Canon Patent Application: Super Telephotos

This patent application is about reducing the thermal expansion and contraction that occurs of the lens barrel.

Current methods of reducing the effect include Canon's signature white color on the lenses, and in this patent they mention they have a heat insulating member inside of the lens.  The concern is that this heat insulation increases the size (and I would imagine the weight) of the lens as well as the cost of the lens.

This patent application deals with how to reduce the effect on the optical performance when temperature changes occur on the lens.

There are several embodiments of lenses mentioned in this document.  They are mostly secondary to the patent application.

focal length 392.55 
f-number 2.90 
half angle of view 3.15 
image height 21.64 
total lens length 372.00 
BF 60.70 

 focal length 292.46 
f-number 2.90 
half angle of view 4.23 
image height 21.64 
lens total length 273.98 
BF 62.03 
 

focal length 488.82 
F number 4.10 
half angle of view 2.53 
image height 21.64 
lens total length 411.90 
BF 71.62 

focal length 778.70 
F number 5.83
Half angle of view 1.59 
image height 21.64 
lens total length 486.03 
BF 71.54

Japan Patent Application 2019-078948