The problem of imaging through thick scattering media is encountered in many disciplines of science, ranging from mesoscopic physics to astronomy. Photons become diffusive after propagating through a scattering medium with an optical thickness of over 10 times the scattering mean free path. As a result, no image but only noise-like patterns can be directly formed. We propose a hybrid neural network for computational imaging through such thick scattering media, demonstrating the reconstruction of image information from various targets hidden behind a white polystyrene slab of 3 mm in thickness or 13.4 times the scattering mean free path. We also demonstrate that the target image can be retrieved with acceptable quality from a very small fraction of its scattered pattern, suggesting that the speckle pattern produced in this way is highly redundant. This leads to a profound question of how the information of the target being encoded into the speckle is to be addressed in future studies.

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Learning-based lensless imaging through optically thick scattering media

An optical multiple-image authentication based on transport of intensity equation

Double-image encryption based on interference and logistic map under the framework of double random phase encoding

Computational microscopy, as a subfield of computational imaging, combines optical manipulation and image algorithmic reconstruction to recover multi-dimensional microscopic images or information of micro-objects. In recent years, the revolution in light-emitting diodes (LEDs), low-cost consumer image sensors, modern digital computers, and smartphones provide fertile opportunities for the rapid development of computational microscopy. Consequently, diverse forms of computational microscopy have been invented, including digital holographic microscopy (DHM), transport of intensity equation (TIE), differential phase contrast (DPC) microscopy, lens-free on-chip holography, and Fourier ptychographic microscopy (FPM). These computational microscopy techniques not only provide high-resolution, label-free, quantitative phase imaging capability but also decipher new and advanced biomedical research and industrial applications. Nevertheless, most computational microscopy techniques are still at an early stage of “proof of concept” or “proof of prototype” (based on commercially available microscope platforms). Translating those concepts to stand-alone optical instruments for practical use is an essential step for the promotion and adoption of computational microscopy by the wider bio-medicine, industry, and education community. In this paper, we present four smart computational light microscopes (SCLMs) developed by our laboratory, i.e., smart computational imaging laboratory (SCILab) of Nanjing University of Science and Technology (NJUST), China. These microscopes are empowered by advanced computational microscopy techniques, including digital holography, TIE, DPC, lensless holography, and FPM, which not only enables multi-modal contrast-enhanced observations for unstained specimens, but also can recover their three-dimensional profiles quantitatively. We introduce their basic principles, hardware configurations, reconstruction algorithms, and software design, quantify their imaging performance, and illustrate their typical applications for cell analysis, medical diagnosis, and microlens characterization.

/pdf/smart-computational-light-microscopes-sclms-of-smart-3otahd6krj.pdf

Smart computational light microscopes (SCLMs) of smart computational imaging laboratory (SCILab)

Abstract Imaging through diffusers presents a challenging problem with various digital image reconstruction solutions demonstrated to date using computers. Here, we present a computer-free, all-optical image reconstruction method to see through random diffusers at the speed of light. Using deep learning, a set of transmissive diffractive surfaces are trained to all-optically reconstruct images of arbitrary objects that are completely covered by unknown, random phase diffusers. After the training stage, which is a one-time effort, the resulting diffractive surfaces are fabricated and form a passive optical network that is physically positioned between the unknown object and the image plane to all-optically reconstruct the object pattern through an unknown, new phase diffuser. We experimentally demonstrated this concept using coherent THz illumination and all-optically reconstructed objects distorted by unknown, random diffusers, never used during training. Unlike digital methods, all-optical diffractive reconstructions do not require power except for the illumination light. This diffractive solution to see through diffusers can be extended to other wavelengths, and might fuel various applications in biomedical imaging, astronomy, atmospheric sciences, oceanography, security, robotics, autonomous vehicles, among many others. 

https://elight.springeropen.com/counter/pdf/10.1186/s43593-022-00012-4

Computational imaging without a computer: seeing through random diffusers at the speed of light

We demonstrate experimentally that the traditional double random phase encoding (DPRE) technique is vulnerable to the cyphertext-only attack (COA). With the statistical ergodic property of the speckle, we show that the plaintext image can be recovered from the cyphertext alone owing to the fact that their energy spectral density functions are identical. Our result reveals the most serious security issue with the DRPE as it suggests that even the one-time-pad does not guarantee its security. This will open up new inside understanding of current optical security techniques.

Cyphertext-only attack on the double random-phase encryption: Experimental demonstration

Imaging through scattering media has been one of the main challenges in optics, and are encountered in many different disciplines of sciences, ranging from biology, mesoscopic physics to astronomy. Recently, various methods have been proposed. In this manuscript, we propose a robust method for imaging through scattering media in a reflective geometry, a scenario widely encountered in non-invasive and marker-free biological imaging. The proposed method relies on the a priori information of a known reference object in the neighborhood of the target, and uses it as an auxiliary to reconstruct the target image. We show that the target image can be analytically reconstructed from the autocorrelation of the recorded speckle if the reference is point-like, otherwise, deconvolution with the reference speckle should be performed. We experimentally demonstrate the proposed method in a proof-of-concept system with an LED illumination through a thick ground glass.

/pdf/imaging-through-scattering-media-with-the-auxiliary-of-a-267jraxjop.pdf

Imaging through scattering media with the auxiliary of a known reference object.

Roadmap on chaos-inspired imaging technologies (CI2-Tech)

Random scattering media prevent light information from directly transmitting through, them as the photons will deviate from their original propagation directions due to the inhomogeneity of the refractive index distribution in scattering media. Based on recent developed methods, light information transmission through scattering media is realized using a memory effect. However, the memory effect range limits it to a small field of view. To enlarge the field of view, in this article, we propose to use the ptychographic iterative engine to deliver information through scattering media. We experimentally demonstrate that the proposed method can deliver images beyond the memory effect range through the scattering layer with outstanding imaging performance.

https://www.mdpi.com/2076-3417/9/5/849/pdf

Image Transmission through Scattering Media Using Ptychographic Iterative Engine

Coherent vortex beams have shown great potential in many applications including information transmission under non-ideal conditions, as information can be encoded in the orbital angular momentum However, inhomogeneity of atmosphere tends to scramble the vortex structure and give rise to speckle It is therefore of great interest to reconstruct the topological charge of a vortex beam after it propagates through a scattering medium Here, we propose a feasible solution for this The proposed method measures holographically the scattered field and reconstructs the spiral phase from it by taking advantage of both the deterministic nature and the ergodicity of the scattering process Our preliminary experiments show promising results and suggest that the proposed method can have great potential in information transmission under non-ideal conditions

Wanqin Yang

Papers

Cyphertext-only attack on the double random-phase encryption: Experimental demonstration

Imaging through scattering media with the auxiliary of a known reference object.

Roadmap on chaos-inspired imaging technologies (CI2-Tech)

Image Transmission through Scattering Media Using Ptychographic Iterative Engine

Recovery of the topological charge of a vortex beam propagated through a scattering layer.