Lighting device for generating linear illumination

Abstract

To improve the efficiency of lighting devices for generating linear illumination while maintaining the same or lower manufacturing costs. [Solution] An illumination device (10) having a lens element (12) having a constant cross-sectional profile over at least a portion of it, and having one or more light sources (14') arranged along the longitudinal direction on one side of the lens element, the lens element having a transparent lens body, the lens body having one or more incident surfaces (61, 62) facing the one or more light sources, through which light emitted from the one or more light sources enters the lens body, one or more reflective surfaces (68, 69) through which at least a portion of the incident light is completely internally reflected within the lens body, and one or more exit surfaces through which the incident light exits the lens body, the lens element and light sources are arranged so that the light exiting the lens body via the exit surfaces converges.

Description

[Technical Field]

[0001] The present invention relates to an illumination device for generating linear illumination along a longitudinal direction, the illumination device having a lens element that defines an optical central plane along a longitudinal direction, the lens element having a constant cross-sectional profile along a longitudinal direction in at least a portion thereof, and having one or more light sources arranged along a longitudinal direction on one side of the lens element. The present invention further relates to an optical inspection device ("inspection device") for an object equipped with such an illumination device. [Background technology]

[0002] The lighting device and inspection device according to the present invention can be used in particular for inspecting transparent material webs or objects such as glass or structured glass, as well as opaque material webs or objects having painted surfaces, for example. Possible defects include, in particular, surface damage and / or, in the case of transparent materials, inclusions such as air bubbles or foreign matter, or non-uniformity.

[0003] For example, see Patent Documents 1 and 2, which disclose a device for surface inspection of a moving product. In this device, the moving surface to be inspected is captured in image format by at least one camera. Furthermore, an illumination configuration is provided in which individual or multiple light sources are selectively activated or deactivated from a number of light sources arranged in a line in the transport direction. The individual images obtained are evaluated to detect defects on the surface.

[0004] Patent Document 3 relates to the determination of the optical quality of plate glass. For this purpose, a color line camera is provided for observing illumination through or by reflection of the glass. The camera's focal point is located on the surface of the glass. Illumination positioned perpendicular to the transport direction alternately illuminates the surface with two different colors.

[0005] A lighting device for generating linear illumination is also known in Patent Document 4. A row of LEDs is used as the light source, and these can be switched independently of each other in at least two groups. An optical element for focusing the light beam is also assigned to the light source, and may consist of, for example, a Fresnel lens or a cylindrical lens.

[0006] Cylindrical lenses have been demonstrated to be suitable for generating linear illumination. They can be manufactured as extruded profiles at relatively low cost and in virtually any length. Image formation is sufficiently good, and they can generate a focused beam of light from the light emitted from an LED, with a focus at a working distance of approximately 50 mm. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] European Patent Application Publication No. 1742041 [Patent Document 2] European Patent Application Publication No. 1030173 [Patent Document 3] German Patent Application Publication No. 19813073 [Patent Document 4] European Patent Application Publication No. 3236198 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The objective of the present invention is to improve the efficiency of lighting devices for generating linear illumination while maintaining the same or lower manufacturing costs. [Means for solving the problem]

[0009] The objective is achieved by the illumination device according to claim 1. The illumination device for generating linear illumination along the longitudinal direction comprises a lens element that defines an optical central plane (also called an optical surface) along the longitudinal direction and further comprises a lens element having a constant cross-sectional profile over at least a portion of the longitudinal direction. The illumination 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, which comprises one or more incident surfaces facing one or more light sources, through which light emitted from one or more light sources enters the lens body; one or more reflective surfaces through which at least a portion of the incident light is completely internally reflected within the lens body; and one or more exit surfaces through which the incident light exits the lens body. The lens element and light sources are arranged such that the light exiting the lens body via the exit surfaces converges.

[0010] The incident, reflective, and exiting surfaces are collectively referred to as "optical surfaces" through which light rays enter, exit, or are reflected by the lens body. These surfaces function optically even when, for example, light rays pass through them without refraction. The quality and tolerance requirements for these surfaces are generally higher than those for non-optical surface areas, for example, because they are aligned parallel to the optical path.

