Optical article with holographic waveguide

Abstract

The invention relates to an optical article having a holographic waveguide. An optical article (200) comprising at least:-a substrate (201), and-a holographic waveguide (202) covering at least a portion of the substrate (201) and comprising:-two main surfaces (203, 204), at least one of the main surfaces conforming to a surface (201a) of the substrate (201), and-at least a first and a second zone (Z1, Z2), the first zone and the second zone are configured such that light incident on the first zone and the second zone (Z1; z2) is directed at least partially towards the first and second zones (Z2; z1) in the first region.

Description

[0001] This application is a divisional application of the invention patent application entitled “Optical product with holographic waveguide”, which has Chinese application number 201880048722.0 and filing date of July 24, 2018, PCT application PCT / EP2018 / 069994. Technical Field

[0002] The present invention relates to the integration of passive and active components, for example within smart glasses and windows, and to the selective collection of light reaching such smart devices and the selective emission of light in the direction of the user. Background Art

[0003] Integration of components within smart glasses or windows has many interesting applications.

[0004] For example, in the case of electrochromic (EC) or liquid crystal glass and windows, sensors are used to measure the light level of the environment and control the activation of the electrochromic element or liquid crystal to avoid glare for the user.

[0005] However, the autonomy of such smart glasses and windows is limited to the batteries that can be integrated in their frames. The integration of sensors in such optical devices can also be complex given the limited available space and may require drilling holes in the frame or special adjustments.

[0006] Another example of smart glasses is a head mounted display, where light generated by the display is directed in the direction of the wearer's eyes using a glass sheet with facets to reflect light emitted by the display in the direction of the wearer's eyes.

[0007] An embodiment of a head mounted display is disclosed, for example, in document WO 2013 / 138107.

[0008] These glass plates have a thickness of several millimeters and are relatively bulky. Furthermore, the glass plates must be flat, which makes their integration in everyday eyewear difficult. The resulting devices can be heavy, uncomfortable, and unsightly for the wearer.

[0009] Some glasses are also equipped with filters adapted to selectively reflect unfavorable wavelengths of light, such as UV or some blue wavelengths, in order to avoid such wavelengths being directed towards the wearer. However, these filters can reflect light towards other users and may also cause unsightly colored reflections. It is therefore desirable to provide a selective filter that allows the unfavorable wavelengths to be collected without reflecting them towards other users.

[0010] Therefore, in addition to the need to selectively collect light received by an eyewear or window in applications where filters or sensors are integrated into the optical device, there is also a need to improve the selective guidance of light emitted towards the user in applications such as head-mounted displays in smart glasses. Summary of the invention

[0011] In view of the above, one object of the present invention is to alleviate at least some of the inconveniences of the prior art.

[0012] In particular, it is an object of the invention to make it easier to integrate intelligent components such as sensors, displays, or photovoltaic cells into optical devices while maintaining a compact design of such optical devices.

[0013] Another object of the present invention is to allow selective collection of wavelengths directed towards an optical device without reflecting those wavelengths towards other users.

[0014] Another object of the invention is to allow the manufacture of glasses incorporating a head mounted display that are lighter, more comfortable and aesthetically pleasing to the user.

[0015] To this end, according to a first aspect, an optical product is proposed, the optical product comprising at least:

[0016] - a substrate, and

[0017] - a holographic waveguide covering at least a portion of the substrate and comprising:

[0018] - two main surfaces, at least one of which corresponds to a surface of the substrate, and

[0019] - at least a first and a second zone, said first and second zones being configured such that light incident on one of said first and second zones is at least partially directed towards the other of said first and second zones.

[0020] According to the invention, the holographic waveguide is formed from a photosensitive material comprising a refractive index that varies spatially as a function of at least one frequency.

[0021] According to one embodiment, the holographic waveguide further comprises a peripheral edge, the first region comprises at least a portion of the peripheral edge of the holographic waveguide, and the second region comprises at least a portion of one of the main surfaces of the holographic waveguide.

[0022] In an embodiment, the optical article may further include one or a combination of the following features:

[0023] - the holographic waveguide extends over at least 10% of the surface of the substrate, preferably over at least 50% of the surface, even more preferably over at least 70% of the surface, even more preferably over the entire surface of the substrate,

[0024] - the optical article comprises a plurality of holographic waveguides,

[0025] - said holographic waveguides are stacked one on top of the other,

[0026] - the holographic waveguide extends over different parts of the surface of the substrate,

[0027] - each holographic waveguide is configured to selectively propagate light of a respective different wavelength between its respective first and second regions,

[0028] - light rays propagated by each holographic waveguide enter or exit from a respective second zone of said waveguide according to different angles relative to a normal to said second zone,

[0029] - the optical article further comprises coupling means located on the periphery of one of the main surfaces of the waveguide and configured to couple light into or out of the holographic waveguide,

[0030] - the coupling means is preferably selected from one of a coating or a grating (eg a holographic grating),

[0031] - the coupling means may be passive or active, the active coupling means being driven or activated by a command signal, the active coupling optical means may for example comprise a set of liquid crystal cells, the activated or driven liquid crystal cells providing an amplitude grating or a phase grating,

[0032] - said first zone extends over at least 50% of the peripheral edge of said holographic waveguide, preferably over at least 70% of said peripheral edge, even more preferably over the entire surface of said peripheral edge,

[0033] - The substrate is selected from the group consisting of:

[0034] o Flat substrate,

[0035] o Bending the substrate,

[0036] o a semi-finished lens blank or an ophthalmic lens, wherein the ophthalmic lens may be a contact lens,

[0037] oMask,

[0038] - at least one of the main surfaces of the holographic waveguide extends parallel to the curved surface of the substrate,

[0039] - the two main surfaces of the holographic waveguide form a front surface and a rear surface, the rear surface is intended to point in the direction of the wearer's eyes, the front surface is intended to point to the external environment, and the second zone is an input zone and the first zone is an output zone.

