Method for calculating optically effective areas of a lighting unit of a lighting device of a motor vehicle

Abstract

Method for calculating optically effective areas (46, 48) of a lighting unit (10) of a lighting device of a motor vehicle, which lighting unit (10) is configured to convert light (22) from a semiconductor light source having a Lambertian emission characteristic into parallel light, wherein first a beam path of light 22 is specified, as it can be emitted from a light-emitting surface of the semiconductor light source 18 and which at the exit from the light-emitting surface is represented by a first central ray 28, the direction of which corresponds to a principal emission direction of the light-emitting surface, and which at the exit from the lighting unit (10) is represented by a second central ray (30), the direction of which coincides with a principal emission direction of the lighting unit (10), a first point (32) is selected which lies on the first central ray (28), a second (34) point is selected,a first plane (36) is determined, which lies on the second central ray (30), and which can be spanned by a unit vector of a connecting line (40) of the two points (32, 34) and a second unit vector whose direction corresponds to the direction of the first central ray (28), a second plane (38) is spanned by the unit vector of the connecting line (40) and by a third vector whose direction corresponds to the direction of the second central ray (30), an optically effective first curve (42) lying in the first plane (36) is calculated, which can be illuminated by light (22) emanating from the light-emitting surface, and a second optically effective curve (44) lying in the second plane (38) is calculated, which can be illuminated by light (22) emanating from the first optically effective curve (42),wherein light (22) emanating from the second optically effective curve (44) is both parallel and homogenized with respect to its luminous flux density, characterized in that a further first curve (42') is calculated, which results from the previously calculated first curve (42) by a predetermined angle (42'') around the first central ray (28), a further second curve (44') is calculated, which results from the previously calculated second curve (44) by a predetermined angle (42'') around the second central ray (30), the further first curve (42') and the further second curve (44') are modified such that light emanating from the modified further second curve (42') is parallel and homogeneous, these steps are repeated until the sum of the predetermined angles equals 360°,that subsequently a first connecting surface connecting all first curves is calculated as a first optical surface (46) and a second connecting surface connecting all second curves is calculated as a second optical surface (48), that the first curve is divided into first sections during the calculation and the second curve is divided into second sections, and that for the calculation it is assumed that every second section is illuminated by exactly one first section.

Description

[0001] The present invention relates to a method according to the preamble of claim 1. Methods for calculating the optically effective areas of a lighting unit of a motor vehicle lighting system, which is configured to convert light from a semiconductor light source exhibiting a Lambertian emission characteristic into parallel light, are known. Known lighting systems utilize optically effective areas that convert the propagation directions of light from a point light source, for example, light from a semiconductor light source such as a light-emitting diode, into parallel light by means of targeted refraction or reflection. An example of a reflective optical surface that accomplishes this is a parabolic reflective surface with a semiconductor light source arranged at its focal point and illuminating the reflective surface.Other examples include the refracting surfaces of a suitably shaped lens and the refracting and reflecting surfaces of a catadioptric attachment. A method for calculating optical surfaces is known from US 8,035,898 B2.

[0002] A disadvantage of such lighting devices is that the luminous flux density of the light emanating from the optical surfaces of the light source is often not homogeneous.

[0003] When using a light source with a Lambertian emission characteristic, such as that found in LEDs positioned at the focal point of a paraboloid, the luminous flux density at the center of the illuminated output cross-section is, for example, much higher than at its edge. This drop in brightness is undesirable in many applications, as a homogeneous luminous flux density is generally perceived as more aesthetically pleasing than a less homogeneous one.

[0004] Against this background, the object of the present invention is to provide a method of the type mentioned at the outset with which optical surfaces of a lighting unit of a lighting device for motor vehicles can be calculated with a luminous flux density distribution that can be specified in the design, in particular with a luminous flux density distribution of parallel light that can be specified as homogeneous.

[0005] This problem is solved by the features of claim 1. The invention differs from the prior art mentioned above by the characterizing features of claim 1.

[0006] According to these characteristics, a beam path of light is first specified, as it can be emitted from a light-emitting surface of the semiconductor light source and which, at the exit from the light-emitting surface, is represented by a first central ray, the direction of which corresponds to a main emission direction of the light-emitting surface, and which, at the exit from the lighting unit, is represented by a second central ray, the direction of which corresponds to a main emission direction of the lighting unit ( 10 ) matches.

[0007] The procedure further involves selecting a first point and a second point on the beam path. The first point lies on the first central ray, and the second point lies on the second central ray.

