Point Spread Function translate to MTF

I have point spread function (PSF) containing x and y data. x=[-25.132,-18.849,-12.566,-6.283,-3,0,3,6.283,12.566,18.849,25.132] y=[0.21446,0.21446,0.21446,0.21446,44,44.15754,44,0.21446,0.21446,0.21446,0.21446] This is point spread function (PSF). From this PSF I would like to calculate the Modulation Transfer Function MTF. I write the matlab code : x=[-25.132,-18.849,-12.566,-6.283,-3,0,3,6.283,12.566,18.849,25.132] y=[0.21446,0.21446,0.21446,0.21446,44,44.15754,44,0.21446,0.21446,0.21446,0.21446] PSF=[x,y] OTF = psf2otf(PSF) plot(OTF) How could I modified correct this code?Any Help is higly welcome. Thank you very much in advance.

cheers

Che-Wen

Answer 1

[Craig Draper]

x=[-25.132,-18.849,-12.566,-6.283,-3,0,3,6.283,12.566,18.849,25.132];

y=[0.21446,0.21446,0.21446,0.21446,44,44.15754,44,0.21446,0.21446,0.21446,0.21446];

LSF = [x,y] % This is more like a line spread function

OTF = fftshift(fft(LSF)); % OTF

MTF = abs(OTF); % absolute value of OTF

MTF = MTF./max(MTF); % normalize

% correct sampling frequency for conversion on frequency bins to frequency

Size = length(MTF);

spacing = 3;% spacing between data points

fsx = abs(1/spacing); % turn into sampling frequency

a = linspace(-Size/2,Size/2,Size); % form scale for conversion based on frequency bins

conversionx = fsx./Size; % conversion factor for frequency bin units to frequency (unit^-1)

Psi = a.*conversionx; % frequency (unit^-1)

plot(Psi,MTF)

xlim([0,Psi(end)])

xlabel('cycles/unit')

ylabel('MTF')