A novel configuration of focused laser differential interferometry (FLDI) was developed, simulated, and tested. The new configuration is referred to as cylindrical FLDI or CFLDI. Using cylindrical lenses in place of standard lenses changes the three-dimensional shape of the focusing beam from a cone shape for FLDI to a triangular sheet for CFLDI, allowing for probing of flat-plate boundary layers closer to the wall. The beam propagation and interference pattern were modeled to determine the transfer functions for one-dimensional sinusoidal disturbances of varying wavelength ($k={10}^1–{10}^6{\mathrm{m}}^{-1}$) and varying spanwise thickness ($L=0–0.076\mathrm{m}$) of the tested area. CFLDI was employed to measure the density perturbations in supersonic blowdown wind tunnel SBR-50 at the University of Notre Dame with the test section width of 0.076.2 m. It was determined that the CFLDI system sufficiently filtered the sidewall boundary layers to measure the spectra of density fluctuations in a plane wall boundary layer. However, accurate measurements of the density disturbances in the freestream flow must account for the contribution of the sidewall boundary layers. This serves as an initial validation of the CFLDI maintaining spatial filtering similar to a regular FLDI.

聚焦激光微分干涉术（FLDI）的新型配置已开发，模拟和测试。新配置称为圆柱FLDI或CFLDI。使用柱面透镜代替标准透镜可以将聚焦光束的三维形状从FLDI的圆锥形状更改为CFLDI的三角形薄片，从而可以探测更靠近壁的平板边界层。对光束传播和干涉图进行建模，以确定变化波长的一维正弦波扰动的传递函数（$ķ={10}^{\mathrm{1个}}–{10}^6{\mathrm{米}}^{-\mathrm{1个}}$）和变化的翼展方向厚度（$\mathrm{大号}=0–0.076\mathrm{米}$）的测试区域。CFLDI被用于测量Notre Dame大学的超音速排污风洞SBR-50中的密度扰动，测试截面宽度为0.076.2 m。已经确定，CFLDI系统充分过滤了侧壁边界层，以测量平面壁边界层中的密度波动光谱。但是，对自由流中密度扰动的精确测量必须考虑到侧壁边界层的影响。这用作CFLDI的初始验证，类似于常规FLDI一样保持空间过滤。