Underwater in-situ plankton imaging system based on microscopic optical tweezers

Marine plankton play an irreplaceable role in the marine ecological environment, and it is also an important and popular research field in biology and oceanography. Microscopic imaging system, with the outstanding advantages of high resolution and high magnification, is one of the most direct and effective in situ observation and research tools for marine plankton. To carry out the detection and research of marine plankton more efficiently and reduce the impact of its free movement on in-situ observation, this paper proposes to combine the optical tweezers with the microscopic imaging technology to design a microscopic optical tweezers based underwater in-situ observation system for plankton. The system uses holographic optical tweezers to enable the capturing of plankton in the water body, which allows it positioned stably and imaged clearly within the field of view. The work described in this paper built a holographic microscopic optical tweezers system in the laboratory and wrote an algorithm for generating phase maps based on diffraction-computed holography, thus break through the limitation that the traditional optical tweezers system can only capture the target at the center of the optical path and realizing free manipulation of targeting plankton in the field of view. Meanwhile, this paper also miniaturizes the laboratory system and completes the design including the underwater chamber and related accessories so that the system can work well underwater. The experiments show that the system can stabilize and image plankton samples well in both static water and flow field, which can meet the requirements of underwater in-situ experiments, indicating that the method has great practical value and application prospects in solving the problem of high-quality in-situ microscopic observation.