阅读说明：本技术 分析生物信号的信号处理设备和使用该设备的生物信号分析装置 (Signal processing device for analyzing biological signal and biological signal analyzing apparatus using the same ) 是由 韩盛皓 卢根植 洪熙善 于 2018-03-06 设计创作，主要内容包括：根据本发明的一个方面的处理生物信号的信号处理设备包括：锁定放大器芯片,其被配置为输出经频率调制的调制信号并且使一个或多个光源能够响应于所述调制信号而被驱动；和多路复用器,其被配置为接收并多路复用从所述光源输出并且然后由多个光测量单元测量的光传感信号；并且所述锁定放大器芯片顺序地解调通过所述多路复用器发送的多个所述光传感信号。(A signal processing apparatus for processing a bio-signal according to an aspect of the present invention includes: a lock-in amplifier chip configured to output a frequency modulated modulation signal and enable one or more light sources to be driven in response to the modulation signal; and a multiplexer configured to receive and multiplex the light sensing signals output from the light sources and then measured by the plurality of light measuring units; and the lock-in amplifier chip sequentially demodulates the plurality of optical sensing signals transmitted through the multiplexer.)

1. A signal processing apparatus for processing a bio-signal, comprising:

a lock-in amplifier chip configured to output a frequency modulated modulation signal and enable one or more light sources to be driven in response to the modulation signal; and

a multiplexer configured to receive and multiplex the light sensing signals output from the light sources and then measured by the plurality of light measuring units,

wherein the lock-in amplifier chip sequentially demodulates the plurality of the optical sensing signals transmitted through the multiplexer.

2. The signal processing apparatus of claim 1, further comprising:

a differential amplifier disposed between the output of the multiplexer and the input of the lock-in amplifier chip and configured to receive the output of the multiplexer and send the output to the lock-in amplifier chip.

3. The signal processing apparatus of claim 1, further comprising:

an analog-to-digital converter configured to convert an output of the lock-in amplifier chip to a digital signal.

4. The signal processing apparatus of claim 1, further comprising:

a light source driver configured to be driven based on the modulation signal,

wherein the light source driver is configured to transmit a driving signal modulated based on the modulation signal to one or more light sources, and

the optical sensing signal contains frequency components of the modulation signal.

5. The signal processing apparatus of claim 4, further comprising:

a plurality of light measuring units configured to output the light sensing signals, respectively,

wherein the light measuring unit is configured to detect output light of the light source driven by the light source driver.

6. The signal processing apparatus of claim 5, further comprising:

a plurality of transimpedance amplifiers configured to convert the optical sensing signals of the optical measurement unit into voltage signals and send the voltage signals to the multiplexer.

7. The signal processing device according to claim 1,

wherein the lock-in amplifier chip classifies the modulation signals according to a predetermined order and sequentially outputs them to the respective light sources, and

the multiplexer transmits the light sensing signals measured by the respective light measuring units to the lock-in amplifier chip according to a predetermined sequence.

8. A body composition analysis device for analyzing biological signals, comprising:

a plurality of light sources;

a plurality of light measuring units;

a signal processing unit configured to transmit a frequency-modulated modulation signal to the light source through a lock-in amplifier chip, receive a light sensing signal measured by the light measuring unit, and remove noise from the light sensing signal through the lock-in amplifier chip; and

a body composition analysis unit configured to analyze a body composition of the subject based on the signal output from the signal processing unit.

9. The body composition analyzing apparatus according to claim 8,

wherein the signal processing unit includes:

the lock-in amplifier chip configured to output a frequency modulated signal; and

a multiplexer configured to receive and multiplex the light sensing signals measured by the light measuring unit, and

the lock-in amplifier chip sequentially demodulates the plurality of optical sensing signals transmitted through the multiplexer.

10. The body composition analyzing apparatus according to claim 8, further comprising:

a differential amplifier disposed between the output of the multiplexer and the input of the lock-in amplifier chip and configured to receive the output of the multiplexer and send the output to the lock-in amplifier chip.

