Rapid Spatial Mapping of Focused Ultrasound Fields Using a Planar Fabry–Pérot Sensor

The data was acquired in order to investigate the potential of a robust
planar Fabry–Pérot sensor for measurement of high acoustic pressures. The sensor
was formed from all hard dielectric materials, and designed to operate at 1550
nm, coupled with a C-L (1516–1610 nm) band wavelength tunable laser and rapid
scanning system. A set of measurements of the field of a single element
spherically focusing HIFU transducer (H101, Sonic Concepts) driven at 1.1 MHz
with a 4 cycle burst, was made with the sensor at a variety of drive levels,
which at the lower end was compared against hydrophone measurements (0.2 mm
PVDF needle hydrophone, Precision Acoustics), and at the higher end was beyond
the damage threshold of conventional commercially available PVDF hydrophones,
and was compared with KZK simulations of the field. Volume scans were also performed to
demonstrate the feasibility of these given the rapid scan times.

The transducer was mounted pointing downwards into a small temperature
controlled tank filled with degassed, deionised water, with manually adjustable
xyz position. The Fabry-Perot sensor was mounted in the bottom of the tank in a
fixed position, and measurements were taken over the sensor area by scanning
the interrogation laser beam.

The directional frequency response of the sensor is included in the
frequency response field in the sensor dataset. This has size [1002, 978, 3],
where [:, 1, :] contains the frequency, [1, :, :] contains the angles, [2:end,
2:end , 1] is the magnitude response, [2:end, 2:end, 2] is the phase response,
and [2:end, 2:end, 3] is the smoothed/corrected magnitude correction (1/mag
response) that as applied to the data.

In total, this records contains 5 data files:

1.
Planar
field scan acquired with the Fabry Perot sensor at the focal plane at low
level, for comparison with hydrophone scans (Fig4).

2.
Planar
scans at the focal plane at three drive levels (Fig 5).

3.
Small
area planar scans at the focal plane at 22 different drive levels, 6 repeats up
to level 13, 3 repeats at levels 13-22: 94 datasets (Fig 6).

4.
Planar
scans at three different axial positions at an intermediate drive level. (Fig
7).

5.
Hydrophone
scans: a planar scan used to define the source boundary condition for KZK
simulations performed as a comparison with scans in file 2. A lateral line scan
acquired for comparison with the Fabry-Perot scan in file 1.

本研究旨在探究一种坚固的平面法布里-珀罗传感器在测量高声压潜力方面的应用。该传感器由全硬质介电材料制成，设计工作波长为1550纳米，与C-L波段（1516–1610纳米）波长可调激光和快速扫描系统相结合。通过该传感器对单元素球形聚焦高强聚焦超声（HIFU）换能器（H101，Sonic Concepts）在1.1 MHz频率下，以4周期脉冲驱动的场进行了测量，并在不同驱动级别下进行了测量，在低驱动级别与水听器测量（0.2 mm PVDF针式水听器，Precision Acoustics）进行了比较，在高驱动级别则超过了传统商用PVDF水听器的损伤阈值，并与KZK场模拟进行了比较。此外，还进行了体积扫描，以展示在快速扫描时间下的可行性。换能器被安装在向下指向的小型温度控制容器中，容器内充满脱气、去离子的水，具有可手动调节的xyz位置。法布里-珀罗传感器固定安装在容器底部，通过扫描询问激光束在该传感器区域内进行测量。传感器的方向性频率响应包含在传感器数据集中的频率响应字段中，其大小为[1002, 978, 3]，其中[:, 1, :]包含频率，[1, :, :]包含角度，[2:end, 2:end, 1]是幅度响应，[2:end, 2:end, 2]是相位响应，[2:end, 2:end, 3]是平滑/校正后的幅度校正（1/幅度响应），该校正应用于数据。总体而言，该记录包含5个数据文件：
1. 使用法布里-珀罗传感器在焦点平面低驱动级别获取的平面场扫描，用于与水听器扫描进行比较（图4）。
2. 焦点平面三个驱动级别的平面扫描（图5）。
3. 焦点平面22个不同驱动级别的微小区域平面扫描，13级以下重复6次，13-22级重复3次：94个数据集（图6）。
4. 中等驱动级别三个不同轴向位置的平面扫描（图7）。
5. 水听器扫描：用于定义KZK模拟源边界条件的平面扫描，与文件2中的扫描进行比较。用于与文件1中法布里-珀罗扫描比较的横向线扫描。