25 May
2010
25 May
'10
11:33 a.m.
Nonsense! The laser head assembly from a DVD player
will do the job
with much less wear of the medium. :)
(There was a design note recently in one of the EE mags (EDN or
Electronic Design) about measuring small distances using exactly
that.)
By using the in-focus signal (suitably derrived from the photodetectors)
and seeing how much current you have to pass through the focus coil to
have the target object in focus?
I wonder if that would have the freqeucny response to read a wax
cylinderr? I think it should do...
-tony