Indicating light display having several light sources

An indicating light display for a motor vehicle, and in particular a raised stop light in the form of a strip which contains a plurality of light sources, also includes optical processing means for redirecting the light received from the light sources so that it will be propagated in the general emission direction. The display thus consists of a series of light cells, each defining a transition zone between each cell and the next. The optical processing means include, in association with each light source, a first element for distributing the light, in a plane at right angles to the general emission direction, on a second element in the form of an optical plate. This optical plate is divided into zones each associated with one of the cells and formed with projecting striations. Each transition between a zone and the next zone is formed with a transition striation which receive light from both of the two adjacent light sources and redirects this towards the general emission direction.

FIELD OF THE INVENTION
 The present invention relates to indicating light displays for motor
 vehicles, applicable especially to light displays of the stop lamp type,
 that is to say brake lights which can be mounted inside the cabin of the
 vehicle and against the rear window of the vehicle, or else be integrated
 into thin components which are situated at the rear of the vehicle, such
 as fins or other aerodynamic elements.
 BACKGROUND OF THE INVENTION
 The first indicating light displays of the above type had the disadvantage
 that they did not provide a homogeneous light, despite various spreading
 arrangements for spreading the light which were used and which consisted
 generally of billets or toroids incorporated in the cover lens of the
 display, or in an optical plate of the display. Although this disadvantage
 is in general tolerable from the point of view of the statutory
 regulations, it is ugly from the aesthetic point of view, especially
 since, nowadays, increasing importance is being attached to the
 homogeneity of the light emitted by indicating lights of vehicles.
 French patent specification No. 2 614 969 discloses an indicating light
 display with a single light source, giving homogeneous illumination. That
 particular display comprises, within a housing, a transparent or
 translucent optical screen which is referred to as a "supplementary lens",
 and which is interposed between a single light source and an optical
 plate. This plate is essentially flat and extends in the direction at
 right angles to the optical axis of the light display. The particular
 geometrical configuration of the supplementary lens ensures that the
 surface density of light flux arriving on the optical plate is essentially
 constant over the whole surface of this plate. Finally, the surface of the
 plate is formed with striations which redistribute, or redirect, the light
 rays emitted from the supplementary lens, so as to transmit to the outside
 of the vehicle a beam within the solid angle provided for in the
 regulations.
 However, vehicle manufacturers have in practice designed stop lights with
 dimensions which are sometimes very large, and which make use of a
 plurality of light sources. It is clearly possible to conceive the use of
 a device that consists of optical sub-assemblies of the kind described in
 the above mentioned French patent specification, juxtaposed together and
 giving homogeneous illumination within each sub-assembly. However, in such
 an arrangement there would then be irregularities in the illumination at
 the junctions, or transition zones, between adjacent sub-assemblies.
 DISCUSSION OF THE INVENTION
 An object of the present invention is to overcome the above mentioned
 drawback, and to provide an indicating light display which may be made in
 a large size and which uses a plurality of light sources, while at the
 same time presenting a homogeneous illumination to the observer, which is
 of particular advantage from the aesthetic point of view.
 Another object of the invention is to enable the number of light sources in
 such an indicating light display to be limited, for a given size, without
 in any way compromising the homogeneity of the light field of the display
 when the latter is lit.
 According to the invention in a first aspect, an indicating light display
 for a motor vehicle, comprising a plurality of light sources together with
 optical processing means which are adapted to redirect the light emitted
 by the light sources so that the light is propagated in a direction which
 is essentially parallel to a general emission direction, is characterised
 in that the optical processing means include, in association with each
 light source, a first element adapted to spread the light, in a plane
 which is essentially at right angles to the general direction of emission
 and in an essentially homogeneous manner, on a corresponding one of a
 plurality of second elements having the general form of a plate and
 adapted to redirect the incident light towards the said general emission
 direction, and in that there is provided at the transition between two
 adjacent ones of the said second elements at least one transition
 striation projecting towards the interior of the indicating light display
 and adapted to redirect into the said general emission direction the light
 emitted from the two homologous light sources associated with the said
 second elements.
 Preferably there is only one said transition striation at the or each said
 transition.
 According to a preferred feature of the invention, each said second element
 has redirecting striations on the surface of that element which faces
 towards the interior of the light display, and each said transition
 striation projects further towards the interior of the said display than
 the said redirecting striations of the said second elements.
 Preferably, each said transition striation has two oblique faces.
 The light sources are preferably essentially aligned with each other.
 According to another preferred feature of the invention the or each said
 transition striation comprises two oblique faces which are opposed in
 relation to a plane containing the said general emission direction.
