Eye-tracking system

Abstract

An eye-tracking system (1) is identified, comprising a radiation source (2) configured to provide radiation, a waveguide (3), and a volume phase hologram (4), wherein the waveguide (3) provides a propagation medium between the radiation source (2) and the volume phase hologram (3), and the radiation is reflected or scattered by a portion of the user's eye (9), coupled back to the radiation source (2), and causes a self-mixed interference signal.

Description

Technical Field

[0006] , ,

[0001] A gaze tracking system is identified.

Background Art

[0002] A gaze tracking system typically irradiates a beam from a radiation source onto a user's eye, collects data, and identifies the position of the eye. In head-mounted wearables, human elements such as hair, eyelashes, or skin may block the light from the light source, which may make the system more susceptible to performance degradation.

Summary of the Invention

Problems to be Solved by the Invention

[0003] The object to be solved is to provide a gaze tracking system with improved reliability.

Means for Solving the Problems

[0004] This object is obtained, inter alia, by the gaze tracking system according to claim 1. Development and convenience are the subject of further claims.

[0005] A gaze tracking system is identified.

[0006] According to at least one embodiment of an eye-tracking system, the eye-tracking system is based on self-mixing interferometry (SMI), particularly within the infrared or visible spectral range. For example, a radiation source (or light source) provides radiation (a beam), which is reflected or scattered from a part of the eye, combined back to the light source, and produces an SMI signal that allows for the determination of eye movements such as eye rotation. In particular, self-mixing interference occurs when a portion of the beam shining on the eye is reflected or scattered, for example, from the cornea or another surface of the eye, such as the inner surface of the retina or the inner surface of a lens, and returns to the laser cavity (or resonator) of the radiation source. Interference with the original radiation from the laser source unit leads to modulation of the laser emission characteristics. For example, the frequency or number of fringes in the SMI signal can provide information about the user's eye rotation. For example, the interference can be detected by a photodiode that provides information. As an alternative or addition, changes in laser emission characteristics such as laser power, laser operating voltage, or laser operating current may be used.

[0007] For example, the radiation source comprises a laser source unit configured to emit a laser beam and irradiate at least a portion of the user's eye, for example, the cornea of ​​the user's eye. For example, the laser source unit comprises one or more laser diodes to generate one or more laser beams. For example, the laser source unit comprises a vertical cavity surface-emitting laser (VCSEL) or an array of VCSELs. VCSELs have a low threshold current and therefore have relatively low power consumption. Furthermore, they can have small dimensions and are available at low cost. However, other laser diodes such as end-emitting lasers, for example, distributed feedback (DFB) lasers or distributed Bragg reflector (DBR) lasers may also be used.

[0008] For example, a laser source unit may be configured to emit radiation with a peak wavelength within the infrared or near-infrared spectral range. Alternatively, a laser source unit may be configured to emit radiation with a peak wavelength within the range of 800 nm to 1500 nm. Alternatively or additionally, a laser source unit may be configured to emit radiation within the visible spectral range.

[0009] For example, an eye-tracking system, particularly a radiation source, includes a detection module. Specifically, the detection module is configured to provide a signal that correlates with the radiation of a laser beam returning from the eye. For example, the radiation is scattered or reflected by the cornea, or the sclera, or another surface of the eye. Therefore, the signal from the detection module contains information about eye rotation.

[0010] For example, the detection module is integrated with the laser source unit and configured to acquire a self-mixing interference signal. For example, the detection module includes a photodiode located behind or inside the laser cavity to measure the output intensity of the laser.

[0011] For example, the active regions of photodiodes and semiconductor lasers are integrated into a common semiconductor body that includes a semiconductor layer formed by epitaxial growth.

[0012] Alternatively, the photodiode may be located behind the rearview mirror of the laser cavity, which is positioned opposite the front mirror. The majority of the radiation is emitted through the front mirror during the operation of the laser source unit.

