Stereoscopic display methods and devices for addressing ophthalmic defects

Abstract

This disclosure relates to a method (20) for displaying stereoscopic images to a user, by a display device (10) comprising a processing unit (11) and a display unit (12), said display unit comprising a first display area for a first image for one eye of the user and a second display area for a second image for the other eye of the user, said method comprising: obtaining (S20) a relative size correction, specific to the user, representative of a difference in size perception between the eyes of said user, estimating (S21) a viewing direction of the user's eyes and estimating, based on the estimated viewing direction, a central point aimed by the user's eyes on the display unit,a modification (S22) of the first image and / or the second image by applying the relative size correction with respect to the estimated center point, a display (S23) of the first image and the second image, obtained after modification, on the first display area and the second display area, respectively. Figure accompanying the abstract: Figure 2,

Description

Title of the invention: Stereoscopic display methods and devices for addressing ophthalmic defects. Technical field

[0001] The present invention belongs to the field of stereoscopic display devices, and relates more particularly to methods and stereoscopic display devices enabling users with ophthalmic defects to perceive stereoscopic images in relief.

[0002] The present invention finds a particularly advantageous, although by no means limiting, application in the case of stereoscopic display devices embedded in motor vehicles. State of the art

[0003] Stereoscopic display devices, as is known, display stereoscopic images that allow a user to see a scene in three dimensions. Stereoscopic images correspond to a pair of images of the same scene, representing said scene from slightly different viewpoints that correspond substantially to the positions of a user's eyes relative to said scene. Thus, a stereoscopic display device comprises a first display area and a second display area, which respectively display a first image intended for the user's left eye and a second image intended for the user's right eye.

[0004] There are different types of stereoscopic display devices. Some stereoscopic display devices require, for example, special glasses to allow the user to perceive the scene represented in relief, while other display devices, called autostereoscopic, allow the user to perceive the scene in relief without the need for special glasses or other accessories.

[0005] Some users with ophthalmic defects, however, are unable to perceive scenes in relief when viewing stereoscopic images presented by a stereoscopic display device. For example, some users may have a difference in size perception between their left and right eyes (aniseikonia), for example, due to anisometropia or, for a user wearing glasses, due to a significant difference in thickness between the left and right lenses of their glasses. Such a difference in size perception between a user's right and left eyes impairs that user's stereoscopic vision, preventing them from perceiving a scene in relief when viewing stereoscopic images. Stereoscopic images. Other ophthalmic defects, such as strabismus, can also affect stereoscopic vision. Description of the invention

[0006] The present invention aims to remedy all or part of the limitations of prior art solutions, in particular those described above, by proposing stereoscopic display methods and devices to improve the stereoscopic vision of users with certain ophthalmic defects, in particular a difference in size perception between the right eye and the left eye (aniseikonia).

[0007] To this end, a method for displaying stereoscopic images to a user is proposed according to a first aspect, by means of a display device comprising a processing unit and a display unit, said display unit comprising a first display area for a first image for one eye of the user and a second display area for a second image for the other eye of the user, said method comprising: - obtaining a relative size correction, specific to the user, representative of a difference in size perception between the eyes of said user, - an estimate of the user's eye direction and, based on that estimated eye direction, an estimate of the central point on the display unit targeted by the user's eyes, - a modification of the first image and / or the second image by applying the relative size correction with respect to the estimated central point, - a display of the first image and the second image, obtained after modification, on the first display area and the second display area, respectively.

[0008] Thus, the proposed solution modifies stereoscopic images by applying a relative size correction between the first image (for example, intended for the left eye) and the second image (for example, intended for the right eye). This relative size correction aims to compensate for the difference in size perception between the user's eyes. Therefore, one of the images will be enlarged (or reduced) relative to the other image in the stereoscopic image pair. This enlargement (or reduction) is further applied relative to a central point targeted by the user on the display unit of the display device, so that the image obtained after enlargement (or reduction) varies with the targeted central point. Indeed, the inventors have observed that taking the targeted central point into account The user's ability to apply relative size correction improves the recovery of depth perception.

[0009] In particular embodiments, the method according to the first aspect may further include one or more of the following optional features, taken individually or in all technically possible combinations.

[0010] In particular modes of implementation of the process according to the first aspect, the relative size correction comprises two correction components to be applied along two orthogonal axes.

[0011] In particular embodiments of the method according to the first aspect, the direction of vision of the user's eyes is estimated based on images of the user acquired by an optical sensor.

[0012] In particular embodiments of the method according to the first aspect, the display device being installed in a vehicle, the optical sensor is a camera of a driver monitoring system of said vehicle.

[0013] In particular embodiments, the method according to the first aspect includes filtering the temporal variations of the estimated vision direction and / or the estimated central point by means of a low-pass filter, with a time constant between 125 ms and 500 ms.

[0014] In particular embodiments of the method according to the first aspect: - the method comprises obtaining a relative position correction, specific to the user, representative of a difference in the direction of vision between the eyes of said user, - the first image and the second image, obtained after modification, are displayed on the first display area and the second display area, respectively, offset from each other by the relative position correction.

