Environmental performance bounds for undersea pulsed laser serial imagers

This paper examines imaging performance bounds for undersea electro-optic identification (EOID) sensors
that use pulsed-laser line scanners to form serial images, typically utilizing one laser pulse for each formed
image element. The experimental results presented include the use of two distinct imaging geometries; firstly
where the laser source and single element optical detector are nearly co-aligned (near monostatic) and
secondly where the laser source is deployed on a separate platform positioned closer to the target (bistatic)
with the detector being positioned much further from the target. The former system uses synchronous
scanning in order to significantly limit the required instantaneous angular acceptance function of the detector
and has the desired intention of acquiring only ballistic photons and the undesirable property of acquiring
multiply-scattered snake photon contributions that indirectly arrive into the detector aperture. The latter
system utilizes a staring detector with a much wider angular acceptance function, the objective being to
deliver maximum photon density to each target element and acquire diffuse, snake and ballistic photon
contributions in order to maximize the signal. The study investigates received pulse energy variance from
both the direct (target) component and the snake (forward scatter) in clear filtered water, as well as various
well-characterized particle suspensions with and without an artificial thin random scattering layer. For each
dataset, efforts were made to measure variance due to device shot noise in order to assess the impact of the
environment on image quality.