| 摘要 |
<p>A device comprises a contact glass (1) on which an original paper is set, a main-body cover (2), a pair of flash lamps (3,4) with reflectors (5,6), a standard reflectance sheet (7) and a pair of photodetectors (8,9). Both the lamps and the detectors are symmetrically arranged with respect to the centre (O). First, one of the two lamps (3) is switched on until the amount of light detected by its corresponding sensor (8) reaches the predetermined value. After it is switched off, the other lamp (4) is switched on and a similar control is given using the other sensor (9).</p> |
