http://www.k-wave.org/forum/topic/photo-acoustic-imaging-1 Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 00:41:23 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/photo-acoustic-imaging-1#post-5319 Tue, 24 Nov 2015 15:15:40 +0000 Bradley Treeby 5319@http://www.k-wave.org/forum/ <p>Hi Kamal,</p> <p>What is it about the output that makes you say you are "getting quite not convincing different plot"? Did you see my response to your query <a href="http://www.k-wave.org/forum/topic/various-input-signal">here</a>?</p> <p>Brad. </p> http://www.k-wave.org/forum/topic/photo-acoustic-imaging-1#post-5310 Sun, 08 Nov 2015 03:13:34 +0000 jnawali123@gmail.com 5310@http://www.k-wave.org/forum/ <p>how we can define the pulse width for the chirp signal.</p> <p>I want to give the chirp signal for 0.1 micron and i have used matlab chirp inbuilt function to go from 2e6 to 7e6. But i am getting quite not convincing different plot.</p> <p>% set the size of the perfectly matched layer (PML)<br /> PML_X_SIZE = 20; % [grid points]<br /> PML_Y_SIZE = 10; % [grid points]<br /> PML_Z_SIZE = 10; % [grid points]</p> <p>% set total number of grid points not including the PML<br /> Nx = 128 - 2*PML_X_SIZE; % [grid points]<br /> Ny = 128 - 2*PML_Y_SIZE; % [grid points]<br /> Nz = 64 - 2*PML_Z_SIZE; % [grid points]</p> <p>% set desired grid size in the x-direction not including the PML<br /> x = 40e-3; % [m]</p> <p>% calculate the spacing between the grid points<br /> dx = x/Nx; % [m]<br /> dy = dx; % [m]<br /> dz = dx; % [m]</p> <p>% create the k-space grid<br /> kgrid = makeGrid(Nx, dx, Ny, dy);</p> <p>% define the properties of the propagation medium<br /> medium.sound_speed = 1540; % [m/s]<br /> medium.alpha_coeff = 0.003660; % [dB/(MHz^y cm)]<br /> medium.alpha_power = 1.5 ; </p> <p>% create the time array<br /> [kgrid.t_array , dt] = makeTime(kgrid, medium.sound_speed);</p> <p>% define a single source point<br /> source.p_mask = zeros(Nx, Ny);<br /> source.p_mask(end - Nx/8, Ny/2) = 1;</p> <p>% define a time varying sinusoidal source<br /> source_freq = 2e6; % [Hz]<br /> source_mag = 1; % [Pa]<br /> t_offset = 5e-6;<br /> K=[2,9];<br /> pulsewidth_min=1e-6;<br /> for k=1:2<br /> source.p=zeros(size(kgrid.t_array));<br /> for i=1:200<br /> my_chirp = chirp(kgrid.t_array(i),source_freq,kgrid.t_array(1)+pulsewidth_min,7e6)+1;<br /> source.p(i) = source_mag*my_chirp;<br /> end</p> <p>for j=201:990<br /> source.p(i)=0;<br /> end<br /> % filter the source to remove high frequencies not supported by the grid</p> <p>source.p = filterTimeSeries(kgrid, medium, source.p);<br /> % figure<br /> % plot(kgrid.t_array,source.p)<br /> % axis('tight')<br /> % define a single sensor point<br /> sensor.mask = zeros(Nx, Ny);<br /> sensor.mask(Nx/8, Ny/K(k)) = 1;<br /> %sensor.mask(Nx/14, Ny/7) = 1;</p> <p>% define the acoustic parameters to record<br /> sensor.record = {'p', 'p_final'};</p> <p>% % run the simulation<br /> sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor);</p> <p>% plot the final wave-field<br /> figure;<br /> imagesc(kgrid.y_vec*1e3, kgrid.x_vec*1e3, sensor_data.p_final + source.p_mask + sensor.mask, [-1 1]);<br /> colormap(getColorMap);<br /> ylabel('x-position [mm]');<br /> xlabel('y-position [mm]');<br /> axis image;</p> <p>% plot the simulated sensor data<br /> figure;<br /> [t_sc, scale, prefix] = scaleSI(max(kgrid.t_array(:)));</p> <p>subplot(2, 1, 1), plot(kgrid.t_array*scale, source.p, 'b-');<br /> xlabel(['Time [' prefix 's]']);<br /> ylabel('Signal Amplitude');<br /> axis tight;<br /> title('Input Pressure Signal');</p> <p>subplot(2, 1, 2), plot(kgrid.t_array*scale, sensor_data.p, 'r-');<br /> xlabel(['Time [' prefix 's]']);<br /> ylabel('Signal Amplitude');<br /> axis tight;<br /> title('Sensor Pressure Signal');</p> <p>end </p>