KR101809481B1

KR101809481B1 - Apparatus for measuring skin moisture using voltage applying electrode and current detection electrode

Info

Publication number: KR101809481B1
Application number: KR1020160020664A
Authority: KR
Inventors: 한창희; 이득기
Original assignee: 주식회사 지파워
Priority date: 2016-02-22
Filing date: 2016-02-22
Publication date: 2017-12-18
Also published as: KR20170099023A

Abstract

A skin measuring apparatus for measuring skin moisture by using a voltage applying electrode and a current detecting electrode is proposed. The skin measuring device for measuring skin moisture according to the present invention includes an electrode driving module for applying a sine wave voltage to a skin of a user through a voltage applying electrode so that an amount of current from the skin can be outputted through a current detecting electrode, A signal detecting section for detecting at least one of an impedance signal and an admittance signal by detecting a current amount from the impedance signal and the admittance signal and analyzing at least one of an impedance signal and an admittance signal to determine a skin information And further, it is possible to analyze the degree of the user's skin moisture and sweat more accurately without any distortion or error even with a simpler structure.

Description

TECHNICAL FIELD [0001] The present invention relates to a skin measuring device for measuring skin moisture using a voltage applying electrode and a current detecting electrode. [0002]

More particularly, the present invention relates to a skin measurement device, and more particularly, to a skin measurement device that applies a sinusoidal voltage to a skin of a user through a voltage application electrode and detects an amount of current from the skin through a current detection electrode. And more particularly, to a skin measuring apparatus for measuring skin moisture using a voltage applying electrode and a current detecting electrode for analyzing the degree of skin moisture and sweat of a user.

The skin exists in the outermost part of the human body and performs important functions such as prevention of invasion of bacteria and harmful substances from the outside, waterproofing, wintering, maintenance of internal body temperature and the like. The most important factor in maintaining the basic function of this skin is the moisture content of the stratum corneum. The moisture content of the appropriate stratum corneum must be maintained to prevent invasion of harmful substances from the outside and to suppress the amount of water evaporation from the inside, thereby performing basic skin functions. Therefore, it is most important that the foundation of skin care starts from moisturizing management and it is most important to know the degree of skin moisture of the person and manage it.

Conventional methods for measuring skin moisture content include an electrical measurement method, an optical measurement method, and a method using an MRI. Among them, an electric method is widely used. In particular, a three-electrode method comprising an R electrode (Reference Electrode), a C electrode (Current Carrying Electrode), and an M electrode (Measuring Electrode) A method of measuring the susceptance is mainly used.

Korean Patent Laid-Open Publication No. 10-2008-0016339 (published on Feb. 21, 2008) discloses a technique of applying a predetermined voltage to a user's skin by R, C, and M electrodes and detecting a current signal flowing in a user's skin, A method of measuring the skin water content and activity of the sweat duct using a current signal and a predefined phase signal has been proposed.

However, in the methods of measuring the degree of hydration of the skin of the R, C, and M electrode methods including the conventional No. 10-2008-0016339, there is a problem that the C electrode and the R electrode necessarily contact the skin at the same time. If the R electrode is first contacted with the skin in the state where the C electrode is not in contact with the skin, the sinusoidal wave applied to the skin from the C electrode may be distorted so that the skin impedance can not be measured and the result is inevitably distorted. Also, since the R, C, and M electrodes must be in stable contact with each other even during skin impedance measurement, there is a problem that a measurement error occurs due to the movement of each electrode.

On the other hand, the skin hydration degree measuring methods of the R, C, and M electrodes are based on the negative feedback structure in which the skin impedance is connected to the R, C, and M electrodes, And the impedance measurement value is distorted due to such phase and amplitude variations. Specifically, the phase and amplitude changes of the sine wave applied to the skin from the C electrode by the negative feedback structure in which the R, C, and M electrodes are connected to the skin impedance are simulated. As shown in FIG. 1, 1), the phase and the amplitude of the sinusoidal wave applied to the actual skin from the C-electrode are changed (the lower waveform shown in Fig. 1). In particular, it is very difficult to calibrate the impedance measurement value because the impedance of the skin changes in real time according to the skin structure and condition and is directly affected by the degree of change of the sinusoidal wave applied.

As the problem of distortion of the impedance measurement value due to the voltage applied to the skin or the distortion of the sinusoidal wave becomes larger, researches for solving and compensating the problem are proceeding. However, all of the circuit structures are added and become complicated, And the efficiency thereof is deteriorating.

