Guo Yilu, Song Hong, Liu Hongbo, Wei He, Yang Ping, Zhan Shuyue, Wang Hangzhou, Huang Hui, Liao Ningfang, Mu Quanquan, Leng Jianxing, Yang Wenjing
Opt Express. 2016 Jun 13;24(12):13101-20. doi: 10.1364/OE.24.013101.
Underwater spectral imaging is a promising method for mapping, classification and health monitoring of coral reefs and seafloor inhabitants. However, the spectrum of light is distorted during the underwater imaging process due to wavelength-dependent attenuation by the water. This paper presents a model-based method that accurately restores brightness of underwater spectral images captured with narrowband filters. A model is built for narrowband underwater spectral imaging. The model structure is derived from physical principles, representing the absorption, scattering and refraction by water and the optical properties of narrowband filters, lenses and image sensors. The model coefficients are calibrated based on spectral images captured underwater and in air. With the imaging model available, energy loss due to water attenuation is restored for images captured at different underwater distances. An experimental setup is built and experiments are carried out to verify the proposed method. Underwater images captured within an underwater distance of 260 cm are restored and compared with those in air. Results show that the relative restoration error is 3.58% on average for the test images, thus proving the accuracy of the proposed method.
水下光谱成像对于珊瑚礁和海底生物的测绘、分类及健康监测而言是一种很有前景的方法。然而，在水下成像过程中，由于水对不同波长的光存在衰减，光的光谱会发生畸变。本文提出了一种基于模型的方法，可精确恢复用窄带滤光片拍摄的水下光谱图像的亮度。构建了窄带水下光谱成像模型。该模型结构源自物理原理，体现了水的吸收、散射和折射以及窄带滤光片、透镜和图像传感器的光学特性。基于在水下和空气中拍摄的光谱图像对模型系数进行校准。利用该成像模型，可恢复在不同水下距离拍摄的图像因水衰减导致的能量损失。搭建了实验装置并开展实验以验证所提方法。对在水下260厘米距离内拍摄的水下图像进行恢复，并与在空气中拍摄的图像进行比较。结果表明，测试图像的平均相对恢复误差为3.58%，从而证明了所提方法的准确性。
