I purchased a part of a LARGE projector on ebay.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=25321&item=3405921488&rd=1
It is definitely quite cool. It has an input with fresnels, a bunch of front surface mirrors, color pass filters to split the light iinto RGB and route the 3 light paths to separate sides of a prism to combine them. It looks like a slide holder was in front of one of the prism sides. There is a motorized lens assembly on the front. 4 mini fans to cool the incoming light and just before the prism.
Now, what to do with it? I want to build a high power projector but don't see a lot of value in 3 monochrome LCDs (one in front of each side of the prism). The best I've come up with is to use it to combine 3 halogen light sources into one bright beam. (just using the prism). I want to use an LCD OHP panel - because I have them and the resolution is great. I think that means a lens to disperse the output, a fresnel to make it parallel, the panel and then a lens from an OHP to focus it.
I also have a couple of LCD projector lenes but am not sure how to use them since they are made for 1.7" displays at about 2" distance.
Creative suggestions that do not include my body parts would be very welcome.
Thanks.
Steve
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=25321&item=3405921488&rd=1
It is definitely quite cool. It has an input with fresnels, a bunch of front surface mirrors, color pass filters to split the light iinto RGB and route the 3 light paths to separate sides of a prism to combine them. It looks like a slide holder was in front of one of the prism sides. There is a motorized lens assembly on the front. 4 mini fans to cool the incoming light and just before the prism.
Now, what to do with it? I want to build a high power projector but don't see a lot of value in 3 monochrome LCDs (one in front of each side of the prism). The best I've come up with is to use it to combine 3 halogen light sources into one bright beam. (just using the prism). I want to use an LCD OHP panel - because I have them and the resolution is great. I think that means a lens to disperse the output, a fresnel to make it parallel, the panel and then a lens from an OHP to focus it.
I also have a couple of LCD projector lenes but am not sure how to use them since they are made for 1.7" displays at about 2" distance.
Creative suggestions that do not include my body parts would be very welcome.
Thanks.
Steve
The advantage of the three-part LCD projectors is that you can get much better color reproduction out of them than you can with single-panel projectors. This is because the light you generate can be filtered in a much pickier (better) manner than with RGB displays, where the filter colors have already been chosen for you. Also, if you're clever and smart, you might devise a way by which you could use LEDs or lasers as sources for light instead of MH lamps, thus giving a much purer color. Colored light from an LED will ALWAYS beat out filtered light from a conventional bulb.
Good luck finding the little monochrome panels though. I imagine that could be a real pain.
Good luck finding the little monochrome panels though. I imagine that could be a real pain.
Also 3 lcd systems have a much better black representation which cannot be achieved with 1 rgb lcd. The black is comprised of full intensity Red, Green and Blue shining on the same area and combining to produce Black.
Because of this, I am probably going with retail DLP instead of DIY LCD. 🙁
Because of this, I am probably going with retail DLP instead of DIY LCD. 🙁
I design and sell video cameras for a living so you are preaching to the choir. We sell single sensor (Bayer color filter) cameras, so I see the value in 3 colors combined. Not something I care to persue in a projector though. Buying, setting up and aligning the three displays would be too much of a headache. I am looking at integrating a 1024x768 flat panel (OHP type) that I have.
My latest thinking on the prism is that I can have selectable light output levels by putting a halogen light at each of the inputs and selecting how many to turn on. 3 600W halogens ought to light things up pretty well - it is a big room so I am aiming for an 8' wide screen. I like the fans for cooling each of the light inputs on the prism.
All those color splitters will have to go on the shelf for now.
My latest thinking on the prism is that I can have selectable light output levels by putting a halogen light at each of the inputs and selecting how many to turn on. 3 600W halogens ought to light things up pretty well - it is a big room so I am aiming for an 8' wide screen. I like the fans for cooling each of the light inputs on the prism.
All those color splitters will have to go on the shelf for now.
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