JP4582977B2 - Method and apparatus for optimized image processing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates generally to digital printing methods and apparatus, and more particularly to methods and apparatus for improving the editing of image data and optimizing the accuracy of the rendered image.
[0002]
[Prior art]
There are various methods and techniques for digitally encoding a document and transferring such a digital representation to an output device. At the coding stage, these range from enthusiast scanners and related software to sophisticated prepress systems. These systems replace the traditional “cut and paste” technique for layout. This approach requires that various document components, such as text, graphic patterns, and photographic images, be placed on a white board by laborious manual work and then duplicated. Instead, now designers can use a computer to manipulate all of these components at once.
[0003]
There are many forms of digitally encoded document output, ranging from laser printing to digital exposure of photographic film, and transfer of images to lithographic plates for later mass printing. In the latter case, the printed image is present on the plate or mat as a pattern of ink receptive (lipophilic) and ink repellent (oleophobic) surface areas. In a dry printing system, the plate is simply inked and the image is transferred onto a recording medium. The plate initially contacts a compliant intermediate surface called a rubber cylinder. This rubber cylinder then applies the image to paper or other recording media. In wet lithographic systems, the non-image areas are hydrophilic and the required ink repellency is provided by first applying a fountain solution (or fountain solution) to the plate prior to inking. The ink repellant fountain solution prevents ink from adhering to non-image areas, but does not affect the oleophilic properties of the image areas.
[0004]
Lithographic plates can also be made by a variety of methods ranging from conventional manual techniques involving light exposure and chemical development to automated processing with computer control. A system for producing plates from a computer utilizes a pulse of electromagnetic radiation generated by one or more laser or non-laser sources to produce a photosensitive plate blank (which can be used immediately or natively depending on the system). Cause physical or chemical changes at selected locations (used after photodevelopment of Alternatively, an ink jet device used to selectively deposit ink repellent or ink receptive spots on the plate blank or a spark discharge device can be used. In a spark discharge device, an electrode placed in contact with or in close proximity to a plate blank causes an electrical spark that changes the characteristics of a predetermined area on the printing surface, thereby producing dots. The dots collectively form the desired image. As used herein, the term “imaging device” includes radiation sources (eg, lasers), inkjet sources, electrodes, and other known means for generating image spots on a printing plate blank. Also, the term “discharge” refers to the emission for image formation made by these devices. The term “image” refers to a lithographic representation of the final document being reproduced. The term “plate” refers to any type of printing member or surface that is capable of recording an image defined by regions that have different affinities for ink and / or fountain fluid. Suitable configurations include conventional flat or curved lithographic plates attached to printing press plate cylinders, but seamless cylinders (eg, plate cylinder roll surfaces), endless belts, and other configurations are also possible. Also included.
[0005]
A second technique for laser imaging involves the use of a transfer material. For example, U.S. Pat. Nos. 3,945,318, 3,962,513, 3,964,389, 4,245,003, 4,395,946, 4,588,674, 4 711,834. In these systems, a polymer sheet that is transparent to the radiation emitted from the laser is covered by a transferable material. In operation, the transfer side of the structure is brought into contact with the receiving sheet and the transfer material is selectively irradiated through the transmission layer. Typically, the transfer material exhibits a high degree of absorption for the laser radiation for imaging, ablating in response to the laser pulse, ie, substantially exploding into gas smoke and black charred strips. . This action, which can be further enhanced by auto-oxidation (eg as in the case of nitrocellulose materials), ensures that the transfer material is removed from the carrier reliably and completely. The material that has not been ablated adheres to the receiving sheet.
[0006]
Alternatively, instead of laser energization, thermal material transfer can be achieved through direct contact. For example, US Pat. No. 4,846,065 describes transferring a lipophilic material to an image carrier using a digitally controlled press head.
[0007]
In order to produce a printing plate, the transfer material and the receiving material are chosen to have different affinities for the fountain liquid and / or ink, and when the transmission layer is removed along with the unirradiated transfer material, The finished imaged plate is left.
[0008]
Another important use of the transfer material is proofing. Those skilled in the art of graphic arts use a color proofing sheet (or simply “color proofing”) to correct the separation image prior to making the final separation plate and to be obtained during the printing process. Evaluate wax color quality. In a typical printing process, multicolor images cannot be printed directly using a single printing plate. Instead, the composite color image is first decomposed into a set of color components, or “separations”. Each of the separations forms the basis of an individual plate. The color into which a multicolor image is separated depends inter alia on the “color model” chosen by the person skilled in the art. The most common color model is based on the cyan, magenta, yellow and black components and is called the “CMYK” color model. If the separation is done properly, the original composite image is generated by subtracting the individual separations. Color proofing represents the final image that will appear at the time of printing and also allows those skilled in the art of graphic arts to see the image.
[0009]
Color proofing can be generated by irradiating and transferring a colorant corresponding to one of the separated colors onto a transparent receiving sheet according to the color distribution in the final image. A transfer sheet corresponding to each color of the color model can be applied to a single receiving sheet and imaged sequentially, thereby producing a single proof. Alternatively, color proofing sets, each corresponding to one of the separation colors, are superimposed on each other during registration, thereby representing the final image.
