Systems and methods are disclosed to measure a PPG signal. In some embodiments, a method may include capturing a plurality of frames of a subject； tracking the position of a region of interest of the subject in each of the plurality of frames； creating a first time series signal, a second time series signal, and third time series signal corresponding with respective color channels of the plurality of frames； normalizing the first, second, and third time series signals, combining the normalized first time series signal, the normalized first time series signal, and the normalized first time series signal into a combined signal； creating a spectral signal from the combined signal； and extracting the PPG signal from the spectral signal.
