CN106344040A - Measuring device and measuring method for raised level square wave modulation photoelectric volume pulse wave - Google Patents

Abstract

The invention discloses a measuring device and measuring method for raised level square wave modulation photoelectric volume pulse wave. A microprocessor outputs raised preset level square waves at different frequencies and with twice ratio relationship; at least four kinds of light emitting diodes are driven; light sent out by the light emitting diodes is received by a photosensitive device after passing through a tested finger; the photosensitive device converts the light into voltage signals; the voltage signals are converted into preset amplitude voltage signals through a current/voltage conversion amplifier; the microprocessor processes the digital signals to obtain photoelectric volume pulse waves and a valley value and a peak value of the photoelectric volume pulse waves to obtain a spectrum value; in the process of collecting the photoelectric signals by the photosensitive device, the noise level is not changed; but the preset level of the square wave signals used as the drive is raised, at the low level part of the square wave signal, the improvement of the square wave signals compared with the noise is obvious; therefore the signal-to-noise ratio of the photoelectric signals obtained by the photosensitive device at the square wave low level section is improved; further, the precision of the digital signals input into a computer is improved.

Description

Raise square wave modulated photoelectric volume pulse wave device and the measuring method of level

Technical field

A kind of the present invention relates to photoplethysmographic fields of measurement, the present invention relates to square-wave frequency modulation photoelectricity raising level Pulse volume wave measuring apparatus and measuring method.

Background technology

Photoplethysmographic (photo plethysmo graphy, hereinafter referred to as ppg) is a kind of important physiology letter Number, widely apply and cardiovascular system and blood constituent are analyzed.As being exactly to adopt 2 kinds in the measurement to blood oxygen saturation Or led (light emitting diode) of more than two kinds measurement ppg and realize.Time division way is generally adopted to gather ppg in these measurements And eliminate the interference of bias light.

In order to improve certainty of measurement, notification number of the prior art is cn 102389313a, and the day for announcing is in March, 2012 28 patent application improves the quality of signal measurement by the use of square wave as pumping signal.

Because existing measurement apparatus are bar none all using analog-digital converter, analog-digital converter is near input limits Exist significantly non-linear when (maximum or minimum amplitude), the analog signal level of particularly input analog-to-digital converter is lower, obtains The uncertainty of the digital conversion results arriving is bigger.

Therefore, using pure square wave as pumping signal when, the letter of the digital signal obtaining in the low level part of square wave Make an uproar very lower than just, thus have impact on the certainty of measurement of signal.

Content of the invention

In order to improve deficiency of the prior art, the technical problem to be solved in the present invention is to provide a kind of level of raising Square wave modulated photoelectric volume pulse wave device and measuring method, this measurement apparatus and measuring method can be realized high accuracy and survey Amount, and circuit structure is simple, device and technological requirement are low, debug the advantages of easy, reliability is high, amount of calculation is little, as detailed below Description:

A kind of square wave modulated photoelectric volume pulse wave device raising level, described photoplethysmographic measurement dress Put including: microprocessor, at least 2 kinds light emitting diodes, light-sensitive device, current/voltage-converted amplifier and analog-digital converter,

Described microprocessor exports different frequency and becomes the square wave raising level of 2 times of ratio, described raises level At least 2 kinds light emitting diodes described in square wave drive, the light that described light emitting diode sends is after tested finger by described photosensitive Device receives, and described light-sensitive device is converted into voltage signal, and described voltage signal is changed through described current/voltage-converted amplifier Become default amplitude voltage signal；

Described default amplitude voltage signal is converted into digital signal by described analog-digital converter, and described microprocessor is to described Digital signal is processed, and obtains photoplethysmographic and its valley and peak value, is obtained by described valley and described peak value Spectral value；

During light-sensitive device collection photosignal, noise level does not change, but as the square wave driving Due to having raised predetermined level, in the low level part of square-wave signal, square-wave signal improves substantially signal compared to noise, thus Improve in square-wave signal low level section, light-sensitive device gets the signal to noise ratio of photosignal, and then improve and be input to calculating The precision of the digital signal in machine.

