Collimator having a holder used to connect rod lens to capillary which holds optical fibers

#Pursuant to 35 USC § 119, this application claims the benefit of Japan Patent Application No. 2001-401039 filed Dec. 28, 2002.

#The present invention relates to a collimator, and, more particularly, to a collimator including optical fibers held by a capillary and a gradient index rod lens which is optically connected to the optical fibers.

#For example, a conventional dual fiber collimator is assembled by connecting its components by a resin or adhesive. A collimator 100 shown in FIG. 1 is of a type in which a resin is impregnated in an optical path and includes optical fibers 12 and 13 held by a capillary 11 and a gradient index rod lens 14. The end face 11a of the capillary 11, which faces the lens 14, and end faces of the optical fibers 12 and 13 are inclined to prevent reflection and returning of light. The end face 14a of the rod lens 14, which faces the optical fibers 12 and 13, is also inclined. The end face 11a of the capillary 11 and the end face 14a of the rod lens 14 are connected together by an adhesive 15.

#The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:

#FIG. 1 is a cross-sectional view of a first conventional collimator;

#FIG. 2 is a cross-sectional view of a second conventional collimator;

#In the drawings, like numerals are used for like elements throughout.

#FIGS. 4 and 5 show a filter module 20 of a collimator type according to a first embodiment of the present invention which uses an optical fiber collimator (dual fiber collimator). The filter module 20 includes a capillary 21, two single mode optical fibers 22 and 23 held in the capillary 21, and a gradient index rod lens 24 which is optically connected to the optical fibers 22 and 23. A wavelength selectivity reflection film 25, which is a dielectric thin film having a wavelength selectivity, is formed on the flat end face of the rod lens 24. Light enters one of the optical fibers 22 and 23 and emerges from the end face of that optical fiber. The output light is collimated by the rod lens 24 and the collimated light is reflected at the wavelength selectivity reflection film 25. The reflected light is condensed by the rod lens 24 and is coupled to the other one of the optical fibers 22 and 23.

#The filter module 20 further includes a cylindrical lens holder 30 which holds the rod lens 24. The lens holder 30 has a lens holding hole 31 where the rod lens 24 is inserted. The rod lens 24 inserted in the lens holding hole 31 is connected to the lens holder 30 by a thermosetting adhesive 32. With the rod lens 24 and the lens holder 30 connected together, an annular end face 30a of the lens holder 30 is connected to the end face 21a of the capillary 21, which faces the rod lens 24, by an optical adhesive 33. The portions connected by the optical adhesive 33, the end portion of the outer surface of the lens holder 30 and the end portion of the outer surface of the capillary 21 are covered with a structural adhesive 34, so that the lens holder 30 and the capillary 21 are integrated.