Method and sensor device for determining a refractive power of an eye, VR glasses and electronic glasses

Abstract

The present invention provides a method for determining a refractive power of an eye, comprising temporally successively irradiating the eye with a plurality of laser beams with different expansions, wherein the laser beams are emitted by at least one laser feedback interferometer, LFI, wherein the plurality of laser beams are irradiated onto the eye in such a way that a portion of the respective laser beam is reflected off the eye back into the LFI and interferes with the laser beam in the LFI, temporally successively detecting a portion of each of the plurality of laser beams with different expansions using a photodetector, wherein the photodetector outputs intensity signals corresponding to the detected portions of the laser beams with different expansions, and determining the refractive power of the eye on the basis of the detected intensity signals of the laser beams with different expansions. The invention further provides a corresponding sensor device having an adjustable lens and an alternative method with a plurality of LFIs, and VR glasses and electronic glasses.

Description

[0001] Description

[0002] title

[0003] Method and sensor device for determining the refractive power of an eye, VR glasses and electronic glasses

[0004] The present invention relates to a method and a sensor device for determining the refractive power of an eye, as well as VR glasses and electronic glasses with a sensor device according to the invention.

[0005] State of the art

[0006] For certain applications, such as virtual reality (VR) glasses and electronic glasses for visual vision, it may be necessary to measure or monitor accommodation, that is, the refractive power of the eye, which is essentially determined by the eye's lens. Various methods are known for this measurement.

[0007] In an autorefractor, light is directed as a cone onto the eye and focused by the eye's lens onto the retina. Light scattered back from the retina is detected by a light sensor and analyzed for optical properties such as shape and sharpness. By moving a lens, the Badal lens, within the autorefractor, this process is repeated for different lens positions to determine optical parameters such as refractive power, cylinder, astigmatism, etc. Other methods include aberometers, Purkinje reflection-based refractometers, dynamic photorefractometers, or the use of a binocular system.

[0008] Another technique uses laser feedback interferometers (LFIs) to detect the eye's accommodation. Special LFI sensors are used to capture gaze gestures. An LFI sensor, with or without a scanner, can also be used for pupil tracking, a technique known as "eye tracking." In such sensors, a laser beam from an LFI is directed into the eye, with some of the radiation reflected back into the LFI cavity, influencing the laser process. These sensors can also be integrated into eyeglasses separately from a camera system.

[0009] DE 102016226294 A1 describes a method and a device for determining the refractive power of a lens in an eye, which uses several convergent beams to irradiate the eye.

[0010] The object of this invention is therefore to provide an improved method and a corresponding device for measuring the refractive power of the eye, which uses a simple design that is easy to integrate into spectacles.

[0011] Disclosure of the invention

[0012] The present invention provides a method for determining the refractive power of an eye according to claim 1, a sensor device for determining the refractive power of an eye according to claim 10, and an alternative

[0013] Sensor device for determining the refractive power of an eye according to claim 12. Furthermore, the invention provides virtual reality (VR) glasses according to claim 18 and electronic glasses according to claim 19.

[0014] Preferred further training courses are the subject of the subclaims.

[0015] Advantages of the invention

[0016] According to the invention, the method for determining the refractive power of an eye comprises successively irradiating the eye with a plurality of laser beams of different expansion, wherein the laser beams are emitted by at least one laser feedback interferometer (LFI), wherein the plurality of laser beams are irradiated onto the eye in such a way that a part of each laser beam is reflected from the eye back into the LFI and interferes with the laser beam in the LFI, successively detecting a part of each of the plurality of laser beams of different expansion with a photodetector, wherein the photodetector outputs intensity signals corresponding to the detected parts of the laser beams of different expansion, and determining the refractive power of the eye based on the detected intensity signals of the differently expanded laser beams.

[0017] According to the invention, the sensor device for determining the refractive power of an eye comprises a laser feedback interferometer (LFI) configured to emit a laser beam on an optical axis, an optical system arranged on the optical axis and configured to irradiate the laser beam onto the eye such that a portion of the laser beam is reflected by the eye and interferes with the laser beam in the LFI, wherein the optical system comprises an adjustable lens configured to adjustably widen the laser beam, a photodetector configured and arranged to detect a portion of the laser beam reflected from the eye and to output a corresponding intensity signal, and a control device configured to: control the LFI, adjust the widening of the laser beam by controlling the adjustable lens.to receive the intensity signal output by the photodetector for each set expansion of the laser beam, and to determine the refractive power of the eye based on the detected intensity signals of the laser beams of different expansions.

[0018] According to the invention, the alternative sensor device for determining the refractive power of an eye comprises a plurality of laser feedback interferometers (LFIs), each configured to emit a laser beam; an optical system configured to irradiate each of the plurality of laser beams with a different beam spread onto the eye, such that a portion of the laser beam is reflected by the eye and interferes with the laser beam in the LFI; and a plurality of photodetectors configured and arranged to each detect a portion of one of the plurality of laser beams and output a corresponding intensity signal, such that each photodetector is assigned to a different LFI.

[0019] a control device which is designed to: switch an emission of each of the majority of the LFIs independently of each other, receive the intensity signal emitted by the majority of the photodetectors, and determine a refractive power of the eye based on the detected intensity signals.

[0020] According to the invention, the VR glasses comprise the sensor device according to the invention, wherein the sensor device is arranged between the eye and a display of the VR glasses.

