Abstract: An optical system, sequentially comprising from an object side to an image side: a first lens having negative refractive power; a second lens having negative refractive power; a third lens having positive refractive power; a fourth lens having positive refractive power, both the object side surface and the image side surface of the fourth lens being convex; a fifth lens having negative refractive power, both the object side surface and the image side surface of the fifth lens being concave; and a sixth lens having positive refractive power, both the object side surface and the image side surface of the sixth lens being convex. The optical system satisfies the following relationship: ?47<f45/f<27, wherein f45 represents a combined focal length of the fourth lens and the fifth lens, and f represents an effective focal length of the optical system.

Abstract: A lens unit is provided that includes: a first lens that is housed inside a lens-barrel, the first lens including a first lens section and a first flange section that juts out from the first lens section in a direction orthogonal to an optical axis direction; a second lens that is housed inside the lens-barrel further toward an imaging plane side than the first lens, the second lens including a second lens section and a second flange section that juts out from the second lens section in a direction orthogonal to the optical axis direction; and a spacing ring that is sandwiched between the first lens and the second lens and that defines a spacing between the first lens and the second lens, the spacing ring includes a main body disposed between the first flange section and the second flange section in the optical axis direction, first protrusion portions that protrude in the optical axis direction from an object side of the main body, and second protrusion portions that protrude in the optical axis direction fr

Abstract: The present disclosure provides a lens unit including: a lens including a first circular shaped portion and a second circular shaped portion arranged in a row along an optical axis direction; and a lens-barrel formed of a resin and formed in a tubular shape, the lens-barrel including: a first inner peripheral face to which the first circular shaped portion is fitted, and a second inner peripheral face to which the second circular shaped portion is fitted and is positioned separated in the optical axis direction from a fitting section where the first circular shaped portion and the first inner peripheral face are fitted, the second circular shaped portion contacts with the second inner peripheral face at three or more portions in a circumferential direction.