[0013] Alternatively, the signal from the detection module may be determined from the electrical operating parameters of each laser source, such as current or voltage. Since these parameters are also affected by self-mixing interference effects, changes in these parameters can similarly allow for the acquisition of information regarding eye rotation.

[0014] According to at least one embodiment of the eye-tracking system, the eye-tracking system comprises a waveguide (or waveguide relay). In particular, the waveguide is located in the beam path between the radiation source and the user's eye. For example, the waveguide extends between the user side and the world side opposite the user side. For example, the waveguide has a thickness in the range of 0.1 mm to 10 mm.

[0015] According to at least one embodiment of the eye-tracking system, the eye-tracking system comprises a volume-phase hologram (VPH).

[0016] According to at least one embodiment of an eye-tracking system, a volume-phase hologram is configured to deflect radiation propagating through a waveguide toward the user's eyes. Similarly, radiation returning from the eyes may be deflected toward the radiation source by the volume-phase hologram.

[0017] Using a VPH, radiation impacting the VPH at a given angle may be deflected in a direction enclosing a specific angle within the VPH, which can be defined, for example, during the manufacturing of the VPH. The VPH can perform one or more optical functions.

[0018] According to at least one embodiment of the eye-tracking system, the optical function includes at least one of deflection, focusing, collimation, and divergence.

[0019] In at least one embodiment, the eye-tracking system comprises a radiation source configured to provide radiation, a waveguide, and a volume-phase hologram, the waveguide providing a propagation medium between the radiation source and the volume-phase hologram, the radiation being reflected or scattered by a portion of the user's eye and coupled back to the radiation source, causing a self-mixed interference signal.

[0020] During operation of the eye-tracking system, radiation can propagate through waveguides from the radiation source to the volume phase hologram. Therefore, the risk of radiation being blocked by user body elements such as hair is avoided, or at least significantly reduced.

[0021] According to at least one embodiment of the eye-tracking system, the eye-tracking system is based on SMI and waveguides, in which a beam is projected onto a VPH and then collected by a sensor through a waveguide, such as a glass waveguide.

[0022] According to at least one embodiment of the eye-tracking system, a volume-phase hologram provides optical functionality suitable for determining the self-mixed interference SMI signal to perform eye-tracking. In particular, the volume-phase hologram is located in the beam path from the radiation source to the eye. Furthermore, the volume-phase hologram may be located in the beam path from the eye back to the radiation source.

[0023] According to at least one embodiment of the eye-tracking system, the waveguide is part of the optical path for radiation returning from the eye between the volume phase hologram and the sensing module.

[0024] The system can only exist in free space at the output of the volume-phase hologram (VPH) between the final surface of the waveguide and the eye. In other words, radiation travels only in free space between the waveguide output surface region and the eye. Therefore, the entire beam path from the radiation source to the portion of the waveguide where the radiation exits the waveguide and heads toward the user's eye can pass through solid material.

[0025] According to at least one embodiment of the eye tracking system, a transparent waveguide (e.g., plastic such as glass, crystal, or polymer) is provided, which can force the beam to follow a specific path in total internal reflection (TIR: total internal reflection) between the radiation source / sensor and the VPH. In particular, the waveguide is transmissive with respect to the wavelength of the propagating beam. Further, the material of the waveguide may have a higher refractive index than the environment such as air.

[0026] The waveguide can provide a propagation medium between the light source and the VPH.

[0027] Similarly, the waveguide can be part of the optical return path after probing the sample between the VPH and the detection module. For example, the sample is the human eye, and the VPH provides an optical function suitable for determining the SMI signal necessary to perform eye tracking.

[0028] Waveguide parameters (thickness, length, refractive index, angle of incidence, wedge, or parallel planes, etc.) are selected and can be optimized overall with the VPH grating for particularly good overall system performance. Further, the wavelength used may be appropriately selected.

[0029] For the overall system performance, a single VPH may be divided into multiple VPHs on the waveguide surface, and each of them may have an individual optical function. In other words, the eye tracking system may include two or more VPHs, and the optical functions of the VPHs may be different from each other. For example, one VPH is configured to collimate the radiation from the radiation source, and a further VPH is configured to focus the radiation.

