A method implemented by an image and signal processing system, the method comprising: collecting light (320; 420) reflected from a subject as digital images; and analyzing (330; 430-460) the light to monitor time-varying physiological parameters of the subject for biometric characterization of one or more human physiological parameters of the subject; wherein analyzing the light further comprises identifying the subject as a human subject from light reflected from the subject at first, second and third wavelengths, wherein the first wavelength comprises a wavelength in the range of 547 nanometers +/- 20 nanometers, wherein the second wavelength comprises a wavelength in the range of 577 nanometers +/- 20 nanometers, and wherein the third wavelength comprises a wavelength in the range of 607 nanometers +/- 20 nanometers; wherein analyzing the light further comprises: computing a first ratio of a pixel intensity of light reflected from the subject at a fourth wavelength divided by a pixel intensity of light reflected from the subject at the second wavelength; computing a second ratio of the pixel intensity of the light reflected from the subject at the fourth wavelength divided by a pixel intensity of the light reflected from the subject at a fifth wavelength; identifying a frequency content of a temporal variation of the first ratio and the second ratio; and computing a heart rate of the human subject from the frequency content of a temporal variation of the first ratio and the second ratio in a frequency band of 0.5 to 4.0 Hertz and computing a respiration rate of the human subject from the frequency content of a temporal variation of the first ratio and the second ratio in a frequency band of 0.05 to 0.5 Hertz, wherein the fourth wavelength comprises a wavelength in the range of 650 nanometers +/- 20 nanometers, and wherein the fifth wavelength comprises a wavelength in the range of 780 nanometers +/- 20 nanometers. collecting light (320; 420) reflected from a subject as digital images; and analyzing (330; 430-460) the light to monitor time-varying physiological parameters of the subject for biometric characterization of one or more human physiological parameters of the subject; wherein analyzing the light further comprises identifying the subject as a human subject from light reflected from the subject at first, second and third wavelengths, wherein the first wavelength comprises a wavelength in the range of 547 nanometers +/- 20 nanometers, wherein the second wavelength comprises a wavelength in the range of 577 nanometers +/- 20 nanometers, and wherein the third wavelength comprises a wavelength in the range of 607 nanometers +/- 20 nanometers; wherein analyzing the light further comprises: computing a first ratio of a pixel intensity of light reflected from the subject at a fourth wavelength divided by a pixel intensity of light reflected from the subject at the second wavelength; computing a second ratio of the pixel intensity of the light reflected from the subject at the fourth wavelength divided by a pixel intensity of the light reflected from the subject at a fifth wavelength; identifying a frequency content of a temporal variation of the first ratio and the second ratio; and computing a heart rate of the human subject from the frequency content of a temporal variation of the first ratio and the second ratio in a frequency band of 0.5 to 4.0 Hertz and computing a respiration rate of the human subject from the frequency content of a temporal variation of the first ratio and the second ratio in a frequency band of 0.05 to 0.5 Hertz, computing a first ratio of a pixel intensity of light reflected from the subject at a fourth wavelength divided by a pixel intensity of light reflected from the subject at the second wavelength; computing a second ratio of the pixel intensity of the light reflected from the subject at the fourth wavelength divided by a pixel intensity of the light reflected from the subject at a fifth wavelength; identifying a frequency content of a temporal variation of the first ratio and the second ratio; and computing a heart rate of the human subject from the frequency content of a temporal variation of the first ratio and the second ratio in a frequency band of 0.5 to 4.0 Hertz and computing a respiration rate of the human subject from the frequency content of a temporal variation of the first ratio and the second ratio in a frequency band of 0.05 to 0.5 Hertz, wherein the fourth wavelength comprises a wavelength in the range of 650 nanometers +/- 20 nanometers, and wherein the fifth wavelength comprises a wavelength in the range of 780 nanometers +/- 20 nanometers.