Patent Number: 
Section: claims

1. An imaging device, comprising:a first scintillator layer;an array of detector elements, wherein the array of detector elements comprises a first detector element;a second scintillator layer, wherein the array of detector elements is located between the first scintillator layer and the second scintillator layer; anda first neutral density filter located between the first scintillator layer and the first detector element and/or a second neutral density filter located between the second scintillator layer and the first detector element;wherein the first detector element is configured to generate a first electrical signal in response to light from the first scintillator layer, and to generate a second electrical signal in response to light from the second scintillator layer;wherein the imaging device further comprises a first plate coupled to the first scintillator layer, and/or a second plate coupled to the second scintillator layer; andwherein the first plate and/or the second plate is configured to provide photons. 2. The imaging device of claim 1, wherein the first neutral density filter and/or the second neutral density filter is configured to improve a signal-to-noise ratio of the imaging device. 3. The imaging device of claim 1, wherein a signal-to noise ratio of the imaging device is based on (1) respective quantum efficiencies (QE1,QE2) of the first and second scintillator layers, (2) respective detective quantum efficiencies (DQE1,DQE2) of the first and second scintillator layers, (3) respective optical yields (α1, α2) of the first and second scintillator layers, (4) optical sensitivities (p1, p2) of the first detector element associated with the first and second scintillators respectively, or (5) a combination of any of the foregoing. 4. The imaging device of claim 1, wherein the second scintillator layer is configured to receive radiation after it has passed through the array of detector elements. 5. The imaging device of claim 1, further comprising a first electrode situated between the first scintillator and the first detector element, wherein the first electrode is configured to allow light from the first scintillator layer to reach the first detector element. 6. The imaging device of claim 5, further comprising a second electrode configured to allow the light from the second scintillator layer to reach the first detector element. 7. The imaging device of claim 6, wherein the second electrode is at least partially transparent to light. 8. The imaging device of claim 6, wherein the second electrode comprises a first opening for allowing the light from the second scintillator layer to pass therethrough. 9. The imaging device of claim 8, wherein the second electrode comprises a second opening. 10. The imaging device of claim 8, wherein the first opening comprises a circular opening, a square opening, a rectangular opening, or a slot. 11. The imaging device of claim 8, wherein the second electrode has a ring configuration. 12. The imaging device of claim 8, wherein the second electrode has a grid configuration, and the first opening is one of a plurality of grid holes. 13. The imaging device of claim 6, wherein the second electrode comprises a chrome layer. 14. The imaging device of claim 6, wherein the second electrode comprises ITO or another transparent conductor. 15. The imaging device of claim 6, wherein the first detector element comprises a hardware component, and wherein the second electrode and the hardware component are in a side-by-side configuration. 16. The imaging device of claim 15, wherein the second electrode comprises a conductor extending along at least a part of a periphery of the second electrode, and one or more optical openings surrounded by the periphery. 17. The imaging device of claim 16, wherein the second electrode further comprises one or more additional conductors extending within a space that is surrounded by the periphery of the second electrode. 18. The imaging device of claim 15, wherein the hardware component comprises at least a part of a thin-film-transistor (TFT). 19. The imaging device of claim 1, wherein the first detector element has a first part configured to generate the first electrical signal in response to the light from the first scintillator layer, and a second part configured to generate the second electrical signal in response to the light from the second scintillator layer. 20. The imaging device of claim 19, wherein the first part is a top side of the first detector element, and the second part is a bottom side of the first detector element. 21. The imaging device of claim 19, wherein the first part comprises a first photodiode, and the second part comprises a second photodiode, and wherein the first photodiode and the second photodiode form a side-by-side configuration. 22. The imaging device of claim 1, further comprising a substrate, wherein the array of detector elements is secured to the substrate, wherein the substrate has a first side and an opposite second side, the first side being closer to a radiation source than the second side. 23. The imaging device of claim 22, further comprising a layer of focusing elements located between (1) the array of detector elements and (2) the first scintillator layer or the second scintillator layer. 24. The imaging device of claim 22, further comprising an optical grid coupled to the first scintillator layer or the second scintillator layer. 25. The imaging device of claim 22, wherein the substrate has a thickness that is less than 2 mm. 26. The imaging device of claim 1, further comprising a first optical grid coupled to the first scintillator layer, and a second optical grid coupled to the second scintillator layer. 27. The imaging device of claim 1, comprising both the first plate and the second plate, wherein both the first scintillator layer and the second scintillator layer are between the first and second plates. 28. An imaging device, comprising:a first scintillator layer;an array of detector elements, wherein the array of detector elements comprises a first detector element;a second scintillator layer, wherein the array of detector elements is located between the first scintillator layer and the second scintillator layer; anda first neutral density filter located between the first scintillator layer and the first detector element and/or a second neutral density filter located between the second scintillator layer and the first detector element;wherein the first detector element is configured to generate a first electrical signal in response to light from the first scintillator layer, and to generate a second electrical signal in response to light from the second scintillator layer;wherein the first electrical signal has a first feature value (e1), and the second electrical signal has a second feature value (e2); andwherein the first neutral density filter and/or the second neutral density filter is configured such that min (e1, e2)/max (e1, e2) is larger than a threshold. 29. The imaging device of claim 28, wherein the first feature value (e1) is a function of quantum efficiency QE1 of the first scintillator layer, optical yield α1 of the first scintillator layer, and optical sensitivity p1 of the first detector element associated with the first scintillator layer; andwherein the second feature value (e2) is a function of quantum efficiency QE2 of the second scintillator layer, optical yield α2 of the second scintillator layer, and optical sensitivity p2 of the first detector element associated with the second scintillator layer. 30. The imaging device of claim 28, wherein the first feature value (e1) is a function of detective quantum efficiency DQE1 of the first scintillator layer, optical yield α1 of the first scintillator layer, and optical sensitivity p1 of the first detector element associated with the first scintillator layer; andwherein the second feature value (e2) is a function of detective quantum efficiency DQE2 of the second scintillator layer, optical yield α2 of the second scintillator layer, and optical sensitivity p2 of the first detector element associated with the second scintillator layer. 31. The imaging device of claim 28, wherein the threshold is larger than 0.5. 32. The imaging device of claim 28, wherein the threshold is larger than 0.7.