Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
LED-BASED LAMP
Document Type and Number:
WIPO Patent Application WO/2010/079397
Kind Code:
A1
Abstract:
A lamp device for low-beam automotive applications has a reflector and a module with LEDs. The module is positioned with regard to the reflector so that the reflector generates at an exit interface of the lamp a beam from light emitted by the LEDs. The module comprises light re-directing means adjacent the LEDs and operative to direct a portion of the light incident on the means to the reflector. This configuration enables to recover light rays that would otherwise not contribute to illuminating the road surface.

Inventors:
ANSEMS, Johannes, P., M. (AE Eindhoven, NL-5656, NL)
DE GRAAF, Jan (AE Eindhoven, NL-5656, NL)
Application Number:
IB2009/055834
Publication Date:
July 15, 2010
Filing Date:
December 18, 2009
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
KONINKLIJKE PHILIPS ELECTRONICS N.V. (Groenewoudseweg 1, BA Eindhoven, NL-5621, NL)
ANSEMS, Johannes, P., M. (AE Eindhoven, NL-5656, NL)
DE GRAAF, Jan (AE Eindhoven, NL-5656, NL)
International Classes:
F21V7/00; F21S8/12; F21V13/04
Domestic Patent References:
WO2008084882A12008-07-17
Foreign References:
EP2009346A12008-12-31
EP1970617A12008-09-17
EP1870633A12007-12-26
US20060109669A12006-05-25
US6102557A2000-08-15
JP2002334605A2002-11-22
US7101062B22006-09-05
Attorney, Agent or Firm:
BEKKERS, Joost, J., J. et al. (High Tech Campus 44, AE Eindhoven, NL-5600, NL)
Download PDF:
Claims:
CLAIMS:

1. A lamp device (200; 300) comprising a reflector (104) and a module (102) with one or more LEDs, wherein: the module is positioned with regard to the reflector so that the reflector generates at an exit interface of the lamp a beam from light emitted by the one or more LEDs; the module comprises light re-directing means (202) adjacent the one or more LEDs and operative to direct a portion of the light incident on the means to the reflector.

2. The device of claim 1, wherein the light re-directing means comprises a further reflector.

3. The device of claim 1 or 2, wherein the light re-directing means comprises a refractor.

4. A module comprising one or more LEDs for use in the lamp device of claim 1 , 2 or 3.

Description:
LED-BASED LAMP

FIELD OF THE INVENTION

The invention relates to a lamp device, in particular, but not exclusively, for automotive applications. The invention also relates to a light source for use in such a lamp device.

BACKGROUND ART

Philips Lumileds has developed a module for automotive applications, wherein all light functions, including high-beam and low-beam, can be implemented with light-emitting diode (LED) technology.

LEDs are based on semiconductor technology. The light is emitted directly out of the semiconductor substrate when a forward voltage is applied. The color depends on the band-gap energy of valence and conduction band for the materials forming the semiconductor. The amber color is directly generated by the LED by Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material. Through a luminescence conversion process, white light is generated. A blue diode in combination with an applied converter material, the color blue and yellow, the combination of which is perceived as white light.

Philips Lumileds has introduced a new phosphor technology, referred to by the name of "Lumiramic". Lumiramic phosphor technology enables targeted production of white LEDs to specific correlated color temperatures (CCT) on the black-body curve, resulting in high volume availability in the most desired color temperatures. Lumiramic phosphor technology utilizes a ceramic phosphor plate and the Philips's Thin Film Flip Chip (TFFC) technology. TFFC technology is the only thin film process that removes the anode and cathode from the light output path and provides an unobstructed plane to which the Lumiramic plate can be applied. This optical alignment is not possible with other thin film technologies. The technology is already being incorporated into the company's LED automotive headlamp products, so that the auto industry's stringent color consistency requirements are met easily and through a completely scalable manufacturing process.

To achieve the targeted light patterns with LED applications in headlamps, two conventional options are available that are already implemented in filament lamps and gas discharge lamps: either the light of the LED is redirected through a reflector or light guide in order to achieve the light pattern on the road, or compact systems can be applied that project the light in the street using a lens. Due to their small sizes, LEDs offer the opportunity to combine both light systems for the first time.

