Device for displaying a first image and a second image in an individual's field of vision

Abstract

The invention relates to a device (100) for displaying a first image and a second image in the field of vision of an individual, said device (100) comprising: - a polarized display element (10); - a first reflective element (30); - a second reflective element (50), characterized in that the polarized display element (10) is configured to emit at least two polarized light beams (2, 3), said device (100) comprising a semi-reflective plate (70) positioned in the optical path of the at least two light beams (2, 3) and having at least one face (71, 72) configured to reflect one of the at least two light beams (2, 3) and transmit the other light beam (2, 3), said semi-reflective plate (70) being arranged to display a first image at a first projection distance and a second image at a second projection distance. Figure for the abstract: Fig. 1

Description

Title of the invention: Device for displaying a first image and a second image in the field of vision of an individual. Technical field of the invention

[0001] The present invention relates generally to a device for displaying a first image and a second image in the field of vision of an individual. State of the art

[0002] Devices are known for displaying a real or virtual image to a user viewing a semi-reflective plate. These devices rely on the Pepper's ghosting effect. Typically, the position of the reflective surfaces allows an image to be projected in front of or behind the semi-reflective plate, creating an impression of depth for a person viewing the semi-reflective plate.

[0003] These devices are functional but do not allow the simultaneous display of a projected image seen by a user looking at the semi-reflective blade upstream of the reflective surface and an image seen behind the reflective surface. Furthermore, they do not allow the content of these two images to be superimposed.

[0004] The invention aims to remedy at least one of the aforementioned drawbacks. Presentation of the invention

[0005] In order to overcome the aforementioned drawbacks of the prior art, the present invention proposes a device for displaying a first image and a second image in the field of vision of an individual, said device comprising: - a polarized display element; - a first reflective element comprising a mirror and a quarter-wave plate; - a second reflective element comprising a reflective surface and a quarter-wave plate, characterized in that the polarized display element is configured to emit at least two polarized light beams, each having a defined polarization in a polarization plane, the polarization plane of one of the at least two light beams being orthogonal to the polarization plane of the other light beam. The device further comprises a semi-reflective blade positioned in the optical path of at least two light beams and having at least one face configured to reflect one of the at least two light beams and transmit the other light beam according to the polarization plane of said at least two light beams, said semi-reflective blade being further arranged to display a first image at a first projection distance from one of the at least two light beams and a second image at a second projection distance from the other light beam said first reflective element and said second reflective element each being configured to reflect at least one of the light beams towards the semi-reflective blade.

[0006] Thanks to the invention, beams having orthogonal polarization planes propagate in the device. Each of the two types of beams makes it possible to project an image at a different projection distance.

[0007] According to the device described in this disclosure, it is therefore possible to project two images at two different projection distances by manipulating the polarization planes of the light beams. These two images projected at two different projection distances make it possible to create depth effects and potentially 3D effects.

[0008] To this end, the invention relies in particular on controlling the polarization of light, in which the light is controlled by the elements of the device according to the invention. This polarization control in the device according to the invention is simple to implement because it is based on optical components that can be integrated into pre-existing state-of-the-art devices and on elements that are readily available commercially. Consequently, the device according to the invention is simple to implement and inexpensive.

[0009] In one embodiment, the at least two light beams have linear polarization. This improves the ease of controlling the polarization in the device according to the invention.

[0010] In one embodiment, the semi-reflective blade includes another face configured to reflect one of the at least two polarized light beams and transmit the other polarized light beam according to the plane of polarization of said at least two light beams.

[0011] In one embodiment, the semi-reflective blade is inclined at 45 degrees in absolute value with respect to an emission axis of the display element. Such an arrangement optimizes the integration of the device into other elements, for example a vehicle dashboard, since it allows for consideration of vehicle layout constraints while limiting the thickness of the semi-reflective blade.

[0012] In one embodiment, the reflective surface of the second reflective element includes a retroreflector or a mirror.

[0013] In one embodiment, the display element comprises a polarized screen configured to emit an initial polarized beam comprising initial light rays, each defined in a plane of polarization, the plane of polarization of the rays Since the initial light rays are parallel to each other, the polarized display element further comprises a half-wave plate positioned on the optical path of at least one of the initial light rays of the initial polarized beam to modify the orientation of the polarization plane of said at least one light ray in order to provide at least two light beams at the output of the display element. This embodiment allows for static control of the polarization, which improves the simplicity of implementation of the device according to the invention and reduces its cost.

[0014] In one embodiment, the display element comprises: - a polarized screen configured to emit an initial light beam comprising initial polarized light rays, each defined in a plane of polarization, the plane of polarization of the initial light rays being parallel to each other, - at least one liquid crystal cell positioned in the optical path of at least one of the initial light rays of the initial beam and configured to control the orientation of the polarization plane of at least one of the light rays. Such an embodiment allows for dynamic polarization control.

[0015] According to this embodiment, the liquid crystal cell is positioned along the optical path of all the rays of the initial polarized beam. The display element further comprises a control circuit for the liquid crystal cell configured to emit at least one control signal having two alternating states: a high state in which the liquid crystal cell is activated to control the emission by the display element of one of the at least two light beams, and a low state in which the liquid crystal cell is not activated to control the emission by the display element of the other light beam. This operation is thus based on time-division multiplexing, the principle of retinal persistence, and the operating principle of active liquid crystal cells. The advantages of this device will be explained in the accompanying figures.

[0016] In this embodiment, the control signal has a duty cycle of 50%.

[0017] In this embodiment, each control signal can have a frequency, said screen having a display frequency equal to twice the frequency of the control signal.

[0018] In this embodiment, wherein the frequency of each high and low state is greater than or equal to 50 Hz.

[0019] In one embodiment, the display element comprises a liquid crystal cell having different activation zones controlled by a control circuit, each activation zone being positioned on the optical path of one of the initial light rays of the initial beam, said control circuit being configured to emit a control signal per activation zone, each signal of command having two states, a high state in which the given activation zone is activated so as to control the emission in the given activation zone of one of the at least two light beams and a low state in which the activation zone is not activated so as to control the emission in said activation zone of the other light beam, at least two activation zones of the liquid crystal cell being controlled by a control signal having different states to control the simultaneous emission of the at least two light beams.

[0020] In this embodiment, the polarized screen may have pixels, each pixel being configured to emit an initial light beam, each activation zone being associated with a pixel and having a size equivalent to that of the given pixel.

