CN102160791A - Self-mixing coherent laser radar invasive blood sugar measuring system - Google Patents
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Abstract
本发明公开了一种自混合相干激光雷达无创血糖测量系统;它包括:可调谐半导体激光器、光探测器和信号处理电路等。所述光探测器置于激光器的后端面或与激光器并排放置,信号处理电路与光探测器相连;本发明用一个无跳模可调谐半导体激光器取代可移动的机械臂,降低系统的机械精度要求,从而便于系统往小型、便携化发展;采用自混合相干的方法进一步简化系统,对信号进行放大,通过简单的元件和结构就能探测到微弱信号。
The invention discloses a self-mixing coherent laser radar non-invasive blood sugar measurement system; it includes: a tunable semiconductor laser, a light detector, a signal processing circuit and the like. The photodetector is placed on the rear face of the laser or placed side by side with the laser, and the signal processing circuit is connected to the photodetector; the present invention replaces the movable mechanical arm with a non-mode-hopping tunable semiconductor laser to reduce the mechanical precision requirements of the system , so as to facilitate the development of the system towards miniaturization and portability; the self-mixing coherent method is used to further simplify the system, amplify the signal, and detect weak signals through simple components and structures.
Description
技术领域technical field
本发明涉及一种可以实现人体无创血糖测量的系统,尤其涉及一种利用调频连续波激光雷达和自混合相干过程无创测量人体血糖浓度的系统。The invention relates to a system capable of realizing non-invasive blood sugar measurement of human body, in particular to a system for non-invasive measurement of human blood sugar concentration by using frequency modulation continuous wave laser radar and self-mixing coherent process.
背景技术Background technique
糖尿病是一种常见多发的疾病,随着人们生活水平的日益提高,糖尿病的发病率也在逐渐增加。近年来,糖尿病已经成为现代疾病中仅次于癌症和心血管疾病的第三大杀手,也被世界卫生组织列为三大疑难病之一。Diabetes is a common and frequently-occurring disease. With the improvement of people's living standards, the incidence of diabetes is gradually increasing. In recent years, diabetes has become the third killer of modern diseases after cancer and cardiovascular diseases, and it is also listed as one of the three difficult diseases by the World Health Organization.
随着人们对糖尿病关注度的增高,如何实现准确、方便、连续、无创测量血糖也成为研究机构讨论的热点。在众多的方案中,光学方法备受瞩目。As people pay more and more attention to diabetes, how to realize accurate, convenient, continuous and non-invasive blood glucose measurement has also become a hot topic in research institutions. Among the many solutions, the optical method has attracted much attention.
血糖浓度光学测量方法从检测对象上来说可以分为两种方式:直接方式和间接方式。直接方式主要是通过对葡萄糖分子本身特性的检测获得血糖浓度,一般选择光谱分析的方法,包括近红外(NIR)光谱分析法、旋光偏振法及拉曼(RAMAN)光谱分析法等;而间接方式则是通过检测血糖对人体血液及组织特性的影响来推算血糖的浓度,一般选择散射分析的方法,检测对象包括组织对光的散射系数,组织液的折射率等。The optical measurement method of blood glucose concentration can be divided into two methods in terms of detection objects: direct method and indirect method. The direct method is mainly to obtain the blood glucose concentration through the detection of the characteristics of the glucose molecule itself. Generally, the method of spectral analysis is selected, including near-infrared (NIR) spectral analysis method, optical polarization method and Raman (RAMAN) spectral analysis method, etc.; while the indirect method The concentration of blood sugar is calculated by detecting the influence of blood sugar on human blood and tissue characteristics. Generally, the method of scattering analysis is selected. The detection objects include the scattering coefficient of tissue to light, the refractive index of interstitial fluid, etc.
目前研究比较多的近红外光谱分析法主要是通过对葡萄糖分子的特征吸收峰强度来进行血糖监测。尽管三十多年来,人们在这一方面进行了大量研究,也取得了很大的进步,但是到目前为止还没有一个可信的工作系统。该方法存在的主要问题是:葡萄糖分子在近红外光谱区没有一个确定的吸收形式;光谱中包含除了葡萄糖以外的其它物质的吸收光谱,这些信号会重叠在一起相互干扰;吸收信号会受到散射信号的极大干扰。Near-infrared spectroscopic analysis, which has been widely studied at present, is mainly used to monitor blood sugar through the characteristic absorption peak intensity of glucose molecules. Although a great deal of research has been done and great progress has been made in this area for more than three decades, there is no credible working system so far. The main problems of this method are: the glucose molecule does not have a definite absorption form in the near-infrared spectral region; the spectrum contains the absorption spectra of other substances except glucose, and these signals will overlap and interfere with each other; the absorption signal will be affected by the scattering signal. great interference.
