A kind of laser focusing device
Technical field
The utility model relates to field of laser processing, is specifically related to a kind of laser focusing device, especially a kind of variable focus spot size and the constant laser focusing device of dutycycle.
Background technology
Utilizing the focused high-energy laser beam to carry out the special process of high-performance metal parts, high performance material preparation and high-performance parts direct forming, is the important component part of advanced manufacturing technology.
In Laser Processing, focal beam spot is pressed desired trajectory and is done two dimension or three-dimensional motion, as in laser melting coating is piled up, focal beam spot is in motion, cladding material is constantly added in the mobile laser focal beam spot in real time realizes cladding, and form the molten road of a rule at the movement locus of hot spot, and the quality of connection between the molten road of this rule itself and each molten road, the metallurgical binding quality of interlayer, surface, molten road and with the intensity of matrix bond face, pattern, homogeneity and the compactness of tissue, molten road surface smoothness, roughness etc., be closely related with light source quality and parameter, the distribution form of luminous energy in the last focal beam spot particularly is to the convection current of melt in the molten bath, it is very big to solidify configuration affect.
When the even part of shaping wall unevenness, conventionally adopt the multi-track overlapping mode, and multi-track overlapping is not only consuming time, throughput rate is low, and surface smoothness is poor, particularly causes the inner inhomogeneous cooling of crucible zone even and cause the metallurgical imperfection of lap-joint easily.For avoiding and improving these problems, can adopt and become the laser facula method, be that wide molten road adopts large spot scanning cladding, narrow molten road adopts small light spot scanning cladding, and in the scanning cladding, change spot size according to the width variation of molten road in good time, can successively pile up the entity that produces three-dimensional wall unevenness by two dimensional motion like this, as part such as wide blade not.Luminous energy distribution form in the laser facula directly influences the cladding layer forming quality, so require in continuously changing the process of focused spot size, the luminous energy distribution form in the hot spot preferably remains unchanged.
In the existing light beam focusing technology, focal beam spot has solid and annular 2 kinds.Chinese invention patent CN101148760A discloses feeding job operation and processing unit (plant) in a kind of ring light light, this device passes through light chopper, the circular section optical beam transformation that to be launched by laser instrument is annular cross section light beam, behind the annular beam expander, focusing becomes annulus taper focused beam, form an annular focal beam spot at the shaping finished surface, in annulus taper focused beam, produce a tapered hollow no light zone, single powder feeding pipe stretched into outward in this no light zone by light beam and with annulus taper focused beam coaxial cable, powder in the powder feeding pipe gas carry or the gravity effect under send in the focal beam spot on the machined surface, powder is in injection or dropping process, all the time be positioned at the hollow area of annulus taper focused beam inside, until near surface of the work, the powder bundle enters focal beam spot, and the powder bundle is between the interior ring of light and outer reticle circle of amyloid plaque external diameter at the ring focusing hot spot that surface of the work forms.This method has realized the coaxial fully of focused beam and feeding, but does not consider to need the hot spot of different-diameter when processing wall unevenness part.
When adopting said apparatus processing wall unevenness part, as shown in Figure 1, among the figure, machined surface hot spot external diameter before D1-translation, machined surface hot spot internal diameter before d1-translation, the angle of α-translation prefocusing light external diameter and surface level, the angle of β-translation prefocusing light internal diameter and surface level, machined surface hot spot external diameter after D2-translation, machined surface hot spot internal diameter after d2-translation, the angle of focused light external diameter and surface level after γ-translation, the angle of focused light internal diameter and surface level after δ-translation, the distance of h-parabolic mirror vertical direction translation, the distance of H-shaven head and workpiece, the distance of A-translation front cone catoptron bottom and machined surface, the distance of B-translation front cone catoptron top and machined surface, Z1-machined surface is to the distance of focus, i.e. defocusing amount, O-focused light focus, dutycycle
For the parabolic mirror mathematical model as shown in Figure 2, the para-curve geometric equation is
, wherein p is parabolical focal length.As seen from the figure,
So,,
, in like manner,
,
,
As shown in Figure 1, before the translation, at the Z1 place,
,
, this moment dutycycle
, again because
,
Upwards behind the translation h, at the Z1 place,
,
, this moment dutycycle
,
At this moment, if will make T
1=T
2, then
, got by the method for undetermined coefficients
, draw, h=0, namely as long as with the translation that makes progress of circular conical surface catoptron, dutycycle namely can change.This shows that after the translation that in this laser focusing system the circular conical surface catoptron made progress, though variation has taken place laser outer diameter, variation has also taken place the dutycycle of ring light hot spot simultaneously, namely variation has taken place in the luminous energy distribution form in the hot spot.
