grinding a concave surface of the semi finished lens color concentration between a center portion and a peripheral portion is maintained at a fixed color concentration independent of the diopter of the lens and the lens is shockproof in the method after mixing a photochromic material with a thermoplastic polycarbonate resin to make a sheet the sheet is processed to have a spherical surface sheet set in a mold and thermoplastic polycarbonate resin is injected in the mold to be bonded with the sheet application_number US 69977696 A description the preferred embodiments of the present invention will be described with reference to the drawings referring to fig1 in the first embodiment a material 2 is supplied to a hopper 1a in an extruder supplied material 2 is pressed out by an extrusion die 1c at the end of the screw 1b to obtain a sheet 3 having a thickness from 0 3 to 1 8 millimeters the thickness of this sheet 3 is determined according to the color of the shade resulting from the reaction of sheet 3 to ultraviolet rays supplied material 2 is made by mixing photochromic material in a thermoplastic polycarbonate resin the photochromic material is made by mixing a polycarbonate type resin containing copolyester carbonate organic photochromic compound and hindered amine type compound at the weight ratio of 100 0 001 to 2 0 and 0 1 to 5 0 there is no limitation to the kinds of organic photochromic compound used in the claimed method it is possible to add one or more compounds of an azobenzene type compound thioindigo type compound dithizone metal complex spiropyrene type compound spirooxazine type compound fulgide type.