High resolution radiation imaging system

Claim 2

A radiation imaging system comprising: a photosensor pixel array, said array comprising a plurality of pixels having a predetermined photosensor pixel pitch between adjoining pixels, each of said photosensor pixels being adapted to generate a respective image data signal, said array being adapted to be sequentially disposed in selected ones of a plurality of sequential imaging positions pursuant to a predetermined imaging cycle, each of said sequential imaging positions being selected such that the area imaged by each respective pixel overlaps a portion of the area imaged by said respective pixel while disposed in the preceding imaging position in said predetermined imaging cycle so as to oversample the imaged area; and an image processor coupled to said photosensor pixel array so as to receive the respective image data signals generated by said photosensor pixels, said image processor being adapted to store said respective image data signals generated during an imaging cycle by said photosensor pixels in each of said respective sequential imaging positions as an unfiltered data set, said image processor further comprising a deblurring filter adapted to selectively filter said data set to generate a non-aliased fine resolution data set having spatial resolution greater than the imaging system Nyquist frequency determined by the pixel pitch of said photosensor array.

Claim 3

The imaging system of claim 1 wherein said plurality of sequential imaging positions comprises respective first, second, third, and fourth sequential imaging positions.

Claim 4

The imaging system of claim 2 wherein said first, second, third, and fourth imaging positions are disposed such that the distance between adjacent sequential imaging positions along a selected axis of movement of said photosensor pixel array is substantially one-half of said predetermined pitch of said pixels.

Claim 5

The imaging system of claim 3 wherein said first through fourth imaging positions are disposed so as to form the corners of a square with sides having a length of one-half said predetermined pitch of said pixels.

Claim 6

The imaging system of claim 2 wherein said photosensor pixel array comprises a plurality of pixels arranged in N rows and M columns.

Claim 7

The imaging system of claim 5 wherein said image processor is adapted to store in each unfiltered data set one image data signal generated by each respective photosensor pixel in each of said respective sequential imaging positions.

Claim 8

The imaging system of claim 6 wherein said deblurring filter is adapted such that said fine resolution data set generated by said filter resolves objects having spatial frequency components above the imaging system's Nyquist frequency.

Claim 9

The imaging system of claim 7 wherein said deblurring filter is adapted such that said fine resolution data set generated by said filter exhibits a spatial resolution capable of resolving objects of a size of one-half the predetermined photosensor pixel pitch.

Claim 10

The imaging system of claim 8 wherein said deblurring filter is adapted to form said fine resolution image in accordance with the equation: ##EQU2## wherein: F(W x , W y ) is the Fourier transform of the desired high resolution image; G(W x , W y )is the Fourier transform of the unfiltered image; H*(W x , W y )is the Fourier transform of the point spread function of the imaging system; |H(W x , W y )| is the modulation transfer function of the imaging system; a represents a positive constant selected to reduce amplification of G at higher spatial frequencies so as to limit the high frequency noise.

Claim 11

The imaging system of claim 8 wherein said deblurring filter is adapted to form said fine resolution image in accordance with the convolution: f(m,n)=Σ.sub.p,q k(m-p,n-q)g(p,q) in which k(m-p, n-q) represents the inverse Fourier transform of K, the Wiener filter spectrum; and g(p,q) represents the unfiltered image.

Claim 12

The imaging system of claim 5 further comprising a display and analysis module coupled to said image processor and adapted to receive the high resolution data set signals.

Claim 13

The imaging system of claim 11 wherein said display and analysis module comprises a display array having at least 2N by 2M display pixels, said display array having a pitch of about one-half said predetermined imaging pixel pitch.

Claim 14

The imaging system of claim 2 wherein said imaging system further comprises a displacement mechanism adapted to sequentially position said photosensor array at respective ones of said imaging positions in accordance with said predetermined imaging cycle.

