EP1963135A2

EP1963135A2 - Rear-view mirror for a motor vehicle

Info

Publication number: EP1963135A2
Application number: EP06842123A
Authority: EP
Inventors: Daniel Goraguer
Original assignee: Holophane SAS
Current assignee: Holophane SAS
Priority date: 2005-12-09
Filing date: 2006-12-08
Publication date: 2008-09-03
Also published as: US20080285157A1; JP2009518228A; WO2007066050A2; WO2007066050A3; FR2894536B1; CN101336175A; FR2894536A1; KR20080082684A

Abstract

The invention relates to a rear-view mirror for a motor vehicle for displaying the image of an object located rearwardly outside of the vehicle comprising a lens (1; 1'; 1"; 1'") and a mirror (2), wherein said lens is embodied in the form of a concave divergent lens provided with an optical axis (A1) and a focal spot (F1; F1'; F1"), the mirror is substantially concave, light beams (Fse, Fc, Fsi) pass through the divergent lens in the direction to the mirror, which convergently reflects the beams substantially devoid of optical distortion in a direction corresponding to a driver's axis of view to the mirror (2) defining a concave reflecting surface (21) substantially corresponding to a segment of cylinder.

Description

Motor vehicle rear view mirror

The present invention relates to a motor vehicle rear view mirror for producing an image located outside and behind the vehicle. By motor vehicle is meant any type of vehicle comprising its own drive or propulsion means, such as passenger cars, utility vehicles (vans, trucks, tractor, etc.), motorcycles. However, the present invention is not limited purely to vehicles traveling on land routes, but can also be applied to other flying or navigating vehicles. The present invention therefore applies very particularly to the field of motor vehicle equipment intended to assist the driver to facilitate or widen his field of vision, in particular towards the rear.

Almost all motor vehicles are equipped with one or two exterior side mirrors allowing the driver to have an image or a field of vision on areas located laterally on the side of the vehicle. Generally, vehicles are also equipped with an interior rearview mirror allowing a field of vision directly behind the vehicle. The present invention will apply very particularly to exterior side mirrors, without however excluding the interior mirror. These side mirrors conventionally include a flat or slightly convex mirror to increase the field of vision at the blind spot, that is to say the area located next to the vehicle, but away from it. This blind spot is particularly dangerous with conventional mirrors when overtaking by another vehicle. Indeed, it sometimes happens that one does not see the vehicle which has entered alongside to carry out the overtaking. This can cause accidents which are sometimes serious. To reduce this blind spot, conventional mirrors are frequently configured convexly at their outermost part in order to extend the field of vision in this blind spot. On the other hand, these conventional mirrors have several disadvantages additional to that of not satisfactorily covering the blind spot. Firstly, the mirror increases the lateral dimensions of the vehicle and thus constitutes not only a projecting element which can collide with another vehicle, a passer-by or any other structure, but also decreases the coefficient of penetration into the air of the vehicle. To overcome this space requirement in parking, it is already known to equip conventional mirrors with a system for folding the mirror along the vehicle. However, the incorporation of folding mechanisms, electric or purely mechanical, generates an increase in the number of parts of the mirror as a whole. And this increase in the number of parts generates of course an increase in the overall cost of the mirror.

On the other hand, mirror systems are already known using lenses in combination with one or more reflecting mirror (s). This is for example the case of US Pat. No. 6,882,146. In this document, the rear view mirror comprises an objective lens situated outside the vehicle, a plane reflecting mirror and a field lens situated inside the vehicle. This mirror therefore uses two different lenses and a flat mirror.

The present invention aims to improve such a mirror and lens mirror so that it is easier to manufacture, easier to assemble, with a reduced number of parts and a reduced cost.

To achieve these goals, the present invention provides a motor vehicle rear view mirror for producing an image of an object located outside the rear of the vehicle, comprising a lens and a mirror, characterized in that the lens is a divergent concave lens. having an optical axis and an optical focus and the mirror is a substantially concave mirror, the light beams passing through the lens diverging in the direction of the mirror which returns the rays convergently substantially without optical distortion in a direction which corresponds to the axis of vision of the conductor towards the mirror, characterized in that the mirror defines a concave reflecting surface which roughly corresponds to a segment of a cylinder. Advantageously, the rear view mirror includes only one lens and only one mirror.

