Method and system for determining the prescription of a person's eye

Abstract

The present invention relates to a system (10) for determining the prescription of a person's eye (2), the system being configured to communicate with a mobile device (12), the system comprising: - at least one first light source (16), the at least one first light source being adapted to irradiate the eye with a first light (20) having a first optical wavelength; - at least one second light source (18), the at least one second light source being adapted to irradiate the eye with a second light (22) having a second optical wavelength different from the first wavelength; and - a calculation module (40), the calculation module comprising a memory (42) and a processor (44), the processor being arranged to execute program instructions stored in the memory to: ● measure the photorefraction of the eye at the first wavelength based on at least one picture of the eye recorded when irradiated with the first light; ● measure the photorefraction of the eye at the second wavelength based on at least one picture of the eye recorded when irradiated with the second light; ● determine the prescription of the eye based on the photorefraction measured at the first wavelength and the photorefraction measured at the second wavelength.

Description

Field of the Invention

[0001] The present invention relates to a method and a system for determining the prescription of a wearer's eye. The present invention further relates to a corresponding computer program product and a computer-readable medium. The present invention further relates to a method for providing an ophthalmic lens adapted to the wearer's prescription. Background Art

[0002] An optical lens is typically determined to be then manufactured according to the wearer's instructions. For example, in the case of an ophthalmic lens for correcting or improving vision, the ophthalmic lens is determined according to the prescription of the wearer corresponding to the wearer's vision requirements.

[0003] The prescription of a person's eye can be determined by measuring the eye's refraction, also known as photorefraction or photoretisnoscopy. The principle of photorefraction involves projecting light into the eye during flash photography and then examining the path of the light emerging from the pupil after scattering in the posterior part inside the eyeball.

[0004] For example, for a myopic wearer, the light from the light source and reflected on the retina enters the camera in such a way that the camera sees a "crescent shape" inside the person's pupil. The size, position, and shape of this crescent depend on the refraction of the wearer's eye. For a given distance (also known as the eccentricity) between the light source and the edge of the camera aperture, the working distance, the diameter of the camera lens, and the pupil diameter, the size of the crescent is proportional to the refractive error. Thus, the power, astigmatism, and axis can be determined based on the measurement of the refractive error in at least three different meridians defined by the axis intersecting the camera center and the light source (see "Two-dimensional simulation of eccentric photorefraction images for ametropes: factors influencing the measurement", Y. Wu, L. N. Thibos, and T. R. Candy, Ophthalmic Physiol. Opt., 2018; 38: 432-446).

[0005] Today's optometrists use accurate but bulky devices that require rather long and impractical measurements to evaluate the wearer's prescription.

[0006] Especially in developing countries, optometrists may be few and have rather low skills, and may not be able to afford the expensive prescription measurement requirements.

[0007] An object of the present invention is to provide a cheap, simple and very fast prescription measurement method and system. Summary of the Invention

[0008] To this end, the present invention proposes a system for determining the prescription of a person's eye, the system being configured to communicate with a mobile device, the system comprising:

[0009] - at least one first light source adapted to irradiate the eye with first light having a first optical wavelength;

[0010] - at least one second light source adapted to irradiate the eye with second light having a second optical wavelength different from the first wavelength; and

[0011] - a calculation module, the calculation module comprising a memory and a processor, the processor being arranged to execute program instructions stored in the memory to:

[0012] o measure the photorefraction of the eye at the first wavelength based on at least one picture of the eye recorded when irradiated with the first light;

[0013] o measure the photorefraction of the eye at the second wavelength based on at least one picture of the eye recorded when irradiated with the second light;

[0014] o determine the prescription of the eye based on the photorefraction measured at the first wavelength and the photorefraction measured at the second wavelength.

[0015] Advantageously, such a system allows a non-invasive, easy-to-use and cheap tool to perform digital refractive measurements, especially in developing countries. In the sense of the present invention, digital refractive measurement is refractive measurement using digital means.

[0016] In fact, although a specific wavelength range of the light source shining on the eye (also called the "dark zone") may not result in a crescent shape corresponding to a specific refractive error, the system allows objective measurement of the refraction of a person's eye at two wavelengths simultaneously and thus measurement of its prescription. Therefore, there is always a possible refractive measurement because at least one picture under at least one of the two light sources should show a crescent shape.

[0017] In addition, the system can be advantageously removably fastened to and associated with a mobile device (such as a smartphone).

