Patent ID: 7535554

Claim:
A displacement measuring method, comprising the steps of: locating a target having a reflective part for a laser beam at a measuring object position of a measuring object such that the reflective part is obliquely inclined with respect to a displacement measuring direction; locating a laser rangefinder at a position which is relatively displaced in the displacement measuring direction relative to the measuring object position; making a laser beam projected from the laser rangefinder to impinge obliquely on the reflective part along a different direction than the displacement measuring direction; with the laser rangefinder, receiving the reflected light returned from the reflective part in the direction generally parallel with the impinging direction of the laser beam; detecting a variation in the distance from the laser rangefinder to the laser beam reflecting position reflective part; and measuring the displacement of the displacement measuring object position in the displacement measuring direction by utilizing correlation between the detected variation and the displacement of the measuring object position in the displacement measuring direction, wherein plural small reflective faces which are generally orthogonal to the impinging direction of the laser beam are formed at the reflective part with their positions shifted successively in the impinging direction, and a beam diameter of the laser beam is set larger than a height of the respective small reflective faces such that the laser beam impinges on the plural small reflective faces of the reflective part at a same time, and the reflected lights from the respective small reflective faces are received with the laser rangefinder.