另一种背景技术利用组织的散射特性来进行血糖分析。在近红外光波段,组织体对光的散射要远远强于吸收,通过对散射光谱的分析可以间接地得到组织体的折射率、散射系数等信息,用合适的理论对其进行处理后即可得到相应的血糖浓度。这种方法相对近红外光谱分析法的优势在于在近红外波段,皮肤对光的散射远大于吸收,从而可以获得较高的信噪比。因此可以考虑从散射分析入手找到一种能达到精度要求的无创血糖测量方法。Another background technique utilizes the scattering properties of tissue for blood glucose analysis. In the near-infrared band, the light scattering of the tissue body is much stronger than the absorption. Through the analysis of the scattering spectrum, the information such as the refractive index and scattering coefficient of the tissue body can be obtained indirectly. After processing it with a suitable theory, the The corresponding blood glucose concentration can be obtained. The advantage of this method over near-infrared spectroscopy is that in the near-infrared band, the skin's light scattering is much greater than its absorption, so a higher signal-to-noise ratio can be obtained. Therefore, it can be considered to start with scattering analysis to find a non-invasive blood glucose measurement method that can meet the precision requirements.
一种利用光学相干层析成像方法来测量人体血糖值的背景技术如V. Larin,M. Motamedi,S. Eledrisi等在他们的文章“Noninvasive Blood Glucose Monitoring With Optical Coherence Tomography”,Diabetes Care,VOL.25,pp.2263~2267,2002中所描述。该系统采用一个1300nm波段的超辐射发光二极管(SLD)作为光源,系统核心为一个迈克尔逊干涉仪。光源发出的光经过分束镜,一部分照射在目标探测物上,一部分作为参考光束照射到一个平面反射镜上,反射回来的探测光和参考光同时进入光探测器发生干涉。系统通过机械臂对参考端的光程进行调制来获得探测物不同层次的信息,并建立起信号斜率与血糖浓度之间的关系。这种无创血糖测量的方法存在的问题是:系统中需要引入一个可移动的机械臂,扫描速度较慢且不利于系统的小型化、便携化;系统信号的强度与探测物反射率有关,当被探测物反射率较小的时候,所得信号很微弱,因此很难实现对极微弱散射光的测量。A kind of background technology that utilizes the optical coherence tomography method to measure the blood glucose level of human body such as V. Larin, M. Motamedi, S. Eledrisi etc. in their article "Noninvasive Blood Glucose Monitoring With Optical Coherence Tomography", Diabetes Care, VOL. 25, pp.2263~2267, described in 2002. The system uses a 1300nm band superluminescent light-emitting diode (SLD) as a light source, and the core of the system is a Michelson interferometer. The light emitted by the light source passes through the beam splitter, and part of it is irradiated on the target detection object, and part of it is irradiated on a plane mirror as a reference beam, and the reflected detection light and reference light enter the photodetector at the same time for interference. The system modulates the optical path of the reference end through the mechanical arm to obtain different levels of information of the detected object, and establishes the relationship between the signal slope and the blood glucose concentration. The problem with this method of non-invasive blood glucose measurement is that a movable mechanical arm needs to be introduced into the system, and the scanning speed is slow and it is not conducive to the miniaturization and portability of the system; the strength of the system signal is related to the reflectivity of the detection object. When the reflectivity of the detected object is small, the obtained signal is very weak, so it is difficult to measure the extremely weak scattered light.
发明内容Contents of the invention
本发明的目的在于针对现有技术的不足,提供了一种自混合相干激光雷达无创血糖测量系统。The purpose of the present invention is to provide a self-mixing coherent laser radar non-invasive blood sugar measurement system for the deficiencies of the prior art.
