Method for detecting eye gaze direction

Abstract

The invention relates to a method for detecting the gaze direction of an eye (10), the method comprising the steps of irradiating at least one wavelength modulated laser beam (1) onto the eye (10), detecting the optical path length (2) of the emitted laser beam (1) based on laser feedback interferometry of the emitted laser radiation with radiation backscattered from the eye, detecting the Doppler shift of the emitted radiation and the backscattered radiation based on laser feedback interferometry, and detecting eye movement of the eye (10) based on the optical path length (2) and the eye velocity.

Description

Technical Field

[0001] The invention relates to a method for detecting a gaze direction of eyes, a gaze direction detection device and a pair of smart glasses. Background Art

[0002] It is known to use eye tracking or eye detection (also called electrooculogram) to determine the movement of the eye and estimate the gaze direction. Known systems for eye tracking are usually based on using camera-based systems in the area of ​​the eye or using electrical or electromagnetic sensors to detect information about the position of the eye. In addition, scanning laser systems are known, which use, for example, micromirrors to scan a laser spot on the eye. All these systems are usually of high complexity and energy consumption, and most of them have limited temporal resolution. Summary of the invention

[0003] In contrast, the method according to the invention with the features of claim 1 is characterized by a particularly energy-saving, cost-effective and temporally high-resolution method for the gaze direction. This is achieved by a method for detecting the gaze direction of an eye, the method comprising the following steps:

[0004] irradiating the eye with at least one wavelength modulated laser beam,

[0005] Detection of the optical path length of the emitted laser beam based on laser feedback interferometry of the emitted laser beam and the radiation backscattered from the eye,

[0006] Based on laser feedback interferometry, the Doppler shift of emitted and backscattered radiation (particularly between frequencies) is detected.

[0007] Detect eye velocity based on Doppler shift, and

[0008] Eye gaze movement is detected based on optical path length and / or eye velocity.

[0009] In other words, in the method, at least one wavelength-modulated laser beam, in particular emitted from a wavelength-modulated laser source, is irradiated onto the eye of the user. The irradiated laser beam is at least partially backscattered at the ocular surface of the eye. The backscattered radiation is the portion of the radiation scattered at the ocular surface that is parallel to the emitted laser beam and is therefore able to interfere with it. The backscattered portion interferes with the incident laser radiation, i.e. with the laser radiation propagating towards the eye. The backscattered portion of the irradiated laser beam may also be referred to as backscattered radiation. By so-called laser feedback interferometry, an overlap of the emitted laser beam and the backscattered radiation is produced, so that there is interference radiation produced thereby. For example, a detector can be used to detect and analyze this generated interference radiation.

[0010] Based on laser feedback interferometry, the optical path length of the emitted laser beam is detected. The optical path length is considered to be the product of the geometric distance covered by the emitted laser beam from the laser source to the surface of the eye and the refractive index of the material present there. This means that if the laser beam is emitted from the laser source directly towards the eye in air (refractive index of about 1), the optical path length approximates the distance between the laser source and the eye very well. For example, if the wavelength of the emitted laser radiation is known, the optical path length can be estimated based on constructive or destructive interference.

[0011] Preferably, the triangle-wave modulated laser light is emitted as a laser beam within a wavelength range. By analyzing the interferometrically emitted and backscattered radiation, in particular by calculating the average value of the resulting interference frequency relative to the two edges of the triangle-wave modulated signal, the optical path length can be detected.

[0012] Furthermore, if there is eye movement relative to the scattered laser radiation, a Doppler shift will occur due to the Doppler effect, in particular between the frequency of the emitted radiation and the frequency of the backscattered radiation. This Doppler shift can be detected by means of laser feedback interferometry. The Doppler shift can then be used to determine the eye velocity. The eye velocity is considered to be the tangential velocity at a point on the eye surface, which corresponds to the point at which the laser radiation impinges on the eye surface. Preferably, the eye velocity comprises an absolute value for the current velocity and a direction of the current velocity.

