Ophthalmic lens with holographic mirror on low birefringence base lens

Abstract

To provide an ophthalmic lens which solves the problem of causing complexity and high cost in a manufacturing process.SOLUTION: The present disclosure relates to an ophthalmic lens comprising a base lens (10) comprising at least one low birefringence material layer (11) and at least one holographic component (20) recorded on a surface of the low birefringence material layer, and a supplemental lens (30) assembled to the base lens (10). The present disclosure also relates to methods of making such optical lenses.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ophthalmic lens having a base lens including a low birefringence material layer having at least one holographic component recorded therein. The present invention also relates to a manufacturing process for such an ophthalmic lens. [Background technology]

[0002] Head-mounted devices with display features are already known, allowing the wearer to visualize augmented reality images or text.

[0003] For this purpose, from the document (US Pat. No. 5,629,999) a method is known which provides an ophthalmic lens fitted into a frame and intended to be worn by a wearer, in which the lens comprises a holographic mirror arranged to reflect light generated by an image source integrated in the frame.

[0004] The mirror is holographic in that it is recorded using a holographic process. More specifically, the holographic mirror is obtained by providing a thin film of unrecorded material on an ophthalmic lens and recording the holographic mirror by creating interference between at least one reference beam and an illumination / object beam in the holographic medium.

[0005] Depending on the configuration of the beam during the recording step, the mirror can be endowed with an optical function that makes it possible to modify the wavelength of the light beam coming from the image source when reflected on the mirror, so that recording can be carried out according to the configuration of the lenses and frames and optionally according to some characteristics of the wearer.

[0006] The quality of a hologram, and in particular the accuracy of the optical function performed by a holographic mirror, depends on the quality of the interference fringes created to record the optical function. This quality is related to the visibility V of the interference fringes, which is directly linked to the angle ψ between the polarization of the illumination / object beam and the polarization of the reference beam. V(ψ)V max cos(ψ) where Vmax is the maximum visibility, ideally 1.

[0007] If the substrate medium is homogeneous and especially has low birefringence, the angle is only linked to the recording setup and can be easily optimized. However, if the substrate medium is birefringent, the angle may vary locally due to the material itself, causing a local reduction in the visibility of the fringes and thus leading to poor quality and homogeneity of the holographic mirror.

[0008] Another problem of recording holographic mirrors on lenses is the complexity of mass-producing such lenses. Indeed, holographic recording may depend on lens properties, such as lens refractive power, the type of head-mounted device in which the lens is integrated, etc., which implies adapting the configuration of each holographic component, and thus the configuration of each recording optical setup, to the lens properties. This introduces complexity and high costs into the manufacturing process. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2016 / 156614 Brochure Summary of the Invention [Means for solving the problem]

[0010] The purpose of the present disclosure is to provide solutions to the shortcomings of the prior art.

[0011] In particular, it is an object of the present disclosure to provide a cheaper and faster method for manufacturing lenses containing holographic components, whatever the optical properties of the lens may be, e.g., with respect to refractive index, transmission, birefringence, absorption filtering, optical power (including progressive power), etc.

[0012] The above mentioned objects are achieved by means of combinations of features set out in the independent claims, while the dependent claims provide particular advantageous embodiments of the invention.

[0013] An ophthalmic lens and a method for manufacturing the same are disclosed.

[0014] An ophthalmic lens according to an embodiment of the present disclosure comprises a base lens including a low birefringence material layer having a holographic component recorded thereon, and an auxiliary lens assembled to the base lens. The low birefringence material layer allows for a high-quality and efficient holographic component. The auxiliary lens can then provide any desired functionality, mechanical and / or optical, simply by assembling the auxiliary lens to the base lens. In particular, the auxiliary lens can be made of a high-birefringence material without compromising the manufacturing cost or complexity of a holographic mirror.

[0015] For example, the base lens may be a flat lens, i.e., without any refractive power, and the auxiliary lens may have a refractive power corresponding to the refractive power of the final lens. In embodiments, the base lens and / or the auxiliary lens may incorporate optical functions. In particular, incorporating polarizing / photochromic / tinting functions on the front side of the base lens while the holographic component is on the back side of the base lens can increase the virtual image contrast because light from the environment is reduced while light coming from the display and reflected by the mirror is not reduced, which is particularly suitable for augmented reality applications.

