WO2024245978A1

WO2024245978A1 - Improvements in or relating to laser beam shaping

Info

Publication number: WO2024245978A1
Application number: PCT/EP2024/064466
Authority: WO
Inventors: Persephone POULTON; Alexander GRIFFITHS
Original assignee: PowerPhotonic Ltd
Current assignee: PowerPhotonic Ltd
Priority date: 2023-05-26
Filing date: 2024-05-25
Publication date: 2024-12-05
Anticipated expiration: 2025-11-26
Also published as: GB2630466A; GB202407497D0; GB2630688A; GB2630467A; WO2024245977A1; GB202407496D0; GB202407498D0; WO2024245976A1

Abstract

A variable laser beam shaping optical apparatus for producing variable laser spot shapes in laser materials processing. A single laser source provides an input beam whose diameter is dynamically increased or decreased and is incident upon a beam shaping optical element. The beam shaping optical element has surface profiles configured to produce a shaped output beam dependent upon the incident input beam diameter. Embodiments are described which produce focused laser spot shapes smoothly varying from Gaussian, through a flat top to a ring and trident using a single beam shaping optical element.

Description

IMPROVEMENTS IN OR RELATING TO LASER BEAM SHAPING

The present invention relates to laser beam shapers and in particular, though not exclusively, to a variable laser beam shaping apparatus in which the beam shape is switched using a single beam shaping element .

Laser beam shaping enhances laser manufacturing processes by tailoring beam profiles to particular processes . The Gaussian profile produced by a single mode laser gives the smallest possible focused spot , which equates to small feature si zes or fine processing . However, some processes benefit from other beam profiles for example , a uni form flat top intensity profile or a ring distribution . The surface pro files for beam shapers to make these beam shapes are well known, however, these are static beam shapers , providing one output beam format .

There is increasing demand for variable beam shaping for laser processing applications to allow the output profiles of the beam to be changed in use . Such changes can be made using reflective , refractive and di f fractive optical systems , but the ability to switch beam profi les requires replaceable optics , switchable or tunable di f fractive optical elements , deformable mirrors , and other complex optical arrangements which can be both costly and increase processing time while the adj ustments are made .

As an alternative to these free-space optical systems fiberbased systems have been proposed . The "Corona fiber" from nLight is a fiber based solution that allows switching of intensity between a central spot , a ring profile , and trident profiles with adj ustable power in each distribution . The fiber has "multiple guiding regions" , with the output adj usted by changing how much power is in each region . The power adj ustment is achieved by shi fting the position of the fibre feeding in the power to the multiple region fibre . All fibers are spliced together and used with a fiber laser to achieve an all fiber solution .

The adj ustable ring mode (ARM) from Coherent is a similar solution to the Corona fibre . US 10 , 807 , 190 describes the system as an apparatus and its use for laser processing along with a method and an optical component . A first laser device provides a first optical feed fiber and a second laser device provides a second optical feed fiber . A beam combining means connected to the first and second feed fibers and to a multi-core optical fiber is adapted to form a composite laser beam by having the first optical feed fiber aligned with a first core of the multicore optical fiber and the second optical feed fiber aligned with at least one second core of the multi-core optical fiber . The first and second cores outputs a composite laser beam to a workpiece to be processed . A control unit individually controls the power density of the output laser beams .

The output profiles from the nLight Corona fiber and Coherent ARM are limited by the refractive index profiles that are possible to manufacture in a fiber . While profiles can be much more complex than the common step-index core/cladding setup, it is di f ficult to produce arbitrary output profiles at the fibre exit .

Additionally, the Coherent ARM solution requires two laser beams , one for the central fiber core and one for the ring . Adj usting the output profile requires adj usting of the output power ratio of the two lasers .

It is an obj ect of the present invention to provide variable beam shaping optical apparatus which obviates or mitigates at least one of the disadvantages of the prior art .

According to a first aspect of the present invention there is provided a variable laser beam shaping optical apparatus comprising : a single laser source providing an input beam; a single beam shaping element on which at least one surface has a surface profile ; and a focusing lens to focus a shaped output beam from the single beam shaping element onto a focal plane ; characterised in that : the apparatus further comprises adj ustment means to vary a diameter of the input beam incident upon the beam shaping element ; the one or more surface profiles are configured to produce di f ferent shaped output beams dependent upon the incident input beam diameter, so that by varying the input beam diameter the shape of the output beam on the focal plane can be switched between di f ferent shapes .

