Patent: 600 f/4 DO IS & 400 f/2.8 DO IS

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]