The Effects of Reflector Design and Lamp Orientation

[Me2!]

many fibre optic strands. In my thoughts you would end up with a single point light source,

That would yield many point sources. Even bundling the ends together the light intensity will be decreased by the spaces between the fibers and the % lost getting it into the fibre in the first place.

You get a higher density light packing and a more efficient system with a elliptical reflector.

[SmC252]

Originally posted by Dazzzla

You must be thinking of silicon based powder coating to with stand that type of temperature. Any thing over about 500°C will cause organic pigments to deteriorate. Have you got a link to the type that you are referring to? The common thermo-type powder coating will not stand high temps.



I think that you will find that the operating voltage for MH lamps is around 90-150Volts. And yes it can still kill.

DJ

500c is 932f, I know these lights don't get over 300C, I was simply saying I have seen powdercoating last on brake calipers that glow red/white hot which is around 1500f, which is past the operating range. I know this is not the working range desired, just saying that at that extreme temp it held up for much longer then I even thought it would, 3 months before any signs of serious wear. Not to mention it was touching and bonded to the actual hot surface, unlike a reflector. There are many cermic coatings that I have used that will withstand 3000f and one even operates at 5000f+ with no problems, but these are not the type of coatings I was talking about.

I know for a fact that the operating voltage for a 175watt MH bulb is about 330volts and appears to be fairly linear as you increase wattages of bulbs. (Almost a 2:1 watts to operating voltage ratio.) The starting voltage has the most current and the most voltage. (5000volts and 4-AMPS on JUST a 175watt ballast!) The imporatant part that I am trying to get through is that it's the current that kills people. Obviously the higher the voltage, the more likely it is that it can shock and kill you as it increase the potential for arcing. If you feel like hurting, try this, touch the positive and a ground, or just get a few mm from each one, it will shock the living hell out of you!

[Me2!]

If you feel like hurting, try this, touch the positive and a ground, or just get a few mm from each one, it will shock the living hell out of you!

This is bizzare "advice" even in jest. Moderator please edit that post.

[SmC252]

Originally posted by Me2!


This is bizzare "advice" even in jest. Moderator please edit that post.

Sorry, no bad intentions, I figure people on here to have 100+ IQ's and to understand it as a joke. (Can I say "If they were dumb enough to try such a thing, we're better off without em?") I think we ALL know electricity is deadly!

Honestly, thanks for the concern though. I'll be more careful.

[Nads]

Me2! Would this shape work to focus the light, or would this again give multiple light images, cos this was the principle that I was thinking of. It would prolly be too expensive to produce, the heat may fracture etc, but it would look good if it worked. and yes I know I spelt Hole wrong!. The glass would `in theory` work as a light guide.

[Nads]

Yes low voltage and amperage can kill. On tv, mythbusters showed that the body can endure extreme high voltage, whereas if the voltage is sufficent, and the amperage is 30ma (yes just 30ma), that is enough to kill, in relation to where the electricity enters the body. ie if the electricity enters thru fingers and exits futher up arm, you will get shocked and withstand a greater potential. if it enters thru fingers and exits thru toes then it goes past or thru the heart, which is stimulated by minute electrical pulses. I would also ask a moderator to edit this post saying to deliberatly arc two wires together. Thats how accidents happen. Mind you, they would be up for a darwin award!!

[Me2!]

The same solid light guide has occured to me and probably everyone who has spent time trying to figure these things out. Basically a fat fiber optic idea. I dont know if it would work you would have to ask a physicist. It's a light guide. This falls into the realm of non-imaging optic theory which is a huge topic. Its study would take you far away from projectors.

Problems i see would be material purity, cost of manufacture.

anyone else got thoughts on this?

[charlie10]

As I understand it, that teardrop shape would work well for concentrating a jet of liquid, but would not work for concentrating a beam of light. It's apparently impossible to concentrate a beam of light in that way.

Basically, you can't reduce the cross-section of a lightbeam without increasing its divergence-angle.

With that teardrop shape, we'd be trying to reduce the cross-section from the circumference of the lamp arc (white circle) to the smaller nozzle tip... ~5? times smaller (*)... , AND reducing the divergence angle from 360 degrees to the angle of the teardrop... ~20 times smaller? Apparently this is impossible.

Even as I write this, I think it must be possible. I mean, a bulb in a mirrored box with a small hole in it... all the light must eventually come out the hole, right???! I just tried it in a ray-tracer, and yes eventually all the light comes out (some after 100 reflections)...

Yet from what I've learned in theory:

- A beam of light from the sun has very small divergence angle. One can focus that beam's cross section to a very small area, using a lens... but, the divergence-angle will increase by at least the same factor.

OR

- A light bulb filament represents a small cross-section, but large divergence angle (it sends light in all directions). One can decrease the divergence angle, using a deep parabolic reflector... but, one will find the beam's cross-section has increased by at least the same amount.

OR (more obviously)

- One can decrease cross-section and divergence-angle, using an iris / aperature... but the lumens will decrease.

The basic principle is known as http://www.google.com/search?q=%22co...+of+etendue%22

(*): liberty taken, measuring in 2D instead of 3D

If someone could relate this to the current LED -array discussion, that would be great.

[Me2!]

Hi Charlie,

Thats not the whole story. What you say seems true in standard optics theory.

When I thought up the same thing he drew I researched it for a few days before I gave up on it and there are 2 fields, one you have discussed (also see the Feynman Lectures for a good discussion of it) and the non-imaging optics field.

For more than twenty-five years, the University of Chicago Nonimaging Optics/Solar Energy Group has been developing novel concentrator designs and optical.elements that achieve performance thought to be impossible under the limitations of imaging optics.

http://hep.uchicago.edu/solar/NIoptics.html

This is a nice summary:

Imaging optical systems like lenses in microscopes and cameras redistribute light so that an entire pencil of rays originating from one point of the source meets again in one image point of the target. For illumination tasks the source is homogeneous, i.e. all points of the source are equivalent and it is unnecessary to distinguish among them. Therefore non-imaging optics require that all radiation from the source, which is intercepted by the optical system, is finally transferred to the desired target. Dropping the unnecessary correspondence between origin and target enables new degrees of freedom for designing illumination devices. Thus, methods of non-imaging optics lead to solutions for many problems that are impossible to solve with imaging systems.

I gave up on it for practical reasons -cost- not because its not viable.

[Nads]

Having started this I soon realised one very important fact. The lamp would have lots of reflected IR, which in turn would overheat the bulb glass, which would in turn lead to failure of the bulb. It was a nice thought whilst it lasted, but you watch some clever person will build it and suceed. If it was to be built, the best place to get some idea of price would be at a glass blower, or some clever Italian in Murano, whom could prolly do it cos when I was in Venice 2 years back, they were producing some VERY similar looking bits of kit

And if this would not work according to the theories above, then can someone explain how it works for a condenser lens, or am I missing something here?

Nothing is impossible, just Improbable!