[0040] According to a second aspect, an optical device is also provided, the optical device comprising:

[0041] - An optical article according to any one of the preceding embodiments, and further comprising:

[0042] at least a sensor, a photovoltaic cell, a light trap or an absorber, the sensor, the photovoltaic cell, the light trap or the absorber being configured to receive light output at the first zone or output by a coupling device, the coupling device being located on the periphery of one of the main surfaces of the waveguide and being configured to couple light into or out of the holographic waveguide, the coupling device being preferably selected from one of a coating or a grating (e.g. a holographic grating), or

[0043] - at least a light emitter configured to emit light towards the second region intended to be coupled into the holographic waveguide.

[0044] As discussed previously, the coupling means may be passive or active.

[0045] In an embodiment, the optical article may further include one or a combination of the following features:

[0046] - said at least one sensor, photovoltaic cell, light emitter, light trap or absorber is placed on said substrate,

[0047] - said optical article is intended to be mounted on a frame and at least a sensor, a photovoltaic cell, a light trap, an absorber or a light emitter is placed on said frame in the vicinity of said holographic waveguide, with optional coupling means between said frame and said optical article,

[0048] According to a third aspect, a method for selectively propagating light in a substrate is also proposed, the method comprising the following steps:

[0049] - providing an optical article, the optical article comprising a substrate and a holographic waveguide, the holographic waveguide covering at least a portion of the substrate and comprising:

[0050] - two main surfaces, at least one of which corresponds to a surface of the substrate, and

[0051] - at least first and second zones, the first and second zones being configured such that light incident on one of the first and second zones is at least partially directed towards the other of the first and second zones

[0052] - illuminating said holographic waveguide with light reaching one of said first and second regions,

[0053] - selectively coupling said light into said waveguide,

[0054] - directing light in said holographic waveguide in the direction of the other of said first and second zones.

[0055] According to an embodiment, the step of providing the optical product comprises:

[0056] - coating a layer of photosensitive material on a substrate,

[0057] - splitting the coherent light beam into at least a first and a second beam,

[0058] - generating an interference pattern in the layer of photosensitive material by overlapping at least the first and second beams by:

[0059] - coupling at least said first beam into said layer of photosensitive material,

[0060] - irradiating said layer of photosensitive material with at least said second beam from the outside of the lens,

[0061] The interference pattern induces a refractive index change that varies spatially as a function of at least one frequency within the photosensitive material.

[0062] The optical article according to the invention allows to guide light from a zone located on the surface of the waveguide towards the periphery of the waveguide. The light guided within the holographic waveguide can be selected according to the wavelength of the light and the orientation relative to the waveguide. This makes it possible to filter out undesirable wavelengths (such as UV or blue wavelengths) without reflecting them towards other users.

[0063] Sensors may be placed at the periphery of the optical article or within the frame of the optical article to measure characteristics of the collected light. For example, such sensors may measure ambient light levels and control electrochromic (EC) or liquid crystal glass.

[0064] The optical article also allows light to be directed from an emitter directed towards the peripheral edge of the optical article to a user. Thus, the optical article can be used in head mounted display applications, for example. Since the optical article is obtained by forming a holographic waveguide on a substrate, the substrate can be a curved ophthalmic lens. Thus, the waveguide can be easily integrated in a curved ophthalmic lens, and the resulting glasses including a head mounted display can be lighter, more aesthetically pleasing, and less bulky. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Further details, aspects and embodiments of the proposed solution will be described, by way of example only, with reference to the accompanying drawings.

[0066] Figure 1A , Figure 1B and Figure 1C Three different embodiments of optical articles according to the invention are illustrated.

[0067] Figure 2A , Figure 2B and Figure 2C The diagram illustrates the principle of holographic waveguide.

[0068] Figure 3A , Figure 3B and Figure 3C Different arrangements of first and second regions of a holographic waveguide and some of their applications are illustrated.

[0069] Figure 4A and Figure 4B A front view and a side view of a holographic waveguide including a coupling device are shown.

[0070] Figure 5 An example of an optical setup used for recording of a holographic waveguide is illustrated.

[0071] Figure 6 An example of arrangement and application of a plurality of holographic waveguides according to the embodiment is illustrated. DETAILED DESCRIPTION

[0072] Figure 1A An optical article 100 according to a first embodiment of the present invention is illustrated. The optical article 100 comprises a substrate 101 and a holographic waveguide 102. The substrate 101 has a first surface 101a and a second surface 101b, respectively. The substrate 101 is a flat surface and can be, for example, a window. The holographic waveguide 102 covers at least a portion of the substrate and comprises a first major surface 103, a second major surface 104, and a peripheral edge 105. Thus, the first major surface 103 coincides with the flat surface of the substrate 101. The second major surface 104 is substantially parallel to the first major surface 103.

