Abstract: An optical system includes a first lens and a second lens, at least one of which is a cemented lens. Outside respective effective regions of the first lens and the second lens, the first lens and the second lens are in contact with a lens or an interval holding member disposed between the first lens and the second lens. Following inequalities are satisfied: 0.96<D1/D2<1.04, and 0.96<D1/D3<1.04, where maximum diameters of the first lens and the second lens are D1 and D2, respectively, and a maximum diameter of the lens or the interval holding member is D3.

Abstract: A lens device includes a lens barrel, a retaining member, a biased portion, and an elastic member. The lens barrel accommodates a plurality of lenses. The retaining member is in contact with at least one of the plurality of lenses. The biased portion is fixed to the retaining member. The elastic member is disposed between the biased portion and the lens barrel in an optical axis direction. The biased portion is disposed inner side of the retaining member and outer side of the lens barrel in a radial direction, and is biased by the lens barrel via the elastic member in the optical axis direction.

Abstract: A lens holding mechanism capable of pressing a peripheral portion of a lens in an optical axis direction while preventing twisting of an elastic member. Wherein the lens holding mechanism includes a lens barrel configured to house a lens, a pressing ring that is movable with respect to the lens barrel in a direction along an optical axis, a rotary ring configured to rotate about the optical axis to move the pressing ring in the direction along the optical axis, and an elastic member disposed between the lens and the pressing ring, wherein the lens barrel has a rotation restricting portion and a movement restricting portion, wherein, the elastic member is biased to a peripheral portion of the lens in the direction along the optical axis by moving the pressing ring in the direction along the optical axis.

Abstract: An airbag apparatus attachment mechanism includes a holder, a supporting member, an urging member, and a functional member. The holder is fastened to a metal core with a fastening member. The supporting member protrudes further forward than an airbag apparatus and is inserted into the holder. The urging member urges the airbag apparatus rearward. The functional member is attached to a part of the supporting member that is inserted in the holder. The functional member includes a spring portion that is thinner than a gap between the supporting member and the holder. The spring portion is disposed in the gap. The functional member is configured such that the spring portion is elastically deformed in a radial direction of the supporting member due to vibration of the airbag apparatus, thereby suppressing the vibration.

Abstract: An airbag apparatus attachment mechanism includes a holder, a supporting member, an urging member, and a functional member. The holder is fastened to a metal core with a fastening member. The supporting member protrudes further forward than an airbag apparatus and is inserted into the holder. The urging member urges the airbag apparatus rearward. The functional member is attached to a part of the supporting member that is inserted in the holder. The functional member includes a spring portion that is thinner than a gap between the supporting member and the holder. The spring portion is disposed in the gap. The functional member is configured such that the spring portion is elastically deformed in a radial direction of the supporting member due to vibration of the airbag apparatus, thereby suppressing the vibration.