In this way, a shaped laser spot of the beam pro file at focus can be changed between shapes such as a Gaussian, a flat top, ring and trident ( ring with a central spot ) with a single optical system by adj usting the diameter of the incident beam on the beam shaping element .

Preferably the apparatus includes a collimating lens .

Preferably the adj ustment means is a variable beam expander . The variable beam expander may take a collimated laser beam as an input and produce a collimated laser beam with increased, decreased, or unchanged diameter . Alternatively, the adj ustment means may be a linear movement member upon which is mounted the beam shaping element . In this way linear movement along the optic axis can move the beam shaping element in the propagation direction of a converging or diverging beam to vary the diameter of the incident beam on the beam shaping element .

In an embodiment , the apparatus comprises in order : the single laser source , the collimating lens , the variable beam expander, the single beam shaping element and the focusing lens . The beam shaping element is designed to refractively shape the incident light to produce a shaped intensity spot at the focus of the focusing lens . As the laser beam incident on the beam shaping element is varied in si ze , the shape produced at focus changes . With a narrow beam, only the central part of the beam shaping element is addressed . As the beam diameter increases , the area of the element that is addressed increases radially .

Preferably, the laser source is a single mode laser source .

Preferably, the beam shaping optical element is a freeform optical component . Preferably, the beam shaping optical element is a refractive optical component . Alternatively the beam shaping optical element may be a reflective optical component .

The one or more surface profiles of the beam shaping element may have radial sections to change the beam output shape dependent on the diameter of the incident input beam . Preferably one or more surface profiles of the beam shaping element are radially symmetric . In this way a central circular section may be configured to provide a first output beam shape such as a Gaussian output beam shape , for example . An annular section arranged radially to the central circular section may provide a second output beam shape such as a flat top, for example . Further annular sections radially distributed can give more output beam shapes such as a ring output beam shape , for example . In this way, the output laser spot shape changes smoothly with input beam diameter . As such, in the example , a rounded flat top may be produced between the Gaussian and the flat top profile . Additionally, an extinction ratio of a ring laser spot shape may be adj usted by adj usting the beam diameter .

The one or more surface profiles of the beam shaping element may be defined as X/Y separable profiles . These may provide rectangular or square sections as compared to radial sections .

Such an arrangement will produce square flat top laser spot shapes , or square frames . Equally, radial profiles with rectangular sections can be configured .

The beam shaping element may comprise an array of beam shaping optical members , wherein the array includes a plurality of sets of beam shaping optical members , each set of beam shaping optical members having a contoured surface di f fering from the contoured surface of the other sets of beam shaping optical members , and the ratio of the sets of beam shaping optical members varies with radial position in the array .

Preferably, the beam shaping optical members are arranged in a symmetrical pattern across the array . More preferably, a first set of beam shaping optical members have a first contoured surface and a second set of beam shaping optical members have a second contoured surface , the first and second sets of beam shaping optical members being arranged to vary in ratio radially outwards from a centre of the optical element .

In this way, as the output profiles from each sub-aperture in an array are additive the output laser spot at the focus of a lens will be a combination of the output profiles from each set of beam shaping optical members , the amount of contribution being determined by the number of members the input laser beam passes through .

Optionally, there may be a plurality of sets of beam shaping optical members . In this way more features of the output laser spot can be incorporated .

The sets of beam shaping optical members may be selected from a group consisting of : spherical lens , aspherical lens , toroidal lens , axicon, flat surface , wedge , of f-centre apex surface and freeform . In this way features from each of these members can be combined in the output laser spot depending on the si ze of the input beam . Preferably the beam shaping optical elements of each set have surface angles selected to adj ust the si ze of each feature in the output laser spot .

Preferably the ratio of the sets of beam shaping optical elements at each radial position is selected to determine the proportion of the optical feature present in the output laser spot so that switching can occur between output profiles dependent upon the input beam si ze .

The beam shaping optical members in the array may have di f fering shapes and/or si zes in a tessellating pattern . The resulting array geometry may be square , rectangular, hexagonal , octagons with squares , alternating triangles or the like .

Preferably the beam shaping optical members are arranged in an array with a pitch smaller than a si ze/area of the input laser beam . In this way, selected members contribute to the intensity distribution of the output laser beam depending on the si ze of the input laser beam .

