Miniature telephoto lens assembly

A lens system, comprising:

• a lens assembly that includes a plurality of refractive lens elements arranged along an optical axis and including, in order from an object side to an image side, a first group comprising a first lens element having a positive refractive power, a second lens element and a third lens element, and a second group comprising a first lens element and a second lens element,
• a stop positioned before the first lens element of the first group;
• and
• a window positioned between the plurality of refractive lens elements and an image plane,
• wherein a smallest gap between lens elements is dMIN,
• wherein a largest gap between lens elements dMAX is a gap between the first and second groups,
• wherein dMAX is larger than 2.25 times any other gap between lens elements,
• wherein at least one surface of at least one of the plurality of refractive lens elements is aspheric,
• wherein the lens assembly has an effective focal length EFL and a total track length TTL, a ratio TTL/EFL smaller than 0.9, and a f number f #smaller than 2.9,
• wherein a center thickness of each lens element is equal to or larger than 0.2 mm,
• wherein a focal length f1 of the first lens element of the first group, a focal length f2 of the second lens element of the first group and a focal length f3 of the third lens element of the first group fulfill the condition 1.2×|f3|>|f2|>1.5×f1,
• wherein a ratio L11/L1e between a largest optical axis thickness L11 and a circumferential edge thickness L1e of the first lens element of the first group is smaller than 3.5, and
• wherein the lens system is embedded in a mobile device.