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Old Dec 23rd 2013, 01:12 PM   #1
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Tubular Optical Filter

A tube having an inside diameter of 2 microns is one centimeter in length. A photon entering the tube will reach the sensor on other end only if its wavelength is not greater than 2 microns and the direction of its travel is does not cause it to be absorbed by the inner walls of the tube.

I wish to encourage any off-angle photons to bend away from the center line and become absorbed by the inner walls of the tube. I wish the angles reaching the other end to be as selective as possible, favoring only the photon paths that are most parallel to the tube. One idea is for the tube to have glass spheres in it that are 2 microns in diameter. This might bend off-angle photons toward the walls.

Suggestions are very welcome.

Thank you for your help.

Jim Adrian
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Old Dec 26th 2013, 12:24 PM   #2
MBW
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I have no idea if this is practical

My idea would be several tightly fitting concentric glass tubes (a rod in the centre), each of slightly different refractive indices.
Perhaps heat these up to a point where the tubes will just fuse, (but not melt completely).
Perhaps start with quite a thick rod of concentric tubes, then draw them out to reduce the rods diameter.
The intention is to create a glass rod with a constant refractive index along the rod, but a varying refractive index from the inside to the outside of the rod.
This will act as a lens where directly longitudinal light will pass undeflected, but any angular offset will be exaggerated.

Last edited by MBW; Dec 26th 2013 at 12:27 PM.
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Old Dec 26th 2013, 05:27 PM   #3
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Tubular Optical Filter

"My idea would be several tightly fitting concentric glass tubes (a rod in the centre), each of slightly different refractive indices.
Perhaps heat these up to a point where the tubes will just fuse, (but not melt completely).
"Perhaps start with quite a thick rod of concentric tubes, then draw them out to reduce the rods diameter.
"The intention is to create a glass rod with a constant refractive index along the rod, but a varying refractive index from the inside to the outside of the rod.
"This will act as a lens where directly longitudinal light will pass undeflected, but any angular offset will be exaggerated."

MBW,

This is a very promising idea. Thank you so much for your help.

Jim Adrian
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