20090051924 | APPARATUS FOR MEASURING THICKNESS OF A SUBSTRATE - An apparatus for measuring thickness is provided. A light source irradiates a front surface or a rear surface of a substrate with a light. A splitter splits the light into a reference light and a measurement light. The reference light is reflected by a reference light reflecting device. An optical path changing device changes an optical path length of light reflected from the reference light reflecting device. A light receiving device measures an interference of the reflected light from the substrate and the reference light from the reference light reflecting device. A thickness of at least one of the front surface, rear surface or inside of the substrate is measured based on a measurement of the interference. | 02-26-2009 |