Device for aerial and dematerialised projection of an autostereoscopic image or a sequence of autostereoscopic images, in particular for use in motor vehicles

Abstract

The invention relates to a system for aerial and dematerialised projection of an autostereoscopic image to an observer, the system comprising: a housing (30) comprising an opaque upper wall (20) which extends in parallel with a plane, referred to as the horizon plane, and is provided with an opening; a front face mirror (10) which is inclined, for example at an angle of 45° with respect to the horizon plane passing through the opening, the mirror having a reflective surface which is oriented towards the observer; a concave mirror (14) which is arranged at the bottom of the front face mirror, faces the opening and is oriented in such a way that its concave and reflective surface is oriented towards the inclined mirror; a screen (16) for displaying an autostereoscopic image, which extends substantially perpendicularly to the horizon plane, the screen being arranged under the opaque upper wall at a distance from the middle of the image of the concave mirror formed by the inclined mirror that is equal to the radius of curvature of the concave mirror, the screen being equipped with a lenticular array, the pitch of which is determined so as to be able to compensate for its apparent modification after reflection by the concave mirror.

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION: DEVICE FOR THE AERIAL AND DEMATERIALIZED PROJECTION OF AN AUTOSTEREOSCOPIC IMAGE OR A SEQUENCE OF AUTOSTEREOSCOPIC IMAGES, IN PARTICULAR FOR USE IN AUTOMOBILES

[0003] Technical field of the invention

[0004] The invention relates to a device for aerial and dematerialized projection of an autostereoscopic image or a sequence of autostereoscopic images. The invention is particularly intended for use in the automotive field, without however being exclusively intended for this use.

[0005] Technological background

[0006] A device for the aerial and dematerialized projection of an object is a device which allows an image of the object to be projected in front of a window made in a box and which gives the observer the illusion of a three-dimensional object floating in space.

[0007] Such a device is known for the projection of real objects. Such a device typically comprises a housing (opaque or not) in which an opening is provided intended to form an observation window for the dematerialized image, an optical system, generally a lens, a Fresnel lens, a set of lenses or a concave mirror, and an object arranged at a distance from the optical system which is configured to orient the image of the object towards the observation window.

[0008] For example, document US6817716 describes such a device comprising a lower compartment in which a real object is illuminated by a light source, an upper compartment comprising an observation window arranged on the front face, a concave mirror and a semi-transparent plane mirror inclined at 45 degrees on the optical axis of the concave mirror on which the observation window is centered, said semi-transparent mirror being arranged between the observation window and the concave mirror in line with the real object. Thus, the illuminated object is partially reflected in the semi-transparent mirror inclined at 45 degrees in the direction of the concave mirror, which returns the light rays through the semi-transparent mirror towards the observation window. The observer then has the impression of seeing the real object floating in front of the observation window.

[0009] A device for projecting an autostereoscopic image has also already been proposed by the applicant in document W02018 / 167410.

[0010] This device comprises a housing comprising a front wall, a rear wall, connected to each other by an upper wall and a lower wall, said front wall comprising an opening forming a window for observing an aerial and dematerialized image of said autostereoscopic digital image.

[0011] The device also comprises an optical system comprising at least one concave spherical mirror having an optical axis, a focal length F, a center of radius of curvature C located on the optical axis, the optical system being arranged in the housing so that it can orient at least part of the incident light received towards the observation window to form there an aerial and dematerialized image of the autostereoscopic digital image.

[0012] The autostereoscopic image is projected by an autostereoscopic image display screen with N viewpoints surmounted by a network of cylindrical lenticules forming an optical component selecting the viewpoints of the autostereoscopic digital image to be projected, housed in the housing opposite the spherical mirror at a distance substantially equal to twice the focal length F, and spaced from the optical axis of the spherical mirror, perpendicular to this optical axis by a distance at least equal to half the height of the display screen, the height being defined according to the axis perpendicular to the optical axis.

[0013] This device advantageously allows the visualization of autostereoscopic images which appear to float in space.

[0014] The inventors, however, sought to improve this device, particularly for automotive applications that face constraints of size and cost. In addition, the inventors sought to improve the quality of the autostereoscopic image perceived by the observer.

[0015] Objectives of the invention

[0016] The invention aims to provide a system for aerial and dematerialized projection of an autostereoscopic image which overcomes at least some of the drawbacks of known solutions.

[0017] The invention also aims to provide, in at least one embodiment, such a projection system which masks the components of the system from the observer.

