Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
2000-03-06
2001-10-23
Brase, Sandra (Department: 2852)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C347S261000
Reexamination Certificate
active
06307579
ABSTRACT:
BACKGROUND OF THE INVENTION
In an image forming apparatus, when taking a 100% (life-size) copy, an image copied on a paper must be realized at a 100% magnification with respect to a document. However, a paper feeding speed and a drum circumferential speed coincide with each other due to a part dispersion of a carrier system, that is, a roller outer-diameter and a fixing roller outer-diameter; for this reason, a magnification error takes place. Moreover, in the case where there is no coincidence in a speed of each unit due to dispersion between oscillators of each motor control circuit, a magnification error takes place. Therefore, in the conventional image forming apparatus, the above 100% magnification is not always realized, and in order to realize the 100% magnification, a part accuracy of each unit must be strictly set, and a correction (adjustment) must be made while recognizing an actual copied image.
In a printer unit of a digital copying machine, a magnification error in its main scanning and feed has been corrected by varying a rotational speed of a polygonal motor and a rotational speed of a photosensitive drum motor (a paper feeding speed and a rotational speed of a photosensitive drum). On the other hand, in a scanner unit, a magnification error in its main scanning and feed has been corrected by varying a rotational speed of a polygonal motor and a scanner speed after a correction on the magnification error of the printer unit is made.
Inherently, in the case of making a correction on a magnification error in a main scanning direction, a lens position of a scanner unit and/or printer unit must be adjusted on the basis of an output signal of a CCD. However, an adjustment of a lens system is very troublesome; for this reason, the magnification error is corrected by a rotational speed of the polygonal motor. Moreover, although it is possible to correct the magnification error in a main scanning direction by image processing, this correction is not employed because there is the case where a disadvantage such as “moire” takes place.
According to the conventional magnification error correction in the main scanning/feed direction, in the case of an electronic sort using no finisher (in the case of image rotation), or in the case where a paper set in a transverse direction is run short out of a paper tray; for this reason, the paper tray is changed over from a paper try in which a paper is set in a longitudinal direction, the main scanning/feed direction in reading is replaced with a feed/main scanning direction in writing; as a result, a magnification error takes place. In order to reduce this magnification error, Jpn. Pat. Appln. KOKAI Publication No. 9-130582 has disclosed a method for correcting a magnification error in a longitudinal-transverse conversion. However, according to this method, in addition to magnification error correction in the feed and main scanning direction, each magnification error in a case of longitudinal-transverse conversion must be corrected.
BRIEF SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a magnification error correction method for an image forming apparatus, which has no need of troublesome processing in correction for an image magnification error in the case of scanning a document and copying it, in addition to in the case of inputting a data from an external device and forming an image using only printer unit, and in the case of scanning the document by a scanner unit, and converting an image main scanning/feed direction so as to form an image by a printer unit.
In order to achieve the above object, according to one aspect of the present invention, there is provided a magnification error correction method comprising the steps of: a first correction step of providing a first polygonal motor correction value and a first drum motor correction value to the polygonal motor and the photosensitive drum motor so that an image formed by the printer unit has a desired magnification, on the basis of the reference pattern data provided from the reference pattern generating unit, and storing these correction values in the memory; and a second correction step of scanning a document, on which a predetermined pattern is printed, by the scanner unit, providing a second polygonal motor correction value and a carriage motor correction value to the polygonal motor and the carriage motor so that an image printed using the printer unit has a desired magnification, storing these correction values in the memory, and providing the drum motor correction value to the photosensitive drum motor.
In the case of inputting an image data from an external device, and forming an image by the printer unit, the image is formed using the first polygonal motor and drum motor correction values.
In the case of scanning the document by the scanner unit, and inverting the image main scanning and feed direction to form the image by the printer unit, the image is formed using the first polygonal motor and carriage motor correction values and the second drum motor correction value calculated by using the first and second polygonal motor correction values and the first drum motor correction value.
The first and second polygonal motor correction values are change rates of the rotational speeds of the polygonal motor after the first and second correction steps are respectively completed with respect to the initial value of the rotational speed of the polygonal motor. The second drum motor correction value is a value calculated by subtracting a difference, obtained by subtracting the second polygonal motor correction value from the first polygonal motor correction value, from the first polygonal motor correction value.
REFERENCES:
patent: 4796054 (1989-01-01), Maeno et al.
patent: 5418603 (1995-05-01), Kusumoto et al.
patent: 5530642 (1996-06-01), Lofthus et al.
patent: 5740505 (1998-04-01), Kusumoto et al.
patent: 6104420 (2000-08-01), Matsumoto
patent: 9-130582 (1997-05-01), None
Brase Sandra
Foley & Lardner
Toshiba Tec Kabushiki Kaisha
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