Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
1999-12-16
2001-05-08
Pendegrass, Joan (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C347S116000, C358S001900, C358S530000, C430S042100
Reexamination Certificate
active
06229554
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to image forming apparatuses and methods for forming an image which form a color print image by printing a plurality of colors on one medium on which one color image is printed over other color images and, more particularly, to an image forming apparatus and a method for forming an image in which the accuracy of color placement on a medium is improved.
2. Description of the Related Art
Especially in an electronic color printer, a color image is formed by mixing toners of black and three primary colors: yellow, magenta and cyan.
There are methods for processing transcriptions of four color images as follows: a method using four photosensitive drums, in which one photosensitive drum is provided for each color and a transcription is processed for each color image on a sheet in sequence; a method using a single photosensitive drum, in which a toner image is developed on the photosensitive drum by selectively using one of four developing devices corresponding to one of four colors and a transcription is performed four times on a sheet; and a method using a single photosensitive drum and a transcription medium, in which each of four color toner images is developed on the transcription medium and the overlapped four color images are copied on a sheet at once. The methods have a disadvantage in that displacement between two color images occurs.
To eliminate deterioration of image quality caused by the displacement, each color has to be overlapped with an accuracy of a few &mgr;ms. To achieve this accuracy, improvement of an accuracy of a photosensitive drum's rotation, improvement of an accuracy of transferring a sheet, or auto adjustment techniques by detecting color displacements have been discussed. However, it is still difficult to achieve enough accuracy to overlap colors and these improvements require a high cost.
Recently, it is desired to improve image quality and to reduce cost related to improving the color displacement.
In a conventional color image forming method, the following method is generally used.
For example, to produce a red color, two colors, yellow and magenta of the three primary colors, are overlapped on a sheet. However, when a red color image is formed, each of the yellow image and magenta image is processed in sequence but separately: that is, the yellow image and the magenta image are processed at slightly different times. Therefore, transcription of each color image is placed at a slightly different position on the sheet. When the displacement of color images is significant, the expected color is not produced and image quality is deteriorated.
Details of the above-mentioned displacement will be explained with reference to
FIGS.1A and 1B
.
FIG. 1A
shows a diagram illustrating an example of a conventional color overlapped image in which there is no color displacement.
In this figure, M indicates magenta, R indicates red, and Y indicates yellow.
In a conventional method, only when a centerline of a magenta straight line is coincident with a centerline of a yellow straight line, will the color displacement not occur so that a clear red straight line is formed.
FIG. 1B
shows a diagram illustrating an example of a color overlapped image which has displacement at a 100-&mgr;m displacement allowance in a conventional manner.
It should be noted that the allowance displacement means a physical minimum amount at which human eyes begin to discern that two images are physically displaced. That is, the 100-&mgr;m allowance displacement indicates that human eyes begin to discern a displacement between two images when the two images are displaced by at least 100 &mgr;m. On the contrary, human eyes can not discern a displacement between two images when the two images are displaced by less than 100 &mgr;m.
In
FIG. 1B
, a displacement
5
is a 100-&mgr;m difference between magenta's centerline and yellow's centerline. In a conventional method, because the magenta line and the yellow line are of the same thickness, the displacement
5
causes a 100-&mgr;m difference
6
between lower edges of the magenta straight line and the yellow straight line and also causes a 100-&mgr;m difference
7
between upper edges of the magenta straight line and the yellow straight line.
Even with the discussed improvement of the accuracy of a photosensitive drum's rotation, the improvement of the accuracy of transferring a sheet and the auto adjustment techniques by detecting color displacements, it is still difficult to eliminate the color displacement when a certain color line is formed by overlapping two lines having the same thickness.
SUMMARY OF THE INVENTION
It is a general object of the present invention to provide an Image forming apparatus and a method for forming an image with a color image technology that eliminates the above-mentioned disadvantages.
A more specific object of the present invention is to provide an image forming apparatus and a method for forming an image with a color image technology in which some color displacement is allowed while maintaining a high image quality at a low cost.
The above objects of the present invention are achieved by an image forming apparatus including a processing part forming a color output image from an input image by overlapping areas of different colors with each other, wherein the areas of the different colors have different sizes. Therefore, the present invention can reduce deterioration caused by a color displacement.
Furthermore, the above objects of the present invention are achieved by a method for forming an image comprising the steps of: (a) forming a color output image from an input image by overlapping areas of different colors with each other, wherein the areas of the different colors have different sizes. Therefore, the present invention can provide a method to reduce deterioration caused by a color displacement.
REFERENCES:
patent: 5617192 (1997-04-01), Tonomoto et al.
patent: 5722003 (1998-02-01), Suzuki et al.
patent: 5754919 (1998-05-01), Sugimoto et al.
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patent: 63-300259 (1988-12-01), None
patent: 8-166700 (1996-06-01), None
patent: 8-166699 (1996-06-01), None
patent: 9-174942 (1997-07-01), None
patent: WO95/25988 (1995-09-01), None
Armstrong Westerman Hattori McLeland & Naughton LLP
Fujitsu Limited
Pendegrass Joan
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