Re: [ATM] LWT setup questions

["Nils Olof Carlin" <nilsolof.carlin@telia.com>]

I have tried the LWT test with a remote-controlled setup:
http://web.telia.com/~u41105032/tester/tester.htm
and with a manually controled one - a 200 mm arm moved by a micrometer, and
a 20 mm arm from the pivot (ball bearings from a butchered hard disk) to the
"wire" (a thin scratch on plexiglass).
The latter failed entirely to give reproducible meaningful results, and I am
convinced it is because with my setup it was impossible to adjust the
micrometer manually, without inadvertently moving the whole tester some
microns each time I touched it. With remote control, no such problem.

A sturdier mount  - such as an optical bench like David Harbour's perhaps -
would no doubt be fine, but I just want to point out a potentially serious
but avoidable problem. I do believe the LWT warrants much more interest than
it seems to have been given.

As for a pinhole light source, a laser diode run at sub-lasering current
will provide a "pinhole" light source far smaller and more intense than any
practical pinhole, I am sure.

Nils Olof



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