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A flat lens is a lens whose flat shape allows it to provide distortion-free imaging, potentially with arbitrarily-large apertures. The term is also used to refer to other lenses that provide a negative index of refraction.〔 Flat lenses require a refractive index close to −1 over a broad angular range.〔 In recent years, flat lenses based on metasurfaces were also demonstrated. == History == Russian mathematician Victor Veselago predicted that a material with simultaneously negative electric and magnetic polarization responses would yield a negative refractive index (an isotropic refractive index of −1), a ‘left-handed’ medium in which light propagates with opposite phase and energy velocities. The first, near-infrared, flat lens was announced in 2012 using nanostructured antennas.〔 It was followed in 2013 by an ultraviolet flat lens in 2013 that used a bi-metallic sandwich.〔 In 2014 a flat lens was announced that combined composite metamaterials and transformation optics. The lens works over a broad frequency range. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「flat lens」の詳細全文を読む スポンサード リンク
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