Abstract
A device (1) for applying light (4) to an inner surface (2) of a cylinder (3), comprising a homogenizer (14), into which light (4) can enter and from which the light (4) can exit, wherein the homogenizer (14) has a cylindrical internal surface (15), on which the light (4) can be reflected after entering and before exiting, and also comprising ways for introducing light (4) into the homogenizing means (14), and focusing arrangements, which can focus light (4) exiting from the homogenizer (14) onto the inner surface (2) of the cylinder (3) to which light (4) is to be applied.
Claims
1. A beam transformation device (12), comprising: a plurality of cylindrical lens arrays, arranged annularly adjacent to one another and each comprise respective cylindrical lenses having cylinder axes (Z) oriented at an angle (γ) of 45° with respect to the radial direction (R) of the annular arrangement.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) FIG. 1 a schematic side view of a first embodiment of a device according to the invention;
(2) FIG. 2 a schematic side view of a second embodiment of a device according to the invention;
(3) FIG. 3 a distribution of beam trajectories typical for meridional rays in a projection onto a plane perpendicular to the cylinder axis of the homogenizing means;
(4) FIG. 4 a distribution of beam trajectories typical for sagittal rays in a projection onto a plane perpendicular to the cylinder axis of the homogenizing means;
(5) FIG. 5 a distribution of beam trajectories typical for the embodiments shown in FIG. 1 and FIG. 2 in a projection onto a plane perpendicular to the cylinder axis of the homogenizing means;
(6) FIG. 6 a perspective view of a homogenizing means;
(7) FIG. 7 a schematic view showing the unit vectors of light in a projection onto a plane perpendicular to the mean direction of light propagation prior to entering in the beam transformation device;
(8) FIG. 8 a schematic view showing the unit vectors of light in a projection onto a plane perpendicular to the mean direction of light propagation after exiting from the beam transformation device;
(9) FIG. 9 a schematic side view of a first embodiment of a beam transformation device according to the invention;
(10) FIG. 10 a perspective view of a second embodiment of a beam transformation device according to the invention;
(11) FIG. 11 a schematic side view of the second embodiment of a beam transformation device according to the invention;
(12) FIG. 12 an illustration of the effect of the second embodiment of a beam transformation device according to the invention:
(13) FIG. 13 a schematic side view of a third embodiment of a beam transformation device according to the invention;
(14) FIG. 14 a schematic side view of the optical paths of the light in the upper region of a device according to the invention using three light sources;
(15) FIG. 15 a schematic side view corresponding to FIG. 14 of the optical paths of the light in the lower region of the device;
(16) FIG. 16 a schematic side view of the optical paths of the light in the lower region of the device corresponding to FIG. 14, rotated by 90° with respect to FIG. 15;
(17) FIG. 17 a schematic crass-section through the light in the region of the light sources when using three light sources;
(18) FIG. 18 a schematic cross-section through the light after the collimator means;
(19) FIG. 19 a schematic cross-section through the light after the compressing means;
(20) FIG. 20 a schematic cross-section through the light upstream of the beam transforming means;
(21) FIG. 21 an exemplary local intensity distribution of the light on the inside of the cylinder to which light is to be applied, in the event that no beam transformation device is used;
(22) FIG. 22 an exemplary local intensity distribution of the light on the inside of the cylinder to which light is to be applied, in the event that a beam transformation device according to the invention is used;
(23) FIG. 23 an overall intensity distribution of the light on the inside of the cylinder to which light is to be applied, in the event that no homogenizing means are used;
(24) FIG. 24 an overall intensity distribution of the light on the inside of the cylinder to which light is to be applied, in the event that homogenizing means are used.
DETAILED DESCRIPTION OF THE INVENTION
(25) In the figures, identical or functionally identical parts or light beams are provided with the same reference symbols.
(26) The embodiment of a device 1 according to the invention depicted in FIG. 1 is used for applying light 4 to an inner surface 2 of a schematically illustrated cylinder 3. In particular, a circular focus area 5 is to be formed with the device 1 according to the invention on the inner surface 2 of the cylinder 3. The device 1 is in the illustrated embodiment located inside the cylinder 3.
