WO2012005685A1

WO2012005685A1 - Integrated led headlamp

Info

Publication number: WO2012005685A1
Application number: PCT/SG2010/000247
Authority: WO
Inventors: Hong Yuan Liu; Lye Hock Sim
Original assignee: I3 Lab Pte Ltd
Priority date: 2010-07-05
Filing date: 2010-07-05
Publication date: 2012-01-12

Abstract

A novel projection type automotive LED headlamp is disclosed, wherein the low beam and high beam functions are integrated in a single lamp unit. The light from low beam lighting module or/and high beam lighting module are reflected toward the projection lens by at least one reflective surface disposed at the proximity of the projection lens. The high-low beam switching is done by electrical means, and no moving part is required.

Description

INTEGRATED LED HEADLAMP

Field of the Invention

This invention relates to an automotive LED headlamp, and more particularly, to a projection-type automotive LED headlamp with high beam and low beam functions integrated within a single lamp unit.

Background

LED Light Source in Headlamp

Traditionally, the vehicle headlamps use either halogen filament or high intensity discharge arc (HID) bulb as the light source.

More recently, solid state lighting devices, such as Light Emitting Diode (LED), are fast becoming preferred light source for automotive headlamp. LED has many advantages compared to the traditional HID/Halogen light sources for a few good reasons listed below:

1. LED is vibration and shock resistant due to the solid state lighting technology;

2. LED has much longer lifetime;

3. LED consumes less electrical power;

4. LED has color temperature close to day light, which is preferable for road illumination at night;

5. LED light source reaches maximal output within milliseconds, no warm-up delay;

6. LED is cold light source and it doesn't contain IR and UV spectrum;

7. LED light source has good potentials to be easily integrated into AFL system.

Low Beam and High Beam

A headlamp system is required to produce a low beam and a high beam.

Low beams direct most of the light downwards and have strict control of upward light to provide safe forward visibility without excessive glare. The Economic Commission for Europe (ECE) regulation specifies low beam with a sharp, asymmetric cut-off preventing significant amounts of light from being cast into the eyes of drivers of preceding or oncoming vehicles.

Figure 1 shows the desired low beam illumination pattern at 25m in front of the headlamp. Low beam pattern required by ECE regulation is, generally speaking, wide in horizontal direction and narrow in vertical direction.

High beams cast most of their light straight ahead, maximizing viewing distance, but producing glare, which may cause safety issue when other vehicles are present on the road. High beam is used when there is no other road user or in severe weather conditions.

Low beam and high beam may be achieved by using separated low beam lamp and high beam lamp, or using an integrated lamp having low beam and high beam functions.

Optical Architecture of Headlamp

Modern headlamp optical architecture is either of a multi-reflector type or a projection type.

In a multi-reflector type headlamp, a light source is located in the vicinity of the focal point of a reflector with multiple facets. The light emitted from the light source is reflected by the reflector facets, and the combination of the reflection from all the reflector facets forms the desired illumination pattern.

In a typical projection type headlamp, there is a light source and its dedicated reflector to form an intermediate spot, and a projection lens to image the intermediate spot to the front direction to form the desired illumination pattern. For creating a low beam pattern, a beam shutter (or known as shield, shade, etc) must be at the projection lens' focal plane to block a portion of the said intermediate spot. For creating a high beam pattern, the shutter is not required and is removed.

Related Arts in Projection Type Headlamp

In recent years, some LED-based projection type headlamp designs and concepts are demonstrated by various companies. US patent 7188984 granted to Visteon reports a typical arrangement of LED module array in which the low beam includes 5-25 modules, and the high beam includes 8-30 modules. Each individual module has a dedicated optical system including an LED light source, a reflector and a projection lens. Another prior art is US patent application 20050239171 filed by Koito in which the low beam includes three similar modules having its own dedicated LED, reflector, shutter, and projection lens. Yet another prior art US patent 7699513 granted to Koito reports a low beam system that uses 4 lighting modules, each having its dedicated optics, and the corresponding high beam system uses 1 lighting module.

Although different in optical design, these prior arts have a common feature that requires a plurality of light modules in the construction of a headlamp. The individual module has its dedicated LED light source, reflector optics, beam shutter and projection lens. A group of said modules are used to form the low beam illumination pattern, while another group of said modules are used to form the high beam illumination pattern.

Above mentioned examples of headlamp occupy large space, which are hardly able to fit into the cars with streamlined industrial design. These systems are costly because each module has dedicated optics (reflector, lens, etc) and the overall number of optical components used in the system is undesirably high. These systems are also very hard to build because each module must be individually aligned with precision, which may have complicated assembly and testing processes.

As the car's industrial design becomes more and more aerodynamic and streamlined, the space for headlamps is very limited. The projection type integrated headlamp system, which only has a single projection lens, is more preferred due to its compact size.

