FR3054330A1 - IMAGE GENERATING DEVICE AND ASSOCIATED HIGH HEAD DISPLAY - Google Patents

Abstract

The invention relates to a device (20) for generating images comprising: - a screen (25) adapted to form at least one image; - a light source (21) adapted to emit at least one light beam for the purpose of screen, and - at least one intermediate optical element (22) disposed on an optical path of said light beam between said light source and said screen. According to the invention, said at least one intermediate optical element comprises a luminescent material. An associated head-up display is also described.

Description

Holder (s): VALEO COMFORT AND DRIVING ASSISTANCE Simplified joint-stock company.

Extension request (s)

Agent (s): VALEO COMFORT AND DRIVING ASSISTANCE.

54) IMAGE GENERATION DEVICE AND ASSOCIATED HIGH HEAD DISPLAY.

FR 3 054 330 - A1

The invention relates to an image generation device (20) comprising:

- a screen (25) adapted to form at least one image,

a light source (21) adapted to emit at least one light ray intended for the screen, and

- at least one intermediate optical element (22) disposed on an optical path of said light ray between said light source and said screen.

According to the invention, said at least one intermediate optical element comprises a luminescent material.

An associated head-up display is also described.

Image generation device and associated head-up display

Technical field to which the invention relates

The present invention relates generally to the field of head-up displays for vehicles, in particular for motor vehicles.

It relates more particularly to an image generation device and a head-up display comprising such a device.

Technological background

The principle of head-up displays for vehicles is to project images, particularly useful for driving, directly into the driver's field of vision.

For this, the head-up displays generally include an image generation device adapted to generate images and a projection device of the generated images adapted to transmit these images to a semi-transparent plate placed in the driver's field of vision.

Most of the image generation devices used today include a light source backlit by a screen suitable for generating the images.

The image generated by the screen must be sufficiently bright to be seen by the driver, which implies that the light source backlit on this screen itself produces sufficient visible light, included in the range of the visible spectrum extending approximately between 400 nanometers (nm) and 800 nm.

Object of the invention

In this context, the present invention provides a particular image generation device in which at least part of the invisible light of wavelength less than 420 nm, emitted by the light source, is converted into visible light (c (i.e. wavelength generally between 400 nm and 800 nm), before backlit the screen.

More particularly, an image generation device is proposed according to the invention comprising:

- a screen adapted to form at least one image,

- a light source adapted to emit at least one light ray intended for the screen, and

- At least one intermediate optical element disposed on an optical path of said light ray between said light source and said screen, said at least one intermediate optical element comprising a luminescent material.

Thus, in contact with the intermediate optical element comprising the luminescent material at least part of the Ultra-Violet (UV) rays, that is to say the wavelength of which generally extends between 100 nm and 420 nm, produced by the light source is converted into visible rays, that is to say the wavelength of which generally ranges between 400 nm and 800 nm.

In addition, advantageously, thanks to the invention, it is not necessary to introduce additional optical elements to those already included in the usual image generation device.

Other non-limiting and advantageous characteristics of the image generation device according to the invention are as follows:

the luminescent material comprises at least one luminophore adapted to be excited by an ultraviolet light ray of wavelength generally between 100 nanometers and 420 nanometers and to re-emit a visible light ray of wavelength generally comprised 400 nanometers and 800 nanometers;

- The luminescent material comprises at least one phosphorescent phosphor;

- Said light source is a light emitting diode;

- The intermediate optical element is a lens adapted to receive at least two light rays emitted by said light source and to transmit these rays in parallel towards said screen;

- The lens is a converging lens disposed between said light source and the screen so that said light source is included in the object focal plane of said converging lens;

- The optical element is a Fresnel lens disposed between the light source and the screen so that said light source is in the object focal plane of said Fresnel lens;

- said image generation device further comprises a light diffuser, adapted to receive said at least one ray emitted by the light source and to diffuse this light ray towards said screen;

- the diffuser comprises a luminescent material, such as a material comprising at least one phosphorescent phosphor;

- The intermediate optical element is a light diffuser adapted to receive said at least one light ray emitted by the light source and to diffuse this light ray towards said screen;

- The intermediate optical element is covered with a layer of said luminescent material;

- The intermediate optical element is made of a material at least partly luminescent;

- The device comprises a reflector closed on one side by said light source and, on the other side, by said screen, and adapted to reflect said at least light ray emitted by the light source towards the screen;

- Said reflector comprises said luminescent material.

The invention also proposes comprising an image generation device as described above and an image projection device adapted to transmit towards a semi-transparent plate at least one image generated by said image generation device .