Korean Patent Publication No. 10-2008-0016339 (published on Feb. 21, 2008)

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to overcome the above-mentioned problems by providing a sine wave voltage to a skin of a user through a voltage application electrode and detecting an amount of current from the skin through a current detection electrode, The present invention provides a skin measuring apparatus for measuring skin moisture using a voltage applying electrode and a current detecting electrode so as to more accurately analyze user's skin moisture and sweat incidence without error.

According to an aspect of the present invention, there is provided a skin measuring apparatus for measuring skin moisture using a voltage application electrode and a current detection electrode, the skin measurement apparatus comprising: An electrode drive module for applying a sinusoidal voltage to the user's skin through the electrode, a signal detector for detecting the amount of current from the skin through the current detection electrode and calculating at least one of an impedance signal and an admittance signal, And a skin information determining unit for analyzing at least one of the signals and calculating the degree of skin moisture and sweat of the user.

The skin measuring device for measuring skin moisture using the voltage applying electrode and the current detecting electrode of the present invention as described above applies a sine wave voltage to the user's skin through a voltage applying electrode and a current amount from the skin through the current detecting electrode It is possible to analyze the moisture content of the user's skin and the degree of occurrence of sweat more accurately without any distortion or error even with a simplified structure.

In particular, it is possible to utilize only a simplified structure using a voltage applying electrode for applying a sinusoidal voltage to the skin and a current detecting electrode for detecting the amount of current flowing through the skin, a structure using only two electrodes.

In addition, since the sinusoidal voltage is fed back to the negative input terminal of the OP-AMP which is provided in the electrode driving module and outputs a sinusoidal voltage, distortion due to the skin impedance is prevented, Can be improved.

In addition, the accuracy of detection of the impedance and the admittance signal can be further improved by compensating the degree of phase delay occurring in the signal detecting section for detecting the impedance and the admittance signal by sharing and using the sine wave voltage applied to the skin.

1 is a simulation graph showing the phase and degree of amplitude variation of a sine wave according to the prior art.
Fig. 2 is an equivalent circuit diagram modeling the skin structure electrically.
3 is a graph showing impedance characteristics according to frequency applied to the skin.
FIG. 4 is a configuration diagram illustrating a skin measurement apparatus for measuring skin moisture using a voltage application electrode and a current detection electrode according to an embodiment of the present invention. Referring to FIG.
FIG. 5 is a block diagram specifically illustrating the structure of the electrode driving module and the signal detector of FIG. 4. Referring to FIG.
FIG. 6 is a configuration diagram more specifically showing the configuration including the lock-in amplifier shown in FIG.
7 is a graph showing a current response waveform according to a sinusoidal voltage input.

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

Fig. 2 is an equivalent circuit diagram modeling the skin structure electrically. 3 is a graph showing impedance characteristics according to frequencies applied to the skin.

First, in order to electrically measure the skin moisture, the physiological structure of the skin must first be electrically modeled. Electrical modeling of the skin structure in relation to the parameters of the Cole equation can be represented as in FIG. Here, the conductance Gp and the capacitance Cp are variable with respect to the frequency, and are an element having the principle of skin horny. The impedance Z _∞ of the deep tissue containing the granular layer is much smaller than the impedance of the keratin within the frequency range below 10 kHz and is obtained from the estimated value of the infinite frequency f _∞ in the impedance vector trace.

Referring to FIG. 2, the impedance is an element that interrupts the flow of the alternating current. The skin impedance is frequency dependent and interferes with the electrical flow of the alternating current. In particular, as shown in Equation (1) below, the impedance Z can be a sum of two vectors of a resistance G and a reactance Xc measured at a specific frequency.

The low-frequency current can not pass through the cell due to the inherently capacitive nature of the skin's membrane, and high-frequency currents can penetrate the cell membrane and specify the impedance as the sum of the intracellular fluid and extracellular fluid components. For this reason, the current at low frequencies below 10 kHz flows only to the skin, the skin impedance is determined by the dominant stratum corneum, and the electric current having a higher frequency is transmitted through the skin to the lower body tissues, It will not be reflected.

In the present invention, in order to measure the impedance of the user's skin based on the skin model shown in FIG. 1, an AC voltage of sinusoidal wave is applied to the user's skin to measure a current flowing at that time, And the skin condition such as skin moisture is measured and analyzed from the measured impedance.

