Eye tracking device and method and AR headset or VR headset

Abstract

The invention relates to an eye tracking device (30, 30a, 30b), with an LFI sensor unit (12) which is configured to emit an infrared laser beam (14) and to record reflection signals (16, 36) of the infrared laser beam (14) and to provide measurement signals for evaluating eye positions and / or eye distances of an eye (18) arranged in the beam path of the infrared laser beam (14), and with an optical unit (20), at least comprising a beam splitter optic (22) which is configured to split and deflect the emitted infrared laser beam (14) into two or more partial beams (24, 26) before it strikes the eye (18) such that each of the partial beams (24, 26) of the infrared laser beam (14) strikes the eye (18) at a different location. It is proposed that the optical unit (20) comprises an LC unit (32) with an LC cell (34) which is provided for interaction with one of the partial beams (24, 26), and wherein the LC cell (34) can be controlled in such a way that the LC cell (34) selectively allows or prevents interference of the respective partial beam (24, 26) with its backscattered reflection signal (16, 36) in the LFI sensor unit (12) by appropriately influencing a polarization of the respective partial beam (24, 26).

Description

State of the art

[0001] An eye-tracking device has already been proposed, comprising a laser feedback interferometry (LFI) sensor unit, which is configured to emit at least one infrared laser beam and to record reflection signals of at least one part of the infrared laser beam and to provide measurement signals for evaluating eye positions and / or eye distances of an eye located in the beam path of the infrared laser beam by exploiting interference properties of the infrared laser light, and comprising an optical unit, comprising at least a beam splitter optic, which is configured to split and deflect the emitted infrared laser beam into two or more partial beams before it strikes the eye, such that each of the partial beams of the infrared laser beam strikes the eye at a different location. Disclosure of the invention

[0002] The invention relates to an eye-tracking device, in particular for smart glasses, such as an AR headset or a VR headset, with a laser feedback interferometry (LFI) sensor unit, which is configured at least to emit at least one infrared laser beam and to record reflection signals, such as reflection signals reflected back from the eye of a user of the smart glasses, of at least a part of the infrared laser beam and to provide measurement signals for evaluating eye positions and / or interpupillary distances of an eye arranged in the beam path of the infrared laser beam by utilizing interference properties of the infrared laser light, in particular interfering in a laser cavity of the LFI sensor unit, and with an optical unit, at least comprising a beam splitter optic, which is configured to split the emitted infrared laser beam into two or more (e.g.four) to split and deflect partial beams so that each of the partial beams of the infrared laser beam strikes the eye or a pupil plane of the eye tracking device at a different location.

[0003] It is proposed that the optical unit comprises a liquid-crystal (LC) unit with at least one LC cell designed to interact with one of the partial beams, and wherein the at least one LC cell is controllable such that it selectively allows or prevents interference of the respective partial beam with its backscattered reflection signal in the LFI sensor unit, particularly in one or more laser cavities of one or more LFI sensors of the LFI sensor unit, by appropriately influencing the polarization of the respective partial beam. Advantageously, active control of partial beams of the LFI sensor unit striking different points on a pupil plane of the eye-tracking device can be achieved. Advantageously, a plurality of LFI laser signals usable separately for eye tracking can be controlled by a single LFI sensor.per LFI sensor of an LFI sensor array. This advantageously allows for high energy and / or space efficiency. Furthermore, it advantageously leads to cost-effectiveness. Advantageously, the use of LFI sensors, especially static LFI sensors without scanners for scanning the infrared laser beams across a target, such as the eye, allows for a particularly high update rate, e.g., with an update frequency of more than 1 kHz. This is significantly higher than update rates achievable with camera-based eye-tracking solutions. The proposed invention advantageously enables a large eye-tracking eyebox in combination with a high update rate.

[0004] The eye-tracking device is a component of smart glasses, such as an augmented reality (AR) system (e.g., an AR headset) or a virtual reality (VR) system (e.g., a VR headset). Smart glasses are also frequently referred to as smart glasses. Alternatively, the eye-tracking device can also be used in other systems, such as head-up displays, ophthalmic examination devices, telescopes, microscopes, etc. AR headsets and / or VR headsets are, in particular, head-worn smart devices that project artificially generated images into a user's field of vision. The LFI sensor unit can include one or more LFI sensors. For example, it is conceivable that the LFI sensor unit could form an LFI sensor array with two, three, or more than three LFI sensors.The LFI sensor(s) can be configured, for example, as a VCSEL, preferably a ViP-VCSEL (vertical-cavity surface-emitting laser with integrated photodiode). The LFI sensor(s) is / are integrated, in particular, into the AR headset and / or the VR headset, preferably the smart glasses, e.g., into a frame, lens, or temple of the smart glasses. The LFI sensor(s) can also be part of a laser projector unit that generates the artificial image content of the AR and / or VR headset, i.e., integrated, for example, together with (RGB) laser diodes. Preferably, however, the LFI sensor(s) is / are configured separately from a laser projector unit that generates the artificial image content of the AR and / or VR headset. Preferably, the LFI sensor(s) are static and illuminate the eye / pupil plane independently of a scanner.Preferably, the infrared laser beam(s) of the LFI sensor unit is / are free from interference by a scanner, such as a controlled MEMS mirror system. The LFI sensor is based on an interferometric measurement method, also known as laser self-mixing. Specifically, the LFI sensor emits a laser beam in the infrared spectrum (the infrared laser signal), which then strikes a reflective surface (e.g., the retina). From this surface, the light of the laser beam is backscattered, so that it re-enters a laser cavity of the LFI sensor. In the laser cavity of the LFI sensor, the backscattered light interferes with a locally oscillating field of the LFI sensor.This leads, in particular, to a modulation of the laser power of the laser source, which can be detected either by a photodiode integrated into a back reflector of the laser cavity or by a direct measurement of a voltage at the laser source. The infrared laser source of the LFI sensor is, in particular, an infrared laser diode. The photodetector of the LFI sensor is, in particular, formed by the photodiode.

