EP1709360B1 - System for illuminating large areas in an even or defined manner - Google Patents

Abstract

The invention relates to a system for illuminating large areas in an even or defined manner. The aim of the invention is to provide a system with which large areas having the defined parameters can be illuminated in an inexpensive and variable manner, said system comprising at least one reflective element that is relatively compact. According to the inventive system, light (1') collimated by a light source (1) is directed onto at least one reflecting element (2) having a Fresnel structure reflecting surface. The reflecting element is provided at least in some areas with a disturbance flank-free Fresnel structure having varying angle inclinations relative to the imminent collimated light. The collimated light is collected by these effective flanks and is scattered by the respectively adjacent effective flank.

Description

The invention relates to an arrangement for uniform or predefinable illumination of large areas with a light source, wherein over the respective area a largely constant illuminance distribution is to be achieved. With the solution according to the invention, for example, a large-scale outdoor lighting, but also in closed rooms can be achieved, so that it is suitable for example for the illumination of traffic or office space. But it can also be a desired predetermined illumination of certain surface areas of a surface to be illuminated, such as in particular outer edge regions of such a surface can be achieved.

When illuminating surfaces with large aperture angles, where the edge radiation is emitted with angles of approx. 120 °, it occurs at the edges of To be illuminated surface areas to a significant drop in the illuminance levels achievable there.

Taking into account the photometric law of removal and the obliquely inclined projection of the radiated light onto the respective surface to be illuminated, illuminance drops occur, with a factor cos (w) ³ relative to the center of the illuminated surface (at 60 °: 0.125). Thus, a reduction in illuminance at the edges with respect to the center of the respective area to 1/8 in conventional solutions is recorded.

For many applications, however, a uniform illumination intensity distribution over the entire surface to be illuminated is desired.

For this purpose, in known solutions specially aspherically shaped and free-form surfaces having reflectors are used, which make high demands on the calculation and the production of such aspheres and free-form surfaces having reflectors. Usually, such reflectors must also be calculated and manufactured separately for the particular application.

In another alternative, it is also state of the art to use separately calculated optical elements with Fresnel structures for such illumination, which allow a variation of the illuminance distribution in relatively wide ranges.

In the conventional Fresnel optics but alternately alternating the so-called active and Störflanken be used, the Störflanken a rather have negative influence on the lighting and often light losses must be accepted.

document EP-A-0 735 311 shows an arrangement for illuminating interiors with large areas with a light source and with a Refelktierenden element whose surface has a structure.

It is therefore an object of the invention to propose ways in which a uniform or predetermined illumination of large areas can be achieved in a cost-effective, variable form and a relatively small size of at least one reflective element to be used can be maintained.

According to the invention this object is achieved with an arrangement having the features of claim 1. Advantageous embodiments and further developments of the invention can be achieved with the features described in the subordinate claims.

The inventive arrangement for uniform or predetermined illumination of large areas, wherein the respective large areas are always to be evaluated in relation to the size of the respective light source, or the light emitted from a light source light radiation, uses at least one reflective element, on which a Fresnel structure is formed and collimated light of the light source is reflected at the surface provided with the Fresnel structure. In the case of the light directed onto this surface, a slight divergence can be tolerated and optionally also compensated by suitable measures on the reflective element.

In this case, an at least partially refractory Fresnel structure is formed on the at least one reflective element. This Fresnel structure is formed of alternating alternating active edges, each with respect to the incident collimated Have light changing angle inclination. As a result, incident collimated light is collected with an active edge oriented at an angle inclination, and the incident collimated light is scattered with the active edge adjacent to such an active flank and oriented in a respective other angle inclination.

In a preferred form, such a Fresnel structure free of fringes should be formed at least in the radially outer region of such a reflective element with respect to the optical axis of the entire system or of the collimated light. Of course, however, it is also possible to provide the entire surface area used for reflection of such a reflective element according to the invention with a Fresnel structure free from disturbing edges.

