Beam collimation lens

Description

[0001] The invention relates to a light emission device, a beam collimation lens and a method for producing a beam collimation lens.

[0002] Light-emitting devices can be used as high-power diode lasers. Such devices are typically used for light emitters with an asymmetric beam field, which has a so-called "fast axis" and a so-called "slow axis."

[0003] The fast axis refers to a vertical axis (perpendicular to the semiconductor wafer) that is perpendicular to the slow axis (parallel to the face of the semiconductor wafer). The slow axis and the fast axis are perpendicular to each other and orthogonal to the beam propagation direction (z-axis). Along the propagation direction, a single emitter with, for example, a dimension on the order of 1 micron has a numerical aperture of 0.5–0.7 in the fast axis and a numerical aperture of 0.05–0.2 in the slow axis.

[0004] The most common fast-axis collimators are plano-cylindrical lenses. These are used to enable low-aberration collimation for fast-axis optics with high numerical aperture.

[0005] Such collimators are typically made of high-quality glass. A high-index material minimizes the maximum lens droop and the degree of surface tilt required to achieve the required refraction. For non-critical performance requirements, homogeneous cylindrical rod lenses, i.e., fibers, can also be used.

[0006] GB2510401 A discloses a micro-optical element for use with a laser diode stack, the element comprising a plurality of biconvex fast-axis collimator elements formed as a monolithic array. An array of inlet lenses is provided on a first surface of the element, and an array of outlet lenses is provided on a second surface of the element, opposite the first surface. The arrangement of the inlet and outlet lenses can be adapted to the arrangement of a plurality of individual emitters arranged in a row or in a two-dimensional array. The monolithic element can be manufactured from fused silica using laser micromachining.

[0007] Collimation elements with glasses that have high transmission values ​​are mainly used for diode lasers in a wavelength range between 800 and 1000nm.

[0008] High-performance light emitters are also available in a wavelength range below 550 nm, particularly in the 400-500 nm range. The selection of glass materials with high transmission values ​​is limited for this wavelength range.

[0009] In addition, the processing methods are complex and therefore very expensive.

[0010] It is an object of the invention to eliminate the disadvantages of the prior art and in particular to provide a device for light emission, a beam collimation lens and a method for producing a beam collimation lens with which a good optical collimation quality can be provided at low cost.

[0011] The object is achieved by the features of the independent claims. Preferred embodiments are defined in the dependent claims.

[0012] The beam collimation lens comprises at least one biconvex collimation element and is made of quartz glass.

[0013] The laser light source emits visible laser light, in particular with wavelengths of less than or equal to 550nm, in particular in a wavelength range from 300nm to 550nm, more particularly from 400-500nm.

[0014] At shorter wavelengths, the industrially available power levels increase significantly, and with them the requirements for minimal absorption in the beam collimation lens. High power levels can lead to significant heating and pose the risk of defocusing, thus degrading beam quality.

[0015] Conventional fast-axis collimation elements with a refractive index n of about 1.80 show a strong temperature increase even at low power levels.

[0016] Collimation elements made of quartz glass with a refractive index of approximately 1.45 exhibit a low temperature increase up to power levels exceeding 200 W. Beam quality can therefore be maintained over a wide power range.

[0017] In a preferred embodiment of the device, it comprises a plurality of laser light sources. The laser light sources can be arranged in a two-dimensional array. Preferably, the laser light sources are arranged in a row next to one another.

[0018] The beam collimation lens preferably has an array of biconvex collimation elements that corresponds to the arrangement of the laser light sources. Advantageously, the beam collimation lens is monolithic.

[0019] The disadvantage of the lower refractive index of quartz glass can be compensated by a corresponding shape of the entrance and exit surfaces. According to the invention, the biconvex collimating element has an acylindrical shape on the exit side and a cylindrical shape on the entrance side.

[0020] By "cylindrical" shape we mean that the cross-section of the collimating element has a circular shape, while an acylindrical shape is a deviation from the circular segment, for example the shape of a polynomial.

[0021] Preferably, the entire entrance surface of the biconvex collimating element is convexly curved and / or the entire exit surface of the biconvex collimating element is also convexly curved. The surface of the collimating element thus has a simple shape, with no concave or flat partial surfaces. This simplifies the manufacturing process.

[0022] Particularly preferably, the entrance surface of the entire beam collimation lens is convexly curved and / or the exit surface of the entire beam collimation lens is also convexly curved, in particular when the device for light emission comprises a plurality of emitters and one beam collimation lens is used for these multiple emitters.

[0023] In a particularly advantageous embodiment of the device, the beam collimation lens is rod-shaped. Rod-shaped means that the lens is cylindrical and is preferably longer in a direction transverse to the light propagation, namely in the fast-axis direction, than in the direction of light propagation.

