Detection system for a head-worn device and head-worn device

Abstract

A detection system (1) for a head-worn device (10), is specified, the detection system comprising a radiation source (2) configured to emit a radiation (7), a wave guide (3) extending between a user side (31) and a world side (32), and a volume phase hologram (4), wherein the waveguide (3) provides a propagation medium between the radiation source (2) and the volume phase hologram (4); the volume phase hologram (4) is configured to couple out the radiation (7) through the world side (32) of the waveguide (3); and the detection system (1) is configured to provide a self-mixing interferometry signal in response to the radiation reflected off or scattered at an external object (9) and coupled back through the world side (32) of the waveguide (3) into the radiation source (2).

Description

[0001] Description

[0002] DETECTION SYSTEM FOR A HEAD-WORN DEVICE AND HEAD-WORN DEVICE

[0003] The present application relates to a detection system for a head-worn device and to a head-worn device.

[0004] In head-worn device such as augmented reality (AR ) or mixed reality (MR ) glasses, it may be helpful to provide information on the environment of the user. However, detection should take place without obstructing the user' s view or impairing the external appearance of the device.

[0005] It is an obj ect to provide a way to provide information on the environment of the user in a reliable and inconspicuous manner.

[0006] This obj ect is achieved, inter alia, by a detection system and a head-worn device according to the independent claims. Developments and expediencies are subj ect of the further claims.

[0007] A detection system

[0008]

[0009] speci f ied. In particular, the detection system is configured for a head-worn device.

[0010] According to at least one embodiment of the detection system, the detection system comprises a radiation source configured to emit a radiation.

[0011] For example, the radiation source comprises a laser source with a cavity configured to emit coherent radiation to irradiate an environment of a user of the head-worn device. For example, the laser source comprises one or more laser diodes to produce one or more laser beams. For example, the laser source comprises a vertical cavity surface-emitting laser (VCSEL ) or an array of VCSELs. VCSELs have a low threshold current and thus have a comparably low power consumption. Further, they can have small dimensions and are available at low cost * However, other laser diodes may also be used, such as edge-emitting lasers, for example distributed feedback ( DFB ) lasers or distributed Bragg reflector ( DBR) lasers.

[0012] For example, the radiation source is configured to emit radiation with a peak wavelength in the infrared or near infrared spectral range. For example, the radiation source is conf igured to emit radiation with a peak wavelength in a range from 800 nm to 1500 nm. Alternatively or in addition, the radiation source may be configured to emit radiation in the visible spectral range.

[0013] According to at least one embodiment of the detection system, the detection system comprises a waveguide. For example, the waveguide extends between a user side and a world side opposite the user side. In particular, the waveguide is arranged in a beam path between the radiation source and an external obj ect arranged on a side of the wave guide that faces away from the user during operation of the head-worn device. For example, the waveguide has a thickness in a range f rom 0. 1 mm to 10 mm.

[0014] In particular, the waveguide is transparent to light in the visible spectral range. The radiation propagates along a predetermined path through the waveguide via total internal reflection ( TIR). In particular, a material of the waveguide may have a ref ractive index which is higher than that of an environment such as air or a potential waveguide coating or encapsulation material. For example, the waveguide comprises a glass, a crystal, or a plastics material such as a polymer.

[0015] According to at least one embodiment of the detection system, the detection system comprises a volume phase hologram (VPH ). Using a VPH, radiation impinging onto the VPH at a predefined angle may be def lected into a direction enclosing a speci f ic angle with the VPH, wherein the speci fic angle can be defined during production of the VPH, for example. The VPH may ful fi l one or more one optical functions. For example, the optical function includes at least one of: deflecting, focussing, converging, collimating, diverging. For example, a volume phase hologram or a combination of volume phase holograms can be configured to provide di fferent optical trans formations, for example a point-to-point trans formation, a point to plane wave trans formation, a plane wave to plane wave trans formation or a plane wave to point trans formation, or a sequence of such optical trans formations.

[0016] According to at least one embodiment of the detection system, the waveguide provides a propagation medium between the radiation source and the volume phase hologram. Thus, the radiation emitted by the radiation source during operation of the detection system and coupled into the waveguide may travel within the waveguide towards the volume phase hologram.

[0017] According to at least one embodiment of the detection system, the volume phase hologram is conf igured to couple out the radiation through the world side of the waveguide. In particular, the radiation propagating in the waveguide may be def lected such that it is coupled out from the waveguide to irradiate a region of the user' s environment. Likewise, radiation returning from the environment may be deflected by means of the volume phase hologram on its way back to the radiation source.

[0018] For example, the volume phase hologram is a transmission volume phase hologram arranged on the world side of the waveguide or a ref lection volume phase hologram arranged on a user side of the waveguide.

[0019] The volume phase hologram may provide an optical function appropriate for irradiating an external obj ect in front of the user. For example, the volume phase hologram is the last beam shaping element in a beam path from the radiation source to the external obj ect. In particular, the volume phase hologram is arranged in a beam path from the external obj ect back to the radiation source. The optical function of the volume phase hologram may be adapted to the way the radiation propagates within the waveguide. For example, the radiation propagating within the waveguide may be collimated, divergent, convergent, or focused.