FIG. 4 is a configuration diagram illustrating a skin measurement apparatus for measuring skin moisture using a voltage application electrode and a current detection electrode according to an embodiment of the present invention. Referring to FIG.

The skin measurement apparatus shown in FIG. 4 includes an electrode drive module 100 for applying a sine wave voltage to a user's skin through a voltage application electrode 101, a signal detection unit 100 for calculating at least one of a skin impedance signal and a skin admittance signal, (200), and a skin information determination unit (300) for calculating the degree of skin moisture and sweat of a user.

Specifically, the electrode driving module 100 applies a sinusoidal voltage to the user's skin through the voltage application electrode 101 so that the amount of current from the skin can be outputted through the current detection electrode 102. The electrode driving module 100 generates a sinusoidal current and amplifies it by operation to change the voltage to the same phase or inverted phase as that of the sinusoidal wave, and then applies the sinusoidal voltage to the skin of the user through the voltage application electrode 101. Accordingly, when the sinusoidal voltage applied to the skin of the user through the voltage application electrode 101 reacts with the impedance of the horny layer of the user's skin, the current signal can be converted and maintained to a predetermined current signal.

The signal detecting unit 200 detects the amount of current from the skin through the current detecting electrode 102 and calculates at least one of a skin impedance signal and a skin admittance signal. Specifically, the signal detecting unit 200 detects the amount and phase of the current detected through the current detecting electrode 102, converts the detected amount and phase into a voltage signal corresponding to the amount of current and phase, And at least one of an impedance signal and an admittance signal is detected and output. In addition, the signal detecting unit 200 detects at least one of an impedance signal and an admittance signal by using the voltage signal corresponding to the amount of current and the phase detected through the current detecting electrode 102 and the sinusoidal voltage applied to the skin It is possible to output it.

The skin information determination unit 300 analyzes at least one of the impedance signal and the admittance signal from the signal detection unit 200 to calculate the degree of skin moisture and sweat of the user.

FIG. 5 is a block diagram specifically illustrating the structure of the electrode driving module and the signal detector of FIG. 4. Referring to FIG.

The electrode driving module 100 shown in FIG. 5 includes a sinusoidal wave generating unit 110 generating a sinusoidal current using a reference voltage to generate a voltage having the same phase or inverted phase as the sinusoidal wave, And an operational amplifier 120 for operationally amplifying the voltage of the phase and applying a sinusoidal voltage to the user's skin through the voltage application electrode 101.

Here, the operational amplifier 120 receives a voltage of the same phase or inverted phase as that of the sinusoidal wave at the positive signal input terminal (+), amplifies the operational amplified signal, and applies the sinusoidal voltage to the voltage application electrode 101. The sinusoidal voltage output to the output terminal is fed back to the negative signal input terminal (-). With this configuration, the operational amplifier 120 can prevent distortion due to the skin impedance, thereby improving the accuracy of skin impedance measurement.

The signal detection unit 200 includes a reference voltage generation unit 220, a current-voltage converter 230, a phase detection compensation unit 210, and a lock-in amplification unit 240.

More specifically, the reference voltage generator 220 generates a reference voltage at a preset voltage level and supplies the generated reference voltage to the sinusoidal wave generator 110 and the current-voltage converter 230 of the electrode drive module 100, respectively Supply. The sinusoidal wave generating unit 110 generates a sinusoidal wave using the reference voltage of a predetermined level as a reference and generates a voltage having the same phase or inverse phase as the sinusoidal wave.

The current-voltage converter 230 receives the reference voltage from the reference voltage generator 220 and detects the amount of current flowing from the current detecting electrode 102 to the stratum corneum of the skin. Then, it is converted into a voltage signal corresponding to the amount and phase of the detected skin. Here, the amount of current flowing to the stratum corneum of the skin and the phase are determined by the impedance component of the skin contacted. The current-voltage converter 230 supplies the converted voltage signal to the lock-in amplifier 240.

The phase detection compensating unit 210 is connected to the sinusoidal wave generating unit 110 to detect the phase of the generated sinusoidal wave and supplies the detected phase to the current-to-voltage converter 230 and the signal processing unit of the lock- And supplies the compensated sinusoidal phase to the lock-in amplifying unit 240. The lock-in amplifying unit 240 compensates for the phase delay.

