| 摘要 |
<p>PURPOSE:To enable a document under carriage to be properly detected even when the document is exposed to the effect of dispersion in element adjustment, dirt or the like by correcting a measured value on the basis of a light quantity received when the document is flowing or not flowing between light emitting and receiving elements. CONSTITUTION:The transistors 22 and 23 of a light emitting section 2 are switched with pulse trains (a) and (b) respectively outputted from an oscillation section 1, according to the state of non-carriage or carriage of a document 6. Light emitted from a light emitting element 21 is received with the light received with the light receiving element 31 of an amplifier section 3. The received light after amplified at amplifiers 32 and 33 undergoes A/D conversion at an A/D converter 34, and each of pulse trains (c) and (d) is temporarily saves as shift pulses in the registers 41 and 42 of a thickness detection section 4. The digital values of the aforesaid pulses are fed to a thickness measurement unit 43, and this unit 43 detects a drop from the initial values of light emitting and receiving quantities under the control of a built-in program. The detected drop value can be used to correct a light receiving level at all times. According to the aforesaid construction, the thickness of the document 6 can be properly detected, and the carrying number thereof can be properly confirmed in a carriage state.</p> |
