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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]