[0005] From the measurement signals of the LFI sensor, the distance to a reflecting object and / or the velocity of a reflecting object moving parallel to the propagation direction of the LFI sensor's laser beam can be determined in a known manner. Furthermore, the direction vector of the movement of the moving reflected object can also be determined using the LFI sensor in a known manner. The optical unit can include additional optics besides the beam splitter optics and the LC unit. In particular, in addition to these components, the optical unit comprises an optical system at least comparable to that of known smart glasses. The division of the infrared laser beam into different partial beams that strike the eye or a pupil plane of the smart glasses at different points serves, in particular, the purpose of enlarging the eyebox of the smart glasses.Preferably, in as many different eye positions as possible, at least one, and preferably exactly one, partial beam should always enter the pupil of the eye or scan the pupil of the eye. This allows, for example, the speed of eye movement and / or the distance of the LFI sensor unit from the eye to be measured at two or more separate locations on the eye. The combined view of the eye positions in which this condition is met is called the eyebox of the data glasses. The beam splitter optics are designed using a beam splitter configuration known to those skilled in the art. The beam splitter optics can be implemented by a meta-optic / meta-lens, for example, a (polarization-separating) meta-surface beam splitter, or a diffractive optic, such as a diffraction grating beam splitter, or by another optical element. A holographic-optical element is also conceivable for the beam splitter.Preferably, the beam splitter optics are polarization-separating beam splitter optics, which, for example, split the infrared laser beam into at least one horizontally polarized and at least one vertically polarized partial beam, or into at least one s-polarized and at least one p-polarized partial beam. Other polarizations, such as circular polarizations, are also conceivable alternatively or additionally. The infrared laser beam is preferably emitted divergently from the LFI sensor unit and, in particular, strikes the beam splitter optics and / or the LC unit divergently. "Provided for" and / or "configured" should be understood to mean, in particular, specifically programmed, designed, and / or equipped.The fact that an object is intended and / or set up for a specific function shall be understood in particular to mean that the object fulfills and / or performs this specific function in at least one application and / or operating state.

[0006] The LC unit is arranged, in particular, in the beam path of the infrared laser beam and / or at least a portion, preferably all, of the partial beams exiting the beam splitter optics. The LC unit is preferably designed to influence, in particular to rotate, the polarization of light passing through it in at least one operating state. The LC unit is preferably switchable. In particular, the polarization-influencing effect of the LC unit can be activated and deactivated. Furthermore, the polarization-influencing effect of the LC unit can be adjustable, e.g., a degree of polarization change. Activation, deactivation, and / or control can be carried out by means of a control unit of the eye-tracking device or by means of an external control unit operatively connected to the eye-tracking device. A "control unit" is understood to mean, in particular, a unit with at least one control electronics module.The term "control electronics" refers in particular to a unit comprising a processor unit, a memory unit, and an operating program stored in the memory unit. An LC cell preferably corresponds to a basic unit of the LC system that can only be controlled collectively. Different LC cells can preferably be controlled separately. In particular, the control unit is designed to apply and / or adjust voltages to the LC cell(s). It is conceivable that the selection of one or more active partial beams is performed by an algorithm, which then controls the LC system (or a filter unit) accordingly. The selection of the partial beam(s) can be based on measurement signals from the LFI sensor unit, e.g., based on a signal-to-noise ratio (SNR), detected velocities, detected distances, spectral distributions, etc.Without an LC unit, light from all partial beams of the beamsplitter optics would always be scattered back into the laser cavity, resulting in a superposition of the interference signals of the partial beams and making it impossible to extract the individual velocities from the individual partial beams. By using the described LC unit or a filter unit explained below in combination with the beamsplitter optics, the interference of partial beams, preferably all but one, can be suppressed by rotating the polarization of the partial beams. This ensures that the polarization of the emitted light of these partial beams no longer matches the polarization of the backscattered light of these partial beams, thus preventing interference in the LFI sensor unit. The interference of the currently selected partial beam can therefore be advantageously isolated from all other partial beams.In particular, interference of a partial beam is prevented if the LC cell rotates a polarization plane between the incident and reflected light by 90° or shifts a phase of the light by 180°. Interference of a partial beam is also prevented if the LC cell does not rotate a polarization plane between the incident and reflected light or shift a phase of the light. It is also conceivable that the LC cell additionally compensates for polarization effects of the scattering object, such as the eye, when preventing or allowing interference. Specifically, the LC unit can be positioned upstream or downstream of the beam splitter optics.In the upstream configuration, the LC unit would be positioned upstream of the beamsplitter optics in the infrared laser beam exiting the LFI sensor unit. It would rotate or not rotate the polarization before the infrared laser beam enters the beamsplitter optics and after the reflected signal exits the beamsplitter optics on its return path. In the preferred downstream configuration, the LC unit would be positioned downstream of the beamsplitter optics in the infrared laser beam exiting the LFI sensor unit. It would rotate or not rotate the polarization after the infrared laser beam exits the beamsplitter optics and before the reflected signal enters the beamsplitter optics on its return path.

[0007] Furthermore, it is proposed that the at least one LC cell is assigned to only a subset of all sections of the beamsplitter optics, preferably only exactly one section, in which only a subset of all partial beams of the infrared laser beam, preferably only one of the individual partial beams of the infrared laser beam, exits the beamsplitter optics. This advantageously allows for a simple and / or compact design. It also advantageously enables the targeted control of different partial beams, preferably without affecting other partial beams. This allows for the advantageous enlargement of an eye-tracking eyebox. In particular, the beamsplitter optics have at least one exit surface with several spatially adjacent subsections through which the partial beams exit the beamsplitter optics.Other sections of the beam splitter optics are preferably also equipped with an LC cell of the LC unit, but can also be designed without LC cells. In this case, the LC unit can only manipulate one partial beam or only a portion of all partial beams, i.e., "switch off" or "switch on".

