Research on Adjustable Cold View Field Diaphragm in Optical System with Linear Array Detector in AIMS

Abstract The infrared Fourier transform spectrometer needs a cold view field diaphragm to reduce stray radiation. For an infrared spectrometer with linear array detectors, the part of the view field diaphragm where the light passes can be regarded as a slit. If the infrared detectors are in small size, the width of the slit is also small, this will cause serious diffraction phenomena. If the width of the view field diaphragm and the optical system are designed by geometric optics theory, the diffraction light cannot be fully received by the detectors, this will cause energy loss. Expanding the width of the view field diaphragm will introduce stray radiation. Meanwhile, spectrometer follow-up optics should be set in cold environments to reduce the infrared background of the instrument. Optical materials have different thermal characteristics, the optical and mechanical structures will deform at low-temperature, and the cold view field diaphragm is installed at room temperature, so it is impossible to guarantee that the cold view field diaphragm remains in its design position when working at low-temperature.
This paper solves the above problems by designing an adjustable cold view field diaphragm installed in its cryogenic vacuum chamber. The width and position of the view field diaphragm can be adjusted when working in cold temperatures, without opening the cryogenic vacuum chamber. Contrasting the interference signal obtained by the detectors in the adjustment process, the system can get the most suitable width and position of the cold view field diaphragm. The above works are based on the spectrometer used in the Accurate Infrared Magnetic Field Measurements of the Sun (AIMS).