Progress towards omnidirectional transformation optics with lenses

We study, theoretically, omni-directional Euclidean transformation-optics (TO) devices comprising planar, light-ray-direction changing, imaging, interfaces. We initially studied such devices in the case when the interfaces are homogeneous, showing that very general transformations between physical and electromagnetic space are possible. We are now studying the case of inhomogeneous interfaces. This case is more complex to analyse, but the inhomogeneous interfaces include ideal thin lenses, which gives rise to the hope that it might be possible to construct practical omni-directional TO devices from lenses alone. Here we report on our progress in this direction

Resolution limits of pixellated optical components.

Pixellated optical components, for example generalised confocal lenslet arrays (GCLAs), enable the design of optical devices which cannot be realised without introducing pixellation or a similar compromise. A key concern is the degradation of imaging quality due to the combined effects of diffraction, worst for smaller pixels, and the visibility of the pixels. Here we examine the effects of these two factors on image quality through use of our custom raytracer, Dr TIM. We also outline future work in developing these ideas more rigorously and applying the conclusions to more complicated devices

Ideal-lens cloaks and new cloaking strategies

Previously [Courtial et al., Opt. Express 26, 17872 (2018)] we presented the theory of transformation optics (TO) with ideal lenses and demonstrated an example, an omnidirectional lens. Here we interpret this omnidirectional lens in two different parameter regimes as ideal-lens cloaks that employ different cloaking strategies: a standard “shrink cloak” in which objects appear smaller (ideally zero) and a novel “abyss cloak” in which interior physical-space positions are mapped to the exterior and thus are visible only from certain directions. We proceed to combine two nested abyss cloaks into another novel, omnidirectional, “bi-abyss cloak.” Our work significantly extends the arsenal of cloaking strategies

Ray-optical transformation optics with ideal thin lenses makes omnidirectional lenses

We present the theory of ray-optical transformation optics (RTO) with ideal thin lenses, and show that ideal-thin-lens RTO devices are omnidirectional lenses. Key to designing such devices are two theorems, the loop-imaging theorem and the edge-imaging theorem, which ensure that the interior physical space is distorted in the same way for all viewing directions. We discuss the possibility of realising such devices using lens holograms or Fresnel lenses, as both are in principle capable of changing the directions of rays incident from a specific point precisely like an ideal thin lens, thereby enabling macroscopic and broad-band RTO devices that work for at least one viewing position. Even when restricted in this way, our work opens up new possibilities in ray optics. Our devices have the potential to form the basis of new microscope objectives, virtual-reality headsets, and medical spectacles

Report from the Annual Conference of the British Society of Echocardiography, November 2016, Queen Elizabeth II Conference Centre, London.

Peer reviewedPublisher PD

Schulsoftware: Stochastik

Copy held by FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Photography at relativistic speeds

In a photo taken with a camera moving at relativistic speed, the world appears distorted. That much has long been clear, but the details of the distortion were slow to emerge correctly. We recently added relativistic raytracing capability to our custom raytracer, Dr TIM, resulting in unique combinations of capabilities. Here we discuss a few observations. In particular, photos can be sharp only if the shutter is placed correctly. A hypothetical window that changes light-ray direction like a change of inertial frame, when combined with suitable shutter placement, can correct for all relativistic-aberration effects

Photography at relativistic speeds

In a photo taken with a camera moving at relativistic speed, the world appears distorted. That much has long been clear, but the details of the distortion were slow to emerge correctly. We recently added relativistic raytracing capability to our custom raytracer, Dr TIM, resulting in unique combinations of capabilities. Here we discuss a few observations. In particular, photos can be sharp only if the shutter is placed correctly. A hypothetical window that changes light-ray direction like a change of inertial frame, when combined with suitable shutter placement, can correct for all relativistic-aberration effects

Comparison of neural networks, evolutionary techniques and thermodynamic group contribution methods for the prediction of heats and vaporization

In this paper we report results for the prediction of thermodynamic properties based on neural networks, evolutionary algorithms and a combination of them. We compare backpropagation trained networks and evolution strategy trained networks with two physical models. Experimental data for the enthalpy of vaporization were taken from the literature in our investigation. The input information for both neural network and physical models consists of parameters describing the molecular structure of the molecules and the temperature. The results show the good ability of the neural networks to correlate and to predict the thermodynamic property. We also conclude that backpropagation training outperforms evolutionary training as well as simple hybrid training. (orig.)SIGLEAvailable from TIB Hannover: RR 8071(99-70)+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Resolution limits of pixellated optical components

Pixellated optical components, for example generalised confocal lenslet arrays (GCLAs), enable the design of optical devices which cannot be realised without introducing pixellation or a similar compromise. A key concern is the degradation of imaging quality due to the combined effects of diffraction, worst for smaller pixels, and the visibility of the pixels. Here we examine the effects of these two factors on image quality through use of our custom raytracer, Dr TIM. We also outline future work in developing these ideas more rigorously and applying the conclusions to more complicated devices