Thus, the concavity of the mirror defines a relatively simple geometric surface which is particularly easy to produce industrially. Indeed, it is easy and known to produce cylindrical surfaces from plates or flat sheets so that the surface obtained meets the definition of a cylinder. By deforming a flat plate or sheet, in one direction it defines a curvature, and in the other perpendicular direction it defines a straight line. This perfectly meets the definition of a cylinder which results from the projection along a generatrix of a directing curve which can have any trajectory. A circular cylinder in fact results from the projection of a circle along a generatrix which passes through the center of the circle, and which advantageously extends perpendicular to the plane in which the circle is defined. On the same geometrical principle, one can define cylinders having the most diverse cross sections: this cross section corresponding to the guiding curve of the cylinder. In practice, cylindrical surfaces are particularly easy to produce, in particular by extrusion or spinning. By passing a flowable material through an extrusion die, we obtain at the outlet a kind of profile whose cross section corresponds exactly to the shape of the hole made at the die. Such an extruded or extruded profile can be qualified as a cylinder. Thus, in the present invention, the concave reflecting surface has a cylindrical configuration and can be produced from a section, a piece, a cut, or more generally a segment of a cylinder.

According to another interesting aspect of the invention, the cylinder is parabolic and has a plane of symmetry and a focal line located in this plane. A parabola is a curve in two dimensions which is characterized by a directrix, a focus and an axis of symmetry. When such a curve is projected along a generatrix perpendicular to both the director and the axis of symmetry, we obtain a cylinder whose section defines a parabola. According to the invention, the concave reflection surface is produced from a section, of a piece or segment of such a parabolic section cylinder. Of course, when the parabola is projected along the generatrix to form the cylinder, the axis of the parabola is projected according to the generatrix so as to form a plane of symmetry and the point focus of the parabola is also projected according to the generatrix so as to form a rectilinear focal line which is situated in the plane of symmetry of the parabolic cylinder. According to an advantageous characteristic of the invention, the plane of symmetry is substantially parallel to the axis of vision of the driver in the direction of the mirror. In other words, the parabolic curvature of the concave reflecting surface extends in a substantially horizontal plane.

According to another aspect of the invention, the reflection surface of the mirror defines a horizontal center line and a vertical center line which intersect substantially in the center of the mirror, the horizontal line having a substantially parabolic curvature, the vertical line being substantially straight, all vertical lines also being straight and all horizontal lines having the same parabolic curvature as the horizontal center line. This definition corresponds to that of a surface formed from a section of cylinder whose directing curve is a parabola.

According to another advantageous characteristic of the invention, the optical focus of the lens defines a focal line. Advantageously, the focal line is arranged substantially vertically relative to the mirror. This focal line can be perfectly straight, substantially straight or even curved. The fact that the lens defines a focal line and not a focal point means that the lens is not of revolution, such as for example a spherical or aspherical lens. Indeed, in the case of a lens of revolution, the optical focus of the lens is punctual and is in the form of a point located on the focal axis which is a line. In the case of a two-dimensional linear optical focus, the optical axis is in the form of an optical plane and the focal line is located in this optical plane.

According to another aspect of the invention, the respective focal lines of the cylinder and of the lens are substantially parallel, but distinct, that is to say not confused. According to another interesting aspect, the focal line of the cylinder is located near the optical axis of the lens. In our case, the optical axis of the lens is an optical plane.

According to another particularly interesting aspect of the invention, the lens comprises a concave front face and a substantially planar rear face oriented towards the mirror, the front face defining an optical surface having a substantially cylindrical configuration. Thus, both the mirror and the lens have a substantially cylindrical configuration. The generators of the two cylinders are advantageously parallel and arranged vertically. According to a first advantageous embodiment, the optical surface defines a horizontal center line and a vertical center line which intersect substantially at the center of the optical surface, the horizontal center line having a curvature in a plane perpendicular to the vertical center line, all the horizontal lines having substantially the same curvature as the horizontal center line in respective planes perpendicular to the vertical center line. Advantageously, the curvature of the horizontal lines is circular so as to define an arc of a circle having a determined radius.

According to a simple embodiment, the vertical center line is straight, as are all the other vertical lines. The optical surface of the lens then responds exactly or substantially to the definition of a cylinder, the guide curve of which is advantageously circular. Such a cylindrical lens is particularly easy to produce, since it can be produced by extrusion because its cross section is constant.

According to a more elaborate practical embodiment, the vertical center line is curved, so that the optical surface has an overall toric configuration. The vertical curvature can advantageously be circular so as to respond to an arc of a circle having a determined radius. However, the curvature can have any other trajectory whatsoever. The vertical curvature further accentuates the concavity of the optical surface. This vertical concavity has the optical result of tightening the vertical field lines so that the subjects visible at the mirror have a "normal" appearance with regard to the horizontal and vertical proportions. Indeed, the horizontal curvature of the lens has the effect of tightening the image at the level of the mirror so that the subjects visible on the mirror are particularly fine, while keeping a normal height. By also bending the optical surface in the vertical direction, this defect in the proportion of subjects at the level of the mirror is corrected. The optical surface then has a configuration which is that of a segment of curved tube, which can generally be described as a torus. This geometric configuration is characterized by the fact that the transverse or horizontal curvature in a plane perpendicular to the vertical or longitudinal curvature is constant, and for example circular.

