Optical device for smart glasses

Abstract

The invention relates to an optical device (20) for smart glasses (50), comprising a first laser device (1) configured to emit a projection light beam (11), a second laser device (2) configured to emit a measurement light beam (12), a first scanner (3), a second scanner (4), and a light beam combiner (5) configured to merge the projection light beam (11) and the measurement light beam (12) into a common light beam (15), the first scanner (3) being configured to deflect the projection light beam (11) emitted by the first laser device (1) about a first axis (30), and the second scanner (4) being configured to deflect the common light beam (15) combined by the light beam combiner (5) about a second axis (40).

Description

Technical Field

[0001] This invention relates to optical devices for smart glasses and smart glasses themselves. Background Technology

[0002] As is well known, oculography (also known as eye tracking) is used in smart glasses for image projection (e.g., image projection onto a user's retina). Exemplarily, oculography is used to adjust the controller of the projection unit of the smart glasses when displaying context-sensitive information. US 7637615 B2 discloses such smart glasses with prism-based eye tracking and retinal projection. Such smart glasses typically have a complex and sophisticated design. Summary of the Invention

[0003] In contrast, the optical device according to the invention, having the features of claim 1, is characterized by a particularly simple, compact, and inexpensive arrangement. This is achieved through the optical device of smart glasses, which includes a first laser device arranged to emit a projection beam, a second laser device arranged to emit a measurement beam, a first scanner, a second scanner, and a beam combiner. The beam combiner is arranged to combine the projection beam and the measurement beam into a common beam, specifically such that the common beam propagates substantially along a common axis. The first scanner is arranged to redirect the projection beam emitted from the first laser device along a first axis. Furthermore, the second scanner is arranged to deflect the beam combined by the beam combiner into a second axis, which is specifically arranged at an angle relative to the first axis. Particularly preferably, these two axes are perpendicular to each other.

[0004] Preferably, the first scanner and the second scanner are each configured as single-axis scanners. In other words, the first scanner and the second scanner are each designed to deflect a corresponding beam in one dimension. For this purpose, the first scanner is preferably pivotable about a first axis. Similarly, the second scanner is preferably pivotable about a second axis.

[0005] Therefore, during the operation of the optical device, two scanners can be used to scan the projected beam around two axes. Thus, the projected beam can be scanned two-dimensionally on the surface to be scanned.

[0006] Specifically, the measurement beam is deflected only by the second scanner, that is, it is scanned one-dimensionally on the surface to be scanned, preferably by scanning lines.

[0007] The advantage of this optical device is that all components can be combined into a single compact assembly. Due to the unique arrangement of the scanner and beam combiner, several different functions can be performed simultaneously using this single component. Because the combined common beam preferably exits the optical device at exactly one point, a particularly versatile and simple arrangement of the optical device can be achieved, for example, when using smart glasses. The two scanners can operate at different scanning frequencies so that the operating modes of the two scanners can be optimally adapted to the respective requirements of the projection beam and the measurement beam. For example, one of the two scanners can operate more economically under the lower requirements of the corresponding beam. Furthermore, due to the independent operating capabilities of the two scanners, particularly high accuracy (e.g., particularly high accuracy with respect to high temporal resolution and / or optical resolution) can be achieved by operating each scanner within the optimal operating range of the corresponding beam due to the independent operating capabilities of the two scanners. Preferably, two-dimensional scanning of the surface can be performed line by line. For this purpose, one scanner can be used as a line scanner, which deflects the laser point along the line direction at a high scanning frequency. The other scanner can be used to gradually build an image by deflecting the laser point along a second axis at a correspondingly lower speed. For measuring beams, scanning with only the slow axis may be advantageous, either because it may interact with the fast axis, or because the laser spot on the surface should have a limited measurement speed.

[0008] Further preferred embodiments of the invention will be set forth in the sub-claims.

