Patent ID: 6990136

Claim:
A laser beam transmission apparatus comprising: a light-incidence optical system having at least first and second lenses disposed on the same optical path, the light-incidence optical system converging and focusing a laser beam emitted from a laser apparatus; and an optical fiber which transmits the laser beam that has been converged and focused by the light-incidence optical system, wherein in the light-incidence optical system, a first distance between an output end of the laser apparatus and the first lens or a second distance between the second lens and a light-incidence end of the optical fiber is freely set according to a relational formula based on a focal distance of each of the first and second lenses, and wherein said relational formula is expressed by b≈ ( f 1 2 ·f 2 +f 1 ·f 2 2 −a·f 2 2 )/ f 1 2 where a is the first distance, b is the second distance, f 1 is the focal distance of the first lens, and f 2 is the second lens, and the following conditions are satisfied: f 1 ≠f 2 ,a≠f 1 , and( a+b )<( f 1 +f 2 ).