# Can someone tell me what is the best collimation material for this application?

1. Nov 11, 2006

### rasgar

I need a collimation material that is faily cheap and has a reflectivity of about 95% for both infrared and visible light. I know polished aluminum meets the criteria for the infrared, and the fused silica also works well for the visible spectrum, but I need somthing that can collimate both.

2. Nov 11, 2006

### physics girl phd

can you give more specifics on the application? I've used aluminum, silver and gold mirrors in IR applications, and multilayer dielectric coated mirrors in large variety of applications. Newport, optosigma, thorlabs and Edmund scientific might be good sources to check out for various types of mirros if you aren't looking for something to be MADE for your application.

3. Nov 12, 2006

### Claude Bile

What parts of the infrared spectrum do you need to collimate? By infrared, do you mean down to 1.5 micron wavelength or down to 10 micron wavelength (or even further?).

Does it need to be broadband, or is it only specific wavelengths you are using?

Claude.

4. Nov 13, 2006

### rasgar

This is a energy gathering application. I intend to collimate the focal point of the beams from a fresnel lens with an off-axis parabolic mirror. It's basically anything that can reflect the most solar radiation. People are saying that it's composed of both infrared and visual radiation, so I want something that can reflect both. Even though an optical engineer told me that the polished aluminum should reflect enough infrared to generate good energy, I want maximum output, and edmund optics charges almost 100 dolars for a off-axis parabolic mirrror that is aluminum, with a radius of only 25mm. I was also hoping that someone would know a cheaper optics company, or at least a cheaper, more reflective material that it could be constructed out of.

5. Nov 13, 2006

### Claude Bile

You can't get much cheaper than aluminium, material-wise and $100 is about as cheap as you get for a mirror from a specialist optics company. You could try Thor Labs or Melles Griot, and compare their prices, but I doubt you will get it much cheaper than$100.

Claude.

6. Jul 16, 2011

### jim hardy

energy gathering?

do you really need pinpoint focus?

The hobbyists have for years bent aluminum roof flashing over parabolic forms cut from plywood to form a parabolic trough, and put a copper tube along the focus. The aluminum polishes easily with automotive finishing equipment.
Can't beat the cost of materials and one could make any parabola he wanted.

Problem with it is re-radiation because it easily makes 400degF above which temperature IR re-radiation equals what you are collecting as visible..so there goes effectiveness. I spent weeks looking for a hobbyist electroplating process to make "blackened nickel" . Blackened nickel is the lazy man's way around that problem for it won't radiate infrared, but it doesn't appear practical for backyard experimenters. At one time (ca 1982) 3M published a preliminary datasheet for blackened nickel tape intended for solar collector pipes but it never made it to market. Now they wont acknowledge they ever mentioned it. But there are some variable emissivity paints around. [at least there were when i last looked twenty years ago.]

Sounds like you have some resources at your disposal - good luck!

Last edited: Jul 16, 2011