11. The body composition analyzing apparatus according to claim 8, further comprising:

an analog-to-digital converter configured to convert an output of the lock-in amplifier chip into a digital signal and transmit the digital signal to the body composition analysis unit.

12. The body composition analyzing apparatus according to claim 8, further comprising:

a light source driver configured to be driven based on the modulation signal,

wherein the optical sensing signal comprises a frequency component of the modulation signal.

13. The body composition analyzing apparatus according to claim 8, further comprising:

a plurality of transimpedance amplifiers configured to convert the optical sensing signals of the optical measurement unit into voltage signals and send the voltage signals to the multiplexer.

14. The body composition analyzing apparatus according to claim 8,

wherein the body composition analysis unit is configured to calculate a reflectance at each discrete wavelength based on the signals sent from the signal processing unit and to calculate a concentration of a chromophore present in the subject based on the reflectance at each discrete wavelength.

15. The body composition analyzing apparatus according to claim 8,

wherein the body composition analysis unit is configured to determine the number and kind of light sources and light measurement units to be driven from the plurality of light sources and the plurality of light measurement units based on at least one of the number, content and kind of chromophores present in the subject.

16. The body composition analyzing apparatus according to claim 8,

wherein the lock-in amplifier chip classifies and sequentially outputs the modulation signals to the corresponding light sources according to a predetermined order, and

the multiplexer transmits the light sensing signals measured by the respective light measuring units to the lock-in amplifier chip according to a predetermined sequence.

17. The body composition analyzing apparatus according to claim 8,

wherein each of the light sources and each of the light measuring units form a pair facing each other.

18. A method of analyzing body composition by analyzing bio-signals, comprising:

outputting an optical signal by a plurality of light sources based on a modulation signal whose frequency is modulated by a lock-in amplifier chip;

measuring the light signals output from the plurality of light sources and reflected from the subject, respectively, by a plurality of light measuring units;

multiplexing the plurality of optical sensing signals measured by the respective plurality of optical measuring units through a multiplexer and then sequentially outputting the plurality of optical sensing signals;

receiving, demodulating and outputting the plurality of optical sensing signals sequentially output through the lock-in amplifier chip; and

analyzing a body composition of the subject based on the signal output from the lock-in amplifier chip.

19. The method of analyzing body composition of claim 15, further comprising:

identifying each light sensing signal synchronized with a timing to output each light sensing signal from the multiplexer.

20. The method of analyzing body composition of claim 15,

wherein the analysis of the body composition includes calculating a reflectance at each discrete wavelength based on the signal output from the lock-in amplifier chip, and calculating a concentration of a chromophore present in the subject based on the reflectance at each discrete wavelength.

Technical Field

The present disclosure relates to a signal processing device that analyzes a biological signal and a biological signal analysis apparatus using the same.

Background

Recently, various techniques for analyzing biometric data of the body using methods for measuring optical properties of turbid media are being developed. These technologies have attracted much attention because they are non-invasive and can provide biometric data, and much attention has been focused on developing research into entry level devices according to the needs of consumers.

These techniques usually calculate the concentration of chromophores in the turbid medium by measuring the absorption coefficient and the scattering coefficient of the turbid medium in the near infrared region. Three methods are known for measuring the absorption coefficient and the scattering coefficient of turbid media. In particular, these methods include a Steady State (SS) method of irradiating light of a predetermined intensity into the turbid medium and calculating the chromophore concentration according to a multi-distance measurement method, a Frequency Domain (FD) method of measuring the amplitude and phase of changes of a modulated light source, and a Time Domain (TD) method of measuring changes over time of a pulsed light source.

The SS method does not require light modulation nor pulse generation and therefore does not require detectors for resolving light reflected from the turbid medium by frequency or time domain. Therefore, the SS method is cheaper than other methods (i.e., FD method or TD method). However, the SS method uses a multiple distance measurement method to separate the absorption coefficient and the scattering coefficient. Therefore, in biological tissues with high heterogeneity, the SS method is more likely to generate distortion during analysis than other methods.

