Wide angle lens system and imaging device having the same
A wide angle lens system, from an object side to an image plane side, includes: a first lens having a positive refractive power; a second lens having a positive refractive power and an exit surface that is convex toward the image plane side; a third lens having a negative refractive power and an exit surface that is concave toward the image plane side; a fourth lens having a positive refractive power and an exit surface that is convex toward the image plane side; a fifth lens having a negative refractive power and an exit surface that is concave toward the image plane side; and a sixth lens having a positive refractive power. The wide angle lens system satisfies the following formulas: 75<FOV<85 2.0<Fno<2.3 where FOV is a field of view of the wide angle lens system in degrees (°) and Fno is an F-number of the wide angle lens system.
1. A wide angle lens system, from an object side to an image plane side, comprising:
a first lens having a positive refractive power;
a second lens having a positive refractive power and an exit surface that is convex toward the image plane side;
a third lens having a negative refractive power and an exit surface that is concave toward the image plane side;
a fourth lens having a positive refractive power and an exit surface that is convex toward the image plane side;
a fifth lens having a negative refractive power and an exit surface that is concave toward the image plane side; and
a sixth lens having a positive refractive power,
wherein the wide angle lens system satisfies Formulas 1, 2, and 3 below:
75<FOV <85 Formula 1
2.0<Fno <2.3 Formula 2
0.6<TTL/ImgH <0.8 Formula 3
where FOV refers to a field of view of the wide angle lens system in degrees(°) and Fno refers to an F-number of the wide angle lens system, and TTL refers to a distance in millimeters (mm) from a center of an entrance surface of the first lens to an image plane, and ImgH refers to a diagonal length of an effective pixel region in millimeters (mm).
2. The wide angle lens system of claim 1 , wherein the fourth lens has a meniscus shape that is convex toward the image plane side.
3. The wide angle lens system of claim 1 , wherein at least one of an entrance surface and an exit surface of the sixth lens has at least one inflection point.
4. The wide angle lens system of claim 1 , wherein the wide angle lens system satisfies Formula 4 below:
0.5< F /ImgH <0.6 Formula 4
where F refers to an effective focal length of the wide angle lens system in millimeters (mm), and ImgH refers to a diagonal length of an effective pixel region in millimeters (mm).
5. The wide angle lens system of claim 1 , wherein the wide angle lens system satisfies Formula 5 below:
0.3< D 1/ D 6<0.4 Formula 5
where D 1 refers to an effective diameter of the first lens in millimeters (mm) and D 6 refers to an effective diameter of the sixth lens in millimeters (mm).
6. The wide angle lens system of claim 1 , wherein the wide angle lens system satisfies Formula 6 below:
5< f 5/ f 3<15 Formula 6
where f5 refers to a focal length of the fifth lens in millimeters (mm) and f3 refers to a focal length of the third lens in millimeters (mm).
7. The wide angle lens system of claim 1 , wherein the wide angle lens system satisfies Formula 7 below:
1.5<(Ind3+Ind4)/2 <1.7 Formula 7
where Ind3 refers to a refractive index of the third lens and Ind4 refers to a refractive index of the fourth lens.
8. The wide angle lens system of claim 1 , wherein the first lens comprises a meniscus lens that is concave toward the image plane side.
9. The wide angle lens system of claim 1 , wherein the second lens comprises a biconvex lens, and
an absolute value of a radius of curvature of an entrance surface of the second lens is less than an absolute value of a radius of curvature of the exit surface of the second lens.
10. The wide angle lens system of claim 1 , further comprising an aperture stop at a side of the first lens facing the object side.
11. The wide angle lens system of claim 1 , further comprising an optical filter provided at a side of the sixth lens facing the image plane side.
12. The wide angle lens system of claim 1 , wherein the first to sixth lenses are aspherical lenses.
13. The wide angle lens system of claim 1 , wherein the first to sixth lenses are plastic lenses.
14. An imaging device comprising:
the wide angle lens system of claims 1 ; and
a solid-state imaging element configured to pick up an image formed by the wide angle lens system.
15. A wide angle lens system, from an object side to an image plane side, comprising:
a first lens having a positive refractive power and an exit surface that is concave toward the image plane side;
a second lens having a positive refractive power and an exit surface that is convex toward the image plane side;
a third lens having a negative refractive power and an exit surface that is concave toward the image plane side;
a fourth lens having a positive refractive power, the fourth lens being an meniscus lens having an exit surface that is convex toward the image plane side;
a fifth lens having a negative refractive power and an exit surface that is concave toward the image plane side; and
a sixth lens having a positive refractive power and an exit surface with at least one inflection point,
wherein the wide angle lens system satisfies Formula 1 below:
0.6<TTL/ImgH<0.8 Formula 1
where TTL refers to a distance in millimeters (mm) from a center of an entrance surface of the first lens to an image plane, and ImgH refers to a diagonal length of an effective pixel region in millimeters (mm).
16. The wide angle lens system of claim 15 , further comprising an aperture stop at a side of the first lens facing the object side.
17. The wide angle lens system of claim 15 , wherein the wide angle lens system satisfies Formulas 2 and 3 below:
75<FOV<85 Formula 2
2.0<Fno<2.3 Formula 3
where FOV refers to a field of view of the wide angle lens system in degrees (°) and Fno refers to an F-number of the wide angle lens system.
18. The wide angle lens system of claim 15 , wherein the wide angle lens system satisfies at least one of Formulas 4 to 7 below:
0.5< F /ImgH <0.6 Formula 4
0.3< D 1/ D 6<0.4 Formula 5
5< f 5/ f 3<15 Formula 6
1.5<(Ind3 30 Ind4)/2 <1.7 Formula 7
where F refers to an effective focal length of the wide angle lens system in millimeters (mm), D 1 refers to an effective diameter of the first lens in millimeters (mm), D 6 refers to an effective diameter of the sixth lens in millimeters (mm), f5 refers to a focal length of the fifth lens, f3 refers to a focal length of the third lens, Ind3 refers to a refractive index of the third lens, and Ind4 refers to a refractive index of the fourth lens.
19. The wide angle lens system of claim 15 , wherein the first lens comprises a meniscus lens that is concave toward the image plane side.