Analysis and Simulation of Space-Time Speckle Effect Based on Synthetic Aperture Imaging Ladar

Speckle reduction of synthetic aperture imaging ladar based on wavelength characteristics

“…The sweep bandwidth of the wavelength in a chirp pulse is ∆λ = λT f = − λ 2 2ρr . As indicated in a previous report [3] , the speckle pattern in the scope of an optical antenna is related to the operating wavelength λ(t f ). The speckle pattern shifts to an average scale in the range direction as the chirped wavelength ranges from λ 0 to λ 0 + ∆λ.…”

“…Moreover, if linear frequency modulation signal is used, the speckle pattern in the scope of the optical antenna is temporally and spatially varied during SAIL data acquisition. Early studies have demonstrated that the speckle pattern shifts an average width in the range direction, which is equivalent to the scale of a footprint [3] . As the ladar platform moves in the azimuth direction, random intensity and phase of the speckle are integrated by the optical receiving antenna aperture and the heterodyne detected with a local-oscillator (LO) signal.…”

“…The resolution element can be divided into M × M pixels, and the coordinate of arbitrary pixel is (x k (i, j), y k (i, j)). The return speckle field in the scope of the receiving antenna can be expressed as a complex amplitude as [3] e speckle (x r , y r ;…”