[0020] According to at least one embodiment of the detection system, the detection system is configured to provide a sel f-mixing interferometry ( SMI ) signal in response to the radiation ref lected of f or scattered at an external obj ect and coupled back through the world side of the waveguide into the radiation source. During operation, the external obj ect may be located in front of the user in a region to be monitored by the detection system.

[0021] In particular, sel f-mixing interference occurs when a portion of the radiation irradiating the external obj ect is ref lected or scattered back from the external obj ect into a cavity ( or resonator ) of the radiation source. For example, the external obj ect is a wall or any other obj ect located in front of the user during operation of the detection system. An interf erence of this portion with the original radiation of the radiation source leads to an SMI signal providing information on a change in a distance and / or a relative velocity between the detection system and the external obj ect. For example, a number or a frequency of interference fringes of the SMI signal may provide the information.

[0022] For example, the interferences cause modulations of a laser output intensity that may be detected by a detector such as a photodiode.

[0023] For example, the detector is integrated in the radiation source and conf igured to obtain a sel f-mixing interf erence signal. For example, the detector comprises a photodiode arranged behind or within the laser cavity in order to measure the output intensity of the laser.

[0024] For example, the photodiode and an active region of a semiconductor laser as radiation source are integrated in a common semiconductor body comprising semiconductor layers formed by epitaxial growth.

[0025] Alternatively, the photodiode may be located behind a back mirror of the laser cavity arranged opposite to a front mirror. Most of the radiation is emitted during operation of the radiation source through the front mirror.

[0026] Alternatively or in addition, modulations of an electrical operation parameter of the radiation source may be used, for example a laser operation voltage or a laser operation current. Changes in these parameters likewise allow information on the external obj ect to be obtained, as these parameters are affected by sel f-mixing interferometry effects as well.

[0027] In at least one embodiment of the detection system, the detection system comprises a radiation source configured to emit a radiation, a waveguide extending between a user side and a world side, and a volume phase hologram, wherein the waveguide provides a propagation medium between the radiation source and the volume phase hologram. The volume phase hologram is configured to couple out the radiation through the world side of the waveguide and the detection system is configured to provide a sel f-mixing interferometry signal in response to the radiation reflected off or scattered at an external obj ect and coupled back through the world side of the waveguide into the radiation source.

[0028] The detection system is in particular based on the idea that sel f-mixing interferometry may be used to detect a relative movement between an external obj ect and a user of the detection system in a precise and reliable manner. For example, the relative distance and / or the relative velocity between the user and an external obj ect located in front of the user may be detected. The waveguide may be used to guide the radiation on its way from the radiation source to the external obj ect and back. Thus, the radiation source can be arranged such that it is invisible in a view onto ( or towards ) the world side of the waveguide. Further, the vision of the user is not impeded by means of the detection system. During operation of the detection system the radiation may propagate through the waveguide from the radiation source to the volume phase hologram. In particular total internal reflection ( TIR ) may force the radiation to follow a certain path within the waveguide.

[0029] According to at least one embodiment of the detection system, the waveguide is transparent to light in the visible spectral range. This way, the waveguide can be integrated into a glass of the head-worn device ( such as into a lens of the head-worn device ) without obstructing the user' s view, more particularly without disturbing a user' s view through the glass towards the user' s environment, i. e. beyond the world side of the waveguide.

[0030] According to at least one embodiment of the detection system, the radiation propagates along a predetermined path through the waveguide via total internal reflection ( TIR ). This way, in combination with the VPH coupling out the radiation from the waveguide, the location where the radiation exits the waveguide and the VPH is predetermined by the detection system.

[0031] According to at least one embodiment of the detection system, the waveguide is a lightguide.

[0032] According to at least one embodiment of the detection system, the radiation travels two times the same path through the waveguide on its way from the radiation source to the external obj ect and back. Thus, the waveguide is also part of an optical path for the radiation returning from the external obj ect between the volume phase hologram and the radiation source. According to at least one embodiment of the detection system, a path of the radiation from the radiation source to the external obj ect is identical to a path of the radiation from the external obj ect back to the radiation source.

[0033] According to at least one embodiment of the detection system, at least a portion of the radiation emitted through the world side of the waveguide has a focal distance from the world side of the waveguide in a range from 10 cm to 10 m. In particular, the focal distance may be selected during manufacturing of the detection system by configuring the volume phase hologram or a plurality of volume phase

[0034] h o 1 o g r a m s accordingly.

[0035] According to at least one embodiment of the detection system, the detection system is configured to emit radiation through the world side of the waveguide along at least two beams, wherein the beams di ffer from one another with respect to an emission direction and / or a focal distance from the world side of the waveguide. For example, two or more beams have a focal distance from the world side of the waveguide in a range from 10 cm to 10 m.

[0036] By the provision of two or more separate beams, the reliability of the detection of an external obj ect located in front of the user may be increased.

