Eye tracking device, ar and / or VR headset, and eye tracking method

Abstract

The invention relates to an eye tracking device (48a-f) for tracking a position and / or gaze direction of an eye (10a-f), for example in an AR and / or VR headset (12a-f), having at least one laser feedback interferometry (LFI) sensor (14a-f), comprising an infrared laser source (16a-f) for radiating an infrared laser signal (18a-f) onto the eye (10a-f) to be tracked, and comprising a photodetector (20a-f) for detecting an interference signal (22a-f, 22'a-f) between the infrared laser signal (18a-f) generated by the infrared laser source (16a-f) and a portion of the infrared laser signal (24a-f) reflected by the eye (10a-f) back to the LFI sensor (14a-f). According to the invention, the eye tracking device (48a-f) comprises an eye polarisation compensation unit (26a-f) which is designed to at least partially compensate for a polarisation difference, caused by an optical property of the eye (10a-f), between the infrared laser signal (18a-f) initially emitted by the infrared laser source (16a-f) and the portion of the infrared laser signal (24a-f) reflected by the eye (10a-f) back to the LFI sensor (14a-f).

Description

[0001] Description

[0002] Eye tracking device, AR and / or VR headset and eye tracking method

[0003] State of the art

[0004] AR and / or VR headsets with eye-tracking devices based on laser feedback interferometry (LFI) sensors have already been proposed. LFI sensors rely on the measurement principle of coherent mixing (interference) of the electromagnetic field emitted by a laser with an electromagnetic field backscattered by an object, in this case, an eye. Only the signal components of the two electromagnetic fields with identical polarizations interfere. However, the eye contains several elements that can influence the polarization of a reflected electromagnetic field. For example, the cornea (primarily due to its individual fibril orientation) and / or the nerve layer of the retina can be birefringent. The retinal pigment epithelium, for instance, can be depolarizing.The type and intensity of this polarization influence varies from person to person. Therefore, known eye-tracking devices based on LFI sensors may only function optimally for a limited group of people.

[0005] Disclosure of the invention

[0006] The invention relates to an eye tracking device for tracking the position and / or direction of gaze of an eye, for example in an AR and / or VR headset, with at least one laser feedback interferometry (LFI) sensor, comprising an infrared laser source for radiating an infrared laser signal onto the eye to be tracked, and comprising a photodetector, in particular integrated into the infrared laser source, for detecting an interference signal between the infrared laser signal generated by the infrared laser source and a part of the infrared laser signal reflected back from the eye to the LFI sensor.

[0007] It is proposed that the eye-tracking device include an eye polarization compensation unit configured to at least partially compensate for a polarization difference, caused by an optical property of the eye, particularly a birefringence property, between the infrared laser signal initially emitted by the infrared laser source and the portion of the infrared laser signal reflected back from the eye to the LFI sensor. This compensation is intended to increase the signal strength of the interference signal. Advantageously, this allows for the optimization of the eye-tracking function. Furthermore, it allows for the maximization of the eye-tracking measurement signal from the LFI sensor. Finally, it allows for the broadening of the suitability of the LFI sensor-based eye-tracking device to include a wider range of users.

[0008] The eye-tracking device is, in particular, part of an augmented reality (AR) system, e.g., an AR headset, or part of a virtual reality (VR) system, e.g., a VR headset. For example, the eye-tracking device can be part of 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 image content into a user's field of vision. The LFI sensor can, for example, be designed as a VCSEL, preferably a ViP-VCSEL ("vertical-cavity surface-emitting laser with integrated photodiode"). The LFI sensor is, in particular, integrated into the AR headset and / or the VR headset, preferably the smart glasses, e.g.,The LFI sensor is integrated into the frame, lens, or temple of the smart glasses. It can also be part of a laser projector unit that generates the artificial image content of the AR and / or VR headset, for example, integrated together with (RGB) laser diodes. Alternatively, the LFI sensor can be separate from the laser projector unit that generates the artificial image content of the AR and / or VR headset. Furthermore, it is conceivable that the AR and / or VR headset has more than one LFI sensor, e.g., two, three, or more than three. The LFI sensor is based on an interferometric measurement method. 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 scattered back, 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 of 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.

[0009] The terms "intended" 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 configured for a specific function should be understood to mean, in particular, that the object fulfills and / or performs this specific function in at least one application and / or operating state.

