Patent ID: 7064837

Claim:
A sensor utilizing attenuated total reflection, comprising: a light source for emitting a light beam; a measuring chip comprising a dielectric block transparent to said light beam, a thin film layer formed on the top surface of said dielectric block, and one or a plurality of liquid-sample holding portions for holding a liquid sample on said thin film layer; an optical system for making said light beam enter said dielectric block at various angles of incidence so that a total internal reflection condition is satisfied at an interface between said dielectric block and said thin film layer; photodetection means for detecting intensity of said light beam totally reflected at said interface; and measurement means for measuring a state of attenuated total reflection, based on the result of detection obtained by said photodetection means; wherein the liquid-sample holding portion of said measuring chip has an opening at its top surface; and wherein said sensor further comprises a lid-means supply means for placing a lid means on said opening to prevent evaporation of said liquid sample.