Neil Collings
University of Cambridge
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Neil Collings.
IEEE\/OSA Journal of Display Technology | 2011
Neil Collings; Tony Davey; Jamie Christmas; Daping Chu; Bill Crossland
An introduction to the technology of liquid crystal on silicon (LCOS) devices leads on to a discussion of the application areas which have been and are being opened up by the development of phase-only devices.
IEEE Photonics Technology Letters | 2008
J. R. Moore; Neil Collings; William A. Crossland; A. B. Davey; Mark L. Evans; Anna M. Jeziorska; M Komarcevic; R. J. Parker; Timothy D. Wilkinson; Huan Xu
Polarization-insensitivity is achieved in a reflective spatial light modulator by laying a quarter-wave plate (QWP) at the incident wavelength directly over the mirror pixels of a silicon backplane, and forming a nematic Freedrickcz cell over the QWP to modulate the reflected phase. To achieve the highest drive voltage from the available silicon process, a switched voltage common front electrode design is described, with variable amplitude square wave drive to the pixels to maintain constant root-mean-square drive and minimize phase fluctuations during the dc balance refresh cycle. The silicon has been fabricated and liquid-crystal-on-silicon cells both with and without the QWP assembled; applications include optically transparent switches for optical networks, beam steering for add-drop multiplexers for wavelength-division-multiplexing telecommunications, television multicast, and holographic projection.
Applied Optics | 2008
A Georgiou; J. Christmas; John R. Moore; Anna M. Jeziorska-Chapman; A. B. Davey; Neil Collings; William A. Crossland
We discuss some fundamental characteristics of a phase-modulating device suitable to holographically project a monochrome video frame with 1280 x 720 resolution. The phase-modulating device is expected to be a liquid crystal over silicon chip with silicon area similar to that of commercial devices. Its basic characteristics, such as number of pixels, bits per pixel, and pixel dimensions, are optimized in terms of image quality and optical efficiency. Estimates of the image quality are made from the noise levels and contrast, while efficiency is calculated by considering the beam apodization, device dead space, diffraction losses, and the sinc envelope.
Journal of Optics | 2008
A Georgiou; J Christmas; Neil Collings; John R. Moore; William A. Crossland
This paper presents a modified version of the Fienup algorithm that can compute an image projecting hologram significantly faster. The proposed method, referred to as Fienup with don’t-care (Fidoc), is sufficiently fast to enable real-time hologram calculation for video projection purposes. It achieves high speed and excellent image quality by dispersing noise in ‘don’t-care’ areas around the image. Through simulations it was shown that for the same amount of computation, reconstruction quality is significantly better when using the Fidoc method instead of the simple GS (Gerchberg‐Saxton) and Fienup algorithms.
Optics Express | 2012
Hung-Chun Lin; Neil Collings; Ming-Syuan Chen; Yi-Hsin Lin
A holographic projection system with optical zoom is demonstrated. By using a combination of a LC lens and an encoded Fresnel lens on the LCoS panel, we can control zoom in a holographic projector. The magnification can be electrically adjusted by tuning the focal length of the combination of the two lenses. The zoom ratio of the holographic projection system can reach 3.7:1 with continuous zoom function. The optical zoom function can decrease the complexity of the holographic projection system.
Journal of Physics D | 2008
Oksana Trushkevych; Neil Collings; Tawfique Hasan; Vittorio Scardaci; A. C. Ferrari; Timothy D. Wilkinson; William A. Crossland; W. I. Milne; Junfeng Geng; Brian F. G. Johnson; S. Macaulay
Dispersions of carbon nanotubes (CNTs) in liquid crystals (LCs) have attracted attention due to their unique properties and possible applications in photonics and electronics. However, these are hard to stabilize, and the loading level in the equilibrium state in LC hosts is small. A practical way to monitor the quality and CNT incorporation in such equilibrium dispersions is required. Here, we compare different methods for characterising equilibrium CNT–LC composite materials.
Optical Engineering | 2011
Hao Zhang; Neil Collings; Jing Chen; Bill Crossland; Daping Chu; Jinghui Xie
Computational holography becomes highly complicated and demanding when it is employed to produce real three-dimensional (3D) images. Here we present a novel algorithm for generating a full parallax 3D computer generated hologram (CGH) with occlusion effect, which is an important property of 3D perception, but has often been neglected in most CGH related works. The ray casting technique is introduced to handle the occlusion issue. Horizontally and vertically distributed rays are projected from each hologram sample to the 3D objects to obtain the complex am- plitude distribution. The proposed algorithm has no restriction on—or ap- proximation to—the 3D objects, and it can produce reconstructed images with correct shading effect and no visible artifacts. An optical experiment is performed to validate our approach, using a phase-only spatial light modulator to optically reconstruct a 3D scene. The experimental result confirmed that the CGHs produced by our algorithm can successfully re- construct 3D images with full parallax and occlusion effect. C 2011 Society of
Journal of Lightwave Technology | 2014
Brian Robertson; Haining Yang; Neil Collings; John R. Moore; Jinsong Liu; Anna M. Jeziorska-Chapman; Mike Pivnenko; Sharon Lee; Adrian Wonfor; I.H. White; William A. Crossland; Daping Chu
A multi-functional 1 × 9 wavelength selective switch based on liquid crystal on silicon (LCOS) spatial light modulator technology and anamorphic optics was tested at a channel spacing of 100 and 200 GHz, including dynamic data measurements on both single beam deflection and multi-casting to two ports. The multi-casting holograms were optimized using a modified Gerchberg-Saxton routine to design the core hologram, followed by a simulated annealing routine to reduce crosstalk at non-switched ports. The effect of clamping the magnitude of phase changes between neighboring pixels during optimization was investigated, with experimental results for multi-casting to two ports resulting in a signal insertion loss of -7.6 dB normalized to single port deflection, a uniformity of ±0.6%, and a worst case crosstalk of -19.4 dB, which can all be improved further by using a better anti-reflection coating on the LCOS SLM coverplate and other measures.
IEEE Communications Magazine | 2005
Timothy D. Wilkinson; Bill Crossland; Neil Collings; F. Zhang; Mark Fan
The role of the optical storage area network is becoming increasingly important in computer network architectures, with the amount of information being presented and requested on the Internet ever increasing. One of the key questions is what is the role of, and how do we control, an optical switch core within a SAN to optimize its performance. In this article we review two potential optical switch technologies and assess their performance as a SAN optical switch core.
Applied Optics | 2012
Zichen Zhang; Haining Yang; Brian Robertson; Mike Pivnenko; Neil Collings; William A. Crossland; Daping Chu
A method to measure the optical response across the surface of a phase-only liquid crystal on silicon device using binary phase gratings is described together with a procedure to compensate its spatial optical phase variation. As a result, the residual power between zero and the minima of the first diffraction order for a binary grating can be reduced by more than 10 dB, from -15.98 dB to -26.29 dB. This phase compensation method is also shown to be useful in nonbinary cases. A reduction in the worst crosstalk by 5.32 dB can be achieved when quantized blazed gratings are used.