Progressive Power Lens Design Method and Progressive Power Lens Design Apparatus

A method of designing a progressive power lens for spectacles that has a distance portion and a near portion of different average prescription powers,

• wherein the progressive power lens includes
• a surface power OHPf in a horizontal direction and a surface power OVPf in a vertical direction of the distance portion on an object-side surface along a principal meridian or a vertical reference line passing through a fitting point, and
• a surface power OHPn in a horizontal direction and a surface power OVPn in a vertical direction of the near portion on the object-side surface along the principal meridian or the vertical reference line,
• the object-side surface includes at least one of elements of a toric surface with the surface power OHPf greater than the surface power OVPf and elements of a toric surface with the surface power OHPn greater than the surface power OVPn, and the eyeball-side surface along the principal meridian or the vertical reference line includes elements that cancel shifts in the surface power by the elements of the toric surface on the object-side surface,
• the method comprises:
• selecting a spectacle specification including a first condition;
• selecting a spectacle specification including a second condition;
• selecting a spectacle specification including a third condition;
• and
• evaluating image sway of a progressive power lens designed on the basis of the selected spectacle specification,
• wherein the first condition includes a condition that the surface power OVPf is greater than the surface power OVPn,
• the second condition includes a condition that the surface power OVPf is smaller than the surface power OVPn,
• the third condition includes a condition that the surface power OVPf is equal to the surface power OVPn and the surface power OHPf is equal to the surface power OHPn,
• in regard to the evaluation of the image sway, a virtual plane having a rectangular pattern with a central vertical grid line passing through the geometric center of the rectangular pattern, left and right vertical grid lines horizontally symmetrical to the central vertical grid line, a central horizontal grid line passing through the geometric center of the rectangular pattern, and upper and lower horizontal grid lines vertically symmetrical to the central horizontal grid line is set through the progressive power lens such that the geometric center is aligned with a point of fixation, and
• geometric misalignment when the images of the rectangular patterns which appear when the progressive power lens moves left and right by a first horizontal angle along with a head within a range in which the line of sight does not move from the geometric center or when the progressive power lens moves up and down by a first vertical angle along with the head within a range in which the line of sight does not move from the geometric center are superimposed such that the geometric centers are aligned with each other is obtained as a sway indicator.

An apparatus for designing a progressive power lens for spectacles that has a distance portion and a near portion of different average prescription powers,

• wherein the progressive power lens includes
• a surface power OHPf in a horizontal direction and a surface power OVPf in a vertical direction of the distance portion on an object-side surface along a principal meridian or a vertical reference line passing through a fitting point, and
• a surface power OHPn in a horizontal direction and a surface power OVPn in a vertical direction of the near portion on the object-side surface along the principal meridian or the vertical reference line,
• the object-side surface includes at least one of elements of a toric surface with the surface power OHPf greater than the surface power OVPf and elements of a toric surface with the surface power OHPn greater than the surface power OVPn, and the eyeball-side surface along the principal meridian or the vertical reference line includes elements that cancel shifts in the surface power by the elements of the toric surface on the object-side surface,
• the apparatus comprises:
• a first unit which, if the average prescription power of the distance portion is plus and the value thereof is at least 3.0 D, preferentially selects a spectacle specification including a first condition;
• and
• a second unit which, if the average prescription power of the distance portion is minus and the absolute value thereof is at least 3.0 D, preferentially selects a spectacle specification including a second condition,
• the first condition includes a condition that the surface power OVPf is greater than the surface power OVPn,
• the second condition includes a condition that the surface power OVPf is smaller than the surface power OVPn, and
• D is dioptre.

An apparatus for designing a progressive power lens that has a distance portion and a near portion of different average prescription powers, the apparatus comprising:

• a unit which assumes an object-side surface and an eyeball-side surface of the progressive power lens having the distance portion and the near portion on the basis of a spectacle specification;
• and
• an evaluation unit which evaluates sway of the progressive power lens having the assumed object-side surface and eyeball-side surface,
• wherein the unit which assumes the surfaces includes
• a first unit which selects a spectacle specification including a first condition,
• a second unit which selects a spectacle specification including a second condition, and
• a third unit which selects a spectacle specification including a third condition,
• the evaluation unit includes
• a unit which sets a virtual plane having a rectangular pattern with a central vertical grid line passing through the geometric center of the rectangular pattern, left and right vertical grid lines horizontally symmetrical to the central vertical grid line, a central horizontal grid line passing through the geometric center of the rectangular pattern, and upper and lower horizontal grid lines vertically symmetrical to the central horizontal grid line through the progressive power lens having the assumed object-side surface and eyeball-side surface such that the geometric center is aligned with a point of fixation, and
• a unit which obtains, as a sway indicator, geometric misalignment when the images of the rectangular patterns which appear when the progressive power lens moves left and right by a first horizontal angle along with a head within a range in which the line of sight does not move from the geometric center or when the progressive power lens moves up and down by a first vertical angle along with the head within a range in which the line of sight does not move from the geometric center are superimposed such that the geometric centers are aligned with each other,
• the first condition includes a condition that the surface power OVPf is greater than the surface power OVPn,
• the second condition includes a condition that the surface power OVPf is smaller than the surface power OVPn, and
• the third condition includes a condition that the surface power OVPf is equal to the surface power OVPn, and the surface power OHPf is equal to the surface power OHPn.