Laser sustained plasma and endoscopy light source

Abstract

To provide laser sustained plasma and an endoscopy light source.SOLUTION: An illumination source includes a laser driver unit configured to emit a plasma sustaining beam. An ingress collimator receives the plasma sustaining beam and produces a collimated ingress beam. A focusing optic receives the collimated ingress beam and produces a focused sustaining beam. A sealed lamp chamber contains an ionizable medium that, once ignited, forms a high-intensity light-emitting plasma having a waist size smaller than 150 microns. The sealed lamp chamber further includes an ingress window configured to receive the focused sustaining beam, and an egress window configured to emit the high-intensity light. An ignition source is configured to ignite the ionizable medium, and an exit fiber is configured to receive and convey the high-intensity light. The-high intensity light is white light with a black body spectrum, and the exit fiber has a diameter in the range of 200-500 micrometers.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 62 / 776,006, entitled "LASER SUSTAINED PLASMA AND ENDOSCOPY LIGHT SOURCE," filed December 6, 2018, which is incorporated herein by reference in its entirety.

[0002] The present invention relates to lighting devices, and more particularly to high-intensity arc lamps. [Background technology]

[0003] A high-intensity arc lamp is a device that emits a high-intensity beam of electromagnetic radiation. The lamp generally includes a gas-containing chamber, e.g., a glass bulb, with an anode and a cathode that are used to excite a gas (an ionizable medium) within the chamber. An electrical discharge is created between the anode and the cathode to provide power to the excited (e.g., ionized) gas and to sustain the light emitted by the ionized gas during operation of the light source.

[0004] FIG. 1 shows an external view and cross-section of a prior art xenon lamp 100 of the low wattage parabolic type. The lamp is constructed entirely of metal and ceramic. The fill gas, xenon, is inert and non-toxic. Lamp subassemblies may be constructed by high temperature brazing into fixtures that constrain the assembly to close dimensional tolerances. FIG. 2 shows some of these lamp subassemblies and fixtures after brazing.

[0005] 1 and 2, the prior art lamp 100 has three main subassemblies: the cathode, the anode, and the reflector. The cathode assembly 3a includes the lamp cathode 3b, a number of posts that hold the cathode 3b to a window flange 3c, a window 3d, and a getter 3e. The lamp cathode 3b is a small pencil-shaped component made, for example, from thoriated tungsten. During operation, the cathode 3b emits electrons that travel across the lamp's arc gap and strike the anode 3g. Because electrons are emitted thermionically from the cathode 3b, the cathode tip must maintain a high temperature and low electron emission in order to function.

[0006] The cathode post 3c holds the cathode 3b firmly in place and conducts current to the cathode 3b. The lamp window 3d may be ground and polished single crystal sapphire (AlO2). Sapphire allows the thermal expansion of the window 3d to match that of the flange 3c, so that a hermetic seal is maintained over a wide operating temperature range. The thermal conductivity of sapphire transports heat to the lamp flange 3c and distributes it evenly to avoid cracking the window 3d. The getter 3e is wrapped around the cathode 3b and mounted on the post. The getter 3e absorbs pollutant gases generated within the lamp during operation, and extends the lamp's life by preventing the pollutants from contaminating the cathode 3b and transporting unwanted materials onto the reflector 3k and window 3d. The anode assembly 3f consists of an anode 3g, a base 3h, and a tubular portion 3i. The anode 3g is generally constructed of pure tungsten and is much blunter in shape than the cathode 3b. This shape is largely due to discharge physics that causes the arc to propagate at its positive electrical attachment point. The arc is typically somewhat conical in shape, with the tip of the cone contacting the cathode 3b and the base of the cone resting on the anode 3g. The anode 3g is larger than the cathode 3b to conduct more heat. Approximately 80% of the waste heat conducted within the lamp is conducted out through the anode 3g and 20% is conducted through the cathode 3b. The anode is generally constructed to have a less heat resistant path to the lamp's heat sink, and therefore the lamp base 3h is relatively large. The base 3h is constructed of iron or other thermally conductive material to conduct the heat load from the lamp anode 3g. The tubular section 3i is a port for evacuating the lamp 100 and filling it with xenon gas. After filling, the tubular portion 3i is sealed, for example clamped or cold welded by a hydraulic tool, so that the lamp 100 is sealed and simultaneously disconnected from the filling and processing station. The reflector assembly 3j includes a reflector 3k and two sleeves 3l. The reflector 3k may be a near-pure polycrystalline alumina body that is glazed with a high temperature material to give the reflector a mirror surface. The reflector 3k is then sealed to the sleeve 3l, and a reflective coating is applied to the glazed inner surface.

