Lighting Unit for a Motor Vehicle Headlight for Generating a Light Distribution Having a Light-Dark Boundary

Abstract

The invention relates to a lighting unit for a motor vehicle headlight for generating a light distribution having a light-dark boundary, wherein the lighting unit (1) comprises a light source (2), a first reflector (R.sub.1) having at least one focal point (F.sub.1R1) in which the light source (2) is arranged, a second reflector (R.sub.2) having at least one focal point (F.sub.1R2), wherein the second reflector (R.sub.2) is arranged downstream of the first reflector (R.sub.1) in the beam path (S), and an aperture (B) arranged between the first reflector (R.sub.1) and the second reflector (R.sub.2). The first reflector (R.sub.1) has a first reflector portion (R.sub.11) and at least one second reflector portion (R.sub.12), the aperture (B) being arranged in such a way that it is associated with the first reflector portion (R.sub.11) of the first reflector (R.sub.1) and is arranged at a small distance (D.sub.1) near the beam (S.sub.11) emitted from the first reflector portion (R.sub.11), and clips the intermediate light image generated in the first reflector portion (R.sub.11) to form a light-dark boundary, and the intermediate light image generated in the second reflector portion (R.sub.12) is substantially free of influence of shadowing of the aperture arrangement.

Claims

1. A lighting unit for a motor vehicle headlight for generating a light distribution with a light-dark boundary, the lighting unit (1) comprising: at least one light source (2); at least one first reflector (R.sub.1) having at least one focal point (F.sub.1R1), wherein the at least one light source (2) is arranged in the at least one focal point (F.sub.1R1); at least one second reflector (R.sub.2) having at least one focal point (F.sub.1R2), wherein the at least one first reflector (R.sub.1) is configured to emit and forward light to the at least one second reflector (R.sub.2) and wherein the at least one second reflector (R.sub.2) is arranged downstream of the at least one first reflector (R.sub.1) in a beam path (S) and is configured to display an intermediate light image generated by the first reflector (R.sub.1); and at least one aperture (B) which is arranged in the beam path (S) between the at least one first reflector (R.sub.1) and the at least second reflector (R.sub.2), wherein: the first reflector (R.sub.1) is constructed in at least two parts (R.sub.11, R.sub.12) and has a first reflector portion (R.sub.11) and at least one separate second reflector portion (R.sub.12), each reflector portion (R.sub.11, R.sub.12) having at least one focal point (F.sub.1R11, F.sub.1R12) in each case, and at least one focal point (F.sub.1R11, F.sub.1R12) of the first and the at least second reflector portion (R.sub.11, R.sub.12) is arranged in each case congruently at the location of the at least one light source (2), the at least two part first reflector (R.sub.11, R.sub.12) splitting is configured to split the beam (S.sub.1) exiting from the at least one light source (2) into at least two separate beams (S.sub.11, S.sub.12), the at least one aperture (B) is arranged in such a way that it is associated with the first reflector portion (R.sub.11) of the first reflector (R.sub.1) and is arranged at a small distance (D.sub.1) near the beam (S.sub.11) emitted from the first reflector portion (R.sub.11), and clips the intermediate light image generated in the first reflector portion (R.sub.11) to form a light-dark boundary, and the at least one aperture (B) is arranged at a greater distance (D.sub.2) away from the beam (S.sub.12) emitted from the at least second reflector portion (R.sub.12) and the intermediate light image generated in the second reflector portion (R.sub.12) is substantially free of influence of shadowing of the aperture arrangement.

2. The lighting unit (1) according to claim 1, wherein: the first reflector (R.sub.1) is constructed in a plurality of parts and has a plurality of reflector portions (R.sub.11, R.sub.12, R.sub.1N) having at least one focal point (F.sub.1R11, F.sub.1R12, F.sub.1R1N), the at least one light source (2) being arranged in each case in the at least one focal point (F.sub.1R11, F.sub.1R12, F.sub.1R1N), the at least one aperture (B) being arranged in such a way that it is exclusively associated with the first reflector portion (R.sub.11) of the first reflector (R.sub.1) and is arranged at a small distance (D.sub.1) near the beam (S.sub.11) emitted from the first reflector portion (R.sub.11), and clips the intermediate light image generated in the first reflector portion (R.sub.11) to form a light-dark boundary, and the at least one aperture (B) being arranged at a greater distance (D.sub.2, D.sub.N) away from the beams (S.sub.12, S.sub.1N) emitted from the second (R.sub.12) and optionally from the further reflector portions (R.sub.1N) of the first reflector (R.sub.1) at a distance and the intermediate light images generated in the second and optionally the further reflector portions (R.sub.12, R.sub.1N) being substantially free of influence of shadowing of the aperture arrangement.

