Optical element comprising at least one holographic diffuser element

Abstract

The present disclosure relates to an optical element intended to be worn in front of the eye of a wearer. This optical element has two main surfaces and comprises at least one holographic diffusing element having a diffusing property resulting from a spatial variation of the refractive index of said holographic diffusing element. This spatial variation of the refractive index is greater than 0.001 at at least one given wavelength over a distance of less than 30 pm. The present disclosure also includes an optical equipment comprising such an optical element and a method for recording a holographic medium onto an optical lens.

Description

Technical Field

[0001] This invention belongs to the field of optical devices, particularly ophthalmology.

[0002] The present invention relates to an optical element comprising at least one holographic diffuser element, and a method for manufacturing such an optical element. Background Technology

[0003] For optical lenses designed to be worn in front of the wearer's eyes, aesthetic standards are very important, such as good-looking lenses. However, the challenge lies in maintaining a high level of comfort, correction, and therapeutic effect while adhering to these aesthetic standards.

[0004] For example, some recently developed optical lenses include diffuse elements on one of their main surfaces, which are protrusions on the surface of the optical lens. Such diffuse elements are obtained by photolithography or by depositing discrete portions of material including the protrusions and then curing the deposited material.

[0005] This type of optical lens allows incident visible light to be diffused in both reflection and transmission. Therefore, when wearing such a known optical lens, at least a portion of the incident visible light is not focused on the wearer's retina, which allows for the slowing of the development of refractive errors in the eye.

[0006] One of the drawbacks of this type of diffuser is the roughness of the lens, which obviously lowers the level of aesthetic standards.

[0007] A diffuser element can create an unfocused beam of light whose width is minimized on a designated plane in front of the wearer's retina. Therefore, a blurred image is projected onto the designated plane.

[0008] Both of these methods have been successfully used as solutions for controlling myopia through optical mechanisms.

[0009] Recent controlled clinical trials have provided evidence that mechanically formed diffuse element arrays in the peripheral visual field are beneficial in slowing myopia progression. The purpose of this diffuse element array is to provide an optically blurred image in front of the retina through slight diffusion, thereby triggering a stop signal for eye growth. These lenses have no diffuse elements in the central area to achieve good vision. The basic principle of this solution is to reduce the contrast of the eye's elongating signal in the peripheral visual field.

[0010] Therefore, all existing versions of myopia control products based on peripheral optical technology must strike a balance between improving myopia control efficiency and reducing the wearer's visual performance under off-center viewing conditions.

[0011] More generally, among all known optical lenses with diffuser elements, the disadvantages of such diffuser elements include:

[0012] - Parasitic diffuse or stray light

[0013] -Contrast loss, and

[0014] - Surface roughness, which may be detrimental to the mechanical resistance of optical lenses.

[0015] Another example of the importance of aesthetic standards is the focus in the field of optics on providing sunglasses or tinted lenses in which the transmitted color seen by the wearer differs from the color seen by an external observer. This would allow for a specific, fashionable look, or conversely, conceal the color or filter to maintain a high level of aesthetic standards, as some wearers desire lenses with a specific reflected color that can be observed by anyone positioned in front of the wearer.

[0016] Therefore, what is usually needed is for optical elements to diffuse incident light without the known drawbacks of diffuser elements.

[0017] A further specific need is for optical elements to effectively slow the progression of myopia without the drawbacks of known diffuse elements. Summary of the Invention

[0018] This invention is defined by the appended independent claims. Additional features and advantages of the concepts disclosed herein are set forth in the following description.

[0019] This disclosure aims to improve this situation. In particular, one object of the present invention is to overcome the aforementioned disadvantages.

[0020] Therefore, this disclosure describes an optical element intended to be worn in front of the wearer's eyes.

[0021] The optical element includes at least one holographic diffuser having diffuse properties resulting from a spatial variation in the refractive index of the holographic diffuser, the spatial variation of which is greater than 0.001 at at least one given wavelength over a distance less than 30 μm.

[0022] Holographic diffusers are well known, as defined, for example, in the following articles: Stephen Wadle, Daniel Wuest, John Cantalupo, and Roderic S. Lakes, “Holographic diffusers”, Optical Engineering, 33(1), (January 1, 1994).

[0023] Depending on the characteristic dimensions of the scattering element in relation to the wavelength under consideration, there are generally three scattering mechanisms:

[0024] - Mirror mechanism - The scattering element is very large compared to the wavelength of the radiation. The physics appropriate for this proportion is geometrical optics. According to the Snell-Descartes law, the term "mirror" refers to the direction of reflected light.

[0025] - Thomson or Rayleigh scattering mechanism - The scattering element is very small compared to the wavelength.

[0026] -Intermediate mechanism—The size of the scattering element is on the same order of magnitude as the wavelength.

[0027] In a diffraction network, scattering elements of the intermediate mechanism are arranged periodically according to a regular lattice. The resulting wavefront superposition forms resonant scattering.

[0028] Throughout the holographic diffuse elements considered in this document, the redistribution of scattering elements is random, based on an irregular or aperiodic lattice. In other words, holographic diffuse elements lack long-range structural order. In terms of the optical properties of the material relative to the relevant wavelength, holographic diffuse materials lack the long-range ordered characteristics of crystalline solids. As a result, although a finite Bragg effect may occur, since any random redistribution of structural elements can be considered as a collection of Bragg planes with different spacing and orientations, the holographic diffuse elements considered throughout this document do not exhibit strict resonant scattering; rather, they primarily exhibit diffuse scattering.

[0029] Due to the specially configured holographic diffuser element, and more specifically due to the spatial variation of the refractive index of the holographic diffuser element, the optical element allows incident optical light to be selectively scattered in a predetermined direction (such as the part of the wearer's eye) when the optical element is worn.

[0030] The spatial variation of the refractive index is greater than 0.001 at at least one given wavelength over a distance less than 30 μm, preferably less than 20 μm. This spatial variation of the refractive index can reach, for example, 0.05 or less over a distance less than 30 μm, near an average value of approximately 1.5. These spatial variations can be measured precisely, for example, by well-known interferometry, where, for holographic diffuse elements as disclosed in this description, the size of interference fringes less than 30 μm, preferably less than 20 μm, can be measured using interferometry.

[0031] The thickness of the at least one holographic element can be less than 100 μm, preferably between 10 μm and 50 μm.

[0032] The at least one given wavelength may be in the infrared range, for example, between 2 μm and 5 μm, or in the UV range, or in the visible light range, preferably in the visible light range, for example, between 350 nm and 750 nm.

[0033] To scatter light at small diffusion angles, such as 2 degrees, 5 degrees, or similar angles, the spatial variation of the refractive index can be limited to 0.01 or 0.02. To scatter light at larger diffusion angles, such as 25 degrees, 30 degrees, or similar angles, a larger spatial variation of the refractive index is permissible.

[0034] In this disclosure, the term "diffuse" is equivalent to "scatter".

[0035] In this disclosure, the main surfaces of the optical element are an ocular-side surface (also referred to as the posterior surface) and an object-side surface (also referred to as the anterior surface). When the optical element is worn in front of the wearer's eye, the ocular-side surface is positioned on the side of the optical element closest to the wearer's eye and the anterior surface is positioned on the opposite side of the optical element.

[0036] Moreover, unlike the multiple protrusions described in the prior art (which inherently result in high surface roughness), the roughness of the main surface of the claimed optical element is not affected by the presence of the holographic diffuser.

[0037] Therefore, each main surface of the optical element described in this disclosure can have a uniform roughness parameter of less than 0.5 μm.

[0038] Optionally, the at least one holographic diffuser element has a diffuse efficiency between 5% and 50% at at least one given wavelength within a predetermined range, for example, between 5% and 40%, between 5% and 30%, or between 5% and 20%. This range of diffuse efficiency is meaningful when the purpose of the optical element is to influence the wearer's visual perception of a scene, such as to control the evolution of myopia.

[0039] Optionally, the at least one holographic diffuser element has a diffuse efficiency between 1% and 5% at at least one given wavelength within a predetermined range. This range of diffuse efficiency is meaningful when the purpose of the optical element is primarily or solely to influence the visual perception of the optical element by an observer, such as the wearer's interlocutor.

[0040] This diffusion efficiency refers to the haze obtained through the at least one holographic diffusion element. For example, this diffusion efficiency can be measured using a haze meter. Keeping the diffusion efficiency below 50% allows the wearer to primarily receive clear or sharp vision, along with a low and controllable level of blur.

[0041] Alternatively, the spatial variation of the refractive index can be configured such that:

[0042] For at least one incident angle direction, when the optical element is exposed to a source beam originating from said incident angle direction, the source beam is scattered by at least one holographic diffuser element, thereby forming at least one scattered beam.

[0043] Each of the scattered beams is centered around a corresponding central angular direction, which is defined as the angular direction with the maximum brightness value.

[0044] Each of the scattered beams has a corresponding diffusion angle, defined as the full width at half maximum (FWHM) of the luminance, with a desired value ranging from 2° to 40°. This range of diffusion angles is meaningful when the purpose of the optical element is to influence the wearer's perception of a scene, such as to control the evolution of myopia. In fact, in this case, the scattered beam illuminates at least a portion of the wearer's pupil. This range is particularly suitable if the optical element is a spectacle lens, considering the typical wearing distance between the optical element, such as a spectacle lens, and the wearer's eye.

[0045] In the context of this disclosure, the source beam can refer to light in the wearer's environment under various common conditions. Examples include diffuse solar radiation. Further examples include artificial light emitted by various light sources, such as display screens. The source beam can also refer to a specially shaped beam emitted by a specific light source arranged in a particular incident angle direction, with the aim of being scattered by holographic diffusers.

[0046] Optionally, the optical element is worn in front of the wearer's eye, and at least one corresponding central angle direction may correspond to the direction toward the pupil of the eye, or for example, the retina of the eye, or for example, the center of rotation of the eye.

[0047] Optionally, the optical element is worn in front of the wearer's eye, and at least one corresponding central angle direction may correspond to the opposite direction to the pupil of the eye, or for example, the retina of the eye, or for example, the direction of the eye's rotation center.

[0048] In some exemplary embodiments, the corresponding central angular direction corresponds to the direction in which the pupil center of the wearer's eye or the eye rotation center is intended to be when the optical element is worn.

[0049] In this embodiment, the desired limiting values ​​(2° and 40°) for each corresponding diffuse angle are suitable for allowing the scattered beam to illuminate the target portion of the wearer's entrance pupil and the entire entrance pupil of the wearer's eye, respectively. This central angle orientation is suitable for influencing the wearer's perception of the scene through the holographic diffuse element.

[0050] Throughout this document, “illuminating” an object is understood to mean directing the scattered beam toward the object, and the scattered beam is defined as being radially defined by the diffuse angle.

