Self-interference holography is a common technique to record holograms of incoherently illuminated scenes. In this review, we survey the main milestones in the topic of self-interference incoherent digital holography from two main points of view. First, we review the prime architectures of optical hologram recorders over more than 50 years. Second, we discuss some of the key applications of these recorders in the field of imaging in general, and for 3D super-resolution imaging, fluorescence microscopy, partial aperture imaging, seeing through a scattering medium, and spectral imaging in particular. We summarize this overview with a general perspective on this research topic and its prospective directions.

Recent advances in self-interference incoherent digital holography

Summary The maximum visibility of the interferences obtainable from two points in a wave field is defined as their degree of coherence γ. By a simple statistical method general formulae are found for deducing γ from illumination data. For any extended lightsource γ is found equal to the amplitude in a certain diffraction image. It does not change by the use of a condensing lens, but depends only on the aperture of the illuminating cone. These properties are applied to the microscopic observation of objects in transmitted light.

The concept of degree of coherence and its application to optical problems

The underwater imaging could be severely degraded by the scattering media because of the backscattered light and signal attenuation, especially in the case of strong scattering for dense turbid medium. In this paper, we propose an improved method for recovering the underwater image combining the histogram stretching and polarimetric recovery in a proper way. In this method, we stretch the histograms of the orthogonal polarization images while maintaining the polarization relation between them, and then, based on the processed orthogonal polarization images, the recovered image with higher quality can be obtained by the traditional polarimetric recovery method. Several groups of experimental results demonstrate that the quality of underwater images can be effectively enhanced by our method, and its performance is better than that of the traditional polarimetric recovery method. In particular, the proposed method is also quite effective in the condition of dense turbid medium.

/pdf/polarimetric-image-recovery-method-combining-histogram-3vaj22dh5i.pdf

Polarimetric image recovery method combining histogram stretching for underwater imaging.

Different from conventional imaging methods, which are based on the first-order field correlation, ghost imaging (GI) obtains the image information through high-order mutual-correlation of light fields from two paths with an object appearing in only one path. As a new optical imaging technology, GI not only provides us new capabilities beyond the conventional imaging methods, but also gives out a new viewpoint of imaging physical mechanism. It may be applied to many potential applications, such as remote sensing, snap-shot spectral imaging, thermal X-ray diffraction imaging and imaging through scattering media. In this paper, we reviewed mainly our research work of ghost imaging via sparsity constraints (GISC) and discussed the application and theory prospect of GISC concisely.

https://www.mdpi.com/2076-3417/8/8/1379/pdf

A Review of Ghost Imaging via Sparsity Constraints

A stable multimodal system is developed by combining two common-path digital holographic microscopes (DHMs): coherent and incoherent, for simultaneous recording and retrieval of three-dimensional (3-D) phase and 3-D fluorescence imaging (FI), respectively, of a biological specimen. The 3-D FI is realized by a single-shot common-path off-axis fluorescent DHM developed recently by our group. In addition, we accomplish, the phase imaging by another single-shot, highly stable common-path off-axis DHM based on a beam splitter. In this DHM configuration, a beam splitter is used to divide the incoming object beam into two beams. One beam serves as the object beam carrying the useful information of the object under study, whereas another beam is spatially filtered at its Fourier plane by using a pinhole and it serves as a reference beam. This DHM setup, owing to a common-path geometry, is less vibration-sensitive and compact, having a similar field of view but with high temporal phase stability in comparison to a two-beam Mach–Zehnder-type DHM. The performance of the proposed common-path DHM and the multimodal system is verified by conducting various experiments on fluorescent microspheres and fluorescent protein-labeled living cells of the moss Physcomitrella patens . Moreover, the potential capability of the proposed multimodal system for 3-D live fluorescence and phase imaging of the fluorescent beads is also demonstrated. The obtained experimental results corroborate the feasibility of the proposed multimodal system and indicate its potential applications for the analysis of functional and structural behaviors of a biological specimen and enhancement of the understanding of physiological mechanisms and various biological diseases.

https://www.spiedigitallibrary.org/journals/journal-of-biomedical-optics/volume-25/issue-3/032010/Common-path-multimodal-three-dimensional-fluorescence-and-phase-imaging-system/10.1117/1.JBO.25.3.032010.pdf

Common-path multimodal three-dimensional fluorescence and phase imaging system.

Imaging through a scattering medium is a challenging task. We propose and demonstrate an interferenceless incoherent opto-digital technique for 3D imaging through a scatterer with a single lens and a digital camera. The light diffracted from a point object is modulated by a scattering mask. The modulated wavefront is projected on an image sensor using a spherical lens and the impulse response is recorded. An object is placed at the same axial location as the point object and another intensity pattern is recorded with identical experimental conditions and with the same scattering mask. The image of the object is reconstructed by a cross-correlation between a reconstructing function and the object hologram. For 3D imaging, a library of reconstructing functions are created corresponding to different axial locations. The different planes of the object are reconstructed by a cross-correlation of the object hologram with the corresponding reconstructing functions.

/pdf/3d-imaging-through-scatterers-with-interferenceless-optical-4cn2elkwgg.pdf

3D Imaging through Scatterers with Interferenceless Optical System.

Coded aperture correlation holography (COACH) is a relatively new technique to record holograms of incoherently illuminated scenes. In this review, we survey the main milestones in the COACH topic from two main points of view. First, we review the prime architectures of optical hologram recorders in the family of COACH systems. Second, we discuss some of the key applications of these recorders in the field of imaging in general, and for 3D super-resolution imaging, partial aperture imaging, and seeing through scattering medium, in particular. We summarize this overview with a general perspective on this research topic and its prospective directions.

Review of 3D Imaging by Coded Aperture Correlation Holography (COACH)

Scattering media have always posed obstacles for imaging through them. In this study, we propose a single exposure, spatially incoherent and interferenceless method capable of imaging multi-plane objects through scattering media using only a single lens and a digital camera. A point object and a resolution chart are precisely placed at the same axial location, and light scattered from them is focused onto an image sensor using a spherical lens. For both cases, intensity patterns are recorded under identical conditions using only a single camera shot. The final image is obtained by an adaptive non-linear cross-correlation between the response functions of the point object and of the resolution chart. The clear and sharp reconstructed image demonstrates the validity of the method.

/pdf/imaging-through-scattering-medium-by-adaptive-non-linear-4fugcvb56l.pdf

Imaging through scattering medium by adaptive non-linear digital processing.

We propose and demonstrate a new imaging technique to noninvasively see through scattering layers with the aid of a spatial light modulator (SLM). A relay system projects the incoherent light pattern emitting from the scattering layer onto the SLM. Two coded phase masks are displayed, one after another, on the SLM to modulate the projected scattered field and the two corresponding intensity patterns are recorded by a digital camera. The above procedure helps to achieve two goals. Firstly, since the coded phase masks are digitally synthesized, the point spread function of the imaging system can be engineered such that the image retrieval becomes more reliable. Secondly, the two recorded intensity patterns are subtracted one from the other and by that the background noise of the recovered image is minimized. The above two advantages along with a modified phase retrieval algorithm enable a relatively easier and accurate convergence to the image of the covered object.

/pdf/spatial-light-modulator-aided-noninvasive-imaging-through-2j0ihce27z.pdf

Saswata Mukherjee

Papers

Recent advances in self-interference incoherent digital holography

3D Imaging through Scatterers with Interferenceless Optical System.

Review of 3D Imaging by Coded Aperture Correlation Holography (COACH)

Imaging through scattering medium by adaptive non-linear digital processing.

Spatial light modulator aided noninvasive imaging through scattering layers