SPECTRAL SENSORS BASED ON LINEAR VARIABLE FILTERS

摘要

In recent years, optical spectral sensing has played an increasingly important role in production environments for process control, materials inspection, and finished product quality. Instruments capable of measuring UV/VIS/NIR properties of materials in transmission or reflection range from simple filter photometers, which can measure at a few discreet wavelengths, to grating-based spectrophotometers which can acquire spectra at high resolution over broad spectral ranges. A new type of spectral sensor has been developed using a linear variable filter (LVF), a spectrally selective bandpass filter having a wedged thickness across the substrate. When coupled to an array detector such as a PDA or CCD, an LVF-based spectral sensor can provide the broad range of a grating system, more channels of information than a filter photometer, and in a much smaller package than either. We will explain the properties of an LVF and the various design forms available for an LVF-based spectral sensor.