US 20070153541 A1
The present invention is directed to methods of mounting a light source, such as, for example a high-efficiency, high-power solid state light source (e.g., a LED) within a handle of an endoscope. One of the methods of the present invention includes removing a portion of a package surrounding the light source to expose a light source chip, positioning the exposed light source adjacent to a chassis within the handle and in contact with an end of a light guide bundle, translating the light source with the exposed light source chip about the end of the light guide while measuring light output from an illumination (i.e., distal) end of the light guide bundle with a photodetector, and securing the exposed light source to the chassis at a position in which maximum light output is measured.
18. An endoscope comprising:
an endoscope body including a light guide extending therethrough, the light guide having an illumination end and a contact end;
a thermally conductive handle attached to the endoscope body; and
a light source with an exposed light source chip positioned on the thermally conductive handle to remove heat from the light source, the exposed light source chip in contact with the contact end of the light guide.
19. The endoscope of
20. The endoscope of
21. The endoscope of
22. The endoscope of
23. An endoscope handle comprising:
a thermally conductive handle;
a light source with an exposed light source chip positioned on the thermally conductive handle to remove heat from the light source; and
a light guide including an illumination end and a contact end, the contact end of the light guide positioned on the exposed light source chip.
24. The endoscope handle of
25. The endoscope handle of
26. The endoscope handle of
27. The endoscope handle of
28. An endoscope comprising:
a thermally conductive handle;
a light guide including an illumination end and a contact end; and
a light source with an exposed light source chip, the light source secured to the thermally conductive handle at a position in which a maximum light output is measured at the contact end of the light guide.
29. The endoscope of
30. The endoscope of
31. The endoscope of
32. The endoscope of
CROSS REFERENCE TO RELATED APPLICATION
This application claims the benefit of the filing date of U.S. Provisional Patent Application Ser. No. 60/611,006, filed on Sep. 17, 2004, the entirety of which is incorporated herein by reference.
This invention relates to a remote illumination device using a high-power LED and a fiber optic light guide.
Light sources for endoscopic use are generally of two types: incandescent filament lamps and arc lamps. Incandescent lamps produce light by passing current through a tungsten filament, causing it to radiate light in proportion to its blackbody color temperature. The hotter the filament, the higher its color temperature and the more nearly it approaches daylight with a color temperature of approximately 5500K. Tungsten filament lamps range in color temperature from approximately 2400-3400K. Because of the low color temperature, objects illuminated by a tungsten filament light source appear slightly yellow due to the low output of blue light from these sources. Arc lamps produce light by creating a plasma between two electrodes within the sealed bulb. White light from these lamps can be produced by choosing the appropriate fill gas (usually Xe) and pressure (usually several atmospheres). Color temperature of common arc lamps is approximately 4000-6000K. Both types of lamps, filament and arc, are very inefficient in converting electrical power to light, and consequently produce large amounts of heat. The heat must be dissipated. It also contributes to a shortened useful life of such light sources.
There have been numerous attempts to utilize low power (<1 W electrical power consumption, typically operating below 100 mW) LEDs coupled to fiber optic light guides as light sources for endoscopy, dentistry, and for remote illumination of objects (as with a flashlight). Most of these prior attempts employ numerous low power LEDs for remote illumination. Multiple LEDs are necessary because the light output from a single, low power LED is very low and there is poor coupling of light emitted by the LED(s) into the optical fiber. An example of several coupling methods appears in U.S. Pat. No. 6,331,156 whereby the inventors place the fiber optic directly in front of either a surface mount or cylindrical LED without the use of additional optical components, coatings or gel. This patent also exemplifies the use of additional optical components in the form of lenses or mirrors in order to collect light generated from a standard, unmodified LED package configuration. US published patent application 2004/0004846 A1 utilizes a lens to couple the light emitted by an LED into a fiber optic. US published patent application 2003/0156430 A1 describes a device that consists of a number of individual LEDs mounted on mirrors, the arrangement of the LEDs and mirrors having a common focal point at the input end of the fiber light guide. U.S. Pat. No. 6,260,994 describes a plurality of LEDs mounted between a spherical or parabolic reflector and a lens, which directs the light emitted by the LEDs into the light guide fiber. In this invention, the LEDs emit light towards the collecting lens and away from the reflector. In U.S. Pat. No. 6,318,887, the LEDs are positioned so as to emit radiation towards a reflector, which then reflects light through a transparent printed circuit board and towards a lens and fiber light guide. In US published patent application 2002/0120181 A1, light emitted by several LEDs is collected along a common optical axis through a series of beam splitting prisms, in at least one embodiment with the use of lenses to couple the light from the LED into the prism, and then into the fiber. In these examples, the LED packages are not modified; multiple, low power LEDs are employed in order to attain a reasonable level of illumination; and in most of these examples, external optical components are employed in order to increase the coupling efficiency between the LEDs and the light guide fiber.
