Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1998-12-31
2000-07-18
Le, Que T.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250573, 318483, G02B 642
Patent
active
060910658
ABSTRACT:
A moisture sensor for detecting moisture on the surface of a transparent material. The moisture sensor includes one or more emitters for producing emitter signals which are influenced by moisture on the transparent material, and one or more detectors for receiving the emitter signals. The detector produces a detector output signal which is filtered and amplified in a pre-demodulation gain and filtering circuit to remove some of the unwanted signal components including noise from ambient light and EMI. Digital Signal Processing filtering is used after the moisture signal is demodulated to a dc signal to discern small signal changes due to moisture events in the presence of large amounts of the noise created by the pre-demodulation gain circuit. The DSP filtering includes a low pass filter stage and a band pass filter stage implemented by a microcomputer using First In First Out shift registers, summing elements and division elements.
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Le Que T.
Libbey-Owens-Ford Co.
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