By using multiple unit cells as elements with the same or di f ferent aperture shapes and dif ferent gradient profiles , and varying the ratio of the elements with radial position, the beam shaper can be designed to allow switching between multiple customised output profiles by dynamically adj usting the si ze of the incident input beam using a beam expander .

The rate at which the output beam profile is varied is directly proportional to the rate of beam expansion or the rate in moving the beam shaping element in the propagation direction of a diverging or converging beam . The rate may be optimised for the target application .

In an alternative embodiment , the apparatus comprises in order : the single mode laser source , the single beam shaping element mounted on linear adj ustment means , the collimating lens and the focusing lens . In this way the output beam shape is varied by moving the beam shaping element in the path of the diverging input beam from the laser source .

In further embodiment , the apparatus comprises in order : the single mode laser source , the collimating lens , the focusing lens and the single beam shaping element mounted on linear adj ustment means . In this way the output beam shape is varied by moving the beam shaping element in the path of the converging beam exiting the focusing lens .

According to a second aspect of the present invention there is provided a method of switching the shape of a laser beam spot comprising the steps :

( a ) providing variable beam shaping optical apparatus according to the first aspect ;

(b ) operating the adj ustment means to vary the diameter of the input beam incident upon the beam shaping element and thereby vary the shape of the output beam to dynamically vary output laser spot shapes at the focal plane of the focusing lens .

Thus by dynamically varying the diameter of the input beam incident upon the beam shaping optical element a smooth transition can be made between output laser spot shapes .

Preferably, the various output laser spot shapes are selected from a group comprising : Gaussian, a flat top, ring and trident ( ring with a central spot ) . Preferably, the laser spot can move from Gaussian through flat top to ring or trident as the diameter is increased .

Preferably, a rate at which the output beam shape is varied is directly proportional to a rate of beam expansion from the variable beam expander . Alternatively, a rate at which the output beam shape is varied may be directly proportional to a rate in moving the beam shaping element on the linear actuator in the propagation direction of a diverging or converging beam.

Preferably, an extinction ratio of a ring laser spot shape is adjusted by adjusting the input beam diameter incident on the beam shaping element.

Preferably, the laser spot at the focus of the focussing lens is positioned on a workpiece and the method includes moving the workpiece relative to the apparatus to provide laser processing on the workpiece. Preferably the method includes laser processing using at least two different laser spot shapes during the same processing operation.

Embodiments of the present invention will now be described with reference to the accompanying drawings of which:

Figure 1 is a schematic illustration of a variable laser beam shaping optical apparatus according to an embodiment of the present invention;

Figures 2 (a) and 2 (b) are (a) top view and (b) side profile of a beam shaping element used in the apparatus of Figure 1;

Figures 3 (a) - (c) are representative output beam profile slices from the apparatus of Figure 1 for varying incident beam diameters on the beam shaping element of Figure 2;

Figures 4 (a) - (c) are corresponding representative output beam profiles showing laser spot shapes of Figures 3 (a) - (c) ;

Figures 5(a) and 5(b) are (a) top view and (b) side profile of an alternative beam shaping element used in the apparatus of Figure 1;

Figures 6 (a) - (d) are representative output beam profile slices from the apparatus of Figure 1 for varying incident beam diameters on the beam shaping element of Figure 5; Figures 7 ( a ) - ( d) are corresponding representative output beam profiles showing laser spot shapes of Figures 6 ( a ) - ( d) ;

Figure 8 is a schematic illustration of a surface of a further refractive beam shaping element comprising an array of at least two di f ferent beam shaping optical members used in the apparatus of Figure 1 ;

Figures 9 ( a ) - ( c ) are representative output beam profiles showing laser spot shapes from the apparatus of Figure 1 for varying incident beam diameters on the beam shaping element of Figure 8 ; and

Figures 10 ( a ) and 10 (b ) are schematic illustrations of a variable laser beam shaping optical apparatus according to further embodiments of the present invention .

