EP0930600A1 - Optical element comprising LED and two lenses for the generation of pointlike light sources for traffic signs and display panels - Google Patents

Abstract

The optical element has an LED (1), at least one converging lens (2) and a diverging lens (3). The LED and the lenses are arranged in a common housing (4) coaxial to the geometric axis of the element and at an angle of inclination to the geometric axis. The light emitted from the LED (1) is essentially all collected by the converging lens (2) and directed in a bundle to the diverging lens (3) which is a known distance away. It is then deflected to provide a predetermined light distribution in the observation direction. The diverging lens (3) is arranged such that all light beams leaving it are at an angle less than the angle of inclination. The housing (4) is formed as a complete cylindrical tube around the LED and the lenses. It is provided on its inside with a light absorbing color and/or structure.

Description

So far, the light was one or two in variable message signs multiple lamps by means of optical fibers on a variety of points of light, which become symbols or characters are arranged, divided and the change between the Display by switching the associated lamps on and off causes.

Since then, light-emitting diodes (LED) with high Light bundling, light intensity and lifespan in a variety of colors or in almost all specified signal colors tried to produce the benefits of LEDs compared to the commonly used Incandescent lamps, like the emission of a directed light beam, much longer life and very favorable energy ratio with colored light, in advertising and information signs and also use traffic signaling. In particular, attempts are made to find the technologically complex To replace fiber optics in variable message signs. But also the use in graphics-capable ads is being promoted because with appropriate wiring, each LED is individually controlled can be and therefore individually programmable representations and information allowed.

LEDs differ from conventional light bulbs not only through the generation of light using semiconductor technology, which is an almost monochromatic colored light generated, but also by integrated optical measures for light control, which, on the one hand, determines the amount of useful light improve, on the other hand, universal, favorable light distribution characteristics in narrow and wide radiating versions generate so that the LED without further optical Measures can be used directly as signal light.

While no overriding for advertising and information signs Regulations regarding their lighting technology Properties exist, such exist in the area of Traffic engineering for a long time, especially light color, Brightness, light distribution, uniformity and above all a low phantom light (pretreating an on Signal light due to incident sunlight) are. The commercially available designs correspond only partially meet these requirements, but nevertheless used as long as customer-specific versions of the LED completely uneconomical and also by some manufacturers are currently impracticable for technological reasons.

In traffic engineering, the LEDs are used directly without additional optical measures used, light color corresponds to Brightness and uniformity mostly meet the requirements, The required light distribution is often only by means of a ballast additional lenses available, the main problem is that high phantom light. The lens crest is usually crystal clear transparent LED body bundles incident sunlight directly on the highly reflective fixtures in the Inside of the LED, such as reflector and reflector edge, Connection flags and contact points from where it is is thrown back. Because of the crystal clear LED body also the phantom light is relatively whitish and unfiltered and often appears brighter than that when the sun is unfavorable actual signal light.

In traffic engineering, the requirement prevails that a sun position of 10 degrees for phantom light assessment perpendicular to the optical axis of the signal (mostly the Direction of maximum light emission) is assumed. At such angles, additional measures must be taken be taken to achieve the effect described above limit.

While with auto switches with a variety of LEDs in signal unit in a fixed arrangement examined in their entirety with regard to phantom behavior and can be improved at variable message signs preferably considered the individual light point optics, so that in any number and arrangement Symbols or characters can be combined.

A known measure is to put a converging lens in a suitable distance in front of a relatively wide beam LED to set (Fig. 8). The slanting sunlight becomes at a sufficient distance from the LED to the converging lens Entirely passed outside the LED and on the housing surfaces absorbed. However, this arrangement has the disadvantage of one large space requirement and is therefore not suitable for universal application.

Another measure is the upstream of horizontal fins (Fig. 9 above) or pipe sections (Fig. 9 Middle) to shield the sunlight, too small, long sun visors or barges (Fig. 9 below), used especially with multiple LED light points, such as which is also common with signal generators in principle. Here is particularly disadvantageous that these attachment elements either protected from weather and dirt by a front screen or need to be cleaned frequently. You will before mainly used for LED arrangements in a rectangular grid.

