Patent ID: 7470235

Claim:
A measuring apparatus for detecting a pulse wave signal indicating a change in a blood flow in the blood vessel of a patient by using light, comprising: a sensor module including a plurality of light-emitting elements to irradiate the blood vessel, and a plurality of light-receiving elements to receive reflected light as a pulse wave signal from the blood vessel, each element being configured to be attached on the surface of the patient; a processor for light emission that causes the plurality of light-emitting elements to emit light one after another; an autocorrelation value calculating processor that calculates autocorrelation values of respective pulse wave signals corresponding to respective combinations of the light-emitting elements, which have emitted light, and the light-receiving elements, which have received light, respectively; and an optimum position identifying processor that selects a combination of a light-emitting element and a light-receiving element, which has outputted a pulse wave signal with a highest autocorrelation value among the respective autocorrelation values, as an optimum combination, wherein the autocorrelation value calculating processor slices waveforms of pulse wave signals in an arbitrary period from the pulse wave signals, respectively, and obtains an autocorrelation between the sliced waveforms and the pulse wave signals to thereby calculate autocorrelation values of the respective pulse wave signals.