Optical imaging of structures within highly scattering material using a lens and aperture to form a spatiofrequency filter

Nick Pfeiffer; Paulman Chan; Glenn H. Chapman; Fartash Vasefi; Bozena Kaminska

doi:10.1117/12.764341

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20 February 2008 Optical imaging of structures within highly scattering material using a lens and aperture to form a spatiofrequency filter

Nick Pfeiffer, Paulman Chan, Glenn H. Chapman, Fartash Vasefi, Bozena Kaminska

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Proceedings Volume 6854, Optical Interactions with Tissue and Cells XIX; 68541D (2008) https://doi.org/10.1117/12.764341
Event: SPIE BiOS, 2008, San Jose, California, United States

Abstract

Angular Domain Imaging (ADI) is a high resolution, ballistic imaging method that utilizes the angular spectrum of photons to filter multiply-scattered photons which have a wide distribution of angles from ballistic and quasi-ballistic photons which exit a scattering medium with a small distribution of angles around their original trajectory. Such spatial gating has been previously accomplished using a scanning array of collimating holes micromachined into a silicon wafer section. We now extend that work to include using a wide-beam, full-field, converging lens and pinhole aperture system to capture images in a single exposure. We have developed an analysis of resolution and sensitivity trade-offs of such a system using Fourier optics theory to show that the system resolution is primarily governed by collimation ability at larger aperture sizes and by spatiofrequency (Fourier space-gated) filtering at smaller aperture sizes. It is found that maximum sensitivity is achieved when spatiofrequency resolution and collimation resolution are equal. Planar, high contrast, phantom test objects are observed in 5 cm thick media with effective scattered to ballistic photon ratios >1.25×10⁷:1 using a wide-beam, full-field lens and aperture system. Comparisons are made between ballistic imaging with the lens and aperture system and with the scanning silicon micromachined collimating array. Monte-Carlo simulations with angular tracking validate the experimental results.

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Nick Pfeiffer, Paulman Chan, Glenn H. Chapman, Fartash Vasefi, and Bozena Kaminska "Optical imaging of structures within highly scattering material using a lens and aperture to form a spatiofrequency filter", Proc. SPIE 6854, Optical Interactions with Tissue and Cells XIX, 68541D (20 February 2008); https://doi.org/10.1117/12.764341

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