According to another interesting aspect of the invention, the vertical center line has a lower region at the level of which its curvature is greater. The curvature of the horizontal lines (which is not necessarily in the horizontal plane) can be kept constant if we consider the lines of curvature in planes which are always perpendicular to the curvature of the vertical line. The increase in the curvature at the level of the lower zone of the optical surface makes it possible to deviate very strongly the beams downwards, that is to say towards the roadway or the pavement, which allows the driver to have a view, certainly distorted, in the area located at the sidewalk. This field of vision on the sidewalk makes it possible in particular to facilitate or improve the parking of the motor vehicle as close as possible to the sidewalk, or at least parallel to the sidewalk. The vertical center line can thus have a substantially constant curvature over most of its height and a greatly increased curvature at its lower zone.

According to yet another interesting aspect of the invention, the lens has a prismatic configuration capable of deflecting the light beams towards the interior of the automobile. This prismatic configuration of the lens corresponds to the combination or association of a lens and a prism making it possible to deflect the beams towards the interior of the vehicle, so that the mirror can be installed more inside the vehicle than would be the case if it weren't for this prismatic configuration. Therefore, the prism incorporated into the lens allows the mirror to be shifted towards the interior of the vehicle, which further reduces the size of the mirror outside the vehicle.

According to another aspect, the optical axis of the lens makes an angle α of the order of 10 degrees relative to the beam passing through the center of the lens and the center of the mirror. The lens has been slightly rotated so that its optical axis is no longer coincident with the beam passing through its center and the center of the mirror. This rotation of the lens optimally covers the blind spot and consequently reduces the field of vision on the vehicle body, which is not necessary. As a result, the field of vision is more oriented towards the side of the vehicle and no longer along the vehicle.

On the other hand, the beam passing through the center of the lens and the center of the mirror makes an angle β of the order of 10 degrees relative to a longitudinal axis of the vehicle. Thus, the optical axis of the lens makes an angle of the order of 15 to 25 degrees relative to the longitudinal axis of the vehicle, which is that of the window of the vehicle door.

Thanks to the invention, it is possible to produce a rearview mirror comprising only one lens and only one mirror. The lens can be a lens defining a linear focal point which can advantageously be combined with a cylindrical mirror which is preferably parabolic. The lens due to its linear local focus generates optical distortions only in the horizontal plane and not at all in the vertical plane. Thus, the mirror only needs to correct the horizontal optical distortions, and a particularly advantageous embodiment is that of a cylindrical mirror whose guiding curve is advantageously parabolic. In any case, the mirror of the invention fulfills a double function, namely that of classic reflection and that of classic month of correction in the manner of a lens. It can thus be considered that the mirror according to the invention incorporates both a conventional mirror and a lens which makes it possible to correct the optical distortion generated by the divergent concave lens. It should be noted that the linear focal lens can be used with any mirror which is not necessarily cylindrical, or parabolic cylindrical. So symmetrical, the mirror of the invention which is cylindrical, and preferably cylindrical parabolic, can be used with any lens which is not necessarily with linear focus. In other words, both the lens and the mirror can be protected separately from each other.

The invention will now be described more fully with reference to the accompanying drawings which give an embodiment of the invention by way of non-limiting example.

In the figures:

FIG. 1 is a schematic perspective view of a lens and a mirror according to a first nonlimiting embodiment of a motor vehicle rear view mirror according to the invention,

FIG. 2 is a schematic optical representation of the mirror of FIG. 1,

FIG. 3 is a view similar to that of FIG. 1 showing a rear view mirror using a lens according to a second embodiment of the invention,

Figures 4a and 4b are schematic perspective representations showing the difference in images between the first and the second embodiment of Figures 1 and 3, Figures 5 and 6 are representations similar to Figures 1 and 3 for a third and a fourth embodiment of a mirror according to the invention, respectively, and

FIGS. 7a, 7b and 7c are views of the mirror revealing the field lines corresponding respectively to the mirror of FIGS. 1, 3 and 5.

