Patent ID: 7379189

Claim:
A temperature/thickness measuring apparatus comprising: a light source that emits light to be transmitted through and reflected at two end surfaces of a measurement target, which is reflected reciprocally at least twice at the two end surfaces of said measurement target; a splitter that splits said light from said light source into measurement light and reference light; a reference light reflecting means for reflecting said reference light from said splitter; an optical path length altering means for altering the optical path length of said reference light reflected at said reference light reflecting means; a reference light transmitting means for transmitting said reference light from said splitter to a reference light radiation position at which said reference light is radiated toward said reference light reflecting means; a measurement light transmitting means for transmitting said measurement light from said splitter to a measurement light radiation position at which said measurement light is radiated toward said measurement target; a light receiving means for measuring a plurality of measurement light interference waveforms obtained as interference of measurement beams each transmitted through or reflected at said measurement target and said reference light reflected from said reference light reflecting means occurs; and a measuring means for measuring the optical path length of said measurement light indicated by the distance between the two end surfaces of said measurement target based upon a reference interference waveform which is one of said plurality of measurement light interference waveforms measured by said light receiving means and a selected interference waveform selected from said plurality of measurement light interference waveforms, which corresponds to a measurement beam reciprocally reflected at the two end surfaces of said measurement target at least twice more than the number of times the measurement beam corresponding to said reference interference waveform is reciprocally reflected at the two end surfaces and measuring the temperature/thickness of said measurement target based upon the optical path length thus measured.