[0011] Unlike cylindrical lenses, total internal reflection occurs within the lens element according to the present invention at the reflective surface. This results in a higher overall light output, especially when using LEDs with broad radiation characteristics as the light source. Compared to using a cylindrical lens and the same LED, the lens element according to the present invention allows for the use of light rays propagating at a large radiation angle, for example, at an angle greater than 60° with respect to the optical surface, thus enabling a lens shape that increases light output. Furthermore, it enables the use of more efficient LEDs with broader radiation characteristics. Such LEDs, combined with the improved image formation performance of the lens according to the present invention, can increase light output by up to 220% compared to conventional LED and cylindrical lens combinations.

[0012] At the same time, if the installation dimensions are the same, the lens element according to the present invention has a significantly smaller volume than a cylindrical lens, thereby reducing the amount of material used and thus the manufacturing cost.

[0013] 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 spotlights and in the automotive field for headlights and taillights. The present invention is based on the recognition that the corresponding shape can also be applied to the lens element, which has a constant cross-sectional profile along the longitudinal direction, at least partially, preferably over the entire optically effective length of the lens element, and particularly preferably over the entire profile length for manufacturing reasons. The problem here is to maintain the required dimensions and surface tolerances over the entire optically effective length of the lens element.

[0014] A cylindrical lens has a circular cross-section. This has the advantage that a uniform stress is formed in the material during cooling after molding, ensuring shape stability and thus sufficient optical quality. Generally, the shape of a TIR lens can also be manufactured as an elongated profile for generating linear illumination by an extrusion molding method. However, the shape of a TIR lens is necessarily significantly less symmetric than a cylinder. Usually, the optical center plane along the longitudinal direction is the only symmetry plane in the profile. Therefore, the corresponding extrusion profile tends to be deformed due to manufacturing factors, especially when manufacturing a very long profile.

[0015] Therefore, it is preferable that at least one exit surface has at least one step, and the step is formed by offsetting at least one exit surface essentially in the direction of the optical center plane.

[0016] By this means, the thickness of the profile, and thus the cross-sectional area of the profile, can be intentionally reduced, and this can be used to perform the cooling of the profile more uniformly. Furthermore, by this method, a profile that is up to 70% lighter than a cylindrical lens having equivalent imaging characteristics can be realized.

[0017] Strictly speaking, even a single step already has an effect on improving the dimensional and shape stability of the profile. As the number of steps increases, the effect in this regard further improves. However, as the number of steps increases, it is offset by an increase in Fresnel losses. A good compromise point has been confirmed for an exit surface having three steps.

[0018] By each step, the exit surface is divided into two adjacent optically functional partial exit surfaces, which are connected to each other by an offset surface that does not have an optical function. Therefore, "at least one exit surface is offset essentially in the direction of the optical center plane" means that the offset surface is located in a plane extending parallel to the center plane and is inclined with respect to the center plane by 15° or less, preferably 12° or less, particularly preferably 10° or less in any case.

[0019] At least one step is particularly preferably formed by an offset of at least one exit surface parallel to the beam direction of the light rays exiting along the edge of the step.

[0020] The edge of the step is located at the place where the plane of the exit surface and the plane of the offset surface intersect. Of course, in reality, the edge is not arbitrarily formed sharp and is usually rounded for manufacturing reasons. A typical radius of rounding is 0.1 to 0.5 mm. Therefore, the geometric specifications are generally understood to include tolerances from the described ideal shape or deviations necessary due to manufacturing techniques.

[0021] At least one step is such that the maximum distance S that the reflected light ray travels from the reflecting surface to the exit surface within the lens body maxThe minimum distance S required for reflected light rays to travel within the lens body from the reflective surface to the exit surface, or for direct light rays to travel within the lens body from the incident surface to the exit surface, is considered. min The following relationship applies: 1 max / S min It is preferable to set the dimensions and arrangement such that <6 is satisfied.

[0022] This method ensures that the thickness of the profile in the optical path direction within the lens does not change beyond what is required by the optical path within the lens element. This ensures that the profile cools sufficiently and uniformly after molding, enabling the manufacture of long profiles while maintaining the tolerances necessary for optical image formation characteristics.