The described square-wave signal as driving, due to having raised predetermined level, in the high level part of square-wave signal, improves Light-sensitive device gets the signal to noise ratio of photosignal.

More than half is optimal for the photosignal dynamic range that the value of described predetermined level gathers for light-sensitive device.

Described microprocessor adopts any one in mcu, arm, dsp or fpga.

A kind of measuring method of the square wave modulated photoelectric volume pulse wave device raising level, methods described include with Lower step:

(1) microprocessor using different frequency and becomes at least 2 kinds of the square wave drive raising level of 2 times of ratio to light Diode；

(2) light that described light emitting diode sends is received by light-sensitive device after tested finger and is converted into voltage signal, Described voltage signal zooms into default amplitude voltage signal through current/voltage-converted amplifier；

(3) described default amplitude voltage signal is converted into digital signal through analog-digital converter and sends into described microprocessor；

(4) described microprocessor carries out separating treatment to described digital signal and obtains photoplethysmographic and eliminate background The interference of light；

(5) valley and peak value are obtained according to described photoplethysmographic；

(6) described valley and described peak value are carried out being calculated absorbance difference, obtained by described absorbance difference Spectral value.

A kind of square wave modulated photoelectric volume pulse wave device raising level and measuring method that the present invention provides, with Prior art is compared and is had the advantage that

Present invention foundation Lambert-Beer's law, using square wave division modulation and digital demodulation techniques, compared to background technology In notification number be cn 102389313a, the day for announcing is the patent application in March 28 in 2012, and the present invention is using raising default electricity At least 2 kinds light emitting diodes of flat square wave drive, the light that light emitting diode sends is received by light-sensitive device after tested finger, enters And default amplitude voltage signal is converted into by current/voltage-converted amplifier, by analog-digital converter by default amplitude voltage Signal is converted into digital signal；Microprocessor is processed to digital signal, gets spectral value.Invention significantly increases In the signal to noise ratio of the photosignal of square-wave signal low level section, improve default amplitude voltage signal, thus improve signal adopting The precision of collection, meets the multiple needs in practical application.

Brief description

The principle schematic of the calculating absorbance that Fig. 1 provides for the present invention；

A kind of structure of square wave modulated photoelectric volume pulse wave device raising level that Fig. 2 provides for the present invention is shown It is intended to；

The schematic diagram of the square wave raising level that Fig. 3 provides for the present invention；

A kind of flow process of square wave modulated photoelectric volume pulse wave method raising level that Fig. 4 provides for the present invention Figure；

A kind of another knot of square wave modulated photoelectric volume pulse wave device raising level that Fig. 5 provides for the present invention Structure schematic diagram.

In accompanying drawing, the list of parts representated by each label is as follows:

1: microprocessor；2: light emitting diode；

3: light-sensitive device；4: current/voltage-converted amplifier；

5: analog-digital converter；Px.1:i/o mouth；

Px.2:i/o mouth；Px.n:i/o mouth；

Px.3:i/o mouth；Px.4:i/o mouth；

R1: first resistor；Vcc: power supply；

R2: second resistance；R3: 3rd resistor；

R4: the four resistance；R5: the five resistance；

R6: the six resistance；C1: the first electric capacity；

C2: the second electric capacity；D1: the first light emitting diode；

D2: the second light emitting diode；D3: the three light emitting diode；

D4: the four light emitting diode；A1: operational amplifier；

Py mouth: i/o mouth.

Specific embodiment

For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with accompanying drawing to embodiment party of the present invention Formula is described in further detail.

Embodiment 1

Due to the pulsation phenomenon of tremulous pulse, make blood flow in blood vessel be in cyclically-varying, and blood be height opaque liquid, The change of therefore pulse beating necessarily causes the change of absorbance, as shown in Figure 1.