The TD method and the FD method do not use the multi-distance measurement method, and thus are more suitable for biological tissues having heterogeneity than the SS method. However, the TD method and the FD method require a detector configured to detect a pulsed or frequency modulated light source and its characteristics. Therefore, the TD method and the FD method have disadvantages in terms of implementation and cost.

The present disclosure employs a Steady State (SS) approach but uses a lock-in amplifier structure to minimize the effects of ambient light and achieve high signal-to-noise ratio (SNR). Lock-in amplifiers refer to amplifiers configured to recover a signal in noise and have been used to remove much more noise than the signal to be detected. The lock-in amplifier may multiply a target signal having a specific frequency and a reference signal having the same frequency as the target signal to extract the amplitude of the target signal. For example, if noise is included in a wide band including the frequency (fa) of a signal to be detected, the signal to be detected and a reference signal having the same frequency as the signal to be detected are multiplied to obtain a harmonic (2fa) belonging to the sum of the two frequencies and a Direct Current (DC) belonging to the difference between the frequencies. The intensity of the Direct Current (DC) belonging to the difference between said frequencies is proportional to the amplitude of the signal to be detected. If a low-pass filter is applied to the signal obtained in this way, the sum of the frequencies is removed, and only the difference between the frequencies is obtained. In this way, if a signal only in a Direct Current (DC) band is detected using a lock-in amplifier, the level of the signal to be detected does not change, but the amplitude of noise is reduced, and thus, noise generated outside the detection apparatus can be effectively removed.

However, the present invention proposes a new method to ensure that the bio-signal analysis apparatus including the plurality of light sources and the plurality of photodetectors described above can effectively eliminate noise.

Disclosure of Invention

Problems to be solved by the invention

The present invention is conceived to solve the above-described problems of the conventional art and provide a signal processing device capable of effectively removing noise from a plurality of optical signals measured by a plurality of optical measuring units and a biological signal analyzing apparatus using the signal processing device.

However, the problem to be solved by the present invention is not limited to the above problem. There may be other problems that need to be addressed by the present disclosure.

Means for solving the problems

As a technical means for solving the above technical problem, a signal processing apparatus for processing a bio-signal according to a first aspect of the present invention includes: a lock-in amplifier chip configured to output a frequency modulated modulation signal and enable one or more light sources to be driven in response to the modulation signal; and a multiplexer configured to receive and multiplex the light sensing signals output from the light sources and then measured by the plurality of light measuring units. Here, the lock-in amplifier chip sequentially demodulates the plurality of optical sensing signals transmitted through the multiplexer. Here, the lock-in amplifier chip sequentially demodulates the plurality of optical sensing signals transmitted through the multiplexer.

Further, a body composition analysis device that analyzes biological signals according to a second aspect of the present disclosure includes: a plurality of light sources; a plurality of light measuring units; a signal processing unit configured to transmit a frequency-modulated modulation signal to the light source through a lock-in amplifier chip, receive a light sensing signal measured by the light measuring unit, and remove noise from the light sensing signal through the lock-in amplifier chip; and a body composition analyzing unit configured to analyze a body composition of the subject based on the signal output from the signal processing unit.

Further, a method of analyzing a body composition by analyzing a biosignal according to a third aspect of the present disclosure includes: outputting an optical signal by a plurality of light sources based on a modulation signal whose frequency is modulated by a lock-in amplifier chip; measuring the light signals output from the plurality of light sources and reflected from the subject, respectively, by a plurality of light measuring units; multiplexing the plurality of optical sensing signals measured by the respective plurality of optical measuring units through a multiplexer and then sequentially outputting the plurality of optical sensing signals; receiving, demodulating and outputting the plurality of optical sensing signals sequentially output through the lock-in amplifier chip; and analyzing a body composition of the subject based on the signal output from the lock-in amplifier chip.

Effects of the invention

According to the above technical means for solving the technical problem of the present disclosure, when removing noise in optical signals sensed by a plurality of optical measurement units, noise in the plurality of optical signals can be cancelled using only a single lock-in amplifier chip. Therefore, the present invention can not only reduce the size of the biosignal analysis device, but also reduce the cost of the parts of the biosignal analysis device.

