| 摘要 |
<p>PURPOSE:To reproduce bar code infomation with good performance by eliminating the influence of external light and reflected light from a hologram disk upon a bar code signal by a low-cut filter part. CONSTITUTION:The reflected beam of a scanning laser beam striking a bar code label is as shown by 4a, but its reflected light incident to a photodetecting element is actually as shown by 4b because it is under the influence of reflection from a hologram surface and external light. This signal is processed by a preamplifier 2 and then a low-cut filter part 6 removes frequency components lower than a bar code signal, obtaining a signal shown by 4c. This signal is amplified by a main amplification part 3, a level comparison part 4 discriminates between a white and a black bar, and a processing part 5 obtains a digital signal shown by 4d, thus decoding bar code information.</p> |
