Customizing the Angular Memory Effect for Scattering Media

Yılmaz, Hasan; Kühmayer, Matthias; Hsu, Chia Wei; Rotter, Stefan; Cao, Hui

doi:10.1103/physrevx.11.031010

Cited by 18 publications

(12 citation statements)

References 45 publications

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“…These results processed by the modified SAI show that the reconstructed images beyond the diffraction-limit can be achieved, which is obviously better than conventional SAI methods. Intriguingly, this directly observed self-imaging phenomenon indicates new potentials for emerging deep-learning-assisted imaging, design of physics-based or physics-aware intelligent technologies for computational imaging [48,49], design of customized speckle [50], and will create new opportunities for bio-imaging (e.g., [2,24,25]), super-resolution imaging through thin scattering layers, and other novel imaging methodologies [51].…”

Section: Discussionmentioning

confidence: 95%

Directly and instantly seeing through random diffusers by self-imaging in scattering speckles

et al. 2023

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Imaging through scattering medium is challenging but important for different applications. Most advances rely on computational image reconstruction from scattering signals. In these conventional investigations, speckles were always treated as scrambled grainy patterns. Directly seeing through scattering diffusers has never been realized. Here, we report a new strategy to see through random diffusers directly using self-imaging of speckles. By analyzing the physics, a direct observation strategy through scattering media is reported with improved image quality. Using this method, we experimentally demonstrated reconstruction-free real-time imaging of static and moving objects with their actual orientation information under single-wavelength and white light illumination. We also proposed a modified speckle autocorrelation imaging (SAI) method inspired by the self-imaging results. Importantly, our strategy requires no pre-calibration or acquisition of point-spread-function, no active control of wavefronts or complicated equipment, nor iterations or carefully adjusted parameters, paving the way towards rapid and high-quality imaging through scattering diffusers.

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Section: Discussionmentioning

confidence: 95%

Directly and instantly seeing through random diffusers by self-imaging in scattering speckles

et al. 2023

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“…Numerically, we model the displacement by performing a translation of the geometry along the x axis, which is modeled with periodic boundary conditions for convenience (Figure 6a). Based on the so-called memory effect for speckle patterns 45,46 , a rigid shift of the PUF should correspond to a proportional shift of the response pattern if the displacement is small. In the following, the shift (sh%) is evaluated as the ratio between the translation and the lateral size of the sample.…”

Section: B Sensitivity To Scatterers Relocationmentioning

confidence: 99%

Quantifying the Sensitivity and Unclonability of Optical Physical Unclonable Functions

Lio¹,

Nocentini²,

Pattelli³

et al. 2022

Preprint

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Due to their unmatched entropy, complexity, and security level, optical Physical Unclonable Functions (PUFs) currently receive a lot of interest in the literature. Despite the large body of existing works, however, one of their core features has never been quantified in detail, namely their physical unclonability. This paper tackles this fundamental and yet largely unaddressed issue. In simulations and/or experiments, the sensitivity of diffraction-based optical responses is investigated with respect to various small alterations such as variation in the position, size, and number of the scatterers, as well as perturbations in the spatial alignment between the physical unclonable function (PUF) and the measurement apparatus. Our analysis focuses on 2D optical PUFs because of their relevance in integrated applications and the need to reply to security concerns that can be raised when the physical structure of the geometry is accessible. Among the results of this study, the sensitivity analysis shows that a positional perturbation of scatterers on the order of 30 nm, i.e., far below the wavelength of the probing laser light of 632 nm wavelength, is sufficient to invalidate the PUF response and thus detect a forgery attempt. These results support and quantify the high adversarial efforts required to clone optical PUFs, even for 2D layouts.

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“…Light propagating through disordered media exhibits an angular correlation called "memory effect" [42][43][44][45][46] : when the incident angle tilts, the transmitted wavefront stays invariant and tilts by the same amount if the input momentum tilt is smaller than roughly one over the medium thickness. Weakly scattering media like a diffuser exhibit a longer memory effect range 47 , and thin layers like a metasurface also have a long memory effects range 48 .…”

Section: Introductionmentioning

confidence: 99%

Thickness bound for nonlocal wide-field-of-view metalenses

Hsu

2022

Light Sci Appl

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Metalenses—flat lenses made with optical metasurfaces—promise to enable thinner, cheaper, and better imaging systems. Achieving a sufficient angular field of view (FOV) is crucial toward that goal and requires a tailored incident-angle-dependent response. Here, we show that there is an intrinsic trade-off between achieving a desired broad-angle response and reducing the thickness of the device. Like the memory effect in disordered media, this thickness bound originates from the Fourier transform duality between space and angle. One can write down the transmission matrix describing the desired angle-dependent response, convert it to the spatial basis where its degree of nonlocality can be quantified through a lateral spreading, and determine the minimal device thickness based on such a required lateral spreading. This approach is general. When applied to wide-FOV lenses, it predicts the minimal thickness as a function of the FOV, lens diameter, and numerical aperture. The bound is tight, as some inverse-designed multi-layer metasurfaces can approach the minimal thickness we found. This work offers guidance for the design of nonlocal metasurfaces, proposes a new framework for establishing bounds, and reveals the relation between angular diversity and spatial footprint in multi-channel systems.

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Customizing the Angular Memory Effect for Scattering Media

Cited by 18 publications

References 45 publications

Directly and instantly seeing through random diffusers by self-imaging in scattering speckles

Directly and instantly seeing through random diffusers by self-imaging in scattering speckles

Quantifying the Sensitivity and Unclonability of Optical Physical Unclonable Functions

Thickness bound for nonlocal wide-field-of-view metalenses

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