Optical waveguides – With optical coupler – Particular coupling structure
Patent
1996-11-26
1998-12-22
Healy, Brain
Optical waveguides
With optical coupler
Particular coupling structure
385 31, 385 36, 385147, 385901, G02B 626
Patent
active
058526935
ABSTRACT:
The apparatus of this invention redirects light input to the apparatus without significant light loss, and preferably without increasing the light's etendue. The apparatus includes a light guide and a redirection member. The member has input, output and reflective surfaces. The member's input surface is joined to the light guide to define an interface, and the member's output surface is situated adjacent to a medium that can be another light guide or redirection member, a gas such as ambient air, or a vacuum, for example. The member is configured to redirect light traveling in the light guide from its reflective surface by a predetermined redirection angle. To prevent light at the largest spread angle present in the light traveling in the light guide, from traveling into the member, reflecting from the reflective surface and traveling back through the input surface to be lost, the relative refractive indices for the light guide or interface material, and member cause the light from the reflective surface to again reflect internally at the member's input surface. Also, to prevent light from traveling from the light guide through the input surface, the output surface and through the medium at an angle that would result in light loss, the relative refractive indices of the member and medium or interface material cause internal reflection of light in the member at the output surface-medium interface. Accordingly, the apparatus of this invention can redirect light with little or no light loss or increase in etendue. For use in relatively large-scale photolithography, the apparatus can include a plurality of light guides and respective redirection members that are combined to create a large, uniform light field. Also, the redirection members can be implemented as beam splitters optically coupled in succession, whose combined output surfaces generate a relatively large light field of uniform intensity. Groups of beam splitters can also be joined by light guides to produce a plurality of separated light fields.
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Healy Brain
Jones Allston L.
Ultratech Stepper, Inc.
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