U.S. patent application number 12/348749 was filed with the patent office on 2009-12-17 for optical element and module for the projection of a light beam, and motor vehicle lamp including a plurality of such modules.
This patent application is currently assigned to C.R.F. Societa' Consortile Per Azioni. Invention is credited to Stefano Bernard, Denis BOLLEA, Davide Capello, Piermario Repetto, Gianluca Rotaris, Sabino Sinesi.
Application Number | 20090310379 12/348749 |
Document ID | / |
Family ID | 34982061 |
Filed Date | 2009-12-17 |
United States Patent
Application |
20090310379 |
Kind Code |
A1 |
BOLLEA; Denis ; et
al. |
December 17, 2009 |
OPTICAL ELEMENT AND MODULE FOR THE PROJECTION OF A LIGHT BEAM, AND
MOTOR VEHICLE LAMP INCLUDING A PLURALITY OF SUCH MODULES
Abstract
An optical element for the projection of a light beam comprises
a solid body (1) of transparent material in which is formed a
cavity (13) able to receive a light source (10), the cavity (13)
extending along the principal axis (z) of the transparent body (1)
and being delimited by a radially inner surface (3) and a terminal
surface (2) of the transparent body (1). The surfaces (2, 3) are
able to receive separate respective portions (I, II) of the light
flux generated by the source (10). The transparent body (1) further
has a radially outer surface (4) which surrounds the radially inner
surface (3). The radially outer surface (4) reflects the portion of
the light flux (I) coming from the radially inner surface (3) along
a direction substantially parallel to the principal axis (z). The
transparent body (1) has, on the opposite side, a central surface
(6) and an annular surface (5) surrounding the central surface (6),
able to receive that portion (II) of the light flux and the
reflected portion of the light flux (I) respectively and to
transmit these light flux portions (I, II) in directions having
predetermined orientations with respect to the principal axis (z).
At least one of the surfaces (2, 3, 5, 6) is rotationally
asymmetric with respect to the principal axis (z) of the
transparent body (1). The surfaces (2, 3, 5, 6) cooperate in such a
way as to shape the overall light flux (I, II) emitted by the
central and annular surfaces (6, 5) into a light intensity
distribution having different divergences in two directions
perpendicular to one another and to the principal axis (z).
Inventors: |
BOLLEA; Denis; (Orbassano,
IT) ; Repetto; Piermario; (Orbassano, IT) ;
Bernard; Stefano; (Orbassano, IT) ; Capello;
Davide; (Orbassano, IT) ; Sinesi; Sabino;
(Orbassano, IT) ; Rotaris; Gianluca; (Orbassano,
IT) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
C.R.F. Societa' Consortile Per
Azioni
Orbassano
IT
|
Family ID: |
34982061 |
Appl. No.: |
12/348749 |
Filed: |
January 5, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11577276 |
Apr 13, 2007 |
|
|
|
PCT/EP2005/055057 |
Oct 6, 2005 |
|
|
|
12348749 |
|
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Current U.S.
Class: |
362/540 |
Current CPC
Class: |
F21Y 2115/10 20160801;
F21S 43/14 20180101; F21V 7/0091 20130101; F21S 43/315 20180101;
F21V 5/04 20130101; H01L 33/58 20130101; H01L 33/60 20130101 |
Class at
Publication: |
362/540 |
International
Class: |
B60Q 1/26 20060101
B60Q001/26 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 14, 2004 |
EP |
04425775.6 |
Claims
1. A lamp (F) for a vehicle comprising at least one portion (F1,
F2, F3, F4) performing a light signaling function, in which the
said portion comprises a plurality of optical modules (M), wherein
said optical modules being disposed on a common support plane (P)
and electrically connected via conductive tracks formed on the said
support plane.
2. A lamp according to claim 1, in which each of the said modules
shapes the beam emitted by the respective source in such a way as
to generate a predetermined angular distribution of light
intensity, the said distribution being substantially symmetrical
with respect to a pair of axes perpendicular to one another and to
the principal axis (z).
3. A lamp according to claim 1 comprising: a container base (15) of
plastics material disposed close to the said support plane on the
opposite side from that of light emission, and a further
transparent element (11) having the function of transmitting the
light from the said modules, wherein said container base (15) and
the said transparent element (11) form a closed and sealed volume
within which the said modules are positioned.