[0023] At least one of the emission surfaces preferably has a convex curved surface, through which light rays that are not reflected (primarily) within the lens body are emitted from the lens body.

[0024] This describes direct rays, which typically enter the lens body via an incident surface near the central plane, exit from the opposite side without total internal reflection, and are focused by a convex exit surface. This represents the (calculated) ideal shape of the illumination device. In reality, due to manufacturing tolerances and the area spread of the light source, a small portion of the reflected rays also exit the lens body via a convex exit surface; therefore, in this sense, rays that are "primarily" not reflected within the lens body refer to these rays.

[0025] At least one emission surface is inclined toward the central surface, and light rays reflected (primarily) within the lens body are emitted from the lens body through this surface.

[0026] ​"Inclined toward the central plane" means that an acute angle is formed on the outside of the lens element between the exit surface and the central plane. If the two exit surfaces are arranged so as to be mirror-symmetric with respect to the central plane, the exit surfaces can also be said to be inclined inward. Inwardly inclined exit surfaces reduce the volume of the lens element, which, like steps, has a positive effect on manufacturing and weight. However, the inclination angle cannot be arbitrarily large because it will impair the image formation characteristics. Specifically, if the inclination is too large, the Fresnel loss increases.

[0027] The reflective surface is preferably designed such that the light rays reflected therein are already focused in the first approximation, and refraction is no longer necessary or desirable when the light rays exit through the emitting surface. Therefore, the emitting surface is preferably inclined with respect to the central axis such that the reflected light rays travel substantially perpendicular to the emitting surface. It is permissible for a small portion of the direct light rays to exit from the lens body through the inclined emitting surface, and in this sense, it refers here to light rays reflected "primarily" within the lens body. In practice, it is impossible for the reflected light rays to travel ideally perpendicular to the emitting surface. For example, this is already impossible given that the light source has an area of ​​spread. In this sense, it is sufficient for the reflected light rays to travel substantially perpendicular to the emitting surface within an angular tolerance of ±3°. Here, "substantially perpendicular" means this state.

[0028] Preferably, at least one step is formed on at least one ejection surface that is inclined toward the central plane.

[0029] The combination of an inward slope and a step on the exit surface further improves the profile for uniform cooling after molding, while simultaneously allowing for a smaller overall size without compromising image formation accuracy.

[0030] The lens volume is preferably, in cross-section, the maximum dimension L max and minimum dimension Lmin has a maximum dimension L max which represents the diameter of the largest circle that can fit entirely within the cross-section, and a minimum dimension L min which represents the minimum straight-line distance between the incident surface and the exit surface, or between the reflecting surface and the exit surface, and the following relationship holds: 1 < L max / L min <5 is satisfied.

[0031] This configuration can also be achieved by setting and arranging the dimensions of at least one step, and by ensuring that the thickness of the profile considering the optical imaging characteristics within the lens does not vary by more than a factor of 5, uniform cooling of the profile after molding is ensured, and it becomes possible to manufacture profiles with a length of up to 6 m while maintaining the tolerances required for optical imaging characteristics.

[0032] The cross-sectional profile has a cross-sectional area and a perimeter, and the ratio of the cross-sectional area to the perimeter is more preferably in the range of 2.0 mm to 4.5 mm, and particularly preferably in the range of 2.5 mm to​​​​​​​​​​​​​​​​​​​​​

[0038] The lens element is particularly preferably made of PMMA.

[0039] The light source is preferably formed by one or more LEDs. For example, multiple light sources for generating light of different wavelengths can, in each case, be formed by multiple identical LEDs arranged adjacent to each other in the longitudinal direction.

[0040] The object of the present invention is also achieved by an optical inspection apparatus for an object having the above-described illumination device, wherein the object and the illumination device can move relative to each other in the direction of movement, the longitudinal direction is arranged laterally with respect to the direction of movement, and the illumination device can be directed toward the object so that light emitted from the lens body through the emission surface irradiates the surface of the object. The optical inspection apparatus further includes an image acquisition device for acquiring an image of the irradiated object and a calculation unit for evaluating the acquired image.