[0009] Particularly preferably, the first scanner is configured to scan the projected beam at a first scanning frequency, while the second scanner is configured to scan the common beam at a second scanning frequency, wherein the second scanning frequency is less than the first scanning frequency. Preferably, the second scanning frequency is at most one-tenth of the first scanning frequency. Particularly preferably, the first scanning frequency is from 10 kHz to 50 kHz. Preferably, the second scanning frequency is from 50 Hz to 200 Hz, more preferably 60 Hz.

[0010] Preferably, the first laser device includes a projection unit arranged to project an image onto the retina of a user's eye using a projection beam. Specifically, the projection beam is therefore visible light. By redirecting the projection beam generated by the projection unit using two scanners, a two-dimensional image can be projected onto the retina of the user's eye. Furthermore, when using the projection beam for retinal projection, the first scanner can operate at a high scanning frequency to achieve a sufficiently high temporal resolution, thereby displaying the user an image with optimal resolution, for example, displaying the user an image with optimal resolution without detecting any flicker.

[0011] Particularly preferably, the second laser device includes an eye-tracking unit configured to determine the optical path length of the measurement beam based on laser feedback interferometry, wherein a portion of the measurement beam is backscattered by the eye, and the eye-tracking unit is configured to determine the eye's viewing direction based on the optical path length. Laser feedback interferometry is considered the detection and analysis of the superposition of the laser beam incident on the eye and the backscattered portion of the incident laser beam, i.e., the detection and analysis of the generated interference radiation. Based on the laser feedback interferometry, the optical path length of the incident laser beam is determined. The optical path length is considered to be the product of the geometric distance covered by the incident laser beam from the laser source to the eye surface and the refractive index of the material present therein. This means that if the laser beam is directly incident on the eye from the laser source in air (refractive index approximately 1), the optical path length very approximately corresponds to the distance between the laser source and the eye. If the wavelength of the incident laser beam is known, the optical path length can be determined, for example, based on constructive or destructive interference. Preferably, a triangularly modulated laser is emitted as the incident laser beam in the specified wavelength. The optical path length can be determined by laser feedback interferometry, specifically by analyzing the backscattered portion of the irradiated laser beam and the interference of the irradiated laser beam, particularly by calculating the average of the resulting interference frequencies relative to the two sides of the triangular modulation signal. For accurate detection, the modulation frequency is preferably a multiple of the second scanning frequency. Particularly preferably, the modulation frequency at the second scanning frequency of 60 Hz is in the range of 1 kHz to 130 MHz, more preferably 5 kHz to 100 kHz, and particularly 10 kHz.

[0012] Preferably, the eye-tracking unit is configured to detect the measurement beam entering the pupil of the eye based on the determined optical path length, and in particular, when the measurement beam is detected to enter the pupil, the viewing direction of the eye is determined based on the scanner position of the second scanner.

[0013] Preferably, the first scanner and / or the second scanner includes a micromirror actuator. More preferably, both the first and second scanners include micromirror actuators. For example, the micromirror actuator may be a micromirror actuated by a microelectromechanical system (MEMS). Preferably, the micromirror actuator can resonate on a corresponding axis. Alternatively, the micromirror actuator can operate at a frequency below the resonant frequency on the corresponding axis. In this case, the micromirror actuator provides a particularly simple and cost-effective way to redirect light generated by two laser devices with a specific degree of accuracy and to scan a surface to be scanned.

[0014] Preferably, the beam combiner has a polarization beam splitter. Preferably, the projection beam and the measurement beam are polarized perpendicularly to each other, particularly in the region where they reside before entering the polarization beam splitter. The projection beam and the measurement beam will thus illuminate the polarization beam splitter, causing the polarization beam splitter to combine the measurement beam and the projection beam into a common beam. The polarization beam splitter allows for a particularly simple and cost-effective design of the optical device.

[0015] Preferably, the beam combiner has holographic optics. Particularly preferably, the holographic optics are designed to deflect the projection beam and the measurement beam at different angles. This allows for particularly flexible, simple, and inexpensive design of the optical device. Preferably, the deflection angles of the holographic optics relative to the measurement beam and the projection beam can be adjusted as needed, thereby enabling any alignment of the projection beam and the measurement beam incident on the holographic optics relative to each other.

