Monday, April 24, 2017

New Camera System Inspired By Animal Vision

Scientists have taken inspiration from how animals' eyes work to create a new way for computer-controlled cameras to 'see'.
In a new paper published today in the journal Science Advances, University of Glasgow researchers describe a new method for creating video using single- cameras. They have found a way to instruct cameras to prioritise objects in images using a method similar to the way brains make the same decisions.
The eyes and brains of humans, and many animals, work in tandem to prioritise specific areas of their field of view. During a conversation, for example, visual attention is focused primarily on the other speaker, with less of the brain's 'processing time' given over to peripheral details. The vision of some hunting animals also works along similar lines.
The team's sensor uses just one light-sensitive pixel to build up moving images of objects placed in front of it. Single-pixel sensors are much cheaper than dedicated megapixel sensors found in digital cameras, and are capable of building images at wavelengths where conventional cameras are expensive or simply don't exist, such as at the infrared or terahertz frequencies.The images the system outputs are square, with an overall resolution of 1,000 pixels. In conventional cameras, those thousand pixels would be evenly spread in a grid across the image. The team's new system instead can choose to allocate its 'pixel budget' to prioritise the most important areas within the frame, placing more higher resolution pixels in these locations and so sharpening the detail of some sections while sacrificing detail in others. This pixel distribution can be changed from one frame to the next, similar to the way biological vision systems work, for example when human gaze is redirected from one person to another.
Dr David Phillips, Royal Academy of Engineering Research Fellow at the University of Glasgow's School of Physics and Astronomy, led the research.
Dr Phillips said: "Initially, the problem I was trying to solve was how to maximise the frame rate of the single-pixel system to make the video output as smooth as possible.
"However, I started to think a bit about how vision works in living things and I realised that building a programme which could interpret the data from our single-pixel sensor along similar lines could solve the problem. By channelling our pixel budget into areas where high resolutions were beneficial, such as where an object is moving, we could instruct the system to pay less attention to the other areas of the frame.
"By prioritising the information from the sensor in this way, we've managed to produce images at an improved frame rate but we've also taught the system a valuable new skill.
"We're keen to continue improving the  and explore the opportunities for industrial and commercial use, for example in medical imaging."
The research is the latest in a string of single-pixel-imaging breakthroughs from the University's Optics Group, led by Professor Miles Padgett, which include creating 3D images, imaging gas leaks, and 'seeing' through opaque surfaces.

Abstract-Efficient terahertz anti-reflection properties of metallic anti-dot structures

Kumar Neeraj, Samiran Choudhury, Debanjan Polley, Rakhi Acharya, Jaivardhan Sinha, Anjan Barman, and Rajib Kumar Mitra

We report the use of micrometer-sized copper (Cu) anti-dot structures as a novel terahertz (THz) anti-reflection coating (ARC) material and their superior performance over conventionally used metallic (Cu) thin films. Cu anti-dot structures of two different thicknesses (7 and 10 nm) with varying anti-dot diameters (100, 200, and 300 μm, inter-anti-dot separation fixed at 100 μm) are deposited on silicon substrates by RF magnetron sputtering and e-beam evaporation. The anti-reflection performance of these samples is studied in the frequency range of 0.3–2.2 THz. While continuous metallic (Cu) thin film minimizes the Fabry–Perot (FP) peak, it also suppresses the primary transmission peak, reducing the advantage due to the former effect. On the contrary, the anti-dot arrays reduce both the absolute amplitude of the FP peak and the amplitude ratio (AR) of the FP peak to the primary peak, making them a superior material for ARC applications. The AR can be further manipulated by varying the anti-dot size. A universal conductivity phase-matching condition, which is a prerequisite for the disappearance of the FP peak, is observed in these samples. The enhanced anti-reflection performance promotes these anti-dot structures as an efficient terahertz ARC material.
© 2017 Optical Society of America

Sunday, April 23, 2017

US Patent Application and Abstract-Terahertz modulator based on low-dimension electron plasma wave and manufacturing method thereof

USPTO Applicaton #: #20170108756 
Inventors: Yongdan HuangHua QinZhipeng ZhangYao Yu

A terahertz modulator based on low-dimension electron plasma wave, a manufacturing method thereof, and a high speed modulation method are provided. The terahertz modulator includes a plasmon and a cavity. The present disclosure discloses the resonance absorption mechanism caused by collective oscillation of electrons (plasma wave, namely, the plasmon). In order to enhance the coupling strength between the terahertz wave and the plasmon, a GaN/AlGaN high electron mobility transistor structure having a grating gate is integrated in a terahertz Fabry-Pérot cavity, and a plasmon polariton is formed arising from strong coupling of the plasmon and a cavity mode.

Abstract- Broadband and Robust Metalens with Nonlinear Phase Profiles for Efficient Terahertz Wave Control

Quanlong Yang, Jianqiang Gu, Yuehong Xu, Xueqian Zhang, Yanfeng Li, Chunmei Ouyang, Zhen Tian, Jiaguang Han, Weili Zhang,

Metasurfaces, 2D artificial electromagnetic media, open up a new frontier of functional device design ranging from radio waves to the visible region. Particularly, metasurface-based lenses are indispensable in various practical terahertz applications. The authors aim at achieving flexible and robust metalenses for efficient terahertz wave control. In general, resolution and efficiency are two inevitable parameters in determining the focusing and imaging abilities of lenses, which however are rarely experimentally demonstrated in the terahertz band. In this Communication, three broadband and robust metalenses with nonlinear phase profiles are proposed, all of which are experimentally investigated by using near-field scanning terahertz microscopy (NSTM) with a spatial resolution of 50 µm. The measurement shows that the metalens can focus a 0.95 THz wave to a spot size of 580 µm and achieve a transmittance efficiency of 45%. In addition, the NSTM system facilitates an experimental investigation of the incidence angle dependence of the terahertz metalens, which proves the robust focusing feature of the proposed device. This demonstration delivers a promising metasurface design for potential applications in imaging and information processing that may be of interest for the entire electromagnetic spectrum.

Saturday, April 22, 2017

Abstract-Design and Fabrication of Waveguide Optics for Imaging Applications

Due to the non-ionizing property, researchers have chosen to investigate terahertz radiation (THz) Imaging instrumentation for Bio-Sensing applications. The present work is to design and fabricate a near field lens that can focus guided terahertz radiation to a microscopic region for the detection of cancer-affected cells in Biological tissue. Operational characteristics such as field of view, optical loss factor, and hydrophobicity must be included to achieve an effective design of the lens.