The conventional response band of Indium Gallium Arsenide (InGaAs) detectors ranges from 0.9 to 1.7μm. The J atmospheric window (1.25μm) in infrared astronomy falls at the center of the response band of InGaAs detectors, making them widely used in this spectral region for infrared astronomy. Three representative Chinese-made Indium Gallium Arsenide focal plane arrays (InGaAs FPAs) were selected, and corresponding interface circuits were designed to match the testing system. Key performance indicators such as dark current, gain, and readout noise were tested.
In order to enhance the observational ability in infrared wavelength, a K-band MCT(Hg-Cd-Te) mosaic camera is constructed for a near-infrared telescope. In this paper methods of low temperature control and vibration measurement of the infrared camera are introduced. In order to suppress the dark current of the MCT detector of the camera, the detector is refrigerated to below 80K using a tube cryocooler in a vacuum chamber. To suppress the scatter light from lens of optics, the lens in front of the detectors should be cooled to below 150K. And in order to avoid damage of the cold optical lens caused by low temperature, two-stage temperature control is carried out on the base-plate of detectors and cold optics. Furthermore, the running cryocooler will cause small vibration of the detector, which will reduce the imaging quality of the camera. An anti-vibration method is designed to reduce the influence of the vibration. A three-axis vibration measurement of the detector is introduced, which provides data basis for the analysis of the influence of vibration on imaging and image correction.
Chinese scientists plan to build an 80 centimeter caliber near-infrared astronomical telescope in Antarctica, consisting of one telescope and two terminal devices. The K-band astronomical imaging system is one of the main terminals. We designed and characterized a 1x3 K-band near-infrared mosaic camera and the MCT detectors form Shanghai Institute of Technical Physics. The single pixel array of this camera is 640x512, with a single pixel size of 15 μm. Three detectors arranged in a mosaic configuration generated a focal plane pixel array of 1920x512. To ensure the optimal performance of the K-band astronomical imaging system, we used Dewar sealing, vacuum maintenance, and thermoacoustic refrigerator to cool the detector to 80K and the optical lens and components to 150K. In addition, a low-noise power supply design and electronic devices with low readout noise are adopted to ensure the minimum dark current and low readout noise of the mosaic infrared camera. The flatness of the mosaic detector is less than 20 μm . Complies with the design specifications for K-band astronomical imaging system.
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