Lens element and corresponding computer-implemented determination method

Abstract

The invention relates to an ophthalmic lens element (1) intended to be worn by a wearer, comprising: at least one prescription portion (2) having a first optical function configured to provide, when the lens element (1) is worn by the wearer, a refractive correction of the wearer's eye based on the wearer's prescription; and a plurality of lenslets (3), each lenslet (3) of said plurality of lenslets being configured to provide at least one second optical function different from the first optical function, wherein each lenslet (3) has a shape, a size and a position such that at least a portion of said lens element (1) has a modulation transfer function (MTF) whose values are configured such that the modulation transfer function of said lens element (1) is lower than or equal to 0.6 in a spatial frequency range comprised between 1 and 5 cycles per degree.

Description

Technical Field

[0001] This invention relates to the field of ophthalmic lenses and optical design.

[0002] More precisely, the present invention relates to a lens element for wear by a wearer, comprising at least one prescription portion and a plurality of microlenses, the at least one prescription portion having a first optical function configured to provide refractive correction of the wearer’s eye based on the wearer’s prescription when the lens element is worn by the wearer, and each of the plurality of microlenses being configured to provide at least one second optical function, the at least one second optical function being different from the first optical function.

[0003] The present invention also relates to a computer-implemented method for determining a lens element intended to be worn by a wearer. Background Technology

[0004] Visual strain refers to the unpleasant visual and visual-related symptoms experienced while reading. Numerous ophthalmic devices, particularly eyeglasses, have been developed to help people with dyslexia and visual strain reduce symptoms of eye fatigue and improve visual performance and comfort during reading activities. The most well-known technology involves providing eyeglasses with tinted lenses. However, these tinted lenses lack aesthetics and privacy in everyday use. Furthermore, they significantly alter color perception and may affect color discrimination performance. Additionally, when worn throughout the day, these lenses can also affect circadian rhythm control, thus causing general fatigue and sleep problems. Summary of the Invention

[0005] Therefore, one object of the present invention is to provide an alternative to the prior art for improving visual comfort and reading skills in people suffering from visual stress.

[0006] According to the present invention, the above-mentioned objective is achieved by a lens element for wearer, the lens element comprising at least one prescription portion and a plurality of microlenses, the at least one prescription portion having a first optical function configured to provide refractive correction of the wearer's eye based on the wearer's prescription when the lens element is worn by the wearer, and each of the plurality of microlenses being configured to provide at least one second optical function, the at least one second optical function being different from the first optical function.

[0007] Each small lens has a shape, size, and position such that at least a portion of the lens element has a modulation transfer function, the value of which is configured such that the modulation transfer function of the lens element 1 is within a spatial frequency range including 1 to 5 cycles per degree.

[0008] One advantage of the lens element according to the invention is the removal of a spatial frequency range centered, for example, approximately 3 Hz / degree. When included in visual stimuli, such as text, those frequencies overstimulate an overexcited visual cortex and cause visual stress. Therefore, by removing these frequencies, the lens element according to the invention reduces visual stress and improves visual comfort and ease of use for patients suffering from this condition.

[0009] According to an embodiment, the modulation transfer function is calculated or computed for wavelengths between 400 and 780 nm, preferably for a wavelength of 550 nm.

[0010] According to an embodiment, a modulation transfer function is calculated or operated for a given pupil diameter.

[0011] Typically, a given pupil diameter falls between 4 mm and 8 mm.

[0012] In the embodiment:

[0013] - Each of the plurality of microlenses has a diameter between 0.1 mm and 2.5 mm.

[0014] - Each of the plurality of small lenses has another small lens in its vicinity;

[0015] - The density of small lenses on a predetermined portion of the lens element is greater than 30%.

[0016] The density of a small lens on a predetermined portion of the lens element can be defined as the ratio between the total surface area of ​​the small lens and the area of ​​the predetermined portion.

[0017] In the following text, the phrase "pre-defined portion of the lens element" refers to:

[0018] - At least a portion of the lens element 1 has a modulation transfer function whose value is less than 0.6 in a spatial frequency range including 1 to 5 cycles / degree, or

[0019] -A sub-part of at least a portion of the lens element 1, the lens element having a modulation transfer function whose value is less than 0.6 over a spatial frequency range including 1 to 5 cycles / degree, or

[0020] - to any part of the lens element 1, including the small lens.

[0021] In one embodiment, the density of small lenses on at least a portion of the lens element is greater than 30%.

[0022] In one embodiment, the density of small lenses on at least a portion of the lens element is greater than 40%.

[0023] Typically, the density of small lenses on at least a portion of the lens element is between 30% and 50% (for discontinuous small lenses).

[0024] In an embodiment, the density of the small lenses on any part of the lens element is greater than 30%.

[0025] In this embodiment, the density of the small lenses on any part of the lens element is greater than 40%.

[0026] Typically, the density of small lenses on any part of the lens element is between 30% and 50% (for discontinuous small lenses).

[0027] According to an embodiment, at least a portion of the modulation transfer function of the lens element exhibits at least one valley in a spatial frequency range including 2 to 6 cycles per degree.

[0028] Typically, the at least one valley has a minimum value between 0.40 and 0.50.

[0029] According to an embodiment, the modulation transfer function of at least a portion of the lens element exhibits at least one peak in a spatial frequency range including 3 to 8 cycles per degree.

[0030] In an embodiment, the at least one peak exhibits a maximum value between 0.40 and 0.60, typically between 0.40 and 0.50.

[0031] In this embodiment, the maximum value of the peak is higher than the minimum value of the valley.

[0032] For example, the area near the microlens could be a 3mm zone surrounding the contour of the microlens.

[0033] In this embodiment, the modulation transfer function of the lens element at a spatial frequency of 3 cycles per degree is less than or equal to 0.4.

[0034] In some examples, for spatial frequencies less than one cycle per degree, the modulation transfer function of the lens element is greater than 0.6. More preferably, for spatial frequencies between five and fifteen cycles per degree, the modulation transfer function of the lens element is greater than 0.2, and more preferably greater than 0.4.

