Device for aerial non-materialized projection of autostereoscopic image or autostereoscopic image sequence, in particular for use in motor vehicle

Abstract

The invention relates to a system for providing an aerial non-materialized projection of autostereoscopic images to an observer, the system comprising: a housing (30) comprising an opaque upper wall (20) extending parallel to a plane referred to as the viewing plane and provided with an opening; a front mirror (10) which passes through the opening at an angle, for example 45 degrees, relative to the horizontal plane, the mirror having a reflective surface facing the observer; a concave mirror (14) arranged at the bottom of the front mirror, facing the opening, and oriented with the concave and reflective surfaces thereof facing the inclined mirror; a screen (16) for displaying autostereoscopic images, which screen extends substantially perpendicular to the horizontal plane, which screen is arranged below the opaque upper wall, the distance from the image center of a concave mirror formed by the inclined mirrors being equal to the radius of curvature of the concave mirror, which screen is equipped with an array of lenses spaced apart from each other, therefore, the obvious change of the light reflected by the concave mirror can be compensated.

Description

Technical Field

[0001] The invention relates to a device for the aerial virtual projection of an autostereoscopic image or a sequence of autostereoscopic images. The invention is particularly, but not exclusively, applicable to the automotive sector. Background Art

[0002] A device for aerial virtual projection of an object is a device that allows the image of an object to be projected in front of a window made in a housing and gives the observer the illusion that the three-dimensional object is floating in space.

[0003] This device is known for projecting real objects. It typically comprises a housing (which may or may not be opaque) that includes an opening for a viewing window that forms a virtual image; an optical system, typically a lens, a Fresnel lens, a set of lenses, or a concave mirror; and an object positioned at a distance from the optical system and configured to direct an image of the object toward the viewing window.

[0004] For example, US Pat. No. 6,817,716 describes a device comprising a lower compartment, wherein a real object is illuminated by a light source; an upper compartment, including an observation window arranged on the front; a concave mirror and a semi-transparent plane mirror, the plane mirror tilted at a 45-degree angle to the optical axis of the concave mirror, the observation window located at the center of the concave mirror, and the semi-transparent plane mirror arranged between the observation window and the concave mirror, in line with the real object. As a result, the illuminated object is partially reflected by the 45-degree tilted semi-transparent mirror to the concave mirror, which then returns the light through the semi-transparent mirror to the observation window. The observer then experiences the sensation of seeing the real object floating in front of the observation window.

[0005] The applicant has also proposed a device for projecting autostereoscopic images in document WO 2018 / 167410.

[0006] The device comprises a housing including a front wall and a rear wall connected to each other by an upper wall and a lower wall, the front wall comprising an opening forming a viewing window for an aerial virtual image of a digital autostereoscopic image.

[0007] The device also includes an optical system comprising at least one concave spherical mirror having an optical axis and a focal length F, with a radius of curvature C centered on the optical axis, wherein the optical system is arranged within the housing so as to be capable of directing at least a portion of received incident light to the observation window, thereby forming an aerial virtual image of the digital autostereoscopic image therein.

[0008] An autostereoscopic image is projected by an autostereoscopic image display screen having N viewpoints, the N viewpoints being superimposed with a cylindrical lens array forming an optical element for selecting the viewpoints of the digital autostereoscopic image to be projected, the optical element being housed in a housing opposite the spherical mirror at a distance substantially equal to twice the focal length F and being spaced apart from the optical axis of the spherical mirror and perpendicular to the optical axis at a distance at least equal to half the height of the display screen, wherein the height is defined along an axis perpendicular to the optical axis.

[0009] The device advantageously allows viewing of autostereoscopic images floating in space.

[0010] However, the inventors have attempted to improve the device, particularly for automotive applications facing space requirements and cost constraints.

[0011] Furthermore, the inventors have attempted to improve the quality of the autostereoscopic image as perceived by the observer. Summary of the Invention

[0012] It is an object of the present invention to provide a system for aerial virtual projection of autostereoscopic images which overcomes at least some of the disadvantages of known solutions.

[0013] It is also an object of the present invention, in at least one embodiment, to provide a projection system that conceals system components from an observer.

[0014] It is also an object of the present invention to provide, in at least one embodiment, a projection system whose components are arranged below the viewer's line of sight toward a viewing area of ​​an aerial virtual image.

