Refractive x-ray element
For reducing absorption in a refractive element, the present invention relates to a refractive element ( 10, 20 ), suitable for refracting x-rays, comprising a body with low-Z material having a first end adapted to receive rays emitted from a ray source and a second end from which the rays received at the first end emerge. The refractive element comprises columns of stacked substantially identical prisms ( 21 ). The invention also relates to lens element.
1. An x-ray refractive element formed of a body of low-Z material having a first end adapted to receive x-rays emitted from an x-ray source and a second end from which the x-rays received at the first end emerge, said x-ray refractive element comprising:
a first row of substantially identical prisms disposed between said first end and said second end along a first direction, and
a second row of substantially identical prisms disposed between said first and second ends along the first direction, each of said prisms of said first row and each of said prisms of said second row being of a substantially triangular shape having two side portions and one base portion,
said first row of substantially identical prisms being arranged on top of said second row of substantially identical prisms in a second direction perpendicular to the first direction such that a base portion of a given prism in said first row faces an intersection point of said side portions of a given prism in said second row.
2. The x-ray refractive element of claim 1 , wherein said prisms of said first and second rows are produced by removal of material, the removed material having a width corresponding to a multiple of a phase-shift length (L 2π ) of 2π.
3. The x-ray refractive element of claim 1 , wherein an intensity transmission of the x-ray refractive element is:
T ( y )=exp(− X ( y )/ l )=exp(− k|y|l ),
where X(y) is the total path length for a ray through the element, l is an attenuation length, k is constant and y is the distance to the optical axis.
4. The x-ray refractive element of claim 1 , wherein an effective aperture is defined by:
D
=
8
δ
2
lF
λ
tan
θ
,
where F is the focal length, δ is the decrement of a real part of an index of refraction, l is an attenuation length and Θ is the side angle of the prisms.
5. The x-ray refractive element of claim 1 , wherein an aperture increase factor (AIF) is defined by:
AIF
=
3.2
·
σ
abs
L
2
π
tan
θ
,
where σ abs is root-mean-square width of a Multi-Prism Lens (MPL) aperture, L 2π is 2π-shift length, and Θ is the side angle of the prisms.
6. The x-ray refractive element of claim 1 , wherein said x-ray refractive element is made of one or more of silicon and diamond.
7. The x-ray refractive element of claim 1 , wherein a focal length is controlled according to a deviation length (y g ) of one end of the element with respect to an incident ray.
8. An x-ray lens formed of a body of low-Z material having a first end adapted to receive rays emitted from an x-ray source and a second end from which the rays received at the first end are refracted, wherein said x-ray lens is comprised of two portions, each of said portions comprising:
a first row substantially identical prisms, disposed between said first end and said second end along a first direction, and
a second row of substantially identical prisms disposed between said first and second ends along the first direction, each of said prisms of said first row and each of said prisms of said second row being of a substantially triangular shape having two side portions and one base portion,
said first row of substantially identical prisms being arranged on top of said second row of substantially identical prisms in a second direction perpendicular to the first direction such that a base portion of a given prism in said first row faces an intersection point of said side portions of a given prism in said second row.
9. The x-ray lens of claim 8 , wherein said prisms of said first and second rows are produced by removing material, the removed material having a width corresponding to a multiple of a phase-shift length (L 2π ) of 2π.
10. The x-ray lens of claim 8 , wherein said first and second rows are displaced relative to each other.
11. The x-ray lens of claim 10 , wherein said first and second rows are rotated relative to each other.
12. The x-ray lens of claim 10 , wherein said first and second rows are arranged in series.
13. An x-ray apparatus, comprising:
at least one x-ray source;
a detector assembly; and
an x-ray refractive element comprising a body of low-Z material having a first end adapted to receive x-rays emitted from an x-ray source and a second end from which the x-rays received at the first end emerge, said x-ray refractive element comprising:
a first row of substantially identical prisms disposed between said first end and said second end along a first direction, and
a second row of substantially identical prisms disposed between said first and second ends along the first direction, each of said prisms of said first row and each of said prisms of said second row of being of a substantially triangular shape having two side portions and one base portion,
said first row of substantially identical prisms being arranged on top of said second row of substantially identical prisms in a second direction perpendicular to the first direction such that a base portion of a given prism in said first row faces an intersection point of said side portions of a given prism in said second row.
14. An x-ray apparatus, comprising:
at least one x-ray source;
a detector assembly; and
an x-ray lens formed of a body formed of low-Z material having a first end adapted to receive rays emitted from an x-ray source and a second end from which the rays received at the first end are refracted, wherein said x-ray lens is comprised of two portions, each of said portions comprising:
a first row of substantially identical prisms, disposed between said first end and said second end along a first direction, and
a second row of substantially identical prisms disposed between said first and second ends along the first direction, each of said prisms of said first row and each of said prisms of said second row being of a substantially triangular shape having two side portions and one base portion,
said first row of substantially identical prisms being arranged on top of said second row of substantially identical prisms in a second direction perpendicular to the first direction such that a base portion of a given prism in said first row faces an intersection point of said side portions of a given prism in said second row.
15. The x-ray apparatus of claim 13 , wherein said prisms of said first and second rows are produced by removal of material, the removed material having a width corresponding to a multiple of a phase-shift length (L 2π ) of 2π.
16. The x-ray apparatus of claim 13 , wherein an intensity transmission of the element is:
T ( y )=exp(− X ( y )/ l )=exp(− k|y|l ),
where X(y) is the total path length for a ray through the element, l is an attenuation length, k is constant and y is the distance to the optical axis.
17. The x-ray apparatus of claim 13 , wherein an effective aperture is defined by:
D
=
8
δ
2
lF
λ
tan
θ
,
where F is the focal length, δ is the decrement of a real part of an index of refraction, l is an attenuation length and Θ is the side angle of the prisms.
18. The x-ray apparatus of claim 13 , wherein an aperture increase factor (AIF) is defined by:
AIF
=
3.2
·
σ
abs
L
2
π
tan
θ
,
where σ abs is root-mean-square width of Multi-Prism Lens (MPL) aperture, L 2π is 2π-shift length, and Θ is the side angle of the prisms.
19. The x-ray apparatus of claim 13 , wherein said x-ray refractive element is made of one or more of silicon and diamond.
20. The x-ray apparatus of claim 13 , wherein a focal length is controlled according to a deviation length (y g ) of one end of the element with respect to an incident ray.
21. The x-ray apparatus of claim 14 , wherein said prisms of said first and second rows are produced by removing material, the removed material having a width corresponding to a multiple of a phase-shift length (L 2π ) of 2π.
22. The x-ray apparatus of claim 14 , wherein said first and second rows are displaced relative to each other.
23. The x-ray apparatus of claim 22 , wherein said first and second rows are rotated relative to each other.
24. The x-ray apparatus of claim 22 , wherein said first and second rows are arranged in series.