Telecentric Zoom Lenses

Abstract

The purpose of this thesis is to study multi-configuration imaging systems and to investigate the limitations of maintaining telecentricity across the zoom range. Telecentricity is a property of an optical system which maintains the centroid and height of objects relative to the image plane regardless of axial changes in the position of the object or image. Telecentric zoom lenses provide a unique design challenge with the necessity for telecentric systems to have very low distortion, while distortion is often the dominant residual aberration in a zoom system [1]. Additionally, the asymmetric stop position will complicate the correction of other odd aberrations and controlling vignetting in a system with a large usable field of view. This analysis will evaluate the impact of multiple configurations on image-side, object-side, and double-sided telecentric systems [2] through modeling and simulation. Design considerations and methods are proposed based on an analysis of applications of telecentric zoom lenses, methods for aberration control, and systems which are currently available.In particular this thesis examines the constraints of designing telecentric systems which can accommodate multiple configurations. Initially idealized first-order telecentric systems are modeled with finite configurations which allow for a zoom ratio of 3, focal length of 25 to 75 mm, and a field of view of 10°. These ideal models are developed with the goal of identifying and minimizing aberrations which will be present in a third-order simulation. A method for describing the degree of telecentricity of a third-order optical system was formed as a function of the aberrations present in the system: Δu ̅=4·W ̅_040/(n'y ̅_I )-W_311/〖n'y〗_E Finally, existing designs of third-order multi-configuration systems are modified to provide telecentric performance throughout the zoom range. A zoom ratio of 3, focal length of 25 to 75 mm, and a field of view of 4° with a maximum telecentricity of 0.2 %. A second iteration, also with a zoom ratio of 3, a focal length of 62 to 168 mm, and a field of view of 4° with a maximum telecentricity of -0.14 %. 1 Chang, Matthew, "Pupil aberration in modular zoom lens design," Ph.D. dissertation, College of Optical Sciences, University of Arizona, AZ, USA, 1998 [Online].2 Miks, Novak, "Design of a double-sided telecentric zoom lens," Department of Physics, Czech Technical University, Prague, Czech Republic, 2012 [Online].