[0051] Based on parameters related to the wearer and / or the eyeglass frame, the desired value for each corresponding diffusion angle can be further customized within the range of 2° to 40°. Examples of parameters related to the wearer include prescription and pupil size. Examples of parameters related to the wearer and the eyeglass frame include vertex distance, tilt angle, and wrap angle.

[0052] "At least one angle of incidence" may, for example, correspond to the wearer's near or far vision. In other words, under given wearing conditions, in terms of vertex distance, tilt angle, and wrap angle, such as typical wearing conditions known to those skilled in the art or wearing conditions specific to a particular wearer, the optical element may be configured such that "at least one angle of incidence" corresponds to a viewing angle associated with a near or, respectively, a distant viewing distance.

[0053] Optionally, the optical element is worn in front of the eye, and the at least one holographic diffuser has the optical function of scattering light to illuminate the pupil or preferably the retina of the eye in order to slow the development of refractive abnormalities in the eye.

[0054] The optical element may have the optical function of scattering light to illuminate the central fovea of ​​the retina of the eye in order to slow the development of refractive errors in the eye.

[0055] For example, the holographic diffuse element may have the optical function of scattering light to create a diffuse image of a light source located in front of the wearer's retina.

[0056] Alternatively, the optical function of the holographic diffuser element may also allow illumination of the peripheral area of ​​the wearer's retina.

[0057] Optionally, the direction of the at least one incident angle corresponds to the wearer's near vision. Near vision refers to the distance and / or angle used for tasks such as reading, using a computer or telephone, manual tasks, or any task that requires proximity to the wearer.

[0058] According to one or more embodiments, the optical element may be a graded optical lens comprising near, intermediate, and far vision zones. Alternatively, the optical element may be single-vision with a single focal length.

[0059] Alternatively, this example of a progressive lens can be associated with a subrange of the desired diffuse angle (e.g., from 15° to 40°). Thus, during near vision, a large area of ​​the wearer's retina is illuminated by scattered light. The wearer needs to adjust to compensate for the scattering that occurs during near vision, thereby slowing the progression of presbyopia.

[0060] Therefore, the holographic element can be configured to scatter only light incident from certain angles of incidence corresponding to a particular type of visual activity.

[0061] The holographic element can also be configured, for example, to transmit light incident from any other angle of incidence without causing any scattering.

[0062] As a result, for example, it is possible to slow myopia by scattering light from distant objects whenever the wearer views them, while simultaneously preventing interference with the wearer during near-vision activities such as reading by transmitting light from near objects without scattering it. Therefore, the holographic element can be configured, for example, to scatter light from an angle of incidence associated with distance vision and to transmit light from an angle of incidence associated with near vision without scattering it.

[0063] Optionally, at least one holographic diffuser element may be diffuse only for light with wavelengths within a predetermined range.

[0064] For example, this range could cover the entire visible light spectrum, meaning approximately 400 nm or wider. Alternatively, this range could cover a narrow spectrum, meaning less than 10 nm wide, such as approximately 5 nm or less.

[0065] For example, the at least one holographic diffuse element has a diffuse efficiency that is maximized for at least one given wavelength within a predetermined range.

[0066] Therefore, a holographic diffuser can be proposed that is efficient for at least three wavelengths corresponding to RGB light from a display (such as a smartphone screen). This holographic diffuser element can specifically scatter green light toward a target area of ​​the wearer's eye, having an equivalent effect on slowing the development of refractive errors in that eye.

[0067] Therefore, the signal ratio used to reduce myopia / total diffusion can be maximized, and thus provide aesthetic / improved comfort compared to classic diffusion.

[0068] For example, the holographic diffuse element can be recorded using coherent blue light.

[0069] It is well known that blue light emitted by a monitor screen is harmful to the retina over time; therefore, it may make sense to scatter the blue light emitted by the scattering component in order to disperse its effects from a single area of ​​the retina.

[0070] Optionally, the optical element may further include a light guide configured to direct the source beam toward the holographic diffuser.

[0071] The purpose of the light guide is to control and guide the source beam toward the holographic diffuser in order to avoid parasitic reflections or unwanted absorption and to provide a higher amount of light toward the central angle as if the light guide were not present.

[0072] Optionally, the desired value of the diffusion angle can be greater than 5°, 8°, 10°, 12° or 15° respectively.

[0073] Optionally, the desired value of the diffusion angle can be less than 35°, 30°, 25°, 23° or 20° respectively.

[0074] The value of the diffusion angle is related to the size of the area targeted by the scattered beam and the distance between the area and the holographic diffuser.

[0075] For example, the area illuminated using a given holographic diffuser may correspond to a known position relative to that diffuser. In this case, the diffuser may be located, for example, on the peripheral portion of the optical element. By positioning the diffuser in the peripheral region of the optical element, the source light beam scattered and guided by the diffuser is a beam transmitted from the optical element toward the wearer's eye, even if the diffuser is not located at the center of the optical element. Meanwhile, the central portion of the optical element can be used to transmit incident light from the scene toward the wearer's eye.

[0076] In another example, the area illuminated using a given holographic diffuser element could be a portion of the wearer's retina through the pupil, or it could cover the entire pupil of the wearer's eye.

[0077] A diffusion angle between 2° and 12° can, for example, allow illumination of only a specific portion of the wearer's retina, which has a predetermined size.

[0078] Assuming a typical vertex distance of approximately 10mm to 15mm and a pupil size of approximately 4mm to 8mm, a diffusion angle between 12° and 20° can allow, for example, illumination of the area corresponding to the entire pupil of the wearer.

[0079] A diffusion angle of 20° or greater can allow, for example, scattered light to intentionally illuminate an angular area larger than the wearer's pupil.

[0080] Alternatively, the holographic diffuse element can be configured to provide refractive power based on a prescription for the wearer's eye.

[0081] An ophthalmic lens is an optical element that includes two opposing primary surfaces and provides refractive power in relation to the shape of at least one of the two primary surfaces.

[0082] For example, one primary surface can be spherical, while the other primary surface can be aspherical, more specifically shaped to provide refractive power based on that prescription. As a result, the refractive power of the optical element can be equal to that of the aspherical primary surface.

[0083] For example, both principal surfaces can be aspherical and each can contribute to providing refractive power based on the prescription. As a result, the refractive function of the optical element can be equal to the combination of the refractive functions of the two aspherical principal surfaces.

[0084] For example, the holographic diffuser is located between two main surfaces, and the holographic diffuser itself can have refractive power. As a result, the refractive function of the optical element can be equal to the combination of the refractive functions of the holographic diffuser and at least one aspherical main surface.

[0085] By enabling the holographic diffuser to contribute to providing refractive power based on a prescription for the wearer's eye, greater flexibility is allowed in terms of the curvature of the main surface. For example, this greater flexibility can be beneficial when seeking to optimize the weight or weight distribution of the optics.

[0086] The holographic diffuser element can be disposed on the eye-side and / or the object-side and / or between the two main surfaces. Preferably, at least the holographic diffuser element is disposed on the eye-side surface. The at least one holographic diffuser element can extend on only a portion of one of the two main surfaces or on all of one of the two main surfaces.

[0087] Optionally, the optical lens includes a plurality of such holographic diffuse elements. At least two of these holographic diffuse elements may be disposed in the same or different regions on at least one of the two main surfaces.

[0088] Alternatively, the at least two holographic diffuse elements may extend on non-overlapping regions of the same main surface, respectively.

[0089] The arrangement of the at least two holographic diffuse elements can follow a regular pattern, or conversely, be random or irregular.

[0090] Optionally, the optical element may include an optical material layer extending over at least a portion of the main surface, and the at least one holographic diffuse element may be formed in such a layer.

[0091] For example, the main surface of the substrate may initially be at least partially covered with a photosensitive material layer suitable for recording the at least one holographic diffuse element. Then, the at least one holographic diffuse element may be recorded on at least a portion of the layer. Finally, the resulting optical element (including the at least one holographic diffuse element) may be processed such that the photosensitive material layer loses its photosensitive optical properties.

[0092] Alternatively, the optical element may be an optical lens, such as an eyeglass lens.

[0093] Of course, this holographic diffuser is not limited to being incorporated into spectacle lenses. Contact lenses would also be suitable. However, compared to spectacle lenses, contact lenses are worn much closer to the wearer's retina. For this reason, in contact lenses, the desired diffuse angle can extend to a wider range than 2° to 40° for some applications, and can extend to 170°, for example, in applications where the entire retina is illuminated by the diffused beam.

[0094] Alternatively, the holographic diffuser element can be configured such that most of the light scattered by the holographic diffuser element is reflected. Such a holographic diffuser element can be referred to as a "holographic diffuser".

[0095] Optionally, the holographic diffuser element can be configured such that most of the light scattered by the holographic diffuser element is reflected from the external environment toward the external environment or, alternatively, reflected from the rear surface toward the wearer. In other words, the holographic diffuser element can be configured such that when the optical element is worn by the wearer facing the scene, most of the light scattered by the holographic diffuser element is reflected toward the scene. Alternatively, when the light source is embedded in the eyeglass frame, the holographic diffuser element can be configured such that when the optical element is worn by the wearer facing the scene, most of the light scattered by the holographic diffuser element is light originating from the embedded light source and reflected toward the wearer.

[0096] The optical element may further include at least one additional holographic element configured such that most of the light scattered by the holographic diffuser is reflected. Such a holographic element may be referred to as a "holographic mirror". The additional holographic mirror may also be diffuse, and therefore also a "holographic diffuser".

[0097] In the example, the optical element includes two opposite main surfaces, and each of the holographic diffuse element and the at least one additional holographic element extends over a non-overlapping region of the same main surface.

[0098] Optionally, each of the holographic diffuse element and the at least one additional holographic element is arranged according to a lattice structure, preferably a circular lattice structure, a square lattice structure or a hexagonal lattice structure.

[0099] Optionally, each of the holographic diffuse element and the at least one additional holographic element is arranged according to a random pattern.

[0100] Diffuse elements, obtained through photolithography or, for example, mechanical means such as sandblasting, essentially follow Lambert's law of emission. In other words, when viewed from any angle, such a diffuse element exhibits approximately the same radiation in both transmission and reflection.

[0101] Conversely, holographic diffuse elements can be adapted to primarily reflect the primary scattered beam while limiting or even preventing the transmission of the secondary scattered beam.

[0102] Conversely, holographic diffusers can be adapted to primarily transmit the primary scattered beam while limiting or even preventing the reflection of the secondary scattered beam.

[0103] For example, this allows only a single scattered beam to be directed toward the wearer's eye, while preventing the simultaneous emission of secondary beams in the angular direction in which the observer may be positioned.

[0104] Alternatively, the holographic diffuser element can be configured such that most of the light scattered by the holographic diffuser element is transmitted.

[0105] Conversely, the at least one holographic diffuser element can be adapted to primarily transmit the primary scattered beam while limiting or even preventing the reflection of the secondary scattered beam.

