Thermal Imaging Publications
TITLE:
“Active mode detection with enhanced pyroelectric sensitivity”, Ricardo Unglaub, Jolanta Celinska, Christopher McWilliams, Carlos Paz de Araujo, Andrzej Pawlak, Scott Jones, Proc. SPIE 7298, Infrared Technology and Applications XXXV, 72980M (May 06, 2009); doi:10.1117/12.818211
ABSTRACT:
A MEMS-less infrared pyroelectric sensor that employs an active detection mechanism based on a strontium bismuth tantalate (SrBi2Ta2O9) ferroelectric sensing material is described and compared to passive modes of operation. A model is based on fundamental performance of ferroelectrics in which the polarization state of the material is actively interrogated enabling improved signal to noise ratio, greater effective pyroelectric coefficient, and chopper-less design. In addition to excellent thermal responsivity in the medium and long wavelength bands and unlimited endurance, the unique design enables selective wavelength tuning of insulating layer and absorber materials to maximize the responsivity at distinct wavelengths.
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TITLE:
“Advanced dynamic pyroelectric focal plane array”, Ricardo A. G. Unglaub, Jolanta B. Celinska, Christopher R. McWilliams, Carlos A. Paz de Araujo, Timothy Forbes, Jayson D. Pankin, Proc. SPIE 7660, Infrared Technology and Applications XXXVI, 76601A (May 03, 2010); doi:10.1117/12.849967;
ABSTRACT:
The pyroelectric effect has been characterized for single-pixel elements consisting of strontium bismuth tantalate (SBT) ferroelectric material as the sensing elements. These pixels have been integrated into second-generation focal plane arrays. The constituent second-generation pixels include thermal insulating layers and an infrared absorber layer. The MEMS-less arrays are operated in active mode, a technique that eliminates radiation choppers found in other passive pyroelectric IR imagers. This paper addresses the results of precursor 2x2 to 14x14 second-generation arrays of SBT elements, the active detection mechanism, and the unique read-out, interrogation signal, and the synchronization electronics. The second-generation 14x14 pixels array was implemented to demonstrate the performance of an active pyroelectric array as a precursor to larger size arrays using different pixel dimensions. The active mode detection eliminates the use of a chopper, enables the dynamic partition of the array into pixel domains in which pixel sensitivity in the domains can be adjusted independently. This unique feature in IR detection can be applied to the simultaneous tracking of diverse contrast objects. In addition, by controlling the thickness of the absorber material the arrays can be optimized for maximum response at specified wavelengths by means of quarter-wavelength interferometry.
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TITLE:
“Characterization of second generation advanced dynamic pyroelectric focal plane array”, Ricardo A. G. Unglaub, jolanta B. Celinska, Christopher R. McWilliams, Carlos A. Paz de Araujo, Jayson Pankin, integrated ferroelectrics , vol. 112, iss. 1, 2010
ABSTRACT:
The pyroelectric effect has been characterized for single-pixel elements consisting of strontium bismuth tantalate (SBT) ferroelectric material as the sensing element. The pixels include also a thermal insulating layer and an infrared (IR) absorber layer. These MEMS-less devices are operated in active mode, a technique that eliminates the need for a radiation chopper found in passive pyroelectric IR imagers. Test results of the SBT pixels of dimensions 7.5 μm × 7.5 μm to 200 μm × 200 μm have shown high endurance to polar cycling, high responsivity values, and very low noise-equivalent temperature difference for focal plane array applications. This paper describes and analyses the results of precursor 2 × 2 arrays using discrete sensing elements, the active detection mechanism, and its unique read-out electronics. A second-generation 32 × 32 pixels array being implemented to demonstrate the performance of a 1k-pixel array as precursor to larger size arrays is also described. The active mode detection, in addition to eliminating the use of a chopper, enables the dynamic partition of the array into pixel domains in which the pixel sensitivities in each domain can be adjusted independently. This unique feature in IR detection is not readily found in other types of IR imagers and can be applied to the simultaneous tracking of diverse contrast objects. By controlling the absorber material thickness, the arrays can be optimized for maximum response at specified wavelengths by means of quarter-wavelength interferometric technique.
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