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US 6,462,874 B1Granted
Optical systems employing stepped diffractive surfaces
AssigneeKSM Associates, Inc.
InventorYakov G. Soskind
Life of this patent
Estimating the term…
Abstract
Optical systems employing stepped diffractive surfaces (13) are provided. Ray tracing through such systems is performed using the grating equation to represent the stepped diffractive surface (SDS). In this way, the SDS can be used to correct a variety of monochromatic and chromatic aberrations by balancing the aberrations of the SDS against the aberrations of non-stepped optical surfaces in the system.
Claims119
A method for reducing at least one aberration of an optical system which comprises:
- (i) a stepped diffractive surface (SDS) which comprises a plurality of steps;
- and
- (ii) an optical surface which has optical power and is not a stepped diffractive surface (non-SDS),
- said method comprising:
- (a) tracing rays through the system by representing the SDS by an equation which describes diffraction by a grating;
- and
- (b) using the rays traced in step (a) to select one or more parameters of the system which reduce said at least one aberration;
- wherein in step (a), rays are traced through individual steps of the SDS using the equation which describes diffraction by a grating.
5 more elements
A method for reducing at least one aberration of an optical system which comprises at least one optical element, said method comprising:
- (a) incorporating an additional optical element in the system which comprises a stepped diffractive surface (SDS) which comprises a plurality of steps;
- and
- (b) selecting the spacing between the SDS and the at least one optical element;
- wherein step (b) is performed by tracing rays through the system by representing the SDS by an equation which describes diffraction by a grating, said equation being used to trace rays through individual steps of the SDS.
1 more element
An optical system having an optical axis and comprising:
- (a) a stepped diffractive surface (SDS) which has a clear aperture and within said clear aperture comprises N concentric planar steps orthogonal to the system's optical axis which define a non-planar base curve, said steps satisfying the relationship;
- |di|\|di+1|<2.0, for i=1 to N−2
- where di (the step depth) is the displacement along the optical axis between step i and step i+1 and where the optical path difference for each step is at least jiλ0, where λ0 is the nominal wavelength of the optical system and ji is the diffractive order of the ith step;
- and
- (b) an optical surface which has optical power and is not an SDS (non-SDS);
- wherein the SDS makes an optically significant contribution to the correction of the optical system's lateral color.
3 more elements
An optical system having an optical axis and comprising:
- (a) a stepped diffractive surface (SDS) which has a clear aperture and within said clear aperture comprises N concentric planar steps orthogonal to the systems's optical axis which define a non-planar base curve, said steps satisfying the relationship:
- |di|\|di+1|<2.0, for i=1 to N−2
- where di (the step depth) is the displacement along the optical axis between step i and step i+1 and where the optical path difference for each step is at least jiλ0, where λ0 is the nominal wavelength of the optical system and ji is the diffractive order of the ith step;
- and
- (b) an optical surface which has optical power and is not an SDS (non-SDS);
- wherein the SDS makes an optically significant contribution to the correction of the optical system's astigmatism.
3 more elements
An optical system having an optical axis and comprising:
- (a) a stepped diffractive surface (SDS) which has a clear aperture and within said clear aperture comprises N concentric planar steps orthogonal to the system's optical axis which define a non-planar base curve, said steps satisfying the relationship:
- |di|\|di+1|<2.0, for i=1 to N−2
- where di (the step depth) is the displacement along the optical axis between step i and step i+1 and where the optical path difference for each step is at least jiλ0, where λ0 is the nominal wavelength of the optical system and ji is the diffractive order of the ith step;
- and
- (b) an optical surface which has optical power and is not an SDS (non-SDS);
- wherein the SDS makes an optically significant contribution to the correction of the optical system's coma.
3 more elements
An optical system having an optical axis and comprising:
- (a) a stepped diffractive surface (SDS) which has a clear aperture and within said clear aperture comprises N concentric planar steps orthogonal to the system's optical axis which define a non-planar base curve, said steps satisfying the relationship:
- |di|\|di+1|<2.0, for i=1 to N−2
- where di (the step depth) is the displacement along the optical axis between step i and step i+1 and where the optical path difference for each step is at least jiλ0, where λ0 is the nominal wavelength of the optical system and ji is the diffractive order of the ith step;
- and
- (b) an optical surface which has optical power and is not an SDS (non-SDS);
- wherein the SDS makes an optically significant contribution to the correction of the optical system's distortion.
