HEAD-MOUNTED DEVICE AND METHOD FOR OPERATING A HEAD-MOUNTED DEVICE FOR FUNCTIONAL NEAR- INFRARED SPECTROSCOPY

A head-mounted device for functional near-infrared spectroscopy and a method for operating a head-mounted device for functional near-infrared spectroscopy are provided .

Functional near-infrared spectroscopy can be employed for monitoring brain functions , cognitive states and brain activity . For this purpose , di f ferent regions of a brain can be illuminated with infrared radiation . By detecting the infrared radiation that is reflected by the brain cortical , the blood oxygen consumption can be determined . The blood oxygen consumption can be determined from the di f ference in absorbance of oxyhemoglobin and deoxyhemoglobin . Thus , the brain is illuminated with two di f ferent wavelengths of infrared radiation and the absorption of the radiation of the two wavelengths is determined . Radiation sources and detectors for functional near-infrared spectroscopy can be incorporated in a head-mounted device . It is thus necessary to integrate at least radiation sources and detectors in a device that can be mounted on a head .

It is an obj ective to provide a head-mounted device for functional near-infrared spectroscopy with a compact setup . It is further an obj ective to provide a method for operating a head-mounted device for functional near-infrared spectroscopy with a compact setup . These obj ectives are achieved by the subj ect matter of the independent claims . Further developments and embodiments are described in dependent claims .

According to at least one embodiment of the head-mounted device for functional near-infrared spectroscopy ( fNIRS ) , the head-mounted device comprises at least one module . The module can be a part of the head-mounted device . The module can be integrated in the head-mounted device or it can be fixed to a part of the head-mounted device . The head-mounted device can be a portable head-mounted device . The head-mounted device can be a portable head-worn device .

The module comprises a radiation source , a radiation sensor and a carrier, wherein the radiation source and the radiation sensor are arranged on the carrier . The radiation source can be configured to emit electromagnetic radiation . In particular, the radiation source can be configured to emit electromagnetic radiation in the infrared range or in the near infrared range . The radiation source can be configured to emit electromagnetic radiation in the direction of the head, once the head-mounted device is mounted to that head . The radiation sensor can be configured to detect electromagnetic radiation . In particular, the radiation sensor can be configured to detect electromagnetic radiation in the infrared range or in the near infrared range . The radiation sensor can be a spectral sensor . With a spectral sensor continuous operation is enabled . The radiation sensor can be configured to detect electromagnetic radiation within a wavelength range . The radiation sensor can comprise a photodiode or a photodetector . The radiation sensor can comprise a single-photon avalanche diode . The carrier can comprise a printed circuit board . The radiation source and the radiation sensor can be fixed to the carrier . The radiation source and the radiation sensor can be arranged next to each other or adj acent to each other on the carrier . The module can comprise a first optical element . The radiation source can be arranged between the carrier and the first optical element . The module can comprise a further first optical element . The radiation sensor can be arranged between the carrier and the further first optical element .

With the head-mounted device fNIRS measurements can be carried out . This can mean, that the head-mounted device is configured to detect data for fNIRS measurements . It is further possible that the head-mounted device is configured to carry out processing of data detected for fNIRS measurements . For carrying out an fNIRS measurement , for example electromagnetic radiation is emitted by the radiation source in the direction of the head on which the head-mounted device is mounted . A part of the electromagnetic radiation can penetrate into the brain . A part of the electromagnetic radiation that entered into the brain is scattered or reflected and leaves the head again . At least a part of this electromagnetic radiation can be detected with the radiation sensor . I f electromagnetic radiation of two di f ferent wavelengths is employed, the di f ference of the absorbance of oxyhemoglobin and deoxyhemoglobin can be calculated . From the absorbance the volume of oxyhemoglobin and deoxyhemoglobin can be determined . For this calculation sampling techniques , algorithms , neural networks and/or fast-Fourier trans formation can be employed . In this way, an fNIRS measurement can be carried out . The fNIRS measurement is a non-invasive method . In the head-mounted device described herein for the module the radiation source and the radiation sensor are arranged on the same carrier . This means , for the module the radiation source and the radiation sensor can be monolithically integrated . Therefore , no separate components are required in the head-mounted device for radiation sources and radiation sensors . Instead, the head-mounted device comprises at least the module that comprises the radiation source and the radiation sensor . Due to this integrated arrangement of a radiation source and a radiation sensor for the module , the module can have a compact si ze . Thus , the module can have a small footprint . This is advantageous for a head-mounted device since its si ze is limited by what can be carried by and/or arranged on a head .

Another advantage of the head-mounted device is that the module can be produced by mass manufacturing . Thus , the module for the head-mounted device can be produced ef ficiently . Furthermore , an easy integration of the radiation source and the radiation sensor within the module is possible . This leads to a better performance of the modules of the head-mounted device .