Referring initially to Figure 1 of the drawings there is illustrated a variable laser beam shaping optical apparatus , generally indicated by reference numeral 10 , including in order along an optical axis : a single laser source 12 providing an input beam 14 ; a collimating lens 24 ; an adj ustment means 20 being a variable beam expander 22 ; a single beam shaping element 16 having a first surface profile 18 ; and a focusing lens 26 according to an embodiment of the present invention . The variable beam expander 22 takes a collimated laser beam 14 as an input and produces a collimated laser beam with increased, decreased, or unchanged diameter . The beam shaping element 16 is designed to refractively shape the incident light to produce a shaped intensity spot 28 at the focal plane 29 of the focusing lens 26 . As the laser beam 14 incident on the beam shaping element 16 is varied in si ze , the shape 28 produced at focus changes . With a narrow beam, only the central part of the beam shaping element 16 is addressed as it is incident upon . As the beam diameter increases , the area of the element 16 that is addressed increases radially . The beam shaping element 16 can be designed in a radial fashion to produce different outputs at focus depending on the input beam 14.

Thus by dynamically adjusting the beam diameter, typically by rotation of the beam expander 22, the rate at which the output beam profile i.e. laser spot shape 28 is varied is directly proportional to the rate of beam expansion. The rate can be optimised for the target application.

As an example, for a narrow input beam, the output profile is approximately Gaussian. For a mid-sized beam, the output profile will be a flat top. For a large input beam, the profile is a ring. Other profiles are possible and they may appear in different orders i.e. narrow beam diameter could give a ring and a wider beam diameter a flat top, for example.

Though the output beam shape profile will switch on the focal plane as the diameter of the input beam is changed, the output profile changes smoothly with input beam diameter. As such, a rounded flat top can be produced between the Gaussian and the flat top profile. Additionally the extinction ratio of the ring can be adjusted by adjusting beam diameter.

This ability to vary the laser spot shape is useful for laser manufacturing processes where additional flexibility on laser beam profiles is desirable, and may be required mid-process or at least without changing the optical setup.

For example, during laser additive manufacture, a Gaussian profile will give the smallest feature size, while a ring profile will allow faster processing of larger features. As the thermal profile is more critical than the intensity profile, being able to tune the extinction ratio of the ring while keeping the spot size the same is an advantage.

Similarly, for laser welding, ring and trident profiles are commonly used. The ability to adjust the ratio of power in the ring to the main spot is useful for optimisation of the welding process .

The beam shaping element comprises of at least two regions separated radially ( or X/Y separably) . In each radial region the surface is engineered to produce a particular shape at focus .

An analytical solution for converting an input Gaussian intensity distribution into a flat top profile at the focus of a lens is known . The refractive surface required has an analytical definition for shaping in one dimension . The ID solution for the phase of the beam shaping element is given by :

Where is a coordinate system scaled according to the input beam . The ID solution is applied in a rotationally symmetric fashion to produce a circular flat top, or in an X / Y separated fashion to produce a square or rectangular flat top .

Figures 2 ( a ) and 2 (b ) show a beam shaping element 16a from above and in cross-section to illustrate a variable flat top and ring example . The first surface profile 18a has an inner region 30 , close to the optical axis , with a surface profile to generate a flat top profile at focus , according to the equation above . This may be referred to as a " field mapper" . A second outer region 32 , away from the optical axis , is described by an axicon with gradient equal to the gradient at the very edge of the inner region 30 . This annular ring is referred to as an "axicon" . This results in a smooth, aspheric surface with no discontinuities .

I f the input beam diameter is set to match the design si ze for the field mapper 30 in the centre , it does not address any of the axicon area 32 of the surface 18a . Therefore , it will be shaped into a flat top . This is shown in Figure 4 (b ) with the representative profile beam slice shown in Figure 3 (b ) . I f the input beam diameter is increased, it ' s central intensity will address the field mapper portion 30 of the surface, while its outer intensity will address the axicon 32. Therefore, the outer part of the beam is shaped into a ring profile, while the inner part is shaped according to the field mapping surface 30. (See Figures 4 (c) and 3 (c) ) . As the beam diameter is increased more power is shaped according to the axicon 32 and less according to the field mapper 30. This results in more power in the ring and a better extinction ratio. In addition, as the increased beam diameter results in a lower beam divergence, the ring thickness will also reduce. (See Figures 4 (d) and 3 (d) ) . If the input beam diameter is reduced below the design size of the flat top beam shaper 30, the output profile becomes approximately Gaussian. It is still shaped slightly by the curvature in the centre of the beam shaper, but it will no longer form a flat top. As the angular content of the centre of the shaper is shallower than the outer axicon 32, the spot size 28 is smaller than the flat top and ring. However, it is larger than an unshaped spot, and is not perfectly Gaussian. (See Figures 4 (a) and 3 (a) ) .

