Patent ID: 7777874

Claim:
A noncontact form measuring apparatus having an objective optical system configured to be movable in the direction of an optical axis thereof, a laser source configured to emit a laser beam, the laser beam running in parallel with the optical axis, entering the objective system at a noncentral point off the optical axis, and being reflected by an inner face of a measurement object, a reflected laser beam entering the objective optical system, an optical position detector configured to receive the reflected laser beam traveling through the objective optical system, and a focusing unit configured to move the objective optical system in the direction of the optical axis according to positional information provided by the optical position detector so that a focal point of the emitted laser beam is positioned on an inner face of the measurement object, the noncontact form measuring apparatus comprising: a reflector arranged between the objective optical system and the inner face of the measurement object and configured and positioned to reflect the laser beam traveling through the objective optical system in an imaginary plane containing the laser beam and the optical axis, so that the reflector reflects the laser beam traveling through the objective optical system toward the inner face of the measurement object and reflects the reflected laser beam from the inner face of the measurement object toward the objective optical system.