Design and evaluation of optical image sensing device for marine plankton monitoring

Marine plankton play an important role in ocean web structure and global environment change. As an alternative to traditional sampling methods, real time imaging systems are particularly useful in studying the abundance and behavior of plankton in the appropriate spatial and temporal scales at high sampling rate. In this paper, the design of a non-invasive, high resolution, low power consumption optical imaging device is presented. The device is designed in a compact size and this makes it suitable to be deployed on underwater vehicle platforms for plankton monitoring. The reported imaging system is a balanced compromise of object distance, focal length of the lens, and the coverage of the sampling area. The results of laboratory evaluation of the combination of different parameters of the optical lens for plankton monitoring are presented. Light illumination based on light emitting diode (LED) is investigated. It is showed that the system is capable of obtaining relatively good resolution images at high sampling rate that allow quantification of the plankton in the appropriate spatial and temporal scales.