[0106] At least one holographic diffuser element can be formed of various optical materials that are largely transparent to scattered light of a given wavelength, that is, have a transmittance greater than 95%, or greater than 98%, or greater than 99%, or conversely, can absorb a considerable portion of light of said wavelength. For example, the transmittance of such optical materials can be less than 95%, less than 90%, less than 80%, and so on. For example, the filtered light can be used to prevent glare or to limit the amount of harmful light delivered to the wearer's eyes.

[0107] Optionally, the at least one holographic diffuse element is at least two holographic diffuse elements disposed in the same or different areas on the at least one main surface.

[0108] Multiple holographic diffusers can serve different purposes, and these purposes can be synergistic. For example, a combination of two holographic diffusers can scatter an incident beam toward different central angles and / or at different diffusion angles. For example, a combination of multiple holographic diffusers (each with wavelength selectivity) can scatter a selected combination of wavelengths without altering any other wavelengths.

[0109] Optionally, the at least one holographic diffuser element is a holographic gradient diffuser element, the diffusion efficiency of which increases from the center of the holographic diffuser element to its periphery. The holographic diffuser element can also function as a solid diffuser cone to scatter light. The diffusion efficiency of the holographic diffuser element may further or alternatively depend on the incident angle, the amplitude, the aperture angle, and / or the wavelength.

[0110] Gradient diffuse elements allow the wearer to experience a smooth visual sensation, whether in a static view or during eye movement.

[0111] This disclosure further describes an optical device that includes at least one of the aforementioned optical elements. For example, the optical device may include at least one optical element comprising one or more holographic diffusers.

[0112] The optical device may be an eye-wearing device, which includes a pair of spectacle lenses mounted on a spectacle frame. At least one of these spectacle lenses may be an optical element as defined above.

[0113] Optionally, the optical device may further include a light source arranged in the direction of the incident angle and configured to emit the source beam.

[0114] This light source can be attached to or integrated into eyeglass frames (such as temples, lens frames, or bridge of the nose).

[0115] This light source can be configured to emit monochromatic or polychromatic light in the visible, IR, or UV spectrum.

[0116] This light source can be used to activate a holographic element, which can be incorporated into the optical element. Therefore, the optical device can be, for example, an augmented reality device.

[0117] This light source can be used to activate photochromic elements that can be incorporated into the optical element, for example, to control the transmission or another optical property of the optical element.

[0118] For example, the optical device may include a motion sensor designed to acquire signals based on the wearer's movements, wherein the light source is illuminated when the acquired signal has a predetermined value. In other words, the motion sensor is configured to detect the wearer's position and / or posture to determine whether the wearer is performing a near-vision task. If the sensor detects that the wearer is currently performing a near-vision task, the light source illuminates to activate the holographic diffuser element.

[0119] This disclosure further describes a method for recording a holographic medium onto an optical lens, the method comprising:

[0120] An unrecorded optical lens is provided, comprising a recording medium extending over the region of interest, the unrecorded optical lens having two main surfaces.

[0121] Provides diffuse objects, and

[0122] A holographic diffuse element is recorded on the recording medium by simultaneously illuminating the area of ​​interest with the following:

[0123] The reference beam, which is a coherent beam, and

[0124] The object beam is a coherent beam of light that is scattered by the diffuse object to obtain the recording optical lens.

[0125] The diffuse object, the reference beam, and the object beam are configured such that the recorded holographic diffuse element has diffuse characteristics resulting from a spatial variation in the refractive index of the holographic diffuse element, the spatial variation of which is greater than 0.001 at at least one given wavelength over a distance less than 30 μm. For example, when recording the holographic diffuse element, the object beam can be obtained by arranging at least a portion of the coherent beam used as the reference beam toward the diffuse object (33) and the mirror (331) such that at least a portion of the coherent beam is reflected by the mirror and scattered by the diffuse object.

[0126] Depending on the desired optical properties of the holographic diffuser to be recorded, the mirror can be planar or curved. The mirror can be deformable or adaptive; in other words, its curvature can be controlled to achieve the desired curvature.

[0127] This disclosure further describes a method for recording a holographic medium onto an optical lens, the method comprising:

[0128] An unrecorded optical lens is provided, comprising a recording medium extending over the region of interest, the unrecorded optical lens having two main surfaces.

[0129] Modeling the optical properties of diffuse objects, and

[0130] A holographic diffuse element is recorded on the recording medium by simultaneously illuminating the area of ​​interest with the following:

[0131] The reference beam, which is a coherent beam, and

[0132] The object beam simulates the coherent beam that will be scattered by the diffuse object to obtain the recorded optical lens.

[0133] The diffuse object, the reference beam, and the object beam are configured such that the recorded holographic diffuse element has diffuse characteristics resulting from a spatial variation in the refractive index of the holographic diffuse element, the spatial variation in the refractive index being greater than 0.001 at at least one given wavelength over a distance less than 30 μm.

[0134] For example, when recording this holographic diffuse element, the reference beam can be provided by a light source facing one of the two main surfaces, and the object beam can be provided, in other words, shaped, by a spatial light modulator facing the other of the two main surfaces, which acts as both a programmable diffuser and a reflector. Of course, as in any interference setup, both beams are actually emitted from the same primary light source and then, through appropriate optical means, oriented, shaped, and transformed, so that both beams are incident on a given point, resulting in wave superposition at that point.

[0135] Here, it is suggested that, using appropriate optical means, the holographic diffuser be recorded, providing the reference beam incident on one main surface of the optical element and the object beam incident on the other opposite main surface of the optical element. This means that these beams propagate in opposite directions.

[0136] Instead, it is suggested that, using appropriate optical means, both the holographic diffuse transmission element and the reference beam and the object beam incident on the same master surface of the optical element be recorded. This implies that these beams propagate together.

[0137] Optional:

[0138] - When recording the holographic diffuse element, the spatial light modulator is positioned in a first position to emit the object beam, and

[0139] The method further includes recording an additional holographic diffuse element on the recording medium by simultaneously illuminating the additional region of interest with the reference beam and the additional object beam, the additional object beam simulating a coherent beam scattered by the additional diffuse object.

[0140] - The spatial light modulator is positioned in a second location to emit the additional object beam when the additional holographic diffuse element is being recorded.

[0141] Optionally, when recording the holographic diffuse element,

[0142] - The reference beam is emitted by a light source facing one of the two main surfaces, and

[0143] - The beam of light is emitted by a spatial light modulator, which acts as a programmable diffuser and faces the arranged mirror, such that the beam of light reflected by the mirror is directed toward another part of the main surface to illuminate the area of ​​interest.

[0144] Depending on the desired optical properties of the holographic diffuser to be recorded, such a mirror can be planar or curved. Furthermore, such a mirror can be adaptive or deformable.

[0145] Both of the above methods may further include obtaining parameters related to the wearer and / or the eyeglass frame, and determining the desired value of the central angle direction and / or the diffuse angle based on the obtained parameters.

[0146] For example, the parameters obtained can be used downstream to provide the diffuse object or to model its optical properties.

[0147] For example, given that the diffuse object has already been provided or its optical properties have already been modeled, the obtained parameters can be used to configure the reference beam and object beam in order to record the holographic diffuse element. Attached Figure Description

[0148] Figure 1 Known diffuse optical elements are shown.

[0149] Figure 2 Depicting in Figure 1 The difference in diffusion characteristics between a known diffuse optical element and an optical element according to an exemplary embodiment.

[0150] Figure 3 The principle of an exemplary setup that can be used to record a holographic diffuser is shown.

[0151] Figure 4 An exemplary holographic setup for recording a holographic transmission diffuser is depicted.

[0152] Figure 5 An exemplary holographic setup for recording an axial prism-shaped holographic transmission diffuser is depicted.

[0153] Figure 6 An exemplary holographic setup for recording a holographic transmission diffuser with specific angular selectivity is depicted.

[0154] Figure 7 The principle of an exemplary setup for recording a holographic diffuser that scatters light toward a target angular region is shown.

[0155] Figure 8 The schematic diagram illustrates the principle of an exemplary setup that can be used to record light from a specific incident angle toward a target angular region.

[0156] Figure 9 An example of an optical device including a transmission diffuser lens is depicted.

[0157] Figure 10An example of an optical device including a light source and a reflective diffuser lens is depicted.

[0158] Figure 11 An exemplary holographic setup for recording a holographic reflector with specific angle selectivity is depicted.

[0159] Figure 12 An exemplary optical element comprising multiple holograms is depicted.

[0160] Figure 13A , Figure 13B , Figure 13C , Figure 13D and Figure 13E Each depicts different possible exemplary arrangements of holograms within the optical elements.

[0161] Figure 14 A general exemplary holographic setup for recording diffuse holograms is depicted.

[0162] Figure 15A The principle of holographic setup for recording planar non-diffuse holograms is described.

[0163] Figure 15B The principle of the holographic setup used to record planar diffuse holograms is described. Figure 16A An example of this holographic setup is depicted. Figure 15C The principle of a holographic setup for recording diffuse holograms using two separate backpropagation beams is described. Figure 16B An example of a holographic setup for recording a diffuse hologram using two separate backpropagation beams is depicted.

[0164] Figure 17A , Figure 17B , Figure 17C , Figure 17D , Figure 17E and Figure 17F Each depicted Figure 16A or Figure 16B Different variations of the exemplary holographic setup.

[0165] Figure 18 It depicts the diffusion of light from a scene by optical elements including a diffuse hologram.

[0166] Figure 19 The image depicts the diffusion of light from a scene by optical elements comprising two diffuse holograms, both of which are based on... Figure 17F The settings were recorded.

[0167] The preceding diagrams are merely illustrative of the possibilities of the apparatus. To make the diagrams clear, they are obviously not to scale. Furthermore, each beam can be monochromatic or polychromatic, and there are no limitations on the wavelength range. Detailed Implementation

[0168] Now for reference Figure 1 It demonstrates a known diffuse optical lens that, for the purpose of scattering incident light, comprises small-sized elements, such as micro-protrusions or micro-recesses. Such small-sized diffuse elements (10) are typically fabricated on the surface of the optical element using photolithography.

[0169] When such a known diffuser is placed in front of the wearer's eye, the small element (10) can provide some useful diffusion of the incident light rays (11). Useful diffusion refers to the diffused light rays or beams reaching the target area, where they reach the pupil of the wearer's eye. In cases where the goal is to slow the progression of myopia, useful diffusion can refer to projecting a blurred image in front of the retina.

[0170] However, the small-sized element (10) also provides most of the useless diffusion of other incident rays (12). Useless diffusion refers to diffuse rays or beams that do not reach the target area, which does not reach the pupil of the wearer's eye.

[0171] Another drawback is that, for the observer, all incident rays (11, 12) are also backscattered, resulting in bright spots on the surface of the optical lens, thus reducing the aesthetics of the optical lens.

[0172] Another drawback is that, when outdoors, the incident sunlight undergoes a high level of diffusion and low contrast, which may be detrimental to visual comfort.