[0021] According to the invention, the electronic glasses comprise the sensor device according to the invention, wherein the sensor device is arranged between the eye and an adjustable optic of the electronic glasses.

[0022] A fundamental idea of ​​the invention is the use of laser focal intensifiers (LFIs) because they are small and therefore easily integrated into a visual device such as VR glasses or other electronic glasses. Furthermore, a fundamental idea of ​​the invention is that the laser beam of the LFI can be adjusted and widened, thus making it easier to irradiate the pupil or eye. Radiation reflected back from the eye, specifically from the retina, interferes with the laser beam of the LFI, from which information about the eye's accommodation is obtained.

[0023] The method generates laser light emission by controlling the LFI (laser focal reflex). If an adjustable lens is present, it is controlled to adjust the focus. Otherwise, the majority of the laser beams are switched through, so that the laser beams of each dilation illuminate the eye. A measurement of the backscattered light intensity is then performed, whereby the backscattered radiation interferes with the laser beam emitted by the LFI. Subsequently, if an adjustable lens is present, it can be controlled to maximize the measured light intensity.

[0024] This provides a sensor device and method for measuring the accommodation depth of an eye, offering the potential for extremely high integration into a head-mounted sensor system. Beam expansion of the laser beam allows for the so-called eyebox problem, i.e., precisely targeting the pupil of the eye. This can be achieved with a single system using an active lens, or with multiple laser beams of varying expansion and different LFIs (Large Field Intensities). In the case of the adjustable lens, the lens replaces larger mechanical lenses, thus ensuring high integration into other systems, such as VR headsets or other electronic eyewear.

[0025] The laser beam enables a coherent measurement method that is robust against externally acting stray light or interference. Furthermore, the sensor device according to the invention eliminates the need for large mechanical components, such as a mechanically adjustable lens, as well as power-intensive sensors such as cameras or wavefront sensors, since the interference arising in the LFI is directly detected and evaluated by means of a simple photodetector.

[0026] Electronic glasses are any corrective lenses that feature electronically adjustable optics. These glasses can be adjusted to the wearer's needs using a sensor device. This includes electronic progressive lenses (eProgressives) and zoom lenses. Glasses with display functions, known as augmented reality glasses, are also possible. Another application of electronic glasses is their use in ophthalmological diagnostic devices for the continuous monitoring of accommodative ability, for example, in the treatment of presbyopia or other refractive errors.

[0027] For the calibration of the sensor device in VR glasses or other electronic glasses, the integrated display or a world camera is used. With a display, images at different focus depths are presented to the user, who must then focus on them. Signals from the LFIs (low focal ratio sensors) are recorded, and the corresponding depth of accommodation is determined via regression. If a world camera is integrated into the glasses, the user can also be instructed to look at their thumb in their outstretched hand and slowly move their hand towards the user. The distance of the hand to the glasses is then determined from the world camera data by tracking the finger (a process known as "finger tracking") and subsequently correlated with the measured intensity.

[0028] According to a preferred embodiment of the method, the method further comprises adjusting a laser beam of selected expansion with the intensity signal of maximum strength from the plurality of laser beams, irradiating the eye with the laser beam of selected expansion, modulating the amplitude of the laser beam of selected expansion, calculating the coupling factor as a function of the modulated amplitude, and calculating the refractive power of the eye based on the determined coupling factors. This allows further information about the eye to be obtained in a simple manner without complex electronics and signal processing.

[0029] According to a preferred embodiment of the method, the method further comprises determining a coupling factor of the laser beam reflected back from the eye into the LFI for each of the plurality of laser beams of different expansion, wherein the refractive power of the eye is determined based on the determined coupling factor of the differently expanded laser beams.

[0030] According to a preferred embodiment of the method, a plurality of laser beams with different degrees of expansion are expanded by an adjustable lens, wherein a different focal length of the adjustable lens is set for each laser beam of the plurality of laser beams. The adjustable lens enables the expansion of the plurality of laser beams in a simple and compact manner.

[0031] According to a preferred embodiment of the method, a plurality of laser beams of different expansions are emitted by a plurality of LFIs. This makes it possible to measure the refractive power simultaneously with several LFIs in the same beam path.

[0032] According to a preferred embodiment of the method, the majority of the laser beams correspond to a majority of the LFIs, with each of the majority of laser beams being emitted by different LFIs. This allows for precise control over the expansion and increases the speed of the measurement.

[0033] According to a preferred embodiment of the method, the majority of LFIs are each assigned a lens or mirror of a different focal length. This achieves the respective widening of the majority of the laser beams in a simple manner.

[0034] According to a preferred embodiment of the method, the photodetector is integrated into the LFI, in particular within a resonator mirror of the LFI. This integration into the LFI results in a particularly compact design.

[0035] According to a preferred embodiment of the method, the laser beams are directed onto the eye via a deflecting optic. The deflecting optic incorporates a holographic element. The holographic element is, in particular, designed as a polymer layer. The holographic element assists in dilating the laser beams to the size of the eye's pupil, or the size of the entire eye. The size of the holographic element can also be the size of the pupil or the eye. In preferred embodiments, this is achieved by a highly transparent hologram (HOE) as the holographic element, which can be formed as a thin polymer film, for example, approximately 5–50 µm thick, on the spectacle lens. In this case, the actual optics in the temple of the spectacle can be very small, so that the polymer film in the spectacle lens acts as the last optical element in the beam path before the eye, thus determining the beam diameter.Alternatively, the deflecting optic can also be a classic optic, such as a telescope system.

