Method for determining at least one geometrical parameter of a subject in a natural posture to determine a vision correction device

Abstract

The present invention relates to such a method, wherein the following steps are performed: a) placing the subject in a natural posture, in which at least one of the subject's gaze directions (GDR, GDL) points to a visual target (20), b) placing an image capture device (12) between the subject's head (50) and the visual target, c) adjusting the relative posture of the image capture device and the subject's head so that the pupil (P) of the image capture device is positioned close to the gaze direction (GDR, GDL) of at least one of the subject's eyes (OR, OL), d) capturing an image of the subject's head, and e) deriving the at least one geometric morphological parameter from the image.

Description

Technical Field

[0001] The invention relates to a method for determining at least one geometrical morphological parameter of a subject in a natural posture to determine a vision correction device. Background Art

[0002] Manufacturing an ophthalmic lens adapted to an individual and a frame in order to provide the individual with an appropriate ophthalmic fit requires fitting data that determines the lens fit to the selected frame.

[0003] In order to obtain these fitting data, the geometric parameters of the subject need to be determined.

[0004] Many documents describe devices and methods for determining such parameters. These parameters are, for example, the interpupillary distance of the subject or the fitting height, which is defined as the vertical distance between the pupil of the subject's eye and the bottom edge of the frame or lens worn by the subject under the conditions of use.

[0005] To be accurate, measuring subject geometry parameters such as fit height requires the subject to be in a natural posture.

[0006] However, it is always difficult to ensure that the subject remains in a natural posture during the capture of images that will allow these parameters to be determined.

[0007] Therefore, the reproducibility of the known methods is not always satisfactory.

[0008] Furthermore, known methods often require the use of specialized instrumentation that is not readily available to the general public.

[0009] Finally, known methods generally require the intervention of an eye care professional. For example, an eye care professional may manually measure the fitting height with a ruler.

[0010] For these reasons, known methods are not able to accurately determine the geometrical morphological parameters of a subject in a natural posture.

[0011] Furthermore, these methods do not allow the subjects to determine the parameters themselves. Summary of the invention

[0012] It is therefore an object of the present invention to provide a simple method for determining at least one geometrical morphological parameter of a subject in a reliable natural posture.

[0013] According to the present invention, the above object is achieved by providing a method for determining at least one geometrical parameter of a subject in a natural posture to determine a vision correction device, wherein the following steps are performed:

[0014] a) placing the subject in a natural posture, in which at least one of the subject's sight directions is directed toward a visual target,

[0015] b) placing an image capture device between the subject's head and the visual target,

[0016] c) adjusting the relative posture of the image capture device and the subject's head so that the pupil of the image capture device is positioned close to the line of sight direction of at least one of the subject's eyes,

[0017] d) capturing an image of the subject's head,

[0018] e) deriving said at least one geometrical parameter from the image.

[0019] By the position adjustment of step c), the subject's eyes remain focused on the visual target. Therefore, the subject's eyes do not focus on the pupil of the camera. Therefore, it is easier for the subject to maintain a posture corresponding to far vision, intermediate vision or near vision, and the subject's eye line of sight is directed straight forward to the visual target. Therefore, by placing the image capture device in front of the subject, the posture adopted by the subject in step a) does not change. The visual target can correspond to a long-range, medium-range or near-range visual task.

[0020] The instructions given to the subjects are simple and easy to follow, which makes the method more reproducible.

[0021] Another object of the present invention is to provide a method that a subject can perform by himself. The subject can then perform the method by himself using his own electronic device. In this way, the subject can determine the geometric parameters by himself at home or at any other location far away from the office of an eye care professional.

[0022] Alternatively, the method according to the invention may also be implemented with dedicated tools and the optional assistance of an eye care professional.

[0023] Advantages and non-limiting features of the present invention are:

[0024] - in steps c) and d), the sight direction of at least one of the subject's eyes is directed toward the visual target;

[0025] - in step c), the relative posture of the image capture device and the subject's head is adjusted by moving the image capture device without moving the subject's head, in step d), the gaze direction of the two eyes of the subject is directed to the pupil of the image capture device, and in step e), the distance between the image capture device and the subject's eyes is taken into account for determining the parameters;

[0026] - In step b), the image capturing means belongs to a personal electronic portable device of the subject;

[0027] - in step b), the subject presses the image capture device against the glass of the window, and in step c), the subject moves the image capture device against the glass of the window;

