System for determining the gaze direction of a person who wears a contact lens in at least one eye and method

Abstract

System for determining the gaze direction of a person wearing a contact lens KL1 (100a) on at least one of their two eyes, wherein this contact lens KL1 (100a) has at least one layer S1 (103a) designed as a geometric pattern GM1 (104a) and made of a material M1 comprising at least an infrared light IR-absorbing material and / or at least an infrared light IR-reflecting material, and the geometric pattern GM1 (104a) is associated with at least one infrared light reflection pattern IR-RM characteristic of this pattern GM1, comprising: - at least one infrared radiation source (110) for illuminating the at least one contact lens KL1 (100a); - at least one IR sensor (111) for detecting an IR reflection pattern on the at least one contact lens KL1 (100a); - at least one VIS sensor (112) for detecting the two eyes of the person in the visible radiation range VIS;and an evaluation unit (113) connected to the infrared radiation source (110) and the at least one IR sensor (111), wherein the evaluation unit (113) is designed and configured to perform a system calibration and, based on the system calibration and the sensor data acquired by the at least one IR sensor (111) and the at least one VIS sensor (112), to determine a current gaze direction of the two eyes of the person.

Description

The invention relates to a system for determining the direction of gaze of a person who wears a contact lens in at least one eye, and to a method for operating such a system. In the prior art, methods and systems are known for determining a person's eye movements, gaze direction, and pupil changes. These methods are commonly known by the English terms "eye tracking" or "gaze tracking." Patent application US 2012 / 0281181 A1 discloses a method for eye tracking using magnetized contact lenses tracked by magnetic sensors and / or reflective contact lenses tracked by video-based sensors. The tracking information from the contact lenses of magnetic and video-based sensors can be used to improve eye tracking and / or combined with other sensor data to enhance accuracy. Furthermore, reflective contact lenses improve blink detection, while eye tracking with magnetized contact lenses is not affected by blinking. Such “eye-tracking” systems primarily focus on the approach of projecting light of specific wavelengths, mostly from the infrared (IR) spectrum invisible to humans, onto the eyes of the respective person and using sensors (camera, video systems) to capture the reflection patterns created at the eye, which are caused by the natural structure of the eyes (cornea, pupil, vitreous body and retina) and then evaluate them to determine a direction of gaze. Several factors play a crucial role here and significantly influence the quality of the collected sensor data, such as eye geometry, the distance between the two eyes, the current gaze direction, the pupil diameter, the position of the emitted light, the ambient light conditions, corneal homogeneity, etc. In the current state of the art, the geometry of the eyes, the distance between the eyes, and the position of the light source(s) are generally approximated by geometric models and algorithms. However, the following disadvantages exist with the methods and systems known in the prior art for determining gaze direction: a) Measurement inaccuracies exist due to anatomical inhomogeneities of the individual eye (without a contact lens). These inhomogeneities fundamentally affect all aspects of the eye's structure, such as inhomogeneities of the cornea, vitreous humor, retina, etc., both within and between individuals. This means that the characteristics of a person's eyes differ, as do the characteristics of the eyes of different people. These differences sometimes lead to significant measurement inaccuracies and can only be approximated through compensatory measures.b) The shape of the IR reflections produced by the eyes (without contact lenses or glasses) depends—among other aspects—on the contraction state of the iris (corresponding to the pupil diameter) and the orientation of the eyes relative to the recording camera system. Since the pupil diameter changes dynamically, for example, depending on the ambient light or due to stress exposure, it also produces dynamic IR reflections. These dynamic IR reflections are very difficult to predict and precisely locate, especially if the recording camera system is not positioned as perpendicular as possible to the occurring light reflection. c) People who, due to their anatomical conditions, require corrective lenses or contact lenses are not suitable for eye / gaze tracking using currently known state-of-the-art methods, or only to a limited extent.The problem here is that both corrective lenses (glasses) and contact lenses known today cause unwanted IR reflections and scattering, which