DE102022124330A1 - Lighting unit and lamp - Google Patents

Abstract

The present invention relates to a lighting unit for a lamp, in particular for a vehicle or bicycle lamp, with a light source and a lens, which are arranged on a common optical axis, the light source having the origin of a Cartesian coordinate system and the optical axis having the z -axis of the coordinate system coincide. The invention further relates to a lamp, in particular a vehicle or bicycle lamp, with such a lighting unit. In order to optimize the illumination of a path section ahead, it is provided that the lens is set up to bundle a light beam incident from the light source into a main light cone which has a trapezoidal cross section perpendicular to the optical axis, the trapezoidal cross section of the main light cone being isosceles and has two base sides of different lengths, the comparatively longer base side being below the comparatively shorter base side with respect to the y-axis of the coordinate system.

Description

The present invention relates to a lighting unit for a lamp, in particular for a vehicle or bicycle lamp, with a light source and a lens, which are arranged on a common optical axis, the light source having the origin of a Cartesian coordinate system (lamp coordinate system) and the optical axis coincide with the z-axis of the coordinate system.

The invention further relates to a lamp, in particular a vehicle or bicycle lamp, with such a lighting unit.

According to the prior art, lights, in particular vehicle or bicycle lights, are known which have a reflector or a lens in order to concentrate light that is emitted by a light source. A light-emitting diode (LED) is usually used as the light source. The light is focused in such a way that the path ahead is illuminated, so that the user can drive even in dark visibility conditions. However, the bicycle lights known from the prior art have lighting units that only inadequately illuminate the path ahead when used as intended. In particular, areas off the path are illuminated in an uncontrolled manner, meaning that the available luminous flux is not fully utilized to illuminate the section of path to be traveled. Furthermore, near and far areas are illuminated inhomogeneously, which has a negative effect on the desired viewing conditions.

It is the object of the present invention to provide a lighting unit and a lamp that eliminate the disadvantages of the prior art. In particular, the illumination of a section of path ahead should be optimized, which is to be traveled when such a lighting unit is used as intended within a vehicle or bicycle lamp or when such a lamp is used as intended.

This task is solved by the lighting unit according to claim 1 and/or the lamp according to claim 11.

According to the invention, the lens is designed to focus a light beam incident from the light source into a main light cone which has a trapezoidal cross-section perpendicular to the optical axis, the trapezoidal cross-section of the main light cone being isosceles and having two base sides of different lengths, the comparatively longer base side being below the comparatively shorter base side in relation to the y-axis of the coordinate system. When the lighting unit and/or the light is used as intended, it is arranged on the handlebar of a bicycle and is arranged at an angle to the flat surface or the flat roadway. The main light cone, which has a trapezoidal cross-section, illuminates the section of the path ahead within an area that is rectangular in a vertical plan view, which means that only the area that is relevant when driving in adverse visibility conditions is illuminated. This ensures that the section of the path ahead is optimally illuminated. In practice, the illuminance within the illuminated area is not sharply limited, but there is a gentle drop in illuminance at the edge, particularly due to the extension of the light source. The gentle drop in illuminance also leads to an irritation-free impression for the user. In addition, the light is operated in an energy-efficient manner because no areas of the environment are illuminated that are unimportant for recognizing the relevant section of the path. In this respect, the illuminance in the relevant area can be increased with constant energy consumption or the operating time of the light can be extended with constant illuminance in the relevant area.

Advantageous further developments are specified below and in the subclaims.

