Design a long-range near infrared LiDAR imaging system for security and surveillance applications

In this paper a review on the state of art on the imaging lidar system useful for security and surveillance applications is discussed. An imaging lidar system design and developed in house is also described. The theoretical approach of the system developed in house is presented. Based on the approach the technical parameters of a proposed long-range lidar system have been finalized and the designed specifications of various components/sub-systems were also derived. A laser transmitter, which operates at the wavelength of 1064 nm in the NIR region is used in the system. An analysis of the system is presented describing the expected values of received energy (Er) / power (Pr) and the SNR of the system have been determined for various values of co-efficient reflectivity and size of the target. Three factors that are affecting the imaging systems have been discussed namely i. resolution requirements in terms of pixels of detector, ii. atmospheric turbulence in terms of index of refraction due to time-varying thermal inhomogeneities, and iii. atmospheric attenuation, which includes absorption and scattering. The use of range gating technique was described, which enables the imaging of the target at a fixed range, while minimizing the atmospheric effects on the image quality. The range gating substantially improves the SNR of the imaging system. The lidar system can be operated in both day and night conditions, even though its use is essentially meant for nighttime conditions as required for security and surveillance.