Single block mounting system for surfacing and edging of a lens blank and method therefor

A method for making a prescription eyeglass lens for a particular user and for a particular selected eyeglass frame having two lens openings each having a vertical reference line and a horizontal reference line, and which two lens openings are horizontally spaced from one another by a horizontal distance measured between said vertical reference lines, said method comprising the steps of:

• providing a lens blank and block assembly including a lens blank having a block fixed to it, said lens blank having a generally spherical front surface and a rear surface, said block being fixed to said front surface, and said block having mounting means for engagement by a holding means which mounting means locates a first reference axis fixed relative to said lens blank and block assembly extending through the center of curvature of said spherical front surface of said lens blank and a second reference axis fixed relative to said lens blank and block assembly and located in a plane perpendicular to said first reference axis and intersecting said first reference axis,
• providing a set of prescription information defining the optical characteristics of a lens to be produced from said lens blank,
• providing a set of frame opening shape data defining the edged shape of the lens to be produced from said lens blank to suit it to the associated lens opening of said selected frame,
• providing data defining the interpupilary spacing of the particular user,
• providing data defining said horizontal spacing between said two lens openings of said selected frame,
• processing the aforesaid data in a computer to generate a first set of machine operating data defining with reference to said first and second reference axes a shape to be given to said rear surface of said lens to cause said lens blank to have the optical characteristics specified by said prescription data and to also generate a second set of machine operating data defining with reference to said first and second reference axes the edged shape to be given the lens cut from said lens blank while it remains fixed to the same block used to support the lens blank when said shape is given to said rear surface of said lens,
• and relating said first and second sets of machine operating data to one another such that the lens defined by said first and second machine operating data when fitted into the associated lens opening of said selected frame will have its optical characteristics properly located relative to the associated eye of the particular user when said frame is worn by said user.