[0030] Light source incoupling is inherently transmittance, refractiveness, or diffraction, and may be performed by an incoupling feature (or incoupling optical element) that can be located on either side of the waveguide relay. For example, the incoupling optical element may be a prism, lens, grating, or additional VPH. For example, the incoupling optical element may be connected to the waveguide in a mechanically stable manner. For example, the incoupling optical element may be mounted to the waveguide. Alternatively, the incoupling optical element and the waveguide may be formed as a single unit.

[0031] According to at least one embodiment of the eye-tracking system, the eye-tracking system comprises an incoupling optical element for coupling radiation from a radiation source to a waveguide.

[0032] For example, radiation travels twice along the same path through the waveguide. Similarly, radiation can pass through an incoupling optical element in the direction toward the eye and the direction toward the eye.

[0033] For example, the waveguide is used for the round-trip path. Therefore, an incoupling VPH is not required. In other words, there is no need to provide additional optical elements such as a VPH to couple the radiation returning from the eye to the radiation source within the waveguide.

[0034] According to at least one embodiment of the eye-tracking system, the waveguide is used for the round-trip path of radiation, and the radiation travels the same path through the waveguide twice. Thus, the beam path from the eye back to the radiation source does not require any optical elements in addition to those provided for the beam path from the radiation source to the eye.

[0035] According to at least one embodiment of the eye-tracking system, the volume phase hologram and the radiation source are fixed together with the waveguide. In particular, the radiation source and the sensing module may be mechanically and stably connected to the waveguide during the manufacturing of the eye-tracking module. Thus, the spatial relationship between these elements and the beam path from the radiation source to the volume phase hologram may be defined during manufacturing. Therefore, during the operation of the eye-tracking system, unintended displacement of the volume phase hologram relative to the radiation source can be avoided or at least significantly reduced.

[0036] According to at least one embodiment of the eye-tracking system, the volume phase hologram is a reflective hologram positioned on the world side of the waveguide, or a transmissive hologram positioned on the user side of the waveguide.

[0037] According to at least one embodiment of the eye-tracking system, the eye-tracking system comprises a further volume phase hologram. The features described above in relation to the volume phase hologram may also apply to the further volume phase hologram. The further volume phase hologram may be located in the beam path between the radiation source and the volume phase hologram. Alternatively, the volume phase hologram may be located in the beam path between the radiation source and the further volume phase hologram.

[0038] According to at least one embodiment of the eye-tracking system, the volume phase hologram is a transmitted volume phase hologram, and the further volume phase hologram is a reflected volume phase hologram, or vice versa. For example, the transmitted volume phase hologram is located on the user side and / or the reflected volume phase hologram is located on the world side of the waveguide.

[0039] According to at least one embodiment of the eye-tracking system, the volume phase hologram and the further volume phase hologram are reflective volume phase holograms. For example, the volume phase hologram is located on the world side and the further volume phase hologram is located on the user side of the waveguide, or vice versa.

[0040] In particular, the following effects may be obtained:

[0041] Systems (especially those including source / sensor + VPH + waveguide) can be pre-assembled with the correct position and angles between components. When design tolerances match manufacturing tolerances, there are fewer degrees of freedom and less risk of misalignment. This allows for greater complexity to be pushed into the system assembly as a whole.

[0042] By using such an architecture, the risk of interference from human elements such as eyelashes, hair, and skin can be reduced.

[0043] It also gives a compact system and frees up some space for other features, such as glass branches.

[0044] Waveguide relays can fix the VPH and source together with the waveguide, thereby maintaining the beam at the glass thickness and the distance and orientation between the source and VPH. In contrast, conventional devices, eye-tracking systems, consist of a source / sensing module and a VPH. The user's eye is the final part of the system, acting as the beam's reflecting surface. These two components are assembled in free space, which allows for alignment margins but also leads to potential misalignment, requiring large tolerances for each component and potentially reducing the system's efficiency.

