Patent Description:
Personal care devices are used to perform personal care activities on skin of a user. Such personal care activities include, but are not limited to, epilating, hair care activities, such as shaving and trimming, or massaging. While the user may know which part of his or her body is being treated by the personal care device, and may be able to tailor the application of the personal care accordingly, the device itself may function in a suboptimal manner for some parts of the body compared to others.

<CIT> discloses an apparatus for determining a location of a personal care device on a user. The apparatus comprises a processor configured to detect a location of one or more parts of the body of a user, detect motions of at least one of the parts of the body of the user induced by the personal care device when the personal care device is in use, and determine the location of the personal care device on the user based on the detected motions of the at least one part of the body of the user in relation to the detected location of the at least one part of the body of the user.

<CIT> discloses a device and a method for determining a position of a mobile device relative to a subject. In an embodiment, the mobile device has a light source to project a light image on the subject during use, while the device has a camera to observe the subject. The camera is used to identify landmarks on the subject's face as well as the light image, allowing the position of the mobile device relative to the subject to be calculated. The light image may be provided such that a surface curvature of the surface of the subject results in a detectable distortion, so that a processing unit can derive a local surface curvature of the surface of the subject. This local surface curvature can be registered relative to the identified landmark positions and be used to generate a model of the subject. Thereby, the overall positioning determination by the device can become more accurate.

In order to operate in an improved or optimal manner, it can be beneficial for a personal care device to identify its approximate position on the body of a user/subject, for example by identifying a portion of the subject's skin to which the personal care activity is being performed. Existing means for determining a location of a device can be ineffective. Therefore, there is a desire for a more effective means for determining an indication of a location of a device with respect to a skin surface of a subject.

The inventors of the present disclosure have recognized that a location of a personal care device may be determined based on a measured degree of curvature of the surface in respect of which the device is being used. For example, it is possible to determine the location of a personal care device relative to a subject's body by measuring the curvature of a region of the body with which the device is in contact and, based on the measured degree of curvature, determining a part of region of a body having a corresponding curvature.

With knowledge of the body part or region in respect of which the device is being used, appropriate action may be taken to improve the performance of the device, for example by adjusting operating parameters of the device so that it operates in a manner more appropriate for the body part where it is being used, analyzing a personal care routine, tracking skin parameters over time, or providing feedback regarding the personal care activity.

According to a first aspect, there is provided a computer-implemented non-therapeutic and non-surgical method of determining a location of a personal care device with respect to a skin surface of a subject, the personal care device being configured to perform a personal care treatment to the skin when in contact with the skin surface. The method comprises receiving data representative of a measured degree of curvature of the skin surface within a first region of the skin surface of the subject, with which the personal care device is in contact; determining, by comparing the measured degree of curvature with curvature information for a plurality of regions of the skin surface of the subject contained in a database, an indication of a location of the first region of the skin surface on the subject; and performing, based on the determined indication of the location of the first region, an action in respect of the personal care device; wherein the data representative of the measured degree of curvature of the skin surface within the first region of the skin surface comprises a measure of a relative orientation of a first surface-engaging element and a second surface-engaging element of a skin surface curvature measurement mechanism, the first and second surface-engaging elements being moveable relative to one another.

Using previously-acquired data regarding the curvature of different parts of a subject's skin surface, a determination may be made of the location of the personal care device based on curvature measurements made while the device is in use. In this way, the device location can be easily determined, such that appropriate actions may be taken based on the determined location.

In some embodiments, the method may further comprise receiving data indicative of a measured displacement of the personal care device between the first region of the skin surface and a second region of the skin surface, with which the personal care device was previously in contact. Determining the indication of the location of the first region may be based further on comparing the data indicative of the measured displacement with position information for the plurality of regions of the skin surface of the subject contained in the database.

The method may, in some embodiments, further comprise, prior to receiving the data representative of the measured degree of curvature of the skin surface within the first region of the skin surface: receiving calibration displacement data indicative of a measured displacement of the personal care device between a plurality of regions of the skin surface of the subject; fitting a computer model of the skin surface of the subject to the received calibration displacement data; determining, from the calibration displacement data and the fitted computer model, curvature information for each region of the plurality of regions; and storing, in the database, the determined curvature information in association with the corresponding region on the skin surface of the subject. This may be considered to be a calibration process.

According to a second aspect, there is provided a processing apparatus configured for determining a location of a personal care device with respect to a skin surface of a subject, the personal care device being configured to perform a personal care treatment to the skin when in contact with the skin surface, the processing apparatus being configured to: receive data representative of a measured degree of curvature of the skin surface within a first region of the skin surface of the subject, with which the personal care device is in contact; retrieve, from a storage medium, curvature information for a plurality of regions of the skin surface of the subject; determine, by comparing the measured degree of curvature with the curvature information for the plurality of regions of the skin surface, a location of the first region of the skin surface on the subject; and generate, based on the determined location of the first region, an instruction of an action to be performed in respect of the personal care device, wherein the data representative of the measured degree of curvature of the skin surface within the first region of the skin surface comprises a measure of a relative orientation of a first surface-engaging element and a second surface-engaging element of a skin surface curvature measurement mechanism, the first and second surface-engaging elements being moveable relative to one another.

According to a third aspect, there is provided a system for determining a location of a personal care device with respect to a skin surface of a subject, the personal care device being configured to perform a personal care treatment to the skin when in contact with the skin surface, the system comprising: a housing to house a communication unit; a skin surface curvature measurement mechanism coupled to the housing and comprising a first surface-engaging element and a second surface-engaging element, the first and second surface-engaging elements being moveable relative to one another, the skin surface curvature measurement mechanism being configured for measuring a degree of curvature of the skin surface of the subject within a first region of the skin surface; and a processing apparatus as discussed herein. The skin surface curvature measurement mechanism is configured to generate the data representative of the measured degree of curvature of the skin surface within the first region of the skin surface, said data comprising a measure of a relative orientation of the first surface-engaging element and second surface-engaging element. The communication unit is configured to communicate the data representative of the measured degree of curvature of the skin surface within the first region of the skin surface to the processing apparatus.

In some embodiments, the system may further comprise at least one orientation sensor configured for measuring an orientation of the first surface-engaging element relative to the housing, and an orientation of the second surface-engaging element relative to the housing. The data representative of the measured degree of curvature of the skin surface within the first region of the skin surface may comprise a measure of the orientation of the first surface-engaging element relative to the housing, and a measure of the orientation of the second surface-engaging element relative to the housing.

The first surface-engaging element and the second surface-engaging element may be pivotally mounted such that they are each pivotable relative to the housing and relative to one another. The data representative of the measured degree of curvature may comprise an average degree of curvature of the skin surface within the first region.