[0015] It is also an object of the present invention, in at least one embodiment, to provide a system that can be seamlessly integrated into a motor vehicle for projecting driving information for use by the driver.

[0016] It is also an object of the present invention, in at least one embodiment, to provide a projection system that is compact and consists of a limited number of components.

[0017] It is also an object of the present invention, in at least one embodiment, to provide a projection system that offers a variety of configurations to accommodate various integration and usage constraints.

[0018] Finally, an object of the present invention is to provide a device for displaying driving information to a driver of a motor vehicle, comprising a projection system according to the invention.

[0019] To this end, the invention relates to a system for the aerial virtual projection of autostereoscopic images directed towards an observer whose eyes are located in a predetermined three-dimensional space, called the eye zone.

[0020] The system according to the invention is characterized in that the system comprises:

[0021] an optical device comprising at least one converging optical element acting like a concave mirror having a radius of curvature R and a focal length F, the optical device being arranged relative to the eye region so as to be capable of directing received light rays to an observation window observable from the eye region;

[0022] An autostereoscopic display screen arranged relative to the optical device so that the emitted light rays, after being reflected from the converging optical element and travelling a distance d equal to twice the focal length F, reach the viewing window, the screen comprising:

[0023] A pixel matrix with N rows and M columns, where each pixel is composed of multiple sub-pixels of different colors;

[0024] An array of lenses superimposed on a pixel matrix has a pitch P determined from a pitch P' (referred to as the nominal pitch) of an autostereoscopic screen (referred to as the nominal screen) using the formula P=P'.(1-C / (SM)), the autostereoscopic screen having the same usage characteristics as the screen of the system and intended to be observed by direct viewing at a distance corresponding to the usage distance of the screen of the system, wherein C is the number of viewpoint portions that are simultaneously visible from the usage distance within the eye zone when the nominal screen with pitch P' is arranged in the projection system instead of the screen, and S is the number of different viewpoints addressed by each pixel of the matrix.

[0025] Thus, the system according to the present invention implements a specific and specially designed autostereoscopic screen, the sole purpose of which is to allow the observation of a virtual reflection of an autostereoscopic image reflected by a converging optical element. This converging optical element is, for example, a concave mirror or a holographic optical element. This converging optical element functions similarly to a concave mirror. In the remainder of this specification, the term "concave mirror" is used primarily for ease of reading, but it should be understood that this concave mirror can be replaced by a holographic optical element without altering the technical effects of the present invention.

[0026] In particular, autostereoscopic screens designed for direct viewing are not suitable for use in devices for virtualizing a screen by reflecting the screen on a concave mirror.

[0027] In fact, such a device for virtualizing a screen must allow finding all the target characteristics in the main lobe of the screen (which specifies the space in front of the screen where the different viewpoints of the autostereoscopic image follow each other at a preferred distance for observing the screen, called the flattening distance and corresponding to the distance at which each eye of the observer perceives only one viewpoint on the entire screen surface), namely: the number of viewpoints, the flattening distance, and the distribution of the viewpoints on the pixel matrix. However, experience has shown that concave mirrors alter all these characteristics, so that autostereoscopic screens designed for direct viewing are rarely or unsuitable for use in devices implementing concave mirrors.

[0028] When the screen is placed in front of a concave mirror at twice the focal length or any other optical system operating in the same way (e.g. a holographic optical element with an active surface at least equal to that of the screen), a reflected image of the screen of the same size but inverted (with a scale of -1) is obtained in return.

[0029] The distortion introduced by the concave mirror requires new rules for defining the parameters of the lens array, which differ from those for the direct-viewing array. To ensure that the virtual copy reflected from the screen exhibits the desired autostereoscopic properties, the characteristics of the screen's lens array must be modified. The presence of the concave mirror alters all previously described parameters. To maintain the desired properties, the array pitch must be reduced by a proportion such that the screen is no longer observable through direct viewing. The inventors have successfully determined the level of pitch correction required for reflected viewing in a concave mirror.

[0030] According to the invention, the reduction in pitch is obtained based on the pitch P' of an autostereoscopic screen (referred to as the nominal screen) having the same usage characteristics as the system's screen but intended to be observed by direct viewing at a distance corresponding to the usage distance of the system's screen using the formula P=P'.(1-C / (SM)), wherein C is the number of viewpoint portions that are simultaneously visible from the usage distance within the eye zone when the nominal screen with pitch P' is arranged in the projection system instead of the screen, S is the number of different viewpoints of the image addressed by each pixel of the pixel matrix, and M is the number of pixels per row of the pixel matrix.

