A semi-quantitative method for the assessment of optical holographic interference fringes is developed. It is found that the fringe loci caused by a general three-dimensional translation of a flat object can be approximately described by a quadratic equation. The equation represents off-centered concentric circles with the location of the center determined by the displacements and the geometry of the holographic system. The location of the center is shifted opposite to the direction of the in-plane component of the displacement with an amount increasing with the amplitude of that component. The radii of the circular fringes decrease as the out-of-plane component of the displacement increases.