Re: ATM Ball Bearing Light Source

[VirgilAJ@aol.com]

You wrote,

<My questions are the following:  Is there some flaw in this method that I
have
<overlooked?  Will the bearing be precise enough for this test, and how do I
<measure it?  Will the illumination be sufficiently bright?  I will be able to
<test this last item in a few days.

I  have aimed a laser at a ball bearing hoping to get a nice pinpoint source.
I remember the reflected light on the white wall inside the garage.  It looked
all cratered and pocked.  It was a projected image of the surface of the ball.
The ball was only 1/32 in and the image must have been a million
magnification!  Could see this also on the mirror at test. The laser was the
only light source at the time.

Shooting the laser at a straight pin in an attempt to produce a slit was
really a surprise. The pin was in the center of the room and the beam was
wider than the pin, so it made a spot on the wall behind the pin.  Another
spot on the opposite wall caused by the reflected light off the pin and a line
circleing the room passing through both spots.  The line around the room was a
pattern of light and dark lines side by side each as tall as the beam
intersection on the pin.    If the pin and the laser had been level the affect
would not have been as dramatic.  As it was the laser was lower than the pin
and aimed up a little.  The line around the room curved up high in the corners
of the room and down in the center of each wall. Kind of a drapery affect.

If you are not right on axis with a moving ball then you may pass out of the
beam.  I remember worrying about looking down the barrel of the laser.  Too
close for comfort.

Plenty bright enough. In fact I even bounced it off a larger ball bearing at
about 100 yards for an artificial star but that was with an aluminized mirror,
so I don't know about brightness there.

I was surprised that intuition didn't work with lasers. Shooting a laser
through a small pinhole produces a larger spot than just a laser does.  Come
to find out that it is a classic diffraction pattern: an Airey disk and about
a dozen rings!!  Just what a star is suppose to look like in a perfect scope
in a perfect atmosphere. 

I complained to Tom Waineo about how no matter what I thought would work, it
threw me a curve.  He said that he used a laser to shine on a cotton ball
behind a pinhole as a bright source.  This you could do with a small diagonal
mirror.  Could put the spot RIGHT on the axis.  Might not even need the mirror
since the cotton lights right up. Could shoot down from above and behind your
precious eye(s)

You can make something work, but don't be surprised if you spend more time
playing with the laser than testing. 

Have fun
Virgil Johnson
Raider of the Lost Dark