Consider arteries fullness degree minimum state, from light source incident illumination not by pulsatile arterial blood absorption, this When output intensity i_maxThe strongest, can be considered the incident illumination i of pulsatile arterial blood；And arteries fullness degree highest state corresponds to The valley point of photoelectric sphyg ripple, i.e. the pulsatile arterial blood effect maximum moment, output intensity i now_minThe weakest, dynamic for pulsation The minimum output intensity i of arteries and veins blood.So, filled to maximum and arterial contraction to absorbance during minimum by recording tremulous pulse Value it is possible to eliminate skin histology, subcutaneous tissue etc. all there is the shadow for absorbance for the human body component of constant absorption feature Ring.

According to the Lambert-Beer's law revised, if i₀, i be respectively incident intensity and output intensity, α be molecular extinction system Number, c is each constituent concentration, and l is light mean optical pathlength in the tissue, and g is the light loss being caused by scattering, then absorbance a can It is expressed as:

$a=-lg\frac{i}{i_0}=-2.303\mathrm{\α}cl+g---\left(1\right)$

If the absorptance of biological tissue is μ_a, then μ_a=α c, substituting into formula (1) can obtain:

A=-2.303 μ_al+g (2)

In light transmission detection, absorbance is mainly made up of the absorption and scattering that are transmitted tissue, wherein blood scattering phase To less, negligible.So, g is only contributed by the tissue in addition to pulsatile arterial blood, keeps not in measurement process Become.If the tissue that is transmitted in addition to pulsatile arterial blood is total to n-layer, i-th layer of absorptance is μ_ti, the absorptance of arterial blood is μ_ab, maximum optical path a length of l when photoelectric sphyg period of wave, upper tremulous pulse filled_max, a length of l of minimum light path during arterial contraction_min, Absorbance a when then tremulous pulse fills₁With absorbance a during arterial contraction₂Can be expressed as:

$a_1=-2.303\underset{i=1}{\overset{n}{\σ}}{\mathrm{\μ}}_{ti}{l}_{max}-2.303{\mathrm{\μ}}_{ab}{l}_{max}+g---\left(3\right)$

$a_2=-2.303\underset{i=1}{\overset{n}{\σ}}{\mathrm{\μ}}_{ti}{l}_{min}-2.303{\mathrm{\μ}}_{ab}{l}_{min}+g---\left(4\right)$

If l is l_maxWith l_minDifference.Because its hetero-organization in addition to pulsatile arterial blood is basicly stable, do not carry out week Phase changes, and therefore this part does not affect on absorbance when tremulous pulse fills and shrinks, i.e. first in formula (3) and formula (4) Component is equal.The difference of absorbance when absorbance when then tremulous pulse fills and arterial contraction is:

δ a=a₁-a₂=-2.303 μ_ab(l_max-l_min)=- 2.303 μ_abl (5)

In superincumbent derivation, the absorbance component of the absorption of non-pulsating blood and each layer tissue and scattering is all disappeared Fall, absorbance difference δ a when tremulous pulse fills and during arterial contraction only absorbs partial contribution by the pulsation of arterial blood, mainly instead Reflect the Change of absorption of the arterial blood of pulsation.Be equivalent in itself in being transmitted tissue, skin, muscle and venous blood etc. The impact of its hetero-organization in addition to pulsatile arterial blood is all removed, and leaves behind pulsatile arterial blood purely and is partly inhaled The measurement of luminosity value of delta a.So, the impact of the individual variation such as skin, skeleton and muscle is all removed.

If incident intensity is i₀, when detecting light intensity and arterial contraction when tremulous pulse fills, detection light intensity is respectively i_minAnd i_max, Absorbance difference δ a when absorbance when then tremulous pulse fills and arterial contraction is:

$m=a_1-a_2=lg\left(\frac{i_0}{i_{min}}\right)-lg\left(\frac{i_0}{i_{max}}\right)=lg\left(\frac{i_{max}}{i_{min}}\right)---\left(6\right)$

Measure the valley i of each photoplethysmographic_minWith peak value i_maxCan get corresponding to photoplethysmographic Absorbance difference δ a, can obtain by δ a_λ1、δa_λ2……δa_λnThe spectral value of composition.

