Optical system and camera module comprising same

An optical system comprising:

• first to fourth lens groups disposed along an optical axis from an object side toward a sensor side and each including at least one lens,
• wherein the first lens group has a refractive power opposite to that of the fourth lens group,
• wherein the second lens group has a refractive power opposite to that of the third lens group,
• wherein the first and fourth lens groups are fixed and the second and third lens groups are movable in a direction of the optical axis,
• wherein each of the first and fourth lens groups includes at least one lens of a non-circular shape,
• wherein a non-circular ratio of at least one lens included in the second lens group is greater than a non-circular ratio of the non-circular lenses included in each of the first and fourth lens groups,
• wherein a non-circular ratio of at least one lens included in the first lens group is greater than a non-circular ratio of at least one lens included in the fourth lens group,
• wherein the non-circular ratio is a ratio of a minimum clear aperture (CH:
• clear height) and a maximum clear aperture (CA) of a lens surface with a large clear aperture among an object-side surface and a sensor-side surface of the non-circular lens,
• wherein when the second and third lens groups are located in a first position, the optical system has a first magnification, and when they are located in a second position different from the first position, the optical system has a second magnification, and
• wherein the second magnification is greater than the first magnification.