Optical: systems and elements – Miscellaneous
Reexamination Certificate
2003-02-20
2004-02-17
Phan, James (Department: 2872)
Optical: systems and elements
Miscellaneous
C358S518000, C347S232000, C359S196100
Reexamination Certificate
active
06693752
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an image forming apparatus, and in particular, to an image forming apparatus capable of eliminating various kinds of deviation such as distortion and positional deviation in an image formed on a recording sheet.
A copying machine, a printer, a facsimile apparatus, etc. (These are hereinafter referred to as “image forming apparatus” collectively.) are equipped with a function to form an image on a recording sheet.
Further, among image forming apparatus of this kind, there is one wherein a latent image is formed on a photoreceptor by means of a laser beam, the latent image is made a toner image, and this toner image is transferred and fixed to a recording sheet.
Further, in such an image forming apparatus using a laser beam, a polygonal mirror and an f&thgr; lens are used for the scanning of the photoreceptor by the laser beam. Therefore, caused by deviation of the characteristics of the f&thgr; lens from the ideal ones, chromatic aberration of the f&thgr; lens, inclination of the polygonal mirror from the ideal direction, deviation of the polygonal mirror from the ideal position, deviation of the reflection angle characteristic of the polygonal mirror from the ideal one, deviation of the position and inclination of the mounting of the photoreceptor from the ideal values, etc., positional deviation, inclination, and distortion of an image (These are hereinafter referred to as “deviations” collectively.) are produced, which makes a cause of image degradation.
Further, in a color image forming apparatus of a tandem type for forming a color image, there are a plurality of f&thgr; lenses, polygonal mirrors, laser beams, and photoreceptors in accordance with the number of colors of an image to be formed, and deviations in these components present a registration error in a color image.
For the purpose of correcting the above-mentioned deviations, there exist several methods. The first method is such that exposure beam is detected by a sensor and registration correction is carried out. In this first method, the main object is to adjust the starting position in the main scanning direction. The second method is such that an image on the intermediate transfer member is read by an image sensor and registration correction is carried out. In this second method, the main object is the positional adjustment of a specified portion in the main/sub-scanning directions. The third method is such that an image of a specified pattern is formed, and this image of the specified pattern is read by a scanner. The main object of this third method is inspection.
That is, in any one of the above-mentioned first method to third method, it has never been taken into consideration to carry out the correction of an image distortion and a registration error in a color image for each pixel on the whole surface of the image at an accuracy within one dot.
SUMMARY OF THE INVENTION
This invention was made in view of the above-mentioned problem, and it is its object to realize an image forming apparatus capable of carrying out the correction of image distortion and registration error in a color image for each pixel on the whole image surface at a high accuracy.
Further, it is its another object to realize an image forming apparatus capable of carrying out the correction of an image distortion and a registration error in a color image for each pixel on the whole image surface at an accuracy within one dot.
That is, the above-mentioned objects are accomplished by any one of the structures (1) to (6) described below.
(1) An image forming apparatus characterized by comprising an image forming means for forming an image on a recording sheet on the basis of image data and outputting it, an image reading means for reading an image on a document and generating image data, a pattern generating means for generating pattern data for recording a set of test patterns at their respective specified positions on a recording sheet, a positional deviation detecting means for detecting the positional deviation from the position of the proper output at each characteristic point included in the set of test patterns generated by said pattern generating means, and a deviation correcting means for calculating operational values for the correction of each pixel with reference to the respective positional deviations of the characteristic points detected by said positional deviation detecting means and carrying out a processing to eliminate the positional deviation of each pixel in image formation by the use of said operational values, thereby the deviation or the inclination of an image when said image is read by said image reading means, can be corrected.
In this structure, the respective positional deviations of characteristic points, which are included in the set of test patterns from image data obtained by the reading of the recording sheet having the image of said set of test patterns recorded on it, from the positions of their proper output are detected. Then, by the calculation of operational values for the correction of each pixel with reference to the detected positional deviation of the characteristic points and the use of said operational values, a processing to eliminate positional deviation or inclination in image formation is carried out.
As the result of this, it is possible to carry out the correction of image distortion for each pixel of the whole image surface.
(2) An image forming apparatus comprising an image forming means for forming an image on a recording sheet on the basis of image data and outputting it, an image reading means for reading an image on a document and generating image data, a pattern generating means for generating pattern data for recording a set of test patterns at their respective specified positions on a recording sheet, a positional deviation detecting means for detecting the positional deviation from the position of the proper output at each characteristic point included in the set of test patterns generated by said pattern generating means, and a deviation correcting means for calculating operational values for the correction of each pixel with reference to the respective positional deviations of the characteristic points detected by said positional deviation detecting means and carrying out a processing to eliminate the positional deviation of each pixel in image formation by the use of said operational values, which is characterized by the positional deviation to be detected by said positional deviation detecting means and the positional deviation to be corrected by said deviation correcting means being deviations in the main scanning direction and in the sub-scanning direction.
In this structure, the respective positional deviations of characteristic points, which are included in the set of test patterns from image data obtained by the reading of the recording sheet having the image of said set of test patterns recorded on it, from the positions of their proper output are detected. Then, by the calculation of operational values for the correction of each pixel with reference to the detected positional deviation of the characteristic points and the use of said operational values, a processing to eliminate positional deviation or inclination in image formation is carried out.
Further, in this structure, because the positional deviation to be detected and the positional deviation to be corrected are deviations in the main scanning direction and in the sub-scanning direction, it is possible to carry out the correction of image distortion at a high accuracy for each pixel of the whole image surface.
(3) An image forming apparatus comprising an image forming means for forming an image on a recording sheet on the basis of image data and outputting it, an image reading means for reading an image on a document and generating image data, a pattern generating means for generating pattern data for recording a set of test patterns at their respective specified positions on a recording sheet, a positional deviation detecting means for detecting the positio
Frishauf Holtz Goodman & Chick P.C.
Konica Corporation
Phan James
LandOfFree
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