DE3004422A1 - PARABOL REFLECTOR - Google Patents

Description

Applicant; Stuttgart, December 15, 1979

Company P 3798 X / Lö

Sidler GmbH & Co.
Bismarckstrasse 72
7400 Tuebingen

Representative;

Kohler-Schwindling-Späth
Patent attorneys
Hohentwielstrasse 41

7000 Stuttgart 1

Parabolic reflector

The invention relates to a reflector, in particular for vehicle lights and headlights, which consists of a consists of transparent material and the light entering from a light source through curved total reflection prisms bundles and radiates again.

Usually reflectors consist of a pressed or molded part made of metal or plastic that is mirrored inside by vapor deposition after shaping. The steaming is relatively complex and the mirror layer is very sensitive, even if it is provided with a protective coating. To these disadvantages Attempts have also been made to fix the light by not reflecting it off a mirrored one Area but through total reflection in the desired

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Way to bundle (DE-OS 2? 14 793). With this well-known Reflector, the inner surface is designed as it has been since then, but not mirrored and the reflector is there made of a transparent material. On the outside or back are from the apex area of the reflector Radiant roof prisms formed. The ridge of the roof prisms or the height of the Roof prisms follow a given function. Around To obtain appropriate dimensions of the roof prisms, it is also necessary to put the reflector surface in to subdivide several ring surfaces, i.e. the individual roof prisms in their longitudinal direction into several sections to divide, which are offset from one another in the manner of a Fresnel lens. This will make that Tool used for production is also expensive and time-consuming.

The object of the laying invention is to provide a reflector to create that not only works without mirroring but also designed as a body of revolution and so that it can be shaped with inexpensive tools.

This object is achieved in a reflector of the type mentioned according to the invention in that the Total reflection prisms are provided on the inner, concave side facing the light source that they are designed as triangular ring prisms that are rotationally symmetrical to the optical axis, that 'one of the three interfaces a ring prism is approximately cylindrical to the optical axis of the reflector, and that one second interface is formed by the reflector back.

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A great advantage of the reflector according to the invention is that it is rotationally symmetrical to the optical Axis is designed and it is therefore easy and inexpensive to manufacture. A tool for shaping such a reflector can, for example, essentially consist of two rotating parts, which the Outer contour or the inner contour of the reflector correspond. Ba the first interface of the ring prisms, for example is cylindrical to the optical axis, demoulding in the direction of the optical axis is possible at any time possible. In order to further improve this demoldability, without changing the mode of action or the quality is noticeably impaired, a conical shape deviating very little from the cylinder jacket shape be provided as the first interface. The elimination of the mirroring means that work processes are possible saved in the manufacture of such a reflector, resulting in a more cost-effective production and a reflector with a longer service life is obtained because the service life of the reflector no longer depends on the integrity of the mirror layer.

The shape and arrangement of the third interface of the ring prisms are chosen so that they are on the one hand as possible result in low light losses and on the other hand to the desired, preferably essentially axially parallel Lead light exit direction. With preferred

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embodiments of the invention are therefore the third Boundaries of the ring prisms aligned approximately parallel to a beam coming from the light source and form thus in each case a section of a truncated cone surface, the apex of which is approximately in the center of the light source (Focal point). The third interface of the ring prism is that of the apex of the reflector has approximately the same distance as the center of the light source, such as a flat surface. The top of the The cone of those boundary surfaces which are closer to the apex of the reflector points in the direction of the beam, whereas the apex of the cone of those third of the ring prisms, which have a greater axial distance from the reflector vertex than the focal point, in the direction points to the reflector apex.

In preferred embodiments of the invention has the back of the reflector, apart from the apex area, approximately the shape of a paraboloid of revolution. The parabola through straight line sections is preferred approximated, of which one is assigned to a ring prism and forms its second boundary surface.

In the described design of the reflector, the light coming from the light source passes through the first Interface enters the ring prism, is totally reflected at the second interface, and passes through the third boundary surface again, whereby it is directed axially parallel or approximately axially parallel. Should the light deviate slightly from the axially parallel alignment in total or in certain areas, it is sufficient to the tendency to change at least one of the three interfaces to the optical axis somewhat.

