| 摘要 |
PURPOSE:To perform precise contactless position sensing of a notched part in an object to be sensed by a method wherein a light is projected on a circumference of the object to be sensed, and sensing is performed by the reception of light at a plurality of optical converters without interruption by the object to be sensed. CONSTITUTION:A semiconductor wafer as an object 12 to be sensed is placed on a turntable 11 which has permeability to light and it is rotated toward A direction. A light is radiated from a light source 14 and projected on the circumference of the object 12 to be sensed from the rear side of the table 11. A light which passes through without being interrupted by the object 12 to be sensed is reflected by a mirror 15 rotated by a driving part 3, and is led to a group of photoconverters 17 through a condenser 16. A position recognition part 2 recognizes a light projecting position to the object 12 to be sensed as a position where the notched part exists when photoconverters 17a-17c individually sense the transmitted light. |
