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A patent application showing a new mirror lens design from Canon is confusing to say the least. I figured the days of the catadioptric lens were well behind us, but here we are.
Specification from the patent:
- Focal length: 400mm
- Aperture: f/5.6
- 2 ω: 1.96
- Image height: 13.66mm
- Back focus: 33.07mm
- Lens length: 247.73mm
The image above from Northlight shows the light path through the lens. The light path is in red, and the mirrors are outlined in blue and labelled.
The blue bits are mirrors. The light comes in through L1, bounces off M1/M2 and through a hole in M1 back to the camera.