LAGESENSOR.

摘要

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 laser source (12) from which radiation passes over a knife edge member (13) and the blank (10) to a detector (15), the items being arranged so that, when the lens has been correctly machined, a surface diffraction effect occurs leading to a detectable signal from the detector (15). The disclosed sensor apparatus could be used during manufacture of items other than contact lenses.