Use optics(RMB click)
Then flick mouse to one side quickly, while simultaneously zooming in(RMB hold).
This will sometimes unzoom your view, and take you out of optics mode.
~OR~
stand still and go to alt-look mode(altx2)
flick mouse to either side while zooming in(RMB hold)
the view will reset and go to optics mode and also zoom in at the place you were looking when you pressed altx2