| US 7,586,602 B2 | ||
| Method and apparatus for improved signal to noise ratio in Raman signal detection for MEMS based spectrometers | ||
| Sandip Maity, Bangalore Karnataka (India); Ayan Banerjee, Bangalore (India); Anis Zribi, Rexford, N.Y. (US); Stacey Kennerly, Niskayuna, N.Y. (US); Long Que, Rexford, N.Y. (US); Glenn Claydon, Wynantskill, N.Y. (US); Shankar Chandrasekaran, Tamil Nadu (India); and Shivappa Goravar, Laxmeshwar Karnataka (India) | ||
| Assigned to General Electric Company, Niskayuna, N.Y. (US) | ||
| Filed on Jul. 24, 2006, as Appl. No. 11/459,449. | ||
| Prior Publication US 2008/0018890 A1, Jan. 24, 2008 | ||
| Int. Cl. G01J 3/44 (2006.01) | ||
| U.S. Cl. 356—301 | 8 Claims |
| 1. A method of Raman detection, comprising:
directing an input optical beam incident upon a sample to be measured that is contained within a portable, integrated spectrometer
instrument, said input optical beam being modulated at a heterodyne frequency;
directing scattered photons by said sample through receiving optics so as to filter Rayleigh scattered photons and pass Raman
scattered photons through a tunable filter, said receiving optics and said tunable filter being contained within the portable,
integrated spectrometer instrument; and
detecting said passed Raman scattered photons at a wavelength passed by said tunable filter through demodulation at said heterodyne
frequency, wherein said passed Raman scattered photons are detected using photon counting using an avalanche photodiode (APD)
operating in a sub-Geiger mode.
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