[0016] For a better understanding of the description and advantages of the present specification, reference is now made to the following brief description of the accompanying drawings and detailed description, in which like reference numerals represent like elements. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram showing a first example of an ophthalmic lens. [Figure 2] FIG. 10 is a diagram showing a second example of an ophthalmic lens. [Figure 3] FIG. 10 is a diagram showing a third example of an ophthalmic lens. [Figure 4] 1 is a diagram schematically illustrating an optical device into which an ophthalmic lens is inserted. [Figure 5a] 1A-1C show schematic diagrams of various optical setups for recording holographic mirrors. [Figure 5b] 1A-1C show schematic diagrams of various optical setups for recording holographic mirrors. [Figure 5c] 1A-1C show schematic diagrams of various optical setups for recording holographic mirrors. [Figure 5d] 1A-1C show schematic diagrams of various optical setups for recording holographic mirrors. [Figure 6] 1 illustrates schematically the main steps of an exemplary embodiment of a method for manufacturing an ophthalmic lens. DETAILED DESCRIPTION OF THE INVENTION

[0018] definition The following definitions are provided to explain this disclosure.

[0019] "Holographic mirrors" (HMs) are known in the art. A mirror is defined as a holographic mirror if it has been recorded using a holographic process. The mirror is used to reflect a light beam generated by an image source, such as a display screen, picoprojector, etc., towards the wearer's eye, resulting in the wearer visualizing the image. The holographic mirror is not used to reconstruct the recorded holographic image, as is the case with conventional hologram viewing.

[0020] The recording configuration can give the mirror an optical function that is independent of the geometry of the layer supporting the holographic mirror: for example, the holographic mirror may or may not have a focal length, may contain different functions in one or several zones, may reflect different wavelengths, may have a determined refractive power, etc.

[0021] A "holographic filter" is an optical filter that is recorded on a support using a holographic process. Such a filter is capable of transmitting a wavelength or a range of wavelengths in a specific direction.

[0022] A "holographic lens" is a lens that is recorded on a support using a holographic process. It can operate for a given wavelength or range of wavelengths to focus light in a given direction or at a given location. On the same support, holographic lenses can be configured to exhibit spectral and / or angular selectivity, with different focal lengths in different zones, and with different spectral or angular selectivities.

[0023] A "holographic deflector" is a holographic component that directs incident light in a direction different from the direction the incident light would otherwise travel.

[0024] A "Fourier hologram" is a hologram that contains an image that can be read by an external source either in transmission or reflection, thereby allowing compact displays to be produced for augmented reality, ophthalmology, or vision correction applications.

[0025] An "edge-lit hologram" is a hologram that allows light to be guided in a thin layer, for example towards suitable sensor, display or filter integration.

[0026] Hereinafter, a holographic component may refer to any one of a holographic mirror, a holographic filter, a holographic lens, a holographic deflector, a Fourier hologram, or an edge-lit hologram.

[0027] Recording of a holographic component on a support is carried out using an optical setup with a light source, e.g., a laser, emitting a light beam. Typically, a polarizing beam splitter allows the beam to be split into two beams: one reference beam and one illumination beam, which illuminate the holographic medium from the same or opposite sides depending on the type of holographic component. The interference caused by the reference and illumination beams on the holographic recording medium allows the holographic component to be recorded. The configuration of the reference and illumination beams allows the function and configuration of the holographic component to be adapted. For example, in the case of a holographic mirror, once the optical setup is set (e.g., geometry, beam size, etc.), the characteristics of the holographic mirror can be changed by changing one or more parameters, including the refractive index ratio between the two beams (affecting fringe contrast and diffraction efficiency), the exposure time (affecting fringe contrast and diffusion efficiency), and the possible use of rotatable supports on which the polarization-maintaining fibers through which the reference and illumination beams pass are positioned (affecting the polarization of the beams when they exit the fibers). It may be noted that multiple reference and / or illumination beams may be used to record a holographic component. Those skilled in the art may refer to document WO 2016 / 156614 for further details on the recording set-up used to achieve the desired holographic component configuration.

[0028] "Head-mounted display devices" (HMDs) are known in the art. Such devices are worn on or around the wearer's head, including helmet-mounted displays, optical head-mounted displays, head-worn displays, etc. Such devices include optical means for displaying images for viewing by the wearer. HMDs may provide superimposed visualization of computer-generated images and a "real-life" field of view. HMDs may be monocular (one eye) or binocular (two eyes). HMDs incorporating lenses according to the present disclosure can take a variety of forms, including eyeglasses, masks such as ski masks or diving masks, goggles, etc. HMDs comprise one or more ophthalmic lenses. In a preferred embodiment, the HMD is eyeglasses provided with ophthalmic lenses, which may be sun lenses.

