[ATM] RE: Foucault Simulation analysis of non-symmetric aberrations

["john sherman" <atm@mail.johnspics.com>]

Hi Bernard, 

>the recipe for making the tiny *round* hole.

I learned that trick right here, on the atm list. I'm sorry I don't remember who posted it - as I recall, a few people have given the same recipe.

Take a nice needle and look at the tip with a loupe (or 25mm eyepiece). It will probably not look very sharp. Sharpen it up with very fine sandpaper or a hone. Take a stack of aluminum foil pieces. I usually cut a bunch of pieces from a beer can and stack them up. Put your stack on a very hard thing, like a steel slab. Poke the needle into the stack of foils, give it a light tap with a small hammer if need be. It is best if the needle doesn't poke all the way thru to the bottom layer. 

Now examine the holes created and you will find a variety of different sizes. Take care to illuminate the hole evenly. I use very fine sandpaper to roughen up a green led.


Also, you can take a small laser pointer and remove the lens. While it is lasing, the diode produces a bar of speckly light which the lens would have focused into a dot. Put a potentiometer in the circuit and up the resistance till it quits lasing. You will then have a nice, bright cone of light from a very small source. I also learned this trick here on the list, so the archive will have lots of details, like the size of the source. 

If you have any more questions, please ask.

John




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