In order to improve the performance of a pulsed laser radar, methods based on wavelet filter and pulses accumulation are investigated. The transmitted pulses and received return waves are modeled for the simulation of signal processing through a filter. It shows that the modeled return waves could be denoised effectively with the wavelet biro3.9 or db9 if it is on the basis of compulsory denoising. However, under the condition of high fidelity requirement for the waveform, the signal-to-noise ratio may not be increased considerably. Thus, a new filter which is based on the combination of pulses accumulation and a followed wavelet transformer is proposed and studied. The results show that it is preferab
The transmitting and receiving optical system for the scannerless laser radar are designed and simulated in ZEMAX. In
the transmitting optical system, in order to increase the operating distance, a beam expander telescope which is used for
reducing divergent angle of laser beam is chosen. To make fully use of light, a micro lens array is used as a beam splitter.
In the receiving optical system, in order to improve the filling factor of APD array, a micro lens array used to replace the
previous usual lens is studied. The simulation shows that the density of the light spot after split was uniform, and
demonstrates that the designed array illumination is feasible. In the part of receiving optical system, each beamspot
through micro lens array can match perfectly with the APD unit cell, and the receiving efficiency is improved effectively.
Signal processing is pivotal to laser radar system. Information like range, target's signature, etc. can be obtained from the
processed laser signals. The received laser pulses for pulse laser radar are modeled. A wavelet filter is designed to
denoise the contaminated laser signals. For the given laser signals, the filter based on the combination of correlation and
thresholding is proposed. The gain of the filter is compared with the traditional thresholding method. It is shown that the
combination of the correlation and thresholding denoising method is more effective for the weak laser radar signal
processing compared with the traditional thresholding method.
The polarization characteristic of laser backscattering from randomly rough surfaces is studied theoretically and
experimentally in this paper. The effect of multiple scattering from rough surfaces is analyzed. The equation for the
backscattering coefficient and the polarization of Gaussian rough surfaces are derived and the simulation is conducted
under several certain conditions. The polarization characteristics of different materials with different shapes are
measured. The experimental results and the simulated numerical values are compared and analyzed in detail.
A receiver with high dynamic response and wide control range are necessary for a laser radar system. In this paper, an
automatic gain control scheme for laser radar receiver is proposed. The scheme is based on a closed-loop logarithmic
feedback method. Signal models for pulse laser radar system are created and as the input to the AGC model. The signal is
supposed to be very weak and with a nanosecond order of pulse width in the light of the property of the laser radar. The
method and the simulation for the AGC will be presented in detail.
Effect ofatmospheric turbulence on the performance oflaserradar is investigated in this paper. The characteristic of the Gaussian laser beam propagating parallel to the ground in weak turbu'ence is primarily considered. The light intensity fluctuation, beam shifting and spread caused by the turbulence are calculated. The effect of turbulence on laser pulse width is also researched. And then the effect ofthe atmospheric turbulence on laser radar is concluded.
A scanner based diode pumped solid state imaging laser radar is introduced in this paper in detail. Three different methods for the acquisition of range and intensity image are described and compared. The image for the range and intensity can be obtained simultaneously based on a PC-based acquisition card technology. The method based on FPGA is more popular but with low effective ladar range. The theory based on the voltage to time conversion technique is simple, but with low range precision.
A homodyne CO<SUB>2</SUB> laser radar vibration system is investigated in this paper. A loudspeaker as a cooperative object is used as a vibration source. The vibration frequency of the loudspeaker varied with the supplied voltage can be measured and can be compared with the pre-set frequency. A simple and feasible method is presented to measure the vibration frequency and amplitude. The vibration amplitude in the magnitude of micro meter can be measured precisely.
A point-scan based laser imaging system is described in this paper. A diode-pumped Nd:YAG laser with high efficiency and high pulse repetition rate is used as the laser source. Any interested area of an object can be imaged and investigated with the system. The technique can have many applications in the field like industry, medical application, defense system and many other fields.
In this paper the expansion, transmission and distributed function of antenna are analyzed, and the optimum characteristics of antenna is obtained. If we accurately calculate intensity of backscatter for target, the sign of light facula and distribution of energy have to be considered on surface of the target. We had built swapping relation equation between coordinates of the radar and object space of the target, using computer the pseudo-color imaging of the basic target are produced by the equation.
In order to navigate through its environment a robot vehicle needs to determine its position relative to a certain target. Now in the robot vision system the light spots measuring technique can be used. A charge coupled device camera is used as a sensor in the technique, but because it needs a complex focusing and processing system, the technique is not simple enough and the method for relative positioning is not quick, the processing is computationally intensive. In order to overcome the these defects a simple and reliable sensor, that is the position sensitive detector (PSD) is used as a close range sensor. In this paper, a new algorithm of measuring light spot, the structure and principle of the PSD are introduced. The scheme of measuring with PSD in the robot vision system is demonstrated. Using the system the robot position relative to the target can be determined.