Digital light-field vision refraction system and methods using same

Abstract

The present disclosure concerns a testing device (500) comprising: a light-field projector display (100) sequentially emitting a plurality of light fields (101); a spatial light modulator (SLM) (3) controllable to modulate the light fields (101); projection optics (4) configured to project the modulated light fields (101) and form at least a virtual image (40) in a projection image plane (400); and wherein the SLM image pattern (61) is configured to add at least one refractive correction to said at least one virtual image (40). A human interface device (HID) (503) is configured to let a user select at least one of the virtual images (40) for which the user perceives as having the best image subjective quality input the refractive correction corresponding to the selected at least one of the virtual images (40) in a data storage unit (509). The present disclosure further concerns a computer-readable medium configured to perform a method for to assess the vision acuity of a user by using the testing device.

Description

Digital Light-Field Vision Refraction System and methods using sameField

[0001] The invention pertains to the field of vision refraction and optometry, more particularly to the use of digital light-field display technologies for the enhancement and acceleration of visual self-refraction techniques.Background

[0002] Current devices and methods for vision acuity testing, or selfrefraction and eyesight quality assessment usually involve the use of physical lenses and static imagery. Current procedures usually involve a patient looking at objects with defined qualities (size, brightness, distance) through a set of lenses with defined properties (sphere, cylinder, prism) to self-assess the quality of her or his eyesight (visual self-refraction). Such methods can be cumbersome, time-consuming, and usually require professional supervision.

[0003] Limitations of current devices and methods stem from the use of physical optical elements (usually lenses). More particularly, the optical elements make it difficult or impossible to simultaneously display multiple distinct corrective powers, as well as to adjust these dynamically. Consequently, current devices and methods often involve presenting a series of static images, each with different corrective powers applied and asking a user to provide feedback on each individual correction. This process, which usually requires repeated sequences to find the appropriate refraction prescription, is time-consuming. It also introduces potential inaccuracies due to the user's reliance on recalling visual sensations from previous images. Furthermore, a professional must interpret responses and manage cases where a user finds decision-making difficult. Another essential role of professional supervision is to ensure patients avoid over-Creal3-15-PCT1accommodation. These factors impose restrictions on the capacity for user diagnosis and deteriorate user experience, thereby constraining the feasibility of conducting comprehensive, population-wide screenings.

[0004] Devices based on digital light-field display technologies can be used in areas which rely on perception of light passing through defined optical elements. In such areas, the digital light-field display can replace the objects / images / drawings being looked at as well as the set of lenses being looked through.Summary

[0005] The present disclosure concerns a testing device for use by a user to assess its vision acuity, the testing device comprising: at least a light-field projector display comprising a plurality of point light sources controllable by an illumination control unit to sequentially illuminate the point light sources and sequentially emit a plurality of light fields; a spatial light modulator (SLM) controllable by a SLM control unit to provide a SLM image pattern on the SLM modulating the light fields; projection optics configured to project the modulated light fields along a reference projection axis and form at least a virtual image in a projection image plane; and wherein the SLM image pattern is configured to add at least one refractive correction to said at least one virtual image.

[0006] The testing device further comprises a human interface device (HID) usable by the user to select at least one of the virtual images for which the user perceives as having the best image subjective quality, or recognizes a characteristic, and configured to input the refractive correction corresponding to the selected at least one of the virtual images in a data storage unit.Creal3-15-PCT1

[0007] The present disclosure further concerns a light-field-based testing device arranged to perform a plurality of test cycles for assessing refraction properties of a user's eye. The device comprises: at least one light-field projector display comprising a plurality of point light sources arranged to be sequentially illuminated by an illumination control unit to sequentially emit a plurality of light fields; a SLM arranged to be driven by an SLM control unit to display an SLM image pattern on the SLM, the SLM image pattern modulating the light fields; projection optics configured to project the modulated light fields along a reference projection axis and form, in a projection image plane, a plurality of virtual images projected sequentially or simultaneously; and a data storage unit comprise a region of a physical memory configured to at least temporarily store input signals.

[0008] The SLM control unit is further configured to apply, to the SLM image pattern, a plurality of refractive corrections including a predefined refractive correction value and additional refractive correction values incrementally varied about the predefined refractive correction value, such that each virtual image of said plurality of virtual images is formed with a corresponding refractive correction. The testing device further comprises a HID operable by the user during a test cycle to select at least one of the virtual images perceived to exhibit best image subjective image quality or a recognizable characteristic. The HID is further configured to input, into, the data storage unit, a best refractive correction corresponding to the selected virtual image; and to provide the best refractive correction to the SLM control unit for use as the predefined refractive correction in a subsequent test cycle.

[0009] The present disclosure further concerns a non-transitory computer-readable medium comprising digital instructions to be implemented by a processing module comprised in the testing device to perform a method to assess the vision acuity of a user, comprising at least a test cycle comprising: a projection step, comprising sequentially projecting a plurality of projection image planes, each comprising at least one virtual image;Creal3-15-PCT1a correction step, comprising controlling the SLM control unit to provide a SLM image pattern configured to add at least one refractive correction to each of said at least one virtual image; and a selection step, comprising using the HID to select, in at least one of said plurality of projection image planes, at least one virtual image that the user perceives as having the best image subjective quality, or a characteristic of said at least one virtual image that the user recognizes, and inputting in the data storage unit the refractive correction of the selected at least one virtual image as a best refractive correction.

[0010] Also disclosed is a non-transitory computer-readable medium storing digital instructions which, when executed by a processing module of the testing device, cause the processing module to perform a method of assessing a user's visual acuity, the method comprising a plurality of test cycle, each test cycle comprising: a projection step comprising controlling the light-field projector display to sequentially project a plurality of projection image planes, each projection image plane comprising at least one virtual image; a correction step, comprising controlling the SLM control unit to provide an SLM image pattern configured to add, to each virtual image, one of a plurality of refractive corrections comprising a predefined refractive correction value and additional refractive correction values incrementally varied about the predefined value; and a selection step, comprising using the HID to select, in at least one of said plurality of projection image planes, at least one virtual image that the user perceives as having best image subjective quality, or exhibiting a a recognizable characteristic; and an input step, comprising storing in the data storage unit a best refractive correction corresponding to the selected virtual image(s) and providing the best refractive correction to the SLM control unit for use as the predefined refractive correction value in a subsequent test cycle.Creal3-15-PCT1

[0011] The system, light-field projector display, and methods allow for a more efficient, faster, more precise, and user-friendly approach to today's standard for visual refraction, making it particularly useful for regular screening, especially where current methods are not sufficiently scalable.

[0012] The light-field-based testing disclosed herein allows a user to control the SLM image pattern directly via the HID device, such that the light-field-based testing device can perform a plurality of test cycles for assessing refraction properties of a user's eye and providing feedback to the user, without requiring an intermediary operator.

[0013] The light-field-based testing and method enable fast, consistent, and repeatable determination of best refractive correction by leveraging digital light-field projection and programmable SLM modulation. Iterative refinement reduces operator workload, improves user throughput, and supports fine granularity beyond discrete mechanical lens steps.Brief description

[0014] Exemplar embodiments of the invention are disclosed in the description and illustrated by the drawings in which:Fig. 1 shows a shows a digital light-field projector display, according to an embodiment;Fig. 2 shows a representation of a virtual pinhole camera;Fig. 3a illustrates an example of the light field projector in the absence of correction;Fig. 3b illustrates an example of the light field projector generating a refractive correction;Fig. 4 shows a testing device comprising the light-field projector display, according an embodiment;Creal3-15-PCT1Fig. 5 shows an example of the testing device comprising two projector displays arranged as a binocular tabletop device;Fig. 6 illustrates a method for determining a refraction eye parameter of a user using the testing device, according an embodiment;Fig. 7 shows an example of a projection image plane comprising simultaneously projected five virtual images and forming a virtual scene;Fig. 8 shows projected virtual images arranged in a 3D pattern generating 3D virtual scenes;Fig. 9 illustrates a projection image plane comprises a plurality of subsets of virtual images, each subset being arranged in a segment of the projection image plane; andFig. 10 illustrates a method for determining a refraction eye parameter of a user using the testing device, the method comprising a plurality of test cycles, according an embodiment.Detailed description

[0015] The present disclosure concerns a digital light-field projector display configured to project virtual images.