[0021] In this embodiment, for each control signal, the state of the given control signal can be continuous.

[0022] In this embodiment, each control signal can have alternating high and low states defined by a duty cycle, the duty cycle of the at least two activation zones controlled by a different control signal being identical.

[0023] The other embodiments listed above are also applicable to this embodiment.

[0024] Of course, the various features, variants, and embodiments of the invention can be combined with one another in various ways, provided they are not incompatible or mutually exclusive. Detailed description of the invention

[0025] The following description with regard to the attached drawings, given by way of non-limiting examples, will make it clear what the invention consists of and how it can be carried out.

[0026] On the attached drawings:

[0027] [Fig. 1] is a schematic representation of a first embodiment of a device according to the present invention in a top view plane;

[0028] [Fig.2] is a schematic representation of a first example of a display element of the device according to the first embodiment in a top view plane;

[0029] [Fig.3] is a first example of a first image and a second image displayed by the first embodiment of the device in [Fig.1];

[0030] [Fig.4] is a second example of a first image and a second image displayed by the first embodiment of the device in [Fig.1];

[0031] [Fig.5] is a schematic representation of a second example of a display element of the device according to the first embodiment in a view plane of above ;

[0032] [Fig.6] is an example of a control signal for the display device according to the second example;

[0033] [Fig.7] is a schematic representation of a third example of an element display of the device according to the first embodiment in a top view plane;

[0034] [Fig.8] is an example of control signals for the display device according to the third example;

[0035] [Fig.9] is a schematic representation of a second embodiment of a device according to the present invention in a top view plane.

[0036] [Fig. 10] is a schematic representation of a third embodiment of a device according to the present invention in a top view plane Variants;

[0037] [Fig. 11] is a schematic representation of different embodiments of dis positives according to the present invention in top-view planes. These different devices are numbered by the letters A to F.

[0038] A first embodiment of a device 100 for displaying a first image and a second image in the field of view of an individual according to the present disclosure will be described with the aid of [Fig.1], [Fig.2], [Fig.3] and [Fig.4].

[0039] The device 100 illustrated in [Fig.1] comprises a display element 10, 20, a first reflective element 30, a second reflective element 50 and a semi-reflective blade 70.

[0040] The display element 10 is configured to emit at least two light beams, here two light beams 2, 3.

[0041] In this disclosure, the two light beams 2 and 3 are polarized beams, each with a plane of polarization. In this example, the plane of polarization of beam 2 is orthogonal to the plane of polarization of the other beam, 3. A plane of polarization is defined as a plane in which the electric field of the light beam propagates; that is, the plane in which the direction and magnitude of the electric field of the light beam are defined. This plane of polarization is perpendicular to the direction of propagation of the light beam.

[0042] Advantageously, the two light beams 2, 3 exhibit linear polarization. To this end, the light beam 2 illustrated in [Fig. 1] has s-polarization (or s-type polarization), also known as perpendicular polarization, defined in a polarization plane perpendicular to the direction of propagation, and the light beam 3 has polarization oriented perpendicular to beam 2, that is, p-polarization (or p-type polarization), also known as parallel polarization, and also defined in a polarization plane oriented parallel to the direction of propagation. Of course, in a variant of device 100, the light beam 2 may have a p-type polarization while the light beam 3 may have an s-type polarization.

[0043] A first example of the display element 10 that can be used in the device 100 will now be described using [Fig.2].

[0044] As illustrated in [Fig. 2], the display element 10 comprises a screen 11. The screen 11 is a polarized screen, that is, it is adapted and / or arranged to emit a polarized beam, referred to hereafter as the initial beam. Here, the initial beam is understood to be the total luminous flux capable of being emitted by the polarized screen 11. To this end, the initial polarized beam comprises initial light rays emitted by the screen 11. Typically, the initial light rays correspond to the rays emitted by pixels of the polarized screen 11.

[0045] For readability reasons, only two initial light rays 12, 13 of the polarized beam are illustrated in the example shown in [Fig.2].

[0046] Since the screen 11 is polarized, the initial light rays 12, 13 are polarized. Typically, in this example, the initial light rays 12, 13 are each defined in a plane of polarization. In particular, in this example, all the initial light rays 12, 13 have a similar polarization.

[0047] By way of non-limiting example, the initial light beams 12, 13 exhibit linear polarization. For this purpose, the initial light beams may exhibit s-type or p-type polarization. In this example, the initial light beams exhibit p-type polarization.

[0048] The display device 10 also includes a half-wave plate 14 positioned in the optical path of at least one of the initial light rays emitted by the screen 11. The half-wave plate 14 has a fast axis and a slow axis. In this example, the fast axis of the half-wave plate 14 is angularly offset from the plane of polarization of the incident light beam by an angle theta (by rotating the half-wave plate 14 with respect to the direction of propagation of the incident light beam). The half-wave plate 14 is specifically configured to rotate the plane of polarization of the initial light ray passing through it around the propagation axis of the light ray in question by an angle equal to twice the angle theta. Thus, in this example, theta can be 45 degrees (°), the initial (or incident) light beam passing through the half-wave plate having, at the exit of the half-wave plate 14, a polarization rotated by 90°.Therefore, in this example, an initial light ray passing through the half-wave plate 14 is transmitted but has its plane of polarization rotated by 90°.

[0049] In the following, any outgoing polarization rotated, with respect to the incident polarization, by an angle equal to two thetas is considered to have passed from type p to s polarization or vice versa from type s to p.

[0050] Thus, for an initial light ray exhibiting an s-type polarization, this polarization is modified into a p-type polarization at the output of the half-wave plate 14 and conversely for an initial light ray exhibiting a p-type polarization, this polarization is modified into an s-type polarization at the output of the half-wave plate 14.

[0051] Similarly, the half-wave plate 14 also acts on the phase of the incident light ray. It is also configured to phase-shift the phase of the incident beam passing through it by 180° (typically introducing a delay of X / 2).

[0052] In the example illustrated in [Fig. 2], the half-wave plate 14 is positioned in the optical path of the initial light ray 12. Thus, since the initial light ray 12 emitted by the screen 11 (i.e., before entering the half-wave plate 14) has a p-type polarization, the initial light ray 12 has an s-type polarization at the output of the half-wave plate 14. The initial ray 12 supplied at the output of the half-wave plate 14 is called (or becomes) light beam 2.

