Examination of nonuniformity of the residual layer by gray-scale histogram: (a) reference gray-scale histogram, (b) with low-viscosity resin, nonuniformity of the residual layer was 71%, (c) with middle-viscosity resin, nonuniformity of the residual layer was 49%, and (d) with high-viscosity resin, nonuniformity of the residual layer was 5%.
