Device, system and method for skin parameter measurement

Abstract

The present invention relates to a device for measuring skin parameters, comprising: a shell structure defining an inner cavity and a first opening at the skin contact end of the inner cavity; a movable component movable relative to the shell structure and configured to protrude the skin contact end through the first opening of the shell structure when no external force is applied to move the movable component relative to the shell structure, the movable component also including a second opening; an optical sensing unit for performing a first skin parameter measurement when the device is in contact with the skin surface, the optical sensing unit being arranged in the inner cavity of the shell structure and including a lighting unit and an imaging unit, the lighting unit being used to illuminate the skin surface by emitting light through the second opening of the movable component, the imaging unit being used to receive light reflected by the illuminated skin surface; and an electrical sensing unit for measuring a second skin parameter, wherein the electrical sensing unit is arranged at a front end portion of the movable component defining the second opening.

Description

Technical Field

[0001] The present invention relates to an apparatus, a system and a method for skin parameter measurement. Background Art

[0002] The measurement of skin parameters provides information related to the skin condition, i.e., oiliness, hydration level, texture, distribution and appearance of pores, color and pigmentation of human skin. Based on this information, skin care systems (i.e., shavers and cleansing systems) can be personalized by adapting the settings of these systems to individual needs. In addition, personalized coaching and guidance on skin care measures, daily skin-related activities, lifestyle, and improvement of environmental conditions can be provided, i.e., by enabling coaching software applications ("coaching apps") to be used with communication devices such as smartphones or tablets.

[0003] Skin parameter measurement devices measure skin oiliness and other skin parameters such as skin texture and pores. Some devices in the consumer, professional, and semi-professional sectors use cameras to acquire images and then apply image processing algorithms to measure human skin parameters.

[0004] However, skin parameter measurement devices known in the art are subject to variability in measurement results due to changes in image acquisition conditions. Specifically, when repeatedly capturing images of the same point on the skin of the same user, even without delay between measurements, the resulting images can exhibit significant variations in the appearance of the imaged skin point. One of the primary causes of this variability is skin doming, a dome-like deformation of the skin that occurs when the device's rigid housing frame presses against the elastic skin surface.

[0005] The effect of skin doming may even be influenced in its extent and characteristics by many factors, including natural skin properties (e.g., human skin properties) such as elasticity, properties of the supporting subcutaneous tissue (e.g., muscle, bone), the design and / or size of the rigid shell frame that is pushed against the skin surface to measure skin parameters, and the pressure level and force used to push the rigid shell frame.

[0006] A person's natural skin properties cannot be controlled by product design measures. However, they are fairly stable over time for the same person and at the same skin location. Although they can be partially extracted from skin parameter measurements for a specific skin location, natural skin properties are not a primary factor in the variability of skin parameter measurements for that specific skin location.

[0007] Furthermore, the size of the rigid housing frame of the skin parameter measurement device is greatly limited, especially by specific product requirements. However, the housing frame can be designed to reduce the variation in the contour and degree of skin ridges to a certain extent.

[0008] However, the last factor mentioned above, namely pressure level and force, has the greatest impact on skin ridges and, therefore, on variations in skin parameter measurements. The force with which a skin parameter measurement device is pressed against the skin can vary significantly, leading to variations in skin ridges. For example, volunteer testing has shown that when asked to "gently touch the forehead or cheek," the forces applied by a group of testers can range from 0 to 15N.

[0009] JPH09253066A discloses a pressure-stabilizing probe for digitally measuring treatment effects through magnetic processing and a blood circulation measurement device using the probe. The pressure-stabilizing probe comprises a cylindrical probe housing; a probe electrode slidable in the axial direction within the housing; and a pressure distribution body attached to the tip of the probe housing for distributing the pressure applied to the probe electrode.

[0010] WO2018 / 029286A1 discloses a device comprising a device for attaching the device to an image recording device and a mechanism configured to apply a predefined pressure to the skin to cause the skin to deform at the predetermined pressure. The mechanism is adapted so that, when the device is attached to the image recording device, an image of the deformed skin is recorded by the image recording device. Furthermore, a system and method for determining skin elasticity are disclosed. Summary of the Invention

[0011] It is an object of the present invention to provide an apparatus, system and method for skin parameter measurement that are capable of reducing variations in skin parameter measurement results, in particular by minimizing skin tenting effects during skin parameter measurement.

[0012] In a first aspect of the present invention, a device for measuring skin parameters is proposed, which includes a shell structure defining an inner cavity and a first opening located at the skin contact end of the inner cavity; a movable part connected to the shell structure via an elastic connecting device, the movable part being movable relative to the shell structure so as to maintain the movable part within the shell structure, and the movable part being configured to protrude from the first opening when no external force is applied to the movable part, the movable part also including a second opening at the front end portion; an optical sensing unit for performing a first skin parameter measurement, the optical sensing unit being arranged in the inner cavity of the shell structure and including a lighting unit and an imaging unit, the lighting unit being used to illuminate the skin surface by emitting light through the second opening of the movable part, the imaging unit being used to receive light reflected by the illuminated skin surface; and an electric sensing unit for measuring a second skin parameter, wherein the electric sensing unit is arranged at the front end portion of the movable part defining the second opening.

[0013] In another aspect of the present invention, a skin care system is provided, comprising a device for measuring skin parameters as disclosed herein and an analysis unit for analyzing the measurement results provided by the device. The skin care system may further comprise an adaptation unit for adjusting system settings based on the analysis results of the analysis unit.

[0014] In another aspect of the present invention, a method for measuring skin parameters using a device as disclosed herein is provided, the method comprising the following steps: when the device is in contact with the skin surface, using an optical sensing unit to perform measurement of a first skin parameter; using an illumination unit to illuminate the skin surface by emitting light through a second opening of a movable part; using an imaging unit to receive light reflected by the illuminated skin surface; and when the device is in contact with the skin surface, using an electrical sensing unit to perform measurement of a second skin parameter.

[0015] In other aspects of the present invention, a computer program is provided, the computer program comprising program code means for causing the computer to perform the steps of the method disclosed herein when the computer program is executed on the computer, and a non-transitory computer-readable recording medium having a computer program product stored therein, which, when executed by a device, causes the method disclosed herein to be performed.

[0016] Preferred embodiments of the invention are defined in the dependent claims.It shall be understood that the claimed system, method and computer program have similar and / or identical preferred embodiments as the claimed device and as defined in the dependent claims.

[0017] The housing structure of the skin parameter measurement device defines a longitudinal direction. When performing skin parameter measurement, the skin contact end is one of the two ends along the longitudinal direction that is closer to the skin surface than the other end. The housing structure can have a cylindrical form defining a cylindrical hollow space (i.e., an inner cavity).

