WO2025009891A1 - Apparatus for measuring skin firmness - Google Patents

Abstract

The present invention relates to an apparatus for measuring skin firmness, capable of quantitatively measuring the firmness of the skin, wherein the apparatus may comprise: a vibration application unit which is in contact with any one point of the skin and applies a predetermined vibration to the skin; a sensing unit which is in contact with the skin at first and second points spaced apart from the vibration application unit by different points, and measures a vibration wave by means of the predetermined vibration applied by the vibration application unit; and a calculation unit for calculating a Young's modulus capable of representing the firmness of the skin on the basis of a measurement value for the vibration wave from the sensing unit.

Description

Skin hardness measuring device

The present invention relates to a skin hardness measuring device, and more specifically, to a skin hardness measuring device capable of quantitatively measuring the hardness of skin.

As interest in skin beauty increases, the demand for skin elasticity measurement is also increasing. Skin hardness can change due to age, humidity, etc. Accordingly, measuring skin hardness may be required in the process of checking skin health and verifying the effectiveness of cosmetics being developed.

Conventional methods for measuring skin hardness include the indentation method, the torsion method, and the suction method. These methods measure skin hardness assuming that the entire skin is composed of a single, homogeneous, and isotropic material.

However, since actual skin is composed of the stratum corneum, epidermis, dermis, and hypodermis, each of which has different hardness, it has been difficult to accurately measure the skin hardness of each layer using conventional measurement methods. In addition, since there is no portable skin hardness/elasticity measurement device, when measuring skin hardness optically, there has been a problem in that the measurement device includes a bulky optical device, making it impossible to carry around.

The present invention is intended to solve various problems including the above-described problems, and aims to provide a skin hardness measuring device that is miniaturized and easy to carry by measuring the hardness of the skin using vibration waves, can measure the hardness of each layer of the skin simultaneously, and can quantitatively calculate and display the hardness of the skin as Young's modulus. However, these tasks are exemplary and the scope of the present invention is not limited thereby.

According to one embodiment of the present invention, a skin hardness measuring device is provided. The skin hardness measuring device may include: a vibration applying unit that contacts a point of the skin and applies a predetermined vibration to the skin; a sensing unit that contacts the skin at a first point and a second point spaced apart from the vibration applying unit by different points and measures a vibration wave caused by the predetermined vibration applied by the vibration applying unit; and a calculation unit that calculates a Young's modulus that can represent the hardness of the skin based on a measurement value of the vibration wave by the sensing unit.

According to one embodiment of the present invention, the sensing unit may include a first vibration sensor that is in contact with the skin at a first point spaced a first distance from the vibration applying unit and measures the vibration wave caused by the predetermined vibration applied from the vibration applying unit; a second vibration sensor that is in contact with the skin at a second point spaced a second distance from the vibration applying unit and measures the vibration wave caused by the predetermined vibration applied from the vibration applying unit so as to be positioned at a different point from the first vibration sensor; and a sensor driving unit that drives the vibration sensors.

(v: 파동 속도, x₁: 진동파 인가 지점으로부터 제 1 지점까지의 이격 거리, x₂: 진동파 인가 지점으로부터 제 2 지점까지의 이격 거리, f: 진동 주파수, △φ: 제 1 지점과 제 2 지점에서의 파동의 위상차)에 의해, 상기 진동파의 진동 주파수(f)에서의 파동 속도(v)를 산출할 수 있다.According to one embodiment of the present invention, the calculation unit calculates, based on the phase difference between the vibration wave measured by the first vibration sensor and the vibration wave measured by the second vibration sensor, and the distances between the point where the vibration applying unit applied the predetermined vibration and the first point and the second point, [Formula 1]

(v: wave velocity, x ₁ : distance from the point of application of the vibration wave to the first point, x ₂ : distance from the point of application of the vibration wave to the second point, f: vibration frequency, △φ: phase difference between waves at the first point and the second point), the wave velocity (v) at the vibration frequency (f) of the vibration wave can be calculated.