[0013] Based on the detected optical path length and eye velocity, eye movement can then be detected. In particular, starting from a known eye position, the gaze direction can be tracked according to any movement of the eye. Therefore, the method allows the gaze movement of the eye to be accurately determined in a particularly simple and effective manner. A specific method using laser feedback interferometry (in particular using the Doppler effect) to detect the gaze direction provides the advantage of a particularly high temporal sampling rate, so that eye movements can be tracked with a particularly high temporal resolution. In addition, the method provides the advantage of using simple and inexpensive components and evaluation algorithms, which have lower energy requirements. In particular, no computationally intensive image data processing is required. In addition, advantageously, no moving parts such as scanning devices will be required, thus providing particularly flexible and robust applicability.

[0014] Preferred further embodiments of the invention are the subject matter of the dependent claims.

[0015] Preferably, the method further comprises the steps of detecting the reflectivity of the eye based on the amplitude and phase of the radiation backscattered by the eye, and detecting the absolute eye position based on the detected reflectivity and the optical path length. In this case, the reflectivity is in particular a complex reflectivity with the amplitude and phase of the radiation backscattered by the eye. By additionally measuring the reflectivity of the eye, the current position of the eye and thus also the gaze direction can be detected particularly accurately. Advantageously, based on the different reflectivities of different parts of the eye, it can be identified which part of the eye the laser beam is currently irradiating, whereby in combination with the optical path length the absolute eye position can be estimated. For example, the reflectivities can differ significantly and also in characteristics when the laser radiation impinges on different parts of the eye. For example, significantly stronger scattering occurs when the laser radiation passes through the cornea and hits the iris of the eye compared to irradiation of the retina. Preferably, the reflectivity determination can therefore be used to determine when an anatomical boundary will move past the laser beam, which is stationary relative to the user's head, in particular during eye movement. In this way, it can be particularly easy and accurate to detect which absolute eye position and thus which eye gaze direction currently exists.

[0016] Preferably, the absolute eye position is detected based on the reflectivity and the optical path length at predetermined points in time. Based on the eye velocity, any eye movement is detected between predetermined times. Preferably, an integration of the detected eye velocity can be performed between predetermined points in time, so that the angle of the eye movement during the eye movement can be estimated. In particular, the absolute eye position will not be detected continuously, but only at specific points in time. Between these points in time, the relative eye movement can be estimated by a particularly energy-efficient method of detecting the eye velocity based on the Doppler shift. In this way, the position and gaze direction of the eye can be detected in a particularly efficient manner.

[0017] Preferably, the eye velocity is determined based on the following equation: D =2v cos(α) / λ, where λ is the wavelength of the incident laser radiation, v is the eye velocity, and F D is the Doppler shift of the emitted and backscattered radiation, and α is the angle between the wave vector k of the incident laser radiation and a tangent line that contacts the ocular surface at the point of impact where the laser radiation impinges on the eye and that lies in the plane spanned by the wave vector k and the surface normal at the point of impact. In particular, the Doppler shift F D corresponds to the difference between the frequency of the emitted laser beam and the frequency of the backscattered radiation. Using the above equation, eye velocity can be detected with a particularly low computational effort, enabling efficient and high-resolution determination of eye movements.

[0018] Particularly preferably, the method further comprises the steps of detecting the rotation rate of the eye and performing a calibration to determine the angle α, wherein the calibration is performed by using the optical path length, the eye velocity and the rotation rate of the eye. By collecting the corresponding parameters, an accurate calibration of the gaze detection can thus be performed to optimally estimate the eye gaze direction at any point in time. Preferably, the calibration step comprises recording a gaze angle map, which comprises recording the measurement data of all parameters for calibration or for a plurality of predetermined gaze angles of the eye, respectively. Using the gaze angle map, it is thus possible to determine in a particularly simple and effective manner which eye gaze angle is currently present when performing the method for a specific parameter set.