SUMMARY OF THE INVENTION

For making an efficient automotive beam shape with a reflector/LED combination, preferably a deep reflector in a certain aperture is used. However, a deep reflector has a large magnification factor and will create high illumination in front of the car and less illumination at the desired points nearby the cut-off line. As known, the cut-off line is the boundary between light and darkness. In designing such reflectors for automotive applications, there is a trade-off between efficiency and beam performance. Efficiency is necessarily decreased in order to obtain high illumination values at the regulation points 75R, 50V and 5OR (for right hand traffic) without too much glare above the horizon. A definition of 75L, 75R, 5OL, 5OR and 50V can be found in, e.g., ECE regulations R 98 for headlamps, specifying maximum or minimum light levels at pre-determined locations within the headlamp's beam. The efficiency is determined by the ratio of the amount of light used in the shaped light beam projected onto the area in front of the vehicle versus the total amount of light available at the light source, here: the LEDs.

The inventors have realized that a significant portion of the light generated by the LEDs is not being used in the eventual beam, owing to the exit angle of this light portion with respect to the optical axis of the reflector/LED system. Too small an angle between a direction of light from the LEDs on the one hand, and the optical axis in the direction of the exit interface of the lamp on the other hand, gives rise to light being scattered beyond the beam. The inventors address the problem of how to increase efficiency while still adhering to the required ECE regulations with regard to light levels near the cut-off line, e.g., in a low- beam lighting system of a road vehicle.

The inventors therefore propose a lamp that comprises a reflector and a module with one or more LEDs. The module is positioned with regard to the reflector so that the reflector generates at an exit interface of the lamp a beam from light emitted by the one or more LEDs. The module comprises a light re-directing means adjacent the one or more LEDs and operative to direct a portion of the light incident on the means to the reflector.

The light re-directing means intercepts a portion of the light, wasted in conventional configurations, and re-directs it towards the reflector. The reflector is configured to generate a beam of desired spatial properties, and adds the thus re-directed light to the conventional beam. As the light re-directing means is mounted close to the LEDs, the means can be very small with regard to a characteristic dimension of the first reflector. That is, the means has a characteristic dimension representative of the dimension of a LED itself. As a consequence of these small dimensions, the light re-directing means hardly blocks any light from the reflector.

The re-directing means comprises, e.g., a further reflector or a refracting element such as a prism, or a combination thereof. The LEDs are manufactured using semiconductor technology. Preferably, the re-directing means is made in the same technology. For example, a reflecting light re-directing means can be made by providing a metal layer on a surface of a suitably shaped element integrated in or otherwise attached or clamped to the substrate accommodating the LEDs. For example, SMD (surface-mount device) technology can be applied in order to solder the reflector, refractor or a combination thereof to the substrate of the LEDs.

For completeness, reference is made to the following publications:

US patent 6,102,557 discloses a headlamp, wherein an auxiliary reflector is arranged at at least one of the portions close to upper, left or right ends of a main reflector, providing an effective section of a reflecting mirror, and outside a range that forms a light distribution characteristic. The auxiliary reflector reflects light in a direction adjacent to a side opposite to a side at which the auxiliary reflector is arranged relative to the light distribution characteristic defined by the main reflector. This allows a headlamp of this type, in which light having a relatively large tilt angle from the optical axis has been conventionally prevented by the housing of the headlamp from being radiated, to effectively radiate such light in a desired direction and in a necessary range. This publication neither teaches nor suggests the use of LEDs as a light source, nor the mounting of light re-directing means right at the source.

Japanese patent application publication 2002-334605 addresses the problem of how to provide a small-sized headlight with an appropriate range of appropriate width and good uniformity, which has no steps on a surface of a reflecting mirror, and which can generate a European-type low beam. The headlight described contains a light source collaborating with a reflecting mirror to form an irradiation beam having V-shaped cutoff. The reflecting mirror has four regions arranged side by side along the optical axis of the mirror. The first region, closest to the exit interface of the lamp, determines a width of the beam. The next, second, region gives the beam its range at the underside of a horizontal part of the cutoff. The third region gives the beam its range at the underside of a sloping part of the cutoff. The fourth region gives the beam its range along a longitudinal axis of a vehicle. The regions are adjoined without steps. The first region of the reflecting mirror has a reflecting face spreading light strongly to the lateral direction. The second and third regions are located on the same side of the light source. This publication neither teaches nor suggests the use of LEDs as a light source, nor the mounting of light re-directing means right at the source.

