How come it seems like custom made flashlights that have multiple emitters (see Milkyspit's Snake Eyes and other mods as examples) seem to emit a single round beam rather than multiple overlapping circles? I don't know anything about optics or light science so how does this work?
Why do multi emitter flashlights create a single round beam?
- Thread starter sygyzy
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StarHalo
Flashaholic
The reflectors in these lights are designed to emit the usual general-use beam profile; a decent-sized hotspot with good spill. Like most flashlights, as you light something from a distance, the definition of the beam profile features isn't very sharp, the edges of the hotspot/corona/spill are soft and blend into one another. So just like taking a handful of flashlights bundled together and pointing them at a wall several feel away, all the individual indistinct beams simply create a larger indistinct beam.
DonShock
Flashlight Enthusiast
It is possible to tweak the beam positions by tilting the reflectors ever so slightly. I know because when I build multi emitter lights with the stock plastic lens, I have to be careful not to overtightenthe lens and push down on the outer edges of the reflectors too much. If I do, the stock lens takes on a slight dome shape and tips the reflectors away from each other and makes a big dim spot instead of a small bright one.
I am sure you could get them to exactly overlap, but that would only work for a fixed distance from the light. Just like there is a fixed focal point for any reflector, the point at which all the beams were perfectly focused would only be a specific point in space. The beam would be more misaligned as you moved closer or farther away. If you align the reflectors to correct the 1" of misalignment, at say 10 feet for example. As you move from the 0-10 feet, the misalignment will get less and less until it is perfectly aligned at exactly 10 feet. But as you move past 10 ft towards 20 ft, the misalignment will grow again until you have the 1" back again at 20 ft. And it will continue to grow the farther away you move from the focus point. But if all the reflectors are parallel to each other, that 1" misalignment is present along the full length of the beam. After just a few feet, it becomes invisible in the normal spread of the beam.
I am sure you could get them to exactly overlap, but that would only work for a fixed distance from the light. Just like there is a fixed focal point for any reflector, the point at which all the beams were perfectly focused would only be a specific point in space. The beam would be more misaligned as you moved closer or farther away. If you align the reflectors to correct the 1" of misalignment, at say 10 feet for example. As you move from the 0-10 feet, the misalignment will get less and less until it is perfectly aligned at exactly 10 feet. But as you move past 10 ft towards 20 ft, the misalignment will grow again until you have the 1" back again at 20 ft. And it will continue to grow the farther away you move from the focus point. But if all the reflectors are parallel to each other, that 1" misalignment is present along the full length of the beam. After just a few feet, it becomes invisible in the normal spread of the beam.
StarHalo
Flashaholic
As the others have noted, any time you have more than one light source, you can only "aim" them for one distance. You could use a focus mechanism that you could operate manually, similar to the Archimedes design (multiple reflectors/soruces on a surface that can be adjusted to varying degrees of concavity/"point-inward-ness".)
It is possible to have a distinct hotspot for each source, all you need is the proper reflector (huge and deep) or lens (optic) to create the thinnest possible beam for each emitter. A trio of Cree R2s behind large aspheric lenses would throw three very well-defined hotspots.
