Patent ID: 7596425

Claim:
A substrate detecting apparatus for detecting an inclined state of a substrate with respect to a horizontal plane, comprising: a supporting device that supports a substrate; and a detector that detects said inclined state of the substrate by measuring a distance to the surface of the substrate supported by said supporting device, said detector including: a distance measuring sensor that measures as reference values distances to at least three measurement points on the surface of the substrate substantially horizontally supported by said supporting device, and subsequently measures as measurement value distances to said at least three measurement points on the surface of the substrate supported by said supporting device; and a determiner that calculates differences between the reference values obtained from said distance measuring sensor and the measurement values obtained from said distance measuring sensor respectively and determines the inclined state of the substrate based on said differences for said at least three measurement points wherein said detector detects an angle of inclination of the substrate as the inclined state of the substrate supported by said supporting device; further comprising a second determiner that determines that the inclined state of the substrate is abnormal when the angle detected by said detector is not less than a predetermined value.