Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
  • G02F1/1333—Constructional arrangements; Manufacturing methods
  • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
  • G02F1/1336—Illuminating devices
  • G02F1/133602—Direct backlight
  • G02F1/133603—Direct backlight with LEDs
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/01—Head-up displays
  • G02B27/0101—Head-up displays characterised by optical features
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/30—Polarising elements
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
  • G02F1/1333—Constructional arrangements; Manufacturing methods
  • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
  • G02F1/1336—Illuminating devices
  • G02F1/133602—Direct backlight
  • G02F1/133605—Direct backlight including specially adapted reflectors
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/01—Head-up displays
  • G02B27/0101—Head-up displays characterised by optical features
  • G02B2027/0118—Head-up displays characterised by optical features comprising devices for improving the contrast of the display / brillance control visibility
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
  • G02F1/1333—Constructional arrangements; Manufacturing methods
  • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
  • G02F1/1336—Illuminating devices
  • G02F1/133602—Direct backlight
  • G02F1/133606—Direct backlight including a specially adapted diffusing, scattering or light controlling members
  • G02F1/133607—Direct backlight including a specially adapted diffusing, scattering or light controlling members the light controlling member including light directing or refracting elements, e.g. prisms or lenses

Definitions

• the invention relates to image generation systems, especially for head-up displays.
• the invention relates to an image generation system and a head-up display for a motor vehicle.
• the invention will find applications, for example, in motor vehicles to inform users of the vehicle, especially its driver.
• This type of head-up display for a motor vehicle requires obtaining an image with a sufficient brightness so that the user, and in particular the driver of the vehicle, can sufficiently see the image, and in any situation, according to the weather conditions and day and night.
• TFT-LCD Thin-Film Transistor Liquid Crystal Display in English
• These TFT-LCD screens require, for the display of an image, a backlight usually made by a plurality of light-emitting diodes (LED or LED for Light-Emitting Diode).
• LED Light-Emitting Diode
• this TFT-LCD screen and the backlight are included in a set called image generation system.
• TFT-LCD screens have the disadvantage of significantly reducing the light output from the backlight: with the use of a conventional TFT-LCD screen, it is estimated that the transmission rate of the screen is about 5% of the light power of the backlight. This low value is due in particular to the first polarizer present in the screen which allows only the light corresponding to a certain polarization, whereas the LEDs produce light with several polarizations: all the polarizations do not correspond to that which passes through the polarizer are then lost.
• the invention aims to overcome at least some of the disadvantages of image generation systems and known displays.
• the invention also aims to provide, in at least one embodiment of the invention, a display that displays an image with sufficient light output.
• the invention also aims to provide, in at least one embodiment, a display and an image generation system which make it possible to use a backlight with a lower power and thus to reduce the power consumption and the power consumption. heat dissipation.
• the invention also aims to provide, in at least one embodiment of the invention, a display and a system for generating images of reduced size.
• the invention relates to an image generation system for a display, in particular a head-up display, comprising:
• said backlighting device comprises:
• At least one light-emitting diode disposed on the support plate and emitting light in the direction of the screen, - at least one reflecting means (26) disposed between the support plate
• An image generation system thus allows the recycling of the light emitted by the light-emitting diodes of the backlighting device coming from a reflection of part of the light in the direction of the support plate. reflection is caused by the passage through the light of the various elements placed between the light emitting diodes and the screen, and by the screen itself. All of these elements are called optical system. This portion of the light again passes through the optical system and is then reflected on the reflective means disposed between the support plate and the screen to be returned to the screen. The optical system and the reflecting means cause a change in the characteristics of the part of the reflected light which, by crossing the optical system again in the direction of the screen, will be partly transmitted to the screen and partly again reflected towards the support plate.
• the device according to the invention may also comprise one or more of the following characteristics, considered individually or in any technically possible combination:
• the reflecting means has a reflection coefficient greater than 90%, preferably greater than 98%.
• the reflecting means are located at least above a portion of the support plate.
• the reflecting means are located above the entire surface of the support plate with the exception of the surface occupied by the light-emitting diodes.
• the reflecting means is a reflective film.
• the reflecting means is a rigid plate whose face on the side of the screen is reflective.
• the rigid plate is mounted at a distance from the support plate so as to obtain an air gap between the rigid plate and the support plate; the reflecting film is disposed substantially over the entire surface of the support plate; with the exception of the area occupied by the light-emitting diodes.