[0035] In an embodiment, the lens element includes a front surface and a rear surface, wherein the rear surface is closer to the wearer's eye when the lens element is worn by the wearer, and the microlens is located on one of the two surfaces and / or between the two surfaces.

[0036] In one embodiment, at least a first portion of the plurality of small lenses is continuous.

[0037] When the microlenses are continuous, the density of the microlenses on at least a portion of the lens element is greater than 70%.

[0038] Typically, when the microlenses are continuous, the density of microlenses on at least a portion of the lens element is between 70% and 100%.

[0039] When the microlenses are continuous, the density of microlenses on any part of the lens element is greater than 70%. In one embodiment, at least a second portion of the plurality of microlenses is arranged according to a predetermined pattern. Typically, the predetermined pattern is selected from linear patterns, hexagonal patterns, rings, spirals, etc.

[0040] In some examples, the first part and the second part can be the same part.

[0041] The pre-defined pattern can be hexagonal.

[0042] In a variant, at least two of the at least second portion of the plurality of small lenses are arranged to form a horizontal line.

[0043] In some embodiments, at least two of the microlenses in at least the second portion of the plurality of microlenses are single-focus and arranged consecutively.

[0044] In an embodiment, each of the at least third portions of the plurality of small lenses has a spherical, aspherical, or tortuous surface shape when covered or under a coating.

[0045] In some embodiments, each of at least the third portion of the plurality of microlenses is monofocal and has an average optical power ranging between 12 diopter and 22 diopter.

[0046] In the example, at least the third part has each small lens with a diameter between 0.1 mm and 0.7 mm.

[0047] In this example, the first portion of the plurality of microlenses comprises 30% of the total number of microlenses. The microlenses in the first portion can be continuous and can be located at the top of the lens. The second portion of the plurality of microlenses comprises 70% of the total number of microlenses. In this example, the microlenses in the second portion can not be continuous, but can be arranged in a linear pattern at the bottom of the lens.

[0048] The upper portion of a lens element means that half of the lens element lies above one of the radial axes of the lens element (here, axis X or axis Y as defined in the lens element). Conversely, the lower portion of a lens element refers to the other half of the lens element, which is located below one of the radial axes of the lens element (similarly, axis X or axis Y as defined in the lens element).

[0049] In another example, the second portion of the plurality of microlenses comprises 70% of the total number of microlenses, while the third portion comprises 30% of the total number of microlenses. Typically, the microlenses in the second portion can be continuous and arranged according to a linear pattern, such as at the bottom of the lens, while the third portion can be randomly arranged at the top of the lens element. The microlenses in the third portion can be single-focus microlenses with high optical power. In some examples, the third portion can be the same as the first and / or second portion.

[0050] In one example, the first part can be the same as the second part. In one embodiment, the small lenses of the first and second parts are arranged continuously along a horizontal line.

[0051] In another embodiment, the second part may be the same as the third part.

[0052] In one embodiment, each small lens has at least one secondary optical function that is multifocal.

[0053] In some embodiments, the microlens has a bifocal second optical function and includes a first portion and a second portion, wherein:

[0054] - The first part is a central circular area with a diameter between 0.5 mm and 1.5 mm.

[0055] - The second part is the outer annular region with an outer diameter between 1 mm and 3 mm.

[0056] In some embodiments, each microlens has a bifocal second optical function and is a diffractive π-Fresnel microlens.

[0057] For example, a diffractive π-Fresnel microlens provides a first principal diffraction order and a second diffraction order, where:

[0058] - The first principal diffraction order is configured to produce a first refractive power, which is included in a range of + / - 0.12 diopters centered on a prescription refractive power of the prescription portion.

[0059] - The second diffraction order is configured to generate a second refractive power such that the absolute value of the difference between the prescription refractive power and the second refractive power is included between 1 diopter and 10 diopter.

[0060] The present invention also relates to a computer-implemented method for...

[0061] Determine the lens elements to be worn by the wearer.

[0062] The lens element includes a prescription portion having a first optical function configured to provide refractive correction based on the wearer's prescription, and a plurality of microlenses in contact with the prescription portion, each of the microlenses providing at least one optical function different from the first optical function of the prescription portion.

[0063] The method includes:

[0064] - Provide (S1) a prescription for correcting the vision of the wearer's eyes,

[0065] - Determine (S2) the shape, size and position of each small lens such that at least a portion of the lens element includes a modulation transfer function (MTF) with a value less than or equal to 0.6 in a spatial frequency range including 1 to 5 cycles per degree.

[0066] In some embodiments, the method includes:

[0067] - Arrange the microlenses according to a predefined regular pattern of adjacent microlenses (S3), wherein the predefined regular pattern has a constant spacing between the two geometric centers of the adjacent microlenses.

[0068] - Adjust (S4) the spacing between the two geometric centers of adjacent small lenses to have a random or pseudo-random arrangement.

[0069] Another object of the present invention is to provide a method for manufacturing a lens element, comprising:

[0070] - The steps of determining the design of the lens element using the computer-implemented method described above.

[0071] - The step of manufacturing the lens element after the design is described.

[0072] In the following text, the term modulation rate or the value of the modulation transfer function refers to the amplitude of the modulation transfer function. Attached Figure Description

[0073] The following description, together with the accompanying drawings which are provided as non-limiting examples, will help to understand the invention and illustrate how to implement it.