The head-mounted device can be used to provide media to a user that is wearing the head-mounted device . For this purpose , the head-mounted device can comprise earphones and/or a display . Since the head-mounted device can be employed to carry out an fNIRS measurement , results of this fNIRS measurement can be used for providing particular media to a user wearing the head-mounted device . The results of an fNIRS measurement can provide information about a psychological state and/or a cognitive state of the user . It is thus possible to sense emotions of a user . The particular media provided to the user can help the user to for example return into a more comfortable emotional state . I f it is for example detected that the user experiences stress , calming music and/or videos or pictures can be provided by the headmounted device . Therefore , the head-mounted device can also be employed for medical applications , for example for recogni zing or treating a depression . It is also possible to detect pain and to thus prevent drug misuse . It is possible to detect real pain and distinguish it from pretended pain . Thus , drugs can be prescribed only i f required . Moreover, a mental state of a user can be monitored . This can help to treat di f ferent psychological situations or conditions .

It is also possible to employ the head-mounted device for monitoring brain activity, in particular for continuous monitoring of brain activity, and/or for monitoring brain functions , in particular for continuous monitoring of brain functions .

Since di f ferent emotions can be sensed in di f ferent regions of the brain the head-mounted device can comprise more than one module . The modules of the head-mounted device can be distributed over the head-mounted device . This can mean, that the modules of the head-mounted device are all arranged at di f ferent positions . This enables to monitor di f ferent emotions .

According to at least one embodiment of the head-mounted device , the head-mounted device further comprises at least one further module , wherein the further module comprises a further radiation source , a further radiation sensor and a further carrier, wherein the further radiation source and the further radiation sensor are arranged on the further carrier and the module is arranged spaced apart from the further module . The further module can be a part of the head-mounted device . The further module can be integrated in the head- mounted device or it can b fixed to a part of the head- mounted device .

The further radiation source can be configured to emit electromagnetic radiation . In particular, the further radiation source can be configured to emit electromagnetic radiation in the infrared range or in the near infrared range . The further radiation source can be configured to emit electromagnetic radiation in the direction of the head, once the head-mounted device is mounted to that head . The further radiation sensor can be configured to detect electromagnetic radiation . In particular, the further radiation sensor can be configured to detect electromagnetic radiation in the infrared range or in the near infrared range . The further radiation sensor can be a spectral sensor . This can mean, that the further radiation sensor is configured to detect electromagnetic radiation within a wavelength range . The further radiation sensor can comprise a photodiode or a photodetector . The further radiation sensor can comprise a single-photon avalanche diode . The further carrier can comprise a printed circuit board . The further radiation source and the further radiation sensor can be fixed to the further carrier . The further radiation source and the further radiation sensor can be arranged next to each other or adj acent to each other on the further carrier . The further module can comprise a second optical element . The further radiation source can be arranged between the further carrier and the second optical element . The further module can comprise a further second optical element . The further radiation sensor can be arranged between the further carrier and the further second optical element .

The module is arranged spaced apart from the further module . This can mean, that the module is arranged at a position that is di f ferent from a position where the further module is arranged .

With the head-mounted device comprising the module and the further module , brain activity can be observed in di f ferent regions of a brain .

According to at least one embodiment of the head-mounted device , the head-mounted device comprises a lock-in ampli fier that is connected with the radiation sensor and with the radiation source or the further radiation source . The lock-in ampli fier can be monolithically integrated with the radiation source and the radiation sensor . The lock-in ampli fier can be configured to synchroni ze the radiation source and the radiation sensor or the lock-in ampli fier can be configured to synchroni ze the further radiation source and the radiation sensor . In this way, the signal-to-noise ratio of the radiation sensor can be improved . The module can comprise the lock-in ampli fier .

According to at least one embodiment of the head-mounted device the further module comprises a further lock-in ampli fier . The further lock-in ampli fier can be monolithically integrated with the further radiation source and the further radiation sensor . The further lock-in ampli fier can be configured to synchroni ze the further radiation source and the further radiation sensor or the further lock-in ampli fier can be configured to synchroni ze the radiation source and the further radiation sensor .

According to at least one embodiment of the head-mounted device the head-mounted device comprises a lock-in ampli fier that is connected with the radiation source and the further radiation sensor . The lock-in ampli fier can be configured to synchroni ze the radiation source and the further radiation sensor . In this way, the signal-to-noise ratio of the further radiation sensor can be improved .

According to at least one embodiment of the head-mounted device the lock-in ampli fier is configured to synchroni ze the radiation source and the radiation sensor . In this way, the signal-to-noise ratio of the radiation sensor can be improved .

According to at least one embodiment of the head-mounted device the lock-in ampli fier is configured to synchroni ze the further radiation source and the radiation sensor . In this way, the signal-to-noise ratio of the further radiation sensor can be improved .

According to at least one embodiment of the head-mounted device the further radiation sensor is configured to detect electromagnetic radiation emitted by the radiation source . This can mean, that the further radiation sensor is configured to detect electromagnetic radiation which is first emitted by the first radiation source and then reflected by the brain cortical . The further radiation sensor is arranged spaced apart from the radiation source . It is thus possible that electromagnetic radiation emitted by the radiation source enters the head on which the head-mounted device is mounted and a part of this electromagnetic radiation can leave the head again so that it can be detected by the further radiation sensor . Since the radiation source and the further radiation sensor are arranged in di f ferent modules , the module and the further module can be arranged at a distance with each other so that the further radiation sensor is configured to detect electromagnetic radiation caused by the radiation source . That electromagnetic radiation is caused by a radiation source means that the electromagnetic radiation is first emitted by the radiation source and then reflected by the brain cortical . It is not necessary that one module has a si ze that allows to emit electromagnetic radiation and to detect that part of the electromagnetic radiation that leaves the head again . Instead, the module and the further module can each have a compact setup and they can be spaced apart from each other in such a way that electromagnetic radiation caused by the radiation source can be detected with the further radiation sensor . As the module and the further module can be positioned independently from each other, they can be positioned to optimi ze the detection of electromagnetic radiation caused by the radiation source with the further radiation sensor . It is also possible to optimi ze the positioning of the module and the further module in order to achieve an optimal penetration depth of electromagnetic radiation in the brain .