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In general there is an opening in the apex of the reflector through which a light source, for example a lightbulb, is inserted and held. In this, in the "shadow" of the light source In the area located, the light from the light source is not reflected and therefore not used. It takes therefore this area cannot be taken into account when designing the reflector.

The material used to manufacture the reflector must be transparent and must be in the area in which the Light beam occurs on the second interface, allow total reflection. In the front area of the reflector, that is, in the area from the open side to approximately the level of the focal point or the center of the light source is enough, all known transparent bulk plastics can be used in particular, since they have a Have a refractive index of at least approximately 1.5. In the rear area, so in the front area transparent plastics can be used in the subsequent part of the reflector that extends up to the apex whose refractive index is preferably in the range above 1.5, such as polycarbonate (PC) with a refractive index η = 1.586. Polystyrene (PS) with a refractive index η = 1.59 can also be used. as well Styrolacrylni i.ril (SAN) with a refractive index of η = 1.567 is suitable. The same also applies to epoxy resins with a refractive index of η = 1.55 - 1.61. It will be understood that glass can also be used. Pure the choice of material as well as the choice of the step height or prism ring width apply in addition to aspects' the stylistics those of the expediency, as well as other-

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on the other hand, that the condition for total reflection is met must become.

In the failure area of the reflector, increased light losses occur, which then does not matter, if this area is used anyway as an opening for the light bulb serving as the light source is. However, there are cases in which there is a lack of space or for other reasons, the apex area of the reflector is closed and also serves as a reflection surface. The light source is then through a side opening or from the front into the Reflector inserted and held. In order to obtain the desired total reflection in this apex area too, so do without mirroring, it is sufficient, as provided in a preferred embodiment, in addition to realizing the features mentioned above, the second interfaces, the are opposite to each other relative to the optical axis, enclose an apex angle of about 90 ° with each other. Since the total reflection prisms are ring prisms, this means nothing else than that the Back of the reflector forming surface of such a ring prism the lateral surface of a truncated cone represents, the cone angle of which is 90 ° (where the Apex of the cone angle points away from the light source), so the reflector no longer points in this area the shape of a paraboloid of revolution, but the shape of a cone. In this amazingly simple one In this way, it is also possible to utilize the apex area of the reflector in an advantageous manner.

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In a preferred further embodiment, the third boundary surfaces of the hanging prisms are convexly curved. Here can also the entire apex area of the reflector be formed by a single total reflection prism, the has the shape of a cone with an apex angle of 90 °, whose base is a convex spherical cap. However, in such an embodiment, at which the step height in the apex area is relatively large compared to the step heights in the rear and front reflector parts, an undesirable in some cases Accumulation of material. Therefore, the apex area is generally divided into approximately equal step heights.

In a preferred embodiment of the invention, the second boundary surfaces of the ring prisms are in the apex area, that is, their rear surfaces, convexly curved, and the third boundary surfaces are flat surfaces on the optical axis of the reflector. This embodiment has the advantage that a larger proportion of light is emitted the apex area is reflected because namely the entire portion of light falling on the second interface is reflected and not a part is lost because after the first total reflection under one unfavorable angle to the third boundary surface of an adjacent ring prism closer to the optical axis notices. It should be noted that there is a double total reflection in the apex area.

The size of the apex area depends on the for the rear reflector part used material or the refractive index of the one used here Materials. The apex region preferably comprises a solid angle of up to approximately 50 °, the tip of the

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Angle approximately in the middle of the light source (focal point) lies. The solid angle at which the second boundary surface is convex and the third boundary surface is a plane surface is limited to about up to 40 °.

In order to arrive at geometrically simple embodiments, at least two of the boundary surfaces of the ring prisms are preferred straight in axial section.

Outside the apex area, the reflector is preferably made of a material whose refractive index is not significantly below, preferably above 1.5. Such plastics are easy to process commercially available as transparent bulk plastics.

