Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
1999-11-16
2001-08-07
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
With optical coupler
Particular coupling structure
C385S033000, C385S901000, C362S551000, C362S556000
Reexamination Certificate
active
06272269
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to fiber optic illuminators and, more particularly, to the use of waveguides for collecting, condensing and homogenizing light from a source and coupling the light into the optical fiber more efficiently. Various light sources, such as lamps, solid-state light sources (gallium nitride or other light emitting diodes for example) and/or fluorescent optical fiber, in conjunction with mixing waveguides, can be employed to produce a large array of colors, including white light, for pumping and/or coupling into colorless and/or fluorescent optical fiber for general illumination purposes.
BACKGROUND
A traditional approach for coupling light from a lamp or other light source into an optical fiber is to concentrate the light at the focal point of an elliptical or parabolic reflector, as generally illustrated in
FIG. 1. A
typical illuminator employs a lamp as the light source
100
, an elliptical reflector
102
, a power source
110
, and in some cases a motorized color wheel
108
. The light from lamp
100
is focused by elliptical reflector
102
onto the input end of an optical fiber
106
. Optical fiber
106
is typically a polymeric type fiber optic cable with a relatively large core (between about 1 mm and about 30 mm in diameter) and a jacket (or cladding, typically polytetrafluoroethylene or other polymer or material) having a lower refractive index than that of the core. The recommended service temperature for this type of optical fiber is less than about 80° C., although where the polymeric optical fiber employs a cross-linked polymer the service temperature may be as high as is 120° C. and even as high as 150° C. intermittently. These types of optical fiber are disclosed in detail in U.S. Pat. No. 5,298,327, U.S. Pat. No. 5,579,429, and U.S. Pat. No. 5,067,831. Each of said patents is hereby incorporated by reference as if fully set forth herein.
Unfortunately, typical lamps (such as tungsten halogen lamps and arc lamps) are extended light sources (due to the finite size of the filament or arc, as the case may be), whereas reflectors function most efficiently when the light source is a point source that can be efficiently collected by the reflector and focused to a small spot on the end of the optical fiber. Optical fibers used typically have a core diameter of between about 3 mm and about 15 mm. Filaments and arcs usually cannot be focused efficiently to such a small spot; they are typically focused to larger spots having an intensity distribution peaked in the center and decreasing towards the edges.
FIG. 2
illustrates a typical elliptical reflector output from a tungsten halogen lamp having a filament 5 mm long. The focused spot size is approximately 20 mm in diameter, and if such a spot is coupled into a 12 mm core optical fiber a substantial amount of light is lost due to the spot over-filling the core. Also, the intensity distribution over the surface of the optical fiber must be kept to a level sufficiently low so as not to exceed the maximum service temperatures as described above. If the illumination spot from the reflector is too intense, the fiber end may overheat and burn. Therefore, the peak of the intensity distribution shown in
FIG. 2
must be kept below a burning threshold, and the remainder of the input area of the optical fiber cannot be illuminated as intensely as the center and the brightness level of the optical fiber output would be correspondingly reduced. The alignment between the lamp, reflector, and optical fiber is of critical importance when using elliptical type reflectors, and when the illuminator requires service or a new lamp is installed re-alignment becomes necessary, since even few millimeters of variation in the filament or arc position results in substantial reduction of optical fiber light output.
Infrared and ultraviolet radiation generated by the lamp must be managed. The ultraviolet radiation can degrade polymeric optical fiber at the input end, thereby substantially reducing light coupling into the fiber optic. Ultraviolet radiation can also photochemically transform certain types of optical fiber into brittle optical fiber, which can be easily broken or cracked. Infrared radiation can cause additional heating at that the input end of the fiber optic, possibly leading to overheating and/or burning of the optical fiber.
The illuminator configuration of
FIG. 1
is typically most useful for relatively low power illuminators or applications where relatively low illumination levels are sufficient. Similar illuminator configurations are described in U.S. Pat. No. 4,704,660, U.S. Pat. No. 4,425,599, and U.S. Pat. No. 5,400,225. Each of said patents is hereby incorporated by reference as if fully set forth herein.
Other methods have been used to increase the coupling efficiency of the light from the light source into the optical fiber. One or more lenses located near the input end of the fiber or between the light source and the fiber input end have been used with some success in illuminators having a light source approximating a point source. However, for higher power illuminators where the light source is larger, the light source still cannot be efficiently imaged onto the small core of the fiber input end, and a substantial fraction of the light is lost as described above.
It is therefore desirable to provide an illuminator in which high intensity illumination may be efficiently coupled into and transmitted through an optical fiber. It is therefore desirable to provide an illuminator in which high intensity illumination may be coupled into and transmitted through the optical fiber without overheating and/or burning the optical fiber. It is therefore desirable to provide an illuminator in which ultraviolet and/or infrared radiation are substantially eliminated from the light input into the optical fiber. It is desirable to provide an illuminator wherein various wavelength components may be selected for output from the illuminator.
SUMMARY
Certain aspects of the present invention may overcome one or more aforementioned drawbacks of the previous art and/or advance the state-of-the-art of optical-fiber-coupled illuminators, and in addition may meet one or more of the following objects:
To provide a fiber optic illuminator using internally reflecting waveguides;
To provide a fiber optic illuminator with multiple output ports using internally reflecting waveguides;
To provide a fiber optic illuminator using internally reflecting waveguides and light sources of up to 1,300,000 lumens luminous flux and/or a color temperature up to 5600 K;
To provide a fiber optic illuminator using internally reflecting waveguides and providing relatively high levels of pumping light for colorless and/or fluorescent optical fiber for general illumination applications;
To provide a fiber optic illuminator using internally reflecting waveguides and solid-state light sources for pumping colorless and/or fluorescent optical fiber;
To provide a fiber optic illuminator using internally reflecting waveguides and solid-state light sources for pumping fluorescent optical fiber to generate white light within the core of the fiber suitable for illumination applications;
To provide a fiber optic illuminator using internally reflecting waveguides and solid-state light sources with phosphorus blend coating for generating white light for pumping colorless and/or fluorescent optical fiber;
To provide a fiber optic illuminator using internally reflecting waveguides and solid-state light sources, each driven by digital-to-analog converters (DACs) and a computer interface, for pumping clear and/or fluorescent optical fiber;
To provide a fiber optic illuminator employing a diffraction grating as a wavelength selector; and
To provide a fiber optic illuminator employing a diffraction grating as a wavelength selector, wherein light from the illuminator selected by the diffraction grating is transmitted by a secondary optical fiber.
One or more of the foregoing objects may be achieved in the present invention by an illu
Alavi David S.
DN Labs Inc.
Palmer Phan T. H.
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