[0016] Preferably, the second laser device is configured to emit multiple measurement beams, preferably parallel measurement beams. Specifically, the multiple measurement beams are emitted at uniform intervals in a common plane. For example, this allows multiple parallel scan lines to be scanned onto the surface to be scanned. Thus, by way of example, if the second laser device includes an eye-tracking unit, each optical path length can be scanned along multiple parallel lines on the eye surface to achieve particularly high accuracy in eye tracking.

[0017] Particularly preferably, the optical device further includes a beam splitter configured and arranged to split the measurement beam into at least two measurement beams. Preferably, the beam splitter is positioned between the second laser device and the second scanner. In this way, several individual measurement beams can be generated in a particularly simple manner, illuminating the surface to be scanned. Splitting a single measurement beam generated by the second laser device into multiple measurement beams provides a particularly simple and cost-effective method. Preferably, the several measurement beams emitted from the second laser device can also be split using a beam splitter, or alternatively, several beam splitters can be used to split the beams to enable scanning of a greater number of measurement beams on the surface to be scanned.

[0018] Preferably, the beam splitter is integrated into the second laser device. Alternatively, the beam splitter is disposed on the second laser device. Furthermore, alternatively, the beam splitter can be integrated into the beam combiner. Additionally, the optical device may include a deflection element for deflecting the measurement beam, wherein, in another alternative, the beam splitter is integrated into the deflection element. According to this variation, a particularly simple, cost-effective, and space-saving design of the optical device can thus be achieved.

[0019] Preferably, the second laser device emits multiple measurement beams, wherein a beam splitter and the multiple measurement beams are aligned to produce an interlaced pattern of scan lines on the surface to be scanned. This means that, using a beam splitter, each of the multiple measurement beams is split into multiple additional measurement beams. For example, the beam splitter can be configured to split each incident measurement beam into three separate measurement beams. For example, if three measurement beams are emitted from the second laser device, this results in a total of nine measurement beams being scanned on the surface to be scanned. In this case, the interlaced pattern is considered to be the pattern of scan lines scanned onto the surface to be scanned, such that the measurement beams separated by the beam splitter intersect each other downstream of the beam splitter, preferably, each measurement beam impacts the surface to be scanned along a scan line, wherein the scan lines are arranged at a uniform interval. In other words, when viewed along a direction on the surface to be scanned, exactly one scan line of each of the three measurement beams initially emitted from the second laser device is alternately positioned perpendicular to the scan line. In this way, the individual, separate measurement beams initially emitted from the second laser device can be further spaced apart on the surface to be scanned, allowing for a simple and clear distinction between these separate measurement beams when evaluating the measurement results.

[0020] Particularly preferably, the optical device further includes a holographic optical element having a first holographic segment and a second holographic segment. The two holographic segments are configured such that a first scanning direction of the measurement beam deflected at the first holographic segment is tilted at a certain angle relative to a second scanning direction of the measurement beam deflected at the second holographic segment. That is, when the measurement beam is incident on the first holographic segment, the measurement beam is deflected such that the resulting scanning direction on the surface to be scanned corresponds to the first scanning direction. Similarly, when the measurement beam is incident on the second holographic segment, the second scanning direction corresponds to the resulting scanning direction on the surface to be scanned. In other words, the two holographic segments cause different deflections of the measurement beam. Preferably, the first scanning direction and the second scanning direction are perpendicular to each other, particularly on the surface to be scanned. In this way, a particularly comprehensive and accurate scan of the surface to be scanned can be performed with a simple arrangement.

[0021] Preferably, the second laser device has at least one surface emitter with an integrated photodiode (also known as a vertical-cavity surface-emitting laser, or VCSEL for short). Using such a second laser device, eye movements can be detected using a particularly simple, compact, and cost-effective design of an eye-tracking device based on laser feedback interferometry. In particular, this second laser device is suitable for detection via the self-mixing effect. Preferably, the photodiode is used to directly detect the superposition of the irradiated laser beam and the backscattered portion within the laser cavity. Particularly preferably, the second laser device may include several surface emitters, each emitting a separate laser beam.

