Patent ID: 9453721
Filing Date: 2016-09-27
CPC Classification: G01B,H01L

Claim Text:
1. A curvature measurement apparatus, comprising: a light emitter configured to emit a laser beam; a first polarization beam splitter configured to separate the laser beam emitted from the light emitter into a first laser beam and a second laser beam which are in different polarization directions and in different travel directions; a reflector configured to reflect any one of the first and second laser beams so that the first and second laser beams travel side by side to a measurement object; a second polarization beam splitter configured to transmit any one of the first and second laser beams mirror-reflected from the measurement object, and to reflect the other laser beam in a direction different from a travel direction of the one laser beam; a one-dimensional first position detector configured to detect an incident position where the first laser beam reflected from or transmitted through the second polarization beam splitter is incident on the first position detector; a one-dimensional second position detector configured to detect an incident position where the second laser beam transmitted through or reflected from the second polarization beam splitter is incident on the second position detector; and a calculator configured to calculate a difference between a displacement of the incident position of the first laser beam detected by the first position detector and a displacement of the incident position of the second laser beam detected by the second position detector, and calculate a curvature change of the measurement object based on a correlation between the calculated difference and the optical path lengths of the first and second laser beams.