A noninvasive device for photoelectrically measuring a property of arterial blood is provided. Light that contacts living tissue with arterial blood is converted into a pair of electrical signals. The electrical signals are processed to provide information of the amplitude of the measured signals and...http://www.google.com/patents/US4586513?utm_source=gb-gplus-sharePatent US4586513 - Noninvasive device for photoelectrically measuring the property of arterial blood