[0022] Furthermore, the present invention provides smart glasses including the described optical device. Preferably, the smart glasses are wearable devices configured to be worn on a user's head. The possibility that the optical device can be constructed as a single component has a particularly advantageous effect, for example, when using an optical device capable of operating via a rechargeable battery, allowing for a compact and flexible structure and lower weight of the smart glasses, thereby allowing for high user comfort.

[0023] Preferably, the optical device is arranged on the temple of the eyeglass frame. Because the optical device can be provided in a particularly compact manner, and as a single device, it also enables a particularly compact and therefore user-friendly design for the smart glasses. In particular, the fact that all components can be arranged on the temple of the eyeglass frame means that wiring can be saved; for example, wiring that must pass through the connector between the temple and the eyeglass frame can be saved, which further benefits the cost-effective and simple design.

[0024] Particularly preferably, the smart glasses also include lenses comprising holographic optical deflecting elements. In this document, the holographic optical deflecting elements are configured to deflect all light beams emitted from the optical device in the direction of the user's eyes when wearing the smart glasses. That is, the light beams deflected by the scanner of the optical device are not directly incident on the user's eyes, but are deflected by the holographic optical deflecting elements in the glasses lenses. Attached Figure Description

[0025] The invention will be described below with reference to exemplary embodiments and accompanying drawings. In the drawings, functionally equivalent components are identified by the same reference numerals, wherein:

[0026] Figure 1 This is a simplified schematic diagram of smart glasses according to a first embodiment of the present invention, which includes an optical device;

[0027] Figure 2 for Figure 1 Detailed view of the optical device;

[0028] Figure 3 A detailed view of the optical device according to a second embodiment of the present invention;

[0029] Figure 4 To pass Figure 1 A simplified illustration of the scan lines produced by the optical device;

[0030] Figure 5 for Figure 1 A simplified illustration of the measurement data from the optical device;

[0031] Figure 6 for Figure 1A simplified schematic diagram of the holographic optical elements of smart glasses; and

[0032] Figure 7 For the reason Figure 6 A simplified schematic diagram of the scan lines deflected by the holographic optical element. Detailed Implementation

[0033] 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 has an optical device 20. The smart glasses 50 includes a lens 52, a frame 51 in which the lens 52 is housed, and temples 53 for holding the smart glasses 50 on the user's head. The smart glasses 50 is thus provided for wearing on the user's head.

[0034] The smart glasses 50 includes an optical device 20, which is used to determine the viewing direction of the user's eyes 10 and simultaneously project an image onto the retina of the user's eyes 10. Figure 1 Detailed view of the optical device 20 of the smart glasses 50 as shown Figure 2 As shown.

[0035] Retinal projection is performed using projection beam 11, and viewing direction detection is performed using measurement beam 12. Projection beam 11 and measurement beam 12 are focused within optical device 20 to form a common beam 15a. Figure 1 As shown, the common beam 15a is directed toward the lens 52 of the smart glasses 50, and is deflected toward the user's eye 10 by a holographic optical deflection element 52a embedded in the lens 52. Figure 1 The surface 10a to be scanned is shown in a simplified form.

[0036] Optical device 20 includes a first laser device 1 having a projection unit, which is configured to project image 10 onto the retina via projection beam 11 (see [link]). Figure 2 For example, the projection unit can be used to display augmented reality or virtual reality. Furthermore, the optical device includes a second laser device 2, which includes a viewing detection unit configured to emit a measurement beam 12 and determine the viewing direction of the eye 10. Preferably, the projection unit is coupled to the viewing detection unit, wherein the viewing detection unit is configured to actuate the projection unit in response to the determined viewing direction. For example, the projected image can be adjusted according to the viewing direction.