3. The lighting unit (1) according to claim 1, wherein the second reflector (R.sub.2) is divided into two or more reflector segments (R.sub.21, R.sub.22, R.sub.2N) in a facet-like manner, a first reflector segment (R.sub.21) of the second reflector (R.sub.2) being associated with the intermediate light image generated in the first reflector portion (R.sub.2) of the first reflector (R.sub.1).

4. The lighting unit (1) according to claim 1, wherein the second reflector (R.sub.2) is divided into two or more reflector segments (R.sub.21, R.sub.22, R.sub.2N) in a facet-like manner, precisely the first reflector segment (R.sub.21) of the second reflector (R.sub.2) being associated with the intermediate light image generated in the first reflector portion (R.sub.11) of the first reflector (R.sub.1).

5. The lighting unit (1) according to claim 1, wherein the at least one aperture (B) is attached directly to or at least near the first reflector portion (R.sub.12) of the first reflector (R.sub.1).

6. The lighting unit (1) according to claim 1, wherein the at least one aperture (B) is attached directly to or at least near the first reflector segment (R.sub.21) of the second reflector (R.sub.2).

7. The lighting unit (1) according to claim 1, wherein an aperture plane (BE) of the at least one aperture (B) corresponds to a focal plane (FE) of the at least one focal point (F.sub.1R21) of the first reflector segment (R.sub.21) of the second reflector (R.sub.2).

8. The lighting unit (1) according to claim 1, wherein at least the first reflector portion (R.sub.11) of the first reflector (R.sub.1) is an ellipsoidal reflector which has a second focal point (F.sub.2R11), the at least one aperture (B) being arranged so that it is spaced at a short distance (D.sub.1) from the second focal point (F.sub.2R11) of the first reflector portion (R.sub.11).

9. The lighting unit (1) according to claim 1, wherein the two or more reflector portions (R.sub.11, R.sub.12, R.sub.1N) of the first reflector (R.sub.1) are ellipsoidal reflectors in each case, each having a second focal point (F.sub.2R11, F.sub.2R12, F.sub.2R1N), the at least one aperture (B) being arranged such that it is arranged at a small distance (D.sub.1) near the second focal point (F.sub.2R11) of the first reflector portion (R.sub.11) and the aperture (B) being arranged at a greater distance (D.sub.2, D.sub.N) away from the second focal points (F.sub.2R12, F.sub.2R1N) of all further reflector portions (R.sub.12, R.sub.1N) of the first reflector (R.sub.1).

10. The lighting unit (1) according to claim 1, wherein the small distance (D.sub.1) from the beam (S.sub.11) and/or from the second focal point (F.sub.2R11) of the first reflector portion (R.sub.11) of the first reflector (R.sub.1) to an aperture edge (BK.sub.1) of the aperture (B) is then defined as near the aperture (B) if the distance (D.sub.1) is less than 1.7 times the value of a reference length (L), and the intermediate light image generated in the first reflector portion (R.sub.11) is clipped to form a light-dark boundary, the reference length (L) being selected as the smallest distance from the distances of the maximum illuminance (E.sub.MAX) of all reflector portions (R.sub.11, R.sub.12, R.sub.1N) of the first reflector (R.sub.1) to the aperture edge (BK.sub.1) of the aperture (B).