[0036] According to a preferred embodiment of the method, a differential measurement signal is generated from intensity signals assigned to at least two different laser beams, from which the refractive power of the eye is determined. This makes it possible to compensate for the static beam distortion caused by the refractive error using the differential measurement signal and to directly determine the eye's accommodation. Furthermore, both LFIs can be measured rapidly in succession by the control unit in such a way that a higher laser power can be emitted briefly without exceeding the eye safety limits.

[0037] According to a preferred embodiment of the sensor device, the LFI is a first LFI, the laser beam is a first laser beam, the optical axis is a first optical axis, and the photodetector is a first photodetector, wherein a second LFI is provided which is configured to emit a second laser beam on a second optical axis, wherein a second photodetector is provided which is configured to detect a part of the second laser beam.The optical system comprises a beam focuser positioned in front of the adjustable lens, which superimposes the first and second optical axes. The optical system further includes lenses of different focal lengths, specific to each LFI (Laser Fibre Inspection), positioned in front of the beam focuser on the respective first and second optical axes. The control unit is configured to generate a differential measurement signal from the intensity signals of the first and second photodetectors and to determine the refractive power of the eye based on this differential measurement signal. As previously described, this allows the static beam distortion caused by refractive error to be factored out using the differential measurement signal, and the accommodation of the eye to be directly measured.Furthermore, both LFIs can be measured quickly one after the other by the control unit in such a way that a higher laser power can be emitted briefly without exceeding the eye safety limits.

[0038] According to a preferred embodiment of the alternative sensor device, the optical system for each LFI comprises its own lens, wherein the lens is in particular a micro-optic, which preferably comprises a metalenser and / or a wafer-based microlens. This represents a particularly compact design.

[0039] According to a preferred embodiment of the alternative sensor device, the majority of LFIs are arranged on a common substrate. This also represents a particularly compact design. According to a preferred embodiment of the alternative sensor device, the optical system comprises an adjustable lens, which is arranged and configured to widen a first group, preferably all, of the majority of the laser beams. This allows the widening of the laser beams to be increased.

[0040] According to a preferred embodiment of the alternative sensor device, the control unit is configured to determine a coupling factor for each set expansion based on the respective intensity signal, and to determine the refractive power of the eye based on the determined coupling factor. Determining the maximum coupling factor indicates the expansion at which the laser beam is maximally reflected back, which occurs when the laser beam is focused on the retina of the eye.

[0041] According to a preferred embodiment of the sensor devices, the control unit is further configured to control the amplitude of the majority of the laser beams, to determine a coupling factor for each amplitude, and to calculate the refractive power of the eye based on the coupling factor of the different amplitudes. This enables precise and rapid measurement, in which the different LFIs are controlled and switched particularly easily. Thus, the measurement frequency can be increased.

[0042] According to a preferred embodiment of the sensor devices, the adjustable lens is either a liquid crystal lens or a mechanically displaceable lens. These two alternatives represent common, established, and therefore reliable implementations of the adjustable lens. The liquid crystal lens is just one type of lens with an adjustable focal length, all of which can be used in principle in this invention. In this case, the control device is configured to control the focal length of the adjustable lens to expand the respective laser beam. In the case of a mechanically displaceable lens, the control device is configured to actuate a corresponding device, such as a sliding table supporting the adjustable lens, to change the position of the adjustable lens.

[0043] The sensor device for determining the refractive power of an eye can also be distinguished by the features and advantages mentioned in connection with the corresponding method as well as the VR glasses and the electronic glasses, and vice versa.

[0044] Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the accompanying drawings.

[0045] Brief description of the drawings

[0046] The present invention will be explained in more detail below with reference to the exemplary embodiments shown in the schematic figures of the drawing.

[0047] They show:

[0048] Fig. 1 shows a schematic representation of a sequence of process steps of a method for determining the refractive power of an eye according to an embodiment of the present invention;

[0049] Fig. 2 shows a schematic representation of a sensor device for determining the refractive power of an eye according to an embodiment of the present invention;

[0050] Fig. 3 shows a schematic representation of a sensor device for determining the refractive power of an eye according to a further embodiment of the present invention;

[0051] Fig. 4 shows a schematic representation of a laser feedback interferometer applicable to the sensor device for determining the refractive power of an eye according to an embodiment of the present invention; Fig. 5 shows a schematic representation of a sensor device for determining the refractive power of an eye according to a further embodiment of the present invention;

[0052] Fig. 6 shows a schematic representation of an alternative sensor device for determining the refractive power of an eye according to an embodiment of the present invention;

[0053] Fig. 7 shows a schematic representation of VR glasses according to an embodiment of the present invention; and

[0054] Fig. 8 shows a schematic representation of electronic glasses for determining the refractive power of an eye according to an embodiment of the present invention;

[0055] In the figures, identical reference symbols denote identical or functionally equivalent elements.

[0056] Fig. 1 shows a schematic representation of a sequence of process steps of a method for determining the refractive power of an eye 2 according to an embodiment of the present invention.

[0057] The procedure for determining the refractive power of an eye 2 comprises the following steps. First, the eye 2 is irradiated successively with a plurality of laser beams 4 of different dispersions. The laser beams 4 are emitted by at least one laser feedback interferometer, LFI, 3. The plurality of laser beams 4 are irradiated successively onto the eye 2 in such a way that a portion of each laser beam is reflected from a retina of the eye 2 back into the LFI 3.

