Abstract
We describe a way to realise transformation-optical devices from structures of micro-structured sheets called generalised confocal lenslet arrays. The resulting devices should work for all visible light, and they should be relatively easy and cheap to (mass-)produce on the scale of metres, but they suffer from field-of-view limitations and significant transmission loss. Furthermore, the mapping between electromagnetic space and physical space is not through stigmatic imaging, but integral imaging. As an example application of this technology, we design and simulate an architectural window that cloaks insulation material with the aim of reducing heat loss.
Highlights
Transformation optics (TO) [1, 2] is an optical design paradigm, developed in the context of metamaterials [3], which appears to distort space when seen through a TO device
In the following we show that a structure comprising planar, homogeneous, surfaces that form the faces of the physical-space simplices and that refract according to a particular generalised law of refraction [13] which can be achieved with generalised confocal lenslet arrays (GCLAs) [34] has the required properties
This appears to be serendipitous, as the lens cloak was designed to be a combination of lenses that images every point back into itself, and this determines the mapping between EM space and physical space
Summary
Transformation optics (TO) [1, 2] is an optical design paradigm, developed in the context of metamaterials [3], which appears to distort space when seen through a TO device. GCLAs perform generalised refraction so general that they are examples of sheets that can appear to—but which do not —create wave-optically forbidden light-ray fields [9] Such windows open up possibilities not normally considered. Other unwanted effects include slight scattering, both for fundamental reasons (the Fourier spectrum of discontinuities is wide, but affects only a small fraction of the light) and for practical reasons such as surface roughness and manufacturing imperfections; a ray offset on the scale of the size of the microlenses; and some blurring of the view due to diffraction caused by the small size of the pixels and imperfect imaging by the (singlet) microlenses, especially if the light makes large angles with the normal to the GCLAs. It is possible to ameliorate the last two effects, in the case of the offset by minimising the diameter of the microlenses (whereby the benefits of miniaturising the microlenses have to be balanced against adverse diffraction effects), in the case of blurring with improved optical engineering
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