[0010] The optical property of the eye that generates the polarization difference can be, for example, a birefringence property of the cornea or a part of the retina, or a depolarization property of retinal pigment epithelia. In particular, the optical properties, such as the birefringence, are individually unique to each eye. The phrase "the polarization difference is at least partially compensated" means, in particular, that after passing through the eye polarization compensation unit, the polarization difference between the portion of the infrared laser signal reflected from the eye to the LFI sensor and the infrared laser signal initially emitted by the infrared laser source is significantly smaller, preferably at least 30% smaller, more preferably at least 60% smaller, and most preferably at least 90% smaller.In particular, it is conceivable that, on the path from the LFI sensor to the eye, a portion of the expected polarization difference is precompensated before the polarization-changing effect of the eye even occurs, and that, on the path from the eye to the LFI sensor, a further portion of the polarization difference is postcompensated after it actually occurs. Specifically, the eye polarization compensation unit is configured to influence the polarization of the infrared laser signal twice: between its emission by the LFI sensor and its detection by the LFI sensor. Specifically, the eye polarization compensation unit is configured for both precompensation and postcompensation of portions of the polarization difference generated by the optical properties of the eye, particularly its birefringence.In particular, the eye polarization compensation unit is configured to prevent any mode of the portion of the infrared laser signal reflected from the eye to the LFI sensor from being orthogonal to any mode of the infrared laser signal initially emitted by the infrared laser source. The eye polarization compensation unit can be at least partially formed integrally with the LFI sensor or a laser projector unit encompassing the LFI sensor, or at least partially integrated into the LFI sensor or the laser projector unit.

[0011] Furthermore, it is proposed that the eye polarization compensation unit comprises at least one polarization-changing optical element, which is arranged in the beam path between the eye and the LFI sensor. This advantageously enables simple, cost-effective, and / or reliable compensation of the polarization change generated by the eye. In particular, the eye polarization compensation unit is designed as an optical element, specifically as an optical component that has an optical function acting on infrared light. The polarization-changing optical element is arranged in a light path of the back-reflected infrared laser signal. Alternatively or additionally, the polarization-changing optical element can be arranged in a light path of the infrared laser signal directed onto the eye.The polarization-changing optical element transmits the back-reflected infrared laser signal, applying in particular the optical function acting on infrared light to the transmitted infrared laser signal. Alternatively, it is also conceivable that the polarization-changing optical element reflects the back-reflected infrared laser signal and, in particular during reflection, applies the optical function acting on infrared light to the reflected infrared laser signal.

[0012] In this context, it is further proposed that the eye-tracking device include an optical element bearing unit for the movable mounting of the polarization-changing optical element, particularly within the beam path of the infrared laser signal. This advantageously enables individualized adjustment of the polarization compensation for each eye. The suitability of the LFI sensor-based eye-tracking device can thus be extended to a wider range of users. In particular, the optical element bearing unit can comprise a holder, e.g., a slide or a rotary slide, for the polarization-changing optical element, which is translationally displaceable, pivotable, tiltable, and / or rotatable. It is conceivable that the eye-tracking device could also include a drive unit, e.g.,The eye tracking device includes an electric motor designed to drive the movement of the polarization-changing optical element supported by the optical element bearing unit. It is also conceivable that the eye tracking device includes a control unit configured to control the movement of the polarization-changing optical element, particularly the drive unit. Alternatively or additionally, it is also conceivable that the optical element bearing unit allows manual movement of the polarization-changing optical element, in particular by manual translational displacement, manual pivoting, manual tilting, and / or manual rotation. Specifically, the movement of the polarization-changing optical element is intended to change / adjust the instantaneous polarization change / polarization compensation.In particular, the polarization of the reflected portion of the infrared laser signal can be altered by moving the polarization-changing optical element. Specifically, an individually optimal position and / or orientation of the polarization-changing optical element can be set for each user via the optical element bearing unit. A "control and / or regulation unit" is understood to be, in particular, a unit with an information input, information processing, and information output. Advantageously, the control and / or regulation unit comprises at least a processor, memory, input and output means, other electrical components, an operating program, control routines, and / or calculation routines. Preferably, the components of the control and / or regulation unit are arranged on a common circuit board and / or advantageously in a common housing.

