Underwater digital holography is a powerful technique to study marine organisms and marine pollution (e.g. micro-plastics), marine evolution, etc. at the microscopic level, in 3D with instantaneous recordings of fluid volumes . At Aberdeen University we have designed and manufactured subsea holocameras since the 1990s; initially in classical analogue form using photographic emulsions, and, latterly, using digital recording of the holograms on electronic sensors with subsequent replay and extraction of data by computer [2,3]. Many of the advantages of classical holography are retained such as 3D (although limited in in-line mode), freedom from parallax and perspective effects, large depth-of-field and high-resolution (down to less than 10 m depending on optical configuration and sensor parameters). Additionally, and crucially, adopting digital recording allows holographic videos to be captured thereby adding the all-important fourth dimension; allowing evaluation in space and time.
One of the most significant and important features of holography, is the ability to replay and focus the holographic image, at high resolution, at any spatial plane within the entire volume of the sample. Such “optical sectioning” allows particle identification to be made at species level, and dimensional measurement, relative location and particle distributions to be extracted and mapped.
The advantages of digital holography for subsea imaging, inspection and mensuration include:
• Non-destructive and in situ observations of living species in the size range of about ten micrometres to several millimetres, in their natural habitat
• High image resolution (down to less than 10 m – depending on configuration)
• Recording and sampling volumes between 1 cm3 and 50 cm3, depending on configuration
• Ability to capture images in 3D-space together with the time-dimension in holographic videos
• 3D viewing and freedom from parallax and perspective effects (but limited in in-line recording)
• Wide range of target sizes from a few micrometres to millimetres and above (depending on configuration and optical parameters)
• The ability to record phase objects such as air bubbles or jellyfish larvae.
The vast data capturing capabilities of digital holography make extraction and analysis of holograms very time consuming and computer intensive. Current software algorithms are not fast enough to cope with the amount of data to be analysed (as much as 2 GB in a single holographic video). Automated image extraction, data processing and image classification is essential for rapid interrogation and analysis of the organisms in the water column .
In this PhD project, new techniques to improve the current state of the art on subsea digital holography will be considered. This could involve one or more of the following:
• Develop software/hardware methods to improve the hologram processing (data extraction) time.
• Investigate hologram recording & processing methods to improve the resolution of extracted images.
• Develop image processing algorithms to automatically classify plankton images.
• Investigate the application of digital holography for imaging and identification of micro-plastics.
Candidates should have (or expect to achieve) a UK honours degree at 2.1 or above (or equivalent) in Electrical/Electronic Engineering; Physics; Software Engineering.
Some background in one or more of the following would be an advantage: general optics, lasers, holography, image processing, computer software/hardware.
• Apply for Degree of Doctor of Philosophy in Engineering
• State name of the lead supervisor as the Name of Proposed Supervisor
• State ‘Self-funded’ as Intended Source of Funding
• State the exact project title on the application form
When applying please ensure all required documents are attached:
• All degree certificates and transcripts (Undergraduate AND Postgraduate MSc-officially translated into English where necessary)
• Detailed CV
Informal inquiries can be made to Dr T Thevar ([email protected]
) with a copy of your curriculum vitae and cover letter. All general enquiries should be directed to the Postgraduate Research School ([email protected]