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Is Canon Developing A Mirror Lens With Auto-Focus?

Canon Patent

That’s what a Canon patent application seems to suggest, a 300mm f/2.3 mirror lens. Read on.

Canon patent application 2023013456 (Japan, published 1/26/2023) discusses optical formulas for a 300mm f/2.3 mirror lens with autofocus. From the patent literature:

An optical system capable of sufficiently correcting curvature of field while being compact, lightweight, and having a large aperture ratio is provided.

Description of the Related Art

As a telephoto imaging optical system having a long focal length, there is a catadioptric imaging optical system having a reflective system and a refracting system. In such a catadioptric imaging optical system, Patent Literatures 1 and 2 disclose an inner focus type imaging optical system that is compact, lightweight, has a large aperture ratio, and has an autofocus function. ing. [0004]However, in the imaging optical systems disclosed in Patent Documents 1 and 2, the configuration of the reflection system cannot sufficiently correct the curvature of field.


The present invention provides an optical system capable of sufficiently correcting curvature of field while having a small size, light weight, and large aperture ratio.

An optical system as one aspect of the present invention has a first group that does not move during focusing and a second group that moves during focusing.

Example 1

  • Focal length: 298.89
  • F-value: 2.28
  • Half angle of view: 4.14
  • Image height: 21.64
  • Overall length: 177.20
  • Back focus: 65.95

Example 2

  • Focal length: 408.04
  • F-value: 5.00
  • Half angle of view: 3.04
  • Image height: 21.64
  • Total length: 189.17
  • Back focus: 47.69

More Canon patent applications are listed here. Some particularly interesting patent applications we think might get into production are these:

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