Burning lens for ARCTIC

Ok I made a lens from a eye piece from an old scope I had.
It burns just fine and all but I have a question on the lens im using. It appears to be two lens combined. Its looks like a biconvex combined with a biconcave... It burns either way direction I put it. But what would be the purpose of combining them? since both ways burn, is one way better than the other. Also, If you have a lens thats not AR coated.. can you buy some kind of wipe on/and dry type? if so any suggestions?

Thanks,
RDCII

It is most likely an achromat.
This means that two lenses of different composition (and therefore different refractive indices) are combined so that when white light passes through them the chromatic aberration that is caused by refraction is minimized.

With monochromatic light (like that from your laser) there is no need to use an achromat. There will be no chromatic aberration with monochromatic light.

You can separate the lenses by firmly pressing the edge of a knife on the "seam" and rolling it along the circumference of the lens.
They residual adhesive can be cleaned from the optics with some acetone.

ah ya wiki achromat lens. Makes sense being used in a scope from a gun.
mmmm so seperate them.. what would that accomplish? smaller size and still focus good to burn? Right now I blows through anything from 6-16' away. Even white paper burns almost instantly. I dont wanna effect that in anyway. My only unanwsered question would be, which direction see to be better? Ill post pics of both burning.


RDCII

RA_pierce said:

It is most likely an achromat.
...
With monochromatic light (like that from your laser) there is no need to use an achromat. There will be no chromatic aberration with monochromatic light.

Click to expand...

Achromats have reduced spherical aberrations too. That helps to get smaller beam spots.

A Thorlabs picture compares two lenses
http://www.thorlabs.com/images/TabImages/p615V20a.jpg