X-ray tube electron beam switching and biasing method and apparatus

Claim 2

X-ray producing apparatus comprising: an X-ray tube including (i) a tube cathode having at least one cathode filament which is energized to thermionically emit electrons; (ii) a tube anode which is a target for electrons thermionically emitted from said cathode; a housing for mounting said X-ray tube, said housing having a window portion to transmit X-rays generated by said tube; means for coupling said cathode and anode to a source including a high voltage source outside said housing, said source for maintaining said cathode and anode at different electric potentials so that electrons from said filament accelerate to a focal spot on said anode; high voltage focus control means comprising a light sensitive switch mounted inside said housing for adjusting the size and shape of said focal spot; and transmission means interposed between said high voltage source and said focus control means including a light pipe defining an optical path for directing open loop control signals to said focus control means from a controller outside said housing.

Claim 3

The apparatus of claim 1 additionally comprising monitoring means mounted inside the housing to monitor a filament energization status, said monitoring means communicating with a sensor outside the housing along an insulating communications path.

Claim 4

The apparatus of claim 2 where said monitoring means includes a light emitting diode that conducts in response to a certain filament energization status, and where the transmission means and communications path comprise separate fiber optic light paths routed through an X-ray tube housing.

Claim 5

The apparatus of claim 3 additionally comprising means located outside the X-ray tube housing for de-activating the X-ray tube in response to a malfunction in the focus control means.

Claim 6

The apparatus of claim 1 where the cathode includes three separately energizeable filaments mounted to a cathode focusing cup, said cup having three surfaces facing the anode at angles so that a filament mounted within a slot in each of the three surfaces directs electrons to a specified target are defined by anode location.

Claim 7

The apparatus of claim 5 where the anode target area for the three filaments overlaps with respect to location of the anode.

Claim 8

In an X-ray tube having a cathode and an anode and at least three separate individually energizable cathode filaments apparatus comprising: means for routing alternating current energization signals to respective selected ones of said cathode filaments to thermionically stimulate electron emissions to propagate electrons toward the anode to define a focal spot thereon; focus control means including bias means and connected to said means for routing to energize a particular combination of cathode filaments to adjust the focus size and shape of said focal spot on a tube anode while maintaining said adjusted focal spot generally superposed over a region with respect to said anode notwithstanding said adjustment; and transmission means for transmitting focus control signals to said focus control means.

Claim 9

In an X-ray tube having a cathode and an anode and at least three separate individually energizable cathode filaments apparatus comprising: means for routing alternating current energization signals to respective selected ones of said cathode filaments to thermionically stimulate electron emissions to propagate electrons toward the anode to define a focal spot thereon; focus control means including bias means and connected to said means for routing to energize a particular combination of cathode filaments to adjust the focus size and shape of said focal spot on a tube anode while maintaining said adjusted focal spot generally superposed over a region with respect to said anode notwithstanding said adjustment; and transmission means for transmitting focus control signals to said focus control means.

Claim 10

The apparatus of claim 7 wherein the focus control means comprises a solid state, light responsive switch for switching among filament energization combinations and said transmission means comprises a fiber optic path coupling a light signal to said switch.

Claim 11

The apparatus of claim 8 wherein said means for routing comprises no more than three conductors for energizing three or more filaments and the control means comprises circuitry for coupling energization signals from two of said three conductors across one of said three or more filaments.

Claim 12

X-ray producing apparatus comprising: an X-ray tube including (i) a tube cathode having three separate cathode filaments which are individually energizable to thermionically emit electrons to an anode; and (ii) a tube anode having an anode surface as a target for said thermionically emitted electrons; a housing for mounting said X-ray tube, said housing having a window portion to transmit X-rays generated by said tube; three cathode energization inputs coupleable to an energization source with one of said inputs connected to all three cathode filaments and the other remaining two inputs coupled to at least one of the three filaments; circuitry inside said housing for controlling energization of said cathode by selectively coupling energization signals at said inputs across a selected one of said three filaments, said circuitry including a solid state switch which changes state in response to a light signal; and fiber optic transmission means for coupling a light source outside said housing to said solid state switch.

