A buried-object detection system composed of a LWIR, a MWIR and a SWIR camera, along with a set of ground and ambient temperature sensors was constructed and tested. The objects were buried in a 1.2x1x0.3 m3 sandbox and surface temperature (using LWIR and MWIR cameras) and reflection (using SWIR camera) were recoded throughout the day. Two objects (aluminum and Teflon) with volume of about 2.5x10-4 m3 , were placed at varying depths during the measurements. Ground temperature sensors buried at three different depths measured the vertical temperature profile within the sandbox, while the weather station recorded the ambient temperature and solar radiation intensity. Images from the three cameras were simultaneously acquired in five-minute intervals throughout many days. An algorithm to postprocess and combine the images was developed in order to maximize the probability of detection by identifying thermal anomalies (temperature contrast) resulting from the presence of the buried object in an otherwise homogeneous medium. A simplified detection metric based on contrast differences was established to allow the evaluation of the image processing method. Finite element simulations were performed, reproducing the experiment conditions and, when possible, incorporated with data coming from actual measurements. Comparisons between experiment and simulation results were performed and the simulation parameters were adjusted until images generated from both methods are matched, aiming at obtaining insights of the buried material properties. Preliminary results show a great potential for detection of shallowburied objects such as land mines and IEDs and possible identification using finite element generated maps fitting measured surface maps.
A new type of tunable guided-wave spectral slicing filter at the 1530nm wavelength regime is reported. The design
allows the selection of equally spaced frequency channels and simultaneously produces nulls that are equally spaced
between the selected channels. This makes it attractive for minimizing crosstalk in dense wavelength division
multiplexing (DWDM) applications. The spectral selection of the filter is based on co-directional polarization coupling
between transverse electric (TE) and transverse magnetic (TM) orthogonal modes in a waveguide by means of a static
strain induced index grating. An etalon-like response results from the sparse arrangement of the grating sections as N
individual coupling regions in tandem with equal spacing between their centers, yielding N-1 equally spaced nulls
between adjacent selected frequencies. Adjustments of the resulting filtering function may be obtained by proper choice
of coupling regions' lengths and spacing. Devices were fabricated using single mode channel waveguides formed by Ti
diffusion on x-cut y-propagating LiNbO3 substrates. Static strain from a periodically delineated surface film was used for
making N = 6 polarization coupling regions. Electrode patterns centered about the optical waveguide and defined by
liftoff were used to tune the filter electrooptically. Experimental results are in good agreement with design theory.