Method for designing group of bi-aspherical type progressive-power lenses, and group of bi-aspherical type progressive-power lenses

A method for producing a group of bi-aspherical type progressive-power lenses with each lens having a progressive refractive power action dividedly allotted to a first refractive surface being an object side surface and a second refractive surface being an eyeball side surface, in which lens,

• when a surface refractive power in a horizontal direction and a surface refractive power in a vertical direction, at a far vision power measurement position F1 on the first refractive surface are DHf and DVf respectively, and
• a surface refractive power in a horizontal direction and a surface refractive power in a vertical direction, at a near vision power measurement position N1 on the first refractive surface are DHn and DVn respectively, a relational expression expressed by the following expressions is satisfied,
• DHf+DHn<DVf+DVn, and DHn<DVn,
• surface astigmatism components at F1 and N1 on the first refractive surface are cancelled by the second refractive surface, and a combination of the first and second refractive surfaces gives a far vision power (Df) and an addition power (ADD) based on a prescription value, said method comprising:
• processing the first refractive surface of the group of bi-aspherical type progressive-power lenses, the group of bi-aspherical type progressive-power lenses having the same first refractive surface;
• selecting each of the lenses of the group of bi-aspherical type progressive-power lenses based on the prescription value;
• processing the second refractive surface of the each of the lenses of the group of bi-aspherical type progressive-power lenses, the group of bi-aspherical type progressive-power lenses having different addition powers.