JP2006106703A - Compensator optics using beam shaping for stability of laser beam delivery system and radially non-symmetric beam forming element to correct energy distribution form distortion caused by lateral direction beam drift - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compensator/remapper and a method for compensation and remapping of a laser beam for control and correction of laser pointing and thermal drift instability in a laser beam delivery system including a laser generating a laser beam and a plurality of optical elements for directing, shaping and focusing the laser beam along a beam path to a target. <P>SOLUTION: A compensator/remapper includes a compensator element and a remapper element. The compensator element receives an input laser beam having a range of input angles and lateral displacements and redirects components of the input laser beam into an aligned laser beam having evenly distributed and parallel components. The remapper element is illuminated by the aligned laser beam from the compensator element and remaps the components of the aligned laser beam into a shaped laser beam having a profile that is optimum for remapping into a flat top laser beam. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to the control and correction of laser aiming and thermal drift instabilities in laser beam delivery systems, and more particularly to compensator optics that use beam shaping for control and correction of laser aiming and thermal drift instabilities, and laser beam delivery. The present invention relates to control and correction of laser aiming and thermal drift instability in a system, and more particularly to a radial asymmetric beam forming element for correcting distortion of a laser beam energy distribution shape due to lateral beam movement.

  Focused directed laser beams are typically used for materials such as metals, polymers, integrated circuits, substrates, ceramics, and other materials, drilling through and micro blind vias, laser imaging, substrate cutting and modification of integrated circuits, and custom manufacturing. , Drilling, cutting, and removal of selected materials and other complex machining and micromachining operations. Such a process is very complex, and in simultaneous or sequential operations, a single or multiple lasers or multiple types of lasers such as visible light lasers, infrared (IR) lasers, ultraviolet (UV) lasers can be used simultaneously or Often includes sequential use. However, in general in such a laser process, the general purpose of a laser system is to control and reliably direct, focus, and focus the energy of one or multiple laser beams to direct each beam to a target spot. Convergence or drawing an aperture region of the laser beam on the target surface.

  However, many problems that occur in prior art conventional laser systems directly affect the “positioning” of the laser beam to the target position in a reliable and controllable manner. The first problem is often referred to as “beam oscillation” or “positioning instability”, as shown in FIGS. 1A and 1B, but the beam axis 10 of the laser beam 12 deviates from the optimum center line 14. It is a radial deviation that is shifted by θ, and often relates to the pulse energy fluctuation of the laser beam, often referred to as “pumping jitter”. Positional instability is inherent in both the characteristics of the laser 16 itself and the normal operation of the laser 16 such as “pumping jitter”.

  A second problem of the prior art is shown in FIGS. 2A and 2B, often referred to as “thermal drift”, which also causes the beam axis 10 of the laser beam 12 to deviate from the optimum centerline 14. Cause. Thermal drift is generally attributed to changes in laser 16 parameters due to laser duty cycle changes, heating during operation, and laser 16 power level changes. It should be noted that “positioning instability” causes an angular deviation from the optimum center line 14 of the beam axis 10, whereas “thermal drift” is a linear radial drift of the beam axis 10 with respect to the optimum center line 14. Is to produce. That is, the beam axis 10 of the laser beam 12 drifts away from the optimum center line 14 in the radial direction while being parallel to the axis of the optimum center line 14.

  Furthermore, the third problem of the prior art is the problem of beam mode changes over time, which results in “hot spots” or distortions of the beam distribution shape. If the beam distribution shape is not uniform or does not have an optimal Gaussian distribution shape, the shape of the distribution shape cannot be shaped into a substantially “flat top” distribution shape, and laser systems such as micromachining and microvia drilling Will adversely affect the quality of processing. This problem is of course further combined with positioning instability and thermal drift.

  In practice, all lasers used for micromachining, such as microvia drilling, exhibit positioning instability, thermal drift and distributed shape distortion, so many attempts have been made to correct or at least control these problems. . For example, prior art laser systems attempt to correct for the effects of “positioning instability” and “thermal drift” using actively controlled servo mirrors. The servo mirror is controlled to redirect the laser beam to correct “positioning instability” and “thermal drift”. However, this type of method detects the actual path of the beam due to positioning instability or thermal instability, compares it with the target optimal path of the beam, and controls the servo mirror to direct the beam to the target path. There is a need. Such methods are not only complex and expensive, but also have inherent time delays in detecting and correcting for effects of positioning instability and thermal drift, and these methods are subject to mechanical and control system tolerances. It introduces its own errors and does not provide a completely satisfactory solution to these problems.

  Other prior art approaches to these problems are to use optical elements in the laser beam path to correct positioning instability and thermal drift, and to optimize the beam for micromachining such as microvia drilling and flat tops. Shape into a distribution shape. However, if the optical beam shaping system is poorly illuminated, that is, if it is illuminated at a certain angle of incidence or with a laterally offset beam as a result of positioning instability, thermal drift or hot spots, optical beam shaping. The element cannot shape the laser beam into the target distribution shape. However, positioning instability and thermal drift inherently cause the beam to reach the beam shaping element at a certain incident angle or a certain lateral displacement, resulting in a poor illumination condition of the beam shaping element and a beam distribution shape. It will be clear that there is a problem with proper shaping.

  The basic problems that arise with using optical elements to correct or compensate for positioning instability and thermal drift are holographic optical elements (HOE) and standard symmetric holographic optical elements (SSHOE) as beam shaping elements. Is shown in FIGS. 3A and 3B. FIG. 3A shows the result of radial displacement due to the thermal drift effect, for example in the case of a holographic optical element (HOE), especially for a standard symmetric holographic optical element (SSHOE) 18 or equivalent lens. Since the SSHOE 18 is symmetrical, the laser beam 12A incident on the SSHOE 18 along the beam axis 10A parallel to the HOE axis 20 emits the SSHOE 18 as a laser beam 12B on the beam axis 10B. The beam axis 10B is coaxial with the beam axis 10A and is a linear extension thereof. More specifically, the laser beam 12A incident on the SSHOE 18 along the beam axis 10A that is parallel to the HOE axis 20 but radially displaced from the HOE axis 20 by a distance D is applied to the same beam axis 10A shown as the beam axis 10B. The SSHOE 18 exits along the axis and remains displaced in the radial direction by a distance D with respect to the HOE axis 20. Thus, the SSHOE 18 or equivalent symmetric lens does not reorient the beam axis 10 of the incident laser beam 12 in the radial direction with respect to the HOE axis 20 of the SSHOE 18, so that the thermal drift effect is corrected or controlled. Is impossible.

  Referring to FIG. 3B, the laser beam 12 </ b> A affected by “positioning instability” enters the incident surface 22 of the SSHOE 18 along the beam axis 10 </ b> A having an angular deviation θ with respect to the HOE axis 20. That is, the laser beam 12A is not parallel to the HOE axis 20. Due to the symmetry of the SSHOE 18 or equivalent symmetric lens, the laser beam 12B exits the exit surface 24 of the SSHOE 18 along the beam axis 10B, which is an extension of the beam axis 10A where the laser beam 12A is incident on the SSHOE 18. Therefore, as in the case of thermal drift, the conventional SSHOE 18 or equivalent symmetric lens cannot correct or control positioning instability and the resulting angular deviation of the beam axis 10.

  However, instabilities and misalignments in the input beam to the beam shift element often result in laser beam distortion caused by the beam shaping optics of a typical beam delivery system, such as a micromachining system for microvia drilling. Other problems can still occur.

  For example, in a typical laser beam delivery system as shown in FIGS. 8A through 8D, the laser 12 typically has a diode-pumped solid state (DPSS) that tends to generate a TEM 00 single mode laser beam with an optimal Gaussian energy distribution shape. It consists of a laser or a diode pumped fiber (DPFL) laser. In a typical system as shown in FIGS. 8A to 8D, the beam shaping optics 26 converts the output beam 12I having an optimal Gaussian distribution shape 12GP into a flat top distribution shape 12FP, ie, a uniform which is particularly advantageous for micromachining operations. Used to reshape the output beam 120 with an energy distribution shape and typically consists of, for example, a diffractive or holographic beam diffuser or shaping optics.

