| 摘要 |
PROBLEM TO BE SOLVED: To secure the alignment error tolerance of a light emitting element to a comparatively large extent by inserting a single relay lens between a first and second condensing lenses and imparting a specific relation to such lens system. SOLUTION: The device is provided with a first condensing lens 11a for receiving a Gauss luminous flux from a light emitting element s and a second condensing lens 11b for projecting the beam waist of the Gauss luminous flux to a light receiving element d. Between these first and second condensing lenses 11a, 11b, a single relay lens 12 is inserted which projects the unmagnified beam waist of the Gauss luminous flux by the first condensing lens 11a to a beam waist position in front of the second condensing lens 11b. Then, the device is so designed that a relation in terms of an expression is satisfied among the focal distance f1 , f2 of the first and the second condensing lens 11a, 11b respectively, the distance (combined length) L between these two lenses 11a, 11b, and the focal distance fr of the relay lens 12. |
