Ophthalmic lens design method and resulting ophthalmic lens

• US 20020176049A1
• Filed: 05/28/2002
• Published: 11/28/2002
• Est. Priority Date: 05/28/2001
• Status: Active Grant

• Current Assignee: Menicon Company Limited
• Original Assignee: Menicon Company Limited
• Inventors: Oyama, Yoshihiko, Sakai, Yukihisa
• Granted Patent: US 6,764,179 B2
• Time in Patent Office: Days
• US Class Current: 351/177
• CPC Class Codes: G02C 13/003 Measuring during assembly or fitting of spectacles
• CPC Class Codes: G02C 7/02 Lenses; Lens systems ; Methods of designing lenses
• CPC Class Codes: G02C 7/028 Special mathematical design techniques
• CPC Class Codes: G02C 7/04 Contact lenses for the eyes disinfection or sterilisation of contact lenses A61L12/00

Abstract

Disclosed is a method of designing an ophthalmic lens including the steps of: (a) determining a preliminary lens shape by preliminary determining a shape of the ophthalmic lens; and (b) varying the preliminary lens shape so as to adjust a position of an image surface at which MTF value is maximized, such that the position of the image surface matches a desired focal length of said ophthalmic lens. A resulting ophthalmic lens constructed according to this method is also disclosed.

Claims

1. A method of designing an ophthalmic lens comprising the steps of:

determining a preliminary lens shape by preliminary determining a shape of said ophthalmic lens; and

varying said preliminary lens shape so as to adjust a peak position of MTF in relation to an image surface distance concerning said preliminary lens shape such that said peak position of said MTF conforms to a desired focal length of said ophthalmic lens.

2. A method according to claim 1, further comprising, for detecting said peak position of said MTF in relation to said image surface distance concerning said preliminary lens shape, the steps of:

determining an area to be designed within an optical zone of said ophthalmic lens with said preliminary lens shape;

determining a spatial frequency for said area to be designed;

determining a plurality of calculating positions within a predetermined range of said image surface distance in which a desired focal position of said ophthalmic lens is located, for said area to be designed; and

calculating said MTF by using said spatial frequency with respect to each of said plurality of calculating positions.

3. A method according to claim 1, wherein said peak position of said MTF is adjusted by varying at least one of a front lens surface, a back lens surface and a lens thickness in said preliminary lens shape.

4. A method according to claim 1, wherein said preliminary lens shape is varied by adjusting at last one of a radius of curvature and an aspheric coefficient of at least one of a front lens surface and a back lens surface.

5. A method according to claim 2, wherein said method is applied for designing a multifocal lens in which said optical zone includes a plurality of segmented optical areas having different focal lengths, said method further comprising the steps of:

determining a plurality of said predetermined range of said image surface distance for a plurality of desired focal positions, respectively;

calculating the MTF by using the spatial frequency so as to detects a plurality of said peak positions of said MTF corresponding to said plurality of said predetermined ranges of said image surface distance; and

varying said preliminary lens shape such that said plurality of said peak positions of said MTF conform to said plurality of desired focal positions, respectively, within corresponding ones of the plurality of the predetermined ranges of said image surface distance.

6. A method according to claim 1, wherein said optical zone includes a toric lens area provided with both of a spherical lens power and a cylindrical lens power that have desired focal positions, respectively, said toric lens area generating two of said peak positions of said MTF, and wherein said preliminary lens shape is varied in said toric lens area so that said two MTF peak positions of said toric lens area conform to said desired focal positions of said spherical lens power and said cylindrical lens power, respectively.

7. A method according to claim 2, further comprising the step of:

imaginary disposing an aplanatic lens having a given constant power in close contact with one of a front and a back lens surface of said ophthalmic lens with said preliminary lens shape, after said preliminary lens shape is defined, wherein said MTF is calculated with respect to said ophthalmic lens with said preliminary lens shape in which aplanatic lens is attached.

8. A method according to claim 2, further comprising the step of:

calculating a center of gravity of total values of said MTF as measured within said predetermined range of said image surface distance, and defining a position of said center of gravity in relation to said image surface distance as a center-of-gravity image surface position, wherein said center-of-gravity image surface position is utilized as said peak position of said MTF, and said preliminary lens shape is varied so that said center-of-gravity image surface position conforms to said desired focal length of said ophthalmic lens.

9. A method according to claim 2, wherein said spatial frequency comprises a spatial frequency V expressed in a unit of length, and said spatial frequency V is converted to a spatial frequency U expressed in a unit of angle on the basis of a formula:

U=V×

(1000/D)×

(π

/180), in which a desired refractive power D in said area to be designed is utilized, while said MTF is calculated by using said spatial frequency U.

10. A method according to claim 2, wherein said predetermined range of said image surface distance is held within a range of a desired refractive power D of said ophthalmic lens and +1 diopter, for calculating said MTF.

11. A method according to claim 2, further comprising, wherein said step for calculating said MTF further includes the steps of:

splitting said area to be designed into segments having a constant area,

projecting a plurality of light rays on said area to be designed such that said plurality of light rays pass through substantially central portions of said segments, respectively, while being arranged with a pitch of 0.001-1 mm, and

performing ray tracing with respect to said plurality of light rays.

12. A method according to claim 2, wherein said area to be designed is specified as a circular area with a diameter of 2-10 mm.

13. A method according to claim 2, wherein said area to be designed amounts to 5-95% of an entire area of said optical zone.

14. An ophthalmic lens having a lens shape designed according to a method of designing said ophthalmic lens comprising the steps of:

defining a preliminary lens shape by preliminary determining a shape of said ophthalmic lens; and

varying said preliminary lens shape so as to adjust a MTF peak position in relation to an image surface distance concerning said preliminary lens shape such that said peak position of said MTF conforms to a desired focal length of said ophthalmic lens.