Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1989-10-13
1990-10-16
Westin, Edward P.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
235462, 235472, G06K 710
Patent
active
049637568
ABSTRACT:
A focused line identifier is useful in a bar code reader employing Scheimpflug optics for focusing an illuminated line from the bar code on a two dimensional array of photodetectors. One line or a small group of lines somewhere on the array is the sharpest focus of a bar code within the working range of a bar code scanner. The best focused line is located with the analog signal before digitizing by generating a signal having an amplitude representative of the high frequency component of the lines of signal from the photodetector array. The maximum high frequency component may be found by passing the signal through a high pass filter for detecting the signal having the largest amplitude. The best focused line is, in effect, found in one field scan and used to open a gate in the next scan for passing the best focused line to a digitizer. One may also hop from the best focused line to a line or lines adjacent to the best focuesd line for feeding a slightly unfocused line to the digitizer. Further, a zone within an array of photodetectors which has the greatest illumination may be selected for disregarding spurious signals from other objects that may happen to lie in the field of view of the bar code reader.
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Bayley Brian J.
Quan Ronald
Hewlett--Packard Company
Westin Edward P.
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