(v: 파동 속도, Y: 피부의 영률, ρ: 피부의 밀도)를 기초로, 상기 영률을 산출할 수 있다.According to one embodiment of the present invention, the calculation unit calculates the wave velocity (v) calculated by [Formula 1] and [Formula 2]

Based on (v: wave velocity, Y: Young's modulus of skin, ρ: skin density), the above Young's modulus can be calculated.

According to one embodiment of the present invention, the vibration applying unit may include an actuator that applies the predetermined vibration to the skin; and an actuator driving unit that is electrically connected to the actuator and drives the actuator.

According to one embodiment of the present invention, the actuator driving unit can drive the actuator so that the actuator can apply the predetermined vibration having a vibration frequency in a band of 10 kHz or less.

(f: 진동 주파수, k_a: 피부의 스프링 상수, ρ: 피부의 밀도)에 의해, 상기 진동 주파수를 사전에 산출하여 저장할 수 있다.According to one embodiment of the present invention, the actuator driving unit can apply the predetermined vibration having a vibration frequency corresponding to the natural frequency of the skin, [Formula 3]

(f: vibration frequency, k _a : spring constant of skin, ρ: density of skin), the vibration frequency can be calculated in advance and stored.

According to one embodiment of the present invention, the spring constant of the skin in the above [Formula 3] can be calculated by [Formula 4] k _a = E / t (k _a : spring constant of the skin, E : Young's modulus of the skin, t : thickness of the skin).

According to one embodiment of the present invention, the first vibration sensor and the second vibration sensor may include a flexible film in which conductive particles are mixed with a silicone material as a vibration transmission medium of the skin.

According to one embodiment of the present invention, the flexible film can be formed with a hardness lower than the hardness of the skin.

According to one embodiment of the present invention, the first vibration sensor and the second vibration sensor are formed in the form of a flexible film with a thickness of 1 mm or less (greater than 0), and are formed by the conductive particles to have a constant conductivity after coming into contact with the skin, so that the shape of the flexible film vibrates accordingly according to the vibration of the skin, thereby changing the resistance.

According to one embodiment of the present invention, the sensor driving unit may include a current source that is connected to the first vibration sensor and the second vibration sensor, respectively, and applies a predetermined current; and a voltmeter that measures a voltage generated from the first vibration sensor and the second vibration sensor.

According to one embodiment of the present invention, the first separation distance of the first vibration sensor and the second separation distance of the second vibration sensor can be formed as different separation distances.

According to one embodiment of the present invention, the device may further include a temperature sensor that comes into contact with the skin at a third point spaced a third distance from the vibration applying unit and measures the temperature of the skin.

According to one embodiment of the present invention, the calculation unit may calculate and store correction data regarding a change in the Young's modulus according to the temperature of the skin in advance, and when calculating the Young's modulus, correct the Young's modulus based on the temperature of the skin measured by the temperature sensor and the correction data.

According to one embodiment of the present invention, the device may further include a constant temperature module that comes into contact with the skin at a third point spaced a third distance from the vibration applying unit, heats or cools the skin to a predetermined temperature and maintains the temperature of the skin at the predetermined temperature.

According to one embodiment of the present invention as described above, by using the principle that the speed at which a vibration wave moves along the skin surface is related to the Young's modulus (hardness) of the skin, by vibrating at a point on the skin and detecting the vibration wave caused by the vibration at a point spaced apart by a predetermined distance, the Young's modulus, which can represent the hardness of the skin, can be calculated based on the measured value for the vibration wave.

In this way, by measuring the hardness of the skin using vibration waves, a skin hardness measuring device can be implemented that can be miniaturized for easy portability, can measure the hardness of each layer of the skin simultaneously and individually, and can quantitatively calculate the hardness of the skin as Young's modulus and display it as an objective and accurate number. Of course, the scope of the present invention is not limited by these effects.

Figure 1 is a schematic diagram schematically showing a skin hardness measuring device according to one embodiment of the present invention.

Fig. 2 is a circuit diagram schematically showing the configuration of the sensing unit of the skin hardness measuring device of Fig. 1.

Figures 3 and 4 are images of vibration detection experiments of the sensing part of the skin hardness measuring device of Figure 1, and graphs showing changes in output voltage according to application and removal of a magnetic field.