[0041] The optical inspection apparatus is configured, for example, to be installed on a conveying or production facility in which an object is transported along the direction of movement. The apparatus is fixedly positioned on the conveying or production facility so that the object is guided and passes through the lens element at a distance preferably corresponding to the focal length of the lens element. This distance, also called the working distance, is measured from the exit end face of the lens element along the central plane to the surface of the object.

[0042] In reality, the luminous beam of this type of TIR lens does not converge on a one-dimensional focal line, but rather forms a waist. Therefore, the term focal length is understood to mean the focal length range in which the illuminance on the surface of the illuminated object does not deviate by more than 25% from the maximum illuminance. Depending on the application, the device may be operated so that the object is guided through the lens element at a working distance outside the focal length range, in which case the concentration of the luminous beam on the surface of the object will be reduced.

[0043] Further features and advantages of the present invention are described below with reference to exemplary embodiments shown in the figures. [Brief explanation of the drawing]

[0044] [Figure 1] This is a cross-sectional view of a lens element according to the first embodiment of the present invention. [Figure 2] This is a cross-sectional view of a lens element according to a second embodiment of the present invention. [Figure 3] This is a cross-sectional view of a lens element according to a third embodiment of the present invention. [Figure 4] Figure 3 shows lens elements with different parameterizations. [Figure 5] This shows a comparison of the illuminance when using the lighting device according to the present invention and the illuminance when using a lighting device having a cylindrical lens. [Modes for carrying out the invention]

[0045] A first embodiment of the illumination device 10 according to the present invention is shown in Figure 1 in a cross-section perpendicular to its longitudinal direction. The illumination device 10 comprises a lens element 12 and a light source 14 arranged along the longitudinal direction on one side of the lens element 12. The lens element 12 has a constant cross-sectional profile shown in the figure, at least over a portion of its longitudinal direction, preferably over its entire optically effective length. The lens element 12 is mirror-symmetric with respect to a central plane 16 extending along the longitudinal direction.

[0046] The lens element 12 has a transparent lens body with three incident surfaces 20, 21, and 22 facing the light source 14, and light emitted from the light source 14 enters the lens body through these incident surfaces. As an example, three rays 24, 25, and 26 traveling in three different directions to the left of the central surface 16 are shown. The peripheral rays represented by rays 24 and 25 enter the lens body through the outer incident surface 20, and the central ray represented by ray 26 enters through the central incident surface 21. The central incident surface 21 has a convex curved surface.

[0047] Furthermore, the lens body is surrounded by two reflective surfaces 28 and 29, where at least a portion of the incident light is reflected entirely within the lens body. Specifically, these are peripheral rays that enter the lens body via the outer incident surfaces 20 and 22.

[0048] Finally, the lens element 12 has three exit surfaces 30, 31, and 32 through which the incident light exits the lens body. The central exit surface 31 has a convex curved surface, and the central light ray, which is not reflected within the lens body, exits the lens body through this surface. Depending on the refractive index of the lens material, the convex curvature of the central incident surface 20 and the central exit surface 31 are matched and dimensionally set such that the focal length of the central light ray, which is not reflected within the lens body, is the same as the focal length of the peripheral light ray, which is (primarily) reflected within the lens body.

[0049] The outer emission surfaces 30 and 32 are arranged symmetrically with respect to both sides of the central plane, and each is inclined toward the central plane. An acute angle (90°-α) is formed between the emission surfaces 30 and 32 and the central plane 16 outside the lens element, where α is the inclination angle between each emission surface and an auxiliary surface 34 that is parallel to the longitudinal direction and perpendicular to the central plane 16. The end face of the lens element on the emission side, which serves as the reference for determining the focal length in the above sense, is also located within the auxiliary surface. Light rays reflected mainly within the lens body, i.e., peripheral rays, are emitted from the lens body via the outer emission surfaces 30 and 32. Due to the arrangement of the two outer emission surfaces 30 and 32, which are inclined inward to be mirror-image symmetric with respect to the central plane 16, the lens element has a gap below the auxiliary surface, resulting in a smaller volume compared to a lens element with a flat emission surface located within the auxiliary surface. However, if the inclination is too steep, it has the disadvantage of causing unacceptable Fresnel loss in the lens element. Furthermore, the overall height of the lens element also increases towards the center plane, which can also be undesirable.