[0007] 3A shows a first perspective view of a prior art cylindrical lamp 300. Two arms 345, 346 project outwardly from a shielded chamber 320. The arms 345, 346 house a pair of electrodes 390, 391 that project inwardly of the shielded chamber 320 and provide an electric field for ignition of an ionizable medium within the chamber 320. Electrical connections for the electrodes 390, 391 are provided at the ends of the arms 345, 346.

[0008] The chamber 320 has an entrance window 326 through which laser light from a laser source (not shown) can enter the chamber 320. Similarly, the chamber 320 has an exit window 328 through which high intensity light from the energized plasma can exit the chamber 320. The light from the laser is focused into the energized gas (plasma) to provide sustaining energy. Ionized media may be added or removed from the chamber by a controlled high pressure valve 398.

[0009] FIG 3B shows a second perspective view of the cylindrical lamp 300 by rotating the view of FIG 3A vertically 90 degrees. A controlled high pressure valve 398 is located generally opposite the sight glass 310. FIG 3C shows a second perspective view of the cylindrical lamp 300 by rotating the view of FIG 3B horizontally 90 degrees. Overall, the interior profile of the chamber 320 matches the exterior profile of the chamber 320.

[0010] An endoscope is a typically long, tubular, illuminated optical instrument (a type of borescope) used to see deep inside the body, in a procedure called endoscopy. Endoscopes are used to examine internal organs such as the throat or esophagus. Specialized instruments are named for the organs they examine. Examples include cystoscopes (bladder), nephroscopes (kidneys), bronchoscopes (bronchi), arthroscopes (joints) and colonoscopes (colon), and laparoscopes (abdomen or pelvis). They can be used for visual examination and diagnosis, or to assist in procedures such as arthroscopy. The light source of the endoscope is typically located remotely from the light exit lumen near the illumination target. Light is transmitted from the light source to the exit lumen via a light guide, such as an optical fiber.

[0011] Minimally invasive endoscopic and robotic surgery are driven by fiber optic light sources. The fibers are typically in the range of 3.0 to 4.8 mm in diameter. However, current light sources can suffer from loss of radiance, which can be problematic in the field of endoscopic and robotic surgery practice. Also, the diameter of the light-guiding fiber is becoming unsuitable for environments where imaging and possibly instrument working channels are required in the same fiber bundle. The current trend is to get more information from the available space, which is shrinking the fiber diameter. For example, smaller fiber bundles may enable procedures that are not currently possible with current methods and devices. Existing light sources do not have sufficient etendue to couple significant levels of light in fibers with diameters smaller than 3 mm. This results in insufficient light for the camera to provide a sufficiently noise-free image. Thus, there is a need to address one or more of the above-mentioned shortcomings. Summary of the Invention

[0012] Embodiments of the present invention provide a laser-sustained plasma and endoscopy light source. Briefly, the present invention is directed to applications where high brightness or irradiance is delivered through small diameter light guides or fibers, less than 1 mm, and therefore more space is available for imaging fiber and / or laser delivery fiber.

[0013] Other systems, methods, and features of the invention will be or become apparent to one with skill in the art upon examination of the following figures and detailed description. All such additional systems, methods, and features are intended to be included herein, be within the scope of the invention, and be protected by the accompanying claims. [Brief description of the drawings]

[0014] The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention. The drawings illustrate embodiments of the invention and, together with the specification, serve to explain the principles of the invention.

