I have just completed designing and building a prototype flashlight that is using a catadioptric focusing lens, giving a 3 degrees focused beam, with a very small amount of side spill.
The lens is designed specifically for use with an LED, it is not a camera lens or telescope lens refitted to a flashlight. The lens has one collimator and two reflectors: a collimator, a reflector on the back, a small reflector on the front of the lens. Emitted light from the LED reflects back from the small reflector on the front, and is focused forward.
The flashlight is using a Cree XM-L2 LED, a amperage regulating circuit (same as is in my EDC-XML-R, with same brightness levels options). It is 1000 lumens on high power, approximately. On high power I measure approximately 40,000 to 50,000 lux. The beam cuts through the night like a saber, can be used as a star pointer. This flashlight is powered from a single 18650 battery, and I’m also developing a longer version to hold 3 batteries, for much extended run time on high of perhaps 3 hours. This short version runs for 1 hour on high (depends on batteries used.)
To the best of my knowledge, no one is producing and selling a flashlight using a catadioptric lens, and no one as far as I can tell has used this lens in a flashlight (might be, but an internet search did not find it.)
I do not have a nave for this flashlight yet. I’m thinking of: Spotter, Searcher, SearchLight, etc.).
looks great! if i understand the orthodox use of the term, i have not seen a catadioptric design for a flashlight before this one, as opposed to TIR-style independent path optics. other combinations of reflective and refractive optics have been tested (for example EBRZM-16 just over 1000 Kcd thrower, which might fit some definitions of catadioptric). i did just find these optics for sale however, and i’m not sure how they define the term: http://www.roithner-laser.com/led_highoptic.html
is the collimator in your light there just to correct aberrations? does it introduce any (chromatic)? it looks lighter-weight than a TIR.
looking forward to seeing the beam pattern from this!
Of finally something interesting after all those gb that are hitting so hard my wallet : p
Cool project and serious implementation, allways wanted to complete my flashlight collection with an catadioptric type of flashlight.
Have seen thise type of lens before, somewhere on sale and studied a bit the theory back then, i have to find where i read abot thyse type of systems.
What are dimensions of the head ? And some beamshots would be cool together with total lumens output of the system with that xml at 3 amps.
Congrats on your original build again, i like it.
Holy cow Wayne!
A Cat flashlight. That’s really thinking outside the box.
I love it.
Couple of questions…what is the f ratio of the optical system, and what is the reflectivity level of the mirrored surfaces?
According to my understanding (had to look up the meaning of the word, ) catadioptric lens simply means a combination of lenses and reflectors. Some telescopes use catadioptric lenses, as do cameras.
Anyway, I’m impressed with the beam. For a XM-L2 LED to produce this high a lux reading at normal power levels is impressive.
is the collimator in your light there just to correct aberrations? does it introduce any (chromatic)?
I don’t know.
It produces a square beam. I’ll get some beam shots soon. The beam is easily viewable through the night air.
The head is 3” diameter, 1.8” long. At first I simply made the head to screw onto a EDC-XML-R flashlight. It worked fine, but looked real funny. So I made the new body, nearly 1.5” diameter at the base, and reduced it to 1.25 part way back, of a similar design to my EDC but fatter. The tail cap is approx. 1.5”, and overall length is 6”. I’m using the EDC-XML-R circuit and tail cap click switch.
Many of my products began with a customer contacting me and wanting a particular design flashlight, and this is the case with this one. However, he wants it longer with 3 batteries and 3x’s longer run time.
I have a circuit on order, which drives from 5.5v to 12v, and powers at 3A, so will be a bit brighter. We all know the XML can be powered up to much higher levels. But I’m really happy with the beam.
Regarding lumens, I think it would be 700. Although the LED is putting out 1000, the lens is only 70% efficient, not so good. But most of the emitted light is in the 3 degrees or so beam, so it is very intense. I have no way to measure lumens. I can measure lux readings, although I have an antique light meter. The circuit I’m using, power level on high setting is exactly 2.8A, it is current regulating not voltage regulating.
I’m trying my best to be realistic with the figures.
I didn’t think of it, someone else invented and patented the lens. I might be the first to take it and try it, perhaps not. Besides a flashlight, what would use a super narrow beam like this? Not a bike light, or head light, it’s too narrow. It’s good mainly for seeing far off, like search and rescue work, hunting varmints, etc.
Generally speaking, I like a beam that is not so narrow, and has a lot of side spill. Makes for a better all around use flashlight. Even I use my EDC-XML-R mostly on low power. But it is nice to have the power when needed.
The XM-L2 LED is not specifically mentioned in the specs, but I believe it would be similar to the smaller P4 LED. I do not really know all the ratios and reflectivity. The efficiency is mentioned (70%) and the Cd/lm are also mentioned (P4 is 139.6/lm.)
I’m glad you think it is nice looking. I was worried about the appearance, such a big and short head. When I was a kid, my older brother teased me about having a big head and a pencil body, so I have issues with that.
Excellent build. Looks good and sounds like it works great as well. I’ve never seen a catadioptic system used in a flashlight before, only in film and DSLR cameras and it’s interest ing when you say it could be used as a star pointer because that’s where I first came across catadioptics, in an astrological telescope. They can give crazy long focal lengths without being too long in structure.
It seems like 1000 lumens and one hour run time on a single 18650 would be a good usable performance and you can always take a couple of fully charged spare 18650’s along just in case.
Lovely job!
I had a Sigma 600mm mirror lens wayyy back in the 80’s.
The main advantage of Catadioptric lenses (mirror lenses) was that they had virtually no chromatic aberrations.
… one of the main problems with long lenses.
i think it’s a great advantage of mirror setups too… i’m unclear on the details of this flashlight optic however. i read that in imaging setups the lens is there to correct spherical aberration only. the lens looks to have some other purpose in this light.
hey Rufusbduck how are you doing, did you get the light? i just got my, really cool stuff, will try to make an review on it when i am in the right mood. so far its the best flashlight in my collection by a great margin, well maybe only my build can rival it a little by the amount of time i like to spend playing with them.
about Catadioptric system definition, i just now realize that my build can be considered a Catadioptric system my ebrzm looks to be in the same category too, lool i looks like i have an hidden love for Catadioptric system and i didn’t know
seriously now, before when i read Catadioptric lens use in flashlight i strictly imagine this type of implementation in my mind :
and it looks like elektrolumens is using similar setup, but its difficult to say for sure just by looking photos.
now i see, i have probably read that pdf that Gj posted in the post above and the source of lens here:
elektrolumens 70% efficiency is relatively good i think for a compact spotlight system. is it hard to make it focus right?
