| CPC G02B 9/64 (2013.01) [G02B 3/04 (2013.01); G02B 13/0045 (2013.01)] | 26 Claims |

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1. An imaging optical lens system comprising seven lens elements, the seven lens elements being, in order from an object side to an image side along an optical path, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element, a sixth lens element and a seventh lens element, and each of the seven lens elements having an object-side surface facing toward the object side and an image-side surface facing toward the image side;
wherein the second lens element has negative refractive power, the object-side surface of the second lens element is concave in a paraxial region thereof, at least one of the object-side surface and the image-side surface of the second lens element is aspheric, the object-side surface of the sixth lens element is concave in a paraxial region thereof, the image-side surface of the sixth lens element is concave in a paraxial region thereof, and the imaging optical lens system further comprises an aperture stop located between the second lens element and the third lens element;
wherein a focal length of the imaging optical lens system is f, a focal length of the first lens element is f1, 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, and the following conditions are satisfied:
−2.50<f/f1<0.15;
0.15<T23/f<2.30; and
0.15<T23/T12<1.80.
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