Elastic plate, method for creating the same, and imaging system

Abstract

A process for creating a flexible sheet or a mask for producing a flexible sheet includes providing a screen having a resolution defined by a basic pattern of screen spots of equal size, each screen spot comprising a discrete element of minimum exposure represented on the screen. In at least a non-solid tonal portion of the sheet or mask, the size of the physical spots is selectively modulated so that each group of four adjacent physical spots in the basic pattern has an unexposed region centered therebetween. Each screen spot in the basic pattern can be an exposed pixel surrounded by eight unexposed pixels, each physical spot corresponding to the resolution of a laser beam used to expose the spot on the mask, wherein the imaging step includes boosting the power of the laser beam used to isolate pixels relative to non-isolated pixels. Masks and sheets and imaging systems for creating them are also disclosed.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority from U.S. Provisional Application No. 62 / 342,475, filed May 27, 2016, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates to printing, and more particularly to flexographic printing, and to methods for improving the tone response curve of printing plates and systems for implementing such methods, including plate making methods. Background Art

[0004] Traditionally, a flexible plate has a flat upper level surface for printing solid areas, a flat lower surface for leaving the substrate unprinted, and a number of mathematically organized printing dots at the upper level (the level that physically touches the print medium onto which the printed image is transferred) with a size corresponding to the density to be reproduced. One printing method is called AM (amplitude modulated) and is characterized by a fixed number of dots per linear inch, which is called the screen ruling or line count. Over time, many variations have been developed, including stochastic screening (also called FM screening, where the dots have a fixed size and the density or frequency of the dots is modulated), and hybrid AM / FM screening, where typically the highlights have a random pattern and the rest follow the traditional AM pattern.

[0005] Methods have also been developed to improve solid rendering by replacing flat surfaces with modulated surfaces. Several modulation patterns are now in common use, including large numbers of square or circular "white" cells organized into mathematical grids or more randomly, into lines / grooves, and more recently, into very high resolution patterns or textures that can take less than 50% of the board to the highest level.

[0006] As a result of research to find the best solid rendering mode, and with improvements in imaging equipment (especially remote level control of the resulting plate's microscopic results), significant reliable improvements have been achieved. Density increases of 0.3 on the density scale are not exceptional (e.g., a cyan density of 1.2 is achieved without a solid pattern and a cyan density of 1.5 with a solid pattern). In addition, these improvements also result in a color shift, typically towards a chromaticity closer to the theoretical chromaticity of the ink. This is caused by thinner ink layers, which are now generally accepted to be a result of high frequency modulation.

[0007] This achieves benefits, but creates a new problem: the dramatic improvement in solid rendering creates a strong discontinuity between solid and nearly solid. This discontinuity is visible in both synthetic gradients (as made, for example, via the gradient function of Adobe Illustrator or other applications that generate PDF gradient structures) and continuous tones (where different separation methods inevitably assign the highest possible density for a given ink to some areas, and other areas, usually nearby areas, a density smoothly just below it). The human eye is extremely sensitive to this discontinuity. As a result, this problem leads to rejection of printed artwork.

[0008] Several mitigation solutions for this discontinuity problem have been presented and widely used. One such mitigation solution is not to use solid patterns in which smooth gradients are required. This means that in practice, algorithms or human operators decide what to consider as solid (to be promoted) and what to consider as non-solid. One method is to consider only synthetic flat line halos as solid, and all the rest (continuous tones, gradients) as non-solid. This is a simple and reasonably practical method (some RIPs allow this to be done automatically). However, the disadvantage of this method is that the benefits of rendering promotion may be lost in important places. For example, without promotion, continuous tones can be continuously printed "dark colors", that is, with a limited range of tones. Highly saturated colors may not be achieved because saturated colors usually include at least one printing ink with high density. Ultimately, many designs stitch flat areas to variable areas. Compared again to other areas, the different treatment of the synthesis of flat line halos may show discontinuities in the final printing result. Detecting this type of discontinuity may require scanning the entire page description using a highly specialized (typically slow) algorithm, and even when detected, there may be no suitable solution.

[0009] Another mitigation scheme for the discontinuity between solid and nearly solid areas is proposed in EP1557279B1 (Dewitte), wherein in at least one embodiment, the solid pattern, more specifically the groove, fades into the screened area. The mitigation scheme can also be customized to potentially avoid undesirable negative effects, such as the generation of moiré patterns. Mathematics teaches that the combination of 2 patterns with different frequencies and / or angles can generate a third pattern with lower strokes and angles. This moiré pattern may be rejected by print buyers because it is usually very noticeable to the naked human eye. Dewitte's method solves this problem by placing a solid rendering pattern at a "rational multiple" of the original pattern, i.e., the solid rendering pattern is selected so that the moiré generated with the original screen pattern is at the same frequency and angle as the original screen. Assuming that the original screen is acceptable to the human eye, the combined effect is typically also acceptable.

[0010] However, given that frequencies and angles that are very well calculated for solid lifting patterns must generally be selected to avoid moiré patterns, the selected frequencies and angles for avoiding moiré patterns may not be optimal for solid lifting. In general, a pattern generated without moiré can only lift solids half as much as an optimal lifting pattern on average.

[0011] Furthermore, the highly non-linear behavior of flexible plate making and printing also means that when a solid pattern fades into a near solid screened area, the resulting tone curve does not always fade as linearly as might be expected. In general, for example, half of a pattern may not have half the boost in density, and it may not boost at all or even work in reverse. Moreover, the addition of conventional screen dots may disturb the pattern in such a way that it no longer works as expected. Attempts to avoid disturbing the pattern with screen dots by maintaining guard zones between patterns may add a further complication, with the risk of further disturbing the solid rendering effect.

[0012] Another problem that is very well known in flexographic printing is (near) dot touch-ups. The ink rendering of flexographic printing can react very nonlinearly when the printed dots are within a certain proximity threshold to each other. Two dots that are relatively close to each other can create a "bridge", where the location of what should be a non-printing area between the dots is so close to the printing surface that it grabs ink, sometimes even more ink than the printed area. This can lead to strong "tone jumps" with difficult-to-predict densities. Until a certain threshold is reached, which may be affected by several variables that may not always be known or predictable, the ink does not bridge between two adjacent dots. Then, with a minimal reduction in the distance between the dots, a bridge may suddenly form. Bridge formation may depend, among other things, on printing pressure, dot shape, anilox roller properties and pressure, ink viscosity and printing speed.

