光纤阵列太阳光学望远镜研究组知识库

为了精确测量非消色差波片的延迟量与快轴方位角，基于拟合光强法与光谱分析法建立了一套高精度测量系统，实现了特定波长下非消色差波片延迟量在0°～360°的高精度测量。对波片延迟量的测量方法及误差来源进行了详细的模拟分析。在拟合光强法下，重点仿真了光源光强抖动变化、检偏器初始安装精度、旋转波片定位精度等随机误差与各项系统误差对测量精度的影响，详细分析了拟合光强法不能精确测量波片延迟量为180°的原因。在光谱分析法下模拟了光源光强抖动变化、光谱的单色精度、检偏器定位精度引入的测量误差。在测量系统的建立中对上述两种测量方法影响较大的误差均进行了抑制，并对探测器的光电响应非线性效应进行了矫正。最后利用该测量系统对标称的λ/4波片、0.356λ波片、λ/2波片进行了相关实测并利用非线性最小二乘法对测量数据进行处理，获得了参考波长在632.8 nm的各波片的相位延迟量与快轴方位角。由该测量系统的实测结果可知：本文采用的拟合光强法测量λ/4波片、0.356λ波片延迟量的测量误差小于0.05°，测量精度比传统光强测量法高一个数量级以上。对于λ/2非消色差波片，在该测量系统下切换终端光强接受设备并采用光谱分析法对其进行测量，测得其延迟量误差小于0.02°，远小于拟合光强法的测量误差0.70°，克服了光强法无法精确测量波片延迟量为180°的缺陷。实测结果与模拟仿真相符。 

and spectral analysis method, which can realize the high-precision measurement of the retardance of nonachromatic waveplates at 0°~360°. The measuring system is composed of a white light source, an aperture diaphragm, a narrow band filter, a Glan Taylor prism as polarization generator, a non-achromatic waveplate to be measured, a Glan Taylor prism as polarization analyzer, an optical power meter or spectrometer. When the phase retardance and the fast-axis position angel of non-achromatic waveplates are measured by the fitting light intensity method, the white light emitted by the white light source is collimated parallel by the collimating system, then it passes through an aperture diaphragm, a narrow filter and a polarization generator, which is modulated into monochromatic linearly polarized light. Next the linearly polarized light goes through the waveplates and the polarization analyzer, is finally received by the optical power meter. During the whole measuring process, the high precision motor drives non-achromatic waveplates that are to be measured to rotate uniformly. However, in the measurement process of spectral analysis measuring method, it is necessary to move the narrow filter out of the optical measurement path, and replace the power meter with the spectrometer as the terminal detection device, in this case, nonachromatic waveplates are not needed to rotate by the motor. Before the formal measurement of the retardance and the initial fast-axis position angle of waveplates, the stability of the measurement system and the sources of measurement errors are analyzed in detail in this paper. Under the light intensity measurement method, the influence of random errors such as light source intensity jetter, the initial fastaxis position angle and the rotating position angle of the rotating waveplate and some system errors like nonlinear effects of photoelectric response of the powermeter and deviation of collimated beam is simulated. And the reason why the fitting light intensity method can not measure the retardance at 180° of nonachromatic waveplates accurately is also analyzed detailly. Under the simulation of the spectral analysis method measuring the retardance of waveplates, we also simulate the influence caused by some random errors such as light source intensity jetter, wavelength monochromaticity and motor positioning errors. Then we suppressed the random errors mentioned above in the two measurement methods in the laboratory. And the nonlinear effect of the photoelectric response of the detector is also corrected. Finally, we measured the non-achromatic λ 4waveplate, 0. 356λ non-achromatic waveplate and λ 2 non-achromatic waveplate at 632. 8 nm by using this measurement system, and the measuring data were fitted by the nonlinear least squares method. The results of the phase retardance and fast-axis position angle of the nonachromatic waveplates were obtained. It can be seen from the actual measurement that the measurement accuracy of the retardance of the λ 4 waveplate and 0. 356λ waveplate by the fitting light intensity method is relatively high, and the measurement error is less than 0. 05°. The measurement accuracy is more than one order of magnitude higher than the traditional light intensity measuring method. Moreover, the measuring device of the fitting light intensity method is simple, fast and easy to operate. For the non-achromatic λ 2 waveplate, the spectral analysis method is adopted to measure the retardance under this system. in this case, the terminal device performed by the powermeter in the fitting light intensity method is switched by the spectrometer and Charge Coupled Device camera. And the narrow band filter is also removed in the light path. From the measurement results, we can know that the measuring error of the retardance is less than 0. 02° by this measuring method, which is much smaller than the 0. 70° of measuring error caused by the fitting light intensity method. So the spectral analysis method overcomes the defect that the retardance at 180° of the non-achromatic λ 2 waveplate can not be accurately measured by the light intensity method. Therefore, the phase retardance of non-achromatic waveplates from 0° to 360° and the fast-axis position angel can be measured accurately by the measurement system designed in this paper, which provides the basis for the accurate measurement of the polarimeter.