The Japanese photography blog, Egami has uncovered more Canon patents. This time they involve a 500mm f/4 and f/5.6 lens plus a 600mm f/4 and 800mm f/5.6 Diffractive Optics (DO) lens design. The patents seem to suggest an emphasis on weight reduction by rearranging the lens group inside the barrel. I have the Canon 400mm f/4 DO IS lens and it is one of my favorite lenses for wildlife photography. You can read the original article by visiting Egami's website.
Canon files thousands of patents a year. Many do not end up in a marketable product. They are the results of a massive research and development effort. The patents protect Canon's intellectual properties and prevent competitors from utilizing the same technology.
Patent Publication No. 2013-92575
- Publication date 2013.5.16
- Filing date 2011.10.24
How to reduce the size of the large-aperture super telephoto lens (translated)
- Effective diameter of the first group with the largest
- I reduce the number of the first group
- It is necessary to reduce aberration by increasing the number
- Can not reduce the aberration and reduce the number
- I increase a refractive power of the first group
- The thickness of the lens increases, the effect of weight reduction is canceled
- Impact of manufacturing error is large high refractive index
Canon Patent
- The aspherical in the first group
- Performing a variance of sensitivity was composed of opposite sign component of the first group, and also, prevent an increase in thickness
- DOE is provided to correct chromatic aberration with a small number of lenses
- Inner focus
- Anti-shake
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