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
  • G02F1/133504—Diffusing, scattering, diffracting elements
• • 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
  • 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
• • 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
  • G02F1/1313—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 specially adapted for a particular application
• • 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
  • G02F1/133504—Diffusing, scattering, diffracting elements
  • G02F1/133507—Films for enhancing the luminance
• • 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
  • G02F1/133528—Polarisers
  • G02F1/133536—Reflective polarizers

Definitions

• Backlighting device image generation device, head-up display and associated manufacturing method
• the present invention generally relates to the field of displays.
• a backlighting device used for example in a head-up display for a motor vehicle, as well as an image-generating device, a head-up display and an associated manufacturing method.
• a so-called “head-up” display forms a virtual image in the field of vision of a motor vehicle driver.
• the latter can thus view information relating to the operation of the vehicle, relating to a traffic lane facing the vehicle, or others, without having to look away from this traffic lane.
• the virtual image, comprising the information to be displayed is then visually superimposed on the environment facing the vehicle.
• a so-called “head-up” display comprises, inside a housing, an image-generating device from which emerges a source light beam and an optical projection system suitable for projecting an image generated by the device for generating images outwards, via the windshield for example, so as to form the virtual image mentioned above.
• Head-up displays for motor vehicles using a liquid crystal display (LCD, for "Liquid Crystal Display”, in English) in their image generation device are often exposed to two types of thermal stress producing heating of the screen: one of these constraints is linked to the light source of the head-up display, and the other to the concentration of the sun's rays on the screen.
• LCD liquid crystal display
• the present invention proposes a backlight device comprising:
• a light source configured to emit a source beam
• a reflector configured to reflect at least part of the source beam into a reflected beam
• a component formed in one piece comprising, on a first face, a polarizer reflective and, on a second face opposite the first face, an optical diffuser, said component being configured to receive and transmit at least part of the reflected beam, characterized in that the first face of the component is placed on the side of the source of light.
• the positioning of the first face of the component on the side of the light source makes it possible to improve the recycling of light inside the backlight device. Indeed, if a portion of the source beam does not have the polarization transmitted by the reflective polarizer, the latter is reflected by the reflective polarizer and can be reintercepted by the reflector and reflected again in the direction of the component. Thus, the transmission of light by the backlight device is improved.
• the optical diffuser is etched on a transparent substrate which carries the reflective polarizer.
• the component may comprise a substrate with a first face carrying the reflective polarizer and a second face opposite the first face and in which the diffuser is formed by etching.
• the engraving is a laser engraving.
• the reflective polarizer is laminated to the optical diffuser.
• the optical diffuser produces a diffusion of light of the Gaussian elliptical type.
• One of the aspects of the invention also relates to an image generating device comprising a backlighting device as described above, further comprising a liquid crystal screen placed downstream of the reflector on the propagation path of the light, the liquid crystal screen comprising a matrix of liquid crystals interposed between an upstream polarizer and a downstream polarizer, said upstream polarizer being capable of selectively transmitting a component of light having a given upstream polarization.
• the reflective polarizer is adapted to reflect a light component having a polarization orthogonal to said upstream polarization.
• the reflector has a main axis parallel to a main direction of the source beam and the component is orthogonal to the main axis of the reflector.
• the liquid crystal screen is tilted with respect to the main direction of the source beam and the component is positioned parallel to the liquid crystal screen.
• One of the aspects of the invention also relates to a head-up display comprising an image generation device as described previously and further comprising an optical projection system capable of returning a light beam generated by the generation device images towards a partially transparent slide.
• one of the aspects of the invention relates to a method for manufacturing a component for a backlight device from a substrate provided with a reflective polarizer on a first face and having a second face opposite the first face, comprising a step of forming an optical diffuser by etching in the second face of the substrate.
• the optical diffuser formation step is a laser etching step.
• FIG. 1 is a schematic view showing the integration of a head-up display according to the invention in a motor vehicle.
• FIG. 2 represents a first embodiment of a backlighting device according to the invention.
• FIG. 3 shows a substrate provided with a reflective polarizer before a step of forming an optical diffuser by laser etching.
• FIG. 4 represents the substrate of FIG. 3 after a step of forming an optical diffuser by laser etching.
• FIG. 5 schematically represents the arrangement of certain components of an image generation device according to the invention.