[0015] [Figure 1] FIG. 1 is a schematic diagram of an exploded view of a high intensity lamp according to the prior art. [Diagram 2] FIG. 2 is a schematic diagram of a cross-sectional view of the prior art high intensity lamp of FIG. [Figure 3A] FIG. 1 is a schematic diagram of a cylindrical laser-driven sealed beam lamp according to the prior art. [Figure 3B] FIG. 3B is a schematic diagram of the cylindrical laser-driven sealed beam lamp of FIG. 3A from a second perspective. [Figure 3C] FIG. 3B is a schematic diagram of the cylindrical laser-driven sealed beam lamp of FIG. 3A from a third perspective. [Figure 4] 1 is a schematic diagram of a first exemplary embodiment of a lamp having a cylindrical plasma lamp chamber. [Diagram 5]1 is a schematic diagram of a second exemplary embodiment of a lamp having a parabolic plasma lamp chamber. [Figure 6] 1 is a flow chart of an exemplary embodiment of a method for producing high intensity light coupled into a small diameter light guide. [Figure 7] FIG. 5 is a schematic diagram of a lamp electrode detail for the first embodiment of FIG. 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The following definitions are useful in interpreting terms applied to features of the embodiments disclosed herein and are intended solely to define the elements within the present disclosure.

[0017] As used in this disclosure, "black body" refers to an object that can absorb all electromagnetic radiation that falls on it. A black body maintained at a constant temperature is a perfect radiator at that temperature because the radiation reaching and leaving the black body must be balanced. Black body spectrum refers to the spectrum of electromagnetic waves that a black body can emit.

[0018] As used in this disclosure, collimated light is light whose rays are nearly parallel and therefore will spread minimally as they propagate.

[0019] As used in this disclosure, "substantially" means "almost" or within normal manufacturing tolerances. For example, a substantially flat window, while intended to be flat by design, may vary from being perfectly flat based on variations due to manufacturing.

[0020] Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

[0021] As mentioned in the Background section, minimally invasive robotic surgery typically uses fiber optic light sources in the diameter range of 3.0 to 4.8 mm. The following exemplary embodiment of the invention describes an endoscopic light source configured to provide white light with a blackbody spectrum in a fiber diameter of 200 to 500 micrometers.

[0022] In a first embodiment of the endoscope light source 400 as shown by FIG. 4, the combined laser source 420 may include multiple laser driver units 102-104. Each laser driver unit 102-104 may emit light of a different wavelength / wavelength band and / or intensity. The light from the laser driver units 102-104 is combined in an optical conduit 401, e.g., an optical fiber, and emitted via an optical expander 105. The output optics of the combined laser source 420 may be configured differently for alternative embodiments. Similarly, in alternative embodiments, the combined laser source 420 may include more or less than three driving units.

[0023] The first laser driver unit 102 provides a portion of the beam 405. The beam 405 is collimated via an entrance collimator 106 and focused, for example, via focusing optics 107, into a plasma-sustaining beam 407. The plasma-sustaining beam 407 enters a cylindrical shielded chamber of the lamp 108 via an entrance window 109. For example, the lamp 108 may be a cylindrical lamp. The shielded chamber of the lamp 108 contains an ionizable medium 425, for example, xenon, krypton, or a mixture of xenon and krypton. Once ignited, the ionizable medium 425 forms a plasma 430 that emits high intensity light 410. The plasma 430 is sustained by energy from the first laser driver unit 102 via the plasma-sustaining beam 407. The plasma 430 may be ignited (ionized) by an electronic ignition module 114, for example, electrodes 790, 791 (FIG. 7). The electronic ignition module 114 may provide power to the electrodes 790, 791 via electrical connections in the arms 745, 746 (FIG. 7) of the lamp 108. Alternatively, the electronic ignition module 114 may be omitted and the plasma may be ignited without electrodes, for example via automatic ignition by the first laser driver unit 102.