It is also advantageous in accordance with the invention to be used reflective elements Fresnel structure a frustum free form on the back so that the collimated light on the respective light source facing surface of the reflective element, through this incident on the respective active edges of the Fresnel structure according to the invention, to these depending on the each angle of inclination of the active surfaces is reflected and refracted after a refraction at the interface, which is opposite to the spurious Fresnel structure on the surface of the reflective element is additionally refracted, so that by such a refraction, the beam can be used advantageously again for the desired uniform large-area illumination ,

In this case, the reflective element to be used according to the invention should be formed from a material which is transparent to the respective light with a known refractive index and the outer surfaces of the Fresnel structure free from interference flare should be coated with a coating which reflects the respective light. Thus, the actual reflective elements may consist of a suitable plastic, which can be processed for example by injection molding or conventional hot embossing.

However, if the reflection of the collimated light takes place directly directly on the surface of a Fresnel structure free of interference flanks, without the respective light impinging on the respective active flanks in advance by the material of a reflective element, the Fresnel structure according to the invention can also be formed exclusively from a correspondingly reflective material or, As already mentioned, such a reflective coating has been formed on a corresponding Fresnel structure free of flanks.

However, it is also possible to use more than one reflecting element with a Fresnel structure free of interference flanks in an arrangement according to the invention. Thus, it is possible to arrange a plurality of such reflective elements in the form of a so-called "array" next to each other, which may also be permanently or detachably connected together. In this form can be quasi, as in a modular system, assemble differently sized and the respective application taking into account arrangements according to the invention.

Both, as well as a plurality of reflective elements on which Fresnel structures are formed fringe-free, should as far as possible in a common plane, which is also aligned as possible parallel or at an inclined angle to the respective surface to be illuminated.

For the desired homogeneous illumination of the respective relatively large area, it is preferable to observe minimum distances to an arrangement according to the invention in order to be able to achieve the desired effects. Thus, the distance A of the one or more reflective element (s) to the surface to be illuminated should be at least five times, preferably at least ten times as large as the diameter or area diagonal of the cross section of the respective collimated light incident on the respective or the mutually correspondingly arranged reflective (e) element (s) is directed to be.

As a result, the effects achievable with the invention can be exploited even better. In this case, it can be considered that one of the two active edges of an adjacent pair of oppositely oriented active edges arranged adjacent to one another, the function of a concave reflex (hollow mirror) and the respective other active edge fulfill the function of a convex mirror (mirror). The active edge performing the function of a convex mirror scatters the light toward the outer edge of the surface to be illuminated, and the active surface performing the function of a concave mirror collects the light toward the focal point, but since the distances of the surface to be illuminated are kept relatively large, too the light reflected accordingly with such an active edge is actually scattered.

The images obtained by the respective differently oriented active surfaces by reflection on the surface to be illuminated are superimposed on the respective surface to be illuminated and equalization of the illuminance over the entire surface to be illuminated is achieved. The light distribution takes place independently of the respective geometry of the light source or the beam geometry of the emitted light radiation from this, so that it can be spoken of an illumination in the so-called "far field". Here, the photometric limit distance of the photometric law of distance should be taken into account.

The invention will be explained in more detail by way of example in the following.

Figur 1

in schematischer Form ein Beispiel einer Anordnung für eine Ausleuchtung großer Flächen;

Figur 2

eine Teildarstellung eines reflektierenden Elementes mit konventioneller Fresnelstruktur, wie es bei einer Anordnung nach Figur 1 eingesetzt werden kann;

Figur 3

in schematischer Form das Reflexionsverhalten einer konventionellen Fresnelstruktur an Wirk- und Störflanke;

Figur 4

das Reflexionsverhalten an einer konventionellen Fresnelstruktur mit Mehrfachreflexionen an der Störflanke;

Figur 5

in schematischer Form das prinzipielle Reflexionsverhalten an einer erfindungsgemäß einzusetzenden störflankenfreien Fresnelstruktur und

Figur 6

in dreidimensionaler Form eine berechnete Beleuchtungsstärkeverteilung über eine Fläche, die mit einer erfindungsgemäßen Anordnung erreichbar ist.

Showing:

FIG. 1

in schematic form an example of an arrangement for illuminating large areas;

FIG. 2

a partial view of a reflective element with conventional Fresnel structure, as it can be used in an arrangement of Figure 1;

FIG. 3

in schematic form, the reflection behavior of a conventional Fresnel structure at the active and Störflanke;

FIG. 4

the reflection behavior on a conventional Fresnel structure with multiple reflections at the Störflanke;

FIG. 5

in schematic form, the principal reflection behavior on a non-stop Fresnel structure to be used according to the invention and FIG

FIG. 6

in three-dimensional form, a calculated illumination intensity distribution over a surface, which can be achieved with an arrangement according to the invention.