[0053] Conversely, the initial light ray 13 does not pass through the half-wave plate 14. Consequently, the p-type polarization of the initial light ray 13 is preserved (i.e., not modified). The initial light ray 13 exiting the display element 10 is then called the light beam 3.

[0054] The display element 10 has an AL emission axis

[0055] By emission axis Al of the display element 10, we mean an axis tangent to a plane of a surface of the display element 10 through which the initial light rays are emitted. Here, typically, the emission axis Al of the display element 10 corresponds to the emission axis of the screen 11, i.e., an axis tangent to the surface of the screen 11 (considered to be planar or having at least a planar part).

[0056] Such an embodiment of the display element provides static control of the polarization of the initial light rays emitted by the screen 11. This control is simple to implement and inexpensive. This effect can also be achieved by surface treatments or retardant films (laminated onto the surface, for example).

[0057] The light beams 2, 3 emitted by the polarized display element 10 propagate in the direction of the semi-reflective blade 70.

[0058] In the present disclosure, the semi-reflective plate 70 is positioned in the optical path of the two light beams 2, 3. The semi-reflective plate has two faces 71, 72, a first face 71 oriented towards the display element 10, 70 and a second face 72, opposite the first face 71 and oriented towards the first reflective element 30 and / or towards the second reflective element (here also towards the second reflective element). As will be explained below, the semi-reflective plate is inclined in absolute value with respect to the display element, with respect to the first reflective element (30) as well as with respect to the second reflective element.

[0059] As illustrated in [Fig.1], the semi-reflective blade 70 is, in this example, inclined with respect to an emission axis Al of the display element 10. Here, typically, the semi-reflective blade 70 is inclined at 45 degrees in absolute value with respect to the emission axis Al of the display element 10, 20.

[0060] In the present disclosure, at least one of the surfaces 71, 72 is configured to reflect one of the at least two light beams 2, 3 and transmit the other light beam 2, 3 according to the polarization plane of said at least two light beams 2, 3.

[0061] In practice in this example, the first face 71 and the second face 72 are configured to transmit at least one of the two light beams and transmit the other light beam according to the polarization plane of said at least two light beams.

[0062] In practice, in this example, the semi-reflective plate 70 (here the two faces 71, 72) is configured to reflect light beams of p-polarization and to transmit light beams of s-polarization. Thus, as illustrated in [Fig. 1], the light beam 3 (of p-polarization) is reflected by the semi-reflective plate 70 (here via the first face 71) and the light beam 2 (of s-polarization) is transmitted by the semi-reflective plate 70 (here via the first 71 and the second face 72 of the semi-reflective plate 70). Of course, in an alternative embodiment, the semi-reflective plate 70 can be configured to reflect light beams of s-polarization and to transmit light beams of p-polarization.

[0063] In this example, the first face 71 of the semi-reflective plate 70 reflects the light beam 3 of p polarization, typically into the field of view of an individual looking at the semi-reflective plate 70. Thus, the light beam 3 after its reflection on the first face 71 of the semi-reflective plate exits the device 100 to propagate into the field of view of the individual.

[0064] In the present disclosure, the set of light beams 3 reflected (here, all the p-polarized light beams emitted by the display element 10) by the first face 71 of the semi-reflective plate 70 creates a first image that is viewable by an individual looking at the semi-reflective plate 70. In particular, here, the first image is seen behind the second face 72 of the semi-reflective plate 70. Thus, the first image corresponds to a ghost of Pepper. It is understood here that the term "behind" the semi-reflective plate is defined according to the direction of the gaze of an individual looking at the semi-reflective plate. In this example, the first image is oriented towards the side of the second face 72, that is to say, positioned between the semi-reflective plate 70 and the second reflecting element 50.

[0065] Conversely, the first face 71 and the second face 72 of the semi-reflective blade 70 transmit the light beam 2 of polarization s. Thus, the light beam 2 of polarization s passes through the semi-reflective plate 70 without being deviated and reaches in this example the first reflective element 30.

[0066] In this example, the first reflective element 30 includes at least one normal vector ni parallel to the emission axis Al of the display element 10. Thus, in this configuration, the semi-reflective blade 70 is inclined at 45 degrees in absolute value with respect to the normal vector ni of the first reflective element 30.

[0067] The first reflective element 30 comprises a mirror 31. Typically, the mirror 31 has an optical axis 01 aligned with at least one normal vector ni of the first reflective element 30. Here, in this example, the mirror 31 is configured to reflect light beams (here of visible light) according to Snell's law.

[0068] The first reflective element 30 also includes a quarter-wave plate 32 positioned upstream of the mirror 31 with respect to the optical path of the light beam 2 passing through the semi-reflective plate 70.

[0069] In this example, the quarter-wave plate 32 of the first reflective element 30 is located between the semi-reflective plate 70 and the mirror 31 of the first reflective element 30 and / or is parallel to the mirror 31 (here it is positioned parallel to the mirror 31 of the first reflective element 30).

[0070] Typically, the quarter-wave plate 32 is configured to extend along an elongation axis B1 orthogonal to the normal vector ni so as to completely cover the mirror 31. Such a configuration allows the quarter-wave plate 32 to be positioned on the optical path of all the light rays reflected by the mirror 31.

[0071] As with the half-wave plate 14, the quarter-wave plate 32 has a slow axis and a fast axis. In practice, the fast axis of the quarter-wave plate 32 is angularly shifted by an angle alphal from the plane of polarization of the light beam incident on this plate.

[0072] The quarter-wave plate 32 is configured to introduce a 90° phase shift on the light wave of the light beam passing through it (causing a delay of X / 4), which allows the polarization of the light beam 2 to be modified. Typically, this allows it to change from linear polarization to elliptical or circular polarization depending on the orientation of the fast axis of the quarter-wave plate 32 (in particular, the orientation of its fast axis relative to the polarization plane of the beam incident on this plate). Thus, in this example, the light beam 2, having an s polarization, passes through the semi-reflecting plate 70, and then through the quarter-wave plate 32. At the output of the quarter-wave plate 32, the polarization of the light beam 2 changes from linear polarization to elliptical or circular polarization. For example, if the angle alphal is 45°, the linearly polarized light beam 2 (incident at the quarter-wave plate 32) The output of the quarter-wave plate 32 will have a circular polarization. Thus, the angle aphal can be equal to the angle theta in absolute value.

