The present invention relates to a device for homogenizing light which contains at least one homogenizing device having an entrance surface and an exit surface for the light to be homogenized. In each case an array of cylindrical lenses on the entrance surface or in the vicinity of the entrance surface, and an array of cylindrical lenses on the exit surface or in the vicinity of the exit surface of the at least one homogenizing device are provided. A configuration for illuminating a surface and a configuration for focusing the light from a laser light source into a linear region of focus are also discussed.
A device of the abovenamed type is disclosed in U.S. Pat. No. 4,733,944. The device for homogenizing that is described therein contains two homogenizing devices spaced apart from one another, each of the homogenizing devices contain two optically functional boundary surfaces through which the light to be homogenized passes. An array of cylindrical lenses is respectively disposed on each of these four boundary surfaces that contribute to homogenization. In this case, each of the two homogenizing devices spaced apart from one another has two arrays of mutually crossed cylindrical lenses. For example, in the case of one of the homogenizing devices a cylindrical lens array having cylinder axes in the vertical is constructed on an entrance surface, and a cylindrical lens array having cylinder axes in the horizontal is constructed on the exit surface.
Thus, such a device for homogenizing can be used to homogenize a laser beam, such as, for example, a beam emanating from an excimer laser or a laser beam emanating from a laser diode bar, both in a first direction and in a second direction perpendicular thereto. For example, in the case of a laser diode bar, such a device for homogenizing can be used to produce a homogenization both on the so-called fast axis and on the so-called slow axis. Furthermore, the abovenamed device known from the prior art is configured as a so-called two-stage device for homogenizing, because the beam to be homogenized experiences the homogenization in each of the homogenizers. A substantially better homogeneity is achieved by the two-stage configuration of the device over a one single-stage homogenizer.
In the case of such two-stage devices for homogenizing known from the prior art, the adjustment of the two homogenizing devices is decidedly difficult to carry out, proves, however, to be disadvantageous. The homogenizing devices must be positioned very accurately relative to one another, each of the homogenizing devices requiring to be adjusted exactly with reference to six axes overall. Furthermore, the focal lengths of the cylindrical lenses of the array are not freely selectable, since an optimum spacing of the cylindrical lenses relative to one another is given for each of the two directions that can be homogenized independently of one another, for example the slow axis and the fast axis. In particular, two-stage devices for homogenizing that operate in the two directions independent of one another react very sensitively to focal length errors of the cylindrical lenses, since the two directions are not independent of one another, as a rule.
It is accordingly an object of the invention to provide a device for homogenizing light and a configuration for illuminating or focusing with such a device which overcomes the above-mentioned disadvantages of the prior art methods and devices of this general type, which can be adjusted easily. Furthermore, the aim is to specify a configuration for illuminating a surface, and a configuration for focusing the light from a laser light source into a linear region of focus.
With the foregoing and other objects in view there is provided, in accordance with the invention, a device for homogenizing light. The device contains at least one homogenizer device having an entrance surface and an exit surface for the light to be homogenized, a first array of cylindrical lenses disposed on the entrance surface or in a vicinity of the entrance surface, and a second array of cylindrical lenses disposed on the exit surface or in a vicinity of the exit surface. The cylindrical lenses of the first and second arrays have cylinder axes aligned parallel to one another.
It is provided that the cylinder axes of the cylindrical lenses of the at least one homogenizing device are aligned parallel to one another. The at least one homogenizing device, configured, for example, as a substrate, therefore fulfills the function of a two-stage homogenizer. For example, in the case of the homogenization of the laser light emanating from a laser diode bar, it follows that the homogenizing device acts on one axis or one direction, that is to say only on the slow axis or only on the fast axis, for example.
In accordance with a further embodiment of the invention, the possibility exists that the device contains a first homogenizer device and a second homogenizer device that in each case have an entrance surface and an exit surface for the light to be homogenized. It can be provided in this case that the first homogenizer device respectively has an array of cylindrical lenses on the entrance surface or in the vicinity of the entrance surface, and an array of cylindrical lenses on the exit surface or in the vicinity of the exit surface, the cylinder axes of which are aligned parallel to one another.