[0018] The movable member is movable relative to the housing structure by means of the elastic connection means. In particular, due to the elasticity of the connection means, when no external force is applied to move the movable member (for example, before the device is brought into contact with the skin surface), the movable member is in an unpressurized state and is constantly biased by a force to protrude from the housing structure at its skin-contacting end through the first opening. The "external force" here refers to any mechanical force that does not originate from the device itself but is applied from an external entity (such as a pressing force against the skin).

[0019] The elastic connection device may include one or more springs, preferably contraction springs. Further preferably, the springs are pre-tensioned prior to integration into the skin parameter measurement device of the present invention. Other examples of the elastic connection device include, but are not limited to, elastic membranes, rubber, and memory materials such as memory foam.

[0020] The second opening is arranged at the front end of the movable member. The front end of the movable member protrudes beyond the first opening when not pressed and initially contacts the skin surface when the device is brought into contact with the skin. When the device is brought into contact with the skin surface during skin parameter measurement, the front end of the movable member initially contacts the skin surface. As the device is further pressed against the skin surface, the skin surface exerts pressure that moves the movable member inward toward the inner cavity of the housing structure. This pressure continuously presses the device against the skin until the skin-contacting end of the housing structure surrounding the movable member also contacts the skin surface.

[0021] In this way, the movable part constitutes a "floating frame" which is not fixed to the rigid housing structure ("rigid frame"), but is movable relative to the rigid housing structure.

[0022] The optical sensing unit is adapted to measure one or more skin parameters, such as oiliness, hydration, texture, pores, color, and pigmentation of human skin. The illumination unit is arranged within the inner cavity of the housing structure in such a manner that light emitted by the illumination unit (e.g., visible light or light outside the visible spectrum, in particular infrared or ultraviolet light) reaches the skin surface in proximity to or in contact with the device (in particular, the movable component) via the second opening of the movable component. The imaging unit preferably comprises a camera, such as a CCD camera or an optoelectronic imaging sensor.

[0023] By using the movable member as a floating frame that is movable relative to the housing structure, the force with which the device presses against the user's skin is not limited by the pressure level, but rather by the elastic force (e.g., spring compression force) of the elastic connection device at a given relative position between the movable member and the housing structure. The elastic force is primarily determined by the characteristics of the elastic connection device itself, and thus can be reasonably controlled to at least minimize variations in force. For example, when using one or more springs for the elastic connection device, the length and / or stiffness (i.e., spring constant) can be selected to minimize variations in the spring compression force.

[0024] Thus, the above-mentioned negative effects caused by variations in the pressure applied by the same or different users of the skin parameter measurement device when measuring the same skin point can be compensated by a better controllable elastic force. In particular, the present invention leads to a reduction in variations in skin ridges, in particular the height of the skin dome.

[0025] In addition to the reduced ridge variation, the resulting ridge itself is also reduced compared to the housing of a device without such a floating frame. This, in turn, improves the ability to reduce variations in visual skin properties due to variations in how different users press the device against their skin for measurement, and even variations in how the same user presses with varying intensities at different measurement occasions. The reduced ridge profile or height also ensures that focused skin parameter measurement images can be obtained even with imaging units that provide a relatively small depth of field (e.g., less than 2.5 mm). As a result, measurement results based on image acquisition using the present invention have less variation and are therefore more reliable for skin analysis.

[0026] The device further comprises an electrical sensing unit for measuring a second skin parameter, preferably skin impedance. Thus, the electrical sensing unit is preferably an impedance sensing unit (e.g., a bioimpedance sensing unit). Skin impedance measurement provides information indicative of skin parameters, such as water content (hydration level, sebum content, and salt content). Thus, the present invention enables a single device capable of simultaneously performing both optical skin parameter measurements and electrical skin parameter measurements (e.g., skin impedance). The resulting skin parameter measurement device is more compact and cost-effective, wherein the ergonomic properties of the device can be optimized.

[0027] The electric sensing unit is arranged at the front end portion of the movable component defining the second opening. Therefore, the electric sensing unit can be embedded in the movable component and does not occupy any additional space in or on the device.

[0028] In particular, by using the movable member as a floating frame, the contact pressure used for skin impedance measurement can be better controlled, significantly reducing pressure-related variations in the skin impedance measurement results. This effect is particularly enhanced when the electrical sensing unit is arranged in the front end portion of the movable member, which defines the second opening. In this way, the inner periphery of the annular shape of the front end portion forms the second opening.

[0029] In a preferred embodiment, the front end portion of the movable member is configured to be annular, preferably configured to have a circular, rectangular or triangular annular shape. In this way, the contact pressure between the movable member (and therefore the skin parameter measurement device) and the user's skin surface has a more uniform pressure distribution, which is conducive to achieving a contact pressure within a range suitable for skin impedance measurement. The "annular shape" within the scope of the present invention is not limited to a circular annular shape, but also includes other annular forms, such as rectangular, triangular, hexagonal or octagonal annular shapes or annular shapes with irregular shaped peripheries.

[0030] Preferably, the ring diameter of the annular shape and / or the diameter of the second opening is in the range of 10-50 mm, more preferably in the range of 15-20 mm. In this way, the annular shape of the movable part and / or the second opening are wide enough to ensure adequate feedback to the operator / user that the device is correctly placed when the device is placed on the skin.

[0031] Further preferably, at least the outer periphery of the annular shape, or the outer periphery and the inner periphery of the annular shape are all circular, rectangular or triangular. For example, the outer periphery of the annular shape can be triangular, and the inner periphery of the annular shape can be circular or rectangular.

[0032] In another preferred embodiment, the electrical sensing unit comprises a plurality of electrical contacts separated from one another and / or distributed within the front end portion of the movable component. In this manner, electrodes suitable for electrical skin parameter measurements (e.g., skin impedance measurements) are provided. The distribution of the electrical contacts along a ring shape makes skin impedance results more reliable, as more parts of the skin can be contacted by the electrodes. Alternatively, the electrical contacts can be arranged to form a contact array.

[0033] In another preferred embodiment, the electric sensing unit comprises two electric contacts, each of the electric contacts being arranged in one of the two semi-ring parts of the front end portion of the movable part. This enables two electrodes to perform skin impedance measurement, wherein each of the electrodes takes the form of a semi-ring, preferably a semicircular arc. The term "semi-ring" is not limited to the case where each electrode covers exactly half of the annular shape (i.e., the circular angle is 180 degrees). Each of the semi-ring parts (e.g., circular, rectangular or triangular) can correspond to a circular angle of less than 180 degrees, wherein the electrodes are preferably separated, for example, by an insulating material.