negatively affect the quality of the collected data and distort the results. The object of the invention is to provide a system for determining the gaze direction of a person who wears a contact lens in at least one eye. Furthermore, the object of the invention is to provide a contact lens that eliminates or at least significantly reduces the aforementioned disadvantages of previous contact lenses used in eye / gaze tracking systems and that is suitable for determining the gaze direction of a person using a system according to the invention. The invention is defined by the features of the independent claims. Advantageous further developments and embodiments are the subject of the dependent claims. Further features, applications, and advantages of the invention will become apparent from the following description and the explanation of exemplary embodiments of the invention illustrated in the figures. The invention is based on the findings and considerations described below. A significant portion of the measurement inaccuracies described above for known eye / gaze tracking systems is caused, on the one hand, by anatomical inhomogeneity and, on the other hand, by the dynamically changing IR reflection patterns of the eyes illuminated with IR light (each without a contact lens). It is therefore necessary to compensate for or control these two factors. The effects of the factor "anatomical inhomogeneity" can initially be reduced by using precisely manufactured, custom-made contact lenses adapted to the individual eye. However, the problem here is that these custom contact lenses themselves cause unwanted IR reflections. This factor can be controlled by the present invention by having the contact lens have at least one or more thin IR-reflective and / or IR-absorbing layers S (e.g., silicon, germanium, sapphire, gold, etc.) that appear transparent to the human eye. This generates known IR reflection patterns on a contact lens according to the invention. Advantageously, a contact lens according to the invention has one, two, or more such layers S. Each of the IR-reflective and / or IR-absorbing layers S has a known (2D or 3D) geometry / shape / pattern, wherein, when irradiated with IR light, the layer S produces IR reflections with known IR reflection patterns depending on the direction of irradiation. For example, such a layer S could have a geometry / shape / pattern like a crosshair with markings for specific distances, or like several triangles in a circular arrangement with a marking at the center of the viewing axis. The center of the gaze axis on the eye can be determined very precisely on the contact lens due to the automatic centering of the contact lens according to the invention on the eye, triggered by repeated blinking, and the known (2D or 3D) geometry / shape / pattern of layer S. The known center of the gaze axis for each eye, as well as knowledge of the (2D or 3D) geometry / shape / pattern of one or more layers S of the respective contact lens and the associated IR reflection patterns, makes it possible, by means of computer-aided evaluation, to determine very precisely the distance between the two gaze axes of a person's eyes, as well as the orientation of the gaze axes of the eyes in three-dimensional space. By using one or more IR-absorbing layers S in / on the contact lens according to the invention, unwanted IR reflections, e.g. from the carrier material of the contact lens, can advantageously be avoided. Furthermore, the accuracy of the system for determining a person's gaze direction can be improved by using IR parallel beam sources instead of IR point light sources to irradiate the eyes with contact lenses. Advantageously, the IR-reflective layer can incorporate nano-reflectors. This minimizes the scattering of IR light, as it ensures that the angles of incidence and reflection of IR light on a contact lens according to the invention remain equal or nearly equal. It is also advantageous to combine specific IR-reflective layers S for different IR wavelengths (e.g., left contact lens coated with a nano-reflective germanium pattern and right contact lens coated with a nano-reflective N-BK7 pattern), so that it can be precisely tracked which IR reflections are caused by which contact lens or which IR-reflective pattern. A further advantage of the present invention is that accurate eye and gaze tracking is also possible for people who rely on wearing contact lenses to correct refractive errors. Such eye and gaze tracking methods and associated systems for recording a person's gaze direction are increasingly used in modern vehicles, aircraft, computer systems, head-mounted interfaces (HMIs), computer consoles, control systems, simulators, etc. Therefore, the use of such IR-reflective and / or IR-absorbing contact lenses, as proposed here, is advantageous even with existing "conventional" "eye / gaze tracking" systems, since only the IR