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空间滤波测速系统中输出信号的基底成分,理论上可以通过差分方法完全消除。但由于由被测物体表面各处散射到光学系统并被探测器接收到的光能量不一致等原因,导致输出信号中仍然有基底成分残留,为信号特别是低频信号的探测带来困难。为了消除差分滤波器输出信号中残留的基底成分,对空间滤波测速仪中的图像传感器型差分滤波器的结构进行了优化设计。列出并分析了图像传感器型差分滤波器的各种可能结构形式,并且选择了几种典型的结构进行了实验。分别在均匀照明和非均匀照明条件下,从功率谱和信噪比两个方面分析了输出信号的质量,为滤波器结构的优化提供了依据。通过对比不同滤波器结构下系统输出信号的质量,得到了一种最为合适的能大大消除输出信号中残留的基底成分的滤波器结构。
The basis components of the output signal in the spatial filter velocimetry system can theoretically be completely eliminated by the differential method. However, due to the scattering of light energy from the surface of the measured object to the optical system and the inconsistency of the light energy received by the detector, residual components of the output signal still remain, which makes it difficult to detect signals, especially low-frequency signals. In order to eliminate the residual components of the differential filter output signal, the structure of the image sensor type differential filter in the spatial filter velocimeter is optimized. Various possible structures of the image sensor differential filter are listed and analyzed, and several typical structures are selected for experiment. Under the conditions of uniform illumination and non-uniform illumination respectively, the quality of the output signal is analyzed from the power spectrum and the signal-to-noise ratio, which provides the basis for the optimization of the filter structure. By comparing the quality of the output signal of the system under different filter structures, a most suitable filter structure can be obtained that can greatly eliminate the residual base composition in the output signal.