CN201481422U - Light-frequency converting pulse oximeter - Google Patents
Light-frequency converting pulse oximeter Download PDFInfo
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- CN201481422U CN201481422U CN2009201679777U CN200920167977U CN201481422U CN 201481422 U CN201481422 U CN 201481422U CN 2009201679777 U CN2009201679777 U CN 2009201679777U CN 200920167977 U CN200920167977 U CN 200920167977U CN 201481422 U CN201481422 U CN 201481422U
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Abstract
The utility model discloses a light-frequency converting pulse oximeter, which is characterized in that the oximeter comprises a red light emitting tube, an infrared light emitting tube, a lighting driver, a light frequency converter, a microprocessor and a liquid crystal display, wherein the red light emitting tube and the infrared light emitting tube are electrically connected with two output ends of the lighting driver respectively; an input end of the lighting driver is connected with a signal end of the microprocessor; the microprocessor comprises an I/O interface having an external interrupting function and a universal serial interface; the I/O interface having the external interrupting function is connected with the light frequency converter; and other I/O interfaces of the microprocessor are connected with an input port of the liquid crystal display. Based on the combination of pulse countering and timing, the light-frequency converting pulse oximeter widens the sampling time, can automatically regulate a sampling time width, and apply digital signal processing so as to realize high speed and high precision of data measurement as well as low power consumption and low cost of products.
Description
Technical field
This utility model relates to a kind of light frequency change type pulse blood oxygen instrument.
Background technology
Pulse blood oxygen instrument is a kind of no wound, and the medical instrument of continuously monitoring human body arterial oxygen saturation has become the conventional configuration device of anaesthetizing monitoring and Intensive Care Therapy in the hospital, also is widely used in various mobile monitorings and sleep monitoring outside the hospital.The development of family and community medicine health care system has proposed new requirement to the design and the manufacturing of pulse blood oxygen instrument, and promptly wishing to provide low price, and high performance wearing type pulse blood oxygen instrument is to be widely used in family and community medicine net.
The operation principle of pulse blood oxygen instrument is according to HbO2 Oxyhemoglobin (HbO
2) and reduced hemoglobin (Hb) in the absorption Spectrum characteristic in HONGGUANG and near infrared light zone, light with two bundle different wave lengths, as the HONGGUANG of 660nm and the near infrared light human finger of 940nm, toe or ear-lobe position are by the photoelectricity volume pulsation wave intensity of light-sensitive element detection transmission (or reflection).This class is organized the line and staff control that all is made up of skin, blood, muscle, skeleton etc., and light is to go up less flutter component of superposition (or claiming AC compounent AC) at a very big stable component (or claiming DC component DC) by the feature of the photoelectricity volume pulsation wave that this class tissue forms.Its AC compounent is because the blood engorgement tremulous pulse causes, DC component then is blood flow when crossing tremulous pulse, by non-tremulous pulse part, i.e. and muscle, venous blood, skin, tissue such as skeleton is to the absorption result of light.Can obtain four variablees by measurement, i.e. HONGGUANG DC component RD_DC, HONGGUANG AC compounent RD_AC, infrared DC component IR_DC, infrared AC compounent IR_AC to the photoelectricity volume pulsation wave of two-beam.Can calculate so-called R-R ratio by these four amounts:
R-R＝(RD_AC/RD_DC)/(IR_AC/IR_DC)
Pick off for specific emission wavelength configuration, R-R ratio and arterial oxygen saturation have a specific functional relationship, this functional relationship is difficult to express with theoretical formula, generally is by clinical and have wound method control experiment to obtain the calibration curve that the calibration data are drawn out R-R ratio and arterial oxygen saturation relation.The data of calibration curve can be stored in the digital signal processing unit of pulse blood oxygen instrument with the mode of tabulation, and instrument can be obtained the arterial oxygen saturation value with look-up method after measurements and calculations go out R-R ratio.
In order to reduce of the influence of factors such as motion artifact and interior external interference to measurement result, can also introduce the three-beam of (for example 880nm) that has specific wavelength or the light beam of more specific wavelengths, the influence that solves variable to be measured and remove disturbance variable according to its mathematical relationship.
Because human body each several part tissue to be measured and individual variation, the excursion of photoelectricity volume pulsation wave DC component itself just reaches 100～200 times, and synergetic AC compounent excursion is generally 0.5%～20% of DC component on it.The specialty pulse blood oxygen instrument designing requirement be when AC compounent be DC component 0.1% the time also can trace pulse wave preferably, detect heart rate and calculating detecting sphygmus and blood oxygen saturation.Like this, directly all very high to the requirement of dynamic range, resolution and the signal to noise ratio of measuring system from primary photoelectricity volume pulse wave measurement alternating current-direct current component.
