A novel opto-mechanical tolerance analysis method for precision lens systems

Traditional tolerance analysis of optical systems does not consider the capabilities of a real manufacturing process and variations caused by the tolerances of optical and mechanical components that occur in the assembly process. In order to have a “Design for Manufacturing” (DFM) optical system, the mechanical engineer has to provide the system assembly variation as an input to the optical design and analysis in order to anticipate the performance of the optical system. The purpose of this study was to develop an opto-mechanical tolerance model to calculate the element tilt, decenter and despace stack-up within a cell. A surface-based opto-mechanical tolerance model of a spherical lens, an aspherical lens, and an assembly algorithm were developed in this study. The Monte Carlo method was also used to obtain the optimum settings of the dimensions. The simulation results were conducted by descriptive statistics. Two “drop-in” assembly design lens groups were studied to calculate the stack-up element tilt and decenter within a cell and the resultant deviations of the optical axes away from the mechanical datum axis. The results indicate that the opto-mechanical tolerance model can analyze the quality parameters critical for a lens system. As a result, the performance of the lens system can be predicted by the opto-mechanical tolerance model before mass production.