[0073] The holographic waveguide 102 further comprises a first zone Z1 and a second zone Z2. The first zone Z1 comprises at least a portion of a peripheral edge 105 of the holographic waveguide 102, and the second zone Z2 comprises at least a portion of one of the two main surfaces 103, 104 of the holographic waveguide 102. Figure 3A , Figure 3B and Figure 3CFor the application considered as shown, the holographic waveguide 102 is configured such that light incident on the first zone Z1 is at least partially guided toward the second zone Z2, the first zone Z1 being the input zone and the second zone Z2 being the output zone, or such that light incident on the second zone Z2 is at least partially guided toward the first zone Z1, the second zone Z2 being the input zone and the first zone Z1 being the output zone. Figure 2A , Figure 2B , Figure 2C The holographic waveguide 102 is further described.

[0074] Figure 1B An optical article 200 according to a second embodiment is illustrated. The optical article 200 comprises a substrate 201 and a holographic waveguide 202. The substrate 201 has first and second surfaces 201a, 201b, respectively. At least the first surface 201a is curved. The substrate 201 may be a semi-finished lens blank, in which case the second surface 201b is flat, such as Figure 1B As shown. The second surface 201b is intended to be machined according to data related to the wearer (such as prescription data including spherical power and astigmatism). The substrate 201 may be an ophthalmic lens, in which case the second surface 201b is curved.

[0075] The holographic waveguide 202 covers at least a portion of the substrate 201 and comprises a first major surface 203, a second major surface 204 and a peripheral edge 205. The first major surface 203 conforms to the curved surface 201a of the substrate 201. The second major surface 204 is substantially parallel to the curved first major surface 203. The holographic waveguide is thus curved and the obtained semi-finished lens blank or ophthalmic lens is thus less bulky, in particular less bulky than a semi-finished lens blank or ophthalmic lens with a typically thick straight waveguide.

[0076] The holographic waveguide 202 further comprises a first zone Z1 and a second zone Z2 as previously described.

[0077] The optical article 200 may further include one or more additional layers 206. The additional layer 206 may be one or more of another holographic waveguide, a protective layer, a film or sheet, a functional layer such as an anti-reflective coating, a polarizing layer, a layer comprising a photochromic element, a layer comprising an electrochromic element, a layer comprising a liquid crystal cell element, and / or an at least partially transparent conductive layer. For example, two at least partially transparent conductive layers may be used to control a layer comprising an electrochromic or liquid crystal cell element, or to control an active holographic waveguide.

[0078] One or more additional layers 206 may be placed on top of the holographic waveguide 202, i.e. on the second major surface 204, such as Figure 1BAs shown, and / or below the first main surface 203 of the holographic waveguide 202. According to a variant, the substrate 201 comprises an additional layer 206 and the first surface 201a of the substrate is formed by the additional layer 206, for example.

[0079] Figure 1C An optical article 300 according to a third embodiment is illustrated. The optical article 300 comprises a first substrate 301, a holographic waveguide 302, and a second substrate 306. The first substrate 301 and the second substrate 306 comprise two major surfaces 301a, 301b and 306a, 306b, respectively. The first substrate 301 and the second substrate 306 further comprise peripheral edges 301c and 306c, respectively. The holographic waveguide 302 comprises a first major surface 303, a second major surface 304, and a peripheral edge 305. The first major surface 303 of the holographic waveguide 302 coincides with the major surface 301a of the first substrate 301, and the second major surface 304 of the holographic waveguide 302 coincides with the first surface 306a of the second substrate 306. Thus, the holographic waveguide is embedded between the first substrate 301 and the second substrate 306 in the optical article 300. The holographic waveguide 302 further comprises a first zone Z1 and a second zone Z2 as previously described.

[0080] Optical article 300 may be an ophthalmic lens, in which case outer surfaces 306b and 301b are preferably curved, such as Figure 1C The optical article 300 may also be a semi-finished blank, in which case only one of the outer surfaces 306b or 301b is curved.

[0081] The first and second surfaces 303, 304 of the holographic waveguide 302 are preferably substantially parallel to each other. The inner surfaces 301a and 306a of the first and second substrates 301, 306 may have the same radius of curvature as the outer surfaces 306b and 301b. In an alternative, the inner surfaces 301a and 306a of the first and second substrates 301, 306 may be flat.

[0082] exist Figure 1B and Figure 1C In the embodiment of the invention, the optical article 200, 300 may be a semi-finished lens blank or an ophthalmic lens, and one of the main surfaces (the back surface) is intended to be directed in the direction of the wearer's eyes, and the other main surface (the front surface) is intended to be directed towards the external environment. The substrates 301 and 306 may take on part of the corrective function, like prescription, astigmatism, lower addition.

[0083] The optical article 300 may be formed by injecting a photosensitive material between the first and second substrates 301, 306, which are held at a given distance corresponding to the width of the holographic waveguide, and a portion of the space between the two substrates 301, 306 is blocked on its periphery. According to another variation, the holographic waveguide 302 may be bonded to the inner surfaces 301a and 306a of the first and second substrates 301, 306. When the holographic waveguide is an active holographic waveguide, the active holographic waveguide is surrounded by two at least partially transparent conductive layers, which are bonded to the inner surfaces 301a and 306a of the first and second substrates 301, 306.

