The label-free computational techniques with phase imaging capability unfolds the domain of quantitative phase imaging (QPI) to a broad range of microscopy applications. However, the presence of scattering layers in the propagation path makes the conventional QPI approaches susceptible due to the light scattering effects in the medium. Owing to this phase imaging challenge through scattering layers, we propose and experimentally demonstrate a technique for the quantitative imaging through scattering layers by integrating the lens-less digital holographic microscopy with speckle correlation approach. The proposed technique utilizes a holographic compact microscopy scheme for the recovery of phase information of the object located at any arbitrary planes behind the scattering medium by utilizing a correlation hologram and an in-line hologram. The QPI capability of the developed system is theoretically introduced and experimentally validated by imaging various standard and unknown phase samples.
We discuss the design and imaging features of a compact digital inline polarization holography system capable of singleshot extraction of complex amplitude information and polarization sensitive information corresponding to an anisotropic sample. The proposed method exploits the lens-less and compact design characteristics of the inline holographic system for the development of a quantitative polarization microscopy system. The quantitative imaging capability and measurement accuracy of the microscopy system is experimentally validated by single-shot detection of the digital polarization in-line holograms and the real-time extraction of full-field imaging features corresponding to standard birefringent targets and real-valued anisotropic samples.
We propose and experimentally demonstrate a technique for the single-shot imaging through a scattering medium based on speckle correlation assisted digital in-line holography. The proposed method enables the reconstruction of the complex amplitude information of the object located at any arbitrary planes behind the scattering medium by retrieving the digital in-line hologram. The technique exploits the potential of speckle correlation approaches and machine learning schemes for the efficient reconstruction of complex amplitude information from the digital in-line hologram scrambled in the speckle pattern. The complex amplitude imaging capability of the proposed technique is theoretically introduced and experimentally validated by imaging various standard and unknown objects.
We propose and experimentally demonstrate a highly stable on-axis near common-path snapshot Fizeau-polarization phase-shifting interferometer by combining the polarization phase-shifting scheme with Fizeau on-axis interferometry. The compact on-axis design of the Fizeau interferometry is achieved by utilizing the characteristic feature of a wire grid polarizer, which generates the orthogonal polarization components required for the proposed polarization phase-shifting scheme. The quantitative phase measurement capability is experimentally validated by estimating the phase profile of various phase-sensitive standard and unknown phase samples.
We demonstrate a snap-shot ghost diffraction imaging approach with potential features of simultaneous recovery of amplitude and phase of a complex-valued object from a single-shot recording of the fields at the detectors. The technique utilizes the spatial averaging as an effective replacement of ensemble averaging in the execution of the cross-correlation of intensity fluctuations at the detector plane. Furthermore, the approach adopts the concept of holography in combination with the ghost diffraction scheme for the simultaneous recovery of phase distribution along with the amplitude of the object. The proposed method is expected to find applications in the two- and three-dimensional real-time quantitative imaging, biological microscopy, tomography, and super-resolution imaging, etc.
Based on Richards-Wolf vectorial diffraction integral, the expression of electric cross-spectral density matrix of linearly polarized circular partially coherent (LPCPC) beams, near the focus of a high numerical aperture (NA) objective, are derived. Numerical calculations are performed to show the influence of initial coherent length and NA of the objective, on the intensity distribution and degree of coherence of the LPCPC beams in the focal region. The results indicated that after focusing the LPCPC beams through a high NA objective a super-length optical needle (<12λ) with wavelength beam size can be obtained. Moreover, the numerical calculations illustrate that the length of the optical needle can be controlled by adjusting the initial coherent length of the LPCPC beams. The influence of NA of the objective on the length of the optical needle is much less than the initial coherent length. Setting the reference vector position on the z-axis, we can find that the coherence of the optical needle on the same wavefront remains unchanged.
A straight effective method to produce partially coherent beams with controllable time-dependent coherence is demonstrated. We theoretically deduce that a time-dependent partially coherent beam can be generated by imposing dynamic random phase on a coherent laser beam. The degree of coherence of the beam is determined by an amplitude control parameter of the dynamic random phase. We experimentally corroborate that after a completely coherent laser beam reflected from a spatial light modulator, loaded with a particular dynamic random phase, this beam is transformed into a partially coherent beam with time-dependent coherence.
Partially coherent beam is generated by imposing dynamic random phase to completely coherent beam. The coherence of partially coherent beam can be controlled by the randomness of random phase. The speckle pattern of the partially coherent beam passing through scattering medium is studied. The speckle pattern can be modulated into a bright focal spot by wavefront shaping. The influence of the coherence on the focusing is investigated.
We investigate the tight focusing of radially polarized ultrashort pulse laser beam. It is found that pulse delay
phenomenon occurs near the focus. This is, near the focus, the photon travels slower than the speed of light.
A partially coherent vortex beam propagating in a turbulent atmosphere is investigated by using extended Huygens-Fresnel diffraction integral. The influence of the turbulence, the spatial coherence, and the topological charges of the incident beam on the propagation characteristics of the beam is studied in great detail. It is shown that the spreading of the partially coherent vortex beam is less influenced by atmospheric turbulence than that of a partially coherent nonvortex beam, and that a partially coherent vortex beam of lower coherence is less influenced than one of higher coherence.
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