Referring first to Figures 1 and 2, we can see very schematically in perspective the two essential components of the mirror according to the first embodiment of the present invention. These two elements are respectively a lens 1 and a mirror 2. The lens and the mirror can be mounted on a common support 3 which can have any suitable shape. In FIG. 1, this support 3 has been schematically represented by a rod or a bar connecting the lens 1 to the mirror 2. This support 3 is an optional element so that the lens 1 and the mirror 2 can be mounted on independent or dissociated supports. In addition to these three elements, the rear view mirror may include a fourth element visible in FIG. 2: it is a shell 4 which envelops the lens 1 and the mirror 2, and optionally the support 3. This shell 4 makes it possible to define an internal housing with the bodywork or the window of the vehicle to accommodate the lens 1 and the mirror 2. The shell 4 is also an optional element.

The lens 1 is a divergent concave lens having a concave front face 10 and a flat rear face 15. Thus, the light beams passing through the lens from its concave face 10 are diffracted in a divergent manner at the exit from the planar face 15. The front face 10 defines a concave optical surface 11 which is here substantially or perfectly cylindrical. Indeed, this optical surface 11 can be defined as having horizontal lines 12 and vertical lines 13 (of which only the vertical center line has been shown). Since the optical surface 11 is cylindrical, the vertical lines 13 are straight lines which are all parallel to each other. On the other hand, the horizontal lines 12 are curves, which are however also parallel to each other. Advantageously, the curvature of the horizontal lines 12 is circular so as to form an arc of a circle having a determined constant radius. Thus, the optical surface 11 can be defined as a section or segment of a circular cylinder.

This lens 1 of general or overall cylindrical or elongated shape defines an optical axis, or more precisely an optical plane A1 which passes through the vertical center line 13. This cylindrical lens therefore defines a focal point F1 which is an optical focal line which s 'extends in the optical plane A1 at a distance from the lens which corresponds to the focal length of the lens. This is visible in Figure 1. This focal distance can be of the order of 8 to 10 centimeters. The linear focal point F1 is of course located on the side of the concave optical surface 11. Since the optical surface 11 is cylindrical, the focal line F1 is a straight line which extends vertically parallel to the vertical center line 13, and therefore perpendicular to the planes in which the horizontal lines 12 are inscribed.

On the other hand, the lens 1 defines a fixing edge 14 which allows for example to grip the lens to fix it on any support.

The mirror 2 comprises a reflecting surface 21 which is here of substantially rectangular shape lying down, that is to say with the long sides extending horizontally and the short sides extending vertically. However, the mirror can define a reflection surface 21 having another configuration, for example oval, elliptical, oblong, polygonal, or of complex geometric shape. According to the invention, the reflection surface 21 has a complex concave configuration. However, the concavity of the reflection surface can be globally or roughly or substantially be related to a segment, section, part or portion of a vertical cylinder. The reflection surface 21 defines a horizontal central line 22 and a vertical central line 23 which intersect substantially at the center Cm of the mirror. Since the cylinder is vertical or upright, the vertical line 23 is a straight line like all other parallel vertical lines. On the other hand, the horizontal line 22 is of substantially or perfectly parabolic shape as well as all the other horizontal lines parallel to the line 22. More precisely, the reflection surface 21 is a segment of a cylinder whose directing curve is parabolic . In other words, the cross section of the cylinder is parabolic in shape. The horizontal line 22 as well as all the other horizontal lines are of parabolic shape and will therefore pass through the central line Cp of the parabolic center of the cylinder. Indeed, any parabola is defined by an axis of parabola or axis of symmetry of parabola as well as by a focal point of parabola. A parabola is further defined by a parabola director (not shown). When the center of the parabola is projected along the generatrix of the cylinder (which is here vertical), this point center is transformed into a center line which corresponds to Cp in figure 1. Likewise, when the axis of symmetry of the parabola is projected along the generatrix of the cylinder, this axis is transformed into a plane of symmetry referenced Ap in FIG. 1. This plane Ap is here arranged vertically, since the mirror 2 is arranged with its vertical center line 23 oriented vertically. Likewise, the focal point of the parabola (which is a point) is transformed into a focal line of parabola after projection along the vertical generatrix of the cylinder. This focal line of the parabola is designated by the reference Fp in FIG. 1. This focal line Fp is parallel to the central line Cp which is also parallel to the vertical center line 23 of the mirror 2. The central parabola line Cp and the Fp parabolic focal line are also visible in Figure 2.

The lens 1 and the mirror 2 are positioned mutually with respect to each other so that the rear plane face 15 of the lens is turned towards the reflection surface 21 of the mirror. However, if we consider that the support 3 defines a support axis, neither the lens 1 nor the mirror 2 is arranged perpendicular to this support axis. Indeed, the lens 1 is slightly turned and the mirror 2 is frankly turned so that the central beam Fc passing through the center Cl of the lens and the center Cm of the mirror 2 is reflected and redirected towards the eye O of the driver. The angle δ between the incident central beam and the reflected central beam is of the order of 20 to 50 degrees. On the other hand, given that the lens 1 is slightly turned, the angle α between the optical axis Al of the lens and the central beam Fc passing through the center of the lens and the center of the mirror is of the order from 5 to 15 degrees, for example 10 degrees.