layer S of the contact lens, or its material, would need to be adapted to the wavelength(s) of the IR camera system used and the algorithms of the calibration and evaluation software to the IR reflection geometries. A contact lens suitable for the system described below for determining a person's gaze direction has a contact surface side with which the contact lens can be arranged on an eye and an outer side opposite the contact surface side, wherein the contact lens has at least one layer S which is designed as a geometric pattern GM and consists of a material M which comprises at least an infrared / IR light absorbing material and / or at least an infrared / IR light reflecting material, and wherein the at least one layer S made of the material M has a transmittance in the range of 0.8 to 1, in particular close to 1, for light in the optically visible wavelength range of 380 to 780 nm, and one or more characteristic infrared light reflection patterns IR-RM are assigned to the geometric pattern MS for this pattern MS. The multiple characteristic infrared light reflection patterns IR-RM may depend on an irradiation direction with IR radiation and / or a detection direction for detecting the infrared light reflection patterns IR-RM by an IR sensor. The term "geometric pattern GM" refers specifically to a two-dimensional shape / pattern of layer S, as it appears when viewed from above the contact lens. The term also includes a three-dimensional geometry / structure of layer S. The terms “IR radiation”, “infrared light” or “IR light” are used synonymously here and refer to electromagnetic radiation, typically with a wavelength between 780 nm and 1 mm. The proposed contact lens with at least one layer S is applied directly to the eye in the usual manner with the contact surface of the contact lens and corrects refractive errors of the respective eye in the usual manner. Furthermore, layer S of the contact lens does not restrict the wearer's vision. In addition, when irradiated with IR light, layer S generates one or more known IR reflection patterns, on the basis of which a precise determination of the gaze direction is possible. Reference is made to the following description of a system according to the invention for determining the gaze direction of a person wearing at least one contact lens according to the invention. Advantageously, at least one layer S is arranged in the region of the outer or contact surface side of the contact lens. Alternatively or additionally, at least one or more additional layers S can be arranged between the contact surface side and the outer surface. Furthermore, alternatively or additionally, at least one or more additional layers S can be arranged in the region of the contact surface side. The term "in the region" here refers in particular to the area directly on or near the relevant side within the contact lens. Advantageously, the contact lens has several layers S. The layer(s) S are advantageously patterned in a planar fashion, i.e. having a known 2D or 3D geometry / pattern. Advantageously, the outer surface of the contact lens is coated with a light-transmitting protective layer with a transmittance of 1 / - 0.5, with layer S located beneath the protective layer. The protective layer may advantageously have an IR-absorbing effect, thus suppressing unwanted IR reflections unrelated to the geometric pattern GM of layer(s) S. Furthermore, the protective layer may provide advantageous protection against mechanical wear of the contact lens and / or advantageous UV protection to reduce UV radiation reaching the eyes, etc. Advantageously, the geometric pattern GM is a rotationally symmetrical pattern, a pattern featuring concentrically arranged rings or segments of circles, or a pattern in the form of a reticle (crosshairs). In principle, the geometric pattern GM can take any form, as long as this is known. Advantageously, material M contains one or more of the following substances: silicon, germanium, sapphire, gold, N-BK7, zinc selenide, zinc sulfide, calcium fluoride, magnesium fluoride, sodium fluoride and potassium bromide. Advantageously, at least one layer of S IR nano-reflectors is present. It is advantageous if at least one layer S is produced by a PVD process (physical vapor deposition). Advantageously, the contact lens has several layers S. Advantageously, at least two of the multiple layers S have a different geometric pattern GM and / or consist of different materials M. The invention relates to a system for determining a gaze direction and / or an eye movement of a person who wears a contact lens KL1 as described above on at least one of his two eyes, wherein this contact lens KL1 has at least one layer S1 which is designed as a geometric pattern GM1 and consists of a material M1 which comprises at least an infrared light IR absorbing material and / or at least an infrared light IR reflecting material. As already described