Eye tracking system, eye glasses and method for operating an eye tracking system

Abstract

An eye tracking system with the following features is provided : - a laser device (2) emitting an output beam (3) of electromagnetic radiation during operation, - a beam multiplexer element (7) generating at least two sensor beams (8) from the output beam (3) of electromagnetic radiation during operation, wherein - the beam multiplexer element (7) is configured to direct the at least two sensor beams (8) on at least two locations (9) on an eye (10) of a user, the laser device (2) is configured to detect electromagnetic radiation of at least one of the at least two sensor beams (8) reflected by the eye (10) of the user. Further, eye glasses and a method for operating an eye tracking system are provided.

Description

[0001] EYE TRACKING SYSTEM, EYE GLASSES AND METHOD FOR OPERATING AN

[0002] EYE TRACKING SYSTEM

[0003] An eye tracking system, eye glasses and a method for operating an eye tracking system are provided .

[0004] It is an obj ect to provide an improved eye tracking system, particularly providing an enlarged eyebox, and / or enabling simpli fied calibration . Further, eye glasses with an improved eye tracking system are to be provided . Further, an improved method for operating an eye tracking system, particularly with an enlarged eyebox and / or enabling simpli fied calibration are to be provided .

[0005] These obj ects are achieved with an eye tracking system of claim 1 , eye glasses with the features of claim 12 and a method for operating an eye tracking system having the steps of claim 16 .

[0006] Improved embodiments and developments of the eye tracking system, the eye glasses and the method for operating an eye tracking system are given in the respective dependent claims .

[0007] According to an embodiment , the eye tracking system comprises a laser device emitting an output beam of electromagnetic radiation during operation . Preferably, the output beam comprises or consists of coherent electromagnetic radiation . Particularly, the eye tracking system comprises one or a plurality of laser devices . Particularly, the laser device emits an output beam of electromagnetic laser radiation during operation . Particularly, the laser device comprises a VCSEL chip (VCSEL, short for "vertical cavity surfaceemitting laser" ) as a light source generating the electromagnetic radiation . Particularly, the output beam of the electromagnetic radiation is a beam of coherent electromagnetic laser radiation .

[0008] For example , the eye tracking system comprises only one single laser device having only one single VCSEL chip as light source . However, it is also possible to use a plurality of VCSEL chips as light sources within the laser device . Further, the VCSEL chips can be comprised by separate laser devices also comprised by the eye tracking system .

[0009] Particularly, each laser device creates at least two sensor beams and tracks the movement of several locations of the eye .

[0010] According to a further embodiment of the eye tracking system, the eye tracking system comprises a beam multiplexer element generating at least two sensor beams from the output beam of the electromagnetic radiation during operation . Preferably, the beam multiplexer element generates at least three sensor beams from the output beam of the electromagnetic radiation during operation . For example , the sensor beams are generated by the multiplexing element by splitting the output beam . During operation of the eye tracking system, the output beam of electromagnetic radiation emitted by the laser device impinges on the beam multiplexer element and is reflected and / or transmitted by the beam multiplexer element , wherein during reflection and / or transmission the beam multiplexer element generates the at least two sensor beams from the output beam of the electromagnetic radiation . For example , the beam multiplexer element comprises an optical structure generating the at least two sensor beams . For example , the optical structure is an active optical structure or a passive optical structure . For example , the optical structure comprises or consists of a phase element . For example , the multiplexer element comprises one , two or a plurality of optical structures . The two or the plurality of optical structures can be equally formed or di f ferent from each other . For example , each optical structure generates and / or directs and or / focuses one sensor beam . Particularly, the beam multiplexer element is configured to spatially multiplex the output beam of electromagnetic radiation . Particularly, the beam splitting element splits one or multiple incident beam ( s ) into a plurality of sensor beams by spatial multiplexing .

