Patent Description:
Presbyopia, short-sightedness brought on by aging, is very common and applies to most of the population of age over <NUM> years. When working optimally, the human eye can focus on objects ranging from around <NUM> away to infinity. This is accomplished by the ciliary muscles changing the shape of the lens inside the eye to maintain the focus of the image onto the retina for objects at different distances. During aging the ciliary muscles suffer from a reduced ability to deform the lens and the eye progressively loses the ability to focus on closer objects.

Presbyopia has traditionally been addressed by using additional lenses in front of the eye, such as a pair of 'reading glasses' which are used when looking at close objects, or additional lenses integrated into an existing pair of glasses, such as 'bifocals' or 'varifocals'. These additional lenses can be used by glancing down.

More recently, liquid-crystal technology, allowing for a controllable change in refractive index by applying an electric field, has been introduced for glasses and contact lenses (see, e.g., "<NPL>; "<NPL>). This allows a controllable change in the optical properties of a lens by application of a voltage or current. Such lenses may be controlled either by a manual switch or by utilizing an orientation sensor detecting when a person wearing the lenses is moving her head, as is described in <CIT>.

In <CIT> devices for determining a distance of an object a user of an electro-active lens is looking at are presented. The optical power of the electro-active lens may be altered based on the determined distance to ensure that the object is correctly focused, without requiring the user to operate a switch, glance down, or dip her head.

<CIT> discloses a tracking device for controlling the focus of electroactive spectacles, the spectacles comprising electroactive lenses, the tracking device comprising: a tracking camera, a tracking controller, and a transmitter; wherein the tracking controller is configured to: capture, via the tracking camera, an image; detect, in the image, a pair of eyes; determine, from the image of the eyes, a target focus; and transmit, via the transmitter, a focus message to the spectacles, the focus message being indicative of the target focus, and instructive to the spectacles to set the focus of the lenses accordingly.

It is an object of the invention to provide an improved alternative to the above techniques and prior art.

More specifically, it is an object of the invention to provide an improved solution for controlling a lens for adjustable vision correction worn in front of an eye of a user of a device, such as a mobile phone, a smartphone, a mobile terminal, a tablet, an e-book reader, a computer screen, or a television set.

These and other objects of the invention are achieved by means of different aspects of the invention, as defined by the independent claims. Embodiments of the invention are characterized by the dependent claims.

According to a first aspect of the invention, a device for controlling at least one lens is provided. The lens is suitable for adjustable vision correction if worn in front of an eye of a user of the device. The device is operative to determine if the user is gazing at the device. The device is further operative, if the user is gazing at the device, to determine a distance between the eyes of the device and the device, and to control the at least one lens of the device to adjust its focal length based on the determined distance. The device is also operative to compare the determined distance to a threshold distance which is representative of a transition between a near-vision regime and a far-vision regime of the eyes, wherein the at least one lens is controlled to adjust its focal length to a focal length suitable for the near-vision regime if the determined distance is below the threshold distance, and to determine a distance between the eyes and the device at which the user is holding the device when trying to read small text and notifying the user, if the distance is gradually increasing over time, that an emerging condition of presbyopia is likely.

According to a second aspect of the invention, a computer implemented method of operating a device for controlling at least one lens is provided. The lens is suitable for adjustable vision correction if worn in front of an eye of a user of the device. The method comprises determining if a user is gazing at the device. The method further comprises, if the user is gazing at the device, determining a distance between the eyes of the user and the device, and controlling at least one lens of the device to adjust its focal length based on the determined distance. The method further comprising comparing he determined distance to a threshold distance which is representative of a transition between a near-vision regime and a far-vision regime of the eyes, wherein the at least one lens is controlled (to adjust its focal length to a focal length suitable for the near-vision regime if the determined distance is below the threshold distance, and determining a distance between the eyes and the device at which the user is holding the device when trying to read small text and notifying the user, if the distance is gradually increasing over time, that an emerging condition of presbyopia is likely.

According to a third aspect of the invention, a computer program is provided. The computer program comprises computer-executable instructions for causing a device to perform the method according to an embodiment of the second aspect of the invention, when the computer-executable instructions are executed on a processing unit comprised in the device.

According to a fourth aspect of the invention, a computer program product is provided. The computer program product comprises a computer-readable storage medium which has the computer program according to the third aspect of the invention embodied therein.