[0034] In another preferred embodiment, the lighting unit is arranged on a lighting circuit board fixedly arranged within the inner cavity of the housing structure and / or the lighting unit includes an LED arrangement comprising a plurality of LEDs. The lighting circuit board, preferably a printed circuit board (PCB), is fixed relative to the housing structure and enables easier, more compact, and more cost-effective integration of the lighting unit into the skin parameter measurement device. The use of LEDs makes the present invention more energy-efficient while facilitating control of the lighting. The polarizer can be fixedly arranged on the PCB, for example, on a side of the PCB facing the second opening of the movable component.

[0035] In another preferred embodiment, the illumination circuit board comprises an annular form having a circuit board opening for transmitting light to the imaging unit, and / or the plurality of LEDs are arranged circumferentially. The circuit board is thus suitable for facilitating optical measurement of skin parameters. During skin parameter measurement, the LEDs provide more uniform illumination of the skin surface.

[0036] In another preferred embodiment, the elastic connection device comprises at least one spring, preferably two springs, wherein at least one spring also preferably comprises a contraction spring. In this way, the integration of the movable part into the housing structure is more reliable and cost-effective, while enabling a compact device.

[0037] In another preferred embodiment, each of the two springs comprises a preloaded spring having a preload force of preferably 0.55 N. The preload force of the spring, preferably a contraction spring, facilitates compressing the movable component in an outward direction of the housing structure so that it can pass through the housing structure via the first opening at the skin contact end. For example, the natural length of the spring may be 18.7 mm, and when the spring is integrated into the skin parameter measurement device as an elastic connection, it is shortened by 7.4 mm, thereby generating a preload force of 0.55 N. Other values ​​for the spring preload force and / or spring stiffness may also be used.

[0038] In particular, a spring preload value of 0.3 N to 1.5 N is preferred in order to achieve contact between the skin parameter measurement device and the skin surface during skin parameter measurement. With a spring preload value equal to or higher than 0.3 N, a "linear guidance mechanism" (i.e., the movable part contacts the skin surface when the housing structure is pushed toward the skin surface and thereby guided by the movable part) is achieved without additional means for preventing "stick-slip" (i.e., internal friction in the mechanism, such as linear guidance of the movable part), which can occur due to spring preload values ​​below 0.3 N. With a spring preload value equal to or lower than 1.5 N, pressing of the skin parameter measurement device on the skin is facilitated by limiting the pressure required to overcome the spring contraction force.

[0039] The spring rate value is preferably selected so that the spring contraction force is overcome to allow the "use position" (see e.g. Figure 5B The required pressing force is kept below the preload level. Furthermore, the spring rate is preferably selected so that the force required to maintain the "use position" is no greater than 1.5 N, more preferably no greater than 0.8 N. A desirable range of spring rate values ​​is 0 to 0.5 N / mm. Zero spring rate values ​​can be achieved using electromagnetic actuators.

[0040] Further preferably, when the skin parameter measurement device is pressed against the skin surface, the movable component ("floating frame") is configured to move inwardly a distance of 3.5 mm until the housing structure surrounding the movable component ("rigid frame") contacts the skin surface. In this application state, the end interface of the front end portion of the movable component also contacts the skin surface and the base surface of the housing structure, wherein due to the convex curvature of the skin surface (e.g., a person's forehead or cheek), the end interface is positioned approximately 1 mm inward relative to the base surface. The value of the inward position of the end interface relative to the base surface can vary depending on factors such as skin characteristics, the location where the device is placed, etc.

[0041] In another preferred embodiment, the movable component includes at least one, preferably two, support elements, each supporting element being configured to support one of the two springs. In this manner, the springs are guided in a direction defined by the support elements, making the spring force more controllable in its direction. The support elements can be configured to hold the wiring of the device (e.g., wiring for the lighting unit and / or imaging unit).

[0042] In another preferred embodiment, at least one of the support elements includes a guide leg that is arranged to pass through a corresponding guide hole fixedly disposed within the inner cavity of the housing structure. For example, the guide hole may be formed in a guide plate that is an integral part of the device or a separate unit, preferably a circuit board. The guide plate is preferably fixed to the inner wall of the housing structure so that the spring is reliably supported, resulting in a more controllable spring force. The guide leg is arranged to pass through the inner space of the spring, thereby ensuring that the spring is supported in a fixed manner.

[0043] The circuit board may be identical to the lighting circuit board, whereby this incorporates the function of guiding the movable part and providing the circuit for the lighting unit.Alternatively, the guide plate may be a separate plate, preferably made of plastic.

[0044] In another preferred embodiment, the lighting unit and / or the imaging unit are fixedly arranged within the movable part. In this way, the lighting unit and / or the imaging unit are fixed relative to the movable part. The requirements regarding the optical properties of the optical sensing unit (e.g., the focal area of ​​an imaging unit such as a camera) are determined by the movable part itself, in particular the size / diameter of the (annular) front end portion and / or the position of the lighting / imaging unit relative to the movable part, regardless of the position of the movable part relative to the housing structure serving as an external rigid frame.

[0045] In another preferred embodiment, the skin contact end of the housing structure comprises an annularly shaped base surface defining the first opening, the annularly shaped base surface preferably having a ring width of 2 mm or more. This ensures a stable base for skin contact. The base surface is preferably a flat surface, thereby evenly increasing stability.

[0046] In another preferred embodiment, the skin parameter measurement device further comprises a trigger unit for detecting the relative position of the movable component and / or the electrical contact relative to the housing structure, so as to trigger the measurement when a predefined relative position is detected. Alternatively, the trigger unit can be configured to detect an impedance value and, when an impedance value above a lower threshold is detected within a predefined duration after the user initiates operation, trigger a signaling to properly perform the measurement.