Referring to Figure 2, we clearly identify the angles α and δ. On the other hand, the central beam Fc is oriented relative to the longitudinal axis of the vehicle by making an angle β which can also be of the order of 5 to 15 degrees, for example 10 degrees. The axis Av can also be considered as the axis of the driver's door or the window of the driver's door. Thus, the mirror according to the invention must be installed on the vehicle so that the central beam makes an angle of β relative to the door. In this case, the lens 1 is located outside the vehicle, while the mirror 2 is located partially inside the vehicle and partially outside the vehicle. Of course, thanks to the shell 4, the mirror 2 can be located in a space which communicates with the interior of the vehicle and which is separated from the exterior of the vehicle by this shell 4. The lens 1 then serves as a shutter of the internal space formed by the shell 4 and of light entering inside this shell where the mirror 2 is arranged.

The viewing angle γ provided by the lens 1 can be of the order of 35 degrees, while with a conventional mirror, the viewing angle is limited to only about 25 degrees. The internal lateral beam Fsi intersects the longitudinal axis Av so as to give a vision of part of the body. In contrast, the exterior side beam Fse allows you to widen your vision at the conventional blind spot of a conventional rear view mirror. Thus, the beams passing through the lens 1 are directed divergently towards the concave mirror 2 which reflects the beams in a convergent manner substantially without optical distortion towards the eye.

0 from the driver.

As regards the mutual orientation of the mirror and the lens, the respective generatrices of the cylinder forming the mirror and of the cylinder forming the lens are arranged in parallel. More concretely, the vertical center line 23 of the mirror is arranged substantially parallel to the vertical center line 13 of the optical surface 11 of the lens 1. Likewise, the horizontal central line 22 of the mirror 2 is located in the same plane as the line horizontal median 12 of the lens 1. Regarding the distance between the lens

1 of the mirror 2, it can be said that the linear focus Fp of the parabolic cylinder of the mirror is located near the linear focus Fl of the lens. This is visible both in Figure 1 and in Figure 2. It can also be noted that the linear focus of the parabolic cylinder Fp is located on the beam Fc passing through the center Cl of the lens and the center Cm of the mirror. The linear foci Fp and Fl preferably extend parallel to one another but are not confused; there is therefore a distance between them. This distinction of the two linear focal points makes it possible to converge the beams reflected by the mirror 2 and directed towards the driver's eye.

Since the lens 1 and the mirror 2 are both cylindrical in configuration and extend along generatrices which are parallel, the view in horizontal cross section of Figure 2 is entirely representative of Figure 1 and can be located at any height of the lens or mirror.

The fact of forming the lens with an optical surface 11 of substantially or perfectly cylindrical configuration is particularly advantageous, both from the optical point of view and from the manufacturing point of view. Indeed, from the optical point of view, there is no optical distortion on the vertical, the beams passing without diffraction or distortion through the lens at the level of the vertical center line 13. Diffraction takes place only in the horizontal plane. As for its manufacture, it is simplified due to the cylindrical shape of the optical surface, which is a relatively simple geometric shape to produce.