[0010]
Mechanically, laser-based imaging systems can take a variety of forms. The laser output can be applied directly to the surface of the substrate via a lens or other beam guiding component, or transmitted from a remotely located laser to the substrate surface using a fiber optic cable. The controller and associated positioning hardware maintain the beam output in the correct orientation with respect to the substrate surface, scan the substrate surface with this output, and position the laser adjacent to a selected location or region of the substrate. Energize. The controller generates an accurate negative or positive image of the original in response to an input image signal corresponding to the original document or drawing to be reproduced on the substrate. The image signal is stored on the data storage device as a bitmap data file or other suitable image format. Such a file is generated by a raster image processor (RIP) or other suitable means. For example, the RIP can receive input data in a page description language that defines all the features necessary to transfer it onto the substrate, or as a combination of a page description language and one or more image data files. The bitmap is configured to define the hue of the color as well as the frequency and angle of the screen.
[0011]
The imaging device can be configured as a flat-type recording device or as a drum-type recording device with the substrate attached to the inner or outer cylindrical surface of the drum. In the case of lithographic printing, a design that is attached to the outside of the drum is more suitable for field use on a lithographic printing machine. In this case, the printing cylinder itself constitutes the drum member of the recording device or plotter.
[0012]
In the drum configuration, the required relative movement between the laser beam and the substrate causes the drum (and the substrate fixed thereon) to rotate about its axis, causing the beam to translate relative to this axis of rotation. , Thereby scanning the substrate circumferentially to “grow” the image axially. Alternatively, the beam can be translated relative to the axis of the drum and an angular increment can be made after each pass across the substrate to "grow" the image on the substrate in the circumferential direction. . In both cases, after scanning with the beam is complete, an image corresponding to the document or drawing original (as positive or negative) has been applied to the surface of the substrate.
[0013]
In order to simultaneously generate several lines of image spots, a plurality of imaging devices can be used, and the imaging speed is improved accordingly. Regardless of the number of imaging devices used, their operation must be accurately controlled so that the discharge occurs at the appropriate time to reach the intended dot position on the printing surface. Each discharge source will move all the way to the substrate while scanning all intended image locations on the substrate along the vertical and horizontal dimensions (corresponding to the circumferential and axial directions for drum imaging). Must be aligned at points. Also, for laser-based imaging, the beam must remain focused on the substrate for maximum energy transfer efficiency.
[0014]
[Problems to be solved by the invention]
The overall efficiency of the imaging device is an important operational criterion. If there is a bottleneck in operation, the performance of the imaging apparatus is reduced, resulting in, for example, a stagnation in the production of lithographic plates. In the case of laser-based imaging systems, bottlenecks can hinder operation at commercially practical imaging speeds. One typical bottleneck is related to the acquisition of image data stored as a bitmap file on the data storage device, as described above. Overlapping (ie, combining) multiple bitmaps in the imaging output process exacerbates this problem.
[0015]
Another bottleneck occurs when the imaging device utilizes a “comb array” of laser imaging devices. In this configuration, a number of laser imaging devices are placed across the dimensions of the substrate. This arrangement can be as simple as a linear arrangement in which each imaging device is equidistant from adjacent devices. Alternatively, groups of imaging devices are grouped into one or more “packs” such that the spacing between devices within a pack is different from the spacing between adjacent packs. . Regardless of configuration, each imaging device is responsible for imaging a different portion of the entire image due to its physical location within the array. Bottlenecks occur because the imaging devices operate simultaneously and the data required by each imaging device typically originates from different locations in the bitmap file. Thus, a large number of mass storage transactions (i.e. reads and seeks) are performed on a file to obtain the necessary data from several non-contiguous locations within the file.
[0016]
One way to optimize the flow of data to the imaging device has been to include a buffer memory within the imaging device. The buffer memory is configured, for example, as one or more buffer pairs, and the imaging device reads data from only one of each pair (eg, “A buffer”). While the imaging device is reading data in the “A buffer”, the other buffer in each pair (eg, “B buffer”) receives data from the data storage device. When the imaging device runs out of data in the “A buffer”, it starts reading data from the “B buffer”. At the same time, the “A buffer” again starts receiving data from the data storage device. When the imaging device runs out of data in the “B buffer”, the roles of “A buffer” and “B buffer” are reversed again. This process continues until the entire image has been processed.
[0017]
Reversing the role of the “A” and “B” buffers improves data throughput and its efficiency, but allows access to image data from many different files or from many files using the comb arrangement of the imaging device. Unable to deal with the specific time delay when accessing image data. Retrieving these files, which are typically stored on mass storage media, entails additional overhead associated with accessing the media. This overhead degrades the efficiency of the imaging device. Furthermore, as the number of files or search requests increases, the overall overhead increases, further slowing the imaging device.
[0018]
It is also important to maintain “registration” (ie, alignment) of the images along all relevant dimensions while the imaging device is operating. Failure to do so will result in inaccurate imaging and / or undesirable artifacts appearing, preventing the final image from appearing. These results can be particularly severe in situations such as lithographic printing.
This is because a typical print job requires continuous application of ink from several plates, resulting in a cumulative collection of defects associated with each plate. Laser imaging imposes particularly demanding requirements. This is because as a result of adjustments along each relevant dimension, distortion may be introduced relative to another dimension.
