Diffusers?

Justin W · Post by **Justin W** » Sun Nov 18, 2007 6:53 pm

Happy Sunday, holographers worldwide!
Aaaaaaaaalrighty then, I am hoping today to pick some of the big brains for insight on using diffusers in holographic setups... I am kinda under the impression that some guys use beam-diffusing somethings often for object beams. I think I can see why. I've been working for some time now with a fairly random assortment of optics salvaged from.... well... wherever I can find them. This boils down to, of course, lots of nasty nasty lenses that either no longer or never did expand a laser beam without junking it up. I have to imagine that rings and motes I see projected onto the surface of the object I am illuminating will show as rings and motes on the surface of my imaged object (yes, I can only imagine this because at this time I am only just recently blessed with a spatial filter, and to date impure reference beams have quite effectively negated any of the finer details of images).

I'm between photomaterials at this time and basically fartin' around on my table (OK, OK - stupid worthless saggy plastic sandbox soon to be retired as it doesn't even pass the 3AM stability test)... I've been aiming beams through various frosted materials - for example - some mis-shapen lumps of frosted glass (result - grainy and mis-shapen), some small pieces of frosted plastic (result - very grainy with a seemingly significant portion of the raw beam remaining raw), the two frosted surfaces of cheesy prisms from edmund scientific (result - a very lossy but pleasantly even distribution of light though still grainy), and even a couple sandwiched layers of rather lightly-frosted sheet glass (result - barely diffused though still frikkin grainy).

If I could arrange things (which I can't) to put a beam through only one frosted surface, would this diffuse a beam?

What is considered a good diffuser to use (findable/salvagable)?

Is there such thing as diffusing a laser beam without the result being grainy?

I'm reflecting some of these diffused beams from my collimator - has anyone ever had good results from reconstructing an H1 for copy with a diffused then collimated beam?

LOL- Again... what do you guys in-the-know use for diffusers?

Much respect and appreciation to anyone willing to provide some insight here!

dave battin · Post by **dave battin** » Sun Nov 18, 2007 7:55 pm

check this thread out it may help, http://holographyforum.org/phpBB2/viewt ... =12&t=4764

Colin Kaminski · Post by **Colin Kaminski** » Mon Nov 19, 2007 6:45 pm

This also may be of help:

http://www.holographyforum.org/HoloWiki ... #Diffusers

Justin W · Post by **Justin W** » Mon Nov 19, 2007 7:38 pm

Did I check the wiki?

Nooooooo......

Thanks, guys, for the feedback!

Here's something I just noticed and am looking real forward to trying when I have some plates to burn again: a lens plus a chip of my "lightly frosted" glass! Nice, even distribution of light and the rings and motes disappear!

We'll see...

Ed Wesly · Post by **Ed Wesly** » Mon Nov 19, 2007 9:56 pm

To minimize the graininess, the bigger the beam is expanded before hitting the glass the better.

Sand-blasted glass works well, and it does not depolarize the light. Check it out with a polarizing filter. But the object, if it is a diffuse reflector, certainly will!

Another type of glass that might be found at a stained glass supplier is called opal flashed glass. It looks very milky white, and seems to give less speckle (graininess), but since it works by scatter, it does depolarize the beam.

Justin W · Post by **Justin W** » Tue Nov 20, 2007 5:50 pm

How cool?
Supercool.

Thank you, Ed, for those great suggestions. I will investigate them. My mommy sure does love beads and glass and junk - maybe she'll have some opal flashed glass!

Again, brother, thanks! Yes, I noticed that - that the speckle (awesome - I learned a new term) reduces with a bit more distance from the lens. Very cool. Lord, I love holography - god is in the details!

JohnFP · Post by **JohnFP** » Tue Nov 20, 2007 6:04 pm

What is it about holography, that some people just don't get it and some can't get enough of it?

Justin, seems you got the bug. Welcome to the club!!!

8)

Justin W · Post by **Justin W** » Tue Nov 20, 2007 10:52 pm

Heheh... that's great, John!

The full spectrum of emotions with this endevour for sure!

Although... I don't see a "flop-sweat" emoticon there... You know... that sensation when you jig up your recently-processed-and-dried transmission hologram back into your reference beam and think maybe you can sorta see an image...

John Klayer · Post by **John Klayer** » Fri Jan 11, 2008 9:31 am

I recently bought some samples of light shaping diffusers from Luminit. I haven't tried making a hologram them yet - maybe this weekend. They have the advantage of directing the diffused light where it is needed instead of everywhere as opal and ground glass does and they maintain polarization. As Ed Wesly said above, the laser beam needs to be spread some before the diffuser to reduce speckle. Testing with a power meter shows that I am getting much more light where I need it than when using the opal glass.