4. A lamp according to claim 3, in which the said transparent
element (11) is able to deflect the light beam emitted from each of
the said modules angularly in the direction of the longitudinal
axis of the said vehicle.
5. A lamp according to claim 3, wherein said transparent element
(11) is able to vary the spread of the light beam emitted by each
of the said modules.
6. A lamp according to claim 1, wherein the axis perpendicular to
the support plane does not coincide with the longitudinal axis of
the vehicle.
7. A lamp according to claim 3, wherein said transparent element
(11) has an inner surface (11') comprising an additional prismatic
component able angularly to deflect the light beam emitted from
each of the said modules in the direction of the longitudinal axis
of the vehicle.
8. A lamp according to claim 1, in which at least one portion of
the said transparent element (1) is coloured.
9. A lamp according to claim 3, having an overall thickness less
than 20 mm.
10. A lamp according to claim 1, wherein the modules (M) relating
to at least a single portion (F1, F2, F3 and F4) of the lamp are
joined together in such a way as to form a single transparent
optical module, obtainable for example by injection moulding.
11. The lamp according to claim 1, wherein the optical module
vehicle comprising: a light source (10) and a solid body (1) of
transparent material having a principal axis (z), in which is
formed a cavity (13) for receiving the light source (10), the said
cavity (13) extending along the said principal axis (z) of the
transparent body (1) and being delimited laterally by a radially
inner surface (3) and at one end by a terminal surface (2) of the
transparent body (1), the said surfaces (2, 3) being able to
receive respective separate portions (I, II) of the light flux
generated by the said source (10), in which the transparent body
(1) further has a radially outer surface (4) which is disposed in
such a way as to surround the said radially inner surface (3), the
said radially outer surface (4) being able to reflect the portion
of the light flux (I) coming from the radially inner surface (3) in
a direction substantially parallel to the principal axis (z) of the
body (1) and in which the transparent body (1) has on the side
opposite that of the cavity (13), a central surface (6) and an
annular surface (5) surrounding the said central surface (6), able
to receive, respectively, the portion of the light flux (II) coming
from the terminal surface (2) and the portion of the light flux (I)
reflected by the radially outer surface (4) and to transmit the
said light flux portions (I, II) in directions having predetermined
orientations with respect to the principal axis (z) of the
transparent body (1); wherein at least one of the said surfaces (2,
3, 5, 6) is rotationally non-symmetric with respect to the said
principal axis (z) of the transparent body (1), the said surfaces
(2, 3, 5, 6) cooperating in such a way as to conform the overall
light flux (I, II) exiting from the said central and annular
surfaces (6, 5) into a light intensity distribution having
different spread in two directions perpendicular to one another and
to the principal axis (z) of the transparent body (1); wherein said
radially outer surface (4) is joined to the radially inner surface
(3) by a substantially flat connecting surface (9) perpendicular to
the said axis (z) of the transparent body (1), the said light
source being disposed flush with the said connecting surface (9),
and wherein said central surface (6) is designed so as to receive
the entire and only portion of the light flux (II) coming from the
terminal surface (2).
Description
BACKGROUND OF THE INVENTION
[0001] This is a divisional of application Ser. No. 11/577,276
filed Apr. 13, 2007. The entire disclosure of the prior
application, application Ser. No.(s) 11/577,276 is considered part
of the disclosure of the accompanying divisional application and is
hereby incorporated by reference.
[0002] The present invention relates in general to modules for the
projection of light beams.
[0003] Modules of this type are already known, for example, from
Japanese Patent Application JP 61-147585, which describes a module
which collimates a light beam, comprising an LED mounted on a
support and a total internal reflection lens having a cavity in
which the LED is housed. Both the lens and the LED are housed in a
cylindrical casing.
[0004] The main advantage of devices described in the Japanese
Patent Application resides in the fact that they have a high
luminous efficiency, that is to say the ratio between the flux
re-emitted by the device and that emitted by the source is
generally greater than 85%, because they exploit total internal
reflection. Another important advantage resides in the fact that it
is not necessary to provide the device with a metal coating to
allow the reflection of the rays incident on the lateral
surfaces.
