Laser processing apparatus and method using polygon mirror
Disclosed is a laser processing apparatus and method for enhancing processing efficiency of an object by means of a polygon mirror. The laser processing apparatus includes a laser generator outputting a laser beam with a predetermined diameter, a polygon mirror rotating on an axis with plural reflection planes to reflect the laser beam incident on the reflection planes from the laser generator, in which the number of the reflection planes is set in order that the laser beam can cover at least two reflection planes of the polygon mirror, and a lens condensing and irradiating the laser beam reflected from the polygon mirror. According to the present invention, it is able to improve the processing efficiency and product yield of an object by dividing the laser beam into the plurality to be incident on the reflection planes of the polygon mirror and repeatedly processing the object in low energy by means of the divided laser beam.
1. 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.
2. The laser processing apparatus according to claim 1 , which further comprises a beam transformer converting a sectional pattern of the laser beam condensed on the lens into an ellipse.
3. The laser processing apparatus according to claim 2 , wherein the beam transformer makes a major axis of the ellipse conform to a processing direction of the object.
4. The laser processing apparatus according to claim 3 , wherein a minor axis of the ellipse corresponds to a processing width of the object and is variable in accordance with a kind of the object and a pattern of processing.