Study On Measurement Methods For Near Field Based On Digital Holography

It brings great scientific significances and application values in imaging biological tissues with high contrast as well as quantificationally measuring physical properties of micro-nano materials,by dynamically measuring the refractive index(RI),surface morphology,thickness etc.of specimens in the near field of interface with high precision and sensitivity.Digital holography(DH)presents the advantages of full-field,non-contact,precise and dynamic measurement for the complex amplitude of object wave.Meanwhile,the analytical methods based on total internal reflection(TIR)and surface plasma resonance(SPR)present the advantages of non-intrusive and sensitive measurement for the parameters of specimens in the near field of interface.This thesis combines the advantages of DH and TIR/SPR based analytical methods and studies the measurement methods for near field based on TIR,SPR-DH theoretically and experimentally.The parameters and their changes of specimens in the near field of prism and metal surfaces will modulate the complex amplitudes(including the amplitude and phase)of the far-field reflected waves in TIR and SPR.Thus,DH is applied to dynamically measure the complex amplitudes of the reflected waves to realize quantitative measurements for the parameters of specimens in the near field.The main work and research results of this thesis are as follows:(1)It is proposed that two-dimensional(2D)RI distribution of the dielectric specimen in the near field of prism surface can be dynamically measured by measuring the phase difference distribution of the far-field reflected wave in TIR using digital holographic interferometry(DHI).Firstly,the experimental system of TIR-DHI based on Mach-Zehnder interferometer is constructed and the experimental measurements for static and dynamic specimens are performed.Then,a compact common-path interference configuration is designed and an experimental prototype of TIR-DHI with the data processing software is constructed.The error analysis of the measurement method and system are also provided.At last,the digital holographic microscopy(DHM)imaging system based on TIR is constructed for the phase imaging of biological tissues in the near field of prism surface.(2)A transmission and TIR integrated DHM is proposed to simultaneously and dynamically measure the RI distribution and thickness distribution of dielectric specimens.The 2D RI distribution of the specimen can be dynamically measured using TIR-DHM.Meanwhile,the thickness distribution can be unambiguously calculated from the phase difference information using transmission DHM.With the help of angular and polarization multiplexing techniques,the integrated DHM system is designed and the experimental measurements for static and dynamic specimens are performed.Moreover,a numerical method is proposed to correct the distorted image induced by the non-perpendicular geometry between the object plane and the optical axis of the illumination wave in TIR.(3)The measurement method for near field based on surface plasma resonance holographic microscopy(SPRHM)is proposed.By measuring the complex amplitude distribution of the far-field reflected wave in SPR using DHM,the tiny variation of RI for the dielectric specimen in the near field of metal surface can be dynamically monitored with high sensitivity.Firstly,a common-path interference configuration based on a single beam splitter is introduced in the prism-coupling SPRHM and the experimental measurement for a standard specimen is performed.Then,the wavelength-multiplexing technique is proposed to extend the measurement range for monitoring the tiny variation of RI.The upgraded experimental system of SPRHM is designed and the experimental measurement for a standard specimen is performed to verify the effectivity of the technique.At last,the amplitude-and phase-contrast SPR imaging for biological tissues in the near field of metal surface are performed using the SPRHM systems with single wavelength and two wavelengths,respectively.(4)The inherent drawbacks of the prism-coupling SPRHM system are analyzed and the SPR configuration based on an oil immersion objective with a high numerical aperture is proposed to be applied in DHM.Firstly,a common-path interference configuration based on a Wollaston prism is introduced to the objective-coupling SPRHM.And the advantages of the system are analyzed and the stability of the system is measured.Then,the principle of measuring the thickness for thin layer specimens in the near field of metal surface based on the four-layer SPR model is analyzed.After that,the experimental measurements for specimens with different physics properties are performed.At last,the principle of measuring the thickness for covered specimens based on the five-layer SPR model is analyzed and the preliminary experimental research is performed.