Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
  • G02C7/00—Optical parts
  • G02C7/02—Lenses; Lens systems ; Methods of designing lenses

Definitions

• the present invention relates to a non-corrective spectacle lens and to a pair of spectacles equipped with such a lens.
• a non-corrective spectacle lens generally has an outer diopter and an inner diopter which are both a portion of a sphere. These two spheres have different radii and separate centers. Gullstrand's law makes it possible to calculate the power of such a lens as a function of the radii of the spheres, of the position of the centers of these spheres as well as of the index of the material used to make the spectacle lens.
• a zero power is chosen and a relationship is thus obtained between the radii of curvature of the diopters, the position of the centers of the spheres corresponding to these diopters as well as the index of the material used.
• Current technological means make it possible to perfectly control the power of an eyepiece and to produce products with tolerances, from a power point of view, of the order of
• a permanent concern in the production of non-corrective lenses is to limit prism faults as much as possible. These defects are greater when the spectacle lens has a significant curvature.
• the present invention relates to such glasses. For glasses whose radius of curvature of the outer diopter is at most equal to about 90 mm, the problems of prism defect are more important and the invention therefore relates more particularly, but not exclusively, to these glasses.
• Document WO99 / 52480 describes a lens whose optical axis is inclined upward relative to the main axis of vision. This upward inclination also makes it possible to cancel the defect in the prism in the visual center.
• this optimization creates a significant prism defect at the bottom of the glass.
• the wearer of such glasses observes for example his feet by lowering his gaze and not the head, the prism presented by the glass in his lower zone gives him the impression that the ground is hiding under his feet. This phenomenon is all the more marked as the curvature of the glass is more pronounced.
• the object of the present invention is therefore to correct this defect and to provide a spectacle lens which makes it possible to reduce the prismatic deviation observed at the bottom of the glass without this prismatic deviation becoming significant at another place in the glass.
• non-corrective spectacle lens intended to be mounted in a frame comprising two branches and composed of two spherical dioptres as well as an optical center.
• the optical axis defined by the straight line passing through the two centers of the spherical diopters makes an angle of at least 10 ° with a horizontal axis.
• the optical axis of the lens, in the mounted and carried position is preferably inclined downward relative to a horizontal axis corresponding to a straight line passing through the pupil of the eye of the wearer of glasses and the area of the ear on which the corresponding branch of the frame rests.
• Such a spectacle lens then has a slight prism value along the main line of vision.
• This low value remains within the tolerances accepted by the standards to which reference is made throughout the profession and does not cause any discomfort to the wearer of the glasses.
• the prismatic deviation inflicted by the glass on a light ray passing through it in its low peripheral zone is reduced: the wearer of glasses who looks down, for example to look at his feet, does not have the feeling that the ground hides beneath him.
• the glass according to the invention advantageously has a negative power of between -0.1 12 and -0.04 diopters.
• This power of the glass is preferably between -0.06 and -0.04 diopters.
• This low power is not perceptible for the wearer of glasses but already makes a good contribution to the reduction of the prismatic defect in the bottom of the glass.
• the thickness of the glass at the optical center is preferably between 1 and 3 mm to have thin glasses.
• the invention also relates to glasses comprising a frame with two arms and two lenses according to the invention.
• Figure 1 shows a pair of perspective glasses.
• Figure 2 is a sectional view along the line II-II in Figure 1.
• Figure 3 shows in front view a circular blank for making a glass according to the invention.
• FIG. 4 shows a non-circular blank for making a glass according to the invention
• FIG. 1 represents a pair of glasses comprising a frame 2 and two lenses 4 produced in accordance with the invention. These lenses are non-corrective lenses and it is for example a pair of sunglasses.
• the shape of the frame and the lenses is given solely by way of illustrative example and cannot limit the scope of the patent application.
• Each glass 4 has a concave inner face 6 and a convex outer face 8.
• the inner and outer faces each have a spherical shape.
• the outer face 8 corresponds to a sphere of center C 1 and of radius R 1 while the inner face 6 corresponds to a sphere of radius R2 and of center C2.
• the centers C1 and C2 are offset and define a straight line 1 0 conventionally called the optical axis.
• the optical axis 10 At the intersection of the optical axis 10 with the glass 4, the latter has a maximum thickness e. This thickness will gradually decrease as we approach the edge of the glass.
• the radius R1 is chosen according to the shape that one wishes to give to the glass 4. For a basic glass 6, this radius will for example be
• the radius R2 and the distance separating the center C 1 from the center C2 are determined by Gullstrand's law. In the present case, these values will for example be chosen to obtain a power of -0.05 diopters.
• FIG. 2 shows a glass 4 in position in front of an eye 12 of a wearer of the glasses.
• This figure represents a horizontal axis 14 which corresponds to the vision axis when the eye looks endlessly, the head of the wearer of the glasses being straight.
