Method for determining refractive characteristics of a subject's eye and associated portable electronic device

Abstract

The method comprises the following steps: a) illuminating a pupil (30) of an eye (3) of a subject (2) by means of a light source of a portable electronic device (1), the light source (12A) being formed by an illuminated area displayed on a screen (11) of the portable electronic device; b) acquiring a photograph of the pupil of the subject's eye by means of an image capture device (10) of the portable electronic device, the photograph comprising an image of a reflection of the light source on the retina of the eye; and c) determining a refractive characteristic of the eye taking into account at least a geometrical feature, a positional feature or an intensity distribution of the image of the reflection. An associated portable electronic device is also described.

Description

Technical Field

[0001] The present invention relates to a method for determining refractive characteristics of an eye of a subject using a measuring device comprising a portable electronic device. Background Art

[0002] Many documents describe devices and methods for determining such refractive characteristics.

[0003] In particular, automated optometry methods for determining an objective value of a subject's refraction are known. These methods are complex and time-consuming. These methods generally involve the use of large and expensive equipment that requires qualified personnel to operate.

[0004] Therefore, access to these auto-optometry methods is limited, and a large portion of the world's population has not benefited from them. Furthermore, these methods are not suitable for direct online ordering of optical equipment and cannot be performed without visiting an eye care specialist. Summary of the invention

[0005] It is therefore an object of the present invention to provide a new method for determining the refractive characteristics of a subject's eye which method is simplified in that it does not require the use of specific materials or the intervention of qualified personnel.

[0006] According to the present invention, the above objects are achieved by providing a method for determining the refractive characteristics of an eye of a subject using a measuring device comprising a portable electronic device, the portable electronic device comprising:

[0007] - a light source adapted to illuminate the pupil of said eye of the subject; and

[0008] - image capture means adapted to acquire a photograph of said pupil illuminated by said light source,

[0009] The method comprises the following steps:

[0010] a) illuminating the pupil of the subject's eye with the light source;

[0011] b) obtaining a photograph of the pupil of the subject's eye, the photograph comprising an image of the reflection of the light source on the retina of the subject's eye;

[0012] c) determining the refractive characteristic of the eye of the subject taking into account at least one of the following characteristics of the image of the reflection of the light source:

[0013] - geometrical characteristics of said image of reflection of said light source,

[0014] - positional characteristics of said image of the reflection of said light source,

[0015] - intensity distribution within said image of reflections of said light source;

[0016] wherein the portable electronic device is held by the subject in front of his eyes,

[0017] - said step a) comprises displaying on the screen of said portable electronic device an illuminated area forming said light source, and

[0018] - In step b), said reflection of said light is collected by said image capturing device.

[0019] This method can be performed by the subject themselves and is performed using only a smartphone or tablet computer without the need for added optical components or the use of an augmented reality display. Therefore, this method can be accessed by a wide range of people, including some people who are excluded from access to existing methods.

[0020] Optionally, non-limiting features of the method for performing virtual testing are defined according to the invention by claims 2 to 14 .

[0021] The method may also include the following optional non-limiting features:

[0022] - the gaze direction of the subject and the viewing direction optically connecting the pupil of the subject's eye and the entrance pupil of the image capture device form an angle of less than 15 degrees, or less than 5 degrees, or less than 1 degree;

[0023] - in step b), the subject directs his or her gaze towards the entrance pupil of the image capture device or towards the light source or visual target;

[0024] - the method comprises the step of synchronizing image capture with display of the illuminated area;

[0025] - repeating steps a) and b) so as to capture said plurality of photographs, and in each of said repeated steps a) the relative position of said image capture device and said subject's eye is modified while said illuminated area remains centered at the same predetermined distance from the center of an entrance pupil of said image capture device;

[0026] - in each of said repeated steps a), the size of said illuminated area varies;

[0027] - in step c), determining the refractive characteristics of the eye of the subject taking into account the relative position of the light source and the pupil of the eye of the subject during the acquisition of each photograph;

[0028] - in step b), the subject wears a corrective ophthalmic lens in front of his eye and in step c), the refractive characteristics of the eye are determined taking into account the optical characteristics of this corrective ophthalmic lens;

[0029] - in a calibration step, when the electronic device is placed against the subject's head, data related to the position of the electronic device in space are acquired by the position determination module;

[0030] - said portable electronic device comprises a smartphone and / or an augmented reality display and / or a device having said image capture device, said image capture device having an effective optical axis passing through the display screen.

[0031] According to the present invention, the above object is also achieved by providing a portable electronic device as claimed in claim 15. The optional features of the above method may also be applied to this portable electronic device. DETAILED DESCRIPTION

[0032] The following description, with reference to the accompanying drawings given by way of non-limiting examples, will make it easy to understand the nature of the invention and how it can be implemented.

[0033] In the attached picture:

[0034] - Figure 1 is a schematic representation of the main steps of a method for determining the refractive characteristics of an eye of a subject according to the invention;

[0035] - Figure 2 is a schematic representation of a subject holding a Figure 1 A portable electronic device of the method;

[0036] - Figure 3 As seen from the position of the image capture device Figure 2 Schematic representation of a subject's eye;

[0037] - FIG. 4A to FIG. 4C yes Figure 2 A schematic front view of a portable electronic device showing an illuminated area displayed on a screen of the portable electronic device;

[0038] - Figure 5 yes Figure 2 A schematic front view of a portable electronic device showing various locations of an illuminated area displayed on a screen of the portable electronic device;

[0039] - Figure 6 is a schematic side view of a subject holding a portable electronic device according to another embodiment; and

[0040] - Figure 7yes Figure 6 Schematic front view of a portable electronic device.

[0041] Figure 1 The main steps of a method are shown which can be used to determine the refractive characteristics of a subject's eye, such as the spherical power of the refractive error of the eye, using a portable electronic device 1, such as a mobile phone or a tablet computer.

[0042] The portable electronic device 1; 1' comprises:

[0043] a light source suitable for illuminating the pupil 30 of the eye 3 of the subject 2, and

[0044] - Image capture means 10 adapted to acquire a photograph of said pupil 30 illuminated by said light source.

[0045] The method for determining the refractive characteristics of the eye 3 of a subject 2 comprises the following steps:

[0046] a) illuminating the pupil 30 of the eye 3 of the subject 2 by means of a light source of the portable electronic device 1; 1', the light sources 12A, 12B, 12C being formed by an illuminated area displayed on the screen 11 of the portable electronic device 1; 1' ( FIG. 4A to FIG. 4C );

[0047] b) obtaining a photograph of the pupil 30 of the subject's eye 3 by means of the image capture device 10 of the portable electronic device 1; 1', the photograph comprising an image of reflection 31 of the light sources 12A, 12B, 12C on the retina of the subject's eye 3 ( Figure 3 );as well as

[0048] c) determining the refractive characteristic of the eye 3 of the subject taking into account at least one of the following characteristics of the image of the reflection 31 of the light sources 12A, 12B, 12C:

[0049] - Geometric characteristics of the image of the reflection 31 of the light source, such as size s ,

[0050] - positional characteristics of the image of the reflection 31 of the light source, such as orientation,

[0051] - The light distribution within the image of the reflection 31 of the light source, such as the intensity profile of the image.

[0052] In the exemplary embodiment described here, in step c), the refractive characteristics of the eye 3 of the subject are determined more specifically by taking into account at least one of the following characteristics of the image of the reflection 31 of the light sources 12A, 12B, 12C:

[0053] - the size of the image of the reflection 31 of the light source s ,

[0054] - the orientation of said image of the reflection 31 of said light source,

[0055] - The intensity profile of said image of the reflection 31 of said light source.