The radiation source and the further radiation sensor can form a sensing channel which can also be called optode . This means , that electromagnetic radiation emitted by the radiation source and reflected by a part of the head on which the head-mounted device is mounted is detected by the further radiation sensor . The modules of the head-mounted device can be connected with each other . Thus , the head-mounted device can be operated in a module network operation mode , in which each module can work with other modules depending on the network setup . The simplest network configuration is , that the module works together with the further module . That can mean that the further radiation sensor is configured to detect electromagnetic radiation emitted by the radiation source .

According to at least one embodiment of the head-mounted device the radiation source comprises a light-emitting diode or a laser . It is also possible that the radiation source comprises two light emitting diodes or two lasers . The lasers can in each case be a laser diode . In each case , the light emitting diodes or the lasers can be configured to emit electromagnetic radiation in the infrared range , in particular in the near infrared range . In this way, the light emitting diodes or the lasers can be employed for fNIRS measurements .

According to at least one embodiment of the head-mounted device the radiation source and the further radiation source each comprise a light-emitting diode or a laser . It is also possible that the radiation source and the further radiation source each comprise two light emitting diodes or two lasers . The lasers can in each case be a laser diode . In each case , the light emitting diodes or the lasers can be configured to emit electromagnetic radiation in the infrared range , in particular in the near infrared range . In this way, the light emitting diodes or the lasers can be employed for fNIRS measurements . According to at least one embodiment of the head-mounted device the radiation source comprises a vertical-cavity surface-emitting laser . It is also possible that the radiation source comprises two vertical-cavity surfaceemitting lasers . Each vertical-cavity surface-emitting laser can be configured to emit electromagnetic radiation in the infrared range , in particular in the near infrared range . Employing lasers as radiation sources has the advantage that the emission of electromagnetic radiation can be synchroni zed with the detection of electromagnetic radiation by the radiation sensor . Thus , the head-mounted device can be operated more ef ficiently .

According to at least one embodiment of the head-mounted device the radiation source and the further radiation source each comprise a vertical-cavity surface-emitting laser . It is also possible that the radiation source and the further radiation source each comprise two vertical-cavity surfaceemitting lasers . Each vertical-cavity surface-emitting laser can be configured to emit electromagnetic radiation in the infrared range , in particular in the near infrared range . Employing lasers as radiation sources has the advantage that the emission of electromagnetic radiation can be synchroni zed with the detection of electromagnetic radiation by the radiation sensor and the further radiation sensor . Thus , the head-mounted device can be operated more ef ficiently .

According to at least one embodiment of the head-mounted device the radiation sensor comprises a photodiode , a photodetector, a spectral sensor or a single-photon avalanche diode . According to at least one embodiment of the head-mounted device the further radiation sensor comprises a photodiode , a photodetector, a spectral sensor or a single-photon avalanche diode .

According to at least one embodiment of the head-mounted device the radiation source is configured to emit electromagnetic radiation of at least two di f ferent wavelengths . The radiation source can be configured to emit electromagnetic radiation of a first wavelength and of a second wavelength, wherein the first wavelength is di f ferent from the second wavelength . For this purpose , the radiation source can comprise two light-emitting diodes or two lasers . For the radiation source one of the light-emitting diodes or lasers can be configured to emit electromagnetic radiation of the first wavelength and the other light-emitting diode or laser can be configured to emit electromagnetic radiation of the second wavelength . The first wavelength can be at least 700 nm and at most 810 nm . The second wavelength can be between 810 nm and 900 nm .

The module can comprise the radiation source and an additional radiation source . The radiation source can be configured to emit electromagnetic radiation of the first wavelength and the additional radiation source can be configured to emit electromagnetic radiation of the second wavelength . The additional radiation source can comprise a light-emitting diode or a laser .

Electromagnetic radiation of two di f ferent wavelengths is required to carry out an fNIRS measurement . Thus , with the head-mounted device advantageously fNIRS measurements can be carried out . According to at least one embodiment of the head-mounted device the radiation source and the further radiation source are each configured to emit electromagnetic radiation of at least two di f ferent wavelengths . The radiation source and the further radiation source can each be configured to emit electromagnetic radiation of a first wavelength and of a second wavelength, wherein the first wavelength is di f ferent from the second wavelength . For this purpose , the radiation source and the further radiation source can each comprise two light-emitting diodes or two lasers . For each radiation source one of the light-emitting diodes or lasers can be configured to emit electromagnetic radiation of the first wavelength and the other light-emitting diode or laser can be configured to emit electromagnetic radiation of the second wavelength . The first wavelength can be at least 700 nm and at most 810 nm . The second wavelength can be between 810 nm and 900 nm .

The further module can comprise the further radiation source and an additional further radiation source . The further radiation source can be configured to emit electromagnetic radiation of the first wavelength and the additional further radiation source can be configured to emit electromagnetic radiation of the second wavelength . The additional further radiation source can comprise a light-emitting diode or a laser .