  As is well known, the input beam 12I generated by the laser 12 is changed in accordance with changes in the parameters of the laser 12, such as changes in the excitation diode current, deviations in the harmonic crystal, changes in pulse transmission frequency and repetition rate. There is a tendency to drift laterally in amounts ranging from microns to hundreds of microns. Typical results of such lateral drift of the beam axis 10 of the input beam 12I from the optimum centerline 14 coaxial with the optical centerline 26CR of the beam shaping optics 26 are schematically shown in FIGS. 8A, 8B, 8C and 8D. It is shown in the figure. 8A and 8B show the situation where the beam axis 10 of the input beam 12I is coaxial with the optical centerline 26CR of the beam shaping optics 26, and FIG. 8B shows the energy of the input beam 12I and the resulting output beam 12O. The distribution shapes are overlaid for comparison. Next, FIGS. 8C and 8D show a situation in which the beam axis 10 of the input beam 12I is laterally displaced with respect to the optical center line 26CR of the beam shaping optical system 26, and FIG. The energy distribution shapes are overlaid for comparison.

  However, as shown in FIGS. 8A to 8D, the lateral misalignment of the input beam 12I with respect to the axis of the beam shaping optical system 26, ie, the misalignment between the situation of FIGS. 8A and 8B and the situation of FIGS. 8C and 8D. Produces a non-uniform energy distribution shape in the output beam 12O. In a typical situation as shown in FIGS. 8C and 8D, for example, the lateral misalignment 64O of the input beam 12I is “insufficient” in the energy distribution shape of the output beam 12O and “insufficient” in the energy distribution shape of the output beam 12O. Will produce either or both of 64D. As illustrated, the hot spot 64S is a region having an energy distribution shape with an energy level higher than the target, and the deficiency 64D is a region having an energy distribution shape with an energy level lower than the target. It should be noted in this regard that the hot spot 64S is typically formed on the side of the lateral deviation 64O of the input beam 12I in the energy distribution shape, whereas the deficiency 64D is typically out of the energy distribution shape. That is, it occurs on the side opposite to the lateral displacement 64O.

  Such distortion in the energy distribution shape of the output beam 12O will obviously degrade the performance of a laser beam delivery system, such as a laser micromachining system. As a result, each such misalignment of the beam axis requires readjustment of the beam delivery system to return to the target flat top distribution shape 12F of the output beam 120. The necessary readjustment of the system is to readjust the beam shaping optics 26 to a new position on the beam axis 10 of the input beam 12I and to adjust the beam axis 10 of the input beam 12I to the optical center line 26CR of the beam shaping optics 26. Readjustment is done by either or both. Both readjustments require significant system downtime. It will be appreciated that the need to readjust the laser beam system optics or laser beam for each lateral deviation of the laser beam, regardless of the cause of the deviation, is a significant problem. This is because typically, for example, in the case of an industrial laser system installed on the production floor, readjustment is required several times a day or several times per change.

  In this regard, when using asymmetric optical elements, including compensators and relocation elements, to address some of the problems arising from unwanted lateral misalignment in the laser beam, such asymmetric elements are typically holographic or It must also be noted that it consists of a diffractive optical element. Such optical elements typically have constant characteristics, but are constant regardless of the possible lateral misalignment of the laser beam, which is sufficient for the full range of possible lateral misalignment of the laser beam in a given system. It cannot be dealt with.

  The present invention provides a solution to these and related problems with the prior art.

  The present invention provides a laser positioning and thermal drift instability in a laser beam delivery system having a laser that generates a laser beam and a plurality of optical elements for directing, shaping, and converging the laser beam to a target along the beam path. The present invention is directed to a compensator / rearranger and method for laser beam compensation and relocation to control and correct for.

  According to the invention, the compensator / relocator comprises a compensator element and a relocator element. The compensator element receives an input laser beam having a range of input angles and lateral displacements and redirects the components of the input laser beam to an aligned laser beam having a uniformly distributed parallel component. The relocator element is illuminated by the aligned laser beam from the compensator element and realigns the components of the aligned laser beam into a shaped laser beam with an optimal distribution shape to relocate to a flat top laser beam To do.

  In various embodiments of the invention, the compensator element may be a computer-generated holographic lens encoded over the entire surface, and the relocator element may be a computer-generated radial symmetric diffractive optical element (RSDOE) or It may be a computer generated radial asymmetric diffractive optical element (NSDOE).

  For example, the compensator element may include a substrate, a field lens disposed on the input side of the substrate, a diffractive optical element shaper disposed on the output side of the substrate, and an aperture defined by the field lens. The compensator element may also include a compensator element formed of a refractive lens element and a computer-generated holographic diffractive optical element shaper disposed on the output side of the compensator element. In this case, the refractive lens forms the substrate of the diffractive optical element shaper, and the shaper forms the aperture. In another embodiment, the compensator element is disposed on the input side of the substrate, a single diffractive optical element that forms an integral field lens element and a shaper element, and an aperture formed on the output side of the substrate. You may have.

  In the presently preferred embodiment of the present invention, the arrayed laser beam output of the shaper element has a non-circular Gaussian distribution shape, and the shaped laser beam output of the repositioner element has a circular Gaussian distribution shape.

  The present invention also provides a system for converting an input energy distribution shape of an input laser beam into a target output energy distribution shape of an output laser beam in a system in which the beam axis of the input laser beam undergoes a lateral deviation that is variable with respect to the radial direction and the size And a radially asymmetric beam forming element.

  The beam shaping element according to the present invention corrects distortion in the output energy distribution shape in which the first distribution shape conversion function for converting the input energy distribution shape to the target output energy distribution shape and the lateral deviation of the input laser beam are introduced. In order to correct the first distribution shape conversion function, an optical element having a distribution shape conversion function having a distribution shape correction conversion function added to the first distribution shape conversion function is provided.

  In a presently preferred embodiment, the distribution shape correction conversion function of the radial asymmetric beam forming element has at least one of an underdistribution shape conversion function and a hot spot distribution shape conversion function. The underdistribution shape conversion function is added to the first distribution shape conversion function in order to add the compensation underenergy distribution shape to the target output energy distribution shape at a position corresponding to a hot spot caused by the lateral deviation of the input laser beam. . Similarly, the hot spot distribution shape conversion function is a first distribution shape conversion function for adding the compensation hot spot energy distribution shape to the target output energy distribution shape at a position corresponding to the shortage caused by the lateral deviation of the input laser beam. To be added.

  Further in accordance with the present invention, the optical axis of the beam forming element is aligned parallel to the beam axis of the input laser beam while being proportional to the maximum expected lateral shift of the beam axis of the input laser beam. Therefore, the input laser beam passes through the beam forming element in a state of being parallel and shifted with respect to the optical axis of the optical element.

  In yet another embodiment, the beam shaping element rotates the distribution shape transformation function about the optical axis of the optical element to allow adjustment of the distribution shape transformation function with respect to the current lateral deviation of the input laser beam. Supported by a rotating mount that allows.

  The present invention will now be described by way of example with reference to the accompanying drawings.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described.

A. Overview In accordance with the present invention, as schematically illustrated in FIGS. 4 and 5A to 5F, one or both of radial displacement due to thermal drift and angular deviation due to positioning instability may occur as shown in FIG. ) 26 can be corrected. As illustrated, the NSE 26 is an equivalent optical element such as an asymmetric hologram optical element (NSHOE), an asymmetric lens, an asymmetric refractive element, or an asymmetric diffractive element. As shown, the NSE 26 is different from the SSHE 18 or equivalent symmetric element, and the path of the beam axis 10 of the laser beam 12 across the NSE 26 is refracted or bent by a correction angle φ while the laser beam 12 passes through the NSE 26. As will be discussed further below, in one embodiment of the NSE 26, the angle φ increases as the radial displacement Δ of the incident beam axis 10 from the centerline axis 28 of the NSE 26 increases. In the second embodiment of the NSE 26, the correction angle φ increases as the incident angle α of the beam axis 10 of the incident laser beam 12 with respect to the plane of the NSE 26 decreases.

  Examples of the drift / deviation correction element 30 for correcting one or both of radial displacement due to thermal drift and angular deviation due to positioning instability are illustrated in FIGS. 5A, 5B and 5C.

  FIG. 5A shows an embodiment of the drift / deviation correction element 30 for correcting the angular deviation of the laser beam 12 due to unstable positioning. As shown in the figure, in this example, the drift / deviation correction element 30 is composed of a single NSE 26, 26A, 26B, 26C, 26D, or 26S such as an asymmetric hologram optical element (NSHOE) or an equivalent asymmetric lens.