11. The lighting unit (1) according to claim 1, wherein the greater distance (D.sub.2, D.sub.N) from the beam (S.sub.12, S.sub.1N) and/or from the second focal point (F.sub.2R12, F.sub.2R1N) of the second reflector portion (R.sub.12) and possibly the further reflector portions (R.sub.1N) of the first reflector (R.sub.1) to an aperture edge (BK.sub.1) of the aperture (B) is then defined as away from the aperture (B), if by introducing the aperture (B) in the beam path (S) the luminous flux of the intermediate light image generated in the second and optionally the further reflector portions (R.sub.12, R.sub.1N) is reduced by at most 10%.

12. The lighting unit (1) according to claim 1, wherein the at least one aperture (B) has a first aperture edge (BK.sub.1) for generating a first light-dark boundary and a second aperture edge (BK.sub.2) for generating a second light-dark boundary and/or is adjustably arranged in the beam path (S) between the at least one first reflector (R.sub.1) and the at least second reflector (R.sub.2).

13. The lighting unit (1) according to claim 1, wherein the at least one light source (2) is an LED light source.

14. The lighting unit (1) according to claim 1, wherein the at least one light source (2) is a laser light source.

15. A motor vehicle headlight (10) having at least one lighting unit (1) according to claim 1.

16. The lighting unit of claim 10, wherein the distance (D.sub.1) is less than 1.5 times the value of a reference length (L).

17. The lighting unit of claim 10, wherein the distance (D.sub.1) is less than 1.3 times the value of a reference length (L).

18. The lighting unit of claim 11, wherein the luminous flux of the intermediate light image generated in the second and optionally the further reflector portions (R.sub.12, R.sub.1N) is reduced by at most 7%.

19. The lighting unit of claim 11, wherein the luminous flux of the intermediate light image generated in the second and optionally the further reflector portions (R.sub.12, R.sub.1N) is reduced by at most 5%.

Description

[0062] Further details, features, and advantages of the invention emerge from the following explanation of the embodiments shown schematically in the drawings. In the drawings:

[0063] FIG. 1 is a sectional view from the side of a lighting unit according to the prior art, which has a first and a second reflector, the second reflector being divided into four reflector segments, each of which being associated with an aperture in the beam path between the first reflector and the second reflector;

[0064] FIGS. 2a to 2d show in each case intermediate light images of the individual reflector segments of the second reflector sketched in FIG. 1;

[0065] FIG. 2e illustrates the overall light image composed of the intermediate light images shown in FIGS. 2a to 2d;

[0066] FIG. 3a is a sectional view from the side of a lighting unit according to the invention with a first reflector constructed in two parts, the beam path being illustrated in this case in a first reflector portion of the first reflector, which first reflector portion is arranged near the aperture and associated therewith;

[0067] FIG. 3b is a sectional view from the side of a further, second reflector portion of the lighting unit according to the invention shown in FIG. 3a, the beam path of that second reflector portion being illustrated in this case in FIG. 3b, which portion is arranged at a greater distance from the aperture;

[0068] FIG. 4a shows an intermediate light image which is generated in the first reflector portion of the first reflector illustrated in FIG. 3a and which has a light-dark boundary;

[0069] FIGS. 4b to 4d show intermediate light images in each case, which images are generated in the second reflector portion of the multi-part first reflector illustrated in FIG. 3b and which are not clipped;

[0070] FIG. 4e illustrates the overall light image composed of the intermediate light images shown in FIGS. 4a to 4d;

[0071] FIG. 5a is a sectional view from the side of an alternative embodiment of the invention with a multi-part first free-form reflector, in which the aperture is attached directly to the second reflector and is associated with a first reflector portion of the first free-form reflector;

[0072] FIG. 5b is a sectional view from the side of a further, second reflector portion of the first free-form reflector of the lighting unit according to the invention shown in FIG. 5a, the beam path of that second reflector portion which is free of shadowing influence by the aperture being illustrated here in FIG. 5b;

[0073] FIG. 6 is an isometric view obliquely from the front of a lighting unit according to the invention;

[0074] FIG. 7 is an isometric view at an angle from the front of a detail of a motor vehicle headlight with the lighting unit according to the invention shown in FIG. 6;

[0075] FIG. 8 is a schematic comparison on the left in the image of an aperture arrangement near the intermediate light image generated by the first reflector portion having a shadowed light-dark boundary, and, in the right half of the image, a generated intermediate light image which is substantially free of influence of shadowing of the aperture arrangement;

[0076] FIG. 9 is a schematic representation of a plurality of intermediate light images arranged at different distances away from an aperture;

[0077] FIG. 10 is a schematic representation of an intermediate light image which is substantially free of influence of shadowing by the aperture arrangement.