above in connection with the contact lens according to the invention, the at least one layer S1 made of material M1 has a transmittance in the range of 0.8 to 1, in particular close to 1, for light in the optically visible wavelength range of 380 to 780 nm. The proposed system comprises: at least one infrared radiation source for illuminating / irradiating the at least one contact lens KL1 on the eye of a person under examination; at least one IR sensor for detecting an IR reflection pattern generated on the at least one contact lens KL1 as a result of irradiation with IR light; and an evaluation unit connected to the infrared radiation source and the at least one IR sensor, wherein the evaluation unit is designed and configured to perform a system calibration and, based on the system calibration and the sensor data acquired by the at least one IR sensor, to determine a current gaze direction and / or eye movement of the two eyes of the person. An advantageous further development of the system also includes at least one VIS sensor for detecting the two eyes in the visible radiation range, wherein the evaluation unit is designed and configured to perform a system calibration and, based on the system calibration and the sensor data acquired by the at least one IR sensor and the at least one VIR sensor, to determine a current gaze direction and / or eye movement of the two eyes of the person. Both the IR sensor and the VIS sensor are sensors (preferably video sensors) for detecting corresponding electromagnetic radiation. They preferably have appropriate optics, detection electronics, and a data interface for providing and forwarding the respective detected sensor data. Advantageously, the person being examined also wears a contact lens KL2 according to the invention on their second eye, wherein this contact lens KL2 has at least one layer S2 which is designed as a geometric pattern GM2 and consists of a material M2 which comprises at least an infrared light IR absorbing material and / or at least an infrared light IR reflecting material. As already described above in connection with the contact lens according to the invention, the at least one layer S2 made of material M2 has a transmittance in the range of 0.8 to 1, in particular close to 1, for light in the optically visible wavelength range of 380 to 780 nm. In an advantageous further development of the system, the geometric patterns GM1 and GM2 of contact lens KL1 and contact lens KL2 are different. Alternatively, the geometric patterns GM1 and GM2 can be identical. In an advantageous further development of the system, the materials M1 and M2 are different. Alternatively, the materials M1 and M2 can be identical. The application of the system according to the invention with two contact lenses KL1, KL2 according to the invention, i.e. one for each eye of the human, is certainly the most relevant application of the system in practice. Advantageously, the evaluation unit is designed and configured to determine, during system calibration, the relative arrangement and orientation of at least one IR sensor, and, if present, at least one VIS sensor, as well as the person's two eyes. This positional data (position and orientation) of the aforementioned units and the eyes is advantageously used to determine a model geometry, based on which a model of gaze-direction-dependent reflection patterns observable on the contact lens can be derived. How such a model geometry and model can be determined is described, for example, in https: / / doi.org / 10.1016 / j.compbiomed.2019.03.025. Furthermore, the evaluation unit is advantageously designed and configured to additionally determine / or at least consider (where these can be provided to the evaluation unit, for example) a relative arrangement and orientation of one or more existing IR radiation sources (wavelength range from 780 nm to 1 mm) and / or one or more VIS radiation sources (wavelength range from 380 to 780 nm) within the framework of system calibration and to provide this information in the model geometry. Furthermore, the evaluation unit is advantageously designed and configured to determine a reflection model during system calibration. This model, taking into account the previously determined and aforementioned model geometry, specifies an IR reflection pattern on the respective contact lens KL1, KL2, observable by the IR sensor, for a multitude of different gaze directions of each eye. The more accurate this reflection model, the more precisely the gaze directions of the person can be determined. The evaluation unit is advantageously designed and configured to use a self-learning algorithm to determine the reflection model. This class of algorithms enables self-learning optimization of the reflection model based on a large number of measurements to capture reflection patterns from a subject's various gaze directions. It is advantageous if at least one