Defrost Design For Eyepiece Window Of Thermal Imager

When one type infrared thermal imager works at low temperature,the window of display controller will frost because of the hot breath of observers.Therefore an automatic control system will be needed to defrost the window of display controller.In this paper,some improvement is made based on the original design of the defrosting circuit.The relationship between temperature and defrost power is explored through the high low temperature test.The empirical formula is summarized through Newton interpolation mathematical methods,and a new defrosting circuit is designed based on this formula.The circuit uses C8051F221 microcontroller as the control core,and uses DS18B20 digital temperature sensor to measure the environment temperature,then uses the internal AD converter to measure the power of the heating device.The open and close time of the device is calculated and controlled according to environment temperature and heating power,so as to adjust the mean power and achieve the purpose of defrosting ultimately.The design simplifies the working procedure of sticking temperature sensor on optical window,and the control circuit can adapt to the change of the window power due to the power measurement function.The interchangeability of the circuit is greatly enhanced and the system debugging is easier.The new designed circuit is validated through environmental experiment,and meanwhile the design is summarized from the aspects of software design,hardware design,system debugging etc.