| 摘要 |
1,266,571. Directing light beams in optical playback apparatus. ROBERT BOSCH G.m.b.H. 3 March, 1969 [1 March, 1968], No. 11109/69. Heading G5R. To centre a movable light spot 3 scanning an F.M. signal recorded in the form of holes 2 in an opaque track 1 on a transparent carrier 6, the spot is caused to have a constant intensity gradient by passing the light through a grey wedge (18, Fig. 4, not shown) and the light passing through the carrier is averaged 10 to generate a regulating signal to control the deflecting device 11. The record is either a photographic film or a metal foil on a transparent substrate. Variations in the intensity of the beam 4, which may be a laser beam, are compensated by a dimmer 14 and photo-cell 15. The deflector 11 is a variable angle prism or an electromagnetically- or piezoelectrically-operated mirror. |
