DE102015213698B3 - Illumination system suitable for applications in metrology and coordinate measuring machine with such a lighting system - Google Patents

Abstract

The invention relates to a lighting system 30; 30a; 50; 50a; 50b; 50c; 60; 70; 80; 90 for generating an incident light bright field for metrology applications comprising a plurality of light sources 31, 32, 33 with mutually different emission spectra and at least one dichroic beam splitter 35 for superimposing or merging the light from at least two of the light sources 31, 32, 33 along an optical axis of the illumination system 30; 30a; 50; 50a; 50b; 50c; 60; 70; 80; 90, wherein on the light path from the light sources 31, 32, 33 to the field to be illuminated of the illumination system 30; 30a; 50; 50a; 50b; 50c; 60; 70; 80; 90 between the light sources 31, 32, 33 and the at least one beam splitter 35 and / or between the at least one beam splitter 35 and the field to be illuminated at least a first homogenization means 37a, 38a, 39a, 40; 41; 51, 52, 53 is provided for light mixing and wherein the at least one homogenizing agent 37a, 38a, 39a, 40; 41; 51, 52, 53 is selected or composed of the optical elements of the group: rod integrators, cavity integrators, fiber bundles, lens and / or mirror arrays, and wherein on or at least one dichroic steel divider (35) comprises at least a first convergent lens (37, 38, 39, 37a, 38a, 39a, 55, 55a) by means of additive machining processes, ablative machining processes and / or by the application of a separately manufactured optical element in the form of an aspheric, a Fresnel lens and / or a diffractive optical element (DOE) is formed. Furthermore, the invention relates to a coordinate measuring machine with such a lighting system 30; 30a; 50; 50a; 50b; 50c; 60; 70; 80; 90th

Description

The invention relates to a lighting system for applications in metrology and a coordinate measuring machine comprising such a lighting system.

In imaging systems in the field of coordinate metrology, light sources are generally needed when an object is to be imaged, because only in extremely rare cases are it self-luminous objects. The ambient lighting is just as rare enough to display the objects in the desired quality. "Image quality" is generally based on human perception, i. H. the sense of sight, derived as a triad of color fastness, sharpness and contrast. While in the increasingly important area of computer vision or machine vision, certain deficits in the image quality can be subsequently corrected, there are also errors which can not be corrected by calculation. This mathematical correction does not succeed regularly if no unambiguous assignment of the error in the image to the imaging error causing it of the imaging system is possible. Mathematically, this means that no bijective imaging of aberrations of the system on the observed effect in the image plane of the imaging system or no development of aberrations is possible.

The aberrations can be caused both by the actual imaging system and by the lighting system. While usually a great deal of care is taken on the design and interpretation of the actual imaging optics (classic: "lens"), a much lower cost is often operated for cost reasons in the lighting. In the upper price segment of light microscopy and in semiconductor lithography this is not true, d. H. There, technically optimal solutions are sought for both lighting and projection. The associated manufacturing, equipment and consequent cost and space requirements is sometimes considerable and excludes from one or more of the above aspects, a use of developed for microscopy and semiconductor lithography technologies in the low-cost range of metrology lighting systems.

Moreover, in the low-cost area, the use of comparatively inefficient light sources is common practice for achieving high illumination intensities, producing large amounts of waste heat. In particular, in the field of optical coordinate metrology, such a heat input into the meter is harmful because the heat input can be computationally compensated only in rare cases. However, this heat input can be bypassed by the light power is coupled via optical fibers. However, this in turn means at least increased design and cost. Furthermore, the light guides are not lossless, d. H. they absorb and thus reduce the achievable illuminance under certain circumstances. In addition, the optical fiber lengths can take considerable lengths in larger machines. In addition, the necessary, not to be exceeded bending radii of the optical fiber can complicate the machine design or stand against a compact design regularly.

For metrology lighting systems, variable illumination settings are needed in most applications because different objects must be illuminated with different illuminations. Variable lighting requires the highest possible degree of efficiency for minimum heat input changes. In the context of this invention, the efficiency is understood to be the quotient of the light coupling into the illumination system for the heat input into the measuring device, wherein the light equivalent in the illumination system is understood here to be the energy equivalent of the light quantity entering the illumination system.

From this viewpoint of efficiency, couplings of the light into the illumination system by optical fibers are ideal since the heat input into the meter tends to zero. However, these systems are - as already stated - consuming and expensive. Further, from the viewpoint of efficiency, LEDs are the favorable solution for light sources. Lasers as light sources would allow similar or even slightly higher efficiencies, but their feature of coherent illumination is often detrimental to imaging. In addition, at high intensities often elaborate safety requirements are to be observed, which justify the use of lasers only for isolated special applications. Arc and gas discharge lamps also achieve a high degree of efficiency with appropriate design, but are due to the high technical complexity and only for special applications into consideration.

For many applications in optical metrology, monochromatic illumination is not desired, but multi-color illumination. The required multicolor varies in the simplest case of two-color illuminations to elaborate modules that provide a variety of different wavelengths, for example, for excitation and fluorescence microscopy. For this fluorescence microscopy are generally beam overlays of different light sources differing in the emission spectrum in cascades of dichroic beam splitters at the expense of the associated production, assembly and adjustment costs. For two-color illumination, overlaying a dichroic beam splitter is the simplest solution. For a typically desired RGB illumination, the dichroic overlay in a so-called X-Cube is the most appropriate solution. Although an overlay on two crosswise arranged dichroic beam splitters achieves the compact design of the X-Cube, it is inferior in terms of illumination quality, since a shadowline forms in the illumination beam.

On the basis of this cited prior art and the problems outlined, it is therefore the object of the invention to provide a simple, compact, efficient and cost-effective multicolour illumination system for metrological applications and a corresponding coordinate measuring machine, which permits homogeneous superimposition of the colors both in the field and in the field in the pupil of the illumination system.

This object is achieved by an illumination system for generating a reflected-light bright field for metrology applications comprising a plurality of light sources with mutually different emission spectra and at least one dichroic beam splitter for superimposing or merging the light from at least two of the light sources along an optical axis of the illumination system, wherein on the light path at least one first homogenizing agent for light mixing is provided from the light sources to the field to be illuminated of the illumination system between the light sources and the at least one beam splitter and / or between the at least one beam splitter and the field to be illuminated, and wherein the at least one homogenizing agent is selected or composed for the light mixture is from the optical elements of the group: rod integrators, cavity integrators, fiber bundles, lens and / or mirror arrays, and wherein on or on the at least one you at least a first converging lens is formed by means of additive machining methods, ablative machining methods and / or by the application of a separately manufactured optical element in the form of an aspheric, a Fresnel lens and / or a diffractive optical element (DOE). By the latter, the illumination system can be made particularly compact, especially when the convergent lens by means of gray-tone lithography, injection molding, casting, casting, stamping, Aufkitten, gluing, laminating, printing, injection molding and / or wringing directly on the entrance or exit surface of the dichroic beam splitter is attached.