The parabolic cylindrical mirror is also advantageous in combination with the cylindrical lens or with any other lens. Indeed, this cylindrical mirror is also easy to produce just like the cylindrical lens, because of the ease with which a cylindrical surface can be produced. The combination of the parabolic cylindrical mirror and the cylindrical lens is however advantageous since the parabolic cylindrical mirror 2 does not need to correct any optical distortion coming from the lens, since the latter does not diffract in the vertical plane . The optical distortion therefore takes place only in the horizontal plane, and this distortion is easily corrected by the mirror 2, thanks to its parabolic cylindrical shape. This gives an image tightened in the horizontal plane and without distortion in the vertical plane. This is shown in Figure 7a which shows the vision of a driver when looking at the mirror. The various points visible on the mirror represent or give an indication of the density of the field lines both horizontal and vertical. The cross on the right of the mirror represents the axis of the roadway at the horizon. It can be seen that the density of the points of the median horizontal field line is high, in particular at the edges, while the density of the points of the vertical field lines is constant. This mirror gives a very tight image horizontally, but real vertically. The proportion of objects is therefore not preserved. Referring to Figure 3, we will now explain how it is possible to correct this lack of proportion. In this second embodiment of FIG. 3, the mirror can be identical to the mirror of the first embodiment. On the other hand, the lens 1a differs from the lens 1 of the first embodiment in that the vertical center line 13 ′ here has a curvature, which advantageously corresponds to an arc of a circle. In the first embodiment, the center line 13 is substantially or perfectly straight and extends parallel to the vertical center line 23 of the mirror 2. In this second embodiment, the curved vertical center line 13 'extends in a plane which also includes the vertical center line 23 of the mirror. The horizontal lines 12 ′ of the lens are curved, as in the first embodiment, and their curvature preferably corresponds to an arc of a circle. The different horizontal lines 12 'are substantially parallel to each other, or more precisely, the different curves 12' extend in the respective planes which are perpendicular to the vertical line 13 '. It can also be said that the plane in which a horizontal curve 12 'extends is perpendicular to the tangent of the vertical line 13' at the level where this plane intersects the line 13 '. Because the curvature of the vertical line 13 'is small, as can be seen in Figure 3, the horizontal curves 12' extend substantially parallel. The rear optical surface 11 ′ of the lens 1 thus defines a torus segment whose cross section is defined by the horizontal lines 12 ′ and whose curved longitudinal extent is defined by the vertical lines 13 ′. A torus can be defined as a tube of circular section which has a defined curvature. Here, this curvature is advantageously circular, just like the curvature of the lines 12 ′.

Such a lens also defines a focal line F1 '. However, because the vertical line 13 'is curved, and no longer straight, the rays passing through the middle line 13' are also diffracted, except at the center Cl. Optically, this has the effect of shrinking the image at mirror level. This is what is shown in Figures 4a and 4b. We see in Figure 4a that an object O, here of rectangular geometric shape for the sake of simplicity, goes to through the lens 1 of the first embodiment to give a substantially square image I at the level of the mirror 2. As a result, the conductor will have a substantially square image Ir. In FIG. 4b, an object O ′ has been taken which has a size greater than the object O in FIG. 4a. In this case, the object O 'is higher than the object O: the long sides of the rectangle of the object O' are greater than the long sides of the object O. Passing through the lens l ', an image F is obtained at the level of the mirror 2 which is of substantially square shape, like the image I in FIG. 4a. As a result, the conductor will have an image Ir 'which is substantially identical to the image Ir of FIG. 4a. It has thus been possible to see that objects O, O 'of vertically different sizes give a reflected image Ir, Ir' which is substantially identical. This is due to the fact that the vertical line 13 ′ of the lens is slightly curved, while the vertical line 13 is perfectly straight. The curvature of the line 13 ′ has the effect of reducing the size of the image F, which corresponds to a narrowing of the optical field lines. Symmetrically, it can be said that an object of identical size will have Ir images of different sizes, the image Ir 'being more vertically tightened than the image Ir.

Thus, with the curvature of the vertical line 13 ′ of the mirror 2 ′, the proportion of the reflected image visible to the driver is roughly, substantially or perfectly restored. This is shown in Figure 7b which is a view similar to that of Figure 7a, with a mirror according to Figure 3, that is to say with a lens l 'whose vertical line 13' is slightly curved. With respect to the representation in FIG. 7a, it can be said that vertical field lines, represented by the lines of vertical points, are spaced apart by intervals which are identical to those in FIG. 7a. On the other hand, it can be noted that the horizontal field lines are tighter, since we see three horizontal field lines in Figure 7b while we only see the median horizontal field line in Figure 7a . We can easily understand from these schematic representations of the image visible on the mirror that the proportion of objects is more respected with the mirror according to FIG. 3: in fact, the spacing of the horizontal points in FIG. 7b is substantially identical to the spacing of the vertical points. This is not the case in FIG. 7a, in which the spacing of the vertical points is substantially greater than the spacing of the horizontal points. Consequently, with a rear view mirror according to FIG. 3, the object retains approximately natural proportions.

An essential characteristic which is common to lenses 1 and 1 is that they both define an optical focus which extends along a line. However, while the optical linear focus F1 of the lens 1 is perfectly rectilinear, the linear optical focus of the lens 1 'is curved, in correspondence with the curvature of the vertical center line 13'.

