Imaging optical system, image capturing device and mobile terminal

An imaging optical system comprising five lens elements, the five 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, a fourth lens element and a fifth lens element;
• each of the five lens elements has an object-side surface towards the object side and an image-side surface towards the image side;
• wherein the second lens element with positive refractive power having the image-side surface being convex in a paraxial region thereof;
• the third lens element with negative refractive power having the image-side surface being concave in a paraxial region thereof;
• the fourth lens element having the object-side surface being convex in a paraxial region thereof;
• the fifth lens element with negative refractive power having the object-side surface being convex in a paraxial region thereof and the image-side surface being concave in a paraxial region thereof, wherein the image-side surface of the fifth lens element comprises at least one convex shape in an off-axis region thereof;
• wherein an absolute value of a curvature radius of the object-side surface of the first lens element is greater than an absolute value of a curvature radius of the image-side surface of the second lens element;
• wherein an axial distance between the object-side surface of the first lens element and an image plane is TTL, a maximum image height of the imaging optical system is ImgH, and the following condition is satisfied:
• TTL
• /
• ImgH
• ≤
• 3.27
• .