A contactless system for measuring and continuously monitoring arterial blood pressure includes a light source configured to illuminate light having at least one predetermined wavelength at a predetermined area of a human subject having an artery therein. A detector responsive to reflected light from the predetermined area is configured to continuously acquire images of the artery in the predetermined area. A processor is configured to process the images and determine: when an image at a proximal location of the predetermined area is darker indicating transition of a pulse wave into the artery at the proximal location and at a proximal time and when an image at a distal location of the predetermined area is darker indicating transition of the pulse wave into the artery at a distal location at a distal time, determine the difference in time between the distal time and the proximal time to calculate a pulse transit time (PTT), determine a length between the proximal location and the distal location, determine a diameter of the artery during a systolic phase of a cardiac pulse, determine a diameter of the artery during a diastolic phase of a cardiac pulse, calculate a pulse wave velocity of the pulse wave, calculate pulse pressure (ΔP), calculate an elastic modulus (E) of the artery, and contactlessly and continuously calculate the arterial blood pressure for each cardiac cycle of the human subject.
