SherbyNet - /page/wikibook/entry.mu

Micron Document

<!DOCTYPE html>

<title>Wavefront coding</title>

</head>

<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Wavefront coding</span></span>

</h1>

</header>

<p>In <a href="Optics" title="Optics">optics</a> and <a href="Signal_processing" title="Signal processing">signal processing</a>, <b>wavefront coding</b> refers to the use of a phase modulating element in conjunction with <a href="Deconvolution" title="Deconvolution">deconvolution</a> to extend the <a href="Depth_of_field" title="Depth of field">depth of field</a> of a digital imaging system such as a video camera.

</p><p>Wavefront coding falls under the broad category of <a href="Computational_photography" title="Computational photography">computational photography</a> as a technique to enhance the depth of field.

</p>

<div class="mw-heading mw-heading2"><h2 id="Encoding">Encoding</h2></div>

<p>The wavefront of a light wave passing through the camera system is modulated using optical elements that introduce a spatially varying optical path length. The modulating elements must be placed at or near the plane of the aperture stop or pupil so that the same modulation is introduced for all field angles across the field-of-view. This modulation corresponds to a change in complex argument of the <a href="Pupil_function" title="Pupil function">pupil function</a> of such an imaging device, and it can be engineered with different goals in mind: e.g. extending the depth of focus.

</p>

<div class="mw-heading mw-heading3"><h3 id="Linear_phase_mask">Linear phase mask</h3></div>

<p>Wavefront coding with linear phase masks works by creating an optical transfer function that encodes distance information.<sup id="cite_ref-LinearPhasePatent_1-0" class="reference"><a href="#cite_note-LinearPhasePatent-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>

</p>

<div class="mw-heading mw-heading3"><h3 id="Cubic_phase_mask">Cubic phase mask</h3></div>

<p>Wavefront Coding with cubic phase masks works to blur the image uniformly using a cubic shaped <a href="Waveplate" title="Waveplate">waveplate</a> so that the intermediate image, the optical transfer function, is out of <a href="Focus_(optics)" title="Focus (optics)">focus</a> by a constant amount. <a href="Digital_image_processing" title="Digital image processing">Digital image processing</a> then removes the blur and introduces noise depending upon the physical characteristics of the processor. <a href="Dynamic_range" title="Dynamic range">Dynamic range</a> is sacrificed to extend the depth of field depending upon the type of filter used. It can also correct <a href="Optical_aberration" title="Optical aberration">optical aberration</a>.<sup id="cite_ref-StanfordPaper_2-0" class="reference"><a href="#cite_note-StanfordPaper-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>

</p><p>The mask was developed by using the <a href="Ambiguity_function" title="Ambiguity function">ambiguity function</a> and the <a href="Stationary_phase_method" class="mw-redirect" title="Stationary phase method">stationary phase method</a>

</p>

<div class="mw-heading mw-heading2"><h2 id="History">History</h2></div>

<p>The technique was pioneered by <a href="Radar" title="Radar">radar</a> engineer Edward Dowski and his thesis adviser Thomas Cathey at the <a href="University_of_Colorado_at_Boulder" class="mw-redirect" title="University of Colorado at Boulder">University of Colorado</a> in the United States in the 1990s. The University filed a patent on the invention.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> Cathey, Dowski and Merc Mercure founded a company to <a href="Commercialize" class="mw-redirect" title="Commercialize">commercialize</a> the method called CDM-Optics, and licensed the invention from the University. The company was acquired in 2005 by <a href="OmniVision_Technologies" title="OmniVision Technologies">OmniVision Technologies</a>, which has released wavefront-coding-based mobile camera chips as TrueFocus sensors.

</p><p>TrueFocus sensors are able to simulate older autofocus technologies that use rangefinders and narrow depth of fields.<sup id="cite_ref-TrueFocusPatent_4-0" class="reference"><a href="#cite_note-TrueFocusPatent-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> In fact, the technology theoretically allows for any number of combinations of focal points per pixel for effect. It is the only technology not limited to EDoF (Extended-Depth-of-Field).

</p>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

<li id="cite_note-LinearPhasePatent-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-LinearPhasePatent_1-0">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://patft.uspto.gov/netacgi/nph-Parser?patentnumber=7218448">US Patent 7218448 - Extended depth of field optical systems</a></span>

</li>

<li id="cite_note-StanfordPaper-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-StanfordPaper_2-0">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://graphics.stanford.edu/courses/cs448a-06-winter/dowski-wavefront-coding-optics95.pdf">Extended depth of field through wave-front coding</a></span>

</li>

/* start https://en.wikipedia.org/ */

.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("./mw/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("./mw/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("./mw/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("./mw/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}

/* end https://en.wikipedia.org/ */

</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://patents.google.com/patent/US5748371A/en">"Extended depth of field optical systems"</a>.</cite></span>

</li>

<li id="cite_note-TrueFocusPatent-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-TrueFocusPatent_4-0">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="http://www.freepatentsonline.com/y2006/0269150.html">Multi-matrix depth of field image sensor</a></span>

</li>

</ol></div>

<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>

<ul><li><a rel="nofollow" class="external text" href="http://lfw.pennnet.com/Articles/Article_Display.cfm?Section=ARTCL&ARTICLE_ID=197348&VERSION_NUM=1">Wavefront coding finds increasing use</a> (Laser Focus World)</li></ul></div><div><div class="zim-footer">

This article is issued from <a class="external text" title="Last edited on 2022-06-01" href="https://en.wikipedia.org/wiki/?title=Wavefront_coding&oldid=1090928364">Wikipedia</a>. The text is available under <a class="external text" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en">Creative Commons Attribution-Share Alike 4.0</a> unless otherwise noted. Additional terms may apply for the media files.

</div>

</div></div>

</div>

</main>

</div>

</body></html>