PHOTOPLOTTER MECHANISM FOR PRECISE APERTURE DISC POSITIONING

摘要

A precise positioning mechanism for positively orienting an aperture disc of a photoplotter. The mechanism inserts an index element into a ring of teeth mounted on or in cooperation with the aperture disc to angularly position the aperture disc so that the optical head axis is concentric with the indexed aperture. Also, an assembly process for mounting the aperture disc on its rotatable shaft to ensure initial radial and angular concentricity of optical head axis and apertures.