B Scan MATLAB imaging

< li > ultrasonic scanning imaging A < / li >

1, generate acoustic signal
Use chirp function to generate linear frequency modulation signal as acoustic signal. For example, generate a signal with frequencies from 2kHz to 8kHz:

Fs = 40e3; % 采样频率
t = 0:1/Fs:0.02; % 采样时间
f0 = 2e3; % 起始频率
f1 = 8e3; % 终止频率
x = chirp(t,f0,t(end),f1);

2. Analog echo signal
conv function is used to convolve acoustic signal and reflected signal to get echo signal. For example, suppose the echo signal is reflected at time 0.005s:

delay = 0.005; % 回波时延
nDelay = round(delay*Fs);
y = conv(x(nDelay:end),x(1:end-nDelay+1));

3. Display A scanning image
plot the echo signal into A scanning image using the plot function.

figure;
plot(t(1:length(y)),y);
xlabel('Time (s)');
ylabel('Amplitude');

• Ultrasound B-scan imaging

1, generate acoustic signal
as A scanning imaging.

2, analog echo signal
as A scanning imaging.

3. Two-dimensional scanning
The acoustic probe is scanned horizontally and longitudinally respectively, and transverse and longitudinal A-scanning results are obtained.

nScan = 100; % 扫描次数
xScan = zeros(nScan,length(y)); % 横向A扫描结果
yScan = zeros(nScan,length(y)); % 纵向A扫描结果
theta = linspace(0,pi/2,nScan);
for i = 1:nScan
    xScan(i,:) = conv(x(nDelay:end).*cos(theta(i)),x(1:end-nDelay+1));
    yScan(i,:) = conv(x(nDelay:end).*sin(theta(i)),x(1:end-nDelay+1));
end

4, two-dimensional image construction
will be horizontal and vertical