EP0489123B1 - Vehicle headlight - Google Patents

Abstract

A vehicle headlight has a parabolic reflector (10), in which is placed a light bulb (11) and the light outlet of which is covered with a light plate (12). On the inner face of the light plate (12) that faces the reflector are arranged optical elements designed in such a manner that each individual element (14) generates a light distribution curve that corresponds to a predetermined light distribution. By superimposing the individual light distributions of all elements (14), the vehicle headlight generates a predetermined light distribution having the required light intensity values.

Description

The invention relates to a vehicle lamp according to the preamble of claim 1.

Such a vehicle lamp is known from US-A-4 545 007. This vehicle lamp has a reflector, a light source and a lens. The lens has on its inner surface facing the reflector optical elements for deflecting the light rays reflected by the reflector. Each element of the lens is designed such that the light rays passing through each element are deflected in the horizontal and / or vertical direction in such a way that they produce the course of a predetermined light distribution that is identical for all elements. The elements are designed as aspherical lenses and divided into several areas with different radii of curvature. The design of the elements, that is to say the determination of the size of the various areas and their radii of curvature, in order to generate the predetermined light distribution is very complex.

Advantages of the invention

The vehicle lamp according to the invention with the features of claim 1 has the advantage that by dividing each element into a plurality of partial prisms, each with flat surfaces, the design of the elements for generating the predetermined light distribution is easily possible.

Advantageous refinements and developments of the invention are specified in the dependent claims.

drawing

An embodiment of the invention is shown in the drawing and explained in more detail in the following description. 1 shows a vehicle lamp in a horizontal section, FIG. 2 shows a section of the lens of the vehicle lamp from FIG. 1, FIG. 3 shows a vertical section through the lens of the vehicle lamp, FIG. 4 shows a horizontal section through the lens, FIG. 5 shows a predetermined light distribution in a network, FIG 6 shows the course of light distribution approximated in a horizontal section through the light distribution with a bell curve, FIG. 7 shows the course of light distribution approximated in a vertical section through the light distribution with a bell curve, FIG. 8 shows the lens in horizontal section in a coordinate system, a coordinate system and Figure 10 shows a variant of the lens of Figure 2.

description

A vehicle lamp shown in FIG. 1 has a reflector 10 in which a light source 11 is inserted. The light exit opening of the lamp is covered with a lens 12. The reflector 10 has one of a paraboloid of revolution formed reflection surface, wherein the filament 13 of the light source 11 is arranged in the focal point of the reflector. A large number of optically active elements 14 are arranged on the lens 12 on the inner surface facing the reflector, by means of which the light beams reflected by the reflector are deflected. Each of the elements 14 is formed in horizontal and vertical section so that each element 14 generates a light distribution which corresponds to a predetermined light distribution in the course. By superimposing the light distributions of the individual elements, the finished light distribution is created in the specified course and with the specified light intensity values. Each element 14 forms a convex lens protruding from the inside of the lens with a curvature directed towards the reflector.

From the left edge of each element 14 as seen in the light exit direction, the light rays are deflected into the right edge region of the predetermined light distribution, the light rays passing through the central region of each element are deflected into the central region of the light distribution and the light rays passing through the right edge of each element become deflected the left edge area of the light distribution. Accordingly, the light rays passing through the upper edge of each element are deflected into the lower region of the light distribution, the light rays passing through the central region of each element into the central region of the light distribution and the light rays passing through the lower edge of each element into the upper edge region of the light distribution .

Each element 14 is divided into a plurality of partial prisms, with a flat surface running tangential to an envelope curve of the inner surface of the element. In the exemplary embodiment, the envelope curve has a convex course overall.

In horizontal and vertical sections through the element, this results in section curves that consist of short straight sections that are strung together.