Summary of the invention
Goal of the invention of the present utility model is, provides a kind of variable spot size and the constant laser focusing device of dutycycle, to overcome the defective of prior art, guarantees that the luminous energy regularity of distribution in the hot spot is constant, realizes the wall unevenness part forming is processed.
To achieve the above object of the invention, the technical solution adopted in the utility model is: a kind of laser focusing device, mainly formed by two catoptrons, one is circular cone parabolic reflective focusing mirror, another piece is faced catoptron directly for the ring taper, two catoptrons are the rotational symmetry structure around central axis, reflecting surface positioned opposite.
In the technique scheme, circular cone parabolic reflective focusing mirror is the first order, it is the second level that catoptron is faced in the ring taper directly, the entrance port that the catoptron inner hollow constitutes laser beam is faced in the ring taper directly, incident laser enters from the entrance port, circlewise behind the light beam, face mirror reflects directly by the ring taper through the mirror reflection of circular cone parabolic reflective focusing again, obtain outgoing beam.
Further technical scheme, catoptron shape face positioned opposite is faced in described circular cone parabolic reflective focusing mirror and described ring taper directly, the shape face center coaxial line of two catoptrons, during work, circular laser beam at first incides on the conical mirror shape face along two catoptron central axis, conical mirror also radially reflexes to the ring taper with incident light focusing and faces directly on the catoptron, and circular cone is faced catoptron directly and continued incident light is reflexed to realization focusing on the focal plane.
Further technical scheme, the circular cone parabolic mirror is top towards incoming laser beam, and has the degree of freedom that moves up and down along axis.Cooperate the motion of laser printhead, encircle taper by the circular cone parabolic mirror relatively along axis and face moving up and down of catoptron directly, can obtain the ring-shaped light spot of filled circles hot spot or different-diameter at machined surface, the hollow of ring-shaped light spot changes than the variation with the hot spot external diameter, also can not change.
The utility model is focusing and the principle of reflection of utilizing focus lamp and catoptron, and the hot spot of laser beam is focused into annulus, and regulates focus lamp that the ring light spot size is changed and dutycycle is constant.Mainly be divided into for two steps: the first step is focused into the light beam of falling the plane annular with laser beam; Second step focused on the beam reflection of falling the plane annular, and formed a plane hollow no light zone in the ring cone-shaped beam.Obtain the focal beam spot of a hollow and annular.
The utility model adopts one-level parabolic reflective focusing mirror and the taper of secondary ring to face catoptron directly, the structure of global focus device is around symmetrical structure, the two-stage catoptron is coaxial, taper face directly catoptron in the periphery around surrounding the parabolic reflective focusing mirror, guaranteed the circular symmetry of focal beam spot in one-piece construction.
The first order is the parabolic reflective focusing mirror in the utility model, plays focussing force, and the second level is that catoptron is faced in taper directly, plays reflex.
Because technique scheme is used, the utility model compared with prior art has following advantage:
The utility model is focused into the hot spot of laser beam circular, and can reach adjusting ring light spot size and the constant purpose of dutycycle at the relative position of vertical optical axis direction by regulating parabolic focus lamp, when the part of the various materials of processing, spot size is adjustable, and dutycycle is constant, thereby the energy density distribution form is constant, can satisfy the needs of different processing methods and material.
Description of drawings
Fig. 1 is processing unit (plant) synoptic diagram in the prior art;
Fig. 2 is parabolic mirror mathematical model synoptic diagram;
Fig. 3 is the bare headed cut-away view of the utility model embodiment;
Fig. 4 is the parabolic focus lamp shaft section of first order figure among Fig. 3;
Fig. 5 is that mirror shaft section figure is faced in second level taper directly among Fig. 3;
Fig. 6 is laser optical head work synoptic diagram.
