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An ultraminiature light source using a double-spiral shaped tungsten filament includes end contact portions which are separated to allow for radial and length-wise unwinding of the spiral. The double-spiral filament is spaced relatively far apart at the end portions thereof so that contact between p

An ultraminiature light source using a double-spiral shaped tungsten filament includes end contact portions which are separated to allow for radial and length-wise unwinding of the spiral. The double-spiral filament is spaced relatively far apart at the end portions thereof so that contact between portions of the filament upon expansion is avoided. The light source is made by fabricating a double-spiral ultraminiature tungsten filament from tungsten foil and housing the filament in a ceramic package having a reflective bottom and a well wherein the filament is suspended. A vacuum furnace brazing process attaches the filament to contacts of the ceramic package. Finally, a cover with a transparent window is attached onto the top of the ceramic package by solder reflow in a second vacuum furnace process to form a complete hermetically sealed package.

대표청구항 ▼

The invention claimed is: 1. A light source comprising: a ceramic base; a generally planar double-spiral shaped filament suspended within said ceramic base; said double-spiral shaped filament material is selected from the group consisting of tungsten, an alloy of tungsten and other incandescent fil

The invention claimed is: 1. A light source comprising: a ceramic base; a generally planar double-spiral shaped filament suspended within said ceramic base; said double-spiral shaped filament material is selected from the group consisting of tungsten, an alloy of tungsten and other incandescent filament material; a transparent lid; said ceramic base includes a reflective bottom, a ledge, and a raised perimeter having a metallic surface; said ledge includes metallic surfaces embedded therein for electrical communication with said double-spiral shaped filament; said double-spiral shaped filament comprises first and second interleaved concentric spiral portions radially converging with decreasing radius and centrally joined together in a central portion; each of said first and second spiral portions of said double-spiral shaped filament includes an end contact portion, a transition portion, an arc shaped portion, an intermediate portion and a central portion, said end contact portion having a large width, said transition portion interconnected to said end contact portion and having a transition width smaller than said end contact portion, said intermediate portion having an intermediate width, said arc-shaped portion having a width initially approximately equal to said width of said transition portion and then gradually tapering to said intermediate width of said intermediate portion, and, each of said intermediate portions terminating and centrally joined together in said central portion; a first gap defined between said first and second spiral portions of said double-spiral shaped filament and a second gap defined between said second and first spiral portions of said double-spiral shaped filament; said first spiral portion being wound in a first direction and said second spiral portion being wound in said first direction; said first and second gaps being substantially constant between said intermediate portions of said spiral portions; said first gap between said transition portion of said first spiral portion and said second spiral portion being relatively larger than said first gap between said intermediate portions of said first and second spiral portions; said second gap between said transition portion of said second spiral and said first spiral portion being relatively larger than said second gap between said intermediate portions of said second and first spiral portions; said first and second gaps near and at said central portion being relatively smaller than said gaps between said intermediate portions of said spiral portions of said double-spiral shaped filament; said end contacts of said first and second spiral portions being bonded to said metal surfaces of said ledge of said ceramic base such that said double-spiral shaped filament is suspended above said reflective base; said transparent lid being soldered to said metal surfaces of said ceramic base forming a sealed chamber within which said double-spiral shaped filament resides and is suspended therein; and, said chamber being at a desired vacuum. 2. A light source as claimed in claim 1 wherein said end contacts of said first and second spiral portions are brazed, electron welded or spot welded to said metal surfaces of said ledge of said ceramic base such that said double-spiral shaped filament is suspended above said reflective base. 3. A light source as claimed in claim 1 wherein said ceramic base is selected from the group consisting of glasses and glass ceramics. 4. A light source as claimed in claim 1 wherein said chamber is filled with halogen or an inert gas. 5. A light source as claimed in claim 1 wherein said reflective bottom of said ceramic base is a metallic surface to provide high reflectance. 6. A light source as claimed in claim 1 wherein said first and second spiral portions have a relatively large radius of curvature in proximity to said end contact portions and wherein said first and second gaps between said first and second spiral portions are relatively large in proximity to said end contact portions. 