retinal imaging

Abstract

A method of imaging a retina (8) of an eye (3) includes determining a position of the eye (3), measuring light reflected or emitted from a point (7) on the retina (8) of the eye (3), and determining a position of the point (7) on the retina (8) based on the position of the eye (3). The method further includes repeating the determining and measuring steps over time to provide multiple measurements of light reflected from the point at different locations on the retina (8) and combining the measurements to form an image (15) of the retina (8).

Description

[Technical Field]

[0001] The present invention relates to retinal imaging, and in particular to point-based imaging that uses the natural rotation of the eye over time. [Background technology]

[0002] Retinal imaging (taking an image of a user's retinal structures) can be used in multiple applications such as biometric authentication, digital biomarkers, etc. Although various methods for retinal imaging exist, there is a continuous need to develop new and improved methods. Summary of the Invention

[0003] According to a first aspect of the present disclosure, there is provided a method for imaging the retina of an eye. The method includes determining a position of the eye (typically a rotational position of the eye, but may also be a linear position / displacement depending on the application), measuring light reflected from or emitted from a point on the retina of the eye, and determining a position of the point on the retina based on the position of the eye. The method further includes repeating the determining and measuring steps over time to provide multiple measurements of light reflected from points at different locations on the retina, and combining the measurements to form an image of the retina.

[0004] In an embodiment of the present disclosure, a single data point sensing module consisting of a low power light source and sensing mechanism (e.g., a photodiode) can be combined and integrated into a head-mounted device for continuous measurements with a functional high speed eye tracking unit for acquiring and constructing retinal images.

[0005] The step of determining the position may include using an eye tracking unit. Any suitable eye tracking unit may be used, but high accuracy and a high repetition rate (e.g., a repetition rate of greater than 60 Hz) are advantageous for the disclosed method. Using separate units for eye tracking and retinal imaging can simplify the system. Eye tracking is typically also used for purposes other than retinal imaging.

[0006] The measuring step may include illuminating the retina of the eye, focusing light reflected from a point on the retina onto a detector, and receiving the focused light at the detector. The detector typically includes a photodiode. Advantageously, the detector does not need to be an imaging detector, since only reflections from a point on the retina are measured at any one time. Thus, the disclosed solution allows imaging of the retina using only a single photodiode. The eye may also be illuminated in other ways, for example, using ambient light. In one embodiment, light is emitted from an emitter and collimated toward the eye. The cornea of ​​the eye focuses the light onto a point on the retina.

[0007] The measurements may include determining one or more of intensity, phase (or optical path length), autofluorescence, and polarization. Any one or more of these properties may be used to construct various images of the retina.

[0008] In addition to measuring reflection from the eye, fluorescence may be used to measure light emitted directly from the eye.

[0009] The measuring step typically involves using optics to direct light emitted / reflected from the eye onto one or more photodiodes. In certain embodiments, the measuring step may involve self-mixing interferometry (SMI), in which light is emitted by an emitter, reflected light is received by the same emitter, and the output from or input to the emitter is measured to determine the phase and / or amplitude of the reflected light. A portion of the light emitted by the emitter can be directed to a detector, such as a photodiode, to measure the output of the emitter and thereby detect the light reflected from the retina.

[0010] The steps of determining the position and measuring the reflected light can be repeated at a repetition rate of greater than 60 Hz. The higher the repetition rate, the greater the number of points on the retina that can be measured and added to the image over a given period of time.

[0011] According to a second aspect of the present disclosure, there is provided an optical device for imaging the retina of an eye, suitable for incorporation into a head-mounted device (e.g., AR glasses). The optical device includes an eye tracking unit configured to determine a position of the eye (typically, the eye tracking unit is configured to determine a rotational position of the eye), and a measurement unit configured to measure light reflected or emitted from a point on the retina of the eye. The optical device further includes a processing unit configured to determine a position of the point on the retina based on the position of the eye, and an imaging unit configured to combine multiple measurements of the reflected light to form an image of the retina.

[0012] The measurement unit may include an emitter for illuminating the retina of the eye and a detector for receiving light reflected from a point on the retina. The emitter may include a light-emitting diode (LED) or a laser diode. The emitter may include a vertical cavity surface-emitting laser (VCSEL) configured to emit light having a wavelength in the range of, for example, 850 nm to 1400 nm. VCSELs can provide a low-power solution. The measurement unit may also include an optical element for directing light from the emitter toward the eye, such as a collimating lens.

[0013] The detector typically comprises a photodiode that measures the intensity of light incident on the photodiode. To increase imaging speed, the detector may comprise multiple photodiodes configured to simultaneously receive light from different points on the retina. Importantly, an image sensor is not required in the proposed solution for retinal imaging, but can be used in place of multiple photodiodes. The detector does not itself receive any spatial information about the retina; such spatial information is instead provided by the eye tracking unit.