[0073] The light beam 2 is then reflected by the mirror 31 and passes back through the quarter-wave plate 32, which has the effect of reintroducing a new 90° phase shift on the light wave of the light beam 2 (typically a new delay of X / 4). The polarization of the light beam 2 is modified to change from circular or elliptical polarization to linear polarization.

[0074] Thus, since the light beam 2 has had its light wave successively phase-shifted by two times 90° (corresponding to a total or cumulative delay of X / 2), the phase of this light wave is delayed by 180° and its polarization plane has a different orientation with respect to the polarization plane of the initial light beam 2 passing for the first time through the quarter-wave plate 32. As a result, the light beam 2 (initially of s-polarization) which has successively passed through the quarter-wave plate 32 twice exhibits a p-type polarization after its second pass through the quarter-wave plate 32. Consequently, the first display element 30 is therefore configured to modify the polarization of the light beam 2. Typically, here the double pass of the light beam through the quarter-wave plate 32 allows the light beam 2 to change from a linear s-polarization to a linear p-polarization.The light beam 2 exiting the first reflective element 30 thus has its polarization modified so as to pass from s polarization to p polarization.

[0075] The first reflective element 30 is also configured to reflect the light beam 2 (in particular all light beams having been previously transmitted by the semi-reflective blade 70) towards the semi-reflective blade 70.

[0076] Thus, after passing twice through the quarter-wave plate 32, the light beam 2 (now of p polarization) propagates again in the direction of the semi-reflective plate 70. In this case, as the light beam 2 has a p polarization, the latter is reflected on the second face 72 of the semi-reflective plate 70.

[0077] In this example, the semi-reflective blade 70 is configured to reflect the light beam 2 (here the previously transmitted beam 2) towards the second reflective element 50. Thus, in this example, the semi-reflective blade 70 is oriented to reflect one of the light beams (here the light beam 2) towards the second reflective element 50.

[0078] The second reflective element 50 may be similar to the first reflective element 30 (i.e., comprise the same optical elements, namely a mirror and a quarter-wave plate as explained above) or be different (i.e., comprise other optical elements as will be explained below). In this example, the second reflective element 50 is different from the first reflective element 30 flexing 30. Typically in this example, the second reflective element 50 includes a reflective surface 51.

[0079] Here, the reflective surface includes a retroreflector 51. The retroreflector is configured to reflect the light beams reaching it in the same direction as the incident direction. Consequently, the light beams reflecting off the retroreflector 51 are not reflected (according to Snell's law). Thus, the beam incident on the retroreflector and the beam reflected by the retroreflector 51 follow the same optical path.

[0080] The retroreflector 51 can be any type of retroreflector configured to reflect visible light. For this purpose, the retroreflector can comprise a cube wedge prism and / or an arrangement of spherical elements (such as, for example, a microlens array) positioned on a mirror.

[0081] The second reflecting element also includes a quarter-wave plate 52 positioned upstream of the retroreflector 51 with respect to the optical path of the light beam 2. The quarter-wave plate 52 is preferably similar to the quarter-wave plate 32 of the first reflecting element 32. Consequently, it also has a slow axis and a fast axis. As described previously, the fast axis of the quarter-wave plate 52 is arranged such that its fast axis is angularly offset from the plane of polarization of the light beam 2 incident to it by an angle α2. As will be described below, the quarter-wave plate 52 is arranged similarly to the quarter-wave plate 32 described above. Thus, in one example, α2 may be 45°. Therefore, the angle α2 may be equal to the angle θ in absolute value.

[0082] In this example, the quarter-wave plate 52 of the second reflective element 50 is located between the semi-reflective plate 70 and the reflective surface 51 of the second reflective element 50 and / or is parallel to the reflective surface 51 (here it is positioned parallel to the retro-reflector 51 of the second reflective element 50).

[0083] Thus, in this embodiment, the light beam 2 (here of p-polarization) is reflected off the second face 72 of the semi-reflective plate 70 and travels towards the second reflecting element 50. It passes through the quarter-wave plate 52 and has the phase of its signal shifted by 90°. Thus, at the exit of the quarter-wave plate 52, the polarization of the light beam 2 is modified. It changes from a linear p-polarization to an elliptical or circular polarization depending on the orientation of the axis of the quarter-wave plate 52 (i.e., the value of the angle α2). This light beam 2 then reaches the retroreflector 52, is reflected off the surface of the retroreflector 51 without being deflected, and passes again through the quarter-wave plate 52. Thus, this second passage through the quarter-wave plate 52 induces a further 90° phase shift in the light beam 2. The polarization of the light beam 2 is therefore again modified to switch from circular or elliptical polarization to linear s-type polarization.

[0084] In this example, the second reflective element 50 is configured to reflect the light beam 2 towards the semi-reflective plate 70. For this purpose, the second reflective element 50, in particular the reflective surface 52 (corresponding here to the retroreflector 52), has at least one normal vector n2 inclined at 45 degrees in absolute value with respect to the semi-reflective plate 70 (here with respect to the elongation axis Cl of the semi-reflective plate 70). In the case where the reflective surface 52 is a mirror, this mirror may have an optical axis aligned with at least one normal vector n2.

[0085] In [Fig. 1], the normal vector ni of the first reflective element 30 and the normal vector n2 of the second reflective element 50 are oriented perpendicularly.

[0086] Thus, after passing twice through the quarter-wave plate 52 of the second reflective element 50, the light beam 2 has a linear polarization s. This beam is directed towards the semi-reflective plate 70. Since the latter has a linear polarization s, it is transmitted by the semi-reflective plate 70. Thus, after passing through the semi-reflective plate 70, the light beam 2 propagates into the field of vision of an individual looking at the semi-reflective plate 70. Typically, this light beam 2 creates a second image which, thanks to the use of the retroreflector 51, is seen in front of the surface 71 of the semi-reflective plate 70.

[0087] As illustrated in [Fig.1], the two light beams 2, 3 propagate towards the field of view of an individual looking at the semi-reflective blade 70.

[0088] As explained above, the semi-reflective blade 70 is arranged to display a first image 5 from here the light beam 3 of p polarization and a second image 6 from the other light beam, here the light beam 2 of s polarization.

[0089] Thus, for an individual looking at the semi-reflective plate 70, these two distinct images 5, 6 are visible. The first image 5 is created by the light beam 3 which was directly reflected by the semi-reflective plate 70 and the second image 6 which followed an optical path in the device 100 greater than the light beam 3.