It is preferably provided that the lighting unit is designed in such a way that the main light cone is inclined along a plane which is inclined by an angle α of +9° relative to the xz plane of the coordinate system and about the x-axis of the coordinate system and along the y-axis of the Coordinate system is offset downwards, an equal luminous flux is generated on each surface element of the same area, which is arranged along the plane perpendicular to the illumination angle. When using a lamp as intended, which is attached to the handlebar of the bicycle in such a way that the optical axis is inclined at an angle of 9 ° with respect to the road, the road coincides with the aforementioned plane, which is opposite to the xz plane of the coordinate system and around its x-axis by an angle α of +9° is inclined and offset downward along the y-axis of the coordinate system. Typically, the offset along the y-axis of the coordinate system is approximately 1 m and is therefore the approximate height of the handlebar above the road. A real route, be it paved or unpaved, usually consists of irregular elements and/or structures, such as pebbles or irregular road surfaces, which always have surface sections (facets) that are oriented at right angles to the viewer or at right angles to the direction of illumination. The advantageous illumination gives the viewer, who perceives the route ahead from an inclined perspective, the impression of homogeneous illumination, which facilitates the recognition of obstacles and the route ahead.

The lighting units and lights known from the prior art have also proven to be disadvantageous because the optics used (lenses or reflectors) do not completely cover the half-space illuminated by the light sources. In the case of a free-form lens, the light emitted between 50° and 90° from the optical axis misses the lens, which corresponds to approximately 40% of the luminous flux generated. As a result, light is emitted non-directionally or absorbed by the housing of the lights, which has a negative impact on the energy efficiency of the lights. In order to increase the energy efficiency of the lamp and/or the lighting unit and to increase the safety of the user, it is preferably provided that the lighting unit has a reflector which concentrically encompasses the light source and is designed to reflect light to the lens, the combination of Light source, reflector and lens are designed in such a way that a secondary light cone results, which allows the surroundings to be illuminated outside of the main light cone. Furthermore, it is preferably provided that the intensity of the secondary light cone is lower than the intensity of the main light cone. The secondary light cone preferably has a homogeneous intensity around the optical axis. As a result, almost all of the light emitted by the light source is used to illuminate the surroundings, which minimizes losses. The illumination takes place within a specified light distribution and is therefore free of any artifacts. Furthermore, areas outside the main light cone are illuminated with a low intensity, which means that, for example, obstacles hanging in the path are recognized by the driver in good time.

According to an advantageous development of the invention, it is provided that the reflector is concave and rotationally symmetrical with respect to the optical axis. The surface of the reflector is designed to be reflective as part of an advantageous development of the invention. In order to achieve homogeneous illumination, even within the framework of the secondary light cone, it is preferably provided that the surface of the reflector is matt with a small specular reflection component. Alternatively, the surface can also be designed white or gray, especially if the intensity of the secondary light cone is to be low. If the secondary light cone is not intended to be rotationally symmetrical, corresponding segments of the reflector can be cut out or made comparatively darker. The reflector is preferably placed in the immediate vicinity of the light source. Preferably, it has a curvature that increases from the inside out and extends to an imaginary line between the light source and the outer areas of the lens, so as to collect all the light emitted by the light source. This effectively minimizes any power losses.

According to a particularly preferred embodiment of the invention, it is provided that the light entry surface of the lens is spherical-convex and preferably has a radius of curvature of 39.5 mm ± 4 mm. The light source is preferably spaced along the optical axis at a distance of 8.36 mm ± 2 mm from the light entry surface. The light exit surface of the lens preferably corresponds to a plane with the following equation with respect to the coordinate system: $$\begin{array}{l}\text{e.g}=\text{f}\left(\text{x},\text{y}\right)={\text{a}}_1+{\text{a}}_2\text{y}+{\text{a}}_3{\text{x}}^2+{\text{a}}_4{\text{<figure-callout id="2" label="y" filenames="DE102022124330A1\_0004.png,DE102022124330A1\_0005.png" state="{{state}}">y</figure-callout>}}^2+{\text{a}}_5{\text{x}}^2\text{y}+{\text{a}}_6{\text{y}}^3+{\text{a}}_7{\text{x}}^4+{\text{a}}_{\mathrm{8th}}{\text{x}}^2{\text{y}}^2+\\ {\text{a}}_9{\text{y}}^4+{\text{a}}_{10}{\text{x}}^4\text{y}+{\text{a}}_{11}{\text{x}}^2{\text{y}}^3+{\text{a}}_{12}{\text{y}}^5+{\text{a}}_{13}{\text{x}}^6+{\text{a}}_{14}{\text{x}}^4{\text{y}}^2+{\text{a}}_{15}{\text{x}}^2{\text{y}}^4+{\text{a}}_{16}{\text{y}}^6+\\ {\text{a}}_{17}{\text{x}}^6\text{y}+{\text{a}}_{18}{\text{x}}^4{\text{y}}^3+{\text{a}}_{19}{\text{x}}^2{\text{y}}^5+{\text{a}}_{20}{\text{y}}^7+{\text{a}}_{21}{\text{x}}^{\mathrm{8th}}+{\text{a}}_{22}{\text{x}}^6{\text{y}}^2+{\text{a}}_{23}{\text{x}}^4{\text{y}}^4+\\ {\text{a}}_{24}{\text{x}}^2{\text{y}}^6+{\text{a}}_{25}{\text{y}}^{\mathrm{8th}}.\end{array}$$