[0018] According to further embodiments that can be considered separately or in combination:

[0019] - the calculation module is embedded in the mobile device;

[0020] - The system for determining a prescription is further configured to communicate with a remote unit that includes a memory and a processor arranged to execute program instructions stored in the memory to store data related at least to the photorefraction of the eye measured at the first wavelength and the photorefraction of the eye measured at the second wavelength;

[0021] - The system is fastened to and removable from the housing of the mobile device;

[0022] - The or each first light source is configured to emit infrared or near-infrared light, and the or each second light source is configured to emit visible light;

[0023] - The system is configured to communicate with a camera that is adapted and configured to record at least one picture of the person's eye when the eye is illuminated by the first light or the second light;

[0024] - The camera is embedded in the mobile device;

[0025] - The camera is embedded in the system;

[0026] - The second light source is arranged at the same distance from the camera as the first light source;

[0027] - The system for determining the prescription of an eye includes at least one set of three first light sources, each first light source being adapted to emit first light at the first optical wavelength;

[0028] - The first light sources of each set are equidistant from the camera and are arranged to define three regularly angularly spaced directions;

[0029] - The processor is arranged to execute program instructions stored in the memory to:

[0030] o illuminate the eye with first light continuously emitted by the or each first light source emitting at the first wavelength,

[0031] o illuminate the eye with second light emitted by the second light source emitting at the second wavelength,

[0032] o record at least one picture of the person's eye through the camera when the eye is illuminated by the first light and / or the second light;

[0033] - The system includes multiple sets of three first light sources, the distances between the camera and each set of first light sources are different, the multiple sets of first light sources are arranged to define the same three regularly angularly spaced directions, and wherein the processor is arranged to execute program instructions stored in the memory to measure the photorefraction of the eye at the first wavelength by irradiating the eye with first light continuously emitted by at least one set of the multiple sets of first light sources, and then measure the photorefraction of the eye at the second wavelength by irradiating the eye with second light emitted by the second light source;

[0034] - The system includes multiple second light sources adapted to emit light having the second optical wavelength; each second light source is equidistant from the camera and is associated with a different direction defined by the first light source and the camera, and wherein the processor is arranged to execute program instructions stored in the memory to select one of these second light sources to irradiate the eye, and then perform the photorefraction measurement of the eye at the second wavelength based on the photorefraction measurement of the eye at the first wavelength;

[0035] - The system includes multiple second light sources adapted to emit light having the second optical wavelength; each second light source is at a different distance from the camera and is associated with the same direction defined by the first light source and the camera, and wherein the processor is arranged to execute program instructions stored in the memory to select one of these second light sources to irradiate the eye, and then perform the photorefraction measurement of the eye at the second wavelength based on the photorefraction measurement of the eye at the first wavelength.

[0036] Another object of the present invention relates to a method for determining the prescription of a human eye by a system according to the present invention, the method at least includes:

[0037] - Measuring the photorefraction of the eye at the first wavelength based on at least one picture of the eye recorded when the eye is irradiated with first light continuously emitted by the or each first light source;

[0038] - Measuring the photorefraction of the eye at the second wavelength based on at least one picture of the eye recorded when the eye is irradiated with second light emitted by the second light source; and

[0039] - Determining the prescription of the eye based on the photorefraction measured at the first wavelength and the photorefraction measured at the second wavelength.

[0040] Further embodiments that can be considered individually or in combination according to the method:

[0041] - Measuring the photorefraction of the eye at the second wavelength and measuring the photorefraction of the eye at the first wavelength with a temporal interval less than 0.5 s;

[0042] - The method further includes determining the distance between the person's eye and the camera;

[0043] - The method further includes determining the interpupillary distance (IPD) of the person;

[0044] - The method further includes determining the orientation of the system relative to the person's eye;

[0045] - The measurement is preferably performed in a dark environment.

[0046] The present invention further relates to a method for providing an ophthalmic lens suitable for a wearer's prescription, the method comprising:

[0047] - Determining the prescription of the wearer's eye according to the foregoing method of the present invention; and

[0048] - Manufacturing the ophthalmic lens according to the determined prescription suitable for the wearer's eye.

[0049] According to another aspect, the present invention further relates to a computer program product comprising one or more sequences of stored instructions that are accessible by a processor and, when executed by the processor, cause the processor to perform the steps of the method for determining the prescription of a wearer's eye according to the present invention, more specifically, at least perform the following steps:

[0050] - Measuring the photorefraction of the eye at the first wavelength based on at least one picture of the eye recorded when the eye is irradiated with the first light emitted by the or each first light source;

[0051] - Measuring the photorefraction of the eye at the second wavelength based on at least one picture of the eye recorded when the eye is irradiated with the second light emitted by the second light source;

[0052] - Determining the prescription of the eye based on the photorefraction measured at the first wavelength and the photorefraction measured at the second wavelength.