Drawings

Fig. 1 is a schematic diagram illustrating a configuration of a lock-in amplifier-based multi-wavelength bio-signal analysis apparatus according to an embodiment of the present disclosure.

Fig. 2 is a diagram showing a detailed configuration of a signal processing unit according to an embodiment of the present disclosure.

Fig. 3 shows optical characteristics of input light incident from a light source into a subject and output light detected by a light measuring unit.

Fig. 4 is a flowchart for explaining a method of analyzing body composition according to an embodiment of the present disclosure.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that the present invention can be easily implemented by those skilled in the art. However, it should be noted that the present disclosure is not limited to these embodiments, but may be implemented in various other ways. In the drawings, parts irrelevant to the description are omitted for the sake of simplifying the explanation, and the same reference numerals denote the same parts throughout the document.

Throughout this document, the term "connected to" or "coupled to" used to indicate connection or coupling of one element with another element includes a case where an element is directly connected or coupled to another element and a case where an element is electrically connected or coupled to another element via still another element. Furthermore, the terms "comprises or comprising" and/or "comprises or including" as used in this document, means that one or more other components, steps, operations, and/or the presence or addition of elements other than the described components, steps, operations, and/or elements is not excluded unless the context indicates otherwise.

Further, throughout the document, the term "object" refers to a target measured by the multi-wavelength biosignal analysis device of the present disclosure, and may include a human or an animal or a part thereof. Furthermore, the subject may comprise various organs, such as skin surfaces, heart, brain or blood vessels or various phantoms (phantoms).

Fig. 1 is a schematic diagram illustrating a configuration of a lock-in amplifier-based multi-wavelength biosignal analysis device (hereinafter, referred to as a "biosignal analysis device") according to an embodiment of the present disclosure.

As shown in fig. 1, the bio-signal analysis device 10 according to the embodiment of the present disclosure includes a plurality of light sources 110, a plurality of light measuring units 120, a signal processing unit 130, and a body composition analysis unit 140.

The plurality of light sources 110 are driven based on a modulation signal whose frequency is modulated by the lock-in amplifier and illuminates light containing a plurality of discrete wavelength components. The light source may be implemented as a Laser Diode (LD) or a Light Emitting Diode (LED) capable of irradiating frequency-modulated light. Meanwhile, the output light output from each light source 110 may include a plurality of discrete wavelength components, and the discrete wavelengths may refer to discontinuous wavelengths in the near infrared region. For example, four or more light sources 110 may be used, and each LD may emit light having a wavelength ranging from 650nm to 1,100nm (nanometers).

In addition, the discrete wavelengths are determined based on chromophores present in subject 20. In particular, the discrete wavelengths may be determined based on the known absorbance of each chromophore. Chromophore refers to an atom or group of atoms that absorbs light. Generally, four chromophores are known, namely oxyhemoglobin (O2Hb), deoxyhemoglobin (HHb), water (H2O), and lipids, which act as chromophores present in the body and affect the absorption spectrum in the near-infrared ray region. These four chromophores are present in various ratios depending on the tissue site. For example, water (H2O), lipids, oxyhemoglobin (O2Hb), and deoxyhemoglobin (HHb) are mainly present in tissues of the arm, leg, etc., while H2O, oxyhemoglobin, and deoxyhemoglobin (excluding lipids) are mainly present in the brain.