[0045] According to at least one embodiment, a waveguide relay is provided having a reflective hologram on the world side and an incoupling of a light source on either side of the waveguide.

[0046] According to at least one embodiment, a waveguide relay is provided having a transparent hologram on the user side and an incoupling of a light source on either side of the waveguide.

[0047] According to at least one embodiment, a waveguide relay is provided having a combination of a world-side reflective VPH (optical function 1) and a user-side transmitted VPH (optical function 2).

[0048] According to at least one embodiment, a waveguide relay is provided having a combination of a user-side reflective VPH (optical function 3) and a world-side reflective VPH (optical function 4).

[0049] The waveguide may be straight or curved. This can be applied to all embodiments.

[0050] For example, eye-tracking systems may be used in applications of augmented reality (AR), virtual reality (VR), mixed reality (MR), or extended reality (XR).

[0051] For example, an eye-tracking device is configured to be integrated into a wearable device worn on the user's head. This wearable device could be a headset, eyeglasses, smart glasses, or a helmet.

[0052] The features described above in relation to at least one embodiment of the eye-tracking system can be combined with other features described in relation to at least one embodiment of the eye-tracking system, provided that they do not conflict.

[0053] In exemplary embodiments and drawings, components that are similar or function similarly are given the same reference numerals. Generally, only differences relating to individual exemplary embodiments are described. Unless otherwise specified, a description of a part or aspect in one exemplary embodiment also applies to the corresponding part or aspect in another exemplary embodiment. [Brief explanation of the drawing]

[0054] [Figure 1] This figure shows an exemplary embodiment of an eye-tracking system. [Figure 2] This figure shows an exemplary embodiment of an eye-tracking system. [Figure 3] This figure shows an exemplary embodiment of an eye-tracking system. [Figure 4] This figure shows an exemplary embodiment of an eye-tracking system. [Figure 5A] This figure shows examples of different waveguide shapes. [Figure 5B] This figure shows examples of different waveguide shapes. [Figure 5C] This figure shows examples of different waveguide shapes. [Figure 6] This figure shows different examples of the optical functions of a user's eye. [Modes for carrying out the invention]

[0055] The diagram is a schematic representation. The elements shown in the diagram and their size relationships to one another are not necessarily to scale. Rather, individual elements may be represented in an exaggerated size in at least one dimension for better representation and / or better understanding.

[0056] An exemplary embodiment of the eye-tracking system 1 is shown in Figure 1, which schematically illustrates the path of beam 8 within the eye-tracking system.

[0057] The eye-tracking system 1 comprises a radiation source configured to provide radiation (beam 8), a waveguide 3, and a volume-phase hologram 4. The waveguide 3 provides a propagation medium between the radiation source 2 and the volume-phase hologram 4. The radiation, guided through the waveguide 3 from the radiation source 2 to the volume-phase hologram 4 by total internal reflection, is deflected by the volume-phase hologram 4, exits the waveguide 3 in the output surface region 35 of the waveguide 3, and illuminates the user's eye 9. The radiation, reflected or scattered by a portion of the user's eye 9 and coupled back to the radiation source 2, causes optical interference with the original radiation in the cavity (or resonator) of the radiation source 2, resulting in a self-mixed interference signal. Since the self-mixed interference signal depends on the rotational position of the eye 9, the self-mixed interference signal can be used to perform eye-tracking.

[0058] In the exemplary embodiment shown in Figure 1, the volume-phase hologram 4 deflects radiation propagating within the waveguide 3, focusing it, for example, towards the user's eye 9. However, another optical function of the volume-phase hologram 4 may be suitable for determining a self-mixed interference signal to perform eye-tracking. This will be described in more detail in relation to Figure 6.

