Lighting device for producing linear lighting

Abstract

The invention relates to an illumination device (10) for generating linear illumination in a longitudinal direction, comprising: a lens element (12) defining an optical center plane (16) in the longitudinal direction and having a constant cross-sectional profile over at least one section; one or more light sources (14, 14 ') arranged on one side of the lens element in the longitudinal direction, the lens element having a transparent lens body, the lens body comprising: one or more coupling-in surfaces (60, 61, 62) facing the light sources through which light emitted by the light sources enters the lens body; one or more reflective surfaces (68, 69) on which at least part of the coupled light is totally reflected within the lens body; and one or more coupling-out surfaces (70, 71, 72) through which the coupled-in light exits from the lens body, and wherein the lens element and the one or more light sources are arranged such that light exiting from the lens body through the coupling-out surfaces converges.

Description

[0001] The invention relates to an illumination device for generating a linear illumination along a longitudinal direction, comprising a lens element defining an optical center plane along the longitudinal direction and having a constant cross-sectional profile along the longitudinal direction over at least one section, one or more light sources arranged on one side of the lens element along the longitudinal direction. The invention further relates to a device for optically detecting an object ("detection device") having such an illumination device.

[0002] The illumination device and the detection device according to the invention are particularly suitable for inspecting transparent material strips or objects (for example, glass or structural glass) and non-transparent material strips or objects (for example, material strips or objects having a painted surface). Possible defects are in particular damage on the surface and / or inclusions (for example, air bubbles or foreign bodies) or inhomogeneities in the transparent material.

[0003] By way of example, reference is made to documents EP 1 742 041 A1 and EP 1 030 173 A1. These documents disclose devices for surface detection of movable products. Therein, at least one camera is used to capture images of the moving surface to be inspected. Furthermore, an illumination configuration is provided, in which individual or multiple light sources of a plurality of light sources arranged in succession in the transport direction are selectively activated or deactivated. The individual images thus generated are evaluated in order to identify defects on the surface.

[0004] Document DE 198 13 073 A1 relates to the determination of the optical quality of flat glass. To this end, a color line array camera is provided, which observes the illumination reflected by the glass or reflected. Here, the focus of the camera lies on the plane of the glass. An illumination device arranged transversely to the transport direction illuminates the surface in two different colors in alternation.

[0005] From document EP 3 236 198 A1, an illumination device for generating a linear illumination is also known. The light sources here are LEDs arranged in a row, which are divided into at least two groups that can be switched independently of one another. Furthermore, the light sources are also assigned a condenser optical element, which can consist, for example, of a Fresnel lens or a cylindrical lens.

[0006] Cylindrical lenses have proven to be suitable for generating a linear illumination. They can be manufactured relatively cost-effectively and are made as extruded profiles in almost any length. The imaging properties are good enough to form the light emitted from the LEDs into a converging light beam with a focal point at a working distance of approximately 50 mm.

[0007] It is an object of the invention to improve the efficiency of the illumination device to generate a linear illumination with relatively low or more favorable manufacturing costs.

[0008] This object is achieved by the lighting device of claim 1. The lighting device for generating a linear illumination along a longitudinal direction comprises a lens element defining an optical center plane, also referred to as optical plane, along the longitudinal direction, and having a constant cross-sectional profile along the longitudinal direction over at least one section. The lighting device further comprises one or more light sources arranged along the longitudinal direction on one side of the lens element. The lens element has a transparent lens body comprising one or more coupling-in faces facing the one or more light sources through which light emitted by the one or more light sources enters the lens body, one or more reflection faces on which at least part of the coupled-in light undergoes total internal reflection within the lens body, and one or more coupling-out faces through which the coupled-in light exits the lens body. The lens element and the light source are arranged such that the light exiting the lens body through the coupling-out faces converges.

[0009] The coupling-in faces, the reflection faces and the coupling-out faces are collectively referred to as the term "optical faces" through which the light beam enters or exits the lens body or on which the light beam is reflected. These faces have an optical function, i.e. the light beam passes through these faces without undergoing refraction, for example. The quality and tolerance requirements for these faces are generally higher than for surface sections that do not have an optical function, since these surface sections are oriented, for example, parallel to the light ray path.

