Kabushiki Kaisha Toshiba

Shunji Kikuchi

Takayuki Sakai

Itsuko Sakai

Masayuki Dohi

Akihiro Hori

Takuto Inoue

Masayuki Narita

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 &#x3b8;aand the second peripheral region having an inclination angle of &#x3b8;a, 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 &#x3b8;aand &#x3b8;asatisfy the following expression:sin(&#x3b8;1+&#x3b8;2&#x2212;arcsin(sin &#x3b8;1/))&#x2267;1.

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Kitakami, Japan

Shunji Kikuchi