Development and Characterization of a white Led-Based Spectrophotometer for UV/VIS Gaseous Pollutants Detection Employing Michelson Interferometer and an Optical Filtering System

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Aim of this paper is the design of an absorption spectrophotometer based on LED technology presenting several advantages such as high luminous efficiency, reliability, long operating duration, low maintenance and low power consumption besides the reduction of analyte temperature variations which occur if Xenon light source is used. An optical filtering system was realized to detect analyte absorption for each wavelength range selected by proper optical filters; also to characterize filtered light beam in terms of its coherence length, thus correlating measured absorption spectrum with light source characteristics, the Michelson interferometer was used. Realized white LED-based spectrophotometer can be used to monitor air quality in hospital rooms or to detect atmospheric pollution deriving from vehicular traffic and different typology of pollutants (e.g., heavy metals deriving by industrial activities). A PC-interfaced control unit acquires and processes raw data provided by sensors (pressure, temperature, humidity, luminosity) and manages the optical filtering system motion by actuating a stepper motor. Whole system operation was tested and obtained results confirm the proper functioning and correct interaction, through PC terminal, between user and control unit.