[0090] The first image 5 resulting from the light beam 3, which was directly reflected by the semi-reflective plate 70, is a virtual image due to the position of the semi-reflective plate 70, particularly the first surface 71 which acts as a mirror. It is associated with a first projection distance and is therefore seen by the user as an image behind the semi-reflective plate 70. Conversely, the second image 6 resulting from the light beam 2 is a virtual image (due to the position of the second reflective element 50). This second image 5 is associated with a second projection distance and is seen by the user as being po positioned in front of the semi-reflective plate 70. Here, by projection distance, we mean the position of the image considered in relation to the semi-reflective plate.

[0091] Thus, in the device 100, the first image 5 and the second image 6 occupy different positions for the user with respect to the semi-reflective blade 70 and are therefore seen at different distances (in front of or behind the semi-reflective blade 70).

[0092] Of course, if the reflective element 51 is a mirror, in that case the second image 6 would be positioned on the side of the second face 72, i.e. between the semi-reflective plate 70 and the second reflective element 50. However, in this variant, the two images are projected at two different projection distances, which makes it possible to obtain two distinct image planes (or depth planes) of the Pepper phantom type.

[0093] Therefore, the use of a retroreflector makes it possible to obtain a greater depth between the first image 5 and the second image 6.

[0094] Fig. 3 illustrates an example of the display of the first 5 and second 6 images seen by a user looking at the semi-reflective blade 70. Here, it can be seen that the first 5 and second 6 images displayed at different projection distances are seen as superimposed for the user and occupy the same area in the user's field of view while being at different projection distances.

[0095] Thus, thanks to the device 100, it is possible to simultaneously display two different images to a user looking at the semi-reflective blade 70. This can be particularly advantageous when the content of these two images is different.

[0096] Typically, [Fig. 4] illustrates a case in which a device 100 is positioned inside a vehicle, specifically in the dashboard T of a vehicle. By adjusting the position of the light beams 2, 3 emitted by the display element 10, two different, non-superimposed images 5, 6 can be seen by a user looking at the semi-reflective blade 70. Here, in this example, the first image 5 (view from behind the semi-reflective blade 70) can correspond to an object recorded by a camera in the vehicle viewing the exterior of said vehicle, while the second image 6 (view from in front of the semi-reflective blade 70) can correspond to the individual's car. Typically, a car or an object positioned in front of the vehicle can correspond to the content of the first image 5. In this case, the individual (here, the driver of the vehicle) perceives a difference in position between the two images.

[0097] It is thus understood that the display element 10 can allow for a multitude of configurations. Typically, the half-wave plate 12 can be positioned at different locations in front of the screen 11. Furthermore, it is possible to have several half-wave plates 12 in the display element 10 positioned at different locations in front of screen 11.

[0098] Variants of device 100 will now be described using Figures 5 to 8.

[0099] In a first embodiment, the device 100 may include other types of display element. To this end, [Fig. 5] and [Fig. 6] illustrate another example of the display element 20 that can be used in the device 100. Only the differences with the display element 10 will be described.

[0100] The display element 20 illustrated in [Fig. 5] comprises a screen 21. As in the previous example, this screen 21 is polarized. The screen 21 is therefore arranged to emit a polarized initial beam. Here, the initial beam emitted by the screen 21 comprises two initial light rays, numbered 22 and 23, having a similar polarization.

[0101] In the example considered, the initial light rays have a linear polarization of type p.

[0102] The display element 20 also includes a liquid crystal cell 24 positioned on the optical path of the initial light rays, here on the optical path of the initial light ray 22 and the initial light ray 23. In practice, the liquid crystal cell covers the entire surface of the screen 21 to control the polarization of all the initial light rays emitted by the screen 21. The liquid crystal cell 24 is configured to control the orientation of the polarization plane of the initial light rays passing through it. In practice, when the cell is activated in this example, the initial light rays 22, 23 exiting the liquid crystal cell 24 have s-type polarization. These initial light rays 22 thus become light beams 2. Conversely, when the liquid crystal cell 24 is not activated, it does not modify the polarization of the light rays 22, 23 passing through it.The initial polarization of the light rays emitted by the screen 21 is therefore preserved, they are therefore in this case of p polarization.

[0103] In this variant, the display element 20 includes a control circuit 25 configured to control (here turn on and off) the liquid crystal cell 24. In practice, the control circuit 25 emits a control signal 26.

[0104] As illustrated in [Fig. 6], this control signal 26 follows a change in the shape of a square wave signal exhibiting two alternating states, a high state and a low state. In practice, in this example, when the control signal 26 is in the low state, the liquid crystal cell 24 is not activated (it deactivates or remains in standby mode). The polarization of the initial light rays passing through it (here, the initial light ray 22) is not modified, as explained above. Conversely, when the control signal 26 is in the high state, the liquid crystal cell 24 is activated. Consequently, in this control signal state, the liquid crystal cell 24 modifies the polarization of the initial light rays passing through it, as explained above.

[0105] Thus, when the control signal 26 is low, the polarized display element 20 emits light beams 3 with the same polarization (here, p-polarization). These light beams are therefore reflected by the semi-reflective plate 70 towards the individual's eye. Consequently, only one image (here, the first image 5) at the first projection distance is emitted by the device 100 when the control signal 26 is low. Conversely, when the control signal 26 is high, the polarization of the two initial light rays 22, 23 is modified, and they become light beams 2, each with s-polarization. These light beams 2 are then transmitted by the semi-reflective plate 70 and follow the optical path as explained above. In this case, device 100 displays the second image 6 at the second projection distance when the control signal 26 is in the high state.

[0106] The screen 21 can thus display one image during the lower slot and a separate image during the upper slot. Two alternately displayed images can therefore be seen by a user looking at the semi-reflective blade 70.

[0107] Thus, in this embodiment, an image at a projection distance for a given control signal state is emitted (by the screen), and then, at the next control signal state, another image at a different projection distance is emitted (by the screen). This alternating display can thus be repeated according to the control signal 26. This embodiment therefore allows the first image 5 and second image 6 to be emitted alternately. This embodiment thus provides dynamic control of the polarization of the initial light rays, the other elements of the device performing static polarization control.

