EP0402740B2 - Method to determine the shape of a reflector - Google Patents

Description

The invention relates to a reflector for a Luminaire and a method for determining the Form of such a reflector.

The lights in question here are meant to be especially for illuminating a room Illumination of an object or also for coupling serve from light into a light guide.

As reflector shapes are in the prior art Known conic curves, namely ellipse, parabola, Hyperbole, circle and straight lines (the latter as so-called singular conic sections). These reflector cut curves as is well known, arise in levels Sectional figures showing the optical axis of the Luminaire included.

a) Ellipse: Die Ellipse ist definiert durch zwei Parameter, nämlich die große Halbachse a und die kleine Halbachse b. Von einem Brennpunkt der Ellipse ausgehende Strahlung wird vom Ellipsoid-Reflektor so reflektiert, daß sie im anderen Brennpunkt gebündelt wird, wonach sich die Strahlung mit einem relativ großen Winkel ausbreitet.

b) Parabel: Die Parabel ist durch einen Parameter (zumeist "p" genannt) definiert. Vom Brennpunkt des Paraboloids abgestrahlte Strahlung wird durch den Reflektor so reflektiert, daß sie zur optischen Achse parallel verläuft.

c) Hyperbel: Die Hyperbel ist durch zwei Parameter bestimmt, die reelle Halbachse a und die imaginäre Halbachse b. Vom Brennpunkt abgestrahlte Strahlung wird so reflektiert, daß sie sich von der optischen Achse entfernt. Die Aufspreizung der Strahlung ist dabei eine Funktion des Abstandes von der optischen Achse; je näher die Strahlung an der optischen Achse verläuft, um so spitzer ist der Winkel zu optischen Achse.

d) Kreis: Der Kreis ist definiert durch einen Parameter, nämlich den Radius r. Vom Mittelpunkt des Kreises abgestrahlte Strahlung wird so reflektiert, daß sie sich wieder im Mittelpunkt bündelt.

e) Gerade: Die Gerade ist definiert durch den sogenannten Richtungsfaktor m. Die optischen Eigenschaften eines geradlinigen Reflektors sind trivial.

The well-known reflector intersection curves ellipse, parabola, hyperbola, circle and straight line each have the following parameters and reflection properties:

a) Ellipse: The ellipse is defined by two parameters, namely the major semiaxis a and the minor semiaxis b. Radiation emanating from one focal point of the ellipse is reflected by the ellipsoid reflector in such a way that it is concentrated in the other focal point, after which the radiation propagates at a relatively large angle.

b) Parabola: The parabola is defined by a parameter (usually called "p"). Radiation emitted from the focal point of the paraboloid is reflected by the reflector in such a way that it runs parallel to the optical axis.

c) Hyperbola: The hyperbola is determined by two parameters, the real semi-axis a and the imaginary semi-axis b. Radiation emitted from the focus is reflected so that it moves away from the optical axis. The spreading of the radiation is a function of the distance from the optical axis; the closer the radiation is to the optical axis, the more acute the angle to the optical axis.

d) Circle: The circle is defined by a parameter, namely the radius r. Radiation emitted from the center of the circle is reflected in such a way that it is concentrated again in the center.

e) Straight line: The straight line is defined by the so-called direction factor m. The optical properties of a rectilinear reflector are trivial.

The reflection properties described above of the conic-shaped reflectors can also be done by varying the parameters mentioned generally not be changed.

In general, the designer is one given certain reflector boundary conditions, according to which the luminaire is to be constructed, for example, the light exit diameter and the length of the lamp due to the structural Given conditions and also the desired one Light distribution at a certain distance from the lamp.

Conventional reflectors with a conic section Cut figures force the designer to significant compromise when the constraints are set closely. Cone-shaped reflectors Section figures allow for given Boundary conditions rarely an optimal design the luminaire with regard to the desired Light distribution. For curve types with two parameters, like ellipse and hyperbola, only the can Focus can be varied, but with limitations given due to the light source used are.

Are the boundary conditions (parameters) and the focus is fixed, so is the shape of the Determined reflector curve.

For example, it is possible to use a parabolic A small spot of light form. The size of the light spot can then, however can only be changed by changing the size of the Overall reflector is changed.

Elliptical reflectors are often used to illuminate a relatively large area. However, this is the light distribution very inhomogeneous within the beam angle and falls with increasing distance from the optical axis to the outside.

