Patent ID: 11940598
Assignee: LARGAN PRECISION CO., LTD.
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 9:
10. A lens system comprising four lens elements, the four lens elements being, in order from an object side to an image side, a first lens element, a second lens element, a third lens element and a fourth lens element, and each of the four lens elements having an object-side surface facing toward the object side and an image-side surface facing toward the image side;
wherein the first lens element has negative refractive power, the fourth lens element has positive refractive power, the object-side surface of the fourth lens element is convex in a paraxial region thereof, the image-side surface of the fourth lens element is concave in a paraxial region thereof, a central thickness of the third lens element is a maximum among central thicknesses of all lens elements of the lens system, a total number of lens elements in the lens system is four, and an axial distance between the first lens element and the second lens element is larger than an axial distance between the third lens element and the fourth lens element;
wherein the lens system further comprises an aperture stop, a minimum value among Abbe numbers of all lens elements of the lens system is Vdmin, an axial distance between the aperture stop and the image-side surface of the fourth lens element is SD, an axial distance between the object-side surface of the first lens element and the image-side surface of the fourth lens element is TD, and the following conditions are satisfied:

13.0<Vdmin<21.0; and

0.40<SD/TD<0.95.