| 摘要 |
A noise cancellation system which balances the photocurrents derived by a measurement signal and a reference signal of a sensor. The invention has application in any measurement device which detects a small signal in combination with high noise content and further utilizes a reference signal. The invention is useful in an optical measurement system by splitting an optical beam into measurement beam and reference optical beams; passing the measurement through a sample cell for measurement information; converting the measurement beam and reference beam into a measurement current representing information signals impressed on a current signal that is modulated by undesirable noise signals and a reference current representing said carrier current signal exclusive of said information signals and modulated by said noise signals repectively; generating a voltage source as a function of said reference current and a feedback control voltage resulting in the flow of a correction current modulated by said noise signals; and combining said measurement current and said correction current in a way which substantially cancels the undesirable nosie signals from said measurement current and produces said feedback control voltage which comprises an output signal containing the information component of said measurement current. Other applications include acoustic, infared, frequency or other types of measurement systems.
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