Dr. Webert Montlouis Profile

Dr. Webert Montlouis

Faculty at Johns Hopkins Univ

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Publications (2)

Proceedings Article | 18 May 2020 Presentation + Paper

Resonance processing of FMCW radar returns for accurate perimeter-breach detection of a flat-trajectory quasicylindrical target

Richard Fauconier, Webert Montlouis, Mandoye Ndoye

Proceedings Volume 11423, 114230M (2020) https://doi.org/10.1117/12.2558492

KEYWORDS: Radar, Missiles, Doppler effect, Filtering (signal processing), Electronic filtering, Target detection, Surveillance

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Proceedings Article | 6 October 2017 Presentation + Paper

Optical fundamentals of an adaptive substance-on-surface chemical recognizer

Richard Fauconier, Mandoye Ndoye, Webert Montlouis

Proceedings Volume 10433, 104330O (2017) https://doi.org/10.1117/12.2278579

KEYWORDS: Sensors, Infrared radiation, Transmitters, Receivers, Polarization, Laser sources, Modulation, Adaptive optics, Signal processing, Phase modulation

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The objective is to identify the chemical composition of (isotropic and homogeneous) thin liquid and gel films on various surfaces by their infrared reflectance spectra. A bistatic optical sensing concept is proposed here in which a multi-wavelength laser source and a detector are physically displaced from each other. With the aid of the concept apparatus proposed, key optical variables can be measured in real time. The variables in question (substance thickness, refractive index, etc.) are those whose un-observability causes many types of monostatic sensor (in use today) to give ambiguous identifications. Knowledge of the aforementioned key optical variables would allow an adaptive signal-processing algorithm to make unambiguous identifications of the unknown chemicals by their infrared spectra, despite their variable presentations. The proposed bistatic sensor system consists of an optical transmitter and an optical receiver. The whole system can be mounted on a stable platform. Both the optical transmitter subsystem and the optical receiver subsystem contain auxiliary sensors to determine their relative spatial positions and orientations. For each subsystem, these auxiliary sensors include an orientation sensor, and rotational sensors for absolute angular position. A profilometer-and-machine-vision subsystem is also included. An important aspect of determining the necessary optical variables is an aperture that limits the interrogatory beams to a coherent pair, rejecting those resulting from successive multiple reflections. A set of equations is developed to characterize the propagation of a coherent pair of frequency-modulated thin beams through the system. It is also shown that frequency modulation can produce easily measurable beat frequencies for determination of sample thicknesses on the order of microns to millimeters. Also shown is how the apparatus’s polarization features allow it to measure the refractive index of any isotropic, homogeneous dielectric surface on which the unknown substance can sit. Concave, convex and flat supporting surfaces and menisci are discussed.

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