[0050] As shown in the figure, the lens element 12 is arranged together with the incident surfaces 20, 21, 22, the reflective surfaces 28, 29, the exit surfaces 30, 31, 32, and the light source 14 so that the light emitted from the lens body via the exit surface is focused.

[0051] A second embodiment of the lighting device 10 according to the present invention is shown in Figure 2 in a cross-section perpendicular to its longitudinal direction. This also comprises a lens element 12 and a light source 14 arranged along the longitudinal direction on one side of the lens element 12. The cross-sectional profile of the lens element 12 is also constant along the longitudinal direction, at least over a portion of it, preferably over its entire optically effective length. This lens element 12 is also mirror-symmetric with respect to a central plane 16 extending along the longitudinal direction.

[0052] In contrast to the lens element 12 in Figure 1, the lens element in Figure 2 has only a single flat emitting surface 40, each of which has five steps formed symmetrically on both sides of the central surface 16. These steps are formed by substantially offsetting the emitting surface 40 in the direction of the optical central surface 16. Each step divides the emitting surface 40 into two adjacent optically functional partial emitting surfaces 40a, 40b, 40c, 40d, 40e, and 40f, which are connected to each other by offset surfaces 42, 43, 44, 45, and 46 that do not have optical function. More precisely, the offset surfaces 42, 43, 44, 45, and 46 are located in a plane inclined at 10° or less with respect to the central surface 16, so that even if the offset surfaces are inclined, the proportion of light rays emitted from the lens element through the offset surfaces 42, 43, 44, 45, and 46 can be kept to a minimum, if any.

[0053] A further difference from the lens element 12 in Figure 1 is that the convex curvature of the central incident surface 51 is significantly stronger. This is because the exit surface 40, including the partial exit surface 40f, extends parallel to the auxiliary surface 34, resulting in a smaller contribution of the central ray to refraction.

[0054] The remaining geometric shapes of the lens element shown in Figure 2, such as the overall height, the inclination angles of the outer incident surfaces 20 and 22, and the inclination angles and curvature of the reflective surfaces 28 and 29, are adapted to the changed optical path within the lens body, thereby causing the light emitted from the lens body through the exit surface 40 to converge again.

[0055] Compared to the lighting device shown in Figure 1, by providing a step instead of an inclined emission surface, Fresnel loss can be reduced, and the overall height of the lens element can also be reduced. However, the cross-sectional shape becomes significantly weaker in some areas, negatively impacting manufacturing quality. Therefore, long profiles with this cross-sectional shape cannot be manufactured stably with sufficient precision.

[0056] Figures 3 and 4 show the same third embodiment of the lighting device according to the present invention. The lens element 12 in Figures 3 and 4 is a combination of the lens elements in Figures 1 and 2. Similar to the lens element 12 in Figure 1, it has three incident surfaces 60, 61, and 62 facing the light source 14, of which the central incident surface 61 has a convex curved surface. In this figure, the light source 14' is shown as an extended light source, unlike before.

[0057] As in both other embodiments, the lens body is periphery defined by two reflective surfaces 68, 69, where at least a portion of the incident light is reflected entirely within the lens body. Again, these are peripheral rays incident on the lens body via the outer incident surfaces 60, 62.

[0058] Finally, the lens element 12 again has three exit surfaces 70, 71, and 72. As in the first embodiment, the outer exit surfaces 70 and 72 are arranged symmetrically with respect to both sides of the central surface, each inclined toward the central surface, and the inclination angle α between the outer exit surfaces 70 and 72 and the auxiliary surface 74 is smaller than in the first embodiment, thereby reducing both Fresnel loss and overall height compared to the first embodiment. The central exit surface 71 also has a convex curved surface, as in the first embodiment, and the central rays that are not reflected within the lens body are emitted from the lens body through this surface. As in Figure 1, the convex curvature of the central incident surface 20 and the central exit surface 71 are matched and dimensioned according to the refractive index of the lens material, so that the focal length of the central rays that are not reflected within the lens body is the same as the focal length of the peripheral rays that are (primarily) reflected within the lens body.

