| 摘要 |
PURPOSE:To realize a wafer detecting unit free of moving mechanism by a method wherein a carrier, wherein wafers are accommodated in its wafer accommodating stages, is provided between a light-emitting section and light-receiving section and the effective light-receiving area of the light-receiving section is larger than the total of the areas of the wafer accommodating stages. CONSTITUTION:In a carrier 1, in its wafer accommodating stages, wafers 2 are accommodated. From a light-emitting section 3, a beam-like optical flux, sufficiently smaller than a wafer 2 in thickness, radiates to travel through one end of the carrier 1, along the wafer surface, and through the other end of the carrier 1. At the other end of the carrier 1, the beam goes into a light- receiving surface 8 of a light-receiving section 7. The beam axis runs along the surfaces of the wafers 2, and the light-emitting section 3 is driven to move in parallel with the direction of the accumulation of the accommodating stages. The light stops short of the light-receiving section 7 when a wafer 2 is in the way of the optical axis. The position of the scanning light-emitting section 3 and the output of the light-receiving section 7 determine if there is a wafer in each of the wafer accommodating stages in the carrier 1 and, if any, its position.
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