[0047] In another preferred embodiment, the optical path of the camera is less than or equal to 60 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. In the accompanying drawings:

[0049] Figure 1 A schematic diagram of a skin parameter measuring device according to the prior art is shown;

[0050] Figure 2 shows that when the device is pressed against the skin surface, Figure 1 Schematic diagram of a skin parameter measurement device;

[0051] Figure 3 shows a graph showing test results regarding skin uplift effects in response to pressing forces;

[0052] Figure 4 A schematic diagram of a skin parameter measurement device according to an embodiment of the present invention is shown;

[0053] Figures 5A-5C Schematic diagram showing a skin parameter measurement device according to another embodiment of the present invention in three different operating states;

[0054] Figure 6A shows a graph representing test results regarding skin doming effects with respect to various spring preloads and designs;

[0055] Figure 6B shows a table representing design parameters for a plurality of skin parameter measurement device embodiments;

[0056] Figure 6C An exemplary design of the housing structure and the skin end of the movable component is shown;

[0057] Figure 7A-7B shows a graph showing comparative measurement results of two designs of movable parts of skin parameter measurement devices for two further embodiments according to the present invention;

[0058] Figure 8FIG2 is a schematic diagram showing a skin parameter measurement device according to another embodiment of the present invention;

[0059] Figure 9 FIG2 is a schematic diagram showing a skin parameter measurement device according to another embodiment of the present invention;

[0060] Figure 10 A- Figure 10 E is a schematic diagram showing various designs of the front end portion of the movable component and the bottom surface of the housing structure of the skin parameter measurement device according to further embodiments of the present invention;

[0061] Figure 11 FIG2 is a schematic diagram showing a skin parameter measurement device according to another embodiment of the present invention;

[0062] Figures 12A-12B The cross-sectional view for two operating states shows the Figure 11 A schematic diagram of a skin parameter measurement device according to an embodiment of the present invention;

[0063] Figure 13 FIG2 is a schematic diagram showing a skin parameter measurement device according to another embodiment of the present invention;

[0064] Figures 14A-14B Schematic diagrams showing a skin parameter measurement device according to another embodiment of the present invention; and

[0065] Figure 15 A skin care system according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0066] Figure 1 A schematic diagram of a skin parameter measurement device 10 according to the prior art is shown. The skin parameter measurement device 10 includes a housing structure 12, which is hollow and defines an inner cavity 20 for holding an optical sensing unit 18, which is configured to perform optical measurements of skin parameters. The optical sensing unit 18 may include a camera platform suitable for measuring skin oiliness, skin texture, and pores. When the skin parameter measurement device 10 is held in position to perform skin parameter measurements on the skin surface 16 of a body part 14 (e.g., a person), the housing structure 12 has a skin contact end 24, which is the end of the housing structure 12. At the skin contact end 24, an opening 22 is formed for transmitting optical signals sent from the optical sensing unit 18 and / or optical signals received by the optical sensing unit 18 during optical skin parameter measurement. Thus, the opening 22 serves as a measurement window.

[0067] However, even without a delay between measurements, devices known in the prior art are subject to variation in the measurement results when repeatedly measuring the same point on the skin surface of the same person. One of the main causes for this variation is skin doming 26, a dome-shaped deformation of the skin surface that occurs when the housing structure 12 of the skin parameter measurement device 10 is pressed against the elastic skin during skin parameter measurement. The housing structure 12 forms a rigid frame that, when pressed against the skin surface, causes the elastic skin to become convex. The effect of skin doming is graphically shown in FIG. Figure 2 middle.

[0068] This skin doming phenomenon increases the variability of skin parameter measurements in two ways. First, it changes the visual characteristics of the skin captured by the optical sensing unit (e.g., an illumination source and a camera). Through the measurement window 22 of the skin parameter measurement device 10, the illumination source (e.g., a dedicated LED) illuminates the otherwise unlit (and therefore darkened) skin surface, causing the camera to "see" the illuminated skin surface. Skin doming causes a change in the visual characteristics captured by the camera because the LEDs, which are specifically positioned to illuminate the skin surface at the desired angle, can be reflected differently at the point of incidence of the light due to differences in the curvature of the skin. Second, if the height of the skin dome exceeds the height of the depth of field (DOF) of the camera, the skin doming can cause the skin to not be captured in focus by the camera. When the captured image is processed using the camera's image processing algorithm, the more or less blurred image leads to erroneous measurements.

[0069] The effect of skin doming may even be influenced in degree and characteristics by many factors, including natural skin properties (e.g., human), such as elasticity, properties of the supporting subcutaneous tissue (e.g., muscle, bone), the design and / or size of the rigid shell frame that is pushed against the skin surface for skin parameter measurement, and the pressure level and force with which the rigid shell frame is pushed.

[0070] While the first two factors are fixed for a given device and a given person whose skin parameters are being measured, pressure level and force have the greatest impact on skin bulging and, therefore, on variations in skin parameter measurements. The force with which a skin parameter measurement device is pressed against the skin can vary significantly, leading to variations in skin bulging. For example, volunteer testing has shown that when asked to "gently touch" the forehead or cheek, the forces applied by a group of testers can range from 0 to 15N.

[0071] Figure 3 A- Figure 3B shows a graph showing the results of a test to find out how the applied force can lead to a higher bulge. The force levels applied in the test ranged from 0.8N to 15N and were divided into three levels: Level 1 for the lightest force, Level 2 for an intermediate force and Level 3 for the strongest force. Figure 3 A refers to a test performed on the skin of the cheek, while Figure 3 B refers to a test performed on the forehead skin. In this test, it was shown that for a range of applied forces, for a fixed window frame with a diameter of 15 mm (i.e., a frame with a window or opening brought into contact with the skin surface for skin parameter measurement), the height of the skin doming can range from 1 mm to 3 mm, resulting in a variation of 2 mm in skin doming.

[0072] Skin parameter measurement devices known from the prior art have particular drawbacks that hinder the analysis of certain skin parameters (e.g., skin oiliness) that require undisturbed light reflection from the skin surface. Solutions proposed in the art to prevent out-of-focus images include autofocus cameras. However, in addition to the undesirable cost increase, such solutions fail to address the problem of strong variations in the reflection of the emitted light due to the strong variations in the skin's doming effect, which can even increase the variability of the measured parameters (e.g., the value of skin oiliness).

[0073] Another solution known in the art proposes using a glass plate or a grid in the focal plane of the camera to flatten the skin ridges. However, this measure strongly affects the light reflection on the skin surface and is therefore not suitable for measuring certain skin parameters, such as skin oiliness.

[0074] There is a need for a solution for measuring skin parameters that can improve the control of skin doming effects without changing the reflective properties of the skin surface.

[0075] exist Figure 4 Schematic diagram of a skin parameter measurement device 100 according to an embodiment of the present invention is schematically shown in FIG, which solves the above-mentioned problems associated with skin parameter measurement devices known in the prior art. The skin parameter measurement device 100 includes a housing structure 112, which defines an inner cavity 120 for holding an optical sensing unit 118. The optical sensing unit 118 includes an illumination unit 118A and an imaging unit 118B. The optical sensing unit 118 is configured to perform optical measurements of skin parameters, such as skin oiliness, texture, pores, and pigmentation. When the device 100 is in contact with a skin surface, the illumination unit 118A illuminates the skin surface by emitting light through a first opening 122 at a skin contact end 124 of the housing structure 112. The emitted light is reflected on the illuminated skin surface and is received by the imaging unit 118B.