[0010] Unlike a cylindrical lens, total reflection occurs on the reflection faces within the lens element according to the invention. This achieves a generally higher light output efficiency, in particular when LEDs with a wide emission characteristic are used as light sources. The lens element according to the invention allows the use of a lens geometry that has an improved light output efficiency compared to a cylindrical lens when using the same LED, since those light rays that extend at a large emission angle (e.g. > 60° to the optical plane) can be used effectively. Furthermore, the lens element according to the invention also allows the use of more efficient LEDs with a wider emission characteristic. This improved imaging performance of such LEDs in combination with the lens according to the invention increases the light output efficiency by up to 220% compared to the use of known LED cylindrical lens combinations.

[0011] At the same time, the lens element according to the invention has a much smaller volume than a cylindrical lens at the same structural size, thereby also reducing the use of material and thus the manufacturing costs.

[0012] The principle of total internal reflection is basically known in various applications related to LED light sources. For example, so-called TIR lenses are used in lighting spots or in the automotive sector for headlamps and tail lamps. The present invention is based on the insight that the respective geometry can also be transferred to a lens element which has a constant cross-sectional profile along its longitudinal direction over at least one section of the lens element, preferably over the entire optically effective length, and, for reasons of manufacturing technology, particularly preferably over the entire profile length. Here, the challenge is to meet the necessary dimensional and surface tolerances over the entire optically effective length of the lens element.

[0013] Cylindrical lenses have a circular cross-section. This has the advantage that uniform stresses are formed in the material during cooling after shaping, which ensure shape stability and thus sufficient optical quality. In general, the geometry of TIR lenses can also be produced as a long profile in an extrusion process to produce linear lighting. However, the symmetry of the geometry of TIR lenses is necessarily significantly lower than that of a cylinder. In general, the optical center plane in the longitudinal direction is the only plane of symmetry of the profile. Accordingly, the respective extruded profile is susceptible to production-induced deformations, in particular when very large lengths are manufactured.

[0014] Therefore, preferably, the at least one outcoupling face has at least one step structure which is formed by a displacement of the at least one outcoupling face essentially in the direction of the optical center plane.

[0015] By this measure, the thickness or the profile cross-sectional area of the profile can be reduced in a targeted manner, which can be used to cool the profile more uniformly. Furthermore, in this way, a profile which is up to 70% lighter than a cylindrical lens with comparable imaging properties can be realized.

[0016] Fundamentally, the individual step structure already contributes to improving the dimensional stability and the shape stability of the profile. With increasing number of step structures, the results in this respect are better. But a larger number of steps leads to an increase in Fresnel losses. A good compromise is a three-step structure of the outcoupling face.

[0017] By each step structure, the outcoupling face is divided into two adjacent optically functional outcoupling sub-faces which are connected to each other by a displacement face which has no optical function. Therefore, the "displacement of the at least one outcoupling face essentially in the direction of the optical center plane" means that the displacement face lies in a plane which extends parallel to the center plane and is in any case inclined to the center plane by no more than 15°, preferably by no more than 12°, particularly preferably by no more than 10°.

[0018] The at least one step structure is particularly preferably formed by an offset of the at least one outcoupling face parallel to the beam direction of the light beam exiting along the edge of the step structure.

[0019] The edge of the step structure is located at the intersection of the plane of the outcoupling face and the plane of the offset face. Of course, the edge is not actually configured arbitrarily sharply, but is usually rounded off for manufacturing reasons. A typical rounding radius is between 0.1 mm and 0.5 mm. The geometrical data should therefore generally be understood as including deviations from the described ideal geometry due to tolerances or manufacturing-technological necessities.

[0020] Preferably, the at least one step structure is dimensioned and arranged such that, for the reflected light beam, the maximum distance S max and, for the reflected light beam, the minimum distance S min or the minimum distance S min of the direct light beam between the in- and outcoupling face in the lens body applies: 1 < S max / S min < 6.

[0021] This measure ensures that the thickness variation of the profile in the direction in which the light beam extends within the lens does not exceed the range required for the optical path within the lens element, which ensures that the profile cools sufficiently uniformly after shaping and enables long profiles to be produced while meeting the tolerances required for the optical imaging properties.

[0022] The at least one outcoupling face preferably has a convexly curved surface through which the light beam which (for the most part) does not undergo reflection within the lens body exits the lens body.

