OPTICAL SYSTEM, IMAGE PICKUP APPARATUS, IN-VEHICLE SYSTEM, AND MOVING APPARATUS

An optical system includes, in order from an enlargement conjugate side to a reduction conjugate side, a front unit including three or more lenses, a diaphragm (ST1, ST2, ST3), and a rear unit including a plurality of lenses. The front unit includes a first positive lens (L1, L21, L31) closest to an enlargement conjugate position, and a second positive lens (L4, L24, L34). A predetermined condition is satisfied.