Improved optical guide system and near-eye display device comprising such a system

Abstract

The invention relates to a light extraction device for an optical system, the device comprising at least one element of the exit optical guide (3) extending in a longitudinal direction z of light propagation, wherein the element of the exit optical guide has a substantially rectangular cross-section along a plane x,y and is orthogonal to the longitudinal direction z, and wherein the element of the exit optical guide (3) has an entrance zone (6) configured for injecting light L in the form of plane waves, and wherein the element of the exit optical guide (3) has an exit zone (8) comprising a plurality of extraction mirrors (9). The extraction device comprises at least one series of a plurality of parallel extraction mirrors (9) having a reflectance of at least 0.01% and a given inclination of 10° to 80°, wherein the element of the exit optical guide (3) is associated with a light-demultiplying element.

Description

[0001] IMPROVED LIGHT GUIDE SYSTEM AND NEAR-EYE DISPLAY DEVICE COMPRISING A TEE SYSTEM

[0002] Technical field

[0003] The present invention relates to the general technical field of optical devices and / or systems used in virtual or augmented reality. The invention relates in particular to the medical field, the educational and cultural field, and the field of games.

[0004] The invention finds its application in particular in navigation, security, transport or prototyping systems in industry.

[0005] The optical system according to the invention operates with any polychromatic or monochromatic light, particularly in the visible range.

[0006] The present invention relates more particularly to a light extraction device and an optical guide system, used in devices, accessories or other instruments having a display near the eye, also called NED (Near Eye Display), such as helmets or special glasses.

[0007] Prior art

[0008] Known near-eye display devices, particularly those with light rays propagating in the open air, have significant drawbacks. In these devices, the mirrors used have large dimensions, thus contributing to increasing the size of said devices. The weight of these devices is also a drawback. Such devices are described in particular in documents US 2012 / 0212400 A1 or FR 2 941 786 A1

[0009] Also known from document FR 2 983 976 is an optical guide with superimposed guide elements. The guide elements, of lamellar shape, are joined on one of their faces and separated by a semi-reflective coating over at least part of their length. Precise positioning of the semi-reflective coating makes the manufacture of such optical guides complex and expensive. In addition, the joined assembly of the two guide elements must be free of dimensional irregularities or air pockets to ensure the perfect operation of the optical guide.

[0010] It is also difficult to control the losses suffered by optical signals propagating through such optical guides.

[0011] Known optical systems, especially those with such optical guides, often provide a restricted field of view in at least one direction, typically a field of view of 26° (horizontal direction) x 20° (vertical direction). This is very often a major drawback in their areas of use.

[0012] When trying to significantly expand the field of vision, another major drawback is the appearance of black bands in the visual field. These black bands are linked to the fact that known optical systems are not able to fill the user's entire pupil. Not all object fields at the output of the guide can be coupled into the pupil of the eye, which has a diameter of about 2 mm to 8 mm, typically about 4 or 5 mm. This phenomenon results in missing object fields at the image surface corresponding to the retina of the eye. The missing object fields result in black areas corresponding to a lack of coupling or gray areas corresponding to ineffective coupling.

[0013] Also known, for example through document US 11,125,927 B1, is a rectangular waveguide comprising a set of parallel extraction mirrors which couple the light into the user's eye. The particular position of the extraction mirrors and their reflection coefficients make it possible to cover the projections of the light rays perceived by the user and consequently a perception of the image fields by the user. The problem of the appearance of black bands is not resolved in this document. Furthermore, the manufacture of such waveguides is complex.

[0014] Presentation of the invention

[0015] The object of the present invention is therefore to overcome the drawbacks of the prior art and to provide a new light extraction device making it possible to substantially widen the field of vision while minimizing the appearance of optical defects such as black bands and improving and homogenizing the quality of the image.

[0016] The object of the present invention is also to overcome the drawbacks of the prior art and to provide a new optical guide system making it possible to substantially widen the field of vision while minimizing the appearance of optical defects such as black bands and improving and homogenizing the quality of the image. Another object of the present invention is to provide a new optical guide system that is more compact and less heavy.

[0017] Another object of the present invention is to provide a new optical guide system or a new light extraction device, which can be manufactured in a simple manner, for example by injection.

[0018] The objects assigned to the invention are achieved by means of a light extraction device for an optical system, comprising at least one output optical guide element extending in a longitudinal direction z of propagation of the light, defined in a direct orthogonal Cartesian reference frame x,y,z, said output optical guide element having a substantially rectangular section in an x,y plane over at least part of its length, the y axis being directed towards a receiving system, the output optical guide element having an input zone for receiving light L from a light source in the form of plane waves, the output optical guide element having an output zone comprising several extraction mirrors, characterized in that the output zone comprises at least one series of several parallel extraction mirrors, the extraction mirrors of a series having on the one hand a reflectance of at least 0,01% and on the other hand a determined inclination angle a, corresponding to an angle of rotation relative to the x axis of the direct orthogonal Cartesian reference frame x,y,z, between 10° and 80° and preferably between 25° and 65° in a y,z plane, the output optical guide element being associated with at least one light multiplier element to generate from a light signal, identical or similar light signals along different optical paths.,

[0019] According to an exemplary embodiment, the extraction mirrors of a series are arranged in the output zone so that one extraction mirror is plumb with the next extraction mirror in a y,z plane.

[0020] According to another exemplary embodiment, the extraction mirrors of a series are arranged in the output zone so that an extraction mirror partially covers the following extraction mirror in a y,z plane.

[0021] According to another embodiment, the extraction mirrors of a series are arranged in the output zone so that an extraction mirror has, with the following extraction mirror, a spacing e m , so that the spacing e m is greater than a value l m .sin(a), l m being the length of the mirrors in a y,z plane.

[0022] According to another exemplary embodiment, the extraction mirrors of a series are arranged in the output zone so that an extraction mirror has, with the following extraction mirror, an offset of x in the x direction and / or an offset d y in y- direction

[0023] According to an exemplary embodiment, the extraction mirrors of the same series each comprise zones having a different reflectance.

