| 摘要 |
A rotating surface optical sensing system having a radiation source controlled by a controlled current generator to emit electromagnetic radiation toward the rotating surface from which it can be directed to a radiation detector to provide corresponding signals to a threshold detector. The controlled current generator uses the threshold detector indications as to whether these signals are beyond a threshold value if validated by a rotation determiner noting rotations of the rotating surface to set the current for the radiation source. An amplifying filter is provided to amplify selected frequency components of the radiation detector output signals as a bandpass filter having a lower cutoff frequency such that relatively slowly varying optical ambient based signals are not amplified but signals from the radiation source directed from the surface to the detector are amplified. This is accomplished by repeatedly sampling the radiation detector output signals when the radiation source is not emitting, and again when it is emitting, and subtracting corresponding ones of such samples followed by integrating the differences so determined. Power supply noise occurring during emissions by the radiation source can be decoupled from the filter.
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