This paper outlines theoretically investigations of the probability density distribution (PDD) of ranging data for the imaging laser radar (ILR) system operating at a wavelength of 905 nm under the fog condition. Based on the physical model of the reflected laser pulses from a standard Lambertian target, a theoretical approximate model of PDD of the ranging data is developed under different fog concentrations, which offer improved precision target ranging and imaging. An experimental test bed for the ILR system is developed and its performance is evaluated using a dedicated indoor atmospheric chamber under homogeneously controlled fog conditions. We show that the measured results are in good agreement with both the accurate and approximate models within a given margin of error of less than 1%.
This paper investigates the signal to interference plus noise ratio (SINR) performance of the imaging laser radar (ILR) system operating at a wavelength of 905 nm using an avalanche photodiode array under the fog condition. We analysis the glow image of the light source, which is formed by the laser spot irradiated on a standard Lambertian target. Based on the proposed theoretical model, we determine the interference due to the glow inter-channel crosstalk under different fog conditions for a targeted channel. We show that, for transmission spans less than several tens of meters the interference due to glow crosstalk is higher than the fog (light to medium) induced losses. However, for a link range longer than 21 m the glow crosstalk induced interference is lower than the heavy fog induced attenuation. The proposed system performance is evaluated by developing an experimental test bed and using a dedicated indoor atmospheric chamber under homogeneously controlled fog conditions. We show that, under different fog conditions experimental results for changing SINR levels match well with the predicted data. The results shown can be used for design optimization of the ILR system when operated under fog conditions.
This paper theoretically and experimentally investigates the performance of the imaging laser radar (ILR) system under the fog condition. Fog is generated and controlled homogeneously within a dedicated indoor atmospheric chamber. A physical model of the reflected laser pulses due to fog and a standard Lambertian target are developed to determine the width of each echo pulse for different fog concentrations. We show that there is a good agreement between the predicted and measured results for the width of backscattered return pulses. Based on experimental results an empirical model of the horizontal and vertical irradiating field of views (FOVs) of ILR under different visibilities is also developed. Consequently, a new model is proposed to predict the horizontal and vertical irradiating FOVs of ILR by using the width of the backscattered return pulse under different fog conditions. The reported results can be used to dynamically adjust the scanning interval based on the variation of the irradiating FOVs of laser radar and improve the precision of target ranging and imaging.
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