THICKNESS MEASURING INSTRUMENT

PURPOSE:To measure the thickness of an object of inspection automatically with high accuracy by projecting light on the top and reverse sides of the object of inspection and measuring the displacement of a measurement point from a reference point by using the reflected light. CONSTITUTION:A surface-side measuring means 20 projects light on the groove bottom 3 of a work 1 and measures the displacement of the groove bottom 3 from a surface-side reference line of reference thickness busing the reflected light. A reverse-side measuring means 21 projects light on nearby the reverse side of the groove bottom 3 of the work 1 and measures the displacement of the reverse surface 4 from a reverse-side reference line of reference thickness by using the reflected light. The processor 40 of an arithmetic means 22 calculates the thickness based on data from the top-side measuring means 20 and data from the reverse-side measuring means 21 and outputs it to a display device 41.