PUNRAP.m demonstrates phase unwrapping using synthetic data for light
passing through a glass bead. Neglect refraction, and simply compute straight line distances.
by Chuck DiMarzio Northeastern University May 2009
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Contents
Set parameters
x=(0:200)*1e-6; % location in meters r=75e-6; % bead radius dn=0.04; % Index of refraction of bead minus that of background lambda=0.6328e-6; % HeNe laser wavelength in microns m=0.3;% prism slope
Compute thickness and phase
y=m*x; field=exp(1i*2*pi*dn*y/lambda); % Complex field phi=angle(field); % Phase
Add some random noise
rand('twister',5489); % mlint doesn't like this line. grvreal=sum((rand(10,length(x))-0.5))*0.65; % Gaussian random variable grvimag=sum((rand(10,length(x))-0.5))*0.65; % Gaussian random variable field1=field+grvreal+1i*grvimag; % Add complex noise to field phi1=angle(field1); % Phase phi2=unwrap(phi1); % Matlab unwrap phase fig1=figure;plot(x*1e6,phi,x*1e6,phi1,x*1e6,phi2);grid on; xlabel('x, Location, \mu m'); ylabel('\phi, phase, rad');
Estimate y from unwrapped phase
yest=phi2*lambda/2/pi/dn; fig2=figure;plot(x*1e6,yest*1e6,x*1e6,y*1e6); grid on; xlabel('x, Location, \mu m'); ylabel('y, thickness, \mu m');
