Optical low-pass filter
AssigneePENTAX Corporation
InventorMasahiro Oono
Life of this patent
Estimating the term…
Abstract
An optical low-pass filter used in association with an imaging element which has a plurality of pixels arranged in vertical and horizontal direction with regularity, is provided with first through third birefringent plates arranged in the order from a light incident side. The low-pass filter separates an incident ray into four rays, a separation width of the rays in the vertical direction being δv, and a separation width of the rays in the horizontal direction being δh. A separation angles of the first through third birefringent plates are θ, (θ−90°) and 0°, respectively, and separation widths of the first through third birefringent plates are (δv×sin θ), (δv×cos θ) and δh, respectively.
Claims36
An optical low-pass filter used in association with an imaging element which has a plurality of pixels arranged in vertical and horizontal direction with regularity, a separation width of said low-pass filter in the vertical direction being δv, separation width of said low-pass filter in the horizontal direction being δh, said low-pass filter comprising:
- a first birefringent plate that separates an incident ray into an ordinary ray and an extraordinary ray polarized in directions perpendicular to each other, at a separation angle of θ, θ being greater than 0° and less than 90°, with respect to the horizontal direction, and a separation width of δv×sin θ;
- a second birefringent plate that separates an incident ray into an ordinary ray and an extraordinary ray polarized in directions perpendicular to each other at a separation angle of (θ−90°) with respect to the horizontal direction, and a separation width of δv×cos θ;
- and
- a third birefringent plate that separates an incident ray into an ordinary ray and an extraordinary ray polarized in directions perpendicular to each other at a separation angle 0° with respect to the horizontal direction and a separation width of δh,
- said first, second and third birefringent plates are arranged in this order from a light incident side, and are configured to separate an incident ray into a plurality of rays having substantially a same energy level even if the incident ray is polarized, whereby high spatial frequency components of the optical image can be removed.
An optical low-pass filter used in association with an imaging element which has a plurality of pixels arranged in vertical and horizontal direction with regularity, a separation width of said low-pass filter in the vertical direction being δv, separation width of said low-pass filter in the horizontal direction being δh, said low-pass filter comprising:
- a first birefringent plate that separates an incident ray into an ordinary ray and an extraordinary ray polarized in directions perpendicular to each other, at a separation angle of θ, θ being greater than −90° and less than 0°, with respect to the horizontal direction, and a separation width of |δb×sin ↓|;
- a second birefringent plate that separates an incident ray into an ordinary ray and an extraordinary ray polarized in directions perpendicular to each other at a separation angle of θ+90° with respect to the horizontal direction, and a separation width of δv×cos θ;
- and
- a third birefringent plate that separates an incident ray into an ordinary ray and an extraordinary ray polarized in directions perpendicular to each other at a separation angle 0° with respect to the horizontal direction and a separation width of δh,
- said first, second and third birefringent plates are arranged in this order from a light incident side, and are configured to separate an incident ray into a plurality of rays having substantially a same energy level even if the incident ray is polarized, whereby high spatial frequency components of the optical image can be removed.
The optical low-pass filter according to claim wherein a thickness of said dummy glass element being adjusted so that said optical low-pass filter has a predetermined thickness regardless of the thickness of each of said first, second and third birefringent plates.
An optical low-pass filter used in association with an imaging element which has a plurality of pixels arranged in vertical and horizontal direction with regularity, a separation width of said low-pass filter in the vertical direction being δv, separation width of said low-pass filter in the horizontal direction being δh, said low-pass filter comprising:
- a first birefringent plate that separates an incident ray into an ordinary ray and an extraordinary ray polarized in directions perpendicular to each other, at a separation angle of θ, θ being greater than 0° and less than 90°, with respect to the horizontal direction, and a separation width of δh×cos θ;
- a second birefringent plate that separates an incident ray into an ordinary ray and an extraordinary ray polarized in directions perpendicular to each other at a separation angle of (θ+90°) with respect to the horizontal direction, and a separation width of δh×sin θ;
- and
- a third birefringent plate that separates an incident ray into an ordinary ray and an extraordinary ray polarized in directions perpendicular to each other at a separation angle 90° with respect to the horizontal direction and a separation width of δv,
- said first, second and third birefringent plates are arranged in this order from a light incident side, and are configured to separate an incident ray into a plurality of rays having substantially a same energy level even if the incident ray is polarized, whereby high spatial frequency components of the optical image can be removed.
An optical low-pass filter used in association with an imaging element which has a plurality of pixels arranged in vertical and horizontal direction with regularity, a separation width of said low-pass filter in the vertical direction being δv, separation width of said low-pass filter in the horizontal direction being δh, said low-pass filter comprising:
- a first birefringent plate that separates an incident ray into an ordinary ray and an extraordinary ray polarized in directions perpendicular to each other, at a separation angle of θ, θ being greater than 90° and less than 180°, with respect to the horizontal direction, and a separation width of |δh×cos θ|;
- a second birefringent plate that separates an incident ray into an ordinary ray and an extraordinary ray polarized in directions perpendicular to each other at a separation angle of θ−90° with respect to the horizontal direction, and a separation width of δh×sin θ;
- and
- a third birefringent plate that separates an incident ray into an ordinary ray and an extraordinary ray polarized in directions perpendicular to each other at a separation angle 90° with respect to the horizontal direction and a separation width of δv,
- said first, second and third birefringent plates are arranged in this order from a light incident side, and are configured to separate an incident ray into a plurality of rays having substantially a same energy level even if the incident ray is polarized, whereby high spatial frequency components of the optical image can be removed.
Dependencies are inferred from the claim text.