Low-cost optical techniques for detecting and imaging different objects underwater

The camera has been commonly used in underwater image acquisition experiments, but the image noise is high, and the distance is limited because of the underwater scattering effect. In this paper, the optical detection device of underwater objects, 520 nm continuous laser modulation by PWM pulse modulation (10 Hz, 60% space ratio), was used to scan and detect two completely different objects (such as advanced resin and green leaves). The photodetectors were used to replace cameras, collect and process the received laser echo signals, and image and display the data. The detected objects images can be visually displayed in the form of grayscale images (resolution of 143 x 62), and the corresponding effects have been discussed. In the experiment, we used a 70 cm long ultra-white glass cylinder and detected a distance of 45 cm, and the results were very consistent with the actual situation. (paper)