Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
1997-08-27
2001-09-25
Le, N. (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S247000
Reexamination Certificate
active
06295077
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an image forming apparatus and, more particularly, to an apparatus for forming an image by processing image data in units of a plurality of samples.
2. Description of the Related Art
Apparatuses employing electrophotography have become increasingly popular as apparatuses for forming images. Electrophotography involves forming an image by scanning a photosensitive element with laser light or light from an LED that conforms to the value of image data. In an apparatus of this kind, the transmission of image data to a laser driver which drives a laser generally is performed in units of single pixels. However, advancements in image processing techniques have been accompanied by higher image processing speed and higher resolution, and it is desired that the speed at which image data is transferred to the laser driver be raised also in an image forming apparatus of the type which relies upon electrophotography.
In order to accommodate this demand for higher transfer speed, data consisting of a plurality of pixels (samples) is packed and then sent to the laser driver, thus making possible a substantial increase in transfer speed. However, when data of a plurality of pixels is transferred to the laser driver in the form of a pack in this manner, fine adjustment of scanning position in the main scan direction of the photosensitive element can only be performed in data pack units.
More specifically, in an image forming apparatus, particularly a color image forming apparatus having four photosensitive drums, in which colors are formed on the plurality of photosensitive drums in respective ones of the colors used and the color images are transferred to a single sheet of recording paper so as to overlap one another and form the final full-color image, the fact that adjustment cannot be made in units of single pixels means that it is not possible to adjust for a subtle positional deviation between colors in the formed image, where the offset is produced physically due to positional deviation in the positions at which the photosensitive drums or lasers for the various colors are disposed. As a consequence, a problem which arises is the formation of a poor quality image in which the positions of the color images that constitute the final full-color image do not coincide.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to solve the problem mentioned above.
Another object of the present invention is to make it possible to adjust the position of an image highly precisely when an image is formed by processing image data in plural-pixel units.
Another object of the present invention is to make it possible to correct the positional deviation between color images in a highly precise manner when an image is obtained by transferring images of a plurality of colors to a common recording medium.
According to the present invention, the foregoing objects are attained by providing, as one embodiment of the invention, an image forming apparatus comprising first converting means for converting means for converting image data, which enters in parallel a plurality of pixels at a time, to a serial image data string, shifting means for shifting, by a predetermined number of pixels, the serial image data string output by the first converting means, wherein the predetermined number of pixels equates to an amount of adjustment for correction of an image position, second converting means for converting the serial image data string, which has been output by the shifting means, to parallel image data a plurality of pixels at a time, and image forming means for forming an image based upon the image data output by the second converting means in parallel a plurality of pixels at a time.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.
REFERENCES:
patent: 3707725 (1972-12-01), Dellhelm
patent: 4521813 (1985-06-01), Yoshida et al.
patent: 4807047 (1989-02-01), Sato et al.
patent: 5206501 (1993-04-01), Sakakibara et al.
patent: 5579092 (1996-11-01), Isobe et al.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Le N.
Nguyen Lamson D.
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