Anyone tried to make a mirror-lens light?

[Canopus]

i found the Arc Tank Light very interesting and thought to myself could that be replicated with a mirror lens like the ones used on SLR cameras.

they are sold everywhere and are around a 100 dollars, (ex. http://amzn.com/B000HCNMPQ)

here is a diagram of how the mirror works, what if an LED emitter is placed instead of the correction lens and a host behind.

 

[Walterk]

I have a 500mm focal length lens, and herefore expect this thing to give a very very narrow beam. Using a Led as you described, would give hardly a visible spot of light projected.
The focal length is 500mm ( I don't know if the focal length for lighting-purpose would be 500 or 250 as it is reflected to the mirror, but then still; ) that is too long to effective catch any Lumen form the Led.

You would still need a correction lens in place of the original correction lens.
Using a pre-collimator lens can make it work, but finding out the right lens for that is a lot of experimenting, or someone with raytracingsoftware to give directions.
The pre-collimator would narrow down the emitted light from the Led to redirect at the right angle to be used by the first mirror.

To my opinion the main advantage of this,over the usual aspheric or reflector set-up, is when you really want a pencil-like beam. Or a unique adjustable specialty light !
It can work, but is a lot of testing before making it work.

Notes:
- Keep in mind the effective surface area of the lens, it is not impressive on its own.
[FONT=&quot]In the thread Formula for calculating throw using aspheric lens (post 93) you see how pre-collimating works.
- Using a cheap telescope and adding a Led is probably cheaper, the same principle I think. Or an aspheric for that matter. But not as much fun!

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[saabluster]

This essentially has already been done and is on the market. Look at the Pelican Recoil lights.

 

[Tally-ho]

This essentially has already been done and is on the market. Look at the Pelican Recoil lights.

Quiet the same. Recoil flashlights has an emitter in front of the mirror. With OP suggestion, LED will be in a pill into a host for better heatsinking.

 

[Walterk]

Like a off-the-shelf 35mm dia flashlight with tight focus?!
Quick and clean build promised :thumbsup:

 

[Canopus]

Ok I just tried a canon 250mm lens with an led daylite. The beam was almost a 18 inches wide from 5 meters, at 10 meters around 40/50 inch size of a large tv.

1/6, 1/125 sec
How will the 500mm mirror lens treat this experiment differently, would the beam be half the size? Or the second mirror cause a dark spot from close distance?

 

[Canopus]

front of the light

most of the beam was from the emitter not the reflector.

 

[Tally-ho]

Quick and clean build promised :thumbsup:

It's up to anyone to decide how clean and quick he wants it.
Maybe it's quicker to have about the same result with an aspheric lens but anyone is free to have fun by testing/experimenting.
An issue with those camera lenses is that they have several grouped glass elements. More glasses, more brightness loss (there is only leica which manufactured a lens with a minimum aperture of f:0 ,95 or something like this (EDIT: there is even less, like f:0.7), very expensive. It is more to mention it than to suggest it for a mod).

 

[Walterk]

How will the 500mm mirror lens treat this experiment differently, would the beam be half the size? Or the second mirror cause a dark spot from close distance?

You shouldn't see the shadows like they show now.
I think you should try this without the reflector from the flashlight, and at several distances to see what focal length works best.

 

[Canopus]

camera lenses is that they have several grouped glass elements. More glasses, more brightness loss

thats why i was thinking about a mirror lens, it only has a single lens at the very back.

i'm only using the 250mm lens trying to figure out what the size of the spot will be. what it doesn't show is whether the mirror lens will produce a halo or spot and at what distance. ​

 

[Tally-ho]

thats why i was thinking about a mirror lens, it only has a single lens at the very back.

Are you sure, well i never had one in hand to figure it out but:

Opteka 500mm f/8 High Definition Telephoto Mirror Lens
Groups/Elements: 8/9
Opteka 500mm f/6.3 High Definition Telephoto Mirror Lens
Groups/Elements: 6/7

I don't know if the mirror counts for one element but probably there isn't only 1 single lens at the very back.
Anyway, good luck with your mod if ever you will try it...and have fun.