| 摘要 |
<p>In one embodiment of the invention the incoming light beam (1) impinges on an objective lens (2) mounted in a carrier (21). The parallel beam is brought to a focus (22) on the surface (41) of the data carrier (4) to a photodetector (3), followed by an amplifier (5). The signal from the latter returns through a curve envelope detector (8) to a peak value detector (9) which operates a switch (91). A sinusoidal pilot signal is injected from an external generator, and this is fed through a filter unit (10) which enables the pilot signal to pass through. Other components include a d.c. power source, adder, motor and phase shifter (20).</p> |
