Microfocus X-ray system

• US 5,020,086 A
• Filed: 02/24/1989
• Issued: 05/28/1991
• Est. Priority Date: 07/05/1983
• Status: Expired due to Term

• Current Assignee: ThermoSpectra Corp (Thermo Fisher Scientific Incorporated)
• Original Assignee: Ridge Corporation
• Inventors: Peugeot, Richard S.
• Primary Examiner(s): Church, Craig E.
• Application Number:
  US07/316,235
• Time in Patent Office: 823 Days
• Field of Search: 378/138, 378/137, 378/113, 378/99, 378/41-43, 358/111
• US Class Current: 378/113
• CPC Class Codes: H01J 35/04 Electrodes ; Mutual position thereof; Constructional adaptations therefor
• CPC Class Codes: H01J 35/147 Spot size control
• CPC Class Codes: H05G 1/32 Supply voltage of the X-ray apparatus or tube

Abstract

A microfocus type X-ray system in which the electron beam current is generally operated in a milliampere range at a constant power, and the beam is subjected to electronic focusing for selected beam width and steering for directional control.

Claims

1. A microfocus X-ray system comprising:

a generally elongated vacuum enclosure;

electron beam generation means positioned within said enclosure for generating an electron beam;

a grid spaced from said electron beam generation means, said grid having an aperture through which an electron beam emitted by said electron beam generation means passes in a line generally along the longitudinal dimension of said enclosure;

acceleration means, including an anode and biasing means for positively biasing said anode with respect to said electron beam generation means, for accelerating electrons of said electron beam;

focusing means for acting on said electron beam as accelerated by said acceleration means and focusing said electron beam into a narrow beam on the order of 1 to 100 microns in width;

a metal target positioned to receive said electron beam and discharge X rays toward an object to be exposed outside of said enclosure;

horizontal beam deflection means responsive to a first square wave electrical signal for precipitously changing the horizontal path of the focused said electron beam such that it precipitously changes the point of impact on said target and therefrom produces X-ray radiation from essentially only two separated points of said target;

vertical beam deflection means responsive to a second square wave electrical signal for changing the vertical path of the focused said electron beam such that it changes the area of impact on said target of said electron beam;

signal means for continuously and sequentially generating said first square wave electrical signal and coupling it to said horizontal deflection means

second signal means for continuously and sequentially generating said second square wave electrical signal and coupling it to said vertical deflection means; and

display means, including X ray-to-visible light conversion means positioned to receive images of said X-ray beams transiting a said object, for sequentially and in real time displaying images only in terms of X rays emanating from said two separated points on said target.

2. A microfocus X-ray system as set forth in claim 1 wherein said display means includes at least one visible image display, a TV camera positioned to view said visual image display, at least one TV monitor coupled to the output of said TV camera, and synchronization means coupled to said signal means, said display means, said TV camera, and said TV monitor for synchronizing the occurrence of each said positioned X-ray beam with a reproduction of the image of said object produced by that beam.

3. A microfocus X-ray system as set forth in claim 1 including viewing means for enabling a viewer to observe one image with one eye derived from said one positioned X-ray beam and enabling the observation of a second image with the other eye of the viewer derived from a second positioned X-ray beam.

4. A microfocus X-ray system as set forth in claim 2 wherein said display means includes a single said TV monitor, and said viewing means includes a first shutter means responsive to said signal means for alternately blocking and unblocking the view of said single TV monitor from one eye of the viewer and second shutter means responsive to said signal means for alternately blocking and unblocking the view of said TV monitor from a second eye of a viewer, such that one perspective view of said object is seen by one eye as a function of the position of said one X-ray beam, and a second perspective view is seen by the other eye of a viewer as a function of the second positioned X-ray beam.

5. A microfocus X-ray system as set forth in claim 2 wherein said display means includes first and second TV monitors coupled to said TV camera, and said viewing means includes means for enabling only a first eye of a viewer to view said first TV monitor and only a second eye of a viewer to view said second TV monitor, and said synchronization means includes means for alternating enabling reproduction by said first and second TV monitors in synchronization with the alternate occurrences of said one said positioned X-ray beam and said second positioned X-ray beam.

6. A microfocus X-ray system as set forth in claim 2 wherein said display means includes:

a video digitizer coupled to the output of said TV camera;

first and second digital memories coupled to the output of said video digitizer;

said video digitizer being coupled to said signal means such that coordinate with a said first value of said electrical signal, said video digitizer provides to said first digital memory a digitally encoded field representative of a first perspective view of a said object during the presence of first positioned X-ray beam, and, coordinate with a second value of said electrical signal, said video digitizer provides to said second digital memory a digitally encoded field representative of a second positioned X-ray beam; and

pictorial computing means alternately responsive to said first and second memories for perspectively combining the fields stored in said first and second memories and providing the same to said TV monitor.

