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Old 8th November 2003, 11:33 PM   #11
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coarse sandpaper makes hotspot softer. the result is even better if both sides of the plexiglas(2-3mm thick) were sanded. but the image is not as sharp. so a large 1mm plexiglas may do the trick. it won't be as good as those expensive fresnel type rear projection screen, but it is DIY

I way make a 50-60" screen, so the quality of image would be acceptable. besides, my eyes are kind of strained after watching 100" picture from 8-10 feet away.
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Old 8th November 2003, 11:47 PM   #12
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yeah the 1mm would be the go, a sandblaster is what we realy want, cos the small pits are the difuser and they are like small crystal chips that light up like the glass bead screen for a front projectors as u probally already know, not sure if u know of it or not but comps are getting modded these days and there are things called apogies, u can get the stick on type or the sandblasted type, the sandblasted way out performs the stick on type as it colects the light and re transmits it in the sandblasting, ive done a etching before on this comp of a dragon and i must admit its bright as, also with the sandblasting idea we could experiment with different coarsness of sands to get the optimum picture vs difuser ratio and brightness, im just hoping we can difuse it enough, i think that we can find a way without the need for a big frensel but i think a big frensel would be the optimum way, either way diy rules man and lets keep it cheap.

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Old 8th November 2003, 11:50 PM   #13
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that diffuser in the lcd's back light can we get a hold of that? that would do the trick just a matter of getting it big enough

trev
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Old 9th November 2003, 02:36 AM   #14
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Have you thought about digging around getting a trashed rptv and using the screen on it--most bigscreens use a fresnel type lens as the screen--it results in much higher gain then just a rear projection smoked glass style screen.
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Old 9th November 2003, 02:55 AM   #15
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The diffusers behind LCD monitors are very similar to the plastic
film architects draw on ( the non Autocad guys or resistance to change guys.) You do get it in various thicknesses and levels of matt. It is available in rolls or sheets of up to size A zero. Two or three layers might work perfect.

Further there are thousands of different types of plastic film available to the screenprinting industry. You even get translucent silver films ,you name it , it is available .

If we all can work together and each person get some samples or offcuts from a supplier or screenprinter , I am sure we can find a rear projection screen material that match the commercial ones for a fraction of the price.
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Old 9th November 2003, 02:59 AM   #16
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Default I love the idea, but I want it bigger

This rear projection stuff looks really cool... but I want something bigger. I'm using a QA-1650 right now, and even though it's not that great of a screen, I am getting a picture over 10' diagonal and I think it looks great. The screen door is pretty bad, but just a touch of fuzzy focus and it's very bearable. I'm more worried about getting a good clear picture and getting a nice enclosure for it now...

I don't need a 10' picture, but I do want to be at least around 80". If I was going to go with a 50" screen, I'd buy a 50" tv.

I love the way that the whole thing can become an enclosure, could be built into the wall or built into a cabinet, but I just don't want to go to all the trouble for that small of a picture...

How do-able is a larger picture?
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Old 9th November 2003, 03:37 AM   #17
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heya kc its very doable to make a 200 inch screen lol but do u have the cash and room for that? rear projection tv's use abit more room then a ohp but realy can be much better then a front projection system, and i must say look better too, but they use abit more room, basically the bigger the picture the farther from the wall it will need to be and the prices in optics like a huge frensel starts to get up there, personally i think 60-70inches is all u need for a rear projection tv, most of the new if not all of the front projection projectors are actually designed for 80"screen size even though they go higher, that also includes crt projectors, 80inch is the biggest i think a home owner realy needs, anything bigger then its for a large home cinema unless u want to feel sick, i think a wide screen would be best at 80inch but thats me, but anyway its doable.

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Old 9th November 2003, 03:40 AM   #18
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How about the plastic that cover flourescent fixtures, they have little diamonds over the whole thing that spreads light evenly. They sell it Lowes, they also have the kind that looks sand blasted but I believe it's not
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Old 9th November 2003, 03:46 AM   #19
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Default I love the idea, but I want it bigger

This rear projection stuff looks really cool... but I want something bigger. I'm using a QA-1650 right now, and even though it's not that great of a screen, I am getting a picture over 10' diagonal and I think it looks great. The screen door is pretty bad, but just a touch of fuzzy focus and it's very bearable. I'm more worried about getting a good clear picture and getting a nice enclosure for it now...

I don't need a 10' picture, but I do want to be at least around 80". If I was going to go with a 50" screen, I'd buy a 50" tv.

I love the way that the whole thing can become an enclosure, could be built into the wall or built into a cabinet, but I just don't want to go to all the trouble for that small of a picture...

How do-able is a larger picture?
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Old 12th November 2003, 08:47 PM   #20
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Lightbulb Building it

I just found this thread on the internet, and I must say that there are to little people builing an RPTV.

I'm building one myself at the moment, and I hope to finish the damn thing before the end of the year.
I'm using a plexi glass screen, which has one satin surface (Atoglas). For as far I can tell up to now this works great if you can bring enough light to the screen. Satinized plexi has a little smaller grain, but is hard to find. What I did was ordering samples from different producers, before ordering.

For the cabinet itself, I use a two-mirror system. This allows a longer projection distance in a relative small cabinet. I found that the downside is that if the angles of the mirrors some times can give very weird images, but this is just trial and error.
At first I started out with a projection panel, but now I'm switching to a LCD projector. The image is MUCH better, and brighter and it was a real bargain.
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