LASER DEVICE

• US 20180138654A1
• Filed: 11/01/2017
• Published: 05/17/2018
• Est. Priority Date: 11/16/2016
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: CHIBA, Tetsuya
• Granted Patent: US 10,637,205 B2
• Time in Patent Office: Days
• CPC Class Codes: B23K 26/032 using optical means
• CPC Class Codes: B23K 26/0626 Energy control of the laser beam B23K26/0622 takes precedence
• CPC Class Codes: B23K 26/38 by boring or cutting
• CPC Class Codes: H01S 3/0007 Applications not otherwise provided for working metals or other materials by laser beam B23K26/00; using photons to produce a reactive propulsive thrust F03H3/00; optical recording of measured values in general G01D15/14; optics in general G02B; holographic processes or apparatus G03H; optical marking or sensing of data record carriers G06K7/10 - G06K7/14, G06K15/12; injection heating of plasma by laser H05H1/22; acceleration of neutral particles by electromagnetic wave pressure H05H3/04
• CPC Class Codes: H01S 3/0014 Monitoring arrangements not otherwise provided for photometry G01J1/00, e.g. G01J1/4257; radiation pyrometry G01J5/00; measuring coherence of light G01J9/00; measuring wavelength of light G01J9/00, e.g. G01J9/0246; measuring optical pulses G01J11/00; calorimetrically measuring power of laser beams G01K17/003
• CPC Class Codes: H01S 3/005 Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B
• CPC Class Codes: H01S 3/067 Fibre lasers
• CPC Class Codes: H01S 3/094003 the pumped medium being a fibre
• CPC Class Codes: H01S 3/0941 of a laser diode
• CPC Class Codes: H01S 3/10069 Memorized or pre-programmed characteristics, e.g. look-up table [LUT]
• CPC Class Codes: H01S 3/1022 by controlling the optical pumping
• CPC Class Codes: H01S 3/1305 Feedback control systems
• CPC Class Codes: H01S 3/1312 by controlling the optical pumping
• CPC Class Codes: H01S 3/2383 Parallel arrangements
• CPC Class Codes: H01S 5/02251 using optical fibres
• CPC Class Codes: H01S 5/06825 Protecting the laser, e.g. during switch-on/off, detection of malfunctioning or degradation
• CPC Class Codes: H01S 5/0683 by monitoring the optical output parameters
• CPC Class Codes: H01S 5/4012 Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms

Abstract

To provide a laser device for adjusting a laser output by detecting the quantity of a reflected beam propagating within an optical fiber more accurately before an optical part is damaged due to an increase in quantity of the reflected beam. A laser device comprises: at least one first photodetector that detects the quantity of a reflected beam being part of a reflected beam returning to an optical fiber of the laser device after being reflected off of a work and propagating mainly through a cladding of the optical fiber; at least one second photodetector that detects the quantity of a reflected beam being part of the reflected beam returning to the optical fiber and propagating mainly through a core of the optical fiber; a power supply unit that supplies a driving current to a laser diode; and a control unit that controls the power supply unit. The control unit controls the driving current to be supplied from the power supply unit to the laser diode in response to both an output from the first photodetector and an output from the second photodetector.

Claims

1. A laser device that outputs a laser beam by means of transmission through an optical fiber using a laser diode as a laser beam source or an excitation beam source, the laser device comprising:

at least one first photodetector that detects the quantity of a reflected beam being part of a reflected beam returning to the optical fiber of the laser device after being reflected off of a work and propagating mainly through a cladding of the optical fiber;

at least one second photodetector that detects the quantity of a reflected beam being part of the reflected beam returning to the optical fiber and propagating mainly through a core of the optical fiber;

a power supply unit that supplies a driving current to the laser diode; and

a control unit that controls the power supply unit, wherein

the control unit controls the power supply unit in response to both an output from the first photodetector and an output from the second photodetector.

2. The laser device according to claim 1, wherein at least one predetermined threshold is set for at least one of the quantity of the reflected beam detected by the first photodetector and the quantity of the reflected beam detected by the second photodetector, and if at least one of the quantity of the reflected beam detected by the first photodetector and the quantity of the reflected beam detected by the second photodetector exceeds the corresponding predetermined threshold, the control unit controls the driving current to be supplied from the power supply unit to the laser diode, thereby changing a laser beam output from the laser device.

3. The laser device according to claim 1, wherein at least one predetermined threshold is set for a quantity P of a reflected beam calculated as P=k₁×

P(1) k₂×

P(2) (k₁ and k₂ are positive real numbers) where P(1) is the quantity of the reflected beam detected by the first photodetector and P(2) is the quantity of the reflected beam detected by the second photodetector, and if the quantity P of the reflected beam exceeds the corresponding predetermined threshold, the control unit controls the driving current to be supplied from the power supply unit to the laser diode, thereby changing a laser beam output from the laser device.

4. The laser device according to claim 1, wherein a series of operations comprising detection of the quantity of the reflected beam by the first photodetector, detection of the quantity of the reflected beam by the second photodetector, a determination as to whether or not the detected beam quantity exceeds the corresponding predetermined threshold, and change of a laser beam output from the laser device in response to excess of the detected beam quantity over the corresponding threshold is performed at a time interval of 100 nsec to 10 msec.

5. The laser device according to claim 1, wherein the beam quantity detected by at least one of the first photodetector and the second photodetector includes a contribution by the quantity of a laser beam output in response to a beam output command from the control unit and traveling in a forward direction substantially opposite to a direction in which the reflected beam travels, and

the control unit determines the quantity of the reflected beam by subtracting the contribution by the quantity of the laser beam traveling in the forward direction from the beam quantity detected by the at least one photodetector.

6. The laser device according to claim 1, wherein at least one of the first photodetector and the second photodetector further functions as an output beam detector that detects the quantity of a laser beam output in response to a beam output command from the control unit and traveling in a forward direction substantially opposite to a direction in which the reflected beam travels.

7. The laser device according to claim 1, wherein the first photodetector is arranged so as to detect a beam leaking from the cladding of the optical fiber.

8. The laser device according to claim 7, wherein the first photodetector is provided near a connection formed of a fused part of the optical fiber.

9. The laser device according to claim 1, wherein the second photodetector is arranged at a terminal of each of multiple optical fibers resulting from branching of the optical fiber.

10. The laser device according to claim 1, wherein in the absence of a reflected beam from the work, actual beam output characteristics responsive to a beam output command from the control unit and at least one of the beam quantity detected by the first photodetector and the beam quantity detected by the second photodetector are measured by following a predetermined schedule, and resultant measurement data is stored in the control unit or a storage unit to be referenced by the control unit, or measurement data stored in the control unit or the storage unit is updated using the resultant measurement data.

11. The laser device according to claim 1, wherein at least one of the first photodetector and the second photodetector is provided at a cutting head.

12. The laser device according to claim 1, wherein at least one of the first photodetector and the second photodetector is a photodiode.

13. The laser device according to claim 1, wherein at least one of the first photodetector and the second photodetector is a fiber temperature sensor.

14. The laser device according to claim 1, further comprising a photodetector temperature sensor that detects the temperature of at least one of the first photodetector and the second photodetector.

15. The laser device according to claim 1, wherein at least one of the first photodetector and the second photodetector includes multiple photodetectors, and if there is a difference in the detected quantity of the reflected beam between the multiple first photodetectors or between the multiple second photodetectors, the control unit controls the driving current to be supplied from the power supply unit to the laser diode based on a maximum beam quantity.