[0037] In this respect, the optical device 20 is characterized in that all components required to generate the common beam 15a can be combined into a single component. To accordingly redirect and focus the projection beam 11 and the measurement beam 12, the optical device 20 includes a first scanner 3, a second scanner 4, and a beam combiner 5, particularly as... Figure 2 As shown. The first scanner 3 and the second scanner 4 are each designed as uniaxial micromirror detectors.

[0038] The first scanner 3 is configured to deflect the projection beam 11 emitted by the first laser device 1 along the first axis 30. As a result, the projection beam 11 is scanned as a line on the second scanner 4.

[0039] Using beam combiner 5, the projection beam 11 deflected by the first scanner 3 and the measurement beam 12 deflected by the deflection element 6 (e.g., a mirror) are combined into a common beam 15. Beam combiner 5 includes holographic optics designed to deflect the projection beam 11 and the measurement beam 12 at different angles.

[0040] The common beam 15 is then deflected by the second scanner 4 along the second axis 40. The second axis 40 is perpendicular to the first axis 30, thus enabling two-dimensional scanning of the projected beam 11 on the surface 10a to be scanned. Therefore, the two scanners 3 and 4 can be operated using different scanning frequencies. In particular, the second scanning frequency of the second scanner 4 is lower than the first scanning frequency of the first scanner 3.

[0041] The measurement beam 12 is scanned as a line on the surface 10a to be scanned by a second scanner 4 that operates only on a single axis. To achieve multidimensional scanning of the surface 10a, it is advantageous that the second laser device 2 is configured to emit several measurement beams 12, 13, and 14 that travel in parallel and separate manner. Particularly high accuracy can be achieved by using a beam splitter 7 to further split each of these separate measurement beams 12, 13, and 14 into multiple beams. For example, the beam splitter 7 can be integrated into the deflection element 6. In the first embodiment shown, three measurement beams 12, 13, and 14 are emitted from the second laser device 2, and each of the measurement beams 12 is further split into three measurement beams by the beam splitter 7, such that a total of nine measurement beams can be scanned along corresponding scan lines 12A, 12B, 12C, 13A, 13B, 13C, 14A, 14B, and 14C on the surface 10a to be scanned.

[0042] Figure 4The diagram schematically illustrates parallel scanning lines 12A, 12B, 12C, 13A, 13B, 13C, 14A, 14B, 14C generated on the surface 10a of the eye 10 to be scanned by optical device 20, wherein the second laser device 2 and beam splitter 7 are coordinated to generate an interlaced pattern 40 of scanning lines 12A, 12B, 12C, 13A, 13B, 13C, 14A, 14B, 14C on the surface 10a to be scanned. The interlaced pattern 40 is characterized in that the first distance 41 between the generated scanning lines 12A, 12B, 12C produced by a single measuring beam 12 emitted by the second laser device 2 downstream of beam splitter 7 is greater than the second distance 42 between all nine generated scanning lines 12A, 12B, 12C, 13A, 13B, 13C, 14A, 14B, 14C. Therefore, it is possible to achieve particularly accurate detection of the viewing direction of the eye 10.

[0043] The determination of the viewing direction of the eye 10 is described in more detail below with reference to a single measurement beam 12. The viewing detection unit is configured to determine the optical path length of the measurement beam 12 based on laser feedback interferometry of the measurement beam 12 and a portion of the measurement beam 12 backscattered by the eye 10.

[0044] First, the measurement beam 12 is irradiated onto the eye 10. On the surface 10a of the eye, the measurement beam 12 is at least partially backscattered, i.e., at least partially reflected. During this process, the irradiated measurement beam 12 is superimposed on a portion of the backscattered portion of the irradiated measurement beam 11, which propagates back parallel to the direction of the second laser device 2.

[0045] The second laser device 2 includes at least one surface emitter with an integrated photodiode. Laser feedback interferometry is performed using the photodiode integrated into the surface emitter to detect the generated interference radiation, i.e., the superposition of the irradiated measurement beam 12 and the backscattered radiation propagating in opposite directions. Since the photodiode is directly integrated into the laser cavity of the surface emitter, the so-called self-mixing effect is used here to detect the generated interference radiation. The optical path length covered by the measurement beam 12 can then be evaluated based on frequency analysis.