[0015] Such provisions make it possible to restore depth vision for a user who also has strabismus.

[0016] In particular embodiments of the method according to the first aspect, obtaining the user-specific relative size correction by the display device involves selecting the relative size correction to be applied from among several user-specific relative size corrections, based on an estimation of an optical state of said user, the optical state of said user comprising at least one parameter from among the following parameters: - the presence or absence of glasses worn by the user, - a type of glasses worn by the user, - the presence or absence of lenses worn by the user.

[0017] In particular embodiments of the method according to the first aspect, the display device being installed in a vehicle, the optical state of the user is estimated based on images acquired by at least one external or internal camera of said vehicle.

[0018] According to a second aspect, a method is proposed for determining, by a display device, a relative size correction for stereoscopic images, specific to a user, representative of a difference in size perception between the user's eyes, the display device comprising a processing unit, a user interface and a display unit, said display unit comprising a first display area of ​​a first calibration image for one eye of the user and a second display area of ​​a second calibration image for the other eye of the user, the first calibration image and the second calibration image being complementary in the absence of an ophthalmic defect, said method comprising an iteration of the following steps until a stopping criterion is met: - an estimate of the user's eye direction and, based on that estimated eye direction, an estimate of the central point on the display unit targeted by the user's eyes, - a modification of the first calibration image and / or the second calibration image by applying a relative correction of candidate size with respect to the estimated central point, - a display of the first calibration image and the second calibration image, obtained after modification, on the first display area and the second display area, respectively, - receiving user feedback via the user interface, - an evaluation of the stopping criterion based on user feedback received, in which the relative size correction is determined for the user based on one or more candidate relative size corrections validated by user feedback.

[0019] In particular embodiments, the method according to the second aspect may further include one or more of the following optional features, taken individually or in all technically possible combinations.

[0020] In particular embodiments of the method according to the second aspect, the first calibration image represents an object in a first color and the second calibration image represents the same object in a second color different from the first color so that, in the absence of an ophthalmic defect, a user perceives the object entirely in a third color which corresponds to the mixture of the first color and the second color.

[0021] In particular embodiments of the method according to the second aspect, the first calibration image and the second calibration image are stereoscopic images representing a first object and a second object such that, in the absence of an ophthalmic defect, a user perceives the second object as being in the background with respect to the first object.

[0022] In particular modes of implementation of the process according to the second aspect, the relative size correction comprises two correction components to be applied along two orthogonal axes.

[0023] In particular embodiments of the method according to the second aspect, the direction of vision of the user's eyes is estimated based on images of the user acquired by an optical sensor.

[0024] In particular embodiments of the method according to the second aspect, the display device being installed in a vehicle, the optical sensor is a camera of a driver monitoring system of said vehicle.

[0025] In particular embodiments, the method according to the second aspect includes filtering the temporal variations of the estimated vision direction and / or the estimated central point by means of a low-pass filter with a time constant between 125 ms and 500 ms.

[0026] In particular embodiments of the method according to the second aspect: - the method further comprises a determination of a relative position correction, specific to the user, representative of a difference in direction of vision between the eyes of said user, - the first calibration image and the second calibration image, obtained after modification, are displayed on the first display area and the second display area, respectively, offset from each other by a relative candidate position correction.

[0027] According to a third aspect, a computer program product is proposed comprising instructions which, when executed by a display device comprising a processing unit and a display unit comprising a first display area for one eye of a user and a second display area for the other eye of the user, configure said display device to implement a process according to any one of the embodiments of this disclosure.

[0028] According to a fourth aspect, a computer-readable recording medium is proposed on which is recorded a set of instructions which, when executed by a display device comprising a processing unit and a display unit comprising a first display area for one eye of a user and a second display area for the other eye of the user, configure said display device to implement a process according to any of the implementation methods of this disclosure.

[0029] According to a fifth aspect, a display device is proposed comprising a processing unit and a display unit comprising a first display area for one eye of a user and a second display area for the other eye of the user, configured to implement a method according to any one of the embodiments of this disclosure.

[0030] According to a sixth aspect, a vehicle, such as a motor vehicle, is proposed, comprising a display device according to any one of the embodiments of this disclosure. Presentation of the figures

[0031] The invention will be better understood upon reading the following description, given by way of non-limiting example, and made with reference to the figures which represent: - [Fig. 1] [Fig. 1]: a schematic representation of an example of a stereoscopic display device, - [Fig.2] [Fig.2]: a diagram illustrating the main steps of an example implementation of a method for displaying stereoscopic images, - [Fig.3] [Fig.3]: a representation of examples of modifications to a image based on a relative size correction and the central point targeted by the user, - [Fig.4] [Fig.4]: a diagram illustrating the main steps of an example implementation of a method for determining relative size correction for a user.

[0032] In these figures, identical reference numerals from one figure to another designate identical or analogous elements. For clarity, the elements shown are not to scale unless otherwise stated.