[0008] Furthermore, it is proposed that the beam splitter optics have at least two, preferably at least four, sub-areas from which separable partial beams can emerge, and that the LC unit has at least two, preferably at least four, LC cells, preferably the same number of LC cells as sub-areas of the beam splitter optics, each of which is assigned to exactly one of the sub-areas of the beam splitter optics, preferably each attached to exactly one of the sub-areas of the beam splitter optics, and wherein the individual LC cells can be controlled such that they selectively allow or prevent interference of the respective partial beams with their respective backscattered reflection signals in the LFI sensor unit by appropriately influencing the polarization of the respective partial beams by means of the assigned LC cell. This advantageously allows a particularly large (eye-tracking) eyebox to be achieved.In particular, the control unit is designed for separate control of the individual LC cells of the LC unit. Furthermore, it is conceivable that the LFI sensor unit has multiple LFI sensors, each generating a separate laser source. In this case, one partial beam per laser source could be influenced by the same LC cell of the LC unit. The LC cell would thus manipulate multiple partial beams, specifically switching them on or off, although these partial beams would all originate from different LFI sensors / laser sources.

[0009] Furthermore, it is proposed that if the beamsplitter optics have at least four sub-areas from which separable partial beams can emerge, the four sub-areas of the beamsplitter optics should be arranged spatially in two dimensions, for example in a matrix form. This advantageously allows for a compact and / or easy-to-manufacture design. It also advantageously enables a particularly large eyebox for eye tracking.

[0010] Additionally, it is proposed that the at least one LC cell(s) of the LC unit be / are arranged such that the emitted infrared laser beam passes through the cell(s) once on its way to the eye and once on its way back from the eye. This advantageously allows for a compact design. Furthermore, it is advantageous that only half the polarization rotation is required compared to when the LC unit passes through only once.

[0011] If at least one LC cell, preferably all LC cells, of the LC unit is / are configured to rotate the polarization of the associated partial beam in at least one operating state, and / or if at least one LC cell, preferably all LC cells, of the LC unit is / are configured to deactivate interference of the associated partial beam(s) in the LFI sensor unit by rotating the polarization by λ / 4 with each passage of the LC cell, then active control of partial beams from the LFI sensor unit striking different points on a pupil plane of the eye-tracking device can advantageously be achieved. For example, s-polarized light is generated and emitted in a laser cavity of an LFI sensor in the LFI sensor unit. The polarization is then rotated by λ / 4 via an LC cell of the LC unit through a λ / 4 plate and then reaches the eye to be tracked.A portion of the reflection signal backscattered by the eye then passes through the same LC cell a second time, changing the polarization by the same value once more, until finally the polarization transitions to a p-polarized state. This p-polarized light then no longer interferes with the internally oscillating wave of the s-polarized light-generating laser cavity of the LFI sensor. Therefore, no speed or distance can be measured for this signal.

[0012] Furthermore, it is proposed that the eye tracking device or an alternative eye tracking device comprises an optical unit with a filter unit having an adjustable neutral density (ND) filter, which is provided for interaction with one of the partial beams, or with several adjustable neutral density (ND) filters, each of which is provided for interaction with one of the partial beams, wherein in particular the individual adjustable ND filters of the filter unit are each assigned to only a portion of all sub-areas of the beam splitter optics, preferably only exactly one sub-area of ​​the beam splitter optics, in which only a portion of all partial beams of the infrared laser beam, preferably only one of the individual partial beams of the infrared laser beam, emerges from the beam splitter optics, and wherein the individual adjustable ND filters can be controlled in such a way thatthat they optionally allow or prevent interference of the respective partial beam(s) with its backscattered reflection signal(s) in the LFI sensor unit by appropriately influencing the intensity of the respective partial beam(s) using the associated adjustable ND filter. This allows, in particular, the same advantages as with the LC cell to be achieved. Compared to the use of LC cells, the laser power of the LFI sensor unit can also be advantageously increased, so that a good / strong reflection signal can be achieved for all partial beams without shining too much light onto the eye. In particular, the associated adjustable ND filters attenuate the corresponding (to be deactivated) partial beams in such a way that...that they can no longer contribute to the interference signal. An adjustable ND filter can, for example, consist of two superimposed and adjustable (rotatable) polarizing filters. The control unit can be designed to automatically adjust the attenuation / darkening provided by the ND filter(s).

[0013] Furthermore, it is proposed that the LC unit and / or the filter unit, in conjunction with the beam splitter optics, is / are designed to selectively generate either a horizontal expansion of the infrared laser beam for one polarization or a vertical expansion of the infrared laser beam for a different polarization, particularly depending on the switching of individual LC cells of an LC unit comprising several LC cells arranged in two dimensions relative to each other, or individual ND filters of a filter unit comprising several ND filters arranged in two dimensions relative to each other. This advantageously allows manipulation of the eyebox size. In particular, the horizontal extent of the eyebox depends on the polarization setting of adjacent LC cells and / or on the attenuation setting of adjacent ND filters.In particular, the vertical extent of the eyebox depends on the polarization setting of superimposed LC cells and / or on the attenuation setting of superimposed ND filters.

[0014] Preferably, the LFI sensor unit comprises a single laser diode with a single laser cavity. Alternatively, it is also proposed that the LFI sensor unit comprises at least two mesa structures directly integrated on the chip level, preferably arranged on a common ASIC (Application-Specific Integrated Circuit), each containing its own active area / laser cavity and separately controllable, with each mesa structure preferably being equipped with its own meta-optics. This advantageously allows the eye-tracking eyebox to be further enlarged. The ASIC can also form the control unit (which switches the LC cells and / or ND filters) or be provided separately and in addition to the control unit. In this case, the LFI sensor unit forms an LFI sensor array with multiple LFI sensors.The individual laser cavities can each be equipped with polarization filters or already provided with preset polarization properties as part of the semiconductor design. The two mesa structures preferably each emit a divergent beam, which then strikes the beam splitter optics and subsequently the LC unit. Depending on the state of the switchable LC cells of the LC unit, a different set of output partial beams is selected, which are then preferably used to measure distance and / or velocity. The meta-optics can be integrated directly into an output facet or another emission surface of one of the laser cavities.A meta-optics is, in particular, an optical system consisting of metamaterials, i.e., specially developed materials that obtain their optical properties by structuring on a subwavelength-like scale (smaller than the wavelength of light), preferably rather than by their chemical composition alone.

