Non-rigidly coupled, overlapping, non-feedback optical systems for spatial filtering of Fourier transform optical patterns and image shape characterization comprises a first optical subsystem that includes a lens for focusing a polarized, coherent beam to a focal point, an image input device that spatially modulates phase positioned between the lens and the focal point, and a spatial filter at the Fourier transform pattern, and a second optical subsystem overlapping the first optical subsystem includes a projection lens and a detector. The second optical subsystem is optically coupled to the first optical subsystem.