[0018] The invention also aims to provide, in at least one embodiment, such a projection system whose components are arranged below the line of sight of the observer towards the viewing area of ​​the aerial and dematerialized image.

[0019] The invention also aims to provide, in at least one embodiment, such a system which can be integrated without particular difficulty within a motor vehicle for the projection of driving information to the driver.

[0020] The invention also aims to provide, in at least one embodiment, such a projection system which is compact and made up of a limited number of components.

[0021] The invention also aims to provide, in at least one embodiment, such a projection system which allows different configurations to adapt to different integration and usage constraints.

[0022] The invention finally aims to provide a device for displaying driving information for a driver of a motor vehicle comprising a projection system according to the invention.

[0023] Statement of the invention

[0024] To do this, the invention relates to a system for aerial and dematerialized projection of an autostereoscopic image intended for an observer whose eyes are positioned within a predetermined three-dimensional space, called an eye box.

[0025] The system according to the invention is characterized in that it comprises: an optical device comprising at least one convergent optical component with behavior identical to that of a concave mirror having a radius of curvature R and a focal length F, said optical device being arranged relative to said eye box so as to be able to direct the light rays that it receives towards a viewing window observable from said eye box, an auto stereoscopic display screen arranged relative to said optical device so that the light rays that it emits can reach said viewing window, after reflection on said convergent optical component, and having traveled a distance d equal to twice the focal length F, said screen comprising: o a matrix of pixels of N lines and M columns, each pixel being composed of a plurality of sub-pixels of different colors, o a lenticular network surmounting said matrix of pixels,and having a pitch P determined from a pitch P', called nominal pitch, of an autostereoscopic screen, called nominal screen, having usage characteristics identical to those of the system screen and intended to be observed in direct vision at a distance corresponding to the usage distance of said system screen, by the formula P=P'.( I -C / (SA J) where C is the number of parts of viewpoints visible simultaneously from said usage distance inside said eye box, when said nominal screen of pitch P' is arranged in said projection system in place of said screen, and S is the number of different viewpoints addressed by each pixel of said matrix.,

[0026] The system according to the invention thus implements a specific autostereoscopic screen specially designed for this sole purpose, to allow observation of the dematerialized reflection of an autostereoscopic image reflected by a converging optical component. Such a converging optical component is for example a concave mirror or a holographic optic. Such a converging optical component has identical behavior to a concave mirror. Throughout the following, the terminology of concave mirror is mainly used to facilitate reading, but it is understood that this concave mirror can be replaced by a holographic optic without modifying the technical effects of the invention.

[0027] In particular, an auto stereoscopic screen designed for direct observation is not suitable for use within a screen dematerialization device implementing a reflection of the screen on a concave mirror.

[0028] Indeed, such a screen dematerialization device must make it possible to find in the main lobe of the screen (which designates the space in front of the screen in which the different viewpoints of the autostereoscopic image follow one another at a preferred viewing distance from the screen, called the flat tint distance and corresponding to the distance at which each eye of the observer perceives only one viewpoint of the image over the entire surface of the screen) all the targeted characteristics: number of viewpoints, flat tint distance and distribution of viewpoints on the pixel matrix. However, practice shows that a concave mirror alters all of these characteristics so that an autostereoscopic screen designed for direct vision is little or not at all suitable for use in a device implementing a concave mirror.

[0029] When a screen is positioned at twice the focal length of a concave mirror or in front of any other optical system with the same behavior, a holographic optical element for example, whose useful surface area would be at least equal to that of the screen, we obtain in return a reflected image of the screen of identical size but inverted (scale -1).

[0030] The deformations induced by the concave mirror require the introduction of new rules for defining the parameters of the lenticular network, different from those of a network in direct vision. In order for the reflected immaterial double of the screen to have the desired autostereoscopic properties, it is necessary to modify the characteristics of the lenticular network of the screen. The presence of a concave mirror transforms all the parameters described previously. To maintain the desired characteristics, the pitch of the network must be reduced in such proportions that the screen would no longer be observable in direct vision. The inventors have succeeded in determining the level of correction of the pitch to be made to allow this observation reflected in a concave mirror.

