TH26183A - Progressive multi-focus lens - Google Patents

Abstract

Multifocal progressive lenses, which provide an exceptionally wide field of vision, can be achieved for wearers without the added time and expense required to manufacture custom lens surfaces. These multifocal progressive lenses belong to the group of multifocal progressive lenses designed under a rule such that basic elements, such as the distance (F) and near (N) temples of the lens, fit into a typical object being worn. Next, in the case of this lens, the refractive power of the surface (in diopters) at the distance (F) temple is used as the basis (Bi). Furthermore, the difference in refractive power between the distance (F) and near (N) temples is used as the addition (Di) (in diopters). Moreover, W(Di,Bi) represents the width of the region where the average refractive power increase of the surface along the horizontal cross-section is achieved. The projection below the near power measurement position (N) is not less than Di/2 in such a case, when two custom progressive multifocal lenses, whose addition is Da and the base curves are B1 and B2, respectively, are selected from a group of progressive multifocal lenses, the following relationship exists for B1 > bB2: W(Da, B1) > W(Da, B2).

Claims (5)

1. A progressive multifocal lens has basic components, consisting of a distance (F) and a near (N) power position, and is part of a group of progressive multifocal lenses designed under predefined rules in such a way that the basic components are intended for typical wearing, where the refractive power (in diopters) at the distance (F) position is used as the basis curve (Bi), where the difference in refractive power between the distance (F) and near (N) positions is used as the addition (Di (in diopters)), and where a custom selection of two progressive multifocal lenses is made where their addition is Da and the basis curves are B1 and B2, respectively, from the group of progressive multifocal lenses. The following relationship exists for (B1>B2: W(Da,B1)>W(Da,B2), where W(Da,Bi)(i=1 or 2) is the width of the region where the average refractive power increase of the horizontal cross-sectional surface extending below the near-field measurement (N) is not less than Di/2. 2. A multifocal progressive lens according to claim 1., in which a single curve passes directly to at least both the far-field (F) and near-field (N) positions as the principal alignment line, the horizontal deviation H of a custom point (P) on the principal alignment line to the wearer's nose with respect to the far-field (F) position is determined by; H = K.Dp/Di, where K is a custom constant that is dependent on inequality 1.1 <= K <= 5.0; Dp is the refractive power of the surface increase at the custom point (P); and Di is the increase. 3. A multifocal progressive lens according to claim 1., in which the change in visual conditions along the horizontal cross-sectional arc intersecting the principal line of focus at a given point (P) occurs such that, in the part where the principal line of focus is not deviated horizontally from the horizontal position of the far-field measurement position (F), the visual conditions are symmetrical with respect to the plane of which the given point (P) is perpendicular to the cross-sectional arc and acts as the plane of symmetry of the mirror such that, in the other part where the principal line of focus is deviated horizontally to the wearer's nose from the horizontal position of the far-field measurement position (F), the change in visual conditions along the cross-sectional arc of focus occurs along another cross-sectional arc extending from the given point (p) to the wearer's ear. 4. Multifocal progressive lenses according to claim 1., where the diopter increase (Di) is in the range of 0.75 diopters to 3.00 diopters, where two custom multifocal progressive lenses, whose diopters are Da and Db respectively, and whose base curves are identical to each other, are selected from a group of multifocal progressive lenses, the following relationship applies for the diopter increase W(Da,X)Db/Da(X=1.00 diopter), where W(Di,X (mm) (i=a or b) represents the width of the region where the value of the horizontal cross-sectional aberration passing directly to the near power measurement position (N) is no more than x. 5. A multifocal progressive lens according to claim 1., where a custom point (P) on the principal aspect ratio, in addition to the far-field (F) and near-field (N) measurement positions, p has two distinct principal curvatures.