Underwater Optical Imaging: The Past, the Present, and the Prospects

Abstract

This paper discusses the current state of underwater optical imaging in the context of physics, technology, biology, and history. The paper encompasses not only the history of human's ability to see underwater, but also the adaptations that various organisms living in oceans or lakes have developed. The continued development of underwater imaging systems at military, commercial, and consumer levels portends well for both increased visibility and accessibility by these various segments. However, the fundamental limits imposed by the environment, as currently understood, set the ultimate constraints. Physics, biology, computer modeling, processing, and the development of technology that ranges from simple cameras and lights to more advanced gated and modulated illumination are described. The future prospects for continuing advancements are also discussed.Index Terms-Underwater optical imaging.

The ICES Working Group on Zooplankton Ecology: Accomplishments of the first 25 years

“…As with acoustics, there have been significant advances in optical imaging. Jaffe (2015) provides insight into what is now possible with underwater imaging well beyond that used to study zooplankton and Benfield et al (2007) describe much needed improvements in automated plankton image identification.…”

Underwater optical impulse response measurement using a chaotic lidar sensor

“…Considering the time bandwidth product of T B = (250µs) · (1 GHz) = 2.5 × 10 5 , the effective modulated signal energy sent into the tank is estimated at 2.08 mJ per measurement. 18 The received signals y 1 (t) and y 2 (t) were digitized simultaneously by a high speed oscilloscope (Agilent Infiniium 54845A) with a 1.5 GHz analog bandwidth, sampling at 8 GS/s with 8 bit resolution. All digital signal processing was performed in Matlab.…”

“…Underwater impulse response measurements can quantify the effects of optical absorption and scattering, [5][6][7] which are relevant to underwater lidar systems. [8][9][10][11][12][13][14][15][16][17][18] These impulse response measurements have been made in the blue-green wavelengths using pulsed bulk lasers 8,19,20 or frequencymodulated continuous-wave (FMCW) systems based on diodes or fiber optic transmitters. 21,22 Properties such as the extinction coefficient of the water and the power spectrum of the backscatter's modulation response can be extracted from these measurements.…”

An underwater chaotic lidar sensor based on synchronized blue laser diodes

“…[1][2][3][4][5][6] Recent work has demonstrated the advantages of wide bandwidth intensity modulation for operation in turbid waters, where high temporal resolution can allow discrimination between the unwanted backscatter signals and the desired return signals from objects of interest. [7][8][9][10][11] Chaotic lidar is a wide bandwidth approach that has been successfully used for turbid water impulse response and ranging measurements.…”