infrared radiation source is designed and configured to emit parallel IR radiation. It is advantageous if all infrared light sources used emit parallel IR radiation. Another aspect of the invention relates to a method for operating a system as described above. The method comprises the following steps. First, the system is calibrated in two steps: determining a relative geometric arrangement and orientation of the at least one infrared radiation source, the at least one IR sensor, and, if present, the at least one VIS sensor and the two eyes of a person to be examined, wherein the person wears a contact lens according to the invention on at least one of his two eyes, and for each eye wearing a contact lens, determining a reflection model which specifies an associated (virtual) IR reflection pattern for a multitude of different viewing directions of the respective eye, which can be detected on the at least one contact lens by at least one IR sensor. In cases where a person wears a contact lens according to the invention in only one eye, commonly known algorithms of (IR) video oculography are advantageously used to determine the visual axis of the eye without the contact lens. Based on the information obtained from the video oculography, a (reflection) model can also be created for the contact lens-free eye, which is integrated into a virtual overall model of the system. In a further step (during operational measurement), the current gaze direction of the eyes and / or eye movement of the person wearing the contact lens(es) is determined, based on the determined arrangement and orientation of the at least one infrared radiation source, the at least one IR sensor, the at least one VIS sensor and the two eyes, the determined reflection model and the current sensor data determined by the at least one IR sensor and the at least one VIS sensor. Advantageously, when determining the current gaze direction of the respective eye, an IR reflection pattern is determined on the respective contact lens and the current gaze direction is determined using the determined reflection model. The proposed method can be used for mobile, stationary, and head-mounted "eye / gaze" tracking systems. The process differs in several steps. This is illustrated by the following examples. 1) If the system is not head-mounted, the first step involves the precise setup, measurement, and calibration of the camera and IR illumination system using methods common in the art (see, for example, https: / / doi.org / 10.1016 / j.cviu.2021.103353, 10.1109 / ICAL.2010.5585376, https: / / doi.org / 10.1016 / j.optlaseng.2018.11.005, https: / / doi.org / 10.3929 / ethz-b-000158067, etc.). Initial values ​​for the distance between the cameras (IR and VIS) and the expected test position of the subjects (e.g., typical seating position in a flight simulator, vehicle simulator, vehicle, etc.) are also determined and entered into the calibration software. Checking the ambient lighting conditions can also be useful at this stage. If it is a head-mounted system, for example as part of a virtual reality headset, the aforementioned steps are unnecessary, since the spatial arrangement of the camera and lighting units is known and predetermined due to the design and way the device is worn. 2) The test subject inserts the contact lenses and assumes a calibration position (e.g., sitting in the driver's seat with head upright, looking straight ahead). 3) All electronic components of the system are switched on (IR, (if present VIS) cameras / sensors, IR light sources, evaluation unit). 4) Subsequently, in a first calibration step, the IR cameras record several images with pronounced IR reflection patterns. These serve, among other things, to precisely determine the distance between the cameras and the contact lenses and to accurately determine the distance between the visual axes of both eyes. Determining these distances is made possible by knowing the pixel resolutions of the cameras and by precisely determining the recorded IR reflection patterns and video images using common algorithms from the field of video oculography (see, for example, Cumulative distribution function (CDF) algorithm, Projection function (PF) algorithm, Edge analysis, Integral projection and Guassian model, Iris shape feature / template matching, Circular Hough transform, Harris corner detector, Isophotes curvature estimation, etc.; see, for example, https: / / www.ijsrp.org / research-paper-0912.php?rp=P09146).Thus, in addition to determining the precise center point of the viewing axis on the contact lens, the geometric proportions of the reflection patterns recorded by the IR sensor / camera can also be ascertained. Because the physical dimensions of the contact lenses and the geometric IR patterns (GM) are known from the reflection model, the proportions of the recorded IR reflections can be related to actual distances, taking into account the pixel resolutions of the cameras. This means that both the distance between the IR cameras and the contact lenses, as well as the distance between the viewing axes, can be determined. Additional information on the optical determination of distances can be found in the following prior art documents: https: / / ieeexplore.ieee.org / document / 6271270, https: / / ieeexplore.ieee.org / document / 7408947, https: / / ieeexplore.ieee.org / document / 8742847 . 