[0031] For example, for addressing sub-pixels based on a pixel matrix, where each pixel contains 3 sub-pixels of different colors, S is equal to 3. Therefore, the pitch P is obtained using the formula P=P'.(1-C / (3.M)).

[0032] If the same matrix is ​​used for integer pixel addressing, then S is equal to 1 and the pitch P is obtained using the formula P=P'.(1-C / M).

[0033] In the remainder of this specification, for ease of reading, addressing of sub-pixels and matrices (each pixel is formed by 3 sub-pixels) is considered, it being understood that the technical teachings provided are applicable, mutatis mutandis, to integer pixel addressing and / or matrices containing sub-pixels other than 3 sub-pixels.

[0034] For example, if a color table displayed on a nominal autostereoscopic screen is reflected in a concave mirror, the image reflected back from the color table exhibits a large number of color stripes for the initially selected flat rendering corresponding to the projection spacing, which is at least two or three lenses of the entire array relative to the screen.

[0035] For example, for a screen with five viewpoints, if the observer perceives five color bars on the screen at any distance from the screen, it means that these color bars have deviated from the flat rendering distance, so that the projection spacing has increased or decreased by 5 sub-pixels, which is the distance between the lenses. If the observer perceives 10 color bars, it means that the projection spacing has increased or decreased by 10 sub-pixels, or two lenses. If the screen displays a single color, it means that the observer is at the flat rendering distance.

[0036] As long as the pitch of the lens array of the nominal screen is known very accurately, for example to one hundredth of a micron, the effect of the concave mirror on the optical path connecting the actual screen surface and the user's eyes through the actual virtual conjugate image can be corrected by machining a new lens array with the corrected pitch.

[0037] As can be seen, this is equivalent to creating a flat rendering outside the projection device very close to the screen for direct viewing. Therefore, this is equivalent to significantly reducing the pitch of the lens array relative to direct viewing.

[0038] If a nominal screen with 5 viewpoints placed in a projection device allows viewing of 12 color bars at the expected 1 meter rendering distance, for example (assuming the screen displays 5 different colors, one for each viewpoint), the 12 color bars reflected in the concave mirror represent 12 / 5 of the lens pitch, since the pitch of the lenses corresponds to the 5 directly viewed colors. This value needs to be reduced by the lens array in order to adapt it to the device according to the invention and divided by the total number of lenses in order to calculate the precise incidence of the pitch to be applied to the machining of the lens array of the screen intended to be placed in the projection device.

[0039] This allows obtaining a system which, through the autostereoscopic images virtualized and reflected by the mirror, allows finding all the features provided in the central lobe.

[0040] For the first time, the pitch correction to be applied to a nominal autostereoscopic screen in order to integrate this screen into a device implementing a concave mirror can be determined simply by knowing the pitch of the nominal screen and determining the number of viewpoint portions that are simultaneously visible from the usage distance within the eye zone when this screen is accommodated in a device according to the invention.

[0041] As previously mentioned, determining the number of simultaneously visible viewpoint portions can be facilitated by displaying a color table on the screen, thereby simultaneously calculating the number of visible color bands from the eye zone corresponding to the screen usage distance.

[0042] Advantageously, according to the present invention, the system further comprises:

[0043] The housing comprises: an opaque front wall extending opposite to an observer; and an opaque upper wall connected to the front wall and extending parallel to a plane (referred to as a viewing plane), the upper wall being provided with an upper opening;

[0044] a front mirror, the front mirror being inclined at an angle α relative to the horizontal while extending at least partially above the upper opening, the mirror having a reflective surface facing the observer;

[0045] a converging optical element disposed at the bottom of the front mirror, facing the opening, and oriented with its reflecting surface toward the inclined front mirror extending above the upper opening, the optical axis of the converging optical element forming an angle δ' with the horizontal;

[0046] The autostereoscopic display screen is tilted at an angle θ relative to the vertical and is arranged below the opaque upper wall at a distance from the center of the image of the converging optical element formed by the tilted mirrors equal to the radius of curvature of the converging optical element;

[0047] The angles α, δ', and θ are related by the following relationship:

[0048] δ'=2.δ, where δ=45°-α;

[0049] θ=β, where β is the angle formed by the observer's gaze direction from the eye region toward the observation window and toward the reflection center of the concave mirror relative to the horizontal.