[0074] On the joint diagram:

[0075] Figure 1 A schematic axial cross-sectional view of a lens element according to the present invention is shown;

[0076] Figure 2a , Figure 2b and Figure 2cThis is a magnified view of the microlens arrangement according to the first embodiment when projected onto a facial plane perpendicular to the main axis (Z-axis) of the lens element;

[0077] Figure 3 A comparison of the modulation transfer function of the lens element according to the first embodiment and the prior art lens is shown;

[0078] Figure 4 A front unfolded view showing the arrangement of the small lenses according to the second embodiment when projected onto a facial plane perpendicular to the main axis (Z-axis) of the lens element;

[0079] Figure 5 An example of the radial distribution of diffractive π-Fresnel microlenses is shown;

[0080] Figure 6 A comparison of the modulation transfer function of the lens element according to the second embodiment and the prior art lens is shown;

[0081] Figure 7 The arrangement of the small lenses according to the third embodiment is shown;

[0082] Figure 8 The geometry of the bifocal refractive lens is shown;

[0083] Figure 9 A comparison of the modulation transfer functions of a lens according to a third embodiment and two prior art lenses is shown;

[0084] Figure 10 A front view showing the arrangement of the small lenses according to the fourth embodiment when projected onto a face plane perpendicular to the main axis (Z-axis) of the lens element;

[0085] Figure 11 A development diagram showing a variant example of the arrangement of the small lenses according to the fourth embodiment is shown;

[0086] Figure 12 The modulation transfer functions of three examples of lens elements according to the fourth embodiment are shown;

[0087] Figure 13 The effect of the first gradient law on the modulation transfer function of the lens element in the first example according to the fifth embodiment is shown;

[0088] Figure 14 The effect of the second gradient law on the modulation transfer function of the lens element in the second example according to the fifth embodiment is shown. Detailed Implementation

[0089] Visual stress is associated with conditions such as dyslexia, migraines, or visual discomfort. A common view of the causes of visual stress is that the striped patterns created by reading text, especially on digital displays, overstimulate the overexcited visual cortex.

[0090] Several studies have shown that not only can tinted lenses or colored covers reduce overstimulation of the visual cortex, but also that overstimulation of the visual cortex can be reduced by removing specific ranges of spatial frequencies of visual stimuli, such as removing reading text near spatial frequencies of 3 cycles per degree.

[0091] Therefore, the present invention proposes a solution to reduce the amplitude of spatial frequencies in visual stimuli near this value, and thus reduce the cause of visual stress.

[0092] More precisely, the present invention relates to a lens element 1 for use by a wearer, having a modulation transfer function that decays approximately every three cycles per degree. The modulation transfer function is defined as the contrast response of an optical system to a periodic sinusoidal pattern passing through the optical system, the response being a function of the spatial frequency of the optical system.

[0093] Specifically, the present invention aims to provide a particular lens design to reduce the value of the modulation transfer function (e.g., the modulation rate of the modulation transfer function) within a specific spatial frequency range (e.g., within a spatial frequency range including 1 to 5 cycles per degree, typically around 3 cycles per degree), thereby allowing us to reduce the energy of visual stress defined within a spatial frequency range including 1 to 10 cycles per degree, while maintaining the value of the modulation transfer function (e.g., the modulation rate) within a spatial frequency range relevant to the reading task, such as for spatial frequencies including 1 to 5 cycles per degree, 15 to 20 cycles per degree, and 20 to 30 cycles per degree.

[0094] In the context of this invention, the term "lens element" can refer to an uncut optical lens, or a contact lens, or a spectacle lens edged to fit a particular eyeglass frame, or a spectacle lens and an optical device adapted to be positioned on the spectacle lens. In the latter case, the optical device can be positioned on the front or rear surface of the ophthalmic lens.

[0095] like Figure 1 As shown, the lens element 1 includes a front surface F1 facing the object side and a rear surface F2 that is closer to the wearer's eye than the front surface.

[0096] Lens element 1 includes a prescription portion 2 that provides refractive correction according to the wearer's prescription, and multiple microlenses 3. Typically, Figure 1 The lens element 1 shown is a lens manufactured to be worn by a wearer. In one variant, Figure 1The lens element shown can be the optical design of lens element 1.

[0097] Prescription part 2 is configured to provide refractive correction to the wearer based on the wearer's prescription under standard wearing conditions.

[0098] The term "prescription" should be understood as a set of characteristics determined by an ophthalmologist, namely optical power, astigmatism, and prism deviation, to correct a wearer's visual impairment. For example, a prescription for a refractive error wearer includes optical power and astigmatism values ​​with an axis for hyperopia.

[0099] Wearing conditions should be understood as the position of lens element 1 relative to the wearer's eyes, such as the wide-angle, the distance from the cornea to the lens, the distance from the pupil to the cornea, the distance from the eye rotation center (ERC) to the pupil, and the bounding angle.

[0100] Wide angle is the angle between the normal to the rear surface of lens element 1 in the vertical plane and the visual axis of the eye in the principal position (usually considered to be horizontal, when the wearer is looking straight ahead).

[0101] The distance from the cornea to the lens is the distance along the visual axis of the eye at the principal position between the cornea and the posterior surface of the lens element 1.

[0102] The distance from the pupil to the cornea is the distance between the pupil and the cornea along the visual axis of the eye.

[0103] The distance from the ERC to the pupil is the distance along the visual axis of the eye between its ERC and the pupil.

[0104] The wrap angle is the angle between the normal to the rear surface of lens element 1 in the horizontal plane and the visual axis of the eye in the dominant position.

[0105] An example of standard wearing conditions can be defined by a wide-angle of -8°, a corneal-to-lens distance of 12 mm, a pupil-to-cornea distance of 2 mm, an ERC-to-pupil distance of 11.5 mm, and a wrap angle of 0°.

[0106] At least some or all of the multiple small lenses 3 may be located on the front surface of the lens element 1.

[0107] Alternatively, at least some or all of the plurality of small lenses 3 may be located on the rear surface of the lens element 1.

[0108] Another possibility is that at least some or all of the multiple small lenses 3 are located between the front and rear surfaces of the lens element 1.

[0109] Alternatively, at least some or all of the plurality of small lenses 3 may be formed on the film in the form of patches deposited on at least one of the front and rear surfaces of the lens element 1.

[0110] In a modified example, at least some or all of the plurality of small lenses 3 can be formed by stacking them on at least one of the front and rear surfaces of the lens element 1.

[0111] The shape, size, and position of each small lens 3 are designed such that at least a portion of the lens element 1 includes a modulation transfer function (MTF) with a value less than or equal to 0.6 in a spatial frequency range including 1 to 5 cycles per degree.