[0037] According to at least one embodiment of the detection system, the volume phase hologram comprises at least two multiplexed optical functions. During the recording of the volume phase hologram the two or more optical functions can be formed within the same holographic film. Thus, a holographic pattern within the volume phase hologram is configured to ful fil two or more optical functions.

[0038] For example, the volume phase hologram with multiplexed optical functions is configured to direct the radiation onto di fferent regions of the user ' s environment and / or to provide di fferent focal distances from the world side of the waveguide. Alternatively or in addition, the optical functions may be configured to perform di fferent optical trans formations.

[0039] According to at least one embodiment of the detection system, the detection system comprises a further volume phase hologram. For example, the further volume phase hologram is configured to deflect radiation propagating within the waveguide towards the environment in front of the user.

[0040] According to at least one embodiment of the detection system, the volume phase hologram and the further volume phase hologram are configured to provide the at least two beams.

[0041] Thus, the volume phase hologram and the further volume phase hologram provide di f ferent beams to irradiate the environment. For example, the volume phase hologram and the further volume phase hologram may represent the last di f fractive optical element within the respective beam path before the radiation impinges onto the external obj ect. Thus both the volume phase hologram and the further volume phase hologram may function as outcoupling elements for the radiation propagating within the waveguide. On its way back from the external obj ect or from two di fferent external obj ects, the radiation may be coupled into the waveguide via the volume phase hologram and the further volume phase hologram.

[0042] Alternatively, the volume phase hologram and the further volume phase hologram may be arranged in a common beam path. For example, the further volume phase hologram is in a beam path between the radiation source and the volume phase hologram or vice versa.

[0043] Features described in connection with the volume phase hologram may also apply for the further volume phase hologram.

[0044] According to at least one embodiment of the detection system, at least a part of the volume phase hologram is laterally spaced from the further volume phase hologram. Thus, the volume phase hologram and the further volume phase hologram do not overlap completely. The volume phase hologram and the further volume phase hologram may also be spaced apart from one another completely.

[0045] According to at least one embodiment of the detec tion system, the volume phase hologram and the further volume phase hologram are formed in separate holographic films. Thus, the volume phase hologram and the further volume phase hologram may be produced independently from one another.

[0046] According to at least one embodiment of the detection system, the volume phase hologram and the further volume phase hologram are formed in a common holographic film. In a view onto the waveguide, the volume phase hologram and the further volume phase hologram may overlap at least in regions or be spaced apart from one another. Thus, the same holographic film may be exposed during production such that multiplexed optical functions are provided within the holographic film.

[0047] According to at least one embodiment of the detection system, the detection system comprises a further radiation source configured to provide a further portion of the radiation. Thus, the radiation emitted by the detection system originates from at least two separate radiation sources.

[0048] Features described in connection with the radiation source may also apply for the further radiation source. The radiation and the further radiation may have the same peak emission wavelength or di fferent peak emission wavelengths.

[0049] According to at least one embodiment of the detection system, the radiation source is configured to irradiate the volume phase hologram and the further radiation source is conf igured to irradiate the further volume phase hologram. In particular, the further volume phase hologram is configured to def lect the further radiation through the world side of the waveguide. For example, the further volume phase hologram is the last di ffractive optical element in the beam path before the further radiation impinges onto the external object.

[0050] According to at least one embodiment of the detection system, the detection system comprises an incoupling optical element for coupling the radiation of the radiation source into the waveguide. The incoupling optical element may be located on any side of the waveguide. For example, the incoupling optical element is a prism, a lens, a grating, or an additional volume phase hologram. For example, the incoupling optical element is connected to the waveguide in a mechanically stable manner. For example, the incoupling optical element is attached to the waveguide. Alternatively, the incoupling optical element and the waveguide may be formed in one piece.

[0051] The detection system may comprise a further incoupling optical element to couple the further radiation of the further radiation source into the waveguide. Alternatively, the same incoupling optical element may be used to couple the radiation and the further radiation into the waveguide.

[0052] For example, the waveguide is used for a back-and-forth path of the radiation. Thus, the incoupling optical element can also be used to couple out the radiation returning from the external obj ect on its way back to the cavity of the radiation source.

[0053] Thus, the beam path from the external obj ect ( s ) back to the radiation source does not require any optical elements in addition to those provided for the beam path from the radiation source to the external obj ect ( s ). In particular, the volume phase hologram may also be used to couple the radiation returning from the external obj ect ( s ) into the waveguide. Thus, there is no need for an additional optical element, such as a volume phase hologram, to couple the radiation coming back from the external obj ect ( s ) into the waveguide towards the radiation source.

[0054] In an equivalent manner, the waveguide may be used tor a back-and-forth path of the further radiation.

[0055] According to at least one embodiment of the detection system, a beam shaping optics is arranged between the radiation source and the volume phase hologram. In particular, the beam P5692-PCT TK / Dec. 2025

[0056] shaping optics may be arranged between the radiation source and the incoupling optical element. For example, the beam shaping optics is a refractive optical element such as a lens. Alternatively or in addition, the beam shaping optics may comprise or consist of a di f f ractive optical element such as a grating or a volume phase hologram.

