Patent ID: 7297962
Filing Date: 2007-11-20
Classification: G01N

Abstract:
1. A method of spectrographic measurement, comprising: (a) generating a plurality of modulation signals at a plurality of modulation frequencies; (b) coupling said modulation signals to an excitation source, said excitation source producing excitation light for illuminating a sample to be assayed, to vary the amplitude of said excitation light by modulating said excitation light with said plurality of modulation signals; (c) sampling a portion of said excitation light which has been varied in amplitude to form a reference optical excitation signal; (d) illuminating said sample to be assayed with said excitation light, causing said sample to emit an output optical signal; (e) imaging said output optical signal on a multielement optical detector having a plurality of elements, whereby each of said elements is associated with a region on said sample to be assayed; (f) generating a plurality of measurement signals using said multielement optical detector, each measurement signal associated with a single one of said elements; (g) generating a plurality of heterodyne signals at a plurality of heterodyne frequencies, each of said heterodyne frequencies being associated with one of said modulation frequencies; (h) for each measurement signal associated with an element of said multielement optical detector, mixing said measurement signal with said heterodyne signals to generate a plurality of low-frequency measurement modulation products, one low-frequency measurement modulation product being associated with each of said modulation frequencies and comprising the difference between a respective modulation frequency and its associated heterodyne frequency and having a measurement amplitude and phase; (i) mixing said reference optical excitation signal with said heterodyne signals to generate a plurality of reference modulation products, one reference modulation product being associated with each of said modulation frequencies and comprising the difference between a single modulation frequency and its associated heterodyne frequency and having a reference amplitude and phase, each of said reference modulation products being associated with one of said low-frequency measurement modulation products; and (j) for each of said plurality of low-frequency measurement modulation products, comparing said low-frequency measurement modulation product to its associated reference modulation product to generate an output signal indicating characteristics of said sample at the region on said sample associated with each of said elements.