Canon Patent: Super Small 28-70mm f/2.8 & 28-60mm f/2.8 Lenses For RF Mount

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A new and rather interesting Canon patent application. Very compact zoom lenses with large aperture.

Canon patent application 2022091621 (Japan) discusses optical formulas for two small and compact zoom lenses with large aperture:

  • 28-70mm f/2.8
  • 28-60mm f/2.8

From the patent literature:

PROBLEM TO BE SOLVED: To provide a zoom lens having a short total length and a small size but having high optical performance, and an image pickup apparatus having the same.

In recent years, with the increasing functionality of image pickup devices, there is a demand for a compact and lightweight zoom lens having a large aperture ratio. As a zoom lens that satisfies this requirement, a negative lead type zoom lens in which a lens group having a negative refractive power is arranged on the object side is known (see Patent Document 1 and Patent Document 2).

In the zoom lens of Patent Document 1, the refractive power of the first lens group is strengthened, and the movement locus of the first lens group during zooming becomes a substantially reciprocating locus, so that the total length of the zoom lens at the telephoto end can be increased. become longer. In addition, the back focus is long, and it is difficult to shorten the total length of the zoom lens. Further, the thickness of the first lens group becomes large due to the aberration correction in the first lens group, which is not preferable from the viewpoint of miniaturization and weight reduction.

In the zoom lens of Patent Document 2, the refractive power of the first lens group is strong in order to obtain a zoom magnification, and the configuration of the subsequent group is a four-group configuration up to the fourth lens group. If a larger aperture ratio is aimed at, it will not be possible to suppress various aberrations and zoom fluctuations of aberrations in the telephoto region, and it will be difficult to satisfy good optical performance over the entire zoom range.

An object of the present invention is to provide a zoom lens having a short overall length, a small size, and high optical performance, and an image pickup apparatus having the same.

In the zoom lens of each embodiment, in order to ensure good optical performance even at a close object distance, two or more lens groups among the lens groups arranged on the image side of the first lens group L1 are focused. It is preferable to have a so-called floating configuration in which the lens moves at the time.

Example 1

  • Focal length: 28.84-67.90
  • F value: 2.91
  • Half angle of view: 32.68-17.67
  • Image height: 18.50-21.64
  • Overall length: 138.40-105.42
  • Back focus: 10.97-21.12

Example 2

  • Focal length: 28.84-60
  • F value: 2.91
  • Half angle of view: 32.68-19.83
  • Image height: 18.50-21.64
  • Overall length: 132.38-106.85
  • Back focus: 13.47-23.82

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

[via asobinet]