[0078] FIG. 1 schematically shows a lighting unit according to the prior art, which has a first reflector R.sub.1 and a second reflector R.sub.2, wherein, in a beam path S of the light symbolized by an arrow, an aperture B is provided between the first reflector R.sub.1 and the second reflector R.sub.2. The second reflector R.sub.2 is divided in this case into four reflector segments R.sub.21, R.sub.22, R.sub.23, and R.sub.24 which are arranged horizontally next to one another and which are associated in each case with the aperture B. The first reflector R.sub.1 is designed in this case, for example, as an ellipsoidal reflector and has a first focal point F.sub.1R1 and a second focal point F.sub.2R1. A light source 2, for example an LED light source, is located in the first focal point F.sub.1R1. The second focal point F.sub.2R1 of the first reflector R.sub.1 is spaced at a short distance D.sub.1 from an aperture edge BK.sub.1 of the aperture B. The aperture B is arranged in such a way that the second focal point F.sub.2R1 of the first reflector R.sub.1 lies in its aperture plane BE. The second reflector R.sub.2 used in this case is, for example, a free-form reflector, each of the reflector segments R.sub.21, R.sub.22, R.sub.23, and R.sub.24 having a focal point Fuzz in each case. These focal points F1R2 of the second reflector R.sub.2 are also arranged in the aperture plane BE. The beam S.sub.1 exiting from the light source 2 and deflected by the reflector R.sub.1 exits from the first reflector R.sub.1 at the same small distance D.sub.1 near the aperture edge BK.sub.1 of the aperture B.

[0079] A disadvantage of this embodiment known from the prior art is at least that the aperture B clips each of the intermediate light images of all four reflector segments R.sub.21, R.sub.22, R.sub.23, and R.sub.24, to form light-dark boundaries. Thus, the overall efficiency of this known lighting unit—expressed as the quotient of the luminous flux used to the luminous flux exiting (in each case specified in lumens [lm])—is disadvantageously reduced.

[0080] The illustrations FIGS. 2a to 2d show in sequence the respective intermediate light images of the individual reflector segments R.sub.21, R.sub.22, R.sub.23, and R.sub.24 of the second reflector R.sub.2 sketched in FIG. 1. Due to the different geometries, each of the reflector segments R.sub.21, R.sub.22, R.sub.23, and R.sub.24 generates different intermediate light images, each having different distortions of the intermediate light image, the light-dark boundary created by the aperture B being both deformed and rotated in the position thereof. The individual facets or reflector segments R.sub.21, R.sub.22, R.sub.23, and R.sub.24 shift the intermediate light image generated by them to different extents in the horizontal direction.

[0081] The light-dark boundary of the overall light image, which is illustrated in FIG. 2e as the sum of the intermediate light images shown in FIGS. 2a to 2d, is—apart from slight scattered light, which occurs in this case in the intermediate light image of the reflector segment R.sub.24 shown in FIG. 2d—generated substantially by the light-dark boundary of the intermediate light image of the reflector segment R.sub.21 shown in FIG. 2a.

[0082] A light image generated in this way is therefore inefficient since the light-dark boundary is only actually required in one of the four intermediate light images, namely in this case in the intermediate light image obtained in the first reflector segment R.sub.21, whereas the light-dark boundary is required in all intermediate light images of the four reflector segments R.sub.21, R.sub.22, R.sub.23, and R.sub.24. With a total luminous flux of 100 lumens [lm] used in this case and an assumed reflectivity of the reflectors used of 0.95 or 95%, an exiting luminous flux of a total of only 53 lumens [lm] is obtained.