It is known the microstructure of the reflection surface to prepare, for example by Roughening, hammer blow or sandblasting, see above that the radiation becomes more homogeneous, i.e. the light intensity is reduced in the middle and on the edge elevated. However, this method has disadvantages in this respect than the width of the scattered light at Do not arithmetically coordinate the design of the luminaire can rather based on experience and is instructed to try. Another disadvantage this method is that the stray light also occurs far outside the beam angle and thus the delimitation of the light spot can be indistinct. It is also known Method of homogenizing light distribution the efficiency of the lamp is relatively low, i.e. in order to achieve a certain predetermined brightness, is a relatively large energy consumption in To take purchase. The results are also regarding the homogenization of the light distribution Can be improved within the beam angle.

A reflector is known from US Pat. No. 3,390,262 known in which only a reflector section near the edge corresponds to a conic section, while eir inner reflector section is constructed differently The transition between the two mentioned reflector sections is discontinuous. The latter has disadvantages in the manufacture of reflectors with regard to Tool. At the discontinuity the reflector cannot work exactly according to the tool be shaped and it gets lively Stray light generated. You have to do with an energy loss count. This is also better known Solution the equalization of the light distribution not reachable to the desired extent.

From DE-OS 35 07 143 is a lamp known, the reflector consists of segments, which are arranged so that each segment of radiation reflected by another area of the Light source goes out so that points on one too receiving radiation receive radiation, which is reflected by several different segments is.

Document US-A-3 398 272 describes one Reflector cut curve that is not conical is. This reflector cut curve is generated there that two constants are specified (certain Angle). By specifying this constant Angle, the reflector is fully defined and is calculated using a mathematical equation.

The invention has for its object a Possibility to construct reflector shapes to show with the desired light distributions produced with great efficiency as required can be. A preparation of the Microstructure of the reflection surface (as above explained) may not be necessary and the reflector should also no seams of a connection from have different curves.

The solution to this problem according to the invention is with their configurations in the claims described.

The two curves between which the invention Reflector runs, in particular two different ellipses (i.e. ellipses with at least one different parameter), two different parabolas (i.e. parabolas with different parameters) or an ellipse and be a parabola.

The reflector shape according to the invention is thus characterized in the latter example, that they are neither a pure ellipse, nor is a pure parabola, but continuous, i.e. over their entire extension, an "in-between" between such conventional known ones Reflector shapes. The reflector shape according to the invention does not correspond to a conic section.

The reflective properties of the invention constructed reflectors are fundamental different from the reflective properties of conical Reflectors and correspond in usually not simple "averages" the reflective properties of the envelopes Reflectors corresponding to curves. With others Words, the light distributions achieved according to the invention are not always an "intermediate thing" between the properties of the used two enveloping curves. This is especially true then when the two enveloping curves are different Conic sections are like a parabola and an ellipse.

The invention does not only suggest certain reflector shapes but gives the luminaire designer also a process in hand like him generally depending on the given Boundary conditions for the lamp and the desired Light distribution an optimal reflector shape can construct the desired Light distribution largely without using additional optical aids such as lenses etc., can be reached.

According to the teaching of the invention Reflector shapes are constructed with which Radiation from one light source optimally into one Radiation conductor can be coupled. Conventional, generate purely ellipsoidal reflectors relatively large angle of incidence between the radiation to be coupled in and the light guide. A However, the reflector according to the invention enables a relatively small angle of incidence between the radiation to be coupled in and the light guide, thereby directing the radiation through the Radiation conductor, e.g. Fiber, is improved.

According to the teaching of the invention, it is also possible to create a reflector that for a given distance, e.g. a meter that Radiation with high efficiency on a certain Can bundle point. The bundling is better than with a paraboloidal reflector.

Compared to the prior art for large beam angle provided ellipsoidal Reflectors enables one according to the invention constructed reflector a relatively uniform Light distribution.

Fig. 1

schematisch einen Schnitt durch ein erstes Ausführungsbeispiel eines Reflektors;

Fig. 2

einen Schnitt durch ein zweites Ausführungsbeispiel eines erfindungsgemäßen Reflektors;

Fig. 3

eine Lichtstärkeverteilung einer Leuchte mit einem herkömmlichen Ellipsoid-Reflektor und

Fig. 4

eine Lichtstärkeverteilung einer Leuchte mit einem erfindungsgemäßen Reflektor gemäß Fig. 2.

Exemplary embodiments of the invention are explained in more detail below with reference to the drawing. It shows:

Fig. 1

schematically shows a section through a first embodiment of a reflector;

Fig. 2

a section through a second embodiment of a reflector according to the invention;

Fig. 3

a luminous intensity distribution of a lamp with a conventional ellipsoid reflector and

Fig. 4

a light intensity distribution of a lamp with a reflector according to the invention as shown in FIG. 2.