According to a fourth aspect, there is provided a personal care device configured to perform a personal care treatment to the skin when in contact with the skin surface, comprising: a main body; a skin surface curvature measurement mechanism comprising a first surface-engaging element and a second surface-engaging element, the first and second surface-engaging elements being moveable relative to one another, the skin surface curvature measurement mechanism being configured for measuring a degree of curvature of the skin surface of the subject within a first region of the skin surface, with which the personal care device is in contact; and a processing apparatus as disclosed herein. The processing apparatus is configured to receive data representative of a measured degree of curvature of the skin surface from the skin surface curvature measurement mechanism wherein said data comprises a measure of a relative orientation of the first surface-engaging element and second surface-engaging element.

The personal care device may, in some embodiments, further comprise an attachment to house a communication unit, the attachment being detachably mountable to the main body. The skin surface curvature measurement mechanism may be coupled to the attachment. The main body may accommodate the processing apparatus. The communication unit may be configured to communicate the data representative of the measured degree of curvature of the skin surface to the processing apparatus.

In some embodiments, the personal care device may further comprise a sensor for acquiring motion data for the personal care device. The processing apparatus may be configured to determine the location of the first region of the skin surface on the subject further based on motion data acquired using the sensor. The motion data may, for example, comprise the data indicative of a measured displacement.

The personal care device may further comprise a housing supporting at least a first treatment element and a second treatment element. The first treatment element may comprise the first surface-engaging element, and the second treatment element may comprise the second surface-engaging element, the first surface-engaging element and the second surface-engaging element each being pivotally mounted relative to the housing such that they are pivotable relative to one another. The skin surface curvature measurement mechanism may comprise a first sensor configured to measure an orientation of the first surface-engaging element relative to the housing, and a second sensor configured to measure an orientation of the second surface-engaging element relative to the housing.

In some embodiments, the personal care device may be an electric shaver. The first treatment element and the second treatment element may both comprise a shaving unit having an external cutting member, an internal cutting member movably arranged relative to the external cutting member, and a skin-supporting rim surrounding the external cutting member and pivotally mounted relative to the housing, wherein the first surface-engaging element and the second surface-engaging element comprise the skin-supporting rim of the shaving unit of, respectively, the first treatment element and the second treatment element.

According to a fifth aspect, there is provided a computer program product comprising a non-transitory computer readable medium, the computer readable medium having computer readable code embodied therein, the computer readable code being configured such that, on execution by a suitable computer or processor, the computer or processor is caused to perform steps of the method disclosed herein.

Embodiments of this present disclosure provide a mechanism by which a location of a device relative to a skin surface of a subject with which the device is in contact may be determined. Some embodiments are described in the context of a handheld shaver, the location of which may be determined relative to the region of a subject's body or face where hairs are being trimmed or cut using the shaver. However, it will be appreciated that the invention is not limited to shaving devices, and embodiments described herein may be implemented in a wide range of personal care devices configured to perform a personal care treatment to the skin when in contact with the skin surface. Thus, the personal care device described herein may, for example, comprise a hair removal device, such as an epilator or an intense pulsed light (IPL) device, a hair care device, such as a shaver, clippers, or a hair trimmer, a skin health analysis device, an electric massager, a phototherapy device or a pain relief device. Other personal care devices configured to perform a personal care treatment to the skin when in contact with the skin surface are also envisaged.

Referring now to the drawings, <FIG> is a schematic illustration of an example of a personal care device <NUM>. The personal care device <NUM> may be intended to be held by a user's hand during use and, as such, may be referred to as a handheld personal care device. The personal care device <NUM> comprises a main body <NUM>, a skin surface curvature measurement mechanism <NUM> and a processing apparatus <NUM>. In some embodiments, the personal care device <NUM> may be formed as an integral device, with its components connected or coupled together in a non-detachable manner. In other embodiments, however, various components of the personal care device <NUM> may be detachable from other components of the personal care device such that the personal care device is considered to be modular.

The main body <NUM> may house one or more components of the device. In some examples, the main body may be intended to be held in the user's hand during use.

The skin surface curvature measurement mechanism <NUM> (also referred to herein as a measurement mechanism <NUM>) is configured for measuring a degree of curvature of the skin surface of the subject within a first region of the skin surface, with which the personal care device is in contact. The measurement mechanism <NUM> may measure skin surface curvature in a number of ways, as described in greater detail below. The processing apparatus <NUM> is configured to receive data representative of a measured degree of curvature of the skin surface from the skin surface curvature measurement mechanism <NUM>. The received data may then be processed by the processing mechanism <NUM> in order to determine a location of the personal care device <NUM>.

The skin surface curvature measurement mechanism <NUM> may, in some embodiments, comprise a plurality of elements pivotally mounted to a portion of the personal care device <NUM>, such that the plurality of elements are pivotally mounted relative to the personal care device and to one another. The elements may be considered to be surface-engaging elements which, during use, are in contact with the skin surface of the subject. By using a measured orientation of the surface-engaging elements of the skin surface curvature measurement mechanism <NUM>, it is possible to determine a degree of curvature of the skin surface. Thus, a skin surface curvature may be determined for a portion of the skin surface with which that the surface-engaging elements are in contact. As the personal care device <NUM> is moved over the subject's skin surface, the skin surface curvature may be determined at more positions, and data representing the skin surface curvature may be communicated to the processing apparatus <NUM> (e.g. by a wired or wireless connection) so that a location of the personal care device can be determined.

Once the data acquired using the skin surface curvature measurement mechanism <NUM> has been transmitted to the processing apparatus <NUM>, the processing apparatus compares the data with existing curvature information for a plurality of regions of the skin surface of the subject. For example, the processing apparatus <NUM> may obtain such curvature information from a database or other data structure stored in a storage medium, such as a memory, associated with the personal care device <NUM>. The curvature information may have been acquired and stored in the storage medium as part of a previously-performed calibration process, such that, for a particular subject, curvature information is known for a plurality of regions or locations. By comparing the curvature data measured for a first region of the skin surface on the subject with the stored curvature information, the processing apparatus <NUM> is able to determine a location of the first region of the skin surface. For example, if the processing apparatus receives data from the skin surface curvature measurement mechanism <NUM> indicating that the first region has a particular curvature c, it may be determined from the comparison with the stored curvature information that a curvature c corresponds with the chin of the subject. Accordingly it may be determined that the personal care device <NUM> is in contact with the chin of the subject. Making such a determination can be useful for adjusting a setting or operating parameter of the personal care device <NUM> to improve the personal care activity. For example, hairs growing from a person's chin are typically coarser than hair growing from a person's cheeks. Therefore, it may be beneficial to increase the speed of a cutting element of a shaver when it is determined that the cutting element of the shaver is positioned at the subject's chin, rather than at the subject's cheeks.