[0011] According to a further embodiment , the eye tracking system uses a third sensor beam impinging on the eye of the user . Particularly, for tracking an eye movement , three unknowns have to be determined, particularly, the hori zontal and vertical displacement of the eye , the angular displacement of the eye and the speed of the eye . Therefore , three measurements have to be carried out . Particularly, the eye has to be probed at three di f ferent locations . For example , the beam splitting element generates three or more sensor beams . In that case , the beam multiplexer element is configured to direct the three or more sensor beams on at least three or more locations on an eye of the user, and the laser device is configured to detect electromagnetic radiation of the three or more sensor beams reflected by the eye of the user . However, i f the multiplexing element only generated two sensor beams , a further laser device , for example comprising a VCSEL chip, can be used for the generation of a third sensor beam . It is also possible , to use several laser devices and split the output beam in a plurality of sensor beams . I f there are used several laser devices , their output beams can be split by one or several multiplexing elements in sensor beams .

[0012] Particularly, the beam multiplexer element generates a plurality of sensor beams from the output beam of electromagnetic radiation during operation . Preferably, the plurality of sensor beams comprises or consists of at least 10 sensor beams .

[0013] According to an embodiment of the eye tracking system, the beam multiplexer element is configured to direct the at least two sensor beams on at least two locations on an eye of a user . Particularly, the beam multiplexer element is configured to direct the at least two sensor beams to a cornea of the eye of the user . Particularly, the user is a human user . In particular, the beam multiplexer element reflects and / or transmits the at least two sensor beams on the at least two locations on the eye of the user . Particularly, the sensor beams are directed to di f ferent locations on the eye of the user . Particularly, the number of locations on the eye of the user to which the sensor beams are directed, is the same number as the sensor beams . In other words , a single location on the eye of the user is allocated to each sensor beam .

[0014] Particularly, the sensor beams create spots on the eye of the user, particularly on the cornea . Particularly preferably, the spots of the sensor beams are spatially separated from each other and do not overlap .

[0015] According to a further embodiment of the eye tracking system, the laser device is configured to detect electromagnetic radiation of at least one of the at least two sensor beams reflected by the eye of the user . I f there are more than two sensor beams generated by the beam multiplexer element , the laser device is particularly configured to detect electromagnetic radiation of one , some or all of the sensor beams generated by the beam multiplexer element . In other words , the laser device is not only configured to emit an output beam of electromagnetic radiation, but also to detect reflected electromagnetic radiation generated from the output beam of electromagnetic radiation .

[0016] According to a further embodiment of the eye tracking system, the beam multiplexer element is configured to generate an input beam of electromagnetic radiation from the electromagnetic radiation reflected by the eye of the user . Particularly, the beam multiplexer element generates a single input beam from the electromagnetic radiation reflected by the eye of the user . Particularly, the laser device is configured to detect the electromagnetic radiation of the input beam . Particularly, the electromagnetic radiation reflected from the eye of the user is bundled to the electromagnetic radiation of the input beam by the same optical structures of the beam multiplexer element generating the sensor beams from the electromagnetic radiation of the output beam . Particularly, the electromagnetic radiations reflected from the eye of the user recombine into a single beam by the same optical structures of the beam multiplexer element generating the sensor beams from the electromagnetic radiation of the output beam .

[0017] Preferably, the electromagnetic radiation within the eye tracking system is coherent electromagnetic laser radiation . In other words , when running through the eye tracking system, coherence of the electromagnetic radiation emitted by the laser device is only af fected to a negligible degree at most .

[0018] According to a further embodiment of the eye tracking system, the beam multiplexer element is configured to focus the at least two sensor beams on the at least two locations of the eye of the user . For example , the at least two sensor beams are focused on di f ferent locations on the cornea of the eye of the user . For example , the beam multiplexer element focuses the at least two sensor beams in a transmission or a reflection geometry on the eye of the user .

[0019] According to a further embodiment of the eye tracking system, the locations of the at least two sensor beams on the eye of the user di f fer in their x-position, and / or their y-position and / or z-position in space . In other words , the beam multiplexer element is configured to direct the sensor beams to di f ferent locations on the eye , particularly, the cornea, of the user within the three-dimensional space . In other words , the beam multiplexer element is not only configured to direct the sensor beams on di f ferent locations in a common plane , but on di f ferent locations in 3D . Preferably, the locations of the sensors beams on the eye of the user, and in particular, on the cornea of the user di f fer all in their x- positions , their y-positions and their z-positions . This enhances the accuracy of eye tracking system and potentially enlarges the eyebox .