Claim 15

The imaging system of claim 13 wherein said displacement mechanism comprises: a displacement platform, a first drive cam coupled to said displacement platform such that motion of said drive cam is translated into movement of said displacement platform along a first selected axis, and a second drive cam coupled to said displacement platform such that motion of said drive cam is translated into movement of said displacement platform along a second selected axis.

Claim 16

The imaging system of claim 14 wherein each of said drive cams has a respective eccentric shape selected to cause displacement of said platform along the respective selected axis upon rotation of the respective cam.

Claim 17

The imaging system of claim 15 wherein said displacement mechanism is adapted such that each of said first and second axes are disposed so that selective movement of said displacement platform along said respective axes displaces said photosensor pixel army to a selected one of said imaging positions.

Claim 18

The imaging system of claim 16 wherein said predetermined pitch between photosensor pixels is about 100 microns.

Claim 19

The imaging system of claim 17 wherein said imaging system is adapted to detect and image incident x-rays.

Claim 22

The process of claim 19 wherein the step of sequentially positioning said array of photosensor pixels further comprises the steps of: displacing said photosensor pixel array in a selected sequence so that said array is respectively disposed at each of four imaging positions during said imaging cycle.

Claim 23

The method of claim 20 wherein the step of displacing said array further comprises sequentially translating said array along a first axis and a second axis, said first and second axes being orthogonal.

Claim 24

The method of claim 21 wherein the distance along said first and second axes between respective ones of said four imaging positions correspond to one-half the photosensor pixel pitch.

Claim 25

The method of claim 22 wherein the step of applying said unfiltered data to a deblurring filter to form said high resolution data set comprises filtering said unfiltered data set to generate an image having a spatial resolution corresponding to one-half the photosensor pixel pitch.

Claim 26

The method of claim 23 wherein the step of applying said unfiltered data set to a deblurring filter further comprises computing said high resolution image data set in accordance with the following relationship: ##EQU3## wherein: F(W x , W y ) is the Fourier transform of the desired high resolution image; G(W x , W y ) is the Fourier transform of the unfiltered image; H*(W x , W y )is the Fourier transform of the point spread function of the imaging system; |H(W x , W y )| is the modulation transfer function of the imaging system; a represents a positive constant selected to reduce amplification of G at higher spatial frequencies so as to limit the high frequency noise.

Claim 27

The method of claim 23 wherein the step of applying said unfiltered data set to a deblurring filter further comprises computing said high resolution image data set in accordance with the following convolution: f(m,n)=Σ.sub.p,q k(m-p,n-q)g(p,q) in which k(m-p, n-q) represents the inverse Fourier transform of K, the Wiener filter spectrum; and g(p,q) represents the unfiltered image.

Claim 28

The method of claim 25 further comprising the step of driving a display and analysis module to present said high resolution data.

Claim 31

The method of claim 27 wherein the step of generating multiple exposures further comprises the steps of selectively sequentially displacing an array of photosensor pixels to be disposed in respective ones of said imaging positions in accordance with an imaging cycle.

Claim 32

The method of claim 28 wherein the step of deblurring said image said data said further comprises the step of passing said data set through a deblurring filter, said deblurring filter comprising a Wiener filter.

Claim 33

The method of claim 29 wherein said imaging positions are selected to cancel aliasing errors in said high resolution data set.

Claim 34

An x-ray imaging system comprising: a photosensor pixel array, said array comprising a plurality of pixels having a predetermined photosensor pixel pitch between adjoining pixels, each of said photosensor pixels being adapted to generate a respective image data signal, said array being adapted to be sequentially disposed in selected ones of a plurality of sequential imaging positions pursuant to a predetermined imaging cycle, each of said sequential imaging positions being selected such that the area imaged by each respective pixels overlaps a portion of the area imaged by said respective pixel while disposed in the preceding imaging position in said predetermined imaging cycle so as to oversample the imaged area; and an image processor coupled to said photosensor pixel array so as to receive the respective image data signals generated by said photosensor pixels, said image processor being adapted to store said respective image data signals generated during an imaging cycle by said photosensor pixels in each of said respective sequential imaging positions as an unfiltered data set, said image processor further comprising a deblurring filter adapted to selectively filter said data set to generate a non-aliased fine resolution data set having spatial resolution greater than the Nyquist frequency determined by the pixel pitch of said photosensor array; and a display and analysis module coupled to said image processor and adapted to be driven by said fine resolution data to generate an output fine resolution array, said output fine resolution array having a greater number of pixels than said photosensor pixel array, said imaging system being adapted such that each of the fine resolution pixels are driven by an individually-variable signal.