[0019]
Manufacturing tolerances also create variations in the dimensions (eg, circumferential direction) of the printing plate cylinder. Thus, in a four-color imaging system that incorporates four different cylinders, each paired with a set of imaging devices, the four circumferential dimensions may not be the same. Accordingly, adjustments must be made to the operation of the imaging device to produce four printing plates with images of the same size in the circumferential direction.
[0020]
From the above description, it is clear that there remains a need for a method that optimizes imaging accuracy while at the same time improving the efficiency of the imaging device.
[0021]
[Means for Solving the Problems]
The present invention facilitates increased throughput between a raw image data file and an imaging device that ultimately applies the completed image onto a recording medium. This improves the processing speed and efficiency of the entire imaging apparatus. In addition, the present invention provides dynamic “zoom” and “shrink” capabilities that allow image size adjustment. This allows, for example, correction of registration errors caused by variations in cylinder diameter and speed, as well as general control over image size. The present invention represents a simple and effective method for optimizing the operation of an imaging device.
[0022]
In one embodiment, the final image is compiled from two or more raw image data files, each file containing one or more portions of the final image. In this embodiment, the buffer memory structure is organized to include at least one buffer memory pair for each raw image data file. The buffer memory structure also has at least one composite image buffer memory for storing all or part of the data from the final bitmap image that is transferred to the recording medium. The composite image buffer memory can be configured to include at least one buffer memory pair. Alternatively, it can be configured as one large memory. In any case, all memories are configured to ensure that image data is always available for efficient operation of the imaging device.
[0023]
During operation, the portion or portions of data from each raw image file that will eventually appear in the final image is identified. These parts are referred to herein as “related segments”. The image data corresponding to the related segment is buffered in the buffer memory pair assigned to the file. Thus, only the relevant segment is copied from the allocated buffer memory pair into the composite image buffer memory. By sequentially copying from each raw image file to the allocated buffer memory pair and then to the composite image buffer memory, the display of the final image on the recording medium is completed as a result.
[0024]
The advantage of copying data from a raw image data file to another allocated buffer memory pair is apparent in terms of data retrieval speed. Typically, the raw image data file is on a data storage device such as a mass storage medium. Associated with mass storage media is data seek and read time. These times affect transactions with mass storage media and contribute to “overhead” that stagnates access to data. During editing of the final image, as the relevant segments are accessed and copied into the composite image buffer, data is retrieved from several files, often by multiple access to the same file or files. It will be necessary.
Thus, the overall overhead for editing the overall final image (eg, the overhead for each mass storage transaction multiplied by the number of transactions) can be large. This degrades system throughput and efficiency. Since the buffer memory pair has no mass storage medium overhead, the data seek time and read time for the former are greatly reduced. Thus, the relevant segment is first read from the raw image data file and placed into the buffer memory pair (with only one or several mass storage transactions), and from the buffer memory pair to the individual device rather than from the mass storage medium By extracting data, the number of accesses to the mass storage medium is significantly reduced, and overall throughput and processing efficiency are improved accordingly.
[0025]
In some cases, related segments from two or more raw image data files may “overlap” in the final image. This can occur, for example, when overlaying a title or other text on a photograph. The title image can be one related segment and the photographic image can be another related segment. When image overlap occurs, one or more of the relevant segments must be determined to dominate the others. Each dominant related segment is said to “contain” one or more other related segments below. To address this situation, embodiments of the present invention first verify that there is an overlap and then determine which relevant segment is dominant. Thus, data from the dominant associated segment (not the corresponding data from the confined segment or segments) is copied from the buffer memory pair into the composite image buffer memory.
[0026]
In another embodiment, the present invention uses an “opaque ink” model to identify dominant relevant segments. In this embodiment, all data from the buffer memory pair representing the relevant segment is copied sequentially for each segment and moved into the composite image buffer memory. Image overlap is addressed by overwriting previously copied data with later copied data. In other words, the opaque ink model operates temporarily and each of the sequentially copied image segments dominates the preceding image segment. As a result, the data last copied to the composite image buffer memory represents the dominant associated segment, which is finally imaged on the recording medium.
[0027]
One advantage of using dominant related segments to control image overlap is the ability to incorporate different print jobs on a single output medium, such as a lithographic plate. For example, the system of the present invention can apply images from two unrelated print jobs, each requiring the same printing material, onto a single plate without overlap. This allows both print jobs to be completed simultaneously, thereby improving operational efficiency and achieving cost savings.
[0028]
In another embodiment, the present invention is based on a technique for editing the final image described above. In this embodiment, at least two imaging devices and one recording medium are provided. The imaging device is, for example, a laser described in US Pat. No. 5,351,617, assigned to the assignee of the present invention, which is incorporated herein by reference. In addition, recording media are also described, for example, in US Pat. No. 5,339,737, Reissue Number 35,512, and US Pat. No. 5,783,364, all assigned to the assignee of the present invention. Lithographic plates, which are also incorporated herein by reference. The imaging device and the recording apparatus are arranged at positions where relative movement is performed.
During this movement, the imaging device is energized in response to data in the composite image buffer memory. (As described above, the data in the composite image buffer memory is an edited version of the relevant segment and, if necessary, an edited version of the dominant related segment). After exposure to the device, you will have a representation of the data in the applied composite image buffer.