[0028] - the steps a) to c) are performed by the subject himself: in step a), the subject is in the natural posture by himself, and in steps b) and c), the image capture device is held and moved by the subject's hands;

[0029] - the image capture device comprises: an inertial motion unit adapted to determine the angular position of the image capture device in space; and a communication device adapted to send information about the angular position of the device in space to the subject; and in step c), the image capture device provides the subject with information about the angular position of the device compared to a target angular position;

[0030] - in step d), the capturing of the image is triggered by the subject, or automatically by the image capturing device when the image capturing device detects the subject's head;

[0031] - the image capture device is attached to a pole and is vertically movable on this pole;

[0032] - in step e), at least one of the following parameters is determined: interpupillary distance, half the interpupillary distance, fitting height;

[0033] - in step e), also determining the dominant eye of the subject;

[0034] - the image capture device is positioned such that during capturing the image of the subject's head, an optical axis of the image capture device is close to or parallel to the direction of sight of the subject;

[0035] - placing a reference element for scaling the image close to the subject's head and, in step d), capturing an image of the reference element together with an image of the subject's head; and

[0036] -In step d), the subject is not wearing a real frame, and the image capture device captures a three-dimensional image of the subject's head, and in step e), a virtual frame is virtually fitted on the three-dimensional image of the subject's head, and a two-dimensional image of the subject's head wearing the virtual frame is derived, and the fitting height parameter is determined based on this two-dimensional image.

[0037] Preferably, in step c), the inclination of the image capture device is adjusted so that the subject's head is within the field of view of the image capture device.

[0038] In an embodiment, in step d), the subject wears the selected frames.

[0039] In another embodiment, in step e), parallax is taken into account for determining said parameters.

[0040] In an embodiment, in step c), the image capture device is moved directly or indirectly by the subject or another person.

[0041] The present invention relates to a system for determining at least one geometrical morphological parameter of a subject in a natural posture for determining a vision correction device, the system comprising:

[0042] - a visual target, the visual target being suitable for being placed in front of the subject so that the subject is in a natural posture when at least one direction of the subject's sight is directed toward the visual target,

[0043] - an image capture device adapted to be placed between the subject's head and the visual target and adapted to capture an image of the subject's head,

[0044] - adjustment means for adjusting the position and / or orientation of the image capture device so that a pupil of the image capture device is positioned close to the line of sight direction of at least one of the eyes of the subject,

[0045] - computing means programmed to derive said at least one geometrical morphological parameter from said image of said subject's head captured with said image capture means. DETAILED DESCRIPTION

[0046] The following description, enriched by the accompanying drawings, which are considered as non-limiting examples, will facilitate the understanding of the invention and see how it is implemented.

[0047] On the attached picture:

[0048] - Figure 1 is a block diagram of steps according to an embodiment of the method of the present invention,

[0049] - Figure 2 is a schematic side view of a first possible relative position of the subject, the electronic device and the target during step d),

[0050] - Figure 3 is a schematic side view of a second possible relative position of the subject, the electronic device and the target during step d),

[0051] - Figure 4 is a schematic diagram of a first possible relative position of the subject, the electronic device and the target during step d), viewed from above.

[0052] In the following, the expression "natural posture" is defined as a posture when the position of the head is not subject to physical constraints such as resting a part of the head on a surface.

[0053] According to the invention, a method for determining at least one geometrical parameter of a subject in a natural posture for determining a vision correction device comprises the following steps:

[0054] a) placing the subject in a natural posture, in which at least one of the subject's gaze directions is directed toward a visual target 20 ( Figure 1 100),

[0055] b) Place the image capture device 10 in front of the subject's head 50 ( Figure 1 200),

[0056] c) adjusting the relative posture of the image capture device 10 and the subject's head 50 so that the pupil P of the image capture device 10 is positioned close to the line of sight direction GDL, GDR of at least one of the subject's eyes OL, OR ( Figure 1 300),

[0057] d) Capturing an image of the subject's head 50 ( Figure 1 400),

[0058] e) deriving at least one geometric parameter from the image ( Figure 1 500).

[0059] In a first embodiment of the method according to the invention, the image capturing means 12 belongs to a portable electronic device 10 which the subject holds with his own hands.

[0060] The portable electronic device 10 is, for example, a smartphone or a digital tablet. For example, the portable electronic device is a personal device of a subject. The portable electronic device comprises a body 11 having a screen and an image capture device 12 .

[0061] Instructions for executing the method may be provided to the subject via a portable electronic device. For example, when the subject runs an application dedicated to implementing the method according to the present invention, the instructions may be displayed on the screen of this device.