[0050] Thus, according to this advantageous variant, the system comprises an inclined planar front mirror extending at least partially above an opening in the wall, through which the light reflected by the converging optical element can pass in order to be reflected in the planar front mirror and form a virtual image of the image of the source of the light in the vicinity of a predetermined viewing area.

[0051] Furthermore, the volume occupied by the system is divided into two parts, one on each side of a median plane (called the horizontal plane).

[0052] The horizontal plane is defined by the upper wall of the system, which is preferably made of an opaque material and is perforated with an opening over which the mirror extends at least partially, tilted at an angle α relative to the horizontal.

[0053] According to one embodiment of the invention, the front mirror passes through the upper opening, thereby demarcating a mirror portion extending above the horizontal plane visible to an observer and a mirror portion extending below the horizontal plane hidden by the opaque wall of the housing.

[0054] According to the present invention, the top of the mirror is closer to the observer, while the bottom of the mirror is farther away from the observer. Other tilts are also possible depending on the application and integration constraints.

[0055] For example, the exposed portion of the mirror is the same size as the portion hidden below the horizontal plane.

[0056] A concave mirror (also known as a converging optic) is located at the bottom of the tilted mirror and is oriented with the concave and reflective surface facing upward, toward the upper opening in the upper wall.

[0057] Therefore, the concave mirror reflects in the portion of the inclined plane front mirror extending above the upper opening and forms a vertical image therein, just as if the concave mirror were placed vertically behind this portion.

[0058] An autostereoscopic screen is positioned below the upper wall, with its back facing the viewer, at a distance equal to the radius of curvature of the concave mirror from the center of the image formed by the tilted front mirror. The screen's upper edge is positioned adjacent to the upper wall, directly below it and hidden from the viewer. The screen is tilted at an angle θ relative to the vertical.

[0059] The image displayed by this screen is also visible on the other side of the horizontal plane, in the form of a conjugate image with a scale of -1. In fact, all the light rays emitted from the screen and hitting the image of the concave mirror are refocused at positions equidistant above the horizontal plane, thus forming a virtual conjugate image of the screen, but this virtual conjugate image is real in the optical sense and can be seen by an observer positioned in front of the device.

[0060] Light rays from the screen are reflected downward by the portion of the tilted flat front mirror that extends below the horizontal plane. They are then reflected upward by the concave mirror and reflected a second time by the visible portion of the tilted flat front mirror, directing them toward the observer's eye. The concave curvature of the mirror directs the light rays so that rays originating from a given point on the screen appear to intersect at the corresponding portion of the screen's conjugate image above the horizontal plane, creating the illusion that the rays actually emanated from that location. To an observer whose eye is positioned along the ray paths, these rays collectively form an image similar to the screen and its display, which would not be visible directly below the horizontal plane.

[0061] The autostereoscopic screen is equipped with a specific lens array, as previously described, so that the image visible to the observer retains the desired autostereoscopic parameters after reflection from the concave mirror. The pitch of the lens array is adjusted relative to the pitch of the screen when viewed directly without reflection from the concave mirror to compensate for the change in apparent pitch after reflection from the concave mirror or even after transmission through a converging optical element (whether a lens with the same radius and focal length, or even a holographic optical element). More specifically, the conic perspective generated by reflection or transmission through the converging optical element changes the perceived pitch. By correcting for the pitch, the device allows the display of three-dimensional images above the horizontal plane, just as an autostereoscopic screen would when viewed directly.

[0062] From the eye zone and near the viewing window, the observer perceives an aerial virtual relief image without the need to observe converging optics or a screen located below the horizontal plane.

[0063] Advantageously, according to the invention, the angle α is 36°, the angle β is 20°, the angle δ′ is 18°, and the angle θ is 20°.

[0064] According to this advantageous variant, these angles are determined so that an observer whose gaze axis towards the projection area forms an angle of 20° with respect to the horizontal can perceive an autostereoscopic image with a mirror inclined at 36° with respect to the horizontal (corresponding to the standard inclination of a windshield of a motor vehicle).

[0065] Thus, the device according to this variant can be integrated into a motor vehicle in order to ensure the aerial virtual projection of an autostereoscopic image for the driver.

