CPC G01N 27/223 (2013.01) [G01N 27/20 (2013.01)] | 18 Claims |
1. An apparatus comprising:
a light emitter operable to produce light having a particular wavelength;
a transmissive cover disposed so as to intersect a path of light emitted by the light emitter, wherein the transmissive cover is substantially transparent to the wavelength of light produced by the light emitter;
a first electrically conductive structure disposed on a first surface of the transmissive cover;
a second electrically conductive structure disposed on a second surface of the transmissive cover, the second surface being different from the first surface, and each of the first and second surfaces intersecting a path of the light produced by the light emitter; and
a controller;
wherein:
each of the first and second electrically conductive structures is coupled electrically to the controller, and
the controller is operable to monitor a respective electrical characteristic of each of the first and second electrically conductive structures such that if the monitored characteristic for a particular one of the first or second electrically conductive structures changes by more than a respective predetermined amount, the controller regulates an optical output produced by the light source;
wherein the controller is operable to monitor signals from the first electrically conductive structure for a change in resistance, and wherein the controller is operable to monitor signals from the second electrically conductive structure for a change in capacitance.
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