually obtained by adding a fine structure to a raster image file, which is then transferred to a corresponding mask used for exposure.

[0005] An example of an existing method for producing a relief plate is shown in Fig. 1A-1E. Fig. 1A shows the content of a raster image file with an image file resolution corresponding to a pixel size p of, for example, 6.35 micrometers. The shown raster image file comprises a substantially circular image area 1 to be printed, with square pixels 4. The image file resolution may for example be 4000 dpi (=25400*1 / p in micrometers). The raster image file is then manipulated with a surface screen pattern shown in Fig. 1B. The surface screen pattern is pasted onto the image area 1, resulting in an edited raster image file shown in Fig. 1C. As shown in Fig. 1C, the resulting image area 1' has fewer printed pixels 4', which are arranged at a distance d from each other.

[0006] Based on the edited raster image file of FIG. 1C, a mask is prepared. In detail, for each pixel 4′ to be printed, a hole or transparent area 5 is lined up on the mask. This may be done using a beam of electromagnetic radiation. As shown in FIG. 1D, such a beam generates holes 2, in this case circular holes 2, which are larger than the size of the pixels 4′. The resulting image on the mask is shown in FIG. 1E. The resolution of the screen pattern, defined as the number of screen elements per inch (pixels 4′ corresponding to holes 5 on the mask), counting along the line where the distance between the nearest screen elements is the smallest, may be, for example, 1414 lpi (=1 / (2*√2)*4000) in the example of FIG. 1E. This is shown in FIG. 1C, which shows that the nearest distance has a value d (in microns), and the screen pattern resolution in lpi is equal to the inverse of d (in microns) multiplied by 25400.

[0007] Thus, according to the method shown in Figures 1A-1E, the surface screening is calculated by modifying an original raster image file, e.g. a tiff file, using software, typically using raster image processing techniques, which operation typically produces a file having a larger size.

[0008] 1A-1E show simple examples of how raster image files can be edited, but more complex software-based image processing techniques may be used to manipulate raster image files, with the disadvantage that such techniques only improve image quality to a limited extent.

[0009] US Patent Application Publication No. 2013 / 0075376(A1) discloses a method for producing a relief printing plate by direct engraving, the method including the steps of generating target three-dimensional shape data from binary image data, calculating exposure data based on the target three-dimensional shape data, providing a predetermined exposure amount to outer image adjacent pixels within a predetermined range of pixels adjacent to an ON pixel, applying laser light to an area of ​​OFF pixels based on the exposure amount data to engrave an outer portion of an area, and applying laser light to the outer image adjacent pixels based on the predetermined exposure amount to form a relief having a protruding shape in which corners of a flange portion of an upper surface of the relief are at least partially chamfered. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] US Patent Application Publication No. 2013 / 0075376(A1) Summary of the Invention

[0011] It is an object of embodiments of the present invention to provide a method and system that can improve image quality in a more robust and simple manner.

[0012] According to a first aspect, there is provided a method of processing a raster image file, the method comprising: receiving a raster image file including image data for a plurality of pixels; analyzing image data of the raster image file; determining control data, and optionally at least one new raster image file, based on the analyzed image data, the control data being data for controlling settings of an imaging device to modify a physical property of a generated imaging feature corresponding to one or more of the plurality of pixels; outputting the raster image file and / or the new raster image file together with control data to an imaging device for imaging a relief master; Includes.

[0013] Among other things, embodiments of the present invention are based on the inventive insight that it is possible to improve image quality if imaging is controlled using control data based on image data contained in the raster image file. For example, imaging may be controlled differently depending on whether the image data contains text and / or pictures and / or bar codes and / or large continuous areas, etc. Thus, according to the inventive method, not only the image data in the raster image file and / or the manipulated image data in the new raster image file are output to the imaging device, but also imaging control data based on an analysis of the image data contained in the raster image file are used directly to control the imaging device, preferably without storing the control data. Such control data can also be included in a relatively small file, e.g. a so-called "job" file, in contrast to the new manipulated raster image files of the prior art, which are usually very large. Optionally, the control data may be included in the raster image file and / or the new raster image file.

[0014] The raster image file is preferably sent to the imaging device without further processing / manipulation of the image data in the raster image file, and it is the control data that allows to achieve results comparable to or better than those obtained with the new manipulated raster image file of the prior art. Moreover, the large file size of the new manipulated raster image file of the prior art requires larger storage and longer transmission times, making such processes slow and extensive. The control data can be included in the raster image file. For example, if the raster image file provides multiple bits per pixel, some bits may be used for the control data. However, if the image data in the raster image file is manipulated (not preferred), the control data may also be added to the new raster image file containing the manipulated data. Alternatively, the control data may be sent to the imaging device separately, for example in a job file.

[0015] In a preferred embodiment, the imaging features correspond to exposed areas of the mask layer. For example, the imaging features may correspond to holes, or areas that have changed transparency as a result of imaging. The change in transparency may be achieved by ablation, bleaching, a change in color, a change in refractive index, or a combination thereof. Preferably, ablation or bleaching is employed.

[0016] In other embodiments, the exposed areas may correspond to exposed areas of a photosensitive layer of a relief master. For example, the imaging device may be a beam of electromagnetic radiation (e.g., a UV laser) and the imaging features may be exposed features of the photosensitive layer. In that case, no mask layer is required, the photosensitive layer is hardened by interaction with the electromagnetic radiation, and after development, the imaging features correspond to the relief features used, for example, for printing. In such an embodiment, the method comprises: Providing a relief master comprising at least one photosensitive layer; receiving a raster image file including image data for a plurality of pixels; analyzing image data of the raster image file; determining control data, and optionally at least one new raster image file, based on the analyzed image data, the control data being data for controlling settings of an imaging device to modify a physical property of a generated imaging feature corresponding to one or more of the plurality of pixels; imaging the relief master using an imaging device, such as a UV laser, using the raster image file and / or the new raster image file together with the control data; developing the relief master to remove non-imaged areas of the relief master; may include.

