View source for Acoustic lens


*https://www.youtube.com/watch?v=KnjzJkBboc4

*[http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1034&context=usafresearch Focusing of longitudinal ultrasonic waves in air with an aperiodic flat lens]

*http://www.nature.com/ncomms/2014/140227/ncomms4398/abs/ncomms4398.html

*http://www.esm.psu.edu/ultrasonics/pdf%20files/877_1.pdf

*[http://www.diyaudio.rs/JBL/JBL%20-%20The%20Acoustical%20Lens%20%281962%29.pdf The acoustical lens 1962 Wireless woirld]

*[http://forums.audioholics.com/forums/loudspeakers/84676-vintage-jbl-acoustic-lenses-do-these-things-work.html Thread: vintage JBL "acoustic lenses"- do these things work?]

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*[http://www.ndk.com/en/sensor/ultrasonic/basic02.html Basic principle of medical ultrasonic probes (transducer)]
*[http://www.sonotech.com.pk/book/271 Basic Principle of Ultrasound.]
 Focusing:
 Mechanical - performed by placing an acoustic lens on the surface of the transducer or using a transducer with a concave face.
 External Focusing - a lens is used on the transducer face to bend the sound waves to a focal point.
 Internal Focusing - the piezoelectric element is formed in a curved element that focus the beam.
 Electronic - using a process called phased array, multiple elements are fired sequentially to focus the beam .
 Beam Focusing
 Array transducers have the ability to be dynamically focused by stimulating each element as shown in the diagram below. 
 The individual wave fronts add  up to a tight beam of ultrasound energy.
 Beam Steering:
 Array transducers have the ability to be steered as well as focused. Like focusing, 
 the beam is directed by sequentially stimulating each element as   shown. 
 This feature creates the sector scan by rapidly steering the beam from left to right 
 to give the two dimensional cross sectional image.


*[http://link.springer.com/chapter/10.1007%2F978-0-387-76540-2_8#page-1 BOOK: PIEZOELECTRIC AND ACOUSTIC MATERIALS FOR TRANSDUCER APPLICATIONS, SPRINGER Low-Attenuation Acoustic Silicone Lens ]
*[http://www.intechopen.com/books/ultrasound-imaging-medical-applications/3d-high-quality-ultrasonic-imaging 3D High-Quality Ultrasonic Imaging]
*[http://iopscience.iop.org/1347-4065/34/1R/312 Acoustic Properties of Lens Materials for Ultrasonic Probes ]
 The acoustic velocities and densities of 20 types of commercial rubber have been measured at a frequency of 2 MHz at room temperature, 
 and they are  evaluated in terms of their application to an acoustic lens or an acoustic window 
 of probes of an ultrasonic diagnostic instrument. 
 Fluorosilicone  rubber and phoshazene rubber have lower acoustic velocities than the human body, 
 and they have excellent impedance matching with the human body. 
 Both  the acoustic velocities and densities of butadiene rubber, polybutadiene rubber, 
 acrylic rubber and polyurethane match those of the human body. 
 It is  also described that rubber having good impedance matching with the human body 
 can be fabricated by adjusting the volume fraction of the added filler. 

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*[http://pc5214.org/index.php5/Project_Phonon_Photon Project Phonon Photon]

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