By means of the at least one homogenizing agent, a light mixture in the field and in the pupil of the illumination system is performed such that the light present uniformly distributed over the field and at least uniformly parcels over the pupil, in particular evenly across the pupil, depending on the design of the homogenizing agent and the light sources becomes. In this case, this light mixture is also made possible for each color or each emission spectrum by the at least one first homogenizing agent. For this purpose, each of the light sources may have a downstream first separate homogenizing agent on the light path from the light source to the at least one beam splitter. Alternatively or additionally, however, it is also possible to provide, on the light path from the at least one beam splitter to the field to be illuminated, a first homogenizing agent which is effective jointly for all colors or emission spectra. However, the latter does not mean that the same amount of light from the respective colors or emission spectra is present in the field and pupil. For this purpose, it is necessary to match the light output of the different light sources and the different light losses on the way to the field to be illuminated. However, the first homogenizing agent, which works together for all colors, only leads to a mixture of light in the field and pupil for each of the individual colors per se; the homogenizing agent can not change the different proportion of colors in the total light of the illumination system.

The said homogenizing agents are known in the field of semiconductor lithography for the homogenization of monochromatic radiation, in particular of coherent laser light radiation. Thus, reference is made to the known literature for the description of the mode of action of these homogenizing agents, see for example for rod integrators or cavity integrators US 4,744,615 A , for lens arrays as so-called honeycomb condensers US 4 498 742 A , for mirror arrays as so-called honeycomb condensers DE 28 03 277 A1 and for the combination of rod integrators with honeycomb condensers US 4,918,583 A ,

The use of these known from semiconductor lithography homogenizing was previously unimaginable for the low-cost range, as the mostly made of special quartz or in special stress situations made of calcium fluoride due to the material and due to the high demands on the accuracy of the mold made very expensive had to be, which is ultimately reflected in the high cost of these elements, which are many times the cost of a lighting system according to the invention.

Meanwhile, however, there are highly accurate manufacturing methods for injection molding precision optics made of plastic, whose dimensional accuracy for a lighting system according to the invention are sufficient. Furthermore, there are now manufacturing methods for high-precision foil printing of lens or mirror arrays in continuous plastic webs. Common to these new production methods is that the optical elements to be machined do not have to be brought into the desired final shape state with great effort by means of removing methods such as milling, turning, drilling and polishing. In the new production methods, the optical element is already transferred almost to its final state during its production. As a result, correspondingly inexpensive optical elements can now be produced, which enables the use of these elements in the low-cost range. For example, Innolite GmbH, c / o Fraunhofer IPT, Steinbachstrasse 17, 52074 Aachen, Germany, is the supplier of such low-cost production methods for small series parts. promod Prototyp Center GmbH, Robert-Bosch-Str. 24, 72160 Horb-Bildechingen or Proto Labs Ltd., Alte-Neckarelzer-Straße 24, 74821 Mosbach.

According to the invention, it has therefore been recognized that a transfer of the homogenization means known from semiconductor lithography to the low-cost range of metrology illumination systems is possible by the new production methods and thus an illumination system for generating an incident light brightfield for measurement technology applications can be realized whose light is uniform is distributed over the field and at least uniformly parceled over the pupil. Such a uniform parceled light distribution is necessary to reduce the measurement error contribution of the illumination system when evaluating coordinates of a workpiece to be measured.

In the context of the present invention, "uniform" is understood to mean a light distribution which, apart from a few percent and apart from the edge region of the field, assumes a constant value over the field of the illumination system. By contrast, in the context of the present invention "uniformly parceled" is understood to mean a light distribution which may have a regular structure or regular intensity fluctuations across the pupil of the illumination system, but this regular structure extends uniformly over the entire pupil apart from the edge region of the pupil. In other words, a uniformly parceled light distribution is a parceled light distribution, the parcels of which are distributed uniformly over the pupil, with the mean intensity values of the parcels following a course of trajectory across the pupil. In this case, the uniformly parceled light distribution in the pupil can also be converted into a virtually uniform or quasi-uniform, depending on the design of the homogenizing agent and depending on the pupil filling by the light source.

This can be illustrated most simply on the basis of the kaleidoscope effect of a rod or cavity integrator. When looking into a rod or cavity integrator, the pupil is divided into individual plots of the same size due to the multiple reflections within the rod (kaleidoscope effect). The longer the rod or cavity integrator is chosen, the greater the number of identical parcels into which the pupil is divided. In this case, an initially uneven distribution of light in a parcel always weighs less, the longer the rod is selected and the more parcels the pupil has thereby. With a theoretically infinitely long rod and with a corresponding pupil or parcel filling by the light source, a completely uniform light distribution over the pupil is finally achieved.

Consequently, the proposed homogenizing agents can not increase the optical conductivity of the illumination system per se. This would also contradict Liouville's theorem of the constancy of phase space. However, the homogenizing means redistributes the light in the pupil to be uniformly distributed throughout the pupil due to the parceling and is absent at the edge of each parcel. As a result of this redistribution of light, the phase space is "perforated" on the one hand and "mixed through" on the other hand, resulting in a homogeneous phase space which also has a measurable higher light conductance. This situation is comparable to that of a cake dough before and after baking. The volume per se, which the cake dough takes before and after baking, remains the same, but the generation of gases during baking significantly increases the total volume of the cake during baking.

In one embodiment of the illumination system according to the invention, at least one first converging lens is arranged on the light path from the light sources to the field to be illuminated of the illumination system between the light sources and the at least one beam splitter and / or between the at least one beam splitter and the field to be illuminated. By one or more first converging lenses between the light sources and the at least one beam splitter, it can be ensured that the light from the various light sources enters with almost similar angular distribution upon entry into the subsequent homogenizing means, so that the resulting pupils for the different colors or Emission spectra are approximately overlap or equal. By the at least one first convergent lens between the at least one beam splitter and the field to be illuminated thus a telecentric color illumination of the field can be ensured.

In a further embodiment, the light sources LED light sources for generating an RGB illumination of the field to be illuminated and are brought together by a so-called X-Cube as a dichroic beam splitter for the RGB illumination of the field. The so-called X-Cube has the advantage in the combination of RGB illumination light compared to the merger by means of two crosswise arranged dichroic beam splitters, that he does not form a shadow line or shadow bars in the field.

