Integrated opto-mechanical modeling with scene-based metrology techniques for structural dynamics compensation

This paper provides a summary of recent work in the development of integrated, multi-physics models for controlled opto-mechanical systems. Standard approaches from the literature are used to model the dynamics of the structure, including piezoceramic actuators, and generate a simple state space system for the actuator-structure dynamics. Next, linear sensitivities of the coefficients of the standard Zernike orthonormal basis set for representing optical aberrations are generated with respect to motions of the optics around the equilibrium point, using commercially available ray-trace software. Using this linear sensitivity representation, the optical path difference (OPD) at a reference pupil plane is reconstructed. Inclusion of additional defocus terms to these Zernike coefficients yields a second aberration function to allow for the reconstruction of the OPD at a defocused pupil plane as well. For both of these planes, Fourier analysis is used to obtain the images produced at the corresponding image plane. The two images are provided to a phase diversity algorithm that returns estimates of the Zernike coefficients, yielding an estimated aberration based on sensed images. Laser metrology sensor signals are modeled via the addition of physically realistic noise to the structural perturbation signals, and are used to develop a control system that autoaligns the structure based on both the laser and phase diversity sensor measurements. The processes described herein are demonstrated on a model of an opto-mechanical system based on an approximate prescription for the Hubble Space Telescope combined with a simple flexible structure.