It can be provided in another embodiment of the invention that the second homogenizer device has an array of cylindrical lenses on the entrance surface or in the vicinity of the entrance surface, or an array of cylindrical lenses on the exit surface or in the vicinity of the exit surface.
Alternatively, it can be provided that the second homogenizer device respectively has an array of cylindrical lenses on the entrance surface or in the vicinity of the entrance surface, and an array of cylindrical lenses on the exit surface or in the vicinity of the exit surface, the cylinder axes of which are aligned parallel to one another.
In particular, it can be provided that the cylinder axes of the cylindrical lenses of the first homogenizer device are aligned perpendicular to the cylinder axes of the cylindrical lenses of the second homogenizer device. In this way, the two directions or axes of the laser light are homogenized separately from one another in the two homogenizer devices, which are, in particular, spaced apart from one another. The two homogenizer devices need no longer be adjusted relative to one another, because the adjustment of the cylindrical lenses, which act for example on one of the two axes, is achieved by the fabrication of the homogenizer device, which can be reproduced at any time within the manufacturing tolerances. In this way, the beam properties are always the same within the constraints of the abovenamed manufacturing tolerances. Furthermore, the two axes such as, for example, the slow axis and the fast axis in the case of a semiconductor laser bar are not subjected to an influence by focal length tolerances of the respective other beam axis. Furthermore, it is possible when homogenizing the laser light with regard to the two axes to select the focal lengths of the cylindrical lenses freely for each of the axes and independently of the respective other axis.
In accordance with an added embodiment of the invention, the focal planes of the cylindrical lenses disposed on the exit surface or in the vicinity of the exit surface are disposed in the entrance surface or in the vicinity of the entrance surface. The homogenization of the light to be homogenized is optimized in this way.
It can be provided that the cylindrical lenses are configured as concave and/or convex lenses or as GRIN lenses (gradient index lenses).
It is provided that the device used in the configuration is an inventive device for homogenizing.
It is provided in accordance with another embodiment of the invention, that the device used in the configuration for focusing likewise is an inventive device for homogenizing.
It can be provided in this case that the device for homogenizing is fashioned in such a way that it homogenizes the laser light only with regard to the slow axis direction.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device for homogenizing light and a configuration for illuminating or focusing with such a device, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
Cartesian coordinate systems have been drawn in in some of the figures in order to improve clarity. Referring now to the figures of the drawing in detail and first, particularly, to
It is to be seen from
Adjoining the fast axis collimation device 2 in the propagation direction Z is a beam transformation device 3. The incident light is rotated by an angle of 90° in the beam transformation device 3, or the divergence of the fast axis (Y direction) is exchanged for that of the slow axis (X direction) such that after the exit from the beam transformation device 3 the divergence in the Y direction is larger than the divergence in the X direction.
The beam transformation device 3 can be a substantially cuboid block made from a transparent material on which a number of cylindrical lens segments serving as beam transformation elements are disposed parallel to one another both on the entrance side and on the exit side. The axes of the beam transformation elements can enclose an angle α of 45′ in this case with the base side of the cuboid beam transformation device 3, which runs in the X direction.
A further collimation device 4 adjoins the beam transformation device 3 in the propagation direction Z of the laser light such that, for example, a beam of 10 mm×10 mm with a divergence of approximately 11 mrad in the Y direction and a divergence of approximately 3 mrad in the X direction can be achieved. The numerical values for divergence and beam diameter relate to the full width of the beam at half the maximum intensity (FWHM). The collimation device 4 is configured as a plano-convex cylindrical lens having a cylinder axis extending in the X direction. Because of the rotation of the laser light in the beam transformation device 3, the collimation device 4 therefore has the same alignment as the fast axis collimation device 2. In the same way as the fast axis collimation device 2, it is also possible for the collimation device 4 to be fashioned differently. In particular, both entrance surface and exit surface can be provided with a convex and/or concave curvature.
