EP0791846A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Optical low-pass filter and optical apparatus having the same
Assignee: Canon Inc
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Filing: 1997-02-21
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Granted: —
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Expires: 2017-02-21
Abstract
Abstract An optical low-pass filter comprises a phase advancing area which advances a phase of a wavefront of an incident pencil of rays with respect to a phase of a wavefront of a center of the incident pencil of rays, and a phase retarding area which retards the phase of the wavefront of the incident pencil of rays with respect to the phase of the wavefront of the center of the incident pencil of rays, the phase advancing area and the phase retarding area alternately existing in the optical low-pass filter, and an optical apparatus comprises an image forming optical system, an image pickup element, and such an optical low-pass filter. <IMAGE>
Inventors
- 👤 Atsushi Okuyama
- 👤 Shuichi Kobayashi
- 👤 Ken Wada
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-25 06:47
CPC Classifications
G; G02; G02B; G02B5/00; G02B5/20; G02B26/00; G02B26/06; G02B27/00; G02B27/42; G02B27/46
Claims Analysis
Total Claims: 38
Claim 1
Independent Claim
106 words
An optical low-pass filter which provides an optical low-pass effect by modulating a wavefront of an incident pencil of rays, comprising: a phase advancing area which advances a phase of a wavefront of an incident pencil of rays with respect to a phase of a wavefront of a center of the incident pencil of rays; and a phase retarding area which retards the phase of the wavefront of the incident pencil of rays with respect to the phase of the wavefront of the center of the incident pencil of rays, said phase advancing area and said phase retarding area alternately existing in said optical low-pass filter.
Claim 2
Dependent Claim
38 words
An optical low-pass filter according to claim 1, wherein said phase advancing area is formed as a shape having a phase advancing action and said phase retarding area is formed as a shape having a phase retarding action.
Claim 3
Dependent Claim
46 words
An optical low-pass filter according to claim 1, wherein said phase advancing area is formed of a material having a refractive index having a phase advancing action and said phase retarding area is formed of a material having a refractive index having a phase retarding action.
Claim 4
Dependent Claim
25 words
An optical low-pass filter according to claim 1, wherein said phase advancing area and said phase retarding area are continuously formed in a rotational direction.
Claim 5
Dependent Claim
38 words
An optical low-pass filter according to claim 1, wherein said phase advancing area and phase retarding area are alternately formed in a rotational direction centered at an origin corresponding to the center of the incident pencil of rays.
Claim 6
Dependent Claim
133 words
An optical low-pass filter according to claim 5, wherein a shape S(ρ, φ) of said optical low-pass filter is expressed as follows by a cylindrical coordinate system (ρ, φ) whose origin corresponds to the center of the incident pencil of rays and in which ρ is a coordinate system (0 ≤ ρ ≤ 1) relative to a radial direction of said optical low-pass filter, which coordinate system is standardized on a radius of an effective portion of said optical low-pass filter, and φ is a coordinate system (0 ≤ φ ≤ 2π) relative to the rotational direction of said optical low-pass filter: S(ρ,φ) = R(ρ) × cos(mφ + δ), where R(ρ) is a radial shape of said optical low-pass filter, m is an integer not less than 2, and δ is a constant.
Claim 7
Dependent Claim
133 words
An optical low-pass filter according to claim 5, wherein a shape S(ρ, φ) of said optical low-pass filter is expressed as follows by a cylindrical coordinate system (ρ, φ) whose origin corresponds to the center of the incident pencil of rays and in which ρ is a coordinate system (0 ≤ ρ ≤ 1) relative to a radial direction of said optical low-pass filter, which coordinate system is standardized on a radius of an effective portion of said optical low-pass filter, and φ is a coordinate system (0 ≤ φ ≤ 2π) relative to the rotational direction of said optical low-pass filter: S(ρ,φ) = m Am × Rm(ρ) × cos{m(φ + δm)}, where Rm(ρ) is a radial shape of said optical low-pass filter, m is an integer, and Am and δm are constants.
Claim 8
Dependent Claim
140 words
An optical low-pass filter according to claim 5, wherein a shape S(ρ, φ) of said optical low-pass filter is expressed as follows by a cylindrical coordinate system (ρ, φ) whose origin corresponds to the center of the incident pencil of rays and in which ρ is a coordinate system (0 ≤ ρ ≤ 1) relative to a radial direction of said optical low-pass filter, which coordinate system is standardized on a radius of an effective portion of said optical low-pass filter, and φ is a coordinate system (0 ≤ φ ≤ 2π) relative to the rotational direction of said optical low-pass filter: S(ρ,φ) = R(ρ) × cos{m(φ + kf(ρ) + δ)} , where R(ρ) is a radial shape of said optical low-pass filter, f(ρ) is an arbitrary function of ρ, m is an integer, and k and δ are constants.