[0076] The skin parameter measurement device 100 further comprises a movable part 113 connected to the housing structure 112 via an elastic connection means. The movable part 113 comprises a hollow interior space and a second opening 116 at the skin contact end 124. The elastic connection means is exemplarily shown as Figure 4 One side of the spring 126 is fixed to the end of the movable part 113 opposite to the second opening 116, while the other side of the spring 126 is fixed to a plate element 132 that protrudes from the inner wall of the housing structure 112.

[0077] When no external force is applied to the skin parameter measurement device 100 (i.e., pressing the skin parameter measurement device 100 against the skin surface), the skin parameter measurement device 100 is in an unpressurized state, wherein the movable member 113 protrudes from the housing structure 112 at the skin contact end 124. Figure 4 As can be seen in FIG, due to the elasticity of spring 126, the front end portion of movable member 113 defining second opening 116 is outside inner cavity 120 of housing structure 112. This front end portion has an end interface 128, which is preferably formed to have an annular shape, such as a circular, rectangular, or triangular annular shape. The base surface 130 of skin contact end 124 of housing structure 112 defining first opening 122 is preferably formed to have an annular shape.

[0078] Due to the elasticity of the spring 126, when the movable part 113 contacts the skin surface and is further pressed against the skin surface, the movable part 113 can move inward and further into the inner cavity 120 of the shell structure 112. Therefore, the movable part 113 acts as a "floating frame" surrounded by the shell structure 112, and the shell structure 112 acts as a "rigid frame". This will Figures 5A-5C Shown in more detail in .

[0079] Figures 5A-5C FIG. 2 is a schematic diagram of a skin parameter measurement device 200 according to another embodiment of the present invention. Figures 5A-5C Skin parameter measurement devices similar to Figure 4 Skin parameter measurement device (same reference numerals indicate the same features in both sets of figures). Figures 5A-5C In the embodiment of FIG. 1 , the illumination unit 118A of the optical sensing unit 118 illustratively includes a plurality of LEDs positioned around the imaging unit 118B including the camera. The plurality of LEDs are arranged on an illumination circuit board 152, preferably a printed circuit board (PCB). Further preferably, the polarizer unit 135 is disposed on the side of the PCB facing the movable member 113. The spring 126 is preferably a pre-tensioned compression spring, so that the movable member 113 is subjected to an outward compressive force.

[0080] In order to prevent the movable part 113 from moving further toward the outside of the shell structure 112 due to the spring force, the movable part 113 includes an abutment element 134, which is pressed against the edge of the skin contact end 124 of the shell structure 112 when no external force is applied to cause the movable part 113 to move inward relative to the shell structure 112.

[0081] Within the housing structure 112, a main circuit board 188 (e.g., a main PCB connected to a power source such as a battery), a battery housing for receiving a battery 184, and / or a wireless connection port 186 may be arranged. At the end of the housing structure 112 opposite the skin contact end of the housing structure 112, a charger socket 182 may be provided for charging the power source of the device (e.g., battery 184). Other functional units such as a storage unit 190 may be additionally integrated into the housing structure 112.

[0082] When the user places the device 200 on his / her skin so that the movable member 113 (floating frame) just contacts the skin surface 16 of the body part 14, the movable member 113 moves minimally inward relative to the housing structure 112 due to the slightest force acting on the end interface of the movable member 113. This application state is schematically shown in FIG. Figure 5A The user holding the skin parameter measurement device 200 can feel the minimum force, so the user is advantageously provided with a prompt to continue pressing.

[0083] When the device 200 is further pressed against the skin surface 16, the movable part 113 continues to move inward relative to the housing structure 112 for a distance (e.g., 1-3 mm) until the housing structure 112 (external rigid frame) just contacts the skin, giving the user a feedback to stop pressing further. Figure 5B This is schematically shown in FIG, which is also the state in which skin parameter measurements can be performed (ie the "use position"). The feedback mechanism reduces the likelihood that the user will press the skin surface particularly hard.

[0084] exist Figure 5C In the embodiment, the skin parameter measurement device 200 is in a state where the movable part 113 is pressed inwardly relative to the housing structure 112, so that the spring 126 is compressed to the maximum extent to reach its innermost position within the inner cavity 120. The application state of the skin parameter measurement device 200 is usually not achieved in actual use because the maximum ridge height expected on the skin surface of the body parts such as the forehead and cheeks is less than that when the spring 126 is compressed to the maximum extent. Figure 5B The maximum distance that the movable part 113 is allowed to move inward after the state.

[0085] The present invention is advantageous with respect to controlling the pressure acting on the surface of the user's skin. The force with which the device is pressed against the user's skin is not characterized by how the pressure is applied externally to the device, but rather by the relationship between the movable member 113 and the housing structure 112 (such as Figure 5B By appropriately selecting the parameters of the spring for the application (such as spring length and stiffness / spring constant), the spring compression force can be controlled to have little or no variation.

[0086] Therefore, it is more convenient to use a device without such a floating frame mechanism (e.g. Figure 1 ) compared to conventional imaging devices. The reduced skin doming height is reduced. Even when using a camera with an imaging unit having a depth of field of less than 2.5 mm, the reduced doming profile helps obtain skin images that are focused for different users. Furthermore, the reduced skin doming effect reduces the variation in visual skin properties that occurs when different users press the device against their skin to measure skin parameters, or even when the same user presses differently at different measurement opportunities. Thus, the present invention achieves skin parameter measurement results with less variation, resulting in higher reliability in skin analysis.

[0087] Another advantage of the present invention is that the movement of the skin parameter measurement device (e.g., the housing structure 112 Figure 5A and Figure 5B The movement between the states shown) is essentially a linear movement perpendicular to the skin surface. This means that not only the intensity of the pressure but also its direction relative to the skin surface can be better controlled, resulting in less variation in skin ridges.

[0088] Yet another advantage of the present invention relates to the fact that the first frame (i.e. the movable part being the floating frame) and then the second frame (i.e. the housing structure being the rigid frame) are brought into contact with the skin surface before performing the measurement. Figure 1 ) devices, this improves feedback to the user because the likelihood of the device being placed at an incorrect angle relative to the user's skin surface is reduced.