US patent 7,101,062 discloses a headlight device comprising a light source, a mirror exhibiting a reflecting surface and a transparent optical deflection element, i.e., a lens, positioned in front of the mirror. The mirror interacts with the light source in order to generate a beam bounded by a line of interruption. The deflection element provides a horizontal displacement of the light without modifying the vertical distribution of the latter. The device also has at least one detachment element, arranged on at least one of the surfaces of the mirror or of the optical deflection element reached by the light, to obtain a line of interruption of the light beam that is not flat. This publication neither teaches nor suggests the use of LEDs as a light source, nor the mounting of light re-directing means right at the source.

BRIEF DESCRIPTION OF THE DRAWING

The invention is explained in further detail, by way of examples and with reference to the accompanying drawing, wherein:

Fig.l is a diagram of a known lamp device;

Figs.2 and 3 are diagrams of embodiments of a lamp device in the invention.

Throughout the Figures, similar or corresponding features are indicated by same reference numerals.

DETAILED EMBODIMENTS

Fig. 1 is a diagram of a known lamp device 100, schematically illustrating the spatial configuration of the components of device 100 in cross section. Device 100 is designed as a low-beam lighting system for use in a road vehicle such as an automobile. Device 100 comprises a light source 102, a reflector 104 and an exit interface 106, e.g., a lens. Light source 102 comprises one or more LEDs. Reflector 104 is shown, by way of example, as having a parabolic or similar smooth cross-section. It is clear to the person skilled in the art that the cross-section of reflector 104 may have any other suitable shape, e.g., elliptic, smooth or stepped, asymmetrical or symmetrical in cross-section, etc. Also, lens 106 is shown as positioned at the rim of reflector 104, and oriented substantially perpendicularly to the optical axis of reflector 104. It will be understood that this is merely an example, and that lens 106 can be mounted slanted and/or at a distance from reflector 104. Source 102 emits light from its upper surface. The rays of the light emitted lie within a region that, in the cross-section, is bounded by extreme rays 108 and 110. One other ray is shown, indicated by reference numeral 112. Note that the rays between ray 108 and 112 are not directed by reflector 104, and thus are prevented from contributing to illuminating the road surface in front of the vehicle. The rays between ray 112 and ray 110 do illuminate the road surface.

Fig.2 is a schematic diagram, in cross-section, of an embodiment 200 of a lamp device according to the invention. Here, light re-directing means 202 is mounted at or near light source 102. Means 202 intercepts the rays between rays 112 and 108 and re-directs them to the road surface in front of the vehicle via reflector 104. In the example shown in Fig.2, means 202 comprises a mirror, properly positioned and oriented to intercept the otherwise wasted rays and re-direct them to the desired area of the road surface via reflector 104. Mirror 202 has been shown as a simple flat mirror. Alternatively, the shape of mirror 202 may be curved so as to control the eventual convergence or divergence of the rays reflected by mirror 202 and reflector 104, and incident on the road surface, thus giving rise to a desired light distribution.

Fig.3 is a schematic diagram, in cross-section, of an embodiment 300 of a lamp device in the invention. Light re-directing means 202 comprises a refracting component. The refracting material of component 202 affects the optical path of the rays as initially emitted by source 102 and that lie between ray 112 and ray 108, as can be seen from comparing Fig.3 to Fig.l. In Fig.l, ray 108 would be wasted, whereas in Fig.3, refracting component 202 causes ray 108 to be directed by reflector 104 and thus contribute to illuminating the ground surface in front of lamp 300. If component 202 is a rectangular slab of a homogeneous refracting material, a ray entering and then exiting the slab is shifted with respect to the original ray that would be present in the absence of the slab. The shifted ray strikes reflector 104 at a location different from the location where the original ray would have struck reflector 104 in the absence of component 202. Accordingly, refracting component 202 can be designed in such a way that the otherwise wasted rays are re-directed towards reflector 104 after exiting component 202. The design may be determined by the shape of a piece of refracting material and/or by the magnitude of the index of refraction that is constant for a homogeneous piece of material or that may be made to vary according to the location within the piece of material, given the light distribution at source 102, the shape of reflector 104 and the desired light distribution of the light incident on the road surface. As an option, refracting component 202 affects the color of the light refracted and eventually projected on the road surface, e.g., by means of component 202 acting as a prism that spatially resolves the entering light into multiple colored beams.