Patent ID: 8175669

Claim:
An apparatus for measuring an oxygen saturation in blood, comprising: a plurality of light emitters, adapted to irradiate a living tissue with a plurality of light beams having different wavelengths; a light receiver, adapted to receive the light beams reflected from or transmitted through the living tissue to generate pulse wave signals in accordance with pulsations of the blood in the living tissue; a separator, operable to separate each of the pulse wave signals into a plurality of amplitude signals each of which is associated with one frequency, thereby generating pairs of amplitude signals each of which is associated with one of a plurality of frequencies; a first processor, operable to calculate a ratio between the amplitude signals in each of the pairs of the amplitude signals; a selector, which is operable to select one of the pairs of the amplitude signals based on the amplitude values of the amplitude signals, wherein the selector selects a pair of the amplitude signals that have maximum amplitude values; and a second processor, operable to calculate the oxygen saturation based on the ratio of the selected one of the pairs of the amplitude signals.