[0020] According to a further embodiment of the eye tracking system, the locations of the at least two sensor beams on the eye of the user are on the cornea of the eye of the user . Particularly, the two sensor beams impinge on an outer surface of the cornea and are reflected by the outer surface of the cornea back to the laser device . Particularly, after being reflected by the eye of the user, the electromagnetic radiation of the sensor beams traverse the beam multiplexer element or impinges on the beam multiplexer element again such that in input beam is generated, which is detected by the laser device .

[0021] According to a further embodiment of the eye tracking system, the locations of the at least two sensor beams are behind the cornea of the eye of the user . For example , the at least two sensor beams are focused behind the cornea of the eye of the user .

[0022] According to a further embodiment of the eye tracking system, the laser device is configured for sel f-mixing interferometry . Particularly, a laser device configured for sel f-mixing interferometry comprises a VCSEL chip as light source . The VCSEL chip particularly has a vertical cavity, wherein a laser active medium is arranged . During detection of the electromagnetic radiation of the electromagnetic radiation of the reflected sensor beams , the electromagnetic radiation of the reflected sensor beams penetrates within the cavity of the VCSEL chip and interfere with the electromagnetic radiation of the output beam, for example .

[0023] A tracking signal is generated from the interference of the electromagnetic radiation of the output beam and the electromagnetic radiation of the input beam within the cavity of the VCSEL chip . The position and / or movement of the eye , particularly of the cornea, can be determined from the interference , in particular . Sel f-mixing interferometry is an interferometric technique wherein an output beam of electromagnetic radiation emitted by a laser device is reflected back into a cavity of the laser device , causing a modulation of an amplitude and / or a frequency of the electromagnetic radiation of the output beam . This makes the laser device sensitive to the distance travelled by the electromagnetic radiation reflected by an external target , such as the eye . Therefore , distance , velocity and / or movement of the target reflecting can be derived . Particularly, sel f-mixing interferometry has the advantage that collimating optics and external photodiodes can be omitted for distance measurement . For example , the laser device is a sel f-mixing interferometric sensor .

[0024] According to an embodiment of the eye tracking system, the laser device provides a tracking signal configured for determining a distance and / or a rotation and / or a velocity and / or a lateral shi ft and / or an angular shi ft of the eye of the user, particularly of the cornea of the user . For example , the eye tracking system has a distance from the eye of the user between 1 centimeter and 10 centimeters , limits included .

[0025] According to a further embodiment , the eye tracking system further comprises a processing unit configured for determining a distance and / or a rotation and / or a velocity and / or a lateral shi ft and / or an angular shi ft of the eye from the tracking signal . Particularly, the tracking system is generated by the laser device from the modulation of the amplitude and / or the frequency of the electromagnetic radiation of the output beam and send to the processing unit for determine the distance and / or the rotation and / or the velocity and / or the lateral shi ft and / or the angular shi ft of the eye and particularly, of the cornea .

[0026] According to a further embodiment of the eye tracking system, the beam multiplexer element is at least one of a volume phase hologram, a surface relief grating, a liquid crystal grating or a polari zer grating . Particularly, the beam multiplexer element is a di f fractive optical element . For example , the beam multiplexer element is made of , or comprises , a transparent material beam transmissive for electromagnetic radiation emitted by the laser device . Particularly, the laser device emits infrared radiation, for example having a wavelength between and including 700 nanometer and 2000 nanometer .

[0027] The volume phase hologram has , in particular, a thickness much larger than the wavelength of the electromagnetic radiation of the laser device . Particularly, the volume phase hologram has an optical structure leading to Bragg refraction of electromagnetic radiation impinging on and / or running through the volume phase hologram . Particularly, the optical structure of the volume phase hologram is comprised by a volume region of the volume phase hologram and a surface of the volume phase hologram is free of the optical structure . In the volume phase hologram particular a number N of optical functions correlate to the number N of sensor beams to be generated from the output beam .