Further details and configurations of the present invention emerge from the following description Embodiments shown in the drawing in connection with the claims. Show it:

Fig. 1 shows an axial section through a reflector open crown area,

FIG. 2 shows a detail of the area II of FIG. 1 in an enlarged view,

3 shows a detail of the area III of FIG. 1 in an enlarged view,

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4 shows an embodiment in an enlarged representation the apex area of a reflector,

5 shows another embodiment of the apex area of the reflector, and

6 shows a third embodiment of the apex area of a reflector with a single, conical Prism.

The reflector 1 shown in half section in Fig. 1 comprises a front reflector part 2, a rear one Reflector part 3 and an apex area 4. In the middle of the apex area 4- an optical one pierces Axis 6 is the reflector, which is also the axis of rotational symmetry of reflector 1. On the optical axis 6 there is also a focal point 7 »in which there is a light source is arranged, the light of which should leave the reflector approximately parallel to the optical axis 6. The reflector 1 consists of a plurality of ring prisms 8, which are rotationally symmetrical to the optical axis 6 and each adjoin one another in the area of a narrow web 9, which results in the mechanical cohesion. at the ring prisms 8 are total reflection prisms with a triangular cross section and three outer surfaces or interfaces, namely a first interface 10, a second interface 11 and one third boundary surface 12. The first boundary surfaces 10 of all ring prisms 8 are cylinder jacket surfaces and are coaxial to the optical axis 6. Minor deviations from the cylinder surface to a conical surface

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can be provided for manufacturing reasons (demouldability) be. The second boundary surfaces 11, which together form the back of the reflector 1 in the front and in the rear Form reflector part, together give approximately the shape of a fiotationsparaboloid, which if necessary. by individual straight sections is approximated, each of which extends from web 9 to the next web 9, ie the step height of the individual ring prisms 8 correspond. The third boundary surfaces 12 are in the front reflector part 2 and in the rear reflector part 3 truncated cone surfaces, with the apex of the cone in the center the light source (focal point 7). At the border between the front reflector part 2 and the rear Reflector part 3, the third interface 12 is a plane surface to the optical axis 6 on which the optical Axis 6 is perpendicular and which intersects the optical axis 6 at the focal point 7. This training the third Boundaries have the advantage that practically no light component is lost through these interfaces as a result of shadowing, namely because the entire luminous flux is the first interfaces 10 meets at a relatively steep angle. The angle of incidence of light at the first Boundary surface 10 and the associated inclination of the second boundary surface 11 lead together with twice that Refraction when light enters a ring prism 8 and the light emerges from the ring prism 8 to the desired Beam focusing, as shown in FIGS. 2 and 3 in detail.

In the reflector 1 shown halfway in FIG. 1, the apex area 4 is designed as a recess, through which a light source, for example an incandescent lamp, can be introduced, the filament of which is inserted into the

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Focal point 7 is brought when the light rays 13 and 14 emerging from the light source after total reflection should leave the reflector 1 as light rays 15 and 16 parallel to the optical axis 6. Should the light beams 15 and 16 form a convergent or a divergent beam, it is sufficient that the Light source something out of the focal point 7 'along to shift the optical axis in one direction or the other, two-way then the inclinations or cone angles of the third boundary surfaces 12 are also adapted accordingly. A divergent or convergent beam formation of all or part of the light can also be achieved by that either the boundary surfaces are curved or their alignment relative to the optical axis 6 is changed in that, for example, the second boundary surfaces 11 no longer have an approximate parabolic contour follow.

There are cases where the light source is not inserted and held through the apex portion 4, but either through a lateral opening or from the front of the reflector 1. In such In some cases, it is desirable that the apex area 4 also acts as a reflector surface. In order not to lose too much light To have to accept, a modification of the shape of the ring prisms is necessary for this purpose, that the second boundary surfaces no longer follow a parabolic contour, but an apex angle enclose each other of about 90 °. FIGS. 4 to 6 show correspondingly designed ring prisms 18 for the apex area 4. The second boundary surfaces 11 · of the ring prisms 18 form in the apex area 4 a conical surface with a cone angle of 90 °.