[0017] Development is preferably accomplished by treatment with a liquid (solvent, water or aqueous solution) or by thermal development, which removes the liquefied or softened material. Examples of possible development techniques are described below.

[0018] The raster image file used in the imaging step and / or the new raster image file preferably represents two-dimensional image data. For example, the file may be a one-bit per pixel file or a multi-level image file having multiple bits per pixel. In other words, it may be a standard raster image file that contains only two-dimensional image data and no three-dimensional data.

[0019] The control data are preferably control data for controlling settings of an exposure means of the imaging device, in particular control data for controlling a beam generating means, more in particular control data for controlling a beam of the beam generating means. Typically the control data comprises at least a first and a second different setting of a control parameter, the first setting being used for a first pixel or group of pixels and the second setting being used for a different second pixel or group of pixels. For example, the first setting may specify a first beam size and / or beam shape and / or beam intensity to be used for the first pixel or group of pixels and the second setting may specify a second different beam size and / or beam shape and / or beam intensity to be used for the different second pixel or group of pixels. In addition to the first and second settings, further settings may be used for further pixels or groups of pixels.

[0020] The control data preferably represents information about one or more properties of an imaging feature or group of imaging features corresponding to a pixel or group of pixels and / or about features to be added to an imaging feature or group of imaging features, or represents one or more pixels that are not imaged. For example, the information about one or more properties of an imaging feature or group of imaging features may include any one or more of the following: The desired size of the imaging feature or group of imaging features corresponding to a pixel or group of pixels; for example the control data can be the diameter of the beam, representing the size of a pixel. The desired shape of the imaging feature or group of imaging features corresponding to the pixel or group of pixels; for example the beam may have a circular, elliptical or rectangular shaped cross section. The desired location of an imaging feature or group of imaging features that corresponds to a pixel or group of pixels; for example, the beam may expose a spot that is in the centre of four neighbouring pixels.

[0021] In other words, the control data may relate to the desired properties such as the size and / or shape or location of the imaging feature, i.e. the physical feature obtained after imaging. The imaging feature may for example correspond to an exposed area or a relief feature (e.g. of a mask layer). The control data may indicate that an additional imaging feature, i.e. an additional physical feature, is to be added.

[0022] For example, the control data may specify to use a beam size for the group of pixels such that adjacent imaging features corresponding to adjacent pixels do not overlap, and to add some additional imaging features between adjacent imaging features corresponding to adjacent pixels of the group of pixels. In this manner, it is possible to obtain a very fine surface screen in the area corresponding to the group of pixels.

[0023] In another example, the control data may specify to use a beam size for the group of pixels such that adjacent imaging features corresponding to adjacent pixels overlap, and to not image some pixels of the group of pixels such that a non-imaging zone is created in the area corresponding to the group of pixels. In this manner, it is also possible to obtain a surface screen in the area corresponding to the group of pixels.

[0024] In other words, the control data can control how pixels or groups of pixels should be imaged, such that different pixels or groups of pixels of the same raster image file can be imaged in different ways.

[0025] The control data preferably includes any one or more, or a combination of, the following: intensity values ​​used to generate an imaging feature or group of imaging features corresponding to a pixel or group of pixels, e.g. intensity values ​​for controlling a beam of an imaging device; by varying the intensity values ​​it is possible to modify the imaging feature, e.g. to change the size of the imaging feature. On / off signaling of a beam of an imaging device to generate an imaging feature or group of imaging features corresponding to a pixel or group of pixels; by varying the on / off signal (e.g. the timing of the on / off signal) it is also possible to vary the imaging feature, e.g. changing the size and / or shape of the imaging feature. the time interval used to generate an imaging feature or group of imaging features corresponding to a pixel or group of pixels, e.g. an on-time value for controlling a beam of an imaging device; changing the time interval also changes the amount of energy used to generate the imaging feature, which affects the physical properties of the imaging feature. ·Beam diameter value or beam shape value for controlling the beam of the imaging device. The number of passes of the imaging step performed by the imaging device; multiple passes may be used to get more energy at an isolated single pixel feature. A single pixel does not have neighbors to "help" the ablation and may require more energy per pixel than a multi-pixel feature. By defining the number of passes for a pixel or a group of pixels, e.g. all single pixels, a clearer image can be obtained. An indication of which of a plurality of exposure heads is used to generate an imaging feature or group of imaging features corresponding to a pixel or group of pixels; for example, a first group of pixels may be exposed with a first exposure head and an image of a second group of pixels may be exposed with a second exposure head. A value representing the beam path of the imaging device, such as a value representing the location of the spot exposed by the beam of the imaging device that is different from the location of the spot in the raster image file; for example, in cases where the beam diameter is smaller than a pixel, the beam may be placed near the center of a pixel or near a corner of a pixel. Or a combination of these.

[0026] According to a preferred embodiment, the analyzing step is carried out so as to determine any one or more of the following: Pixels that contribute to the image contained in the image data, and pixels that do not contribute to the image contained in the image data. image areas having pixels contributing to the image contained in the image data, areas having no pixels contributing to the image contained in the image data, image areas in which all pixels contribute to the image contained in the image data; in other words the edges of the various image and non-image areas may be determined. Screen ruling or screen frequency is the resolution of a halftone screen, usually measured in lines per inch (lpi) and specifies the distance between a line of equidistant dots. Each dot corresponds to a halftone area. The screen angle used, at which the separate color halftones are imaged. for one or more target pixels of said plurality of pixels, a number of neighbouring pixels of the target pixel that contribute to an image contained in the image data, and / or for one or more target pixels of said plurality of pixels, a number of neighbouring pixels of the target pixel that do not contribute to an image contained in the image data; in this way it can be determined whether a pixel is isolated or is part of the edge of an image area or is completely surrounded by other pixels of the image. For one or more target pixels of said plurality of pixels, the orientation or location of neighboring pixels of the target pixel that contribute to the image contained in the image data. For example, it may be indicated how far away other pixels are from the target pixel, or how many other pixels there are. This may be useful in deciding to strengthen a target pixel if there are not enough other pixels nearby. An isolated pixel, or a group of contiguous pixels in a small area in the middle of nowhere, may not be strong enough to survive the washout process; for example, it may be indicated that there is a line of red pixels next to a single pixel. For one or more target pixels of said plurality of pixels, information regarding the size of the image area to which the target pixel belongs. For one or more target pixels of said plurality of pixels, the structure of the image area (e.g. dot, line, character) to which the target pixel belongs. For one or more target pixels of said plurality of pixels, the distance between the target pixel and an edge of the image area.

