Patent Description:
In the prior art, different kinds of wrist-worn body sensors are known which measure for example heart rate activity from a user's wrist. Also, optical heart rate sensors are known which are used in the upper arm or forearm. However, these kinds of heart rate sensors that are placed in connection with user's arm or wrist do not suit for everyone and especially those having problems with their arms or those who use their arms extensively so that the wrist-worn heart rate sensors disturb their workout.

It is also known in the prior art that heart rate activity can be measured from the user's ear. <CIT> discloses an integrated device to calculate heart rate and body activity. The device consists of an accelerometer and a heart rate monitor within a miniature device placed over the ear. Such placement over the ear is done using magnets. The device includes a microcontroller, a vibrator and a wireless networking module, which allows it to communicate with other devices, such as smart phones, computers, etc. Heart rate is extracted using reflected photo plethysmography from behind the ear. The means of measuring this is done using infrared LEDs and photodiodes. The means for affixing the device onto the ear comprises a body containing a magnet and the same body is also fixed to a flexible material, which contains another magnet. In other words, the device disclosed in <CIT> is a one-piece device comprising two magnets which are connected to each other through the flexible material. The documents <CIT>, <CIT>, <CIT>, <CIT> as well as <NPL>" also disclose different kind of ear sensors.

One of the problems associated with the prior art is that with a one-piece device the placement of the device is limited and the device becomes larger and therefore heavier which is a downside when using the device in sports such as running or other hard-paced exercise. Another problem with the prior art is that strength of the magnetic connection between the two magnets cannot be changeable in cases where the ear size is different or the need for the intensity varies. Further a problem with the one-piece device is a risk that the device will stick to hair or other sports equipment or cloths.

An object of the present invention is to provide an effective body sensor which can be freely attached to the user's body. A further object of the present invention is to provide an effective ear-worn heart rate sensor which can be firmly attached to the user's ear.

The objects of the invention are achieved by a body sensor which is characterized by what is stated in the independent claim. The preferred embodiments of the invention are disclosed in the dependent claims.

The invention relates to a body sensor to be used in connection with a body part, for example in connection with a nose, a lip, an arm or an ear, and preferably in connection with an earlobe. The body sensor uses an optical sensor to measure user's body activity such as heart rate, blood pressure or oxygen saturation and transmits the information via wireless connection for example via Bluetooth to a mobile application. Charging of the body sensor is provided through at least one charging pad when the body sensor is placed in a charger.

The invention is based on the idea of providing a compact body sensor which comprises two separate parts each having a magnetic coupling part.

According to the invention the body sensor comprises a sensor part and a separate connecting part for securing the sensor part to other side of the user's body part such as an ear. In other words, the body sensor comprises two separate parts which are to be connected to opposite sides of the user's body part. The sensor part comprises a housing having a first surface and a second surface opposite to the first surface and the housing enclosing components of the sensor part inside the housing. The components of the sensor part comprise a circuit board, an optical sensor, a first magnetic coupling part, a transparent window and one or more other components. The circuit board is provided between the first surface of the housing and the second surface of the housing within the housing and preferably such that the circuit board extends substantially parallel to the first surface or to the second surface of the housing inside the housing. The optical sensor is configured to measure body activity, such as heart rate, blood pressure or oxygen saturation by optical measurement and the optical sensor is provided between the circuit board and the first side surface within the housing. In other words, the optical sensor is provided inside the housing in a place which is located between the first surface of the housing and the circuit board provided inside the housing. The transparent window is provided on the first surface of the housing and directly facing the optical sensor such that the transparent window is configured to allow light pass from the optical sensor through the first surface of the housing when the optical sensor is sending light to outside of the housing and receiving light from outside of the housing through the first surface of the housing to the optical sensor. The optical sensor and the transparent window are provided successively in the direction from the first surface toward the second surface. The transparent window and the optical sensor can be separate parts or the transparent window can be an integral part of the optical sensor. The first magnetic coupling part is provided in connection with the optical sensor such that the first magnetic coupling part provides an effective magnetic coupling with a second magnetic coupling part placed on the other side of the user's body part such as an ear so that the transparent window is provided firmly against user's body part such as an ear in order to allow the light from the optical sensor to reach the skin of the body part and measure the body activity such as heart rate according to the optical measurement. The sensor part further comprises one or more other components provided inside the housing. The separate connecting part is independent from the sensor part and comprises a second magnetic coupling part configured to provide a magnetic coupling with the first magnetic coupling part via the first surface of the housing for securing the sensor part to other side of the user's body part such as an ear.

