Patent Time!
More diffractive optic patents from Canon. This time, another 600 f/4 IS DO lens and a 400 f/2.8 DO IS.

With the cost of the new super telephotos from Canon, I can't imagine what new DO lenses would cost.

Continue reading for the patent breakdown….

Patent Publication No. 2012-88427

  • 2012.5.10 Release Date
  • 2010.10.18 filing date

Example 1

  • Focal length f = 585.00mm
  • Fno 4.12
  • Image height 21.64mm
  • Length 468.50mm lens
  • BF 90.78mm
  • 15 sheets of 9 group lens configuration
  • One aspherical surface a
  • 2 UD glass sheet
  • One fluorite
  • A plane diffraction

Example 2

  • Focal length f = 391.86mm
  • Fno 2.88
  • Image height 21.64mm
  • Length 367.51mm lens
  • BF 50.01mm
  • Lens Construction 14 elements in 9 groups sheet
  • 2 2 aspherical surface
  • 1 UD glass sheet
  • One fluorite
  • A plane diffraction
  • Group 3 consists of positive and negative positive
  • Inner Focus (group 2)
  • Strengthen the refractive power of the front lens group, and to shorten the overall length, the sensitivity is increased, it is difficult to manufacture and assembly
  • The number of lens group at the end of the super-telephoto lens is determined by the balance of the total length and chromatic aberration
  • And shorten the length and reconcile, the correction of chromatic aberration, the number will increase
  • It is important to the length of each degree
  • Weight of the first lens group, 70% to 9 on the whole
  • Canon patents is reduced to three the first group
  • Aspherical and one eye in group 1 group, field curvature correction, the distortion
  • Diffractive optical element and the second two groups in the first group, the chromatic aberration correction

Source: [EG]

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