[0016] Fig. 1 shows a digital light-field projector display 100 comprising a light device 1 provided with a plurality of light sources (two point-light sources 10 are shown in Fig. 1). The point light sources 10 can be sequentially illuminated such as to sequentially emit a plurality of light fields 101. The light fields 101 can be collimated with collimating optics 2 before sequentially illuminating a SLM 3 under a different set of incident angles. The SLM 3 is configured to provide a reference SLM image pattern 60 in an SLM plane 31. The reference SLM image pattern 60 modulates each of the light fields 101 in accordance with the reference SLM imageCreal3-15-PCT1pattern 60. Each modulated light field 101 is modulated by the reference SLM image pattern 60 of the SLM 3 and carries out a corresponding image information. The light-field projector display 100 can further comprise projection optics 4 configured to project the modulated light fields 101 along a reference projection axis 170. The projected modulated lightbeams 101 form virtual viewpoints 20 at a pupil exit plane 6 and form virtual images 40 in a projection image plane 400. Each virtual image 40 reproducing the reference SLM image pattern 60 from the SLM 3.

[0017] Each virtual viewpoint 20 can be represented as a virtual pinhole camera through which each virtual image 40 is projected on the projection image plane 400. The virtual images 40 can then be computed by using virtual pinhole cameras for imaging a virtual scene.

[0018] The projection image plane 400 corresponds to a projection plane in which the virtual image 40 is projected. The projection image plane 400 is at a projection distance d that is between the pupil exit plane 6 and infinity. For our purposes usually the virtual image plane 40 is between 2 m and 6 m. In other embodiments, the projection distance d can be a "medium" projection distance d, for example a projection distance d between 1 and 2 cm, such as about 1.5 cm. In other embodiments, the projection distance d can be a "near" projection distance d, for example a projection distance d of 40 cm or 30 cm or less. The virtual image 40 can be projected in the projection image plane 400 with varied refraction prescriptions.

[0019] The projected image 40 or plurality of projected images 40 in the projection image plane 400 forms a virtual scene.

[0020] Fig. 2a shows a representation of a virtual pinhole camera where the virtual image 40 of a virtual scene 30 is projected on the projection image plane 400 through the virtual pinhole 20, along the reference projection axis 170. Fig. 2b shows a two-dimensional representation of the virtual pinhole camera of Fig. 2a.Creal3-15-PCT1

[0021] Fig. 3a illustrates an example of the light field projector 100 in the absence of correction. Fig. 3a shows the reference SLM image pattern 60 of one of the projected virtual images 40. The reference SLM image pattern 60 comprises a plurality of image components 601. One of the image components 601 (represented in black) is aligned with the reference projection axis 170 and, viewed from the virtual viewpoint 20, appears as if it was focused at infinity.

[0022] Fig. 3b illustrates an example of the light field projector 100 generating a refractive correction. The SLM 3 is configured to provide a corrected SLM image pattern 61 comprising the refractive correction, such that the virtual images 40 projected by light field projector 100 comprises a refractive correction. In the example of Fig. 3b, a negative refractive correction is generated. The corrected SLM image pattern 61 corresponds to an SLM image pattern that is shifted in the plane of the SLM 3 relative to the reference SLM image pattern 60 as a function of said at least one refractive correction parameter. The corrected SLM image pattern 61 can correspond to an SLM image pattern that is rotated in the plane of the SLM 3 relative to the reference SLM image pattern 60 as a function of said at least one refractive correction parameter.

[0023] In Fig. 3b, the image components 601 (represented in black) is not aligned with the reference projection axis 170. Viewed from the virtual viewpoint 20, the image component 601 appears as if it was focused at a finite projection distance d at virtual focal point 25, providing the negative refractive correction.

[0024] The light-field projector display 100 can comprise an SLM control unit 82 (see Fig. 1) configured to control an SLM signal 85 which creates the SLM reference image pattern 60 and the corrected SLM image pattern 61 on the SLM 3. The light-field projector display 100 can further comprise an illumination control unit 81 configured to control an illumination signal 83 which powers specific point light sources 10 of the light device 1 in a specific time dependent fashion. The SLM control unit 82 can beCreal3-15-PCT1synchronized with the illumination control unit 81 via a synchronization communication signal 84. In particular, the illumination control unit 81 can control the light device 1 to sequentially illuminate the plurality of point light sources 10 and sequentially emit the plurality of light fields 101.

[0025] International Application No. W02023052809, entitled "Lightfield projector generating optically corrected virtual images and method of generating corrected virtual images by using the light field projector", filed on Sept. 28, 2021, and which is hereby incorporated by reference, describes features of the light-field projector display 100 for this purpose.

[0026] Fig. 4 shows a system (hereafter called testing device) 500, according an embodiment and comprising the light-field projector display 100. The testing device 500 is configured to be used to determine refraction features of one or both eyes of a user. For instance, the testing device 500 is configured to test a user's visual perception, determining an eye parameter of a user, or determine a visual refraction value of a user.

[0027] In the illustrated example, the testing device 500 comprise two light-field projector displays 100. In this configuration, the virtual images 40 generated by one of the projector displays 100 can be projected along the reference projection axis 170 in one of the user's eyes. The virtual images 40 generated by the other the light-field projector display 100 can be projected along the reference projection axis 170 in the other user's eye. Alternatively, the testing device 500 can comprise a single light-field projector display 100. In this configuration, the virtual images 40 can be projected along a single reference projection axis 170 in one or both eyes of the user.

[0028] The projection optics 4 can comprise optical elements and / or an eyepiece (exit lens) configured to maximize the efficacy and user experience of the testing process. For example, the projection optics 4 can comprise a binocular device.Creal3-15-PCT1

[0029] The testing device 500 can further include a HID 503 configured to allow a user to interact with the virtual image(s) 40 in a projection image plane 400 as will be explained below. The HID can comprise a clicker wheel, joystick, pushbuttons, or touchpad, a keyboard, a mouse, a joystick. The HID 503 can further comprise a microphone or set of microphones to record voice or similar vocal commands. The HID 503 can be configured to communicate with the light-field projector display 100 in a wired manner or wirelessly.

[0030] In one aspect, the testing device 500 comprises an eye tracking device (or pupil tracking device) 506. The eye tracking device 506 can be configured to be used to allow the user to interact with the light-field projector display 100, for example by indicating the sharpest (most in focus) object on the projection image plane 400. The eye tracking device 506 can be configured to verify in real-time the position and movements of the user's eye, ensuring the user sees the light-field projector display 100 at optimal position, and automatically align the light-field projector display 100 with the user's eyes. The eye tracking device 506 can be further configured to determine incorrect position of user's eye. The eye tracking 506 can be further configured to determine the size of the pupil of the user's eye and determine the number of illumination points the pupil captures.

[0031] In an embodiment, the testing device 500 can further comprise an emitting and display device 507. The emitting and display device 507 can comprise a speaker, a headphone or a similar sound emitting or vocalizing device, or a visual emitting device. The emitting and display device 507 can be configured to guide, direct the user through the procedure or setup process or similar, provide feedback, encouragement or similar, alert support staff or any other person to provide help, support or similar, announce results or any other information, device damage, device status and similar.Creal3-15-PCT1

[0032] In an embodiment, the testing device 500 can include connection 508 to computer or device networks (wired or wireless).

[0033] The testing device 500 may include a data storage unit 509 to store unit information, calibrations, procedures or any of the data described below, or any other information. The storage unit 509 can comprise a region of a physical memory storage used to at least temporarily store an input signal.

[0034] The system 500 further comprises a processing module 510.

[0035] In one aspect, the testing device 500 can include a sensor device 51 including one or more sensors. The sensor device 51 can be connected directly to the light-field projector display 100 or connected wirelessly or over a computer network. The sensor device 51 can be configured to measure ambient light, ambient sound, movement, shock or similar. The sensor device can be further configured to sense, record, evaluate and otherwise use environment data, record conditions and alert, storage conditions, or risk of device damage.

