Gradient index light conductor

Claim 2

A light beam transmitting transparent conductor consisting of an elongated optical transparent element having a refractive index distribution in Each cross-section perpendicular to the center axis of said element approximately satisfying the following relationship n N(1 - ar2) where N represents the refractive index at said center axis in any element crosssection, n represents the refractive index at a radial distance r from said center axis in said cross-section, and a is a positive constant in said cross-section, said transparent element having an input end face and an output end face each perpendicular to said center axis and having an optimum spot size at said input end face represented by the following formula Wo NOT = square root ( lambda /No pi ) .2 3/4 . ao 1/4 where Wo represents the optimum spot size at said input end face, lambda represents the wave length of a light beam to be transmitted through said transparent element, No represents the refractive index value N at said input end face, and ao is the value of a at said input end face, at least one of the factors N and a being such that the value thereof increases gradually from at least said input end face of said element toward an intermediate portion of said element along said center axis so that said element has an optimum spot size gradually increasing from said intermediate portion toward said input end face in such a manner that a light beam accurately introduced into said element upon said input end face with proper mode matching is transmitted axially through said element and exits therefrom at said output end face.

Claim 3

A light-beam transmitting transparent conductor as claimed in claim 1 in which said element has a cross-sectional radius which increases from said intermediate portion toward said at least one end surface.

Claim 4

A light beam transmitting conductor consisting of at least two sections disposed in end-to-end relationship to provide a long conductor, each of said sections consisting of a rod-shaped transparent element having a refractive index distribution in each cross-sections perpendicular to the center axis of said element approximately satisfying the following relation n N (1-ar2) where N represents the refractive index at said center axis in any element cross-section, n represents the refractive index at a radial distance r from said center axis in said cross-section, and a is a positive constant in said cross-section, each said transparent element having two opposite end faces each of which is perpendicular to said center axis and having an optimum spot size at one of its end faces represented by the following formula Wo Square Root ( lambda /No pi ) . 2 3/4.ao 1/4 where Wo represents the optimum spot size at said one end face, lambda represents the wave length of a light beam to be transmitted through said transparent element, No represents the refractive index value N at said one end face, and ao is the value of a at said one end face, at least one of said two elements having at least one of the factors N and a thereof gradually increasing from at least said one end face which is disposed adjacent an end face of the other of said to elements toward an intermediate portion of said one element along said center axis so that said at least one of said two elements has an optimum spot size which increases gradually from said intermediate portion toward said one end face in such a manner that a light beam exiting from an end face of said other element is accurately introduced into said one element upon said one end face with proper mode matching and is axially transmitted through said one element.

Claim 5

A light beam transmitting conductor consisting of at least two sections disposed in end-to-end relationship to provide a long conductor, each of said sections consisting of a rod-shaped transparent element having a refractive index distribution in each cross-sections perpendicular to the center axis of said element approximately satisfying the following relation n N (1-ar2) where N represents the refractive index at said center axis in any element cross-section, n represents the refractive index at a radial distance r from said center axis in said cross-section, and a is a positive constant in said cross-section, each said transparent element having two opposite end faces each of which is perpendicular to said center axis and having an optimum spot size at one of its end faces represented by the following formula Wo Square Root ( lambda /No pi ) . 2 3/4.ao 1/4 where Wo represents the optimum spot size at said one end face, lambda represents the wave length of a light beam to be transmitted through said transparent element, No represents the refractive index value N at said one end face, and ao is the value of a at said one end face, at least one of said two elements having at least one of the factors N and a thereof gradually increasing from at least said one end face which is disposed adjacent an end face of the other of said to elements toward an intermediate portion of said one element along said center axis so that said at least one of said two elements has an optimum spot size which increases gradually from said intermediate portion toward said one end face in such a manner that a light beam exiting from an end face of said other element is accurately introduced into said one element upon said one end face with proper mode matching and is axially transmitted through said one element.