| 摘要 |
A progressive power lens includes: a pair of an outer refractive surface and an inner refractive surface, at least one of the outer refractive surface and the inner refractive surface being a progressive surface, relationships as follows being defined with respect to a lens to be actually worn: SV = SPH + CYL ‹ cos AX 2 Dm �¢ 1 = N - 1 ‹ Cm �¢ 1
and Dm �¢ 2 = 1 - N ‹ Cm �¢ 2
where: SPH represents a spherical power; CYL represents a cylindrical power; AX represents a cylinder axis; ADD represents an addition power; N represents a refractive index of the lens; SV represents a vertical refractive power; Cm I represents a curvature of a cross-section of an outer surface taken along a main fixation line; Cm2 represents a curvature of a cross-section of an inner surface taken along the main fixation line; Dm1 represents a surface power of the cross-section of the outer surface taken long the main fixation line; Dm2 represents a surface power of the cross-section of the inner surface taken along the main fixation line; PA represents a pantoscopic angle, the angle being defined as positive when formed in a direction is which the lens is laid down; Y represents a vertical distance from a prism reference point, the distance being defined as positive when taken in an upper direction of the lens fitted in a frame; Yf represents a Y-coordinate of a point located on the main fixation line and within the vertical distance Y of 5<Y<15; and Yn represents a Y-coordinate of a point located on the main fixation line and within the vertical distance Y of -15<Y<-5,
relationships as follows being defined with respect to a lens designed for a standard pantoscopic angle: Dm �¢ 1 �¢ o = N - 1 ‹ Cm �¢ 1 �¢ o
and Dm �¢ 2 �¢ o = 1 - N ‹ Cm �¢ 2 �¢ o
where: Cm1o represents a curvature of a cross-section of an outer surface taken along the main fixation line; Cm2o represents a curvature of a cross-section of an inner surface taken along the main fixation line; Dm1o represents a surface power of the cross-section of the outer surface taken along the main fixation line; Dm20 represents a surface power of the cross-section of the inner surface taken along the main fixation line; and PAo represents a pantoscopic angle defined as positive when formed in a direction in which the lens is laid down,
relationships as follows being defined: ”PA = PA - PAo
and ”Dm Y = Dm �¢ 1 Y + Dm �¢ 2 Y - Dm �¢ 1 �¢ o Y + Dm �¢ 2 �¢ o Y
where: ”PA represents a deviation of the pantoscopic angle between the pantoscopic angle of the lens to be actually worn and the standard pantoscopic angle; and ”Dm(Y) represents a difference between a sum of the surface powers of the cross-sections of the outer surface and the inner surface of the lens to be actually worn taken along the main fixation line and a sum of the surface powers of the cross-sections of the outer surface and the inner surface of the standard lens taken along the main fixation line, and
relationships as follows being satisfied: ”PA ‰ 0 and ”Dm Yf ‰ ”Dm Yn
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