本发明的目的是通过以下技术方案来实现的:一个利用调频连续波激光雷达实现无创血糖测量的系统,它包括:可调谐半导体激光器、光探测器和信号处理电路等。所述光探测器置于激光器的后端面或与激光器并排放置,信号处理电路与光探测器相连;可调谐半导体激光器发出的光经被测皮下组织散射后返回被光探测器接收,所述光探测器探测光强变化信号并将其发送给信号处理电路;所述信号处理电路包括滤波模块和微处理器模块,两个模块并行独立运行,所述滤波模块包含两个不同频率的滤波器;信号处理电路分析光强变化信号的频谱信息,根据光强随频率变化的关系推算血糖浓度。The object of the present invention is achieved through the following technical solutions: a system for realizing non-invasive blood glucose measurement by using frequency-modulated continuous wave laser radar, which includes: tunable semiconductor laser, optical detector and signal processing circuit, etc. The photodetector is placed on the rear end face of the laser or placed side by side with the laser, and the signal processing circuit is connected to the photodetector; the light emitted by the tunable semiconductor laser is scattered by the subcutaneous tissue under test and then returned to be received by the photodetector. The detector detects the light intensity change signal and sends it to the signal processing circuit; the signal processing circuit includes a filtering module and a microprocessor module, the two modules operate independently in parallel, and the filtering module includes two filters of different frequencies; The signal processing circuit analyzes the spectrum information of the light intensity change signal, and calculates the blood sugar concentration according to the relationship between the light intensity and the frequency change.
进一步地,所述探测器置于扫频激光器后端,所述可调谐半导体激光器发出的光经被测组织散射后返回激光器进行自混合相干过程,置于激光器后端的探测器探测由自混合相干引起的激光器发射光强变化信号。Further, the detector is placed at the back end of the frequency-sweeping laser, and the light emitted by the tunable semiconductor laser is scattered by the measured tissue and returns to the laser to perform a self-mixing coherent process. The detector placed at the back end of the laser detects The resulting laser emits a light intensity change signal.
进一步地,所述探测器与扫频激光器并排放置,所述探测器探测由皮肤表面反射光和被测皮下组织散射光相干引起的光强变化信号。Further, the detector is placed side by side with the frequency-sweeping laser, and the detector detects a light intensity change signal caused by coherence between light reflected from the skin surface and scattered light from the subcutaneous tissue under test.
进一步地,所述可调谐半导体激光器为无跳模可调谐半导体激光器。Further, the tunable semiconductor laser is a mode-hop-free tunable semiconductor laser.
进一步地,对可调谐激光器进行周期性频率调制,使其出射光波的频率,呈周期性快速连续变化。Further, periodic frequency modulation is performed on the tunable laser, so that the frequency of the emitted light wave changes periodically and rapidly continuously.
进一步地,所述周期性频率调制为锯齿波或三角波函数。Further, the periodic frequency modulation is a sawtooth or triangular wave function.
进一步地,所述可调谐半导体激光器中心波长位于850nm附近的近红外波段。Further, the central wavelength of the tunable semiconductor laser is in the near-infrared band around 850nm.
进一步地,所述所述滤波模块包含两个不同频率的滤波器,所述滤波器对光探测器探测到的激光器输出光强变化信号进行滤波,根据得到的在这2个不同频率的信号强度差推算组织的散射系数和组织液中的血糖浓度。Further, the filtering module includes two filters of different frequencies, and the filters filter the output light intensity change signal of the laser detected by the photodetector, according to the obtained signal intensities at the two different frequencies The difference is used to estimate the scattering coefficient of the tissue and the blood glucose concentration in the interstitial fluid.
进一步地,所述微处理器模块对光探测器探测到的激光器输出光强变化信号进行快速傅立叶变换获得输出信号的频谱,通过信号频率与其所经历的光程的关系获得信号随散射光程长度的变化曲线,从而进一步推算组织的散射系数和组织液中的血糖浓度。Further, the microprocessor module performs fast Fourier transform on the laser output light intensity change signal detected by the photodetector to obtain the frequency spectrum of the output signal, and obtains the signal from the relationship between the signal frequency and the optical path length experienced by the signal. The change curve of the tissue, so as to further calculate the scattering coefficient of the tissue and the blood glucose concentration in the interstitial fluid.
本发明的有益效果是,本发明用一个无跳模可调谐半导体激光器取代可移动的机械臂,降低系统的机械精度要求,从而便于系统往小型、便携化发展;采用自混合相干的方法进一步简化系统,对信号进行放大,通过简单的元件和结构就能探测到微弱信号。The beneficial effect of the present invention is that the present invention replaces the movable mechanical arm with a non-mode-hopping tunable semiconductor laser, which reduces the mechanical precision requirements of the system, thereby facilitating the development of the system towards miniaturization and portability; the method of self-mixing coherence is further simplified The system amplifies the signal and detects weak signals through simple components and structures.