[0029] An "image source" (IS) is known in the art. An image source is any light source capable of emitting a light beam suitable for displaying an image for visualization by a wearer. Visualization occurs after an illumination beam from the image source is reflected by a holographic mirror. In embodiments of the present disclosure, the IS is typically off-axis in that it can be located next to the wearer's temple, for example, on a temple component of an HMD, such as a temple component of eyeglasses. In embodiments of the present disclosure, the IS can be any image source configured to display a virtual image (computer-generated image). The IS can be a screen (e.g., OLED, LCD, LCOS, etc.), a phase and / or amplitude SLM (spatial light modulator), a projector such as a picoprojector (MEMS or DLP, which may use LEDs, diodes, lasers, etc.) together with its light source (e.g., laser, laser diode, etc.), or any other source. The IS can also include any other image source (computer-generated image source), and / or control electronics, and / or a power source, and / or optional optical elements, etc.

[0030] Eye lenses An ophthalmic lens 1 according to an embodiment of the present disclosure will now be described with reference to FIGS.

[0031] The ophthalmic lens 1 comprises a base lens 10 including a layer 11 in which a holographic component 20 is recorded, and an auxiliary lens 30 assembled to the base lens 10 .

[0032] As shown schematically in Fig. 4, according to an embodiment, the ophthalmic lens 1 is configured to be fitted into a head-mounted display device HMD 5 comprising a frame 50 in which an integrated image source 51 is positioned. In this embodiment, the holographic component 20 may comprise a holographic mirror. The image source 51 is then configured to illuminate said holographic mirror and, upon reflection on said holographic mirror 20, cause the wearer to visualize a virtual image, which is superimposed on the wearer's actual vision of their environment. In the case of a wearer with refractive error, the ophthalmic lens 1 is configured to correct both the wearer's virtual vision (vision of the image generated by the image source) and their actual vision (vision of the wearer's environment).

[0033] A particular application is an augmented reality device in which optical conjugation is performed between the eye's pupil and an image source. In this configuration, the HMD 5 may include a movable micromirror interposed between the image source and the lens, which moves according to the position of the eye's pupil so as to follow the movement of the eye's pupil. Furthermore, in this configuration, a holographic mirror recorded on the lens is configured to perform optical conjugation between the image source and the pupil. Given that the distance between the holographic mirror and the pupil is very short, this implies that the mirror has a significant refractive power, for example, in the range of +40D to +60D.

[0034] Another possible application is an imaging system that is not conjugate with the eye's pupil, but instead has an image source placed near the focal point of a holographic mirror, which sends a virtual image to infinity.

[0035] The base lens 10 of the ophthalmic lens 1 is at least partially transparent. The base lens 10 can be flat, curved, spherical, cylindrical, or completely freeform. The geometry of the base lens can be freeform, circular, square, etc. The auxiliary lens can be flat, curved, spherical, cylindrical, or completely freeform. The geometry of the auxiliary lens can be freeform, circular, square, etc.

[0036] Layer 11 of base lens 10 is made of a low birefringence material to enable recording of high-quality holographic components 20. As mentioned above, the visibility V of the interference fringes created to record an optical function depends on the angle Ψ between the polarization of the illumination beam and the polarization of the reference beam. Birefringent materials induce an inherent change in polarization that reduces the visibility of the interference fringes along the surface of the recorded layer.

[0037] Here, a material with low birefringence is considered to be one in which the visibility of the fringes across the surface of the material layer is at least 80% of the maximum visibility Vmax, which corresponds to a variation in angle Ψ of about 0° to 38°, and which corresponds to less than the width of one fringe, with light fringes corresponding to a parallel polarization state and dark fringes corresponding to a perpendicular polarization state.

[0038] The following materials have low birefringence and are suitable for forming layer 11 of the base lens in which the holographic components are recorded: thermosetting polythiourethane resins available from Mitsui Toatsu Chemicals under the trade names MR-7™ and MR-8™; allyl diglycol carbonate (ADC), also known as CR-39 or sold by Essilor under the trade name Orma®; Triacetate cellulose (TAC), 1.74 refractive index material, mineral glass

[0039] On the other hand, auxiliary lens 30 does not need to contain a holographic mirror and therefore can include at least one layer of a highly birefringent material. For example, the auxiliary lens can be made of polycarbonate. However, auxiliary lens 30 can also be made of a low birefringent material or various layers, some of which are highly birefringent and some of which are low birefringent.

[0040] According to an embodiment, the low birefringence material layer 11 has no refractive power and therefore does not provide correction to the wearer. The ophthalmic lens 1 may have a determined refractive power. In that case, the refractive power may be provided by the auxiliary lens 30. The ophthalmic lens 1 may not provide any refractive power. In that case, the auxiliary lens 30 may be a plano lens, i.e. a lens with no refractive power, but is used to increase the mechanical properties of the base lens 10 (if the base lens 10 is very thin, for example less than 1 mm thick) and / or to provide at least one optical function to the ophthalmic lens.