5 shows a variant of the mirror of Figure 3. The mirror 2 can be identical to that of the first and second embodiments of Figures 1 and 3. As for the lens 1 ", it differs from the lens in that that the curvature of the vertical line 13 "is greatly increased at its lower zone. One can thus divide the vertical line 13 "into two zones, namely a main zone 131 which extends over most of the height of the lens and a lower zone 132 which is approximately limited to the lower quarter of the height of the The curvature of the main zone 131 can be identical to the curvature of the line 13 ′ of the second embodiment of FIG. 3. The curvature of the zone 131 can advantageously be circular so as to define an arc of a circle. at the lower zone 132, it has an accentuated curvature, which can also correspond to an arc of a circle. The increase in the curvature in the zone 132 achieves a thickening of the lens, as can be seen in FIG. the "horizontal" lines 12 "have a curvature, which can advantageously be identical, and correspond to an arc of a circle. The different curvatures 12 "extend in planes which are perpendicular to the line 13", as in the second embodiment. Thus, the curvatures 12 "at the level of the lower zone 132 extend in planes which are more and more vertical, since the curvature of the vertical line 13" at the level of the zone 132 is very strong. The designation of the 12 "lines under the term of" horizontal "lines is here somewhat erroneous, since the lines 12" in the area 132 extend in shots that deviate considerably from the horizontal. However, for the sake of clarity and understanding, these lines 12 "are still designated by the term horizontal lines, since they extend in planes which are perpendicular to the vertical line 13". Symmetrically, the vertical line 13 "is not strictly vertical, since it has two distinct curvatures. It can still be said that the line 13" extends in a vertical plane which also contains the midline vertical 23 of the mirror 2. As in the first two embodiments, this lens 1 "defines an optical focus in the form of a focal line F1".

As regards the image visible at the exit of the rear view mirror of FIG. 5, it corresponds to the representation of FIG. 7c. The density of the horizontal lines is substantially identical to that of FIG. 7b, since the curvatures of the horizontal lines 12 "are substantially identical. On the other hand, the density of the vertical lines is greatly increased at the level of the lower part of the mirror corresponding to the lower zone 132 of the lens. In fact, it can be seen that the density of the vertical lines is substantially constant over most of the height of the mirror corresponding to the main zone 131. An increase in the density of the lines can, however, be observed. vertical with respect to FIG. 7b. This is due to a slightly greater curvature of the line 13 "compared to the line 13 '. On the other hand, the density of the vertical lines in the lower part of the mirror is very high, which makes it possible to have a vision on the lower part of the roadway directly next to the vehicle. With such a rear view mirror, the driver can have a vision of the sidewalk along which he wants to park. He can then park his car with great precision parallel to the sidewalk and as close as possible to the sidewalk. Thus, it can be said that the main function of the lower zone 132 is to give a vision to the driver of the roadway directly next to his vehicle. Of course, the images at the lower part of the mirror are very strongly distorted, while the distortion is limited or zero at the level of the major part of the mirror. The rear view mirror in FIG. 5 therefore gives a practically ideal and particularly extended vision. The objects retain their proportionality both horizontally and vertically, the blind spot is particularly well covered, and moreover the driver has a vision at the level of the sidewalk along which he wants to park.

Again, the lens 1 "also defines a linear optical focus F1" which is slightly curved corresponding to the line 13 ".

Referring again quickly to FIG. 2, it can be seen that the lens is located outside the vehicle shown diagrammatically by the line Av, while the mirror 2 straddles this line. This means that the mirror is for a part located outside the vehicle and for another part located inside the vehicle. For various reasons, it may be preferable to place the mirror as inside as possible. This is possible thanks to the rear view mirror of FIG. 6 in which the lens "incorporates a prism 16. The prism has the well-known function of deflecting the light beams without diffraction or optical distortion. The prism 16 is here incorporated into the lens of so as to constitute a one-piece optical part, the optical surface 11 ′ may be identical to that of the lens in FIG. 3. The prism 16 has the effect of increasing the thickness of the lens on the right side and of reducing the thickness of the lens on the left side, when looking at FIG. 6. This means that the front face 15 of the lens 1a "extends in a plane which is pivotally offset around a vertical axis with respect to the faces fronts of the lenses of the other embodiments. This change of orientation of the front face has the effect of giving the lens a prismatic function capable of deflecting the light beams at the exit of the lens without distortion or diffraction. As a result, the light beams are shifted to the right, so that the mirror 2 can be shifted to the right, that is to say inside the passenger compartment of the vehicle. By further increasing the inclination of the front face 15 of the prism 16, the mirror 2 can be shifted more correspondingly inside the passenger compartment of the vehicle. Such a prismatic function can be implemented in the other embodiments of FIGS. 1, 3 and 5. It is the same with the lower zone 132 of FIG. 5 which can be implemented in the other embodiments of the FIGS. Figures 1, 3 and 6. An ideal rear view mirror can be seen in the combination of the embodiments of FIGS. 5 and 6, giving an image corresponding to FIG. 7c with a mirror located inside the passenger compartment of the vehicle.

It should be noted that in all the embodiments, the mirror can be identical and advantageously formed by a segment of a cylinder having a parabolic directing curve. This is because all the lenses of the various embodiments define an optical focus in the form of a line, not a point.