[0015] In this context, it is proposed that the LFI sensor unit comprises an integrated polarization unit, particularly one configured as a meta-optics, or an external polarization unit, which is configured to ensure that the infrared laser beam of a single laser of the LFI sensor unit, or the infrared laser beam and one or more other emitted infrared laser beams of a laser array formed by several combined mesa structures or by several separate single lasers fixed relative to one another, are fixedly polarized before their initial impact on the optical unit. In the case of a laser array, they are preferably at least partially fixedly polarized differently. This advantageously allows for a compact design. Furthermore, it advantageously simplifies the design of the beam splitter optics.The integrated polarization unit can be implemented, for example, by wafer-level optics, nano-structuring of an exit facet of the respective LFI sensor of the LFI sensor unit and / or nano-imprint optics.

[0016] In particular, the beam splitter optics and / or the LC unit are designed to control the partial beams by adjusting the polarizations.

[0017] Furthermore, the AR or VR headset is proposed, equipped with a head mount and eye-tracking device. This allows for a larger eyebox to be advantageously used for the eye-tracking function of the smart glasses. This can improve user-friendliness and / or user comfort.

[0018] Furthermore, an eye-tracking method, in particular by means of the eye-tracking device, preferably for the AR headset or the VR headset, is proposed, wherein at least the infrared laser beam is emitted by the laser feedback interferometry (LFI) sensor unit, reflection signals of at least a part of the infrared laser beam are recorded, and measurement signals for evaluating eye positions and / or eye distances of an eye arranged in the beam path of the infrared laser beam are provided by exploiting interference properties of the infrared laser light, wherein the emitted infrared laser beam is split and deflected by the optical unit comprising at least the beam splitter optics into two or more partial beams before striking the eye, such that each of the partial beams of the infrared laser beam strikes the eye at a different location.wherein a liquid crystal (LC) unit of the optical unit with one or more LC cells, which in particular are each assigned only to a part of all sub-areas of the beam splitter optics, preferably only to exactly one sub-area of ​​the beam splitter optics, and / or a filter unit of the optical unit with an adjustable neutral density (ND) filter or with several adjustable neutral density (ND) filters, which in particular are each assigned only to a part of all sub-areas of the beam splitter optics, preferably only to exactly one sub-area of ​​the beam splitter optics, is provided for interaction with one or more of the partial beams, wherein in particular only a part of all partial beams of the infrared laser beam, preferably only one of the individual partial beams of the infrared laser beam, emerges from the beam splitter optics in the sub-area(s), and wherein the individual LC cell(s) or the individual ND filter(s) is / are controlled in such a way as tothat the individual LC cell(s) or the individual ND filter(s) selectively allows or prevents interference of the respective partial beam(s) with its backscattered reflection signal(s) in the LFI sensor unit by appropriately influencing the polarization of the respective partial beam(s) by means of the associated LC cell or by appropriately influencing the intensity of the respective partial beam(s) by means of the associated ND filter. Advantageously, this allows for active control of partial beams of the LFI sensor unit that strike different points on a pupil plane of the eye tracking device.

[0019] The eye-tracking device, the AR headset or VR headset, and the method according to the invention are not limited to the application and embodiment described above. In particular, the eye-tracking device, the AR headset or VR headset, and the method according to the invention may, to achieve a functionality described herein, comprise a different number of individual elements, components, units, and process steps than those specified herein. Furthermore, values ​​within the specified limits of this disclosure are also considered disclosed and freely usable. drawing

[0020] Further advantages become apparent from the following description of the drawings. The drawings illustrate exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. A person skilled in the art will expediently consider the features individually and combine them into meaningful further combinations.

[0021] They show: Fig. 1 A schematic representation of a pair of data glasses designed as an augmented reality headset with an eye-tracking device, Fig. 2 a schematic representation of part of the eye tracking device, Fig. 3 a schematic representation of an eye with points of impact of partial beams of an infrared laser beam of a laser feedback interferometry sensor unit of the eye tracking device, Fig. 4 an exemplary beam splitter optic comprising four sub-areas for an optical unit of the eye tracking device, Fig. 5 an alternative eye tracking device with an alternative optical unit, Fig. 6 another alternative eye tracking device with an alternative laser feedback interferometry sensor unit and Fig. 7 a schematic flowchart of an eye tracking procedure that can be carried out using the eye tracking device. Description of the exemplary implementations

[0022] The Fig. Figure 1 schematically shows an example of a pair of smart glasses 10. In the illustrated case, the smart glasses 10 are designed as an AR (Augmented Reality) headset. Alternatively, the smart glasses 10 could also be designed as a VR (Virtual Reality) headset or a hybrid of AR and VR headsets. The smart glasses 10 have a head mounting device 68. The head mounting device 68 defines the position of an eye 18 and a pupil plane 28 within the smart glasses 10. The smart glasses 10 include an image generation unit 70, which is designed to generate and output a visible image and superimpose it on a real-world image. In the example shown, this is achieved by scanning RGB laser beams, which are reflected back to the eye 18 by an optical element in the lens (see the indicated visible laser beams 72 in Figure 1). Fig. 1) The data glasses 10 have an internal control unit 74. Alternatively or additionally, the data glasses 10 can be connected to an external control unit 76 (wirelessly). The internal control unit 74 and / or the external control unit 76 can be used to control the image generation unit 70.