[0005] In general, to provide illumination apparatus, several
modules of this type can be disposed on a common support plane, on
which are disposed a multiplicity of sources. The direction of
collimation is perpendicular to the said support plane, and the
distribution of intensity is radially symmetric with respect to the
said direction of collimation.
[0006] In order to apply this arrangement, or other similar
arrangements, to motor vehicle lamps it is necessary to obtain
optical performance which cannot be achieved through the
above-cited devices. In fact, for the purpose of minimizing the
thickness of the lamp, it is in general necessary that the support
plane on which the collimation modules are installed be parallel to
the covering of the motor car; this covering is typically inclined
with respect to the plane perpendicular to the motor vehicle axis
in such a way that the collimation direction forms a corresponding
angle relative to the motor vehicle axis. This therefore makes it
necessary to introduce a prismatic component to reorientate the
light beam leaving the collimator; it is possible to design the
collimator in such a way that the beam exit direction is inclined
with respect to the axis perpendicular to the support plane, but in
general this requires that at least one portion of the lateral
surface be coated with a reflecting coating, which reduces the
efficiency and increases cost.
[0007] Alternatively, a prismatic component can be introduced
through a prism structure formed on the exit surface of the
collimator (Patent Application WO 00/24062), or on an additional
glass positioned in front of the collimator itself.
[0008] Moreover, for the different signaling functions of the lamp
it is necessary for the light beams emitted from the system to
satisfy determined requirements of spread imposed by the
regulations which are in force.
[0009] For example, in the case of the stop function, the spread of
the beam in the horizontal plane (parallel to the road) is critical
in that spread half-angles greater than 20.degree. are required,
whereas the spread half-angle in the vertical direction is
distinctly less (10.degree.). By utilizing radially symmetrical
modules (as described in Patent Applications JP 61-147585 and WO
00/24062) a distribution with substantially the same spread in the
horizontal and vertical directions is in general obtained; to
satisfy the photometric regulations in the horizontal direction
therefore involves achieving a vertical spread greater than that
required, with consequent wastage of luminous flux, increase of
consumption and/or the number of light sources and therefore the
cost.
[0010] International Patent Application WO 00/24062 presents a
possible solution to this problem by introducing a different
prismatic component for the different collimators constituting the
system, in such a way that the combination of these collimators
makes it possible to generate a predetermined distribution of
light. The limitation of this solution lies principally in the fact
that, for a certain direction of observation, only the part of the
device including the collimators which collimate the light in this
direction of observation will appear illuminated.
[0011] Generally, to produce a predetermined light distribution,
these collimators can be combined with prismatic systems or micro
lenses able to spread the exit beam from the collimator and,
possibly, to modify the direction thereof.
[0012] The prismatic power is obtained with a single interface
(between the material constituting the collimator and air), which
limits the possible angle of deviation to the angle of total
internal reflection (TIR) between the two materials constituting
the interface (for example 41.8.degree. in the case of a
methacrylate-air interface); moreover, for angles close to the TIR
angle the losses by reflection at the prismatic interface become
significant and limit the efficiency of the module. A possible
alternative is that of providing a second transparent prism,
physically separated from the collimator and having the prisms on
the internal interface (for example air-methacrylate) facing
towards the collimator outlet; this makes it possible to divert the
light in a more efficient manner by exploiting the refraction both
on the (prismatic) inner wall and on the smooth outer wall. This
arrangement can be combined with the previous one in such a way as
to divide the prismatic power over several interfaces, thereby
reducing the inclination of the prisms and maximizing the
transmission efficiency of the device.
[0013] One interesting solution for production of a thin lamp
having LED devices was proposed by the applicant for the present
application in U.S. Pat. No. 5,841,596 and U.S. Pat. No. 5,884,995;
the said solution is represented in FIG. 2. These patents relate to
a micro telescope device of the Cassegrain type. As known, the
Cassegrain telescope is formed by a primary reflector which
collects the light coming from outside and reflects it towards a
secondary reflector; the secondary reflector further closes the
beam and finally the image is created on the desired plane. Because
of its particular geometry the Cassegrain telescope has an obscure
zone corresponding to the secondary reflector, where the light
cannot be captured. These two patents exploit the inverse
principle, that is the light beam is generated by a quasi-point
source S, for example of the LED type, which is located at the
image plane of the telescope, and the light is extracted by the
primary reflector RP after having been reflected by the secondary
reflector RS. The device F is generally of transparent plastics or
resin.
