Underwater Holographic Detection System Of Marine Plankton

Ocean plays an irreplaceable role in the process of the ecosystem balance and regulation, the study of marine plankton is an important issue of marine scientific research. Plankton is a complex and large biomes, including zooplankton and phytoplankton. The research of plankton has a vital significance in many aspects, such as the origin of life, the discovery of new gene, the development of drugs, the protection of environment and global climate changes. It has become a hot topic.A new approach of digital holography and microscopy technology has been combined to take images of plankton without intrusion and interference. It combined the amplification characteristics of microscope objective and the large depth of field of holography.Digital In-line Holographic Microscopy (DIHM) system was designed, not only to record holographic images of the plankton fields but also to reconstruct the tomographic images at different depth fields for the use of image analysis. Copepods, noctiluca and various algae could be observed in the experiments. Favorable results from the experiments have shown that DIHM is an appropriate and highly effective method for aquatic plankton study.Underwater laser holographic detection system has been designed and completed. The system consists of the light cabin and the receiver cabin, the cable is connected between the two. The battery is located in the light cabin and the receiving compartment includes microscopic imaging amplification unit and storage unit. The CCD communicates with PC 104 and captures images. The system is 1340 mm length,156 mm width and 156 mm height. It works underwater 200 m, through pressure testing, tightness testing and shallow water detection experiment, the system enables detection of underwater plankton.In this paper, the digital In-line Holographic Microscopy (DIHM) system are presented and the experiments of marine plankton imaging based on DIHM are carried out.The obtained results demonstrated that minimum size of the object that can be clearly imaged with the DIHM system was 7.8 ?m with the field depth of 10 mm, which was much larger than those optical microscopes could ever achieve. The system can ensure sufficient magnification and obtain a large depth of field exploration simultaneously. The resolution meets the demand of detecting zooplankton and phytoplankton.After the shallow field experiments, It found that the water disturbance, ambient light and the conjugate image interfere with the quality of image, and the actual situation is more complicated. The system needed to research how to reduce the noise and eliminate the conjugate image. Taking into account the practicality issue, without changing the function of the system, equipment miniaturization is an important problem in underwater detection. At the same time on the basis of digital in-line holographic microscopy system, hoping to achieve off-axis digital holographic microscopy system instrumentation and integration.