Optical system and camera module comprising same

A zoom optical system comprising a first lens group, a second lens group, a third lens group, and a fourth lens group which are sequentially arranged in a direction from a subject side to an image side,

• wherein each of the first lens group to the fourth lens group includes at least two lenses,
• wherein the second lens group and the third lens group are movable,
• wherein an effective focal length (EFL) in a wide angle mode is defined by an expression below,
• 5.5
• <
• EFL
• wide
• H
• imageD
• <
• 6.5
• ,
• and
• here, EFLwide is the EFL of the zoom optical system in the wide angle mode, HimageD is a half value of a diagonal length of a pixel area of an image sensor, and the pixel area of the image sensor is an area in which light-receiving pixels are arrayed in the image sensor which is located at an image plane behind the fourth lens group,
• wherein, when zooming is performed from the wide angle mode to a telephoto mode, a movement stroke of the third lens group is defined by an expression below,
• 4
• <
• TTL
• STROKE
• 3
• <
• 8
• ,
• here, TTL (total track length) is a distance from a surface of the image sensor to a first surface of the zoom optical system, and STROKE3 is the movement stroke of the third lens group.