Reflectivity

Extremely bright.. dual level brightness .. Excellent focusable optics. It will project a tight square that's about 8' across at ~120'
This is the best flashlight I've ever used. I use it to temporarily light up a room by reflecting the beam off of anything.
It's overkill for camping. Hardwired it will do the job you need, but it may be to simple and inexpensive for some people.

..This IS an and unpaid endorsement for the Duracell Durabeam 1300 lumen flashlight

I think I might need one of those!

I think I need one too.....not sure what for

You'll put your eye out!

I have one similar, so bright it beats headlights on my truck hands down, and can focus down to a clear image projected of the LED cluster.

http://www.uncg.edu/iar/elight/learn/determine/lc_sub/mat_prop.html

GA. The ellipsoidal spotlight can easily handle this distance.

https://en.wikipedia.org/wiki/Source_Four#Barrel

This sounds like a job for a "light pipe" (fibre optic). They are used to bring outside sunlight into buildings. One would expect that they could be and are routinely connected to light sources to do what you want.

How do you figure? Light 'pipe' is used to bring light from a source, through an opaque or thick surface (like a building) without power being consumed at the point of illumination.

He didn't mention not having power available the the point of illumination.

If the surface to be illuminated is not accessible, then one would sure not want a powered device in that area as getting to it would be problematic. So a passive device is indicated.

The surface is located ~120 feet from a potential light source.-That is very non-specific. The light source could be parallel with the plane of the surface for all we know, thereby giving the surface no illumination at all. Need more detail.You say that the surface is inaccessible. Is it in a ravine on the moon? An alternate universe?
I am assuming that light incident on the surface would be ~99% reflected.Why? You haven even mentioned the specific angle of incidence or range or ballpark,..... something! which I think would be rather important here.
You haven't even mentioned where viewers will be and a description of what you want them to be able to see.
"More details provide you can, better answer have you will!"Yoda

Laser?

I agree. The use of a laser system was also among my first thoughts, but I have assumed (probably erroneously) that such systems are incredibly expensive.

This is a joke? Right?

Give me an example where lasers are used as a source of basic illumination?

Where are your project details?

Indoors or out? Temp? humidity? Power consumption? Cost?

cough overkill cough $1500 RGB (white) graphic projector.

Depends how bright you want it illuminated. A car headlamp would pick it out at 120', but not focussed on your 8' diameter.

Road sign makers use small clear glass beads as retroreflectors. They are embedded in a clear varnish. More details. Browse these and choose those that can tolerate the outdoor weather and UVYou can also buy stick on, or buy a used white movie projection screen with retro embedded already(outdoor survival???)

Retro reflective paints etc

I have no idea from the information supplied as to whether price plays a role or not, but I feel that a secondhand Xenon (Spelling?) car headlight, especially one using the (I believe) Japanese system bulbs, as against the relatively expensive European system, might help.

You do need the in car Xenon High voltage unit and the wiring, don't forget!! Thats the bit that "hums" when the headlights are running!!

Xenon uses relatively little power at 12 volts nominal, as against conventional bulbs. But modern LED headlights probably use even less and may have a longer life.

The European system does have one possible advantage in that there is a large lense incorporated and if this was made adjustable, then the size of the illuminated area would be adjustable.

As both systems have been around some time, a scrap yard purchase, especially if one is found that has only been externally damaged, which no one would want to fit on their car, might be the cheapest alternative.

Spare bulbs from the same source should be pennies instead of around $100 each!!!

I hope this helps.

Let us know how you get on!!!

Thanks Andy.

No problem, thats why we "meet" online to help each other......

Let us all know what you finally decide to do and do make some pictures as well....

Thanks back for a great idea in the first place, proper CR4 stuff!!

I do believe you are tackling the impossible. The only way to get that high a reflected power might be through total critical angle reflection. Instead of playing 20 questions (and no answers), could you elaborate a little bit more on the why and the situation of this disc? What is your present potential light source? Are you able to manipulate the disc to aim the sharply reflected light?

More details, otherwise we are just feeling up the elephant, once again.

Why provide details when he can provide frustration?

I know a thing or two about lighting, but I'm done

I don't see why you think this is impossible. The LBT has two 27 foot wide first surface mirrors. These mirrors are above 95% reflectance. The light source they view are much farther away than only 120 feet. And who hasn't started a design by first assuming ideal parts that cannot exist.

I agree that the OP has not posted anywhere near enough information for us to provide a definitive answer. We don't know if this is or is not limited to visible light. We also have no idea how bright this unreachable item is supposed to be illuminated. Bright enough for a person to admire Raphael's exquisite choices of pigment or only bright enough that the diffuse illumination on this cliff will be seen by aircraft flying by at night. We have no idea how bright any background illumination will be beyond or in front of this object so a clear contrast be easily discerned or is the goal to hide a change in depth by illuminating objects farther away just as bright as things much nearer.

Maybe it's an amphitheater for a flea circus, and the fleas like the heat from the lamp...

...or a rudder for a buck's dutt.

Question #20: Is it a drive-in movie theater? That has already been invented, gone (mostly) out of business except for a few notable exceptions, and been turned into white trash trailer parks in Kansas.

http://www.larsonelectronics.com/p-47085-15-million-candle-power-rechargeable-hid-pistol-grip-handheld-spotlight-35w-hid-25-hour-run-time.aspx

Silver, the metal with the highest reflectivity, darkens in air. Aluminium is a little lower, but self protects with Al2O3 layer and is the reflector of choice.

If you want a mirror the beam follows optical laws. If you want broad spectrum emission, as from a white paint, that is about 70% in all directions.

What is the application?

But I don't suppose the material can be selected, it sounds like an existing (or proposed) object he wants to illuminate. I don't think he wants to project the reflection anywhere specific, just to make it visible. But until we know more detail, and how strongly he wants it illuminated etc, we're stuck.