EP3452865A1

EP3452865A1 - Device for generating images and head-up display including such a device

Info

Publication number: EP3452865A1
Application number: EP17723943.1A
Authority: EP
Inventors: Pierre Mermillod
Original assignee: Valeo Comfort and Driving Assistance SAS
Current assignee: Valeo Comfort and Driving Assistance SAS
Priority date: 2016-05-04
Filing date: 2017-04-28
Publication date: 2019-03-13
Also published as: FR3051049B1; FR3051049A1; WO2017191052A1

Abstract

The invention relates to a device (30) for generating a multi-colour image formed from a set of pixels (4) including: a plurality of light sources (31, 32, 33) each emitting a source light beam (11, 12, 13) at a different emission wavelength (λ_0,B, λ_0,G, λ_0,R); a first optical system (34, 35, 36) that directs the source beams toward beam-deviating means (50) that deviate each source beam in a deviation direction (θ, θ') that varies as a function of time; and a scattering module (40) that intercepts each deviated source light beam (71, 72, 73) in order to generate a scattered light beam (7) having a main scattering direction, the scattering module (40) comprising a scatterer (41) and a second optical system (42). According to the invention, the second optical system comprises at least two separate optical lenses (48, 49) having preset constringences and refractive indices so that the main scattering directions for the various emission wavelengths are substantially parallel.

Description

Image generating device

and head-up display comprising such a device

TECHNICAL FIELD TO WHICH THE INVENTION RELATES The present invention relates generally to the field of displays and screens for projecting multicolored images.

It relates more particularly to a device for generating a multicolored image formed of a set of pixels.

It also relates to a head-up display comprising such a device.

BACKGROUND TECHNOLOGY

Devices for generating a multicolored image formed of a set of pixels comprising:

a plurality of monochromatic light sources at different emission wavelengths;

a control unit adapted to activate, for a given pixel of said image, each light source at respective activation times, each light source emitting, when it is activated by said control unit, a source light beam at said emission wavelength;

a first optical system directing said transmitted source light beams to beam deflection means adapted to deflect each source light beam in a variable deviation direction as a function of time.

In this type of devices, the source light beams emitted for a given pixel of the image are deflected in the same direction of deflection towards a transparent display panel on which the multicolored image is formed.

In order to increase the illumination aperture of the source light beams, provision may furthermore be made to use in the device, in place of the transparent display panel, a diffuser intercepting each source light beam deviated and generating, at from it, a diffused light beam having a main direction of diffusion.

However, the use of such a diffuser results in the light beams scattered at the same emission wavelength have different main directions of diffusion. The multicolored image generated by the device therefore changes color depending on the viewing angle under which a individual would look at the broadcaster.

Thus, it can be provided that the device preferably comprises a second optical system arranged with respect to said beam deflection means so that the light beams scattered at the same emission wavelength have substantially parallel main directions of diffusion.

However, the second optical system generally has optical aberrations, and in particular chromatic aberrations, axial and transverse, so that the light beams scattered at different wavelengths are spatially separated downstream of the diffuser and the second optical system.

The multicolor image generated by the image generation device can then have iridescent pixels, which degrades the quality of the images generated.

OBJECT OF THE INVENTION

In order to overcome the aforementioned drawback of the state of the art, the present invention proposes an image generation device making it possible to reduce or even eliminate the effects of chromatic aberrations.

More particularly, there is provided according to the invention a device for generating a multicolored image formed of a set of pixels comprising:

a plurality of monochromatic light sources at different emission wavelengths, each light source being adapted to emit a source light beam at said emission wavelength;

a first optical system directing said source light beams emitted to beam deflection means, said beam deflecting means being adapted to deflect each source light beam in a variable deviation direction as a function of time; and

a scattering module intercepting each source light beam deflected in a given deflection direction to generate a scattered light beam having a main direction of diffusion from the pixel associated with this deflection direction, said diffusion module comprising:

a diffuser adapted to broadcast said deviated source light beams, and

a second optical system arranged with respect to said beam deflection means so that the light beams scattered at the same emission wavelength exhibit main directions of diffusion substantially parallel.