For the constants a ₁ ,...,a ₂₅ the following applies: _a1 = 22.3548, _a2 = 0.101228, _a3 = -0.0373368, _a4 = -0.0436413, a ₅ = -0.000279657, _a6 = 0.0000275515, _a7 = -0.0000435405, _a8 = -0.0000400083, a ₉ = -0.0000684328, _a10 = -0.0000120918, _a11 = -0.0000125668, _a12 = -3.70917*10 ^-6 , _a13 = 5.0224*10 ^-7 , _a14 = 9.13991*10 ^-7 , _a15 = 1.25403*10 ^-6 , _a16 = 4.33133*10 ^-7 , _a17 = 2.79949*10 ^-8 , _a18 = 4.83011*10 ^-8 , _a19 = 3.23232*10 ^-8 , _a20 = 6.63658*10 ^-9 , _a21 = -6.59067*10 ^-10 , _a22 = -1.75199*10 ^-9 , _a23 = -2.98079*10 ^-9 , _a24 = -2.22453*10 ^-9 , _a25 = -4.79623*10 ^-10 .

With the proposed geometry, a solid angle of ± 54° is covered by the lens with respect to the optical axis. The lens is preferably made of PMMA, but can alternatively consist in particular of glass, silicone, PC, POC or similar polymers. An LED, in particular a dome-free LED, with a single or two square emitting surfaces is preferably used as the light source.

• 1a-c eine Leuchteinheit in unterschiedlichen perspektivischen Darstellungen,
• 1d eine Linse in perspektiver Darstellung,
• 2a die Beleuchtungsstärke des Hauptlichtkegels auf einem Schirm,
• 2b die Beleuchtungsstärke des Sekundärlichtkegels auf einem Schirm und
• 3a-d schematische Ansichten einer Leuchte beim bestimmungsgemäßen Gebrauch.

Specific embodiments of the invention are described below with reference to the figures. Show it:

• 1a -c a lighting unit in different perspective views,
• 1d a lens in perspective representation,
• 2a the illuminance of the main light cone on a screen,
• 2 B the illuminance of the secondary light cone on a screen and
• 3a -d schematic views of a lamp when used as intended.

The 1a -c show a lighting unit 1 in different perspective views, each of which has a light source 2 and a lens 3 with a light entry surface 4 and a light exit surface 5. The lens 3 and the light source 2 are arranged on a common optical axis which coincides with the z-axis of a Cartesian coordinate system. The optical axis intersects the light entry surface 4 of the lens 3 at its pole (vertex). The lens 3 is set up to bundle a light beam incident from the light source 2 into a main light cone which has a trapezoidal cross section perpendicular to the optical axis. The illuminance of the main light cone along a plane that is arranged perpendicular to the optical axis is for the far field relevant here within a diagram with the axes x', y' in 2a shown, where the axes x 'and y' are parallel but offset from the axes x, y of the luminaire coordinate system. The representation of the illuminance is unitless and logarithmic. The trapezoidal cross section of the light cone is isosceles and has two parallel base sides 6, 7 of different lengths. The comparatively longer base 7 of the main light cone is arranged below the comparatively shorter base 6 of the main light cone in relation to the y-axis of the coordinate system. The corners of the trapezoidal main light cone are rounded in the illustrated embodiment. The light distribution of the main light cone is limited to a distribution of light within the area which has a trapezoidal cross-section. Outside of this, the illuminance disappears. The illuminance increases from very small values on the (longer) base side 7 to a high value on the shorter base side 6 and therefore just below the horizon x '.

