Study On The Mechanism And Application Of Vortex Beam And Laser Speckle

Laser speckles are commonly found in the process of optical imaging,and may be considered as the ultimate limiting noise in the optical imaging measurements with coherent light.The presence of the speckles limits the ability of the optical imaging system to extract information from the images,weakening the ability of the observer to extract details from the coherent image.As noises in the image,laser speckles need to be suppressed.However,the speckles play an important role in the optical metrology.The speckle is sensitive to the movement of the surface,and carries information about the characteristics of the illuminated scattering object.It led very quickly to the development of several techniques using the random intensity distribution of the speckle as a carrier of information related to local changes in the surface,and setting the basis for the speckle metrology in coherent optics.Vortices occur naturally in a random optical wave such as a speckle field,there are many vortices interspersed between the bright speckles,and the correlation properties of the vortex points are related to those of the field.These optical vortices in the random speckle field are often referred to as “speckle vortices”.The phase vortices in the laser speckle contain a wealth of speckle field information,which determine the distribution of the speckle field.Therefore,the most common research in the laser speckle field is often related to the speckle vortices.From the point of view of the basic physics and the applied physics,the study of the speckle vortices is very important.The speckle vortex has a leading role in the study of singular optics.Now,it has also been widely used in the field of optical micro-manipulation,super-resolution imaging,optical information storage and transmission,life sciences,and so on.In this paper,the mechanism and the application of the vortex beam and the laser speckle are studied.The main contents and results are as follows:Review of the micro-measurement technologies using optical vortex.Optical vortex interferometer(OVI)and optical vortex metrology(OVM)are introduced.OVI is based on the principle that a regular vortex net is generated by the interference of three plane waves.In OVI,the vortex points are stable and point-like structure,which can be located with high accuracy.Not need to extract the fringe maxima or minima,the vortex points can be traced accurately.Compared with fringe patterns,vortices net can bring more information on the evolution of wavefront.OVM is based on the fact that phase singularities are well-defined geometrical points with unique core structures,which serve as their fingerprints and endow the phase singularities with valuable information and capability as identifiable optimal markers.The displacement can be determined by tracing the movement of registered phase singularities with their correspondence being identified by the fingerprints.Study on the generation of speckle vortices by Archimedean spiral micro-hole array.Optical vortices that exist in the random speckle fields often contain useful phase information.These optical vortices are called speckle vortices.The distribution of the speckle field is determined by these optical vortices.Speckle vortices can be generated by random diffuse reflection points(spiral micro-holes).In order to study the speckle vortices quantitatively,we established a micro-hole array model based on the law of Archimedean spiral arrangements.In the experiments,a gray image of an Archimedean spiral micro-hole array is displayed on the screen of a liquid crystal spatial light modulator(LC-SLM),and the resulting optical field is captured using a CCD camera.Both the numerical simulations and experimental results show that this model can be used to generate speckle vortices.Study on the generation of optical vortices by apodized photon sieve.As a novel diffractive optical element,photon sieves have good focusing properties.Based on the LC-SLM,we proposed a method to generate optical vortices and verify the focusing properties by using the apodized photon sieves.The apodized photon sieve is obtained by using a Gaussian window function to modulate the general photon sieve.Focusing properties of the apodized photon sieve are studied by numerical simulations and experiments.The experimental results also demonstrate that photon sieves can be used to generate optical vortices.The existence of optical vortices is confirmed by the formation of fork fringes.The apodized photon sieve is expected to have some practical applications in focusing analysis,optical imaging,and optical communication.Study on the deformation measurement based on the optical vortex phase shifting.In order to realize the digital control of phase shifting in electronic speckle pattern interferometry,a method for(out-of-plane and in-plane)displacement measurements by application of phase shifting based on optical vortex was proposed.In the experiment,vortex beam is generated by a LC–SLM,and the phase shifts are obtained by rotating the vortex beam around its axes.Furthermore,the vortex beam that is generated by the LC-SLM can be used as a reference light in the experiment.The out optical field is captured by a CCD camera.Four speckle patterns with phase-step ?/2 are captured by the CCD before and after the deformation,respectively.The phase difference of the deformed object is obtained by unwrapping.Experimental results demonstrate the efficacy of the proposed method for micro-displacement measurement.Study on the electronic speckle measurement based on Talbot effect.We designed an experimental scheme to measure the micro-displacement.In the experiment,a Talbot array hologram is generated and displayed on the LC–SLM screen,and the diffracted intensity on the surface of the object is captured by a CCD camera.The information about the displacement is codified in the intensity pattern.The translational displacement and in-plane displacement are obtained by the digital speckle correlation measurement(DSCM)method.Both the numerical simulations and experimental results demonstrate the efficacy of the proposed method.This method is simple and easy,and can be used as an alternative method to measure the deformation displacement.