[0023] The data glasses 10 have an eye-tracking device 30. The eye-tracking device 30 has a laser feedback interferometry (LFI) sensor unit 12. The LFI sensor unit 12 is configured to emit an infrared laser beam 14. The LFI sensor unit 12 includes an LFI sensor for this purpose. The LFI sensor unit 12 shines the infrared laser beam 14 onto the pupil plane 28. If an eye 18 is positioned in the pupil plane 28, the infrared laser beam 14 scatters at the eye 18, thus generating a reflection signal 16, 36. If the infrared laser beam 14 has been split into several partial beams 24, 26 before striking the eye 18, the eye 18 generates a separate reflection signal 16, 36 for each partial beam 24, 26, provided that the partial beams 24, 26 also strike the eye 18. The LFI sensor unit 12 is configured to record the reflection signals 16, 36 from parts of the infrared laser beam 14.The LFI sensor unit 12 includes a photosensor, e.g., a photodiode. The LFI sensor unit 12 is configured to generate measurement signals based on the detected reflection signals 16, 36. The LFI sensor unit 12, particularly in conjunction with the control unit 74, 76, is configured to evaluate the measurement signals. The LFI sensor unit 12, particularly in conjunction with the control unit 74, 76, is designed to provide the eye positions and / or distances of the eye 18 located in the beam path of the infrared laser beam 14 by utilizing interference properties of the infrared laser light. The basic operating principle of LFI sensors for determining distances and velocities is known to those skilled in the art from the literature and is therefore not explained in detail here.

[0024] The Fig. Figure 2 shows a schematic representation of part of the eye tracking device 30. The eye tracking device 30 has an optical unit 20. The optical unit 20 is arranged in a beam path of the infrared laser beam 14. The optical unit 20 has a beam splitter optic 22. The infrared laser beam 14 strikes an entrance surface of the beam splitter optic 22 at a divergent angle. The beam splitter optic 22 is configured to split and deflect the emitted infrared laser beam 14 into two or more partial beams 24, 26 before it strikes the eye 18, such that each of the partial beams 24, 26 of the infrared laser beam 14 strikes the eye 18 and / or the pupil plane 28 at a different location (see Figure 2). Fig. 3. The hatching of the points of impact is intended to indicate a polarization of the corresponding partial beam 24, 26). An area within which an eye 18 can be arranged such that at least one of the partial beams 24, 26 strikes the eye 18 is called an eyebox 78, in particular an eye-tracking eyebox, and is shown in the Fig. Figure 3 shows a schematic representation. The separate partial beams 24, 26 formed from the common input signal (infrared laser beam 14) exit the beam splitter optics 22 on one output side of the beam splitter optics 22 with different properties (e.g., polarizations, focusing, beam directions, etc.). The beam splitter optics 22 has several sub-areas 38, 40 from which separable partial beams 24, 26 can emerge. In the Fig. Figure 2 shows two sub-areas 38 and 40 and two partial rays 24 and 26 as examples. Fig. Figure 4 alternatively shows a beam splitter optic 22 with four sub-areas 38, 40, 44, 46. This beam splitter optic 22 would accordingly generate four partial beams 24, 26. Thus, four separable partial beams 24, 26 could emerge from the four sub-areas 38, 40, 44, 46 of the beam splitter optic 22. The four sub-areas 38, 40, 44, 46 of the beam splitter optic 22 of the Fig. The four components are spatially arranged in two dimensions relative to each other. The four sub-areas 38, 40, 44, 46 of the beam splitter optic 22 are... Fig. The four elements are arranged in a matrix form.

[0025] The optical unit 20 comprises a liquid crystal (LC) unit 32. The LC unit 32 includes an LC cell 34. The LC cell 34 is configured to interact with one of the partial beams 24, 26 exiting the beam splitter optics 22. The at least one LC cell 34 can be controlled, e.g., by the control unit 74, 76, such that the LC cell 34 selectively allows or prevents interference of one of the partial beams 24, 26 with its backscattered reflection signal 16, 36 in the LFI sensor unit 12 by correspondingly influencing a polarization of the respective partial beam 24, 26 or of the reflection signal 16, 36 of the respective partial beam 24, 26. The LC unit 32 has in the Fig. In the exemplary case 2, an additional LC cell 42 is also shown. Each of the LC cells 34, 42 is in the exemplary case of the Fig. 2 each only exactly to the sub-area 38, 40 of the beam splitter optics 22. The LC cells 34, 42 are each attached to exactly one of the sub-areas 38, 40 of the beam splitter optics 22. The individual LC cells 34, 42 can then be controlled, in particular by means of the control unit 74, 76, such that they selectively allow or prevent interference of the respective partial beams 24, 26 with their respective backscattered reflection signals 16, 36 in the LFI sensor unit 12 by correspondingly influencing a polarization of the respective partial beams 24, 26 or the associated reflection signals 16, 36 by means of the assigned LC cell 34, 42, depending on the setting / control of the respective LC cell 34, 42.The LC cells 34, 42 of the LC unit 32 are arranged such that the LC cells 34, 42 of the LC unit 32 are passed once by the partial beams 24, 26 of the emitted infrared laser beam 14 on the way from the LFI sensor unit 12 to the eye 18 and once by the reflection signal 16, 36 of the infrared laser beam 14 on the way from the eye 18 to the LFI sensor unit 12.

[0026] The LC cells 34, 42 of the LC unit 32 are configured to rotate the polarization of the associated partial beam 24, 26 in at least one operating state. The LC cells 34, 42 can, for example, be configured such that when a voltage is applied, the polarization of transmitted light signals is rotated, and when no voltage is applied, the polarization of transmitted light signals is not rotated. Alternatively, the LC cells 34, 42 could be configured such that when a voltage is applied, the polarization of transmitted light signals is not rotated, and when no voltage is applied, the polarization of transmitted light signals is not rotated. Furthermore, different voltages other than zero for rotation and non-rotation are also conceivable.The LC cells 34, 42 of the LC unit 32 are configured to deactivate the interference of the associated partial beams 24, 26 in the LFI sensor unit 12 by rotating the polarization each time the corresponding LC cell 34, 42 passes by λ / 4, at least in one of the operating states.

