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, wherein the first electrically conductive structure is arranged for detecting a mechanical defect in 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, wherein the second electrically conductive structure is arranged for detecting presence of moisture; 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; and 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. 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, wherein the first electrically conductive structure is arranged for detecting a mechanical defect in 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, wherein the second electrically conductive structure is arranged for detecting presence of moisture; 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, 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; and 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.