[0041] However, even if layer 11, and possibly the entire base lens 10, and possibly auxiliary lens 30, have no optical power, they may have curved surfaces to provide good aesthetics. In a non-limiting example, low birefringence material layer 11 includes a front surface 12 and a back surface 13, both of which may be spherical and therefore have no optical power.

[0042] According to another embodiment, the low birefringence material layer 11 may include a refractive power. The auxiliary lens 30 may be configured to provide a refractive power complementary to the refractive power of the low birefringence material layer 11 to achieve the desired refractive power of the lens 1.

[0043] 1, base lens 10 comprises only low birefringence material layer 11, and holographic component 20 is recorded on low birefringence material layer 11. When base lens 10 comprises only said layer 11, holographic component 20 may be recorded on either front surface 12 or back surface 13 of layer 11, which form the front or back surface, respectively, of base lens 10. An auxiliary lens 30 may be assembled on the front surface, or more preferably, on the back surface, of base lens 10.

[0044] In embodiments, some examples of which are shown in Figures 2 and 3, the base lens 10 and / or the auxiliary lens 30 are configured to provide at least one optical function, such as amplitude filtering, spectral filtering (such as edge-pass or band-pass filtering, such as short-pass or long-pass, or filtering of a specific color, for example, by incorporating coloring or photochromic or electrochromic functionality), or polarization.

[0045] To provide the above optical functions, the base lens 10 and / or the auxiliary lens 30 may comprise two or more layers. For example, if the base lens provides the optical function, the optical function may be performed by the low birefringence material layer 11 (e.g., layer 11 may be tinted to provide sun / UV protection), or by at least one additional layer 14 assembled to the low birefringence material layer 11, or a combination of layer 11 and additional layer 14.

[0046] In that case, the relative positions of the holographic element 20 and the additional layer 14 of the base lens 10 and the position of the auxiliary lens 30 (i.e., assembled to the front or back surface of the base lens 10) may be determined according to the optical function provided by the additional layer and / or the auxiliary lens 30.

[0047] By way of non-limiting example, if the optical function is one of polarization, photochromic, or filtering by a colored layer, the holographic component 20 may preferably be recorded on the back surface 13 of the layer 11, while the optical function is implemented on the front surface of the holographic component 20 by either the layer 11 itself or an additional layer 14, assembled to the low-birefringence material layer 11 on its front surface 12. This allows the optical function implemented by the additional layer or the layer 11 itself, when the ophthalmic lens 1 is incorporated into a frame having an image source, to be applied only to light from a "real-life" field of view, and not to light from the image source, and then reflected by the mirror. Therefore, it is not necessary to adapt the configuration of the holographic mirror to take into account the effect of the optical function. Furthermore, in this case, the presence of the polarization / photochromic / colored functions enhances the contrast of the virtual image, since light from the environment is reduced, while light from the virtual source is not.

[0048] In that case, the auxiliary lens 30 may also be assembled to the back surface of the base lens 10 (which would be the back surface of layer 11 if the additional layer 14 is assembled to the front surface of layer 11).

[0049] A first example of an optical function that can be provided by the base lens 10 or the auxiliary lens 30 is at least partial coloring. Either the layer 11 or the additional layer 14 of the base lens 10 or a layer of the auxiliary lens 30 can be formed of a coloring material, such as a material including blue-cut functionality, as disclosed in WO 2018 / 054984. The layer 11, the additional layer 14, or a layer of the auxiliary lens 30 can also contain a UV-absorbing dye (such as the dyes commercially available from BASF under the trade names TINUVIN® 477 or 479). If the holographic component 20 is recorded on the back side of the low-birefringence material layer 11, providing a UV-absorbing dye reduces the amount of UV reaching the holographic component and reduces any yellowish appearance that such a component may have.

[0050] 2, according to another example, the base lens 10 comprises an additional photochromic layer 14, such as a photochromic polyurethane layer 14. In another embodiment, the auxiliary lens 30 may comprise such a photochromic layer.

[0051] According to another example shown in Figure 3, the base lens 10 can comprise a polarizing cell 15. The polarizing cell 15 typically comprises two low birefringence material layers with a polarizing thin film positioned between them. In this case, the low birefringence material layer 11 with the holographic element 20 recorded therein can be one of the two low birefringence material layers of the cell.