Typically, chromophores have their own absorption spectrum in the near infrared region. Water shows a peak around the 980nm wavelength region, while lipid shows a peak around the 930nm wavelength region. Further, oxyhemoglobin and deoxyhemoglobin intersect each other at an isosbestic point near the 800nm wavelength region. According to an embodiment, the bio-signal analysis device 10 comprises 4 light sources 110 and may irradiate the frequency modulated light at four discrete wavelengths determined based on the absorbance of water, lipids, oxygenated hemoglobin and deoxygenated hemoglobin. In particular, the four discrete wavelengths include a first discrete wavelength adjacent to a peak region of water and a second discrete wavelength adjacent to a peak region of lipids, and may include a third discrete wavelength before an isosbestic point and a fourth discrete wavelength in a region adjacent to the isosbestic point of the absorption spectra of known oxyhemoglobin and deoxyhemoglobin. Here, the third discrete wavelength may be selected from a region in which oxyhemoglobin and deoxyhemoglobin have a relatively large difference in absorption, in consideration of the absorbance of deoxyhemoglobin. For example, the first discrete wavelength may be about 975nm and the second discrete wavelength may be about 915 nm. Further, the third and fourth discrete wavelengths may be about 688nm and about 808nm, respectively, but may not be limited thereto.

According to another embodiment, the biosignal analysis device 10 can also be implemented to include five, six, seven, or eight light sources configured to illuminate light of a wavelength different from the first to fourth discrete wavelengths. Thus, the fifth to eighth discrete wavelengths to be added may be determined based on unique properties (e.g., peaks) shown in the absorption spectra of chromophores other than the above-described chromophores (i.e., water, lipids, oxygenated/deoxygenated hemoglobin). For example, the fifth to eighth discrete wavelengths to be added may be determined based on a peak in an absorption spectrum of collagen, melanin, methemoglobin (MetHb), or CO hemoglobin (COHb) in addition to the above chromophores. However, the present disclosure may not be limited thereto, and the wavelength to be added may be selected in consideration of various conditions. For example, the wavelength to be added may be selected based on the center of gravity of the absorption spectrum of the chromophore.

In this way, the biosignal analysis device 10 includes four or more light sources 110 determined based on unique properties shown in the absorption spectrum of chromophores present in the body, and thus, the body composition analysis unit 140 can more accurately calculate the concentration of each chromophore.

The light measuring unit 120 is configured to detect output light reflected and introduced from the subject 20. The light measuring unit 120 may convert the detected output light into an electrical signal and provide the electrical signal to the signal processing unit 130.

The light measuring unit 120 may be implemented as an Avalanche Photodiode (APD), but may not be limited thereto. The light measuring unit 120 may be implemented in various forms such as a photodiode, a phototransistor, a photomultiplier tube (PMT), a photocell, and the like. Further, the light measuring unit 120 may be implemented to include a new type of light sensor developed as the technology advances.

Further, the light measuring unit 120 may be disposed at a predetermined distance from the light source 110 to measure light emitted and introduced from the subject.

The signal processing unit 130 receives the light sensing signals from the plurality of light measuring units 120 and measures the signals using lock-in amplifiers, and then transmits the signals to the body composition analyzing unit 140. The detailed configuration of the signal processing unit 130 will be described with reference to the drawings.

Meanwhile, there may be a plurality of light sources 110 and a plurality of light measuring units 120, and each light source 110 and each light measuring unit 120 may form a pair facing each other. For example, the arrangement of the first light source and the second light source may be predetermined to sense the output light from the first light measuring unit and the output light from the second light measuring unit, respectively. Then, the light sensing signals sensed by the respective light measuring units may be sequentially transmitted to the lock-in amplifier chip 131 to identify from which light source each light sensing signal is output.

Fig. 2 is a diagram showing a detailed configuration of a signal processing unit according to an embodiment of the present disclosure.

The signal processing unit 130 includes a lock-in amplifier chip 131, a differential amplifier 132, a multiplexer 133, a transimpedance amplifier 134, and an analog-to-digital converter 135.

The lock-in amplifier chip 131 is configured to output a frequency-modulated modulation signal. Further, the lock-in amplifier chip 131 multiplies the modulation signal by a reference signal having the same frequency as the modulation signal according to the synchronous demodulation method and maintains a Direct Current (DC) frequency using only a low pass filter, and thus can effectively maintain a desired signal and remove a noise signal.