[0019] Preferably, the rotation rate of the eyes is detected based on the rotation rate of the user's head, wherein in particular a rotation rate sensor is used to detect the rotation rate of the head. Preferably, the rotation rate sensor is part of an inertial measurement unit, which is preferably configured to detect any acceleration in addition to the rotation rate and, for example, can also detect the geomagnetic field in addition. An absolute orientation sensor is particularly advantageous, which is particularly configured to detect the rotation rate around three axes and preferably detects any acceleration and further preferably detects the geomagnetic field. In order to detect the rotation rate of the head, the rotation rate sensor can be arranged on the user's head, for example. In particular, the rotation rate of the eyes is detected based on the following assumption: when the line of sight is focused on a point defined in space, the eyes perform a rotation that is completely opposite to the rotation of the head. Therefore, calibration can be performed in a particularly simple manner.

[0020] Preferably, the method further comprises the following steps: detecting the maximum eye velocity during the eye movement, and predicting the eye movement end position based on the maximum velocity. Thereby, the operation of the input unit and / or the output unit is performed based on the eye movement end position. Particularly preferably, the adjustment of the image parameters of the image projected by the image projection unit is performed based on the eye movement end position. In particular, the position where the eye movement stops in the case of a rapid eye movement (i.e., a so-called saccadic movement) can be predicted. Preferably, the prediction of the eye movement end position is based on the assumption that the eye performs a uniformly accelerated movement during such an eye movement. That is, there is a constant positive acceleration during the first half of such an eye movement, and a constant (especially of the same magnitude) negative acceleration is generated during the second half of the eye movement. By detecting the first half of the corresponding speed curve, i.e., the speed of the eye movement from rest until the maximum speed during the movement, the second half of the speed curve can be estimated, in particular based on the assumption of mirror symmetry. In this way, in particular by integrating the detected speed curve, the end point of the eye movement can be estimated. Preferably, the maximum speed during the eye movement is determined based on the detection of a reduced eye speed following an increase in the eye speed.

[0021] Preferably, at least two laser beams are irradiated onto the eye, the two laser beams being aligned such that the angle and / or the distance between the wave vector of each laser beam and at least one of the two mutually orthogonal axes of rotation in each case is not equal to zero. In order to detect a rotational movement of the eye about the axis of rotation, it is advantageous if the wave vector of the laser beam encloses the largest angle with the axis of rotation and, at the same time, is maximally spaced therefrom. For example, if the distance and / or the angle enclosed with the axis of rotation is equal to zero, the laser beam is insensitive to any rotational movement about this axis. In other words, according to this relationship, it is advantageous to align the two laser beams such that each of them is particularly sensitive to one of the rotation rates of the eye about the two mutually orthogonal axes of rotation. Preferably, in the specific case where both laser beams are incident on the same point on the surface of the eye, the laser beams are aligned such that the projections of the two laser beams onto the tangent planes at the eye and at the point of incidence are orthogonal to each other. This means that, in this case, the portions of the two laser beams tangential to the eye surface are orthogonal to each other at the common point at which the laser beams are incident on the eye. Preferably, the tangent portions of the two laser beams are aligned vertically and horizontally, respectively. Eye movements in any direction can therefore be detected particularly easily and precisely.

[0022] Furthermore, the invention provides a gaze detection device for detecting a gaze direction. The gaze detection device comprises a laser device configured to irradiate at least one laser beam onto an eye, and a control device configured to actuate the laser device, the control device being configured to perform the described method. The eye detection device is characterized by a particularly simple and inexpensive design, including a high detection rate and a low energy requirement.

[0023] Preferably, the laser device comprises at least one surface emitter (also called vertical cavity surface emitting laser, or VCSEL for short) with a photodiode integrated therein. With such a laser device, eye movements can be detected with an eye tracking device based on laser feedback interferometry having a particularly simple, compact and cost-effective design. Such a laser device is particularly suitable for detection using self-mixing effects. Preferably, in this case, a photodiode is used for detecting the overlap of emitted and backscattered radiation directly in the laser cavity. Particularly preferably, the laser device can comprise a plurality of surface emitters, each emitting a laser beam.

