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.