[0031] This reduction in pitch is obtained according to the invention from the pitch P' of an autostereoscopic screen, called a nominal screen, having usage characteristics identical to those of the system screen but intended to be observed in direct vision at a distance corresponding to the usage distance of said system screen, by the formula P=P'.(1-C / SM), where C is the number of parts of viewpoints visible simultaneously from said usage distance inside the eye box, when said nominal screen of pitch P' is arranged in said projection system in place of said screen, S is the number of different viewpoints of the image addressed by each pixel of said pixel matrix and M is the number of pixels per line of the pixel matrix.

[0032] For example, for sub-pixel addressing from a pixel matrix where each pixel includes 3 sub-pixels of different colors, then S is equal to 3. Thus, the step P is obtained by the formula P=P' .(1-C / (3. M)).

[0033] If the same matrix is ​​used for whole pixel addressing, then S is equal to 1 and the pitch P is obtained by the formula P=P' .(1-C / M).

[0034] Throughout the following and to facilitate reading, we consider sub-pixel addressing and a matrix in which each pixel is formed of 3 sub-pixels, it being understood that the technical teachings provided apply mutatis mutandis to full pixel addressing and / or to matrices comprising a number of sub-pixels other than 3.

[0035] For example, if a color pattern displayed on a nominal autostereoscopic screen is reflected in a concave mirror, the reflected image of this color pattern, in return, presents at the initially chosen flat tint a number of color bars corresponding to a projected pitch having gained at least two or three lenses for the entire network compared to the screen.

[0036] For example, for a 5-viewpoint screen, if the observer perceives, at any distance from the screen, 5 color bars on the screen, this means that he or she has deviated from the flat tint distance to the point that the projected pitch has increased or decreased by 5 subpixels, that is, by the pitch of one lens. If the observer perceives 10 color bars, it is because the projected pitch has increased or decreased by 10 subpixels, that is, by two lenses. If the screen displays a single color, it is because the observer is at the flat tint distance.

[0037] To the extent that it is possible to know very exactly the pitch of the lenticular network of a nominal screen, for example to 100 eme to within a micron, it becomes possible to correct the effect of the concave mirror on the optical path which connects the surface of the real screen to the user's eyes via the real dematerialized conjugated image, by machining a new lenticular network with the corrected pitch.

[0038] We see that this amounts to creating a flat tint in direct vision outside the projection device at a very short distance from the screen. This therefore amounts to considerably reducing the pitch of the lenticular network compared to use in direct vision.

[0039] If a nominal 5-point screen placed in the projection device allows 12 color bars to be viewed at the desired flat tint distance of 1 m for example (assuming the screen displays 5 distinct colors, each color corresponding to a point-of-view), and since the pitch of a lens corresponds to 5 colors in direct vision, 12 color bars in reflection in the concave mirror represent the 12 / 5 emes of the pitch of the lenses. It is necessary to reduce the lenticular network by this value to adapt it to the device according to the invention and to divide it by the total number of lenses to calculate the exact incidence on the pitch which will be applied to the machining of the lenticular network of the screen intended to be arranged in the projection device.

[0040] This makes it possible to obtain a system whose dematerialized autostereoscopic image reflected by the mirror makes it possible to find all the characteristics expected in the central lobe.

[0041] For the first time, it becomes possible to simply determine the pitch correction to be made to a nominal autostereoscopic screen, for its integration into a device using a concave mirror, by knowing the pitch of the nominal screen and by determining the number of parts of viewpoints visible simultaneously from said usage distance inside said eye box, when this screen is housed in the device according to the invention.

[0042] As seen previously, this determination of the number of parts of viewpoints visible simultaneously can be facilitated by displaying a color chart on the screen, which makes it possible to count, from said eye box corresponding to the distance of use of the screen, the number of color bands visible simultaneously.

[0043] Advantageously and according to the invention, the system further comprises: a housing comprising an opaque front wall extending opposite said observer and an opaque upper wall connected to said front wall and extending parallel to a plane, called the horizon plane, said upper wall being provided with an upper opening, a front face mirror inclined at an angle ε with respect to the horizontal while extending at least partially above said upper opening, said mirror having a reflecting surface oriented towards said observer, said converging optical component is arranged at the foot of the front face mirror, opposite said opening and oriented so that its reflecting surface is oriented towards said inclined mirror extending above said upper opening, said converging optical component having an optical axis forming an angle δ with respect to the horizontal;said autostereoscopic display screen is inclined at an angle 0 relative to the vertical, arranged under the opaque upper wall at a distance from the middle of the image of the converging optical component formed by the inclined mirror equal to the radius of curvature of said converging optical component, said angles ex, ô' and 0 being linked by the following relationships: ô'=2.ô where ô=45°-cx;

[0044] 0=P where P is the angle formed, with respect to the horizontal, by the direction of the observer's gaze, from the eye box, towards the said viewing window and directed towards the centre of the reflection of the concave mirror.