3 more elements
An optical system having an optical axis and comprising:
- (a) a stepped diffractive surface (SDS) which has a clear aperture and within said clear aperture comprises N concentric planar steps orthogonal to the system's optical axis which define a non-planar base curve, said steps satisfying the relationship:
- |di|\|di+1|<2.0, for i=1 to N−2
- where di (the step depth) is the displacement along the optical axis between step i and step i+1 and where the optical path difference for each step is at least jiλ0, where λ0 is the nominal wavelength of the optical system and ji is the diffractive order of the ith step;
- and
- (b) an optical surface which has optical power and is not an SDS (non-SDS);
- wherein the SDS makes an optically significant contribution to the correction of the optical system's spherical aberration.
3 more elements
An optical system having an optical axis and comprising:
- (a) a stepped diffractive surface (SDS) which has a clear aperture and within said clear aperture comprises N concentric planar steps orthogonal to the system's optical axis which define a non-planar base curve, said steps satisfying the relationship:
- |di|\|di+1|<2.0, for i=1 to N−2
- where di (the step depth) is the displacement along the optical axis between step i and step i+1 and where the optical path difference for each step is at least jiλ0, where λ0 is the nominal wavelength of the optical system and ji is the diffractive order of the ith step;
- and
- (b) an optical surface which has optical power and is not an SDS (non-SDS);
- wherein the SDS makes an optically significant contribution to the correction of two of the optical system's spherical aberration and:
- (1) the SDS's non-planar base curve is defined by the equation φ(R,z)=0, where R is a radial coordinate and z is an axial coordinate, and
- (2) the SDS has step widths λi(R,di) given by the equation:
- w i ( R , d i ) = d i [LeftBracketingBar] ∂ ϕ ( R , z ) ∂ z ∂ ( R , z ) ∂ R [RightBracketingBar] .
6 more elements
An optical system having an optical axis and comprising:
- (a) a stepped diffractive surface (SDS) which has a clear aperture and within said clear aperture comprises N concentric planar steps orthogonal to the system's optical axis which define a non-planar base curve, said steps satisfying the relationship:
- |di|\|di+1|<2.0, for i=1 to N−2
- where di is the displacement along the optical axis between step i and step i+1 and where the optical path difference for each step is at least jiλ0, where λ0 is the nominal wavelength of the optical system and ji is the diffractive order of the ith step;
- and
- (b) an optical surface which has optical power and is not an SDS (non-SDS);
- wherein;
- (1) the optical system has a field view of view;
- and
- (2) the SDS has a constant step depth selected to increase the SDS's average diffraction efficiency over the field at λ0.
6 more elements
An optical system having an optical axis and comprising:
- (a) a stepped diffractive surface (SDS) which has a clear aperture and within said clear aperture comprises N concentric planar steps orthogonal to the system's optical axis which define a non-planar base curve, said steps satisfying the relationship;
- |di|\|di+1|<2.0, for i=1 to N−2
- where di (the step depth) is the displacement along the optical axis between step i and step i+1 and where the optical path difference for each step is at least jiλ0, where λ0 is the nominal wavelength of the optical system and ji is the diffractive order of the ith step;
- and
- (b) an optical surface which has optical power and is not an SDS (non-SDS);
- wherein:
- (1) the optical system has a field view;
- and
- (2) the SDS has a constant step depth selected to that the maximum diffraction efficiency at λ0 occurs at an intermediate field point within the field of view.
6 more elements
An optical system having an optical axis and comprising:
- (a) a stepped diffractive surface (SDS) which has a clear aperture and within said clear aperture comprises N concentric planar steps orthogonal to the system's optical axis which define a non-planar base curve, said steps satisfying the relationship;
- |di|\|di+1|<2.0, for i=1 to N−2
- where di (the step depth) is the displacement along the optical axis between step i and step i+1 and where the optical path difference for each step is at least jiλ0, where λ0 is the nominal wavelength of the optical system and ji is the diffractive order of the ith step;
- and
- (b) an optical surface which has optical power and is not an SDS (non-SDS);
- wherein the diffraction efficiency of the SDS is optimized for a wavefront incident on the SDS which is non-planar.
3 more elements
An optical system having an optical axis and comprising:
- a stepped diffractive surface (SDS) which has a clear aperture and within said clear aperture comprises N concentric planar steps orthogonal to the system's optical axis which define a non-planar base curve, said steps satisfying the relationship:
- |di|\|di+1|<2.0, for i=1 to N−2
- where di (the step depth) is the displacement along the optical axis between step i and step i+1 and where the optical path difference for each step is at least jiλ0, where λ0 is the nominal wavelength of the optical system and ji is the diffractive order of the ith step;
- and
- (b) an optical surface which has optical power and is not an SDS (non-SDS);
- ‘wherein the diffraction efficiency of the SDS is optimized for a planar wavefront which, at the SDS, has a direction of propagation which is oriented at a non-zero angle to the optical axis.
