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US 7,621,677 B2Granted
Optical coupler for a light emitting device with enhanced output brightness
AssigneeYLX Incorporated
InventorsYi Yang, Li Xu, Yi Li
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AssigneeYLX Incorporated
InventorsYi Yang, Li Xu, Yi Li
Estimating the term…
A light source is described where the light emitted by a solid-state light emitting device such as an LED is coupled into an optical waveguide such as an optical fiber. A highly reflective coupler (reflector) is disposed around the LED and a segment of the waveguide adjacent the LED. Light emitted from the LED that falls outside of the numerical aperture of the waveguide leaks out of the waveguide, but is reflected back to the waveguide by the reflector. The reflected light is re-reflected or scattered by the LED or the substrate the LED is mounted on, and the re-reflected or scattered light that falls within the numerical aperture of the waveguide is coupled into the waveguide. As a result, light coupling efficiency is increased and the output brightness of the light at the other end of the fiber is enhanced.
A light source comprising:
A light source comprising:
A light source comprising:
A light source comprising:
A light source comprising:
A light source comprising:
A coupling device for collecting light from a light emitting device, comprising:
A method for coupling light emitted by a light emitting device into a waveguide, comprising:
A light source comprising:
Dependencies are inferred from the claim text.
From the US filing history. Foreign family members aren’t listed.
Coupling light guides with opto-electronic elements: coupling with non-coherent light sources and/or radiation detectors, e.g. lamps, incandescent…
The coupling comprising intermediate optical elements, e.g. lenses, holograms: the intermediate optical element having redirecting reflective…
Optical elements, systems or apparatus
About 10 months of term left · ends 21 Aug 2027 (estimated)
1. Field of the Invention
This invention relates to light sources, and in particular, it relates to light sources using solid state light emitting devices.
2. Description of the Related Art
FIG. 1 illustrates a prior art light source where light emitted by a light emitting device is directly coupled into a fiber.
FIGS. 2a and 2b illustrate a light source employing a reflective coupling device for coupling light from a light emitting device into a waveguide according to a first embodiment of the present invention.
FIGS. 3a and 3b illustrate a light source employing a reflective coupling device for coupling light from a light emitting device into a waveguide according to a second embodiment of the present invention.
Embodiments of the present invention provide a light source where the light emitted by a light emitting device is coupled into an optical waveguide. It employs a highly reflective coupler (reflector) which helps to recycle the light from the light emitting device that falls outside of the numerical aperture of the waveguide back to the light emitting device, thereby increasing the coupling efficiency and enhancing the output brightness of the light source. The light emitting device may be a light emitting diode (LED), a laser diode, or other solid-state light emitting devices. The light emitting device may also be a wavelength conversion material such as a phosphor that converts a shorter wavelength light to a longer wavelength light, or any other suitable device that emits light. An LED is used as an example in the embodiments shown in FIGS. 2a-5.
In a first embodiment of the present invention illustrated in FIGS. 2a and 2b, an LED chip 12 is mounted on a substrate 11. A highly reflective layer 11a (having a reflectivity of, for example, 50% or higher for the light emitted by the LED) may be provided underneath the active region of the LED. The reflective layer 11a may be formed of a metal coating. Alternatively, or in addition, the surface of the LED 12 may be a roughed surface to reflect and scatter light. An optical fiber 14 is disposed on the LED 12, either directly with the end surface of the fiber contacting the LED surface, or with an air gap in between as described in more detail later. A reflector 16 with a curved, highly reflective surface surrounds the LED 12 and a section of the fiber 14 adjacent the LED. An optical medium 18 such as a gel is filled in the space enclosed by the reflector 16, the fiber 14 and the substrate 11. Preferably, the optical medium 18 is an index matching material having a refractive index approximately equal to that of the fiber cladding 14a, the latter being lower than the refractive index of the fiber core. One example of an index matching material is an index matching gel. FIG. 2b is a top cross-sectional view of the light source showing the LED 12 (partially shown), the fiber 14 and the reflector 16.
As shown in FIG. 2a which is a cross-sectional view in a plane through the center axis of the fiber 14, the light emitted by the LED 12 that has an angle falling within the numerical aperture of the fiber 14 is coupled into and travels along the fiber via total internal reflection by the fiber cladding 14a. The light emitted by the LED 12 that falls outside of the numerical aperture of the fiber 14 leaks out of the fiber, is reflected back by the reflector 16, and re-enters the fiber 14. The reflected light strikes the LED 12, and a majority of it is reflected or scattered by the reflective layer 11a under the LED and/or by the roughed surface of the LED back into the fiber 14 at various angles. The reflected light that has an angle falling within the numerical aperture of the fiber 14 is coupled into the fiber, while reflected light that falls outside of the numerical aperture of the fiber leaks out of the fiber and is reflected back by the reflector 16 again. The reflection process may happen many times. Thus, by using the reflector 16, light emitted by the LED 12 that would otherwise leak out of the fiber 14 can be couple into the fiber, thereby increasing the overall coupling efficiency of the light into the fiber. As a result, the brightness of the light at the output end of the fiber 14 is increased.