[0024] According to an exemplary embodiment, the extraction mirrors of the same series have a different reflectance from one extraction mirror to another.

[0025] According to an exemplary embodiment, the reflectance of the extraction mirrors of the same series increases when moving from one extraction mirror to the next, in the direction of propagation of the light.

[0026] According to an exemplary embodiment, the upper and / or lower ends of the extraction mirrors of a series are respectively disjointed from an upper face and / or a lower face of the output guide element.

[0027] According to an exemplary embodiment, the output zone comprises at least two superimposed series of extraction mirrors.

[0028] According to an exemplary embodiment, the multiplication element comprises at least one partially reflective coupling blade, extending at least partially into the output optical guide element.

[0029] According to an exemplary embodiment, the multiplication element comprises at least one additional block associated with at least one partially reflective coupling blade, said additional block being fixed on at least part of a face of said output optical guide element.

[0030] The objects assigned to the invention are also achieved using an optical guide system for a near-eye display device comprising:

[0031] - an input optical guide element having an input zone configured to be associated with a light injection system,

[0032] - at least one light extraction device as presented above,

[0033] - the input optical guide element being superimposed on at least one output optical guide element, presenting a mutual spacing so as to delimit a medium of different optical index between said guide elements,

[0034] - the mutual spacing extending between on the one hand a first longitudinal end of the input and output optical guide elements and on the other hand a transition block, the guide elements forming at their other longitudinal end a continuity of material with the transition block,

[0035] - the transition block comprising a generally cylindrical free end covered with a cylindrical or generally cylindrical mirror and thus forming an optical coupling system between the input optical guide element and at least one output optical guide element,

[0036] - the transition block being associated with at least one multiplier element.

[0037] According to an exemplary embodiment, the multiplier element comprises at least one coupling blade which is flat and parallel to the extraction face and passes at least partly through said transition block.

[0038] According to an exemplary embodiment, the coupling blade comprises a portion projecting from the transition block, said projecting portion penetrating into the output optical guide element at an intermediate height located between an upper face and a lower face of said output optical guide element, up to the vicinity of the first extraction mirror.

[0039] The objects assigned to the invention are also achieved using an optical guide system for a near-eye display device comprising:

[0040] - an input optical guide element having an input zone configured to be associated with a light injection system,

[0041] - at least one light extraction device as presented above,

[0042] - the input optical guide element being superimposed on at least one output optical guide element, presenting a mutual spacing so as to delimit a medium of different optical index between said guide elements,

[0043] - the mutual spacing extending between on the one hand a first longitudinal end of the input and output optical guide elements and on the other hand a transition block, the guide elements forming at their other longitudinal end a continuity of material with the transition block,

[0044] - the transition block comprising a generally cylindrical free end covered with a generally cylindrical mirror and thus forming an optical coupling system between the input optical guide element and at least one output optical guide element,

[0045] - the output optical guide element is superimposed on at least one complementary output optical guide element by having an additional mutual spacing so as to delimit a medium of different optical index between the output optical guide element and the complementary output optical guide element, - the transition block comprises an upper part in the extension of the input optical guide element and the output optical guide element,

[0046] - the transition block has a lower part in the extension of the complementary output optical guide element,

[0047] - the upper part being connected to the lower part by an intermediate transition block, which is associated with at least one multiplier element,

[0048] - the intermediate transition block extending in the extension of the additional mutual spacing.

[0049] According to an exemplary embodiment, the intermediate transition block projects from the transition block.

[0050] According to an exemplary embodiment, the extraction mirrors of the complementary output optical guide element have an inclination angle ai relative to the x axis of the direct orthogonal Cartesian reference frame x,y,z, different from the inclination angle a.

[0051] According to an exemplary embodiment, the input optical guide element has an upper face and a lower face which partly delimits the mutual spacing, the lower and upper faces having a mutual inclination of an angle P of between - 10° and + 10°.

[0052] According to an exemplary embodiment, the generally cylindrical free end of the transition block and the cylindrical or generally cylindrical mirror have an axis of symmetry inclined relative to a direction orthogonal to a face of the input optical guide element.

[0053] According to an exemplary embodiment of the optical guide system, the input optical guide comprises a partially reflective layer which extends longitudinally in said input optical guide over a portion of its length and at least over a portion of its width.

[0054] According to an exemplary embodiment, the partially reflective layer extends in a substantially median zone of the thickness of the input optical guide and is separate from the longitudinal end of said input optical guide.

[0055] According to an exemplary embodiment, the partially reflective layer has a reflectance of between 40% and 60% and preferably equal to 50%.

[0056] The objects assigned to the invention are also achieved using an optical system for displaying near the eye, such as a headset or smart glasses, for virtual, augmented, mixed or extended reality, comprising at least one light extraction device as presented above and a system for injecting light in the form of plane waves, comprising at least one display as a light source.

[0057] The objects assigned to the invention are also achieved using an optical system for displaying near the eye, such as a headset or smart glasses, for virtual, augmented, mixed or extended reality, comprising an optical guide system as presented above and a system for injecting light in the form of plane waves, comprising at least one display as a light source.

[0058] As used herein, the term "multiplier element" should be understood broadly as an optical element whose function is to generate, from a light signal, identical or similar light signals along different optical paths. The resulting plurality of light signals is then recombined into a single image in a receiving system, which may be a user's eye or a system comprising an optical sensor.

[0059] The terms "light source" or "light source" should be understood as a set of pixels or image elements that emit monochromatic or polychromatic light. An example would be a display or micro-display.

[0060] Furthermore, the ability to use plane waves simplifies the configuration of the light extraction device and the optical guide system and therefore reduces their cost.

[0061] The optical system according to the invention is advantageously integrated into a virtual or augmented reality headset.

