On Tue, 2 Feb 1999 18:44:35 +0000 (GMT) ard_at_p850ug1.demon.co.uk (Tony
Duell) writes:
>>
>> Tony Duell wrote:
>> > A photomultiplier isn't that bad to use. OK, it needs a kilovolt
>or so of
>> > EHT. But apart from that it's a fairly easy device to connect up
>and get
>> > a useable signal from. There should be a lot of them still about,
>and
>> > small ones aren't that expensive second-hand.
>>
>> The tricky part is how to mate this with the mechanical assembly.
>Even
>> the laserdisc players that used a HeNe laser still used a
>semiconductor
>> photodetector that was directly mounted on the sled.
>
>I assume the HeNe tube didn't move with the sled, right (far to much
>mass, the servo would never lock). Couldn't you do something similar
>with
>the photomultiplier - mount it on the chassis and somehow direct the
>light beam onto it?
Actually, I saw a prototype laserdisk player in a museum somewhere
(I think it was in the LA Museum of Science , but it was a long time
ago) that had the following arrangement: The HeNe laser tube was
bolted down, along with some optics, and a spinning platter/servo motor
mounted on a carriage. The *PLATTER* moved during seeks! It was
really quite bizarre to watch.
They used a *BIG* servo motor to move the carriage, if memory serves.
Jeff
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Received on Tue Feb 02 1999 - 18:36:44 GMT