The signal processing method that early stage analog pulse blood oxygen instrument is taked is to shine tissue to be measured with time-multiplexed HONGGUANG and infrared light pulse signal sequence, convert the detected photoelectric current pulse signal of light-sensitive device to voltage pulse signal with current-to-voltage convertor, time-multiplexed HONGGUANG is separated with the infrared light pulse sequence, respectively two-way pulse train is reduced into successive volume ripple signal with high-order low-pass filter then, at last the alternating current-direct current component on each road is separated and the gain of regulating each road is respectively satisfied the requirement of follow-up analog-digital converter certainty of measurement to guarantee signal amplitude.The gain-adjusted of direct current channel also can partly or entirely replace with regulating the method that drives light intensity.The shortcoming of this method is the analog circuit complexity, the parameter matching requirement height of each analog channel, and the performance indications that reached also are very limited.
At this defective of board design, people begin to attempt directly the detected photoelectric current pulse signal of light-sensitive device being changed into digital signal with high-resolution analog-digital converter, and process after this can be finished by Digital Signal Processing.Directly the detected photoelectric current pulse signal of light-sensitive device is converted to digital signal and satisfy the certainty of measurement requirement, the resolution of the analog-digital converter that is adopted will reach 20 at least, is preferably in more than 22.Though the Sigma-Delta ∑-Δ pattern number converter that generally uses can satisfy the requirement of voltage resolution at present, because its lag characteristic when pulse signals is sampled has limited the application in this occasion.Existing digital pulse blood oxygen instrument still adopts the pattern number converter relatively one by one more than 16, and for denoising and interference free performance, the signal input stage before the analog-digital converter often adopts charge integrator to replace current-to-voltage convertor.For remedying the deficiency of system dynamics scope, 20 charge integration patterns have just been selected as Chinese invention patent ZL99813986.6 disclosed " Direct Digital formula blood oxygen instrument and be used for the method for calculating oxygenation levels value "
Number converter, the method for regulating the drive current of luminous tube with digital to analog converter simultaneously and adding controlled diverter before analog-digital converter strengthens the dynamic range of system.But because the high-resolution analog-digital converter price that adopted is higher, so this design also lacks cost advantage to the application scenario of community medicine and family health care.
The another kind of method of Direct Digital pulse blood oxygen instrument design is directly will convert its frequency and transmission (or reflection) the proportional electric impulse signal of light intensity from the optical signal that tissue receives to light frequency converter (LFC), electric impulse signal is carried out frequency counting and carries out digital signal processing, obtain blood oxygen saturation and heart rate value.Document Jeff Bachiochi, TSL230R-Based Pulse Oximeter, CIRCUIT CELLAR, Issue 173, and December 2004, introduced the experimental program of this design among the P26..This scheme adopts decide sampling time driven for emitting lights diode and simultaneously the pulse that LFC exports is counted, and represents DC component with the step-by-step counting meansigma methods in successive sampling period, and the variable quantity of each sampling period counted number of pulses is then represented AC compounent.But the frequency range of present available LFC is below the 1MHz, in order under limited LFC output impulsive condition, to obtain enough resolution to AC compounent, experimental program has been selected the sampling time of 31.25mS for use, selects for use manual mode to regulate the luminous tube drive current to guarantee obtaining suitable counted number of pulses in the sampling time simultaneously.What the document provided obviously only is the most preliminary a kind of conception, and for practical application, Chang sampling time all is unacceptable to certainty of measurement and power consumption like this, and the adjusting of dynamic range also must be carried out automatically in real time by measuring system.If the method that adopts the pulse period to measure replaces the frequency measurement method of above-mentioned document, the drive current that then will regulate luminous tube automatically makes organizes LFC output pulse all to have the precision that enough width are measured with hold period for any thickness, but accomplish this point, when measuring than thin tissue, the drive current of luminous tube and pulsed light intensity can be adjusted to very little value, and this will cause the serious reduction of signal to noise ratio.Timing resolution is low more, and desired pulse width values is big more, and the decline of signal to noise ratio is also serious more.Introduced a kind of among the Chinese invention patent CN1915167A by having the microprocessor of catching logic interfacing to fix a number train of pulse stored counts and catch the method for timing of electric impulse signal.This method has solved problems such as speed, power consumption and dynamic range adjustment to a certain extent, but COEFFICIENT K is a constant in this method, cause measuring the dark and tissue of skin color when thicker, cause representing the train of pulse number of pulse wave amplitude very few, signal to noise ratio reduces, and still has certain defective.