[0024] The high intensity output light 410 leaves the chamber of the lamp 108 through the output window 110 and is optically coupled to the exit fiber 113. For example, the high intensity output light 410 may be approximately white in color and may be collimated through the output collimating optics 111 into a collimated beam 411 and then focused through the output focusing optics 112 to the input face of the exit fiber 113. For example, the collimating optics 111 may be as simple as a single positive lens, a multi-lens beam expander based on a positive and negative lens assembly, or a parabolic mirror, or a combination of a parabolic mirror and a combination of positive and negative lenses. The light is emitted at an output face 414, for example an output face located at the distal end of the endoscope close to the illumination target. The exit fiber 113 has a fiber diameter 415, for example in the range of 200-500 micrometers.

[0025] A first laser driver unit 102, for example a low power (150 watt) 979 nm first laser driver unit 102, can generate plasma in xenon, krypton or mixed noble gases with a plasma waist size of 150 microns or less that can be efficiently coupled into the diameter of the exit fiber 113 under pressures ranging from 10 bar to 50 bar in the lamp 108. This is not possible with standard endoscope light sources, for example xenon short arc solutions or non-laser solid state light sources.

[0026] The second laser driver unit 104 has a different wavelength than the first laser driver unit 102. For example, the second laser driver unit 104 may generate a 10-100 mW beam at 803 nm (or other wavelength), which may be mixed with the plasma sustaining beam generated by the first laser driver unit 102 for fluorescence-based diagnostics. The light from the second laser driver unit 104 is preferably mixed with visible light at the output of the lamp 108 to excite dyes for fluorescence techniques. Alternatively, the fluorescence excitation beam generated by the second laser driver unit 104 may be mixed with high intensity light at the output of the lamp 108. For example, the beams may be mixed using a dichroic coated mirror at less than 45 degrees that reflects one wavelength and passes the other, where the two beams being mixed are orthogonal, but the mixing mirror is at less than 45 degrees. Alternatively, a mix cube with the same functionality may be used. The diagonals of the cube are the mixing surfaces, while the facets where the beams enter (vertically) may be coated with specific coatings to shape the properties of the beams mentioned above.

[0027] A first laser driver unit 102, e.g., a 150W laser diode stack, is coupled to the optical conduit 401, e.g., through beam correction optics (not shown). The beam correction or shaping optics described and required herein are used to shape the enhanced diode stack light output, which has different divergence in the horizontal and vertical planes, into a more symmetrical beam pattern with nearly uniform divergence in all directions. The optical conduit 401 may be, e.g., a 200 micrometer laser fiber, maintaining 95% of the power at, e.g., a numerical aperture (NA) of 0.15, although other NA ranges, e.g., 90% of the power at 0.2 NA, or even 80% of the power at 0.3 NA, may be practical. The latter two examples may show lower system output, but may still be sufficient for some applications.

[0028] Since the first laser driver unit 102 generates a beam that is invisible to the human eye, a third laser driver unit 103 generating visible light, e.g., a low power red laser less than 5 mW, may be mixed with the output of the first laser driver unit 102 and / or the second laser driver unit 104, so that optical alignment of all optical components 105, 106, 107, 111, 112 and lamp 108 can be performed using visible light instead of using other means, e.g., an IR converter to visualize the position of the 979 nm wavelength beam.

[0029] The output of the optical conduit 401 may be terminated in a fiber connector (not shown), allowing a modular approach to switching the laser drive units 102, 103, 104. The fiber connector is coupled to beam conditioning optics, such as an optical expander 105, an input collimator 106, such as a collimating lens, and an input focusing optic 107, such as a focusing lens. The optical expander 105 shapes the beam waist of the laser at the focal point. The NA of the input focusing optic 107 is preferably in the range of 0.4 to 0.6.