[0027] Alternatively or additionally, the optical unit 20 can be fitted with a filter unit 50a (see below). Fig. 5) with an adjustable neutral density ND filter 48a, which is designed to interact with one of the partial beams 24, 26. The ND filter 48 could be provided in place of one of the LC cells 34, 42. The adjustable ND filter 48 could be controlled, in particular by means of the control unit 74, 76, such that the adjustable ND filter 48 selectively allows or prevents interference of the respective partial beam 24, 26 with its backscattered reflection signal 16, 36 in the LFI sensor unit 12 by correspondingly influencing the intensity of the respective partial beam 24, 26 by means of the associated adjustable ND filter 48.

[0028] In the Fig. 5 and Fig. Figure 6 shows two further embodiments of the invention. The following descriptions and drawings are essentially limited to the differences between the embodiments, whereby, with regard to identically designated components, in particular components with the same reference numerals, reference is also generally made to the drawings and / or the description of the other embodiments, in particular the Fig. 1 to 4, reference can be made. The reference numerals of the exemplary embodiment in the Fig. Numbers 1 to 4 have no suffix. In the exemplary embodiments of the Fig. 5 and Fig. 6. To distinguish the embodiments, the letters a and b are appended to the reference numerals.

[0029] In the Fig. Figure 5 schematically shows an alternative eye tracking device 30a with an alternative optical unit 20a. In the exemplary embodiment of the Fig. In 5, the LC unit 32 is replaced by the filter unit 50a, i.e., all LC cells 34, 42 are replaced by adjustable ND filters 48a, 52a. The alternative optical unit 20a includes the filter unit 50a with the multiple adjustable neutral density ND filters 48a, 52a. The multiple adjustable neutral density ND filters 48a, 52a are each configured to interact with a partial beam 24a, 26a of an infrared laser beam 14a, which is split by a beam splitter optic 22a of an optical unit 20a and emitted by an LFI sensor unit 12a of the alternative eye-tracking device 30a.The individual adjustable ND filters 48a, 52a can be controlled in such a way that they optionally allow or prevent interference of the respective partial beams 24a, 26a with associated backscattered reflection signals 16a, 36a in the LFI sensor unit 12a by appropriately influencing the intensity of the respective partial beams 24a, 26a by means of the respective assigned adjustable ND filters 48a, 52a.

[0030] The LC unit 32 and / or the filter unit 50a, in conjunction with the beam splitter optics 22, 22a, are designed to selectively generate either a horizontal expansion of the infrared laser beam 14, 14a for one polarization or a vertical expansion of the infrared laser beam 14, 14a for a different polarization. This occurs depending on the switching of individual LC cells 34, 42 of an LC unit 32 comprising several LC cells 34, 42 arranged in two dimensions relative to each other (see figure). Fig. 4) or individual ND filters 48a, 52a of a filter unit 50a comprising several ND filters 48a, 52a arranged in two dimensions relative to each other (e.g. one ND filter 48a, 52a per sub-area 38, 40, 44, 46 of the Fig. 4).

[0031] In the Fig. Figure 6 schematically depicts another alternative eye-tracking device 30b. This alternative eye-tracking device 30b includes an alternative LFI sensor unit 12b. The alternative LFI sensor unit 12b includes an ASIC (Application-Specific Integrated Circuit) 62b. Two separate mesa structures 58b and 60b are arranged on the ASIC 62b. The mesa structures 58b and 60b form a laser array. The use of laser arrays with more than two mesa structures 58b and 60b is also conceivable. The two mesa structures 58b and 60b are separately controllable. Each of the two mesa structures 58b and 60b has its own active area / laser cavity 54b and 56b, respectively. Both mesa structures 58b, 60b each emit a divergent infrared laser beam 14b, 66b, which interacts with a common beam splitter optic 22b of an optics unit 20b of the further alternative eye tracking device 30b.Each of the divergent infrared laser beams 14b, 66b is split by the beam splitter optics 22b into at least two partial beams 24b, 24'b, 26b, 26'b. The partial beams 24b, 24'b, 26b, 26'b then strike an LC cell 34b of an LC unit 32b of the optics unit 20b. Depending on the set switching state of the switchable LC cell 34b, one set of partial beams 24b, 26b or another set of partial beams 24'b, 26'b is selected and their signals are used to generate the measurement signals for eye tracking.

[0032] The alternative LFI sensor unit 12b includes a polarization unit 64b. The polarization unit 64b is shown as an integrated polarization unit 64b. In this configuration, the polarization unit 64b could be a meta-optic, specifically a meta-optic integrally formed with the respective mesa structures 58b and 60b. Alternatively, the polarization unit 64b could also be an external polarization unit 64b. The polarization unit 64b is configured such that the infrared laser beam 14b and the further emitted infrared laser beam 66b are fixedly polarized before their initial impact on the optical unit 20b. As an alternative to the laser array with the described mesa structures 58b and 60b, a laser array consisting of several fixedly positioned individual lasers (not shown) could also be used.Preferably, such an alternative laser array also has the same or a similar polarization unit 64b / meta-optics as the laser array with the mesa structures 58b, 60b.

[0033] The Fig.Figure 7 shows a schematic flowchart of an eye-tracking method, in particular using one of the eye-tracking devices 30, 30a, 30b described above. In at least one process step 100, the LFI sensor unit 12, 12a, 12b emits at least one infrared laser beam 14, 14a, 14b. In at least one further process step 110, the emitted infrared laser beam 14, 14a, 14b is split into two or more partial beams 24, 24a, 24b, 24'b, 26, 26a, 26b, 26b by an optical unit 20, 20a, 20b comprising at least one beam splitter optic 22, 22a, 22b before it strikes the eye 18. The infrared laser beam 14, 14a, 14b is split and deflected into two or more partial beams 24, 24a, 24b, 24'b, 26, 26a, 26b, 26'b such that each of the partial beams 24, 24a, 24b, 24'b, 26, 26a, 26b, 26'b of the infrared laser beam 14, 14, 14b later strikes the eye 18 at a different point.In at least one further process step 120, the partial beams 24, 24a, 24b, 24'b, 26, 26a, 26b, 26'b are manipulated by LC cells 34, 42 of the LC unit 32 and / or by adjustable ND filters 48a, 52a of the filter unit 50a.