According to the invention, said second optical system comprises at least two distinct optical lenses, said optical lenses having refractive indices and predetermined constringences so that the main directions of diffusion for at least two different emission wavelengths are substantially parallel.

Thus, thanks to the use of at least two optical lenses with different optical properties, it is possible to design a second optical system with which, for at least two different emission lengths, the angular and transverse differences between the scattered light beams for the same pixel are reduced.

Advantageously, said at least two predetermined emission wavelengths are selected from said emission wavelengths as the smallest emission wavelength and the largest emission wavelength. .

Other nonlimiting and advantageous features of the device according to the invention, taken individually or in any technically possible combination, are as follows:

the first optical lens has a first constringence greater than 50 in absolute value, and the second optical lens has a second constringence of less than 50 in absolute value;

the image generating device comprises three light sources with three different emission wavelengths, and said second optical system comprises a third optical lens having a refractive index and a predetermined constringence so that the three main directions of diffusion for said three emission wavelengths are substantially parallel;

at least one of the optical lenses of said second optical system is made of an organic material;

said organic material is a polymeric material of the polycarbonate or polymethyl methacrylate type;

at least one of the optical lenses of said second optical system is made of a mineral material;

said mineral material is a crown glass or a flint glass. The invention also proposes a head-up display comprising a device for generating a multicolored image as defined above.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT The following description with reference to the accompanying drawings, given by way of non-limiting examples, will make it clear what the invention consists of and how it can be implemented.

In the accompanying drawings:

Figure 1 is an overall view in partial section of a motor vehicle comprising a head-up display comprising an image generating device according to the invention;

Figure 2 is a schematic view of the image generating device of Figure 1;

Fig. 3 is an exploded view showing the beam deflection means and the scattering module of Fig. 2;

FIG. 4 represents an exemplary embodiment of a second optical system;

FIG. 5 represents an alternative embodiment of the second optical system comprising three lenses.

In the preamble, it will be noted that the identical or similar elements of the different embodiments shown in the different figures will be referenced by the same reference signs and will not be described each time.

In Figure 1, there is shown a head-up display 1 equipping a vehicle, here a motor vehicle 2.

In general, this display 1 is intended to project images in the field of view of an individual 3 located inside the vehicle 2 (it is shown in Figure 1 that one of the eyes of the individual 3 ). It will be considered in the remainder of the description that this individual 3 is the driver of the motor vehicle 2.

These images may include, for example, information relating to the vehicle 2 (speed, engine speed, fuel level, distance to other vehicles, etc.) or instructions as to the route to be followed by the vehicle 2 ( in combination with an onboard navigation system for example). To project these images, the display 1 comprises an image generating device for generating one or more images, in particular multicolored images, each image being formed of a set of pixels.

The image generation device 30 receives signals from the onboard computer (not shown) of the vehicle 2 and generates as a function of these signals, from each pixel of the generated image (see for example the pixel 4 of FIG. 1), a primary light beam 7 (only a primary light ray starting from the pixel 4 of the image is represented in FIG. 1) representing a scene to be projected in the field of view of the conductor 3.

For this purpose, the display 1 also comprises an optical projection system of the scene to the driver 3 located inside the vehicle 2.

This optical projection system comprises in particular a reflecting mirror 8 and a combiner 9 (see FIG. 1).

The reflecting mirror 8 is here a spherical mirror but alternatively, it could be a plane mirror or a mirror of parabolic, elliptical or aspherical shape.

As represented in FIG. 1, the reflecting mirror e intercepts the primary light beam 7 generated by the display of the scene and reflects the primary light beam 7 towards the combiner 9.

The combiner 9 is here disposed between the windshield 23 of the vehicle 2 and the eyes of the driver 3 and is mounted on a base 13 placed in a dashboard 14 of the vehicle 2.

Advantageously, there may be provided between the combiner and the base, the combiner adjusting means for changing its position and / or its orientation relative to the dashboard.