[0036] In an embodiment, the testing device 500 can include a biometric authentication device 52 configured to identify the user. The biometric authentication device 52 can comprise an iris scanner or similar reader of biological marks of the user. The biometric authentication device 52 can be used to recall previous measurements, providing unique identification of measurements.

[0037] The testing device 500 can comprise an adjustment device 511 configured to perform mechanical adjustments, manual or electronic for prism angles, providing an extended range of diopter and prism measurements. The adjustment device allows for a comprehensive evaluation of the user's visual performance, including assessments of binocular vision and prismatic adjustments. In order to move the zero point, for example around the rough refraction prescription.Creal3-15-PCT1

[0038] The testing device 500 can be embodied as either a freestanding unit, a tabletop unit, or a headset device. As a headset, the light-field projector display 100 can be securely affixed to the user's head using straps, bands, belts, or similar means or simply held in place by the user's hands.

[0039] Fig. 5 shows an example of the testing device 500 comprising two projector displays 100 arranged as a binocular tabletop device comprising a base 504 and a supporting column 505 supporting the projector displays 100 and that can be adjusted in height. The tabletop device 504 further comprises (that can be adjusted in height) a forehead rest 501 and / or a chinrest 502 to ensure accurate and consistent positioning of the user's head relative to the light-field projector display 100. The testing device 500 can further comprise the HID 503. In the example of Fig. 5, the HID 503 is mounted on the tabletop device 504 and is arranged as a wheel and clicker. The bae 504 can comprise control electronics.Method for determining a refraction

[0040] The present disclosure further concerns a non-transitory computer-readable medium comprising digital instructions to be implemented by a processing module 510 comprised in the testing device 500 to perform a method to assess a refraction correction of a user.

[0041] The method comprises using the testing device 500 to perform at least a test cycle comprising (see Fig. 6): a projection step (M1), comprising sequentially projecting a plurality of projection image planes 400, each comprising at least one virtual image 40; a correction step (M2), comprising controlling the SLM control unit 82 to provide a SLM image pattern 61 configured to add at least one refractive correction to each of said at least one virtual image 40; and a selection step (M3), comprising using the HID 503 to select, in at least one of said plurality of projection image planes 400, at least one virtual image 40 that the user perceives as having the best image subjectiveCreal3-15-PCT1quality, or a characteristic of said at least one virtual image 40 that the user recognizes, and inputting in the data storage unit 509 the refractive correction of the selected at least one virtual image 40 as a best refractive correction.

[0042] During the selection step, the virtual image 40 that the user perceives as having the optimal subjective quality can correspond to the virtual image 40 that appears the sharpest.

[0043] The virtual images 40 can be displayed to the user by sequentially illuminating the SLM 3 by the light fields 101 such as to generate at least one modulated light field 101 configured to form said at least one virtual image 40, and sequentially projecting said at least one modulated light field 101 to project the virtual images 40 comprising said at least one refractive correction.Over-minusinq

[0044] In one aspect, the method can comprise using the testing device 500 to perform an over-minusing test. The testing device 500 is used with uncorrected acuity to ascertain the level of visual capability of the user. Here, the virtual images 40 can be shifted in the projection image plane 400 from a far projection distance d (for example beyond 6 m) to a near projection distance d (for example 30 cm or less), such as to represent different refractive values for correction, and such that the user can recognize the first moment the virtual images 40 become legible. Preferably, the virtual images 40 is shifted from far to near projection distance d. The projection image plane 400 can further comprise virtual images 40 that appear distant from the user within peripheral imagery on the projection image plane 400 to encourage the user to maintain accommodation on distant objects to avoid over accommodation.

[0045] During this step, an overminused refraction prescription can be detected by adding positive diopters, typically +0.50. This allows forCreal3-15-PCT1blurring the virtual images 40 such that they appear father to compensate for correction from the user's brain that would like to make the virtual images 40 appear closer. In other words, this allows for minimizing possible accommodation with the testing device 500. It further allows for verifying whether the user can still accurately discern the virtual images 40 with the same visual acuity. If it is the case, it indicates that the initial refraction prescription was overminused. The over-minusing test allows for identifying the least negative (or most positive) corrective sphere.Static liqht-field refraction procedure

[0046] In one embodiment, the method for determining a refraction eye parameter can comprise a static light-field refraction procedure.

[0047] A virtual scene can comprise a single virtual image 40 that can be projected at a specific location on the projection image plane 400 (single image scene). Alternatively, a virtual scene can comprise a plurality of virtual images 40 simultaneously projected at different locations on the projection image plane 400 (multiple-image scene). In the latter case, the location of each of the simultaneously projected virtual images 40 can remain the same for all the sequentially projected virtual scenes.

[0048] Each virtual image 40 can comprise any one of an optotype, a pattern, a shape.

[0049] Fig. 7 shows an example of a projection image plane 400 comprising simultaneously projected five virtual images 40 and forming a virtual scene 30.Creal3-15-PCT1Static light-field refraction procedure: spherical power determination

[0050] In one aspect, the static light-field procedure comprises a spherical power determination procedure, wherein the refractive correction comprises a spherical power correction.

[0051] During the correction step, the sequential projection of projection image planes 400 can be performed with increasing or decreasing the spherical power correction of the virtual images 40. Decreasing the spherical power allows for counteracting user overaccommodation. For example, the spherical power correction of the virtual images 40 can be increased or decreased by increments of one diopter (1 D) or smaller. For example, the spherical power correction can be incrementally increased or decreased until an interval of 0.25 diopter (0.25 D) is reached.

[0052] In the case of the multiple-image virtual scene, each projection image plane 400 can comprise a plurality of virtual images 40 having different spherical power corrections. For example, each projection image plane 400 can comprise virtual images 40 with increasing or decreasing spherical power corrections from left to right or top to bottom in the projection image plane 400.

[0053] During the selection step, the best refractive correction comprises the optimal spherical power correction of the selected virtual image 40 that provides the perceived optimal subjective quality.Static light-field refraction procedure: cylinder power determination

[0054] In another aspect, the static light-field procedure comprises a cylinder power determination procedure, wherein the refractive correction comprises a cylinder axis correction.Creal3-15-PCT1

[0055] In the cylinder power determination procedure, the correction step comprises increasing or decreasing the cylinder axis correction of the virtual images 40 of the projection image planes 400. For example, the cylinder axis corrections can range between 0° and 180° and can be increased or decreased by increments of between 1° and 30°.

[0056] In the case of the multiple-image virtual scene, each projection image plane 400 can comprise virtual images 40 having different cylinder axis corrections. For example, each projection image plane 400 can comprise virtual images 40 with increasing or decreasing cylinder axis corrections from left to right or top to bottom in the projection image plane 400.

[0057] During the selection step, the selected virtual image 40 provides the refractive correction.

[0058] During the selection step, it may happen that no virtual image 40 is selected if none of the projected virtual images 40 has an optimal subjective quality.

[0059] The best cylinder power correction can comprise the optimal cylinder axis correction determined during the cylinder power determination procedure and best spherical power correction that was determined during the spherical power determination procedure above.

[0060] In some embodiments, the selection step can comprises using the HID 503 to adjust (for example increase or decrease) the refraction correction (for example spherical power or cylinder axis correction) of the virtual image 40 in at least one of the projection image plane 400 of the projected sequence.

[0061] The virtual image 40 can correspond to a circular spoked wheel. For example, in the case the projection image plane 400 comprises theCreal3-15-PCT1plurality of virtual innages 40, six virtual innages 40 can be simultaneously projected.Static light-field refraction procedure: coarse and fine tuning of cylinder power determination

[0062] The cylinder power determination procedure can comprise a first step of determining a "coarse" best cylinder axis correction and a "fine" best cylinder axis correction.

[0063] During the first step, the correction step is performed by increasing or decreasing the cylinder axis correction by "coarse" increments, for example between 10° and 30°. During the selection step, the best refractive correction comprises a "coarse" optimal cylinder axis correction of the selected virtual image 40 that provides the perceived optimal subjective quality.