[0027] The control data may be calculated based on an algorithm or may be attributed according to a predefined property table or according to predefined rules.

[0028] According to an example embodiment, the analyzing step includes analyzing a plurality of groups of pixels of the raster image file, and the determining step includes determining control data for at least one of the plurality of groups based on the analyzing step, for example, a different beam size may be used for one or more groups compared to one or more other groups of pixels.

[0029] Each group preferably comprises a number of neighbouring pixels, the number being at least 2, preferably at least 4, more preferably at least 6, most preferably at least 8, even more preferably at least 24, for example at least 48.

[0030] The groups may correspond to tiles of pixels. The tiles may be of any shape, e.g. rectangular or square. The analyzing step may include deriving whether the tiles are trivial or non-trivial based on at least one predefined triviality criterion, and the determining step may include determining, for each non-trivial tile, at least one characteristic, on which the control data is based. The determining step may further include determining a path through the trivial tiles, the path dividing the raster image file into a first part and a second part, e.g. a left part and a right part. Optionally, the path may divide the raster image file into three or more parts. This is advantageous when two or more sources are used for the imaging beam (exposure head) that image the mask simultaneously and independently of each other. The triviality criterion may be whether the tile contains or does not contain pixels that contribute to the image. Another triviality criterion may be whether a tile contains simple image data, e.g., no contributing pixels, all contributing pixels, only linework and no screening, etc. The latter is useful for determining whether a tile can be split to be imaged by different exposure heads. For example, linework is usually not an issue when a tile is split, but splitting a tile that contains a screened area is much more risky.

[0031] According to an exemplary embodiment in which an imaging device with several parallel imaging beams is used, the groups may correspond to several strips, the width of the strip substantially corresponding to the width imaged by the several imaging beams. In general, the width of the strip is the width of the number of pixels imaged by the group of parallel beams of the imaging head. If the imaging head includes, for example, 6 beams, the width of the strip is 6 pixels wide. However, it is also possible to image simply every second pixel with a fixed number of beams, in which case the width of the strip is 11 pixels. The length of the strip corresponds to the size of the image file in the direction parallel to the beam movement, and its maximum length may correspond to the maximum length of the beam path. In a setup in which the master is placed on a rotating drum, the maximum length may correspond to the circumference of the drum.

[0032] In an exemplary embodiment, the analyzing step includes analyzing the group of pixels in combination with data from one or more neighboring groups to determine, for every pixel of the plurality of pixels, whether the pixel is an imaging pixel and / or whether the pixel is part of an image item smaller than a predetermined size and / or whether the pixel is surrounded by one or more non-imaging pixels.

[0033] In an exemplary embodiment, the analyzing step includes a step of deriving image items having predetermined size characteristics, and the determining step includes a step of generating a new raster image file in which a surface screening pattern is added to the image items having the predetermined size characteristics and not to the remainder of the image data.

[0034] Raster image files may be 1 BPP (1 bit per pixel) files or multi-level image files with multiple bits per pixel (so that pixels can have different gray levels). Raster image files may have any one of the following file formats: TIFF, LEN, JPEG, JPG, BMP, JDF, PNG, etc.

[0035] Optionally, the control data may be stored in a multi-level raster image file, such as a multi-level TIFF file, or in a job file (a generalized description file that can be interpreted by an imaging device), such as a JSON file. However, the derived control data may also be applied directly using hardware, and storing the control data and applying the control data "on the fly" is preferred.

[0036] The imaging device may be a system including an imager and optionally different units for pre- or post-processing (eg, exposure units, washers, dryers, light finishers) to generate a relief master.

[0037] According to an example embodiment, the control data indicates any one of the following: Applying the determined intensity to one pixel of multiple pixels. For one or more image areas of the image data that are larger than the predetermined size, applying the determined intensity to the one or more image areas. For one or more isolated pixels of the plurality of pixels, adding an additional imaging feature to the isolated imaging feature corresponding to the isolated pixel and / or applying an increased intensity to generate the isolated imaging feature, if present, the added imaging feature; in other words, a beam with a higher intensity may be used for the isolated pixel; alternatively, the emission time may be increased for the isolated pixel. For one or more image areas of image data that are smaller than a predetermined size, adding additional imaging areas within or adjacent to the one or more image areas. For one or more isolated pixels of the plurality of pixels, changing the location of the center of the beam away from the center of the pixel.

[0038] According to an exemplary embodiment, the control data is derived and applied directly to the imaging device without the storage of a file.

[0039] According to an exemplary embodiment, the control data is derived by considering further aspects related to the printing and / or processing conditions. Such printing conditions are, for example, printing direction, nature of the printing substrate, nature of the anilox roll (size, ruling of pits), printing speed, printing pressure, type of ink, and combinations thereof. For example, it may be important to consider the printing direction because it determines which parts of the image feature are impacted first more strongly than other parts of the image feature, and as a result, such other parts may be processed differently compared to the parts impacted first. The parts of the image feature that are impacted first may be enhanced, for example, by using a larger beam diameter or by adding imaging features. Examples of processing conditions include, for example, the type of light source used (LED vs. light tube), the type of development used (e.g., thermal development vs. solvent development).

[0040] In embodiments of the invention, the control data may be determined prior to imaging or may be determined during imaging, for example imaging may commence as soon as a portion of the control data has been determined, said portion being a portion relating to the first portion being imaged.