[0112] For example, at least a portion of the lens element 1 includes a modulation transfer function whose value at a spatial frequency of 3 cycles per degree is less than or equal to 0.6. Preferably, at least a portion of the lens element 1 includes a modulation transfer function whose value at a spatial frequency of 3 cycles per degree is less than or equal to 0.5. More preferably, at least a portion of the lens element 1 includes a modulation transfer function whose value at a spatial frequency of 3 cycles per degree is less than or equal to 0.4.

[0113] For example, the modulation transfer function (MTF) of lens element 1 is greater than 0.6 for spatial frequencies of less than one cycle per degree, and greater than 0.2, more preferably greater than 0.4, for spatial frequencies between five and fifteen cycles per degree. Therefore, by ensuring a reasonably good MTF at higher spatial frequencies, for example, between five and fifteen cycles per degree, lens element 1 according to the invention provides good visual acuity for distant objects / letters in addition to reducing visual stress during reading.

[0114] This means that the modulation transfer function (MJF) of the lens element includes values ​​higher than 0.6 for spatial frequencies below one cycle per degree, and values ​​higher than 0.4 for spatial frequencies between five and fifteen cycles per degree. In this example, the MJF of the lens element includes values ​​in the spatial frequency range between five and fifteen cycles per degree, which are superior to values ​​in the spatial frequency range between one and five cycles per degree, and preferably superior to values ​​in the spatial frequency range of three cycles per degree. This means that the MJF is attenuated for spatial frequencies between one and five cycles per degree, and preferably for spatial frequencies of three cycles per degree.

[0115] For example, the size of each microlens 3 is between 0.1 mm and 2.5 mm. For a microlens 3 with a circular profile, the size is defined as the diameter of the microlens 3.

[0116] For example, each of the plurality of small lenses 3 has another small lens in its vicinity, and the vicinity of the small lens can be an area with a radius of less than 3 mm surrounding the contour of the small lens.

[0117] For example, the density of the small lenses 3 on a predetermined portion of the lens element 1 is between 30% and 100%.

[0118] In the first embodiment, the small lens 3 is arranged along a horizontal line. The term "horizontal" refers to a relative position and must be understood as the wearer standing or sitting under the most common wearing conditions of the lens element 1. It generally corresponds to a direction defined by an axis connecting the centers of rotation of the two eyes within a margin of + / -5 degrees. It can also be described as a 0-180° TABO orientation.

[0119] In this disclosure, lens element 1 is defined using an orthogonal reference system (O, x, y, z). Typically, the origin O corresponds to the optical or geometric center of lens element 1. Therefore, lens element 1 is arranged to extend according to two spatial directions defined along the x and y axes, which intersect the optical axis (z-axis) of lens element 1. These two spatial directions define the field or surface of lens element 1.

[0120] In this embodiment, adjacent small lenses are aligned along one of two spatial directions (see...). Figure 1 and Figures 2a-2c Typically, the small lens is aligned between the two opposite edges of the lens element 1, such that the small lens forms a straight line between the two opposite edges of the lens element 1.

[0121] Figure 2a and Figure 2b A front view of a first embodiment of lens element 1 is shown when projected onto a facial plane perpendicular to the main axis (axis Z) of the lens element.

[0122] It can be observed that each of the consecutive small lenses is arranged along the same direction (parallel to one of the radial axes X or Y of the lens element 1), so that the consecutive small lenses form a horizontal line in the projection plane.

[0123] On every horizontal line, the small lens 3 is continuous. By continuous, we mean that the small lenses 3 are actually in contact: they are in contact with each other along the boundary or at a point.

[0124] In this first embodiment, the small lens 3 can be of several different types: single-focus, multi-focus, or progressive.

[0125] When the small lens 3 is a single focal point, they can have different shapes: spherical, aspherical, or complex.

[0126] In the first example, multiple small lenses 3 cover the entire surface of lens element 1, such as Figure 2a As shown. In the second example, multiple small lenses 3 cover the lower half of the lens element 1, as... Figure 2b As shown. In the third example, multiple small lenses 3 form a rectangular array contained in the lower half of the lens element 1, as shown. Figure 2c As shown.

[0127] Figure 3 A comparison is shown between the horizontal axis profile of the modulation transfer function of the lens element 1 (planar curve) according to the invention and the horizontal axis profile of a regular single-view lens (dashed curve), wherein the lens element according to the invention has a plurality of aspherical microlenses with a size of about 1.1 mm on one side, the distance between the vertices of the microlenses is 2.4 mm, and the aspherical microlenses are arranged in a horizontal line covering 40% of the surface of the lens element 1.

[0128] In this disclosure, the modulation transfer function is implemented by a computer.

[0129] Typically, the modulation transfer function of a portion of lens element 1 is calculated by selecting the portion having a simulated aperture (i.e., an aperture stop), hereinafter referred to as the pupil located in the optical design of lens element 1 (the simulated optical design of the lens element). Preferably, the pupil has a center centered on the wearer's potential central visual gaze, for example, between 0 degrees and 20 degrees defined from two radial directions of lens element 1 for the wearer's potential central visual gaze. Typically, such an angle corresponds to a point spaced 0 mm and 15 mm from the center O of lens element 1, a distance typically corresponding to the gaze position in the lens element during reading with a single-vision lens.

[0130] Therefore, the modulation transfer function on different parts of the lens element 1 can be calculated by spatially scanning the surface (or field of view) of the lens element 1 using pupils defined at different locations of the lens element.

[0131] Typically, the aperture or pupil has a circular shape with a diameter ranging from 4 mm to 8 mm to mimic the variation in the wearer's normal pupil size.

[0132] Furthermore, for calculation purposes, the circular portion of lens element 1 selected via the pupil (e.g., aperture) includes a portion or all of the microlenses of lens element 1. In this disclosure, the density of microlenses on the portion selected via the pupil is at least 30%, typically between 70% and 100% when the microlenses are continuous, and between 30% and 50% when the microlenses are discontinuous. Preferably, the circular portion includes a half portion containing microlenses and another half portion without any microlenses.

[0133] In this disclosure, the modulation transfer function is calculated using a process known to those skilled in the art, such as using software that allows the simulation of lens element 1.