[0062] In this case, the front camera of the smartphone is advantageously used, which is placed next to the screen so that the subject can read the instructions and capture the image without turning the smartphone over.

[0063] Alternatively, the portable electronic device may be a portable electronic device equipped with a support that allows the portable electronic device to be placed in front of the subject's head. The support is, for example, a stand that is adapted to be movable and height-adjustable.

[0064] In a second embodiment (not shown in the figures), an image capture device is attached to the pole and can be moved vertically. For example, the image capture device is a camera or a smartphone.

[0065] In this case, instructions for performing the method may be provided to the subject via a screen placed on the pole or given verbally to the subject by an operator who assists the subject in performing the method.

[0066] Step a)

[0067] In step a), if Figure 1 As shown in box 100 in FIG. 1 , the subject is placed in a natural posture.

[0068] Preferably, the subject is in a natural position on his own.

[0069] To this end, the subject is instructed to gaze at a visual target 20 ( Figures 2 to 4 ).

[0070] At least one of the subject's sight lines GDL, GDR points to the visual target 20. Preferably, in step a), both of the subject's sight lines GDR, GDL point to the visual target 20.

[0071] The gaze direction GDR, GDL of each eye OR, OL of the subject is defined as the line connecting the pupil of the eye to the point at which the eye is focused ( Figure 4 ). This gaze direction also corresponds to the line passing through the center of eye rotation and the center of the pupil.

[0072] For example, if the geometrical parameters are to be determined under far vision conditions, the subject is instructed to fixate on a target 20 placed as far away as possible from him. This target 20 can be, for example, the horizon or a building or any target placed in front at a distance D1 greater than five meters. Figures 2 to 4This is shown in Figures 1 and 2. The Figures are schematic and not drawn to scale.

[0073] In this case, the natural posture adopted by the subject is preferably a posture in which he looks straight ahead at the horizon without any constraints. This natural posture is also called an upright posture and corresponds to the position in which the individual spends the least effort. The corresponding sight direction is the main sight direction.

[0074] In this natural position, the Frankfurt plane of the head is horizontal. The Frankfurt plane is defined as the plane passing through the lower edge of the eye socket (e.g., a point known as the left orbital point) and the upper edge of each ear canal or external auditory meatus (a point known as the midpoint of the upper edge of the external auditory meatus).

[0075] In a particularly advantageous embodiment, the subject can be in front of the window 30 by himself and look directly at a distant target in front through the window 30. Then, the subject's sight directions GDR, GDL are the main sight directions, and the subject's posture is an upright posture.

[0076] If the geometrical parameters are to be determined under visual conditions, the subject is instructed that he should fix his gaze on a target placed at a distance of about one meter (e.g. between 80 cm and 5 m). This target can be, for example, a wall or a picture on a computer screen. In this case, the situation is similar to Figures 2 to 4 The situation shown.

[0077] If the geometrical parameters are to be determined under near vision conditions, the subject is instructed to gaze at a target placed at a reading distance of, for example, 25 cm to 50 cm from him. This target may, for example, consist of text or a book placed in one of the subject's hands or on a support, for example, a table. In this case, the subject's line of sight may be inclined toward the target, with a non-zero angle relative to the horizontal. In this case, the natural posture is preferably a posture that the subject naturally takes when reading text (not shown in the figure).

[0078] Step b)

[0079] In step b), the image capture device 12 is placed in front of the subject's head 50 .

[0080] This image capture device 12 can capture two-dimensional or three-dimensional images. For example, the image capture device can be a front or rear camera of a smartphone or tablet, or a device for acquiring three-dimensional data (such as an image acquired using an infrared camera and infrared dots projected on the subject's head to identify the face of the user of the smartphone).

[0081] like Figures 2 to 4As shown, the image capture device 12 is placed between the subject's head 50 and the visual target 20. This is verified at any distance between the head 50 and the visual target 20.

[0082] Image capture device 20 may be placed in front of the subject's head by the subject or another person.

[0083] In a first embodiment, a portable electronic device including an image capture device is preferably placed by the subject in front of him / her.

[0084] In the particularly advantageous embodiment, the subject may place the portable electronic device in front of his head 50 by placing the portable electronic device against the window 30. The subject presses the portable electronic device 10 with the image capture device 12 against the glass of the window 30. For example, the subject holds the image capture device at arm's length.