Claim 13

X-ray producing apparatus comprising: an X-ray tube including (i) a tube cathode having three separate cathode filaments which are individually energizable to thermionically emit electrons to an anode; and (ii) a tube anode having an anode surface as a target for said thermionically emitted electrons; a housing for mounting said X-ray tube, said housing having a window portion to transmit X-rays generated by said tube; three cathode energization inputs coupleable to an energization source with one of said inputs connected to all three cathode filaments and the other remaining two inputs coupled to at least one of the three filaments; circuitry inside said housing for controlling energization of said cathode by selectively coupling energization signals at said inputs across a selected one of said three filaments, said circuitry including a solid state switch which changes state in response to a light signal; and fiber optic transmission means for coupling a light source outside said housing to said solid state switch.

Claim 14

X-ray producing apparatus comprising: an X-ray tube including a tube cathode having at least one cathode filament which is energized to thermionically emit electrons and a tube anode which is a target for electrons thermionically emitted from said cathode; a housing for mounting said X-ray tube, said housing having a window portion to transmit X-rays generated by said tube; means for coupling said cathode and anode to a source outside said housing, said source for maintaining said cathode and anode at different electric potentials so that electrons from said filament accelerate to a focal spot on said anode; high voltage focus control circuitry having a photo transistor switch mounted inside said housing for adjusting the size and shape of said focal spot; and a light pipe for routing visible open loop control signals to said focus control circuitry from a controller outside said housing to turn on and off said switch.

Claim 15

X-ray producing apparatus comprising: an X-ray tube including a tube cathode having at least one cathode filament which is energized to thermionically emit electrons and a tube anode which is a target for electrons thermionically emitted from said cathode; a housing for mounting said X-ray tube, said housing having a window portion to transmit X-rays generated by said tube; means for coupling said cathode and anode to a source outside said housing, said source for maintaining said cathode and anode at different electric potentials so that electrons from said filament accelerate to a focal spot on said anode; high voltage focus control circuitry having a photo transistor switch mounted inside said housing for adjusting the size and shape of said focal spot; and a light pipe for routing visible open loop control signals to said focus control circuitry from a controller outside said housing to turn on and off said switch.

Claim 16

The apparatus of claim 11 wherein said cathode comprises a multiple segment cathode cup located for modifying electron flow from said at least one filament and said focus control circuit comprises means for electrically energizing segments of said cup to different electric potentials by tapping a bias voltage from an energization input to said filament.

Claim 17

An X-ray tube comprising: an anode defining a target for intercepting a bean of electrons such that collisions between said electrons and the anode generate x-radiation from an anode focal spot; a cathode for producing said flow of electrons, said cathode including one or more individually energizable filaments which emit electrons and a segmented focusing cup having two or more separated electrically energizable focus control segments; a tube housing enclosing said cathode and said anode in a portion so that said flow of electrons strikes said anode; and means for selectively energizing said one or more filaments; and means for biasing the segments of said focusing cup to adjust the flow of electrons to said anode for adjusting the size of the focal spot to different non-zero values, and for adjusting the shape of said focal spot; said means for biasing mounted inside said housing and coupled to said means for energizing to tap energy from said means for energizing without the addition of a separate energy source.

Claim 18

An X-ray tube comprising: an anode defining a target for intercepting a bean of electrons such that collisions between said electrons and the anode generate x-radiation from an anode focal spot; a cathode for producing said flow of electrons, said cathode including one or more individually energizable filaments which emit electrons and a segmented focusing cup having two or more separated electrically energizable focus control segments; a tube housing enclosing said cathode and said anode in a portion so that said flow of electrons strikes said anode; and means for selectively energizing said one or more filaments; and means for biasing the segments of said focusing cup to adjust the flow of electrons to said anode for adjusting the size of the focal spot to different non-zero values, and for adjusting the shape of said focal spot; said means for biasing mounted inside said housing and coupled to said means for energizing to tap energy from said means for energizing without the addition of a separate energy source.

Claim 19

In an x-ray tube having multiple, individually energizable cathode filaments mounted to an electrically biased cathode focusing cup, apparatus comprising: means for routing alternating current energization signals to said cathode filaments to thermionically stimulate electron emission; first focus control means connected to said means for routing to energize said cathode filaments in a preselected one of a set of combinations of said filaments to produce a desired focus size and shape on a tube anode; and second focus control means for adjusting the bias on said cathode focusing cup for adjusting the size of the focus size among various non-zero sizes; transmission means for transmitting focus control signals to said first and second focus control means while isolating said first and second control means from ground potential.