[0024] The beam collimation lens can be designed as a biconvex cylinder so that it can be used for a large number of laser light sources arranged in a row.

[0025] The biconvex cylinder can be equipped with a cross-section that has a circular segment on the inlet side.

[0026] Such a beam collimation lens has a simple geometry and can therefore be manufactured easily and cost-effectively, for example in a fiber drawing process.

[0027] Rod-shaped beam collimation lenses can also be easily combined to form a beam collimation lens array for laser light sources arranged in a two-dimensional array, for example by gluing beam collimation lenses together along their long sides.

[0028] The object is achieved by a beam collimation lens, in particular for fast-axis collimation, for a light emission device as described above.

[0029] The beam collimation lens comprises at least one biconvex collimating element and is made of fused silica. The entrance surface of the biconvex collimating element is convexly curved, and the exit surface of the biconvex collimating element is also convexly curved, allowing sufficient refraction to be achieved despite the low refractive index of the fused silica.

[0030] In an advantageous embodiment, the biconvex collimation element has an entrance surface with an area of ​​0.2mm 2< -10 mm 2< , and / or with a length of 2mm-12mm and / or with a height of 0.1mm-0.85mm.

[0031] The entrance surface refers to the surface of the biconvex collimation element facing the light source.

[0032] In an advantageous embodiment, the biconvex collimation element has an exit surface with an area of ​​0.6 mm 2< -30 mm 2< and / or with a length of 2 mm - 12 mm and / or a height of 0.3 mm - 2.5 mm.

[0033] The exit surface refers to the surface of the biconvex collimation element facing away from the light source.

[0034] The biconvex collimation element can have a maximum curvature depth of 0.1mm on the entrance side and / or a maximum curvature depth of 0.5mm on the exit side.

[0035] The biconvex collimation element can have a focal length of 0.2mm to 1.8mm.

[0036] The heights refer to the optically effective areas. Because the entrance is close to the emitter and there is a large divergence, the optically effective height is smaller at the entrance side than at the exit side. However, the collimating element can be manufactured so that the entrance and exit sides have approximately the same height.

[0037] The above dimensions can also apply to the entire beam collimation lens.

[0038] In a preferred embodiment, the beam collimation lens is manufactured using a fiber drawing process. The beam collimation lens then preferably has the overall shape of a biconvex cylinder.

[0039] The peripheral surfaces of the beam collimation lens, i.e., the surfaces on the cylinder surface, are glossy and precisely shaped. The beam collimation lens has no matte surfaces on its circumference, even on the non-optical, upward- and downward-facing peripheral surfaces. Neither saw marks nor traces of a pressing tool are visible on the peripheral surface.

[0040] The non-optical side surfaces transverse to the cylinder axis may be matt due to a separation step and, for example, have saw marks.

[0041] In a preferred embodiment, the beam collimation lens is rod-shaped.

[0042] The object is further achieved by a method for producing a beam collimation lens as described above with the following steps.

[0043] First, a biconvex preform made of quartz glass is provided. Its cross-sectional area is, in particular, a factor of 100 to 10,000 larger than the cross-sectional area of ​​the collimation element of the beam collimation lens to be manufactured.

[0044] The preform is manufactured using conventional glass manufacturing processes, such as grinding and polishing. The required dimensional accuracy of the lens can be achieved with reasonable effort by scaling it up using conventional production of a large preform.

[0045] The preform is heated, particularly to temperatures of 2000-2200°C. For this purpose, the preform, which has a shape congruent with the collimation element to be manufactured, is introduced into a suitable furnace.

[0046] After heating, the beam collimation lens is peeled off, which results in scaling, i.e., reducing the cross-sectional area. This is typically done using a peel-off device consisting of rollers. The peel force is adjusted to the desired scaling.

[0047] When peeled off, after leaving the furnace, the beam collimation lens may still have a temperature of several hundred degrees, which is well below the glass transition temperature, and may have its final cross-section.

[0048] Cooling can take place in air.

[0049] Rod-shaped lenses can then be cut to the desired length.

[0050] Due to the large scaling from the preform to the final part, the individual components can be produced cost-effectively in large quantities.

[0051] If desired, rod-shaped beam collimation lenses can then be glued together to form a two-dimensional collimation field.

[0052] The problem is also solved by using a light emission device as described above for processing non-ferrous metals.

[0053] Short wavelengths are suitable for processing non-ferrous metals to enable efficient processing.

[0054] High-power diode lasers with shorter wavelengths can be provided in a simple and cost-effective manner using a beam collimation lens as described above.

[0055] The invention is explained using the following figures. They show: Figure 1: a cross-sectional view of a device according to the invention; Figure 2: a perspective view of a beam collimation lens according to the invention; Figure 3: a schematic representation of the manufacture of a beam collimation lens.