[0058] In certain embodiments, the majority of laser beams 4 of different expansions are expanded by an adjustable lens 61.

[0059] Here, for each laser beam 4 of the plurality of laser beams 4, a different expansion of the laser beam 4 is set by the adjustable lens 62. In further embodiments, the plurality of laser beams 4 with different expansions are emitted by a plurality of LFIs 3. In these embodiments, each of the plurality of LFIs 3 is assigned a lens 62 or a mirror with a different focal length. In further embodiments, the plurality of laser beams 4 corresponds to a plurality of LFIs 3. Here, each of the plurality of laser beams 4 is emitted by different LFIs 3.

[0060] Next, a portion of each of the plurality of laser beams 4 with different expansions is sequentially detected by a photodetector 7 M2, and corresponding intensity signals are output to a control unit 8. Now, in a generally optional step, a coupling factor of the laser beam 4, which is essentially reflected at the retina 22 and back into the LFI 3, is determined M3 for each of the plurality of laser beams 4 with different expansions. Then, the refractive power of the eye 2 is determined M4 based on the determined coupling factors or the detected intensity signals of the differently expanded laser beams 4.

[0061] In further embodiments, the following, essentially optional, process steps are carried out. Accordingly, the process further comprises setting M5 of a laser beam 4 with a selected expansion using the intensity signal of maximum strength or the largest coupling factor from the majority of laser beams 4. The eye 2 is then irradiated M6 with the laser beam 4 of the set expansion. An amplitude of the laser beam 4 of the set expansion is modulated M7. The coupling factor is then calculated M8 as a function of the modulated amplitude.

[0062] Furthermore, the refractive power of eye 2 is calculated based on the determined coupling factors M9.

[0063] Fig. 2 shows a schematic representation of a sensor device 1 for determining the refractive power of an eye 2 according to an embodiment of the present invention. The sensor device 1 for determining the refractive power of an eye 2 comprises a laser feedback interferometer, LFI 3, which is configured to emit a laser beam 4 on an optical axis 5. Furthermore, the sensor device 1 comprises an optical system 6, which is arranged on the optical axis 5 and configured to irradiate the laser beam 4 onto the eye 2.

[0064] The optical system 6 has an adjustable lens 61, which is configured to adjustably widen the laser beam 4. In some embodiments, the adjustable lens 61 is designed as a liquid crystal lens. In other embodiments, the adjustable lens 61 is designed as a mechanically movable lens, for example, as a MEMS-actuated lens. The laser beam 4 is directed towards the eye 2, where the radiation passes through the pupil 21 and is focused on the retina 22. Fig. 2 shows the case in which the radiation is maximally focused on the retina 22, i.e., the beam diameter of the laser beam 4 on the retina 22 is minimized. A portion of the radiation from the laser beam 4 is reflected back to the LFI 3. There, the reflected light interferes with the laser beam 4.

[0065] Furthermore, the sensor device 1 comprises a photodetector 7, which is designed and arranged to detect the reflected part of the laser beam 4 and output a corresponding intensity signal. In this embodiment, the photodetector 7 is arranged on one side of the LFI 3 facing away from the eye 2. In another embodiment, the photodetector 7 is integrated into the LFI 3. In some of these embodiments, the photodetector 7 is integrated into a resonator mirror 31, 32 of the LFI 3.

[0066] The sensor device 1 further comprises a control unit 8, which is configured to control the LFI 3. That is, the control unit 8 can switch the emission of the laser beam 4 generated by the LFI 3 on and off and regulate its output power within a specific range. Furthermore, the control unit 8 is configured to control the expansion of the laser beam 4 by actuating the adjustable lens 61. The control unit 8 is also configured to receive the intensity signal output by the photodetector 7 for each set expansion of the laser beam 4. In preferred embodiments, the control unit 8 is also configured to determine a coupling factor for each set expansion based on the respective intensity signal. Thus, the control unit 8 is also configured to determine a refractive power of the eye 2 based on the intensity signals or coupling factors.In preferred embodiments, the control unit 8 is configured to adjust the adjustable lens 61 to dilation with the intensity signal of maximum strength and then to determine the refractive power of the eye 2 based on the subsequently acquired intensity signals. The amplitude of the laser beam can be modulated to increase the accuracy of the determined refractive power. Integrated into electronic glasses 20 or virtual reality (VR) glasses 10, the refractive power of the eye 2 can thus also be recorded over time.

[0067] In the exemplary embodiments, the control device 8 is configured to control the amplitude of the majority of the laser beams 4, particularly when the adjustable lens is set to a maximum intensity. The control device 8 is also configured to determine a coupling factor for each amplitude and to calculate the refractive power of the eye 2 based on the coupling factor of the different amplitudes.

[0068] Using the previously described method, laser light is generated by controlling the LFI, and the laser beams 4 are emitted along the optical axis 5 towards the eye 2. The adjustable lens 61 adjusts the focus. Subsequently, the backscattered light intensity is measured with the photodetector 7, whereby the backscattered radiation interferes with the laser beam 4 emitted by the LFI. The adjustable lens 61 can then be controlled to maximize the measured light intensity. Furthermore, amplitude modulation of the LFI 3 can be used to improve measurement accuracy.

[0069] Fig. 3 shows a schematic representation of a sensor device 1 for determining the refractive power of an eye 2 according to a further embodiment of the present invention. The embodiment shown in Fig. 3 is compatible with the embodiment(s) of the sensor device 1 described above.

