Phys.org August 26, 2024 Ghost imaging in the time domain allows for reconstructing fast temporal objects using a slow photodetector. The technique involves correlating random or pre-programmed probing temporal intensity patterns with the integrated signal measured after modulation by the temporal object. However, the implementation of temporal ghost imaging necessitates ultrafast detectors or modulators for measuring or pre-programming the probing intensity patterns, which are not available in all spectral regions especially in the mid-infrared range. An international team of researchers (China, Finland) demonstrated a frequency down conversion temporal ghost imaging scheme that enables to extend the operation regime to arbitrary […]
Category Archives: Imaging technology
Pyramid optical networks for unidirectional image magnification and demagnification
Phys.org August 1, 2024 Researchers at UC California developed a pyramid-structured diffractive optical network design (P-D2NN), optimized specifically for unidirectional image magnification and demagnification. The diffractive layers were pyramidally scaled in alignment with the direction of the image magnification or demagnification, to inhibit image formation in the opposite direction, thus achieved the desired unidirectional imaging operation using a much smaller number of diffractive degrees of freedom within the optical processor volume. The design maintained its unidirectional image magnification/demagnification functionality across a large band of illumination wavelengths. It allowed a unidirectional magnifier and a unidirectional demagnifier operation simultaneously in opposite directions, […]
High-speed electron camera uncovers new ‘light-twisting’ behavior in ultrathin material
Phys.org July 10, 2024 Manipulating the polarization of light at the nanoscale is key to the development of next-generation optoelectronic devices. This is typically done via waveplates using optically anisotropic crystals, with thicknesses on the order of the wavelength. A team of researchers in the US (Stanford, SLAC Nation Acceleration Laboratory, Harvard University, Columbia University, Florida State University, UCLA) used a novel ultrafast electron-beam-based technique sensitive to transient near fields at THz frequencies to observe a giant anisotropy in the linear optical response in Tungsten ditelluride (WTe2). They demonstrated that it is possible to tune THz polarization using a 50 […]
Researchers leverage shadows to model 3D scenes, including objects blocked from view
Phys.org June 18, 2024 Existing methods for single-view 3D reconstruction with Neural radiance fields (NeRF) rely on either data prior to hallucinate views of occluded regions which may not be physically accurate, or shadows observed by RGB cameras which are difficult to detect in ambient light and low albedo backgrounds. A team of researchers in the US (MIT, industry) proposed using time-of-flight data captured by a single-photon avalanche diode to overcome these limitations models two-bounce optical paths with NeRF using lidar transient data for supervision. By leveraging the advantages of both NeRF and two-bounce light measured by lidar they reconstructed […]
Researchers unveil single-shot and complete polarization imaging system using metasurfaces
Phys.org May 2, 2024 When light scatters off an object, its polarization, in general, changes—a transformation described by the object’s Mueller matrix. Mueller matrix imaging is an important technique in science and technology to image the spatially varying polarization response of an object of interest, to reveal rich information otherwise invisible to traditional imaging. An international team of researchers (USA – UC San Diego, Germany) conceptualized, implemented, and demonstrated a compact Mueller matrix imaging system—composed of a metasurface to produce structured polarization illumination and a metasurface for polarization analysis—that could, in a single shot, acquire all 16 components of an […]
Pushing back the limits of optical imaging by processing trillions of frames per second
Phys.org March 25, 2024 Despite real-time femtophotography advantages over conventional multi-shot approaches, existing techniques confront restricted imaging speed or degraded data quality by the deployed optoelectronic devices application scope, acquisition accuracy, and hindered by the limitations in the acquirable information imposed by the sensing models. An international team of researchers (Canada, France) overcame these challenges by developing swept coded aperture real-time femtophotography (SCARF). This enables all-optical ultrafast sweeping of a static coded aperture during the recording of an ultrafast event, bringing full sequence encoding of up to 156.3 THz to every pixel on a CCD camera. They demonstrated SCARF’s single-shot ultrafast […]
Holographic message encoded in simple plastic
Phys.org March 18, 2024 Researchers in Austria produced a sub-terahertz holographic image of a two-dimensional 576-bit data code using a diffractive phase-plate element. The phase plate was designed to encode a focused image of the data code into a phase modulation profile. The complex phase plate structure is fabricated from polylactic acid using fused deposition modeling, a common three-dimensional-printing technique. The simplified optical setup, consisted of a 0.14 THz diverging source, the holographic phase plate, and a scanning detector, without the need for additional optical elements. The information stored in the data code was an example of a cryptographic private […]
Projection mapping leaves the darkness behind
Phys.org March 18, 2024 Projection mapping (PM) typically requires a dark environment to achieve high-quality projections, limiting its practicality. Researchers in Japan overcame this limitation by replacing conventional room lighting with heterogeneous projectors. These projectors replicated environmental lighting by selectively illuminating the scene, excluding the projection target. They developed distributed projector optimization framework designed to effectively replicate environmental lighting and incorporated a large-aperture projector, in addition to standard projectors, to reduce high-luminance emitted rays and hard shadows. To validate their approach, they conducted a series of quantitative and qualitative experiments. They successfully demonstrated that their projector-based lighting system significantly enhanced […]
Building images photon-by-photon to increase the information content provided by microscopes
Phys.org February 6, 2024 A flawless recording of single-photon spatiotemporal information poses significant challenges for the microscope data acquisition (DAQ) system. An international team of researchers (Italy, Switzerland) has presented a DAQ module based on the digital frequency domain principle, able to record essential spatial and temporal features of photons. They used the module to extend the capabilities of established imaging techniques based on single-photon avalanche diode (SPAD) array detectors. They used the module to introduce a robust multispecies approach encoding the fluorophore excitation spectra in the time domain. By combining time-resolved stimulated emission depletion microscopy with image scanning microscopy, […]
A new wavelength of scientific exploration with single-photon detectors
Phys.org January 31, 2024 Superconducting nanowire single-photon detectors (SNSPDs) are a mature photon-counting technology as demonstrated by their figures of merit such as high detection efficiencies and very low dark count rates. However, scaling SNSPDs to large array sizes for mid-infrared applications requires sophisticated readout architectures in addition to superconducting materials development. Researchers at NIST, Boulder, Colorado, developed an SNSPD array design that combined a thermally coupled row-column multiplexing architecture with a thermally coupled time-of-flight transmission line for mid-infrared applications. It required only six cables and could be scaled to larger array sizes. The demonstration of a 64-pixel array showed […]