Question about lighting

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I know that is about all I have been doing for the last three weeks for about 12 hrs a day.I amm an old man with a poor memory so give me a break.
joking aside, I know that it is mainly a matter of heat, but my thought was that by using a beam splitter/combiner , you would be able to isolate the lights for cooling.
all of this stuff is hard to absorb when you haven' realy tried to seriously learn anything new for 30 or so years. but thanks for caring enough to respond.
Hey, were all getting old gramps, dont sweat it. ;)

There is a good basic summary at in the theory section. Or see the threads for newbies
You have to wade through a lot of chatter here from people that have been playing with this stuff for a while.

I don't understand what you mean by using a beamsplitter. You dont want the light split. It has to come from a point, spread to pass through the lcd and back to a point at the final lens. This path keeps the light rays controlled for imaging.

I am reading the newbies section again for the umpteenth time, but will continue until at least some of it sinks in.
my thought was that using a beam splitter in reverse would let you combine two lights into a single point , allow you to isolate the lamps completely for heat and double your light out put. ie: get 600 watts of light from two less costly 300 watt bulbls. possibly even use halogen because they would be thermally isolated from the panel.
does this make any sense at all?
Yes, but...

You could combine the light from two halogen lamps using a beam splitter, and you could put a dichroic filter somewhere between the lamps & the LCD. But the halogen light would still be very yellow. LCD panels have color filters that are designed for a cold cathode fluorescent light, with a color temperature in the 5000 - 6000 K range. If you use 3000 K halogen, then the image will suffer, like shooting outdoor film under tungsten light.

The other problem with this idea is simple geometry: Most DIY projectors need all the light they can get, so they try to capture the largest possible solid angle of light coming from the lamp. It would be very difficult to design a beam splitter/combiner that would do that. You would have to use some kind of collimation (ie. elliptical reflectors with positive lenses) to form each lamp's output into a nearly parallel beam. The two beams could be combined, and the resulting output beam spread (with another lens) to match a fresnel at the LCD. That is quite a lot of extra stuff, just to avoid paying for a MH lamp & ballast. (Some of those are as low as $100, and last for 10000 - 20000 hours!) Also, each reflector, lens, combiner, filter, etc. loses about 10% of the light hitting it. So it might actually give you less light than one lamp by itself!

MH lamps are also a bargain to run, since they are much more efficient than halogen lamps.
guy, do you know how beam spliters work? i tried several times to understand a 2 beam to 1 spliter but no luck. There are dual lamp (both at once) working projectors (up to 5000-6000 lumnes) but have no idea how it works. Is it posible for you to pos some pic?

beem splitter

oh well, it was just a thought. I understand that you are saying that it is possible, just not practical for use in this application. As to halogen bulbs, that even though they are used in many ohp's they give you a yellowed image.
I understand that mh setups can be had for a relativly low price, I was just trying to think of a temp alternitive that would not completely cripple me already wounded bank account.
halogen lamps

These lamps can be very tempting, since you can spend just a couple of dollars for a lamp that connects directly to your power lines. You can certainly build a very cheap projector using a halogen lamp to start, and then maybe later upgrade to a MH lamp. You will have to go to some pains to filter out all that IR the halogen will send to the LCD, but people have been putting LCDs on overhead projectors for a long time.

Just don't spend a lot of money on a projector design that uses halogen lamps.
can't s[end money you don't have.
my aim is to use a 5" lcd tv for projector sinc the panel is an easy strip and has an rca input as well as tuner & stereo .
currently off work due to heart condition and just looking for something productive to keep from going stir crazy. was thinking of using a crt lens for the short throw and fast speed.
will just keep looking for salvagable parts.
thanks for your input.
low cost projector

Sure, you can make a projector with a 5" LCD TV and a CRT lens.

With a halogen lamp you will need a fan to pull air over & under the LCD, and then past the lamp. Use a small piece of Lexan XL10 from Home Depot as a UV filter, to protect your LCD. You may want to try a fresnel about 20 mm before the LCD, to direct more light into the lens. You can use page magnifiers from an office supply place, like Staples.

Home Depot has very cheap 100 Watt and 250 Watt wide pin capsule Halogen lamps. I would avoid the dirt-cheap 300 Watt long tubes.
VERY greatful for the advice.
going into the hospital fri. but should be able to start on pj nest week.
have a line on a dead big screen for lens and may have cash for other items. so I would expect to have something viable in a week or two.
will post with pics when I have something to show.
Thanks again for all your advice.
let me know

I hope your procedure goes well. I'm sure all the other people reading this thread do, as well.

If you do get around to building the projector, check how hot the LCD is getting (and fresnels, if you include them). If it is overheating, you may see the image go black or clear in a big spot. Turn off the lamp immediately (but leave the fan running) if you see that. Too much overheating can damage your LCD permanently. Then post another message in this thread and you will get some helpful suggestions.
Fluid UV-IR filter

Hey guy,
I just wanted to ask you somenthing that has nothing to do with this thread.
What ever happened to that water UVIR filter you were going to buid?
The last post I read about that was in "HiLLBiLLY'S 7" Lilliput Projector" p. 7.
did you post anything about that since? I would like to see it.
I thought of something that I think has not been done before.

filter + condenser

I will post my thoughts and designs... if you show me where...
thanx, and sorry for the rude disruption of the thread.
water-based filter

I have a great big one and a small one, both about half-finished! About that time, I got my projector running and found no heat problems at all using a simple hot mirror to remove IR.

My inspiration for building water-based filters was the extremely high prices I found for new hot mirror filters. Since then I have found some much cheaper versions, like Rosco's Thermashield film and's heat reducing glass.

These methods are so much simpler than building a water-based filter & radiator, getting all the plumbing right, maintaining it, etc. So the water-based filter idea should probably be reserved for 1000 Watt+ projectors that really more than 90% IR removal.
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