[0013] It is conceivable that the polarization-changing optical element remains in the path of the infrared laser signal at all times during its movement through the optical element storage unit. Alternatively, it is proposed that the optical element storage unit be configured to selectively insert the polarization-changing optical element into the beam path to activate the polarization change and selectively remove the polarization-changing optical element from the beam path to deactivate the polarization change. This allows the eye polarization compensation unit to be advantageously activated and deactivated as needed. For example, in a user whose eye produces only small or no polarization changes upon reflection of infrared light, the eye polarization compensation unit can be completely deactivated.It is conceivable that, depending on the required polarization change / polarization compensation, different suitable polarization-changing optical elements can be introduced / positioned in the beam path of the infrared laser signal using the optical element storage unit.

[0014] If the optical element bearing unit is configured to rotate the polarization-changing optical element in the beam path to adjust a polarization change angle generated by the polarization-changing optical element, the degree of polarization change / polarization compensation can advantageously be set in a simple, efficient, and, in particular, easily controllable manner. Specifically, the optical element bearing unit comprises a rotating carriage on which the polarization-changing optical element is mounted. The rotating carriage can be configured to allow rotation of the polarization-changing optical element about an optical axis of the infrared laser source.

[0015] If the polarization-changing optical element, rotatably mounted by means of the optical element bearing unit, is designed as a multirefractive crystal or as a polarizer, particularly one that polarizes infrared laser signals to their intrinsic mode, a simple and / or cost-effective design can advantageously be achieved. The rotatably mounted multirefractive crystal can be non-A / 2 and / or non-A / 4 retarding.

[0016] Alternatively, if the polarization-changing optical element is designed as a delay plate, for example as an A / 2 plate or an A / 4 plate, a simple and / or cost-effective design can be advantageously achieved. Preferably, the delay plate, for example the A / 2 plate or the A / 4 plate, is rotatably arranged in the beam path of the infrared laser signal by means of the optical element bearing unit. The use of delay plates that generate delays other than A / 2 or A / 4 as the polarization-changing optical element is also conceivable.

[0017] Furthermore, it is proposed that the eye polarization compensation unit includes at least one laser source bearing unit configured to rotate the infrared laser source around an optical axis. This allows for the advantageous adjustment of the degree of polarization change / polarization compensation in a simple, efficient, and, in particular, easily controllable manner. Specifically, the polarization of the infrared laser signal initially emitted by the infrared laser source is rotated by the mechanical rotation of the infrared laser source itself. This also changes the polarization of the portion of the infrared laser signal reflected from the eye to the LFI sensor. By rotating the source, the mutually orthogonal component of the polarizations of the two interfering infrared laser signals can be advantageously minimized.It is conceivable that the laser source storage unit is designed as a rotating carriage on which the infrared laser source is mounted. In addition to the infrared laser source, one or more further elements of an optical system of the eye tracking device can also be arranged on this rotating carriage, such as a collimating lens positioned in the beam path of the infrared laser signal.

[0018] It is further proposed that the eye polarization compensation unit comprises at least one liquid crystal cell arrangement configured to manipulate, in particular to change / rotate, the polarization of infrared laser signals as a function of an electrical control signal. This advantageously enables particularly precise and preferably highly accurate polarization compensation. In particular, a control unit for controlling the liquid crystal cell arrangement is provided. Specifically, the liquid crystal cell arrangement is positioned in the beam path of the portion of the infrared laser signal reflected from the eye to the LFI sensor. Alternatively or additionally, the liquid crystal cell arrangement can also be positioned in the beam path of the initially emitted infrared laser signal.Preferably, the polarization of the respective infrared laser signal is changed when passing through the liquid crystal cell arrangement.

[0019] Furthermore, it is proposed that the eye polarization compensation unit include at least one adjustable Babinet compensator. This allows for the advantageously simple, efficient, and, in particular, cost-effective adjustment of the degree of polarization change / compensation. A stepless adjustment of the polarization change / compensation is advantageously possible. Specifically, the Babinet compensator is formed by two wedge-shaped elements made of a birefringent material such as calcite, which are arranged relative to each other such that their respective optical axes are identical or at least parallel. Specifically, the wedge-shaped elements are moved relative to each other, i.e., pushed towards or away from each other, to adjust the Babinet compensator.In particular, the Babinet compensator is arranged in the beam path of the reflected portion of the infrared laser signal and / or the initially emitted infrared laser signal. Preferably, the polarization of the respective infrared laser signal is changed by passing through the Babinet compensator. Combinations of several identical or different polarization-influencing / polarization-changing optical elements and / or other elements that influence the polarization are conceivable.