[0033] Furthermore, the order of steps shown in these figures is given only as a non-limiting example of this disclosure which may be applied with the same steps performed in a different order and / or with steps performed in parallel and / or jointly. Description of the implementation methods

[0034] Fig. 1 schematically represents an example of an embodiment of a display device 10. As illustrated by Fig. 1, the display device 10 comprises a processing unit 11 and a display unit 12.

[0035] The display unit 12 is a stereoscopic display unit, that is to say, it comprises a first display area for a first image for one eye (for example, the left eye) of the user and a second display area for a second image for the other eye (for example the right eye) of the user. The first and second images are therefore stereoscopic images in that they are intended to be presented to different eyes of the user of the display device 10.

[0036] As indicated above, there are different types of stereoscopic display units, and the choice of a particular type of stereoscopic display unit for the display device 10 is only one non-limiting implementation variant of this disclosure. Some stereoscopic display units, for example, require special glasses to allow the user to perceive the scene depicted in three dimensions.This is the case, for example, when the first and second images are displayed with lights of different polarizations, separable for the user's right and left eyes using polarized glasses, or when the first and second images are displayed successively (time-multiplexed, the first and second display areas potentially overlapping) and separable for the user's right and left eyes using blocking glasses (synchronized with the display, which alternately block the user's left and right eyes), etc. Other display units, known as autostereoscopic, allow the user to perceive the scene in relief without the need for special glasses or other accessories.This is the case, for example, when the first image and the second image are spatially multiplexed on the same screen, separable for the user's right and left eyes by means of, for example, parallax barriers or a lenticular system, or on two screens worn by the user respectively in front of the user's right eye and in front of the user's left eye (for example, in the case of virtual or augmented reality glasses), etc.

[0037] In the case where the display device 10 is installed in a vehicle, such as a motor vehicle, the display unit 12 is, for example, a remote autostereoscopic display unit located away from the user (i.e., not worn by the user). For example, the display unit 12 corresponds to the dashboard of the motor vehicle. However, following other examples, nothing precludes considering other types of stereoscopic display units and / or other operating environments besides a vehicle.

[0038] The processing unit 11 comprises, for example, one or more processors (CPU, DSP, GPU, FPGA, ASIC, etc.) and one or more memories (magnetic hard drive, electronic memory, optical disk, etc.) in which, for example, a computer program product is stored in the form of a set of instructions. program code to be executed by the processor(s) to implement all or part of the process steps that will be described below.

[0039] In certain embodiments, and as illustrated in [Fig. 1], the display device 10 may optionally include a user interface 13, allowing the user to interact with the display device 10. Generally, any type of user interface can be considered, and the choice of a particular type for the user interface 13 is only a non-limiting variant of the implementation of this disclosure. For example, the user interface 13 may include one or more of the following: a touchscreen (in which case the user interface 13 may be integrated in whole or in part into the display unit 12), a scroll wheel, a joystick, a keyboard, a mouse, etc. The user interface 13 may, for example, be a smartphone communicating with the processing unit 11.

[0040] Fig. 2 schematically represents the main steps of an example of implementation of a method 20 for displaying stereoscopic images implemented by the display device 10.

[0041] As illustrated by [Fig.2], the display method 20 includes a step S20 for obtaining a relative size correction, specific to the user, representative of a difference in size perception between the eyes of said user.

[0042] As previously stated, the relative size correction aims to compensate for the difference in size perception between the eyes of the user of the display device 10. Thus, after the application of the relative size correction, an object in a scene represented by stereoscopic images is perceived as being substantially the same size by both eyes of the user in question; that is, the difference in size perception is substantially canceled out by the application of the relative size correction. The relative size correction is therefore "specific" to the user in question in that it is adapted to substantially cancel out the difference in size perception for that user (the difference in size perception, and therefore the associated relative size correction, varying from one user to another).

[0043] The relative size correction can correspond to a magnification factor or a reduction factor to be applied to one of the stereoscopic images, that is, to be applied either to the first image or to the second image. Alternatively, the relative size correction can correspond to a magnification factor to be applied to one of the stereoscopic images (for example, the first image) and a reduction factor to be applied to the other stereoscopic image (for example, the second image if the magnification factor is applied to the first image). Thus, depending on the example considered, applying the relative size correction amounts to modifying only one of the stereoscopic images (the first image or the second image), or to modify both stereoscopic images (both the first image and the second image).

[0044] Furthermore, a magnification factor or a reduction factor may consist of a single component to be applied to the entire image under consideration, or it may comprise several components, for example, two components to be applied along two axes orthogonal to each other, for example in the case of a user with significant astigmatism. Indeed, in the case of astigmatism, the correction introduced by a lens is not the same in all directions and is broken down into two distinct corrections along two orthogonal axes, which do not necessarily correspond to the horizontal and vertical axes. Where applicable, the relative size correction may comprise two different components to be applied along these two orthogonal axes, which aim to compensate for the differences in corrections introduced by the lenses.These two different axes can be predefined (e.g., horizontal and vertical) or their definitions in the display unit coordinate system 12 can be included in the relative size correction, especially if the axes do not correspond to the horizontal and vertical axes and / or are user-specific.