[0030] The focused output of this laser drive system, including the plasma sustaining beam 407, is delivered through an entrance window 109 into the lamp 108, 208. In a first embodiment, the lamp may be configured as a cylindrical sealed cavity lamp 108 with a sapphire entrance window 109 for the laser entrance and a sapphire exit window 110 for the high intensity visible exit light as shown in FIG. 4. The cylindrical sealed cavity lamp 108 generates an expanded beam 410 with an NA of 0.4-0.6. Exit collimating optics 111 receive and collimate the expanded beam 410 to produce a collimated high intensity beam 411. Exit focusing optics 112 at the output of the lamp 108 focus the collimated light 411 into a focused output light 412, which is introduced into an exit fiber 113.

[0031] A second exemplary embodiment of an endoscopic light source 500 is shown in Figure 5. The combined laser source 420, lamp entrance optics 106, 107, exit focusing optics 112, and exit fiber 113 are substantially the same as those described in the first embodiment shown by Figure 4.

[0032] In the second exemplary embodiment 500, the lamp may be configured as a parabolic reflector cavity designed lamp 208 with a sapphire entrance window 109 for laser entry and a sapphire exit window 110 for high intensity visible exit light. The lamp entrance optics 106, 107 focus the plasma sustaining beam 407 into the lamp focus region 530 of the parabolic reflector cavity designed lamp 208, and thus the plasma 430 energized by the plasma sustaining beam 407 is located in the lamp focus region 530. The parabolic reflector cavity designed lamp 208 reflects the high intensity light generated by the plasma 430 to produce a collimated beam 511 with a beam size limited by the diameter of the exit window 110 and a configurable divergence. Note that because the emittance of a parabolic reflector is determined by the diameter (or aperture) of the parabolic mirror (assuming the parabolic mirror is completely filled with expanded light) divided by the source (plasma) spot size, e.g., 150 microns or so, the emittance is about 8 times smaller than a typical endoscopic xenon lamp, thereby coupling more light into the exit fiber 113 than previous techniques. Exit focusing optic 112 at the output of lamp 208 focuses collimated light 511 into focused output light 512, which is introduced into exit fiber 113.

[0033] 6 is a flow chart of an exemplary embodiment of a method for generating high intensity light coupled into a small diameter light guide. However, as would be understood by a reasonably skilled person in the art of the present invention, any process description or block in the flow chart should be understood as representing a module, segment, portion of code, or step that includes one or more instructions for implementing a particular logical function in the process, and alternative implementations in which functions may be performed in an order other than that shown or described, including substantially simultaneously or in reverse order, depending on the functionality involved, are within the scope of the present invention. The method is described with reference to FIG. 4 and FIG. 6.

[0034] As indicated by block 610, a plasma sustaining beam 407 having a power of 150 W or less is generated, for example by the first laser driver unit 102. One or more other light sources may be mixed into the plasma sustaining laser beam. For example, the output of a second laser driver unit 104 generating a different wavelength than the first laser driver unit 102, for example a 10-30 mW laser at 803 nm±15 nm, and / or the output of a third laser driver unit 103 generating visible light, for example a low power red laser. The second laser driver unit 104 preferably generates 5-10 mW of comparable power.

[0035] As indicated by block 620, the ionizable medium 425 is ignited in the shielded chamber of the lamp 108 to form a plasma 430. For example, the ionizable medium 425 may be xenon, krypton, or a mixture of xenon and krypton. The ionizable medium 425 may be ignited by the first laser driver unit 102 and / or by non-electrode ignition agents (not shown), for example, using a pair of electrodes 790, 791 (FIG. 7) that extend into the chamber of the lamp 108. A plasma sustaining beam 407 is introduced into the shielded chamber of the lamp 108 through an entrance window 109, and the plasma sustaining beam 407 provides energy to sustain the plasma 430, as indicated by block 630.