[0020] Furthermore, it is proposed that the eye polarization compensation unit be at least partially comprised of at least one additional infrared laser source, which is configured to project another infrared laser signal onto the eye. This signal preferably has a wavelength at least substantially identical to that of the infrared laser signal of the primary infrared laser source, or a wavelength substantially different from that of the primary infrared laser source, and a polarization state (e.g., polarization angle) different from that of the primary infrared laser source. This advantageously enables precise and preferably particularly accurate and / or easily controllable polarization compensation. Preferably, the two infrared laser signals have polarizations differing by approximately 45°. However, other angles are also conceivable.Preferably, the polarization angles / polarization states of the two infrared laser signals differ by at least 5°, preferably by at least 15°. There can be more than one additional infrared laser source with more than one different polarization angle / polarization state. The infrared laser sources can be operated in parallel or sequentially. The eye polarization compensation unit, which is at least partially designed as the additional infrared laser source, can be at least partially integrated into the LFI sensor or into the laser projector unit containing the LFI sensor. The LFI sensor or the laser projector unit then preferably forms at least part of the eye polarization compensation unit. It is also conceivable that the laser source emits a linearly polarized infrared laser signal, while the additional laser source emits a circularly polarized infrared laser signal, or vice versa.In particular, the infrared laser signal from the infrared laser source can exhibit a linearly polarized polarization state. The infrared laser signal from the second infrared laser source can also exhibit a linearly polarized or a circularly polarized polarization state. Furthermore, it is conceivable that both laser sources emit circularly polarized light, for example, right- or left-handed circularly polarized light. Additionally, various mixed states of the aforementioned polarizations (e.g., elliptically polarized infrared laser signals) are conceivable.

[0021] In this case, the eye polarization compensation unit is specifically designed as an array with two or more infrared laser sources that emit infrared laser signals with different polarizations. The "essentially identical wavelengths" are at least similar enough to interfere with each other. Preferably, the deviation of the essentially identical wavelengths is less than 1% of the longer of the two wavelengths. It is conceivable that a wavelength of at least one of the infrared laser sources can be varied, at least within a small range. The two infrared laser sources can be operated simultaneously (in parallel). Alternatively, the two infrared laser sources can be operated sequentially. In particular, the two infrared laser sources can be controlled, activated, and / or deactivated independently of each other.The term "significantly different wavelengths" refers in particular to wavelengths whose difference is so large that cross-interference between the infrared laser signals of the two infrared laser sources is avoided / or at least essentially impossible.

[0022] Additionally, it is proposed that the control unit be designed to find an optimal compensation setting that differs individually for each eye by executing a search algorithm, for example, a gradient descent search algorithm or a local search algorithm. The execution of the search algorithm includes stepwise adjustment and / or activation of the eye polarization compensation unit and a comparison of the resulting interference signals. This advantageously allows for high user-friendliness. Furthermore, it advantageously allows for high accuracy of the polarization compensation. The measurement signal of the LFI sensor can also be advantageously optimized, in particular maximized.In particular, the search algorithm successively acquires images of the eye's infrared reflection signal and, in doing so, incrementally changes the polarization setting of the eye polarization compensation unit, specifically the position and / or orientation of the polarization-changing optical element, the position and / or orientation of the infrared laser source(s), the control setting of the liquid crystal cell array, and / or the setting of the Babinet compensator, etc. A signal-to-noise ratio is then determined from each of the acquired images. The search algorithm then approximates the optimal setting by maximizing the acquired signal-to-noise ratio. Alternatively, the application of an alpha-beta search algorithm is also conceivable.When adjusting the eye polarization compensation unit stepwise, for example, the position, rotation state, or relative position of individual components of the eye polarization compensation unit can be changed. When activating the eye polarization compensation unit stepwise, for example, a different infrared laser source of the eye polarization compensation unit can be activated successively (e.g., first the infrared laser source with a first polarization state and then the next infrared laser source with a second polarization state, or vice versa).

[0023] Furthermore, an AR and / or VR headset is combined with the eye tracking device and / or an eye tracking method for tracking the position and / or gaze direction of an eye, preferably by means of the eye tracking device, wherein an infrared laser signal is emitted onto an eye to be tracked from an infrared laser source of a laser feedback interferometry (LFI) sensor, and wherein an interference signal between the infrared laser signal generated by the infrared laser source and a part of the infrared laser signal reflected from the eye to the LFI sensor is detected by a photodetector, in particular integrated into the infrared laser source, wherein, in particular to increase the signal strength of the interference signal, an optical property of the eye, in particular a birefringence property of the eye,It is proposed that the polarization difference generated between the infrared laser signal initially emitted by the infrared laser source and the portion of the infrared laser signal reflected from the eye to the LFI sensor be at least partially, preferably at least to a large extent, compensated by an eye polarization compensation unit. This advantageously optimizes an eye tracking function. Advantageously, the eye tracking measurement signal of the LFI sensor can be maximized. Furthermore, the suitability of the LFI sensor-based eye tracking device can be extended to a large group of people. "Large extent" is understood to mean, in particular, 51%, preferably 66%, preferably 75%, and most preferably 90%.