Throughout the present disclosure, the at least one lens is either one or two contact lenses, or one or two lenses of a pair of glasses. The optical properties of the lens can be adjusted in a controllable manner. In particular, the index of refraction of at least a part of the lens may be adjusted by applying an electric field, a voltage, or an electric current. Thereby, the focal length of the part of the lens can be adjusted.

Focal length is measured in meters, and is the inverse of optical power, also known as focal power, dioptric power, refractive power, focusing power, or convergence power.

Lenses which have an electrically controllable focal length are commonly referred to as electro-active lenses and may, e.g., be based on liquid-crystal technology, as is known in the art. The lens may be controlled to adjust its focal length by switching between two or more states having different focal lengths. Alternatively, the focal length of the lens may be continuously adjustable.

The invention makes use of an understanding that lenses for adjustable vision correction, such as electro-active lenses, worn by a user may be controlled by a device which is associated with the user. In particular, the device may be a device which the user is frequently or occasionally gazing at, such as a mobile phone, a smartphone, a mobile terminal, a tablet, an e-book reader, a computer screen, or a television set. Typically, such devices are located at a distance from the user which would necessitate the use of additional lenses, such as reading glasses, bifocals, or varifocals, or actively setting electro-active lenses worn by the user to a mode which is suitable for a near-vision regime of the eye of the user, e.g., if the user is suffering from presbyopia.

Embodiments of the invention are advantageous in that electro-active lenses worn by the user are automatically controlled to adjust their focal length to values which are suitable for correctly focusing on the device if the user is gazing at the device. Embodiments of the invention may, e.g., be utilized for correcting presbyopia by compensating the lack of ability to focus on closer objects if the user is gazing at a device located at close distance. This is achieved by the device determining if the user is gazing at the device. If the user is gazing at the device, the distance between the eye and the device is determined, and the electro-active lens or lenses are controlled to adjust its/their focal length based on the determined distance. In other words, the lenses worn by the user are only adjusted if required, i.e., if the user is gazing at the device. Embodiments of the invention alleviate the need for the user to actively operate a switch or move her head for adjusting the focal length of her lenses.

The solution described herein is advantageous over the known electro-active lenses which are adjusted based on a distance to an object the user is looking at which is determined by a range finder which is integrated with the lenses. This is the case since lenses which are used together with embodiments of the invention are lighter and can be manufactured at lower cost, since range-finding devices are rather complex, and often too complex to be integrated with contact lenses. In other words, rather than integrating range-finding and/or gaze detection capabilities with electro-active lenses, either within a contact lens or into the frame of glasses, embodiments of the invention rely on a device which the user is gazing at. This is particularly advantageous for devices which are operated and/or held by a hand of the user, since the distance between the eye and the device is limited by the user's anatomy, i.e., the user's arm.

According to an embodiment of the invention, the at least one lens is controlled to adjust its focal length further based on information pertaining to an eye disease or an eye condition of the user, such as presbyopia, longsightedness (hyperopia), or short-sightedness (myopia). Such information may be obtained from the user's optician prescription, medical records, a database maintained by a lens manufacturer, or the like. The information may be provided by the user, retrieved over the Internet, or received from the lens, e.g., over a communication link between the device and the lens. In order to retrieve the information, the lens, a batch of lenses, and/or the user, is/are preferably identified in a request for retrieving the information. The information may also relate to a threshold distance which is representative of a transition between a near-vision regime and a far-vision regime of the eye of the user, as is described below.

According to the claimed invention, the determined distance is compared to a threshold distance which is representative of a transition between a near-vision regime and a far-vision regime of the eye. Presbyopia, e.g., becomes prominent in the near-vision regime. The at least one lens is controlled to adjust its focal length to a focal length suitable for the near-vision regime if the determined distance is below the threshold distance. Optionally, the at least one lens is controlled to adjust its focal length to a focal length suitable for the far-vision regime if the determined distance is equal to or above the threshold distance. Controlling the lens to switch between a near-vision regime and a far-vision regime is particularly suitable for lenses which are switchable between two different focal lengths. For instance, the focal length of the known liquid-crystal based lenses is decreased when activated, making them suitable for correcting presbyopia in the activated state.