A single processor equipped with components such as a signal generator, a filter, a mixer (or a phase detector), and the like, which is configured to perform the function of a lock-in amplifier (Analog device sa da2200) has recently been developed and commercialized, and the lock-in amplifier chip 131 of the present disclosure refers to a part of the integrated processor. Further, with regard to detailed internal configuration and operation of the lock-in amplifier chip 131, a data table of a distributed product is referred to, and detailed description thereof will be omitted.

The light source driver 112 is configured to receive the frequency-modulated modulation signal supplied from the lock-in amplifier chip 131 and drive the light source 110 based on the modulation signal. Since the light source 110 is driven based on the modulation signal, the optical signal output from the light source 110 also contains a modulation frequency component.

There may be a plurality of the light measuring units 120, and the light signal measured by each light measuring unit 120 is converted from a current signal to a voltage signal through the transimpedance amplifier 134 and then transmitted to the multiplexer 133. For this, transimpedance amplifiers 134 are connected to the plurality of optical impedance measurement units 120, respectively, and signals output from the plurality of transimpedance amplifiers 134 are multiplexed by the multiplexer 133 and then sent to the lock-in amplifier chip 131. Here, since the transimpedance amplifiers 134 are respectively connected to the light measuring units 120, an optimum gain can be set for the output power of each optical signal.

The multiplexer 133 is configured to receive the optical sensing signals measured by the plurality of optical measuring units 120 through the respective transimpedance amplifiers 134 and multiplex the optical sensing signals. Specifically, the multiplexer 133 sequentially transmits the plurality of light sensing signals to the lock-in amplifier chip 131, thereby making it possible to measure a signal obtained by removing as much noise signals as possible from the light sensing signals measured from the plurality of light measuring units 120 using only a single lock-in amplifier chip 131.

Further, the multiplexer 133 is configured to sequentially sort the signals received from the respective transimpedance amplifiers 134 and then transmit the signals to the lock-in amplifier chip 131. During this process, some of the light sensing signal may be lost. That is, when the multiplexer 133 transmits the optical sensing signal measured by a specific light measuring unit to the lock-in amplifier chip 131, the optical sensing signal measured by another light measuring unit may not be transmitted to the lock-in amplifier chip 131 but may be discarded.

Meanwhile, the multiplexer 133 operates as a multiplexer to output any one of the photo-sensing signals in response to the selection signal, synchronize the photo-sensing signal selected by the multiplexer 133 with the synchronous demodulation timing of the lock-in amplifier chip 131, and input the photo-sensing signal output from the multiplexer 133 into the lock-in amplifier chip 131 to remove noise.

The differential amplifier 132 is configured to receive the output of the multiplexer 133 and differentially amplify the output, and then send it to the lock-in amplifier chip 131. Therefore, the effect of removing noise from the light sensing signal can be further improved. The single output unit configured other than the differential amplifier 132 may be selected by a designer.

The analog-to-digital converter 135 is configured to convert the output signal generated by the lock-in amplifier chip 131 into a digital output signal. Further, the analog-to-digital converter 135 is configured to send the converted signal to the body composition analyzing unit 140.

A method of identifying the optical signals measured by the respective optical measuring units 120 will be described.

The lock-in amplifier chips 131 are configured to supply modulation signals to the respective light sources 110 at the same frequency or different frequencies, and perform synchronous demodulation of multiplying each modulation signal by a reference signal having the same or different frequency to remove noise of the optical sensing signal output from the corresponding measurement unit 120. For example, the lock-in amplifier chip 131 performs synchronous demodulation on the modulation signal transmitted from the first optical measurement unit based on the first reference signal, and performs synchronous demodulation on the modulation signal transmitted from the second optical measurement unit based on the second reference signal.

For this, the lock-in amplifier chip 131 may perform synchronous demodulation while maintaining the reference frequency or changing the reference frequency according to the order to output each of the optical sensing signals in a state where the multiplexer 133 previously sets the order and time to output each of the optical sensing signals.

