An Equivalent Tolerance Design Method for Imaging System

The traditional tolerance analysis of optical design does not consider the capability of the manufacturing process and the quality variation of the assembly process caused by the manufacturing errors of optical and mechanical components. This paper presents an equivalent tolerance design method in which an enlarged field angle is used during the optical design process. The method comprises of four steps of: (I) provides an optical system which satisfies its specification; (II) performs the sensitivity analysis; (III) defines an enlarged field angle of the optical system based on the previous step (II); and (IV) redesigns the optical system with an enlarged field angle to meet the specification. An enlarged field angle was involved in the optical system design process, so as to achieve the effect of tolerance design. A 2.5 X close-up lens for digital-micro-imaging is applied to the study of the equivalent tolerance design method. As a result, the performance of this lens can meet the designed specifications.