[0041] According to a second aspect of the present invention there is provided a method for generating a relief structure, the method comprising: Providing a relief master comprising a substrate layer, at least one photosensitive layer, and a mask layer (integral or additional); performing a method according to any one of the previous embodiments; imaging a relief master using the raster image file and / or the new raster image file together with the control data such that an image is generated in the mask layer; exposing the imaged relief master to electromagnetic radiation through the imaged mask layer; Removing soluble or liquefiable material (for development) and optionally further steps such as drying, light finishing, cutting.

[0042] The invention also relates to a relief structure obtainable by such a method.

[0043] The mask layer may be an integral part of the relief master or may be a separate item that is attached to the relief master prior to exposure to electromagnetic radiation.

[0044] The imaging device used in the imaging step may be configured to generate electromagnetic radiation capable of modifying the transparency of the mask layer. The change in transparency may be achieved by ablation, bleaching, a change in color, a change in refractive index, or a combination thereof. Preferably, ablation or bleaching is employed.

[0045] Examples of solidifiable materials that may be used in embodiments of the present invention include photosensitive compositions that solidify or harden by chemical reactions that lead to polymerization and / or crosslinking. Such reactions may be radical, cationic or anionic polymerization, and / or crosslinking. Other means for crosslinking are condensation or addition reactions, for example the formation of esters, ethers, urethanes, or amides. Such compositions may include initiators and / or catalysts that are triggered by electromagnetic radiation. Such initiators or catalysts can be photoinitiator systems with one or more components that form radicals, acids or bases, which then initiate or catalyze the reactions that lead to polymerization or crosslinking. The required functional groups can be attached to low molecular weight monomers, oligomers, or polymers. In addition, the compositions may include additional components such as binders, fillers, colorants, stabilizers, surfactants, inhibitors, modifiers, and other additives, which may or may not carry functional groups used in the solidification reaction. Depending on the components used, it is possible to obtain flexible and / or rigid materials after solidification and after post-processing is completed. The radical reaction may be a radical polymerization, a radical crosslinking reaction, or a combination thereof. It is preferred that the photosensitive layer not be rendered insoluble, solid, or metallized by the radical reaction.

[0046] The removal of the soluble or liquefiable material is preferably achieved by treatment with a liquid (solvent, water or aqueous solution) or by thermal development, whereby the liquefied or softened material is removed. Treatment with a liquid may be carried out by spraying the master with the liquid, brushing or rubbing the master in the presence of the liquid. The nature of the liquid used is oriented by the nature of the master employed. If the layer to be removed is soluble, emulsifiable or dispersible in water or an aqueous solution, water or an aqueous solution may be used. If the layer is soluble, emulsifiable or dispersible in an organic solvent or mixture, an organic solvent or mixture may be used. The liquid preferably comprises a petroleum fraction, for example naphthenic or aromatic, in a mixture with an alcohol, such as benzyl alcohol, cyclohexanol or an aliphatic alcohol having 5 to 10 carbon atoms, for example optionally also comprising further components, such as alicyclic hydrocarbons, terpene hydrocarbons, substituted benzenes such as diisopropylbenzene, esters having 5 to 12 carbon atoms, or glycol ethers.

[0047] For thermal development, a thermal development unit may be used in which a flexible plate is fixed to a rotating drum. The thermal development unit further includes an assembly for heating the at least one additional layer and an assembly for contacting the outer surface of the heated at least one additional layer with an absorbent material for absorbing the material in the molten state. The heating assembly may include a heatable underlay for an IR lamp arranged on the flexible plate and / or the at least one additional layer. The absorbent material may be pressed against the surface of the at least one additional layer, for example by means of an optionally heatable roll. The absorbent material may move continuously over the surface of the flexible plate while the drum rotates, repeatedly removing the material of the at least one additional layer. In this way, the melted material is removed while the non-melted areas remain, forming a relief.

[0048] According to a further aspect, there is provided a processing module configured to perform the method steps of any one of the preceding embodiments.

[0049] According to yet another aspect, an imaging system is provided comprising such a processing module and an imaging device configured for imaging a relief master using the raster image file together with control data and / or a new raster image file such that an image is generated in a mask layer of the relief master.

[0050] Optionally, the imaging system may further comprise an exposure unit, a washer, a dryer, a light finisher, or any other post-exposure unit to generate the relief structure as described above. Optionally, a controller may be provided to control various units of the imaging system. Optionally, one or more pre-processing modules may be provided upstream of the processing module, such as a raster image processing (RIP) module that converts an image file, such as a pdf file, into a raster image process file.

[0051] The accompanying drawings are used to illustrate presently preferred, non-limiting exemplary embodiments of the method and system of the present invention, and the above and other advantages of the features and objects of the present invention will become more apparent when read in conjunction with the accompanying drawings, and the invention will be better understood from the following detailed description. [Brief description of the drawings]

[0052] [Figure 1A] FIG. 1 shows a schematic diagram of a prior art embodiment; [Figure 1B] FIG. 1 shows a schematic diagram of a prior art embodiment; [Figure 1C] FIG. 1 shows a schematic diagram of a prior art embodiment; [Figure 1D] FIG. 1 shows a schematic diagram of a prior art embodiment; [Figure 1E] FIG. 1 shows a schematic diagram of a prior art embodiment; [Diagram 2] 1 illustrates three exemplary embodiments of the system and method according to the present invention. [Diagram 3]1 illustrates three exemplary embodiments of the system and method according to the present invention. [Figure 4] 1 illustrates three exemplary embodiments of the system and method according to the present invention. [Diagram 5] 1 illustrates three exemplary embodiments of the system and method according to the present invention. [Figure 6] 1A-1C illustrate two exemplary embodiments of the steps of analyzing an underlying raster image file to determine control data. [Figure 7] 1A-1C illustrate two exemplary embodiments of the steps of analyzing an underlying raster image file to determine control data. [Figure 8] 11A-11C illustrate the impact of different control data on imaging characteristics according to different example embodiments. [Figure 9] 11A-11C illustrate the impact of different control data on imaging characteristics according to different example embodiments. [Figure 10A] FIG. 11 illustrates a further exemplary embodiment of analyzing a raster image file to determine control data. [Figure 10B] FIG. 11 illustrates a further exemplary embodiment of analyzing a raster image file to determine control data. [Figure 10C] FIG. 11 illustrates a further exemplary embodiment of analyzing a raster image file to determine control data. [Figure 10D] FIG. 11 illustrates a further exemplary embodiment of analyzing a raster image file to determine control data. [Figure 11] 13A-13C show further exemplary embodiments for varying the location of the center of the beam. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] 2 shows a first embodiment of a system comprising a raster image processing (RIP) module 10 and an imaging system 100. The imaging system 100 includes a processing module 110 and an imaging system 120.