[0052] For example, the polarizing cell 15 can be formed from a three-layer stack of TAC-PVA-TAC (PVA stands for polyvinyl alcohol), in which case one of the TAC layers can also form the low birefringence material layer 11 in which the holographic component 20 is recorded. The polarizing cell 15 can also be formed from a three-layer stack of PC-PVA-PC (PC stands for polycarbonate), in which case PC is a high birefringence material, in which case the base lens 10 does not form part of the cell 15 but comprises the low birefringence material layer 11 assembled to the cell 15. According to another example not shown, the auxiliary lens 30 can comprise such a polarizing cell 15.

[0053] According to yet another example, the base lens 10 or the auxiliary lens 30 may include an electrochromic cell (not shown).

[0054] Finally, at least one of the base lens 10 and the auxiliary lens 30 may be provided with a coating 16 on its outer surface, such as an abrasion-resistant coating (also known as a hard multilayer coating) and / or an anti-reflection coating. If the holographic component 20 is recorded on the back surface of the low-birefringence material layer 11, said surface preferably forms the back surface 22 of the base lens 10, and the coating 16 is preferably deposited on the front surface 21 of the base lens. An additional coating 16 may be provided on the back surface 22 of the base lens 10, covering the holographic component 20. An intermediate additional layer may be provided between the holographic component and the coating 16.

[0055] If the coating is an anti-reflective coating, the coating may be deposited before recording holographic element 20 to enhance the quality of the recording and to protect the holographic element.

[0056] According to another embodiment, the holographic element 20 may be recorded on the front surface of the low birefringence material layer 11, said holographic element 20 forming the front surface of the base lens 10 or covered by an additional layer, the base lens 10 being provided with a coating on its front surface and possibly also on its back surface.

[0057] 2 and 3, the base lens 10 may include two or more additional layers 14 to provide a desired function or functions. At least one additional layer may be, for example, a photochromic layer 14 or a polarizing cell 15, and at least one other layer 16 may include one or more coatings (such as abrasion-resistant, anti-reflective coatings, etc.). The supplemental lens 30 may also include one or more layers that achieve several desired optical functions.

[0058] The holographic element 20 recorded on the surface of the low birefringence material layer 11 is configured to provide at least one optical function such as a mirror function, a filtering function, etc. According to one example, the holographic element 20 can be a holographic filter. According to another example, the holographic element 20 can be a holographic mirror that further includes a filtering function. For example, the holographic mirror 20 may be configured to reflect only a specific range of wavelengths of light, such as blue, red, or green light. If the holographic component is a mirror, it may be curved or off-axis and may reflect a specific range of wavelengths emitted from the image source of the HMD. In that case, the type of wavelengths reflected may depend on the image source. The mirror may also be a flat mirror configured to reflect wavelengths from the wearer's actual field of view. The holographic mirror 20 may also provide a desired optical power, such as in the example given above, where the holographic mirror provides an optical conjugate between the image source of the HMD and the wearer's pupil.

[0059] The holographic element 20 may also incorporate features such as optical waveguides.

[0060] As previously indicated, the holographic element 20 is recorded by creating interference between at least one reference beam and an illumination beam on a thin film of holographic recording material. In embodiments, it is possible to maintain the same setup for recording the holographic element in a given base lens geometry, whatever the final lens. This is the case, for example, when the holographic element is a holographic filter. In this case, recording can be performed before or after auxiliary lenses are assembled to the base lens.

[0061] In other embodiments, it is possible to adapt the setup for recording the holographic component 20 according to the configuration of the final lens 1. For example, in an augmented reality application where the holographic component is a mirror, the setup for recording the holographic mirror can be adapted according to the refractive power of the final lens. In this case, an auxiliary lens 30 provides the refractive power and, if made of a low-birefringence material, is preferably assembled to the base lens 10 during recording of the holographic mirror. Conversely, if the auxiliary lens 30 is made of a high-birefringence material, the auxiliary lens can be replaced with an equivalent lens made of a low-birefringence material. The setup can also depend on the position of the holographic component within the final lens, i.e., whether the holographic component is assembled to the back or front of the base lens, and whether the auxiliary lens 30 is assembled to the back or front of the base lens.

[0062] In an embodiment, layer 11 may comprise a plurality of recorded holographic components 20. As a first example, low birefringence material layer 11 may be provided with different filters or mirrors configured to filter or reflect different ranges of wavelengths. In this case, the components 20 are preferably recorded on the same surface of layer 11. In another example, low birefringence material layer 11 comprises, on its first surface (back surface), a first off-axis holographic mirror configured to reflect light within the wavelength range emitted by the display or image source, and layer 11 further comprises, on its second surface (front surface), a second holographic mirror, such as, for example, a plane mirror that prevents light not reflected by the first mirror from being seen by a person with whom the wearer is conversing.