[0024] The eye-tracking device, the AR and / or VR headset, and / or the eye-tracking method according to the invention are not limited to the application and embodiment described above. In particular, the eye-tracking device, the AR and / or VR headset, and / or the eye-tracking 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 the value ranges stated in this disclosure are also considered disclosed and freely usable.

[0025] drawing

[0026] Further advantages become apparent from the following description of the drawings. The drawings illustrate six exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. It is advantageous for those skilled in the art to also consider the features individually and combine them into meaningful further combinations.

[0027] They show:

[0028] Fig. 1 shows a schematic representation of an AR and / or VR headset with an eye tracking device,

[0029] Fig. 2 shows a schematic representation of the eye tracking device,

[0030] Fig. 3a shows an interference signal recorded by means of a photodetector of an LFI sensor of an eye tracking device without an eye polarization compensation unit,

[0031] Fig. 3b shows an interference signal recorded by means of a photodetector of an LFI sensor of an eye tracking device equipped with an eye polarization compensation unit.

[0032] Fig. 4 shows a schematic flowchart of an eye-tracking method for tracking the position and / or gaze direction of an eye using the eye-tracking device; Fig. 5 shows a schematic first alternative eye-tracking device.

[0033] Fig. 6 schematically shows a second alternative eye tracking device,

[0034] Fig. 7 schematically shows a third alternative eye-tracking device,

[0035] Fig. 8 schematically shows a fourth alternative eye-tracking device and

[0036] Fig. 9 schematically shows a fifth alternative eye-tracking device.

[0037] Description of the exemplary implementations

[0038] Figure 1 shows a schematic representation of an AR and / or VR headset 12a. The AR and / or VR headset 12a includes an eye-tracking device 48a. Figure 2 shows a schematic representation of the eye-tracking device 48a. The eye-tracking device 48a is configured to track the position and / or gaze direction of an eye 10a. The eye-tracking device 48a includes a laser feedback interferometry (LFI) sensor 14a. The LFI sensor 14a includes an infrared laser source 16a. The infrared laser source 16a is configured to generate an infrared laser signal 18a. The infrared laser source 16a emits the infrared laser signal 18a onto the eye 10a to be tracked. Optical elements 50a, 52a can be arranged in a beam path 30a of the infrared laser signal 18a. In the embodiment shown in Fig. 2, two optical elements 50a, 52a are shown by way of example.A first optical element 50a is designed as a collimation lens and is arranged directly behind an output of the infrared laser source 16a. A second optical element 52a is designed as a hologram, which is arranged in front of the eye 10a. The second optical element 52a could also be a lens, a mirror, a grating, etc.

[0039] The infrared laser signal 18a is reflected by the eye 10a. The eye 10a reflects a portion of the initial infrared laser signal 18a back to the LFI sensor 14a as a reflected / reflected infrared laser signal 24a. The eye-tracking device 48a includes a photodetector 20a. The photodetector 20a is integrated into the LFI sensor 14a. The photodetector 20a is integrated into the infrared laser source 16a. The LFI sensor 14a, in particular the photodetector 20a, is configured to detect an interference signal 22a, 22'a (see Figures 3a and 3b) between the infrared laser signal 18a generated by the infrared laser source 16a and the portion of the infrared laser signal 24a reflected back from the eye 10a to the LFI sensor 14a. The strength and / or signal-to-noise ratio of the interference signal 22a, 22'a depends on the relative polarization of the infrared laser signals 18a, 24a.The greater the polarization difference between the infrared laser signals 18a, 24a, the worse / smaller the signal-to-noise ratio and / or the strength of the interference signal 22a, 22'a.