In a further embodiment, a plurality of first converging lenses are formed on or at the at least one dichroic beam splitter on its light entrance side relative to the light path from the light sources to the field of the illumination system to be illuminated, the shapes of this first condenser lens being designed such that the dispersing effect of the beam splitter is reduced to the light passing through it. This ensures that the different power of the dichroic beam splitter for the different colors or emission spectra is compensated by the different refractive power of the individual converging lenses, that the light distributions of the different colors with respect to the angular distribution with respect to the optical axis on the light exit side of the beam splitter itself approximately equal to each other.

In one embodiment, the at least one first converging lens is arranged on the light path from the light sources to the field to be illuminated of the illumination system after the at least one first homogenization means. By means of the at least one first converging lens between the at least one beam splitter and the field to be illuminated, a telecentric illumination of the field can be ensured, whereby a uniform intensity distribution in the field and a uniform intensity distribution in the pupil can be ensured at the same time by the homogenizing agent.

In a further embodiment, at least one further second homogenizing agent for the light mixture is arranged on the light path from the light sources to the field to be illuminated of the illumination system after the at least one first converging lens, wherein the second homogenizing agent for light mixing is selected or composed of the optical elements of the group: Bar integrators, cavity integrators, fiber bundles, lens and / or mirror arrays. By using two homogenizing agents, the necessary light mixing requirement can be distributed among two different homogenizing agents. As a result, otherwise undesirable lengths of the single integrator can be avoided, for example, in rod or cavity integrators.

In one embodiment, in each case a first homogenizing means for mixing the light of the light source is provided between the light sources and the at least one beam splitter. This makes it possible to pre-mix the light separately for each of the colors or the emission spectra before the different colors are combined in the at least one dichroic beam splitter. This leads overall to a more compact design, since on the one hand two successive stages are used in homogenizing, whereby the homogenization is divided into two homogenizing, which may well be of different design and on the other hand, the first stage of the homogenizing immediately after the light sources and thus before at least one dichroic beam splitter is provided, as a result of which, at least in the case of rod or cavity integrators, the length of the second homogenizing agent after the at least one dichroic beam splitter is shortened.

In a further embodiment, Fresnel lenses are respectively arranged as first collecting lenses between the light source and the first homogenizing means. As a result, the divergence of the light of the light sources can be adjusted, whereby the light rays enter the subsequent homogenizing agent at as optimal an angle as possible for a light mixture. In this case, the Fresnel lenses can also be formed on the homogenization means, whereby a more compact design is made possible.

In one embodiment of the illumination system according to the invention, the light sources LED light sources for generating an RGB illumination of the field to be illuminated and at least a first converging lens is formed on or at the at least one dichroic steel divider, wherein on the light path from the light sources to the field to be illuminated At least one further second homogenizing agent for light mixing is arranged, wherein the at least one further second homogenizing agent for light mixing is selected or composed of the optical elements of the group: bar integrators, cavity integrators, fiber bundles, lens and / or mirror arrays. A second homogenizer allows the mixture of the light optimally divided between the two stages of homogenizing agents. By dividing the light homogenization in two stages, it is possible to make the homogenization of the field almost decoupled from the homogenization of the pupil by the corresponding positioning of the two homogenizing agents in the beam path.

In a further embodiment, at least one further second homogenizing agent for light mixing is provided on the light path from the light sources to the field to be illuminated of the illumination system after the at least one first homogenizing agent, wherein the second homogenizing agent for light mixing is selected or composed of the optical elements of the group: Bar integrators, cavity integrators, fiber bundles, lens and / or mirror arrays. In addition to the advantage of decoupling the homogenization in the field and in the pupil, the two-stage light homogenization also has an advantage with regard to the chromatic aberrations of the illumination system. The first stage of the homogenizing agent achieves a basic homogenization of the individual colors or emission spectra before the individual colors are combined with a respectively similar degree of homogeneity by the dichroic beam splitter. The residual chromatic aberrations produced by the dichroic beamsplitter can then be successfully extracted by the second stage of the homogenizers. Overall, this results in a lighting system, which is not dependent on the use of achromats or apochromats in its individual modules, which in turn can reduce costs.

In one embodiment, at least one of the homogenizing means in the form of rod integrators or cavity integrators has a tapering cross section along its longitudinal extent, the aspect ratio of which may also change along the longitudinal extent, and / or the at least one homogenizing agent in the form of rod integrators or cavity integrators has at several surface portions its surface has different local curvatures of the surface. This makes it possible to specifically control and optimize the light mixture within the illumination field. In particular, the light conductance can be redistributed between the X direction and the Y direction of the field.

In a further embodiment, the second homogenization means is composed of two mirror arrays which provide for a redistribution of the light conductance values in the two orthogonal directions of the field. This makes it possible to adapt the light source size or the emission angle distribution to the field size or the aspect ratio of the desired illumination field.

In one embodiment, the second homogenizing agent is composed of lens arrays and forms a so-called honeycomb condenser, wherein the honeycomb condenser is embodied by means of at least one sandwich-type spacer. Such a sandwich construction allows for separate production and quality testing of the honeycomb condenser, whereby an assembly-and adjustment-friendly optical element is produced with the finished honeycomb condenser, which optical element can be integrated into the lighting system in a manufacturing process without much effort. In particular, a honeycomb condenser, the lens arrays of which consist of continuous films printed, pressed and / or molded plastics, is also still very inexpensive to produce.

In a further embodiment, the illumination system according to the invention has at least one diffuser, wherein the diffuser is selected or composed of diffractive and / or refractive and / or holographic and / or scattering elements with regular and / or irregular structures. As a result, existing variations in the field and in the pupil can be subsequently smoothed after the homogenization of the light.

The object of the present invention is in addition to an illumination system according to the invention also solved by a coordinate measuring machine for detecting the coordinates of a workpiece, which comprises at least one optical sensor and an inventive illumination system for illuminating the workpiece during a measurement of the coordinates of the workpiece with the optical sensor.

Further features and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention with reference to the figures, the essential details of the invention show, and from the claims. The individual features can be realized individually for themselves or for several in any combination in a variant of the invention.

