Photo detector of an X-ray imager
View Patent ↗An X-ray imager includes a photo detector, a pixel array, a scan line and a data line. The photo detector includes a plurality of X-ray sensitive particles that are configured to be electrically isolating and to generate charge carriers upon absorption of X-ray photons. In one example embodiment, the photo detector includes a layer of an electrically isolating material, within which the plurality of X-ray sensitive particles are distributed. The pixel array includes multiple pixels each defined by a space between a first surface and a second surface of the layer. The scan line is configured to activate a corresponding row of the pixels in the pixel array. The data line is configured to read data from a corresponding column of the pixels in the pixel array.
1. An X-ray imager, comprising:
a photo detector having a plurality of X-ray sensitive particles that are configured to be electrically isolated and to generate charge carriers upon absorption of X-ray photons, wherein the generated charge carriers are confined within the X-ray sensitive particles;
a layer within which the plurality of X-ray sensitive particles are distributed;
a pixel array in which each pixel is defined by a space between a first surface and a second surface of the layer;
a scan line for activating a corresponding row of the pixels in the pixel array; and
a data line for reading data from a corresponding column of the pixels in the pixel array.
2. The X-ray imager of claim 1 , wherein the layer is made of an electrically isolating material.
3. The X-ray imager of claim 2 , wherein each of the plurality of X-ray sensitive particles is coated with an electrically isolating film.
4. The X-ray imager of claim 2 , wherein the plurality of X-ray sensitive particles have varying sizes.
5. The X-ray imager of claim 2 , wherein the plurality of X-ray sensitive particles have varying densities in a direction of incident X-ray photons.
6. The X-ray imager of claim 2 , wherein the layer further includes an electrically isolating structure to divide the layer into multiple portions, in which the plurality of X-ray sensitive particles are disposed.
7. The X-ray imager of claim 2 , wherein the layer and the plurality of X-ray sensitive particles have different dielectric constants.
8. The X-ray imager of claim 2 , wherein the layer includes a binder material for binding the X-ray sensitive particles to form a composite particle-in-isolating-binder material.
9. The X-ray imager of claim 2 , wherein:
the scan line is provided on the first surface of the layer; and
the data line is provided on the second surface of the layer opposite to the first surface.
10. The X-ray imager of claim 9 , wherein the scan line is configured to be substantially orthogonal to the data line.
11. The X-ray imager of claim 2 , further comprising:
pixel electrodes provided on a same side of the layer on which the scan line and the data line are disposed;
a common electrode provided on a surface of the layer; and
a first switching element for selectively coupling a corresponding pixel electrode to the data line according to a signal received from the scan line.
12. The X-ray imager of claim 11 , further comprising a storage capacitor coupled to the corresponding pixel electrode.
13. The X-ray imager of claim 11 , further comprising a second switching element for selectively coupling the corresponding pixel electrode to a constant voltage when resetting and biasing the photo detector.
14. The X-ray imager of claim 13 , further comprising a storage capacitor coupled to the corresponding pixel electrode.
15. The X-ray imager of claim 14 , wherein the second switching element is coupled in parallel to the storage capacitor.
16. The X-ray imager of claim 1 , wherein the plurality of X-ray sensitive particles are pre-treated to reduce charge trapping bonds on surfaces of the X-ray sensitive particles.
17. The X-ray imager of claim 1 , further comprising a charge amplifier coupled to the data line for measuring an amount of the charge carriers released in the X-ray sensitive particles.
18. A method for measuring an X-ray exposure, comprising:
applying an external electrical field to a photo detector having a layer of an electrically isolating material and X-ray sensitive particles distributed within the layer; and
reading out charges induced by an internal electrical field for determining an amount of the X-ray exposure, wherein the internal electrical field is established when electrons and holes of charge carriers generated and confined within the X-ray sensitive particles during the X-ray exposure are drawn to opposite sides of the X-ray sensitive particles by the external electrical field.
19. The method of claim 18 , further comprising resetting the photo detector to a predetermined bias state after reading out the charges.
20. The method of claim 19 , further comprising resetting the photo detector to the predetermined bias state by removing or reversing the external electrical field.
21. The method of claim 18 , further comprising reversing the external electrical field to discharge the charges before the X-ray exposure.