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US 6,473,232 B2Granted
Optical system having a diffractive optical element, and optical apparatus
AssigneeCanon Kabushiki Kaisha
InventorHideki Ogawa
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AssigneeCanon Kabushiki Kaisha
InventorHideki Ogawa
Estimating the term…
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.
An optical system, comprising:
Dependencies are inferred from the claim text.
Drawings are temporarily unavailable. Open the PDF at USPTO
From the US filing history. Foreign family members aren’t listed.
Structurally combined with optical elements not having diffractive power: such optical elements having dioptric power
Having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations…:…
Optical elements, systems or apparatus
Term ended 6 Mar 2021 (estimated)
1. Field of the Invention
The present invention relates to an optical system having a diffractive optical element, and more particularly to an optical system suited to optical apparatuses, such as film cameras, video cameras, digital cameras, telescopes, projectors, etc., in which a diffractive optical element and a refracting optical element are combined to effect achromatism well.
2. Description of Related Art
These and further objects and features of the invention will become apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings.
FIG. 1 is a sectional view of an optical system according to a first embodiment of the invention.
FIG. 2 is a sectional view of an optical system according to a second embodiment of the invention.
Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.
FIGS. 1, 2 and 3 are sectional views showing the essential parts of optical systems OL according to first, second and third embodiments of the invention, respectively. In the examples shown in FIGS. 1, 2 and 3, the invention is applied to the photographing optical systems OL of the telephoto type, of the Gauss type and of the inverted telephoto type, respectively. In FIGS. 1, 2 and 3, reference character DO denotes a diffractive optical surface which is a lens surface having a diffraction grating provided thereon. The diffraction grating is formed in a concentric-circles shape rotationally-symmetrical with respect to an optical axis, and the form of a section of the diffraction grating is the blazed type. Reference character SP denotes an aperture stop for determining the brightness of the optical system OL, and reference character IP denotes an image plane.
FIGS. 4 and 5 are diagrams for explaining the diffractive optical surface according to the invention. In the state shown in each of FIGS. 4 and 5, a diffraction grating 2 of the blazed type is provided on a lens surface 1a on one side of a lens 1. In FIG. 4, reference numeral 4 denotes an effective surface having a desired diffracting function of the diffraction grating, and reference numeral 3 denotes a side surface which is obtained when forming the diffraction grating 2 of the blazed type on the lens surface 1a and does not take part in the diffracting function (hereinafter referred to as the “non-effective surface”).