Single-focus lens system and camera
View Patent ↗A fixed-focus lens system includes, in order from an object side to an image side, a first lens element having negative power, the first lens element having a convex surface opposite to an object, a second lens element having positive power, the second lens element having a concave surface opposite to the object, a third lens element having positive power, a fourth lens element having negative power, and a fifth lens element having positive power. A half angle of view of the fixed-focus lens system is 50 degrees or more, and a shape of the convex surface on the object side of the first lens element has at least one inflection point at a part except for the optical axis. With this configuration, a fixed-focus lens system capable of favorably correcting various aberrations can be provided.
1. A fixed-focus lens system comprising, in order from an object side to an image side:
a first lens element having negative power, the first lens element having a convex surface on the object side;
a second lens element having positive power, the second lens element having a concave surface on the object side;
a third lens element having positive power;
a fourth lens element having negative power;
a fifth lens element having positive power, and
a sixth lens element having negative power, wherein
a half angle of view of the fixed-focus lens system is 50 degrees or more,
a shape of the convex surface on the object side of the first lens element has at least one inflection point at a part except for an optical axis, and
a condition (5) and a condition (6) shown below are simultaneously satisfied,
nL 1>1.6 (5)
vL 1>30 (6)
wherein,
nL 1 is a refraction factor of the first lens element at a d-line, and
vL 1 is an Abbe number of the first lens element.
2. The fixed-focus lens system according to claim 1 , wherein a condition (1) shown below is satisfied,
1.7<( L 1 R 1+ L 1 R 2)/( L 1 R 1− L 1 R 2)<5.0 (1)
wherein,
L 1 R1 is a radius of curvature of a surface on the object side of the first lens element, and
L 1 R2 is a radius of curvature of a surface on the image side of the first lens element.
3. The fixed-focus lens system according to claim 1 , wherein a condition (2) shown below is satisfied,
2.1< f 2/ f< 10.0 (2)
wherein,
f2 is a focal length of the second lens element at a d-line, and
f is a focal length of an entire system at the d-line.
4. The fixed-focus lens system according to claim 1 , wherein a condition (3) shown below is satisfied,
−5.0< f 4/ f<− 1.0 (3)
wherein,
f4 is a focal length of the fourth lens element at a d-line, and
f is a focal length of an entire system at the d-line.
5. The fixed-focus lens system according to claim 1 , wherein a condition (4) shown below is satisfied,
1.0< f 5/ f< 5.0 (4)
wherein,
f5 is a focal length of the fifth lens element at a d-line, and
f is a focal length of an entire system at the d-line.
6. The fixed-focus lens system according to claim 1 , wherein a condition (7) shown below is satisfied,
0.15< f/TTL< 0.30 (7)
wherein,
f is a focal length of an entire system at a d-line, and
TTL is an entire optical length of the fixed-focus lens system.
7. The fixed-focus lens system according to claim 1 , wherein a shape of a surface on the image side of the sixth lens element has at least one inflection point at the part except for the optical axis.
8. A camera comprising:
the fixed-focus lens system according to claim 1 to form an optical image of an object; and
an imaging device configured to convert the optical image formed by the fixed-focus lens system into an electrical image signal.
9. A camera comprising:
the fixed-focus lens system according to claim 2 to form an optical image of an object; and
an imaging device configured to convert the optical image formed by the fixed-focus lens system into an electrical image signal.
10. A camera comprising:
the fixed-focus lens system according to claim 3 to form an optical image of an object; and
an imaging device configured to convert the optical image formed by the fixed-focus lens system into an electrical image signal.
11. A camera comprising:
the fixed-focus lens system according to claim 4 to form an optical image of an object; and
an imaging device configured to convert the optical image formed by the fixed-focus lens system into an electrical image signal.
12. A camera comprising:
the fixed-focus lens system according to claim 5 to form an optical image of an object; and
an imaging device configured to convert the optical image formed by the fixed-focus lens system into an electrical image signal.
13. A camera comprising:
the fixed-focus lens system according to claim 6 to form an optical image of an object; and
an imaging device configured to convert the optical image formed by the fixed-focus lens system into an electrical image signal.
14. A camera comprising:
the fixed-focus lens system according to claim 6 to form an optical image of an object; and
an imaging device configured to convert the optical image formed by the fixed-focus lens system into an electrical image signal.