Mechanical alignment of optical systems: practical limits and accuracy estimation

Traditional alignment techniques for optical systems are usually based on iterative procedures where each optical element is positioned and aligned with push-pull systems and the feedback is provided by the images acquired on the focal planes. The long-term stability of those optomechanical mounts can be critical and, in order to overcome this limitation a new mounting has been proposed together with a new alignment strategy based on the direct mechanical measurement of the optical surfaces. In this paper, the practical alignment limitations of this technique and the best possible strategy will be presented with the support of different experiments. A software used to predict the accuracy of the CMM measurements will also be described together with the validation results on a dummy optical system.