The threshold distance may be configured by the user, in accordance with properties of the lens, e.g., as recommended by the lens manufacturer, or based on the user's optician prescription. As an alternative, the threshold distance may also be learned by detecting the distance at which the user is holding the device so as to read more comfortably. For instance, the device may detect that the user is extending her arm every time she reads text with small font size. It will also be appreciated that an emerging condition of presbyopia may be detected by the device based on detecting that the user is extending her arm when trying to read small text, and at which distance the device is held. If the distance is gradually increasing over time, an emerging condition of presbyopia is likely and the user is notified.

According to an embodiment of the invention, if the user is not gazing at the device, the at least one lens is controlled to adjust its focal length to a focal length suitable for a far-vision regime of the eye. In other words, if the user is not gazing at the device, it is assumed that she is gazing at an object at a distance which is commensurate with the far-vision regime. For instance, the known liquid-crystal based lens is suitable for the far-vision regime when inactivated.

According to an embodiment of the invention, it is determined that the user is gazing at the device if the device is operated by a hand of the user. That is, if the user is touching the touchscreen of a smartphone or pressing buttons on a mobile phone, it is inferred that she is gazing at the device. Advantageously, detecting that the user is operating the device with a hand is less complex than other solutions for gaze detection or eye tracking, such as image processing, which are described further below.

According to an embodiment of the invention, the user, the lens, or both, are identified. This is advantageous since the user may require an assurance that only a device which is under her control is able to control the lenses she is wearing. Thereby, it is avoided that any nearby device, such as a friend's television or a tablet operated by a person sitting next to the user, controls the user's lenses. The user may be identified based on face recognition, i.e., by image processing an image acquired by a camera, e.g., a front-facing camera of a smartphone or tablet. The lens may be identified by wirelessly retrieving information from the lens over a communication link. For instance, the lens may transmit an identifier to the device, such as an identifier of the lens, a batch of lenses, or information identifying the user to which the lens is prescribed. Instead of, or in addition to, information identifying the lens, the device may receive information pertaining to optical properties of the lens from the lens. Optionally, the lens is controlled to adjust its focal length only if the user and/or the lens are successfully identified.

According to an embodiment of the invention, if the user is not gazing at the device, an object in the surroundings of the device at which the user is gazing is determined, a distance between the eye and the object is determined, and the at least one lens is controlled to adjust its focal length based on the determined distance. This may be achieved based on any known means of gaze detection, eye tracking, and range finding, which are elucidated further below. Advantageously, the device, e.g., smartphone, mobile terminal, tablet, or the like, may be utilized for controlling the lens or lenses worn by the user even if she is not gazing at the device, but rather at an object, such as a television set, a person, a wall, and so forth.

Even though advantages of the invention have in some cases been described with reference to embodiments of the first aspect of the invention, corresponding reasoning applies to embodiments of other aspects of the invention.

Further objectives of, features of, and advantages with, the invention will become apparent when studying the following detailed disclosure, the drawings and the appended claims. Those skilled in the art realize that different features of the invention can be combined to create embodiments other than those described in the following.

The above, as well as additional objects, features and advantages of the invention, will be better understood through the following illustrative and non-limiting detailed description of embodiments of the invention, with reference to the appended drawings, in which:.

The invention will now be described more fully herein after with reference to the accompanying drawings, in which certain embodiments of the invention are shown. Rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

<FIG> illustrates a user <NUM> gazing at different objects and devices. For instance, user <NUM> may gaze <NUM> at her smartphone <NUM> to read a webpage or type an email. Alternatively, user <NUM> may gaze <NUM> at a book <NUM> she is reading, of she may gaze <NUM> at a television set <NUM>. User <NUM> is illustrated as wearing glasses <NUM> in front of her eyes <NUM>, e.g., for correcting an eye disease or an eye condition such as presbyopia, longsightedness (hyperopia), short-sightedness (myopia), or the like.

With reference to <FIG>, illustrating glasses <NUM> in further detail, it is assumed here that at least one of the lenses <NUM> comprised in glasses <NUM> has an adjustable focal length within at least a part <NUM> of lens <NUM>. Lenses having an adjustable focal length are also known as electro-active lenses and may, e.g., be based on a liquid-crystal layer which is provided on an underlying lens having focal length f<NUM>. When activated, using an electric field, a voltage, or an electric current, which is applied over or passed through the liquid-crystal layer, the focal length of lens <NUM> is adjusted to a value f<NUM> + Δf, where the change in focal length Δf is due to a change in refractive index of the liquid-crystal layer. As an example, lens <NUM> may comprise a liquid-crystal layer such that, when the liquid-crystal layer is activated by applying an electric field, a voltage, or passing an electric current, the focal length f<NUM> + Δf is decreased from its value f<NUM> in the inactive state. Thereby, lens <NUM> is suitable for correcting presbyopia when activated.