[0059] Waveguide 3 extends between the user side 31 and the world side 32 on the opposite side of the user side 31. Total internal reflection occurs at both the user side 31 and the world side 32, resulting in the beam 8 being guided from the radiation source 2 to the volume phase hologram 4. At the volume phase hologram 4, the radiation propagating through the waveguide and colliding with the volume phase hologram may be deflected with high efficiency, resulting in nearly perfect collision radiation coupling out of waveguide 3 towards the user's eye.

[0060] For example, waveguide 3 may have a thickness in the range of 0.1 mm to 10 mm. For example, waveguide 3 may include a glass or plastic material that is transparent to radiation from radiation source 2.

[0061] The eye-tracking system 1 may further include an incoupling optical element 5 positioned in the beam path from the radiation source 2 to the waveguide 3. In the exemplary embodiment shown in Figure 1, the incoupling optical element 5 is a prism. The incoupling optical element 5 is configured such that radiation from the radiation source 2 is coupled to the waveguide 3 at an incoupling angle greater than or equal to the critical angle of total internal reflection with respect to the normal of the waveguide at this position in the waveguide 3.

[0062] The waveguide 3 and the incoupling optical element 5 are configured such that radiation coupled within the waveguide 3 collides with the volume phase hologram 4 after a predetermined number of total reflections on the user side 31 and the world side 32. This can be achieved by appropriately selecting waveguide parameters such as thickness or refractive index and / or the angle at which the radiation is coupled to the waveguide 3. For example, Figure 1 shows a case where six total reflections occur within the waveguide 3 in the beam path from the radiation source 2 to the volume phase hologram 4. However, a different number of total reflections may apply depending on, for example, the waveguide parameters, the incoupling angle, and / or the distance between the radiation source 2 and the volume phase hologram 4. Thus, the radiation propagates within the waveguide 3 along a predetermined beam path.

[0063] Other optical elements may be used as incoupling optical elements, such as additional volume phase holograms. Alternatively, diffractive optical elements such as diffraction gratings may be used.

[0064] In the exemplary embodiment shown in Figure 1, the radiation is coupled to waveguide 3 on the user side 31 of waveguide 3. However, the radiation may also be coupled to waveguide 3 on the world side or side of waveguide 3.

[0065] In the exemplary embodiment shown in Figure 1, the waveguide 3 is flat. However, other shapes may be used for the waveguide 3.

[0066] Examples of waveguide shapes are shown in Figures 5A to 5C. In Figure 5A, waveguide 3 is curved. In the example in Figure 5B, the waveguide has a wedge shape.

[0067] In the example shown in Figure 5C, the waveguide 3 includes multiple parts, for example, a first waveguide portion 33 and a second waveguide portion 34. For example, the first waveguide portion has a lens shape, and the second waveguide portion has a wedge shape. These and other shapes of the waveguide 3 can be applied to all exemplary embodiments of the eye-tracking system 1.

[0068] Waveguide 3 is also part of the optical path for radiation returning from eye 9, particularly between volume phase hologram 4 and radiation source 2. Specifically, the waveguide can be used as the round-trip path for radiation, with the radiation traveling twice along the same path through waveguide 3. As a result, the optical path returning from eye 9 to radiation source 2 requires no additional optical elements beyond those used for the optical path from radiation source 2 to eye 9.

[0069] As shown in Figure 2, the radiation source 2 may include a detection module 22 for acquiring a self-mixing interference signal.

[0070] The radiation source 2 further includes a laser source unit 21.

[0071] For the sake of clarity, the laser source unit 21 and the detection module 22 are not explicitly represented in Figures 1, 3, and 4.

[0072] The detection module 22 is configured to provide a signal that correlates with the radiation returning from the eye. This radiation, scattered or reflected by the cornea, sclera, or another surface of the eye, interferes with the radiation in the cavity of the radiation source 2, causing self-mixing interference that provides information about eye rotation.

[0073] For example, the detection module may include a photodiode to acquire the number or frequency of interference fringes and / or to monitor the output parameters of the laser source unit 21, such as the output intensity or output wavelength of the emitted radiation. Alternatively, the detection module 22 may be configured to derive a self-mixed interference signal by monitoring operating parameters of the laser source unit 21, such as current or voltage.