[0036] The plasma 430 is maintained in the chamber of the lamp 108 with a plasma waist size of 150 microns or less, as shown by block 640. For example, the waist size may be controlled via the power level of the first laser driver unit 102 and / or by the lamp entrance optics 105, 106, 107. The plasma 430 emits high intensity light 410, e.g., visible light exhibiting a black box spectrum. The chamber of the lamp 108 emits the high intensity light 410 generated by the plasma 430 through the chamber exit window 110, as shown by block 650. The high intensity light 410 may be collimated into a collimated beam 411 via the exit collimating optics 111 and then focused to form a focused output light 412. The focused output light 412 is coupled into an exit fiber 113 having a diameter of 500 μm or less, e.g., 200-500 micrometers, as shown by block 660.

[0037] It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.

Claims

1. an incident laser source comprising a first laser driver unit (102) configured to emit a plasma sustaining beam; an incident collimator (106) configured to receive the plasma sustaining beam and produce a collimated incident beam (406); an incident focusing optic (107) configured to receive the collimated incident beam and generate a focused sustain beam; A shielded lamp chamber (108) containing an ionizable medium that, when ignited, forms a high intensity light emitting plasma (410, 411) with a waist size of less than 150 microns, an entrance window (109) configured to receive the focused sustain beam; an exit window (110) configured to emit high intensity light (410) generated by the plasma; a shielded lamp chamber further comprising: an ignition source configured to ignite the ionizable medium; an exit fiber (113) configured to receive and transmit said high intensity light; Equipped with the high intensity light comprises white light having a blackbody spectrum; the exit fiber has a diameter in the range of 200 to 500 micrometers; illumination source.

2. The illumination source of claim 1 , wherein the ignition source further comprises a pair of electrodes (790, 791).

3. The illumination source of claim 1 , wherein the ignition source further comprises the first laser driver unit.

4. The illumination source of claim 1 , wherein the ionizable medium comprises xenon and / or krypton.

5. 10. The illumination source of claim 1, wherein the plasma sustained laser is on the order of 150 W.

6. 2. The illumination source of claim 1, wherein the incident laser source further comprises a second laser driver unit (104) configured to generate a second wavelength in the range of 10-30 mW that is mixed with the plasma sustaining beam.

7. 7. The illumination source of claim 6, wherein the incident laser source further comprises a third laser driver unit (103) configured to generate a visible beam mixed with the plasma sustaining beam and the second wavelength.

8. 10. The illumination source of claim 1 , wherein the first laser driver unit further comprises a 150 W laser diode stack coupled through beam correction optics to a 200 micrometer laser fiber with a numerical aperture (NA) range of 0.15 to 0.

3.

9. 2. The illumination source of claim 1, wherein the incident laser source further comprises a third laser driver unit (103) configured to generate a visible beam mixed with the plasma sustaining beam and the second wavelength.

10. 10. The illumination source of claim 9, wherein the third laser driver unit comprises a red laser having a power level of less than 5mW.

11. the input laser source further comprises an output fiber assembly configured to receive and mix light from the first laser driver unit, the second laser driver unit, and the third laser driver unit; 10. The illumination source of claim 9, wherein the output fiber assembly is terminated in a connector coupled to an optical expander (105).

12. the optical expander is configured to shape the beam waist of the laser at the focal point; The illumination source of claim 11, wherein the numerical aperture (NA) of the entrance focusing optics is in the range of 0.4 to 0.

6.

13. 10. The illumination source of claim 1, wherein the shielded lamp chamber is configured as one of the group consisting of a cylindrical shielded cavity and a parabolic reflector cavity.

14. 1. A method for producing high intensity light coupled into a small diameter light guide, comprising: igniting an ionizable medium in a shielded lamp chamber to form a plasma; generating a plasma-sustaining laser beam having a power of 150 W or less; providing energy to the plasma with the plasma sustaining laser beam; maintaining said plasma in said chamber with a plasma waist size of 150 microns or less; emitting high intensity light generated by the plasma through a chamber exit window; coupling the high intensity light into an exit fiber having a diameter of 500 μm or less; A method comprising:

15. The method of claim 14 further comprising mixing the plasma sustaining laser beam with a second laser beam in the range of 10-30 mW.

16. The method of claim 14 further comprising the step of mixing the plasma sustaining laser beam with a visible laser beam.

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