It will be appreciated that embodiments of the invention are not limited to liquid-crystal based lenses. On the contrary, embodiments of the invention may utilize any type of lens having a controllable focal length. Moreover, as an alternative to glasses <NUM> comprising lenses <NUM>, embodiments of the invention may also utilize electro-active contact lenses <NUM> having an adjustable focal length within at least a part <NUM> of contact lens <NUM>, as is illustrated in <FIG>.

Further with reference to <FIG>, glasses <NUM> are illustrated as comprising a lens control unit <NUM> which is integrated into a frame of glasses <NUM>. Lens control unit <NUM> is operative to receive a control signal transmitted by a device for controlling at least one lens for adjustable vision correction, in accordance with an embodiment of the invention, or a remote control unit <NUM>, as is described below. It will be appreciated that lens control unit <NUM> may comprise analog or digital electronic circuitry, or a combination therefor, depending on the technology used for transmitting and receiving the control signal. Lens control unit <NUM> may alternatively be integrated into lens or lenses <NUM>, similar to lens control unit <NUM> which is integrated into contact lens <NUM> shown in <FIG>.

In the following, embodiments of the device for controlling at least one lens for adjustable vision correction worn in front of an eye of a user of the device are described, with further reference to <FIG> and <FIG> in which device <NUM> is exemplified as a smartphone. For the sake of simplicity, embodiments of the invention are described as controlling one lens <NUM> of glasses <NUM>, but corresponding embodiments for controlling both lenses <NUM> of glasses <NUM>, or one or two contact lenses <NUM>, may easily be envisaged.

In <FIG>, user <NUM> is illustrated as holding and operating device <NUM> with a hand <NUM>. Device <NUM> comprises a display <NUM>, such as a touchscreen, at which user <NUM> is gazing <NUM>, and a processing module <NUM>, which is described in further detail below with reference to <FIG>.

Device <NUM> is operative to determine if user <NUM> is gazing <NUM> at device <NUM>. If it is determined that user <NUM> is gazing <NUM> at device <NUM>, a distance between the eyes <NUM> of user <NUM> and device <NUM> is determined, and lens <NUM> is controlled to adjust its focal length based on the determined distance. For the sake of clarification, it is noted that the distance between eyes <NUM> and device <NUM> corresponds to the length of dashed lines <NUM> illustrated in <FIG>.

Device <NUM> may be operative to determine if user <NUM> is gazing at device <NUM> in a number of ways. For instance, device <NUM> may comprise a front-facing camera <NUM> and processing module <NUM> which is operative to acquire an image from camera <NUM>, and to determine if user <NUM> is gazing <NUM> at device <NUM> based on image processing, as is known in the art (see, e.g., "<NPL>). As an alternative, the gaze of eyes <NUM> may be determined based on any other known eye-tracking technique, e.g., by detecting infrared light which is reflected from eyes <NUM> and sensed by a camera <NUM>, by tracking the corneal reflection (the first Purkinje image) and the center of the pupils of eyes <NUM> over time, utilizing images which are periodically acquired from camera <NUM>, or by tracking reflections from the front of the cornea (first Purkinje image) and the back of the lens (fourth Purkinje image) of eyes <NUM> over time.

As a further alternative, device <NUM> may be operative to determine that user <NUM> is gazing <NUM> at device <NUM> if it is detected that device <NUM> is operated by user <NUM>. For instance, it may be detected that a finger of hand <NUM>, or another finger, is touching touchscreen <NUM>, or a button which device <NUM> is provided with (not shown in <FIG>). In other words, it is inferred that user <NUM> is likely to gaze <NUM> at device <NUM> while actively operating it.

