Pin Point Light Source (Construction Plans Needed)

How much money do you have for the project, and how much hands-on work do you want to do? Do you need white light, or would a particular color, like monochromatic green, be better?

Some options as examples: from Cree (http://www.cree.com/) you can buy large (100 mm diameter) white LED module kits for $200 that are ready to assemble, or you can get small 3 mm two-pin white LEDs for which you'll need to supply the wiring, power source, and support structure. (You'll need to contact Cree for pricing for small quantities of these (http://www.cree.com/ ledlamps HB3 round).

For either of these options, you'll probably want a pinhole to let the light pass through. Depending on your use, you can make your own by drilling a hole in a piece of metal or you can buy a precision pinhole from Edmund Optics (http://www.edmundoptics.com/) online catalog. Either way, you'll need a support structure to hold the pinhole in place.

Would a pinhole be sufficient, or does the light need to be collimated? If it needs to be collimated, you'll need a lens system. There are various options if you need a lens.

Have you considered a laser diode + collimating lenses? (Usbport's point about the light spectum should be taken into account).

Can you specify required aperture and intensity?

I've got a green laser pointer that has a pretty fine point. Cost was about $35 as I recall.

(and no, I don't mean a light saber!)

Thanks all for the suggestions.

The one that works best happens to be the least expensive and easiest to build.

A white LED behind of piece of aluminum foil with a 0.020" hole (a needle) aimed onto the polished surface of a .25" diameter ball bearing an inch and a half away.

When the reflected image of the light is seen on the spherical surface of the ball bearing from 100 feet away, the size of the

point source will be reduced and will approximate the seconds of arc of a star on a clear night.

I was not able to model the point source in the above rendering but I think you get the idea. The fixtures are small brass tubing. A suitable plastic box from Radio Shack and we are done.

Thanks to all who responded.

Laughing Jaguar

May be you can try the pointer LED used with Power point display. The battery operated pointer costs about US$ 2 or less. It can really give a small spot of light about 10 meters away !!!

You need to be careful in selecting your 'white' LED if you are concerned about chromatic issues. Most 'white' LEDs fool the human eye/brain system by providing light at three fairly narrow peaks in the red, green, and blue parts of the spectrum. Some more advanced types use a phosphor to add outputs at other wavelengths, but the final result is quite different from a black body radiator such as a star.

Google Artifical star,

there are thousands of pages of how to make an artificial star from Amateur telescope makers from round the world.

Joe

GA. Hey, LJ - check it out.