[0056] In this method, the determination of the refractive characteristics of the subject's eye 3 is based on the eccentric photorefraction technique, which is a retinal retinoscopy technique, as described, for example, in the article "Eccentric Photorefraction: Optical Analysis and Empirical Measures" by WR Bobier and OJ Braddick (American Journal of Optometry and Physical Optics, 1985, Vol. 62, No. 9, pp. 614-620).

[0057] Refractive characteristics that can be determined using this technique include the spherical power of the refractive error of the eye being characterized, the cylindrical power of this refractive error, and the orientation of the axis of the corresponding cylinder.

[0058] According to this technique, the light sources 12A, 12B, 12C illuminating the pupil 30 of the eye 3 are laterally displaced relative to the entrance pupil E10 of the image capture device 10 (see, for example, Figure 4A In the embodiment described here, the light sources 12A, 12B, 12C have an emitting surface forming a small light spot.

[0059] When the subject's eye 3 has refractive error, in the photo of the eye 3 acquired by the image capture device 10, the image of the reflection 31 of the light sources 12A, 12B, 12C on the retina of the eye 3 only occupies a part of the image of the pupil 30 of the eye, and this part is in the shape of a crescent ( Figure 3 ). More precisely, this retinal reflection 31 is bounded by two curved arcs which intersect each other to form two tips of a crescent.

[0060] Therefore, the magnitude of the detected reflection 31 s Information about the value of the refractive error of eye 3 is provided.

[0061] Here, the size of the reflection 31 s Indicates that this reflection is in the direction x' parallel to the measurement axis xo o The width of the image capture device 10 is measured along the axis of the image capture device 10, the measurement axis passing through the center O of the entrance pupil E10 and through the point O1 at which the light source 12A, 12B, 12C is centered. In other words, the size sis the range of the reflection 31 along the direction x'o. s is the width of this reflection 31 in the plane of the pupil 30 of the eye, in real space.

[0062] In real space, the size of the reflection 31 s The size of this reflected image can be measured, for example, in a photograph of the eye 3 captured by the image capture device 10 s I The size of the image of the reflection 31 measured in the photograph of the eye 3 captured by the image capture device 10 is determined by s I It may be determined, for example, as the full width at half maximum of an intensity peak of an intensity profile of the image.

[0063] It is then known that the value of the refractive error of eye 3, which is equal to the spherical power of the refractive error of this eye 3, can be determined on the basis of:

[0064] - the above-mentioned size of the crescent reflection 31 of the light source 12A, 12B, 12C on the retina of the eye s ,

[0065] - The diameter of the pupil 30 r ,

[0066] - the distance d between the entrance pupil E10 of the image capture device 10 and the pupil 30 of the eye 3 of the subject 2 cam ,as well as

[0067] The eccentricity e between the light sources 12A, 12B, 12C and the entrance pupil E10 of the image capture device 10 .

[0068] This eccentricity e represents the lateral displacement between the light sources 12A, 12B, 12C and the entrance pupil E10 of the image capture device 10 .

[0069] More precisely, the eccentricity e is determined as the minimum distance between:

[0070] - entrance pupil E10 of the image capture device 10, and

[0071] - Light sources 12A, 12B, 12C.

[0072] Therefore, the eccentricity e is determined as the distance e1 between:

[0073] - the point of the entrance pupil E10 closest to the light sources 12A, 12B, 12C, and

[0074] - The point of the light source 12A, 12B, 12C closest to the entrance pupil E10.

[0075] The sign of the refractive error (negative for myopia and positive for hyperopia) can be determined based on the reflection 31 relative to the viewing direction z. o The viewing direction optically connects the pupil 30 of the eye 3 to the entrance pupil E10 of the image capture device.

[0076] When the reflection 31 and the light source are located in the observation direction z o In this case, for example, both the reflector 31 and the light sources 12A, 12B, 12C can be located below the viewing direction zo, or located in the viewing direction z. o On the other hand, when this reflection 31 is located in the viewing direction z o When the eye is on the side opposite to the light source, the refractive error is positive.

[0077] As for the astigmatism characteristics (including the cylinder power of the refractive error of the eye 3 and the orientation of the axis of the corresponding cylinder), they can be measured by measuring the corresponding multiple axes x o 、x P 、x Q Several photographs of the eye 3 of the subject 2 are taken to determine that these measurement axes have different respective orientations relative to the subject's face / eye ( Figure 5 As explained above, these measuring axes x o 、x P 、x Q Each of the bars identifies a direction that passes through the center O of the entrance pupil E10 of the image capture device 10 and through the point O1, P1, Q1 about which the light source 12A, 12B, 12C is centered during the associated photograph acquisition.

[0078] The size of the reflection 31 can therefore be determined for each of these orientations and therefore for the different meridians of the eye 3. s .

[0079] Furthermore, for each of these orientations, that is to say, for these measuring axes x o 、x P 、x Q The shape of the crescent image of the reflection 31 can be used to determine the shape of this reflection 31 relative to the relevant measurement axis x. o 、x P 、x Q This orientation corresponds here to the axis of the crescent being perpendicular to the relevant measuring axis x. o 、x P 、x Q The axis of the crescent is the axis passing through the two tips of the crescent.

[0080] Then, according to the measurement axis x o 、x P 、x Q The corresponding multiple orientations determine the magnitude of the reflection 31 s This set of values ​​of the angle of inclination and the angle of tilt determines the cylinder of the ametropia of the eye 3 and the orientation of the axis of the corresponding cylinder. This determination can be carried out, for example, as described in the article "Measurement of astigmatism by automated infrared photoretinoscopy" by Gekeler F., Schaeffel F., Howland HC. and Wattam-Bell J. (Optometry and Vision Science, July 1997, 74 (7), pp. 472-82).

[0081] The refractive characteristics of the subject's eye can also be determined based on the intensity profile of the reflection 31 of the light source on the retina of the subject's eye 3, rather than based on the size of the retinal reflection 31. s to be sure.

[0082] In this case, the illuminated area displayed on the screen 11 to form the light source preferably comprises a plurality of small illuminated points, rather than a plurality of small illuminated points as in Figure 4A The different points are displayed at different positions on the screen so as to have different eccentricities with respect to the entrance pupil of the image capture device. For example, the points can be positioned on the screen so as to form an array of points. This feature improves the linearity of the slope of the intensity profile of the retinal reflection 31.

[0083] This intensity profile of the retinal reflection 31 is a cross section of the intensity of said reflection 31 through the meridian of the pupil 31 (e.g., through a meridian of the pupil parallel to said measurement axis). In other words, this intensity profile is a collection of values ​​representing the variation of intensity (that is, representing the variation of the optical power within the reflection 31, or the variation of the optical power per area) as a function of the position on said meridian of the pupil.

[0084] For example, determination of the refractive characteristics of the subject's eye based on this intensity profile can be achieved according to the following article: "Slope-based eccentric photorefraction: theoretical analysis of different light source configurations and effects of ocular aberrations" by A. Roorda, M. Campbell and W. Bobier (Journal of the Optical Society of America, A, Vol. 14, No. 10, October 1997, pp. 2547-2556).

[0085] In the present method, the refractive characteristics of the subject's eye can also be determined based on the following two factors:

[0086] - the size / orientation of the retinal reflection 31, and

[0087] -Intensity profile of retinal reflection 31.

[0088] In this case, the values ​​of the refractive features determined from the size / orientation may, for example, be averaged with those derived from the intensity profile to obtain estimates of these refractive features with improved accuracy / reliability.

[0089] The eccentric photo-optometry technique, the principles of which have been reviewed above, is typically accomplished using specialized equipment that is expensive and designed to be operated almost exclusively by eye care specialists.

