System for optical scanning over a large depth of field and obta

Details System for optical scanning over a large depth of field and obta System for optical scanning over a large depth of field and obta

1984-09-20

1988-05-03

Westin, Edward P.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

250568, 235462, 235472, G06K 710

Patent

active

047422203

ABSTRACT:
Optical scanning apparatus of the invention has a scanning range with a large depth of field through the use of a plurality of light sources, which are disposed in a cluster and directed at the bar code to be read thereby increasing the amount of light at the focal plane. This increases the depth of field in which the scanner is effective. A rectangular aperture stop with a length several times the width controls the F/# and allows an increased amount of light to reach the photodetector. A rectangular receiving slit provides an elliptical field of view of the photodetector with the long axis aligned with the bars of the code to be read, so that the scanner is able to "see" a major portion of the bar or space instead of a small area which may contain printing errors. Thus the intensity of illumination on the object being scanned is maximized, while the depth of the field, and the signal to noise ratio of the receiving system is also maximized so as to enable the resolution of fine, dense, bar codes.

REFERENCES:
patent: 3417234 (1968-12-01), Sundblad
patent: 3853403 (1974-12-01), Bentley
patent: 3985999 (1976-10-01), Yoneyama
patent: 4056804 (1977-11-01), Whitfield et al.
patent: 4104616 (1978-09-01), Isshiki et al.
patent: 4288690 (1981-09-01), Sanner
patent: 4408120 (1983-10-01), Hara et al.
patent: 4538072 (1985-09-01), Immler et al.

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