[0173] It is recommended to replace the small-sized diffuser elements mentioned above with a diffuser fabricated using holographic methods on the thickness of the optical element.

[0174] Holographic diffusers are easy to manufacture, can incorporate various additional optical functions, and can be customized to each wearer's needs or brand preferences.

[0175] More specifically, a holographic diffuser is recorded to exhibit angle-selective diffuse characteristics in reflection or transmission.

[0176] To achieve this, the holographic diffuser has a spatial variation of refractive index greater than 0.001 at at least one given wavelength over a distance of less than 30 μm.

[0177] like Figure 2The optical element, which includes one or more holographic diffusers (20), can be configured to preferentially scatter light within a predetermined angular region, compared to known optical elements that include diffuse elements (such as depressions or protrusions) (which scatter light approximately equally in all directions in both reflection and transmission). For example, light from different rays (11, 12) can be scattered by a given holographic diffuser (20) to preferentially illuminate the target angular region while illuminating other angular regions less, and simultaneously limit backscattering.

[0178] In other words, unlike known mechanical diffusers, holographic diffusers can be configured to primarily provide or only provide useful diffusion.

[0179] In fact, the target angle zone corresponds to a predetermined area around, for example, the central angle position where the wearer's eyes are intended to be located.

[0180] Therefore, due to this holographic diffuser, most of the incident light is scattered into the target corner region, while the energy of the light scattered outside the target corner region is limited.

[0181] Compared to using known diffusers obtained through photolithography, using a holographic diffuser can reduce the total amount of scattered light in each angular direction while still providing the same amount of light toward the target angular region.

[0182] Through this diffusion property, holographic diffusers can provide better aesthetics and reduce contrast loss during outdoor activities.

[0183] The size, location, and orientation of the predetermined angular region should be determined based on the application. The holographic diffuser can be configured such that the size of the predetermined angular region is within a wide range of 2° to 40°, for example, from 2° to 37°, near the central angular location. This size is particularly suitable for holographic diffusers incorporated into spectacle lenses. Such holographic diffusers can be designed, for example, to scatter ambient light and incorporated into optical lenses of any type of active or passive eyewear. Such holographic diffusers can also be incorporated into active eyewear including a light source and designed, for example, to scatter light emitted by said light source.

[0184] The holographic diffuser can be further configured to scatter only light from a specific angle of incidence. An example configuration is to scatter only or primarily light from the gaze reduction angle associated with near-vision activities, which are myopia-inducing activities. Simultaneously, the holographic diffuser can be configured to scatter little or no light from the gaze reduction angle associated with intermediate or distance vision activities, which are beneficial activities for slowing myopia progression.

[0185] This can be achieved, for example, by recording different diffusion patterns: low diffusion in the central portion of the optical element and strong diffusion in the peripheral portion of the optical element. With this configuration, optical elements including such holographic diffusers allow for slowing the development of myopia in the wearer during every type of visual activity.

[0186] The term "slowing down the progression of myopia" refers to the optical function provided by a holographic diffuser under standard wearing conditions, which prevents light from focusing onto the wearer's retina, thereby reducing the development of refractive errors. In this case, the holographic diffuser can scatter light across a wide angular region, for example, 1° to 30°, near the central propagation direction.

[0187] The general principles of holographic recording methods will then be described. Figure 3 The principle of an exemplary setup that can be used to record a holographic diffuser is shown.

[0188] Holographic recording is a method that allows for the creation of exotic and custom-made components. The idea is to record optical functions in or on a medium, such as a holographic material or a CCD camera, through interference between a reference beam (30) and an object beam (31). The recorded object or the recorded optical function can be a transmissive or reflective object.

[0189] Prior to exposure in the holographic setup, a photosensitive material (photopolymer or dichromate gelatin) is deposited onto a substrate. The substrate may be transparent (such as glass or polymer) or opaque. The substrate may be stained. The substrate is preferably not birefringent to avoid potential uniformity problems in holographic recording. The substrate may be planar or curved. The substrate may also be referred to as a “plate” in this document. A substrate covered with a layer of photosensitive material may also be referred to as a “holographic plate” (32) in this document. The photosensitive material may be, for example, dichromate gelatin or a photopolymer. The layer thickness of the photosensitive material typically includes between 10 μm and 100 μm, for example, between 15 μm and 50 μm. These materials may be sensitive to visible or non-visible light. A material may be sensitive to several wavelength ranges (e.g., blue and green). Several different material layers sensitive to different wavelength ranges may be present. The photosensitive material may be deposited on one of the main surfaces of the optical element (i.e., on the eye-side main surface, or on the object-side main surface, or, if desired, on both main surfaces, for example, to provide two different layers with two different functions).

[0190] The primary surface on the eyeball side may be preferred because it is typically less exposed to impact than the object-side surface.

[0191] For example, when the optical element is colored and includes a holographic diffuser, the object-side main surface may be preferred.

[0192] To record an image in a holographic setup, a physical or virtual object is required (33). For a transmissive holographic diffuser, this object will be a transmissive object. For a reflective holographic diffuser, this object can be transmissive and / or reflective.

[0193] Figure 3 An exemplary method for recording a holographic diffuser is based on an object made using machinery (33).

[0194] The optical features of the object (33) were carefully selected and matched with the desired optical features of the holographic diffuser to be recorded.

[0195] In fact, a holographic diffuser recorded using a given object has optical characteristics that closely resemble those of the given object. In other words, when a holographic diffuser is illuminated with the same source beam used on a given object to record the holographic diffuser, the holographic diffuser scatters the source beam in almost the same way as the given object.

[0196] Any recorded holographic diffuser can also be further used as a master holographic diffuser, that is, as an object for subsequently recording other largely identical holographic diffusers (33).

[0197] Instead of using mechanically made objects, virtual objects (33) created using computer-generated holograms (CGH) can be used. In this case, the interference pattern is calculated by computer. For a diffuser, the interference pattern is a random interference pattern. One of the earliest algorithms was introduced by Lohmann and Brown in 1969. It allows for the calculation of binary holograms. Other methods can be used to improve diffraction efficiency. Using CGH, the hologram is calculated and contains all the necessary images and functions, such as serving as a diffuser and another optical function. Transmission amplitude and / or phase spatial light modulators (SLMs) can also be used. SLMs allow for the continuous selection of different objects (33) as needed to suit various applications.

[0198] Object 33 may further have at least some of the optical characteristics sought by the holographic diffuser to be recorded, such as deflection angle, angular selectivity, shape, graininess, focusing effect, etc.

[0199] Now for reference Figure 4 It depicts an exemplary holographic setup for recording a holographic transmission diffuser. Figure 4A coherent light source (40) (e.g., a laser) emits a beam, which is optionally split into two parts (or beams) using a polarization beam splitter (41), each part having a specific polarization. When the second part is unnecessary for a holographic setup, the polarization beam splitter (41) manages the incident power of the reference beam (30). This beam propagates using a polarization-maintaining fiber (42), and an object (33) is placed in its path. Due to the optical properties of the object, one part of the beam is transmitted through the object (33) without being scattered and forms the reference beam (30), while the other part of the beam is scattered by the object (33) and forms the object beam (31).

[0200] Generally speaking, the bundle leaving the polarization-maintaining fiber always diverges.

[0201] For example, it might be desirable to collimate such a beam. To do this, in Figure 4 In this example, an optical lens can be arranged between the polarization-maintaining fiber and the object (33). In this example, the optical function of such an optical lens is selected to collimate the incident beam.

[0202] According to other examples, the optical function of such an optical lens can alternatively be selected to make the beam guided toward the object (33) more divergent, less divergent, or convergent.

[0203] According to yet another example, the bundle leaving the polarization-preserving fiber can be directed directly toward the object (33) without placing an optical lens in the middle.

[0204] More generally, the holographic setup is configured such that the substrate is exposed to at least the object beam (31) and the reference beam (30). Optionally, a polarizing beam splitter (41) can be used to split the single beam into two beams. These two beams can then be used as the reference beam and the object beam, respectively. Additional beams may be required, which can be provided by using one or more additional polarizing beam splitters. The aperture, the orientation of the two beams, the distance between the two beams, the distance between the object and the holographic plate, the wavelength of the light source, and the number of beams (at least two, but possibly more) allow for the definition of the holographic diffuser. WO 2016156614A1 describes the generally known principles of holographic recording applied to ophthalmic optics and the recording parameters that affect the optical properties of the recorded holographic element.

[0205] An object (33) can be placed in the path of a reference beam (30) so that, according to the optical properties of the object (33), it both transmits and scatters the reference beam (30), thus generating an object beam (31). The interference pattern at the holographic plate (32) between the reference beam (30) and the object beam (31) is used to record the holographic diffuser. Additional beams can be used further.

[0206] In general, the interference pattern used to record the holographic diffuser can be obtained between different diffuse beams (different object beams) and a transmitted reference beam (if one already exists).

[0207] pass Figure 4 and Figure 6 The setup presented in the image can be considered, if desired, for the orientation of the holographic plate (32) within the optical elements of the holographic diffuser to be recorded. For the diffuser lens, granularity, color, angle, intensity distribution, diffusion pattern, wavelength used, uniformity of diffusion, etc., can be managed. The holographic diffuser can be configured to transmit only, reflect only, or both.

[0208] A diffuser can be characterized by its diffusion efficiency, diffusion coefficient, or grain size. Grain size can be managed by selecting the grain size of the diffuse object (33) and / or the distance between the holographic plate (32) and the diffuse object (33). Classical recording parameters (such as the energy used for recording) are also ways to manage haze, grain size, and more generally, the efficiency of a holographic diffuser. Generally, a holographic diffuser has a diffusion efficiency, or haze, expressed as a percentage at a given wavelength. Haze coefficients ranging from less than 1% to 100% can be obtained. A diffusion efficiency of 100% means that all of the incident beam is scattered. Ignoring light absorption, a diffusion efficiency of 50% means that half of the energy of the incident beam is scattered, and the remainder is transmitted or reflected without being scattered. Haze can be selected, for example, between 5% and 20% (but higher values ​​up to 45% are possible) to avoid significant interference with the direct line of sight through the optical elements. In the case of optical elements used for the exemplary purpose of controlling the evolution of myopia, a diffuse efficiency of less than 50% and greater than 5% allows for providing the wearer with a mostly clear image of the scene with a manageable level of blur. A diffuse efficiency of less than 5%, for example less than 2%, or less than 1%, may still be suitable and even preferred for some other applications, such as for aesthetic applications that focus on influencing the color of at least a portion of the optical element as seen by the observer. The granularity of the diffuser can be, for example, less than 1 μm for a high-haze diffuser (measured on an 80% diffuser) and greater than 20 μm for a low-haze diffuser (measured on a 5% diffuser).

[0209] A holographic diffuser can be recorded using a coherent beam of light with a specific wavelength. Therefore, the diffusion efficiency of the holographic diffuser can be maximized for that specific wavelength. Diffusive efficiency close to its maximum value can be provided across a wide wavelength range. When this wide wavelength range is comparable to the entire visible spectrum, the holographic diffuser allows for a more powerful effect on the evolution of myopia.

