Tolerance compensation in micro-optics

Abstract

In contrast to microelectronics which may be considered two-dimensional in first approximation, micro-optical systems extend over three dimensions. Due to the lack of a uniform material system, complex micro-optical systems are constructed using a modular concept. The modular setup of such hybrid systems results in an isolated manufacture of the individual components and their later assembly in a single system. Designing a micro-optical system, all relevant requirements and constraints defined by the manufacturing processes and the application of the system in a real ambience must be considered. Furthermore, every individual manufacturing step adds its own tolerances to the system. To maintain the overall function of a system under the given manufacturing conditions, the system design has to be robust with respect to the expected tolerances. The system's robustness will result from considering process knowledge in the state of modeling already. Process knowledge of non-silicate manufacturing processes is collected and stored in a knowledge database. On basis of these data, process-dependent inaccuracies and tolerances can be used to design robust functional components and functional units (subsystems). This approach of robust, tolerance compensating design is applied to the design of an infrared gas sensor, a micro-optical distance sensor, and a lens of variable refraction power.