  First, considering the geometrical aspect of angular deviation due to positioning instability as shown in FIG. 5A, the laser beam 12 having angular deviation resulting from positioning instability is considered to be emitted from one point, that is, the laser 16. Then, the beam axis 10 of each laser beam 12 is emitted outward from the point with an angular deviation θ determined by the degree of fluctuation, which continues until the laser beam 12 strikes the plane of the NSE 26. Considering the element arrangement shown in FIG. 5A, it can be seen that the incident angle α between the beam axis 10 and the plane of the NSE 26A decreases with a certain correlation as the angular deviation θ increases. It can also be seen that the radial displacement Δ between the center line axis 28 of the NSE 26A and the point where the beam axis 10 enters the NSE 26A increases as the angular deviation θ increases. In other words, the angular deviation θ is inversely proportional to the incident angle α with respect to the NSE 26A and is proportional to the radial displacement Δ from the center line axis 28 of the NSE 26A.

  Obviously, correction of angular deviation due to instability of positioning requires reorientation, i.e. bending or refraction, of the beam axis 10 of the laser beam 12 with a correction angle φ that directs the laser beam 12 in an appropriate manner. Will. In this regard, for example, the correction angle φ may be configured to be parallel to the HOE axis 20 as soon as the beam axis 10 exits the NSE 26A. In another example, the correction angle φ may be configured to direct the laser beam 12 over a selected point or region that is a predetermined distance away from the NSE 26A, such as an entrance surface of a second NSE (not shown).

  In either case, as can be seen from the above description of the angular deviation geometry, the magnitude of the correction angle φ must therefore increase with increasing radial displacement Δ or decreasing incident angle α. Therefore, in the first embodiment of the angle correction NSE 26A, for example, the angle correction NSE 26A, which is NSHOE or an equivalent asymmetric lens, is set so that the correction angle φ increases in proportion to the radial distance from the central axis of the angle correction NSE 26A. Composed. As described above, therefore, as the angular deviation θ of the beam axis 10 increases, the radial displacement Δ of the beam axis 10 from the central axis of the angle correction NSE 26A increases, and the correction angle φ also increases.

  In the second embodiment of the angle correction NSE 26A, the angle correction NSE 26A is configured such that the correction angle φ increases as the incident angle α decreases, that is, as the angle deviation θ of the beam axis 10 increases. However, from the relationship between the angular deviation θ, the incident angle α, and the radial displacement Δ, it can be seen that the two examples of the angle correction NSE 26A are equivalent.

  Therefore, as shown in FIG. 5A, the angle correction NSE 26A of the drift / deviation correction element 30 corrects the angular deviation θ by bending or refracting the laser beam 12 with a correction angle φ proportional to the angular deviation θ. . As a result, any laser beam 12 having a beam axis 10 that is not parallel to the HOE axis 20 is bent at a correction angle φ, the beam axis 10 is parallel to the HOE axis 20, or the beam axis 10 is selected focus or Oriented to the area.

  The result of the operation of the angle correction NSE 26A is shown in FIG. 5B. FIG. 5B is an end view of the laser 16 showing a possible distribution of the corrected beam 12C centered on the optimum centerline 14 compared to a possible distribution of the uncorrected beam 12U.

  Next, FIG. 5C shows an embodiment of the drift / deviation correction element 30 that corrects the radial displacement of the laser beam 12 due to thermal drift. As described above, the cause of the thermal drift or similar radial displacement is not the angular deviation of the beam axis 10 from the target optimum center line 14 but the radial displacement from the optimum center line 14. Thus, radial displacement, i.e., thermal drift, results in a beam axis 10 having an incident angle α of about 90 ° with respect to NSE 26, and correction of radial displacement Δ is a function of radial displacement Δ rather than incident angle α. It becomes.

  As illustrated, in this example, the drift / deviation correction element 30 includes a displacement correction NSE 26B followed by a collimating NSE 26C, and each may be, for example, an asymmetric hologram optical element or an equivalent asymmetric lens.

  In the present embodiment, as described above, the correction angle φ of the displacement correction NSE 26B is the radial displacement Δ between the center line axis 28 of the displacement correction NSE 26B and the point where the beam axis 10 of the laser beam 12 is incident on the plane of the displacement correction NSE 26B. In the radial direction in proportion to The effect of the drift correction NSE 26B is therefore to refract or bend the laser beam 12 at a correction angle φ proportional to the radial displacement Δ of the beam axis 10, ie, an angle proportional to the thermal drift of the laser beam 12. It is. Since the displacement of the beam axis 10 of the laser beam 12 resulting from the thermal drift is radial and the beam axis 10 of the laser beam 12 is therefore substantially parallel to the optimum centerline 14, the beam axis 10 is normally incident on the displacement correction NSE 26B. Perpendicular to the surface. As described above, the correction angle φ imposed by the displacement correction NSE 26B condenses, that is, directs or focuses the beam axis 10 on a point or a small area at a certain distance from the displacement correction NSE 26B. As shown in FIG. 5C, the focus of the displacement correction NSE 26B is on or near the incident surface of the second element of the drift / deviation correction element 30 shown as collimating NSE 26C.

  The collimating NSE 26C is similar in some respects to the inverse transform of the angle correction NSE 26A. That is, as shown in the figure, the laser beams 12 are transmitted from the correction NSE 26B so that each beam axis 10 has an angle α, that is, an angle similar to the angular deviation θ, with respect to the HOE axis 20 of the collimating NSE 26C. The light enters the collimating NSE 26C. As shown in the figure, the collimating NSE 26C redirects each incident laser beam 12 with a correction angle φ inversely proportional to the incident angle α so that the beam axis of the laser beam emission collimating NSE 26C is parallel. Bend.

  The drift / deviation correction element 30 comprising the displacement correction NSE 26B followed by the collimating NSE 26C therefore first redirects the laser beam 12 to reduce the radial displacement of each laser beam 12 and is at a predetermined distance. Correcting radial displacement due to thermal drift by focusing or directing the laser beam 12 in a predetermined region and then correcting the relative angle of the beam axis 10 to be parallel to the target optimum centerline 14. Can do.

  The operation of the drift / deviation correction element 30 is shown in FIG. 5D. FIG. 5D shows a possible distribution of the corrected beam 12C centered on the optimum centerline 14 compared to the uncorrected beam 12U.

  Next, considering the case shown in FIG. 5E, the angular deviation due to positioning instability and the radial displacement due to thermal drift rarely occur separately, and it is more common for both effects to exist in a given situation. You will see that. Thus, many if not all laser beams 12 exhibit both angular deviation and radial displacement, and a given laser beam 12 from NSE 26D centerline axis 28 impinges on NSE 26D. The radial distance can be due to radial displacement or angular deviation, or to some extent, both.

  Thus, the two-element drift / deviation correction element 30 may be configured using, for example, the deviation correction NSE 26A and the subsequent displacement correction NSE 26B. Each of these functions as described above. By this combination, first, the angular deviation of the laser beam 12 is corrected, and each laser beam 12 is redirected to the output laser beam 12 having the parallel beam axis 10 by the correction angle φ determined by the angular deviation. Attach. Therefore, in this first stage, the angular deviation is effectively changed to the radial displacement and the radial displacement is changed to the angular displacement, and the output laser beam 12 shows only the radial displacement. In a subsequent second stage, radial displacement will be corrected as discussed in FIG. 5C to provide the final laser output beam 12.

  Another embodiment of the drift / deviation correction element 30 is shown in FIG. 5E. This is a combination of the characteristics of both the angle correction NSE 26A and the displacement correction NSE 26B in a single angle / displacement correction NSE 26D, and is composed of NSHOE, for example. In this example, the correction angle φ is a function of both the radial displacement of the collision laser beam 12 from the HOE axis 20 and the incident angle α of the laser beam 12 to the angle / displacement correction NSE 26D. NSE 26D performs both functions of angle correction NSE 26A and displacement correction NSE 26B.

  In either embodiment, the output of the drift / deviation correction element 30 passes through the collimating NSE 26C to become the parallel beam 12 and is passed through the shaper element 26S. In this respect, the order of the collimating NSE 26C and the shaper element 26S may be arranged in any way, such as NSHOE, HOE, aspheric optical elements and other elements that perform the necessary functions. You can see that it can be made up of.

  The results of the embodiment shown in FIG. 5E are shown in FIG. 5F comparing the possible distribution of the corrected beam 12C about the optimum centerline 14 with the drift uncorrected beam 12UD and the angle uncorrected beam 12UA.

B. DETAILED DESCRIPTION OF THE INVENTION Having described the general method and apparatus of the present invention for correcting or compensating for the angular and radial drift of a laser beam, the present invention will now be described with reference to the general principles and apparatus described above. Examples will be described.