In a preferable embodiment the first magnetic coupling part in the sensor part is a magnet and the second magnetic coupling part in the separate connecting part is a magnet. In another embodiment the first magnetic coupling part in the sensor part is a magnet and the second magnetic coupling part in the separate connecting part is made of magnetic material or comprises magnetic material such that the magnetic coupling is formed between the first and second magnetic coupling part. In a still other embodiment the first magnetic coupling part is made of magnetic material or comprises magnetic material such that the magnetic coupling is formed between the first magnetic coupling part and the second magnetic coupling part being a magnet.

The components of the sensor part are provided in the housing in the following order from the first surface toward the second surface: the transparent window, the optical sensor, the circuit board and the first magnetic coupling part.

In a preferred embodiment the optical sensor and the first magnetic coupling part are provided on opposite surfaces of the circuit board. The circuit board may be a two-sided circuit board and the optical sensor is connected to the first surface of the circuit board and the first magnetic coupling part is provided in connection with the second surface of the circuit board. The first surface of the circuit board is facing toward the first surface of the housing and/or the second surface of the circuit board is facing toward the second surface of the housing. The first magnetic coupling part may be in contact with the circuit board or in a proximity of the circuit board.

Alternatively, the circuit board is provided parallel to the first surface of the housing and the optical sensor and the first magnetic coupling part are provided on opposite surfaces of the circuit board.

In a preferred embodiment the optical sensor and the first magnetic coupling part are at least partly superposed in the direction from the first surface toward the second surface, or the optical sensor and the first magnetic coupling part are at least partly superposed in the direction from the optical sensor toward the second surface. This is a very advantageous embodiment since the magnetic coupling provided between the first magnetic coupling part and the second magnetic coupling part are provided such that the optical sensor is at least partly between said magnetic coupling parts and is therefore firmly placed against the user's body part.

In a further embodiment the first magnetic coupling part is provided concentrically with the optical sensor in the direction from the first surface toward the second surface. In this embodiment the optical sensor is the most firmly placed against the user's body part because it is directly in the effect field of the first magnetic coupling.

In another embodiment the components are provided in the housing in the following order from the first surface toward the second surface: the transparent window, the optical sensor and the circuit board, and further such that the first magnetic coupling part is provided at least partly superposed with the transparent window within the housing between the circuit board and the first surface.

The other components of the sensor part further comprise a rechargeable battery configured to provide power to the sensor part or the other components of the sensor part further comprise a rechargeable battery configured to provide power to the sensor part and at least one charging pad connected to the battery for recharging the battery.

In an embodiment the at least one charging pad is arranged to extend from the second surface of the housing toward the first surface and in contact with the circuit board.

In an embodiment the rechargeable battery is arranged to form part of the first magnetic coupling part; or alternatively the rechargeable battery is arranged to form the first magnetic coupling part. This means that the first magnetic coupling part may be provided in connection with the rechargeable battery either as part of the rechargeable battery, for example as an additional casing of the rechargeable battery, or the rechargeable battery may be made of a magnetic material so that the rechargeable battery forms the first magnetic coupling part.

In an embodiment the other components of the sensor part are provided in parallel with the optical sensor; or alternatively the other components of the sensor part are provided in parallel with the first magnetic coupling part; or alternatively the other components of the sensor part are provided in parallel with the optical sensor and the first magnetic coupling part.

In an embodiment the optical sensor comprises a wireless communication component; or alternatively the circuit board comprises a wireless communication component.

In an embodiment the body sensor is an ear heart rate sensor for measuring heart rate activity from a user's ear, the heart rate sensor comprises an optical sensor configured to measure heart rate activity by optical heart rate measurement, and the separate connecting part is independent from the sensor part and comprises the second magnetic coupling part configured to provide the magnetic coupling with the first magnetic coupling part via the first surface of the housing for securing the sensor part to other side of the user's ear.

