Research On Luminance Characteristics And Testing Technology Of Low Light Image Intensifier Fluorescence Screen

Low-level-light image intensifier is the key component in night vision technology. It goes through development period of first generation, second-generation, ultra second-generation, third generation and fourth generation. In the United States, the third-generation image intensifier is in production and fourth generation image intensifier is in stage of research. In China, this technology lags behind the USA by 20 to 25 years. Research on third generation is ongoing. Image intensifier screen parameter testing device is required but not available in China, and online test equipment involving upgrading the device level is embargoed to China. In order to meet the requirement of China's research on third generation dim-light image intensifier, research on a dim-light image intensifier screen luminescence properties and testing technology is launched. The testing method for image intensifier fluorescence screen brightness, uniformity and luminescence efficiency and afterglow is put up. Image intensifier fluorescence screen parameter testing System and thermal electronic surface-emitting sources are developed. The optimal working parameters of image intensifier screen testing System and the test results of fluorescence screen are given.Based on the analysis of the luminescence mechanism of the fluorescence screen, it is found that four parameters may be used to characterize the performance of the fluorescence screen. Main parameters representing the screen performance are its brightness, light emitting uniformity, efficiency and afterglow. Corresponding to the test requirements of these four main parameters, it is put up that adopting a million grade CCD imaging brightness meter for the testing of screen brightness and uniformity; Adopting optical flux detectors and optical power meter, ampere meter for testing the light emitting efficiency ; adopting Photosensitive cell detector and signal processor for testing afterglow. All these lay a foundation for the design and successful development of low-light-level image intensifier fluorescence screen Testing System.To measure the relines of four main parameters of dim-light image intensifier fluorescence screen, including brightness, uniformity, efficiency and afterglow, a thermal electronic surface-emitting source with the required performance need to be developed. With heat radiation formula under vacuum condition, heat balance equation of plane spiral filament is derived. It is shown that at work condition every point of the plane spiral filament has the same temperature. Based on thermal emission equation it is determined every point of the filament emits the same thermal electrons. UsingΦ0.3 mm tantalum wire, a flat spiral filament is developed. The spacing of filament is 1 mm, the diameter isΦ8 mm, and thermal electron emission characteristics of the plane spiral filament is studied. In cylindrical coordinate system, by solving the axisymmetric electrostatic field Laplace equation, electric field distribution of the electronic surface-emitting sources is achieved. By solving the trajectory equation in axial symmetry field, the e-trajectory of hot-electron surface emission source is achieved. In theory the physical parameters to achieve a uniform thermal electronic surface-emitting source is determined. By repeatedly tested and verified, eventually an electron-emission surface source with electronic properties of divergence, uniform, converging and submerging is developed.A dim-light image intensifier fluorescence screen parameter testing System is successfully developed for National Defense Key Laboratory. This testing system can test the four key performance parameters, brightness, uniformity, efficiency and afterglow of dim light image intensifier fluorescence screen. This system use computer control for the operation process, records the testing parameters with computer. The test results are comparative with super second-generation image intensifier. So it meets the urgent need for national defense project.A screen (nude screen) afterglow testing method is proposed. That is, with first anode voltage of -4000 V, and second anode voltage increased from -3990 V to -4010 V, a rejection electronic field is formed instantly then electrons are inspired. The testing results are basically same as the super second-generation image intensifier.