[0028] The surface relief grating, particularly, has a surface structure as optical structure within at least one of its main surfaces . The surface structure is particularly configured for di f fracting and / or refracting electromagnetic radiation of the laser device . The polari zer grating has as the surface relief grating, a surface structure as optical structure within at least one of its main surfaces , in particular . The surface structure is particularly configured for di f fracting and / or refracting electromagnetic radiation of the laser device dependent on its polari zation .

[0029] Particularly preferably, the beam multiplexer element comprises or consists of a volume phase hologram . Manufacturing of a beam multiplexer element which is suitable for use in the present eye tracking system is , for example , described in one of the following documents : DE 102022128337 . 2 , 102023107190 . 4 , the disclosure content of which is incorporated herein by reference . Particularly, the beam multiplexer element can be manufactured adapted to the speci fic application with the disclosed methods .

[0030] According to a further embodiment of the eye tracking system, the beam multiplexer element comprises a photocured material . Particularly preferably, a photocurable material is used when manufacturing the beam multiplexer element . Particularly, during manufacturing of the beam multiplexer element a phase information of the optical structure is recorded by the photocurable material , for example by holographic methods , such as by copying a holographic master . Particularly, the photocured material is a crosslinked polymer, wherein crosslinking took place by radiation with electromagnetic radiation having a wavelength of the output beam of the electromagnetic radiation .

[0031] The eye tracking system according to the present disclosure is particularly based on the idea to use the beam multiplexer element in order to generate at least two , preferably three or a plurality, of sensor beams from the output beam of the laser device . With the help of the beam multiplexer element , a plurality of sensor beams is provided for sensing a target movable in 3D, such as the eye of a user, leading to a precise tracking of the movable target .

[0032] Particularly, in combination with sel f-mixing interferometry the amount of tracking information captured by a single laser device is increased by using the plurality of sensor beams generated with the help of the beam multiplexer element so that tracking accuracy of the eye tracking system can be enhanced .

[0033] Further, an eyebox of eye glasses with the eye tracking system, particularly of VR / AR glasses with the eye tracking system, can be enhanced due to the enhanced tracking information . With the term "eyebox" , the spatial region is meant where the eye recogni zes an image provided by the eye glasses . It is desired to achieve a large eyebox, since then the human user also recogni zes the image displayed by the eye glasses , i f the eye glasses are not perfectly arranged before the eyes or are shi fted during use .

[0034] Further, calibration of the eye tracking system can be simpli fied and / or accelerated due to enhanced tracking information . Calibration is important , particularly since eye glasses comprising the eye tracking system easily slip during use . Particularly, calibration of the present eye tracking system provides the parameters of the eye tracking system to be calibrated directly . Particularly, each source measures multiple locations and creates a more unique frequency trace from these locations combining the information of each location in an interference pattern .

[0035] The eye tracking system is particularly configured to be comprised by eye glasses . Features and embodiments disclosed at present in connection with the eye tracking system can also be embodied within the eye glasses and vice versa .

[0036] Particularly, the eye glasses comprise an eye tracking system as already described . Particularly, the eye glasses are configured for augmented reality applications and / or virtual reality applications . In other words , the eye glass are , particularly AR / VR glasses .

[0037] According to an embodiment of the eye glasses , the beam multiplexer element is integrated within a glass of the eye glasses . For example , the beam multiplexer element is the glass of the eye glasses . In that case , the beam multiplexer element is particularly transparent for visible light . The term "transparent" means , particularly in this context , that the element indicated with this term transmits at least 80% of visible light or at least 85% of visible light or at least 90% of visible light .

[0038] Particularly, by integrating the beam multiplexer element within the glasses of the eye glasses , a position of the beam multiplexer element relative to the laser device can be fixed in an improved and easy manner . Compared to an optical element , for example being arranged at a temple laterally to the glasses , relative arrangement of the beam multiplexer element with respect to the laser device is more reliable . According to a further embodiment of the eye glasses , the beam multiplexer element is comprised by a foil adhered to a glass of the eye glasses . In other words , the beam multiplexer element can have the form of a foil , for example a plastic foil , fixed to the glass .