[0085] The subject is then instructed to visually overlap pupil P of image capture device 12 with target 20 at step c).

[0086] In a second embodiment, the pole is placed in front of the subject by the subject by themselves being in front of the pole or by another person (eg, an operator assisting the subject) by leading the subject to the pole.

[0087] The subject may sit or stand in front of the image capture device 12 .

[0088] Step c)

[0089] In step c), the relative posture of image capture device 12 and subject's head 50 is adjusted so that pupil P of image capture device 12 is positioned close to the gaze direction GDL, GDR of at least one of the subject's eyes OL, OR.

[0090] The image capture device is positioned close to the line of sight of at least one of the subject's eyes. Preferably, the pupil P of the image capture device 12 is placed between the eyes OL, OR ( Figure 2 , Figure 4 ) in one of the sight directions GDR.

[0091] Otherwise, preferably, the image capture device is placed within a solid angle of about 1 to 10 degrees around the direction of sight of the at least one eye ( Figure 3 ).

[0092] Figure 3 An example is shown in which the pupil of the image capture device is offset relative to both gaze directions of the subject.

[0093] For example, it is offset towards the floor.

[0094] To perform such adjustments, the subject's head 50 and / or the image capture device 12 may be moved relative to each other.

[0095] The image capture device may be moved directly or indirectly by the subject or another person.

[0096] The subject may move his head and / or the image capture device 12 by himself.

[0097] In the first embodiment, the portable electronic device 10 is preferably moved directly by the subject holding it in the hand. The relative posture of the image capture device 12 and the subject's head 50 is adjusted by moving the image capture device 12 without moving the subject's head 50.

[0098] In the aforementioned particularly advantageous embodiment, the subject moves the portable electronic device 10 with the image capture device 12 against the glass of the window 30. More precisely, the subject moves the portable electronic device by translating the portable electronic device 10 against the window. The subject's head 50 remains in the same position.

[0099] For example, the subject is asked to move the image capture device, here a smartphone, until the pupil P of the image capture device 12 is placed directly in front of one of the subject's eyes OL or OR. The pupil P of the image capture device 12 is then visually overlapped with the target 20.

[0100] Advantageously, in such circumstances the subject's head will typically be completely within the field of view of the image capture device.

[0101] In a second embodiment, the subject can move his head 50 relative to the image capture device attached to the pole. When the image capture device is vertically movable, it can move up and / or down on the pole. The subject can move by himself and can move the image capture device by himself directly or indirectly, for example manually or using a remote control or by giving instructions to another person to move the image capture device. Alternatively, the movement of the subject and / or the image capture device can be guided by another person, such as an eye care professional.

[0102] Preferably, in step c), the inclination and / or position of the image capture device is adjusted so that the subject's head is within the field of view of the image capture device.

[0103] Preferably, the image capture device is positioned such that an optical axis of the image capture device is close to or parallel to the line of sight direction of the subject during capturing said image of the subject's head in step d).

[0104] In the case of the first embodiment, this may be achieved manually by the subject.

[0105] Preferably, the image capture device 12 is oriented so that its optical axis is parallel to the subject's line of sight axes GDL, GDR ( Figure 2 and Figure 3 ).

[0106] When the image capture device 12 is part of a smartphone or tablet, the optical axis of the image capture device is typically perpendicular to the screen of the device. Thus, this screen is placed perpendicular to the subject's line of sight. Figures 2 to 4 This situation is shown.

[0107] This can be easily achieved in the particularly advantageous embodiment described, in which the portable electronic device 10 with the image capture device 12 is pressed against the glass of the window 30. Then, the body 11 of the portable electronic device 10 supporting the screen is placed against the glass of the window 30, which means that the optical axis OA of the image capture device 12 is almost perpendicular to the glass of the window 30.

[0108] Therefore, the subject can easily look straight through the glass of the window 30 , thereby making at least one of his sight directions GDR, GDL perpendicular to the glass of the window 30 and parallel to the optical axis of the image capture device 12 .

[0109] exist Figure 2 In a case where an entrance pupil P of the image capture device 12 is aligned with a pupil PR of one eye OR (eg, the right eye OR) of the subject and a target 20, the optical axis of the image capture device overlaps with a line of sight direction GDR of the eye OR.

[0110] In this case, an observation line OBLR1 connecting the pupil PR of the subject's right eye OR and the pupil P of the image capture device 12 overlaps with the line of sight direction GDR of this right eye OR.