Embodiments of the invention will be explained in more detail with reference to FIGS. In these shows

1 a coordinate measuring machine in gantry design;

2 a schematic representation of a first embodiment of a lighting system;

3 a schematic representation of a second embodiment of a lighting system;

4 a schematic representation of a third embodiment of a lighting system;

5a a schematic representation of a first embodiment of a rod or cavity integrator;

5b a schematic representation of a second embodiment of a rod or cavity integrator;

5c a schematic representation of a third embodiment of a rod or cavity integrator;

6 a schematic representation of a fourth embodiment of a lighting system;

7 a schematic representation of a fifth embodiment of a lighting system;

8th a schematic representation of a sixth embodiment of a lighting system;

9 a schematic representation of a seventh embodiment of a lighting system;

10 a schematic representation of an eighth embodiment of a lighting system;

11a a schematic representation of a first embodiment of a honeycomb condenser with a first spacer;

11b a schematic representation of a second spacer for a honeycomb condenser;

11c a schematic representation of a third spacer for a honeycomb condenser;

12 a schematic exploded view of a honeycomb condenser in sandwich construction;

13 a schematic representation of a ninth embodiment of a lighting system;

14 a schematic representation of a tenth embodiment of a lighting system;

15a a schematic representation of a light source with a first homogenizing agent in the form of a first rod integrator; and

15b a schematic representation of a light source with a first homogenizing agent in the form of a second rod integrator.

1 shows purely by way of example a coordinate measuring machine 24 in so-called gantry construction. Coordinate measuring machines in bridge or column construction, as well as multi-point measuring instruments or articulated-arm coordinate measuring machines, are also commonly used in coordinate metrology.

The coordinate measuring machine 24 has a stylus 6 on, the interchangeable on a probe 5 is attached and the opposite the probe 5 in the three coordinate directions x, y and z can be deflected. The deflection of the stylus 6 in the three coordinate directions x, y and z is about three in the probe 5 detected encoder detected. The probe 5 in turn, it can be moved in the three coordinate directions x, y and z. For this purpose, the portal mechanism has a measuring unit 2 on, in the coordinate direction indicated by the arrow y opposite the measuring table 1 can be moved. Along the measuring table 1 spanning traverse of the measuring unit 2 in turn, the so-called measuring slide 3 movably guided in the direction indicated by the arrow x. On the measuring slide 3 again, the quill is 4 guided movably in the vertical direction indicated by the arrow z, so that the probe 5 can be moved via the portal mechanism in the three coordinate directions x, y and z. The measurement of a workpiece is now carried out such that the stylus 6 the workpiece to be measured 7 probed at intended measuring points, wherein in the probe 5 the deflection of the stylus 6 opposite the probe 5 is measured in the three coordinate directions x, y and z. Additionally, at the three incremental scales 8a - 8c , which are scanned by optical read heads, the current position of the probe 5 measured in the three coordinate directions x, y and z. To determine a measuring point, the scale measurement values now become 8a - 8c with the through the encoder in the probe 5 determined stylus deflections computed correctly and generated from this a measurement point.

To be able to measure now complex workpieces with a complex geometry, usually different styli are needed, which are kept in a magazine, not shown, and automated via a Changing device on the probe 5 can be changed. The different styli usually have one or more probe shafts, at the ends of probes, such as a probe ball or a cylinder can be attached. For example, a horizontal hole will only be made with a horizontally aligned stylus shaft, ie with a so-called laterally arranged stylus 6 , while a vertical hole can only be measured with a vertically aligned probe shaft.

The control of the measurement process and the drive means of the coordinate measuring machine, as well as the recording and evaluation of the measured values determined in this case by a control and evaluation 9 , which is realized here by way of example in this embodiment by a single computer. The control and evaluation unit 9 can also be connected to a control panel, not shown, with the control lever via the coordinate measuring machine can also be moved manually in the coordinate directions x, y and z, as well as other functions, such as a stylus change or operation of the measurement program can be made.

Alternatively to a probe 5 can the coordinate measuring machine 24 of the 1 also be equipped with an optical measuring system. This optical measuring system comprises a CCD or CMOS sensor or other photosensitive array for the spatially resolved conversion of light into computer-stored and usable signals, a lens and an illumination system for illuminating the workpiece to be measured. The optical measuring system can be moved selectively, for example with the help of the coordinate measuring machine to the point to be measured of the workpiece. There are then taken with the help of the CCD or CMOS sensor, the lens and the illumination system recordings of the workpiece. By applying image processing software to the images taken and taking into account the scale readings 8a - 8c of the coordinate measuring machine are then output the coordinates of the relevant structures considered.

It is understood that the present invention also applies to other types of coordinate measuring machines than those in 1 shown coordinate measuring machine 24 can be used in gantry design, especially in coordinate measuring machines in bridge or stand construction.

The 2 shows by way of example a first embodiment of a lighting system according to the invention 30 for metrological applications in one of the aforementioned coordinate measuring machines. It shows the 2 the arrangement of three light sources 31 . 32 . 33 with different emission spectra or colors around the input surfaces of a so-called X-Cube 35 with its crosswise arranged dielectric mirror surfaces for the colors red and blue. In the beam path between the light sources 31 . 32 . 33 and the x-cube entrance pages must be a collection and collimation of the light source emission to prevent light loss and thus an energy input into the environment of the coordinate measuring machine. To minimize the assembly and the adjustment effort, the necessary collecting lenses 37 . 38 . 39 advantageous directly on the respective entry surfaces of the so-called X-cube 35 be applied. Shown here is in 2 a version with Fresnel collimating lenses. As a result, short focal lengths can be realized, resulting in a compact design. In principle, however, it is also possible to apply other lenses or diffractive structures. For all cases of refractive lenses as converging lenses aspheres should preferably be installed, since with them on the one hand aberrations can be reduced and because on the other hand, a higher numerical aperture (NA) light source side can be realized. In addition, the shape of the lenses on the entrance surface should be designed to account for the dispersion of the material so that as much collimated RGB light as possible is present at the output of the X-Cube.

But even with the best possible collimation or alignment of the RGB light along an axis, this light will not be distributed homogeneously over the exit surface of the so-called X-Cube. However, a homogenization of the RGB light in the spatial and angular space can be achieved by using a so-called honeycomb condenser (WaKo). 41 consisting of two microlens arrays MLA1, MLA2, and a Fourier lens FL. Such a honeycomb condenser 41 with appropriate design, a complete mixing of all light rays in the field and in the pupil. Thus, any existing direction of the light rays is directed to any location in the field plane. This results in a homogeneous and uniform illumination in the field level with almost constant intensity over the entire illumination field, see the curves I (x) in accordance with colors or emission spectra 2 , Here, I means the local intensity at a field point plotted along the X-axis of the illumination system. The curves NA (x) in 2 For each field point along the X-axis, the proportion of numerical aperture from which the respective field point receives light of corresponding color. In this case, the numerical aperture NA is another measure of the size of the pupil and is given by the sine of the opening angle of the edge light rays, which just reach the field point. Due to the extensive constancy of the different curves NA (x) it can be seen that almost all field points of the Illumination field have an equal and constant pupil for all colors. In contrast, the curves I (NA) describe the intensity distribution of the RGB light via the NA or pupil. It should be noted that in an enlarged view of the curves I (NA) would be noted that they are parceled out due to the plots of the honeycomb condenser, the value I (NA) at the edge of each parcel drops to 0. However, the parceling due to the microlens arrays used is so fine that the zeros in the illustrated scale of curves I (NA) of the 2 can not be displayed. Due to this fact, over large parts of the pupil there is thus no uniform but a uniformly parceled intensity distribution.

