The invention relates to non-corrective unit lens goggles and safety helmets comprising one-piece protector as well as method for designing and manufacturing such one-piece protector. the method according to the invention for designing one-piece protector (300) for non-corrective unit lens goggles or safety helmets wherein said protector (300) has front surface (302) and rear surface (304), wherein The method is computer implanted and comprises the following steps: providing front surface geometry of said protector (300)； providing predetermined local relation of said front surface geometry to predetermined center of rotation of at least one of the user's eyes； calculate predetermined portion (307a, 307b) of posterior surface geometry of said protector (300) attributed to said at least one of said user eyes by establishing nonzero negative power and prism minimization as used by plurality of lines of user vision crossing said posterior surface (304) within said predetermined portion (307a, 307b) and said front surface (302) due to eye rotations of said at least between said user eyes around said center of predetermined rotation of said at least one of said user eyes, wherein said predetermined portion (307a, 307b) of said posterior surface geometry is freeform surface geometry.a invenção refere-se a óculos de lente unitária não corretiva e capacetes de segurança que compreende protetor de peça única, assim como método para projetar e fabricar tal protetor de peça única. o método de acordo com a invenção para projetar protetor de peça única (300) para óculos de lente unitária não corretiva ou capacetes de segurança em que o dito protetor (300) tem superfície frontal (302) e superfície posterior (304), sendo que o método é implantado por computador e compreende as seguintes etapas: fornecer geometria de superfície frontal do dito protetor (300)； fornecer relação local predeterminada da dita geometria de superfície frontal em relação a centro de rotação predeterminado