[0045] The S20 step of obtaining the user-specific relative size correction consists, for example, of receiving said relative size correction via the user interface 13 or from equipment separate from the display device 10, for example, equipment worn by the user (smartphone, connected glasses, etc.) or a remote server in which relative size corrections for one or more users are stored.

[0046] Following another example, the user-specific relative size correction can be calculated during the retrieval step S20 from information received via the user interface 13 or from equipment separate from the display device 10, for example, equipment worn by the user (smartphone, smart glasses, etc.) or a remote server in which information relating to one or more users is stored. This information corresponds, for example, to the data from the user's medical prescription. For example, the magnification (or reduction) factor of the relative size correction can be calculated based on the number K of diopters of difference between the user's left and right eyes. For example, the relative size correction can magnify an image by 1.5% multiplied by K, which corresponds to a magnification factor of (100 + 1.5 x Æ) / 100.

[0047] Following another example, the S20 obtaining step can implement a method for determining the relative size correction, aimed at calibrating the difference in size perception between the user's eyes by presenting them with (stereoscopic) calibration images. A non-limiting example of method 40 for determining relative size correction is described below with reference to [Fig. 4],

[0048] It should be noted that it is also possible, in certain examples, to have several specific relative size corrections for the same user. For example, the relative size correction to be applied to a user may vary depending on the user's optical condition, i.e., depending on the presence or absence of glasses, and / or the type of glasses present in the case of a user with several pairs of glasses, and / or the presence or absence of contact lenses. In such a case, the S20 obtaining step may also include, in certain examples, the selection of the relative size correction to be applied from among several relative size corrections specific to that user, based on an estimate of the user's optical condition (presence or absence of glasses, type of glasses present, presence or absence of contact lenses, etc.).For example, external equipment on a motor vehicle, such as surround-view cameras, can be used to assess the user's vision, including detecting the presence or absence of eyeglasses and, potentially, the type of eyeglasses worn. Internal equipment, such as the camera in a driver monitoring system (DMS), can also be used, either alternatively or in addition, to assess the user's vision. A DMS camera, for instance, can assess the user's vision by comparing the apparent size of the two eyes and can even detect the combination of eyeglasses and contact lenses (typically monofocal lenses to correct aniseikonia and glasses to correct presbyopia).This detection is carried out, for example, by comparing the apparent size of the eyes.

[0049] As illustrated by [Fig.2], the display method 20 includes a step S21 of estimating a direction of vision of the user's eyes and estimating, as a function of the estimated direction of vision, a central point aimed by the user's eyes on the display unit 12.

[0050] Indeed, as previously indicated, the relative size correction aims to compensate for the difference in size perception between the eyes of the user of the display device 10. Thus, after applying the relative size correction, an object in a scene represented by stereoscopic images is perceived as having substantially the same size (and the same shape in the case of different components applied along orthogonal axes) for both eyes of the user in question. However, the inventors have found that correcting the difference in size perception is not always sufficient to achieve a Good overlay and restoration of depth perception are essential. Indeed, if the enlargement (or reduction) is performed relative to an arbitrary point such as the center or corner of the image, this will generally be insufficient to restore depth perception. Instead, this enlargement (or reduction) should be performed relative to a central point that corresponds to a point the user is looking at on the display unit 12. This central point is estimated during step S21 by estimating the user's viewing direction relative to said display unit 12. Thus, the way in which the enlargement (or reduction) is performed depends on the central point the user is looking at.

[0051] Generally, any method known to a person skilled in the art can be implemented to estimate the user's vision direction relative to the display unit 12 and, from the estimated vision direction, to estimate the central point aimed at by the user on the display unit 12. The choice of a particular estimation method is only a non-limiting variant of implementation of this disclosure.

[0052] For example, the user's line of sight can be estimated based on images of the user acquired by one or more optical sensors, which may be an integral part of the display unit 10 or may belong to other equipment communicating with the display unit 10. In the case where the display unit 10 is installed in a motor vehicle, the optical sensor corresponds, for example, to a camera of a driver monitoring system (DMS) of said motor vehicle. The line of sight can thus be estimated in a frame of reference of said driver monitoring system and conventionally transferred to a frame of reference of the display unit 12 to determine the central point aimed at by the user.

[0053] In practice, the user's viewing direction must be tracked over time to follow the variations of the central point targeted by the user on the display unit 12. Indeed, the user does not always look in the same place, and it is therefore necessary to track the movements of the user's viewing direction. In such a case, it may be advantageous to implement filtering of the temporal variations of the estimated viewing direction and / or the estimated central point by means of a low-pass filter, in order to avoid tracking erratic movements of the viewing direction and / or the central point. For example, the low-pass filter, optionally implemented to filter these temporal variations, has a time constant between 125 ms and 500 ms.

[0054] As illustrated by [Fig.2], the display method 20 also includes a step S22 of modifying the first image and / or the second image by applying the relative size correction with respect to the estimated central point.

