Optical system and camera module comprising same

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 positive refractive power on an optical axis,
• wherein the second lens group has 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 an object surface of a lens closest to the second lens group among lens surfaces of the first and second lens groups has a minimum effective aperture,
• wherein a sensor-side surface closest to an image sensor among lens surfaces of the first and second lens groups has a maximum effective aperture,
• wherein the lens with the minimum average effective aperture within the first and second lens groups is disposed between an object-side lens and a sensor-side lens of the first lens group, and the lens with the maximum is a last lens of the second lens group,
• wherein an optical axis distance from an apex of an object-side surface of the first lens group to an image surface of the image sensor is TTL (Total track length), ½ of a maximum diagonal length of the image sensor is ImgH, a maximum optical axis distance (mm) from the object-side surface of the first lens group to the sensor-side surface of the second lens group is TD, and an largest effective aperture among effective apertures of object-side and sensor-side surfaces of the first and second lens groups is CA_Max,
• wherein the following Equations satisfy:
• 0.5<TTL/ImgH<3
• 0.5<TD/CA_max<1.5.