3 more elements
An optical system having an optical axis and comprising:
- (a) stepped diffractive surface (SDS) which has a clear aperture and within said clear aperture comprises N concentric planar steps orthogonal to the system's optical axis which define a non-planar base curve, said steps satisfying the relationship:
- |di|\|di+1|<2.0, for i=1 to N−2
- where di (the step depth) is the displacement along the optical axis between step i and step i+1 and where the optical path difference for each step is at least jiλ0, where λ0 is the nominal wavelength of the optical system and ji is the diffractive order of the ith step;
- and
- (b) an optical surface which has optical power and is not an SDS (non-SDS);
- wherein the diffraction efficiency of the SDS is optimized over a spectral range.
3 more elements
A stepped diffractive surface having an optical axis and a clear aperture, said surface comprising, within said clear aperture, N concentric planar steps orthogonal to the optical axis which define a non-planar base curve defined by the equation φ(R,z)=0, where R is a radial coordinate and z is an axial coordinate, said steps satisfying the relationship:
- |di|\|di+1|<2.0, for i=1 to N−2
- where di (the step depth) is the displacement along the optical axis between step i and step i+1 and where the optical path difference for each step is at least jiλ0, where λ0 is the nominal wavelength of the optical system and ji is the diffractive order of the ith step;
- and
- wherein:
- (A) the stepped diffractive surface has step width λi (R,di) given by the equation:
- w i ( R , d i ) = d i [LeftBracketingBar] ∂ ϕ ( R , z ) ∂ z ∂ ( R , z ) ∂ R [RightBracketingBar] ;
- and
- (B) the step depths are not all equal within a diffraction order.
5 more elements
A stepped diffractive surface having an optical axis and a clear aperture, said surface comprising, within said clear aperture, N concentric planar steps orthogonal to the optical axis which define a non-planar, aspheric base curve defined by the equation φ(R,z)=0, where R is a radial coordinate and z is an axial coordinate, said steps satisfying the relationship:
- |di|\|di+1|<2.0, for i=1 to N−2
- where di (the step depth) is the displacement along the optical axis between step i and step i+1 and where the optical path difference for each step is at least jiλ0, where λ0 is the nominal wavelength of the optical system and ji is the diffractive order of the ith step;
- wherein
- (A) the stepped diffractive surface has step widths λi(R,di) given by the equation:
- w i ( R , d i ) = d i [LeftBracketingBar] ∂ ϕ ( R , z ) ∂ z ∂ ( R , z ) ∂ R [RightBracketingBar] ;
- and
- (B) the step depths are not all equal within the diffraction order.
4 more elements
A method for reducing at least one aberration of an optical system which has an optical axis and comprises:
- (i) a stepped diffractive surface (SDS) which has a clear aperture and within said clear aperture comprises N concentric planar steps orthogonal to the system's optical axis which define a non-planar base curve, said steps satisfying the relationship:
- |di|\|di+1|<2.0, for i=1 to N−2
- where di (the step depth) is the displacement along the optical axis between step i and step i+1 and where the optical path difference for each step is at least jiλ0, where λ0 is the nominal wavelength of the optical system and ji is the diffractive order of the ith step;
- and
- (ii) an optical surface which has optical power and is not a stepped diffractive surface (non-SDS);
- said method comprising:
- (a) tracing rays through the system by representing the SDS by an equation which describes diffraction by a grating;
- and
- (b) using the rays traced in step (a) to select one or more parameters of the system which reduce said at least one aberration;
- wherein in step (a), rays are traced through individual steps of the SDS using the equation which describes diffraction by a grating.
7 more elements
A method for reducing at least one aberration of an optical system which has an optical axis and comprises at least one optical element, said method comprising:
- (a) incorporating an additional optical element in the system which comprises a stepped diffractive surface (SDS) which has a clear aperture and within said clear aperture comprises N concentric planar steps orthogonal to the system's optical axis which define a non-planar base curve, said steps satisfying the relationship:
- |di|\|di+1|<2.0, for i=1 to N−2
- where di (the step depth) is the displacement along the optical axis between step i and step i+1 and where the optical path difference for each step is at least jiλ0, where λ0 is the nominal wavelength of the optical system and ji is the diffractive order of the ith step;
- and
- (b) selecting the spacing between the SDS and the at least one optical element;
- wherein step (b) is performed by tracing rays through the system by representing the SDS by an equation which describes diffraction by a grating, said equation being used to trace rays through individual steps of the SDS.
3 more elements
Dependencies are inferred from the claim text.