[0008] Next, a first plane and a second plane are defined. The first plane is spanned by a unit vector of a line connecting the two points and a second unit vector whose direction corresponds to the direction of the first central ray. The second plane is spanned by the unit vector of the connecting line and by a third vector whose direction corresponds to the direction of the second central ray.

[0009] Furthermore, an optically effective first curve lying in the first plane is calculated, which can be illuminated with light emanating from the light-emitting surface.

[0010] Similarly, a second optically effective curve lying in the second plane is calculated, which can be illuminated by light emanating from the first optically effective curve. The calculation is performed such that the light emanating from the second optically effective curve is both parallel and homogenized with respect to its luminous flux density.

[0011] Next, another first curve is calculated, which is derived from the previously calculated first curve by rotating it around the first central ray by a predetermined angle. Similarly, another second curve is calculated, which is derived from the previously calculated second curve by rotating it around the second central ray by the same predetermined angle. The second and third first curves are then modified so that light emanating from the modified second curve is parallel and homogeneous.

[0012] These steps of rotating by predetermined angles and calculating further first and second curves are preferably repeated until the sum of the predetermined angles equals 360° (or another desired angular width). Subsequently, a first connecting surface linking all first curves is calculated as a first optical surface, and a second connecting surface linking all second curves is calculated as a second optical surface.

[0013] This second optical surface is characterized by the fact that the light emanating from it is aligned parallel to the light source and has a homogeneous luminous flux density.

[0014] The lighting unit has, in particular, at least two optically effective surfaces with which the light beam emanating from the light source is shaped. The optical surfaces can be reflective or refracting surfaces. Through the interaction of the at least two optical surfaces, a light beam emanating from a half-space radiator, such as a light-emitting diode, can be converted into parallel light, and at the same time, the luminous flux density can be influenced over the entire cross-section of the light beam perpendicular to the direction of propagation. In this way, it is particularly possible to specify a lighting unit that provides parallel light with a homogeneous luminous flux density.

[0015] A preferred embodiment is characterized by the fact that the optically effective surfaces are mirror-reflective surfaces.

[0016] It is also preferred that the specularly reflective surfaces are specularly coated concave mirrors.

[0017] Furthermore, it is preferred that the specularly reflecting surfaces are interfaces of an optical fiber where total internal reflections take place.

[0018] Another preferred embodiment is characterized by the fact that the optically effective surfaces are refractive surfaces of lenses.

[0019] Of the optically effective surfaces, one can be a refracting surface and another a reflective surface.

[0020] It is also preferred that the predetermined angle has a value between 1° and 10°.

[0021] Furthermore, it is preferred that the first curve is divided into first sections during the calculation and the second curve is divided into second sections.

[0022] Another preferred embodiment is characterized by the fact that every second section is illuminated by exactly one first section.

[0023] It is also preferred that the position, shape, and size of the first and second sections are determined by the following boundary conditions: Second sections illuminated by adjacent first sections are themselves adjacent to each other. The first and second sections are shaped such that light emanating from a second section has an opening angle smaller than the solid angle of the light illuminating the first section from the semiconductor light source that illuminates the second section.Both the first and second curves are monotonically curved or straight lines, and the size, position, and shape of the first and second sections are predetermined such that differences between the luminous flux densities in the beams emanating from the second sections are smaller than differences between the luminous flux densities emanating from the first sections. Further advantages will become apparent from the following description, the drawings, and the dependent claims. It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the present invention.

[0024] Exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description.

[0025] These show, each in schematic form: Fig. 1 a lighting unit for a lighting device of a motor vehicle; Fig. 2 a section through the lighting unit from the Fig. 1; Fig. 3 an initial beam path of a central beam emanating from the semiconductor light source and whose course is influenced by the action of the two optical surfaces; Fig. 4 a first curve and a second curve interacting with it; and Fig. 5 an arrangement of n first curves whose connecting surface gives a first optically effective surface, together with an arrangement of n second curves whose connecting surface gives a second optically effective surface.

[0026] In detail, the Fig. 1 lighting unit 10 for a motor vehicle lighting system. The lighting unit10 has a lower part 12 and an upper part 14 on.

[0027] Fig. Figure 2 shows a cross-section through the lighting unit. 10 from the Fig. 1. How Fig. 2 shows, is in the lower part 12 a first reflector 16 arranged, which is powered by a semiconductor light source 18 is illuminated. From a first optically effective surface 20 of the first reflector 16 reflected light 22 the semiconductor light source 18 falls on a second visually effective surface 24 a second reflector 26 A central ray of the optically effective second surface 24 outgoing light 22 the semiconductor light source 18 , whose direction is the main radiation direction of the second reflector 26 corresponds to lies in the intersection plane of the Fig. 2.

