Patent ID: 9551569
Date: 2017-01-24
CPC Classifications: G01B,G02B

Claim:
1. An apparatus for curvature and thin film stress measurement, comprising: a first light source and a second light source being configured to be located side by side and apart with a first distance, a first light beam from the first light source is tilted or inclined relative to a second light beam from the second light source; a first collimator and a second collimator, the first light beam from the first light source and the second light beam from the second light source projecting on a specimen apart with a second distance after being approximately collimated by the first collimator and the second collimator, such that the first light beam and the second light beam are brought to a sharp focus on the detector, after reflection from the specimen, wherein the first light beam from the first light source is tilted or inclined relative to the second light beam such that the first distance is larger than the second distance: a beam splitter being configured to be located between the first collimator and the second collimator and the specimen; and a detector, the beam splitter reflecting the first light beam and the second light beam reflected from the specimen to the detector specimen and calculating a curvature of the specimen according to a separation between spots of the first and second light beams on the detector, wherein the spots of the first and second light beams on the detector overlap if the specimen is flat.