초록 ▼

A modification to a commercial Fourier Transform (FT) Raman spectrometer is presented for the elimination of thermal backgrounds in the FT Raman spectra. The modification involves the use of a mechanical optical chopper to modulate the continuous wave laser, remote collection of the signal via fiber

A modification to a commercial Fourier Transform (FT) Raman spectrometer is presented for the elimination of thermal backgrounds in the FT Raman spectra. The modification involves the use of a mechanical optical chopper to modulate the continuous wave laser, remote collection of the signal via fiber optics, and connection of a dual-phase digital-signal-processor (DSP) lock-in amplifier between the detector and the spectrometer's collection electronics to demodulate and filter the optical signals. The resulting Modulated Fourier Transform Raman Fiber-Optic Spectrometer is capable of completely eliminating thermal backgrounds at temperatures exceeding 300.degree. C.

대표청구항 ▼

[ What is claimed is:] [1.] An apparatus for analyzing a sample, comprising:(a) a continuous wave laser for irradiating the sample at a selected wavelength of electromagnetic radiation suitable for Raman spectrometry;(b) a rotating mechanical optical chopper, positioned between the sample and said c

[ What is claimed is:] [1.] An apparatus for analyzing a sample, comprising:(a) a continuous wave laser for irradiating the sample at a selected wavelength of electromagnetic radiation suitable for Raman spectrometry;(b) a rotating mechanical optical chopper, positioned between the sample and said continuous wave laser, for modulating the electromagnetic radiation of said continuous wave laser into pulses;(c) a fiber-optical probe, positioned between the sample and said rotating mechanical chopper, said fiber-optical probe having two optical fibers, each with a distal end, the distal end of the first optical fiber transmitting the modulated electromagnetic radiation onto the sample, the distal end of the second optical fiber receiving the reflected electromagnetic radiation from the sample;(d) sample collection optics, operatively positioned at the other end of the second optical fiber, for collecting the reflected electromagnetic radiation of the sample into a beam;(e) an interferometer, mounted to receive the beam from said sample collection optics, for manipulating the beam into an interference beam, said interferometer comprising a beamsplitter, a moving mirror, and a stationary mirror;(f) a detector, positioned to receive the interference beam optically, for detecting the wavelengths of the interference beam and generating an output signal;(g) a dual-phase, digital signal processor lock-in amplifier, connected to said detector and said optical chopper, for demodulating and low-pass filtering the output signal of said detector; and,(h) sample collection electronics, connected to said dual-phase digital signal processor lock-in amplifier, for acquiring spectrally the demodulated and filtered signal of said amplifier.