[0053] The present invention also relates to a computer-readable storage medium having a program recorded thereon; wherein the program causes the computer to at least execute the method of the present invention.

[0054] The present invention also relates to a computer-readable medium carrying one or more sequences of instructions of the computer program product according to the present invention.

[0055] Unless otherwise specifically stated, it will be apparent from the following discussion that throughout the specification, discussions using terms such as "computing", "operation", etc. refer to actions and / or processes of a computer or computing system or similar electronic computing device that manipulate and / or transform data represented as physical (such as electronic) quantities within the registers and / or memories of the computing system into other data similarly represented as physical quantities within the memories, registers or other such information storage, transmission or display devices of the computing system.

[0056] Embodiments of the present invention may include a device for performing the operations herein. This device may be specially constructed for the desired purpose, or it may comprise a general-purpose computer or a digital signal processor ("DSP") selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer-readable storage medium, such as but not limited to any type of disk, including floppy disks, optical disks, CD-ROMs, magneto-optical disks, read-only memory (ROM), random access memory (RAM), electronically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic or optical cards, or any other type of medium suitable for storing electronic instructions and capable of being coupled to a computer system bus.

[0057] The processes and displays presented herein are not inherently related to any particular computer or other device. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized devices to perform the desired method.

[0058] The desired structure of various such systems will become apparent from the following description. Additionally, embodiments of the present invention are described without reference to any specific programming language. It will be appreciated that various programming languages may be used to implement the teachings of the present invention described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Embodiments of the present invention will now be described, by way of example only and with reference to the following drawings, in which:

[0060] - Figure 1 and Figure 2 is a perspective view of a system for determining the prescription of a person's eye according to the present invention;

[0061] - Figure 3 is a schematic diagram of a system suitable for determining the prescription of a person's eye according to a first embodiment of the present invention;

[0062] - Figure 4Illustration of a flowchart of a method for determining the prescription of a person's eye according to a first embodiment of the present invention;

[0063] - Figure 5 Illustration of a light source arrangement that can be used in a system for determining the prescription of an eye according to a second embodiment of the present invention;

[0064] - Figure 6 Illustration of a flowchart of a method for determining the prescription of a person's eye according to a second embodiment of the present invention;

[0065] - Figure 7 Illustration of a light source arrangement that can be used in a system for determining the prescription of an eye according to a third embodiment of the present invention;

[0066] - Figure 8 Illustration of a flowchart of a method for determining the prescription of a person's eye according to the third and fourth embodiments of the present invention; and

[0067] - Figure 9 Illustration of a light source arrangement that can be used in a system for determining the prescription of an eye according to a fourth embodiment of the present invention.

[0068] The elements in the drawings are illustrated only for simplicity and clarity and are not necessarily drawn to scale. For example, the dimensions of some elements in the drawings may be enlarged relative to other elements to help increase the understanding of the embodiments of the present invention. Detailed Description

[0069] The present invention relates to a method and a system for determining the prescription of a person's eye. Such a system is adapted and configured to implement the method for determining the prescription of a person's eye according to the present invention.

[0070] The prescription includes a set of optical characteristics determined by an ophthalmologist to correct the visual defects of a wearer, such as spherical power, cylindrical power, cylindrical axis, add power, and prescription prism.

[0071] Reference Figure 1 and Figure 2 , the system 10 according to the present invention is configured to communicate with a mobile device 12, in particular a smart phone. For example, the system 10 can communicate with the mobile device 12 in a wired or wireless manner or via the mobile device.

[0072] Preferably, the system is adapted to be fastened to the housing 14 of the mobile device 12, as Figure 1 and Figure 2 shown.

[0073] Figure 1 Shows the system 10 before it is fastened to the mobile device 12, andFigure 2 Shows the system after being fastened to the housing 14 of the mobile device 12.

[0074] In the following description, a smartphone is used as an example of such a mobile system. However, other mobile systems such as tablet personal computers or laptop computers can also be used.

[0075] Figure 3 A schematic diagram of a system 10 according to a first embodiment of the present invention is shown.

[0076] The system 10 includes a first light source 16 and a second light source 18. The first light source 16 and the second light source 18 are each adapted to irradiate a person's eye 2 with a first light 20 having a first optical wavelength and a second light 22 having a second optical wavelength, respectively. The second optical wavelength is different from the first optical wavelength.

[0077] Each of the first light source 16 and the second light source 18 can be configured to irradiate the eye directly or indirectly, for example, by being reflected by a mirror.

[0078] Preferably, the first light source is configured to emit infrared or near-infrared light so as not to change the pupil diameter during refractive measurement and thus prescription determination.