[0014] The principal advantage of the telescopic system lies in the
fact that it makes it possible to restrict the thickness of the
lamp; another advantage is that the device can have a high
width-to-height ratio, which means that it can cover an extended
surface of the lamp whilst the overall thickness thereof remains
limited.
[0015] The principal disadvantage of this device lies in the fact
that the extraction of the light does not take place over the
entire exit surface of the device but only from the circular outer
ring, in correspondence with the primary reflector RP, with the
consequence that a darker central region is evident.
[0016] A further disadvantage lies in the fact that it is necessary
selectively to coat some portions RPR of the lamp with reflecting
metal layers which reduce the efficiency and involve a significant
increase in production costs.
SUMMARY OF THE INVENTION
[0017] The object of the present invention is the production of a
lamp which overcomes the limitations of the above-described
solutions, in particular: [0018] improving the uniformity of
illumination from the surfaces of the lamp, [0019] maximizing the
efficiency and therefore limiting the number of sources and
reducing the associated costs, [0020] reducing the thickness,
[0021] limiting the manufacturing costs of the optical components
by eliminating the metallic coatings.
[0022] According to the invention this object is achieved by means
of an optical element for the projection of a light beam, having
the characteristics defined in claim 1.
[0023] By means of such an element it is possible to provide a
module operating to control the light emitted from a quasi-point
source (for example an LED of SMD type or in the form of a chip).
It is therefore possible to construct an illumination device, in
particular a motor vehicle lamp, in which each individual signaling
function is constituted by a plurality of the said modules
juxtaposed and/or interconnected. The surfaces of these modules
work both in refraction and in total internal reflection in a
similar manner to that envisaged in Patent Applications JP
61-147585 and WO 00/24062; however, the said Patent Applications
describe modules able to generate only radially symmetrical
intensity distributions.
[0024] The intensity distribution generated by the modules of the
present invention is, on the other hand, rotationally asymmetrical,
which therefore makes it possible to minimize the number of
sources/modules necessary to achieve a specific signaling
function.
[0025] A further object of the invention comprises a module for the
projection of a light beam, comprising an optical element according
to the invention and a lamp for a vehicle including such
module.
[0026] Preferred embodiments are defined in the dependent
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Various preferred but non-limitative embodiments of the
invention will now be described making reference to the attached
drawings, in which:
[0028] FIG. 1 shows a typical photometric distribution for one
function of a lamp;
[0029] FIG. 2 shows the prior art;
[0030] FIG. 3 is a three dimensional schematic representation of an
optical element for the projection of a light beam according to the
invention;
[0031] FIGS. 4a, b are schematic representations in longitudinal
section of the optical element of FIG. 3;
[0032] FIG. 5 is a plan view of the optical element of FIG. 3;
[0033] FIG. 6 shows a ray trace within the element of FIG. 3;
[0034] FIG. 7 illustrates a light intensity distribution obtainable
with a module including the optical element of FIG. 3;
[0035] FIGS. 8a, b illustrate a variant of the element of FIG. 3 in
a view similar to that of FIGS. 4a, 4b;
[0036] FIG. 9 illustrates the ray trace through a surface of the
optical element of Figure 3;
[0037] FIG. 10 is an exploded view of a surface of the optical
element of FIG. 3;
[0038] FIG. 11 illustrates a further variant of the optical element
of FIG. 3;
[0039] FIG. 12 illustrates a motor vehicle lamp formed by several
portions, each portion operating a light signaling function, within
which is arranged a plurality of modules according to the
invention;
[0040] FIGS. 13 and 14 illustrate the logical sequences necessary
to bring the photometric distribution of the modules of a lamp on
the plane normal to the longitudinal direction of the vehicle by
the introduction of prisms;
[0041] FIG. 15 is an exploded view of a portion of a lamp;
[0042] FIG. 16 is a view similar to that of FIG. 12, in which a
portion of the lamp is represented on an enlarged scale; and
[0043] FIG. 17 shows a comparison of the thicknesses of lamp of
traditional type with one formed using the modules according to the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0044] With reference to FIGS. 3 to 5, module M for the projection
of a light beam comprises a light source 10 which is adapted to be
disposed on a support plane P and an optical element able to convey
the light emitted by the source 10 in a direction substantially
perpendicular to the support plane P. This optical element has a
solid body 1 of transparent material. The module in question is
characterized by the fact that it is not obtainable as a single
surface of revolution about the axis passing through the source and
perpendicular to the support plane and by the fact that the module
shapes the beam into an intensity distribution of light having a
different spread in two directions perpendicular to one another and
to the support plane.