In Figure 1, an arrangement for illuminating large areas 5 is shown in schematic form. In this case, collimated light 1 'of a light source 1 is directed onto a reflective element 2 provided with a Fresnel structure and reflected back from this in the direction of the surface 5 to be illuminated with a correspondingly large aperture.

In Figures 2 and 3 partial representations are shown in which conventional, provided with a Fresnel structure reflective elements are shown with their respective beam guidance.

Thus, FIG. 2 indicates how the collimated light of the light source 1 impinges on the active edges of a conventional Fresnel structure by the material of a reflective element, is reflected on the respective active edges in a radially outward angle and on the outer surface, as the angle of incidence Boundary surface of the reflective element is refracted accordingly.

With the schematic representation according to FIG. 3, it should be clarified how a part of the incident collimated light 1 'is not only at an active flank 6 of a conventional Fresnel structure, but also at a Störflanke 7 is reflected, so that this part, which reflects both on active as well as on Störflanken leads to a greater illumination, with a correspondingly increased illuminance of the central central region of the respective surface to be illuminated.

As can be clearly seen from FIG. 4, a part of the collimated light 1 'strikes a disturbing flank directly, is reflected by it onto an active flank and then reflected back to the interfering flank by the active flank and then from the reflective element 2 to illuminate a surface , The proportion of the light reflected by the reflective element 2 thereby emerges almost in parallel therefrom, so that an undesired increase in the illuminance occurs in the central region of the surface to be illuminated.

In the case of the reflective elements 2 illustrated in FIGS. 3 and 4, such unwanted light guidance, which occurs in particular as a result of the reflections at the parasitic edges, could be avoided if a disturbing flank angle of 0 ° has been observed, this angle being considered with respect to the optical axis shall be. In an embodiment according to FIG. 3, a light beam would then emerge from the reflecting element 2 after the reflection on a vertical interfering edge at the same angle to the right, so that it would impinge with the same distance on the other side of the surface to be illuminated. An analogous behavior would show a light beam on the opposite side of the reflective element 2, so that then no increase in the illuminance in the central Central area of the surface to be illuminated would be recorded. However, such Fresnel structures are unsuitable because of the usual shaping manufacturing processes, since they make a non-destructive demolding impossible.

However, FIG. 5 is intended to illustrate in schematic form the advantageous reflection behavior of a Fresnel structure free of disturbing edges on a reflective element 2 which can be used in the invention.

Thus, the collimated light 1 'emitted by the light source 1, not shown here, impinges on a planar planar boundary surface of an otherwise transparent reflecting element 2, at least approximately orthogonally, on the respective active edges 3 and 4, which are parallel to the collimated one Light is aligned, are inclined at a respective opposite angle, and is reflected according to the angle of incidence on this, reflective here coated active edges 3 and 4, the respective angle of incidence, reflected. The respective reflected light is then correspondingly refracted on the opposite surface of the reflective element 2. In this case, FIG. 5 clearly shows that the collimated light 1 'incident from the active surfaces 3 and 4 oriented at different angle inclinations is respectively reflected in opposite directions and additionally broken.

Depending on the position / distance of the active edges 3 and 4 with respect to the optical axis of the incident collimated light 1 ', the respective light reflected on the active edges 3 and 4 and possibly additionally additionally refracted light will once in the direction of deflected the radially outer edge of the surface to be illuminated 5 and the other of the active surfaces 3 or 4 directs light in focused form to a corresponding focus and with a correspondingly large distance between the reflective element 2 and surface to be illuminated 5 on the focal point in the optical Axis is arranged, in the radially outer direction further outwards from, so that thereby the present invention desired effect of a uniform illuminance, which is to be achieved over the entire area to be illuminated 5 set.

In addition, in an unillustrated form, starting from the optical axis of an arrangement according to the invention, the respective angles of inclination of active edges 3 and 4 of a Fresnel structure free of interference fringes can be adapted according to their distances with respect to the optical axis and correspondingly different angles of inclination of active surfaces 3 and 4 on the reflecting element are maintained become.

