Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1987-07-24
1991-01-01
Groody, James J.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358466, H04N 140
Patent
active
049822942
ABSTRACT:
Apparatus for enhancing and thresholding scanned microfilm images, specifically for removing single pixel noise therefrom, and accompanying methods for use therein are disclosed. Specifically, this apparatus convolves each one of a pre-defined group of incoming pixel values with a corresponding one of a pre-defined set of coefficients in order to generate an convolved pixel value. The convolved pixel is then compared against a threshold level to produce a thresholded pixel value indicative of the results of the comparison. The inventive apparatus also includes a noise processing circuit that contains a noise tracker and a noise detector and filter circuit. The noise tracker is used to produce a noise value that tracks a noise level present in the threshold pixel value. The noise detector and filter circuit filters pixel noise from the thresholded pixel value and, in response thereto, produces a corresponding output pixel value for a current incoming pixel value being processed and provides a signal to the noise tracker that pixel noise has been detected. A background tracker, which also forms part of the inventive apparatus, produces a background value that tracks a background level present in the incoming pixel values. The background value and the noise value are combined to produce an error signal which, in turn, is used, along with a deaveraged value of the current incoming pixel value, to set the threshold level for the current pixel value being processed. Specific apparatus for the background tracker and the noise tracker, and accompanying methods for use therein, are also disclosed herein.
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Penny, R. E. "Dynamic Threshold Setting Circuit" IBM Technical Disclosure vol. 18 No. 6 11/75 pp. 1962-1965.
Lewis Scott
Morton Roger R. A.
Redden John E.
Arndt Dennis R.
Eastman Kodak Company
Groody James J.
Harvey David E.
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