Patent ID: 7812283

Claim:
A laser irradiation method comprising: bending a laser beam emitted from a laser oscillator by a mirror tilted by a predetermined angle; making the laser beam pass through a first convex lens so as to form a linear beam due to astigmatism; blocking a low-intensity part of the linear beam by a slit; and projecting to an irradiation surface an image of the linear beam at the slit by using a second convex lens; wherein the slit, the second convex lens, and the irradiation surface are arranged so that a distance (M 1 ) between the slit and the second convex lens and a distance (M 2 ) between the second convex lens and the irradiation surface satisfy equations 1 and 2: M 1 =f ( s+D )/ D [Equation 1] M 2 =f ( s+D )/ s [Equation 2] where s is a width of the slit, D is a length of the linear beam in the long-side direction, and f is a focal length of the second convex lens.