The study of photoelectric detection technology for underwater projects

Abstract

The traditional methods to detect underwater objects are based on the acoustic detecting techniques. However, since the transmutation of the sound wave in ocean is often influenced by the oceanic boundary conditions and ambient factors such as salinity, temperature and pressure of the sea water, acoustic detecting techniques will cause large error in orientation and direction, which makes it difficult to capture and discriminate small objects. Instead, the photoelectric detection technology for underwater objects has the advantages of precise direction and orientation due to the high propagation velocity of light in water, consequently, the influence of ambient factors can be negligible. In this paper, we described the theory of underwater photoelectric detection and the system structure. Two kinds of experimental system are set up. One is imaging photoelectric detecting system; the other is non-imaging photoelectric detecting system. The underwater photoelectric detecting systems are made up of a short pulsed laser, a received optical system, narrowband optical filters, high-speed photoelectric detectors, a high-speed data acquisition and processing system etc. Both of the imaging and non-imaging photoelectric systems are employed to detect the reflection of target plane and simulated ship wakes. The key factors that affect the detection performance are analyzed in the paper. The experimental results show that for the imaging system, utilizing range-gated techniques can decrease the interference from background optical noise, while for the non-imaging system, using combining filters can suppress the backscattered optical noise from water. The conclusion is that both imaging and non-imaging photoelectric detection system are suitable for detecting underwater objects or their wakes.