[0111] exist Figure 3 In a case where the entrance pupil P of the image capture device 12 is offset relative to the line of sight direction GDR of the subject, the optical axis OA of the image capture device 12 is parallel to the line of sight direction GDR of the subject.

[0112] In this case, the observation line OBLR2 connecting the pupil of the subject's right eye OR and the pupil P of the image capture device 12 forms a non-zero angle with the line of sight direction GDR of this right eye OR.

[0113] Alternatively, particularly in the case where the subject holds the image capture device without applying the image capture device to a window, the optical axis of the image capture device 12 can be tilted compared to the subject's line of sight axes GDR, GDL, as long as the subject's eyes OL, OD appear in the captured image, that is, as long as the subject's eyes OD, OL are in the field of view of the image capture device 12.

[0114] This situation is achieved through Figure 2 and 3 The portable electronic device 10A is shown in dotted line form.

[0115] In a second embodiment, the image capture device may or may not be able to be tilted relative to the column. If tilting is possible, such adjustment can be performed by the subject or by the operator. Otherwise, only position adjustment is achieved.

[0116] Alternatively, the pupil of the image capture device can also be placed between the eyes of the subject.Then, the pupil of the image capture device remains close to the two sight directions of the subject.

[0117] In an embodiment, the image capture device comprises: an inertial motion unit suitable for determining the angular position of the device in space; and a communication device suitable for sending information about the angular position of the device in space to the subject; and, in step c), the image capture device provides the subject with information about the angular position of the device compared to the target angular position.

[0118] For example, the image capture device provides the subject with information regarding the angular position of the optical axis of the image capture device compared to a horizontal axis or plane.

[0119] The information can be displayed on a portable electronic device or on a screen of a column. The information can also be given by an acoustic signal.

[0120] This is particularly the case when the image capture device belongs to a portable electronic device such as a smartphone or tablet. Smartphones and tablets may be equipped with gyroscope means capable of determining their orientation in space. A target angular position may be specified and a computing device of the portable electronic device may be programmed to implement the comparison. The inertial motion unit may also include an accelerometer and / or a magnetometer.

[0121] Preferably, in step c), the sight direction GDL of the subject's other eye OL is kept pointing toward the visual target 20, such as Figure 4 shown.

[0122] This means that the pupil P of the image capture device 12 is placed close to or in the line of sight direction GDR of one eye OR of the subject, while the other eye OL remains focused on the visual target 20 .

[0123] To this end, the size of the portable electronic device 10 is limited so that it does not block the field of view of the subject's other eye OL, OR. Therefore, the other eye can remain focused on the target 20 ( Figure 4 ).

[0124] Alternatively, the image capture device 12 may be offset upward or downward to allow the subject to keep both of his eyes OR, OL focused on the target 20 ( Figure 3 ). When the image capture device 12 deviates from the subject's line of sight GDR, GDL (e.g. Figure 3 In the case shown), the subject can keep both of his eyes OL, OR focused on the visual target 20 while capturing the image in step d).

[0125] Advantageously, adjusting the subject's eyes with respect to the image capture device is thus avoided.

[0126] This is particularly advantageous when determining geometrical parameters under far-sighted conditions.

[0127] Advantageously, the subject uses a small portable electronic device, with the pupil of the image capture device placed between the eyes of the subject, which does not block the subject's line of sight when the portable electronic device is placed between the eyes of the subject. This allows the subject to focus both of their eyes on the visual target when capturing the image in step d). This small portable electronic device is, for example, a smartphone and typically has a width of about 5 to 8 centimeters.

[0128] The entrance pupil of the image capture device can then be at the same level as the pupil of the eye.

[0129] In step d), the image may be captured in a natural posture without making adjustments with respect to the image capture device 12 .

[0130] In the case of intermediate and near vision measurements, accommodation is expected. However, the use of this method allows to maintain the accommodation of the eye with respect to a target placed at a predetermined distance. The measurement then corresponds exactly to the visual conditions set by the visual target.

[0131] In any case, the fact that one eye remains focused on the visual target causes the image of the eye to be captured under the visual conditions set by the visual target, without interference caused by placing an image capture device between the eye and the target.

[0132] Alternatively, during the image capture in step d), the gaze direction of both eyes of the subject may be directed towards the entrance pupil of the image capture device and the eyes may be focused on this entrance pupil. This is taken into account in step e).

[0133] Step d)

[0134] In step d), an image of the subject's head is captured by said image capturing device placed in the posture relative to the subject's head determined in step c) of the method according to the invention.