[0039] According to a further embodiment of the eye glasses , the laser device is integrated into a temple of the eye glasses . In such a way, the eye glasses can be manufactured in a very compact manner .

[0040] The eye tracking system can be operated with the method described in the following . Features and embodiments disclosed in connection with the eye tracking system can therefore also be embodied within the method for operating the eye tracking system and vice versa .

[0041] According to an embodiment of the method for operating an eye tracking system, a laser device is operated to emit an output beam of electromagnetic radiation .

[0042] According to a further embodiment of the method, at least two sensor beams are generated from the output beam of electromagnetic radiation with a beam multiplexer element . Preferably, more a plurality of sensor beams is generated by the beam multiplexer element from the electromagnetic radiation of the output beam .

[0043] According to a further embodiment of the method, the at least two sensor beams are directed on at least two locations on the eye of a user with the beam multiplexer element . According to a further embodiment of the method, the at least two sensor beams reflected by the eye of a user are detected with the laser device .

[0044] Particularly, the method for operating the eye tracking system comprises the steps :

[0045] - operating the laser device to emit the output beam of electromagnetic radiation,

[0046] - generating the at least two sensor beams from the output beam of electromagnetic radiation with the beam multiplexer element ,

[0047] - directing the at least two sensor beams on the at least two locations on the eye of the user with the beam multiplexer element , and

[0048] - detecting the at least two sensor beams reflected by the eye of the user with the laser device .

[0049] Particularly, the method steps mentioned above are carried out in the given order .

[0050] Further advantageous embodiments and developments of the eye tracking system, the eye glasses and the method for operating an eye tracking system result from the exemplary embodiment described below in connection with the Figures .

[0051] Figure 1 shows a schematic view of an eye tracking system according to an exemplary embodiment .

[0052] Figure 2 shows schematically a flow diagram of a method for operating an eye tracking system according to an exemplary embodiment . Figure 3 shows schematically a plan view on a detail of an eye glass according to an exemplary embodiment .

[0053] Figure 4 shows schematically a perspective view on the detail of an eye glass according to Figure 3 .

[0054] In the exemplary embodiments and figures , identical , similar or identically acting elements are provided in each case with the same reference numerals . The elements illustrated and their si ze ratios to one another should not be regarded as being to scale , but rather individual elements , such as for example elements , components , devices and regions , may have been made exaggeratedly large to illustrate them better and / or to aid comprehension .

[0055] The eye tracking system 1 according to the exemplary embodiment of Figure 1 comprises a laser device 2 emitting an output beam 3 of electromagnetic radiation during operation . For example , the laser device 2 comprises a VCSEL chip 4 having a vertical cavity 5 , wherein a laser active medium 6 is arranged .

[0056] Further, the eye tracking system 1 of Figure 1 comprises a beam multiplexer element 7 , for example a volume phase hologram, generating a plurality of sensor beams 8 from the electromagnetic radiation of the output beam 3 . The beam multiplexer element 7 directs the sensor beams 8 on di f ferent locations 9 on an eye 10 of a user . Particularly, each sensor beam 8 generates a focused spot 11 at the locations 9 on the eye 10 of the user, particularly on a cornea 12 of the eye 10 of the user ( see also Figures 3 and 4 ) . In the schematic view of Figure 1 , the spots 11 of the di f ferent sensor beams 8 at the di f ferent locations 9 are all illustrated to be in one plane for easy representation . However, the spots 11 of the plurality of sensor beams 8 are all located on di f ferent locations 9 within the three- dimensional space . The locations 9 are characteri zed by three-dimensional coordinates x, y and z referring to an x- position, a y-position and a z-position of the locations 9 . Particularly, all coordinates can di f fer from each other . In such a way, movement of the eye 10 can be ef ficiently and accurately tracked .

[0057] The sensor beams 8 are reflected back to the beam multiplexer element 7 by the eye 10 of the user and particularly by the cornea 12 of the user . The sensor beams 8 reflected back from the eye 10 of the user run again through the beam multiplexer element 7 which generates an input beam 13 of electromagnetic radiation . The electromagnetic radiation of the input beam 13 is detected by the laser device 2 .