  Referring to FIGS. 6A, 6B, and 6C, an example of exemplary systems 32A, 32B, and 32C, collectively referred to hereinafter as system 32, is shown. Each system has a compensator and relocator 34 of the present invention. As described below, the compensator / relocator 34 accepts the input beam over a range of input angles and lateral displacements and subsequently shapes the input beam from the compensator / rearranger 34 into a final output beam. The input distribution shape of the input beam is “rearranged” to provide an output beam with an optimal output distribution shape for the element.

  As shown in FIGS. 6A, 6B, and 6C, the system 32 includes a laser 36 that generates a laser beam. The generated laser beam is generally identified as beam 38 and is transmitted along beam path 40 to one or more targets 42. It should be noted that in some systems, the beam 38 may be divided into a group of beamlets that can be steered individually or in groups, but for purposes of the present invention it will be generically referred to as beam 38 in the following description. It is to be. As shown, the beam path 40 typically includes a number of optical elements 44 such as a lens 44L and a mirror 44M that form, focus and shape the beam 38 along the beam path 40.

  The optical element 44 of a typical laser system 32 includes, for example, an up telescope assembly 44LT, which is an assembly of a plurality of lenses 44L that initially shape and focus the emitted beam 38 of the laser 36. A compensator / rearranger 34 may follow the up telescope assembly 44LT. The compensator and relocator 34, described in detail below, is selected as the optimal redistributed distribution shape for the subsequent shaper 46 to be relocated to the final shaped beam 38S with the shaped distribution shape 38SP. It may consist of one or more elements that reposition the input beam 38I to the compensator and relocator 34 in the relocated beam 38R having 38RP. In one presently preferred embodiment in the system 32 for microvia drilling, for example, the relocated distribution shape 38RP is a circular Gaussian distribution shape and the shaped distribution shape 38SP is typically a “flat top” distribution shape, ie, The distribution shape has a substantially uniform energy distribution over the diameter of the beam 38. Thereafter, the subsequent aperture 48 further shapes the beam 38S, and in particular shapes the laterally distributed shape image of the beam 38S.

  Finally, as shown, the beam path 38 further includes a fixed mirror 44M and a galvano-controlled movable mirror 44M for redirecting and maneuvering the beam 30 or beamlet 30B, typically, A final lens 44L such as an Fθ lens for finally shaping and focusing the beam 30 or the beamlet 30B will be provided.

C. Compensator / Relocator 34
As described above, according to the present invention, the beam path 40 accepts an input beam 38I having an input distribution shape 38IP and is optimally redistributed for a subsequent shaper 46 that rearranges it to a final distribution shape. “Reposition” the distribution shape of the input beam 38I to provide a relocated beam 38R having 38RP. In a presently preferred embodiment of the present invention, compensator and relocator 34 has a compensator 34C element, which typically has a range of input angles and lateral displacements. An aligned beam having a beam component that receives an input beam 38I having a beam or beam component and is essentially uniformly distributed and parallel, eg, having a non-circular distribution shape that uniformly illuminates a subsequent relocator 34R element 38A is generated. Thereafter, the rearranger 34R rearranges the output aligned beam 38A into a rearranged beam 38R having an optimal rearranged distribution shape 38RP such as a circular Gaussian distribution shape. The repositioned beam 38R may then be repositioned by the shaper 46 into a shaped beam 38S having, for example, a flat top distribution shape.

D. Compensator 34C
In a presently preferred embodiment of the compensator and relocator 34, the compensator 34C element is a computer generated hologram element, or “CGH”, illuminated by the input beam 38I with different input angles and different lateral displacements. The input beam 38I is formed into a uniform and parallel aligned beam 38A that illuminates the repositioner 34R. In the current embodiment, for example, the input beam 38I to the compensator 34C may have essentially any distribution shape, and the aligned distribution shape 38AP may be, for example, a non-circular distribution shape.

  In one presently preferred embodiment of the invention, compensator 34C is implemented as a holographic lens encoded over its entire surface. Since the coding surface of compensator 34C, or any portion thereof, therefore has all the information necessary to relocate input beam 38I to aligned beam 38A, compensator 34C is the surface of compensator 34C. Regardless of where the input beam 38I is illuminated, the input beam 38I will be repositioned. However, it should be noted that the compensator 34C may be implemented in other forms, as will be described later.

  Considering in detail the implementation and operation of the compensator 34C described above with reference to FIGS. 5A-5F, one or both of radial displacement due to thermal drift and angular deviation due to instability in positioning may be asymmetric element (NSE) 26. This can be corrected by the compensator 34C. As described above, the NSE 26 is, for example, an asymmetric hologram optical element (NSHOE), that is, a certain type of CGH element, or an equivalent optical element such as an asymmetric lens, an asymmetric refractive element, or an asymmetric diffraction element. As described above, the NSE 26 is different from the SSHE 18 or equivalent symmetric element, and the path of the beam axis 10 of the laser beam 12 across the NSE 26 is refracted or bent at a correction angle φ while the laser beam 12 passes through the NSE 26. Or For example, as described above, in one embodiment of the NSE 26, the angle φ increases as the radial displacement Δ of the incident beam axis 10 from the centerline axis 28 of the NSE 26 increases. In another embodiment of the NSE 26, the correction angle φ increases as the incident angle α of the beam axis 10 of the incident laser beam 12 relative to the plane of the NSE 26 decreases.

  Referring now to FIGS. 7A, 7B, 7C and 7D, a presently preferred alternative embodiment of a single or multiple compensator 34C element that performs lateral drift and angular error correction and compensation is shown. As will be appreciated by those skilled in the art, single or multiple compensator 34C elements may be implemented using the principles, structures and elements described hereinabove with respect to the various forms of single and multiple NSEs 26. it can. The single or plural compensators 34C elements include, for example, a multifunctional refractive optical element (MFDOE), an integrated multifunctional refractive optical element (IMFDOE), a multifunctional holographic optical element (MFCGH), a multifunctional Fresnel prism (MFFZP), It can be embodied as an optical assembly capable of performing other CGH and target functions.

  For example, the compensator 34C shown in FIG. 7A includes a substrate 50 having a field lens 52 on the input side 50I and a DOE shaper 54 on the output side 50O, and the field lens 52 and the DOE shaper 54 are made of holographic optical elements. And the field lens 52 defines an aperture 56. The field lens 52 and the DOE shaper 54 are typically CGH elements configured to perform lateral drift and angular error correction and compensation, as described above, and the aperture 56 includes the compensator 34C. The passing beam is shaped, and the portion of the input beam 30I outside the range of the field lens 52 and the DOE shaper 54 is blocked.

  Next, FIG. 7B shows a compensator 34 </ b> C having an aperture 56, but the DOE shaper 54 is realized as a CGH element on the output surface of the refractive lens element constituting the field lens 52. As shown in the drawing, in this embodiment, since the refractive lens constituting the field lens 52 functions as a substrate, a separate substrate 50 is not required.

  FIG. 7C shows one embodiment of a compensator 34C using a substrate 50, where the field lens 52 and the shaper 54 are integrated into a single compound or composite holographic DOE lens element mounted on the input side 50I of the substrate 50. The Further, the present embodiment has an opening 60 formed on the output side 50O of the substrate 50.

  Finally, FIG. 7D shows one embodiment of compensator 34C, where field lens 52 and shaper 54 are again integrated into a single compound or composite holographic DOE lens element mounted on input side 50I of substrate 50. Is done. However, in this example, the opening 56 is formed by a DOE deflection opening that surrounds the field lens 52 and the shaper 54 element on the input side 50I. As will be understood by those skilled in the art, the deflection aperture is functionally an aperture, but the portion of the input beam 30I that is outside the range of the field lens 52 and shaper 54 elements is excluded from deflection.

E. Relocator 34R
Referring now to FIG. 7E, there is shown one embodiment of a relocator 34R that can be used in the compensator and relocator 34 in conjunction with the compensator 34C.

  As described above, compensator 34C is illuminated by input beam 38I, but the components of input beam 38I have different input angles and different lateral displacements, so they are parallel in a uniform distribution that illuminates relocator 34R. The input beam 38I is formed on the aligned beam 38A. For example, if the arrayed beam 38A has a non-circular Gaussian distribution shape, the repositioner 34R will re-arrange the arrayed beam 38A with an optimal distribution shape shown as a distribution shape 38RP, eg, a circular Gaussian distribution shape. Rearrange to beam 38R. The relocated beam 38R is then repositioned by the shaper 46 into a shaped beam 38S having a shaped distribution shape 38SP, such as a flat top distribution shape.

