To provide a surface plasmon sensor capable of suppressing an irregurality in heating and quantity of light by allowing a laser beam to enter the surface of the sensor in a beam diffused state and capable of certainly measuring even the small surface of the sensor.
A holding member 58 (rail part 58A) is moved in a Y-direction by predetermined quantity. By this constitution, the incident angle range of the laser beams M1 and M2 incident on a measuring region E1 and a reference region E2 is changed from θ1 to θ2. For example, when the incident angle range θ1 is set to a range of incident angles α1-α2, the incident angle range θ2 becomes a range of α3-α4 and the incident angle range of the laser beams M1 and M2 entering the measuring region E1 and the reference region E2 changes. The holding member 58 is continuously moved until a dark line U is detected.
Kato Kazunori
Katsuichi Nishimoto
Hiroshi Fukuda
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