FR3066285B1 - LUMINOUS DEVICE WITH RECTANGULAR SECTION OPTICAL FIBER FLASHING IMAGER - Google Patents

Abstract

The invention relates to a light module (2) comprising an illuminating surface (8.2) capable of forming a light beam, and a rectangular imager (12) capable of forming a light image from the light beam emitted by the illuminating surface ( 8.2). The module comprises an optical fiber (8) with a core of rectangular section and, at a first end, an input face (8.1) of light emitted by a light source (4) and at a second end a face of output (8.2) of light forming the illuminating surface.

Description

The invention relates to the field of lighting and light signaling, in particular for a motor vehicle.

The patent document published under the number WO 2016/050503 A1 discloses a light-signaling device for a motor vehicle, configured to display a pictogram on an area of a transmission display screen. The screen corresponds to a closing window of the housing of the device. The pictogram is produced by a first light module that can include an electromechanical microsystem matrix mirrors able to be controlled and produce different pictograms. The light source of the first module is of the laser or electroluminescence diode type. The module may include collimation means between the light source and the imager, as well as an optical focusing system between the imager and the screen, in order to obtain a clear image of the pictogram. Such means, however, are expensive and subject to imperfections. The device may also include a second light module configured to illuminate another area of the display screen, separate from the area displaying the pictogram. Such a device is interesting in that it combines several light-signaling functions in the same device, one of the light-signaling functions including the pictogram display.

The published patent document EP 1 793 261 A1 discloses a light device configured to display pictograms on a photoluminescent screen. Such a device has for main application the display of pictograms in the field of vision of the driver of a vehicle, the windshield of the vehicle then forming the photoluminescent screen. Such an application is commonly referred to as "head-up display". This teaching is therefore not suitable for displaying bright images for people around the vehicle, such as from a rear light. The invention aims to overcome at least one of the disadvantages of the state of the art mentioned above. More particularly, the invention aims to allow a bright image display, such as a pictogram, which is clear and with simple and inexpensive means. The subject of the invention is a light module comprising an illuminating surface capable of forming a light beam; a rectangular imager capable of forming a luminous image from the light beam emitted by the illuminating surface; remarkable in that the module comprises an optical fiber with a core of rectangular section and, at a first end, a light input face emitted by a light source and, at a second end, a light output face forming the illuminating surface.

Advantageously, the illuminating surface is less than or equal to 0.04 mm 2.

According to an advantageous embodiment of the invention, the rectangular section of the core of the optical fiber has a width and a length, at least one of said width and length being less than or equal to 200 μm and / or greater than or equal to 50 μm.

According to an advantageous embodiment of the invention, the optical fiber has a length, from the input face to the output face, which is greater than or equal to 100 mm.

According to an advantageous embodiment of the invention, the imager is electrically controlled.

According to an advantageous embodiment of the invention, the imager is a transmissive LCD imager.

According to an advantageous embodiment of the invention, the imager is an electromechanical microsystem forming a matrix of micro-mirrors pivoting between two positions.

Advantageously, the imager has a 4: 3 or 16: 9 format.

Advantageously, the luminous image is a pictogram, that is to say a schematic graphical representation, more particularly a stylized figurative design having a sign function, such as an arrow, an exclamation point, etc.

According to an advantageous embodiment of the invention, the module further comprises a lens or a mirror disposed optically between the illuminating surface and the imager.

According to an advantageous embodiment of the invention, the lens or the mirror is anamorphic and configured so that the beam emitted by the illuminating surface covers more than 90% of the active surface of the imager. By active surface is meant the surface participating in the formation of the light image.

According to an advantageous embodiment of the invention, the lens is divergent, the maximum angle of incidence of the light beam emitted by the illuminating surface, on the imager, being less than or equal to 30 °.

According to an advantageous embodiment of the invention, the optical fiber has a numerical aperture of between 0.12 and 0.2.

According to an advantageous embodiment of the invention, the module further comprises at least one mirror optically disposed between the illuminating surface and the imager.