[0062] The optical guide system according to the invention also has the enormous advantage of being very compact and lightweight. For a compactness similar to that of a known optical system, the field of vision is substantially increased.

[0063] A remarkable advantage of the optical guide according to the invention lies in obtaining an enlarged field of vision. Indeed, the maximum field of vision obtained, expressed in the air, is at least 20° in the horizontal direction and at least 40° in the vertical direction, thus substantially increasing the field of vision, in particular in the vertical direction and avoiding the appearance of black bands in the field of vision.

[0064] The optical system according to the invention makes it possible, for example, to increase the displacement zone of the receiving system, typically the user's eye, and thus guarantee acceptable detection. This zone, called "eyebox", varies according to the embodiments according to the invention, typically 15 mm (H: horizontally) x 12 mm (V: vertically), for a pupil with a diameter of 4 mm, using a light extraction guide.

[0065] The optical system according to the invention makes it possible to obtain a homogeneous distribution of light intensity, even for large object fields. This distribution or homogeneous distribution of light is obtained by implementing two distinct optical functions.

[0066] The first function allows the set of object fields (image) to be decomposed into subsets of fields (sub-images). Then the subsets of object fields are multiplied. These are therefore two successive optical field multiplication operations, when two partially reflective plates are used.

[0067] The second function allows the recombining, using the light extractor, of the subsets of fields into a complete set of fields with a view to multiplying them in one or more directions along the optical extraction guide.

[0068] Brief description of the figures

[0069] Other characteristics and advantages of the invention will appear on reading the detailed description which follows, a description made with reference to the appended drawings given as illustrative and non-limiting examples, in which:

[0070] - figures 1 and 2 are illustrations of an example of an image surface seen respectively with a circular pupil and without a circular pupil,

[0071] - figure 3a is a schematic illustration of a central and longitudinal section of a first exemplary embodiment of a light extraction device according to the invention,

[0072] - figure 3b is a schematic illustration of a central and longitudinal section of a second exemplary embodiment of a light extraction device according to the invention,

[0073] - figure 3c is a schematic illustration of a central and longitudinal section of a third exemplary embodiment of a light extraction device according to the invention,

[0074] - figure 3d is a schematic illustration of a central and longitudinal section of a fourth exemplary embodiment of a light extraction device according to the invention,

[0075] - figure 3e is a schematic illustration of a central and longitudinal section of a fifth exemplary embodiment of a light extraction device according to the invention,

[0076] - figure 4 is a schematic illustration of a central and longitudinal section of an exemplary embodiment of an optical guide system according to the invention,

[0077] - figure 4a is a schematic illustration of a central and longitudinal section of another exemplary embodiment of an optical guide system according to the invention,

[0078] - Figure 4b is a schematic illustration of a top view of the optical guide system of Figure 4a,

[0079] - Figure 5 is a schematic illustration of the operation of the optical guide system of Figure 4,

[0080] - figure 6 is a schematic illustration of a central and longitudinal section of an exemplary embodiment of another optical guide system according to the invention,

[0081] - Figure 7 is a schematic illustration of the operation of the optical guide system of Figure 6, and

[0082] - Figure 8 is a schematic illustration of a central and longitudinal section of an additional exemplary embodiment of an optical guide system according to the invention.

[0083] Detailed description of the invention

[0084] Figure 1 is an example of an image obtained on a user's retina with a prior art optical system when the field of vision is widened. The observed black or gray bands appear on the plane of the retina of the user's eye due to the presence of the user's pupil. This pupil is circular and has a diameter of approximately 2 mm to 8 mm and not all object fields output from such a known system can be coupled into the pupil of the eye.

[0085] For comparison, Figure 2 illustrates the same image in the absence of a pupil. This image, devoid of black or gray bands, is also obtained using an extraction device or an optical guide system according to the invention. Despite the presence of the user's pupil, it is possible, thanks to the invention, to restore a complete image in the plane of the retina. Figure 3a is a schematic illustration of a central and longitudinal section of a first exemplary embodiment of a light extraction device according to the invention. This figure illustrates very schematically the positioning of a pupil 1 and a plane of the retina 2 of the user, receiving the light at the output of the extraction device.

[0086] The extraction device comprises an output optical guide element 3 extending in a longitudinal direction z of propagation of the light signal. The space is advantageously identified by a direct orthogonal Cartesian reference frame x, y, z. The z axis corresponds to a direction of propagation in one direction or the other, in said output optical guide element 3, of the optical fields emitted by a light source. The y axis then corresponds to the direction of extraction of the light signal from the output optical guide element 3.

[0087] The output optical guide element 3 has a substantially rectangular section along an x,y plane orthogonal to the longitudinal direction z. The optical guide element has an upper face 4 and a lower face 5, which are substantially planar. The lower face 5 constitutes, for example, the light extraction face in the z,x plane.

[0088] The element of the output optical guide 3 has an input zone 6 for receiving light L in the form of plane waves. This injection of light is obtained by means of an associated light injection system 7, mounted or fixed on the input zone 6.

[0089] The element of the output optical guide 3 further has an output zone 8 comprising several extraction mirrors 9. The terms “extraction mirror” must be understood as being an element or member that is at least partially reflective, that is to say transparent or partially transparent for at least part of the spectrum of the wavelengths used, ranging for example from 400 nm to 800 nm.

[0090] In the exemplary embodiment shown in Figure 3a, the output zone 8 comprises a series of several parallel extraction mirrors 9. According to an exemplary embodiment, these extraction mirrors 9, of the same series, are identical and / or equidistant.

[0091] The extraction mirrors 9 have, for example, a reflectance of at least 0.01%, preferably between 0.1% and 95% and more preferably between 1% and 20%. Remarkably and unexpectedly, the use of extraction mirrors 9 which can have an extremely low reflectance makes it possible to achieve satisfactory performance for the extraction device.

