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Analog Thresholding Scheme for Medium Resolution Scanners

IP.com Disclosure Number: IPCOM000075852D
Original Publication Date: 1971-Nov-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Hall, RE: AUTHOR [+2]

Abstract

This thresholding scheme provides nearly identical gray-level patterns for a character regardless of contrast, making the use of fixed thresholding patterns possible. Ideal characters are consistently formed with single bit wide lines which provides greater accuracy with less hardware.

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Analog Thresholding Scheme for Medium Resolution Scanners

This thresholding scheme provides nearly identical gray-level patterns for a character regardless of contrast, making the use of fixed thresholding patterns possible. Ideal characters are consistently formed with single bit wide lines which provides greater accuracy with less hardware.

Final video from a scan head, monitored by a peak black circuit, is fed into a four-level quantizer 10 (Fig. 1) which defines four specific gray ranges between white and black. These values are converted to two-bit binary numbers and supply analog information to decision matrix 20 (Fig. 2).

The decision matrix 20 is an electronic window which slides over the character grid in gray-level shift register 11 (Fig. 1). Black/ white decisions are made on the center bit position of the matrix, by logical manipulation of the analog and digital information found within its confines. Bits are called "black" only if they conform to given feature patterns. Each column of the matrix can be considered a part of a vertical scan of video; likewise, adjacent columns indicate adjacent scans. Assuming the pattern is scanned bottom-to-top and right-to-left, the matrix will be filled with analog (A) and digital (D) information as shown in Fig.
2. Digital information is fed back from the digital shift register 12. Thresholding is then accomplished by analyzing the output signals generated from decision matrix 20.

Initially, the decision bit and o...