[0135] This image may be a two-dimensional image or a three-dimensional image of the subject's head.

[0136] In step d), the capturing of the image is triggered by the subject, or automatically by the image capturing device when the image capturing device detects the subject's head.

[0137] In the first embodiment described here, when the image capture device is positioned in front of the subject's eyes as instructed, that is, when the pupil P of the image capture device is in the line of sight of one of the subject's eyes or close to the line of sight of at least one of his eyes, the subject holds the portable electronic device 10 with his hand and can directly manually trigger the capture of the image.

[0138] In the second embodiment described here, the image capture device is placed on a pole. In this case, the subject preferably triggers the capture of the image with a remote control. Alternatively, another person (e.g., an eye care professional) can trigger the capture of the image.

[0139] In all cases, the image capture device can be programmed to recognize the subject's head in the field of view of the image capture device and automatically trigger the capture of an image when the subject's head is detected in the image, or more accurately, when the subject's eyes are detected. The capture of an image can also be triggered when no movement is detected, meaning that the image capture device is correctly positioned.

[0140] To this end, the image is automatically captured and processed using software or an application integrated in an image capture device or portable electronic device or column for identifying the subject's head and / or eyes. The image may also be sent and processed on another device or a remote server including the software. Such software is well known to those skilled in the art.

[0141] In step d), the subject may or may not be wearing the selected frame to which the lenses are to be fitted.

[0142] Advantageously, a reference element for scaling the image may be placed close to the subject's head and in step d) an image of this reference element may be captured together with the image of the subject's head.

[0143] This reference element is preferably an object with specific international standard dimensions, such as a credit card. Alternatively, the reference element can be any object with known dimensions.

[0144] The subject can then determine this size and enter this size into the portable electronic device or column.

[0145] If the subject is wearing the selected frame, the frame size, which is usually indicated within one of the temples of the frame, can be used as a reference element for scaling the image.

[0146] Alternatively, no reference element is used and in step e) the image may be scaled using two reference points of the subject's head, as described below.

[0147] Step e)

[0148] In step e), at least one geometrical parameter is derived from the image captured in step d).

[0149] More precisely, at least one of the following parameters is determined: interpupillary distance, half the interpupillary distance, fitting height.

[0150] In step d), during capturing the image of the subject's eyes, the sight lines of both eyes of the subject are directed towards said pupils of the image capture device, and the distance between the image capture device and the eyes of the subject is taken into account when determining said parameters.

[0151] In a first embodiment of the method, the portable electronic device may comprise a GPS device and / or other positioning means allowing the position of the portable electronic device in space to be determined.

[0152] Different positioning devices can be considered. For example, for use in an eye care practitioner's office, a time-of-flight camera or laser and detection sensors can be added to a portable electronic device. At home, an individual can use, for example, a smartphone as a portable electronic device, and the smartphone's inertial measurement unit can be used as a positioning device.

[0153] For example, through a calibration step, the distance between the image capture device and the subject's eyes is determined.

[0154] In this case, in a calibration step, the subject places the portable electronic device on his head, for example against his forehead, and the position of his head is recorded with the aid of the GPS and / or positioning device. The subject then holds the device at a distance at which the image is captured, and this position is also recorded. The distance between the subject's head and the image capture device can then be easily determined. Alternatively, the distance between the subject's head and the image capture device can be determined by other means, for example, by placing a reference object of known size (e.g., a credit card or a printed target of a scaled image) in the field of view of the image capture device.

[0155] In the event that pupil P of image capture device 12 is not placed in the direction of sight of one of the subject's eyes, a parallax error may be determined, which may be taken into account when determining the parameters.

[0156] For example, when the pupil P of the image capture device is placed below the direction of the subject's line of sight, the parallax error may be determined in order to determine the fitted height of the subject.

[0157] When the pupil P of the image capture device is offset laterally, ie, laterally in the horizontal plane from the subject's line of sight, a parallax error may be determined to determine the interpupillary distance or half the interpupillary distance.

[0158] The interpupillary distance is determined by measuring the distance between the centers of the images of the pupils of the captured images. The left-right pupil distance is determined by measuring the distance between the center of the image of each pupil and the image of the middle of the bridge of the frame.

[0159] In embodiments where the subject is wearing their actual chosen frame during step d) of image capture, the fit height may be determined by measuring the distance between the center of the image pupil of the subject's eye and the bottom edge of the image of the lens on said captured image.