[0024] Preferably, the laser device comprises a beam splitting element which is configured to split a single laser beam into at least two laser beams. This makes the configuration of the eye tracking apparatus particularly simple and cost-effective.

[0025] Particularly preferably, at least one laser beam emitted by the laser device is directed directly onto the eye. Alternatively or additionally, the gaze detection device may further comprise a deflection element, which is configured to deflect at least one laser beam emitted by the laser device onto the eye. Preferably, the deflection element is a micromirror actuator, in particular a micromirror actuator that can be operated in a controllable manner. Alternatively, preferably, the deflection element is a holographic optical element.

[0026] Furthermore, the present invention relates to smart glasses comprising an eye tracking device as described above. Preferably, the laser device comprises at least one laser source arranged on the glasses frame and / or on the temples. In this case, the frame is particularly regarded as the area of ​​the smart glasses surrounding the lenses, while the temples are particularly regarded as the retaining temples connected to the frame and extending, for example, to the ears of the user. For example, a plurality of laser sources can be arranged distributed around the glasses lens on the glasses frame, thereby allowing a particularly precise scanning of the eye over the entire range of movement. Alternatively or additionally, one or more laser sources can be integrated, preferably molded into the glasses lens.

[0027] Particularly preferably, the smart glasses further comprise a rotation rate sensor, which is configured to detect any rotation of the user's head. Preferably, the rotation rate sensor is part of the inertial measurement unit and / or the absolute orientation sensor. Thus, all hardware required for gaze detection and calibration of the gaze detection can be integrated into a single device, whereby a particularly high level of user convenience can be achieved.

[0028] Preferably, the smart glasses further comprise an input and / or output device, which is configured to receive an input from a user and / or to provide an output to a user. Preferably, the input and / or output device comprises a projection device, which is configured to project an image, in particular onto a retina of an eye of the user. Preferably, the input and / or output device is coupled to an eye tracking device, in particular via a control device of the eye tracking device, such that the input and / or output device can be controlled, in particular depending on eye movements. This may enable a particularly user-friendly operation of the smart glasses, a particular type of gaze detection, which provides a high level of accuracy, while also enabling particularly low energy consumption and low costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In the following, the present invention will be described by way of example embodiments in conjunction with the accompanying drawings. In the accompanying drawings, components with the same function are each represented by the same reference numeral, wherein:

[0030] Figure 1 is a simplified schematic diagram of a pair of smart glasses according to a first embodiment of the present invention.

[0031] Figure 2 is used Figure 1 Simplified schematic detail view of the gaze detection process of smart glasses.

[0032] Figure 3 is used Figure 1 Another simplified schematic detail view of smart glasses implementing gaze detection.

[0033] Figure 4 is from when performing gaze detection Figure 1 Simplified schematic representation of the measurement data of the smart glasses.

[0034] Figure 5 is another simplified schematic diagram of a pair of smart glasses according to a second embodiment of the present invention, and

[0035] Figure 6 is a simplified schematic diagram of a pair of smart glasses according to a third embodiment of the present invention. DETAILED DESCRIPTION

[0036] Figure 1 A simplified schematic diagram of a pair of smart glasses 50 according to a first embodiment of the present invention is shown. The smart glasses 50 include glasses lenses 52, glasses frames 51 in which the glasses lenses 52 are accommodated, and glasses temples 53 for holding the smart glasses 50 on the user's head. Therefore, the smart glasses 50 are configured to be worn on the user's head.

[0037] The smart glasses 50 include a gaze detection device 20, by which the gaze detection device 20 can detect the gaze direction of the user's eye 10. To this end, the gaze detection device 20 includes a laser device 3 and a control device 4, which is configured to operate the laser device 3 to perform a corresponding method for detecting the gaze direction of the eye 10. For compact design, the control device 4 is arranged in the temple 53 of the smart glasses 50.

