While specifying a lens for an imaging system can seem like a complex task, we learned in our last article on imaging lenses (www.qualitymag.com/articles/91115-imaging-lens) that the key is breaking the selection down into manageable pieces. Last time we discussed resolution, working distance, depth of field and field of view, and this time we will be diving into distortion, relative illumination and telecentricity. These specifications help to give a more complete understanding of how a lens will perform and what you can expect to achieve.
If you’ve used a lens (whether on your camera phone or machine vision system), then you are probably familiar with distortion. Distortion is a geometric error in the imaging of an object or scene, resulting from variations in magnification across the field of view. Distortion can present itself in a number of different ways; barrel, pincushion and keystone are the most common forms that you might run into.