[0210] Multiple coherent beams can be used to record the holographic diffuser, each with a specific, corresponding wavelength. Therefore, the diffusion efficiency of the holographic diffuser will be maximized for the specific wavelength.

[0211] For example, the wavelength could correspond to those wavelengths typically emitted by a display screen. As a result, the holographic diffuser scatters light emitted by such a display screen without significantly scattering sunlight. Therefore, the holographic diffuser can be specifically used for activities related to viewing electronic display devices.

[0212] The surface roughness of the optical element is unaffected by the holographic diffuser. For example, the optical device may have a coating. The surface roughness of a uniformly deposited coating can range from 0.05 μm to 0.5 μm, thereby making the surface roughness of the optical element less than 0.5 μm.

[0213] The shape of the holographic diffuser is another manageable parameter. This shape can be circular, elliptical, square, toroidal, etc. The shape depends primarily on the shape of the reference beam (30). Therefore, the holographic diffuser can cover the entire optical element or only a portion of it, such as a circular portion, a ring, etc. The holographic diffuser can be recorded region by region. Due to the mask or template, selected areas can avoid any holographic diffuser.

[0214] The output beam can also be circular, square, ring-shaped, linear, etc., and its shape depends primarily on the shape of the object beam (31), which is selected based on the desired angular acceptance for illuminating, for example, the entrance pupil of the wearer.

[0215] A holographic diffuser can be configured to uniformly scatter incident light perpendicular to the surface of a plate, or it can introduce at least one diffusion angle. This diffusion angle can also be managed through optical settings. For example, a diffusion ring can be recorded. An example application is an optical element that includes a holographic diffuser configured to deflect light from the fovea to another point on the retina.

[0216] Holographic diffusers can be achromatic and diffuse the entire visible spectrum equally, or they can be monochromatic and diffuse only a narrow range of the visible spectrum. This spectral selectivity can be managed by the properties of the holographic material and by the duration and power (energy) of the exposure. Thus, a holographic diffuser can be proposed that is effective, for example, for at least three wavelengths corresponding to the RGB light from a smartphone display screen. A possible use, for example, is to slow the progression of myopia due to near-vision screen use.

[0217] Multiple holographic diffusers can be combined into a single optical element, for example, by having different shapes or grain sizes over different regions. Each holographic diffuser can extend over a separate region and have different optical characteristics (grain size, shape, orientation, wavelength, etc.). Alternatively, holographic diffusers can extend over overlapping regions. Therefore, the local optical properties of the optical element can be the sum of the optical properties of the different diffusers. For example, at least two diffusers can be used, each specific to a different wavelength, to have different diffusion directions or shapes or focused areas on the retina. Possible applications include, for example, chromatic aberration compensation or inversion.

[0218] Holographic diffusers can be configured to have specific optical functions. These functions can be related to transmission or reflection (e.g., a holographic diffuser can also be a holographic mirror), spectral characteristics (e.g., a holographic diffuser can absorb light within a specific wavelength range, thus acting as a filter), refractive functions (e.g., a holographic diffuser can also be an optical lens, an ophthalmic lens, such as a spherical lens, cylindrical lens, aspherical lens, axonal prism, or microlens), and so on. This level of function can be recorded for the same wavelength range or for a different wavelength range. This level of function can be recorded on the same side or opposite sides of the lens. This level of function can be recorded on the entire lens or a portion of the lens.

[0219] For example, reflective optics can be achieved by using two back-propagating beams, one as a reference beam and the other as an object beam. Figure 11 , Figure 14 and Figure 16B As depicted in the text. Figure 15C The general principle of a setup without mirrors is described, in which two back-propagating beams are provided separately. Another possibility is to provide a back-propagating object beam as a reflection of a reference beam. This can be achieved, for example, by adding a mirror (331) to the holographic setup, which can be on-axis or off-axis, planar or curved, etc. Figure 16A , Figure 17A , Figure 17B and Figure 17D An example of a setup including such a mirror for reflecting a reference beam and thus providing a beam of objects is depicted. Figure 15A and Figure 15B The general principle of such a mirror setup is also described. Holographic diffusers with reflective optics (i.e., pure or partial reflection) can be used in active or switchable eyewear. For example, a special embedded light source can be arranged to illuminate the holographic diffuser from the same side where the wearer's eyes are located when the eyewear is worn. The holographic diffuser can thus reflect and scatter light from the embedded light source, for example, back to the wearer's eyes. Such a holographic diffuser can use, for example... Figure 11 The settings are used to record.

[0220] Transmission optics can be achieved by including specific lenses (34) in the holographic setup (e.g.) Figure 5 This can be achieved by using an axial prism or diffuse meniscus lens (as shown above) or by managing the shape of the interference beam. Possible uses include adjusting the shape and / or position and / or spatial extension of the diffused image and / or the focal point of this image on the retina, and / or the shape of the diffuser on the optical element. For example, a holographic diffuser can be formed to extend only at the edge of the optical element.

[0221] The optical functions defined above can allow for the integration of various services provided by smart eye-wearing devices, such as light or distance measurement, image display, and so on.

[0222] A holographic gradient diffuser is one type of possible holographic diffuser. One way to record such a diffuser is to replicate a master gradient diffuser that has been mechanically obtained. Another way is to obtain a circular gradient holographic diffuser by managing the energy of the recording bundle, for example, using a gradient circular density.

[0223] Similarly, a linear gradient holographic diffuser can be obtained using a gradient linear density. Possible applications of gradient diffuser elements are now described. Considering an optical element with a linear gradient holographic diffuser, this diffuser provides the observer with a visual effect that is disconnected from the illumination of the optical element. For example, light from the lower portion of the optical element may cause diffuse reflection at the center of the optical element, but not at the bottom. A linear gradient holographic non-diffuse mirror can also be recorded if desired.

[0224] The center of the gradient preferably has low haze, or may be a haze-free aperture, and the haze can increase with the distance of the diffuse region from the center of the diffuser. Therefore, the gradient circular density is darker at the center and becomes brighter at its edges.

[0225] As for the example of an axiprism, the management of the reference beam and the object beam can allow for the realization of a holographic diffuser that covers the entire optical element and has specific angular selectivity. Figure 6 Possible setups for recording such a holographic diffuser are depicted, for a holographic diffuser in transmission, and Figure 11 This is used for holographic diffusers in reflections. This selectivity can relate to, for example, the need for diffused light only when the wearer is reading and, for example, looking at the bottom of the lens.

[0226] A coherent light source (40) emits a beam, which is split into two separate beams by a polarization beam splitter (41). Each beam propagates through a corresponding polarization-maintaining fiber (42). One beam is used as a reference beam (30) and directly illuminates the holographic plate (32). The other beam illuminates the holographic plate from a different angle of incidence region compared to the reference beam (30). A diffuse object is placed in the path of this other beam. The scattered light forms an object beam (31). The holographic diffuser is recorded by the interference pattern formed on the holographic plate (32) between the reference beam (30) and the object beam (31).

[0227] In this configuration, when the optical element is worn in front of the wearer's eye, the holographic diffuser can scatter incident light from an angle corresponding to the area seen by the wearer through the bottom of the optical element toward a specific point or larger area of ​​the wearer's retina. In this case, the direction of the incident angle corresponds to the wearer's near vision. Focusing can occur in a plane located in front of the wearer's retina or in a plane tangent to the wearer's retina. Focusing can be achieved by configuring the object bundle of this recording setup to provide a specific optical function (e.g., corresponding to a lens, such as an axonometric prism).

[0228] In this scenario, although incident light from a specific incident direction is scattered by the holographic diffuser, the wearer's vision of incident light from any other incident angle is transmitted through the holographic diffuser and is unaffected by haze.

[0229] Another advantage is that someone viewing the wearer will not see any haze, diffuse reflection, or markings on the optics being worn. In fact, outside the diffusion angle, the lens transmittance is close to 100%, and the haze is close to 0%, which is equivalent to the classic haze of the optics without any diffusers. Such holographic diffusers for near vision can be recorded on the entire optics as described above, or alternatively, on only a portion of the optics.

[0230] This near-vision diffusion property can also be combined with lens effects to focus light from short distances (e.g., in near vision, such as reading) onto the wearer's retina or pupil through a diffusion effect. This can be achieved by adding a lens to the object (33) in the recording setup.

[0231] This near-field diffusion property can also be combined with angle selectivity. This allows for the avoidance of unpleasant reflections from the observer to the wearer. Such a holographic diffuser can be recorded on the entire optical element or on one or more portions of the optical element.

[0232] However, when near-vision diffusion characteristics are combined with lens effects or angle-selective characteristics in a holographic diffuser, the resulting haze is limited to values ​​ranging from 0% to less than 50%.

[0233] In addition to the preceding description, the following discussion describes two examples of recording settings for recording holographic diffusers, with the aim of maximizing useful diffuse while minimizing useless diffuse.

[0234] For pedagogical purposes, and to provide accurate figures, both examples refer to recording a holographic diffuser between the two main surfaces of a spectacle lens to be mounted on a spectacle frame.

[0235] Moreover, in both examples, useful diffuse refers to the scattered light that enters the wearer's eye when wearing glasses.

[0236] To minimize unwanted diffuse, it is recommended to record one of the following bundles: a reference bundle (30) or an object bundle (31), converging toward a predetermined angular direction in which a reference point of the eye will be located when the eyeglass frame is worn. Examples of reference points may include the center of the pupil or the center of eye rotation.

[0237] Then, when the recorded holographic diffuser is illuminated by the incident beam, the light is scattered into a scattered beam directed toward the target angular region near the central angular direction that matches the predetermined angular direction mentioned above.

[0238] The diffusion angle can be defined, for example, such that the area it covers at the corneal location is close to the pupil size, for example, between 1 mm and 8 mm. For example, a scattered beam (whose diffusion angle is defined as the full width at half maximum of the luminance, which is approximately 17°) can illuminate a 4 mm wide area located at a distance of approximately 14 mm from the lens.

[0239] In this way, most of the diffused light will reach the eye, while the overall diffuse amount of the lens may be limited. In fact, if the wearer's eye were to be illuminated with the same amount of light by using a classical diffuser made by photolithography instead of a holographic diffuser, the classical diffuser would need to globally scatter a much higher amount of light in all angular directions considered.

[0240] In this case, the diffuser can cover the entire lens or only a small portion of the lens center (or very close to the lens center), and the amount of diffused light can be increased by guiding light from the peripheral area of ​​the lens to the diffuse area according to the guidance in the holographic medium. Optical coupling can be achieved through the diffuse area or the grating area.

[0241] The table below provides some values ​​for the diffusion angle for different wearing conditions of eyeglass lenses.