  In one presently preferred embodiment, the reorderer 34R accepts a uniform and parallel arrayed beam 38A from the compensator 34C and parallelizes the distribution shape of the arrayed beam 38A, which may have a non-circular Gaussian distribution shape. Radial symmetric refractive optical element (RSDOE) or asymmetric refractive optical element (NSDOE) that forms a relocated beam 38R having a target distribution shape for a shaper 46, such as a circular Gaussian distribution shape As a CGH.

  Although some of the element configurations of the compensator / rearranger 34 of the present invention have already been discussed, it is mentioned above that the compensator / rearranger 34 can be composed of many elements arranged in many ways. You will understand from the explanation. However, the currently preferred compensator / rearranger 34 configuration is a two-element design with a DOE element followed by a CGH element. In this two-element configuration, the distance between the optical systems of the two elements is about 50 mm to 1500 mm with an optimum distance of 50 mm, and the optimum net aperture of the compensator / rearranger 34 is about 0.4 mm to 25 mm.

  Finally, the optical elements of the present invention are commercially available, for example, obtained from MEMS Optical, Huntsville, Alabama, Heptagon, Finland, SUSS Microoptics, Neuchatel, Switzerland, or Digital Optics, Charlotte, North Carolina. Possible or manufacturable by them.

  Since the invention described above can be modified without departing from the spirit and scope of the invention contained herein, all of the materials shown in the above description and accompanying drawings are subject to the inventive concept herein. It should be construed as merely illustrative, and not as limiting the invention.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described. Since the description of the first embodiment and FIGS. 1 to 7 has many overlapping portions, the description will be omitted as appropriate, and the portions according to the present embodiment will be mainly described.

To address the above-mentioned problems of the prior art,
1) Either one or both of the radial displacement due to thermal drift and the angular deviation due to unstable positioning are corrected by an asymmetric element.
2) Correct radial (lateral) displacement and positioning instability in the form of compensators and repositioned asymmetric elements.
3) Realign the laser beam drifted in the lateral direction (radial direction), remove the “hot spots” from the energy distribution shape of the output beam of the beam shaping element, and change the target energy distribution shape of the output beam of the beam shaping element. Recover.
And there are devices and elements for carrying out this method. Among these, 1) and 2) are the same as those described in the first embodiment with reference to FIGS.

  Therefore, an embodiment corresponding to the above 3), that is, radial asymmetric diffraction for correcting lateral misalignment and beam shaping by a holographic beam forming optical element will be described.

  For example, the beam shaping optical system is usually used to reshape the input beam 12I having the optimal Gaussian distribution shape 12GP into the output beam 120 having the flat top distribution shape 12FP, as already described in the first embodiment. However, for many reasons, it has already been mentioned that the laser beam input to the beam shaping optics can be subject to lateral misalignment, i.e., radial misalignment with respect to the optical centerline of the beam shaping optics. As described above, such a lateral shift in the input beam can cause unwanted “hot spots” and “insufficiency” in the energy distribution shape of the output beam 12O.

  In addition, as described above in this specification, an asymmetric optical element may be used to correct the radial displacement of the laser beam due to thermal drift and the angular deviation of the laser beam due to unstable positioning. Further, the energy distribution shape of the input beam may be “rearranged” by using a compensator and a rearrangement element so that an output beam having an optimum output distribution shape can be provided to subsequent elements such as a beam shaping element. These methods may be used to address issues arising from lateral misalignment of the laser beam into the beam shaping optics, and the laser beam may be redirected or reshaped as necessary, but all of these methods In this case, it is not necessarily usable or preferable. For example, using separate optics may increase the cost and / or complexity of the system to an unacceptable or uneconomical level, or unacceptably reduce the energy conversion efficiency of the system. I don't know.

  Also, such asymmetric optical elements, including compensators and relocation elements, typically consist of holographic or diffractive optical elements, but usually have certain characteristics. However, since the lateral misalignment of the laser beam is not constant and varies over a relatively wide range of directions and quantities, holographic and diffractive optics provide the full range of possible lateral misalignment of the laser beam in a given system. There is a risk that it will not be able to cope with it.

  According to this aspect of the present invention, therefore, the problem arising from the lateral misalignment of the input beam to the beam shaping optical element is preferably solved, and in many cases without the need for a separate optical element. Must. Also, a solution to these problems should preferably be provided by fixed optical elements such as holographic or diffractive optical elements with constant characteristics. This is because fixed optical elements are less expensive and less complex than variable elements. This solution, however, must be able to quickly adjust or adapt the fixed optics to the actual lateral deviation of the input beam. Actual lateral misalignment can occur over a relatively wide range in both direction and quantity.

  9A and 9B show an asymmetric beamforming optical element 62 having a beam shaping conversion function 62T for reshaping an input beam 12I having a Gaussian distribution shape 12GP to an output beam 12O having a flat top distribution shape 12FP. At this time, the beam axis 10 of the input beam 12I has a lateral shift 64 with respect to the optical axis of the beam shaping optical element 62.

  As schematically illustrated in FIGS. 9A and 9B, the energy distribution shape conversion function implemented in the asymmetric beam forming optical element 62 as the beam forming conversion function 62T is designed to convert the input Gaussian distribution shape 12GP to the asymmetric distribution shape 12NP. Is done. As will be described later, the asymmetric distribution shape 12NP and the corresponding beamforming conversion function 62T are designed to compensate for the expected range of beamforming distortion introduced by the lateral misalignment of the input beam. In this respect and the point of the next explanation, the beamforming conversion function 62T has the Gaussian distribution shape 12GP of the input beam 12I, the expected range of the lateral deviation of the input beam 12I, and the target flat top distribution shape 12FP in the output beam 12O. Determined by and a function of the asymmetric distribution shape 12NP required to occur.

  The transformation function performed by the beamforming transformation function 62T, with reference to FIGS. 9A and 9B, has a Gaussian distribution shape 12GP and a beam axis 10 centered on the centric centerline 62C of the asymmetric beamforming optical element 62. The description may be made in consideration of the asymmetric distribution shape 12N generated from the beam forming conversion function 62T by the illumination of the input beam 12I. The beam forming conversion function 62T that generates the output beam 120 having the asymmetric distribution shape 12NP from the input beam 12I has a feature that the asymmetric distribution shape 12NP compensates for distortion caused by the lateral deviation of the input beam 12I with respect to the asymmetric beam forming optical element 62. Designed to have.

  In a typical case as shown in FIGS. 9A and 9B, the asymmetric distribution shape 12NP is substantially composed of a flat top distribution shape 12FP having a superimposed compensation distribution shape 12CP, and the specific shape of the compensation distribution shape 12CP is , Depending on the specific distortion introduced into the distribution shape of the output beam 120 due to the drift of the input beam 12I. In a typical example, for example, the compensation distribution shape 12CP has one or both of a superposed asymmetric hot spot distribution shape 12HP and a superposed asymmetric underdistribution shape 12DP, and is introduced by a lateral deviation of the input beam. It depends on the expected distortion.

  Considering the components of the typical compensation distribution shape 12CP individually, the asymmetric underdistribution shape 12DP compensates or cancels at least to some extent the hot spot 64H that occurs in the energy distribution shape of the output beam 120 due to the deviation of the input beam 12I. Designed to do. As shown, the asymmetric under-distribution shape 12DP is typically along the transformation radius 62R and a flat-top distribution shape of the asymmetric flat-top distribution shape 12NP so that it is substantially superimposed on the potential hot spot 64H. The 12FP component is offset from the optical center line 62C of the beam forming optical element 62 with respect to the outer peripheral edge of the 12FP component. The asymmetric underdistribution shape 12DP typically does not extend along the entire circumference of the asymmetric flat top distribution shape 12NP, but extends only along the portion expected to include the hot spot 64H. It should also be noted that the conversion radius 62R typically extends in a radial or lateral direction in which the beam axis 10 of the input beam 12I is offset from the optical centerline 62C of the asymmetric beamforming optical element 62. That is. This is because the hot spot 64H normally occurs in this direction.