 According to the invention in a second aspect, an optical plate including
 optical processing means which are adapted to redirect in a general
 emission direction the light emitted from a light source and arriving on
 the plate with a given first angle of incidence which is substantially
 constant, is characterised in that at least one portion of the said
 optical processing means is also exposed to the light from a second light
 source arriving with a substantially constant second angle of incidence,
 and is adapted to redirect the light from the two light sources towards
 the said general emission direction.
 In this second aspect of the invention, the said portion of the optical
 processing means preferably comprises at least one projecting striation
 having two faces; and preferably also, there is a single said projecting
 striation in the or each said portion of the plate.
 According to a preferred feature of this said second aspect of the
 invention, redirection striations, projecting from the surface of the said
 plate are provided, and in that the said at least one projecting striation
 at the said transitions projects by a greater extent away from the optical
 plate than do the redirection striations.
 In some embodiments of this second aspect, there are, in each said portion
 of the plate, a plurality of the said projecting striations.
 The value of the said second angle of incidence is preferably equal and
 opposite to the value of the said first angle of incidence.
 Preferably, the or each said projecting striation has two oblique faces
 which are opposed with respect to a plane at right angles to a line
 joining the two associated light sources.
 Further features and advantages of the invention will appear more clearly
 on a reading of the following detailed description of some preferred
 embodiments of the invention, which is given by way of non-limiting
 example only and with reference to the accompanying drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
 Before we proceed with the description, three orthogonal directions X, Y
 and Z will be defined. These directions will be used in the drawings and
 in the following description. Y is the direction of the optical axes of
 the elements of the indicating light displays shown in the drawings. X and
 Z are the horizontal and vertical directions, respectively, in the display
 as mounted in a vehicle.
 Reference is first made to FIG. 1, which shows an optical cell comprising a
 housing 10, having a base on which a light source is mounted. This light
 source may for example be a so-called Brewster diode 20. An opaque wall 30
 extends across the housing 10 within the latter, and has a central
 circular aperture 31. The aperture 31 is filled by a hemispherical lens 40
 for spreading the light rays issued from the diode 20. This lens 40 is
 preferably made integral with the opaque wall 30, and has an inner face 41
 which is striated, and an outer face 42 which is also striated. The cell
 includes a second plate 50 which is transparent and which has striations
 60 on its inner face. Such an optical cell, from which an indicating light
 display can be formed by adding a cover lens to it, or by using the plate
 50 to close off the display, so that the plate 50 then acts as a cover
 lens (and is in that case provided with means for diffusing the light), is
 of a generally known type. Accordingly, no further details of its
 operation need be described here, this being such as to ensure that the
 illumination that emerges through the plate 50 is homogeneous in the X and
 Z directions, due to the striations 60 on its inner face and the
 striations on the outer face 42 of the supplementary lens 40, respectively
 (or inversely). In this connection, reference is invited to the above
 mentioned French patent specification No. 2 614 969.
 Reference is now made to FIG. 2, which shows an embodiment of an indicating
 light display (F) in which a single housing 10 contains six optical cells
 100 to 600, each of which is similar to the cell shown in FIG. 1. In the
 embodiment shown in FIG. 2, opaque walls 110, 210, 310, 410 and 510 extend
 in the Y direction between the base of the housing 10 and a first plate 30
 which includes six supplementary lenses 140, 240, 340, 440, 540, 640. The
 second plate 50 of the light display has six redirection, or
 redistribution, zones 150, 250, 350, 450, 550, 650 which are all made
 integral with each other in this particular embodiment, but which could
 equally well be made as separate components and secured together.
 In order to ensure homogeneous transition of the illumination between two
 adjacent zones 150, 250 etc., a transition zone R is provided. This
 transition zone R receives the light rays emitted by each of the two
 supplementary lenses 140 etc. of the two adjacent cells concerned. Within
 each transition zone R, optical treatment means are provided, for acting
 on the light rays emitted from the two associated supplementary lenses.
 The operation of these optical processing means will now be described in
 more detail, in particular with reference to FIG. 3.
 Referring accordingly to FIG. 3, this is a detail view of the transition
 zone between two adjacent redirection zones 350 and 450 of the indicating
 light display shown in FIG. 2. It will of course be understood that FIG. 3
 and the associated description apply equally well to the transitions
 between all the various redirection zones 150 etc. and their adjacent
 zones 250 etc. in the light display shown in FIG. 2.
 In FIG. 3, the transition zone R is exposed simultaneously to the light
 rays emitted from the supplementary lens 340 and those emitted from the
 supplementary lens 440. The rays from the lens 340 arrive with individual
 angles of incidence the values of which are closely approximate to a first
 mean angle of incidence .alpha.. It should be noted that the angle of
 incidence is defined with respect to the Y direction and measured
 positively in the trigonometric sense. The rays from the lens 440 arrive
 with individual angles of incidence which are substantially equal and
 which are closely approximate to a second mean angle of incidence .beta..
