Re: ATM Wave Length Foucault Data! :)

["Andrew Schott" <aschott@digital.net>]

Be Aware: The so called "White" LED's aren't very good sources of
panchromatic light.  They are essentially a blue LED chip mounted in a thin
crust of yellow/green phosphor that "fills in" the missing spectra and makes
a fluorescent looking light that only looks white.  Run the light from your
LED through a prism and you'll find a very strong spike in the blue spectrum
with a couple of other spikes in the warmer end for balance.  I don't know
how this will effect your mirror tests as the light from the LED usually
isn't even homogenous.  I have several white LED's and the brighter ones are
blotchy in their color purity.  Like a badly adjusted TV yoke, the blue
kinda seeps out around the edges with more white concentrated in central
zones.

But it is bright and it is a cold light that should outlast any of the
"grain-o-wheat" bulbs they use in model trains.

Isn't amazing that in just 10 years the Laser pointer has gone from
prestigious executive board-meeting status symbol to cat toy.

Andrew.


----- Original Message -----
From: James Lerch <jlerch1@tampabay.rr.com>
To: <atm@shore.net>
Sent: Tuesday, March 27, 2001 6:43 PM
Subject: Re: ATM Wave Length Foucault Data! :)


>
> I'll look into the Hobby Shop bulb, at the moment I picked up a white LED
> from Radio Shack today.
>
> The focus on the camera was set to manual thru out the test recordings
(even
> though moving the focus on the camera made no difference in the image)  To
> change color I just turned off one LED and turned the next one on,
adjusted
> the elevation of the tester, then adjusted to try and find the outer zone
> again.  No idea why the Red images seemed out of focus....
>
> The yellow LED was the dimmest, only emitting  63% intensity of the Red
Led.
> (Red     = 3000mcd)
> (Blue    = 2600mcd)
> (Yellow = 1900mcd)
>
> Another aspect out of my control was the exposure setting of the camera.
>
>
> James Lerch
> St. Petersburg, FL
> http://lerch.yi.org/atm for my latest ATM adventures
>
>
>
> ----- Original Message -----
> From: "Bob May" <bobmay@nethere.com>
> To: "atml" <atm@shore.net>
> Sent: Tuesday, March 27, 2001 12:28 PM
> Subject: Re: ATM Wave Length Foucault Data! :)
>
>
> >
> > For a nice small light, stop by a good model train hobby shop and get a
> > really small bulb.  They have some that are about .040" in diameter
> although
> > they run at 1.5V, that shouldn't be too much of a problem as the current
> > draw is about 20ma or so.
> > On another note, I noticed that the red images were rather out of focus
> and
> > the yellow images are dim which tend to destroy detail.  Also, you
> probably
> > need to clean up your workspace as you have a bunch of scratches on your
> > mirror surfaces and you really shouldn't have such.  Scratches tend to
> make
> > little hollows as they go away as the material nearby goes and fills up
> the
> > hole.
> > Bob May
> > My new web space address is http://webu.wigloo.com/bobmay/ or
> > http://nav.to/bobmay
> > and my new email address is bobmay@nethere.com
> > "On two occasions, I have been asked [by members of Parliament], 'Pray,
> Mr.
> > Babbage, if you put into the machine wrong figures, will the right
answers
> > come out?' I am not able to rightly apprehend the kind of confusion of
> ideas
> > that could provoke such a question."
> > -- Charles Babbage
> >
> >
>
>
>