Procedure for Over-all Lens Evaluation Using OTF Data

Abstract

A method is described for making use of large amounts of photoelectric test data, recorded in the form of OTF curves and filed in computer-accessible form, to evaluate image quality over the field in an arbitrary image plane or to locate an optimum image plane by computer processing of the recorded data. Merit parameters such as the OTF, the predicted photographic resolution, the Strehl criterion, and others, are obtained as over-the-field averages, with arbitrary weighting of information from different parts of the field, and also may be reported from individual field points, in various ways. The method has been tested on a wide-angle aerial photographic objective, and example results for this lens are given. Assessment of the possible utility of such a procedure is based on discussion of the practical feasibility of acquiring large amounts of test data by automated instruments, on the computer requirements and processor time needed, and examples of the variety of evaluation tasks that may be performed, with relative ease once the imagery has been mapped throughout the image space. It is concluded that the method does offer possibilities for practical use and may be a desirable way to utilize directly OTF-type test information, in mass, to facilitate decision making in respect to design, fabrication quality, or individual performance of an actual prototype or production lens.