A bit of history about Canon and catadioptric (mirror) lenses
Keppler's Vault 61: Mirror Lenses - mike eckman dot com
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A bit of history about Canon and catadioptric (mirror) lenses
Catadioptric Lens: The Catadioptric Optical System Used A Combination Of Lenses Along With Mirrors To Reflect A 360° Field Of View Into The Optics Of The Lens. - Better Photography
Catadioptric lenses for 360° inspection
Bird Snapping] The power of a 500mm lens (Minolta 500mm f8 reflex lens) | Bird Snapping
Catadioptric system - Wikipedia
MTO 500mm f/8 - a fine example of a catadioptric lens