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Correcting for Lens Distortions | Details | Hackaday.io
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<p>Certain types of camera lenses (such as in the webcam used in this project) introduce <em><a href="https://en.wikipedia.org/wiki/Distortion_(optics)">d</a><a href="https://en.wik
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Correcting for Lens Distortions | Details | Hackaday.io
<p>Certain types of camera lenses (such as in the webcam used in this project) introduce <em><a href="https://en.wikipedia.org/wiki/Distortion_(optics)">d</a><a href="https://en.wikipedia.org/wiki/Distortion_(optics)">istortion</a></em> characteristics to the images such that objects along the optical axis of the lens occupy disproportionately large areas of the image. Objects near the periphery occupy a smaller area of the image. The following figure illustrates this effect:
</p><p><img style="width: 306px; height: 305px;" height="305" width="306" data-src="https://cdn.hackaday.io/images/6703811468324904457.jpg" class="lazy">
</p><p>This so-called <em>barrel distortion</em> results in the fact that the representation of distance relations in the real world is not the same as in the camera image -- i.e. distance relations in the camera image are <em>non-linear</em>.
</p><p>However, in this project, <em>linear</em> distance relations are required
to estimate the servo motor angles from the camera images. Hence, lens
distortions have to be corrected by remapping the camera images to a
<em> <a href="https://en.wikipedia.org/wiki/Rectilinear_lens">rectilinear representation</a></em>. This procedure is also
called
<em>unwarping</em>. To correct for lens distortions in the camera images I made use of <em></em><a href="http://opencv.org/">OpenCV's</a><em></em> camera calibration tool.
</p><h1>Estimation of lens parameters using OpenCV</h1><p>For unwarping images OpenCV takes the <em><a href="https://en.wikipedia.org/wiki/Distortion_(optics)#Software_correction">radial </a></em><a href="https://en.wikipedia.org/wiki/Distortion_(optics)#Software_correction">and the</a><em><a href="https://en.wikipedia.org/wiki/Distortion_(optics)#Software_correction"> tangential distortion factors</a></em> into account. <em>Radial</em> distortion is pretty much what leads to the <em>barrel</em> or <em>fisheye</em> effect described above. Whereas, <em>tangential</em> distortion describes the
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<p>Certain types of camera lenses (such as in the webcam used in this project) introduce <em><a href="https://en.wikipedia.org/wiki/Distortion_(optics)">d</a><a href="https://en.wikipedia.org/wiki/Distortion_(optics)">istortion</a></em> characteristics to the images such that objects along the optical axis of the lens occupy disproportionately large areas of the image. Objects near the periphery occupy a smaller area of the image. The following figure illustrates this effect:
</p><p><img style="width: 306px; height: 305px;" height="305" width="306" data-src="https://cdn.hackaday.io/images/6703811468324904457.jpg" class="lazy">
</p><p>This so-called <em>barrel distortion</em> results in the fact that the representation of distance relations in the real world is not the same as in the camera image -- i.e. distance relations in the camera image are <em>non-linear</em>.
</p><p>However, in this project, <em>linear</em> distance relations are required
to estimate the servo motor angles from the camera images. Hence, lens
distortions have to be corrected by remapping the camera images to a
<em> <a href="https://en.wikipedia.org/wiki/Rectilinear_lens">rectilinear representation</a></em>. This procedure is also
called
<em>unwarping</em>. To correct for lens distortions in the camera images I made use of <em></em><a href="http://opencv.org/">OpenCV's</a><em></em> camera calibration tool.
</p><h1>Estimation of lens parameters using OpenCV</h1><p>For unwarping images OpenCV takes the <em><a href="https://en.wikipedia.org/wiki/Distortion_(optics)#Software_correction">radial </a></em><a href="https://en.wikipedia.org/wiki/Distortion_(optics)#Software_correction">and the</a><em><a href="https://en.wikipedia.org/wiki/Distortion_(optics)#Software_correction"> tangential distortion factors</a></em> into account. <em>Radial</em> distortion is pretty much what leads to the <em>barrel</em> or <em>fisheye</em> effect described above. Whereas, <em>tangential</em> distortion describes the
Correcting for Lens Distortions | Details | Hackaday.io
