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Hello all, I have had an idea for an artsy/marketing move for some time, to advertise some community websites I run. Plus I believe in adding excitement to our otherwise boring region.

I'm a geek, and have toyed with high power laser systems (for lightshow use), and club lights. I looked heavily into attempting to build high output LCD projectors using various metal halidr and xenon lamp sources, but I believe there would be no way to cool the LCD panel as it would absorb too much heat. Contrast ratio would be horrible.

So I started to peek around at drive in movie theater setups, since this is close to what I would be trying to achieve.

What kind of prices does old 35mm projection equipment fetch? 4KW xenon lamp house, rectifier and the projection head? Lenses?
This would require no audio. My idea is projecting onto specific buildings, most likely a short 35mm loop that has been transferred from computer (film recorded).

I can't help but think about trying to build a DLP head that mated with a 4kw lamphouse, but I'd imagine the heat abosorbed from that powerful of a lamp source would fry the DLP chip... the idea still circles and if I had the equipment I would probably look into it.

I've been peeking at ebay and from time to time bits and pieces come up (xenon bulbs, reflectors, linear rectifiers). Never the right sizes, and I'm not knowledgable enough to know what fits what. The one thing that seems to bug me is the rectifier. Almost all say they are 3 phase. Are they generally 480vac or 208vac? Does anyone know the output voltage (volts, amps, ac/dc?) I've seen that switch mode supplies exist but obviously that isn't going to happen scrapping up surplus equipment.

I'm just trying to figure out how feasable this type of stunt would be to someone without alot of money, but inginuitive?

I actually wouldn't mind seeing an outdoor theater in our community. There are a few sites where it would be good, but NIMBY folks would fight the noise as there are neighborhoods all around.

Thanks in advance for any insight.

(For those that have any interest, these are my old notes from looking at the LCD panel projection hacks... none of it would hold a candle to using a 4kw xenon drive in style setup but may be of interest to the really bored) http://wiki.757.org/doku.php?id=projects:lcd__overhead_projector

Reminds me of when I tried showing a movie on low-hanging clouds when I worked at the GrandView Drive-In, using a mirror to reflect the image upward. Even burning 11mm carbons at 120 amperes and 65 volts DC (7800 watts), I could never get more than a dim, diffuse image on the clouds. Of course, the lenses I had were intended for a "throw" of only about 250 feet, and much longer focal lengths would be needed for clouds at several thousand feet.

For both 35mm and DLP Digital Cinema Projectors, up to 7000 watt Xenon lamps may be used. The newer 2K digital projectors are much more light efficient than the older
1280 x 1024 DLP models, and should be in the same ballpark as 35mm film for light levels.

But I'm afraid for extra long throws onto low hanging clouds or distant buildings, a more specular source like lasers or parabolic arc spotlights is still the way you need to go.

Maybe you could buy a surplus spotlight from "Batman"?

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John P. Pytlak, Senior Technical Specialist
Customer Technical Services
Entertainment Imaging
Research Labs, Building 69, Room 7525A
Eastman Kodak Company
Rochester, NY 14650-1922
Telephone: +1 585-477-5325 Cell: +1 585-781-4036 Fax: +1 585-722-7243
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Website: http://www.kodak.com/go/motion

[This message has been edited by John Pytlak (edited April 10, 2006).]

If you're going to use a loop, expect to make it long enough to dissipate the heat it'll absorb on each pass. You'll also need to think about how to keep it clean, as it'll pick up any dust that might be around. Overall life might also be an issue. With proper handling, you can play a full-length feature for a long-long time. A loop will accumulate a high number of plays in much less time.

John's dealt with the light issues. That shouldn't be a problem for you.

You can find used equipment almost everywhere. It's just a matter of what fits your needs. Used stuff shows up on Ebay from time to time. Many companies, from the smallest mom & pop to the largest chains can have equipment that they don't intend to use in their own operations anymore. Gaining access to it is a matter of developing the appropriate contacts. Many theatre equipment supply companies also have back warehouses, with machinery in various ages and conditions. You can frequently negotiate reasonably good prices, based on your needs.

Finally, take advantage of the want-ad sections of discussion boards like this one. You never know what might come up.