Summary of the invention
This utility model provides a kind of and combines with timing based on step-by-step counting, the pulse blood oxygen instrument of a kind of Digital Signal Processing that will widen in the sampling time is to solve that aforementioned prior art is measured the measuring speed that LFC output pulse frequency and period measurement run into and precision is low, power consumption is high, cost is high and dynamic range is difficult for the problem of regulating.
This utility model adopts following technical scheme to realize: comprise red light-emitting pipe, infraluminescence pipe, emission driver, light frequency transducer, microprocessor and LCDs, described red light-emitting pipe and infraluminescence pipe are electrically connected with the two-way outfan of emission driver respectively, the input of this emission driver is connected with the microprocessor signals end, this microprocessor contains the I/O mouth and the USB (universal serial bus) of band external interrupt function, and the I/O mouth of this band external interrupt function is connected with the light frequency transducer; Other I/O mouths of this microprocessor are connected with the input port of LCDs.
Described USB (universal serial bus) is connected with central processing system or wireless transmitting unit.
Described red light-emitting pipe (3) and infraluminescence pipe (4) produce the HONGGUANG and the infrared light pulse of specified time interval respectively under the driving of emission driver (2).
The utility model has the advantages that: pulse blood oxygen instrument only depends on the accuracy of timekeeping of system to IR_T (n) and RD_T (n) to the measurement of transmission (or reflection) light intensity, and it is irrelevant with the output frequency of LFC, for reaching the Oximetry requirement, can adopt the microprocessor of elapsed time clock more than 8MHz.Timing window T0 can be made as 0.5 millisecond, can reach required precision.This blood oxygen instrument need not regulated light intensity, only regulates expansion time IR_T_INIT and RD_T_INIT automatically by software, can reach the requirement of certainty of measurement under professional pulse blood oxygen instrument noiseproof feature and the weak perfusion condition.Simplify design, improved signal to noise ratio.Realize real-time processing and heart rate and the blood oxygen levels demonstration in real time and the transmission of measurement data.Be a kind ofly to combine with timing, will widen in the sampling time, and can regulate the sampling time width automatically based on step-by-step counting, the pulse blood oxygen instrument of Applied Digital signal processing, thus reach the high-speed of DATA REASONING, the low-power consumption of high accuracy and product, low cost.
Description of drawings
Fig. 1 is a structured flowchart of the present utility model.
Fig. 2 is the driving pulse of luminous tube of the present utility model and the sequential chart of corresponding light frequency transducer output pulse.Wherein I is an infraluminescence pipe driving pulse; II is a red light-emitting pipe driving pulse; III is a light frequency transducer output pulse string.
The specific embodiment
Below in conjunction with drawings and Examples this utility model is described in further detail:
Referring to Fig. 1, this device comprises red light-emitting pipe 3, infraluminescence pipe 4, emission driver 2, light frequency transducer 5, microprocessor 1 and LCDs 6.Described red light-emitting pipe 3 and infraluminescence pipe 4 are electrically connected with the two-way outfan of emission driver 2 respectively, the input of emission driver 2 is connected with microprocessor 1 signal end, this microprocessor 1 program control emission driver 2 can accurately produce the interval of HONGGUANG and infrared light pulse.This microprocessor 1 contains the I/O mouth and the USB (universal serial bus) of band external interrupt function.The I/O mouth of the band external interrupt function of microprocessor 1 connects light frequency transducer 5, and other I/O mouths of microprocessor 1 connect the input port of LCDs 6, and LCDs 6 is born Presentation Function, also is the platform of man-machine communication.The USB (universal serial bus) of microprocessor 1 can connect central processing system or wireless transmitting unit (not shown).When measuring, tissue 7 places between red light-emitting pipe 3, infraluminescence pipe 4 and the light frequency transducer 5.
Microprocessor 1 can be any I/O mouth, USB (universal serial bus) with external interrupt function, and the microprocessor of Timing should be selected the higher system clock frequency as far as possible for use.In the present embodiment, system clock is 8MHz, and timing resolution is 125ns.Microprocessor 1 is periodically exported two pulse signals chronologically, drive infraluminescence pipe 4, red light-emitting pipe 3 successively by emission driver 2, the light pulse of sending is received by light frequency transducer 5 after tissue 7 decay and modulation, and converts the I/O mouth that frequency and the linearly proportional train of pulse of pulse light intensity are sent to microprocessor 1 to.The train of pulse that microprocessor 1 utilizes internal clocking and timer that light frequency transducer 5 is exported carries out stored counts and timing simultaneously, counting corresponding light frequency converter 5 trains of pulse are counted IR_CNT and RD_CNT, simultaneously with used time IR_T and RD_T and timing window T0 comparison, as IR_T or RD_T during greater than timing window T0, stop the driving of corresponding luminous tube, and holding time IR_T and RD_T.Microprocessor 1 calculates corresponding DC component and AC compounent according to detected every road light pulse cycle and undulate quantity thereof, thereby tries to achieve the volume pulsation wave datum by common pulse blood oxygen instrument, detecting sphygmus and blood oxygen saturation and heart rate value.The gained result can show by LCDs 6 on the one hand, can send data to central processing system or wireless transmitting unit by USB (universal serial bus) on the other hand, realizes telemetry function.