[0064] During the second step, the correction step is performed by increasing or decreasing the cylinder axis correction by "fine" increments, for example between 1° and 5°. The correction step can be initiated by applying the "coarse" best cylinder axis correction to the virtual image(s) 40. During the selection step, the best refractive correction comprises a "fine" best cylinder axis correction of the selected virtual image 40 that provides the perceived optimal subjective quality.

[0065] The best refractive correction comprises the "fine" best cylinder axis correction. The best refractive correction can further comprise the best spherical power correction determined in the previous spherical power determination procedure.Creal3-15-PCT1Static light-field refraction procedure: second eye examination

[0066] The static light-field refraction procedure can be performed for one eye of the user and then repeated for the other user's eye.Static light-field refraction procedure: binocular power procedure

[0067] The static light-field refraction process can further comprise a binocular power procedure whereby the refraction correction is performed for both eyes simultaneously. During binocular power procedure, the best binocular power required for clear and comfortable vision correction is determined. In the binocular power procedure, the correction step can comprise adding varying refractive power, for example ranging between ±0.25 D or between ±0.5 D for over-refraction.

[0068] During the projection step, the virtual images 40 can be configured to form duochrome red / green projection image planes 400. The projection image planes 400 can be shown sequentially to both user's eyes (individually and together) for comparison.

[0069] The binocular power procedure allows for balancing the refractive prescription, i.e., to ensure the refraction prescription is not over minused. Indeed, a virtual images 40 in green will appear sharper such that the users' eye tends to accommodate and is not relaxed.Static light-field refraction procedure: prismatic evaluation and close vision correction procedure

[0070] The static light-field refraction process can further comprise a prismatic evaluation and close (reading) vision correction procedure, wherein the projection step comprises simultaneously projecting a plurality of the virtual images 40 that moves within the projection image plane 400, for example horizontally or vertically in the projection image plane 400.Creal3-15-PCT1For example, at least one of the virtual images 40 can move relative to the other virtual images 40 to ascertain binocular fusion ability.

[0071] A Light-field Maddox Rod / Maddox Wing simulation can be used to identify the user's full stereoscopic prescription needs.

[0072] Close or reading vision can be evaluated with the correction step comprising spherical power corrections that are added to the virtual images 40, in addition to the best spherical power correction and the best cylinder power correction determined during the spherical power determination procedure and the cylinder power determination procedure, respectively. Moreover, the projection image planes 400 can be arranged such as to be at close distance to the user's eyes when using the testing device 500, for example, at a projection distance d of 40 cm or 30 cm or less.Static light-field refraction procedure: corrections verification procedure

[0073] The static light-field refraction process can further comprise a corrections verification procedure, wherein during the projection step, the virtual images 40 projected on the projection image plane 400 form a standard Snellen chart. In other words, the virtual images 40 are configured to display symbols corresponding to the ones of a standard Snellen chart. During the correction step, the best refractive correction, including among others the best spherical power correction and the best cylinder power correction, and determined during the spherical power determination and cylinder power determination procedures are applied to the virtual images 40.

[0074] During the selection step, the user can use the HID 503 to select the symbol(s) on the standard Snellen chart that he perceives as having the optimal sharpest and / or best legibility.Creal3-15-PCT1

[0075] In one aspect, the corrections verification procedure can comprise a step of comparing the best refractive correction to a previously best refractive correction (a previous refraction prescription).

[0076] The corrections verification procedure can further comprise projecting the sequence of virtual images 40 such as displaying several patterns comprising a refractive correction varying from +0.25 D to +0.50 D. The selection step the comprises selecting the sharpest pattern. This allows for minimizing the risk of overminus correction. amic liqht-field refractionDynamic light-field refraction procedure: best spherical power determination

[0077] A dynamic light-field refraction procedure can comprise the best spherical power determination (best vision sphere refraction) procedure, wherein the projection step comprises projecting the sequence of projection image planes 400, each projection image plane 400 comprising a plurality of virtual images 40.

[0078] During the projection step, the plurality of virtual images 40 can be simultaneously projected at different locations that remain unchanged from one projection image plane 400 to another, such as to produce fixed virtual scenes in time. Alternatively, plurality of virtual images 40 can be simultaneously projected at locations that vary from one projection image plane 400 to another, such as to produce moving virtual scenes in time.

[0079] During the correction step, different spherical power corrections are applied to the virtual images 40 simultaneously projected on the projection image plane 400. The spherical power corrections applied to the virtual images 40 can further vary from one projection image plane 400 to another.Creal3-15-PCT1

[0080] In one aspect, the spherical power corrections vary from one projection image plane 400 to another with an increment that can be as small as 0.004 D and can be increased between each projection image plane 400. For example, the virtual scenes can be sequentially projected with a projection frequency of 1 / 30th of a second such that the spherical power correction is incremented every 1 / 30th of a second.

[0081] During the selection step, the user can use the HID 503 to select the virtual images 40 in one of the projection image planes 400 that he perceives as the sharpest and / or as having the best legibility. The refractive correction of the selected virtual images 40 in the projection image plane 400 corresponds to the best spherical power. The selection step can further comprise inputting the best spherical power in the data storage unit 509.

[0082] In one aspect, the selection step can comprise using the HID 503 to select the virtual images 40 in one of the projection image planes 400 for which the user

[0083] The selection step can further comprise using the HID 503 to input to select the virtual images 40 that the user perceives as having the best image subjective quality, where the best image subjective quality includes a characteristic of the virtual image 40. The characteristic can include the shape and / or size of the virtual image 40. The characteristic can further include the orientation of the virtual image 40, for example in the case the virtual image 40 comprises a letter (such as the letter "E") or a Landolt ring.

[0084] By varying the spherical power correction with small increments, it is possible to obtain a refractive power accuracy of below 0.25 D.

[0085] The best spherical power determination procedure can be gamified such that the user is rewarded (sounds, points, etc.) during the selection step.Creal3-15-PCT1

[0086] In an embodiment, the method comprises a plurality of test cycles. The method can further comprises using the processing module 510 to calculate an average best refractive correction based on the best refractive corrections inputted in the data storage unit 509 at each test cycle.Dynamic light-field refraction procedure: determining cylinder specifications - Cylinder power and cylinder axis determination

[0087] The dynamic light-field refraction procedure can further comprise a cylinder power and cylinder axis correction determination procedure comprising, during the projection step, projecting the sequence of projection image planes 400 comprising the virtual images 40 having a circular shape.

[0088] During the correction step, cylinder axis correction varies between 0° and 180°, for example from 0° to 180° and then from 180° to 0°. The cylinder axis correction can be randomly or sequentially applied to the virtual images 40. For example, the cylinder axis correction can be applied to the virtual images 40 with values varying from 0° to 180°. The variation of cylinder power correction can be performed with increments of 0.25 D, 0.5 D, or 1.0 D.

[0089] During the selection step, the HID 503 is used to select at least one of the virtual images 40 when the user identifies the moment when any one of the virtual images 40 is sharpest. The best refractive correction comprising the best cylinder axis and power correction is then inputted to the testing device 500.

[0090] The best refractive correction can further comprise the best sphere refraction determined during the best spherical power determination procedure described above.Creal3-15-PCT1

[0091] In an embodiment, the method comprises a plurality of test cycles. The method can further comprises using the processing module 510 to calculate an average best average best cylinder axis and power correction, based on the best average best cylinder axis and power correction corrections inputted in the data storage unit 509 at each test cycle.

[0092] In the case the sum of squared errors from the average best cylinder axis and power correction is greater than a predetermined value, the average best cylinder axis and power corresponds to the absence of astigmatism. In that case, the cylinder axis correction determination procedure can be terminated and an input signal set to a zero value can be inputted in the testing device 500, indicating the absence of astigmatism.

[0093] In the contrary, the cylinder axis and power correction determination procedure can further comprise performing the correction step where a fixed cylinder axis correction is applied to the virtual images 40 and a varying cylinder power back and forth between a predetermined interval.