7. A light source as claimed in claim 6 wherein each of said end contact portions of said first and second spiral portions include a transitional portion, a supporting portion, and an electrical connection portion. 8. A light source as claimed in claim 1 wherein: said end contact portions of said first and second spiral portions of said double-spiral shaped filament each include a transitional portion, a supporting portion and an electrical connection portion; said transitional portions of each of said end contacts of said first and second spiral portions of said double-spiral shaped filament have a relatively large radius of curvature; and, said first and second gaps between said transitional portions of said end contact portions of said first and second spiral portions and the respective intermediate portions of said double-spiral shaped filament are relatively large. 9. A light source as claimed in claim 1 wherein the size of said first gap between said end contact portion of said first spiral portion and said second spiral portion being relatively larger than said first gap between said intermediate portions of said first and second spiral portions and the size of said second gap between said end contact portion of said second spiral and said first spiral portion being relatively larger than said second gap between said intermediate portions of said second and first spiral portions, said sizes of said first and second gaps are determined by the amount the filament expands due to thermal effects during operation. 10. A light source as claimed in claim 1 wherein the diameter of the intermediate portions of the double-spiral shaped filament is approximately 1.15 mm (1,150 μm). 11. A light source as claimed in claim 1 wherein the double-spiral shaped filament is less than 100 μm wide. 12. A light source as claimed in claim 1 wherein said reflective base is gold plated. 13. A light source as claimed in claim 1 wherein said reflective base is selected from the group consisting of a reflective refractory metal, a refractory ceramic carbide, a boride, and a nitride. 14. A light source as claimed in claim 1 comprising: said double spiral shaped tungsten filament having a substantially constant thickness; a carrier package having a transparent window; said double spiral shaped tungsten filament being suspended within said package; a fiber optic guide; and, said fiber optic guide being affixed to said transparent window of said package. 15. A light source as claimed in claim 14 wherein said window of said package is spaced apart from said filament approximately 0.58 mm (580 μm). 16. A light source as claimed in claim 14 wherein said guide is affixed to said transparent window by using one or more of the following selected from the group of optical adhesive, ultrasonic welding, solder, braze, and glass frit. 17. A light source as claimed in claim 14 wherein said guide is affixed in proximity to said window using a coupling affixed to said package. 18. A light source as claimed in claim 17 wherein said coupling includes male and female coupling halves. 19. A light source as claimed in claim 17 further comprising a lens residing between said window and said optic fiber. 20. A process for making an ultraminiature light source, said ultraminiature light source comprises: a ceramic base; a generally planar double-spiral shaped filament suspended within said ceramic base; said double-spiral shaped filament material is selected from the group consisting of tungsten, an alloy of tungsten and other incandescent filament material; a transparent lid; said ceramic base includes a reflective bottom, a ledge, and a raised perimeter having a metallic surface; said ledge includes metallic surfaces embedded therein for electrical communication with said double-spiral shaped filament; said double-spiral shaped filament comprises first and second interleaved concentric spiral portions radially converging with decreasing radius and centrally joined together in a central portion; each of said first and second spiral portions of said double-spiral shaped filament includes an end contact portion, a transition portion, an arc shaped portion, an intermediate portion and a central portion, said end contact portion having a large width, said transition portion interconnected to said end contact portion and having a transition width smaller than said end contact portion, said intermediate portion having an intermediate width, said arc-shaped portion having a width initially approximately equal to said width of said transition portion and then gradually tapering to said intermediate width of said intermediate portion, and, each of said intermediate portions terminating and centrally joined together in said central portion; a first gap defined between said first and second spiral portions of said double-spiral shaped filament and a second gap defined between said second and first spiral portions of said double-spiral shaped filament; said first spiral portion being wound in a first direction and said second spiral portion being wound in said first direction; said first and second gaps being substantially constant between said intermediate portions of said spiral portions; said first gap between said transition portion of said first spiral portion and said