External/internal optical adapter for FTIR spectrophotometer

摘要

A Fourier Transfer Infrared (FTIR) spectrophotometer having reduced baseline noise. The system and method include internal or external optical adapters having a moveable beamsplitter for splitting the source light beam into a reference beam and a sample beam, and may include a variable bandpass filter, variable preamplifier and reversed biased photodiodes.

主权项

1. An adapter for use with an FTIR spectrophotometry system having a light source generating a source light beam of coherent light, said adapter comprising
a sealed housing for receiving the source light beam directed along a propagation path; an optical system within the housing including a single moveable beamsplitter having first and second reflecting surfaces, each coated with a reflecting layer, said beamsplitter for splitting the source light beam into:
(1) a reference beam reflected by the first reflecting surface to form a first linear path different from the source path, and(2) a sample beam reflected by the second reflecting surface to form a second linear path different from the source path and different from the first linear path,wherein the beamsplitter and its first and second reflecting surfaces are moveable together in a direction perpendicular to the propagation path of the source beam between the first and second linear paths to minimize source noise and to minimize a centerburst of a waveform of an interferogram of the reference beam and the sample beam;
a reference cell within the housing, said reference cell including a reference for interacting with the reference beam wherein said interacting yields an output reference beam having a direction; a reference light detector for detecting at least a portion of the output reference beam based on the direction of the output reference beam and generating a reference signal representative of the detected light; a sample cell within the housing, said sample cell including a sample for interacting with the sample beam wherein said interacting yields an output sample beam having a direction; a sample light detector for detecting at least a portion of the output sample beam based on the direction of the output sample beam and generating a sample signal representative of the detected light; a detector circuit for producing a difference signal proportional to the difference between the reference signal and the sample signal; and a processor configured to determine a spectrum of the sample based on the difference signal.