| CPC G02B 9/58 (2013.01) [G02B 1/041 (2013.01)] | 26 Claims |

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1. An imaging system lens assembly comprising four lens elements, the four 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 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 object-side surface of the first lens element is convex in a paraxial region thereof, the second lens element has positive refractive power, and the object-side surface of the third lens element is convex in a paraxial region thereof;
wherein 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, an axial distance between the image-side surface of the fourth lens element and an image surface is BL, an f-number of the imaging system lens assembly is Fno, an Abbe number of the first lens element is V1, a refractive index of the first lens element is N1, a curvature radius of the object-side surface of the third lens element is R5, a curvature radius of the image-side surface of the third lens element is R6, a curvature radius of the object-side surface of the fourth lens element is R7, a curvature radius of the image-side surface of the fourth lens element is R8, and the following conditions are satisfied:
0<TD/BL<0.42;
1.0<Fno<4.0;
22.0<V1/N1<40.5; and
0<(|R5|+|R6|)/(|R7|+|R8|)<1.2.
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