In US published patent application 2003/0231843, numerous low power LEDs are coupled into individual fibers, which are combined together at the distal end of the device to produce intense light for curing dental epoxy. This patent application describes an approach in which the LED package and light guide fiber are modified in order to increase the optical coupling efficiency between the two. In one embodiment, the cladding material from the fiber is removed and the fiber core is placed within the LED epoxy lens. The exterior of the epoxy lens is coated with a low refractive index “clad” that produces total internal reflection of the light emitted by the LED. Some of the light reflected by this LED clad can make its way into the core of the fiber and be transmitted to the distal end of the device. This patent application also includes a description of a taper attached to the external surface of the LED dome lens that couples the light into the fiber. Again, however, additional optical elements (cladding or tapers applied to the LED) are used. Also, the device employs numerous low power LEDs to attain sufficient light output from the device. This type of arrangement would be difficult if not impossible to implement with a high power LED because of the high operating temperature of these LEDs (up to 135 degrees C.). At high temperatures, the epoxy used in typical LED packages will melt or crack due to thermal cycling. In addition, high temperatures will cause the epoxy to discolor, typically becoming yellow. This will impart a yellow cast to the light, thereby lowering its effective color temperature and its desirability as a visual light source. In addition, discoloration will absorb lower wavelengths of light emitted by the LED, particularly those wavelengths in the blue and UV region of the spectrum that are essential for epoxy curing and fluorescence applications.
Recent advances in light emitting diodes (LEDs) have seen the advent of very high power LEDs, up to 5 W. This invention utilizes a high power white light LED as a light source for medical and industrial endoscopes. The high power, very small size, and high efficiency of these devices makes it possible to design an untethered endoscope; an endoscope without a light guide umbilical connecting the endoscope to an external light source. As a result, in some embodiments, the invention is directed to an endoscope with a light source mounted within a handle of the endoscope. In certain embodiments, a battery to power the light source is also positioned in the handle so that the endoscope is untethered. An advantage of this embodiment is that a user has full range of motion without being tied to an external power source. In addition, another advantage is that the endoscope is light in weight.
In general, the invention relates to an endoscope with a battery powered, high power LED incorporated into the endoscope handle. By close coupling of a light guide bundle to the LED without the use of additional optical components, a large amount of the light emitted by the LED can be coupled directly into the fibers of the light guide bundle. As a result, a greater amount of light from the LED can be transmitted to the distal end of the endoscope which illuminates objects under investigation. Embodiments of the present invention do not include auxiliary optics, such as lenses or mirrors, disposed between the light source and the light guide bundle, but instead rely on the small size of the LED's emitting region and the close placement (e.g., direct contact or close proximity) of the light guide bundle to the emitting region. Because the LED itself is very efficient in converting electrical energy into light and the described optical interface is very efficient at coupling this light from the LED into the light guide fiber, this new light source can be powered by small batteries that will operate for a considerable length of time without the need for battery replacement or recharging, and without making the endoscope handle cumbersome or unwieldy. The lack of auxiliary optics between the light source and the light guide bundle simplifies the mechanical design and volume of space within the handle needed for the light source. The high light output and high coupling efficiency of the light emitted by the LED into the light guide fiber increases battery lifetime and/or permits the use of smaller capacity, and smaller volume batteries.