[0134] Typically, the point spread function (PSF) is calculated, which gives the degree of diffusion (blurring) of the image of a point object on a portion of the lens element 1 selected by the pupil. For this purpose, for example on a plane simulating the surface of the retina, a point source emitting in a monochromatic or multicolor visible spectrum between 400 nm and 780 nm (L) is typically used to calculate the PSF. Advantageously, the PSF is calculated for a center wavelength between 540 and 560 nm, for example, at a center wavelength of 550 nm. The modulation transfer function is then calculated based on the Fourier transform of the calculated PSF.

[0135] In this disclosure, the horizontal profile of the modulation transfer function corresponds to the variation of the modulation transfer function estimated or calculated along the horizontal x-axis of the lens element. Typically, the horizontal modulation transfer function corresponds to the tangent of the Fourier transform of the point spread function along the horizontal x-axis of the lens element 1. Conversely, the vertical profile of the modulation transfer function corresponds to the variation of the modulation transfer function calculated or estimated along the vertical y-axis of the lens element 1, and the vertical modulation transfer function corresponds to the tangent of the Fourier transform of the point spread function along the vertical y-axis of the lens element.

[0136] In the following example, pupil size refers to or is defined as a specific portion of lens element 1. This means that a pupil diameter of 4 mm corresponds to a circular portion of 4 mm diameter defined on lens element 1, and therefore refers to the diameter of a specific portion of lens element 1.

[0137] The modulation transfer function in the example of this disclosure is calculated using a monochromatic light source with a wavelength of 550 nm and a pupil diameter (aperture) of 4 mm. The portion of lens element 1 selected via the pupil diameter is located in the region of lens element 1 that includes at least one microlens, as described above. Furthermore, in this case, the circular portion selected via the pupil diameter (or aperture) includes one half containing a microlens and the other half without any microlens.

[0138] exist Figure 3 As can be observed, the modulation transfer function decreases over a spatial frequency range encompassing 0 to 2 cycles per degree. The modulation transfer function of the lens element 1 according to the invention exhibits a valley with a minimum value equal to 0.45 near a spatial frequency range of 3 cycles per degree. Then, the modulation transfer function increases over a spatial frequency range encompassing 3 to 5 cycles per degree. Here, it can be observed that the modulation transfer function exhibits a peak value between 3 and 7 cycles per degree, with a maximum value equal to 0.5 near 6-7 cycles per degree. The modulation transfer function decreases over a spatial frequency range encompassing 7 to 60 cycles per degree.

[0139] This means that for spatial frequencies included between 1 and 5 cycles per degree, preferably for spatial frequencies of about 3 cycles per degree, the modulation transfer function is attenuated; then for spatial frequencies included between 5 and 7 cycles per degree, the modulation transfer function is increased; and finally for spatial frequencies above 10 cycles per degree, the modulation transfer function is attenuated.

[0140] In other words, this means that the modulation transfer function exhibits a higher value in the spatial frequency range that includes 3 to 7 cycles per degree than the modulation transfer function exhibited in the spatial frequency range that includes 1 to 3 cycles per degree.

[0141] It can also be seen that the modulation rate of the modulation transfer function of lens element 1 in the spatial frequency range including 0 Hz and 60 Hz per degree is lower than that of the modulation transfer function associated with a regular single-view lens (dummy curve).

[0142] In the second embodiment, the small lenses 3 are arranged in a continuous manner as shown in the image. Figure 4 The hexagonal array shown can cover the entire surface of lens element 1 (defined by axes x and y) or only a portion of the lower part of lens element 1. In this embodiment, the small lens is a so-called diffractive π-Fresnel lens. A diffractive π-Fresnel lens exhibits... Figure 5 The diagram shows radially distributed Fresnel microlenses. The phase function of a diffractive π-Fresnel microlens has a π-phase jump at the nominal wavelength λ0. For human visual applications, L0 is considered to be, for example, 550 nm. The diffractive π-Fresnel microlenses present an axis perpendicular to their planes and passing through their center. The diffractive π-Fresnel lenses diffract primarily in two diffraction orders associated with two refractive powers, P0(λ0) and P1(λ0). This means that when light is received, they concentrate the light onto two distinct regions along their axis.

[0143] For example, the refractive power P0(λ0) is included in the range of + / - 0.12 diopters centered on the prescription optical power of the prescription portion.

[0144] For example, the refractive power P1(λ0) is such that the absolute value of the difference between it and the prescription optical power is between 1 diopter and 10 diopter. Preferably, the refractive power P1(λ0) is such that the absolute value of the difference between it and the prescription optical power is between 2 diopter and 6 diopter.

[0145] Figure 6A comparison of the modulation transfer function (MTF) of lens element 1 according to the second embodiment and that of a regular single-vision lens (dummy curve) is shown. The lens element according to the second embodiment has π-Fresnel microlenses arranged in a hexagonal array with diopters P0(λ0) and P1(λ0) equal to 0 diopters and 4 diopters (flat curve), respectively. The step of the hexagonal array is 2 mm, covering 100% of the surface of lens element 1. The MTF is monochromatic, calculated at a wavelength of 550 nm, and the pupil diameter is 4 mm. Similarly, in the case of lens element 1 according to the invention, the MTF exhibits a valley with a minimum value (equal to 0.43 here) around a spatial frequency of 3 cycles per degree. The MTF then increases over a spatial frequency range including 3 to 5 cycles per degree. Here, it can be observed that the MTF exhibits a peak between 3 and 7 cycles per degree, with a maximum value equal to 0.5 around 5 cycles per degree. The modulation transfer function decreases over a spatial frequency range that includes 7 to 60 cycles per degree.

[0146] This means that for spatial frequencies included between 1 and 4 cycles per degree, preferably for spatial frequencies of approximately 3 cycles per degree, the modulation transfer function is attenuated; then for spatial frequencies included between 3 and 7 cycles per degree, the modulation transfer function is increased; and finally for spatial frequencies above 10 cycles per degree, the modulation transfer function is attenuated.

