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Technical Discussions
S.Muralidharan
S.Muralidharan
09:54 Oct-24-2003
Geometrical focus of array transducers

I want to understand what is meant by geometrical focus of aray transducers(convex andlinear). Does it mean a lens in front of every element having a geometrical centre or a lens in front of the array colectively having a single geometrical focus point.
Thanks in advance for the clarification


    
 
 Reply 
 
Paul A. Meyer
R & D,
GE Inspection Technologies, USA, Joined Nov 1998, 47

Paul A. Meyer

R & D,
GE Inspection Technologies,
USA,
Joined Nov 1998
47
05:40 Oct-24-2003
Re: Geometrical focus of array transducers
Geometric focus refers to that part of the focusing due to the physical shape of the transducer or lenses attached to it. For example, bending an array transducer around a 30 cm radius cylinder would give it a 30 cm geometric focus. Similarly, all of the individual array elements could be curved to produce a focus in the transverse direction. This can also be done with lenses.
The diffraction of sound causes a 'natural focus' even on flat of nonfocused transducers. The 'natural focus' is dependent on the size, shape, and frequency of the transducers as well as the transmission medium.
So 'geometric focused' is used to indicate the mechanical aspects of the transdcuer focus independent of these diffractive effects.
I hope this helps.
Paul

----------- Start Original Message -----------
: I want to understand what is meant by geometrical focus of aray transducers(convex andlinear). Does it mean a lens in front of every element having a geometrical centre or a lens in front of the array colectively having a single geometrical focus point.
: Thanks in advance for the clarification
------------ End Original Message ------------




    
 
 Reply 
 
S.Muralidharan
S.Muralidharan
09:11 Oct-25-2003
Re: Geometrical focus of array transducers
----------- Start Original Message -----------
: Geometric focus refers to that part of the focusing due to the physical shape of the transducer or lenses attached to it. For example, bending an array transducer around a 30 cm radius cylinder would give it a 30 cm geometric focus. Similarly, all of the individual array elements could be curved to produce a focus in the transverse direction. This can also be done with lenses.
: The diffraction of sound causes a 'natural focus' even on flat of nonfocused transducers. The 'natural focus' is dependent on the size, shape, and frequency of the transducers as well as the transmission medium.
: So 'geometric focused' is used to indicate the mechanical aspects of the transdcuer focus independent of these diffractive effects.
: I hope this helps.
: Paul
: : I want to understand what is meant by geometrical focus of aray transducers(convex andlinear). Does it mean a lens in front of every element having a geometrical centre or a lens in front of the array colectively having a single geometrical focus point.
: : Thanks in advance for the clarification
------------ End Original Message ------------

Thanks Paul for the clarification.
A linear array transducer of 80 elements having geometrical focus at 70 mm will be understood , from your explanation as:
The individual elements are curved with 70 mm radius on their face side so that the line connecting all the geometrical focus points of all 80 elements will produce a geometrical focus line in the transverse direction to the direction of propogation.i.e parallel to the transducer face.Hope I am clear in my communication and I also believe this is what you meant ,Paul.
Thanks for your time and help.




    
 
 Reply 
 
Paul A. Meyer
R & D,
GE Inspection Technologies, USA, Joined Nov 1998, 47

Paul A. Meyer

R & D,
GE Inspection Technologies,
USA,
Joined Nov 1998
47
03:27 Oct-27-2003
Re: Geometrical focus of array transducers
To avoid confusion, I will email to you a sketch. If anyone else would like a copy, contact me.
Thanks,
Paul
----------- Start Original Message -----------
: : Geometric focus refers to that part of the focusing due to the physical shape of the transducer or lenses attached to it. For example, bending an array transducer around a 30 cm radius cylinder would give it a 30 cm geometric focus. Similarly, all of the individual array elements could be curved to produce a focus in the transverse direction. This can also be done with lenses.
: : The diffraction of sound causes a 'natural focus' even on flat of nonfocused transducers. The 'natural focus' is dependent on the size, shape, and frequency of the transducers as well as the transmission medium.
: : So 'geometric focused' is used to indicate the mechanical aspects of the transdcuer focus independent of these diffractive effects.
: : I hope this helps.
: : Paul
: : : I want to understand what is meant by geometrical focus ofaray transducers(convex andlinear). Does it mean a lens in front of every element having a geometrical centre or a lens in front of the array colectively having a single geometrical focus point.
: : : Thanks in advance for the clarification
: Thanks Paul for the clarification.
: A linear array transducer of 80 elements having geometrical focus at 70 mm will be understood , from your explanation as:
: The individual elements are curved with 70 mm radius on their face side so that the line connecting all the geometrical focus points of all 80 elements will produce a geometrical focus line in the transverse direction to the direction of propogation.i.e parallel to the transducer face.Hope I am clear in my communication and I also believe this is what you meant ,Paul.
: Thanks for your time and help.
------------ End Original Message ------------




    
 
 Reply 
 
Joerg Schulze-Clewing
Joerg Schulze-Clewing
02:42 Oct-28-2003
Re: Geometrical focus of array transducers
There is also some excellent simulation software from researchers.
For folks that have Matlab here is one from the experts in
Norway:

http://heim.ifi.uio.no/~sverre/papers/01_Matlab.pdf

I am not sure but I believe the underlying Matlab rountines
are available from them as freeware.

Regards, Joerg.

----------- Start Original Message -----------
: To avoid confusion, I will email to you a sketch. If anyone else would like a copy, contact me.
: Thanks,
: Paul
: : : Geometric focus refers to that part of the focusing due to the physical shape of the transducer or lenses attached to it. For example, bending an array transducer around a 30 cm radius cylinder would give it a 30 cm geometric focus. Similarly, all of the individual array elements could be curved to produce a focus in the transverse direction. This can also be done with lenses.
: : : The diffraction of sound causes a 'natural focus' even on flat of nonfocused transducers. The 'natural focus' is dependent on the size, shape, and frequency of the transducers as well as the transmission medium.
: : : So 'geometric focused' is used to indicate the mechanical aspects of the transdcuer focus independent of these diffractive effects.
: : : I hope this helps.
: : : Paul
: : : : I want to understand what is meant by geometrical focus of aray transducers(convex andlinear). Does it mean a lens in front of every element having a geometrical centre or a lens in front of the array colectively having a single geometrical focus point.
: : : : Thanks in advance for the clarification
: : Thanks Paul for the clarification.
: : A linear array transducer of 80 elements having geometrical focus at 70 mm will be understood , from your explanation as:
: : The individual elements are curved with 70 mm radius on their face side so that the line connecting all the geometrical focus points of all 80 elements will produce a geometrical focus line in the transverse direction to the direction of propogation.i.e parallel to the transducer face.Hope I am clear in my communication and I also believe this is what you meant ,Paul.
: : Thanks for your time and help.
------------ End Original Message ------------




    
 
 Reply 
 
Yasin KUMRU
Yasin KUMRU
22:12 Feb-03-2016
Re: Geometrical focus of array transducers
In Reply to Paul A. Meyer at 05:40 Oct-24-2003 .

I have a question about the focusing effect in medical ultrasonic imaging. I have a single element having a focus at 6 cm. How can I implement this focsing effect in matlab? Actually I am trying to find SNR. As expected, SNR will be max at this focus point. But I obtained this maxima at 0 cm because in my matlab code, Focusing is not implemented. How can I implement this focusing at a certain point for this single transducer? Thanks in advance.

    
 
 Reply 
 

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