Electromagnetic radiation of two di f ferent wavelengths is required to carry out an fNIRS measurement . Thus , with the head-mounted device advantageously fNIRS measurements can be carried out . According to at least one embodiment of the head-mounted device the radiation source and the radiation sensor are monolithically integrated . The module can comprise a chip or can form a chip . Since the radiation source and the radiation sensor are monolithically integrated, the module can have a compact setup . This enables , that the head-mounted device has a compact setup .

According to at least one embodiment of the head-mounted device the radiation source and the radiation sensor are monolithically integrated and the further radiation source and the further radiation sensor are monolithically integrated . The module can comprise a chip or can form a chip . The further module can comprise a chip or can form a chip . Since the radiation source and the radiation sensor are monolithically integrated, the module can have a compact setup . Since the further radiation source and the further radiation sensor are monolithically integrated, the further module can have a compact setup . This enables , that the headmounted device has a compact setup .

According to at least one embodiment of the head-mounted device the radiation sensor is configured to detect electromagnetic radiation emitted by the radiation source . The radiation sensor is arranged spaced apart from the radiation source . It is thus possible that electromagnetic radiation emitted by the radiation source enters the head on which the head-mounted device is mounted and a part of this electromagnetic radiation can leave the head again so that it can be detected by the radiation sensor . The radiation source and the radiation sensor can form a sensing channel which can also be called optode . This means , that electromagnetic radiation emitted by the radiation source and transmitted by a part of the head on which the head-mounted device is mounted is detected by the radiation sensor .

According to at least one embodiment of the head-mounted device the head-mounted device comprises earphones . In other words , the head-mounted device can comprise headphones . The earphones can be arranged in such a way that they are adj acent to the ears of a user once the head-mounted device is mounted to the head of the user . The earphones can be configured to provide media, for example music . The media provided by the earphones can be selected by the head-mounted device based on results of fNIRS measurements . This has the advantage that a user does not have to choose media but suitable media depending on the determined psychological state can be provided by the earphones . It is also possible that the content provided by the earphones is adapted based on results of fNIRS measurements . For example , content can be provided by the earphones that can change or improve the mood of the user or actively reduce stress .

According to at least one embodiment of the head-mounted device the head-mounted device comprises a display . The display can be comprised by glasses of the head-mounted device . The display can phase the eyes of a user once the head-mounted device is mounted to the head of the user . The head-mounted device can comprise virtual-reality and/or arti ficial reality glasses . The display can be configured to provide content . For example , the display is configured to provide videos or pictures . The content provided by the display can be adapted to results of fNIRS measurements in the same way as described for the earphones . Thus , the display can be employed in the same way as the earphones or in an additional way to adapt the provided content to the psychological state determined by fNIRS .

According to at least one embodiment of the head-mounted device the head-mounted device comprises a control unit that is configured to control what is provided by the earphones and/or the display in dependence of a functional nearinfrared spectroscopy measurement of the head-mounted device . The control unit can comprise a microcontroller . The control unit can be configured to control the content that is provided by the earphones and/or the display . The control unit can be configured to control the content provided by the earphones and/or the display in such a way that in case an undesired psychological state is sensed by fNIRS the content is provided to improve the psychological state of the user . For example , i f stress is sensed by fNIRS , calming media such as calming music can be provided to the user . Therefore , the head-mounted device can advantageously be employed to improve the psychological state of a user . What an improvement of a psychological state is and how it can be achieved might be sub j ective .

According to at least one embodiment of the head-mounted device the head-mounted device comprises at least one of a motion sensor, an accelerometer, a gyroscope , an ambient light sensor . With at least one of these additional sensors the psychological state of a user can further be analyzed or can be analyzed with an improved accuracy . It is for example possible to detect motion sickness . Information obtained with at least one of these additional sensors can be employed for controlling media provided by the earphones and/or the display . For example , at least one of these sensors can be employed to detect the type of motion of the user, for example walking, running, cycling etc . This information can improve the analysis of the psychological state of the user . Furthermore , the signal-to-noise ratio of the fNIRS measurement can be improved and arti facts can be removed . The control unit can be configured to control the content provided by the earphones and the display in dependence of measurements of at least one of a motion sensor, an accelerometer, a gyroscope , an ambient light sensor . It is also possible to provide an alert signal to the user based on measurements of at least one of a motion sensor, an accelerometer, a gyroscope , an ambient light sensor . This can for example be the case i f motion sickness or nausea is sensed . The module and/or the further module can comprise at least one of a motion sensor, an accelerometer, a gyroscope , an ambient light sensor .

According to at least one embodiment of the head-mounted device the head-mounted device comprises a processing unit that is connected with the radiation sensor . The processing unit can be configured to process or to analyze signals detected by the radiation sensor . The processing unit can be connected with the lock-in ampli fier and/or with a further lock-in ampli fier . The processing unit can be configured to determine results of an fNIRS measurement . This can mean, that the processing unit is configured to determine the volume of oxyhemoglobin and deoxyhemoglobin within an area of the brain . The processing unit can be connected with the control unit . The processing unit can be connected with the control unit via a data connection . The processing unit can be configured to transmit data to the control unit . For example , the processing unit can be configured to transmit data about fNIRS measurements to the control unit . The control unit can be configured to transmit data received from the processing unit to an external device , such as a cloud or a cloud application . The processing unit can be employed to process detected data and to determine content to be provided to a user based on the results of the data processing .

