Patent ID: 8427644

Claim:
An optical displacement meter configured to measure a position of a measurement target, the optical displacement meter comprising: an objective lens; a broadband light source placed at a confocal point opposite to the measurement target with respect to the objective lens; a spatial filter placed at a position of a confocal point achieved when light reflected from the measurement target returns, the spatial filter being configured to extract light under measurement of a wavelength focused on the measurement target and to specify the wavelength of the light under measurement; a polarizer configured to divide the light under measurement collimated and caused to propagate in one direction into linearly polarized beams in first and second directions orthogonal to a propagating direction; a wavelength plate that allows passage of the linearly polarized beams in the first and second directions to produce elliptically polarized light having a phase difference commensurate with a light wavelength; a polarized light separator configured to divide the elliptically polarized light into first and second polarized light components in the first and second directions; a light receiving element configured to detect quantities of the first and second polarized light components; and a computing circuit configured to perform computation of (A−B)/(A+B) by use of light quantity signals A and B, which respectively correspond to the quantities of the first and second polarized light components detected by the light receiving element.