In one aspect, the invention is directed to a method of mounting a light source within a handle of an endoscope. The method includes the following steps: removing a portion of a lens and an index matching solution from a light source package to expose a portion of a light source chip and form an exposed light source package; positioning the exposed light source package so that a securing surface of the exposed light source package is disposed adjacent to a chassis within the handle of the endoscope and a light emitting surface of the exposed light source package is in contact with a contact end of a light guide bundle, the light guide bundle extending from the contact end to an illumination end disposed on the working end of the endoscope; translating the exposed light source package about a plane containing the contact end while measuring light output from the illumination end with a photodetector to align the exposed light source package with the contact end; and securing the exposed light source package to the chassis at the position in which maximum light output is measured.
This aspect of the invention can include one or more of the following features. In some embodiments, the light mounted is a LED. In certain embodiments, the chassis is formed of a metal (e.g., aluminum) and a layer of thermally conductive grease is disposed between the securing surface and the chassis to facilitate conduction of heat from the exposed light source package. In some embodiments, the exposed light source package is secured to the chassis with screws, such as for example screws that are formed of a non-conductive material. In certain embodiments, the exposed light source package is battery powered, and may be conditioned to provide constant power to the light source chip, such as for example by a pulse width modulation circuit.
In another aspect, the invention is directed to a method of mounting a LED within a handle of an endoscope. The method includes the following steps: positioning a LED including a LED chip supported by a securing surface and having an exposed light emitting surface so that the securing surface is disposed adjacent to a chassis within the handle of the endoscope and the light emitting surface is in contact with a contact end of a light guide bundle, the light guide bundle extending from the contact end to an illumination end disposed on the working end of the endoscope; translating the exposed LED package about a plane containing the contact end while measuring light output from the illumination end with a photodetector to align the exposed LED package with the contact end; and securing the exposed LED package to the chassis at the position in which maximum light output is measured.
This aspect of the invention can include one or more of the following features. In some embodiments, the chassis is formed of a metal (e.g., aluminum) and a layer of thermally conductive grease is disposed between the securing surface and the chassis to facilitate conduction of heat from the exposed LED package. In certain embodiments, the LED is secured to the chassis with screws, such as for example that are formed of a non-conductive material. In some embodiments, the LED package is battery powered, and may be conditioned to provide constant power to the LED chip. In certain embodiments, the battery powered exposed LED package is conditioned by a pulse width modulation circuit.
While the above embodiments have been described as relating to endoscopes (e.g., medical endoscopes, industrial endoscopes), this invention also has applications in other areas, such as, for example, fiber optic lighting for microscopy, fiber optic lighting for still and video photograph. In addition, this invention can also be applied to other regions of the light spectrum, such as ultraviolet, near infrared, and infrared and can be used in other types of optical observations, such as fluorescence, absorbance, and transmittance measurements.
Other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiments, and the accompanying drawings, in which:
One embodiment of this invention utilizes a high power LED (Luxeon III Model LXHL-LW3C, Lumileds Lighting, LLC, 370 W, Trimble Road, San Jose, Calif. 95131) with a typical forward voltage of 3.7V and operating current at 700 mA. This device can be safely operated up to a current of 1 A with a corresponding typical forward voltage of 3.9V. This white LED has a typical color temperature of 5500K. The LED chip has an emitting surface of approximately 1 mm×1 mm, and is coated with a wavelength conversion phosphor (and/or fluorophor) that emits a broadband continuum of visible white light between about 470-700 nm.
The light emitting area of the LED is coupled to a small 1 mm square or round bundle of light guide fibers; a typical light guide bundle size used in endoscopes. The light guide bundle is composed of hundreds of individual glass (or plastic) fibers grouped together to form a single bundle at the light source, and either a single bundle or multiple bundles at the distal end of the endoscope. Such bundles can take on a variety of shapes at the distal end depending upon the design of the particular endoscope: one or more round bundles, a circular halo, a crescent, or the like. Small diameter fibers, typically 30-50 micrometers in diameter, are employed because these small fibers are flexible (necessary for flexible endoscopes that bend during use), or because they are required to fit into the narrow spaces around the optics either in the shaft or distal head of the endoscope.