[0013] Aspects of the claimed invention may alleviate the near-point bridging problem at least in part by affecting the shape in a way that makes the bridge less abrupt and grabs less ink.Aspects of the claimed invention may simultaneously alleviate discontinuities between solid and nearly solid areas. Summary of the invention

[0014] One aspect of the present invention is a process for creating a flexible plate or a mask for producing a flexible plate. A step in the process includes providing a screen having a resolution defined by a basic pattern of screen spots of equal size, each screen spot including a discrete element of minimum exposure represented on the screen. The plate or mask is created by selectively modulating the size of the physical spots on the plate or mask corresponding to the screened spots in at least a portion of the plate or mask corresponding to the non-solid tonal area of ​​the plate, so that each group of four adjacent physical spots in the basic pattern has an unexposed area centered therebetween. In one embodiment, each screen spot in the basic pattern includes an isolated pixel, which includes an exposed pixel surrounded by 8 unexposed pixels. In such an embodiment, each screen spot may include a single pixel, and each physical spot may correspond to the resolution of a laser beam used to expose the spot on the mask, wherein the process also includes imaging the mask with a laser beam. The step of imaging the mask with a laser beam may include boosting the power of the laser beam used to image each isolated pixel relative to the power of the laser beam used to image the non-isolated pixels. The size of the unexposed area between the four adjacent imaged spots can be optimized by adjusting the power of the laser beam corresponding to each imaged physical spot to obtain optimization of ink transfer in printing.

[0015] The process of defining a screen may include defining a first screen super-cell, and then for each pixel located at (X,Y) in the first screen super-cell, assigning a location (X', Y') in a second super-cell by applying a first mathematical formula (X'= fx(X,Y); Y'= fy(X,Y)), and then setting the value in the second super-cell not filled by the first mathematical formula to an empty pixel value. The first mathematical formula follows a set of rules, including that (i) X' and Y' are integers, (ii) no two pixels of the first super-cell are transformed into the same pixel in the second super-cell, and (iii) all pixels (X',Y') are located on a high-resolution basic pattern, wherein surrounding each pixel (X',Y') are at least 8 empty pixels not filled by the mathematical formula. The first super-cell may have lines per inch (Lpi) and angle (Ang) such that applying fx(X,Y) and fy(X,Y) may create lines per inch (Lpi' = f3(Lpi) and angle (Ang' = f4(Ang)) in the second super-cell. For the desired Lpi and desired Ang for the second super-cell, the inverse transformation formula may be applied (Lpi" = f3(Lpi)). -1 (Expected Lpi); Ang” = f4 -1 (desired Ang)), thus creating a screen with lines per inch Lpi" and angle Ang".

[0016] A plurality of screens, each corresponding to an ink color, may be created by: for each screen, calculating the desired number of lines per inch and angles Lpi" and Ang" for the group; identifying closely matching groups of strokes / angles that do not contain second-order moiré; generating a plurality of first screening super cells corresponding to the closely matching groups of strokes / angles; and converting each of the plurality of first screening super cells into a corresponding second screening super cell. The second super cell may be created to have a size and desired strokes and angles, wherein a third super cell is created to have the same size and the same desired strokes and angles as the second super cell, the third super cell corresponding to a screen configured to improve highlights, wherein the second and third super cells may be merged into a fourth super cell. The merger may be implemented by performing operations including: (a) for each pixel, determining the cell to which the pixel belongs; (b) based on the determined cell, determining from which of the second and third super cells to copy information, and (c) copying information from the second super cell or the third super cell as determined in step (a) into the fourth super cell. The determination in step (b) may be random, including but not limited to random determination performed using a blue noise determination, or it may be systematic. The process may include copying information from the second supercell at a relatively high tone density, and copying information from the third supercell at a relatively low tone density, and steps (a)-(c) may be performed for the entire threshold array. The third supercell may be created by applying a second mathematical formula (X'= fx(X,Y); Y'= fy(X,Y)), wherein the function pair (fx,fy) in the second mathematical formula is different from the function pair in the first mathematical formula but follows the same rules.

[0017] This process can be used in combination with highlight improvement techniques, such as by applying the process to an original screen that embodies the highlight improvement techniques in at least a portion of it, or switching to solid AM dots at certain highlight levels.

[0018] Another aspect of the invention includes a flexible sheet, or a mask for making a flexible sheet, produced by any of the processes described herein. The resulting sheet or mask may have one or more areas with a first high resolution basic pattern and one or more areas with a second high resolution basic pattern.

[0019] Yet another aspect of the invention includes an imaging system, such as an imagesetter, for generating a mask for making a flexible plate. Such an imaging system includes a laser source configured to expose portions of the mask to radiation corresponding to discrete spots identified in an imaging data file, the laser source having an adjustable laser power for modulating the size of the imaged spots on the mask. The imaging system also includes a controller including a processor configured to receive imaging data and convert the imaging data into operating instructions for the laser source, the imaging data including a screen of a resolution defined by a basic pattern of screen spots of equal size, each screen spot including a discrete element of minimum exposure represented on the screen. The controller is configured to create a plate or mask by selectively modulating the size of physical spots created by the laser on the mask corresponding to the screened spots in at least a portion of the plate or mask corresponding to non-solid tonal areas of the plate so that each group of four adjacent physical spots in the basic pattern has an unexposed area centered therebetween. The exposed spots of the imaging data may include isolated spots, each of which includes an exposed spot surrounded by eight unexposed spots, in which case the controller is configured to identify the isolated spots and command the laser source to use a relatively greater power for creating imaged spots corresponding to the isolated spots in the imaging data than for creating imaged spots corresponding to non-isolated spots in the imaging data. In particular, the physical spots corresponding to the imaging data may include circular spots that do not completely overlap with each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figures 1A-1E Each depicts an exemplary high-resolution basis pattern.

[0021] Figure 2 and 3 Each depicts an exemplary screened area formed from an exemplary high resolution basis pattern.

[0022] Figure 4A A conventional supercell with conventional AM points is illustrated.

[0023] Figure 4B A supercell with corresponding points defined by an exemplary high resolution basis pattern is illustrated.

[0024] Figure 4C A supercell with corresponding dots comprising another exemplary high-resolution basis pattern is illustrated.

[0025] Figure 5 A super cell is illustrated.

[0026] Fig. 6A Portions of an exemplary screen containing a combination of "solid" dots and dots defined by isolated pixels are illustrated.

[0027] Figure 6B A portion of an exemplary screen containing dots defined by isolated pixels is illustrated, wherein the dots in certain locations have been removed.

[0028] Fig. 7A Depicted is the original transition screen, where the tones below critical gray have been modulated by removing dots.

[0029] Figure 7B Describes the transformation Fig. 7A to use a new transition screen after isolating pixels.

[0030] Figure 8 Depicted is a screen of combined supercells with two different dispersed grid patterns.

[0031] Fig. 9A and 9B An exemplary random screen including isolated pixels is depicted.

[0032] Fig. 10A It is a miniature photograph using printed dots formed by a plate made using a standard AM screen.

[0033] Fig. 10B is a miniature photograph using printed dots formed by using a plate produced using an exemplary screen having dots including isolated pixels.

[0034] Fig.11A A screen with a conventional AM dot comprising 20 exposure pixels is depicted.

[0035] Fig. 11B A screen with dots each comprising 4 isolated exposed pixels is depicted.

[0036] Fig.12 An exemplary screen over a large tonal range is illustrated, with various segments magnified and highlighted.

[0037] Fig.13A An exemplary highlight region of a screen comprising a combination of solid AM dots and dots comprising isolated exposed pixels is depicted.

[0038] Fig. 13B is a method according to one embodiment of the present invention. Fig.13A Miniature photograph of the printed dots formed by the plate produced using the screen pattern shown in .