[0054] The RIP module 10 converts the source image file, here a pdf file, into a raster image file that goes to the processing module 110 of the imaging system 100 and then to the imaging device 120. The RIP module 10 is the component used in image processing to produce a raster image file, also known as a bitmap. The source image file may be a page description in a high-level page description language, such as PostScript, Portable Document Format, XPS, or another bitmap. In the latter case, the RIP applies either a smoothing or an interpolation algorithm to the input bitmap to generate an output bitmap. Raster image processing is the process of turning vector digital information, for example a PostScript file, into a high-resolution raster image file. Usually, the RIP module 10 is implemented either as a software component of an operating system or as a firmware program executed on a microprocessor. The RIP module 10 may further include layout functionality. If multiple small images need to be printed, such images may be grouped according to a printing pattern. This grouping may also be performed by the RIP module 10.

[0055] The raster image file output by the RIP module 10 is input to a processing module 110. In the processing module 110, the following steps are performed: receiving a raster image file including image data for a plurality of pixels; analyzing image data of a raster image file; determining control data based on the analyzed image data, the control data being data for controlling settings of an imaging device to modify a physical property of a generated imaging feature corresponding to a plurality of pixels; · Outputting the control data to an imaging device 120 for imaging the relief master.

[0056] 3 illustrates a second embodiment of a system comprising a raster image processing (RIP) module 10 and an imaging system 100. The imaging system 100 includes a processing module 110 and an imaging system 120.

[0057] The RIP module 10 converts the first image file, here a pdf file, into a raster image file which enters the processing module 110 of the imaging system 100. In the processing module 100, the following steps are performed: receiving a raster image file including image data for a plurality of pixels; analyzing image data of a raster image file; determining control data and at least one new raster image file based on the analyzed image data, the control data being data for controlling settings of an imaging device to modify physical properties of generated imaging features corresponding to a plurality of pixels; Outputting the new raster image file together with the control data to the imaging device 120 for imaging the relief master.

[0058] In the embodiment of Figure 2, the raster image file is not modified, and the control data includes control information for controlling settings of the imaging device to change the imaging depending on the image area in the raster image file. In the embodiment of Figure 3, the raster image file is modified (e.g., pixels may be added or removed depending on the image data contained in the raster image file) to create a new raster image file, and the control data includes control information for controlling settings of the imaging device 120 to change the imaging depending on the image area in the raster image file.

[0059] The control data may be included in the raster image file or in a new raster image file, or may be included in a separate job file, or may be sent directly to imaging 120. If the control data is included in a file, imaging device 120 may be provided with an interpreter function for interpreting the file and may be configured to generate suitable control signals for controlling imaging device 120 based on the control data included in the file.

[0060] 4 shows a schematic example where the control data is generated based on a very simple example of a raster image file. The raster image file comprises 15x15 pixels. The processing module 110 may analyze the raster image file and determine the pixels that contribute to the image contained in the image data and the pixels that do not contribute to the image contained in the image data. For example, the analyzing step reveals a central image area I where all pixels contribute to the image, and a peripheral image area NI where no pixels contribute to the image.

[0061] Control data may then be generated for the image area I. In this example, the generated control data represents the desired size of the imaging features corresponding to the pixels and the desired shape of the imaging features corresponding to the pixels. More particularly, the control data characterizes the diameter and shape of the beam generated by the imaging device. For example, the control data may specify the beam diameter to be used in the image area I. FIG. 8 shows the effect of using a small or large beam diameter for imaging. Depending on the size of the beam, it is possible to create or not create non-imaging zones between the image features, i.e. imaging features corresponding to adjacent pixels may or may not overlap. Also, the distance between adjacent imaging features can be adjusted by adjusting the beam size. In this case, the control data is used to control the diameter of the beam. In a first example, a beam with a diameter larger than the pixel size is used, and the imaged areas of the beam overlap. This ensures that the mask material is completely removed, and the size of the image features increases slightly, which can be used to compensate for the reduction in the image feature size due to subsequent process steps. In a second example, a beam with a diameter smaller than the pixel size is used, and the imaged areas of the beam do not overlap. In this manner, the mask is only partially removed, leading to the formation of a structured surface of the relief features that may improve the ink-bearing ability of the relief structures and can result in high quality printed images.

[0062] In the illustrated examples of Fig. 4 and Fig. 8, the same beam diameter is used for all pixels of the image area I, but the skilled person will understand that it is also possible to vary the beam diameter within an image area. For example, the beam size can be larger near the edges and smaller in the center of the image area I. In this way, it is possible to create closed edges of the image area I. This may be advantageous to keep the ink in the relief area corresponding to the image area I. Small beams may be located in the center of the pixel or at the corners of the pixel. In the latter case, the distribution of the beams in neighboring pixels may vary, for example in the case of four pixels forming a square, the beams may be located near the center of the four pixels, or at the outermost corners of the pixels, or in one of the other possible configurations.

[0063] Instead of using the beam diameter as the control parameter, other parameters can be used to control the size and / or shape of the beam, for example any one of the following parameters may be used: intensity value to control the beam of the imaging device, beam on / off signal, beam on time, number of beam passes, etc.