[0092] The extraction mirrors 9 have a determined inclination angle a. The latter is the rotation angle relative to the x axis of the direct orthogonal Cartesian reference frame x,y,z. In an exemplary embodiment, illustrated in particular in figures 3a, 3b and 3c, the angle a is between 10° and 80° and preferably between 25° and 65° in a y,z plane of the direct orthogonal Cartesian reference frame x,y,z.

[0093] The output optical guide element 3 is associated with a light multiplying element for generating, from a light signal, a plurality of identical or similar light signals along different optical paths. The light multiplying element is, for example, a partially reflective coupling plate 10 extending into the output optical guide element 3.

[0094] According to an exemplary embodiment, the coupling blade 10 extends from the end or the vicinity of the end of the entry zone 6, to the vicinity of the or a first extraction mirror 9. By vicinity, it is necessary to understand a spacing of between 0 pm and 20 mm.

[0095] According to another exemplary embodiment, the light multiplier element may comprise several coupling blades 10. The coupling blade 10 is for example metallic.

[0096] The coupling blade 10 comprises, for example, at least one metal layer with a thickness preferably less than a few tens of nanometers and / or at least one layer of dielectric material with a thickness preferably between a few tens of nanometers and a few tens of micrometers.

[0097] By way of example, the coupling blade 10 comprises at least one metal layer with a thickness preferably less than 20 nanometers and / or at least one layer of dielectric material with a thickness preferably between a few 50 nanometers and 10 micrometers.

[0098] The light multiplying element advantageously has a reflectance of between 20% and 70% and preferably of between 40% and 50%. This reflectance can be obtained by adjusting the thickness of the coupling blade 10 and / or by choosing a given material or layers of given materials to produce the coupling blade 10.

[0099] The coupling blade 10 may also, according to another embodiment, have zones of zero reflectance and zones of reflectance equal to or close to 100%, the respective dimensions of which are determined to obtain a determined reflectance for said entirety of the coupling blade 10. The coupling blade 10 is for example in the form of a checkerboard. The value of the reflectance may also be modulated from one zone to another.

[0100] As an exemplary embodiment, the multiplier element comprises at least one partially reflective coupling blade 10, which extends in the output optical guide element 3 from the vicinity of one end of the input zone 6, to the vicinity of a first extraction mirror 9.

[0101] According to an exemplary embodiment, the extraction mirrors 9 of a series are arranged in the output zone 6 so that an extraction mirror 9 has, with the following extraction mirror 9, a spacing e m , so that e m is greater than a value Im.sin(a), 1m being the length of the extraction mirrors 9 in a y,z plane. There is therefore no overlap, even partial, of the extraction mirrors 9 of the same series in the y, z plane. The spacing e m for an output optical guide element 3 having a thickness of 4 mm and a value l m .sin(a) of 3 mm, is for example between 3 mm and 7 mm.

[0102] According to another exemplary embodiment, the extraction mirrors 9 of a series are arranged in the output zone 8 so that an extraction mirror 9 is plumb with the following extraction mirror 9 in a y,z plane.

[0103] According to yet another embodiment, the extraction mirrors 9 of a series are arranged in the output zone 8 so that an extraction mirror 9 at least partially covers the following extraction mirror 9 in a y,z plane. The spacing e m is then less than the value l m .sin(a). For example, for an element of the output optical guide 3 having a thickness of 4 mm and a value l m .sin(a) of 3 mm, the spacing e m is between 0.1 mm and 3 mm.

[0104] According to another exemplary embodiment, the extraction mirrors 9 of a series are arranged in the output zone 8 so that an extraction mirror 9 has, with the following extraction mirror 9, an offset d x in the x direction and / or an offset d y in the y direction. advantageously, the offset d x and / or the shift of yis for example between 50 pm and 2 mm. The length and width dimensions of the extraction mirrors 9 are chosen so as to allow such offsets in the output guide element 3. The upper and / or lower ends of the extraction mirrors 9 of a series are for example disjointed respectively from the upper face 4 or from the lower face 5. Figure 3b is a schematic illustration of a central and longitudinal section along the z axis of a second exemplary embodiment of a light extraction device, in which the output zone 8 comprises two superimposed series of extraction mirrors 9.

[0105] For example, the extraction mirrors 9 of the first series have an inclination angle a determined relative to the x axis of the direct orthogonal Cartesian reference frame x,y,z.

[0106] The second series of extraction mirrors 9 have an inclination angle ai determined with respect to the x-axis of the direct orthogonal Cartesian reference frame x,y,z. The angle ai is the rotation angle with respect to the x-axis of the direct orthogonal Cartesian reference frame x,y,z.

[0107] Figure 3c is a schematic illustration of a central and longitudinal section along the z axis of a third exemplary embodiment of a light extraction device according to the invention. According to this exemplary embodiment, the multiplication element comprises an additional block 11 associated with at least one partially reflective coupling blade 10. The additional block 11 is for example fixed on the extraction face, in this case the lower face 5, of said output optical guide element 3.

[0108] According to an exemplary embodiment, the additional block 11 extends from the vicinity of one end of the entry zone 6 to the level of a first extraction mirror 9. The interface of the additional block 11 and the extraction face comprises a coupling blade 10.

[0109] According to an exemplary embodiment, the additional block 11 comprises at least one face coated with an absorbent layer and / or inclined at an angle close to or identical to an angle of inclination a or ai of the extraction mirrors 9.

[0110] As an example of embodiment, a second coupling blade 10 can be integrated into the additional block 11.

[0111] The material constituting the additional block 11 is for example identical to the material constituting the output guide element 3.

[0112] The additional block 11 is advantageously fixed on the lower face 5 of the output guide element 3. The interface of the additional block 11 and the output guide element 3, more precisely of the lower face 5, advantageously comprises the partially reflective coupling blade 10. According to another exemplary embodiment, the or another coupling blade 10 can be integrated into the additional block 11, at an intermediate height.

[0113] The additional block 11 can also integrate two or more coupling blades 10 arranged between the lower face and the upper face of said additional block 11, at different intermediate heights.