[0063] Ophthalmic lens manufacturing method With reference to FIG. 6, the main steps of the method 100 for manufacturing an ophthalmic lens 1 according to the above will now be described.

[0064] The method includes a step 110 of forming a holographic element 20 on a layer of low birefringence material 11, which includes a sub-step 111 of depositing a thin film F of holographic material on a major surface of the layer of low birefringence material 11. The layer of low birefringence material 11 may have previously undergone a thermoforming step to provide it with a desired curvature.

[0065] Holographic materials are known in the art. Such materials include dichromated gelatin and photopolymers. Non-limiting examples of suitable photopolymers are commercially available from Polygrama under the trade name SM-TR™. The holographic material can be deposited by polymer jetting, spray coating, dip coating, or spin coating. The holographic material can be deposited on the front or back of the low birefringence material layer 11 over the entire surface or only in specific areas, for example, by pad printing. In the case of dip coating, the holographic material is deposited on both major surfaces of the layer 11, and one of the thin films can be subsequently removed.

[0066] Next, step 110 involves exposing the thin film of holographic material to sunlight 112 while exposed to the holographic setup to effectively record the holographic component. Referring to FIGS. 5a-5d, recording of the holographic component is performed by generating interference between a reference beam RB and an illumination beam IB on a thin film of holographic material F. The two beams are from the same light source S, allowing for interference between the beams. The aperture, beam orientation, beam separation, source wavelength, and number of beams (at least two, but may be three or more) can define the optical function to be recorded. In particular, the spatial configuration of the reference beam reflects the spatial configuration (orientation, distance, width, i.e., shape and size of the zone projected onto the lens, etc.) that will be implemented to illuminate the holographic component after the lens is fitted into the frame.

[0067] The recording setup may be configured such that at least one of the reference beam RB and the illumination beam IB propagates through a low-birefringence material layer before reaching the holographic material film. As mentioned above, the use of a low-birefringence material layer as a support for the holographic component provides better quality of the recorded holographic component compared to the use of a birefringence material layer in terms of increased visibility of the fringes.

[0068] However, some parasitic reflections that produce parasitic holograms may occur due to the reflection of one of the beams at the interface between the holographic material and the layer of material supporting the holographic material. This is also true if the recording setup is configured so that the reference beam RB and the illumination beam IB do not propagate through a layer of low-birefringence material before reaching the thin film of holographic material.

[0069] The use of a low birefringence layer allows the use of antireflection coatings that can be designed for a specific polarization, which can be more efficient and easier to design than antireflection coatings designed for two orthogonal polarizations, as is the case when the layer of material supporting the holographic material is birefringent.

[0070] Furthermore, parasitic reflections can be more easily reduced by choosing a configuration in which at least one of the reference beam and the illumination beam enters the holographic material at an angle close to the Brewster's angle with appropriate polarization. Light emitted by a light source S (typically a laser) is guided to the low-birefringence material layer 11 by, for example, an optical fiber, which may include a single-mode fiber, preferably a polarization-maintaining (PM) single-mode fiber, or a large-core-area fiber, preferably a PM large-core-area fiber. A beam splitter is used to split the beam into a reference beam and an illumination beam.

[0071] One or more lenses selected from monofocal lenses, bifocal lenses and multifocal lenses such as progressive lenses, and optionally plane mirrors may be used to shape the illumination and reference beams, for example, according to the configuration of the holographic component to be recorded. Other means may also be used to shape the illumination and / or reference beams, such as lenses with variable focal lengths, spatial light modulators and adaptive mirrors. This configuration preferably: To fit the lenses and holographic components to the wearer, data about the wearer are taken into account, including for example interpupillary distance, eye rotation center position, prescription, functional preferences, etc. This list is not exhaustive. Frame data including the geometry of the frame (position of the width carrying the image source relative to the lens, size of the lens), possible accessories to be embedded such as eye trackers, etc. This list is not exhaustive. Supplementary lens data including the lens power and its optical properties (refractive index, transmittance, diffusion, etc.). This list is not exhaustive. Base lens data, including the base lens configuration (embedded features) and its optical properties. This list is not exhaustive. Display data: type of display (screen, e.g. OLED, LCD, LCOS, etc.; coherent or incoherent light source, e.g. LED, laser, diode laser, OLED, etc.; combination of light source and screen), presence of active or passive optical system to project the image with the desired specifications (collimator, focus, deflector, etc.), geometric dimensions of the display, physical characteristics of the display (e.g. bandwidth), etc. This list is not exhaustive.

