The Design And Study Of Cryogenic Infrared Temperature Difference Source System

Recently,with the promotion of the precision of infrared systems,space exploration and space monitoring has got a series of more effective technology methods.To guarantee the high accuracy requirement of these systems,especially the systems which are applied in the cryogenic space,a peculiar cryogenic infrared source system which can simulate the environment of the space should be designed for the correction and accurate measurement,such as the cryogenic infrared temperature difference source system.Cryogenic infrared temperature difference source system is one of the equipment to test it,which functions correcting the inhomogeneity and measuring the sensitivity of the infrared system.The mainly content of this paper is the design processes and results analysis of the cryogenic infrared temperature difference source system.The structure of cryogenic infrared temperature difference source system mainly contains two modules,one is vertical vacuum chamber,and the other one is collimation system.A blackbody background,a blackbody target,a multiple target and a liquid nitrogen tank are placed in the vacuum chamber,which are used to a stable low temperature radiation signal together.They are the most important elements of the system.On the other hand,the function of collimation system is simulating the light path of the space observation and provides a signal with the infrared window to the infrared testing system.In the design of key technologies,the size of the blackbody background is up to 120 mm.Besides,the diameter of the blackbody targets is over 50 mm.The temperature difference among them is the low temperature radiation signal.The method of cooling the system is liquid nitrogen bath.In addition,the structures of the background and target are surface sources which include four kinds of optional cooling board structure,that are cylindrical type,hollow type,serpentine tube and serpentine slot.The choice of their structure depends on their periods of cooling and their temperature uniformity.Additionally,the system determines the distribution of temperature probes and heating plates according to the cooling process and the target heating process.And a PLC control system is used for adjusting and controlling the temperature of them.On the other hand,the structure of collimation system is parabolic reflective parallel tube,with 704 mm in focus,and 5° in view.According to the band of the system,the germanium infrared window has been chosen.Moreover,the secondary mirror is adopted with the off-axis structure whose magnitude is 200 mm in order to avoid the central blocking problem.In addition,the stray light analysis is required to ensuring the regularly operating of the entire system.According to the result of this analysis,the radiation correction scheme of the system is determined,which can improve the precision of the temperature difference source systemIn this paper,the design of the cryogenic infrared temperature difference source system,the operating temperature of the background signal has been set at 80 K.Besides,the range of system target signal temperature is between 80 and 300 K.The design can ensure all the requirements of the inhomogeneity correction and the sensitivity measurement for the system.