[0084] Optical article 300 may also be a window, in which case both exterior surfaces 306b or 301b are flat.

[0085] It may be noted that the holographic waveguide may extend over at least 10% of the surface of one of the previously described substrates, preferably over at least 50% of said surface, even more preferably over at least 70% of said surface, and even more preferably over the entire surface of the substrate.

[0086] The holographic waveguide is formed of a photosensitive material comprising a refractive index that varies spatially according to at least one frequency. The holographic waveguide is recorded using a holographic arrangement. The holographic waveguide may be passive or active. When the photosensitive material is mixed with a liquid crystal, an active holographic waveguide may, for example, be activated or deactivated. Examples of active holographic gratings are, for example, holographic polymer dispersed liquid crystals (H-PDLC) disclosed in WO 2017 / 005608, Polycrips or Polyphems described in document EP 2187254 A1.

[0087] Figure 2A The recording of a holographic waveguide HW in a photosensitive layer PHL formed of a photosensitive material is schematically illustrated. The photosensitive material may be, for example, a photopolymer or dichromated gelatin and is deposited on a substrate (not shown) such as previously described.

[0088] Photopolymers can be in any physical state (liquid, solid, paste, etc.) and include those that are solid and those that are liquid under standard conditions. Photopolymer formulations typically contain one or more monomers or oligomers that exhibit, for example, ethylenically unsaturated photopolymerizable moieties and a photoinitiating system having at least one component that polymerizes sensitive to the irradiation wavelength. They may contain a combination of photoinitiators and photosensitizers that allow for an increased range of spectral sensitivity to visible light.

[0089] These photopolymer formulations may contain various additives such as, in a non-exhaustive list, polymers, solvents, plasticizers, transfer agents, surfactants, antioxidants, thermal stabilizers, defoamers, thickeners, leveling agents, catalysts, and the like.

[0090] Examples of photopolymers include commercial photopolymers such as OmniDex (EI du Pont de Nemours (EP0377182 A2)), Bayfol HX (formerly Bayer, now Covestro), Darol (Polygrama), or SM-TR photopolymer (Polygrama).

[0091] Photopolymer formulations can also be mixed with liquid crystal mixtures to form active holographic waveguides. Depending on their composition, in particular on the presence or absence of solvents and their viscosity, different types of processing can be envisaged. Formulations containing solvents can be processed in different ways, for example by spin coating, dip coating, spray coating or rod coating, or coating by inkjet printing on flat substrates such as glass (inorganic or organic), or by spin coating, dip coating, spray coating or rod coating, or coating by inkjet printing on curved substrates such as glass (inorganic or organic) in order to obtain the desired thickness. After coating, a step of evaporation of the solvent(s) is usually necessary to obtain the photopolymer layer ready to be recorded. When the formulations do not contain solvents, they can be used in the same way when their viscosity is not too high. In this case, an evaporation step is not necessary.

[0092] Some of the methods described for coating a substrate with a photosensitive material can also be applied to a substrate comprising additional layers.

[0093] The thickness of the photosensitive layer is typically comprised between 1 μm and 100 μm, preferably comprised between 4 μm and 60 μm.

[0094] The photosensitive layer PHL is viewed from the side. As in any holographic setup, the layer of photosensitive material is exposed to at least two different beams: a reference beam RB and an object beam OB. Depending on the application considered, the reference beam RB and the object beam OB can be formed by parallel, converging or diverging light rays.

[0095] The reference beam RB is incident on a second zone Z2 of one of the two main surfaces of the photosensitive layer, and the object beam OB is incident on a first zone Z1 of one edge of the photosensitive layer PHL. The object beam OB is coupled into the photosensitive layer and propagates at least partially through the photosensitive layer. Since the photosensitive layer is formed of a material having a refractive index higher than that of the surrounding air, the photosensitive layer forms a waveguide. Therefore, the light included in the object beam OB is guided in the photosensitive layer PHL. An interference pattern is formed by the superposition of the object beam OB and the reference beam RB in the photosensitive layer. The interference pattern is recorded in the photosensitive material as a refractive index change after a specific treatment of the photosensitive material. Therefore, the refractive index of the photosensitive material varies spatially according to at least one frequency. In particular, the refractive index varies according to the intensity of the interference pattern.

[0096] When the photosensitive material is a photopolymer, the refractive index change is caused by the polymerization of monomers or oligomers.

[0097] When a photopolymer is mixed with a liquid crystal, the refractive index variation is caused by the alternation of areas with liquid crystal and polymerized monomers or oligomers. Depending on the recipe used, bright interference fringes can be formed by liquid crystals or by polymerized monomers or oligomers. By applying tension on two electrodes formed by a conductive layer (which is placed on both sides of the photosensitive layer on which the holographic waveguide is recorded), the liquid crystal can change its orientation and therefore change the effective refractive index as seen by the light passing through the photosensitive layer. By appropriately choosing the photopolymer recipe and the liquid crystal mixture recipe, the refractive index in the area including liquid crystal can be matched to the refractive index in the area including the polymerized photopolymer. Therefore, depending on the tension applied to the conductive layer (which is placed on both sides of the holographic waveguide), the holographic waveguide can be activated or deactivated.