[0045] This body 1 has a principal axis z which, in the mounted
condition illustrated in FIG. 4, is substantially perpendicular to
the support plane P. In the body 1 is formed a cavity 13 which
extends along the axis z of the body 1 and is delimited by a
radially inner surface 3 and by a terminal surface 2 of the body 1.
The cavity 13 is able to house the source 10.
[0046] With reference to FIG. 4, the light source 10, preferably of
solid state type, is then disposed between the support plane P of
the body 1 and the surfaces 2 and 3 of the solid body itself.
Technologically, the solid state source can be integrated in the
module M by chip on board technology or by SMD. The chip on board
technology (COB) is differentiated from SMD technology (Surface
Mounted Device) by the use of semi-conductors directly on the
printed circuit in place of discrete components within the plastics
casing, that is to say the LED is composed only of the
semi-conductor element (die), secured by adhesive to the support
plate with a drop of epoxy resin. The principal advantage of COB
technology lies in the fact that it can produce very thin lamps
because all packaging typical of an LED is eliminated.
[0047] The body 1 further has a radially outer surface 4,
preferably curved, disposed in such a way as to surround the
radially inner surface 3 and, on the side opposite the cavity 13, a
central surface 6, preferably curved and aligned with the terminal
surface 2, and an annular surface 5 which surrounds this central
surface 6. On one side the annular surface 5 is joined to the
radially outer surface by means of a connecting surface 8. On the
other side the annular surface 5 is joined to the central surface 6
by means of a connecting surface 7.
[0048] With reference to FIG. 6, the transparent body 1 has two
distinct working zones, a central zone which works exclusively in
transmission, and a peripheral zone which works in reflection,
preferably total internal type (TIR) or possibly obtained by means
of a reflecting metal layer. To separate the functions of the solid
body 1 in a strict manner implies the necessity of dividing the
light flux emitted by the source 10 into two parts I and II; the
fact of maintaining the two light beams I and II separated makes it
possible to avoid one zone of the device having to work for both
beams, and therefore in an approximated manner, thus reducing the
overall efficiency of the module in a significant manner.
[0049] The separation of the light emitted by the LED source 10
into two distinct light beams I and II takes place at the first
interface; the terminal surface 2 collects a part II of the light
coming from the source 10 and directs it towards the central
surface 6. The radially inner surface 3 collects the other part I
of the light flux coming from the source 10 and directs it towards
the radially outer surface 4 which works in total internal
reflection, which in turn reflects it towards the annular surface
5. This beam separation prevents any of the flux from finishing on
the connecting collar 8. In order that the light flux be separated
correctly it is important to calculate the meeting point between
the terminal surface 2 and the radially inner surface 3; in fact,
the meeting point of the two interfaces determines, by Snell's Law,
the extreme rays beyond which the two beams I and II cannot go, as
shown in FIG. 6. By working in this way the beams I and II are
independent from one another and in this way it is possible to
separate and treat the projecting of the part undergoing just
transmission in a different manner from the part which undergoes
total internal reflection.
[0050] The light emitted by the source 10 which is collected
through the terminal surface 2 is directed towards the exit
interface formed by the central surface 6. The terminal surface 2
has a rotational symmetry with respect to the axis z normal to the
support plane P passing through the centre of the source 10, whilst
the interface 6 is generally not a surface of revolution.
[0051] For the purpose of maximizing the overall efficiency of the
module M the ray which is collected at the extremity of the
terminal surface 2 is deviated according to Snell's Law and made
incident at the edge of the central surface 6, as shown in FIG. 6.
Any other ray incident on the terminal surface 2 is also incident
on the central surface 6 and contributes to the formation of the
distribution of luminous intensity.
