| Diabetes is a serious disease to human health. At present, there is no cure and effective treatment of diabetes, usually through frequent testing and insulin injections to carry out strict control of blood glucose concentration in order to reduce or mitigate the cause of long-term complications of diabetes. Invasive blood glucose testing technology has been widely used in hospitals for clinical diagnosis and family health care. However, this technology is inconvenient to people with diabetes because it exists issues such as limited measuring frequency, likely to cause discomfort, or even infections, as well as the high cost, due to the need for blood. So,non-invasive blood glucose detection technology research has become hot topics in the field of the international biomedical research. Many domestic and foreign research institutions and companies are actively pursuing their research, according to different principles, a variety of detection methods, including electrochemistry, microwave technology, electromagnetic sensing principle, thermal spectroscopy, electrical impedance spectroscopy, body fluids (saliva, sweat, urine, etc.) collection and optical methods etc. Compared with other methods, optical (or derivative technology) method is a rapid, non-invasive, multidimensional characteristics of information and is used in the most. By shining light through human interstitial fluids at translucent dermal positions such as finger tips, ear lobes, or through ocular aqueous humor in the eyes, information about the glucose levels including the speed of light, phase, intensity, frequency, polarization angle can be obtained optically by near-infrared spectroscopy, mid-infrared spectroscopy, polarizer, Raman spectroscopy, photo acoustic spectroscopy, optical coherence imaging measurement method.Indeed, investigation of the polarization changes induced by glucose is an ancient technique for noninvasive glucose measurement in human. Because a glucose solution rotates a polarized light beam's polarization proportional to its concentration, various polarized metric glucose sensors have been developed, such as using Faraday rotators to directly modulate the beam's polarization state or using a Zeeman laser in optical heterodyne detection. In the study of polarization change, direct photoelectric detection system has the advantage of easy, but because of the poor sensitivity, it is almost no employed. Heterodyne method is most used in investigation of the polarization changes because of its high sensitivity. However, the disadvantages of this method are that it is sensitive to phase change, large drift, and frequently calibration.Great deal of research work about non-invasive glucose monitor method was carried out. Despite considerable progress, however, until now truly non-invasive glucose monitor in blood is not a reality. In this paper, the non-invasive blood glucose measurement technology of polarized light is studied deeply and systematically to overcome the limitation of the current non-invasive blood glucose measurement technology.(1) First, we have launched a new orthogonal twin-polarized light (OTPL) non-invasive method which allows us to measure the blood glucose level through aqueous humor by a noninvasive optical method, without blood test or use lancets, therefore without extraction, which converts micro-angle rotated by optical active substance such as glucose to energy difference of OTPL, amplifies the signals by high-sensitivity lock-in amplifier made of relevant principle, controls Faraday coil current to compensate changes in deflection angle caused by blood glucose, and calculates to obtain blood glucose concentration using the linear relationship between blood glucose concentration and Faraday coil current. Comparing with optical heterodyne detection, this approach not only improves the measurement sensitivity, but also eliminated the impact of the phase.(2) An OTPL blood glucose measurement experimental system has been developed. Collimated beam from a laser diode passed through polarizer becomes linearly polarized light. The light is modulated by a photo modulator which was driven by Positive and Negative Alternation Square Wave Signals (PNASWS) generated by functional generator and amplified by power amplifier. The intensity of the modulated light is detected by photo detector. When sample is placed on beam path, so signal difference is detected by photo detector and is finally detected by lock-in amplifier. Especially the Faraday rotator is introduced as the calibration the light path and the compensation of rotation angle caused by rotation of material. The current loaded into the Faraday rotator coils can be an important parameter to calculate blood glucose concentration.(3) With the developed experimental system of OTPL, experiments of glucose concentration measurement of glucose solution and serum solution are conducted. In glucose solution experiment, the lowest concentration of glucose 40mg/dl, a correlation coefficient of 0.9821, the average standard deviation of glucose concentration for the 12.47mg/dl are measured; In serum solution experiments, the lowest concentration of glucose 64mg/dl, a correlation coefficient of 0.95, the average standard deviation of glucose concentration of 20.63mg/dl are measured. Obviously, the linearity of glucose solution is better than serum solution, because of single component of the glucose solution, transmission better, while serum solution containing ingredients other than the addition of glucose, and transmission poor, in the same tine, the other components in the solution may also affect the measurement.Comparing with experimental results of standard deviation of 25mg/dl, the use of a heterodyne polarimeter measurement of optical rotation method of active media, performed by Chien-ming Wu, etc., this study measured serum solution rotation experiment, the average standard deviation of glucose concentration with a considerable. Comparing with the heterodyne Polari meter measurement of optical rotation of activity of media conducted by Chien-ming Wu, etc. in 2006, that the standard deviation of Chien-ming Wu test was 25mg/dl, this study shows the average standard deviation of glucose concentration obviously reduce, while in the serum solution experimental, the average standard deviation of glucose concentration is 20.63mg/dl, and while in the glucose experiments, the average standard deviation of glucose concentrations is 12.47mg/dl. These results indicate that OTPL can measure glucose solution at human blood glucose levels, and the OTPL method's feasibility is approved experimentally.Optical rotation experiments of the relevant material such as local anesthetics pentobarbital sodium and anticoagulant lithium heparin are carried out. Optical rotation experiment of similar concentrations of anesthetic pentobarbital sodium shows that the experimental concentration of this solution has strong L-optical properties, which equals to 1000mg/dl glucose solution numerically, and would have a significant effect to the OTPL optical rotation experiment of rabbit serum solution. Therefore, in the following OTPL optical rotation experiment of rabbit serum solution, we do not use anesthetic pentobarbital sodium to get rabbit blood , but take rabbit blood directly from the rabbit heart. Although anticoagulant lithium heparin with a certain amount of optical rotation properties, OTPL optical rotation experiment of the lithium heparin shows that in the experimental lithium heparin concentration (4ml of distilled water per tube), no significant rotation effect is found. Therefore,using the experimental concentration of heparin lithium as anticoagulant does not affect the experiment.(4) The major defects of OTPL non-invasive blood glucose measurement are high modulation voltage, and with square-wave voltage mutations interfere. The measuring principle of polarized light modulated by sine wave is analysised theoretically. Based on the current measurement method of OTPL, in order to reduce the OTPL high modulation voltage, and square-wave voltage interfere with the impact of mutations, and further proposed a sine wave modulation of the polarized light method. A theoretical analysis of the detected signal is launched and conducted With the Jones matrix and the Bessel functions, which is decomposed into 3 components--dc component, fundamental frequency, harmonic component. Lock-in amplifier locks processing baseband component from the phase and frequency, and outputs DC voltage, and thus obtain relationship of blood glucose concentration and the lock-in amplifier output DC voltage. A experimentof polarized light modulated by Sine wave to measure the concentration of glucose solution is performed. In glucose solution experiment, the lowest concentration of glucose 64mg/dl, a correlation coefficient of 0.9852, an] average standard deviation of glucose concentration for the 43.06mg/dl are measured. Experimental result shows that there is also good linearity in measurement of polarized light modulated by Sine wave t, also to achieve the level of human blood glucose levels, but the average standard deviation of the glucose concentration is much greater than that of OTPL measurement. The stability and the sensitivity of the measurement of polarized light modulated by Sine wave is bad than that of OTPL measurement, but the lower voltage of polarized light modulated by Sine wave is its outstanding advantage.This study has laid a good foundation of furthering the non-invasive blood glucose study of polarized light.
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