Since the angle of the axicon remains the same the ring size does not change. Since the angle of the axicon matches the maximum angle of the field mapper, the flat top has the same size as the ring.

Figures 5(a) and 5(b) show a beam shaping element 16b from above The first surface profile 18b has an the inner region 30a, close to the optical axis, now with a flat surface. A beam passing wholly through this central portion will be unshaped. An outer region 32a, away from the optical axis is described by an axicon with angle specified to produce a particular ring size at focus.

If the input diameter is small enough, the Gaussian shaped input beam fits entirely through the central portion and remains unshaped. This is shown in Figure 7 (a) with the representative profile beam slice shown in Figure 6(a) . As the beam diameter is increased, incident power will hit the axicon area 32a and be shaped into a ring. The larger the beam diameter, the more power will be in the ring and the less in the central spot. The boundary between the flat region and the axicon acts as a soft aperture, and causes some diffractive effects which modify the profile of the ring and central spot, as can be seen in Figures 6 (b) - (d) and 7 (b) - (d) .

It will be appreciated that the first surface profile 18 could be designed as X/Y separable instead of radially symmetric, to produce square flat tops, or square frames.

Figure 8 illustrates a surface of a refractive optical beam shaping element 16c comprising an array of at least two different beam shaping optical members 34. There may be any number of members in an n x n or n x m array. In the illustration there is an 13 x 14 array. From an origin 40 at the centre of the array, the ratio of the differing beam shaping members 34 varies radially across the array. The beam shaping members of the first 36 (shaded) and second sets 38 (unshaded) provide different shaped intensity profiles on a single laser beam passing through the element 16c. While a square member shape 34 is shown, the members may take any form which provides a tessellating pattern.

In the prior art lens arrays, the lenses in the array are all identical having the same aperture shape and surface profiles. The lens aperture shape and the F-number dictates the shape and size of the output laser spot for a beam passing though the laser beam shaping optical component. In the beam shaping element 16c used in the present invention by providing differing surface profiles i.e. different gradient profiles on the substrate, the output laser spot can be shaped into more complex profiles with multiple features. By varying the surface profiles radially on the surface of the component, different output beam profiles can be generated when different input beam diameters are incident on the laser beam shaping optical component. The element 16c shown has 13 x 13 micro-optic members 34 and is generally formed by micro-machining of around 10mm² square or rectangular 1mm thick substrate plate made of fused silica, quartz glass, sapphire, ZnSe or the like. It will be appreciated that any number of members may be incorporated. The present applicants use a freeform direct-write process in fused silica as described in US9089927, incorporated herein by reference, to create the element 16c.

Each set 36,38 of beam shaping optical members are selected to individually provide a desired focused laser spot output profile. The sets of beam shaping optical members 36,38 may be a spherical lens, an aspherical lens, a toroidal lens, an axicon, a flat surface, a wedge, an off-centre apex surface or alternatively a freeform surface. Any beam incident upon the members 34 will have an output formed of a combination of the features of the members 36,38 through which it passes. The intensity profile of the output beam will be dependent on the ratio of the first set of members 36 to the second set of members 38. Thus the radial distribution shown in Figure 8 will provide an output laser spot having the features from the shaded members 36 only if the input laser source has a size which lies only on shaded members 36. As the input laser beam size is increased a portion of the features from the second set of members 38 is introduced and the output laser spot will show a combination of the features. When the input laser beam size is increased to a size which almost fills the element 16c surface a near equal mix of the features is seen. In this way an input laser source can dynamically change or switch from a spot with features of a first set of members 36 to those of a combined set of members 36,38 by merely expanding the diameter of the input laser source beam. For example, if the shaded lenses, members 36, follow a spherical lens profile, the output of a narrow beam will be a square flat top at the focal plane. If the unshaded lenses, members 38, are axicons, a larger beam will be incident upon some spherical lenses and some axicons, resulting in an output that is an additive combination of a ring and a square flat top. As the beam size increases, proportionally more optical power will be present in the ring profile than in the square profile.

