Spectacle lens design method

1. A spectacle lens design method for designing a spectacle lens attached to a spectacle frame having a bend angle of 200 degrees or larger, comprising:

setting a distance portion, a near portion having power different from power of the distance portion, and a progressive portion which is disposed between the distance portion and the near portion and has power progressively varying on at least either an object side refractive surface or an eyeball side refractive surface included in the spectacle lens;

adding astigmatic power for canceling aberration produced by the bend angle of the spectacle frame at a design reference point of the distance portion to the entire distance portion and astigmatic power for canceling aberration produced by the bend angle of the spectacle frame at a design reference point of the near portion to the entire near portion on either the object side refractive surface or the eyeball side refractive surface of the spectacle lens;

determining an aspherical surface addition quantity which provides the optimum optical properties throughout the object side refractive surface or the eyeball side refractive surface of the spectacle lens; and

adding prismatic power for canceling prismatic power produced by the bend angle of the spectacle frame at the design reference point of the distance portion to the entire distance portion and prismatic power for canceling prismatic power produced by the bend angle of the spectacle frame at the design reference point of the near portion to the entire near portion on either the object side refractive surface or the eyeball side refractive surface of the spectacle lens;

wherein the aspherical surface addition quantity determining step determines the aspherical surface addition quantity by setting a plurality of reference lines extending radially from a geometrical center of the spectacle lens through the distance portion of the spectacle lens to the edge of the spectacle lens and a plurality of reference lines extending through the near portion of the spectacle lens to the edge of the spectacle lens, calculating aspherical surface addition quantities providing the optimum optical properties on the respective reference lines, and calculating aspherical surface addition quantities for areas between the reference lines by interpolation.

2. The spectacle lens design method according to claim 1 , wherein the distance portion located in an upper area of the lens for viewing a distant place, the near portion located in a lower area of the lens for viewing a near object, and the progressive portion smoothly connects the distance portion and the near portion for viewing an intermediate distance.

3. The spectacle lens design method according to claim 2 , wherein the spectacle lens comprises a main meridian that extends in a central area of the distance portion in a vertical direction, turns in a direction toward a user's nose in the progressive portion, and extends in the vertical direction in the near portion.

4. The spectacle lens design method according to claim 1 ,

wherein the aspherical surface addition quantity is determined as a function of a distance r from the geometrical center and an angle θ in the anticlockwise direction from an X axis along each reference line.

5. The spectacle lens design method according to claim 4 ,

wherein at least two of the plurality of reference lines extending radially from a geometrical center of the spectacle lens through the distance portion of the spectacle lens are provided between the X axis and a Y axis.

6. The spectacle lens design method according to claim 1 , wherein the interpolation obtains an equation of a smoothly curved line including the aspherical surface addition quantities on the respective reference lines.