Single-emitter line beam system

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.

We claim: 
     
         1 . A system, comprising:
 a plurality of spaced-apart single-emitter diode lasers, each configured to emit a corresponding laser beam;   a coherence-reducing optical system 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 coherence-reducing optical system including a diffraction grating situated to receive the laser beams propagating along parallel beam axes and form diffracted laser beams that propagate at a diffraction angle along respective parallel diffracted beam axes so as to provide an optical path length difference among the diffracted laser beams; and   a line beam optical system situated to receive the reduced coherence beam and to direct a line beam to a target.   
     
     
         2 . The system of  claim 1 , wherein the coherence-reducing optical system includes a light guide situated to receive the diffracted laser beams at a light guide input aperture;
 wherein the light guide is situated so as to provide an optical path length difference among the laser beams based on multiple reflections of the diffracted laser beams in the light guide.   
     
     
         3 . The system of  claim 2 , wherein the light guide has a longitudinal axis that is situated to provide selected respective asymmetric incidence angles with respect to opposite marginal propagation beam axes associated with the diffracted beams at the light guide input aperture so as to asymmetrically receive the diffracted beams;
 wherein the light guide is situated so as to provide an optical path length difference among the laser beams based on the asymmetric incidence angles and subsequent propagation through the light guide.   
     
     
         4 . The system of  claim 3 , wherein the light guide is situated so that an angular beam diameter of the diffracted laser beams received by the light guide is at most the larger of the asymmetric incidence angles to the light guide. 
     
     
         5 . The system of  claim 3 , wherein the diffraction angle and the asymmetric incidence angles are selected in relation to each other so as to increase a total optical path length difference among the laser beams. 
     
     
         6 . The system of  claim 1 , further comprising a beam spacing optical system situated to receive the laser beams and to direct the laser beams along parallel close-packed axes that are more closely spaced than associated emitted beam axes so as to form a close-packed combined beam, wherein the diffraction grating is situated to receive the close-packed combined beam. 
     
     
         7 . The system of  claim 6 , wherein the beam spacing optical system includes at least one rhomboidal prism situated to direct at least one of the laser beams along a corresponding close-packed axis. 
     
     
         8 . The system of  claim 7 , wherein the beam spacing optical system is situated to direct at least one of the laser beams along an axis that is perpendicular to an associated close-packed axis. 
     
     
         9 . The system of  claim 2 , further comprising a cylindrical mirror situated to receive the diffracted beams and to convergently direct the diffracted beams to the light guide. 
     
     
         10 . The system of  claim 9 , further comprising one or more optical elements situated to optically couple the convergently directed diffracted beams into the light guide. 
     
     
         11 . The system of  claim 1 , wherein the diffraction grating is a reflective diffraction grating. 
     
     
         12 . The system of  claim 11 , further comprising a beam stop situated to receive a beam portion other than the diffracted laser beams. 
     
     
         13 . The system of  claim 2 , wherein the light guide has a longitudinal axis that is symmetrically situated with respect to marginal beam propagation axes associated with the diffracted laser beams. 
     
     
         14 . A method, comprising:
 directing a plurality of laser beams having respective beam axes so as to form a combined beam;   diffracting the combined beam with a diffraction grating so as to form a diffracted combined beam at a diffraction angle with the beam axes of the laser beams parallel to each other as received at the diffraction grating and parallel to each other as diffracted by the diffraction grating to provide a first optical path length difference among the laser beams associated with the diffraction angle;   coupling the diffracted combined beam into a light pipe with respect to a longitudinal axis of the light pipe so as to homogenize the intensity of the diffracted combined beam across at least one axis that is orthogonal to the longitudinal axis and to produce an output beam and to provide a second optical path length difference among the laser beams based on propagation of the laser beams in the light pipe, wherein a total optical path length difference is greater than either the first optical path length difference or the second optical path length difference; and   forming a line beam at a target based on the output beam of the light pipe.   
     
     
         15 . The method of  claim 14 , wherein the diffracted combined beam is coupled into the light pipe so that opposite marginal beam axes of the laser beams of the diffracted combined beam have asymmetrical incidence angles with respect to the longitudinal axis of the light pipe at an entrance aperture so as to provide a third optical path length difference among the laser beams. 
     
     
         16 . The method of  claim 15 , wherein the beam axes with a longest path length delay associated with the diffraction grating are directed into the light pipe at a largest angle of the asymmetric incidence angles. 
     
     
         17 . The method of  claim 15 , wherein the light guide is situated so that an angular beam diameter of the received diffracted combined beam is at most the larger of the asymmetric incidence angles to the light guide. 
     
     
         18 . The method of  claim 14 , further comprising directing the laser beams through a beam spacing optical system so as to reduce a spacing between at least two of the beam axes so as to define close-packed axes that are more closely spaced than the beam axes as emitted from the single-emitter diode lasers and so as to form a close-packed combined beam, wherein the diffraction grating is situated to receive the close-packed combined beam. 
     
     
         19 . The method of  claim 18 , wherein the beam spacing optical system includes at least one rhomboidal prism situated to direct at least one of the laser beams along a corresponding one of the close-packed axes. 
     
     
         20 . The method of  claim 19 , wherein the beam spacing optical system is situated to direct at least one of the laser beams along an axis that is perpendicular to an associated close-packed axis.