[0034] In at least one further process step 130, the partial beams 24, 24a, 24b, 24'b, 26, 26a, 26b, 26'b are scattered by the eye 18, so that reflection signals 16, 36 are generated. A portion of the reflection signals 16, 36 is reflected back by the eye 18 to the LFI sensor unit 12, 12a, 12b. In at least one further process step 140, the reflection signals 16, 36 originating from the partial beams 24, 24a, 24b, 24'b, 26, 26a, 26b, 26'b are manipulated again on their return path to the LFI sensor unit 12, 12a, 12b by the LC cells 34, 42 of the LC unit 32 and / or by the adjustable ND filters 48a, 52a of the filter unit 50a. In at least one further process step 150, the portion of the infrared laser beam 14, 14a, 14b that reaches the LFI sensor unit 12, 12a, 12b is recorded.In the LFI sensor unit 12, 12a, 12b, the recorded part is interfered with and measurement signals are provided, depending on the polarization of the output and input signals, for the evaluation of eye positions and / or eye distances of the eye 18 arranged in the beam path of the infrared laser beam 14, 14a, 14b.In process steps 120 and 140, in which the respective light signals from the LC unit 32 and / or from the filter unit 50a are manipulated, the individual LC cells 34, 42 and / or the individual adjustable ND filters 48a, 52a are controlled such that the individual LC cells 34, 42 or the individual adjustable ND filters 48a, 52a selectively cause interference of the respective partial beams 24, 24a, 24b, 26, 26a, 26b, 26'b with their backscattered reflection signals 16, 36 in the LFI sensor unit 12, 12a, 12b by correspondingly influencing the polarization of the respective partial beams 24, 24a, 24b, 24'b, 26, 26a, 26b, 26'b by means of the respective associated LC cells 34, 42 and / or by a corresponding influence on the intensity of the respective partial beams 24, 24a, 24b, 24'b, 26, 26a, 26b, 26'b by means of the respective associated adjustable ND filter 48a, 52a to allow or prevent.In at least one further process step 160, the distance of the eye 18 from the LFI sensor unit 12, 12a, 12b and / or the speed of a movement of the eye 18 are calculated and / or determined based on the measurement signals. In at least one further process step 170, the determined distance and / or the determined speed is output, e.g., by the control unit 74, 76. The output is then processed, for example, by the data glasses 10 or by a third-party device and / or applied for at least one function.