Detailed description of an exemplary embodiment

The description which follows with reference to the accompanying drawings, given by way of nonlimiting examples, will make it clear what the invention consists of and how it can be carried out.

In the accompanying drawings:

- Figure 1 is a schematic representation of a head-up display according to the invention in position in the vehicle;

- Figure 2 is a schematic sectional representation of a first embodiment of the image generation device according to the invention;

- Figure 3 is a schematic sectional representation of a second embodiment of the image generation device according to the invention; and,

- Figure 4 is a schematic sectional representation of a third embodiment of the image generation device according to the invention.

In Figure 1, there is shown the main elements of a display 1 head up intended to equip a vehicle, for example a motor vehicle.

Such a display 1 is suitable for creating a virtual image I in the field of vision of a driver of the vehicle, so that the driver can see this virtual image I and the possible information that it contains without having to look away.

To this end, the display 1 comprises a semi-transparent plate 10 placed in the driver's field of vision (see FIG. 1), an image generation device 20 adapted to generate images and a projection device 30 of images suitable for transmitting in the direction of said semi-transparent plate 10 the images generated by the image generation unit 20.

More specifically, the semi-transparent blade 10 is here a combiner 10, that is to say a semi-transparent blade dedicated to the head-up display 1.

Such a combiner 10 is here placed between the windshield 2 of the vehicle and the driver's eyes.

Alternatively, the semi-transparent blade could be confused with the windshield of the vehicle. In other words, in this variant, it is the windscreen of the vehicle which has the function of semi-transparent blade for the head-up display.

Furthermore, here, the image projection device 30 comprises a folding mirror arranged so as to reflect the images generated by the image generation device 20 in the direction of the semi-transparent plate 10. Here, said image mirror folding is a plane mirror.

Alternatively, the image projection device could include a plurality of mirrors and / or other optical elements such as a lens for example.

In FIGS. 2 to 4, a first, a second and a third embodiment of the image generation device 20 according to the invention are shown more precisely, in section in a plane perpendicular to the plane of FIG. 1.

In its three embodiments, identical or similar elements will be referenced identically.

Whatever the embodiment of the invention, the image generation device 20 comprises a screen 25 adapted to form at least one image, a light source 21 adapted to emit at least one light ray intended for the screen 25, and at least one intermediate optical element 22; 24; 23, 26 arranged on an optical path of said light ray emitted by the light source 21 intended for the screen 25.

More precisely, in the three proposed embodiments, the screen 25 is a liquid crystal display (or LCD for “Liquid Crystal Display”), for example with thin film transistors (or TFT for “Thin-Film Transistor).

This screen 25 is adapted to form an image intended for the projection device 30. To do this, whatever the envisaged embodiment, the screen 25 is backlit by the light source 21, placed at a distance from the latter.

In other words, an input face 25A of said screen 25, facing the light source 21, is backlit by said light source 21, and an output face 25B of this screen 25, facing the folding mirror of the device 30 image projection, transmits the image towards said 30 image projection device for display in the 1 head-up display.

In the first and second embodiments of the generation device 20 according to the invention, said generation device 20 actually comprises a plurality of light sources 21. In these two embodiments, it comprises four light sources 21, arranged as a single row.

In the third embodiment, the image generation device 20 comprises a single light source 21.

As a variant, it could also be envisaged, whatever the embodiment of the image generation device, that said image generation device comprises between two and ten light sources, for example arranged in one or two rows .

Whatever the embodiment of the generation device 20 according to the invention, the light sources 21 are conventionally mounted on a support (not shown).

In practice, in the three proposed embodiments, each light source 21 is a light emitting diode (or LED for “Light Emitting Diode”), and the LED, or all of the LEDs, is mounted on a printed circuit playing the support role.

Alternatively, especially when using a direct chip mounting technique (or "On Chip Board"), one can use, as a support, the heat sink usually associated with light sources.

In practice, LEDs emit a multitude of light rays towards the screen 25.

More precisely, each LED is adapted to emit, following an electrical stimulation, a plurality of light rays, belonging in particular to either the visible range, that is to say the range of visible wavelengths approximately between 400 nanometers and 800 nm approximately, that is to say in the Ultra-Violet range, that is to say in the range of wavelengths comprised approximately between 100 nm and 420 nm. (The overlapping of the ranges given above corresponds to the visible border, which varies in particular depending on the individual.)

Whatever the embodiment envisaged, the intermediate optical element 22; 24; 23, 26 is disposed between the light source (s) 21 and said screen 25.