附图说明Description of drawings
图1为本发明实施方式:激光雷达调频连续波与自混合相干技术相结合实现无创血糖测量的结构示意图。Fig. 1 is a schematic structural diagram of an embodiment of the present invention: combining laser radar frequency modulation continuous wave and self-mixing coherent technology to realize non-invasive blood glucose measurement.
图2为本发明的另一种实施方式:激光雷达调频连续波技术实现无创血糖测量的结构示意图。探测器与扫频激光器并排放置,探测由皮肤表面反射光和被测皮下组织散射光相干引起的光强变化信号。FIG. 2 is another embodiment of the present invention: a structural schematic diagram of non-invasive blood glucose measurement realized by laser radar frequency modulation continuous wave technology. The detector and the frequency-sweeping laser are placed side by side to detect the light intensity change signal caused by the coherence of the reflected light from the skin surface and the scattered light from the subcutaneous tissue under test.
图3为激光雷达调频连续波与自混合相干技术相结合实现无创血糖测量系统的运作流程示意图。Fig. 3 is a schematic diagram of the operation flow of the non-invasive blood glucose measurement system realized by combining laser radar frequency modulation continuous wave and self-mixing coherent technology.
图4为自混合相干技术的工作原理详细示意图。Fig. 4 is a detailed schematic diagram of the working principle of the self-mixing coherent technology.
图5为调制信号和到达探测器的信号光束的频率变化波形简易示意图。图(a)。Fig. 5 is a simplified schematic diagram of frequency variation waveforms of the modulated signal and the signal beam reaching the detector. Figure (a).
图6为对探测器获得信号做快速傅里叶变换以后的频谱图。Fig. 6 is a spectrogram after performing fast Fourier transform on the signal obtained by the detector.
图7为信号处理部分软件流程图。Figure 7 is a software flow chart of the signal processing part.
图8为自混合相干激光雷达无创血糖测量系统对不同葡萄糖浓度下的人体组织液的信号的FFT变换图.Fig. 8 is the FFT transformation diagram of the signal of human interstitial fluid under different glucose concentrations by the self-mixing coherent lidar non-invasive blood glucose measurement system.
图9为对FFT信号取对数的图。Fig. 9 is a graph of taking the logarithm of the FFT signal.
图10为仿真信号斜率与组织散射系数的对比图。Fig. 10 is a comparison chart of the simulated signal slope and the tissue scattering coefficient.
具体实施方式Detailed ways
本发明将激光雷达调频连续波技术和自混合相干技术应用到无创血糖测量上来,实现了以简单的系统完成无创血糖浓度检测。The invention applies laser radar frequency modulation continuous wave technology and self-mixing coherent technology to non-invasive blood sugar measurement, and realizes non-invasive blood sugar concentration detection with a simple system.
不失其通用性,下面将以锯齿波作为可调谐半导体激光器调制信号为例来说明系统的工作原理。Without losing its versatility, the working principle of the system will be explained below by taking the sawtooth wave as the modulation signal of the tunable semiconductor laser as an example.
图4为自混合相干干涉系统工作原理的详细示意图。激光器出射光波的频率可以表示为:Fig. 4 is a detailed schematic diagram of the working principle of the self-mixing coherent interference system. The frequency of the light wave emitted by the laser can be expressed as:
(1) (1)
上式中,表示锯齿调制信号的斜率,表示调制初始频率。In the above formula, Indicates the slope of the sawtooth modulated signal, Indicates the modulation initial frequency.
如图4所示,假设经历光程为的光波,其背向散射光强为,将处看作一个虚拟的反射面,则可以引入反射率概念:As shown in Figure 4, it is assumed that the experienced optical path is The light wave has a backscattered light intensity of , and the point is regarded as a virtual reflective surface, then the concept of reflectivity can be introduced:
(2) (2)
上式中,为激光器出射的初始光强,散射系数与光在皮肤组织中的衰减有关。In the above formula, is the initial light intensity emitted by the laser, and the scattering coefficient is related to the attenuation of light in skin tissue.