[0066] If applicable, the tilting mirror is formed by a windshield of a motor vehicle and the opaque upper wall of the housing is formed by a portion of the frontal area of ​​the vehicle.

[0067] Of course, the system according to the invention can be used for other applications, the angle value is not set and can be varied according to the conditions of use and the application, in order to maintain the same result.

[0068] The present invention also relates to a display device for driving information of a motor vehicle, comprising a windshield, a steering wheel, and a front dashboard extending between the windshield and the steering wheel, characterized in that the display device comprises a projection system according to the present invention, wherein the tilting mirror is formed by the windshield, the opaque wall is formed by the front dashboard, the front dashboard comprises an opening for forming an upper projection opening for an autostereoscopic image, wherein a converging optical element and an autostereoscopic screen are accommodated below the front dashboard, so that a vehicle driver sitting in front of the windshield can view the driving information by means of an aerial virtual projection of the autostereoscopic image displayed on the display screen in a predetermined projection area, the predetermined projection area extending above the front dashboard.

[0069] Thus, according to the present invention, the frontal area of ​​the motor vehicle acts as the upper wall and extends along the horizontal plane, with the windshield acting as a tilted front mirror (under certain conditions, such as the angle, shape, and any surface treatment relative to the vertical). The frontal area of ​​the motor vehicle is the substantially flat space between the vehicle dashboard and the windshield. This space can therefore usefully serve as the opaque upper portion extending along the horizontal plane of the system according to the present invention. If the curvature of the windshield is sufficiently uniform and homogeneous, it can complement the concave curvature of the main mirror, which needs to be adjusted to take this into account.

[0070] Light from the autostereoscopic screen is reflected by the section of the windshield below the opening in the instrument panel. The screen needs to be slightly tilted so that its conjugate image is orthogonal to the gaze axis to avoid keystone distortion. The light is then reflected downward onto a concave mirror and then onto the section of the windshield above the opening in the instrument panel, directing the light toward the eye area.

[0071] According to an advantageous variant, the windshield is tilted 36° relative to the horizontal, and the concave mirror is tilted 20° relative to the vertical, so as to provide an upright image, seen as a reflection in the windshield, to an observer whose gaze axis forms an angle of approximately 20° with the desired projection area of ​​the spatial virtual image. The critical parameter is the actual verticality of the concave mirror image in the reflected portion of the windshield. Slight variations in the position and angles of all components reconstruct the position, size, and tilt of the virtual image of the screen, positioned directly above the horizontal plane.

[0072] Thus, according to this alternative embodiment, a projection system allows information on the dashboard (e.g., speedometer, navigation information, GPS, etc.) to be projected to the viewer's eyes by displaying it on an autostereoscopic screen. This information is then projected to the driver's eyes through the windshield and a concave mirror. The system according to this variant benefits from the presence of a windshield and uses the lower, usually opaque portion of the windshield to create a front mirror. The windshield may need to be treated to provide this reflective function.

[0073] Advantageously, according to the invention, the concave mirror has a radius of curvature of 300 mm and a focal length of 150 mm.

[0074] Of course, other mirrors may be used without compromising the principles of the present invention.

[0075] The invention also relates to a method for generating a system for aerial virtual projection of an autostereoscopic image directed to an observer whose eyes are located in a predetermined three-dimensional space, called the eye zone, comprising the following steps:

[0076] Selecting an autostereoscopic screen, which is referred to as a nominal screen, having predetermined usage characteristics and formed by a pixel matrix of N rows and M columns and a stacked lens array with a predetermined pitch P';

[0077] Arranging a nominal screen in a projection system, the projection system including a converging optical element acting like a concave mirror having a radius R and a focal length F, the converging optical element being arranged relative to the eye region so as to be capable of directing received light rays to a viewing window observable from the eye region, the nominal screen being arranged relative to the converging optical element so that emitted light rays, after reflection from the converging optical element, are capable of reaching the viewing window, wherein a distance d traveled by the light rays is equal to twice the focal length F;

[0078] Displaying the color table on a nominal autostereoscopic screen;

[0079] Calculate the number C of colors that are simultaneously observed within the eye region from the use distance;

[0080] Manufacturing an autostereoscopic screen, which is called a dedicated screen, having the same predetermined usage characteristics as the nominal screen and a lens array with a pitch P calculated by the formula P=P'.(1-C / (SM)), where S is the number of different viewpoints addressed by each pixel of the matrix;

[0081] Replace the nominal screen with a dedicated screen.

