Apparatus and method for fluorescence spectroscopy of remote sample

Abstract

A fluorescence spectrometer (10) includes an excitation light source (12) and an excitation light input mirror (14) for reflecting excitation light produced by the light source and directing the light along a spectrometer light path (24). A reflecting arrangement (16) receives the excitation light directed along the spectrometer light path (24) and focuses the excitation light along a sample light path (20) to a distant focal point (32) at which a sample may be located. The reflecting arrangement (16) also serves to collect light emitted or reflected from the sample at the distant focal point (32) and to reflect the collected or returned light back along the spectrometer light path (24) in a direction opposite to the direction of the excitation light. The excitation light input mirror (14) is adapted to pass wavelengths in a target fluorescence spectrum and, therefore, wavelengths within this range pass along the spectrometer light path (24) through the excitation light input mirror (14) to a returned light detecting arrangement (18) which provides an output indicating the relative intensity of a desired wavelength constituent of the returned light. The excitation light may be chopped at a frequency different from the frequency at which background light is produced. Where the excitation light is chopped or produced intermittently, the signal produced in response to the background light at the returned light detecting arrangement (18) may be removed electronically to provide an output resulting solely from the excitation light incident upon the sample.