[0089] Figure 6A Graphs showing test results on the skin doming effect with various spring preloads and device designs are shown. Curves A, B, C, and D represent the measured values ​​of the skin doming height (vertical axis) under different configurations of spring preload (0.8 N or 1.5 N, respectively) and applied to the skin surface (cheek or forehead, respectively) for a number of devices enumerated from 1 to 6 (horizontal axis). The device design parameters "floating edge thickness", "floating edge shape" and "fixed edge thickness" are shown in Figure 6B"Floating edge thickness" and "floating edge shape" refer to the width of the front end interface of the movable member and its geometry, i.e., the shape of a ring, either round (circular) or flat (rectangular). "Fixed edge thickness" refers to the width of the base surface of the skin contacting end of the housing structure. Figure 6C An exemplary design is shown: the floating edge thickness of the circular movable component 109 (floating edge) is denoted by h1 and the fixed edge thickness of the housing structure 108 (fixed edge) is denoted by h2.

[0090] Tests showed that a preload of 0.8N achieved better results in terms of skin dome height and skin bulge change. In addition, using a spring with a preload of 0.8N, when the skin parameter measurement device was pressed against the skin surface with a force of 0.8N to 15N, the skin bulge height ranged from 1.5mm to 2.3mm, given a skin bulge change of 0.8N. Compared with the prior art device ( Figure 3 A- Figure 3 This skin elevation change was significantly reduced compared to the value presented in B) (2 mm).

[0091] Figure 7A-7B A graph is shown representing the results of comparative measurements using two designs of the measurement window frame (ie the frame defining the second opening of the measurement window) about the movable part. Figure 7A In FIG, the measurement results for a circular measurement window frame are shown, where the diameter of the window frame is 15 mm and the device is pressed against the skin surface of the forehead with low pressure. Figure 7A The measurements were obtained without pressure control, i.e. using a rigid measuring window frame without suspension to limit the pressure. Figure 7B , measurement results are shown for a rectangular measurement window frame, where the window frame has dimensions of 9.5 mm x 12.4 mm and the device is pressed against the skin surface of the forehead with low pressure (specifically, a pressure between 1 N and 2 N). Comparative measurements show that, compared to the rectangular measurement window frame, the circular measurement window frame better homogenizes the skin bulges in all directions and minimizes the effects of orientation, i.e., in the circular measurement frame, the device is held or placed on the skin surface, over the skin bulges.

[0092] A (circular) measurement window frame with the same size as or larger than the rectangular field of view (FOV) of the camera used as the imaging unit is preferred for obtaining an unobstructed image. Specifically, the camera's FOV is defined by its viewing angle and its distance to the focal plane. Therefore, the size of the measurement window frame can be selected based on these two camera parameters. The window frame further preferably has dimensions of 12 mm x 9 mm or larger.

[0093] Figure 8A schematic diagram of a skin parameter measurement device 300 according to another embodiment of the present invention is shown. Figures 5A-5C The embodiment shown differs in that the optical sensing unit 118 is fixedly arranged in the movable part 115. Figure 8 As exemplarily shown in FIG, the illumination unit 118A and the imaging unit 118B (e.g., a camera) of the optical sensing unit 118 are fixedly included in a rear end portion of the movable part 115, which is the end opposite the front end portion defining the skin end interface and the second opening 116. Advantageously, the focus area of ​​the camera is defined relative to the annular skin end interface forming the skin contact ring, regardless of the relative position of the spring-loaded floating frame (i.e., the movable part 115) relative to the external rigid frame (i.e., the housing structure 112). In order to ensure controlled skin swelling in this case, the spring preferably has a low stiffness or zero stiffness (e.g., between 0 and 0.5 N / mm) and / or a defined preload (e.g., 0.8 N).

[0094] Preferably, the rear end portion of the movable member 115 has a larger cross-section than the rear end portion so that the optical sensing unit can be securely included in the movable member 115. However, this is not a limitation of the present invention, and other forms (e.g., cylindrical) having a varying or constant diameter may also be used for the movable member.

[0095] In the following, other embodiments of the skin parameter measurement device are described, which in addition to the above (ie Figure 4 、 Figures 5A-5C 、 Figure 8 ) embodiment, in addition to the features included in the embodiment, further comprising an electrical sensing unit for measuring a second skin parameter, preferably skin impedance, wherein the electrical sensing unit is further preferably arranged at the front end portion of the movable component defining the second opening. However, Figures 1-8 Features described in one embodiment may be independently applied to other embodiments below, and vice versa.

[0096] Bioimpedance can be measured by placing two or more electrical contacts or an array of electrical contacts at a fixed distance from each other on the skin surface. An electrical signal, preferably a harmonic signal (e.g., an electrical signal including one or more harmonics), is sent through the electrodes, where the difference in amplitude and phase between the input signal and the received signal is measured. This can be particularly useful for measuring skin impedance, which can be an indicator of various skin properties, such as water content (hydration), sebum content, and / or salt content (e.g., expressed as a percentage).

[0097] In part, the distance between the electrical contacts (i.e., electrodes) and the signal frequency determine the skin depth at which impedance can be measured. They also determine the effect of certain skin parameters, such as hydration, on the measured skin impedance.

[0098] Stable contact between the skin surface and the electrodes is conducive to obtaining reliable results in skin impedance measurements. Since the skin can have a variety of flexible textures, changes in contact pressure lead to changes in the form and size of the contact interface between the skin surface and the skin parameter measurement device. This leads to changes in the measurement results. The reason for the change in contact pressure is usually the force used by the operator when pressing the skin parameter measurement device to the skin surface, and the angle at which the device is maintained relative to the skin surface when the device is being pressed against the skin. Any angle that deviates from the perpendicular angle relative to the skin surface may result in differences in pressure distribution and thus in changes in the measured skin impedance. Finally, for electrical contacts with a smaller contact area (i.e., the area of ​​the skin surface contacted by the electrical contacts), these effects are greater than for electrical contacts with a larger contact area.

[0099] Figure 9 FIG4 shows a skin parameter measurement device 400 according to an embodiment of the present invention. The skin parameter measurement device 400 includes Figure 4 , and further includes an electric sensing unit, which preferably includes two electric contacts 136 formed at the movable member 117. Exemplarily, the electric contacts 136 are provided at the front end portion of the movable member 117 to extend inwardly from the skin end interface of the movable member 117. Alternatively or additionally, the electric contacts 136 may extend inwardly along the movable member 117 over its entire length or covering a portion of the entire length.

[0100] The present invention thus provides a combination of an optical measuring device and an electrical measuring device, resulting in a skin parameter measurement device with greater applicability than devices known in the prior art.

[0101] exist Figure 9 In the figure, two electrical contacts are shown as an example. However, the number of electrical contacts may be more than two. As mentioned above, the front end portion of the movable member 117 may be formed into an annular shape, preferably a circular, rectangular, or triangular annular shape. Further preferably, the electrical sensing unit 136 includes a plurality of electrical contacts, which are fixedly separated from each other and distributed within the annular shape of the front end portion of the movable member 117.

