12 July 2007 Dynamic optical tomographic imager with optimized digital lock-in filtering
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We describe a new dynamic optical tomography system that is, unlike currently available analog instrumentation, based on digital data-acquisition and filtering techniques. At the heart of this continuous wave instrument is a digital signal processor (DSP) that collects, collates, processes, and filters the digitized data set. A digital lock-in filter that has been designed for this particular application maximizes measurement fidelity. The synchronously-timed processes are controlled by a complex programmable logic device (CPLD) that is also used in conjunction with the DSP to orchestrate data flow. Real-time data rates as high as 140Hz can be achieved. The operation of the system is implemented through a graphical user interface designed with LabVIEW software, Performance analysis shows very low system noise (~600fW RMS noise equivalent power), excellent signal precision (<0.04% - 0.2%) and long-term system stability (<1% over 40 min). A large dynamic range (~195dB) accommodates a wide scope of measurement geometries and tissue types. First experiments on tissue phantoms show that dynamic behavior is accurately captured and spatial location can be correctly tracked using this system.
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Joseph M. Lasker, Joseph M. Lasker, James M. Masciotti, James M. Masciotti, Yang Li, Yang Li, Chris Fong, Chris Fong, Andreas H. Hielscher, Andreas H. Hielscher, } "Dynamic optical tomographic imager with optimized digital lock-in filtering", Proc. SPIE 6629, Diffuse Optical Imaging of Tissue, 662903 (12 July 2007); doi: 10.1117/12.728578; https://doi.org/10.1117/12.728578

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