[0045] Thus and according to this advantageous variant, the system comprises an inclined front face plane mirror which extends at least partially above an opening made in a wall through which rays reflected by a converging optical component can pass to be reflected in the front face plane mirror and form, at a predetermined viewing area, a dematerialized image of the image at the origin of its rays.

[0046] Furthermore, the volume occupied by the system is divided into two parts, each on either side of a median plane, called the horizon plane.

[0047] This horizontal plane is materialized by the upper wall of the system, which is preferably made of an opaque material. This upper wall is pierced with an opening and the mirror inclined at an angle ex with respect to the horizontal extends at least partially above this opening.

[0048] According to one embodiment of the invention, the front face mirror passes through the upper opening so as to delimit a portion of mirror extending above the horizon plane visible to the observer and a portion of the mirror extending below the horizon plane, masked by said opaque walls of the housing.

[0049] According to the invention, the top of this mirror comes towards the observer and the bottom of the mirror moves away from it. Other inclinations are possible depending on the uses and integration constraints.

[0050] The emerging part of the mirror is for example the same size as the hidden part below the horizon plane.

[0051] At the foot of the inclined mirror is the concave mirror (also referred to by the terminology of converging optical component), oriented so that the concave and reflecting face is turned upwards, opposite the upper opening made in the upper wall.

[0052] Thus the concave mirror is reflected in the part of the inclined front face of the plane mirror which extends above the upper opening and forms a vertical image there as if the concave mirror were placed vertically behind the latter.

[0053] At a distance equal to the radius of curvature of the concave mirror from the middle of the image of the latter formed by the inclined front mirror is the autostereoscopic screen, under the upper wall, with its back turned to the observer. The upper edge of the screen is located near the upper wall, just below the latter, which makes it invisible to the observer. This screen is inclined at an angle 0 relative to the vertical.

[0054] The image displayed by this screen is visible identically on the other side of the horizon plane, in the form of a conjugate image at scale -1. In fact, all the light rays emanating from the screen and touching the image of the concave mirror are refocused at an equivalent distance above the horizon plane to form a non-material conjugate image of the screen and nevertheless real in the optical sense, visible to the observer placed in front of the device.

[0055] Light rays from the screen are reflected downward by the part of the inclined front-face plane mirror extending below the horizon plane, then they are reflected upward by the concave mirror and are reflected a second time by the visible part of the inclined front-face plane mirror, which directs them towards the observer's eyes. The concave curvature of the mirror directs the rays in such a way that those coming from a given point on the screen appear to intersect on the homologous part of the conjugate image of the screen above the horizon plane, creating the illusion that they actually emanate from that location. For the observer whose eyes are in their path, these rays together form an image analogous to that of the screen and to what it displays, the latter remaining invisible directly below the horizon plane.

[0056] The autostereoscopic screen is provided with a specific lenticular grating, as previously described, such that the image visible to the observer maintains the expected autostereoscopic parameters after being reflected by the concave mirror. The pitch of the lenticular grating is adjusted relative to that of a screen observed directly, without reflection by a concave mirror, in order to compensate for the modification of its apparent pitch after reflection in a concave mirror or after transmission through a converging optical component, whether it is a lens of the same radius and focal length or a holographic optical component. More precisely, the conical perspective resulting from reflection or transmission through a converging optical component modifies the perceived pitch.Thanks to the prior pitch correction, the device allows a three-dimensional image to be displayed above the horizon plane, identical to that of an autostereoscopic screen observed live.

[0057] From the eye box and at the level of the viewing window, the observer perceives an aerial and dematerialized relief image, without seeing the converging optical component or the screen located below the horizon plane.

[0058] Advantageously and according to the invention, said angle ex is 36°, said angle P is 20°, said angle ô' is 18° and said angle 0 is 20°.

[0059] According to this advantageous variant, the angles are determined so that an observer whose gaze axis towards the projection zone forms an angle of 20° to the horizontal can perceive the autostereoscopic image with a mirror inclined at 36° to the horizontal, which corresponds to the standard inclination of a windshield of a motor vehicle.

