Fourier transform of any grade can be realized in the free space of Fres-nel diffraction on spherical wave illuminating objects.

• 通过球面波照明物体的自由空间菲涅耳衍射,实现任意级次分数傅里叶交换,指出了菲涅耳衍射与分数傅里叶变换的一致性。