Abstract
Acoustic holographic rendering in complete analogy with optical holography are useful for various applications, ranging from multi-focal lensing, multiplexed sensing and synthesizing three-dimensional complex sound fields. Conventional approaches rely on a large number of active transducers and phase shifting circuits. In this paper we show that by using passive metamaterials as subwavelength pixels, holographic rendering can be achieved without cumbersome circuitry and with only a single transducer, thus significantly reducing system complexity. Such metamaterial-based holograms can serve as versatile platforms for various advanced acoustic wave manipulation and signal modulation, leading to new possibilities in acoustic sensing, energy deposition and medical diagnostic imaging.
Highlights
Metamaterials, a family of artificial materials with engineered micro-structures, can provide flexible and unusual effective material properties offer new possibilities of designing and fabricating holograms
A hologram can be realized with pixel-by-pixel modulation of the phase or/and the amplitude on the acoustic waves
While active phased array-based holographic rendering methods allow real-time adaptive control over each transducer element, the passive holograms we demonstrated here are advantageous for applications where simplicity, robustness and small volume are preferred over adaptive control
Summary
Metamaterials, a family of artificial materials with engineered micro-structures, can provide flexible and unusual effective material properties offer new possibilities of designing and fabricating holograms. A variety of electromagnetic holograms based on metamaterials have been experimentally demonstrated[3,4,5,6]. We demonstrate the designs and experimental realizations of two acoustic metamaterial-based holograms (a concept schematic of a holographic rendering is shown in Fig. 1a): one projects a letter ‘A’ pattern on the image plane, while the other focus energy onto multiple circular spots of different sizes. Good agreement was found between the measured holographic reconstruction and the designed patterns Such acoustic metamaterial-based holograms are direct acoustic transposition of optical computer generated holograms, but pave the way to advanced acoustic wave manipulation and complex field reconstruction using passive acoustic metamaterials without the need of phase-shifting circuitry and transducer arrays.
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