Theoretical And Experimental Research Of Lensless Coherent Diffractive Imaging

Coherent diffraction imaging as a new promising type of optical imaging technologyhas been widely used in many fields such as wavefront phase detection, adaptiveoptics, optical image restoration and so on. At the same time, wavefront phasedetection as a key issue of coherent diffraction imaging has gradually attractedpeople’s attention. In order to obtain the phase information of the object wave, peoplehas put forward many wavefront phase detection methods like holography, the phaseinversion technique, shack-hartmann wavefront sensor, phase difference detection,etc.But with the development of science and technology, people’s demand on precisionand accuracy has improved to a high level, so the traditional technology can’t meetthe needs of high precision measurement. Recently, we proposed a new coherentdiffraction imaging method which is based on convolution-solution sampling array.By recording one fresnel diffraction intensity pattern, this method can achieve thewavefront reconstruction process. Besides this, this technique has the advantage ofwide wavelength application range and good real-time performance. But this methodrequires the use of an imaging lens, the use of which would reduce imaging resolutionof imaging system and increase the demand for external environment. In addition,lens aperture also bring a tough restriction to experiment system. So it is urgent tofind a new lensless coherent diffraction imaging technology to meet the needs ofpeople.In this paper, we introduce a new lensless coherent diffraction imaging technologywhich is based on fresnel diffraction and could avoid the use of high quality imaginglens. In addition, we also discussed the application of this method in the three-dimensionalcoordinate measurement and put forward a new lensless method to measure thetopological charge of an optical vortex through its fresnel diffraction intensity pattern.Main contents are as follows:1. The development history and research status of coherent diffraction imagingtechnique are introduced in detail. Many coherent diffraction imaging methodscommonly used are concluded and summarized. And the theory and characteristicsamong holography, the phase inversion technique, shack-hartmann wavefront sensorand phase difference detection are discussed.2. Based on fresnel diffraction put forward a kind of lensless coherent diffractionimaging technology. By mean of record the fresnel intensity pattern of object wavepassed through the multihole sampling array, we can obtain the wave front of objectwave by impose some digital processing on the recorded diffraction pattern. Comparewith other methods, this method has a widely wavelength adaptive scope form X-ray,visible light to electron beam band. In this paper, the principle of this method isintroduced, the feasibility of this method is discussed and the optimum distance isfound.3. A new3-D coordinate measurement method based on lensless coherent diffractionimaging technology is proposed. Only need one fresnel diffraction intensity pattern,the coordinate of initial point could be measured accurately without iterationalgorithm and optical imaging lens. As has fantastic ability to adapt to theenvironment, this method can be applied to many fields. In this paper, the feasibilityof the method is approved through computer simulation, the error analysis is given.4. A new method to measure topological charge of optical vortex is introduced. Byimpose inverse fresnel transform on fresnel diffraction pattern which optical vortexpassed through an annular aperture, the topological charge of optical vortex could beobtained. Because this method does not require the use of lens, this can improve theimaging resolution and reduce the requirements experiment system. In this paper, theinfluence of experiment parameter is researched and analyzed.