The embodiment shown in <FIG> is formed of a single unit. In other embodiments, the skin surface curvature measurement mechanism <NUM> may form part of, or be housed by, a separate attachment, which can be removably attached or connected to the main body <NUM> of the personal care device <NUM>. <FIG> is a schematic illustration of an example of a personal care device <NUM> in which the skin surface curvature measurement mechanism is part of a unit which can be detached from the main body <NUM>. The personal care device <NUM> includes the main body <NUM> and the processing apparatus <NUM> as shown in the example of <FIG>. However, the personal care device <NUM> further comprises an attachment <NUM> to house a communication unit <NUM>, the attachment being detachably mountable to the main body <NUM>. The attachment <NUM> may be mounted to the main body <NUM> of the personal care device <NUM> using attachment mechanisms that will be familiar to those skilled in the art. Enabling the attachment <NUM> to be removed and reattached to the main body <NUM> may be beneficial so that the attachment, or components thereof, may be cleaned or easily replaced. For example, an attachment for use in one type of treatment (e.g. shaving) may be removed and replaced with an attachment for use with another type of treatment (e.g. exfoliating).

In the example shown in <FIG>, the skin surface curvature measurement mechanism <NUM> is coupled to the attachment <NUM>. In some examples, the measurement mechanism <NUM> may form part of the attachment <NUM>. The main body <NUM> accommodates the processing apparatus <NUM> in this example. However, in other examples, the processing apparatus <NUM> may be located in the attachment <NUM> itself.

The communication unit <NUM> is configured to communicate the data representative of the measured degree of curvature of the skin surface to the processing apparatus <NUM>. Thus, while, in some examples, the data acquired using the skin surface curvature measurement mechanism <NUM> may be communicated directly from the measurement mechanism to the processing apparatus <NUM> (as indicated by the dashed line in <FIG>), in other examples, the data may be communicated to the processing apparatus via the communication unit <NUM> (as indicated by the dashed lines in <FIG>).

Complementary electrical connections (not shown) may be provided on the attachment <NUM> and on the main body <NUM> where the attachment may be mounted, to facilitate communication of power and/or data between components in the attachment <NUM> (e.g. the skin surface curvature measurement mechanism <NUM>) and components in the main body <NUM> (e.g. the processing apparatus <NUM>).

The skin surface curvature measurement mechanism <NUM> may be able to acquire sufficient curvature data to enable a location of the personal care device <NUM>, <NUM> to be determined. However, according to some embodiments of the invention, additional data may be acquired and used to determine the location of the personal care device <NUM>, <NUM> more accurately. In some embodiments, the personal care device <NUM>, <NUM> may further comprise a sensor <NUM> for acquiring motion data for the personal care device. The motion data may, for example, comprise data describing how the personal care device has been moved or displaced during a defined measurement period. The processing apparatus <NUM> may be configured to determine the location of the first region of the skin surface on the subject further based on motion data acquired using the sensor <NUM>, as is described in greater detail below. The sensor <NUM> may be any sensor capable of measuring, amongst other things, a displacement of the personal care device <NUM>, <NUM> and or, more specifically, displacement of the skin surface curvature measurement mechanism <NUM> of the personal care device. In one example, the sensor <NUM> may comprise an inertial measurement unit (IMU). An IMU, which will be familiar to those skilled in the art, may use an accelerometer, a gyroscope and/or a magnetometer to measure various parameters (e.g. specific force, angular rate and/or orientation) of a device in which the IMU is installed. The sensor <NUM> may be positioned in the main body <NUM>, or in the attachment <NUM>, as indicated by the use of the dashed lines to represent the sensor in <FIG>. Data acquired using a sensor <NUM> is communicated to the processing apparatus <NUM> via a wired or wireless connection for use in determining the device location. In some embodiments, the data may be communicated from the sensor <NUM> to the processing apparatus <NUM> via the electrical connections mentioned above.

In some examples, with the use of a Kalman filter, a gravity vector may be estimated from data acquired using the IMU (e.g. from data acquired using accelerometers in the IMU) along three special axes. The gravity vector may be used (with or without data from a gyroscope of the IMU) to estimate an orientation of the skin surface curvature measurement mechanism <NUM> with respect to the gravity field, which can help to increase the accuracy of the location determination made by the processing apparatus <NUM>. In some examples, it may be assumed that the part of the subject with which the personal care device is being used is oriented in a particular way during use; for example, it may be assumed that a user's head is upright or slightly tilted during a shaving activity.

<FIG> is a schematic illustration of a further example of a personal care device <NUM>, according to various embodiments of the invention. The personal care device <NUM> includes the main body <NUM>, the processing apparatus <NUM> and the skin surface curvature measurement mechanism <NUM>. The personal care device <NUM> may further comprise a housing <NUM> supporting at least a first treatment element <NUM> and a second treatment element <NUM>. The first treatment <NUM> may comprise a first surface-engaging element <NUM>, and the second treatment element <NUM> may comprise a second surface-engaging element <NUM>. Each surface-engaging element <NUM>, <NUM> is pivotally mounted relative to the housing <NUM> such that they are pivotable relative to one another. Thus, as the surface-engaging elements <NUM>, <NUM> engage the skin surface of a subject, each surface-engaging element may independently pivot depending on the curvature of the surface that it contacts. The skin surface curvature measurement mechanism <NUM> comprises a first sensor <NUM> configured to measure an orientation of the first surface-engaging element <NUM> relative to the housing <NUM>, and a second sensor <NUM> configured to measure an orientation of the second surface-engaging element <NUM> relative to the housing. The relative orientations of the first and second surface-engaging elements <NUM>, <NUM> are used by the processing apparatus <NUM> to determine the location of the first region of the skin surface on the subject, with which the personal care device <NUM> is in contact.