[0098] When the reference beam RB and the object beam OB are formed by parallel rays, the refractive index varies according to a frequency that depends on the angle between the reference beam RB and the object beam OB. When at least one of the RB or the object beam OB is convergent or divergent, the refractive index varies spatially according to other frequencies.

[0099] Figure 2B and Figure 2C Two different ways of reading a holographic waveguide are schematically illustrated.

[0100] exist Figure 2B In the embodiment of the present invention, beam B1 is incident on a first zone Z1 on the edge of the photosensitive layer PHL. Some of the light from beam B1 is coupled to the photosensitive layer and coupled into the holographic waveguide. The coupled light is at least partially guided inside the holographic waveguide toward a second zone Z2. Then, the light is coupled out of the holographic waveguide and out of the second zone Z2, forming beam B2.

[0101] Only the portion of beam B1 corresponding to the object beam is effectively coupled into the holographic waveguide HW. When the wavelength used for reading is the same as the wavelength used for recording, beam B2 coming out of the holographic waveguide corresponds to the reference beam RB, so that the rays of B2 have the same angular redispersion as the reference beam RB, but propagate in the opposite direction. Otherwise, when the wavelength used for reading is different from the wavelength used for recording, the angular redispersion of the rays of beam B2 depends on the spatial refractive index variation or change corresponding to the recorded interference pattern.

[0102] exist Figure 2B In the embodiment of the invention, light reaching a zone Z1 on the edge of the holographic waveguide HW is redistributed at a specific angle to come out of a zone Z2 on one of the main surfaces of the holographic waveguide HW.

[0103] exist Figure 2C In the embodiment of the present invention, beam B2 is incident on a second zone Z2 of one of the main surfaces of the photosensitive layer PHL. Some of the light from beam B2 is coupled into the photosensitive layer PHL and into the holographic waveguide HW. The coupled light is at least partially guided inside the holographic waveguide HW towards the first zone Z1. Then, the light is coupled out of the holographic waveguide HW and comes out of the first zone Z1 of the holographic waveguide, forming beam B1. Beam B1 corresponds to the object beam OB, but propagates in the opposite direction.

[0104] The portion of beam B2 corresponding to the object beam OB is effectively coupled into the holographic waveguide HW. When the wavelength used for reading is the same as the wavelength used for recording, the beam B1 coming out of the holographic waveguide corresponds to the object beam OB, so that the rays of B1 have the same angular redispersion as the object beam OB, but propagate in the opposite direction. Otherwise, when the wavelength used for reading is different from the wavelength used for recording, the angular redispersion of the rays of beam B1 depends on the spatial refractive index variation corresponding to the recorded interference pattern.

[0105] exist Figure 2C In an embodiment, light incident on the second zone Z2 of the holographic waveguide HW at a specific angle may be collected on an edge of the holographic waveguide HW near the first zone Z1.

[0106] Therefore, the holographic waveguide HW is capable of selectively propagating light incident on one of the first zone Z1 and the second zone Z2 to the other of the first and second corresponding zones Z2, Z1. Light entering or exiting the first and second zones has an angular redispersion defined by a refractive index that varies spatially along at least one frequency corresponding to the interference pattern recorded in the photosensitive material. Further, for a specific wavelength depending on the refractive index variation corresponding to the recording of the interference pattern, the holographic waveguide selectively propagates light incident on one of the first zone Z1 and the second zone Z2 to the other of the first and second corresponding zones Z2, Z1.

[0107] Figure 3A , Figure 3B and Figure 3C Different non-limiting arrangements of first and second regions of the holographic waveguide are illustrated.

[0108] Figure 3A A top view of a holographic waveguide HW is shown, the holographic waveguide comprising a first zone Z1 extending over the entire peripheral edge of the holographic waveguide and a second zone Z2 extending over one of the main surfaces of the holographic waveguide.

[0109] In this arrangement, light reaching the second zone Z2 can, for example, be collected and directed towards the first zone Z1 of the peripheral edge of the holographic waveguide. Thus, the holographic waveguide can be used to reject harmful wavelengths, such as UV or some blue wavelengths comprised between 380nm and 450nm, which are not transmitted through the substrate and are not directed towards other users. Thus, the holographic waveguide can act as a selective filter. The light coming out of the first zone Z1 can be collected by an absorber or a light trap. Alternatively, the light can be collected by a photovoltaic cell, which supplies power to a battery arranged in the frame of the optical device, which battery, for example, provides power for electrodes of electrochromic or liquid crystal glass and a window or head-mounted display.

[0110] Figure 3B A top view of a holographic waveguide HW is shown, the holographic waveguide comprising a first zone Z1 extending over a portion of a peripheral edge of the holographic waveguide and a second zone Z2 extending over one of the main surfaces of the holographic waveguide.

[0111] exist Figure 3B In the arrangement shown, the first zone Z1 may have a size of, for example, 2 mm 2 The size of the light emitter LE, such as a light emitting diode, can be directed towards the second zone Z2 of the main surface of the holographic waveguide. Thus, the holographic waveguide can be used, for example, to illuminate the eye of the wearer of the ophthalmic lens with a specific wavelength comprised between 470 nm and 510 nm. For example, such wavelengths can be used in light therapy to treat circadian rhythm disorders such as delayed sleep phase syndrome and can also be used to treat seasonal affective disorder.

