I'm here to help anyone who is interested in building a rear projection, I have succesfully build a rear projection tv use a design I found at www.draperinc.com. I don't know if there are calculation that you can use to figure out how far your projector from the I just used trail and error and it works.
To start out figure how big you want screen, 40" to 50" inches are easy to make but 60 and up are harder, unless you are going to but the projector directly behind you screen. After you figure out how big you want your screen find a mirror that is a couple of inches smaller than your screen or one the size of screen. You need a large mirror if you want to keep it small and keep the image bright.
Now for the projector, first build it so that the image will show correctly on the this mean that it shows up on the wall like a regular tv. Mine is made with the Sony PSone Lcd, a 42 watt(2700 lumen) compact floruescent light bulb and the Figinon rear projection tv lense.
Build a frame for the screen just something to hold it up, my screen was made from a piece of plex-glass and a opaque show curtain. Now here is were the trail and error come in, you have to figure out how to position your mirror and projector to get a image that fits you screen and is focused. Once you get it just right build the rest of your frame around it.
Once you get it build you notice that the screen is %100 viewable from a distance and at eye level, this is because the light rays coming from the projector are not the same length, thats why the center is brighter than the other areas around the screen. The longer the light rays are the darker they are when they reach your eyes. You would need a larger fresnel lense the size of screen to make the light ways equal when they reach your eyes.
I wish could add pictures but I dont how to but more than one image on a single post.
To start out figure how big you want screen, 40" to 50" inches are easy to make but 60 and up are harder, unless you are going to but the projector directly behind you screen. After you figure out how big you want your screen find a mirror that is a couple of inches smaller than your screen or one the size of screen. You need a large mirror if you want to keep it small and keep the image bright.
Now for the projector, first build it so that the image will show correctly on the this mean that it shows up on the wall like a regular tv. Mine is made with the Sony PSone Lcd, a 42 watt(2700 lumen) compact floruescent light bulb and the Figinon rear projection tv lense.
Build a frame for the screen just something to hold it up, my screen was made from a piece of plex-glass and a opaque show curtain. Now here is were the trail and error come in, you have to figure out how to position your mirror and projector to get a image that fits you screen and is focused. Once you get it just right build the rest of your frame around it.
Once you get it build you notice that the screen is %100 viewable from a distance and at eye level, this is because the light rays coming from the projector are not the same length, thats why the center is brighter than the other areas around the screen. The longer the light rays are the darker they are when they reach your eyes. You would need a larger fresnel lense the size of screen to make the light ways equal when they reach your eyes.
I wish could add pictures but I dont how to but more than one image on a single post.
Attachments
rmccol
heya bud, glad to see you have made one of the rear projection tv's! somthing that there isnt much about in here and congrats on your effort and research, im interseted in such a device but i had a slightly different plan, basically the thing was going to be the shape of a crt screen at the back and not using any mirrors, not sure if it would work but i think it could give us run for our money in the optics and trying to get them right, it would be good to set one up so its inbuilt into a wall that way it is like a flat screen just on the wall, either that or cabinet ect, either way there is alot of potentional here for this and i think it would be good if more wer into it, as for your screen it sounds spot on to me, i was going to go with the sandblasted plexi for a front projection screen but here where i am right now its abit hard to get hold of a sandblaster so ill wait till i go back to aust, anyway keep us posted and lets get the ideas in this flowing.
Trev
heya bud, glad to see you have made one of the rear projection tv's! somthing that there isnt much about in here and congrats on your effort and research, im interseted in such a device but i had a slightly different plan, basically the thing was going to be the shape of a crt screen at the back and not using any mirrors, not sure if it would work but i think it could give us run for our money in the optics and trying to get them right, it would be good to set one up so its inbuilt into a wall that way it is like a flat screen just on the wall, either that or cabinet ect, either way there is alot of potentional here for this and i think it would be good if more wer into it, as for your screen it sounds spot on to me, i was going to go with the sandblasted plexi for a front projection screen but here where i am right now its abit hard to get hold of a sandblaster so ill wait till i go back to aust, anyway keep us posted and lets get the ideas in this flowing.
