Lamp unit for a portable lamp, and portable lamp

Abstract

The invention relates to a lamp unit for a portable lamp, in particular for a hand lamp, a head-mounted lamp or a bicycle lamp, said lamp unit comprising a light source and a lens which are positioned on a common optical axis, the light source coinciding with the origin of a Cartesian coordinate system (lamp coordinate system) and the optical axis coinciding with the z-axis of the coordinate system. The invention also relates to a portable lamp, in particular a hand lamp, a head-mounted lamp or a bicycle lamp comprising such a lamp unit. In order to provide a lamp unit for a portable lamp, in particular for a hand lamp, a head-mounted lamp and a bicycle lamp, and a portable lamp, in particular a hand lamp, a head-mounted lamp and a bicycle lamp, said lamp unit and portable lamp optimising the illumination of a path section ahead, according to the invention: the lens is designed to focus a light beam incident from the light source to form 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.

Description

[0001]Lighting unit for a portable lamp and portable lamp The present invention relates to a lighting unit for a portable lamp, in particular for a hand lamp, headlamp or bicycle lamp, with a light source and a lens arranged on a common optical axis, wherein the light source coincides with the origin of a Cartesian coordinate system (lamp coordinate system) and the optical axis coincides with the z-axis of the coordinate system. Furthermore, the invention relates to a portable lamp, in particular a hand lamp, headlamp or bicycle lamp with such a lighting unit. According to the prior art, portable lamps, in particular hand lamps, headlamps or bicycle lamps, are known which have a reflector or a lens for focusing light 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, allowing the user to cycle even in poor visibility conditions. However, state-of-the-art portable lights, particularly handheld lights, headlamps, and bicycle lights, have light units that 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 being traveled. Furthermore, near and far areas are illuminated inhomogeneously, which negatively impacts the desired visibility conditions.The object of the present invention is to provide a lighting unit for a portable light, in particular for a handheld light, a headlamp, and a bicycle light, and a portable light, in particular a handheld light, a headlamp, and a bicycle light, which overcome the disadvantages of the prior art. In particular, the illumination of a path section ahead is to be optimized, which is to be traveled during the intended use of such a lighting unit within a portable light or during the intended use of such a portable light. This object is achieved by the lighting unit according to claim 1 and / or the portable light according to claim 11.According to the invention, the lens is configured to focus a light beam incident from the light source into a main light cone having a trapezoidal cross-section perpendicular to the optical axis, wherein the trapezoidal cross-section of the main light cone is isosceles and has two base sides of different lengths, wherein the comparatively longer base side is below the comparatively shorter base side with respect to the y-axis of the coordinate system. During intended use of the lighting unit and / or the portable light, it is arranged in the hand, on the forehead, or on the handlebar of a bicycle and is aligned at an angle to the essentially flat surface or the flat roadway.The main light cone, which has a trapezoidal cross-section, illuminates the section of the path ahead within a rectangular area when viewed vertically, thus only illuminating the area that is relevant when moving, particularly when cycling, in adverse visibility conditions. This ensures optimal illumination of the section of the path ahead. In practice, the illuminance within the illuminated area is not sharply defined, but rather there is a gentle decline in illuminance at the edges, particularly due to the extension of the light source. This gentle decline in illuminance also creates a non-irritating impression for the user. In addition, the portable light is energy-efficient because no areas of the surroundings that are unimportant for recognizing the relevant section of the path are illuminated.In this respect, the illuminance in the relevant area can be increased with constant energy consumption or the operating time of the portable lamp can be extended with constant illuminance in the relevant area. Advantageous further developments are specified below and in the subclaims. Preferably, the lighting unit is designed such that the main light cone produces an equal luminous flux on each surface element of the same area, which is arranged along the plane perpendicular to the illumination