• FIG. 6 represents a second embodiment of a backlighting device according to the invention.
• FIG 1 there is shown schematically the main elements of a head-up display 1, intended for example to equip a vehicle 2, in particular a motor vehicle.
• the display 1 of Figure 1 is adapted to project a virtual image 3 in the field of vision of a driver 4 of the vehicle 2, so that the driver 4 can see this virtual image 3 and any information that it contains without having to look away.
• the display 1 comprises a partially transparent blade 5 placed in the field of vision of the driver 4, an image generating device 6 adapted to generate an image light beam 7 and an optical projection system 8 adapted to return, in the direction of said partially transparent plate 5, the image light beam 7 generated by the image generating device 6 after passing through a transparent window 9.
• the light beam returned in the direction of the partially transparent plate 5 is partly reflected by the partially transparent plate 5 in the direction of the conductor 4 and thus produces the virtual image 3.
• the partially transparent blade 5 is here merged with the windshield of the vehicle 2. In other words, it is the windshield of the vehicle 3 which has the function of partially transparent blade 5 for the head-up display 1.
• the image generating device 6 and the projection optical system 8 are here placed in a housing 22, one opening is closed by the transparent window 9 already mentioned.
• the image generating device 6 comprises a backlight device 10, a liquid crystal screen 11 covering the backlight device 10, a first heat sink 12 and a second heat sink 13.
• the backlighting device 10 comprises a light source 14 of the matrix type of light-emitting diodes, a reflector 15 and an optical component 16.
• the light source 14 is configured to emit a source beam that diverges around a main direction D
• the reflector 15 receives at least part of the source beam and reflects at least part of it into a reflected beam in the direction of the optical component 16. The reflected beam is collimated here.
• the optical component 16 receives at least part of the reflected beam and transmits at least part of it in a diffused beam to the liquid crystal screen 11.
• the diffused beam illuminates the liquid crystal screen 11 so that the screen liquid crystals 11 allows at least part of the diffused beam to pass to form the image light beam 7.
• the optical component 16 is a dedicated component formed in one piece and comprising on a first face a reflective polarizer 17 and on a second face, opposite the first face, an optical diffuser 18.
• an optical diffuser 18 By formed of a single holding, it is understood that the optical component 16 consists of a single piece.
• reflective polarizer is meant a polarizer operating in reflection, that is to say reflecting a determined polarization component Pd and transmitting the orthogonal polarization component.
• optical diffuser is meant an optical element performing an angular spreading of an incident light.
• the first face is positioned on the side of the reflector 15, which corresponds to the side of the light source 14. This configuration makes it possible to improve the recycling of light inside the backlight device 10. Indeed, if a portion of the source beam does not have the polarization transmitted by the reflective polarizer, this is reflected by the reflective polarizer 17 and can be reintercepted by the reflector 15, then reflected again in the direction of the optical component 16.
• One of the advantages of forming the optical component 16 in one piece is to limit the reflections between the reflective polarizer 17 and the optical diffuser 18. The limitation of these reflections makes it possible to improve the contrast perceived directly on the screen. liquid crystal 11.
• the optical component 16 is obtained by the following process:
• the reflective polarizer can be made of plastic material, for example PVA-TAC-acrylic, and makes it possible to transmit the light arriving on its surface in a given polarization and to reflect the light arriving in a polarization orthogonal to the given polarization.
• a diffusing structure can for example be printed on the rear face (that is to say the face not directly receiving the incident light) of a plastic reflective polariser, of the polycarbonate type, by means of laser engraving, for example by laser machining (in English “Femtosecond laser patterning”); the diffusing structure corresponds to a graining distributed on the rear face so as to diffuse the light according to a given diffusion distribution.
• Figure 3 shows a substrate 25 provided on a first face 23 with a reflective polarizer.
• the substrate 25 has a transparent layer 24, here in polycarbonate, defining a second face opposite the first face 23. It is proposed here to apply a laser etch to this second face in order to form an optical diffuser.
• Figure 4 shows the substrate 25 of Figure 3 after application of laser etching to the second face defined by the transparent layer 24.
• the reflective polarizer 17 is laminated to the optical diffuser 18 using a transparent optical glue.
• the optical diffuser 18 can be made of injected plastic material, such as polycarbonate.
• the thickness of the optical diffuser 18 in the optical component 16 can be between 0.2 mm and 1 mm, and preferably equal to 0.5 mm.
• the optical diffuser 18 can be made of a plastic film, for example polycarbonate.
• the thickness of the film can be between 0.1 mm and 0.25 mm, and preferably equal to 0.125 mm.
• the material of the optical diffuser 18 has a detection temperature greater than or equal to 120° C. with a load equal to 1.8 MPa, and greater than or equal to 130° C. with a load equal to 0.45 MPa.
• the reflective polarizer 17 on the optical diffuser 18 is preferably made of plastic material and is heated to a temperature between 30° C. and 60° C. This procedure makes it possible to reduce the mechanical tensions inside the optical diffuser 18 and to guarantee better adhesion with the reflective polarizer.
