DIY Rear Projection TV

[MikeCAVE]

Wow glad I tripped into here!!! Awesome feedback... IM into making a 3 wall cave for gaming, most of you have probable seen!
So I need rear screen material but I don't want it to be COSTLY... I did also hear about the OPaque curtain but then somone told me that's not gonna have enough light...

My projectors are NEC VT440 & 2 LT155, 1,100 lumens and 1,500
What and where to buy and how much is what I want to know?
The size I'd like to acheive is 6x8 for each wall... Give or take when everything is set... I have a rear screen 20x30 from Dalite which cost $110 which does look nice.. Im sure getting anthing bigger is gonna be way to much...

Any Ideads Tnx Alot

Mike

[jrhilton]

JR most people in here use desktop lcd monitors

You guys should certainly get awards for ingenuity. Sounds to me like you are getting a good projector/rear projection TV for a bargain price, good work, is all I can say!

As for a light source, metal halide is a good one, they last for ages, but watch out, most pump out a lot of UV, even if there are no marks on the glass of the bulb!

One thing does interest me though, you say that the screens are vga so the colouring of the actual lcd is accurate, I’m not arguing with you there, I’m sitting in front of a laptop screen now and it looks perfect, but when you shine a light source with a spectrum of light output with a relatively high variance around the stated value, e.g. a metal halide bulb, surely you then suffer subtractive filtering so the colour value will change when the light goes through the panel, e.g. basically do you get general colour casts . This is a common problem with Film projection. Or have I got over excited and put a physics lab coat on and have started to read too much into all of this?

As for screens, there are equations for working out what the best colour screen for different colour temperature values are, but I never paid much attention to them, they are probably on the internet somewhere, as when you got an answer, there was usually never any screen that exactly matched what you needed anyway. Though if you are dealing with Rear Projection, you thankfully don't need to worry about this.



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[jrhilton]

Here are some links I though might be usefull to anyone thinking of making a ground glass screen:

http://www.philsan.com/ground_glass.htm

http://rhoadescameras.bizland.com/Ca...ound_glass.htm

http://www.phototechmag.com/previous...kas/dokas.html

These pages are all writen by people making ground glass focusing plates for large format sheet film cameras, but they are exactley the same as for a rear projection tv.

Further to what David asked in an earlier post, aluminum oxide is a great grinding medium or failing that silicon carbide, but this is not as good as aluminum oxide, you should be able to get grinding compounds/pastes containing both of these from an automotive parts shop, or the internet somewhere.

[jrhilton]

I have a rear screen 20x30 from Dalite which cost $110 which does look nice.. Im sure getting anthing bigger is gonna be way to much...

Yeah, you won't get a Dalite one of size 6x8 feet for under $3500 to $4000 USDs, but that is what quality costs, since the 1950's they have always produced great products.

As for alternatives, I would guess a pice of glass of size 6x8 would be very expensive too, plus dangrous. I'll give it some thought as to what you could use as an alternative.

[ace3000_1]

As for a light source, metal halide is a good one, they last for ages, but watch out, most pump out a lot of UV, even if there are no marks on the glass of the bulb!

yeah they do , they are suposed to be the one bulb that pumps out the most uv, the bulb i have has a uv stop in it wich filters out the uv, not all but atleast 50%, better then none, some use plexi glass as uv filters and some dont use anything, myself i use plexi in my design anyway and a fair amount of it to hold my frensels together, yep and its a optical grade too well it would want to be at 200euro's for half a sheet.

Trev

[dbc105]

How does a euro relate the a US dollar? Who or what is Dalite? I have been in the basement looking at the Pioneer RPTV that I removed the back from. I am going to take some measurements this afternoon and remove the CRT lenses to see if these look like usable parts. I am worried about focal length. Do I have to host an image to post it here or will the forum host it? I guess what I mean to ask is how do I post a pic or drawing? ater I get the measurements I can post a drawing showing what confines I am looking at.
Thanks,
David

[rmccoll]

Another screen idea is to use those plastic sheets that cover flourescent light, the kind you see in schools and office buildings they come in alot of textures and they are cheap. You can also use a thin sheet of HDPE plastic, this plastic is used to make those flexiable cutting boards. You can get a sheet from www.usplastics.com

Got a question. Can a 75 watt MR16 light bulb put out 2200 lumens because I found that does and I dont think the specs on it were right. Most 75 watt bulbs put out about 900-1000 lumens and highest I have seen one go was 1200 lumens.

[jrhilton]

You could use 'Low-E' insulated glass or any other insulated glass with an inert gas in the middle of two pains, as insualting glass will stop UV but better still it will also reduce the amount of IR hitting the LCD. Small pieces of Low-E glass, e.g. 10x10 inches, are not that expensive at all.

[jrhilton]

Who or what is Dalite

David, Dalite, or rather 'DA-LITE' are one of the best manafactures of screens for projection applications, IMO the best. They are a German Firm, seem to remember they started back in the 1950's. They make wonderful rear projection screens as well, with lots of options.

Here is their web page:
http://www.da-lite.com

They make every sort of screen, they will also make one of a kind screens for you. But as with all good screens, they cost a lot of money. Most people don't realise that a good screen will cost much more than a good projector. You can easilly spend $10,000 + on a screen.

1 EUR = 1.23840 USD as of 2004.01.31 15:33:13 GMT,
or
1 USD = 0.807495 EUR

David, is there a chance of some pics of the inside of your Pioneer RPTV, as I would be interested to see what they are like inside these days, as i'm sure many other people would be!

[dbc105]

jr, I will have to try to bring a camera home with me next weekend. I don't have one but I can borrow one at work. I have made a drawing with measurements that may help also, if I can get it posted. I removed the bracket that holds the lenses and the CRTs. I then removed the center CRT. There was water? between the CRT and the first lense. The first lense is in a sphere. Above that is an adjustable double lense. Of course there are 3 of these in a row. The size of the CRT screen is about 5" x 4". The screen on the TV is 40" wide by 30" tall. I would like to reuse these lenses if possible. They already have the correct focal length. If I can mount a lcd where the CRT was and have the light come up through it. I don't know about fresnels or the sphere shaped lense. If I can find someone I can borrow a camera from I will get some pics up sooner. Maybe this drawing will give an idea of what I have. I know the mirror angle is wrong and it is not in proportion but it will give you an idea.
Thanks,
David