Optical system and image pickup apparatus having the same

An image pickup apparatus comprising:

• an optical system;
• and
• an image sensor configured to receive light from the optical system,
• wherein the optical system includes, in order from an object side to an image side, a front unit of a positive refractive power, a diaphragm, and a rear unit of a positive refractive power,
• wherein the front unit includes, in order from the object side to the image side, a positive lens L11, a positive lens L12, and a negative lens L13,
• wherein the rear unit includes, in order from the object side to the image side, a negative lens L21, a positive lens L22, and a positive lens L23, and
• wherein the following conditional expressions are satisfied:
• 1.00<fF/fR<2.00
• 1.00<f22/f
• where fF is a focal length of the front unit, fR is a focal length of the rear unit, f22 is a focal length of the positive lens L22, and f is a focal length of the optical system.