Hi
I stumpled upon various posts in this forum of Uho's DIY lenses. He has a good
info page for that and I really would like to make such a magnifying lens too, BUT not for ~200€!
So I just wonder if this could be done with this cheapo lenses, assuming that they are plano-convex, or meniscus at least:
https://de.aliexpress.com/item/China-ZnSe-Co2-Laser-Focus-Lens-12mm-Diameter-FL38-1mm-1-5inches-For-CO2-Laser-Engraving/32812296054.htmlThen I just for fun put a d=20mm/f=76,2mm and a d=12/f=38,1mm lens in this simulation page.
So the overall length of the "scope" would be ~10cm, I used a 5mm diameter for the Seek lens.
![](http://p-bg.de/seek/lens_test.jpg)
Do you think this is doable? Of cause I would not expect super sharp images...
And another question: To get proper focal length of the lenses that I draw on that page, I first set the refractive index of the lenses to 2.39 for ZNSE@~12µm, then I manipulated the bend-side of the lenses so that the beams from a light source meet at the focal length from the specs.
The question is now, as others mentioned here, they would rather use a Germanium lens because of its higher (~4) refractive index to make the lens shorter... But
thats what I dont understand, if you use a GE lens the focal point would be closer to the lens... shure, but dont you choose the lens on its focal length? So should'nt make a 70mm GE lens no difference to a 70mm ZNSE lens with the only difference that the GE lens would have a much more "konvexetivity"
![Shocked :o](https://www.eevblog.com/forum/Smileys/default/shocked.gif)