An extended spectral observer framework in application to multiple-channel optical measurements

The problem of multiple-wavelength optical measurement arises in oximetry, glucometry and other biomedical fields as well as in other applications. Due to the apparatus complexity, commercial devices, however, suffices in a few, say 2 or 3, wavelengths. The study describes the design principles of a multiple-channel optical system with an increased number of wavelengths. The development is performed with the emphasis on the DSP and its adjustment to the application requirements. Several basic principles of signal processing are involved. Conceptually, the DSP framework represents an extended spectral observer, where each resonator relates to a probe waveform or, contrarily, to a disturbance. Among other parameters, unknown or time-varying frequencies may be teamed using methods of adaptive filtering. The resonator bandwidth can be properly adjusted with regard to the changing signal-to-noise ratio. A decimation procedure implemented in the DSP is linked with the waveform generation. This extended framework of signal processing enables an optimized engineering design of the multiple-light optical system with adjustable performance.