[0079] The second light source is preferably configured to emit visible light, for example, configured to emit green light around 550 nm. The visible light allows overcoming the disadvantages of prescription determination offset caused by using infrared light and the fact that the eye is very colored.

[0080] The second light source can be configured to emit red light that allows better retinal reflection.

[0081] Preferably, the light source is a light-emitting diode (LED). Preferably, the spectral bandwidth of the light source is very narrow, with a half-width of less than 50 nm.

[0082] Infrared LEDs with different spectral bands can also be considered to more accurately infer the prescription function model of the wavelength.

[0083] The system 10 further includes a camera 30 that is adapted to and configured to record at least one picture of a person's eye when the eye is irradiated with the first light or the second light.

[0084] A very narrow band-pass filter (i.e., with a half-width of less than 50 nm) can be applied to the camera so that when one of the wavelengths used is infrared, the camera only collects the infrared signal from the light source and its reflection on the retina, rather than the infrared signal from the sun or any incandescent lamp (for example, this infrared signal may affect the measurement result). Alternatively, the filter can also be a high-pass filter that allows no light to pass through except infrared light.

[0085] Preferably, the camera is embedded in the system 10 such that it can acquire pictures of a person's eyes in "selfie" mode or "standard photo" mode. The person can also take pictures of himself / herself in front of a plane mirror to perform his / her refractive measurement.

[0086] In addition, the system can also be tilted relative to the smartphone to meet the best ergonomic requirements.

[0087] Although in the preferred embodiment the camera is embedded in the system, the camera can be embedded in the smartphone, and the system is configured to communicate with the camera of the smartphone and is arranged such that when the eyes are irradiated with the first light or the second light, the camera of the smartphone can record pictures of the person's eyes.

[0088] Preferably, the second light source 18 is arranged at the same distance from the camera 30 as the first light source 16. The distance between the first light source or the second light source and the camera is preferably included between 0 and 30 mm.

[0089] The system further includes a calculation module 40, which includes a memory 42 and a processor 44. The processor is arranged to execute program instructions stored in the memory to implement a method for determining the prescription of a person's eyes according to the present invention.

[0090] Reference Figure 4 , the method includes:

[0091] - A first irradiation step S10,

[0092] - A first acquisition step S12

[0093] - A first photorefractive measurement step S14,

[0094] - A second irradiation step S20,

[0095] - A second acquisition step S22

[0096] - A second photorefractive measurement step S24,

[0097] - A prescription determination step S30.

[0098] During the first irradiation step S10, the person's eyes 2 are irradiated with the first light 20 having the first optical wavelength by the first light source 16.

[0099] Then, in S12, when the eyes 2 are irradiated with the first light 20, at least one first picture is acquired and recorded by the camera 30.

[0100] During the first photorefractive measurement step S14, the photorefraction of the eyes at the first wavelength is measured based on the (multiple) first pictures of the eyes recorded when the eyes are irradiated with the first light.

[0101] Photorefraction is an objective optometry method based on retinal photoreflection pictures. The refractive state can be calculated from the amplitude and position of this photoreflection using mathematical formulas or based on physical simulation models.

[0102] During the second irradiation step S20, the same eye 2 of a person is irradiated with a second light 22 having a second optical wavelength by a second light source 18.

[0103] Then, in S22, when the eye 2 is irradiated with the second light, at least one second picture is acquired and recorded by the camera 30.

[0104] During the second photorefraction measurement step S24, the photorefraction of the eye at the second wavelength is measured based on at least one second picture of the eye recorded when the eye is irradiated with the second light.

[0105] The second irradiation step should follow the first irradiation step closely, i.e., fast enough so that the eye pupil does not have time to constrict, to ensure a larger pupil size and avoid eye movement, blinking... Preferably, the measurement of the photorefraction of the eye at the second wavelength and the measurement of the photorefraction of the eye at the first wavelength are temporally separated by less than 0.5 s.

[0106] Then, in S30, the prescription of the eye is determined based on the photorefraction measured at the first wavelength and the photorefraction measured at the second wavelength.

[0107] More specifically, the diopter measured at the first wavelength and the diopter measured at the second wavelength can be compared and used to correct the first refractive measurement of the person's eye to determine the prescription of the person's eye.

[0108] Alternatively, the above individualized first refractive measurement and second refractive measurement can be mixed with an average correction table via a weighting function.

[0109] Preferably, the calculation module 40 is embedded in the smartphone 12. Alternatively, the calculation module 40 can be embedded in the system 10. Thus, the refractive measurement and prescription determination are performed via local analysis within the application, which applies pattern recognition algorithms to measure the size, position, and shape of the crescent, as well as the pupil diameter.

