Optical Beam Control

Preface

The function of optical beam control is to meet the requirements of optical beam for pointing, pointing stability (jitter), quality of optical beam, slew maneuver, object sensing, and tracking. It is a multidisciplinary field consisting of optics, control theory, structures, thermal analyses, vibrations, atmospheric turbulence, and lasers. The wavelengths of primary interest for imaging satellites and laser systems are in the visible range and near-infrared range. Because of small wavelengths, the performance requirements are challenging. Typical telescope beam widths range from 3 to 5 microradians; to avoid most pointing loss, our residual jitter must remain below 30% of that width (that is, roughly 0.9–1.5 microradians), while absolute pointing errors must stay under one-tenth of the beam width (around 0.3–0.5 microradians). At the same time, for diffraction limited performance the primary mirror surface root-mean-square error should be less than one-thirtieth of a wavelength, which corresponds to about 30 nanometers in the visible. Achieving these numbers relies on cutting-edge optomechanical systems, advanced control laws, and a deep understanding of how optics, structures, thermal effects, vibrations, atmospheric turbulence, and lasers interact.

Because optical beam control sits at the intersection of so many disciplines, the designers of these systems should be knowledgeable not only of their own disciplines, but also of the basic principles of all the disciplines ...