Trev
I hung a shower curtain and projected a 40-50in image. The quality was incredibly well, sharp and bright. But the midle is obviously brighter than the edges. I believe it is because the plastics refract lights, and at eye level, more refracted light from the center of the curtain will get to eyes than those from the sides. So I folded the curtain to make a two-layer, and the screen is more evenly lightened. but you have to make two layers closely together, otherwise the image is fuzzy. I would try to strech it on a frame.
rmccoll: is the plaxiglas used for supporting the curtain?
and do you know the price range of draper's rear projection products? I think they use big fresnles to make rear projection screens.
rmccoll: is the plaxiglas used for supporting the curtain?
and do you know the price range of draper's rear projection products? I think they use big fresnles to make rear projection screens.
18wheeler
huh interesting, i think what we need ultimatly is a good difuser that wont eat too much light yet yeald a bright image that is even, i have tried plexi painted white on one side for the front projection system but plexi uses light, it was 3mm thick plexi, i think ultimatley a 1mm or 1.5mm thick plexi would do the trick, maybe plexi in the white coulor or a difused plexi, i did try to see what it was like on the other side of the plexi to see if i could see much of a picture on the otherside and yess quite bright actually and clear, i dont know how evenly lit it was as it was only on a small piece of scrap but i think its got potentional, i maybe going to get more plexi this week so ill have a look and see if i can get a few samples to try different types and to see whats best or if this idea is worth persuing, an idea i had was the chistmas spray u put on your windows at christmas for the snow afect, this stuff is quite translucent and difused, abit like the phosfourus in a crt so maybe this will work, the only thing is it will have to be evenly spayed, another idea yeah yeah they keep coming eh? lol is to use the contact u put on school books, use the white that is quite transmisive too and easy to aply, anyway any thoughts keep them coming.
Trev
huh interesting, i think what we need ultimatly is a good difuser that wont eat too much light yet yeald a bright image that is even, i have tried plexi painted white on one side for the front projection system but plexi uses light, it was 3mm thick plexi, i think ultimatley a 1mm or 1.5mm thick plexi would do the trick, maybe plexi in the white coulor or a difused plexi, i did try to see what it was like on the other side of the plexi to see if i could see much of a picture on the otherside and yess quite bright actually and clear, i dont know how evenly lit it was as it was only on a small piece of scrap but i think its got potentional, i maybe going to get more plexi this week so ill have a look and see if i can get a few samples to try different types and to see whats best or if this idea is worth persuing, an idea i had was the chistmas spray u put on your windows at christmas for the snow afect, this stuff is quite translucent and difused, abit like the phosfourus in a crt so maybe this will work, the only thing is it will have to be evenly spayed, another idea yeah yeah they keep coming eh? lol is to use the contact u put on school books, use the white that is quite transmisive too and easy to aply, anyway any thoughts keep them coming.
Trev
My show curtain is taped to the plexi-glass and mounted to the frame.
The price of the RPS depends on the size of your screen, you have fill out a order form and they send the price to you, but i know its probably really high.
The screen I made is not good, you need something that can get the light to your eyes like a large fresnel lens, I believe edmund scientific sells a large fresnel for a solar oven.
Here is another picture, I bought a $20 camera to take the pictures thats why they're so bad.
The price of the RPS depends on the size of your screen, you have fill out a order form and they send the price to you, but i know its probably really high.
The screen I made is not good, you need something that can get the light to your eyes like a large fresnel lens, I believe edmund scientific sells a large fresnel for a solar oven.
Here is another picture, I bought a $20 camera to take the pictures thats why they're so bad.
Attachments
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.
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.
18wheeler
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.
trev
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.
trev
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.
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.
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?
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?
kc
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.
Trev
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.
Trev
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?
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?
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.
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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