[0070] The embodiment shown in Fig. 3 differs in that the laser beams 4 are directed onto the eye 2 via a deflecting optic 63. The deflecting optic 63 incorporates a holographic element. This holographic element assists in widening the laser beams 4 to the size of the pupil 21 of the eye 2. In further embodiments, the laser beam 4 is widened to the size of the entire eye 2 in order to reliably focus a sufficient amount of light onto the retina 22. The size of the deflecting optic 63 or the holographic element can also be the size of the pupil 21 or the eye 2.

[0071] In preferred embodiments, this is achieved by a highly transparent hologram (HOE) as the holographic element, which is formed as a thin polymer film, for example approximately 5–50 µm thick, on the spectacle lens. In this case, the optical system 6 or the entire sensor device 1 in the temple of the spectacle can be so small that the polymer film in the spectacle lens acts as the last optical element in the beam path before the eye 2, determining the beam diameter. In further embodiments, the deflecting optics 63 are conventional optics, such as a telescope system. The deflecting optics 63 direct the laser beam 4 onto the eye 2 and irradiate it. In further embodiments, the deflecting optics 63 are used to manipulate a surface of the eye 2.

[0072] The control unit 4 is connected to the adjustable lens 61, the LFI 3 and the photodetector 7 in the same way as shown in Fig. 2, but is not shown in Fig. 3 for clarity.

[0073] Fig. 4 shows a schematic representation of a laser feedback interferometer 3 applicable to the sensor device 1 , 1 ' for determining a refractive power of an eye 2 according to an embodiment of the present invention.

[0074] The LFI 3 has a first resonator mirror 31 with reflectivity R1 and a second resonator mirror 32 with reflectivity 2, between which the laser beam 4 propagates with an optical power PO. In the embodiment of the LFI 3 shown in Fig. 4, the resonator mirrors are configured as Bragg gratings. The propagation constant βi nt is due to an internal frequency co mtThe time t is given. The first resonator mirror 31 serves as a high-reflector mirror, so that the reflectivity R2 is approximately 1. This internal resonator 33 formed by the resonator mirrors 31, 32 has a length L. n Since the reflectivity R2 of the first mirror is less than 1, the second resonator mirror 32 serves as an output coupling mirror, so that its reflectivity R2 is typically significantly less than 1. Thus, a laser beam 4 with optical power P02 is emitted.

[0075] This light strikes the retina 22 of eye 2 and is reflected back into the internal resonator with an optical feedback power Pf and a reflectivity R3. The retina 22 thus functions as an external resonator mirror and has a distance L ex t from the second resonator mirror 32. The laser beam 4 contained therein propagates with an external propagation constant β. ex t, which is also the product of an external frequency co mt and the time t is.

[0076] The optical feedback performance is as follows:

[0077] P f = P2(l - m- cos 2 ■ ß ext ■ L ext ))

[0078] , where m represents the amplitude of the laser beam, which can be modulated in some embodiments. If all the above parameters are approximately constant, the coupling constant is directly derived from the amplitude m. Otherwise, the coupling factor is determined in a known manner.

[0079] In certain embodiments, the photodetector 7 is integrated into the LFI 3. In preferred embodiments, the photodetector 7 is integrated into the first resonator mirror 31 of the LFI 3, in particular as a Bragg layer in the Bragg grating of the first resonator mirror 31.

[0080] Fig. 5 shows a schematic representation of a sensor device 1 for determining the refractive power of an eye 2 according to a further embodiment of the present invention. The embodiment of a sensor device 1 shown in Fig. 5 is based on and compatible with the previously described embodiments of the sensor devices 1.

[0081] In this embodiment, the sensor device 1 has a first LFI 3a which emits a first laser beam 4a on a first optical axis 5a. The light reflected back from the retina 22 of the eye 2 is detected by a first photodetector 7a.

[0082] Furthermore, a second LFI 3b is provided, which is configured to emit a second laser beam 4b on a second optical axis 5b. A second photodetector 7b is also provided, which is configured to detect a portion of the second laser beam 4b.

[0083] The optical system 6 comprises a beam focuser 64 positioned upstream of the adjustable lens 62, which superimposes the first optical axis 5a with the second optical axis 5b. In this embodiment, the beam focuser 64 is configured as a beam splitter or beam combiner. In other embodiments, the beam focuser 64 is configured as a prism.

[0084] The optical system 6, furthermore, upstream of the beam bundler 64 for the respective LFI 3a, 3b, each comprises its own lenses of different focal lengths on the respective first and second optical axes 5a, 5b.

[0085] Furthermore, it can be seen that the adjustable lens 61 in this embodiment is designed as a mechanically displaceable lens, although a corresponding sliding table or translator for moving the adjustable lens 61 along the optical axis 5a, 5b is not shown in Fig. 5. In further embodiments, the adjustable lens 61 is designed as a piezo-mechanical or MEMS-actuated line. In addition, a further, optional lens 65 can be seen in Fig. 5, which is used for further beam expansion. In these embodiments, the control unit 8 is configured to generate a differential measurement signal from the intensity signals of the first and second photodetectors 7 and to determine the refractive power of the eye 2 based on the differential measurement signal.Thus, a differential measurement signal is generated from at least two different laser beams, each with its own intensity signal, from which the refractive power of eye 2 is determined. This allows the static beam distortion caused by the refractive error to be factored out and the accommodation of eye 2 to be directly measured. Furthermore, both LFIs 3a and 3b can be measured rapidly in succession by the control unit 6 in such a way that a higher laser power can be emitted briefly without exceeding the eye safety limits.