Figure 5 is a schematic diagram showing the correlation between the wavelength and frequency of vibration, penetration depth, and propagation speed of vibration during the skin hardness measurement process of the skin hardness measurement device of Figure 1.

Figure 6 is a schematic diagram schematically showing a skin hardness measuring device according to another embodiment of the present invention.

<Explanation of symbols>

100: Vibration application unit

110: Actuator

120: Actuator drive unit

200: Sensing part

210: 1st vibration sensor

211: Magnetic Sponge

220: 2nd vibration sensor

221: Magnetic Sponge

230: Sensor drive unit

231: Current source

232: Voltmeter

300: Operation section

400: Temperature sensor

500: Constant Temperature Module

1000, 2000: Skin hardness measuring device

V: Vibration wave

S: Skin

Hereinafter, various preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art, and the following embodiments can be modified in various different forms, and the scope of the present invention is not limited to the following embodiments. Rather, these embodiments are provided to more faithfully and completely convey the idea of the present invention to those skilled in the art. In addition, the thickness and size of each layer in the drawings are exaggerated for convenience and clarity of explanation.

Hereinafter, embodiments of the present invention will be described with reference to drawings that schematically illustrate ideal embodiments of the present invention. In the drawings, for example, variations in the shapes depicted may be expected depending on manufacturing techniques and/or tolerances. Accordingly, embodiments of the present invention should not be construed as being limited to the specific shapes of the regions depicted in this specification, but should include, for example, variations in shapes resulting from manufacturing.

FIG. 1 is a schematic diagram schematically showing a skin hardness measuring device (1000) according to one embodiment of the present invention, and FIG. 2 is a circuit diagram schematically showing the configuration of a sensing unit (200) of the skin hardness measuring device (1000) of FIG. 1. In addition, FIGS. 3 and 4 are images of vibration detection experiments of the sensing unit (200) of the skin hardness measuring device (1000) of FIG. 1, and graphs showing changes in output voltage according to application and removal of a magnetic field.

The skin (S) is divided into the stratum corneum, the epidermis, the dermis, and the hypodermis. The stratum corneum has a thickness of less than about 40 ㎛ and a hardness of about 500 MPa. The epidermis has a thickness of about 50 ㎛ to 100 ㎛ and a hardness of about 1 MPa. The dermis has a thickness of about 1 mm and a hardness of about 88 kPa to 300 kPa. The hypodermis has a thickness of several mm and a hardness of about 30 kPa.

If we look at the relationship between the hardness of the sound transmission medium and sound, the speed of sound in air is about 340 m/s, the speed of sound in crystal is about 1,500 m/s, and the speed of sound inside iron is about 5,000 m/s. In other words, the higher the Young's modulus (hardness) of the medium, the faster the speed of sound propagation. If we apply this to skin (S), we can see that the harder the skin (S) is, the faster the propagation speed of the vibration wave moving inside the skin.

Accordingly, the present invention proposes a skin hardness measuring device (1000) capable of measuring the hardness (Young's modulus) of skin (S) using an actuator (vibrator) that applies vibration and a vibration sensor that can measure vibration waves.

The basic principle is to apply vibration to the skin (S) and utilize the fact that the speed at which the vibration wave moves on the surface or inside of the skin is related to the Young's modulus (hardness) of the skin (S). As a measurement method, the vibration of the skin (S) is measured by a vibration sensor located at a certain distance from the vibrator, and the amplitude of the skin vibration over time is measured.

As illustrated in FIG. 1, a skin hardness measuring device (1000) according to one embodiment of the present invention may largely include a vibration applying unit (100), a sensing unit (200), and a calculation unit (300).

As illustrated in Fig. 1, the vibration applying unit (100) can apply a predetermined vibration to the skin (S) by coming into contact with a point (P0) of the skin (S).

For example, the vibration applying unit (100) may include an actuator (110) that applies the predetermined vibration to the skin (S) and an actuator driving unit (120) that is electrically connected to the actuator (110) and drives the actuator (110).

When the actuator driving unit (120) applies a predetermined driving signal to the actuator (110), the actuator (110) in contact with the skin (S) vibrates, causing a vibration wave (V) to move along the surface or inside of the skin (S).