[0108] As illustrated in [Fig. 6], the control signal 26 has a duty cycle corresponding to the ratio between the time the control signal 26 is in the high state and the time it is in the low state. Here, this duty cycle is typically 50% so that the individual viewing the semi-reflective plate 70 has the impression of viewing both the front and back images simultaneously, even though they are displayed alternately. To enhance this impression, the control signal 26 has a frequency, and the screen 21 of the display element 20 also has a frequency. Typically, the screen 21 has a display frequency equal to twice the frequency of the control signal 26. Advantageously, the frequency of each high and low state is greater than or equal to 50 Hz. Typically, in this example, the frequency of each high and low state is 50 Hz, and that of the screen is 100 Hz.Such a configuration allows a user to have the impression of seeing both images 5 and 6 simultaneously, even though they are actually emitted at different times.

[0109] A third will now be described using [Fig.7] and [Fig.8]. variant of display element 80 that can be included in device 100.

[0110] In this embodiment, the display element 80 comprises a polarized screen 81. The screen 81 is therefore arranged to emit an initial polarized beam. Here, the initial beam emitted by the screen 81 comprises at least two initial light rays, numbered 82, 83, having a similar polarization.

[0111] In the example considered, the initial light rays 82, 83 exhibit a linear polarization of type p.

[0112] As in the previous example, the display element 80 also includes a liquid crystal cell 84. In this example, the liquid crystal cell 84 has a plurality of activation zones 88. Each activation zone 88 is positioned on the optical path of one of the initial light rays. In practice, each activation zone 88 covers at least one pixel pi to control the orientation of the polarization plane of the at least one pixel it covers. Here, each activation zone covers one pixel. Thus, each activation zone 88 is associated with a pixel and has a size equivalent to that of the given pixel.

[0113] As in the previous example, the display element 80 also includes a control circuit 85 configured to control (here, activate and deactivate) each activation zone. Unlike the previous example, the control circuit 85 controls each activation zone 88 of the liquid crystal cell 84 via a control signal 86. Thus, in this embodiment, there are as many control signals 86 as there are activation zones 88.

[0114] In this example, only two control signals 88a, 88b are shown. Here, control signal 86a controls the activation of the activation zone 88a positioned on the optical path of the initial beam 82, and control signal 86b controls the activation of the activation zone 88b positioned on the optical path of the initial beam 83. These control signals 86a, 86b can each have a high state to activate the activation zone to which it is associated, inducing a change in the polarization of the initial beam positioned on the optical path of this activation zone, and a low state to deactivate or not activate the liquid crystal cell 84 in order to maintain the polarization of the initial light beam emitted from the screen 81.

[0115] As illustrated in this figure, the activation zone 88a of the liquid crystal cell 84 is controlled by a control signal 86a having a different state from the control signal 86b controlling the activation zone 88b. Such a configuration makes it possible to control the simultaneous emission of the two light beams 2, 3 and thus to simultaneously emit the first image 5 and the second image 6.

[0116] In practice, to obtain simultaneous transmission of the first and second images by the device 100, the control signal 86a is in the high state, the other signal of Control 86b is in the low state. Such a configuration allows the emission of the s-polarized light beam 2 and the emission of the p-polarized beam 3 simultaneously.

[0117] During the emission of the first image and the second image, the control signals 86a, 86b present a state which is continuous in time (i.e. it is not modified).

[0118] The screen 81 can thus display at least two images simultaneously, in particular a first image displayed by the activation zone controlled by the control signal 86a in the low state (low slot) and a second image displayed by the activation zone controlled by the control signal 86b in the high state (high slot). Two images displayed simultaneously can thus be seen by a user looking at the semi-reflective blade 70.

[0119] To control all the activation zones 88, the control circuit may include a synchronization unit 89 so as to control the activation of several activation zones simultaneously.

[0120] In practice, this synchronization unit 89 is configured to synchronize the emission of several control signals 86a synchronized with each other so that the display element simultaneously emits several light beams 3 (called first light beams) of the same polarization (here, p-polarization). These different control signals are identical; they thus follow an identical variation (they are in the same low state in this example).

[0121] Similarly, this synchronization unit 89 is also configured to synchronize the emission of several control signals 86b synchronized with each other so that the display element simultaneously emits several light beams 2 (called second light beams) of the same polarization (here of polarization s) which is orthogonal to the polarization of the first light beams 3. These different control signals are identical, they thus follow an identical variation (they are in the same high state in this example).

[0122] The synchronization unit 89 is also configured to synchronize the transmission of the first and second signals with each other. In practice, the synchronization unit 89 acts on the duty cycles of the control signals 86a (also called first control signals) and the control signals 86b (also called second control signals). Typically, the duty cycle of the first control signals 86a is identical to the duty cycle of the second control signals 86b.

[0123] In one embodiment, it is understood that it is also possible, via the control circuit 85, to emit a single first control signal 86a configured to simultaneously control several activation zones and to emit a single second signal Control signal 86b is used to simultaneously control several other activation zones. In this case, the activation zones controlled by the first control signal 86a form a primary activation zone, and the activation zones controlled by the second control signal 86b form a secondary activation zone. The operation of such a configuration is similar to that described above, in which the first control signal 86a and the second control signal 86b are synchronized. They have the same duty cycle. Furthermore, the state of these signals must be different to simultaneously control the emission of the first image 5 and the second image 6.

[0124] In this case, it is understood that the screen 81 can thus display two images simultaneously, namely a first image displayed by the activation zones controlled by the control signal 86a in the low state (low slot) and a second image displayed by the activation zones controlled by the control signal 86b in the high state (high slot). Two images displayed simultaneously can thus be seen by a user looking at the semi-reflective blade 70.

[0125] In another embodiment, the liquid crystal cell may cover only one or more areas of the screen 81 (areas comprising one or more adjacent and / or separate pixels), each area being associated with an activation zone. In this example, the plurality of activation zones forms a main activation zone. It is typically controlled by a single control signal 86 which activates all the activation zones of the liquid crystal cell 84.

[0126] In this case, the polarization of the initial beams emitted by pixels not covered by the liquid crystal cell 84 remains unchanged, whereas that emitted by the pixels covered by the liquid crystal cell 84 is changed when the control signal 86 of the main activation area goes high. Such a configuration can thus operate similarly to [Fig. 2] when the control signal is high. In this case, the first and second images are displayed simultaneously. Conversely, when the control signal 86 is low, only one image is displayed by the device 100.

[0127] Thus it is understood that dynamic control (based on the use of liquid crystal cells) offers different implementation configurations which facilitates the control of the polarization since the latter can adapt to different constraints.