[0086] In further embodiments, a plurality of laser beams 4a, 4b of different focal lengths are emitted analogously from a plurality of LFIs 3a, 3b. The plurality of laser beams 4a, 4b corresponds to the plurality of LFIs 3a, 3b, wherein each of the plurality of laser beams 4 is emitted by different LFIs 3a, 3b. In some of these embodiments, the plurality of LFIs 3a, 3b are each assigned to a lens 62 or a mirror of different focal lengths. The plurality of LFIs 3a, 3b and laser beams 4a, 4b can, for example, be 3, 5, 6, 8, 10 or more. The control device 4 is connected to the adjustable lens 61, the LFIs 3a, 3b, and the photodetectors 7a, 7b in the same way as shown in Fig. 2, but is not shown in Fig. 5 for clarity.

[0087] Fig. 6 shows a schematic representation of an alternative sensor device 1' for determining the refractive power of an eye 2 according to an embodiment of the present invention.

[0088] The sensor device 1' shown in Fig. 6 for determining the refractive power of an eye 2 does not require an adjustable lens 61. This alternative sensor device 1' comprises a plurality of laser feedback interferometers, LFI 3a, 3b, each configured to emit a laser beam 4a, 4b. The sensor device 1' includes an optical system 6 configured to illuminate each of the plurality of laser beams 4a, 4b with a different dispersion onto the eye 2.

[0089] The sensor device 1' also comprises a plurality of photodetectors, which are designed and arranged to each detect a part of one of the plurality of laser beams 4a, 4b, such that each photodetector 7 is assigned to a different LFI 3a, 3b.

[0090] Furthermore, the sensor device 1' includes a control unit 8 in an analogous manner to the embodiment in Fig. 2, except that the control unit 8 is now not connected to an adjustable lens, but only to the LFIs 3a, 3b and the photodetectors 7a, 7b.

[0091] The control device 8 is configured to control an emission of each of the plurality of LFI 3 independently of each other, to receive an intensity signal emitted by each of the plurality of photodetectors 7a, 7b, to determine a coupling factor for each of the plurality of laser beams 4a, 4b based on the intensity signals, and to determine a refractive power of the eye 2 based on the determined coupling factors.

[0092] In further preferred embodiments, a plurality of laser beams 4 of different expansions are emitted analogously by a plurality of LFIs 3a, 3b. The plurality of laser beams 4a, 4b corresponds to the plurality of LFIs 3a, 3b, wherein each of the plurality of laser beams 4a, 4b is emitted by different LFIs 3a, 3b. In some of these embodiments, each of the plurality of LFIs 3a, 3b is associated with a lens 62a, 62b or a mirror of different focal length. These lenses 62a, 62b, as well as the LFIs 3a, 3b, are arranged perpendicular to the optical axis 5. In some of these embodiments, the lens 62a, 62b is designed as a micro-optic, which may comprise a metalinfrared and / or a wafer-based microlens. In preferred embodiments, the majority of LFIs 3a, 3b and in particular the lenses 62a, 62b are arranged on a common substrate.Such a dedicated line The majority of LFIs 3a, 3b and corresponding laser beams 4a, 4b can be, for example, 3, 5, 6, 8, 10 or more.

[0093] Thus, instead of the adjustable lens 61, an array of LFI sensors, each with its own wafer-level optics, can be integrated, allowing beam manipulation to be achieved by switching the LFIs 3a, 3b instead of adjusting the TFL. Such a sensor array can therefore comprise a multitude of LFIs 3a, 3b arranged side-by-side in a 1D or 2D structure, which can then emit differently expanded laser beams 4a, 4b with or, in some embodiments, without their own individual lens 62a, 62b, and with different focal lengths. The eye 2 is then irradiated with the different laser beams 4a, 4b sequentially by switching the LFIs 3a, 3b. The integration of such a sensor array into eyeglass frames or behind a so-called "pancake" optic of VR headsets is explained further below with reference to Figures 7 and 8.Integrated into such electronic glasses 20 or VR glasses 10, the refractive power of the eye can also be recorded over time.

[0094] In Fig. 6, two lenses 65 are arranged in front of a deflecting optic 63 designed analogously to the embodiment shown in Fig. 3 or 5. The two lenses 65 form a common beam spreader for the two laser beams 4a, 4b. In further embodiments, the optical system 6 of such an alternative sensor device 1' nevertheless includes an adjustable lens 61, which is arranged and designed to spread a first group, preferably all, of the majority of the laser beams 4a, 4b.

[0095] Fig. 7 shows a schematic representation of VR glasses 10 according to an embodiment of the present invention. Fig. 8 shows a schematic representation of electronic glasses 20 for determining the refractive power of an eye 2 according to an embodiment of the present invention.

[0096] The alternative sensor device 1', as well as the sensor device 1 described above, can be built directly in a package and integrated directly into a spectacle frame or temple. Furthermore, the sensor devices 1 and 1' can be installed behind the pancake lens of a VR headset, i.e., the VR glasses 11 shown. Multiple such sensors within the frame of the glasses are also conceivable in order to compensate for effects caused by non-orthogonal alignment of the sensors with respect to the lens.

[0097] The virtual reality (VR) glasses 10 shown in Fig. 7 comprise the sensor device 1, 1' according to the invention as described above for determining the refractive power of an eye 2. In these VR glasses 10, the sensor device 1 is arranged between the eye 2 and a display 11 of the VR glasses.