[0082] The advantages and technical effects of the projection device according to the present invention apply mutatis mutandis to the method for developing an aerial virtual projection system according to the present invention.

[0083] The present invention also relates to a system for aerial virtual projection of autostereoscopic images and a device for displaying driving information of a motor vehicle, the common features of the system and the device being all or part of the features described above or below. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] Other objects, features and advantages of the present invention will become apparent on reading the following description, which is given by way of non-limiting example only and with reference to the accompanying drawings, in which:

[0085] Figure 1 is a schematic diagram of a projection system according to a first embodiment of the present invention;

[0086] Figure 2 is a diagram of a display device for driving information of a motor vehicle according to one embodiment of the present invention;

[0087] Figure 3 is a schematic diagram of an autostereoscopic screen of a projection system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0088] Throughout the drawings, strict adherence to scale and proportion is not required for the sake of illustration and clarity.

[0089] The same reference numbers are used throughout the drawings to designate the same, similar or like elements.

[0090] The embodiments described with reference to the drawings relate to displaying autostereoscopic images.

[0091] Figure 1 A system according to an embodiment of the invention is schematically shown, which is intended to be integrated inside a motor vehicle, such as Figure 2 Shown schematically.

[0092] exist Figure 1 In the figure, the dotted lines represent the paths of the light rays and the image and the conjugate image of the concave mirror.

[0093] The system comprises an opaque housing 30 comprising an upper wall 20 provided with an opening 22 through which an inclined front mirror 10 extends.

[0094] The front mirror 10 is tilted at an angle α relative to the horizontal. The mirror 10 has a reflecting surface facing an observer. The observer is located on the right side of the device and is looking at a predetermined projection area 18.

[0095] The front mirror 10 defines a mirror portion extending above a horizontal plane that is visible to an observer and a mirror portion extending below the horizontal plane that is concealed by the housing 30 .

[0096] The system further comprises a concave mirror 14 which is arranged at the bottom of the front mirror 10 , facing the opening 22 , and oriented with its concave and reflecting surface facing the inclined front mirror 10 .

[0097] For example, the radius of this concave mirror is 300 mm, the focal length is 150 mm, and the useful area is 150 mm, i.e. F / 1. The optical axis of the mirror forms an angle δ' with the horizontal.

[0098] The system further comprises a display screen 16 for displaying an autostereoscopic image tilted by an angle θ relative to vertical.

[0099] The screen is arranged below the opaque upper wall at a distance from the center of the image of the concave mirror formed by the inclined mirror equal to the radius of curvature of the concave mirror 14 .

[0100] The inclination of the screen 16 must allow the emitted light rays to reach the inclined plane mirror 10 so that they can be reflected downwards to the concave mirror 14 .

[0101] The screen is equipped with an array of lenses with a defined spacing to compensate for the apparent changes in the light after reflection from the concave mirror.

[0102] Figure 3 An autostereoscopic screen 16 is schematically shown, comprising a matrix of pixels 16a arranged in rows and columns, each pixel consisting of a plurality of sub-pixels of different colors, each sub-pixel being assigned to a viewpoint of the autostereoscopic image to be displayed. The screen also includes a lens array 16b superimposed on the matrix 16a. Each lens is tilted at a non-zero angle (e.g., 18°) relative to the column direction of the matrix. According to other embodiments, a vertical array may also be used.

[0103] As mentioned before, nothing prevents using pixel addressing of image viewpoints.In the remainder of this specification, sub-pixel addressing of a pixel formed by three sub-pixels with different colors (ie S equals 3) is considered.

[0104] The pitch P of the array 16b of screens 16 is determined based on the pitch P' (referred to as the nominal pitch) of an autostereoscopic screen (referred to as the nominal screen) having the same usage characteristics as the system's screens and intended to be observed by direct viewing at a distance corresponding to the usage distance of the system's screens using the formula P=P'.(1-C / (3.M)), where C is the number of viewpoint portions that are simultaneously visible from the usage distance within the eye zone when the nominal screen with pitch P' is arranged in the projection system instead of the screen, and M is the horizontal resolution of the pixel matrix.

