SPIE Proceedings [SPIE 6th International Symposium on Advanced Optical Manufacturing and Testing Technologies (AOMATT 2012) - Xiamen, China (Thursday 26 April 2012)] 6th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optoelectronic Materials and Devices for Sensing, Imaging, and Solar Energy - Research on voltage characteristic of the third generation low-light-level image intensifier tube's output signal to noise ratio