Patent ID: 8593624

Claim:
A refractive index measuring apparatus comprising: a light source; a beam splitter that splits light from the light source into test light and reference light; a first probe optical system that collects the test light and then irradiates the test light onto a surface of a test object; a second probe optical system that collects the test light transmitted through the test object; a driving unit that displaces the first probe optical system and the second probe optical system on one optical axis such that an optical axis of the first probe optical system and an optical axis of the second probe optical system maintain coaxiality; a light-receiving element that allows the test light collected by the second probe optical system to interfere with the reference light and thereby obtains an interference signal; and a calculating unit that calculates a refractive index of the test object, based on the interference signal obtained by the light-receiving element, wherein a probe of one of the first probe optical system and the second probe optical system has an end with an exposed part and a non-exposed part, wherein a diameter of the exposed part is smaller than a wavelength of light irradiated therefrom and the non-exposed part is covered with an opaque covering layer.