[0057] For example, the beam shaping optics is configured to control the propagation of the radiation within the waveguide. For example, the beam shaping optics may collimate, converge, focus, or diverge the radiation propagating within the waveguide.

[0058] According to at least one embodiment of the detection system, the volume phase hologram is a transmission volume phase hologram arranged on the world side of the waveguide or a ref lection volume phase hologram arranged on the user side of the waveguide. In both cases the volume phase hologram may be combined with one or more further volume phase holograms arranged on the world side and / or the user side of the waveguide.

[0059] According to at least one embodiment of the detection system, the detection system is configured to detect a change in a distance and / or a relative velocity between the detection system and the external obj ect. Such changes may be reliably detected with a high repetition rate and a high accuracy at low power consumption by means of sel f-mixing interferometry. In particular, a number or a frequency of interference f ringes detectable in the SMI signal may be used to derive information on these changes. According to at least one embodiment of the detection system, the detection system is configured to detect a self-mixing interferometry signal resulting from a Doppler shift. The Doppler shift can be caused by a relative movement between the detection system and the external object. And / or the Doppler shift can be caused by modulating a wavelength of the radiation. This makes possible to determine a distance between the detection system and the external object, in particular an absolute distance. And it makes possible to determine a velocity of the external object (relative to the detection system), in particular an absolute velocity. To be more precisely, only velocity components are detectable which are directed along (and thus parallel to) the direction of propagation of the radiation where the radiation interacts with the external object. The external object, more precisely, is the object with which the radiation emitted from the detection system interacts (e.g., by scattering or reflection) before it is coupled back into the detection system (where it causes the self-mixing interferometry signal. The external object, more precisely, is located in the user's environment. Modulating the wavelength of the radiation can be accomplished, e.g., by changing a length (more particularly an optical length) of a cavity of the radiation source. This change in length can be caused by, e.g., varying an operation voltage or an operation current of the radiation source. This can be readily accomplished, e.g., in case of a VCSEL as the radiation source. According to at least one embodiment of the detection system, the volume phase hologram and the radiation source are fixed together with the waveguide. In particular, the radiation source may be mechanically stably connected to the waveguide during production of the detection system. Thus, the spatial relationship between these elements and the beam path from the radiation source to the volume phase hologram may be defined during production. During operation of the detection system an unintended displacement of the volume phase hologram with respect to the radiation source can be avoided or at least greatly reduced.

[0060] Further, a head-worn device comprising a detection system is speci fied. In particular, the detection system may be embodied as described above. For example, the head-worn device is a headset, a pair of glasses, a pair of smart glasses or a helmet.

[0061] For example, the detection system may be used for augmented reality (AR ), mixed reality (MR ) or extended reality ( XR ) applications. In particular, the detection system may be designed such that the waveguide and all optical elements located within a field of view of the user, for instance one or more volume phase holograms, are transparent so that the user ' s vision is not, or at least not signi ficantly, disturbed.

[0062] According to at least one embodiment of the head-worn device the waveguide and all optical elements of the detection system located within a field of view of the user wearing the head-worn device are transparent to light in the visible spectral range. This way, it can be achieved that said user's vision ( through the head-worn device ) is not disturbed, at least not signi ficantly. In this regard, the detection system can be, as far as within the user' s field of view, largely or even fully invisible to the user wearing the head-worn device.

[0063] According to at least one embodiment of the head-worn device, the detection system is integrated into the head-worn device such that the volume phase hologram overlaps with a lens of the head-worn device in a view onto the world side of the waveguide. Thus, the region ( s ) where the radiation is coupled out from the waveguide or coupled back into the waveguide may overlap with the transparent lens of the head-worn device. Consequently, a frame of the head-worn device that supports the glasses does not require any openings in order to enable the emission and / or detection of the radiation. This facilitates an inconspicuous integration of the detection system.

[0064] According to at least one embodiment of the head-worn device, the detection system is integrated into the head-worn device comprising a transparent lens, wherein the VPH and at least a portion of the waveguide, more particularly the waveguide in full, is integrated into the lens. This way, the radiation can be emitted from ( and be received by) the detection system within the user' s field of view. A user' s view through the lens ( and through the VPH and the waveguide ) can be undisturbed by the detection system, at least largely undisturbed.

[0065] Features described above in connection with at least one embodiment of the detection system or the head-worn device can be combined with other features described in connection with at least one embodiment of the detection system or the head-worn device unless they are contradictory.

[0066] Further features and configurations wil l become apparent from the subsequent description of the exemplary embodiments in connection with the figures.

[0067] In the exemplary embodiments and figures similar or similarly acting constituent parts are provided with the same reference signs. Generally, only the di fferences with respect to the individual exemplary embodiments are described. Unless speci fied otherwise, the description of a part or aspect in one exemplary embodiment applies to a corresponding part or aspect in another exemplary embodiment as well. In the Figures:

[0068] Figures 1A and 1B show an exemplary embodiment of a head-worn device comprising a detection system in a side view ( Figure 1A) and a plan view ( Figure 1B);

[0069] Figure 2 shows beams emitted during operation of the detection system according to the exemplary embodiment of Figures 1A and 1B;

[0070] Figures 3A and 3B show an exemplary embodiment of a head-worn device comprising a detection system in a side view ( Figure 3A) and a plan view ( Figure 3B );

[0071] Figure 4 shows an exemplary embodiment of a detai l of the detection system in a sectional view;

[0072] Figure 5 shows an exemplary embodiment of a detai l of the detection system in a sectional view; and

[0073] Figures 6A to 6C show di fferent examples of shapes of a waveguide.

