Single-emitter line beam system

Patent metadata

Field	Value
Publication number	US-9709810-B2
Application number	US-201514614194-A
Country	US
Kind code	B2
Filing date	Feb 4, 2015
Priority date	Feb 5, 2014
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

A line beam system includes a single-emitter light engine including a plurality of separately spaced single-emitter diode lasers, each emitter configured to emit a diode laser beam. Beam spacing optics are optically coupled to the single-emitter light engine and situated to provide propagation axes of the diode laser beams in a close-packed parallel configuration. A light pipe having a longitudinal axis is situated to provide an output beam with a homogenized intensity profile across one or more axes by receiving a close-packed, combined beam and reflecting the beam within the light pipe. Coherence reduction is produced by diffraction of a close-packed combined beam or by propagation in the light pipe.

First claim

We claim:

1. A line beam system, comprising:
a plurality of spaced-apart single-emitter diode lasers, each configured to emit a corresponding laser beam along a respective emitted beam axis;
a coherence-reducing optical system situated to receive the laser beams and establish an optical path length difference among the laser beams so as to produce a reduced coherence beam; and
a line beam optical system situated to receive the reduced coherence beam and to direct a line beam to a target;
wherein the coherence-reducing optical system includes a light guide having a longitudinal axis that is situated at selected respective asymmetric incidence angles with respect to opposite marginal emitted beam axes at a light guide input aperture so as to asymmetrically receive the emitted beam axes, the light guide producing the coherence-reduced output beam based on path length differences in the light guide and the asymmetric incidence angles.

2. The line beam system of claim 1 , wherein the light guide is situated so that an angular beam diameter of the received emitted beams is at most the larger of the asymmetric incidence angles to the light guide.

3. The line beam system of claim 1 , wherein the coherence-reducing optical system includes a diffraction grating situated to receive and reduce a coherence of the emitted beams by providing a diffracted beam having a beam path difference associated with a diffraction angle.

4. The line beam system of claim 3 , further comprising a beam spacing optical system that receives the emitted beams and directs the emitted beams along close-packed axes that are more closely spaced than the emitted beam axes as a close-packed, combined beam, wherein the diffraction grating receives the close-packed combined beam and reduces the coherence of the close-packed, combined beam.

5. The line beam system of claim 1 , further comprising a beam spacing optical system that receives the emitted beams and directs the emitted beams along close-packed axes that are more closely spaced than the emitted beam axes as a close-packed, combined beam to the coherence-reducing optical system.

6. The line beam system of claim 5 , wherein the beam spacing optical system includes at least one rhomboidal prism that directs at least one of the emitted beams along a respective one of the close-packed axes.

7. The line beam system of claim 6 , wherein the beam spacing optical system is situated to direct at least one of the emitted beams along an axis that is orthogonal to the close-packed axis.

8. The line beam system of claim 4 , further comprising:
a cylindrical mirror situated to receive the diffracted beam and direct the diffracted beam into the light guide.

9. The line beam system of claim 8 , wherein the light guide is a light pipe situated so that an angular beam diameter of the received diffracted beam is at most the larger of the asymmetric incidence angles to the light guide.

10. The line beam system of claim 3 , wherein the diffraction grating is a reflective diffraction grating.

11. A method, comprising:
collimating a plurality of single-emitter diode laser beams, each beam having a corresponding emitted beam axis;
directing the collimated single-emitter diode laser beams to produce a close-packed, combined beam;
reducing a coherence of the close-packed, combined beam based on an optical path length difference among the beams by launching the close-packed, combined beam into a light pipe so that opposite marginal emitted beam axes have asymmetrical incidence angles with respect to a longitudinal axis of the light pipe at an entrance aperture and by homogenizing the intensity of the combined beam across at least one axis that is orthogonal with respect to the longitudinal axis; and
forming a line beam at a target based on the homogenized coherence-reduced output beam.

12. The method of claim 11 , further comprising:
diffracting the close-packed, combined beam with a diffraction grating so as to form a diffracted beam and reduce beam coherence.

13. The method of claim 12 , wherein emitted beam axes with a longest path length delay associated with the diffraction grating are directed into the light pipe at a largest incidence angle with respect to the longitudinal axis of the light pipe.

14. The line beam system of claim 3 , further comprising:
at least two single emitter diode laser modules situated to include respective pluralities of the plurality of spaced-apart single-emitter diode lasers, each respective plurality situated spaced apart with respect to a first axis so that the diode lasers of the respective plurality emit beams parallel to a second axis, wherein the at least two single emitter laser diode modules are displaced with respect to each other along a third axis, wherein the first, second, and the third axes are substantially mutually orthogonal;
a beam-spacing optical system that receives the emitted beams and forms a close-packed combined beam, the beam-spacing optical system includes at least one rhomboid prism that establishes a close-packed beam propagation axis;
a beam directing optical system that includes:
a cylindrical mirror situated to receive the coherence-reduced beam from the diffraction grating and converge the coherence-reduced beam;
a fold mirror situated to receive the coherence-reduced beam from the cylindrical mirror;
a cylindrical lens situated to receive the coherence-reduced beam from the fold mirror;

a polarizing mirror situated to receive the coherence-reduced beam and reflect the coherence-reduced beam in a first state of polarization; and
a beam shaping optical system situated to receive the coherence-reduced beam in the first state of polarization
wherein the light guide is situated to receive the coherence-reduced beam from the beam shaping optical system so as to produce the coherence-reduced output beam.

15. The line beam system of claim 14 , further comprising a beam dump, wherein the polarizing mirror is situated to transmit portions of the line beam to the beam dump that are received from the target.

16. The line beam system of claim 3 , wherein the emitted beam axes are parallel to each other at the input and output of the diffraction grating.

17. The line beam system of claim 1 , wherein an entrance aperture of the light guide is rectangular shaped.

18. The method of claim 11 , wherein the entrance aperture of the light pipe is rectangular shaped.

19. The method of claim 12 , wherein the emitted beam axes are parallel to each other at the input and output of the diffraction grating.

20. A line beam system, comprising:
a plurality of spaced-apart single-emitter diode lasers, each configured to emit a corresponding laser beam along a respective emitted beam axis;
a coherence-reducing optical system including a light guide situated to receive the laser beams and to establish an optical path length difference among the laser beams so as to produce a reduced coherence beam, the light guide having a rectangular shaped input aperture and a longitudinal axis perpendicular to the input aperture and situated with respect to the emitted beam axes so that opposite marginal beam axes have asymmetric incidence angles at the input aperture, the light guide producing the coherence-reduced output beam based on path length differences in the light guide and the asymmetric incidence angles; and
a line beam optical system situated to receive the reduced coherence beam and to direct a line beam to a target.

Assignees

• Nlight Photonics Corp
• Nlight Inc

Inventors

• Karlsen Scott R
• Senders David C

Classifications

• G02B27/0994

  Fibers, light pipes (optical fibers per se G02B6/02) · CPC title

• G02B6/4296

  coupling with sources of high radiant energy, e.g. high power lasers, high temperature light sources · CPC title

• G02B6/262

  Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements · CPC title

• G02B27/108

  for sampling a portion of a beam or combining a small beam in a larger one, e.g. wherein the area ratio or power ratio of the divided beams significantly differs from unity, without spectral selectivity · CPC title

• G02B5/04

  Prisms · CPC title