[0055] As previously stated, the relative size correction can correspond to an enlargement (or reduction) factor to be applied to one of the stereoscopic images, that is, to be applied either to the first image or to the second image. Alternatively, the relative size correction can correspond to a factor (enlargement or reduction) to be applied to one of the stereoscopic images (for example, the first image) and a factor (enlargement or reduction) to be applied to the other stereoscopic image (for example, the second image). Thus, depending on the example considered, applying the relative size correction amounts to modifying only one of the stereoscopic images (the first image or the second image), or to modifying both stereoscopic images (both the first and second images).

[0056] The modification applied to one of the stereoscopic images during step S22 corresponds to an enlargement (or reduction) relative to the estimated center point targeted by the user. For example, it is a homothety whose center corresponds to the estimated center point and whose ratio corresponds to the enlargement (or reduction) factor. This modification may also conventionally involve resampling the digital pixels of the image to be modified. Indeed, the various digital pixels of the stereoscopic images are initially positioned at the level of the physical pixels of the display unit 12.Due to the enlargement or reduction, these digital pixels no longer correspond to the positions of the physical pixels of the display unit 12, and it is therefore necessary to resample the modified image to obtain new digital pixels for the physical pixel grid of the display unit 12. Generally, any resampling method can be implemented, and the choice of a particular method is only one non-limiting variant of the implementation of this disclosure. For example, resampling may involve bilinear or bicubic interpolation.

[0057] As illustrated by [Fig.2], the display method 20 includes a step S23 of displaying the first image and the second image, obtained after modification, on the first display area and the second display area of ​​the display unit 12, respectively.

[0058] Figure 3 schematically represents examples of modifications applied to one of the stereoscopic images. In these examples, it is considered, without limitation, that the modification applied corresponds to an enlargement applied to the first image, which is to be displayed by the first display area of ​​the display unit 12.

[0059] As illustrated by part a) of [Fig. 3], the first image represents a scene with a triangular object 30. Parts b) and c) of [Fig. 3] represent the object 30 obtained after enlarging the first image obtained by considering different central points aimed by the user on the display unit 12 (first display area), but considering the same magnification factor in both cases.

[0060] In the example illustrated by part b) of [Fig.3], the central point 31a aimed at by the user is located in the lower left corner of the first display area of ​​the display unit 12. The object obtained after enlarging the first image, considering the central point 31a as the center of the homothety, is designated by the reference 30a.

[0061] In the example illustrated by part c) of [Fig.3], the central point 31b aimed at by the user is located substantially at the center of the object 30, that is to say that the user is looking at this object 30. The object obtained after enlarging the first image, taking into account the central point 31b as the center of the homothety, is designated by the reference 30b.

[0062] As can be seen in parts b) and c) of [Fig.3], the object 30a, 30b displayed on the first display area of ​​the display unit 12 varies with the central point 31a, 31b aimed by the user on said display unit 12. It is this taking into account the central point actually aimed by the user (rather than considering an arbitrary point independent of the direction of vision of the user) which makes it possible to modify the stereoscopic images in such a way as to improve the perception in relief of the object represented, by the user.

[0063] As illustrated by [Fig.2], in certain embodiments, steps S21, S22, S23 can be iterated, for example to track the movement of the central point aimed at by the user on the display unit 12 and / or to process new stereoscopic images (i.e., process a new first image / second image pair), for example in the case of successive stereoscopic images of a stereoscopic (3D) video stream.

[0064] As indicated above, other ophthalmic defects can affect the user's depth perception. For example, a user with strabismus will have significantly different vision directions for their right and left eyes, so that the central point being viewed is not the same for both eyes. Without correction, the user's right and left eyes will not be looking at the same point in the scene depicted in the first and second images, which can impair depth perception in the event of a significant discrepancy.

[0065] In order to restore depth perception in the case of strabismus, the display method 20 may, in certain embodiments, include a step (not shown in the figures) for obtaining a relative position correction, specific to the user, representing a difference in the direction of vision between the eyes said user. In these examples, during step S23, the first image and the second image obtained after modification are then displayed on the first display area and the second display area, respectively, offset from each other by the relative position correction.

[0066] The relative position correction aims to compensate for the difference between the central points aimed at by the user's right and left eyes respectively on the display unit 12. Thus, after application of the relative position correction, the first image and the second image are positioned offset from each other so that the user's right and left eyes, although having different directions of vision, look substantially at the same place in the scene represented by said first image and said second image.

[0067] The step of obtaining the user-specific relative position correction consists, for example, of receiving said relative position correction via the user interface 13 or from equipment separate from the display device 10, for example, equipment worn by the user (smartphone, connected glasses, etc.) or a remote server in which relative position corrections for one or more users are stored.

[0068] Following another example, the user-specific relative position correction can be calculated during the retrieval step from information received via the user interface 13 or received from equipment separate from the display device 10, for example, equipment worn by the user (smartphone, smart glasses, etc.) or a remote server in which information relating to one or more users is stored. This information corresponds, for example, to the data from a medical prescription of the user.

