An optical sensor generates blood pressure data by obtaining two dimensional images of the surface of the patient's body, such as in the vicinity of the radial artery in the wrist area. Blood flow in the patient causes light to be reflected off a flexible reflective surface applied against the patient with a hold down pressure, and the scattering of light is sensed with a two-dimensional array of photo-detectors. The output of the photo-detectors during systolic and diastolic events is calibrated against known blood pressure measurements taken with a conventional air-cuff sphygmomanometer. Linear calibration relationships between output signal and blood pressure are obtained during calibration for some set of the photo-detectors. When blood pressure data is obtained from the patient, the linear calibration relationship between output signals and blood pressure is applied to the output signals from the set of photo-detectors, resulting in blood pressure data. The method provides for compensation for changes in hold down pressure and translation or rotation of the optical sensor relative to the patient. A preferred optical sensor arrangement for use in performing the method is also described.