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Exponential time decay and laser scanning instrument
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| simran@teleline.es 2005-04-25, 8:59 pm |
| Hi all-
I have written the following code to study the effect of fluorescence
lifetime decay in a theoretical laser scanning microscope:
%%%%%%%%%
function f1=DFD;
%create data set
data=zeros(1,256);
data(:,:)=0.7;
data(128:168)=0.3;
t=[1:256]-128;
%bi-exponential decay function
a= 0.8935; b= -0.376;
filter=fftshift(a*exp(b*t));
%apply function on data
f1=ifft(fft(filter).*fft(data));
f1=f1./max(f1(:))*data(1,1);
figure, plot(t,fftshift(f1),'r:',t,data,'b-')
axis([-128 128 0 1])
xlabel('time, or pixel position')
ylabel('pixel brightness')
title('exponential lifetime decay')
%%%%%%%%%
The data-set represents one scan line that includes a central block
with lower brightness values. I want to study the theoretical effect of
the fluorescence life time decay on the edges in the data-set:
When the scanner moves from a lighter to a darker pixel the lifetime
decay effect blurs the sharp edge as photons excited at pixel x-1 (and
x-2 etc) arrives at pixel location x and increases its pixel brightness
value.
However, when the scanner moves from a darker pixel to a lighter pixel
the lifetime effect should be much smaller (as the contribution to
pixel brightness x is much smaller from the preceding darker pixels).
In my model the effect is the same, which is clearly wrong.
Could someone please recommend how this can be modeled.
Many thanks in advance.
-Peter
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| simran@teleline.es 2005-04-25, 8:59 pm |
| Sorry, there was a typo in the code. It should be:
%%%%%%%%%
function f1=DFD;
%create data set
data=zeros(1,256);
data(:,:)=0.7;
data(128:168)=0.3;
t=[1:256]-128;
%bi-exponential decay function
a= 0.8935; b= -0.376;
filter=fftshift(a*exp(b*t));
%apply function on data
f1=ifft(fft(filter).*fft(data) );
f1=f1./max(f1(:))*data(1,1);
figure, plot(t,fftshift(f1),'r:',t,data,'b-')
axis([-128 128 0 1])
xlabel('time, or pixel position')
ylabel('pixel brightness')
title('exponential lifetime decay')
%%%%%%%%%
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