US Patent 11181720 Telephoto lens and image pickup apparatus using the same

A telephoto lens includes first, second and third lens units. The first lens unit has positive refractive power front-side lens, first rear-side lens, and second rear-side lens units. The first lens unit has a negative lens element satisfying 0.5≤|f/fLn|≤4.908. The third lens unit has positive and negative lens elements. The first rear-side lens unit includes a predetermined negative lens element and a positive lens element. Lens elements of the front-side lens unit include at least one positive lens element. The second rear-side lens unit has a positive lens element. Conditional Expression 0.247≤ΔGFGR1/f≤0.5 is satisfied. f and fLn are focal lengths of the telephoto lens and predetermined negative lens element. ΔGFGR1 is an axial distance from an object-side surface in the front-side lens unit to an object-side surface in the first rear-side lens unit.