Patent ID: 8040529

Claim:
A displacement sensor including a confocal displacement meter that determines a surface displacement from a light collecting position at time a light receiving amount becomes maximum and comprises: a first light projecting unit that emits light having a first wavelength; a first light receiving unit that receives the light having the first wavelength; a sweep light collecting unit that collects the light emitted from the first light projecting unit toward a measurement object to illuminate the measurement object, changes continuously a collecting position of the light along an optical axis direction of the collected light, causes reflected light of the light with which the measurement object is illuminated to travel in a direction opposite to an optical path of the light emitted from the first light projecting unit, and leads the reflected light to the first light receiving unit; and a first optical path separating unit that separates an optical path of the reflected light from an optical path from the first light projecting unit to the measurement object; the displacement sensor comprising: a second light projecting unit that emits light having a second wavelength different from the first wavelength to the measurement object; a second optical path separating unit that separates an optical path of the light having the second wavelength reflected on the measurement object through the optical path of the reflected light; and a second light receiving unit that receives the light whose optical path is separated by the second optical path separating unit, and wherein the second light receiving unit is a telecentric optical system including an imaging device and an opening diaphragm, a diameter of the opening diaphragm being designed such that the telecentric optical system has a depth of field not lower than a range in which the light collecting position is changed by the sweep light collecting unit.