k-Wave

1. Hussain
   

   Member
   Joined: Feb '12
   Posts: 14

   Hello Bradley,

   1. I'm working on the simulations using focused detector in 3D. I'm getting the signal from the object when it's in focus with the detector. Now when i move the source from the focus, still i'm able to receive the signal(even if the detector is not focusing). Is there any particular reason for this?

   2. Photo-acoustic imaging defines the boundary of the object very clearly. In my simulations i'm using a spherical object and plot time Vs recorded pressure. The signal looks like the one in the image attached.
   http://imageshack.us/photo/my-images/35/centertime.jpg/
   I would like to know if it's possible for me to see the signal from the surface that's closer to detector and also from surface opposite to the detector.

   I'm indeed thankful to you for continuously guiding me.

   Regards,

   Hussain

   Posted 12 years ago #

2. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi Hussain,

   1. The directivity of a large single element detector arises because the output signal comes from spatially averaging the pressure field over the detector surface. This averaged signal will be much stronger when the acoustic waves all arrive in phase (for example, if a photoacoustic object is placed in the focus). When an object is not in the focus, acoustic waves will still reach the detector, but the average will be much weaker due to destructive interference.

   2. Why do you expect to get two different signals from the front and back surfaces? If it is because you are trying to model a band-limited detector, you can try filtering the recorded sensor data using applyFilter or gaussianFilter. An example of how these can be used is given here.

   Brad.

   Posted 12 years ago #

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