Device <NUM> may be operative to determine the distance between eyes <NUM> and device <NUM> utilizing a number of different techniques. For instance, device <NUM> may be operative to determine the distance by using structured light, i.e., by projecting a known pattern of light, and by detecting light which is reflected by objects in the surroundings, such as the head, face, or eyes <NUM> of user <NUM>. This can be achieved imperceptibly to user <NUM> by utilizing infrared light. As an alternative, device <NUM> may be provided with a time-of-flight camera <NUM> which is capable of measuring the time-of-flight of light emitted by device <NUM> and which is reflected by the head, face, or eyes <NUM>, of user <NUM> and detected by camera <NUM>. Another alternative for determining the distance between eyes <NUM> and device <NUM> is image processing combined with perspective scaling. In addition, techniques which are used for gesture recognition, such as Microsoft's Kinect and Intel's RealSense, or radio-frequency radars such as Google's Soli, may be utilized.

As yet a further alternative, the distance between eyes <NUM> and device <NUM> may be determined by detecting that device <NUM> is held and/or operated by a hand of user <NUM>, e.g., hand <NUM>, and determining the distance based on user <NUM>'s anatomy, such as the length of user <NUM>'s arm and optionally her habit of holding device <NUM>. Advantageously, this is less complex than the solutions described above, and may be achieved by utilizing touchscreen <NUM> or any other touch- or pressure-sensitive surface of device <NUM>. Optionally, device <NUM> may utilize a default value distance for the distance between eyes <NUM> and device <NUM> if it is detected that device <NUM> is held and/or operated by a hand of user <NUM>. Such a default value may, e.g., be configured by user <NUM>. Using a default value for the distance between eyes <NUM> and device <NUM> is particularly advantageous if that distance is below a threshold distance which is representative of a transition between a near-vision regime and a far-vision regime of eye or eyes <NUM>, as is described further below. In such case, device <NUM> may be operative to control lens <NUM> to adjust to a focal length suitable for the near-vision regime of eye(s) <NUM>, in response to detecting that user <NUM> is gazing <NUM> at device <NUM>, without determining the distance based on an actual measurement using one of the techniques described above.

Device <NUM> is further operative to, subsequent to determining the distance between eyes <NUM> and device <NUM>, either by measuring the distance or by inferring the distance based on detecting that device <NUM> is held and/or operated by a hand of user <NUM>, to control lens <NUM> to adjust its focal length based on the determined distance. Lens <NUM> may be controlled to adjust its focal length by switching between at least two states having different focal lengths. Alternatively, the focal length of lens <NUM> may be continuously adjustable.

Device <NUM> may additionally be operative to adjust the focal length of lens <NUM> further based on information pertaining to an eye disease or an eye condition of user <NUM>, such as presbyopia. An example of such information is, e.g., a threshold distance which is representative of a transition between a near-vision regime and a far-vision regime of eye or eyes <NUM>, or information which is obtained from user <NUM>'s optician prescription. The information may be provided by user <NUM>, received from lens <NUM> via a wireless communication link, or retrieved over the Internet, e.g., from a database provided by the lens manufacturer. In order to retrieve the information from the database, lens <NUM>, a batch of lenses, or user <NUM>, is preferably identified in the request for retrieving the information.

Device <NUM> further is operative to compare the determined distance to the threshold distance which is representative of a transition between a near-vision regime and a far-vision regime of eye(s) <NUM>. In this case, lens <NUM> is controlled to adjust its focal length to a focal length suitable for the near-vision regime if the determined distance is below the threshold distance, since presbyopia becomes prominent in the near-vision regime. Controlling lens <NUM> to switch between a near-vision regime and a far-vision regime is particularly suitable for electro-active lenses which are switchable between two different focal lengths. For instance, the focal length of the known liquid-crystal based lenses described above is decreased when activated, making them suitable for correcting presbyopia in the activated state.

The threshold distance may be configured by user <NUM> in accordance with properties of lens <NUM>, e.g., as recommended by the lens manufacturer or based on user <NUM>'s optician prescription. As an alternative, the threshold distance may also be learned by detecting the distance at which user <NUM> is holding device <NUM> so as to read more comfortably. For instance, device <NUM> may be operative to detect that user <NUM> is extending her arm every time she reads text with small font size, and to determine the distance between eyes <NUM> and device <NUM> when adjusted for comfortable reading. This also is utilized for detecting an emerging condition of presbyopia, if the thereby determined distance is gradually increasing over time. In such case, user <NUM> is notified that she is likely to suffer from presbyopia.