• the backlighting device comprises at least one light recycling filter emitted by the light-emitting diodes, located between the light-emitting diodes and the screen, ensuring the transmission of a portion of the light towards the screen and the return non-transmitted light to the light-emitting diodes.
• the recycling filter makes it possible to send a part of the light back to the light-emitting diodes.
• This part of the reflected light is advantageously light whose characteristics do not comply with characteristics necessary for a backlight of good quality, in particular because this part of the light would have been lost at the level of the LCD screen.
• This part of the light is then reflected on the reflecting means in the direction of the screen. This reflection and the crossing of the various elements of the optical system allow a change in the characteristics of the light that returns to the recycling filter.
• At least one light recycling filter is a polarization filter adapted to let the light arriving on the polarization filter with a particular polarization and adapted to reflect the light arriving on the polarization filter with a polarization different from the polarization special.
• the polarization filter makes it possible to reflect the portion of the light whose polarization is different from this polarization. special. The light usually lost at the liquid crystal screen is thus reflected towards the reflecting means.
• the reflecting means and the optical system allow a change in the polarization of the reflected light, and said reflected light in the direction of the screen is filtered again by the polarization filter.
• At least one light recycling filter is a prismatic filter adapted to allow the light arriving on the prismatic filter to pass at an angle of incidence less than a predetermined angle and in a given plane, and adapted to reflect the part of the remaining light.
• the prismatic filter makes it possible to let only the light arriving substantially perpendicular to the filter in a given plane, in order to reduce the divergence of the light in the direction of the LCD screen.
• the light reflected by the prismatic filter is reflected back onto the reflective means and returns to the prismatic filter, and a portion of this reflected light arriving on the filter with an angle of incidence less than the predetermined angle passes through the filter and another part is reflected again.
• the backlight device comprises at least two prismatic filters, each filtering according to the incidence of light in a plane, and arranged so that the planes in which they filter the incidence are substantially perpendicular.
• the backlighting device comprises a lens array adapted to collimate the light coming from the light emitting diodes in the direction of the liquid crystal screen.
• the lens array provides a collimated light directed towards the liquid crystal screen to limit losses.
• the backlight device comprises a diffuser adapted to homogenize the light from the light emitting diodes.
• the homogenization of the light allows a good distribution of the light on the liquid crystal screen.
• the diffuser also makes it possible to mask the inside of the backlighting device.
• the liquid crystal screen is inclined at a predefined angle with respect to the support plate and the recycling filter or filters.
• the predefined angle provides a vertical virtual image as part of the use of the image generation system in a head-up display.
• the system comprises a housing surrounding the space of the device between the support plate and the screen and whose inner walls are reflective.
• the housing allows the reflection of light that does not propagate in a straight line between the light-emitting diodes and the LCD screen, in one direction or the other: the housing makes it possible not to lose this light by making sure that it propagates only in the space between the support plate and the LCD screen.
• the image generation system comprises, successively and in this order, between the support plate and the screen:
• the invention also relates to a display, in particular a head-up display, characterized in that it comprises an image generation system according to the invention.
• the invention also relates to an image generation system and a display characterized in combination by all or some of the characteristics mentioned above or below. 5. List of figures
• FIG. 1 is a schematic view of a section of an image generation system according to one embodiment of the invention
• FIG. 2 is a diagrammatic view of a support plate of a system of image generation according to one embodiment of the invention
• Figure 3 is a schematic view of an image generation system and a head-up display according to the invention.
• FIG. 1 represents a schematic view of a section of an image generation system 10 according to one embodiment of the invention.
• the image generation system 10 comprises a liquid crystal screen, here a thin-film transistor LCD 12, and a backlighting device 14.
• Thin-film transistor LCD 12 is commonly referred to as a TFT-LCD (for Thin-Film Transistor Liquid Crystal Display), and allows image formation by the image generation system.
• the backlighting device 14 comprises in particular at least one and preferably a set of light-emitting diodes 16, also called LEDs or LEDs (for Light Emitting Diodes in English, and used in the following description), placed on a support plate.
• the support plate consists of a printed circuit 18, also called PCB (for Printed Circuit Board in English).
• the printed circuit used may for example be type F 4 (for Flame Resistant 4 in English) or IMS (for Insulated Metal Substrate in English).