[0098] The electronic glasses 20 shown in Fig. 8 comprise the sensor devices 1, 1' according to the invention, as described above, for determining the refractive power of an eye 2, wherein the sensor device 1 is arranged between the eye 2 and an adjustable optic 21 of the electronic glasses 20. Although ordinary glasses are shown in Fig. 8, the electronic glasses 20 described here include any corrective eyewear that has electronically adjustable optics. The electronic glasses 20 are adjusted to the wearer's needs by means of the sensor device 1, 1'. In preferred embodiments, the electronic glasses 20 are electronic progressive lenses. In further embodiments, the electronic glasses 20 are designed as zoom glasses or as glasses with display functions, so-called augmented reality glasses.

[0099] The display 11, integrated into the VR glasses 11 and the electronic glasses 20, can be used for the calibration routine of the sensor device 1, 1'. Images at various focus depths are presented to the user, who must then focus on them. Signals from the LFIs 3, 3a, 3b are recorded, and the corresponding depth of accommodation is determined via regression. If a world camera is integrated into the glasses 10, 20, the user can also be instructed to look at their thumb in their outstretched hand and slowly move their hand towards the user. The distance of the hand to the glasses 10, 20 is determined from the world camera data by tracking the finger (a process known as "finger tracking") and subsequently correlated with the measured intensity.Furthermore, it is conceivable that the sensor device 1, 1' measures not only absolute accommodation but also relative accommodation between different image planes and classifies the depth to which the user is currently looking, e.g., near vs. far. This can be used to build a focus-based user interface or to implement a dynamic object display in which objects are dynamically shown or hidden. Another application of electronic glasses 20 is their use in ophthalmological diagnostic devices for the continuous monitoring of accommodative ability, for example, in the treatment of presbyopia or other visual impairments.Such electronic glasses can also serve with enhanced user interaction, for example by using accommodation data to control applications, such as zoom functions or context switching in user interfaces based on the gaze focus determined by the method.

[0100] Although the present invention has been fully described above with reference to the preferred embodiment, it is not limited to this embodiment but can be modified in many different ways.

Claims

Claims 1. Method for determining the refractive power of an eye (2), comprising: - Time-sequential irradiation (M1) of the eye (2) with a plurality of laser beams (4; 4a, 4b) of different spreads, wherein the laser beams (4; 4a, 4b) are emitted from at least one laser feedback interferometer (3; 3a, 3b), LFI (3; 3a, 3b), wherein the plurality of laser beams (4; 4a, 4b) are irradiated onto the eye (2) in such a way that a part of the respective laser beam is reflected from the eye (2) back into the LFI (3; 3a, 3b) and interferes with the laser beam (4; 4a, 4b) in the LFI (3; 3a, 3b), - Temporarily successive detection (M2) of a part of each of the plurality of laser beams (4; 4a, 4b) of different expansion with a photodetector (7), wherein the photodetector (7) outputs intensity signals corresponding to the detected parts of the laser beams (4; 4a, 4b) of different expansion, and - Determining (M4) the refractive power of the eye (2) based on the detected intensity signals of the differently expanded laser beams (4; 4a, 4b).

2. The method according to claim 1, further comprising: - Setting (M5) a laser beam (4; 4a, 4b) of selected expansion with the intensity signal of maximum strength from the plurality of laser beams (4; 4a, 4b), - Irradiating (M6) the eye (2) with the laser beam (4; 4a, 4b) of set expansion, - Modulating (M7) an amplitude of the laser beam (4; 4a, 4b) of set expansion, - Calculating (M8) a coupling factor as a function of the modulated amplitude, and - Calculate M9) the refractive power of the eye (2) based on the determined coupling factors.

3. The method of claim 1, further comprising: Determine (M3) a coupling factor of the laser beam (4; 4a, 4b) reflected back from the eye (2) into the LFI (3; 3a, 3b) for each of the plurality of laser beams (4; 4a, 4b) of different expansion, wherein the determination of the refractive power of the eye (2) is based on the determined coupling factor of the differently expanded laser beams (4; 4a, 4b).

4. Method according to any of the foregoing claims, characterized by the fact that The majority of laser beams (4; 4a, 4b) of different expansions are expanded by an adjustable lens (61), wherein for each laser beam (4; 4a, 4b) of the majority of laser beams (4; 4a, 4b) a different focal length of the adjustable lens (62) is set.

5. Method according to any of the foregoing claims, characterized by the fact that the majority of laser beams (4; 4a, 4b) of different spreads are emitted from a majority of LFIs (3a, 3b).

6. Method according to claim 4, characterized by the fact that the majority of the laser beams (4a, 4b) correspond to a majority of the LFIs (3a, 3b), wherein each of the majority of the laser beams (4a, 4b) is emitted by different LFIs (3a, 3b).

7. Method according to claim 5, characterized by the fact that the majority of the LFIs (3a, 3b) are each assigned a lens (62a, 62b) or a mirror of different focal lengths.

8. Method according to any of the foregoing claims, characterized by the fact that the photodetector (7; 7a, 7b) is integrated into the LFI (3; 3a, 3b), wherein the photodetector (7; 7a, 7b) is in particular integrated into a resonator mirror of the LFI (3; 3a, 3b).

9. Method according to any of the foregoing claims, characterized by the fact that the laser beams (4; 4a, 4b) are directed onto the eye (2) via a deflecting optic (63). are, wherein the deflecting optics (63) has a holographic element, wherein the holographic element is in particular designed as a polymer layer.