[0039] Fig.14 Depicted is a 3x3 building block for detection of isolated pixels.

[0040] Fig.15A A cluster of 4 adjacent pixels is depicted, showing the area exposed by the laser corresponding to each pixel at an exposure level that does not result in overlap of the exposed areas.

[0041] Fig. 15B A cluster of 4 adjacent pixels is depicted showing the area exposed by the laser corresponding to each pixel using a laser power intended to cause each exposed area to overlap sufficiently to produce a solid dot.

[0042] Fig. 15C A cluster of 4 adjacent pixels is depicted, which shows the area exposed by the laser, which corresponds to a region between Fig.15A and 15B Each pixel of the laser exposure levels between the laser exposure levels, leaving an unexposed area in the center.

[0043] Fig.16 is a schematic illustration of an imaging system. DETAILED DESCRIPTION

[0044] One aspect of the present invention involves solving or alleviating the above problems by using a screen pattern constructed in a large portion of the tonal scale of an ultra-high resolution basis pattern from discrete imaged spots that are exposed with adapted (typically higher) laser powers than have been conventionally used in the art. The actual screen shapes (such as circular dots) then become virtual shapes in the digital film and on the printing plate, resulting in actual printed dots with fewer of the above disadvantages, and in addition creating a smooth gradient to a lifted solid.

[0045] In a preferred embodiment, the high-resolution basic pattern can be equal to the pattern for solid rendering. One such pattern is illustrated in FIG. 1 . The square grid 100 is an imaging system high-resolution grid (e.g., 4000ppi). The laser images the black spots 102 and does not image the white spots 104. Therefore, on the black LAMS layer, the black spots are ablated, resulting in the creation of dots in these areas. By adjusting the size of the ablated black spots by adjusting the laser power, the dot formation can be optimized with respect to the ink transfer during the printing process. For a specific set of operating conditions (ink viscosity, the material of the structure of the substrate receiving the ink, etc.), the solid ink density (SID) can be optimized by selecting the size of the black spots corresponding to the peak in the SID. The white area is not exposed and results in the formation of the board surface below the highest level. However, because the frequency is so high, the lower surface of the white area is still very higher than the lower level without printing. In fact, the height difference between the white and black sections may be only about 50 microns (while the total relief is usually >500 microns).

[0046] Figure 1AThe pattern illustrated in is just one of many that have been found to create ultra-high solid density if and only if the black spots are imaged with a well-regulated laser power, as is well known in the art. Figure 1B-1E The pattern shown in the figure can be used in conjunction with the above Figure 1A The same way as described can be used, as long as the pattern has black spots that are discrete from each other (meaning that none of the 8 pixels surrounding the black spot are black).

[0047] The solid areas just follow the basic pattern. For the screened areas, imaging still only occurs on the black spots determined by the high-resolution grid. However, to make lower densities, some black spots are no longer imaged (while all white spots are still always unimaged). This creates a Figure 2 , where each cluster 200 of black spots 102 (each representing, for example, 1 hit of laser power) resembles a conventional "screened dot" as it would have been rendered in accordance with the prior art. After creating the plate and printing these dots, a printed dot will be created that will be closer in shape to the prior art printed dot, but with better properties.

[0048] This advantage can be understood by studying actual typical printed shapes of elastic printed dots, such as for example on plastic substrates, e.g. Fig. 10A and 10B As shown in , these figures show miniature photographs of patches of dots printed on film with black ink using grayscale (not color) in mid-tones (ink bridging). Fig. 10A Shown are dots formed using a standard AM screen. Fig. 10B Dots formed using an exemplary screen as described herein are shown.

[0049] Effect of touch tone jump

[0050] Now refer to Figure 3 , although human imagers continue to see bridging behavior of dots, the actual printed spots are never continuous (because the spots are imaged on a high-resolution, discrete grid). Testing of many substrates shows that this reduces ink bridging. Although some bridges may still form, such bridges do not grab the excess ink typically associated with traditional schemes where each screened dot is rendered solid.

[0051] By providing 8 empty pixels around each laser processed pixel, the resulting pattern, by design, does not cover the board area. However, experiments have shown that the best solid rendering is achieved by optimizing the laser power applied to the scattered pixels. In fact, ideally the laser power and the pixel pattern should be adjusted to each other. The fact that the pixels are scattered allows such adjustment with fewer (if any) defects. The imaging system can optimize the laser power (typically a higher power than normally used) for the entire board only if the entire board includes scattered pixels as described herein, or a more advanced system can automatically detect areas with a need for optimized laser power based on the fact that the points are scattered and in the expected position. Methods for adjusting laser power are known in the art, such as the PixelBoost function available in Esko's Grapholas user interface, using, for example, an Esko CDI imager upgraded to the "UV Flattop Option", such as a roll equipped with an upright UV head and gradient index (or aspheric) lens, with a LUST servo drive, using a "Flattop" exposure profile in conjunction with a "High Res" option, such as described, for example, in the Esko Technical Memorandum entitled "Upgrade to Flattop / Round top Option", Revision 4, dated March 11, 2011, which is incorporated herein by reference. The foregoing features are also standard in Esko's CDI Crystal system.

[0052] exist Fig.161 depicts a portion of an exemplary imaging system, including a laser source 1600 and a processor 1602 for controlling the laser source, a memory 1604 for storing imaging data files corresponding to a screen as described herein. The laser source 1600 has an adjustable laser power for modulating the size of the imaged spots on the mask. The controller 1602 typically includes one or more computer processors programmed with instructions, and may also include hardware controls. The controller is configured to receive imaging data and convert the imaging data into operating instructions for the laser source, which in accordance with aspects of the present invention may include selectively modulating the size of the physical spots created by the laser on the mask. Thus, for imaging data including a screen having a resolution defined by a basic pattern of screen spots of equal size, each screen spot including the smallest exposed discrete element represented on the screen, the laser creates physical spots on the mask corresponding to the screened spots. As is known in the art, the mask is then used during a UV exposure step for exposing the plate, which is then further processed to form a finished plate. The plate or mask created by the process described herein results in a plate in which each set of four adjacent physical spots in the basic pattern has an unexposed area centered therebetween. The "smallest exposed discrete element represented on the screen" can be a pixel, such as in a system utilizing isolated pixels as described herein, or can be a collection of pixels corresponding to the smallest dots utilized in a lower resolution screen. In the case of a system utilizing isolated pixels, the controller (in software and / or hardware) is configured to identify the isolated pixels and sufficiently boost them to leave an unexposed portion centered among each group of four exposed isolated pixels. In the case of a system using a lower resolution screen, the system can be configured to modulate the laser power associated with each pixel so that each collection of 4 smallest exposed discrete elements (e.g., dots) has an appropriate unexposed portion among them, without the need for the controller to identify isolated pixels.

[0053] A screen as described herein can be constructed by taking a conventional screen and perforating it with the desired high-resolution elementary pattern. The perforation may, for example, necessitate an algorithm in which each pixel of the conventional screen is compared with the corresponding pixel of the high-resolution pattern. If both are black, the resulting pixel will be black; in any other case, it will be white. The method described corresponds to a process that can be implemented by superimposing films or by using a hardware device that is programmed to image only the filled pixels according to the high-resolution elementary discrete pattern (and thus ignore any other black pixels).

