Fig. 1. Basic setup of a spatial filtering velocimeter.

Fig. 2. Schematic diagram of (a) a rectangular-type spatial filter with rectangular transmittance and (b) its transmittance function.

Fig. 3. Power spectrum of a rectangular-type spatial filter with rectangular transmittance for n=10.

Fig. 4. Schematic diagram of (a) a rectangular-type differential spatial filter with rectangular transmittance and (b) its transmittance function.

Fig. 5. Power spectrum of a rectangular-type differential spatial filter with rectangular transmittance for n=10.

Fig. 6. Power spectra Hp(fx,0) for a rectangular-type rectangular-transmission spatial filter with n=2, 4, 8, and 16.

Fig. 7. Power spectra Hp(fx,0) for a differential rectangular-type rectangular-transmission spatial filter with n=2, 4, 8, and 16.

Fig. 8. Dependence of the specific bandwidth on the number of spatial periods n for both common and differential filters.

Fig. 9. Influence of pedestal components fxp=0 on the deviation of the central frequency fx=1/p. The signal (red curve) and pedestal components (green curve) are separately calculated and plotted. The two of them are plotted together by the blue curve.

Fig. 10. Influence of higher spatial frequencies on the deviation of the central frequency fx=1/p. The signal fxp=1 (red curve) and higher spatial frequencies (green curve) are separately calculated and plotted. The two of them are plotted together by the blue curve.

Fig. 11. Interaction of fxp=1 and fxp=−1 on the deviation of central frequency fx=1/p. fxp=1 (red curve) and fxp=−1 (green curve) are separately calculated and plotted. The two of them are plotted together by the blue curve.

Fig. 12. Dependence of the peak value of transmittance on the number of spatial periods n for (a) common and (b) differential filters.