[0090] In contrast, the method for determining the refractive characteristics of the eye 3 of the subject 2 as defined above can be implemented by the subject 2 himself and performed using only a smartphone or tablet computer without the need for added optical components, or using an augmented reality display. Therefore, this method can be accessed by a wide range of people, including some people who are excluded from access to existing methods.

[0091] Furthermore, forming the light source by displaying an illuminated area on the screen of the portable electronic device provides great flexibility, so that the characteristics of the light source, such as its size, position and / or shape, can be easily changed during a series of measurements.

[0092] By displaying the illuminated area on this screen to form the light source, it is also possible to display instructions and / or feedback photos that help the subject to achieve a correct determination of ametropia in an area close to the gaze direction suitable for eccentric photo-optometry. Therefore, the subject can see these instructions and / or feedback photos without deviating his gaze direction from the direction suitable for eccentric photo-optometry.

[0093] In a first embodiment, the portable electronic device 1 configured to implement the above method is a standard general-purpose smart phone or tablet computer (in Figure 2 ), without requiring any additional components other than a dedicated computer program, the execution of which causes the steps of the method to be performed.

[0094] In a second embodiment, the portable electronic device configured to implement the above method is an augmented reality device (eg, Figure 6 and Figure 7 Schematically represented) or virtual reality device.

[0095] These two embodiments 1; 1' of the portable electronic device will be presented first.

[0096] Next, the main characteristics of the method implemented by this device will be described in detail.

[0097] Next, features that improve the accuracy of determining eye refractive errors, particularly when screen brightness or lighting capabilities are limited, will be described in the section on lighting condition management.

[0098] First embodiment of the portable electronic device

[0099] As described above, the portable electronic device 1 according to this first embodiment is a smartphone or a tablet computer (eg Figure 2 As indicated, it is a smart phone).

[0100] The portable electronic device is small, thin and light enough so that it can be hand-held, preferably with just one hand 5. The portable electronic device has the shape of a flat and thin plate.

[0101] A screen 11 of the portable electronic device 1 , for example a backlit LCD screen (“Liquid Crystal Display” screen) or an OLED screen (“Organic Light Emitting Diode” screen), occupies more than half of the front face 13 of the portable electronic device 1 .

[0102] The image capture device 10 is located on the same face 13 as the screen 11. The field of view of the image capture device and the light emitted by the screen 11 extend on the same side of the portable electronic device 1. The image capture device 10 is a small general-purpose digital camera that is optimized to take pictures of a subject's face, a document about the size of an A4 or B4 page, or a global scene including elements from about 0.3 meters to infinity. The camera does not protrude significantly, or even at all, from the front face 13 of the device. The entrance pupil E10 of the image capture device 10 is located near the entrance face of the lens of the image capture device 10 (e.g., as shown in FIG. 1 ). Figure 4A Schematically represented), and its diameter is close to the diameter of the incident surface.

[0103] Here, the portable electronic device 1 includes an optional communication module (not shown in the figure), which can exchange data between the portable electronic device 1 and a remote computer or server via a communication network (such as the Internet).

[0104] The portable electronic device 1 also includes a position determination module (not shown in the figure), which is suitable for transmitting data related to the position and / or orientation of the portable electronic device. This module includes an inertial unit, which includes an accelerometer (e.g., a three-axis accelerometer) and / or a gyroscope. This module may also include a magnetometer or a digital compass, which can determine the orientation of the portable electronic device relative to the direction of the local magnetic field at the location of the portable electronic device.

[0105] The portable electronic device 1 further comprises a control unit (not shown in the figure), which comprises at least a processor and a memory.

[0106] It is noteworthy that, apart from a special-purpose computer program (e.g., a computer application) sometimes referred to as a "applet" stored in the memory (the execution of which by the processor causes the steps of the above-described method to be performed), the portable electronic device 1 has no additional features or components compared to a standard general-purpose stand-alone smart phone or tablet computer that is primarily designed for communications (i.e., making phone calls, participating in video conferences, or accessing web pages).

[0107] In particular, the portable electronic device 1 does not comprise any additional, specific optical components to be placed in front of the image capturing device 10 or in front of the screen 11 .

[0108] Thus, when step a) of the method is performed by this portable electronic device 1, the light emitted by the light sources 12A, 12B, 12C illuminating the pupil 30 of the eye 3, formed by displaying an illuminated area on the screen 11, reaches this eye 3 directly without interacting with any other optical component of the portable electronic device 1. More precisely, this light reaches the eye 3 of the subject 2 without interacting with any optical component, except for a corrective ophthalmic lens or a contact lens optionally worn by the subject 2.

[0109] Similarly, when step b) of the method is performed due to this portable electronic device 1, the reflection 31 of the above light on the retina of the subject 2 is collected directly by the image capture device 10 without interacting with any other optical component of the portable electronic device 1. Therefore, when step b) is performed by this portable electronic device 1, no optical components are optically located between the eye 3 of the subject 2 and the portable electronic device 1, except for the corrective ophthalmic lenses or contact lenses optionally worn by the subject 2.

[0110] Second embodiment of the portable electronic device

[0111] As described above, in this second embodiment, the portable electronic device is an augmented reality device or a virtual reality device. Figure 6 and Figure 7 As indicated, the portable electronic device 1 ′ is an augmented reality device, ie a device enabling the subject 2 to directly see his environment E and at the same time see information, photographs or light sources visually superimposed on this environment E, displayed by a screen.

[0112] The portable electronic device 1' comprises:

[0113] - here a screen similar to and even identical to the screen 11 of the first embodiment,

[0114] an image capture device which is similar or even identical here to the image capture device 10 of the first embodiment, and

[0115] A head-mounted structure 35 ′ configured to hold said screen 11 and image capture device 10 and to be worn on the head 4 of the subject 2 .

[0116] Since this screen and image-capturing device are the same as those of the first embodiment, they are labeled with the same reference numerals 10 and 11, respectively.

[0117] In this example, the portable electronic device 1' comprises a smartphone 20 the same or similar to that of the first embodiment or any device capable of providing images to a subject, the smartphone or device comprising a screen 11 and an image capture device 10 such as those described above.

[0118] The portable electronic device 1' comprises a first optical combiner 30' which is optically coupled to the image capture device 10 so as to displace and / or deviate its optical axis. The field of view comprising the combination of the image capture device 10 and the first optical combiner 30' is referred to as z F The first optical combiner 30' is configured so that the optical axis z F It extends to the front of the screen 11 and passes through the screen 11, while the optical axis of the naked image capture device 10 passes by the screen 11 without passing through it.

[0119] The first optical combiner 30' may include a semi-reflective mirror and / or an optical deflection system, such as a light guide. Figure 6 and Figure 7 In the examples shown, these include:

[0120] a half mirror 32' optically inserted between the eye 3 of the subject 2 and the screen 11, for example placed in front of the screen 11 in an inclined manner relative to the screen 11, and

[0121] - an optical deviation system 31 ′ which deviates the field of view of the image capture device 10 towards the semi-reflective mirror 32 ′ so that, after reflection on this semi-reflective mirror 32 ′, the above-defined displaced optical axis z F Through the screen 11. The optical deviation system 31' can be realized by a light guide or by a right angle prism with a 90 degree deviation.

[0122] The portable electronic device 1' further comprises a second optical combiner 34', which is configured to superimpose the virtual image of the screen 11 onto the environment E of the subject 2. The second optical combiner 34' may comprise a half-mirror, which is arranged to reflect the light emitted by the screen 11 towards the eye 3 of the subject 2. This half-mirror may be a bare transparent sheet, which may be optionally slightly curved to increase the optical distance between the screen 11 and the subject's eye 3, that is, from an optical point of view, the virtual image is projected in front of the subject's eye 3, away from the eye, for example 1 meter or 2 meters in front of its eye 3, or even at infinity.

