Non-technical: When a condenser is incorporated into an optical microscope, it produces a cone of inclined illumination incident on the sample under study resulting in improved imaging resolution. However, existing condensers typically comprises multiple lenses (or mirrors) and diaphragms that should be mechanically adjusted. In order to simplify the use of microscopes and further improve imaging resolution a novel optical condenser, which does not require moving parts, lenses, or mirrors, is proposed. The new optical condenser is formed by a hollow hemisphere containing a large number of near-infrared light emitting diodes (LEDs) in its internal surface. This approach, named as Electronic-Controlled Condenser (ECC), allows for multiple inclined illumination angles and doubles the resolution of the microscope. The proposed ECC is simple and cost-effective and will be particularly important for near-infrared imaging microscopy. Infrared microscopy has broad applications in inspection, metrology, and reliability analysis which are invaluable diagnostic assessments for the semiconductor, optoelectronic, and photonic industries. The research activities proposed in this effort will provide excellent interdisciplinary training for graduate and undergraduate students in the areas of simulation, optics, advanced microscopy, and nano- and micro-fabrication. Results obtained under this effort will be disseminated through journal publications and conference presentations.
Independent electronic control of each near-infrared LED in an ECC will allow the implementation of a large variety of illumination configurations, which includes but are not limited to, bright and dark field microscopy, omni-directional, inclined, and circular illumination, infrared tomography, and direct Fourier optics filtering techniques. In addition, the availability of LEDs emitting at different wavelengths in the near-infrared will enable the realization of ECCs emitting quasi-monochromatic or polychromatic illumination where the wavelength selection is determined by specific near-infrared microscopy applications. Other important attributes of the proposed next generation condensers for far-field near-infrared microscopy include real-time and raster-free images, it dispenses the need of imaging post-processing reconstruction, and it is simple to use and cost effective. This effort encompasses research on simulations, fabrication, spatial and temporal electronic control of a large array of LEDs, and transformative imaging concepts to achieve simple wide-field near-infrared subwavelength resolution. Research under this proposal spans a broad range of technical and educational issues in science and engineering, and addresses important applications. Four major research thrusts were identified in this proposal: 1. Simulations: simulations will be performed to determine optimum spatial light intensity distribution and resolution limit corresponding to various illumination configurations. 2. Spatial and temporal filtering: a comprehensive study will be carried out on image resolution and contrast under a variety of spatial and temporal illumination schemes implemented by direct electronic control of individual or groups of LEDs in an ECC. 3. Fabrication: control nanostructures will be fabricated to verify the resolution limit for the various illumination arrangements. 4. Imaging procedures: the optimum imaging illumination procedures for a variety of samples commonly used in the semiconductor and photonic industries will be investigated. When integrated, these studies will result in a simple and practical subwavelength resolution technique in the near-infrared. ECCs with multiple spatial and temporal illumination configurations represents a transformative technology in the area of near-infrared microscopy. The proposed research will further the understanding on the resolution limits and will significantly advance the state of the art of near-infrared microscopy imaging.