An advantage of the invention is that as the sensor part and the separate connecting part are provided as separate elements of the body sensor the placement of the body sensor is suitable for many kinds of body parts such as ears and especially earlobes or noses or palms and especially in an area between the forefinger and the thumb. Further advantage of the invention is that as the sensor part comprises a small number of components it can be made as thin as possible which means that there is a small lever arm in the sensor part, whereby the sensor part stays stable when placed on the user's body part. Another advantage of the invention is that the separate connecting part can be changed when other kind of magnetic coupling is needed, for example a more powerful magnetic coupling when the user is running and less powerful magnetic coupling when the user is sleeping.

The invention is described in detail by means of specific embodiments with reference to the enclosed drawings, in which.

<FIG> shows an embodiment of a body sensor <NUM> in which a sensor part <NUM> and a separate connecting part <NUM> are provided on opposite sides of the user's ear E. Although all the figures show an ear E as a body part the invention is not limited to the use of the body sensor <NUM> only in connection with an ear and therefore the ear E is represented as a dashed block in the figures. The sensor part <NUM> comprises a housing <NUM> having a first surface 20a placed against the ear E and a second surface 20b opposite to the first surface 20a. The housing <NUM> encloses components of the sensor part <NUM> inside the housing <NUM>. The housing <NUM> in other words comprises two surfaces, the first surface 20a and the second surface 20b, such that the components of the sensor part <NUM> are provided between the surfaces 20a, 20b or such that the components are provided to extend from one surface toward the other surface. The housing <NUM> may comprise also side surfaces or alternatively the first surface 20a and the second surface 20b are configured such that they can be connected to each other providing a space between the first surface and the second surface where the components of the sensor part <NUM> are placed. The first surface 20a and the second surface 20b may have a curved shape or any other suitable shape for providing a housing <NUM>. The components of the sensor part <NUM> are in this embodiment a circuit board <NUM>, an optical sensor <NUM> configured to measure body activity by optical measurement, a first magnetic coupling part <NUM>, a transparent window <NUM> provided on the first surface 20a of the housing <NUM> configured to allow light pass from the optical sensor <NUM> through the first surface 20a outside of the housing <NUM>, a rechargeable battery <NUM> configured to provide power to the sensor part <NUM> and a charging pad <NUM> connected to the battery <NUM> for recharging the battery <NUM>. The charging pad <NUM> extends from the second surface 20b of the housing <NUM> toward the first surface 20a. The components of the sensor part are provided in the housing <NUM> in the following order from the first surface toward the second surface: the transparent window <NUM>, the optical sensor <NUM>, the circuit board <NUM> and the first magnetic coupling part <NUM>. In this embodiment the transparent window <NUM>, the optical sensor <NUM> and the first magnetic coupling <NUM> are provided on top of each other in a transverse direction in relation to the first surface 20a such that the circuit board <NUM> is provided between the optical sensor <NUM> and the first magnetic coupling part <NUM>. The optical sensor <NUM> is provided on the circuit board <NUM>, or the optical sensor <NUM> is attached on the surface of the circuit board <NUM> such that the optical sensor <NUM> and the circuit board <NUM> form a compact assembly and the first magnetic coupling part <NUM> is provided on the other side of the circuit board <NUM> than the optical sensor <NUM> and preferably in a direct contact with the optical sensor <NUM> and the circuit board <NUM> assembly. In other words, the optical sensor <NUM> and the circuit board <NUM> form a uniform assembly and the first magnetic coupling part <NUM> is provided in connection with the assembly, preferably in a direct contact with the assembly. The transparent window <NUM>, the optical sensor <NUM>, the circuit board <NUM> and the first magnetic coupling <NUM> are arranged immediately successively in the housing <NUM> from the first surface 20a of the housing <NUM> toward the second surface 20b of the housing <NUM>. Being arranged immediately successively in the housing <NUM> means that the transparent window <NUM>, the optical sensor <NUM>, the circuit board <NUM> and the first magnetic coupling <NUM> are provided either against each other or such that there is only structure of the housing between them or alternatively such that some of said transparent window <NUM>, said optical sensor <NUM>, said circuit board <NUM> and said first magnetic coupling <NUM> are against each other and some of them have the structure of the housing between them. In other words, the transparent window <NUM>, the optical sensor <NUM>, the circuit board <NUM> and the first magnetic coupling part <NUM> are provided in the housing such that the first magnetic coupling part <NUM>, the optical sensor <NUM> and the transparent window <NUM> are provided along the same line from the first surface 20a of the housing <NUM> toward the second surface 20b of the housing <NUM>, and such that when the second magnetic coupling part <NUM> of the separate connecting part <NUM> is forming a magnetic coupling with the first magnetic coupling part <NUM> of the sensor part <NUM> the transparent window <NUM>, the optical sensor <NUM> and the circuit board <NUM> are provided between the first magnetic coupling part <NUM> and the second magnetic coupling part <NUM> and the magnetic coupling between the first magnetic coupling part <NUM> and the second magnetic coupling part <NUM> is provided through the transparent window <NUM>, the optical sensor <NUM> and the circuit board <NUM>.