[0074] During operation of the eye-tracking system, the optical path of radiation from the radiation source 2 to the eye 9 and backward extends entirely within the solid material, except for the space between the output surface region 35 and the eye.

[0075] As a result, the risk of human elements such as hair potentially obstructing the beam path from radiation source 2 to volume phase hologram 4 can be avoided.

[0076] Furthermore, the beam path between the radiation source 2 and the volume phase hologram 4 can be precisely defined during the manufacturing of the line-of-sight tracking system 1 by properly aligning the radiation source 2 with respect to the waveguide 3 and the volume phase hologram 4.

[0077] The optical function performed by the volume phase hologram 4 can be defined with high precision during the manufacturing of the volume phase hologram. The thickness of the volume phase hologram, i.e., the extension of the volume phase hologram along the normal of the waveguide 3, is large compared to the wavelength of the radiation emitted by the radiation source during operation. For example, the thickness is at least twice or at least ten times greater than the wavelength of the radiation from the radiation source 2.

[0078] The volume phase hologram 4 can be transmitted within the visible spectrum, and as a result, when, for example, an eye-tracking device is used for augmented reality or mixed reality applications, the vision of a user passing through the waveguide 3 containing the volume phase hologram 4 is not disturbed, or at least not significantly disturbed.

[0079] In the exemplary embodiment shown in Figure 1, the volume phase hologram 4 is a reflected volume phase hologram 42 located on the world side 32 of the waveguide 3, and the incoupling of the radiation source 2 may be acquired on any side of the waveguide 3.

[0080] However, other configurations, such as those shown in Figures 2 to 4, can also be applied.

[0081] In the exemplary embodiment shown in Figure 2, the volume phase hologram 4 is a transmitted volume phase hologram 43 located on the user side 31 of the waveguide 3. As described in relation to Figure 1, the incoupling of the radiation source 2 may be acquired on either side of the waveguide 3. Further features described in relation to Figure 1 also apply to this exemplary embodiment.

[0082] As shown in Figures 3 and 4, multiple volume phase holograms may be used instead of a single volume phase hologram, and each volume phase hologram may have an individual optical function. Further features described in relation to Figure 1 also apply to these exemplary embodiments.

[0083] In the exemplary embodiment shown in Figure 3, an additional volume phase hologram 41 is positioned between the volume phase hologram 4 and the radiation source 2. The radiation deflected by the additional volume phase hologram 41 collides with the volume phase hologram 4, which directs the radiation towards the user's eye 9. In this exemplary embodiment, the volume phase hologram 4 and the additional volume phase hologram 41 are reflection phase holograms 42.

[0084] The volume phase hologram 4 and the further volume phase hologram 41 are positioned on different sides of the waveguide 3. Thus, this exemplary embodiment provides a waveguide relay having a combination of a reflected VPH on the user side 31 (having a first optical function) and a reflected VPH on the world side 32 (having a second optical function different from the first optical function).

[0085] In the exemplary embodiment shown in Figure 4, volume phase hologram 4 is a transmitted volume phase hologram 43 located on the user side 31 of waveguide 3, and a further volume phase hologram 41 is a reflected volume phase hologram 42 located on the world side 32 of waveguide 3. For example, the further volume phase hologram 41 can collimate radiation from a radiation source onto volume phase hologram 4, and volume phase hologram 4 can focus this colliding radiation toward the user's eye 9. Thus, a waveguide relay is provided having a combination of a reflected VPH on the world side (having a first optical function) and a transmitted VPH on the user side (having a second optical function different from the first optical function).

[0086] Unlike the exemplary embodiments shown in Figures 1 to 4, the radiation does not necessarily need to be focused on the user's eye 9. Figure 6 shows possible optical functions.

[0087] Lines 701, 702, and 703 represent focused radiation, and the focal point may be located near the cornea (focused radiation 702), behind the cornea (focused radiation 701), or in front of the eye (focused radiation 703).