The lock-in amplifier 240 detects and outputs at least one of the impedance and the admittance from the voltage signal output from the current-voltage converter 230 based on the compensated sinusoidal phase supplied from the phase detection compensator 210 . Specifically, the lock-in amplifier 240 detects only the phase synchronized with the compensated sinusoidal phase to detect the resistance component of the skin impedance signal or the conductance component of the skin admittance signal, And the susceptance component of the admittance, respectively.

FIG. 7 is a configuration diagram more specifically showing a configuration including the lock-in amplifier shown in FIG.

The lock-in amplifier 240 shown in FIG. 7 is supplied with the voltage signal output from the DC-to-voltage converter 230 and the compensated sinusoidal phase through the phase detection compensator 210, A lock-in filter unit (not shown) for selectively filtering only the components synchronized with the compensated sinusoidal phase supplied from the phase detector, or selectively filtering the components that have been turned off by 90 degrees, and outputting the filtered voltage components to the DC voltage waveform And an AD conversion section 242 for respectively detecting an impedance signal or an admittance signal for detecting the voltage value of the output filtered DC voltage signal.

In detail, the lock-in filter unit 241 selectively filters the voltage signal output from the DC-to-voltage converter 230 through only the voltage component synchronized with the compensated sinusoidal phase through the phase detection compensating unit 210, and selectively filters off the voltage components. Then, the filtered DC voltage waveform is supplied to the AD converter 243. Thus, the AD converter 243 measures and outputs the voltage value of the DC voltage waveform filtered by the lock-in filter unit.

The method of detecting the impedance signal and the admittance signal of the lock-in amplifier 240 configured as described above will be described in more detail as follows.

The sinusoidal voltage applied to the skin of the user is proportional to the voltage magnitude (A) of the following equation (2), and is a sine function obtained by multiplying the angular frequency (?) By the time (t).

Thus, the current response from the skin can be shown as Equation (3) below.

Where B is another size and Ø is the shifted phase angle.

Therefore, the impedance function (Z) to which the Ohm's law is applied can be detected as shown in the following equation (4).

7 is a graph showing a current response waveform according to a sinusoidal voltage input.

As shown in FIG. 7, it can be confirmed that the current response waveform is detected in the same manner as expressing the response impedance inputted by dividing the sine function into a real part (') and an imaginary part (' ').

In order to detect the magnitude (| Z |) of the response impedance through the impedance function Z by dividing the sine function into a real part (') and an imaginary part (' ') have.

The magnitude of the response impedance (| Z |) is given by Equation (9).

The shifted phase angle? Shown in FIG. 7 can be detected using Equation (10) below.

Here, the real part Z 'of the impedance function is a response according to an in-phase, and the imaginary part Z' 'is a phase corresponding to an out-of-phase.

From an electrical point of view, the impedance function can be expressed as a real part of a resistance component and an imaginary part of a reactance component. Therefore, the lock-in amplifier 240 detects only the phase synchronized with the compensated DC voltage signal to detect the DC resistance component of the skin impedance signal, and detects only the phase that has been turned off by 90 degrees to detect the reactance component of the skin impedance signal can do. Since the electrical model of the skin proposed in the technique of the present invention is composed of only resistors and capacitors, the measured reactance components are the same as the capacitances.

The skin measurement device for measuring the skin moisture content according to the present invention can be used for various applications such as a mobile communication terminal, a PDA (Personal Digital Assistant), a portable game machine, an MP3 player, a Portable Multimedia Player (PMP), a Digital Multimedia Broadcasting Or a terminal. That is, the skin measurement device for measuring the skin moisture level can be implemented as a part of a portable terminal. In addition, the skin measurement device for measuring the skin moisture level may not be implemented as a part of the portable terminal, but may be realized as a single article having an independent configuration.

As described above, the skin measuring device for measuring skin moisture using the voltage applying electrode and the current detecting electrode of the present invention applies a sine wave voltage to the user's skin through the voltage applying electrode, It is possible to analyze the degree of the user's skin moisture and sweat more accurately without any distortion or error even with a simplified structure. In particular, it is possible to utilize only a simplified structure using a voltage applying electrode for applying a sinusoidal voltage to the skin and a current detecting electrode for detecting the amount of current flowing through the skin, a structure using only two electrodes.