In this way, when the actuator (110) applies vibration to the skin (S), it is necessary to select an optimal frequency that takes into account the modulus and thickness of the skin (S), and when considering the above-mentioned matters, it may be desirable for the actuator driving unit (120) to drive the actuator (110) so that the actuator (110) can apply the predetermined vibration having a vibration frequency in a band of 10 kHz or less.

In addition, the hardness (Young's modulus) of the skin (S) can change depending on the degree of aging, and the hardness can also change depending on the moisturizing state, health condition, environment, etc. When the resonance phenomenon is utilized to measure the hardness of the skin (S), the resonance frequency, vibration amplitude, phase difference between the vibration source vibration and the vibration detected by the sensor, etc. can change depending on the minute change in the Young's modulus of the skin (S), so the precision of the hardness measurement can be further improved.

Since the skin hardness measuring device (1000) of the present invention uses the vibration of the skin (S), it can utilize the resonance phenomenon (resonance vibration) to amplify the measurement signal and reduce noise compared to the signal.

For example, the Young's modulus of the skin (S) varies greatly depending on the body part, but can be within 1 MPa. For example, in the case of the cheek, the Young's modulus is 250 kPa, and in this case, the resonance frequency can be calculated as follows.

First, the spring constant of the skin (S) per unit area can be calculated using the following [Formula 4].

[Formula 4]

k _a = E/t

k _a : spring constant of the skin

E: modulus of skin

t: thickness of skin

Here, t in the above [Formula 4] is the approximate skin thickness, and in the case of the cheek, it can be assumed to be approximately 1.5 mm according to several related references.

In this way, when the spring constant of the skin (S) is calculated by the above [Formula 4], the actuator driving unit (120) of the vibration applying unit (100) can calculate and store the vibration frequency in advance by the following [Formula 3] so that the actuator (110) can apply the predetermined vibration having the vibration frequency corresponding to the natural frequency of the skin (S).

[Formula 3]

f: vibration frequency

k _a : spring constant of the skin

ρ: skin density

In general, since the mass per unit area of the skin (S) is approximately 1.65 kg/m ² , the vibration frequency f for the resonance phenomenon can be approximately 1,568 Hz.

Accordingly, when the actuator driving unit (120) drives the actuator (110) by setting the vibration of the driving motor to 1,568 Hz, and the actuator (110) applies the predetermined vibration to the skin (S) at the corresponding vibration frequency, the sensing unit (200) to be described later can detect a vibration wave (V) having a frequency close to this frequency.

As illustrated in FIG. 1, the sensing unit (200) can measure a vibration wave (V) caused by the predetermined vibration applied by the vibration applying unit (100) by coming into contact with the skin (S) at a first point (P1) and a second point (P2) spaced apart from the vibration applying unit (100) by different points.

For example, the sensing unit (200) may include a first vibration sensor (210) that comes into contact with the skin (S) at a first point (P1) spaced apart from the vibration applying unit (100) by a first distance (d1) and measures a vibration wave (V) caused by the predetermined vibration applied by the vibration applying unit (100), a second vibration sensor (220) that comes into contact with the skin (S) at a second point (P2) spaced apart from the vibration applying unit (100) by a second distance (d2) and may be positioned at a different point from the first vibration sensor (210) and measures a vibration wave (V) caused by the predetermined vibration applied by the vibration applying unit (100), and a sensor driving unit (230) that drives the first vibration sensor (210) and the second vibration sensor (220).

More specifically, the sensor driving unit (230) may be configured with a current source (231) that applies a predetermined current and a voltmeter (232) that measures a voltage generated from the first vibration sensor (210) and the second vibration sensor (220), which are connected to the first vibration sensor (210) and the second vibration sensor (220), respectively, as illustrated in FIG. 2.

In addition, since the vibration sensor (210, 220) is advantageous in detecting vibrations the closer it is to the skin (S), it may be desirable to limit the Young's modulus of the material to 600 kPa or less in order to form the hardness of the material for manufacturing the vibration sensor (210, 220) to be similar to or lower than that of the skin (S).

