Simultaneous Achromatic and Varifocal Imaging with Quartic Metasurfaces in the Visible
Simultaneous Achromatic and Varifocal Imaging with Quartic Metasurfaces in the Visible
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DOI：
10.1021/acsphotonics.9b01216
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发表时间：
2020-01-01
期刊：
影响因子：
7
通讯作者：
Majumdar, Arka
中科院分区：
文献类型：
--
作者：
Colburn, Shane;Majumdar, Arka
成像系统的两个关键指标是其放大率和光学带宽。虽然高质量成像系统如今通过光学变焦实现了跨越整个可见光谱的带宽和放大率的大变化，但这些通常需要具有不适合尺寸受限应用的庞大元件的透镜组件。Metalenses提出了一种小型化的方法，但它们的强色差和缺乏变焦，消色差元件限制了它们的实用性。尽管示例性宽带消色差超透镜可经由色散工程实现，但在实践中，这些设计限于小的物理孔径，因为大面积透镜将需要具有对于制造不可行的纵横比的相位补偿散射体。然而，许多应用需要更大的面积来收集更多的光子以获得更好的信噪比，而且还必须使用非偏振光。在本文中，我们同时实现消色差操作在可见光波长和变焦控制使用偏振不敏感，混合光学数字系统与区域不受色散工程散射体。我们推导出相位方程的共轭超颖表面，产生一个集中的加速光束的彩色焦移控制和广泛的可调焦距范围为4.8毫米（667屈光度的变化）。利用这个共轭对，我们实现了一个近光谱不变的点扩散函数在可见光区。然后，我们将联合收割机的元表面与后捕获反卷积算法相结合，在非相干白色光下成像全色图案，展示了消色差的5倍变焦范围。同时消色差和变焦超透镜可以在各种领域中应用，包括增强现实，植入式显微镜和机器视觉传感器。
Two key metrics for imaging systems are their magnification and optical bandwidth. While high-quality imaging systems today achieve bandwidths spanning the whole visible spectrum and large changes in magnification via optical zoom, these often entail lens assemblies with bulky elements unfit for size-constrained applications. Metalenses present a methodology for miniaturization, but their strong chromatic aberrations and the lack of a varifocal, achromatic element limit their utility. Although exemplary broadband achromatic metalenses are realizable via dispersion engineering, in practice, these designs are limited to small physical apertures as large area lenses would require phase compensating scatterers with aspect ratios infeasible for fabrication. Many applications, however, necessitate larger areas to collect more photons for better signal-to-noise ratio and furthermore must also operate with unpolarized light. In this paper, we simultaneously achieve achromatic operation at visible wavelengths and varifocal control using a polarization-insensitive, hybrid optical-digital system with area unconstrained by dispersion-engineered scatterers. We derive phase equations for a pair of conjugate metasurfaces that generate a focused accelerating beam for chromatic focal shift control and a wide tunable focal length range of 4.8 mm (a 667-diopter change). Utilizing this conjugate pair, we realize a near spectrally invariant point spread function across the visible regime. We then combine the metasurfaces with a postcapture deconvolution algorithm to image full-color patterns under incoherent white light, demonstrating an achromatic 5x zoom range. Simultaneously achromatic and varifocal metalenses could have applications in various fields including augmented reality, implantable microscopes, and machine vision sensors.