For example, if modulation signals based on first to fourth frequency modulations are provided to the first to fourth light sources, light sensing signals sensed by the first to fourth light measuring units, respectively, are transmitted to the multiplexer 133. In this case, the multiplexer 133 sequentially outputs the photo-sensing signals from the first light measuring unit to the second light measuring unit, to the third light measuring unit, and then to the fourth light measuring unit, and sequentially performs synchronous demodulation on the respective photo-sensing signals by using the same frequency as the lock-in amplifier chip 131 or different frequencies (i.e., the first frequency, the second frequency, the third frequency, and the fourth frequency) according to the above-described order.

Further, the body composition analyzing unit 140 is configured to identify the output signals of the respective light measuring units synchronized with the light sensing signals of the respective light measuring units output through the ADC 135 after the synchronous demodulation in the lock-in amplifier chip. Body composition analysis is then performed based on the output signal.

The body composition analysis unit 140 is configured to control the overall operation of the biosignal analysis device 10. Further, the body composition analysis unit 140 is configured to perform various body composition analyses based on the output signals of the respective light measurement units 120 received through the signal processing unit 130.

To this end, the body composition analyzing unit 140 executes a bio-signal analyzing program stored in a memory (not shown) to control driving of the plurality of light sources, calculates reflectance at each discrete wavelength based on output light detected from the plurality of light measuring units 120, and calculates the concentration of a chromophore present in the subject 20 to analyze the body composition of the subject 20. In this case, the body composition analysis unit 140 may be implemented as a processor for a general purpose computing device or as an embedded processor.

First, the body composition analyzing unit 140 may determine the number of the light sources 110 and the light measuring unit 120 to be driven based on at least one of the number, content, and kind of the at least one chromophore present in the subject 20.

For example, if the number of chromophores present in the subject 20 is four, the body composition analysis unit 140 may drive at least four light sources 110 based on the unique properties of the chromophores shown in the respective absorption spectra.

Then, the body composition analyzing unit 140 may drive the light measuring unit 120 to receive the output light detected by the light measuring unit 120. Then, the body composition analysis unit 140 may calculate the reflectance at each discrete wavelength based on the output light. The details thereof will be described with reference to the accompanying drawings.

Fig. 3 shows optical characteristics of input light incident from a light source into a subject and output light detected by a light measuring unit.

As shown in the right diagram in fig. 3, if frequency-modulated input light is irradiated from a light source into the subject 20, the input light is scattered and absorbed by various components including chromophores present in the subject 20.

The graph 300 shown on the left side of fig. 3 shows the characteristics of input light L _ In and output light (i.e., reflected light) L _ Out In a steady state using a lock-In amplifier. When the frequency-modulated input light L _ In is irradiated from the light source into the subject 20, the reflected light L _ Out detected by the light measuring unit 120 shows an amplitude attenuation 302 with respect to the input light L _ In.

The body composition analysis unit 140 calculates the reflectance at each discrete wavelength using the amplitude attenuation 302 occurring at each discrete wavelength, and calculates the concentration value of each chromophore based on the calculated reflectance. To this end, the signal processing unit 130 may use a diffuse approximation of the radiation transfer equation.

Step 1: the body composition analysis unit 140 obtains a frequency domain diffusion model calculated using the green's function in the diffusion approximation. Here, the diffusion model uses the extrapolated boundary conditions as sample (subject) -space boundary conditions. Thus, assume a certain distance Z from the sample surface_bThe energy fluence at (a) is 0.Z_bCan be defined as shown in the following equation 1.

[ equation 1]

Z_b＝2D(1+R_eff)/(1-R_eff)

In the above equation 1, R_effRepresenting the effective reflectivity as affected by the refractive index. If the refractive index of the sample is 1.4 and the refractive index of air is 1.0, R_effMay be 0.493. Further, D represents a diffusion coefficient and is defined as l_tr/3. Here, |_trCan be defined as shown in the following equation 2.

[ equation 2]

l_tr(transmission mean free path) — (μ_a+μ_s')^-1

Meanwhile, the diffusion model may be stored in advance in a memory (not shown) of the biological signal analysis apparatus 10.

Step 2: then, the body composition analysis unit 140 measures the optical signal based on the lock-in amplifier. The signal processing unit 130 measures the output light corresponding to equation 3 based on the steady state method.