Claim 20

In an x-ray tube having multiple, individually energizable cathode filaments mounted to an electrically biased cathode focusing cup, apparatus comprising: means for routing alternating current energization signals to said cathode filaments to thermionically stimulate electron emission; first focus control means connected to said means for routing to energize said cathode filaments in a preselected one of a set of combinations of said filaments to produce a desired focus size and shape on a tube anode; and second focus control means for adjusting the bias on said cathode focusing cup for adjusting the size of the focus size among various non-zero sizes; transmission means for transmitting focus control signals to said first and second focus control means while isolating said first and second control means from ground potential.

Claim 21

The apparatus of claim 14 wherein each focus control means comprises a solid state, light responsive switch, a first switch for switching among filament energization combinations and a second switch for controllably biasing said cathode cup, and said transmission means comprises first and second fiber optic paths coupling a light signal to each said switch.

Claim 22

The apparatus of claim 15 wherein said means for routing comprises three conductors for energizing three filaments and the control means comprises circuitry for coupling energization signals from two of said three conductors across one of said three filaments.

Claim 23

An X-ray tube comprising: an anode defining a target for intercepting a beam of electrons such that collisions between said electrons and the anode generate x-radiation from an anode focal spot; a cathode for producing said flow of electrons, said cathode including one or more individually energizable filaments which emit electrons and a segmented focusing cup having two or more separated electrically energizable focus control segments; a tube housing enclosing said cathode and said anode on a position so that said flow of electrons strikes said anode; means for selectively energizing said one or more filaments; and means for biasing the segments of said focusing cup to adjust the flow of electrons to said anode among different non-zero values thereby controlling the size and shape of the focal spot; said means for biasing mounted inside said housing and coupled to said means for energizing.

Claim 24

An X-ray tube comprising: an anode defining a target for intercepting a beam of electrons such that collisions between said electrons and the anode generate x-radiation from an anode focal spot; a cathode for producing said flow of electrons, said cathode including one or more individually energizable filaments which emit electrons and a segmented focusing cup having two or more separated electrically energizable focus control segments; a tube housing enclosing said cathode and said anode on a position so that said flow of electrons strikes said anode; means for selectively energizing said one or more filaments; and means for biasing the segments of said focusing cup to adjust the flow of electrons to said anode among different non-zero values thereby controlling the size and shape of the focal spot; said means for biasing mounted inside said housing and coupled to said means for energizing.

Claim 25

The tube of claim 17 wherein said focusing cup comprises three conductive segments separated by a said insulating material where two outer segments can be energized to the same potential and a third segment disposed between said two outer segments is energized to a different potential.

Claim 26

The tube of claim 18 wherein said means for energizing comprises low voltage alternating potential at a high negative D.C. potential for energizing the filaments, and said means for biasing comprises means for rectifying the filament energization inputs and coupling said rectified inputs to said cup segments, and further comprising switch means for selectively coupling said means for rectifying to said filaments, and means, isolated from said high negative D.C. potential, for activating said switch means.

Claim 27

An X-ray tube comprising an anode having a rotating surface defining at least two focal spot regions and a cathode having two or more filaments which are connected to a high negative D.C. potential to direct electrons to said focal spots, said cathode further including a segmented focusing cup for controllably changing the shape of said focal spots, and circuitry for energizing said two or more filaments as well as for selectively energizing the focusing cup, said bias control circuitry including a switch electrically isolated by light pipe optical coupling at or near the high magnitude electrical potential of said filament for selectively changing the bias on said focusing cup.

Claim 28

An X-ray tube comprising an anode having a rotating surface defining at least two focal spot regions and a cathode having two or more filaments which are connected to a high negative D.C. potential to direct electrons to said focal spots, said cathode further including a segmented focusing cup for controllably changing the shape of said focal spots, and circuitry for energizing said two or more filaments as well as for selectively energizing the focusing cup, said bias control circuitry including a switch electrically isolated by light pipe optical coupling at or near the high magnitude electrical potential of said filament for selectively changing the bias on said focusing cup.