[0069] Following another example, the user-specific relative position correction can be determined by separately estimating, during step S21, the user's right eye vision direction and left eye vision direction.

[0070] Following another example, the acquisition step may implement a method for determining the relative position correction, aimed at calibrating the difference in size perception between the user's eyes by presenting them with calibration (stereoscopic) images. A non-limiting example for determining the relative position correction is described below.

[0071] Fig. 4 schematically represents the main steps of an example of implementation of a method 40 for determining relative size correction of stereoscopic images.

[0072] The determination method 40 is, for example, implemented by a display device 10 as shown in [Fig. 1]. It should be noted that it is possible to use the same display device 10 to implement both the method 20 display and determination process 40 (determination process 40 being implemented, for example, during step S20 of obtaining display process 20). It is also possible, following other examples, to use for determination process 40 a display device that is physically distinct from the display device 10 used for display process 20, the display device 10 used for display process 20 being, for example, mounted in a motor vehicle but not the one used for determination process 40.

[0073] In principle, the determination method 40 relies on displaying a first calibration image on the first display area of ​​the display unit 12, and a second calibration image on the second display area. The first and second calibration images are complementary in the absence of an ophthalmic defect. By "complementary in the absence of an ophthalmic defect," it is meant that when the first and second calibration images are displayed by the display unit 12 without applying any correction, they form a predetermined pattern recognizable to a user without an ophthalmic defect.For a user with a difference in size perception between their eyes, when the first and second calibration images are displayed by the display unit 12 without applying any relative size correction, they do not form this predetermined pattern. For a user with a difference in size perception between their eyes, the predetermined pattern is perceived by the user only when the first and second calibration images are displayed by the display unit 12 with a relative size correction applied to compensate for that user's difference in size perception.Therefore, the determination method 40 will test several candidate relative size corrections to modify the first and second calibration images until the user recognizes the predetermined pattern. This means that the candidate relative size correction, which led the user to recognize the predetermined pattern, is well-suited to the user. For example, it is possible to search for the candidate relative size correction that yields the best results in terms of complementarity between the modified first and second calibration images. In this case, the relative size correction determined specifically for this user corresponds to the candidate relative size correction validated by the user as providing the best results.Following another example, it is possible to search for several candidate relative size corrections for which the user can recognize the predetermined pattern. In this case, the specifically determined relative size correction... for this user can be determined from several user-validated candidate relative size corrections, allowing them to recognize the predetermined pattern.

[0074] Generally, different types of complementary calibration images can be considered, provided that the first and second calibration images allow the user to detect when the difference in size perception between their eyes is correctly corrected by a relative candidate size correction, through the recognition of said predetermined pattern. The choice of a particular type of calibration image is only one non-limiting implementation variant of this disclosure.

[0075] Following an example, the first calibration image may represent an object in a first color, and the second calibration image may represent the same object, in the same position, in a second color different from the first color. The first and second colors are, for example, primary colors. Thus, in the absence of an ophthalmic defect, or when the difference in size perception is correctly corrected, the user perceives the object entirely in a third color that corresponds to the mixture of the first and second colors. The object entirely in the third color therefore corresponds to the predetermined pattern to be detected. For example, the object corresponds to a simple geometric shape (square, triangle, circle, etc.) filled with the first color (first calibration image) or the second color (second calibration image).In some examples, the first and second colors may be colors adapted to compensate for possible chromatic aberration problems of the user (color blindness, etc.), i.e. allowing a user with a chromatic aberration problem to detect the predetermined pattern (object entirely in the third color).

[0076] Following another example, the first calibration image and the second calibration image can be stereoscopic images representing a first object and a second object such that, in the absence of an ophthalmic defect, or when the difference in size perception is correctly corrected, the user perceives the second object as being in the background relative to the first object. Having the first object in the foreground relative to the second object thus corresponds to the predetermined pattern to be detected. For example, the first calibration image and the second calibration image can represent several identical objects (e.g., squares, triangles, circles, etc.) of which only one (the first object) should be perceived as being in the foreground relative to the other objects (the second objects).

[0077] Following another example, the first calibration image can represent a first object and the second calibration image can represent a second object different from the first object but with a complementary shape to that of the first object. Thus, in the absence of an ophthalmic defect, or when the difference in size perception is correctly corrected, the user perceives a third object with a recognizable shape that corresponds to a combination of the shapes of the first object and the third object. For example, the first and second objects may correspond to complementary semicircles (or semi-disks), so that the third object corresponds to a complete circle (or disk), and so on.

[0078] As illustrated by [Fig.4], the determination method 40 comprises a step S40 of estimating the direction of vision of the user's eyes and an estimation, based on the estimated direction of vision, of a central point aimed by the user's eyes on the display unit 12. Everything previously described with reference to the estimation step S21 of the display method 20 is also applicable to the estimation step S40 of the determination method 40.

