High-resolution, gated infrared images were taken of tin samples shock heated to just below the SOS K melting point Sample surfaces were eiurapoUshed or dian^ 10 mm. A high explosive in contact with a 2-mm-thick tin sample induced a peak sample stress of 18 GPa. interferometer data from similarly-driven tin shots indicate that immediately after shock breakout the samples spall near the free (imaged) surface with a scab thickness of about 0.1 mm Images were taken with gate widths of 0.2 to 0.S us and start times ranging from 0.3 to 1.5 us after shock breakout. The camera and experimental techniques were described previously. (2002)]. Infrared radiation (3 to 5 urn) from the sample was imaged onto a gated InSb camera array with lens systems capable of resolving features on the order of 0.1 mm. Assuming a dynamic emissivity of 0.1, calculated temperatures were around 700 K for the millimeter-sized hot spots and 450 K in the surrounding area. The images showed different amounts and physical distribution of hot spots. Although there was a trend to more and higher-temperature hot spots with larger grain size, the hot spots do not appear to map directly to individual gain shapes or boundaries.
When testing infrared readouts, detector-readout hybrid assemblies or focal plane arrays (FPAs), performance optimization is usually limited to adjustment of biases or clock rails, or subtle changes in readout timing. These generally result in global changes to the characteristics of the entire array rather than affecting individual pixels and channels. Using a scanning system that incorporates per channel gain normalization and a redundant time delay and integrate (ThI) architecture m the readout pixels can be enhanced or deselected usmg an on-chip static RAM accordmg to user defmed critena resulting m improved uniformity of performance.A series of tests can be run automatically that evaluate each pixel's behavior at the readout or the hybrid level. When compared to or compiled against array wide averages or system specifications a map of dead or degraded pixels is created and the timing necessary to either normalize each channel from a gain standpoint or mask out individual pixels is applied to the device under test. This technique has been successfully applied to 480x6 (120x4x6 in ThI) scanning architectures in both InSb and HgCdTe systems as well as multiple-chip and dual-band configurations. This paper describes a methodology and details how readout devices were screened and selected for hybridization and FPA build. The chip architecture and control timing is discussed to show how normalization and deselection was accomplished with a minimum of clock lmes involved A software utility is presented that allowed easy graphical interface to the user for mampulatmg the functions of the device Algonthms for optimizing performance are then discussed and evaluated Trade-offs made m optimizing one parameter against another are analyzed Finally, results are presented demonstrating improved performance customized by pixel to smt application specifications
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