Patent ID: 8174682

Claim:
A shape measuring instrument comprising: a laser diode for emitting a laser beam; a first optical system irradiating a surface of an object to be measured with laser beam emitted from the laser diode; a second optical system for focusing the laser beam reflected from the surface of the object to be measured; and a line sensor for detecting the laser beam from the second optical system, wherein the first optical system includes: an optical path displacing unit for displacing an optical path of the laser beam such that the laser beam from the second optical system is properly focused on the line sensor, wherein the optical path displacing unit includes: a glass plate rotatable about an axis of rotation wherein rotation causes a parallel displacement of the laser beam at the displacing unit and a displacement of the laser beam in a direction forming an angle of 90° to the line sensor at the line sensor; a rotating unit for rotating the glass plate; and a rotating unit controller for controlling the rotating unit, wherein the rotating unit controller measures an amount of light received by the line sensor corresponding to an angle of rotation of the rotating unit and causes an angle of rotation of the rotating unit to coincide with the angle of rotation of the rotating unit obtained when the maximum value of an amount of light received by the line sensor was measured.