[0054] Although easy to implement, the aforementioned method may have some disadvantages. A first disadvantage may be the generation of unwanted moiré patterns. Modern high-quality screen dots are carefully designed to create a more or less equal surface of dots, and to more or less mathematically correct the average position of the dots. Removing pixels according to the high-resolution pattern may cause some dots to lose / retain more pixels than other dots, with a slight drift in the average position. This may happen quite systematically according to the mathematical interference pattern between the original screen and the high-resolution basic pattern, which interference pattern may become visible to the human eye, leading to the rejection of the printed result.

[0055] A second disadvantage may be the loss of grayscale. In the simplest case, the screen may have as many grayscales as there are pixels in one printed dot. In more complex schemes, additional grayscales are created by modulating the printed dots in size so that the overall average grayscale rises in much smaller steps (at the expense of a slight modulation added to the pattern, with the risk of being visible). In practice, such modulation is applied using a blue noise pattern so that the visibility of the modulation is minimized. However, the superimposed blue noise pattern may be a game-changer. Based on the systematic nature of the interference, some grayscales may risk losing all their added dots, while other grayscales may keep all their added dots. This results in "staircaseization": some steps are strongly compressed while others are enlarged.

[0056] However, it would be ideal to construct a screen without the aforementioned drawbacks while still producing the desired lines and angles. The subject screen construction method uses a transformation from a specially designed base screen with different lines, angles, and resolutions. The screen is transformed into the desired screen with the requested lines and angles via a method as discussed below.

[0057] The operations discussed below are preferably implemented on screen super cells (also called threshold arrays). The preferred embodiment uses super cell screening, which uses threshold arrays. Other screening methods can be used to achieve comparable results by applying the same logic, but while some methods may require ripping page descriptions at different resolutions and angles, the super cell method has no such requirement.

[0058] Figures 4A-4C The transformation used to transform a conventional supercell into a supercell suitable for implementing the current invention is illustrated. For ease of explanation, Figures 4A-4C A super-cell with only 1 screen dot is illustrated, but the same logic can be applied to super-cells of any size or angle. Also, the explanation is provided with reference to a pure bitmap, although the super-cell has a threshold for each pixel, this does not change the logic, and it also illustrates that the method can also be applied to a bitmap array screening method.

[0059] Figure 4B An example using an ultra-high resolution pattern called DDWSI is illustrated. Figure 4C An example using a slightly lower pattern at 45 degrees called WSI is shown. In the DDWSI example, for each pixel in the original supercell, the position in the new supercell is found by applying the mathematical formula of the shape

[0060] X' = ​​fx(X,Y)

[0061] Y' = fy(X,Y)

[0062] The value of the new super-cell pixel found is equal to the value of the original super-cell pixel. For binary input, the output is binary. For the threshold array, the threshold is copied. This will not fill the entire new super-cell. Unreached pixels are set to white (in the case of a binary bitmap) or to maxThresholdValue + 1 in the threshold array (indicating pixels that will never be converted to black).

[0063] Functions fx and fy have the following properties:

[0064] The results X' and Y' are integers

[0065] Different inputs lead to different outputs (no two pixels in the original grid are transformed into the same pixel in the output grid)

[0066] All output pixels (X', Y') lie on the high-resolution basis pattern.

[0067] • Surrounding each output pixel are 8 pixels that are never reached by the transform.

[0068] The function pair (fx, fy) thus determines the high-resolution basic grid. Figure 4B and 4C The following example shows how to create a Figure 4A The input points show the results of two such function pairs.

[0069] Function

[0070] DDWSI pattern ( Figure 4B ):

[0071] Fx(X,Y) = 2X

[0072] Fy(X,Y) = 2Y

[0073] WSI pattern ( Figure 4C ):

[0074] Fx(X,Y) = 2X + 2Y

[0075] Fy(X,Y) = 2X – 2Y.

[0076] In some cases, the shape of the virtual point is largely preserved, while in other cases the shape undergoes larger changes. However, the following generally applies:

[0077] 2 equal-sized dots are transformed into 2 equal-sized virtual dots (each with the same number of black spots)

[0078] · Continuous points are converted into points with "virtual" continuity.

[0079] An approximation of a circle will be converted into an approximation of a circle. The same applies to a square and even to a random pattern with some approximation features.

[0080] The above operation is performed for each pixel in the super-cell, resulting in a new super-cell that is generally larger than the original super-cell. Figure 5 ), the new supercell can be found by taking the outer boundaries of the transformed pixels.

[0081] Example

[0082] The exemplary computer code for performing the aforementioned operations is as follows:

[0083]

[0084] Following the same logic, screen strokes and angles will change under this operation (assuming equal resolution).

[0085] Lpi' = f3(Lpi)

[0086] Ang' = f4(Ang)

[0087] In the example of WSI:

[0088] f3(Lpi) = Lpi / (2*sqrt(2))

[0089] f4(Ang) = Ang + 45 (assuming angle expressed in degrees).

[0090] End users generally do not anticipate changes in stroke and angle to improve the tonal scale of their prints. The trick now is to apply the inverse transformation formula on the requested screen stroke and angle:

[0091] Lpi = f3 -1 (Wanted Lpi)

[0092] Ang = f4 -1 (Wanted Ang).

[0093] This formula gives us a new stroke and angle for each requested stroke and angle, from which a conventional screen is calculated (or derived from a database). The industry has long worked out how to sensibly create a conventional screen at almost any stroke and angle. In the case of flexographic printing, the requested stroke is typically around 150 lpi, and the transformation has a scale between 2.5 and 3 (2*sqrt(2) for the WSI case). This results in the construction of a screen of around 400 lpi at a resolution of 4000 ppi, which is well within the reach of current screening technology.

[0094] For most patterns (especially the WSI and DDWSI mentioned above), the transformation results in screens that have been proven to work well. The flexo angles (7.5, 22.5, 37.5, 52.5, 67.5, 82.5) happen to transform on themselves or on other angles in the flexo set (e.g. 22.5 transforms to 67.5, for which a screen set already exists).

[0095] Transformations with larger scaling effects may become impractical, but are also of little interest because they correspond to lower solid pattern frequencies, which produce less density boost.

[0096] The disclosed method thus has the following features:

[0097] Any line or angle can be achieved

[0098] No moiré effect caused by systematic loss of pixels or displacement of pixels

[0099] • A solid pattern is equal to the pattern determined by the transform if and only if the regular screen from which it is transformed is 100% completely black (as is normally the case).

[0100] • No pixel is ever "black" except those determined by the high resolution grid. This means that all points in the resulting digital film are "discrete", meaning that all of its 8 neighboring pixels are white.

[0101] • The virtual shape of the new screen resembles the shape of the original screen, within the limits imposed by the pixels allowed to be imaged.