[0094] The selection step can be performed by inputting the best refractive correction comprising the best cylinder axis and power correction to the testing device 500 when the user identifies the moment when any one of the virtual images 40 is sharpest. The selection step can be repeated such as to input a plurality of best refractive corrections and an average best refractive correction, corresponding to an average best cylinder axis and power, can be calculated by the processing module 510 and inputted to the data storage unit 509.

[0095] Alternatively, the cylinder axis correction determination procedure, the virtual image 40 can comprise a rotating image, for example a rotating wheel with spokes, or clock face with moving hands.Creal3-15-PCT1

[0096] For example, the projection step can comprise rotating the spokes or hands of the virtual image 40 such as it makes a complete 360° tour around its axis. The rotation rate can be between 1 s and 10 s, or between 3 s and 5 s, for example 4 s.

[0097] During the correction step, the cylinder axis correction can be varied with the rotation angle of the rotating virtual image 40. For example, the spokes and / or hands of the virtual image 40 comprising a rotating wheel with spokes or a clock face, can be varied relative to the angle of the spoke and hand.

[0098] During the selection step, the HID can be used to input to the data storage unit 509 the refractive correction corresponding to the best cylinder axis correction when the user identifies the moment when the rotating spoke, or hand is at its sharpest.

[0099] The virtual scenes 30 can be gradually changed by applying the refractive power correction such that the change in cylinder power correction between the virtual images 40 is decreased such as to get to a refractive power accuracy of 0.25D and a precision of the cylinder axis correction up to 1 ° to 5°, depending on the cylinder power value.

[0100] The cylinder power and angle correction determination procedure can be repeated for the first and second eye of the user.

[0101] For binocular vision, prismatic evaluation and close (reading) vision and final verification, the binocular power procedure and prismatic evaluation and close vision correction procedure described above can be used.Creal3-15-PCT1Dynamic light-field refraction procedure: cube gradient light-field refraction

[0102] In an embodiment, the dynamic light-field refraction procedure can further comprise a cube gradient light-field refraction procedure, whereby the user is allowed to self-assess refractive powers by interacting with a digital environment projected by the testing device 500.

[0103] During the projection step, the plurality of virtual images 40 are spatially distributed on the projection image plane 400 to form a 3D pattern. For example, the virtual images 40 be arranged to form a 3D grid arrangement (such as a Rubik's cube). In the example shown in Fig. 8, the 3D grid arrangement forms a grid arrangement comprising 3 x 3 x 3 virtual images 40, or a grid arrangement comprising 4 x 4 x 4 virtual images 40.

[0104] During the correction step, different refractive corrections can be applied to the virtual images 40. The different refractive corrections can be applied to the virtual images 40 in relation to their position in the 3D virtual scene 30. For example, the spherical power corrections applied to the virtual images 40 can increase along the one axis of the 3D virtual scene 30 (for example along the y axis). The cylindrical power corrections applied to the virtual images 40 can increase along another axis of the 3D virtual scene 30 (for example along the x axis). The cylinder axis corrections applied to the virtual images 40 can increase along yet another axis of the 3D virtual scene 30 (for example along the z axis). The correction and selection steps can be performed for the refractive corrections increasing along the different axis of the 3D virtual scene 30 with a first increment.

[0105] During the selection step, the HID 503 can be configured to select at least one of the virtual images 40 (for example, the sharpest virtual image(s) 40) by moving a cursor through the 3D pattern. To that end, the HID 503 can be configured as a touchscreen, pointer, or cursor adapted to indicate a specific position corresponding to a virtual image 40 in the 3D virtual scene 30.Creal3-15-PCT1

[0106] In an embodiment, the method comprises a plurality of test cycles. During the projection step of the subsequent test cycles, the at least one of the virtual images 40 selected during the previous rest cycle can be repositioned in the center of the 3D pattern. During the projection step of the subsequent test cycles, the correction step can comprise using a second increment that is smaller than the increment used in the preceding test cycle.

[0107] For binocular vision, prismatic evaluation and close (reading) vision and final verification, the binocular power procedure and prismatic evaluation and close vision correction procedure described above can be used.

[0108] The testing device 500 allows for testing the refraction properties of a user's eye rapidly and without requiring individually changing conventional physical lenses.First acuity liqht-field refraction game

[0109] The method can further comprise a first acuity light-field refraction game configured to measure a user's eye acuity by using the testing device 500 to detect when the user can recognize a symbol projected by the testing device 500. The first acuity light-field refraction game can be used to test the actual vision of the user and is not destined to make any correction to the user's vision.Initiation

[0110] The first acuity light-field refraction game can comprise an initiation procedure aimed at ensuring that the user's eye is positioned at a suitable distance from the projection optics 4. Otherwise, the user will never see the virtual images 40 sharp, whatever the correction. Optionally,Creal3-15-PCT1T1 the game can start with a user reaction time determination sequence (see "User reaction time compensation below).Acuity mode

[0111] The first acuity light-field refraction game can comprise an acuity mode procedure wherein, during the projection step, the projection image plane 400 comprise a plurality of virtual images 40, each virtual image 40 comprising a random symbol that can be rotated or not. For example, the random symbol can comprise a number, Landolt ring, the letter E, etc.

[0112] The projection step can be repeated such as to comprise a plurality of iterations of the projection steps. During a first iteration, the virtual images 40 can have a size corresponding to 20 / 10 of the Snellen chart or similar (pictures, images, cars, houses, ...).

[0113] During the subsequent iterations of the projection step, the size of the virtual images 40 can be increased, for example up to a size corresponding to the 20 / 100 size of the Snellen chart. The increase in size of the virtual images 40 can be regular or variable. The increase rate can depend on an external factor, such as the best refractive correction determined during the first iteration of the projection step, or such as the age of the user. In one example, the first acuity light-field refraction game comprises ten iterations of the projection step.

[0114] During the selection step, the HID 503 is used to select at least one of the virtual images 40 that the user can recognize, i.e., identify and / or discern without ambiguity. The recognition can be based on the virtual image 40 shape as such and / or characteristics of the virtual image 40, such as a rotation of the virtual image 40. The best refractive correction corresponding to the refractive correction of the selected virtual image 40 is inputted to the testing device 500. The HID 503 can be further used to input to the testing device 500 a corresponding input signal comprising anCreal3-15-PCT1indication of the recognized virtual images 40 and / or the recognized characteristics of the virtual image 40.

[0115] The processing module 510 can be configured to determine if the recognition was correct or not as the user correctly states what the object is, from the input signal and deliver a corresponding status. The emitting and display device 507 can be configured to indicate the status. For example, the emitting and display device 507 can comprise a display configured to flash a color (red or green) depending on the status.

[0116] In an embodiment, the method comprises a plurality of test cycles. The processing module 510 can then be further configured to discard incorrect recognitions and calculate the best refractive correction by only using correct recognitions.

[0117] The processing module 510 can be further configured to calculate the best refractive correction only if the ratio of correct to incorrect recognitions is above a threshold value. For example, the threshold value can correspond to 33% or above. In one aspect, the threshold value can be used to re-run the method (acuity mode procedure) using the best refractive correction as the refractive correction added during the correction step. This allows for avoiding performing the method with too many different refractive corrections (spherical powers corrections).

[0118] The processing module 510 can be further configured to process the recognition data. For example, the processing module 510 can be configured to discard recognitions that were too fast or too slow as they might indicate a loss of attention or other problems. The processing module 510 can be configured to discard outlier recognition data, for example using mean and standard deviation. The processing module 510 can be configured to discard correct recognitions that occurred with a recognition time (see below) of about the same duration as when most recognition were incorrect recognitions (theoretically, a user always hittingCreal3-15-PCT1a single key could still score some good hits). Similarly, a mistakenly usage of the HID 503 could score as a correct recognition.

[0119] The number of correct recognitions can be viewed as corresponding to the user's acuity. To that end, the emitting and display device 507 can be configured to show the number of correct recognitions.Recognition time

[0120] The processing module 510 can be further configured to determine a recognition time of a user, i.e., the time elapsed between the projection of one of the projection image planes 400 and the time the user selects, using the HID 503, said at least one virtual image 40 for which he has recognized said characteristic.

