IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
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출원번호 |
US-0156960
(2002-05-30)
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우선권정보 |
JP-0063398 (2000-03-08) |
발명자
/ 주소 |
|
출원인 / 주소 |
|
대리인 / 주소 |
Fitzpatrick, Cella, Harper & Scinto
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인용정보 |
피인용 횟수 :
7 인용 특허 :
63 |
초록
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An optical system includes a diffractive optical element having a diffraction grating provided, on a lens surface having a curvature, in a concentric-circles shape rotationally-symmetrical with respect to an optical axis. The sign of the curvature of the lens surface having the diffraction grating p
An optical system includes a diffractive optical element having a diffraction grating provided, on a lens surface having a curvature, in a concentric-circles shape rotationally-symmetrical with respect to an optical axis. The sign of the curvature of the lens surface having the diffraction grating provided thereon is the same as the sign of a focal length, at a design wavelength, of a system composed of, in the optical system, a surface disposed nearest to an object side to a surface disposed immediately before the lens surface having the diffraction grating provided thereon, and is different from the sign of the distance from the optical axis to a position where the center ray of an off-axial light flux enters the lens surface having the diffraction grating provided thereon. Further, the apex of an imaginary cone formed by extending a non-effective surface of the diffraction grating is located adjacent to the center of curvature of the lens surface having the diffraction grating provided thereon.
대표청구항
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1. An optical system, comprising:a diffractive optical element having a diffraction grating provided, on a lens surface having curvature, in a concentric-circles shape rotationally-symmetrical with respect to an optical axis,wherein a sign of the curvature of the lens surface having said diffraction
1. An optical system, comprising:a diffractive optical element having a diffraction grating provided, on a lens surface having curvature, in a concentric-circles shape rotationally-symmetrical with respect to an optical axis,wherein a sign of the curvature of the lens surface having said diffraction grating provided thereon is the same as a sign of a focal length, in a design wavelength, of a system composed of, in said optical system, a surface disposed nearest to a front side to a surface disposed immediately before the lens surface having said diffraction grating thereon, and is different from a sign of a distance from the optical axis to a position where a center ray of an off-axial light flux enters the lens surface having said diffraction grating provided thereon,wherein the following condition is satisfied: |DL/R|< 0.3where DL is a distance from (a) the apex of an imaginary cone formed by extending a non-effective surface of said diffraction grating to (b) the center of curvature of the lens surface having said diffraction grating provided thereon, and R is a radius of curvature of the lens surface having said diffraction grating provided thereon. 2. An optical system according to claim 1, wherein said optical system satisfies the following condition: |D/R|< 5where D is a distance from the center of curvature of the lens surface having said diffraction grating provided thereon to a focus, at the design wavelength, of the system composed of, in said optical system, the surface disposed nearest to the front side to the surface disposed immediately before the lens surface having said diffraction grating provided thereon. 3. An optical system according to claim 1, wherein said optical system satisfies the following condition: C 1 ·P<0where P is a refractive power of the lens surface having said diffraction grating provided thereon, and C 1 is a phase coefficient for a second-degree term when a phase shape of said diffraction grating is expressed by the following equation: Y )=(2π/λ 0 )( C 1 Y 2 +C 2 Y 4 +C 3 Y 6 +. . . )where Y is the height in a vertical direction from the optical axis, λ 0 is the design wavelength, and C i is a phase coefficient (i=1, 2, 3 . . . ). 4. An optical system according to claim 1, wherein said diffraction grating is a laminated diffraction grating. 5. An optical system according to claim 4, wherein said laminated diffraction grating is an adjacently-laminated diffraction grating in which two diffraction gratings are disposed adjacent to each other across an air layer. 6. An optical apparatus comprising an optical system according to claim 5, wherein said adjacently-laminated diffraction grating is provided between two adjacent lens surfaces having substantially the same curvature, and is composed of three layers, including, in order from the front side, a first layer, a second layer and a third layer, said second layer being the air layer,wherein said optical apparatus is selected from the group of optical apparatuses consisting of an image pickup apparatus, a film camera, a video camera, a digital camera, an observation apparatus, a telescope, a binocular, a projection exposure apparatus, and a stepper for manufacturing a semiconductor device. 