Big Pixel Research Articles

Creating Wavelength‐Selective Polarization Digital Numbers

AbstractPolarization and wavelength are two important properties of light for understanding optics. Engineered polarization and wavelength profiles have received considerable interest due to their unusual optical features and more degrees of freedom. However, to simultaneously control polarization and wavelengths, conventional methods suffer from big pixel size, complicated fabrication process, and limited levels in phase control. The unprecedented capability of metasurfaces in the light control has shown much promise to tackle these challenges. Polarization digital numbers with ten different wavelengths are proposed and experimentally realized. A geometric metasurface is used to simultaneously realize wavelength multiplexing, phase multiplexing, and polarization rotation, creating wavelength‐selective polarization digital numbers. A deep learning approach is used to increase the identification accuracy of the digital numbers. The approach can simultaneously control wavelength and polarization, providing more design flexibility. This work may find applications in many fields such as virtual reality, image steganography, and anti‐counterfeiting.

Magnetic field vector ambiguity resolution in a quiescent prominence observed on two consecutive days

Context. Magnetic field vector measurements are always ambiguous, that is, two or more field vectors are solutions of the observed polarisation. Aims. The aim of the present paper is to solve the ambiguity by comparing the ambiguous field vectors obtained in the same prominence observed on two consecutive days. The effect of the solar rotation is to modify the scattering angle of the prominence radiation, which modifies the symmetry of the ambiguous solutions. This method, which is a kind of tomography, was successfully applied in the past to the average magnetic field vector of 20 prominences observed at the Pic du Midi. The aim of the present paper is to apply this method to a prominence observed with spatial resolution at the THÉMIS telescope (European site at Izaña, Tenerife Island). Methods. The magnetic field vector is measured by interpretation of the Hanle effect observed in the He I D3 5875.6 Å line, within the horizontal field vector hypothesis for simplicity. The ambiguity is first solved by comparing the two pairs of solutions obtained for a “big pixel” determined by averaging the observed Stokes parameters in a large region at the prominence centre. Each pixel is then disambiguated by selecting the closest solution in a propagation from the prominence centre to the prominence boundary. Results. The results previously obtained on averaged prominences are all recovered. The polarity is found to be inverse with a small angle of about −21° between the magnetic field vector and the long axis of the filament. The magnetic field strength of about 6 G is found to slightly increase with height, as previously observed. The new result is the observed decrease with height, of the absolute value of the angle between the magnetic field vector and the long axis of the filament. Conclusions. This result is in excellent agreement with prominence magnetohydrodynamical models.

A Study of Trends in Buying Pattern of Smartphones In India

The rapidly growing demand of Smartphone has created a buzz around the world. Nowadays, most of the consumers opt to have a Smartphone. The increasing innovation in mobile phone industries has brought this craze among the people on Smartphone. India has witnessed a dramatic growth in the number of mobile phone users in the recent past. Equally impressive has been the increase in internet access. Although mobiles allow us to stay connected, it is the convergence of internet access and smartphones that has resulted in tectonic shifts in consumer awareness, outlook and behaviour. Smartphone is configured by an operating system with advanced computing capability and connectivity. Generally Smartphone has high sensor big touch screens and high pixel cameras with lots of features and applications. Mostly people use applications for internet browsing, email, navigation, social media, listening music, reading news, games, finance, health and fitness, taking notes, calendar, weather forecast and lots of other things. These features and applications in Smartphone somehow have made people's life easier either in daily life, at work or for entertainment purpose. As a result, the market of Smartphone has been escalating every year with increasing innovations.

A multiresolution approach to discrete tomography using DART.

In discrete tomography, a scanned object is assumed to consist of only a few different materials. This prior knowledge can be effectively exploited by a specialized discrete reconstruction algorithm such as the Discrete Algebraic Reconstruction Technique (DART), which is capable of providing more accurate reconstructions from limited data compared to conventional reconstruction algorithms. However, like most iterative reconstruction algorithms, DART suffers from long computation times. To increase the computational efficiency as well as the reconstruction quality of DART, a multiresolution version of DART (MDART) is proposed, in which the reconstruction starts on a coarse grid with big pixel (voxel) size. The resulting reconstruction is then resampled on a finer grid and used as an initial point for a subsequent DART reconstruction. This process continues until the target pixel size is reached. Experiments show that MDART can provide a significant speed-up, reduce missing wedge artefacts and improve feature reconstruction in the object compared with DART within the same time, making its use with large datasets more feasible.