entspricht. Für die Konstanten a₁,...,a₂₅ gilt dabei: a₁ = 22,3548, a₂ = 0,101228, a₃ = -0,0373368, a₄ = -0,0436413, a₅ = -0,000279657, a₆ = 0,0000275515, a₇ = -0,0000435405, a₈ = -0,0000400083, a₉ = -0,0000684328, a₁₀ = -0,0000120918, a₁₁ = -0,0000125668, a₁₂ = -3,70917*10^-6, a₁₃ = 5,0224*10^-7, a₁₄ = 9,13991*10^-7, a₁₅ = 1,25403*10^-6, a₁₆ = 4,33133*10^-7, a₁₇ = 2,79949*10^-8, a₁₈ = 4,83011*10^-8, a₁₉ = 3,23232*10^-8, a₂₀ = 6,63658*10^-9, a₂₁ = -6.59067*10^-10, a₂₂ = -1.75199*10^-9, a₂₃ = -2.98079*10^-9, a₂₄ = -2.22453*10^-9, a₂₅ = -4.79623*10^-10. In order to produce such a trapezoidal cross-sectional light distribution, the lens 3 has a spherical-convex light entry surface 4 with a radius of curvature of 39.5 mm. The light source 2 has a distance A of 8.36 mm from the light entry surface 4 of the lens 3 along the optical axis. In the exemplary embodiment shown, the lens 3 is made of PMMA and the light exit surface 5 is a plane with reference to the coordinate system of the equation $$\begin{array}{l}\text{e.g}=\text{f}\left(\text{x},\text{y}\right)={\text{a}}_1+{\text{a}}_2\text{y}+{\text{a}}_3{\text{x}}^2+{\text{a}}_4{\text{<figure-callout id="2" label="y" filenames="DE102022124330A1\_0004.png,DE102022124330A1\_0005.png" state="{{state}}">y</figure-callout>}}^2+{\text{a}}_5{\text{x}}^2\text{y}+{\text{a}}_6{\text{<figure-callout id="3" label="y" filenames="DE102022124330A1\_0004.png,DE102022124330A1\_0005.png" state="{{state}}">y</figure-callout>}}^3+{\text{a}}_7{\text{x}}^4+{\text{a}}_{\mathrm{8th}}{\text{x}}^2{\text{<figure-callout id="2" label="y" filenames="DE102022124330A1\_0004.png,DE102022124330A1\_0005.png" state="{{state}}">y</figure-callout>}}^2+\\ {\text{a}}_9{\text{<figure-callout id="4" label="y" filenames="DE102022124330A1\_0004.png,DE102022124330A1\_0005.png" state="{{state}}">y</figure-callout>}}^4+{\text{a}}_{10}{\text{x}}^4\text{y}+{\text{a}}_{11}{\text{x}}^2{\text{<figure-callout id="3" label="y" filenames="DE102022124330A1\_0004.png,DE102022124330A1\_0005.png" state="{{state}}">y</figure-callout>}}^3+{\text{a}}_{12}{\text{<figure-callout id="5" label="y" filenames="DE102022124330A1\_0004.png,DE102022124330A1\_0005.png" state="{{state}}">y</figure-callout>}}^5+{\text{a}}_{13}{\text{x}}^6+{\text{a}}_{14}{\text{x}}^4{\text{<figure-callout id="2" label="y" filenames="DE102022124330A1\_0004.png,DE102022124330A1\_0005.png" state="{{state}}">y</figure-callout>}}^2+{\text{a}}_{15}{\text{x}}^2{\text{<figure-callout id="4" label="y" filenames="DE102022124330A1\_0004.png,DE102022124330A1\_0005.png" state="{{state}}">y</figure-callout>}}^4+{\text{a}}_{16}{\text{<figure-callout id="6" label="y" filenames="DE102022124330A1\_0006.png" state="{{state}}">y</figure-callout>}}^6+\\ {\text{a}}_{17}{\text{x}}^6\text{y}+{\text{a}}_{18}{\text{x}}^4{\text{<figure-callout id="3" label="y" filenames="DE102022124330A1\_0004.png,DE102022124330A1\_0005.png" state="{{state}}">y</figure-callout>}}^3+{\text{a}}_{19}{\text{x}}^2{\text{<figure-callout id="5" label="y" filenames="DE102022124330A1\_0004.png,DE102022124330A1\_0005.png" state="{{state}}">y</figure-callout>}}^5+{\text{a}}_{20}{\text{<figure-callout id="7" label="y" filenames="DE102022124330A1\_0006.png" state="{{state}}">y</figure-callout>}}^7+{\text{a}}_{21}{\text{x}}^{\mathrm{8th}}+{\text{a}}_{22}{\text{x}}^6{\text{<figure-callout id="2" label="y" filenames="DE102022124330A1\_0004.png,DE102022124330A1\_0005.png" state="{{state}}">y</figure-callout>}}^2+{\text{a}}_{23}{\text{x}}^4{\text{<figure-callout id="4" label="y" filenames="DE102022124330A1\_0004.png,DE102022124330A1\_0005.png" state="{{state}}">y</figure-callout>}}^4+\\ {\text{a}}_{24}{\text{x}}^2{\text{<figure-callout id="6" label="y" filenames="DE102022124330A1\_0006.png" state="{{state}}">y</figure-callout>}}^6+{\text{a}}_{25}{\text{y}}^{\mathrm{8th}}\end{array}$$