Thus, the intermediate optical element is adapted to direct the light rays which it receives from each light source 21 in the direction of the screen 25.

More specifically, in the first embodiment, the intermediate optical element 22 is a lens 22 adapted to receive at least two light rays emitted by the light sources 21 and to transmit these rays in parallel towards said screen 25.

In practice, such a lens is here a converging lens 22 having a relatively short focal distance.

This convergent lens 22 is disposed between the light sources 21 and the screen 25 so that said light sources 21 are included in the object focal plane of said convergent lens 22.

Advantageously, the light emitted by the light sources 21 is then collimated on the screen 25, that is to say that the light rays entering through the input face 25A of the screen 25 are mutually parallel and perpendicular to this entry face 25A.

Advantageously, this configuration distributes the light over the entire input face 25A of the screen 25.

Alternatively (not shown), it could be envisaged that the lens is a Fresnel lens.

This Fresnel lens would then be placed between the light sources and the screen so that said light sources are included in the object focal plane of said Fresnel lens.

Advantageously, according to this variant, the distance separating the screen and the light sources can be greatly reduced.

In the second embodiment of the image generation device 20 according to the invention, the intermediate optical element is a light diffuser 24 adapted to receive at least part of the light rays emitted by the light sources 21 and to diffuse these light rays towards said screen 25.

In practice, the extension plane of the diffuser 24 is here parallel to the extension plane of the screen 25.

Here, the diffuser 24 is attached to the input face 25A of said screen 25, so that the diffuser 24 and the screen 25 are in contact with each other.

Advantageously, thanks to the diffuser 24, the whole of the input face 25A of the screen 25 receives a uniform light.

According to a variant not shown of this second embodiment of the device according to the invention, said image generation device further comprises a reflector, disposed on an optical path of at least one light ray emitted by the light sources.

In practice, the reflector is closed on one side by said light sources and, on the other side, by said screen.

The image generation device thus forms a closed enclosure. Advantageously, the internal elements of the image generation device are then protected from dust or other external aggressions. The closed enclosure also ensures that no stray rays are emitted from the light sources directly towards the other elements of the head-up display (folding mirror and / or the semi-transparent blade).

The reflector is adapted to reflect said at least light ray emitted by light sources towards the screen. To do this, an internal face of this reflector, that is to say receiving the light rays emitted by the source, has a high reflection coefficient (for example diffuse reflection). For this purpose, the internal face can for example be white. It can alternatively be covered with a reflective layer, for example chromium, silver or aluminum, in order to obtain a high reflection coefficient (for example specular reflection).

According to the third embodiment of the image generation device 20, said image generation device 20 comprises two intermediate optical elements, namely both a lens 23 such as those described in the first embodiment of the invention and a diffuser 26 such as that described in the second embodiment of the device according to the invention.

In practice, the diffuser is arranged between the lens 23 and the screen 25.

In this third embodiment, the diffuser 26 is attached to the input face of the screen 25, so that said screen 25 and said diffuser 26 are in contact with each other with their extension plane respective parallel between them.

It is also possible to provide a reflector in this third embodiment, similar to that described in the second embodiment.

Finally, it is possible to provide an additional embodiment of the invention, in which the intermediate optical element is a reflector such as that described above in the variants of the second and third embodiments. In this additional embodiment, the generation device could then include neither lens nor diffuser.

Remarkably, whatever the embodiment of the device according to the invention, at least one of said intermediate optical elements 22; 24; 23, 26 included in said image generation device 20 comprises a luminescent material.

Advantageously, the image generation device according to the invention does not include additional optical elements compared to the generation devices already known.

In the third embodiment comprising two intermediate optical elements 23, 26, either the lens 23 only comprises the luminescent material, or the diffuser 26 only comprises the luminescent material, or both the lens 23 and the diffuser 26 comprises the luminescent material .

In the first and second embodiments of the invention, the lens 22, respectively the diffuser 24, each comprises said luminescent material.

The luminescent material is adapted to be stimulated by a light ray of given wavelength, and to re-emit another light ray, having another wavelength.

Here, the luminescent material used is adapted to be stimulated by an ultraviolet light ray of wavelength generally between 100 nanometers and 420 nanometers and to re-emit a visible light ray of wavelength generally between 400 nanometers and 800 nanometers.

Thus, the luminescent material is transparent (or inactive) for the light rays belonging to the visible domain, insofar as it lets these rays pass. On the other hand, the luminescent material is active for the light rays of the Ultra-Violet domain insofar as it transforms, in a way, these rays into light rays belonging to the visible domain.