[0102] Avoid color overlay moiré

[0103] When creating 3 screens for the colors CMYK, it is known that the scribing lines and angles must be carefully chosen so that the resulting interference pattern does not contain second order moiré. The formula for this can be found, for example, in U.S. Patent No. 5,155,599 to Delabastita, which is incorporated herein by reference in its entirety.

[0104] Since the disclosed transformation changes strokes and angles, it risks introducing moiré between colors if not performed carefully. The following algorithm avoids introducing moiré:

[0105] a) Start with the requested line and angle set;

[0106] b) converting this according to the formula mentioned above;

[0107] c) For this set, find a closely matching scribe line / angle set that does not contain second order moiré. Depending on the technique used, this is generally possible with a deviation of <1% on scribe lines and <0.1 degrees on angles;

[0108] d) Generate 3 screens;

[0109] e) Convert the 3 screens according to the above algorithm.

[0110] The above scheme works because the moiré frequencies of the converted screens are converted in the same way as the original frequencies (purely for reasons that interfere with the mathematical linearity of the formula). The above-mentioned formula of Delabastita involves the moiré period, which is in fact infinite (the 0 in the equation refers to the frequency of the moiré, and the period is the inverse of this). The conversion will then divide the moiré by the frequency conversion factor, which for WSI is (2*sqrt(2)). Since any real number divided by infinity remains infinite, the converted screen set is also free of second-order moiré.

[0111] The important detail is the form of the rosette. This is determined by the linear drift of the dot centers compared to each other. Placing all dot centers on top of each other at the origin creates a dot-centered rosette, while the more accepted sharply centered rosette requires a drift of one of the colors (mostly black) over half the diagonal of the unit square. Since all distances transform with a frequency factor and an angular drift, this is also done for the rosette drift distance.

[0112] Replaceable structure

[0113] Many alternatives to the above method can be constructed. For example, in a first alternative embodiment, a simple method for creating a high-resolution basic pattern can be combined with other aspects of the enhancement method described herein. For example, a simple multiplication formula (X'= X*2, Y'= Y*2) can be followed by the perforation method. The resulting combination comes from the benefits and disadvantages of both methods and must be considered a compromise. In a second alternative embodiment, a completely new screen can be calculated that applies the best practices of screen design to the modified pixel grid. In fact, screen design best practices are generally developed for pure square pixel grids, but their goals can be largely easily transferred to other grids. For example, an attempt to keep all screen points of equal size can be performed on an alternative pixel grid. Managing the Fourier transform of the screen is only slightly more complex than the method described above and is not a problem for contemporary computer capabilities.

[0114] The method as described herein works on all grayscales and can thus be used across the entire tonal range. However, it is not necessary to use it across the entire tonal range. Some users may want to apply the technique only to a certain extent, and not, for example, in extreme highlights. In a preferred embodiment, the technique is applied at least in the region from 100 to 20%. Below 20%, the printing environment may dictate whether to use the technique described herein, a highlight improvement technique known in the art, or a combination thereof.

[0115] Therefore, a method including the highlight improvement technique is now described. A simple method is by converting an original screen that already includes the highlight improvement technique (e.g. a hybrid screen such as Esko Samba screen, Esko PerfectHighlight screen, HDFlexo screen - using FM-style modulation in the highlights) to the new screen of the present invention.

[0116] The new screen formed according to aspects of the present invention is created by converting every pixel of the original, thus also inheriting the dedicated highlight modulation (e.g., virtual FM point). Fig. 7A and 7B In the figure, Fig. 7A depicts the original transition screen (Samba screen - tones below critical gray are modulated by removing dots), and Figure 7B Depicted is a new screen after transformation of the original screen, which results in the same modulation.

[0117] However, due to the conversion to a higher resolution grid, the highlight improvement technique parameters may require scaling (eg via different transition points or minimum dot size). This simple approach has the advantage that it does not create discontinuities in the new screen, but it limits highlights to also using high resolution isolated pixels.

[0118] Another highlight improvement method is by fading in the highlight improvement screen into a new screen for a specific tonal range. First calculate supercells with the desired strokes and angles. Using any prior art highlight improvement technique, calculate equal sized supercells with the exact same desired strokes and angles. Modern screening techniques can generate the desired prior art screen properties as described, such as, for example, using Esko's Screen Manager.

[0119] Next, combine the two super units into a third super unit as follows:

[0120] a) For each pixel, determine the cell to which it belongs. By way of explanation, a is an element of the screen grid, which is formed by the screen lines and angles. For AM screens, a cell is a placeholder for a single dot. Determining the cell to which a pixel belongs is done by using the pixel coordinates and determining which grid element these coordinates fall into. The assignment of pixels to screen cells is a mathematical operation based on the lines and angles of the requested screen. A simple way is to assign each pixel to the screen dot center that is closest to it (taking closer points into account as they are repeated over the edges of a super cell). This is a prior art technique used in many screen calculation algorithms.

[0121] b) Based on the cell, determine from which of the two super cells the information is copied. This determination can be purely random, such as using blue noise, or systematic (e.g. in a checkerboard pattern).

[0122] The foregoing steps can be performed for the entire threshold array or individually for each bitmap array found by bisecting the two threshold arrays with the current threshold. In this case, the result will typically no longer be a threshold array, and the result will then have to be stored as a bitmap array group and used by the bitmap array screen method in the RIP, which functionality is established in the most current advanced PDF RIPs. As known in the art, the threshold array represents a threshold for each pixel in the repeating tile, which determines the grayscale at which the pixel must be turned on or off in the final dual-level output. Such an array can also be represented as an array of bitmaps. Each bitmap then represents the pixels turned on for one grayscale. Therefore, another way to merge the original super-cell with the new super-cell is to first convert the two threshold arrays into bitmaps, one bitmap for each grayscale, and then apply this step by merging the bitmaps. The new screen is then represented as a series of bitmaps. In an alternative embodiment, such as in a more advanced RIP, such as Esko FlexRIP and Esko Imaging Engine, a multi-threshold array bitmap can be used. In such a bitmap, each pixel can have multiple thresholds (a pixel can be turned on and off multiple times with different thresholds). In a system with such capabilities, merging different screens can result in a single multi-threshold bitmap rather than multiple bitmap arrays.

[0123] One embodiment of the previous method includes staying closer to the first supercell at a higher density (e.g., at 20%), and closer to the second supercell at a lower density (e.g., closer to 0%). In this way, a smooth transition occurs between the newly proposed screen and the known features of the prior art highlight improvement screens.

[0124] exist Fig. 6A A possible result is illustrated in , which illustrates two types of screen dots: dots based on a conventional screen (continuous dots 600 on a regular grid) and dots based on the newly proposed screen (clusters 602 of three pixels spaced apart and standing on a dispersed grid).

[0125] In another example, blue noise may be applied without a second super-cell (or with an empty super-cell). Figure 6B The result illustrated in comprises a dispersed cluster of dots 700 according to the current invention, which are randomly scattered in space. In this method, the highlight effect (FM-style modulation) is achieved directly on the new screen: for example, in order to obtain tones below the critical gray scale, the virtual dots are no longer reduced in size, but are gradually removed in a blue noise manner (such as by using the EskoSamba screen technology).