[0123] The portable electronic device 1' according to this second embodiment requires slightly more components than the portable electronic device 1 of the first embodiment: in addition to the smartphone 20, it also requires a head-mounted structure 35' integrating the above-mentioned optical components 30', 34'. However, this head-mounted structure 35' is now a common, widely spread product, which is much cheaper than a dedicated professional reflectometer device.

[0124] Due to the first optical combiner 30', the portable electronic device according to this second embodiment is able to measure the ametropia using eccentric photo-optography for very small eccentricity values. F Through the screen 11, a very small lateral displacement can be obtained between this axis and the light source formed by displaying the illuminated area on the screen 11. Realizing this measurement for small eccentricity values ​​enables accurate measurement of small refractive error values.

[0125] Furthermore, in this second embodiment, the relative position of the subject's eye 3 relative to the light source displayed on the screen 11 and relative to the image capture device 10 is very stable and can therefore be accurately determined before or during the execution of the method for determining the refractive characteristics of the subject's eye.

[0126] The subject also spontaneously focuses his eyes 3 on elements that are far away from him, since he always sees his distant surroundings, since the screen 11 of the portable electronic device is only superimposed on its surroundings in a semi-transparent manner and therefore does not obstruct the subject's 2 field of vision.

[0127] Alternatively, the portable electronic device according to this second embodiment can be implemented as a virtual reality device. In this case, the subject does not see the environment directly, but sees a picture of the environment displayed on a screen of the device placed in front of his eyes, the environment usually with additional features. For example, the picture of the subject's environment is captured by a front camera, the field of view of which extends opposite to the screen.

[0128] The portable electronic device according to this second embodiment can be implemented by an image capture device that is not integrated into the electronic device including the screen, rather than by the above-mentioned smart phone. In addition, the screen and the image capture device can be respectively adapted to emit and capture infrared light, rather than visible light, so that during this refractive error measurement, the subject's eyes are not disturbed and their pupils remain wide open.

[0129] Detailed presentation of a method for determining the refractive characteristics of a subject's eye

[0130] During the performance of the method, the portable electronic device 1 ; 1 ′ is held by the subject 2 , either in his hand 5 , in both hands or on his head 4 .

[0131] When held in the subject's hand 5 or both hands, the portable electronic device 1 is held at approximately one arm's length from the subject's head 4 (held at a distance of between 0.2 meters and 1 meter).

[0132] In addition to the features related to the following (described in detail below):

[0133] - a position and / or distance calibration based on data delivered by a position determination module of the portable electronic device 1,

[0134] - modification of the position / orientation of the image capture device 10 relative to the subject's eye 3, and

[0135] - distance conversion,

[0136] The method can be implemented in the same way by the first embodiment of the portable electronic device 1 and by the second embodiment of the portable electronic device 1 ′.

[0137] The method is described below in the context of determining the refractive characteristics of the eye based on the size and orientation of the retinal reflection 31. However, as mentioned above, these refractive characteristics may also be determined based on one or several intensity profiles of the reflection.

[0138] Prior to steps a) and b), the method comprises a preliminary Calibration Steps ( Figure 1 ).

[0139] During this calibration step, the portable electronic device 1 determines the optical distance d between the pupil 30 to be illuminated and the entrance pupil E10 of the image capture device 10 .

[0140] In the case where the method is performed by the portable electronic device 1 according to the first embodiment, this optical distance d is the distance between the pupil 30 to be illuminated and the entrance pupil E10 ( Figure 2 ) cam , the difference being that a reflector is inserted in the optical path connecting the screen 11 with the eye 3 of the subject 2 .

[0141] In the case where the method is performed by the portable electronic device 1' according to the second embodiment, this optical distance d is the geometric distance between:

[0142] - the pupil of the eye 3, and

[0143] - An image capture device from the subject's perspective.

[0144] In other words, this optical distance d is the geometric distance d′ between the pupil of the eye 3 and the virtual image of the entrance pupil of the image capture device 10. cam , which virtual image is formed by optical components 30 ′, 34 ′ optically inserted between the eye 3 and the image capture device 10 .

[0145] The optical distance d between the pupil 30 to be illuminated and the entrance pupil of the image capture device 10 can be determined by scaling a photograph of the subject's face, eyes or eyes taken by the image capture device 10 when in the use position (i.e., for example, held at arm's length from the eye 3).

[0146] To this end, the subject may be motivated to hold a predetermined object (e.g., a credit card) close to his eyes by a message displayed on the screen 11 or an auditory message. Then, the above-mentioned photo is acquired by the image capture device 10. The predetermined object has a known size (e.g., a known width), and its value is stored in the memory of the portable electronic device.

[0147] From the size of this object measured in the acquired photograph and thus expressed as a number of pixels, the portable electronic device 1; 1 'determines the optical distance d between the pupil 30 and the entrance pupil E10 of the image capture device 10. To this end, the portable electronic device 1; 1 'can use a calibration curve or a lookup table relating the size of this object measured in the acquired photograph to said distance d, this calibration curve or lookup table being stored in a memory of the portable electronic device 1; 1 '.

[0148] Determining the optical distance d by scaling a photograph of the face, eyes or eyes of a subject acquired by the image capture device 10 may also be done in the following manner:

[0149] - in the photograph, identifying at least two salient points of the subject's face, and

[0150] - determining said distance d as a function of the distance (expressed as a number of pixels) between the two salient points at least in the captured image.

[0151] These salient points are points of the face that can be easily identified and accurately located by image analysis. One of these points may, for example, be located at the medial or lateral commissure or the center of the pupil in one eye of the subject.

[0152] The reference distance between the two identified salient points is stored in a memory of the portable electronic device, and the portable electronic device is configured to:

[0153] - comparing the distance between two identified salient points in the captured image with this reference distance, and

[0154] - Based on the result of this comparison the optical distance d is determined.

[0155] The above-mentioned photo scaling is also used to determine a conversion coefficient C which relates the size of an element of the subject's eye in the image captured by the image capture device 10 (expressed as a number of pixels) to the actual size of this element in real space (expressed, for example, in millimeters). This conversion coefficient C is used in step c) to determine the diameter of the pupil 30 of the eye 3 from the photograph or photographs of the eye 3 acquired in step b). r and the size of the retinal reflection 31 s .

[0156] Alternatively, in the case where the method is performed by the portable electronic device 1 according to the first embodiment, the optical distance d can be determined based on data related to the position of the portable electronic device 1 in space acquired by the position determination module of the portable electronic device 1, and the optical distance is then equal to the geometric distance d between the pupil 30 of the eye 3 and the entrance pupil E10 of the image capture device 10 cam .

[0157] To this end, the subject 2 may be motivated by a message displayed on the screen 11 or by an auditory message:

[0158] - place the portable electronic device 1 against their head 4 (e.g. against their forehead), and then

[0159] - Place the portable electronic device 1 in its position for carrying out the method (at approximately arm's length in front of the subject).

[0160] The acceleration signal delivered by the inertial unit is then integrated over time between these two situations, thus providing a distance d between the pupil 30 of the eye 3 and the image capture device 10 (in its position of use). cam data.

[0161] exist Figure 1 In the example represented, the calibration step So is performed before steps a) and b). However, alternatively, the calibration step So may be performed after steps a) and b) or during a series of several successive performances of steps a) and b).

[0162] The method further comprises before steps a) and b) Step S'o of giving the measurement instruction to the subject ( Figure 1 ).

[0163] During this step, the subject 2 is motivated to look at a certain point or in a certain direction by a message displayed on the screen 11 or by an auditory message.

[0164] More precisely, during the execution of the method, during this step S'o, the subject 2 is encouraged to direct his gaze towards:

[0165] - the entrance pupil E10 of the image capture device 10, or

[0166] - the light sources 12A, 12B, 12C, or

[0167] - Visual Target 6.