The output cross sections for varying input beam sizes are illustrated in Figure 9 (a) - (c) . The beam shaper surface is for Figure 8 which consists of two different members 34: axicons (unshaded) 38 and parabolic (conic = -1) lenses (shaded) 36. The centre of the array consists of only lenses, while the outer edge is only axicons. The intermediate region has a 50/50 ratio of the two members. A small input beam, say 2mm, will only be shaped by the lens members 36, producing a mildly shaped flat top output seen in Figure 9(a) . As the beam size is increased, the ratio of axicons to lenses that the beam is incident upon changes, pushing more power into a ring output, see Figure 9(b) as the ring is being formed and Figure 9(c) in which a completed ring is present together with inner spot. Using this beam shaping element 16c in conjunction with a beam expanding telescope, as illustrated in Figure 1, provides a straightforward mechanism for dynamic beam shaping. While the principle has been demonstrated here for a variable trident output, the individual members 34 could take a wide variety of forms, including more arbitrary surfaces.

The dynamic output could also be achieved with the static beam shaper element 16c without the need for a beam expander if the beam shaping component is position in the diverging path of the input laser source before a collimating lens, or the converging path after focusing, see Figure 10 (a) and 10 (b) . By translating the beam shaper element 16c along the optical axis the incident beam diameter will change. This will simultaneously change the output spot size.

Reference is now made to Figures 10 (a) and 8 (b) which illustrate variable laser beam shaping optical apparatus 10a, 10b, according to further embodiments of the present invention . Like parts to the apparatus 10 of Figure 1 have been given the same reference numerals to aid identi fication of the component parts . For apparatus 10a, 10b the variable beam expander 22 adj ustment means 20 is removed and instead the beam shaping element 16d, e is located on a linear actuator 22a , b so that it can be moved in the beam propagation direction along the optical axis . In the embodiment of apparatus 10a, the beam shaping element 16d is located between the laser source 12a and the collimating lens 24a in the divergent beam 14a . As the beam shaping element 16d is translated along the optical axis the incident beam diameter on the element 16d will change . In the embodiment of apparatus 10b, the beam shaping element 16e is located after the focusing lens 26b in the convergent beam 14b . As the beam shaping element 16e is translated along the optical axis the incident beam diameter on the element 16e will change .

Thus dynamically adj usting the beam diameter, by translation of the beam shaping element 16d, e the rate at which the output beam profile i . e . laser spot shape 28a, b is varied is directly proportional to the rate in moving the beam shaping element in propagation direction of diverging/ converging beam . The rate can be optimised for the target application .

While the beam shaping element 16a-c is illustrated with a first surface profile 18 only on its output surface , it will be appreciated that a surface profile may alternatively be on the input surface or both the input and output surfaces may have surface profiles which together provide the shaped output beam which varies with the diameter of the input beam .

The principal advantage of the present invention is that it allows variable beam shaping, producing outputs such as Gaussian, flat top, ring and tridents ( ring with a central spot ) with a single optical system . The beam profiles can be changed and adj usted by simple mechanical translation or rotation . This is useful for laser manufacturing processes where additional flexibility on laser beam profiles is desirable and may be required mid-process or at least without changing the optical setup . Unlike the prior art Corona fiber and ARM solutions , this solution is agnostic to the method of delivery for the input beam . It does not require a fiber-based input and can be implemented with any free space collimated beam . The output mode profiles are not restricted by fiber geometry . Freeform optics advantageously provide wide flexibility in output profile options .

Claims

1 . A variable laser beam shaping optical apparatus comprising : a single laser source providing an input beam; a single beam shaping element on which at least one surface has a surface profile ; and a focusing lens to focus a shaped output from the single beam shaping element onto a focal plane ; characterised in that : the apparatus further comprises an adj ustment means to vary a diameter of the input beam incident upon the beam shaping element ; and the one or more surface profiles are configured to produce shaped output beams dependent upon the incident input beam diameter , so that by varying the input beam diameter the shape of the output beam at the focal plane can be switched between di f ferent beam shapes .

2 . A variable laser beam shaping optical apparatus according to claim 1 wherein various shaped output beams are selected from a group comprising : Gaussian, a flat top, ring and trident ( ring with a central spot ) .

3 . A variable laser beam shaping optical apparatus according to claim 1 or claim 2 wherein the apparatus includes a collimating lens .

4 . A variable laser beam shaping optical apparatus according to any preceding claim wherein the adj ustment means is a variable beam expander .

5 . A variable laser beam shaping optical apparatus according to any one of claims 1 to 3 wherein the adj ustment means is a linear actuator upon which is mounted the beam shaping element to move the beam shaping element in the propagation direction of a converging or diverging beam and vary the diameter of the incident beam on the beam shaping element .