[0126] It is also possible to mix and match different patterns. Using the same techniques as described above, super cells with two different dispersed grid patterns 800 and 802 can be combined, such as Figure 8 In the combination of different patterns, each of the two different scattered grid patterns is related to each other so that the combination of patterns does not violate the scattered rule in the merged screen (every pixel must be isolated). An example of two compatible patterns is the DDWSI and WSI patterns: The two patterns are converted to:

[0127] X_WSI = X_DDWSI + Y_DDWSI

[0128] Y_WSI = X_DDWSI – Y_DDWSI.

[0129] These patterns can be combined in at least two ways:

[0130] 1. Generate a new screen using the conversion to WSI. Then merge the DDWSI pattern on a cell-based criterion (e.g. blue noise: apply DDWSI to cells farthest from each other first) by adding the missing pixels to the WSI grid.

[0131] 2. Generate a new screen using the conversion to DDWSI. Then merge the WSI pattern on a cell-based criterion by removing pixels in the DDWSI grid.

[0132] Another approach is to start combining WSI points with "normal" solid AM points at a certain threshold. Fig.11A and 11B To understand the advantages of the method of combining a "normal" continuous AM dot and a "WSI" dot including an isolated pixel (which reduces the number of exposed pixels by 8). Fig. 11B As shown in , at smaller dot sizes, the WSI dot consists of only 4 exposure pixels, so only 4 grayscale levels are possible and the dot is a "square" shape, while Fig.11A The conventional AM dot shown in has 20 pixels, and thus 20 gray levels, which has a better ability to approximate more rounded shapes.

[0133] Another option is to replace the dots with the WSI pattern with solid dots when the dots become smaller than a certain surface, or when the hue to be represented becomes below a certain threshold. Ideally, the transition from WSI dots to solid dots should be made in a way that minimizes detection by the human eye. One way to do this is to gradually replace the WSI dots with solid dots in an optimal distribution, so that the points that are farthest from each other are replaced first, using the furthest distance algorithm. Thus, in Fig.12In the exemplary implementation depicted in , WSI dots begin to be replaced by AM dots at a certain size, namely at tones with WSI dots of 6 pixels. Further down the tonal scale, WSI dots of 5 and 4 pixels are also replaced by AM dots, where the AM dots also decrease in size. In even lighter tones, where only solid AM dots remain, other highlight improvement techniques may be employed, as described herein, including the use of FM techniques with dot removal.

[0134] Ideally, the printed dot size of a WSI dot should be equal to the printed size of an AM dot. Therefore, a WSI to AM size ratio is identified, which indicates the ratio of the WSI dot relative to the AM dot that replaces it (e.g., a ratio of 4:20 indicates that a WSI dot of 4 pixels will be replaced by an AM dot containing 20 pixels).

[0135] This ratio may depend on the printing conditions and may be determined empirically by printing screens using different ratios and selecting the ratio that does not produce a visible transition for a given set of conditions. Fig.13A and 13B As shown in , at a ratio of 4:20 for the particular printing conditions used, the solid dot print has dots equal in size to the WSI dots, and the transition is thus not visible. Highlighting effect techniques known for use with solid or AM dots, such as the use of supporting dots, etc., can then be used below the threshold where all dots are solid.

[0136] To mix WSI and solid dots, the screen can be represented in a multi-threshold array (or in a single multi-threshold bitmap) so that each pixel in the bitmap can have more than 1 threshold level. For example, to represent a solid dot in a light color, the pixels must be connected to each other and form a specific dot size. To increase the color and dot size, more pixels are turned on at higher thresholds until the WSI / solid transition point, at which point the dot becomes a WSI dot with isolated pixels, so some pixels are turned off again. The AM dot that replaces the WSI dot is placed at the same position (i.e., the center of the AM dot falls on the same screen grid as the center of the WSI dot). To achieve this, the AM dot can be generated from a dot value function rather than by merging the AM screen into the WSI screen. At each WSI dot position, the AM dot value function determines the appropriate threshold so that a specific circular shape is obtained with appropriate tone modulation.

[0137] The method is not limited to raw AM screens. The described embodiments can be used to perfectly transform a random screened supercell into a new supercell where all points are on a high resolution dispersed pixel grid. In such embodiments, "apparent" scribing will be reduced as it is effective for AM screening. Thus, high frequency patterns, such as used, for example, in high quality compensation, can be transformed with much lower frequency results that are more realistic for flexographic printing. Fig. 9A and 9B As shown in , this method can be applied to any super-cell screen, to any bitmap array screen, and is easily extended to any shape of screening.

[0138] Laser tuning

[0139] The screening patterns described herein with characteristic basic patterns are ideally used in combination with an imaging unit capable of pixel boosting. It should be understood that the laser modulation used to control the size of each basic element (e.g., isolated pixel) of the basic pattern can be tuned or optimized for each set of printing conditions (ink, substrate, temperature, etc.) to maximize ink retention characteristics. For example, an ESKO CDI unit as described herein can have a controllable boost amount between 100-400% of the "normal" intensity (power) of the laser.

[0140] The laser system can be programmed to identify isolated pixels using a detection algorithm, such as by using Fig.14 The same structure can be used to identify single pixel diagonals (which can also be lifted) by finding the center-exposed pixel with exposure neighbors located in (a) only the northwest and southeast corners or (b) only the northeast and southwest corners.

[0141] Therefore, a screen containing WSI dots as described herein is ideally implemented using a combination of software that creates the desired digital pattern and an exposure system that is programmed to detect isolated pixels and modulate the size of the isolated pixels when creating the mask. The mask is then ideally used to make a plate using a system that is designed to create a flat top pixel structure, as known in the art. An exemplary imager that can be programmed to lift isolated pixels to create a mask with microcells as described herein is a CDI digital imager manufactured by Esko Graphic Imaging GmbH of Itzehoe, Germany, with GRAPHOLAS (version 10.3.0 or higher) software installed and capable of creating flat top dots. In particular, Esko's "Full HD" and CDI Crystal systems, which include pixel lifting and inline UV capabilities, are ideal for practicing the steps described herein. Lifting isolated pixels provides a level of fine tuning with resolution that is generally unavailable using only features in the screen. Such fine tuning allows tones to be defined in the screen, as well as the ability to use hardware to modulate the defined ink transfer capabilities.

[0142] Although described herein in conjunction with Esko hardware, the invention is not limited to any particular manufacturer's system. Systems for creating flat top spots using UV exposure are known in the art. In an Esko system, for example, such a system may be equipped with a specific UV head and a servo system capable of turning the roll at a desired speed, and with high resolution optics, such as gradient index or aspheric focusing lenses. The use of flat top exposure is particularly desirable because it maintains the exposure on the top of the plate, making a more obvious "hole" for the ink to fill when the plate is created from the mask. In general, the use of UV heads that do not mimic bank lights and do not have a wide angle distribution is also possible.

