Optical imaging system having seven lenses of various refractive powers

1. An optical imaging system comprising:

a first lens having a concave image-side surface;

a second lens having negative refractive power;

a third lens having negative refractive power;

a fourth lens having positive refractive power and a convex object-side surface in a paraxial region;

a fifth lens having a concave object-side surface and a convex image-side surface in a paraxial region;

a sixth lens having convex object-side and image-side surfaces in a paraxial region; and

a seventh lens having a refractive power,

wherein the first to seventh lenses are sequentially disposed in numerical order along an optical axis of the optical imaging system from an object side of the optical imaging system toward an imaging plane of the optical imaging system,

wherein the optical imaging system has a total number of seven lenses with refractive power,

wherein the optical imaging system satisfies 0.5<L1234TRavg/L7TR<0.9, where L1234Travg is an average value of overall outer diameters of the first to fourth lenses, L7TR is an overall outer diameter of the seventh lens, and L1234Travg and L7TR are expressed in a same unit of measurement, and

wherein the optical imaging system satisfies 0.05<R1/R6<0.9, where R1 is a radius of curvature of an object-side surface of the first lens, and R6 is a radius of curvature of an image-side surface of the third lens.

2. The optical imaging system of claim 1 , wherein an object-side surface of the first lens is convex.

3. The optical imaging system of claim 1 , wherein an image-side surface of the seventh lens is concave.

4. The optical imaging system of claim 1 , wherein a distance along the optical axis from an object-side surface of the first lens to the imaging plane is 6 mm or less.

5. The optical imaging system of claim 1 , wherein at least one inflection point is formed on either one or both of an object-side surface and an image-side surface of the sixth lens.

6. The optical imaging system of claim 1 , wherein at least one inflection point is formed on either one or both of an object-side surface and an image-side surface of the seventh lens.

7. The optical imaging system of claim 1 , wherein the optical imaging system further satisfies 0.1<L1w/L7w<0.3, where L1w is a weight of the first lens, L7w is a weight of the seventh lens, and L1w and L7w are expressed in a same unit of measurement.

8. The optical imaging system of claim 1 , further comprising a spacer disposed between the sixth and seventh lenses,

wherein the optical imaging system further satisfies 0.5<S6d/f<1.2, where S6d is an inner diameter of the spacer, f is the overall focal length of the optical imaging system, and S6d and f are expressed in a same unit of measurement.

9. The optical imaging system of claim 1 , wherein the optical imaging system further satisfies 0.4<L1TR/L7TR<0.7, where L1TR is an overall outer diameter of the first lens, and L1TR and L7TR are expressed in a same unit of measurement.

10. The optical imaging system of claim 1 , wherein the optical imaging system further satisfies 0.5<L1234TRavg/L7TR<0.75.

11. The optical imaging system of claim 1 , wherein the optical imaging system further satisfies 0.5<L12345TRavg/L7TR<0.76, where L12345TRavg is an average value of overall outer diameters of the first to fifth lenses, and L12345TRavg and L7TR are expressed in a same unit of measurement.

12. The optical imaging system of claim 1 , wherein the fifth lens has a negative refractive power.

13. The optical imaging system of claim 1 , wherein a paraxial region of an object-side surface of the seventh lens is concave or convex.