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Canon Patent For 400mm f/4 DO Lens

Canon Patent

Canon Patent

Egami (translated) spotted another patent filed by Canon. It is for a 400mm f/4 lens with diffractive optical elements (to reduce flare).

Patent description (machine translated):

  • Patent Publication No. 2013-64858
    • 2013.4.11 Release Date
    • Filing date 2011.9.16
  • Example 1
    • Focal length f = 392.12mm
    • Fno. 4.12
    • Half angle of ω = 3.16 °
    • Image height Y = 21.64mm
    • 262.14mm length lens
    • BF 69.97mm
    • Two fluorite
  • Materials and anomalous partial dispersion DOE to use, reduce the chromatic aberration
  • Refractive power of the diffractive surface
    • Strong, but can reduce the chromatic aberration of the element itself, flare increases
    • The weaker, other optical element DOE play a role
  • Refractive optical unit
    • DOE anomalous partial dispersion and bonding materials
    • DOE aspherical surface on the opposite side of the
  • Vibration control
  • Inner Focus
[via Egami]
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