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How to identify dichros

vk2fro

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IF you like me your projector build is way slow and you may have some dichro kit from o-like, dave at LSP or similar.

Its been over a year since I got mine from dave at LSP and I forgot what dichros actually came in my kit. Here I was with a post fully written on PL asking for assistance, then I spotted "son of Sun" (my LED torch).

The torch (flashlight to you guys in the US), emits a nice white light.

So I picked up the purple coloured dichro. I shone the torch at one side. On my hand I saw a yellowish green spot, and on the wall a reddish purple tint.

So from that I assumed I had a "pass blue/green, reflect red" dichro.

With the yellow coloured one I got a yellow green spot again, and a blue reflection. So I'd found the blue dichro (pass green, reflect blue)..

Next to test with a laser. It so happens I have a 10 mw badly collimated B&W tek labby. Perfect. I stuck each dichro in front of the laser at roughly 45°. You can do this with a 445 but I'd excercise extreme caution with a high powered one.

The yellow/green coloured one bounced all of the blue light from the laser onto the cd case I was using as a beamstop (10mw is impossible to see through my goggles, so I had to do without!). The purple coloured one let most of it through. If you have a few different coloured pointers you can experiment. I dont have a red, but I bet if I bounced one off the reflect red, I would end up with some wierdo colour while the blue laser is running (probably pink). At this point I was intrigued by how the knobs moved the beam. And I found out just how accurate they are - they will make farfield alignment easy. I'm going to get a quad of them for bounce mirrors to make nearfield a craptonne easier as well.

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Its pleasing to know that I have the right setup for the lasers I intend to buy. For the life of me couldn't remember which dichro set I had ordered.

So if you dont know what your dichros are, shine a white torch at them. You'll soon discover what they pass and what they reflect. Then double check with a low powered laser (preferably under 5mw, I used 10mw as its the lowest power in the house atm).
 

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Things

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Sounds like something that could be added to the projector reference if you don't mind :)
 

vk2fro

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Nov 30, 2009
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Go for it!

edit: just noticed in the pic I added, that my B&W tec stabilized while I was fiddling - green led is off :p
 
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