Statistical Properties Of High Repetition Rate Pulse Laser Radar Range And Its Image Quality Evaluation

As a fast developing technique, Laser radar has been widely used in city digitization, building survey, heritage restoration, collision avoidance as well as navigation. However, instead of focusing on the basic theory, most researches nowadays emphasize on technology development and application. So this PHD thesis studies range statistical characteristic and image quality evaluation of range image from both theory and experiments, several research achievements have been obtained:Using the principle of time-of-flight, then deducing from constant threshold as well as peak discrimination, we obtained the probability density distribution of the range data. The analytical solutions of probability density distribution of the range data is the product of noise statistical distribution and the first derivative of the pulse-echo at constant threshold discrimination mode; while the probability density distribution of the range data at peak signal discrimination mode is the negative product of derivative noise statistical distribution and the second derivative of the pulse-echo. This result established the relation between range data distribution density and laser echo pulse/noise distribution.The simulation model of time-of-flight laser radar ranging has been established. This model provides a way to study the statistical distributions of laser radar ranging data, which takes laser pulse shape, target characteristics, noise statistical characteristics, system bandwidth into account. The simulation model designed in MATLAB environment could be used to examine the impact of laser echo and noise on the laser radar ranging data discrete distribution. Moreover, by analyzing and comparing both simulation results and analytical solutions, statistical distributions of laser radar range data at different conditions are obtained which provides a theoretical basis for optimal designing of the laser radar.High repetition rate diode laser radar system has been established in which systematic parameters could be easily adjusted such as laser power, laser pulse width, etc. and range data analyzing software has been designed. The impact of laser echo and noise on laser radar ranging distribution has been studied. Besides, the experimental results fit well with the analytical solution and simulation results.The conception of "range noise" has been proposed based on study of laser radar ranging statistical characteristics. Moreover,"mean square error of range" and "signal-to-noise ratio of range" have been introduced to evaluate the pros and cons of laser radar range imaging quality. The influence of laser radar systematic parameter on laser radar range imaging quality has been analyzed with the one-dimensional range imaging simulation model. This research shows with the increase of pulse width, pulse bandwidth and threshold level the laser radar range imaging quality becomes better initially, but starts to decline after a certain point. This finding indicates that there is a best condition for each parameter to obtain best laser radar range imaging quality.In addition, the thesis has also proposed a novel method to raise signal-to-noise ratio of laser echo detection with signal delay superimposed which has raised19%of signal to noise ratio at14.8ns delay.These studies have proposed solid support for optimal design and application of high repetition rate laser radar.