[0114] According to another exemplary embodiment, one or more coupling blades 10 can be integrated into the output optical guide element 3 at the input zone 6. The additional block 11, with or without coupling blades 10, can also be fixed to any one of the faces of the output optical guide element 3. The additional block 11 can, for example, be positioned on the lower face 5 at different positions.

[0115] Figure 3d illustrates another example embodiment of the extraction device in which the output guide element 3 is superimposed on another output guide element 3a, each integrating at least one series of extraction mirrors 9. The output guide elements 3 and 3a are advantageously connected, at their respective faces 5 and 4a, facing each other, by means of the additional block 11 associated with a coupling blade 10.

[0116] The output guide elements 3 and 3a have, over a portion of their length along the z axis and their width along the x axis, a gap, to delimit a space 3b forming a thin layer of air or filled with a material of optical index different from that of said output optical guide elements 3 and 3a. The multiplier element thus comprises the additional block 11 associated with a coupling blade 10. The latter is advantageously located at the interface of the additional block 11 of the output optical guide element 3.

[0117] Figure 3e illustrates another exemplary embodiment of the extraction device in which the output guide element 3 is superimposed on another output guide element 3a, each integrating at least one series of extraction mirrors 9.

[0118] The output guide elements 3 and 3a have, over their entire length along the z axis and their width along the x axis, a gap to delimit a space 3b forming a thin layer of air or filled with a material with an optical index different from that of said output optical guide elements 3 and 3a. The multiplier element then comprises a set of semi-reflecting mirrors M1 and M2 arranged respectively in the output optical guide elements 3 and 3a. The semi-reflecting mirrors M1 and M2 are for example superimposed and have a respective inclination 012 and as.

[0119] According to another embodiment, the mirror M2 is totally reflective to avoid loss of light.

[0120] According to an exemplary embodiment, the respective inclinations 012 and as of the semi-reflecting mirrors M1 and M2 are different from the inclinations a and ai of the series of extraction mirrors 9 located downstream (in the direction of propagation of the light) in the corresponding output optical guide element 3 or 3a. As examples, the values ​​for a2 and as are respectively 60° and 68°.

[0121] Figure 4 is a schematic illustration of a central and longitudinal section along the z axis of an exemplary embodiment of an optical guide system according to the invention.

[0122] The optical guide system comprises an input optical guide element 12 having a longitudinal input end 13, which is intended to be associated with a light injection system 7, not shown. The optical guide system also comprises at least one light extraction device as described above.

[0123] The input optical guide element 12 is superimposed on the output optical guide element 3 by having a mutual spacing 14, so as to delimit a thin layer of air between said input optical guide elements 12 and output 3. This spacing can also delimit a space filled by a material having an optical index different from that of the input optical guide elements 12 and output 3.

[0124] The mutual spacing 14 extends between, on the one hand, a longitudinal end 13 of the input 12 and output 3 optical guide elements and, on the other hand, a transition block 15 located at another longitudinal end of said input 12 and output 3 optical guide elements. The input 12 and output 3 optical guide elements advantageously form, at their other longitudinal end, a continuity of material with the transition block 15. The transition block 15 and the input 12 and output 3 optical guide elements are, for example, made in a single piece or assembled, for example by gluing.

[0125] The transition block 15 has a generally cylindrical free end covered with a cylindrical mirror 16 or generally cylindrical and thus forms an optical coupling system between the input optical guide element 12 and at least the output optical guide element 3. A cylindrical or generally cylindrical shape, in particular for the cylindrical mirror 16 or for the transition block 15, means that the cylindrical shape can locally have deformations which make it possible to correct possible aberrations. The terms "generally cylindrical" must also be understood as including, where appropriate, a perfect or almost perfect cylindrical shape or one devoid of deformations.

[0126] The transition block 15 is advantageously associated with at least one demultiplier element. For example, the transition block 15 integrates at least one demultiplier element, for example in the form of a coupling blade 10. The coupling blade 10 is partially reflective and its reflectance is between 20% and 70% and preferably between 40% and 50%.

[0127] The coupling blade 10 is for example flat and parallel to the lower 15a and upper 15b faces of the transition block 15 or parallel at least to the lower 5 and upper 4 faces of the output optical guide element 3. This avoids the appearance of ghost images.

[0128] The coupling blade 10 advantageously extends to an area located in the vicinity of the generally cylindrical mirror 16 with a longitudinal end, its opposite longitudinal end 10a extending for example to the end 15c of the transition block 15. The coupling blade 10 is for example continuous or discontinuous by having gaps.

[0129] According to an exemplary embodiment of the optical guide system, the coupling blade 10 comprises a projecting portion on the end 15c of the transition block 15. This projecting portion penetrates into the output optical guide element 3 at an intermediate height located between the upper face 4 and the lower face 5 of said output optical guide element 3. Its opposite longitudinal end 10a extends to the vicinity of the first extraction mirror 9.

[0130] The input optical guide element 12, for example of rectangular cross-section, has an upper face 17 and a lower face 18. The lower face 18, which partly delimits the mutual spacing 14, has for example with respect to said upper face 17 an inclination of an angle P of between -10° and +10°. When the angle P is zero, the upper 17 and lower 18 faces are parallel. The choice of the angle P makes it possible to optimize the optical coupling obtained by the transition block 15 associated with the cylindrical mirror 16.

[0131] According to an exemplary embodiment, the cylindrical free end of the transition block 15 and the cylindrical mirror 16 have an axis of symmetry inclined relative to a direction D, orthogonal to the upper face 17 or lower face 18 of the input optical guide element 12. This inclination advantageously has an angle 9 of between -10° and +10°. The choice of angle 9 can for example be used to shift ghost images or reflections out of the field of vision.

