Underwater Real-Time 3D Acoustical Imaging: Theory, Algorithm and System Design

121 Pages·2019·5.36 MB·English

by  Cheng Chi

Signals and Communication Technology
Cheng Chi
Underwater
Real-Time 3D
Acoustical
Imaging
Theory, Algorithm and System Design
Signals and Communication Technology
Thisseriesisdevotedtofundamentalsandapplicationsofmodernmethodsofsignal
processing and cutting-edge communication technologies. The main topics are
information and signal theory, acoustical signal processing, image processing and
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“Signals and Communication Technology” is indexed by Scopus.
More information about this series at http://www.springer.com/series/4748
Cheng Chi
Underwater Real-Time 3D
Acoustical Imaging
Theory, Algorithm and System Design
123
Cheng Chi
AcousticResearch Laboratory, Tropical
Marine Science Institute
National University ofSingapore
Singapore
ISSN 1860-4862 ISSN 1860-4870 (electronic)
Signals andCommunication Technology
ISBN978-981-13-3743-7 ISBN978-981-13-3744-4 (eBook)
https://doi.org/10.1007/978-981-13-3744-4
LibraryofCongressControlNumber:2018968372
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To my beloved Yu, my parents and sister
Preface
Underwater real-time three-dimensional (3-D) acoustical imaging systems are able
to capture real-time 3-D acoustical video. Other underwater acoustical imaging
systems suchas side-scan andmulti-beam sonars canonly obtaintwo-dimensional
(2-D) images. Additionally, compared to underwater optical cameras, underwater
real-time 3-D acoustical imaging systems achieve much longer imaging distance.
Thus, underwater real-time 3-D acoustical imaging systems are becoming
increasingly important in many applications such as underwater construction, pipe
inspection, dredging, archaeology, anti-terrorist and diver detection.
This book will cover the theory, algorithms and system design of underwater
real-time3-Dacousticalimaging.Theexistingunderwaterreal-time3-Dacoustical
imaging systems are narrowband. The techniques involved in developing narrow-
band systems, such design of large sparse 2-D arrays, fast beamforming are pre-
sentedinourbook.Moreimportantly,thisbooksummarizestherecentadvancesin
wideband and ultrawideband underwater real-time 3-D acoustical imaging, which
will be very useful for developing next-generation underwater real-time 3-D
acoustical imaging systems. The simulation technique of underwater real-time 3-D
acoustical imaging is also given in this book. It will help readers to learn and
develop underwater real-time 3-D acoustical imaging systems fast.
In Chap. 1, this book presents an overview of underwater real-time 3-D
acoustical imaging. The basic theories of underwater real-time 3-D acoustical
imaging are introduced in Chap. 2. Chapter 3 shows the fast 3-D beamforming
methodsforunderwaterreal-time3-Dacousticalimaging.Thedesigntechniquesof
large sparse 2-D arrays of underwater 3-D acoustical imaging, including narrow-
band, wideband and ultrawideband, are presented and discussed in Chap. 4. The
simulationtechniquefordesigningthese3-DsystemsisgiveninChap.5.Thesteps
ofdesigningunderwaterreal-time3-DacousticalsystemsarepresentedinChap.6.
Finally, this book outlines the future research potentials in Chap. 7.
Singapore Cheng Chi
November 2018
vii
Acknowledgements
The author would like to express my sincere thanks to Prof. Zhaohui Li,
Prof.RenqianWang,Prof.QihuLi,Prof.JiyuanLiu,Dr.PengWang,Dr.JianCui,
Dr. Yang Zhang, Dr. Yu Hao and Dr. Pallayil Venugopalan.
The author thanks the editors of this series and the Springer team for their
valuable guidance and assistance.
ix
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Underwater Real-Time 3-D Acoustical Imaging Systems . . . . . . . 1
1.1.1 Practical Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1.2 Systems at Simulation Stages . . . . . . . . . . . . . . . . . . . . . . 6
1.1.3 Summary of the Systems . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.2 Key Techniques in Developing Underwater Real-Time 3-D
Imaging Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3 Structure of This Book . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2 Basic Theory for Underwater Real-Time 3-D Acoustical
Imaging. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1 Data Model for Underwater Real-Time 3-D Imaging . . . . . . . . . . 11
2.2 Imaging Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.2.1 Beamforming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.2.2 Acoustic Holography . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
2.2.3 Summary of the Imaging Methods . . . . . . . . . . . . . . . . . . 17
2.3 Parameters for Underwater Real-Time 3-D Acoustical
Imaging Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.4 Image Displaying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3 Fast 3-D Beamforming Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.1 Basic Beamforming Theory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.1.1 Time-Domain Delay-and-Sum Beamforming . . . . . . . . . . . 23
3.1.2 Frequency-Domain Direct Beamforming . . . . . . . . . . . . . . 24
3.1.3 Delay Approximation. . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
3.2 General Techniques for Different Beamforming Methods . . . . . . . 26
3.2.1 Dynamic Focusing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.2.2 Partial Overlapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
xi
xii Contents
3.3 Time-Domain FFT Beamforming. . . . . . . . . . . . . . . . . . . . . . . . . 28
3.4 CZT Beamforming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.5 NUFFT 3-D Beamforming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.5.1 NUFFT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.5.2 Beamforming with NUFFT . . . . . . . . . . . . . . . . . . . . . . . 37
3.5.3 Accuracy Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3.6 Compuational Load for Direct Method, CZT and NUFFT
Beamforming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.6.1 Equispaced 2-D Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.6.2 Arbitrary 2-D Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.6.3 Comparison. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.6.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
4 Design of Underwater Large Sparse 2-D Arrays . . . . . . . . . . . . . . . 55
4.1 Concept of Designing Large 2-D Arrays for Underwater 3-D
Imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
4.2 Narrowband 2-D Array. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.2.1 Definition of Narrowband Beam Pattern . . . . . . . . . . . . . . 56
4.2.2 Design Based on Simulated Annealing . . . . . . . . . . . . . . . 57
4.3 Fast Computation of Wideband Beam Pattern . . . . . . . . . . . . . . . 58
4.3.1 Definition of Wideband Beam Pattern. . . . . . . . . . . . . . . . 59
4.3.2 Fast Computation Method . . . . . . . . . . . . . . . . . . . . . . . . 60
4.3.3 Performance Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . 65
4.4 Wideband Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.4.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.4.2 Design Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.4.3 Performance of the Designed Array . . . . . . . . . . . . . . . . . 72
4.5 UWB Ultrasparse 2-D Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
4.5.1 Feasibility of Using theUWB Techniquefor Underwater
3-D Imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
4.5.2 Directivity of UWB 2-D Arrays . . . . . . . . . . . . . . . . . . . . 77
4.5.3 Modulation Technique for Improving SNR . . . . . . . . . . . . 81
4.5.4 Simulation for Ultrasparse UWB 3-D Imaging . . . . . . . . . 84
4.6 Ultralarge Ultrasparse UWB 2-D Arrays . . . . . . . . . . . . . . . . . . . 86
4.6.1 Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
4.6.2 Directivity of Ultralarge Ultrasparse UWB 2-D Arrays . . . 89
4.6.3 Simulation for High-Resolution UWB Underwater 3-D
Imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97