Short-pulse Laser Detection Technology

Short Pulse Laser Radar has many important applications in the Theater Missile Defense System, Geoscience Laser Altimeter System, Moon Orbiter Laser Altimeter and high-speed 3D imaging and so on. With the development of our country, Operating range of the Pulse Laser Radar is far from meeting the demands of the development of national civilian and military applications, so our country urgently needs to develop the Pulse Laser Radar which can operate long range. A effective method of improving operating range is adopting shorter pulse laser, which is also one of development directions of Pulse Laser Radar.This paper focuses on the study of the detect system of Pulse Laser Radar. At fist A new way to calculate minimal receivable power of optical receiver with detecting directly short pulse laser signals is given, which is deduced on the base of two statistic concept: false alarm probabilities and detection probabilities of signal detection theory. Then minimal receivable laser energy of optical receiver, maximal operating range of Pulse Laser Radar and the rating of signal to noise compared with different laser pulse width( 0.1 ns ,1 ns and 10 ns ), this paper achieve that if the shorter laser pulse width, the lower the minimal receivable laser energy of optical receiver, the further the maximal operating range, the higher the SNR, the higher the sensitivity and the higher single-shot measurement precision under outputting same laser energy of laser diode. So this paper verified that the shorter laser pulse's width, the superior detect system according detection theories.The ranging mode and timing discriminate method of the short pulse detect system are analyzed in detail, and the proposed research project is explained. The project adopts pulse laser ranging in incoherent detect mode, variable gain post-amplifier and high-pass timing discriminate method, detect object with a single APD, and obtain intensity signal and stop signal simultaneously.A variety of noise on the system to detect the effects of sensitivity are analyzed theoretically. A broadband, low noise short pulse laser detect system is designed according to these theories, in which 1ns pulse laser is used. A high voltage generated circuit of APD, whose output voltage is 228V,is designed with separating parts. Output voltage is stable at 200μs. A high-speed transimpedence amplifier circuit with optimized noise, a broadband, low noise, variable gain post-amplifier and a high-pass timing discriminator are designed. At the same time, minimal receivable optical power, signal to noise ratio and other parameters are calculated theoretically. At last, a peak detector is designed whose response speed is about 2ns.