Incremental printing of symbolic information – Thermal marking apparatus or processes – Multicolor
Reexamination Certificate
2000-09-01
2003-01-21
Pham, Hai (Department: 2861)
Incremental printing of symbolic information
Thermal marking apparatus or processes
Multicolor
C347S177000
Reexamination Certificate
active
06509919
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to a printing apparatus and method wherein an image is written by transferring a colorant from a translucent sheet of donor film onto a substrate, and more particularly relates to an apparatus and method for sensing a donor colorant to detect a donor mispick condition.
BACKGROUND OF THE INVENTION
In a printing apparatus that employs a color thermal transfer process, a translucent donor sheet comprises a film material containing an applied colorant. At the printhead of such apparatus, heat energy is used to selectively transfer colorant from the donor sheet onto a receiver substrate material to produce the final image. As representative examples, types of thermal printing apparatus include those that employ resistive printheads, such as is disclosed in U.S. Pat. No. 5,519,428 (Van Peteghem), as well as printing apparatus that employ laser thermal printheads, such as is disclosed in U.S. Pat. No. 5,268,708 (Harshbarger et al.) The receiver material onto which an image is written could be a paper substrate, a film substrate (such as an intermediate that holds an image that will be transferred to another receiver medium, as is disclosed in the Harshbarger et al. patent), or other substrate material used for imaging.
In such printing apparatus, the donor colorant can be a dye, ink, pigment, or other suitable material that is transferred from a donor sheet onto a receiver medium. Conventional color printers provide donor colorant in the standard (CMY or CMYK) process colors, cyan (C), magenta (M), and yellow (Y), with the possible addition of black (K) donor. The donor supply source can be a roll that provides a continuous ribbon on which successive CMY or CMYK color patches are provided as described in the Van Peteghem patent. Optionally, the donor supply source can be a mechanism that provides the printhead with a single sheet of donor at a time, such as a tray, for example.
Whether the donor is provided in roll or sheet form, it is important that the printing apparatus be able to identify the color of the donor that is supplied to the printhead. In addition, it is also important to have donor sheet material correctly loaded in the proper position and orientation, so that printing is accurate and to minimize the possibility of damage to printhead components. If, for example, donor sheet material is fed with the wrong side of the sheet facing the printhead, colorant could be improperly transferred onto printhead components, making it necessary to clean or even to replace the printhead. With sheet feeding apparatus, if multiple sheets are inadvertently picked from a tray (or fed from a manual feed slot), a jam condition can occur, causing damage to printhead components if not detected.
Conventional printing apparatus have solved the above-noted problems of color identification, donor orientation, and mispick detection in a number of ways. Where donor is provided in ribbon form (such as disclosed in the Van Peteghem patent noted above), mispick is not a problem, since the donor is fed from a source roll to a take-up roll. Proper donor orientation is typically obtained by methods such as keying the supply roll to allow its insertion in only the correct manner or by supplying the donor ribbon in reloadable cassette form, such as is disclosed in U.S. Pat. No. 5,415,486 (Wouters et al.). For donor in ribbon form, color detection is inherently a simpler problem than it is for donor supplied in sheet form. This is because donor patches on the ribbon, as manufactured, follow each other in a known sequence. However, printers using donor ribbon have employed a number of different techniques for color detection, as noted below.
Notching is one solution that has been employed to solve the above-noted problems. U.S. Pat. No. 5,196,868 (No et al.) discloses detection of a notch in an image receiver sheet for sensing proper orientation (that is, “coated side up”). U.S. Pat. No. 4,536,772 (Isogai) discloses sensing notch position in a sheet-fed donor media to indicate donor color. Notching is easy to detect; however, this method requires a manufacturing step and is a limited solution for differentiation between colors that might be similar. Significantly, notching, by itself, does not provide a solution for mispick detection where multiple sheets are picked.
As another method for color identification, markings have been provided on donor media for optical sensing. For example, U.S. Pat. No. 5,393,149 (lima) discloses optical sensing of an ink ribbon cartridge using identifying marks readable through the cartridge housing. U.S. Pat. No. 4,573,059 (Shinma et al.) discloses optical sensing of marks placed on the edge of an ink donor sheet, where physical dimensions of the mark itself indicate the corresponding donor color. U.S. Pat. No. 5,978,005 (Hadley) discloses use of a delimiting stripe to define the borders between colors in a color thermal ribbon, with an indexing stripe to indicate the beginning of each sequence of color patches. While such markings on an edge of the donor material can be used to identify color, providing marks correctly positioned in manufacture can be costly.
Optical sensing of the donor color itself, possible when a donor is translucent, has been employed as a method for color identification. U.S. Pat. No. 4,710,781 (Stephenson, reissued as RE 33,260) discloses, for a thermal printer using a ribbon donor, sensing red and yellow LEDs that transmit light through a translucent donor. Using this method, photosensors are adapted to detect particular wavelengths of transmitted light above or below specific threshold values. Truth-table logic, based on detection by a pair of photosensors, is then used to determine the color of the patch sensed, based on this wavelength detection. Similarly, U.S. Pat. No. 5,466,075 (Kouzai et al.) discloses, for an ink sheet, use of three color sources transmitted through a translucent identifying portion (ID mark) in the donor and three corresponding sensors used to help distinguish color patches. Notably, in the Kouzai et al. disclosure, a specific ID mark is provided adjacent to each patch on the donor. The ink donor color itself is not sensed.
The use of multiple light sources as disclosed in both the Stephenson and Kouzai et al patents noted above provides crude differentiation of color patches for ribbon donor. By sensing, over specific narrow wavelengths, the characteristic levels of light energy transmitted through a translucent color donor by light sources, emitting light over corresponding narrow wavelengths, some level of color differentiation is possible. However, these existing methods have significant drawbacks for printing apparatus used in applications such as color proofing (for example, for the device disclosed in the Harshbarger patent noted above). Using conventional methods, photosensors are designed for fairly crude detection thresholds that allow for a wide possible range due to factors such as component aging, LED and sensor cost, and batch manufacturing differences. For this reason, such an approach has limitations where specially formulated colors (that is, colors other than the standard process CMYK colors) are used. It can be difficult or impossible to detect specially formulated colors using a detection scheme that uses the coarse “truth table” decision mechanisms disclosed in either Stephenson and Kouzai et al patents. Moreover, it can be impossible to detect subtle color shifts between donors, such as have become expected in printers used for color proofing. (For example, different yellow donors are preferred for printing in Europe than are used in the U.S.)
Certainly, it would be possible to employ an array of sensors similar to those used within color scanners, as disclosed in U.S. Pat. No. 5,027,195 (Cooley et al.) and in U.S. Pat. No. 4,930,008 (Suzuki et al.) However, such scanner devices are optimized for scanning the full dimensions of an image area and providing data on the primary RGB (Red, Green, and Blue) color content as sampled at an array comprisin
Schultz Michael E.
Spurr Robert W.
Tehranchi Babak
Eastman Kodak Company
Pham Hai
Rushefsky Norman
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