[0059] Simultaneously, as in the second embodiment, multiple steps are provided on the outer exit surfaces 70 and 72. In this example, three steps are arranged symmetrically on both sides of the central surface 16. These steps are formed by offsetting the outer exit surfaces 70 and 72. Each step divides the exit surfaces 70 and 72 into two adjacent optically functional partial exit surfaces 70a, 70b, 70c, 70d and 72a, 72b, 72c, 72d, respectively, which extend parallel to the auxiliary surface 74 or the exit-side end surface at the same inclination angle α and are connected to each other by offset surfaces 76, 77, 78 and 79, 80, 81, respectively (see Figure 4). Edges are formed where the surfaces of the partial exit surfaces and the surfaces of the offset surfaces intersect.

[0060] A retaining rim 82 for attaching a lens element to a housing (not shown) of the illumination device is integrally formed on the lateral outer side of each of the reflective surfaces 68, 69 and the outer emission surfaces 70, 72.

[0061] Figure 3 shows, as an example, four rays 84, 85, 86, and 87 traveling in four directions to the left of the central plane 16. The peripheral rays represented by rays 84, 85, and 86 enter the lens body via the outer incident surface 60, while the central ray represented by ray 87 enters via the central incident surface 61. As can be seen, for example, from rays 85 and 86, the offset surfaces 76, 77, and 78 extend parallel to the beam direction of the rays emitting along the respective edges of their steps. Therefore, these offset surfaces have no optical function. Because the rays converge, the offset surfaces are also not parallel to each other, and when viewed from the outside to the inside, increasing intermediate angles β1 to β3 are formed between the partial emission surface and each offset surface.

[0062] The embodiment of the illumination device shown in Figures 3 and 4 combines the advantages of both embodiments shown in Figures 1 and 2. The stepped and gently inclined exit surface reduces Fresnel loss and simultaneously reduces the overall height of the lens element. At the same time, by combining the inclination and step of the outer exit surface, it is possible to provide a profile with a cross-section that has fewer weak points, and therefore, it is possible to manufacture long profiles while maintaining the tolerances necessary for optical image formation characteristics.

[0063] In particular, as shown by rays 84 and 86 in Figure 3, the maximum distance S over which the reflected ray 86 travels within the lens body from the reflective surface 68 to the partial emission surface 70c is significant. max The minimum distance S over which the reflected light ray 84 travels from the reflecting surface 68 to the partially emitted surface 70a. min The ratio S max / S min The steps are sized and positioned so that the difference is approximately 5.5.

[0064] Furthermore, as can be seen in Figure 4, the lens volume is the maximum dimension L in cross-section. max and minimum dimension L min It has the maximum dimension L max This indicates the diameter of the largest circle that fits completely within the cross-section, and the minimum dimension L minThis indicates the minimum straight-line distance between the reflective surface 68 and the partial emission surface 70a, and the ratio L between them. max / L min It remains at 3.7.

[0065] This method ensures that the profile thickness in the optical path direction within the lens does not change more than required by the optical path within the lens element. This ensures that the profile cools sufficiently uniformly after molding, enabling the manufacture of long profiles while maintaining the tolerances necessary for optical image formation characteristics.

[0066] Finally, in this embodiment, the cross-sectional profile with dimensions of 60 mm width and 30 mm height is 710 mm 2 It has a cross-sectional area and a circumference of 215 mm, resulting in a ratio of cross-sectional area to circumference of 3.3 mm.

[0067] Each of these three features—especially when all three are combined—ensures uniform cooling of the molded profile, thus enabling manufacturing in 6m lengths while maintaining the tolerances required for optical image formation characteristics.

[0068] Figure 5 shows a comparison of the illuminance when using the illumination device of the present invention equipped with a TIR lens as shown in Figures 3 and 4, with the illuminance when using an illumination device equipped with a cylindrical lens, at two different working distances, plotted along the central plane. The length of each illumination device was 300 mm. The x-axis in the horizontal direction plots the longitudinal distance from the center of the illumination device to both sides in millimeters. The y-axis plots the illuminance on the illuminated object surface in lx.

