Air Force Research Laboratory, Nondestructive Evaluation Branch (AFRL/RXLP), 2230 Tenth Street, Wright-Patterson AFB, Ohio 45433, USA.
J Acoust Soc Am. 2011 Nov;130(5):2789-96. doi: 10.1121/1.3640841.
Modeling and experimental results of an ultrasonic aperiodic flat lens for use in air are presented. Predictive modeling of the lens is performed using a hybrid genetic-greedy algorithm constrained to a linear structure. The optimized design parameters are used to fabricate a lens. A method combining a fiber-disk arrangement and scanning laser vibrometer measurements is developed to characterize the acoustic field distribution generated by the lens. The focal spot size is determined to be 0.88 of the incident wavelength of 80-90 kHz at a distance of 2.5 mm from the lens. Theoretically computed field distributions, optimized frequency of operation, and spatial resolution focal length are compared with experimental measurements. The differences between experimental measurements and the theoretical computations are analyzed. The theoretical calculation of the focal spot diameter is 1.7 mm which is 48% of the experimental measurement at a frequency of 80-90 kHz. This work illustrates the capabilities of a hybrid algorithm approach to design of flat acoustic lenses to operate in air with a resolution of greater than the incident wavelength and the challenges of characterizing acoustic field distribution in air.
介绍了一种用于空气中的超声非周期平面透镜的建模和实验结果。使用受线性结构约束的混合遗传贪婪算法对透镜进行了预测建模。优化的设计参数用于制造透镜。开发了一种结合光纤盘布置和扫描激光测振仪测量的方法来表征透镜产生的声场分布。在距离透镜 2.5 毫米处，确定焦点光斑尺寸为 80-90 kHz 入射波长的 0.88。理论计算的场分布、优化的工作频率和空间分辨率焦距与实验测量值进行了比较。分析了实验测量值与理论计算值之间的差异。在 80-90 kHz 的频率下，理论计算的焦点光斑直径为 1.7 毫米，是实验测量值的 48%。这项工作说明了使用混合算法设计在空气中工作的平面声透镜的能力，分辨率大于入射波长，以及在空气中对声场分布进行特征描述的挑战。