[0060] A device according to this variant can therefore be integrated into a motor vehicle to ensure the aerial and dematerialized projection of an autostereoscopic image for a driver.

[0061] Where appropriate, the inclined mirror is formed by a windshield of a motor vehicle and said opaque upper wall of said housing is formed by a portion of the front shelf of the vehicle.

[0062] Of course, other applications can be targeted by a system according to the invention and the angle values ​​are not fixed and can vary depending on the conditions of use and the applications in order to maintain the same result.

[0063] The invention also relates to a device for displaying driving information for a motor vehicle comprising a windshield, a steering wheel and a front panel extending between the windshield and the steering wheel, characterized in that said display device comprises a projection system according to the invention in which said inclined mirror is formed by said windshield, said opaque wall is formed by said front panel within which an opening is provided to form said upper opening for projecting said autostereoscopic image, said converging optical component and said autostereoscopic screen being housed under the front panel, such that a driver of the vehicle seated in front of said windshield can view driving information by aerial and dematerialized projection of autostereoscopic images displayed on said display screen in a predetermined projection zone extending above said front panel.

[0064] Thus, and according to the invention, the front shelf of the motor vehicle acts as an upper wall and extends along the horizontal plane and the windshield acts (under certain conditions of angle relative to the vertical, shape and surface treatments) as an inclined front mirror. The front shelf of a motor vehicle is the substantially flat space located between the dashboard and the windshield of the vehicle. This space can therefore usefully act as an opaque upper portion extending along the horizontal plane of the system according to the invention. In the case where the curvature of the windshield is sufficiently regular and homogeneous, it could complement the concave curvature of the main mirror which will have to be adjusted to take this into account.

[0065] The rays emitted by the car stereo screen are reflected by the part of the windshield located below the opening in the dashboard. It is necessary for the screen to be slightly inclined so that its conjugate image is orthogonal to the axis of vision and to avoid trapezoidal distortions. The rays are then reflected downwards, towards the concave mirror, then towards the part of the windshield above the opening in the dashboard, where they are directed towards the eye box.

[0066] According to an advantageous variant, the windshield is inclined by 36° with respect to the horizontal and the concave mirror is inclined by 20° with respect to the vertical to ensure a vertical image of the latter seen in reflection in the windshield, for an observer whose axis of vision forms an angle of the order of 20° with the desired projection zone of the aerial and dematerialized image. The important parameter is the almost verticality of the image of the concave mirror in the reflective part of the windshield. Small modifications of position and angle of all the components each restore the position, size and inclination of the virtual image of the screen, just above the horizon plane.

[0067] Thus, according to this embodiment variant, the projection system makes it possible to project information from the dashboard (for example speedometers, navigation information, GPS, etc.) towards the eyes of the observer by displaying them on the autostereoscopic screen. This information is then projected by the windshield and the concave mirror towards the eyes of the driver. The system according to this variant takes advantage of the presence of the windshield and uses its lower part, generally opaque, to make it a front-facing mirror. A possible treatment of the windshield may be necessary to provide it with this reflective functionality.

[0068] Advantageously and according to the invention, the concave mirror has a radius of curvature of 300 mm and a focal length of 150 mm.

[0069] Of course, other mirrors can be used without compromising the principle of the invention.

[0070] The invention also relates to a method for producing a system for aerial and dematerialized projection of an autostereoscopic image intended for an observer whose eyes are positioned within a predetermined three-dimensional space, called an eye box, said method comprising the following steps: selection of an autostereoscopic screen, called a nominal screen, having predetermined usage characteristics and formed of a matrix of pixels of N lines and M columns and surmounted by a lenticular network of predetermined pitch P', arrangement of said nominal screen in a projection system comprising a convergent optical component with behavior identical to that of a concave mirror of radius R and focal length F, said convergent optical component being arranged relative to said eye box so as to be able to direct the light rays that it receives towards a viewing window observable from said eye box,said nominal screen being arranged in relation to the converging optical component so that the light rays which it emits can reach said viewing window, after reflection on said converging optical component, the light rays having traveled a distance d equal to twice the focal length F, displaying a color pattern on said nominal autostereoscopic screen, calculating the number C of colors observed simultaneously from said usage distance inside said eye box, manufacturing an autostereoscopic screen, called a dedicated screen, having the same predetermined usage characteristics as those of said nominal screen and a lenticular network of pitch P calculated by the formula P=P' .(lC / (SJVfj) where S is the number of different viewpoints addressed by each pixel of said matrix, replacing said nominal screen with said dedicated screen.,

[0071] The technical advantages and effects of the projection device according to the invention apply mutatis mutandis to the method of developing an aerial and dematerialized projection system according to the invention.