According to an advantageous embodiment of the invention, the module further comprises a first mirror and a second mirror, optically disposed between the illuminating surface and the imager so as to fold the light beam emitted by the illuminating surface of an angle. between 150 ° and 210 °, preferably between 170 ° and 190 °. The invention also relates to a light device comprising a light module capable of forming a light image, and a projection screen of the light image, remarkable in that the light module is according to the invention.

According to an advantageous embodiment of the invention, the projection screen is diffusing so as to diffuse the light image from the face of said screen opposite to the face receiving the light image of the light module.

According to an advantageous embodiment of the invention, the projection screen is non-diffusing so as to allow the light module to project the light image onto a surface outside the device.

The measurements of the invention are interesting in that they make it possible to display a particularly variable luminous image, with great clarity and with a simple construction of the light module. In particular, they make it possible to illuminate all or almost all of the active surface of a rectangular imager. They also make it possible to deport the light source or sources, including their power supply and their thermal management. The rectangular sections of the commercially available optical fiber cores are usually square or with a length / width of 2: 1; the use of an anamorphic lens or mirror makes it possible to deform the light image in such a way as to modify the format, for example to change from a square format to a 4: 3 or 16 format: 9 current on the imagers including the liquid crystal panel type (LCD). The use of a diverging optical system, between the illuminating face and the imager allows to open the light beam and thereby shorten the optical path, while limiting the angle of incidence on the imager. This angle is advantageously less than or equal to 30 ° for a liquid crystal panel type imager. Other features and advantages of the present invention will be better understood from the description and drawings in which: FIG. 1 schematically illustrates a light module according to a first embodiment of the invention; FIG. 2 illustrates the principle of optical operation of an optical fiber, such as that of the light module of FIG. 1; - Figure 3 illustrates in section two types of optical fiber for a light module according to the invention; FIG. 4 illustrates a change in image format by using an anamorphic lens in a light module according to the invention; FIG. 5 schematically illustrates a light module according to a second embodiment of the invention.

FIG. 1 illustrates a light module according to a first embodiment of the invention.

The module 2 essentially comprises a light source 4, for example of the electroluminescence diode type, a convergent lens 6, such as a biconvex type, an optical fiber 8, a diverging lens 10, an imager 12 and a screen 14. More specifically, the optical fiber 8 comprises an input face 8.1 and an output face 8.2 of the light. The light emitted by the light source 4 forms a cone of divergent light illuminating the lens 6. This converts the light beam towards the input face 8.1 of the optical fiber 8. The light then propagates inside the the optical fiber 8, by successive reflections on the diopter formed on the outer surface of the core of the fiber. The light rays then leave the optical fiber 8 through the outlet face 8.2, forming a divergent light cone. A lens 10 may be arranged to open the beam by increasing its divergence angle. The optionally enlarged light beam illuminates the imager 12. The latter may in particular be a liquid crystal transmissive screen, adapted to be electrically controlled so as to modify the light beam passing therethrough. The latter then illuminates the screen 14 in order to display a bright image, such as a pictogram.

The exit face of the optical fiber 8, forming an illuminating face, the lens 10, the imager 12 and the screen are advantageously aligned along the optical axis 16 of the light module 2.

The core of the optical fiber 8 has a rectangular section so that the light rays, entered into the fiber by the input face 8.1 and as and when they are propagated along said fiber of rectangular section, form a light beam of rectangular section. For this purpose, the fiber may have a sufficient length, such as greater than or equal to 100 mm, to ensure satisfactory rectangular shaping of the light beam. The light beam emitted by the output face 8.2 then has a rectangular section, which allows it to illuminate optimally the imager 12 which is also rectangular. The luminous image thus produced on the screen 14 can thus be produced by making maximum use of the active surface of the imager 12.

The reduced section of the output face of the optical fiber makes said face comparable to a point light source, which is particularly advantageous from an optical point of view. This means that the light image produced by the imager and projected on the screen is essentially clear without the need for optical correction means.