For example, the vibration sensor (210, 220) can be manufactured by mixing conductive particles (e.g., milled carbon fiber) with a soft silicone material (e.g., silicone 00-30, hardness 60 kPa) that is lower than the hardness of human skin, in order to ensure close contact with the skin (S).

In this way, the manufactured vibration sensor (210, 220) is formed in a flexible film form with a thickness of 1 mm or less (greater than 0), and can be formed to have a constant conductivity after coming into contact with the skin (S) by the conductive particles.

In addition, the vibration sensor (210, 220) may include a flexible film (211, 221) in which conductive particles are mixed with a silicone material as a vibration transmission medium of the skin (S). The flexible film (211, 221) may be formed with a medium having a very low hardness and a hardness lower than that of the skin (S). For example, in the case of silicone rubber (Shore 0010), the hardness may be about 20 kPa, which is similar to the hardness of the skin (Hypordermis), which is 30 kPa.

In addition, it may be preferable that the first separation distance (d1) of the first vibration sensor (210) and the second separation distance (d2) of the second vibration sensor (220) are formed with different separation distances, and at this time, it may be preferable that the vibration applying unit (100) and the vibration sensors (210, 220) are separated by several millimeters to several centimeters.

The following relates to an example of driving a vibration sensor (210, 220) manufactured as in the above-described embodiment. The example of manufacturing and driving of the vibration sensor (210, 220) described in the present invention are merely intended to explain an example of manufacturing and driving the vibration sensor (210, 220) for easy understanding of the present invention. The vibration sensor (210, 220) of the present invention is not necessarily limited thereto, and any known vibration sensor may be used as long as it is a sensor that is attached to the skin (S) and can detect vibration.

FIG. 3 shows an example of implementing a vibration sensor (210, 220) in which vibration is applied using magnetic force in an environment other than the skin (S) and the vibration is detected by a change in resistance. When a coil that generates a magnetic field is placed near a vibration sensor (210, 220) and a certain amount of current is repeatedly applied/removed to the coil to generate an oscillating magnetic field, the vibration sensor (210, 220) repeatedly bends and straightens depending on the presence or absence of the magnetic field. This change in shape changes the electrical resistance of the vibration sensor (210, 220). At this time, the material of the vibration sensor (210, 220) can be manufactured to contain both magnetic particles (e.g., NdFeB particles or Ferrite particles) and conductive particles in order to receive a magnetic force.

More specifically, by making the corner of the vibration sensor (210, 220) formed in the form of a square film come to the center of the coil, the vibration sensor (210, 220) can be arranged so that the deformation (corner bending and straightening) can be easily observed. At this time, since the resistance of the vibration sensor (210, 220) is high, an electrode of a certain shape (linear shape) can be painted and arranged on the surface of the vibration sensor (210, 220) with conductive paint in order to easily observe the change in electrical resistance.

In order to reduce the resistance, as shown in Fig. 3, a pair of electrodes (a pair of white lines at the edge of Fig. 3) formed to be long and straight were placed, and current was applied between them. In this way, the area between the two electrodes, i.e., the area with a wide width and a short length, is advantageous for reducing the resistance, so the output signal increases, which can be advantageous for vibration detection.

Due to the oscillating magnetic field generated in the above coil, the film-shaped vibration sensor (210, 220) changes shape by receiving an attractive or repulsive force depending on the application and removal of the magnetic field, and as a result, the electrical resistance inside the vibration sensor (210, 220) changes.

Accordingly, the vibration sensor (210, 220) was found to be able to detect the presence and intensity of vibration by detecting changes in the measured voltage by an electrical method, that is, vibration applied to the vibration sensor (210, 220), according to the application and removal of a magnetic field, as shown in FIG. 4.

In addition, in the above-described embodiment, the sensing unit (200) is exemplified as including two vibration sensors (210, 220), but is not necessarily limited thereto and may include a very different number of vibration sensors depending on the precision of skin hardness measurement required for the skin hardness measuring device (1000).

