Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2000-11-21
2003-03-11
Lee, Susan S. Y. (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C347S130000
Reexamination Certificate
active
06532029
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to imaging systems and, more particularly, to a method and a system for compensating for an offset of a dot or series of dots in an imaging system, such as in an electrophotographic system (e.g., color printers).
2. Description of the Related Art
One of the difficulties in designing imaging systems such as electrophotographic (EPG) printers, inkjet printers, and laser printers is overcoming a problem known as “imaging offset.” This problem results in poor image quality in both monocolor (i.e., black and white) and multicolor systems. To better understand the background of this problem, imaging offset will be explained with reference to an EPG printer.
In general, imaging offset results from physically misaligned exposure units, e.g., light-emitting diodes (LEDs), that are used in the EPG printer to form an image. Exposure units may become misaligned from either errors during the manufacturing process or damage to the EPG printer after manufacture. Additionally, to ensure that exposure units are perfectly aligned, strict manufacturing tolerances must be maintained, which is difficult and increases costs.
In an EPG system such as a printer or a copier, an electrostatic latent image is formed on a charged surface of a photoreceptor by exposing the photoreceptor with a high-intensity light source such as an LED array. Prior to exposure, the surface of the photoreceptor is uniformly charged. The LEDs then create a charged pattern (known as a “latent image”) corresponding to the image that is to be printed. The latent image is then developed into a toner image by adhering charged toner particles to the charged pattern on the photoreceptor. The toner image is transferred to paper using an electrostatic transfer process. The toner image is then fused to the paper by heat. The photoreceptor is then cleaned prior to the next imaging cycle of the system.
Imaging offset occurs in the EPG imaging process at the point when the LEDs create the charged pattern. As mentioned above, LEDs may be misaligned during the manufacturing process (e.g., mounting of LED chips) or after the manufacturing process due to damage to the EPG printer or any intermediary device (e.g., SFL error). Misaligned LEDs are offset from an ideal linearity by different distances. An image resulting from this nonlinear array of LEDs is of poor quality.
Imaging offset similarly occurs in multicolor imaging. Multicolor EPG copying and printing requires the EPG process explained above for monocolor images to be repetitively performed for each color. Different stations for each of the different colors (e.g., yellow, magenta, cyan, and black) apply toner of a specific color. In multicolor imaging, the toner powder images should be superimposed upon each other in near perfect registry (or alignment) to produce high-quality color images. If misregistration occurs, the color images may blur, and color hue shifts may occur. Misaligned LEDs therefore cause these registration problems.
In view of the foregoing, a need exists for a method and a system for compensating for imaging offset to avoid the linearity and registration problems described above.
SUMMARY OF THE INVENTION
The present invention overcomes the imaging-offset drawbacks of conventional imaging systems and provides imaging systems that produce clear, crisp, and true-color images free from imaging offset.
According to one aspect of the present invention, a method of compensating for imaging offset of a dot produced by an exposure unit on a substrate in an imaging system. The dot has an uncompensated dot position and an ideal dot position. The uncompensated dot position is out of alignment with the ideal dot position. To compensate for this misalignment, the imaging offset is determined as a distance between the ideal dot position and the uncompensated dot position. Based on the determined imaging offset, the uncompensated dot position is then matched to the ideal dot position.
One of the advantages of the present invention is that imaging offset is substantially eliminated in the imaging process. Accordingly, images produced by, for example, printers and copiers are clear, crisp, and free of errors. In addition, images produced by color systems do not suffer from registration problems of one color upon the other. Accordingly, color image provide clear, true colors.
Cost savings is another advantage of the present invention. More specifically, conventional approaches attempting to reduce imaging offset by apply strict manufacturing tolerances during the production of, for example, light-emitting diode (LED) printer heads (LPHs). This strict adherence is expensively and, ultimately, falls short of success because of the size and number of diodes in the LPHs. In accordance with the present invention, imaging offset may be corrected regardless of the misalignment in diodes of the LPHs. Accordingly, inexpensively produced LPHs may be used to produce images of the highest quality.
The matching of the dot to the ideal dot position may be accomplished, for example, by delaying a formation of the dot on the substrate by an amount of time corresponding to the imaging offset. Alternatively, a time factor based on the imaging offset may be determined. The exposure unit may then be actuated to produce a dot at a time modified by the time factor. The time factor may be based on both a magnitude of the distance of the imaging offset, as well as a direction of the imaging offset.
Another advantage of the present invention related to the applicability of its methodology. More specifically, the compensation method may be implemented by an on-board software module. In alternative embodiments, the method of the present invention may performed from a remote location. In this embodiment, an imaging system is in communication with a processor that causes the exposure unit to be actuated so that the dot is produced at the ideal dot position.
REFERENCES:
patent: 5196864 (1993-03-01), Caine
patent: 5471550 (1995-11-01), Kurachi
patent: 5831626 (1998-11-01), Sano et al.
patent: 6002413 (1999-12-01), Nishizawa et al.
patent: 6055005 (2000-04-01), Appel et al.
patent: 6055006 (2000-04-01), Murano
patent: 6198896 (2001-03-01), Nakayasu et al.
patent: 6408156 (2002-06-01), Miyazaki et al.
patent: 64-4775 (1989-01-01), None
patent: 4-45966 (1992-02-01), None
patent: 4-281476 (1992-10-01), None
patent: 8-204924 (1996-08-01), None
patent: 9-247428 (1997-09-01), None
Aetas Technology Incorporated
Douglas Frederic M.
Lee Susan S. Y.
LandOfFree
Imaging-offset compensation methods and systems does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Imaging-offset compensation methods and systems, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Imaging-offset compensation methods and systems will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3076789