Spread field imaging collimators for radiation-based imaging and methods of using the same

A method for image processing, comprising:

• obtaining an image, wherein the image is an object image at a distance from a collimator having repetitive basic patterns, each basic pattern is a (X×Y) aperture pattern, wherein the image has M sections and each of the M sections has X rows and Y columns of pixels, wherein each of M, X, and Y is an integer greater than 0, and the X rows and Y columns of pixels in each of the M sections are indexed from 1 to (X×Y);
• deriving (X×Y) sub-images from the image, wherein each sub-image has M sections and each section of each sub-image has X rows and Y columns of pixels, the (X×Y) sub-images are indexed from 1 to (X×Y), wherein for each j-th section of each i-th sub-image, the i-th pixel has a pixel value equal to a pixel value of the i-th pixel of the j-th section of the image and other pixels of the j-th section of the i-th sub-image are set to 0, where i traverses from 1 to (X×Y), and j traverses from 1 to M;
• providing (X×Y) projection patterns by projecting a point source at a plane located at the distance from the collimator with the point source being directly above one of the apertures of the basic pattern;
• for each of the (X×Y) sub-images, calculating a projection by performing convolution of the respective sub-image with a corresponding one of the projection patterns, thereby obtaining (X×Y) projected sub-images;
• and
• summing up the (X×Y) projected sub-images, thereby obtaining a projection of the image.

A method of misalignment correction in an imaging system, comprising:

• providing a collimator and a detector, the detector having a digitized pixel grid;
• illuminating the collimator with a flood light source;
• recording signal intensities in each pixel of the digitized pixel grid, wherein the signal intensities are caused by the illuminating of the collimator;
• deriving a descriptor from the recorded signal intensities;
• generating a series of offsets to be introduced to the digitized pixel grid;
• finding a selected offset from the series of offsets that optimizes the descriptor;
• and
• regenerating the digitized pixel grid based on an actual offset derived from the selected offset.