Patent ID: 7164519

Claim:
A laser processing apparatus processing an object by a laser beam, comprising: a laser generator emitting a laser beam with a predetermined diameter; a polygon mirror rotating on an axis with plural reflection planes and reflecting the laser beam emitted from the laser generator on the reflection planes whose number is adjusted to make plural reflection planes be covered by laser beam; a lens condensing the laser beam reflected on the polygon mirror and irradiating the laser beam on the object; a polygon mirror driver actuating the polygon mirror with a predetermined angular velocity; a stage settling the object thereon; and a stage transfer unit moving the stage toward the reverse of a rotating direction of the polygon mirror wherein the number of the reflecting planes, N of the polygon mirror, is established to keep a loss rate on each reflection plane over 100%, when a loss angle formed by a laser beam with reduced energy for the whole laser beam incident on the reflection plane of the polygon mirror is defined as t θ = arc ⁢ ⁢ cos [ ⁢ 1 - 1 2 ⁢ R 2 ⁢ { R 2 - ( R - h ) 2 - R 2 - ( R - h - D ) 2 + D 2 } ] ; and the loss rate on the reflection plane of the polygon mirror is defined as t r = C2 C1 = t θ ⁢ N 2 ⁢ π × 100 ⁢ ( % ) , where a radius of a circumcircle of the polygon mirror is R; the diameter of the laser beam is D; and a vertical height from the center of the polygon mirror to the center of the laser beam incident on the polygon mirror is h; an arc length corresponding to the reflection plane on which the laser beam is irradiated is C1: and an arc length for the portion of the loss angle is C2.