Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
1998-06-15
2001-02-13
Ngo, Hung N. (Department: 2874)
Optical waveguides
With optical coupler
Particular coupling structure
C385S125000, C385S146000
Reexamination Certificate
active
06188820
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a waveguide for the transmission of guided radiation from a medium with a high refraction index to a medium with a lower refraction index. The waveguide according to the invention is in particular suitable for the delivery of concentrated sunlight into a solar receiver, but may also be used in radio telescopes, fiber optics waveguides and the like.
BACKGROUND OF THE INVENTION
A radiation delivery waveguide of the kind to which the present invention refers is, inter alia, described in PCT/US95/04915, the entire disclosure of which is incorporated herein by reference.
The radiation delivery waveguide described in PCT/US95/04915 is used in a guided radiation receiver assembly comprising a first transparent medium with a first refraction index n
1
and a receiver chamber having an aperture and holding a second transparent medium having a second refraction index n
2
. The waveguide is transparent and has a third refraction index n
3
substantially equal to or greater than n
1
. The transparent radiation delivery waveguide has a first, radiation intake portion in optical contact with the first transparent medium and held tightly within the aperture, and a second tapered radiation delivery portion of non-circular cross-sectional shape, projecting into the receiver chamber.
Due to the specific design of the above radiation delivery waveguide, total and Fresnel reflections of the transmitted radiation at the waveguide/second transparent medium boundary inside the receiver chamber are minimized and extraction of the delivered radiation is maximized.
The radiation delivery waveguide described above is particularly advantageous for use in the field of solar energy transfer, specifically for transferring concentrated radiation from optical concentration systems to a solar receiver. In this case, the radiation delivery waveguide as well as the concentrator constituting the first transparent medium, is made of a solid transparent medium, particularly of fused silica. However, calculations show that with large scale solar energy systems and, consequently, large scale receivers, the radiation delivery waveguide will have such dimensions that if made of solid transparent material it will be extremely heavy and expensive.
It is accordingly the object of the present invention to provide an improved, less expensive radiation delivery waveguide, and a radiation delivery assembly using such a waveguide.
SUMMARY OF THE INVENTION
In accordance with the invention there is provided a guided radiation receiver assembly comprising a first transparent medium with a first refraction index n
1
, a receiver chamber having an aperture and holding a second transparent medium having a second refraction index n
2
, and a transparent radiation delivery waveguide having a third refraction index n
3
substantially equal to or greater than n
1
, which transparent radiation delivery waveguide has a first, radiation intake portion in optical contact with said first transparent medium and held tightly within said aperture, and a second, tapered radiation delivery portion of non-circular cross-sectional shape, projecting into the receiver chamber, wherein said radiation delivery waveguide consists of a transparent vessel holding a transparent liquid medium.
In accordance with the present invention, for the purposes of light extraction, the refraction index n
3
is that of the vessel.
The invention further provides a radiation delivery waveguide having a tapered radiation delivery portion of non-circular cross-sectional shape comprising a transparent housing holding a transparent liquid medium.
By one embodiment, the first transparent medium is a solar light concentrator made integral with said waveguide. In such an embodiment the radiation delivery waveguide and concentrator preferably form together a single vessel holding a single body of transparent liquid medium.
If desired, the radiation delivery waveguide may be linked to a heat exchanger for heat withdrawal from the transparent liquid medium therein.
The vessel of the radiation delivery waveguide according to the invention may be of any suitable radiation-resistant material, e.g. fused silica. Due to the relatively small width of the vessel walls and the relatively low density and price of the transparent liquid medium as compared to fused silica or similar materials, the radiation delivery guide in accordance with the present invention is of a relatively low weight and inexpensive.
Furthermore, in accordance with the invention the radiation delivery portion of the waveguide may hold additional elements made of transparent material having an index of refraction different from that of the liquid so as to interfere with a generally circular manner of radiation propagation inside the radiation delivery waveguide and thereby allow for a more effective light extraction into the receiver. Such elements may be in the form of transparent solid rods or cylindrical hollow components, either empty or filled with liquid.
REFERENCES:
patent: 3467098 (1969-09-01), Ayres
patent: 3900245 (1975-08-01), Dyott et al.
patent: 5005944 (1991-04-01), Laakmann et al.
patent: 5165773 (1992-11-01), Nath
patent: 5412750 (1995-05-01), Nath
patent: 63-113406 (1988-05-01), None
Ngo Hung N.
Norris McLaughlin & Marcus P.A.
Yeda Research and Development Company Israeli Company of the Wei
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