Adjoining the collimation device 4 in the propagation direction Z is a first homogenizer or homogenizing device 5 and a second homogenizer or homogenizing device 6 adjoining the former. On their entrance surface 7, the homogenizing device 5 has an array of cylindrical lenses 9 whose cylinder axes extend in the X direction (see also
The configuration contains a second homogenizing device 6 downstream of the first homogenizing device 5 in the beam propagation direction Z. On their entrance surface 7 and on their exit surface 8, the second homogenizing device 6 respectively has a cylindrical lens array having cylindrical lenses 9 that extend in the Y direction (see also
The device for homogenizing in this case contains the first and the second homogenizing devices 5, 6. Overall, the laser light is thus homogenized in two directions or axes in the inventive device, the second stage acting only on the X direction, and the first stage only on the Y direction.
The cylindrical lenses 9 of the homogenizing devices 5, 6 can be configured as convex (see
The laser light emerges from the second homogenizing device 6 in a fashion homogenized to the greatest extent, and can be used to illuminate a surface remote from the device.
The embodiment, depicted in
The configuration further contains the fast axis collimation device 2 that can be configured like the fast axis collimation device 2 in accordance with
In the beam direction downstream of the fast axis collimation device 2, the inventive configuration contains a slow axis collimation device 10 that is configured in the exemplary embodiment depicted as an array of cylindrical lenses on the entrance and on the exit sides of the slow axis collimation device 10. The cylinder axes of the cylindrical lenses of the slow axis collimation device 10 extend in this case in the Y direction. In particular, the slow axis collimation device can be disposed in such a way that one of the partial beams of the laser light that emanate from in each case one of the emitters enters each of the cylindrical lenses on the entrance side. Each of the partial beams is collimated by the corresponding cylindrical lenses with regard to the slow axis or with regard to the X direction.
The embodiment of the slow axis collimation device 10 depicted in
The embodiment, depicted in
Owing to the passage through the cylindrical lenses 9 of the homogenizing device 6, the individual partial beams of the laser light are very effectively superimposed on one another in the slow axis direction or in the X direction. The laser light emerging from the homogenizing device 6 can be focused by a focusing device 11 disposed downstream of the homogenizing device 6 in the propagation direction Z. In the exemplary embodiment depicted, the focusing device 11 is configured as a rotationally symmetrical plano-convex lens. The focusing device 11 can also be formed by other configurations, for example by a biconvex lens or by a number of cooperating lenses. This lens can focus the laser radiation 10 with regard to the fast axis or the Y direction, and serve at the same time as field lens for the homogenizing device 6 acting only on the slow axis or X direction. It is possible here in practice for the focus of the lens serving as the focusing device 11 to lie with regard to the fast axis in a plane in which the field of the laser light is homogenized in the slow axis direction by the lens acting as field lens.
The laser radiation that has passed through the homogenizing device 10 is illustrated in
The focusing device 11 focus the laser light into a linear region of focus that extends in the X direction and has a very slight extent in the Y direction. It is possible, for example, for the extent of the region of focus to be smaller than 1 mm, or smaller than 0.5 mm, in the Y direction or in the fast axis direction. It is possible, moreover, for the width of the linear region of focus to be larger than 5 mm or larger than 20 mm in the X direction or in the slow axis direction. The distance d between the exit surface of the focusing device 11 and the linear region of focus can be comparatively large, for example larger than 50, in particular larger than 200 mm.
Number | Date | Country | Kind |
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10 2004 011 074.3 | Mar 2004 | DE | national |
10 2004 034 253.9 | Jul 2004 | DE | national |
This is a continuing application, under 35 U.S.C. §120, of copending international application PCT/EP2004/009325, filed Aug. 20, 2004, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German patent applications DE 10 2004 011 074.3, filed Mar. 6, 2004 and DE 10 2004 034 253.9, filed Jul. 14, 2004; this application further claims the priority of international application PCT/EP2004/008944, filed Aug. 10, 2004; the prior applications are herewith incorporated by reference in their entirety.
Number | Date | Country | |
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Parent | PCT/EP04/08944 | Aug 2004 | US |
Child | 11516475 | Sep 2006 | US |
Parent | PCT/EP04/09325 | Aug 2004 | US |
Child | 11516475 | Sep 2006 | US |