Patent ID: 7655900

Claim:
An intensity modulation type optical sensor comprising: a sensor head including a optical component which is supplied with light from a light source and modulates a intensity of the light on the basis of an alternating current (AC) measured object changing with time; a first photoelectric converter which receives and converts the light modulated by the sensor head into an electric signal; a first divider which calculates a normalized received signal indicating a degree of modulation from a ratio of an AC component and a direct current (DC) component of the electrical signal converted by the first photoelectric converter; a fiber coupler which separates a part of the light before being supplied to the sensor head to obtain reference light; a second photoelectric converter which receives and converts the reference light into an electric signal; a second divider which calculates a normalized reference signal from a ratio of an AC component and a DC component of the electrical signal converted by the second photoelectric converter; and a subtractor which calculates a value of the AC measured object by subtracting the normalized reference signal from the normalized received signal.