  The boost-invariant longitudinal space, defined by the parameter
$\sigma=\frac{1}{2}b^-P^+$ can be studied from the Fourier transformation of
distributions over the conjugate variable skewness $\xi$. We investigate quark
Wigner distributions in the $\sigma$ space in dressed quark model and found
diffraction patterns that are analogous to the single slit experiment of light
in optics. The width of the central maxima varies with energy transfer to the
system and essentially $\xi$ behaves like a slit-width. Qualitatively similar
diffraction pattern is reported recently in other models. In this model, we
compute all the leading twist GTMDs with non-zero skewness for quarks which
provides Wigner distributions under Fourier transformation.
