Lens Design And System Optimization For Foveated Imaging

Foveated imaging addresses the need for compact wide-angle imagers capable of high-resolution and compressed data transmission. The principle behind foveated imaging is to cover a wide field-of-view (FOV) with a relatively simple and compact low-resolution lens, and use a liquid crystal spatial light modulator (SLM) to correct wavefront aberrations at any selected field point. The SLM correction provides a high-resolution fovea that can be actively moved anywhere within the FOV. While most research has focused so far mainly on SLM performance, the general trend being to increase SLM resolution and modulation depth, the actual lens design and system optimization aspects were often neglected. In this paper, we propose a wide-angle lens design intended for foveated imaging applications, and discuss typical tradeoffs. Taking this design as an example, we present a method to estimate the smallest SLM resolution required to correct the wavefront error effectively, showing that with the appropriate design, this resolution can be reduced up to 10 times compared to current designs. Increasing the SLM resolution beyond this point and increasing the modulation depth above one wavelength is not necessary, and will actually reduce the performance of the imaging system. We also demonstrate the importance of fabrication tolerances, and we propose a method to calibrate the SLM in order to cancel out all additional wavefront aberrations introduced by fabrication and assembly errors. © 2008 Copyright SPIE - The International Society for Optical Engineering