• IMS Insulated Metal Substrate in English
• the printed circuit board 18 allows both the physical medium and the electrical connection (to a power supply and any other electronic components not shown) of the LEDs 16.
• the LEDs 16 are placed so as to emit light in the direction of the light. screen 12.
• the screen 12 is inclined by a predefined angle, preferably between 0 ° and 40 ° so as to obtain an image virtual vertical in the context of using the image generation system in a head-up display.
• the lens array 20 comprises an LED lens 16, each lens being disposed at above each LED 16.
• a diffuser 22 allowing the homogenization of the light, so as to illuminate the screen 12 in a homogeneous manner to allow the formation of an image of good quality, that is to say brightness substantially uniform.
• the diffuser 22 can hide the inside of the backlight device.
• one or more recycling filters grouped under the reference 24, for example: two crossed prismatic filters, allowing the light arriving on the prismatic filters to pass through with an angle of incidence less than a predetermined angle and in a given plane perpendicular to the plane of the prismatic filter.
• a light beam arriving on a prismatic filter with an angle of incidence greater than the predetermined angle and in a plane different from the given plane will be even less reflected that said plane of incidence of the beam is different from the given plane.
• the use of the two crossed prismatic filters in particular filters in substantially perpendicular planes, makes it possible to filter the major part of the light beams, so that the beams light arriving on the filter outside an angle of incidence cone equal to the predetermined angle will be reflected.
• Prismatic filters are here films of polymer material composed of a multitude of microprisms aligned in the plane of the prismatic filter along lines perpendicular to the given plane.
• This type of film is for example marketed by 3M under the name of BEF (for Brightness Enhancement Film in English).
• BEF Brightness Enhancement Film in English
• a polarization filter for passing light arriving on the polarization filter with a particular polarization and adapted to reflect the light arriving on the polarization filter with a different polarization.
• the light emitted by the LEDs 16 being a non-polarized light, only the portion of this light having a polarization collinear with this particular polarization passes through the polarization filter, the rest of the light being reflected.
• the polarization filter is here a film of polymer material. This type of filter is marketed for example by the company 3M under the name of DBEF (for Dual Brightness Enhancement Film in English).
• the various recycling filters 24 therefore make it possible, for example, to reflect light which would have been filtered at the level of the screen 12 itself because of its internal components, in particular straight polarisers, by reflection of the light which does not have any light. polarization, or to reflect light that propagated in a cone of lighting too wide. This portion of the light reflected by the recycling filter (s) in the direction of the printed circuit is subsequently called recycled light.
• the image generation system 10 comprises a reflective means, here a reflective film 26 disposed substantially over the entire surface of the printed circuit 18 with the exception of the area occupied by the LEDs 16 and which allows to reflect almost all the light recycled, which then propagates back to screen 12.
• a reflective means here a reflective film 26 disposed substantially over the entire surface of the printed circuit 18 with the exception of the area occupied by the LEDs 16 and which allows to reflect almost all the light recycled, which then propagates back to screen 12.
• the space contained therein, between the printed circuit 18 and the screen 12 is surrounded by a housing 28, generally called light box especially in the automotive field.
• a housing 28 is made of a reflective material such as polycarbonate (abbreviated PC).
• PC polycarbonate
• the housing 28 must have a very flat polished surface.
• the reflective film 26, the optical system and the housing 28 allow, due to the reflection of light on or through their respective surfaces, to change the characteristics of the recycled light, including its polarization and its direction of propagation.
• the recycled light which is reflected by the reflective film 26 and which propagates towards the screen 12 has a different polarization and an angle of incidence with the recycling filter or filters different, and therefore can cross the recycling filters 24 if these characteristics allow the passage of light through the recycling filter or filters 24. If the light still does not have the characteristics necessary for crossing the recycling filter or filters, the light is recycled again and the cycle described above is repeated.
• This cycle is represented in FIG. 1 by arrows 30, 31, 32, 34, 36, 37.
• the LEDs 16 emit unpolarized light.
• Two arrows 30, 31 represent two parts of this polarized light, of respective polarizations P1 and P2.
• the polarization filter passes the portion of the light whose polarization is equal to P1.
• the portion of the polarization light P1 therefore passes through the polarization filter and moves towards the screen 12 in the direction represented by the arrow 32. and the portion of the polarization light P2 is recycled, i.e., reflected back to the printed circuit 18, as represented by the arrow 34.