[0074] The figures are schematic representations. The elements illustrated in the figures and thei r si ze relationships among one another are not necessarily true to scale. Rather, individual elements may be represented with a si ze exaggerated in at least one dimension for the sake of better representability and / or for the sake of better understanding.

[0075] An exemplary embodiment of a head-worn device 10 with a detection system 1 is schematically illustrated in Figures 1A and 1B. Exemplarily, the head-worn device 10 is configured as a pair of glasses with a f rame 11 and lenses 12.

[0076] However, the detection system 1 may also be used for other head-worn devices such as a headset or any other head-worn device configured for augmented reality, extended reality, or mixed reality applications.

[0077] The detection system 1 comprises a radiation source 2 configured to emit a radiation 7, a waveguide 3 extending between a user side 31 and a world side 32 and a volume phase hologram 4. The waveguide 3 provides a propagation medium between the radiation source 2 and the volume phase hologram. The volume phase hologram 4 is conf igured to couple out the radiation 7 through the world side 32 of the waveguide 3. The detection system 1 is configured to provide a sel f-mixing interf erometry signal in response to the radiation ref lected off or scattered at an external obj ect 9 and coupled back through the world side 32 of the waveguide 3 into the radiation source 2.

[0078] The detection system 1 of the exemplary embodiment of Figures 1A and IB further includes two further radiation sources 25 and two further volume phase holograms 41.

[0079] As schematically illustrated in Figure 1B, the radiation 7 emitted by the radiation source 2 is guided within the waveguide 3 from the radiation source 2 to the volume phase hologram 4 due to total internal reflection. The further portions 75 of the radiation emitted by the further radiation sources 25 are guided via the waveguide 3 to the further volume phase holograms 41. Thus, each of the volume phase holograms 4, 41 is irradiated by a dedicated radiation source

[0080] In the exemplary embodiment of Figure 1B, the volume phase hologram 4 and the further volume phase hologram 41 are configured as transmission volume phase holograms located at the world side 32 of the waveguide 3.

[0081] However, the volume phase hologram 4 and the further volume phase holograms 41 may also be arranged on the user side 31 and be configured as reflection volume phase holograms. In both cases, the radiation 7 guided within the waveguide 3 is coupled out through the world side 32 of the waveguide 3 to irradiate di f ferent spots located in front of the user during operation of the head-worn device 10.

[0082] As illustrated in Figures 1B and 2, the volume phase hologram 4 and the further volume phase holograms 41 each provide a beam 71 wherein the beams 71 may di ffer from one another with respect to an emission direction and / or with respect to a focal distance 79 from the world side 32 of the waveguide 3. By increasing the number of beams 71, the reliability of the detection of an external obj ect 9 in front of the user can be increased.

[0083] Radiation reflected of f or scattered at an external obj ect 9 and coupled back into the radiation source 2 causes an optical interference with the original radiation within a cavity 21 of the radiation source 2, resulting in a self-mixing interferometry signal ( cf. Fig. 4 ). The sel f-mixing interferometry signal may provide information on a relative movement of the external obj ect 9 with respect to the user. A change in a distance and / or a relative velocity between the detection system 1 and the external obj ect 9 can be derived from the sel f-mixing interferometry signal that reports on a change of optical path di fference over time.

[0084] This change can be measured with a high signal-to-noise ratio and exploited for monitoring the environment in front of the user, in particular because of the large numerical aperture provided by the volume phase hologram 4 and minimal losses of the radiation within the waveguide 3 on its way back to the radiation source 2.

[0085] Accordingly, further portions 75 of the radiation 7 emitted by and reflected or scattered back to the further radiation sources 25 causes an SMI signal.

[0086] For example, the radiation source 2 and the further radiation sources 25 may be configured as vertical cavity surface¬ emitting lasers. The radiation source 2 and the further radiation sources 25 may also be integrated in a single semiconductor laser chip having a plurality of emission regions. For example, a VCSEL array may be used.

[0087] In the exemplary embodiment of Figures 1A and IB, the volume phase hologram 4 and the further volume phase holograms 41 are located in separate optical paths. However, two or more volume phase holograms may be located within the same optical path. In this case, the optical function to be obtained can be collectively provided by the combination of volume phase holograms 4, 41.

[0088] At the volume phase hologram 4, the radiation propagating in the waveguide 3 and impinging onto the volume phase hologram 4 may be deflected with a high ef ficiency so that almost the complete impinging radiation may be coupled out from the waveguide 3 through the world side 32 of the waveguide 3. This likewise applies to the further portions 75 emitted by the further radiation sources 25 impinging onto the respective further volume phase hologram 24.

