Lensless Multispectral Camera Based on a Coded Aperture Array

Multispectral imaging can be applied to water quality monitoring, medical diagnosis, and other applications, but the principle of multispectral imaging is different from the principle of hyper-spectral imaging. Multispectral imaging is generally achieved through filters, so multiple photos are required to obtain spectral information. Using multiple detectors to take pictures at the same time increases the complexity and cost of the system. This paper proposes a simple multispectral camera based on lensless imaging, which does not require multiple lenses. The core of the system is the multispectral coding aperture. The coding aperture is divided into different regions and each region transmits the light of one wavelength, such that the spectral information of the target can be coded. By solving the inverse problem of sparse constraints, the multispectral information of the target is inverted. Herein, we analyzed the characteristics of this multispectral camera and developed a principle prototype to obtain experimental results.

Study on Hyper Spectral Imaging

Spectroscopy deals with how light behave in the target and recognize materials bases on their different spectral signatures. Spectrum describes the amount and range of radiation that is emitted, reflected or transmitted from the target. Hyper spectral data acquisition and exploitation by providing imaging sensors and software solutions covering hundreds of spectral bands from UV-VIS to SWIS is used to observe Earth, atmospheric science, space situation awareness etc. The work focuses primarily on hyper spectral imaging, data acquisition methods, Image resolution improvement strategies.

Ceramic Material based Optical Antenna for Multiband Photonics Applications

In this article, design and development of a multiband ceramic material-based Optical antenna is discussed. Square shaped aperture is utilized to excited silicon based dielectric resonator. This type of excitation system provides the capability to create triple hybrid mode (HEM11δ, HEM12δ and HEM11δ+2) inside the cylindrical shaped ceramic material. Due to this feature, the proposed aerial is operating over diverse frequency bands i.e. 117.5-140 THz, 158-165.5 THz and 175.2-190.5 THz respectively. Stable radiation characteristics as well as good value of gain (about 4.0 dBi) makes the proposed Nano-radiator applicable for hyper spectral imaging system (125 THz) and VLC for wireless LAN (160/180THz).

Calibration of a Hyper-Spectral Imaging System Using a Low-Cost Reference

In this paper, we present a hyper-spectral imaging system and practical calibration procedure using a low-cost calibration reference made of polytetrafluoroethylene. The imaging system includes a hyperspectral camera and an active source of illumination with a variable spectral distribution of intensity. The calibration reference is used to measure the relative reflectance of any material surface independent of the spectral distribution of light and camera sensitivity. Winter road conditions are taken as a test application, and several spectral images of snow, icy asphalt, dry asphalt, and wet asphalt were made at different exposure times using different illumination spectra. Graphs showing measured relative reflectance for different road conditions support the conclusion that measurements are independent of illumination. Principal component analysis of the acquired spectral data for road conditions shows well separated data clusters, demonstrating the system’s suitability for material classification.

Proof of Principle for Direct Reconstruction of Qualitative Depth Information from Turbid Media by a Single Hyper Spectral Image

In medical applications, hyper-spectral imaging is becoming more and more common. It has been shown to be more effective for classification and segmentation than normal RGB imaging because narrower wavelength bands are used, providing a higher contrast. However, until now, the fact that hyper-spectral images also contain information about the three-dimensional structure of turbid media has been neglected. In this study, it is shown that it is possible to derive information about the depth of inclusions in turbid phantoms from a single hyper-spectral image. Here, the depth information is encoded by a combination of scattering and absorption within the phantom. Although scatter-dominated regions increase the backscattering for deep vessels, absorption has the opposite effect. With this argumentation, it makes sense to assume that, under certain conditions, a wavelength is not influenced by the depth of the inclusion and acts as an iso-point. This iso-point could be used to easily derive information about the depth of an inclusion. In this study, it is shown that the iso-point exists in some cases. Moreover, it is shown that the iso-point can be used to obtain precise depth information.

Sub-diffractional cavity modes of terahertz hyperbolic phonon polaritons in tin oxide

Hyperbolic phonon polaritons have recently attracted considerable attention in nanophotonics mostly due to their intrinsic strong electromagnetic field confinement, ultraslow polariton group velocities, and long lifetimes. Here we introduce tin oxide (SnO2) nanobelts as a photonic platform for the transport of surface and volume phonon polaritons in the mid- to far-infrared frequency range. This report brings a comprehensive description of the polaritonic properties of SnO2 as a nanometer-sized dielectric and also as an engineered material in the form of a waveguide. By combining accelerator-based IR-THz sources (synchrotron and free-electron laser) with s-SNOM, we employed nanoscale far-infrared hyper-spectral-imaging to uncover a Fabry–Perot cavity mechanism in SnO2 nanobelts via direct detection of phonon-polariton standing waves. Our experimental findings are accurately supported by notable convergence between theory and numerical simulations. Thus, the SnO2 is confirmed as a natural hyperbolic material with unique photonic properties essential for future applications involving subdiffractional light traffic and detection in the far-infrared range.