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# Bilinear Function Circuit

IP.com Disclosure Number: IPCOM000079338D
Original Publication Date: 1973-Jun-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 43K

IBM

## Related People

Burke, MJ: AUTHOR [+2]

## Abstract

The inherent distortion caused by the optics in an optical character recognition (OCR) scanner, causes nonlinearity in the scanning control system. This circuit provides the necessary correction factor to linearize the position control apparatus.

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Bilinear Function Circuit

The inherent distortion caused by the optics in an optical character recognition (OCR) scanner, causes nonlinearity in the scanning control system. This circuit provides the necessary correction factor to linearize the position control apparatus.

Fig. 1 shows a typical error curve encountered when making the initial mechanical setup of the scanning mechanism. The straight line ABC with a breakpoint at X(o) represents an approximate linear representation of the error condition. In order to compensate for the nonlinearity, a bilinear function is used. f(X) = m(1)x+b(1) x </- X(o)

m(2)x+b(2) x >/- X(o) where:

b(2) = K = (m(1) - m(2)) x(o) + b(1)

x(o) = Breakover point.

The circuit of Fig. 3 is designed to have zero output up to V(in) = V(X(o)), where V(X(o)) is continuously variable from some negative value to some positive value, as shown in Fig. 2. Also, the gain is continuously variable from some negative to some positive value for V(in) > V(X(o)). The actual range of gain and breakpoint voltages depends on circuit constants.

The bilinear circuit is utilized in a system, as shown in Fig. 4. The system gain and offset adjustment are set to match the line segments at position X < X(o). The potentiometer P1 (Fig. 3) is adjusted so that the breakpoint X(o) is set to V(X(o)). The gain potentiometer P2 is adjusted to match the line segment at positions X > X(o).

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