| 摘要 |
<p>PURPOSE:To facilitate the handling of a pattern reader by radiating successively plural light beams having different image forming positions to perform the scan operation and therefore increasing greatly the range of distance where an information pattern can be optically detected with high accuracy. CONSTITUTION:The light beams delivered from a light emitting diode 10 are made incident on a rotary polyhedral mirror 5 via one of convex lenses 9a-9d and then delivered toward a protecting plate 2 by flat plate mirrors 7a-7d to be scanned by a prescribed angle. The lenses 9a-9d have different refractive powers and the light beams to be scanned have different image forming positions respectively. A light receiving element 13 defines the information that can obtain the clearest electric signal among the reflected beams made incident through a toric lens 12 as the normal input. Then the accurate information is obtained at the image forming position of one of sour scan beams.</p> |