[0132] Figure 4a is a schematic illustration of a central and longitudinal section of another exemplary embodiment of an optical guide system and Figure 4b is a schematic illustration of a top view of said optical guide system. In this exemplary embodiment, the input optical guide element 12 is separated from the output optical guide element 3 by the additional block 11 whose thickness corresponds to the mutual spacing 14. The additional block 11, constituting an optical coupling zone, can for example be made in a single block with the input 12 and output 3 optical guide elements. The output optical guide element 3 integrates for example two superimposed series of extraction mirrors 9 and the coupling blade 10. The generally cylindrical mirror 16 advantageously covers one of the superimposed ends of the additional block 11 and of the input 12 and output 3 optical guide elements.

[0133] Figure 5 is a schematic illustration of the operation of the optical guide system of Figure 4. The optical guide system according to the invention makes it possible to fill the pupil 1 with all the object fields from the light source. A plurality of image portions are then advantageously recombined into a single image by the eye of an observer or by an optical sensor system.

[0134] Figure 6 is a schematic illustration of a central and longitudinal section of another exemplary embodiment of an optical guide system according to the invention.

[0135] The optical guide system comprises an input optical guide element 12 and at least one light extraction device as described above. The output optical guide element 3 is advantageously superimposed on at least one complementary output optical guide element 19 by having an additional mutual spacing 20 so as to delimit a medium of different optical index, for example a thin layer of air or gas or a solid material, between the output optical guide element 3 and the complementary output optical guide element 19. The additional mutual spacing 20 is therefore delimited by the lower face 5 of the output optical guide element 3 and by an upper face 21 of the complementary output optical guide element 19. The latter also has a lower face 22, constituting the light extraction face, facing the pupil 1.

[0136] The transition block 15 comprises an upper part 15d located in the extension of the input optical guide element 12 and the output optical guide element 3. The transition block 15 also comprises a lower part 15e located in the extension of the complementary output optical guide element 19.

[0137] The upper part 15d is connected to the lower part 15e by an intermediate transition block 23. The intermediate transition block 23 is associated with at least one reduction element. The reduction element comprises, for example, a coupling blade 10.

[0138] The interface of the intermediate transition block 23 and the upper transition block 15d is advantageously constituted, at least in part, by the coupling blade 10. The thickness of the intermediate transition block 23, coated by the coupling blade 10, corresponds to the thickness of the additional mutual spacing 20, which is located in the extension of said intermediate transition block 23.

[0139] The intermediate transition block 23 and the associated coupling blade 10 advantageously project from the upper 15d and lower 15e parts of the transition block 15.

[0140] The coupling blade 10 covers, for example, the entire upper face of the intermediate transition block 23. According to another exemplary embodiment, the coupling blade 10 covers a portion of the upper face of the intermediate transition block 23.

[0141] The free face 23a of the intermediate transition block 23 and the corresponding free end of the coupling blade 10 longitudinally delimit the additional mutual spacing 20. The free face 23a of the intermediate transition block 23 and the corresponding free end of the coupling blade 10 have, for example, a radius of curvature identical to or close to the radius of the cylindrical mirror 16.

[0142] According to another exemplary embodiment, the free face 23a is flat and inclined at an angle close to or identical to an angle of inclination a or ai of the extraction mirrors 9.

[0143] The free face 23a and the free end of the coupling blade advantageously comprise an absorbent coating.

[0144] According to another exemplary embodiment, at least one complementary coupling blade 10 can be integrated into the intermediate transition block 23 and / or into the lower part 15e and / or into the part 15d of the transition block 15.

[0145] The extraction mirrors 9 of the complementary output optical guide element 19 have, for example, an inclination angle ai, different from the inclination angle a in the output optical guide element 3. According to another preferred embodiment, the angles a and al are identical.

[0146] Figure 7 is a schematic illustration of the operation of the optical guide system of Figure 6. The optical guide system according to the invention makes it possible to fill the pupil 1 with a maximum of object fields.

[0147] Figure 8 is a schematic illustration of a central and longitudinal section of an additional exemplary embodiment of an optical guide system. The latter comprises the input optical guide element 12 having a longitudinal input end 13, which is intended to be associated with a light injection system 7, not shown. The optical guide system also comprises at least one light extraction device as described above.

[0148] The input optical guide element 12 is superimposed on the output optical guide element 3 by having the mutual spacing 14, so as to delimit a thin layer of air between said input optical guide elements 12 and output 3. This spacing can also delimit a space filled by a material having an optical index different from that of the input optical guide elements 12 and output 3.

[0149] The mutual spacing 14 extends between, on the one hand, the longitudinal end 13 of the input 12 and output 3 optical guide elements and, on the other hand, the transition block 15.

[0150] The transition block 15 has a generally cylindrical free end covered with a cylindrical mirror 16 or generally cylindrical and thus forms an optical coupling system between the input optical guide element 12 and at least the output optical guide element 3.

[0151] The transition block 15 is advantageously associated with at least one multiplier element constituted by the coupling blade 10. The coupling blade 10 is partially reflective and its reflectance is between 20% and 70% and preferably between 40% and 50%.

[0152] The coupling blade 10 is for example flat and parallel to the lower 15a and upper 15b faces of the transition block 15 or parallel at least to the lower 5 and upper 4 faces of the output optical guide element 3. This avoids the appearance of ghost images.

[0153] The coupling blade 10 advantageously extends to an area located in the vicinity of the generally cylindrical mirror 16 with a longitudinal end, its opposite longitudinal end 10a extending for example to the end 15c of the transition block 15, to a projecting area on the end 15c or to an area set back from the end 15c. The coupling blade 10 is for example continuous or discontinuous with gaps.

[0154] According to the exemplary embodiment of the optical guide system illustrated, the coupling blade 10 comprises a projecting portion on the end 15c of the transition block 15. This projecting portion penetrates into the output optical guide element 3 at an intermediate height located between the upper face 4 and the lower face 5 of said output optical guide element 3. Its opposite longitudinal end 10a extends for example to the vicinity of the first extraction mirror 9. The coupling blade 10 has for example a projecting or recessed portion by a distance of between 0 mm and 20 mm.

