Non-Reflective Surface or Polarizing Surface

**hgetnet** · Nov9-09, 05:24 PM

Hello Physics Forums goers:

Ok, I have a project that deals with image analysis. The idea is to make the process very easy upon myself and make the background on which I will place objects as dark as possible.

1st idea I have is that of a surface that will polarize light when light reflects from it. I googled for such a surface and I couldnt find any.

2nd idea is to have a surface that deflects or reflects away a polarized light.

3rd idea is to have a non-reflective surface that absorbs most (if not all) light that falls upon it. Again, I couldnt find any such material for sell.

ANYONE KNOW WHERE I CAN BUY ANY ONE OF THESE SURFACES?

Thanks in advance.

p.s. 1- the material can not be velvet or anything that can not be wiped with a piece of damp cloth.
2- the material should withstand a medium vibration (a bit above cellphone vibration) for 10 minutes at a time.

**berkeman** · Nov9-09, 06:01 PM

Originally Posted by hgetnet

Hello Physics Forums goers:

Ok, I have a project that deals with image analysis. The idea is to make the process very easy upon myself and make the background on which I will place objects as dark as possible.

1st idea I have is that of a surface that will polarize light when light reflects from it. I googled for such a surface and I couldnt find any.

2nd idea is to have a surface that deflects or reflects away a polarized light.

3rd idea is to have a non-reflective surface that absorbs most (if not all) light that falls upon it. Again, I couldnt find any such material for sell.

ANYONE KNOW WHERE I CAN BUY ANY ONE OF THESE SURFACES?

Thanks in advance.

p.s. the material can not be velvet or anything that can not be wiped with a piece of damp cloth.

For the first example, can you just use a mirror behind a polarizing sheet? Whatever light gets reflected off of that would seem like it would be polarized...

**hgetnet** · Nov9-09, 07:19 PM

Originally Posted by berkeman

For the first example, can you just use a mirror behind a polarizing sheet? Whatever light gets reflected off of that would seem like it would be polarized...

I thought about that but the mirror would not be able to stand the vibration that I am going to subject the surface to. I should have stated that in my request, but I appreciate the fast response.

**berkeman** · Nov9-09, 07:21 PM

Originally Posted by hgetnet

I thought about that but the mirror would not be able to stand the vibration that I am going to subject the surface to. I should have stated that in my request, but I appreciate the fast response.

Ah. But you can get some pretty strong first-surface mirrors (FSMs). What dimensions are you thinking of for the reflective sheet? What vibration accelerations are you anticipating?

**hgetnet** · Nov9-09, 08:39 PM

Originally Posted by berkeman

Ah. But you can get some pretty strong first-surface mirrors (FSMs). What dimensions are you thinking of for the reflective sheet? What vibration accelerations are you anticipating?

FSMs sound like something I need to research more! Thanks!!!

For the reflective sheet, I am thinking 11" X 11 ". Anything slightly above or below will do as well.

For the vibration, I am thinking of something like the magnitude of a vibrating cellphone (please excuse my limited knowledge in mechanical engineering). Or if it makes sense, I am thinking of a vibration that is capable of separating a number of small pebbles (m&m's or any similar shaped objects) clamping on top of eachother so that it is easy to optically analyze them.

**Bob S** · Nov9-09, 09:51 PM

If you reflect light off of a non-metallic surface at Brewster's angle, the light is polarized. You could reflect light off the front surface of an opaque plate glass sheet (I have seen opaque black). The refracted light is all absorbed in the glass. See
http://hyperphysics.phy-astr.gsu.edu...pt/polref.html
Bob S