[0072] The invention also relates to a system for aerial and dematerialized projection of an autostereoscopic image and a device for displaying driving information for a motor vehicle, characterized in combination by all or part of the characteristics mentioned above or below.

[0073] List of figures

[0074] Other aims, characteristics and advantages of the invention will appear on reading the following description given solely for non-limiting purposes and which refers to the appended figures in which:

[0075] - figure 1 is a schematic view of the projection system according to a first embodiment of the invention,

[0076] - figure 2 is a view of the device for displaying driving information of a motor vehicle according to one embodiment of the invention,

[0077] - Figure 3 is a schematic view of an auto stereoscopic screen of a projection system according to one embodiment of the invention.

[0078] Detailed description of an embodiment of the invention

[0079] In the figures, scales and proportions are not strictly respected, for the purposes of illustration and clarity.

[0080] Identical, similar or analogous elements are designated by the same references in all figures.

[0081] The embodiments described in connection with the figures relate to the display of an autostereoscopic image.

[0082] Figure 1 schematically illustrates a system according to an embodiment of the invention intended to be integrated within a motor vehicle as represented schematically by Figure 2.

[0083] In Figure 1, the dotted lines represent the paths of the light rays and the conjugate images of the image and the concave mirror.

[0084] The system comprises an opaque housing 30 comprising an upper wall 20 provided with an opening 22 through which an inclined front-facing mirror 10 extends.

[0085] This front-facing mirror 10 is inclined at an angle ε with respect to the horizontal. The mirror 10 has a reflective surface oriented towards the observer. This observer is located to the right of the device and looks towards a predetermined projection zone 18.

[0086] The front face mirror 10 delimits a portion of mirror extending above the horizon plane visible to the observer and a portion of the mirror extending below the horizon plane masked by the housing 30.

[0087] The system also comprises a concave mirror 14 arranged at the foot of the front face mirror 10, opposite the opening 22 and oriented so that its concave and reflective surface is oriented towards the inclined front face mirror 10.

[0088] This concave mirror has for example a radius of 300 mm, a focal length of 150 mm for a useful zone of 150 mm, or F / l. The mirror has an optical axis forming an angle δ' with respect to the horizontal. The system also comprises a display screen 16 of an autostereoscopic image inclined at an angle θ with respect to the vertical.

[0089] The screen is arranged under the opaque upper wall at a distance from the middle of the image of the concave mirror formed by the inclined mirror, equal to the radius of curvature of the concave mirror 14.

[0090] The inclination of the screen 16 must allow the emitted light rays to reach the inclined plane mirror 10 so that these rays can be reflected downwards towards the concave mirror 14.

[0091] This screen is equipped with a lenticular network whose pitch is determined to be able to compensate for its apparent modification after reflection by the concave mirror.

[0092] Figure 3 schematically illustrates an autostereoscopic screen 16 comprising a matrix of pixels 16a arranged in rows and columns, each pixel being composed of a plurality of sub-pixels of different colors each assigned to a viewpoint of the autostereoscopic image to be displayed. The screen also comprises a lenticular network 16b which surmounts the matrix 16a. Each lens is inclined at a non-zero angle relative to the direction of the columns of the matrix (for example 18°). According to other embodiments, it is also possible to use a vertical network.

[0093] As previously stated, there is nothing to prevent the use of pixel-based addressing of the image viewpoints. Throughout the following, we consider sub-pixel addressing of pixels each formed by three sub-pixels of different colors (in other words, S is equal to 3).

[0094] The pitch P of the network 16b of the screen 16 is determined from the pitch P', called the nominal pitch, of an autostereoscopic screen, called the nominal screen, having usage characteristics identical to those of the screen of the system and intended to be observed in direct vision at a distance corresponding to the usage distance of the screen of the system, by the formula P=P' .(1-C / 3.M) where C is the number of parts of viewpoints visible simultaneously from the usage distance inside the eye box, when said nominal screen of pitch P' is arranged in said projection system in place of said screen, and M is the horizontal resolution of the pixel matrix. For example, if we consider a 5-inch screen with 5 points of view and a resolution of 800 x 480. This screen is placed at a distance of 300 mm from the concave mirror in square format with a side of 150 mm, whose focal length is 150 mm and the radius of curvature is 300 mm.Once placed in the system, the observer sees 12 color bars from the eye box (assuming one color is displayed on the screen per point of view). The pitch of a lens corresponding to 5 colors in direct vision, 12 color bars in reflection in the concave mirror represent 12 / 5. emes of the lentil step.

