Dual/multiple-energy x-ray sensor with separation between pixels and active circuitry
A dual/multi-energy x-ray image sensor with stacked two-dimensional pixel arrays. Each pixel in one pixel array has a corresponding “overlaid” pixel in the other pixel array. The pixel arrays are stacked parallel and aligned so that they are nominally normal to the x-ray path, and so that a straight path taken by an x-ray photon from the x-ray source to a pixel in one pixel array will also nominally intersect the corresponding pixel in the other pixel array(s). The energy image sensor provides an x-ray scanning detector system, which has increased signal levels and signal-to-noise ratios over dual- or multi-energy detectors using linear diode arrays, specifically when the pixel arrays are TDI pixel arrays that offer higher sensitivities in high-speed line-scan applications. Signal processing circuitry is placed on a periphery of the pixel arrays and shielded. Dual-to-multiple energy applications can be accomplished by increasing the number of stacked pixel arrays.
1. A multi-energy x-ray detector, comprising:
a plurality of two-dimensional x-ray detecting pixel arrays disposed in a vertically parallel arrangement directly above each other, the arrangement positioning corresponding pixels in the pixel arrays that are vertically parallel to each other to be nominally normal to a straight-line x-ray path emanating from a x-ray source disposed above or below the plurality of pixel arrays;
MOS devices for receiving signals from the pixels, the MOS devices disposed on the pixel arrays and positioned away from the pixels; and
an x-ray shielding disposed one of the pixel arrays, positioned to shield the MOS devices on all the pixel arrays,
wherein each pixel array has a different spectral response.
2. The multi-energy x-ray detector of claim 1 , wherein the MOS devices are positioned at a coincident end portion of the pixel arrays.
3. The multi-energy x-ray detector of claim 1 , wherein the pixels contain scintillator material that converts x-ray photons to lower-energy or visible photons that are detectable by photodiodes.
4. The multi-energy x-ray detector of claim 1 , wherein the pixels contain photodiodes or photoelements that are resistant to radiation damage.
5. The multi-energy x-ray detector of claim 4 , wherein the photodiodes or photoelements and the MOS devices are integrated on a semiconductor chip.
6. The multi-energy x-ray detector of claim 5 , wherein the semiconductor chip is a silicon CMOS chip.
7. The multi-energy x-ray detector of claim 6 , wherein the MOS devices are CMOS field-effect transistors.
8. The multi-energy x-ray detector of claim 5 , wherein the semiconductor chip is designed or processed with radiation hardening.
9. The multi-energy x-ray detector of claim 1 , wherein the pixel arrays are comprised of a plurality of smaller separate pixel arrays, the smaller pixel arrays tiled together in a lateral, arced, staggered, or overlapping arrangement to form a full pixel array.
10. The multi-energy x-ray detector of claim 1 , wherein the pixel arrays are separated by a filter that attenuates certain energies of x-rays.
11. The multi-energy x-ray detector of claim 1 , wherein visible-light optics are not used.
12. The multi-energy x-ray detector of claim 1 , wherein the pixels of the pixel arrays are not in a rectangular grid pattern.
13. The multi-energy x-ray detector of claim 1 , further comprising a software algorithm to compensate for parallax or misalignment between corresponding pixels.
14. The multi-energy x-ray detector of claim 1 , wherein the x-ray shielding is a plurality of x-ray shields.
15. The multi-energy x-ray detector of claim 1 , wherein the plurality of pixel arrays are a set of two pixel arrays, wherein one pixel array of the set of pixel arrays is configured to detect higher-energy x-ray photons than another pixel array of the set of pixel arrays, to form a dual-energy x-ray detector.
16. A method of multi-energy x-ray detecting imaging, comprising:
passing x-rays from an x-ray source through a plurality of pixel arrays disposed in a vertically parallel arrangement directly above each other, the arrangement positioning corresponding pixels in the pixel arrays that are vertically parallel to each other to be nominally normal to a straight-line path of the x-rays, wherein each pixel array possesses a different spectral response;
converting the x-rays in the pixel arrays to electrical charge signals proportional to the x-ray signals for the corresponding spectral responses;
processing electrical charge signals in MOS devices that are also disposed on the plurality of pixel arrays, but shielded from incident x-rays; and
combining the electrical charge signals from corresponding pixels in the plurality of pixel arrays to generate a multi-energy image.
17. The method of claim 16 , wherein the combining the electrical charge signals forms a spectral image.
18. The method of claim 16 , further comprising tilling smaller separate pixel arrays together in a lateral, arced, staggered, or overlapping arrangement to form a full pixel array of the plurality of the pixel arrays.
19. The method of claim 16 , further comprising adding a filter between the pixel arrays to attenuate certain energies of x-rays.
20. The method of claim 16 , wherein the plurality of pixel arrays are a set of two pixel arrays, one pixel array of the set of pixel arrays being configured to detect higher-energy x-ray photons than another pixel array of the set of pixel arrays, to generate a dual-energy image.