According to at least one embodiment of the head-mounted device the head-mounted device comprises a processing unit that is connected with the radiation sensor and the further radiation sensor . The processing unit can be configured to process or to analyze signals detected by the radiation sensor and signals detected by the further radiation sensor . The processing unit can be configured to determine results of an fNIRS measurement . This can mean, that the processing unit is configured to determine the volume of oxyhemoglobin and deoxyhemoglobin within an area of the brain . The processing unit can be connected with the control unit . The processing unit can be connected with the control unit via a data connection . The processing unit can be configured to transmit data to the control unit . For example , the processing unit can be configured to transmit data about fNIRS measurements to the control unit . The control unit can be configured to transmit data received from the processing unit to an external device , such as a cloud or a cloud application . The processing unit can be employed to process detected data and to determine content to be provided to a user based on the results of the data processing . The head-mounted device can comprise a synchroni zation unit that is connected with the modules and the processing unit . The synchroni zation unit can be configured to define the exact emitting timing of the radiation sources in the module network . The module can comprise the synchroni zation unit . Modules , which comprise a synchroni zation unit are master modules in the network . According to at least one embodiment of the head-mounted device the radiation source is configured to emit pulsed electromagnetic radiation . This can mean that the radiation source is configured to emit electromagnetic radiation with a varying intensity . The head-mounted device can in this case be operated in a pulsed operation mode . The intensity can vary regularly . The time during which electromagnetic radiation is emitted by the radiation source can be synchroni zed with the time during which a corresponding radiation sensor detects electromagnetic radiation caused by the radiation source . Thus , it is not necessary that the radiation sensor detects electromagnetic radiation continuously . Instead, it is only necessary for the radiation sensor to detect electromagnetic radiation during the time that a pulse of electromagnetic radiation from the radiation source reaches the respective radiation sensor . With this , the signal-to-noise ratio of the radiation sensors can be improved .

According to at least one embodiment of the head-mounted device the radiation source and the further radiation source are configured to emit pulsed electromagnetic radiation . This can mean that the radiation source and the further radiation source are configured to emit electromagnetic radiation with a varying intensity . The intensity can vary regularly . The time during which electromagnetic radiation is emitted by a radiation source can be synchroni zed with the time during which a corresponding radiation sensor detects electromagnetic radiation emitted by the radiation source . Thus , it is not necessary that the radiation sensor detects electromagnetic radiation continuously . Instead, it is only necessary for the radiation sensor to detect electromagnetic radiation during the time that a pulse of electromagnetic radiation from the corresponding radiation source reaches the respective radiation sensor . With this , the signal-to-noise ratio of the radiation sensors can be improved .

According to at least one embodiment of the head-mounted device the head-mounted device comprises a band that extends over a region of a head when the head-mounted device is mounted on the head, wherein the module and/or the further module is fixed to the band . The band can comprise a flexible material . The band can connect a part of the head-mounted device arranged at a front side of a head once the headmounted device is mounted on the head with a part of the head-mounted device arranged at a back side of the head . Once the head-mounted device is mounted, the band can extend over the top region or another region of the head and can be adapted to the shape of the head . The band can thus provide more stability for mounting the head-mounted device on a head . I f regions of interest of the brain are located close to the position of the band it is advantageous to arrange the module and/or the further module fixed to the band . Thus , these regions of interest can be analyzed via fNIRS .

According to at least one embodiment of the head-mounted device , the head-mounted device is free of a connection to an external energy source . This can mean, that the head-mounted device is independent of an external energy source . It is possible that the head-mounted device is not connected with an external energy source . The head-mounted device can comprise an energy source as for example a battery . The module and the further module can be connected with the energy source of the head-mounted device . The energy source can be configured to provide the module and the further module with energy . The energy source can be configured to provide at least one of the control unit , the processing unit , the synchroni zation unit , earphones and a display with power . The head-mounted device is thus advantageously independent of an external energy source . This enables to use the head-mounted device in mobile applications and it allows the user to move more freely .

Furthermore , a method for operating a head-mounted device for functional near-infrared spectroscopy is provided . The headmounted device can preferably be employed for the method for operating a head-mounted device for functional near-infrared spectroscopy described herein . This means all features disclosed for the head-mounted device are also disclosed for the method for operating a head-mounted device for functional near-infrared spectroscopy and vice-versa .

According to at least one embodiment of the method for operating a head-mounted device for functional near-infrared spectroscopy, the method comprises emitting electromagnetic radiation by a radiation source , wherein the radiation source is comprised by a module , the module further comprising a radiation sensor and a carrier, wherein the radiation source and the radiation sensor are arranged on the carrier . It is possible that electromagnetic radiation of the first wavelength is emitted by the radiation source and electromagnetic radiation of the second wavelength is emitted by an additional radiation source of the module .

The method further comprises detecting electromagnetic radiation by the radiation sensor, wherein the module is comprised by the head-mounted device . With the method for operating a head-mounted device , the head-mounted device described herein can be operated . Thus , the method for operating a head-mounted device has the same advantages as the head-mounted device .

