Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1994-07-12
1999-04-27
Lee, Thomas D.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358455, 358458, 382252, H04N 140
Patent
active
058985077
ABSTRACT:
In an image processing apparatus of this invention, an error diffusion processing means having a multi level signal conversion means changes the conversion characteristics of the multi level signal conversion means, e.g., corrects the output value of error diffusion processing, on the basis of an output from a means for detecting a variation in toner attachment amount or image forming condition. That is, this invention executes error diffusion processing as follows when an input dimension is different from an output dimension (e.g., input dimension=reflection factor or density, output dimension=number of gradation levels) with respect to a multi-value conversion means because error diffusion processing cannot be simply performed. The input dimension is set to coincide with the output dimension (an output signal is set to coincide with the input signal), this output signal is changed in accordance with a variation in image density, and an error between the changed output signal and the input signal is calculated, thereby executing error diffusion processing. Even when the gradation characteristics per pixel vary due to the influence of a change in environment or aging, or the number of gradation levels decreases due to the variation, the gradation characteristics in a local area can be maintained good, and initial image quality can be provided over a long period of time.
REFERENCES:
patent: 5107332 (1992-04-01), Chan
patent: 5289294 (1994-02-01), Fujisawa
patent: 5414531 (1995-05-01), Amemiya et al.
An Adaptive algorithm for Spatial Greyscale Robert W. Floyd and Louis Steinberg ProK SID vol. 17 (2), pp. 75-77, 1976.
Kanno Hiroki
Nakane Rintaro
Kabushiki Kaisha Toshiba
Lee Thomas D.
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