The calculation of the elements 14 is described below for a lens 12 which is inclined with respect to the vertical axis 16 of a motor vehicle and pivoted with respect to a transverse axis 17 of the motor vehicle. A coordinate system is defined by the vertical axis 16, the transverse axis 17 arranged perpendicular to the vertical axis and a longitudinal axis 18 of the motor vehicle perpendicular to the vertical and transverse axes, which is also referred to as a network. First, a desired light distribution is specified in a known manner in the form of lines of the same light intensity arranged on a measuring screen arranged perpendicular to the optical axis of the lamp extending parallel to the longitudinal axis 18 of the vehicle, so-called isolux lines 19. The course of the isolux lines is in one on the measuring screen a horizontal axis 21, on which the horizontal angle ω A to the optical axis of the luminaire is plotted, and a coordinate system containing a vertical axis 22, on which the vertical angle γ A to the optical axis is plotted.

The angle of inclination β and the swivel angle α, which is also referred to as the sweep angle, of the lens 12, more precisely the outer surface of the lens, is also predetermined, for example by the installation conditions determined by the manufacturer of the motor vehicle, the lens being adapted to the shape of the body of the motor vehicle can. For the calculation, the lens is now divided into a certain number of elements 14 both in the horizontal and in the vertical direction, so that the length L of each element is given in the horizontal direction and the height H in the vertical direction. The refractive index n des for the Material used lens is also assumed to be known. The calculation is now carried out in a large number of horizontal and vertical sections through the light distribution, with each section resulting in a curve for the light distribution, plotted over the horizontal exit angle ωA or over the vertical exit angle γA of the light beams. For each cut, the calculation of the elements is carried out in such a way that for the required exit angle ωA or γA of the light beams 22, the required entry angle ωE or γE of the light beams 22 into the element is calculated, that is to say the angle between the perpendicular on the straight line Section and the rays of light. The line segment is the tangent to the envelope of the inner surface of the element in the entry area of the light rays for the respective calculation step. Here, the entry angle is kept constant for a straight section. During the calculation, the exit angle ωA or γA is started from the right or bottom in the respective light distribution curve and the exit angle for the next calculation step is changed by a specific value. A horizontal section through the light distribution at a certain angle γA includes a horizontal section through the respective element at a distance from the upper edge of the element given by the distance of the angle γA from the lower edge of the light distribution. The same applies to vertical cuts through the light distribution and the element. The entry angle ωE or γE can be calculated using the following equations:

ωE =

Eintrittswinkel horizontal

γE =

Eintrittswinkel vertikal

α =

Schwenkwinkel der Lichtscheibe

β =

Neigungswinkel der Lichtscheibe

n =

Brechungsindex des Lichtscheibenmaterials

Here mean:

ωE =

Entry angle horizontal

γE =

Entry angle vertical

α =

Swivel angle of the lens

β =

Tilt angle of the lens

n =

Refractive index of the lens material

Since, in the present example, the reflector 10 is formed by a paraboloid of revolution, the light rays 22 are reflected by the latter parallel to the optical axis 18 of the lamp. Thus, the entry angle calculated using equations (1a) and (1b) is at the same time the swivel or inclination angle of the straight section 23 of the element on the inner surface facing the reflector with respect to the transverse or vertical axis.

In the case of a curved lens, that is to say a non-constant pivot or inclination angle, a mean pivot or inclination angle αM or βM can be used for the equations (1a) and (1b), which is present in the middle of the respective element. If the light rays are not reflected parallel to the optical axis by the reflector, different from the one described above, then the angle at which the light rays that pass through the element run to the optical axis must be taken into account when determining the pivoting or tilting angle of the element.

   bzw. $${\text{(2b) I(γ}}_{\text{A}}\text{) = Imax · e}{\text{}}^{{\text{-(R · γ}}_{\text{A}}{\text{)}}^{\text{2}}}$$