According to at least one embodiment of the method, the method further comprises detecting electromagnetic radiation emitted by the further radiation source by the radiation sensor . This can mean that the method further comprises detecting electromagnetic radiation caused by the further radiation source by the radiation sensor .

According to at least one embodiment of the method, the method further comprises emitting electromagnetic radiation by a further radiation source . The further radiation source is comprised by a further module that also comprises a further radiation sensor and a further carrier, wherein the further radiation source and the further radiation sensor are arranged on the further carrier . It is possible that electromagnetic radiation of the first wavelength is emitted by the further radiation source and electromagnetic radiation of the second wavelength is emitted by an additional further radiation source of the further module .

According to at least one embodiment of the method, the method further comprises detecting electromagnetic radiation emitted by the further radiation source by the radiation sensor . This can mean that the method further comprises detecting electromagnetic radiation caused by the further radiation source by the radiation sensor . The radiation sensor is arranged spaced apart from the further radiation source . It is thus possible that electromagnetic radiation emitted by the further radiation source enters the head on which the head-mounted device is mounted and a part of this electromagnetic radiation can leave the head again so that it can be detected by the radiation sensor . Since the further radiation source and the radiation sensor are arranged in di f ferent modules , the module and the further module can be arranged at a distance from each other so that the radiation sensor is configured to detect electromagnetic radiation caused by the further radiation source . As the module and the further module can be positioned independently from each other, they can be positioned to optimi ze the detection of electromagnetic radiation caused by the further radiation source with the radiation sensor .

The module is arranged spaced apart from the further module .

The module and the further module are comprised by the headmounted device .

According to at least one embodiment of the method content is provided by earphones and/or a display of the head-mounted device , wherein the content is changed in dependence of a functional near-infrared spectroscopy measurement of the head-mounted device . This can mean, that via an fNIRS measurement a cognitive state is sensed that is undesired . In this case , the content provided by the head-mounted device can be changed . Thus , it is possible that the content provided by the head-mounted device is changed under predefined conditions , which are for example particular psychological states . These states can be undesired states as stress , motion sickness or nausea . The content provided by the head-mounted device can be changed in such a way that content is provided which is assumed to improve the psychological state of the user . Therefore , the head-mounted device can advantageously be employed to improve the psychological state of a user .

The following description of figures may further illustrate and explain exemplary embodiments . Components that are functionally identical or have an identical ef fect are denoted by identical references . Identical or ef fectively identical components might be described only with respect to the figures where they occur first . Their description is not necessarily repeated in successive figures .

With figure 1 the principle of functional near-infrared spectroscopy is explained .

Figure 2 shows an exemplary embodiment of a module .

Figure 3 shows an exemplary embodiment of a further module .

Figure 4 shows another exemplary embodiment of a module .

Figure 5 shows another exemplary embodiment of a further module .

Figure 6 shows an exemplary embodiment of a head-mounted device .

Figure 7 shows another exemplary embodiment of a headmounted device .

Figure 8 shows another exemplary embodiment of a module . Figure 9 shows another exemplary embodiment of a further module .

Figure 10 shows a lock-in ampli fier .

Figure 11 shows another exemplary embodiment of a module .

Figure 12 shows another exemplary embodiment of a further module .

With figures 13 and 14 exemplary embodiments of the method for operating a head-mounted device for functional near-infrared spectroscopy are described .

Figure 15 shows another exemplary embodiment of a headmounted device .

With figure 1 the principle of functional near-infrared spectroscopy is explained . In figure 1 a cross section through a part of a head 37 of a person with a brain 38 is depicted . On the left side of figure 1 electromagnetic radiation, for example in the near infrared range , enters the brain 38 . The electromagnetic radiation is partially reflected and/or scattered within the brain 38 and a part of the electromagnetic radiation leaves the brain 38 again on the right side of figure 1 . This electromagnetic radiation that leaves the brain 38 again, can be detected . The electromagnetic radiation comprises two di f ferent wavelengths and from their absorbance the brain 38 activity in the region where the electromagnetic radiation penetrated the brain 38 can be calculated . As di f ferent psychological states lead to brain 38 activity in di f ferent regions of the brain 38 , determining the brain 38 activity in di f ferent regions allows to determine the psychological state of the person .

Figure 2 shows an exemplary embodiment of a module 21 of an exemplary embodiment of a head-mounted device 20 . The module 21 comprises a carrier 25 . On the carrier 25 a radiation source 23 and a radiation sensor 24 are arranged next to each other . On the radiation source 23 a first optical element 39 is arranged so that the radiation source 23 is arranged between the carrier 25 and the first optical element 39 . On the radiation sensor 24 a further first optical element 40 is arranged so that the radiation sensor 24 is arranged between the carrier 25 and the further first optical element 40 . The radiation source 23 can comprise a light-emitting diode or a laser, for example a vertical-cavity surface-emitting laser . The radiation sensor 24 can comprise a photodiode or a photodetector or a spectral sensor or a single-photon avalanche diode . The radiation source 23 is configured to emit electromagnetic radiation of at least two di f ferent wavelengths . The radiation source 23 and the radiation sensor 24 are monolithically integrated . The radiation source 23 can be configured to emit pulsed electromagnetic radiation .