[0069] Curve 90 shows the illuminance of the lighting device according to the present invention at a distance of 50 mm from the object surface, along the central plane. Curve 91 shows the illuminance of the lighting device according to the present invention at a distance of 150 mm from the object surface, along the central plane. Curve 92 shows the illuminance of the lighting device equipped with a cylindrical lens at a distance of 50 mm from the object surface, along the central plane. Curve 93 shows the illuminance of the lighting device equipped with a cylindrical lens at a distance of 150 mm from the object surface, along the central plane.

[0070] As shown in the figure, the illumination device having a TIR lens element according to the present invention can achieve significantly higher absolute illumination than when using a cylindrical lens. When the working distance is 150 mm, the illuminance is increased by more than 120% when using the TIR lens element, and even when the working distance is 50 mm, it is nearly 30% higher than when using a cylindrical lens element. In connection with this, the illumination device according to the present invention equipped with a TIR lens element has significantly lower dependence of illuminance on the working distance. The variation in illuminance across the entire working distance range from 50 mm to 150 mm is less than 25%.

[0071] In all cases, the lighting fixtures extend only 60 mm longitudinally from the illustrated area. Therefore, regardless of each lighting fixture and its respective working distance, it can be seen that the illuminance decreases slightly at the edges when the working distance is short, and significantly when the working distance is long. This phenomenon basically occurs only at the edges and is practically negligible because the longitudinal dimension of the lighting fixtures used is only a few meters. [Explanation of Symbols]

[0072] 1. Lighting device 12 lens elements 14,14′ light source 16 Center plane 20 Outer entrance plane 21 Central entrance plane 22 Outer entrance plane 24 Rays 25 Rays 26 Rays 28 Reflective surface 29 Reflecting surface 30 Outer exit surface 31 Central exit surface 32 Outer exit surface 34 Auxiliary surface 40 Exit surface 40a Partial exit surface 40b Partial exit surface 40c Partial exit surface 40d Partial exit surface 40e Partial exit surface 40f Partial exit surface 42 Offset surface 43 Offset surface 44 Offset surface 45 Offset surface 46 Offset surface 50 Outer incident surface 51 Central incident surface 52 Outer incident surface 54 Ray 55 Ray 56 Ray 58 Reflecting surface 59 Reflecting surface 60 Outer incident surface 61 Central incident surface 62 Outer incident surface 68 Reflecting surface 69 Reflecting surface 70 Outer exit surface 70a Outer partial exit surface 70b Outer partial exit surface 70c Outer partial exit surface 70d Outer partial exit surface 71 Central exit surface 72 Outer exit surface 72a Outer partial exit surface 72b Outer partial exit surface 72c Outer partial exit surface 72d Outer partial exit surface 74 Auxiliary surface 76 Offset surface 77 Offset surface 78 Offset surface 79 Offset surface 80 Offset surface 81 Offset surface 82 Retaining Rim 84 Ray of light 85 Rays of light 86 Rays of light 87 Rays of light 90 Illuminance profile of lens element according to the present invention 91 Illuminance profile of lens element according to the present invention 92 Illuminance Profile of Cylindrical Lens Element 93 Illuminance Profile of Cylindrical Lens Element α Inclination angle of the outer exit surface

Claims

1. A lighting device (10) for generating linear illumination along the longitudinal direction, The optical central plane (16) is defined along the longitudinal direction, and the lens element (12) further has a constant cross-sectional profile along the longitudinal direction, at least in part. The lens element (12) is provided with one or more light sources (14, 14') arranged along the longitudinal direction on one side thereof. The lens element (12) has a transparent lens body, the lens body having one or more incident surfaces (20, 21, 22, 50, 51, 52, 60, 61, 62) facing the one or more light sources, the incident surface through which light emitted from the one or more light sources (14, 14') enters the lens body, one or more reflective surfaces (28, 29, 58, 59, 68, 69) through which at least a portion of the incident light is completely internally reflected within the lens body, and one or more exit surfaces (30, 31, 32, 40, 70, 71, 72) through which the incident light exits the lens body. The illumination device (10) is arranged such that the lens element (12) and the light sources (14, 14') are aligned so that the light emitted from the lens body is focused via the emission surfaces (30, 31, 32, 40, 70, 71, 72).