[0168] The visual target 6 is preferably located in a direction close to the direction optically connecting the subject's eye 3 with the light source or entrance pupil E10.

[0169] Due to this message, during the execution of the method, subject 2 directs his gaze towards one of these elements.

[0170] Therefore, due to the above message, during the execution of this method:

[0171] - Subject 2's gaze direction z G as well as

[0172] - A viewing direction z optically connecting the pupil 30 of the subject's eye 3 and the entrance pupil of the image capture device 10 o

[0173] Close to each other, forming an angle θ of less than 15 degrees, or preferably less than 5 degrees, or even more preferably less than 1 degree.

[0174] Make this gaze direction z G Close to the viewing direction z o is preferred, since this enables determination of a refractive error of the eye 3 which is close to the central vision refractive error of this eye 3 .

[0175] Observation direction z o is the direction presented just in front of the eye 3 by the average optical path connecting the pupil 30 of the eye 3 and the entrance pupil E10 of the image capture device 10. In the first embodiment of the portable electronic device 1 in which no additional optical components are inserted between the eye 3 and the image capture device 10, the viewing direction z o is the direction of a line passing through the center of the pupil 30 of the eye 3 and passing through the center O of the entrance pupil E10 of the image capture device 10 ( Figure 2 In the second embodiment of the portable electronic device 1 ′, the viewing direction z o This is the direction in which the image capture device 10 is optically and visually located when viewed from the eye 3 .

[0176] Preferably, the message requires the subject to look at the visual target 6, which is located near the viewing direction z o and in a direction away from the subject. Thus, during one or more acquisitions of a photograph of the subject's eye 3, this eye 3 is focused on said visual target 6 away from the subject. This makes the determination of the above-mentioned refractive characteristics of this eye 3, performed in step c), easier and more accurate.

[0177] During step S'o, the subject is also encouraged to reduce the ambient light intensity as much as possible, and / or go to a place with low ambient light intensity.

[0178] Now describe in detail Steps a) and b) .

[0179] As described above, in step a), the illuminated area is displayed on the screen 11 of the portable electronic device 1; 1' to form light sources 12A, 12B, 12C ( Figure 2 and 4A to Figure 4C ). During this step, the majority of the rest of the screen 11 (in particular around the illuminated area) is dark and emits no light, or at least emits light of negligible intensity compared to the light emitted by said illuminated area.

[0180] The light source preferably illuminates the pupil of the eye by flashes (i.e. by brief light pulses) rather than continuously. In fact, photo-optometry is more accurate than dilation of the pupil 30 of the eye 3, and by brief or intermittent illumination of this pupil, contraction / closure of the pupil can be avoided, or at least smaller than with continuous illumination. The duration of this flash (defined, for example, as the full-time width at half maximum of this light pulse) is preferably less than 0.1 seconds, or even less than 0.03 seconds. If the emission of this flash is repeated periodically with a given period, the ratio of this flash duration to said period is preferably less than ten percent (10%).

[0181] In order to prevent contraction / closure of the illuminated pupil 30, the screen 11 is also controlled so that the illuminated areas displayed on the screen 11 emit a limited amount of blue light. In fact, blue light is known to cause pupil contraction / closure.

[0182] For example, equal to

[0183] - the intensity of blue light emitted by the illuminated area (ie, the intensity of light emitted by the illuminated area in the wavelength range between 400 nanometers and 520 nanometers) divided by

[0184] - The total intensity of the light emitted by this lit area

[0185] The ratio is maintained below ten percent (10%).

[0186] For example, when the screen 11 is an LCD screen having red, green and blue pixels, the blue pixels are switched off during steps a) and b).

[0187] The operation of the image capture device 10 and the screen 11 are synchronized so that the photograph or photographs acquired in step b) are acquired at the same time that the pupil 30 of the eye is illuminated by the illuminated area displayed on the screen 11 .

[0188] Specifically, when the pupil 30 is illuminated by the above-mentioned flash, the image capture device 10 is controlled so that the lapse time (ie, integration time) of taking a photograph of the eye 3 covers the lapse time of emitting the flash.

[0189] In an exemplary embodiment of the method described here, in step a), the illuminated area provides a time-varying illumination which varies periodically over time with a given modulation frequency F. For example, the emission of the light flash described above is repeated with this modulation frequency F.

[0190] In step b), a plurality of photographs of the pupil 30 of the eye 3 of the subject 2 are then acquired in synchronization with the time-varying illumination.

[0191] This feature enables time / frequency filtering of the sequence of images of the retinal reflection 31 thus acquired in order to recover the components of said sequence having said modulation frequency.

[0192] The modulation frequency F is preferably different from the power supply frequency. Due to the above-mentioned time / frequency filtering, noise components varying at the power supply frequency, which is typically equal to 50 Hz, 60 Hz or an integer multiple of one of these base frequencies, can thus be removed from the image sequence. As an example, the modulation frequency F can be between 5 Hz and 30 Hz, which results in a good suppression of noise components at the power supply frequency.

[0193] The set of steps including step a) and step b) may be performed only once. However, in the exemplary embodiment of the method described herein, Figure 1 As indicated, this set of steps is performed several times in succession so as to obtain multiple photographs of the pupil 30 of the eye 3 of the subject 2, including an image of the retinal reflection 31, for corresponding multiple postures of the head 4 of the subject 2 relative to the light sources 12A, 12B, 12C, that is, for corresponding multiple positions and / or orientations of the light source relative to the head 4 of the subject 2.

[0194] Here, more specifically, the group of steps including step a) and step b) is performed several times in succession, so that ( Figure 5 ):

[0195] - obtaining a plurality of photographs of the eye for respective plurality of values ​​of the light source eccentricity, and

[0196] - for respective multiple measurement axes x having different respective orientations relative to the face / eyes of the subject 2 o 、x P 、x Q , obtain multiple photos of the eye 3 so that the astigmatism characteristics of the eye 3 can be determined.

[0197] In addition, for various sizes of the illuminated areas of the light sources 12A, 12B, 12C (such as FIG. 4A to FIG. 4C This set of steps is also performed several times in succession.

[0198] During a first set of successive executions of the set of steps comprising steps a) and b), the position of the illuminated area 12A displayed on the screen 11 varies from one execution to another. During this plurality of executions of step a), the illuminated area 12A is thus successively centered on a corresponding plurality of different positions O1, O2, O3, ... on the screen 11, such as Figure 5 These positions are defined relative to the screen 11 of the portable electronic device 1; 1'.

[0199] The illuminated area 12A is thus successively centered at a plurality of different predetermined offset distances d from the center O of the entrance pupil E10 of the image capture device 10. o,1 d o,2 d o,3 ……place.

[0200] The eccentricity e between the light source 12A and the entrance pupil E10 of the image capture device 10 thus varies from one execution of step a) to another.

[0201] Carrying out such a collection of measurements for a plurality of values ​​of eccentricity leads to an increased accuracy of the refractive characteristic finally determined in step c).

[0202] The illuminated area 12A is successively centered at various positions O1, O2, O3, ... along the first measuring axis x. o Positioned, the first measurement axis is fixed relative to the portable electronic device 1; 1' and passes through the centre O of the entrance pupil E10 of the image capture device.

[0203] During this first set of successive executions of steps a) and b), the portable electronic device 1; 1' remains fixed relative to the subject 2. Thus, the relative position and orientation of the image capture device 10 and the eye 3 of the subject 2 remain the same. The relative orientation of the screen 11 and the eye 3 of the subject 2 also remains the same. Thus, during this first set of repetitions of the illumination and acquisition steps a) and b), the first measurement axis x o The orientation of the eyes 3 and face 4 relative to the subject 2 remains the same.

