Optical lens system, image capturing unit and electronic device

An optical lens system comprising, in order from an object side to an image side:

• a first lens element with positive refractive power having an object-side surface being convex in a paraxial region thereof;
• a second lens element having negative refractive power;
• a third lens element with positive refractive power having an image-side surface being convex in a paraxial region thereof, wherein both of an object-side surface and the image-side surface of the third lens element are aspheric;
• and
• a fourth lens element with negative refractive power having an image-side surface being concave in a paraxial region thereof, wherein the image-side surface of the fourth lens element has at least one convex shape in an off-axis region thereof, and both of an object-side surface and the image-side surface of the fourth lens element are aspheric;
• wherein the optical lens system has a total of four lens elements, an air gap in a paraxial region is between any two of the first lens element, the second lens element, the third lens element and the fourth lens element that are adjacent to each other;
• wherein a central thickness of the second lens element is CT2, a central thickness of the fourth lens element is CT4, an axial distance between the first lens element and the second lens element is T12, an axial distance between the second lens element and the third lens element is T23, an axial distance between the third lens element and the fourth lens element is T34, and the following conditions are satisfied:
• 1.45<CT2/CT4;
• 0.80<CT2/(T12+T23+T34)<3.0;
• and
• 0.85<T12/(T23+T34).