A kind of square wave modulated photoelectric volume pulse wave device raising level, referring to Fig. 2, this raises the square wave of level Modulation photoplethysmographic measurement apparatus include: microprocessor 1, at least 2 kinds light emitting diodes 2, light-sensitive device 3, electric currents/electricity Pressure switching amplifier 4 and analog-digital converter 5,

Microprocessor 1 exports different frequency and becomes the square wave raising level of 2 times of ratio, and the square wave raising level drives Dynamic at least 2 kinds light emitting diodes 2, the light that light emitting diode 2 sends is received by light-sensitive device 3 after tested finger, light-sensitive device 3 It is converted into voltage signal, voltage signal is converted into default amplitude voltage signal, analog digital conversion through current/voltage-converted amplifier 4 Default amplitude voltage signal is converted into digital signal by device 5, and microprocessor 1 is processed to digital signal, obtains photoelectricity volume Pulse wave and its valley and peak value, obtain spectral value by valley and peak value.

After the embodiment of the present invention raises predetermined level, during light-sensitive device 3 collection photosignal, noise level does not have Change, but as the square-wave signal driving due to having raised predetermined level, in the low level part of square-wave signal, square wave Signal improves substantially compared to noise, thus improve the signal to noise ratio of the photosignal in square-wave signal low level section；Compared to Notification number in background technology is cn 102389313a, and the day for announcing is March 28 in 2012 using pure square wave as pumping signal Patent application, the embodiment of the present invention considerably improves the signal to noise ratio of the photosignal in square-wave signal low level section, and then Improve the quality that light-sensitive device 3 gets photosignal.

Further, since raising predetermined level, noise level is not changed in, and in the high level part of square-wave signal, square wave is believed Number also have some improvement compared to noise, improve the signal to noise ratio of the photosignal in square-wave signal high level section.

And then, the signal to noise ratio of the photosignal being got due to light-sensitive device 3 is integrally strengthened, so improve be input to micro- The precision of the digital signal in processor 1, microprocessor 1 carries out process to digital signal and can obtain spectral value.

Wherein, the preferred light-sensitive device of the value of predetermined level 3 collection photosignal dynamic range more than half when, when big When equal to 1/2 dynamic range, the photosignal quality highest that collected by light-sensitive device 3.

Default amplitude voltage signal is converted into digital signal by analog-digital converter 5, microprocessor 1 to digital signal at Reason, obtains photoplethysmographic and its valley and peak value, obtains spectral value by valley and peak value.

Wherein, the quantity of light emitting diode 2 is more than or equal to 2.When implementing, the quantity of light emitting diode 2 is according to reality Needs in application are set, and the embodiment of the present invention is without limitation.

Wherein, default amplitude is set according to the needs in practical application, and when implementing, the embodiment of the present invention is to this It is not limited.

Wherein, microprocessor 1 can be using any one in mcu, arm, dsp or fpga.

In sum, because the embodiment of the present invention is with respect to the application documents in background technology, considerably improve in side The signal to noise ratio of the photosignal of ripple low level section, and also improve the signal to noise ratio of the photosignal in square-wave signal high level section, And then improve the photosignal signal to noise ratio of whole level section, improve the precision of the digital signal being input in microprocessor, Microprocessor carries out process to digital signal and can obtain spectral value.

Embodiment 2

A kind of square wave modulated photoelectric volume pulse wave method raising level, referring to Fig. 3 and Fig. 4, the method includes Following steps:

101: microprocessor 1 using different frequency and becomes at least 2 kinds of the square wave drive raising level of 2 times of ratio to send out Optical diode 2；

102: the light that light emitting diode 2 sends is received by light-sensitive device 3 after tested finger and is converted into voltage signal, electricity Pressure signal zooms into the voltage signal of default amplitude through current/voltage-converted amplifier 4；

103: voltage signal is converted into digital signal through analog-digital converter 5 and sends into microprocessor 1；

104: microprocessor 1 carries out separating treatment and obtains photoplethysmographic and eliminate bias light and do to digital signal Disturb；

105: valley and peak value are obtained according to photoplethysmographic；

For the sake of concise explanation, illustrate it is assumed that λ 1, λ 2, λ 3 and λ 4 wavelength taking 4 kinds of wavelength light emitting diodes 2 as a example Light emitting diode driving raise square wave frequency be respectively 8 times of f, 4 times of f, 2 times of f, 1 times of f.It is assumed that the sampling of analog-digital converter 5 Frequency is f_s, and f_s=2f, and ensure level intermediate samples high and low in λ 1 drive signal.

