John W. Matthews

Advanced optics for LED flashlights

Since the invention of the flashlight in the late nineteenth century, it has proven indispensable for both civilian and military use. To date, the prevailing optical element used for collecting and concentrating light from the source has been the paraboloidal reflector. The advent of LED light sources, recent theoretical developments in nonimaging optics and advances in polymer optics are revolutionizing flashlight optics. We present new classes of optical solutions that provide superior efficiency, beam shaping, and active beam control. These solutions are patent pending.

High-Fidelity Adaptive Compression for Cognitive Spectral Monitoring

A key aspect of the cognitive radio paradigm for maximizing spectral usage is spectral monitoring. However, continuous monitoring of a wide frequency band with high sensitivity and spectral resolution can generate unmanageable amounts of data. By applying an adaptive compression algorithm to measured ultrawideband spectral data we show that it is possible to obtain spectral data compression ratios of 10, 000 or more, allowing the datarate to be reduced below 1 Mbps, sufficient for streaming to disk, broadcasting over a wireless link, or performing further processing. A key aspect of the approach is the fidelity with which the spectral signals are preserved. We show compression results applied to measured data, and discuss an architecture for implementing the data compression algorithms in real-time.

Power line field sensing to support autonomous navigation of small unmanned aerial vehicles

Autonomous navigation around power lines in a complex urban environment is a critical challenge facing small unmanned aerial vehicles (SUAVs). As part of an ongoing development of an electric and magnetic field sensor system designed to provide SUAVs with the capability to sense and avoid power transmission and distribution lines by monitoring their electric and magnetic field signatures, we have performed field measurements and analysis of power-line signals. We discuss the nature of the power line signatures to be detected, and optimal strategies for detecting these signals amid SUAV platform noise and environmental interference. Based on an analysis of measured power line signals and vehicle noise, we have found that, under certain circumstances, power line harmonics can be detected at greater range than the fundamental. We explain this phenomenon by combining a model of power line signal nonlinearity with the quasi-static electric and magnetic signatures of multiphase power lines.

A novel photonic magnetometer for detection of low frequency magnetic fields

A novel photonic magnetometer for a variety of applications is being developed. The detection mechanism is similar to existing fiber optic magnetometers, in which a magnetostrictive element transduces magnetic field variations into changes in optical path length, subsequently detected through optical interferometry. Single-axis and three-axis vector magnetometers have been designed, and other application-specific configurations have also been investigated. The sensor noise floor is estimated at 20 pT/√Hz for frequencies of 0.1 Hz and above, with a dynamic range of over 100,000 nT. The sensor can be compact (down to 1 cm3) and can consume less than 100 milliwatts of power. These features, combined with its low 1/f noise and wide dynamic range, make the photonic magnetometer an easily deployable detector of low-frequency magnetic fields. Potential applications of the novel photonic magnetometer, including space-based measurement of geomagnetic fields, medical biomagnetic imaging, vehicle detection, mine detection, heading sensors, low-frequency communications, and deep eddy current nondestructive evaluation, have been explored as well.