[0155] The lower face 18, which partly delimits the mutual spacing 14, has for example, with respect to said upper face 17, an inclination of an angle P of between -10° and +10°. When the angle P is zero, the upper 17 and lower 18 faces are parallel. The choice of the angle P makes it possible to optimize the optical coupling obtained by the transition block 15 associated with the cylindrical mirror 16.

[0156] According to an exemplary embodiment, the cylindrical free end of the transition block 15 and the cylindrical mirror 16 have an axis of symmetry inclined relative to a direction D, orthogonal to the upper face 17 or lower face 18 of the input optical guide element 12. This inclination advantageously has an angle 9 of between -10° and +10°. The choice of angle 9 can for example be used to shift ghost images or reflections out of the field of vision.

[0157] The input optical guide 12 advantageously comprises a partially reflective layer 25 which extends longitudinally in said input optical guide (12) over a portion L_TRbl of its length and at least over a portion of its width. Advantageously, the inner longitudinal edge 25 has a radius of curvature greater than or equal to the radius of curvature of the cylindrical mirror 16. For example, when the length L1 is approximately 27.3 mm, the portion L_TRbl is approximately 6.7 mm.

[0158] According to an exemplary embodiment, the partially reflective layer 25 extends in a substantially median zone of the thickness el of the input optical guide 12 and is separate from the longitudinal end 13 of said input optical guide 12. The end of the partially reflective layer 25 has, for example, a spacing z_TRbl from the longitudinal end 13 of between 0 mm and 20 mm.

[0159] The spacing e_TRbl between the partially reflective layer 25 and the lower face 18 is advantageously between 0 mm and el, with el being the thickness of the input optical guide 12 of approximately 2 mm. As an indication, the thickness of the output optical guide 3 is approximately 6.75 mm.

[0160] According to an exemplary embodiment, the partially reflective layer 25 has a reflectance of between 40% and 60% and preferably equal to 50%.

[0161] The partially reflective layer 25, for example metallic, typically has a thickness of between ten nanometers and one micrometer.

[0162] The operation of the optical system illustrated in Figure 8 is detailed below. The source image (OBJECT) emitted by a micro-screen is coupled into the input optical guide 12 by a coupling element called an “incoupler”. The coupled light propagates into the input optical guide 12 by total internal reflection (TIR).

[0163] Upon encountering this partially reflective layer 25, the light (the image) is split and continues to propagate in the input optical guide 12 by total internal reflection (TIR).

[0164] The split light arrives and propagates in a coupling zone called the transition zone corresponding to the transition block 15, until it is reflected by the cylindrical coupling mirror 16.

[0165] The split light then encounters a “bis transition zone” comprising a partially reflective layer (typically a reflectance of 50%) corresponding to the coupling blade 10, which is partially reflective and may, for example, protrude into the output optical guide 3.

[0166] Upon encountering this partially reflective layer, the split light is separated into two, a reflected part propagating directly towards the output optical guide 3 and a transmitted part continuing to propagate by total internal reflection (TIR) ​​in the transition zone until propagating in the output optical guide 3.

[0167] The light is then extracted from the output optical guide 3 using a series of parallel extraction mirrors 9. These have, for example, an identical angle of inclination, for example 30°. The extraction mirrors 9 are partially reflective with identical or different reflectance coefficients. The extraction mirrors 9 may be plumb or partially overlap each other. The light extracted from the output optical guide 3 is coupled into the pupil 1 of the eye. It is then necessary to have more than one mirror to couple the light into the eye. Otherwise, not all the light (i.e. from the OBJECT fields) reaches the eye, which generates black bands in the IMAGE formed on the retina 2 of the eye.

[0168] Obviously, the invention is not limited to the preferred embodiments described above and shown in the various figures, and those skilled in the art can make numerous modifications and imagine other variants without departing from the scope or framework of the invention defined by the claims.

Claims

Claims 1. Light extraction device for an optical system, comprising at least one output optical guide element (3) extending in a longitudinal direction z of propagation of the light, defined in a direct orthogonal Cartesian coordinate system x,y,z, said output optical guide element (3) having a substantially rectangular section in an x,y plane over at least part of its length, the y axis being directed towards a receiving system, the output optical guide element (3) having an input zone (6) for receiving light L from a light source in the form of plane waves, the output optical guide element (3) having an output zone (8) comprising several extraction mirrors (9), characterized in that the output zone (8) comprises at least one series of several parallel extraction mirrors (9), the extraction mirrors (9) of a series having on the one hand a reflectance of at least 0.01% and on the other hand a determined inclination angle a,corresponding to an angle of rotation relative to the x axis of the direct orthogonal Cartesian reference frame x,y,z, between 10° and 80° and preferably between 25° and 65° in a y,z plane, the output optical guide element (3) being associated with at least one light multiplier element to generate, from a light signal, identical or similar light signals along different optical paths., 2. Extraction device according to claim 1, characterized in that the extraction mirrors (9) of a series are arranged in the output zone (8) so that one extraction mirror (9) is plumb with the next extraction mirror (9) in a y,z plane.

3. Extraction device according to claim 1, characterized in that the extraction mirrors (9) of a series are arranged in the output zone (8) so that one extraction mirror (9) partially covers the next extraction mirror (9) in a y,z plane.

4. Extraction device according to claim 1, characterized in that the extraction mirrors (9) of a series are arranged in the outlet zone (8) so that an extraction mirror (9) has, with the following extraction mirror (9), a spacing e m , so that the spacing e m is greater than a value l m .sin(a), l m being the length of the mirrors in a y,z plane.

5. Extraction device according to any one of claims 1 to 4, characterized in that the extraction mirrors (9) of a series are arranged in the output zone (8) so that an extraction mirror (9) has with the following extraction mirror (9) an offset d x in the x direction and / or an offset d y in y direction.

