High-resolution non-line-of-sight imaging employing active focusing

Cao, Ruizhi; Goumoëns, Frédéric De; Blochet, Baptiste; Xu, Jian; Yang, Changhuei

doi:10.1038/s41566-022-01009-8

Cited by 43 publications

(18 citation statements)

References 35 publications

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“…The computation consumption is much less than the transmission matrix method, which needs the help of powerful GPUs and a calculation time of more than an hour, 34 or the wavefront-modulation-based NLOS method, which requires 10 min to obtain the hidden image. 40 Because the most time consumption of the MPC-HIO algorithm comes from the FFT process, the computation complexity is also comparable to the state-of-the-art phasor wave model. 20 To demonstrate the effectiveness of the proposed model in calculating speckle patterns, the correlation between captured speckle and calculated speckle, which is calculated using eq 1 and the Fresnel diffractive equation, is compared with the following equation: ) where I and I′ separately represent the actual and calculated speckle patterns.…”

Section: ■ Resultsmentioning

confidence: 99%

“…The time to project 2048 different patterns and obtain the corresponding signal is about 8.5 min, which is less than the 40 min for the wavefront-modulation-based NLOS method to obtain the focus point. 40 More speckle patterns can be generated to improve the image quality of the reconstructions. Sophisticated algorithms such as two-step iterative shrinkage/ thresholding algorithms 45 can also help improve the performance for imaging objects with complex structures, 29 if one does not mind the extra computation cost these algorithms bring.…”

Section: Acsmentioning

confidence: 99%

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Speckle Pattern Calculation and Scattering Imaging for General Surface Scattering Problem

Ji,

Zhang,

Wang

et al. 2024

ACS Photonics

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Establishing accurate models for light scattering has attracted widespread attention in optical research. Existing works include the linear system model and the Lambertian model, which achieve imaging small objects through a scattering medium or identifying scenes hidden from the direct line of sight. However, predicting speckle patterns accurately at a specific location after scattering with minimal computational resources remains a challenge. In this work, we introduce a scattering model that considers a scattering surface as a wavefront modulation matrix, which is validated by using the finitedifference time-domain simulation method. The modulating parameters of the scattering surface are retrieved, and the speckle patterns can be accurately calculated by utilizing the retrieved modulating parameters quickly. The results of simulations and experiments demonstrated that the calculated speckles are highly correlated to their corresponding ground truths captured by a charge-coupled device (CCD) sensor. Further experiments show that images of objects hidden from the line of sight can be reconstructed via these calculated speckle patterns. This work provides a general solution to the surface scattering problem and can enhance the utilization of conventional coded imaging techniques in scattering imaging problems.

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Section: ■ Resultsmentioning

confidence: 99%

Section: Acsmentioning

confidence: 99%

Speckle Pattern Calculation and Scattering Imaging for General Surface Scattering Problem

Ji,

Zhang,

Wang

et al. 2024

ACS Photonics

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“…Flat metalenses can be directly applied in far-field subdiffraction imaging, including superoscillation imaging, aperture-scanning Fourier ptychography, − subpixel scanning single photon imaging, and high-resolution nonline-of-sight imaging Figure displays far-field subdiffraction imaging systems based on aperture-scanning Fourier ptychography, which integrates two innovations in classical optics: synthetic aperture imaging and phase retrieval.…”

Section: Lightweight Laser System Based On Planar Optical Elementsmentioning

confidence: 99%

Multiscale Optical Field Manipulation via Planar Digital Optics

Luo

2023

ACS Photonics

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Replacing curved and bulky optical elements with thin and lightweight counterparts is a persistent pursuit of the optical society. Metasurfaces, as two-dimensional artificial metamaterials, have attracted much attention because of their exceptional ability to manipulate electromagnetic waves such as amplitude, phase, polarization, propagation direction, and so on. With the great advances in planar digital optics and vector optical field manipulation via metasurfaces, planar optics with multiscale optical field manipulation from subwavelength meta-atoms (tens of nanometers) to large-scale planar devices (hundreds of millimeters) is highly desired in practical applications, which may replace conventional optical devices with superior performance and decreased weight or even create completely new functionalities. Here, we give a perspective on the multiscale optical field manipulation based on planar optics. Particular emphasis is given to multifunctional optical field manipulation, intelligent design, and mass fabrication, as well as their potential applications in lightweight laser systems, diffractive sails, integrated optics, etc.

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“…They can be divided into active and passive methods. Active methods use controlled light sources to illuminate the hidden scene [Cao et al 2022;Katz et al 2014;Luesia et al 2022;Velten et al 2013], while passive methods rely on ambient illumination [Bouman et al 2017;Krska et al 2022] or light emitted by hidden objects themselves [Saunders et al 2019]. In our work, an active laser source emits light pulses to illuminate the hidden scene.…”

Section: Related Workmentioning

confidence: 99%

Virtual Mirrors: Non-Line-of-Sight Imaging Beyond the Third Bounce

et al. 2023

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Non-line-of-sight (NLOS) imaging methods are capable of reconstructing complex scenes that are not visible to an observer using indirect illumination. However, they assume only third-bounce illumination, so they are currently limited to single-corner configurations, and present limited visibility when imaging surfaces at certain orientations. To reason about and tackle these limitations, we make the key observation that planar diffuse surfaces behave specularly at wavelengths used in the computational wave-based NLOS imaging domain. We call such surfaces virtual mirrors. We leverage this observation to expand the capabilities of NLOS imaging using illumination beyond the third bounce, addressing two problems: imaging single-corner objects at limited visibility angles, and imaging objects hidden behind two corners. To image objects at limited visibility angles, we first analyze the reflections of the known illuminated point on surfaces of the scene as an estimator of the position and orientation of objects with limited visibility. We then image those limited visibility objects by computationally building secondary apertures at other surfaces that observe the target object from a direct visibility perspective. Beyond single-corner NLOS imaging, we exploit the specular behavior of virtual mirrors to image objects hidden behind a second corner by imaging the space behind such virtual mirrors, where the mirror image of objects hidden around two corners is formed. No specular surfaces were involved in the making of this paper.

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High-resolution non-line-of-sight imaging employing active focusing

Cited by 43 publications

References 35 publications

Speckle Pattern Calculation and Scattering Imaging for General Surface Scattering Problem

Speckle Pattern Calculation and Scattering Imaging for General Surface Scattering Problem

Multiscale Optical Field Manipulation via Planar Digital Optics

Virtual Mirrors: Non-Line-of-Sight Imaging Beyond the Third Bounce

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