Patent ID: 6724531
Filing Date: 2004-04-20
Classification: G02B

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, a separation width of said low-pass filter in the vertical direction being &dgr;v, separation width of said low-pass filter in the horizontal direction being &dgr;h, 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 &thgr;, &thgr; being greater than 0Â° and less than 90Â°, with respect to the horizontal direction, and a separation width of &dgr;vÃ—sin &thgr;; 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 (&thgr;âˆ’90Â°) with respect to the horizontal direction, and a separation width of &dgr;vÃ—cos &thgr;; 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 0Â° with respect to the horizontal direction and a separation width of &dgr;h, 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.