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Old 31st May 2003, 03:10 PM   #11
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Not all lcd monitors can be used in this project due to problems getting the controller boards out of the way.Others have broken ground in this area by actually opening up their lcd monitors and found specific ones which can be used,in particular the NEC 1545v & samsung 150mp. Mods such as cable lengthening are not very easy to do,if they were, everyone would.
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Old 31st May 2003, 04:35 PM   #12
Psionic is offline Psionic  Canada
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Old overhead projectors usually have warped fresnel lenses in them.

Also, don't ask about those 2' x 3' fresnels that come out of projection TV's, or are used as TV magnifiers. Their focal length is way too long. Pretty much any giant fresnel lens you find is going to have too long a focal length for diy projection, unless it was custom made.

One more thing: fresnel is pronounced "fray-nell"
Its french, deal with it...
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Old 31st May 2003, 10:58 PM   #13
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The 2 million candle power hand held battery powered spotlights won't work. But i forget the proper explanation as to why...so if someone could fill that info in ..that would be great.
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Old 1st June 2003, 03:02 AM   #14
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A good lcd monitor will yield far better results than a panel. Remember-these panel's technology are many years old, and things have gotten better.
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Old 1st June 2003, 03:54 AM   #15
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Quote:
Originally posted by Sir_Vival
A good lcd monitor will yield far better results than a panel. Remember-these panel's technology are many years old, and things have gotten better.
Keep in mind though; you will still be blown away by a nice vga projection panel with 1.2 million colors. In fact, if you are just getting into diy projection, many of us recommend buying a projection panel and overhead projector first. This way you will get a good handle on how everything works, what your limits are, and what can be improved if you later build a custom setup. There are only a few better feelings than powering on your setup for the first time and having a clear, crisp, and bright, 8 foot screen that looks damn good.
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Old 1st June 2003, 05:57 AM   #16
Logvin is offline Logvin  United States
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Quote:
Originally posted by Psionic


One more thing: fresnel is pronounced "fray-nell"
Its french, deal with it...

Dang! Ive been lurking on these boards for 4 weeks and saying "Fress-Nell" the whole time! No wonder the guys at Home-Depot look at me funny...
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Old 1st June 2003, 07:05 PM   #17
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Default Lighting

Mh lights are the optimum light source for diy projector, reasons being , more lumens per watt, a colder transmisive light and the correct colour temp ranging from 3900 - 4200.

A light is as good as its reflector
In order to get the right intensity and brightness output of a projection unit u need to capture the light efficiently as possible.
In order to do that a small burning arc metal halide is required with a small parobolic reflector assembly (some OHP Projectors have these already) placed close to the burning arc postion of the bulb. The most efficient bulbs for doing this is the 150w hqi mini mh and a 250w hqi mh, reasons being the side walls of these bulbs are very low profile as to a 400w + mh bulb enabling us to get close to the parobolic reflector.

Light Spreding
In order to spread the light over the lcd we use what is called a frensel lens and also a condenser lens. A condenser lens absorbs and magnifies our light source to a varible beam width enabling us to cover the whole lcd with intense light. There are 2 types of condensers that covers our perpose, 1 is a double condenser and 2 is a single condenser. The 2nd single condenser is what we use for LCD projection as we can vary the beam width to the size of the lcd and the no1 double condensser does not alow the beam to be ajusted to cover our whole lcd so we use the single condenser. A frensel lens is what we use to magnify light intensity and also spread the light evenly across the lcd thus removing any hot spots from our light source. The best type of frensel to use is a type with many rings and made for projection, a page mag frensel will work but has too less a rings to get a ring free image.

Mirrors
Mirrors are comonly used in projectors and serv a couple of different purposes. 1 of the main purposes is space saving or restricted acess lighting and the other is correcting an image to the correct way around for projection. Mirrors use light, there are 2 types and the best is a front surface projection mirror, a standard type mirror will use alot of light and also make the image abit blury or ghosty but however if u use a mirror no more than 2mm thick after the lcd for projecting the image the right way round the image will be sufficient however keep in mind this is not the most efficient manner as this mirror will use alot more light than a surface type mirror. The best way for projection and the use of mirrors is have the mirror to mirror the light source not the lcd image this is used widly to save space and to make your enclosure's smaller. 1 other type of mirror we use is called a cold mirror, we use these to filter out infrared rays in the light spectrum of the light souce to cut down radiated heat in the light its self therfore the lcd running cooler under the intense light.

Filters
Filters are what we use to cut certain rays in the light for a couple of different perposes. 1 being a uv light filter glass to stop any discolourisation of the lcd and damage to other components, and 2 being the cold mirror mentioned above to help the lcd run much cooler under the intense light source.


happy diy and good luck
Trev

P.S Darn good thread verbose maybe we all might learn somthing out of here lol
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Old 5th June 2003, 11:14 AM   #18
moi is offline moi  Reunion
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whaouu!!

nice thread

maybe some pics ??

thanks to all of you for this help
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Old 11th June 2003, 08:31 PM   #19
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Old 11th June 2003, 08:54 PM   #20
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Ok LOL I have been saying fresssss nellll also So how does it sound Fray( as in my pants are Frayed)? frA-nell LOL
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