Meta‐Lens Particle Image Velocimetry

Abstract

Fluid flow behavior is visualized through particle image velocimetry (PIV) for understanding and studying experimental fluid dynamics. However, traditional PIV methods require multiple cameras and conventional lens systems for image acquisition to resolve multi‐dimensional velocity fields. In turn, it introduces complexity to the entire system. Meta‐lenses are advanced flat optical devices composed of artificial nanoantenna arrays. It can manipulate the wavefront of light with the advantages of ultrathin, compact, and no spherical aberration. Meta‐lenses offer novel functionalities and promise to replace traditional optical imaging systems. Here, a binocular meta‐lens PIV technique is proposed, where a pair of GaN meta‐lenses are fabricated on one substrate and integrated with a imaging sensor to form a compact binocular PIV system. The meta‐lens weigh only 116 mg, much lighter than commercial lenses. The 3D velocity field can be obtained by the binocular disparity and particle image displacement information of fluid flow. The measurement error of vortex‐ring diameter is ≈1.25% experimentally validates via a Reynolds‐number (Re) 2000 vortex‐ring. This work demonstrates a new development trend for the PIV technique for rejuvenating traditional flow diagnostic tools toward a more compact, easy‐to‐deploy technique. It enables further miniaturization and low‐power systems for portable, field‐use, and space‐constrained PIV applications.

Advanced manufacturing of dielectric meta-devices

“…More detailed reviews about the applications of metasurfaces across various domains can be found in previous literature [326][327][328][329] . This miniaturization advantage of meta-devices has led to notable advancements in various applications, including aerial [330] , terrestrial [331] , and underwater [318,332] environments, particularly benefiting modern consumer optoelectronic devices such as augmented reality (AR), virtual reality (VR), and unmanned aerial vehicles [333] , among others. In contrast to digital optoelectronic devices, there is considerable interest in optical analog signal processing due to the rising demand for extensive real-time data processing in the era of big data.…”

“…[312] Fig. 19 Advanced applications, such as imaging [12,[313][314][315] , display [26,28] , analog computing [316,317] , metrology [43,[318][319][320] , communications [321][322][323] , and light sources [17,133] utilizing dielectric meta-devices, have emerged in the past years.…”

Achromatic Single Metalens Imaging via Deep Neural Network

“…Bridging this gap, recent advancements have seen numerous collaborations between metalens technology and artificial intelligence (AI). Cooperations concentrate on augmenting metalens capabilities through various means, such as AI-assisted metalens design, , disparity computation, − and the formation of meta-neurons . These AI-driven approaches signify a promising direction in overcoming the existing limitations of metalens technology and present a way to restore high-fidelity images from a single-color metalens camera.…”

Monocular Metasurface for Structured Light Generation and 3D Imaging with a Large Field-of-View

“…Recently, the emergence of the optical metasurface, − a kind of digitally structured material composed of subwavelength-spaced thin elements, greatly advances the development of digital optics by downscaling the pixel sizes of the structural inclusions to the subwavelength scale, which enables us to overcome the bottlenecks of conventional optics . Various intriguing optical phenomena and laws have been discovered, including extraordinary Young’s interference, generalized refractive and reflective law, generalized Fresnel formulas, asymmetric spin–orbit interaction, and generalized geometric phase .…”

“…Since the subwavelength structural inclusions can implement independent phase, amplitude, and polarization modulation, enhanced, multifunctional, or even totally new functionalities can be realized, including vector vortex beam generation and determination, − wide-FOV planar beam scanning and imaging . In the field of imaging, researchers have utilized metasurfaces to achieve functionalities such as underwater binocular sensing and intelligent depth perception. − Within the realm of structured light imaging, there is an increasing interest of researchers in using a metasurface to achieve comprehensive space coverage by leveraging its subwavelength-scale unit cells, far surpassing the DOE counterpart. As the point cloud count strictly depends on the unit cell numbers, metasurfaces have demonstrated their superiority in the creation of point clouds with an extremely large number unattainable by the DOE counterpart. − In the meantime, the thinness and lightweight nature of metasurfaces can offer additional advantages in integration simplicity and reduction in design complexity and manufacturing costs.…”