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A system for use in a bar code processing system using a combination of a first derivative signal and a second derivative signal to determine the bar edge. The predominant signal in determining the edge is the second derivative signal. A zero-cross of the second derivative signal occurs at the bar e

A system for use in a bar code processing system using a combination of a first derivative signal and a second derivative signal to determine the bar edge. The predominant signal in determining the edge is the second derivative signal. A zero-cross of the second derivative signal occurs at the bar edge. The first derivative signal is used to qualify the point in time in the second derivative signal for which a zero-cross is examined the system is particularly suited for near filled operation.

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An apparatus for detecting an edge in a scanned signal representing optical indicia read by a scanner, comprising: a first differentiation circuit connected to receive the scanned signal and to produce a first derivative signal indicative of a derivative of the scanned signal; a second differentiati

An apparatus for detecting an edge in a scanned signal representing optical indicia read by a scanner, comprising: a first differentiation circuit connected to receive the scanned signal and to produce a first derivative signal indicative of a derivative of the scanned signal; a second differentiation circuit connected to receive the first derivative signal to produce a second derivative signal indicative of a derivative of the first derivative signal; means for delaying said second derivative signal by a sufficient short period of time to ensure that a first reference crossing is detected in said second derivative signal; an edge qualifying circuit connected to receive the first derivative signal, said edge qualifying circuit outputting a detect enabling signal corresponding to a preset value of the first derivative signal; and an edge detecting circuit connected to receive the delayed second derivative signal and the detect enabling signal, the edge detecting circuit outputting an edge detection signal when the second derivative signal reaches a predetermined value following receipt of the detect enabling signal.