[0023] Described here is the direct light beam, which enters the lens body through the in- coupling face near the centre plane and exits again on the opposite side without total reflection, while being focused on the convex outcoupling face. This describes the (calculated) ideal geometry of the illumination device. In reality, due to manufacturing tolerances and the areal extension of the light source, a small proportion of the reflected light beam also exits the lens body through the convex outcoupling face, in the sense that “for the most part” the light beam which does not undergo reflection within the lens body is also mentioned here.

[0024] The at least one outcoupling face is inclined towards the centre plane through which the light beam which (for the most part) undergoes reflection within the lens body exits the lens body.

[0025] "Tilted towards the central plane" describes the case where an acute angle is formed between the coupling surface and the central plane on the outside of the lens element. Therefore, in the case where the two coupling surfaces are arranged mirror-symmetrically with respect to the central plane, it can also be said that the coupling surfaces are tilted inwards. Due to the inwardly tilted coupling surfaces, the lens element has a smaller volume, similar to a stepped structure, which has a positive impact on manufacturing and weight. However, the tilt angle cannot be chosen arbitrarily large, as this comes at the cost of sacrificing imaging characteristics. Specifically, an excessively large tilt angle leads to higher Fresnel loss.

[0026] The reflecting surface is preferably designed such that the light beam reflected thereon is already focused in the first approximation, so that when the beam exits through the coupling surface, refraction is no longer needed or desired. Therefore, the coupling surface is preferably inclined relative to the central axis, such that the reflected beam extends substantially perpendicular to the coupling surface. It is tolerable if a small portion of the direct beam exits the lens body through the inclined coupling surface; in this sense, it is also mentioned that "most" of the beam is reflected within the lens body. In practice, it is also impossible for the reflected beam to ideally extend perpendicularly to the coupling surface. This is impossible because, for example, the light source is planar. In this sense, it is sufficient if the reflected light extends perpendicularly to the coupling surface within an angular tolerance of + / -3°. Here, this is considered substantially perpendicular.

[0027] At least one stepped structure is preferably formed in at least one coupling surface that is inclined toward the central plane.

[0028] The combination of the inward tilt of the coupling surface and the stepped structure further improves the uniform cooling of the profile after forming, while maintaining a small structural size without sacrificing imaging accuracy.

[0029] The lens volume preferably has a maximum extension dimension L in cross-section. max and minimum extension size L min The maximum extension dimension L max Let L represent the diameter of the largest circle that lies entirely within the cross-section, and the smallest extension dimension L within it. min This represents the minimum linear distance between the input and output surfaces, or between the reflecting and output surfaces, where: 1 < L max / L min <5.

[0030] This design can also be achieved by dimensional design and arrangement of at least one stepped structure, and ensure that the thickness variation of the profile does not exceed 5 factors (Faktor) while taking into account the optical imaging characteristics within the lens. This ensures uniform cooling of the profile after forming and enables the manufacture of profiles up to 6 meters long, while meeting the tolerances required for optical imaging characteristics.

[0031] The cross-sectional profile has a cross-sectional area and a circumferential length, the ratio of the cross-sectional area to the circumferential length being further preferably between 2.0 mm and 4.5 mm, particularly preferably between 2.5 mm and 4.0 mm.

[0032] The design also relates to a further improvement of the cooling of the profile after the shaping.

[0033] The ratio between the length and the maximum width of the lens element is at least 10:1, preferably 20:1, particularly preferably 50:1.

[0034] The length is the maximum extension of the lens element in the longitudinal direction. The maximum width is the maximum extension of the lens element perpendicular to the center plane.

[0035] The lens element has an extrudable profile.

[0036] The extrudable profile is a profile whose cross-section perpendicular to the longitudinal direction remains constant at all times. In plastic shaping, the extrusion process is used for this purpose. Furthermore, the profile is designed in such a way that it can be manufactured within the desired tolerances.

[0037] The lens element is particularly preferably made of PMMA.

[0038] The light source is preferably formed by one or more LEDs. Thus, for example, a plurality of light sources for generating light of different wavelengths can be formed by a plurality of LEDs of the same construction arranged next to one another in the longitudinal direction.

