Holographic diffuser - anyone with experience in ?

Dear forum members,

I am building an LED-light source with tuneable colour as a substitute for a home movie projector lamp, to get better results at the video transfer.

My problem is, I can´t get a diffuser which makes a uniform colour distribution, without killing too much of the brightness.

There IS a solution, a so-called holographic diffuser could do the job. Those things take nearly 90% of the input light and deliver a well-diffused and ***collimated*** beam at the other side.

They are not necessarily expensive, as they are used for background lightning applications in cars, handhelds a.s.o., but normal stupid customers like me can only buy very tiny, ultra-high-precision, ultra-high priced holographic diffusers like the ones sold by www.edmundoptics.com.

ANY Idea where to get a sheet of a cheap low-precision holographic diffuser foil is welcome. I guess this stuff could be of interest for other lamp builders as well.

Regards

Dudeldi

Hmmm, are those the same sheets they use in laptopscreens? If so, a visit to a local repairman might do the trick... /ubbthreads/images/graemlins/icon3.gif

Oh btw, /ubbthreads/images/graemlins/wink.gif

The few suppliers I could find claim that those diffusers direct 90% of the incoming light into a well defined area, which can be sqare, round, or ellliptic; for example, a backlit TV screen diffuser would take all the light which would go to the ceiling or the floor and direct it into the horizontal.

I plan to take such a diffuser to mix the light from different color LEDs. To ask a computer repairman is a good idea!

Thanks

Dudeldi

Re: Holographic diffuser - anyone with experience

They are typically plastic and are rather expensive. Being plastic would probably make them unsuitable for your application due to the heat involved, no? This is normally the case in projection applications unless you use heat rejecting glass. In any case, check out this link. Some have suggested that this is the material used by SureFire.

http://www.poc.com/lsd/default.asp

Wilkey

Re: Holographic diffuser - anyone with experience

I dont think heat would be an issue. It sounds like DUDE is making an LED based adjustable light source to compensate for film degredation while transfering from film to video. An old non-working LCD tv would probably do the trick. Find one cheap and gut it.
Jeff

Re: Holographic diffuser - anyone with experience

Yesss, you are right - I want to compensate for fading, because software alone can´t do the trick on 1940´s Agfacolor home movies.

I tested a piece of laptop screen diffuser foil in the meantime, but it has virtually no directing effect.

POC is the leading supplier of this stuff, that´s right as well - and there is even a company which makes Lamps with really large holo diffusers.

Those things are, as said, expensive, if bought as optical components from a science vendor, but you could also get a Pack of half a mile X 50 Inches on a roll for lamp / screen manufacturing for a few cent per meter.

Maybe my english is too bad to fill out the sample request forms properly, or maybe those companies simply do not react to private people, or maybe this stuff is needed to build a nuclear bomb so they do not sell to europeans - no clue why, but it is ***absolutely*** impossible for me to get a sheet or two of this cheap plastic foil.

Re: Holographic diffuser - anyone with experience

How about using an EL panel instead? Not sure if this would be bright enough, but it'd certainly be even, and would let you pick your colour more or less at will.