FIG. 2 illustrates in more detail the principle of the optical fiber 8 of the light module 2 of FIG. 22. It can be observed that the optical fiber 8 has, at the entrance face 8.1, a cone of light acceptance. , represented by two broken lines and forming an angle 2Qmax. The light rays meeting the input face 8.1 with angles of incidence less than or equal to those of the acceptance cone will undergo at the level of the diopter 8.3 on the outer surface of the core of the optical fiber 8 successive reflections by the principle of total reflection. The optical fiber advantageously comprises a core 8.4 in transparent or translucent material, surrounded by a sheath 8.5 also in transparent or translucent material. The core 8.4 of the fiber 8 has a slightly higher refractive index (difference of a few tenths, hundredths or thousandths) than the sheath 8.5 and can therefore confine the light which is entirely reflected multiple times at the interface between the two. materials (because of the phenomenon of total internal reflection). The assembly is generally covered with a protective plastic sheath (not shown). When a light ray enters an optical fiber at one of its ends at a suitable angle, it undergoes multiple internal total reflections. This ray then propagates to the other end of the optical fiber almost without loss, by taking a zigzag path. The propagation of light in the fiber can be done with very little loss even when the fiber is bent.

An optical fiber is often described according to two parameters: - the normalized index difference, which gives a measure of the index jump between the core and the sheath: Δ = nc η \ where nc is the refractive index of the heart, and ησ that of the sheath; and the numerical aperture ("numerical aperture"), which is the sinus of the maximum angle of entry of the light into the fiber so that the light can be guided without loss, measured in relation to to the axis of the fiber. The numerical aperture O.N. is equal to sin 9max = ^ n2 - n2.

FIG. 3 illustrates in cross-section two possible configurations of the optical fiber 8. On the left, the core 8.4 of the fiber 8 has a square section, that is to say a rectangular section where the width / is equal to the length L. To the right, the core 8.4 'of the fiber 8' has a rectangular non-square section, that is to say where the width / is less than the length L. The sheaths 8.5 and 8.5 'follow the heart 8.5 and 8.5 ', respectively, and advantageously have a circular outer surface.

Such optical fibers are commercially available from Mitsubishi Cable Industries Ltd, including fibers of the type "THF® Square Core Optical Fiber". They have a numerical aperture O.N. between 0.12 and 0.2. The core section has dimensions (width and length) greater than or equal to 50 μm and / or less than or equal to 200 μm. The maximum angle 9max, with the optical axis, light rays coming out of the output face 8.2 of the optical fiber is quite low, in this case between 7 ° and II. Approximately 5 ° for numerical apertures between 0.12 and 0.2. The use of a diverging lens, such as the lens 10 (Figure 1) is interesting because it allows to open the light beam and thereby reduce the optical path.

Figure 4 schematically illustrates the change in light image format that can be brought about by the use of an anamorphic lens. By way of example, the fiber 8 having a rectangular section core emits at its output face 8.2 a light beam of generally square section. However, most imagers, such as liquid crystal transmissive slabs, have an image format different from a square, such as a 4: 3 or 16: 9 format. An anamorphic lens such as the lens 10 'and allows to deform the light beam to adapt to the format of the imager and thus illuminate all or almost all of its active surface.

FIG. 5 illustrates a light module according to a first embodiment of the invention. The reference numbers of FIG. 1 are used to designate the identical or corresponding elements, these numbers however being increased by 100. Reference is also made to the description of these elements in relation to the first embodiment and FIGS. to 4. Specific reference numerals between 100 and 200 are used to designate elements specific to this embodiment.

The light module 102 of FIG. 5 differs from that of FIG. 1, essentially in that it comprises two mirrors 111.1 and 111.2 placed between the lens 110 and the imager 11. These two mirrors make it possible to fold the light beam and thus to gain in compactness since the light beam reflected by the second mirror III. 2 propagates along an optical axis 116.3 which is generally parallel to the optical axis 116.1 aligning the exit face 108.2, the lens 110 and the first mirror 116.1. The light beam folded by the first mirror 116.1 propagates towards the second mirror 116.2 along the optical axis 116.2.

It is interesting to note that the optical fiber 108 can undergo bending without the propagation of light rays within said fiber being disturbed. This then confers a certain freedom as to the location of the light source (s) 104. The power supply and / or heat dissipation problems can then be deported away from the module. It is even possible to pool one or more light sources with several light modules. It is understood that what has been detailed above also applies to the first embodiment, this ability being intrinsic to the optical fiber.