[0121] The recognition time can be used as a compensation constant to determine actual time when the user recognizes the virtual image 40 and to compensate a possible lag between the virtual image 40 recognition and the interaction with the HID 503.

[0122] In a possible configuration, the acuity mode procedure can comprises an evaluation step comprising projecting virtual images 40 corresponding to the largest virtual image 40 from a range of virtual image 40 sizes (for example different sizes of the Snellen chart). Using the HID 503, the recognition time can be determined depending on the symbol size. The evaluation step can be performed prior to, or at the end of, the acuity mode procedure. In the latter case, the evaluation step can be used to evaluate change in the recognition time.Refraction prescription mode

[0123] In an embodiment, the method comprises a plurality of test cycles. During the first test cycle, the correction step can comprise applyingCreal3-15-PCT1a predetermined refractive correction value to said at least one virtual images 40. The predetermined refractive correction value can correspond to the result of autorefraction, a previous refraction prescription, an external input, or any other input or 0 if not known. The predetermined refractive correction value can be varied in the subsequent test cycles, for example in the increments of + / - 2 D.

[0124] The selection step can be performed as described for the acuity mode procedure of the first acuity light-field refraction game. The processing module 510 can be configured to determine a user recognition time (reaction time) and to use the best refractive correction inputted to the testing device 500 to track the recognition times and applied refraction prescription.

[0125] The correction step can further comprise shifting (increasing or decreasing) the predetermined refractive correction based on the recognition time, for example to a predetermined refractive correction corresponding to a statistically faster recognition time. The increment by which the predetermined refractive correction is shifted may also depend on the recognition time. For example, the increment can be varied in order to increase the recognition time. For instance, the increment can be increased from 0.25 D to 0.5 D since the user takes too much time to recognize the virtual image 40 when the refractive correction is varied by a 0.25 D increment. The refractive correction can then be decreased in the subsequent repeated correction steps by increment from ±2 D to ±0.25 D, for example for 15 to 25 of repeated correction steps.

[0126] During the repeated correction steps, the predetermined refractive correction can be shifted until the recognition time does not statistically differ. The plurality of best refractive corrections determined for each repeated correction steps can be inputted to the testing device 500 and stored in the data storage unit 509. The plurality of best refractive corrections can then be used (for example in the processing module 510) to define a function between the recognition time and the applied refractiveCreal3-15-PCT1correction. A minimum of the function represents the best refractive correction. The minimum of the function can be determined mathematically or statistically. Alternatively, the function can be manually evaluated.

[0127] Since the refraction prescription mode procedure allows for determining the best refractive correction by using the minimum of a function, there is no need to determine the user's recognition time. More generally, the first acuity light-field refraction game is not prone to overminusing.Second acuitv liqht-f ield refraction qame

[0128] The second acuity light-field refraction game can be used for gamified evaluation of myopia of a user. During the projection step, the projection image plane 400 comprise a plurality of virtual images 40 projected at different optical distances.

[0129] For example, a first subset of said plurality of virtual images 40 are projected at a far projection distance d, for example a projection distance d of more than 6 m. For example, the scene created by the projection image plane 400 can show a corridor or any other scene extending into a distance, tunnel, or open space like meadow or any other landscape, or even imaginary landscape. An important feature of the projection image plane 400 is an unobstructed view into the distance.

[0130] Further during the projection step, the light-field projector display 100 can be configured to project a second subset of said plurality of virtual images 40 at a medium projection distance d, for example a projection distance d between 6 m to near 30 cm. The virtual image 40 at the medium projection distance d can be configured to attract attention of the user.Creal3-15-PCT1

[0131] In one example, the second subset comprise a single medium virtual image 40. The medium virtual image 40 can comprise a representation of an animal or cartoon character. The size of the medium virtual image 40 can be chosen so that it occupies about the same angular area of the user's visual field regardless of distance (i.e., objects further are larger).

[0132] In some aspects, the medium virtual image 40 can be configured to move across the projection image plane 400 and user's field of vision. In this case, it is important that the medium projection distance d remains substantially constant. For example, the distance between the medium virtual image 40 and the user's eye should remain substantially constant.

[0133] In some aspects, the medium virtual image 40 can advantageously comprise only one recognizable characteristic. For example, if the characteristic to be recognized is a rotation of the medium virtual image 40, then the medium virtual image 40 should not comprise other characteristics such as a movement of the medium virtual image 40, in order to avoid confusing identification and information.

[0134] The projection step can comprise increasing the size of the medium virtual image 40 if the user is unable to recognize the correct characteristics. The size of the medium virtual image 40 can be increased by increments that are the same or similar to the ones used in Snellen chart in the acuity mode procedure of the first acuity light-field refraction game.

[0135] The testing system 500 can be configured to trigger a positive indication and make the medium virtual image 40 disappear from the projection image plane 400 when the characteristics is correctly recognized.

[0136] In an embodiment, the method comprises a plurality of test cycles. The projection distance d of the medium virtual image 40 generated in the subsequent test cycles can be varied, for example by increments of 0.2 D, 0.25 D or 0.5 D.Creal3-15-PCT1

[0137] The range of the projection distance d of the medium virtual image 40 can be limited depending on previous recognitions by the user. For example, if the users struggled to identify the medium virtual image 40 at a projection distance d beyond 2 D, the medium virtual images 40 projected in the further projection steps can be projected at a projection distance d less than 2 D.

[0138] The processing module 510 can be configured to use the best refractive corrections stored in the data storage unit 509 during the plurality of test cycles to determine the projection distance d of the medium virtual image 40 for which the user has inputted the recognized characteristics, the number of repetitions of the projecting and selection steps and possibly the recognition time. From the determined projection distances d, a limit projection distance diim at which the user is no longer able to recognize the medium virtual images 40 can be evaluated. The limit projection distance diim can be used to estimate the user's refraction prescription.

[0139] The method can further comprise a dynamic diopter recognition game (DDR) allowing the user to self-assess its refraction prescription by rapidly interacting with segmented images.

[0140] During the dynamic diopter recognition game, the projection step comprises simultaneously projecting the projection image planes 400, wherein each projection image plane 400 comprises a plurality of subsets of virtual images 40, each subset being arranged in a segment 401-404 of the projection image plane 400 (see Fig. 9). The correction step comprises controlling the SLM control unit 82 to provide a subset of virtual images 40 in one of the segments 401-404 with a different refractive correction the refractive correction applied to the other subsets of virtual images 40 in the other segments 401-404. The refraction correction can be a dioptric property such as sphere power, cylinder power, or cylinder axis.Creal3-15-PCT1

[0141] During the selection step, the HID 503 can be used to select the segment 401-404 of the projection image plane 400 containing the sharpest virtual image 40. The HID 503 can comprise a touchpad segmented into quadrants corresponding to the segments 401-404, keys, joystick or other input to select the segment 401-404 containing the sharpest virtual images 40. The refractive correction corresponding to the selected segment 401- 404 can be stored in the data storage unit 509.

[0142] The refraction correction applied to the virtual images 40 in the different segments 401-404 can be such that when the user uses the testing device 500, the virtual images 40 appear to move from a far to a near projection distance d, giving the impression of virtually approaching the user. The refraction correction applied to the virtual images 40 can be such that when the virtual images 40 get at a near projection distance d (for example 30 cm), the virtual images 40 disappears. After a virtual image 40 has disappeared, another virtual image 40 can be projected with the virtual approach movement in rapid succession.

[0143] The virtual movement of the virtual images 40 can be fast. For example, the virtual images 40 can virtually move from a far projection distance d (such as 6 m) to a near projection distance d (such as 30 cm) in 5 s or less).

[0144] The speed of the virtual approach movement can increase in time (from one projected projection image plane 400 to another) based on user recognition time. Since the virtual images 40 are replaced in rapid succession, for example without delay between virtual the projection of a subsequent virtual image 40, the user must react promptly to select the segment 401-404 of the projection image plane 400 containing the sharpest virtual image 40.