[0046] Figure 5 An exemplary spectrum of the resulting interferometric radiation is schematically shown, which can be detected using an integrated photodiode of a surface emitter. Axis 71 corresponds to frequency, and axis 70 corresponds to amplitude. The detected frequencies of the interferometric radiation are marked in the figure, for example, frequencies determined by Fourier analysis. Exemplary values ​​for several different measurement beams 12, 13, and 14 are shown in the figure.

[0047] Due to the triangulation of the wavelengths of the irradiated measurement beams 12, 13, and 14, the peak frequencies depend on the optical path length 2. Therefore, measurement beams 12, 13, and 14, which collectively cover a relatively short optical path length, will result in lower frequencies. If measurement beams 12, 13, and 14 enter the eye 10 through the pupil 16, the corresponding optical path length (in this case, up to the retina) is significantly longer compared to the outer region of the eye 10. The corresponding peak frequencies 46, 47, and 48 determined in this case fall within the higher frequency range 44. Peak frequencies appearing in the range 45 indicate that the corresponding measurement beams 12, 13, and 14 at that measurement point have irradiated the outer side of the eye 10.

[0048] The different peak frequencies (i.e., the frequency shifts of the peak frequencies) within regions 44 and 45 are caused by the different optical path lengths of the measurement beams 12, 13, and 14 covering the holographic optical deflecting element 52a in the optical device 20 and the spectacle lens 52 (see [reference]). Figure 1 For example, the measurement beams 12, 13, and 14 deflected in the region of edge 52c cover a shorter optical path length than the measurement beams 12, 13, and 14 deflected in the region of edge 52b. Due to the multiple scan lines 12A, 12B, 12C, 13A, 13B, 13C, 14A, 14B, and 14C, this can also be used to determine more precise information about the instantaneous orientation of the eye 10, such as the position of the pupil 16 within the region 10a to be scanned.

[0049] When using holographic optical element 8, another optimization of the described eye-tracking can be achieved, such as... Figure 6 The illustration is schematic. For example, a holographic optical element 8 can be used instead of a holographic optical deflector 52a. The holographic optical element 8 has a plurality of holographic segments 81, 82, 83, 84, 85. Five holographic segments 81, 82, 83, 84, 85 are shown as an example. However, any number of holographic segments can be used. The holographic segments 81, 82, 83, 84, 85 are designed such that the measurement beams 12, 13, 14 scanned along the holographic segments 81, 82, 83, 84, 85 are differentially deflected.

[0050] Specifically, Figure 6 Holographic optical elements can be used to create Figure 7 The scan line pattern shown. Each of the three vertical scan lines 86, 87, and 88 is generated by deflecting exactly one measurement beam at exactly one of the first three holographic segments 81, 82, and 83 (see [reference]). Figure 6If the measurement beam is scanned along one of the other two holographic segments 84 and 85, these measurement beams are deflected such that the corresponding scan lines 89 and 90 are arranged perpendicular to the other three scan lines 86, 87, and 88, i.e., arranged horizontally. In this way, in particular, the position and movement of the pupil 16 of the eye 10 can be accurately detected in a wide variety of eye positions.

[0051] Changes in optical device 20, such as Figure 3 As shown, it represents an optical device 20 of the smart glasses 50 according to a second embodiment of the present invention, similar to... Figure 2 Detailed views. The second embodiment essentially corresponds to... Figure 1 The first embodiment differs in that an alternative beam combiner 5 is used. In the second embodiment, the beam combiner 5 includes a polarization beam splitter. The projection beam 11 and the measurement beams 12, 13, 14 are emitted into the polarization beam splitter, and thus they are focused. For this purpose, the projection beam 11 and the measurement beams 12, 13, 14 are polarized perpendicularly to each other. In the polarization beam splitter, a beam splitter 7 is also integrated, which splits the incident measurement beams 12, 13, 14 into several individual measurement beams in each case. The polarization beam splitter can also be provided with a very simple and inexpensive optical device 20.