The other components of the sensor part <NUM> are provided in this embodiment in parallel with the first magnetic coupling part <NUM> so that the rechargeable battery <NUM> and the charging pad <NUM> are provided next to the first magnetic coupling part <NUM>. Other electronical components are provided in connection with the circuit board <NUM>, which can be one-sided circuit board <NUM> or two-sided circuit board <NUM>.

<FIG> also shows a separate connecting part <NUM> which is independent from the sensor part <NUM> and comprises a second magnetic coupling part <NUM> configured to provide a magnetic coupling with the first magnetic coupling part <NUM> via the first surface 20a of the housing <NUM> for securing the sensor part <NUM> to other side of the user's ear. The separate connecting part <NUM> is preferably placed on the front side of the user's ear such that a back side 3b of the separate connecting part <NUM> is against the user's ear and a front side 3a of the separate connecting part <NUM> is visible. The front side 3a of the separate connecting part <NUM> may comprise jewellery or other surface structure. Alternatively, the whole separate connecting part <NUM> may comprise jewellery or be formed of one piece or multiple piece of jewellery.

The body sensor <NUM> comprises two separate parts: the sensor part <NUM> and the separate connecting part <NUM>. When the body sensor <NUM> is used, i.e. in a use mode, the user's ear or other body part is placed between the first surface 20a of the housing <NUM> of the sensor part <NUM> and the separate connecting part <NUM> such that the magnetic coupling is provided between the first magnetic coupling part <NUM> and second magnetic coupling part <NUM> via the user's ear E or via some other body part.

<FIG> shows another embodiment of a body sensor <NUM> in which the transparent window <NUM>, the optical sensor <NUM>, the circuit board <NUM> and the first magnetic coupling <NUM> are provided on top of each other in a transverse direction in relation to the first surface 20a of the housing <NUM> similarly as shown in <FIG>. The transparent window <NUM>, the optical sensor <NUM>, the circuit board <NUM> and the first magnetic coupling <NUM> are arranged immediately successively in the housing <NUM> similarly as shown in <FIG>. In this embodiment the rechargeable battery <NUM> is arranged to form part of the first magnetic coupling part <NUM> or alternatively the rechargeable battery <NUM> is arranged to form the first magnetic coupling part <NUM>. As the rechargeable battery <NUM> and the first magnetic coupling part <NUM> are combined in this embodiment the sensor part <NUM> is provided in a very compact form. The separate connecting part <NUM> shown in <FIG> is similar as shown in <FIG>. In this embodiment when the second magnetic coupling part <NUM> of the separate connecting part <NUM> is forming a magnetic coupling with the first magnetic coupling part <NUM> of the sensor part <NUM> the transparent window <NUM>, the optical sensor <NUM> and the circuit board <NUM> are provided between the first magnetic coupling part <NUM> and the second magnetic coupling part <NUM> and the magnetic coupling between the first magnetic coupling part <NUM> and the second magnetic coupling part <NUM> is provided through the transparent window <NUM>, the optical sensor <NUM> and the circuit board <NUM> similarly as in connection with the <FIG> with the exception that the first magnetic coupling part <NUM> and the rechargeable battery <NUM> are combined as one.