[0039] The object is also achieved by a device for optically detecting an object, the device having an illumination device as described above, wherein the object and the illumination device can be moved relative to one another in a movement direction, wherein the longitudinal direction is arranged transversely to the movement direction, and wherein the illumination device can be aligned to the object such that the light emitted from the lens body through the outcoupling surface falls on the surface of the object. The device for optical detection also comprises a capturing device for capturing an image of the illuminated object and a computing unit for evaluating the captured image.

[0040] The device for optical detection is configured for installation in, for example, a transport device or a production device with which the object is transported in the movement direction. The device is fixedly arranged on the transport device or production device such that the object is guided past the lens element at a distance which preferably corresponds to the focal length of the lens element. This distance, also referred to as working distance, is measured from the outcoupling side end face of the lens element to the surface of the object along the center plane.

[0041] In practice, the light bundle of such a TIR lens does not converge on a one-dimensional focal line, but rather forms a light waist. The focal length is therefore to be understood as a focal length range, within which the deviation of the illumination intensity on the illuminated object surface from the maximum illumination intensity does not exceed 25%. In certain applications, the device can also be operated in such a way that the object is guided past the lens element at a working distance that lies outside the focal length range, which leads to a reduced concentration of the light bundle on the object surface. BRIEF DESCRIPTION OF DRAWINGS

[0042] Further features and advantages of the present application will be described below on the basis of embodiments in the drawings. In the drawings: Figure 1 A cross section of a lens element according to a first embodiment of the application is shown; Figure 2 A cross section of a lens element according to a second embodiment of the application is shown; Figure 3 A cross section of a lens element according to a third embodiment of the application is shown; Figure 4 A lens element according to different parameterizations of the application is shown; and Figure 3 Figure 5 A comparison of the illumination intensity using an illumination device according to the application and using an illumination device with a cylindrical lens is shown.

[0043] A first embodiment of an illumination device 10 according to the application is shown in a cross section in a lateral direction to its longitudinal direction in Figure 1 The illumination device 10 comprises a lens element 12 and a light source 14 arranged on one side of the lens element 12 in the longitudinal direction. The lens element 12 has the shown cross-sectional profile on at least one section and preferably on its entire optically effective length in the longitudinal direction. The lens element 12 is mirror-symmetric with respect to a center plane 16 extending in the longitudinal direction.

[0044] The lens element 12 has a transparent lens body with three coupling-in faces 20, 21, 22 facing the light source 14, through which the light emitted by the light source 14 enters the lens body. As an example, three light bundles 24, 25, 26 extending in three different directions on the left side of the center plane 16 are shown. The edge light bundles represented by the light bundles 24, 25 enter the lens body through the outer coupling-in face 20, while the central light bundle represented by the light bundle 26 enters the lens body through the intermediate coupling-in face 21. The intermediate coupling-in face 21 has a convexly curved surface.

[0045] ​The lens body is also defined in the peripheral direction by two reflecting surfaces 28, 29, on which at least part of the light coupled in is totally reflected within the lens body. In particular, these totally reflected lights are edge beams which enter the lens body via the out-coupling surfaces 20, 22.

[0046] Finally, the lens element 12 also has three out-coupling surfaces 30, 31, 32, through which the light coupled in exits the lens body. The intermediate out-coupling surface 31 has a convexly curved surface, through which the central beam which has not been reflected within the lens body exits the lens body. The convex curvature of the intermediate in-coupling surface 20 and the intermediate out-coupling surface 31 is matched to one another and dimensioned in accordance with the refractive index of the lens material, such that the focal length of the central beam which has not been reflected within the lens body is the same as that of the (mainly) edge beams which have been reflected within the lens body.

[0047] The out-coupling surfaces 30, 32 are arranged symmetrically on either side of the central plane and are each inclined towards the central plane. Outside the lens element, an acute angle (90° - a) is formed between the out-coupling surfaces 30, 32 and the central plane 16, where a is the angle of inclination between the respective out-coupling surface and an auxiliary plane 34 which is parallel to the longitudinal direction and perpendicular to the central plane 16. The out-coupling side end face of the lens element, which in the above sense constitutes the reference for the determination of the focal length, also lies in the auxiliary plane. The (mainly) edge beams which have been reflected within the lens body exit the lens body via the out-coupling surfaces 30, 32. Since the two inwardly inclined out-coupling surfaces 30, 32 are arranged mirror-symmetrically with respect to the central plane 16, the lens element has a cavity below the auxiliary plane, and thus has a smaller volume compared to a lens element having flat out-coupling surfaces lying in the auxiliary plane. However, the inclination should not be too great, since otherwise the lens element no longer produces tolerable Fresnel losses. Furthermore, the structural height of the lens element in the direction of the central plane would also increase, which can likewise be undesirable.

