Canon Patent Application: DO Supertelephotos

Another patent for diffractive optics (DO) super telephotos has appeared.  This seems to be a subject of ongoing R&D inside of Canon, with several patent applications listed for these lenses using diffractive optics.

There was a rumor about super telephotos for the RF mount using Diffractive Optics, perhaps this is related.  For supertelephoto lenses, the back focus is so large, that the lens could be made for just about any mount.

This patent application describes two lens embodiments, one for a 300mm 2.8 and another for a 400mm 2.8 DO supertelephoto.

Focal distance      392.58 
F number              2.91 
a half field angle    3.15 
Image height         21.64 
length of the lens  363.53 
BF                   59.15 

Focal distance      293.40 
F number              2.91 
a half field angle    4.22 
Image height         21.64 
length of the lens  274.00 
BF                   59.35

Japan Patent Application 2018-189878