The length A of the straight section can be calculated from the specification of the light distribution, ie how much light is to emerge at the relevant angle ωA or γA. For this purpose, the respective light distribution curve resulting in the horizontal or vertical section can be approximated by the so-called Gaussian bell curve, which represents the probability density of the normal distribution. The bell curve gives the light intensity I as a function of the exit angle ωA or γA and the maximum light intensity Imax. in the middle of the light distribution curve: $${\text{(2a) I (ω}}_{\text{A}}\text{) = Imax · e}{}^{{\text{- (Q · ω}}_{\text{A}}{\text{)}}^{\text{2nd}}}$$

respectively. $${\text{(2b) I (γ}}_{\text{A}}\text{) = Imax · e}{}^{{\text{- (R · γ}}_{\text{A}}{\text{)}}^{\text{2nd}}}$$

The parameters Q and R are correction variables for adapting the bell curve to the respective light distribution curve, by means of which the width of the bell curve can be varied. The maximum light intensity Imax results for ωA = 0 ° or γA = 0 °.

$${\text{(3b) B(γ}}_{\text{A}}\text{) =}\frac{{\text{I(γ}}_{\text{A}}\text{) · cos β}}{{\text{ΣI(γ}}_{\text{A}}{\text{) · cos γ}}_{\text{E}}}\text{· H}$$

The length A (horizontal) or B (vertical) of the line section concerned can be calculated using the following equation: $${\text{(3a) A (ω}}_{\text{A}}\text{) =}\frac{{\text{I (ω}}_{\text{A}}\text{) · Cos α}}{{\text{ΣI (ω}}_{\text{A}}{\text{) · Cos ω}}_{\text{E}}}\text{· L}$$

$${\text{(3b) B (γ}}_{\text{A}}\text{) =}\frac{{\text{I (γ}}_{\text{A}}\text{) · Cos β}}{{\text{ΣI (γ}}_{\text{A}}{\text{) · Cos γ}}_{\text{E}}}\text{· H}$$

bestimmt, wieviel Licht an den betreffenden Punkten ωA bzw. γA der Lichtverteilungskurve gelangen muß.In the above equations, ΣI (ω _A ) or ΣI (γ _A ) means the sum of the light intensity values at all points ωA or γA of the light distribution curves used for the calculation. The relationship $$\frac{{\text{I (ω}}_{\text{A}}{\text{or γ}}_{\text{A}}\text{)}}{{\text{ΣI (ω}}_{\text{A}}{\text{or γ}}_{\text{A}}\text{)}}$$

determines how much light must reach the relevant points ωA and γA of the light distribution curve.

$${\text{(4b) Y(ω}}_{\text{A}}{\text{) = cos ω}}_{\text{E}}{\text{· A(ω}}_{\text{A}}\text{) + D}$$

für die Berechnung im horizontalen Schnitt und $${\text{(4c) X(γ}}_{\text{A}}{\text{) = sin γ}}_{\text{E}}{\text{· B(γ}}_{\text{A}}\text{) + E}$$

$${\text{(4d) Z(γ}}_{\text{A}}{\text{) = cos γ}}_{\text{E}}{\text{· B(γ}}_{\text{A}}\text{) + F}$$

für die Berechnung im vertikalen Schnitt. In den Gleichungen (4a) bis (4b) bedeuten C, D, E und F die X, Y, bwz. Z-Koordinaten des Endpunktes des vorhergehenden Geradenabschnitts. Für die Berechnung des ersten Geradenabschnitts kann für C, D, E und E der Wert Null eingesetzt werden, da die Berechnung ausgehend vom Ursprung des Kooridnatensystems durchgeführt wird.Particularly for the production of the shape of the lens on a computer-controlled machine tool, it is advantageous to specify it in a right-angled coordinate system. For this purpose, a coordinate system is specified, with an axis X parallel to the optical axis of the lamp, an axis Y parallel to the transverse axis of the motor vehicle and an axis Z parallel to the vertical axis of the motor vehicle, the coordinate origin being placed, for example, in the upper left corner of the lens. The coordinates X, Y, Z of the end point of the respective line segment can then be calculated as follows: $${\text{(4a) X (ω}}_{\text{A}}{\text{) = sin ω}}_{\text{E}}{\text{A (ω}}_{\text{A}}\text{) + C}$$