Figure 2 shows a typical integrated headlamp system 100. Traditionally, the integrated headlamp has a movable beam shutter 130 at the focal plane 410 of the projection lens 400. In such an integrated system, there is only one light source 110. The high/low beam switching is done by moving the shutter 130, which is located at the focal plane 410 of the projection lens 400 and has two stable positions (low beam position and high beam position). There is a mechanism, e.g. motor or solenoid 150, to drive the shutter 130 into either position accordingly. When the shutter 130 is in low beam position, it blocks a portion of the intermediate spot formed by the light source 110 and reflector 120 therefore, forms the desired cut-off line for the low beam illumination pattern; When the shutter 130 is in high beam position, it moves away from the light path and all the incoming light passes through so that the high beam pattern is formed.

The above mentioned integrated headlamp system has a few drawbacks:

1 ) This optical architecture is applicable for single light source only, but not multiple light sources. Single LED light source doesn't have enough luminous flux (brightness) for both low beam and high beam.

2) As there are moving parts in the system, the system may have potential reliability issue because the moving mechanism may fail due to motor/solenoid related malfunction or the parts may simply wear-out.

Challenges for LED-Based Integrated Headlamp

It is highly desirable to have an integrated automotive LED headlamp, which is bright enough for low beam and high beam illumination, has only one projection lens and therefore is compact in volume, and in the meantime, doesn't require any moving part (e.g. movable beam shutter) for beam switching.

In order to provide enough luminous flux for the low beam and high beam illumination, multiple LED light sources must be used: at least one LED light source (and its dedicated optics, e.g. reflector and beam shutter) for constructing the low beam intermediate spot, and at least one LED light source (and its dedicated optics, e.g. reflector) for constructing high beam intermediate spot.

In order to use the single projection lens, the low beam intermediate spot and high beam intermediate spot are required to be superimposed (overlapped) at the focal plane of the projection lens. It is not uncommon the dedicated optics for low beam and high beam are physically interfered with each other in the system and partially block each other's light path.

As a result of this said interference and blockage, depending on the optics layout, either the beam patterns are incomplete, or there is a dark area at the boundary of the high-low beams. Neither effect is desired for vehicular illumination application.

Summary of the Invention

Thus, it is an object of the present invention to provide a LED-based integrated headlamp that can solve the above-described problems.

In the present invention, the optical system has a single projection lens; The system has at least one reflective surface near the projection lens; The system has at least two independent lighting modules: one is low beam lighting module and one is high beam lighting module.

The said low beam lighting module is to form an intermediate spot which is located at the focal plane of the projection lens; The intermediate spot has a sharp horizontal cut-off line and an oblique kink towards one side.

The said high beam lighting module is to form an intermediate spot which is located at the focal plane of the projection lens; The intermediate spot is centred at the focal point of the projection lens.

The low beam and high beam switching is done by electrically turning on or off the low beam lighting module or high beam lighting module. There is no light path blockage between the low beam lighting module and the high beam lighting module. There is no moving part in the headlamp. Description of the Drawings

The above as well as other advantages of the present invention will become apparent to those skilled in the art from the following detailed description of the embodiments when considered in the light of the accompanying drawing in which:

Figure 1 is the ECE regulation illumination pattern for low beam;

Figure 2 is an illustration of a typical integrated headlamp;

Figure 3 is an exemplary embodiment of a low beam lighting module according to the present invention;

Figure 4 is an exemplary embodiment of a high beam lighting module according to the present invention;

Figure 5 is a side view showing the optics arrangement and the light path for the low beam lighting module in an embodiment according to the present invention;

Figure 6 is a side view showing the optics arrangement and the light path for the high beam lighting module in an embodiment according to the present invention;

Figure 7 is a side view showing the optics arrangement and the light paths for the low beam and high beam lighting modules in an embodiment according to the present invention;

Figure 8 is a side view showing another embodiment according to the present invention;

Figure 9-1 is the illumination pattern for low beam according to the present invention;

Figure 9-2 is the illumination pattern for high beam according to the present invention;

Figure 9-3 is the illumination pattern for the combination of low beam and high beam according to the present invention. Detailed Description of the Invention

The following detailed description and appended drawings describe and illustrate various exemplary embodiments of the present invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner.

The present invention has at least two independent lighting modules, one is low beam lighting module 200 and one is high beam lighting module 300.

Figure 3 is an exemplary embodiment of the low beam lighting module 200. The low beam lighting module 200 is to form an intermediate spot 250 which is located at the focal plane of the projection lens (not shown). The intermediate spot 250 has a portion blocked by a fixed beam shutter 240 and has a sharp horizontal cut-off line and an oblique kink towards one side.

The said low beam lighting module 200 may be constructed by any known art, for example, it may contain an LED light source 210, a parabolic reflector 220, a cylindrical lens 230 and a fixed beam shutter 240.

Figure 4 is an exemplary embodiment of the high beam module 300. The high beam lighting module 300 is to form an intermediate spot 350 which is located at the focal plane of the projection lens (not shown). The intermediate spot 350 is centred at the focal point of the projection lens.