[0112] This arrangement can also be used to perform eye tracking by building an integrated eye tracker into a pair of glasses. Eye trackers mainly use a camera as a sensor and an IR source (primarily an LED) to illuminate the tracked eye. The camera measures the orientation or position of the eye. A holographic waveguide can be used to guide the IR light in the direction of the wearer's eye. A holographic grating acting as a reflector can be placed on top of the lens. The holographic grating is configured to reflect light from the wearer's eye in the direction of a camera integrated in the hinge or temple of the frame.

[0113] Alternatively, the first zone Z1 may be a zone having a width of several mm. 2 The size of the light sensor. Similar to Figure 3A For example, light entering the holographic waveguide on the second zone Z2 and exiting the first zone Z1 can be collected by a sensor and the resulting device can then be used as a dosimeter.

[0114] Figure 3C A plurality of holographic waveguides HW1, HW2, HW3, HW4 are shown. The holographic waveguides HW1, HW2, HW3, HW4 are adjacent to each other and cover at least a portion of the aforementioned substrate. Each holographic waveguide HW1, HW2, HW3, HW4 comprises a first zone Z11, Z12, Z13, Z14 and a second zone Z21, Z22, Z23, Z24, respectively. The second zone Z21, Z22, Z23, Z24 extends over the entire surface of the holographic waveguide HW1, HW2, HW3, HW4. The first zone Z11, Z12, Z13, Z14 extends over a portion of the peripheral edge of the holographic waveguide HW1, HW2, HW3, HW4.

[0115] Different holographic waveguides HW1, HW2, HW3, HW4 can be used to collect light arriving at different parts of the substrate corresponding to the second zones Z21, Z22, Z23, Z24 of the holographic waveguides HW1, HW2, HW3, HW4 and measure the collected light coming out of the first zones Z11, Z12, Z13, Z14 using, for example, different sensors S1, S2, S3, S4.

[0116] This arrangement can be used to detect light incident on different parts of the substrate, potentially from different directions, and can be used to control electrochromic or liquid crystals of smart glasses or windows.

[0117] This arrangement can also be used to detect different wavelengths incident on different parts of the substrate, and can be used to control a tunable filter depending on the amount of light detected. An example of a tunable filter that can be used is given in WO 2017 / 032649.

[0118] Figure 4A and Figure 4BA front view and a side view of a holographic waveguide HW comprising a coupling device CD are illustrated. The coupling device CD is located on the periphery of one of the main surfaces of the holographic waveguide. In an alternative, the coupling device CD may be located on the peripheral edge of the holographic waveguide. The coupling device is configured to couple light into or out of the holographic waveguide, i.e. to extract or inject light into the holographic waveguide. For example, the coupling device may be selected from a coating, a protrusion and / or recessed structure, a diffusing element or a holographic grating (such as a Bragg grating recorded in the holographic waveguide). For example, the protrusion and / or recessed structure may be formed by a single protrusion or recessed structure located on the substrate in contact with the holographic waveguide, or by periodically continuous protrusions and / or recesses, thereby forming a corrugated grating, or even more complex structures, such as a diffractive optical element. Examples of such recessed and / or protrusion structures are described, for example, in document WO 2009 / 032721.

[0119] exist Figure 4A and 4B In the example of , light incident on the holographic waveguide HW on a second zone Z2 on one of the main surfaces of the holographic waveguide is at least partially guided towards a first zone Z1 of the holographic waveguide HW. A portion of the light guided towards the first zone Z1 is coupled out, i.e. extracted from the holographic waveguide by the coupling device CD and propagates out of the holographic waveguide HW in the direction of an optical component configured to receive the light output by the coupling device. Such an optical component may be a sensor, a photovoltaic cell, a light trap or an absorber placed on the frame of the smart glasses or the window.

[0120] Alternatively, light may be coupled into (i.e., injected into) the holographic waveguide HW via the coupling device CD, and then the light is partially guided from the coupling device CD towards the second zone Z2 of the holographic waveguide HW. An optical component such as a light emitter is located on the frame of the smart glasses or window near the holographic waveguide so that light is emitted in the direction of the coupling device CD.

[0121] Therefore, the position of the optical component in the frame of the glasses or window can be adjusted by selecting the position of the coupling device so that the light emitted or received by the optical component is directed towards the coupling device. According to the present invention, it enables greater flexibility in the design and integration of the optical component in the frame of the glasses or window.

[0122] Figure 5 An example of an optical setup for recording a holographic waveguide on a photosensitive layer 402 placed on a substrate 401 is illustrated.

[0123] The optical setup 400 comprises, for example, a coherent light source such as a laser 403 emitting light along an initial linear polarization, a half-wave plate 404 , a polarizing beam splitter 405 , two mirrors 407 , 408 , a first beam forming component 409 and a second beam forming component 406 .

[0124] The optical setup 400 is adapted to generate a reference beam RB and an object beam OB from a single laser beam BO. The reference beam RB is intended to be directed towards at least a portion of a main surface 402a of the photosensitive layer 402 corresponding to the second zone Z2 of the holographic waveguide. The object beam OB is intended to be directed towards at least a portion of a peripheral edge 402b of the photosensitive layer 402 corresponding to the first zone Z1 of the holographic waveguide HW.