Optionally, device <NUM> may additionally be operative to control lens <NUM> to adjust its focal length to a focal length suitable for the far-vision regime, if the determined distance is equal to or above the threshold distance. This may, e.g., be the case if device <NUM> is located at a greater distance from user <NUM>, such as a tablet placed on a table in front of user <NUM>, or the television set <NUM> illustrated in <FIG>.

Device <NUM> may further be operative to control lens <NUM> to adjust its focal length to a focal length suitable for a far-vision regime of eye(s) <NUM>, if the user is not gazing at device <NUM>, as is illustrated in <FIG>. That is, if user <NUM> is not gazing at device <NUM>, it is assumed that she is gazing <NUM> at an object at a distance which is commensurate with the far-vision regime of eye(s) <NUM>. For the liquid-crystal based lens described above, the far-vision regime corresponds to an inactive state of the liquid-crystal layer.

The focal length suitable for a near-vision regime of eye <NUM>, and the focal length suitable for a far-vision regime of eye <NUM>, respectively, may be pre-determined values configured by user <NUM>, a lens manufacturer, or derived from user <NUM>'s optician prescription. In particular, the respective values of the focal length for the near-vision regime and the far-vision regime may correspond to two distinct focal lengths supported by lens <NUM>.

Device <NUM> may be operative to control lens <NUM> to adjust its focal length by transmitting a control signal. The control signal may, e.g., be transmitted by a radio module <NUM> supporting a wireless communication technology such as Bluetooth, Wireless Local Area Network (WLAN)/WiFi, or a cellular standard, in particular according to 3rd Generation Partnership Project (3GPP) technical specifications. As an alternative, radio module <NUM> may utilize a near-field technology such as Radio-Frequency IDentification (RFID). As yet a further alternative, device <NUM> may be operative to emit coded light, in particular visible coded light using display <NUM>. A communication link established between radio module <NUM> and lens <NUM>, or lens control unit <NUM>, may also be utilized for exchanging information identifying user <NUM> and/or lens <NUM>, or information pertaining to the optical properties of lens <NUM>.

The control signal may be transmitted as a message containing one or more information elements. The control signal, the message, or the one or more information elements, may comprise information representative of at least one of the determined distance, a target focal length for lens <NUM>, and a target state of at least two states of lens <NUM> which have different focal lengths. Alternatively, the control signal may toggle lens <NUM> between two states having different focal lengths, e.g., between an inactive state and an active state. Radio module <NUM> may also be operative to transmit control signals of different frequency, wherein each frequency is associated with one of at least two states of lens <NUM>. Even further, lens <NUM> may be operative to assume a first state, e.g., an inactive state of the liquid-crystal layer, if the control signal is not received, and a second state, e.g., an active state of the liquid-crystal layer, if the control signal is received. In this case, device <NUM> may, e.g., be operative to transmit the control signal, via radio module <NUM>, for controlling lens <NUM> to assume a state having a focal length which is commensurate with the near-vision regime of eye(s) <NUM> as long as user <NUM> is gazing at device <NUM>, if it is determined that the distance is below the threshold distance. Advantageously, the electric potential, voltage, or current, which is required for activating lens <NUM> may be harvested from the received control signal, as is known in the art of RFID.

As an alternative, rather than transmitting the control signal directly to lens control unit <NUM> comprised in glasses <NUM>, or lens control unit <NUM> comprised in contact lens <NUM>, respectively, the control signal may be transmitted to a remote control unit <NUM> worn by user <NUM>. Remote control unit <NUM> comprises processing module <NUM>, a first radio module <NUM> for communicating with device <NUM>, and a second radio module <NUM> for communicating with lens <NUM>. Remote control unit <NUM> is operative to control lens <NUM> based on the control signal received via first radio module <NUM> by transmitting a second control signal via second radio module <NUM>. Using remote control unit <NUM> for controlling the focal length of lens <NUM> is advantageous in that it may be located closer to lens <NUM> than device <NUM>, facilitating usage of short-ranged technologies like RFID for controlling lens <NUM> by means of the second control signal. Thereby, the power received by lens control unit <NUM> may be increased, which is advantageous for embodiments relying on energy harvested from the received control signal for activating lens <NUM>.

