Cascaded spiral diffractive lenses (cSDL) based on liquid crystal (LC) technology, offer low voltage (⪅10Vrms) direct addressing, for wide aperture (>25mm OD) transparent lenses with very high fill factors (>98%), and broad tunable focal range (>4 Diopters). The two cascaded devices are conventional LC cells, manufactured using a single direct laser writing lithographical process on a transparent ITO covered glass substrate. In this presentation we will present our latest results, employing dual frequency materials, the use of the lenses in zoom systems, and in dynamic achromatic image capture. We will present implementations with both 24 and 72 electrodes, allowing for quasi analogue tuning in the whole tuning range. We will also present the employed direct addressing electronics.
Reconfigurable diffractive lenses manufactured in liquid crystal are presented. The lenses show an unprecedented performance in terms of active diameter and focal distance range when compared to any other transparent adaptive lens. The lenses are characterized by an active area free of electronic components, with a fill factor of 98% which combined with a low operating voltage (⪅10Vrms), open for applications ranging from eye contact lenses to space applications. The addressing of the liquid crystal is done exclusively from the periphery of the device. The lenses are based on tunable spiral diffractive lenses (SDL) for which the focal length may be changed by changing the topological charge, i.e. twist of the spiral in the lens. The twist in the resulting wavefront is eliminated by cascading two spiral plates with opposite twists emulating a conventional diffractive lens. The presented lenses have a tuning range from -2 to +2 diopters and an active diameter of 25mm.
A project-based teaching course for postgraduate students in the field of Photonics Engineering is based on the implementation of a Spectrophotometer. Hard and soft skills are evaluated in the implementation with an auto-evaluation criteria.
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