Patent ID: 7466500

Claim:
A lens unit capable of varying power for forming an image onto an image pickup element, the lens unit comprising: a plurality of lens groups in which a distance between a k-th lens group counting from an object side and a (k+1)-th lens group arranged at an image side of the k-th lens group changes for varying power; a diaphragm arranged between a position at an image side of the k-th lens group and a lens surface facing the object side of a lens closest to the image in the (k+1)-th lens group; and a shutter with an aperture in a noncircular shape whose dimension along a direction of a minimum width of the aperture is 2H s , the shutter fulfilling following conditional formulas, the shutter being arranged on the image side and next to the (k+1)-th lens group: H1<H s , and 0.1<( H 2H +H 2L )/ H 1<3.0, where H 1 is a height of a light flux from an optical axis at a position where the shutter is arranged, the light flux being an outermost light flux out of a light flux forming an image on the optical axis when the diaphragm is full-opened, H 2H is a height of a light flux from an optical axis at a position where the shutter is arranged, the light flux being an outermost light flux out of a light flux forming an image at a maximum image height position when the diaphragm is full-opened, and H 2L is a height of a light flux from an optical axis at a position where the shutter is arranged, the light flux being an innermost light flux out of a light flux forming an image at a maximum image height position when the diaphragm is full-opened.