Studies On Readout Integrated Circuit And Testing System For Uncooled Infrared Focal Plane Array

Infrared Focal Plane Array (IRFPA) is the key part of the infrared system and thermal imaging devices, and it is widely applied in military and civil fields. So some western developed countries have been putting great emphasis on its research and development for a long time. Uncooled infrared focal plane array (UIRFPA) based on microbolometers has become one of the most important trends in IRFPAs, which consists of infrared sensor arrays and readout integrated circuit (ROIC). The complementary metal oxide semiconductor (CMOS) ROIC is becoming a main developing direction of ROIC, and is also one of the core technologies for IRFPA, which plays an important part in both IRFPA and the infrared system.Compared with several main werstern developed courtries, just the same as other technologies of UIRFPA, in our courtry the CMOS ROIC technology and the technology testing the IRFPAs'performance including measuring the CMOS ROIC characteristics are begun later, which were started in the nities of the 20th century. Owing to the significance of IRFPA for military applications,it is urgent to develop our own IRFPA, which should be sped up from several key technologies such as CMOS ROICs of UIRFPA and its testing technology (which are materials, ROIC, the process of device, testing and signal processing.).This paper emphatically presents the theoretical and experimental research on the ROIC of microbolometer-based UIRFPA and its testing technology, which main contents are as follows:(1) Some technologies relating to CMOS ROIC are analyzed, the noise characteristics of CMOS ROIC are intensively analyzed, and a few basic types of structure of the ROIC are compared, which mainly include the structures of self-integrator (SI), direct injection (DI), source follower per detector (SFD) and capacitor feedback transimpedance amplifier (CTIA). In these structures, the DI structure's circuit is simple and has high photon current injection efficiency, but has low uniformity and high KTC noise, and the CTIA structure's circuit has high stability of detector bias, high linearity, low noise, high uniformity and great dynamic range, which characteristics the other structures'circuit don't have, but is complex and has great power consumption.(2) A type of ROIC structure that combining bolometer current direct injection (BCDI) structure with capacitor feedback transimpedance amplifier (CTIA) structure is proposed, the structure has the advantages of the DI and CTIA structures and overcomes the inherent disadvantages of them simultaneously, which is adaptive to large-scale IRFPAs. Based on the above structure, a complete CMOS ROIC of FPA with this structure is designed, the designed circuit has correlated double sampling (CDS) circuits which has high noise depressing ability. The simulated and measured results of the ROIC's defferent part circuits indicate that the designed ROIC has characteristics of low noise, low power consumption and high dynamic range etc.(3) A low-cost and modularized testing system which can be used to test the FPA's performance is designed, which contains the modules of black body source, infrared optical system, bias voltage controller and so on, the charareistic parameters of FPA to be measured are pointed out, and the functions of every modules are analyzed. The the testing system has characteristics of being extended, being on-line configurated, and compatibility. A calibrating experiment on a practically put up testing system has been fulfilled, the calibrated results show that the designed testing system is highly reliability and can meet the requirements of testing IRFPAs'charateristics.(4) And at last, an experimental ROIC chip which is for 32×32 pixel IRFPA and fabricated in our laboratory is tested by using the testing system, the testing results show that the designed CMOS ROIC chip has correct readout function, achieves its expected characteristic parameters as the requirements of designs and is coincide with the above simulated results, hence indicate the correction of the designed CMOS ROIC with the structure proposed by us, and verify its characteristics of low noise, low power consumption and high linearity etc .