New Canon Patents for 20mm f/1.8, 28mm f/1.8 and 24mm f/1.8 Lenses

New Canon Patent applications discusses optical formulas for three RF mount lenses. These lenses are 20mm f/1.8, 28mm f/1.8 and 24mm f/1.8 with backlight control.

From the patent literature:

An object of the present invention is to provide an optical system that is less affected by unnecessary light and has high optical performance.

Description of the Related Art

There is a demand for further improvement in performance and miniaturization of photographing optical systems. [0005]When trying to improve the performance of an optical system, the number of lenses constituting the optical system increases. On the other hand, if an attempt is made to reduce the size of the optical system by shortening its overall length, the distance between the lenses constituting the optical system and the distance between the optical system and the imaging surface will be shortened. As a result, unnecessary light (ghost) caused by reflection of light on each lens surface easily reaches the imaging surface.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide an optical system that is less affected by unnecessary light and has high optical performance.

Example 1

  • Focal length: 28.60
  • F-value: 1.85
  • Half angle of view: 37,1
  • Image height: 20.15
  • Total length: 81.00
  • Back focus: 13.20

Example 2

  • Focal length: 20.60
  • F-value: 1.85
  • Half angle of view: 46.4
  • Image height: 18.71
  • Overall length: 84.87
  • Back focus: 11.00

Example 3

  • Focal length: 24,72
  • F-value: 1.85
  • Half angle of view: 41.2
  • Image height: 19.34
  • Total length: 81.00
  • Back focus: 11.00

[via asobinet]

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