Claim 29

The X-ray tube of claim 20 wherein said switch comprises a photo transistor optically coupled to a selectively energizable photodiode, said photodiode electrically isolated from said cathode by a fiber optic coupling.

Claim 30

The X-ray tube of claim 20 wherein said focusing cup is divided into three segments and said circuitry includes means for energizing a first and second of said segments to a first potential and for maintaining a third intermediate segment at a different potential.

Claim 31

In an X-ray tube of the rotating anode type, apparatus for focusing electrons from a tube cathode to focal spots on said anode comprising: first and second individually energizeable filaments coupled to an isolation transformer which supplies an alternating current signal to said filaments; a three segment cathode focusing cup having slots in which said first and second filaments are mounted, said cup having a middle section electrically isolated by solid insulating material from two outside segments; a step-up transformer having a set of input and a set of output windings, for stepping up the alternating current signal across the filaments; first and second switch means to selectively couple the alternating current signal across one or the other of said filaments to the input windings of said transformer wherein said switch means comprises photo transistors and fiber optic light pipe coupling for energizing said photo transistors; a rectifier to full wave rectify a stepped up voltage from the output windings of said transformer; and means for coupling a D.C. bias from the rectifier to said segments to maintain the middle segment at a different potential than the outside segments and thereby focus electrons emitted by an energized filament.

Claim 32

In an X-ray tube of the rotating anode type, apparatus for focusing electrons from a tube cathode to focal spots on said anode comprising: first and second individually energizeable filaments coupled to an isolation transformer which supplies an alternating current signal to said filaments; a three segment cathode focusing cup having slots in which said first and second filaments are mounted, said cup having a middle section electrically isolated by solid insulating material from two outside segments; a step-up transformer having a set of input and a set of output windings, for stepping up the alternating current signal across the filaments; first and second switch means to selectively couple the alternating current signal across one or the other of said filaments to the input windings of said transformer wherein said switch means comprises photo transistors and fiber optic light pipe coupling for energizing said photo transistors; a rectifier to full wave rectify a stepped up voltage from the output windings of said transformer; and means for coupling a D.C. bias from the rectifier to said segments to maintain the middle segment at a different potential than the outside segments and thereby focus electrons emitted by an energized filament.

Claim 33

An X-ray tube comprising: an anode defining a target for intercepting a beam of electrons such that collisions between said electrons and the anode generate x-radiation from an anode focal spot; a cathode for producing said flow of electrons, said cathode including one or more individually energizable filaments which emit electrons and a segmented focusing cup having two or more energizable focus control segments electrically separated from each other by one or more solid insulating members; a tube housing enclosing said cathode and said anode in a position so that said flow of electrons strikes said anode; means for selectively energizing said one or more filaments; and means for biasing the segments of said focusing cup to adjust the flow of electrons to said anode thereby adjusting among different non-zero values the size and shape of the focal spot; said segments separated at a surface facing said incandescent filaments, anode, or other sources of conducting material by gaps which isolated said segments from each other while avoiding contamination of said insulating members by evaporated material from above causes, wherein said slots extend into said cathode cup to said insulating members but inhibit deposition of evaporated material onto said insulating members due to their indirect, non-straightline path through said cup to said insulating members.

Claim 34

An X-ray tube comprising: an anode defining a target for intercepting a beam of electrons such that collisions between said electrons and the anode generate x-radiation from an anode focal spot; a cathode for producing said flow of electrons, said cathode including one or more individually energizable filaments which emit electrons and a segmented focusing cup having two or more energizable focus control segments electrically separated from each other by one or more solid insulating members; a tube housing enclosing said cathode and said anode in a position so that said flow of electrons strikes said anode; means for selectively energizing said one or more filaments; and means for biasing the segments of said focusing cup to adjust the flow of electrons to said anode thereby adjusting among different non-zero values the size and shape of the focal spot; said segments separated at a surface facing said incandescent filaments, anode, or other sources of conducting material by gaps which isolated said segments from each other while avoiding contamination of said insulating members by evaporated material from above causes, wherein said slots extend into said cathode cup to said insulating members but inhibit deposition of evaporated material onto said insulating members due to their indirect, non-straightline path through said cup to said insulating members.

Claim 35

The X-ray tube of claim 24 wherein said focusing cup comprises three conductive segments separated by an insulating material where two outer segments can be energized to the same potential and a third segment disposed between said two outer segments is energized to a different potential.

