Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1991-06-24
1993-11-02
Rosenberger, Richard A.
Optics: measuring and testing
By polarized light examination
With light attenuation
356401, G01B 1114
Patent
active
052588238
ABSTRACT:
An alignment system incudes a sensor device including a pair of a light emitting element and a light receiving element, for detecting an edge of a substrate without contact thereto; a driving device for supporting the substrate and for moving the substrate; and a control device for controlling the driving device so as to position the substrate, wherein the control device controls the driving device so that the sensor device produces an output of a level which is within a predetermined tolerance range with respect to a set level, and wherein the control device is operable to renew the set level at a predetermined timing on the basis of (i) a first output of the sensor device corresponding to an output of the sensor device as produced in a first state in which light from the light emitting element of the sensor device is received by the light receiving element of the sensor device without being blocked and (ii) a second output of the sensor device corresponding to an output of the sensor device as produced in a second state in which the light reception of the light receiving element is completely blocked.
REFERENCES:
patent: 4853880 (1989-08-01), Akamatsu et al.
patent: 4887904 (1989-12-01), Nakazato
Canon Kabushiki Kaisha
Hantis K. P.
Rosenberger Richard A.
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