Study On The Key Technologies Of A Novel Large-range Laser Warning System

As laser menace is increasing quickly, laser warning technologies are being researched and the laser warning equipments are being rapidly developed all over the world. To meet the demand of the military project, "Development of a Novel Laser Warning System Used for Large-Sized Land Targets", some problems regarding the laser warning system are studied in this dissertation. Some valuable results are obtained which are summarized as follows:By analyzing the scattering effects caused by the transmission of laser through the atmosphere and using Mie's scattering theory, the mathematical model that presents the relation between laser irradiance of atmospheric scattering is derived. The time domain characteristics of the scattering signal distribution of 1.06μm laser under the condition of city suburb model are obtained by theoretical analysis and numerical calculation. That is, the maximum intensity of aerial scattering laser decreases slowly with the abaxial distance of detector and is inversely proportional to the distance; and the aerial visibility only affects the scattering intensity, instead of the distribution of scattering intensity. These characteristics provide the theoretical basis for the development of the scattering laser warning system at 1.06μm.Due to the fact that the false alarm probability increases with the number of warning unit and interference factors such as gunfire flash and reflection light of the sun are of single time characteristics, a accumulating detector that has the function of counting and timing is designed and a detecting model that combines multiple-unit correlation detection and the aforementioned accumulating detector is presented. As a consequence, such system can effectively reduce false alarm probability by using threat grade warning.On the basis of extensive study and summarization various coherent detecting methods, a new scheme to measure laser wavelength is presented by analyzing the localization of the interference stripes of optical wedge and the relation of the stripes'interval to the incident laser wavelength. When parallel laser beam is perpendicularly incident onto an optical wedge, some equal-width stripes occur on the surface of the wedge whose space period can be transformed into time domain period by linear charge coupled device (CCD). The incident laser wavelength can be calculated from the intervals of the stripes obtained by Discrete Fourier Transform (DFT). In order to improve the measuring precision of the laser wavelength, the modified formula, which has a universal purpose, of the DFT's discrete error is derived. The validity of the method is validated by experimental results.A method of quick measuring several missile-guiding laser wavelengths is proposed by digital filters so as to raise the response speed and reduce the computing time of laser warning receiver. In the signal processing of laser warning receiver, the digital filters that are designed by using the digital filter iterative formula derived from DFT can quickly detect several missile-guiding laser wavelengths. The method can effectively raise the response speed.Considering the effects of the inherent noise caused by the non-uniformity of CCD on the detection of weak signal of incident laser, the generation mechanism and the correction algorithms of the non-uniformity of CCD are studied. The idea that the techniques of non-uniformity correction are applied in laser warning receiver is proposed to improve its detection sensitivity and increase its action distance.The idea of fuzzy-decision-based laser menace source recognition is presented on the basis of analyzing the uncertainty of the technical parameters, such as the laser energy, the laser wavelength and the repetitive frequency, to recognize menace source. The mathematical fuzzy models of laser technique parameters, such as the laser energy, the laser wavelength and the repetitive frequency, are set up, and fuzzy rule library of laser menace source recognition is designed by using fuzzy decision theory. Therefore, laser menace source can be identified correctly.