Imaging through a diffusive medium has a wide range of biological and medical applications. However, multiple scattering through a turbid medium distorts the spatiotemporal information of the incident light. We propose a method based on a light field tomography that allows imaging of an object through a turbid medium without requiring any prior knowledge of medium/target or inverting ill-posed diffusion equation. The approach employs ballistic photons via time gating, and maps projections of different angles onto a 1-D detector by using a cylindrical lens array. This ballistic photon measurement along with depth retrieval capacity enables 3D imaging through turbid medium.
FMCW-LiDAR (Frequency-modulated continuous wave - Light detection and ranging) measures object distance by measuring the temporal interferogram with frequency-swept laser beams. However, to capture 3D scenes, most current FMCW-LiDARs rely on raster scanning of the laser beam, which compromises either image resolution or volumetric frame rate. In this work, we present a scanning-free FMCW-LiDAR by introducing a computational imaging framework. Specifically, the 3D scene is captured using a one-dimensional linear sensor integrated with a series of lens and prism arrays. Additionally, we employ the compressed sensing principle, enabling us to efficiently capture high-resolution 3D scenes.
In modern digital imaging systems, the recording of high-speed, high-resolution video has been hindered by the limited data transfer bandwidth of electronics. Here we demonstrate ultrahigh-pixel-rate compressed photography using time delay integration (TDI) in which both the spatial and temporal resolutions are greatly enhanced. A dynamic scene is spatially encoded with a pseudo-random pattern, temporally modulated by the TDI camera, and streamed to a host computer for post-processing. The system can record a 0.85-megapixel video at a 200kHz frame rate (170 gigapixels per second). The corresponding pixel rate is two orders of magnitude greater than that of a conventional camera.
Optical imaging has served as a primary method to collect information about biosystems across scales—from functionalities of tissues to morphological structures of cells and even at biomolecular levels. However, to adequately characterize a complex biosystem, an imaging system with a number of resolvable points, referred to as a space-bandwidth product (SBP), in excess of one billion is typically needed. Since a gigapixel-scale far exceeds the capacity of current optical imagers, compromises must be made to obtain either a low spatial resolution or a narrow field-of-view (FOV). The problem originates from constituent refractive optics—the larger the aperture, the more challenging the correction of lens aberrations. Therefore, it is impractical for a conventional optical imaging system to achieve an SBP over hundreds of millions. To address this unmet need, a variety of high-SBP imagers have emerged over the past decade, enabling an unprecedented resolution and FOV beyond the limit of conventional optics. We provide a comprehensive survey of high-SBP imaging techniques, exploring their underlying principles and applications in bioimaging.
KEYWORDS: 3D image processing, 3D displays, Digital holography, 3D image enhancement, Digital imaging, Speckle, Holography, Image enhancement, Scattering, Multiplexing, Digital micromirror devices, Light scattering
In digital 3D holographic displays, the generation of realistic 3D images has been hindered by limited viewing angle and image size. Here we demonstrate a digital 3D holographic display using volume speckle fields produced by scattering layers in which both the viewing angle and the image size are greatly enhanced. Although volume speckle fields exhibit random distributions, the transmitted speckle fields have a linear and deterministic relationship with the input field. By modulating the incident wavefront with a digital micro-mirror device, volume speckle patterns are controlled to generate 3D images of micrometer-size optical foci with 35° viewing angle in a volume of 2 cm × 2 cm × 2 cm.
When a light propagates through highly disordered medium, its optical parameters such as amplitude, phase and polarization states are completely scrambled because of multiple scattering events. Since the multiple scattering is a fundamental optical process that contains extremely high degrees of freedom, optical information of a transmitted light is totally mingled. Until recently, the presence of multiple scattering in an inhomogeneous medium is considered as a major obstacle when manipulating a light transmitting through the medium. However, a recent development of wavefront shaping techniques enable us to control the propagation of light through turbid media; a light transmitting through a turbid medium can be effectively controlled by modulating the spatial profile of the incident light using spatial light modulator.
In this work, stand-alone scattering optical device is proposed; a holographic photopolymer film, which is much economic compared to the other digital spatial light modulators, is used to record and reconstruct permanent wavefront to generate optical field behind a scattering medium. By employing our method, arbitrary optical field can be generated since the scattering medium completely mixes all the optical parameters which allow us to access all the optical information only by modulating spatial phase profile of the impinging wavefront. The method is experimentally demonstrated in both the far-field and near-field regime where it shows promising fidelity and stability. The proposed stand-alone scattering optical device will opens up new avenues for exploiting the randomness inherent in disordered medium.
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