  Next, the asymmetric hot spot distribution shape 12HP is configured to compensate or cancel the deficiency 64D that occurs in the energy distribution shape of the output beam 12O due to the deviation of the input beam 12I to at least a significant extent. The asymmetric hot spot distribution shape 12HP is typically the optical centerline of the asymmetric beamforming optical element 62 along the transformation radius 62R and towards the outer periphery of the flat top distribution shape 12FP component of the asymmetric flat top distribution shape 12NP. Deviation from 62C. The asymmetric hot spot distribution shape 12HP also typically does not extend along the entire circumference of the asymmetric flat top distribution shape 12NP, but only along the portion expected to contain the deficiency 64D. However, it should be noted in this case that the conversion radius 62R is typically a radial or lateral direction in which the beam axis 10 of the input beam 12I deviates from the optical centerline 62C of the asymmetric beamforming optical element 62. Is to extend in the opposite direction, that is, in the opposite direction to the asymmetrical insufficient distribution shape 12DP. This is because the shortage 64D usually occurs in this direction.

  Considering briefly the beam forming conversion function 62T, as described above, the beam forming conversion function 62T is based on the energy distribution shape of the input beam 12I, the energy distribution shape of the output beam 12O, and the expected lateral deviation of the input beam 12I. It is determined by the compensation distribution shape 12CP necessary to compensate or correct the distortion expected to occur. In this example, therefore, in the case of corresponding to the asymmetric distribution shape 12NP, the beam forming conversion function 62T is a flat having an additional compensation conversion function 62CT including one or both of the hot spot conversion function 62TH and the insufficient conversion function 62TD. It consists of a top conversion function 62TF.

  The operation of the asymmetric beam forming optical element 62 occurs when the asymmetric beam forming optical element 62 is illuminated by an input beam 12I having a beam axis 10 that is offset relative to the optical center line 62C of the asymmetric beam forming optical element 62. This can be explained in consideration of the energy distribution shape of the output beam 12O and the energy distribution shape of the output beam 12O generated when illuminated by the input beam 12I having the beam axis 10 not shifted. If the input beam 12I is not offset with respect to the asymmetric beamforming optical element 62, the resulting output beam 12O is thus an additional asymmetric hot spot distribution shape 12HP and an asymmetric underspot distribution shape 12D, as determined by the specific beamforming transformation function 62T. Will have an asymmetric distribution shape 12NP consisting of a flat top distribution shape 12FP with one or both of the above. However, it should be noted that if the input beam 12I is not displaced laterally, there may not be distortion of the energy distribution shape, so the output beam trying to correct the distortion for which the beamforming conversion function 62T does not exist. This means that distortion may be introduced into the energy distribution shape of 12O. This consideration will be discussed further below.

  However, if the beam-forming optical element 62 is illuminated by an input beam 12I that is offset from the optical centerline 62C of the beam-forming optical element 62, the resulting output beam 12O will have a flat top distribution shape 12F. The reason why such a result occurs is that the compensation conversion function 62CT component of the beamforming conversion function 62T introduces distortions such as the hot spot 62H and the deficiency 64D into the energy distribution shape of the output beam 12O and the lateral deviation of the input beam 12I. This is because the generated distortion is compensated or canceled.

  Considering now a further aspect of the present invention, the lateral misalignment 64 of the beam axis 10 of the input beam 12I is relative to the path of the beam through the system, i.e. the optical of the asymmetric beamforming optical element 62. It has been described herein above that the direction and size can vary greatly with respect to the centerline 62C. However, since the beam forming conversion function 62T is asymmetric, the influence of the beam forming conversion function 62T on the energy waveform of the input and output beams depends not only on the size of the lateral displacement 64 with respect to the beam forming conversion function 62T but also on the radial direction. Will be.

  In other words, the hot spot and the insufficient circumferential position in the output energy distribution shape are determined by the radial direction of the lateral deviation of the input beam. Thus, hot spots and deficient positions in the output beam energy distribution shape will appear to rotate around the axis of the output beam that is proportional to the radial direction of lateral misalignment. Since the beam forming conversion function 62T is asymmetrical, if the rotational position of the beam forming conversion function 62T is constant, the radial deviation of the lateral deviation is caused in the rotational direction with respect to the generated hot spot or the insufficient rotational position of the beam forming conversion function 62T. It will appear as a shift or change. Misalignment of the rotational direction of the beam forming conversion function 62T and the lateral misalignment may result in uncorrected hot spots and deficiencies by the beam forming conversion function 62T and even introduction of further hot spots and deficiencies by the beam forming conversion function 62T. There is sex.

  In addition, as described above, when the input beam 12I is aligned with the axis of the asymmetric beam forming optical element 62, that is, when the input beam is not laterally shifted, the beam forming conversion function 62T is actually operated in the horizontal direction. Due to the lack of direction misalignment, there is a possibility that hot spots and shortages are introduced in an attempt to correct shortages and hot spots that do not actually exist, and distortion that is to be removed may be introduced.

  The asymmetric beam forming optical element 62 is therefore an asymmetric beam forming optical element 62 that adapts to variations in the direction and magnitude of the lateral deviation of the input beam and introduces it without correcting distortion in the output beam. Must be designed to avoid aligning.

  The asymmetric beam forming optical element 62 is preferably composed of a fixed optical element such as a diffractive or holographic beam diffuser or a shaping optical system in order to reduce complexity and cost. However, as a result, a given asymmetric beamforming optical element 62 may provide a compensation effect only with a relatively small range of lateral displacement magnitude and angle.

  These problems can, however, be addressed by the design of the asymmetric beamforming optics 62. For example, first considering the variation in magnitude of the lateral misalignment, including the absence of lateral misalignment, in the presently preferred embodiment, the asymmetric beamforming optical element 62 is supported by an offset mount 68. As shown in FIG. 9C, the offset mount 68 includes an asymmetric beamforming optical element 62, ie, the optical centerline 64C of the beamforming transformation function 62T, parallel to the nominal beam axis 10, but offset relative to the nominal beam axis. The asymmetric beam forming optical element 62 is supported so as to be displaced by 70. Also, an offset 70 is selected that is approximately equal to or slightly larger than the expected maximum lateral deviation 64 of the input beam 12I, so that the beam axis 10 can be adjusted even when the maximum lateral deviation 64 is relative to the optical center line 64C. Do not coincide with the optical center line 64C.

  Also, the beamforming conversion function 62T is preferably designed to have a “width” and “diameter” that can be adequately adapted to the expected direction and expected size of the lateral misalignment 64. In other words, the beamforming transformation function 62T has a radius that is equal to or slightly larger than the maximum expected lateral deviation 64, so that the width required to accommodate the maximum expected lateral deviation 64 is reduced. Designed to be able to provide.

  Since the offset mount 68 provides an offset for the beamforming conversion function 62T, the input beam 12I will always pass through the beamforming conversion function 62T between the optical centerline 64C of the beamforming conversion function 62T and the outer diameter. As a result, even in the case of the maximum lateral deviation 64, it is ensured that the input beam 12I passes through the beam forming conversion function 62T regardless of the direction of the lateral deviation 64. Further, since the offset 70 is larger than the maximum lateral deviation 64 of the input beam 12I, the input beam 12I does not coincide with the optical center line 64C, and there is no distortion to be corrected. It is possible to avoid introducing intentional distortion.

  Finally, it should be noted about this point that the distortion effect of the lateral deviation 64 of the input beam 12I typically increases with the magnitude of the lateral deviation 64. However, instead, the effect of one or both of the component elements of the compensation conversion function 62CT, for example, the hot spot conversion function 62TH and the shortage conversion function 62TD, is also designed to increase as the lateral shift 64 increases. The correction effect of the compensation conversion function 62CT follows the magnitude of the lateral deviation.

  As a result of the above aspects of the present invention, the effect of variations in the magnitude of the input beam deviation relative to the axis of the beamforming transformation function 62T will tend to self-compensate. That is, the decrease or increase in the amount of displacement decreases or increases the displacement compensation effect by moving the input beam radially inward or outward along one or both of the hot spot conversion function 62TH and the insufficient conversion function 62TD. In this way, as long as the beamforming conversion function 62T can be adapted to the size of the maximum expected deviation, in most cases it can be adequately adapted to the magnitude of the deviation without further complexity. However, it should be noted that it is generally preferred not to design the beamforming transformation function 62T to accommodate excessive deviations. This is because such a design reduces the “fit” between the conversion function and the shift in a smaller shift range.