The various lenses 1, l ', 1 "and l" can be used independently of the parabolic cylindrical mirror, and even of any mirror. In other words, these lenses can be used in optical devices other than a rear view mirror. Each lens can thus be protected independently. As for the parabolic cylindrical shape mirror, it can also be used independently of the lenses 1 to ". Indeed, its parabolic cylindrical shape is particularly advantageous for design and manufacturing reasons, so that this mirror can be implemented in other applications, other than a rear-view mirror, so independent protection of this mirror is also possible.

The lenses 1, l ', 1 "and l" all have an overall rectangular configuration. However, the lens can have any other global configuration, for example round, oblong, elliptical, square, etc., while retaining an overall, substantially or perfectly cylindrical optical surface.

Unlike mirrors using revolution lenses with a point optical focus, the mirror of the present invention responds to a linear geometry so that the mirror, but also the lens, has a generally, substantially or perfectly cylindrical configuration with guiding geometry curves relatively simple, like a circle or a parabola.

Claims

1.- Motor vehicle rear view mirror for producing an image of an object located outside the rear of the vehicle, comprising a lens (1; the; 1 "; the") and a mirror (2), characterized in that the lens is a divergent concave lens having an optical axis (Al) and an optical focus (Fl; Fl ';

5 Fl ") and the mirror is a substantially concave mirror, the light beams

(Fse, Fc, Fsi) passing through the diverging lens towards the mirror which returns the rays in a convergent manner substantially without optical distortion in a direction which corresponds to the axis of vision of the conductor towards the mirror, characterized in that the mirror (2) defines a surface

10 of concave reflection (21) which corresponds substantially to a segment of a cylinder.

2. A rearview mirror according to claim 1, comprising a single lens and a single mirror.

15

3. A mirror according to claim 1 or 2, wherein the cylinder defines a substantially parabolic directing curve, so that the cylinder is parabolic and has a plane of symmetry and a focal line located in this plane.

> 0

4.- rear view mirror according to claim 4, wherein the plane of symmetry is substantially parallel to the axis of vision of the driver towards the mirror.

»5

5. A rear-view mirror according to any one of the preceding claims, in which the reflecting surface (21) of the mirror defines a horizontal center line (22) and a vertical center line (23) which substantially intersect at the center (Cm) of the mirror, the horizontal line having a substantially parabolic curvature, the vertical line being

SW substantially straight, all vertical lines also being straight and all horizontal lines having the same parabolic curvature as the horizontal center line.

6. A mirror according to any one of the preceding claims, in which the optical focus of the lens defines a focal line.

7. A rearview mirror according to claim 6, wherein the focal line is arranged substantially vertically relative to the mirror.

10

8. A rear view mirror according to claims 3 and 6 or 7, wherein the respective focal lines of the cylinder and the lens are substantially parallel, but distinct.

9. A rearview mirror according to claim 6 or 7, wherein the focal line of the cylinder is located near the optical axis of the lens.

10.- A mirror according to any one of the preceding claims, in which the lens comprises a concave front face and a

0 substantially planar rear face oriented towards the mirror, the front face defining an optical surface (11) having a substantially cylindrical configuration.

11. A mirror according to claim 10, in which the surface

»5 optical defines a horizontal center line (12; 12 '; 12") and a vertical center line (13; 13'; 13 ') which intersect substantially at the center (Cl) of the optical surface, the horizontal center line having a curvature in a plane perpendicular to the vertical center line, all horizontal lines having substantially the same curvature as the center line

SW horizontal in respective planes perpendicular to the center line.

12. A mirror according to claim 11, in which the vertical center line (13) is straight, as are all the other vertical lines.

13. A rearview mirror according to claim 11, wherein the vertical center line (13 '; 13 ") is curved, so that the optical surface has an overall toric configuration.

14. A mirror according to claim 11, 12 or 13, in which the vertical center line (13 ") has a lower zone (132) at which its curvature is greater.

15. A mirror according to any one of the preceding claims, in which the lens (1 '") has a prismatic configuration (16) capable of deflecting the light beams towards the interior of the automobile.

16. A mirror according to any one of the preceding claims, in which the optical axis (Al) of the lens makes an angle α of »0 of the order of 10 degrees relative to the beam (Fc) passing through the center ( Cl) of the lens and the center (Cm) of the mirror.

17. Mirror according to any one of the preceding claims, in which the beam (Fc) passing through the center (Cl) of the »5 lens and the center (Cm) of the mirror makes an angle β of the order of 10 degrees from a longitudinal axis (Av) of the vehicle.