psf2otf (Image Processing Toolbox User's Guide)

Image Processing Toolbox User's Guide

Convert point-spread function to optical transfer function

Syntax

OTF = psf2otf(PSF)
OTF = psf2otf(PSF,OUTSIZE)

Description

OTF = psf2otf(PSF) computes the fast Fourier transform (FFT) of the point-spread function (PSF) array and creates the optical transfer function array, OTF, that is not influenced by the PSF off-centering. By default, the OTF array is the same size as the PSF array.

OTF = psf2otf(PSF,OUTSIZE) converts the PSF array into an OTF array, where OUTSIZE specifies the size of the OTF array. OUTSIZE cannot be smaller than the PSF array size in any dimension.

To ensure that the OTF is not altered because of PSF off-centering, psf2otf postpads the PSF array (down or to the right) with 0's to match dimensions specified in OUTSIZE, then circularly shifts the values of the PSF array up (or to the left) until the central pixel reaches (1,1) position.

Note that this function is used in image convolution/deconvolution when the operations involve the FFT.

Class Support

PSF can be any nonsparse, numeric array. OTF is of class double.

Example

PSF  = fspecial('gaussian',13,1);
OTF  = psf2otf(PSF,[31 31]); % PSF --> OTF
subplot(1,2,1); surf(PSF); title('PSF');
axis square; axis tight
subplot(1,2,2); surf(abs(OTF)); title('Corresponding |OTF|');
axis square; axis tight

See Also

otf2psf, circshift, padarray

poly2mask qtdecomp