Patent ID: 6574031
Filing Date: 2003-06-03
Classification: G01N

Abstract:
A method for electronically processing detector output to digitally balance optical intensities to a desired level of balance at a frequency f, comprising the steps of:amplifying the detector output, wherein the detector output comprises the baseband signal I and the difference signal &Dgr;I(t); digitizing the amplified detector output; dividing the digitized amplified detector output in real time by the balance function &bgr;(t), where &bgr;(t)=1+&agr; sin(2&pgr;ft+&phgr;), where phase &phgr; is in phase with the &Dgr;I(t) signal at frequency f, and where &agr; is adjusted by a computer across time to achieve the desired level of balance; synchronously demodulating the function V(t)/&bgr;(t) at frequency f, wherein V(t) is the digitized amplified detector output; digitally low pass filtering the digital demodulated signal to reduce the bandwidth; averaging the V(t)/&bgr;(t) signal using a digital low pass filter identical in characteristics to the demodulated filtering; and transmitting the digital demodulated difference signal and the averaged baseband signal to the computer for adjustment of &agr; across time to achieve the desired level of balance.