New Patent
Canon has filed a patent for the optical formula of a new EF 300 f/4L IS II.

Patent Publication No. 2012-159726

  • 2012.8.23 Release Date
  • 2011.2.1 filing date

Example 3

  • F = 300mm focal length
  • Fno. 4.0
  • Tele ratio 0.68
  • Inner Focus
  • φr = 68.8mm
  • φg1 = 67.8mm
  • φg2 = 70.2mm
Technical background
  • When the miniaturization of the optical system, longitudinal chromatic aberration, chromatic aberration of magnification is remarkable
  • As the focal length becomes longer, the telephoto lens system, chromatic aberration is noticeable
  • There is a method of correcting the aberrations of a material having an anomalous dispersion resin, the resin is difficult to produce high-precision thick
  • There is a method of sandwiching a thin glass resin material, the bonding peeling distortion problem bonding at high temperature

Canon patent

  • Joining three or more optical elements
  • The outer diameter of the resin is increased to reduce the distortion at the time of bonding
  • Not adhere to each other resin outer glass element
  • Between the optical element of the outside is gone, adhesive, the thickness of the adhesive distribution occurs
  • Using a sealing agent to prevent change in shape of the resin and the refractive index change due to moisture absorption
  • Do the black outer peripheral portion of the glass element
  • Prevent flare and ghosting resin at the outer periphery
  • Surface resin glue is not good

Source: [EG]


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