[0029]
Typically associated with each imaging device is an “imaging zone”. This zone is an area on the recording medium that is scanned by a specific imaging device. , In one example, the imaging device is in a linear array and the recording medium rotates on a drum or cylinder. The array of devices extends axially along the cylinder, and each device scans a circumferential line along the recording medium as the cylinder rotates. After each complete rotation, the device array is indexed axially and the imaging device scans adjacent lines. This process of scanning and axial advancement continues until the entire image area of the recording medium has been completely scanned. (The process of scanning and axial advancement can occur simultaneously when each imaging device performs a helical scan. In this case, the imaging device performs a constant motion across the recording medium.) At this point, each imaging device is , The imaging zone has been scanned with an axial length equal to the spacing between adjacent imaging devices (and also represents the total distance the array is indexed as a whole).
[0030]
It is not uncommon for one dimension (eg, “width”) of a related segment to span several imaging zones. In such cases, one embodiment of the present invention determines which imaging zone its associated segment spans after defining the imaging zone for each imaging device. This embodiment provides a pair of buffer memories for each such zone (whether the relevant segment extends in whole or in part). Thus, instead of having a pair of buffer memories for each raw image data file, this embodiment provides a pair of buffer memories for each imaging device required by each raw image data file. The data from each raw image file is then buffered in the buffer memory pair assigned to the imaging device required for that file. This method of providing additional buffer memory pairs further improves the throughput of raw image data.
[0031]
In one type of this embodiment, the invention includes an imaging apparatus having two or more imaging devices, a support for the recording medium, and a device that provides relative rotation between the imaging device and the support. This embodiment also includes a buffer memory structure having at least a pair of buffer memories, a composite image buffer, a control unit, and a drive unit. The control unit communicates with the buffer memory structure and the composite image buffer and copies selected portions of the data in the former to the latter. It should be noted that these selected parts can be related segments or, if necessary, superior related segments specified by the control unit (both defined above). The drive unit communicates with the control unit, the composite image buffer, and the imaging device.
The purpose of the drive unit is to activate the appropriate imaging device during scanning, depending on the data in the composite image buffer. As a result, an image corresponding to the data in the composite image buffer is applied on the recording medium. In a further embodiment, the control unit, the drive unit or both can be a digital computer.
[0032]
In another embodiment, the present invention optimizes the image through adjustment of the image size and resolution. In this embodiment, a raw position signal is generated that indicates the position of the imaging device relative to the recording medium when in relative motion. A resolution enhancement parameter and an image size parameter are defined and multiplied by the raw position signal to generate a high frequency “sub-pixel clock”. The optimized position signal is generated by dividing the sub-pixel clock by at least one pixel prescaler. The pixel prescaler helps determine the size of the pixel as described below. During relative movement, the imaging device is energized in response to the image data at a position indicated by the optimized position signal, not by the raw position signal. As a result, an optimized display of image data is applied on the recording medium.
[0033]
In one type of this embodiment, the present invention provides an image optimization apparatus having two or more imaging devices, a support for a recording medium, and a device that provides relative motion between the imaging device and the support. To do. This embodiment also includes a sensing system that determines the position of the imaging device relative to the recording medium. Typically, this sensing system has a position encoder in communication with the phase locked loop. The phase locked loop is responsive to the signal generated by the position encoder, the resolution enhancement parameter, and the image size parameter. Further, the phase locked loop generates a second signal whose frequency is determined by the resolution enhancement parameter and the image size parameter. In general, this second signal (sub-pixel clock) represents the product of encoder signals multiplied by the resolution enhancement parameter and the image size parameter. Since the frequency of the subpixel clock is higher than the frequency of the encoder signal, this clock gives submicron resolution to the pixel position on the recording medium.
[0034]
The distance between the centers of adjacent image pixels is fixed and is equal to a specific number of subpixel clock pulses determined by the image resolution. The frequency of the subpixel clock is reduced by dividing it by at least one pixel prescaler. This allows the origin of each pixel to be adjusted relative to the center point of that pixel. In essence, this adjustment affects the actual size of the image data element or pixel output on the recording medium.
[0035]
Manufacturing or assembly tolerances can cause orientation variations between imaging devices. To compensate for this variation, an offset register responsive to the sub-pixel clock is provided for each imaging device to adjust the latter origin. Each pixel prescaler (typically one for each imaging device) is associated with and responds to a corresponding offset register. These registers communicate with the associated pixel prescaler to determine the placement of the first pixel on the recording medium for each column of pixels. When the imaging device is a drum type recording device, the offset value is typically adjusted for each rotation of the recording medium to correct for variations in the reference line.
[0036]
Further included in this type of embodiment is a control unit that communicates with and responds to the sensing system and image data, and at least one drive unit. The drive unit communicates with the control unit and the imaging device. The drive unit is responsive to at least one pixel prescaler and associated offset register to selectively activate the imaging device during relative movement and at that particular position in response to the image data and the optimized position signal. To do. The drive unit determines the shape and duration of the signal that activates each imaging device, but it cannot begin driving the imaging device until it is enabled by the pixel prescaler. Thus, the drive unit cooperates with the pixel prescaler to determine the overall pixel size. In fact, the drive unit can continue to drive the imaging device as the pixel prescaler crosses the boundary between adjacent regions of pixels.