7. An optical system according to claim 5, wherein each of said two diffraction gratings of said adjacently-laminated diffraction grating are formed with ultraviolet-curable plastic. 8. An optical system according to claim 1, wherein said diffraction grating is a blazed-type diffraction grating. 9. An optical apparatus comprising:an optical system comprising a diffractive optical element having a diffraction grating provided, on a lens surface having curvature, in a concentric-circles shape rotationally-symmetrical with respect to an optical axis,wherein a sign of the curvature of the lens surface having said diffraction grating provided thereon is the same as a sign of a focal length , in a design wavelength, of a system composed of, in said optical system, a surface disposed nearest to a front side to a surface disposed immediately before the lens surface having said diffraction grating thereon, and is different from a sign of a distance from the optical axis to a position where a center ray of an off-axial light flux enters the lens surface having said diffraction grating provided thereon,wherein the following condition is satisfied: DL/R|< 0.3where DL is a distance from (a) the apex of an imaginary cone formed by extending a non-effective surface of said diffraction grating to (b) the center of curvature of the lens surface having said diffraction grating provided thereon, and R is a radius of curvature of the lens surface having said diffraction grating provided thereon. 10. An optical apparatus according to claim 9, wherein said optical apparatus is selected from the group of optical apparatuses consisting of an image pickup apparatus, a film camera, a video camera, a digital camera, an observation apparatus, a telescope, a binocular, a projection exposure apparatus, and a stepper for manufacturing a semiconductor device. 11. An optical system, comprising:a diffractive optical element having a diffraction grating provided, on a lens surface having curvature, in a concentric-circles shape rotationally-symmetrical with respect to an optical axis,wherein a sign of the curvature of the lens surface having said diffraction grating provided thereon is the same as a sign of a focal length, in a design wavelength, of a system composed of, in said optical system, a surface disposed nearest to a front side to a surface disposed immediately before the lens surface having said diffraction grating thereon, and is different from a sign of a distance from the optical axis to a position where a center ray of an off-axial light flux enters the lens surface having said diffraction grating provided thereon,wherein an apex of an imaginary cone formed by extending a non-effective surface of said diffraction grating is located adjacent to the center of curvature of the lens surface having said diffraction grating provided thereon,wherein said diffraction grating is a laminated diffraction grating, andwherein said laminated diffraction grating is an adjacently-laminated diffraction grating in which two diffraction gratings are disposed adjacent to each other across an air layer. 12. An optical system according to claim 11, wherein each of said two diffraction gratings of said adjacently-laminated diffraction grating are formed with ultraviolet-curable plastic. 13. An optical apparatus, comprising:an optical system according to claim 11. 14. An optical apparatus according to claim 13, wherein said optical apparatus is selected from the group of optical apparatuses consisting of an image pickup apparatus, a film camera, a video camera, a digital camera, an observation apparatus, a telescope, a binocular, a projection exposure apparatus, and a stepper for manufacturing a semiconductor device. 15. An optical apparatus according to claim 14, wherein said adjacently-laminated diffraction grating is provided between two adjacent lens surfaces having substantially the same curvature, and is composed of three layers, including, in order from the front side, a first layer, a second layer and a third layer, said second layer being the air layer. 16. An optical system, comprising:a diffractive optical element having a diffraction grating provided, on a lens surface having curvature, in a concentric-circles shape rotationally-symmetrical with respect to an optical axis,wherein a sign of the curvature of the lens surface having said diffraction grating provided thereon is the same as a sign of a focal length, in a design wavelength, of a system composed of, in said optical system, a surface disposed nearest to a front side to a surface disposed immediately before the lens surface having said diffraction grating thereon, and is diff erent from a sign of a distance from the optical axis to a position where a center ray of an off-axial light flux enters the lens surface having said diffraction grating provided thereon,wherein the following condition is satisfied: DL/R|< 0.3where DL is a distance from (a) the apex of an imaginary cone formed by extending a non-effective surface of said diffraction grating to (b) the center of curvature of the lens surface having said diffraction grating provided thereon, and R is a radius of curvature of the lens surface having said diffraction grating provided thereon,wherein the apex of the imaginary cone is located on the optical axis, andwherein said diffraction grating is entirely a blazed-type diffraction grating.
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