To enhance the light mixing property of the illumination system according to the invention 30 can analogously to the illumination systems according to the invention described below 50 . 50a . 50b . 50c . 60 . 70 . 80 . 90 each rod integrators 51 . 52 . 53 as the first homogenizing agent immediately after the light sources 31 . 32 . 33 be used. As a result, the previously described honeycomb condenser 41 thus to another second homogenizing agent according to the present invention.

The 3 shows an advantageous possibility 30a for mechanical simplification of the structure according to the invention 2 , Here, the required microlens array MLA1 of the honeycomb condenser 41 into the entry collection lenses 37 . 38 . 39 of the 2 displaced forward. This will be the lens 37a . 38a . 39a of the 3 no rotationally symmetric lenses 37 . 38 . 39 be more, but have short-wave 2D shape deviations from the ideal aspherical basic form. A further advantage of the advancement of the microlens array MLA1 is that the dispersion can be taken into account by the three entrance sides each having slightly different MLAs in the surface of the converging lenses 37a . 38a . 39a exhibit. Advantageously, the microlens array MLA2 should be transferred to the exit surface of the X-cube. This, modeled by the MLA2 exit surface of the X-Cube has the reference numeral 40 in the 3 , Through this combination of collecting lenses 37 . 38 . 39 and the first microlens array MLA1 of the honeycomb condenser to new converging lenses 37a . 38a . 39a on the entry sides of the X-Cube and the design 40 of the second microlens array MLA2 on the exit side of the X-cube becomes a particularly compact design of the illumination system according to the invention 30a reached.

Also at the in 3 illustrated lighting system 30a can bar integrators 51 . 52 . 53 according to the following 4 to 15b as first homogenizing agents are used, whereby the homogenizing agents 37a . 38a . 39a . 40 In this case, they are to be regarded as further second homogenizing agents in the sense of the present invention. Of course, alternatively or additionally below the homogenizing agents 37a . 38a . 39a . 40 further homogenizing agents 41 ; SA; 65 ; 65a ; 85 according to the 7 to 14 for enhancing the light mixing properties of the lighting system 30a be provided. In the former case then the homogenizing agents 37a . 38a . 39 . 40 first homogenizing agent in the context of the present invention. It should be noted that due to the double character of the elements 37a . 38a . 39a these combine lenses as well as homogenizers in conjunction with element 40 are. In addition, it should be noted that in one embodiment of a first light mixture by rod integrators 51 . 52 . 53 at the light sources 31 . 32 . 33 according to the 15a and 15b these bar integrators may have first converging lenses F, so that in this case the converging lenses 37a . 38a . 39a of the lighting system according to the invention 30a are no longer first collecting lenses.

The lenses or MLAs 37 to 39 . 37a to 39a such as 40 on the entrance and exit surfaces of the lighting systems 30 and 30a can be produced in different ways: gray-tone lithography, injection molding, casting, stamping ... etc.

The application to the entry and exit surface can be done by applying, gluing, laminating, printing, casting, spraying or wringing. Optionally, however, a direct processing of the inlet and outlet surface can be considered. Thus, in general, the following methods can be used to produce these elements: additive machining processes, abrasive machining processes and / or the application of a separately fabricated optical element.

The 4 shows an embodiment of a lighting system according to the invention 50 , which requires very little adjustment effort. In the lighting system 50 are no longer on the entry surfaces of the X-Cube collecting lenses. Instead, so-called rod integrators 51 . 52 . 53 positioned on the entrance surfaces whose emissions are superimposed in the X-Cube as before. Instead of rod integrators, so-called cavity integrators can also be positioned in front of the entry surfaces of the X-Cube. Furthermore, fiber outputs can also be used. However, the latter two solutions are more expensive in terms of manufacturing costs, assembly and adjustment to achieve a good beam overlay. Due to this structure, initially no collimated beam is produced at the X-Cube. Output. Depending on the beam angle of the rod integrators, the dispersion will also lead to different bundle openings for the different colors at the exit of the X-Cube.

The 5a to 5c show three special designs for bar integrators. In the 5a the lateral surfaces of the rod having a constant cross-section over its length are deterministically surface-modulated (in the sketch sinusoidal), so that the surface has different local curvatures. This modulation allows for angular homogenization, which the bar alone would not allow. In general, however, all deterministic and statistical surface modifications come into question, depending on what the angular spectrum of the light bundle coupled into the rod looks like. The 5b shows a funnel-shaped copy of the rod, which allows an adjustment of the aspect ratio between the input and output side. The 5c shows surface-modulated formations of funnel-shaped rod integrators. These allow in addition to the aspect ratio change and angle homogenization also a redistribution of light conductance from one direction in any other, especially also orthogonal direction. Thus, aspect ratios (field size) and angle spectrum (NA) for selectable directions can be adjusted independently of each other. However, the light conductance remains constant over all directions and locations.

The surface modulation transversely to the orientation of the homogenizing agent and the variable over the length of the cross-section of the homogenizing agent are basically feasible even with cavity integrators.

The 6 shows a variation 50a of in 3 illustrated illumination system 50 with a collimation sphere or sphere 55 on the output side of the X-Cube 35 , This can be the lens 55 generally be performed as a chromatically corrected lens. Furthermore, the lens may also be shown as a Fresnel lens as shown 55 be executed. Through such a lens 55 It is then possible on the one hand to collimate the light beams or to align them parallel to the optical axis and, on the other hand, to correct the longitudinal chromatic aberration of the illumination system.

The 7 shows a training 50b of in 6 illustrated illumination system 50a in which below the X-Cube 35 a honeycomb condenser (WaKo) 41 consisting of two microlens arrays MLA1, MLA2 in combination with a Fourier lens FL for further light mixing or image of the output of the X-cube light leaving the illumination field. The number of lenses of the microlens arrays MLA1, MLA2 determines the number of parcels into which the incident light beam is split, in order then to average out inhomogeneities in the image plane by simultaneously superimposing all the parcels. Through such a WaKo 41 homogeneous illumination can be achieved both in the space of the field and in the angular space of the pupil. In addition, the WaKo 41 be designed as a telescope, so that in the X and Y direction of the field different field widths can be achieved. This is in 7 represented by the different widths in the X and Y directions I (x), I (y), I (NAx), I (NAy).