[0079] As illustrated in [Fig. 4], the determination method 40 also includes a step S41 of modifying the first calibration image and / or the second calibration image by applying a candidate relative size correction with respect to the estimated center point. As previously stated, the determination method 40 will test several candidate relative size corrections until the user recognizes the predetermined pattern for the first and second calibration images. For example, the initially considered candidate relative size correction is zero, i.e., no relative size correction is applied.Following another example, the initial candidate relative size correction may be a theoretical relative size correction calculated from a user's prescription, in which case the determination process 40 aims to refine this theoretical relative size correction (to take into account, in particular, the possible natural evolution of the ophthalmic defect). Everything described previously with reference to step S22 for modifying the display process 20 is also applicable to step S41 for modifying the determination process 40.

[0080] As illustrated in [Fig. 4], the determination method 40 also includes a step S42 for displaying the first calibration image and the second calibration image, obtained after modification, on the first display area and the second display area of ​​the display unit 12, respectively. Everything described previously with reference to the display step S23 of the display method 20 is also applicable to the display step S42 of the determination method 40.

[0081] As illustrated in [Fig. 4], the determination method 40 includes a step S43 of receiving user feedback via the user interface 13 of the device display 10, and an S44 step for evaluating a predetermined stopping criterion based on user feedback received.

[0082] User feedback determines whether the stopping criterion is met. Generally, if user feedback indicates that other candidate relative size corrections should be considered (for example, if user feedback modifies the candidate relative size correction under consideration), then the stopping criterion is not met. Conversely, if user feedback indicates that it is no longer necessary to consider other candidate relative size corrections (after user feedback has previously validated at least one candidate relative size correction as capable of detecting the predetermined pattern), then the stopping criterion is met.For example, if the user does not validate the candidate relative size correction via user interface 13 (if they have not detected the predetermined pattern), the user feedback may indicate that the candidate relative size correction is unsuitable and / or needs to be modified. The modification required to update the candidate relative size correction is, for example, included in the user feedback. When the user feedback modifies the candidate relative size correction, it means that other candidate relative size corrections must be tested, so the stopping criterion is not checked (reference S44a in [Fig. 4]), and steps S40, S41, S42, S43, and S44 are iterated.The modification to be made may, for example, change a magnification or reduction factor, along one or two axes, or change the axes along which the different components of the candidate relative size correction are considered (for example, by rotating the previously considered orthogonal axes with a predetermined angular step, for example, equal to 15°), etc. The candidate relative size correction obtained after modification is then used during the next iteration of steps S40, S41, S42, S43, S44.

[0083] The user can validate the candidate relative size correction used when they have detected the predetermined pattern, that is, when the first calibration image and the second calibration image, obtained after modification and displayed by the display unit 12, are perceived as complementary by the user. Generally, the stopping criterion can be checked, depending on the examples considered, as soon as a candidate relative size correction is validated by the user, or after a plurality of candidate relative size corrections have been validated by the user. For example, it is possible to iterate steps S40, S41, S42, S43, S44 until a predetermined number Ne (Ne greater than or equal to 1) of candidate relative size corrections is validated, or until the user considers that a sufficient number of candidate relative size corrections have been validated, etc.When user feedback indicates that it is not necessary to test other related fixes. of candidate size (for example, if the user feedback validates the candidate size relative correction used and if the number of candidate size relative corrections validated by the user is equal to Ne, or if the user feedback explicitly indicates that it is no longer necessary to test other candidate size relative corrections and that at least one candidate size relative correction has been previously validated by the user, etc.), the stopping criterion is checked (reference S44b on [Fig.4]).

[0084] As illustrated in [Fig. 4], the method 40 includes a step S45 for determining the user-specific relative size correction to be used by the display method 20, based on the candidate relative size corrections validated by the user. If the user has validated only one candidate relative size correction, the relative size correction determined specifically for that user then corresponds to the candidate relative size correction validated by the user via the user interface 13. If the user has validated several candidate relative size corrections, then the relative size correction determined specifically for that user is determined based on all or some of the candidate relative size corrections validated by the user.For example, the relative size correction determined specifically for this user corresponds to the average, possibly weighted, of the candidate relative size corrections validated by the user via user interface 13.

[0085] As indicated above, other ophthalmic defects can affect the user's depth perception. For example, a user with strabismus will have significantly different vision directions for the right and left eyes, so that the central point targeted is not the same for the right and left eyes. In such cases, it may be necessary to determine a relative position correction for this user, in addition to the relative size correction. To this end, the determination method 40 may further include, in certain embodiments, a step (not shown in the figures) for determining a relative position correction specific to this user, representative of a difference in vision direction between the user's eyes.As with relative size correction, it is possible to test different candidate relative position corrections by displaying the first and second calibration images, obtained after modification, on the first and second display areas respectively, offset from each other by a candidate relative position correction. If necessary, the stopping criterion is not checked if user feedback modifies the candidate relative position correction. As with relative size correction, the user can validate one or more candidate relative position corrections, and the determined relative position correction. specifically by this user is determined based on the relative position correction(s) candidates validated by this user.

