海水水体的点扩展函数（PSF）及光学传递函数（OTF）描述了海水中光或图像传输的性质，是研究海水光学性质及水下图像系统的基本参数。探讨了用图像传输的理论测量海水点扩展函数或光学传递函数的方法，在实验室中建立了一套测量和计算系统；对不同长度的散射水体进行了测量，得到了一维和二维的海水点扩展函数曲线，测量结果与理论分析相符合。

Because light is scattered and absorbed by seawater, the images obtained underwater are always blurry after transmitted through a certain distance. The point spread function (PSF) and modulation transfer function (MTF) are important properties of seawater to predict underwater light propagation and underwater image quality. We describe the laboratory facilities to measure the PSF and MTF of water body by the image transmission method and the restoration methods of underwater blurred images. The measured results are given and compared with the theories. The blurred images of a bar target transmitted through different water paths are restored with the measured MTF using a Wiener filter.

The East China Sea is a typical case 2 water environment, where concentrations of phytoplankton pigments, suspended matter, and chromophoric dissolved organic matter (CDOM) are all higher than those in the open oceans, because of the discharge from the Yangtze River and the Yellow River. By using a hyperspectral semianalytical model, we simulated a set of remote-sensing reflectance tbr a variety of chlorophyll, suspended matter, and CDOM concentrations. From this simulated data set, a new algorithm for the retrieval of chlorophyll concentration from remote-sensing reflectance is proposed. For this method, we took into account the 682-nm spectral channel in addition to the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) channels. When this algorithm was applied to a field data set, the chlorophyll concentrations retrieved through the new algorithm were consistent with field measurements to within a small error of 18%, in contrast with that of 147% between the SeaWiFS ocean chlorophyll 2 algorithm and the in situ observation.

The theory and experiments for a multichannel optical system for pseudocolor encoding of images are presented. Spatial-frequency pseudocolor encoding is accomplished by spatial filtering different-colored spectra in different channels. Density pseudocolor encoding is accomplished by the incoherent addition of three primary color images: a contrast-reversal image in one color, a positive image in the second color, and a contrast half-reversal image in the third color. This is a simple, real-rime'technique. It has no resolution loss that is due to the use of gratings or halftone screens, and the optical system does not require Fourier-transform lenses with large relative apertures.