Digital signal sequencesCan be expressed as:

$d_i^t=d_i^{\mathrm{\λ}1}+d_i^{\mathrm{\λ}2}+d_i^{\mathrm{\λ}3}+d_i^{\mathrm{\λ}4}+d_i^b---\left(7\right)$

Wherein,WithIt is respectively wavelength X 1, the photoplethysmographic of λ 2, λ 3 and λ 4,For The dark current of bias light and light-sensitive device 3, summation signals (the abbreviation background letter of the offset voltage of current/voltage-converted amplifier 4 Number, the effect of level portions is raised including each wavelength).

It is assumed that sample frequency f_sRaise the change frequency of square-wave signal and bias light far above modulation, in minimum drive signal The a cycle of frequency can be approximately considered the amplitude of each road square-wave signal and the amplitude of background light signal is constant.With the most front 16 As a example sampled data:

$\begin{array}{c}\left\{\begin{array}{c}{d}_1^{\mathrm{\λ}1}=d_3^{\mathrm{\λ}1}=d_5^{\mathrm{\λ}1}=d_7^{\mathrm{\λ}1}=d_9^{\mathrm{\λ}1}=d_{13}^{\mathrm{\λ}1}=d_{15}^{\mathrm{\λ}1}=d_a^{\mathrm{\λ}1}\\ d_2^{\mathrm{\λ}1}=d_4^{\mathrm{\λ}1}=d_6^{\mathrm{\λ}1}=d_8^{\mathrm{\λ}1}=d_{10}^{\mathrm{\λ}1}=d_{12}^{\mathrm{\λ}1}=d_{14}^{\mathrm{\λ}1}=0\\ d_1^{\mathrm{\λ}2}=d_2^{\mathrm{\λ}2}=d_5^{\mathrm{\λ}2}=d_6^{\mathrm{\λ}2}=d_9^{\mathrm{\λ}2}=d_{10}^{\mathrm{\λ}2}=d_{13}^{\mathrm{\λ}2}=d_{14}^{\mathrm{\λ}2}=d_a^{\mathrm{\λ}2}\\ d_3^{\mathrm{\λ}2}=d_4^{\mathrm{\λ}2}=d_7^{\mathrm{\λ}2}=d_8^{\mathrm{\λ}2}=d_{11}^{\mathrm{\λ}2}=d_{12}^{\mathrm{\λ}2}=d_{15}^{\mathrm{\λ}2}=d_{16}^{\mathrm{\λ}2}=0\\ d_1^{\mathrm{\λ}3}=d_2^{\mathrm{\λ}3}=d_3^{\mathrm{\λ}3}=d_4^{\mathrm{\λ}3}=d_9^{\mathrm{\λ}3}=d_{10}^{\mathrm{\λ}3}=d_{11}^{\mathrm{\λ}3}=d_{12}^{\mathrm{\λ}3}=d_a^{\mathrm{\λ}3}\\ d_5^{\mathrm{\λ}3}=d_6^{\mathrm{\λ}3}=d_7^{\mathrm{\λ}3}=d_8^{\mathrm{\λ}3}=d_{13}^{\mathrm{\λ}3}=d_{14}^{\mathrm{\λ}3}=d_{15}^{\mathrm{\λ}3}=d_{16}^{\mathrm{\λ}3}=0\\ d_1^{\mathrm{\λ}4}=d_2^{\mathrm{\λ}4}=d_3^{\mathrm{\λ}4}=d_4^{\mathrm{\λ}4}=d_5^{\mathrm{\λ}4}=d_6^{\mathrm{\λ}4}=d_7^{\mathrm{\λ}4}=d_8^{\mathrm{\λ}4}=d_a^{\mathrm{\λ}4}\\ d_9^{\mathrm{\λ}4}=d_{10}^{\mathrm{\λ}4}=d_{11}^{\mathrm{\λ}4}=d_{12}^{\mathrm{\λ}4}=d_{13}^{\mathrm{\λ}4}=d_{14}^{\mathrm{\λ}4}=d_{15}^{\mathrm{\λ}4}=d_{16}^{\mathrm{\λ}4}=0\\ d_1^b=d_2^b=d_3^b=d_4^b=d_5^b=d_6^b=d_7^b=d_8^b=d_9^b=d_{10}^b=d_{11}^b=d_{12}^b=d_{13}^b=d_{14}^b\end{array}\right.\\ =d_{15}^b=d_{16}^b=d_a^b\end{array}---\left(8\right)$