[0143] Systems that can be used to create the desired panel properties as described herein are not limited to the exemplary systems discussed herein. The term "mask" as used herein can refer to any type of structure used during the panel exposure step. Although shown and described herein with respect to a UV exposure system for creating a mask, it should be understood that a laser system for directly ablating panel material can also be programmed to modulate the laser power in a manner to create the desired effect on the panel. Any method for modulating the size of the openings on the mask that is not limited to laser exposure can be used. Similarly, any panel manufacturing method that uses a mask or otherwise can transform the screen information in such a manner that it creates a desired panel structure corresponding to the screen having the ink transfer characteristics caused thereby can be used in conjunction with the screen structure described herein.

[0144] Prints created using plates created by the systems and methods described herein tend to have dot gain that is less dependent on screen rulings, and the dot gain curve has minimized tonal jumps. The technique also minimizes dot bridging.

[0145] Although described herein in conjunction with a screen having a WSI structure as described herein (i.e., a high resolution basic pattern of isolated dots), and there are advantages to using such a screen in combination with laser lifting, any system that can be tuned to selectively modulate the size of the physical spots on a plate or mask corresponding to the screened spots may be used to create the desired ink transfer characteristics so that each set of four adjacent physical spots in the basic pattern has an unexposed area centered therebetween. For example, Fig. 15B As shown in , laser exposure of each pixel is typically selected to provide overlapping spots to completely cover the solid area. However, laser modulation can be used to provide a smaller spot size corresponding to each exposed pixel so that an unexposed area centered among four adjacent spots appears, such as Fig. 15C As shown in Fig.15A and 15C As shown in both examples, the spots formed by the laser are not as Fig. 15B Although Fig.15A , but it should be noted that configurations in which the spots do not touch may also be used, such as if the solid ink density is adjusted to be less than a maximum, but with the same uniformity of the ink film on the substrate. Thus, for example, instead of creating a high resolution screen with isolated pixels, a lower resolution screen may be used in conjunction with laser modulation that ensures that regardless of the screen dot size, the structures actually imaged contain small unexposed areas that provide the ink transfer advantages discussed herein.

[0146] Although the invention is illustrated and described herein with reference to particular embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.

Claims

1. A method for creating an elastic plate, the method comprising the following steps: (a) providing image information corresponding to ink bearing and non-ink bearing portions of the plate, the ink bearing portions comprising a plurality of ink bearing elements; (b) creating a mask used in exposing the plate during an exposure step in accordance with the image information by: (i) superimposing on the image information a basic pattern of spots of equal size, each spot corresponding to an imaged discrete element represented on the mask and having a size corresponding to the size of the smallest discrete element formed on the mask, wherein the basic pattern includes spots corresponding to the imaged elements aligned in horizontal and vertical rows, wherein the spacing between adjacent horizontal rows is equal to the spacing between adjacent vertical rows, and the closest spots corresponding to the imaged elements in adjacent rows are centrally aligned vertically with each other, and the closest spots corresponding to the imaged elements in adjacent columns are centrally aligned horizontally with each other; (ii) selecting dimensions for forming each imaged discrete element in at least a portion of the mask corresponding to non-solid toned areas of the plate so that each group of four adjacent imaged discrete elements has an unimaged area centered therebetween; as well as (c) Optimizing dot formation with respect to ink transfer of the printing process by adjusting the size of the imaged discrete elements by adjusting the laser power of the laser beam.

2. A method for creating an elastic plate, the method comprising the following steps: (a) providing image information corresponding to ink bearing and non-ink bearing portions of the plate, the ink bearing portions comprising a plurality of ink bearing elements; (b) creating a mask used in exposing the plate during an exposure step in accordance with the image information by: (i) superimposing on the image information a basic pattern of spots of equal size, each spot corresponding to an imaged discrete element represented on the mask and having a size corresponding to the size of the smallest discrete element formed on the mask, wherein the basic pattern comprises spots corresponding to the imaged elements aligned in horizontal and vertical rows, wherein the spacing between adjacent horizontal rows is equal to the spacing between adjacent vertical rows, and wherein the closest spots corresponding to the imaged elements in adjacent rows and columns are centrally aligned and diagonally aligned with each other; (ii) selecting dimensions for forming each imaged discrete element in at least a portion of the mask corresponding to non-solid toned areas of the plate so that each group of four adjacent imaged discrete elements has an unimaged area centered therebetween; as well as (c) Optimizing dot formation with respect to ink transfer of the printing process by adjusting the size of the imaged discrete elements by adjusting the laser power of the laser beam.

3. The method of claim 2, wherein the nearest spots corresponding to imaged elements in adjacent rows and columns are centrally aligned with each other on a diagonal line having a rise:run of 1:1 and -1:

1.

4. The method of claim 2 wherein the nearest spots corresponding to imaged elements in adjacent rows and columns are centrally aligned with each other on a diagonal line having a rise:run of 1:2 and -2:1 or -1:2 and 2:

1.

5. A method for creating a flexible plate, the method comprising the steps of: (a) providing image information corresponding to ink bearing and non-ink bearing portions of the plate, the ink bearing portions comprising a plurality of ink bearing elements; (b) creating a mask used in exposing the plate during an exposure step in accordance with the image information by: (i) superimposing on the image information a basic pattern of spots of equal size, each spot corresponding to an imaged discrete element represented on the mask and having a size corresponding to the size of the smallest discrete element formed on the mask, wherein the basic pattern includes spots corresponding to the imaged elements aligned in horizontal and vertical rows, wherein the spacing between adjacent horizontal rows is not equal to the spacing between adjacent vertical rows, and wherein the closest spots corresponding to the imaged elements in adjacent rows and columns are centrally aligned and diagonally aligned with each other; (ii) selecting dimensions for forming each imaged discrete element in at least a portion of the mask corresponding to non-solid toned areas of the plate so that each group of four adjacent imaged discrete elements has an unimaged area centered therebetween; as well as (c) Optimizing dot formation with respect to ink transfer of the printing process by adjusting the size of the imaged discrete elements by adjusting the laser power of the laser beam.

6. The method of claim 5, wherein the spacing between adjacent horizontal lines is half the spacing between adjacent vertical lines.

7. The method of claim 6 wherein the nearest spots corresponding to imaged elements in adjacent rows and columns are centrally aligned with each other on a diagonal line having a rise:run of 2:1 and 2:-1.

8. A method according to any one of claims 1-7, wherein each imaged discrete element corresponds to the spatial resolution of a laser beam used to form the discrete imaged elements on a mask, the method further comprising imaging the mask using a laser beam to ablate openings in a mask layer disposed on the plate.

9. The method of claim 8 , comprising providing a screen having a resolution defined by a basic pattern of screen spots of equal size, each screen spot comprising a discrete element of minimum exposure represented on the screen, wherein each screen spot in the basic pattern comprises an isolated pixel comprising an exposed pixel surrounded by eight unexposed pixels, and wherein the step of imaging the mask with a laser beam comprises boosting the power of the laser beam used to image each isolated pixel relative to the power of the laser beam used to image non-isolated pixels.

10. A method according to any one of claims 1 to 7, comprising selecting a size of the imaged discrete elements that corresponds to a peak in solid ink density for a particular set of operating conditions.

11. The method of any one of claims 1-7, wherein each of four adjacent imaged discrete elements has a size that is larger in area than an unimaged region centered therebetween.