In general and by way of example, the imager may be a 3.5 inch (71 mm × 53 mm) commercially available 3.5 inch (Thin-Film Transistor) type monochrome liquid crystal panel. The screen can have a useful dimension of 90mm x 60mm. However, it should be noted that the imager can also be an imager working in reflection, such as an electromechanical microsystem (MEMS, acronym for "Microelectromechanical Systems") forming a matrix of micro mirrors pivoting between two positions.

In general, the screen 14 may be transparent and diffusing so as to display the light image on the face opposite to that receiving the light beam from the imager. Alternatively, the screen may be transparent and non-diffusing so as to project the light image on a separate screen of the screen 14, such as for example an outer surface of the light module.

Claims (14)

claims 1. Light module (2; 102) comprising: - an illuminating surface (8.2; 108.2) capable of forming a light beam; - a rectangular imager (12; 112) adapted to form a light image from the light beam emitted by the illuminating surface (8.2; 108.2); characterized in that the module comprises: - an optical fiber (8; 108) with a core (8.4; 8.4 ') of rectangular section and at a first end an entrance face (8,1; 108,1) of light emitted by a light source (4; 104) and at a second end an exit face (8.2; 108.2) of light forming the illuminating surface and in that the rectangular section of the core (8.4; 8.4 ') of the fiber optical (8; 108) has a width (I) and a length (L), at least one of said width (I) and length (L) being less than or equal to 200 μm and / or greater than or equal to 50 μm. 2. Light module (2; 102) according to claim 1, characterized in that the optical fiber has a length, from the input face (8.1; 108.1) to the output face (8.2; 108.2), which is greater than or equal to 100mm. 3. Light module (2; 102) according to one of claims 1 or 2, characterized in that the imager (12; 112) is electrically controlled. 4. Light module (2; 102) according to one of claims 1 to 3, characterized in that the imager is a transmissive LCD imager (12; 112). 5. Light module according to one of claims 1 to 3, characterized in that the imager is an electromechanical microsystem forming a matrix of micro-mirrors pivoting between two positions. 6. Light module (2; 102) according to one of claims 1 to 5, characterized in that said module further comprises a lens (10; 10 '; 110) or a mirror arranged optically between the illuminating surface (8.2; 108.2) and the imager (12; 112). Light module (2) according to claim 6, characterized in that the lens (10 ') or the mirror is anamorphic and configured so that the beam emitted by the illuminating surface covers more than 90% of the active surface of the light. imager (12). 8. Light module (2; 102) according to one of claims 6 and 7, characterized in that the lens (10; 10 ': 110) is divergent, the maximum angle of incidence of the light beam emitted by the surface illuminant (8.2; 108.2) on the imager (12; 112) being less than or equal to 30 °. 9. Light module (2; 102) according to one of claims 1 to 8, characterized in that the optical fiber (8; 108) has a numerical aperture of between 0.12 and 0.2. 10. Light module (102) according to one of claims 1 to 9, characterized in that said module further comprises at least one mirror (111.1; 111.2) optically disposed between the illuminating surface (108.2) and the imager (112). 11. Light module (102) according to one of claims 1 to 9, characterized in that said module further comprises a first mirror (111.1) and a second mirror (111.2) optically disposed between the illuminating surface (108.2). and the imager (112) so as to fold the light beam emitted by the illuminating surface (108.2) by an angle of between 150 ° and 210 °, preferably between 170 ° and 190 °. 12. Luminous device comprising a light module (2; 102) capable of forming a light image, and a projection screen (14; 114) of the light image, characterized in that the light module (2; 102) is according to one of claims 1 to 11. 13. Lighting device according to claim 12, characterized in that the projection screen (14; 114) is diffusing so as to diffuse the light image from the face of said screen opposite to the face receiving the light image of the light module. . 14. Light device according to claim 12, characterized in that the projection screen (14; 114) is non-diffusing so as to allow the light module to project the light image onto a surface outside the device.