angle, along a plane which is inclined with respect to the xz plane of the coordinate system and about the x axis of the coordinate system by an angle ^ of +9°±5°, in particular +9°±3°, and offset downwards along the y axis of the coordinate system. During the intended use of a bicycle light which is attached to the handlebar of the bicycle in such a way that the optical axis is inclined by an angle of approx.9° relative to the roadway, the roadway coincides with the previously mentioned plane, which is inclined relative to the xz-plane of the coordinate system and around its x-axis by an angle ^ of +9° and offset downwards 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 roadway. Similar initial situations arise when a hand lamp and a head lamp are used as intended. A real route, whether 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 observer or at right angles to the direction of illumination.This advantageous illumination creates the impression of homogeneous illumination for the observer, who perceives the path ahead from an inclined perspective, which facilitates the recognition of obstacles and the path ahead. State-of-the-art lighting units and portable lights have also proven to have disadvantages because the optics used (lenses or reflectors) do not completely cover the half-space illuminated by the light sources. In the case of a freeform lens, the light emitted between 50° and 90° from the optical axis misses the lens, which corresponds to approximately 40% of the generated luminous flux. As a result, light is emitted undirected or absorbed by the lamp housing, which negatively impacts the energy efficiency of the lamps.In order to improve the energy efficiency of the luminaire and / or the lighting unit and to increase user safety, it is preferably provided that the lighting unit has a reflector that concentrically surrounds the light source and is designed to reflect light towards the lens, wherein the combination of light source, reflector and lens is designed such that a secondary light cone is produced that allows illumination of the surroundings outside 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. Preferably, the secondary light cone 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 predetermined light distribution and is therefore free of any artifacts.Furthermore, areas outside the main light cone are illuminated with low intensity, which means that, for example, obstacles hanging in the path can be recognized by the driver in good time. According to an advantageous development of the invention, the reflector is concave and rotationally symmetrical with respect to the optical axis. The surface of the reflector is reflective within the scope of an advantageous development of the invention. To ensure homogeneous illumination, also within the scope 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 white or gray, particularly if the intensity of the secondary light cone is to be low.If the secondary light cone is not to be rotationally symmetrical, corresponding segments of the reflector can be cut out or made comparatively darker. The reflector is preferably positioned in the immediate vicinity of the light source. It preferably has a curvature that increases from the inside to the outside and extends to an imaginary line between the light source and the outer regions of the lens in order to collect all the light emitted by the light source. Any power losses are thereby effectively minimized. According to a particularly preferred embodiment of the invention, the light entry surface of the lens is spherically convex and preferably has a radius of curvature of 39.5 mm ± 4 mm. The light source is preferably spaced from the light entry surface at a distance of 8.36 mm ± 2 mm along the optical axis.The light exit surface of the lens preferably corresponds to a plane with the following equation with respect to the coordinate system: z = f (x,y) = a1 + a2 y + a3 x. 2 + a4 y 2 + a5 x 2 y + a6 y 3 + a7 x 4 + a8 x 2 y 2 + a9 y 4 + a10 x 4 y + a11 x 2 y 3 + a12 y 5 + a13 x 6 + a14 x 4 y 2 + a15 x 2 y 4 + a16 y 6 + a17 x 6 y + a18 x 4 y 3 + a19 x 2 y 5 + a20 y 7 + a21 x 8 + a22 x 6 y 2 + a23 x 4 y 4 + a24 x 2 y 6 + a25 y 8<h2 style=";text-align:left;direction:ltr">For constants a1,…,a25 we get: 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<h2 style=";text-align:left;direction:ltr"> -6 <h2 style=";text-align:left;direction:ltr"> , a13 = 5.0224*10<h2 style=";text-align:left;direction:ltr"> -7 <h2 style=";text-align:left;direction:ltr"> , a14 = 9.13991*10<h2 style=";text-align:left;direction:ltr"> -7 <h2 style=";text-align:left;direction:ltr"> , a15 = 1.25403*10<h2 style=";text-align:left;direction:ltr"> -6 <h2 style=";text-align:left;direction:ltr"> , a16 = 4.33133*10<h2 style=";text-align:left;direction:ltr"> -7 <h2 style=";text-align:left;direction:ltr"> , a17 = 2.79949*10<h2 style=";text-align:left;direction:ltr"> -8 <h2 style=";text-align:left;direction:ltr"> , a18 = 4.83011*10<h2 style=";text-align:left;direction:ltr"> -8 <h2 style=";text-align:left;direction:ltr"> , a19 = 3.23232*10<h2 style=";text-align:left;direction:ltr"> -8 <h2 style=";text-align:left;direction:ltr"> , a20 = 6.63658*10<h2 style=";text-align:left;direction:ltr"> -9 <h2 style=";text-align:left;direction:ltr"> , a21 = -6.59067*10<h2 style=";text-align:left;direction:ltr"> -10 <h2 style=";text-align:left;direction:ltr"> , a22 = -1.75199*10<h2 style=";text-align:left;direction:ltr"> -9 <h2 style=";text-align:left;direction:ltr"> , a23 = -2.98079*10<h2 style=";text-align:left;direction:ltr"> -9 <h2 style=";text-align:left;direction:ltr"> , a24 = -2.22453*10<h2 style=";text-align:left;direction:ltr"> -9 <h2 style=";text-align:left;direction:ltr"> , a25 = -4.79623*10<h2 style=";text-align:left;direction:ltr"> -10. With the proposed geometry, the lens covers a solid angle of ± 54° with respect to the optical axis. The lens is preferably made of PMMA, but can alternatively be made of glass, silicone, PC, POC or similar polymers. The light source used is preferably an LED, in particular a dome-free LED, with a single or two square radiating surfaces. Specific embodiments of the invention are described below with reference to the figures. They show: Fig. 1a-c a lighting unit in different perspective views, Fig. 1d a lens in a perspective view, Fig. 2a the illuminance of the main light cone on a screen, Fig. 2b the illuminance of the secondary light cone on a screen and Fig. 3a-d schematic views of a bicycle light during intended use.1a-c show a lighting unit 1 for a portable light, in particular a handheld light, a headlamp, or a bicycle light, in different perspective views, each comprising 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 that 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 configured to focus a light beam incident from the light source 2 into a main light cone that has a trapezoidal cross-section perpendicular to the optical axis. The illuminance of the main light cone along a plane perpendicular to the optical axis is plotted for the relevant far field within a diagram with the axes x', y' in Fig.2a, where the axes x' and y' are parallel but offset to the axes x, y of the luminaire coordinate system. The representation of the illuminance is otherwise 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 side 7 of the main light cone is arranged below the comparatively shorter base side 6 of the main light cone with respect 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 the light within the area with a trapezoidal cross-section. Outside of this area, the illuminance disappears.The illuminance increases from very low values ​​at the (longer) base side 7 to a high value at the shorter base side 6 and thus just below the horizon x'. In order to produce such a trapezoidal light distribution in cross-section, the lens 3 has a spherically 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 illustrated embodiment, the lens 3 is made of PMMA and the light exit surface 5 is a plane which, with reference to the coordinate system, corresponds to the equation z = f (x,y) = a1 + a2 y + a3 x. 2 + a4 y 2 + a5 x 2 y + a6 y 3 + a7 x 4 + a8 x 2 y 2 + a9 y 4 + a10 x 4 y + a11 x 2 y 3 + a12 y 5 + a13 x 6 + a14 x 4 y 2 + a15 x 2 y 4 + a16 y<h2 style=";text-align:left;direction:ltr"> 6 <h2 style=";text-align:left;direction:ltr"> + a17 x<h2 style=";text-align:left;direction:ltr"> 6 <h2 style=";text-align:left;direction:ltr"> y + a18 x<h2 style=";text-align:left;direction:ltr"> 4 <h2 style=";text-align:left;direction:ltr"> y<h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> + a19 x<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> y<h2 style=";text-align:left;direction:ltr"> 5 <h2 style=";text-align:left;direction:ltr"> + a20 y<h2 style=";text-align:left;direction:ltr"> 7 <h2 style=";text-align:left;direction:ltr"> + a21 x<h2 style=";text-align:left;direction:ltr"> 8 <h2 style=";text-align:left;direction:ltr"> + a22 x<h2 style=";text-align:left;direction:ltr"> 6 <h2 style=";text-align:left;direction:ltr"> y<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> + a23 x<h2 style=";text-align:left;direction:ltr"> 4 <h2 style=";text-align:left;direction:ltr"> y<h2 style=";text-align:left;direction:ltr"> 4 <h2 style=";text-align:left;direction:ltr"> + a24 x<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> y<h2 style=";text-align:left;direction:ltr"> 6 <h2 style=";text-align:left;direction:ltr"> + a25 y<h2 style=";text-align:left;direction:ltr"> 8 <h2 style=";text-align:left;direction:ltr"> entspricht. For constant use a1,…, a25 gilt data: 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<h2 style=";text-align:left;direction:ltr"> -6 <h2 style=";text-align:left;direction:ltr"> , a13 = 5.0224*10<h2 style=";text-align:left;direction:ltr"> -7 <h2 style=";text-align:left;direction:ltr"> , a14 = 9.13991*10<h2 style=";text-align:left;direction:ltr"> -7 <h2 style=";text-align:left;direction:ltr"> , a15 = 1.25403*10<h2 style=";text-align:left;direction:ltr"> -6 <h2 style=";text-align:left;direction:ltr"> , a16 = 4.33133*10<h2 style=";text-align:left;direction:ltr"> -7 <h2 style=";text-align:left;direction:ltr"> , a17 = 2.79949*10<h2 style=";text-align:left;direction:ltr"> -8 <h2 style=";text-align:left;direction:ltr"> , a18 = 4.83011*10<h2 style=";text-align:left;direction:ltr"> -8 <h2 style=";text-align:left;direction:ltr"> , a19 = 3.23232*10<h2 style=";text-align:left;direction:ltr"> -8 <h2 style=";text-align:left;direction:ltr"> , a20 = 6.63658*10<h2 style=";text-align:left;direction:ltr"> -9 <h2 style=";text-align:left;direction:ltr"> , a21 = -6.59067*10<h2 style=";text-align:left;direction:ltr"> -10 <h2 style=";text-align:left;direction:ltr"> , a22 = -1.75199*10<h2 style=";text-align:left;direction:ltr"> -9 <h2 style=";text-align:left;direction:ltr"> , a23 = -2.98079*10<h2 style=";text-align:left;direction:ltr"> -9 <h2 style=";text-align:left;direction:ltr"> , a24 = -2.22453*10<h2 style=";text-align:left;direction:ltr"> -9 <h2 style=";text-align:left;direction:ltr"> , a25 = -4.79623*10<h2 style=";text-align:left;direction:ltr"> -10. Fig. 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 towards the lens 3 that does not arrive directly from the lens 3. The combination of light source 2, reflector 8 and lens 3 is designed such that a secondary light cone is produced that illuminates the surroundings outside the main light cone. The illuminance of the secondary light cone along a plane arranged perpendicular to the optical axis is shown within a diagram with the axes x', y' in Fig. 2b, wherein the axes x' and y' are parallel to but offset from the axes x, y of the luminaire coordinate system, analogous to Fig. 2a. The light distribution of the secondary light cone is circular in cross-section and preferably has an essentially 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 surrounds the light source 2. Furthermore, the reflector 8 is concave and rotationally symmetrical with respect to the optical axis, wherein the reflector 8 has a greater curvature with increasing distance from the opening 9. The concavely curved section of the reflector 8 extends to a limiting ray 10, which is a linear connection between the light source 2 and the outer edge of the lens 3. Starting from this intersection line, the reflector 8 has an optically inactive region 16, which merges into an annular holding structure 17 for attaching the reflector 8 to a housing of the lamp. Fig. 1d shows a further perspective view of the lens 3. Figs. 3a-c show schematic representations of a portable lamp 11 with a lighting unit 1 according to the invention during intended use.For this purpose, the light 11 is designed as a bicycle light 111 and attached to the handlebar 12 of a bicycle 13. In addition to the lighting unit 1 and a housing, the bicycle light 111 can optionally have a heat sink, control electronics, a switch, and additional lighting devices for daytime running lights and / or for lateral visibility. It can optionally be designed as a battery-powered light or for connection to the accumulator of an e-bike. The optical axis of the bicycle light 111 or the lighting unit 1 is inclined downwards by a leading angle α of 9° relative to a horizontal line. Assuming a height of the bicycle light 111 of approximately 1 m above the roadway 14, the main light cone illuminates the roadway 14 within a rectangular area in front of the bicycle 13 (Figs. 3b, 3c). The secondary light cone creates an illuminated area that, in contrast, is hyperbolically shaped.In all of this, the area illuminated by the main light cone falls entirely within the area illuminated by the secondary light cone (Fig. 3c). To give the user the impression of homogeneous illumination of the upcoming section of the road by the main light cone, the illuminance is adjusted such that a constant vertical illuminance is achieved on the roadway 14, which is inclined by 9° relative to the optical axis. This results in, as schematically shown in Fig. 3d, an equal luminous flux on each surface element 15 arranged along the roadway 14 perpendicular to the direction of illumination. The schematically illustrated surface elements 15 each have a uniform and therefore identical surface area.Reference numeral 1 lighting unit 2 light source 3 lens 4 light entry surface 5 light exit surface 6 short base side 7 long base side 8 reflector 9 opening 10 boundary beam 11 light 111 bicycle light 12 handlebar 13 bicycle 14 roadway 15 surface element 16 non-active area 17 support structure A distance.

