Optical system, imaging device, and moving body

An optical system comprising a front group, a diaphragm, and a rear group in order from an object side, wherein

• the optical system includes a lens A having positive refractive power and being closest to the object side in the front group and a lens B having negative refractive power and being closest to an image side in the rear group,
• an object-side surface of the lens B has a concave surface with respect to the object side,
• a number of lenses having refractive power and included in the front group and the rear group is eight or less in total, and
• the optical system satisfies following conditions:
• 1.59
• <
• NdLB
• <
• 2.3
• (
• 1
• )
• 1.6
• <
• TLSB
• /
• BF
• <
• 10.
• (
• 2
• )
• 0.2
• <
• fR
• /
• f
• <
• 1.05
• (
• 3
• )
• where
• NdLB is a refractive index at a d-line of the lens B,
• TLSB is a distance from the diaphragm to an image-side surface of the lens B,
• BF is an air conversion distance from a lens surface closest to the image side in the rear group to the image plane,
• fR is a focal length of the rear group, and
• f is a focal length of the optical system.