Patent ID: 7330278

Claim:
An optical displacement measurement device for introducing light from a light source to an object through an optical system having an objective lens and for detecting light reflected from the object by a detection section to thereby measure a displacement of the object relative to the objective lens, wherein the objective lens is a conical lens for advancing the light toward the object and for receiving light reflected from the object to direct to the detection section, and the displacement of the object relative to the objective lens is measured in consideration that a shape of a detected image detected by the detection section varies depending on the displacement of the object relative to the objective lens, wherein the conical objective lens is a lens having a conical shape for receiving and refracting the light reflected from the object when the object is placed in a displacement measurement range defined between a far-side intersecting point and a near-side intersecting point, such that the light returns toward a detection section side and forms an image of the object, the size of which varies according to the displacement of the object relative to the objective lens, the far-side intersecting point being a point at which an outermost running light which is refracted at an external circumferential portion of the conical objective lens intersects a central optical axis of the conical objective lens, and the near-side intersecting point being a point at which a light portion refracted at a tip end of the conical objective lens intersects the outermost running light.