Proceedings PaperDevelopment of an optomechanical statistical tolerancing method for cost reduction
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Optical systems generally require a high level of optical components positioning precision resulting in elevated manufacturing cost. The optomechanical tolerance analysis is usually performed by the optomechanical engineer using his personal knowledge of the manufacturing precision capability. Worst case or root sum square (RSS) tolerance calculation methods are frequently used for their simplicity. In most situations, the chance to encounter the worst case error is statistically almost impossible. On the other hand, RSS method is generally not an accurate representation of the reality since it assumes centered normal distributions. Moreover, the RSS method is not suitable for multidimensional tolerance analysis that combines translational and rotational variations. An optomechanical tolerance analysis method based on Monte Carlo simulation has been developed at INO to reduce overdesign caused by pessimist manufacturing and assembly error predictions. Manufacturing data errors have been compiled and computed to be used as input for the optomechanical Monte Carlo tolerance model. This is resulting in a more realistic prediction of the optical components positioning errors (decenter, tilt and air gap). Calculated errors probabilities were validated on a real lenses barrels assembly using a high precision centering machine. Results show that the statistical error prediction is more accurate and that can relax significantly the precision required in comparison to the worst case method. Manufacturing, inspection, adjustment mechanism and alignment cost can then be reduced considerably.