2. The illumination device (10) according to claim 1, characterized in that at least one emission surface (40, 70, 72) has at least one step, the step being formed by the at least one emission surface (40, 70, 72) being essentially offset in the direction of the optical central plane (16).

3. The lighting device (10) according to claim 2, characterized in that the at least one step is formed by an offset of the at least one emitting surface (40, 70, 72) parallel to the beam direction of the light rays emitted along the edge of the step.

4. The aforementioned at least one step represents the maximum distance S over which the reflected light rays travel within the lens body from the reflective surfaces (58, 59, 68, 69) to the emitting surfaces (40, 70, 72). ｍａｘ The minimum distance S required for reflected light rays to travel within the lens body from the reflective surfaces (58, 59, 68, 69) to the exit surfaces (40, 70, 72), or for direct light rays to travel within the lens body from the incident surfaces (21, 51, 61) to the exit surfaces (31, 40, 71), is such that the reflected light rays travel within the lens body from the incident surfaces (21, 51, 61) to the exit surfaces (31, 40, 71). ｍｉｎ For this relationship, 1 < S ｍａｘ / S ｍｉｎ The lighting device (10) according to claim 2 or 3, characterized in that the dimensions and arrangement satisfy condition 6.

5. The illumination device (10) according to any one of claims 1 to 4, characterized in that at least one emitting surface (31, 71) has a convex curved surface, and light rays that are not reflected within the lens body are emitted from the lens body through the surface.

6. The illumination device (10) according to any one of claims 1 to 5, characterized in that at least one emitting surface (30, 32, 70, 72) is inclined toward the central surface (16), and light rays reflected within the lens body are emitted from the lens body via the surface.

7. The lighting device (10) according to claim 6 in combination with any one of claims 2 to 4, characterized in that the at least one step is formed on the at least one emission surface (30, 32, 70, 72) which is inclined toward the central surface (16).

8. The lens volume has, in cross-section, a maximum dimension L ｍａｘ and a minimum dimension L ｍｉｎ where the maximum dimension L ｍａｘ indicates the diameter of the largest circle that fits entirely within the cross-section, and the minimum dimension L ｍｉｎ indicates the minimum straight-line distance between the incident surfaces (20, 21, 22, 50, 51, 52, 60, 61, 62) and the exit surfaces (30, 31, 32, 40, 70, 71, 72), or between the reflecting surfaces (28, 29, 58, 59, 68, 69) and the exit surfaces (30, 31, 32, 40, 70, 71, 72), and the following relationship: 1 < L ｍａｘ / L ｍｉｎ < 5 holds, and the lighting device according to any one of claims 1 to 7 is characterized thereby.

9. The lighting device (10) according to any one of claims 1 to 8, characterized in that the cross-sectional profile has a cross-sectional area and a perimeter, and the ratio of the cross-sectional area to the perimeter is in the range of 2.0 mm to 4.5 mm, preferably 2.5 mm to 4.0 mm.

10. The illumination device (10) according to any one of claims 1 to 9, characterized in that the lens element has an aspect ratio between its length and maximum width of at least 10:1, preferably 20:1, and particularly preferably 50:

1.

11. The illumination device (10) according to any one of claims 1 to 10, characterized in that the lens element has an extrudeable profile.

12. The illumination device (10) according to any one of claims 1 to 11, characterized in that the lens element is made of PMMA.

13. The lighting device (10) according to any one of claims 1 to 12, 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 at least one emission surface (30, 32, 70, 72) has three steps.

15. An optical inspection apparatus for an object having an illumination device (10) according to any one of claims 1 to 14, wherein the object and the illumination device (10) can move relative to each other in the direction of movement, the longitudinal direction is arranged laterally with respect to the direction of movement, and the illumination device can be directed toward the object such that light emitted from the lens body through the emission surfaces (30, 31, 32, 40, 70, 71, 72) irradiates the surface of the object. The device includes an image acquisition device for acquiring an image of the irradiated object, The optical inspection apparatus having a calculation unit for evaluating the acquired image.

Images