The combiner 9 intercepts the primary light beam 7 reflected by the reflecting mirror 8 and reflects it itself towards the conductor 3 so as to form an image 16 of the scene generated by the image generation device 30 which is visible by the driver 3.

Advantageously, the image generating device 30, the reflecting mirror 8 and the combiner 9 are arranged relative to one another so that the display 1 projects the image 16 of the scene into the field of view of the image. driver 3 but outside the vehicle 2, here at the front of the hood 17 of the vehicle 2. This image 1 6 of the scene is formed, in a preferred direction 21, at a distance from the conductor 3 which is generally between 1, 8 and 2.5 meters.

As the combiner 9 is partially transparent, the image 1 6 of the scene is visible by the driver 3 without it having to divert too much the eyes of the road when in driving situation.

The structure and operation of the image generation device according to the invention will now be described in more detail with reference to FIGS. 2 to 5.

As shown in FIG. 2, this image generation device 30 firstly comprises a plurality of monochromatic light sources 31, 32, 33, here three in number.

In the present application, it is considered that these light sources 31, 32, 33 are monochromatic insofar as their emission spectrum has an emission peak (maximum intensity value) for a precise emission wavelength λ ₀ having a spectral width Δλ ₀ such that (λ ₀ ) ² / Δλ ₀ "1 μηι. In other words, it was considered that a light source is monochromatic if its temporal coherence length is greater than 1 micron.

A light source emitting laser radiation is an example of a monochromatic source.

The light sources 31, 32, 33 of the image generation device are here three laser diodes emitting at different wavelengths, respectively in blue (A ₀ , B = 470 nm), green (λ ₀ , ν = 532 nm), and red (A ₀ , R = 650 nm).

Preferably, the emission wavelengths of the different light sources are chosen so as to maximize the space of accessible colors by superposing one or more wavelengths.

These light sources 31, 32, 33 are activated by a control unit 20 which receives signals from the on-board computer (not shown) of the vehicle 2.

Each light source 31, 32, 33 emits, when activated by the control unit 20, a source light beam 1 1, 1 2, 1 3 at the corresponding emission wavelength of the source. The first light beam source 1 1 is therefore blue to the wavelength Â _0, B, the second source light beam 12 is therefore green to the wavelength λ _0, ν, the third light beam source 13 is red at the length wave ₀ , R.

Preferably, collimation means are provided arranged just downstream of the light sources 31, 32, 33 for collimating the source light beams 1 1, 12, 13 which at the output of the light sources 31, 32, 33 are strongly divergent.

The source light beams 1 1, 12, 13 are here three parallel beams separated laterally from each other due to the separation of the light sources 31, 32, 33.

The image generation device 30 comprises a first optical system 34, 35, 36 for superimposing and directing the three source light beams 1 1, 12, 13 emitted by the light sources 31, 32, 33 towards beam deflection means 50.

In the particular embodiment shown in FIG. 2, this first optical system comprises three mirrors 34, 35, 36.

Preferably, these mirrors 34, 35, 36 are plane dichroic mirrors, oriented for example at 45 ° with respect to the direction of propagation of the source light beams 1 1, 12, 13 so that they are reflected with an angle 90 ° to the beam deflection means 50.

In addition, the mirrors 35, 36, 37 are preferably arranged with respect to the light sources 1 1, 12, 13 and with respect to one another so that the source light beams 1 1, 12, 13 are superimposed and then form together a polychromatic light beam.

These beam deflection means 50 then deviate each source light beam 1 1, 12, 13 in a direction of deviation variable as a function of time.

The beam deflection means here comprise (see FIG. 2) an oscillating mirror 50 movable plane rotated about two crossed oscillation axes: a first oscillation axis 51 and a second oscillation axis 52 which is perpendicular to the first oscillation axis 51.

This two-dimensional oscillation mirror 50 may for example be of the "MEMS" (acronym for "Micro-Electromechanical System") type.

Such oscillating mirror 50 MEMS present according to one of the axes oscillation 51, 52 a uniform oscillation movement at a low frequency, generally less than 1000 Hz, typically between 50 and 100 Hz.