[0083] FIG. 3a shows a lighting unit 1 according to the invention having a two-part first reflector R.sub.1 having a first reflector portion R.sub.11 and a second reflector portion R.sub.12, the beam path S of the first reflector portion R.sub.11 of the first reflector R.sub.1 being illustrated in this case in FIG. 3a. This first reflector portion R.sub.11 is arranged near the aperture B and is associated therewith. The aperture B is provided in the beam path S between the first reflector R.sub.1 and the second reflector R.sub.2. The second reflector R.sub.2 is divided in this case, for example, into four reflector segments R.sub.21, R.sub.22, R.sub.23, and R.sub.24 is arranged approximately horizontally next to one another, only the first reflector segment R.sub.21 being associated with the aperture B. The two reflector portions R.sub.11 and R.sub.12 of the first reflector R.sub.1 are designed in each case as ellipsoidal reflectors and each have a first focal point F.sub.1R11 or F.sub.1R12 and a second focal point F.sub.2R11 or F.sub.2R12. A light source 2, for example an LED light source, is located in the first focal point F.sub.1R11 or F.sub.1R12 of the two reflector portions R.sub.11 and R.sub.12.

[0084] FIG. 3b shows the beam path S in the second reflector portion R.sub.12 of the first reflector R.sub.1 for the lighting unit 1 according to the invention shown in FIG. 3a.

[0085] As can be seen from FIG. 3a, the second focal point F.sub.2R11 of the first reflector portion R.sub.11 is spaced at a short distance D.sub.1 from an aperture edge BK.sub.1 of the aperture B, wherein the beam S.sub.11 exiting from the light source 2 and deflected by the first reflector portion R.sub.11 exits from the first reflector R.sub.1 at this small distance D.sub.1 near the aperture edge BK.sub.1 of the aperture B. The aperture B thereby clips the intermediate light image generated in the first reflector portion R.sub.11, to form a light-dark boundary. This clipped intermediate light image is illustrated in FIG. 4a.

[0086] As illustrated in FIG. 3b, the second focal point F.sub.2R12 of the second reflector portion R.sub.12 of the first reflector R.sub.1 is spaced at a greater distance D.sub.2 away from an aperture edge BK.sub.1 of the aperture B. The smaller distance D.sub.1 of the second focal point F.sub.2R11 of the first reflector portion R.sub.11 from the aperture edge BK.sub.1 is in any case smaller than the greater distance D.sub.2 of the second focal point F.sub.2R12 of the second reflector portion R.sub.12 from the aperture edge BK.sub.1. The aperture B is arranged in such a way that the second focal point F.sub.2R11 of the first reflector portion R.sub.11 and the second focal point F.sub.2R12 of the second reflector portion R.sub.12 lie in each case in the aperture plane BE of the aperture B.

[0087] The second reflector R.sub.2 used in this case is, for example, a free-form reflector, each of the four reflector segments R.sub.21, R.sub.22, R.sub.23, and R.sub.24 having a focal point F.sub.1R21, F.sub.1R22, F.sub.1R23, or F.sub.1R24 in each case. These focal points F.sub.1R21, F.sub.1R22, F.sub.1R23, and F.sub.1R24 of the four reflector segments R.sub.21, R.sub.22, R.sub.23 and, R.sub.24 of the second reflector R.sub.2 are also arranged in the aperture plane BE.

[0088] The first reflector segment R.sub.21 of the second reflector R.sub.2 is associated with the intermediate light image generated in the first reflector portion Rn of the first reflector R.sub.1, this intermediate light image being shown in FIG. 4a.

[0089] The further reflector segments R.sub.22, R.sub.23, and R.sub.24 of the second reflector R.sub.2 are associated with the second reflector portion R.sub.12 of the first reflector R.sub.1. The corresponding intermediate light images of the second, third, and fourth reflector segments R.sub.22, R.sub.23, and R.sub.24 are shown in the illustrations FIG. 4b to FIG. 4d. Since the aperture B is arranged at a greater distance D.sub.2 away from the beam S.sub.12 emitted from the second reflector portion R.sub.12, the intermediate light images of the second, third, and fourth reflector segment R.sub.22, R.sub.23 R.sub.24 are substantially free of influence of shadowing of the aperture arrangement.