[0204] Preferably, the method comprises a second set of illumination and acquisition steps a) and b) performed successively, identical to the first set described above, except that the illuminated area 12A is successively illuminated during this second set at positions P1, P2, P3, ..., centered along a axis different from the first measurement axis x O The second measuring axis x P position( Figure 5 ).

[0205] As explained above in the section on the principle of eccentric photo-optometry, it is possible to realize two or even three different measurement axes x O 、xP This measurement enables the astigmatism characteristics of the subject's eye 3 to be determined.

[0206] In order to make this determination as accurate as possible, the second measuring axis x P With the first measuring axis x O The angle between φ and φ is preferably between 60 and 120 degrees. The second axis also passes through the center O of the entrance pupil E10 of the image capture device 10 .

[0207] The method may also comprise a third set of illumination and acquisition steps a) and b) being performed successively, during which the position of the illuminated area 12A displayed on the screen 11 is along a line different from the first measurement axis x. O and the second measuring axis x P The third measuring axis x Q varies from one execution to another ( Figure 5 ). This third axis also passes through the center O of the entrance pupil E10 of the image capture device 10. The angle between this axis and the first axis is preferably between 30 and 60 degrees.

[0208] In an exemplary embodiment of the method described herein, portable electronic device 1; 1' remains fixed relative to eyes 3 and face 4 of subject 2 throughout the first, second and third set of executions of steps a) and b).

[0209] However, alternatively, and in the case where the portable electronic device 1 ( Figure 2 ) in the case of the method being implemented, the orientation of the electronic device 1 relative to the subject's head 4 can be varied from one set of acquisitions to another in order to modify the orientation of the measurement axis. In this case, the illuminated areas 12A are displayed at the same successive positions O1, O2, O3 on the screen, independently of the set under consideration, and the modification of the orientation of the measurement axis is performed by moving the portable electronic device 1 about an axis approximately parallel to the observation axis z o Obtained by rotating about the axis.

[0210] Alternatively, steps a) and b) can also be performed only for each measuring axis x O 、x P 、x Q In this case, the illuminated area 12A remains centered at the same predetermined offset distance d from the center O of the entrance pupil E10 of the image capture device 10 from one acquisition to another. o,1 Place.

[0211] In another variation, in the portable electronic device 1 ( Figure 2) in the case of implementing the method, steps a) and b) are repeated so as to capture a plurality of photographs of the eye 3, and in each of the repeated steps a) the relative position of the image capture device 10 and the subject's eye 3 is modified while the illuminated area 12A remains centered at the same predetermined distance d from the center O of the entrance pupil E10 of the image capture device 10. o,1 In this variant, more specifically, by moving the portable electronic device 1 about a substantially parallel axis of observation z o The electronic device 1 is rotated about its axis, modifying the orientation of the electronic device 1 relative to the subject's head 4 between each execution of step a). Thus, the orientation of the measurement axis changes from one execution of step a) to another, while the eccentricity remains the same. This enables the astigmatism characteristics of the eye 3 to be determined, as explained above in the section on the principle of eccentric photo-optometry.

[0212] The method may also comprise a fourth set of successive executions of the illumination and acquisition steps a) and b), during which the size (here the diameter of the illuminated area) varies from one execution to another. During this plurality of executions of step a), the illuminated areas 12A, 12B, 12C thus successively present a corresponding plurality of different diameters φ A ,φ B ,φ C ( FIG. 4A to FIG. 4C ). These various diameters may be comprised between 1 mm and 15 mm.

[0213] For a larger diameter of the illuminated area, the total amount of light available to illuminate the retina of the eye 3 is higher, but then the light source thus formed is less point-like. Thanks to this fourth set of acquisitions, photographs of the eye 3 acquired for various illumination conditions are available. This makes it possible to select a posteriori among these photographs the photographs acquired under the illumination conditions that best suit the subject 2 and the environment in which these acquisitions were carried out.

[0214] In any event, illuminating the retina of eye 3 by displaying a wide illuminated area (such as illuminated area 12C, for example, a 10 mm wide area) on screen 11 allows the retina to be illuminated at a higher intensity than a point light source, which is valuable when the subject's environment is not completely dark.

[0215] In an exemplary embodiment of the method described here, after some or all of step b) has been performed, the photo or one of the photos acquired in step b) is displayed on the screen 11 of the portable electronic device 1; 1' as a kind of feedback photo. The subject 2 can thus check whether step b) was successful, meaning that the photo acquired actually includes a clearly discernible image of the retinal reflection 31. A message can also be displayed on the screen, asking the subject 2 to confirm that step b) was successful, otherwise steps a) and b) are performed again.

[0216] Steps a') and b')

[0217] Here, the method comprises the following steps immediately following steps a) and b) ( Figure 1 ):

[0218] a') illuminating the pupil 30 of the eye 3 of the subject 2 by displaying an extended illuminated area on the screen 11 of the portable electronic device 1; 1', said extended illuminated area filling at least one tenth, preferably one third, of the total area of ​​said screen, and

[0219] b′) acquiring a photograph of said pupil 30 of the eye 3 of the subject 2 by means of the image capture device 10 of the portable electronic device 1 ; 1 ′.

[0220] This extended illuminated area is large enough so that in the image acquired in step b′), the reflection of the light emitted by the extended illuminated area on the retina of the eye 3 reaches the entire pupil 30 of the eye.

[0221] Therefore, in the photograph obtained in step b'), the image of the pupil 30 can be accurately identified and depicted, thereby accurately determining the diameter of the pupil 30. r .

[0222] Alternatively, steps a′) and b′) may be omitted, and then in step c) the diameter of the pupil 30 is determined by processing the photograph or photographs acquired in step b).

[0223] Step c)

[0224] Recall that in the exemplary embodiment described here, during the execution of steps a) and b), the illuminated area spot provides a time-varying illumination with said modulation frequency F and in step a) a sequence of multiple images including the retinal reflection 31 is captured.

[0225] Step c) then comprises a step of filtering the image of said sequence in order to extract the component of this sequence that varies at the modulation frequency F.

[0226] For example, such filtering can be achieved by synchronous demodulation. This can also be achieved by selecting among the images the images acquired when the flash illuminating the subject's eye 3 is on, and discarding the other images, subtracting from the images the images acquired when the flash is off to obtain a corrected image, and then calculating a filtered image by averaging these corrected images together (e.g., by calculating their sum).

[0227] Alternatively, such time and / or frequency filtering may be applied to quantities determined from the image sequence (e.g., retinal reflection size s) rather than being applied directly to the acquired image sequence itself.

[0228] In any case, for each of the aforementioned executions of steps a) and b), the size of the retinal reflection 31 is determined by image analysis from the photographs acquired in step b) or from the components of said image sequence extracted by filtering. s For example, by measuring the size of the image of this reflection 31 in the photograph and expressing it as the number of pixels s I Multiply by the conversion factor C determined in the calibration step So to obtain the magnitude s .

[0229] Due to the repetition of steps a) and b) for different values ​​of eccentricity e, and for several measuring axes x with different orientations o 、x P 、x Q , in step c) the magnitude of the retinal reflection 31 is determined s and a set of several corresponding values ​​of the tilt angle.

[0230] The refractive characteristics of the eye 3 are then determined according to the following, which refractive characteristics here include the spherical power and the cylindrical power of the refractive error of the eye 3 and the orientation of the axis of the corresponding cylinder:

[0231] - Size of Retinal Reflection 31 s And this set of values ​​of the tilt angle,

[0232] - the corresponding value of the eccentricity e of the light source, and the measurement axis x o 、x P 、x Q relative to the corresponding orientation of the eye 3 of the subject 2,

[0233] the optical distance d between the pupil 30 of the eye 3 and the entrance pupil E10 of the image capture device 10 , here determined during the calibration step So, and

[0234] - the diameter of the pupil 30 determined from the photograph of the eye 3 taken in step b') r The value of .