[0056] Figure 1 shows a cross-sectional view of a light emission device 1. The device 1 comprises several laser light sources 2 arranged in a row, as well as a beam collimation lens 3 for fast-axis collimation.

[0057] The beam collimation lens 3 comprises biconvex collimation elements 4 and is made of quartz glass.

[0058] The laser light sources 1 emit visible laser light with wavelengths of less than 550 nm, in particular in a wavelength range of 300-500 nm.

[0059] The biconvex collimation element 4 has a maximum curvature depth 13 of 0.1 mm on the entrance side 6.

[0060] The biconvex collimation element 4 has a maximum curvature depth 14 of 0.5 mm on the exit side 5.

[0061] The entrance surface 7 has a height 10 of 0.1mm-0.85mm, the exit surface 8 has a height 12 of 0.3mm-2.5mm.

[0062] The beam collimation lens 3 is preferably manufactured such that a large part of the area 19 between the entrance and exit sides has a constant height 20.

[0063] The contour of the exit side 5 can follow the following polynomial. z h = h 2 R 1 + 1 − 1 + k h 2 R 2 + ∑ n = 1 N A n ⋅ h n

[0064] Preferably, the form follows a tenth-order polynomial. The coefficients are, for example, R=-0.3mm; k=-1; A 4 =-3,2812 mm -3< , A 6 =16,414 mm -5< , A 8 =-241,567 mm -7< and A 10 =822,595 mm -9< .

[0065] Figure 2shows a perspective view of a beam collimation lens 3 according to the invention. The beam collimation lens 3 is rod-shaped, so that the adjacent biconvex collimation elements 4 merge into one another and form a common entrance surface 7 and exit surface 8.

[0066] The entrance surface 7 and the exit surface 8 have a length 11 of 2 mm-12 mm.

[0067] Figure 3 shows a schematic representation of the production of a beam collimation lens 3.

[0068] First, a biconvex preform 15 made of quartz glass is provided.

[0069] In a furnace 16, the preform 15 is heated to temperatures of 2000-2200°C.

[0070] After heating, the beam collimation lens 3 is peeled off with a roller peeling device 17, whereby the cross-sectional area is reduced.

[0071] The cross-section is checked with a measuring system 18 after leaving the furnace 16.

[0072] Cooling takes place in air.

[0073] Subsequently, rod-shaped beam collimation lenses 3 are cut to a desired length.

Claims

1. A beam collimating lens for a light-emitting device for fast-axis collimation, the beam collimating lens comprising at least one biconvex collimating element and being made of quartz glass, characterized in in that the biconvex collimating element (4) has an acylindrical shape on the exit side (5) and a cylindrical shape on the entry side (6).

2. The beam collimating lens according to claim 1, wherein the biconvex collimating element comprises - an entrance area (7) with an area of 0.2 mm2-10 mm2 and / or an entrance area (7) with a length (9) of 2 mm-12 mm and / or an entrance area (7) with a height (10) of 0.1 mm-0.85 mm and / or - an exit area (8) with an area of 0.6 mm2 - 30 mm2 and / or an exit area (8) with a length (11) of 2 mm - 12 mm and / or an exit area (8) with a height (12) of 0.3 mm - 2.5 mm and / or - on the entrance side (6) a maximum curvature depth (13) of 0.1 mm and / or - on the exit side (5) a maximum curvature depth (14) of 0.5 mm and / or - a focal length of 0.2 mm to 2 mm, preferably of 0.2-1.8 mm.

3. The beam collimating lens according to claim 1 or 2, wherein the beam collimating lens (3) is produced in a fiber drawing process.

4. The beam collimating lens according to claim 1 to 3, wherein the beam collimating lens (3) is rod-shaped.

5. A light-emitting device comprising at least one laser light source (2) and at least one beam collimating lens (3) according to one of claims 1 to 4, for fast-axis collimation, characterized in that the laser light source (2) emits visible laser light, in particular with wavelengths smaller than 550 nm, more particularly in a wavelength range of 300-500 nm.

6. The device according to claim 5, wherein the device (1) has a plurality of laser light sources (2) and the beam collimating lens (3) preferably has an array of biconvex collimating elements (4), in particular the laser light sources (2) are arranged side by side.

7. The device according to one of the preceding claims 5 or 6, wherein the beam collimating lens (3) is rod-shaped.

8. A method for producing a beam collimating lens (3) having at least one biconvex collimating element (4) according to claims 1 to 4, comprising the following steps - providing a biconvex quartz glass preform (15), the cross-sectional area of which is larger, in particular by a factor of 100 to 10,000, than the cross-sectional area of the collimating element (4) of the beam collimating lens (3) to be produced; - heating the preform (15), in particular to temperatures of 2000-2200°C; - pulling off the beam collimating lens (3); - cooling; - in particular cutting to the desired length.