[0090] For this purpose, FIG. 4e shows the overall light image as the sum of the intermediate light images shown in FIGS. 4a to 4d. Since the aperture B only acts on the intermediate light image that is obtained from the pairing of the first reflector portion R.sub.11 of the first reflector R.sub.1 and the first reflector segment R.sub.21 of the second reflector R.sub.2 associated therewith, the light-dark boundary of the overall light image is generated only in the first reflector segment R.sub.21 of the second reflector R.sub.2. The other intermediate light images obtained from the second, third, and fourth reflector segments R.sub.22, R.sub.23, and R.sub.24 are advantageously not shadowed or clipped, since the distance D.sub.2 of the aperture B from the second focal point F.sub.2R12 of the second reflector portion R.sub.12 of the first reflector R.sub.1 is further away compared to the small distance D.sub.1 and therefore the intermediate light images of the reflector segments R.sub.22, R.sub.23, and R.sub.24 are substantially free of shadowing influences.

[0091] In the overall light image of the lighting unit 1 according to the invention shown in FIG. 4e, with a total luminous flux of 100 lumens [lm] used and an assumed reflectivity of the reflectors used of 0.95 or 95%, an exiting luminous flux of a total of 62 lumens [lm] is obtained.

[0092] In comparison to the above-mentioned example according to FIG. 1 known from the prior art, in the case of a lighting unit 1 according to the invention having a two-part first reflector having the two reflector portions R.sub.11, R.sub.12 according to the illustrations FIGS. 3a and 3b, this results particularly advantageously in an increase in the efficiency of the luminous flux—starting from 53 lumens [lm] with the light distribution known from the prior art as shown in FIG. 2e—to 62 lumens [lm] according to the light distribution according to the invention as illustrated in FIG. 4a. This corresponds to an absolute increase in efficiency of 9 lumens [lm] or a relative increase in overall efficiency of around 17%.

[0093] The two illustrations FIG. 5a and FIG. 5b each relate to an alternative embodiment of the invention and each show a lighting unit 1 with a multi-part first reflector R.sub.1, which is designed here as a two-part free-form reflector. For this purpose, the reflector R.sub.1 has a first reflector portion R.sub.11 with a focal point F.sub.1R11, the aperture B being arranged at a distance D.sub.1 near the beam S.sub.11 emitted from the first reflector portion R.sub.11. The aperture B clips the intermediate light image generated in the first reflector portion R.sub.11, to form a light-dark boundary.

[0094] The second reflector R.sub.2 is segmented in this case, for example, into four reflector segments R.sub.21, R.sub.22, R.sub.23, and R.sub.24 arranged next to one another. The aperture B is attached in this case directly to the second reflector R.sub.2 on its first reflector segment R.sub.21 and is only associated with the first reflector portion R.sub.11 of the first free-form reflector. Furthermore, only the first reflector segment R.sub.21 of the second reflector R.sub.2 is associated in this case with the intermediate light image generated in the first reflector portion R.sub.11 of the first reflector R.sub.1. This is shown in FIG. 5a.

[0095] FIG. 5b shows a further, second reflector portion R.sub.12 of the first free-form reflector of the lighting unit according to the invention shown in FIG. 5a, the beam path S of the second reflector portion R.sub.12 which is free of shadowing influence by the aperture B being illustrated here in FIG. 5b. The second, third, and fourth reflector segments R.sub.22, R.sub.23, and R.sub.24 of the second reflector R.sub.2 are associated with the intermediate light image generated in the second reflector portion R.sub.12 of the first reflector R.sub.1. These intermediate light images are advantageously not clipped or shadowed because of the lack of an aperture.

[0096] FIG. 6 is a detailed view of a lighting unit 1 according to the invention. In the image shown above, the lighting unit 1 comprises a light source 2 which is positioned behind or below the first reflector R.sub.1. The reflector R.sub.1 is constructed in one piece in this case and has two reflector portions R.sub.11 and R.sub.12. Dashed arrows indicate a first beam S.sub.11 of the light exiting from the first reflector portion R.sub.11 and a second beam S.sub.12 of the light exiting from the second reflector portion R.sub.12. The aperture B between the first reflector R.sub.1 and the second reflector R.sub.2 has a triangular aperture with three aperture edges BK.sub.1, BK.sub.2, and BK.sub.3, the aperture edges forming the three sides of the triangular aperture.