Claim 36

In an X-Ray tube, a segmented cathode focusing cup comprising: three conductive cup segments coupled together yet electrically separated from each other by insulating blocks brazed to said segments to form a monolithic structure, in combination said segments and blocks configured such that at a surface of said cup facing an incandescent filament, tube anode, or other source of conductive material, said segments are physically separated by slots extending into a body of said monolithic structure, said slots communicating with said insulating blocks to complete isolation of said segments along a non-direct path so that said insulating blocks are not susceptible to change in resistance from conductive evaporants from incandescent filaments and other sources inside said X-ray tube.

Claim 37

In an X-Ray tube, a segmented cathode focusing cup comprising: three conductive cup segments coupled together yet electrically separated from each other by insulating blocks brazed to said segments to form a monolithic structure, in combination said segments and blocks configured such that at a surface of said cup facing an incandescent filament, tube anode, or other source of conductive material, said segments are physically separated by slots extending into a body of said monolithic structure, said slots communicating with said insulating blocks to complete isolation of said segments along a non-direct path so that said insulating blocks are not susceptible to change in resistance from conductive evaporants from incandescent filaments and other sources inside said X-ray tube.

Claim 38

The focusing cup of claim 26 wherein said insulating blocks are alumina or other ceramic segments brazed to the conductive nickel or other metal cup segments.

Claim 39

An X-ray apparatus including a tube, said apparatus comprising: (a) an anode defining a target for intercepting a beam of electrons, said anode being of a material such that collisions between said electrodes and said anode generate x-radiation from an anode focal spot; (b) a cathode unit for producing said flow of electrons, said cathode including three separate individually energizeable filaments which, in response to energization, emit electrons, said cathode unit further comprising a segmented focusing cup having three or more electrically energizeable focus control segments, said segments being electrically separated from one another by solid insulating members, said segments being separated at a surface facing said filaments, anode, or other sources of conducting material by gaps which isolate said segments from each other while avoiding contamination of said insulating members by evaporated material, wherein gaps said extend into said cathode cup to said insulating members but inhibit deposition of evaporated material onto said insulating members due to their indirect, non-straightline path through said cup to said insulating members; (c) a tube housing enclosing said cathode unit and said anode in a position so that aid flow of electrons strikes said anode; (d) means for selectively energizing said filaments in a selected one of a set of combination; (e) means for biasing the segments of said focusing cup in controllably variable amounts to adjust the flow of electrons to said anode for adjusting among different non-zero values at least one of the size and shape of the focal spot, and (f) control mcans for applying an open loop control signal to at least one of said energizing and biasing means, said control means comprising at least one light sensitive switch coupled to high voltage circuitry within said tube and a fiber optic light pipe communicating between said switch within said tube and the exterior of said tube.

Claim 40

An X-ray apparatus including a tube, said apparatus comprising: (a) an anode defining a target for intercepting a beam of electrons, said anode being of a material such that collisions between said electrodes and said anode generate x-radiation from an anode focal spot; (b) a cathode unit for producing said flow of electrons, said cathode including three separate individually energizeable filaments which, in response to energization, emit electrons, said cathode unit further comprising a segmented focusing cup having three or more electrically energizeable focus control segments, said segments being electrically separated from one another by solid insulating members, said segments being separated at a surface facing said filaments, anode, or other sources of conducting material by gaps which isolate said segments from each other while avoiding contamination of said insulating members by evaporated material, wherein gaps said extend into said cathode cup to said insulating members but inhibit deposition of evaporated material onto said insulating members due to their indirect, non-straightline path through said cup to said insulating members; (c) a tube housing enclosing said cathode unit and said anode in a position so that aid flow of electrons strikes said anode; (d) means for selectively energizing said filaments in a selected one of a set of combination; (e) means for biasing the segments of said focusing cup in controllably variable amounts to adjust the flow of electrons to said anode for adjusting among different non-zero values at least one of the size and shape of the focal spot, and (f) control mcans for applying an open loop control signal to at least one of said energizing and biasing means, said control means comprising at least one light sensitive switch coupled to high voltage circuitry within said tube and a fiber optic light pipe communicating between said switch within said tube and the exterior of said tube.