那么扫频半导体激光器的后端面,前端面与通过皮肤组织散射回来的经历不同光程的光所对应的虚拟反射面之间就构成了一个复合谐振腔(compound cavity)。根据自混合相干理论,背向散射光对激光器出射功率所带来的影响可以表示为:Then, a compound cavity is formed between the rear end face and the front face of the frequency-sweeping semiconductor laser and the virtual reflection face corresponding to the light scattered back through the skin tissue and experiencing different optical paths. According to the self-mixing coherence theory, the influence of backscattered light on the output power of the laser can be expressed as:
(3) (3)
(4) (4)
上式中为有散射光影响时激光器的阈值增益,表示无散射光影响时激光器的阈值增益,表示激光器腔长,表示上述虚拟反射面与激光器后端面所组成的新谐振腔腔长,表示散射进入激光器的光波的频率,表示外部反馈系数:In the above formula is the threshold gain of the laser under the influence of scattered light, Indicates the threshold gain of the laser without the influence of scattered light, is the laser cavity length, Indicates the cavity length of the new resonant cavity formed by the above-mentioned virtual reflector and the rear end face of the laser, represents the frequency of light waves scattered into the laser, Denotes the external feedback coefficient:
(5) (5)
表示激光器前端面的反射系数,表示前述虚拟反射面的反射系数。 Indicates the reflection coefficient of the front face of the laser, Indicates the reflection coefficient of the aforementioned virtual reflective surface.
对其进行简化可以得到:Simplifying it gives:
(6) (6)
上式中由激光器本身参数决定,由激光器调制参数决定,由激光器调制参数与光束所经历过程共同决定。In the above formula Determined by the parameters of the laser itself, Determined by the laser modulation parameters, It is determined by the modulation parameters of the laser and the process experienced by the beam.
由此可以看出,激光器输出功率的变化为不同频率余弦函数的线性叠加,频率值由光束所经历的光程决定,对应该频率的幅值大小由相应的反射系数决定,系统对信号的放大由激光器本身参数决定。根据上文对反射系数的定义,这里的反射系数与光在组织中传播的衰减系数有关,那么通过快速傅立叶变换得到信号频谱,就能分析光束所经历光程与其光强衰减量之间的关系,如图5和图6所示。It can be seen from this that the change of the output power of the laser is a linear superposition of cosine functions of different frequencies, the frequency value is determined by the optical path experienced by the beam, and the amplitude corresponding to the frequency is determined by the corresponding reflection coefficient. It is determined by the parameters of the laser itself. According to the definition of reflection coefficient above, the reflection coefficient here is related to the attenuation coefficient of light propagating in tissue, then the signal spectrum can be obtained by fast Fourier transform, and the relationship between the optical path experienced by the beam and its light intensity attenuation can be analyzed , as shown in Figure 5 and Figure 6.
已有研究表明,光在组织中的传输满足Beer-Lambert定理:Existing studies have shown that the transmission of light in tissues satisfies the Beer-Lambert theorem:
(7) (7)
上式中表示入射光强,表示反射回来的光强,表示光在组织中传播的光程,由下式决定:In the above formula Indicates the incident light intensity, Indicates the reflected light intensity, Indicates the optical path of light propagating in the tissue, It is determined by the following formula:
(8) (8)
上式中表示组织的吸收系数,表示组织的散射系数。In the above formula represents the tissue absorption coefficient, Indicates the scattering coefficient of the tissue.
背景技术的研究已证明,近红外光入射时,在皮肤组织中吸收系数远远小于散射系数,因此光在组织中的衰减指数主要受散射系数影响。Research on the background technology has proved that when near-infrared light is incident, the absorption coefficient in skin tissue is much smaller than the scattering coefficient, so the attenuation index of light in tissue is mainly affected by the scattering coefficient.
根据Mie散射理论,血糖浓度升高时,人体组织散射系数将随之减小。由前述分析可得,从自混合相干系统所得的信号中可以提取出组织散射系数,从而通过实验标定可以得到血糖浓度变化与频域信号斜率之间的关系。According to the Mie scattering theory, when the blood sugar concentration increases, the scattering coefficient of human tissue will decrease accordingly. From the foregoing analysis, it can be concluded that the tissue scattering coefficient can be extracted from the signal obtained from the self-hybrid coherent system, so that the relationship between the blood glucose concentration change and the signal slope in the frequency domain can be obtained through experimental calibration.
