Research On Computer Simulation And Nonuniformity Correction Of UMBIRFPA

The uncooled microbolometer infrared focal plane arrays (IRFPA) is the leading edge of research on infrared technology in information science today. In this paper, the history, present status and trend in development of infrared technology, infrared detectors and UMBIRFPA were rounded represented. The military and civil applications of UMBIRFPA were introduced. Especially, much prospect of UMBIRFPA is described.There are various techniques involved in the development of UMBIRFPA, such as principle of the device, micro-machined technique, readout integrated circuit(ROIC), signal process, infrared imaging, device capsulation and so on. In this paper, the physical model of UMBIRFPA is established and computer simulated based on the research on the principle of microbolometer. At the same time, the nonunifomity of UMBIRFPA is deeply studied.Microbolometer, which is the key part of UMBIRFPA, is the unit absorbing the Infrared radiation and changing it into heat quantity and electrical quantity. The author studied the construction and principle of the microbolometer and analyzed infrared radiation, transmission, imaging and absorbing. Then the computing method of thermal equilibrium process is given. As the microbolometer which is voltage biased express some characters different from other infrared detectors under the effect of electric heat and infrared radiation together, the computing method of parameters ,such as responsivity, noise, noise equivalent temperature different(NETD), noise equivalent power(NEP), optical gain, detectivity and so on is given in this paper. Some of these parameters are particular compared with other detectors, and some have difference between microbolometer and other detectors.Nonuniformity which must be corrected in all focal plane array is more greater in UMBIRFPA. It is special that nonuniformity be effected by substrate temperature in UMBIRFPA. The costly constant temperature system must be employed if using the traditional two point correction method, moreover, the system is more complex. In this paper, the reason for which the substrate temperature effects the nonuniformity of UMBIRFPA is analyzed. It is brought forward that using three point correction method to minish the substrate temperature's influence on nonuniformity of UMBIRFPA. The principle of the new method, the way to realize the method and the flow process to obtain the correction coefficients were given simultaneously. With the method, the control range of substrate temperature can be increased from 0.01k to 5K, and the temperature method can be changed from cooling to heating. So the cost and complexity of system can be reduced.As UMBIRFPA is a new type of infrared detecting device, its work principle is complex and its performance is affected by many factors. In the initial stage of developing, the design experiment and theoretical understanding are little interiorly. Furthermore, the problems such as sensitivity reduced, dynamic range shortened, nonuniformity increased come forth if UMBIRFPA is not designed properly. Even it can't be used in imaging. This will cause a large waste because UMBIRFPA is produced on IC production line, the investment is huge and the period is long. The author established s software simulation system base on the principle of UMBIRFPA. The system can simulate the transfer process of photo-thermal and thermal-electric at a given parameter setting of structure, environment and circuit. On the basis of circuit structure, the calibration, parameter adjusting and signal readout can be simulated, the vary process of readout circuit, readout voltage, optical gain, optical gain rate, and uniformity can be given. In addition, all kinds of character parameters of device can be forecasted. By means of simulating the model, it can help people to realize the principle and laws of microbolometer, analyze the improper factors in design course, verify the rationality of different design scheme, confirm the best setting of some parameters. Consequently, the expense in the produce process can...