[0242] Pupil diameter (mm) Eye-lens distance (mm) Diffuse angle (degrees) 2 12 9.5 8 12 37 2 15 7.6 8 15 30

[0243] When using contact lenses, the distance between the contact lens and the pupil is approximately 3mm to 5mm. The table below provides the values ​​for the diffusion angle for different contact lens wearing scenarios.

[0244]

[0245] Figure 7 The illustration shows an exemplary recording principle along with an image of an eye to illustrate the effect of the recorded holographic diffuser. Figure 4 This is an example of the corresponding record settings.

[0246] In this example, the diffuse object (33) is illuminated by at least one polarized beam and scatters the polarized beam to form an object beam.

[0247] Both the object beam and the converging reference beam (70) illuminate the optical lens including the holographic plate (32).

[0248] The interference pattern between the object beam and the reference beam causes the holographic diffuser on the holographic plate (32) to record.

[0249] In this example, once the holographic diffuser is recorded, incident light from an angle of incidence matching the angle of incidence of the converging reference beam is scattered by the holographic diffuser and directed toward the target angular region (71). The target angular region is defined by the central angular direction and the diffusion angle. Both the central angular direction and the diffusion angle are specific to the optical properties of the holographic diffuser. These optical properties relate to the optical properties of the diffuser object (33) in the recording setup. For example, the diffusion angle may be the size of the wearer's pupil when wearing the optical lens, or half of the size, or 1.5 times the size, or twice the size.

[0250] However, scattering incident light from other directions can be meaningful.

[0251] For example, activities such as using mobile phones or computers can induce myopia, and it may be useful to provide diffused light specifically for these conditions, while limiting diffused light for outdoor activities (which are not myopia-inducing) to enhance contrast.

[0252] One way to provide this angular selectivity is to provide a recording setup that provides a recording bundle (70) converging to the target angular region, thus providing the desired central angular direction, while another recording bundle (72) provides the desired diffuse direction. Figure 8 The illustration shows an exemplary recording principle corresponding to this example, along with an image of an eye, to illustrate the effect of the recorded holographic diffuser.

[0253] For example, the reference beam (72) can be emitted from an angle of incidence corresponding to the normal viewing angle at the reading distance. At the same time, the object beam (70) can be emitted so that it can be focused, for example, toward the center of eye rotation after being refracted by optical lenses.

[0254] For near vision (NV) applications, the angle of the input light, excluding light from the bottom of the lens, can range from 0 to 80 degrees. The diffuser can cover only the bottom third of the lens (the bottom portion of the lens) or the portion of the lens involved by the NV portion of the graduated lens. For far vision (FV) applications, the angle of the input light can be the same or skylight can be used, and is between 45 and 80 degrees. In this case, the diffuser can be placed at the top third of the lens, or the portion of the lens involved by the FV portion of the graduated lens.

[0255] As mentioned earlier and later, a holographic layer with selective spectral sensitivity can also be used to add wavelength selectivity, so that diffusion mainly occurs at the wavelengths used by RGB displays.

[0256] The recorded holographic diffuser can be used as the master holographic diffuser: as a diffuse object that can be copied using the recording settings described above.

[0257] Alternative replication techniques can involve optical replication, for example, on a photosensitive material deposited on a plastic sheet. For instance, a holographic diffuser can also be projected onto a photosensitive material in a photolithography setup with UV exposure. The photosensitive material can be the same as the holographic material. More generally, a mechanically fabricated diffuser, a holographic diffuser, or a CGH diffuser can be used as the diffuser object in any of the above recording setups. As a result, the diffuser object is replicated to record a new holographic diffuser.

[0258] The following sections will describe some exemplary uses of optical lenses that incorporate holographic diffusers.

[0259] Figure 9 A transmissive lens including a holographic diffuser (32) is depicted. Ambient light (90) from any incident angle direction is scattered by the holographic diffuser (32) into a scattered beam (91) that is guided toward the wearer's eye.

[0260] The scattered beam extends in the direction of the central angle. The diffusion angle of the scattered beam can be chosen to illuminate the entire retina or to illuminate multiple parts of the retina.

[0261] Figure 10A reflective diffuser lens including a holographic diffuser (32) is depicted. This lens is an eyeglass lens mounted on an eyeglass frame. A switchable light source (92) is further integrated into the frame, for example, in the temple. The switchable light source (92) can be a white light source (e.g., an LED) or a colored light source (e.g., a green LED). The different types of diffusers described above can also be used or designed for this application. Incident light (90) from the switchable light source (92) is scattered by the holographic diffuser (32) and reflected into a scattered beam (91) guided toward the wearer's eyes. The scattered beam (91) can have a... Figure 9 The examples depict the same central angle direction and diffuse angle.

[0262] The optical elements may further include additional elements configured to cooperate with the holographic diffuser. Examples of such additional elements include light guides for directing light toward the holographic diffuser. This allows the optical elements to scatter more light, thus improving light intensity and potential contrast.

[0263] Optical elements can be incorporated into an optical device that further includes additional elements configured to cooperate with the holographic diffuser. Examples of such additional elements may include a light source for activating the holographic diffuser, and may further include a sensor (such as a position sensor, motion sensor, or accelerometer) for triggering the activation of the light source. This allows, for example, the use of sensors to detect a type of visual activity of the wearer that may induce an undesirable evolution of the wearer's visual impairment. Upon detection of said type of visual activity, the holographic diffuser can be automatically activated to mitigate or prevent said undesirable evolution.

[0264] The inventors have further developed another application for the manufacture of holographic recordings of optical elements and devices for slowing the progression of myopia, without the drawbacks of known diffuse elements.

[0265] Specifically, Figure 12 An optical element (36) designed to be worn in front of a wearer's eyes is depicted. This optical element has two opposing main surfaces and can be conceptually divided into multiple non-overlapping regions. Multiple holograms are each arranged within the optical element or on one of its main surfaces and extend over different areas of the multiple regions.

[0266] All the advantages of holographic recording compared to photolithography explained above apply.

[0267] Another advantage of holographic lenses over mechanically formed lenses is that they can be designed for particularly small spectral bandwidths, such as 5 nm to 20 nm, with exceptionally high efficiency. This allows holographic lenses to be particularly effective in myopia control, unlike mechanically formed lenses which can affect the wearer's vision through the lens.

[0268] In addition, some known holographic materials have high transparency, thus allowing light originating from the scene to be effectively transmitted to the wearer.

[0269] Furthermore, some types of holograms are passive, while others are active. Typically, activation of an active hologram can be performed electrically, optically, mechanically, or by another method. Changes in function or characteristics (e.g., in terms of angle or aperture) or deactivation of components can be achieved using, for example, active photopolymers or liquid crystals, such as H-PDLC (holographic polymer-dispersed liquid crystal) described in WO 2017005608A1. When illuminated by light within a specific, narrow wavelength range (e.g., light emitted from a dedicated light source), an optically active hologram exhibits a predetermined birefringence in reflection; however, it is inactive as long as it is not illuminated by light within this specific wavelength range. Therefore, an advantage of active holograms is that their presence within the optical elements is indistinguishable to the wearer when inactive.

[0270] In the example, such as Figure 12 As actually shown above, the optical element can be an eyeglass lens designed to cooperate with one or more switchable light sources (92) arranged near the optical element (36) to activate one or more of the holograms when needed. For example, one or more switchable light sources can be embedded in the temple portion of the eyeglass frame.

[0271] Incident light (90) from a switchable light source (92) is scattered by at least one holographic mirror and reflected into a corresponding reflected beam (93) that is directed toward the wearer’s eye.

[0272] Once the optical function of a hologram is activated, it depends on the purpose sought.

[0273] For example, an off-axis curved holographic lens can be used to reflect and focus light from a light source embedded in the temple of an eyeglass frame toward the retina of a nearsighted wearer. This off-axis curved holographic lens has a positive power determined according to the wearer's prescription.

[0274] Alternatively, one might expect to use a defocused image in front of the retina or to illuminate the wearer's eye with unfocused light.

[0275] The purpose of simply illuminating the wearer's eyes can be achieved by using off-axis curved lenses with low positive or negative optical power, or by using planar off-axis lenses.

[0276] One or more of the holographic mirrors may further be diffuse, in other words, holographic diffuse elements, which have diffuse properties in reflection resulting from spatial variations in the refractive index of the holographic diffuse elements, said spatial variations in the refractive index being greater than 0.001 at at least one given wavelength over a distance of less than 30 μm.

[0277] The arrangement of holograms can be random or according to a regular pattern (such as squares, hexagons, circles, etc.).

[0278] Figure 13A An optical element (36) with a circular pattern comprising concentric rings is depicted. Each ring includes multiple adjacent or neighboring regions. A corresponding hologram (35) extends from the center of each such region. Figure 13A The superscript is marked as a point.

[0279] Figure 13B An optical element (36) with a square pattern (here, an upright square grid) is depicted. Each vertex of the square is associated with a single corresponding region surrounding said vertex. A corresponding hologram (35) extends from each such region. Figure 13B The superscript is marked as a point.

[0280] Figure 13C Optical elements (36) with square patterns (here, diagonally or centrally centered square grids) are also depicted. The center of each square is associated with a single corresponding region surrounding said vertex. A corresponding hologram (35) extends from each such region. Figure 13C The superscript is marked as a point.

[0281] Figure 13D An optical element with a random pattern (36) is depicted. The arrangement of multiple regions does not follow any form of ordered lattice. A corresponding hologram (35) extends from each such region. Figure 13D The superscript is marked as a point.

[0282] These regions can be similar or different sizes. Holograms can also have different properties, such as their spectral characteristics, their diffusion angles, their central diffusion directions, etc.

[0283] For example, Figure 13E An optical element (36) is depicted, which has the same characteristics as... Figure 13C Most of the similar square patterns differ in that... Figure 13EIn this configuration, a first set of regions is formed by a first region having a first size, and a second set of regions is formed by a second region having a second size. A corresponding first hologram (35a) of the first size extends from each first region, and a corresponding second hologram (35b) of the second size extends from each second region.

[0284] Therefore, a pattern can be composed of holograms that are all the same size or have different sizes.

[0285] In the example, all holograms can provide the same optical functionality and jointly establish the desired wavefront on a designated plane corresponding to, for example, a portion of the wearer's retina.

[0286] Conversely, at least two of the holograms in an optical element can have different characteristics, in other words, they can provide different optical functions. This distinction allows for consideration of the specific shape of a particular wearer's retina.

[0287] Furthermore, the holograms can be arranged such that two or more holograms are adjacent, thus forming a cluster. For example, through a circular pattern with concentric rings formed by adjacent regions, the holograms can be the same size as the corresponding regions and therefore adjacent.

[0288] It's even possible for each hologram to be adjacent to at least one other hologram. This could be the case in a square pattern (e.g., Figure 13B In the case of a hexagonal pattern, each point, and therefore each hologram, has four neighbors, or in the case of a hexagonal pattern, each point, and therefore each hologram, has six neighbors.

[0289] Conversely, holograms can be isolated, in other words, not adjacent to each other.