[0048] It can be seen that the lens element 12 and its in-coupling surfaces 20, 21, 22, reflecting surfaces 28, 29 and out-coupling surfaces 30, 31, 32, as well as the light source 14, are arranged such that the light exiting the lens body via the out-coupling surfaces converges.

[0049] In Figure 2 a second embodiment of the illumination device 10 according to the application is shown in a cross-section transverse to the longitudinal direction of the illumination device 10. This illumination device likewise comprises a lens element 12 and a light source 14 arranged on one side of the lens element 12 in the longitudinal direction. The cross-sectional profile of the lens element 12 in the longitudinal direction likewise remains constant over at least one section and preferably over its entire optically effective length. And this lens element 12 is also mirror-symmetric with respect to a central plane 16 which extends in the longitudinal direction.

[0050] Unlike the lens element 12 according to Figure 1 The lens element according to Figure 2 has only a single flat outcoupling face 40 in which five step structures are formed symmetrically on either side of the central plane 16. These step structures are formed by an offset of the outcoupling face 40 essentially in the direction of the optical central plane 16. Each step structure divides the outcoupling face 40 into two adjacent optically functional outcoupling sub-faces 40a, 40b, 40c, 40d, 40e, 40f which are connected to one another by offset faces 42, 43, 44, 45, 46 which have no optical function. More precisely, the offset faces 42, 43, 44, 45, 46 lie in planes which are inclined by no more than 10° with respect to the central plane 16, whereby the offset faces can be inclined such that only a proportion of the light beam as small as possible or even no light beam at all exits from the lens element through the offset faces 42, 43, 44, 45, 46.

[0051] Another difference from the lens element 12 according to Figure 1 lies in the fact that the convex curvature of the intermediate incoupling face 51 is significantly greater, since the outcoupling face 40, including the outcoupling sub-face 40f, extends parallel to the auxiliary plane 34, and thus has a weaker refractive effect on the central light beam.

[0052] The remaining geometry of the lens element according to Figure 2 (e.g. the structure height, the inclination of the outcoupling faces 50, 52 and the inclination and curvature of the reflection faces 58, 59) is adapted to the varying light beam path within the lens body such that the light exiting from the lens body through the outcoupling face 40 is again convergent.

[0053] Compared to the illumination device according to Figure 1 by replacing the inclined outcoupling face by a step structure, the Fresnel losses can be reduced and the structure height of the lens element is also reduced. However, the cross section is substantially reduced in certain positions, which has a negative effect on the production quality. Thus, long profiles with such a cross section cannot be reliably manufactured with sufficient precision.

[0054] Figure 3 and Figure 4 shows the same third design variant of the illumination device according to the application. The lens element 12 according to Figure 3 and Figure 4 is a combination of the lens elements according to Figure 1 and Figure 2 . Like the lens element according to Figure 1The lens element has three in-coupling facets 60, 61, 62 facing the light source 14, of which the middle in-coupling facet 61 has a convexly curved surface. Unlike before, the light source 14' is shown as an extended light source in this figure.

[0055] Like the two other embodiments, the lens body is circumferentially limited by two reflecting facets 68, 69 on which at least part of the in-coupled light is totally reflected within the lens body. Here, the totally reflected light is also the edge light beams that enter the lens body through the out-coupling facets 60, 62.

[0056] Finally, the lens element 12 likewise has three out-coupling facets 70, 71, 72. Like in the case of the first embodiment, the outer out-coupling facets 70, 72 are arranged symmetrically on both sides of the central plane and are each tilted towards the central plane, wherein the tilt angle a between the outer out-coupling facets 70, 72 and the auxiliary plane 74 is smaller than the tilt angle a of the first embodiment, which reduces the Fresnel losses while reducing the structural height. Like in the case of the first embodiment, the middle out-coupling facet 71 has a convexly curved surface through which the middle light beams that have not been reflected within the lens body exit the lens body. Like in the case of the Figure 1 , the convex curvatures of the middle in-coupling facet 61 and the middle out-coupling facet 71 are mutually matched and dimensioned according to the refractive index of the lens material such that the focal length of the central light beams that have not been reflected within the lens body is the same as the focal length of the edge light beams that have been reflected within the lens body.