$${\text{(4b) Y (ω}}_{\text{A}}{\text{) = cos ω}}_{\text{E}}{\text{A (ω}}_{\text{A}}\text{) + D}$$

for the calculation in the horizontal section and $${\text{(4c) X (γ}}_{\text{A}}{\text{) = sin γ}}_{\text{E}}{\text{· B (γ}}_{\text{A}}\text{) + E}$$

$${\text{(4d) Z (γ}}_{\text{A}}{\text{) = cos γ}}_{\text{E}}{\text{· B (γ}}_{\text{A}}\text{) + F}$$

for the calculation in vertical section. In the equations (4a) to (4b), C, D, E and F denote the X, Y, bwz. Z coordinates of the end point of the previous line segment. For the calculation of the first line segment, the value zero can be used for C, D, E and E, since the calculation is based on the origin of the coordinate system.

If the lens is either only inclined, i.e. the swivel angle α zero or only swiveled, i.e. the inclination angle β zero, the calculation can be carried out using the equations given above, as described, by setting the corresponding angle to zero in the equations.

In a departure from what has been described above, each element 14, as shown in FIG. 10, can also be designed as a concave lens molded into the inside of the lens with a curvature pointing away from the reflector. In this case, from the left edge of each element, the light rays are deflected into the left edge region of the light distribution, the light rays passing through the middle region of each element into the middle region of the light distribution and the light rays passing through the right edge of each element into the right edge region of the light distribution . Accordingly, the light rays passing through the upper edge of each element are deflected into the upper edge area of the light distribution and the light rays passing through the lower edge into the lower edge area of the light distribution.

Claims (4)

1. Vehicle lamp with a reflector (10), a light source (11) and a lens plate (12) which, on its inner surface facing the reflector (10), has optical elements (14) for deflecting the light beams reflected from the reflector (10), each element (14) being constructed such that the light beams passing through an element (14) are deflected in each case in the horizontal and/or vertical direction such that said beams produce the shape a prescribed light distribution identical for all elements (14), characterised in that each element (14) is subdivided into a multiplicity of subprisms having flat surfaces extending tangentially to an envelope of the inner surface of the element (14), each subprism being assigned to a region of the light distribution, and the surface of the subprism being determined by the amount of light assigned to this region of the light distribution.
2. Vehicle lamp according to Claim 1, characterised in that each element (14) is constructed as a concave lens, so that with reference in each case to the horizontal direction the left-hand edge region, in the light exit direction, of an element (14) deflects the light beams into the left-hand edge region of the light distribution, the central region of an element (14) deflects the light beams into the central region of the light distribution and the right-hand edge region of an element (14) deflects the light beams into the right-hand edge region of the light distribution, and correspondingly in the vertical direction the upper edge region of an element (14) deflects the light beams into the upper edge region of the light distribution, the central region of an element (14) deflects the light beams into the central region of the light distribution and the lower edge region of an element deflects the light beams into the lower edge region of the light distribution.
3. Vehicle lamp according to Claim 1, characterised in that each element (14) is constructed as a convex lens, so that with reference in each case to the horizontal direction the left-hand edge region, in the light exit direction, of an element (14) deflects the light beams into the right-hand edge region of the light distribution, the central region of an element (14) deflects the light beams into the central region of the light distribution and the right-hand edge region of an element (14) deflects the light beams into the left-hand edge region of the light distribution, and correspondingly in the vertical direction the upper edge region of an element (14) deflects the light beams into the lower edge region of the light distribution, the central region of an element (14) deflects the light beams into the central region of the light distribution and the lower edge region of an element deflects the light beams into the upper edge region of the light distribution.
4. Vehicle lamp according to one of the preceding claims, characterised in that the lens plate (12) is arranged inclined and/or swivelled.

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