Patent ID: 6577790
Filing Date: 2003-06-10
Classification: G02B

Abstract:
An optical device, comprising:an output fiber; a first rod lens; a second rod lens; an input fiber; and an optical function element, the first rod lens converting a beam leaving an end face of the output fiber into a substantially parallel light ray, and after passing through the optical function element, the substantially parallel light ray being condensed by the second rod lens and then entering the input fiber, wherein optical axes of the output fiber, the first rod lens, the second rod lens, and the input fiber all coincide, a refractive index distribution of the first rod lens is expressed by nA(r)2=n0A2Â·{1âˆ’(gAÂ·r)2+h4A(gAÂ·r)4+h6A(gAÂ·r)6+h8A(gAÂ·r)8+ . . . },â€ƒâ€ƒEq. 55 wherein r denotes a radial distance from the optical axis of the first rod lens, n0A a refractive index on the optical axis of the first rod lens, and gA, h4A, h6A, and h8A refractive index distribution coefficients,a refractive index distribution of the second rod lens is expressed by nB(r)=n0B2Â·{1âˆ’(gBÂ·r)2+h4B(gBÂ·r)4+h6B(gBÂ·r)6+h8B(gBÂ·r)8+ . . . },â€ƒâ€ƒEq. 56 wherein r denotes a radial distance from the optical axis of the second rod lens, n0B a refractive index on the optical axis of the second rod lens, and gB, h4B, h6B, and h8B refractive index distribution coefficients,a relationship of &thgr;FAÂ·&thgr;FB>0â€ƒâ€ƒEq. 57 is satisfied, wherein &thgr;FA indicates an angle between a line normal to an outgoing face of the output fiber and an optical axis of the optical device as a whole and &thgr;FB denotes an angle between a line normal to an incident face of the input fiber and the optical axis of the optical device as a whole,when &thgr;3A and &thgr;3B are defined by &thgr;3A=n0AÂ·gAÂ·WAÂ·(nFAâˆ’nLA)&thgr;FA/(nMÂ·nLA)+(nMâˆ’n0A)Â·&thgr;QA/nMâ€ƒâ€ƒEq. 58 and&thgr;3B=n0BÂ·gBÂ·WBÂ·(nFBâˆ’nLB)&thgr;FB/(nMÂ·nLB)+(nMâˆ’n0B)Â·&thgr;QB/nM,â€ƒâ€ƒEq. 59 wherein nFA indicates a core-center refractive index of the output fiber, nFB a core-center refractive index of the input fiber, WA an interval between the output fiber and the first rod lens, WB an interval between the second rod lens and the input fiber, nLA a refractive index of a medium between the output fiber and the first rod lens, nLB a refractive index of a medium between the second rod lens and the input fiber, nM a refractive index of a medium between the first rod lens and the second rod lens, &thgr;QA an angle between a line normal to an outgoing face of the first rod lens and the optical axis of the optical device as a whole, and &thgr;QB an angle between a line normal to an incident face of the second rod lens and the optical axis of the optical device as a whole, &thgr;3A and &thgr;3B satisfy0&lE;|&thgr;3Aâˆ’&thgr;3B|&lE;&pgr;/180â€ƒâ€ƒEq. 60 andrelationships of 0&lE;|&thgr;PA|&lE;15Â·(&pgr;/180)â€ƒâ€ƒEq. 61 and0&lE;|&thgr;PB|&lE;15Â·(&pgr;/180)â€ƒâ€ƒEq. 62 are satisfied, wherein &thgr;PA denotes an angle between a line normal to an incident face of the first rod lens and the optical axis of the optical device as a whole, and &thgr;PB an angle between a line normal to an outgoing face of the second rod lens and the optical axis of the optical device as a whole.