Research On The Method Of Lensless Digital Holographic Microscopy Based On LED

Digital holography involves the use of photoelectric sensors to record the interference pattern of object light and reference light,then reconstructed it by the computer to obtain not only the amplitude information but also the phase information of a sample.Apparently such a technology is far more advantageous over the traditional optical imaging methods.It has found wide applications in many fields such as phase microscopy,interferometry,particle detection,cell observation and so on.However,the complex optical path design of digital holography and the use of strongly coherent laser as a light source have also caused difficulties in the application of digital holography.The improvement of this method has also been the concern of many researchers at home and abroad.An example is lensless digital holography method based on the weak coherent light source,e.g.LED.It not only simplifies the optical system,but also has a significant advantage in the aspects of structure,size and power consumption of the system.Nevertheless,quite a few issues still need to be solved,such as the application of theoretical model,the realization of specific algorithms and so on.In this paper,the theoretical model of the lensless digital holographic microscopic imaging method based on the weakly coherent light source was established through the systematic description of the various aspects involved in the two-step digital holography imaging process.In the aspect of recording,the coherence of weak coherent light source,the influence of recording light path on the reconstructed image and the cause of the interference images were discussed.As for the aspect of reconstruction,different algorithms of diffraction,the phase unwrapping algorithm and the optimization algorithm to eliminate the interference image were derived.Following that,the simulation experiments were carried out on the MATLAB platform to verify the correctness of the theory,and also to explore the influence of the specific parameters such as the recording distance,the reconstruction distance,the reference light angle,the interference noise and so on.More exactly,a lensless digital holographic microscopy system platform based on weak coherent light source was constructed.The hardware included a 3D printer as the mechanical frame,a LED,an industrial camera,a micropore,the slave computer and a self-designed black box.The application program was developed with the functions of image acquisition,image processing and image reconstruction,based on MFC.On the platform,the imaging experiments are carried out,the effects of the coherence of LED,the distance of light source and the recording distance on the system imaging were investigated experimentally and explained.As a result,the optimal imaging parameters were given.This platform was further used for the preliminary application research.In more detail,the digital hologram of breast cancer cells(MDA-MB-453)were successfully recorded.The amplitude and phase information of the sample was reconstructed from the digital hologram.The reconstructed results were the qualitatively compared with those of the optical microscopy imaging.The phase information of the sample was quantitatively analyzed,and the thickness of the sample was estimated according to the model of phase and thickness conversion.Digital image processing was adopted to eliminate the interference image and noise in the reconstructed image.Consequently,the signal to noise ratio was improved.Moreover,the amplitude and phase diagram with certain application value were obtained.