Apparatus and methods for high performance radiographic imaging array including reflective capability
View Patent ↗Embodiments of methods/apparatus according to the application can include radiographic imaging device comprising an imaging array of pixels or a plurality of photosensors including a first side to receive light from a scintillator and a second side to pass second light responsive to impingement of the scintillator light and a reflective layer configured to reflect third light responsive to impingement of the second light. Exemplary photosensors can absorb a prescribed amount of the scintillator light received through a first transparent side and the third light received through a second transparent side. Exemplary reflective arrangements can be selected based upon scintillotor emission characteristics and/or photosensor absorption characteristics. Embodiments of radiographic detector arrays and methods can reduce photosensor thickness to reduce noise, reduce image lag and/or increase charge capacity. Embodiments can maintain the quantum efficiency of a reduced thickness photosensor.
1. A radiographic imaging device comprising:
a scintillator;
a plurality of photosensitive elements, each photosensitive element extending between a first side to receive first light from the scintillator and a second opposite side to pass second light responsive to impingement of the first light;
a reflective layer spaced from the plurality of photosensitive elements and configured to receive the second light from the plurality of photosensitive elements and configured to reflect third light responsive to impingement of the second light; and
a substrate on the second side of the plurality of photosensitive elements, wherein photosensitive element characteristics of the plurality of photosensitive elements are selected to absorb a prescribed amount of the first light received through the first side and the third light received through the second side, wherein the reflectivity of the reflective layer is greater than 50%, wherein a thickness of said each photosensitive element of the plurality of photosensitive elements is configured to pass at least 50% of at least one wavelength of the first light, wherein the first light is between 400-700 nm.
2. The device according to claim 1 , wherein the photosensitive element characteristics are based on an emission characteristic of a material comprising the scintillator.
3. The device according to claim 1 , wherein the absorption of the third light comprises at least 35% of total absorption of the plurality of photosensitive elements for light between 550 nm to 700 nm or the absorption of the third light increases an absorption of the plurality of photosensitive elements for at least one wavelength of the light between 550 nm to 700 nm by more than 20%.
4. The device according to claims 1 , wherein a-Si semiconductor portions of photosensors forming the plurality of photosensitive elements includes a thickness of less than 400 nm, or wherein semiconductor portions of the photosensors include a thickness of less than 400 nm.
5. The device according to claim 1 , wherein the reflective layer is selected to preferentially reflect a prescribed band of wavelengths or a reflection coefficient of the reflective layer is highest for wavelength selected between 540 and 650 nm.
6. The device according to claim 1 , wherein the reflective layer is selected to increase quantum efficiency based on emission characteristics of the scintillator and absorption characteristics of photodiodes forming the plurality of photosensitive elements.
7. The device according to claim 1 , further comprising an optically transparent dielectric formed between the reflective layer and the plurality of photosensitive elements, wherein the dielectric characteristics comprise at least one of absorption coefficient as a function of wavelength or index of refraction as a function of wavelength or the index of refraction is a complex variable.
8. The device according to claim 1 , wherein the reflective layer comprises a plurality of deposited dielectrics forming a dielectric stack, a metal, an organic layer, or a dielectric film, where the reflective layer is universally deposited over a glass substrate corresponding to an imaging array or under the glass substrate corresponding to the imaging array.
9. The device according to claim 1 , wherein the at least one readout element comprises at least one transistor formed vertically under a photosensor being a photosensitive element or at least one transistor formed co-planar with the photosensor, and wherein the photosensor comprises PIN photodiodes, MIS photo-sensors, photo-transistors and photo-conductors.
10. The device according to claim 1 , wherein the reflective layer comprises light-scattering particles diffused throughout a reflection control layer to reduce light scattering between pixels or a light-absorbing colorant grid applied to the reflection control layer to reduce light scattering between the pixels.
11. The device according to claim 1 , where the reflective layer comprises a reflective control layer including a diffuse reflector to increase the angular distribution of the reflective light as compared to the incident light.
12. The device according to claim 1 , further comprising an optical reset arrangement arranged below the reflector layer for resetting the plurality of photosensitive elements using the second side, the reflector layer to enable reset light from the optical reset arrangement to pass therethrough to reset the plurality of photosensitive elements.
13. The device according to claim 1 , wherein the photosensitive element characteristics comprise at least one of photosensitive element area, photosensitive element pitch, photosensitive element sensitivity, wherein the photosensitive element characteristics for each of photosensor layers therein comprise absorption coefficient as a function of wavelength, index of refraction as a function of wavelength, or thickness, and wherein scintillator properties comprise at least one of scintillator thickness, scintillator composition, scintillator x-ray absorption coefficient, and scintillator light emission spectra.
14. The device according to claim 1 , wherein characteristics of the reflector layer comprises at least one of spectral reflectance or angular distribution of reflected light.
15. The device according to claim 1 , wherein the absorption of the third light increases an absorption of the plurality of photosensitive elements for at least one wavelength of the light between 550 nm to 700 nm by more than 10%.
16. A method for operating a radiographic imaging apparatus for capturing a plurality of x-ray images of an object comprising:
providing a scintillation screen for receiving incident radiation and responding by emitting excited radiation at a first band of wavelengths;
providing an array of photosensors, each photosensor extending between a first side and a second side, the first side for receiving first light at the first band of wavelengths from the scintillator, the second side for passing a portion of the first light that was not absorbed as second light responsive to impingement of the first light;
providing a reflective layer for receiving the second light and for reflecting a portion of the second light as third light responsive to impingement of the second light; and
providing a substrate over the second side for supporting the array of photosensitive elements, said each photosensor of the array of photosensors absorbing a prescribed amount of the first light and absorbing a prescribed amount of the third light received through the second side, wherein the reflectivity of the reflective layer is greater than 50%, wherein the absorption of the third light comprises at least 15% of total absorption of the plurality of photosensitive elements for light between 550 nm to 700 nm.
17. The method of claim 16 , wherein at least one layer of the photosensors has a reduced thickness to pass a prescribed amount of a selected wavelength band through the second sides, wherein the reduced thickness of the at least one layer of the photosensors is configured to reduce dark current generated by each photosensor or to reduce image lag generated by said each photosensor, which are dependent on a number of total electrical traps in said each photosensor.
18. The method of claim 16 , comprising providing an optical reset arrangement arranged below the substrate for resetting the photosensors using the second side, the reflector arrangement to enable reset light from the reset arrangement to pass therethrough to reset the photosensors.
19. The method of claim 16 , wherein the reflective layer comprises light-scattering particles diffused through a reflection control layer to reduce light scattering between pixels or a light-absorbing colorant grid applied to the reflection control layer to reduce light scattering between the pixels.
20. A method for operating a radiographic imaging apparatus for capturing a plurality of x-ray images of an object comprising:
providing a scintillation screen for receiving incident radiation and responding by emitting excited radiation at a first band of wavelengths;
providing an array of photosensors, each photosensor extending between a first side and a second side, the first side for receiving first light at the first band of wavelengths from the scintillator, the second side for passing a portion of the first light that was not absorbed as second light responsive to impingement of the first light;
providing a reflective layer for receiving the second light and for reflecting a portion of the second light as third light responsive to impingement of the second light; and
providing a substrate over the second side for supporting the array of photosensitive elements,
said each photosensor of the array of photosensors absorbing a prescribed amount of the first light and absorbing a prescribed amount of the third light received through the second side, wherein the reflectivity of the reflective layer is greater than 50%, wherein a thickness of said each photosensitive element of the plurality of photosensitive elements is configured to pass at least 50% of at least one wavelength of the first light, wherein the first light is between 400-700 nm.