Polarized object beam

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John Klayer

Polarized object beam

Post by John Klayer »

Should it make a difference if the object beam is polarized? Does a diffuse reflecting object just scramble the polarization? From what I observe, even if the object light is polarized, the reflected light is random. I'm wondering if there may be a bit more polarization in one direction than the rest that I can't detect but should try to align by a 1/2 wave plate with the reference beam. I tried finding the reflected polarization with a polarizing filter and a polarization axis finder with no result.
Kaveh

Polarized object beam

Post by Kaveh »

You will find that the specular highlights of an object will retain polarization, but other areas will depolarize. The only way of making sure that the plate sees light of only polarization would be to put a giant polaroid film between the recording plate and the object. But you probably get more noise from that than you save by eliminating the wrong polarization.

A nice trick is to use a reference beam with opposite polarization to that illuminating the object. So you use horizontal polarization in the ref beam, but illuminate the object with vertical. Then the highlights will be eliminated from the recording. In effect you get rid of highlights. If you are using a 1/2 wave plate, then by rotating it and watching the object through a polaroid film, you can control how much highlight you want. This is good for getting rid of very bright highlights that create burnout on H2s.
Ed Wesly

Polarized object beam

Post by Ed Wesly »

Wow! I like that tip of using orthogonal polarization vectors to combat overly bright specular highlights! Brilliant! I wished I had thought of that!

There is a way of making the object beam somewhat polarized, and that is to use a paint whose pigment is metallic flakes, Krylon #1401, Bright Silver, for instance or equivalent. It really does wonders for Single Beam Reflections!
John Klayer

Polarized object beam

Post by John Klayer »

Thanks Kaveh,

The 90 degree idea may make my idea work!
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