The development of a subsea holographic camera for the imaging and analysis of marine organisms

摘要

In this overview of the entire HoloMar system, we describe the design, development and field deployment of the fully-functioning, prototype, underwater holographic camera (HoloCam) followed by the dedicated replay facility (HoloScan) and the associated image processing and extraction of data from the holograms. The HoloCam consists of a laser and power supply, holographic recording optics and holographic plate holders, a water-tight housing and a support frame. It incorporates two basic holographic geometries, in-line and off-axis such that a wide range of species, sizes and concentrations can be recorded. After holograms have been recorded and processed they are reconstructed in full three-dimensional detail in air in a dedicated replay facility. A computer controlled microscope, using video cameras to record the image at a given depth, is used to digitise the scene. Specially developed software extracts a binarised image of an object in its true focal plane and is classified using a neural network. The HoloCam was deployed on separate cruises in a Scottish sea loch (Loch Etive) to a depth of 100 m and over 300 holograms recorded.