[ equation 3]

In equation 3 above, R represents the measured output light, A andrepresenting the amplitude and phase components of the signal reflected and introduced from the subject in the measured output light. Furthermore, C₀Andrepresenting the amplitude and phase included in the output light by the device itself, regardless of the subject. The required C for the calculation is calculated by calibration in the following step 2-1₀。

Step 2-1: the body composition analysis unit 140 may calculate C before measuring the subject₀The value of (c). In particular, a signal processing unitThe element 130 may utilize a known absorption coefficient μ_aAnd scattering coefficient mu_s' measuring the subject and predicting the reflectance of the output light reflected from the subject. Then, the signal processing unit 130 substitutes the measured output light and the predicted amplitude of the output light in equation 3 to obtain C₀. However, in some embodiments, the body composition analysis unit 140 may not perform the operation of step 2-1. In this case, the signal processing unit 130 may receive the determined C₀。

Referring again to step 2, the body composition analyzing unit 140 uses C previously obtained₀To compensate for device-induced (i.e. device-induced phase and amplitude) error values from the measured output light R. Then, the body composition analyzing unit 140 may calculate the reflectance of the obtained output light R according to equation 3.

And step 3: the signal processing unit 130 may obtain the chromophore concentration of the subject to be tested by fitting the reflectance of the output light to the diffusion model of step 1. Here, the body composition analysis unit 140 may perform least squares fitting on the amplitude and phase of the output light.

The body composition analysis unit 140 may analyze the constituent components in the subject 20 using the respective concentrations of the chromophores.

As described above, the biosignal analysis device 10 according to the embodiment of the present disclosure provides a method of measuring the concentration of a chromophore using a predetermined number of the light sources 110 and the light measuring unit 120.

Fig. 4 is a flowchart for explaining a method of analyzing body composition according to an embodiment of the present disclosure.

First, a plurality of light sources are driven based on a modulation signal whose frequency is modulated by the lock-in amplifier chip 131 (S410). As described above, the lock-in amplifier chip 131 generates a predetermined modulation frequency and sequentially supplies the modulation frequency to the corresponding light sources.

Then, the plurality of light measuring units measure respective light signals output from the plurality of light sources and reflected from the subject (S420).

Then, the multiplexer 133 multiplexes the light sensing signals measured by the respective plurality of light measuring units and sequentially outputs the plurality of light sensing signals (S430). In this case, the order of outputting the light sensing signals may be predetermined to identify from which light measuring unit each light sensing signal is output.

Then, the lock-in amplifier chip 131 receives the plurality of light sensing signals sequentially output, performs demodulation thereon, and then outputs them (S440).

Then, a process of analyzing the body composition of the subject is performed based on the signal output from the lock-in amplifier chip 131 (S450). In this process, the reflectance at each discrete wavelength is calculated based on the signal output from the lock-in amplifier chip 131, and the concentration of the chromophore present in the test is calculated based on the calculated reflectance. Details of which have been described above.

The above-described signal processing method or body composition analysis method according to an embodiment of the present disclosure may be embodied in a storage medium including instruction codes executable by a computer, for example, in a program module executed by a computer. Computer readable media can be any available media that can be accessed by the computer and includes all volatile/nonvolatile and removable/non-removable media. Further, computer readable media may include all computer storage media. Computer storage media includes all volatile/nonvolatile and removable/non-removable media implemented in a particular method or technology for storage of information such as computer readable instruction code, data structures, program modules or other data.

The above description of the present disclosure is provided for the purpose of illustration, and it will be understood by those skilled in the art that various changes and modifications may be made without changing the technical concept and essential features of the present disclosure. It is therefore clear that the above embodiments are illustrative in all respects and do not limit the disclosure. For example, components described as a single type may be implemented in a distributed manner. Also, components described as distributed may be implemented in combination.

The scope of the present disclosure is defined by the following claims, not by the detailed description of the embodiments. It should be understood that all modifications and embodiments conceived from the meaning and scope of the claims and equivalents thereof are included in the scope of the present disclosure.