Wafer detecting device wherein light receiver has an effective surface larger than the dimensional range covering all the wafers being detected

A wafer detecting device usable with a carrier having a plurality of wafer carrying portions disposed, along an axis, in stories for carrying wafers thereon, said device comprising:

• light emitting means for emitting light so that it passes through the carrier from a first side thereof to a second side thereof and in a direction substantially parallel to a plane in which a wafer is carried on a wafer carrying portion of the carrier;
• and
• light receiving means disposed at said second side of the carrier, for detecting the presence or absence of the light passed through the carrier;
• wherein said light emitting means includes scanning means for translating the light in a direction substantially parallel to said axis and over a dimensional range covering all the wafer carrying portions disposed along said axis, and wherein said light receiving means is fixed relative to the carrier and include optical means disposed at said second side of the carrier for directing to a light receiving surface of said light receiving means the light emerging from the carrier in the dimensional range covering all the wafer carrying portions.

A wafer detecting device usable with a carrier having a plurality of wafer carrying portions disposed in stores along a wafer axis for carrying wafers thereon, said device comprising:

• light emitting means for emitting light so that it passes through the carrier from a first side thereof to a second side thereof and in a direction substantially parallel to a plane in which a wafer is carried on a wafer carrying portion of the carrier;
• and
• light receiving means disposed at said second side of the carrier, for detecting the presence or absence of the light passed through the carrier;
• wherein said light emitting means includes scanning means for translating the light in a direction substantially parallel to the axis and over a dimensional range covering all the wafer carrying portions disposed along said axis, and wherein said light receiving means is fixed relative to the carrier and includes optical means for directing, to a light receiving surface of said light receiving means, the light emerging from the carrier in the dimensional range covering all the wafer carrying portions disposed along said axis and wherein said optical means is disposed at said second side of the carrier and includes optical path changing means.