Wherein,WithIt is respectively wavelength X 1, the optical signal of λ 2, λ 3 and λ 4 and background signal The amplitude of (including the effect that each wavelength raises level portions).

In other words, enter row operation with every 16 digital signals of order for one group:

$\begin{array}{c}{d}_{16n+1}-d_{16n+2}+d_{16n+3}-d_{16n+4}+d_{16n+5}-d_{16n+6}+d_{16n+7}-d_{16n+8}+d_{16n+9}-d_{16n+10}+\\ d_{16n+11}-d_{16n+12}+d_{16n+13}-d_{16n+14}+d_{16n+15}-d_{16n+16}=8d_{an}^{\mathrm{\λ}1},n=0,1,\mathrm{2......}\end{array}---\left(9\right)$

Obtain the photoplethysmographic of 8 times of wavelength X 1And completely eliminate background signal and (include each Wavelength raises the effect of level portions)Impact.

$\begin{array}{c}{d}_{16n+1}+d_{16n+2}-d_{16n+3}-d_{16n+4}+d_{16n+5}+d_{16n+6}-d_{16n+7}-d_{16n+8}+d_{16n+9}+d_{16n+10}-\\ d_{16n+11}-d_{16n+12}+d_{16n+13}+d_{16n+14}-d_{16n+15}-d_{16n+16}=8d_{an}^{\mathrm{\λ}2},n=0,1,\mathrm{2......}\end{array}---\left(10\right)$

Obtain the photoplethysmographic of 8 times of wavelength X 2And completely eliminate background signal and (include each Wavelength raises the effect of level portions)Impact.

$\begin{array}{c}{d}_{16n+1}+d_{16n+2}+d_{16n+3}+d_{16n+4}-d_{16n+5}-d_{16n+6}-d_{16n+7}-d_{16n+8}+d_{16n+9}+d_{16n+10}+\\ d_{16n+11}+d_{16n+12}-d_{16n+13}-d_{16n+14}-d_{16n+15}-d_{16n+16}=8d_{an}^{\mathrm{\λ}3},n=0,1,\mathrm{2......}\end{array}---\left(11\right)$

Obtain the photoplethysmographic of 8 times of wavelength X 3And completely eliminate background signal and (include each Wavelength raises the effect of level portions)Impact.

$\begin{array}{c}{d}_{16n+1}+d_{16n+2}+d_{16n+3}+d_{16n+4}+d_{16n+5}+d_{16n+6}+d_{16n+7}+d_{16n+8}-d_{16n+9}-d_{16n+10}-\\ d_{16n+11}-d_{16n+12}-d_{16n+13}-d_{16n+14}-d_{16n+15}-d_{16n+16}=8d_{an}^{\mathrm{\λ}4},n=0,1,\mathrm{2......}\end{array}---\left(12\right)$

Obtain the photoplethysmographic of 8 times of wavelength X 4And completely eliminate background signal and (include each Wavelength raises the effect of level portions)Impact.

Calculate wavelength X 1, the valley of the photoplethysmographic of λ 2, λ 3 and λ 4 and peak value: i respectively_minλ1、i_maxλ1、i_minλ2、 i_maxλ2、i_minλ3、i_maxλ3、i_minλ4And i_maxλ4；

106: valley and peak value are carried out being calculated absorbance difference, spectral value is obtained by absorbance difference.

