Optical imaging system, image capturing unit and electronic device

An optical imaging system comprising four lens elements, the four 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 and a fourth lens element;

• 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 concave in a paraxial region thereof and has at least one convex shape in an off-axis region thereof, the object-side surface of the first lens element is aspheric, the object-side surface of the third lens element is convex in a paraxial region thereof, the image-side surface of the fourth lens element is concave in a paraxial region thereof, the image-side surface of the fourth lens element has at least one inflection point, and the optical imaging system has a total of four lens elements;
• wherein the optical imaging system further comprises an aperture stop, an axial distance between the object-side surface of the first lens element and an image surface is TL, a focal length of the optical imaging system is f, 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, an axial distance between the aperture stop and the image-side surface of the fourth lens element is SD, 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, and the following conditions are satisfied:
• 3.0<TL/f<6.0′
• T23<T12;
• T34<T12;
• 0.34<SD/TD<1.20;
• and
• 0.50 mm<IL<4.0 mm.

An optical imaging system comprising four lens elements, the four 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 and a fourth lens element;

• 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 concave in a paraxial region thereof, the image-side surface of the second lens element is concave in a paraxial region thereof, the image-side surface of the fourth lens element is concave in a paraxial region thereof, and the optical imaging system has a total of four lens elements;
• wherein the optical imaging system further comprises an aperture stop, an axial distance between the object-side surface of the first lens element and an image surface is TL, a focal length of the optical imaging system is f, a focal length of the fourth lens element is f4, an axial distance between the aperture stop and the image-side surface of the fourth lens element is SD, 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, a curvature radius of the object-side surface of the first lens element is R1, a curvature radius of the image-side surface of the first lens element is R2, an Abbe number of the fourth lens element is V4, and the following conditions are satisfied:
• 3.0<TL/f<10.0;
• 0.34<SD/TD<1.20;
• (R1+R2)/(R1−R2)<0.90;
• −3.0<f/f4<−0.55;
• and
• 10.0<V4<23.0.

An optical imaging system comprising four lens elements, the four 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 and a fourth lens element;

• 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 concave in a paraxial region thereof and has at least one convex shape in an off-axis region thereof, the object-side surface of the first lens element is aspheric, the object-side surface of the third lens element is convex in a paraxial region thereof, and the optical imaging system has a total of four lens elements;
• wherein an axial distance between the object-side surface of the first lens element and an image surface is TL, a focal length of the optical imaging system is f, a focal length of the second lens element is f2, a minimum value among Abbe numbers of all lens elements of the optical imaging system is Vmin, and the following conditions are satisfied:
• 3.50<TL/f<5.0;
• Vmin<22.5;
• and
• −3.0<f/f2<0.40;
• wherein a vertical distance between an inflection point on the image-side surface of the fourth lens element and an optical axis is Yi42, and the image-side surface of the fourth lens element has at least one inflection point satisfying the following condition:
• 0.10<Yi42/f<1.20.