Structured X-ray conversion screen fabricated with molded layers

• US 20070138409A1
• Filed: 12/15/2005
• Published: 06/21/2007
• Est. Priority Date: 12/15/2005
• Status: Active Grant

• Current Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Original Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Inventors: Daniel, Jurgen
• Granted Patent: US 7,358,506 B2
• Time in Patent Office: Days
• US Class Current: 250/483.100
• CPC Class Codes: G01T 1/20 with scintillation detectors

Abstract

An improved method of forming an X-ray conversion screen is described. The method uses a mold to mold a scintillating material layer including cavities in the scintillating material layer. By repeated moldings, the phosphor layer is built up. The cavities may be filled with a pixel cell separating material or coated with a reflective material such as a sputtered metal to optically isolate each pixel. Various methods for minimizing Swank noise are also described.

Claims

1. A method of forming an X-ray conversion screen comprising the operations of:

forming a substrate;

forming a conversion screen material on a substrate, the conversion screen material including a scintillating material;

bringing a first mold in contact with the conversion screen material such that the first mold molds the conversion screen material;

removing the first mold such that cavities remain in the conversion screen material, at least some of the cavities positioned to separate adjacent pixels, the conversion screen material forming a first layer of the conversion screen.

2. The method of claim 1 further comprising the operation of:

filling the cavities with a filler material.

3. The method of claim 2 wherein the filler material is a reflective cell wall material.

4. The method of claim 3 wherein the filler material is an opaque material.

5. The method of claim 2 further comprising the operation of forming a second layer of the conversion screen, the operation of forming the second layer comprising the operations of:

bringing a second mold in contact with a second set of conversion screen material such that the second mold molds the second set of conversion screen material, an opposite side of the second set of conversion screen material attached to the first layer of the conversion screen; and

removing the second mold such that a second set of cavities remain in the second set of conversion screen material, at least some of the cavities aligned with the filler material.

6. The method of claim 5 further comprising the operation of filling the second set of cavities with a reflective cell wall material.

7. The method of claim 1 wherein the substrate includes a plurality of sensors for detecting visible light with a wavelength ranging between 400-800 nm.

8. The method of claim 7 wherein the sensors are positioned between the location of adjacent filled cavities.

9. The method of claim 1 wherein the substrate is glass coated with a reflective material.

10. The method of claim 1 wherein a second layer is formed over the first scintillating material layer, the method further comprising the operations of:

forming a second substrate including a release layer;

bringing a second mold in contact with a second set of conversion screen material such that the second mold molds the second set of conversion screen materials, an opposite side of the conversion screen material to attach to the release layer of the second substrate, the second set of conversion screen material forming a second scintillating material layer;

removing the second mold such that cavities remain in the second scintillating material layer;

bonding the molded surface of the first layer to the molded surface of the second layer; and

,

using the release layer to release the second substrate from the second scintillating material layer.

11. The method of claim 10 further comprising the operation of:

forming a third substrate including a release layer;

bringing a third mold in contact with a third set of conversion screen material such that the conversion screen material forms a molded surface that mirrors a molding surface of the third mold, an opposite side of the conversion screen material to attach to the release layer of the third substrate, the third set of conversion screen material forming a third scintillating material layer;

removing the third mold such that cavities remain in the third scintillating material layer;

bonding the molded surface of the third layer to the second layer such that the cavities in the third layer approximately match the cavities in the second layer; and

,

using the release layer to release the second substrate from the second scintillating material layer.

12. The method of claim 2 wherein a second layer is formed over the first scintillating material layer, the method further comprising the operations of:

forming a second substrate including a release layer;

bringing a second mold in contact with a second set of conversion screen material such that the conversion screen material forms a molded surface that mirrors a molding surface of the second mold, an opposite side of the conversion screen material to attach to the release layer of the second substrate, the second set of conversion screen material forming a second scintillating material layer;

removing the second mold such that cavities remain in the second scintillating material layer;

bonding the molded surface of the first layer to the molded surface of the second layer;

using the release layer to release the second substrate from the second scintillating material layer; and

,

filling the cavities in the second scintillating material layer with the filler material.

13. The method of claim 2 wherein a second layer is formed over the first scintillating material layer, the method further comprising the operations of:

forming a second substrate including a release layer;

bringing a second mold in contact with a second set of conversion screen material such that the conversion screen material forms a molded surface that mirrors a molding surface of the second mold, an opposite side of the conversion screen material to attach to the release layer of the second substrate, the second set of conversion screen material forming a second scintillating material layer;

removing the second mold such that cavities remain in the second scintillating material layer;

filling the cavities in the second scintillating material layer with an opaque material;

bonding the molded surface of the first layer to the molded surface of the second layer; and

using the release layer to release the second substrate from the second scintillating material layer.

14. The method of claim 1 wherein the substrate includes a plurality of transparent waveguides oriented in a direction approximately perpendicular to a surface of the substrate.

15. The method of claim 1 further comprising depositing a metal) material over the scintillating material layer, the metal material to reflect light generated by the scintillating material.

16. The method of claim 1 further comprising attaching the X-ray conversion screen to a sensor array.

17. The method of claim 1 wherein the conversion screen material also includes a radiation-crosslinkable polymer mixed with the scintillating material, the method further comprising the operation of exposing the polymer to radiation to cross link the polymer prior to removal of the mold.

18. The method of claim 1 wherein the walls of the cavities are coated with a reflective or opaque material and the cavities remain unfilled.

19. A method of forming an X-ray imaging system comprising the operations of:

molding a first layer of X-ray conversion material including a scintillating material with a first mold to form a first layer of an X-ray conversion screen;

filling in cavities to form an approximately planar surface of the first layer of the X-ray conversion screen;

molding a second layer of X-ray conversion material including scintillating material with a second mold over the first layer;

filling in cavities to form an approximately planar surface of the second layer of the X-ray conversion screen; and

,

positioning the X-ray conversion screen over a sensor array such that X-rays striking the X-ray conversion screen are converted into light which is detected by the sensor array.

20. A structure to minimize Swank noise comprising:

a plurality of sensors;

a scintillating material x-ray conversion screen deposited over the plurality of sensors; and

,

a plurality of transparent waveguides oriented approximately perpendicularly to a surface of the plurality of sensors, the transparent waveguide to guide photons generated at near a top of the X-ray conversion screen to the plurality of sensors.

21. A structure to minimize Swank noise comprising:

a plurality of sensors;

a scintillating material layer deposited over the plurality of sensors, the scintillating material layer having a higher concentration of scintillating material in the upper layers and a lower concentration of scintillating material at lower layers closer to the plurality of sensors, the scintillating material distribution to reduce the effects of Swank noise.