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The first boundary surfaces 10 are furthermore cylinder jacket surfaces · The third boundary surfaces 12 · are lens-shaped curved; the third boundary surfaces 12 'of the individual ring prisms 18, as can be seen in Fig. 4-, a Kind of Fresnel lens or Fresnel lens. According to the illustration, the apex area comprises a solid angle of 50 °, the tip of which is at the focal point 7 (Fig. 4).

As can be seen from FIG. 4, in the embodiment shown there, certain areas of the amount of light coming from the light source, which are each shown hatched and after total reflection at the boundary surfaces 11 'runs radially to the optical axis * »6. As a result, however, the light of a beam region 19 is lost, which namely falls after the total reflection cuf the third boundary surface 12 of the ring prism 18 adjacent to the inside. In addition, the light from a beam area 20 is lost, namely that it falls on the first boundary surfaces 10. The light losses according to the beam area 20 cannot be avoided, but the light losses in the beam area 19 can be switched off if, according to the arrangement according to FIG At the same time, the second boundary surfaces 11 ″ are designed to be curved in order to obtain total reflection in such a way that the reflected beam is directed radially to the optical axis 6. The ring prism 18 of the apex area 4, which has the largest diameter and adjoins the rear area 3, can, however

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opposite Pig. 4- remain unchanged.

In the arrangements according to FIGS. 4 and 5, the νοώ focal point 7 incoming light reflected back to the focal point; the light emerging from the reflector apex area thus forms a slightly divergent one Beam.

It can also cover the entire apex area 4- through one single conical prism 21 be formed, in which only compared to the arrangement according to Pig. 4 the first Boundaries 10 are omitted. The cone angle is also 90 ° and there is double total reflection at the second interface 11 '. The curvature of the third Boundary surface 12 'can be chosen differently, approximately so that the exiting light beam is aligned parallel to the optical axis 6, or so that it is reflected back through the focal point.

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Claims (10)

Claims 1. Reflector, especially for vehicle lights and. Headlamp, which is made of a transparent material and which is the one entering from a light source Focuses light through curved total reflection prisms and wiede'r emits, characterized in that the total reflection prisms (8 or 18) on the inner, concave side facing the light source are provided that they are used as the optical axis (6) rotationally symmetrical triangular ring prisms (8 or 18) are designed that a first (10) of the three boundary surfaces »of a ring prism is approximately cylindrical to the optical Axis (6) of the reflector (1) is formed, and that a second boundary surface (11 or 11 or 11 ") is formed by the rear side of the reflector. 2. Reflector according to claim 1, characterized in that the third interface (12) · approximately parallel to a beam coming from the light source (focal point 7) is aligned and thus a section a truncated cone surface, the cone apex approximately in the middle of the light source (focal point 7) lies. 3. Reflector according to claim 1, characterized in that the reflector rear side, apart from the apex area (4 ·) has approximately the shape of a paraboloid of revolution. 130033/0336 4. Reflector according to claim 1 or 2, with a closed The apex area, characterized in that in the apex area (4) the second boundary surfaces (11 ' or 11 ") enclose an apex angle of approximately 90 ° with one another. 5. reflector according to claim 4, characterized in that that the second boundary surfaces (11 ') of a ring prism (1.8) form a conical surface and the third boundary surfaces (12 ·) are convexly curved. 6. Reflector according to claim 4, characterized in that the "second boundary surfaces (11") of an annular prism (18 ¹ ) are convexly curved and the third boundary surfaces (12 ") are plane surfaces. 7. Reflector according to one of the preceding claims, characterized in that the apex region (4) comprises a solid angle of up to about 60 °, the apex of this angle being approximately in the middle of the Light source (focal point 7) is located. 8. Reflector according to one of the preceding claims, characterized in that the width of the first Boundaries (10) of the ring prisms of a reflector is different. 130033/0336 ./. 300U22 9 · Reflector according to one of the preceding claims, characterized in that at least two of the
Boundaries of the ring prisms (8 or 18) are straight in axial section. 10. Reflector according to one of the preceding claims, characterized in that it is outside the
Vertex area (4) consists of a material,
whose refractive index is not significantly below, preferably above 1.5. 130033/0336