[0052] The surface 6 is rotationally asymmetric, being designed in
such a way as to form a luminous intensity distribution of
substantially uniform and rectangular shape, as shown in FIG. 1,
which shows the test points which are taken to validate the
individual functions of the lamp. In FIGS. 4a, b and 5 can be seen
how upon rotating the body through 90 degrees the central surface 6
has a different section. Central surface 6 can be segmented into
several parts 6a, b, c as illustrated in FIG. 8.
[0053] The connecting surface 7, of substantially conical form, is
designed in such a way as not to interfere with the light exiting
at large angles from the central surface 6, and at the same time in
such a way as not to interfere with the extraction of light from
the radially outer surface 4 which works in total internal
reflection.
[0054] For each light function in a vehicle it is generally
required that at the centre of the luminous intensity distribution,
which corresponds to the axis passing through the vehicle the
majority of the flux falls within the first .+-.10 horizontal
degrees and the first .+-.5 vertical degrees. In that the central
surface 6 has the purpose of generating a rectangular and
substantially uniform intensity distribution of light it is
necessary to add the luminous flux I to the central part of the
distribution. To do this the radially outer surface 4 is used,
which exploits the principle of total internal reflection.
[0055] The radially inner surface 3 is of substantially cylindrical
form, with axis of rotation coincident with the axis z normal to
the support plane P and passing through the centre of the source
10. Each section of this surface 3 is substantially an aspherical
lens profile and is constructed in such a way that the rays which
are generated by the source 10 and incident on the surface 3
generate a single virtual point source 10', as shown in FIG. 9.
[0056] The radially outer surface 4 has a generally ellipsoidal or
parabolic shape, and makes use of the fact that the cylindrical
surface 3 generates a virtual source 10' by making one of the two
foci of the ellipsoid, or the focus of the parabola, substantially
coincident with this source 10'. In this way the light beam is
controlled and it is possible to direct the light in the desired
direction. The radially outer surface 4 can be constructed with
several paraboloid or ellipsoid parts according to the distribution
of light intensity which it is desired to obtain. One example is
shown in FIG. 10, where the radially outer surface 4 has been
sub-divided into three elliptical surfaces 4a, b, c to direct the
light flux I into the angular directions where the majority of the
flux is required. A second focus of the ellipsoid is determined on
the basis of angular considerations on the beam reflecting from the
surface 4.
[0057] If a part of the radially outer surface 4 is a paraboloid,
the focus will coincide with the virtual source 10'. If a
paraboloid or an ellipsoid is used as the radially outer surface 4,
reflection takes place by total internal reflection so that it is
superfluous to coat this surface 4 with a metallic layer for the
purpose of obtaining the reflection of the incident beam I.
Consequently, a constructional simplification, and a significant
reduction in costs is obtained and above all there is no loss of
efficiency which any coating introduces. Nevertheless, in
particular cases it can be necessary to provide a coating, even a
partial one, on the radially outer surface 4.
[0058] The radially outer surface 4 may be continuous or may be
segmented into segments 4a', 4b', 4c' as illustrated in FIG. 11.
The surface 4 may be rotationally asymmetric with respect to the
principal axis z passing through the centre of the source 10 and
can vary geometrically from zone to zone as a function of the
distribution of light intensity which it is desired to obtain. The
annular surface 5 is generally flat and collects the flux coming
exclusively from the interface 4.
[0059] In FIG. 7 is shown a distribution of light intensity
obtained with a module M according to the invention.
[0060] The body 1 rests on the support plane P via the flat
parallel support surface 9 which has no optical power. The support
surface 9 joins the radially inner surface 3 to the radially outer
surface 4.
[0061] With reference to FIGS. 12 and 16, a lamp F for a motor
vehicle comprises one or more portions F1, F2, F3, F4 each
operating a light function, and each of which comprises a plurality
of modules M according to the invention. In particular, the portion
F1 has the function of stop light signaling-tail light, the portion
F2 has the function of direction indicator, the portion F3 has the
function of back up lamp, and the portion F4 has the rear fog lamp
function. The lamp F further includes a plastics container 15 and a
transparent element 11 which performs the dual function of
transmitting the light emitted by the modules M and directing this
light along the axis of the vehicle.