According to the other oscillation axes 51, 52, the oscillating mirror 50 MEMS has a resonant oscillation movement at a high frequency, generally greater than 10 kHz, here between 20 and 30 kHz.

Due to the resonance, the rotational speed of the oscillating mirror 50 along the latter axis is not uniform but is non-linear:

it is zero at the edge of movement, when the angle of rotation (relative to a rest position) of the oscillating mirror 50 is the largest, and

- it increases to reach a maximum value at its rest position, then

it decreases to reach zero speed on the other edge of the movement.

As represented in FIG. 2, the source light beams 1 1, 12, 13 are incident on the oscillating mirror 50 at the same point of intersection 53 of the oscillating mirror 50 corresponding to the intersection of the oscillation axes 51, 52.

The oscillating mirror 50 then reflects the source light beams 1 1, 12, 13 in respective deflection directions according to the orientation (ie angles) of the oscillating mirror 50 with respect to the oscillation axes 51, 52. The beams bright sources 1 1, 12, 13 reflected and deflected by the oscillating mirror 50 will respectively referenced 71, 72, 73 in the following description.

Thanks to the cross-rotation movements of the oscillating mirror 50 around the two oscillation axes 51, 52, the deviated source light beams 71, 72, 73 have variable directions of deviation as a function of time and in this case periodically as a function of the movement of oscillation of the oscillating mirror 50. The deviated source light beams 71, 72, 73 thus perform a scanning movement (see line 5 in FIG. 2).

The image generation device 30 also then comprises a diffusion module 40 intended to intercept each deviated source light beam 71, 72, 73 in a given deflection direction to generate a scattered light beam having a main direction of diffusion.

As shown in FIG. 3, this diffusion module 40 comprises, on the one hand, a second optical system 42 and, on the other hand, a diffuser 41. The diffuser 41 is here placed downstream of the second optical system 42 but, alternatively, the diffuser could be placed upstream of the second optical system without this changing the operating principle of the diffusion module.

This diffuser 41 of the diffusion module 40 is intended to diffuse the source light beams 71, 72, 73 deviated by the oscillating mirror 50, which are also transmitted by the second optical system 42.

The diffuser 41 is here a diffuser of the "Multi-Lens Array" (MLA) type. Such a diffuser is composed of a multitude of microlenses, a given radius and arranged next to each other in a regular arrangement, for example of the honeycomb type, while respecting a gap between the center of each micro-lens about 100 μηι. This type of diffuser makes it possible to open the diffusion indicator of the deviated source light beams 71, 72, 73 incident on the diffuser 41 by defocusing them, the angle of opening of the diffusion cone being directly related to the focal distance of each micro-lens).

FIG. 3 shows several deviated source light beams 71, 72, 73, 74 through the oscillating mirror 50. In particular, the deviated source light beams, which are respectively referenced 72 and 74, result from the deviation of a source light beam. 12 emitted by the second light source 32 at the green emission wavelength, this deviation being done respectively in two directions of deviation which are marked by the angles Θ and θ 'with respect to an optical axis 47 of the second optical system 42.

The first deviated source light beam 72 in the angle deflection direction Θ is transmitted by the second optical system 42 according to a first transmitted light beam 78. The second deviated source light beam 74 at the same wavelength in the direction of angle deviation θ 'is transmitted by the second optical system 42 according to a second transmitted light beam 70.

In known manner, and as shown in FIG. 3, the second optical system 42 is configured and arranged with respect to the oscillating mirror 50 so that the transmitted light beams 70, 78 at the same emission wavelength (here in the green) are transmitted in substantially parallel directions. These transmission directions are here parallel to the optical axis 47 of the second optical system 42.

The transmitted light beams 70, 78 by the second system optics 42 are then diffused by the diffuser 41 to each give rise to scattered light beams: a main scattered light beam 7 in a main direction of diffusion which is here parallel to the optical axis 47 of the second optical system 42.

As shown in FIG. 3, the diffuser 41 also gives rise to other diffused light beams 75, 76 around the main direction of diffusion of the diffused light beam 7. The angular distribution of these secondary scattered light beams 75, 76 is a function of of the intensity indicator which is characteristic of the diffuser 41.

