MCT Focal Plane Array Research Articles

A Novel MCT Focal Plane Array Thermally Stressed at Low Temperatures

The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mercury-cadmium-telluride</i> (MCT) focal plane arrays (FPA) have being populating most of the ground and space instrumentation devoted to near- and short-wave infrared (NIR-SWIR) during the last decades. The ASTEROID project is a fully European initiative to achieve a local manufacturer ready to develop MCT FPAs of ≥ 2k2 class. In order to test and characterize such detectors, special facilities are demanded. In this way, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Institut de Física d’Altes Energies</i> (IFAE) has conducted a research to validate the hybridization reliability of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">readout integrated circuit</i> (ROIC) and the MCT detector, which is performed through indium bumps soldering technique. The hybridization reliability was measured by subjecting the ASTEROID detector to several thermal cycles in a temperature range that surpass the detector operating temperature. At every individual thermal cycle, a set of images was captured, analyzed and compared each other to track any pixel degradation. Finally, making use of image classification and segmentation algorithms, the measured number of damaged pixels was determined and the results are presented in this paper.

Infrared backscatter imaging spectroscopy of trace analytes at standoff

We are developing a proximal noncontact detection technique for trace amounts of hazardous materials using diffuse reflectance infrared spectral signatures. Spectroscopy is performed at a distance by tuning a quantum cascade laser system through its wavelength range (6-11 μm) as the active illumination source and collecting a portion of the diffusely reflected light from the target onto an MCT focal plane array. The signals from each collected frame are binned and processed into an image hypercube that contains spectral and spatial information. The primary motivation of this work is to protect the loss of life by detecting trace explosives on contaminated surfaces before attacks occur. Here, we present results from backscatter experiments on trace samples with low loading and fill factors on glass substrates and compare them with a conventional benchtop analysis technique, FTIR diffuse reflectance. The backscatter results illustrate the ability to detect explosives at 1 m distance at the nanogram level, which is beyond the capability of the benchtop FTIR diffuse reflectance measurement.

IR Microscopic Imaging of Pathological States and Fracture Healing of Bone

The application of IR microscopic imaging to the study of bone disease and fracture healing is demonstrated. Samples of normal and osteoporotic human iliac crest biopsies were prepared and examined at ∼6–10 μm spatial resolution and 8 cm−1 spectral resolution with a 64 × 64 MCT focal plane array detector coupled to a Fourier transform infrared (FT-IR) microscope and a step-scanning interferometer. Two spectral parameters, one that monitors the extent of mineral (hydroxyapatite) formation in the tissue and another that monitors the size/perfection of the crystals, were compared in the samples generated from normal and pathological tissues. The average mineral levels in the osteoporotic sample were reduced by ∼ 40% from the normal. In addition, the crystal size/perfection was substantially enhanced in the disease state. The applicability of IR imaging techniques to the study of therapeutic intervention was also investigated in a study of the effects of estrogen therapy on fracture healing in rat femurs. Femurs were examined by IR microscopic imaging 4 weeks after fracture. IR imaging showed that the mineral level was enhanced in estrogen-treated samples. In addition, the crystals were larger/more perfect in the treated specimens. These data demonstrate the utility of IR spectroscopic imaging for the study of pathological states of hard tissue.