<FIG> shows an embodiment of a body sensor in which the transparent window <NUM>, the optical sensor <NUM>, the circuit board <NUM> and the first magnetic coupling part <NUM> are provided in the housing <NUM> similarly as shown in <FIG> and the rechargeable battery <NUM> is provided between the first magnetic coupling part <NUM> and the second surface 20b of the housing <NUM>. In this embodiment the magnetic coupling forming between the first magnetic coupling part <NUM> and the second magnetic coupling part <NUM> is provided through the transparent window <NUM>, the optical sensor <NUM> and the circuit board <NUM>.

<FIG> shows an embodiment in which the transparent window <NUM>, the optical sensor <NUM>, the circuit board <NUM> and the first magnetic coupling part <NUM> are provided inside the housing <NUM> similarly as in connection with <FIG>. In this embodiment the rechargeable battery <NUM> is provided next to the transparent window and/or the optical sensor <NUM>, i.e. on the same side of the circuit board <NUM> as the transparent window <NUM> and the optical sensor <NUM> in the housing <NUM>.

<FIG> shows an embodiment of a sensor part <NUM> of a body sensor <NUM> in which the optical sensor <NUM> is provided within the first magnetic coupling part <NUM>. The first magnetic coupling part <NUM> comprises a through hole suitable for the optical sensor <NUM> such that when the optical sensor <NUM> is provided in the through hole the first magnetic coupling part <NUM> surrounds the optical sensor <NUM>. The first magnetic coupling part <NUM> having a through hole creates magnetic flux which operates similarly with regards to the first magnetic coupling part arranged in the through hole, as when the first magnetic coupling part <NUM> is provided at least partly superposed with the optical sensor <NUM> in a direction from the first surface 20a toward the second surface 20b. In other words, the first magnetic coupling part <NUM> having a through hole through the first magnetic coupling part which the through hole is such that the optical sensor <NUM> can be arranged in the through hole such that the first magnetic coupling part <NUM> surrounds the optical sensor <NUM> generates an equivalent magnetic flux through the optical sensor <NUM> as a first magnetic coupling part <NUM> arranged superposed with the optical sensor such that the optical sensor <NUM> is arranged between the transparent window <NUM> in the first surface 20a of the housing <NUM> and the first magnetic coupling part <NUM> in a direction from the first surface 20a toward the second surface 20b. In the embodiment shown in <FIG> the first magnetic coupling part <NUM> having a through hole is arranged partly in the area of the transparent window <NUM>. The magnetic flux created by the first magnetic coupling part <NUM> goes through the optical sensor <NUM> which is arranged in the through hole in the middle of the first magnetic coupling part <NUM> such that the magnetic coupling between the first magnetic coupling part <NUM> and the second magnetic coupling part <NUM> provided on the opposite side of the ear E is equivalent to the magnetic coupling created between a first magnetic coupling part provided superposed to the optical sensor in a direction from the first surface 20a toward the second surface 20b and a second magnetic coupling part <NUM> of the separate connecting part <NUM> provided on the opposite side of the ear E.

<FIG> shows an embodiment of a sensor part <NUM> of a body sensor <NUM> in which the housing <NUM> of the sensor part <NUM> is made watertight such that the transparent window <NUM> forms part of the first surface 20a of the housing in a watertight manner. The optical sensor <NUM> is provided next to the transparent window <NUM> and the first magnetic coupling part <NUM> is arranged next to the optical sensor <NUM> in a direction from the first surface 20a to the second surface 20b. In other words, the optical sensor <NUM> is arranged between the first magnetic coupling part <NUM> and the transparent window <NUM> in the direction from the first surface 20a to the second surface 20b. In still other words, the first magnetic coupling part <NUM> is arranged at least partly superposed relative to the optical sensor <NUM> in the direction from the second surface 20b of the housing <NUM> toward the first surface 20a of the housing <NUM>. Further the first magnetic coupling part <NUM> is arranged at least partly superposed with the optical sensor <NUM> and the transparent window <NUM> when viewed from the second surface 20b toward the first surface 20a. In other words, the magnetic flux generated by the first magnetic coupling part <NUM> affects through the optical sensor <NUM> and through the transparent window <NUM> forming part of the first surface 20a of the housing <NUM>, such that the first magnetic coupling part <NUM> provides magnetic interaction with the second magnetic coupling part <NUM> of the separate connecting part <NUM> through the optical sensor <NUM> and the transparent window <NUM> as well as through the ear E. The sensor part <NUM> also comprises circuit board <NUM> and a battery <NUM> provided within the housing <NUM> similarly as described earlier.

