Patent ID: 7242485

Claim:
A displacement gauge comprising: a light emitting portion for emitting light to be projected onto a measurement subject; an objective lens for receiving light emitted from said light emitting portion and projecting light onto said measurement subject; an exciting portion for vibrating said objective lens along a first direction at a preset amplitude; a position detector for detecting the position of said objective lens that is moved in said first direction; a light diaphragm portion for passing a reflected light from said measurement subject; a light receiving portion for receiving light passing through said light diaphragm portion; a displacement operation portion for acquiring a detected position from said position detector at the moment when the light received amount of light received by said light receiving portion is maximum, and calculating the displacement on said measurement subject based on said detected position; an objective lens scan portion connected to said objective lens, said objective lens scan portion has a rotational axis, said objective lens scan portion moving said objective lens in a second direction orthogonal to said first direction around the rotational axis; and an operation processing portion for calculating the two dimensional displacement regarding said measurement subject, based on the measurement result of displacement at each measuring point, by moving said objective lens along said second direction by said objective lens scan portion to move a measuring point on said measurement subject in a predetermined amount of movement and measuring the displacement at plural measuring points.