Colour sensitive lens-less imaging

Abstract

This thesis presents a novel nanophotonic Metal-Insulator-Metal (MIM) grating structure that diffracts incident light by filtering colour based on interference. The grating creates two independent self-images (Talbot patterns) for two almost arbitrarily tuneable wavelengths in the visible spectrum. Lens-less imaging is promising for its ability to be implemented in extremely small image sensors. Physical dimensions of lenses are prohibiting image sensors to scale with CMOS scaling trends. The grating substitutes a physical part of the angle sensitive pixel (ASP), a method for lens-less imaging. It is explored that by postprocessing this structure on top of a digital pixel array, colour sensitivity is added to the previouslymonochromatic angle sensitive pixel lens-less imaging method. Where multichromatic scenes would previously deteriorate ASP array reconstruction quality, the proposed MIM ASP uses the wavelength dimension to its advantage. The thesis states that using a patterned nanophotonic Metal-Insulator-Metal structure that filters colour based on interference on top of a pixel array, lensless imaging in nearfield scenario’s takes a step forward by adding high Q-factor wavelength separation, opening a new dimension of distinguishability without compromising SNR.