[0057] At the same time, like in the second embodiment, the outer out-coupling facets 70, 72 are provided with a plurality of step structures. In this case, three step structures are arranged symmetrically on both sides of the central plane 16. These step structures are formed by offsets of the outer out-coupling facets 70, 72. See Figure 4 Each step structure divides the out-coupling facet 70, 72 into two adjacent optically functional out-coupling sub-facets 70a, 70b, 70c, 70d or 72a, 72b, 72c, 72d, respectively, which extend parallel to the auxiliary plane 74 or the out-coupling side end face with the same tilt angle a and are connected to each other by offset facets 76, 77, 78 or 79, 80, 81. At the intersection of the plane of the out-coupling sub-facet and the plane of the offset facet, an edge is formed, respectively.

[0058] A retaining edge 82 for mounting the lens element in a housing (not shown) of a lighting device is integrally formed on the outside of the reflecting facets 68, 69 and the outer out-coupling facets 70, 72.

[0059] In Figure 3In the example shown, four light beams 84, 85, 86, 87 are shown as examples which extend in four different directions on the left side of the center plane 16. The edge light beams represented by the light beams 84, 85, 86 enter the lens body through the out-coupling face 60, while the central light beam represented by the light beam 87 enters the lens body through the in-coupling face 61. As can be seen, for example, from the light beams 85 and 86, the offset faces 76, 77 and 78 extend parallel to the light beam directions of the light beams which are emitted along the respective edges of the step structure. The offset faces thus do not have an optical function. Since the light beams extend in a converging manner, the offset faces are also not parallel to one another, but rather, viewed from the outside to the inside, the included angles β1 to β3 between the out-coupling sub-faces and the respective offset faces increase gradually.

[0060] According to Figure 3 and Figure 4 the illumination device according to Figure 1 and Figure 2 combines the advantages of both embodiments. On the basis of the step structure and the less steep out-coupling faces, the Fresnel losses are reduced, while the structural height of the lens element is also reduced. At the same time, by combining the steepness of the out-coupling faces with the step structure, a profile is successfully provided which has fewer weak points in its cross section, so that long profiles can be produced and the tolerances required to meet the optical imaging properties can be met.

[0061] In particular, as shown in Figure 3 on the basis of the light beams 84 and 86, the step structure is designed and arranged in such a way that the ratio of the maximum distance S max traveled by the reflected light beam 86 in the lens body between the reflection face 68 and the out-coupling sub-face 70c to the minimum distance S min traveled by the reflected light beam 84 in the lens body between the reflection face 68 and the out-coupling sub-face 70a is approximately 5.5. max min

[0062] Furthermore, as shown in Figure 4 the lens volume has a maximum extension L max and a minimum extension L min in the cross section, wherein the maximum extension L max represents the maximum circular diameter which lies completely within the cross section, and wherein the minimum extension L min represents the minimum linear distance between the reflection face 68 and the out-coupling sub-face 70a, the ratio L max / L min between the maximum extension and the minimum extension is kept at 3.7.

[0063] ​​This measure ensures that the profile does not vary in thickness in the direction in which the light beam extends within the lens by more than the range required by the optical path within the lens element, which ensures that the profile cools sufficiently uniformly after being shaped and enables long profiles to be produced while meeting the tolerances required by the optical imaging properties.

[0064] Finally, the cross-sectional profile of this embodiment, with a width of 60 mm and a height of 30 mm, has a cross-sectional area of 710 mm 2 and a circumference of 215 mm, so that the ratio of the cross-sectional area to the circumference is 3.3 mm.

[0065] Each of these three features, in particular the combination of all three features, ensures that the profile cools uniformly after being shaped and thus enables a length of 6 meters to be produced while meeting the tolerances required by the optical imaging properties.