[0147] In other words, this means that the modulation transfer function exhibits a higher value in the spatial frequency range that includes 3 to 7 cycles per degree than the modulation transfer function exhibited in the spatial frequency range that includes 1 to 3 cycles per degree.

[0148] It can also be seen that the modulation rate of the modulation transfer function of lens element 1, which covers the spatial frequency range between 0 and 60 cycles per degree, is lower than the modulation rate of the modulation transfer function of a regular single-view lens (dummy curve).

[0149] The third embodiment relates to a lens element 1 specifically designed for more sensitive patients who are more susceptible to visual stress than others. For these, a more advanced filtering of the spatial frequencies of interference occurs around 3 cycles per degree. In other words, in this embodiment, the reduction in the modulation transfer function is stronger near the spatial frequencies of 3 cycles per degree. It was found that reading performance in standard (i.e., non-dyslexical) patients was not affected by 0.5 diopters of refractive blur. Refractive blur refers to the equivalent defocus of 0.5 diopters relative to emmetropia or corrected visual acuity. The highest spatial frequency range involved in the reading task is between 10 and 15 cycles per degree and between 20 and 30 cycles per degree. These ranges correspond to the resolution levels required for word and single-letter recognition.

[0150] Therefore, the lens element 1 according to the third embodiment exhibits a modulation transfer function that, on the one hand, decreases more strongly around 3 cycles per degree of spatial frequency, and on the other hand, is comparable to (and even better than) the modulation transfer function of a lens that introduces 0.5 diopters of refractive blur for other spatial frequency ranges.

[0151] In this third embodiment, the small lens of the lens element 1 is a continuous refractive bifocal small lens.

[0152] For example, such as Figure 7 As shown, the bifocal lenses are arranged in a hexagonal array outside the central portion. The bifocal lenses present a first part consisting of a central circular area and a second part consisting of an outer annular area. The cross-sectional profile of the outer annular area can be of any type, such as spherical or non-spherical. For example, the first part produces a first portion of refractive power, and the second part produces a second portion of refractive power. Figure 8 The geometry of the bifocal refractive lens is shown.

[0153] For example, the diameter of the central circular region is between 0.5 and 1.5 mm. Preferably, the diameter of the central circular region is between 1 mm and 1.25 mm.

[0154] For example, the outer annular region has an outer diameter between 1 mm and 3 mm. Preferably, the outer annular region has an outer diameter between 1.3 mm and 1.8 mm.

[0155] For example, the first part produces a first part of refractive power, which is included in the range of + / - 0.12 diopters centered on the prescription refractive power of the prescription part.

[0156] For example, the second part generates a second portion of refractive power such that the absolute value of the difference between the prescribed refractive power and the second portion of refractive power is included between 1 diopter and 10 diopter. Preferably, the second part generates a second portion of refractive power such that the absolute value of the difference between the prescribed refractive power and the second portion of refractive power is included between 2 diopter and 6 diopter.

[0157] Figure 9A comparison of the modulation transfer functions (MTF) of a diffraction-limited lens (dashed line), a single-vision lens introducing +0.5 diopter defocus (dotted line), and a lens element according to a third embodiment is shown. The bifocal microlens has an additional central power of 0 diopter, a refractive peripheral power of 3.5 diopter, and a central diameter of 1.41 mm. The distance between the centers of the two microlenses is 2 mm, and the portion of lens element 1 covered by the hexagonal array is 100%. The MTF is monochromatic at a wavelength of 550 nm and is calculated for a pupil diameter of 4 mm. It can be seen that the reduction in modulation at the spatial frequency of 3 cycles per degree is stronger than in the first and second embodiments (the MTF value is approximately 0.32).

[0158] In the fourth embodiment, the microlens is a refractive miniature high-power microlens. The microlens is spherical. In a variant, the microlens may be aspherical. The miniature high-power microlens exhibits a circular profile and center. For example, as... Figure 10 As shown, the small, high-power microlenses are continuous and organized in a hexagonal array with an empty central region. Preferably, the microlenses are arranged in a horizontal line, such as... Figure 2b or Figure 2c As shown.

[0159] For example, a small, high-magnification microlens has an average optical power ranging from 12 to 22 diopters. Preferably, a small, high-magnification microlens has an average optical power ranging from 14 to 20 diopters. More preferably, a small, high-magnification microlens has an average optical power ranging from 16 to 18 diopters.

[0160] Advantageously, the arrangement of small, high-power refracting lenses allows for adjustment and management of the contrast reduction level at three cycles per degree of spatial frequency, while maintaining very good performance (i.e., high MTF values) at both high and low spatial frequencies. Regarding low spatial frequencies, these are crucial in the first step of rapid scene recognition and classification. Excessive degradation at these frequencies could impair scene and object perception, thus requiring high contrast. Similarly, high contrast is needed at high spatial frequencies to ensure good visual acuity.

[0161] In order to reduce periodic interference bounces in the modulation transfer function curve introduced by the small aperture of the refractive high-power microlens and to improve the performance of the lens element 1 according to the fourth embodiment, the spatial organization of the refractive high-power microlens can be adjusted by introducing some randomization at the center position of the refractive high-power microlens. Figure 11 It represents the randomized hexagonal arrangement of the center positions of small, high-magnification refracting lenses.

[0162] For example, for at least a portion of a plurality of small high-magnification microlenses, the positional offset of the center of each small high-magnification microlens is less than a randomization distance of 0.1 mm. Preferably, the positional offset of the center of each small high-magnification microlens is less than a randomization distance of 0.08 mm.

[0163] Figure 12 The modulation transfer function (MTF) of different arrangements of the refractive small high-power microlens of the fourth embodiment is shown. The refractive small high-magnification microlens has an average optical power of 17 diopters and a diameter of 0.3 mm. The MTF corresponds to the horizontal cross section and is calculated using a pupil diameter of 4 mm. These arrangements correspond to hexagonal arrangements with no randomization of the microlens center position, a distance of 0.3 mm between the center of one microlens and the center of another nearby microlens (solution A), and hexagonal arrangements with randomized spatial variations of + / -0.06 mm (solution B) and + / -0.08 mm (solution C) for each microlens center.

