Modelling and impact of the turbulence effect on flash and cumulative 2D active imaging system

Abstract

Abstract In the topic of 2D active imaging systems, two technologies exist for image acquisition. The flash mode consists of a very short and intense laser shot, associated with a short time integration of the sensor (range of hundreds of nanoseconds). The second is the cumulative mode which consists of the integration of many low level energy laser pulses over a long-time integration of the sensor (range of tens of milliseconds). Cumulative mode systems have existed for a long time in the near infrared band. But for the past few years, new sensors are available in the short wave infrared (SWIR) band. Cumulative mode in the SWIR band can provide 2D active imaging systems with very low risk considering the eye safety aspects. Moreover, with a similar design, cumulative systems can overcome the range of flash systems, thanks to their ability to average turbulence effects over the sensor integration time. So, in this paper we have proposed a scintillation noise comparison for each mode. First, we exposed the two types of available models, a numerical model, used for image generation. Second one, an analytical model, used for a quick evaluation of the design of a 2D active imaging system. Both models were compared, especially in their area of validity. Then for a specific scenario, we estimated the gain in term of range performance between a cumulative and a flash system.