Specific examples of personal care devices in which the present invention may be embodied are now discussed with reference to <FIG>. <FIG> is an illustration of part of a personal care device <NUM> which, in this example, comprises an electric shaver. In <FIG>, part of the main body <NUM> is shown, along with the attachment <NUM>, which is mounted to the main body. <FIG> is a plan view illustration of the attachment <NUM> of <FIG>. The attachment <NUM> may be pivotally mounted, such that the attachment may pivot relative to the main body <NUM> about a pivot point <NUM>. The personal care device <NUM> also includes the housing <NUM>. In the example shown in <FIG> and <FIG>, the housing <NUM> supports three treatment elements <NUM>, <NUM>, <NUM>, each of which comprises a shaving unit. In other examples, more or fewer treatment elements may be provided on the attachment <NUM>. The shaving unit of each treatment element <NUM>, <NUM>, <NUM> has an external cutting member <NUM> and an internal cutting member <NUM> movably arranged relative to the external cutting member. The internal cutting member <NUM> sits underneath the external cutting member <NUM> and, therefore, may only be visible through slits in the external cutting member. For this reason, the internal cutting member <NUM> is shown with dashed lines. In some examples, the internal cutting member <NUM> may rotate relative to (e.g. in an opposite direction to) its corresponding external cutting member <NUM> to effect cutting of hairs extending from the subject's skin. Each treatment element <NUM>, <NUM>, <NUM> also includes a skin-supporting rim <NUM> surrounding the external cutting member <NUM> and pivotally mounted relative to the housing <NUM> (about an axes indicated by crosshairs). In this example, the skin-supporting rim <NUM> of each respective treatment element <NUM>, <NUM>, <NUM> comprises a surface-engaging element (e.g. the surface engaging elements <NUM>, <NUM>). Thus, in use, the treatment elements <NUM>, <NUM>, <NUM> of the personal care device <NUM> are placed against the skin surface of the subject whose hair is to be cut, and the skin-supporting rim <NUM> is caused to pivot relative to the housing <NUM> in a manner dependent upon the curvature of the surface of the skin with which the skin-supporting rim is in contact.

The above example, described with reference to <FIG> and <FIG>, relates to an electric shaver having three shaving units. More generally, a personal care device (e.g. the personal care device <NUM>) may be an electric shaver, wherein the first treatment element <NUM> and the second treatment element <NUM> both comprise a shaving unit having an external cutting member <NUM>, an internal cutting member <NUM> movably arranged relative to the external cutting member, and a skin-supporting rim <NUM> surrounding the external cutting member and pivotally mounted relative to the housing <NUM>, wherein the first surface-engaging element <NUM> and the second surface-engaging element <NUM> comprise the skin-supporting rim <NUM> of the shaving unit of, respectively, the first treatment element <NUM> and the second treatment element <NUM>.

As noted above, one or more sensors (e.g. the sensors <NUM>, <NUM>) may be used to measure respective orientations of the surface-engaging elements <NUM>, <NUM>, <NUM> relative to the housing <NUM>, and various techniques may be used to achieve this. In <FIG>, a pair of fulcrums <NUM>, or pivot points, is shown positioned at opposite sides of each shaving unit and, therefore, each skin-supporting rim <NUM>. Each skin-supporting rim <NUM> is mounted such that it is able to pivot about an axis defined by the respective pair of fulcrums <NUM>. The orientation of each skin-supporting rim <NUM> relative to the housing <NUM> may be measured by detecting contact (or a degree of contact) with an engagement surface <NUM> positioned beneath one side of skin-supporting rim. Various embodiments of the engagement surface <NUM> and the interaction of each skin-supporting rim <NUM> with its corresponding engagement surface are described below with reference to <FIG>, <FIG> and <FIG>.

<FIG> are side view illustrations showing attachments <NUM>, <NUM>, respectively, and each having a cutaway section to illustrate the pivotal movement of the surface-engaging elements. In both <FIG>, the cutaway section reveals a treatment element <NUM>, having a shaving unit formed of an internal cutting member <NUM> and an external cutting member <NUM> and a skin-supporting rim <NUM>. The skin-supporting rim <NUM> is attached to (or an extension of) a base <NUM>, via which the skin-supporting rim is pivotally mounted to a fulcrum <NUM> about which the skin-supporting rim may pivot in the direction indicated by the arrow A. In the embodiments shown in <FIG>, different sensors are used to measure the orientation of the skin-supporting rim <NUM> relative to the housing <NUM>.

In the attachment <NUM> of <FIG>, a multiple-point resistive force sensor <NUM> is provided for measuring the orientation of the skin-supporting rim <NUM> relative to the housing <NUM>. In this embodiment, when a force is applied to the side of the skin-supporting rim <NUM> (e.g. as a result of the skin-supporting rim being pressed against the skin surface of a subject), causing it to pivot towards the force sensor <NUM>, the skin-supporting rim compresses a spring <NUM>, thereby applying a force to the force sensor. When a force is applied by a spring <NUM> onto the force sensor <NUM>, a resistance within the force sensor changes, and is measured by electronic components (not shown) within the attachment <NUM> and/or the main body <NUM> (not shown in <FIG>). The force applied to the force sensor <NUM> is proportional to the amount of compression of the spring <NUM> caused by the skin-supporting rim <NUM>. Each skin-supporting rim <NUM> is provided with a corresponding spring <NUM> and, in the example shown, the force sensor <NUM> comprises a <NUM>-point thin film resistive force sensor. In other examples, a separate force sensor <NUM> may be provided for each spring <NUM>.

In the attachment <NUM> of <FIG>, a switch-type sensor is provided for measuring the orientation of the skin-supporting rim <NUM> relative to the housing <NUM>. The sensor in this embodiment comprises a first switch <NUM> located beneath the skin-supporting rim <NUM> one side of the pivot, and a second switch <NUM> located beneath the skin-supporting rim at an opposing side of the pivot. When a force is applied to one side of the skin-supporting rim <NUM> (e.g. as a result of the skin-supporting rim engaging the skin surface of a subject) nearest the first switch <NUM>, the skin-supporting rim <NUM> is caused to pivot towards and engage the first switch, thereby activating the first switch. When a force is applied to the side of the skin-supporting rim <NUM> nearest the second switch <NUM>, the skin-supporting rim <NUM> is caused to pivot towards and engage the second switch, thereby activating the second switch. Each skin-supporting rim <NUM> of the attachment is provided with a corresponding pair of switches, such that the orientation of each skin-supporting rim can be measured. One or both of the first and second switches <NUM>, <NUM> may comprise a capacitive switch configured to react to (i.e. be activated by) the presence of (e.g. engagement with) the skin-supporting rim <NUM>. By using the first and second switches <NUM>, <NUM> for each skin-supporting rim <NUM>, three orientations of each skin-supporting rim may be measured: a first orientation when the skin-supporting rim is tilted towards the first switch, a second orientation when the skin-supporting rim is tilted towards the second switch, and a third orientation when the skin-supporting rim is not tilted towards either switch, such that neither the first switch nor the second switch are activated.

