MTF of an optical system by a photographic technique

Abstract

The superiority of the mtf as a guide to the performance of an optical system over standard resolution tests is well established. The Applied Optics Research Group of the Guided Weapons Divisions is mainly concerned with the measurement of the performance of large optical systems such as telescopic sights and projection systems. In many instances such systems may not be moved, so the measurement of performance necessitates taking the measuring equipment to the system. Hence mtf measurement on a standard electronic bench is not a viable proposition. In 1967 a photographic technique, now well established, was developed at BAC. The simplicity and versatility of the equipment required for the initial measurements made this method of obtaining the mtf particularly suitable for large optical systems. This paper details the equipment required and methods used to obtain the mtf by this photographic technique and discusses the particular problems encountered.