[0028] The two optically effective surfaces 20 and 24 They interact in such a way that a semiconductor light source, which can be considered point-like, is emitted. 18 , e.g. a light-emitting diode, outgoing light beam is converted into parallel light and at the same time a homogeneous luminous flux density is established in a beam cross-section lying perpendicular to the main direction of light propagation.

[0029] Fig. Figure 3 shows a beam path of a light source from the semiconductor light source 18 outgoing and in its course through an action of the two optical surfaces 20 , 24 influenced central beam.

[0030] The two optically effective surfaces 20 and 24 can be generated by first creating a beam path of light 22 is specified as it is from a light-emitting surface of the semiconductor light source 18is emittable and that at the exit from the light emission surface through a first central beam 28 is represented, the direction of which corresponds to a main emission direction of the light-emitting surface.

[0031] Furthermore, the beam path should be enhanced with a second central beam as it exits the lighting unit. 30 and a corresponding main beam direction of the lighting unit 10 agree.

[0032] Starting from the first central ray 28 will be a first point 32 selected, the one on the first central beam 28 lies. Additionally, a second point 34 selected, the one on the second central beam 30 lies.

[0033] Based on this, a first level 36 and a second level 38 determined. The first level 36 is defined by a unit vector of a connecting line40 of the two 32 and 34 and a second unit vector can be spanned, the direction of which is the direction of the first central ray 28 corresponds.

[0034] The second level 38 is defined by the unit vector of the connecting line 40 and spannable by a third vector, the direction of which corresponds to the direction of the second central ray 30 corresponds.

[0035] The directions of the first central ray 28 and the second central ray 30 They do not necessarily have to lie in a plane; they can also be skew lines, i.e., non-parallel lines that do not intersect.

[0036] Fig. Figure 4 illustrates a calculation of one in the first level 36 lying first curve 42 and a calculation of one in the second level 38 lying second curve 44 Both curves42 , 44 are calculated under the premise that the light incident on them is from the semiconductor light source 18 at the curves 42 , 44 is reflected specularly, and that at the first curve 42 and at the second bend 44 The resulting reflections lead to the effect that the second optically effective surface 24 The outgoing light beam consists of parallel-aligned light with homogeneous luminous flux density perpendicular to the main propagation direction of the light propagating in the light beam.

[0037] The following is an example of such a calculation: In the calculation, the first curve is 42 divided into first sections, and the second curve 44is divided into second sections. For the calculation, it is assumed that every second section is illuminated by exactly one first section, with the position, shape, and size of the first and second sections being determined by the following boundary conditions: Second sections illuminated by adjacent first sections are themselves adjacent to each other. The first and second sections are shaped such that light emanating from a second section has an opening angle smaller than the solid angle of the light with which the first section is illuminated by the semiconductor light source that illuminates the second section. Both the first curve 42 as well as the second curve 44are monotonically curved or are straight lines, and the size, position and shape of the first sections and the second sections are predetermined such that differences between the luminous flux densities in the beams emanating from the second sections are smaller than differences between the luminous flux densities emanating from the first sections.

[0038] In further calculation steps, the initial first curve is used to create... 42 and this initial second curve 44 Further first curves and further second curves are calculated iteratively. The result of these calculations is in the Fig. 5 shown. Fig. 5 shows an arrangement 46 of n first curves 42 together with an arrangement 48 of n second curves 44 . Exactly one first curve each 42 This forms exactly one second curve 44a pair of curves that has the desired effect of producing parallel and homogeneous light.

[0039] These families of curves, or arrangements 46 , 48 of curves 42 , 44 are calculated as follows: A first curve 42 serves as the initial first curve 42 to calculate another first curve 42' The second curve serves a similar purpose. 44 , which interact with the initial first curve 42 The described parallelization and homogenization results in the initial second curve 44 to calculate a further second curve 44' For those in the Fig. 5 curves shown 42 , 42' , 44 , 44' It is assumed that such a relationship of cooperation exists.

[0040] For calculating the next first curve 42' The initial first curve will be 42in a first step by a predetermined angle 42'' , for example by 1° to 10°, around the first central ray 28 turned around.

[0041] Similarly, the initial second curve 44 for calculating the further second curve 44' in the second step by the predetermined same angle 44'' even 42'' , for example, by 1° to 10°, around the second central ray 30 turned around.

