Beyond centration: how to create, read, and use a datum system per ISO-10110-6 (2015)

摘要

Optical designs have traditionally been designed around an axis of symmetry to which the actual components mustconform within specified tolerances. Until recently and with few exceptions, it has been sufficient for the drawings ofthe several elements to call out local surface tilt tolerances at the physical centers of each element (or between two planefaces.) DIN 3140 and ISO 10110-6 (1996) created a formal framework for specifying surface tilt. While surface tilt mayhave been the specification, it wasn’t always a convenient method of measurement in the shop: Edge thickness variation,beam deviation, or axis decenter are sometimes better fits to the production and QA capabilities or optomechanicalrequirements. In the U.S., subsets of ASME Y14.5M were combined with text drawing notes allowing both greaterflexibility and frequent and occasionally expensive misunderstandings.With modern optical manufacturing and design techniques allowing widespread utilization of rotationally invariantaspheres, torics and biconics, and freeform optics – many with non-circular edges – the terms “centration” and “tilt” areno longer adequate to specify the geometric relationships between one or more surfaces and their mechanical boundariesand constraints. In response, ISO 10110-6 (2015) has been greatly expanded to meet the needs of an advancing industry– and to support measurement methods more directly associated with optomechanical requirements and shopcapabilities. This article is a tutorial to aid in understanding and using this essential document.