7. A microfocus X-ray system as set forth in claim 2 wherein:

said image display means includes first and second spaced image visible light displays, and each having an image responsive X-ray input, and said input of said visible light display being spaced wherein a selected image area of an object is projected by X-ray radiation from one said separated point of said target onto a selected central position of a said input of said first visible light display, and said selected image area of said object is projected by X-ray radiation from another said separated point of said target onto a like selected central position of the input of said second visible light image display, such that X-ray beams from image areas of said object other than said selected image area of said object are projected onto non-like positioned areas of said inputs of said visible light displays, such that visible light outputs of said first and second visible light displays produce non-like reproduction of other than said selected image area of said object; and

combining means for adding and displaying in register, the outputs of said visible light display means, such that the detail of said selected image area is enhanced and all other of view rendered indistinct.

8. A microfocus X-ray system as set forth in claim 7 wherein said combining means includes:

a first TV camera coupled to view the output of said first visible light display, and a second TV camera coupled to view the output of said second visible light display;

image combination means coupled to the outputs of said first and second TV cameras including means for summing the discrete pixels of views of the outputs of said first and second cameras for providing as an output a compositive TV image, wherein said selected image area is enhanced and other areas of said object appear indistinct; and

a television monitor coupled to the output of said image combination means.

9. A microfocus X-ray system comprising:

an elongated vacuum enclosure having first and second detachable chambers;

electron beam generation means positioned in said first chamber and comprising a filament-cathode and a grid spaced from said filament-cathode, said grid having an aperture through which an electron beam emitted by said filament-cathode passes in a line which is generally along the longitudinal dimension of said enclosure, said beam passing from said first chamber into said second chamber;

said second chamber being tubular and extending around said electron beam;

a focusing coil wound around said beam and adjacent to said tubular second chamber;

an anode having an opening therethrough for passage of said electron beam, said anode being positioned immediately between said grid and said focusing coil;

a metal target positioned at an extreme end of said second chamber which is downstream in terms of the passage of said beam, and said target being electrically connected to said anode;

beam deflection means positioned proximate to said electron beam and, responsive to electrical signals, for selectively positioning said electron beam onto selected areas of a target;

a window of X-ray permeable material positioned adjacent to said target through which emitted X-rays, responsive to bombardment of said target by said electron beam, pass from said second chamber;

first biasing means for applying a heater voltage to said filament-cathode, second biasing means for adjustably applying a negative voltage to said grid with respect to said filament-cathode, and third biasing means for adjustably applying an accelerating voltage to said anode, said accelerated voltage being connected as a negative potential on said filament-cathode with respect to said anode;

power control means responsive to electron beam current passing in circuit between said filament-cathode and target for controllably adjusting the voltage of said second biasing means for effecting a grid bias of a value for maintaining a selected value of electron beam power; and

focusing control means coupled to said focusing coil and responsive to the voltage of said third biasing means for applying an electrical input to said focusing coil of a level which varies as a function of anode-to-cathode voltage for maintaining an electron spot size within the range of 10 to 100 microns.

10. A microfocus X-ray system as set forth in claim 9 wherein:

said signal means includes means for generating electrical signals representative of a circular deflection path of said electron beam and thereby a circular path of origin of said X-ray beam;

a plurality of digital memories including means for storing in each memory a digitally encoded image;

a video digitizer coupled to the output of said TV camera and said signal means and including means for providing to each of said digital memories a digitally encoded image representative of an image derived from a discrete X-ray beam position; and

computing means, responsive to said digital memories and the digital representation of discrete images stored in said digital memories, for combining said images electrically and providing the same to said TV monitor, whereby tomographic representation of a plane in an object subject to multiple positioned X-ray beams is providable as an output to said TV monitor.

11. An X-ray system as set forth in claim 9 wherein:

said filament includes first and second filament conductive prongs, and said first and second mating electrical conductors include first and second conductive receptacles for receiving said first and second conductive prongs; and

said grid has a threaded periphery outboard of said aperture, and said third mating electrical conductor includes a mating threaded receptacle for receiving said grid.

12. An X-ray system as set forth in claim 10 wherein:

said system includes an X-ray imaging means responsive to said X rays for providing a real time visual presentation of X-ray patterns;

said system includes a mateable electrical plug attached to and positioned within said first chamber and having first, second, and third mateable conductive members;

said first biasing means includes means for connection, from outside to inside of said first vacuum chamber and to said first and second mateable conductive members, such that a filament bias is applied to said first and second conductive members;

said biasing means include means for connection, from outside to inside of said first vacuum chamber, to said third mateable conductive member of said negative voltage; and

said electron beam generation means includes first and second mating electrical conductors connected to said filament-cathode and configured to interplug with said first and second mateable conductive members, and a third mating electrical conductor connected to said grid and configured to interplug with said third mateable conductive member, such that said electron beam generation means may be plugged and unplugged from within said first chamber.