[0037]
Note that the position encoder may be an angular position encoder. The one or more control units, drive units, and sensing systems can be digital computers.
[0038]
Another embodiment of the present invention includes both the buffering method and the optimization method described above. Specifically, in this embodiment, at least two imaging devices and one recording medium are provided and arranged to move relative to each other. Further provided is a buffer memory structure having at least a pair of buffer memories for each raw image data file. The memory structure further includes a composite image buffer memory. During the period of operation, relevant segments of data or, if necessary, dominant relevant segments of data are identified. Corresponding image data is placed from each raw image file into a pair of allocated buffer memories. The relevant segment (or dominant relevant segment) of data is copied from the pair of allocated buffers into the composite image buffer memory.
[0039]
In this embodiment, a raw position signal indicating the position of the imaging device with respect to the recording medium during relative movement is further generated. The raw resolution signal is multiplied by the defined resolution enhancement parameter and image size parameter to generate a subpixel clock. In cooperation with an associated offset register, an optimized position signal is generated by dividing the sub-pixel clock by at least one pixel prescaler. During relative movement, the imaging device is activated in response to the data in the composite image buffer and the optimized position signal. As a result, an optimized display of the data in the composite image buffer is applied on the recording medium.
[0040]
In one type of this embodiment, the present invention provides an image processing apparatus having two or more imaging devices, a support for the recording medium, and a device that provides relative motion between the imaging device and the support. Supply. This embodiment further includes a buffer memory structure having at least a pair of buffer memories, a composite image buffer, a control unit, a drive unit, and a sensing system. The control unit communicates with the sensing system, the buffer memory structure, and the composite image buffer. The control unit copies selected portions of the data in the buffer memory structure to the composite image buffer. Note that these selected parts can be related segments or, if necessary, dominant related segments. The sensing system determines the position of the imaging device relative to the recording device. As mentioned above, this sensing system typically has a position encoder in communication with the phase locked loop. The phase locked loop is responsive to the signal generated by the position encoder, the resolution enhancement parameter, and the image size parameter. In addition, the phase locked loop generates a second signal whose frequency is determined by the resolution enhancement parameter and the image size parameter. In general, this second signal means the product of the encoder signal multiplied by the resolution enhancement parameter and the image size parameter and the division by at least one pixel prescaler.
[0041]
The drive unit that also communicates with the control unit, the composite image buffer, and the imaging device is responsive to at least one pixel prescaler and its associated offset register. The drive unit controls the shape and duration of the signal that activates the imaging device, but does not drive the latter until enabled by at least one pixel prescaler. The imaging device is driven during relative movement and at its specific position in response to data in the composite image buffer. This applies an optimized display of the image on the recording medium.
[0042]
In any of the embodiments described above, the one or more control units, drive units, and sensing systems can be digital computers. Accordingly, one embodiment of the present invention includes a product that includes computer readable code for editing image data and applying corresponding images. This code reads the raw image data file, puts the contents of this file into a buffer, identifies the relevant segment from this file, copies this relevant segment, and activates the imaging device to apply the corresponding image Contains several parts. In another embodiment, the program storage medium tangibly embodies a computer-executable instruction program that accomplishes the method steps for image data editing and image application described above.
[0043]
The image optimization described above can also be achieved using a digital computer. In this case, the product includes computer readable code for optimizing the registration of the image data. This code generates raw position signals, defines resolution enhancement parameters, image size parameters, defines at least one pixel prescaler and associated offset register, generates optimized position signals, and is optimized A plurality of portions for activating the imaging device in response to the received position signal and registering the corresponding image are included. In a further embodiment, the program storage medium tangibly embodies a computer-executable instruction program to achieve the above-described method steps for image optimization.
[0044]
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
[0045]
DETAILED DESCRIPTION OF THE INVENTION
The foregoing and other objects, features, and advantages of the present invention, as well as the invention itself, will be more fully understood from the following description of various embodiments, taken in conjunction with the accompanying drawings. I will.
[0046]
As shown in the drawings for purposes of illustration, the present invention may be embodied in an image processing system. The system of the present invention improves operational efficiency and eliminates image alignment errors.
[0047]
The image processing apparatus of the present invention includes an improved buffer memory structure and a phase locked loop for dynamic image adjustment. The present invention avoids the aforementioned problems of inefficiency and poor image alignment.
[0048]
In the following detailed description and drawings, the same elements are identified with the same reference numerals.
[0049]
FIG. 1 is a block diagram of an embodiment of an image processing apparatus 100. A typical printing press uses one or more imaging stations, each having an assigned image processing device 100. The image processing apparatus 100 includes a buffer memory structure 104, a composite image buffer 108, and a drive unit 110, all in electrical communication with the control unit 102. The buffer memory structure 104 includes one or more buffer memory pairs 106. Although FIG. 1 shows only three pairs of buffer memory 106, this is for clarity only.
Any number of pairs of buffer memory 106 is within the scope of the present invention. In one embodiment, a pair of buffer memories 106 are provided for each raw image data file that is a component of the final image.
[0050]
In a further embodiment, a pair of buffer memories 106 are provided for each imaging device 112 required by each raw image data file. This is illustrated in FIG. 2, which illustrates the image zone buffer structure 200. Each zone corresponds to one imaging device 112. For clarity, only eight zones (zone 0 (202) to zone 7 (216)) are shown in FIG. However, any number of zones is within the scope of the present invention.