[0088] Alternatively, a volume-phase hologram or a combination of multiple volume-phase holograms can provide collimated radiation 704.

[0089] Alternatively, divergent radiation 705 and / or asymmetric radiation 706 may be provided by a single volume phase hologram or multiple volume phase holograms.

[0090] In particular, the combination of a waveguide and at least one volume phase hologram allows for highly reliable line-of-sight tracking based on auto-mixing interferometry.

[0091] This patent application claims priority to German patent applications No. 102023119331.7 and 102023131058.5, the disclosures of which are incorporated herein by reference.

[0092] The inventions described herein are not limited by the description given with reference to exemplary embodiments. Rather, the invention encompasses any novel features, and in particular any combination of features including any combination of features in the claims, even if such features or combinations are not expressly shown in the claims or exemplary embodiments. [Explanation of symbols]

[0093] List of reference symbols 1. Eye-tracking system 2 Radiation source 21 Laser source unit 22 detection modules 3 Waveguides 31. User side 32 World side 33 First waveguide section 34 Second waveguide section 35 Output surface area 4. Volume Phase Hologram 41 Further Volume Phase Holograms 42 Reflective Volume Phase Hologram 43. Transmissive Volumetric Hologram 5. Incoupling Optical Elements 701, 702, 703 Focused radiation 704 Collimated radiation 705 Divergent radiation 706 Asymmetric radiation 8 beams 9 eyes

Claims

1. Eye-tracking system (1), - A radiation source (2) configured to provide radiation, - Waveguide (3), - Volume phase hologram (4), Equipped with, - The waveguide (3) provides a propagation medium between the radiation source (2) and the volume phase hologram (3), - The radiation is reflected or scattered by part of the user's eye (9), returns to the radiation source (2), and combines, causing a self-mixing interference signal. Eye-tracking system (1).

2. The volume phase hologram (4) provides optical functionality suitable for determining the self-mixed interference signal in order to perform eye-tracking. The eye-tracking system according to claim 1.

3. The optical function includes at least one of deflection, focusing, collimation, and divergence. The eye-tracking system according to claim 2.

4. The volume phase hologram (4) is configured to deflect the radiation propagating within the waveguide toward the user's eye (9). An eye-tracking system according to any of the preceding claims.

5. The waveguide (3) is part of the optical path for the radiation returning from the eye between the volume phase hologram and the sensing module. An eye-tracking system according to any of the preceding claims.

6. The waveguide (3) is used as the round-trip path for the radiation, and the radiation travels the same path through the waveguide (3) twice. An eye-tracking system according to any of the preceding claims.

7. The eye-tracking system (1) includes an incoupling optical element (5) for coupling the radiation from the radiation source (2) to the waveguide (3). An eye-tracking system according to any of the preceding claims.

8. The radiation travels only within the free space between the output surface region of the waveguide and the eye. An eye-tracking system according to any of the preceding claims.

9. The volume phase hologram and the radiation source are fixed together with the waveguide. An eye-tracking system according to any of the preceding claims.

10. The volume phase hologram (4) is a reflective hologram (42) placed on the world side (32) of the waveguide, or a transmissive hologram (43) placed on the user side (31) of the waveguide (3). An eye-tracking system according to any of the preceding claims.

11. The eye-tracking system (1) further includes a volume phase hologram (41), An eye-tracking system according to any of the preceding claims.

12. The volume phase hologram (4) and the further volume phase hologram (41) each have individual optical functions. The eye-tracking system according to claim 11.

13. The volume phase hologram (4) is a transmitted volume phase hologram (43), and the further volume phase hologram (41) is a reflected volume phase hologram (42), or vice versa. The eye-tracking system according to claim 11 or 12.

14. The volume phase hologram (4) and the further volume phase hologram (41) are reflective volume phase holograms (42). The eye-tracking system according to claim 11 or 12.

15. The eye-tracking device (1) is configured to be integrated into a wearable device to be worn on the user's head. An eye-tracking system according to any of the preceding claims.

Images