Another measure is to use the Signal color in colored lenses or LED bodies (tinting). The sunlight has to pass through the colored component twice, especially the foreign color components of the light be filtered out, the LED light only once, the Coloring for the actual signal color as permeable as possible is. This makes sunlight essential weakened, the useful light is reduced to a much lesser extent Dimensions. The disadvantage is not only the lower useful light intensity, what by a higher number of light points must be compensated, but also the phantom light in Signal color which is compared to white phantom light is viewed as particularly critical in many applications.

Another disadvantage is the usually circular symmetry Light emission from the LEDs, which leads to that a large proportion of light is unused in irrelevant areas is emitted if not also optical measures against being taken.

Furthermore, they have commercially available LEDs Emission characteristics that are usually required with the Light distribution of the light points do not match well. This often means disproportionate without additional optics more LEDs are used just to dim in Areas still have enough light. In many cases cannot do the required light distribution at all without Additional measures can be achieved.

The object of the invention is a universal LED optics to develop for variable message signs, which without Windscreen and with a smooth outer surface can and the advantages of LED, such as low energy consumption, long service life and freedom from maintenance benefits, on the other hand has almost no phantom light, which individually adjustable, especially oval light distributions enables to different without significant loss of light LED designs, LED suppliers or radiation characteristics is adaptable and the smallest possible center distance Adjacent optics allowed.

This is achieved according to the invention in that in the optical element a light source, preferably a light-emitting diode (LED), at least one converging lens and one diverging lens, from one common housing, essentially coaxial to geometric axis of the element are arranged, wherein the converging lens at every point of the diffusing lens facing surface emerging at an angle g divergent light beams as completely as possible on the Scattering lens bundles, whereby the scattering lens is designed that practically all light rays emerging from it are included Your inclination below a defined inclination angle Á lie, and being the housing as a tubular Envelope of light source, collecting and scattering lens, on his Completely closed circumference and inside provided with a light-absorbing color and structure is.

The invention will now be described with reference to the drawings. 1 to 7 show preferred embodiments in FIG Section, Fig. 8 and 9 previously common solutions in comparison.

Fig. 1 shows a vertical section through an inventive Optics. The light source 1, in all examples as an LED shown with a wide radiation pattern, sends its light 6 on the coaxially arranged immediately in front of it Collecting lens 2. This is on the one hand better light beam possible than by using a tight-knit LED, on the other hand, can affect the light beam become. Internals 19 are shown within the LED 1. They are used for power supply and positioning of the actually luminous semiconductor chip 20, but form also an auxiliary reflector 21, which emits the side Reflected and have light in the main emission direction therefore high-gloss surfaces. That is why the LED works for optics in the immediate vicinity not as Spotlight, it sends a mixture of direct and reflected light rays. The light can only very poorly focused, which is why for the lens geometries also no physically exact information given can only be qualitative descriptions of their Characteristics.

Step at any point on the surface of the converging lens 2 Beams of light 7, whose divergence S ∨ by Art and size of all internals 19, 20 and 21 is conditional and for each position of the converging lens 2 must be determined specifically. The geometry of the converging lens is therefore preferably in iterative calculations. Be favorably the light beams 7 deflected so that as many as possible of their light rays fall through the scattering lens 3, which arranged coaxially to the converging lens at a certain distance is. There, the light beams 7 are deflected or scattered that the desired light distribution 8 is achieved.

The angle Á gives the light incidence limit for stray light, especially the light of the low-lying sun 12, which should not yet generate phantom light. The regulations go from a position of the sun of 10 degrees vertically above the Reference axis (usually the direction of the highest useful light intensity) out. Because of inevitable tolerances and the Size of the sun diameter itself is recommended Setting this inclination angle Á to about 9 degrees, es any other angle can also be chosen become. The size of the angle Á determines the entire geometry of the optics.