[0095] Since we display one image viewpoint per subpixel, the number of lenses in the screen array considered is equal to (800 pixels x 3) / 5, i.e. 480 lenses.

[0096] The total step correction is therefore equal to 12 / 5 = 2.4 lenses.

[0097] This corresponds to a correction per lens equal to 2.4 / 480 = 0.005.

[0098] In other words, the pitch of the lenses must therefore be reduced by 0.5%.

[0099] If the known pitch P' of a lens is 0.270 mm, the necessary pitch correction amounts to removing 0.00135 mm per lens.

[0100] Although this value of 1.35 microns seems relatively small, its impact is actually considerable for optimal observation of the autostereoscopic image reflected by the concave mirror. This correction is crucial for being able to operate an autostereoscopic screen in reflection in a concave mirror.

[0101] In the embodiment of Figure 1, the angle ex is 36°, the angle P is 20°, the angle ô' is 18°, the angle ô is 9° and the angle 0 is 20°.

[0102] Figure 2 schematically illustrates the system of Figure 1 integrated into a vehicle to form a device for displaying driving information for a motor vehicle comprising a windshield 100, a steering wheel 110 and a front panel 200 extending between the windshield 100 and the steering wheel 110.

[0103] The windshield 100 forms the inclined mirror of the projection system and the front board 200 forms the upper opaque wall of the projection system.

[0104] This front board 200 includes an opening 220 which forms the opening through which the light rays projected by the concave mirror (not visible in FIG. 2) are reflected in the windshield 100.

[0105] The windshield 100 extends above the opening to receive the light rays projected by the concave mirror.

[0106] In addition, the car stereo screen (not visible in the figure) must be tilted so that the rays emitted by it can be reflected in the windshield.

[0107] For example, the windshield has an inclination of 36° relative to the horizontal (oc=36°), the concave mirror has an optical axis having an inclination of 18° relative to the horizontal and the autostereoscopic screen has an inclination of 20° relative to the vertical (0=20°) such that a driver whose gaze has an angle of 20° relative to the horizontal (P=20°) can view the screen image at the predetermined viewing area which extends above the front face of the vehicle.

[0108] The person skilled in the art will easily understand that the autostereoscopic screen and the concave mirror of the projection system are housed in a housing arranged under the front board 200 according to the configuration described in connection with FIG. 1.

[0109] Thus, the driver of the vehicle can view driving information, which is projected from the autostereoscopic display screen, to a predetermined projection area which extends above the front dashboard 200, between the windshield 100 and the driver.

[0110] The system according to the invention can also be modified to adapt to certain usage constraints. For example, it is possible to deviate from the theoretical values ​​of the angles mentioned in the document or to arrange the screen at a distance different from the theoretical distance of the concave mirror.

[0111] For example, if the distance from the screen to the center of the concave mirror's reflection is less than or greater than twice the focal length of the concave mirror, the system can still allow the viewing of an autostereoscopic image, but the real dematerialized image will then be closer (or further) from the observer, being enlarged (or shrunk).

[0112] It is also possible to voluntarily change the value of 0, accepting to encounter small trapezoidal deformations of the image, to correct the feeling of verticality of the screen image in order to have objects displayed consistent in orientation with the surface of the dashboard for example. Thus, it is possible to choose an angle 0 of 12° instead of the theoretical angle of 20° for certain applications.

Claims

CLAIMS 1. System for aerial and dematerialized projection of an autostereoscopic image intended for an observer whose eyes are positioned within a predetermined three-dimensional space, called an eye box, said system being characterized in that it comprises: an optical device comprising at least one converging optical component (14) with behavior identical to that of a concave mirror having a radius of curvature R and a focal length F, said optical device being arranged relative to said eye box so as to be able to direct the light rays that it receives towards a viewing window observable from said eye box, an autostereoscopic display screen (16) arranged relative to said optical device so that the light rays that it emits can reach said viewing window, after reflection on said converging optical component (14), and having traveled a distance d equal to twice the focal length F,said screen comprising: o a matrix of pixels of N lines and M columns, each pixel being composed of a plurality of sub-pixels of different colors, o a lenticular network surmounting said matrix of pixels, and having a pitch P determined from a pitch P', called nominal pitch, of an autostereoscopic screen, called nominal screen, having usage characteristics identical to those of the screen of the system and intended to be observed in direct vision at a distance corresponding to the usage distance of said screen of the system, by the formula P=P'.(1-C / (SM)) where C is the number of parts of viewpoints visible simultaneously from said usage distance inside said eye box, when said, nominal screen of pitch P' is arranged in said projection system in place of said screen, and S is the number of different viewpoints addressed by each pixel of said matrix.

