Object Recognition Technology Research Based On Laser Speckle Image

The complex environmental background usually affects people's acquisition and judgment of target information.For targets that cannot be observed directly,people cannot identify target features effectively.Under such a premise,the target information cannot be recognized directly according to its speckle image for the target hidden behind the scattering medium.However,speckle images carry a large amount of information related to the physical characteristics of the target surface,that is,it contains the characteristic information of targets.These information can be used as the basis for the identification of hidden targets.By identifying the speckle image of the target,it can play an important role in medical detection,astronomical observation,target detection and other fields.After analyzing and researching the existing speckle image recognition methods,this topic proposes a method of stacking short-exposure image's frequency spectrum combined with Fourier transform algorithm to recover and recognize the target speckle image.There is no need to perform autocorrelation operation and select a phase recovery algorithm to process the speckle image,which effectively reduces the complexity of the algorithm.The main research contents are as follows:(1)The phase of the scattering medium is introduced into the pupil function,and the point spread function(PSF)of the scattering imaging system is calculated according to this new pupil function.Then,the short-exposure PSF and long-exposure PSF of the scattering imaging system are numerically simulated and analyzed.Finally,The optical transfer function(OTF)of the scattering imaging system is calculated,.And the OTF of the scattering imaging system under short exposure and long exposure conditions are numerically simulated respectively.Then,the three-dimensional and cross-sectional diagrams of the modulation transfer function(MTF)are drawn.The results show that the speckle phenomenon is obvious in the short-exposure PSF and short-exposure MTF,and the speckle is basically eliminated in the long-exposure PSF and long-exposure MTF.(2)A light path model for acquiring the target's speckle image is established.And the recovery and recognition of the target object's speckle image are simulated.Firstly,the method of stacking short-exposure image's frequency spectrum is used to analyze the imaging of two point light sources of equal intensity.Then,the Fourier transform fringes are recovered from the speckle image.The feasibility of this method is verified.Secondly,Matlab is used to simulate from three aspects: the influence of the number of stacking times and the circular aperture's size on the speckle image's recovery and recognition of the target object,and the speckle images' recovery and recognition of different targets.It is verified that the method of stacking short-exposure image's frequency spectrum combined with Fourier transform algorithm can recover the target feature information from the speckle image,and then identify the target.(3)The experimental platform of the scattering imaging system is designed and built.The appropriate optical instruments are selected and the experimental parameters are confirmed.Then,the target object's size and the aperture's size are calculated and determined from the known experimental parameters.Through the experimental optical path,the experiment of collecting the speckle image of the target object is completed.And then Matlab is used to process the acquired speckle images and analyze the results.The experimental results show that the features of the target object can be identified from the restored image.Compared with the original speckle image,the target information is obvious.In this paper,through the analysis of laser speckle's statistical characteristics and optical transfer function of scattering imaging system,and using the characteristics of short-exposure imaging and long-exposure imaging of scattering imaging system,the target object hidden behind the scattering medium is recovered and identified.The final results show that the laser speckle image of target can effectively restore the target image and identify the target features.