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<strong>New Patent
</strong>Canon has filed a patent for the optical formula of a new EF 300 f/4L IS II.</p>
<p><strong>Patent Publication No. 2012-159726</strong></p>
<ul>
<li>2012.8.23 Release Date</li>
<li>2011.2.1 filing date</li>
</ul>
<p><strong>Example 3</strong></p>
<ul>
<li>F = 300mm focal length</li>
<li>Fno. 4.0</li>
<li>Tele ratio 0.68</li>
<li>Inner Focus</li>
<li>φr = 68.8mm</li>
<li>φg1 = 67.8mm</li>
<li>φg2 = 70.2mm</li>
</ul>
<div><strong><a href="http://www.bhphotovideo.com/c/product/129188-USA/Canon_2530A004_Telephoto_EF_300mm_f_4_0L.html/bi/2466/kbid/3296" target="_blank">Canon EF 300 f/4L IS at B&H Photo</a></strong></div>
<div><!--more--><strong>Technical background</strong></div>
<ul>
<li>When the miniaturization of the optical system, longitudinal chromatic aberration, chromatic aberration of magnification is remarkable</li>
<li>As the focal length becomes longer, the telephoto lens system, chromatic aberration is noticeable</li>
<li>There is a method of correcting the aberrations of a material having an anomalous dispersion resin, the resin is difficult to produce high-precision thick</li>
<li>There is a method of sandwiching a thin glass resin material, the bonding peeling distortion problem bonding at high temperature</li>
</ul>
<p><strong>Canon patent</strong></p>
<ul>
<li>Joining three or more optical elements</li>
<li>The outer diameter of the resin is increased to reduce the distortion at the time of bonding</li>
<li>Not adhere to each other resin outer glass element</li>
<li>Between the optical element of the outside is gone, adhesive, the thickness of the adhesive distribution occurs</li>
<li>Using a sealing agent to prevent change in shape of the resin and the refractive index change due to moisture absorption</li>
<li>Do the black outer peripheral portion of the glass element</li>
<li>Prevent flare and ghosting resin at the outer periphery</li>
<li>Surface resin glue is not good</li>
</ul>
<p><strong>Source: [<a href="http://egami.blog.so-net.ne.jp/2012-08-24" target="_blank">EG</a>]</strong></p>
<p><strong><span style="color: #ff0000;">c</span>r</strong></p>
