Acousto-optical signal processors require diffraction limited images positioned to accuracies of one percent or less. Wavefront tolerances are twentieth wave. On the other hand, the light is usually monochromatic. Fields of view are modest and, in fact, negligible where fast (N.A.-55) optics are required, e.g., laser diode collimators, objective lens are, typically, scan lenses. Some aberrations are not critical but field curvature must be corrected and the system must be aplantic.