[0064] 5 shows a further example in which the control data is generated based on a very simple example of a raster image file. The processing module 110 may analyze the raster image file and determine the pixels that contribute to the image contained in the image data and the pixels that do not contribute to the image contained in the image data. For example, here the analyzing step reveals a first image area I1 in which all pixels contribute to the image, a second image area I2 in which there is a single isolated pixel, and a surrounding image area NI that does not contribute to the image.

[0065] Control data may then be generated for the image areas I1, I2. In this example, the generated control data represents a desired size of the imaging feature corresponding to the pixel and a desired shape of the imaging feature corresponding to the pixel. More particularly, the control data characterizes the diameter and shape of the beam generated by the imaging device. For example, the control data may specify a beam diameter used in the image area I1 to have a first value and a beam diameter used in the image area I2 to have a second value different from the first value. In this example, the beam diameter used for isolated pixels of the image area I2 may be chosen to be larger than the beam diameter used in the larger image area I1. In this way, it is possible to avoid that the relief area corresponding to the image area I2 is too small. In the illustrated example, the same beam diameter is used for all pixels of the larger image area I1, but a person skilled in the art will understand that it is also possible to vary the beam diameter within an image area. Instead of using the beam diameter as a control parameter, as mentioned in relation to FIG. 4, other parameters may also be used to control the size and / or shape of the beam.

[0066] Fig. 6 shows a further example of a raster image file comprising image areas I1-I5 representing text, and image areas I6-I9 representing barcodes, and image areas I10, I11 representing graphics, and a non-image area NI. The processing module 110 may analyze the raster image file and determine pixels contained in the image data that contribute to the image and pixels contained in the image data that do not contribute to the image. For example, here the analyzing step reveals image areas I1-I11, where all pixels contribute to the image, and a surrounding image area NI, where no pixels contribute to the image. It is noted that the analyzing step could also classify image areas I1-I5 as a single text area and image areas I6-I9 as a single barcode area, where within the text area some pixels contribute to the text but others do not, and within the barcode area some pixels contribute to the barcode but others do not.

[0067] The analysis may be performed on a tile-by-tile basis. In FIG. 6, the raster image is divided into four tiles, a, b, c, and d. The analyzing step may include deriving whether the tile is trivial or non-trivial based on a predefined triviality criterion. In the current example, tiles a, b, and c are classified as non-trivial since they all contain relevant image areas, and tile d is a trivial tile since it does not require any processing by the imaging device. The determining step may include determining a characteristic for each non-trivial tile, and in the current case, control data may be determined for each tile. For example, for a trivial tile such as tile d, the control data may be a command to "skip the tile". In this manner, tile d can be omitted entirely during imaging, saving time.

[0068] Control data may then be generated for the image areas I1-I11. Control data generated for the text areas I1-I5, and for the barcode areas I6-I9 may be such that the edges of the characters and bars are nicely contoured. For example, barcodes are easier to read with a higher ink density on the print (better ink coverage). This can be achieved by surface screening, which can be turned on for such areas using appropriate control data.

[0069] FIG. 7 shows an example similar to that of FIG. 6, with the difference that the analysis is performed strip by strip, see strips a, b, c, d, e, f, g running from top to bottom through the pixel area. The analyzing step may include deriving whether the strip is trivial or non-trivial based on a predefined triviality criterion. In the present case, strips b, c, d, e, f, g are non-trivial since they all contain relevant image areas, and strip a is a trivial strip. Instead of simply classifying the strips as trivial or non-trivial, more than two classes may be used. For example, in strip b, it may be determined that the strip contains text, and in strip c, it may be determined that the strip contains linework. The width of the strip may substantially correspond to the width imaged by several parallel imaging beams of the imaging device.

[0070] Control data may then be generated for strips a-g. The control data generated for strips a-g may take into account that image areas I1-I5 contain text, and ensure that edge zones of adjacent strips match well. Even in such an embodiment, for a trivial tile such as tile d, the control data may be a command to "skip tile". In this way, tile a can be omitted entirely during imaging, saving time.

[0071] In more advanced embodiments, pixels may be added or removed and this may be indicated in the control data. Alternatively, a new raster image file may be prepared as in the embodiment of FIG.

[0072] 9 shows a first example (Example 1) in which the control data indicates to use a first beam diameter d1 and not to image some pixels in the image area I. The beam diameter d1 is relatively large such that adjacent imaged pixel features overlap. By not imaging some pixels, small unimaged zones Z1 remain in the imaged area (i.e., a surface screening pattern is obtained), and such zones Z1 create small valleys in the resulting relief structure. Such valleys may improve the ink carrying ability of the relief structure, which can result in a high quality printed image.

[0073] FIG. 9 further illustrates a second example (Example 2) in which the control data uses a second beam diameter d2 and adds several imaging features to the imaging area I. The beam diameter d2 is relatively small so that adjacent imaging pixel features do not overlap. By adding several imaging features Pa, a very fine surface screen pattern of small imaging zones is created, such zones creating many small peaks in the resulting relief structure. Such a pattern of many small peaks may improve the ink carrying ability of the relief structure, resulting in a high quality of the printed image.

[0074] Those skilled in the art will appreciate that there are many variations of Examples 1 and 2. Also, different beam sizes (as shown in the example of FIG. 8) may be combined for the same imaging area I, such that in some parts of the imaging area the pixel features overlap and in other parts the pixel features do not overlap.

[0075] 10A-10D show further examples of steps of analyzing a raster image file. As shown in FIG. 10A, the raster image file includes image areas representing text, and image areas representing graphics, and non-image areas. The analysis may be performed on a tile-by-tile basis. In FIG. 10A, the raster image is divided into a number of tiles T. FIG. 10B shows several different tiles T in more detail: an empty tile T1, a filled tile T2, a linework tile T3, and a screened tile T4. For example, the size of the tile T may be 512×512 pixels. For example, the control data for the filled tile T2 may indicate that a surface screen should be applied, while the control data for the tile T4 may indicate beam-related information at pixel level.

