Field D J, Nachmias J
Vision Res. 1984;24(4):333-40. doi: 10.1016/0042-6989(84)90058-0.
In the Fourier representation of space, the parameter of phase plays a crucial role. In this study, several experiments were performed involving discrimination of various phase relations of fundamental (2 c/deg) to second harmonic (4 c/deg) at low contrast levels. The results were consistent with a model involving four "channels", each optimally sensitive to one of the following phase relations: + cosine (bright bar), -cosine (dark bar), +sine (left edge), and -sine (right edge).