6 . A variable laser beam shaping optical apparatus according claim 3 wherein the apparatus comprises in order : the single laser source , the collimating lens , the variable beam expander, the single beam shaping element and the focusing lens .

7 . A variable laser beam shaping optical apparatus according to any preceding claim wherein the beam shaping optical element is a refractive optical component .

8 . A variable laser beam shaping optical apparatus according to claim 7 wherein the one or more surface profiles have radial sections to change the beam output shape dependent on the diameter of the incident input beam .

9 . A variable laser beam shaping optical apparatus according to claim 8 wherein the one or more surface profiles radially symmetric .

10 . A variable laser beam shaping optical apparatus according to claim 9 wherein the one or more surface profiles have a central circular section configured to provide a Gaussian output beam shape .

11 . A variable laser beam shaping optical apparatus according to claim 10 wherein the one or more surface profiles have an annular section arranged radially to the central circular section configured to provide a flat top output beam shape .

12 . A variable laser beam shaping optical apparatus according to claim 11 wherein the one or more surface profiles have further annular sections radially distributed configured to provide a ring output beam shape .

13 . A variable laser beam shaping optical apparatus according to claim 7 wherein the one or more surface profiles vary in a separated x/y profile providing rectangular sections .

14 . A variable laser beam shaping optical apparatus according to claim 13 wherein the rectangular sections are square to provide square laser spot shapes or frames .

15 . A variable laser beam shaping optical apparatus according to any one of claims 1 to 7 wherein the beam shaping element comprises an array of beam shaping optical members , wherein the array includes a plurality of sets of beam shaping optical members , each set of beam shaping optical members having a contoured surface di f fering from the contoured surface of the other sets of beam shaping optical members , and the ratio of the sets of beam shaping optical members varies with radial position in the array .

16 . A variable laser beam shaping optical apparatus according to claim 15 wherein the beam shaping optical members of each set of beam shaping optical members are selected from a group consisting of : spherical lens , aspherical lens , toroidal lens , axicon, flat surface , wedge , of f-centre apex surface and freeform .

17 . A variable laser beam shaping optical apparatus according to claim 15 or claim 16 wherein the beam shaping optical elements of each set have surface angles selected to adj ust the si ze of each feature in the output beam shape .

18 . A variable laser beam shaping optical apparatus according to any one of claims 15 to 17 wherein the beam shaping optical members in the array have di f fering shapes and/or si zes in a tessellating pattern providing an array geometry selected from a group consisting : square , rectangular, hexagonal , octagons with squares , and alternating triangles .

19 . A variable laser beam shaping optical apparatus according to claim 5 wherein the apparatus comprises in order : the single laser source , the single beam shaping element mounted on the adj ustment means comprising the linear actuator, the collimating lens and the focusing lens .

20 . A variable laser beam shaping optical apparatus according to claim 5 wherein the apparatus comprises in order : the single laser source , the collimating lens , the focusing lens and the single beam shaping element mounted on the adj ustment means comprising the linear actuator .

21 . A method of varying the shape of a laser beam comprising the steps :

( a ) providing variable beam shaping optical apparatus according to and one of claims 1 to 20 ;

(b ) operating the adj ustment means to vary the diameter of the input beam incident upon the beam shaping element and thereby vary the shape of the output beam to provide various output laser spot shapes at a focal length of the focusing lens .

22 . A method of varying the shape of a laser beam according to claim 21 wherein the various output laser spot shapes are selected from a group comprising : Gaussian, a flat top, ring and trident ( ring with a central spot ) .

23 . A method of varying the shape of a laser beam according to claim 21 or claim 22 wherein the adj ustment means is a variable beam expander and a rate at which the output beam shape is varied is directly proportional to a rate of beam expansion from the variable beam expander .

24 . A method of varying the shape of a laser beam according to claim 21 or claim 22 wherein the adj ustment means is a linear actuator and a rate at which the output beam shape is varied is directly proportional to a rate in moving the beam shaping element on the linear actuator in the propagation direction of a diverging or converging beam .

25 . A method of varying the shape of a laser beam according to any one of claims 21 to 24 wherein an extinction ratio of a ring laser spot shape is adj usted by adj usting the input beam diameter incident on the beam shaping element .