As illustrated in Fig. 1, the calculation unit (300) is electrically connected to the vibration application unit (100) and the sensing unit (200), and can calculate the Young's modulus, which can represent the hardness of the skin (S), based on the measurement value of the vibration wave (V) in the sensing unit (200).

Here, the operation unit (300) may be connected by wires and installed together with the vibration application unit (100) and the sensing unit (200) within one main body, but is not necessarily limited thereto, and may be installed externally separately from the main body in which the vibration application unit (100) and the sensing unit (200) that come into contact with the skin (S) are installed by wirelessly connecting.

The calculation unit (300) can calculate the wave velocity (v) at the vibration frequency (f) of the vibration wave (v) based on the phase difference between the vibration wave (V) measured by the first vibration sensor (210) located at the first point (P1) and the vibration wave (V) measured by the second vibration sensor (220) located at the second point (P2), and the distances (d1, d2) from the point (P0) where the vibration applying unit (100) applies the predetermined vibration to the first point (P1) and the second point (P2).

For example, the calculation unit (300) can convert the sensor values corresponding to the amplitudes of the vibration wave (V) measured by the first vibration sensor (210) located at the first point (P1) and the vibration wave (V) measured by the second vibration sensor (220) located at the second point (P2) through the following process, thereby finally calculating the wave velocity (v) at the vibration frequency (f) of the vibration wave (v) by the following [Formula 1].

- y ₁ (t): sensor value measured at point 1 (P1) (real function), function of time, t

- y ₂ (t): sensor value measured at point 2 (P2) (real function), function of time, t

- Y ₁ (f): Fourier transform value of y ₁ (complex function), frequency, function of f

- Y ₂ (f): Fourier transform value of y ₂ (complex function), frequency, function of f

- Cross-power spectrum, Y ₁₂ (f)

- (φ ₂ -φ ₁ ): phase difference of the wave between the first point (P1) and the second point (P2), a function of the frequency f

[Formula 1]

v: wave velocity

x ₁ : Distance from the point of vibration application to the first point

x ₂ : Distance from the point of vibration application to the second point

f: vibration frequency

△φ: Phase difference of waves at point 1 and point 2

In this way, when the wave velocity (v) is calculated by the above [Formula 1], the calculation unit (300) can calculate the Young's modulus based on the wave velocity (v) calculated by the above [Formula 1] and the following [Formula 2].

[Formula 2]

v: wave velocity

Y: modulus of skin

ρ: skin density

Fig. 5 is a schematic diagram showing the correlation between the wavelength and frequency of vibration, penetration depth, and propagation speed of vibration during the skin hardness measurement process of the skin hardness measurement device (1000) of Fig. 1. In Fig. 5, for convenience of explanation, it is assumed that the skin (S) is composed of only two layers, a high-hardness layer (e.g., Epidermis or Demis) and a low-hardness layer (e.g., Hypodermis).

Referring to Figure 5, the wavelength of waves that can be transmitted may vary depending on the Young's modulus of each layer. In the lower layer where the Young's modulus is low, only waves with relatively long wavelengths can be transmitted, and in the upper layer where the Young's modulus is high, waves with relatively short wavelengths can also be transmitted. In the lower layer where the Young's modulus of the sound transmission medium is low, the wave transmission speed is relatively slow, and conversely, in the higher layer, the wave transmission speed can be relatively fast.

Accordingly, a wave starting from the vibrator position (P0 in FIG. 1) of FIG. 5 passes through two layers with different Young's moduli and reaches the sensor position (P1, P2 in FIG. 1), but since the two waves with different wavelengths (or frequencies) reach the vibration sensor at different speeds, a speed dependence depending on the frequency may occur.

This can be schematically represented as in the graph on the right side of Fig. 5. This graph shows that a part with a higher frequency has a higher speed. As in the image on the left side of Fig. 5, if it is assumed that the skin is composed of two layers, the graph on the right side of Fig. 5 will show two different speeds depending on the frequency, and if the skin is composed of four layers as in reality, the graph on the right side of Fig. 5 will show four different speeds depending on the frequency. Using these results and the above-described relationship between speed and Young's modulus, it is possible to simultaneously measure different Young's moduli of each layer of the skin.