[0066] Figure 5 A graph is shown in Figure 8, which shows the comparative results for the illumination intensity on an object surface along the central plane at two different working distances using the following illumination devices: an illumination device according to the application with a TIR lens according to Figure 3 and Figure 4 an illumination device with a cylindrical lens. The length of each illumination device is 300 mm. On the horizontal x-axis, the distance in mm is plotted in the longitudinal direction from the center of the illumination device to the sides. On the y-axis, the illumination intensity in lx is plotted on the surface of the illuminated object.

[0067] Curve 90 represents the illumination intensity on the object surface at a distance of 50 mm along the central plane of the illumination device according to the application. Curve 91 represents the illumination intensity on the object surface at a distance of 150 mm along the central plane of the illumination device according to the application. Curve 92 represents the illumination intensity on the object surface at a distance of 50 mm along the central plane of the illumination device with a cylindrical lens. Curve 93 represents the illumination intensity on the object surface at a distance of 150 mm along the central plane of the illumination device with a cylindrical lens.

[0068] It can be seen from this graph that significantly higher absolute illumination intensities can be achieved using the illumination device according to the application with a TIR lens element than with an illumination device with a cylindrical lens. For a working distance of 150 mm, the illumination intensity is more than 120% higher when using a TIR lens element than when using a cylindrical lens element, and for a working distance of 50 mm, it is still nearly 30% higher. The dependence of the illumination intensity on the working distance is therefore significantly lower for the illumination device according to the application with a TIR lens element. Over the entire working distance range of 50 mm to 150 mm, the change in the illumination intensity is less than 25%.

[0069] Since in each case the illumination device extends only 60 mm more in the longitudinal direction than shown in the diagram, it can be observed irrespective of the respective illumination device and the respective working distance that the intensity towards the edge decreases slightly when the working distance is small, and that the intensity towards the edge decreases significantly when the working distance is large. This effect only occurs essentially at the edge and is negligible in practice since the illumination devices used have a size of several meters in the longitudinal direction. List of reference signs

[0070] 10 illumination device 12 lens element 14, 14' light source 16 center plane 20 out-coupling face 21 in-coupling face 22 out-coupling face 24 light beam 25 light beam 26 light beam 28 reflecting face 29 reflecting face 30 out-coupling face 31 in-coupling face 32 out-coupling face 34 auxiliary plane 40 out-coupling face 40a out-coupling sub-face 40b out-coupling sub-face 40c out-coupling sub-face 40d out-coupling sub-face 40e out-coupling sub-face 40f out-coupling sub-face 42 offset face 43 offset face 44 offset face 45 offset face 46 offset face 50 out-coupling face 51 in-coupling face 52 out-coupling face 54 light beam 55 light beam 56 light beam 58 reflecting face 59 reflecting face 60 out-coupling face 61 in-coupling face 62 out-coupling face 68 reflecting face 69 reflecting face 70 out-coupling facet 70a out-coupling sub-facet 70b out-coupling sub-facet 70c out-coupling sub-facet 70d out-coupling sub-facet 71 intermediate out-coupling facet 72 out-coupling facet 72a out-coupling sub-facet 72b out-coupling sub-facet 72c out-coupling sub-facet 72d out-coupling sub-facet 74 auxiliary plane 76 offset facet 77 offset facet 78 offset facet 79 offset facet 80 offset facet 81 offset facet 82 holding edge 84 light beam 85 light beam 86 light beam 87 light beam 90 luminance profile of a lens element according to the present invention 91 luminance profile of a lens element according to the present invention 92 luminance profile of a cylindrical lens element 93 luminance profile of a cylindrical lens element α tilt angle of the out-coupling facet

Claims

1. A lighting device (10) for generating linear illumination along the longitudinal direction, comprising: A lens element (12) that defines an optical center plane (16) along the longitudinal direction and has a constant cross-sectional profile in at least one segment along the longitudinal direction; One or more light sources (14, 14') are arranged along the longitudinal direction on one side of the lens element (12). The lens element (12) has a transparent lens body, which includes: one or more coupling surfaces (20, 21, 22, 50, 51, 52, 60, 61, 62) facing the one or more light sources, through which light emitted by the one or more light sources (14, 14') enters the lens body; one or more reflecting surfaces (28, 29, 58, 59, 68, 69), on which at least part of the coupled light undergoes total internal reflection within the lens body; and one or more coupling surfaces (30, 31, 32, 40, 70, 71, 72), through which the coupled light exits from the lens body, and The lens element (12) and the one or more light sources (14, 14') are arranged such that light emitted from the lens body through the coupling surfaces (30, 31, 32, 40, 70, 71, 72) converges.

