Multifocal diffractive optical device

Claim 2

A diffractive multifocal optical element comprising a phase zone plate containing annular concentric zones in which the zones are spaced substantial­ly proportional to √n and the zones possess stepped facets that introduce a discontinuity in optical path length of less than λ/2 where λ is the design wavelength.

Claim 3

The diffractive multifocal optical element of claim 1 wherein the phase zone plate contains facets which provide an alternating stepped repetitive pattern in accordance with √n spacing in the optical element and wherein the depth of the steps of the facets are less than λ/2(η′-η), where η′ and η are the indices of refraction of the lens and the medium in which the lens is interacting and λ is the design wavelength.

Claim 4

The diffractive multifocal optical element of claim 2 wherein: a. the facet of one of the alternating zones has an inclined curved profile that is interrupted at the zone boundary by another curved profile providing the differently inclined curved facet of the other alternating zone, b. the zones are spaced substantially proportional to √n, c. the depth of the facets are less than λ/2, d. the zones are cut so as to direct yellow light to at least two primary focal points in at least adequate intensities for visual usage at each such primary focal point, and, e. but for the alternating pattern, the element would not have such intensity.

Claim 5

A bifocal optical element of the Cohen lens design wherein the odd and even zones of the phase zone plate a. conform to r n ≃√ n d λ spacing, b. are contiguous and free of a non-refractive step interface at at least every other zone boundary, and leave a sloped profile at such contiguous interface, c. the cross-section of each odd zone has the same general profile and the cross-section of each even zone has the same general profile, d. the general profile of the odd zones is different from that of the even zones, and e. the depth of steps for the zones are less than λ/2.

Claim 6

A bifocal optical element of the Cohen lens design wherein the odd and even zones of the phase zone plate a. conform to r n ≃√ n d λ spacing, b. are contiguous and free of a non-refractive step interface at at least every other zone boundary, and leave a sloped profile at such contiguous interface, c. the cross-section of each odd zone has the same general profile and the cross-section of each even zone has the same general profile, d. the general profile of the odd zones is different from that of the even zones, and e. the depth of steps for the zones are less than λ/2.

Claim 7

A bifocal optical element of the Cohen lens design comprising a faceted step phase zone plate containing an alternating profile wherein: a. the phase zone plate conforms to r n ≃√ 2 n d λ ; b. the alternating profile occurs within the full-period spacing; c. the facets have a depth less than about λ/2; d. the zones are cut so as to direct yellow light to at least two primary focal points in at least adequate intensity for visual usage at each such primary focal point, and e. but for such alternating profile the zones would not have such intensity for visual usage.

Claim 8

A bifocal optical element of the Cohen lens design comprising a faceted step phase zone plate containing an alternating profile wherein: a. the phase zone plate conforms to r n ≃√ 2 n d λ ; b. the alternating profile occurs within the full-period spacing; c. the facets have a depth less than about λ/2; d. the zones are cut so as to direct yellow light to at least two primary focal points in at least adequate intensity for visual usage at each such primary focal point, and e. but for such alternating profile the zones would not have such intensity for visual usage.

Claim 9

An optical element comprising optically diffractive facets providing two different curved profiles that are joined at radii r n through transition profiles located about such radii, which transition profiles have profile curvatures that are different from said two different curved profiles whereby to form annular and concentric zones at such transition profiles which zones are spaced substantially proportional to √n and the zones are cut so as to direct yellow light to at least two primary focal points in at least adequate intensity for visual usage at each such primary focal point, which element but for the curved profiles would not have such intensity for visual usage.

Claim 10

An optical element comprising optically diffractive facets providing two different curved profiles that are joined at radii r n through transition profiles located about such radii, which transition profiles have profile curvatures that are different from said two different curved profiles whereby to form annular and concentric zones at such transition profiles which zones are spaced substantially proportional to √n and the zones are cut so as to direct yellow light to at least two primary focal points in at least adequate intensity for visual usage at each such primary focal point, which element but for the curved profiles would not have such intensity for visual usage.

Claim 11

The optical element of claim 2 wherein the repetitive pattern comprises zones having a profile embraced by the equation d = D o · {1/2 + 1/2 · cos (π · r²b²)} where d is the depth of the repetitive profile, r is the radial position of the zone, b is the radius of the 1 st zone, and D o is the facet depth for the design wavelength.

Claim 12

The optical element of any one of claims 1 to 7 in the form of an ophthalmic lens.

Claim 13

The ophthalmic lens of claim 8 in the form of a contact lens and an intraocular lens.

Claim 14

An ophthalmic contact lens containing at least two phase zone plates within its optic zone, at least one of which contains the optical elements of claim 1.

Claim 15

An ophthalmic contact lens having within its optic zone, (1) a phase zone plate which contains the optical elements of claim 1 and (2) a pure refractive portion.