Single-shot Incoherent Digital Holography Based On Spatial Light Modulator

Digital holography develops rapidly,which is based on the principle of optical imaging to record the light field information of the object on a CCD or CMOS of a photo coupler,and then reconstruct the original light field through a numerical reconstruction algorithm on the computer.If a high coherence laser is used for recording,a lot of speckle noises will be produced.And the reflections from the optical components in the optical path will also produce parasitic interference.While the incoherent digital holography uses the incoherent light source illumination to realize interference recording,which is a good way to overcome this shortcoming.As the most noteworthy issue in the incoherent digital holography,the Fresnel incoherent correlation holography has a common-path,which can eliminate the interference of the external environment during recording effectively,and it can improve the stability and practical stability of the device.Different imaging systems such as confocal microscopy,fluorescence microscopy,telescope imaging,etc.can also be realized by changing the optical path in front of the SLM.SLM is the core device of the FINCH imaging system and has two functions.Firstly,as a beam splitter,it divides the amplitude of incident light waves into light and reference light waves.Secondly,as a phase shifter,and the phase shift algorithm is combined in the reconstruct process.The removal of the zero-order image and the conjugate image is eliminated.By this method requires acquisition multiple holograms,only static objects can be observed and measured,limiting its scope of application.The single-shot of coaxial digital holography can be realized by changing the structure of the optical path,but this technique is slightly complex in construction and system adjust process,and it will increase the cost and increase the recording elements,which makes it disadvantageous for practical application.Of course,you can use CS algorithms to realize the single-shot.However,the numerical calculation of the compression sensor is relatively sophisticated,and the operating procedure takes more time,and the block effect will appear when high resolution imaging is applied.In recent years,SLM has been widely used in digital holography because of its unique performance.And we can use SLM's the characteristic of separable region coding to study it and realize single-shot.This article maximizes the use of spatial light modulator with partition able coding to modulate the phase characteristics.The following FINCH systems have been analyzed and studied as follows:(1)Based on the theory of digital holography,the whole process of holographic recording and reconstruction is derived according to the basis of wave optics theory.This process analyzes the several advantages of digital holography compared with traditional holography,and focuses on the point spread function of the coaxial digital holography system,and analyzes the elimination the zero-order image and the conjugate image in this system.(2)Based on the theory of incoherent digital holography,the mathematical function of point spread function,lateral magnification and reconstruction distance of FINCH system are derived.And the main aspects affecting the resolution of the system and the method of improving resolution are systematically analyzed.(3)A single-shot experiment optical path based on FINCH system is built.The masks are made by using the characteristic of separable region coding of the spatial light modulator.The two different forms of mask are loaded on the SLM to achieve single exposure.The first is a single optical axis in the mask but with three phase shift factors of 0 °,120 ° and 240 ° at the same time.The second method is to load 0°,120°,and 240° at the same time.Each phase has an independent optical axis,the corresponding sub-hologram does not overlap on the CCD,the sub-hologram corresponding to the more phase shift factor is extracted using a simple extraction procedure,and phase shift technology is used in the computer and Numerical simulation reconstruction algorithm diffraction reconstruction.(4)A microscopic single-shot based on the FINCH system is built,and the microscopic imaging is verified and improved according to the single-shot method of FINCH.