 In the present embodiment, the angles .alpha. and .beta. have opposite
 signs, because the cells of the apparatus in this embodiment are identical
 to each other. However, the angles .alpha. and .beta. could if desired
 have any values whatever, between 0 and 90.degree..
 The zone 350 carries on its inner face, in the transition zone between the
 cells 300 and 400, vertical striations 360 which are adapted to redirect,
 by internal reflection, the light rays emitted from the supplementary lens
 340, in such a way as to give these rays a direction which is essentially
 parallel to the Y direction. Similarly, the zone 450 carries on its inner
 face vertical striations 460 for redirecting, again by internal
 reflection, the light rays from the supplementary lens 440, so that these
 rays too are given a direction which is essentially parallel to the Y
 direction. In the transition zone of the internal faces of the zones 350
 and 450 there is a single transition striation S, which is in the form of
 a projecting tooth as shown in FIG. 3, projecting towards the interior of
 the indicating light display and having two faces SO3 and SO4. These two
 faces are symmetrical with the Y direction in this embodiment, since the
 values of .alpha. and .beta. are equal and opposite to each other. The
 superficial light flux density received by the zones 350 and 450 is
 substantially constant, due to the fact that the optical cells are
 identical with each other, so that the illumination emitted from the zones
 350 and 450 is constant outside the transition zone R.
 The function of the transition striation S is to ensure that the rays
 arriving in the transition zone R are also diverted in the Y direction. To
 this end, the striation S projects in the Y direction sufficiently far
 towards the interior of the indicating light display for its face SO3 to
 intersect essentially the rays emitted from the supplementary lens 340 and
 directed towards the zone 450. These rays, all of which reach the face SO3
 with an angle of incidence which is substantially equal to .alpha., pass
 through the zone R by refraction across the face SO3, and then by internal
 reflection on the face SO4. The inclination of the faces SO3 and SO4 is
 such that the rays then leave the plate 50 in a direction which is
 essentially parallel to the Y direction. Similarly, the face SO4
 essentially intercepts the rays emitted by the supplementary lens 440 and
 directed towards the zone 350, and these rays, which arrive at the face
 SO4 with an angle of incidence which is substantially equal to .beta., are
 diverted in the Y direction by refraction through the face SO4 followed by
 internal reflection on the face SO3.
 The indicating light display shown in FIGS. 2 and 3 accordingly delivers
 illumination which is generally constant in the X direction. As to
 distribution of the illumination in the Z direction, this is ensured by
 the internal striations 41 of the supplementary lenses, which are
 identical with each other.
 Reference is now made to FIG. 4, which shows another version of the
 striation S, in the form of a first transition striation S3 having two
 faces S31 and S32, together with a second transition striation S4 which
 has two faces S41 and S42. In this version, the faces S31 and S41 receive
 the rays which have been emitted by the supplementary lens 340, while the
 faces S32 and S42 receive rays emitted from the supplementary lens 440.
 This embodiment enables the same function as that of the single striation
 S in FIG. 3 to be obtained again, but with the striations S3 and S4
 intercepting and redirecting in the Y direction, essentially, those rays
 which have been emitted from one cell and directed towards the cover lens
 of the adjacent cell. This avoids any increase in the maximum thickness of
 the plate 50.
 If the width of the transition zone has to be large, or if it is desired to
 reduce the thickness of the front plate 50, it is possible to provide a
 device which has the same function as the striation S, but using a
 plurality of striations, having two oblique faces which are essentially
 symmetrical and which are aligned on the internal face of the front plate
 50.
 It is appropriate to add to the description just given that, in practice,
 an indicating light display made in accordance with the invention could
 equally enclose a cover glass having billets or toroids for spreading the
 light emitted from the second or front plate 50 within the solid angle
 prescribed by regulations.
 In addition, the use of the supplementary lenses 40 and front plates 50
 enables the angles .alpha. and .beta., which define the extent of the
 zones of the plates 50 associated with each light source, to be increased.
 It is thus possible, in an indicating light display according to the
 invention, to increase the length of the display as compared with a
 conventional indicating light display, while retaining the same number of
 light sources. It is also possible to reduce the number of light sources
 for a given length of indicating light display, which improves the selling
 price of the unit.
 Thus, an indicating light display made in accordance with the invention can
 be substantially elongated, making use of a plurality of aligned light
 sources, thereby conforming with the general current trend in the form of
 raised stop lights, while improving the aesthetic appearance of the
 illumination given by this light by providing an illumination which is
 perfectly homogeneous, and without in any way allowing the internal
 construction of the display to appear from outside.
 The invention is of course not limited to the embodiments described above.
 In particular, a person familiar with this particular technical field will
 be able to form light displays having any forms and lengths whatever,
 making use of the cells which may for example be square, triangular or
 hexagonal.