Ellis I. Betensky

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.

Fundamental considerations for zoom lens design

Zoom lens design requires a very strong understanding of geometrical optics and how it directly relates to an optical system. Understanding both first-order optics and pupil conjugation is absolutely essential to ensure that a lens zooms correctly and avoids discontinuities. This tutorial paper explains these first-order considerations in detail and illustrates how to derive a starting configuration. The tutorial also shows how to proceed toward a final lens optimization.

The AWMC metric for zoom lens assessment

High density digital sensors combined with digital zooming have eliminated the need for many small magnification range zoom lenses. Instead, lens designers now must design and assess zoom lenses for ever-increasing magnification ranges. The number of zoom positions for designing and assessing must increase as well, but assessing multi-spectral Modulation Transfer Function (MTF) data for many zoom positions becomes overwhelming. In this paper an efficient and effective metric, Area-Weighted Modulation-Cycles (AWMC), is proposed and reviewed for assessing imaging properties efficiently in a zoom system.gh density digital sensors combined with digital zooming have eliminated the need for many small magnification range zoom lenses. Instead, lens designers now must design and assess zoom lenses for ever-increasing magnification ranges. The number of zoom positions for designing and assessing must increase as well, but assessing multi-spectral Modulation Transfer Function (MTF) data for many zoom positions becomes overwhelming. In this paper an efficient and effective metric, Area-Weighted Modulation-Cycles (AWMC), is proposed and reviewed for assessing imaging properties efficiently in a zoom system.

Lens design with Forbes aspheres

Lens design is a continually expanding field being driven by applications with increasingly difficult packaging and imaging constraints. In order to meet the challenges posed by current and future design tasks, axisymmetric aspheric optical surfaces deviating from conicoids are required. Practical use of such surfaces is being enabled by ever-improving manufacturing and metrology methods. In this paper lens design with Forbes orthogonal aspheres is investigated. The significant advantages of such an orthogonal representation for design of systems with good performance and manufacturability are highlighted.

Understanding how entrance and exit pupils have determined the evolution of the modern zoom lens design (tutorial)

In this tutorial the position of the aperture stop, rather than the number of moving groups, is used as a means of examining the design characteristics, and explaining how new designs have evolved. In addition to lens diameters, as determined by paraxial locations and the effects of aberration of the pupils, the position of the pupils, and their shapes as a function of zooming will be examined. The primary objective of the tutorial is to provide insight and a better understanding of zoom lens fundamentals, towards the selection of a design starting point; whether from an existing design, or from basic principles.