<FIG> shows an embodiment of a sensor part <NUM> of a body sensor <NUM> and a separate connecting part <NUM> arranged on the opposite side of the ear E than the sensor part <NUM>. The housing <NUM> of the sensor part <NUM> is made watertight such that the transparent window <NUM> forms part of the first surface 20a of the housing in a watertight manner similarly as in the embodiment shown in <FIG>. Difference to the embodiment shown in <FIG> is the first magnetic coupling part <NUM> which in this embodiment is arranged to surround the optical sensor <NUM>. In other words, the first magnetic coupling part <NUM> comprises a through hole in the first magnetic coupling part <NUM> in which the optical sensor <NUM> is provided such that the first magnetic coupling part <NUM> surrounds the optical sensor from the sides of the optical sensor <NUM>. The through hole of the first magnetic coupling part <NUM> is arranged to go through the first magnetic coupling part <NUM> such that when the first magnetic coupling part <NUM> is arranged inside the housing <NUM> against the first surface 20a of the housing <NUM> or in the vicinity of the first surface 20a the through hole extends through the first magnetic coupling part <NUM> in the direction of the first surface 20a of the housing <NUM> to the second surface 20b of the housing <NUM> and such that the optical sensor <NUM> arranged in the through hole is against the transparent window <NUM> of the housing <NUM> or in the vicinity of the transparent window <NUM> of the housing <NUM>. Other components of the sensor part <NUM> are provided inside the housing <NUM> according to what is described earlier. The magnetic flux generated by the first magnetic coupling part <NUM> provides magnetic coupling through the optical sensor <NUM> arranged within the first magnetic coupling part <NUM> and through the transparent window and through the ear E with the second magnetic coupling part <NUM> of the separate connecting part <NUM>.

In the embodiments shown in the figures the optical sensor <NUM> and the first magnetic coupling part <NUM> are at least partly superposed in the direction from the first surface 20a toward the second surface 20b or the first magnetic coupling part <NUM> is provided concentrically with the optical sensor <NUM> in the direction from the first surface 20a toward the second surface 20b. This means that the magnetic flux generated by the first magnetic coupling part <NUM> affects through the optical sensor <NUM> so that the magnetic coupling between the first magnetic coupling part <NUM> and the second magnetic coupling part <NUM> provides a firm attachment between the user's ear E and the transparent window <NUM> through which the optical sensor <NUM> operates.

<FIG> shows an embodiment of a sensor part <NUM> of a body sensor <NUM> in which the optical sensor <NUM>, the transparent window <NUM> and the first magnetic coupling part <NUM> are directly next to each other within the structure of the housing <NUM> such that said optical sensor <NUM> and said transparent window <NUM> are placed directly on top of each other and the first coupling part <NUM> is placed such that part of the first coupling part is placed directly on top of the transparent window <NUM> and the optical sensor <NUM> and part of the first coupling part <NUM> is placed only on top of the transparent window <NUM>. In other words, the optical sensor <NUM>, the transparent window <NUM> and the first magnetic coupling part <NUM> are provided directly next to each other inside the housing in the direction from the first surface 20a toward the second surface 20b. The rechargeable battery <NUM> and the charging pads <NUM>, as in this embodiment there are two charging pads <NUM>, are placed next to the optical sensor <NUM>, the transparent window <NUM> and the first magnetic coupling part <NUM> inside the housing.