• the thickness of the reflective polarizer 17 in the optical component 16 is less than or equal to 0.15 mm.
• the thickness of the reflective polarizer 17 in the optical component 16 is equal to 0.075 mm.
• the reflective polarizer 17 can operate at temperatures greater than or equal to 105°C.
• the optical diffuser 18 is defined by a diffusion indicator with a maximum intensity in a main direction, and for example, angular widths in certain directions.
• the type of diffusion produced by the optical diffuser 18 is of the Gaussian elliptical type.
• the diffusion half-height width in the lengthwise direction of the liquid crystal display 11 is 30 degrees
• the diffusion half-height width in the width direction of the liquid crystal display liquids 11 is 20 degrees.
• the liquid crystal screen 11 comprises a matrix of liquid crystals interposed between an upstream polarizer 19 and a downstream polarizer 20, the upstream polarizer 19 being located on the side of the optical component 16.
• the upstream polarizer 19 is configured to selectively transmit a component of light having an upstream polarization Pa in the matrix of liquid crystals.
• a suitable activation of certain elements of the matrix of liquid crystals selectively allows the passage of the light received from the upstream polarizer 19 by modifying the polarization of the latter through the elements of the matrix of liquid crystals and transmission or not through the downstream polarizer 20.
• the determined polarization Pd reflected by the reflective polarizer 17 is adjusted orthogonally to the upstream polarization Pa. In other words, the polarization of the light Pt transmitted by the reflective polarizer 17 is aligned with the direction of polarization transmitted by the upstream polarizer 19 of the liquid crystal screen 11.
• FIG. 5 schematically illustrates this setting.
• the diffused beam has a polarization which will be transmitted by the upstream polarizer 19 of the crystal screen. liquids 11 and cross it. In this way, the absorption of the diffused beam in the liquid crystal screen 11 is reduced while its transmission is improved, which limits the heating of the liquid crystal screen 11.
• the reflector 15 has a constant height in the direction defined by the main direction of emission of the light source 14, thus a main axis parallel to the main direction of emission D of the light source 14.
• the reflector 15 is made of plastic material with a layer of metallization applied to the interior walls of the reflector 15.
• the material of the reflector 15 has a detection temperature greater than or equal to 120° C. with a load equal to 1.8 MPa and greater than or equal to 130°C with a load equal to 0.45 MPa. This makes it possible to preserve the mechanical and thermal properties of the reflector over the entire operating range of the image-generating device 6, for example, between -40°C and 105°C.
• Aluminum or silver can be used for metallization.
• the reflection coefficient of the reflector 15 is greater than or equal to 60%, preferably greater than or equal to 80%. This parameter reduces light loss by absorption and improves the uniformity of the virtual image 3.
• the geometry of the reflector 15 can be optimized in order to improve the recycling efficiency of the reflective polarizer 17.
• the shape of the reflector 15 is tapered, with the narrower part positioned closer to the source. of light 14.
• the reflector 15 can have walls whose inclination makes it possible to maximize the reflective surface seen from the reflective polarizer 17.
• the curvature of the walls of the reflector 15 can be optimized to improve the collimation of the source beam .
• the optical component 16 is orthogonal to the main axis of the reflector.
• the normal direction of the liquid crystal screen 11 is inclined with respect to the direction of the main axis of the reflector 15.
• Figure 6 illustrates a second embodiment of the backlight device 6 according to the invention.
• the normal direction of the liquid crystal screen 11 is inclined with respect to the direction of the main axis of the reflector 15.
• the normal direction of the optical component 16 is also inclined relative to the direction of the main axis of the reflector 15.
• the inclination is between 12 degrees and 24 degrees.
• the inclination is greater than 13 degrees.
• the optical component 16 is parallel to the liquid crystal screen 11.
• the geometry of the reflector 15 is then adapted to this configuration so as not to degrade the optical characteristics of the perceived virtual image 3, such as the contrast, the luminance and the uniformity of the virtual image 3.
• the reflector still has a main axis parallel to the main direction of emission of the light source but is asymmetrical.
• the edges of the reflector 15 intercept a fictitious surface inclined at an angle of inclination with respect to a plane orthogonal to the main axis of the reflector 15.
• the fictitious surface is parallel to the liquid crystal screen 11.

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• Physics & Mathematics (AREA)
• Nonlinear Science (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Mathematical Physics (AREA)
• Instrument Panels (AREA)
• Liquid Crystal (AREA)
• Devices For Indicating Variable Information By Combining Individual Elements (AREA)

Applications Claiming Priority (2)

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• 2022
  • 2022-02-08 FR FR2201106A patent/FR3132577B1/fr active Active
• 2023
  • 2023-01-20 CN CN202380020994.0A patent/CN118696265A/zh active Pending
  • 2023-01-20 EP EP23701881.7A patent/EP4476589A1/de active Pending
  • 2023-01-20 US US18/836,641 patent/US20250138311A1/en active Pending
  • 2023-01-20 WO PCT/EP2023/051452 patent/WO2023151925A1/fr not_active Ceased

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