[0145] The testing device 500 can comprise an adaptive algorithm running on the processing module 510, wherein the adaptive algorithm is configured to vary the refractive corrections (dioptric properties) applied toCreal3-15-PCT1the virtual innages 40 as a function of the user selections, ensuring a more accurate determination of the best refractive power. Randomness in the applied refractive corrections can be introduced occasionally to prevent predictable patterns and overminusing.

[0146] The testing device 500 can be further configured to provide auditory cues, like music or sound effects, to encourage prompt reactions (for example via the emitting and display device 507).

[0147] The testing device 500 can be further configured to provide specific visual cues to the virtual images 40. For example, the specific visual cues can comprise colors (such as red / green) to assist in determining the refractive correction (for example having the same dioptric powers, but one using green and the other red).

[0148] The testing device 500 can be further configured to detect astigmatism. To that end, the virtual images 40 can comprise distinct line patterns at different angles (for example all segments containing lines in the same pattern and same sphere power, but each segment with different cylinder properties). The choice of specific images or visual cues is critical to accurate assessments.

[0149] Final result in terms of prescription and acuity can be verified by other methods or using a physical trial frame after the game.

[0150] The game is explicitly paced to prevent overaccommodation and overthinking on the side of the user.Scheiner principle

[0151] The method can further comprise a Scheiner principle refraction procedure. This procedure allows for determining the best spherical starting point to investigate cylindrical prescription.Creal3-15-PCT1

[0152] During the projection step, each projection image plane 400 comprises a single virtual image 40 appearing at a projection distance d corresponding to infinity. The light device 1 of the light-field projector display 100 can be configured to illuminate only certain point light sources 10, other point light sources 10 being turned off. The illuminated point light sources 10 can be arranged such that they form a triangular shape on the light device 1 (considering the physical shape of the light device 1 and properties of optical path).

[0153] The eye tracking device 506 can be configured to provide a feedback to inform the selection of the illuminated point light sources 10 and to ensure that the distance between the illuminated point light sources 10 is less than the user's pupil diameter. In this configuration, the system 500 can be individually adjusted for each user.

[0154] Due to the optical properties of the testing device 500, the projection image plane 400 provides the same properties as the Scheiner Principle implemented using physical light source and an opaque disc.

[0155] The user can apply digital sphere power correction using the HID 503 such that the virtual image 40 created by the illuminated point light sources 10 corresponds to a single image (the light fields 101 illuminated point light sources 10 converge to a single image). The user can be informed in what direction to search by the shape of the triangle. The amount of sphere required will equal the user's prescription.

[0156] More generally, the light field based testing device 500 is configured to execute a plurality of test cycles for assessing refraction properties of a user's eye. The device 500 comprises a light field projector display 100 having a plurality of point light sources 10. An illumination control unit 81 is configured to sequentially illuminate the point light sources 10 to sequentially emit a plurality of light fields 101 .Creal3-15-PCT1

[0157] The device 500 further comprises a spatial light modulator (SLM) 3 controllable by an SLM control unit 82 to provide an SLM image pattern 61 on the SLM 3, the SLM image pattern 61 modulating the light fields 101. Projection optics 4 are configured to project the modulated light fields 101 along a reference projection axis 170 and to form, in a projection image plane 400, a plurality of virtual images 40 presented sequentially or simultaneously.

[0158] The device 500 further comprises a data storage unit 509 comprising a region of physical memory configured to at least temporarily store input signals.

[0159] The SLM control unit 82 is configured to apply, to the SLM image pattern 61, a plurality of refractive corrections including a predefined refractive correction value and additional refractive correction values incrementally varied about the predefined refractive correction value. Each virtual image 40 of the plurality is thus formed with a corresponding refractive correction.

[0160] The HID 503 is operable by the user, during a test cycle, to select at least one of the virtual images 40 perceived to exhibit best subjective image quality or a recognisable characteristic.

[0161] The HID 503 is further configured to input, into the data storage unit 509, a best refractive correction corresponding to the selected virtual image(s) 40, and to provide the best refractive correction to the SLM control unit 82 for use as the predefined refractive correction in a subsequent test cycle.

[0162] The present disclosure further concerns a non-transitory computer-readable medium storing digital instructions which, when executed by the processing module 510 of the testing device 500, cause the processing module 510 to perform a method of assessing a user's visualCreal3-15-PCT1acuity, the method (see Fig. 10) comprising a plurality of test cycles, each test cycle comprising: a projection step comprising controlling the light-field projector display 100 to sequentially project a plurality of projection image planes 400, each projection image plane 400 comprising at least one virtual image 40; a correction step, comprising controlling the SLM control unit 82 to provide an SLM image pattern 61 configured to add, to each virtual image 40, one of a plurality of refractive corrections comprising a predefined refractive correction value and additional refractive correction values incrementally varied about the predefined value; and a selection step, comprising using the HID 503 to select, in at least one of said plurality of projection image planes 400, at least one virtual image 40 that the user perceives as having best image subjective quality, or exhibiting a a recognizable characteristic; and an input step, comprising storing in the data storage unit 509 a best refractive correction corresponding to the selected virtual image(s) 40 and providing the best refractive correction to the SLM control unit 82 for use as the predefined refractive correction value in a subsequent test cycle.

[0163] Across successive test cycles, the predefined value is updated toward the user's optimal correction. The step size may be adaptive: larger increments at initial cycles (rapid coarse search), smaller increments near convergence (fine adjustment). The correction trajectory can be modelled as a search over parameter space (sphere S, cylinder C, axis A), optionally including higher order aberrations.

[0164] To mitigate order bias, the SLM control unit 82 can be configured to apply, to the SLM image pattern 61, said plurality of refractive corrections in a random sequence and to ensure luminance / contrast consistency across virtual images (40).Creal3-15-PCT1

[0165] Optionally, a clinician may monitor selections via a networked HID 503 while the processing module 510 executes locally.Creal3-15-PCT1Reference Numbers and1 light device10 point light source100 projector display101 incident light field170 reference projection axis2 collimating optics20 virtual viewpoint, virtual pinhole25 virtual viewpoint, virtual focal point201 modulated light field3 spatial light modulator (SLM)30 virtual scene31 SLM plane4 projection optics40 virtual image400 projection image plane500 testing device501 forehead rest502 chinrest503 human interface device (HID)504 base505 supporting colum506 eye tracking device507 emitting and display device508 connection509 data storage unit510 processing module511 adjustment device51 sensor device52 biometric authentication device6 pupil exit plane60 reference SLM image pattern61 corrected SLM image pattern601 image component81 illumination control unit82 SLM control unit83 illumination signal84 synchronization communication signal85 SLM signal d projection distance dlim limit projection distanceCreal3-15-PCT1

Claims

Claims1. A light-field- based testing device (500) arranged to perform a plurality of test cycles for assessing refraction properties of a user's eye, the device (500) comprising: at least one light-field projector display (100) comprising a plurality of point light sources (10) arranged to be sequentially illuminated by an illumination control unit (81) to sequentially emit a plurality of light fields (101); a spatial light modulator (SLM) (3) arranged to be driven by an SLM control unit (82) to display an SLM image pattern (61) on the SLM (3), the SLM image pattern (61) modulating the light fields (101); projection optics (4) configured to project the modulated light fields (101) along a reference projection axis (170) and form, in a projection image plane (400), a plurality of virtual images (40) projected sequentially or simultaneously; and a data storage unit (509) comprise a region of a physical memory configured to at least temporarily store input signals; wherein the SLM control unit (82) is further configured to apply, to the SLM image pattern (61), a plurality of refractive corrections including a predefined refractive correction value and additional refractive correction values incrementally varied about the predefined refractive correction value, such that each virtual image (40) of said plurality of virtual images (40) is formed with a corresponding refractive correction; wherein the testing device (500) further comprises a human interface device (HID) (503) operable by the user during a test cycle to select at least one of the virtual images (40) perceived to exhibit best image subjective image quality or a recognizable characteristic; and wherein the HID (503) is further configured to input, into, the data storage unit (509), a best refractive correction corresponding to the selected virtual image (40); and to provide the best refractive correction toCreal3-15-PCT1the SLM control unit (82) for use as the predefined refractive correction in a subsequent test cycle.

