Beam homogenizer, laser irradiation apparatus, and laser irradiation method

• US 8,237,085 B2
• Filed: 11/14/2007
• Issued: 08/07/2012
• Est. Priority Date: 11/17/2006
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Tanaka, Koichiro
• Primary Examiner(s): Evans, Geoffrey S
• Application Number:
  US11/939,649
• Publication Number:
  US 20080118203A1
• Time in Patent Office: 1,728 Days
• Field of Search: 219/121.73, 219/121.74, 385/31, 385/33, 385/34, 385/15, 385/133, 359/201.2, 359/213.1, 359/214.1, 359/232, 359/234
• US Class Current: 219/121.74
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0052 the light source comprising a laser diode coupling into light guides using intermediate optical elements G02B6/4204; semiconductor lasers having optical devices external to the laser cavity H01S5/005
• CPC Class Codes: G02B 27/0994 Fibers, light pipes optical fibers per se G02B6/02
• CPC Class Codes: G02B 5/005 Diaphragms for cameras G03B9/02
• CPC Class Codes: G02B 6/0096 the lights guides being of the hollow type

Abstract

An effect of interference is eliminated and intensity of a laser beam is homogenized. The beam homogenizer 100 includes reflecting mirrors 103 and 104 which are provided so that reflecting surfaces thereof face each other. The laser beam LB propagates through a space between the reflecting mirrors 103 and 104 while being reflected therebetween, so that intensity distribution of the laser beam LB is homogenized, but the laser beam LB also interferes. The first reflecting mirror 103 and the second reflecting mirror 104 are oscillated in a direction perpendicular to a direction in which the laser beam LB is scanned, intensity distribution of the laser beam LB in an oscillation direction is temporally averaged.

Claims

1. A beam homogenizer comprising:

a pair of mirrors provided parallel to a direction of a laser beam travels, each having a reflecting surface facing each other; and

means for vibrating the pair of mirrors at a first frequency while the laser beam passes through a laser input portion of the pair of mirrors to a laser output portion of the pair of mirrors.

2. The beam homogenizer according to claim 1, wherein the means for vibrating the pair of mirrors includes a piezoelectric element.

3. The beam homogenizer according to claim 1, wherein the laser beam is emitted from a continuous wave laser oscillator,

when a scanning velocity of the laser beam on a surface to be irradiated is V, a length in a scanning direction of the laser beam on the surface to be irradiated is d, and the first frequency is f₁,

the f₁ satisfies f₁≧

V/d.

4. A laser irradiation apparatus comprising:

a laser oscillator outputting a laser beam;

a beam homogenizer provided on an exit side of the laser oscillator, wherein the beam homogenizer including;

a pair of mirrors provided parallel to a direction of the laser beam travels, each having a reflecting surface facing each other;

means for vibrating the pair of mirrors at a first frequency while the laser beam passes through a laser input portion of the pair of mirrors to a laser output portion of the pair of mirrors; and

a projection lens provided on an exit side of the beam homogenizer.

5. The laser irradiation apparatus according to claim 4, wherein the means for vibrating the pair of mirrors includes a piezoelectric element.

6. The laser irradiation apparatus according to claim 4, wherein the laser output portion of the beam homogenizer and a surface to be irradiated are optically in a position of conjugate relation by the projection lens.

7. The laser irradiation apparatus according to claim 4,

wherein the laser beam has a wavelength being smaller than an amplitude of vibration of the pair of mirrors, and

wherein the amplitude of vibration of the pair of mirrors is equal to or smaller than 10 μ

M.

8. The laser irradiation apparatus according to claim 4, wherein the laser beam is emitted from a continuous wave laser oscillator,

when a scanning velocity of the laser beam on a surface to be irradiated is V, a length in a scanning direction of the laser beam on the surface to be irradiated d, and the first frequency is f₁,

the f₁ satisfies f₁≧

V/d.

9. The laser irradiation apparatus according to claim 4, wherein the projection lens is vibrated at a second frequency.

10. The laser irradiation apparatus according to claim 9,

wherein the laser beam is emitted from a continuous wave laser oscillator,

when a scanning velocity of the laser beam on a surface to be irradiated is V,

and a length in a scanning direction of the laser beam on the surface to be irradiated d, and

the second frequency is f₂,

the f₂ satisfies f₂≧

V/d.

11. The laser irradiation apparatus according to claim 4, further comprising a slit provided between the beam homogenizer and the projection lens along with an optical path.

12. A laser irradiation method comprising:

passing a laser beam through a beam homogenizer; and

irradiating an object to be irradiated with the laser beam,

wherein the beam homogenizer includes a pair of mirrors provided parallel to a direction of the laser beam travels, each having a reflecting surface facing each other,

wherein irradiation with the laser beam is performed while the pair of mirrors of the beam homogenizer is vibrated at a first frequency.

13. The laser irradiation method according to claim 12, wherein the laser beam which has passed through the beam homogenizer passes through an oscillating projection lens.

14. The laser irradiation method according to claim 12, wherein the laser beam which has passed through the beam homogenizer passes through an oscillating projection lens;

and

wherein the laser beam is emitted from a continuous wave laser oscillator, when a scanning velocity of the laser beam on a surface to be irradiated is V, a length in a scanning direction of the laser beam on the surface to be irradiated d, and the first frequency is f₁,

the f₁ satisfies f₁≧

V/d.

15. A laser irradiation method comprising:

entering a laser beam into a beam homogenizer;

shielding ends of the laser beam emitted from the beam homogenizer; and

irradiating an object to be irradiated with the laser beam of which the ends are shielded,

wherein the beam homogenizer includes a pair of mirrors provided parallel to a direction of the laser beam travels, each having a reflecting surface facing each other; and

wherein irradiation with the laser beam is performed while the pair of mirrors of the beam homogenizer is vibrated at a first frequency.

16. The laser irradiation method according to claim 15,

wherein the laser beam has a wavelength being smaller than an amplitude of vibration of the pair of mirrors, and

wherein the amplitude of vibration of the pair of mirrors is equal to or smaller than 10 μ

m.

17. The laser irradiation method according to claim 15, wherein the laser beam is emitted from a continuous wave laser oscillator, when a scanning velocity of the laser beam on a surface to be irradiated is V, a length in a scanning direction of the laser beam on the surface to be irradiated d, and the first frequency is f₁,

the f₁ satisfies f₁≧

V/d.