| 摘要 |
<p>PURPOSE:To prevent malfunction caused by externally disturbed light beam along with extending light projecting period and shortening light projecting pulse width. CONSTITUTION:Burst pulses having higher frequency than that of externally disturbed light beam and the like, are projected to a light projecting element 2a of sensor part 2, by several second period. By projecting intermittently the burst pulses having higher frequency than that of externally disturbed light beam, reflected light beam having higher frequency in all the reflected light beam of the said projected light beam, is discriminated from externally disturbed light beam and therethrough a user of the device can be sensed and detected.</p> |