[0160] The adaptation height can be derived from this measure by means of a scaling factor of the determined image and optionally after correction due to parallax errors.

[0161] For example, for the angle θ between the subject's gaze direction GDR and the observation line OBLR2 connecting the pupil of the subject's eye OR and the pupil P of the image capture device 12, the correction value FH for the adaptation height is 校正 = equal to the initially determined fit height FH based on the captured image 测量 The value is subtracted from the distance DVO (between the subject's eye and the ophthalmic lens placed in the frame) Figure 3 The product of the angle θ (not shown) and the tangent of the angle θ: FH 校正 =FH 测量 -DVO.tan(θ).

[0162] The distance between the eye and the lens is determined as the distance between the center of rotation of the eye and the back surface of the lens. It is estimated to be about 24 mm.

[0163] The angle θ is determined, for example, by an inertial motion unit and / or due to processing of the captured images. The angle may also be estimated. The angle is typically between 1 and 10 degrees.

[0164] The angle θ may be defined in an application dedicated to implementing the method according to the invention.

[0165] The individual or eye care practitioner can adjust the position of the smartphone with the help of an indicator on the live video (for example, in the case of an eye care practitioner) or with the help of the individual's sonar signals.

[0166] If there is no image of a reference element for scaling the image on the captured image, two reference points of the subject's head may be used to scale the image. For example, the center of the image of the subject's pupil may be detected on the captured image, and the subject's interpupillary distance may be measured by another device (e.g., with a pupillometer or ruler). The image may then be scaled by using the value of the interpupillary distance so determined and comparing it to the distance between the images of the centers of the pupil images. Other salient points of the head may be used.

[0167] When an individual wears glasses, the size of the glasses can be used. For example, the width of the left or right rim or the width of the bridge of the nose can be used, as indicated on the inside of one of the temples.

[0168] In another embodiment, in step d), the subject does not wear the real frame. In this case, in step d), a three-dimensional image of the subject's head is captured by the image capture device.

[0169] In an additional step, a virtual representation of the frame selected by the subject is determined ( Figure 1 This determination may include: retrieving a model of the selected frame from a database, scanning a real frame using a 3D scanner to determine the virtual representation of the frame, or measuring some elements of the real frame (e.g., width, length of temples, width of nose bridge, etc.).

[0170] Advantageously, when using the method for online ordering of glasses according to the invention, a set of frames having geometrical features adapted to the subject's head is selected from a frame database, based on a captured three-dimensional image of the subject's head. This database contains virtual representations of different frames.

[0171] The virtual representation of the selected frame is referred to as the virtual frame hereinafter. It comprises at least a list of geometric features of the selected frame, such as the length of the temples, the width of the nose bridge, the width of the rim, the wrap angle, and the overall width.

[0172] The step of selecting a suitable frame may be accomplished by virtually fitting a virtual frame to a three-dimensional image of the subject's head, as is known, for example, from document WO 2015101738.

[0173] In a further step, the selected frames are presented to the subject and the subject selects the frame he wishes to purchase from this selection.

[0174] In step e), the virtual spectacles frame is virtually fitted on the three-dimensional image of the subject's head, and a two-dimensional image of the subject's head wearing the virtual spectacles frame is derived.

[0175] Virtual fitting refers to overlaying a virtual frame on a three-dimensional image of the head so that it is placed on the head as it would be placed on the head when worn by the subject. To this end, methods of virtual fitting are well known, in which a significant portion of the virtual frame is superimposed on a significant area of ​​the three-dimensional image of the head.

[0176] Once the virtual frame has been virtually fitted onto the three-dimensional image of the subject's head, the projection of the three-dimensional representation thus obtained is determined in the frontal plane, which is perpendicular to the sagittal plane of the subject's head and perpendicular to the Frankfurt plane of the subject's head.

[0177] This projection forms a two-dimensional image of a head equipped with a virtual frame.

[0178] As described above, the fitting height of the subject equipped with the selected frame is determined based on the two-dimensional image thus determined. The left and right pupil distance can also be determined based on the two-dimensional image as the distance between the center of the pupil of each eye and the middle of the bridge of the frame.

[0179] In the case where the subject is instructed to place the pupil of the image capture device in the sight direction of one of his eyes, that is, the pupil of the image capture device is overlapped with the target without specifying the sight direction in which the eye should be placed, the subject's dominant eye can also be determined as the eye corresponding to the sight direction in which the subject places the pupil of the image capture device. The image of the dominant eye is actually located at the center of the captured image.