5) Based on the physical spatial conditions determined in step 1 and entered into the calibration software, or already stored therein (in the case of a head-mounted system), and the determined distance between the viewing axes, the evaluation unit creates an initial simplified, virtual model of reality, i.e., the model geometry. This model includes the spatial arrangement of the cameras, IR light sources, the test subject's eyes (vitreous geometry and anterior chamber), the position of the contact lenses on the test subject's eyes, and, for example, the atlanto-occipital joint between the head and cervical spine. Using this simplified model geometry, the position and shape of the IR reflections, and consequently the direction of the viewing axis, can be approximated for different viewing directions. Furthermore, a comparison between actually measured IR reflections and IR reflections predicted by the model becomes possible.This actual-target comparison also enables manual and software-supported readjustment of the virtual model, so that after calibration it corresponds as closely as possible to reality. In this context, the publications "Video-oculographic measurement of 3-dimensional eye rotations" by Dietmar Ott et al. (1990) and "General Theory of Remote Gaze Estimation Using the Pupil Center and Corneal Reflections" by Guestrin et al. (2006) should be mentioned. These describe how, using a contact lens with two known points (applied with paint) or two corneal reflections, the three-dimensional orientation of the eye and the gaze axis can be determined using imaging techniques. This basic concept can be applied to the described invention. Insofar as at least three spatially separated but physically known IR reflection points per contact lens can be unambiguously determined at any time during image acquisition, the three-dimensional orientations of the eyes in space, and thus the gaze axes, can be determined. 6) In this step, the virtual (reflection) model is calibrated to the test subject (first with the head stationary, then with head movement). This requires a refinement of the model geometry of the virtual model. This is done using a series of actual-target value comparisons, as described in step 5, in which the test subject fixes on specific, spatially known markers in different viewing directions (first with the head stationary, then with head movement towards the markers). In head-stationary systems, the markers are displayed in the known virtual space, and head movement is not further considered in the virtual model. An initial reflection model is advantageously improved iteratively until the expected IR reflections match the actually observed IR reflections. Once this is achieved, the system is fully calibrated. Once the system is calibrated, the exact spatial position of the eyes, the lines of sight, and the position of the head in three-dimensional space can be determined, recorded, and evaluated. The position and orientation of the head can be determined using known methods (e.g., described in 10.1109 / TPAMI.2008.106 or https: / / doi.org / 10.1016 / j.eswa.2014.08.003) and additionally by the shape of the currently detected IR reflections on contact lenses KL1 and KL2 and the relative position of the eyes. For example, a slight rotation and tilt of the head to the right and downwards results in a rotation of the IR reflections, as well as a lowering of an imaginary line connecting the two eyes. 7) After the system has been calibrated using steps 1-6, the system is ready to determine the gaze direction of a person wearing a contact lens in at least one eye, based on the data captured by the cameras. Further advantages, features, and details will become apparent from the following description, in which – possibly with reference to the drawings – at least one embodiment is described in detail. Identical, similar, and / or functionally equivalent parts are identified by the same reference numerals. Figures 1-3 show vertical cross-sections through contact lenses according to the invention, Figures 4a-f show contact lenses in plan view with different geometric patterns GM of a layer S, Figure 5 shows a highly schematic representation of a system according to the invention, and Figure 6 shows a highly schematic sequence of a method according to the invention. Figures 1-3 show vertical cross-sections through contact lenses 100 according to the invention, each having a contact surface 101, with which the