Advantageously, thanks to the intermediate optical element comprising the luminescent material, the screen 25 receives more light rays belonging to the visible domain.

In other words, the backlight of the screen 25 is of better quality insofar as more light rays belonging to the visible domain reach the entry face 25A of said screen 25.

As a result, the image output from screen 25 is brighter.

In practice, the luminescent material here comprises at least one phosphorescent phosphorescent compound (conventionally called "phosphor" in English).

This phosphorescent phosphor compound is capable of emitting a visible light ray, by de-excitation following an excitation by an ultra-violet light ray. The phenomenon of de-excitation giving rise to the emission of a visible light ray can persist after the moment of excitation, this is why we speak rather of phosphorescence (as opposed to fluorescence).

The phosphor compound used is for example chosen from the following list of compounds: ZnS: Ag + (Zn, Cd) S: Ag, ZnS: Ag + ZnS: Cu + Y2C> 2S: Eu,

ZnS: Ag + (Zn, Cd) S: Cu, Y ₂ O ₂ S: Tb, (Zn, Cd) S: Cu, CI + (Zn, Cd) S: Ag, CI, lnBO ₃ : Tb + lnBO ₃ : Eu + ZnS: Ag, Ca ₅ (F, CI) (PO ₄ ) 3: Sb, Mn or one of their mixture.

In practice, whatever the embodiment of the image generation device according to the invention, at least one of the intermediate optical elements 22; 24; 23, 26 is covered with a layer of said luminescent material (or a blade formed of said luminescent material and attached to the intermediate optical element concerned).

Alternatively, it is possible that one of the intermediate optical elements 22; 24; 23, 26 is made of an at least partly luminescent material.

For example, in cases where the intermediate optical element is the lens 22 or the diffuser 24, it is possible to introduce phosphors such as those described above in the composition intended to be molded to form the lens 22 or the diffuser 24 .

Furthermore, in the variants mentioned above where said image generation device comprises the reflector, it is conceivable that this reflector comprises the luminescent material.

In practice, the internal face of the reflector, namely that having a high reflection coefficient, is then itself covered with a layer of transparent material comprising phosphors such as those presented above.

Claims (13)

1. Device for generating (20) images comprising: - a screen (25) adapted to form at least one image, - a light source (21) adapted to emit at least one light ray intended for the screen (25), and - at least one intermediate optical element (22; 24; 23, 26) disposed on an optical path of said light beam between said light source (21) and said screen (25), characterized in that said at least one intermediate optical element (22; 24; 23, 26) comprises a luminescent material. 2. Device according to claim 1, in which the luminescent material comprises at least one luminophore adapted to be excited by an ultraviolet light ray of wavelength generally between 100 nanometers and 420 nanometers and to re-emit a visible light ray of overall wavelength 400 nanometers and 800 nanometers. 3. Device according to one of claims 1 and 2, wherein the luminescent material comprises at least one phosphorescent phosphor. 4. Device according to one of claims 1 to 3, wherein said light source (21) is a light emitting diode. 5. Device according to one of claims 1 to 4, wherein the intermediate optical element is a lens (22; 23) adapted to receive at least two light rays emitted by said light source (21) and to transmit these rays parallel towards said screen (25). 6. Device according to one of claims 1 to 5, wherein the intermediate optical element is a Fresnel lens disposed between the light source (21) and the screen (25) so that said light source (21 ) or in the focal plane object of said Fresnel lens. 7. Device according to one of claims 1 to 6, further comprising a light diffuser (26), adapted to receive said at least one ray emitted by the light source (21) and to diffuse this light ray towards said screen (25). 8. Device according to claim 7, wherein the diffuser (24) comprises a luminescent material, such as a material comprising at least one phosphorescent phosphor. 9. Device according to one of claims 1 to 4, wherein the intermediate optical element is a light diffuser (24) adapted to receive said at least one light ray emitted by the light source (21) and to diffuse this Ray 5 bright towards said screen. 10. Device according to one of claims 1 to 9, wherein the intermediate optical element (22; 24; 23, 26) is covered with a layer of said luminescent material. 11. Device according to one of claims 1 to 9, wherein the intermediate optical element (22; 24; 23, 26) is made of a material at least partly luminescent. 12. Head-up display (1) comprising a device for generating (20) images according to one of claims 1 to 11 and a device for projecting (30) images suitable for transmitting towards a semi-slat transparent (10) to 15 minus an image generated by said image generation device (20).