[0051]
In brief overview, FIG. 2 shows two raw image data files having a dimensional range (eg, “width”) across several imaging zones. The “alpha” file (218) extends from zone 1 (204) to zone 3 (208). The “beta” file (220) extends from zone 2 (206) to zone 7 (216). In this example, three pairs of buffer memory 106 are provided to the “alpha” file (218), one for each of the three zones to which the “alpha” file (218) is passed. Similarly, six pairs of buffer memory 106 are provided for the “beta” file (220), one pair for each of the six zones to which the “beta” file (220) is passed. In this embodiment, a pair of buffers 106 are provided for each zone where each raw image data file that is a component of the final image has been passed in whole or in part.
[0052]
During operation, the contents of the raw image data file are read into the buffer memory pair 106. Depending on the total amount of available memory, each of the raw image data files is partially or fully read into the buffer memory pair 106. If only a portion of the raw image data file is read into a pair of buffer memories 106, that portion is preferably a portion within the zone associated with that buffer memory pair 106. However, obtaining data from each raw image data file in its entirety and placing it in the buffer memory pair 106 can be accomplished efficiently based on a single mass storage retrieval transaction, thereby reducing data access overhead. It can be made.
[0053]
The relevant segment from each of the raw image data files is identified and copied from a location within each data file into the buffer memory pair 106 and further copied into the composite image buffer 108. Alternatively, all or part of each raw image data file including both related and “unrelated” segments can be copied into the buffer memory pair 106. In this case, only the relevant segment is extracted from the buffer memory pair 106 and copied into the composite image buffer 108.
[0054]
There may be overlap of related segments. An example of this is shown in FIG. 2, where an “alpha” file (218) and a “beta” file (220) overlap in zone 2 (206) and zone 3 (208). If there is an overlap, the dominant related segment is identified. In this example, only one file “Beta” (220) dominates within Zone 2 (206) and Zone 3 (208). (It is not necessary for the same file to be dominant in each zone.) Data representing the dominant associated segment, rather than the confined segment or segments, is then copied into the composite image buffer 108.
[0055]
In one embodiment, the dominant relevant segments are defined according to the opaque ink model. In this embodiment, all data representing the relevant segment stored in the buffer memory pair 106 is copied into the composite image buffer 108. Image overlap is addressed by overwriting the previously copied data with the previously copied data. Thus, the data that was last copied to the composite image buffer memory 108 will represent the dominant relevant segment that is ultimately imaged on the recording medium 114.
[0056]
Also shown in FIG. 1 is a device 116 that provides relative motion, such as a motor. Device 116 provides relative movement between imaging device 112 and recording medium support 118. Since the recording medium 114 is attached to the support 118, the recording medium 114 also moves relative to the imaging device 112. FIG. 1 shows that the support 118 has a drum shape and the recording medium 114 has a cylinder shape, but other configurations are within the scope of the present invention. For example, the support 118 can have a flat table structure, and the recording medium 114 can have a flat surface. If desired, the support 118 can be easily incorporated into the design of conventional lithographic printing presses and can operate as a printing press plate cylinder. Thus, device 116 is the same motor that is used to rotate the print cylinder during printing. Alternatively, the support 118 can be provided on a stand-alone plate making or calibration device. In either configuration, the support 118 and the recording medium 114 are formed so as to be closely attached.
[0057]
The drive unit 110 is in electrical communication with the composite image buffer 108 and the imaging device 112. Again, for clarity, only eight imaging devices 112 are shown in FIG. 1, but any number of imaging devices 112 is within the scope of the present invention. During operation, the drive unit 110 energizes the imaging device 112 in response to data in the composite image buffer 108 while relative motion is taking place. Thereby, the “as an image” display of the data in the composite image buffer 108 is applied to the recording medium 114.
[0058]
Also shown in FIG. 1 is a sensing system 120 that is in electrical communication with the control unit 102. This sensing system 120 communicates the position of the support 118 (and thus the recording medium 114) relative to the imaging device 112 to the control unit 102. Sensing system 120 includes a position encoder 122 and a phase locked loop 124. The position encoder 122 identifies the relative position between the recording medium 114 and the imaging device 112 in relative motion and generates an output signal indicative of that position. This signal is called a “raw position signal”. If the support 118 has a drum shape and the recording medium 114 is rotated past the imaging device 112, the position encoder 122 may be an angle encoder. The angle encoder provides an output signal indicative of the angular position of the support 118 relative to the imaging device 112.
[0059]
FIG. 3 shows a phase locked loop clocking scheme 300. The output signal of the position encoder 122 is supplied to the phase comparator 302 in the phase locked loop 124. The phase locked loop 124 includes a low pass filter amplifier 304 and a voltage controlled oscillator 306. As is well known, the general purpose of any phase-locked loop is to produce an output signal that is in phase with the input signal.
When the phase of the input signal changes, the phase-locked loop changes its output signal so that the phase of the output signal matches the phase of the input signal. This is typically done by feeding back the output of the voltage controlled oscillator to the input of the phase comparator. In this embodiment, the output signal 312 of the voltage controlled oscillator fed back to the phase comparator 302 is first divided by the image size parameter 308 and the resolution enhancement parameter 310. The effect of this two-stage division is to change the frequency of the output signal 312 of the voltage controlled oscillator. This changed frequency is related to the frequency of the output signal of the position encoder 122 multiplied by the image size parameter 308 and the resolution enhancement parameter 310. Furthermore, the output signal 312 of the voltage controlled oscillator remains in phase with the output signal of the position encoder 122.
