ABSTRACT: Although the use of blind deconvolution of image restoration is a widely known concept, only few reports have discussed in
detail its application to solving problem of restoration of underwater range-gated laser images. A comparative study of underwater
image restoration using the Richardson-Lucy algorithm, the least-squares algorithm, and the multiplicative iterative algorithm
for blind deconvolution is presented. All the deconvolution approaches use denoised underwater images and Wells’ small angle
approximation theory of derived point spread function as the initial object and degradation guess, respectively. Owing the
underwater no-reference imaging environment, image quality judgment based on the blur metric method is incorporated in our
comparison to determine the appropriate deconvolution iteration number for each algorithm, which objectively evaluates the
image restoration results. The performance of the three algorithms applied to underwater image restoration is discussed and
Keywordsunderwater imaging-image restoration-blind deconvolution-Richardson-Lucy algorithm-least-squares algorithm-multiplicative iterative algorithm
Optical Review 04/2012; 17(3):123-129. · 0.66 Impact Factor
ABSTRACT: Although the use of blind deconvolution of image restoration is a widely known concept, little literatures have discussed
in detail its application in the problem of restoration of underwater range-gated laser images. With the knowledge of the
point spread function (PSF) and modulation transfer function (MTF) of water, underwater images can be better restored or enhanced.
We first review image degradation process and Wells’ small angle approximation theory, and then provide an image enhancement
method for our underwater laser imaging system by blind deconvolution method based on small angle approximation. We also introduce
a modified normalized mean square error (NMSE) method to validate the convergence of the blind deconvolution algorithm which
is applied in our approach. The results of different initial guess of blind deconvolution are compared and discussed. Moreover,
restoration results are obtained and discussed by intentionally changing the MTF parameters and using non-model-based PSF
as the initial guess.
Keywordsunderwater imaging-image restoration-blind deconvolution-modulation transfer function (MTF)-point spread function (PSF)
Frontiers of Optoelectronics in China 04/2012; 3(2):169-178.
ABSTRACT: A new critical angle refractometer (CAR) for high accuracy refractive index measurement of liquid has been developed. The instrument improves the accuracy by two reflections in an elongated parallelogram prism, and acquires the angular reflectivity without any angle scanning parts through introduction of a point source with a divergent beam and a charge coupled device. In addition, it employs a simple and robust measurement method that gets the critical angle by differentiating the angular reflectivity. Through investigating absorbing media with absorption index κ (the imaginary part of refractive index) from 0 to 10(-2.1), the theoretical calculation shows that the proposed two-reflection CAR would outperform the traditional one-reflection CAR on lowering the principal error from the differentiation method and improving the ability of getting the critical angle. By testing two typical liquids-salt-water solution and milk, the preliminary experiment indicates that this two-reflection divergent differentiating critical angle refractometer is feasible and of high accuracy.
The Review of scientific instruments 05/2011; 82(5):053108. · 1.52 Impact Factor
ABSTRACT: In this paper, the gain and noise of underwater laser range-gated imaging systems based on intensified CCD (ICCD) are theoretically analyzed. Combined with experimental results, the quality of underwater images at different system parameters is objectively evaluated from the aspect of modulation degree and histogram of grayscale distribution. Comprehensive selection disciplines of micro-channel plate (MCP) gain in applications is generalized according to the coherence between theory and experiment, and a scheme of auto gain control (AGC) based on image analysis is proposed for underwater range-gated imaging systems.
Journal of Modern Optics 03/2010; 57(5):408-417. · 1.17 Impact Factor
ABSTRACT: Marine micro-bubbles are one of those important constituents that influence scattering characteristics of water column. Monte Carlo Based simulations show that a water entrained bubble cloud generate a characteristic backscatter of incident laser light [M. Xia, J. Opt. A: Pure Appl. Opt. 8, 350 (2006)]. This characteristic can be used to detect and localize bubble clouds, leading to wide ranging applications, especially in optical remote sensing. This paper describes tests of an underwater lidar system applied to detecting cloud of micro-bubbles. Laboratory experiments demonstrate that the system is capable of detecting bubbles ranging from diameter 10 microm approximately 200 microm, over a distance of 7-12 m from the detector. The dependence of the lidar return signal on size distribution of bubbles, concentration, thickness and location of bubble clouds is studied and compared with simulation results.
Optics Express 09/2009; 17(20):17772-83. · 3.59 Impact Factor