In the embodiments shown in <FIG>, the skin-supporting rim <NUM> of each treatment element <NUM>, <NUM>, <NUM> are the surface engaging elements whose orientation relative to the housing <NUM> is measured in order to determine the degree of curvature of the skin surface. However, in other embodiments, surface-engaging elements may be provided for curvature measurement, which are not part of the treatment element of the personal care device. <FIG> are plan view illustrations of examples of attachments <NUM>, <NUM> in which separate surface engaging elements are provided for measuring the curvature of the skin surface, in addition to the treatment elements for performing a personal care activity. In <FIG>, surface-engaging elements <NUM>, <NUM>, <NUM> are provided between pairs of treatment elements <NUM>, <NUM>, <NUM>. In this embodiment, each surface-engaging element <NUM>, <NUM>, <NUM> may be configured to pivot about a respective fulcrum <NUM>, <NUM>, <NUM>, and compress a respective spring <NUM>, <NUM>, <NUM> as a force is applied to the surface-engaging element. Each spring <NUM>, <NUM>, <NUM> is in contact with a resistive force sensor <NUM>, such that, as each spring is compressed, a resistance within the force sensor changes by an amount proportional to the applied force, and is measured by electronic components (not shown) in the attachment <NUM> or the personal care device to which is it attached. The arrangement of <FIG> functions in a manner similar to the arrangement shown in <FIG>.

In some embodiments, the treatment elements <NUM>, <NUM>, <NUM> of <FIG> may also be arranged to pivot, as shown in the arrangements of <FIG>, such that the resistive force sensor <NUM> is able to measure an orientation of each treatment element in addition to the orientation of each surface-engaging element <NUM>, <NUM>, <NUM>. In such an arrangement, additional curvature information (i.e. curvature information from the surface-engaging elements <NUM>, <NUM>, <NUM> and curvature information from the treatment elements <NUM>, <NUM>, <NUM>) may be obtained as the personal care device is moved over the skin surface of a subject. In other examples, the surface-engaging elements <NUM>, <NUM>, <NUM> may be provided on a device having just one treatment element. Thus, curvature information may be measured on such a device, even though it may contain just one treatment element.

In an alternative embodiment, the skin surface curvature measurement mechanism comprises one or more flexible sensors comprising a plurality of capacitive sensors. In <FIG>, an attachment <NUM> is shown having three treatment elements <NUM>, <NUM>, <NUM> which, in this example, may be treatment elements other than shaving units, such as brushes. The skin surface curvature measurement mechanism in this embodiment comprises three flexible sensors <NUM>, <NUM>, <NUM>. Each flexible sensor <NUM>, <NUM>, <NUM> has a grid of capacitive sensors mounted thereon. In one example, electrodes (e.g. silver nanowires) are layered in a multi-layer stack on a flexible insulating substrate, with intermediate layers of polydimethylsiloxane (PDMS). When a skin-engaging element of each of the treatment elements <NUM>, <NUM>, <NUM> engage a skin surface, it pivots and engages one or more of the sensors <NUM>, <NUM>, <NUM>, causing them to flex (e.g. as a result of a force being applied to the sensor). The surface of the electrodes is therefore caused to change, from which a measure of the curvature of the skin can be made. In other embodiments, fewer sensors of this type may be employed; for example, a single ring-shaped sensor made be provided, which is capable of determining a measure of the curvature of a skin surface with which it is in contact.

<FIG> is a plan view illustration of an attachment <NUM> according to a further embodiment. In this embodiment, each treatment element <NUM>, <NUM>, <NUM> respectively comprises a rotatable brush <NUM>, <NUM>, <NUM>, for example for massaging or exfoliating a subject's skin. Each brush <NUM>, <NUM>, <NUM> is rigidly mounted within a respective rim <NUM>, <NUM>, <NUM>, which is pivotally mounted to the housing <NUM>, in a manner similar to the skin-supporting rim <NUM> of the attachments <NUM>, <NUM> shown in <FIG> respectively. A spring <NUM>, <NUM>, <NUM> is positioned beneath one side of each rim <NUM>, <NUM>, <NUM>, such that, as a force is applied to that side of the brush, its respective rim <NUM>, <NUM>, <NUM> is caused to pivot and compress the spring. The force applied to compress each spring is measured by a resistive force sensor <NUM>, in a manner similar to that discussed with reference to <FIG>.

<FIG> is a side view illustration of an example of a personal care device <NUM> which, in this example, is a hair trimmer or clipper. The personal care device <NUM> comprises a body <NUM> which can be held by a user while a personal care activity (e.g. trimming or cutting hair) is performed. A treatment element <NUM> is provided which, in this example, may comprise a blade or a pair or reciprocating blades configured to cut a hair that is encountered by the treatment element. The personal care device <NUM> further comprises a skin surface curvature measurement mechanism <NUM> which comprises a first surface-engaging element <NUM> and a second surface-engaging element <NUM> rotatable about a fulcrum <NUM> relative to the first surface-engaging element. In this embodiment, the first surface-engaging element <NUM> is in a fixed position relative to the body <NUM>, but the second surface-engaging element <NUM> is able to pivot about the fulcrum <NUM> in response to its engagement with the changing curvature of a skin surface of a subject with whom the personal care device <NUM> is contact. Thus, in use, the treatment element <NUM> and the first surface-engaging element <NUM> engage a skin surface of the subject as the personal care device <NUM> is moved over the skin surface. Data representative of the curvature, measured by the skin surface curvature measurement mechanism <NUM>, is processed using a processing apparatus <NUM> associated with the personal care device <NUM>, and a location of the personal care device with respect to the skin surface of the subject may be determined. In some embodiments, a sensor <NUM> may be provided, and may form part of the skin surface curvature measurement mechanism <NUM>. The sensor <NUM> is configured to measure an orientation of the first surface-engaging element <NUM> relative to the second surface-engaging element <NUM>. In the example shown in <FIG>, the sensor comprises a spring <NUM> and a force sensor <NUM> (e.g. a resistive force sensor). The spring <NUM> is arranged to be bent or twisted as the second surface-engaging element <NUM> pivots about the fulcrum <NUM>. The spring <NUM> engages the force sensor <NUM> such that, as the second surface-engaging element <NUM> pivots and causes the spring to twist, the force applied by the spring on the force sensor changes relative to the change in relative orientations of the first and second surface-engaging element <NUM>. An indication of the force measured by the force sensor <NUM> is received by the processing apparatus <NUM>, which determines the location of the personal care device <NUM> in the manner described herein.