[0128] A second embodiment of a device 200 according to this disclosure will now be described with reference to [Fig. 9]. The device 200 comprises the same elements as those of the first embodiment. Thus, only the differences with the first embodiment will be described.

[0129] The device 200 therefore comprises a polarized 10, 20 or 80 display element As shown in one of the previous examples, the first reflective element 30, the second reflective element 50, and the semi-reflective plate 70 are included. In this embodiment, the first reflective element 30 and the second reflective element 50 each comprise the same elements as those previously shown. Thus, the first reflective element 30 comprises a mirror 31 and a quarter-wave plate 32 as described above, and the second reflective element 50 comprises a quarter-wave plate 52 and a reflective surface 51 including a retroreflector 51.

[0130] Thus, the quarter-wave plates 31,51 are each configured to modify the polarization of the light beam entering the corresponding display element so as to provide at the output of the first display element or the second display element a light beam having a cumulative delay of 180 degrees and a polarization plane rotated with respect to the polarization plane of the beam incident to the display element considered.

[0131] In this example, the semi-reflective blade 70 is positioned between the first display element 30 and the second reflective element 50. The display element 10, 20, 80 is positioned to emit an initial light beam directed towards the user's field of view.

[0132] In this example, the semi-reflective blade 70 is positioned between the second reflective element 50 and the first reflective element 30. The semi-reflective blade 70 is inclined at 45 degrees in absolute value with respect to: - to an emission axis Al of the display element 10, 20, 80, - to at least one normal vector ni of the first reflecting element 30, and - to at least one normal vector n2 of the second reflecting element 50.

[0133] Unlike the first embodiment, the semi-reflective blade 70 is configured to transmit light beams having a p polarization and to reflect light beams having an s polarization.

[0134] Thus, in this example, the p-polarized light beam 3 emitted by the display element 10, 20, 80 is transmitted by the semi-reflective plate 70 and passes directly into the image space of the device 200, directly reaching the individual's field of vision. Conversely, the s-polarized light beam 2 is reflected by the semi-reflective plate 70 (here, by the second surface 72 of the semi-reflective plate) and propagates towards the first reflective element 30. As it propagates through the first reflective element 30, the phase of the light beam 2 has a cumulative delay of 180 degrees, and the polarization plane of this light beam 3, initially s-polarized, is modified to become p-polarized due to the two successive passes of the light beam 2 through the quarter-wave plate 32 of the first reflective element 30. Thus, this light beam 2 (now s-polarized) The light beam 2 then propagates towards the second reflecting element 50. To do this, it passes through the semi-reflecting plate 70 and is reflected back into the second reflecting element 50 (here against the retroreflector 51), inducing, as explained in the first example, a total or cumulative delay of X / 2 as it transitions from a p-polarization to an s-polarization due to the two successive passes of the light beam 2 through the quarter-wave plate 52 of the second reflecting element 50. Since the second reflecting element 50 includes a retroreflector 51 (at the level of the reflecting surface), the second reflecting element 50 is configured to reflect the light beam 2 back in the same direction as the incident direction. Consequently, the light beam 2 is reflected back towards the semi-reflecting plate 70.As the latter exhibits a polarization s following its reflection in the second reflective element 50, this light beam 2 is reflected on the semi-reflective plate 70 (in particular on the first face 71) and then propagates towards the field of vision of the individual (i.e. in the image field of the device 200).

[0135] A third embodiment of a device 300 according to this disclosure will now be described using [Fig. 10].

[0136] Device 300 comprises the same elements as those of the first embodiment. Thus, only the differences with the first embodiment will be described. Here, the screen of the display element emits initial light rays of s-polarization. Thus, the half-wave plate 14 or the liquid crystal cell 24, 84 is in this example configured to change the polarization of the initial light rays from s-polarization to p-polarization.

[0137] The device 300 therefore includes a polarized display element 10, 20 or 80 as shown in one of the previous examples, the first reflective element 30, the second reflective element 50 and the semi-reflective blade 70. In this embodiment, the first reflective element 30 faces the user's field of view.

[0138] In this example, the semi-reflective blade 70 is positioned between the display element 10, 20, 80 and the second reflective element 50. The semi-reflective blade 70 is inclined at 45 degrees in absolute value with respect to: - to an emission axis Al of the display element 10, 20, 80, - to at least one normal vector ni of the first reflecting element 30, and - to at least one normal vector n2 of the second reflecting element 50.

[0139] However, in this example, the semi-reflective blade is rotated 90° (counter-clockwise) relative to the semi-reflective blade 70 illustrated in [Fig.1].

[0140] In this embodiment, the semi-reflective blade 70 is configured to transmit light beams having an s polarization and to reflect light beams having a p polarization.

[0141] Thus, in this example, the light beam 2 of s-polarization emitted by the display element 10, 20, 80 is transmitted by the semi-reflective plate 70 and propagates towards the second reflective element 50. Upon reflection from the second reflective element 50, the orientation of the polarization plane of this light beam 2, initially of s-polarization, is modified to a p-polarization due to the two successive passes of the light beam 2 through the quarter-wave plate 52 of the second reflective element 50, and the phase of the light beam 2 exiting the second display element has a cumulative delay of 180 degrees. As the second reflective element 50 has a retroreflector 51, the second reflective element 50 is configured to reflect the light beam 2 back in the same direction as the incident direction. Consequently, the light beam 2 is reflected back towards the semi-reflective plate 70.As the latter exhibits a p polarization following its optical path taken in the second reflective element 50, this light beam 2 is reflected on the semi-reflective plate 70 (in particular on the second face 72) and then propagates towards the field of vision of the individual (i.e. in the image field of the device 300).

[0142] The light beam 3 emitted by the display element 10, 20, 80 has a p polarization. After being emitted, it is reflected off the semi-reflective plate 70 (in particular the first face 71) and is directed towards the first reflective element 30. As it propagates through the first reflective element 30, the plane of polarization of this light beam 3, initially of p polarization, is changed to an s polarization by means of two successive passes of the light beam 3 through the quarter-wave plate 32 of the first reflective element 30. By reflection on the mirror 31 of the first reflective element, the light beam 3 is returned towards the semi-reflective plate 70. Being of s polarization, it passes through the semi-reflective plate 70 without being deviated and then propagates in the direction of the individual's field of vision (i.e., out of the device 300).