The functionality described herein may also be divided between device <NUM> and remote control unit <NUM>. For instance, device <NUM> may be operative to only transmit the determined distance, and remote control unit <NUM> may be operative to compare the determined distance to a threshold distance, and so forth. In other words, remote control unit <NUM> may receive information which is independent from the optical properties of lens <NUM>, and /or eye conditions of user <NUM>, and generate the second control signal based on the optical properties of lens <NUM> and/or information about the eye condition of user <NUM>.

Further with reference to <FIG>, if it is detected that user <NUM> is not gazing at device <NUM>, but gazing <NUM> into a different direction, device <NUM> may further be operative to determine an object in the surroundings of device <NUM> at which user <NUM> is gazing, determine a distance between eyes <NUM> and the object, and control lens <NUM> to adjust its focal length based on the determined distance. For instance, as is illustrated in <FIG>, device <NUM> may detect that user <NUM> is gazing <NUM> at book <NUM>, or gazing <NUM> at television set <NUM>.

Even though embodiments of the device for controlling at least one lens for adjustable vision correction have been described in relation to smartphone <NUM> illustrated in <FIG>, it will be appreciated that corresponding embodiments may be envisaged for other types of devices, such as mobile phones, mobile terminals, tablets, e-book readers, computer screens, or television sets, e.g., television set <NUM>.

If user <NUM> has several devices, such as smartphone <NUM> and television set <NUM>, they may either independently of each other or cooperatively control lens <NUM>. For instance, each of the devices may independently send a control signal to lens <NUM> if it has detected that user <NUM> is gazing at it. As an alternative, the devices may cooperatively determine the object which user <NUM> is gazing at, and/or the distance between eyes <NUM> and the object. The distance may, e.g., be determined based on a 3D image which is generated from 2D images captured by cameras which the devices are provided with, e.g., front-facing camera <NUM> of smartphone <NUM> and camera <NUM> of television set <NUM>. Alternatively, one or more of the devices may be operative to emit structured light and detect light reflected from objects in the surroundings. As yet a further alternative, device <NUM> may also comprise a rear-facing camera in addition to front-facing camera <NUM>, and may determine an object which user <NUM> is gazing at, and the distance between eyes <NUM> and the object, by image processing images captured by front-facing camera <NUM> and the rear-facing camera.

In a scenario involving several devices, one of the devices, e.g., smartphone <NUM>, may have the role of a master device which transmits the control signal to lens <NUM> based on information, such as distance to one or more objects, a gaze of eyes <NUM>, or images, received from other devices, e.g., from television set <NUM>.

In order to further elucidate the invention, embodiments of the method of a device <NUM> for controlling at least one lens <NUM> for adjustable vision correction are now described with reference to <FIG>. The device may, e.g., be a mobile phone, a smartphone, a mobile terminal, a tablet, an e-book reader, a computer screen, or a television set.

Method <NUM> comprises determining <NUM> if the user is gazing at device <NUM>, and if <NUM> the user is gazing at device <NUM>, determining <NUM> a distance between eyes <NUM> and device <NUM>, and controlling <NUM> lens <NUM> to adjust its focal length based on the determined distance. Preferably, lens <NUM> is controlled to adjust its focal length by transmitting <NUM> a control signal to lens <NUM>. The control signal is either transmitted to lens <NUM> or glasses <NUM> comprising the lens, or a lens control unit <NUM> comprised therein, or to a remote control unit <NUM> which is operative to control lens <NUM>. The control signal may comprise information representative of at least one of the determined distance, a target focal length which may optionally be derived <NUM>, and a target state of at least two states of lens <NUM> which may optionally be derived <NUM>, wherein the at least two states have different focal lengths.

Optionally, lens <NUM> is controlled to adjust its focal length further based on information pertaining to an eye disease or an eye condition of user <NUM>. Such information may, e.g., be retrieved <NUM> from lens <NUM>, or from a database. Method <NUM> may optionally comprise identifying <NUM> user <NUM> and/or lens <NUM>.

The target focal length or target state may, e.g., be derived <NUM> by comparing <NUM> the determined distance to a threshold distance which is representative of a transition between a near-vision regime and a far-vision regime of eye(s) <NUM>, wherein lens <NUM> is controlled to adjust its focal length to a focal length suitable for the near-vision regime <NUM> if the determined distance is below <NUM> the threshold distance. Optionally, lens <NUM> is controlled to adjust its focal length to a focal length suitable for the far-vision regime <NUM> if the determined distance is equal to or above <NUM> the threshold distance.

