Ewan Findlay

Miniaturization of zoom lenses with a single moving element

We present an analysis of single-moving-element zoom lenses in the thin-lens limit and show how the length of these zoom lenses is determined by the zoom-factor, sensor-dimension and the depth-of-focus. By decreasing the sensor size and extending the depth-of-focus, the lengths of these zoom lenses can be reduced significantly. As an example we present a ray-traced design of a miniaturized single-moving-element zoom lens with a 2.3 x zoom-factor and show how the exploitation of modern miniaturized detector array combined with wavefront coding enables a reduction in length of almost three orders-of-magnitude to 10mm.

Experimental demonstration of hybrid imaging for miniaturization of an optical zoom lens with a single moving element

We experimentally demonstrate a miniaturized zoom lens with a single moving element based on the concepts and analysis described in Opt. Express 17, 6118 (2009). We show that the implementation of either a cubic or a generalized cubic phase-modulation function makes miniaturization possible in addition to providing extended-depth-of-field imaging. We present recovered images for zoom lenses employing both phase-modulation functions and conclude that the generalized-cubic-phase function yields higher image quality without the artifacts present for the pure-cubic-phase function.

Miniaturization and simplification of zoom lenses using wavefront coding

Traditional zoom lens designs employ multiple moving lens elements to provide simultaneous control of focal length and focal plane. We present an approach to a design of a simplified zoom lens by employing a single moving element to control only the focal length. We show that the defocus in miniaturized zoom lenses with a single moving element can be corrected by the use of wavefront coding, although this introduces a modest reduction in signal-noise-ratio. As an example, we present a design of a miniaturized 10 mm long wavefront coded 2.3x optical zoom lens with a single moving lens element.

Digital image processing as an integral component of optical design

The design of modern imaging systems is intricately concerned with the control of optical aberrations in systems that can be manufactured at acceptable cost and with acceptable manufacturing tolerances. Traditionally this involves a multi-parameter optimisation of the lens optics to achieve acceptable image quality at the detector. There is increasing interest in a more generalised approach whereby digital image processing is incorporated into the design process and the performance metric to be optimised is quality of the image at the output of the image processor. This introduces the possibility of manipulating the optical transfer function of the optics such that the overall sensitivity of the imaging system to optical aberrations is reduced. Although these hybrid optical/digital techniques, sometimes referred as wavefront coding, have on occasion been presented as a panacea, it is more realistic to consider them as an additional parameter in the optimisation process. We will discuss the trade-offs involved in the application of wavefront coding to low-cost imaging systems for use in the thermal infrared and visible imaging systems, showing how very useful performance enhancements can be achieved in practical systems.

Wavefront-coded zoom lens with a single moving element

Traditional zoom lens designs employ multiple moving lens elements to provide simultaneous control of focal length and focal plane. We present an example of a simplified and compact zoom lens design by employing a single moving element to control only the focal length. In this zoom lens, wavefront coding is used to control the defocus. We describe the principles of operation with special attention to image processing. We simulate imaging and image restoration capabilities and present that the zoom lens provides high imaging quality.