Figure 3 shows an exemplary embodiment of a further module 22 of an exemplary embodiment of a head-mounted device 20 . The further module 22 comprises a further carrier 28 . On the further carrier 28 a further radiation source 26 and a further radiation sensor 27 are arranged next to each other . On the further radiation source 26 a second optical element 41 is arranged so that the further radiation source 26 is arranged between the further carrier 28 and the second optical element 41 . On the further radiation sensor 27 a further second optical element 42 is arranged so that the further radiation sensor 27 is arranged between the further carrier 28 and the further second optical element 42 . The further radiation source 26 can comprise a light-emitting diode or a laser, for example a vertical-cavity surfaceemitting laser . The further radiation sensor 27 can comprise a photodiode or a photodetector or a spectral sensor or a single-photon avalanche diode . The further radiation source 26 is configured to emit electromagnetic radiation of at least two di f ferent wavelengths . The further radiation source 26 and the further radiation sensor 27 are monolithically integrated . The further radiation source 26 can be configured to emit pulsed electromagnetic radiation .

Figure 4 shows a top view on another exemplary embodiment of the module 21 of an exemplary embodiment of the head-mounted device 20 . The module 21 comprises the carrier 25 on which the radiation source 23 and an additional radiation source 43 are arranged next to each other . The radiation source 23 is configured to emit electromagnetic radiation of a first wavelength and the additional radiation source 43 is configured to emit electromagnetic radiation of a second wavelength that is di f ferent from the first wavelength . On each of the radiation source 23 and the additional radiation source 43 a first optical element 39 can be arranged . Next to the radiation source 23 and the additional radiation source 43 the radiation sensor 24 is arranged . The further first optical element 40 is arranged on the radiation sensor 24 .

Figure 5 shows a top view on another exemplary embodiment of the further module 22 of an exemplary embodiment of the headmounted device 20 . The further module 22 comprises the further carrier 28 on which the further radiation source 26 and an additional further radiation source 44 are arranged next to each other . The further radiation source 26 is configured to emit electromagnetic radiation of a first wavelength and the additional further radiation source 44 is configured to emit electromagnetic radiation of a second wavelength that is di f ferent from the first wavelength . On each of the further radiation source 26 and the additional further radiation source 44 a second optical element 41 can be arranged . Next to the further radiation source 26 and the additional further radiation source 44 the further radiation sensor 27 is arranged . The further second optical element 42 is arranged on the further radiation sensor 27 .

Figure 6 shows an exemplary embodiment of the head-mounted device 20 for fNIRS . The head-mounted device 20 comprises at least one module 21 and at least one further module 22 . In figure 6 , the head-mounted device 20 comprises three modules 21 and two further modules 22 . This is however only an example , the head-mounted device 20 can comprise any number of modules 21 and further modules 22 . The head-mounted device 20 partially surrounds the head 37 of a user once it is mounted to that head 37 of the user . The head-mounted device 20 can thus partially follow the shape of a head 37 . The modules 21 and the further modules 22 are distributed over the head-mounted device 20 . This means , the modules 21 and the further modules 22 are arranged at di f ferent positions of the head-mounted device 20 . The modules 21 and the further modules 22 are arranged spaced apart from each other . The modules 21 and the further modules 22 can each be configured to emit electromagnetic radiation in the direction of the brain 38 of the user . The head-mounted device 20 further comprises earphones 29 . The head-mounted device 20 is free of a connection to an external energy source 36 . Figure 7 shows another exemplary embodiment of the headmounted device 20 . The head-mounted device 20 comprises three modules 21 and three further modules 22 . The modules 21 and the further modules 22 are arranged at di f ferent positions of the head-mounted device 20 . The further radiation sensor 27 of at least one of the further modules 22 is configured to detect electromagnetic radiation caused by the radiation source 23 of at least one of the modules 21 . This can mean, that for each module , the radiation sensor is configured to detect electromagnetic radiation emitted by a radiation source that is not comprised by the respective module but by another module . This enables a compact si ze of the modules .

The head-mounted device 20 comprises a display 30 . The display 30 can be arranged in glasses of the head-mounted device 20 or in front of the eyes of the user once the headmounted device 20 is mounted to the head 37 of the user . The head-mounted device 20 further comprises a control unit 31 that is configured to control what is provided by the display 30 in dependence of an fNIRS measurement of the head-mounted device 20 . I f the head-mounted device 20 also comprises earphones 29 , the control unit 31 can be configured to control what is provided by the earphones 29 in dependence of an fNIRS measurement of the head-mounted device 20 . The headmounted device 20 further comprises at least one processing unit 32 that is connected with the radiation sensors 24 and the further radiation sensors 27 . The processing unit 32 can be configured to process data detected by the radiation sensors 24 and the further radiation sensors 27 . The processing unit 32 can be connected with the control unit 31 .

The head-mounted device 20 further comprises at least one sensor 33 which can be one of a motion sensor, an accelerometer, a gyroscope , an ambient light sensor . The head-mounted device 20 further comprises an energy source 36 that is configured to provide the modules 21 , the further modules 22 , the control unit 31 , the processing unit 32 , the lock-in ampli fier 34 , the synchroni zation unit and the sensor 33 with energy .

The head-mounted device 20 further comprises a band 35 that extends over a top region of a head 37 when the head-mounted device 20 is mounted on the head 37 , wherein at least one module 21 and/or at least one further module 22 is fixed to the band 35 .