Claims

Claims 1. Lighting unit (1) for a portable light (11), in particular for a hand lamp, headlamp, or bicycle light (111), with a light source (2) and a lens (3) arranged on a common optical axis, wherein the light source (2) coincides with the origin of a Cartesian coordinate system and the optical axis coincides with the z-axis of the coordinate system, characterized in that the lens (3) is configured to focus a light beam incident from the light source (2) into a main light cone having a trapezoidal cross-section perpendicular to the optical axis, wherein the trapezoidal cross-section of the main light cone is isosceles and has two base sides (6, 7) of different lengths, wherein the comparatively longer base side (7) is below the comparatively shorter (6) base side with respect to the y-axis of the coordinate system.Lighting unit (1) according to claim 1, characterized in that the lighting unit (1) is designed such that the main light cone along a plane which is inclined with respect to the xz-plane of the coordinate system and about the x-axis of the coordinate system by an angle ^ of +9°±5°, in particular +9°±3°, and offset downwards along the y-axis of the coordinate system, generates an equal luminous flux on each surface element (15) of the same area which is arranged along the plane perpendicular to the illumination angle.

3. Lighting unit (1) according to one of 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 towards the lens (3), wherein the combination of light source (2), reflector (8) and lens (3) is designed such that a. A secondary light cone is produced which allows illumination of the surroundings outside the main light cone.

4. Lighting unit (1) according to claim 3, characterized in that the intensity of the secondary light cone is lower than the intensity of the main light cone.

5. Lighting unit (1) according to one of claims 3 or 4, characterized in that the secondary light cone has a homogeneous intensity around the optical axis.

6. Lighting unit (1) according to one of claims 3 to 5, characterized in that the reflector (8) is concave and rotationally symmetrical with respect to the optical axis.

7. Lighting unit (1) according to one of claims 3 to 6, characterized in that the light-reflecting surface of the reflector (8) is white.

8. Lighting unit (1) according to one of claims 1 to 7, characterized in that the light entry surface (4) of the lens (3) is spherically convex and preferably has a radius of curvature of 39.5 mm ± 4 mm. 9.Lighting unit (1) according to one of claims 1 to 8, 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).

10. Lighting unit (1) according to one of claims 1 to 9, characterized in that the light exit surface (5) of the lens (3) corresponds, with respect to the coordinate system, to a plane with the following equation: z = f (x, y) = a1 + a2 y + a3 x. 2 + a4 y 2 + a5 x 2 y + a6 y 3 + a7 x 4 + a8 x 2 y 2 + a9 y 4 + a10 x 4 y + a11 x 2 y 3 + a12 y 5 + a13 x 6 + a14 x 4 y 2 + a15 x 2 y 4 + a16 y 6 + a17 x 6 y + a18 x 4 y3 + a19 x 2 y 5 + a20 y 7 + a21 x 8 + a22 x 6 y 2 + a23 x 4 y 4 + a24 x 2 y 6 + a25 y 8 , where the following applies to the constants a1,…,a25: 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 11. Portable lamp (11), in particular a hand lamp, head lamp or bicycle lamp (111), characterized in that the lamp (11) has a lighting unit (1) according to one of claims 1 to 10.

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