Color image forming apparatus driving a recording-element...

Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic

Reexamination Certificate

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Details

C347S132000, C347S237000

Reexamination Certificate

active

06323887

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and method for controlling driving of a light-source device, and more particularly, to an apparatus and method for controlling driving of a recording head used for forming a permanent visual image on a recording medium according to an electrophotographic method.
2. Description of the Related Art
Conventionally, when forming a permanent visual image on a recording medium according to an electrophotographic method, it is necessary to form a latent image by projecting light emitted from a light-source device onto a photosensitive member.
For that purpose, recording heads, each including, for example, an LED (light-emitting diode) array, particularly, a self-scanning LED array (hereinafter termed a “SLED”), have been known.
A SLED head, serving as a recording head having SLED chips arranged in the form of an array, outputs an amount of light necessary for exposing a photosensitive member of an image forming apparatus by emission of light-emitting thyristors. Conventionally, when using four SLED heads arranged in parallel as an exposure light source of a four-drum-tandem-type color printer, and, for example, forming an image only by one (for example, the K station) of Y (yellow), M (magenta), C (cyan), and K (black) stations (image forming units) depending on image data, only a SLED head necessary for exposure of the photosensitive member is driven and lit while stopping the operations of the SLED heads of other stations.
However, when only the SLED head of one station is driven in order to emit light from the light-emitting thyristors of that head, the temperature of the SLED head gradually increases, causing a decrease in the amount of light. That is, a difference in the amount of light is produced between a SLED head which is continuously lit and a SLED head for which driving has just started, due to a difference in the temperature.
If a full-color image is output (i.e., by emitting light from all of the SLED heads of the four stations) after the above-described case of using only the K station, a deviation occurs in color balance and a sharp image cannot be formed, because the amount of exposure by heads which have not been driven is larger than that of the head which has been driven.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an image forming apparatus and a method for controlling the apparatus in which differences in the amount of light among recording heads can be prevented.
It is another object of the present invention to provide an image forming apparatus and a method for controlling the apparatus in which a sharp image having excellent color balance can be formed.
According to one aspect of the present invention, an image forming apparatus includes a plurality of image forming units corresponding to different colors. Each of the plurality of image forming units includes a recording element array in which recording elements are arranged in the form of an array, a transfer-element array for transferring respective operations of the recording elements, and scanning means for causing the recording-element array to perform scanning by controlling transfer elements constituting the transfer-element array. The apparatus also includes means for also operating the scanning means of image forming units which do not directly contribute to image formation from among the plurality of image forming units, when forming an image by selectively using the plurality of image forming units.
According to another aspect of the present invention, a method for controlling an image forming apparatus including a plurality of image forming units corresponding to different colors is provided. Each of the plurality of image forming units includes a recording-element array in which recording elements are arranged in the form of an array, and a transfer-element array for transferring respective operations of the recording elements. When forming an image by selectively using the plurality of image forming units, the recording-element arrays of image forming units which do not directly contribute to image formation from among the plurality of image forming units are also caused to perform scanning by controlling transfer elements of the concerned image forming units.
The foregoing and other objects, advantages and features of the present invention will become more apparent from the following detailed description of the preferred embodiment taken in conjunction with the accompanying drawings.


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