contact lens 100 is arranged on an eye, an outer surface 102 opposite the contact surface 101, and at least one layer S 103. Figure 1 shows a layer S 103 arranged between the contact surface 101 and the outer surface 102. Figure 2 shows two layers S 103a and 103b arranged between the contact surface 101 and the outer surface 102. Figure 3 shows a layer S 103 arranged on the outer surface 102. Fig. 4a -f show contact lenses 100 according to the invention in top view with layers S 103 formed as different geometric patterns GM 104. Fig. 5 shows a highly schematic representation of a system according to the invention for determining the gaze direction of a person wearing a contact lens KL1 100a or KL2 100b according to the invention on each of their two eyes. The contact lens KL1 100a on the eye shown on the left in Fig. 5 has a layer S1 103a made of material M1, which is designed as a geometric pattern GM1 according to Fig. 4d. The contact lens KL2 100b on the eye shown on the right in Fig. 5 has a layer S2 103b made of material M2, which is designed as a pattern similar to the geometric pattern GM2 according to Fig. 4e. Materials M1 and M2 each consist of an infrared light absorbing material and / or an infrared light reflecting material. The system further comprises two infrared radiation sources 110a, 110b for illuminating the contact lenses 100a, 100b with parallel infrared light, a first combination of IR sensor 111a and VIS sensor 112a, which serves to detect an IR reflection pattern on the eye shown on the left in Fig. 5, and a second combination of IR sensor 111b and VIS sensor 112b, which serves to detect an IR reflection pattern on the eye shown on the right in Fig. 5. The system further comprises an evaluation unit 113, which is connected to the infrared radiation sources 110a, 110b, the IR sensors 111a, 111b and the VIS sensors 112a, 112b, wherein the evaluation unit 113 is designed and configured to perform a system calibration and, based on the system calibration and the sensor data acquired by the IR sensors 111a, 111b and the VIR sensors 112a, 112b, to determine a current gaze direction for each of the two eyes. Fig. 6 shows a highly schematic sequence of a method according to the invention for operating a system as shown above in Fig. 5. The procedure comprises the following steps. In a first step 201, the system is calibrated. This calibration step 102 is divided into a sub-step 201a, in which a relative geometric arrangement and orientation of the infrared radiation sources 110a, 110b, the IR sensors 111a, 111b, the VIS sensors 112a, 112b and the two eyes of the person wearing the contact lenses 100a, 110b are determined. In a further substep 201b, a mathematical reflection model is determined for each eye wearing a contact lens. This reflection model specifies an associated (virtual) IR reflection pattern for a multitude of gaze directions of the respective eye, which can be detected with the IR sensor assigned to the respective eye. If this reflection model is available, the system can be operated operationally. In a further step, the current gaze direction of the eyes of the person wearing the contact lens(es) 100 is determined based on the determined arrangement and orientation of the infrared radiation sources 110a, 110b, the IR sensors 111a, 111b, the VIS sensors 112a, 112b, the two eyes, the reflection models determined for both eyes, and the current sensor data determined by the IR sensors 111a, 111b and the VIS sensors 112a, 112b. Although the invention has been further illustrated and explained in detail by means of preferred embodiments, the invention is not limited by the disclosed examples, and other variations can be derived from them by a person skilled in the art without departing from the scope of protection of the invention. It is therefore clear that a multitude of possible variations exist. It is also clear that the embodiments mentioned as examples are truly only examples and are not to be understood in any way as limiting, for example, the scope of protection, the possible applications, or the configuration of the invention.Rather, the preceding description and the description of the figures enable the person skilled in the art to implement the exemplary embodiments in concrete terms, whereby the person skilled in the art, with knowledge of the disclosed inventive concept, can make various changes, for example with regard to the function or the arrangement of individual elements mentioned in an exemplary embodiment, without leaving the scope of protection defined by the claims and their legal equivalents, such as a further explanation in the description. Reference symbol list 100, 100a,b Contact lens 101 Contact surface side of the contact lens 100 102 Outside of the contact lens 100 103, 103a,b Layer S 104, 104a,b Geometric pattern GM of layer S 103 110 Infrared radiation source 111 IR sensor 112 VIS sensor 113 Evaluation unit 201, 201a, 201b, 202 Process steps