[0038] The laser device 3 includes a total of five surface emitters 3a, 3b, 3c, 3d, 3e as laser sources. Four of the five surface emitters 3a, 3b, 3c, 3d are distributedly arranged on the eyeglass frame 51 around the eyeglass lens 52. The fifth surface emitter 3e is arranged on the eyeglass temple 53. Each surface emitter 3a, 3b, 3c, 3d, 3e is configured to irradiate a wavelength-modulated laser beam 1 onto the eye 10. In this case, triangular-wave modulated laser light is emitted as the laser beam 1 within a wavelength range. For the sake of clarity, only a single laser beam 1 emitted by the first surface emitter 3a is shown in the figure. Each laser beam 1 is directed onto the ocular surface 11 of the eye 10 as a separate laser spot 30a, 30b, 30c, 30d, 30e.

[0039] Figure 2The laser spots 30a, 30b, 30c, 30d of the first four surface emitters 3a, 3b, 3c, 3d arranged on the eyeglass frame 51 are shown. Figure 3 , the fifth laser spot 30e generated by the fifth surface emitter 3e is displayed on the side of the eye 10.

[0040] like Figure 2 and Figure 3 As shown, the laser spots 30a, 30b, 30c, 30d, and 30e are preferably located in or near the region of the iris 12 of the eye 10. As a result, when the eye 10 moves, the pupil 13 of the eye 10 often moves close to or passes through the laser spot 1, so that the position and movement of the pupil 13 can be detected with high accuracy to determine the gaze direction of the eye with high accuracy.

[0041] The implementation of the method for detecting the gaze direction of eye 10 is described in detail below, which is based on only a single laser beam 1 .

[0042] Firstly, a laser beam 1 is irradiated onto the eye 10. At the eye surface 11, the laser beam 1 will be at least partially backscattered. As a result, an overlap of the irradiated laser beam 1 and the part of the backscattered radiation propagating backwards in parallel in the direction of the surface emitter 3a is produced. With the help of a photodiode integrated in the surface emitter 3a, laser feedback interferometry is performed to detect the interference radiation generated due to the overlap of the irradiated laser radiation 1 and the radiation backscattered in the opposite direction. Since the photodiode is directly integrated into the laser cavity of the surface emitter 3a, the detection of the generated interference radiation is performed by the so-called self-mixing effect.

[0043] exist Figure 4 Schematically shown in FIG. 2 is an exemplary spectrum 25 of the generated interference radiation which can be detected by the integrated photodiode of the surface emitter 3 a. Axis 25 a corresponds to the frequency and axis 25 b corresponds to the amplitude. Reference numeral 26 denotes the peak frequency of the detected interference radiation, which is detected, for example, by Fourier analysis. As a result of the triangular wave modulation of the wavelength of the emitted laser beam 1, the peak frequency 26 depends on the optical path length 2. The optical path length 2 (see Figure 1 ) corresponds to the distance between the surface emitter 3a and the eye surface 11 covered by the laser beam 1. When the laser beam 1 is irradiated directly onto the eye 10, Figure 1 In the first embodiment, the optical path length 2 corresponds to the shortest distance between the surface emitter 3a and the eye surface 11. Therefore, in case the wavelength of the emitted laser beam 1 is known, the optical path length 2 can be detected for a specific eye position (i.e. for a specific gaze direction) based on laser feedback interferometry.

[0044] Figure 4An exemplary spectrum 25 is shown, which is recorded during a constant movement of the eye surface 11 relative to the laser beam 1, i.e. during a rotation of the eye 10. During this movement, due to the Doppler effect, a shift 27 of the peak frequency 26 occurs towards a shifted peak frequency 26' as shown by the dashed line. Therefore, the resulting Doppler shift of the emitted and backscattered laser radiation can be detected based on the spectrum 25. Based on this Doppler shift, the instantaneous eye velocity of the movement of the eye 10 as well as the direction of movement can be detected.

[0045] In order to calculate the eye velocity using the Doppler shift, the angle α between the eye surface 11 and the laser beam 1 is detected and used to compensate for any tilted position of the irradiated laser radiation 1 relative to the eye surface 11. In detail, the angle α describes the minimum angle between the laser beam 1 and the plane 35, which is arranged at the corresponding laser spot 30b tangential to the eye surface 11 (see Figure 3 ).

