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help on project for custom made projector, spherical mirrors.

help on project for custom made projector, spherical mirrors.

help on project for custom made projector, spherical mirrors.

(OP)
Hi Everyone, I tried this thread before but it didn't go through so here it goes again.
I'm a Physical Computing teacher at the School of Visual Arts in NY and I also have a new media studio based in NY.
I'm doing a public art commission for the University of New Mexico that incorporates a custom made projector, since my field of expertise is computers and electronics I need help designing the optical system, or counseling on how to even start.
To give an idea of the problem...the projected image is 30 feet diameter (circular), the projector is at 31 feet from the center of the screen. The original size of the image to project is about 6 inches in diameter and the projector is 15 feet off-center with the screen, what we were thinking to solve with a spherical mirror (like the ones used on short throw projectors).
We will use a couple of 2000W metal halide lamps as light source.
You have more info of the project at www.federicomuelas.com/blue_flower. Any ideas on how to even start to working the optical system out? places to look for help? etc?
Thanks!!!
Federico
 

RE: help on project for custom made projector, spherical mirrors.

The thread went through (I read it), but I imagine it was removed (possibly because this isn't directly related to professional engineering practice?).  This one may get removed again...

Dan - Owner
http://www.Hi-TecDesigns.com

RE: help on project for custom made projector, spherical mirrors.

(OP)
oh, I see, but how  designing a optical system doesn't relate to professional engineering practice?
 

RE: help on project for custom made projector, spherical mirrors.

It's not so much whether designing an optical system relates or not to "professional engineering" practice, it's more whether the question is being asked by an "engineering professional".

Per the logo (top LH corner), the focus (no pun intended) of these fora is to create "INTELLIGENT WORK FORUMS FOR ENGINEERING PROFESSIONALS". Many members take that literally and will Red Flag any threads that are not from (or perceived to be not from) a non-engineering professional.

RE: help on project for custom made projector, spherical mirrors.

Additionally, since you are also technically recruiting, that is not allowed in the forums.

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: help on project for custom made projector, spherical mirrors.

"Any ideas on how to even start to working the optical system out? places to look for help? etc?"
That's not recruiting, that's asking for advice.

RE: help on project for custom made projector, spherical mirrors.

(OP)
Ok everyone,
I'm stepping out of the forum,  I don't want anyone to feel uncomfortable about this issue.
I'm not trying to recruit anyone (or at least I think I'm not), and although I'm not an engineer professional I have a master in computer art and I teach Physical Computing in the Master in Computer Arts in the School of Visual Arts. In fact there are two engineers helping me to figure out the technical part of the project. I met them through the "Nuts and Bolts" forum, the same way I'm doing with this forum, just asking for advice on where to start, and then they decide to help all the way because the found the project interesting.
But I think I misinterpreted the function of this forum and I apologize if I have offended anyone.
Best
Federico
 

RE: help on project for custom made projector, spherical mirrors.

Federico,

I'm usually the heavy-handed red flagger on these forums, but thought your original post (while not quite profession-related) was still within the bounds of reason.  Others may disagree.  I would suggest sticking around for a little while longer to see if anyone is able to offer any further help.  If not, the thread will either go unanswered or someone will red flag it again.

It may be better to find someone who has professional experience in optics first, then point them back to this thread for specific questions.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: help on project for custom made projector, spherical mirrors.

(OP)
Hi everyone.
Sorry for the super long thread, but let me formulate some specific questions regarding the Custom made projector. I realized I was to vague in my previous posting.

The Department of Optical Engineering of the School of Engineering of UNM will be helping on the design of the projector but I would like to figure out as much as possible on my part before start working with them.

I'm attaching two PDFs with drawings of the projector,  if you can give me some advice on the following questions I would really appreciate!

Thanks.

Lights:
Since the lifespan of the OSRAM 6,000 W lamp is so short and the price of the bulb so high, is it possible to use three Sylvania 2,000 W? if so, how they would be aligned? Could each lamp support the heat produced by the other two? Even if we are using two 230 mm cooling fans?

Heat dissipation:
Regarding the fans... ideally the air flow should be ascending, right? but I'm afraid that the air coming from the top fan could create some kind of "hot Air" mirage on the image. if so, what would be more effective in terms of cooling the lights? Reversing the air flow (descending) or put the fan side/side or bottom/side on the projector? Would it be a good idea to combine Peltier Junctions with the fans?

I'm thinking on using a Schott KG-5 Heat absorbing glass to dissipate the heat before it reaches the water container but... two problems, first, the glass only comes in small sizes, 75mm square and can only take up to 300 Degrees Celsius (enough for these lights?), can anyone else think about a different heat Cut-out filter I could use instead?

Water container:

Based on the tests I have made, the water container doesn't modify the focal point on the projector, since the back and front sides of the glass are parallel and perpendicular to the projection axis, am I right?