Claim 35

An x-ray imaging system comprising: a photosensor pixel array, said array comprising a plurality of pixels having a predetermined photosensor pixel pitch between adjoining pixels, each of said photosensor pixels being adapted to generate a respective image data signal, said array being adapted to be sequentially disposed in selected ones of a plurality of sequential imaging positions pursuant to a predetermined imaging cycle, each of said sequential imaging positions being selected such that the area imaged by each respective pixels overlaps a portion of the area imaged by said respective pixel while disposed in the preceding imaging position in said predetermined imaging cycle so as to oversample the imaged area; and an image processor coupled to said photosensor pixel array so as to receive the respective image data signals generated by said photosensor pixels, said image processor being adapted to store said respective image data signals generated during an imaging cycle by said photosensor pixels in each of said respective sequential imaging positions as an unfiltered data set, said image processor further comprising a deblurring filter adapted to selectively filter said data set to generate a non-aliased fine resolution data set having spatial resolution greater than the Nyquist frequency determined by the pixel pitch of said photosensor array; and a display and analysis module coupled to said image processor and adapted to be driven by said fine resolution data to generate an output fine resolution array, said output fine resolution array having a greater number of pixels than said photosensor pixel array, said imaging system being adapted such that each of the fine resolution pixels are driven by an individually-variable signal.

Claim 36

The imaging system of claim 31 wherein said plurality of sequential imaging positions comprises respective first, second, third, and fourth sequential imaging positions.

Claim 37

The imaging system of claim 32 wherein said first, second, third, and fourth imaging positions are disposed such that in each respective imaging position each photosensor pixel is centered on one of the respective areas representing a corresponding pixel element in the output fine resolution array, and further the four imaging positions are disposed such that each area representing a pixel element in said output high resolution array is centered on a respective photosensor pixel in only one of said four imaging positions.

Claim 38

The imaging system of claim 33 wherein the distance between adjacent sequential imaging positions along a selected axis of movement of said photosensor pixel array is substantially one-half of said predetermined pitch of said photosensor pixels.

Claim 39

The imaging system of claim 34 wherein said imaging system further comprises a displacement mechanism adapted to move said photosensor array so as to selectively dispose said photosensor array in a selected one of said imaging positions, said displacement mechanism comprising: a displacement platform, a first drive cam coupled to said displacement platform such that motion of said drive cam is translated into movement of said displacement platform along a first selected axis, and a second drive cam coupled to said displacement platform such that motion of said drive cam is translated into movement of said displacement platform along a second selected axis.

Claim 40

The imaging system of claim 35 wherein each of said drive cams has a respective eccentric shape selected to cause displacement of said platform along the respective selected axis upon rotation of the respective cam.

Claim 41

The imaging system of claim 36 wherein said displacement mechanism is adapted such that each of said first and second axes are disposed so that selective movement of said displacement platform along said respective axes displaces said photosensor pixel array to a selected one of said imaging positions.

Claim 42

The imaging system of claim 37 further comprising a scintillator optically coupled to said photosensor pixel array and disposed to receive radiation passing from an object to be imaged.

Claim 43

The imaging system of claim 37 wherein said photosensor array comprises a radiation absorptive photosensitive material such that radiation incident on said imaging system is absorbed by said material and converted into mobile charge particles to generate said image data signals.