Device for accurate positioning of lens blank - has optical element transmitting light only in direction normal to reference image to avoid parallax errors

摘要

The equipment is used for the accurate positioning of a lens blank (14) with reference to the plane surface (17) of a screen (16) on which is projected the image of a reference point system. To this end an optical element (26) through which light can be transmitted in only one direction is interposed between the lens blank and the reference point system image with its axis of transmission normal to the plane surface (17). When positioning the blank the operator is compelled to view truly vertically, thus avoiding parallase errors. The optical element (26) may be a sheet of spar or quarz. USE/ADVANTAGE - Production of spectacles lenses. Simple, accurate positioning system.