[0290] In this context, optical elements can be conceptually categorized into two types of regions as defined below:

[0291] - Each hologram extends over the corresponding area of ​​the first type.

[0292] -At the same time, no hologram extends over any area of ​​the second type.

[0293] At the same time, one region of the first type is not adjacent to another region of the first type.

[0294] Since each hologram reflects a beam of light toward the wearer's eye when activated, multiple holograms reflect multiple beams together, thus creating a generated wavefront. The generated wavefront can be calculated based on the recorded optical function of each hologram and based on the position of the holograms (i.e., their arrangement within the optical elements).

[0295] The same calculations can be performed in reverse order. For example, it may be desirable to establish a specific desired wavefront at a particular location (e.g., on the wearer's retina, behind, or in front). The corresponding optimal arrangement of holograms, each with known refractive power, can be calculated using this desired wavefront and the desired associated location as input.

[0296] The recorded optical function of a given hologram or multiple holograms may further include an image (e.g., a cross) such that when the hologram is activated, the image is formed at a desired location by reflection and, optionally, by diffusion if the hologram is also a holographic diffuser.

[0297] The desired features of a given hologram depend on the following:

[0298] - Parameters related to the wearer, such as prescriptions and other eye-related parameters.

[0299] - Parameters related to the eyeglass frame containing optical elements, such as size and angle.

[0300] These desired characteristics of a given hologram are used as the basis for determining the characteristics of the recording setup used to record this given hologram.

[0301] As already explained, the holographic recording setup is configured such that the substrate is exposed at least to an object beam corresponding to the object to be recorded and a reference beam corresponding to the second part of the optical function.

[0302] All the types of holographic setups already described can be used to record holographic diffusers:

[0303] - A mechanically made diffuser (33) can be placed next to the mirror (331), such as Figure 15B and Figure 16A As shown,

[0304] - A diffuser (33) made using computer-generated hologram (CGH) technology can be combined with a mirror.

[0305] - The amplitude and / or phase spatial light modulator (SLM) can be controlled as needed to generate modulated light that can be directly used to record any kind of holographic diffuser (including holographic diffusers).

[0306] - The reference beam and the object beam are provided from the same source as two counter-propagating beams. Both the reference beam and the object beam can be directed toward the region of interest. The object beam is formed by light scattered by a mechanically made diffuser, or by light shaped by a diffuser made using CGH technology, or by light modulated by SLM, such as... Figure 15C and Figure 16B As shown.

[0307] In addition, diffuse objects (mechanical, master hologram, or transmission SLM) can be placed in front of deformable mirrors (DMD, DLP, etc.).

[0308] All of these programmable devices each allow for the recording of personalized holographic diffusers.

[0309] All these diffuse objects may also contain at least some of the characteristics of the resulting recorded diffuser, such as deflection angle, angular selectivity, shape, graininess, focusing effect, etc.

[0310] Figure 11 An example of a holographic recording setup suitable for recording off-axis curved diffuser lenses on spectacle lenses is presented. As already mentioned, off-axis curved diffuser lenses are suitable for scattering light from a light source arranged in the temples of spectacle frames toward a specific location, such as the retina of a myopic wearer.

[0311] In order to record different holograms on different areas of the eyeglass lens, such as Figure 14 As shown, the reference beam can be designed using optics such as lens arrays, preferably active components such as SLM, DMD, or DLP, to create a tailored wavefront, or, when the design is fixed, to create a passive, tailored optics. The features of the hologram can be tailored to the wearer's prescription.

[0312] although Figure 11 and Figure 14 The holographic recording setups represented in the text all depict holograms being recorded directly on spectacle lenses, but do not require the substrate to be a spectacle lens or to have any specific shape. For example, holograms can be recorded on prescription lenses, plano lenses, or patches that can be applied to prescription or plano lenses to form composite optical elements such as spectacle lenses.

[0313] In yet another embodiment, the optical element can address the recent problem of providing different apparent colors for the wearer and the observer.

[0314] In fact, from an aesthetic point of view, it may make sense to have lenses with clear color markings without affecting the wearer's color perception.

[0315] One possibility is to provide a lens coating with high reflectivity for a specific wavelength, but without affecting the wearer's vision. Another approach is to use classic, mechanically fabricated narrowband lenses (e.g., mechanically fabricated thin layers) with optical properties characteristic of narrowband lenses. However, a drawback of mechanically fabricated lenses, including mechanically fabricated thin layers, is that the complementary narrowband filter may exhibit color transmission.

[0316] As explained in EP 21305404.2, this drawback can be overcome by not using a narrow-band lens, but instead by using the combined effects of dye and skin albedo.

[0317] The inventors have identified an alternative solution to this problem in the use of holographic diffusers as a replacement technology, whose optical functions are carefully selected to decouple the lens color perceived by the observer from the wearer's color perception.

[0318] The reflection of a hologram is classically mirror-like, with low angular receptivity and colors that change with the direction of reflection. Aesthetically, this last point is significant because it allows for rainbow reflections to be presented to the observer.

[0319] Holographic diffusers typically exhibit low angular receptivity, but solutions and corresponding recording settings are presented below to maximize this angular receptivity.

[0320] What these solutions have in common is that a narrowband diffuse hologram is recorded on one side of the substrate, preferably on the object side, which is the side opposite to the wearer when worn. By tuning the recording wavelength, a specific narrowband can be selected within a broad spectrum, including, for example, blue, green, and yellow.

[0321] As a result, the resulting holographic diffuser reflects the incoming ambient light through diffuse reflection.

[0322] This diffuse reflection is efficient enough to be visible to the observer under ambient light of any intensity level.

[0323] Due to its narrow band, diffuse reflection is colored, with colors that are highly saturated.

[0324] The diffuse hologram has both diffuse reflection and filtered transmission. The diffuser is invisible to the wearer during transmission. Compared to specular reflection, the inventors have noted that the spectrum of light transmitted by this holographic diffuser does not have high filtering efficiency. In other words, this holographic diffuser only slightly affects color perception during transmission, that is, through the substrate. Therefore, wearers of optical lenses including one or more of these holographic diffusers will not have the impression of wearing colored lenses.

[0325] Besides disrupting the apparent color of optical lenses in reflection and transmission, other applications are also meaningful, such as providing aesthetic filters to mask or hide any unsightly aspects of lenses, microstructures for myopia control, or recently developed types of optical functions, such as structures for ARE or focusing lenses. Of course, the wavelength filtered by the diffuse hologram should differ from the wavelength of interest of the element to be hidden.

[0326] Furthermore, it can be meaningful to veil the natural colors of filters that might be considered unattractive (such as filters for colorblind wearers). To do this, additional functionality that filters light during transmission can be added to holographic diffusers. For example, some holograms can act as blue cutoff filters in the 460nm to 510nm or 440nm to 520nm bandwidth, or as yellow cutoff filters in the 560nm to 660nm bandwidth.

[0327] Figure 15A The principle of a setup that can be used to record holograms is shown, and Figure 15B The principle of a setup that can be used to record holographic diffusers is illustrated. The recorded object is primarily a reflective object, but it can also have specific, selected optical functions in transmission.

[0328] exist Figure 15A In the process, the reference beam (30) is guided toward the mirror (331). Both the reference beam and the resulting reflected beam illuminate the holographic plate (32), thereby forming an interference pattern for recording the holographic mirror.

[0329] exist Figure 15B In this process, a reference beam (30) is directed toward the combination of the diffuse object (33) and the mirror (331). The resulting object beam (31) and the reference beam (30) both illuminate the holographic plate (32), thereby forming an interference pattern for recording the holographic diffuser.

[0330] Figure 16A The holographic setup shown follows Figure 15B The principle described herein is to establish a planar diffuser on the holographic plate. A single beam can be transmitted through a polarization-maintaining fiber (42). This beam illuminates the holographic plate (32) as a reference beam (30). After being reflected by the mirror (331) and transmitted by the diffused object (33), this beam further illuminates the holographic plate (32) as an object beam (31).

[0331] The combination of a reference beam and an object beam allows for recording of planar diffuse holograms.

[0332] This diffuser is preferably monochromatic. It reflects and diffuses only the visible spectral range corresponding to the spectral selectivity of the holographic material.

[0333] The wavelengths and bandwidths of reflection and diffusion are defined by the wavelengths of the recording laser(s), the recording settings, and the photosensitive materials used.

[0334] In embodiments where the purpose is to provide lenses with different apparent colors for the observer and the wearer, the relevant spectrum is visible light, and therefore a visible light laser is used. Thus, the wavelength is included between 350 nm and 750 nm.

[0335] For example, a given type of photopolymer can be used to record objects capable of diffusely reflecting light within a narrow band selected from a larger wavelength band spanning from blue to yellow. Another type of photopolymer could allow recording objects capable of diffusely reflecting light within a narrow band corresponding to red wavelengths.

[0336] The reflection bandwidth is mainly between 5nm and 15nm.

[0337] Experimental results show that the reflection efficiency of a diffuse holographic mirror can be at least as high as 95%.

[0338] The substrate is transparent to the rest of the visible light range, with a transparency of approximately 90% limited by Fresnel reflection and the inherent transmission of the substrate.

[0339] For uniformly deposited coatings, the roughness of the holographic coating after exposure typically ranges from 0.05 μm to 0.5 μm.

[0340] Figure 16A and Figure 16B Various modifications to the holographic setup depicted above are possible.

[0341] For example, the image could bypass a diffuser on a lens, and the diffuse reflection would allow the image to appear when an observer views the lens. Therefore, the image could not be colored, or it could be a mirror with the same color as the diffuser, but the image would be more visible to the observer.

[0342] For example, multiple diffuse mirrors can be recorded for multiple different wavelengths to produce different diffuse reflections for the perspectives of two different observers.

[0343] A rainbow diffuser can be obtained using a single recording wavelength. To explain the effect of holograms on the observer's color perception, the following section discusses... Figure 18 It describes the diffusion of light from a scene by an optical element comprising multiple identical narrowband diffuse holograms extending over different regions, or equivalently, an optical element comprising a single narrowband diffuse hologram extending over the entire main surface of the optical element and having substantially uniform optical properties.

[0344] The first incident ray (180) is depicted as being guided toward a diffuser (35). The first incident ray is ambient light spanning a wide wavelength range, including a narrow band associated with the diffuser. Due to the diffuse reflection properties of the mirror, the first incident ray is reflected into a first set of reflected rays (181), which have multiple corresponding reflection angles near a first central angular direction (not shown).

[0345] The same applies to the second incident ray (183), which also corresponds to ambient light and is reflected by another identical holographic diffuser as a second set of reflected rays (184) near the direction of the second central angle (not shown).

[0346] from Figure 18 From the observer's perspective depicted on the left, the diffused light is provided by two holograms (35), but at different levels. The amount of light reaching the observer from the first set of reflected rays (181) is less than the amount of light from the second set of reflected rays (184).

