Discover the most talked about and latest scientific content & concepts.

Concept: Multi-spectral image


Most surviving biblical period Hebrew inscriptions are ostraca-ink-on-clay texts. They are poorly preserved and once unearthed, fade rapidly. Therefore, proper and timely documentation of ostraca is essential. Here we show a striking example of a hitherto invisible text on the back side of an ostracon revealed via multispectral imaging. This ostracon, found at the desert fortress of Arad and dated to ca. 600 BCE (the eve of Judah’s destruction by Nebuchadnezzar), has been on display for half a century. Its front side has been thoroughly studied, while its back side was considered blank. Our research revealed three lines of text on the supposedly blank side and four “new” lines on the front side. Our results demonstrate the need for multispectral image acquisition for both sides of all ancient ink ostraca. Moreover, in certain cases we recommend employing multispectral techniques for screening newly unearthed ceramic potsherds prior to disposal.

Concepts: Imaging, Multi-spectral image


Multispectral imaging is a powerful tool that extends the capabilities of the human eye. However, multispectral imaging systems generally are expensive and bulky, and multiple exposures are needed. Here, we report the demonstration of a compact multispectral imaging system that uses vertical silicon nanowires to realize a filter array. Multiple filter functions covering visible to near-infrared (NIR) wavelengths are simultaneously defined in a single lithography step using a single material (silicon). Nanowires are then etched and embedded into polydimethylsiloxane (PDMS), thereby realizing a device with eight filter functions. By attaching it to a monochrome silicon image sensor, we successfully realize an all-silicon multispectral imaging system. We demonstrate visible and NIR imaging. We show that the latter is highly sensitive to vegetation and furthermore enables imaging through objects opaque to the eye.

Concepts: Eye, Demonstration, Image sensor, Imaging, Visible spectrum, Human eye, Eye color, Multi-spectral image


BACKGROUND: Contact-type spectrophotometers have been widely used to measure skin color to determine the color values and melanin and hemoglobin contents. Recently, a spectral camera was introduced to evaluate two-dimensional color distribution. However, its application to skin color measurement has been limited. METHODS: The original spectral imaging system developed for facial skin consisted of a spectral camera and an original lighting unit for uniform irradiation of the face. The distribution of skin chromophores in the face, including melanin and oxy- and deoxyhemoglobin, was calculated from the reflectance data for each pixel of the spectral images. In addition, to create a mean spectral image of the group, a face morphing technology for spectral data was proposed. Using the system, we determined the characteristics of the dark circles around the eyes and also evaluated the effects of an anti-dark circle cosmetic. RESULTS: This system enabled the sensitive detection of skin chromophores in the face. Melanin content increased and hemoglobin oxygen saturation ratio decreased locally in the infraorbital areas of women with dark circles compared with those of women without dark circles. In addition, we were able to detect improvement in the dark circles after 6 weeks' use of anti-dark circle cosmetic products by visualizing the distribution of the relative concentrations of melanin and hemoglobin oxygen saturation ratio. CONCLUSION: Using a spectral camera, we developed a non-contact image-processing system that was capable of capturing a wide area of the face to visualize the distribution of the relative concentrations of skin chromophores in the face.

Concepts: Oxygen, Ultraviolet, Color, Melanin, Face, Human skin color, Eye color, Multi-spectral image


We present, to the best of our knowledge, the first experimental demonstration of a new imaging system for in situ measurement of the two-dimensional (2D) distribution of the surface temperature of microscopic specimens. The main component of the system is an imaging tandem acousto-optical tunable filter (TAOTF) synchronized with a video camera. A set of TAOTF spectroscopic images (up to a few hundreds) is taken by the TAOTF imaging system to fit the measured spectral curves in each pixel to the Planck radiation function and determine the temperature and emissivity of the sample using the gray body approximation. It is experimentally shown that this technique provides aberration-free spectral imaging suitable for precise multispectral imaging radiometry (MIR).

Concepts: Energy, Measurement, Test method, Systems of measurement, Black body, Imaging, Camera, Multi-spectral image


Multispectral colloidal metasurfaces are fabricated that exhibit greater than 85% absorption and ≈100 nm linewidths by patterning film-coupled nanocubes in pixels using a fusion of bottom-up and top-down fabrication techniques over wafer-scale areas. With this technique, the authors realize a multispectral pixel array consisting of six resonances between 580 and 1125 nm and reconstruct an RGB image with 9261 color combinations.

Concepts: Liquid crystal display, RGB color model, Photography, Imaging, Image processing, Digital camera, Pixel, Multi-spectral image


Existing multispectral imagers mostly use available array sensors to separately measure 2D data slices in a 3D spatial-spectral data cube. Thus they suffer from low photon efficiency, limited spectrum range and high cost. To address these issues, we propose to conduct multispectral imaging using a single bucket detector, to take full advantage of its high sensitivity, wide spectrum range, low cost, small size and light weight. Technically, utilizing the detector’s fast response, a scene’s 3D spatial-spectral information is multiplexed into a dense 1D measurement sequence and then demultiplexed computationally under the single pixel imaging scheme. A proof-of-concept setup is built to capture multispectral data of 64 pixels × 64 pixels × 10 wavelength bands ranging from 450 nm to 650 nm, with the acquisition time being 1 minute. The imaging scheme holds great potentials for various low light and airborne applications, and can be easily manufactured as production-volume portable multispectral imagers.