[0110] However, the calculation module 40 can be at least partially embedded in the mobile device 10 and / or the smartphone 12 and / or a remote unit (not shown).

[0111] In fact, the system 10 for determining a prescription can be further configured to communicate with a remote unit that includes a memory and a processor arranged to execute program instructions stored in the memory to store data related to at least the retinoscopy of the eye measured at the first wavelength and the retinoscopy of the eye measured at the second wavelength. Then, when the processor of the remote unit executes the corresponding program instructions stored in the memory of the remote unit, the determination of the eye prescription S30 can also be performed by the remote unit. In this case, the measured data is stored in the cloud, and identification and / or machine learning algorithms are used to analyze the results. In this case, a personal account can be created to track the evolution of the personal prescription with relevant graphics in the application.

[0112] The measurement is preferably carried out in a low-light environment to expand the pupil of the person to the maximum value, thereby reducing the width of the dark area.

[0113] In addition, the method can advantageously include a step for determining the distance between the person's eye and the camera. The distance measurement can be carried out by a simple 1-pixel time-of-flight (ToF) sensor or a ToF pixel array. However, a sensor that measures the amount of light reflected from the object being measured can also be used to determine the distance between the person's eye and the camera.

[0114] The distance can also be determined by the stereoscopic combination of the images captured by the camera of the smartphone and the images captured by the camera of the system. The distance can also be determined by the front or rear camera of the smartphone or the camera of the system and the associated image processing. For example, considering that the iris size of each person is approximately the same, the distance can be estimated. In another embodiment, the person using the system can wear some goggles of known size as a reference for estimating the distance between the eye and one of the cameras.

[0115] The method can further advantageously include a step for determining the interpupillary distance (IPD) of the person.

[0116] Advantageously, the method can further include a step for determining the orientation of the system relative to the person's eye in order to accurately determine the axis position of astigmatism. This orientation can be determined using the inertial motion unit (IMU) of the smartphone. Another way to evaluate this orientation is to evaluate the angle between the line separating the centers of the two eyes and the axis between the normal axis defined in the camera aperture of the system and the line separating the centers of the two eyes.

[0117] In addition, although in the presently described embodiment, the first photorefractive measurement step S14 is implemented before the second illumination step S20 and the second acquisition step S22, it should be understood that in an alternative embodiment of the present invention, the photorefractive measurement at the first wavelength may be implemented after all acquisitions at the first and second wavelengths are performed, in order to reduce the measurement time, since the photorefractive measurement step may take some time.

[0118] Figure 5 A second and preferred embodiment of the system according to the present invention is shown. This second embodiment differs from the previous embodiment in that the system includes a set of three first light sources 16A, 16B, and 16C, each light source being adapted to irradiate the human eye 2 with first light 20 having a first optical wavelength, respectively.

[0119] In this preferred embodiment, the system still only has one second light source 18.

[0120] The first light sources 16A, 16B, and 16C of the set are arranged equidistant from the camera 30 and are arranged to define three regularly angularly spaced directions, also referred to as meridians X A , X B and X C .

[0121] In addition, the second light source 18 is preferably arranged at the same distance from the camera 30 as the first light sources 16.

[0122] According to this second embodiment, the processor 44 is arranged to execute program instructions stored in the memory 42 to implement a second embodiment of the method according to the present invention for determining the prescription of a human eye.

[0123] See Figure 6 , the second embodiment of this method differs from the previous embodiment in that, for each of the first light sources 16A, 16B, and 16C of the set, the step S10 of irradiating the eye with the first light and the step S12 of acquiring and recording a corresponding first picture by the camera when the eye is irradiated with the first light are continuously repeated. The step of irradiating the eye with the first light source 16K is denoted as S10-K, and the step of acquiring and recording a corresponding first picture by the camera when the eye is irradiated with the first light source 16K is denoted as S12-K, where K is A, B, or C. Thus, the photorefraction of the eye at the first wavelength is measured before measuring the photorefraction of the eye at the second wavelength by irradiating the eye with the second light emitted by the second light source.

[0124] In other words, all measurements at the first wavelength are completed before a single measurement at the second wavelength.

[0125] According to the three directions X A , XB and X C For the measurements on X and for several distances between the set of first light sources and the camera, this second embodiment allows an accurate measurement of the eye refraction at infrared wavelengths and thus an accurate determination of the prescription of a person's eye. In fact, based on the measurements in three directions X A 、X B and X C the complete refraction, i.e., the diopter, the astigmatism and the axis, can be determined.

[0126] Figure 7 FIG. 3 shows a third embodiment of a system according to the present invention. This third embodiment differs from the previous embodiments in that the system includes n sets of three first light sources 16-Ai, 16-Bi and 16-Ci, where i is an integer between 1 and n. Each first light source is adapted to irradiate the person's eye 2 with a first light 20 having a first optical wavelength, respectively.

