Based on microscopic imaging, optical systems can effectively detect defects on the surface of laser gyro reflector without causing damage. However, the minimum detection size is limited by the resolution of the microscopic imaging system. To detect submicron-level defects on laser gyro reflector substrate, a surface scanning dual-source scattering measurement scheme based on scattering measurement technology is proposed. Utilizing the Finite Difference Time Domain (FDTD) method and the detection scheme, an electromagnetic scattering model of the laser gyro reflector substrate is established to simulate the characteristics of defects and the distribution of electromagnetic fields. An experimental platform for surface scanning dual-source scattering measurement is established, and polystyrene latex (PSL) spheres with a diameter of 200nm are deposited on the surface of the laser gyro reflector substrate to verify the effectiveness of the proposed method. Scattering imaging experiments in both bright and dark fields are conducted on the USAF 1951 standard resolution plate to obtain the directional characteristics of dark field scattering. Additionally, standard-sized rectangular line patterns, dots, and checkerboard patterns of 1-10μm are fabricated using reactive ion beam etching to create defect samples of photomask patterns, and scattering imaging experiments are conducted on these samples to obtain the detection distribution of bright field patterns. The results indicate that the system can achieve a detection resolution better than 175nm. This method provides a reference for the detection of substrate in inertial guidance systems.
The InGaAs infrared detector, as the core component of photoelectric conversion in the Synchronization Monitoring Atmospheric Corrector (SMAC), is responsible for measuring short-wave infrared spectral and polarization information. Among them, the service life of the thermoelectric cooler (TEC) poses a bottleneck for the overall lifespan of the infrared detector, and its reliability directly affects the normal operation of the detector. A thorough analysis is conducted for the working mechanism of the infrared detector utilized by SMAC and the failure mechanism of the TEC, and the lifetime characteristic of the product is comprehensively evaluated and analyzed through lifespan testing. To minimize time costs, an innovative accelerated lifetime test method is proposed, which utilizes temperature change rate as the accelerated stress. A lifetime test system is developed. Meanwhile, the dark current, relative spectral response, and cooling current of the infrared detector have been measured before and after the lifetime test based on the segmented uniform illumination light source. The experimental results reveal that after a cumulative lifetime test of approximately 120 days, the infrared detector underwent approximately 170,000 temperature cycles. The maximum delta value in the relative spectral responsivity of the infrared detector pre and post the life test is -1.86%, and the maximum increase in the TEC refrigeration drive current is 8.6%. The service life and performance changes of the detector could satisfy the requirements of space payloads. Moreover, the lifetime test system significantly improves test efficiency and exhibits excellent stability and scalability, fully capable of meeting the needs of lifetime tests under different temperature stress levels.
In recent decades, polarization imaging has garnered much interest and research focus, due to its wide range of applications in the fields of atmospheric remote sensing, astronomy, biomedical and target detection, etc. Linear division-of-focal plane (DoFP) polarimeters deploying metal wire grid micro-polarization array as the polarization state analyzer (PSA) possess the capacity to capture polarization properties of the scene target during a single snapshot and benefit from their rugged and compact designs. However, these systems acquire the polarization measurements through spatial modulation and inevitably lead to spatial resolution loss, which cause instantaneous field of view (IFOV) errors and degradation of polarimetric accuracy. In response to this challenge, various interpolation/demosaicking methods tailored to DoFP imaging to fill the missing polarization information have emerged in recent years. This survey aims to explore these methods and briefly describe their effectiveness in enhancing the image restoration performance, highlighting their advantages and disadvantages. Lastly, according to current progress, some suggestions are made for high accuracy polarimetric measurements, especially for polarization remote sensing applications at different scales.
In order to select the devices with high reliability and stability with the potential of aerospace application from the scientific shortwave infrared array detector, the performance test and screening experiment of the shortwave infrared array COMS photoelectric conversion detector equipped with Synchronous Monitoring Atmospheric Corrector were carried out. Firstly, according to the aerospace application requirements, the main performance parameters of shortwave infrared array CMOS devices are simulated and analyzed. Secondly, a set of special image acquisition system of shortwave infrared array CMOS device is designed. Aiming at the performance parameters which can cover the whole spectrum, such as photo response nonuniformity, defect pixels, nonlinearity error and so on, a wide spectrum testing platform based on segmented uniform light source is built. Aiming at the monochromatic performance parameters such as quantum efficiency, a multispectral testing platform based on continuous tunable light source is built. Finally, the performance screening experiments of shortwave infrared array CMOS detectors are carried out by using these test systems, and performance parameters of the tested devices are obtained. The experimental results show that the photo response nonuniformity of the optimized shortwave infrared CMOS detector is 2.79% in 1380 nm band, the number of defect pixels is 4, the maximum non-repeatability of quantum efficiency is 2.18%, and the nonlinearity error is less than 1.16%. The index of the selected device meets the needs of aerospace applications. The research results provide a reference for the screening method and performance evaluation of shortwave infrared array detectors.
In order to meet the application requirements of a space borne polarizing radiometer infrared band, a high-precision on-orbit temperature control scheme for the infrared detector combining active temperature control and passive temperature control is proposed. The infrared detector is installed on the heat sink copper block, and the temperature of heat sink copper block is controlled at -20°C~-30°C through the method of auxiliary cold plate + heat pipe thermal conduction. Combined with the infrared detector built-in three-level thermoelectric cooler, the photosensitive surface temperature of the infrared detector is cooled to below -60°C by a method of constant current driving. In order to ensure the measurement accuracy of infrared radiation polarization, the short-term temperature fluctuation of the photosensitive surface of the infrared detector is required to be less than 0.03°C/s. This article has designed the infrared detector temperature control scheme verification test, and actually measured the stability of infrared detector temperature and dark current. The results of the simulation and tests show that the range of infrared detector heat sink temperature is - 25±5°C, the range of infrared detector photosensitive surface temperature is -65°C ~ -75°C,the rate of short-term temperature change of the infrared detector photo-sensitive surface is better than 0.01°C/s, and the dark current fluctuation is less than 1.3pA. Satisfying the on-orbit high-precision polarization measurement requirements.
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