Browse Prior Art Database

A METHOD OF REAL TIME HISTOGRAM FORMATION

IP.com Disclosure Number: IPCOM000026660D
Original Publication Date: 1993-Feb-28
Included in the Prior Art Database: 2004-Apr-06
Document File: 6 page(s) / 301K

Publishing Venue

Xerox Disclosure Journal

Abstract

The concept described here is a real time hardware method which can be utilized by an imaging system scanner for forming a histogram of video (i-e., grey) data. The histogram thus created could then be used by the scanner to optimize the subsequent scan to a particular document. This system is unique in that a full resolution histogram of the video data is created during a prescan of the document without the aid of software processing. Other scanning systems which attempt to perform this function typically use simple peak detector circuits, either analog or digital, and are therefore extremely sensitive to noise.

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Page 1 of 6

XEROX DISCLOSURE JOURNAL

A METHOD OF REAL TIME HISTOGRAM FORMATION Thomas R. Beikirch

Proposed Classification

U.S. C1.358/443; 382118
Int. C1. H04N 1/00; GO6K 9/46, G06K 9/66

a

Histogram

Histogram of Retrace Data

I I 8 bit Retrace Data
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min R FIG. 3 R max

XEROX DISCLOSURE JOURNAL - Vol. 18, No. 1 Januarymebruary 1993 77

Distribution

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Page 2 of 6

A METHOD OF REAL TIME HISTOGRAM FORMATION(Cont'd)

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78 XEROX DISCLOSURE JOURNAL - Vol. 18, No. 1 Januaryflebruary 1993

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Page 3 of 6

A METHOD OF REAL TIME HISTOGRAM FORMATION(Cont'd)

The concept described here is a real time hardware method which can be utilized by an imaging system scanner for forming a histogram of video (i-e., grey) data. The histogram thus created could then be used by the scanner to optimize the subsequent scan to a particular document. This system is unique in that a full resolution histogram of the video data is created during a prescan of the document without the aid of software processing. Other scanning systems which attempt to perform this function typically use simple peak detector circuits, either analog or digital, and are therefore extremely sensitive to noise.

The histogram circuit described is used only to calculate the maximum and minimum document reflectance values. The description, however, does not preclude usage of the histogram circuit and/or data for other scanning and image processing purposes, for example, adaptive thresholding.

The purpose of the histogram circuit is to form a histogram of the document image reflectance data and then, based on that histogram, calculate the minimum and maximum reflectance which constitutes at least a prescribed percentage of the total image area. The minimum and maximum reflectances, known as Rmin and Rmax respectively, are communicated to a Video Controller/ Interface (VC/I) via a serial interface where Rmin and Rmax are used by a shading circuit to adjust scanner gain and offset for optimum performance.

For every complete document scan, the scan carriage must both scan and retrace. For optimum efficiency, the retrace is arranged to happen first. It is during the retrace or 'prescan' that the histogram is determined.

At the beginning of a prescan, a...