The geometry of the lens 3 is set so that the emerging light rays 8 with their inclinations β always stay below the inclination angle Á. Hiefuch will ensures that even in the reverse direction no Sunbeam 12 if it is at an angle g greater / equal Á meets the optics, the same way back either via the reflector 21 or directly to Chip 20 of LED 1 is found and the LED lights up simulated. Nevertheless, light rays 22 up to the LED 1 penetrate. You meet others, not immediately surfaces 23 involved in the light radiation, or often reflected several times on the vitreous of the LED and broken and also produce a in this way too certain phantom light. The length of the optics is therefore preferred set so that no sunbeam at all 12, which has an angle of incidence g greater or equal has the angle of inclination Á up to the converging lens 2 or LED 1 can penetrate. This is the case inside with the most matt, light-absorbing Surface structure, e.g. Circumferential grooves and preferred executed in black, so that there are all incident light rays 12 can absorb as well as possible.

It is immediately apparent that sun rays 12 with any steeper angle of incidence g in the housing 4 further be absorbed in front, so that for all positions of the sun Above the angle of inclination Á the phantom freedom is assumed can be.

The housing 4 is completely closed on the circumference, on the one hand, to be able to absorb light anywhere on the other hand, to allow light exchange within the device prevent, but also to prevent lens contamination prevent.

The optics are fastened in a matrix plate 24. The Dimensions of the components are not much larger in the Diameter than the LED itself, so there is a corresponding tight arrangement possible. When accepting certain The diameter can also lose more light be reduced.

It is possible to achieve a smooth exterior Spread lens 3 with a flat front surface and the To install scattering elements completely on the inside, it is even conceivable that the lens 3 is completely flat without Perform refraction of light if the from the converging lens 2 generated light distribution already corresponds. In this case could also be a common instead of the lenses 3 Front window can be arranged in front of the device.

Fig. 2 shows a design that is generally smaller Has length than in Fig. 1. The divergent Beams of light 7 cross each other before hitting onto the scattering lens 3 and there form a focal spot 9. For this purpose, the converging lens 2 needs a higher light refraction than in the previous example. Depending on the desired light distribution 8 and the resulting refractive power of the scattering lens 3 there is also the possibility that all sun rays 12 having an angle of incidence g greater than / equal to that Have inclination angle Á, absorbed on the housing wall become.

The focal spot 9 also creates a space between Housing wall and useful light rays, which either through a constriction of the housing 4 at this point, better but by installing at least one aperture 10 that Phatom light behavior can significantly improve.

3 shows an aperture 10 in the area of the focal spot 9, whose opening 11 to the circumference of the light beam 7 is adjusted. It keeps sun rays 12 from penetrating further completely into the interior of the housing.

The light absorption on a housing wall takes place through an inevitable surface gloss never completely, so that light rays diffusely reflected on the housing wall can get to the LED. Another improvement of the Phantom light effects are possible when all penetrating Light rays 12 are intercepted at the aperture 10 can.

Fig. 4 shows such an optics in elevation and plan. The Scattering lens 3 has a focal point 14 in the area of Focal spot 9, where there is also an aperture 10. Of the The distance to the lens 3 and the aperture size is so chosen that the focal point of sun rays 12, which are parallel with the inclination of the inclination angle Á, is within the aperture 10 or just behind. This means that no sunbeam can penetrate further into the interior.

Under certain circumstances, slight light losses, represented by the cut useful light beam 13, to be accepted. It is also shown that the Aperture 10 is not required here in the upper area of the optics is because no sunlight can get there.

The formation of the diverging lens with focus 14 has Consequence that the light distribution 8 according to the optical imaging laws an upside down image of the aperture 11 and the light distribution prevailing there and intensity results. The determination of the light distribution In this case, the appropriate detail design of the Collecting lens 2 take place by the light beam 7 be pivoted more or less. At most kick increased losses due to edge light rays 13 at the aperture 10, or useful light rays no longer striking the scattering lens 3 on.