In the embodiment shown in Fig. 1 is the optical axis with the reference numerals 1 provided. The reflector cut curve according to the invention R is shown with a solid line. The whole reflector is created either by Rotation of the curve R around the optical axis 1 or by translational displacement of the curve R when a trough-shaped reflector is created shall be.

The shape of the reflector cut curve R is formed such that it lies between two narrowing (envelope) curves in the manner described in more detail below, which are an outer ellipse E ₁ and an inner ellipse E _{2 in the} embodiment shown in FIG. 1. The ellipses E ₁ and E ₂ differ with respect to at least one parameter (a and / or b).

The use of two ellipses according to FIG. 1 as an envelope for the reflector cut curve R enables a reflector shape with which, in particular, radiation can be optimally coupled into a light guide, that is to say the coupled radiation has a relatively small angle of incidence. For this purpose, the two ellipses E ₁ , E ₂ and the reflector intersection curve R have a common optical axis 1. Two focal points F ₁ , F ₂ coincide. A fixed point O is also at the location of the focal points F ₁ , F ₂ . The fixed point O defines a polar angle and a distance ratio described in more detail below.

The reflector formed in this way is not an ellipsoid.

As can be seen in FIG. 1, the reflector intersection curve R runs much closer to the inner ellipse E ₂ in the vicinity of the apex than as it approaches the edge R _{a of} the reflector. This is explained in more detail below using the "distance ratio".

The embodiment shown in Fig. 1 can be modified so that instead of two ellipses two parabolas as enveloping curves for the reflector cut curve R side by side be placed. To with such a constructed Reflector a strong concentration of radiation in achieve a given distance from the lamp is to be able (reverse to the one described above Embodiment according to FIG. 1) provided that the reflector shape close to the Apex (i.e. on the optical axis) closer to the outer parabola (not shown) lies than on the inner parabola (not shown). With increasing Approaching the edge of the lamp is approaching then the reflector intersection curve R of the inner parabola. The reflector is not a paraboloid.

With the reflector shape described above with two parabolas as envelopes, one becomes Luminaire whose radiation is not exactly parallel is aligned to the optical axis, but something is reflected inwards. So it can without using a lens in a given Distance from the lamp creates a light spot whose diameter is smaller than that Opening diameter of the lamp.

In the embodiment shown in Fig. 1, the course of the reflector section curve R between its two enveloping ellipses E ₁ , E ₂ by means of a beam 2 emanating from a fixed point O, which coincides with the focal points F ₁ , F _{2 of} the ellipses, and that of described polar angle α described this beam. The beam 2 intersects the ellipses E ₁ , E ₂ and the reflector intersection curve R. The intersection points are provided with the reference symbols A, B and C, respectively. 1 shows two positions of the traveling beam 2, 2 ', the corresponding reference numerals being provided with a line in the second position.

A distance ratio k can now be defined as follows: k = (b - c) / (a - c), where a is the distance between points A and O, b is the distance between points B and O and c is the distance between points C and O.

In the exemplary embodiment according to FIG. 1, the distance ratio k in the region of the vertices S ₁ , S ₂ and S _{R of} the curves E ₁ , E ₂ and R is relatively small, ie the vertex S _{R of} the reflector R is closer to the vertex S ₂ inner envelope ellipse E ₂ as at the vertex S _{1 of} the outer envelope ellipse E ₁ .

As the polar angle α increases, the distance ratio changes in such a way that near the edge R _{a of} the reflector, the reflector is closer to its outer envelope ellipse E ₁ than to its inner envelope ellipse E ₂ .

The variation of the distance ratio as a function of the polar angle α can be represented analytically, for example, by the following equations: k = U × (α / α Max ) y + V k = U × logα / α Max + V k = U × e α / α max + V where α _{max is} the largest polar angle of the traveling beam 2 (corresponding approximately to the beam 2 'in FIG. 1), ie the angle of the beam grazing the edge R _{a of} the reflector section curve R. In the above equations (I), (II) and (III), y means a real number, in particular 1 and also U and V each mean real numbers.

The reflector should not have any discontinuities have, i.e. the change in the distance ratio as a function of the polar angle α follow steady function. The reflector preferably has a constantly differentiable form. This also applies to the other exemplary embodiment shown in FIG. 2 of a reflector according to the invention.

Above is the construction according to the invention of a reflector based on polar coordinates described. Polar coordinates have certain here Advantages, but it is also possible to Cartesian or use other coordinates.

The reflector R shown in Fig. 2 is used to generate a uniform light distribution. An ellipse E and a parabola P are placed side by side so that the focal point F _{1 of} the parabola coincides with a focal point F _{2 of} the ellipse E. The fixed point O, which defines the beam 2 and the polar angle a, also lies in the two focal points on the optical axis 1.