second spiral portion being relatively larger than said first gap between said intermediate portions of said first and second spiral portions; said second gap between said transition portion of said second spiral and said first spiral portion being relatively larger than said second gap between said intermediate portions of said second and first spiral portions; said first and second gaps near and at said central portion being relatively smaller than said gaps between said intermediate portions of said spiral portions of said double-spiral shaped filament; said end contacts of said first and second spiral portions being bonded to said metal surfaces of said ledge of said ceramic base such that said double-spiral shaped filament is suspended above said reflective base; said transparent lid being soldered to said metal surfaces of said ceramic base forming a sealed chamber within which said double-spiral shaped filament resides and is suspended therein; and, said chamber being at a desired vacuum, comprising the steps of: fabricating a double-spiral ultraminiature tungsten filament from tungsten foil; placing braze preform over two metal contacts of a suitable chip carrier package; positioning end contacts of said tungsten filament into engagement with said braze preform covering said contacts of said chip carrier package; placing said chip carrier package with said filament positioned therein into a vacuum furnace, said chip carrier package having a base plated with a material selected from the group of reflective refractory metal, refractory ceramic carbide, boride, and nitride; heating, under desired vacuum, said chip carrier package, said tungsten filament, and said braze preform to approximately 800° C.; cooling said chip carrier package, said tungsten filament, and said brazing and increasing pressure to atmospheric pressure; applying solder preform to the perimeter of a lid having a transparent portion; nicking said solder preform to create a discontinuity therein; applying said lid having a transparent portion and having a solder preform tack welded over said perimeter of said lid to said chip carrier package, said chip carrier package includes an upper lip having a gold plating which resides over a nickel plating; holding said lid with said solder affixed thereto into engagement with said chip carrier package; placing said chip carrier package with said lid held in place into said furnace under desired vacuum; heating, under desired vacuum, said chip package to the eutectic temperature of solder to remelt and reflow said solder to seal said chip carrier package under said desired vacuum; and, cooling to room temperature and restoring atmospheric pressure within said furnace. 21. A process for making an ultraminiature light source as claimed in claim 20 further comprising the steps of: applying electrical power to said tungsten filament before applying said lid to said chip carrier package. 22. A process for making an ultraminiature light source as claimed in claim 20 wherein said state of heating, under desired vacuum, said chip carrier package, said tungsten filament, and said braze preform to approximately 800° C. is continued until the braze melts and/or wets said end contacts of said tungsten filament. 23. A process for making an ultraminiature light source, said ultraminiature light source comprises: a ceramic base; a generally planar double-spiral shaped filament suspended within said ceramic base; said double-spiral shaped filament material is selected from the group consisting of tungsten, an alloy of tungsten and other incandescent filament material; a transparent lid; said ceramic base includes a reflective bottom, a ledge, and a raised perimeter having a metallic surface; said ledge includes metallic surfaces embedded therein for electrical communication with said double-spiral shaped filament; said double-spiral shaped filament comprises first and second interleaved concentric spiral portions radially converging with decreasing radius and centrally joined together in a central portion; each of said first and second spiral portions of said double-spiral shaped filament includes an end contact portion, a transition portion, an arc shaped portion, an intermediate portion and a central portion, said end contact portion having a large width, said transition portion interconnected to said end contact portion and having a transition width smaller than said end contact portion, said intermediate portion having an intermediate width, said arc-shaped portion having a width initially approximately equal to said width of said transition portion and then gradually tapering to said intermediate width of said intermediate portion, and, each of said intermediate portions terminating and centrally joined together in said central portion; a first gap defined between said first and second spiral portions of said double-spiral shaped filament and a second gap defined between said second and first spiral portions of said double-spiral shaped filament; said first spiral portion being wound in a first direction and said second spiral portion being wound in said first direction; said first and second gaps being substantially constant between said intermediate portions of said spiral portions; said first gap between said end contact transition portion of said first spiral portion and said second spiral portion being relatively larger than said first gap