(27) In the illustrated embodiment, the device 1 includes four light sources 6 which may, for example, be the ends of optical fibers, wherein laser light can be coupled into the optical fibers. The light 4 emanating from the light sources 6 (see exemplary distribution with three light sources in FIG. 17) is collimated by collimating means 7 (see exemplary distribution with three light sources in FIG. 18) and reflected by mirrors 8 onto compressing means 9, wherein the compressing means 9 are realized by a reflective four-sided pyramid. FIG. 19 shows an exemplary distribution for three light sources downstream of the compressing means 9.
(28) The device further includes a cone 10 with a reflective outer surface onto which the compressed light 4 is reflected by the pyramid. Starting from this cone 10, the light 4 is directed radially outwards onto the reflective inner surface of a hollow cone 11 where the light is reflected upwardly in FIG. 1, so that the light 4 now propagates again in the axial direction of the cylinder 3.
(29) The cone 10 with the reflective outer surface and the hollow cone 11 with the reflective inner surface together form beam expansion means configured to expand and shape the light 4 so that the beam cross-section of the light has off-center an intensity maximum or several intensity maxima. In this context, see the exemplary distribution with three light sources in FIG. 20.
(30) A first embodiment of a beam transformation device 12 according to the invention is arranged downstream of the hollow cone 11 in the propagation direction of the light 4. The beam transformation device 12 is shown again in more detail in FIG. 9.
(31) The beam transformation device 12 includes a plurality of cylindrical lens arrays 121, each having a plurality of cylindrical lenses 122. The individual cylindrical lens arrays 121 are arranged in a ring. Each of the cylinder axes Z of the cylindrical lenses 122 is oriented approximately at an angle γ of 45° relative to the radial direction R of the ring.
(32) The individual cylindrical lenses 122 are formed, for example, as biconvex lenses with a convex surface on the entrance side and a convex surface on the exit side of the beam transformation device 12. Here, the mutual distance of these two convex surfaces to each other corresponds in particular to the sum of the focal lengths of these two convex surfaces or to twice the focal lengths of the convex surfaces if the focal lengths are equal. Each of the cylindrical lenses 122 then forms a Kepler telescope.
(33) FIG. 7 and FIG. 8 each show respective schematic views illustrating the unit vectors of sub-beams of the light 4 in a projection onto a plane perpendicular to the mean direction of propagation of the light 4 before entering into and after exiting from the beam transformation means 12. As can be seen, the unit vectors are rotated by 90° by the cylindrical lenses that are oriented at an angle of 45° relative to the radial direction.
(34) This adds a sagittal component to the previously collimated sub-beams of the light 4. FIG. 3 to FIG. 5 illustrate this relationship. FIG. 3 to FIG. 5 show distributions of beam trajectories in a projection onto a plane perpendicular to the cylindrical axis of a cylindrical medium in which the light propagates. FIG. 3 illustrates a distribution typical for meridional rays and FIG. 4 shows a distribution of beam trajectories typical for sagittal rays.
(35) The sub-beams of the light 4 have for full collimation essentially only a meridional component. When passing through the beam transformation device 12, a sagittal component is added to the sub-beams of the light 4. Such distribution having a sagittal component is shown in FIG. 5.
(36) Another hollow cone 13 with a reflective inner surface is arranged in the propagation direction of light 4 downstream of the beam transformation device 12. The light 4 is reflected at the inner surface of the hollow cone 13 toward a homogenizing means 14, as shown schematically in FIG. 6.
(37) The homogenizing means 14 is constructed as a hollow cylinder with a reflective, patterned inner surface 15. The patterns of the inner surface 15 are concave cylinder sections with cylinder axes extending parallel to the cylinder axis of the hollow cylinder. The concave cylinder sections are arranged consecutively in the circumferential direction of the hollow cylinder. The homogenizing means 14 can be significantly longer than shown in the schematic diagram of FIG. 6.