[0014] According to a third aspect of the present disclosure, there is provided a head-mounted device including one or two optical devices according to the second aspect. The optical devices are preferably incorporated into the stem (the portion extending along the side of the head behind the user's eyes) of the head-mounted device. The optical elements are configured to substantially transmit light in the visible spectrum while reflecting at least light having a wavelength substantially equal to that of the light from the emitters. This allows the optical elements to be positioned directly in front of the user's eyes, directing IR or NIR light from the emitters to the eyes for retinal imaging while allowing visible light to pass through the optical elements so that the user can see unimpeded through the device. [Brief explanation of the drawings]

[0015] [Figure 1A] FIG. 1 is a schematic diagram of a configuration for retinal imaging using an optical device according to one embodiment. [Figure 1B] 1A-1C are schematic diagrams of the above configuration with the eyes in different rotational positions. [Figure 2A] FIG. 10 is a schematic diagram of another configuration for retinal imaging using an optical device according to another embodiment. [Figure 2B] 1A-1C are schematic diagrams of the above configuration with the eyes in different rotational positions. [Figure 3] 1 is a schematic diagram of a head-mounted device according to an embodiment having an optical device for retinal imaging. [Figure 4]FIG. 10 is a schematic diagram of a head-mounted device according to another embodiment having an optical device located within the stem of the device. [Figure 5] 1 is a schematic diagram of an optical device according to an embodiment comprising two detectors; [Figure 6] FIG. 1 is a schematic diagram of a retinal image formed from a user's random scan path. DETAILED DESCRIPTION OF THE INVENTION

[0016] 1A shows a schematic diagram of an optical device 1 for retinal imaging according to one embodiment. Device 1 comprises an emitter 2 (e.g., including one or more VCSELs) for emitting light toward eye 3 and a detector 4 for detecting light reflected from eye 3. Device 1 further comprises a separate eye tracking unit 5 for tracking the rotational position of eye 3 over time. Optical device 1 also comprises an optical element 6 for directing light from the emitter toward eye 3 and directing reflected light from eye 3 toward detector 4. Eye 3 focuses at least a portion of the incident light onto spot 7 on retina 8 of eye 3. Light reflected from spot 7 is received by detector 4. Detector 4 can therefore be used to measure reflected light from retina 8.

[0017] 1B shows the optical device 1 after the eye 3 has rotated to a new position. As the eye 3 rotates relative to the device 1, the position of the spot 7 on the retina 8 changes (from A to B in the figure). Thus, over time, an image of the retina 8 can be obtained by combining multiple measurements.

[0018] 2A and 2B show another embodiment in which self-mixing interferometry (SMI) is used to measure light reflected from the retina 8. For clarity, the same reference numbers have been used in different figures to indicate similar or equivalent features, and the reference numbers are not intended to limit the scope of the illustrated embodiments.

[0019] FIG. 2A shows a schematic diagram of an optical device 1 for retinal imaging. The device includes an emitter 2 and a detector 4. The detector 4 is configured to measure the output of the emitter 2 (rather than the light reflected from the eye 3 as in FIGS. 1A and 1B). A large portion (e.g., 99%) of the light emitted by the emitter 2 is directed toward the eye 3 by an optical element 6. The eye 3 focuses the light onto a spot 7 on the retina 8. The light reflected from spot 7 is then received back by the emitter 2. The received light interferes with the light in the emitter 2, causing a change in the output from the emitter 2. This change in output is measured by the detector 4, which receives a small portion of the emitted light.

[0020] FIG. 2B shows the device 1 when the eye 3 is rotated and the position of the spot 7 on the retina 8 changes accordingly.

[0021] Generally, in embodiments, the rotational position of the eye 3 may be mapped to the location of the focal spot 7 on the retina 8. Multiple measurements may be combined to provide an image of the retina 8. The image may be a plot of the intensity of light reflected from the retina 8 versus position on the retina 8.

[0022] FIG. 3 shows a system 9 having two optical devices 1 integrated into a pair of glasses 10 (e.g., AR smart glasses). The smart glasses 10 are head-mounted devices that hold the optical devices 1 fixed relative to the eyes 3. This allows the optical devices 1 to measure retinal reflexes over the time the smart glasses 10 are worn to provide a sufficiently detailed image of the retina 8. Each optical device 1 includes an emitter for emitting light and a detector unit 11 for receiving reflected light from the corresponding eye 3. The emitter and detector unit 11 can use SMI, for example, using VCSEL emitters. The emitter and detector unit 11 may include an emitter 2 and a detector 4, for example, as shown in FIG. 1A or 2A.

[0023] Figure 4 shows a schematic diagram of a system according to an embodiment similar to that of Figure 3, but where the emitter and detector device 11 is located within the stem 12 of the smart glasses 10. Here, the optical element 6 also reflects light towards the eye 3. This embodiment may provide a more compact solution.