不失其通用性,下面将仍以锯齿波作为可调谐激光器调制信号为例来说明该系统在信号放大上的优势:Without losing its versatility, the following will still take the sawtooth wave as the modulation signal of the tunable laser as an example to illustrate the advantages of the system in signal amplification:
如上述推导,自混合相干激光雷达无创血糖测量方法所得有效信号可以表示为:As deduced above, the effective signal obtained by the self-hybrid coherent lidar non-invasive blood glucose measurement method can be expressed as:
(9) (9)
上式中表示激光器前端面的反射系数,由激光器调制参数决定。In the above formula Indicates the reflection coefficient of the front face of the laser, Determined by laser modulation parameters.
同样按照上述推导方法,引入虚拟反射面,背景技术中所述啁啾光学相干层析成像法在对皮肤组织进行探测的时候,所得信号可以表示如下:Also according to the above derivation method, a virtual reflection surface is introduced. When the chirped optical coherence tomography method described in the background technology detects skin tissue, the obtained signal can be expressed as follows:
(10) (10)
上式中表示对应光波经历光程的时间延时,为对应虚拟反射面的反射系数()。In the above formula Indicates the time delay of the corresponding light wave through the optical path, for correspondence The reflection coefficient of the virtual reflector ( ).
那么探测器所得到的干涉信号可以表示为:Then the interference signal obtained by the detector can be expressed as:
(11) (11)
上式中表示光源的频率调制斜率,为参考镜面反射系数。In the above formula Indicates the frequency modulation slope of the light source, is the reference specular reflection coefficient.
比较可得自混合相干系统对信号的放大倍数可以表示为:Comparing the amplification factors that can be obtained from the hybrid coherent system to the signal can be expressed as:
(12) (12)
由此可见放大倍数主要由激光器端面反射率决定。It can be seen that the magnification Mainly by the reflectivity of the laser end face Decide.
下面将根据附图和实施例,具体说明此发明,本发明的目的和效果将变得更加明显。The invention will be described in detail below according to the accompanying drawings and embodiments, and the purpose and effect of the invention will become more obvious.
图1为本发明的一种实施方式的示意图。如图1所示,本发明的自混合相干激光雷达无创血糖测量系统由三部分组成:可调谐半导体激光器、光探测器和信号处理电路。Fig. 1 is a schematic diagram of an embodiment of the present invention. As shown in Figure 1, the self-mixing coherent lidar non-invasive blood glucose measurement system of the present invention consists of three parts: a tunable semiconductor laser, a light detector and a signal processing circuit.
激光器可以采用中心波长在850nm附近的相干长度较长的无跳模可调谐半导体激光器。The laser can adopt a non-mode-hopping tunable semiconductor laser with a center wavelength near 850nm and a long coherence length.
将激光器固定在待测皮肤组织上方,使其出射的激光能照射到皮肤组织,并保证由皮肤组织散射回的信号光能够再次进入激光器。将光探测器放置在激光器的后端面,监测激光器输出光波的光强变化。光探测器输出的信号将由信号处理电路进行数据处理。Fix the laser above the skin tissue to be tested, so that the laser light emitted by it can irradiate the skin tissue, and ensure that the signal light scattered by the skin tissue can enter the laser again. A photodetector is placed on the rear end face of the laser to monitor the light intensity change of the laser output light wave. The signal output by the light detector will be processed by the signal processing circuit.
信号处理电路包括两个模块:滤波模块和微处理器模块,两个模块并行独立运行。滤波模块包含两个不同频率的滤波器,分别对光探测器的输出信号进行滤波;微处理器模块通过软件对光探测器的输出信号进行数据处理,信号处理的软件流程图如图7所示。The signal processing circuit includes two modules: a filter module and a microprocessor module, and the two modules run in parallel and independently. The filter module contains two filters with different frequencies, which respectively filter the output signal of the photodetector; the microprocessor module performs data processing on the output signal of the photodetector through software, and the software flow chart of signal processing is shown in Figure 7 .
