Optical system and camera module comprising same

An optical system comprising:

• first to eighth lenses disposed along an optical axis from an object side toward a sensor side,
• wherein the first lens has positive (+) or negative (−) refractive power on the optical axis,
• wherein the second lens has positive (+) refractive power on the optical axis,
• wherein the third lens has negative (−) refractive power on the optical axis,
• wherein the seventh lens has positive (+) refractive power on the optical axis,
• wherein the eighth lens has negative (−) refractive power on the optical axis,
• wherein at least one of an object-side surface and a sensor-side surface of the seventh lens has at least one critical point,
• wherein each of an object-side surface and a sensor-side surface of the eighth lens has a critical point,
• wherein at least one of the object-side surface and the sensor-side surface of the eighth lens has a freeform surface shape in which a lens surface orthogonal to the optical axis in a first direction and a lens surface orthogonal to the optical axis in a second direction are asymmetrical, wherein the freeform surface has symmetrical lens surfaces on both sides of the first direction with respect to the optical axis and symmetrical lens surfaces on both sides of the second direction with respect to the optical axis, and
• wherein a center thickness of the second lens is a maximum of center thicknesses of the lenses of the optical system.

An optical system comprising:

• a first lens group having three or less lenses on an object side;
• and
• a second lens group having five or less lenses on a sensor side of the first lens group,
• wherein the first lens group has a positive (+) refractive power on the optical axis,
• wherein the second lens group has a negative (−) refractive power on the optical axis,
• wherein a number of lenses of the second lens group is less than twice a number of lenses of the first lens group,
• wherein a lens surface closest to the second lens group among the lens surfaces of the first and second lens groups has a minimum effective diameter,
• wherein a last lens closest to an image sensor among lens surfaces of the first and second lens groups has a maximum effective diameter,
• wherein a sensor-side surface closest to the second lens group among the first lens groups has a concave shape,
• wherein an object-side surface closest to the first lens group among the second lens group has a concave shape,
• wherein a sensor-side surface of the last lens has a freeform surface shape with a critical point,
• wherein a sensor-side surface closest to the image sensor has a freeform surface shape in which a lens surface orthogonal to the optical axis in a first direction and a lens surface orthogonal to the optical axis in a second direction are asymmetrical, and
• wherein the freeform surface has symmetrical lens surfaces on both sides of the first direction with respect to the optical axis and symmetrical lens surfaces on both sides of the second direction with respect to the optical axis.