Patent ID: 8142085
Filing Date: 2012-03-27
Classification: G02B,G03B

Abstract:
1. An aperture unit comprising: three or more diaphragm blades; a base plate that supports the three or more diaphragm blades such that the blades are linearly movable in directions perpendicular to an optical axis; a drive lever connected to the blades, the drive lever being rotatable; and an aperture motor that rotates the drive lever, wherein two or more of the blades that linearly move in a first direction have aperture edges having different shapes, and a polygonal aperture is formed by the aperture edges of the two or more blades and an aperture edge of at least one of the blades that linearly moves in a second direction opposite to the first direction, wherein movement distances and movement speeds of the two or more blades that move in the first direction from an open aperture state to a closed aperture state are respectively different from one another, and among the two or more blades, blades that move large distances at high speeds have aperture edges that are parallel to aperture edges of blades that move small distances at low speeds, wherein, in a range from a reference aperture value to a specific aperture value, the polygonal aperture is formed by aperture edges of the two or more blades that linearly move in the first direction and an aperture edge of the at least one blade that linearly moves in the second direction, the reference aperture value being an aperture value at which a polygonal aperture is formed only by the aperture edges of the blades when the blades are moved from the open aperture state, and wherein, in a range from the specific aperture value to the closed aperture state, an aperture is formed by aperture edges of two blades that move in opposite directions.