Fig. 4 further shows that the focal point 14 only in vertical Direction is required. The floor plan shows that with the help of the vertical scatter optics 15 on the inside the scattering lens 3 a horizontal spread of the emitted Light 8 takes place so that a total of any oval light distribution can be achieved.

5 shows the deflection of the light distribution 8 by one Angle e, which is defined by a horizontal lens structure 16 is effected. This will increase visibility in those cases improved in which the display device is not oblique can be tilted downwards. At the same angle e phantom light sensitivity also improves because also the sun rays 12 down by this amount be directed against the aperture 10.

In all versions with non-circular symmetry Light distributions, panels and optics are recommended non-circular design of the optics, so that the correct assembly is ensured by positive locking.

Fig. 6 shows an oval design in addition to the round shape for optics with horizontal axis of symmetry, in particular also oval-radiating optics, as well as an egg-shaped design with only one positioning option.

In a further embodiment of the invention, the housing 4 can also be split, making the bezel light can be integrated. The subdivision allows in particular the construction of a modular system with different Light distributions and manufacturer-specific LED designs. Fig. 7 shows such a modular system optical, mechanical and electrical interfaces represents.

In the front housing 4 are the lens 3 and the aperture 10 housed, the rear housing contains each Converging lens and the LED. While the front housing 4 velvet Aperture 10 is the same here, the rear housing varies by LED type. Because each LED design has its own radiation pattern must also have the converging lens be customized. If every LED type in focal spot 9 has approximately the same light distribution they can be combined with different lenses 3 become. These can have the same outer facade, the different spreading structures are on the Inside. An LED 1a in SMD technology is shown above, which practically always soldered onto a circuit board is. So all LED 1a can on a common board 17a, which is also the wiring and power supply includes, be attached. The circuit board 17a after soldering on extensions 18a of the associated housing 4a snapped so that the optics are all one below the other be supported and aligned. Even the mix with other types of LEDs are possible; 4b in the circuit board 17a. Below is an LED 1b shown in standard design ⊘3 or ⊘5 mm. This can either also be soldered onto a circuit board 17b, for this exact extensions 18b are on Housing 4b attached. But it can also be freely wired be what is especially with small quantities and individually built devices recommended.

Especially with free wiring it is possible to use the Moving housing parts against each other and so the look to adjust. For this purpose, at the contact points 25 Thread, snap grooves or the like may be attached. All Optics are attached in a common matrix plate 24 and have the same appearance for the viewer. Of course, different front housings can also be used 4 with different apertures 10. Furthermore can all representations also with colored lenses or Light sources run what that through the lenses self-generated reflex phantom light reduced. Both collecting line 2 as well as scattering lens 3 can also be used as a Fresnel lens be executed.

The representations of the LED or light sources are only exemplary. The rapid development in this area constantly creates new designs and functional principles, what ongoing adaptations of housing 4 and converging lens 2 require. Of course, any can other light sources are used.

Claims (17)