[0235] Determination of these refractive characteristics is performed according to eccentric photo-optography, the principles of which have been reviewed above.

[0236] It should be noted that in the case where the method is executed by the portable electronic device 1 according to the first embodiment, the eccentricity e is determined as the minimum distance e1 between the entrance pupil E10 of the image capture device 10 and the light sources 12A, 12B, 12C as described above.

[0237] In the case of the method being performed by a portable electronic device 1' according to the second embodiment, the eccentricity e is determined very similarly by taking into account a virtual image of the portable electronic device 1' projected by the additional optics 30', 34' in front of the subject 2. This virtual image comprises an image of the entrance pupil of the image capture device 10 and an image of the light source. In this case, the eccentricity e is determined as the minimum distance e1' between the image of the entrance pupil of the image capture device 10 and the image of the light source.

[0238] The measurement axis x may be determined based on the orientation of the portable electronic device 1 ; 1 ′ relative to the head 4 or the eye 3 of the subject 2 . o 、x P 、x Q This final orientation relative to the orientation of the eye 3 of the subject 2 is determined by numerical analysis of one of the captured photographs.

[0239] Alternatively, the measuring axis x may be determined based on the orientation of the portable electronic device 1 relative to the vertical direction. o 、x P 、x Q The orientation of the portable electronic device relative to the vertical direction relative to the orientation of the eye 3 of the subject 2 is determined based on the data acquired in step b) by the inertial unit of the portable electronic device 1 when the corresponding photo or photos are acquired.

[0240] Considering the size of the retinal reflection 31 s A set of several values ​​of , each corresponding to a different value of the eccentricity e, improves the accuracy of the refractive characteristics thus determined, compared to the case where the eccentricity remains the same for all acquired photographs. s These refractive characteristics are determined using this set of values ​​of and the corresponding values ​​of the eccentricity e as input data, for example, by a curve fitting process.

[0241] If in step b) the photograph or photographs are taken while the subject 2 is wearing a corrective ophthalmic lens in front of or in contact with his eye 3, then the refractive characteristic or characteristics of this lens are taken into account when determining the refractive characteristics of his eye 3. For example, if a contact lens is present on the subject's eye 3, the spherical power of this lens is determined according to the size of the corneal reflection 31 as explained above and below. s The determined spherical powers are added.

[0242] If in step S' o, the subject 2 is asked to look at the image capture device 10 or at the light sources 12A, 12B, 12C, then it is considered that during the acquisition of the photograph, the subject's eye 3 is focused on the image capture device 10 or on the light sources 12A, 12B, 12C, respectively. In the process of determining the refractive characteristics, the portable electronic device 1; 1' then considers that during the acquisition of the photograph of this eye 3, the subject's eye 3 is focused on an object located at a limited distance (more specifically, at the optical distance d), that is, adjusted on this object. For this purpose, a suitable correction is applied to the size of the reflection 31 from the retina s The refractive characteristics of the eye 3 are derived. For example, if the optical distance d is equal to 1 meter, and if according to the size of the retinal reflection s The determined spherical power is equal to -2 diopters, so the value of the spherical power finally determined and transmitted by the portable electronic device 1; 1' is equal to -3 diopters.

[0243] If, at step S'o, the subject 2 is asked to look at a visual target 6 located several meters in front of him, the portable electronic device 1; 1' can determine the refractive characteristics taking into account that during the acquisition of the photograph, the subject's eye 3 was focused on an object located at infinity. In this case, the above correction can be omitted.

[0244] The method may further comprise the step of transmitting, by means of the communication module of the portable electronic device 1; 1', the refractive characteristics of the eye 3 of the subject 2 determined in step c) to a remote data server.

[0245] The method may also include a step of proposing to the subject 2 to order an optical device from a remote online supplier, the characteristics of which are automatically (i.e., without requiring an action from the subject 2) preselected based on the refractive characteristics determined in step c). These characteristics may include the spherical power and / or cylindrical power of one or more corrective ophthalmic lenses of the optical device. During this step, the optical device is ordered via the communication module of the portable electronic device 1; 1'.

[0246] Lighting Condition Management

[0247] Illuminating the pupil 30 of the eye 3 by means of an illuminated area displayed on the screen 11 of the portable electronic device 1; 1' provides several advantages and great flexibility, as explained above.

[0248] However, depending on the particular portable electronic device under consideration, the brightness of the light source formed by the illuminated area may be quite small compared to the brightness of the light source of a conventional retinoscope.It is however preferred that this method be performed in a dark or very dimly lit environment E.

[0249] Thus, in the embodiment described here, the method comprises a set of steps that enable checking whether the lighting conditions in the environment E are sufficient to determine the refractive characteristics of the eye 3 of the subject 2, in particular whether the ambient light intensity is sufficiently small. More specifically, the method here comprises the following steps:

[0250] -Measure the ambient light intensity I A and / or the intensity I of the reflection 31 of the light sources 12A, 12B, 12C on the retina of the subject's eye 3 R ,

[0251] - Determine a lighting condition parameter which takes into account the measured ambient light intensity I A and / or the measured intensity I of the reflection R ,

[0252] - comparing said parameter with a predetermined threshold, and

[0253] -Depending on the result of this comparison, determine:

[0254] - the determination of a plurality of refractive characteristics or a refractive characteristic of the eye 3 of the subject is feasible and / or reliable, or vice versa,

[0255] - the determination of these refractive characteristics or this refractive characteristic is not feasible or reliable, and the ambient light intensity I A Should be lowered.

[0256] The ambient light intensity I may be directly measured by a dedicated sensor (such as a photodiode or a camera) other than the image capture device 10. A .

[0257] The ambient light intensity can also be measured indirectly by processing one or more of the photos acquired in step b) or b'). In this case, the ambient light intensity I A Determined to be equal to or representative of an average brightness level of pixels of the photograph or of pixels of a given area of ​​the photograph.

[0258] Here, the intensity I of the reflection 31 is measured indirectly by processing one or several of the photographs obtained in step b). R For example, this intensity represents the average brightness level of the pixels of the image of the reflection 31 .

[0259] The lighting condition parameters subsequently determined represent the feasibility of determining the refractive characteristics of the subject's eye 3 under the lighting conditions in the subject's environment E.

[0260] The lighting condition parameter can be determined as representing the ambient light intensity I A Divide by the intensity of the reflection I RFor example, the lighting condition parameter can be equal to this ratio I A / I R , which is a signal-to-noise ratio,

[0261] Alternatively, the lighting condition parameter may be determined as representing the ambient light intensity I alone. A , or represents the intensity of the reflection I R The reciprocal of 1 / I R .

[0262] When the lighting condition parameter is found to be less than a predetermined threshold, the portable electronic device determines that determination of the plurality of refractive characteristics or one refractive characteristic of the subject's eye 3 is feasible and / or reliable.

[0263] This predetermined threshold may be equal to the value of said lighting condition parameter in the event that the intensity of ambient light incident on the subject's face is equal to a threshold of 1000 cd / m2, or preferably equal to 300 cd / m2 or even more preferably equal to 50 cd / m2.

[0264] Otherwise, it is not feasible or reliable for the portable electronic device to determine the multiple refractive characteristics or one refractive characteristic of the eye 3, and the ambient light intensity I A In this case, a message may be displayed on the screen 11, or emitted as an auditory message, asking the subject to reduce the ambient light intensity.

