Method and device for producing and using multiple origins of x-radiation

Abstract

An x-ray tube source is disclosed that allows differential phase shift, attenuation, and x-ray scattering features of an object to be acquired in a single exposure. Such multiplexed x-ray tube source includes multiple x-ray spot origins controlled in such a way that each slightly separated spot is temporally modulated “ON and OFF” at differing frequencies. In an x-ray interferometer system, such x-ray tube source forms multiple illumination beams of a single angular view of an object's feature but each with different interference fringe locations. A composite image can be acquired with a high frame-rate digital detector as a component element in such x-ray interferometer system. Such composite image can be subsequently de-multipexed and separately presented according to each spot-source illumination beam. Such isolated images of an object's feature, each having different fringe locations, allows for post-acquisition “fringe-mapping” analysis of the feature's full interaction with x-rays, including refraction, scattering, and absorption.

Claims

1. An x-ray tube device useful for temporal-multiplexed x-ray interferometry, the device comprising: a vacuum chamber; a cathode comprised of an array of electron emitters for multiple electron beams, wherein said electron emitters are time-controlled sources of electron flow, said emitters being independently controllable; an anode comprised of an electron target of x-ray generating material, wherein said multiple electron beams produce multiple spots of x-ray origins; and, controlling circuitry to independently pulse ON and OFF the electron emitters.

2. The x-ray tube device of claim 1, in which the electron target anode is a disk that is rotated about an axis rather than a fixed anode.

3. The x-ray tube device of claim 1, in which the electron target anode is a cylinder that is rotated about an axis rather than a fixed anode.

4. The x-ray tube device of claim 3 wherein the x-ray tube is comprised of: a vacuum chamber; an array of electron emitters for multiple electron beams; a cylindrical electron target rotated about its longitudinal axis and simultaneously linearly translated along said axis, wherein said linear translation is oscillating.

5. The x-ray tube device of claim 4 wherein the x-ray tube is comprised of: a vacuum chamber; an array of non-pulsed electron emitters for multiple continuous electron beams; a cylindrical electron target rotated about its longitudinal axis and simultaneously linearly translated along said axis, wherein said electron target is comprised of a first material arrayed in a discrete pattern of stepped spatial frequencies and a second material of similar arrayed pattern interlaced with said first material, said first material selected for its x-ray generating properties and said second material selected for its property of not generating detectable x-rays, wherein said arrayed patterns of materials are perpendicular to said axis of target rotation and said linear translation of electron target provides to alternatively align and/or misalign said emitters of electron beams with said x-ray generating material; and, controlling circuitry.

6. The x-ray tube of claim 5, in which the arrayed patterns of x-ray generating material is comprised of structural features, such as ridges and/or grooves, instead of being interlaced with a second material with the property of not generating detectable x-rays.

7. The x-ray tube device of claim 2 wherein the x-ray tube is comprised of: a vacuum chamber; an array of non-pulsed electron emitters for multiple continuous electron beams; a rotating disk electron target, wherein said electron target is comprised of a first material arrayed in a discrete pattern of stepped spatial frequencies and a second material of similar arrayed pattern interlaced with said first material, said first material selected for its x-ray generating properties and said second material selected for its property of not generating detectable x-rays, wherein said arrayed patterns of materials are concentric to said axis of target rotation; said multiple electron beams producing multiple x-ray origin positions, said positions being controllable via steering circuitry such that the electron beams are swept radially on the target, such sweeping to alternatively align and/or misalign said emitters of electron beams with said x-ray generating material; and, controlling circuitry.

8. The x-ray tube of claim 7, in which the arrayed patterns of x-ray generating material is comprised of structural features, such as ridges and/or grooves, instead of being interlaced with a second material with the property of not generating detectable x-rays.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0022] The invention will be further described, by way of example only, with reference to the accompanying drawings, in which:

[0023] FIG. 1 is a diagrammatic view of a rotating anode x-ray tube consisting of a metal-coated cylinder attached to a rotational driving motor and a linear actuator, and presented opposite an array of individually-pulsed electron sources;

[0024] FIG. 2 is a diagrammatic view of a rotating anode x-ray tube consisting of a patterned metal-coated cylinder attached to a rotational driving motor and a linear actuator, and presented opposite an array of continuous electron sources;

[0025] FIG. 3 is a diagrammatic view of a rotating anode x-ray tube consisting of a motor-driven metal-coated disk, and presented opposite an array of continuous electron sources controlled by electron focusing and sweeping optics.

DETAILED DESCRIPTIONS OF THE DRAWINGS

[0026] In a preferred embodiment of the present invention a rotating anode consists of a driven metal-coated cylinder attached to a driving motor (FIG. 1). Alternatively, a fixed anode or a rotating anode consisting of a metal-coated disk can be used, albeit with reduced capability for heat dissipation. The assembly of FIG. 1 is comprised of a vacuum envelope of metal and glass or ceramic, to stand off the high voltage between the anode 101 and the cathode 102. Typically, the rotor 103 is inside the envelope and the stator 104 is outside the envelope. A slip coupling 105 provides rotational power transfer while allowing longitudinal movement of the cylinder. The envelope walls 106 provide sufficient resistance to reactive forces. Longitudinal slewing of the cylinder is provided by a linear actuator 107 and actuator controller 108.