corresponds. For the constants a ₁ ,...,a ₂₅ the following applies: _a1 = 22.3548, a ₂ = 0.101228, a ₃ = -0.0373368, a ₄ = -0.0436413, a ₅ = -0.000279657, a ₆ = 0.0000275515, a ₇ = -0.0000435405, a ₈ = -0.0000400083, a ₉ = -0.0000684328, a ₁₀ = -0.0000120918, a ₁₁ = -0.0000125668, a ₁₂ = -3.70917*10 ^-6 , a ₁₃ = 5.0224*10 ^-7 , a ₁₄ = 9.13991*10 ^-7 , a ₁₅ = 1.25403*10 ^-6 , a ₁₆ = 4.33133*10 ^-7 , a ₁₇ = 2.79949*10 ^-8 , a ₁₈ = 4.83011*10 ^-8 , a ₁₉ = 3.23232*10 ^-8 , a ₂₀ = 6.63658*10 ^-9 , a ₂₁ = -6.59067*10 ^-10 , a ₂₂ = -1.75199*10 ^-9 , a ₂₃ = -2.98079*10 ^-9 , a ₂₄ = -2.22453*10 ^-9 , a ₂₅ = -4.79623*10 ^-10 .

1c shows the lighting unit 1 with an additional reflector 8, which concentrically surrounds the light source 2 and is designed to reflect the light to the lens 3 that does not enter there directly from the lens 3. The combination of light source 2, reflector 8 and lens 3 is designed in such a way that a secondary light cone results, which illuminates the surroundings outside the main light cone. The illuminance of the secondary light cone along a plane perpendicular to the optical axis is within a diagram with axes x', y' in 2 B shown, where the axes x' and y' are analogous to 2a are parallel but offset to the x,y axes of the luminaire coordinate system. The light distribution of the secondary light cone is circular in cross section and preferably has a substantially homogeneous illuminance. The main light cone runs completely within the secondary light cone. The reflector 8 has an opening 9 which is arranged coaxially to the optical axis and accommodates or encompasses the light source 2. Furthermore, the reflector 8 is concave and rotationally symmetrical with respect to the optical axis, with the reflector 8 having a greater curvature as the distance from the opening 9 increases. The concavely curved section of the reflector 8 extends up to a boundary beam 10, which is a linear connection between the light source 2 and the outer edge of the lens 3. Starting from this cutting line, the reflector 8 has an optically inactive area 16, which merges into an annular holding structure 17 for fastening the reflector 8 to a housing of the lamp.