[0105] For example, consider a 5-inch screen with five viewpoints and a resolution of 800 × 480. The screen is placed 300 mm from the concave mirror, shaped like a square with sides of 150 mm, a focal length of 150 mm, and a radius of curvature of 300 mm. Once placed in the system, the observer can see 12 color bars from the eye zone (assuming the screen displays one color per viewpoint). Since the lens spacing corresponds to the five directly visible colors, the 12 color bars reflected in the concave mirror represent 12 / 5 of the lens spacing.

[0106] With each sub-pixel displaying one image viewpoint, the number of lenses in the array of the screen under consideration is equal to (800 pixels x 3) / 5, or 480 lenses.

[0107] Therefore, the total pitch correction is equal to 12 / 5 = 2.4 lenses.

[0108] This corresponds to a lens correction equal to 2.4 / 480 = 0.005.

[0109] In other words, the lens spacing must be reduced by 0.5%.

[0110] If the known lens pitch P' is 0.270 mm, the necessary pitch correction is equivalent to removing 0.00135 mm from each lens.

[0111] Although the value of 1.35 microns seems relatively small, it is actually quite large for optimal viewing of autostereoscopic images reflected in concave mirrors. This correction is crucial in order to be able to use autostereoscopic screens that reflect in concave mirrors.

[0112] exist Figure 1 In the embodiment, the angle α is 36°, the angle β is 20°, the angle δ' is 18°, the angle δ is 9°, and the angle θ is 20°.

[0113] Figure 2 Schematic diagram of the vehicle integrated Figure 1A system is provided to form a display device for driving information of a motor vehicle, the motor vehicle including a windshield 100, a steering wheel 110, and a front instrument panel 200 extending between the windshield 100 and the steering wheel 110.

[0114] The windshield 100 forms a tilted mirror of the projection system and the front dashboard 200 forms an opaque upper wall of the projection system.

[0115] The front panel 200 includes an opening 220, a concave mirror ( Figure 2 Light projected through the opening (not shown) is reflected in the windshield 100.

[0116] The windshield 100 extends above the opening to receive the light projected by the concave mirror therein.

[0117] Furthermore, the autostereoscopic screen (not shown) must be tilted so that the light emitted therefrom can be reflected in the windshield.

[0118] For example, the windshield is tilted 36° (α=36°) relative to the horizontal, the optical axis of the concave mirror is tilted 18° relative to the horizontal, and the autostereoscopic screen is tilted 20° (θ=20°) relative to the vertical, so that a driver whose line of sight is at an angle of 20° (β=20°) relative to the horizontal can see the image of the screen near a predetermined viewing area extending above the front of the vehicle.

[0119] It is easy for those skilled in the art to understand that Figure 1 In the described configuration, the autostereoscopic screen and concave mirror of the projection system are housed in a housing arranged below the front instrument panel 200 .

[0120] Therefore, the vehicle driver can see the driving information projected from the autostereoscopic display screen to a predetermined projection area extending above the front instrument panel 200 between the windshield 100 and the driver.

[0121] 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 herein, or to arrange the screen at a different distance from the theoretical distance of the concave mirror.

[0122] For example, if the distance from the screen to the reflecting center of the concave mirror is less than or greater than twice the focal length of the concave mirror, the system can still allow viewing of autostereoscopic images, but the actual virtual image will be closer (or farther) from the observer by enlarging (or shrinking).

[0123] It is also possible to actively change the value of θ by accepting that small trapezoidal distortions are encountered in the image in order to correct the vertical impression of the image on the screen, for example to display objects in an orientation consistent with the surface of the dashboard. Therefore, for some applications, an angle θ of 12° can be selected instead of the theoretical angle of 20°.

Claims

1. A system for aerial virtual projection of autostereoscopic images directed toward an observer whose eyes are located within a predetermined three-dimensional space called an eye zone, characterized in that the system comprises: an optical device comprising at least one converging optical element (14) acting like a concave mirror having a radius of curvature R and a focal length F, said optical device being arranged relative to said eye region so as to be capable of directing received light rays to an observation window observable from said eye region; An autostereoscopic display screen (16) is arranged relative to the optical device so that the emitted light rays can reach the observation window after being reflected on the converging optical element (14) and traveling a distance d equal to twice the focal length F, the screen comprising: A pixel matrix with N rows and M columns, where each pixel is composed of multiple sub-pixels of different colors; A lens array superimposed on the pixel matrix has a pitch P determined from a pitch P', called nominal pitch, of an autostereoscopic screen, called nominal screen, using the formula P=P'.(1-C / (SM)), the autostereoscopic screen having the same usage characteristics as the screen of the system and intended to be observed by direct viewing at a distance corresponding to the usage distance of the screen of the system, wherein C is the number of viewpoint portions that are simultaneously visible from the usage distance within the eye zone when the nominal screen with pitch P' is arranged in the projection system instead of the screen, and S is the number of different viewpoints addressed by each pixel of the matrix.