2. The testing device according to claim 1, comprising a single light-field projector display (100) configured to project said at least one virtual image (40) in one or both eyes of the user when the latter is using the testing device (500).

3. The testing device according to claim 1, comprising two light-field projector displays (100), each light-field projector display (100) being configured to project said at least one virtual image (40) in one eye of the user when the latter is using the testing device (500).

4. A non-transitory computer-readable medium storing digital instructions which, when executed by a processing module (510) of the testing device (500) according to any one of claims 1 to 3, cause the processing module (510) to perform a method of assessing a user's visual acuity, the method comprising a plurality of test cycles, each test cycle comprising: a projection step comprising controlling the light-field projector display (100) to sequentially project a plurality of projection image planes (400), each projection image plane (400) comprising at least one virtual image (40); a correction step, comprising controlling the SLM control unit (82) to provide an SLM image pattern (61) configured to add, to each virtual image (40), one of a plurality of refractive corrections comprising a predefined refractive correction value and additional refractive correction values incrementally varied about the predefined value; and a selection step, comprising using the HID (503) to select, in at least one of said plurality of projection image planes (400), at least one virtual image (40) that the user perceives as having best image subjective quality, or exhibiting a a recognizable characteristic; andCreal3-15-PCT1an input step, comprising storing in the data storage unit (509) a best refractive correction corresponding to the selected virtual image(s) (40) and providing the best refractive correction to the SLM control unit (82) for use as the predefined refractive correction value in a subsequent test cycle.

5. The non-transitory computer-readable medium according to claim 4, wherein each projection image plane (400) comprises a single virtual image (40); and wherein the selection step comprises selecting said single virtual image (40) in one of the sequentially projected virtual image planes (400).

6. The non-transitory computer-readable medium according to claim 4, wherein each projection image plane (400) comprises a plurality of virtual images (40) spatially distributed on the projection image plane (400); and wherein the selection step comprises selecting at least one of the virtual images (40) in each projection image plane (400) of the sequence of projection image planes (400).

7. The non-transitory computer-readable medium according to claim 6, wherein said plurality of virtual images (40) in each projection image plane (400) have different refractive corrections.

8. The non-transitory computer-readable medium according to any one of claims 4 to 7, wherein the refractive correction comprises a spherical power correction, a cylinder axis correction, or cylinder power correction.

9. The non-transitory computer-readable medium according to any one of claims 4 to 8, wherein the refractive correction of said at least one virtual image (40) isCreal3-15-PCT1varied between each sequentially projected projection image planes (400) with increasing or decreasing increments.

10. The non-transitory computer-readable medium according to any one of claims 4 to 9, wherein the refractive correction comprises a cylinder axis correction; and wherein the cylinder axis correction is varied between each sequentially projected projection image planes (400) between 0° and 180° and increased or decreased by increments of between 1° and 30°.

11. The non-transitory computer-readable medium according to claim 10, wherein each test cycle comprises a first step of performing the correction step by varying the cylinder axis correction by increments of between 10° and 30° and performing the selection step by inputting in the data storage unit (509) the refractive correction of the selected at least one virtual image (40) as a coarse best refractive correction; and a second step of performing the correction step by varying the cylinder axis correction by increments of between 1° and 5° and performing the selection step by inputting in the data storage unit (509) the refractive correction of the selected at least one virtual image (40) as a fine best refractive correction.

12. The non-transitory computer-readable medium according to claim 6, wherein the spatial distribution of said plurality of virtual images (40) does not vary from one projection image plane (400) to another.

13. The non-transitory computer-readable medium according to claim 6, wherein the spatial distribution of said plurality of virtual images (40) varies from one projection image plane (400) to another.Creal3-15-PCT114. The non-transitory computer-readable medium according to claim 6, wherein the plurality of virtual images (40) are spatially distributed on the projection image plane (400) to form a 3D pattern.

15. The non-transitory computer-readable medium according to claim 14, wherein the correction step comprises varying the refractive correction depending on the position of the virtual image (40) in the 3D pattern; and wherein the selection step comprises selecting at least one of the virtual images (40) in the 3D pattern in each projection image plane (400) of the sequence of projection image planes (400).

16. The non-transitory computer-readable medium according to claim 15, wherein the HID 503 is configured to select said at least one of the virtual images (40) by moving a cursor through the 3D pattern.

17. The non-transitory computer-readable medium according to any one of claims 4 to 16, wherein said at least one virtual image (40) comprises any one of: an optotype, a pattern, a shape, a symbol, a letter, a number, or a Landolt ring.

18. The non-transitory computer-readable medium according to claims 6 and 17, wherein the projection step comprises projecting said plurality of virtual images (40) on the projection image plane (400) to form a standard Snellen chart.

19. The non-transitory computer-readable medium according to claim 17, wherein said at least one virtual image (40) comprise a rotating image.Creal3-15-PCT120. The non-transitory computer-readable medium according to claims 8 and 19, wherein the cylinder axis correction is varied with the rotation angle of the rotating virtual image (40).

21. The non-transitory computer-readable medium according to claims 4 and 20, wherein the selection step further comprises using the processing module (510) to determine a recognition time of a user, comprising determining the time elapsed between the projection of one of the projection image planes (400) and the time the user selects, using the HID (503), said at least one virtual image (40) for which he has recognized said characteristic.

22. The non-transitory computer-readable medium according to claim 6 or 7, wherein said plurality of virtual images (40) are projected at different optical distances.

23. The non-transitory computer-readable medium according to claim 22, wherein a first subset of said plurality of virtual images (40) are projected at a projection distance d of more than 6 m and a second subset of said plurality of virtual images (40) are projected at a projection distance d between 6 m to 30 cm.

24. The non-transitory computer-readable medium according to claim 23, wherein said second subset of said plurality of virtual images (40) are configured to move across each projection image plane (400).

25. The non-transitory computer-readable medium according to claim 6 or 7, wherein said plurality of virtual images (40) comprises a plurality of subsets of virtual images (40), each subset being arranged in a segment (401 -404)Creal3-15-PCT1of the projection image plane (400); wherein the correction step comprises controlling the SLM control unit (82) to provide a subset of virtual images (40) in one of the segments (401-404) with a different refractive correction the refractive correction applied to the other subsets of virtual images (40) in the other segments (401-404); wherein the selection step comprises using the HID (503) to select the segment (401-404) of the projection image plane (400).

26. The non-transitory computer-readable medium according to claim 5, wherein the projection step comprises a single virtual image (40) appearing at a projection distance d corresponding to infinity.

27. The non-transitory computer-readable medium according to claim 26, wherein the illumination control unit (81) is configured to control the point light sources (10) to illuminate less than the total number of said plurality of point light sources (10); and wherein the illuminated point light sources (10) are arranged to form a triangular pattern.

28. The non-transitory computer-readable medium according to claim 27, wherein the correction step comprises using the HID (503) to add refractive correction to the virtual image (40) for the latter to appears as a single image.

29. The non-transitory computer-readable medium according to claim 14, wherein, during the projection step of the subsequent test cycles, said at least one of the virtual images (40) selected during the previous rest cycle is repositioned in the center of the 3D pattern.Creal3-15-PCT130. The non-transitory computer-readable medium according to claim 4, wherein the refractive correction is varied between each test cycle.

31. The non-transitory computer-readable medium according to claim 4, wherein during a first test cycle, the correction step comprises applying a predetermined refractive correction value to said at least one virtual images (40).

32. The non-transitory computer-readable medium according to claim 31, wherein the predetermined refractive correction value is varied in the subsequent test cycles.

33. The non-transitory computer-readable medium according to claim 4, wherein the method further comprises using the processing module (510) to calculate an average best refractive correction based on the best refractive corrections inputted in the data storage unit (509) at each test cycle.

34. The non-transitory computer-readable medium according to claim 18, wherein, during a first test cycle, the projection step comprises projecting the plurality of virtual images (40) with a size corresponding to 20 / 10 of the Snellen chart; and wherein during the subsequent test cycles, the size of the virtual images 40 is increased.Creal3-15-PCT1

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