[0097] The aperture B is positioned in such a way that a first aperture edge BK.sub.1 of the aperture B is optically not active in this case and is arranged somewhat at a distance away from the first beam S.sub.11 and from the second beam S.sub.12. A second aperture edge BK.sub.2 and a third aperture edge BK.sub.3 of the aperture B are optically active in this case. The first beam S.sub.11 is focused in this case near the optically active aperture edge BK.sub.3. The second beam S.sub.12 is focused near the optically active aperture edge BK.sub.2.

[0098] This allows that [0099] (i) only the intermediate light image generated in the third reflector portion R.sub.11 is clipped by the optically active first aperture edge BK.sub.3 to form a light-dark boundary, and [0100] (ii) only the intermediate light image generated in the second reflector portion R.sub.12 is clipped by the optically active second aperture edge BK.sub.2 to form a light-dark boundary.

[0101] The intermediate light image generated in the first reflector portion R.sub.11 remains substantially free of influence of shadowing of the aperture edge BK.sub.2. The intermediate light image generated in the second reflector portion R.sub.12 remains substantially free of influence of shadowing of the aperture edge BK.sub.3.

[0102] The second reflector R.sub.2 is segmented in this case, for example, into a plurality of reflector segments, with three reflector segments R.sub.21, R.sub.22, and R2.sub.3 arranged next to one another being considered in more detail for the following description. Only the first reflector segment R.sub.21 of the second reflector R.sub.2 is associated in this case with the intermediate light image generated in the first reflector portion R.sub.11 of the first reflector R.sub.1. The intermediate light images generated in the second and third reflector segments R.sub.22, R.sub.23 are advantageously not clipped, which increases the overall efficiency of the lighting unit 1 shown.

[0103] The aperture B shown in this case also has a further, second aperture edge BK.sub.2, which, analogously to the preceding description, can in turn serve for selective shadowing of the intermediate light image of a further reflector segment of the second reflector R.sub.2.

[0104] FIG. 7 is a detailed view of a motor vehicle headlight 10 with the lighting unit 1 according to the invention shown in FIG. 6. The lighting unit 1 is already in the installed position within the motor vehicle headlight 1 and is installed with the corresponding housing components of the headlight. A diffusing screen, which merely serves to protect the motor vehicle headlight 1 and which has no optical function, has been removed in this case in the view of FIG. 7 for a better overview and is not shown.

[0105] FIG. 8 is a schematic comparison of an aperture arrangement of a first reflector constructed in two parts, for example an ellipsoidal reflector, according to the invention. On the left in the picture, an intermediate light image generated by the first reflector portion R.sub.11 with a shadowed light-dark boundary is illustrated. The aperture edge BK.sub.1 is arranged in this case at a small distance D.sub.1 near the second focal point F.sub.2R11 of the first reflector portion R.sub.11. This distance D.sub.1 is selected to be equal to a reference length L. The reference length L, which can be used to assess or categorize the distance between the corresponding beam and the aperture B or—as is the case here—for an ellipsoid reflector between the second focal point F.sub.2R11 of the first reflector portion R.sub.11 the first reflector R.sub.1 and the aperture B, is determined as follows: [0106] For all reflector portions R.sub.11, R.sub.12, R.sub.1N of the first reflector R.sub.1, the distance between the maximum of the illuminance E.sub.MAX and the aperture edge of the aperture is measured; [0107] the smallest of these measured distances is selected as the reference length L.

[0108] The loss of luminous flux of the aperture arrangement shown in the left half of FIG. 8 is over 15% in this case.

[0109] In the right half of FIG. 8, an aperture arrangement is shown, the distance between the aperture edge BK.sub.1 of the aperture B and the second focal point F.sub.2R12 of the second reflector portion R.sub.12 being arranged at a greater distance D.sub.2 from the aperture. The distance D.sub.2 in this case is greater than one and a half times the value of the reference length L. The intermediate light image generated is, by definition, substantially free of influence of shadowing of the aperture arrangement. The loss of luminous flux of the aperture arrangement shown in the right half of FIG. 8 is below 7% in this case.

