Magnetic stabilization method and system in infrared, visible and ultraviolet spectroscopy

Abstract

In a spectroscopic analysis system, a broadband light source emits infra-red, visible or ultra-violet light which is transmitted through a fluid in a sample cell to a broadband detector. Changes in transmitted intensity are related to measurand in the fluid. A rotatable optical modulator or chopper, driven by an electric motor and located in the optical path, has light-transmissive optical elements, and non-transmissive regions. A non-contact magnetic field generator applies a magnetic field to the modulator or chopper to damp or brake the rotation. In an aspect, the modulator is an electrically conductive, non-ferromagnetic wheel, disc or cylinder in which eddy currents are induced. Optical elements may be apertures, filters, cuvettes, etc. A Hall effect sensor, rotary encoder, optical switch, etc. may determine angular speed or position of the modulator, and a PID controller may be used to maintain rotation speed at a setpoint by modulating an electromagnetic field generator.