[0127] For each set i, the first light sources 16-Ai, 16-Bi and 16-Ci are arranged equidistant from the camera 30. Of course, the distances between the camera and a set of first light sources are different. These sets of first light sources are arranged on three meridians X A 、X B and X C respectively.

[0128] In this third embodiment, the system includes a plurality of second light sources adapted to emit light having a second optical wavelength, preferably three second light sources 18-A, 18-B, 18-C, as Figure 7 shown.

[0129] The three second light sources 18-A, 18-B, 18-C are equidistant from the camera and preferably regularly angularly spaced apart.

[0130] Compared with a set of three first light sources, the three second light sources 18-A, 18-B, 18-C are arranged at the same distance from the camera.

[0131] Each second light source 18-A, 18-B, 18-C is associated with a different meridian X A 、X B and X C respectively.

[0132] According to this third embodiment, all the measurements at the first wavelength are completed before a single measurement at the second wavelength. Thus, the processor 44 is arranged to execute program instructions stored in the memory to measure the photorefraction of the eye at the first wavelength by irradiating the eye with the first light continuously emitted by at least one set of each first light source, and then to measure the photorefraction of the eye at the second wavelength by irradiating the eye with the second light emitted by the second light source.

[0133] Advantageously, the processor may further be arranged to execute program instructions stored in the memory to implement step S40 of selecting one of these second light sources to illuminate the eye and then performing a photorefractive measurement of the eye at a second wavelength based on the photorefractive measurement of the eye at the first wavelength. In fact, a first estimate of the eye refraction can be obtained from the first photorefractive measurement step S14, thus allowing to define a strategy for selecting the visible light source to be turned on. For example, the second light source associated with the meridian with the most accurate infrared measurement can be selected to have the best visible light measurement accuracy.

[0134] According to the measurements in three directions X A , X B and X C and for several distances between this set of first light sources and the camera, this third embodiment allows to accurately measure the eye refraction at the infrared wavelength and thus accurately determine the prescription of a person's eye. In fact, according to the measurements in three directions X A , X B and X C , the complete refraction, i.e., the diopter, astigmatism and axis, can be determined.

[0135] In addition, using several sets of first light sources at different distances from the camera allows for a more accurate first refraction measurement and thus allows for a more accurate prescription determination, especially when this prescription is important.

[0136] Figure 9 A fourth embodiment of a system according to the invention compatible with the previous embodiments is shown. This fourth embodiment differs from the third embodiment in that the system includes a plurality of second light sources 18-i, which are adapted to emit light having a second optical wavelength and are arranged in another way to be detailed hereinafter.

[0137] Figure 9 Three second light sources 18-1, 18-2, 18-3 are shown in

[0138] Each second light source 18-i is associated with a set i of three first light sources 16-Ai, 16-Bi, 16-Ci and is thus arranged at the same distance from the camera 30 as all three first light sources of this set i. Thus, each second light source 18-1, 18-2, 18-3 is arranged at a different distance from the camera 30.

[0139] According to this fourth embodiment, with reference to Figure 8In the flowchart, the processor can advantageously be further arranged to execute program instructions stored in the memory to implement step S40 of selecting one of these second light sources to illuminate the eye and then performing a photorefractive measurement of the eye at a second wavelength based on the photorefractive measurement of the eye at the first wavelength. In fact, a first estimate of the eye refraction can be obtained from the first photorefractive measurement step S14, thus allowing the definition of a strategy for selecting the visible light source to be turned on. For example, based on the first refraction measurement, the second light source arranged at a certain distance from the camera providing the measurement of the eye refraction outside the dark area can be selected to have the best visible light measurement accuracy, and considering the inherent chromatic aberration of the eye between the first light and the second light, more specifically in the case of infrared light and visible light.

[0140] According to the measurements in three directions X A 、X B and X C and for several distances between this set of first light sources and the camera, this fourth embodiment allows the accurate measurement of the eye refraction at the infrared wavelength and thus the accurate determination of the prescription of a person's eye. In fact, according to the measurements in three directions X A 、X B and X C the complete refraction, i.e., the diopter, astigmatism and axis, can be determined.

[0141] Furthermore, using several sets of first and second light sources at different distances from the camera allows for a more precise refraction measurement and thus a more accurate prescription determination, especially when this prescription is important.

[0142] Another object of the present invention is a method for providing an ophthalmic lens adapted to the prescription of a wearer, the method comprising:

[0143] - determining the prescription of the wearer's eye according to the present invention and as described above; and

[0144] - manufacturing the ophthalmic lens according to the determined prescription adapted to the wearer's eye.

