Deceased Digital Projectors as a source of optical goodies.

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g4lab
Posts: 1437
Joined: Fri May 23, 2008 11:07 am

Deceased Digital Projectors as a source of optical goodies.

Post by g4lab »

Last night I stripped a ten year old digital projector that a friend gave me.

It was not working an supposedly parts no longer available. So I attacked it with a screwdriver. It had some pretty nice parts in it that would have been a shame to throw into the land fill.

The unit came with no lamp but I pulled the power supply module for the Metal Halide lamp which I think in this case was 150 watts.

The optical layout is similar to a three ccd camera. A prism housing combines three beams which then go to a focusable zoom lens. There is an Lcd pixel generator on each of three surfaces and when you look at the three surfaces you see what the lens is looking at in either R G or B. I actually didn't have the heart to take that apart. The prism (presumably) and lens were mounted to a nice aluminum casting.

On top of each of those three surfaces was an extremely high quality polarizer.

Between the place where the the arc lamp pointed and the three surfaces of the prism were trains of optics with a nicely made fresnel style prism to make a right angle turn, various condensing lenses, some fresnel style ,
other lenses, and some very large interference filters to start getting the light filtered to the color it was destined to be in the prism. These filters were pretty big but not as saturated and dense as the finals in the prism.

There were some great first surface mirrors.

Finally most of the glass in the interference filters and lenses was water white low iron glass. Looks clear rather than green when looked at edge on. This is not common.

I thought it was worth the labor to strip and then wrap the above mentioned goodies.

augusthouse
Posts: 1195
Joined: Sat Sep 16, 2006 1:39 am
Location: New South Wales Australia

Post by augusthouse »

That is an interesting report Gene. I had not thought of mining a digital projector for components.

I have been playing around with a right-angle prism and watching what it does with light and also used it to test subject positioning.

(I am continually intrigued by mirrors. They are essentially flat, yet depth-of-field is still defined?? The actual mathematics involved here is beyond my mental ability to comprehend.)

The R G B aspects that you mentioned are also of interest. I have been exploring the idea of reversing the process via software in order to work with the individual colour channels (export, stack and apply adjustments to each channel separately then merge). Should be an interesting excercise.
I'm still gathering reference material and experimenting. :smt073

I just purchased a handful of surface mirrors (ebay# 220274655182), mainly for lighting purposes; but I will keep my eye out for retired digital projectors from now on. I have found interesting parts in photographic enlargers in the past; but these projectors sound like gold mines.

Craig
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

g4lab
Posts: 1437
Joined: Fri May 23, 2008 11:07 am

Post by g4lab »

All the components have to stand up to considerable enlargement so when you look at them with the naked eye they all look great. The polarizers look to be the best I have ever seen. I do have a pretty large collection of them.

There is a Fresnel right angle prism to turn the light 90 degrees before
it hits the splitters and precolor filters. Instead of a big expensive right angle prism there are a bunch of smaller ones with their hypotenuses where the big ones would be. Stair step looking

A sort of Fresneled condenser with little squares And a thin wedge too.

And I have not found water white glass to be easy to find.

I think mining might be the right word. :D

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