In addition, the location of the frequency at which the speed changes according to the frequency in Fig. 5 is correlated with the depth from the surface of the skin to the boundary between the two layers in the image on the left side of Fig. 5. Therefore, the location of the frequency at which the speed changes can also be used to determine the boundary between the skin layers.

FIG. 6 is a schematic diagram schematically showing a skin hardness measuring device (2000) according to another embodiment of the present invention.

As illustrated in FIG. 6, a skin hardness measuring device (2000) according to another embodiment of the present invention may further include a temperature sensor (400) that comes into contact with the skin (S) at a third point (P3) spaced apart from the vibration applying unit (100) by a third distance (d3) and measures the temperature of the skin (S).

For example, the temperature sensor (400) can measure the temperature of the skin (S) at the point in time when the vibration applying unit (100) described above applies a predetermined vibration to the skin (S) and the sensing unit (200) measures a vibration wave (V) caused by the predetermined vibration, by coming into contact with the skin (S) at the third point (P3).

Accordingly, the calculation unit (300) calculates and stores correction data regarding changes in Young's modulus according to the temperature of the skin (S) in advance, so that when calculating the Young's modulus, the Young's modulus can be corrected based on the temperature of the skin (S) measured by the temperature sensor (400) and the correction data.

In addition, a skin hardness measuring device (2000) according to another embodiment of the present invention may further include a constant temperature module (500) that, instead of the temperature sensor (400) described above, comes into contact with the skin (S) at a third point (P3) spaced apart from the vibration applying unit (100) by a third distance (d3), heats or cools the skin (S) to a predetermined temperature set in advance, and maintains the temperature of the skin (S) at the predetermined temperature.

For example, the constant temperature module (500) can heat or cool the skin (S) to a predetermined temperature set in advance using a Peltier element or a heating device using a heating wire, and when the temperature of the skin (S) reaches the predetermined temperature set in advance, the temperature of the skin (S) can be maintained at a constant temperature set in advance by appropriately turning the Peltier element or the heating device on/off.

In addition, the constant temperature module (500) is exemplified by using the Peltier element or the heating device using a heating wire, but is not necessarily limited thereto, and any type of cooling device or heating device capable of heating or cooling the skin (S) to a predetermined temperature set in advance may be used.

As described above, when the temperature of the skin (S) is adjusted to the predetermined temperature by the constant temperature module (500), the vibration applying unit (100) described above applies a predetermined vibration to the skin (S), and the sensing unit (200) can measure a vibration wave (V) caused by the predetermined vibration, and while the vibration is applied and the vibration wave (V) is measured, the constant temperature module (500) can continuously maintain the temperature of the skin (S) at the predetermined temperature.

In this way, the skin hardness measuring device (2000) according to another embodiment of the present invention may have the effect of inducing the hardness of the skin (S) to be measured more accurately with a constant precision without being affected by temperature by further including an additional device such as a temperature sensor (400) or a temperature control module (500).

Therefore, according to the skin hardness measuring device (1000, 2000) according to various embodiments of the present invention, by using the principle that the speed at which a vibration wave moves along the skin surface is related to the Young's modulus (hardness) of the skin, by vibrating at a certain point on the skin and detecting the vibration wave caused by the vibration at a point spaced apart by a predetermined distance, the Young's modulus that can represent the hardness of the skin can be easily calculated based on the measurement value for the vibration wave.

Therefore, by measuring the hardness of the skin using vibration waves, a skin hardness measuring device (1000, 2000) can be implemented that can be miniaturized for easy portability, can measure the hardness of each layer of the skin simultaneously, and can quantitatively calculate the hardness of the skin as Young's modulus and display it as an objective and accurate numerical value.

Although the present invention has been described with reference to the embodiments shown in the drawings, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined by the technical idea of the appended claims.