1d shows another perspective view of the lens 3.

The 3a -c show schematic representations of a lamp 11 with a lighting unit 1 according to the invention when used as intended. For this purpose, the lamp 11 is designed as a bicycle lamp and is attached to the handlebar 12 of a bicycle 13. In addition to the lighting unit 1 and a housing, the lamp 11 can optionally have a heat sink, control electronics, a switch and additional lighting devices for a daytime running light and/or for side visibility. It can optionally be designed as a battery light or for connection to the battery of an e-bike. The optical axis of the lamp 11 or the lighting unit 1 is inclined downwards relative to a horizontal by a forward angle α of 9 °. If the height of the lamp 11 is assumed to be approximately 1 m above the road 14, the main light cone will illuminate the road 14 within a rectangular area in front of the bicycle 13 ( 3b , 3c ). The secondary light cone creates an illuminated area that is hyperbolic in shape. In all of this, the main light falls through area illuminated by the cone completely into the area illuminated by the secondary light cone ( 3c ).

So that the user has the impression that the section of path ahead is homogeneously illuminated by the main light cone, the illuminance is set in such a way that a constant vertical illuminance results on the roadway 14, which is inclined by 9° relative to the optical axis. From this it follows, as in 3d is shown schematically, an equal luminous flux on each surface element 15, which is arranged along the roadway 14 perpendicular to the direction of illumination. For this purpose, the surface elements 15 shown schematically each have a uniform and therefore identical surface area.

Reference symbols

1

Light unit

2

light source

3

lens

4

Light entry surface

5

Light exit surface

6

short base

7

long base side

8th

reflector

9

opening

10

Boundary beam

11

lamp

12

Handlebar

13

Bicycle

14

roadway

15

surface element

16

inactive area

17

Support structure

A

Distance

Claims (11)

