30 April 2018 Real-time holographic heterodyne spatial filtering
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Traditionally, homodyne and heterodyne detection is a combination of a frequency mixer followed by a low-pass filter. Mixing two signals of frequencies f1 and f2, generates sum and difference frequencies signals and their integer multiples. Both multiplication heterodyne and phase sensitive detection have been demonstrated optically by using photorefractive, four-wave mixing [FWM). The multiplicative characteristic of FWM was used for mixing, and the response time of the photorefractive medium is used for low-pass filtering. If one of the input beams is both spatially and temporally modulated using a wobbling rotating mirror, depending on which mode is heterodyned, one can generate an orthogonal set of Bessel band-pass filters. This scheme can be integrated part within parallel data acquisition systems for applications involved nondestructive testing.
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Jed Khoury, Jed Khoury, "Real-time holographic heterodyne spatial filtering", Proc. SPIE 10649, Pattern Recognition and Tracking XXIX, 106490V (30 April 2018); doi: 10.1117/12.2304785; https://doi.org/10.1117/12.2304785

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