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Canon publishes patents for a very compact 28-70mm f/2.8 zoom lens


Canon has published a patent for two new zoom lens in the 28-70mm f/2.8 and 28-60mm f/2.8 focal length ranges. What makes them particularly interesting, though, is how tiny they are, for zooms with such wide aperture zooms, with both coming in at a little over 105mm long at the shorter end of their focal length limit of ~28mm. Even at their maximum zooms of 60mm and 67.9mm, they still only hit 132.38mm and 138.40mm respectively, making them very compact indeed.

The “Problem to be solved”, according to the Asobinet’s quote from the patent is “to provide a zoom lens having a short total length and a small size but having high optical performance”. And it suggests that thanks to recent development in cameras – namely, Canon’s gone mirrorless – it’s now possible to create a zoom lens of this focal length range and wide aperture that meets these parameters.

Overview

  • [Public number] P2022091621
  • [Release date] 2022-06-21
  • INDUSTRIAL APPLICABILITY: A zoom lens and an image pickup device having the same.
  • [Filing date] 2020-12-09
  • [Applicant]
    [Identification number] 000001007
    [Name or name] Canon Inc.
  • 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.
  • [0002]
    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).
  • [0006]
    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.
  • [0007]
    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, various aberrations and zoom fluctuations of aberrations in the telephoto region cannot be suppressed, and it becomes difficult to satisfy good optical performance over the entire zoom range.
  • [0008]
    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.
  • [0038]
    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 – 28-70mm f/2.8

  • 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 – 28-60mm f/2.8

  • 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

As always, a patent doesn’t necessarily mean that a lens is on the way, but given the drive for smaller and lighter gear – which was kinda the whole selling point for mirrorless – it wouldn’t surprise me if we eventually heard one of these being announced.

[via Asobinet]





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