Claim 9
Dependent Claim
142 words
An optical low-pass filter according to claim 5, wherein a shape S(ρ, φ) of said optical low-pass filter is expressed as follows by a cylindrical coordinate system (ρ, φ) whose origin corresponds to the center of the incident pencil of rays and in which ρ is a coordinate system (0 ≤ ρ ≤ 1) relative to a radial direction of said optical low-pass filter, which coordinate system is standardized on a radius of an effective portion of said optical low-pass filter, and φ is a coordinate system (0 ≤ φ ≤ 2π) relative to the rotational direction of said optical low-pass filter: S(ρ,φ) = m Am × Rm(ρ) × cos{m(φ + fm(ρ) + δm)}, where Rm(ρ) is a radial shape of said optical low-pass filter, fm(ρ) is an arbitrary function of ρ, m is an integer, and Am and δm are constants.
Claim 10
Dependent Claim
147 words
An optical low-pass filter according to claim 5, wherein a gradient refractive index N(ρ, φ) of said optical low-pass filter is expressed as follows by a cylindrical coordinate system (ρ, φ) whose origin corresponds to the center of the incident pencil of rays and in which ρ is a coordinate system (0 ≤ ρ ≤ 1) relative to a radial direction of said optical low-pass filter, which coordinate system is standardized on a radius of an effective portion of said optical low-pass filter, and φ is a coordinate system (0 ≤ φ ≤ 2π) relative to the rotational direction of said optical low-pass filter: N(ρ,φ) = N0 + Nr(ρ) × cos(mφ + δ), where N0 is a refractive index relative at the origin, Nr(ρ) is a gradient refractive index relative to the radial direction, m is an integer not less than 2, and δ is a constant.
Claim 11
Dependent Claim
148 words
An optical low-pass filter according to claim 5, wherein a gradient refractive index N(ρ, φ) of said optical low-pass filter is expressed as follows by a cylindrical coordinate system (ρ, φ) whose origin corresponds to the center of the incident pencil of rays and in which ρ is a coordinate system (0 ≤ ρ ≤ 1) relative to a radial direction of said optical low-pass filter, which coordinate system is standardized on a radius of an effective portion of said optical low-pass filter, and φ is a coordinate system (0 ≤ φ ≤ 2π) relative to the rotational direction of said optical low-pass filter: N(ρ,φ) = N0 + m Am × Nrm(ρ) × cos{m(φ + δm)} , where N0 is a refractive index relative at the origin, Nrm(ρ) is a gradient refractive index relative to the radial direction, m is an integer, and Am and δm are constants.
Claim 12
Dependent Claim
154 words
An optical low-pass filter according to claim 5, wherein a gradient refractive index N(ρ, φ) of said optical low-pass filter is expressed as follows by a cylindrical coordinate system (ρ, φ) whose origin corresponds to the center of the incident pencil of rays and in which ρ is a coordinate system (0 ≤ ρ ≤ 1) relative to a radial direction of said optical low-pass filter, which coordinate system is standardized on a radius of an effective portion of said optical low-pass filter, and φ is a coordinate system (0 ≤ φ ≤ 2π) relative to the rotational direction of said optical low-pass filter: N(ρ,φ) = N0 + Nr(ρ) × cos{m(φ + kf(ρ) + δ)} , where N0 is a refractive index relative at the origin, Nr(ρ) is a gradient refractive index relative to the radial direction, f(ρ) is an arbitrary function of ρ, m is an integer, and k and δ are constants.
Claim 13
Dependent Claim
157 words
An optical low-pass filter according to claim 5, wherein a gradient refractive index N(ρ, φ) of said optical low-pass filter is expressed as follows by a cylindrical coordinate system (ρ, φ) whose origin corresponds to the center of the incident pencil of rays and in which ρ is a coordinate system (0 ≤ ρ ≤ 1) relative to a radial direction of said optical low-pass filter, which coordinate system is standardized on a radius of an effective portion of said optical low-pass filter, and φ is a coordinate system (0 ≤ φ ≤ 2π) relative to the rotational direction of said optical low-pass filter: N(ρ,φ) = N0 + m Am × Nrm(ρ) × cos{m(φ + fm(ρ) + δm)} , where N0 is a refractive index relative at the origin, Nrm(ρ) is a gradient refractive index relative to the radial direction, fm(ρ) is an arbitrary function of ρ, m is an integer, and Am and δm are constants.