[0060]
In this embodiment, the frequency of the voltage controlled oscillator output signal 312 operates as a subpixel clock, providing submicron resolution to pixel locations on the recording medium 114. This output signal 312 is then divided by at least one pixel prescaler 316. The at least one pixel prescaler 316 is in communication with at least one associated offset register 320 and is used to enable the drive unit 110. As a result, the starting point of each pixel can be adjusted with respect to its center point, and the overall pixel size is corrected. The offset register 320 has a division function similar to the pixel prescaler 316 and emits a single pulse. Accordingly, the offset register 320 can also be considered as a “single pulse prescaler”.
[0061]
The rate at which the image data 314 is transferred to the imaging device 112 can be varied by adjusting the frequency of the output signal 312 of the voltage controlled oscillator using the two-stage division described above. This allows adjustment of the size and resolution of the image as it is displayed on the recording medium 114. For example, the division by the resolution enhancement parameter 310 can increase the frequency of the output signal 312 of the voltage controlled oscillator. This increase in frequency allows the control unit 102 to identify small changes in the position of the recording medium 114 relative to the imaging device 112. Thus, the drive unit 110 can energize the imaging device 112 at higher frequencies. As a result, the spacing between the individual “dots” produced by the imaging device 112 that produces the finished image on the recording medium 114 will be closer. With this close spacing, the final image will have an improved resolution compared to that obtained without multiplication.
[0062]
In another example, the division by the image size parameter 308 changes the frequency of the output signal 312 of the voltage controlled oscillator. This means “enlargement” and “reduction” of the dimensions of the final image displayed on the recording medium 114. This is useful, for example, in adjusting the final image for drum or plate size variations due to manufacturing tolerances. Appropriate registration (ie registration) is obtained by adjusting the size of the final image.
[0063]
At least one offset register 320 responsive to the subpixel clock is used to compensate for variations in the “start line reference” between the imaging devices 112. This occurs when one imaging device has a different orientation compared to the other, typically due to manufacturing or assembly tolerances.
Thus, an imaging device discharge that is oriented in the wrong direction will have a different trajectory than other imaging devices. As a result, no discharge can be obtained that reaches a dimensionally consistent dot position on the recording medium, which causes distortion in the image.
[0064]
In order to compensate for differences in the start line reference, one embodiment includes a unique offset register 320 for each imaging device 112. In this configuration, each imaging device 112 has an assigned pixel prescaler 316 associated with a unique offset register 320. The offset register 320 communicates with its associated pixel prescaler 316 and enables the drive unit 110. Thus, the pixel prescaler 316 and the drive unit 110 together determine the dot size that is actually applied. Orientation variations are compensated by selection of an appropriate value in the offset register 320 for each imaging device. Furthermore, the pixel prescaler 316 operates on the output signal 312 of the voltage controlled oscillator after being affected by the image size parameter 308 and the resolution enhancement parameter 310. This distributes the effects of these parameters evenly throughout the image.
[0065]
The subpixel clock is generated by changing the values of the image size parameter 308 and the resolution enhancement parameter 310 and adjusting the frequency of the raw position signal. By dividing the sub-pixel clock by at least one pixel prescaler 316, an optimized position signal is generated. These parameters, which are integers or fractional values, and prescaler values accomplish such adjustments by fundamentally frequency modulating the raw position signal. The user can select the values of these parameters, for example by using registers and counters, and communicate these values using the control interface 318. Despite the discrete nature of the parameter values, as a result of frequency modulation, the effect is smooth with respect to the output signal 312 of the analog voltage controlled oscillator. This allows adjustments to improve image size and resolution to be taken in smoothly and uniformly throughout the image, resulting in visually satisfactory results.
[0066]
Further embodiments of the present invention include the additional feature that the digital computer plays the role of one or more of the control unit 102, drive unit 110, or sensing system 120. Thus, many of the operations described above, such as buffering and image optimization, can be performed in software rather than assigned computer hardware. Reading raw image data files, identifying image overlap, copying image data between buffers, and activating the imaging device 112 can also be done in software. Note that since FIG. 1 is a block diagram, the listed items are shown as individual elements. However, in actual implementations of the invention, they can be an integral part of other electronic devices such as digital computers.
[0067]
From the foregoing description, it will be appreciated that the image processing system provided by the present invention provides a simple and effective way to ensure efficient system operation while maintaining proper image size and image alignment. I will. The problem of low system throughput due to slow data access times is largely eliminated.
[0068]
The image processing system described above facilitates dynamic control of image size and image alignment. Thus, unacceptable image registration errors are reduced or eliminated.
[0069]
Those skilled in the art will appreciate that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above-described embodiments are not to be construed as limiting the invention described herein but are to be considered exemplary in all respects. The scope of the invention is, therefore, indicated by the appended claims rather than the foregoing description, and all modifications that are equivalent in meaning and scope to the claims are intended to be included within the scope of the invention. ing.