Calculate the absorbance difference δ a of each wavelength using formula (6)_λ1、δa_λ2、……δa_λn, and by absorbance difference Constitute spectral value.

In sum, because the embodiment of the present invention is with respect to the application documents in background technology, considerably improve in side The signal to noise ratio of the photosignal of ripple low level section, and also improve the signal to noise ratio of the photosignal in square-wave signal high level section, And then improve the photosignal signal to noise ratio of whole level section, improve the precision of the digital signal being input in microprocessor, Microprocessor carries out process to digital signal and can obtain spectral value.

Embodiment 3

As shown in figure 5, a kind of square wave modulated photoelectric volume pulse wave device raising level, employ 4 kinds and light Diode 2, four i/o mouth px.1, px.2, px.3 and px.4 of microprocessor 1 pass through first resistor r1, second resistance respectively R2,3rd resistor r3 and the 4th resistance r4 drive the first light emitting diode d1, the second light emitting diode d2, the 3rd light emitting diode D3 and the 4th light emitting diode d4, the first light emitting diode d1, the second light emitting diode d2, the 3rd light emitting diode d3 and the 4th The tested finger of light printing opacity that light emitting diode d4 sends is received by light sensor 3, light sensor 3 received signal warp Cross the electric current/electricity being made up of operational amplifier a1, the first electric capacity c1, the second electric capacity c2, the 5th resistance r5 and the 6th resistance r6 Pressure switching amplifier 4 is converted into default amplitude voltage signal, and then analog-digital converter 5 is with highest driven for emitting lights diode 2 frequency Two speeds default amplitude voltage signal is converted into digital signal microprocessor 1 is sent to by py mouth.Digital signal exists Different wave length photoplethysmographic first isolated by microprocessor 1: 16 digital signals that every order obtains are one group, according to

$\begin{array}{c}{d}_{16n+1}-d_{16n+2}+d_{16n+3}-d_{16n+4}+d_{16n+5}-d_{16n+6}+d_{16n+7}-d_{16n+8}+d_{16n+9}-d_{16n+10}+\\ d_{16n+11}-d_{16n+12}+d_{16n+13}-d_{16n+14}+d_{16n+15}-d_{16n+16}=8d_{an}^{\mathrm{\λ}1},n=0,1,\mathrm{2......}\\ d_{16n+1}+d_{16n+2}-d_{16n+3}-d_{16n+4}+d_{16n+5}+d_{16n+6}-d_{16n+7}-d_{16n+8}+d_{16n+9}+d_{16n+10}-\\ d_{16n+11}-d_{16n+12}+d_{16n+13}+d_{16n+14}-d_{16n+15}-d_{16n+16}=8d_{an}^{\mathrm{\λ}2},n=0,1,\mathrm{2......}\\ d_{16n+1}+d_{16n+2}+d_{16n+3}+d_{16n+4}-d_{16n+5}-d_{16n+6}-d_{16n+7}-d_{16n+8}+d_{16n+9}+d_{16n+10}+\\ d_{16n+11}+d_{16n+12}-d_{16n+13}-d_{16n+14}-d_{16n+15}-d_{16n+16}=8d_{an}^{\mathrm{\λ}3},n=0,1,\mathrm{2......}\\ d_{16n+1}+d_{16n+2}+d_{16n+3}+d_{16n+4}+d_{16n+5}+d_{16n+6}+d_{16n+7}+d_{16n+8}-d_{16n+9}-d_{16n+10}-\\ d_{16n+11}-d_{16n+12}-d_{16n+13}-d_{16n+14}-d_{16n+15}-d_{16n+16}=8d_{an}^{\mathrm{\λ}4},n=0,1,\mathrm{2......}\end{array}$

Respectively obtain 8 times of wavelength X 1, the photoplethysmographic of λ 2, λ 3 and λ 4With And completely eliminate background signal (including the effect that each wavelength raises level portions)Impact.

Obtain the photoplethysmographic of each wavelength, calculate λ 1, the photoplethysmographic of λ 2, λ 3 and λ 4 accordingly Valley and peak value: i_minλ1、i_maxλ1、i_minλ2、i_maxλ2、i_minλ3、i_maxλ3、i_minλ4And i_maxλ4.

