Low-loss collimators for use in fiber optic rotary joints

Abstract

Fiber optic collimators are disclosed for use in fiber optic rotary joints (20) providing for improvement in insertion loss performance. One embodiment of the fiber optic collimator has a gradient-index rod lens (61) possessing a pitch of less than one-quarter. Improvement in insertion loss arises due to the increase in the effective focal length of the lens as the pitch is reduced, allowing the collimator to achieve a longer working distance. The increase in the effective focal length is accompanied by an increase in the back focal length of the lens, compared to the zero back focal length of the more typical quarter-pitch gradient-index rod lens. The increased back focal length can be filled by a cylindrical glass spacer (64), to which an optical fiber (68) is attached, resulting in a collimator with very similar form factor to the usual quarter-pitch gradient-index rod lens collimator. The increased back focal length can also be filled by a form of right-angle prism (71), to which an optical fiber is attached such that the fiber is oriented at 90 degrees to the optical axis of the lens useful for applications of pancake-style hybrid slip rings wherein the desired direction of fiber ingress to the rotary joint is perpendicular to the rotation axis of the rotary joint.

Dependencies are inferred from the claim text.