[0125] The laser beam B0 from the laser 403 has an initial linear polarization. The laser 403 can directly emit the linear polarization beam B0, or an additional quarter-wave plate can be used to obtain the linear polarization beam B0. The polarization direction can be changed by rotating the half-wave plate 404. Then, the laser beam B0 is divided into two laser beams B01 and B02 using a polarization beam splitter 405 by reflecting light having a first linear polarization and transmitting light having a second linear polarization perpendicular to the first linear polarization. The half-wave plate 404 is rotated to control the intensity of each of the two laser beams B01 and B02. Two mirrors 407 and 408 are used to guide the first beam B01 toward the peripheral edge 402b of the photosensitive layer 402. The first beam B01 is formed into an object beam OB using a first beam forming component 409. The object beam OB is formed by converging light and is focused into the peripheral edge 402b of the photosensitive layer 402. Using a second beam forming component 406, the reference beam RB is formed by parallel, divergent or converging light, depending on the application. The first and second beam forming assemblies 406, 409 may include one or more lenses for forming a converging or diverging beam. For example, the first and second beam forming assemblies 406, 409 may also include a mask for delimiting the zones Z1, Z2 and / or the liquid crystal matrix to control the intensity and / or phase of the beams B01, B02. Alternatively, the substrate 401 used for recording the holographic waveguide may include a mask for delimiting the extent of the (multiple) holographic waveguides recorded into the photosensitive layer. The substrate 401 may be rotated to increase the size of the first zone Z1 of the holographic waveguide relative to the size of the focused object beam OB.

[0126] By translating and rotating the substrate 401 and by adjusting the position of the first and second regions on the photosensitive layer 402, different holographic waveguides can be recorded on the same photosensitive layer 402. For each recording of a new holographic waveguide HW, the first beam forming assembly 406 can be selected according to the desired reference beam RB. In one embodiment, after recording one or more holographic waveguides in the same photosensitive layer 402, the photosensitive layer can be retrieved from the substrate 401 and placed in Figure 1A , Figure 1B on one of the substrates 101, 201.

[0127] In another embodiment, the holographic waveguide HW is recorded directly on one of the photosensitive layers 102, 202, which covers Figure 1A , Figure 1B , Figure 1C In yet another embodiment, Figure 1C The photosensitive layer 302 is directly recorded and embedded between the first and second substrates 301 and 306.

[0128] like Figure 3C As previously shown, different holographic waveguides may be adjacent and in contact with each other, or may be separated by spaces formed by the photosensitive layer 402. The spaces between different holographic waveguides may be used to achieve Figure 6 Other features shown.

[0129] Figure 6 A top view of a photosensitive layer comprising four peripheral holographic waveguides HW01, HW02, HW03, HW04 and one central holographic waveguide HW00 is illustrated.

[0130] A portion of the second zone Z200 of the central holographic waveguide HW00 is placed at the center of the photosensitive layer, with a peripheral portion extending toward the edge of the photosensitive layer. The first zone Z100 is placed on the peripheral edge of the photosensitive layer.

[0131] The peripheral holographic waveguides HW01, HW02, HW03, HW04 are adjacent to the central portion of the second zone Z200, and the holographic waveguides HW01 and HW04 are also adjacent to the peripheral portion of the second zone Z200 of the central holographic waveguide HW00. Figure 3C The holographic waveguides HW1, HW2, HW3, HW4 described previously. The holographic waveguides HW01, HW02, HW03, HW04 respectively comprise a first zone Z101, Z102, Z103, Z104 located on a portion of the peripheral edge of each holographic waveguide. Advantageously, the photosensitive layer further comprises three waveguides W1, W2 and W3. The waveguides are formed by the photosensitive layer portions included between the holographic waveguides. A holographic mirror is formed on top of each waveguide, the holographic mirror being configured to couple out light guided into the waveguide.

[0132] This arrangement can also be used to build an integrated eye tracker in the frame of the glasses. The IR light emitted by the IR LED integrated in the frame of the glasses is then directed to the three waveguides W1, W2, W3 towards the center of the ophthalmic lens. The IR light is then coupled out of the waveguides via the holographic reflector and then directed towards the wearer's eyes.

[0133] The light reflected by the wearer's eye is then directed towards the ophthalmic lens, more specifically towards the direction of at least some of the second zones of the holographic waveguides HW00, HW01, HW02, HW03, HW04 acting as input zones. The light is then directed towards the first zones Z100, Z101, Z102, Z103, Z104 of the holographic waveguides HW00, HW01, HW02, HW03, HW04 at the peripheral edge of the ophthalmic lens. The amount of light collected by each holographic waveguide in the output zones Z100, Z101, Z102, Z103, Z104 can then be measured by sensors S0, S1, S2, S3, S4. For example, the sensors can be placed in the vicinity of the corresponding output zones Z100, Z101, Z102, Z103, Z104 on the peripheral edge of each holographic waveguide. When the sensors SO, S1 , S2, S3, S4 or the light emitters LE1 , LE2, LE3 are not placed directly on the peripheral edge of each holographic waveguide, alternative coupling means may be used.

[0134] According to this embodiment, the orientation of the wearer's eye may be determined based on the differences in the measured reflections of the five different zones formed by the input zone of the holographic waveguide. For example, due to differences in the surface, absorption, and geometry of each part of the eye, the light reflected by the wearer's eye may differ depending on which parts of the eye (sclera, pupil, and iris) are illuminated.

