REFRACTION SENSOR

摘要

The present invention comprises the following: a light source (2) for outputting light; an optical bandpass filter (3) in which a dielectric multilayer film (8) is formed on one end surface (7A) of an optical fiber (7), an object of measurement (9) is in contact with one end (8B) of the dielectric multilayer film (8) opposite the other end (8A) thereof that is in contact with the optical fiber (7), and in which light output from the light source (2) is incident via the optical fiber (7); a measurement unit (4) for measuring the spectrum of reflected light reflected by the object of measurement (9); and a refractive index calculation unit (5) for calculating the refractive index of reflected light on the basis of the center wavelength of the reflected light spectrum measured by the measurement unit (4). The dielectric multilayer film (8) has disposed in substantially the center thereof a cavity layer (10), and a reflective multilayer film provided on both sides of the cavity layer (10) and comprising a laminate of a plurality of high refractive index layers (11) and a plurality of low refractive index layers (12). The combined optical thickness of the high refractive index layers (11) and the low refractive index layers (12) is lambda0/2 when the center wavelength of the light output from the light source (2) is lambda0, and the optical thickness of each of the high refractive index layers (11) and the low refractive index layers (12) is different from a value of lambda0/4.