Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2002-10-10
2004-09-21
Brooke, Michael S. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S104000
Reexamination Certificate
active
06793307
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention generally relates to printers and printer methods and more particularly relates to a printer capable of forming an image on a receiver substrate according to type of receiver substrate, and a method of assembling the printer.
Digital prepress color proofing is an example of a printing application in which there are significant demands for accuracy in representation of images. In digital prepress color proofing, the goal is to produce a “proof sheet” that will resemble as closely as possible the final output of a color printing system (e.g., an offset color printer). This requires that the proof sheet match both expected color reproduction as well as “look and feel” of the receiver substrate. The more accurately a prepress proofing system reproduces paper thickness, weight, color, gloss, and other characteristics in the color proof, the better the system will provide final output prints that meet customer expectations.
Color proofing devices are known. A laser thermal printer having color proofing capability is disclosed in commonly assigned U.S. Pat. No. 5,268,708 titled “Laser Thermal Printer With An Automatic Material Supply” issued Dec. 7, 1993 in the name of R. Jack Harshbarger, et al. The Harshbarger, et al. device is capable of producing a proof on a number of different paper stocks that differ by weight, gloss, color, and other characteristics. For a high-quality imaging system such as is disclosed in the Harshbarger, et al. patent, it is possible to vary specific parameters in the printing process in order to achieve a desired result.
According to the Harshbarger, et al. patent, a printer accepts a rasterized image from a prepress workstation and a printer device prints this raster image, with the necessary color density, onto an intermediate receiver. This intermediate receiver holds the image in reversed or “mirrored” form. The intermediate receiver is ultimately used to transfer an image onto a preconditioned, prelaminated paper substrate. In this regard, a prelamination procedure, performed using a laminator apparatus, is used to precondition the paper substrate for printing by applying a thin layer of laminate material onto the surface of the paper substrate. This prelamination procedure conditions the surface of the paper substrate for accepting the image transferred from the intermediate receiver, allowing a predictable and accurate response to colorant levels. When a sheet of paper substrate is thus prepared, an image is then transferred from the intermediate receiver using the laminator apparatus to provide appropriate levels of heat and pressure as it presses the intermediate receiver against the preconditioned paper substrate. The image is thus transferred to the sheet of paper substrate. It should be noted that this image transfer operation is carried out completely inside the laser thermal printer disclosed in the Harshbarger, et al. patent.
It is known that one of the key parameters that can be varied by a laser thermal printer, whether transferring colorant directly to the paper substrate or first to an intermediate receiver, is colorant density. Density can be controlled within a specified range of values by varying the exposure energy levels applied, which in turn determines the amount of colorant transferred by a marking apparatus during the printing process. By varying exposure energy applied to create the image on an intermediate receiver, a laser thermal printer can emulate the actual printing performance of an offset color press or other printers when using paper substrates having certain characteristics. Similarly, an inkjet printer or electrophotographic printer can be adjusted so as to emulate color press output, by varying the amount of colorant applied or by adjusting operational variables such as drying time or fusing temperature and speed. In any event, chief among the characteristics of the paper substrate is the color of the paper substrate, which serves as a background for the printed image. However, paper substrates can vary widely in color content, ranging from a bright white color that is typical of photographic papers, to duller colors such as are typical of newsprint papers. In order to adjust printer exposure to correctly compensate for paper color, an operator using a digital prepress proofing system makes densitometer measurements of paper color content prior to printing. Such measurements provide values that can be used to calculate an appropriate amount of compensation in printer exposure (or in other operational variables) for a given type of paper substrate. However, the need for the operator to make densitometer measurements of paper color content prior to printing is time-consuming, prone to operator error and therefore costly. Hence, a problem in the art is increased costs due to the need for the operator to make densitometer measurements of paper color content prior to printing.
The densitometer measurements mentioned hereinabove are used to calibrate the printer. In other words, for the system disclosed in the Harshbarger, et al. patent, initial compensation for paper characteristics is based on measurements taken as a part of overall system calibration. In the process for calibrating the printer located at a specific site, the RGB density of a paper type typically used at that site is measured using a densitometer. Then, in modeling colorant density versus exposure for a printer, the density of the underlying paper substrate is subtracted from colorant density measurements. It should be noted that this procedure provides a workable estimate for making calibration adjustments. However, if a site uses two or more papers that vary widely in color characteristics, some compromise in calibration strategy must then be used. Therefore, another problem in the art is the need to compromise calibration strategy if a site uses two or more papers that vary widely in color characteristics.
Additional compensation for paper substrate characteristics is provided by dot-gain profiles used with prior art prepress proofing systems, such as the system disclosed in the Harshbarger, et al. patent. A dot-gain profile models the real-world behavior of offset color printing inks when applied to paper at various values of halftone screen, where there is typically some amount of “gain” in the nominal dot size based on ink spreading and other factors. The Harshbarger, et al. device allows an operator to set-up and use a number of different dot-gain profiles, based on factors such as the specific press being emulated, the specific paper being used, and the specific screen size being employed. Based on the dot-gain profile selected, and a predetermined target density, the printer adjusts dot characteristics and exposure when creating the image on the intermediate receiver in order to emulate the real-world behavior of ink on paper substrate. In order to use dot-gain profiles effectively, an operator must know, in advance, details about the paper that will be used for the proof and, ultimately, for the print job. Therefore, another problem in the art is pre-knowledge the operator must acquire concerning details about paper properties that will be used in making the proof.
Still other compensation for paper substrate characteristics can be applied during other phases of the imaging process. For example, with the system disclosed in the Harshbarger, et al. patent, the prelaminate material itself can have characteristics that affect the color of the paper substrate. Additionally, the colorant transfer process, in which the image is transferred from an intermediate receiver onto the paper substrate, requires adjustment to compensate for paper characteristics. An apparatus designed for colorant transfer must typically vary heat, pressure, and contact time to control the effectiveness of colorant transfer, affecting the density of the final printed image. Hence, another problem in the art is need for the operator to ascertain how the prelaminate material will affect color of the paper and the need for the operat
Sanger Kurt M.
Spurr Robert W.
Tredwell Timothy J.
Brooke Michael S.
Eastman Kodak Company
Rushefsky Norman
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