In the embodiments described herein, the processing of data from the skin surface curvature measurement mechanism is performed by a processing apparatus or processor (e.g. the processing apparatus <NUM>). According to a further aspect, the present invention provides such a processing apparatus. <FIG> is a schematic illustration of an example of a processing apparatus <NUM> configured for determining a location of a personal care device with respect to a skin surface of a subject. The processing apparatus <NUM> is configured to receive data <NUM> representative of a measured degree of curvature of the skin surface within a first region of the skin surface of the subject, with which the personal care device is in contact. The data <NUM> may, for example, be acquired using the skin surface curvature measurement mechanism <NUM>, <NUM> discussed above. The processing apparatus <NUM> is further configured to retrieve, from a storage medium <NUM>, curvature information for a plurality of regions of the skin surface of the subject. The storage medium <NUM> may, for example, comprise a memory storing a database or lookup table of curvature information for the plurality of regions of the skin surface of the subject. The processing apparatus <NUM> is further configured to determine, by comparing the measured degree of curvature with the curvature information for the plurality of regions of the skin surface, a location of the first region of the skin surface on the subject, with which the personal care device is in contact. For example, if the curvature measured in the first region corresponds to curvature information in the storage medium that was obtained from a chin region, then it may be determined that the data representative of the measured degree of curvature was also obtained from the chin region of the subject. In some embodiments, the processing apparatus <NUM> may also receive motion data for the personal care device, for example from a motion sensor, such as the sensor <NUM>. The motion data may, for example, comprise data describing how the personal care device has been moved or displaced during a defined measurement period. The processing apparatus <NUM> may be configured to determine the location of the first region of the skin surface on the subject further based on motion data. A sensor used to capture the motion data may be any sensor capable of measuring, amongst other things, a displacement of the personal care device and or, more specifically, displacement of the skin surface curvature measurement mechanism <NUM> of the personal care device. For example, the motion data may be acquired by an inertial measurement unit (IMU). The processing apparatus <NUM> is further configured to generate, based on the determined location of the first region, an instruction <NUM> of an action to be performed in respect of the personal care device. For example, the processing apparatus <NUM> may generate an instruction (e.g. an instruction signal) to cause the personal care device to increase its power (e.g. cutting power) while it is located in the chin region. In other examples, the instruction of an action to be performed may comprise an instruction to provide feedback (e.g. via a user interface of the personal care device) to the subject regarding the personal care activity. In yet further examples, the instruction of an action to be performed may comprise an instruction to track parameters (e.g. skin parameters) over a period of time, for the provision of health and/or beauty advice.

As noted previously, the attachment <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be detachable from a main body <NUM> of a personal care device. The attachment discussed herein may be considered to be a system in its own right. Thus, according to a further aspect, the present invention provides such a system. <FIG> is a schematic illustration of an example of a system <NUM> for determining a location of a personal care device with respect to a skin surface of a subject. The system <NUM> comprises a housing <NUM> to house a communication unit <NUM>. The system <NUM> further comprises a skin surface curvature measurement mechanism <NUM> coupled to the housing <NUM>, the skin surface curvature measurement mechanism being configured for measuring a degree of curvature of the skin surface of the subject within a first region of the skin surface. The system <NUM> further comprises a processing apparatus <NUM>, <NUM> as described herein. As discussed with reference to <FIG>, the processing apparatus <NUM>, <NUM> is configured to receive data representative of a measured degree of curvature of the skin surface within a first region of the skin surface of the subject, with which the personal care device is in contact and, based on the data and other retrieved curvature information, determine a location of the first region.

The skin surface curvature measurement mechanism <NUM> is configured to generate the data representative of the measured degree of curvature of the skin surface within the first region of the skin surface. For example, the skin surface curvature measurement mechanism <NUM> may generate the data using techniques described herein. The communication unit <NUM> is configured to communicate the data representative of the measured degree of curvature of the skin surface within the first region of the skin surface to the processing apparatus <NUM>, <NUM>. In some examples, the communication of the data between the communication unit <NUM> and the processing apparatus <NUM>, <NUM> may be achieved using known data transmission methods. For example, the communication unit <NUM> may transmit the data to a receiver associated with and/or connected to the processing apparatus <NUM>, <NUM>.

The curvature of the skin surface may be measured in various ways using the skin surface curvature measurement mechanism <NUM>. In some embodiments, as described above, the skin surface curvature measurement mechanism <NUM> may comprise a first surface-engaging element <NUM> and a second surface-engaging element <NUM> (see <FIG>), and the first and second surface-engaging elements may be moveable relative to one another. In such examples, the data representative of the measured degree of curvature of the skin surface within the first region of the skin surface comprises a measure of a relative orientation of the first surface engaging element <NUM> and second surface engaging element <NUM>.

In embodiments in which the curvature data is acquired using a measurement of relative orientations of surface-engaging elements, the system <NUM> may comprise at least one orientation sensor <NUM>, <NUM> configured for measuring an orientation of the first surface-engaging element <NUM> relative to the housing <NUM>, and an orientation of the second surface-engaging element <NUM> relative to the housing. Each of the at least one sensors <NUM>, <NUM> may, in some embodiments, comprise a force sensor or a switch, as described in embodiments herein. The data representative of the measured degree of curvature of the skin surface within the first region of the skin surface may therefore comprise a measure of the orientation of the first surface-engaging element <NUM> relative to the housing <NUM>, and a measure of the orientation of the second surface-engaging element <NUM> relative to the housing.

In some embodiments of the system <NUM>, the first surface-engaging element <NUM> and the second surface-engaging element <NUM> are pivotally mounted such that they are each pivotable relative to the housing <NUM> and relative to one another. For example, the first and second surface-engaging elements <NUM>, <NUM> may be mounted in a manner similar to that shown in the embodiments of <FIG>.

The data representative of the measured degree of curvature may comprise an average degree of curvature of the skin surface within the first region. The average degree of curvature may be calculated from curvatures measured in multiple different 'directions' or normal planes as explained below. A curvature of a surface at a particular point is a measure of how the surface bends at that point. For example, at a point on the skin surface, consider a plane that contains the normal (outward) vector at that point. Such a normal plane cuts the skin surface in a plane curve. This curve will in general have different curvatures for different normal planes. The principal curvatures kp<NUM> and kp<NUM> are the maximum and minimum of these curvatures.