In the embodiment shown in Fig. 2 is the distance ratio as defined above k of the reflector R between the enveloping curves E and P constant.

By changing the distance ratio k the optical properties of the reflector Change R as needed. The closer the distance ratio k is 1.0, the more similar are the optical properties of the reflector R those of a parabolic reflector.

The optical properties of the reflector R in the exemplary embodiment according to FIG. 2 are determined by the parameters a, b of the ellipse E, the parameter p of the parabola P, the distance between the vertices S _E and S _{P of} the ellipse E and the parabola P on the optical axis 1 and the distance ratio k described above.

In a modification of that described in Fig. 2 Embodiment can the distance ratio k also vary as a function of the polar angle α, especially according to the above functions (1), (2) and (3).

The exemplary embodiment according to FIG. 2 can also be modified such that the focal points of the parabola or ellipse do not coincide. The distance between the vertices S _E and S _P on the optical axis 1 can also be reduced; in extreme cases, the two vertices can coincide.

It is also possible, in a modification of the exemplary embodiment 2 the ellipse outside to arrange the parabola, i.e. the size ratio reverse from parabola and ellipse.

Furthermore, the exemplary embodiments shown in FIGS. 1 and 2 can be modified such that the optical axes of the enveloping curves E ₁ , E ₂ , E, P do not coincide in each case. The optical axis of one envelope curve can be slightly inclined with respect to the optical axis of the other envelope curve.

The above-described exemplary embodiments of curves enveloping the reflector shape, such as E ₁ , E ₂ , E, P, can be done using equations ax 2nd + bxy + cy 2nd + bx + ey + f = 0 are described, where a, b, c, d, e and f are constants and x and y are variables.

The light distribution of an inventive Reflector can be both mathematically and empirically be determined. A mathematical statement is particularly easy when an analytical Expression for the distance ratio or the course of the curve R is given, so that the Tangent can be calculated by differentiation can. From the tangents to a variety of Points, each with constant angular distances from each other on the reflector cut curve R selected, result from the reflection law ("angle of incidence equals angle of reflection") the directions of those leaving the lamp Radiate and this results in one given distance from the luminaire the intensity distribution, i.e. the number of arriving Light rays per unit area.

In order to produce a single homogeneously illuminated light spot on a wall remote from the lamp with a reflector R according to FIG. 2 without the use of aids (caps or the like), it is provided that the light beam S reaching the opening edge _{Ra of} the reflector R with the optical axis 1 includes an angle β which is equal to the angle β 'which the beam S' reflected at the edge forms with the optical axis. In this case, the direct radiation from the light source at location O and the reflected radiation form the same light cone.

The light source does not necessarily have to be arranged in the focal points F ₁ , F ₂ or at location O.

3 and 4 show a comparison of the light intensity distributions in a conventional luminaire with an ellipsoid reflector and a luminaire according to the invention according to FIG. 2. In FIG. 3, the light intensity distribution I _{1 of} a luminaire with a conventional ellipsoid reflector is a function of the beam angle in applied in the usual way. It can be seen from curve I ₁ that the brightness drops sharply starting from a maximum at 0 ° to the side.

In contrast, in a reflector according to the invention, the light intensity distribution I ₂ according to FIG. 4 is substantially more uniform and remains almost constant within a certain angle. 4 is constructed as described above with two conic section curves, namely a parabola with p = 39.0, an ellipse with a = 90.2 and b = 56.0 and a distance ratio k of 0.22 (constant).

It is possible to have a reflector surface according to the invention to be faceted to give certain Light sources using a coiled wire have an aesthetically disruptive appearance of light and dark rings in the light spot to avoid.

Especially with a trough-shaped reflector the shape does not necessarily have to be in relation to the central longitudinal plane of the reflector symmetrical be. Rather, the lower part of the reflector differ from the top to make an optimal Adaptation to the required lighting too to reach.

Claims (1)

1. A method of generating a reflector shape whose cutting line (R) is not of the shape of a conic section in a plane including the optical axis (1) of the lamp, characterized in that the points of the reflector cutting line (R) are determined such as to each lie on straight lines (2, 2') starting from an origin (O) that is fixed with reference to the reflector and to form a different angle (α,α') with the optical axis (1) for each point (B, B') on the reflector cuting line (R), and in that the locus of the point (B, B') on the straight line (2, 2') between two conic sections (E₁, E₂; P, E) enveloping the reflector cutting line (R) between them is determined such that the distances of the point (B, B') from the points of intersection (A, C) of the straight line (2, 2') with the enveloping conic sections (E₁, E₂; P, E) are determined by a given distance ratio (k).

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