Lighting unit (1) for a lamp (11), in particular for a vehicle or bicycle lamp, with a light source (2) and a lens (3), which are arranged on a common optical axis, the light source (2) having the origin a Cartesian coordinate system and the optical axis coincide with the z-axis of the coordinate system, characterized in that the lens (3) is set up to concentrate a light beam incident from the light source (2) into a main light cone which is perpendicular to the optical axis has a trapezoidal cross-section, the trapezoidal cross-section of the main light cone being isosceles and having two base sides (6, 7) of different lengths, the comparatively longer base side (7) being below the comparatively short one (6) in relation to the y-axis of the coordinate system. Base page is. Light unit (1). Claim 1 , characterized in that the lighting unit (1) is designed such that the main light cone is inclined along a plane which is inclined by an angle α of +9° relative to the xz plane of the coordinate system and about the x-axis of the coordinate system and along the y -Axis of the coordinate system is offset downwards, an equal luminous flux is generated on each surface element (15) of the same area, which is arranged along the plane perpendicular to the illumination angle. Lighting unit (1) according to one of the Claims 1 or 2 , characterized in that the lighting unit (1) has a reflector (8) which concentrically surrounds the light source (2) and is designed to reflect light to the lens (3), wherein the combination of light source (2), reflector (8) and lens (3) is designed such that a secondary light cone is obtained which allows illumination of the surroundings outside the main light cone. Light unit (1). Claim 3 , characterized in that the intensity of the secondary light cone is lower than the intensity of the main light cone. Lighting unit (1) according to one of the Claims 3 or 4 , characterized in that the secondary light cone has a homogeneous intensity around the optical axis. Lighting unit (1) according to one of the Claims 3 until 5 , characterized in that the reflector (8) is concave and rotationally symmetrical with respect to the optical axis. Lighting unit (1) according to one of the Claims 3 until 6 , characterized in that the light-reflecting surface of the reflector (8) is white. Lighting unit (1) according to one of the Claims 1 until 7 , characterized in that the light entry surface (4) of the lens (3) is spherical-convex and preferably has a radius of curvature of 39.5 mm ± 4 mm. Lighting unit (1) according to one of the Claims 1 until 8th , characterized in that the light source (2) is spaced along the optical axis at a distance of 8.36 mm ± 2 mm from the light entry surface (4) of the lens (3). Lighting unit (1) according to one of the Claims 1 until 9 , characterized in that the light exit surface (5) of the lens (3) corresponds to a plane with the following equation with respect to the coordinate system: $$\begin{array}{l}\text{e.g}=\text{f}\left(\text{x},\text{y}\right)={\text{a}}_1+{\text{a}}_2\text{y}+{\text{a}}_3{\text{x}}^2+{\text{a}}_4{\text{y}}^2+{\text{a}}_5{\text{x}}^2\text{y}+{\text{a}}_6{\text{y}}^3+{\text{a}}_7{\text{x}}^4+{\text{a}}_{\mathrm{8th}}{\text{x}}^2{\text{y}}^2+\\ {\text{a}}_9{\text{y}}^4+{\text{a}}_{10}{\text{x}}^4\text{y}+{\text{a}}_{11}{\text{x}}^2{\text{y}}^3+{\text{a}}_{12}{\text{y}}^5+{\text{a}}_{13}{\text{x}}^6+{\text{a}}_{14}{\text{x}}^4{\text{y}}^2+{\text{a}}_{15}{\text{x}}^2{\text{y}}^4+{\text{a}}_{16}{\text{y}}^6+\\ {\text{a}}_{17}{\text{x}}^6\text{y}+{\text{a}}_{18}{\text{x}}^4{\text{y}}^3+{\text{a}}_{19}{\text{x}}^2{\text{y}}^5+{\text{a}}_{20}{\text{y}}^7+{\text{a}}_{21}{\text{x}}^{\mathrm{8th}}+{\text{a}}_{22}{\text{x}}^6{\text{y}}^2+{\text{a}}_{23}{\text{x}}^4{\text{y}}^4+\\ {\text{a}}_{24}{\text{x}}^2{\text{y}}^6+{\text{a}}_{25}{\text{y}}^{\mathrm{8th}},\end{array}$$

where the following applies to the constants a ₁ ,...,a ₂₅ : _a1 = 22.3548, a ₂ = 0.101228, a ₃ = -0.0373368, a ₄ = -0.0436413, a ₅ = -0.000279657, a ₆ = 0.0000275515, a ₇ = -0.0000435405, a ₈ = -0.0000400083, a ₉ = -0.0000684328, a ₁₀ = -0.0000120918, a ₁₁ = -0.0000125668, a ₁₂ = -3.70917*10 ^-6 , a ₁₃ = 5.0224*10 ^-7 , a ₁₄ = 9.13991*10 ^-7 , a ₁₅ = 1.25403*10 ^-6 , a ₁₆ = 4.33133*10 ^-7 , a ₁₇ = 2.79949*10 ^-8 , a ₁₈ = 4.83011*10 ^-8 , a ₁₉ = 3.23232*10 ^-8 , a ₂₀ = 6.63658*10 ^-9 , a ₂₁ = -6.59067*10 ^-10 , a ₂₂ = -1.75199*10 ^-9 , a ₂₃ = -2.98079*10 ^-9 , a ₂₄ = -2.22453*10 ^-9 , a ₂₅ = -4.79623*10 ^-10 . Lamp (11), in particular vehicle or bicycle lamp, characterized in that the lamp (11) has a lighting unit (1) according to one of the Claims 1 until 10 having.

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