Patent ID: 7252575

Claim:
A polishing apparatus comprising: a top ring for holding a workpiece; a rotating polishing table having a polishing surface which is brought in sliding contact with the workpiece; a pulsed light source energizing at a sampling time; a light transmission unit provided in said polishing surface, wherein said top ring is controlled such that said light transmission unit passes across a center of the workpiece; a light-emitting unit for applying light from said pulsed light source to a surface, being polished, of the workpiece; a light-receiving unit for receiving reflected light reflected from the surface of the workpiece and transmitted through said light transmission unit; a spectroscope unit for dividing the reflected light received by said light-receiving unit into a plurality of light rays having respective wavelengths; light-receiving elements for detecting the light rays divided by said spectroscope unit, wherein each of said light-receiving elements accumulates the detected light rays as electrical information during a sampling period and releases the electrical information; and a control unit for controlling said pulsed light source to energize when said pulsed light source faces the center of the workpiece.