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Open Access research with a European policy impact...

The Strathprints institutional repository is a digital archive of University of Strathclyde's Open Access research outputs. Strathprints provides access to thousands of Open Access research papers by Strathclyde researchers, including by researchers from the European Policies Research Centre (EPRC).

EPRC is a leading institute in Europe for comparative research on public policy, with a particular focus on regional development policies. Spanning 30 European countries, EPRC research programmes have a strong emphasis on applied research and knowledge exchange, including the provision of policy advice to EU institutions and national and sub-national government authorities throughout Europe.

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Design of diffractive optical elements for beam shaping of micro-pixellated LED light to a tightly focused spot

Liu, J.S. and Caley, A.J. and Gu, E. and Girkin, J.M. and Dawson, M.D. and Taghizadeh, M.R. (2008) Design of diffractive optical elements for beam shaping of micro-pixellated LED light to a tightly focused spot. Journal of Physics D: Applied Physics, 41 (9). ISSN 0022-3727

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Abstract

Tightly focused spots with small central lobes, high central intensity and low sidelobe intensity are desirable for many light-emitting diode based micro-projection system applications. Diffractive optical elements (DOEs) offer a potentially low cost and flexible choice for realizing this task. We have approached the design of suitable elements using two methods: various step size simulated quenching (VSSQ) and multiresolution various step size simulated quenching followed by direct binary search (M-VSSQ-DBS). M-VSSQ-DBS greatly increases the central intensity of the spots, and only slightly influences the sidelobe intensity, most often favourably reducing it. When the central lobe size is 0.8 times that of the geometrical-optics limit, the peak intensity can be as high as 97.73% that of the geometrical spot, and the relative maximum sidelobe intensity is 51.14% of the peak intensity. The designs are tolerant to variations in the actual width of the light source and to lateral misalignment. We verify the designed DOE using rigorous diffraction theory, i.e. the finite-difference time-domain method. The results obtained by scalar and rigorous diffraction theory are in excellent agreement with each other.