Again by i_minλ1、i_maxλ1、i_minλ2、i_maxλ2、i_minλ3、i_maxλ3、i_minλ4And i_maxλ4Calculate the suction corresponding to each wavelength Luminosity value of delta a, can obtain by absorbance difference δ a_λ1、δa_λ2……δa_λnThe spectral value of composition.

In sum, because the embodiment of the present invention is with respect to the application documents in background technology, considerably improve in side The signal to noise ratio of the photosignal of ripple low level section, and also improve the signal to noise ratio of the photosignal in square-wave signal high level section, And then improve the photosignal signal to noise ratio of whole level section, improve the precision of the digital signal being input in microprocessor, Microprocessor carries out process to digital signal and can obtain spectral value.

It will be appreciated by those skilled in the art that accompanying drawing is the schematic diagram of a preferred embodiment, the embodiments of the present invention Sequence number is for illustration only, does not represent the quality of embodiment.

The foregoing is only presently preferred embodiments of the present invention, not in order to limit the present invention, all spirit in the present invention and Within principle, any modification, equivalent substitution and improvement made etc., should be included within the scope of the present invention.

Claims (5)

1. a kind of square wave modulated photoelectric volume pulse wave device raising level is it is characterised in that described photoelectricity volume arteries and veins Wave measuring apparatus of fighting include: microprocessor, at least 2 kinds light emitting diodes, light-sensitive device, current/voltage-converted amplifier and mould Number converter,

Described microprocessor exports different frequency and becomes the square wave raising level of 2 times of ratio, the described side raising level At least 2 kinds light emitting diodes described in ripple driving, the light that described light emitting diode sends is after tested finger by described light-sensitive device Receive, described light-sensitive device is converted into voltage signal, and described voltage signal is converted into pre- through described current/voltage-converted amplifier If amplitude voltage signal；

Described default amplitude voltage signal is converted into digital signal by described analog-digital converter, and described microprocessor is to described numeral Signal is processed, and obtains photoplethysmographic and its valley and peak value, obtains spectrum by described valley and described peak value Value；

During light-sensitive device collection photosignal, noise level does not change, but as the square-wave signal driving Due to having raised predetermined level, in the low level part of square-wave signal, square-wave signal improves substantially compared to noise, thus improving In square-wave signal low level section, light-sensitive device gets the signal to noise ratio of photosignal, and then improves and be input in computer Digital signal precision.

2. a kind of square wave modulated photoelectric volume pulse wave device raising level according to claim 1, its feature It is, the described square-wave signal as driving, due to having raised predetermined level, in the high level part of square-wave signal, improves light Sensing device gets the signal to noise ratio of photosignal.

3. a kind of square wave modulated photoelectric volume pulse wave device raising level according to claim 1, its feature It is, more than half is optimal for the photosignal dynamic range that the value of described predetermined level gathers for light-sensitive device.

4. a kind of square wave modulated photoelectric volume pulse wave device raising level according to claim 1, its feature It is, described microprocessor adopts any one in mcu, arm, dsp or fpga.

5. a kind of for a kind of square-wave frequency modulation photoelectricity volume raising level described in any claim in Claims 1-4 The measuring method of pulse wave measuring apparatus is it is characterised in that the method comprising the steps of:

(1) microprocessor using different frequency and become 2 times of ratio at least 2 kinds light-emitting diodes of square wave drive raising level Pipe；

(2) light that described light emitting diode sends is received by light-sensitive device after tested finger and is converted into voltage signal, described Voltage signal zooms into default amplitude voltage signal through current/voltage-converted amplifier；

(3) described default amplitude voltage signal is converted into digital signal through analog-digital converter and sends into described microprocessor；

(4) described microprocessor carries out separating treatment to described digital signal and obtains photoplethysmographic and eliminate bias light Interference；

(5) valley and peak value are obtained according to described photoplethysmographic；

(6) described valley and described peak value are carried out being calculated absorbance difference, spectrum is obtained by described absorbance difference Value.