2. System according to claim 1, characterized in that it further comprises: a housing (30) comprising an opaque front wall (20) extending opposite said observer and an opaque upper wall connected to said front wall and extending parallel to a plane, called the horizon plane, said upper wall being provided with an upper opening (22), a front face mirror (10) inclined at an angle ex relative to the horizontal while extending at least partially above said upper opening (22), said front face mirror having a reflecting surface oriented towards said observer, and in that: said converging optical component (14) is arranged at the foot of the front face mirror, opposite said opening (22) and oriented so that its reflecting surface is oriented towards said inclined front face mirror (10) extending above said upper opening,said converging optical component having an optical axis forming an angle δ' with respect to the horizontal; said auto stereoscopic display screen (16) is inclined at an angle θ with respect to the vertical, arranged under the opaque upper wall (20) at a distance from the middle of the image of the converging optical component formed by the inclined front face mirror, equal to the radius of curvature of said concave mirror, said angles θ, θ' and θ being linked by the following relationships: o θ'=2.θ where θ=45°-cx o θ=P where P is the angle formed, with respect to the horizontal, by the direction of the observer's gaze, from the eye box, towards said viewing window and directed towards the center of the reflection of the converging optical component.

3. System according to claim 2, characterized in that said front face mirror (10) inclined at an angle ex relative to the horizontal passes through said upper opening (22) so as to delimit a portion of mirror extending above the horizon plane visible to the observer and a portion of the mirror extending below the horizon plane masked by said opaque walls of the housing.

4. Projection system according to one of claims 2 or 3, characterized in that said angle ex is 36°, said angle P is 20°, said angle ô' is 18° and said angle 0 is 20°.

5. Projection system according to one of claims 1 to 4 characterized in that said convergent optical component is a concave mirror or holographic optics.

6. Projection system according to claim 5, characterized in that said converging optical component is a concave mirror (14) having a radius of curvature of 300 mm and a focal length of 150 mm.

7. Device for displaying driving information for a motor vehicle comprising a windshield (100), a steering wheel (110) and a front panel (200) extending between the windshield (100) and the steering wheel (110), characterized in that said display device comprises a projection system according to one of claims 2 to 4, in which said inclined front face mirror is formed by said windshield, said opaque wall is formed by said front panel within which an opening (220) is provided to form said upper opening for projecting said autostereoscopic image, said converging optical component and said autostereoscopic screen being housed under the front panel,such that a driver of the vehicle seated in front of said windshield can view driving information by aerial and dematerialized projection of autostereoscopic images displayed on said display screen in a predetermined projection zone extending above said front panel., 8. Method for producing an aerial and dematerialized projection system of a autostereoscopic image intended for an observer whose eyes are positioned within a predetermined three-dimensional space, called an eye box, said method comprises the following steps: selection of an autostereoscopic screen, called a nominal screen, having predetermined usage characteristics and formed of a matrix of pixels of N lines and M columns and surmounted by a lenticular network of predetermined pitch P', arrangement of said nominal screen in a projection system comprising a convergent optical component with behavior identical to that of a concave mirror of radius R and focal length F, said convergent optical component being arranged relative to said eye box so as to be able to direct the light rays which it receives towards a viewing window observable from said eye box,said nominal screen being arranged with respect to the converging optical component so that the light rays which it emits can reach said viewing window, after reflection on said converging optical component, the light rays having traveled a distance d equal to twice the focal length F, displaying a color pattern on said nominal autostereoscopic screen, calculating the number C of colors observed simultaneously from said usage distance inside said eye box, manufacturing an autostereoscopic screen, called a dedicated screen, having the same predetermined usage characteristics as those of said nominal screen and a lenticular network of pitch P calculated by the formula P=P' .(lC / (S Vfj) where and S is the number of different viewpoints addressed by each pixel of said matrix, replacing said nominal screen with said dedicated screen.,

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