Wherein: 1, laser beam, 2, first order parabolic reflective focusing mirror, 3, second level taper faces catoptron directly.
Embodiment
Below in conjunction with drawings and Examples the utility model is further specified.
Embodiment one:
Referring to accompanying drawing 3 to shown in the accompanying drawing 5, a kind of laser focusing device, catoptron 3 these two-stage catoptrons and laser beam 1 coaxial arrangement are faced in first order parabolic reflective focusing mirror 2 and second level taper directly, and first order parabolic reflective focusing mirror 2 is faced top, catoptron 3 plane directly with second level taper and is placed in the same way, and it is vertical with worktable as shown in Figure 5 that catoptron 3 is faced in second level taper directly.Laser beam 1 is faced catoptron 3 hollow spaces directly and is passed and shine first order parabolic reflective focusing mirror 2 from the second level, through reflect focalization, face catoptron 3 reflections directly through second level taper then, forms the focusing ring shaped light beam.By regulating first order parabolic reflective focusing mirror 2 in the position of vertical direction, can regulate the ring light spot size, make on the machined surface hot spot dutycycle constant, it is constant namely to have guaranteed to be radiated in the hot spot on the machined surface luminous energy distribution form.
Fig. 6 is laser optical head work synoptic diagram, and wherein: the working condition of shaven head when solid line represents not move parabolic focus lamp, dotted line are represented the working condition of shaven head behind the mobile parabolic focus lamp.
Change by spot size, change molten road size, and dutycycle is constant, does not then influence camber and the flatness in molten road.
In the present embodiment, first order parabolic reflective focusing mirror and second level taper are faced the relative and bottom surface of catoptron directly and are parallel to each other, it is hollow structure that catoptron is faced in second level taper directly, above first order parabolic reflective focusing mirror, reach reflected light path and arrange that wherein hollow space is the laser beam entrance port.Laser beam along with this around the incident of symmetrical structure coaxial direction, passing the hollow space that second level taper faces catoptron directly is radiated on the first order parabolic reflective focusing mirror, form the reflect focalization ring light after reflection, the reflect focalization ring light converges after facing mirror reflects directly through second level taper again.When regulating the vertical direction position of first order parabolic mirror, can make to face directly through second level taper and converge the ring light spot size (D outer diameter) that forms after the mirror reflects and change, dutycycle (T) is constant simultaneously.
Verify as follows: shown in accompanying drawing 3, among the figure, hot spot external diameter before D1-translation, hot spot internal diameter before d1-translation, the angle of α-translation prefocusing light external diameter and surface level, the angle of β-translation prefocusing light internal diameter and surface level, hot spot external diameter after D2-translation, hot spot internal diameter after d2-translation, the angle of focused light external diameter and surface level after γ-translation, the angle of focused light internal diameter and surface level after δ-translation, the distance of parabolic mirror bottom and worktable before the distance of h-parabolic mirror vertical direction translation, A-translation, the distance of parabolic mirror top and worktable after B-translation, Z1-worktable is apart from the distance of focus, be defocusing amount, as shown in Figure 3, before the translation, at defocusing amount Z1 place
,
, at this moment
Upwards behind the translation h, the incident angle of corresponding light does not change, so at defocusing amount Z1 place,
,
, at this moment,
, namely dutycycle is constant.
To sum up, the parabolic reflective focusing mirror moves up, and can obtain external diameter at the sustained height place and change (D
1≠ D
2), the constant (T of dutycycle
1=T
2) ring-shaped light spot.
The vertical distance of general laser optical head and workpiece can not random variation, from laser beam can appear according to the possibility less than workpiece away from too, otherwise it is excessive too closely then can dutycycle to occur, cladding also can not be carried out.The utility model device can namely at the sustained height place, by changing parabolic focus lamp vertical direction position in the shaven head, can change spot size under the constant situation of laser optical head and workpiece vertical position, guarantee that simultaneously dutycycle does not change.