Thanks to the arrangement of the second optical system 42 relative to the oscillating mirror 50, the scattered light beams 7 at the same emission wavelength have substantially parallel main directions of diffusion.

However, without particular precautions, the deflected light beams 71, 72, 73 at different wavelengths are transmitted by the second optical system 42 in different transmission directions so that the diffuser 41 diffuses the transmitted light beams in main directions. different diffusion rates for different wavelengths.

As a result, the image projected by the diffuser 41 may be tainted with chromaticism and the pixels of the image may appear iridescent.

It is therefore one of the objectives of the invention to reduce or even eliminate the effect of chromatism so that the scattered light beams 7 at different wavelengths are scattered in substantially identical main directions of diffusion.

For this purpose, according to the invention and as shown in FIG. 4, the second optical system 42 comprises at least two distinct optical lenses 48, 49, these optical lenses 48, 49 having refractive indices and predetermined constringences of so that the main diffusion directions 7 for at least two different predetermined transmission wavelengths are substantially parallel.

The constringence of a material (also called "Abbe number" or dispersion coefficient) characterizes its ability to disperse light as a function of wavelength. The smaller the constringence, the higher the chromatic dispersion and the greater the constringence, the greater the chromatic dispersion is weak.

Generally, materials with low constractions, typically less than 50, have high refractive indices greater than about 1.6. Conversely, materials with strong constrangences greater than 50 have low refractive indices, typically between 1.5 and 1.6. Nevertheless, it is possible to design optical glasses with both a high index and a high constringence (eg SCHOTT's LaK 34 glass with index 1, 729 and constractionence 54.5 for the D-line helium) or glasses with both a low index and a low constringence (eg OHARA S-TIL1 glass of index 1, 548 and constringence 45.8 for the c / of the helium).

Advantageously, these two different predetermined transmission wavelengths are chosen from the emission wavelengths A ₀ , B, A ₀ , R, A ₀ , R being the most significant emission wavelength. small, that is to say here the blue emission wavelength A ₀ , B and the largest emission wavelength, that is to say here the wavelength d red emission A ₀ , R.

An example of this embodiment is shown in Figure 4 where the second optical system comprises a first optical lens 48, here convergent and biconvex shape, and a second optical lens 49, divergent and planar-concave.

Preferably, the first optical lens 48 has a first constringence greater than 50 in absolute value, and the second optical lens 49 has a second constringence of less than 50 in absolute value. For example, it is possible to use a plastic lens (for example an aspheric polycarbonate or Zeonex lens) and a glass lens (for example a glass spherical lens).

The second optical system 42 of FIG. 4 is such that the light beam deflected 71 at the first wavelength A ₀ , B (blue) and the light beam deflected 73 at the third wavelength A ₀ , R (red ) are refracted and transmitted by the two optical lenses 48, 49 so that the two transmitted light beams 77, 79 respectively at the first wavelength A ₀ , B and the third wavelength A ₀ , R are parallel . The light beams diffused by the diffuser 41 at these two wavelengths A ₀ , B _J AO, R, will thus have essentially identical main directions of diffusion, and the chromaticism of the image will be reduced.

As shown in FIG. 4, the transmitted light beam 78 at the second emission wavelength A ₀ , B (green) is not parallel to the two other transmitted light beams 77, 79 at the other wavelengths A ₀ , B, A ₀ , R However, the angular differences between the transmission directions are reduced compared to a second optical system of the prior art.

Advantageously, at least one of the two optical lenses 48, 49 of the second optical system 42 is made of an organic material, preferably a polymeric material of the polycarbonate or polymethyl methacrylate (PMMA) type. This allows in particular to reduce the total weight of the second optical system 42.

For example, in the embodiment shown in Figure 4, the first lens 48, which has a thickness of 25 mm and a rectangular section of 120 mm x 25 mm is made of PMMA so that its weight is limited to 180 grams.