This function is similar to the above-described variation of the aspect ratio between input and output at the rod integrator. However, it differs in that with the microlens array alone, no redistribution of light conductance between the axes of the system is possible. Therefore, field width ratio and illumination ratio are "reciprocal". Thus, the restriction of the field in the Y direction is paid for by increasing the intensity distribution in the pupil in the Y direction, see I (y) and I (NAy) in comparison to I (x) and I (NAx) in FIG 7 ,

The addition of microlens arrays can also in the embodiments of the rod integrators according to 5b) or c), since honeycomb condensers in the configuration shown can be used for suppression of beam direction noise. Thus, for example, the homogeneous and time-invariant illumination in the field would also be possible for temporally changing light sources. The interface in the X-Cube 35 where the prisms collide, is through the honeycomb condenser 41 also averaged out, or caused by her inhomogeneity in the primary physical space is washed out by it. The honeycomb condenser 41 also allows subsequent homogenization of the chromatic defects at the interfaces in the X-Cube 35 ,

The rod integrators 51 . 52 . 53 of the embodiment 50b according to the 7 represent first homogenizing agent in the sense of the present invention. Accordingly, the honeycomb condenser 41 a further second homogenizing agent, which in the beam path of the light sources 31 . 32 . 33 to the field to be illuminated subsequently the first homogenizing means, the X-cube and the condenser lens 55 is arranged.

Analogous to the in 3 shown displacement of the MLA1 on the X-Cube can be the MLA1 accordingly 8th for the embodiment 50c in the exit surface of the X-Cube 35 be placed. This preserves the condenser lens 55 additionally the microlens function of the MLA1 and becomes a multi-function lens 55a , which are analogous to the lenses 37a . 38a . 39a through the microlenses loses the original rotational symmetry.

As already related to 7 in terms of the effect of the honeycomb condenser 41 If necessary, field widths can also be changed independently of one another in two directions. However, no loss-free change of the optical conductivity is possible here. In other words, changes in the light conductance are only possible by dimming. A "redistribution" of optical moduli from the X to the X direction is with a honeycomb condenser 41 not possible.

However, such a lossless change in the light conductance in one direction is at the expense of the other direction with a mirror arrangement SA consisting of two mirror arrays 57 . 58 possible, see the exemplary embodiment 60 in 9 , The mirror arrays are two periodically arranged mirror arrays 57 . 58 , which in addition to a homogenization analogous to the honeycomb condenser 41 Also allow redistribution of Lichtleitwerten from one direction in the other direction. This redistribution is carried out analogously to the redistribution by the mantle surface modulation of the rod integrator according to the 5a respectively. 5c ,

In the 9 is this lossless Lichtleitwertänderung in one direction at the expense of the other direction through the two intensity distributions I (x) and I (y) over the field directions X and Y shown. When changing the mirror arrays 57 . 58 or their assignment to mirrors, for example, the intensity distribution I (x) in the field direction X can be widened. In return, the intensity distribution I (y) in the field direction Y is then reduced. These are in the 9 the states before and after the Lichtleitwertanpassung shown and the linkage of I (x) with I (y) in the Lichtleitwertänderung indicated by arrows.

Frequently, apparent increases in light conductance are advantageously achieved with microlens arrays. However, on closer examination, these apparent increases in light conductance are only achieved by a trick. The honeycomb condenser is designed so that a holey distribution results in the phase space. That is, not all places in the field are exposed, or there are no longer all angles of incidence, or both. The often associated negative influence on the illumination and thus image quality is then circumvented by the holey distribution is washed out again. This is done by so-called diffusers. An embodiment 70 with such diffusers is in the 10 shown, the diffusers D in the most appropriate form both at the entrance and at the exit of the honeycomb condenser 41 are arranged. In the diffusers D, it may be z. B. to ground glass, holographic but also irregularly structured surfaces. Mandatory to phase space filling is only a diffuser D, this should preferably behind the honeycomb condenser 41 be installed.

Typically, the location of the microlens arrays MLA1, MLA2 in the honeycomb condenser 41 relative to each other for proper function of importance. Misalignments generally indicate deviations from the desired or best possible homogenization. The complex assembly and adjustment devices, such as. B. in semiconductor lithography systems for setting all 6 degrees of freedom are quite common, can not be used in the low-cost area of a lighting system for metrology applications. Nevertheless, in order to achieve a good and stable alignment of the lens arrays to each other, it is advisable to use the honeycomb condenser 41 to do as a sandwich. The two microlens arrays MLA1, MLA2 represent the sandwich levels, between which suitable spacers 71 . 72 , or 73 are inserted, see 11a) to c). Both 11b) and 11c) only the spacer is shown.

Basically, a honeycomb condenser would be 41 with irregular structures or an irregular pattern across the optical axis particularly useful. However, the microlens arrays MLA1 and MLA2 would also have to be designed with irregularly sized cells. However, irregular lens distributions have so far not been specifically pursued in the microlens arrays since they are not easy to implement in terms of production technology. With the diffusers D, however, this irregular processing already exists. This irregular processing in the diffusers D thus represents an additional degree of freedom, with which under certain circumstances field profiles or their distributions can be adjusted.

The spacers 71 . 72 . 73 can have hexagonal, square, round, n-square or even completely irregular structures. Conceivable according perforated plastic films or plates. But also punched sheets or glued, welded, soldered honeycomb structures in plastics or sheet metal as well as ceramic structures can be used. In addition to the associated costs, the choice of material is also decisively determined by whether the spacer only has to ensure the distance, or whether it should additionally have a stiffening function, for example if the WaKo is to become very large in comparison to its thickness. The latter would be in a honeycomb condenser 41 with a short focal length and a large area of the case.

The 12 shows the most expedient embodiment of a low-cost homogenizer 65a with high stability. A first diffuser D is followed by a first spacer or spacer S followed by the two microlens arrays MLA1 and MLA2, likewise with a spacer or spacer S therebetween. The conclusion is again formed by a spacer or spacer S, which supports a second diffuser D.

