Well lets start with the easy stuff first
-We can make the outside of the tv(the box) out of MDF. Stuff is both easy and cheap to make and work with.
-Add some casters to it like the do on the floor
-I saw once at a show a piece of glass that had a projector behind it. Had a awesome picture to it(was playing games) but it was directly behind it and the pic was only about 37in while the projector was a good 7ft away. This means that we are gonna have to figure out some sort of mirror system to this. What I know we are gonna have to do is have a mirror at the back of the tv and it should be placed at the midway of the screen. The projector is gonna need to be at the bottom.
-The optics thing is gonna be a little challenging for me as I don't have my college physics book. You want X size diagnol screen your gonna need Y size mirror and the projector is gonna have to sit z distance away from it
Basically we would use a OHP at the back of the TV to project the image, the problem that I have ran into is the optics though.
Sigh I am dead tired rite now and will get to this explaining more of this tomorrow, hope the ACAD image shows up
-We can make the outside of the tv(the box) out of MDF. Stuff is both easy and cheap to make and work with.
-Add some casters to it like the do on the floor
-I saw once at a show a piece of glass that had a projector behind it. Had a awesome picture to it(was playing games) but it was directly behind it and the pic was only about 37in while the projector was a good 7ft away. This means that we are gonna have to figure out some sort of mirror system to this. What I know we are gonna have to do is have a mirror at the back of the tv and it should be placed at the midway of the screen. The projector is gonna need to be at the bottom.
-The optics thing is gonna be a little challenging for me as I don't have my college physics book. You want X size diagnol screen your gonna need Y size mirror and the projector is gonna have to sit z distance away from it
Basically we would use a OHP at the back of the TV to project the image, the problem that I have ran into is the optics though.
Sigh I am dead tired rite now and will get to this explaining more of this tomorrow, hope the ACAD image shows up
Attachments
Ive been thinking of similar with my MH setup. BUT by me useing the fuji lens I have it projects HUGe very fast. This has a 1" focal length from screen. A 5" panel (4x3" LCD) is 110 on the dot when panel right on the lens. 1" back from lcd makes a 5' image (4'x3') at 4' from screen!!!. Extreemly clear can see everything in focus. All light from tv hits projected area (somthing I couldnt do with my other lenses). And its very bright too at this size. Any larger ='s pixely screen door so its just right. I have to use a white screen though or the whites are too bright. Color bleeding was fixed by useing BEF by 3m. Blue tint commen with lcd's is due to polarisers not strong enuff at this level on typical lcd (though OHP ones will work). I have DBEF which does this polarizing on its own and helps contrast tons. But without a perfect reflector system it dimms the pic-not brighten it. With a cool light source and a contained reflector right against the DBEF it would work good-tons better really.
Now I had the idea of front projection too with this setup. Useing some surplus front projection screen i had found. The fiber optic stuff. The main thing is-since I have plyed witht he idea. Is to keep the light source from showing on screen. Hot spotting in a way. Hold a flashlight behind a bedsheet and see what I mean. So the projected image must be lower than the front screen and pushed forward by a front surface mirror directly off the lens. So I would place the LCD projecter at the bottem angled upwards. Use the lens to keystone correct. Place mirror right in front of lens on the right angle to project image forward and the lens's light wouldnt be seen this way. Plus the longest distance between two sides on a rectangle is diagnal. Refering to the tv box. Whatcha think?
Now I had the idea of front projection too with this setup. Useing some surplus front projection screen i had found. The fiber optic stuff. The main thing is-since I have plyed witht he idea. Is to keep the light source from showing on screen. Hot spotting in a way. Hold a flashlight behind a bedsheet and see what I mean. So the projected image must be lower than the front screen and pushed forward by a front surface mirror directly off the lens. So I would place the LCD projecter at the bottem angled upwards. Use the lens to keystone correct. Place mirror right in front of lens on the right angle to project image forward and the lens's light wouldnt be seen this way. Plus the longest distance between two sides on a rectangle is diagnal. Refering to the tv box. Whatcha think?
rear projection setup
Hi All:
First post here. Have an awesome working rear projection setup. (Elmo SD305, NEC1545v, n5 processor) Looking for the best screen material for no hotspots, or a way to use keystoning to avoid it entirely.
