Two coherent sources ${\mathrm{S}}_1 \mathrm{and} {\mathrm{S}}_2$ are separated by a small distance d, the fringes obtained on the screen will be:

If P be a point on a particular fringe lying in xy plane, then path difference  between two rays emerging from ${\mathrm{S}}_1 \mathrm{and} {\mathrm{S}}_2$ must remain constant. It can be shown that locus of P in xy plane (the screen) will be concentric circles.