Research On Ghost Imaging Technique And Its Application

Ghost imaging(GI)is a novel non-locally imaging technique.By intensity correlation between the signal and reference beam,GI could non-locally obtain an image of the object.Computational ghost imaging(CGI),which provides a way to obtain the light field of the reference path by a calculation rather than an experimental detection,has simplified the realization of GI,and made it possible to use one detector in GI system.However,the existing ghost imaging methods have the problems of long imaging time and poor image quality.How to solve these two problems has attracted a lot of attentions.Information can be encrypted by multiple degrees of freedom of light,such as phase,wavelength,spatial frequency and polarization.At the same time,light is a natural medium for processing images or holograms.Optical encryption has the characteristics of parallel high speed processing,it plays an increasingly important role in information security and intellectual property protection.The optical encryption based on ghost imaging greatly reduces the amount of transmitted data,improves the information security.And the application of ghost imaging in information hiding can further improve the security of hidden information.In this desertation,we propose an orthogonal speckle ghost imaging scheme,the ghost imaging scheme for reducing atmospheric turbulence disturbance with orbital angular momentum,and discuss the optical encryption scheme based on computational ghost imaging,the information hiding scheme based on ghost imaging.The main results are as follows:(1)We propose a ghost imaging scheme based on orthogonal speckles,where discrete cosine transform(DCT)speckle and Haar wavelet transform(HWT)speckle are used as orthogonal speckles.By using the symmetry of the orthogonal speckles,the object reconstruction can be quickly obtainedby using the inverse matrix of orthogonal speckles.The results show that the two orthogonal speckles can greatly reduce the number of ghost imaging measurements without reducing the image quality.Compared with DCT speckles,the HWT speckles can further improve the quality and the speed of imaging due to its lower computational complexity.In addition,an edge detection scheme based on Hare wavelet speckles is also presented,the results show that we can use low-resolution speckles of HWT to recover high-resolution edge images.(2)Secondly,we present a ghost imaging scheme based on orbital angular momentum to reduce the interferece of atmospheric turbulence.Orbital angular momentum is the basic characteristic of the beam with helical phase.By using orbital angular momentum,quantum ghost imaging can be realized to enhance the image of the object.Because the orbital angular momentum is inevitably disturbed by atmospheric turbulence,the quality of ghost image is reduced due to the interference.We use Bessel-Gaussian beam with self-recovery,instead of Laguerre-Gaussian beam,in the quantum ghost imaging system,to guaranteethe quality of ghost imaging.The simulation results show that ghost imaging using Bessel-Gaussian beams has strong resistance to atmospheric turbulence interference,in comparison with those results using Laguerre-Gaussian beam.(3)Thirdly,we proprose a double-key optical encryption scheme based on computational ghost imaging in the thesis.Because the traditional optical encryptionscheme using random phase key requires a large number of key and a long transmission time,the new proposed scheme replaces the random phase key with a Toeplitz matrix phase key.By using the Toeplitz matrix,we can obtain the other phase keys by cyclic shifting one phase key.In order to overcome the decrease of security,we furtherintroduce the axial distance as another key in the proposed scheme.Experimental and simulation results show that the use of double keys can not only reduce the amount of keys transmitted,but also effectively improve the security of the optical encryption scheme.(4)Using multi-wavelength multiplexing,an optical encryption scheme based on multi-wavelength light source ghost imaging is also proposed.The phase mask matrix of the speckle sequence is modulated into a random Toeplitz matrix.The corresponding wavelength of the speckle is the wavelength of the random trichrome light.The phase mask and the wavelength are used as two keys of the proposed optical encryption scheme.After all speckles reach the object through the same axial distance,the image of the object can be restored by using compressed sensing technique.The simulation results show that although the security of the proposed scheme is the same as that of phase-to-distance double-key optical encryption schemes,the number of measurements required for the proposed scheme is greatly reduced.(5)We finally propose an information hiding scheme based on ghost imaging in the paper.At first,we obtain a new watermark image with GI technique.Before embedding the watermark image into the host image,the new watermark image is obtained by the original watermark image as the object in a GI system.At this time,the new watermark image is a randomly distributed image.Then the new watermark image is embedded into the host image.The restoration is to extract the encrypted new watermark image at first,and then recover the original watermark image through the key and compressed sensing recovery algorithm.The least significant bits(LSB)algorithm is used for embedding and extracting process.The simulation results show that the original watermark image can not be obtained without the key,however,the original watermarking image can be fully recoveredwith the key.The proposed information hiding scheme can effectively improve the security,and has a strong robustness to image occlusion and salt and pepper noise.