US Patent 8109841 Putter face and golf putter having the same

A putter face includes microscopic protrusions which have stiffness higher than that of a golf ball and which are smaller than intervals between dimples of the golf ball, each of the microscopic protrusions having an end having a protrusion front edge surface formed in a planar shape, a periphery of the protrusion front edge surface including linear portions facing each other and curve portions facing each other, the linear portions extending in a horizontal direction of a face plane of the putter face or striking the golf ball, the periphery of the protrusion front edge surface forming a racetrack shape (i) which is defined by a pair of the linear portions facing each other and a pair of the curve portions facing each other and (ii) which has a shorter diameter of not less than 0.1 mm but not more than 0.2 mm.