| 摘要 |
An edge detection method includes preparing a transparent substrate which includes a first main face having a first main region and a first peripheral region and a second main face having a second main region and a second peripheral region, the first peripheral region having an inclination angle of &thetas;a1 and the second peripheral region having an inclination angle of &thetas;a2, causing measuring light to enter the first peripheral region from a direction perpendicular to the first main region, detecting a non-emitting region where the measuring light is not emitted from the second peripheral region, and detecting an edge of the transparent substrate on the basis of the non-emitting region, wherein if a refractive index of the transparent substrate is n, the inclination angles &thetas;a1 and &thetas;a2satisfy the following expression: n×sin(&thetas;a1+&thetas;a2−arcsin(sin &thetas;a1/n))≧1. |