[0145] The present invention as disclosed above has the advantage of providing a non-invasive, easy-to-use and inexpensive tool for performing electronic refraction measurements, especially in developing countries.

[0146] In fact, combining the measurements at two wavelengths with more specifically an infrared light source (to obtain a larger pupil) and a visible light source allows for the accurate determination of the prescription of a person's eye.

[0147] Furthermore, the present invention can be easily performed on children and thus can provide a simple system for parents who want to monitor the prescription evolution of their children.

[0148] In addition, the present invention allows for the accurate measurement of the interpupillary distance of a person, which is a very important parameter for providing a suitable pair of glasses for the wearer.

[0149] The present invention has been described above by means of embodiments without limiting the general inventive concept.

[0150] Many further improvements and variations can be proposed by those skilled in the art who have referred to the foregoing illustrative embodiments. These embodiments are given by way of example only and are not intended to limit the scope of the present invention, which is determined only by the appended claims.

[0151] In fact, although in the disclosed embodiments, the acquisition corresponding to each light source is performed sequentially, some acquisitions can be performed simultaneously to reduce the measurement time.

[0152] Alternatively, the first light source can be an infrared light source, and the second light source can be configured to emit blue light around 550 nm. In this case, the weighted average of the refractions measured with the two wavelengths corresponds to the actual refraction and thus to a good prescription.

[0153] According to another embodiment, the system can include waveguides associated with some of the first and / or second light sources (e.g., the most central light sources) to virtually bring the light sources closer to the camera.

[0154] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that different features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope of the present invention.

Claims

1. A system (10) for determining the prescription of a person's eye (2), the system being configured to communicate with a mobile device (12), the system comprising: at least one first light source (16), the at least one first light source being adapted to irradiate the eye with a first light (20) having a first optical wavelength; at least one second light source (18), the at least one second light source being adapted to irradiate the eye with a second light (22) having a second optical wavelength different from the first optical wavelength; and a calculation module (40), the calculation module including a memory (42) and a processor (44), the processor being arranged to execute program instructions stored in the memory to: measure the photorefraction of the eye (2) at the first optical wavelength based on at least one picture of the eye recorded when irradiated with the first light (20); measure the photorefraction of the eye (2) at the second optical wavelength based on at least one picture of the eye recorded when irradiated with the second light (22); determine the prescription of the eye (2) based on the photorefraction measured at the first optical wavelength and the photorefraction measured at the second optical wavelength.

2. The system according to claim 1, wherein, the calculation module (40) is embedded in the mobile device (12).

3. The system according to claim 1, wherein, the system (10) for determining the prescription is further configured to communicate with a remote unit, the remote unit including a memory and a processor arranged to execute program instructions stored in the memory to store at least data related to the photorefraction of the eye measured at the first optical wavelength and the photorefraction of the eye measured at the second optical wavelength.

4. The system according to any one of claims 1 to 3, wherein, the system (10) is configured to be removably fastened to the housing (14) of the mobile device (12).

5. The system according to any one of claims 1 to 3, wherein, the first light source (16) is configured to emit infrared or near-infrared light, and the second light source (18) is configured to emit visible light.

6. The system according to any one of claims 1 to 3, wherein, the second light source (18) is arranged at the same distance from the camera (30) as the first light source (16), the camera being adapted and configured to record at least one picture of the person's eye (2) when the eye is irradiated with the first light (20) or the second light (22).

7. The system according to claim 1 or 2, wherein, the system (10) for determining the prescription of the eye includes at least one set of first light sources (16A, 16B, 16C), each set of first light sources consisting of three first light sources, each first light source being adapted to emit a first light at the first optical wavelength.

8. The system according to claim 7, wherein, The first light sources (16A, 16B, 16C) of each group are equidistant from the camera (30) and are arranged to be located in three regularly angularly spaced directions (X A , X B , X C ), and the camera is adapted and configured to record at least one picture of the person's eye (2) when the eye is illuminated by the first light (20) or the second light (22).

9. The system according to claim 1 or 2, wherein, The processor (44) is arranged to execute program instructions stored in the memory (42) to: Irradiate the eye (2) with first light (20) continuously emitted by the first light source (16) emitting at the first optical wavelength; Irradiate the eye (2) with second light (22) emitted by the second light source (18) emitting at the second optical wavelength; Record at least one picture of the person's eye by a camera (30), the camera being adapted and configured to record at least one picture of the person's eye when the eye is irradiated with the first light (20) or the second light (22).