[0040] The eye tracking device 48a includes an eye polarization compensation unit 26a. The eye polarization compensation unit 26a is configured to at least partially compensate for a polarization difference between the infrared laser signal 18a initially emitted by the infrared laser source 16a and the portion of the infrared laser signal 24a reflected by the eye 10a to the LFI sensor 14a, thereby increasing the signal strength of the interference signal 22a, 22'a. This compensation is achieved by increasing the signal strength of the interference signal 22a, 22'a. The eye polarization compensation unit 26a can, among other things, be configured to change the polarization of the reflected infrared laser signal 24a. The eye polarization compensation unit 26a comprises a polarization-changing optical element 28a.The polarization-changing optical element 28a is configured as a multi-refractive crystal. Alternatively, the polarization-changing optical element 28a could also be configured as a polarizer that polarizes infrared laser signals 18a, 24a to their intrinsic mode. The polarization-changing optical element 28a is arranged in the beam path 30a between the eye 10a and the LFI sensor 14a. The eye tracking device 48a includes an optical element bearing unit 32a. The optical element bearing unit 32a is configured for the movable mounting of the polarization-changing optical element 28a. The optical element bearing unit 32a is configured for the selective insertion of the polarization-changing optical element 28a into the beam path 30a to activate the polarization change.The optical element storage unit 32a is configured for the selective removal of the polarization-changing optical element 28a from the beam path 30a to deactivate the polarization change. The optical element storage unit 32a is also configured for rotating the polarization-changing optical element 28a within the beam path 30a to adjust the polarization angle generated by the polarization-changing optical element 28a. For this purpose, the optical element storage unit 32a comprises a translational-rotational carriage 54a on which the polarization-changing optical element 28a is mounted.

[0041] The eye tracking device 48a includes a control unit 46a. The control unit 46a is configured to control the optical element storage unit 32a. The control unit 46a is configured to find an optimal compensation that is individually different for each eye 10a. For this purpose, the control unit 46a is configured to execute a search algorithm. The execution of the search algorithm includes a stepwise adjustment and / or activation of the eye polarization compensation unit 26a and a comparison of the resulting interference signals 22a, 22'a.

[0042] Figures 3a and 3b each show interference signals 22a, 22'a recorded by the photodetector 20a of the LFI sensor 14a for an exemplary birefringent eye 10a. The interference signal 22a in Figure 3a was recorded without the eye polarization compensation unit 26a. The interference signal 22'a in Figure 3b was recorded with the eye polarization compensation unit 26a. A brightness scale 56a shown in Figures 3a and 3b describes the strength of the interference signal 22a, 22'a. The darker an area is in Figures 3a and 3b, the lower the signal strength of the interference signal 22a, 22'a. The X and Y axes of the diagrams in Figures 3a and 3b show the angles of incidence of the infrared laser signal 18a in two different spatial dimensions in degrees.A comparison of Figures 3a and 3b shows that without the eye polarization compensation unit 26a, the minima of the signal strength of the interference signal 22a, 22'a are significantly larger and more pronounced. The signal strength of the interference signal 22a drops to less than 20%, while with the eye polarization compensation unit 26a, the signal strength of the interference signal 22'a always remains above 80%.

[0043] Figure 4 shows a schematic flowchart of an eye-tracking method for tracking the position and / or gaze direction of eye 10a using the eye-tracking device 48a. In a process step 58a, the infrared laser signal 18a from the infrared laser source 16a of the LFI sensor 14a is directed onto the eye 10a to be tracked. In a further process step 62a, the eye 10a reflects the incident infrared laser signal 18a. The individual optical properties of the eye 10a generate the polarization difference between the reflected infrared laser signal 24a and the initially emitted infrared laser signal 18a. In a further process step 64a, the polarization difference of the infrared laser signal 24a reflected by the eye 10a and / or the infrared laser signal 18a radiated onto the eye 10a is at least partially compensated by the eye polarization compensation unit 26a.It is conceivable that the same eye polarization compensation unit 26a is traversed twice, once on the way to eye 10a and once on the way from eye 10a, so that the compensation of the polarization difference of process step 64a occurs proportionally on the outward path from the infrared laser source 16a to eye 10a and on the return path from eye 10a to the photodetector 20a. Of course, the compensation of the polarization difference of process step 64a can also occur entirely on the outward path or entirely on the return path. In a further process step 60a, the interference signal 22a, 22'a between the initial infrared laser signal 18a and the polarization-compensated reflected infrared laser signal 24a is detected by the photodetector 20a.In an optional further procedure step 66a, the search algorithm can be performed by iteratively adjusting and / or activating the eye polarization compensation unit 26a and evaluating the resulting interference signals 22a, 22'a in order to obtain a maximum signal strength.