Claim 14
Dependent Claim
148 words
An optical low-pass filter according to claim 1, wherein a wavefront aberration W(ρ, φ) which occurs in a pencil of rays transmitted through said optical low-pass filter is expressed as follows by a cylindrical coordinate system (ρ, φ) whose origin corresponds to the center of the incident pencil of rays and in which ρ is a coordinate system (0 ≤ ρ ≤ 1) relative to a radial direction of said optical low-pass filter, which coordinate system is standardized on a radius of an effective portion of said optical low-pass filter, and φ is a coordinate system (0 ≤ φ ≤ 2π) relative to a rotational direction of said optical low-pass filter: W(ρ,φ) = Wr(ρ) × Wt(φ), provided that the following conditions are satisfied: Wr(0.3)/ Wr(0.6)>0, Wr(0.6)/Wr(0.9)>0, where Wr(ρ) is a wavefront aberration relative to the radial direction and Wt(φ) is a wavefront aberration relative to the rotational direction.
Claim 15
Dependent Claim
168 words
An optical low-pass filter according to claim 1, wherein a wavefront aberration W(ρ, φ) which occurs in a pencil of rays transmitted through said optical low-pass filter is expressed as follows by a cylindrical coordinate system (ρ, φ) whose origin corresponds to the center of the incident pencil of rays and in which ρ is a coordinate system (0 ≤ ρ ≤ 1) relative to a radial direction of said optical low-pass filter, which coordinate system is standardized on a radius of an effective portion of said optical low-pass filter, and φ is a coordinate system (0 ≤ φ ≤ 2π) relative to a rotational direction of said optical low-pass filter: W(ρ,φ) = Wr(ρ) × Wt(φ), and an amount of variation, Wr'(ρ), in the wavefront aberration relative to the radial direction is expressed as Wr'(ρ) = ∂W(ρ)/∂ρ, provided that the following conditions are satisfied: Wr'(0.3)/Wr'(0.6)>1, Wr'(0.6)/Wr'(0.9)<1, where Wr(ρ) is a wavefront aberration relative to the radial direction and Wt(φ) is a wavefront aberration relative to the rotational direction.
Claim 16
Dependent Claim
165 words
An optical low-pass filter according to claim 1, wherein a shape S(ρ, φ) of said optical low-pass filter is expressed as follows by a cylindrical coordinate system (ρ, φ) whose origin corresponds to the center of the incident pencil of rays and in which ρ is a coordinate system (0 ≤ ρ ≤ 1) relative to a radial direction of said optical low-pass filter, which coordinate system is standardized on a radius of an effective portion of said optical low-pass filter, and φ is a coordinate system (0 ≤ φ ≤ 2π) relative to a rotational direction of said optical low-pass filter: S(ρ,φ) = R(ρ) × T(φ), and an amount of variation in shape, R'(ρ), relative to the radial direction is expressed as R'(ρ) = ∂R(ρ)/∂ρ, provided that the following conditions are satisfied: R'(0.3)/R'(0.6)>1, R'(0.6)/R'(0.9)<1, where R(ρ) is a shape of said optical low-pass filter relative to the radial direction and T(φ) is a shape of said optical low-pass filter relative to the rotational direction.
Claim 17
Dependent Claim
173 words
An optical low-pass filter according to claim 1, wherein a gradient refractive index N(ρ, φ) of said optical low-pass filter is expressed as follows by a cylindrical coordinate system (ρ, φ) whose origin corresponds to the center of the incident pencil of rays and in which ρ is a coordinate system (0 ≤ ρ ≤ 1) relative to a radial direction of said optical low-pass filter, which coordinate system is standardized on a radius of an effective portion of said optical low-pass filter, and φ is a coordinate system (0 ≤ φ ≤ 2π) relative to a rotational direction of said optical low-pass filter: N(ρ,φ) = N0 + Nr(ρ) × Nt(φ) , and an amount of variation in refractive index, Nr'(ρ), relative to the radial direction is expressed as Nr'(ρ) = ∂N(ρ)/∂ρ, provided that the following conditions are satisfied: Nr'(0.3)/Nr'(0.6)>1, Nr'(0.6)/Nr'(0.9)<1, where N0 is a refractive index at the origin, Nr(ρ) is a gradient refractive index relative to the radial direction, and Nt(φ) is a gradient refractive index relative to the rotational direction.
