Flashlight physics

fhapgood

Newly Enlightened
Joined
Sep 4, 2004
Messages
52
Location
Boston
Flashlights come in several geometries: a straight tube, a tube with what I will call a tulip head,
with a reflector that looks like a cup, and a tube with a flat flared face. Probably there are others. My
question is: what does the geometry tell you about the behavior of the beam? What is the difference
in performance between a deep cup and shallow cup? Suppose I want a certain throw or spill shape --
like a very long throw or a very wide spill. What should I expect the lights capable of either to look like?
On a related matter -- Do real flashlights have lenses that actively shape the beam or is it all done with
reflector design? Are there trends of some sort on this issue??
 

mrlysle

Enlightened
Joined
Mar 10, 2011
Messages
649
Location
West Virginia
It gets really complicated because of the different emitters used. Small die like the XR-E, and larger, XP-G, and larger still, the new XM-L. Plus there are multi die emitters, even bigger still. The reflectors can be smooth, or textured. (aka "orange peel" or even lop, "light orange peel") Generally, small die emitters with deep smooth reflectors throw well. But there are some lights with textured reflectors throw well also. There are lots of lights with the "straight tube" shape that are very floody, and also some that are great throwers, depending on die size and reflector shape. Very small changes in the curvature of the reflector walls can make a huge difference. there are so many folks here on the forums that are way more knowledgeable than me that can hopefully give you better answers.
 

DM51

Flashaholic
Joined
Oct 31, 2006
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Borg cube #51
You posted this in LED Flashlights, but it is an interesting topic that applies to other types of light as well as LED ones, so I'm going to move it to the General section.
 

angelofwar

Flashlight Enthusiast
Joined
Nov 17, 2007
Messages
3,336
Location
South Carolina
DM51 doesn't miss a beat...probably woke up at 3a.m. to post this...LOL!

Yeah, lots of stuff goes into shaping light. One thing to look up is "Surefire DARPA". SF spent alot of money to figure out how to "push" every bit of light out the front when the first started developing there optics, as seen in the old KL3's. Brightest, Farthest throwing 19 lumens you'll ever see. My KL3 (I still have one, sold the other) out throws some ofmy 100 lumen lights, albeit in a pencil beam, but hey, science takes time.

Now we have the TIR/TIROS lenses, and SF went back to fresnel len (seen in light houses) with the M3LT.
 
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