In an example, analogous to a reflecting element 2, as shown in FIG. 5, however, the surface of a reflecting element 2 into which the light exits and breaks again may also be concave and / or convexly curved at least in some areas , As a result, once a non-excludable divergence of the directed to the corresponding surface of the reflective element 2 collimated light 1 'compensated and optionally for the desired homogeneous illumination of the respective surface 5 improved exit angle of such formed in a curved shape surface of reflective elements 2 broken light to be exploited.

FIG. 6 shows, in three-dimensional form, a calculated illumination intensity distribution over an illuminated surface 5, which can be achieved with an example of an arrangement according to the invention.

The surface 5 to be illuminated considered here had a circular shape with a diameter of 7100 mm, with a distance of the surface from the reflecting element 2 of 2500 mm.

The following additional parameters of an example of an arrangement according to the invention were taken into account in the calculation:

A maximum peripheral beam inclination of 55 ° was assumed for light reflected at a reflecting element 2 which is directed onto a surface to be illuminated. This Randstrählwinkel correspond to the respective outer light rays, as they can be seen in Figure 1.

This resulted in an illumination intensity drop of cos ³ (55) = 0.189, which would correspond to about 19% with respect to the center of the surface to be illuminated.

By means of the calculation for a reflecting element 2 according to the invention, a clear compensation could be detected for this, so that a uniform illumination intensity distribution over the rather large area could be achieved.

The calculation was based on the well-known aspheric equation: $$\mathrm{z}\mathrm{=}\mathrm{(}\mathrm{1}\mathrm{/}\mathrm{r}\mathrm{\times }{\mathrm{H}}^{\mathrm{2}}\mathrm{)}\mathrm{/}\left(\mathrm{1}\mathrm{+}\sqrt{\left(\mathrm{1}\mathrm{-}\mathrm{cc}\right)\mathrm{x}{\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">H</figure-callout>}}^{\mathrm{2}}\mathrm{/}{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">r</figure-callout>}}^{\mathrm{2}}}\mathrm{+}{\mathrm{A}}_{\mathrm{2}}{\mathrm{<figure-callout\; id="2"\; label="H"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">H</figure-callout>}}^{\mathrm{2}}\mathrm{+}{\mathrm{A}}_{\mathrm{4}}{\mathrm{<figure-callout\; id="4"\; label="H"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">H</figure-callout>}}^{\mathrm{4}}\mathrm{+}{\mathrm{A}}_{\mathrm{6}}{\mathrm{<figure-callout\; id="6"\; label="H"\; filenames="imgf0003.png"\; state="\{\{state\}\}">H</figure-callout>}}^{\mathrm{6}}\mathrm{+}{\mathrm{A}}_{\mathrm{8th}}{\mathrm{H}}^{\mathrm{8th}}\mathrm{...}\right)$$

It was from a recourse radius
r = 157.67 mm
a conic parameter cc = -1
A ₂ = 0
A ₄ = -1.73625E-7
A ₆ = 1.23325E-11 and
A ₈ = -5.0425E-16 is displayed.

As h, the respective distance from the optical axis was considered.

The reflective element was made of a transparent material with a refractive index of n = 1.49.

Claims (7)

1. System for illuminating large areas (5) in an even or defined manner, with a light source, from which collimated light (1') is directed onto at least one reflected element (2), with a reflecting surface of the type of a Fresnel structure, characterised in that an interference flank free Fresnel structure is formed with alternatingly interchanging active flanks (3, 4) at least in some areas, which each comprise alternating angle inclinations with regard to the incoming collimated light, one with a light collecting, and one with a light diffusing effect.
2. System according to Claim 1, characterised in that an interference flank free Fresnel structure is formed in the radial outer area of a reflecting element (2) in relation to the optical axis.
3. System according to Claim 1 or 2, characterised in that the interference flank free Fresnel structure is formed on the back of reflecting elements (2).
4. System according to one of the preceding Claims, characterised in that several reflecting elements (2) are arranged adjacently on a level and form an array.
5. System according to one of the preceding Claims, characterised in that the distance A between the reflecting element(s) (2) and the area to be illuminated is at least a fifth of the diameter or the surface diagonal of the cross-section of the collimated light.
6. System according to one of the preceding Claims, characterised in that the relevant angle of inclination of the alternatingly arranged active flanks (3, 4) change radially towards the outside starting from the optical axis.
7. System according to one of the preceding Claims, characterised in that the surface of the reflecting element located opposite the interference flank free Fresnel structure is concavely and/or convexly arced at least in part.

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