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Today's long-range infrared cameras (LRIRC) are used in many systems for the protection of critical infrastructure or national borders. The basic technical parameters of such systems are noise equivalent temperature difference (NETD); minimum resolvable temperature difference (MRTD); and the range of detection, recognition and identification of selected objects (DRI). This paper presents a methodology of the theoretical determination of these parameters on the basis of technical data of LRIRCs. The first part of the paper presents the methods used for the determination of the detection, recognition and identification ranges based on the well-known Johnson criteria. The theoretical backgrounds for both approaches are given, and the laboratory test stand is described together with a brief description of the methodology adopted for the measurements of the selected necessary characteristics of a tested observation system. The measurements were performed in the Accredited Testing Laboratory of the Institute of Optoelectronics of the Military University of Technology (AL IOE MUT), whose activity is based on the ISO/IEC 17025 standard. The measurement results are presented, and the calculated ranges for a selected set of IR cameras are given, obtained on the basis of the Johnson criteria. In the final part of the article, the obtained measurement results are presented together with an analysis of the measurement uncertainty for 10 LRIRCs. The obtained measurement results were compared to the technical parameters presented by the manufacturers. [ABSTRACT FROM AUTHOR]

(1) Background: The modeling, characterization, and mitigation of transient lasers, thermal stress, and thermo-optic effects (TOEs) occurring inside high energy lasers have become hot research topics in laser physics over the past few decades. The physical sources of TOEs are the un-avoidable residual absorption and scattering in the volume and on the surface of passive and active laser elements. Therefore, it is necessary to characterize and mitigate these effects in real laser systems under high-power operations. (2) Methods: The laboratory setup comprised a 10-kW continuous wave laser source with a changeable beam diameter, and dynamic registration of the transient temperature profiles was applied using an infrared camera. Modeling using COMSOL Multiphysics enabled matching of the surface and volume absorption coefficients to the experimental data of the temperature profiles. The beam quality was estimated from the known optical path differences (OPDs) occurring within the examined sample. (3) Results: The absorption loss coefficients of dielectric coatings were determined for the evaluation of several coating technologies. Additionally, OPDs for typical transmissive and reflective elements were determined. (4) Conclusions: The idea of dynamic self-compensation of transient TOEs using a tailored design of the considered transmissive and reflecting elements is proposed. [ABSTRACT FROM AUTHOR]

Polarimetric imaging cameras require polarimetric calibration to accurately estimate the incident Stokes vector of incoming radiation. This calibration establishes a relationship between changes in the sensor signal and incident Stokes vector. In the standard procedure, an imager is presented with a set of input Stokes vectors with two different radiance values. In the long-wavelength infrared (LWIR) and mid-wavelength infrared bands, blackbodies with different temperatures are used for each set of Stokes vectors. The radiometric offset is subtracted, and standard radiometric or nonuniformity correction procedures are performed in a separate step. This paper proposes an alternative all-in-one approach that combines radiometric calibration, nonuniformity correction, and polarimetric calibration. The standard and proposed methods are compared for a division-of-time LWIR polarimeter. The proposed calibration method achieves an RMS error of 0.34% compared with the conventional technique's error of 0.83%, yielding a factor of 2.4 improvement in the reconstructed accuracy of a linear Stokes vector; in addition, it is less time-consuming and less prone to ambient temperature fluctuations than the typical two-point method. The method also accounts for beam wander and narcissus effects and enables simple, straightforward polarimetric measurement.