Canon Patent Application: Diffractive Optics 500 and 600mm Super Telephotos

Canon continues to pour money and resources into the development of diffractive optics super telephotos.  We have seen a prototype of a 600mm for over a year now, and here's another patent application that describes 500mm and 600mm diffractive optics super telephotos.

From my understanding, this patent deals with instead of making the gains by using a diffractive element size of the lens, in this case, they want to use a diffractive optical element to reduce the weight.

Focal distance 584.99 
F number 4.12 
a half field angle (degree) -- 2.12 
Image height 21.64 
Whole length of the lens 474.74 
BF 109.42 

Focal distance 487.49 
F number 4.12 
a half field angle (degree) -- 2.54 
Image height 21.64 
Whole length of the lens 409.74 
BF 98.42

Japan Patent Application 2019-008047