| 摘要 |
Using two light beams directed onto the bar code at predetermined angles, left-side and right-side shadows are generated which have a strong contrast to the rib edges. Separate images of the left-side and right-side shadows are projected onto two photo diode rows via an optical device followed by a beam dividing prism. The rising and falling edges of the pulse series derived from the diode rows correspond to the left-side and right-side rib edges. In a logic unit, a resultant pulse series which corresponds to the bar code signal is recombined from these two pulse series.
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