摘要:
我们研制的地基气辉成像干涉仪(ground based airglow imaging interferometer,GBAII)样机成功地探测了地球上空90—100 km的大气风速和温度.为了提高GBAII的探测精度,本文研究GBAII所拍摄的成像干涉条纹的定标:对干涉条纹中心位置定标、电荷耦合器(CCD)暗噪声和平场定标、整个光学系统衰减系数定标、步进步长定标、光程差随入射角变化量定标、仪器响应度定标和零风速相位定标等理论和实验进行了研究.利用最小二乘法对GBAII拍摄的30幅成像干涉图的圆心坐标定标在CCD(123.3,121.1)像素位置;利用632.8 nm激光获得GBAII所用CCD的平场定标系数矩阵,分别得到平场前后的干涉图并检测出CCD的噪声和坏点;利用GBAII获得图像的边缘亮环相位与中心亮斑相位的差值对入射角10.24?时,光程差相对0?入射角时变化了0.356个条纹;拍摄200幅成像干涉图的实验离散点进行正弦拟合后的均方根标准偏差达90.34%,该完整干涉条纹的步进间隔为4.06 nm,对应步进相位为0.0094π;针对正演公式中GBAII的系统衰减系数对所拍摄的原始干涉图利用IDL编程得到光学系统衰减系数的多项式,拟合的均方根标准偏差达99.98%;采用632.8 nm激光作光源,简化了GBAII的响应度表达式,通过实验得其响应度为4.97×10?3 counts·(Rayleigh·s)?1;针对GBAII室外观测,给出零风速定标的矩阵表达式后,对532.0 nm和632.8 nm激光的对应零风速相位分别为?9.2442?和?68.6353?.本文提供了多种定标方法,并逐一通过实验进行验证,为国内被动遥感探测高层大气风场提供了强有力的实验支持.
Abstract:
Ground based airglow imaging interferometer (GBAII) prototype made by our group is used to successfully detect the atmospheric wind velocity and temperature at the altituded of 90–100 km. In order to improve GBAII's velocity accuracy, its calibrations are studied in this paper where covered are the calibration of imaging interference fringe center position, CCD dark noise and flat field, the decay coefficient of GBAII's optical system, the phase step length, GBAII's optical path difference with the angle of incidence, GBAII instrument response and the zero wind speed phase calibration, etc. The theoretical and experimental researches of calibration show the following conclusions. The fringe center coordinates by shooting 30 imaging interference fringes are confirmed on the pixel of CCD (123.3, 121.1) by using the least squares method; by 632.8 nm laser for the CCD flat field calibration, the parameters of CCD's flat field coefficients, dark intensity, dead pixels and the imaging interference fringes before and after flat field are all obtained, respectively; the comparison between GBAII's one edge fringe bright whose incidence angle of 10.24? and the center fringe bright whose incidence angle of 0? shows that the edge fringe phase is stepped by 0.356 fringes relative to the center fringe. After taking the sample of 200 imaging interference fringes, from the sine fit curve of the phase step interval at an incident angle of 10.24?, the fitted root mean square (RMS) deviation is obtained to be 90.34% and the step interval of 4.06 nm for one interference fringes is corresponding to the stepped phase of 0.0094π; According to the forward formula, GBAII's system decay coefficient calibration is performed after taking imaging interference fringes by IDL programming, the RMS deviation of fitted curve is 99.98%;GBAII's response is 4.97 × 10?3 counts (Rayleigh·s)?1 from the 632.8 nm laser experiment; GBAII's zero wind speed calibration phases are obtained to be ?9.2442? and?68.6353? for the 532.0 nm and 632.8 nm lasers for the outdoor experiment, respectively. This paper provides a series of calibration methods for GBAII and these methods are all verifies experimentally. These calibration methods can support the upper atmospheric wind field passive measurement.
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