Reduced aliasing distortion optical filter, and an image sensing device using same
AssigneeCanon Kabushiki Kaisha
InventorsNobuhiro Takeda, Takashi Sasaki, Masato Ikeda
Life of this patent
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Abstract
During the exposure of an image sensing device, the optical image of a subject is rotated by one revolution or a plurality of revolutions relative to the sensing surface of the image sensing device along a plane perpendicular to the plane of the image sensing device while the orientation of the image is maintained substantially horizontally and vertically with respect to the sensing surface. The radius r of this rotation is set so as to satisfy the equation r = ω 0 2 π ρ where ρ represents trap frequency and ω0 the initial zero point of a Bessel function of the first kind of order zero.
Claims37
An image sensing apparatus comprising:
- image forming means for forming an image for luminance signal and an image for color signal of a subject on a sensing surface of an image sensing device;
- optical image rotating means for rotating an optical image of the subject during an exposure interval of said image sensing device in such a manner that the optical image makes one or a plurality of revolutions relative to the sensing surface along a plane perpendicular to the surface of said image sensing device while orientation of the optical image is substantially maintained vertically and horizontally with respect to the surface of said image sensing device, said optical image rotating means forming the optical image of the subject on the sensing surface via said image forming means;
- and
- setting means for setting a size of a rotational path of the optical image of the subject by said optical image rotating means, the size being determined according to a pitch of pixels of said image sensing device in the case of forming the image for luminance signal by the image of forming means, and the size being determined according to an arranging period of a color filter of said image sensing device in the case of forming the image for color signal by the image forming means.
An optical spatial filter device for controlling a spatial frequency characteristic of an optical image for luminance signal and an optical image for color signal delivered by an image forming optical system and formed on an image sensing device, said device comprising:
- luminous flux rotating means for rotating a luminous flux, which is delivered by the image forming optical system, on a sensing surface of said image sensing device along a closed path along a plane perpendicular to the optic axis of said image forming optical system while orientation of the luminous flux is substantially maintained vertically and horizontally;
- setting means for setting a size of a rotation al path of the optical image of the subject by said optical image rotating means, the size being determined according to a pitch of pixels of said image sensing device in the case of forming the image for luminance signal by the image forming optical system, and the size being determined according to an arranging period of a color filter of said image sensing device in the case of forming the image for color signal by the image forming optical system;
- and
- control means for controlling said luminous flux rotating means in such a manner that the luminous flux is made one or more revolutions of the size set by said setting means, during an exposure interval of said image sensing device.
A method of controlling a spatial frequency characteristic of an optical image for luminance signal and an optical image for color signal formed on an image sensing device and reducing aliasing distortion of the optical image, comprising the steps of:
- determining a spatial frequency characteristic of the optical image on the basis of a pitch of pixels of the image sensing device in the case of forming the image for luminance signal, and on the basis of an arranging period of a color filter of said image sensing device in the case of forming the image for color signal;
- obtaining a spatial-frequency limiting characteristic relationship between a zero-point frequency of the spatial frequency characteristic of the optical image, the zero-point frequency being on an image forming surface of said image sensing device when the optical image has been rotated at a predetermined rotational velocity about the optic axis, and radius of curvature of this rotation;
- deciding radius of curvature which prevails when a trap frequency in the spatial frequency characteristic of said image sensing device is made to coincide with the zero-point frequency of the spatial-frequency limiting characteristic;
- and
- rotating the optical image, in accordance with a radius of curvature decided, at a predetermined velocity relative to the sensing surface of said image sensing device.
An image sensing apparatus comprising:
- optical image rotating device to rotate an optical image of a subject during an exposure interval of an image sensing device in such a manner that the optical image makes one or a plurality of revolutions relative to the sensing surface along a plane perpendicular to the surface of said image sensing device while orientation of the optical image is substantially maintained vertically and horizontally with respect to the surface of said image sensing device;
- and
- setting devices arranged to set a size of a rotational path of the optical image of the subject by said optical image rotating device the size being determined according to a pitch of pixels of said image sensing device in the case of forming the image for luminance signal and the size being determined according to an arranging period of a color filter of said image sensing device in the case of forming the image for color signal.
Dependencies are inferred from the claim text.