Topic
Chromatic aberration
About: Chromatic aberration is a research topic. Over the lifetime, 6115 publications have been published within this topic receiving 84144 citations.
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TL;DR: The authors' simulations show that a version of the lens operating at the frequency of visible light can be realized in the form of a thin slab of silver, which resolves objects only a few nanometers across.
Abstract: Optical lenses have for centuries been one of scientists’ prime tools. Their operation is well understood on the basis of classical optics: curved surfaces focus light by virtue of the refractive index contrast. Equally their limitations are dictated by wave optics: no lens can focus light onto an area smaller than a square wavelength. What is there new to say other than to polish the lens more perfectly and to invent slightly better dielectrics? In this Letter I want to challenge the traditional limitation on lens performance and propose a class of “superlenses,” and to suggest a practical scheme for implementing such a lens. Let us look more closely at the reasons for limitation in performance. Consider an infinitesimal dipole of frequency v in front of a lens. The electric component of the field will be given by some 2D Fourier expansion,
10,974 citations
TL;DR: Integrating the Pancharatnam–Berry phase with integrated resonant nanoantennas in a metalens design produces an achromatic device capable of full-colour imaging in the visible range in transmission mode.
Abstract: Metalenses consist of an array of optical nanoantennas on a surface capable of manipulating the properties of an incoming light wavefront. Various flat optical components, such as polarizers, optical imaging encoders, tunable phase modulators and a retroreflector, have been demonstrated using a metalens design. An open issue, especially problematic for colour imaging and display applications, is the correction of chromatic aberration, an intrinsic effect originating from the specific resonance and limited working bandwidth of each nanoantenna. As a result, no metalens has demonstrated full-colour imaging in the visible wavelength. Here, we show a design and fabrication that consists of GaN-based integrated-resonant unit elements to achieve an achromatic metalens operating in the entire visible region in transmission mode. The focal length of our metalenses remains unchanged as the incident wavelength is varied from 400 to 660 nm, demonstrating complete elimination of chromatic aberration at about 49% bandwidth of the central working wavelength. The average efficiency of a metalens with a numerical aperture of 0.106 is about 40% over the whole visible spectrum. We also show some examples of full-colour imaging based on this design. Integrating the Pancharatnam–Berry phase with integrated resonant nanoantennas in a metalens design produces an achromatic device capable of full-colour imaging in the visible range in transmission mode.
1,063 citations
TL;DR: Results show that, at low spatial frequencies below 0.5 cycles/deg, contrast sensitivity is greater to the chromatic gratings, consisting of two monochrome gratings added in antiphase, than to either monochromatic grating alone.
Abstract: A method of producing red-green and blue-yellow sinusoidal chromatic gratings is used which permits the correction of all chromatic aberrations. A quantitative criterion is adopted to choose the intensity match of the two colours in the stimulus: this is the intensity ratio at which contrast sensitivity for the chromatic grating differs most from the contrast sensitivity for a monochromatic luminance grating. Results show that this intensity match varies with spatial frequency and does not necessarily correspond to a luminance match between the colours. Contrast sensitivities to the chromatic gratings at the criterion intensity match are measured as a function of spatial frequency, using field sizes ranging from 2 to 23 deg. Both blue-yellow and red-green contrast sensitivity functions have similar low-pass characteristics, with no low-frequency attenuation even at low frequencies below 0.1 cycles/deg. These functions indicate that the limiting acuities based on red-green and blue-yellow colour discriminations are similar at 11 or 12 cycles/deg. Comparisons between contrast sensitivity functions for the chromatic and monochromatic gratings are made at the same mean luminances. Results show that, at low spatial frequencies below 0.5 cycles/deg, contrast sensitivity is greater to the chromatic gratings, consisting of two monochromatic gratings added in antiphase, than to either monochromatic grating alone. Above 0.5 cycles/deg, contrast sensitivity is greater to monochromatic than to chromatic gratings.
991 citations
IBM1
TL;DR: The implementation of a computer-controlled aberration correction system in a scanning transmission electron microscope, which is less sensitive to chromatic aberration, is reported here and allows dynamic imaging of single atoms, clusters of a few atoms, and single atomic layer ‘rafts' of atoms coexisting with Au islands on a carbon substrate.
Abstract: Following the invention of electron optics during the 1930s, lens aberrations have limited the achievable spatial resolution to about 50 times the wavelength of the imaging electrons. This situation is similar to that faced by Leeuwenhoek in the seventeenth century, whose work to improve the quality of glass lenses led directly to his discovery of the ubiquitous "animalcules" in canal water, the first hints of the cellular basis of life. The electron optical aberration problem was well understood from the start, but more than 60 years elapsed before a practical correction scheme for electron microscopy was demonstrated, and even then the remaining chromatic aberrations still limited the resolution. We report here the implementation of a computer-controlled aberration correction system in a scanning transmission electron microscope, which is less sensitive to chromatic aberration. Using this approach, we achieve an electron probe smaller than 1 A. This performance, about 20 times the electron wavelength at 120 keV energy, allows dynamic imaging of single atoms, clusters of a few atoms, and single atomic layer 'rafts' of atoms coexisting with Au islands on a carbon substrate. This technique should also allow atomic column imaging of semiconductors, for detection of single dopant atoms, using an electron beam with energy below the damage threshold for silicon.
836 citations
TL;DR: In this article, a planar lens without chromatic aberrations at three wavelengths is presented, which is based on low-loss dielectric resonators which introduce a dense spectrum of optical modes to enable dispersive phase compensation.
Abstract: The replacement of bulk refractive optical elements with diffractive planar components enables the miniaturization of optical systems. However, diffractive optics suffers from large chromatic aberrations due to the dispersion of the phase accumulated by light during propagation. We show that this limitation can be overcome with an engineered wavelength-dependent phase shift imparted by a metasurface and demonstrate a design that deflects three wavelengths without dispersion. A planar lens without chromatic aberrations at three wavelengths is also presented. Our design is based on low-loss dielectric resonators which introduce a dense spectrum of optical modes to enable dispersive phase compensation. The suppression of chromatic aberrations in metasurface-based planar photonics will find applications in lightweight collimators for displays, and chromatically-corrected imaging systems.
773 citations