12. The method of any one of claims 1-7, wherein each adjacent imaged discrete element in the set of four adjacent imaged discrete elements touches or overlaps at least two other elements in the set.

13. The method of any one of claims 1-7, wherein no adjacent smallest discrete imaged elements in the set of four adjacent imaged discrete elements touches or overlaps another element in the set.

14. The method of any one of claims 1-7, wherein the exposing step comprises exposing the plate using a UV exposure configured to produce a flat top spot.

15. The method of any one of claims 1-7, further comprising applying the method to an original screen that embodies a highlight improvement technique in at least a portion of the screen.

16. The method of claim 9, comprising converting a first pixel in a first screen into a group of four pixels in a second screen, wherein each exposed first screen pixel is converted into 1 exposed and 3 unexposed second screen pixels.

17. The method of claim 16, wherein each second screen pixel represents a highest resolution level of the mask or the plate.

18. An elastic sheet produced by the method according to any one of claims 1 to 17.

19. A resilient sheet according to claim 18, wherein the sheet comprises one or more areas having a first basic pattern and one or more areas having a second basic pattern.

20. The elastic sheet of claim 19, wherein the sheet comprises a mixture of dots formed from a first basic pattern and solid AM dots in highlight areas embodying a highlight improvement technique.

21. An imaging system for producing a mask for making a flexible sheet, the mask comprising a mask layer disposed on a printing plate and having openings in the mask layer, the imaging system comprising: a laser source configured to ablate portions of the mask layer to form openings corresponding to discrete imaged elements corresponding to equal-sized spots identified in the imaging data file, the laser source having an adjustable laser power for modulating the size of a laser beam used to ablate the imaged elements in the mask layer; a controller including a processor configured to receive imaging data and convert the imaging data into operating instructions for a laser source, the imaging data including imaging data including image information corresponding to ink bearing and non-ink bearing portions of the plate, the ink bearing portions including a plurality of ink bearing elements, the imaging data including a base pattern including spots superimposed on the image information, each spot corresponding to an imaged discrete element represented on the mask and having a size corresponding to a size of a smallest discrete element formed on the mask, wherein the base pattern includes spots corresponding to the imaged elements aligned in horizontal and vertical rows, wherein a spacing between adjacent horizontal rows is equal to a spacing between adjacent vertical rows, and nearest spots corresponding to imaged elements in adjacent rows are centrally aligned vertically with each other, and nearest spots corresponding to imaged elements in adjacent columns are centrally aligned horizontally with each other; and The controller is configured to create the mask by ablating each imaged discrete element in at least a portion of the mask corresponding to non-solid toned areas of the plate using a laser beam having a size such that each group of four adjacent imaged discrete elements has an unablated area centered therebetween.

22. An imaging system for producing a mask for making a flexible sheet, the mask comprising a mask layer disposed on a printing plate and having openings in the mask layer, the imaging system comprising: a laser source configured to ablate portions of the mask layer to form openings corresponding to discrete imaged elements corresponding to equal-sized spots identified in the imaging data file, the laser source having an adjustable laser power for modulating the size of a laser beam used to ablate the imaged elements in the mask layer; a controller including a processor configured to receive imaging data and convert the imaging data into operating instructions for a laser source, the imaging data including imaging data including image information corresponding to ink bearing and non-ink bearing portions of the plate, the ink bearing portions including a plurality of ink bearing elements, the imaging data including a base pattern including spots superimposed on the image information, each spot corresponding to an imaged discrete element represented on the mask and having a size corresponding to a size of a smallest discrete element formed on the mask, wherein the base pattern includes spots corresponding to imaged elements aligned in horizontal and vertical rows, wherein a spacing between adjacent horizontal rows is equal to a spacing between adjacent vertical rows, and nearest spots corresponding to imaged elements in adjacent rows and columns are centrally aligned and diagonally aligned with each other; and The controller is configured to create the mask by ablating each imaged discrete element in at least a portion of the mask corresponding to non-solid toned areas of the plate using a laser beam having a size such that each group of four adjacent imaged discrete elements has an unablated area centered therebetween.

23. The imaging system of claim 22, wherein the nearest spots corresponding to imaged elements in adjacent rows and columns are centrally aligned with each other on a diagonal line having a rise:run of 1:1 and -1:

1.

24. The imaging system of claim 22, wherein the nearest spots corresponding to imaged elements in adjacent rows and columns are centrally aligned with each other on a diagonal line having a rise:run of 1:2 and -2:1 or -1:2 and 2:

1.

25. An imaging system for producing a mask for making a flexible sheet, the mask comprising a mask layer disposed on a printing plate and having openings in the mask layer, the imaging system comprising: a laser source configured to ablate portions of the mask layer to form openings corresponding to discrete imaged elements corresponding to equal-sized spots identified in the imaging data file, the laser source having an adjustable laser power for modulating the size of a laser beam used to ablate the imaged elements in the mask layer; a controller including a processor configured to receive imaging data and convert the imaging data into operating instructions for a laser source, the imaging data including imaging data including image information corresponding to ink bearing and non-ink bearing portions of the plate, the ink bearing portions including a plurality of ink bearing elements, the imaging data including a base pattern including spots superimposed on the image information, each spot corresponding to an imaged discrete element represented on the mask and having a size corresponding to a size of a smallest discrete element formed on the mask, wherein the base pattern includes spots corresponding to imaged elements aligned in horizontal and vertical rows, wherein a spacing between adjacent horizontal rows is not equal to a spacing between adjacent vertical rows, and nearest spots corresponding to imaged elements in adjacent rows and columns are centrally aligned and diagonally aligned with each other; and The controller is configured to create the mask by ablating each imaged discrete element in at least a portion of the mask corresponding to non-solid toned areas of the plate using a laser beam having a size such that each group of four adjacent imaged discrete elements has an unablated area centered therebetween.

26. The imaging system of claim 25, wherein the spacing between adjacent horizontal lines is half the spacing between adjacent vertical lines.

27. The imaging system of claim 26, wherein the nearest spots corresponding to imaged elements in adjacent rows and columns are centrally aligned with each other on a diagonal line having a rise:run of 2:1 and 2:-1.

28. An imaging system according to any one of claims 21-27, wherein the controller is configured to identify each spot corresponding to the imaged discrete element in the basic pattern as an isolation spot, the isolation spot comprising an exposed spot surrounded by 8 unexposed spots, and command the laser source to use a relatively larger power to expose or ablate the imaged discrete elements corresponding to the isolation spots in the imaging data than to ablate the imaged discrete elements that do not correspond to the isolation spots in the imaging data.

29. The imaging system of claim 27, wherein each ablated imaged discrete element in the set of four adjacent imaged discrete elements has a circular perimeter that does not completely overlap with the perimeter of another ablated imaged discrete element in the set of four adjacent imaged discrete elements.

30. A plate production system comprising the imaging system of claim 29, wherein the plate production system further comprises a UV exposure system for exposing the plate to UV radiation in a pattern corresponding to the mask, the UV exposure system being configured to produce a flat top spot.

Images