[0110] FIG. 9 is a schematic representation of a plurality of intermediate light images spaced at different distances from an aperture B or from its aperture edge BK.sub.1. The maximum illuminance of each individual intermediate light image has a specific minimum distance from the aperture or from the aperture edge, the shortest of these distances being defined as the reference length L. By definition, an intermediate light image is precisely near the aperture edge when the smallest distance of the maximum of the illuminance of the intermediate light image from the aperture edge exceeds a specified value.

[0111] As an example, 1.5 times the value of the reference length L is shown as a dashed line in FIG. 9 as the limit value. In FIG. 9, the two middle intermediate light images shown are positioned away from the aperture edge by definition since their distances D.sub.1 and D.sub.2 are greater than the limit value given in this case of 1.5 times the reference length L. The outer left intermediate light image is by definition near the aperture edge, since it is at a distance according to the reference length L from the aperture edge of the aperture B. Likewise, the outer right intermediate light image shown in FIG. 9 is only at a small distance D.sub.3 away from the aperture B and is therefore near the aperture edge.

[0112] FIG. 10 is a schematic representation of an intermediate light image which is substantially free of influence of shadowing by the aperture arrangement of the aperture B. The hatched region labeled 93% is limited by the isoline within which 93% of the luminous flux of the intermediate light image is located. The non-hatched outer region of the intermediate light image thus represents that edge region of the light image through which 7% of the luminous flux flows. By introducing the aperture B into the beam path, the luminous flux of the intermediate light image generated is reduced by less than 7% in this case.

LIST OF REFERENCE SIGNS

[0113] 1 Lighting unit [0114] 2 Light source [0115] 10 Motor vehicle headlight [0116] B Aperture [0117] BE Aperture plane [0118] BK.sub.1 (First) aperture edge of the aperture [0119] BK.sub.2 Second aperture edge of the aperture [0120] D.sub.1 Distance of the aperture from the beam of the first reflector portion [0121] D.sub.2 Distance of the aperture from the beam of the second reflector portion [0122] D.sub.N Distance of the aperture from the beam of the third or further reflector portion [0123] E.sub.MAX Maximum illuminance [0124] F.sub.1R1 (First) focal point of the first reflector [0125] F.sub.1R11 (First) focal point of the first reflector portion of the first reflector [0126] F.sub.1R12 (First) focal point of the second reflector portion of the first reflector [0127] F.sub.1R1N (First) focal point of the third or further reflector portion of the first reflector [0128] F.sub.2R1 Second focal point of the first reflector [0129] F.sub.2R11 Second focal point of the first reflector portion of the first reflector [0130] F.sub.2R12 Second focal point of the second reflector portion of the first reflector [0131] F.sub.2R1N Second focal point of the third or further reflector portion of the first reflector [0132] F.sub.1R2 (First) focal point of the second reflector [0133] F.sub.1R21 (First) focal point of the first reflector segment of the second reflector [0134] F.sub.1R22 (First) focal point of the second reflector segment of the second reflector [0135] F.sub.1R2N (First) focal point of the third or further reflector segment of the second reflector [0136] FE Focal plane of the (first) focal point of the first reflector segment of the second reflector [0137] L Reference length [0138] R.sub.1 First reflector [0139] R.sub.11 First reflector portion of the first reflector [0140] R.sub.12 Second reflector portion of the first reflector [0141] R.sub.1N Third or further reflector portion of the first reflector

LIST OF REFERENCE SIGNS (CONTINUED):

[0142] R.sub.2 Second reflector [0143] R.sub.21 First reflector segment of the second reflector [0144] R.sub.22 Second reflector segment of the second reflector [0145] R.sub.2N Third or further reflector segment of the second reflector [0146] S Beam path [0147] S.sub.1 Beam from the first reflector [0148] S.sub.11 Beam of the first reflector portion of the first reflector [0149] S.sub.12 Beam of the second reflector portion of the first reflector [0150] S.sub.1N Beam of the third or further reflector portion of the first reflector