New Solutions in Underwater Imaging and Vision Systems

Bonin‐Font, Francisco; Burguera, Antoni; Oliver, Gabriel

doi:10.1002/9783527675418.ch2

Cited by 5 publications

(5 citation statements)

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“…Collecting visual observations in underwater environments is a difficult task and a technological challenge [1]. Refraction, non-uniform lighting and shadows, light scattering and absorption: all reduce our ability to collect and interpret quality visual information [1][2][3]. Small suspended particles in water Figure 1.…”

Section: Introductionmentioning

confidence: 99%

“…Image contrast is also lowered with shorter visual range as the light attenuation will reduce the illumination of distant targets. These factors remain the outstanding challenges in underwater imaging and limit the application of visual observations in many sectors [1,2,4].Various optical and acoustic imaging systems for mitigating or solving these problems are under constant development and refinement. However, a general technological solution for high-quality images in all seawater conditions remains elusive.…”

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confidence: 99%

“…For more reliable operations at different depths and water conditions, artificial lighting is generally provided, and with the development of LED technology, several affordable solutions are becoming available for routine monitoring activities [4,5,9]. More sophisticated-but also more expensive-systems make use of laser lights to take advantage of collimated, narrow and monochromatic beams, allowing sensible reductions in scattering volumes [10,11].Lasers can be used as continuous light sources or as strobed (pulsed) lights as in-line scanners (LIDARs) and all range-gated systems [2,10,12,13]. Range-gated imaging systems are based on a relatively simple concept in which the camera shutter is synchronised with the light source emitting nanosecond length pulses and only opens for a time window around the instant when the signal of the illuminated object of interest reaches the camera (Figure 1).…”

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confidence: 99%

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confidence: 99%

“…Lasers can be used as continuous light sources or as strobed (pulsed) lights as in-line scanners (LIDARs) and all range-gated systems [2,10,12,13]. Range-gated imaging systems are based on a relatively simple concept in which the camera shutter is synchronised with the light source emitting nanosecond length pulses and only opens for a time window around the instant when the signal of the illuminated object of interest reaches the camera (Figure 1).…”

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confidence: 99%

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Range-Gated Imaging System for Underwater Monitoring in Ocean Environment

et al. 2018

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High-quality video observations are very much needed in underwater environments for the monitoring of several ecosystem indicators and to support the sustainable development and management of almost all activities in the ocean. Reliable video observations are however challenging to collect, because of the generally poor visibility conditions and the difficulties to deploy cost-effective sensors and platforms in the marine environment. Visibility in water is regulated by natural light availability at different depths, and by the presence of suspended particles, scattering incident light in all directions. Those elements are also largely variable in time and space, making it difficult to identify technological solutions that can be used in all conditions. By combining state-of-the-art "time of flight" (ToF) image sensors and innovative pulsed laser illumination, we have developed a range-gated camera system (UTOFIA) that enables affordable and enhanced 3D underwater imaging at high resolution. This range-gated solution allows users to eliminate close-range backscattering, improving quality of the images and providing information on the distance of each illuminated object, hence giving access to real-time 3D measurements. Furthermore, as the system is based on pulsed laser light, it is almost independent of natural light conditions and can achieve similar performances at an extended depth range. We use this system to collect observations in different oceanographic conditions and for different applications, including aquaculture monitoring, seafloor mapping, litter identifications and structure inspection. Performances are evaluated by comparing images to regular cameras and by using standard targets to assess accuracy and precision of distance measurements. We suggest that this type of technology can become a standard in underwater 3D imaging to support the future development of the ocean economy.Sustainability 2019, 11, 162 2 of 13 create a turbid environment that strongly increases light scattering and enhances the absorption probability of photons [3]. When the light source is the sun, this process effectively decreases the amount of ambient light present at any depth and limits the range of visual observations. With artificial illumination, the range for underwater vision can be extended (for example we can move deeper) but at the cost of degrading image contrast due to (forward-and back-) scattering generated by suspended particles. The situation is similar to driving a car in foggy conditions with the headlights on: increasing the power of illumination does not improve the visibility, as the backscattering increases proportionally. Image contrast is also lowered with shorter visual range as the light attenuation will reduce the illumination of distant targets. These factors remain the outstanding challenges in underwater imaging and limit the application of visual observations in many sectors [1,2,4].Various optical and acoustic imaging systems for mitigating or solving these problems are under constant develo...

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Section: Introductionmentioning

confidence: 99%

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confidence: 99%