Patent ID: 7692791

Claim:
A target substance-detecting apparatus comprising: a target substance-detecting element comprising metal structures; a light irradiation section for irradiating the target substance-detecting element with a light; a light-polarizing section which polarizes the irradiating light and separates an output light emitted from the target substance-detecting element into a first polarized light and a second polarized light having a vibration direction different from that of the first polarized light; a first light-receiving section for outputting a first signal according to intensity of the first polarized light; a second light-receiving section for outputting a second signal according to intensity of the second polarized light; and a control section which determines a peak of absorbance of the first polarized light by measuring the absorbance from the first signal, determines a peak of absorbance of the second polarized light by measuring the absorbance of the second polarized light from the second signal, and controls the target substance-detecting element so that the peak value of the first absorbance is maximized and simultaneously the peak value of the second absorbance is minimized by controlling an incidence angle of formed by a vibration direction of the incident light and a main axis of the target substance-detecting element.