[0347] Given that, for example, the narrow band is green light, this means that an observer will not perceive the same amount of green light from two holograms (or from two parts of a holographic diffuser in the case of a single hologram covering the entire optical element), and therefore their corresponding colors (as perceived by the observer) will be different.

[0348] A multicolor diffuser can be obtained by using different recording wavelengths to record different reflection diffusers in different areas of the lens.

[0349] As an explanation, Figure 19 The optical elements comprising two distinct narrow-band diffuse holograms extending across the same region depict the diffusion of light from a scene.

[0350] For example, one of the mirrors diffuses green light, while the other diffuses orange light. Considering... Figure 18 Using the same incident ray (180) depicted above, two sets of reflected rays (181, 182) are obtained, one set corresponding to the green wavelength and the other set corresponding to the orange wavelength. As a result, depending on the observer's position, the colors of the lens regions where the two diffuse holograms are located appear different, in this example spanning from green to orange.

[0351] use Figure 16A The settings produce a recording with a diffuser that has low angular receptivity. For the observer, the color diffusion is visible at an angle close to + / -10° to the normal of the lens surface.

[0352] By managing the object beam and reference beam, the setup can be improved to increase the field of the diffuser.

[0353] Figures 17A to 17F Different possibilities for this recording setup with a converging reference beam (30) are shown. These setups can also be converted to a diverging beam. Figures 17A to 17F This is merely an illustration of the possibilities of this setup. For example, there are no restrictions on the color of the laser source (40). A green light source has already been used for the first demonstration. To make the diagram clear, it is obvious that proportions were not followed.

[0354] The different components in these setups can obviously be combined to form another setup.

[0355] The holographic plate (32) is mainly incident on the reference beam (30) with a normal, but it can also be oriented to change the direction of reflection or the dominant wavelength of the reflection.

[0356] Figure 17A A holographic setup with a plane mirror (331) and a plane diffuser (33) is depicted.

[0357] Figure 17B A holographic setup with a curved mirror (331) and a curved diffuser (33) is depicted.

[0358] Figure 17C A holographic setup with a reflective SLM used as a programmable diffuser (33) and a reflector (331) is depicted.

[0359] Figure 17D A holographic setup is depicted with an adaptive mirror used as a programmable reflector (331) and a transmissive SLM used as a programmable diffuser (33).

[0360] Figure 17E A holographic setup with ring illumination for the object bundle (31) is depicted.

[0361] Figure 17F A holographic setup with moving illumination as an object bundle (31) is depicted.

[0362] Figure 17F The embodiment is particularly useful because it allows multiple different holograms to be recorded on different areas of the lens using bundles of objects (31) with different orientations.

[0363] One possibility is to tune the orientation of the object beam so that all holograms with the same level of reflected light are recorded in a given angular direction. As a result, an observer located in the given angular direction will have a uniform perception of the color of the optical elements reflected by the holographic diffuser.

[0364] It can be based on Figure 17F Another specific recording configuration of the typical setup depicted above ensures that the light intensity reaching the eye is globally constant for the wearer, regardless of the gaze direction. For this configuration, one possibility is to shape the reference beam so that the focal point is close to the angular direction corresponding to the wearer's eye rotation center.

[0365] Figure 4 , Figure 6 , Figure 11 , Figure 14 , Figure 16A , Figure 16B and Figures 17A to 17FThe different setups shown are based on the polarization-preserving fiber (42) and lenses that manage the shape of the reference beam (30). The focusing lens can be a combination of multiple lenses to increase the field of the reference beam, such as a fisheye lens. The fiber can be suppressed and the beam placed in free space, as in a classic holographic setup. Reflective optics can also be used instead of multiple lenses to shape the reference beam (30).

[0366] Figure 17C and Figure 17D The SLM and adaptive mirror presented are configured to shape the diffuse beam or object beam (31) of the reflection. It is evident that such a programmable device can be used instead of the ground-shaping reference beam (30), or both the shaping reference beam and the object beam.

[0367] Similarly, Figure 17E The ring optics depicted can be used to indiscriminately shape the reference beam (30) and / or the object beam (31). In this case, recording of the diffuser can be performed regionally or non-regionally. Therefore, large light fields can be established using both large optics and ring optics.

[0368] To obtain a large diffuse reflection field, the function can also be recorded in sections. To do this, the holographic plate (32) is mounted on a movable mount with angular displacement or, for example, on a hexagon. Thus, different areas can be recorded. If the holographic material is sufficiently reactive, these areas can be recorded rapidly over a few seconds (e.g., 2 seconds). Therefore, the orientation can be gradually changed during smooth motion, and / or a pulsed laser (such as a millisecond or nanosecond laser) can be used for recording the holographic diffuser.

[0369] Regarding the expected angular range of the diffuser's field of view as seen by the observer, the shape and size of the reference beam depend primarily on the expected angular acceptance.

[0370] For a beam of objects, the mirror (331) behind the diffuser (33) can be as follows: Figure 17A The depicted plane mirror or such Figure 17B The curved mirror depicted has a curvature calculated to cover a wide field of view. In particular, if the mirror (331) is also curved, the diffuser (33) itself can also be curved to cover the wide field of view of the mirror.

[0371] On one side of the reference beam, if the beam is collimated, the diffuser will be seen by an observer in front of the wearer. To increase the visibility angle of the diffused color, the reference beam must either converge at a point behind the lens or diverge in front of the substrate and be reflected due to the curved mirror.

[0372] Different recording directions can also be used to open the field of view. For example, two diverging beams can be used to create a curved mirror, and a diffuser can be added to the object beam to achieve a diffuse effect. Using this setup, color diffusion can be seen at an angle of approximately 45° (around + / - 22° near the normal to the lens surface). A diffuser can also be placed in the path of the reference beam to make it diverge.

[0373] For clear lenses, using only one beam and the reflection on the lens for the object beam setup is a preferred solution. For sunglass lenses or tinted lenses, it is preferable to use one beam as a reference beam and at least a second beam as the object beam setup.

Claims

1. An optical element intended to be worn in front of a wearer's eye, said optical element having two main surfaces, in, The optical element includes at least one holographic diffuser element having diffuse characteristics resulting from a spatial variation in the refractive index of the holographic diffuser element, the spatial variation in refractive index being greater than 0.001 at at least one given wavelength over a distance less than 30 µm. The holographic diffuse element is formed by scattering elements based on a non-periodic lattice distribution.

2. The optical element according to claim 1, wherein, The two main surfaces are configured to provide refractive power based on a prescription for the wearer's eye.

3. The optical element according to claim 1, wherein, The at least one holographic diffuse element extends over only a portion of one of the two main surfaces or over all of one of the two main surfaces.

4. The optical element according to claim 1, wherein, The at least one holographic diffuse element is a holographic gradient diffuse element, and the diffuse efficiency of the holographic gradient diffuse element increases from the center of the holographic diffuse element to the periphery of the holographic diffuse element.

5. The optical element according to claim 1, wherein, The at least one holographic diffuse element has a diffuse efficiency between 5% and 50% at at least one given wavelength within a predetermined range.

6. The optical element according to claim 1, wherein the spatial variation of the refractive index is configured such that: - For at least one incident angle direction, when the optical element is exposed to a source beam originating from the incident angle direction, the source beam is scattered by at least one holographic diffuser element, thereby forming at least one scattered beam. ● Each of the scattered beams is centered around a corresponding central angular direction, which is defined as the angular direction with the maximum brightness value, and ● Each of the scattered beams has a corresponding diffusion angle, which is defined as the full width at half maximum of the brightness, and the diffusion angle has a desired value between 2° and 40° depending on at least one direction.

7. The optical element according to claim 1, wherein, The spatial variation of the refractive index is configured such that the at least one holographic diffuse element has the optical function of scattering light to illuminate the retina of the eye in order to slow the development of refractive abnormalities in the eye.

8. The optical element according to claim 1, wherein, The at least one holographic diffuser element is a holographic diffuser mirror.

9. The optical element according to claim 8, wherein, The at least one holographic diffuse element has a diffuse efficiency between 1% and 5% at at least one given wavelength within a predetermined range.

10. An optical device intended to be worn in front of a wearer's eye, comprising: An optical element, wherein the optical element comprises at least one holographic diffuser having diffuse properties resulting from a spatial variation in the refractive index of the holographic diffuser, the spatial variation in the refractive index being greater than 0.001 at at least one given wavelength over a distance less than 30 µm, and A light source, arranged to illuminate the at least one optical element at the at least one given wavelength. in, The holographic diffuse element is formed by scattering elements based on a non-periodic lattice distribution.

11. The optical device of claim 10, further comprising a motion sensor, the motion sensor being designed to acquire signals based on the wearer's movement, wherein, The light source is lit when the acquired signal has a predetermined value.

12. A method for recording a holographic medium onto an optical lens, the method comprising: An unrecorded optical lens is provided, the unrecorded optical lens comprising a recording medium extending over a region of interest, the unrecorded optical lens having two main surfaces. Provides diffuse objects, and A holographic diffuse element is recorded on the recording medium by simultaneously illuminating the region of interest with the following: A reference beam, wherein the reference beam is a coherent beam, and An object beam, which is a coherent beam of light scattered by the diffuse object to obtain the recording optical lens. The diffuse object, the reference beam, and the object beam are configured such that the recorded holographic diffuse element has diffuse characteristics resulting from a spatial variation in the refractive index of the holographic diffuse element, wherein the spatial variation in refractive index is greater than 0.001 at at least one given wavelength over a distance less than 30 µm. The holographic diffuse element is formed by scattering elements based on a non-periodic lattice distribution.

13. The method according to claim 12, wherein, When the holographic diffuse element is recorded, the reference beam and the object beam form two separate beams, which are respectively guided toward opposite main surfaces of the unrecorded optical lens.

14. A method for recording a holographic medium onto an optical lens, the method comprising: An unrecorded optical lens is provided, the unrecorded optical lens comprising a recording medium extending over a region of interest, the unrecorded optical lens having two main surfaces. Modeling the optical properties of diffuse objects, and A holographic diffuse element is recorded on the recording medium by simultaneously illuminating the region of interest with the following: A reference beam, wherein the reference beam is a coherent beam, and An object beam, which simulates a coherent light beam that will be scattered by the diffused object to obtain a recording optical lens. The diffuse object, the reference beam, and the object beam are configured such that the recorded holographic diffuse element has diffuse characteristics resulting from a spatial variation in the refractive index of the holographic diffuse element, wherein the spatial variation in refractive index is greater than 0.001 at at least one given wavelength over a distance less than 30 µm. The holographic diffuse element is formed by scattering elements based on a non-periodic lattice distribution.

15. The method according to claim 14, wherein, When recording the holographic diffuse element, the reference beam is provided by a light source, and the object beam is provided by a spatial light modulator that serves as a programmable diffuser and reflector. The reference beam is directed toward the first of the two main surfaces, and the object beam is directed toward the second of the two main surfaces.

Images