Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1995-08-14
2001-07-17
Popovici, Dov (Department: 2622)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S001200, C382S254000
Reexamination Certificate
active
06262809
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image processing apparatus, and more particularly, it relates to an image processing apparatus for forming an image by reproducing density data in units of respective picture elements with a laser beam.
2. Description of the Related Art
In a recording apparatus of a scan recording type, various systems are employed for digitally reproducing variable densities of images. Such digital gradation reproducing methods include a dither method, an intensity modulation system and a pulse duration modulation system. The dither method is adapted to change on-off area rates of picture elements contained in a plurality of picture elements which are processed as a unit, thereby expressing the variable density of an image. The intensity modulation system is adapted to averagely apply laser energy to picture elements while modulating laser emission intensity in a multistep manner with respect to each picture element, thereby changing the variable density. The pulse duration modulation system is adapted to modulate an emission time per unit picture element while maintaining constant laser emission intensity, as disclosed in Japanese Patent Laying-Open Nos. 61-225971 (1986) and 62-116959 (1987), for example.
In the dither method of processing a plurality of picture elements as a unit, a moire noise which is specific to this method results in a deterioration of the image quality.
In the intensity modulation system, it is possible to basically output the variable density in one-to-one correspondence to the as-read image data, thereby attaining high resolution with fine and smooth gradation characteristics. In a highlight portion, however, it is difficult to attain excellent gradation reproducibility due to a requirement for delicate variable-density control. Further, rough graininess of a half tone portion is stressed due to an influence by the backing of an image recording paper.
On the other hand, the pulse duration modulation system does not have the problem of graininess that arises in the intensity modulation system. However, this system generally moves centers of gravity of picture elements with respect to units of two picture elements. When density data of 400 DPI are reproduced, for example, only reproducibility of 200 DPI is substantially attained to reduce resolution. When the pulse duration modulation system is employed in a unit of a single picture element, on the other hand, the laser emission time is considerably reduced in a picture element having low density, leading to insufficient stability of the image quality in view of toner adhesion.
SUMMARY OF THE INVENTION
An object of the present invention is to improve graininess of a half tone portion in an image processing apparatus while maintaining resolution.
Another object of the present invention is to improve gradation reproducibility of a highlight portion in an image processing apparatus while maintaining resolution.
Still another object of the present invention is to attain continuity of processing in an image processing apparatus at a boundary portion between different types of images which are contained in an original.
A further object of the present invention is to enable tone control while improving graininess of a half tone portion with no influence on a character image.
In order to attain the aforementioned objects, an image processing apparatus according to a first aspect of the present invention is directed to an apparatus for processing image data obtained by reading an original image every picture element, which comprises processing means for successively dividing picture elements arranged along a main scanning direction into an adjacent pair and reducing image data of one picture element by a first prescribed quantity while increasing that of the other picture element by the first prescribed quantity.
The image processing apparatus having the aforementioned structure shifts density data between an adjacent pair of picture elements while maintaining the density of the overall pair, whereby it is possible to improve graininess of a half tone portion while maintaining resolution.
In order to attain the aforementioned objects, an image processing apparatus according to a second aspect of the present invention is directed to an apparatus for processing image data obtained by reading an original image every picture element, which comprises detection means for detecting a difference between the quantities of image data of adjacent picture elements, decision means for deciding a data shift quantity in response to the difference detected by the detection means, means for reducing image data of one of the adjacent picture elements by the data shift quantity decided by the decision means, and means for increasing image data of the other one of the adjacent picture elements by the data shift quantity decided by the decision means.
The image processing apparatus having the aforementioned structure decides the data shift quantity in response to a density difference between adjacent picture elements, whereby continuity is attained in processing at a boundary portion between different types of images.
In order to attain the aforementioned objects, an image processing apparatus according to a third aspect of the present invention is directed to an apparatus for processing image data obtained by reading an original image every picture element, which comprises addition means for adding a first prescribed quantity to image data of each of adjacent picture elements, means for subtracting a second prescribed quantity from image data of one of the picture elements, and means for increasing image data of the other picture element by the second prescribed quantity.
The image processing apparatus having the aforementioned structure increases the image data of each of adjacent picture elements by a first prescribed quantity to thereafter shift the density data, whereby it is possible to control the tone while improving graininess of a half tone portion.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
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Itoh Tetsuya
Kawaguchi Toshikazu
Sawada Shigeru
Burns Doane , Swecker, Mathis LLP
Minolta Co. , Ltd.
Popovici Dov
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