Examples of how a curvature (in one of the normal planes) at a point may be determined are discussed with reference to <FIG> and <FIG>. <FIG> are diagrams showing how a curvature may be measured using skin surface curvature measurement mechanisms according embodiments disclosed herein. The examples shown in <FIG> are based on a skin surface curvature measurement mechanism having a surface-engaging element <NUM> similar to that shown in the embodiments of <FIG>. An axis at the center of the three treatment elements <NUM>, <NUM>, <NUM> (e.g. in the center of the housing <NUM> of <FIG>), and perpendicular thereto (e.g. extending out of the page in <FIG>) when the treatment elements are in their neutral, non-pivoted positions, is assumed to be an approximation of the normal to the skin surface at the center of the personal care device, when the personal care device is in use. Such a normal axis <NUM> is indicated in <FIG>. Now, consider a normal plane through this assumed surface normal and perpendicular to a pivot axis <NUM> of the surface-engaging element <NUM> (e.g. of one of the treatment elements <NUM>, <NUM>, <NUM>). <FIG> show such a normal plane <NUM>; the normal plane is the plane of the page. From an angle αi, which can be considered to represent the orientation of the skin surface normal at the center of the treatment element <NUM> with respect to the skin surface normal <NUM> at the center of the device, one can calculate a curvature ki (the reciprocal of the radius of curvature) as shown in <FIG>. Curvature can be positive (as in <FIG>) or negative (as in <FIG>). In embodiments having three surface-engaging elements (e.g. of three treatment elements <NUM>, <NUM>, <NUM>), three curvature values k<NUM>, k<NUM>, k<NUM> can be determined. An average degree of curvature (kav = Σi ki/N where N is the number of surface-engaging elements) and a curvature range ( <MAT>) may be determined. The values of kav and Δk have an approximate relation to the principal curvatures according to the following relationships: <MAT> <MAT>.

If the number of surface-engaging elements N is larger than <NUM>, then values of kav and Δk are calculated using the above relationships. The relationship between kav and Δk and the principal curvatures may be more accurate when measurements are obtained from a greater number of surface-engaging elements.

In embodiments having just two surface-engaging elements (i.e. where N = <NUM>), the two pivot axes typically are aligned parallel to one another, and curvature is registered only in a single plane perpendicular to the pivot axes. In this case only kav is calculated.

In other embodiments where N = <NUM>, a single pivot axis may connect the two surface-engaging elements, as shown in the example of <FIG>. In this example, which is based on the embodiments of <FIG>, a first surface-engaging element <NUM> and a second surface-engaging element <NUM> are pivotally connected to a fulcrum <NUM>. In this example, a bisector <NUM> that divides the opening angle into to equal halves may be taken as the assumed normal axis to the skin surface, as indicated in <FIG>.

According to a further aspect, a computer-implemented non-therapeutic and non-surgical method is provided. <FIG> is a flowchart of an example of a computer-implemented non-therapeutic and non-surgical method <NUM> of determining a location of a personal care device with respect to a skin surface of a subject. The method <NUM> comprises, at step <NUM>, receiving data representative of a measured degree of curvature of the skin surface within a first region of the skin surface of the subject, with which the personal care device is in contact. The received data is acquired or measured using a skin surface curvature measurement mechanism <NUM>, <NUM> and using techniques described herein. For example, as a user moves the personal care device over the surface of their skin, the data may be measured and received by a processor or processing apparatus performing the method <NUM>. At step <NUM>, the method <NUM> discloses determining, by comparing the measured degree of curvature with curvature information for a plurality of regions of the skin surface of the subject contained in a database, an indication of a location of the first region of the skin surface on the subject. The method <NUM> comprises, at step <NUM>, performing, based on the determined indication of the location of the first region, an action in respect of the personal care device. The action to be performed depends on the nature of the personal care device. In some examples, the action performed may include adjusting an operating parameter of the personal care device, such as a motor speed, or a cutting length of a blade.

As noted above, the location of the personal care device with respect to the skin surface (i.e. the location of the first region) may be determined more accurately when data indicative of the motion of the personal care device is also taken into account. Thus, a motion sensor, such as an IMU may be provided in the personal care device and used to measure the movement of the device. <FIG> is a flowchart of a further example of a method <NUM> of determining a location of a personal care device with respect to a skin surface of a subject. The method <NUM> includes the steps <NUM>, <NUM> and <NUM> of <FIG>. In some embodiments, the method <NUM> may further comprise, at step <NUM>, receiving data indicative of a measured displacement of the personal care device between the first region of the skin surface and a second region of the skin surface, with which the personal care device was previously in contact. Thus, the displacement may be measured using the motion sensor, such as the IMU, and may provide information indicating a previous location from which the device has moved. In one example, the data may indicate that a personal care device such as a shaver has been moved from the second region to the first region in a movement representative of a move from the top of the subject's chin to the top right part of the subject's chin. In such examples where data indicative of a measured displacement is available, determining the indication of the location of the first region may further be based on comparing the data indicative of a measured displacement with position information for the plurality of regions of the skin surface of the subject contained in the database. Thus, if is it determined the data indicative of a measured displacement corresponds to position information (e.g. previously-acquired data indicating two positions, or the movement between the two positions), then that determination may help to reinforce the determination of the location of the first region made using the curvature data from the skin surface curvature measurement mechanism.

The curvature information that is compared in step <NUM> with the data received in step <NUM> may be acquired during a calibration process performed by the subject prior to use of the personal care device, or during its first use. In some embodiments, the method <NUM> may further comprise a series of steps prior to receiving (at step <NUM>) the data representative of the measured degree of curvature of the skin surface within the first region of the skin surface. At step <NUM>, the method <NUM> may comprise receiving calibration displacement data indicative of a displacement of the personal care device between a plurality of regions of the skin surface of the subject. The calibration displacement data indicative of the displacement may, for example, be received during a calibration process as discussed above, using the motion sensor (or calculated from data acquired using the motion sensor) of the personal care device in the manner disclosed herein. When the personal care device is to be used by a user for the first time, the user may be prompted to perform a calibration. Each user of the personal care device may, for example, perform a personalized calibration of the personal care device by moving the device over their skin (or a portion thereof) the first time they use the device, so that the calibration displacement data indicative of the displacement can be measured. Measured calibration displacement data for a subject may be stored in association with the subject, for example as part of a user profile. In some embodiments, a user may be prompted to start the calibration process with the personal care device in a particular position, such as on their chin, to provide a defined reference to the location of the personal care device during the calibration. In some examples, curvature data may also be acquired during the calibration process (e.g. using the skin surface curvature measurement mechanism) and, in such examples, the curvature data may also be stored in association with the data representative of the displacement.