[0058] Figure 1 particularly shows the output beam 3 and the sensor beams 8 before impinging on the target to be tracked, at present the eye 10 of the user, in the left part of the Figure and the electromagnetic radiation reflected by the target to be tracked in the right part of the Figure in order to enhance visibility of the run of the electromagnetic radiation within the eye tracking system 1 .

[0059] It is possible that the sensor beams 8 generated by the beam multiplexer element 7 are focused at infinity or collimated . Further, it is possible that the beam multiplexer element 7 generates diverging sensor beams 8 . It is also possible that the beam multiplexer element 7 generates a plurality of sensor beams 8 , wherein one sensor beam 8 or several sensor beams 8 are , for example , focused at infinity or collimated or diverging . In other words , the beam multiplexer element 7 can be embodied such that the sensor beams 8 are di f ferent from each other in their optical function .

[0060] In a first step S I of the method for operating an eye tracking system 1 according to the exemplary embodiment of Figure 2 , a laser device 2 is operated to emit an output beam 3 of electromagnetic radiation .

[0061] In a second step S2 , at least two sensor beams 8 are generated from the electromagnetic radiation of the output beam 3 with the beam multiplexer element 7 .

[0062] In a next step S3 , the at least two sensor beams 8 are directed on at least two locations 9 on the eye 10 of a user with the beam multiplexer element 7 .

[0063] In step S4 , electromagnetic radiation reflected by the eye 10 of the user is detected with the laser device 2 .

[0064] The eye glasses according to the exemplary embodiment of Figures 3 and 4 comprise a frame 14 , two temples 15 and two glasses 16 fixed within the frame 14 . Particularly, Figures 3 and 4 exemplarily show only one glass 16 of the eye glasses and the tracking of one eye 10 with the help of the eye tracking system 1 . Particularly, the eye glasses comprises two eye tracking systems 1 , each for tracking of the movement of one eye 10 .

[0065] The eye glasses of Figures 3 and 4 comprise an eye tracking system 1 as , for example , described in connection with Figure 1 . The eye tracking system 1 comprises a laser device 2 with a VCSEL chip 4 , which is fixed to one temple 15 and illuminates the glass 16 within the frame 14 with electromagnetic radiation of an output beam 3 ( Figure 4 ) . Within the glass 16 of the eye glasses a beam multiplexer element 7 , for example a volume phase hologram, is integrated . The electromagnetic radiation of the output beam 3 impinges on the beam multiplexer element 7 .

[0066] The beam multiplexer element 7 is arranged in a reflection configuration and multiplexes the electromagnetic radiation of the incoming output beam 3 in three sensor beams 8 . The sensor beams 8 are directed to the eye 10 , in particular to a cornea 12 , of a user . The sensor beams 8 create multi focal spots 11 on the cornea 12 of the eye 10 ( Figure 3 ) . Particularly, each sensor beam 8 is focused on a di f ferent location 9 on the eye 10 of the user .

[0067] The cornea 12 reflects the sensor beams 8 back to the beam multiplexer element 7 , which generates a single input beam 13 from the electromagnetic radiation of reflected sensor beams 8 . The input beam 13 is directed by the beam multiplexing element 7 to the VCSEL chip 4 and penetrates into the cavity 5 of the VCSEL chip 4 . Sel f-mixing interference takes place within the cavity 5 of the VCSEL chip 4 and a tracking signal is produced . The tracking signal is forwarded to a processing unit , which determines a distance and / or a rotation and / or a velocity and / or a lateral shi ft and / or an angular shi ft of the eye 10 .

[0068] The features and exemplary embodiments described in connection with the Figures can be combined with each other according to further exemplary embodiments , even i f not all combinations are explicitly described . Furthermore , the exemplary embodiments described in connection with the Figures may alternatively or additionally have further features according to the description in the general part .

[0069] The invention is not limited to the description of the exemplary embodiments . Rather, the invention comprises each new feature as well as each combination of features , particularly each combination of features of the claims , even i f the feature or the combination of features itsel f is not explicitly given in the claims or the exemplary embodiments .