Claims

1. A method for determining at least one geometrical parameter of a subject in a natural posture to determine a vision correction device, in, Perform the following steps: a) placing the subject in a natural posture (100), in which at least one of the subject's gaze directions (GDR, GDL) points to a visual target (20), and the visual target (20) is suitable for being placed in front of the subject, b) placing (200) an image capture device (12) between the subject's head (50) and the visual target (20), c) adjusting (300) the relative posture of the image capture device (12) and the subject's head (50) so that the pupil (P) of the image capture device (12) is positioned in the gaze direction (GDR, GDL) of at least one of the subject's eyes (OR, OL) or within a solid angle of 1 to 10 degrees of the gaze direction (GDR, GDL), d) capturing (400) an image of the subject's head (50), e) deriving (500) said at least one geometrical parameter from the image, Wherein, in steps c) and d), the sight direction (GDR, GDL) of at least one of the eyes (OR, OL) of the subject points to the visual target (20).

2. The method according to claim 1, in, - in step c), the relative posture of the image capture device (12) and the subject's head (50) is adjusted by moving the image capture device (12) without moving the subject's head (50), and in step d), the gaze directions (GDR, GDL) of the subject's two eyes (OR, OL) are directed toward the pupil (P) of the image capture device (12), - In step e), the distance between the image capture device (12) and the subject's eyes (OR, OL) is taken into account for determining the parameter.

3. The method according to claim 1, in, In step b), the image capturing device (12) is a personal electronic portable device belonging to the subject.

4. The method according to claim 1, in, In step a), the subject looks into the distance through a window (30), in step b), the subject presses the image capture device (12) against the glass of the window (30), and in step c), the subject moves the image capture device (12) against the glass of the window (30).

5. The method according to claim 1, in, The steps a) to c) are performed by the subject himself: in step a), the subject is in the natural posture by himself, and in steps b) and c), the image capture device (12) is held and moved by the subject's hands.

6. The method according to claim 1, in, The image capture device (12) comprises: an inertial motion unit, which is suitable for determining the angular position of the image capture device (12) in space; and a communication device, which is suitable for sending information about the angular position of the image capture device in space to the subject; and in step c), the image capture device (12) provides the subject with information about the angular position of the image capture device compared to a target angular position.

7. The method according to claim 1, in, In step d), the image capturing is triggered by the subject or automatically by the image capturing device (12) when the subject's head (50) is detected by the image capturing device (12).

8. The method according to claim 1, in, The image capture device is attached to a pole and is vertically movable on the pole.

9. The method according to claim 1, in, In step e), at least one of the following parameters is determined: interpupillary distance, half the interpupillary distance, fitting height.

10. The method according to claim 1, in, In step e), the dominant eye of the subject is also determined.

11. The method according to claim 1, in, The image capture device (12) is positioned such that an optical axis (OA) of the image capture device (12) is close to or parallel to a line of sight direction (GDR, GDL) of the subject during capture of the image of the subject's head (50).

12. The method according to claim 1, in, A reference element for scaling the image is placed close to the subject's head (50), and in step d) an image of the reference element is captured together with an image of the subject's head (50).

13. The method according to claim 1, in, - in step d), the subject does not wear a real frame and the image capture device (12) captures a three-dimensional image of the subject's head (50), - in step e), a virtual frame is virtually fitted on the three-dimensional image of the subject's head (50) and a two-dimensional image of the subject's head (50) wearing the virtual frame is derived, - Determine the fitting height parameters based on this 2D image.

14. A system for determining at least one geometric morphological parameter of a subject in a natural posture to determine a vision correction device, the system include: - a visual target (20) adapted to be placed in front of the subject so that the subject is in a natural posture when at least one of the subject's gaze directions (GDL, GDR) is directed towards the visual target (20), - an image capture device (12) adapted to be placed between the subject's head (50) and the visual target (20) and adapted to capture an image of the subject's head (50), - adjustment means for adjusting the position and / or orientation of the image capture device (12) so that the pupil (P) of the image capture device (12) is positioned in the direction of sight (GDR, GDL) of at least one of the eyes (OR, OL) of the subject or within a solid angle of 1 to 10 degrees of the direction of sight (GDR, GDL), - a computing device programmed to derive said at least one geometrical parameter from said image of said subject's head (50) captured with said image capture device (12), Wherein, in steps c) and d), the sight direction (GDR, GDL) of at least one of the eyes (OR, OL) of the subject points to the visual target (20).

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