[0089] In this exemplary embodiment, the radiation 7 and the further portion 75 use di f f erent volume phase holograms 4, 41 to irradiate di fferent spots in front of the user. The further volume phase holograms 41 have no, or at least no signi f icant, impact on the radiation 7 of the radiation source 2 on its way to the external obj ect 9 and back.

[0090] Likewise, the volume phase hologram 4 has no, or at least no signi f icant, impact on the further portions 75 of the radiation emitted by the further radiation sources 25. The radiation source 2 and the further radiation sources 25 may emit radiation with the same peak emission wavelength or with di fferent peak emission wavelengths.

[0091] Alternatively, the further portions 75 of the radiation 7 may be provided by a single radiation source 2, for example by splitting the radiation into two or more portions irradiating the volume phase hologram 4 and the further volume phase holograms 41.

[0092] The volume phase hologram 4 and the further volume phase holograms 41 are arranged laterally side by side so that these volume phase holograms can be produced independently from one another. However, they may also be produced in the same holographic film.

[0093] The waveguide 3 is also part of an optical path for the radiation 7 returning from the external object 9, in P5692-PCT TK / Dec. 2025

[0094] particular between the volume phase hologram 4 and the radiation source 2 as wel l as between the further volume phase holograms 41 and the further radiation sources 25.

[0095] In particular, the waveguide 3 can be used for a back-and- forth path of the radiation, wherein the radiation travels two times the same path through the waveguide 3.

[0096] Consequently, the optical path from the external obj ect 9 back to the radiation source 2 or to the further radiation sources 25 does not require any optical elements in addition to those optical elements used for the optical paths from the radiation source 2 and the further radiation sources 25 towards the external ob ect 9.

[0097] For example, the waveguide 3 may have a thickness in a range from 0. 1 mm to 10 mm. For example, the waveguide 3 comprises a glass or a plastics material transparent to the radiation

[0098] In the exemplary embodiment shown in Figure 1B, the radiation 7 is coupled into the waveguide 3 at the user side 31 of the waveguide 3. However, the radiation may also be coupled into the waveguide 3 at the world side 32 or at a side face of the waveguide 3.

[0099] As illustrated in the detai l of Figure 4, the detection system 1, in particular the radiation source 2, may comprise a sensing module 22 to obtain the sel f-mixing interferometry signal. The radiation source 2 further comprises a cavity 21 representing a resonator of a laser such

[0100]

[0101] a VCSEL. For easier representation, the cavity 21 and the sensing module 22 are not explicitly reproduced in the further f igures.

[0102] The sensing module 22 is configured to provide the signal correlated to a change in optical path length of the radiation returning from the external obj ect 9 and coupled back into the cavity 21. The returning radiation interferes with the radiation within the cavity 21 of the radiation source 2, thereby causing a sel f-mixing interference providing information on a relative movement of the external ob j ect 9.

[0103] For example, the sensing module 22 comprises a photodiode to detect an output intensity of the radiation 7. The photodiode may be integrated into the laser chip or be provided as a separate component. The sel f-mixing interference causes a modulation of the output intensity. A number or a frequency of interference fringes detectable in the output intensity of the radiation 7 may be used to derive information on the external obj ect 9.

[0104] Alternatively, the sensing module 22 may be configured to derive the self-mixing interferometry signal by monitoring an electrical operation parameter such as a current or a voltage of the radiation source 2. These electrical operation parameters are likewise modulated due to sel f-mixing interference effects within the cavity 21.

[0105] As illustrated in Figure 1A, the volume phase hologram 4 and the further volume phase holograms 41 defining the output region of the emitted radiation 7 during operation overlap with the lens 12 of the head-worn device 10. These volume P5692-PCT TK / Dec. 2025

[0106] phase holograms are further used to couple the radiation returning from the external obj ect 9 back into the waveguide 3 towards the radiation source 2. Consequently, the detection system 1 does not require any openings within the frame 11 to emit or receive radiation. Further, the waveguide 3 can be designed such that the radiation source 2 does not negatively affect the optical appearance of the head-worn device 10 or the user' s vision through the lenses 12.2.

[0107] The optical function to be performed by the volume phase hologram 4 and the further volume phase holograms 41 can be defined in a highly precise manner during production of the volume phase holograms 4, 41. A thickness of the volume phase hologram 4, i. e. an extension of the volume phase hologram along a normal to the waveguide 3, is large compared to the wavelength of the radiation 7 emitted by the radiation source 2 during operation. For example, the thickness is at least by a factor of 2 or at least by a factor of 10 larger than the wavelength of the radiation of the radiation source 2.

[0108] For example, the emission direction with respect to the waveguide 3 and / or the focal distance from the world side 32 of the waveguide 3 may be reliably defined. For example, a focal distance 79 of at least one beam 71 is in a range from 10 cm t o 10 m.

[0109] The detection system 1 may further include an incoupling optical element 5 arranged in the beam path from the radiation source 2 to the waveguide 3.