2. The lighting device (10) according to claim 1, characterized in that, At least one coupling surface (40, 70, 72) has at least one step structure, which is formed by offset of the at least one coupling surface (40, 70, 72) substantially in the direction of the optical center plane (16).

3. The lighting device (10) according to claim 2, characterized in that, The at least one stepped structure is formed by offsetting the beam direction of the beam coupled out along the edge of the at least one coupling surface (40, 70, 72) parallel to the beam direction of the beam coupled out along the edge of the stepped structure.

4. The lighting device (10) according to claim 2 or 3, characterized in that, The at least one stepped structure is designed and arranged such that the maximum distance S traveled by the reflected light beam within the lens body between the reflecting surfaces (58, 59, 68, 69) and the coupling surfaces (40, 70, 72) is such that... max And the minimum distance S that the reflected light beam travels within the lens body between the reflecting surfaces (58, 59, 68, 69) and the coupling surfaces (40, 70, 72). min Or the minimum distance S traveled by a direct beam of light between the coupling surfaces (21, 51, 61) and the coupling surfaces (31, 40, 71) in the lens body. min Applicable to: 1<S max / S min <6。 5. The lighting device (10) according to any one of the preceding claims, characterized in that, At least one coupling surface (31, 71) has a raised, curved surface through which a light beam that is not reflected within the lens body exits the lens body.

6. The lighting device (10) according to any one of the preceding claims, characterized in that, At least one coupling surface (30, 32, 70, 72) is inclined toward the central plane (16), and the light beam reflected within the lens body exits the lens body through the coupling surface.

7. The lighting device (10) according to claim 6 in conjunction with any one of claims 2 to 4, characterized in that, The at least one stepped structure is formed in at least one coupling surface (30, 32, 70, 72) inclined toward the central plane (16).

8. The lighting device according to any one of the preceding claims, characterized in that, The lens volume has the maximum elongation dimension L in cross-section. max and minimum extension size L min The maximum extension dimension L max The maximum diameter of the circle that lies entirely within the cross-section, and wherein the minimum extension dimension L is... min This represents the minimum linear distance between the input surface (20, 21, 22, 50, 51, 52, 60, 61, 62) and the output surface (30, 31, 32, 40, 70, 71, 72), or between the reflecting surface (28, 29, 58, 59, 68, 69) and the output surface (30, 31, 32, 40, 70, 71, 72), where applicable: 1 < L max / L min < 5.

9. The lighting device (10) according to any one of the preceding claims, characterized in that, The cross-sectional profile has a cross-sectional area and a circumferential length, wherein the ratio of the cross-sectional area to the circumferential length is between 2.0 mm and 4.5 mm, preferably between 2.5 mm and 4.0 mm.

10. The lighting device (10) according to any one of the preceding claims, characterized in that, The aspect ratio between the length and maximum width of the lens element is at least 10:1, preferably 20:1, and particularly preferably 50:

1.

11. The lighting device (10) according to any one of the preceding claims, characterized in that, The lens element has an extrudable profile.

12. The lighting device (10) according to any one of the preceding claims, characterized in that, The lens element is made of PMMA.

13. The lighting device (10) according to any one of the preceding claims, characterized in that, The light source (14, 14') is formed by one or more LEDs.

14. The lighting device (10) according to any one of claims 2 to 13, characterized in that, The at least one coupling surface (30, 32, 70, 72) has a three-step structure.

15. An apparatus for optically detecting an object, comprising an illumination device (10) according to any one of the preceding claims, wherein, The object and the lighting device (10) are movable relative to each other in the direction of motion, wherein the longitudinal direction is arranged transversely to the direction of motion, and wherein the lighting device is alignable with the object such that light emitted from the lens body through the coupling surfaces (30, 31, 32, 40, 70, 71, 72) falls on the surface of the object. The device includes an acquisition device for acquiring images of an illuminated object and a computing unit for evaluating the acquired images.

Images