between said intermediate portions of said first and second spiral portions; said second gap between said end contact transition portion of said second spiral and said first spiral portion being relatively larger than said second gap between said intermediate portions of said second and first spiral portions; said first and second gaps near and at said central portion being relatively smaller than said gaps between said intermediate portions of said spiral portions of said double-spiral shaped filament; said end contacts of said first and second spiral portions being bonded to said metal surfaces of said ledge of said ceramic base such that said double-spiral shaped filament is suspended above said reflective base; said transparent lid being soldered to said metal surfaces of said ceramic base forming a sealed chamber within which said double-spiral shaped filament resides and is suspended therein; and, said chamber being at a desired vacuum, comprising the steps of: fabricating a generally planar double-spiral ultraminiature tungsten filament from tungsten foil; bonding end contacts of said tungsten filament to said chip carrier package by a suitable process selected from the group of brazing, electron beam welding, spot welding and laser welding; evacuating a furnace to a desired vacuum and placing a lid having a window and said tungsten filament bonded to said chip carrier package therein to remove surface contaminants and water; aligning and joining said lid having a window to said chip carrier package. 24. A process for making an ultraminiature light source as claimed in claim 23 wherein said step of aligning and joining said lid to said chip carrier includes sealing by a suitable process selected from the group of soldering, brazing, electron beam welding and laser welding. 25. A process for making an ultraminiature light source, said ultraminiature light source comprises: a ceramic base; a generally planar double-spiral shaped filament suspended within said ceramic base; said double-spiral shaped filament material is selected from the group consisting of tungsten, an alloy of tungsten and other incandescent filament material; a transparent lid; said ceramic base includes a reflective bottom, a ledge, and a raised perimeter having a metallic surface; said ledge includes metallic surfaces embedded therein for electrical communication with said double-spiral shaped filament; said double-spiral shaped filament comprises first and second interleaved concentric spiral portions radially converging with decreasing radius and centrally joined together in a central portion; each of said first and second spiral portions of said double-spiral shaped filament includes an end contact portion, a transition portion, an arc shaped portion, an intermediate portion and a central portion, said end contact portion having a large width, said transition portion interconnected to said end contact portion and having a transition width smaller than said end contact portion, said intermediate portion having an intermediate width, said arc-shaped portion having a width initially approximately equal to said width of said transition portion and then gradually tapering to said intermediate width of said intermediate portion, and, each of said intermediate portions terminating and centrally joined together in said central portion; a first gap defined between said first and second spiral portions of said double-spiral shaped filament and a second gap defined between said second and first spiral portions of said double-spiral shaped filament; said first spiral portion being wound in a first direction and said second spiral portion being wound in said first direction; said first and second gaps being substantially constant between said intermediate portions of said spiral portions; said first gap between said end contact transition portion of said first spiral portion and said second spiral portion being relatively larger than said first gap between said intermediate portions of said first and second spiral portions; said second gap between said end contact transition portion of said second spiral and said first spiral portion being relatively larger than said second gap between said intermediate portions of said second and first spiral portions; said first and second gaps near and at said central portion being relatively smaller than said gaps between said intermediate portions of said spiral portions of said double-spiral shaped filament; said end contacts of said first and second spiral portions being bonded to said metal surfaces of said ledge of said ceramic base such that said double-spiral shaped filament is suspended above said reflective base; said transparent lid being soldered to said metal surfaces of said ceramic base forming a sealed chamber within which said double-spiral shaped filament resides and is suspended therein; and, said chamber being at a desired vacuum, comprising the steps of: fabricating a generally planar double-spiral ultraminiature tungsten filament from tungsten foil; bonding end contacts of said tungsten filament to said chip carrier package by a suitable process selected from the group of brazing, electron beam welding, spot welding and laser welding; cleaning said package and said lid using a glow discharge plasma, ion beam, out-gassing and burn-in of said filament; and, aligning and joining said lid having a window to said chip carrier package.