In addition, since the sinusoidal voltage is fed back to the negative input terminal of the operational amplifier which is provided in the electrode driving module and outputs a sinusoidal voltage, distortion due to the skin impedance is prevented, Can be improved. In addition, the accuracy of detection of the impedance or the admittance signal can be further improved by compensating the degree of phase delay occurring in the signal detecting section for detecting the impedance or the admittance signal by sharing and using the sinusoidal voltage applied to the skin.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the following claims And changes may be made without departing from the spirit and scope of the invention.

Claims

An electrode driving module for applying a sinusoidal voltage to the skin of the user through the voltage application electrode so that the amount of current from the skin can be output through the current detection electrode;
A signal detecting unit for detecting an amount of current from the skin through the current detecting electrode and calculating at least one of an impedance signal and an admittance signal; And
A skin information determination unit for analyzing at least one of the impedance signal and the admittance signal to calculate the degree of skin moisture and sweat of the user;
, &Lt; / RTI &
The electrode driving module
A sinusoidal wave generating unit for generating a sinusoidal current using the reference voltage to generate a voltage having the same phase or inverted phase as the sinusoidal wave; And
An operational amplifier for operating and amplifying a voltage having the same phase or an inverted phase as the sinusoidal wave and applying the sinusoidal voltage to the user's skin through the voltage application electrode;
Lt; / RTI >
The signal detector
A reference voltage generator for generating and outputting a reference voltage at a preset voltage level;
A current-voltage converter for detecting an amount of current from the skin through the current detection electrode and converting the amount of current into a voltage signal corresponding to the detected current amount and phase;
A lock-in amplifier for detecting and outputting at least one of the impedance signal and the admittance signal from the voltage signal output from the current-voltage converter using the phase of the sinusoidal voltage applied to the skin; And
The phase of the sinusoidal wave applied to the skin is detected, and the detected phase is compensated for the phase delay occurring in the signal processing process of the current-voltage converter and the lock-in amplifier, and the compensated sinusoidal phase is inputted to the lock- A phase detection compensating unit for supplying the phase detection signal;
, &Lt; / RTI &
The operational amplifier
And a positive signal input terminal for receiving a voltage having the same phase or inverted phase as that of the sinusoidal wave to amplify and amplify the voltage to apply the sinusoidal voltage to the voltage application electrode,
And the sinusoidal voltage output to the output terminal is fed back to the negative signal input terminal. The apparatus for measuring skin moisture using the voltage application electrode and the current detection electrode.

The method according to claim 1,
The signal detector
Detecting a current amount and a phase through the current detection electrode, converting the current amount and phase into a voltage signal corresponding to the current amount and phase,
Wherein at least one of the impedance signal and the admittance signal is detected using the converted voltage signal and the waveform of a sinusoidal wave applied to the skin, wherein the skin moisture is measured using the voltage application electrode and the current detection electrode Skin measuring device.

The method according to claim 1,
The lock-in amplifying unit
A compensated sinusoidal phase is supplied through the phase detection compensating unit 210 and a compensated sinusoidal phase supplied from the phase detector in the voltage signal output from the current- A lock-in filter unit for selectively filtering only the components synchronized with the reference voltage, or selectively filtering the components that have been turned off by 90 degrees, and outputting the filtered voltage components as DC voltage waveforms; And
An AD converter for detecting a voltage value of the output filtered DC voltage signal and detecting the impedance signal or the admittance signal, respectively;
And the current detection electrode is used to measure skin moisture.

The method according to claim 1,
The sinusoidal voltage applied to the user's skin through the electrode driving module is a sine function which is proportional to the voltage magnitude A of Equation 2 and is multiplied by the time t,
&Quot; (2) "

&Quot; (3) "

The current response from the skin is shown in Equation (3) below,
Here, B is another size, and? Is a shifted phase angle. The skin measuring device measures skin moisture using a voltage application electrode and a current detection electrode.

5. The method of claim 4,
The signal detector
The impedance function (Z) to which the Ohm's law is applied is detected by the following equation (4)
&Quot; (4) "

We divide the sine function into real parts (V ', I', Z ') and imaginary parts (V ", I", Z ") and detect the magnitude (| Z |) of the response impedance through the impedance function For example, it is detected using the following expressions (5) to (9)
&Quot; (5) "

&Quot; (6) "

&Quot; (7) "

&Quot; (9) "

The phase angle? Is detected using Equation (10) below,
&Quot; (10) "

Wherein the real part Z 'of the impedance function is a response according to an in-phase and the imaginary part Z' is a phase according to an out-of-phase. A skin measuring device for measuring skin moisture using an electrode and a current detecting electrode.

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