Claim 18
Dependent Claim
168 words
An optical low-pass filter according to claim 1, wherein a wavefront aberration W(ρ, φ) which occurs in a pencil of rays transmitted through said optical low-pass filter is expressed as follows by a cylindrical coordinate system (ρ, φ) whose origin corresponds to the center of the incident pencil of rays and in which ρ is a coordinate system (0 ≤ ρ ≤ 1) relative to a radial direction of said optical low-pass filter, which coordinate system is standardized on a radius of an effective portion of said optical low-pass filter, and φ is a coordinate system (0 ≤ φ ≤ 2π) relative to a rotational direction of said optical low-pass filter: W(ρ,φ) = Wr(ρ) × Wt(φ), and an amount of variation, Wr'(ρ), in the wavefront aberration relative to the radial direction is expressed as Wr'(ρ) = ∂W(ρ)/∂ρ, provided that the following conditions are satisfied: Wr(0.25)/Wr(0.75)<0, Wr'(0.3)/Wr'(0.6)<0, where Wr(ρ) is a wavefront aberration relative to the radial direction and Wt(φ) is a wavefront aberration relative to the rotational direction.
Claim 19
Dependent Claim
166 words
An optical low-pass filter according to claim 1, wherein a shape S(ρ, φ) of said optical low-pass filter is expressed as follows by a cylindrical coordinate system (ρ, φ) whose origin corresponds to the center of the incident pencil of rays and in which ρ is a coordinate system (0 ≤ ρ ≤ 1) relative to a radial direction of said optical low-pass filter, which coordinate system is standardized on a radius of an effective portion of said optical low-pass filter, and φ is a coordinate system (0 ≤ φ ≤ 2π) relative to a rotational direction of said optical low-pass filter: S(ρ,φ) = R(ρ) × T(φ) , and an amount of variation in shape, R'(ρ), relative to the radial direction is expressed as R'(ρ) = ∂R(ρ)/∂ρ, provided that the following conditions are satisfied: R(0.25)/R(0.75)<0, R'(0.3)/R'(0.6)<0, where R(ρ) is a shape of said optical low-pass filter relative to the radial direction and T(φ) is a shape of said optical low-pass filter relative to the rotational direction.
Claim 20
Dependent Claim
176 words
An optical low-pass filter according to claim 1, wherein a gradient refractive index N(ρ, φ) of said optical low-pass filter is expressed as follows by a cylindrical coordinate system (ρ, φ) whose origin corresponds to the center of the incident pencil of rays and in which ρ is a coordinate system (0 ≤ ρ ≤ 1) relative to a radial direction of said optical low-pass filter, which coordinate system is standardized on a radius of an effective portion of said optical low-pass filter, and φ is a coordinate system (0 ≤ φ ≤ 2π) relative to a rotational direction of said optical low-pass filter: N(ρ,φ) = N0 + Nr(ρ) × Nt(φ) , and an amount of variation in refractive index, Nr'(ρ), relative to the radial direction is expressed as Nr'(ρ) = ∂N(ρ)/∂ρ , provided that the following conditions are satisfied: Nr(0.25)/Nr(0.75)<0, Nr'(0.3)/Nr'(0.6)<0, where N0 is a refractive index at the origin, Nr(ρ) is a gradient refractive index function relative to the radial direction, and Nt(φ) is a gradient refractive index function relative to the rotational direction.
Claim 21
Dependent Claim
53 words
An optical low-pass filter according to claim 1, wherein said phase advancing area and said phase retarding area exist with a predetermined period in a rotational direction centered at an origin corresponding to the center of the incident pencil of rays, said predetermined period differing from area to area in a radial direction.
Claim 22
Dependent Claim
128 words
An optical low-pass filter according to claim 21, wherein a wavefront aberration W(ρ, φ) which occurs in a pencil of rays transmitted through said optical low-pass filter is expressed as follows by a cylindrical coordinate system (ρ, φ) whose origin corresponds to the center of the incident pencil of rays and in which ρ is a coordinate system (0 ≤ ρ ≤ 1) relative to the radial direction of said optical low-pass filter, which coordinate system is standardized on a radius of an effective portion of said optical low-pass filter, and φ is a coordinate system (0 ≤ φ ≤ 2π) relative to the rotational direction of said optical low-pass filter: where Wri(ρ) is a wavefront aberration relative to the radial direction and mi and δi are constants.
Claim 23
Dependent Claim
18 words
An optical low-pass filter according to claim 22, wherein said optical low-pass filter satisfies the following condition: m1<m2.
Claim 24
Dependent Claim
24 words
An optical low-pass filter according to claim 1, wherein said phase advancing area and said phase retarding area are formed in a step-formed shape.
