In this chapter, we will review a number of adaptive optics concepts that have been used for applying correction to propagation and imaging systems. Functional block diagrams are used to illustrate the concepts. The blocks represent functions that can be optical, electronic, mechanical, or many combinations of these. The second half of this book deals with the details in the subsystems represented by the boxes in these diagrams. At this conceptual level, we can regard these boxes as having the following functions:
Optics: A train of transmissive or reective optics Corrector: An optical element that can change the wavefront of a beam Sampler: An optical element that can separate one beam from another
(presumably without distorting the phase) WFS: Wavefront sensor Imager: A collection of optics that forms an image and delivers it to
detectors Target: The plane in space where a well-corrected beam is required Receiver: A device that converts optical information to electronic signals Control: Electronic processing Tagger: An optical device that can tag part of a beam Laser: The laser
The system concept should be chosen carefully. A system used for correcting atmospheric turbulence in an astronomical telescope probably will not be useful correcting low-order modes in a high-power laser. The brute-force techniques for moving large optics will be much too slow for correcting high-frequency vibrations. We will examine these approaches and explore their pros and cons.