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<strong>Patent Time!
</strong>More diffractive optic patents from Canon. This time, another 600 f/4 IS DO lens and a 400 f/2.8 DO IS.</p>
<p>With the cost of the new super telephotos from Canon, I can’t imagine what new DO lenses would cost.</p>
<p>Continue reading for the patent breakdown….</p>
<p><!--more--></p>
<p><strong>Patent Publication No. 2012-88427</strong></p>
<ul>
<li>2012.5.10 Release Date</li>
<li>2010.10.18 filing date</li>
</ul>
<p><strong>Example 1</strong></p>
<ul>
<li>Focal length f = 585.00mm</li>
<li>Fno 4.12</li>
<li>Image height 21.64mm</li>
<li>Length 468.50mm lens</li>
<li>BF 90.78mm</li>
<li>15 sheets of 9 group lens configuration</li>
<li>One aspherical surface a</li>
<li>2 UD glass sheet</li>
<li>One fluorite</li>
<li>A plane diffraction</li>
</ul>
<p><strong>Example 2</strong></p>
<ul>
<li>Focal length f = 391.86mm</li>
<li>Fno 2.88</li>
<li>Image height 21.64mm</li>
<li>Length 367.51mm lens</li>
<li>BF 50.01mm</li>
<li>Lens Construction 14 elements in 9 groups sheet</li>
<li>2 2 aspherical surface</li>
<li>1 UD glass sheet</li>
<li>One fluorite</li>
<li>A plane diffraction</li>
<li>Group 3 consists of positive and negative positive</li>
<li>Inner Focus (group 2)</li>
<li>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</li>
<li>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</li>
<li>And shorten the length and reconcile, the correction of chromatic aberration, the number will increase</li>
<li>It is important to the length of each degree</li>
<li>Weight of the first lens group, 70% to 9 on the whole</li>
<li>Canon patents is reduced to three the first group</li>
<li>Aspherical and one eye in group 1 group, field curvature correction, the distortion</li>
<li>Diffractive optical element and the second two groups in the first group, the chromatic aberration correction</li>
</ul>
<p>Source: [<a href="http://egami.blog.so-net.ne.jp/2012-05-23" target="_blank">EG</a>]</p>