[0110] Figures 4 and 5 illustrate two examples of an incoupling

[0111]

[0112] element P5692-PCT TK / Dec. 2025

[0113] In the exemplary embodiment shown in Figure 4, the incoupling optical element 5 is a prism. The incoupling optical element 5 is configured such that the radiation from the radiation source 2 is coupled into the waveguide 3 at an incoupling angle with respect to a normal to the waveguide at this position of the waveguide 3, which is equal to or larger than the critical angle for total internal reflection.

[0114] The waveguide 3 and the incoupling optical element 5 are configured such that the radiation coupled into the waveguide 3 impinges onto the volume phase hologram 4 after a predetermined number of total internal reflections at the user side 31 and the world side 32. This can be obtained, for example, by appropriately selecting waveguide parameters such as the thickness or the refractive index and / or the angle at which the radiation is coupled into the waveguide 3 and / or a distance between the radiation source 2 and the volume phase hologram 4. Thus, the radiation 7 propagates within the waveguide 3 along a predetermined beam path.

[0115] In the exemplary embodiment of Figure 5, the incoupling optical element 5 comprises an additional volume phase hologram configured as a transmission volume phase hologram 43. Alternatively, a di ffractive optical element such as a di ffraction grating may be used.

[0116] Further, a beam shaping optics 6 is arranged between the radiation source 2 and the incoupling optical element 5 in the example of Figure 5. For example, the beam shaping optics 6 is a lens that collimates the radiation 7.

[0117] Such a beam shaping optics 6 may also be used in connection with other incoupling optical elements

[0118]

[0119] Further, the beam shaping optics 6 may ful f il other c optical functions. For example, the beam shaping optics 6 ma’> converge or focus or diverge the radiation 7.

[0120] The radiation source 2 and the further radiation source 25 illustrated in Figures 1A and IB may use separate incoupling optical elements or a common incoupling optical element wherein the incoupling optical element ( s ) may be configured as described in connection with Figures 4 or 5, for instance.

[0121] In the exemplary embodiments of Figures 1A and IB, the waveguide 3 is curved. However, other shapes may also be used for the waveguide 3.

[0122] Examples of waveguide shapes are illustrated in Figures 6A to 6C. In Figure 6A the waveguide 3 is curved. In the example of Figure 6B, the waveguide has a wedge shape. Alternatively, the waveguide 3 may be flat.

[0123] In the example of Figure 6C, the waveguide 3 comprises a plurality of parts, for example a first waveguide part 33 and a second waveguide part 34. For example, the first waveguide part 33 has a lens shape and the second waveguide part 34 has a wedge shape. These and other shapes of the waveguide 3 may apply to al l exemplary embodiments of the detection system 1.

[0124] The exemplary embodiment of Figures 3A and 3B essentially corresponds to the exemplary embodiment of Figures 1A and IB.

[0125] In contrast, the detection system 1 comprises a volume phase hologram 4 that includes a plurality of multiplexed optical functions. During production, the same holographic film is exposed such that multiplexed optical functions are provided P5692-PCT TK / Dec. 2025

[0126] within the same holographic film. As in the exemplary embodiment of Figures 1A and IB, the volume phase hologram 4 with multiplexed optical functions may be used to provide several beams 71 that di ffer from one another with respect to the emission angle and / or with respect to the focal distance 79.

[0127] As illustrated in Figures 3A and 3B, a single radiation source 2 is sufficient to illuminate the volume phase hologram 4.

[0128] By means of the described detection system, the user may be provided with information on external obj ects. For example, the user can be warned i f he is approaching a wall or i f an external obj ect is moving towards the user.

[0129] One or more volume phase holograms 4, 41 can be used to focus di f ferent beams at di f ferent depths tor an improved threedimensional sensing performance.

[0130] The detection system 1 can be integrated into a head-worn device 10 such that a high sensing performance can be obtained without negatively af f ecting the user' s vision or the optical appearance of the head-worn device 10.

[0131] The invention described herein is not restricted by the description given with reference to the exemplary embodiments. Rather, the invention encompasses any novel feature and any combination of features, including in particular any combination of f eatures in the claims, even i f this feature or this combination is not itsel f explicitly indicated in the claims or exemplary embodiments. Re f erences