[0046] The calibration can be performed to determine the angle α based on the rotation rate of the eye 10. The rotation rate of the eye 10 is detected based on the rotation rate of the user's head, wherein the rotation rate sensor 6 integrated in the temple 53 of the glasses is used to detect the rotation rate of the head during the rotation while focusing on a stationary point in space with the eye 10. The rotation rate of the eye 10 is estimated under the assumption that the eye performs a movement opposite to the movement of the head.

[0047] In addition to detecting the frequency of the impinging and backscattered laser radiation, the signal-to-noise ratio of the backscattered radiation is detected, thereby detecting the reflectivity of the eye 10. The reflectivity is different for different areas of the eye 10. In particular, when the laser beam 1 passes through an anatomical boundary of the eye 10, such as the iris 12 or the pupil 13, the detected reflectivity changes. Therefore, the reflectivity of the eye 10 can be used to estimate which area of ​​the eye 10 is currently impinging on the laser beam 1. Therefore, the instantaneous absolute eye position of the eye 10 can be detected in combination with the detected optical path length 2.

[0048] Thus, any eye movement can be detected using the eye tracking device 20 based on laser feedback interferometry, wherein any eye movement of the eye 10 can be detected and tracked. In combination with a determination of the absolute eye position, which, for example, will only be performed at predetermined times and additionally based on reflectivity, the instantaneous gaze direction of the eye 10 can thereby be detected. Using the components required to perform the determination of the gaze direction, a particularly high temporal resolution of the gaze direction determination can be achieved with a low energy requirement. In addition, particularly low-cost components can be used.

[0049] Figure 5A simplified schematic diagram of a pair of smart glasses 50 according to a second embodiment of the present invention is shown. The second embodiment corresponds substantially to Figure 1 The first embodiment is similar to the first embodiment, but differs in that the laser device 3 is configured alternatively. Figure 5 In a second embodiment of the eye tracking device 20, the laser device 3 comprises four surface emitters 3a, 3b, 3c, 3d with integrated photodiodes, all of which are arranged on the temple 53. Therefore, the laser beam 1 emitted by the surface emitters 3a, 3b, 3c, 3d will be irradiated indirectly onto the eye 10. In particular, the laser beam 1 is irradiated onto the eyeglass lens 52, taking the focal point 1' on the eyeglass lens 52 as an example. A deflection element 54 in the form of a holographic optical element is integrated in the eyeglass lens 52 to deflect the laser beam 1 towards the eye 10. In this way, an alternative arrangement of the laser device 3 can be provided, by which the method for detecting gaze can also be performed.

[0050] also, Figure 5 The smart glasses 50 of the second embodiment further include an input and / or output device 7, which is configured to provide an output to the user. The input and / or output device 7 includes a projection unit, which is configured to project an image onto the retina of the eye 10. The projection unit can be used, for example, to display augmented reality or virtual reality. Preferably, the projection unit is connected to the control device 4, wherein the control device 4 is configured to operate the projection unit in response to the detected gaze direction. For example, the projected image can be adjusted according to the gaze direction.

[0051] Figure 6 A simplified schematic diagram of a pair of smart glasses 50 according to a third embodiment of the present invention is shown. The third embodiment example substantially corresponds to Figure 5 , but with an alternative embodiment of the laser device 3.

[0052] In the third embodiment example, the laser device 3 includes only a single surface emitter 3a as a laser source. A single laser beam 1 emitted from the single surface emitter 3a is split into two or more laser beams 1a, 1b using a beam splitting element 30. Figure 5 In the second embodiment, the two laser beams 1a, 1b are directed indirectly to the eye 10 via a deflection element 54 in the eyeglass lens 52. For example, Figure 6 As shown, the two laser beams 1a, 1b can be focused on a common point on the eye 10. According to an example of a third embodiment, another particularly advantageous configuration and arrangement of the smart glasses 50 can be provided by beam splitting.