Optical element for traffic signs, in particular Variable message signs, billboards or the like from a light source, especially a light emitting diode (LED) (1), at least one converging lens (2) and one diverging lens (3), which in a common housing (4) essentially coaxial to the geometric axis (5) of the element are arranged, and one of the geometric axis (5) fixed upwards in the direction of radiation Inclination angle Á, which is from the light source (1) outgoing light (6) through the converging lens (2) if possible fully grasped and bundled on in a certain Distance scattering lens (3) directed and from this to achieve a predetermined light distribution (8) in the Direction of observation is directed, characterized in that the converging lens (2), which is at every point of its Scattering lens (3) facing surface emerging, under an angle S ∨ divergent light beam (7) as completely as possible on the lens (3) that the scattering lens (3) is designed so that as many as possible from it emerging light rays (8) with their inclination β are below the inclination angle Á and that the Housing (4) as a tubular envelope of light source (1), converging lens (2) and diverging lens (3) formed its circumference completely closed and inside with a light-absorbing color and / or structure is provided. Optical element according to claim 1, characterized in that the divergent light beams (7) before hitting cross each other on the lens (3) and there form a focal spot (9). Optical element according to claim 1 or 2, characterized in that the housing (4) between the converging lens (2) and Scattering lens (3) constricts at least one point, in particular has an aperture (10), the opening of which (11) preferably the common outline of all light beams (7) is adapted and the surface of one has light-absorbing color and / or structure. Optical element according to one of claims 1 to 3, characterized characterized in that the distance between the converging lens (2) and scattering lens (3) so dimensioned and the refraction each point of the scattering lens (3) is set so that in essentially each light beam (12) coming from one direction with the same or greater inclination g than the inclination angle Á falls from the outside onto the lens (3) onto which Housing inner wall or a panel (10) deflected and is absorbed there. Optical element according to one or more of claims 1 to 4, characterized in that the housing (4) or at least one aperture (10) in the beam path of the Useful light (7) protrudes and any light component (13) shields and absorbs. Optical element according to one or more of claims 2 to 5, characterized in that at the position of the Focal spots (9) an aperture (10) is present, which a has such an opening (11) that not a single light beam (12) from one direction with the same or greater Inclination g as the inclination angle Á from the outside to the Scattering lens (3) falls, pass through the aperture (11) can. Optical element according to claim 6, characterized in that the diverging lens (3) has a focal point (14) which lies in the area of the focal spot (9), and thereby the light emission characteristics of the optics according to the optical mapping laws essentially that of the Upside down geometry of the aperture (11) and corresponds to the prevailing light distribution and intensity, which by appropriate alignment of the divergent Beam of light (7) by means of appropriate design the converging lens (2), even if Loss of light (13) on the diaphragm (10) can be determined can. Optical element according to claim 6 and 7, characterized in that the focal point (14) of the diverging lens (3) is only vertical Direction is effective while in horizontal Direction of light scattering through suitable optical structures (15), especially on the inside of the lens (3), which is the radiation characteristic of the optics any oval distortion. Optical element according to one or more of claims 1 to 8, characterized in that the design of the Scattering lens (3) through suitable optical structures (16) Swiveling the main direction of light emission with respect to the geometric axis of the optical element (5) the angle e, especially downwards. Optical element according to one or more of claims 1 to 9, characterized in that the cross sections of the Components, like the installation opening circular, oval, can be egg-shaped or any other shape (Fig. 6). Optical element according to one or more of claims 1 to 10, characterized in that the housing (4) consists of several parts, at least scattering lens (3) and Aperture (10) in a housing part, converging lens (2) and Light source (1) installed in another housing part are. Optical element according to one or more of claims 1 to 11, characterized in that housing parts, lenses, Panels and light sources as a modular system for implementation of optics with different radiation characteristics, Luminous intensity and light color, as well as for the use of Light sources of different types and manufacturers, are designed. Optical element according to one or more of claims 1 to 12, characterized in that any components, in particular housing parts for adjusting the optics against each other are slidably connected. Optical element according to one or more of claims 1 to 13, characterized in that at least one lens, preferably the diffusing lens (3) or the light source itself in the emitted light color and in any intensity is colored transparent. Optical element according to one or more of claims 1 to 14, characterized in that the light sources (1), especially LED, several or all optics in one common board (17) sit, which usually also their interconnection and / or control and others Contains device components and the optics with each other supports and holds in precise alignment with each other. Optical element according to claim 15, characterized in that the housing part containing the light source (1) extensions (18), with the help of which the light source the board (17) exactly positioned for the soldering process be or the board (17) as a positioning aid and Support the optics can act. Optical element according to one or more of claims 1 to 16, characterized in that collecting lens (2) and / or scattering lens (3) are designed as a Fresnel lens.

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