Other types of light guides can be coupled to the LED in the manners described herein, including: liquid light guides, plastic or glass fibers, plastic or glass rods, and tapers made from fibers (glass and plastic) or solid tapers (glass and plastic). Single glass or plastic fibers may comprise the light guide. Such fibers around 1 mm in diameter are typically flexible. In order to accommodate a small light guide bundle of less than the LED emitting area, a fiber optic or solid plastic or glass taper may be placed between the LED emitting surface and the bundle, acting as an adapter that captures substantially all of the light emitted from the LED and efficiently couples it into the fiber bundle that delivers the light to the distal end of the instrument.
The details of the endoscope or other device in which the light source is used are known to those skilled in the art, for example as disclosed in U.S. Pat. No. 6,260,994 (incorporated herein by reference in its entirety). This holds true whether the light source is used in a medical or industrial endoscope (either flexible or rigid) or other application areas such as fiber optic lighting, delivery of light from other regions of the spectrum, other types of optical observations such as fluorescence, absorbance, and transmittance measurements, and remote light sources akin to fiber optic flashlights, used primarily for visual inspection.
The high-power white light-emitting LED chip is commercially supplied encapsulated in a silicone optical gel covered by a plastic dome lens assembly, which spreads the emitted light over a 160 degree angle (total included angle at which 90% of the total luminous flux is captured). A considerable amount of light can be captured by placing the light guide at the surface of this dome lens or utilizing additional optical components (lenses, mirrors, tapers, etc.) to couple the light into the fiber bundle. However, a much larger portion of light can be captured by moving the light guide adjacent to the surface of the LED chip.
Other embodiments of the invention are also anticipated and are now described.
In some instances, it is desirable to employ an index matching material between the fiber bundle and the LED chip, or the combination of the LED chip and its phosphor. The index matching material helps to couple the emitted light into the light guide, and typically has an index of refraction between that of the light emitting surface and that of the light guide. The material can be a gel. Examples of when an index matching material is desirable are: when the emitting surface is a substrate that the LED chip is mounted to, such as sapphire (n=1.76, where “n” is the refractive index), or when the LED chip is the emitting surface and it possesses a high refractive index. Examples of LED chips with very high refractive indices include chips manufactured from gallium nitride (n=2.5), gallium phosphide (n=3.31), and gallium arsenide (n=4.02). The amount of light coupled into the light guide from the LED can be increased, potentially by up to a factor of two, when an appropriate index matching material is employed between the LED and the fiber. The index matching material may also substitute for the silicone encapsulent 300; the silicone encapsulent 300 being a specific type of index matching material.
While the preferred embodiment of this invention utilizes a Luxeon III LED with a 1 mm square emitting surface, other LED package designs also lend themselves to the inventive technique of capturing light by a light guide, which may be accomplished with a fiber bundle. Some examples of these other package designs include the industry standard T1 —(3 mm) and T1¾ (5 mm) packages in which the LED chip is enclosed in an epoxy dome lens. It is readily apparent to those skilled in the art to understand how the epoxy package can be removed down to the level of the LED chip and coupled to the light guide. Similarly, the flat package design of the Microsemi (Microsemi Corporation, 580 Pleasant Street, Watertown, Mass. 02472) UPW3LEDxx readily lends itself to fiber coupling by directly bonding the light guide fiber to the face of the window adjacent to the LED chip, with or without an index matching material between the window and the fiber as is described in
Power for the LED is supplied by a rechargeable lithium ion battery. The battery is connected to the endoscope handle via a DC connector mounted in the handle, occupying the traditional position of a light guide umbilical cable or light guide post. Two multistrand wires connect the LED to the battery connector. Power from the battery is unregulated in one embodiment, but can be conditioned by a pulse width modulation circuit in other embodiments to provide a more constant power to the LED. Because the nominal operating voltage of the LED is 3.6V and the lithium ion battery, fully charged, is nominally 3.6-3.9V the LED operates initially at full power (about 800 mA of current) and slowly decreases in power as the battery's voltage and current drop. With a 1650 mA-hour lithium ion battery, this provides approximately 2 hours of useful light output for the endoscope before the battery requires recharging.
Other embodiments will occur to those skilled in the art and are within the following claims.