[0062] For achievement of a lamp function it is in fact necessary
to have a plurality of modules M; the number of these modules M
depends principally on the flux which the LED source 10 can emit,
and must be such as to satisfy the photometric characteristics
required by the various motoring regulations in use. By way of
example, for the stop lamp function of the lamp F it is possible to
utilize sixteen devices of the type described and sixteen LED
sources having a nominal flux of two lumens each.
[0063] If it is desired to limit the overall thickness of the lamp
F, the modules M must be carried on a reference plane substantially
parallel to the silhouette of the vehicle at the point at which the
lamp is installed. In the majority of practical cases of
application to vehicles the axis perpendicular to the support plane
on which the modules are installed does not coincide with the
longitudinal axis of the vehicle, that is to say the central
direction of distribution of the light intensity; it is therefore
necessary that the distribution of intensity generated by the
individual modules be centered in correspondence with the axis of
the vehicle. This thus makes it necessary to introduce a prismatic
component which functions as an interface between the optical axis
of the lamp F and the longitudinal axis of the vehicle.
[0064] This can be done in two ways:
[0065] (1) by modifying the surfaces of the optical element 1 in
such a way as to produce a rotationally asymmetric intensity
distribution centered in the direction of the longitudinal axis of
the vehicle;
[0066] (2) by designing the modules M in such a way that the
intensity distribution of light leaving the modules M is centered
in a direction perpendicular to the support plane and arranging
that the transparent optical element 11 operates to divert the
light leaving the modules M, for example through a refractive or
diffractive prismatic system.
[0067] The second arrangement is characterized by a greater
modularity in that the optical element 1 has a geometry
substantially independent of the geometry of the lamp and
associated installation on the vehicle, depending instead uniquely
on the geometric characteristics of the source and the photometric
characteristics relating to the signaling function which each
module M must achieve; in this sense, modules of identical geometry
can be installed on different vehicles simply by modifying the
prismatic form of the additional transparent element envisaged in
solution (2) indicated above. This solution is illustrated in more
detail herein below.
[0068] With reference to FIGS. 13, the distribution of light
intensity D of the module M is created along the optical axis z of
the optical element 1 (FIGS. 13a and 13b) normal to the support
surface P of the device itself, and only thereafter is diverted
along the axis z0 of the vehicle by means of the prismatic
component of the transparent element 11 (FIG. 13c). The
introduction of the prismatic system makes it possible directly to
displace along the axis, to D', the initially designed distribution
D (FIG. 13d). For moderately off-axis lamps, that is for those
lamps the disposition of which is strongly inclined with respect to
the longitudinal axis z0 of the vehicle, the solution of
constructing the distribution with respect of the axis z of the
lamp itself in order then to divert it by means of the prism into
the correct direction is the best, as long as it is desired to
contain the thickness of the lamp. In the case of moderately
off-axis lamps it is in fact very difficult, by adding optical
power to the transparent element and making use of a collimator of
the type such as those known, to succeed in achieving a
non-symmetrical light intensity distribution. In particular cases
it is possible directly to utilize a prismatic component also in
the solid body 1, thereby making it possible to reduce the angle of
the prisms on the transparent element 11, as shown in FIG. 14.
[0069] Another advantage of this configuration lies in the fact
that it has a high tolerance in assembly phase; this is because the
distribution of light intensity is generated by the module M and
the prismatic transparent element 11 now only has the purpose of
diverting the generated beam, wherever the device M is positioned
behind the transparent element the distribution is correctly
centered with respect to the axis z0 of the vehicle.
[0070] The prismatic component is introduced into the internal part
of the transparent element 11, as shown in FIGS. 15 and 16, and is
able to correct all the angular differences existing between the
optical axis z of the module M and vehicle axis z0.
[0071] Each module M of the lamp portion F which performs a given
signaling function produces all the intensity distribution relating
to this signaling function (contrary to what is envisaged by Patent
Application WO 00/24062); this means that for each direction of
observation the surface of the whole of the lamp portion dedicated
to a given signaling function is uniformly illuminated.
[0072] In FIG. 17 is proposed the comparison between a lamp FT
designed with traditional technology (with incandescent source) and
a lamp F designed by utilizing the devices according to the
invention. The thickness difference is evident and has as its
principal advantage the simplification of the design of the
bodywork of the motor vehicle and a reduction in costs in that it
is no longer necessary to form a pocket for receiving the lamp.
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