Method and apparatus for remote position sensing using edge diffraction

US5024527A · kind A · utility

Assignee

• British Aerospace Public Limited Co. · GB

Inventor

• Andrew Harrison · Houston, US

Key dates

• Filing date: Mar 31, 1989
• Grant date: Jun 18, 1991
• Expiry date: Mar 31, 2009

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T82/148
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

Contact lenses can be made by machining an inner concave surface into a plastics material blank, then mounting the blank in a lathe and machining the outer convex surface thereon. Repeated measurement with a micrometer is needed during the latter machining to ensure that the lens vertex is correctly formed. To avoid this, the sensor described herein comprises a remote laser source from which radiaiton passes the lens vertex in the blank to a detector, the items being arranged so that, when the lens has been correctly machined, a surface diffraction effect occurs at the vertex leading to a detectable signal from the detector. The basis of the technique is the projection of an image of an edge diffraction intensity distribution through a slit to the detector while the non-diffracted component of the laser beam is prevented from reaching the detector. The high intensity laser diffraction edge pattern generates a narrow symmetric output signal from the detector as the edge traverses the slit, thereby enabling test piece positions to be located along the translation axis. The disclosed sensor apparatus may use the same technique during manufacture of items other than contact lenses and …