Shearlet system filters

returns the Fourier transforms of the shearlet filters defined by the shearlet system
`psi`

= filterbank(`sls`

)`sls`

as a 3-D real-valued array. The array size is
*M*-by-*N*-by-*K*, where
*M* and *N* are the values of the two-element row vector
ImageSize of
`sls`

. *K* is the number of shearlets including the
lowpass filter, *K* = `numshears(sls)`

+ 1.