Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1999-05-12
2002-09-24
Rogers, Scott (Department: 2624)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C382S275000, C347S237000
Reexamination Certificate
active
06456397
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to digital imaging apparatus and methods, and more particularly to a system for imaging graphic-arts constructions using digitally controlled laser output.
BACKGROUND OF THE INVENTION
Various methods and technologies exist for encoding documents digitally and transferring the digital representations to output devices. At the encoding stage, these range from hobbyist scanners and associated software to elaborate prepress systems. Such systems have replaced traditional “cut and paste” approaches to layout, which required painstaking manual arrangement of the various document components—text, graphic patterns and photographic images—onto a white board for subsequent reproduction. Instead, designers can now manipulate all of these components at once using computers.
Output of the digitally encoded documents can take numerous forms, ranging from laser printing to digital exposure of photographic films to transfer of the image to lithographic plates for subsequent mass-quantity printing. In the latter case, the image to be printed is present on a plate or mat as a pattern of ink-accepting (oleophilic) and ink-repellent (oleophobic) surface areas. In a dry printing system, the plate is simply inked and the image transferred onto a recording material; the plate first makes contact with a compliant intermediate surface called a blanket cylinder which, in turn, applies the image to the paper or other recording medium. In a wet lithographic system, the non-image areas are hydrophilic, and the necessary ink-repellency is provided by an initial application of a dampening (or “fountain”) solution to the plate prior to inking. The fountain solution prevents ink from adhering to the non-image areas, but does not affect the oleophilic character of the image areas.
Lithographic plates can be fabricated in various ways, ranging, once again, from traditional manual techniques involving photoexposure and chemical development to automated procedures involving computer control. Computer-to-plate systems can utilize pulses of electromagnetic radiation, produced by one or more laser or non-laser sources, to create physical or chemical changes at selected points of sensitized plate blanks (which, depending on the system, may be used immediately or following conventional photodevelopment); ink-jet equipment used to selectively deposit ink-repellent or ink-accepting spots on plate blanks; or spark-discharge equipment, in which an electrode in contact with or spaced close to a plate blank produces electrical sparks to alter the characteristics of certain areas on a printing surface, thereby creating “dots” which collectively form a desired image. As used herein, the term “imaging device” includes radiation sources (e.g., lasers), ink-jet sources, electrodes and other known means of producing image spots on recording media such as printing plate, proofs, or paper, and the term “discharge” means the image-forming emissions produced by these devices. The term “plate” refers to any type of printing member or surface capable of recording an image defined by regions exhibiting differential affinities for ink and/or fountain solution; suitable configurations include the traditional planar or curved lithographic plates that are mounted on the plate cylinder of a printing press, but can also include seamless cylinders (e.g., the roll surface of a plate cylinder), an endless belt, or other arrangement.
A second approach to laser imaging involves the use of transfer materials. See, e.g., 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; and 5,819,661. With these systems, a polymer sheet transparent to the radiation emitted by the laser is coated with a transferable material. During operation the transfer side of this construction is brought into contact with an acceptor sheet, and the transfer material is selectively irradiated through the transparent layer. Typically, the transfer material exhibits a high degree of absorbence for imaging laser radiation, and ablates—that is, virtually explodes into a cloud of gas and charred debris—in response to a laser pulse. This action, which may be further enhanced by self-oxidation (as in the case, for example, of nitrocellulose materials), effects removal of the transfer material from its carrier. Material that survives ablation adheres to the acceptor sheet.
Alternatively, instead of laser activation, transfer of the thermal material can be accomplished through direct contact. U.S. Pat. No. 4,846,065, for example, describes the use of a digitally controlled pressing head to transfer oleophilic material to an image carrier.
To create a printing plate, the transfer and acceptor materials are chosen to exhibit different affinities for fountain solution and/or ink, so that removal of the transparent layer together with unirradiated transfer material leaves a suitably imaged, finished plate.
Another important application of transfer materials is proofing. Graphic-arts practitioners use proofing sheets (or simply “proofs”) to show what the final printed image will look like before going to the expense of an actual print run. This facilitates correction of the separation images prior to producing final separation plates, as well as evaluation of the color quality that will be obtained during the printing process. In typical printing processes, multicolor images cannot be printed directly using a single printing plate. Rather, composite color images are first decomposed into a set of constituent color components, or “separations”, each of which serve as the basis for an individual plate. The colors into which the multicolor image is decomposed depends on the particular “color model” chosen by the practitioner. The most common color model is based on cyan, magenta, yellow and black constituents, and is referred to as the “CMYK” color model. If the separation is performed properly, combination of the individual separations produces the original composite image. A proof represents, and permits the practitioner to view, the final image as it will appear when printed.
A proof may be produced by irradiative or thermal transfer of a coloring agent, corresponding to one of the separation colors, directly to paper or to an intermediate transfer (acceptor) sheet according to the distribution of that color in the final image. The individual color separations may be checked separately or combined to produce a single-sheet proof. Alternatively, a set of proofs each corresponding to one of the colors may be overlaid on each other in registration, thereby revealing the final image.
Mechanically, laser-based imaging systems can take a variety of forms. Laser output may be provided directly to the surface of a substrate via lenses or other beam-guiding components, or transmitted to the surface from a remotely sited laser using a fiber-optic cable. A controller and associated positioning hardware maintains the beam output at a precise orientation with respect to the substrate surface, scans the output over the surface, and activates the laser at positions adjacent selected points or areas of the substrate. The controller responds to incoming image signals corresponding to the original document or picture being copied onto the substrate to produce a precise negative or positive image of that original. The image signals are stored as a bitmap data file on a computer. Such files may be generated by a raster image processor (RIP) or other suitable means. For example, a RIP can accept input data in page-description language, which defines all of the features required to be transferred onto the substrate, or as a combination of page-description language and one or more image data files. The bitmaps are constructed to define the saturation and hue of the color as well as screen frequencies and angles.
The imaging apparatus can be configured as a flatbed recorder or as a drum recorder, with the substrate mounted to the interior or exterior cylindrical surface of the drum. In the case of lithographic printing, the
Bildman Mark S.
Cabana Glenn E.
Chase Kenneth P.
Presstek Inc.
Rogers Scott
Testa Hurwitz & Thibeault LLP
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