[0102] In this way, angular changes during the user's handling of the skin parameter measurement device are minimized. Preferably, the "diameter" of the annular shape (i.e., the maximum, average, or minimum distance between two opposite sides of the annular shape, particularly at the outer or inner periphery of the annular shape) is large enough to ensure appropriate feedback to the user that the device is correctly placed when placed on the skin. For example, the diameter may be in the range of 10 mm to 50 mm, more preferably between 15 mm and 20 mm.

[0103] Figure 10 A- Figure 10 C shows a plurality of exemplary electrical contacts distributed on a circular ring shape of a movable part. Figure 10 In A, two electrical contacts 138, 140 are provided in the base surface 146 of the front end portion of the movable member, wherein the electrical contacts 138, 140 each include a plurality of teeth. Figure 10 In FIG. B, the electrical contacts 142 are distributed circularly on the base surface 146, and each electrical contact 142 has a trapezoidal shape. Figure 10 In FIG. 1C , circular electrical contacts 144 are distributed circularly on a base surface 146 .

[0104] Figure 10 D- Figure 10 E shows an exemplary form of the base surface 146 of the movable member, which defines the second opening 116. Figure 10 D, the base surface 146 has a rectangular annular shape at both peripheries thereof, and Figure 10 The base surface 146 in E has a triangular annular shape at its outer periphery and a circular annular shape at its inner periphery.

[0105] In addition, the elastic connection device (in Figure 9 Two springs 126 (illustrated as springs 126 in the figure) enable the floating frame (i.e., movable member 117) to move back and forth within the rigid frame (i.e., housing structure 112). Preferably, the skin-contacting end of the housing structure includes an annular base surface for contacting the skin surface, with the annular base surface having a ring width of 2 mm or greater. This ensures a stable base of skin contact when the floating frame is completely flush with the base surface when the measurement tool is pressed against the skin surface.

[0106] Figure 11A skin parameter measurement device 500 according to another embodiment of the present invention is shown. Here, the movable member 150 has a circular ring shape at its front end. Two electrical contacts 148a, b are arranged within the ring shape, forming a portion of the movable member 150. Specifically, the electrical contacts 148a, b each have an arcuate shape, separated by two portions of the movable member 150. The housing structure 112 is disposed so as to surround the movable member 150. An illumination circuit board 152, preferably a printed circuit board (PCB), is fixedly disposed within the interior cavity of the housing structure 112, with a plurality of LEDs 154 (illumination unit) arranged circumferentially around a central aperture 170 of the illumination circuit board 152. A camera 156 (imaging unit) is disposed within the interior cavity of the housing structure 112, inwardly relative to the illumination circuit board 152. When the device 500 is brought near or into contact with the skin surface, light 154 emitted by the LEDs travels to the skin surface via the second opening 116 of the movable member 150. Light reflected from the skin surface then travels through the central hole 170 of the lighting circuit board 152 to the camera 156 .

[0107] exist Figures 12A-12B middle, Figure 11 The device 500 is shown in side view. Figure 12A In the embodiment, the device 500 is in an unpressed state, and in Figure 12B In FIG. 5 , the device 500 is in contact with the skin surface (not shown), and the movable member 150 moves inwardly due to skin bulging (not shown).

[0108] The movable part 150 (floating frame) preferably comprises a first portion made of plastic and a second portion forming the electrical contacts 148a, b. The first portion comprises two guide legs 162 that carry the spring 160 and extend through the lighting circuit board 152 via two guide holes formed therein. This ensures balanced linear movement of the device 500 during use. When in the default uncompressed state, the natural length of the spring 160 is illustratively 18.7 mm. When shortened by 7.4 mm, a preload of 0.55 N is provided.

[0109] Typically, when the user presses the skin analysis tool to his / her head, the skin end interface 164 of the movable member 150 (floating frame) is brought into contact with the skin surface ( Figure 12A From this position, the floating frame further pressed against the skin surface can move inwards by a distance of 2.5 mm (in Figure 12AThe movable member 150 moves from the base surface 166 of the housing structure 112 (shown as d1) to the base surface 166 of the housing structure (external static frame or rigid frame) in contact with the user's skin surface. Taking into account the convex curvature of the skin surface of a body part such as the forehead or cheek, the distance between the skin end interface 164 of the movable member 150 and the base surface 166 of the housing structure 112 in contact with the skin surface in this final position (in Figure 12B (shown as d2 in the figure) is 1 mm. At this point, the calculated spring force due to compression is 0.81 N. Given the small expected changes in the length of the compression spring, between +0.5 mm and -0.5 mm (the symbols + and - refer to increases and decreases in spring length, respectively), the change in spring force will be within the range of +0.02 N and -0.02 N (the symbols + and - refer to the direction of the spring force when the length decreases and increases, respectively). Therefore, the change in spring force is advantageously low.

[0110] The camera 156 used in the current embodiment has a depth of field of + / - 1.5 mm. Furthermore, the camera 156 has a focal plane that is 0.5 mm inward from the ideal final position of the floating frame's skin-end interface 164. This is to account for the average level of skin doming that occurs due to the pressure exerted on the skin surface by the floating frame due to spring 162. This inward bias of the focal plane is due to the fact that the skin only bulges in one direction due to the natural curvature (on the forehead and cheeks) and due to the effects of pressure.

[0111] In further embodiments, the floating frame can be supported using means other than guide legs, and the springs can be guided using other means for positioning. When guide legs are used, any or all of the legs can provide additional functional passages (e.g., tunnels) for carrying wires from the skin-contacting end of the device to the lumen, or even to the end of the device opposite the skin-contacting end. Additionally, any number or all of the legs can be used to support the springs using additional guides or other mechanisms to create a balanced spring-loaded floating system. The force can also be adjusted to accommodate different users and / or different applications if the overall dimensions of the frame are different for different parts of the body and / or images to be measured.

[0112] To ensure that an image is captured only when the floating frame has moved inward sufficiently (e.g., a predetermined distance) to allow contact between the external rigid frame and the skin surface, thereby ensuring that the skin is within the camera's focus area, a first detection unit is preferably added to detect the relative position of the floating frame relative to the external rigid frame. This detection can preferably serve as a trigger for the camera to capture an image.

