Patent – EF 28 f/1.8 DO & Others

EF 28 f/1.8 DO

Canon files patent for new DO lenses

  • Patent publication 2009-198960
  • Published 03/09/2009
  • Filing date 2008/02/25

Example 1

  • Focal length f = 27.14mm
  • Fno = 1.85
  • Angle of 77.1 °

Example 2

  • Focal length f = 24.50mm
  • Fno = 1.45
  • Angle of 82.9 °

Example 3

  • Focal length f = 25.00mm
  • Fno = 1.45
  • Angle of 81.8 °

Example 4

  • Focal length f = 24.33-36.50-47.00mm
  • Fno = 3.4-4.0-4.7
  • 83.3-61.3-49.4 ° angle

Example 5

  • Focal length f = 26.00-39.00-50.23mm
  • Fno = 3.4-4.0-4.7
  • 79.5-58.0-46.6 ° angle

Information

  • General retrofocus
  • In general SLR wide angle lens
  • Many chromatic aberration
  • Using high-dispersion glass, as excessive compensation around
  • General diffractive optics
  • Can correct chromatic aberrations
  • Where it is difficult to use
  • Manufacturing difficulties
  • Aberration can not fine-lattice

Patented Features

  • Adopted retrofocus
  • Chromatic aberration correction over the entire
  • Diffractive optical elements, aspherical and low dispersion, employing anomalous dispersion lens
  • The lenses focus mechanism
  • Front lens is fixed
  • Second lens to focus
  • Floating mechanism
  • The optical system of patents
  • Lateral chromatic aberration to occur around the first lens
  • Not easily corrected by increasing the number of lenses
  • Diffractive optics correction to put the image side than the diaphragm
  • Only increase the power of the diffractive optical element
  • Chromatic aberration correction using a bonded lens

This is an older patent application, but I think it’s still important to see diffractive optics are not dead within Canon R&D.

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