Research On The Stochastic Resonance Technology For Reconstructing Weak Optical Images Overwhelmed By Strong Noise

The reconstruction of weak optical images is one of the key technologies to achieve high quality and high precision target detection in strong scattering environments.The technology is aimed at improving the detection capacity of imaging systems in scattering environments and has important applications in areas such as national defense,remote sensing,transport and rescue.When optical images propagate through scattering media,absorption and scattering seriously attenuates the energy of signals and produces much noise.Conventional detection technologies of weak optical images improve the image quality by filtering noise based on the difference between noise and signals in optical properties.However,these filtering-based imaging technologies have difficulty in reconstructing the weak optical images overwhelmed by strong noise when noise and signals have similar optical properties.The technology of the weak optical image reconstruction via optical stochastic resonance(OSR)can reinforce and reconstruct weak signals by coupling with noise under nonlinear optical effects.The nonlinear image reconstruction technology has a strong ability of noisy image recovery,and effectively deals with the scattering noise similar to the optical properties of signals.The weak optical image reconstruction via OSR is a new type of the detection technology of weak optical images.Further study on its theory and technology is needed.The main contents and innovative achievements of this dissertation are summarized as following:1.Considering the influences of the applied voltage,the noise intensity,and the noise correlation length,the optical quasi-particle model is built and provides the theoretical foundation for studying the weak optical image reconstruction via OSR.By regarding the light beam as a particle beam composed of a large number of optical quasi-particles,tracking the trajectory of quasi-particles,and studying the response of quasi-particles to the refractive index change of the nonlinear crystal,the energy redistribution phenomena and the angle spectrum evolution characteristics of incoherent noise are accurately revealed in the process of OSR.2.The reconstruction of underwater weak optical images via OSR is investigated.This work provides theoretical guidance for the application of OSR in underwater imaging.Based on the constructed theoretical model of the nonlinear reconstruction of underwater weak optical images,the influences of forward scattering on underwater laser imaging and the effect of underwater weak image reconstruction via OSR are accurately revealed.It is found that the weak ballistic signals can trigger seeded modulation instability(SMI)in the condition of large angle scattering.The higher the proportion of the ballistic signal component is,the stronger the triggered SMI is.3.The discrete image recovery via OSR based on optically-induced photonic lattices is proposed and investigated.By reasonably adjusting the modulation depth of optically-induced photonic lattices,mode coupling between signals and noise is enhanced and the nonlinear reconstruction effect of weak optical images is improved with the interplay of the channel effect and the self-focusing nonlinearity.The cross-correlation coefficient is improved from 0.49 to 0.65 at the modulation depth of1.However,as long as either nonlinear effect dominates the nonlinear process,the image quality will decrease.4.The white-light image reconstruction technology via SMI is proposed and implemented.The signals of each wavelength interact with each other and collectively contribute to OSR in the process of nonlinear white-light image reconstruction,whereas the signals in different wavelengths hold different instability gains.We also demonstrate the white-light image reproduction based on the asynchronous detection.By asynchronously and sensitively detecting the induced refractive index gradient in the crystal,the images overwhelmed by strong noise are preferably reproduced.As a result,the cross-correlation coefficient is improved from 0.3 to 0.62 and the cross-correlation gain of 2.1 is obtained.5.The logical white-light image reconstruction technology based on SMI is proposed and implemented.By asynchronously detecting the gradient potential and reasonably changing the relative position of the detection plane and the potential,the nonlinear interaction between light waves is presented in different forms.The positively logical image reconstruction evolves into the inversely logical image reconstruction.The technology can recover both noise-hidden bright objects and noise-hidden dark objects under several illumination and scattering conditions.The nonlinear image reconstruction technology has a strong ability of recording,reproducing and reversing the weak optical images.6.The weak optical image reconstruction via OSR based on the magneto-optical molecular reorientation effect is proposed.The influences of the boundary condition and the dimension constraint on the image reconstruction are avoided.The weak image signals are enhanced and reconstructed by coupling with scattering noise under the magneto-optical molecular reorientation effect.By deriving the intensity perturbation gain and performing the numerical simulation,the results suggest that the cross-correlation coefficient is improved from 0.3 to 0.41 by reasonably controlling the magnetic field direction,the light intensity and the correlation length.