Claims

1. A method for detecting the gaze direction of an eye (10), comprising the following steps: irradiating at least one wavelength-modulated laser beam (1) onto the eye (10), detecting an optical path length (2) of the irradiated laser beam (1) based on laser feedback interferometry of the irradiated laser beam (1) and the portion of the laser beam (1) backscattered from the eye (10), Based on laser feedback interferometry, the Doppler shift of the irradiated laser beam (1) and the backscattered portion is detected, detecting eye velocity based on the Doppler shift, and detecting eye movement of the eye (10) based on the optical path length (2) and the eye velocity, detecting the reflectivity of the eye (10) based on the amplitude and phase of the portion of the laser beam (1) backscattered from the eye, and detecting the absolute eye position based on the reflectivity and the optical path length (2), wherein the detection of the absolute eye position is performed at predetermined time points, and wherein eye movement between the predetermined time points is detected based on the eye velocity.

2. The method according to claim 1, wherein: Eye velocity detection is based on the following equation: F D = 2 v cos(α) / λ, where: v is the eye velocity; F D is the Doppler frequency corresponding to the Doppler shift of the irradiated laser beam (1) and the backscattered portion of the emitted laser beam (1), α is the angle between the direction of the irradiated laser beam (1) and a tangent to the ocular surface (11), the tangent to the ocular surface (11) being in contact with the ocular surface (11) at the point of impact of the laser beam (1) on the eye (10), and the tangent to the ocular surface (11) also being located in the plane spanned by the wave vector and the surface normal at the point of impact; and λ is the wavelength of the irradiated laser beam (1).

3. The method according to claim 2, further comprising the steps of: detecting a rotation rate of the eye (10); and Calibrate to determine the angle α, Wherein the calibration is based on the optical path length (2), the eye velocity and the rotation rate of the eye (10).

4. The method according to claim 3, wherein: The rotation rate of the eye (10) is detected based on the rotation rate of the user's head detected by means of a rotation rate sensor (6).

5. The method according to any one of the preceding claims, further comprising the steps of: Detecting maximum eye velocity during eye movements, and The eye movement end position is predicted according to the maximum eye velocity.

6. A method according to any one of the preceding claims, wherein: At least two laser beams (1) are irradiated onto the eye (10), wherein the two irradiated laser beams (1) are aligned so that the angle and / or the distance between the wave vector of each irradiated laser beam (1) and at least one of two mutually orthogonal rotation axes of the eye (10) are respectively non-zero.

7. A gaze detection device for detecting a gaze direction, comprising: a laser device (3) configured to direct at least one laser beam (1) onto an eye (10), and A control device (4) configured to operate the laser device (3) and to perform the method according to any one of the preceding claims.

8. The gaze detection device according to claim 7, wherein: The laser device (3) comprises at least one surface emitter (3a, 3b, 3c, 3d, 3e) with an integrated photodiode.

9. The gaze detection device according to claim 7 or 8, wherein: The laser device (3) comprises a beam splitting element (30) configured to split a single laser beam (1) into at least two laser beams (1a, 1b).

10. The gaze detection device according to any one of claims 7 to 9, wherein: The at least one laser beam (1) is directed directly onto the eye (10), and / or wherein the gaze detection device (20) further comprises: a deflection element (54) configured to deflect the at least one laser beam (1) irradiated by the laser device (3) onto the eye (10).

11. A pair of smart glasses comprising a gaze detection device according to any one of claims 7 to 10, wherein: The laser device (3) comprises at least one laser source which is arranged on a spectacle frame (51), in particular around a spectacle lens (52), and / or on a spectacle temple (53) and / or in the spectacle lens (52).

12. A pair of smart glasses according to claim 11, further comprising a rotation rate sensor (6), the rotation rate sensor (6) being configured to detect rotation of the user's head.

13. A pair of smart glasses according to any one of claims 11 to 12, further comprising an input and / or output device (7) configured to receive input from a user and / or provide output to the user.

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