该实施方式的工作过程如下:对可调谐激光器进行周期性频率调制,如以锯齿波或三角波的形式调制,使其出射光波的频率(波长)呈周期性快速线性连续变化。激光器的出射光束照射到皮肤组织上,有部分背向散射光将返回耦合进入激光腔内,在激光腔中完成一个自混合相干过程,实现光程信息到激光器出射光强频率信息的转换。此时放置在激光器后侧的探测器接收由自混合相干引起的激光器发射光强变化信号,将其转换为电信号输入信号处理电路。信号处理电路中的滤波模块包含两个不同频率的滤波器,分别对光探测器的输出信号进行滤波,得到在两个不同频率的信号强度。前述分析表明,它们分别代表经历不同光程长度的散射信号,可以通过两者之间的强度差推算组织的散射系数和组织液中的血糖浓度。信号处理电路中的微处理器模块首先对接收到的信号进行快速傅立叶变换获得信号的频谱,并通过信号频率与其所经历的光程的关系建立起信号随散射光程长度的变化曲线;接着对滤波器输出信号与通过快速傅立叶变换所获得信号频谱进行比较修正;最后参照医学参数建立系统信号与人体血糖浓度之间的对应关系。整个系统无需可移动精密机械部件,能够满足仪器小型化、便携化的需要;同时根据前述分析,散射光在激光腔中的自混合相干能对信号进行放大,放大倍数可通过对激光器端面反射率进行合理设计来确定,无需再加外部放大电路,降低了引入电噪声的风险。The working process of this embodiment is as follows: periodic frequency modulation is performed on the tunable laser, such as in the form of a sawtooth wave or a triangular wave, so that the frequency (wavelength) of the outgoing light wave changes periodically, rapidly and linearly. The output beam of the laser is irradiated on the skin tissue, and some of the backscattered light will be coupled back into the laser cavity, and a self-mixing coherent process is completed in the laser cavity to realize the conversion from the optical path information to the frequency information of the laser output light intensity. At this time, the detector placed on the back side of the laser receives the light intensity change signal emitted by the laser caused by self-mixing coherence, and converts it into an electrical signal for input to the signal processing circuit. The filter module in the signal processing circuit includes two filters with different frequencies, which respectively filter the output signal of the photodetector to obtain signal strengths at two different frequencies. The above analysis shows that they respectively represent scattering signals with different optical path lengths, and the scattering coefficient of the tissue and the blood glucose concentration in the interstitial fluid can be estimated from the intensity difference between the two. The microprocessor module in the signal processing circuit first performs fast Fourier transform on the received signal to obtain the spectrum of the signal, and establishes the change curve of the signal with the scattered optical path length through the relationship between the signal frequency and the optical path it has experienced; The output signal of the filter is compared and corrected with the signal spectrum obtained by the fast Fourier transform; finally, the corresponding relationship between the system signal and the blood sugar concentration of the human body is established with reference to the medical parameters. The whole system does not need movable precision mechanical parts, and can meet the needs of miniaturization and portability of the instrument; at the same time, according to the above analysis, the self-mixing coherence of scattered light in the laser cavity can amplify the signal, and the magnification can be determined by the reflectivity of the laser end face It is determined by a reasonable design that there is no need to add an external amplifier circuit, which reduces the risk of introducing electrical noise.
附图8和9给出了该实施例的仿真计算结果。仿真采用蒙特卡洛方法对光子在组织中的传输进行追踪,组织模型选用人体组织液参数。从图中可以看到,葡萄糖浓度增大时FFT信号的衰减斜率减小,这说明该系统信号的斜率能够反映溶液中葡萄糖浓度的变化。Accompanying drawing 8 and 9 has provided the simulation calculation result of this embodiment. The simulation uses the Monte Carlo method to track the transmission of photons in the tissue, and the tissue model uses the parameters of human tissue fluid. It can be seen from the figure that the attenuation slope of the FFT signal decreases when the glucose concentration increases, which shows that the slope of the system signal can reflect the change of the glucose concentration in the solution.
附图10为葡萄糖浓度连续变化时,仿真所得信号斜率与Mie散射理论计算所得散射系数之间的比较。从图中可以看出信号斜率随葡萄糖浓度变化增大而降低,与Mie散射理论计算值基本符合。当葡萄糖浓度变化20mM时,相应的信号斜率变化约10dB/mm。假设激光雷达在皮下组织的有效测量范围为1mm,探测器的探测精度为0.1 dB,则理论上系统对血糖探测的灵敏度可达0.2mM,即3.6mg/dL,可以满足便携式血糖监测的要求。Accompanying drawing 10 is the comparison between the signal slope obtained by simulation and the scattering coefficient calculated by Mie scattering theory when the glucose concentration changes continuously. It can be seen from the figure that the signal slope decreases with the increase of glucose concentration, which is basically consistent with the calculated value of Mie scattering theory. When the glucose concentration changes by 20mM, the corresponding signal slope changes by about 10dB/mm. Assuming that the effective measurement range of the lidar in the subcutaneous tissue is 1 mm, and the detection accuracy of the detector is 0.1 dB, the theoretical sensitivity of the system to blood sugar detection can reach 0.2 mM, that is, 3.6 mg/dL, which can meet the requirements of portable blood sugar monitoring.