• This portion of the recycled light is reflected on the reflective film 26 towards the 12, and a part of this reflected light has a modified polarization now equal to PI, represented by the arrow 36.
• This part of the polarization light P1 therefore passes through the polarization filter after recycling and reflection, as shown on the arrow 37.
• the same phenomenon occurs in a similar way as a function of the angle of incidence of the light, thanks to the prismatic filters .
• the reflective film 26 does not cover the LEDs 16 so as not to obscure them and thus to allow the backlighting of the screen 12.
• the only part of the recycled light that is not reflected back to the screen 12 is the light that arrives on the printed circuit 18 on the surface occupied by the LEDs 16.
• a reflective means especially if the thickness of these means is important, the holes formed by the margin around each LED can be beveled to optimize the reflective surface without disturbing the lighting of the e notch.
• the reflective film 26 is a film made of polycarbonate (PC) having a reflection coefficient greater than 90%, preferably greater than or equal to 98%.
• PC polycarbonate
• Other materials can be envisaged for the reflective film 26, provided that these are adapted to the other constraints of the image generation system 10, in particular thermal stresses: the reflective film 26 surrounds the LEDs 16 which emit with high luminous power and therefore give off heat. This heat can alter the reflective film 26 if it is not made of a suitable material. This thermal stress is all the more important that the image generation system 10 is in an environment of limited size in which the heat evacuation is difficult, typically for on-board use, for example in a vehicle.
• the film may also, in other embodiments, be composed of a multitude of polymer layers, including polycarbonate, polymethyl methacrylate (PMMA), etc., for example a film marketed by the company 3M under the name of ES.
• polycarbonate polymethyl methacrylate
• PMMA polymethyl methacrylate
• the reflecting means is of another form, for example a rigid plate whose side of the screen side is reflective with properties similar to the reflective film 26 presented above.
• the rigid plate may also be disposed either directly in contact with the support plate, or spaced therefrom so as to leave between the two a blade of air for better heat dissipation by ventilation.
• the device may also comprise a multitude of reflecting means according to these different embodiments.
• the different reflecting means may further be adapted to reflect each optimally a particular wavelength.
• the device may include several reflecting means to return the largest possible amount of light to the screen.
• FIG. 2 represents a schematic view of a printed circuit 18 of an image generation system 10 according to one embodiment of the invention.
• the LEDs 16 of the backlighting device 14 are here eight in number, distributed uniformly over the entire surface of the printed circuit 18. Each LED is composed of a base 16a and an optical portion 16b.
• the LEDs 16 are surrounded by the reflective film 26 which occupies the surface of the printed circuit 18 which is not occupied by the LEDs 16.
• a margin area is provided around each LED 16 on which there is no reflective film 26 to prevent the reflective film 26 from disturbing the light emission by the LEDs 16 and to prevent the reflective film 26 from being altered by too much heat dissipation by the LEDs.
• the invention also relates to a head-up display comprising an image generation system 10 according to the invention.
• the image generation system 10 described with reference to FIG. 1 forms an image using the TFT-LCD screen 12.
• said display Downstream of the screen 12 in the direction of movement of the light beam, said display comprises at least one semi-reflective plate 126 and a reflection device 125 interposed on the path of the image between the screen 12 and the semi blade reflector 126, the reflection device 125 comprising one or more planar or concave mirrors, as shown in FIG. 4.
• the path of the image is symbolized by three dotted arrows which are reflected on the device of FIG. reflection 125 before displaying through the semi-reflecting blade 126.
• the latter allows a magnification and / or, by transparency, a display of the image beyond the semi-reflective blade, particularly beyond the pare -brise equipped vehicle, at a virtual screen 130, obtained using the semi-reflective blade 126.
• This blade 126 has a reflectivity at least equal to 20%, which allows the user to see through the blade the road taken by the vehicle, while enjoying a high contrast to see the image displayed.
• the display of the image can take place at the windshield of the vehicle equipped with said display.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Nonlinear Science (AREA)
• Mathematical Physics (AREA)
• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Liquid Crystal (AREA)

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Citations (6)

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• 2014
  • 2014-04-17 FR FR1400928A patent/FR3020147B1/fr active Active
• 2015
  • 2015-04-16 WO PCT/FR2015/051031 patent/WO2015159029A1/fr active Application Filing
  • 2015-04-16 EP EP15725747.8A patent/EP3132308A1/de not_active Ceased

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