• the horizontal axis is for example defined by a straight line which would pass through the pupil of the eye and through the area of the ear on which a branch 1 6 of the frame 2 would rest.
• FIG. 2 shows an angle ⁇ between l optical axis and the horizontal plane.
• a reference system may be the one used in certain standards.
• the ANSI Z87 standard. 1 -1 989 retains the head ALDERSON
• FIG. 5 shows the frame 2 in the wearing position as defined by the above-mentioned ANSI standard.
• ⁇ we can first of all mark the position of the optical center 1 8 of the lens 4. Then, in a vertical plane containing this optical center 1 8, we determine a vertical line 30 tangent to the outer diopter 8, as well as the point 32 of contact between the outer diopter 8 and the vertical line 30. If the vertical plane passing through both the center of the outer diopter and the optical center 18 is chosen, the contact point 32 corresponds to the intersection of the outer diopter 8 with a horizontal straight line, for example the straight line 1 4, which passes through the center of the outer diopter 8.
• the optical center 1 8 of the glass 4 is located towards the bottom of the glass.
• the optical center 1 8 is located substantially in the lower quarter of the glass 4.
• the optical center is generally located in the lower half of the glass; the angle ⁇ formed by the optical axis and the horizontal has a value of at least 10 degrees.
• the glass 4 is inclined relative to the vertical and has a pantoscopic angle greater than 5 degrees.
• This pantoscopic angle is the angle formed by the vertical line 20 and a plane on which would rest the inner face 6 of the glass. This angle p is shown in Figure 2
• the four tables below indicate the prismatic deviation for glasses using base 6 and base 8 lenses and whether or not having a negative power of -0.05 diopters.
• the first table considers the light beam passing through the visual axis while the second table concerns the light beam passing through the bottom of the glass. For each table, we consider three positions of the optical axis:
• the optical axis passes through the middle of the glass.
• the angle formed by the optical axis 1 0 and the horizontal viewing axis 1 4 is 6.525 ° for a base lens 6 and 9.180 ° for a base lens 8;
• the optical axis passes to the lower quarter of the glass.
• the angle between the optical axis 10 and the horizontal visual axis 1 4 is 1 2.96 ° for a base lens 6 and 1 7, 67 ° for a base lens 8.
• the glasses according to the invention will have an optical axis inclined by 10 degrees and more relative to the horizontal. According to the drawing retained for the frame, it will be noted that the intersection between the optical axis and the outer diopter of the lens is located in the lower half of the latter (see FIG. 3).
• the upper limit which will be observed for the angle ⁇ is that which corresponds to an excessive prismatic deviation value along the visual axis. It can be seen, for example, that for a basic lens 6, the optical center can be placed entirely at the lower edge of the lens without inflicting excessive deviation along the visual axis (see tables 1 and 2).
• the glasses according to the invention are for example obtained from a blank 22 in the form of a circular cap.
• a blank 22 has two spherical dioptres and is delimited by an edge peripheral.
• the spherical dioptres correspond to the inner 6 and outer 8 faces of the glasses 4.
• a clipping line 24 is shown.
• This line has an upper edge and a lower edge and the distance vertically between these edges is called H. It corresponds to the geometric height of the glass 4.
• the optical center 1 8 of the glass is placed in turn to the geometric center of the blank 22. Geometrically, it is located in the lower half of the glass 4.
• the optical center is placed here at a distance h from the lower edge of the clipping line 24.
• the height h is substantially equal in the case of FIG. 3 to third of the total height H of the glass 4.
• the spectacle lens 4 can also be obtained from a blank 23 such as that described in document FR-2 740 231.
• the optical center 18 is here offset relative to the geometric center 26 of the blank.
• the latter is not circular. It has two opposite rectilinear edges as well as two opposite edges in the shape of an arc of a circle. Marks 28 make it possible to locate the optical center 1 8 on the blank 23.
• This figure shows the clipping line 24 of the glass which is arranged relative to the optical center 1 8 in the same way as for the blank 22 of FIG. 3. Once a right lens and a left lens are trimmed, these are put in place in the frame 2 shown in FIG. 1. The optical centers of the two glasses 4 are then separated by a distance ⁇ .
• This distance ⁇ is for example chosen to be less than the distance separating the two pupils of the wearer of the glasses.
• the principle described in the document US-1,741,536 cited in the preamble to the present patent application is then used in order to limit defects in the prism towards the lateral edges of the glass.
• the power of the glasses can be chosen to be different from -0.05 diopters.

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• Health & Medical Sciences (AREA)
• Ophthalmology & Optometry (AREA)
• Physics & Mathematics (AREA)
• General Health & Medical Sciences (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Eyeglasses (AREA)

Applications Claiming Priority (3)

Publications (1)

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ID=8847263

Family Applications (1)

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Cited By (1)

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Citations (2)

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• 2000
  • 2000-02-22 FR FR0002203A patent/FR2805353B1/fr not_active Expired - Fee Related
• 2001
  • 2001-02-22 WO PCT/FR2001/000524 patent/WO2001063343A1/fr not_active Application Discontinuation
  • 2001-02-22 EP EP01907880A patent/EP1171794A1/de not_active Ceased
  • 2001-02-22 AU AU35748/01A patent/AU3574801A/en not_active Abandoned

Patent Citations (2)

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