Claims

1. An optical product (100; 200; 300), comprising at least: - a substrate (101; 201; 301), and -Holographic waveguide (102; 202； 302), the holographic waveguide covers at least a portion of the substrate (101; 201; 301) and comprises: - two main surfaces (103, 104; 203, 204; 303, 304), at least one of which corresponds to a surface (101a; 201a; 301a) of the substrate (101; 201; 301), and - at least a first zone and a second zone (Z1, Z2), said first zone and said second zone being configured such that light incident on one of said first zone and said second zone (Z1; Z2) is at least partially directed towards the other of said first zone and said second zone (Z2; Z1).

2. The optical article (100; 200; 300) according to claim 1, wherein: - the holographic waveguide (102; 202; 302) further comprises a peripheral edge (105; 205; 305), - said first zone (Z1) comprises at least a portion of a peripheral edge of said holographic waveguide, and - said second zone (Z2) comprises at least a portion of one of the main surfaces of said holographic waveguide (102; 202; 302).

3. The optical product (100; 200; 300) according to claim 1 or 2, characterized in that The holographic waveguide (102; 202; 302) extends over at least 10% of the surface of the substrate, preferably over at least 50% of the surface, even more preferably over at least 70% of the surface, even more preferably over the entire surface of the substrate.

4. The optical article (100; 200; 300) according to any one of the preceding claims, characterized in that The optical article includes a plurality of holographic waveguides.

5. The optical article (100; 200; 300) according to claim 4, characterized in that Each holographic waveguide is configured to selectively propagate light of respective different wavelengths between its respective first and second regions.

6. The optical article (100; 200; 300) according to claim 4 or 5, characterized in that Light propagating through each holographic waveguide enters or exits from a corresponding second zone (Z2) of the waveguide according to different angles relative to a normal to the second zone.

7. The optical article (100; 200; 300) according to any one of the preceding claims, characterized in that: - the optical article further comprises a coupling device (CD) located on the periphery of one major surface of the waveguide and configured to couple light into or out of the holographic waveguide, and - said coupling means (CD) is preferably selected from one of a coating or a grating.

8. The optical article (100; 200; 300) according to any one of the preceding claims, characterized in that The first zone (Z1) extends over at least 50% of the peripheral edge of the holographic waveguide, preferably over at least 70% of the peripheral edge, even more preferably over the entire surface of the peripheral edge.

9. The optical article (100; 200; 300) according to any one of the preceding claims, characterized in that The substrate is selected from the group consisting of: - a flat substrate (101), - a curved substrate (201), - A semi-finished lens blank (201) or an ophthalmic lens (301).

10. The optical article (200; 300) according to any one of the preceding claims, characterized in that At least one of the main surfaces (203, 204; 303, 304) of the holographic waveguide (202; 302) extends parallel to the curved surface (201a; 301a) of the substrate (201; 301).

11. The optical article (100; 200; 300) according to any one of the preceding claims, characterized in that The two main surfaces of the holographic waveguide form a front surface and a rear surface, the rear surface is intended to point in the direction of the wearer's eyes, the front surface is intended to point to the external environment, and the second zone is an input zone and the first zone is an output zone.

12. An optical device (100; 200; 300), comprising: - An optical article according to any one of claims 1 to 11, and further comprising at least a sensor (S1, S2, S3, S4), a photovoltaic cell, a light trap or an absorber, the sensor, the photovoltaic cell, the light trap or the absorber being configured to receive light output at the first zone (Z1) or output by a coupling device (CD) according to claim 7, or - at least a light emitter (LE) configured to emit light towards said second zone (Z2) intended to be coupled into said holographic waveguide (HW).

13. The optical device (100; 200; 300) according to claim 12, characterized in that The optical article (100; 200; 300) is intended to be mounted on a frame and at least the sensor (S1, S2, S3, S4), photovoltaic cell, light trap, absorber or light emitter (LE) is placed on the frame near the holographic waveguide.

14. A method for selectively propagating light in a substrate, the method comprising the steps of: - providing an optical article (100; 200; 300), the optical article comprising a substrate (101; 201; 301) and a holographic waveguide (102; 202; 302), the holographic waveguide covering at least a portion of the substrate (101; 201; 301) and comprising: - two main surfaces (103, 104; 203, 204; 303, 304), at least one of which corresponds to a surface (101a; 201a; 301a) of the substrate (101; 201; 301), and - at least a first zone and a second zone (Z1, Z2), said first zone and said second zone being configured such that light incident on one of said first zone and said second zone (Z1; Z2) is at least partially directed towards the other of said first zone and said second zone (Z2; Z1), - illuminating said holographic waveguide (102; 202; 302) with light reaching one of said first zone and said second zone (Z1; Z2), - selectively coupling said light into said waveguide, - directing light in the holographic waveguide in the direction of the other of the first zone and the second zone (Z2; Z1).

15. The method according to claim 14, characterized in that: The step of providing the optical product comprises: - coating a layer of photosensitive material (402) on the substrate (401), - splitting the coherent light beam (B0) into at least a first beam and a second beam (B01, B02), - generating an interference pattern in the layer of photosensitive material (402) by overlapping at least the first beam and the second beam (RB, OB) by: - coupling at least the first beam (OB) into the layer of photosensitive material (402), - irradiating said layer of photosensitive material with at least said second beam (RB) from the outside of the lens, The interference pattern induces a refractive index change that varies spatially according to at least one frequency within the photosensitive material (402).

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