John - the laser folks have tried to project into clouds. The issue is they aren't solid, so the beam goes into the cloud. If your near the scanning setup looking at the cloud, everything is okay. If you are off axis, you just see the green beams going thru the clouds

That is pretty wild that you tried that though.

As far as optics and cooling and what not, I guess it should be possible to filter the air (heppa filters from vacumes and build a film cooling rig. Perhaps enclose it as much as possible.

Thanks for the tips! I'm going to have to start pinging various surplus suppliers to see what can be had!!

DO NOT project any kind of laser onto or into clouds -- or up to the sky at all!!! There have been several incidents of pilots being blinded by such, and new Federal laws created stiff prison term penalities after 9-11. Sometimes the FAA will give special permits for such if you give them ample notice, but I wouldn't risk it given today's large number of amateur flyers up there --often without flight plan! How would you feel if you blinded someone or caused a crash?! If you are using a search light or projector, that's different, but a laser often cannot be seen until an aircraft is suddenly upon it, which is why banyone using sky lasers is suspected of being linked to terrorists these days.

Sorry, I've been into the laser stuff for a while. Step one is a CDRH certification on the projection system, it is some 62 pages of paperwork describing the safety interlocks to protect the operator and other people within close range to the projection system. Some of the questions are pretty rough when it comes to specifics on the actual laser system itself. Other parts seem very easy, kill switches and labels.

After you have a variance on the projection system, you file a notice with the CDRH that you are going to perform a laser show. The aperwork looked pretty specific in terms of the venue, and heights above audience. Good stuff. If unterminated beams are involved, there is additional notification you give to the FAA. You generally give them a set of parameters as to where the unterminated beams will be, and I believe they declare a no fly zone. There is software that helps determine the numbers you need to turn over given GPS cordinates and angles or some such.

When the whole terrorist laser thing came up, lots of friends emailed me about it. I've seen lots of discussion on the subject.

I think some of it may be a bit blown out of porportion. A laser emits a coherent beam, but it isn't really *that* coherent. There is a lens called a collimator that helps correct the beam divergence. But if you take a gas filled laser (which has better coherency properties over the higher powered YAG and solid state lasers) and aim it at a building 500 feet away, you will notice that the beam is razor fine at the exit of the laser, but is a huge dot on the wall 500 feet away. The 5 watts of power is now dissipated over that circle (if a temoo laser) which may be a good 5" round. Still dangerous, but the farther you get the bigger the dot gets, and the weaker the power per centimeter of surface. I don't know the exact calculation, but it probably doesn't take too long to drop to safe exposure levels.

Next thing that is wild is this. The US has strict laws against what is called "Crowd scanning." In other countries they will often aim 5 to 20 watt lasers straight into the crowds! I've never seen this myself except in videos, but it happens often. What happens is the computer is driving the mirrors at a very high speed, so the laser is moving over the crowd at a very high rate. The power from the laser is now dissapated because the exposure time is small. They use a device that monitors the signals from the computer that will shutter the laser (Hopefully they use this device) if the computer should lock up, or there is some sort of other failure in the scan system. If the beam stops, or perhaps drops below a certain speed - it becomes dangerous. I've heard people use the same type of setup for the high powered, pulsed lasers. These are NOT safe to aim into a crowd even with high scanning speeds due to the means they use to lase. If you take a 5mw laser pointer, the dot can be seen across a big room. If you put it up to a scan system considered weak by todays standards, you might only be able to see the scanned image 5" away from the scanners using a white card, and it will be faint.

There was an episode of hard copy or a similiar show some years back where people got into a helicopter and they hit it with a laser and hit it with a searchlight to show the differences. In that instance I believe the searchlight was worse.

There was a case of an American pilot hit by a laser emitted from a Russian ship of some sort... that wasn't light show stuff, that was high powered IR purposely aimed.

Also there was a CSI Miami episode (haven't seen it myself yet) where supposidly they go to a plane crash, look at the guys eyes and recognize that he was hit with a laser pointer. Not gonna happen. If someone was trying to interfere with planes by flashblinding the pilots, it would take a high powered system, and there would be a visible line going back to the source. It wouldn't be very mobile, although I'll admit probably more mobile than a 7kw drive in rig

There *were* issues in Vegas with the Casinos running sky scanning shows and planes from what I've heard.

Hope this clears up some of the things from the laser world.