An optical system as a real time analyser [ECG application]

Time-frequency representation (TFR) is an important tool for the analysis of non-stationary signals such as speech and sonar. Also, biological signals (in the authors' case the ECG) naturally belong to the family of multicomponent non-stationary signals. That is, the characteristics of the biological signal depend on many individual parameters which contribute to the signal. The information related to the start and duration of the contribution of a component to the signal is not well understood by analyzing the signal in time or in frequency domain. Therefore, to get the exact structure of the electrical activity of the body time-frequency techniques are necessary. An optical processor that is capable of representing the Wigner-Ville distribution of 1-D signals is investigated. The system performance was demonstrated for both mono-component and multi-component signals. It is quite possible to perform 2-D filtering by introducing a third transparency driven by the PC for downloading any 2-D kernel function on the (x,w) plane. This filtering and research into improvement of the components, especially for the 2-D light modulators, will continue as future work. It has been shown that by using optics the time-frequency analysis of a signal in real time is now possible.