[0027] High speed rotation (e.g. 7000 RPM) allows for dissipation of residual heat from the array of fine focusing electron emitters 109. The array consists of a source of electrons 110 and electron gating and focusing optics 111. Further heat dissipation is allowed by modest adjustment of the linear actuator 107, such that multiple helical paths are traversed on the surface of the metal cylinder. The pulsed electron columns impact regions on the metal cylinder do not change position relative to the view port 112 of the tube assembly. The linear actuator will reverse direction automatically, providing another helical path albeit in opposite twist direction, hence more surface of the metal cylinder is used to dissipate heat buildup.

[0028] In another preferred embodiment of the present invention a rotating anode consists of a driven metal-coated cylinder attached to a driving motor (FIG. 2). The assembly is comprised of a vacuum envelope of metal and glass or ceramic, to stand off the high voltage between the anode 201 and the cathode 202. Typically, the rotor 203 is inside the envelope and the stator 204 is outside the envelope. A slip coupling 205 provides rotational power transfer while allowing longitudinal movement of the cylinder. The envelope walls 206 provide sufficient resistance to reactive forces. Longitudinal slewing of the cylinder is provided by a linear actuator 207 and actuator controller 208.

[0029] High speed rotation (e.g. 7000 RPM) allows for dissipation of residual heat from the array of course focusing electron emitters 209. The array consists of a source of electrons 210 and electron focusing optics 211. Further heat dissipation is allowed by modest adjustment of the linear actuator 207, such that multiple helical paths are traversed on the surface of the metal cylinder. The electron columns impact regions on the metal cylinder do not change position relative to the view port 212 of the tube assembly. The linear actuator 207 will reverse direction automatically, providing another helical path albeit in opposite twist direction, hence more surface of the metal cylinder is used to dissipate heat buildup. More significantly, linear actuation changes the alignment of the electron beams with metal sections of the anode. This allows on/off cycling of each electron column, and hence, the pulsing of the associated x-ray spot. One complete cycle of the linear actuator may take one half second.

[0030] The cylinder anode is partially coated in metal, which produce hard x-rays, and partially uncoated or covered in electrically insulating material, which prevent the generation of hard x-rays. Specifically, adjacent longitudinal regions of identical length on the anode are metal coated in simple patterns, each with different frequencies of the coating pattern.

[0031] One complete cycle of the linear actuator will be precisely the distance of one longitudinal region of the partially coated anode. The linear actuator will reverse direction automatically, providing electrical continuity, followed by discontinuity, in the vacuum gap between the cathode and cylindrical anode. The result, as the anode metallic sections alternatively align and/or misalign with the emitters of the electron beams, is multiple x-ray spots from the same tube that flash on and off at different rates (e.g. 2 Hz for one spot, 4 Hz for the next spot, 8 Hz, for the next spot, 16 Hz for the next spot, 32 Hz for the next spot, etc.).

[0032] In another preferred embodiment of the present invention a rotating anode consists of a driven metal-coated disk attached to a driving motor (FIG. 3). The assembly is comprised of a vacuum envelope of metal and glass or ceramic, to stand off the high voltage between the anode 301 and the cathode 302. Typically, the rotor 303 is inside the envelope and the stator 304 is outside the envelope. An anode stem 305 provides rotational power transfer. The envelope walls 306 provide sufficient resistance to reactive forces. A view port provides almost unimpeded transmission of x-rays 307.

[0033] The anode 308 is shown in side and face views in FIG. 3. High speed rotation (e.g. 7000 RPM) allows for dissipation of residual heat from the array of course focusing electron emitters, consisting of a source of electrons 309 and electron focusing and steering optics 310.

[0034] The steering of the electron columns proceeds in radially, in respect to the anode disk, and will reverse direction automatically. One complete cycle of the electron sweeping action may take one half second.

[0035] The disk anode is partially coated in metal, which produce hard x-rays, and partially uncoated or covered in electrically insulating material, which prevent the generation of hard x-rays. Specifically, adjacent concentric regions of identical radial length on the disk anode are metal coated in simple patterns, each with different frequencies of the coating pattern.

[0036] One complete cycle of the swept electron beamlets will be precisely the distance of one radial distance region of the partially coated anode. The sweeping action will reverse direction automatically, providing electrical continuity, followed by discontinuity, in the vacuum gap between the cathode and cylindrical anode. The result is multiple x-ray spots from the same tube that flash on and off at different rates (e.g. 2 Hz for one spot, 4 Hz for the next spot, 8 Hz, for the next spot, 16 Hz for the next spot, 32 Hz for the next spot, etc.).

DETAILED DESCRIPTION OF THE INVENTION

[0037] The present invention overcomes the drawbacks of the prior art by allowing scattering and phase-contrast images to be obtained with a single exposure. A typical multiple exposure method requires the repositioning of an analyzer grating, or alternatively, the repositioning of the origin spot within the x-ray tube. This allows “fringe mapping” across a feature within a sample and at least six separate images are required. This invention allows all six images to be acquired simultaneously and separated in post-acquisition processing, followed by image analysis to derive the phase and/or scattering images. This invention allows all needed images to be acquired simultaneously and separated in post-acquisition processing, followed by image analysis to derive the phase and/or scattering images.

[0038] This invention accomplished this by use of multiplexing x-ray phase radiography using a multiplexed x-ray tube source which can generate spatially and temporally modulated radiation for parallel imaging processing. Demultiplexing of the composite image recovers the original separate channels from the multiplexed signal. This allows for an increase in imaging speed and reduction of object motion artifacts and setup motion artifacts in the resulting x-ray phase images.