[0265] It should be noted that, as described above, in the method according to the invention, the refractive characteristics of the eye 3 of the subject 2 can also be determined based on one or more intensity profiles of the retinal reflection 31. In this case, steps So, So', a), b), a'), b') and c) can be performed in a similar manner to that described above, but with slight modifications compared to the case of determination based on the size of the reflection 31. However, in this case, the method does not include a fourth set of successive executions of the above steps a) and b), during which the size of the light source varies.

[0266] The method for determining one or more refractive characteristics of eye 3 of subject 2 that has been presented above can be applied to the determination of one refractive characteristic or multiple refractive characteristics of each of the two eyes of subject 2 .

[0267] In other embodiments of the method, in which the method is implemented by means of the first embodiment of the portable electronic device 1, the screen 11 and the image capture device 10 of this device 1 may be pointed at a mirror. In this case, the subject looks at the portable electronic device 1 through this mirror. The optical distance between the subject's eye 3 and the point it is looking at is thus increased. As a result, the subject's eye 3 is focused on a point that is optically farther than if the subject 2 were looking directly at the portable electronic device without the mirror, which improves the accuracy of the determination of the refractive characteristic or characteristics of this eye 3.

Claims

1. A method for determining refractive characteristics of an eye (3) of a subject (2) using a portable electronic device (1; 1'), the portable electronic device (1; 1') comprising: - a light source (12A, 12B, 12C) suitable for illuminating the pupil (30) of the eye (3) of the subject; as well as - an image capture device (10) adapted to acquire a photograph of said pupil (30) illuminated by said light source (12A, 12B, 12C), The method comprises the following steps: a) illuminating the pupil (30) of the eye (3) of the subject (2) by means of the light source (12A, 12B, 12C); b) acquiring a plurality of photographs of the pupil (30) of the subject's eye (3), the photographs comprising images of reflections (31) of the light source (12A, 12B, 12C) on the retina of the subject's eye (3); c) determining the refractive characteristic of the eye (3) of the subject taking into account at least one of the following characteristics of the image of the reflection (31) of the light source: - geometrical characteristics of the image of the reflection (31) of the light source, - a position characteristic of the image of the reflection (31) of the light source, - intensity distribution within the image of the reflection (31) of the light source; The portable electronic device (1; 1') is held by the subject (2) in front of his eyes (3). - said step a) comprises displaying on the screen (11) of said portable electronic device (1; 1') an illuminated area forming said light source (12A, 12B, 12C), and - in step b), the reflection (31) of the light source is collected by the image capture device (10), The method further comprises modifying the position (O1, O2, O3, P1, P2, P3) and / or orientation and / or size (φ) of the light source (12A, 12B, 12C) between the acquisition of two different photos of the plurality of photos. A , ϕ B , ϕ C ) steps, wherein, in step a), the illuminated area is provided with time-varying illumination at a temporal frequency different from the power supply frequency, in step b), a sequence of a plurality of images comprising the reflections is captured, and in step c), a step of filtering the images of the sequence to recover a component of the sequence having the temporal frequency is performed.

2. The method according to claim 1, wherein: When acquiring each of the photographs, the posture of the head (4) of the subject (2) relative to the light source (12A, 12B, 12C) is different, and in step c), the refractive characteristics are determined by at least taking into account the geometric characteristics and / or position characteristics and / or intensity distribution of each of the images of the reflection (31) of the light source (12A, 12B, 12C) on each of the acquired photographs.

3. The method according to claim 1 or 2, wherein: The position (O1, O2, O3, P1, P2, P3) and / or orientation and / or size (φ) of the illuminated area displayed on the screen (11) is modified between two acquisitions of the photographs by modifying the position and / or size of the illuminated area displayed on the screen (11) and / or by modifying the relative position and / or orientation of the portable electronic device (1) and the head (4) of the subject (2). A , ϕ B , ϕ C ).

4. The method according to claim 2, wherein: Repeating steps a) and b) to capture the plurality of photos, and - in each of the repeated steps a), the illuminated area is centered at a different predetermined distance (d ) from the center (O) of the entrance pupil (E10) of the image capture device (10) o,1 , d o,2 , d o,3 ), the relative positions of the image capture device (10) and the subject's eye (3) remain the same, - in each of said repeated steps b), the photograph of the pupil (30) of the subject's eye (3) comprises a pupil (30) centered at said different predetermined distances (d o,1 , d o,2 , d o,3 ) when an image of the reflection (31) of the illuminated area at ) is obtained.

5. The method of claim 1, further comprising determining an optical distance (d 10 ) between an entrance pupil (E10) of the image capture device (10) and a pupil (30) of the subject's eye by scaling a photograph of the subject's eye (3) or head (4) acquired by the image capture device (10). cam ), and wherein, In step c), taking into account the optical distance (d cam ) to determine the refractive characteristics.

6. The method according to claim 5, wherein: During step b), the photograph of the subject's eyes (3) or head (4) is zoomed by identifying the image of two salient points of the subject's head (4) on the photograph or by identifying the image of a predetermined object held close to the subject's head.

7. The method according to claim 1, further comprising the steps of: - acquiring data about the position of the electronic device (1; 1') in space by means of a position determination module embedded in the electronic device (1; 1'), and - determining the relative position of the electronic device (1; 1') and the subject's head (4) taking into account this data.

8. The method according to claim 1, wherein: In step a), the light source (12A, 12B, 12C) illuminates the pupil (30) of the eye with a flash, and the image capture device (10) is synchronized to capture images simultaneously when the eye (3) is illuminated by this flash.

9. The method according to claim 1, wherein: In step a), the illuminated area emits a limited amount of blue light.

10. The method according to claim 1, further comprising the steps of: - measuring the intensity of ambient light and / or the intensity of the reflection (31) of the light emitted by the light source (12A, 12B, 12C) on the retina of the eye (3) of the subject, - determining a lighting condition parameter taking into account said measured ambient light intensity and / or said measured intensity of the reflection (31), and - comparing said parameter with a predetermined threshold value.

11. The method according to claim 1, wherein: - in step a), the light emitted by the light source (12A, 12B, 12C) directly illuminates the pupil (30) of the subject's eye (3) without interacting with any other optical components of the portable electronic device (1); and wherein, - In step b), the reflection (31) of the light source (12A, 12B, 12C) on the retina of the eye (3) is collected directly by the image capture device (10) without interacting with any other optical components of the portable electronic device (1).

12. A portable electronic device (1; 1'), comprising: - a light source (12A, 12B, 12C) suitable for illuminating the pupil (30) of the eye (3) of the subject (2); - an image capture device (10) adapted to acquire a photograph of said pupil (30) illuminated by said light source (12A, 12B, 12C); and - a control unit programmed to perform the following steps: a) illuminating the pupil (30) of the eye (3) of the subject (2) by means of the light source (12A, 12B, 12C); b) obtaining a photograph of the pupil (30) of the eye (3) of the subject (2), the photograph comprising an image of the reflection (31) of the light source (12A, 12B, 12C) on the retina of the eye (3) of the subject; c) determining a refractive characteristic of the eye (3) of the subject taking into account at least one of the following characteristics of the image of the reflection (31) of the light source: - geometrical characteristics of the image of the reflection (31) of the light source, - a position characteristic of the image of the reflection (31) of the light source, - intensity distribution within the image of the reflection (31) of the light source; The control unit is programmed so that the portable electronic device (1; 1') is held by the subject (2) himself in front of his eyes (3): - said step a) comprises displaying on the screen (11) of said portable electronic device (1; 1') an illuminated area forming said light source (12A, 12B, 12C), and - in step b), the reflection (31) of the light source is collected by the image capture device (10), wherein, in step a), the illuminated area is provided with time-varying illumination at a temporal frequency different from the power supply frequency, in step b), a sequence of a plurality of images comprising the reflections is captured, and in step c), a step of filtering the images of the sequence to recover a component of the sequence having the temporal frequency is performed.

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