2. The system according to claim 1, wherein: The system further comprises: A housing (30) comprising: an opaque front wall (20) extending opposite to the observer, and an opaque upper wall connected to the front wall and extending parallel to a plane referred to as a viewing plane, the upper wall being provided with an upper opening (22); a front mirror (10) tilted at an angle α relative to the horizontal and extending at least partially above the upper opening (22), the front mirror having a reflective surface facing the observer; Its characteristics are: The converging optical element (14) is arranged at the bottom of the front mirror, facing the opening (22), and oriented with its reflecting surface toward the inclined front mirror (10) extending above the upper opening, the optical axis of the converging optical element forming an angle δ' with the horizontal; The autostereoscopic display screen (16) is tilted at an angle θ relative to the vertical and is arranged below the opaque upper wall (20) at a distance from the center of the image of the converging optical element formed by the tilted front mirror equal to the curvature radius of the concave mirror; The angles α, δ' and θ are related by the following relationship: δ'=2.δ, where δ=45°-α; θ=β, where β is the angle formed by the observer's gaze direction from the eye region toward the observation window and toward the reflection center of the converging optical element relative to the horizontal.

3. The system according to claim 2, characterized in that The front mirror (10) is inclined at an angle α relative to the horizontal through the upper opening (22), thereby demarcating a mirror portion extending above the horizontal plane visible to the observer and a mirror portion extending below the horizontal plane hidden by the opaque wall of the housing.

4. The projection system according to claim 2 or 3, characterized in that: The angle α is 36°, the angle β is 20°, the angle δ′ is 18°, and the angle θ is 20°.

5. The projection system according to any one of claims 1 to 4, characterized in that The converging optical element is a concave mirror or a holographic optical element.

6. The projection system according to claim 5, wherein: The converging optical element is a concave mirror (14) with a curvature radius of 300 mm and a focal length of 150 mm.

7. A display device for driving information of a motor vehicle, comprising a windshield (100), a steering wheel (110), and a front instrument panel (200) extending between the windshield (100) and the steering wheel (110), characterized in that: The display device comprises a projection system according to any one of claims 2 to 4, wherein the inclined front mirror is formed by the windshield, the opaque wall is formed by the front dashboard, the front dashboard comprises an opening (220) for the upper projection opening for forming the autostereoscopic image, wherein the converging optical element and the autostereoscopic screen are accommodated below the front dashboard so that a vehicle driver sitting in front of the windshield can view driving information by means of an aerial virtual projection of the autostereoscopic image displayed on the display screen in a predetermined projection area, the predetermined projection area extending above the front dashboard.

8. A method for generating a system for aerial virtual projection of an autostereoscopic image directed to an observer whose eyes are located in a predetermined three-dimensional space called an eye zone, the method comprising the steps of: selecting an autostereoscopic screen, which is referred to as a nominal screen, has predetermined usage characteristics and is formed by a pixel matrix of N rows and M columns and a stacked lens array with a predetermined pitch P'; arranging the nominal screen in a projection system, the projection system comprising a converging optical element acting like a concave mirror having a radius R and a focal length F, the converging optical element being arranged relative to the eye zone so as to be capable of directing received light rays to an observation window observable from the eye zone, the nominal screen being arranged relative to the converging optical element so that emitted light rays, after being reflected on the converging optical element, are capable of reaching the observation window, wherein the distance d traveled by the light rays is equal to twice the focal length F; displaying a color table on the nominal autostereoscopic screen; Calculating the number C of colors simultaneously observed within the eye region from the usage distance; manufacturing an autostereoscopic screen, referred to as a dedicated screen, having the same predetermined usage characteristics as the nominal screen and a lens array with a pitch P calculated by the formula P=P'.(1-C / (SM)), where S is the number of different viewpoints addressed by each pixel of the matrix; The nominal screen is replaced with the dedicated screen.

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