Bonaccini D, Smartt R N
Appl Opt. 1988 Dec 15;27(24):5095. doi: 10.1364/AO.27.005095.
The use of a tunable etalon in the measurement of spectral profiles of solar corona emission lines is investigated. The etalon is a y-cut plate of lithium niobate. A suitable tuning range for the line is +/-1 A corresponding to an applied voltage of +/-1000 V for a thickness of 0.1 mm. A passband of 0.2 Acan realistically be obtained with an appropriate free spectral range of 6 A. Thermal analysis shows that a temperature excursion of 0.05 degrees C corresponds to a spectral drift of <0.05 FWHM. An emission line profile is obtained by scanning an ordinary-ray passband through the emission line, while measuring the difference between this signal and that from an adjacent extraordinary-ray passband. Using polarization chopping, the scattered-light component due to the sky and instrument is efficiently removed. The extraordinary-ray (reference) passband is insensitive to the applied voltage; hence the reference signal is substantially unaffected by the spectral modulation in the scattered light due to the solar absorption spectrum.
研究了在测量日冕发射线光谱轮廓中使用可调谐标准具的情况。该标准具是一块钽酸锂的Y切割板。对于厚度为0.1mm的情况，该谱线合适的调谐范围是±1Å，对应于±1000V的施加电压。通过6Å的适当自由光谱范围，实际可获得0.2Å的通带。热分析表明，0.05℃的温度偏移对应于<0.05半高宽的光谱漂移。通过扫描普通光线通带穿过发射线，同时测量该信号与相邻异常光线通带信号之间的差异，可获得发射线轮廓。使用偏振斩波，可有效去除由于天空和仪器产生的散射光分量。异常光线（参考）通带对施加电压不敏感；因此，参考信号基本上不受由于太阳吸收光谱导致的散射光中的光谱调制影响。