[0164] from Figure 12 It can be inferred that the introduced randomization reduces interference bounce in the modulation transfer function curve. The higher the level of randomization, the lower the modulation transfer function value.

[0165] Alternatively, randomization can be introduced by changing the diameter of the microlens instead of the position of its center.

[0166] For example, the diameter of a small, high-power microlens can be between 0.1 mm and 0.7 mm. Preferably, the diameter of a small, high-power microlens can be between 0.2 mm and 0.4 mm.

[0167] In the fifth embodiment, the lens element 1 according to the invention corresponds to a lens element 1 according to each of the first, second, third, and fourth embodiments, on which the gradient law is applied. The gradient law means a function of variation that alters the parameters of the lens element 1 in order to further reduce the modulation transfer function around a spatial frequency of 3 cycles per degree and / or increase the modulation transfer function away from that spatial frequency.

[0168] In the first example, the lens element is designed according to the third embodiment, i.e., it has multiple refractive bifocal microlenses. The parameter that varies in lens element 1 is the surface ratio between the second part, i.e., the outer annular region, and the first part. Figure 13The diagram illustrates the change in the modulation transfer function when the ratio of the first portion is reduced from 54% (Case A) of the entire surface of the refractive bifocal lens to 45% (Case B) and then to 36% (Case C). More precisely, the refractive bifocal lenses under consideration are arranged in a hexagonal array with adjacent centers spaced 1.5 mm apart. The first portion produces zero first power. The second portion produces 3.5 diopters of second power. The diameter of the central circular region varies from 1.16 mm to 1.06 mm to 0.95 mm.

[0169] The modulation transfer function (MTF) is monochromatic, evaluated at a wavelength of 550 nm, corresponding to a horizontal cross-section, and calculated for a pupil diameter of 4 mm. It can be observed that the smaller the first portion, the smaller the MTF value at low spatial frequencies. Therefore, the surface ratio between the second and first portions of the bifocal microlens is a parameter based on which lens element 1 can be optimized to achieve the desired MTF.

[0170] In the second example, the lens element is first designed according to the third embodiment, that is, it has multiple refractive bifocal microlenses. The parameter that varies in lens element 1 is the distance between the centers of two adjacent refractive bifocal microlenses. Figure 14 The diagram illustrates the change in the modulation transfer function as the distance between the centers of two adjacent refractive bifocal microlenses is reduced from 2 mm (Case A) to 1.5 mm (Case B) and then to 1 mm (Case C). More precisely, the diameter of the central circular region varies from 1.41 mm to 1.06 mm to 0.70 mm. In all cases, the surface area ratio of the central circular region relative to the entire surface of the refractive bifocal microlens remains equal to 45%. In all cases, the first portion of optical power generated by the central circular region is zero. In all cases, the second portion of optical refractive power generated by the outer annular region remains equal to 3.5 diopters.

[0171] The modulation transfer function (MTF) is monochromatic, evaluated at a wavelength of 550 nm, corresponding to a horizontal cross-section, and calculated for a pupil diameter of 4 mm. It can be observed that the larger the distance between two adjacent refractive bifocal microlenses, the lower the MTF value at low spatial frequencies. Therefore, the distance between the refractive bifocal microlenses is a parameter based on which lens element 1 can be optimized to achieve the desired MTF.

[0172] According to the present invention, other ways of designing multiple small lenses allow for customization of the modulation transfer function of lens element 1 in order to optimize its value for approximately three cycles per degree of spatial frequency and other spatial frequency ranges.

[0173] For example, the microlenses may not be continuous, or in other words, the density of the microlenses may be reduced.

[0174] In another example, when the microlens is a diffractive π-Fresnel microlens, the nominal wavelength λ0 can be changed. If the nominal wavelength λ0 increases, the +1 order energy ratio will increase, and therefore the modulation transfer function will decrease at lower spatial frequencies.

[0175] The present invention also relates to a computer-implemented method for determining the lens element to be worn by a wearer.

[0176] The lens element includes a prescription portion having a first optical function configured to provide refractive correction based on the wearer's prescription, and a plurality of microlenses in contact with the prescription portion, each of the microlenses providing at least one optical function different from the first optical function of the prescription portion.

[0177] The method includes:

[0178] - Provide (S1) a prescription for correcting the vision of the wearer's eyes,

[0179] - Determine (S2) the shape, size, and position of each small lens such that at least a portion of the lens element includes a modulation transfer function (MTF) with a value less than or equal to 0.6 in a spatial frequency range including 1 to 5 cycles per degree.

[0180] In some embodiments, the method includes:

[0181] - The small lenses 3 are arranged according to a regular pattern (S3) between adjacent small lenses 3, wherein the regular pattern has a constant spacing between the two geometric centers of adjacent small lenses 3.

[0182] - Adjust (S4) the spacing between the two geometric centers of adjacent small lenses 3 so as to have a random or pseudo-random arrangement.

[0183] Examples of random permutations are in Figure 11 As shown in the figure, some randomization is introduced at the center of the refracting small high-power lens.

[0184] The pseudo-random arrangement of microlenses can be defined as follows. Starting with a regular arrangement where the distance between the two geometric centers of adjacent microlenses is constant, when located on the regular arrangement, the center C0 of a considered microlens has coordinates (xc0, yc0) in a plane perpendicular to the optical axis of lens element 1. Let S represent the characteristic dimension of the regular arrangement, for example, the distance between two microlenses in a square or hexagonal arrangement. The position of the center of the considered microlens in the pseudo-random arrangement will be (xc, yc), for example, |xc-xc0| < PxS and |yc-yc0| < PxS, where P is a percentage between 0 and 100%, representing the variability of the position in the pseudo-random arrangement.

[0185] In one variant, the center position of the small lens under consideration in a pseudo-random arrangement can be defined such that sqrt((xC-xC0)) 2 + (yc-yc0) 2 )<PxS.

