Moisture sensing device

Claim 1

A sensor device for detecting the amount of moisture on a transparent screen, comprising: at least one light conducting element; means for affixing the at least one light conducting element to the screen on the side thereof which is not exposed to the moisture, each of said at least one light conducting elements having associated therewith at least one pair of lenses, a beam emitter, and a beam receiver, the emitter and receiver being spatially separated from one another in a horizontal plane, each of the at least one pair of lenses comprising a first lens through which an emitted beam passes, the first lens being configured for reducing the dispersion of a divergent beam generated by the beam emitter, and a second lens through which a reflected beam passes, the second lens serving to focus the reflected beam towards the beam receiver; and a reflective material layer applied directly to said light conducting element, substantially covering the side thereof which is remote from the transparent screen, such coverage and location allowing a wider beam to be effectively used for a given screen thickness, thereby permitting a larger measuring area for detecting the amount of moisture thereon than would be possible if the reflective material layer were applied on a side of the light conducting element which faces the screen; the emitter and receiver being arranged in such a way that beams issuing from the emitter are reflected from the screen with an intensity which depends on the amount of moisture thereupon and are then reflected between reflective material layer and the screen before passing through an associated second lens to the beam receiver, said beam receiver issuing a signal which is in inverse proportion to the amount of moisture on said screen.