Device for collimating a light beam, high-power laser, and focusing optical unit and method for collimating a light beam

Abstract

A device for collimating a light radiation field of a light source (L) having a beam characteristic which is different in a first plane (FAC) from that of a second plane (SAC). The device comprises at least one first collimating lens (10) and a second collimating lens (20). The device has an additional optical element (30) in order to collimate the light radiation field in different planes to the first and to the second plane.

Claims

1. A device for collimating a light radiation field emanating from at least one light emitter with a beam characteristic with regard to an emission angle relative to a beam direction which is different in a first plane than in a second plane, such that the first and the second planes are orthogonal to one another, wherein the first plane is spanned by a fast axis direction of the light emitter and the beam direction, and the second plane is spanned by a slow axis direction of the light emitter and the beam direction, the device comprising: at least one first collimation lens part which performs a first function for fast axis collimating the light radiation field in the first plane, and at least one second collimation lens part which performs a second function for slow axis collimating the light radiation field in the second plane, wherein the device comprises an additional optical element part which performs a third function for collimating unaligned portions of the light radiation field, which have not yet been aligned parallel by the first and the second collimation lens parts, such that the unaligned portions of the light radiation field are aligned parallel to the beam direction and such that the light radiation field is collimated in at least one further plane that is different than the first plane and the second plane, the first collimation lens part, the second collimation lens part and the additional optical element part are integrally formed as an integrally formed collimation lens which carries out the first, the second and the third functions in a combined manner, and for performing the third function, the additional optical element part of the integrally formed collimation lens has a surface topography which has a form of a two-dimensional even-order polynomial.

2. The device according to claim 1, wherein the additional optical element part is formed by a region on the integrally formed collimation lens.

3. The device according to claim 2, wherein the region is arranged on an entrance side on the integrally formed collimation lens in a radiation direction and a surface of the second collimation lens part for collimating the light radiation field in the second plane is arranged on an exit side on the integrally formed collimation lens in the radiation direction.

4. The device according to claim 2, wherein, in a radiation direction, the region on the integrally formed collimation lens and a surface of the second collimation lens part for collimating the light radiation field in the second plane are arranged on an exit side on the integrally formed collimation lens.

5. The device according to claim 2, wherein the region is arranged on an entrance side on the integrally formed collimation lens in a radiation direction and a surface for collimating the light radiation field in the first plane is arranged on an exit side on the integrally formed collimation lens in the radiation direction.

6. The device according to claim 2, wherein the region is arranged on an exit side on the integrally formed collimation lens in a radiation direction and a surface for collimating the light radiation field in the first plane is arranged on an exit side on the integrally formed collimation lens in the radiation direction.

7. The device according to claim 1, wherein the second integrally formed collimation lens has a surface topography of a form:
h(x,y)=a.sub.20x.sup.2+a.sub.40x.sup.4+a.sub.22x.sup.2y.sup.2+a.sub.60x.sup.6+a.sub.42x.sup.dy.sup.2+a.sub.24x.sup.2y.sup.4, wherein h indicates a height of the surface in the beam direction, and x and y are orthogonal coordinate axes in a plane perpendicular to the beam direction (R) and the parameters a are not equal to zero.

8. A high-power diode laser comprising at least one emitter and at least one device according to claim 1.

9. The high-power diode laser according to claim 8 comprising an array of a plurality of emitters arranged alongside one another in an origin plane along the first plane and/or along the second plane, and an additional optical element is assigned to each emitter.

10. A module comprising a device according to claim 1 and a focusing optical unit or comprising a high-power diode laser and the focusing optical unit.

11. A collimation lens array, being designed, for performing a first function of two or a plurality of first collimation lens parts for fast axis collimating a light radiation field in a first plane and being designed for performing a second function of two or a plurality of second collimation lens parts for slow axis collimating the light radiation field in a second plane, which is arranged orthogonally to the first plane and intersects the latter in a line along a beam direction, wherein the collimation lens array is designed for performing a third function of an additional optical element per the first and/or the second collimation lens parts, for additionally collimating unlaigned portions of the light radiation field, which have not yet been aligned parallel to the beam direction by the first and the second collimation lens parts, in a further plane that is different than the first plane and the second plane, wherein the fast axis collimations, the slow axis collimations and the additional collimations are carried out in a combined manner by an integrally formed collimating lens, which comprises the first collimation lens parts, the second collimation lens parts and the additional optical element parts integrally combined, and wherein for performing the third function of the additional optical elements, the integrally formed collimating lens has a surface topography which has a form of a two-dimensional even-order polynomial.

12. A method for collimating a light radiation field with a beam characteristic which is different in a first plane than in a second plane, comprising the following steps: first fast axis collimating of the portions of the light radiation field of the first plane, second slow axis collimating of the portions of the light radiation field of the second plane, further collimating of portions of the light radiation field which have not yet been aligned parallel to the beam direction by the first and the second collimations, wherein the first, the second and the third collimations are carried out in a combined manner by one integrally formed optical element and wherein the integrally formed optical element has a surface topography which has a form of a two-dimensional even-order polynomial.

Description

(1) The invention is explained with reference to the following figures, in which:

(2) FIG. 1: shows a device in accordance with the prior art

(3) FIG. 1a: shows a detail of the device in accordance with FIG. 1

(4) FIG. 2: shows the light radiation field after the collimation in the first and second planes of the device in accordance with FIG. 1

(5) FIG. 3: shows one exemplary embodiment of the device according to the invention

(6) FIG. 3a: shows a detail of the device from FIG. 3

(7) FIG. 4: shows the light radiation field after the collimation of the device from FIG. 3

(8) FIGS. 5a to 6c: show comparative experiments concerning the devices from FIGS. 1 and 3.

