Study Of Performance And Signal Processing Circuit Of Microbolometer Arrays

Infrared thermal imaging technique is an important component of night-vision technology and representation of the military power and the weapon equipment level of one country. Uncooled infrared thermal imaging technique based on microbolometer arrays plays an important role in current infrared thermal imaging technique due to its advantages such as small bulk, light weight, low power consumption, high reliability and high performance-cost ratio. According to the development actuality of uncooled infrared thermal imaging technique in our country, considering that the import microbolometer arrays for commercial applications have bad operation performance and image quality for low ambient temperature, the performance and signal processing circuit of micobolometer arrays is studied in this dissertation, to develop the thermal imaging system of microbolometer arrays for military applications with high performance, low power consumption, small bulk and endurable ambient temperature range of -40~60℃.Based on the uncooled infrared thermal imaging principle, the theory of uncooled infrared thermal imaging system is studied to prepare for the deep study of performance and signal processing circuit of micobolometer arrays.According to the structure and principle of microbolometer arrays, the characteristics of thermal response and power consumption of microbolometer arrays are deeply studied, the influences to the sensitive performance, power consumption and image quality of microbolometer arrays caused by their operating temperature, biased voltage and heat structure are discussed respectively, and the reason for the import microbolometer arrays for commercial applications have bad operation performance and image quality for low ambient temperature is found out.Relying on the performance study result of microbolometer arrays, the ambient temperature adaptability experiment and the biased voltage adaptability experiment are conducted respectively for microbolometer arrays, and it is proposed according to the experiment results that the import microbolometer arrays working at multi operating temperatures and corresponding biased voltages could improve their sensitive performance, power consumption and image quality for low ambient temperature.Since the import microbolometer arrays work at a single operating temperature and can not endure the ambient temperature range for military applications, a high-precision, multi-operating-temperature TEC (thermal-electrical-cooler) temperature control method is presented and the corresponding circuit is designed, to make the import microbolometer arrays automatically switch to different operating temperatures and biased voltages according to different ambient temperatures, and then to advance the operation performance and image quality, extend the endurable ambient temperature range, and reduce the power consumption of the thermal imaging system of microbolometer arrays to meet the military application requirements.As the uncooled infrared thermal imaging system with traditional one-off calibration suffers the response characteristic excursion, a real-time calibrating method based on two-point correction is presented and the corresponding calibrating circuit is designed to update the nonuniformity correction coefficients, compensate the response characteristic excursion and advance the image quality of the thermal imaging system of microbolometer arrays.Considering the miniaturization requirement of the thermal imaging system of microbolometer arrays, a new imaging project is proposed and the corresponding signal processing circuit based on FPGA is designed using NiosII configurable software processor embedded in FPGA instead of DSP to reduce the bulk of microbolometer arrays and the thermal imaging system.At the end of this dissertation, using the test equipments in cooperate company and the existing performance module, the operation performance and image quality of the thermal imaging system of microbolometer arrays developed in this dissertation are evaluated and the developed thermal imaging system is also applied in the multi-spectrum image fusion system. The evaluation results and application results indicate that the thermal imaging system of microbolometer arrays developed in this dissertation can meet the military application requirements.