The 13 shows a compact, efficient, stable lighting system 80 in quasi-monolithic design, which allows a homogeneous multi-color lighting a field. In this lighting system 80 is by means of a further spacer or spacer S of the sandwich honeycomb condenser 65a of the 12 on the suitably fresnellierte exit surface optics 55 of the X-Cube 35 applied. After exiting the lighting system 80 can be a structuring of the pupil of the lighting system 80 by inserting a diaphragm Σ. This diaphragm Σ partially fades the beam bundles which are homogeneous in the spatial space. Subsequently, the Fourier lens FL translates the partially dimmed location in a partially dimmed direction in the illumination field. One obtains a location-independent structured illumination, see the illustrated curves I (x) for the intensity distribution over the field and I (NA) for the intensity distribution over the pupil of the illumination system 80 with a so-called annular aperture Σ. However, the diaphragm Σ can basically be designed arbitrarily, in order to allow any structured illumination. Basically, the aperture could also be installed between MLA1 and MLA2 (direct dimming in the angle spectrum). However, they would then have to be written frequently according to the number of cells and be significantly reduced, which would greatly increase the effort and the influence of manufacturing tolerances. A summary of aperture Σ and Fourier lens FL in another sandwich plane with a spacer S of the sandwich honeycomb condenser 65a is also possible. Such a structure is left in the 13 shown.

The 14 shows a manufacturing technology simpler version of a lighting system according to the invention 90 , Here is the sandwich honeycomb condenser 65a of the 13 through a rod integrator 85 been replaced. This embodiment 90 points to the embodiment 80 the advantage of less complexity and possibly better stability. However, this embodiment requires 90 for a corresponding homogenization more space, since the homogenization via multiple total reflections takes place on the Stabmantelfläche, which requires sufficient rod length for a sufficient number of reflections. The 14 is not to scale with respect to the ratio of rod cross section to rod length.

The curves I (x) in 14 show the intensity distributions for the different colors in the field direction X of the illumination system 90 , It can be clearly seen that the intensity for each of the colors or the emission spectra over large parts of the field in the X direction is almost constant and therefore uniform. The different colors of the light sources 31 . 32 . 33 are represented by different lines. The curves I (NA) describe the intensity distributions of the RGB light via the NA or pupil. It should be noted that if we look closely at the curves I (NA) we would see that they are parceled out due to the kaleidoscope effect of the rod integrator, with the value I (NA) falling to 0 at the edge of each plot. However, the parceling due to the bar integrator used is so fine that the zeros in the illustrated scale of curves I (NA) of the 2 can not be displayed. Due to this fact, over large parts of the pupil there is thus no uniform but a uniformly parceled intensity distribution.

The 15a shows by way of example the coupling of the LED light beam into a rod integrator, for example the rod integrator 51 in front of the X-Cube 35 , The LED light source L, for example, the light source 31 the embodiments 50 . 50a . 50b . 50c . 60 . 70 . 80 . 90 , stands before a collecting Einkoppellinse F, which advantageously as a Fresnel lens F on the inlet side of the rod integrator 51 is executed. In the cavity between LED light source L and Fresnel lens F can advantageously be filled to increase the numerical aperture (NA) an immersion medium I. The rod integrator 51 can be glued to the LED light source L. In the event that the whole arrangement is carried out inexpensively in plastic optics, but the LED light source L can also be pressed. For high-performance designs, a heat sink K made of thermally highly conductive material will advantageously be in contact with the LED light source L or the LED housing. The embodiments in the 15a and in the 15b clarify differences, as they result from the different light conductance of LED light sources L and rod integrators 51 respectively. 52 can result. In general, the luminous area of the LED light source will be small against the LED housing. Depending on the required homogenization and the required luminous area at the bar outlet, it may then be necessary to use a bar with a large cross - section as in the design of the 15a or a rod with a small cross section corresponding to 15b to use. In the event that the rod cross-section is equal to or smaller than the LED housing cross-section, the rod end shall be designed with a corresponding projection to clasp the LED, see 15b , The projection should be advantageously adapted to increase the efficiency of the collecting force of the lens F, so that the marginal rays of the LED light source L after collection by the converging lens F already perform a total reflection on the rod shell surface and do not enter the projection.

Claims (16)