10. The system according to claim 7, wherein, The system (10) includes multiple sets of first light sources (16-Ai, 16-Bi, 16-Ci), each set of first light sources consisting of three first light sources, the distances between the camera (30) and each set of first light sources being different, the camera (30) being adapted and configured to record at least one picture of the person's eye when the eye is irradiated by the first light (20) or the second light (22), the multiple sets of first light sources being arranged to be located in the same three regularly angularly spaced directions (X A , X B , X C ), and wherein the processor (44) is arranged to execute program instructions stored in the memory to measure the photorefraction of the eye at the first optical wavelength by irradiating the eye with first light continuously emitted by each first light source of at least one of the multi - groups, and then measure the photorefraction of the eye at the second optical wavelength by irradiating the eye with second light emitted by the second light source.

11. The system according to claim 8, wherein, The system (10) includes multiple sets of first light sources (16-Ai, 16-Bi, 16-Ci), each set of first light sources consisting of three first light sources, the distances between the camera (30) and each set of first light sources being different, and the multiple sets of first light sources being arranged to be located in the same three regularly angularly spaced directions (X A , X B , X C ), and wherein the processor (44) is arranged to execute program instructions stored in the memory to measure the photorefraction of the eye at the first optical wavelength by irradiating the eye with first light continuously emitted by each first light source of at least one of the multi - groups, and then measure the photorefraction of the eye at the second optical wavelength by irradiating the eye with second light emitted by the second light source.

12. The system according to claim 9, wherein, The system (10) includes multiple sets of first light sources (16-Ai, 16-Bi, 16-Ci), each set of first light sources consisting of three first light sources. The distances between the camera (30) and each set of first light sources are different. The multiple sets of first light sources are arranged to be located in the same three regularly angularly spaced directions (X A , X B , X C ), and wherein the processor (44) is arranged to execute program instructions stored in the memory to measure the photorefraction of the eye at the first optical wavelength by irradiating the eye with first light continuously emitted by each first light source of at least one of the multi - groups, and then measure the photorefraction of the eye at the second optical wavelength by irradiating the eye with second light emitted by the second light source.

13. A method for determining a prescription of a person's eye (2) by a system (10) for determining a prescription of a person's eye, the system being configured to communicate with a mobile device (12), the system comprising: At least one first light source (16), the at least one first light source being adapted to irradiate the eye with first light (20) having a first optical wavelength; At least one second light source (18), the at least one second light source being adapted to irradiate the eye with second light (22) having a second optical wavelength different from the first optical wavelength; and A calculation module (40), the calculation module including a memory (42) and a processor (44), the processor being arranged to execute program instructions stored in the memory to: Measure the photorefraction of the eye (2) at the first optical wavelength based on at least one picture of the eye recorded when the eye is irradiated with the first light (20); Performing photorefraction of the eye (2) at the second optical wavelength based on at least one picture of the eye recorded when the eye is irradiated with a second light (22); Determining a prescription for the eye (2) based on the photorefraction measured at the first optical wavelength and the photorefraction measured at the second optical wavelength; The method at least includes: Performing photorefraction of the eye at the first optical wavelength based on at least one picture of the eye recorded when the eye is irradiated with a first light continuously emitted by the first light source (16); Performing photorefraction of the eye at the second optical wavelength based on at least one picture of the eye recorded when the eye is irradiated with a second light emitted by the second light source (18); and Determining a prescription for the eye based on the photorefraction measured at the first optical wavelength and the photorefraction measured at the second optical wavelength.

14. The method according to claim 13, further comprising determining a distance between the person's eye (2) and the camera (30), the camera being adapted and configured to record at least one picture of the person's eye (2) when the eye is irradiated with the first light (20) or the second light (22).

15. A method for providing an ophthalmic lens suitable for a wearer's prescription, the method comprises: Determining a prescription for the wearer's eye based on the method according to any one of the preceding claims 13 or 14; and Manufacturing the ophthalmic lens according to the determined prescription suitable for the wearer's eye.

16. A computer program product, the computer program product comprising one or more sequences of stored instructions that can be accessed by a processor and, when executed by the processor, cause the processor to perform at least the following steps: Performing photorefraction of the eye at the first optical wavelength based on at least one picture of the eye recorded when the eye is irradiated with a first light having a first optical wavelength emitted by a first light source; Performing photorefraction of the eye at the second optical wavelength based on at least one picture of the eye recorded when the eye is irradiated with a second light having a second optical wavelength different from the first optical wavelength emitted by a second light source; Determining a prescription for the eye based on the photorefraction measured at the first optical wavelength and the photorefraction measured at the second optical wavelength.

17. A computer-readable medium carrying one or more sequences of instructions of the computer program product according to claim 16.

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