Forty years of modern zoom lens design

Brought on by the availability of large computers and optimizations programs, zoom lens design has advanced continuously during the past forty years. Changes in applications, manufacturing, and requirements have all contributed to a large and growing knowledge of zoom lens design. As a result entirely new zoom lens forms have been developed for use in a variety of cameraas and instruments. Most of the new designs are characterized by complex motions of zooming groups, and particularly by moving the aperture stop during zooming. Continuing to find ways to control the internal pupil imaging, the compound zoom lens has been developed. By performing the zooming operation on both sides of an intermediate image, the pupils and images are located advantageously.