Patent ID: 8107088

Claim:
A displacement sensor comprising: a light projecting unit for applying light by an intensity signal having a specific frequency component; an open portion including a light shielding member configuring an opening, the light shielding member shielding at least one portion of the light applied from the light projecting unit, the opening passing other portions of the light applied from the light projecting unit, and the open portion having the light passed through the opening as a new diverging light by cutting out the applied light; a sweep converging unit for converging and applying the diverging light passed through the opening towards a measuring object, and continuously changing a converging position of the light by a predetermined mode along an optical axis direction of the converging light, and guiding a reflected light of the light applied onto the measuring object to the open portion by advancing the reflected light in an opposite direction with respect to an optical path of the diverging light; an optical path separating element for separating the optical path of the reflected light passed through the opening from the optical path of the irradiation light from the light projecting unit to the opening; a light receiving unit for receiving the reflected light separated from the optical path of the irradiation light by the optical path separating element, and outputting a light receiving signal corresponding to an incident light quantity; a filter unit for obtaining a filter processed signal by removing the signal of the specific frequency component from the light receiving signal; and a processing unit for acquiring information on a distance to the measuring object based on the filter processed signal; wherein the open portion changes a proportion of the reflected light passing through the opening when the converging position of the reflected light from the measuring object changes by operation of the sweep converging unit; the specific frequency component of the signal intensity of the light applied by the light projecting unit is a frequency component different from a frequency component of the light receiving signal, which changes by the operation of the sweep converging unit, or a frequency component of one portion of the frequency component of the light receiving signal; and the processing unit acquires the information on the distance to the measuring object based on change of the filter processed signal, which occurs by the operation of the sweep converging unit.