[0186] The computer-implemented method described above is typically used to manufacture lens element 1 (i.e., the physical lens element). Typically, the method for manufacturing lens element 1 includes:

[0187] - The steps for determining the design of lens element 1 using the computer-implemented method described above,

[0188] - The step of manufacturing the lens element 1 after the design.

Claims

1. A lens element (1) intended to be worn by a wearer, comprising at least one prescription portion (2) having a first optical function configured to provide, when the lens element (1) is worn by the wearer, a refractive correction of the wearer's eye based on the wearer's prescription, and a plurality of lenslets (3), each lenslet (3) of said plurality of lenslets being configured to provide at least one second optical function different from the first optical function, wherein each lenslet (3) having a shape, a size and a position such that at least one portion of said lens element (1) has a modulation transfer function (MTF) whose values are configured such that said at least one portion of said lens element (1) is lower than or equal to 0.6 in said modulation transfer function in a spatial frequency range comprised between 1 and 5 cycles per degree, while maintaining values of the modulation transfer function in a spatial frequency range related to a reading task, wherein said modulation transfer function decreases from a spatial frequency of 0 cycle per degree and decreases to less than or equal to 0.6 at a spatial frequency of 3 cycles per degree, said modulation transfer function being calculated for at least one given visible wavelength, and wherein: each lenslet of said plurality of lenslets (3) has a diameter comprised between 0.1 mm and 2.5 mm, each lenslet of said plurality of lenslets (3) has another lenslet in its vicinity, said vicinity of a lenslet being a zone having a radius of less than 3 mm around the contour of a given lenslet; the density of lenslets (3) is greater than 30% on at least one portion of said lens element (1).

2. The lens element (1) according to claim 1, wherein, the value of said modulation transfer function (MTF) at a spatial frequency of 3 cycles per degree is lower than or equal to 0.

4.

3. The lens element (1) according to claim 1, comprising a front surface (Fl) and a back surface (F2), the back surface (F2) being closer to the eye of the wearer when the lens element (1) is worn by the wearer, wherein, said lenslets (3) are located on at least one of the front surface (Fl) and the back surface (F2) and / or between them.

4. The lens element (1) according to claim 1, wherein, at least a first portion of said plurality of lenslets (3) is continuous.

5. The lens element (1) according to claim 1, wherein, at least a second portion of said plurality of lenslets (3) is arranged according to a predefined pattern.

6. The lens element (1) according to claim 5, wherein, at least two lenslets of said at least second portion of said plurality of lenslets (3) are arranged to form a horizontal line.

7. The lens element (1) according to claim 5, wherein, at least two lenslets of said at least second portion of said plurality of lenslets (3) are single vision and are arranged continuously.

8. The lens element (1) according to claim 5, wherein: each lenslet of at least a third portion of said plurality of lenslets (3) is single vision and has an average optical power comprised between 12 and 22 dioptres.

9. The lens element (1) according to claim 8, wherein, each lenslet (3) of said at least third portion has a diameter comprised between 0.1 mm and 0.7 mm.

10. The lens element (1) according to claim 1, wherein, each lenslet (3) has a second optical function which is bifocal and each lenslet comprises a first portion and a second portion, wherein: said first portion is a central circular area having a diameter comprised between 0.5 mm and 1.5 mm, said second portion is an outer peripheral annular area having an outer diameter comprised between 1 mm and 3 mm.

11. The lens element (1) according to claim 1, wherein, Each lenslet (3) has a bifocal second optical function, and each lenslet (3) is a diffractive pi-Fresnel lenslet.

12. The lens element (1) according to claim 11, wherein, The diffractive pi-Fresnel lenslet provides a first main diffraction order and a second diffraction order, wherein: - the first main diffraction order is configured to produce a first dioptric power comprised within a range of + / - 0.12 dioptres centered on the prescribed optical power of the prescription portion, - the second diffraction order is configured to produce a second dioptric power such that the absolute value of the difference between the prescribed optical power and the second dioptric power is comprised between 1 dioptre and 10 dioptres.

13. The lens element (1) according to claim 1, wherein, The value of the modulation transfer function of the at least one portion of the lens element is higher than 0.6 for spatial frequencies below 1 cycle per degree and higher than 0.2 for spatial frequencies between 5 cycles per degree and 15 cycles per degree.

14. A computer-implemented method for determining a lens element (1) intended to be worn by a wearer, wherein The lens element (1) comprises a prescription portion having a first optical function configured to provide a dioptric correction based on a prescription of the wearer and a plurality of lenslets in contact with the prescription portion, each of the lenslets providing at least one optical function different from the first optical function of the prescription portion; wherein the method comprises: - providing (SI) a prescription for correcting the vision of the eye of the wearer; - determining (S2) the shape, size and position of each lenslet (3) such that at least one portion of the lens element (1) has a modulation transfer function (MTF) with a value lower than or equal to 0.6 in a spatial frequency range comprised between 1 and 5 cycles per degree, while preserving the value of the modulation transfer function in a spatial frequency range related to a reading task, wherein the modulation transfer function decreases starting from a spatial frequency of 0 cycle per degree and decreases to less than or equal to 0.6 at a spatial frequency of 3 cycles per degree, The modulation transfer function is calculated for at least one given visible wavelength, and wherein: each lenslet of the plurality of lenslets (3) has a diameter between 0.1 mm and 2.5 mm, each lenslet of the plurality of lenslets (3) has another lenslet in its vicinity, the vicinity of a lenslet being a zone having a radius of less than 3 mm around the contour of the given lenslet; The density of lenslets (3) is greater than 30% on at least one portion of the lens element (1).

15. The method according to claim 14, wherein the method comprises: - arranging (S3) lenslets (3) according to a predefined regular pattern of adjacent lenslets having a constant pitch between two geometric centers of adjacent lenslets, - adjusting (S4) the pitch between two geometric centers of adjacent lenslets so as to have a random or pseudo-random arrangement.

16. The method of claim 14, wherein, The value of the modulation transfer function of the at least one portion of the lens element is higher than 0.6 for spatial frequencies below 1 cycle per degree and higher than 0.2 for spatial frequencies between 5 cycles per degree and 15 cycles per degree.

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