[0086] More generally, it should be noted that the implementation and realization methods considered above have been described as non-limiting examples, and that other variants are therefore conceivable.

[0087] In particular, the method 40 for determining the relative size correction has been described by considering that the central point targeted by the user on the display unit 12 is estimated from an estimated viewing direction during a step S40, and that this estimated central point is used during the modification step S41. However, following other examples, there is nothing to preclude not performing the estimation step S40 and instead performing the modification with respect to a predetermined point on the display unit 12, which corresponds, for example, to the center of an object represented by the first and second calibration images, which the user is asked to look at during the determination method 40. In other words, the estimation step S40 does not have to be performed if the first and second calibration images are such that the central point targeted by the user is known a priori.

Claims

Demands

1. A method (20) for displaying stereoscopic images to a user, by means of a display device (10) comprising a processing unit (11) and a display unit (12), said display unit comprising a first display area for a first image for one eye of the user and a second display area for a second image for the other eye of the user, said method comprising: - obtaining (S20) a relative size correction, specific to the user, representative of a difference in size perception between the eyes of said user, - estimating (S21) a direction of vision of the user's eyes and estimating, as a function of the estimated direction of vision, a central point aimed by the user's eyes on the display unit,- a modification (S22) of the first image and / or the second image by applying the relative size correction with respect to the estimated central point, - a display (S23) of the first image and the second image, obtained after modification, on the first display area and the second display area, respectively.

2. Method (20) according to claim 1, wherein the relative size correction comprises two correction components to be applied along two orthogonal axes.

3. A method (20) according to any one of the preceding claims, wherein the direction of vision of the user's eyes is estimated based on images of the user acquired by an optical sensor.

4. Method (20) according to claim 3, wherein, the display device being installed in a vehicle, the optical sensor is a camera of a driver monitoring system of said vehicle.

5. Method (20) according to any one of the preceding claims, comprising filtering the temporal variations of the estimated vision direction and / or the estimated center point by means of a low-pass filter, with a time constant between 125 ms and 500 ms.

6. A method (20) according to any one of the preceding claims, wherein obtaining (S20) the user-specific relative size correction by the display device involves the selection of the relative size correction to be applied from among several relative size corrections specific to said user, based on an estimate of an optical state of said user, the optical state of said user comprising at least one parameter from among the following parameters: - the presence or absence of glasses worn by the user, - a type of glasses worn by the user, - the presence or absence of lenses worn by the user.

7. Method (20) according to claim 6, wherein, the display device being installed in a vehicle, the optical state of the user is estimated based on images acquired by at least one external or internal camera of said vehicle.

8. A method (40) for determining, by a display device (10), a relative size correction for stereoscopic images, specific to a user, representative of a difference in size perception between the user's eyes, the display device comprising a processing unit (11), a user interface (13) and a display unit (12), said display unit comprising a first display area of ​​a first calibration image for one eye of the user and a second display area of ​​a second calibration image for the other eye of the user, the first calibration image and the second calibration image being complementary in the absence of an ophthalmic defect, said method comprising an iteration of the following steps until a stopping criterion is met: - an estimate (S40) of the user's eye vision direction and an estimate, based on the estimated vision direction, of a central point targeted by the user's eyes on the display unit, - a modification (S41) of the first calibration image and / or the second calibration image by applying a relative correction of candidate size with respect to the estimated central point, - a display (S42) of the first calibration image and the second calibration image, obtained after modification, on the first display area and the second display area, respectively, - a reception (S43) of user feedback via the user interface, - an evaluation (S44) of the stopping criterion based on the user feedback received, in which the relative size correction is determined based on one or more candidate relative size corrections validated by the user feedback.

9. Method (40) according to claim 8, wherein the first calibration image represents an object in a first color and the second calibration image represents the same object in a second color different from the first color so that, in the absence of an ophthalmic defect, a user perceives the object entirely in a third color which corresponds to the mixture of the first color and the second color.

10. Method (40) according to claim 8, wherein the first calibration image and the second calibration image are stereoscopic images representing a first object and a second object such that, in the absence of an ophthalmic defect, a user perceives the second object as being in the background with respect to the first object.

11. Method (40) according to any one of claims 8 to 10, wherein the relative size correction comprises two correction components to be applied along two orthogonal axes.

12. Method (40) according to any one of claims 8 to 11, comprising filtering the temporal variations of the estimated vision direction and / or the estimated center point by means of a low-pass filter with a time constant between 125 ms and 500 ms.

13. Product computer program comprising instructions which, when executed by a display device (10) comprising a processing unit (11) and a display unit (12) comprising a first display area for one eye of a user and a second display area for the other eye of the user, configure said display device to implement a method (20, 40) according to any one of the preceding claims.

14. 24 Display device (10) comprising a processing unit (11) and a display unit (12) comprising a first display area for one eye of a user and a second display area for the other eye of the user, configured to implement a method (20, 40) according to any one of claims 1 to 12.

15. Vehicle comprising a display device (10) according to claim 14.

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