Method for spectral restoration of underwater images: theory and application

Underwater multispectral imaging is a promising technique for high-fidelity underwater color reproduction and mapping of kelp, sea grass, corals, etc. However, as light propagates through water, light is severely absorbed and scattered by water, causing image dim, hazy and distorted in its spectrum and color. In this paper, calibration of water attenuation coefficient based on underwater images and restoration of underwater multispectral images are discussed. Multispectral images of an underwater object are captured at different underwater distances. Technique has been proposed to calibrate the water attenuation coefficient based on underwater images of different distances and restore the raw images. Analysis was also conducted to search for the least number of distances for coefficient calibration and restoration. By comparing the restored underwater images with the images captured in air, its found that the technique proposed in this paper provides accurate restoration of underwater spectral images, with a relative residual error of 5.87% in average for all test images.