Emission driver 2 adopts fixed pulse voltages and current drives infraluminescence pipe 4, red light-emitting pipe 3 luminous, and the method for this fixed pulse current drives can be simplified hardware designs, saves volume and cost.
Further specify the operation principle of the time width of expanding step-by-step counting below in conjunction with accompanying drawing 2.
Pulse train I is the infraluminescence pipe driving pulse that microprocessor 1 sends among the figure, and its period T is the sampling period of pulse wave.The sampling period is 8.33 milliseconds in the present embodiment, and promptly sample frequency is 120Hz.The elapsed time clock of microprocessor is 8MHz.Timing window T0 can be made as 0.5 millisecond, and its driving pulse width can change in the output pulse period less than 0.5ms+1 light frequency transducer greater than 0.5 millisecond along with the variation of pulse wave when normal the measurement.
Pulse train II is the red light-emitting pipe driving pulse that microprocessor 1 sends among the figure, and the setting of its cycle and pulsewidth is the same with infrared driving pulse, and there is the time-delay of one 50 ц s in the forward position of this pulse to the tailing edge of infrared driving pulse.
Pulse train III is the train of pulse of light frequency transducer 5 outputs among the figure, the time of corresponding infrared and HONGGUANG driving pulse, light frequency transducer 5 will be exported the train of pulse of two string upper frequencies (being generally 100KHz), represent with two black rectangle among the figure, IR_T and RD_T equal the width of corresponding infrared and HONGGUANG driving pulse respectively during the accounting for of this two black rectangle, and the number of the pulse that is comprised equals infrared respectively and HONGGUANG counted number of pulses IR_CNT and RD_CNT.At the T_DARK remaining time in a sampling period, light frequency transducer 5 will be exported the train of pulse of lower frequency (usually below 100Hz), represent with square wave among the figure, the frequency of this train of pulse and the umber of pulse that is comprised are determined by the dark current and the external interference light intensity of photoelectric device, should be eliminated this influence to Measurement and Data Processing the time.
Below describe the digital signal processing method of the time expansion of this utility model pulse count in detail, may further comprise the steps:
A. behind the instrument electrification reset, microprocessor 1 cuts out external interrupt, timing window T0 is set, drive infraluminescence pipe 4 and red light-emitting pipe 3 successively by I, II sequential, counting corresponding light frequency converter 5 trains of pulse are counted IR_CNT and RD_CNT, simultaneously with used time IR_T and RD_T and timing window T0 comparison, as IR_T or RD_T during greater than timing window T0, stop the driving of corresponding luminous tube, and holding time IR_T and RD_T.
B. in the follow-up sampling period, microprocessor cuts out external interrupt, drive infraluminescence pipe 4 and red light-emitting pipe 3 successively, and the train of pulse of light-to-frequency converter 5 outputs is carried out pulse stored counts IR_CNT and RD_CNT and used time IR_T and RD_T and relatively also preservation of timing window T0 simultaneously.
C. in sampling period of III sequential, low-frequency pulse string to dark current and surround lighting generation carries out pulse timing, when beginning, opens the external interrupt function of I/O mouth in this cycle, from the first time external interrupt pick up counting, extract and interrupt used time D ARK_T for the second time, and close the external interrupt function.
D. the digital signal processing method of light frequency change type pulse blood oxygen instrument.The predetermined expansion time is respectively IR_T_INIT and RD_T_INIT.To arbitrary sampling period n, measured infrared and HONGGUANG train of pulse stored count IR_CNT (n) and RD_CNT (n), accumulative total is IR_T (n) and RD_T (n) when accounting for, to timing DARK_T (n) one of in the low-frequency pulse of dark current and surround lighting generation.The value of calculation of the corresponding sampled point n of then infrared pulse frequency with HONGGUANG is respectively:
IR_X(n)＝IR_T_INIT*IR_CNT(n)/IR_T(n)-IR_T_INIT/DARK_T(n)
RD_X(n)＝RD_T_INIT*RD_CNT(n)/RD_T(n)-RD_T_INIT/DARK_T(n)
In the formula, subtrahend is the pulse wave amplitude sampled value error term of the pulse frequency representative that produces of dark current and surround lighting, and minuend is the pulse wave amplitude sampled value of the pulse frequency representative that records between action period of driving pulse,
E. all detect IR_X (n) and RD_X (n) whether in 8000H ± 50% scope in each sampling period, otherwise calculate expansion time IR_T_INIT and RD_T_INIT again.