Claim 25
Dependent Claim
39 words
An optical low-pass filter according to claim 24, wherein said phase advancing area and said phase retarding area are alternately formed in the rotational direction centered at an origin corresponding to the center of the incident pencil of rays.
Claim 26
Dependent Claim
146 words
An optical low-pass filter according to claim 25, wherein a shape S(ρ, φ) of said optical low-pass filter is expressed as follows by a cylindrical coordinate system (ρ, φ) whose origin corresponds to the center of the incident pencil of rays and in which ρ is a coordinate system (0 ≤ ρ ≤ 1) relative to a radial direction of said optical low-pass filter, which coordinate system is standardized on a radius of an effective portion of said optical low-pass filter, and φ is a coordinate system (0 ≤ φ ≤ 2π) relative to the rotational direction of said optical low-pass filter: S(ρ,φ) = Step(R(ρ) × cos(mφ + δ)) , where R(ρ) is a basic shape of said optical low-pass filter relative to the radial direction, δ is a constant and Step(f) is a function for converting the continuous function f into a predetermined step function.
Claim 27
Dependent Claim
19 words
An optical low-pass filter according to claim 1, further comprising a shape which corrects an error occurring during molding.
Claim 28
Dependent Claim
108 words
An optical low-pass filter comprising: a phase advancing area which advances a phase of a wavefront of an incident pencil of rays with respect to a phase of a wavefront of a center of the incident pencil of rays; and a phase retarding area which retards the phase of the wavefront of the incident pencil of rays with respect to the phase of the wavefront of the center of the incident pencil of rays, at least either one of said phase advancing area and said retarding area being provided as a plurality of phase advancing areas or a plurality of phase retarding areas in said optical low-pass filter.
Claim 29
Dependent Claim
72 words
An optical low-pass filter comprising: an area having an optical path length longer than an optical path length of a center of said optical low-pass filter; and an area having an optical path length shorter than the optical path length of the center of said optical low-pass filter, said area having the longer optical path length and said area having the shorter optical path length alternately existing in said optical low-pass filter.
Claim 30
Independent Claim
119 words
A method of manufacturing an optical low-pass filter, comprising the steps of: charging a material into a mold; and removing the material molded by the mold, said optical low-pass filter alternately including a phase advancing area which advances a phase of a wavefront of an incident pencil of rays with respect to a phase of a wavefront of a center of the incident pencil of rays, and a phase retarding area which retards the phase of the wavefront of the incident pencil of rays with respect to the phase of the wavefront of the center of the incident pencil of rays, and said mold having a shape which corrects an error occurring during molding of said optical low-pass filter.
Claim 31
Dependent Claim
32 words
A method of manufacturing an optical low-pass filter according to claim 30, wherein the error includes an error of a shape of said optical low-pass filter which occurs during the molding thereof.
Claim 32
Dependent Claim
33 words
A method of manufacturing an optical low-pass filter according to claim 30, wherein the error includes a non-uniformity of a refractive index of said optical low-pass filter which occurs during the molding thereof.
Claim 33
Dependent Claim
20 words
A method of manufacturing an optical low-pass filter according to claim 30, wherein the material includes a synthetic resin material.
Claim 34
Dependent Claim
19 words
A method of manufacturing an optical low-pass filter according to claim 30, wherein the material includes a glass material.
Claim 35
Dependent Claim
93 words
An optical apparatus comprising: an image forming optical system; an image pickup element; and an optical low-pass filter, said optical low-pass filter alternately including a phase advancing area which advances a phase of a wavefront of an incident pencil of rays with respect to a phase of a wavefront of a center of the incident pencil of rays, and a phase retarding area which retards the phase of the wavefront of the incident pencil of rays with respect to the phase of the wavefront of the center of the incident pencil of rays.
Claim 36
Dependent Claim
26 words
An optical apparatus according to claim 35, wherein said optical low-pass filter is provided in a vicinity of a stop of said image forming optical system.
Claim 37
Dependent Claim
54 words
An optical apparatus according to claim 35, wherein said optical low-pass filter is arranged in such a manner that a direction in which its phase advancing or retarding action is large is inclined in the range of 30° to 60° with respect to a direction of array of pixels of said image pickup element.
Claim 38
Dependent Claim
50 words
An optical apparatus according to claim 35, wherein said optical low-pass filter is arranged in such a manner that a direction in which its phase advancing or retarding action is large is inclined by approximately 45° with respect to a direction of array of pixels of said image pickup element.
References Cited (Backward Citations)
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