[0072] In some embodiments in which the holographic component 20 is a mirror configured to reflect the virtual image generated by the image source of the HMD, the recording optics include: a reference beam RB simulating the beam of the image source used to illuminate said holographic component, so that the representation of the virtual image can be visualized by the wearer when wearing the frame; The lighting beam IB The distance at which the wearer visualizes the displayed virtual image when wearing the frame, and / or the direction of visualization of said displayed image by the wearer when wearing the frame, and / or Number of holographic mirror areas for the wearer to visualize the displayed virtual image when wearing the frame It is configured to define It is configured as follows.

[0073] An exemplary embodiment of the recording of a holographic mirror intended for use in an HMD is shown in Figures 5a to 5e. Figure 5a presents the setup used to record a plane mirror. In this case, the reference beam RB is an illuminating transmitted beam reflected by a plane mirror M placed after layer 11.

[0074] Figure 5b shows the setup used for recording on an off-axis plane mirror. In this case, the illumination beam IB is a collimated beam, and the reference beam RB is another collimated beam originating from an off-axis position corresponding to the position after the image source IS relative to the holographic mirror. This embodiment is suitable for light sources that are SLMs (spatial light modulators) or light field displays (LFDs).

[0075] Figure 5c shows a setup for recording an off-axis curved mirror. In this case, the illumination beam IB is collimated, and the reference beam RB, which has the properties of, for example, a display or image source, reaches the membrane F at the desired position, focus, and angle. This embodiment is suitable for HMDs with a screen as the image source and / or HMDs that require optical conjugation between the pupil and the image source.

[0076] Figure 5d presents a setup that records both an off-axis mirror for visualizing the display or image source and a privacy filter for an external viewer. In this case, the illumination beam IB is a collimated beam, a first reference beam RB1 has the properties of the display and image source and enters layer 11 at the desired position, focus, and angle, and a second reference beam RB2 is an illumination collimated beam reflected by a plane mirror M placed after layer 11.

[0077] Other setups can also be created for other types of optical functions.

[0078] According to an embodiment, the base lens 10 is formed only by the layer 11 in which the holographic component is recorded. According to another embodiment, the base lens 10 further comprises at least one additional layer 14 and / or an additional coating 16.

[0079] Therefore, the manufacture 100 of the lens 1 optionally also includes a step 113 of assembling the low birefringence material layer 11 with any additional layers 14, for example to allow the base lens 10 to incorporate other optical functions such as those listed above (e.g., tinting, photochromic, electrochromic, polarizing functions, etc.). This step can be performed differently according to the type of function to be incorporated in the additional layer (e.g., coating can be performed by dipping, spin coating, etc.).

[0080] The order in which steps 110 and 113 are performed can vary according to the functions performed in the base lens.

[0081] According to a first embodiment, step 113 of assembling the low birefringence material layer 11 to an additional layer 14 (which may include a photochromic or electrochromic cell 15 or a layer thereof) may be performed prior to recording 110 of the holographic component. This may be the case, for example, if the additional layer is a layer providing a polarization, photochromic, electrochromic or filtering function in an augmented reality application. In that case, the additional layer is preferably provided in front of layer 11 prior to recording of the holographic mirror, in order to enhance the contrast between the virtual image from the image source of the HMD and the image from the wearer's environment.

[0082] According to another embodiment, step 113 may be performed after recording 110 of the holographic element.

[0083] The method also includes a step 120 of assembling the layer of low birefringence material 11 to the auxiliary lens 30. This assembling 120 can be performed by gluing, casting, clipping, additive manufacturing, for example by depositing voxels of material that will form the auxiliary lens 30 directly onto the base lens.

[0084] In another embodiment, step 120 may be performed using a back-injection process, during which the base wafer 10 is placed in a mold and an injected material is provided on the surface where the auxiliary lenses are to be formed, for example the back surface.

[0085] In an embodiment, the assembling step 120 may be performed after the step 112 of assembling the low birefringence material layer 11 to the additional layer 14 .

[0086] Step 120 may be performed after step 110 of recording the holographic component in the low birefringence material layer 11 or before if, for example, the auxiliary lens 30 is low birefringent and provides a refractive power and the construction of the holographic component needs to take said refractive power into account, in which case the auxiliary lens 30 is part of the recording setup of the holographic component.

[0087] The method also includes a step 130 of depositing at least one coating 16, such as, for example, an anti-reflective coating or a hard multilayer coating. The coating may be deposited on a major surface (i.e., front or back) of the base lens 10, on either the low birefringence material layer 11 or the additional layers 14, if any. Step 130 can then be performed before recording the holographic element 20 or after this step. Step 130 may be performed after assembling base lens 10 with auxiliary lens 30, in which case it involves depositing coating 16 on the front or back surface of the resulting lens 1.

