Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2003-02-27
2004-03-09
Pendegrass, Joan (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C347S234000
Reexamination Certificate
active
06704035
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus for electrophotography/electrostatic recording color cameras, color printers, color facsimiles and the like, and more particularly, to a color image forming apparatus that uses a laser for writing.
2. Description of the Related Art
As one example of the above-described technology the invention disclosed in Japanese Laid-Open Patent Application No. 8-149241 is known. In this invention, which is aimed at making it easy to expand a system, an image forming apparatus and its peripheral equipment are connected to each other by a system controller universal bus.
That is, in the invention of Japanese Laid-Open Patent Application No. 8-149241, a system control unit equipped with a CPU is connected to a printer unit and a plurality of scanner units as well as an image memory unit by a universal bus, image data from the image processing terminal equipment from the printer unit and the scanner unit is stored in the image memory unit via the universal bus, and image formation carried out by processing image data from the image processing terminal equipment in response to a data request, so system expansion can be carried out easily by connecting image processing terminal equipment to the universal bus.
According to such conventional art, expanding a system composed of a printer controller plus a scanner plus an image forming apparatus requires only a printer controller universal bus as a data transmission path, making system expansion easy.
However, when for example data read from the scanner unit undergoes image processing and the image-processed data is then printed out, the data is once stored in the system bus image memory, returned to the image processor inside the scanner unit and then transferred to the image forming apparatus via the system bus. In such a case, the amount of traffic on the bus increases, reducing transfer efficiency and resulting in reduced printer performance.
Such a problem can be solved by for example by using the system bus as the interface between the printer controller and the image forming apparatus and between the printer controller and the scanner unit, and using a different interface between the scanner unit and the image forming apparatus. With this type of interface configuration, the image forming apparatus must be compatible with both interfaces and the lighting timing control of a laser diode (LD) of each color must also be made compatible with both interfaces.
Additionally, as an image forming apparatus that adjusts a sub-scanning regist up to the timing of an operation commencement signal from a regist sensor and an electrostatic latent image formation operation commencement and in which a succeeding operation commencement signal becomes active during electrostatic latent image formation, there is for example a so-called tandem-type color image forming apparatus in which the image formation units are aligned along a conveyer belt.
In such type of image forming apparatus, the tandem configuration comprises a circuit that takes image data from an image input apparatus and controls a timing between each color and a laser diode control board for each color. However, it is necessary to match the timing of the image input apparatus and the timing laser diode control boards of the individual colors.
Accordingly, such an image forming apparatus has two requirements:
(A) The sub-scanning write position is determined by the timing delay to the commencement of writing from the reference regist sensor. The timing of the data request to the image input apparatus and the timing of the commencement of the FGATE for the laser diode control board must be synchronized to a rotation of a polygon mirror.
(B) In order to achieve high-speed operation, a method of electrostatic latent image formation simultaneously over a plurality of lines using a plurality of laser diodes has come to be used. Additionally, there is such a thing as write resolution, and sometimes images are written using a resolution greater than that of the original image (for example a resolution of 1200 dpi as opposed to 600 dpi of the original image), so a magnification process sometimes is performed at the laser diode control boards.
However, making the circuit that takes image data from the image input apparatus and controls the timing between each color compatible with the variety of write laser diode control board configurations and operating modes described above increases the scale of the circuitry and complicates control, which is undesirable.
Additionally, conventionally, copiers, printers and the like are equipped with an image forming apparatus that performs cyclical line scans on a photosensitive surface that moves in a sub-scanning direction using a laser beam carrying image information. The image formation unit of the image forming apparatus is equipped with a laser diode control board that generates a write signal for driving a laser diode in response to image data to be written sent from the application board, and which generates write signal corresponding to various image data sent from different application boards, for example a printer controller, a copy application, a FAX application, and so forth.
However, even with the three types of applications used as examples above, resolution differs because of differences in function among the applications. For example, among printer controllers, resolutions of 1200, 600 and 300 dpi are standard, but among copier applications a resolution of 600 dpi is standard while among FAX applications resolution is not measured in terms of dpi but in terms of lines per mm. In short, image density is variegated. As a result, it is necessary that the laser diode control board of the image formation unit variably control a rotation speed of a polygon motor and the frequency with which the LD is lit. However, such adjustment is not easy, and complicates the process of carrying out accurate image formation for applications of so many different kinds.
A multiplication method that sets the write density of the image forming apparatus to a 1200 dpi that is a minimum multiple of the image density and that doubles the difference between the image density and the write density using a line memory is commonly in wide use. However, even employing such a method, the interface between the application board and image formation unit is not uniform and incompatibilities can arise, making accurate image formation difficult. Such difficulties are particularly pronounced in the formation of color images of the tandem type, in which it is necessary to adjust the write positions of each of the colors.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide an image forming apparatus in which the above-described drawbacks are eliminated.
Another and more specific object of the present invention is to provide an image forming apparatus in which drive timing control of a laser diode for accommodating different interfaces can be performed simply.
Another, further and more specific object of the present invention is to provide an image forming apparatus that uses a data transfer method that guarantees the above-described operation of (A) and that solves the above-described problem of (B).
Still another, further and more specific object of the present invention is to provide an image forming apparatus that provides superior application board expansion capabilities for producing image data to be written and that includes means for generating a laser write signal that can form an image of a quality suited to color image processing.
The above-described objects of the present invention are achieved by providing a color image forming apparatus for forming a color image on a storage medium using a laser beam generated from a laser generating means, the color image forming apparatus comprising:
a plurality of image data interfaces provided between the color image forming apparatus and a peripheral device;
image data interface conver
Kobayashi Shinji
Shinohara Tadashi
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Pendegrass Joan
Ricoh & Company, Ltd.
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