基于双向剪切干涉的光谱分辨率增强

Spectral Resolution Enhancement Based on Two-Dimensional Shear Interference

对于宽谱段、高分辨率的光谱测量场景,在探测面阵像素与像元尺寸受限的情况下,提出了双向剪切干涉的倾斜记录干涉图方式,以进行面阵探测器的多行像素拼接,在提高长波谱段分辨率的同时,避免单位剪切量增加造成的短波信息截止。以Wollaston棱镜偏振干涉具验证旋转像面的双向剪切干涉方式,计算剪切量在探测器二维空间上的载频关系,由等相位倾斜条纹衔接多列像素构成完整的干涉图。通过FRED软件模拟偏光干涉过程,以方解石晶体、C-RED ONE型探测器为例,验证等强度的1064,1550,1970nm准单色谱线,结果显示:转角斜率为1/3时,双向剪切干涉复原谱线的位置误差小于1nm,幅度比例达到0.9958…0.9759…1,1970nm光谱分辨率提高至13nm,为原值的2.38倍;对比复原棕榈蜡的近红外反射率光谱,768pixel的扩展光程差反演的光谱显示出更多吸收特征,较320pixel光程差反演的光谱分辨率增强,但因拼接误差在短波方向引入了一定的高频扰动。对影响拼接精度的剪切量进行误差分析,给出成像放大率一定时,转角误差容限与像面转角、观测波长、剪切角与分段光程差间的关系。基于像面旋转的双向剪切干涉光谱仪,解决了单纯提高剪切量带来的分辨率增强与高频截止的矛盾,拓展了系统参数的求解范围以及相关的误差容限,为宽谱段、高分辨率测量提供了选择。

For the case of broad spectrum and high resolution spectral measurement under limited number of pixels and the pixel size of the photodiode array, we propose a recording oblique interferogram scheme based on the two- dimensional （2D） shear interference, which is used to stitch those pixels on different rows of the focal plane array to improve the resolution in the long-wave and avoid the cut-off in the short-wave caused by increase in unit shear. We use the Wollaston prism polarization interferometer to verify the 2D-directional shear interference by rotating the image plane, and calculate the carrier frequency relation of the lateral shear volume in the coordinates of CCD. The complete interferogram is composed of several columns by connecting the margin pixels of equal-phase. Using the FRED software to simulate the polarization interference process, we calculate 1064 nm, 1550 nm, and 1970 nm laser lines from quasi-monochromatic when using calcite crystal and C-RED ONE detector. The results show that when the slope of the rotation angle is 1/3, the position precision of retrieved spectral lines by 2D-shear interference is less than 1 nm, and the amplitude ratio is 0. 9958 ： 0. 9759 ： 1. The spectral resolution at 1970 nm increases to 13 nm, which is 2.38 times of the original value. The near-infrared reflectance spectra of the wax are compared with two kinds of recovery. The spectra inversion of the extended optical path difference including 768 pixels shows more absorption characteristics, showing a higher spectral resolvability compared to the inversion by optical path difference of 320 pixels, though some high-frequency disturbance is introduced in the short-wave direction. The relationship between the angle error tolerance and the rotating angle, the observed wavelength, the shear angle and the segmented optical path difference is given when imaging magnification is constant. Based on the 2D shear interference spectrometer by rotating the photodiode array, the contradiction between the high spectral resolution and the high-frequency cut-off caused by simply increasing the amount of shear is avoided, which expands the solution range of system parameters and related error tolerance, providing a choice for wide range and high-spectral measurement.