Claims

[1] Eye tracking device (30, 30a, 30b), in particular for smart glasses (10), such as an AR headset or VR headset, with a laser feedback interferometry (LFI) sensor unit (12) which is at least configured to emit at least one infrared laser beam (14) and to receive reflection signals (16, 36) of at least part of the infrared laser beam (14) and to provide measurement signals for evaluating eye positions and / or eye distances of an eye (18) arranged in the beam path of the infrared laser beam (14) by exploiting interference properties of the infrared laser light, and with an optical unit (20), at least comprising a beam splitter optic (22), which is configured to split and deflect the emitted infrared laser beam (14) into two or more partial beams (24, 26) before it strikes the eye (18) in such a way that each of the partial beams (24, 26) of the infrared laser beam (14) strikes the eye (18) or a pupil plane (28) of the eye tracking device (30) at a different location, characterized by, that the optical unit (20) comprises a liquid-crystal (LC) unit (32) with at least one LC cell (34) which is provided for interaction with one of the partial beams (24, 26), and wherein the at least one LC cell (34) can be controlled in such a way that the at least one LC cell (34) selectively allows or prevents interference of the respective partial beam (24, 26) with its backscattered reflection signal (16, 36) in the LFI sensor unit (12) by appropriately influencing a polarization of the respective partial beam (24, 26). [2] Eye tracking device (30, 30a, 30b) according to claim 1, characterized by, that the at least one LC cell (34) is assigned to only a part of all sub-areas (38, 40) of the beam splitter optics (22), preferably only exactly one sub-area (38, 40) of the beam splitter optics (22), in which only a part of all partial beams (24, 26) of the infrared laser beam (14), preferably only one of the individual partial beams (24, 26) of the infrared laser beam (14), exits from the beam splitter optics (22). [3] Eye tracking device (30, 30a, 30b) according to claim 1 or 2, characterized bythat the beam splitter optics (22) has at least two, preferably at least four, sub-areas (38, 40) from which separable partial beams (24, 26) can emerge, and that the LC unit (32) has at least two, preferably at least four, LC cells (34, 42), each of which is assigned to exactly one of the sub-areas (38, 40) of the beam splitter optics (22), preferably each of which is attached to exactly one of the sub-areas (38, 40) of the beam splitter optics (22), and wherein the individual LC cells (34, 42) can be controlled such that they selectively cause interference of the respective partial beams (24, 26) with their respective backscattered reflection signals (16, 36) in the LFI sensor unit (12) by appropriately influencing a polarization of the respective partial beams (24, 26) by means of the assigned LC cell (34, 42) allow or prevent. [4] Eye tracking device (30, 30a, 30b) according to any one of the preceding claims, characterized by , that the beam splitter optics (22) has at least four sub-areas (38, 40, 44, 46) from which separable partial beams (24, 26) can emerge, wherein the four sub-areas (38, 40, 44, 46) of the beam splitter optics (22) are arranged spatially in two dimensions, for example in matrix form relative to each other. [5] Eye tracking device (30, 30a, 30b) according to any one of the preceding claims, characterized by , that the at least one LC cell (34) or the LC cells (34, 42) of the LC unit (32) is / are arranged such that the at least one LC cell (34) or the LC cells (34, 42) of the LC unit (32) is / are passed once by the emitted infrared laser beam (14) on the way to the eye (18) and once by the reflection signal (16, 36) of the infrared laser beam (14) on the way from the eye (18). [6] Eye tracking device (30, 30a, 30b) according to any one of the preceding claims, characterized by, that the at least one LC cell (34), preferably all LC cells (34, 42), of the LC unit (32) is / are configured to rotate a polarization of the associated partial beam (24, 26) in at least one operating state. [7] Eye tracking device (30, 30a, 30b) according to claim 6, characterized by , that the at least one LC cell (34), preferably all LC cells (34, 42), of the LC unit (32) is / are configured to deactivate, at least in one operating state, an interference of the associated partial beam(s) (24, 26) in the LFI sensor unit (12) by rotating the polarization by λ / 4 each time the LC cell (34, 42) passes. [8] Eye tracking device (30, 30a, 30b), in particular for smart glasses (10), such as an AR headset or VR headset, preferably according to one of the preceding claims, with a laser feedback interferometry (LFI) sensor unit (12) which is at least configured to output at least one infrared laser beam (14) and to record reflection signals (16, 36) of at least one part of the infrared laser beam (14) and to provide measurement signals for evaluating eye positions and / or eye distances of an eye (18) arranged in the beam path of the infrared laser beam (14) by exploiting interference properties of the infrared laser light, and with an optical unit (20), at least comprising a beam splitter optic (22), which is configured to split and deflect the emitted infrared laser beam (14) into two or more partial beams (24, 26) before it strikes the eye (18) in such a way that each of the partial beams (24, 26) of the infrared laser beam (14) strikes the eye (18) at a different point, characterized by, that the optical unit (20) has a filter unit (50a) with an adjustable neutral density (ND) filter (48a) which is provided for interaction with one of the partial beams (24, 26), or with several adjustable neutral density (ND) filters (48a, 52a) which are each provided for interaction with one of the partial beams (24, 26), wherein the individual adjustable ND filters (48a, 52a) can be controlled in such a way that they selectively allow or prevent interference of the respective partial beam(s) (24, 26) with its backscattered reflection signal(s) (16, 36) in the LFI sensor unit (12) by appropriately influencing an intensity of the respective partial beam(s) (24, 26) by means of the associated adjustable ND filter (48a, 52a). [9] Eye tracking device (30, 30a, 30b) according to any one of the preceding claims, characterized by, that the LC unit (32) and / or the filter unit (50a) in conjunction with the beam splitter optics (22) is / are designed to selectively generate either a horizontal expansion of the infrared laser beam (14) for one polarization or a vertical expansion of the infrared laser beam (14) for a further polarization different from the polarization, in particular depending on a switching of individual LC cells (34, 42) of an LC unit (32) comprising several LC cells (34, 42) arranged in two dimensions relative to each other or individual ND filters (48a, 52a) of a filter unit (50) comprising several ND filters (48a, 52a) arranged in two dimensions relative to each other. [10] Eye tracking device (30b) according to any one of the preceding claims, characterized by, that the LFI sensor unit (12) has at least two mesa structures (58b, 60b) integrated directly on the chip level, preferably arranged on a common ASIC (Application-Specific Integrated Circuit) (62b), each comprising its own active area / laser cavity (54b, 56b) and separately controllable, wherein preferably each of the mesa structures (58b, 60b) is provided with its own meta-optics. [11] Eye tracking device (30b) according to any one of the preceding claims, characterized by, that the LFI sensor unit (12) has an integrated polarization unit (64b), in particular designed as a meta-optics, or an external polarization unit, which is configured to ensure that the infrared laser beam (14) of a single laser of the LFI sensor unit (12) or the infrared laser beam (14) and one or more further emitted infrared laser beams (66b) of a laser array formed by several combined mesa structures or by several separate single lasers fixed to each other are fixedly polarized before first striking the optics unit (20), and in the case of a laser array preferably at least partially differently fixed polarized. [12] AR headset or VR headset with a head attachment device (68) and with an eye tracking device (30, 30a, 30b) according to any of the preceding claims. [13] Eye tracking method, in particular by means of an eye tracking device (30, 30a, 30b) according to any one of claims 1 to 11, preferably for an AR headset or VR headset according to claim 12, wherein at least one infrared laser beam (14) is emitted from a laser feedback interferometry (LFI) sensor unit (12), reflection signals (16, 36) of at least part of the infrared laser beam (14) are recorded, and measurement signals for evaluating eye positions and / or eye distances of an eye (18) arranged in the beam path of the infrared laser beam (14) are provided by exploiting interference properties of the infrared laser light, and wherein the emitted infrared laser beam (14) is split and deflected by an optical unit (20) comprising at least one beam splitter optic (22) into two or more partial beams (24, 26) before striking the eye (18) such that each of the partial beams (24, 26) of the infrared laser beam (14) strikes the eye (18) at a different point, characterized by, that a liquid-crystal (LC) unit (32) of the optical unit (20) with one or more LC cells (34, 42), and / or a filter unit (50) of the optical unit (20) with one or more adjustable neutral density (ND) filters (48, 52), is provided for interaction with one or more of the partial beams (24, 26), wherein the individual LC cell(s) (34, 42) or the individual ND filter(s) (48, 52) is / are controlled such that the individual LC cell(s) (34, 42) or the individual ND filter(s) (48, 52) selectively causes interference of the respective partial beam(s) (24, 26) with its backscattered Reflection signal(s) (16, 36) in the LFI sensor unit (12) by a corresponding influence on a polarization of the respective partial beam(s) (24, 26) by means of the associated LC cell (34,42) or by appropriately influencing the intensity of the respective partial beam(s) (24, 26) by means of the associated ND filter (48, 52) allows or prevents.

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