<FIG> shows another embodiment of a sensor part <NUM> of a body sensor <NUM> in which the optical sensor <NUM>, the transparent window <NUM> and the first magnetic coupling part <NUM> are placed directly next to each other within the structure of the housing <NUM> such that the optical sensor <NUM> is placed on top of the transparent window <NUM> and the first magnetic coupling part <NUM> is placed on top of the optical sensor <NUM> or alternatively the first magnetic coupling part <NUM> is placed on top of the transparent window <NUM> such that the optical sensor <NUM> is within the first magnetic coupling part <NUM>. The optical sensor <NUM> being within the first magnetic coupling part <NUM> means for example such that the first magnetic coupling part <NUM> comprises a recess in which the optical sensor <NUM> is provided such that the first magnetic coupling part <NUM> surrounds the optical sensor <NUM> on its sides but such that the optical sensor is operable through the transparent window <NUM>. In other words, a surface of the first magnetic coupling part <NUM> facing toward the transparent window <NUM> is preferably provided substantially on a same level as a surface of the optical sensor <NUM> facing toward the transparent window <NUM>. Placing directly next to each other within the structure of the housing <NUM> means that the part can be placed directly next to each other without having any structures of the housing <NUM> between the parts or such that there is only structures of the housing <NUM> between some or all of the parts, however, no other components are provided between the optical sensor <NUM>, the transparent window <NUM> and the first magnetic coupling part <NUM> or the transparent window <NUM> and the combination of the optical sensor <NUM> and the first magnetic coupling part <NUM>. In the embodiment shown in <FIG> the optical sensor <NUM>, the transparent window <NUM> and the first magnetic coupling part <NUM> are directly on top of each other such that the whole of the optical sensor <NUM> is on top of the transparent window <NUM> and the first magnetic coupling part <NUM> is placed to cover the optical sensor <NUM>. Alternatively, the transparent window <NUM> and the combination of the optical sensor <NUM> and the first magnetic coupling part <NUM> are directly on top of each other such that the whole of the optical sensor <NUM> is on top of the transparent window <NUM> and the first magnetic coupling part <NUM> is provided around the optical sensor <NUM>. The first magnetic coupling part <NUM> can then be a ring magnet arranged around the optical sensor <NUM>. In this case, the first magnetic coupling part <NUM> surrounds the optical sensor <NUM> and looks similar as in <FIG> when viewed from above. The sensor part <NUM> shown in figures <NUM> and <NUM> are seen from above in a direction from the second surface 20b toward the first surface 20a.

Claim 1:
A body sensor (<NUM>) for measuring body activity of a user, the body sensor (<NUM>) comprises:
- a sensor part (<NUM>) comprising a housing (<NUM>) having a first surface (20a) and a second surface (20b) opposite to the first surface (20a), said housing (<NUM>) enclosing components of the sensor part (<NUM>) inside the housing (<NUM>), the components comprising:
a circuit board (<NUM>) provided between the first surface (20a) and the second surface (20b) within the housing (<NUM>),
an optical sensor (<NUM>) configured to measure body activity by optical measurement, the optical sensor (<NUM>) being provided between the circuit board (<NUM>) and the first surface (20a) within the housing (<NUM>),
a first magnetic coupling part (<NUM>),
a transparent window (<NUM>) provided on the first surface (20a) of the housing (<NUM>) and directly facing the optical sensor (<NUM>) such that the transparent window (<NUM>) is configured to allow light pass from the optical sensor (<NUM>) through the first surface (20a) to outside of the housing (<NUM>) and from outside of the housing through the first surface (20a) to the optical sensor (<NUM>), and
one or more other components provided inside the housing (<NUM>); characterized in that the first magnetic coupling part (<NUM>) is provided concentrically with the optical sensor (<NUM>) in the direction from the first surface (20a) toward the second surface (20b),
the components are provided in the housing (<NUM>) in the following order from the first surface toward the second surface: the transparent window (<NUM>), the optical sensor (<NUM>) and the circuit board (<NUM>), and further such that the first magnetic coupling part (<NUM>) is provided at least partly superposed with the transparent window (<NUM>) within the housing (<NUM>) between the circuit board (<NUM>) and the first surface (20a),
and
the body sensor (<NUM>) comprises:
- a separate connecting part (<NUM>) being independent from the sensor part (<NUM>) and comprising a second magnetic coupling part (<NUM>) configured to provide a magnetic coupling with the first magnetic coupling part (<NUM>) via the first surface (20a) of the housing (<NUM>) for securing the sensor part (<NUM>) to other side of a user's body part,
the sensor part (<NUM>) and the separate connecting part (<NUM>) are provided as separate elements of the body sensor (<NUM>).