Optical imaging system

Abstract

An optical imaging system includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens disposed in order from an object side, wherein TTL/(2*IMG HT)≤0.6 is satisfied, where TTL is a distance on an optical axis from an object-side surface of the first lens to an imaging plane of an image sensor, and IMG HT is half a diagonal length of the imaging plane of the image sensor.

What is claimed is: 
     
         1 . An optical imaging system comprising:
 a first lens has positive refractive power, a convex object-side surface and a concave image-side surface;   a second lens has negative refractive power, a convex object-side surface and a concave image-side surface;   a third lens has positive refractive power;   a fourth lens has negative refractive power and a concave image-side surface;   a fifth lens has refractive power;   a sixth lens has refractive power, a convex object-side surface and a concave image-side surface; and   a seventh lens has negative refractive power,   wherein the first to seventh lenses are disposed sequentially from an object side,   wherein the optical imaging system has a total of seven lenses,   wherein 0<f1/f<1.8, −4<f2/f<−1 and |f4/f|>3 are satisfied, where f1 is a focal length of the first lens, f2 is a focal length of the second lens, f4 is a focal length of the fourth lens, and f is a focal length of the optical imaging system.   
     
     
         2 . The optical imaging system of  claim 1 , wherein 1<f12/f<2 is satisfied, where f12 is a combined focal length of the first lens and the second lens. 
     
     
         3 . The optical imaging system of  claim 1 , wherein |f1/f2|<1 is satisfied. 
     
     
         4 . The optical imaging system of  claim 1 , wherein −2<f2/f3<0 is satisfied, where f3 is a focal length of the third lens. 
     
     
         5 . The optical imaging system of  claim 4 , wherein f3/f>3 is satisfied. 
     
     
         6 . The optical imaging system of  claim 1 , wherein −2<f7/f<0 is satisfied, where f7 is a focal length of the seventh lens. 
     
     
         7 . The optical imaging system of  claim 1 , wherein 25<v1−v2<45 is satisfied where v1 is an Abbe number of the first lens, and v2 is an Abbe number of the second lens. 
     
     
         8 . The optical imaging system of  claim 7 , wherein v1−v3<35 is satisfied where v3 is an Abbe number of the third lens. 
     
     
         9 . The optical imaging system of  claim 1 , wherein D1/f<0.1 is satisfied, where D1 is a distance on an optical axis from the image-side surface of the first lens to the object-side surface of the second lens. 
     
     
         10 . The optical imaging system of  claim 1 , wherein BFL/f<0.3 is satisfied, where BFL is a distance on an optical axis from an image-side surface of the seventh lens to an imaging plane. 
     
     
         11 . The optical imaging system of  claim 1 , wherein the third lens has a convex object-side surface. 
     
     
         12 . The optical imaging system of  claim 11 , wherein the third lens has a convex image-side surface. 
     
     
         13 . The optical imaging system of  claim 1 , wherein the fourth lens has a concave object-side surface. 
     
     
         14 . The optical imaging system of  claim 1 , wherein the fifth lens has positive refractive power. 
     
     
         15 . The optical imaging system of  claim 1 , wherein the seventh lens has a concave image-side surface. 
     
     
         16 . The optical imaging system of  claim 1 , wherein at least three of the first to seventh lenses have a refractive index of greater than 1.64. 
     
     
         17 . The optical imaging system of  claim 1 , wherein at least two of the first to seventh lenses have a refractive index of greater than 1.66. 
     
     
         18 . The optical imaging system of  claim 17 , wherein the second lens and the fourth lens have a refractive index of greater than 1.66.