[0132] 1 detection system

[0133] 10 head-worn device

[0134] 11 frame

[0135] 12 lens

[0136] 2 radiation source

[0137] 21 cavity

[0138] 22 sensing module

[0139] 25 further radiation source

[0140] 3 waveguide

[0141] 31 user side

[0142] 32 world side

[0143] 33 first waveguide part

[0144] 34 second waveguide part

[0145] 4 volume phase hologram

[0146] 41 further volume phase hologram

[0147] 43 transmission volume phase hologram 5 incoupling optical element

[0148] 6 beam shaping optics

[0149] 7 radiation

[0150] 71 beam

[0151] 75 further portion of radiation

[0152] 79 focal distance

[0153] 9 external obj ect

Claims

P5692-PCT TK / Dec. 2025Cl aims1. A detect i on system ( 1 ) for a head-worn devi ce ( 1 0 ), compri s i ng:a radi ation source ( 2 ) conf igured to emi t aradi ati on ( 7 );a waveguide ( 3 ) extending between a us er s ide ( 31 ) and a world s ide ( 32 ); anda volume pha s e hologram ( 4 );wherei nthe waveguide ( 3 ) provides a propagation medium between the radi ati on source ( 2 ) and the vol ume phas e hol ogram ( 4 );the volume pha s e hologram ( 4 ) i s conf igured to coupl e out the radi ation ( 7 ) through the world s ide ( 32 ) o f the waveguide ( 3 ); andthe detection system ( 1 ) i s conf igured to provide a s el f -mixing interf erometry s ignal in respons e to the radi ati on re fl ected o f f o r s cattered at an externa lobj ect ( 9 ) and coupl ed back through the world s ide ( 32 ) o f the waveguide ( 3 ) into the radi ation source ( 2 );i n parti cul a r wherei n at l east a porti on o f the radi ati on emi tted through the world s ide ( 32 ) o f the waveguide ( 3 ) has a focal di stance f rom the world s ide o f the waveguide in a range from 1 0 cm to 1 0 m.

2. The detection system according to cl aim 1,wherein the radi ati on ( 7 ) travel s two times the s ame path through the waveguide ( 3 ) on i ts way from the radi ati on source ( 2 ) to the externa l obj ect ( 9 ) and back; i n parti cul a r wherein a path o f the radi ation ( 7 ) f rom the radi ation source ( 2 ) to the externa l obj ect ( 9 ) i s identi ca l to a path o f the radi ati on ( 7 ) from the externa l obj ect ( 9 ) back to the radi ation source ( 2 ).

3. The detect i on system accordi ng to cl aim 1 or 2, wherein the waveguide i s transparent to l i ght i n the vi s ibl e spectra l range; i n parti cul a r wherein al so the vol ume phas e hologram ( 4 ) i s transparent to l ight in the vi s ibl e spectral range.

4. The detection system according to any one o f the preceding cl aims,wherei n the vol ume phas e hol ogram ( 4 ) compri s es at l east two multipl exed opti cal functions.

5. The detecti on system accordi ng to any one o f the precedi ng cl aims,wherein the detecti on system ( 1 ) i s con fi gured to emi t radi ati on through the world s ide ( 32 ) o f the waveguide ( 3 ) along at l east two beams ( 71 ), wherein the beams ( 71 ) di f f er from one anothe r wi th respect to an emi s s i on di recti on and / or a foca l di stance ( 7 9 ) from the world s ide ( 32 ) o f the waveguide ( 3 ).

6. The detecti on system accordi ng to any one o f the precedi ng cl aims,wherein the detecti on system ( 1 ) compri s es a furthe r vol ume phas e hol ogram ( 41 ).

7. The detecti on system accordi ng to cl aim 5 and cl aim 6, wherein the vol ume phas e hol ogram ( 4 ) and the furthe r vol ume phas e hol ogram ( 41 ) are con fi gured to provide the at l east two beams ( 71 ).

8. The detection system according to claim 6 or 7,wherein at l east a part o f the volume phas e hologram ( 4 ) i s l ateral l y spaced from the furthe r vol ume phas e hol ogram ( 41 ).

9. The detecti on system accordi ng to any one o f cl aims 6 to 8,wherein the vol ume phas e hol ogram ( 4 ) and the furthe r vol ume phas e hol ogram ( 41 ) are formed i n a common hol ographi c f i lm ( 4 0 ).1 0. The detecti on system accordi ng to any one o f the preceding cl aims,wherein the detecti on system ( 1 ) compri s es a furthe r radi ati on source ( 25 ) con fi gured to provide a furthe r portion ( 75 ) o f the radi ation ( 7 ).

11. The detecti on system accordi ng to cl aim 1 0 with back re f erence to any one o f cl aims 6 to 9,wherein the radi ati on source ( 2 ) i s con fi gured to i rradi ate the vol ume phas e hol ogram ( 41 ) and the furthe r radi ati on source i s conf igured to i rradi ate the f urther volume phas e hol ogram ( 41 ).

12. The detection system according to any one o f the precedi ng cl aims,wherein the detecti on system ( 1 ) compri s es an i ncoupl i ng opti cal el ement ( 5 ) for coupl ing the radi ation o f the radi ati on source ( 2 ) i nto the waveguide ( 3 ).

13. The detecti on system accordi ng to any one o f the preceding cl aims,wherein the detecti on system i s con fi gured to detect a change i n a di stance and / or a rel ative vel oci ty between the detection system ( 1 ) and the external obj ect ( 9 ).

14. A head-worn devi ce ( 10 ) compri s i ng a detecti on system ( 1 ) accordi ng to any one of the preceding claims.

15. The head-worn devi ce according to cl aim 14,wherein the detecti on system ( 1 ) i s i ntegrated i nto the head- worn devi ce ( 10 ) such that the vol ume phas e hol ogram ( 4 ) overl aps with a l ens ( 12 ) o f the head-worn devi ce ( 10 ) in a vi ew onto the world s ide ( 32 ) o f the waveguide ( 3 ).

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