Ultra-thin camera lenses of the future could see the light of day

Nanowerk  June 11, 2020 The fabrication of state-of-the-art metasurfaces typically involves several expensive, time-consuming, and potentially hazardous processing steps. Researchers in Sweden have developed a method to construct phase-gradient metasurfaces from an exposed standard electron beam resist. They demonstrated the advantages of the method by constructing high-performance flat optics for the entire visible wavelength range. The method dramatically cuts the required processing time, cost, and reduces safety hazards. The method could be a step towards large-scale production of metasurfaces…read more. Open Access TECHNICAL ARTICLE

Seeing the invisible: Polarizer adjustments increase visibility of transparent objects

Phys.org  May 19, 2020 In biological microscopy and X-ray imaging, many transparent objects or structures are difficult to observe due to their low absorption of light. Researchers in China have demonstrated that adjusting the polarizers can optically compute the spatial differentiation of the incident light field along different directions. They improved contrast by tuning a uniform constant background as a bias, creating a virtual light source that casts a shadow on the measured images. Based on this bias approach, they can distinguish the phase increases and decreases in light field distribution and quantify the optical thickness of observed objects with […]

Seeing Through Opaque Media

Technology.org  May 12, 2020 While fluorescence microscopy can provide nano- to microscale resolution, the resolution decreases rapidly along with depth into biological tissue because most biological tissue is opaque. Researchers at Caltech have developed a method that utilizes the correlation between the dynamic speckle-encoded fluorescence and ultrasound-modulated light signal that originate from the same location within a sample. They imaged fluorescent targets with an improved resolution of ≤75 µm (versus a resolution of 1.3 mm with direct optical imaging) within a scattering medium with 17 ms decorrelation time. The new imaging modality paves the way for fluorescence imaging in highly scattering tissue in […]

Unprecedented 3D images of live cells plus details of molecules inside

Nanowerk  April 20, 2020 Label-free contrasts of Quantitative phase imaging (QPI) and molecular vibrational imaging (MVI) are inherently complementary and difficult to integrate due to their reliance on different light–matter interactions. Researchers in Japan present a unified imaging scheme with simultaneous and in situ acquisition of quantitative phase and molecular vibrational contrasts of single cells in the QPI framework using the mid-infrared photothermal effect. The research may enable new analyses, especially for studying complex and fragile biological phenomena such as drug delivery, cellular disease, and stem cell development…read more. Open Access TECHNICA L ARTICLE Concept of MV-QPI. (a) Principle of […]

New optical system could lead to devices that can recognize objects instantly

Technology.org  March 5, 2020 Diffractive optical network is a recently introduced optical computing framework that merges wave optics with deep-learning methods to design optical neural networks. Previous diffractive approaches employed monochromatic coherent light as the illumination source. Researchers at UCLA designed a broadband diffractive optical neural network that simultaneously processes a continuum of wavelengths generated by a temporally incoherent broadband source to all-optically perform a specific task learned using deep learning. They fabricated and tested seven different multi-layer, diffractive optical systems that transform the optical wavefront generated by a broadband THz pulse to realize a series of tunable, single-passband and […]

Lasers and terahertz waves combined in camera that sees ‘unseen’ detail

Science Daily  February 18, 2020 The core challenge in THz cameras is not about collecting an image, but preserving the objects spectral fingerprint that can be easily corrupted by the technique. Researchers in the UK used a single-pixel camera to image sample objects with patterns of THz light. The prototype they built can detect how the object alters different patterns of THz light. By combining this information with the shape of each original pattern the camera reveals the image of an object as well as its chemical composition. The camera creates THz electromagnetic waves very close to the sample, similar […]

Using long-wavelength terahertz radiation to produce video with a high frame rate

Phys.org  February 10, 2020 Long-wavelength terahertz radiation which is considered to be much safer than X-ray radiation has not been used in security and medical devices because its energy is so low and it has been difficult to create high-resolution images using them. Instead of building a more sensitive sensor researchers in the UK made the waves more readable to conventional technology. They converted the terahertz radiation into green light by directing it into a cloud of excited cesium atoms. Once the cloud was formed, the researchers fired a secondary terahertz laser through a moving object, which allowed a “shadow […]

Army wants tech that can identify people through walls

Fedscoop  January 30, 2020 A new request for information is soliciting white papers on portable technology that can detect, identify, and monitor persons, animals, and materials behind multi-leveled obstruction(s) from a long standoff range, a technology that works both in the city and that can be deployed in dense foliage. The ideal system should be able to read biometric data, perform knowledge management functions and use machine learning and artificial intelligence to improve its science-fiction-like vision powers. Army is looking for information about technology that is ready to be used. Whether any such exists is uncertain. While wall-penetrating technology has […]

How to take a picture of a light pulse

Phys.org  January 27, 2020 Measuring the shape of the laser light wave with high accuracy required for investigating materials to medical diagnostics requires a large, complex experimental setup. In their experiment an international team of researchers (Germany, Austria) hit a tiny crystal of silicon oxide with the laser pulse to be investigated. While this laser pulse penetrates the crystal, another strong infrared pulse is fired at the target changing the energy state of the electrons so that they become mobile. As soon as the electrons can move through the crystal, they are accelerated by the electric field of the first […]

Deep learning enables real-time imaging around corners

Science Daily  January 16, 2020 A team of researchers in the US (Stanford University, Princeton University, Southern Methodist University, Rice University) developed an imaging system which uses a commercially available camera sensor and a powerful laser source that is similar to the one found in a laser pointer. The laser beam bounces off a visible wall onto the hidden object and then back onto the wall, creating a speckle pattern that encodes the shape of the hidden object. It can distinguish submillimeter details of a hidden object from 1 meter away. The system can be combined with other imaging systems […]