Waveguide arrays and method for contrast enhancement

A waveguide image transfer array comprising:

• a plurality of optical waveguide segments having a core and cladding lying in a parallel axial array of a selected length, said cladding being preferentially reducible relative to the core, said array having opposite optically finished ends exposing portions of the core and the cladding, at least one of the ends of the array having a reduced cladding portion forming a treated darkened surface layer to a depth sufficient to absorb incident radiation directed at the cladding and to render the exposed portions of the cladding opaque resulting in an enhanced, relatively uniform, array length independent enhanced contrast and reduced cross-talk compared with an untreated array.

A method for treating end surfaces of a waveguide array formed of a plurality of optical waveguide segments of a selected length extending between fused together end surfaces thereof, each of said waveguide segments including a core surrounded by a cladding, said cladding being a glass having reducible cations surrounding the core formed of a glass free of said cations and having a substantially higher glass transition temperature comprising the steps of:

• exposing at least one surface of the waveguide to a reducing atmosphere;
• maintaining the reducing atmosphere for a selected time and at a selected temperature sufficient to produce an absorbent, non-fluorescent surface layer on the exposed surface of the cladding glass to a depth sufficient to result in contrast characteristics for the array independent of wavelength and array length.

A method for treating end surfaces of a fiber optic image transfer device, formed of a plurality of optical waveguide segments, each of said waveguides including a core surrounded by a cladding and having fused together end portions in a parallel axial array of a selected length, to substantially eliminate cross-talk from light entering surfaces, said cladding being a glass having reducible cations surrounding the core formed of a glass free of said cations and having a substantially higher glass transition temperature comprising the steps of:

• exposing at least one surface of the waveguide to a reducing atmosphere for a time and at a temperature sufficient to produce light absorbing, non-fluorescent surface layer on the exposed surface of the cladding glass to a depth sufficient to result in a relatively uniform light transmitting characteristic greater than an unexposed array.

A waveguide comprising:

• at least one waveguide segment of a selected length having a core and cladding and extending between optically finished ends exposing portions of the core and the cladding, at least one of the ends of waveguide having a surface layer developed in the cladding to a depth sufficient to absorb incident radiation directed at the cladding without secondary emission and to render the exposed portions of the cladding opaque for enhancing contrast and reducing cross-talk relative to an array without developed surface layers.

A method for treating at least one end surface of a waveguide formed of a waveguide segment extending between optically finished surfaces each waveguide segment including a core surrounded by a cladding comprising the steps of:

• preferentially developing an opaque surface layer in the cladding sufficient to absorb incident radiation directed at the cladding without secondary emission, and to product a contrast characteristic in said waveguide greater than an undeveloped cladding.