Imaging optical system, image capturing device, and electronic device

An imaging optical system, comprising six lens elements, the six 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, a fifth lens element and a sixth lens element;
• wherein the first lens element has positive refractive power in a paraxial region thereof;
• the sixth lens element has positive refractive power in a paraxial region thereof, at least one of an object-side surface and an image-side surface of the sixth lens element is aspheric, and the sixth lens element is made of plastic material;
• an absolute value of a focal length of the first lens element is smallest among absolute values of focal lengths of all lens elements, a central thickness of the first lens element is larger than a central thickness of the sixth lens element;
• wherein a focal length of the imaging optical system is f, a curvature radius of an image-side surface of the fourth lens element is R8, an f-number of the imaging optical system is Fno, and the following conditions are satisfied:
• −0.50<f/R8, and
• 1.50<Fno<2.50.