On the front projection - if I go this route what can I do to increase the distance from the projector to the screen? The image gets too big too fast. No one wants to have a projector between themselves and the screen!
There must be a perfect surplus lens for this somewhere!
Hi All:
First post here. Have an awesome working rear projection setup. (Elmo SD305, NEC1545v, n5 processor) Looking for the best screen material for no hotspots, or a way to use keystoning to avoid it entirely.
On the front projection - if I go this route what can I do to increase the distance from the projector to the screen? The image gets too big too fast. No one wants to have a projector between themselves and the screen!
There must be a perfect surplus lens for this somewhere!
Re: rear projection setup
I suggest Dacron sail cloth for a rear projection system. If I had more available room (and hadn't gotten a great deal on a powered screen) in the area intended to be my "theatre" I wouldn't have sold my Dacron screen. The image was excellant!
As for the lens issue..if you find a sollution Please Share! It's a common problem it seems 🙁 To counter this effect I place my PJ where I want it...then make my desktop background "black" (mine is an HTPC) I disable web content on my desktop (hide icons) then simply "resize" my projected image to fit my screen. For this reason I find an HTPC to be superior to more conventional sollutions.
With regards to the "Grand Wega" design...I have recently recieved a lens I purchased from ebay...it's an enlarger lens from a photo enlarger. 9 inches across by 3.5 inches thick...focal length of 8 inchs. At 6 feet from the screen it produces a gorgeous image that is an easy 72 inches diagonal...not so good for front projection.,..unless you happen to have a barn or aircraft hanger for a theatre 😱
So since I don't have a barn or hanger to use I think I'm gonna build a DIY telescope with it 😎
zardoz
proto5 said:
I suggest Dacron sail cloth for a rear projection system. If I had more available room (and hadn't gotten a great deal on a powered screen) in the area intended to be my "theatre" I wouldn't have sold my Dacron screen. The image was excellant!
As for the lens issue..if you find a sollution Please Share! It's a common problem it seems 🙁 To counter this effect I place my PJ where I want it...then make my desktop background "black" (mine is an HTPC) I disable web content on my desktop (hide icons) then simply "resize" my projected image to fit my screen. For this reason I find an HTPC to be superior to more conventional sollutions.
With regards to the "Grand Wega" design...I have recently recieved a lens I purchased from ebay...it's an enlarger lens from a photo enlarger. 9 inches across by 3.5 inches thick...focal length of 8 inchs. At 6 feet from the screen it produces a gorgeous image that is an easy 72 inches diagonal...not so good for front projection.,..unless you happen to have a barn or aircraft hanger for a theatre 😱
So since I don't have a barn or hanger to use I think I'm gonna build a DIY telescope with it 😎
zardoz
reducer lens
Nice to talk to you guys- been lurking, learning & building for a month or so. Sorry for the closeness to your user name, protos, I had no idea you were out there! Anyway- on the lens issue- I see where you can get zoom or telephoto lenses for slide projectors......(I'm assuming we need a telephoto?) I wonder if they can be adapted?
BTW- I'm using the grey rear projection screen from Dazian. It seems as bright from the front as from the back and almost kills the hotspot- BUT it is not nearly as bright of an image as I get from front projecting onto a white shower curtain.....
I'd go front projection IF I can figure out how to increase distance from projector to screen! There has to be a solution to this....
I'll post pics soon.
Nice to talk to you guys- been lurking, learning & building for a month or so. Sorry for the closeness to your user name, protos, I had no idea you were out there! Anyway- on the lens issue- I see where you can get zoom or telephoto lenses for slide projectors......(I'm assuming we need a telephoto?) I wonder if they can be adapted?
BTW- I'm using the grey rear projection screen from Dazian. It seems as bright from the front as from the back and almost kills the hotspot- BUT it is not nearly as bright of an image as I get from front projecting onto a white shower curtain.....
I'd go front projection IF I can figure out how to increase distance from projector to screen! There has to be a solution to this....
I'll post pics soon.
ok guys now that I am a little less tired here is some of the things that I have though about.
Box construction would need to be plywood as MDF would be way to heavy.
The overall depth of this would be almost twice the depth of the current RPTV witch are constrained to 29 inches so this thing would be have to build in two parts at the current configuration.