[0044] Figures 5 to 9 show 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, particularly those with the same reference numerals, reference may also be made to the drawings and / or the description of the other embodiments, especially Figures 1 to 4. To distinguish the embodiments, the letter "a" is appended to the reference numerals of the embodiment in Figures 1 to 4. In the embodiments of Figures 5 to 9, the letter "a" is replaced by the letters "b" to "f".

[0045] Figure 5 schematically shows a first alternative eye tracking device 48b. The first alternative eye tracking device 48b comprises a first alternative eye polarization compensation unit 26b with a first alternative polarization-changing optical element 28b. The first alternative polarization-changing optical element 28b is configured as a delay plate. The delay plate can be an A / 2 plate or an A / 4 plate.

[0046] Figure 6 schematically shows a second alternative eye tracking device 48c. The second alternative eye tracking device 48c has a laser feedback interferometry (LFI) sensor 14c, which includes an infrared laser source 16c for directing an infrared laser signal 18c onto a tracked eye 10c. The second alternative eye tracking device 48c has a second alternative eye polarization compensation unit 26c. The second alternative eye polarization compensation unit 26c has a laser source storage unit 34c. The laser source storage unit 34c is configured to rotate the infrared laser source 16c about an optical axis 36c of the infrared laser source 16c.

[0047] Figure 7 schematically shows a third alternative eye tracking device 48d. The third alternative eye tracking device 48d includes a control unit 46d. The third alternative eye tracking device 48d includes a laser feedback interferometry (LFI) sensor 14d, which comprises an infrared laser source 16d for emitting an infrared laser signal 18d onto a tracked eye 10d. The eye 10d reflects part of the emitted infrared laser signal 18d back to the LFI sensor 14d as a reflected infrared laser signal 24d. The third alternative eye tracking device 48d includes a third alternative eye polarization compensation unit 26d. The third alternative eye polarization compensation unit 26d comprises a liquid crystal cell array 38d.The liquid crystal cell arrangement 38d is designed to manipulate a polarization of infrared laser signals 18d, 24d depending on an electrical control by the control and / or regulation unit 46d.

[0048] Figure 8 schematically shows a fourth alternative eye tracking device 48e. The fourth alternative eye tracking device 48e has a fourth alternative eye polarization compensation unit 26e with a second alternative polarization-changing optical element 28e. The second alternative polarization-changing optical element 28e is designed as an adjustable Babinet compensator 40e.

[0049] Figure 9 schematically shows a fifth alternative eye tracking device 48f. The fifth alternative eye tracking device 48f has a laser feedback interferometry (LFI) sensor 14f, which includes an infrared laser source 16f for directing an infrared laser signal 18f onto an eye 10f to be tracked. The fifth alternative eye tracking device 48f has a fifth alternative eye polarization compensation unit 26f. The fifth alternative eye polarization compensation unit 26f is formed by a further infrared laser source 42f. The additional infrared laser source 42f is configured to project a further infrared laser signal 44f onto an eye 10f to be tracked. The additional infrared laser signal 44f has a wavelength that is at least essentially identical to the infrared laser signal 18f of the infrared laser source 16f.The additional infrared laser signal 44f has a different polarization state than the infrared laser signal 18f from the infrared laser source 16f. The additional infrared laser signal 44f has a different polarization angle than the infrared laser signal 18f from the infrared laser source 16f.

Claims

1. Claims 1. Eye tracking device (48a-f) for tracking the position and / or gaze direction of an eye (10a-f), for example in an AR and / or VR headset (12a-f), with at least one laser feedback interferometry (LFI) sensor (14a-f), comprising an infrared laser source (16a-f) for illuminating an infrared laser signal (18a-f) onto the eye to be tracked (10a-f), and comprising a photodetector (20a-f), in particular integrated into the infrared laser source (16a-f), for detecting an interference signal (22a-f, 22'af) between the infrared laser signal (18a-f) generated by the infrared laser source (16a-f) and a part of the signal reflected from the eye (10a-f) to the LFI sensor (14a-f). Infrared laser signal (24a-f), characterized by an eye polarization compensation unit (26a-f) which is designed, in particular, to increase the signal strength of the interference signal (22a-f, 22'af),to at least partially compensate for a polarization difference generated by an optical property of the eye (10a-f), in particular a birefringence property of the eye (10a-f), between the infrared laser signal (18a-f) initially emitted by the infrared laser source (16a-f) and the part of the infrared laser signal (24a-f) reflected by the eye (10a-f) to the LFI sensor (14a-f).

