Laser processing apparatus and laser processing method

1. A laser processing apparatus, comprising:

a laser light source emitting a laser beam;

a monitor light source emitting a monitor light with a wavelength different from that of the laser beam;

an irradiation optical system applying the laser beam emitted from the laser light source and the monitor light emitted from the monitor light source to an object and surroundings thereof so that an application angle onto the object is the same while scanning an irradiation position of the laser beam and the monitor light along a predetermined direction;

an optical filter provided on the opposite side to the irradiation optical system with respect to the object, the optical filter interrupting the laser beam and transmitting the monitor light;

a photo-detector detecting the monitor light transmitted through the optical filter; and

a control section controlling a start and a stop of pulse oscillation of the laser beam emitted from the laser light source,

wherein the control section stops the pulse oscillation of the laser beam with respect to the laser light source in the case in which the monitor light applied from the irradiation optical system is detected by the photo-detector; while it starts the pulse oscillation of the laser beam with respect to the laser light source in the case in which no monitor light applied from the irradiation optical system is detected at the photo-detector.

2. A laser processing apparatus according to claim 1 , wherein a wavelength of the monitor light emitted from the monitor light source is shorter than a wavelength of the laser beam emitted from the laser light source.

3. A laser processing apparatus according to claim 1 , wherein a difference between a peak wavelength of a sensitivity at the photo-detector and a wavelength of the monitor light emitted from the monitor light source is smaller than a difference between a peak wavelength of the sensitivity at the photo-detector and a wavelength of the laser beam emitted from the laser light source.

4. A laser processing apparatus according to claim 1 , wherein the irradiation position of the laser beam and the monitor light is scanned at a speed of less than 1 m/s.

5. A laser processing apparatus according to claim 1 , wherein the irradiation optical system includes such a scanning path that the irradiation position of the laser beam gets across the object from outside the object, and thereafter reaches outside the object, and

wherein the control section controls a start and a stop of a pulse oscillation of the laser beam when the irradiation optical system reciprocates along the scanning path.

6. A laser processing apparatus according to claim 1 , wherein the control section has a function of changing a repetition frequency at the time when the laser light source pulse-oscillates the laser beam, and makes the repetition frequency higher than that at the start of pulse oscillation at least once while the laser light source emits the laser beam.

7. A laser processing apparatus according to claim 1 , wherein the control section has a function of changing an energy per one pulse at the time when the laser light source pulse-oscillates the laser beam, and makes the energy smaller than that at the start of pulse oscillation at least once while the laser light source emits the laser beam.

8. A laser processing method, comprising the steps of:

applying a laser beam emitted from a laser light source and a monitor light, a wavelength thereof being different from that of the laser beam, emitted from a monitor light source to an object and surroundings thereof so as to follow the same optical path while scanning an irradiation position of the laser beam and the monitor light along a predetermined direction via the irradiation optical system;

detecting the monitor light selectively transmitted through an optical filter provided on the opposite side to the irradiation optical system with respect to the object; and

stopping pulse oscillation of the laser beam with respect to the laser light source in the case in which the monitor light applied from the irradiation optical system is detected by the photo-detector, and in the meantime, starting the pulse oscillation of the laser beam with respect to the laser light source in the case in which no monitor light applied from the irradiation optical system is detected by the photo-detector.

9. A laser processing method according to claim 8 , wherein a wavelength of the monitor light emitted from the monitor light source is shorter than a wavelength of the laser beam emitted from the laser light source.

10. A laser processing method according to claim 8 , wherein a difference between a peak wavelength of a sensitivity at the photo-detector and a wavelength of the monitor light to be emitted from the monitor light source is smaller than a difference between a peak wavelength of the sensitivity at the photo-detector and a wavelength of the laser beam to be emitted from the laser light source.

11. A laser processing method according to claim 8 , wherein the irradiation position of the laser beam and the monitor light is scanned at a speed of less than 1 m/s.

12. A laser processing method according to claim 8 , wherein the irradiation optical system reciprocates an irradiation position of the laser beam so as to get across the object along a first direction, and thereafter to get across the object again along a second direction opposite to the first direction.

13. A laser processing method according to claim 8 , wherein a repetition frequency of pulse oscillation is set to be higher than that at the start of emission of the laser beam at least once while the laser light source emits the laser beam.

14. A laser processing method according to claim 8 , wherein an energy per one pulse at the time of pulse oscillation is set to be smaller than that at the start of emission of the laser beam at least once while the laser light source emits the laser beam.