Claims (16)

A vibration applying unit that comes into contact with a certain point of the skin and applies a predetermined vibration to the skin; A sensing unit that comes into contact with the skin at first and second points spaced apart from the vibration applying unit by different points, and measures a vibration wave caused by the predetermined vibration applied from the vibration applying unit; and A calculation unit that calculates a Young's modulus that can represent the hardness of the skin based on the measurement value of the vibration wave in the sensing unit; A skin hardness measuring device comprising: In paragraph 1, The above sensing part, A first vibration sensor that comes into contact with the skin at the first point spaced a first distance from the vibration applying unit and measures the vibration wave caused by the predetermined vibration applied from the vibration applying unit; A second vibration sensor that is positioned at a different point from the first vibration sensor and is in contact with the skin at a second point spaced a second distance from the vibration applying unit, and measures the vibration wave caused by the predetermined vibration applied from the vibration applying unit; and A sensor driving unit that drives the above vibration sensors; A skin hardness measuring device comprising: In the second paragraph, The above operation unit, A skin hardness measuring device that calculates a wave velocity (v) at a vibration frequency (f) of the vibration wave by the following [Formula 1] based on the phase difference between the vibration wave measured by the first vibration sensor and the vibration wave measured by the second vibration sensor, and the distances between the point where the vibration applying unit applies the predetermined vibration and the first point and the second point. [Formula 1]

v: wave velocity x ₁ : Distance from the point of vibration application to the first point x ₂ : Distance from the point of vibration application to the second point f: vibration frequency △φ: Phase difference of waves at point 1 and point 2 In the third paragraph, The above operation unit, A skin hardness measuring device that calculates the Young's modulus based on the wave velocity (v) calculated by the above [Formula 1] and the following [Formula 2]. [Formula 2]

v: wave velocity Y: modulus of skin ρ: skin density In paragraph 1, The above vibration applying unit is, An actuator for applying the predetermined vibration to the skin; and An actuator driving unit electrically connected to the above actuator and driving the actuator; A skin hardness measuring device comprising: In paragraph 5, The above actuator driving unit, A skin hardness measuring device that drives the actuator so that the actuator can apply the predetermined vibration having a vibration frequency in a band of 10 kHz or less. In paragraph 5, The above actuator driving unit, A skin hardness measuring device, wherein the vibration frequency is calculated in advance and stored by the following [Formula 3] so that the actuator can apply the predetermined vibration having a vibration frequency corresponding to the natural frequency of the skin. [Formula 3]

f: vibration frequency k _a : spring constant of the skin ρ: skin density In paragraph 7, The spring constant of the skin in the above [Formula 3] is, A skin hardness measuring device, calculated by the following [Formula 4]. [Formula 4] k _a = E/t k _a : spring constant of the skin E: modulus of skin t: thickness of skin In the second paragraph, The first vibration sensor and the second vibration sensor, A skin hardness measuring device comprising a flexible film in which conductive particles are mixed with a silicone material as a vibration transmitting medium of the skin. In Article 9, The above flexible film, A skin hardness measuring device formed with a hardness lower than the hardness of the above skin. In Article 9, The first vibration sensor and the second vibration sensor, A skin hardness measuring device formed in a flexible film form with a thickness of 1 mm or less (greater than 0), and formed to have a constant conductivity after contact with the skin by the conductive particles. In the second paragraph, The above sensor driving unit, A current source connected to each of the first vibration sensor and the second vibration sensor, respectively, and applying a predetermined current; and A voltmeter for measuring the voltage generated from the first vibration sensor and the second vibration sensor; A skin hardness measuring device comprising: In the second paragraph, A skin hardness measuring device, wherein the first separation distance of the first vibration sensor and the second separation distance of the second vibration sensor are formed as different separation distances. In paragraph 1, A temperature sensor that comes into contact with the skin at a third point spaced a third distance from the vibration applying portion and measures the temperature of the skin; A skin hardness measuring device further comprising: In Article 14, The above operation unit, A skin hardness measuring device which calculates and stores correction data regarding changes in the Young's modulus according to the temperature of the skin in advance, and corrects the Young's modulus based on the temperature of the skin measured by the temperature sensor and the correction data when calculating the Young's modulus. In paragraph 1, A constant temperature module that contacts the skin at a third point spaced a third distance from the vibration applying unit, heats or cools the skin to a predetermined temperature set in advance, and maintains the temperature of the skin at the predetermined temperature; A skin hardness measuring device further comprising:

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