[0143] Figure 11 illustrates another embodiment of the device according to this disclosure. Each device comprises the same elements as those shown above, one of any display elements 10, 20, 80 shown previously, a semi-reflective plate 70, a first reflective element 30 comprising a mirror 31 and a quarter-wave plate 32, and a second reflective element 50 preferably comprising a retroreflector 51 and a quarter-wave plate 52.

[0144] We can see that: - the device in configuration A (similar to device 100) has an arrangement symmetric to the arrangement of the device in configuration F (axial symmetry here vertical); - the device of configuration C has a symmetrical arrangement to the arrangement of the device in configuration D (similar to device 300) (axial symmetry here vertical); - the device of configuration B (similar to device 200) has an arrangement symmetric to the arrangement of the device of configuration E (axial symmetry here vertical).

[0145] Consequently, the light beams 2, 3 of configurations A and F follow similar optical paths, the light beams 2, 3 of configurations C and D follow similar optical paths and the light beams 2, 3 of configurations B and E follow similar optical paths.

[0146] The present invention is in no way limited to the embodiments described and represented, but a person skilled in the art will be able to make any variation in accordance with the invention.

Claims

Demands

1. Device (100, 200, 300) for displaying a first image and a second image in the field of view of an individual, said device (100, 200, 300) comprising: - a polarized display element (10, 20, 80); - a first reflective element (30) comprising a mirror (31) and a quarter-wave plate (32); - a second reflective element (50) comprising a reflective surface (51) and a quarter-wave plate (52), characterized in that the polarized display element (10, 20, 80) is configured to emit at least two polarized light beams (2, 3) each having a defined polarization in a plane of polarization, the plane of polarization of one of the at least two light beams (2, 3) being orthogonal to the plane of polarization of the other light beam (2, 3), said device (100, 200, 300) further comprising a semi-reflective plate (70) positioned on the optical path of the at least two light beams (2,3) and having at least one face (71, 72) configured to reflect one of the at least two light beams (2, 3) and transmit the other light beam (2, 3) according to the polarization plane of said at least two light beams (2, 3), said semi-reflective plate (70) being further arranged to display a first image at a first projection distance from one of the at least two light beams (2, 3) and a second image at a second projection distance from the other light beam (2, 3), said first reflective element (30) and said second reflective element (50) each being configured to reflect at least one of the light beams (2, 3) towards the semi-reflective plate (70).

2. Device (100, 200, 300) according to claim 1, wherein the at least two light beams (2, 3) have linear polarization.

3. Device (100, 200, 300) according to any one of claims 1 to 2, wherein the semi-reflective blade (70) comprises another face (71, 72) configured to reflect one of the at least two polarized light beams (2, 3) and transmit the other polarized light beam (2, 3) according to the polarization plane of said at least two light beams (2, 3).

4. Device according to any one of claims 1 to 3, wherein the semi-reflective blade (70) is inclined at 45 degrees in absolute value with respect to an emission axis of the display element (10, 20, 80).

5. Device according to any one of claims 1 to 4, wherein the reflective surface (51) of the second reflective element (50) comprises a retroreflector or a mirror.

6. A device according to any one of claims 1 to 5, wherein the display element (10) comprises a polarized screen (11) configured to emit an initial polarized beam comprising initial light rays (12, 13) each defined in a plane of polarization, the plane of polarization of the initial light rays (12, 13) being parallel to each other, the polarized display element (10) further comprising a half-wave plate (14) positioned on the optical path of at least one of the light rays (12, 13) of the initial polarized beam to modify the orientation of the plane of polarization of said at least one light ray in order to provide at the output of the display element (10) said at least two light beams (2, 3).

7. Device (100, 200, 300) according to any one of claims 1 to 5, wherein the display element (20, 80) comprises: - a polarized screen (21, 81) configured to emit an initial light beam comprising initial polarized light rays (22, 23, 82, 83) defined each in a plane of polarization, the plane of polarization of the light beams (22, 23, 82, 83) being parallel to each other, - at least one liquid crystal cell (24, 84) positioned on the optical path of at least one of the initial light rays (22, 23, 82, 83) of the initial beam and configured to control the orientation of the plane of polarization of at least one of the initial light rays (22, 23, 82, 83).

8. A device according to claim 7, wherein the liquid crystal cell (24, 84) is positioned on the optical path of all the initial light rays of the initial polarized beam, the display element (20, 80) further comprising a control circuit (25, 85) for the liquid crystal cell (24, 84) configured to emit at least one control signal (26, 86) having two alternating states, a high state in which the liquid crystal cell (24, 84) is activated so as to control the emission by the display element (20, 80) of one of the at least two light beams (2, 3) and a low state in which the

9.

10.

11.

12.

13.

14.

15. liquid crystal cell (24, 84) is not activated so as to control the emission by the display element (20, 80) of the other light beam. Device (100, 200, 300) according to claim 8, wherein the control signal (26, 86) has a duty cycle of 50%. Device (100, 200, 300) according to any one of claims 8 to 9, characterized in that each control signal (26) has a frequency, said screen (21, 81) having a display frequency equal to twice the frequency of the control signal (26, 86). Device (100, 200, 300) according to claim 10, wherein the frequency of each high and low state is greater than or equal to 50 Hz. Device (100, 200, 300) according to claim 7, wherein the display element (80) comprises a liquid crystal cell (86) having different activation zones (88) controlled by a control circuit (85), each activation zone (88) being positioned on the optical path of one of the initial light rays (81, 82) of the initial beam, said control circuit (85) being configured to emit a control signal (86) per activation zone (88), each control signal (86) having two states, a high state in which the given activation zone (88) is activated so as to control the emission in the given activation zone (88) of one of the at least two light beams (2,3) and a low state in which the activation zone (88) is not activated so as to control the emission in said activation zone (88) of the other light beam (23), at least two activation zones (88) of the liquid crystal cell (84) being controlled by a control signal (86) having different states to control the simultaneous emission of the at least two light beams (2, 3). Device according to claim 12, wherein the polarized screen has pixels, each pixel being configured to emit an initial light beam, each activation zone (88) being associated with a pixel and having a size equivalent to that of the given pixel. Device according to any one of claims 12 to 13, wherein for each control signal (86), the state of the given control signal (86) is continuous. A device according to any one of claims 12 to 13, wherein each control signal (86) has alternating high and low states defined by a duty cycle, the duty cycle of at least two activation zones controlled by a different control signal being identical.

Images