[0024] 5 shows a schematic diagram of an optical device 1 according to one embodiment comprising two detectors 4a and 4b (or two photodiodes in the same detector). Multiple adjacent detectors 4a and 4b arranged in the image plane can be positioned to image different locations 7a and 7b on the retina 8. This adds additional data points at any given time, at the expense of other system parameters (e.g., power consumption).

[0025] 6 shows a schematic image of the retina 13 and a trajectory 14 of a user's gaze over time. The combination 15 of image 13 and trajectory 14 shows a retinal image as may be provided by an embodiment.

[0026] Embodiments allow for the measurement of a single data point on the retina by measuring reflections from the retina with a detector. The information collected from this point is then related to the current eye position via an eye tracking unit. This combination of data allows for the construction of an image of the retina over time based on the continuous natural movement of the eye, as each eye position returns a specific data point. Incorporation into a head-worn device allows for continuous measurements over time. The use of passive eye movement and a single data point to construct a retinal image provides the following advantages: - Extremely power efficient design with minimal component count. - Low complexity due to fewer parts. - The solution relies on natural eye movements and therefore does not require any mechanical or moving elements.

[0027] Although specific embodiments have been described above, the scope of the claims is not limited to these embodiments. Each feature disclosed may be incorporated into any of the described embodiments, either alone or in any suitable combination with other features disclosed herein. [Explanation of symbols]

[0028] 1 Optical Devices 9 Optical system 2 Emitter 10. Glass 3 eyes 11 Emitter and detector device 4. Detector 12 Stem 5 Eye Tracking Unit 13 Retinal Images 6 Optical Elements 14 Gaze trajectory 7 Spots 15 Composite Images 8. Retina

Claims

1. 1. A method for imaging a retina (8) of an eye (3), said method comprising: determining the position of the eye (3); measuring light reflected or emitted from a point (7) on the retina (8) of the eye (3); determining the position of the point (7) on the retina (8) based on the position of the eye (3); repeating the determining and measuring steps over time to provide multiple measurements of light reflected or emitted from points at different locations on the retina (8); and combining said measurements to form an image (15) of said retina (8).

2. said determining the position comprises using an eye tracking unit (5); The method of claim 1.

3. The measuring step includes: illuminating the retina of the eye; and focusing light reflected from said point (7) on said retina (8) onto a detector (4); receiving the focused light at the detector (4).

3. The method according to claim 1 or 2.

4. the illuminating step includes emitting light using an emitter and directing the emitted light to the eye using an optical element. The method of claim 3.

5. The detector (4) comprises a photodiode. The method of claim 3.

6. the measuring step includes determining one or more of light intensity, phase, polarization, and autofluorescence intensity; The method of claim 1.

7. the measuring step includes self-mixing interferometry (SMI), in which the light is emitted by an emitter (2) and the reflected light is received by the same emitter (2), and the output from or input to the emitter (2) is measured to determine the phase and / or amplitude of the reflected light; The method of claim 1.

8. A portion of the light emitted by the emitter (2) is directed to a detector (4), The method of claim 7.

9. the steps of determining the position and measuring the reflected light are repeated at a repetition rate of greater than 60 Hz. The method of claim 1.

10. An optical device (1) for imaging the retina (8) of an eye (3), suitable for incorporation into a head-mounted device (10), said optical device (1) comprising: an eye tracking unit (5) configured to determine the position of the eye (3); a measurement unit configured to measure light reflected or emitted from a point (7) on the retina (8) of the eye (3); a processing unit configured to determine the position of the point (7) on the retina (8) based on the position of the eye (3); an imaging unit configured to combine multiple measurements of the reflected or emitted light to form an image (15) of the retina, Optical device (1).

11. The measuring unit an emitter (2) for illuminating the retina of the eye (3); a detector (4) for receiving the light reflected from the point (7) on the retina (8), Optical device (1) according to claim 10.

12. the emitter (2) comprises a light emitting diode (LED) or a laser diode; An optical device (1) according to claim 11.

13. the emitter (2) comprises a vertical cavity surface emitting laser (VCSEL) configured to emit light having a wavelength in the range of 800 nm to 1400 nm; An optical device (1) according to claim 11.

14. The measurement unit further comprises an optical element (6) for directing light from the emitter (2) to the eye (3). An optical device (1) according to claim 11.

15. the detector (4) comprises a photodiode for measuring the intensity of light incident on the photodiode; An optical device (1) according to claim 11.

16. A head-mounted device (10) comprising one or two optical devices (1) according to claim 14.

17. The emitter (2) and the detector (4) included in at least one of the optical devices (1) are integrated into the stem (12) of the head-mounted device (10), and the optical element (6) is configured to substantially transmit light in the visible spectrum while reflecting at least light having a wavelength substantially equal to that of the light of the emitter (2). A head-mounted device (10) according to claim 16.

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