Patent ID: 7557991

Claim:
A laser irradiation apparatus comprising: a laser oscillator; and an optical system for shaping a laser beam emitted from the laser oscillator into a linear beam spot having a long-side direction and a short-side direction; wherein the optical system includes: a first cylindrical lens array for dividing the laser beam emitted from the laser oscillator in the long-side direction; a first cylindrical lens for superposing the laser beams divided by the first cylindrical lens array; a second cylindrical lens array for dividing the laser beam emitted from the laser oscillator in the short-side direction; a second cylindrical lens for superposing the laser beams divided by the second cylindrical lens array, thereby forming a homogeneous plane; and a third cylindrical lens for projecting the homogeneous plane to an irradiation surface; wherein the first cylindrical lens is disposed between the second cylindrical lens and the third cylindrical lens, wherein the first cylindrical lens array comprises a cylindrical lens which is asymmetric along a generatrix thereof, and wherein a displacement of the homogeneous plane toward the irradiation surface depends on a thickness of the first cylindrical lens in the long-side direction.