Progressive power multifocal lens

Details Progressive power multifocal lens Progressive power multifocal lens

G - Physics

02

C

G02C 7/06 (2006.01)

Patent

CA 2194954

A progressive power multifocal lens designed by attaching importance to an intermediate vision and a near vision in such a manner as to ensure broad intermediate vision viewing portion and near vision viewing portion and to have a well-balanced viewing zone among the distance, near and middle portions, whereby a resultant image of an object is little varied or fluctuated, especially, in lateral directions. For example, a far vision power measuring position is located at a point which is 14 mm upwardly away from the geometrical center of the lens. Moreover, a near vision power measuring position is located at a point which is 17.5 mm downwardly away from the geometrical center and further is 2.5 mm inwardly to the nose of a wearer. Furthermore, an eye-point position, through which a visual line runs when the wearer looks to the front thereof, is located at the geometrical center. Additionally, assuming that the far vision power measuring position is selected as a center and that a direction, in which a horizontal half-line extends right-wardly from the far vision power measuring position, is determined as a reference direction whose azimuth angle is 0, a nearly sectorial domain corresponding to azimuth angles of 30 to 150 degrees is used as a far viewing distinct vision zone in which the astigmatism is not more than 0.5 diopters irrespective of the value of an addition. Further, a principal fixation line running through the far vision power measuring position, the eye-point position and the near vision power measuring position divides the surface of the lens into a nose-side part and an ear-side part in such a way that these parts are asymmetric in the horizontal or lateral direction.

Une position F de mesure permettant de mesurer les dioptries lointaines est établie en une position située 14 mm au-dessus du centre géométrique O de la lentille. Une position de mesure N, permettant de mesurer les dioptries proches, est établie en une position située 17,5 mm au-dessous du centre géométrique O de la lentille et 2,5 mm vers le nez de l'utilisateur. Une position de point oculaire E, constituant la position par laquelle le regard de l'utilisateur de la lentille passe lorsque l'utilisateur regarde devant, est située à 1,0 mm vers le nez de l'utilisateur, à partir du centre géométrique O de la lentille, dans le sens horizontal. Une région de vision nette lointaine est définie par un secteur Df comportant deux rayons dirigés à 30 et 150 DEG par rapport à une ligne de référence s'étendant vers la droite dans le sens horizontal à partir de la position de mesure F de dioptrie lointaine. L'astigmatisme dans cette région est fixé, au maximum, à 0,5 dioptries. La lentille est asymétrique par rapport à la ligne de vue principale, qui passe par les trois points, c'est-à-dire le point de mesure F relatif aux dioptries lointaines, la position de point oculaire E et la position de mesure N pour les dioptries proches. Cette lentille multifocale progressive permet d'obtenir une partie intermédiaire et une partie proche assez large, donne peu de balancement et met l'accent sur les dioptries intermédiaires.

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