2. Eye tracking device (48a-b; 48d-e) according to claim 1, characterized in that the eye polarization compensation unit (26a-b; 26d-e) comprises at least one polarization-changing optical element (28a-b; 28d-e) which is arranged in the beam path (30a-b; 30d-e) between the eye (10a-b; 10d-e) and the LFI sensor (14a-b; 14d-e).

3. Eye tracking device (48a-b; 48e) according to claim 2, characterized by an optical element bearing unit (32a-b; 32e) for a movable bearing of the polarization-changing optical element (28a-b; 28e).

4. Eye tracking device (48a-b) according to claim 3, characterized in that the optical element storage unit (32a-b) is configured for selectively inserting the polarization-changing optical element (28a-b) into the beam path (30a-b) to activate the polarization change and for selectively removing the polarization-changing optical element (28a-b) from the beam path (30a-b) to deactivate the polarization change.

5. Eye tracking device (48a-b) according to claim 3 or 4, characterized in that the optical element bearing unit (32a-b) is configured to rotate the polarization-changing optical element (28a-b) in the beam path (30a-b) to adjust a polarization change angle generated by the polarization-changing optical element (28a-b).

6. Eye tracking device (48a) according to claim 5, characterized in that the polarization-changing optical element (28a) rotatably mounted by means of the optical element bearing unit (32a) is designed as a multi-refractive crystal or as a polarizer, in particular polarizing infrared laser signals (18a, 24a) to their intrinsic mode.

7. Eye tracking device (48b) according to one of claims 2 to 5, characterized in that the polarization-changing optical element (28b) is designed as a delay plate.

8. Eye tracking device (48c) according to one of the preceding claims, characterized in that the eye polarization compensation unit (26c) has at least one laser source storage unit (34c) which is configured to rotate the infrared laser source (16c) about an optical axis (36c) of the infrared laser source (16c).

9. Eye tracking device (48d) according to one of the preceding claims, characterized in that the eye polarization compensation unit (26d) has at least one liquid crystal cell arrangement (38d) which is configured to manipulate a polarization of infrared laser signals (18d, 24d) depending on an electrical control.

10. Eye tracking device (48e) according to one of the preceding claims, characterized in that the eye polarization compensation unit (26e) has at least one adjustable Babinet compensator (40e).

11. Eye tracking device (48f) according to one of the preceding claims, characterized in that the eye polarization compensation unit (26f) is at least partially formed by at least one further infrared laser source (42f) which is configured to emit a further infrared laser signal (44f) with a polarization state different from the infrared laser signal (18f) of the infrared laser source (16f) onto the eye (1 Of).

12. Eye tracking device (48a-f) according to one of the preceding claims, characterized by a control and / or regulation unit (46a-f) which is provided for finding an individually different optimal compensation for each eye (10a-f) by means of an execution of a search algorithm, for example a search algorithm performing a gradient method or a search algorithm performing a local search, wherein the execution of the search algorithm comprises a stepwise adjustment and / or activation of the eye polarization compensation unit (26a-f) and a comparison of the resulting interference signals (22a-f, 22'af).

13. AR and / or VR headset (12a-f) with an eye tracking device (48a-f) according to any of the preceding claims.

14. Eye tracking method for tracking the position and / or gaze direction of an eye (1 Oa-f), preferably by means of an eye tracking device (48a-f) according to one of claims 1 to 12, wherein an infrared laser signal (18a-f) is emitted from an infrared laser source (16a-f) of a laser feedback interferometry (LFI) sensor (14a-f) onto an eye (10a-f) to be tracked, and wherein an interference signal (22a-f, 22'af) is generated by a photodetector (20a-f), in particular integrated into the infrared laser source (16a-f), between the infrared laser signal (18a-f) generated by the infrared laser source (16a-f) and a part of the infrared laser signal reflected from the eye (10a-f) to the LFI sensor (14a-f). (24a-f) is detected, characterized in that, in particular to increase the signal strength of the interference signal (22a-f, 22'af), an optical property of the eye (10a-f), in particular a birefringence property of the eye (10a-f),The polarization difference generated between the infrared laser signal (18a-f) initially emitted by the infrared laser source (16a-f) and the part of the infrared laser signal (24a-f) reflected from the eye (10a-f) to the LFI sensor (14a-f) is at least partially compensated by an eye polarization compensation unit (26a-f).

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