[0042] After turning, the first, rotated curve lies 42' and the rotated second curve 44' each in a new angular position and a new plane, which result from the rotations from the planes spanned before the rotation.

[0043] The property that from the initial second curve 42Reflected light, which is aligned parallel and has a homogeneous luminous flux density, does not behave invariantly under rotation. These properties are, in fact, lost during rotation.

[0044] Therefore, a further first curve lying in its new plane will then be added. 42' and a further second curve lying in its second plane 44 determined, which again possess the aforementioned properties of parallelization and homogenization of the luminous flux density.

[0045] This process is repeated until the planes / curves have been rotated 360°. Fig. Figure 5 shows a possible result of such a calculation.

[0046] A first, visually effective curved surface in the room 46 , which in the example shown is a reflection surface, results as the connecting surface of all first curves.

[0047] A second, visually effective curved surface in the room 48, which in the example shown is also a reflection surface, results as the connecting surface of all second curves. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 8035898 B2

[0001]

Claims

[1] Method for calculating optically effective areas (46, 48) of a lighting unit (10) of a lighting device of a motor vehicle, which lighting unit (10) is designed to convert light (22) of a semiconductor light source having a Lambertian emission characteristic into parallel light, characterized by, that first a beam path of light 22 is specified, as it can be emitted from a light-emitting surface of the semiconductor light source 18 and which at the exit from the light-emitting surface is represented by a first central ray 28, the direction of which corresponds to a principal emission direction of the light-emitting surface, and which at the exit from the illumination unit (10) is represented by a second central ray (30), the direction of which coincides with a principal emission direction of the illumination unit (10), a first point (32) is selected which lies on the first central ray (28), a second point (34) is selected which lies on the second central ray (30), a first plane (36) is determined which can be spanned by a unit vector of a connecting line (40) of the two points (32, 34) and a second unit vector, the direction of which corresponds to the direction of the first central ray (28),a second plane (38) is spanned by the unit vector of the connecting line (40) and by a third vector whose direction corresponds to the direction of the second central ray (30), an optically effective first curve (42) lying in the first plane (36) is calculated, which can be illuminated by light (22) emanating from the light-emitting surface, and a second optically effective curve (44) lying in the second plane (38) is calculated, which can be illuminated by light (22) emanating from the first optically effective curve (42), wherein light (22) emanating from the second optically effective curve (44) is both parallel and homogenized with respect to its luminous flux density, a further first curve (42') is calculated, which results from the previously calculated first curve (42) by a predetermined angle (42'') around the first central ray (28),A further second curve (44') is calculated, which results from the previously calculated second curve (44) by rotating the previously calculated second curve (44) around the second central ray (30) by the predetermined angle (42''), the further first curve (42') and the further second curve (44') are modified such that light emanating from the modified further second curve (42') is parallel and homogeneous, these steps are repeated until the sum of the predetermined angles equals 360°, and subsequently a first connecting surface linking all the first curves is calculated as a first optical surface (46), and a second connecting surface linking all the second curves is calculated as a second optical surface (48). [2] Method according to claim 1, characterized by , that the optically effective surfaces (46, 48) are specularly reflective surfaces. [3] Method according to claim 2, characterized by, that specularly reflective surfaces are specularly coated concave mirrors. [4] Method according to claim 2, characterized by , that the specularly reflecting surfaces are interfaces of an optical fiber where internal total reflections take place. [5] Method according to claim 1, characterized by that the optically effective surfaces are refracting surfaces of lenses. [6] Method according to any one of the preceding claims, characterized by , that the predetermined angle has a value between 1° and 10°. [7] Method according to any one of the preceding claims, characterized by , that the first curve is divided into first sections during the calculation and the second curve is divided into second sections. [8] Method according to claim 7, characterized by , that the calculation assumes that every second section is illuminated by exactly one first section. [9] Method according to claim 8, characterized by that the position, shape, and size of the first and second sections are determined by the following boundary conditions: Second sections illuminated by adjacent first sections are themselves adjacent. The first and second sections are shaped such that light emanating from a second section has an aperture angle smaller than the aperture solid angle of the light illuminating the first section from the semiconductor light source that illuminates the second section. Both the first and second curves are monotonically curved or are straight lines, and the size, position, and shape of the first and second sections are predetermined such that differences in the luminous flux densities in the beams emanating from the second sections are smaller than differences in the luminous flux densities emanating from the first sections.

Images