eHoloCam - an electronic holographic camera for subsea analysis

Recently we have developed an underwater holographic camera for the analysis of plankton and other marine organisms. This camera (HoloMar) was unique in that it was able to record simultaneous in-line and off-axis holograms to cover a range of size of marine organisms from a few microns to tens of millimetres and at concentrations from a few particles per cubic centimetre to dense aggregates. However, HoloMar suffered for being physically large and heavy and difficult to deploy. It also was based on the use of photographic emulsions to record the holograms. To overcome some of these difficulties we have started to develop a new holographic camera (eHoloCam) based on digital holography. In electronic or digital holography (eHolography) an electronic hologram is directly recorded onto a CCD or CMOS sensor and then numerically reconstructed by simulation of the optical hologram reconstruction. In this paper, we discuss some of the possible optical layouts and algorithms under consideration. We present some eHolograms produced in the laboratory prototypes of the eHoloCam