Apparatus and method for sensing an insertion state of a wafer i

Details Apparatus and method for sensing an insertion state of a wafer i Apparatus and method for sensing an insertion state of a wafer i

1998-11-10

2000-03-28

Font, Frank G.

Radiant energy

Photocells; circuits and apparatus

With circuit for evaluating a web, strand, strip, or sheet

25055937, 356375, G01N 2186

Patent

active

06043502&

ABSTRACT:
An apparatus for sensing an insertion state of a wafer disposed in a slot of a wafer cassette, includes a stage supporting the wafer cassette that is movable relative to a light beam source and photo-detector positioned on either side of the wafer cassette. A position determining mechanism is connected to the photo-detector and a timer is connected to the position determining mechanism. The position determining mechanism receives, from the photo-detector, a position signal indicative of a wafer disposed in the light path. The timer generates a pulse signal that is received by the position determining mechanism after a predetermined time period has elapsed from a time when the position signal is received by the position determining mechanism. The position determining mechanism generates a decision signal, indicative of a wafer incorrectly loaded in a slot of the wafer cassette, when the position signal and pulse signal overlap.

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patent: 5225691 (1993-07-01), Powers et al.
patent: 5239182 (1993-08-01), Tateyama et al.
patent: 5319216 (1994-06-01), Mokuo et al.
patent: 5513948 (1996-05-01), Bacchi et al.

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