Lighting system ( 30 ; 30a ; 50 ; 50a ; 50b ; 50c ; 60 ; 70 ; 80 ; 90 ) for generating an incident bright field for metrology applications comprising a plurality of light sources ( 31 . 32 . 33 ) with mutually different emission spectra and at least one dichroic beam splitter ( 35 ) for superimposing the light from at least two of the light sources ( 31 . 32 . 33 ) along an optical axis of the illumination system ( 30 ; 30a ; 50 ; 50a ; 50b ; 50c ; 60 ; 70 ; 80 ; 90 ), characterized in that on the light path of the light sources ( 31 . 32 . 33 ) to the field of the illumination system to be illuminated ( 30 ; 30a ; 50 ; 50a ; 50b ; 50c ; 60 ; 70 ; 80 ; 90 ) between the light sources ( 31 . 32 . 33 ) and the at least one beam splitter ( 35 ) and / or between the at least one beam splitter ( 35 ) and the field to be illuminated at least a first homogenizing agent ( 37a . 38a . 39a . 40 ; 41 ; 51 . 52 . 53 ) is provided for light mixing, wherein the at least one homogenizing agent ( 37a . 38a . 39a . 40 ; 41 ; 51 . 52 . 53 ) is selected or composed of the optical elements of the group: rod integrators, cavity integrators, fiber bundles, lens and / or mirror arrays, andwherein or on the at least one dichroic steel divider ( 35 ) at least one first converging lens ( 37 . 38 . 39 ; 37a . 38a . 39a ; 55 ; 55a ) is formed by means of additive processing methods, ablative processing methods and / or by the application of a separately manufactured optical element in the form of an asphere, a Fresnel lens and / or a diffractive optical element (DOE). Lighting system ( 30 ; 30a ; 50 ; 50a ; 50b ; 50c ; 60 ; 70 ; 80 ; 90 ) according to claim 1, wherein on the light path from the light sources ( 31 . 32 . 33 ) to the field of the illumination system to be illuminated ( 30 ; 30a ; 50 ; 50a ; 50b ; 50c ; 60 ; 70 ; 80 ; 90 ) between the light sources ( 31 . 32 . 33 ) and the at least one beam splitter ( 35 ) and / or between the at least one beam splitter ( 35 ) and the field to be illuminated at least one first converging lens ( 37 . 38 . 39 ; 37a . 38a . 39a ; 55 ; 55a ; F) is arranged. Lighting system ( 30 ; 30a ; 50 ; 50a ; 50b ; 50c ; 60 ; 70 ; 80 ; 90 ) according to claim 1 or 2, wherein the light sources ( 31 . 32 . 33 ) LED light sources (L) for generating an RGB illumination of the field to be illuminated and by a so-called X-cube as a dichroic beam splitter ( 35 ) for the RGB illumination of the field. Lighting system ( 30 ; 30a ) according to claim 1, wherein a plurality of first converging lenses ( 37 . 38 . 39 ; 37a . 38a . 39a ) on or at the at least one dichroic beam splitter ( 35 ) on the light entrance side with respect to the light path from the light sources ( 31 . 32 . 33 ) are formed to the field to be illuminated of the illumination system and wherein the shapes of this first converging lens ( 37 . 38 . 39 ; 37a . 38a . 39a ) are designed so that the dispersion effect of the beam splitter ( 35 ) is reduced to the light passing through it. Lighting system ( 30 ; 30a ) according to claim 1 or 4, wherein the at least one first converging lens ( 37 . 38 . 39 ; 37a . 38a . 39a ) on the light path from the light sources ( 31 . 32 . 33 ) to the field of the illumination system to be illuminated ( 30 ; 30a ) after the at least one first homogenizing agent ( 51 . 52 . 53 ) is arranged. Lighting system ( 30 ; 30a ) according to claim 5, wherein on the light path from the light sources ( 31 . 32 . 33 ) to the field of the illumination system to be illuminated ( 30 ) after the at least one first convergent lens ( 37 . 38 . 39 ; 37a . 38a . 39a ) at least one further second homogenizing agent ( 41 ; SA; 65 ; 65a ; 85 ) is arranged for light mixing, wherein the second homogenizing agent ( 41 ; SA; 65 ; 65a ; 85 ) is selected or composed of the optical elements of the group: rod integrators, cavity integrators, fiber bundles, lens and / or mirror arrays. Lighting system ( 30 ; 30a ; 50 ; 50a ; 50b ; 50c ; 60 ; 70 ; 80 ; 90 ) according to one of claims 1 to 3, wherein between the light sources ( 31 . 32 . 33 ) and the at least one beam splitter ( 35 ) in each case a first homogenizing agent ( 51 . 52 . 53 ) for mixing the light of the light source ( 31 . 32 . 33 ) is provided. Lighting system ( 30 ; 30a ; 50 ; 50a ; 50b ; 50c ; 60 ; 70 ; 80 ; 90 ) according to claim 7, wherein between the light source ( 31 . 32 . 33 ) and the first homogenizing agents ( 51 . 52 . 53 ) Fresnel lenses (F) are arranged as first collecting lenses. Lighting system ( 30 ; 30a ; 50 ; 50a ; 50b ; 50c ; 60 ; 70 ; 80 ; 90 ) according to claim 8, wherein the Fresnel lenses (F) on the homogenizing means ( 51 . 52 . 53 ) are formed. Lighting system ( 30 ; 30a ; 50 ; 50a ; 50b ; 50c ; 60 ; 70 ; 80 ; 90 ) according to one of claims 7 to 9, wherein the light sources ( 31 . 32 . 33 ) LED Light sources (L) for generating an RGB illumination of the field to be illuminated and wherein at least a first convergent lens ( 37 . 38 . 39 ; 37a . 38a . 39a ; 55 ; 55a ) on or at least one dichroic steel divider ( 35 ) is formed and wherein on the light path of the light sources ( 31 . 32 . 33 ) to the field of the illumination system to be illuminated ( 30 ; 30a ; 50 ; 50a ; 50b ; 50c ; 60 ; 70 ; 80 ; 90 ) after the at least one first convergent lens ( 37 . 38 . 39 ; 37a . 38a . 39a ; 55 ; 55a ) at least one further second homogenizing agent ( 41 ; SA; 65 ; 65a ; 85 ) is arranged for light mixing, wherein the at least one further second homogenizing agent ( 41 ; SA; 65 ; 65a ; 85 ) is selected or composed of the optical elements of the group: rod integrators, cavity integrators, fiber bundles, lens and / or mirror arrays. Lighting system ( 30 ; 30a ; 50 ; 50a ; 50b ; 50c ; 60 ; 70 ; 80 ; 90 ) according to one of the preceding claims, wherein on the light path from the light sources ( 31 . 32 . 33 ) to the field of the illumination system to be illuminated ( 30 ; 30a ; 50 ; 50a ; 50b ; 50c ; 60 ; 70 ; 80 ; 90 ) after the at least one first homogenizing agent ( 37a . 38a . 39a . 40 ; 51 . 52 . 53 ) at least one further second homogenizing agent ( 37a . 38a . 39a . 40 ; 41 ; SA; 65 ; 65a ; 85 ) is provided for light mixing, wherein the second homogenizing agent ( 37a . 38a . 39a . 40 ; 41 ; SA; 65 ; 65a ; 85 ) is selected or composed of the optical elements of the group: rod integrators, cavity integrators, fiber bundles, lens and / or mirror arrays. Lighting system ( 30 ; 30a ; 50 ; 50a ; 50b ; 50c ; 60 ; 70 ; 80 ; 90 ) according to claim 1, 6, 10 or 11, wherein at least one of the homogenizing agents ( 51 . 52 . 53 ; 85 ) in the form of the rod integrators or the cavity integrators along its longitudinal extent has a tapered cross-section, the aspect ratio of which may also change along the longitudinal extent and / or the at least one homogenizing agent ( 51 . 52 . 53 ; 85 ) in the form of the rod integrators or the cavity integrators has at different surface portions of its surface on different local curvatures of the surface. Lighting system ( 70 ) according to claim 6, 10 or 11, wherein the second homogenizing agent (SA) consists of two mirror arrays ( 57 . 58 ), which provide for a redistribution of the light-conducting values in the two orthogonal directions of the field. Lighting system ( 30 ; 50b ; 50c ; 70 ; 80 ) according to claim 6, 10 or 11, wherein the second homogenizing agent ( 41 ; 65 ; 65a ) is composed of lens arrays and a so-called honeycomb condenser ( 41 ; 65 ; 65a ) and wherein the honeycomb condenser ( 41 ; 65 ; 65a ) is carried out by means of at least one sheet-like spacer (s) in sandwich construction. Lighting system ( 30 ; 50b ; 50c ; 70 ; 80 ) according to one of the preceding claims, wherein the lighting system ( 30 ; 50b ; 50c ; 70 ; 80 ) comprises at least one diffuser (D), wherein the diffuser (D) is selected or composed of diffractive and / or refractive and / or holographic and / or scattering elements with regular and / or irregular structures. Coordinate measuring machine ( 24 ) for detecting the coordinates of a workpiece ( 7 ) comprising at least one optical sensor and a lighting system ( 30 ; 30a ; 50 ; 50a ; 50b ; 50c ; 60 ; 70 ; 80 ; 90 ) according to one of the preceding claims for illuminating the workpiece ( 7 ) during a measurement of the coordinates of the workpiece ( 7 ) with the optical sensor.

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