Patent ID: 6012813
Filing Date: 2000-01-11
Classification: G02C

Abstract:
An aspherical spectacle-lens comprising:a first and a second refractive surface, with at least one of said refractive surfaces having an aspherical shape, wherein at least one of curved surfaces forming the first and second refractive surfaces, corresponding to the aspherically shaped surface has a configuration represented by the following equation (1): ##EQU17## where (x,y,z) represents coordinates of a point on an aspherical surface and satisfied (y.epsilon.[a, b].andgate.z.epsilon.[c, d]); m.sub.y is an order of a spline function in a direction of a y-axis (m.sub.y is an integer which is not less than 4); m.sub.z is an order of the spline function in a direction of a z-axis (m.sub.z, is an integer which is not less than 4); n.sub.y is the number of inner knots in [a, b] in the direction of the y-axis (n.sub.y is an integer which is not less than 4); n.sub.z is the number of inner knots in [c, d] in the direction of the z-axis (n.sub.z, is an integer which is not less than 4); N.sub.my,i (y) represents an ith m.sub.y -th-order normalized B-spline function in a case that knots in the direction of the y-axis are .xi..sub.0, .xi..sub.1, .xi..sub.2, . . . , .xi..sub.ny+2my-1 (""i"" is an integer within [0, n.sub.y +m.sub.y -1], and a position of each knot meets the following condition: .xi..sub.0, .ltoreq..xi..sub.1 .ltoreq. . . . <.xi.m.sub.y -1.ltoreq.a<.xi.m.sub.y, .ltoreq. . . . .ltoreq..xi..sub.m.sbsb.y -1.ltoreq.a<.xi.m.sub.y, .ltoreq. . . . .ltoreq..xi..sub.ny+my-1 <b.ltoreq..xi..sub.ny+my .ltoreq. . . . .ltoreq..xi..sub.ny+my-1 ; N.sub.mz,i (z) represents an jth m.sub.z -th-order normalized B-spline function in a case that knots in the direction of the z-axis are .xi..sub.0, .xi..sub.1, .xi..sub.2, . . . , .xi..sub.nz+2mz-1, (""j"" is an integer within [0, n.sub.z +m.sub.z -1], and a position of each knot meets the following condition: .xi..sub.0 .xi..sub.1 .ltoreq. . . . .ltoreq..xi.m.sub.z -1.ltoreq.c<.xi.m.sub.z, .ltoreq. . . . .ltoreq..xi..sub.n.sbsb.z.sub.+m.sbsb.z.sub.-1 <d.ltoreq..xi..sub.nz+mz .ltoreq. . . . .ltoreq..xi..sub.n.sbsb.z.sub.+2m.sbsb.z-1 ; and c.sub.i,j is a coefficient corresponding to a combination of integers ""i"" and ""j"").