Claims

System for determining the gaze direction of a person wearing a contact lens KL1 (100a) on at least one of their two eyes, wherein this contact lens KL1 (100a) has at least one layer S1 (103a) designed as a geometric pattern GM1 (104a) and made of a material M1 comprising at least an infrared light IR-absorbing material and / or at least an infrared light IR-reflecting material, and the geometric pattern GM1 (104a) is associated with at least one infrared light reflection pattern IR-RM characteristic of this pattern GM1, comprising: - at least one infrared radiation source (110) for illuminating the at least one contact lens KL1 (100a); - at least one IR sensor (111) for detecting an IR reflection pattern on the at least one contact lens KL1 (100a); - at least one VIS sensor (112) for detecting the two eyes of the person in the visible radiation range VIS;and an evaluation unit (113) connected to the infrared radiation source (110) and the at least one IR sensor (111), wherein the evaluation unit (113) is designed and configured to perform a system calibration and, based on the system calibration and the sensor data acquired by the at least one IR sensor (111) and the at least one VIS sensor (112), to determine a current gaze direction of the two eyes of the person. System according to claim 1, wherein the person wears a contact lens KL2 (100b) on his second eye, wherein this contact lens KL2 (100b) has at least one layer S2 (103b) which is designed as a geometric pattern GM2 (104b) and consists of a material M2 comprising at least an infrared light IR absorbing material and / or at least an infrared light IR reflecting material, and the geometric pattern GM2 (104b) is associated with at least one infrared light reflection pattern IR-RM characteristic of this pattern GM2. System according to claim 1 or 2, wherein the evaluation unit (113) is designed and configured to determine, within the scope of system calibration, a relative spatial arrangement and orientation of the IR radiation source (110), the at least one IR sensor (111), the at least one VIS sensor (112) and the two eyes of the person. System according to one of claims 1 to 3, wherein the evaluation unit (113) is designed and configured to determine, within the framework of system calibration, for each eye with contact lens (100a, 100b), a reflection model which specifies for a plurality of viewing directions an associated virtual IR reflection pattern of the respective contact lens (100a, 100b) detectable by the IR sensor. System according to one of claims 1 to 4, wherein the layer S1 (103a) of the contact lens KL1 (100a) made of material M1 has a transmittance in the range of 0.8 to 1, in particular close to 1, for light in the optically visible wavelength range of 380 to 780 nm. System according to one of claims 1 to 5, wherein the layer S2 (103b) of the contact lens KL2 (100b) made of material M2 has a transmittance in the range of 0.8 to 1, in particular close to 1, for light in the optically visible wavelength range of 380 to 780 nm. System according to one of claims 1 to 6, wherein the geometric pattern GM1 (104a) and / or the geometric pattern GM2 (104b) is a rotationally symmetrical pattern or has concentrically arranged circular rings or circular segments or is designed in the form of a reticle (crosshairs). System according to any one of claims 1 to 7, wherein the material M1 and / or the material M2 comprises one or more of the following substances: silicon, germanium, sapphire, gold, N-BK7, zinc selenide, zinc sulfide, calcium fluoride, magnesium fluoride, sodium fluoride and potassium bromide. System according to any one of claims 1 to 8, wherein the at least one layer S1 (103a) and / or the at least one layer S2 (103b) comprises IR nano-reflectors. Method for operating a system according to any one of claims 1 to 9, comprising the steps: - Calibrating (201) the system by the steps: - Determining (201a) a relative geometric arrangement and orientation of the at least one infrared radiation source (110), the at least one IR sensor (111), the at least one VIS sensor (112) and the two eyes of the person wearing the contact lens(es) (100a, 100b), and - Determining (201b) a reflection model which specifies an associated virtual IR reflection pattern for a plurality of viewing directions of the respective eye wearing a contact lens (100a, 110b);and- Determining (202) a current gaze direction of the eyes of the person wearing the contact lens(es) (100a, 100b) based on the determined arrangement and orientation of the at least one infrared radiation source (110), the at least one IR sensor (111), the at least one VIS sensor (112) and the two eyes, the determined reflection model and the current sensor data determined by the at least one IR sensor (111) and the at least one VIS sensor (112).

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