Application Research Of Kalman Filter In Optical Atomic Magnetometer

The basic principle of atomic magnetometer is based on physical properties that Cs atomic larmor precession frequency is proportional to the intensity of outside world magnetic field, by examining precession frequency of polarized atoms, so as to realize the precise measurement of the external magnetic field. Atomic magnetometer was regarded as one of the top ten emerging technologies in Technology Review magazine in 2008.High sensitivity magnetometer has a large number of applications. In terms of magnetic archaeology and biomedical imaging, it is used for searching for a permanent electric dipole in the neutron and for natural foundation symmetry test. In life, it can show us direction in a strange environment and measure the magnetic anomalies before an earthquake; In the field of medicine, observation of cardio-cerebral weak magnetic by magnetic field distribution can quickly and accurately find lesions abnormal, and mri can accurately diagnose the body healthy. In industry, the magnetic field distribution can be observed by magnetic measurements on the surface of the metal, so as to guide the workpiece surface is smooth and achieve the purpose of the nondestructive flaw detection; In the field of geological exploration, the location of the well and mineral resources can be quickly and accurately judgment by the magnetometer; In the field of military, magnetometer can play an important role in space probe on the satellite and deep-water submarine positioning, magnetic fuze and geomagnetic navigation technology.According to the research time of the magnetometer, it can be divided into successively flux-gate magnetometer, proton magnetometer, optically pumped magnetometer and superconducting magnetometer, and the atomic magnetometer. Because of the low sensitivity,the flux-gate magnetometer is not suitable for some strict measurement,but for site don't requirement high measurement sensitivity, it is still used by many people. Superconducting magnetometer has high sensitivity, it is suitable for extremely weak magnetic field measurement, due to its high sensitivity it can be applied to the medical field to detect the quantity of the human brain and heart magnetic field distribution, NDT and archaeological field, but in the superconducting magnetometer, superconducting material is extremely strict to the requirement of temperature. Optical atomic magnetometer is developed in this ten years and it is a kind of high sensitivity magnetometer, is currently the world's cutting-edge research direction in the field of weak magnetic field measurement. Compared with superconducting magnetometer, atomic magnetometer has higher sensitivity, lower cost and smaller volume,which determines a broader range of application and prospect of optical atomic magnetometer.The purpose of this article is on the basis of the experiment system of all-optical cesium atomic magnetometer, introducing the Kalman filter to seek breakthrough in the field of software algorithm, to improve the sensitivity of the all-optical cesium atomic magnetometer.Provide a new method and a reference to improve the sensitivity of atomic magnetometer. The study is carried on from four aspects.The first part, first of all, the background of the magnetometer has carried on, and then introduces the atomic magnetometer level of development both at home and abroad and the development trend of atomic magnetometer in the future, and finally put forward this topic research content,purpose, significance and structure arrangement.Next, we describe the work principle of the magnetometer, based on this topic research the Cs atoms under the condition of the external magnetic field with the interaction of light.The characteristics of the Cs atoms, Zeeman Effect of Larmor procession and alkali metal atoms in Larmor procession and Spin relaxation techniques are described briefly. We design the overall scheme of Cesium atomic magnetometer and the specific physical system structure.The physical system of Cs atomic magnetometer is built successfully.The third part of this paper introduces the principle of the closed-loop cesium atomic magnetometer system, and introduces in detail the sinusoidal modulation locked frequency,half high width of frequency, frequency dispersion zero locked frequency, understanding the digital frequency tracking system and its work process. Performance test of the closed-loop system are introduced, respectively for the magnetic field tracing test, closed-loop sensitivity test and response speed test.The fourth part introduces the principle of Kalman filter, and understands the space model of Kalman filter,formula derivation and flow chart of Kalman filter. Then make test of Kalman filter, respectively for first degree curves, second degree curves and periodic curves and then carries on the analysis.The fifth part is the filtering application part, first introduced the phase-locked amplifier,and analyzes the principle and operation process of phase-locked amplifier, in the analysis of the phase-locked amplifier find the medium with Kalman filter. Filter with the measured data of atomic magnetometer, respectively for the data of stable magnetic field and data of mutation magnetic field. Finally, research and prospect of Kalman filter were applied to real time closed-loop test system. Application system block diagram has been put forward and the possible problems and method to solve the problem has been given.