(38) The light 4 is homogenized in the homogenizing means 14 by multiple reflections on the inner surface 15 so as to produce substantially the same intensity along the entire circular focus area 5. The homogenization is enhanced by admixing to the light 4 with the beam transformation device 12 a sagittal component, as described with reference to FIG. 3 to FIG. 5.
(39) FIG. 21 illustrates how low the homogeneity is without the beam transformation device 12. In contrast, FIG. 22 shows a very homogeneous distribution of the light 4 across the circular focus area 5. FIG. 23 shows how low the homogeneity is without the homogenizing means 14. In contrast, FIG. 24 shows a very homogeneous distribution of the light 4 across the circular focus area 5.
(40) The patterning of the homogenizing means 14 also ensures good homogenization of the circular focus area 5 on the inner surface 2 of the cylinder 3.
(41) The light 4 exiting from the homogenizing means 14 is focused by a lens means acting as a focusing means 16 onto the inner surface 2 of the cylinder 3 onto which light 4 is to be applied. The lens means 16 is formed in particular as a toroidal lens means 16 producing a circular focus area 5 on the inner surface 2 of the cylinder 3. The toroidal lens means 16 includes a peripheral torus-shaped outer surface 17, by which the light 4 is refracted such that the light 4 is focused on the inner surface 2 of the cylinder 3.
(42) The second embodiment shown in FIG. 2 differs from the first embodiment shown in FIG. 1 in that a mirror means 18 also operating as a focusing means is employed instead of the lens means 16. The mirror means 18 is constructed in particular as a toroidal mirror means 18, so that the toroidal mirror means 18 also produces a circular focus area 5 on the inner surface 2 of the cylinder 3. In this case, the toroidal mirror means 18 has a reflective toroidal inner surface 19, by which the light 4 is reflected onto the inner surface 2 of the cylinder 3.
(43) FIG. 10 and FIG. 11 show a second embodiment of a beam transformation device 20 according to the invention. This second embodiment includes two consecutively arranged cylindrical lens arrays 21, 22, wherein the cylinder axes of the cylindrical lenses 23, 24 of these cylindrical lens arrays 21, 22 enclose an angle of 45° with one another.
(44) Also in this embodiment, the individual cylindrical lenses 23, 24 are each formed for example as biconvex lenses with a convex surface on the entrance side and a convex surface on the exit side of the beam transformation device 20. The mutual distance between these two convex surfaces to each other corresponds in particular to the sum of the focal lengths of these two convex surfaces or to twice the focal length of the convex surfaces if the focal lengths are equal. Each of the cylindrical lenses 23, 24 forms hereby a Kepler telescope.
(45) In FIG. 12, the azimuth angle of an incident light beam is denoted by A.sub.1, and the azimuth angle of the exiting light beam by A.sub.3. A.sub.2 indicates the azimuth angle of the light beam after exiting from the first cylindrical lens array 21. Furthermore, FIG. 12 shows the directions Z.sub.23 and Z.sub.24 of the cylinder axes of the cylindrical lenses 23, 24 of the cylindrical lens arrays 21, 22. These enclose an angle of 45° with each other.
(46) FIG. 12 illustrates how the azimuth angle of a light beam passing through the beam transformation device 20 is rotated by the two cylindrical lens arrays 21, 22 together by 90°. In this case, the angle α between the azimuth angle A.sub.1 and the direction Z.sub.23 is transformed by the first cylindrical lens array 21 by an angle −α. Thereafter, the angle β between the azimuth angle A.sub.2 and the direction Z.sub.24 is transformed by the second cylindrical lens array 22 by an angle −β.
(47) Accordingly, due to the angle of 45° between the directions of Z.sub.23 and Z.sub.24 of the cylinder axes of the cylindrical lenses 23, 24, the azimuth angle of the light beam passing through the beam transformation device 20 is rotated by 90°.
(48) FIG. 13 shows another embodiment of a beam transformation device 25, which is constructed similar to the beam transformation device 20 shown in FIG. 10 and FIG. 11, but includes four instead of two cylindrical lens arrays. In particular, two first cylindrical lens array 21 and two second cylindrical lens arrays 22, which are arranged consecutively in the propagation direction of the light, are provided in the beam transformation device 25.
