| 摘要 |
<p>PURPOSE: To give a means for extending the effective life of a laser such as a laser diode. CONSTITUTION: When a laser diode 12 is used as a scanner for scanning a coded symbol such as a bar code, it is necessary to perform a continuous operation only when the symbol is located within the region of a target 18, but the life can be extended by operating the laser only intermittently when the continuous operation is not required. Therefore, a detection device 22 for detecting the state transition of light reflected from a target region is provided and a counter 26 for counting the number of transitions is provided. When the symbol is located in the target region, much larger number of transitions than a case without the symbol can be detected and counted so that two states are identified by using the difference in the number of transitions, and the laser diode is fumed on for a continuous operation only when the coded symbol is read into the target region.</p> |