[0076] 10C shows a sample map of tiles containing pixels that contribute to the image (black tiles Tc) and tiles containing non-contributing pixels (white tiles Tnc). A path in the form of a stitching line SL through the connected white tiles Tnc can split the image data into two parts that can be exposed simultaneously with two separate exposure heads H1, H2 without visible stitching defects. Also, if a strip of white tiles Tnc is determined and said strip extends over the length of the image, the control data may indicate that the strip may be skipped.

[0077] FIG. 10D shows a sample of a map with tiles that contain pixels that may belong to the screened portion of the image (black tiles T4) and tiles that do not belong to the screened portion of the image (white tiles). In this case, when evaluating along the vertical and horizontal lines respectively, all pixels inside a tile share the same state (contributing to the image or not, like tiles T1 and T2) or if the number of state changes inside this tile is less than two (such as T3'), the tile becomes white (i.e., irrelevant for the detection of screen ruling and angle). The screen detection algorithm can then be applied only to relevant tiles, i.e., tiles such as tile T3 shown and tile T4 shown. To avoid interference between the number of parallel laser beams and the repetition of the screen, it is advantageous to know the ruling and angle of the screen of the image file, and in such an example, the control data may indicate the tiles that belong to the screened portion of the image and the settings applied by the imaging device for such tiles (e.g., number of beams).

[0078] As discussed above and illustrated in Figure 10B, processing module 110 may analyze the raster image file to determine tiles T2, T3, T4 that contribute to an image contained in the image data, and tiles T1 that do not contribute to an image contained in the image data. In addition, as illustrated in Figure 10C, the analysis by processing module 110 may also categorize tiles according to their relevance for screen ruling and angle detection.

[0079] FIG. 11 shows how the location of the center of the beam may vary away from the center of the pixel of the image feature. An image feature of a raster image file is composed of 4 pixels, and in example a) a beam smaller than the pixel is located at the center of the pixel. In example b) the beam is shifted towards the outer corner of the pixel, this configuration may be advantageous for very small image features, and it is possible to create a surface structure on such features and compensate for the loss in size during subsequent process steps. In example c) the beam is shifted towards the center of the image feature, which can be used to reduce the size of the image feature. These examples show only extreme cases, and all other possible location combinations are possible. This principle can also be applied to larger image features, where the beam is located at the center of the pixel for all pixels, except for pixels whose boundaries are away from or close to the image feature, where the beam may be shifted towards the outside or inside of the image feature. It is clear that varying the location of the beam may be combined with different beam sizes for different locations. For example, a small beam size may be used for the inner pixels of the image feature and a large beam size for pixels at or near the boundary of the image feature, or vice versa. In this manner, the boundaries of image features may be strengthened to produce sharp edges or weakened to produce soft edges that can be used to reduce trail edge voids when printing. In addition to modifying the beam size, adding or omitting beam exposures to locations at or near the boundaries of image features may be used, such that adding an exposure spot at or near the boundary can strengthen the image feature and removing an exposure spot can weaken the image feature. These modifications may be made to all pixels at or near the same pixel boundary, but it is also possible to strengthen or weaken the boundary in a specific direction.In particular, when the print direction is taken into account, image features such as the edges of bar codes can be adjusted accordingly. Using a small radius along with additional exposure spots along the borders of the test can be used to produce very smooth and sharp characters.

[0080] A person skilled in the art will readily recognize that the various steps of the above-mentioned methods can be performed by a programmed computer. Some embodiments herein are also intended to cover program storage devices, e.g., digital data storage media, which are machine or computer readable and encode a program of machine-executable or computer-executable instructions, which perform some or all of the steps of the above-mentioned methods. The program storage device may be, for example, a digital memory, a magnetic storage medium such as a magnetic disk or tape, a hard drive, or an optically readable data storage medium. The embodiments are also intended to cover a computer programmed to perform the steps of the above-mentioned methods.

[0081] The functionality of the various elements shown in the figures, including any functional blocks labeled "processing module", is provided through the use of dedicated hardware as well as hardware capable of executing software in association with appropriate software. When provided by a processing module, functionality may be provided by a single dedicated processor, by a single shared processor, or by multiple individual processors, some of which may be shared. Moreover, the explicit use of the term "processing module" should not be construed as exclusively referring to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (DSP) hardware, network processors, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), read only memory (ROM) for storing software, random access memory (RAM), and non-volatile storage. Other hardware, conventional and / or custom, may also be included. For example, in Figures 2 and 3, processing module 110 or portions thereof may be added to an actual imaging machine (including imaging device 120). Alternatively, the processing module 110 may be a separate module external to the imaging machine, or may be located partially inside and partially outside the actual imaging machine.

[0082] While the principles of the present invention have been described above in relation to specific embodiments, it should be understood that this description is made purely by way of example and not as a limitation on the scope of protection defined by the appended claims.

Claims

1. providing a relief master comprising a substrate layer, at least one photosensitive layer, and a mask layer; receiving a raster image file including image data for a plurality of pixels; analyzing the image data of the raster image file; determining control data, and optionally at least one new raster image file, based on the analyzed image data, the control data being data for controlling settings of an imaging device to modify physical properties of a generated imaging feature corresponding to one or more of the plurality of pixels; outputting said raster image file and / or said new raster image file together with said control data to an imaging device (120) for imaging a relief master; imaging the relief master using the raster image file and / or the new raster image file together with the control data such that an image is generated in the mask layer; exposing the imaged relief master to electromagnetic radiation through the imaged mask layer; 23. A method for generating a relief structure comprising:

2. The method of claim 1 , wherein the imaging feature corresponds to a hole or an area that has changed transparency as a result of the imaging.

3. 3. The method of claim 1 or 2, wherein the raster image file and / or the new raster image file used in the imaging step represent two-dimensional image data, such as a one bit per pixel file or a multi-level image file having multiple bits per pixel.