10. Method according to any of the foregoing claims, characterized by the fact that a differential measurement signal is generated from intensity signals assigned to at least two different laser beams (4a, 4b), from which the refractive power of the eye (2) is determined.

11. Sensor device (1) for determining the refractive power of an eye (2), comprising a laser feedback interferometer, LFI (3; 3a, 3b), which is configured to emit a laser beam (4; 4a, 4b) on an optical axis (5), an optical system (6) which is arranged on the optical axis (5) and configured to irradiate the laser beam (4; 4a, 4b) onto the eye (2) such that a part of the laser beam (4; 4a, 4b) is reflected by the eye (2) and interferes with the laser beam (4; 4a, 4b) in the LFI (3; 3a, 3b), wherein the optical system (6) comprises an adjustable lens (61) which is configured to adjustably widen the laser beam (4; 4a, 4b), a photodetector (7; 7a, 7b) which is designed and arranged to detect a part of the laser beam (4; 4a, 4b) reflected at the eye (2) and to output a corresponding intensity signal, and a control device (8) which is set up for: - to control the LFI (3, 3a, 3b), - to adjust the widening of the laser beam (4; 4a, 4b) by controlling the adjustable lens (61), - to receive the intensity signal output by the photodetector (7; 7a, 7b) for each set expansion of the laser beam (4; 4a, 4b), and - to determine the refractive power of the eye (2) based on the detected intensity signals of the laser beams (4; 4a, 4b) of different dilation.

12. Sensor device (1) according to claim 10, characterized by the fact that the LFI (3a, 3b) is a first LFI (3a), the laser beam (4a, 4b) is a first laser beam (4a), the optical axis (5a, 5b) is a first optical axis (5a), and the photodetector (7a, 7b) is a first photodetector (7a). wherein a second LFI (3b) is provided which is configured to emit a second laser beam (4b) on a second optical axis (5b), wherein a second photodetector (7b) is provided which is configured to detect a part of the second laser beam (4b), wherein the optical system (6) comprises a beam bundling device (64) positioned in front of the adjustable lens (62), which superimposes the first optical axis (5a) with the second optical axis (5b), wherein the optical system (6) further comprises lenses of different focal lengths on the respective first and second optical axes (5a, 5b) positioned in front of the beam bundler (64) for the respective LFI (3a, 3b), wherein the control device (8) is configured to - to generate a differential measurement signal from the intensity signals of the first and second photodetector (7), and - to determine the refractive power of the eye (2) based on the differential measurement signal.

13. Sensor device (1') for determining the refractive power of an eye (2), comprising a plurality of laser feedback interferometers, LFI (3a, 3b), each configured to emit a laser beam (4a, 4b), an optical system (6) which is configured to irradiate each of the plurality of laser beams (4a, 4b) with a different dispersion onto the eye (2), such that a part of the laser beam (4; 4a, 4b) is reflected by the eye (2) and interferes with the laser beam (4; 4a, 4b) in the LFI (3; 3a, 3b), a plurality of photodetectors (7a, 7b) which are designed and arranged to each detect a part of one of the plurality of laser beams (4a, 4b) and output a corresponding intensity signal, such that each photodetector (7a, 7b) is assigned to a different LFI (3a, 3b), and a control device (8) which is set up for: - to switch an emission of each of the majority of the LFI (3a, 3b) independently of each other, -to receive the intensity signal emitted by the majority of the photodetectors, -, and - a refractive power of the eye (2) based on the detected intensity signals to determine.

14. Sensor device (1') according to claim 12, characterized by the fact that the optical system (6) for each LFI (3a, 3b) comprises its own lens (62a, 62b), wherein the lens (62a, 62b) is in particular a micro-optic which preferably comprises a metalens and / or a wafer-based microlens.

15. Sensor device (1') according to claim 12 or 13, characterized by the fact that the majority of LFIs (3a, 3b) are arranged on a common substrate.

16. Sensor device (1 ') according to one of claims 12 to 14, characterized by the fact that the optical system (6) comprises an adjustable lens (61) which is arranged and configured to widen a first group, preferably all, of the majority of the laser beams (4a, 4b).

17. Sensor device (1 ; 1 ') according to one of claims 11 to 16, wherein the control device is configured to, - to determine a coupling factor for each set expansion based on the respective intensity signal, and - to determine the refractive power of the eye (2) based on the determined coupling factor.

18. Sensor device (1 ; 1 ') according to one of claims 10 to 17, characterized by the fact that the control device (8) is further equipped to - to control the amplitude of the majority of the laser beams (4a, 4b), - to determine a coupling factor for each amplitude, and - to calculate the refractive power of the eye (2) based on the coupling factor of the different amplitudes.

19. Sensor device (1 ; 1 ') according to one of claims 10, 11 or 16, characterized by the fact that the adjustable lens (61) is a liquid crystal lens or a mechanically movable lens.

20. Virtual Reality, VR, glasses (10) comprehensive the sensor device (1 ; 1 ') for determining the refractive power of an eye (2) according to one of claims 10 to 19, wherein the sensor device (1; 1') is arranged between the eye (2) and a display (11) of the VR glasses.

21. Electronic glasses (20), comprehensive the sensor device (1; 1') for determining the refractive power of an eye (2) according to one of claims 10 to 19, wherein the sensor device (1; 1') is arranged between the eye (2) and an adjustable optic (21) of the electronic glasses (20).

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