[Brief description of the drawings]
FIG. 1 is a block diagram of an image processing apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of an image zone buffer according to an embodiment of the present invention.
FIG. 3 is a block diagram of a phase-locked loop clocking scheme according to an embodiment of the present invention.
[Explanation of symbols]
100: Image processing apparatus
102 ... Control unit
104: Buffer memory structure
106: Buffer memory pair
108 ... Composite image buffer
110 ... Drive unit
112 ... Imaging device
114 ... Recording medium
116 ... Relative motion supply device
118 ... Recording medium support
120 ... Sensing system
122 ... Position encoder
124 ... Phase-locked loop
200 ... image zone buffer structure
202 ... Zone 0
204 ... Zone 1
206 ... Zone 2
208 ... Zone 3
216 ... Zone 7
218 ... "Alpha" file
220 ... "Beta" file
300 ... Phase-locked loop clocking method
302 ... Phase comparator
304: Low-pass filter amplifier
306 ... Voltage controlled oscillator
308 ... Image size parameter
310 ... Resolution improvement parameter
312 ... Voltage controlled oscillator output signal
314 ... Image data
316: Pixel prescaler
318 ... Control interface
320: Offset register

Claims (11)

Providing a plurality of raw image data files;
Providing a plurality of imaging devices;
Supplying a recording medium;
Providing each raw image data file with a buffer memory structure comprising at least a pair of buffer memories;
Providing relative motion between the imaging device and the recording medium;
Identifying from each of the raw image data files at least one related segment that is part of the composite image that is the final image obtained from a plurality of raw images;
Placing image data corresponding to the at least one related segment from each raw image data file into the at least one pair of buffer memories associated with the raw image data file;
Copying the at least one related segment from the related at least one pair of buffer memories into a composite image buffer;
Generating a raw position signal indicative of the position of the imaging device relative to the recording medium;
Defining resolution enhancement parameters;
Defining image size parameters;
Defining at least one offset register;
Defining at least one pixel prescaler responsive to the offset register;
The raw position signal and the feedback signal are applied to a phase-locked loop to generate a subpixel clock, and the feedback signal is obtained by multiplying the subpixel clock by the resolution enhancement parameter and the image size parameter, and the subpixel Generating an optimized position signal by dividing a clock with the at least one pixel prescaler;
During the relative movement, the imaging device is activated in response to the data in the composite image buffer and the optimized position signal, thereby optimizing the data in the composite image buffer on the recording medium. Image processing method comprising the step of applying the displayed display. Providing the buffer memory structure comprises:
Defining an imaging zone for each imaging device, which is an area on a recording medium scanned by the imaging device;
Determining which imaging zones are required to image each raw image data file;
For each raw image data file, further comprising the step of providing a pair of buffer memories for each of the imaging zones are required, the method of claim 1. Placing in the buffer further comprises placing image data corresponding to the at least one associated segment from each raw image data file into the pair of buffer memories provided to each required imaging zone. The image processing method according to claim 2 , further comprising: Identifying the at least one related segment comprises:
Determining the presence of at least one overlap of a plurality of related segments in the composite image;
Determining a dominant related segment having a dominant in the composite image for each overlap;
It said dominant related segments, and a step of classifying as the at least one associated segments, The method of claim 1. Within the composite image buffer, the at least one related segment follows an opaque ink model that handles image overlap by allowing sequentially copied image segments to dominate the preceding image segment; the method of claim 1, further comprising the step of allowing it to be overwritten by dominant relevant segments. Multiple imaging devices;
A support for the recording medium;
A device that provides relative motion between the imaging device and the support;
A buffer memory structure comprising at least a pair of buffer memories;
A composite image buffer;
A sensing system for determining the position of the imaging device relative to the recording medium, comprising a position encoder and a phase locked loop, wherein the position encoder generates a first signal indicative of the position, the phase locked loop comprising: Receiving the first signal and a feedback signal to generate a second signal, wherein the feedback signal is obtained by dividing the second signal by (i) a resolution enhancement parameter and (ii) an image size parameter; A sensing system wherein the second signal has a frequency determined by the resolution enhancement parameter and the image size parameter;
Responsive to the sensing system and in electrical communication with the buffer memory structure and the composite image buffer and operative to copy selected portions of data in the buffer memory structure into the composite image buffer Unit,
Data in the composite image buffer in electrical communication with the control unit, the composite image buffer, and the imaging device, responsive to at least one pixel prescaler, and during the relative motion, at a specific position of the relative motion. And a drive unit for energizing the imaging device in response to thereby applying an optimized display of the data in the composite image buffer to the recording medium. The image processing apparatus according to claim 6 , wherein the position encoder is an angular position encoder. The second position signal indicates a continuous imaging position and represents the product of the resolution enhancement parameter and the first signal, and the second position signal is thereby increased relative to the first signal. The image processing apparatus of claim 6 , wherein the image processing apparatus supplies the determined position resolution. The image processing of claim 6 , wherein the second signal indicates a continuous imaging position and represents a product of the image size parameter and the first signal, the second signal thereby scaling the image size. apparatus. The image processing apparatus of claim 6 , wherein the second signal is further divided by the at least one pixel prescaler. The image processing apparatus according to claim 6 , wherein at least one of the control unit, the driving unit, and the sensing system comprises a digital computer.

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