Whats the principle behind Schuster Focusing?

[TachyonLord]

I know its something related to the asymmentry in the i-d curve but its still not clear.

 

[davenn]

I know its something related to the asymmentry in the i-d curve but its still not clear.

there's lots of info on google etc, here's a couple of links, I'm sure with just a little effort, you can find many more

https://iopscience.iop.org/article/10.1088/0031-9120/26/1/011/pdf

https://www.quora.com/Whats-Schusters-method-in-optics-How-do-I-perform-it

If, after reading some articles, there is something specific you don't understand, link to the article and
state the bit you are having trouble with Dave