*jwding@ustc.edu.cn; jinwending@ustc.edu; phone 86 187-5608-5711(mobile); fax 86 551 6360-1592
The micro-sized internal structure in acoustic image
by 3D impulse scanning acoustic microscopy
Jinwen Ding*
a1
, Kang Li
b
, Ning Li
c
, Guochao He
a2
, Qingping Zhang
a1
a1
CAS Key Laboratory of Materials for Energy Conversion, Department of Material Science and
Engineering;
a2
School of Computer and Technology,
University of Science and Technology of China, 96 Jinzhai Road, Hefei, China 230026;
b
Anhui Province Coal Science Research Institute, 81 Xuancheng Road, Hefei, China 230001;
c
Special Equipment Safety Inspection Institute of Jiangsu Province, Suzhou Branch,
188 Pinglong Road, Suzhou, China 215031
ABSTRACT
The properties of a solid specimen depend on its elastic property and microstructures, which are not only in nano size but
also in micro-sized scale. Impulse acoustic microscope is a technology, employing a focused ultrasound probe beam in
immersion to penetrate into a solid specimen, and to detect the internal micro-sized structure by acoustic imaging for a
solid bulk material. Acoustic lens produces such a probe beam into a specimen and receives response radiations reflected
from the specimen. The characters of an acoustic lens determine the precision and quality of acoustical imaging; and the
relevant controlling techniques are also important peripheral elements for the system. But it is ignored or has not raised
attention that the acoustic interaction behavior between the focused ultrasound probe beam and an internal micro-sized
structure in a bulk - diffraction, scatter phenomena - usually also presents an inevitable impact on acoustic images. In this
paper, the authors try to introduce these principles to demonstrate that these factors are the fundamental keys, to promote
the performance of Impulse Scanning Acoustic Microscopy.
Keywords: Impulse scanning acoustic microscope, acoustic Lens, focused beam, acoustical imaging, Three-Dimensional
image, diffraction, scatter, signal aberration
1. INTRODUCTION
Nowadays modern industry pays more attention to high precision products, which are widely used in high-tech fields. It
demands more highly reliable quality of such products than in traditional fields. The micro-sized internal defects inside
the solid material hide extreme risk in some modern applications. On the one hand, the properties of a solid specimen
depend on its elastic property and microstructures, not only in nano size but also in micro-sized scale in material
engineering. Scanning Acoustic Microscope (SAM) is such a technology with a capability, employing a focused
ultrasound probe beam in immersion to penetrate into a solid specimen, to measure the elastic property in a micro-sized
region of a specimen, and to detect the internal micro-sized structures by acoustic imaging for a solid bulk material. The
method is a non-destructive detecting technique. SAM provides three traditional kinds of acoustical imaging – A-Scan,
B-Scan and C-Scan in a Two-Dimensional imaging way. These images give the chance to see the information about the
internal structures (void, inclusion and defects) in micro scale of the material [1,2,3].
The properties of acoustic lens determine the fundamental resolution of SAM. The precision of mechanical scanning
system and the relevant controlling techniques is also important peripheral elements for SAM; Besides these native and
external factors, it is not raised any attention or even is ignored, that the ultrasound interaction behaviors between a
focused ultrasound probe beam and an internal structure in a bulk - diffraction, scatter phenomena - also play an
inevitable role in acoustical imaging. Edge diffraction caused by a focused probe beam with a sharp edge of elements
(microstructure) was reported by Ding & Levin et al. In the paper the authors introduced the edge diffraction mechanism
and its impact on 2D acoustical images, and gave experimental investigation on 3D imaging features by the diffracted
waves (2012). These ultrasound interactions cause fine ultrasound response, and result in a very imperceptible formation
in Two-Dimensional images. Diffraction and scatter phenomena are the result of interaction, caused by focused probe
beam and the micro edge of the internal structures. These formations influence all Two-Dimensional acoustic images,
resulting in additional acoustic pulse signal in A-Scan image, a pattern with a symmetrical parabola around the edge of
an internal structure in B-Scan image, and a blurred edge of a structure in C-Scan image [4]. All of these formations by
Proc. of SPIE Vol. 9903 99032N-1