  Next, considering the influence of fluctuation in the radial direction of the lateral deviation of the input beam, the fluctuation in the radial direction of such lateral deviation is caused by the output energy distribution shape with respect to the rotational direction position of the beam forming conversion function 62T. It has already been described above in this specification that it appears as an apparent shift or offset in the rotational direction of the distortion appearing in. For example, since the circumferential direction “tilt” of the asymmetric hot spot distribution shape 12HP and the asymmetrical insufficient distribution shape 12HD component of the conversion function is relatively “steep”, a relatively small shift in the rotational direction may have a large influence. . This is particularly a concern when both components of the hot spot conversion function 62TH and the shortage conversion function 62TD are present, or when the conversion function is asymmetric in the rotational direction.

  According to the present invention, such an apparent rotation between the distortion appearing in the output distribution shape due to the lateral deviation of the input beam and the distortion appearing in the output distribution shape due to the rotational direction position of the beamforming transformation function 62T. The effect of direction misalignment is preferably adjusted by rotating the beamforming transformation function 62T about the optical centerline 64C. In accordance with the present invention, therefore, the asymmetric beamforming optical element 62 is supported on the offset mount 68 by a rotating bearing 72, as shown in FIG. 9D. By means of the rotating bearing 72, the asymmetric beam forming optical element 62 causes the optical center of the beam forming conversion function 62T to achieve an optimal rotational positional relationship between the laterally offset input beam 12I and the beam forming conversion function 62T. It can be rotated around the line 64C.

  In this regard, it should be noted that the beam forming conversion function 62T is not only a variation in the radial direction of the lateral displacement 64, but generally due to the asymmetry of the beam forming conversion function 62T and the appropriate shaping of the beam forming conversion function 62T. That is, it is possible to adjust so as to compensate for various sizes of the lateral displacement 64.

  Therefore, according to the present invention, the effect of the beamforming conversion function 62T on the energy waveforms of the input beam 12I and the output beam 12O depends on both the magnitude of the lateral deviation of the input beam relative to the asymmetric beamforming optical element 62 and the angular direction. It will be decided. Further in accordance with the present invention, the effects of variable lateral and rotational misalignment of the input beam 12I that cause distortions in the energy distribution shape of the output beam are offset by a fixed amount relative to the input beam and are longitudinal with respect to the input beam. A beam shaping element having an energy distribution shape conversion function that rotates in the direction can be compensated to generate an output beam having a target energy distribution shape. Furthermore, according to the present invention, when the energy distribution shape conversion function has one or both of the hot spot distribution shape conversion component and the under-distribution shape conversion component, the input beam 12I and beam forming for achieving the target output beam energy distribution shape The optimal lateral and rotational relationship with the transformation function 62T can be adjustably achieved by adjusting the rotational position of the beamforming transformation function 62T relative to the input beam 12I.

Example of Beamforming Transform Function 62T of FIGS. 9C and 9D In a further aspect of the invention as shown in FIG. 9D, for an input beam 12I that has undergone a variable lateral drift to obtain the energy distribution shape of the target output beam 12O. The alignment and realignment of the beamforming transformation function 62T can be easily automated. In this method, a partial mirror 76 is mounted in the path of the output beam 120, and the image of the beam 12 is reflected by an optical sensor 78 such as a sensor made of a charge coupled device or a photosensitive resistive material. The energy distribution shape of the output beam 120 can be monitored at an appropriate part of the spectrum. For example, the optical sensor 78 is a two-dimensional position sensitive detector such as that manufactured and sold by Hamamatsu Corp. An image showing the energy distribution shape of the output beam 12O is then passed to the processor controller 80. The processor controller 80 determines whether the energy distribution shape of the output beam 120 matches the target distribution shape. If the processor controller 80 determines that the energy distribution shape of the output beam 12O does not match the target distribution shape within acceptable tolerances, the processor controller 80 drives the rotary bearing 72 via a suitable drive mechanism 82. The asymmetric beam forming optical element 62 is rotated until the rotational position between the input beam 12I and the beam forming conversion function 62T produces the energy distribution shape of the target output beam 12O.

  Finally, the present invention as described above is further illustrated in FIGS. 10A, 10B, 10C and 10D. 10A and 10B are phase surface views of two exemplary asymmetric beamforming optics according to the present invention, and FIGS. 10C and 10D are corresponding cross-sectional views.

  The present invention is further illustrated in FIGS. 11A through 11E. 11A to 11E show cross-sectional views of the energy distribution shape of a laser beam according to the present invention. For example, FIG. 11A shows a beam with a hot spot on the left side, but with a generally acceptable energy distribution shape. FIG. 11B shows a beam drifting to the right, and the beam distribution shape is improved by drifting the beam to the right by the optical element of the present invention. FIG. 11C shows a beam drifted to the right by a distance of 100 microns, which is optimal for the asymmetric beamforming optics described. FIG. 11D shows the case where the beam continues to drift to the right by 150 microns, so that the right side of the distribution shape begins to “rise”. Finally, FIG. 11E shows the case where the beam has drifted to the right by 200 microns, resulting in a mirror image of that shown in FIG. 11A. These examples thus show that the asymmetric beamforming optics of the present invention as shown provides an acceptable beam distribution shape up to, for example, a beam drift up to an upper limit of 200 microns and is adaptable to that extent.

  Since the invention described above can be modified without departing from the spirit and scope of the invention contained herein, all of the materials shown in the above description and accompanying drawings are subject to the inventive concept herein. It should be construed as merely illustrative, and not as limiting the invention.

It is explanatory drawing of the angular deviation of the laser beam by positioning instability. It is explanatory drawing of the angular deviation of the laser beam by positioning instability. It is explanatory drawing of the radial direction drift of the laser beam by a thermal drift. It is explanatory drawing of the radial direction drift of the laser beam by a thermal drift. It is explanatory drawing of the radial direction displacement and angular deviation of a laser beam. It is explanatory drawing of the radial direction displacement and angular deviation of a laser beam. It is explanatory drawing of the method of this invention for correct | amending an angular deviation or radial displacement. It is explanatory drawing which shows the combination of the optical element and optical element for correct | amending the angular deviation and radial direction drift of a laser beam. It is explanatory drawing which shows the combination of the optical element and optical element for correct | amending the angular deviation and radial direction drift of a laser beam. It is explanatory drawing which shows the combination of the optical element and optical element for correct | amending the angular deviation and radial direction drift of a laser beam. It is explanatory drawing which shows the combination of the optical element and optical element for correct | amending the angular deviation and radial direction drift of a laser beam. It is explanatory drawing which shows the combination of the optical element and optical element for correct | amending the angular deviation and radial direction drift of a laser beam. It is explanatory drawing which shows the combination of the optical element and optical element for correct | amending the angular deviation and radial direction drift of a laser beam. It is explanatory drawing of the system by which this invention is implement | achieved. It is explanatory drawing of the system by which this invention is implement | achieved. It is explanatory drawing of the system by which this invention is implement | achieved. It is explanatory drawing of a typical compensator and a rearranger. It is explanatory drawing of a typical compensator and a rearranger. It is explanatory drawing of a typical compensator and a rearranger. It is explanatory drawing of a typical compensator and a rearranger. It is explanatory drawing of a typical compensator and a rearranger. It is explanatory drawing of the beam shaping optical system for the input laser beam aligned with the axis | shaft of the beam shaping optical system, and the input laser beam shifted to the horizontal direction with respect to the axis | shaft of a beam shaping optical system. FIG. 8B is an explanatory diagram for comparison of superposition of input / output beam energy distribution shapes for the situation shown in FIG. 8A. It is explanatory drawing of the beam shaping optical system for the input laser beam aligned with the axis | shaft of the beam shaping optical system, and the input laser beam shifted to the horizontal direction with respect to the axis | shaft of a beam shaping optical system. FIG. 8D is an explanatory diagram for overlay comparison of input / output beam energy distribution shapes for the situation shown in FIG. It is a figure which shows operation | movement of an asymmetrical beam forming optical element. It is a figure which shows operation | movement of an asymmetrical beam forming optical element. It is a figure which shows the asymmetrical beam forming optical element mounted in the offset mount. It is a figure which shows the asymmetrical beam forming optical element mounted in the offset mount using a rotation bearing. 2 is a phase surface and corresponding cross-sectional view of two exemplary asymmetric beamforming optics according to the present invention. FIG. 2 is a phase surface and corresponding cross-sectional view of two exemplary asymmetric beamforming optics according to the present invention. FIG. 2 is a phase surface and corresponding cross-sectional view of two exemplary asymmetric beamforming optics according to the present invention. FIG. 2 is a phase surface and corresponding cross-sectional view of two exemplary asymmetric beamforming optics according to the present invention. FIG. It is a cross-sectional view showing the energy distribution shape of the laser beam according to the present invention. It is a cross-sectional view showing the energy distribution shape of the laser beam according to the present invention. It is a cross-sectional view showing the energy distribution shape of the laser beam according to the present invention. It is a cross-sectional view showing the energy distribution shape of the laser beam according to the present invention. It is a cross-sectional view showing the energy distribution shape of the laser beam according to the present invention.