I was thinking of building the projector using alans plans
http://people.eecs.ku.edu/~astaples/projector/design.htm
Cloth I have no idea on but altec and zardoz have both got some good ideas, epspecially altecs about the flashlight.
I have though about using a acryllic or just straigt plexi glass for the image to be projected on. I have noticed that the plastic screen is a soft plastic and easily bendable.
The advantage of the RPTV is that we allready have a dark room but as the light will be enclosed in it by the box. I am also leaning towards the LCD over the CRT design as I really don't want to spend $4k on a RPTV to have it suffer from burn in. I also will be able to control everything VIA my HTPC.
Box construction would need to be plywood as MDF would be way to heavy.
The overall depth of this would be almost twice the depth of the current RPTV witch are constrained to 29 inches so this thing would be have to build in two parts at the current configuration.
I was thinking of building the projector using alans plans
http://people.eecs.ku.edu/~astaples/projector/design.htm
Cloth I have no idea on but altec and zardoz have both got some good ideas, epspecially altecs about the flashlight.
I have though about using a acryllic or just straigt plexi glass for the image to be projected on. I have noticed that the plastic screen is a soft plastic and easily bendable.
The advantage of the RPTV is that we allready have a dark room but as the light will be enclosed in it by the box. I am also leaning towards the LCD over the CRT design as I really don't want to spend $4k on a RPTV to have it suffer from burn in. I also will be able to control everything VIA my HTPC.
proto5
Thats a nice pic! What bulb you useing? Anyhow keep in mind that if you do increase the distance from projector to front screen it will also increase the light decay rate and be dimmer. This is a big advantage of the rear projection as it has a extreemly short throw distance the lumens stay high. Also by being in a box its not as effected by ambient lighting. Though of cource it will dimm aswell with lights on. My buddys 5' (I think?) rear projection RCA tv is dimm if you dont pull the curtains and dimm the lights. During the day you have to be RIGHT in front of it. 30o to either side and you get extreeme color washout. The rear pj also limits the viewing angle on most manufac. screens so as to increase the forward brghtness like BEF film does.
If you bring the image back down with a condesor it will also loose some light due to reflection-refraction and absorbtion of the lens. Another factor is that light at harsh angles like your short throw lens will not wanna be rebent by the condensor too well.
Thats a nice pic! What bulb you useing? Anyhow keep in mind that if you do increase the distance from projector to front screen it will also increase the light decay rate and be dimmer. This is a big advantage of the rear projection as it has a extreemly short throw distance the lumens stay high. Also by being in a box its not as effected by ambient lighting. Though of cource it will dimm aswell with lights on. My buddys 5' (I think?) rear projection RCA tv is dimm if you dont pull the curtains and dimm the lights. During the day you have to be RIGHT in front of it. 30o to either side and you get extreeme color washout. The rear pj also limits the viewing angle on most manufac. screens so as to increase the forward brghtness like BEF film does.
If you bring the image back down with a condesor it will also loose some light due to reflection-refraction and absorbtion of the lens. Another factor is that light at harsh angles like your short throw lens will not wanna be rebent by the condensor too well.
rear projection
After messing around with both front & rear I've come to the following conclusion
Front projection is way brighter!
Was using rear proj screen from Dazian- does real well in eliminating hotspot- but still loses alot of lumens.
When you go with a more translucent screen for more light-you get hotspot city.
I've concluded that you need a screen like a real RPTV to do rear proj. (fresnel-lenticular big$$$$$)
BTW- my Phillips 50" RPTV- HDTV monitor is VERY bright even in daytime viewing- your friends set must be way outdated!
After messing around with both front & rear I've come to the following conclusion
Front projection is way brighter!
Was using rear proj screen from Dazian- does real well in eliminating hotspot- but still loses alot of lumens.
When you go with a more translucent screen for more light-you get hotspot city.
I've concluded that you need a screen like a real RPTV to do rear proj. (fresnel-lenticular big$$$$$)
BTW- my Phillips 50" RPTV- HDTV monitor is VERY bright even in daytime viewing- your friends set must be way outdated!
There has got to be something that we are missing here though and I have a feeling that it might be something simple.
Much desired bump,
What if you dropped down the wattage on the bulbs? I noticed the GWII only has a 100W.
What if you dropped down the wattage on the bulbs? I noticed the GWII only has a 100W.
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