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US 5,471,344 AGranted
Photographing apparatus having optical low-pass filter
AssigneeCanon Kabushiki Kaisha
InventorSaburo Sugawara
Life of this patent
Estimating the term…
Abstract
A photographing apparatus comprising an optical low-pass filter of phase grating type in which a plurality of prism portions, convex or concave in cross section, are arrayed in succession at a predetermined pitch, the arrangement being such that the aperture center or the optical axis of a photo taking lens is located substantially at an apex position of a concave or convex portion which is formed by a prism portion and its adjacent prism portion.
Claims12
A photographing apparatus comprising:
- taking lens means for determining an optical axis;
- and
- an optical member including a plurality of prism portions arrayed in succession at a predetermined pitch,
- wherein said optical member is arranged so that the optical axis is substantially located at a concave portion formed by one prism portion of said optical member and another prism portion adjacent said one prism portion, and
- wherein a cross section of each of said plurality of prism portions is of a trapezoidal shape, and
- wherein each of said trapezoidal-shaped prism portions has a slope plane and a top plane portion, and assuming that a width of said slope plane is B and a deviation amount between an apex of the concave portion and the optical axis is D, the following condition is satisfied:
- .vertline.D.vertline./B<0.33,
- and
- wherein assuming that the width of said top plane portion is A, the pitch is P, a first order diffraction angle of said optical member is .theta..sub.f, and a refraction angle of said slope plane is .theta..sub.r, the following further conditions are satisfied:
- 0.15<A/P<0.35,
- and
- 0.5<.theta..sub.r /.theta..sub.f <1.4.
9 more elements
A photographing apparatus comprising:
- a taking lens, which determines an optical axis;
- and
- an optical low-pass filter comprising a pair of low-pass filter portions each including prism portions each having slope planes and a plane portion, which have a boundary portion between said prism portions that are adjacent, said prism portions being arrayed at a predetermined pitch P,
- wherein said low-pass filter portions are positioned adjacent to each other at an adjoining portion of said optical low-pass filter, and
- wherein said prism portions of one of said pair of low-pass filter portions are shifted with respect to said prism portions of the other of said pair of low-pass filter portions, along the adjoining portion, by a deviation amount of P/2, and
- wherein said optical low-pass filter is arranged so that the optical axis intersects the boundary portion of one of said prism portions.
3 more elements
A photographing apparatus comprising:
- a taking lens, which determines an optical axis;
- and
- an optical low-pass filter comprising a pair of low-pass filter portions each including prism portions each having slope planes and a plane portion, which have a boundary portion between said prism portions that are adjacent, said prism portions being arrayed at a predetermined pitch P,
- wherein said low-pass filter portions are positioned adjacent to each other at an adjoining portion of said optical low-pass filter, and
- wherein said prism portions of one of said pair of low-pass filter portions are shifted with respect to said prism portions of the other of said pair of low-pass filter portions, along the adjoining portion, by a deviation amount, which is less than or equal to the pitch P of said prism portions, and
- wherein said optical low-pass filter is arranged so that the optical axis intersects the boundary portion of one of said prism portions, and
- wherein assuming that a refraction angle of a light flux at said slope planes is .theta..sub.r, and a first order diffraction angle of said optical filter is .theta..sub.f, the following condition is satisfied:
- 0.5<.theta..sub.r /.theta..sub.f <1.4.
5 more elements
An apparatus comprising:
- taking lens means having an aperture;
- a stop for changing a diameter of the aperture;
- and
- an optical low-pass filter, including a plurality of prism portions disposed at a predetermined pitch, each of said prism portions having a top portion;
- wherein a center of the aperture is substantially coincident with a center of one of said top portions;
- and
- wherein said apparatus satisfies the following relationship:
- 0.5<.theta..sub.r /.theta..sub.f <1.4,
- wherein .theta..sub.f is the first-order diffraction angle of said optical low-pass filter and .theta..sub.r is the refraction angle of light of said slope forming said top portions.
6 more elements
An apparatus comprising:
- taking lens means;
- and
- an optical low-pass filter provided in an optical path of said taking lens means, said optical low-pass filter comprising a plurality of prism portions arranged in succession at a predetermined pitch, each of said prism portions having slope planes;
- wherein said apparatus satisfies the relationship:
- 0.5<.theta..sub.r /.theta..sub.f <1.4,
- wherein .theta..sub.f is the first-order diffraction angle of said optical low-pass filter and .theta..sub.r is the refraction angle of light of said slope planes.
3 more elements
Dependencies are inferred from the claim text.