图2为本发明的第二种实施方式的示意图。如图2所示,该实施方式由三部分组成:可调谐半导体激光器、光探测器和信号处理电路。Fig. 2 is a schematic diagram of a second embodiment of the present invention. As shown in Figure 2, this embodiment consists of three parts: a tunable semiconductor laser, a photodetector and a signal processing circuit.
激光器可以采用中心波长在850nm附近的相干长度较长的无跳模可调谐半导体激光器。The laser can adopt a non-mode-hopping tunable semiconductor laser with a center wavelength near 850nm and a long coherence length.
将激光器固定在待测皮肤组织上方,使其出射的激光能照射到皮肤组织。光探测器与激光器并排放置,接收由皮肤散射回的携带血糖信号的光束。光探测器输出的信号将由信号处理电路进行数据处理。Fix the laser above the skin tissue to be tested so that the laser light emitted from it can irradiate the skin tissue. A photodetector is placed alongside the laser and receives the beam of light that carries the blood sugar signal scattered back from the skin. The signal output by the light detector will be processed by the signal processing circuit.
该实施方式的信号处理电路与第一种实施方式相同。The signal processing circuit of this embodiment is the same as that of the first embodiment.
该实施方式的工作方式如下:对可调谐激光器进行周期性频率调制,如以锯齿波或三角波的形式调制,使其出射光波的频率(波长)呈周期性快速线性连续变化。激光器的出射光束照射到皮肤组织上,一部分作为参考光束在皮肤表面被反射,一部分作为信号光束经皮下组织散射,信号光和散射光同时被光探测器接收。由于信号光束与散射光束之间存在光程差,两者在探测器上相互干涉,探测器接收到的光强信号随时间变化,信号频谱包含血糖浓度信息。将探测器接收到的信号输入信号处理电路进行数据分析。信号处理电路工作方式与第一种实施方式相同。The working method of this embodiment is as follows: the tunable laser is periodically frequency modulated, such as in the form of a sawtooth wave or a triangular wave, so that the frequency (wavelength) of the outgoing light wave changes periodically, rapidly and linearly. The output beam of the laser is irradiated on the skin tissue, part of it is reflected on the skin surface as a reference beam, and part of it is scattered through the subcutaneous tissue as a signal beam, and the signal light and scattered light are received by the photodetector at the same time. Due to the optical path difference between the signal beam and the scattered beam, the two interfere with each other on the detector, the light intensity signal received by the detector changes with time, and the signal spectrum contains blood glucose concentration information. The signal received by the detector is input into the signal processing circuit for data analysis. The working mode of the signal processing circuit is the same as that of the first embodiment.
本发明结构上更简单,无需专门设立参考镜面,使系统结构紧凑、简单,适合实现无创血糖测量方法的小型化、便携化;另一方面,系统自混合相干对信号进行放大,探测微弱信号时无需再加外部放大电路,降低了引入电噪声的风险,提高了血糖探测的灵敏度。The present invention is simpler in structure, does not need to set up a special reference mirror, makes the system compact and simple, and is suitable for realizing the miniaturization and portability of the non-invasive blood glucose measurement method; There is no need to add an external amplifier circuit, which reduces the risk of introducing electrical noise and improves the sensitivity of blood glucose detection.
以上内容仅为本发明的实施例,其目的并非用于对本发明所提出的系统及方法的限制。在本发明的精神和权利要求的保护范围内,对本发明做出的任何修改和改变,都落入本发明的保护范围。例如,本发明也适用于探测溶液的浓度、探测物质的散射系数等应用。The above content is only an embodiment of the present invention, and its purpose is not to limit the system and method proposed by the present invention. Within the spirit of the present invention and the protection scope of the claims, any modifications and changes made to the present invention fall within the protection scope of the present invention. For example, the present invention is also applicable to applications such as detecting the concentration of a solution, detecting the scattering coefficient of a substance, and the like.
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