Method and apparatus for on-line tiled thresholding in scanners based on prescan

Claim 1

A method of scanning data information from an original and converting said data information to a digital representation of the original, the method comprising the steps of: (a) scanning the original by linewise, optical scanning to produce a data signal representing grey-level values of points along lines of the original; (b) dividing the original into a plurality of zones, each zone in the plurality of zones including a plurality of pixels, each pixel in the plurality of pixels having a corresponding grey-level value determined from segments of the lines which have been optically scanned during scanning, said segments being positioned in a parallel side by side relationship; (c) calculating for each zone a statistical distribution by registering a frequency of occurrence of the grey-level values received from the plurality of pixels during the scanning; (d) determining a fixed threshold value for each zone in response to the statistical distribution of the grey-level values, said determination of the fixed threshold value starting prior to termination of the prescanning; (e) storing the fixed threshold value of each zone; (f) comparing a plurality of the grey-level values in one of the plurality of zones to the fixed threshold value of the one zone; (g) generating binary values in response to said comparison; and (h) generating an electric representation of the original in response to the binary values.

Claim 2

A method of scanning data information from an original and converting said data information to a digital representation of the original, the method comprising the steps of: (a) scanning the original by linewise, optical scanning to produce a data signal representing grey-level values of points along lines of the original; (b) dividing the original into a plurality of zones, each zone in the plurality of zones including a plurality of pixels, each pixel in the plurality of pixels having a corresponding grey-level value determined from segments of the lines which have been optically scanned during scanning, said segments being positioned in a parallel side by side relationship; (c) calculating for each zone a statistical distribution by registering a frequency of occurrence of the grey-level values received from the plurality of pixels during the scanning; (d) determining a fixed threshold value for each zone in response to the statistical distribution of the grey-level values, said determination of the fixed threshold value starting prior to termination of the prescanning; (e) storing the fixed threshold value of each zone; (f) comparing a plurality of the grey-level values in one of the plurality of zones to the fixed threshold value of the one zone; (g) generating binary values in response to said comparison; and (h) generating an electric representation of the original in response to the binary values.

Claim 6

A method of scanning an original comprising the steps of: (a) scanning the original by linewise, optical scanning to provide a first data signal representing grey-level values of points along lines of the original; (b) dividing the original into a plurality of zones, each zone in the plurality of zones comprising pixels from segments of the lines which have been optically scanned during scanning, said segments being positioned in a parallel side by side relationship; (c) calculating for each zone a statistical distribution by registering a frequency of occurrence of the grey-level values received during the scanning; (d) determining a fixed threshold value for each zone in response to the statistical distribution of the grey-level values, said determination of the fixed threshold value starting prior to the termination of the scanning; (e) storing the fixed threshold value of each zone; (f) scanning the original a second time by linewise, optical scanning to produce a second data signal representing grey-level values of the points along the lines of the original; (g) comparing the grey-level values of the second data signal in one of the plurality of zones to the fixed threshold value of the zone; (h) generating binary values in response to said comparison; and (i) generating an electric representation for the original in response to the binary values.

Claim 7

A method of scanning an original comprising the steps of: (a) scanning the original by linewise, optical scanning to provide a first data signal representing grey-level values of points along lines of the original; (b) dividing the original into a plurality of zones, each zone in the plurality of zones comprising pixels from segments of the lines which have been optically scanned during scanning, said segments being positioned in a parallel side by side relationship; (c) calculating for each zone a statistical distribution by registering a frequency of occurrence of the grey-level values received during the scanning; (d) determining a fixed threshold value for each zone in response to the statistical distribution of the grey-level values, said determination of the fixed threshold value starting prior to the termination of the scanning; (e) storing the fixed threshold value of each zone; (f) scanning the original a second time by linewise, optical scanning to produce a second data signal representing grey-level values of the points along the lines of the original; (g) comparing the grey-level values of the second data signal in one of the plurality of zones to the fixed threshold value of the zone; (h) generating binary values in response to said comparison; and (i) generating an electric representation for the original in response to the binary values.