Remote PPG Signal Alignment for Tissue Perfusion Analysis

The patent applies preliminary action by determining relative delays between PPG signals from different image regions before performing the averaging operation. The processor calculates time delays for each region relative to a reference region and pre-aligns the signals by compensating for these delays. This preliminary time alignment ensures that when signals are averaged to create the global PPG signal, they are synchronized in time, preventing destructive interference and maintaining high signal-to-noise ratio while still covering large tissue areas.

The patent applies segmentation by dividing the image into multiple regions of interest, each potentially containing different tissue types. For each region, a separate PPG signal is extracted and analyzed. The processor then determines relative delays for each region and performs time-aligned averaging only after regional analysis. This segmentation approach allows the system to maintain information about perfusion characteristics in different tissue regions while still producing an overall global PPG signal, thereby preventing loss of discriminatory information between physiological and pathological changes.

The patent applies parameter changes by dynamically adjusting the time alignment parameter for each regional PPG signal based on its relative delay. The processor calculates the time delay for each region relative to a reference region and applies a time shift parameter to compensate for this delay before averaging. This parameter adjustment ensures that all regional signals are synchronized to the same time reference, eliminating destructive interference that would otherwise occur when averaging signals with different phase relationships, thereby maintaining both signal strength and accuracy in the global PPG signal.