[0088] According to one example, the base lens 10 may include an anti-reflective coating 16 deposited prior to recording of the holographic element 20 to improve recording by eliminating any ghost reflections. Since the step 111 of recording the holographic material is preferably carried out at 80°C, an anti-reflective coating that can withstand this temperature is preferably selected. According to another example, after recording of the holographic component, a hard multilayer coating may be provided, since the deposition process of the HMC requires a heating step at about 100°C to 120°C, and such temperatures can be withstood by the holographic component.

[0089] According to another example, the hard multi-layer coating and / or anti-reflective coating may be deposited on either the front or back surface of the lens obtained after assembling the base lens 10 with the auxiliary lens 30 .

[0090] FIG. 6 shows a non-limiting, exemplary embodiment of a method comprising step 110 of forming a holographic element 20 on a low birefringence material layer 11, step 112 of assembling said layer with an additional layer 14 incorporating an optical function, then step 120 of assembling the thus obtained base lens with an auxiliary lens, and finally step 130 of depositing at least one coating 16 on the thus obtained ophthalmic lens.

[0091] A final lens is obtained that has high quality holographic elements 20 recorded in the low birefringence material layer 11, as well as any suitable optical function that may be provided by either the base lens or the auxiliary lens. [Explanation of symbols]

[0092] 1. Ophthalmic lenses 5. Head-mounted display device (HMD) 10 Base Lens 11 Low birefringence material layer 12 Front 13 Back 14 Additional Layers 15 Polarizing Cell 16 Coating 20 Holographic Components 21 Front 22 Back 30 Auxiliary Lens 50 frames 51 Image Source

Claims

1. - frame (50); an ophthalmic lens (1) fitted in said frame and having a refractive power, said ophthalmic lens (1) comprising: a base lens (10) comprising at least one layer (11) having no refractive power and at least one holographic mirror (20) recorded on the back surface of said layer (11); an auxiliary lens (30) assembled to the base lens (10), the auxiliary lens (30) providing the optical power of the ophthalmic lens; an ophthalmic lens (1), comprising: said base lens (10) designed to provide an amplitude or spectral filtering function in front of said holographic mirror (20); and an image source (51) arranged within said frame (50) and configured to illuminate said holographic mirror (20); A head-mounted display device comprising: The layer (11) in which the holographic mirror (20) is recorded is - thermosetting polythiourethane resins, - allyl diglycol carbonate, cellulose triacetate, and - material with refractive index of 1.74 A head mounted display device formed from a material selected from the group consisting of:

2. 2. The head mounted display device of claim 1, wherein the base lens (10) includes one of a polarizing function, a photochromic or electrochromic cell, or a colored layer.

3. the base lens (10) has a front surface (21) and a back surface (22), the back surface being formed by the back surface (13) of the layer (11) in which the holographic mirror (20) is recorded; A head mounted display device according to any one of claims 1 to 3, wherein the front surface (21) of the base lens is covered with a hard multi-layer coating (16).

4. 1. A method of manufacturing an ophthalmic lens, comprising: - depositing (111) a thin film of unrecorded holographic medium on the back surface of a layer (11) having no refractive power, said layer (11) having the holographic mirror (20) recorded thereon; - thermosetting polythiourethane resins, - allyl diglycol carbonate, cellulose triacetate, and - material with refractive index of 1.74 a depositing step (111) formed of a material selected from the group - performing holographic recording of said holographic medium (112) by generating interference between a reference beam and an illumination beam to form a holographic mirror in said layer (11); a step (120) of assembling said layer (11) with an auxiliary lens (30) providing a refractive power, said assembling being carried out after or before the step of performing the holographic recording; Including, The method, wherein the layer (11) in which the holographic mirror (20) is recorded and / or at least one additional layer (14) assembled to the layer (11) before or after the step of performing the holographic recording is designed to provide an amplitude or spectral filtering function in front of the holographic mirror (20).

5. 5. The method of claim 4, wherein during the holographic recording (112), at least one of the reference beam and the illumination beam propagates through the layer (11) before reaching the holographic medium.

6. 6. The method according to claim 4 or 5, further comprising a step of thermoforming the layer (11) before the step of performing holographic recording, the step of thermoforming being carried out to achieve a desired curvature.

7. The method according to any one of claims 4 to 6, wherein the assembling step (120) is performed by additive manufacturing, gluing, casting, clipping or injection.

8. 8. The method according to any one of claims 4 to 7, further comprising depositing at least one coating (130) comprising a hard multilayer coating and / or an abrasion resistant coating on the front and / or back surface of a lens obtained by assembling said layer (11) to said auxiliary lens (30), or on a base lens (10) comprising said layer (11) before assembling it to said auxiliary lens (30).

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