The said high beam module 300 may be constructed by any known art, for example, it may contain an LED light source 310, an ellipsoidal reflector 320.

Figure 5~8 shows some exemplary embodiments of the optical arrangement according to the present invention.

The present invention has a projection lens 400.

The present invention comprises a reflective surface 510 disposed near the projection lens 400. The said reflective surface 510 is tilted. The reflective surface 510 is on one side of the projection lens optical axis.

Figure 5 is a side view showing the optical arrangement for low beam light path according to the present invention: The reflective surface 510 is above the optical axis and tilted backwards at angle . The reflective surface 510 is to fold the light path from low beam lighting module 200. In this exemplary diagram, the low beam path is folded upwards.

In this exemplary embodiment, the reflective surface 510 folds the light path of the low beam lighting module 200 upward. The virtual image 260 of the low beam lighting module 200 and its associated intermediate spot 250 is shown in Figure 5. The virtual light path is tiled up to at angle

^ with regard to the focal point 420 of the projection lens 400. The angle ^ may be expressed as below: 0 < Θ < atan(D/4f) where the D is the diameter of the projection lens, and f is the effective focal length of the projection lens.

Figure 6 is a side view showing the optical arrangement for high beam light path according to the present invention. The high beam module 300 is tilted downwards to angle & with regard to focal point 420 of the projection lens 400.

The angle Θ may be expressed as below:

0 < Θ < atan(D/4f) where the D is the diameter of the projection lens, and f is the effective focal length of the projection lens.

Figure 7 is a side view showing the integration of the high beam and low beam light path according to the present invention. In this exemplary embodiment, the high beam intermediate spot 350 and the virtual image of the low beam intermediate spot 250 are superimposed (overlapped) at the focal plane 410 of the projection lens 400.

The low beam light path is folded by the reflective surface 510 and passes through the projection lens 400 to form the low beam illumination pattern.

The high beam light path passes through the projection lens 400 to form the high beam illumination pattern. There is no blockage between the low beam lighting module 200 and the high beam lighting module 300.

The beam switching is done by electrically turning on/off the low beam lighting module 200 and high beam lighting module 300.

Figure 8 shows another exemplary embodiment of the present invention, which is a side view of the optical arrangement. Both the low beam light path and high beam light path are folded by two separated reflective surfaces, first reflective surface 510 and second reflective surface 520, near the projection lens 400. The virtual images of the intermediate spots from the low beam and high beam are superimposed (overlapped) at the focal plane 410 of the projection lens 400.

Please be noted that the Figure 7 and 8 are for illustration purpose only. The actual light paths of the low beam and high beam lighting module may be further folded to reduce the system package size, and many modifications may be made without departing from the spirit and scope of the present invention.

Figure 9-1 shows a low beam illumination contour diagram at 25m;

Figure 9-2 shows a high beam illumination contour diagram at 25m;

Figure 9-3 shows the combination of high low beam contour diagram at 25m.

The said first reflective surface 510 and second reflective surface 520 in present invention may be formed by any suitable material including, but limited to, glass, plastic, and metal.

The said reflective surfaces may be coated with high-reflectivity coating to enhance the reflectivity.

In present invention, multiple lighting modules are integrated into one projection system, where other related arts have to have multiple projection systems to create the same effect.

In present invention, no moving part (like movable beam shutter) is required in the projection system for switching high-low beam, where other related arts have to have at least one moving part. The arrangement of placing at least one reflective surface near the projection lens for high-low beam integration is novel to our best knowledge. Although the present invention has been described in accordance with the embodiments shown, many modifications may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims.

Claims

Claims What is claimed is:

1. An automotive headlamp comprising

At least one first lighting module for producing light to construct the low beam;

At least one second lighting module for producing light to construct the high beam;

One projection lens for projecting the low and high beam;

At least one reflective surface disposed in the proximity of said projection lens to reflect light from one of said lighting modules for constructing the low beam or high beam into said projection lens;

wherein said lighting module to construct the low beam and said lighting module to construct the high beam do not block each other module's light path before the projection lens.

2. The automotive headlamp in Claim 1 , wherein the light source for constructing the low beam is made of solid state lighting device, e.g. LED.

3. The automotive headlamp in Claim 1 , wherein the light source for constructing the high beam is made of solid state lighting device, e.g. LED.

4. An automotive headlamp comprising

One projection lens for projecting the low and high beam;

At least one first reflective surface disposed in the proximity of said projection lens to reflect light from said lighting module for constructing the low beam into said projection lens;

At least one second reflective surface disposed in the proximity of said projection lens to reflect light from said lighting module for constructing the high beam into said projection lens; wherein said lighting module to construct the low beam and said lighting module to construct the high beam do not block each other module's light path before the projection lens.

5. The automotive headlamp in Claim 4, wherein the light source for constructing the low beam is made of solid state lighting device, e.g. LED.

6. The automotive headlamp in Claim 4, wherein the light source for constructing the high beam is made of solid state lighting device, e.g. LED.