Acoustic Magnifying Lens for Far‐Field High Resolution Imaging Based on Transformation Acoustics

Based on transformation acoustics and effective medium theory, a magnifying lens is proposed at sound frequencies, which is employed to realize the far‐field high resolution imaging with matched impedance to free space. Different from the acoustic superlens that creates images with sub‐wavelength features in narrow frequency band, the proposed acoustic magnifying lens enables high‐resolution imaging over broadband that can be captured directly by normal microphone in the far field. Since the acoustic lens is made of inhomogeneous but nearly isotropic sub‐wavelength structures, the design will be greatly simplified without considering the influence of anisotropic mass density or bulk modulus exhibited by most meta‐atoms. The high‐resolution imaging effect is demonstrated both numerically and experimentally, showing promise for a variety of potential applications such as medical imaging, biomedical sensors, as well as focused ultrasound surgery.