Lenses:
I guess the best real solution for this finite/finite conjugate will be to use two Achromatic Lenses to increase the image performance of the system and be able to adjust the focal length, comments?

Image distortion:
To correct the distortion on the image because the off-axis position of the projector I was thinking on using a Aspheric mirror, such us the one they use in short throw projectors. I guess programs such us OLIVE won't be able to calculate the variables of such a complex element, right? should I work directly with the manufacturer of the mirror (holographix LLC may be?).

This is the best I can do in terms of formulating these question, forgive me for any or all the mistakes I may have made.

Any advice will be highly appreciated!.
Thanks  
Fede

 

RE: help on project for custom made projector, spherical mirrors.

As long as your fans are strong enough (good airflow), it won't matter a whole lot which way you blow the heat (up or down)... just make sure you're blowing it away from components, including  the lamps themselves.  Yes, hot air tends to rise, but with a forced flow it will go where you tell it to.

I'm not sure if the Peltier junctions would do you more harm than good... it depends on what part you're trying to cool.  They are extremely inefficient, so if you're simply trying to cool the airflow near the bulbs it will be worthless... you still have to somehow remove the heat from the other side of the junction (more fans!).  If you're trying to keep an item cool directly (e.g., the base of an LED), then direct attachment can certainly help, but you'll still need to get rid f the extra heat.   I don't think you have such an option with the bulbs, so without knowing more about the system build I would probably ignore Peltiers.

Will heat hitting the water sample cause a problem?  It may give some interesting effects with localized water eddies, especially with the ink.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: help on project for custom made projector, spherical mirrors.

(OP)
Thanks a lot Dan,
let's forget about peltiers then. We would have to add to the fans some air filter anyway, to keep everything dust free, right?.

also, I wonder if we can use a Monolithic multi-faceted mirror for combining multiple beams from different light sources (three 2000w bulbs) by reflection.
Thanks
Federico
 

RE: help on project for custom made projector, spherical mirrors.

For this application, you won't need perfect alignment of all three lamps, just "close enough"... plenty of light is going to get blocked at the edges anyway.

Is this is a short-term or long-term display?  If short term, I probably wouldn't worry too much about dust in the airways, it won't have enough time to collect (unless your environment is dust-ridden.
 

Dan - Owner
http://www.Hi-TecDesigns.com

RE: help on project for custom made projector, spherical mirrors.

(OP)
hum, I see what you mean, so the lamps don't need to be totally on the axis of the projection, right? I'll try some arrangement for the three lenses and post it as an image if you don't mind.

the piece is permanent (at least 20 years!...) but the cleaning of the piece will be part of the maintenance of the building, I just need to make sure there is an easy access to the parts that need to be clean. and that they know what are they doing too...
thnx Dan
f


 

RE: help on project for custom made projector, spherical mirrors.

There are assertions in the website that are not supportable by physics, i.e., "the definition of the image is infinite" is nonsensical, since any real optical system is limited by aberrations and diffraction limit.

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: help on project for custom made projector, spherical mirrors.

(OP)
You're right, thanks for the note IRstuff. it was a way to emphasize that the projector definition is not dictated by a LCD screen as in LCD projectors since is merely optical. but its an erroneous definition.

RE: help on project for custom made projector, spherical mirrors.

Have you run tests of the projector under real conditions? I'm not sure that you have sufficient cooling capacity, and it's not obvious how access to the projector will be limited to prevent burn injury.  The projector will get EXTREMELY hot without a massive cooling fan.  Strict natural convection would likely result in surface temperatures on the rear of the projector exceeding 200°C.   

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

RE: help on project for custom made projector, spherical mirrors.

(OP)
good point IRstuff,
The projector will have a series of sensors (such us liquid and heat sensors) to shut the piece down in case there is some water leak or too much heat. so we will install a K-type thermocouple close to the lamps to make sure that the back of the projector can only be opened once the temp has dropped enough after turning the projector off.

IRstuff, do you mean 200 degrees per light?, then, if we end using three lights we shouldn't use aluminum for the frame, to close to the melting point, we should go with Stainless steel instead.



 

RE: help on project for custom made projector, spherical mirrors.

No, that was the exterior of the projector housing; the interior will probably be a LOT hotter.  Note that the bulbs you mentioned are specified to be fully operable at over 400°C.

I took, I think, 4 kW on something like 3.5ftx6ft of convection area with 10W/m^2-K natural convection coefficient.  Very crude, admittedly...  That resulted in a 205°C rise above ambient, hence the need for big fans.  Based on a still relatively hot 20°C rise (against 49°C ambient), you can only dissipate about 200 W through the housing, which means that the remainder of the bubl power must be removed by blowing air, or a liquid cooling system.

TTFN

FAQ731-376: Eng-Tips.com Forum Policies

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