(9) FIG. 7: diagrammatically shows another exemplary embodiment of the device according to the invention.

(10) FIG. 1 shows a device for collimating a light beam in accordance with the prior art. The light radiation field L of a light source (of an emitter) has a beam direction R and passes successively through a first collimation lens 10 and a second collimation lens 20.

(11) The light source (emitter) is not shown in the present figure. The emitter defines an origin plane from which the light radiation field L extends with a beam direction R. Two planes extend along this beam direction R, a first plane F (fast axis) and a plane S orthogonal thereto (slow axis), which intersect in the beam direction. The light radiation field L has a different beam characteristic with regard to divergence in the first plane F than in the second plane S.

(12) In this case, the portion of the light radiation field is collimated in the fast axis plane F in the first collimation lens 10. The light radiation field L then has a new characteristic and is referred to as light radiation field L1. The light radiation field L1 enters the second collimation lens 20, which collimates the light in the slow axis plane S. The directed (collimated) light radiation field L1 in turn has a new characteristic downstream of the second collimation lens 20 and is referred to as light radiation field L2.

(13) FIG. 1a shows a detail of the collimation lens 20 from FIG. 1 having an entrance side E20 and an exit side A20. A surface 21 for collimating the light radiation field in the second plane is arranged at the exit side A20. The surface 21 is formed in a cylindrical fashion in the present case.

(14) FIG. 2 shows a simulation of the field after an FAC and SAC collimation by a device from the prior art in accordance with FIG. 1. The blurred regions at the edge of the field are discernible, which result from the non-collimated portions of the light radiation field which lie on neither of the two planes.

(15) FIG. 3 shows one embodiment of the device according to the invention. In terms of its construction, the device from FIG. 3 corresponds to the device from FIG. 1 with a first collimation lens 10 and a collimation lens 20′. The second collimation lens 20′ is formed with an additional optical element 30 in the present case. Likewise as in FIG. 1, the light radiation field of a light source L firstly passes through the first collimation lens 10 and then propagates as light radiation field L1 further through the second collimation lens 20′ and leaves the second collimation lens 20′ as light radiation field L2′. In another embodiment, which is diagrammatically shown in FIG. 7, the device according to the invention is formed as a single collimating lens having a first collimation lens part 10, a second collimation lens part 20′ and an additional optical element part 30 which are integrally formed as one element.

(16) FIG. 3a shows the detail from FIG. 3 corresponding to FIG. 1, namely a part of the lens of the second collimation lens 20′. The collimation lens 20′ has the entrance side E20 and the exit side A20. A surface 21′ for collimating the light radiation field in the second plane is manufactured integrally with the second additional optical element 30. The surface 21′ is formed basically in a cylindrical fashion with a polynomial curvature in a manner similar to the surface 21 from FIG. 2a.

(17) However, this cylindrical embodiment is superimposed with a freeform surface forming the additional optical element 30. In the present case, the region of the combined surfaces 30, 21′, in addition to the convexity of the basically cylindrical embodiment, is formed in a slightly concave fashion transversely with respect thereto.

(18) The freeform surface is fashioned according to the formula
h(x,y)=a.sub.20x.sup.2+a.sub.40x.sup.4+a.sub.22x.sup.2y.sup.2+a.sub.60x.sup.6+a.sub.42x.sup.4y.sup.2+a.sub.24x.sup.2y.sup.4.
This enables the collimation of the light radiation field in the slow axis plane and additionally the collimation of the light which propagates neither in the slow axis plane nor in the fast axis plane.

(19) The freeform surface can be fashioned in particular according to the polynomial
h(x,y)=a.sub.20*x.sup.2+a.sub.22*x.sup.2*y.sup.2+a.sub.40*x.sup.4
wherein a.sub.20 and a.sub.40 are less than zero and a.sub.22 is greater than zero, for example a.sub.20=−6.250e.sup.−02, a.sub.22=−2.14e.sup.−03 and a.sub.04=−1.07e.sup.−04. The value of the coefficients is typically defined depending on the refractive power of the collimation lens, that is to say for example on the type and thickness of the glass.

(20) FIG. 4 shows a simulation of the light radiation field after FAC and SAC in combination with the additional collimation by the element 30 in the different plane with respect thereto. In contrast to the simulation from FIG. 2, blurred edge regions are no longer evident here. The energy in a defined region is increased. This is also shown in FIGS. 5a to c (prior art in accordance with FIG. 1) in comparison with FIGS. 6a to c (device in accordance with FIG. 3).

(21) FIGS. 5a and 6a each show the profile of the light radiation field after the collimation and the focusing by a focusing optical unit. In this case, FIG. 6a reveals a smaller widening of the beam profile by the non-optimally collimated “skew” propagation directions, wherein additionally a higher intensity is able to be ascertained centrally. FIGS. 5b and 6b show the normalized beam profile in the fast axis plane. The comparison shows the improvement in the beam cross section and the reduced secondary maxima. FIGS. 5 c and 6 c show the enclosed energy in a defined region. The comparison shows a significantly improved efficiency of the proposed solution. By way of example, with the solution according to the invention with the used set-up of FAC and SAC or SAC with optimization according to the invention and focusing optical unit, 90% of the energy is focused into a region that is smaller by a factor of 2 in comparison with the prior art.