| 摘要 |
In a system for recording, for example, a wiring pattern on a photosensitive recording surface 12, in which a light beam from laser tube 4 is modulated by a picture signal read from memory 1, variations in the rotational speed of polyhedral mirror 7 which scans the light beam across the surface 12 may cause distortion in the recorded picture. To avoid this the picture signals are read out at a rate corresponding to the position of the light beam sensed by a photosensor 16 mounted behind a scale 15 comprising alternately transparent and opaque sections (fig. 3). To ensure synchronization even when no signal is to be recorded on surface 12 the output of laser 4 is modulated between a high (write) level and a level too low to affect the recording surface, but still detectable by photosensor 16. The output signal of the photosensor may be held constant by an amplifier, the gain of which is controlled by the picture signals (fig. 5). Beam splitter 11' allows a single laser to be used for both recording and position sensing and thus reduces the manufacturing cost. <IMAGE> |
