Precision and Intelligence Laboratory, Tokyo Institute of Technology, Yokohama, Japan.
IEEE Trans Ultrason Ferroelectr Freq Control. 2011 Dec;58(12):2720-6. doi: 10.1109/TUFFC.2011.2134.
A liquid lens was fabricated with a focal point that can be varied in the axial and radial directions. We have been developing a variable-focus liquid lens that employs acoustic radiation force and does not contain any mechanical moving parts. Our liquid lens is more compact and has a faster response than conventional mechanical lenses. Rapid scanning of its focus at 1 kHz has been realized by excitation with an amplitude-modulation (AM) signal. The liquid lens consists of a cylindrical acrylic cell (inner diameter: 10 mm; thickness: 3 mm), two immiscible liquids with different refractive indices (water and silicone oil), and an annular piezoelectric lead zirconate titanate transducer with four electrodes. The oil-water interface functions as a lens surface and it can be deformed by the acoustic radiation force generated by the transducer; this enables the lens to act as a variable-focus lens. The variation of the oil-water interface was observed by optical coherence tomography. The laser beam path through the lens was calculated by ray-tracing simulations. The oil-water interface could be deformed and its focal point could be varied in three dimensions by controlling the input voltages of the PZT electrodes. The displacement angle in the radial direction was approximately 3° when two of the electrodes were excited by an input voltage of 45 V at a frequency of 1.9 MHz. The dynamic performance of the lens was investigated using a high-speed cam- era. Excitation by AM signals with a phase difference caused the hemispherical water droplet to oscillate, enabling the focus to be scanned in the axial and radial directions.
一种具有可在轴向和径向方向上改变焦点的液体透镜被制造出来。我们一直在开发一种采用声辐射力且不包含任何机械运动部件的可变焦液体透镜。与传统的机械透镜相比,我们的液体透镜更加紧凑,响应速度更快。通过激励调幅(AM)信号,实现了其焦点的 1 kHz 快速扫描。液体透镜由圆柱形丙烯酸池(内径:10 毫米;厚度:3 毫米)、两种具有不同折射率的不混溶液体(水和硅油)以及带有四个电极的环形锆钛酸铅压电换能器组成。油-水界面充当透镜表面,并且可以通过换能器产生的声辐射力来变形;这使得透镜能够作为可变焦透镜发挥作用。通过光学相干断层扫描观察油-水界面的变化。通过光线追踪模拟计算透镜中的激光束路径。通过控制 PZT 电极的输入电压,可以改变油-水界面的形状并在三维空间中改变焦点位置。当两个电极在 1.9 MHz 频率下以 45 V 的输入电压激励时,在径向方向上的位移角约为 3°。使用高速摄像机研究了透镜的动态性能。通过具有相位差的 AM 信号激励,导致半球形水滴发生振荡,从而能够在轴向和径向方向上扫描焦点。