US5013133A — Diffractive optical imaging lens systems

Claim 1

Independent Claim 100 words

A method of reducing aberrations in an image of an object formed by a diffractive optical element having an optical axis, using an aperture stop which has an aperture, said object being on the object side of said element and said image being formed on the image side of said element, which said method comprises the step of positioning the aperture stop so that the optical axis of the element passes through the aperture and with the stop at a location on the object side and away from said element a sufficient distance from said element to reduce said aberrations.

Claim 2

Independent Claim 100 words

A method of reducing aberrations in an image of an object formed by a diffractive optical element having an optical axis, using an aperture stop which has an aperture, said object being on the object side of said element and said image being formed on the image side of said element, which said method comprises the step of positioning the aperture stop so that the optical axis of the element passes through the aperture and with the stop at a location on the object side and away from said element a sufficient distance from said element to reduce said aberrations.

Claim 3

Dependent Claim 74 words

The method according to claim 1 wherein the diffractive optical element has a focal length for a design wavelength λ 0 and focuses light of wavelength λ 0 , said distance being equal to the product of the focal length of said element and the ratio ##EQU27## where λ is the wavelength of light from said object which illuminates said element and f is the focal length for λ equal to λ 0 .

Claim 4

Dependent Claim 18 words

The method according to claim 1 wherein said distance is equal to the focal length of said element.

Claim 5

Dependent Claim 46 words

The method according to claim 1 wherein light from the object passes through the aperture and the element and further comprising the step of removing any phase variation of the light passing through said aperture by an amount sufficient to correct spherical aberration of said image.

Claim 6

Dependent Claim 85 words

The method according to claim 1 wherein said element has a plurality of successively spaced zones, said zones each having a width defined by γm+1-γm where r depends on wave length λ 0 and focal length f according to the following relationship: ##EQU28## and which further comprises adjusting the width of said zones by a distance sufficient to reduce said aberrations when said element has a finite focal length with respect to light of wave length λ from said object, where m is an integer.

Claim 7

Dependent Claim 96 words

The method according to claim 1 wherein the positioning step comprises translating said aperture stop position in relation to the position of said element to provide sufficient distortion in said image as manifested by the height of said image being proportional to the product of the focal length of said element and a ray angle, θ, between the optical axis of said element and a beam of light through said element which is incident on said image so that the beam of light through said element scans across a plane containing said image at constant velocity.

Claim 8

Dependent Claim 27 words

The method according to claim 1 further comprising the step of bending said element a sufficient amount to provide correction for at least one of said aberrations.

Claim 9

Dependent Claim 119 words

A diffractive optical imaging system which comprises a diffractive optical element having an optical axis, a focal length, f, for light of wavelength λ 0 from an object which illuminates said element and forms an image of the object, said element having a front focal plane and an image plane on object and image sides thereof, said focal plane and image plane being perpendicular to the optical axis of said element, said image being focused in said image plane, an aperture stop disposed on the one of said sides wherein the object or image is located furthest from the element such being the longest conjugate distance at a distance from said element sufficient to reduce aberrations in said image.

Claim 10

Dependent Claim 119 words

A diffractive optical imaging system which comprises a diffractive optical element having an optical axis, a focal length, f, for light of wavelength λ 0 from an object which illuminates said element and forms an image of the object, said element having a front focal plane and an image plane on object and image sides thereof, said focal plane and image plane being perpendicular to the optical axis of said element, said image being focused in said image plane, an aperture stop disposed on the one of said sides wherein the object or image is located furthest from the element such being the longest conjugate distance at a distance from said element sufficient to reduce aberrations in said image.

Claim 11

Dependent Claim 25 words

The system according to claim 8 wherein said stop is located in said front focal plane with the aperture thereof intersected by said optical axis.

Claim 12

Dependent Claim 30 words

The system according to claim 8 wherein said stop is located a distance t from said element where ##EQU29## where λ is the wavelength of light which forms said image.

Claim 13

Dependent Claim 80 words

The diffractive optical element and the aperture stop comprising an optical system according to claim 8 wherein said element has a zone structure of m zones each of radius r from said optical axis, the radii of said zones having the following relationship: ##EQU30## where x is an integer and the location of said stop is defined by ##EQU31## where t is the distance of the stop from said element and λ is the wavelength of light forming the image.

Claim 14

Dependent Claim 26 words

The system according to claim 8 further comprising a phase corrector element in said aperture for correcting spherical aberration of said image due to said element.

Claim 15

Dependent Claim 50 words

The system according to claim 11 wherein said element is an anamorphic element and said zones are parallel to each other, r being the spacing of said zones from a centerline of said element running through the center of said element and coincident with the optical axis of said element.

Claim 16

Dependent Claim 24 words

The system according to claim 11 wherein said element has a surface relief structure with a height profile defined by the following equations: ##EQU32##

Claim 17

Dependent Claim 25 words

The system according to claim 11 where said element is a lens and said object and image sides are on opposite sides of said lens.

Claim 18

Dependent Claim 86 words

The system according to claim 8 wherein said aperture has a margin, said element has power φ and has finite conjugates with said object a finite distance from said element, said element has a conjugate parameter T where ##EQU33## where m is the paraxial lateral magnification of said element, and said distance is proportional to ##EQU34## where y is the height above the optical axis on the element of a marginal ray from the optical axis at the object plane through the margin of said aperture.

Claim 19

Dependent Claim 52 words

The system according to claim 16 wherein said element is bent and has a radius of curvature to a point on the optical axis and said distance is proportional to ##EQU35## and C sub is the reciprocal of the radius of curvature of the element about a point on the optical axis.

Claim 20

Dependent Claim 44 words

The system according to claim 16 wherein said element provides for imaging at the image plane at a design wavelength λ 0 and the element has zones of width which are determined by ##EQU36## where λ 0 is the design wavelength of the element.

Claim 21

Dependent Claim 26 words

The system according to claim 8 wherein said lens is an f - θ scan element of focal length f and said distance is about (2/3)f.

Claim 22

Dependent Claim 34 words

The system according to claim 19 wherein said lens has a finite curvature from the center about the optical axis about a center along the optical axis on the object side of said lens.

Claim 23

Dependent Claim 18 words

The system according to claim 20 wherein the reciprocal of radius of said curvature is approximately -1/2 f.

Claim 24

Dependent Claim 52 words

The system according to claim 8 wherein said element is designed for imaging at a design wavelength and is a planar f-θ scan lens of focal length f, power φ, and design wavelength λ, said distance is either ##EQU37## and said lens has Fresnel zones which are of width related to ##EQU38##

Claim 25

Dependent Claim 64 words

The system according to claim 8 wherein said element is a scan lens disposed in the path of a beam which is scanned across the image plane, a scanner for deflecting said beam and causing it to be scanned across the image plane, said scanner having a surface from which said beam is deflected, and said scanner defining said aperture stop on said surface.

Claim 26

Dependent Claim 30 words

The method according to claim 1 whenever said positioning step is carried out to position said aperture stop on the side of said element which has the longest conjugate distance.

Claim 27

Dependent Claim 28 words

The method according to claim 1 where said object is effectively at infinity as said positioning step is carried out to position said stop on said object side.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1994-05-06	1994-11-05	1995-05-07	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1998-05-06	1998-11-05	1999-05-07	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2002-05-06	2002-11-05	2003-05-07	$7700.00	Window Closed / Lapsed

Diffractive optical imaging lens systems

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