What is the best surface for reducing scattered reflections?

[kitatit]

Hi guys and girls.

I have a current project where I have a scanned beam that will be hitting a black anodised surface at a perpendicular angle. I want to eliminate or reduce as far as possible the scattered reflections so they don't illuminate the surrounding area.

I understand that there is a relationship between the wavelength of light and the surface finish of the surface which will influence the reflected characteristics of the beam so I was thinking of having the aluminium etched before it is anodised the give a matt finish but I'm not sure if this will be enough. I figure this will just defuse it.

What I'm looking for is something to absorb close to 100% of it.

Do you think something like black Scotch brite pad would work? E.g. Gluing the pad to the surface to trap the reflections.

I'm picturing the beam getting trapped in the porous structure similar to acoustic sound absorbers.

What are you thoughts? Any suggestions on other materials that may be better suited to the task?

It will be a scanned approx 5W RGB beam.

Cheers
Kit

[WookieBoy]

Hi Kit.

You could try black wool surge... or standard theatre drape material.

It's prety good at being non reflective(though I've not tried it with 5W of laser!) and it's self extinguishing if the worst happens and you burn it...
Also it's pretty readily available and you should be able to get a free sample to test it with...

[kitatit]

Hi Wookie

Cool Ill have a look at that. I need something for a backdrop too and that
Should fit the bill for that too.

Cheers
Kit

[-bart-]

How big is the surface area ?

Recent link here.

[kitatit]

Hi Bart damn! You have got me looking for 3M black velvet paint now!

Very exciting product.

I have quiet a few components that could do with being painted with that.

Probably going to be super expensive if I could even get it shipped to oz.

Thanks for the heads up.

Cheers
Kit

[mixedgas]

Any carbon based flat black paint or black engine block paint. Not as nice as Velvet, but it works.

Steve

[kitatit]

Hi Steve

Thanks. I had some black enamel engine paint in the shed, so I gave it a quick test. It said it had ceramic in it. Not sure if it had carbon in it.

Do the chalkboard paints have carbon in them?
http://www.gerdneumann.net/english/i...cal-paint.html
This paint looks good but maybe the chalkboard paint from a local hardware store might be just as good.

Do you know what has happened to the 3M Velvet black paint? The astronomy forums mention it a lot but it seem the rights to it changed hands a few times and the trail seems to be a bit cold. If I could find it, do you think it would have volatiles in it that would make it expensive to ship to Australia? Also do you have any idea how expensive it is?

Here are some very rough test results so far;

Pic 1 taken in semi dark room. The incoming beam is hitting an off white wall just behind the camera.




Pic 2 is the black enamel engine paint on aluminium (not a very thick coat and it wasn't very matte)




Pic 3 was a pair a new jet black denim jeans (Which i left a burn mark in.... %$#%$%$%@^


Do you know what types of paint have carbon?

Thanks
Kit

Any carbon based flat black paint or black engine block paint. Not as nice as Velvet, but it works.

Steve

[kitatit]

Oh, BTW. My original idea of using a Scotch brite pad was hopeless Back to the drawing board. Lucky I have my clued up PL fiends to help me

[-bart-]

If it is a single spot (~3x3 cm) you want to terminate, try a stack of razorblades. This is said to have excellent absorption.

I have not done any measurements, but a simple setup I did once looked promising.

[kitatit]

Hi Bart. No it's a long, narrow area 3.1m long by 15mm wide that the beam terminates on which needs the treatment. Also I'd like to coat some of the internal surfaces of the optics path. E.g. I have a motor that has an 8mm shaft with a 5mm hole down the centre. The beam passes throught the hole in the shaft. It would be nice to reduce some of the stray scatter there too.