During the calibration, as the personal care device is moved, data indicative of a measured displacement (e.g. from the IMU) may be recorded in terms of the displacement of the personal care device in three dimensions (e.g. Δx, Δy, Δz). The skin surface curvature measurement mechanism measures data representative of a curvature of the skin surface as the personal care device is moved over the skin surface, providing orientation data (α<NUM>,. From the data indicative of a measured displacement, the processing apparatus is able to calculate a current position of the device relative to a position of the device when the data collection started. From the orientation data, values representing curvature of the skin surface can be calculated, as discussed above. The relative position data is stored in the storage medium (e.g. the memory) together with the concurrently obtained curvature values. Data sampling and processing in this way may continue until a defined amount of data has been acquired, or until the calibration process is otherwise ended. In other embodiments, data indicative of a measured displacement (e.g. from an IMU) may not be acquired, and the calibration of the personal care device may be performed based just on the orientation data from the skin surface curvature measurement mechanism.

In some embodiments, at the end of the calibration process (e.g. indicated by the user pressing a button on the personal care device or by the expiration of a predefined amount of time), the processing apparatus may be configured to determine whether or not a sufficient amount of data has been acquired. For instance, the processing apparatus may be configured to determine whether the spatial extent of the subject's skin surface that has been covered fits within expected minimum and maximum boundaries. If it is determined that the data is incomplete (e.g. that more data is required from the calibration), then the user may be asked to repeat or supplement the calibration process either immediately or at a later time.

If, on the other hand, it is determined that the amount and/or quality of data acquired is complete and/or adequate, then the method <NUM> may proceed to a model fitting step. Thus, the method <NUM> may further comprise, at step <NUM>, fitting a computer model of the skin surface of the subject to the received calibration displacement data indicative of the displacement of the personal care device. The processing apparatus may, for example, be configured to fit a model (e.g. a face model) to the stored relative position data. The face model may, for example, be a general CAD-like model of a human face controlled by a set of model parameters that determine the distances between facial landmarks (e.g. the chin, corners of the mouth, ears, jaw angles, and the like) and the shape of facial elements (e.g. flatter or rounder cheeks, neck, and the like). In other examples, the model may comprise a model of another part of the subject's body.

At the start of the model fitting process, a coronal plane (i.e. a plane dividing a subject's face between a left side and a right side) and the chin may be identified in a "point cloud" formed by the relative position data. In some embodiments, machine learning techniques may be applied to aid the identification. The face model (which may be provided with model parameters based on average or arbitrary values) may be aligned to the coronal plane and the chin identified in the relative position data. In some embodiments, the alignment process may involve applying a least squares fit process. In such a process, for each point in the relative position data, the distance to the surface of the face model may be calculated. The sum of the squares of these distances provides a measure for the goodness of the fit of the model to the measured position data, for the current model parameters. The model parameters may then be adapted by an optimization algorithm until the sum of squares is reduced or minimized. A good optimization algorithm may converge to a global minimum, which represents the best possible fit of the model to the measured data. For embodiments where the personal care device comprises a beard trimmer or shaver, only the lower part of the face model (below the nose-ear line) and related model parameters may be used. Thus, the method <NUM> may further comprise, at step <NUM>, determining, from the calibration displacement data and the fitted computer model, curvature information for each region of the plurality of regions.

In some examples, curvature information may be estimated from the fitted model. For example, it may be clear from a point cloud of displacement data which parts of the data correspond to certain parts of the subject's body or face, and curvature information may be known or predetermined for those areas. In other examples, curvature information may be acquired along with the calibration displacement data, and the curvature information may be stored in association with the corresponding calibration displacement data.

For a selected number of points on the fitted face model, a set of corresponding curvature values may be calculated (e.g. via interpolation and averaging of the curvature values linked to the nearest relative position data). The fitted model and corresponding curvature values may then be stored in the memory. Thus, at step <NUM>, the method <NUM> may further comprise storing, in the database, the determined curvature information in association with the corresponding region on the skin surface of the subject.

Steps of the methods <NUM>, <NUM> may be performed using the processing apparatus <NUM>, <NUM> described herein.

According to a further aspect, the invention provides a computer program product. <FIG> is a schematic illustration of an example of a computer-readable medium <NUM> in communication with a processor <NUM>. According to some embodiments, a computer program product comprises a non-transitory computer-readable medium <NUM>, the computer-readable medium having computer-readable code embodied therein, the computer-readable code being configured such that, on execution by a suitable computer or processor <NUM>, the computer or processor is caused to perform steps of the method <NUM>, <NUM> disclosed herein. The processor <NUM> may comprise, or function in a manner similar to the processing apparatus <NUM>, <NUM>.

The processor or processing apparatus <NUM>, <NUM>, <NUM> can comprise one or more processors, processing units, multi-core processors or modules that are configured or programmed to control the system <NUM> in the manner described herein. In particular implementations, the processor or processing apparatus <NUM>, <NUM>, <NUM> can comprise a plurality of software and/or hardware modules that are each configured to perform, or are for performing, individual or multiple steps of the method described herein.

The term "module", as used herein is intended to include a hardware component, such as a processor or a component of a processor configured to perform a particular function, or a software component, such as a set of instruction data that has a particular function when executed by a processor.

It will be appreciated that the embodiments of the invention also apply to computer programs, particularly computer programs on or in a carrier, adapted to put the invention into practice. The program may be in the form of a source code, an object code, a code intermediate source and an object code such as in a partially compiled form, or in any other form suitable for use in the implementation of the method according to embodiments of the invention. For example, a program code implementing the functionality of the method or system according to the invention may be sub-divided into one or more sub-routines. An embodiment relating to a computer program product comprises computer-executable instructions corresponding to each processing stage of at least one of the methods set forth herein. These instructions may be sub-divided into sub-routines and/or stored in one or more files that may be linked statically or dynamically. Another embodiment relating to a computer program product comprises computer-executable instructions corresponding to each means of at least one of the systems and/or products set forth herein. These instructions may be sub-divided into sub-routines and/or stored in one or more files that may be linked statically or dynamically.

Claim 1:
A computer-implemented non-therapeutic and non-surgical method (<NUM>) of determining a location of a personal care device with respect to a skin surface of a subject, the personal care device being configured to perform a personal care treatment to the skin when in contact with the skin surface, the method comprising:
receiving (<NUM>) data representative of a measured degree of curvature of the skin surface within a first region of the skin surface of the subject, with which the personal care device is in contact;
determining (<NUM>), by comparing the measured degree of curvature with curvature information for a plurality of regions of the skin surface of the subject contained in a database, an indication of a location of the first region of the skin surface on the subject; and
performing (<NUM>), based on the determined indication of the location of the first region, an action in respect of the personal care device,
characterized in that the data representative of the measured degree of curvature of the skin surface within the first region of the skin surface comprises a measure of a relative orientation of a first surface-engaging element and a second surface-engaging element of a skin surface curvature measurement mechanism, the first and second surface-engaging elements being moveable relative to one another.