OPTICAL SYSTEM FOR LONG DISTANCE TRANSMISSION, AND SCAN LENS FOR LONG DISTANCE TRANSMISSION

Japanese Patent JP3786658

B2

PROBLEM TO BE SOLVED: To provide an optical system for long distance transmission in which beams are projected on an object through a long transmission system by scanning the beams in the initial stage of the transmission system, and a lens therefor. SOLUTION: The optical system for long distance transmission comprises a laser beam source, a plurality of galvano mirrors for scanning laser beams in a two-dimensional (or one-directional) manner, a scan lens comprising a relay lens L1 provided in an optical path behind the galvano mirrors to once condense the laser beams and a collimate lens L2 to correct the condensed laser beams to parallel beams while the distance between the lenses L1 and L2 is set to be the sum (f1+f2) of the focal length f1 and f2 of the lenses L1 and L2, and a plurality of guide pipes to surround the beams, and the distance Γ from the galvano mirrors to the object is set to be larger than 2(f1+f2).