Calculating defocused, images

s_opticsDefocusWVF

We use wavefront methods to introduce defocus a diffraction limited lens.

* The code at the top of this script shows the steps explicitly.
* The code at the end shows a simpler way to set the defocus, but
  it hides the computations.

The logic in both cases is this

* We create a shift-invariant optics with wavefront parameters
* We specify the pupil diameter and the focal length
* We then set the defocus and recompute the oi.

Understanding the wavefront approach requires knowing a little bit about Zernike polynomials. Tutorials emphasizing the wavefront methods are described in t_wvf<TAB> tutorials.

See also: sceneCreate, s_opticsDefocus, opticsDefocusCore, humanWaveDefocus,

Test scene
Wavefront method
Now we compute with the oi as usual
Here is the point spread. Diffraction-limited in this case.
Adjust the defocus (in diopters)
Compute
The new pointspread
An alternative approach using only the oi<> methods
This should be the equivalent code
END

ieInit

Test scene

% scene = sceneCreate('freqorient',[512 512]);
scene = sceneCreate('point array',[512 512],128);

scene = sceneSet(scene,'fov',1.5);
ieAddObject(scene);

Warning: Colon operands must be real scalars. This warning will become an error
in a future release.

Wavefront method

% This the explicit method for creating the wavefront and building the
% oi
wvf0 = wvfCreate('wave',sceneGet(scene,'wave'));

% This is how to set the focal length and pupil diameter explicitly.
% A lot of optics is in millimeters.  Not a great thing.
wvf0 = wvfSet(wvf0,'focal length',8);    % Millimeters
wvfGet(wvf0,'focal length','mm')
wvf0 = wvfSet(wvf0,'pupil diameter',3);  % Millimeters
wvfGet(wvf0,'pupil diameter','mm')

% We calculate the pointspread explicitly
wvf0 = wvfCompute(wvf0);

% Finally, we convert the wavefront representation to a shift-invariant
% optical image with this routine.
oi0 = wvf2oi(wvf0);

oiPlot(oi0,'psf 550');

% Here is the summary
fprintf('f# %0.2f and defocus %0.2f\n',oiGet(oi0,'fnumber'),oiGet(oi0,'wvf','zcoeffs','defocus'));

ans =

    8.0000


ans =

     3

f# 2.67 and defocus 0.00

Now we compute with the oi as usual

oi0 = oiCompute(oi0,scene,'crop',true);
oi0 = oiSet(oi0,'name','WVF: Diffraction limited');
oiWindow(oi0);

Here is the point spread. Diffraction-limited in this case.

% Notice the Airy disk units are not right in this plot.  Help!
oiPlot(oi0,'psf 550');

Adjust the defocus (in diopters)

diopters = 1.5;

wvf1 = wvfCreate('wave',sceneGet(scene,'wave'));

% Make a new one with some defocus
wvf1 = wvfSet(wvf1,'zcoeffs',diopters,'defocus');
wvf1 = wvfCompute(wvf1);
oi1 = wvf2oi(wvf1);
oiPlot(oi1,'psf 550');

fprintf('f# %0.2f and defocus %0.2f\n',oiGet(oi1,'fnumber'),oiGet(oi1,'wvf','zcoeffs','defocus'));

f# 5.73 and defocus 1.50

Compute

oi1 = oiCompute(oi1,scene,'crop',true);
oi1 = oiSet(oi1,'name','Defocused');
oiWindow(oi1);

The new pointspread

oiPlot(oi1,'psf 550');
set(gca,'xlim',[-20 20],'ylim',[-20 20]);

An alternative approach using only the oi<> methods

wvf = wvfCreate('wave',sceneGet(scene,'wave'));

oi = oiCreate('wvf',wvf);   % Diffraction limited
oi = oiCompute(oi,scene);
oi = oiSet(oi,'name','DL');
oiWindow(oi);

oiPlot(oi,'psf 550');
set(gca,'xlim',[-20 20],'ylim',[-20 20]);

This should be the equivalent code

wvf = oiGet(oi,'optics wvf');
wvf = wvfSet(wvf,'zcoeffs',diopters,'defocus');
oi = oiSet(oi,'optics wvf',wvf);
oiPlot(oi,'psf 550');
set(gca,'xlim',[-20 20],'ylim',[-20 20]);

oi = oiCompute(oi,scene);
oi = oiSet(oi,'name','defocused');
oiWindow(oi);

%{
  % This is what happens in the oiSet() above
  wvf1 = oiGet(oi,'wvf');
  wvf1 = wvfSet(wvf1,'zcoeffs',1.5,'defocus');
  wvf1 = wvfCompute(wvf1);
  oi1  = wvf2oi(wvf1);
%}