A position detection system. In representative embodiments, the position detection system comprises a support structure having a cavity, a first light source configured to emit light into at least part of the cavity, a second light source configured to emit light into at least part of the cavity, a first image sensor configured to capture at least part of the light emitted into the cavity by the first and second light sources, an article moveable relative to the support structure, a protuberance attached to the article, and a computation circuit configured to receive a signal from the first image sensor. Movement of the support structure moves the protuberance within the cavity. The computation circuit is configured to compute the location of the protuberance from shadows cast by the protuberance onto the first image sensor.