13. A microfocus X-ray system comprising:

an elongated vacuum enclosure;

electron beam generation means positioned in said enclosure and comprising a filament-cathode and a grid spaced from said filament-cathode, said grid having an aperture through which an electron beam emitted by said filament-cathode passes in a line which is generally along the longitudinal dimension of said enclosure;

a focusing coil positioned around said beam;

an anode having an opening therethrough for passage of said electron beam, said anode being positioned immediately between said grid and said focusing coil;

a metal target positioned at an extreme end of said enclosure which is downstream in terms of the passage of said beam and positioned to receive said electron beam and discharge X rays toward an object to be exposed outside of said enclosure, and said target being electrically connected to said anode;

beam deflection means positioned proximate to said electron beam and, responsive to electrical signals, for selectively positioning said electron beam onto different areas of said target, such that X rays emanate from different areas of said target;

first biasing means for applying a heater voltage to said filament-cathode, second biasing means for adjustably applying a negative voltage to said grid with respect to said filament-cathode, and third biasing means for adjustably applying an accelerating voltage to said anode, said accelerating voltage being connected as a negative potential on said filament-cathode with respect to said anode;

power control means responsive to electron beam current for controllably adjusting the voltage of said second biasing means for effecting a grid bias of a value for maintaining a selected value of electron beam power; and

focusing control means coupled to said focusing coil and responsive to the voltage of said third biasing means for applying an electrical input to said focusing coil of a level which varies as a function of anode-to-filament-cathode voltage for maintaining an electron spot size within the range of 10 to 100 microns.

14. A system as set forth in claim 13 wherein said power control means is further responsive to the voltage of said third biasing means.

15. A system as et forth in claim 14 wherein said enclosure comprises first and second openably attached chambers, said filament-cathode being in said first chamber, and said target being in said second chamber, and said system includes pressure sensing means for providing an electrical output representative of the pressure within said enclosure, and pumping means responsive to said electrical output for maintaining a vacuum pressure in said enclosure between 10^-4 to 10^-6 Torr.

16. A microfocus X-ray system comprising:

an elongated vacuum enclosure having first and second vacuum chambers;

electron beam generation means including a cathode positioned within said first chamber for generating an electron beam having a beam powered upward to approximately 800 watts and including a filament-cathode and a grid spaced from said filament-cathode, said grid having an aperture through which an electron beam emitted by said filament-cathode passes in a line which is generally along the longitudinal dimension of said enclosure, said beam passing from said first chamber into said second chamber;

focusing means including a focusing coil for focusing said electron beam into a narrow beam;

acceleration means including an anode having an opening therethrough for passage of said electron beam, said anode being positioned intermediately between said grid and said focusing coil;

first biasing means for applying a heater voltage to said filament-cathode, second biasing means for adjustably applying a negative voltage to said grid with respect to said filament-cathode, and third biasing means for adjustably applying an accelerating voltage to said anode, said accelerating voltage being connected as a ground potential to said anode and as a negative potential on said filament-cathode;

focusing control means coupled to said focusing coil and responsive to the voltage of said third biasing means for applying an electrical input to said focusing coil of a level which varies as a function of anode-to-filament-cathode voltage for maintaining a selected electron beam size;

an X-ray emitting target positioned at an extreme end of said second chamber which is downstream in terms of the passage of said beam, said target being electrically connected to said anode;

power control means responsive to both the voltage of said third biasing means and electron beam current passing in circuit between said filament-cathode and target for controllably adjusting the voltage of said second biasing means for effecting a grid bias of a value for maintaining a selected value of electron beam power;

horizontal beam deflection means responsive to a first square wave electrical signal for precipitously changing the horizontal path of the focused said electron beam such that it precipitously changes the point of impact on said target and therefrom produces X-ray radiation from essentially only two separated points of said target;

vertical beam deflection means responsive to a second square wave electrical signal for changing the vertical path of the focused said electron beam such that it changes the area of impact on said target of said electron beam;

first signal means for continuously and sequentially generating said first square wave electrical signal and coupling it to said horizontal deflection means;

second signal means for continuously and sequentially generating said second square wave electrical signal and coupling it to said vertical deflection means; and

display means, including X ray-to-visible light conversion means positioned to receive images of said X-ray beams irradiating an object, for sequentially and in real time displaying discrete images only in terms of different and separated X-ray beams, and said display means includes at least one visible light display, a TV camera positioned to view said visual image display, at least one TV monitor coupled to the output of said TV camera, and synchronization means coupled to said signal means, said display means, said TV camera, and said TV monitor for synchronizing the occurrence of each separated X-ray beam with a reproduction of the image of an object produced by that beam.