Claims

1. An optical device (20) for smart glasses (50), comprising: - A first laser device (1) is configured to emit a projection beam (11). - A second laser device (2) is configured to emit a measurement beam (12). - First scanner (3). - Second scanner (4) - Beam combiner (5), which is configured to combine the projection beam (11) and the measurement beam (12) into a common beam (15), and - Beam splitter (7), which is arranged to split the measurement beam (12) into at least two separate measurement beams (12, 13, 14). The first scanner (3) is configured to redirect the projection beam (11) emitted by the first laser device (1) on the first axis (30). The second scanner (4) is configured to redirect the common beam (15) emitted by the beam combiner (5) on the second axis (40), and Multiple measurement beams (12, 13, 14) emitted from the second laser device (2) and the beam splitter (7) are aligned to generate an interlaced line pattern (40) of scan lines (12A, 12B, 12C, 13A, 13B, 13C, 14A, 14B, 14C) on the surface to be scanned (10a).

2. The optical device (20) according to claim 1, wherein, The first scanner (3) is configured to scan the projection beam (11) at a first scanning frequency, wherein the second scanner (4) is configured to scan the common beam (15) at a second scanning frequency, and wherein the second scanning frequency is less than the first scanning frequency.

3. The optical device (20) according to claim 1 or 2, wherein, The first laser device (1) includes a projection unit configured to project an image onto the retina of a user's eye (10) using the projection beam (11).

4. The optical device (20) according to claim 1 or 2, wherein, The second laser device (2) includes a viewing detection unit configured to determine the optical path length (25) of the measurement beam (12) based on the laser feedback interference of the measurement beam (12), wherein the measurement beam (12) has a backscattered portion from the eye (10), and the viewing detection unit is configured to determine the viewing direction of the eye (10) based on the optical path length (25).

5. The optical device (20) according to claim 1 or 2, wherein, The first scanner (3) and / or the second scanner (4) include a micromirror actuator.

6. The optical device (20) according to claim 1 or 2, wherein, The beam combiner (5) includes a polarization beam splitter, particularly wherein, The projection beam (11) and the measurement beam (12) are polarized perpendicularly to each other.

7. The optical device (20) according to claim 1 or 2, wherein, The beam combiner (5) includes holographic optical elements specifically designed to deflect the projection beam (11) and the measurement beam (12) at different angles.

8. The optical device (20) according to claim 1 or 2, wherein, The second laser device (2) is configured to emit multiple separate measurement beams (12, 13, 14).

9. The optical device (20) according to claim 1, wherein, The beam splitter (7): -Integrated into the second laser device (2), or - Arranged on the second laser device (2), or -Integrated into the beam combiner (5), or -Integrated into a deflection element (6), which is configured to deflect the measurement beam (12).

10. The optical device (20) according to claim 8 further includes a holographic optical element (8), the holographic optical element (8) having a first holographic segment (81) and a second holographic segment (82), wherein, The two holographic segments (81, 82) are formed such that the first scanning direction of the measurement beam (12) deflected at the first holographic segment (81) is tilted at an angle relative to the second scanning direction of the measurement beam (12) deflected at the second holographic segment (82).

11. The optical device (20) according to claim 1 or 2, wherein, The second laser device (3) includes at least one surface emitter with an integrated photodiode.

12. A pair of smart glasses (50), comprising an optical device (20) according to any one of claims 1 to 11, wherein, in particular, The optical device (20) is arranged on the temple (53) of the eyeglasses.

13. The smart glasses (50) according to claim 12 further includes a spectacle lens (52) having a holographic optical deflection element (52a), wherein, The holographic optical deflection element (52a) is configured such that all the light beams (15a) emitted by the optical device (20) are deflected toward the eyes (10) of the user of the smart glasses (50).

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