With figure 7 also exemplary embodiment of the method for operating a head-mounted device 20 for functional nearinfrared spectroscopy is described . The method comprises emitting electromagnetic radiation by the radiation source 23 of at least one of the modules 21 . In a next step electromagnetic radiation caused by the radiation source 23 is detected by the further radiation sensor 27 of at least one of the further modules 22 . The method further comprises emitting electromagnetic radiation by the further radiation source 26 of at least one of the further modules 22 . In a next step electromagnetic radiation caused by the further radiation source 26 is detected by the radiation sensor 24 of at least one of the modules 21 . Content can be provided by earphones 29 and/or the display 30 of the head-mounted device 20 , wherein the content is changed in dependence of an fNIRS measurement of the head-mounted device 20 . Using the lock-in ampli fier 34 the time during which electromagnetic radiation is emitted by a radiation source can be synchroni zed with the time during which a corresponding radiation sensor detects electromagnetic radiation caused by the radiation source . Figure 8 shows another exemplary embodiment of the module 21. In comparison to the embodiment shown in figure 2, in the embodiment of figure 8, the module 21 comprises a lock-in amplifier 34. The lock-in amplifier 34 is arranged on the carrier 25. The lock-in amplifier 34 is monolithically integrated with the radiation source 23 and the radiation sensor 24.

Figure 9 shows another exemplary embodiment of the further module 22. In comparison to the embodiment shown in figure 3, in the embodiment of figure 9, the further module 22 comprises a further lock-in amplifier 45. The further lock-in amplifier 45 is arranged on the further carrier 28. The further lock-in amplifier 45 is monolithically integrated with the further radiation source 26 and the further radiation sensor 27.

Figure 10 shows a lock-in amplifier 34. The further lock-in amplifier 45 can have the same setup as the lock-in amplifier 34. The lock-in amplifier 34 comprises a first input 46 where it can receive signals from the further radiation sensor 27. The lock-in amplifier 34 comprises a second input 47 where it can receive signals from the radiation source 23. The second input 47 is connected with a phase displacement unit 48. The first input 46 and the phase displacement unit 48 are connected with a multiplier 49. The multiplier 49 is connected with a low pass filter 50. The low pass filter 50 can be connected with the processing unit 32.

Figure 11 shows a top view on another exemplary embodiment of the module 21. The only difference to the embodiment shown in figure 4 is that the module 21 comprises a lock-in amplifier 34 as described with figure 8. Figure 12 shows a top view on another exemplary embodiment of the further module 22 . The only di f ference to the embodiment shown in figure 5 is that the further module 22 comprises a further lock-in ampli fier 45 as described with figure 9 .

With figures 13 and 14 exemplary embodiments of the method for operating a head-mounted device 20 for functional nearinfrared spectroscopy are described . With figure 13 it is shown that the further radiation sensor 27 is configured to detect electromagnetic radiation caused by the radiation source 23 . Moreover, the radiation sensor 24 is configured to detect electromagnetic radiation caused by the further radiation source 26 . In figure 14 , the head-mounted device 20 comprises a plurality of modules 21 and further modules 22 that can interact in di f ferent ways , for example as shown in figure 13 .

Figure 15 shows another exemplary embodiment of the headmounted device 20 . The head-mounted device 20 comprises at least four modules 21 and any number of further modules 22 . The modules 21 and the further modules 22 are connected with a synchroni zation unit 51 . The synchroni zation unit 51 can be configured to define the exact emitting timing of the radiation sources 23 , 26 in the module network . The modules 21 , the further modules 22 and the synchroni zation unit 51 are connected with the processing unit 32 . The processing unit 32 is connected with the control unit 31 . The control unit 31 can be connected with the sensor 33 or the sensors 33 . The control unit 31 can further be connected with earphones 29 and/or a display 30 . The control unit 31 can further be connected with an external device 52 . All components of the head-mounted device 20 can be connected with the energy source 36 of the head-mounted device 20 . It will be appreciated that the disclosure is not limited to the disclosed embodiments and to what has been particularly shown and described hereinabove . Rather, features recited in separate dependent claims or in the description may advantageously be combined . Furthermore , the scope of the disclosure includes those variations and modi fications , which will be apparent to those skilled in the art . The term " comprising" , insofar it was used in the claims or in the description, does not exclude other elements or steps of a corresponding feature or procedure . In case that the terms " a" or " an" were used in conj unction with features , they do not exclude a plurality of such features . Moreover, any reference signs in the claims should not be construed as limiting the scope .

This patent application claims the priority of German patent application 102022119105 . 2 , the disclosure content of which is hereby incorporated by reference .

References

20 head-mounted device

21 module

22 further module

23 radiation source

24 radiation sensor

25 carrier

26 further radiation source

27 further radiation sensor

28 further carrier

29 earphones

30 display

31 control unit

32 processing unit

33 sensor

34 lock-in ampli fier

35 band

36 energy source

37 head

38 brain

39 first optical element

40 further first optical element

41 second optical element

42 further second optical element

43 additional radiation source

44 additional further radiation source

45 further lock-in ampli fier

46 first input

47 second input

48 phase displacement unit

49 multiplier

50 low pass filter 51 synchronization unit

52 external device