Pulse oximeter probe-off detection system

A sensor which generates at least first and second intensity signals from a light-sensitive detector which detects light of at least first and second wavelengths transmitted through body tissue carrying pulsing blood;

• the sensor comprising:
• at least one light emission device;
• a light sensitive detector;
• and
• a plurality of louvers positioned over the light sensitive detector to accept light from the at least one light emission device originating from a general direction of the at least one light emission device and then transmitting through body tissue carrying pulsing blood, wherein the louvers accept the light when the sensor is properly applied to tissue of a patient.

A method of processing one or more signals to detect a condition of improper positioning of an optical probe, the method comprising:

• expecting to receive at least first and second intensity signals from a light-sensitive detector which detects light of at least first and second wavelengths transmitted through body tissue carrying pulsing blood;
• blocking light originating from an angle oblique to a proximate relationship between the detector and a light source;
• and
• receiving one of an un-interpretable signal or signal other than the expected first and second intensity signals because the light is blocked;
• and
• indicating a probe off condition.