Optionally, if user <NUM> if it is determined <NUM> that user <NUM> is not gazing at device <NUM>, method <NUM> may further comprise controlling the at least one lens to adjust its focal length to a focal length suitable for a far-vision regime <NUM> of eye(s) <NUM>.

The distance between eyes <NUM> and device <NUM> may, e.g., be determined by detecting that device <NUM> is held and/or operated by a hand <NUM> of user <NUM>, and determining the distance based on an anatomy of user <NUM>.

Optionally, it may be determined <NUM> that user <NUM> is gazing at device <NUM> if device <NUM> is operated by a hand <NUM> of user <NUM>.

Further, method <NUM> may optionally comprise, if the user is not gazing <NUM> at device <NUM>, determining <NUM> an object in the surroundings of device <NUM> at which user <NUM> is gazing, determining <NUM> a distance between eyes <NUM> and the object, and controlling <NUM> lens <NUM> to adjust its focal length based on the determined distance.

Method <NUM> may further comprise additional or alternative steps in accordance with embodiments of the invention described throughout this disclosure, in particular with reference to <FIG>.

In <FIG>, an embodiment <NUM> of processing module <NUM> comprised in device <NUM> is shown. Processing module <NUM> comprises a processing unit <NUM>, such as a general purpose processor, and a memory <NUM>. Memory <NUM> comprises computer-executable instructions <NUM>. Processing module <NUM> may optionally comprise one or more interfaces <NUM> ("I/O" in <FIG>) for communicating with touchscreen <NUM>, camera <NUM>, and radio module <NUM>, in accordance with what is described hereinbefore. When executed on processor <NUM>, computer-executable instructions cause device <NUM> to perform an embodiment of the invention, in particular an embodiment of method <NUM> described with reference to <FIG>. More specifically, device <NUM> becomes operative to determine if user <NUM> is gazing at device <NUM>, and if user <NUM> is gazing at device <NUM>, determine a distance between eyes <NUM> and device <NUM>, and control lens <NUM> to adjust its focal length based on the determined distance. In addition, device <NUM> may become operative to perform additional or alternative functionality described throughout this disclosure.

An alternative embodiment <NUM> of processing module <NUM> is shown in <FIG>. Processing module <NUM> comprises a gaze module <NUM> for determining if user <NUM> is gazing at device <NUM>, a distance module <NUM> for determining, if user <NUM> is gazing at device <NUM>, a distance between eyes <NUM> and device <NUM>, and a control module <NUM> for control lens <NUM> to adjust its focal length based on the determined distance. Processing module <NUM> may comprise additional or alternative modules which are operative to implement functionality described throughout this disclosure, e.g., a user/lens identification module <NUM> for identifying user <NUM> and/or lens <NUM>, and/or a lens/eye information module <NUM> for providing information pertaining to an eye disease or an eye condition of user <NUM> and/or optical properties of lens <NUM>.

Embodiments of the device for controlling at least one lens for adjustable vision correction, and in particular embodiments of processing module <NUM> or <NUM>, may be implemented by means of any suitable combination of software, executed on a processor, or hardware, such as analog or digital electronics, Integrated Circuits (ICs), Application Specific ICs (ASICs), and the like. It will be appreciated that the specific functional modules illustrated in <FIG> only serve as examples, and embodiments of the device and the processing module may use any suitable combination of functional modules other than those described herein and illustrated in <FIG>.

Claim 1:
A device (<NUM>, <NUM>) for controlling at least one lens, the device comprising means (<NUM>-<NUM>, <NUM>, <NUM>, <NUM>) configured to:
determine if a user is gazing at the device, and
if the user is gazing at the device:
determine a distance between the eyes of the user and the device, and
control the at least one lens of the device to adjust its focal length based on the determined distance, the means being further configured to:
compare the determined distance to a threshold distance which is representative of a transition between a near-vision regime and a far-vision regime of the eyes, wherein the at least one lens is controlled to adjust its focal length to a focal length suitable for the near-vision regime if the determined distance is below the threshold distance,
characterized in that the means are configured to
determine a distance between the eyes and the device at which the user is holding the device when trying to read small text and to notify the user, if the distance is gradually increasing over time, that an emerging condition of presbyopia is likely.