Claims (24)

Controlling laser positioning and thermal drift instability in a laser beam delivery system having a laser generating a laser beam and a plurality of optical elements for directing, shaping and focusing the laser beam to a target along a beam path In the compensator / relocator for correction,
A compensator element for receiving an input laser beam having a range of input angles and lateral displacements, and relocating and redirecting components of the input laser beam into an aligned laser beam having a uniformly distributed parallel component;
Relocation that is illuminated by the aligned laser beam from the compensator element and that realigns the components of the aligned laser beam into a shaped laser beam having an optimal distribution shape to relocate to a flat top laser beam The compensator / rearranger has a compensator element.   The compensator / rearranger of claim 1, wherein the compensator element is a computer generated holographic lens encoded over the entire surface.   The compensator and relocation according to claim 1, wherein the relocator element is a computer generated holographic radial symmetric diffractive optical element (RSDOE) or a computer generated holographic asymmetric diffractive optical element (NSDOE). vessel.   The compensator element has a substrate, a field lens disposed on the input side of the substrate, a diffractive optical element shaper disposed on the output side of the substrate, and an aperture defined by the field lens. The compensator / rearranger according to claim 1.   The compensator element includes a compensator element formed of a refractive lens element, and a computer-generated holographic diffractive optical element shaper disposed on the output side of the compensator element, wherein the refractive lens is the diffractive optical element The compensator / rearranger according to claim 1, wherein a substrate of a shaper is formed, and the shaper forms an opening.   The compensator element has a substrate, a single diffractive optical element disposed on the input side of the substrate and forming an integral field lens element and a shaper element, and an opening formed on the output side of the substrate. The compensator / rearranger according to claim 1.   The compensator / rearranger according to claim 1, wherein the arrayed laser beam output of the shaper element has a non-circular Gaussian distribution shape.   The compensator / rearranger according to claim 1, wherein the shaped laser beam output of the relocator element has a circular Gaussian distribution shape. Controlling laser positioning and thermal drift instability in a laser beam delivery system having a laser generating a laser beam and a plurality of optical elements for directing, shaping and focusing the laser beam to a target along a beam path In the method for correcting,
Redirecting a component of the input laser beam having a range of input angles and lateral displacements to an aligned laser beam having a uniform distributed parallel component;
Repositioning the components of the aligned laser beam into a shaped laser beam having a distribution shape optimal for repositioning into a flat top laser beam. A method for controlling and correcting laser positioning and thermal drift instability according to claim 9,
Redirecting the component of the input laser beam is performed by a computer generated holographic lens encoded over the entire surface. A method for controlling and correcting laser positioning and thermal drift instability according to claim 9,
Repositioning the components of the aligned laser beam is performed by a computer generated holographic radial symmetric diffractive optical element (RSDOE) or a computer generated holographic asymmetric diffractive optical element (NSDOE) . A method for controlling and correcting laser positioning and thermal drift instability according to claim 9,
The step of redirecting the component of the input laser beam is performed by a compensator element, the compensator element being a substrate, a field lens disposed on the input side of the substrate, and a diffraction disposed on the output side of the substrate. The method comprising: an optical element shaper; and an aperture defined by the field lens. A method for controlling and correcting laser positioning and thermal drift instability according to claim 9,
Redirecting the component of the input laser beam is performed by a compensator element formed of a refractive lens element and a computer-generated holographic diffractive optical element shaper disposed on the output side of the compensator element; The method of claim 1, wherein the refractive lens forms a substrate of the diffractive optical element shaper, and the shaper forms an aperture. A method for controlling and correcting laser positioning and thermal drift instability according to claim 9,
The step of redirecting the component of the input laser beam is performed by a compensator element, the compensator element being disposed on the input side of the substrate and forming an integral field lens element and a shaper element. The method comprising: a single diffractive optical element; and an opening formed on an output side of the substrate. A method for controlling and correcting laser positioning and thermal drift instability according to claim 9,
The method of claim 1, wherein the arrayed laser beam has a non-circular Gaussian distribution shape. A method for controlling and correcting laser positioning and thermal drift instability according to claim 9,
The method, wherein the shaped laser beam has a circular Gaussian distribution shape. To convert an input energy distribution shape of an input laser beam, which has an optical element having a distribution shape conversion function and has a beam axis subjected to a lateral deviation variable in radial direction and size, into an output laser beam having a target output energy distribution shape In the radially asymmetric beam forming element,
The distribution shape conversion function includes a first distribution shape conversion function for converting the input energy distribution shape into the target output energy distribution shape, and the output energy distribution shape in which a lateral deviation of the input laser beam is introduced. The radial asymmetric beam forming element having a distribution shape correction conversion function added to the first distribution shape conversion function to correct the first distribution shape conversion function so as to correct distortion.   The distribution shape correction conversion function includes the first distribution shape conversion function for adding a compensation insufficient energy distribution shape to the target output energy distribution shape at a position corresponding to a hot spot caused by a lateral deviation of the input laser beam. And a first distribution for adding a compensation hot spot energy distribution shape to the target output energy distribution shape at a position corresponding to a shortage caused by a lateral deviation of the input laser beam. The radial asymmetric beam forming element according to claim 17, further comprising at least one of a hot spot distribution shape conversion function added to the shape conversion function.   The optical axis of the beam forming element is aligned parallel to the beam axis of the input laser beam, while the input laser beam is parallel and offset to the optical axis of the optical element. 18. The diameter of claim 17, wherein the diameter is shifted from a beam axis free of misalignment of the input laser beam by a distance proportional to a maximum expected lateral misalignment of the beam axis of the input laser beam through the forming element. Directionally asymmetric beamforming element.   The beam shaping element can rotate the distribution shape conversion function around the optical axis of the optical element to allow adjustment of the distribution shape conversion function with respect to the current lateral deviation of the input laser beam. The radial asymmetric beam forming element according to claim 19, wherein the radial asymmetric beam forming element is supported by a rotating mount. In a method of converting an input energy distribution shape of an input laser beam having a beam axis subjected to a lateral deviation variable with respect to a radial direction and a magnitude to an output laser beam having a target output energy distribution shape,
A step of performing a distribution shape conversion function on the input laser beam, and the step of performing a first distribution shape conversion function for converting the input energy distribution shape into the target output energy distribution shape; A distribution shape added to the first distribution shape conversion function to correct the first distribution shape conversion function so as to correct distortion in the output energy distribution shape in which a lateral deviation of the input laser beam is introduced Performing the correction conversion function.   23. The method of claim 21, wherein the input energy distribution shape of an input laser beam that undergoes a variable lateral displacement with respect to radial and magnitude is converted to an output laser beam having a target output energy distribution shape. A deficiency distribution shape conversion function added to the first distribution shape conversion function to add a compensation deficiency energy distribution shape to the target output energy distribution shape at a position corresponding to a hot spot caused by deviation; and the input laser beam A hot spot distribution shape conversion function added to the first distribution shape conversion function in order to add a compensation hot spot energy distribution shape to the target output energy distribution shape at a position corresponding to a shortage caused by a lateral displacement of Before having at least one step of performing Method.   The method according to claim 21, wherein an input energy distribution shape of an input laser beam subjected to a lateral deviation variable in radial direction and magnitude is converted into an output laser beam having a target output energy distribution shape. The shape correction conversion function is incorporated into one beam forming element, and the optical axis of the beam forming element is aligned parallel to the beam axis of the input laser beam, while the input laser beam is the optical element. From the beam axis free from the deviation of the input laser beam by a distance proportional to the maximum expected lateral deviation of the beam axis of the input laser beam so as to pass through the beam forming element in a state parallel and displaced with respect to the optical axis of Said method characterized in that it is shifted. 24. The method of claim 23, wherein the input energy distribution shape of an input laser beam that undergoes a variable lateral shift with respect to radial and magnitude is converted to an output laser beam having a target output energy distribution shape, wherein the beam-forming element includes Supported by a rotation mount that enables rotation of the distributed shape conversion function about the optical axis of the optical element, and the distributed shape conversion with respect to the current lateral deviation of the input laser beam by rotation of the beam forming element The method further comprising the step of adjusting the function.

Images