6. Extraction device according to any one of claims 1 to 5, characterized in that the extraction mirrors (9) of the same series each comprise zones having a different reflectance.

7. Extraction device according to any one of claims 1 to 6, characterized in that the extraction mirrors (9) of the same series have a different reflectance from one extraction mirror to another.

8. Extraction device according to any one of claims 1 to 7, characterized in that the reflectance of the extraction mirrors (9) of the same series increases when moving from one extraction mirror (9) to the next, in the direction of propagation of the light.

9. Extraction device according to any one of claims 1 to 8, characterized in that the upper and / or lower ends of the extraction mirrors (9) of a series are disjointed respectively from an upper face (4) and / or a lower face (5) of the output guide element (3).

10. Extraction device according to any one of claims 1 to 9, characterized in that the exit zone (8) comprises at least two superimposed series of extraction mirrors (9).

11. Extraction device according to any one of claims 1 to 10, characterized in that the multiplication element comprises at least one partially reflective coupling blade (10), extending at least partially into the output optical guide element (3).

12. Extraction device according to any one of claims 1 to 10, characterized in that the reduction element comprises at least one additional block (11) associated with at least one partially reflective coupling blade (10), said additional block (11) being fixed on at least part of a face of said output optical guide element (3).

13. Optical guide system for near-eye display device comprising: - an input optical guide element (12) having an input zone configured to be associated with a light injection system (7), - at least one light extraction device according to any one of claims 1 to 12, - the input optical guide element (12) being superimposed on at least one output optical guide element (3) by having a mutual spacing (14) so ​​as to delimit a medium of different optical index between said guide elements (12, 3), - the mutual spacing (14) extending between on the one hand a first longitudinal end of the input (12) and output (3) optical guide elements and on the other hand a transition block (15), the guide elements (12, 3) forming at their other longitudinal end a continuity of material with the transition block (15), - the transition block (15) comprising a generally cylindrical free end covered with a cylindrical mirror (16) or generally cylindrical and thus forming an optical coupling system between the input optical guide element (12) and at least one output optical guide element (3), - the transition block (15) being associated with at least one multiplier element.

14. Optical guide system according to claim 13, characterized in that the multiplier element comprises at least one coupling blade (10) which is flat and parallel to the extraction face and passes at least partly through said transition block (15).

15. Optical guide system according to claim 14, characterized in that the coupling blade (10) comprises a portion projecting from the transition block (15), said projecting portion penetrating into the output optical guide element (3) at an intermediate height located between an upper face (4) and a lower face (5) of said output optical guide element (3), up to the vicinity of the first extraction mirror (9).

16. Optical guide system for near-eye display device comprising: - an input optical guide element (12) having an input zone configured to be associated with a light injection system (7), - at least one light extraction device according to any one of claims 1 to 12, - the input optical guide element (12) being superimposed on at least one output optical guide element (3) by having a mutual spacing (14) so ​​as to delimit a medium of different optical index between said guide elements (12, 3), - the mutual spacing (14) extending between on the one hand a first longitudinal end of the input (12) and output (3) optical guide elements and on the other hand a transition block (15), the guide elements (12, 3) forming at their other longitudinal end a continuity of material with the transition block (15), - the transition block (15) comprising a generally cylindrical free end covered with a cylindrical mirror (16) or generally cylindrical and thus forming an optical coupling system between the input optical guide element (12) and at least one output optical guide element (3), - the output optical guide element (3) is superimposed on at least one complementary output optical guide element (19) by having an additional mutual spacing (20) so as to delimit a medium of different optical index between the output optical guide element (3) and the complementary output optical guide element (19), - the transition block (15) comprises an upper part (15d) in the extension of the input optical guide element (12) and the output optical guide element (3), - the transition block (15) comprises a lower part (15e) in the extension of the complementary output optical guide element (19), - the upper part (15d) being connected to the lower part (15e) by an intermediate transition block (23), which is associated with at least one multiplier element, - the intermediate transition block (23) extending in the extension of the additional mutual spacing (20).

17. Optical guide system according to claim 16, characterized in that the intermediate transition block (23) projects from the transition block (15).

18. Optical guide system according to claim 16 or 17, characterized in that the extraction mirrors (9) of the complementary output optical guide element (19) Tl have an inclination angle ai relative to the x axis of the direct orthogonal Cartesian reference frame x,y,z, different from the inclination angle a.

19. Optical guide system according to any one of claims 13 to 18, characterized in that the input optical guide element (12) has an upper face (17) and a lower face (18) which partly delimits the mutual spacing (14), the lower (18) and upper (17) faces having a mutual inclination of an angle P between - 10° and + 10°.

20. Optical guide system according to any one of claims 13 to 19, characterized in that the generally cylindrical free end of the transition block (15) and the cylindrical (16) or generally cylindrical mirror have an axis of symmetry inclined relative to a direction orthogonal to a face of the input optical guide element (12).

21. Optical guide system according to any one of claims 13 to 19, characterized in that the input optical guide (12) comprises a partially reflective layer (25) which extends longitudinally in said input optical guide. (12) over part of its length (Ll) and at least over part of its width.

22. Optical guide system according to claim 21, characterized in that the partially reflecting layer (25) extends in a substantially middle zone of the thickness (el) of the input optical guide (12) and is separate from the longitudinal end (13) of said input optical guide (12).

23. Optical guide system according to claim 21 or 22, characterized in that the partially reflective layer (25) has a reflectance of between 40% and 60% and preferably equal to 50%.

24. Optical system for near-eye display of the headset or smart glasses type, for virtual, augmented, mixed or extended reality, comprising at least one light extraction device according to any one of claims 1 to 12 and a system (7) for injecting light in the form of plane waves, comprising at least one display as a light source.

25. Optical system for near-eye display of the headset or smart glasses type, for virtual, augmented, mixed or extended reality, comprising an optical guide system according to any one of claims 13 to 23 and a system (7) for injecting light in the form of plane waves, comprising at least one display as a light source.

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