Concepts: Quantum mechanics, Optics, Light, Electromagnetic radiation, Measurement, Wavelength, Imaging, Multi-spectral image


Adoptive T cell therapy (ACT) has shown great promise in melanoma, with over 50 % response rate in patients where autologous tumor-reactive tumor-infiltrating lymphocytes (TIL) can be cultured and expanded. A major limitation of ACT is the inability to generate or expand autologous tumor-reactive TIL in 25-45 % of patients tested. Methods that successfully identify tumors that are not suitable for TIL generation by standard methods would eliminate the costs of fruitless expansion and enable these patients to receive alternate therapy immediately.

Concepts: Imaging, Multi-spectral image


Proteins and small molecules from ancient objects and cultural heritage can provide key information and contribute to study the context of objects and artists. However, all present- day protocols and strategies for the analysis of ancient samples are often invasive and require micro sampling. Here, we present a new method for the non-invasive analysis of proteins and small molecules: the technique uses a special ethyl-vinyl acetate film functionalized with strong cation/anion exchange and C8 resins, for interacting with both proteins and small molecules present on the surface of the objects, followed by LC-MS/MS analysis. The new method was fully validated for the determination of both proteins and small molecules on several types of supports, showing excellent analytical performances such as for example R2 of the calibration curve of 0.98 and 0.99 for proteins and small molecules, low but very repeatable recoveries, particularly adequate for investigations on precious ancient samples that must not be altered by the analytical procedure. ESEM images and LED multispectral imaging confirmed that no damages or alterations occurred onto the support surfaces and no residues were left from the extractive film. Finally the new method was applied for the characterization of the binders of a historical fresco of the XVI century from the Flemish painter Paul Brill, and of a recently discovered fresco from Isidoro Bianchi (XVII century). Moreover the method was employed for the identification of the colorant used by Pietro Gallo (XIV century) on a wood panel. The method here reported can be easily applied to any other research on ancient precious objects and cultural heritage, since it does not require micro sampling and the proteins/small molecules extraction can be performed directly in situ, leaving the object unchanged and intact.

Concepts: Protein, Method acting, In situ, Object-oriented programming, Centuries, Imaging, Multi-spectral image, 2nd millennium


Most color simulators for color deficiencies are based on the tristimulus values and are intended to simulate the appearance of an image for dichromats. Statistics show that there are more anomalous trichromats than dichromats. Furthermore, the spectral sensitivities of anomalous cones are different from those of normal cones. Clinically, the types of color defects are characterized through Rayleigh color matching, where the observer matches a spectral yellow to a mixture of spectral red and green. The midpoints of the red/green ratios deviate from a normal trichromat. This means that any simulation based on the tristimulus values defined by a normal trichromat cannot predict the color appearance of anomalous Rayleigh matches. We propose a computerized simulation of the color appearance for anomalous trichromats using multispectral images. First, we assume that anomalous trichromats possess a protanomalous (green shifted) or deuteranomalous (red shifted) pigment instead of a normal (L or M) one. Second, we assume that the luminance will be given by L+M, and red/green and yellow/blue opponent color stimulus values are defined through L-M and (L+M)-S, respectively. Third, equal-energy white will look white for all observers. The spectral sensitivities of the luminance and the two opponent color channels are multiplied by the spectral radiance of each pixel of a multispectral image to give the luminance and opponent color stimulus values of the entire image. In the next stage of color reproduction for normal observers, the luminance and two opponent color channels are transformed into XYZ tristimulus values and then transformed into sRGB to reproduce a final image for anomalous trichromats. The proposed simulation can be used to predict the Rayleigh color matches for anomalous trichromats. We also conducted experiments to evaluate the appearance of simulated images by color deficient observers and verified the reliability of the simulation.

Concepts: Simulation, Operations research, Computer graphics, Color blindness, Multi-spectral image, Radiance


With recent proliferation in compact and/or low-cost clinical multispectral imaging approaches and commercially available components, questions remain whether they adequately capture the requisite spectral content of their applications. We present a method to emulate the spectral range and resolution of a variety of multispectral imagers, based on in-vivo data acquired from spatial frequency domain spectroscopy (SFDS). This approach simulates spectral responses over 400 to 1100 nm. Comparing emulated data with full SFDS spectra of in-vivo tissue affords the opportunity to evaluate whether the sparse spectral content of these imagers can (1) account for all sources of optical contrast present (completeness) and (2) robustly separate and quantify sources of optical contrast (crosstalk). We validate the approach over a range of tissue-simulating phantoms, comparing the SFDS-based emulated spectra against measurements from an independently characterized multispectral imager. Emulated results match the imager across all phantoms (<3  %   absorption, <1  %   reduced scattering). In-vivo test cases (burn wounds and photoaging) illustrate how SFDS can be used to evaluate different multispectral imagers. This approach provides an in-vivo measurement method to evaluate the performance of multispectral imagers specific to their targeted clinical applications and can assist in the design and optimization of new spectral imaging devices.

Concepts: In vivo, IMAGE, Imaging, Application software, Multi-spectral image, Emulator