Canon Japan has filed a new lens patent on 135mm f/2 Apodization lens. From Wikipedia:
An apodization function is used to purposely change the input intensity profile of an optical system, and may be a complicated function to tailor the system to certain properties. Usually it refers to a non-uniform illumination or transmission profile that approaches zero at the edges.
Patent publication number 2016-218444
Release date 2016.12.22
Application date 2015.5.20
Example
Focal length 130.98
F number 2.06
Field of View 9.38
Image height 21.64
Lens total length 159.05
BF 53.99
Canon’s patent
Even when there is vignetting, a good blurred image at all angle of view
via: EG