4. The control data is information about one or more properties of an imaging feature corresponding to a pixel, or a group of imaging features corresponding to a group of pixels; Information about the imaging feature or features to be added to a group of imaging features; The method according to any one of claims 1 to 3, wherein the method represents one or both of the following:

5. The information about one or more properties of an imaging feature or group of imaging features may include: a desired size of an imaging feature corresponding to a pixel or a group of imaging features corresponding to a group of pixels; a desired shape of an imaging feature corresponding to a pixel or a group of imaging features corresponding to a group of pixels; and a desired location of an imaging feature corresponding to a pixel or a group of imaging features corresponding to a group of pixels; The method of any one of claims 1 to 4, comprising one or more of:

6. The control data is - intensity values ​​used to generate an imaging feature corresponding to a pixel or a group of imaging features corresponding to a group of pixels, e.g. intensity values ​​for controlling a beam of said imaging device; an on / off signal for a beam of said imaging device to generate an imaging feature corresponding to a pixel or a group of imaging features corresponding to a group of pixels; a time interval used to generate an imaging feature corresponding to a pixel or a group of imaging features corresponding to a group of pixels, e.g. an on-time value for controlling a beam of the imaging device; A value of a beam diameter or a beam shape for controlling the beam of the imaging device; the number of passes through the imaging step performed by the imaging device; an indication of one of the exposure heads to be used to generate an imaging feature corresponding to a pixel or a group of imaging features corresponding to a group of pixels; and a value representing a beam path of the imaging device, such as a value representing a location of a spot exposed by the beam of the imaging device that is different from the location of the spot in a starting raster image file; The method according to any one of claims 1 to 5, comprising a combination of one or more of:

7. The analyzing step includes: Pixels that contribute to an image included in the image data; non-image-contributing pixels included in the image data; an image area having pixels that contribute to an image included in said image data; an image area where no pixels contribute to the image contained in said image data; an image area in which all pixels contribute to an image contained in said image data; Screen ruling, Screen angle, For one or more target pixels of the plurality of pixels, a number of neighboring pixels of the target pixel that contribute to an image included in the image data; For one or more target pixels of the plurality of pixels, a number of neighboring pixels of the target pixel that do not contribute to an image included in the image data; For one or more target pixels of the plurality of pixels, an orientation or location of neighboring pixels of the target pixel that contribute to an image included in the image data; information for one or more target pixels of said plurality of pixels about a size of an image area to which said target pixel belongs; For one or more target pixels of said plurality of pixels, the structure of the image area to which the target pixel belongs, such as a dot, a line, a character, etc.; and for one or more target pixels of the plurality of pixels, a distance between the target pixel and an edge of the image area; The method of any one of claims 1 to 6, wherein the method is carried out to reveal one or more combinations of:

8. the analyzing step includes analyzing groups of pixels of the raster image file; The method of any one of claims 1 to 7, wherein the determining step comprises determining control data for at least one of the plurality of groups of pixels based on the analysing step.

9. The method of claim 8 , wherein the group of pixels corresponds to a tile of pixels.

10. 10. The method of claim 9, wherein the analyzing step comprises deriving whether a tile is trivial or non-trivial based on at least one predetermined triviality criterion.

11. The method of claim 10 , wherein the determining step includes determining at least one characteristic for each non-trivial tile, and the control data is based on the characteristics.

12. 12. The method of claim 10 or 11, wherein the determining step comprises determining a path through trivial tiles, the path dividing the raster image file into a first portion and a second portion, or into a further portion.

13. A method according to any one of claims 8 to 12, wherein each group comprises a number of neighbouring pixels, said number being at least 2, preferably at least 4, more preferably at least 6, most preferably at least 8, even more preferably at least 24, such as at least 48.

14. A method according to any one of claims 8 to 13, wherein for use with an imaging device having several parallel imaging beams, the groups of pixels may correspond to a number of strips, the width of a strip corresponding to the number of imaging beams.

15. The analyzing step comprises, for every pixel of the plurality of pixels: whether the pixel is an imaging pixel; whether said pixel is part of a graphical item that is smaller than a predetermined size; Whether the pixel is surrounded by one or more non-imaging pixels 15. A method according to any one of claims 8 to 14, comprising analysing a group of pixels in combination with the data of one or more neighbouring groups to determine one or more of:

16. the analyzing step includes deriving image items having predetermined size characteristics; A method according to any preceding claim, wherein the determining step comprises generating a new raster image file in which a surface screening pattern is added to the image item having the predetermined size characteristic and not to the remainder of the image data.

17. A method according to any preceding claim, wherein the raster image file is a 1 bit per pixel file.

18. The control data is applying the determined intensity to a pixel of said plurality of pixels; for one or more image areas of the image data that are greater than a predetermined size, applying the determined intensity to the one or more image areas; For one or more isolated pixels of the plurality of pixels, one or both of adding an additional imaging feature to an isolated imaging feature corresponding to the isolated pixel and applying a predetermined intensity to the isolated imaging feature, if present, to generate the added imaging feature; for one or more image areas of the image data that are smaller than a predetermined size, adding additional exposure areas within or near the one or more image areas; and for one or more isolated pixels of said plurality of pixels, varying a location of a center of a beam away from a center of said pixel; The method according to any one of claims 1 to 17, wherein the method is any one of the following:

19. A method according to any preceding claim, wherein the control data is derived and applied directly to the imaging device without storage of a file.

20. The method according to any one of the preceding claims, wherein the control data are derived by taking into account further aspects related to one or both of the printing conditions and / or processing conditions.

21. removing soluble or liquefiable material; Further steps such as drying, light finishing and cutting; The method of any one of claims 1 to 20, further comprising:

22. A processing module (110) configured to perform the receiving, analyzing, determining, and outputting steps in the method according to any one of claims 1 to 21.

23. The processing module (110) of claim 22; an imaging device (120) configured for imaging the relief master using the raster image file together with one or both of the control data and the new raster image file such that an image is generated in a mask layer of the relief master; An imaging system (100) comprising:

24. A relief structure obtained by a method according to any one of claims 1 to 21.

Images