[0070] References

[0071] 1 eye tracking system

[0072] 2 laser device

[0073] 3 output beam

[0074] 4 VCSEL chip

[0075] 5 cavity

[0076] 6 laser active medium

[0077] 7 beam multiplexer element

[0078] 8 sensor beam

[0079] 9 location

[0080] 10 eye

[0081] 11 spot

[0082] 12 cornea

[0083] 13 input beam

[0084] 14 frame

[0085] 15 t emp 1 e

[0086] 16 glass

[0087] S I , S2 , S3 , S4 method steps

Claims

Claims1. Eye tracking system (1) comprising:- a laser device (2) emitting an output beam (3) of electromagnetic radiation during operation,- a beam multiplexer element (7) generating at least two sensor beams (8) from the output beam (3) of electromagnetic radiation during operation, wherein- the beam multiplexer element (7) is configured to direct the at least two sensor beams (8) on at least two locations (9) on an eye (10) of a user,- the laser device (2) is configured to detect electromagnetic radiation of at least one of the at least two sensor beams (8) reflected by the eye (10) of the user.

2. Eye tracking system (1) according to the previous claim, wherein the beam multiplexer element (7) is configured to generate an input beam (13) of electromagnetic radiation from the electromagnetic radiation reflected by the eye (10) of the user .

3. Eye tracking system (1) according to any of the previous claims, wherein the beam multiplexer element (7) is configured to focus the at least two sensor beams (8) on the at least two locations (9) of the eye (10) of the user.

4. Eye tracking system (1) according to any of the previous claims, whereinthe locations (9) of the at least two sensor beams (8) differ in their x-position and / or their y-position and / or their z- position in space.

5. Eye tracking system (1) according to any of the previous claims, wherein the locations (9) of the at least two sensor beams (8) on the eye (10) of the user are on the cornea (12) of the eye (10) of the user.

6. Eye tracking system (1) according to any of the previous claims, wherein the locations (9) of the at least two sensor beams (8) on the eye (10) of the user are behind the cornea (12) of the eye (10) of the user.

7. Eye tracking system (1) according to any of the previous claims, wherein the laser device (2) is configured for self-mixinginterferometry .

8. Eye tracking system (1) according to any of the previous claims, wherein the laser device (2) provides a tracking signal configured for determining a distance and / or a rotation and / or a velocity of and / or a lateral shift and / or an angular shift of the eye (10) .

9. Eye tracking system (1) according to the previous claim, further comprising a processing unit configured for determining a distance and / or a rotation and / or a velocity and / or a lateral shift and / or an angular shift of the eye (10) from the tracking signal.

10. Eye tracking system (1) according to any of the previous claims, wherein the beam multiplexing element (7) is at least one of a volume phase hologram, a surface relief grating, a liquid crystal grating or a polarizer grating.

11. Eye tracking system (1) according to any of the previous claims, wherein the beam multiplexing element (7) comprises a photocured material .

12. Eye glasses comprising an eye tracking system (1) according to any of the previous claims, the eye glasses being configured for augmented reality applications and / or virtual reality application.

13. Eye glasses according to the previous claim, wherein the beam multiplexing element (7) is integrated with a glass (16) of the eye glasses.

14. Eye glasses according to any of claims 12 or 13, wherein the beam multiplexing element (7) is comprised by a foil adhere to a glass (16) of the eye glasses.

15. Eye glasses according to any of claims 12 or 13, wherein the laser device (2) is integrated to a temple (15) of the eye glasses.

16. Method for operating an eye tracking system (1) , comprising the steps:- operating a laser device (2) to emit an output beam (3) of electromagnetic radiation,- generating at least two sensor beams (8) from the output beam (3) of electromagnetic laser radiation with a beam multiplexer element (7) ,- directing the at least two sensor beams (8) on at least two locations (9) on the eye (10) of a user with the beam multiplexer element (7) , and- detecting electromagnetic radiation of at least one of the at least two sensor beams (8) reflected by the eye (10) of the user with the laser device (2) .

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