At first, analyze according to the detecting sphygmus and blood oxygen saturation measuring principle that background technology is introduced, the R-R ratio calculation be the relative ratio of two-beam alternating current-direct current component, irrelevant with the value of expanding time IR_T_INIT and RD_T_INIT, so after obtaining IR_X (n) and RD_X (n) value, just can calculate the alternating current-direct current component of two-beam volume pulsation wave as common blood oxygen instrument, obtain detecting sphygmus and blood oxygen saturation and heart rate value.
Claims (3)
1. light frequency change type pulse blood oxygen instrument, it is characterized in that: comprise red light-emitting pipe (3), infraluminescence pipe (4), emission driver (2), light frequency transducer (5), microprocessor (1) and LCDs (6), described red light-emitting pipe (3) and infraluminescence pipe (4) are electrically connected with the two-way outfan of emission driver (2) respectively, the input of this emission driver (2) is connected with microprocessor (1) signal end, this microprocessor (1) contains the I/O mouth and the USB (universal serial bus) of band external interrupt function, and the I/O mouth of this band external interrupt function is connected with light frequency transducer (5); Other I/O mouths of this microprocessor (1) are connected with the input port of LCDs (6).
2. light frequency change type pulse blood oxygen instrument according to claim 1, it is characterized in that: described USB (universal serial bus) is connected with central processing system or wireless transmitting unit.
3. light frequency change type pulse blood oxygen instrument according to claim 1 is characterized in that: described red light-emitting pipe (3) and infraluminescence pipe (4) produce the HONGGUANG and the infrared light pulse of specified time interval respectively under the driving of emission driver (2).
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| CN2009201679777U CN201481422U (en) | 2009-08-05 | 2009-08-05 | Light-frequency converting pulse oximeter |
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| CN2009201679777U CN201481422U (en) | 2009-08-05 | 2009-08-05 | Light-frequency converting pulse oximeter |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102319075A (en) * | 2011-08-17 | 2012-01-18 | 天津大学 | Blood oxygen saturation measuring device and measuring method |
| CN102512176A (en) * | 2011-12-06 | 2012-06-27 | 中国科学院深圳先进技术研究院 | Digital signal processing method for light-frequency conversion type pulse oximeter |
| CN110087545A (en) * | 2016-12-27 | 2019-08-02 | 阿尔卑斯阿尔派株式会社 | Sensor module and organism related information display system |
| JP2019528954A (en) * | 2016-09-29 | 2019-10-17 | コーニンクレッカ フィリップス エヌ ヴェＫｏｎｉｎｋｌｉｊｋｅ Ｐｈｉｌｉｐｓ Ｎ．Ｖ． | Optical vital sign sensor |
-
2009
- 2009-08-05 CN CN2009201679777U patent/CN201481422U/en not_active Expired - Lifetime
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102319075A (en) * | 2011-08-17 | 2012-01-18 | 天津大学 | Blood oxygen saturation measuring device and measuring method |
| CN102512176A (en) * | 2011-12-06 | 2012-06-27 | 中国科学院深圳先进技术研究院 | Digital signal processing method for light-frequency conversion type pulse oximeter |
| CN102512176B (en) * | 2011-12-06 | 2014-06-18 | 中国科学院深圳先进技术研究院 | Digital signal processing method for light-frequency conversion type pulse oximeter |
| JP2019528954A (en) * | 2016-09-29 | 2019-10-17 | コーニンクレッカ フィリップス エヌ ヴェＫｏｎｉｎｋｌｉｊｋｅ Ｐｈｉｌｉｐｓ Ｎ．Ｖ． | Optical vital sign sensor |
| CN110087545A (en) * | 2016-12-27 | 2019-08-02 | 阿尔卑斯阿尔派株式会社 | Sensor module and organism related information display system |
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Address after: Qin 066004 West Street in Hebei province Qinhuangdao City Economic and Technological Development Zone No. 112 Patentee after: Kangtai medical system (Qinhuangdao) Limited by Share Ltd Address before: 066004 Qinhuangdao city of Hebei province the Yellow River Development Zone West Road No. 24 Patentee before: Qinhuangdao Contec Medical Systems Co.,Ltd. |
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