Optical gauge with adjustable light path bending mirror

An optical gauge having a table for carrying thereon an object of measurement and an optical system so arranged that said table and said optical system are movable relative to each other in three dimensions and adapted to irradiate the object with light downwardly from above and receive the light reflected by the object placed on the table to measure more than one dimension and determine the profile of the object on the basis of the image obtained by the optical system, wherein the optical gauge comprises:

• a mirror holder ring fitted to a lower end portion of the optical system and rotatable around the optical axis of the optical system;
• a light path bending mirror secured to the mirror holder ring such that the light path bending mirror is rotatable around an axis perpendicular to the optical axis of the optical system to turn the light path originating from the optical system in order to irradiate a lateral side of the object of measurement with light and turn back the light reflected by the object to make it enter the optical system;
• and
• a mirror rotary angle sensor for detecting the rotary angle of the light path bending mirror around the optical axis.