JPS5577709A - Optical coupling device - Google Patents

Abstract

PURPOSE: To impart versatility by using three rod lenses.

CONSTITUTION: Rod lenses 21W23 whose refractive indices gradually decrease from the center toward the periphery within the section perpendicular to the central axis and whose respective lengths are substantially 1/4 period of the zigzag periods of light are so adjoined that the central axes mutually align, whereby the optical coupling device is provided. With this arrangement, the rays entering at an angle θ to the rod lenses of 1/4 period are converted to the rays parallel to the central axis from the point of a distance X from the central axis and since the relationships of X=θ/(n₀g) [n₀ is refractive index on the central axis, g is parameter] hold between the angle θ and distance X, the light emitting from the light emitting element 4 of an optical transmitter-receiver 2 becomes the parallel luminous flux of the beam diameter approximately identical to the core diameter of the optical fiber 3 and this luminous flux emits from the rod lens 21 and enters the optical fiber 3. The light emitted from the optical fiber 3 becomes the parallel luminous flux of the beam diameter approximately identical to the outside diameter of a ring-form photo detector 5 and emits from the rod lens 23, thus arriving at the ring-form photo detector 5.

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