Progressive intensity phase bifocal

• US 4,881,805 A
• Filed: 11/12/1987
• Issued: 11/21/1989
• Est. Priority Date: 11/12/1987
• Status: Expired due to Term

• Current Assignee: Allen L. Cohen
• Original Assignee: Allen L. Cohen
• Inventors: Cohen, Allen L.
• Primary Examiner(s): Sugarman, Scott J.
• Application Number:
  US07/120,262
• Time in Patent Office: 740 Days
• Field of Search: 351/160 H, 351/160 R, 351/161, 351/162, 623/6, 350/162.16, 350/162.22
• US Class Current: 351/161
• CPC Class Codes: G02B 5/1876 Diffractive Fresnel lenses; Zone plates; Kinoforms G02B5/1842, G02B5/1847 take precedence; optical systems having diffractive correction means G02B27/0037; Fresnel lenses operating by refraction G02B3/08
• CPC Class Codes: G02B 5/1895 such optical elements having dioptric power
• CPC Class Codes: G02C 2202/20 Diffractive and Fresnel lenses or lens portions
• CPC Class Codes: G02C 7/042 Simultaneous type
• CPC Class Codes: G02C 7/044 Annular configuration, e.g. pupil tuned

Abstract

An ophthalmic contact lens containing more than one phase plate within its optic zone, including contact lens, especially of a Cohen lens design, which possesses phase plate optics within its optic zone that progressively shift the intensity of light focussed by bifocal phase plates between the diffractive focal powers by utilizing eshelettes in the phase plates of varying depths and heights which are cooperatively aligned relative to the lens base curve surface that they openly face.

Claims

1. An ophthalmic contact or intraocular lens containing more than one phase plate within its optic zone.

2. The ophthalmic contact or intraocular lens of claim 1 wherein there are at least two phase plates within the optic zone.

3. The ophthalmic contact or intraocular lens of claim 1 wherein each phase plate obeys the same phase plate formula.

4. The ophthalmic contact or intraocular lens of claim 3 wherein the formula is:

space="preserve" listing-type="equation">r.sub.m =√

2 m w f

w=the wavelength of light

f=focal length of 1^st order diffraction.

5. The ophthalmic contact or intraocular lens of claim 1 in which the lens possesses phase plate optics within its optic zone that progressively shift the intensity of light focussed by bifocal phase plates between the diffractive focal powers by utilizing echelettes in the phase plates of varying depths and heights which are cooperatively aligned relative to the lens base curve surface that they openly face.

6. The ophthalmic contact or intraocular lens of claim 5 in which the lens is of a Cohen lens design.

7. The ophthalmic contact or intraocular lens of claim 6 in which each of the individual phase plates obeys the same phase plate formula.

8. The ophthalmic contact or intraocular lens of claim 7 wherein the formula is:

space="preserve" listing-type="equation">r.sub.m =√

2 m w f

w=the wavelength of light

f=focal length of 1^st order diffraction.

9. The ophthalmic contact or intraocular lens of claim 8 wherein the echelette depths are monotonically increasing from the lens center outward.

10. The ophthalmic contact or intraocular lens of claim 8 wherein the echelette depths are monotonically decreasing from the lens center outward.

11. The ophthalmic contact or intraocular lens of claim 6 wherein each echelette is set back from the base curve according to its specific depth.

12. The ophthalmic contact or intraocular lens of claim 6 wherein the deepest echelettes have a depth h and are placed to touch the base curve of the lens, and each echelette of a differing depth ah are set back a distance b=(1-a)/2 from the base curve.

13. The ophthalmic contact or intraocular lens of claim 11 wherein the echelette depths are monotonically increasing from the lens center outward.

14. The ophthalmic contact or intraocular lens of claim 11 wherein each echelette is set back from the base curve according to its specific depth in such a manner that allows for drapage of the lens.

15. The ophthalmic contact or intraocular lens of claim 14 wherein the deepest echelettes have a depth h and are placed to touch the base curve of the lens, other echelette of a differing depth ah are set back a distance c from the base curve where c is given by the formula c=bh(n'"'"'-n)/(n-1), with n'"'"' equal to the refractive index of the contact lens and n equal to the refractive index of tear layer of the eye.

16. The ophthalmic contact or intraocular lens of claim 14 wherein the echelette depths are monotonically increasing from the lens center outward.

17. The ophthalmic contact or intraocular lens of claim 14 wherein the echelette depths are monotonically decreasing from the lens center outward and where the peripheral portion of the lens is cut back from the base curve at least to the point where it lays tangent to the outermost echelettes so as to allow for full drapage of the contact lens.