[0113] The present invention can be configured to signal that the skin impedance measurement was performed correctly when proper contact between the electrical contacts and the skin is detected. This can be achieved, for example, by a second detection unit that checks the device's impedance reading relative to a lower threshold. The skin typically has a specific impedance range. For an applied electrical signal, at a frequency of 32kHz, this specific impedance range is 4 to 45k ohms for the average person. In the case of a standalone device with a user interface (UI), after a predefined duration has passed after pressing the "measure" button, if a value above the lower threshold has been detected within the predetermined time period, or conversely, no value above the lower threshold has been detected within the predetermined time period, the device can indicate via the UI that a correct measurement has been obtained. In the case of a "connected device," the user can, for example, start the measurement via a smartphone app. If a value above the lower threshold is not obtained after a predefined duration from the start of the measurement, the user can receive a message (e.g., via the app) indicating that the measurement result is incorrect and should be redone.

[0114] To ensure the correct pressure level during impedance measurement, a third detection unit can be added to detect the relative position of the electrodes relative to the fixed outer frame. Impedance measurements are performed only when a predetermined relative position along the longitudinal direction of the fixed outer frame is detected. This detection can serve as a trigger to take an impedance reading at the moment the spring is fully compressed.

[0115] Figure 13 Schematic diagram of a skin parameter measurement device 600 according to yet another embodiment of the present invention is shown. In this embodiment, the housing structure 112 of the skin parameter measurement device 600 includes a removable portion 172. A button 173 for turning the device 600 on and / or off is preferably arranged on one side of the housing structure 112.

[0116] Figures 14A-14B Schematic diagrams of the movable components of the present invention are respectively shown. Figures 14A-14B The illustrated movable parts 174, 176 include two electrical contacts 148a, b, each of which has an arcuate shape and is separated by a plastic portion of the movable parts 174, 176. The electrical contacts 148a, b are supported by the plastic portion of the movable parts 174, 176. In addition, a plug 178 or wiring 180 is provided for each of the two exemplary movable parts 174, 176, for example, for connecting to a lighting circuit board and / or a main power circuit board (main PCB) of the device. The movable parts 174, 176 can be attached to a housing structure (e.g., via a means for detachable mechanical connection, such as a clip) to form a skin parameter measurement device.

[0117] The combination of a ring electrode of sufficient diameter and a spring suspension in a rigid frame with a sufficient, preferably flat, base surface facilitates the realization of a device that provides feedback to the user when the device is stably positioned on the skin surface, as described above. Furthermore, in a stably positioned position, the pressure-induced changes in the impedance measurement are reduced to an acceptably low level, resulting in sufficiently low measurement variations.

[0118] The combination of spring-suspended ring electrodes and optical sensing functionality creates a complete solution in which contact pressure for electrical skin parameter measurements (e.g., skin impedance measurement) and skin swelling for optical skin parameter measurements (e.g., skin imaging) are better controlled. Other advantages of this combined solution are a more compact and cost-effective design with optimized ergonomics.

[0119] Figure 15 A preferred skin care system 700 is shown comprising a skin parameter measurement device 701, an analysis unit 702 for analyzing skin parameter measurement results provided by the device 701, and an adaptation unit 703 for adjusting settings of the system based on the analysis results. The skin parameter measurement device 701 may be any embodiment of the present invention described above.

[0120] Although the present invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description should be considered illustrative or exemplary rather than restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0121] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0122] The computer program may be stored / distributed on suitable media such as optical storage media or solid-state media provided together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

[0123] Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A device for measuring at least one skin parameter, comprising: - a housing structure (112) defining an interior cavity (120) and a first opening (122) at a skin contacting end (124) of the interior cavity (120); - a movable member (113, 117) connected to the housing structure (112) via an elastic connection means (126), the movable member (113, 117) being movable relative to the housing structure (112) so that the movable member (113, 117) is at least partially retained within the housing structure (112), and being configured to protrude from the first opening (122) when no external force is applied to the movable member (113, 117), the movable member (113, 117) further comprising a second opening (116) at a front end portion; an optical sensing unit (118) for performing measurement of a first skin parameter, the optical sensing unit being arranged in the inner cavity of the housing structure and comprising an illumination unit (118A) for illuminating the skin surface by emitting light through the second opening (116) of the movable component, and an imaging unit (118B) for receiving light reflected by the illuminated skin surface; as well as - an electrical sensing unit (136) for measuring a second skin parameter, wherein the electrical sensing unit (136) is arranged at a front end portion of the movable part (113, 117) defining the second opening (116).

2. The apparatus according to claim 1, wherein the front end portion of the movable member (113, 117) is configured to be ring-shaped.

3. The device according to claim 2, wherein the electric sensing unit (136) comprises a plurality of electric contacts which are separated from each other and / or distributed within the front end portion of the movable part (113, 117).

4. The device according to claim 3, wherein the electric sensing unit (136) comprises two electric contacts, each of the electric contacts being arranged in one of the two half-ring parts of the front end part of the movable part (113, 117).

5. The device according to claim 1, wherein the lighting unit (118A) is arranged on a lighting circuit board (152), and the lighting circuit board (152) is fixedly arranged within the housing structure (112).

6. The apparatus of claim 5, wherein the lighting circuit board (152) comprises an annular form having a circuit board opening (170) for transmitting light to the imaging unit (118B).

7. The apparatus of claim 1, wherein the elastic connection means comprises at least one spring.

8. The device according to claim 7, wherein the elastic connection device comprises two springs, and each of the two springs comprises a preloaded spring.

9. The apparatus according to claim 8, wherein the preload spring has a preload force of 0.55N.

10. Apparatus according to claim 7, wherein said movable part (113, 117) comprises at least one supporting element (162) for carrying said spring.

11. The device according to claim 1, wherein the illumination unit (118A) and / or the imaging unit (118B) is fixedly arranged within the movable part (113, 117).

12. The device according to claim 1, wherein the device further comprises a triggering unit for detecting a relative position of the movable part (113, 117) with respect to the housing structure (112) so as to trigger the measurement of the skin parameter when a predefined relative position is detected.

13. A skin care system (700), comprising: - The device according to claim 1, for measuring skin parameters; as well as - an analysis unit (702) for analyzing the measurement results provided by the device.

14. A method for measuring skin parameters using the device according to claim 1, comprising the steps of: - performing a measurement of a first skin parameter using the optical sensing unit when the device is in contact with the skin surface; - using the lighting unit to illuminate the skin surface by emitting light through the second opening of the movable member; - receiving light reflected by the illuminated skin surface using the imaging unit; as well as - performing a measurement of a second skin parameter using the electrical sensing unit when the device is in contact with the skin surface.

15. A computer program product comprising a computer program which, when executed on a computer, causes the computer to perform the steps of the method according to claim 14.

Images