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<p><strong></p>
<div id="attachment_6592" class="wp-caption alignnone" style="width: 310px"><img class="size-medium wp-image-6592" title="24DO" src="http://www.canonrumors.com/wp-content/uploads/2011/05/24DO-300x133.png" alt="" width="300" height="133" /><p class="wp-caption-text">EF 28 f/1.8 DO</p></div>
<p></strong></p>
<p><strong>Canon files patent for new DO lenses
</strong></p>
<ul>
<li>Patent publication 2009-198960</li>
<li>Published 03/09/2009</li>
<li>Filing date 2008/02/25</li>
</ul>
<p><strong>Example 1</strong></p>
<ul>
<li>Focal length f = 27.14mm</li>
<li>Fno = 1.85</li>
<li>Angle of 77.1 °</li>
</ul>
<p><strong>Example 2</strong></p>
<ul>
<li>Focal length f = 24.50mm</li>
<li>Fno = 1.45</li>
<li>Angle of 82.9 °</li>
</ul>
<p><!--more--><strong>Example 3</strong></p>
<ul>
<li>Focal length f = 25.00mm</li>
<li>Fno = 1.45</li>
<li>Angle of 81.8 °</li>
</ul>
<p><strong>Example 4</strong></p>
<ul>
<li>Focal length f = 24.33-36.50-47.00mm</li>
<li>Fno = 3.4-4.0-4.7</li>
<li>83.3-61.3-49.4 ° angle</li>
</ul>
<p><strong>Example 5</strong></p>
<ul>
<li>Focal length f = 26.00-39.00-50.23mm</li>
<li>Fno = 3.4-4.0-4.7</li>
<li>79.5-58.0-46.6 ° angle</li>
</ul>
<p><strong>Information</strong></p>
<ul>
<li>General retrofocus</li>
<li>In general SLR wide angle lens</li>
<li>Many chromatic aberration</li>
<li>Using high-dispersion glass, as excessive compensation around</li>
<li>General diffractive optics</li>
<li>Can correct chromatic aberrations</li>
<li>Where it is difficult to use</li>
<li>Manufacturing difficulties</li>
<li>Aberration can not fine-lattice</li>
</ul>
<p><strong>Patented Features</strong></p>
<ul>
<li>Adopted retrofocus</li>
<li>Chromatic aberration correction over the entire</li>
<li>Diffractive optical elements, aspherical and low dispersion, employing anomalous dispersion lens</li>
<li>The lenses focus mechanism</li>
<li>Front lens is fixed</li>
<li>Second lens to focus</li>
<li>Floating mechanism</li>
<li>The optical system of patents</li>
<li>Lateral chromatic aberration to occur around the first lens</li>
<li>Not easily corrected by increasing the number of lenses</li>
<li>Diffractive optics correction to put the image side than the diaphragm</li>
<li>Only increase the power of the diffractive optical element</li>
<li>Chromatic aberration correction using a bonded lens</li>
</ul>
<p>This is an older patent application, but I think it’s still important to see diffractive optics are not dead within Canon R&D.</p>
<p><strong><span style="color: #ff0000;">c</span>r</strong></p>
<p><strong> </strong>