Advantageously, for certain particular optical configurations, at least one of the optical lenses 48, 49 of the second optical system 42, here the second lens 49, is made of a mineral material. This allows in particular to have access to index values and wider constringences than for an organic or polymeric material.

In particular, the second lens 49 may be formed in a crown glass having a high constringence, typically greater than 50, or in a flint glass, having a low constringence, typically less than 50.

In other embodiments, the second optical system could for example comprise more than two optical lenses.

In particular, as shown in FIG. 5, when the image generation device (30) comprises three light sources 31, 32, 33 at three emission wavelengths A ₀ , B, λ _0, ν, A ₀ , R different, it is particularly advantageous that the second optical system 90 comprises, in addition to the first two lenses 91, 92, a third optical lens 93 having a refractive index and a predetermined constringence so that the three main directions of diffusion for said three emission wavelengths A ₀ , B, A ₀ , V, A ₀ , R are substantially parallel.

Claims

1. Device (30) for generating a multicolored image formed of a set of pixels (4) comprising:

a plurality of monochromatic light sources (31, 32, 33) at different emission wavelengths (A ₀ , B, A ₀ , V, A ₀ , R), each light source (31, 32, 33) ) being adapted to emit a source light beam (1 1, 12, 1 3) at said emission wavelength (A ₀ , B, λ ₀ , ν, A ₀ , R);

a first optical system (34, 35, 36) directing said source light beams (1 1, 1 2, 1 3) transmitted to beam deflecting means (50), said beam deflecting means (50) being adapted to deflecting each source light beam (1 1, 1 2, 1 3) in a direction of deflection (Θ, θ ') variable as a function of time; and

a diffusion module (40) intercepting each deviated source light beam (71, 72, 73) in a given deflection direction (θ, θ ') to generate a scattered light beam (7) having a main direction of diffusion from the pixel (4) associated with this deflection direction (θ, θ '), said diffusion module (40) comprising:

a diffuser (41) adapted to diffuse said deviated source light beams (71, 72, 73), and

a second optical system (42) arranged with respect to said beam deflecting means (50) so that the scattered light beams (7) at the same emission wavelength (A ₀ , B, A ₀ , V, Λ ₀ , R) have substantially parallel main directions of diffusion;

characterized in that said second optical system (42) comprises at least two distinct optical lenses (48,49), said optical lenses (48,49) having predetermined refractive indices and constringences so that the main directions of diffusion ( 7) for at least two different predetermined transmission wavelengths (A ₀ , B, A ₀ , R) are substantially parallel.

An image generating device (30) according to claim 1, wherein said at least two different predetermined transmission wavelengths (A ₀ , B, A ₀ , R) are selected from said wavelengths. transmitting (A _0, B, _0, R, A _0, R) as the emission wavelength (A _0, B) smaller and the emission wavelength (A ₀ , R) the largest.

An image generating device (30) according to claim 1 or 2, wherein:

the first optical lens (48) has a first constringence greater than 50 in absolute value, and

the second optical lens (49) has a second constringence of less than 50 in absolute value.

4. An image generating device (30) according to one of claims 1 to 3, comprising three light sources (31, 32, 33) at three emission wavelengths (A ₀ , B, A ₀ , V, A ₀ , R) and wherein said second optical system (90) comprises a third optical lens (93) having a refractive index and a predetermined constringence so that the three main directions of diffusion for said three lengths of emission wave (A ₀ , B, A ₀ , V, A ₀ , R) are substantially parallel.

The image generating device (30) according to one of claims 1 to 4, wherein at least one (48; 91,93) of the optical lenses of said second optical system (42; 90) is embodied in an organic material.

An image generating device (30) according to claim 5, wherein said organic material is a polymeric material of the polycarbonate or polymethylmethacrylate type.

An image generating device (30) according to one of claims 1 to 6, wherein at least one (49; 92) of the optical lenses of said second optical system (42; 90) is made of a material mineral.

An image generating device (30) according to claim 7, wherein said mineral material is a crown glass or a flint glass.

Head-up display (1) having an image generating device (30) according to one of claims 1 to 8.